UNITED 

STATES 

MINERAL 

RESOURCES 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 820 

UNITED 

STATES 

MINERAL 

RESOURCES 

DONALD A. BROBST and WALDEN P. PRATT, Editors 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 820 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1973 
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secreta·ry 

GEOLOGICAL SURVEY 

Doyle G. Frederick, Acting Director 

Library of Congress catalog-card No. 73-600060 

First printing 1973 

Second printing 1973 

Third printing 1981 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 
FOREWORD 

Minerals and mineral fuels are literally the cornerstones of modern 

life. They constitute the source materials for most of the things we use, 

and they supply the energy that powers our machines and heats and cools 

the air where we live and work. In short, they are the physical source of 

most of the necessities, conveniences, and comforts of life in the United 

States today. 

Most mineral resources are nonrenewable, for the deposits from which 

they are extracted are not being naturally reformed at any where near 

the rate we are using them. They are extendable, however, in the sense 

that new deposits are discovered by exploration, and deposits once too 

poor in quality to recover economically are made available by advancing 

technology. And, of course, many mineral products can be recycled. 

Because of our dependence on minerals and mineral fuels, the question 

of the magnitude of usable resources is of mounting concern. Generally 

the problem has been assessed in terms of proved reserves-workable deposits that have already been discovered and inventoried. To plan our 

future, however, we need some idea of the magnitude of resources that 

are geologically available if we are able to find and use them economically. 

As a part of our response to the Mining and Mineral Policy Act of 

1970, the Geological Survey provides in this volume the first overall assessment of mineral resources since that of the President's Materials Policy 

Commission in 1952. It goes beyond traditional resource appraisals, which 

have considered mainly inventoried reserves, to examine the geologic 

availability of resources that will be needed in future generations. For 

many minerals, these appraisals are preliminary at best, for not enough 

is known about their origin, distribution, or the geologic environments 

favorable for their occurrence to assess their potential now. But at the 

least they represent a beginning, a take-off from which we can expect to 

enlarge our knowledge of our mineral-resource endowment with advancing science and exploration. 

ROGERS C. B. MORTON 

Secretary of the Interior 

In 

PREFACE 

The work on this volume began in January 1972, 

but in a broader sense its production began many 

years ago. The chapters were written by geologists 

most of whom have had many years of experience 

studying the geology of mineral deposits, and more 

particularly the commodities about which they have 

written here. A total of nearly 2,300 man-years of 

professional experience in the geology of mineral 

resources is represented by the authors of the volume, and about 30 man-years went directly into its 

preparation. Each chapter contains not only a synthesis of the state of knowledge of the geology of 

the commodity, but also an appraisal of the known 

resources, and an examination of the geologic possibilities for finding additional deposits. 

In January 1972, responsibility for the preparation of the volume was assigned to us as co-editors, 

and we were given a tentative list of commodities 

and authors. We provided each author with a suggested outline of general topics to be covered, and 

some guidelines as to scope and philosophy of approach, but beyond that we avoided any attempt to 

fit each chapter into a stereotype. Moreover, the 

types of commodities range from the major metals 

and industrial minerals such as copper, silver, and 

fluorspar, which have been the subject of geologic 

research for years, to other commodities that are of 

such varied geologic nature (such as pigments or 

gemstones) or of such minor present importance 

(such as scandium or thallium) that they cannot be 

treated from the same viewpoint as the major minerals. The chapters range, therefore, from comprehensive summary reports to general essays that 

reflect the_ individuality of the authors as well as 

the variation among commodities. 

Throughout the book the emphasis is on geology, 

but each chapter contains some summary information on uses, technology, and economics. These summaries are not meant to be exhaustive, however, and 

additional details are in the 1970 edition of "Mineral Facts and Problems" (Bulletin 650 of the U.S. 

Bureau of Mines) ; indeed, we regard that book and 

the present volume as being complementary. 

In the examination of the geologic possibilities for 

finding new deposits-in many respects the principal innovative contributions of this volume-we 

asked the authors to frankly apply the limits of their 

ingenuity and not only to summarize current 

theories but also to express their own intuitive ideas, 

however speculative and unconventional they may 

seem, that have come from years of study devoted 

to the origin of mineral deposits. Readers will see 

that some authors have speculated more courageously than others. In any case, we believe readers 

will find all the chapters interesting, and many 

stimulating; and a few we believe can be frankly 

characterized as intellectually exciting. 

Most chapters include a section on prospecting 

techniques, and a summary of geologic or related 

problems on which the authors believe research 

might be most fruitful in the continuing efforts to 

find new resources. 

An integral part of the book is the bibliographic 

material cited at the conclusion of each chapter, in 

lieu of repetition of detailed descriptions already in 

print. Index and "spot" maps are not included in 

most chapters because they are available elsewhere, 

and in many cases with more detail than could possibly be included here. Maps showing the distribution of known deposits of many commodities in the 

United States are available in the Mineral Resource 

(MR) map series of the U.S. Geological Survey and 

in the National Atlas of the United States. 

The first three chapters deal not with resources 

of specific commodities but with general information that is pertinent to the study of mineral resources. In the introductory chapter we discuss the 

purposes of the book, the distinctions between reserves and various categories of resources, and some 

general conclusions drawn from our view of the book 

in its entirety. In the second chapter V. E. McKelvey 

discusses the problems of mineral-resource estimates 

and public policy. In the third chapter, R. L. Erickson discusses some new points of view on the relation 

of reserves and resources to the crustal abundance 

of elements. 

We acknowledge with thanks the cooperation of 

our colleagues in all phases of the preparation of 

this volume. Whatever success the book may attain 

is due entirely to a total effort. A paragraph of 

acknowledgment originally submitted as a part of 

the chapter on "Nuclear fuels" is given here instead 

because we feel it applied to all chapters: "The 

writers have drawn freely from published informav 
VI PREFACE 

tion, not all of which is cited, and from their colleagues, none of whom are given specific credit. The 

reader should be aware that the paper could not 

have been written without these sources." We extend 

specific thanks to Michael Fleischer for preparation 

of summaries of geochemical information that are 

included in many chapters. 

DONALD A. BROBST 

WALDEN P. PRATT 
CONTENTS 

Forevvord ---------------------------------------------------------------

Preface ----------------------------------------------------------------- Introduction, by Donald A. Brobst and Walden P. Pratt ---------------------

Mineral resource estimates and public policy, by V. E. McKelvey -------------

Crustal abundance of elements, and mineral reserves and resources, by Ralph L. 

Erickson ------------------------------------------------------------ Abrasives, by Robert E. Thaden -------------------------------------------

Aluminum and bauxite, by Sam H. Patterson and John R. Dyni -------------

Antimony, by M. H. Miller ----------------------------------------------

Arsenic, by J. L. Gualtieri ------------------------------------------------

Asbestos, by Andrevv F. Shride --------------------------------------------

Barite, by Donald A. Brobst ----------------------------------------------

Beryllium, by Wallace R. Griffitts -----------------------------------------

Bismuth, by J. W. Hasler, M. H. Miller, and R. M. Chapman ----------------

Bitumen-bearing rocks, by W. B. Cashion ----------------------------------

Cadmium, by Helmuth Wedovv, Jr. ----------------------------------------

Chromium, by T. P. Thayer -----------------------------------------------

Clays, by John W. Hosterman ---------------------------------------------

Coal, by Paul Averitt ----'------------------------------------------------

Cobalt, by John S. Vhay, Donald A. Brobst, and Allen V. Heyl ---------------

Construction stone, by Robert A. Laurence ---------------------------------

Copper, by Dennis P. Cox, Robert G. Schmidt, James D. Vine, Harold Kirkemo, 

Elizabeth B. Tourtelot, and Michael Fleischer --------------------------

Diatomite, by David L. Durham -------------------------------------------- Evaporites and brines, by George I. Smith, Charles L. Jones, William C. Culbertson, George E. Ericksen, and John R. Dyni -------------------------

Feldspar, by Frank G. Lesure ---------------------------------------------

Fluorine, by R. G. Worl, R. E. Van Alst~ne, and D. R. Shavve ----------------

Gallium, germanium, and indium, by Robert A. Weeks ----------------------

Gem stones, by Robert E. Thaden -----------------------------------------

Geothermal resources, by L. J. P. Muffler -----------------------------------

Gold, by Frank S. Simons and William C. Prinz ----------------------------

Graphite, by Paul L. Weis -----------------------------------------------

Helium, by Dvvight E. Ward and Arthur P. Pierce --------------------------

Iron, by Harry Klemic, Harold L. James, and G. Donald Eberlein ------------

Kyanite and related minerals, by Gilbert H. Espenshade ---------------------

Lead, by H. T. Morris, Allen V. Heyl, and Robert B. Hall -------------------

Lightweight aggregates, by A. L. Bush ------------------------------------ Limestone and dolomite, by Harold A. Hubbard and George E. Ericksen ------

Lithium, cesium, and rubidium-the rare alkali metals, by James J. Norton --

Magnesian refractories, by Alfred J. Bodenlos and T. P. Thayer -------------

Manganese, by John Van N. Dorr II, Max D. Crittenden, Jr., and Ronald G. 

Worl --------------------------------------------------------------- Mercury, by E. H. Bailey, A. L. Clark, and R. M. Smith --------------------

Mica, by Frank G. Lesure ------------------------------------------------

Molybdenum, by R. U. King, D. R. Shawe, and E. M. MacKevett, Jr. ----------

Nickel, by Henry R. Cornwall ---------------------·------------------------ Niobium (columbium) and tantalum, by Raymond L. Parker and John W. 

Jldams -------------------------------------------------------------- Nuclear Fuels: 

Introduction, bv Warren I. Finch ------------------------------------- Uranium, by Warren I. Finch, Jlrthur P. Butler, Jr., Frank C. Armstrong, 

and Jllbert E. Weissenborn --------------------------------------- Thorium, by Mortimer H. Staatz and Jerry C. Olson --------------------

Page 

III 

v 

1 

9 

21 

2.7 

35 

45 

51 

63 

75 

85 

95 

99 

105 

111 

123 

133 

143 

157 

163 

191 

197 

217 

223 

237 

247 

251 

263 

277 

285 

291 

307 

313 

333 

357 

365 

379 

385 

401 

415 

425 

437 

443 

455 

456 

468 

VII 
VIII CONTENTS 

Page 

Oil and gas, by T. H. McCulloh ------------------------------------------- 477 

Oil shale, by William C. Culbertson and Janet K. Pitman -------------------- 497 

Peat, by Cornelia C. Cameron --------------------------------------------- 505 

Phosphate deposits, by James B. Cathcart and R. A. Gulbrandsen ------------ 515 

Pigments and fillers, by C. Ervin Brown ----------------------------------- 527 

Platinum-group metals, by Norman J Page, Allen L. Clark, George A. Desborough, and Raymond L. Parker ------------------------------------- 537 

Rare-earth elements, by John W. Adams and Mortimer H. Staatz ------------ 547 

Rhenium, by R. U. King ------------------------------------------------- 557 

Sand and gravel, by Warren Yeend --------------------------------------- 561 

Scandium, by John W. Adams -------------------------------------------- 567 

Selenium, by H. W. Lakin and D. F. Davidson ------------------------------ 573 

Silica sand, by Keith B. Ketner ------------------------------------------- 577 

Silver, by Allen V. Heyl, W. E. Hall, Albert E. Weissenborn, H. K. Stager, 

W. P. Puffett, and Bruce L. Reed ------------------------------------ 581 

Sulfur, by Alfred J. Bodenlos ---------------------------------------------- 605 

Talc, by C. Ervin Brown ------------------------------------------------- 619 

Tellurium, by D. F. Davidson and H. W. Lakin ----------------------------- 627 

Thallium, by Keith Robinson ---------------------------------------------- 631 

Tin, by C. L. Sainsbury and Bruce L. Reed --------------------------------- 637 

Titanium, by Harry Klemic, Sherman P. Marsh, and Margaret Gooper ------- 653 

Tungsten, by S. Warren Hobbs and James E. Elliott ------------------------ 667 

Vanadium, by R. P. Fischer ---------------------------------------------- 679 

Zeolites in sedimentary rocks, by Richard A. Sheppard ---------------------- 689 

Zinc, by Helmuth Wedow, Jr., Thor H. Kiilsgaard, Allen V. Heyl, and Robert B. 

llall ---------------------------------------------------------------- 697 Zirconium and hafnium, by Harry Klemic, D~vid Gottfried, Margaret Cooper, 

and Sherman P. Marsh ----------------------------------------------- 713 
UNITED STATES MINERAL RESOURCES 

INTRODUCTION 

By DoNALD A. BROBST and WALDEN P. PRATT 

CONTENTS 

Page 

The purpose of this book ------------------------- 1 

Resources or reserves? --------------------------- 1 

A 1Narning -------------------------------------- 2 

Our dependence on minerals ---------------------- 3 

Classification of resources ------------------------ 3 

Public a1Nareness, resource estimates, and geologic 

availability ------------------------------------ 5 

General conclusions ------------------------------ 6 

Mineral potential: 1Nhere do 1Ne stand? --------- 6 

Lo1N-grade ores and the environment ---------- 7 

Economics and 1Naste ------------------------- 7 

The energy factor --------------------------- 8 

The need for research ---------------------------- 8 

References cited --------------------------------- 8 

FIGURE 

Page 

1. Classification of mineral resources used in this 

volume ---------------------------------- 4 

TABLE 

Page 

1. Potential U.S. resources of some important mineral commodities ------------------------- 7 

THE PURPOSE OF THIS BOOK 

Our civilization is dependent on minerals. Few 

people living in the United States and other developed nations pass through a single day without using 

raw or manufactured materials that have been been 

made from, processed by, fertilized with, or in some 

other way affected by minerals or mineral products. 

Without a steady supply of minerals our civilization could not survive. 

Unlike most other natural resources, minerals 

are not renewable. They are formed in the earth's 

crust by infinitesimally slow natural geologic processes acting for thousands or millions of years. 

Once removed and used, they cannot be grown again. 

The vital question, then, is this : Is our supply of 

minerals running out? 

To answer this question, as it applies to nearly 

all the mineral commodities in use today, is the 

general aim of this book. More specifically, the book 

attempts to provide answers to three basic questions 

about each mineral commodity: (1) How important 

is it to our present industrial civilization and standard of living? (2) how much of it do we have and 

to what extent is it economically and technologically 

available? and ( 3) how and where can we find more? 

The emphasis here is on domestic resources, but 

many chapters include information on foreign resources, generally most complete for those commodities for which we are most dependent upon sources 

abroad. 

The answers to the above questions are matters 

that should be of concern not only to geologists 

(both professional and student), but also to exploration managers, research administrators, economists 

and economic analysts, legislators, lawyers, planners, magazine and newspaper editors, and indeed 

many segments of the public at large. The book has 

been written with this varied audience in mind. 

The descriptions of the geology and origin of mineral deposits in each chapter necessarily involve 

some scientific jargon, but discussions of the uses, 

importance, history of exploitation, resources, and 

problems needing research are cast largely in nontechnical language so that they may be of use to 

scientist and nonscientist alike. 

RESOURCES OR RESERVES? 

A fundamental concept in the evaluation of mineral resources is the distinction between resources 

and reserves. Detailed definitions vary (the entire 

problem of resource terminology is currently being 

U.S. GEOL. SURVEY PROF. PAPER 820 

1 
2 UNITED STATES MINERAL RESOURCES 

studied by the National Commission on Materials 

Policy), but the principal distinction is based on 

current economic availability: reserves are known, 

identified deposits of mineral-bearing rock from 

which the mineral or minerals can be extracted 

profitably with existing technology and under present economic conditions ; whereas resources include 

not only reserves but also other mineral deposits 

that may eventually become available-either known 

deposits that are not economically or technologically 

recoverable at present, or unknown deposits, rich or 

lean, that may be inferred to exist but have not yet 

been discovered. A simple analogy from the field of 

personal finance, suggested by our colleague J. E. 

Gair, may be helpful in clarifying this important 

distinction: Reserves are represented by the funds 

in one's bank account and by other liquid assets; 

resources then include, in addition, all other assets 

and, more importantly, all income one may expect 

to receive, from whatever source, through the duration of one's lifetime. We will discuss various categories of resources and their relation to reserves 

later in this introduction, but for the present we 

would emphasize that because reserves are the only 

part of the total resource that is immediately available, they are of paramount concern to the mineral 

industry, and reserve estimates for most mineral 

commodities are generally available and are undergoing constant revision. For most minerals, however, current reserves are only a small part of the 

total resource. The remainder of the total-the potential resour·ces-are by far the most important 

for the long term, and they receive major emphasis 

in this book. Mineral resources, whether real or 

potential, are geologic entities-concentrations of 

one or more elements in the earth's crust. Because 

such concentrations occur as the result of geologic 

processes, the question of how and where to find 

more of them can ultimately be resolved only 

through the understanding of geologic principles and 

the application of geologic insight; accordingly, the 

chapters of this volume deal with predictions based 

on geologic reasoning, and have been written by 

geologists. 

A WARNING 

Implicit in the distinction between reserves and 

resources is a serious danger, which we state now 

and will reiterate throughout this volume: Potential resources are not reserves ; they are "birds in 

the bush," or to return to the analogy already used, 

they are frozen assets and next year's income, and 

cannot be used to pay this month's bills. No matter 

how optimistic an outlook is engendered by estimates 

of vast resources, such resources cannot be mined, 

much less used, until. they have been converted into 

the category of reserves, whether by discovery (of 

undiscovered resources of minable quality), or by 

improvements in technology (for recovering identified subeconomic resources), or by both. For nearly 

all minerals, the estimates of potential resources 

indicate quantities that may become available only 

if we vigorously pursue geologic and technologic 

re8earch to discover new mineral deposits in regions and geologic environments that are known to 

be favorable, to discover new favorable regions and 

environments, to discover new kinds of mineral 

deposits not previously recognized, to improve existing exploration techniques and develop new ones, 

and to improve extractive technology for processing 

low-grade ores that are not now economically recoverable. Readers of this volume must therefore 

be cautioned that the resource estimates contained 

herein are indeed estimates, not measurements; and 

they present an optimistic outlook for many commodities only in the context that they represent a 

potential, not a reality. Using these estimates in 

any effort to optimize our domestic resource outlook may only defeat the purpose if they are removed from this context or are quoted without 

adequate qualification. We have attempted to insure 

against such misinterpretation by repeating definitions of the appropriate resource terminology on 

all tables of resource estimates in this volume. 

Even with these qualifiers, some may criticize this 

volume for its articulation of a philosophy that they 

may consider to be unrealistic. We can only offer 

the response that in the fairly recent past, each of 

the kinds of geologic and technologic research enumerated in the preceding paragraph has in fact 

resulted in the conversion of potential resources 

into minable reserves-"rock in the box," in mining 

parlance; a few examples are the discoveries of the 

huge Kidd Creek zinc-copper-silver ore deposit in 

Ontario and the disseminated gold deposits of Carlin 

and Cortez in Nevada, and the development of technology for processing taconite iron ores. 

Indeed the events of the last 20 years are the best 

reason for optimism. In 1952, the recoverable reserves of lead were estimated to be 7.1 million tons, 

of which only about 1 million tons was called proved 

reserve. These figures were quoted on page 41 of 

volume 2 of "Resources for Freedom" (President's 

Materials Policy Commission, 1952), better known 

as the Paley report. Farther down on that page we 

find the following statement, "The poor discovery 

record of the past few decades provides little basis 

for optimism that the equivalent of the southeast 
INTRODUCTION 3 

Missouri district can be expected to turn up in the 

future ; the major hope lies in the development of 

some new methods of prospecting, as, for example, 

methods that would indicate the probability of deposits in the absence of surface ontcrops." Drilling 

in the mid-1950's on the west side of the Southeast 

Missouri district resulted in the discovery of the 

large unexposed deposits of lead ore known as the 

Viburnum Trend. By 1970, half a dozen mines were 

operating, and the reserves of lead in Missouri alone 

had increased to 30 million tons. (See the chapter 

on "Lead" in this volume.) The Viburnum Trend 

will yield more lead than the total production of the 

old part of the district. With the phoenixlike rejuvenation of the Southeast Missouri district, the 

Viburnum Trend becomes the perfect example of a 

potential resource converted to a reserve. 

We see no reason why such discoveries and developments cannot be expected to continue in the 

future. To point the direction to potential resources 

and to attempt to evaluate them are the objectives 

of this book. 

OUR DEPENDENCE ON MINERALS 

Few people are fully aware of their daily dependence upon minerals. An awareness is growing as 

the fragilities of modern civilization, stemming 

from population growth and economic expansion, 

become recognizable not only as world and national 

problems, but also as personal problems. The availability of mineral resources to meet the projected 

demands will critically affect future events. 

It is important, therefore, to be able to predict the 

occurrence of minerals, with some degree of realism, 

on several different scales of both time and space; 

we must know not only in which direction a particular mine opening should be extended to continue in 

an ore body, but over a longer time period, we must 

know where prospecting and exploration should be 

concentrated to discover new deposits of each kind 

of mineral-and the likelihood of success. In other 

words, where are our potential mineral resources 

and how large are they? How long will they last? 

For which minerals, if any, are we "in good shape"? 

Is our supply of any minerals unlimited? Of which 

ones do we have very little, or are we likely to run 

out in the near future? For these, is there a geologic 

probability that more can be discovered in the 

United States ?-that is, are there geologic environments in which such minerals are likely to occur? 

If so, where? And what problems are likely to be 

encountered in finding and extracting them? If 

domestic resources are not likely to be sufficient, 

then to which parts of the globe must we look for 

adequate resources in the future? These are the 

questions to which the authors of this volume have 

addressed themselves. 

CLASSIFICATION OF RESOURCES 

What, then, is a mineral resource? To begin with, 

we may define a mineral resource as a concentration 

of elements in a particular location in or on the 

earth's crust (or, now, also in the oceans), in such 

a form that a usable mineral commodity-whether 

it be an element (such as iron or aluminum), a 

chemical compound (such as salt or borax), a mineral (such as emerald or asbestos), or a rock (such 

as marble, coal, or gypsum)-can be extracted from 

it. The perceptive reader will recognize that such a 

definition has little practical value if the particular 

mineral commodity cannot be extracted at a profit. 

As already suggested, this feasibility of profitable 

extraction, or economic availability, is one of two 

parameters that distinguish between resources and 

reserves ; the other parameter is the degree of certainty of existence. These two parameters were 

originally formulated into a classification of resources by V. E. McKelvey (1972), whose presentation of these concepts is so vital to the philosophy 

of resources, and whose classification is so important as the cornerstone of the present volume, that 

we have included his article as the second chapter 

of this volume. We will summarize McKelvey's resource classification by stating merely that he defines reserves as economically recoverable material 

in identified deposits, and applies the term 'resources 

to include "deposits not yet discovered as well as 

identified deposits that cannot be recovered now." 

The terms recoverable, par-amarginal, and submarginal designate successively lower degrees of economic recoverability; paramarginal resources are 

defined as low-grade resources that are recoverable 

at prices as much as 1.5 times those prevailing now, 

and submarginal resources are those of still lower 

grade. (See fig. 4, p. 12.) 

In this volume we use a similar classification of 

resources; but because of our conviction that the 

long-range potential lies in resources that have not 

yet been discovered, our classification places less 

emphasis on the definition of various levels of economic recoverability, and more emphasis on evaluating the undiscovered-defining the various degrees 

of certainty. For the purpose of this volume, we 

distinguish three different such degrees (fig. 1). 

Identified resources are specific bodies of mineralbearing rock whose existence and location are 

known. They may or may not be evaluated as to 

extent and grade. Identified resources include 
4 UNITED ST'ATES MINERAL RESOURCES 

u 

:c 

; 

> 0 

u 

u 

g::: 

Identified resources 

RESERVES 

EXPLANATION 

VI Potential resources= Conditional+ Hypothetical 

~ + Speculative 

FIGURE 1.-Glassi:fication of mineral resources used in this 

volume. 

1·eserves-masses of rock whose extent and grade 

are known to a greater or lesser degree and whose 

grade and physical nature are such that they may 

be extracted at a profit with existing technology and 

at present price levels. These last constraints of 

technology and economics exclude from the category 

of reserves many mineral deposits that are known 

and evaluated but are not profitably or technologically minable at present, and to this important category of identified but subeconomic resources we 

apply the informal term conditional resourcesresources that may eventually become reserves when 

conditions of economics or technology are met. 

Conditional resources have an immediate potential, 

because they are known, and their assessment provides a target for technologic research. This term 

is used in the volume primarily as a convenience, 

because most authors were unable to distinguish 

the paramarginal and submarginal categories in 

McKelvey's classification. 

We divide the remaining potential resources, all 

undiscovered, into two informally designated categories. Hypothetical resources are here defined as 

undiscovered resources that we may still reasonably 

expect to find in known districts; speculative resources are defined as undiscovered resources that 

may exist elsewhere-either conventional types of 

deposits in broad geologic terranes in which as yet 

there are no discoveries, or else unconventional 

types of resources that have only recently been 

recognized (or are yet to be recognized) as having 

some potential. 

The utility of this distinction can be demonstrated 

by a few examples. In evaluating sandstone-type 

uranium deposits, for instance, we would consider 

as hypothetical resources the deposits that have so 

far eluded discovery in the known districts of New 

Mexico or Wyoming; our geologic knowledge tells 

us that there is good reason to expect we will find 

more deposits in those areas similar to the deposits 

already known, and our estimate of hypothetical 

resources is, in this case, an attempt to quantify 

the potential of these undiscovered resources, mainly 

on the basis of the extent of unexplored but favorable ground. A different kind of geologic perspective, on the other hand, suggests that there is still 

some likelihood of finding not just new deposits, 

but new major uranium districts. Our estimate of 

these speculative resources, even though it may be 

only an order of magnitude, is an attempt to quantify the resource potential of sedimentary basins 

that are known to exist but have not been sufficiently tested for uranium. 

Resources of copper can be used as another example of the distinction between hypothetical and 

speculative resources. We are justified in hypothesizing, for instance, that porphyry copper deposits 

are concealed under basin fill in and near the known 

copper districts of the southwest, whereas the discovery in recent years of porphyry-type copper deposits of Paleozoic and Precambrian age in Eastern 

North America permits us to speculate that whole 

new regions have some potential for new discoveries. 

Yet another example of the distinction between 

hypothetical and speculative resources involves the 

black bedded deposits of barite such as those currently being mined principally in Nevada and Arkansas. The known deposits are scattered over wide 

areas of both States, and chances are excellent that 

new deposits -hypothetical resources -will be 

found. But recent geologic studies of these deposits 

suggest that they are related more to sedimentary 

processes than was formerly believed. If this is true, 

then the potential for the discovery of new deposits 

and districts in other sedimentary basins-speculative resources-is likewise excellent. This example 

is an indication of how the reexamination and study 

of basic geologic principles can help to open new 

areas and environments favorable for exploration. 

One further aspect of the value of such a distinction is that it has forced us to realize that the 

speculative resources of some commodities are relatively low. From a worldwide geologic perspective, 

we can say that the regions with significant potential for discovery of iron, or phosphorite, or marine 

evaporites, are largely known; thus, the significant 

undiscovered resources fall under the heading of 
INTRODUCTION 5 

"hypothetical," rather than "speculative." For some 

commodities, this may simply reflect insufficient 

knowledge of regional geology to identifiy other 

promising areas, but for others it is an expression 

of confidence that the favorable terranes have all 

been identified. 

The entire field in the diagram of figure 1 represents our total primary resources (as distinct from 

secondary resources, such as recycled scrap, which 

are not considered in this volume) -identified reserves, plus potential resources, which consist of 

conditional, hypothetical, and speculative resources. 

Conversions of potential resources into reserves are 

made by discovery, technologic advance, or changes 

in economic conditions. The same processes may 

lead to similar conversions from outside the fieldto make potential resources from materials at present inconceivable as resources. 

A corollary of the emphasis of this volume on 

geologic rather than economic factors is that our 

classification is less concerned with the degrees of 

feasibility of recovery defined by McKelvey. We 

recognize that the concepts of paramarginal and 

submarginal resources are valid, but because of the 

broader objectives of this volume, nearly all our 

authors found that a single degree of distinction 

based on economic recoverability was difficult 

enough to obtain for identified resources, let alone 

for undiscovered resources, without the further 

complication of another degree defined by a specific 

price factor. Thus, nearly all the chapters of this 

volume differentiate three major categories of resources-identified, hypothetical, and speculative; 

within the first category, most chapters differentiate 

between recoverable identified resources (reserves), 

and subeconomic identified resources (conditional 

resources). In only a few chapters have the authors 

attempted to extend the levels of economic recoverability into the hypothetical and speculative fields, 

and where this has been done, it is generally in 

terms of "recoverable" versus "subeconomic" -for 

example, "subeconomic hypothetical resources." 

Special problems are posed in classifying the 

resources found in sea-floor manganese nodules, in 

metal-bearing muds of the Red Sea, and in the 

recently discovered metal-bearing sedimentary rocks 

of the Belt Supergroup in Idaho and Montana. Some 

authors were reluctant to characterize the deposits 

in these three environments as identified resources. 

We see no question that they are identified, in that 

they broadly fit the criteria of being known as to 

existence and location; but we well realize that they 

are not fully evaluated. Our decision to classify 

these resources as "identified," for consistency of 

treatment within this volume, may therefore be regarded as arbitrary and is in no way binding on 

our authors or on our readers. We note, however, 

that officials of two major U.S. mining companies 

were recently reported to have said they "expect to 

be selling metal made from the [sea-floor] nodules 

by the end of the decade" (Faltermayer, 1972, p. 

170). Such expectations, in our view, are not likely 

to have been predicated on resources that are undiscovered. 

PUBLIC AWARENESS, RESOURCE ESTIMATES, 

AND GEOLOGIC AVAILABILITY 

Public awareness of our dependence on mineral 

resources appears to be growing. With this growth 

in awareness-and indeed responsible for some of 

it-is a growth in the number of magazine and 

newspaper articles, and even books, that attempt 

to evaluate our supply of mineral resources and in 

some cases to forecast economic or cultural trends 

that are dependent on this supply. (See, for example, 

Faltermayer, 1972; Meadows and others, 1972; U.S. 

News and World Report, 1972.) The almost universal tendency of such articles is to discuss mineral 

resources principally from the perspective of economic availability under a given set of conditions, 

thereby overlooking the vital fact that reserves are 

but a part of resources. The results are, we feel, 

disturbing. Evaluations predicated only on knowledge (or estimates) of current reserves can easily 

lead to forecasts of the death of the industrial society in a short time. On the other hand, evaluations based on another kind of assumption suggest 

that a rise in prices will increase the reserves and 

bring much more material to market economically 

from lower and lower grade material in larger and 

larger deposits. This reasoning too is fallacious because elements are available in the earth's crust in 

very finite amounts. But in both instances, the 

reasoning leads to serious misinterpretations because it does not give adequate consideration to the 

single factor that ultimately determines all levels 

and degrees of mineral potential: geologic availability. Geologic availability concerns the existence 

and concentration of certain elements or combinations of elements and is the most fundamental characteristic of a mineral commodity that governs its 

commercial use. 

Assessment of geologic availability of a commodity requires basic knowledge of the geology, 

mineralogy, and geochemistry of that material, the 

geologic environments in which it occurs, and its 

concentration in those environments. The technology of exploration, mining, beneficiation, recov-
6 UNITED STATES MINERAL, RESOURCES 

ery, and use is founded upon this information. 

Studies of geologic availability are indispensable--

at all levels of commerce, industry, and government-for any economic planning that considers 

the available supply or use of primary mineral commodities and their byproducts. 

Generally, however, public concepts of the magnitude of mineral resources are based on evaluations 

of economic rather than geologic availability, and 

even these are subject to numerous problems. Sound, 

accurate estimates of reserves for large regions are 

highly difficult to compile, for many reasons. Reserve data from industrial deposits may not be 

available because of the problems of competition 

and taxes. Managements of many companies believe 

that in the competitive atmosphere of business they 

should not release information about their rese~ves. 

Some States tax the reserves in the ground held by 

mining companies, making it economically advantageous, and in some cases necessary, to produce at 

capacity for years from deposits that are continually 

reported to be nearly exhausted. Definition of tonnages of mineral resources of sufficiently high grade 

to be minable at current prices is difficult enough 

without trying to distinguish grades minable at 1.5 

or more times greater than the current price. Economic evaluations of a specific mineral deposit have 

become a complex task for a team of specialists, 

including not only geologists but also mining engineers, ore dressers, metallurgists, and economists. 

So many complex factors govern price at any given 

time that it would seem foolhardy to estimate resources in each of the economic categories and 

expect the results to be meaningful for very long. 

At some time, however, the pressures of both 

economic and geologic factors will meet in crisis. 

Economic factors may be altered rapidly. Changes 

in demand and use alter patterns of production and 

consumption; new deposits are sought elsewhere; 

substitutes will be sought; and new technology will 

be developed as the ingenuity of man is focused on 

solving the problems. But there is no economic 

availability if there is no geologic availability. Of 

the two factors, geologic availability is the more 

fundamental because without it economic availability is not pertinent. Just as no biological miracle 

can make it possible to extract blood from a turnip, 

neither technological magic nor astronomic dollar 

value can make it possible to extract gold or aluminum or borax or mica from rocks in which they are 

not present. Geologic availability, therefore, is the 

ultimate determinant of mineral potential, and it 

is geologic availability that is stressed in the evaluations of potential mineral resources in this volume. 

Few chapters in the volume attempt to distinguish 

between tonnages now recoverable and those available only at subeconomic levels of the three 

"certainty-of-existence" categories shown in figure 

1, but virtually every chapter offers a quantitative 

evaluation in numbers or words for the resources 

in each of the three categories, and the use of the 

threefold terminology has been applied as rigorously 

and uniformly as practical in each chapter. 

GENERAL CONCLUSIONS 

We realize that this book lacks a plot sufficient to 

induce its readers into proceeding through it from 

cover to cover. Therefore, we offer here some general conclusions on several aspects of the Nation's 

mineral-resource position, which have emerged 

from our editorial overview of the chapters as 

a whole. Of first importance is a summary answer 

to the principal question to which the volume is 

directed : Where do we stand with regard to resources of each commodity? Other conclusions pertain to the increasing importance, as resources, of 

large volumes of low-grade rocks, and attendant 

environmental problems; the problem of enormous 

quantities of potential mineral byproducts that are 

now literally being wasted ; the factor of energy in 

the extraction of minerals; and finally, the pressing 

need for vigorous research along many lines. 

MINERAL POTENTIAL: WHERE DO WE STAND? 

Each chapter of the volume has its own calculation or other evaluation of resources governed by 

those factors deemed by the authors to be important 

to the respective commodity. There is no way to 

make the data in each chapter absolutely comparable. We would prefer that users of the volume read 

the chapters of interest to them in order to obtain 

the best possible understanding of the authors' presentation of resource data, and then formulate their 

own conclusions. We have, however, compiled a 

table that shows resource appraisals on a numerical 

scale, for commodities of major importance, put 

into perspective in terms of the ·minimum anticipated cumulative demand 1 for the period 1968-2000 

as compiled by the U.S. Bureau of Mines (1970). 

Once again we emphasize that the resources indicated here are for the most part potential, and that 

their eventual availability as reserves is entirely 

dependent on continued geologic and technologic 

research as well as economic factors. 

1 In using "demand" values for purposes of comparison we do not 

represent them as being specific goals to be reached. This volume presents 

no social or political judgments; its sole purpose is to make available 

reliab!e geologic resource facts and assessments for public policy decision as 

well as for use by the minerals industry. 
INTRODUCTION 7 

TABLE 1.-Potential U.S. resources of some important mineral commodities, in relation to minimum anticipated cumulative demand to year 2000 A.D. 

ST=short tons. lb=pounds. 

LT=long tons. Tr oz=troy ounces. 

Identified resources: Includes reserves, and materials other than re- serves that are rea~onably. well known as to location, extent, and grade, 

that may be explOitable m the future under more favorable economic 

conditions or with improvements in technology. 

Hypothetical resources: Undiscovered but geo~ogically predictable deposits 

of materials similar to present identified resources. I. Domestic resources (of the category shown) are greater than 10 

times the minimum anticipated cumulative demand 1968-2000 II. Domestic resources are 2 to 10 times the MACD. · III. Domestic resources are approximately 75 percent to 2 times the 

MACD. 

IV. Domest~c resources are approximately 35-75 percent the MACD. V. Domest!c resources are approximately 10-35 percent the MACD. VI. Domestic resources are less than 10 percent of the MACD. 

IdentiMinimum anticipated fled Hypothetical Commodity cumulative demand, re- resources 1968-20001 sources 

Aluminum ------ 290,000,000 ST II Not estimated. Asbestos -------- 32,700,000 ST v VI 

Barite ---------- 25,300,000 ST II II Chromium _______ 20,100,000 ST VI VI 

Clay ------------ 2,813,500,000 ST III II 

Copper ---------- 96,400,000 ST III III 

Fluorine -------- 37,600,000 ST v v Gold ------------ 372,000,000 Tr oz HI Not estimated. Gypsum --------- 719,800,000 ST I I 

Iron ------------ 3,280,000,000 ST II I 

Lead ------------ 37,000,000 ST III IV 

Manganese ------ 47,000,000 ST III Not estimated. 

Mercury -------- 2·,600,000 flasks v Not estimated. 

Mica, scrap ------ 6,000,000 ST II I Molybdenum _____ 3,100,000,000 lbs I I 

Nickel ---------- 16,200,000,000 lbs III Not estimated. 

Phosphate ------- 190,000,000 ST II I 

Sand and gravel _ 56,800,000,000 ST III Not estimated. 

Silver ---------- 3, 700,000,000 Tr oz III III 

Sulfur ---------- 473,000,000 LT I I 

Thorium -------- 27,500 ST 2 II Not estimated. 

Titanium (Ti02) 38,000,000 ST II II Tungsten ________ 1,100,000,000 lbs IV IV 

Uranium -------- 1,190,000 ST II III 

Vanadium ------- 420,000 ST II Not estimated. 

Zinc ------------ 57,000,000 ST II II 

1 As estimated by U.S. Bureau of Mines, 1970. 2

• For thorium, maximum anticipated cumulative demand 1968-2000, 

wh1ch assumes commercial development of economically attractive thorium reactors by 1980. 

Careful study of both this table and the volume 

in its entirety leads to the conclusion that only a 

few commodities are readily available to the United 

States in quantities adequate to last for hundreds 

of years. By no means is it too early to become 

concerned about future mineral supplies-and to 

start planning. Charles F. Park (1968) wrote of 

the decrease in mineral supplies that is placing 

modern American affluence in jeopardy. The real 

extent of our dependence on mineral resources places 

in jeopardy not merely affluence, but world civilization. 

LOW-GRADE ORES AND THE ENVIRONMENT 

The impelling need for minerals poses environmental problems of concern to all. Probably foremost among these is the fact that for many minerals future production will depend on mining enormous volumes of low-grade ores, with necessarily 

strong environmental impact. The problem can be 

temporary, and can be solved, as witness the utilization of the manganese deposits in the Nikopol 

region, U.S.S.R., described in the chapter on "Manganese." But in most areas the opposing factions of. 

industry and environmentalist are still just facing 

off. We believe the problem must be met squarely, 

realistically, and soon, by frank and objective exchange-not merely between small groups representing the mining industry on the one hand and 

outdoor enthusiasts on the other but between 

industry and the public at large. The environment 

is far bigger then any small interest group. Ultimately, a concerned public must decide in which 

order to place its priorities, and each faction of that 

public is entitled to basic information on the need 

for and availability of mineral resources as a foundation on which to base its decisions. Thus, as only 

two examples of such factions, the enthusiastic 

hiker-whether fisherman, Scout leader, or vacationing city dweller-must realize that his dacroncovered aluminum-frame backpack, his nylon fishing line, his polyurethane foam pad, and even his 

dehydrated foods are either made of or processed 

by mineral products, which continue to be used up 

and must continue to be made available. Conversely, 

the miner must realize that his assertion of need to 

develop a new copper deposit, when the technology 

of extraction may leave not only important potential byproducts but half the copper itself in the 

ground, may sound more like expediency than need. 

It is beyond the scope of this volume to attempt 

a comprehensive review or evaluation of the mineral-environmental problem in general. Our purpose here is simply to indicate that the chapters of 

this volume provide some of the basic information 

on which such reviews or evaluations should be 

based. 

ECONOMICS AND WASTE 

A major aspect of resources that appears in many 

of these chapters is the extent to which many potential byproducts or coproducts are literally being 

wasted-lost forever-because there is no apparent 

economic incentive for recovering them. Some minerals go into slurry ponds, some into slags, some up 

the flue. Examples of such commodities are the 

vanadium in magnetite deposits; selenium, tellurium, and gold lost through in-place leaching of 

porphyry copper deposits; fluorine, vanadium, urani urn, scandi urn, and rare earths in marine phosphorites; cadmium, bismuth, and cobalt in lead 

ores ; and several metals in coal ash. Strictly speak-
8 UNITED STATES MINERAL· RESOURCES 

ing, these resources belong in the category of conditional resources, but we believe there is a significant 

distinction between resources that are not economically minable under present conditions and those 

that either are not recovered because of selective 

mining, or are discarded because of selective processing. In many cases the perspective of geologic 

availability makes possible the view that what may 

seem economical for the short term is not necessarily so for the long term, and these potential 

resources should not be overlooked or misused. 

THE ENERGY FACTOR 

Extraction and processing of all minerals requires 

some form of energy, and it is a safe generalization 

to say that to produce a fixed amount of any given 

commodity, the lower the grade of ore, the greater 

is the quantity of energy required. Although this 

volume contains individual chapters on mineral 

energy resources, a comprehensive evaluation of 

energy resources in the context of their specific 

relation to extraction of minerals is far beyond the 

scope of the book. The reader should bear in mind 

that as the mining industry turns to lower and lower 

grades of many ores, the cost and availability of the 

required energy are probably the single most important factors that will ultimately determine 

whether or not a particular mineral deposit can be 

worked economically. 

THE NEED FOR RESEARCH 

Potential resources are transformed into reserves 

not by moving rock, but by expanding the artificial 

boundaries of geologic knowledge and economic 

availability that delimit "reserves" from "resources" ; hence, the potential of most of the resources discussed in this volume can be realized 

only as a result of applied research. Development 

of new technologies will make economic extraction 

of conditional resources feasible; innovative application of old geologic theory and the creation of new 

concepts of ore formation can be expected to lead 

to the discovery of conventional mineral deposits in 

favorable regions (hypothetical resources) ; research 

and exploration can be counted on to discover some 

new types of deposits and some new ore environments and regions that we do not know about now 

(speculative resources). 

Clearly, to these factors of geologic and economic 

availability we must also add the factor of human 

ingenuity. W. E. Pratt (1943), vice president of 

Standard Oil Co., in speaking some years ago of 

petroleum exploration, cogently expressed a viewpoint that is equally pertinent for mineral exploration: "* * * physical conditions in the earth's crust 

impose fewer and less formidable obstacles to the 

development of commercial oil fields over the earth 

than do some of our mental and social habits * * * . 

Whatever the geological conditions may be and 

whatever technique we employ, we find oil in the 

earth very rarely unless we have first acquired an 

appropriate mental attitude * * *. Where oil really 

is, then, in the final analysis, is in our own heads !" 

The chapters of this volume constitute a beginning 

effort to cultivate the "appropriate mental attitude" 

and to articulate the resulting ideas in terms of 

where and in what magnitudes our future mineral 

resources might be found. Only by continuing this 

effort, through vigorous pursuit of exploration, research, and technologic development, can we confidently expect to locate these potential resources and 

convert them into usable reserves. 

REFERENCES CITED 

Faltermayer, Edmund, 1972, Metals: the warning signals 

are up: Fortune, October 1972, p. 109-112, 164, 169-

170, 174-176. 

McKelvey, V. E., 1972, Mineral resource estimates and public policy: American Scientist, v. 60, no. 1, p, 32-40; 

reprinted in this book. 

Meadows, D. H., Meadows, D. L., Randers, Jfijrgen, and 

Behrens, W. W. III, 1972, The limits to growth: New 

York, Universe Books, 205 p. 

Park, C. F., Jr., 1968, Affluence in jeopardy: San Francisco, 

Freeman, Cooper & Go., 368 p. 

Pratt, W. E., 1943, Oil in the Earth: Lawrence, Kansas 

Univ. Press, 110 p. 

President's Materials Policy CommisfSion, W. S. Paley, chm., 

1952, Resources for freedom: Washington, U.S. Govt. 

Printing Office, 818 p., 5 vols. 

U.S. Bureau of Mines, 1970, Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, 1291 p. 

U.S. News and World Report, 1972, U.S. becoming a "have 

not" in raw materials-what to do?: U.S. News and 

World Report, v. 73, no. 23, p. 81-84. 
UNITED STATES MINERAL RESOURCES 

MINERAL RESOURCE ESTIMATES AND PUBLIC POLICY 

By V. E. McKELVEY 

CONTENTS 

Page 

Introduction ------------------------------------- 9 

Concepts of reserves and resources ---------------- 11 

Examples of estimates of potential resources ------- 13 

Quantifying the undiscovered --------------------- 14 

Need for review of resource adequacy ------------- 17 

Selected bibliography ----------------------------- 18 

FIGURES 

Page 

2. Graph showing per capita energy consumption 

compared to per capita Gross National Product 10 

3. Graph showing per capita steel consumption compared to per capita Gross National Product ___ 10 

4. Diagram showing classification of mineral reserves and resources ----------------------- 12 

5. Graph showing domestic reserves of elements 

compared to their abundance in the earth's 

crust -------------------------------------- 16 

TABLE 

Page 

2. Some estimates of U.S. crude-oil reserves and resources ------------------------------------ 14 

INTRODUCTION 

Not many people, I have found, realize the extent 

of our dependence on minerals. It was both a surprise and a pleasure, therefore, to come across the 

observations of George Orwell in his book "The Road 

to Wigan Pier." When describing the working conditions of English miners in the 1930's, he evidently was led to reflect on the significance of coal : 

Our civilization ... is founded on coal, more completely 

than one realizes until one stops to think about it. The 

machines that keep us alive, and the machines that make 

the machines are all directly or indirectly dependent upon 

coal . . . . Practically everything we do, from eating an ice 

to crossing the Atlantic, and from baking a loaf to writing 

a novel, involves the use of coal, directly or indirectly. For 

all the arts of peace coal is needed ; if war breaks out it is 

needed all the more. In time of revolution the miner must go 

on working or the revolution must stop, for revolution as 

much as reaction needs coal . . . In order that Hitler may 

march the goosestep, that the Pope may denounce Bolshevism, 

that the cricket crowds may assemble at Lords, that the 

Nancy poets may scratch one another's backs, coal has got 

to be forthcoming. 

To make Orwell's statement entirely accurateand ruin its force with complications-we should 

speak of mineral fuels, instead of coal, and of other 

minerals also, for it is true that minerals and mineral fuels are the resources that make the industrial 

society possible. The essential role of minerals and 

mineral fuels in human life may be illustrated by a 

simple equation 

L 

p 

in which the society's average level of living (L), 

measured in its useful consumption of goods and 

services, is seen to be a function of its useful consumption of all kinds of raw materials (R), including metals, nonmetals, water, soil minerals, biologic 

produce, and so on; times its useful consumption of 

all forms of energy (E) ; times its useful consumption of all forms of ingenuity (J), including political 

and socio-economic as well as technologic ingenuity; 

divided by the number of people (P) who share in 

the total product. 

This is a restatement of the classical economists' 

equation in which national output is considered to 

be a function of its use of capital and labor, but it 

shows what capital and labor really are. Far from 

being mere money, which is what it is popularly 

thought to mean, capital represents accumulated 

usable raw materials and things made from them, 

usable energy, and especially accumulated knowlU.S. GEOL. SURVEY PROF. PAPER 820 

9 
10 UNITED STATES MINERAL RESOURCES 

edge. And the muscle power expended in mere physical toil, which is what labor is often thought to 

mean, is a trivial contribution to national output 

compared to that supplied by people in the form of 

skills and ingenuity. 

This is only a conceptual equation, of course, for 

numerical values cannot be assigned to some of its 

components, and no doubt some of them-ingenuity 

in particular-should receive far more weight than 

others. Moreover, its components are highly interrelated and interdependent. It is the development 

and use of a high degree of ingenuity that makes 

possible the high consumption of minerals and fuels, 

and the use of minerals and fuels are each essential 

to the availability and use of the other. N evertheless, the expression serves to emphasize that level 

of living is a function of our intelligent use of 

natural resources, and it brings out the importance 

of the use of energy and minerals in the industrial 

society. As shown in figure 2, per capital Gross Na10,000r--------r,----,,.------,....,----.,---~ 

.... 

zz 

0 _ w _, 8000t-

... <( 

CL> 

~-:J:J 

cno Zw 

0 ... 6000i-

(J<( 

>o 

~() 

a::u.. 

~0 

w (I) 40001- <(~ 

... <( -a: 

CL~ 

<(0 

(J..J 

ffi ~ 20001-

CLz 

., ' 

O·iJJ • • • I 

. . 

• 

.. 

_I I 

0 $1000 $2000 $3000 $4000 

PER CAPITA GNP IN 1967 

-

-

-

-

$5000 

FIGURE 2.-Per capita energy consumption compared to per 

capita Gross National Product (GNP) in countries for 

which statistics are available in the United Nations '"Statistical Year-book" for 1967. 

tional Product among the countries of the world is, 

in fact, closely related to their per capita consumption of energy. Steel consumption also shows a close 

relation to per capita GNP (fig. 3), as does the consumption of many other minerals. 

Because of the key role that minerals and fuels 

play in economic growth and in economic and military security, the extent of their resources is a 

(I) 600~­

~ 

<( 

a: 

~ 

0 

::! 500~ 

LJ CL 

~ 

:J 

(I) 

z 

0 

~ 300r-

~ I 

t 200~ CL 

<( 

(J 

a: 

w 

Q. 

.. 

100;- • 

• .,# 

.. . . 

.. 

• • 

• 

• 

$5000 

PER CAPITA GNP IN 1967 

FIGURE 3.-Per capita steel consumption compared to per 

capita Gross National Product (GNP) in countries for 

which statistics are available in the United Nations "Statistical Yearbook" for 1967. 

matter of great importance to government, and 

questions concerning the magnitude of resources 

arise in conjunction with many public problems . 

To cite some recent examples, the magnitude of 

low-cost coal and uranium reserves has been at the 

heart of the question as to when to press the development of the breeder reactor-which requires 

a research-and-development program involving such 

an enormous outlay of public capital that it would 

be unwise to make the investment until absolutely 

necessary. 

Similarly, estimates of potential oil and gas resources are needed for policy decisions related to 

the development of oil shale and coal as commercial 

sources of hydrocarbons, and estimates are needed 

also as the basis for decisions concerning prices and 

import controls. · 

Faced with a developing shortage of natural gas, 

the Federal Power Commission is presently much 

interested in knowing whether or not reserves reported by industry are an accurate indication of the 
MINERAL RESOURCE ESTIMATES AND PUBLIC POLICY 11 

amount of natural gas actually on hand; it also 

wants to know the extent of potential resources and 

the effect of price on their exploration and development. At the regional or local level, decisions with 

respect to the designation of wilderness areas and 

parks, the construction of dams, and other matters 

related to land use involve appraisal of the distribution and amount of the resources in the area. 

The questions of the need for an international 

regime governing the development of seabed resources, the character such arrangement should 

have, the definition of the area to which it should 

apply also involve, among other considerations, 

analysis of the probable character, distribtuion, and 

magnitude of subsea mineral resources. 

And coming to the forefront is the most serious 

question of all-namely, whether or not resources 

are adequate to support the continued existence of 

the world's population and indeed our own. The possibility to consider here goes much beyond Malthus' 

gloomy observations concerning the propensity of 

a population to grow to the limit of its food supply, 

for both population and level of living have grown 

as the result of the consumption of nonrenewable 

resources, and both are already far too high to 

maintain without industrialized, high-energy, and 

high mineral-consuming agriculture, transportation, 

and manufacturing. I will say more about this question later, but to indicate something of the magnitude of the problem let me point out that, in attaining our high level of living in the United States, we 

have used more minerals and mineral fuels during 

the last 30 years than all the people of the world 

used previously. This enormous consumption will 

have to be doubled just to meet the needs of the 

people now living in the United States through the 

remainder of their lifetimes, to say nothing about 

the needs of succeeding generations, or the increased 

consumption that will have to take place in the 

lesser developed countries if they are to attain a 

similar level of living. 

CONCEPTS OF RESERVES AND RESOURCES 

The focus of most of industry's concern over the 

extent of mineral resources is on the magnitude of 

the supplies that exist now or that can be developed 

in the near term, and this is of public interest also. 

Many other policy decisions, however, relate to the 

much more difficult question of potential supplies, 

a question that to be answered properly must take 

account both of the extent of undiscovered deposits 

as well as deposits that cannot be produced profitably now but may become workable in the future. 

Unfortunately, the need to take account of such 

deposits is often overlooked, and there is a widespread tendency to think of potential resources as 

consisting merely of materials in known deposits 

producible under present economic and technologic 

conditions. 

In connection with my own involvement in resource appraisal, I have been developing over the 

last several years a system of resource classification 

and terminology that brings out the classes of resources that need to be taken into account in appraising future supplies, which I believe helps to 

put the supply problem into a useful perspective. 

Before describing it, however, I want to emphasize 

that the problem of estimating potential resources 

has several built-in uncertainties that make an accurate and complete resource inventory impossible, 

no matter how comprehensive its scope. 

One such uncertainty results from the nature of 

the occurrence of mineral deposits, for most of them 

lie hidden beneath the earth's surface and are difficult to locate and to examine in a way that yields 

accurate knowledge of their extent and quality. 

Another source of uncertainty is that the specifications of recoverable materials are constantly changing as the advance of technology permits us to mine 

or process minerals that were once too low in grade, 

too inaccessible, or too refractory to recovery profitably. Still another results from advances that make 

it possible to utilize materials not previously visualized as usable at all. 

For these reasons the quantity of usable resources 

is not fixed but changes with progress in science, 

technology, and exploration and with shifts in economic conditions. We must expect to revise our 

estimates periodically to take account of new developments. Even incomplete and provisional estimates are better than none at all, and if they 

differentiate known, undiscovered, and presently 

uneconomic resources they will help to define the 

supply problem and provide a basis for policy decisions relating to it. 

The need to differentiate the known and the recoverable from the undiscovered and the uneconomic 

requires that a resource classification system convey two prime elements of information: the degree 

of certainty about the existence of the materials 

and the economic feasibility of recovering them. 

These two elements have been recognized in existing terminology, but only incompletely. Thus as 

used by both the mining and the petroleum industries, the term reserves generally refers to economically recoverable material in identified deposits, 

and the term resources includes in addition deposits 

not yet discovered as well as identified deposits that 
12 UNITE·D ST'A TES MINERAL RESOURCES 

cannot be recovered now (for example, Blonde] and 

Lasky, 1956). 

The degree of certainty about . the existence of 

the materials is described by terms such as proved, 

probable, and possible, the terms traditionally used 

by industry, and measured, indicated, and inferred, 

the terms devised during World War II by the Geological Survey and the Bureau of Mines to serve 

better the broader purpose of national resource 

appraisal. Usage of these degree-of-certainty terms 

is by no means standard, but all their definitions 

show that they refer only to deposits or structures 

known to exist. 

Thus, one of the generally accepted definitions of 

possible ore states that it is to apply to deposits 

whose existence is known from at least one exposure, and another definition refers to an ore body 

sampled only on one side. The definition of inferred 

reserves agreed to by the Survey and the Bureau 

of Mines permits inclusion of completely concealed 

deposits for which there is specific geologic evidence and for which the specific location can be 

described, but it makes no allowance for ore in unknown structures of undiscovered districts. The 

previ9us definitions of both sets of terms also link 

them to deposits minable at a profit; the classification system comprised of these terms has thus 

neglected deposits that might become minable as 

the result of technologic or economic developments. 

To remedy these defects, I have suggested that 

existing terminology be expanded into the broader 

framework shown in figure 4, in which degree of 

certainty increases from right to left and feasibility of economic recovery increases from bottom 

to top. Either of the series of terms already used 

to describe degree of certainty may be used with 

reference to identified deposits and applied not only 

to presently minable deposits but to others that 

have been identified with the same degree of certainty. Feasibility-of-recovery categories are designated by the terms recoverable, paramarginal, and 

submarginal. 

Paramarginal resources are defined here as those 

that are recoverable at prices as much as 1.5 times 

those prevailing now. (I am indebted to S. P. 

Schweinfurth for suggesting the prefix para to indicate that the materials described are not only those 

just on the margin of economic recoverability, the 

common economic meaning of the term marginal.) 

At first thought this price factor may seem to be 

unrealistic. The fact is, however,-that prices of many 

mineral commodities vary within such a range from 

place to place at any given time, and a price elasIdentified Undiscovered 

Proved I Probable I Possible 

1 I 

u 

«< 

.. 

u Reserves > 0 

u 

u 

I I 

I I - «< 

c 

;o 

.. 

«< Resources E 

«< 

.. 

«< 

-t- + + + -

• s 

011 

~ 

E 

:I 

I I I 

Degree of certainty 

FIGURE 4.-Classification of mineral reserves and resources. 

Degree of certainty increases from right to left, and 

feasibility of economic recovery increases from bottom to 

top. 

ticity of this order of magnitude is not uncommon 

for many commodities over a space of a few years 

or even months, as shown by recent variations in 

prices of copper, mercury, silver, sulfur, and coal. 

Deposits in this category thus become commercially 

available at price increases that can be borne without serious economic effects, and chances are that 

improvements in existing technology will make them 

available at prices little or no higher than those 

prevailing now. 

Over the longer period, we can expect that technologic advances will make it profitable to mine 

resources that would be much too costly to produce 

now, and, of course, that is the reason for trying to 

take account of submarginal resources. Again, it 

might seem ridiculous to consider resources that 

cost two or three times more than those produced 

now as having any future value at all. But keep in 

mind, as one of many examples, that the cutoff 

grade for copper has been reduced progressively not 

just by a factor of two or three· but by a factor of 

10 since the turn of the century and by a factor of 

about 250 over the history of mining. Many of the 

fuels and minerals being produced today would once 

have been classed as submarginal under this definition, and it is reasonable to believe that continued 

technologic progress will create recoverable reserves 

from this category. 
MINERAL RESOURCE ESTIMATES AND PUBLIC POLICY 13 

EXAMPLES OF ESTIMATES OF POTENTIAL 

RESOURCES 

of critics have (for example, Inglis, 1971), the 

advisability of enlarging nuclear generating capacity 

until the breeder is ready for commercial use. 

For most minerals, the chief value of this classi- Until recently the only information available about 

fication at present is to call attention to the informa- petroleum resources consisted of estimates of proved 

tion needed for a comprehensive appraisal of their reserves prepared annually by the American Petropotential, for we haven't developed the knowledge leum Institute and the American Gas Association, 

and the methods necessary to make meaningful plus a few estimates of what has been called ultiestimates of the magnitude of undiscovered deposits, mate production, that is, the total likely to be 

and we don't know enough about the cost of pro- eventually recovered. A few years ago, however, the 

ducing most presently noncommercial deposits to API began to report estimates of total oil in place 

separate paramarginal from submarginal resources. in proved acreage, and the Potential Gas Committee 

Enough information is available for the mineral began to estimate possible and probable reserves of 

fuels, however, to see their potential in such a natural gas, defining them as consisting of gas 

framework. expected to be found in extensions of identified fields 

The fuel for which the most complete information and in new discoveries in presently productive strata 

is available is the newest one-uranium. As a result in producing provinces. It also introduced another 

of extensive research sponsored by the Atomic En- category, speculative resources-equivalent to what 

ergy Commission, uranium reserves and resources 1 have called "undiscovered'' -to represent gas to 

are reported in several cost-of-recovery categories, 1 be found in nonproducing provinces and in presently 

from less than $8 to more than $100 per pound ~f unproductive strata in producing provinces. 

UaOs. For the lower cost ores, the AEC makes pen- In 1970 the National Petroleum Council released 

odic estimates in two degree-of-certainty categories, a summary of a report on "Future Petroleum Provone that it calls reasonably assured reserves and the inces of the United States," prepared at the request 

other it calls additional resources, defined as ura- of the Department of the Interior, in which it renium surmised to occur in unexplored extensions of ported estimates of crude oil in the combined 

known deposits or in undiscovered deposits in known probable-possible class and in the speculative cateuraniurn districts. Bot~ the AEC and. the Geo_Iogical gory. In addition, NPC estimated the amounts that 

Survey have made estimates from time to time of would be available under two assumptions as to the 

resources in other degree-of-certainty and cost-of- percent of the oil originally in place that might be 

recovery categories. recovered in the future (table 2). NPC did not assess 

Ore in the less-than-$8-per-pound class is minable the cost of such recovery, but the average recovery 

now, and the AEC estimates reasonably assured is now about 30 percent of the oil in place, and NPC 

reserves to be 143,000 tons and additional resources expects it to increase gradually to about 42 percent 

to be 167,000 tons of UaOs-just about enough to in the year 2000 and to 60 percent eventually. The 

supply the lifetime needs of reactors in use or NPC estimates do not cover all potentially favorable 

ordered in 1968 and only half that required for areas either on land or offshore but, even so, in the 

reactors expected to be in use by 1980. The Geo- sum of these various categories NPC sees about 12 

logical Survey, however, estimates that undiscov- times as much oil remaining to be discovered and 

ered resources of presently minable quality may produced as exists in proved reserves alone. 

amount to 750,000 tons, or about 2.5 times that in The Potential Gas Committee's estimates of poidentified deposits and districts. Resources in the tential gas resources similarly do not cover all 

$8- to $30-a-pound category in identified and undis- favorable areas, but they indicate that resources in 

covered deposits add only about 600,000 tons of the probable, possible, and speculative categories 

Ua08 and thus do not significantly increase potential are about twice that of proved reserves and past 

reserves. production. Because about 80 percent of the gas 

But tens of millions of tons come into prospect originally in place is now recovered, paramarginal 

in the price range of $30 to $100 per pound. Ura- and submarginal resources in ordinary gas reservoirs 

nium at such prices would be usable in the breeder are not as large as for crude oil. Paramarginal and 

reactor. The breeder, of course, would utilize not submarginal gas resources may be significant, howonly U235 but also U238 , which is 140 times more ever, in kinds of rocks from which gas is not now 

abundant than U235 • Plainly the significance of ura- recovered, namely impermeable strata and coal. In 

nium as a commercial fuel lies in its use in the the Rocky Mountain province, for instance, Haun, 

breeder reactor, and one may question, as a number Barlow, and Hallinger (1970) recently estimated 
14 UNITED STATES MINERAL RESOURCES 

TABLE 2.-Some estimates of U.S. crude-oil reserves and resources, in billion barrels 

[API, American Petroleum Institute; NPC, National Petroleum Council] 

In identified fields or stuctures In undiscovered 

fields and structures Proved Probable-possible (speculative) 

~overable at present rate 1 ---------------

Additional at 42 percent recovery ---------·- Additional at 60 percent recovery ----------- Oil originally in place ----------------------

31 (API) 

47 (NPC) 

69 (NPC) 

74 (NPC) 

22 (NPC) 

40 (NPC) 

67 (NPC) 

21 (NPC) 

37 (NPC) 

388 (API) 2 227 (NPC) 209 (NPC) 

Total oil originally in place ----------------- Ultimate production 2 

---------------------

2200 (Hendricks and Schweinfurth, 1968) . 190 (Hubben, 19·69); 353 (Moore, 1966); 433 (Weeks) 3 ; 450 (Elliott 

and Linden, 1968) ; 432-495 ( NPC) ; 550 (Hendricks and Schweinfurth, 1968) . 

1 Average recovery is 30 percent of oil in place. 2 Includes past production of 86 billion barrels. a See McKelvey (1968, Table II, p. 18). 

potential gas resources in ordinary reservoirs to be 

in the range of 100 to 200 trillion cubic feet, but 

pointed out that gas in impermeable strata which 

might be released by nuclear stimulation would be 

several times that amount. Gas occluded in coalnow only a menace in this country as a cause of 

explosions-is already recovered in some Europe·an 

mines and is also a potentially large resource. 

The uncertainties concerning potential coal resources center not on their total magnitude, as they 

do for oil and gas, but on the amounts available at 

present prices. Because coal beds have great lateral 

continuity, geologic mapping and stratigraphic studies make it possible to project them long distances 

from their outcrops and to categorize them in terms 

of thickness of beds, thickness of overburden, rank 

of coal, and other features that affect cost. The Geological Survey has prepared such estimates, but the 

cost of recovering coal in the various categories has 

yet to be determined. Coal in beds more than 14 

inches thick totals at least 3.3 trillion tons in the 

United States, but estimates of the amounts minable at present prices have ranged from 20 to 220 

billion tons. (See U.S. Office of Science and Technology, "Energy R and D and National Progress.") 

Because 20 billion tons represents nearly a 40-year 

supply at present rates of consumption, it is easy 

to see why the studies needed to determine how 

much would be available at various costs have not 

been undertaken. The question is by no means only 

of academic interest, for the nuclear power development program was justified in part in its early years 

on the assumption that reserves of low-cost coal 

were extremely limited, and part of the continued 

growth of the nuclear power industry is said to be 

the result of the difficulty power companies are 

having in acquiring low-cost reserves. 

QUANTIFYING THE UNDISCOVERED 

Considering potential resources in the degree-ofcertainty, cost-of-recovery framework brings out 

the joint role that geologists, engineers, mineral 

technologists, and economists must play in estimating their magnitude. Having emphasized the importance of the economic and technologic side of 

the problem, I want now to turn to the geological 

side and consider the problem of how to appraise 

the extent of undiscovered reserves and resources. 

It is difficult enough to estimate the extent of unexplored resources of the inferred or possible class. 

In fact, it is even difficult to estimate measured or 

proved reserves with a high degree of accuracy until 

they have been largely mined out. Thus, estimates 

of proved reserves prepared in advance of appreciable production commonly have an error of about 

25 percent, and the error in estimates of incompletely explored deposits is usually much larger. 

Generally the combination of the geologist's inherent 

conservatism and the lack of information on the 

geology of concealed areas leads to estimates that 

err in being too low rather than too high. 

One eminent mining geologist reported that, having recognized these effects, he once arbitrarily 

tripled his calculations to arrive at an estimate of 

the ore remaining in a producing district; twice the 

amount of his inflated estimate, however, was found 

and mined over the next 20 years, and more was in 

prospect. To match many such stories are at least 

a few prematurely deserted mills and mine installations built on the expectation of finding ore that 

did not materialize. Both kinds of experiences emphasize the difficulty of appraising the extent of 

mineral deposits even in partly explored areas. In 

the light of such experiences one is justified in asking-as many well-informed people have-whether 

estimates of the magnitude of undiscovered deposits 

can have enough reliability to make them worthwhile. 

The fact that new districts are still being discovered for nearly every commodity and that large 

areas favorable for the occurrence of minerals of 

all kinds are covered by alluvium, volcanics, glacial 
MINERAL RESOURCE ESTIMATES AND PUBLIC POLICY 15 

drift, seawater, or other materials that conceal possible mineral-bearing rocks or structures assures us 

that undiscovered deposits are still to be found. 

Qualitatively, at least, we know something about 

the distribution of minerals with respect to other 

geologic phenomena and, if this is so, we have a 

chance of developing quantitative relations that will 

give us at least a start. 

Two principal approaches to the problem have 

been taken thus far. One is to extrapolate observations related to rate of industrial activity, such as 

annual production of the commodity; the other is to 

extrapolate observations that relate to the abundance of the mineral in the geologic environment 

in which it is found. 

The first of these methods has been utilized by 

M. K. Hubbert (1969), C. L. Moore (1966), and 

M. A. Elliott and H. R. Linden (1968) in estimating ultimate reserves of petroleum. The essential 

features of this approach are to analyze the growth 

in production, proved reserves, and discovery per 

foot of drilling over time and to project these rate 

phenomena to terminal values in order to predict 

ultimate production. Hubbert has used the logistic 

curve for his projections, and Moore has utilized the 

Gompertz curve, with results more than twice as 

high as those of Hubbert. As Hubbert has pointed 

out, these methods utilize the most reliable information collected on the petroleum industry; modern 

records on production, proved reserves, number of 

wells drilled, and similar activities are both relatively complete and accurate, at least as compared 

with quantitative knowledge about geologic features 

that affect the distribution of petroleum. 

The rate methods, however, have an inherent 

weakness in that the phenomena they analyze reflect 

human activities that are strongly influenced by 

economic, political, and other factors that bear no 

relation to the amount of oil or other material that 

lies in the ground. Moreover, they make no allowance for major breakthroughs that might transform 

extensive paramarginal or submarginal resources 

into recoverable reserves, nor do they provide a 

means of estimating the potential resources of unexplored regions. Such projections have some value 

in indicating what will happen over the short term 

if recent trends continue, but they can have only 

limited success in appraising potential resources. 

Even the goal of such projections, namely the 

prediction of ultimate production, is not a useful 

one. Not only is it impossible to predict the quantitative effects of man's future activities but the concept implies that the activities of the past are a 

part of an inexorable process with only one possible outcome. Far more useful, in my opinion, are 

estimates of the amounts of various kinds of materials that are in the ground in various environments ; such estimates establish targets for both the 

explorer and the technologist, and they give us a 

basis for choosing among alternative ways of meeting our needs for mineral supplies. 

The second principal approach taken thus far to 

the estimation of undiscovered resources involves 

the extrapolation of data on the abundance of mineral deposits from explored to unexplored ground 

on the basis of either the area or the volume of 

broadly favorable rocks. In the field of metalliferous 

deposits, Nolan (1950) pioneered in extrapolation 

on the basis of area in his study of the spatial and 

size distribution of mineral deposits in the Boulder 

Dam region and in his conclusion that a similar 

distribution should prevail in adjacent concealed 

and unexplored areas. Weeks (1958, 1965) and Pratt 

( 1950) played similar roles with respect to the estimation of petroleum resources-Weeks extrapolating on the basis of oil per unit volume of sediment 

and Pratt on the basis of oil per unit area. Many 

of the estimates of crude oil that went into the 

NPC study were made by the volumetric method, 

utilizing locally appropriate factors on the amount 

of oil expected per cubic mile of sediment. Olson and 

Overstreet (1964) have since used the area method 

to estimate the magnitude of world thorium resources as a function of the size of areas of igneous 

and metamorphic rocks as compared with India and 

the United States, and A. P. Butler (written commun., 1958) used the magnitude of sandstone uranium ore reserves exposed in outcrop as a basis for 

estimating the area in back of the outcrop that is 

similarly mineralized. 

Several years ago, Zapp (1962) and Hendricks 

(1965) introduced another approach, based on the 

amount of drilling required to explore adequately 

the ground favorable for exploration and the reserves discovered by the footage already drilleda procedure usable in combination with either the 

volumetric or areal approach. Recently J. B. Zimmerman and F. L. Long (cited in "Oil and Gas 

Journal, 1969") applied this approach to the estimation of gas resources in the Delaware-Val Verde 

basins of west Texas and southeastern New Mexico; 

and Haun, Barlow, and Hallinger (1970) used it to 

estimate potential natural gas resources in the 

Rocky Mountain region. In the field of metals, 

Lowell (1970) has estimated the number of undiscovered porphyry copper deposits in the southwestern United States, Chile and Peru, and British Columbia as a function of the proportion of the 
16 UNITED S·TATES MINERAL RESOURCES 

favorable pre-ore surface --adequately explored by 

drilling, and Armstrong (1970) has similarly estimated undiscovered uranium reserves in the Gas 

Hills area of Wyoming on the basis of the ratios 

between explored and unexplored favorable areas. 

I have suggested another variant of the areal 

method for estimating reserves of nonfuel minerals 

which is based on the fact that the tonnage of 

minable reserves of the well-explored elements in 

the United States is roughly equal to their crustal 

abundance in percent times a billion or 10 billion 

(fig. 5). Obviously this relation is influenced by the 

CJ) 

z 

~109 

... 

I[ 

0 

I 

CJ) 

z 

-:107 

ct: 

CJ) 

w 

> 

I[ 

w 

CJ) 

w 

I[ 105 

5::! 

... 

CJ) 

w 

~ 

0 

0 

10 ~~~~~~~~~~~~~~~~ULLUWW 

10-6 10-4 10-2 1 

ABUNDANCE (A) IN EARTH'S CRUST, IN PERCENT 

FIGURE 5.-Domestic reserves of elements compared to their 

abundance in the earth's crust. Tonnage of ore minable 

now is shown by a dot; tonnage of lowergrade ores whose 

exploitation depends upon future technological advances 

or higher prices is shown by a bar. 

extent of exploration, for it is only reserves of the 

long-sought and well-explored minerals that display 

the relation to abundance. But it is this feature 

that gives the method its greatest usefulness, for 

it makes it possible to estimate potential resources 

of elements, such as uranium and thorium, that 

have been prospected for only a short period. Sekine 

(1963) tested this method for Japan and found it 

applicable there, which surprised me a little, for I 

would not have thought Japan to be a large enough 

sample of the continental crust to bring out this 

relationship. 

The relation between reserves and abundance, of 

course, can at best be only an approximate one, useful mainly in order-of-magnitude estimates, for 

obviously crustal abundance of an element is only 

one of its properties that lead to its concentration. 

That it is an important factor, however, may be 

seen not only in its influence on the magnitude of 

reserves but also in other expressions of its influence 

on the concentrations of the elements. For example, 

of the 18 or so elements with crustal abundances 

greater than about 200 parts per million, all but 

fluorine and strontium are rock forming in the 

sense that some extensive rocks are composed chiefly 

of minerals of which each of these elements is a 

major constituent. Of the less abundant elements, 

only chromium, nitrogen, and boron have this distinction. Only a few other elements, such as copper, 

lead, and zinc, even form ore bodies composed 

mainly of minerals of which the valuable element 

is a major constituent, and in a general way the 

grade of minable ores decreases with decreasing 

crustal abundance. A similar gross correlation exists 

between abundance of the elements and the number 

of minerals in which they are a significant constituent. 

Members of a committee of the Geology-and the 

Conservation of Mineral Resources Board of the 

Soviet Union have described a somewhat similar 

method for the quantitative evaluation of what they 

call predicted reserves of oil and gas, based on estimates of the total amount of hydrocarbons in the 

source rock and of the fraction that has migrated 

into commercial reservoirs--estimates that would 

be much more difficult to obtain for petroleum than 

for the elements. Probably for this reason not much 

use has been made of this method, but it seems 

likely that quantitative studies of the effects of the 

natural fractionation of the elements might be of 

some value in estimating total resources in various 

size and grade categories. 

Some studies of the grade-frequency distribution 

of the elements have, in fact, been undertaken by 

geochemists in the last couple of decades, and, 

taking off from Nolan's work, several investigators 

have studied the areal and size-frequency distribution of mineral deposits in conjunction with attempts to apply the methods of operations research 

to exploration (for example, Allais, 1957; Slichter, 

1960; Griffiths, 1964; DeGeoffroy and Wu, 1970, 

and Harris and Euresty, 1969). None of these studies has been concerned with the es~imation of undiscovered reserves, but they have identified two 

features about the distribution of mineral deposits 

that may be applicable to the problem. 

One is that the size distribution of both metalliferous deposits, expressed in dollar value of production, and of oil and gas, expressed in volumetric 

units, has been found to be log normal, which means 
MINERAL RESOURCE ESTIMATES AND PUBLIC POLICY 17 

that of a large population of deposits, a few contain 

most of the ore (for example, Slichter, 1960; Kaufman, 1963). In the Boulder Dam area, for example, 

4 percent of the districts produced 80 percent of the 

total value of recorded production. The petroleum 

industry in the United States has a rule of thumb 

that 5 percent of the fields account for 50 percent 

of the reserves and 50 percent of fields, for 95 percent. And in the USSR, about 5 percent of the oil 

fields contain about 75 percent of the oil, and 10 

percent of the gas fields have 85 percent of the 

gas reserves. 

The other feature of interest is that in many deposits , the g;oade-tonnage distribution is also log 

normal, and the geochemists have found this to be 

the case also with the frequency distribution of 

minor elements. 

These patterns of size- and grade-frequency distribution will not in themselves provide information 

on the magnitude of potential resources, for they 

describe only how minerals are distributed and not 

how much is present. But if these patterns are combined with quantitative data on the incidence of 

congeneric deposits in various kinds of environments, the volume or area of favorable ground, and 

the extent to which it })as been explored, they might 

yield more useful estimates of potential resources 

than are obtainable by any of the procedures so far 

applied. Thus, estimates of total resources described 

in terms of their size- and grade-frequency distributions could be further analyzed in the light of 

economic criteria defining the size,- grade, and accessibility of deposits workable at various costs, 

and then partitioned into feasibility-of-recovery and 

degree-of-certainty categories to provide targets for 

exploration and technologic development as well as 

guidance for policy decisions. 

Essential for such estimates, of course, is better 

knowledge than is now in hand for many minerals 

on the volume of ore per unit of favorable ground 

and on the characteristics of favorable ground itself. 

For petroleum the development of such knowledge 

is already well advanced. For example, whereas most 

estimates of resources have been based on an assumed average petroleum content of about 50,000 

barrels per cubic mile of sediment, varied a little 

perhaps to reflect judgments of favorability, the 

range in various basins is from 10,000 to more than 

2,000,000 barrels per cubic mile. As shown by the 

recent analysis by Halbouty and his colleagues 

( 1970) of the factors affecting the formation of 

giant fields, the geologic criteria are developing that 

make it possible to classify sedimentary basins in 

terms of their petroleum potential. Knowledge of 

the mode of occurrence and genesis of many metalliferous minerals and of the geology of the terranes 

in which they occur is not sufficient to support comprehensive estimates prepared in this way. But for 

many kinds of deposits enough is known to utilize 

this kind of approach on a district or regional basis, 

and I hope a start can soon be made in this direction. 

NEED FOR REVIEW OF RESOURCE 

ADEQUACY 

Let me return now to the question of whether or 

not resources are adequate to maintain our present 

level of living. This is not a new question by any 

means. In 1908 it was raised as a national policy 

issue at the famous Governors' Conference on Resources, and it has been the subject of rather extensive inquiry by several national and international 

bodies since then. In spite of some of the dire predictions about the future made by various people 

in the course of these inquiries, they did not lead 

to any major change in our full-speed-ahead policy 

of economic development. Some of these inquiries, 

in fact, led to immediate investigations that revealed a greater resource potential for certain 

minerals than had been thought to exist, and the 

net effect was to alleviate rather than heighten 

concern. 

Now, however, concern about resource adequacy 

is mounting again. The overall tone of the recent 

National Academy of Sciences' report on "Resources 

and Man" was cautionary if not pessimistic about 

continued expansion in the production and use of 

mineral resources, and many scientists, including 

some eminent geologists, have expressed grave 

doubts about our ability to continue on our present 

course. The question is also being raised internationally, particularly in developing countries where 

concern is being expressed that our disproportionate 

use of minerals to support our high level of living 

may be depriving them of their own future. 

Personally, I am confident that for millennia to 

come we can continue to develop the mineral supplies needed to maintain a high level of living for 

those who now enjoy it and raise it for the impoverished people of our own country and the world. 

My reasons for thinking so are that there is a 

visible undeveloped potential of substantial proportions in each of the processes by which we create 

resources and that our experience justifies the belief that these processes have dimensions beyond 

our knowledge and even beyond our imagination at 

any given time. 

Setting aside the unimaginable, I will mention 

some examples of the believable. I am sure all geolo-
18 UNITED STATES MINERAL RESOURCES 

gists would agree that minable undiscovered deposits remain in explored as well as unexplored areas 

and that progress in our knowledge of regional 

geology and in exploration will lead to the discovery of many of them. With respect to unexplored 

areas, the mineral potential of the continental margins and ocean basins deserves particular emphasis, 

for the technology that will give us access to it is 

clearly now in sight. For many critical minerals, 

we already know of substantial paramarginal and 

submarginal resources that experience tells us 

should be brought within economic reach by technological advance. The process of substituting an 

abundant for a scarce material has also been pursued successfully, thus far not out of need but out 

of economic opportunity, and plainly has much potential as a means of enlarging usable resources. 

Extending our supplies by increasing the efficiency of recovery and use of raw materials has 

also been significant. For -example, a unit weight 

of today's steel provides 43 percent more structural 

support than it did only 10 years ago, reducing proportionately the amount required for a given purpose. Similarly, we make as much electric power 

from 1 ton of coal now as we were able to make 

from 7 tons around the turn of the century. Our 

rising awareness of pollution and its effects surely 

will force us to pay even more attention to increasing the efficiency of mineral recovery and use as a 

means of reducing the release of contaminants to 

the environment. For similar reasons, we are likely 

to pursue more diligently processes of recovery, reuse, and recycling of mineral materials than we 

have in the past. 

Most important to secure our future is an abundant and cheap supply of energy, for if that is 

available we can obtain materials from low-quality 

sources, perhaps even country rocks, as Harrison 

Brown (1954, p. 174-175) has suggested. Again. I 

am personally optimistic on this matter, with respect to the fossil fuels and particularly to the 

nuclear fuels. Not only does the breeder reactor 

appear to be near enough to practical reality to 

justify the belief that it will permit the use of 

extremely low-grade sources of uranium and thorium that will carry us far into the future, but during the last couple of years there have been exciting 

new developments in the prospects for commercial 

energy from fusion. Gothermal energy has a large 

unexploited potential, and new concepts are also 

being developed to permit the commercial use of 

solar energy. 

But many others do not share these views, and it 

seems likely that soon there will be a demand for a 

confrontation with the full-speed-ahead philosophy 

that will have to be answered by a deep review of 

resource adequacy. I myself think that such a review is necessary, simply because the stakes have 

become so high. Our own population, to say nothing 

of the world's, is already too large to exist without 

industrialized, high energy- and mineral-consuming 

agriculture, transportation, and manufacturing. If 

our supply of critical materials is enough to meet 

our needs for only a few decades, a mere tapering 

off in the rate of increase of their use, or even a 

modest cutback, would stretch out these supplies 

for only a trivial period. If resource adequacy cannot be assured into the far-distant future, a major 

reorientation of our philosophy, goals, and way of 

life will be necessary. And if we do need to revert 

to a low resource-consuming economy, we will have 

to begin the process as quickly as possible in order 

to avoid chaos and catastrophe. 

Comprehensive resource estimates will be essential for this critical examination of resource adequacy, and they will have to be made by techniques 

of accepted reliability. The techniques I have described for making such estimates have thus far 

been applied to only a few minerals, and none of 

them have been developed to the point of general 

acceptance. Better methods need to be devised and 

applied more widely, and I hope that others can be 

enlisted in the effort necessary to do both. 

SELECTED BIBLIOGRAPHY 

Allais, M., 1957, Methods of appraising economic prospects 

of mining exploration over large territories: Management Sci., v. 2, p. 285-347. 

Armstrong, F. C., 1970, Geologic factors controlling uranium 

resources in the Gas Hills District, Wyoming, in Wyoming Geol. Assoc. Guidebook 22d Ann. Field Conf.: p. 

31-44. 

Blonde!, F., and Lasky, S. F., 1956, Mineral reserves and 

mineral resources: Econ. Geology, v. 60, p. 686-697. 

Brown, Harrison, 1954, The challenge of Man's 'future: 

Viking Press, 290 p. 

Bush, A. L., and Stager, H. K., 1956, Accuracy of ore-reserve estimates for uranium-vanadium deposits on the 

Colorado Plateau: U.S. Geol. Survey Bull. 1030-D, p. 

137. 

Buyalov, N. I., Erofeev, N. S., Kalinen, N. A.1 Kleschev, 

A. 1., Kudryashova, N. M., L'vov, M. S., Simakov, S. N., 

and Vasil'ev, V. G., 1964, Quantitative evaluation of 

predicted reserves of oil and gas: New York, Consultants 

Bur.; translation. 

DeGeoffroy, J., and Wu, S. M., 1970, A statistical study of 

ore occurrences in the greenstone belts of the Canadian 

Shield: Econ. Geology, v. 65, no. 4, p. 496-504. 

Elliott, M. A., and Linden, H. R., 1968, A new analysis of 

U.S. natural gas supplies: Jour. Petroleum Technology, 

v. 20, p. 135-141. 
MINERAL RESOURCE ESTIMATES AND PUBLIC POLICY 19 

Griffiths, J. C., 1962, Frequency distributions of some natural 

resource materials, in Tech. Conf. on Petroleum Production, 23d: Mining Industry Expt. Sta. Circ. 63, p. 174-

198. 

--·- 1964, Exploration for natural resources: Operations 

Research,v. 14,p. 189-209. 

Halbouty, M. T ., King, R. E., Klemme, H. D., Dott, R. H., 

Sr., and Meyerhoff, A. A., 1970, Factors affecting formation of giant oil and gas fields, and basin classification, 

pt. 2 of World's giant oil and gas fields, geologic factors 

affecting their formation, and basin classification, in 

Geology of giant petroleum fields-a symposium: Am. 

Assoc. Petroleum Geologists Mem. 14, p. 528-555. 

Halbouty, M. T., Meyerhoff, A. A., King, R. E., Dott, R. H., 

Sr., Klemme, H. D., and Shabad, Theodore, 1970, Giant 

oil and gas fields, pt. 1 of World's giant oil and gas 

fields, geologic factors affecting their formation, and 

basin classification, in Geology of giant petroleum fields 

-a symposium: Am. Assoc. Petroleum Geologists Mem. 

14, p. 502-528. 

Harris, D. P., and Euresty, D., 1969, A preliminary model 

for the economic appraisal of regional resources and exploration based upon geostatistical analyses and computer simulation: Colorado School Mines Quart., v. 

64, p. 71-98. 

Haun, J. D., Barlow, J. A., Jr., and Ballinger, D. E., 1970, 

Natural gas resources, Rocky Mountain region: Am. 

Assoc. Petroleum Geologists Bull., v. 54, p. 1706-1708. 

Hendricks, T. A., 1965, Resources of oil, gas, and naturalgas liquids in the United States and the world: U.S. 

Geol. Survey Circ. 522, 20 p. 

Hendricks, T. A., and Schweinfurth, S. P., 1969 [Unpub. 

memo., Sept. 14, 1966], cited in United States petroleum 

through 1980: Washington, D.C., U.S. Dept. Interior, 

Office of Oil and Gas, 92 p. 

Hubbert, M. K., 1969, Energy resources, chapter 8 in Resources and man, a study and recommendations by the 

Committee on Resources and Man of the Division of 

Earth Sciences, National Academy of Science-National 

Research Council: San Francisco, Calif., W. H., Freeman and Co., p. 157-242. 

Inglis, D. R., 1971, Nuclear energy and the Malthusian 

dilemma: Atomic Scientists Bull., v. 27, no. 2, p. 14-18. 

Kaufman, G. M., 1963, Statistical decision and related techniques in oil and gas exploration: Englewood, N. J., 

Prentice-Hall, 307 p. 

Lasky, S. G., 1950, Mineral-resource appraisal by the U.S. 

Geological Survey: Colorado School Mines Quart., v. 

45, no. 1A, p. 1-27. 

--- 1950, How tonnage and grade relations help predict 

ore reserves: Eng. and Mining Jour., v. 151, no. 4, p. 

81-85. 

Lowell, J. D., 1970, Copper resources in 1970: Mining Eng., 

v. 22, p. 67-73. 

McKelvey, V. E., 1960, Relations of reserves of the elements 

to their crustal abundance: Am. Jour. Sci., v. 258-A 

(Bradley volume), p. 234-241. 

--- 1968, Contradictions in energy resource estimates, in 

Energy-Proc. 7th Bienn. Gas Dynamics Symposium, 

Gas Dynamics Lab., Northwestern Univ.: Evanston, Ill., 

Northwestern Univ. Press, p. 18-26. 

Moore, C. L., 1966, Projections of U.S. petroleum supply to 

1980: Washington, D.C., U.S. Dept. Interior, Office of 

Oil and Gas, 42 p. 

National Academy of Scienees-N ational Research Council, 

1969, Resources and man: San Francisco, Calif., W. H. 

Freeman and Co., 259 p. 

National Petroleum Council, 1970, Future petroleum provinces of the United States-a summary: Washington, 

D.C., Natl. Petroleum Council, 138 p. 

Nolan, T. B., 1950, The search for new mining districts: 

Econ. Geology, v. 45, p. 601-608. 

Oil and Gas Journal, 1969, Vast Delaware-Val Verde reserve seen: Oil and Gas Jour., v. 67, no. 16, p. 44. 

Olson, J. C., and Overstreet, W. C., 1964, Geologic distribution and resources of thorium: U.S. Geol. Survey Bull. 

1204, 61 p. 

Orwell, George, 1937, The road to Wigan Pier: London, 

Victor Gollancz, Ltd., 264 p.; reprinted in 1958 by Harcourt, Brace and World, New York. 

Potential Gas Committee, 1969, Guidelines for the estimation of potential supply of natural gas in the United 

States, in Potential supply of natural gas in the United 

States (as of December 31, 1968): Golden, Colo., Colorado School Mines Found., Inc., p. 21-30. 

Pratt, W. E., 1950, The earth's petroleum resources, in Fanning, L., M., ed., Our oil resources [2d ed.]: New York, 

McGraw-Hill, p. 137-153. 

Rodionov, D. A., 1965, Distribution functions of the element 

and mineral contents of igneous rocks-A special research report: New York, Consultants Bur., p. 28-29; 

translation. 

Sekine, Y ., 1963, On the concept of concentration of oreforming elements and the relationship of their frequency in the earth's crust: lnternat. Geology Rev., v. 

5, p. 505-515. 

Slichter, L. B., 1960, The need of a new philosophy of prospecting: Mining Eng., v. 12, p. 570-576. 

Slichter, L. B., and others, 1962, Statistics as a guide to 

prospecting, in Math and computer applications in mining and exploration-a symposium: Tucson, Arizona 

Univ. Coli. Mines, Proc., p. F-1-27. 

U.S. Office of Science and Technology, 1965, Energy R and 

D and national progress: Washington, D.C., U.S. Govt. 

Printing Office. 

Weeks, L. G., 1950, Concerning estimates of potential oil 

reserves: Am. Assoc. Petroleum Geologists Bull., v. 34, 

p. 1947-1953. 

--- 1958, Fuel reserves of the future: Am. Assoc. Petroleum Geologists Bull., v. 42, p. 431-438. 

--- 1965, World offshore petroleum resources: Am. Assoc. 

Petroleum Geologists Bull., v. 49, p. 1680-1693. 

Zapp, A. D., 1962, Future petroleum producing capacity of 

the United States: U.S. Geol. Survey Bull. 1142-H, 36 p. 

UNITED STATES MINERAL RESOURCES 

CRUSTAL ABUNDANCE OF ELEMENTS, AND 

MINERAL RESERVES AND RESOURCES 

By RALPH L. ERICKSON 

CONTENTS 

Abstract of conclusions -------------------------- Abundance-resource-reserve relationships _________ _ 

References cited ----------------------------------

FIGURE 

6. Graph showing domestic reserves of elements 

compared to their abundance in the earth's 

crust --------------------------------------

TABLES 

3. Abundance, mass, reserves, and resources of some 

metals in the earth's crust and in the United 

States crust ------------------------------- 4. Ratio of potential resources to known reserves __ 

Page 

21 

21 

25 

Page 

25 

Page 

22 

24 

source relation is intermediate between crustal abundance 

and reserve abundance are those that have not been vital to 

our economy in the past, whose prices are subject to great 

fluctuation, or whose past source has been chiefly as a byproduct. Thus, the scheme of predicting resource potentials 

in relation to crustal abundance seems valid-if we search 

for an element hard enough, we find it in about the quantities we might expect. 

If we accept the abundance-reserve relationship, it follows 

that R=2.45 X 10' is a minimum total resource estimate because the relationship is based upon currently recoverable 

resources and does not include resources whose feasibility 

of economic recovery is not established. Substantial variations of total resource estimates from this formula probably are caused by geologic factors and the inherent geochemical nature of the element. However, recent discoveries 

of several new types of mineral deposits indicate that we 

need to critically examine our criteria for where and how to 

look for mineral deposits. Certainly, significant mineral deposists remain undiscovered because exploration efforts are 

commonly confined to the classic environments of ore deposition. 

ABUNDANCE-RESOURCE-RESERVE 

RELATIONSHIPS 

The table of abundance, reserves, and potential 

ABSTRACT OF CONCLUSIONS resources of some metals in the earth's crust and 

Crustal abundance data and the reserve-abundance United States crust presented in this chapter pro-

(R=A X 10&-10

) relationship of McKelvey are combined to vi des a broad general framework in which to excalculate the total amounts of several metals in the earth's 

crust, in various segments of the crust, in United States amine the relation between abundance, reserves, and 

crust, in United States crust to a 1-kilometer depth, and in resources. The abundance data used for mass and 

the potential currently recoverable resources. Marginal re- resource calculations are based upon the work of 

sources are not reported. The potential recoverable resource Lee and Yao (1970). These authors have taken into 

for most elements should approach R=2.45A X 106

, where A account oceanic crust, variation with depth of conis abundance expressed in grams per metric ton or parts per 

million and R is resource expressed in metric tons. Those tinental crust, and variation between shield areas, 

metals whose known reserves most closely approach the folded belts, and volcanic arcs. They also provide 

calculated potential recoverable resource are the metals that reasonable figures for thickness and mass of the 

have been most diligently sought for the longest time (lead, various subdivisions of earth's crust. 

copper, ·zinc, silver, gold, molybdenum). Those metals whose McKelvey (1960) reviewed the principal apknown reserves are very much less than the calculated potential recoverable resource (nickel, tin) are the metals proaches to the problem of estimating ore reserves 

usually found in geologic environments not common in the and suggested a new method based on the fact that 

United States. Those metals whose reserve-potential re- the tonnage of minable reserves of the well-explored 

U.S. GEOL. SURVEY PROF. PAPER 820 

21 
22 UNITED STATES MINERAL RESOURGE.S 

elements in the United States at that time was 

roughly equal to their crustal abundance times 1 

billion or times 10 billion. 

I realize that abundance figures for some of the 

elements are still unproved, that reserve figures are 

always questionable, and that the assumption of 

log-normal distribution of trace elements in the 

earth's crust is not universally accepted. However, 

even rather large changes in abundance or reserve 

estimates will not affect the concepts discussed here. 

Table 3 combines the abundance data of Lee and 

Yao and the reserve-abundance relationship of McKelvey with my own attempt at calculating the total 

amounts of several metals in the earth's crust, various segments of the crust, United States crust, 

United States crust to a 1-kilometer depth, and potential resources of recoverable ores. 

Study of the table permits speculation about 

the position of the United States and the world with 

respect to mineral resources. For example, one could 

consider the total amount of an element present in 

the United States crust to a 1-kilometer depth as the 

ultimate United States resource of that element and 

portion it out by mineralogy or rock type. If an element tends to be lithophile, and thus occurs chiefly 

in silicate minerals, then a high percentage is probably forever unavailable as a resource. If an element 

is sulfophile, probably a greater amount is available 

as a resource. Or one might estimate, by working 

portion it out by mineralogy or rock type. If an element present at various grade levels in the United 

States crust to a 1-kilometer depth. 

Table 3 shows that the most commonly sought 

metals, except lead, are more abundant in oceanic 

crust than in continental crust. This permits the 

speculation that perhaps we should make resource 

target maps showing the areas of the world where 

segments of oceanic crust are within reasonable exploration depths. 

The part of the table showing resource potential 

TABLE 3.-Abundance, mass, reserves, and resources of som-e 

[Abundance in grams/metric ton (g/mt); mass and reserves in metric tons (mt). 

Element 

Antimony --------------- Beryllium ---------------

Bismuth ----------------

Cob&t ----------------- Copper ----------------- Gold -------------------

Lead ------------------- Lithium ---------------- Mercury ---------------- Molybdenum ------------

Nickel ----------------- Niobium ---------------- Platinum --------------- Selenium ---------------

Silver ------------------ Tantalum -------------- Tellurium -------------- Thorium --------------

Tin -------------------- Tungsten ---------------

Gold- schmidt 6 

(g/mt) 

1 

6 

.2 40 

70 

.001 16 

65 .5 

2.3 100 

20 

.005 

.09 

.02 

2.1 

.0018 

11.5 

40 

1 

4 

Total earth's crust 

Vinogradov 7 

(g/mt) 

0.5 

3.8 

.009 18 

47 .0043 16 

32 .083 

1.1 

58 

21 

.05 

.07 

2.5 

.001 

Lee and Yao 8 

(g/mt) 

0 62 

1.3 

.0043 25. 

63 .0035 

12 

21 .089 

1.3 

89 

19 .046 

.075 

.075 

1.6 

.00055 

5.8 

1.7 

1.1 

MtX10 12 

14.9 

31.2 .1 600 

1,510 .084 290 

500 2.1 

31.2 2.130 

460 1.1 

1.8 

1.8 

38.4 .013 

Oceanic crust 

8 G/mt 

0.91 

.83 

.0066 37 

85 .0035 10 

20 .11 

1.5 140 

18 .075 

.1 

.091 

.43 

.00088 

MtX1()112 

8.1 

7.4 

.059 330 

760 .032 90 

180 .9 14.6 1,200 

160 .67 

.89 

.82 

8.8 

.0078 37 

16.8 

8.3 

Continental crust 

8 G/mt 

0.45 

1.5 

.0029 18 

50 .0035 13 

22 .08 

1.1 

61 

20 

.028 

.059 

.065 

2.3 

.00036 

6.8 

1.6 

1.2 

MtX10 12 

6.8 

23.8 .041 270 

760 

.052 200 

320 1.2 

16.6 

920 

300 .43 

.91 

.98 

Continental 

crust segments 

Shield areas 

8 G/mt 

0.46 

1.5 

.003 19 

52 .0034 13 

21 .078 

1.1 

64 

20 

.031 

.054 

.067 

2.3 

.00038 

6.6 

1.5 

1.2 

4.9 

16.7 .029 190 

550 .035 

.140 220 .81 11.6 .680 210 .30 

.64 

.70 24.3 .0036 140 68 40.8 

26.4 

40.8 2,250 Uranium ---------------

Zinc -------------------

--------------------------------------------------------------------------~-------

16.3 

12.7 

22.6 80 870 

1.7 

94 

13 

2.5 

1.3 

2.5 

83 

4.2 

1.9 

.94 

1 

120 7.8 1.·030 2.2 81 

34.7 .005 

.100 24 

18.1 

33 

1,220 2.1 

83 

G/mt 

Aluminum -------------- 81,300 Barium ----------------- 430 Chromium -------------- 200 Fluorine ---------------- 800 

Iron ------------------- 50,000 

Manganese -------------- 1,000 

Phosphorus ------------- 1,200 Titanium --------------- 4,400 Vanadium -------------- 150 

G/mt 

80;500 

650 

83 

660 46,500 

1,100 

930 

4,500 91 

G/mt 

83,000 390 

110 

450 58,000 

1,300 

1,200 

6,400 

140 

MtX10 15 

1,990 9.4 

2.6 

10.8 1,392 31.2 

28.8 

153.6 3.36 

G/mt 

84,000 370 

160 

420 75,000 

1,800 

1,400 

8,100 

170 

1 U.S. Bureau Mines (1970); 1 short ton =0.91 mt. 2 Recoverable resource potential = 2.45 A X 10 6 (abundance A expressed in g /mt). 

MtX10 15 

747 3.3 

1.4 

3.74 667 

16 

12.5 

72.1 

1.51 

G/mt 

83,000 400 

77 

470 48,000 

1,000 

1,200 

5,300 

120 

MtX10ts 

1,242 6.1 

1.2 

7.1 725 

15.2 

16.3 

81.5 

1.85 

G/mt 

84,000 

400 

81 

470 49,000 

1,100 

1,200 

5,500 

120 

MtX10 15 

869 

4.3 

.84 

5 508 

10.6 

11.4 

57.1 

1.3 

3 U.S. Bureau Mines ( 1970); 1 short ton =0.91 mt; does not include United States reserve. 4 Recoverable resource potential =2.45 A X17.3X10 6 (abundance A expressed in gfmt; land area of world is 17.3 times United States land area). 5 U.S. Bureau Mines ( 1970); data on world basis. 6 Goldschmidt (1954, p. 74-75). 7 Vinogradov ( 1962, p. 649-650). 8 Lee and Yao ( 1970, p. 778-786). All c&culations are based on this work. 9 Very hiah. 
CRUSTAL ABUNDANCE OF ELEMENTS, AND MINERAL RESERVES AND RESOURCES 23 

and ratio of potential to known reserves is particularly interesting and informative. The resource potential is calculated from the formula R=2.45A X 106 

as explained below. The rationale for this calculation assumes that (1) McKelvey's relation of reserves to crustal abundance is valid, (2) U.S. 

Bureau of Mines reserve figures are of the correct 

order of magnitude, and (3) trace elements are 

log-normally distributed in the earth's crust. R is 

expressed in metric tons and A is expressed in grams 

per metric ton or parts per million. In the McKelvey formula, R=AX109 - 10, R is expressed in short 

tons and A in percent. 

Lead is used as the base of calculation because known reserves of minable lead ore already 

exceed R=A X 1010• Continental crustal abundance 

of lead is 13 ppm or 0.0013 percent. Substituting 

in McKelvey's formula, R=AX1010, we get: 

R=0.0013X1010=13X106 metric tons. Known United 

States reserves of lead are 31.8X106 metric tons or 

metals in the earth's c.rust and in the United States crust 

2.45 times greated than APbX1010• This factor (2.45) 

is greater for lead than for any other commonly 

sought metal except molybdenum, which has about 

the same factor. If we use assumptions 1 and 3 

above, then currently recoverable resources of all 

trace elements should approach 2.45AX106 • Obviously the 2.45 factor will increase as lead reserves 

of any other metal increase above 2.45AX106 • Another very simple method of calculating potential 

recoverable resource assumes that the resource 

should approach 0.01 percent of the total amount 

of each element available in the United States crust 

to a 1-kilometer depth, as shown in table 3. It is 

important to remember that the McKelvey formula 

relates crustal abundance to currently recoverable 

reserves ; therefore, my use of his formula restricts 

the calculated resource potential (table 3) to identified and undiscovered resources recoverable under 

present economic conditions. Paramarginal and submarginal resources as defined by McKelvey (1972) 

Calculations= mass (metric tons) X abundance (decimalized) =total content of element] 

Continental cru:st segments-Con. United States World 

United 

States Recoverable Ratio Recoverable Ratio 

Folded belts United States crust crust to Reserve 1 resource of Reserve a resource of 

1-km potential 2 potential potential ' potential Grade 5 

depth to to reserve reserve 

8G/mt MtX10 12 8G/mt M1lX10 12 MtX10 9 MtX10 6 MtX10 8 MtX10 6 MtX10 8 

0.43 1.9 0.45 0.41 11.2 0.10 1.1 11 3.6 19 5 Unknown. 

1.6 7.1 1.5 1.4 38 .073 3.7 50 .016 64 4,000 .0025 .012 .0029 .0025 .07 .013 .007 .5 .081 .12 1.5 Ui 80 18 16 440 .025 44 1,760 2.14 763 360 

46' 210 50 45 1,230 77.8 122 1.6 200 2,120 10 0.86 percent. .0038 .017 .0035 .003 .085 .002 .0086 4.1 .011 .15 14 

13 60 13 12 330 31.8 31.8 1 .54 550 1,000 3 percent. 23 100 22 20 550 4.7 54 12 .78 933 1,200 .086 .39 .08 .072 2.0 .013-.028 .20 15-6.8 .11 3.4 30 

1 6 1.1 1 27 2.83 2.7 1 2 46.6 23 Unknown. 

53 .240 61 55 1,500 .18 149 830 68 2,590 38 1.5 percent. 19 90 20 20 550 Unknown 49 Unknown Unknown 848 Unknown 

.022 .u .028 .026 .71 .00012 .07 560 .009 1.2 133 

.071 .27 .059 .055 1.5 .025 .14 6 .695 2.5 36 

.062 .28 .065 .059 1.6 .05 .16 3.2 .16 2.75 18 

2.4 10.4 23 2.1 57.5 .0015 5.6 4,000 .274 97 354 

.00031 .0016 .00036 .00031 .0085 .0077 .0009 .11 .054 .015 .3 

7.1 32 6.8 s .160 .54 16.7 31 1 288 288 Unknown. 

1.7 7.7 1.6 1.4 38 3.9 9? 5.8 68 12 0.6 percent. 1.2 5.4 1.2 1.1 30 .079 2.!) 37 1.2 51 42 

2.3 10.4 2.2 2 55 .27 5.4 20 .83 93 112 77 350 81 73 2,000 31.6 198 6.3 81 3,400 42 4 percent. 

Ratio of Ratio of 

Gjmt MtX10 15 G/mt MtX10 15 MtX10 12 MtX10 6 MtX10 6 potential MtX10 6 MtX 10 9 potential to to reserve reserve 

82,000 373 83,000 74.5 2,000 8.1 203,000 24,000 1,160 3,519 3,000 390 1.8 400 .37 10 30.6 980 32 76.4 17 223 

68 .36 77 .070 1.92 1.8 189 387 696 3.26 47 

480 2.1 470 4.30 11.8 4.9 1,151 235 35 20 600 

4,000 217 48,000 43.5 1,200 1,800 118,000 65 87,000 2,035 23 930 4.6 1,000 .9 24.9 1 2,450 2,450 630 42 67 

1,100 4.9 1,200 .98 26.8 931 2,940 3 15,000 51 34 

5,000 24.4 5,300 4.9 1.30 25 13,000 516 117 225 2,000 110 .55 120 .11 3 .115 294 2,560 10 5.1 500 

Calculation of mass of crustal segments 

Total earth's crust ----------------------24X10 18 mt. Oceanic crust ---------------------------8.9X10 18 mt (87 percent of total crust). Continental crust _______________________ 15.1X10 18 mt (63 percent of total crust). 

Shield areas ---------------------------10.6X10 18 mt (30 percent of continental crust or 43.8 percent of total crust). Folded belts ____________________________ 4.54X10 18 mt (30 percent of continental crust or 19.1 percent of total crust). 

United States crust _____________________ 0.90X10 18 mt (based upon United States as 1/17 of land area of world's continental crust). 

United States crust to 1-km depth ________ 24.6X10 15 mt (based upon average thickness continental crust =36.5 km; therefore 1 km is 2.74 per- cent of United States crust). 
24 UNITED STATES MINERAL RESOURCES 

are not included. (See "Introduction" to this voluume.) 

Some of the metals are listed in table 4 in order 

TABLE 4.-Ratio of potential reBourceB to known reBerveB 

United States 

Ph ------ 1 

Mo ----- 1 

Cu ------ 1.6 

Ag ----- 3.2 

Au ----- 4.1 

Zn ------ 6.3 

Sb ------ 11 

Hg ------ 15 

u ------- 20 

Th ------ 31 

w ------ 37 Ni ______ 830 

Sn ------Very high 

WO'I'ld 

Sb --------- 5 

Cu --------- 10 

Pb --------- 10 

Sn --------- 12 

Au --------- 14 

Ag --------- 18 

Mo --------- 23 

Hg --------- 30 

Ni ---------- 38 

Zn --------- 42 

w u ----------

__________ 112 42 

Th _________ 288 

of increasing ratio of potential resources to known 

reserves, as shown in table 3. The ratios indicate, 

for example, that we can anticipate discovery of 

about 4 times as much minable gold ore as our present known reserves. Because lead was chosen as the 

base for calculating potential resources, its ratio is 

necessarily one. 

It is interesting that for the United States those 

metals whose known reserves most closely approach 

the potential recoverable resources are the metals 

most diligently sought for the longest time (lead, 

molybdenum, copper, silver, gold, zinc). Although 

uranium is a relatively recently sought metal, the 

intensity of the search for it has moved its ratio 

close to the ratio of the traditionally sought metals. 

Thus, the scheme of predicting resource potentials 

in relation to crustal abundance seems valid-if we 

search for an element hard enough, we find it in 

about the quantities we might expect. The largest 

ratios, for nickel and tin, are caused by lack of 

known favorable host rocks in the United States. 

However, the large ratios suggest that we should 

take another look for these metals in the United 

States, but perhaps in different geologic environments from those in which we have traditionally 

looked. Commonly, the higher the ratio, the greater 

is the tendency for the element to form oxide or 

silicate minerals rather than the commonly sought 

sulfide ores. 

Those metals with intermediate ratios are those 

that have not been vital to our economy in the past, 

or whose prices are subject to great fluctuation, or 

whose past source has been chiefly as a byproduct. 

But certainly these elements must also be present 

in the crust in crudely predictable amounts. 

As we might expect, the ratios for world resources generally are much higher than United 

States ratios because many land areas of the world 

have not been intensely explored. Those few metals 

that do have lower potential ratios than the United 

States (antimony, tin, and nickel) are contained in 

old, well-known districts-the antimony of mainland China, the tin of Bolivia, Cornwall, and Malaysia, and the nickel of shield areas such as Canada 

and Australia. 

Data on a few of the elements listed in table 3 

deserve further comment. The tell uri urn ratio of 

potential resource to known reserve (0.11) indicates 

that we have 10 times more known reserves than 

predictable by R==2.45 AX106 • Perhaps the crustal 

abundance figure is too low, but there is another, 

more important factor: most tellurium production 

comes as a byproduct of copper refining, and the 

known reserve figure for tellurium is equated with 

copper production and reserve ( 0.4lb' of tellurium 

per ton of copper produced). Therefore, copper.· ore 

that averages 0.86 percent Cu contains only 0.00017 

percent tellurium. Thus we are in the unique situation of equating our known tellurium reserves to 

raw materials that contain only 1.7 ppm tellurium! 

Obviously rock containing 1. 7 ppm tellurium, exclusive of other metals, could not be considered ore 

grade, and the relationship R==2.45 A X 106 does not 

apply. 

The same explanation holds for the low selenium 

(6) and bismuth (0.5) ratios. Selenium reserves 

also are equated with copper production (1 lb selenium per ton copper produced or about 4.3 ppm 

selenium in 0.86 percent copper ore). Bismuth reserves are equated to lead reserves (about 7 lbs bismuth per ton of western United States lead or 100 

ppm bismuth in 3-percent lead ore). 

Ratios that are extremely high can usually be explained by what we already know about the geochemistry and United States distribution of that 

element. Aluminum, for example, shows a very high 

ratio of potential resource to known reserve. Aluminum occurs chiefly in silicates, whereas currently 

minable aluminum ore (bauxite) is a weathering 

product and the vertical extent to which weathering 

can occur is limited. Thus much of the crust is removed from a possible resource category for aluminum until we can economically recover aluminum 

from feldspar or clay. 

The high manganese ratio (2,450) results from a 

reserve figure based upon a 35-percent manganese 

concentrate produced by normal concentration 

methods. The word "normal" is the clue to the high 

ratio. The U.S. Bureau of Mines estimates that 

manganese deposits in the United States contain 

68 million tons of manganese, but they are low grade 

and must be considered resources. However, if the 
CRUSTAL ABUNDANCE OF ELEMENTS, AND MINERAL RESERVES AND RESOURCES 25 

68 million tons were called reserve, then the ratio 

would be reduced to about 36. 

Using the information in table 3, I have modified 

McKelvey's original diagram relating domestic reserves to crustal abundance (fig. 6) . Domestic re-

(/) 

z 

~ 109 

1-

a:: 

~ 101 

(/) 

z 

~ 101 

(/) 

w 

> 106 

a: 

w 

(/) 

w 

a: 105 

0 

1-

(/) 

~ 104 

0 

0 

10 ~~~~uw~~~-U~~~~-WUillill-LUmill-W~ 

10-7 10-6 10-s 10-4 10-3 10-2 10-1 1 10 

ABUNDANCE (A) IN CONTINENTAL CRUST, IN PERCENT 

FIGURE 6.-Domestic reserves of elements compared to their 

abundance in the, earth's crust. Modified from McKelvey 

(1960). 

serves of some metals have increased and new 

element-abundance numbers for continental crust 

are available since McKelvey first published this 

diagram in 1960. Because actual reserves of lead 

and molybdenum now equal 2.7 AX1010, potential 

recoverable resources of the other elements also 

should approach this line. Note that the factor is 2.7 

on this diagram and 2.45 on the table of abundance, 

mass, and reserves. This is because reserve tonnages 

on this figure are calculated in short tons to conform with McKelvey's original work. The 2.45 factor applies for the metric system. Of course, this 

line will continue to shift as additional reserves are 

discovered, but it does give us some broad measure 

of what we might expect. 

It is a simple fact, but often overlooked, that we 

cannot expect to find reserves or resources of the 

least abundant elements in the same magnitude as 

the more abundant elements. Thus, in a crude way, 

because copper is about 20,000 times more abundant 

than gold in the earth's crust, we can expect that 

recoverable resources of copper should be about 

20,000 times greater than recoverable resources of 

gold. This simple relationship, of course, is modified 

by the inherent geochemical nature of each element. 

If we accept the abundance-reserve relationship, 

it follows that R==2.45Xl06 is a minimum total resource estimate because the relationship is based 

upon currently recoverable resources and does not 

include resources whose feasibility of economic recovery is not established. Total resource estimates 

of an element that vary substantially from this 

formula probably are caused by geologic factors 

and the inherent geochemical nature of the element. 

However, the discovery of Carlin-type gold deposits, Spor Mountain beryllium deposits, and Precambrian Belt Supergroup copper deposits, all in the 

last decade, indicate that we need to critically examine our criteria for where and how to look for 

mineral deposits. Certainly, significant mineral deposits remain undiscovered because exploration 

efforts are commonly confined to the classic environments of ore deposition. 

As analytical techniques improve, as our understanding of geochemical processes improves, and as 

exploration methods improve so that we can confidently explore and examine the crust to a reasonable depth, the reserve-resource-abundance relation should become more closely defined. Perhaps 

then we can determine whether ore deposits are 

chiefly formed by different ore-forming processes 

in a uniform crust or because of differences in 

original composition of crustal segments. 

REFERENCES CITED 

Goldschmidt, V. M., 1964, Geochemistry: Oxford, Clarendon 

Press, 730 p. \ 

Lee, Tan, and Yao, Chi-lung, 1970, Abundance of chemical 

elements in the earth's crust and its major tectonic 

units: lnternat. Geology Rev., v. 12, no. 7, p. 778-786. 

McKelvey, V. E., 1960, Relation of reserves of the elements 

to their crustal abundance: Am. Jour. Sci., v. 258-A, 

(Bradley volume) p. 234-241. 

-- 1972, Mineral resource estimates and public policy: 

Am. Scientist, v. 60, no. 1, p. 32-40; reprinted in this 

volume. 

U.S. Bureau Mines, 1970, Mineral facts and problems, 1970: 

U.S. Bur. Mines Bull. 650, 1291 p. 

Vinogradov, A. P., 1962, Average contents of chemical elements in the principal types of igneous rocks of the 

earth's crust: Geochemistry, no. 7, p. 641-664. 

UNITED STATES MINERAL RESOURCES 

ABRASIVES 

By RoBERT E. THADEN 

CONTENTS 

Page 

Abstract of conclusions -------------------------- 27 

Introduction ------------------------------------- 27 

The natural abrasives ---------------------------- 28 

Diamond ------------------------------------ 29 

Corundum ----------------------------------- 29 

Emery -------------------------------------- 30 

Garnet -------------------------------------- 31 

Silica sand ---------------------------------- 32 

Tripoli -------------------------------------- 32 

The artificial abrasives --------------------------- 32 

Potential resources ------------------------------- 33 

Selected references ------------------------------- 33 

TABLE 

Page 

5. Resources of abrasive materials in the United 

States ------------------------------------- 33 

ABSTRACT OF CONCLUSIONS 

Abrasives are substances used to clean, dress, or comminute 

other substances. They are of critical importance to the 

economy of industrial nations. The principal natural abrasives are diamond, corundum, emery, garnet, tripoli, and 

silica sand, and the United States is fortunate to have identified resources of most of them which will serve as supply 

at current rates of consumption for from 50 years to more 

than 100,000 years. The United States has no commercial 

deposits of diamond, but manufactured diamond already satisfies more than one-half of the domestic requirements. Other 

artificial abrasives, principally aluminum oxide, silicon carbide, and steel shot and grit, manufactured from abundant 

raw materials, have supplanted natural abrasives in about 

90 percent of all critical applications and, together with 

"artificial" diamond, encroach on the few remaining uses for 

which the natural abrasives in shortest supply once were 

thought uniquely qualified. 

INTRODUCTION 

Abrasives are those substances that are used to 

clean or dress the surfaces of other materials, or to 

comminute other materials by abrasion and percussion. Because of their great differences in hardness, 

abrasives have many thousands of applications. 

The deliberate removal of solid material by abrasive action consumes the bulk of all hard abrasives. 

This includes such diverse operations as grinding 

valve seats with abrasive-charged paste, sharpening tool blades with appropriately shaped abrasive 

stone blocks, grinding and polishing bearing surfaces on machine components with bonded granular abrasive wheels, sandblasting inscriptions on 

tombstones, and slabbing and drilling rock with 

abrasive-charged discs, wires, and drill bits. 

The cleaning function employs abrasives softer 

than the material being cleaned to remove a surface film of foreign material with minimal damage, 

as in brushing the teeth with dentifrice, or in scouring porcelain bathroom fixtures or automobile paint 

with abrasive soap. 

Comminution can be effected by heavy abrasive 

wheels or by abrasive pebbles tumbling or cascading in a mill. By the latter process, ores, for example, are reduced to the size required for their 

further metallurgical treatment, small parts are 

deburred, wheat is ground to flour, and talc and 

paint pigments are ground to the size appropriate 

for their ultimate use. 

Strictly speaking, neither sandblasting nor the 

crushing of ore by cascading pebbles of shot are 

abrasive operations, inasmuch as the action is one 

of percussion. Nevertheless, these processes are included here not only because both the "abrasive" 

materials and the effects are the same as though 

the operations had been accomplished by abrasive 

action, but because historically the abrasives used 

in percussive applications have not been differentiated in tables of production statistics from the 

same materials used for true abrasive purposes. 

The first applications of loose grains of quartz and 

of quartz sandstone and other naturally bonded 

U.S. GEOL. SURVEY PROF. PAPER 820 

27 
28 UNITED STATES MINERAL RESOURCES 

stones for abrasive purposes are lost in prehistory. 

Early in the first millennium B.C., the hard natural 

abrasives diamond, corundum, and garnet already 

were known, at least in India and Greece. By A.D. 

1500, the artificial bonding of loose natural abrasive grains was introduced, first as sheets and later 

as blocks and wheels. The first bonding agent was 

shellac, the next was rubber, and in the last half 

of the 19th century. synthetic resins, m.etals, and 

ceramics were introduced. When powerad grinding 

equipment became available about 1860, the use of 

abrasives assumed a large role in metalworking 

operations that had been accompli~;hed previously 

by saws, chippers, shapers, lathes, and milling machines, but the major surge in the use of abrasives 

came about 1900 with the commercial introduction 

of the first of the artificially produced hard abrasive materials, aluminum oxide and silicon carbide. 

The use of steel rod and shot as pulverizers in tumbling mills and of steel grit as a sandblast medium 

also was introduced about 1900. Artificial aluminum 

oxide and silicon carbide, mostly used for dressing 

metals and slabbing stone, have dominated the 

market for hard abrasives for many years and currently account for about 90 percent of all the hard 

abrasives used in this country. 

The continued use of certain natural abrasives 

testifies to their desirable qualities as yet poorly 

matched by the artificial abrasives and to their 

lesser cost per unit of work. It is not to be expected, 

however, that those natural abrasives which still 

dominate a few specialized applications will continue to retain their fairly exclusive use. As Coes 

(1971, p. 33) insisted. 

corundum and emery * * * [and] several other natural minerals are used as abrasives although their total value is only 

a small fraction of the value of the synthetic abrasives used. 

Furthermore, their usage is highly specific. In time, exis·ting syntihetic abrasives will probably replace all of these, but 

the economic incentive is now lacking to work out the techniques for using them * * *. To replace these natural agents 

by new synthetic materials is probably quite possible, but 

the size of the market has, so far, seemed ·inadequate to 

justify the necessary research. Development of such synthetics probably must wait for the exhaustion of the supply 

of natural material or a substantial increase in its cost. At 

the moment this situation does not seem imminent * * *. 

In general, the need for hard abrasives in industry in the United States is overwhelmingly satisfied by synthetic, not natural, materials, and the 

trend toward lower demand for natural abrasives 

will continue. Modern technology is increasingly devoted to automatic machinery operated at high 

speeds and high pressures to produce finishes of 

high precision and is, therefore, correspondingly 

dependent upon the uniformity inherent in the artificial abrasives as well as upon their capability of 

being tailored to specific needs--characteristics not 

shared by the natural abarsives. Industry is not 

dependent upon the naturally occurring materials. 

All natural abrasives currently in use can be replaced by artificial abrasives after a short changeover period or after minor research, should the 

need arise. Nearly all the current consumption of 

natural· abrasives is dictated by tradition or by 

cost-principally by cost-and not by the unique 

qualities or the availability of the abrasives, so 

whether or not the United States has vast resources 

of the natural abrasives is largely of academic interest. The artificial abrasives, of course, are derived from natural materials, but resources of these 

materials seem to be abundant. 

THE NATURAL ABRASIVES 

The number of naturally occurring abrasive substances commonly in use is large. These substances 

represent more than 30 different mineral species and 

of some species, many varieties. The principal hard 

natural abrasives are diamond, corundum, emery, 

and garnet. Staurolite, kyanite, sillimanite, epidote, 

andalusite, topaz, bertrandite, and other hard minerals may have, or may have had, a minor and 

occasional local use. Natural abrasives of moderate 

hardness include the silica minerals, quartz (including quartz sand and river silt), chert, flint, jasper, 

chalcedony, tripoli, diatomite, and rottenstone; the 

feldspars; tl.le volcanic glasses, pumice, perlite, and 

obsidian ; and rocks such as basalt, granite, and 

quartzite, mostly used as grinding pebbles. A few 

of the more common abrasives of inferior hardness 

are apatite, dolomite, calcite (including chalk and 

whiting), clays, and talc. 

Not many of the natural abrasive substances are 

valuable enough to be transported long distances. 

Most are abrasives of opportunity, generally termed 

"regional" abrasives. They are consumed close to 

the point of production to the exclusion of other 

abrasives far more efficient but far more costly. 

Examples of some of these regional abrasives are 

quartz sand-several million tons of which is consumed annually, river silt, ground limestone, and 

ground feldspar. The resources of these materials 

relative to their local consumption are virtually 

unlimited. Only a few of the naturally occurring 

abrasives deserve individual description. These are 

the abrasives that are reputed to have certain desirable qualities and applications to specialized purposes, 

that are costly or in short supply, or that are not 

readily replaced by artificial abrasives. 
ABRASIVES 29 

DIAMOND 

Diamond, carbon crystallized in the cubic system, 

is the hardest natural substance known. Of all the 

diamond produced, only a small fraction is suitable 

for gemstones owing to inclusions, polycrystallinity, 

twinning, unpleasing color, or other flaws. The material unsuitable for gemstones is used in industry. 

Only a small portion of industrial diamond goes 

into manufactured goods such as phonograph 

needles, instrument bearings, and wire-drawing 

dies ; most is used for abrasives. Pencillike tools 

for scribing or cutting glass, or for truing and 

dressing abrasive wheels, have a whole diamond 

crystal or a large fragment set into the face of the 

tool. Rock drills also have their working faces implanted with diamond crystals, commonly in an 

annular pattern at the end of a steel pipe. By rotating the pipe, a cylindrical core of rock can be cut 

from the earth for inspection. Most industrial diamonds are crushed to powder and used in a slurry 

of oil or water for faceting gems-especially diamond, which can be abraded by virtually no other 

material, drilling holes in instrument bearings, or 

polishing optical parts; some are bonded to wheels 

or disks and used for such purposes as slabbing rock, 

sharpening carbide and other hardfaced tools, and 

precision-grinding hard ceramic forms to tolerances 

of a few millionths of an inch. 

Diamond abrasive is of critical importance to 

industry. Until 1955, the entire supply was imported because the United States has no commercial deposits of its own. In 1955, a commercial 

process for producing artificial industrial diamonds 

was perfected in the United States. Production in 

the United States now is in excess of 15 million 

carats annually, and it continues to rise. It is· supplemented by at least three other manufacturers 

throughout the world. The drop in imports of 

natural industrial diamond by the United States has 

not yet matched the rise in production of artificial 

diamonds because of increasing industrial activity 

and the discovery of new applications for abrasive 

diamond. Imports have dropped, however, from a 

high of about 20 million carats to about 13 million 

carats (about 3 tons) annually and are expected to 

drop further as economics and the increasing capabilities of the existing and anticipated manufacturers of artificial diamond allow. 

Most imported diamond comes from the Union of 

South Africa, but because a single distributing corporation markets nearly 90 percent of the world 

diamond production, the purchase of large lots of 

industrial diamond probably implies the inclusion 

of small quantities from such other diamondproducing countries as Angola, Congo, Rhodesia, 

Ghana, Guinea, Ivory Coast, Liberia, Sierra Leone, 

South-West Africa, Tanzania, Brazil, Guyana, India, Indonesia, and Venezuela. Diamond is known in 

the Soviet Union in the Ural Mountains and at the 

recently discovered deposits near Yakutiya; but 

little, if any, Soviet diamond comes to the world 

market. 

Natural diamond normally occurs only in an unusual type of peridotitic igneous rock known as 

kimberlite which was injected into overlying rocks 

mostly as cylindrical bodies, or "pipes," from deep 

in the crust of the earth. Of several hundred pipes 

known throughout the world, only a few contain 

diamonds, and of these only a few contain diamonds 

in commercial quantity. Two kimberlite pipes are 

known near Murphreesboro, Ark. One contains uneconomic quantities of diamond; the other, apparently, no diamond. Although diamond has been 

found in at least half the States, neither the original 

diamond-bearing pipes nor the alluvial placer concentrations derived from them have been discovered. The few stones found in the North-Central 

States probably were carried south from undiscovered Canadian sources by the continental glaciers 

of the fairly recent past. 

It is at least possible that diamonds can form in 

highly metamorphosed rock; these are common in 

the Southeastern States, California, Montana, and 

elsewhere where diamonds have been found. But 

ultramafic rocks also are known in these areas, and 

kimberlite pipes cannot be ruled out as the sources 

of these diamonds simply because they have not yet 

been discovered. Usually neither the topographic 

expression of pipes nor the surface appearance of 

weathered kimberlitic material is so exceptional as 

to indicate readily the presence of pipes, and the 

pipes are easily hidden by surficial material because 

they do not cover large areas-the largest diamond 

pipe known in the world covers barely 350 acres. 

Perhaps the best way to prospect for kimberlites or 

other diamondiferous rocks is to pan stream samples 

for diamonds, which are heavy and remain in the 

concentrate, and especially to look for those other 

few heavy and unusual minerals that almost universally accompany diamond-chrom.e diopside and 

pyrope garnet, together with the more common 

ilmenite. 

CORUNDUM 

Corundum is aluminum oxide crystallized in the 

hexagonal system. After diamond it is the hardest 

known natural substance. Two forms of corundum 

are common : ( 1) prismatic crystals which range in 

size from sugary aggregates to large crystals that 
30 UNITED STATES MINERAL RESOURCES 

commonly taper from the middle toward each end 

and exhibit a pronounced transverse parting, and 

( 2) large polycrystalline blocks. Corund urn crystals 

normally are translucent or opaque white, gray, 

blue, red, brown, black, or green, but some are 

transparent red, pink, blue, or bluish-green, or exhibit asterism or other pleasing chatoyancy, and 

these are valued as gemstones known to the jewelry 

trade as ruby and sapphire. 

Abrasive corundum is used nearly exclusively as 

crushed, carefully sized grit and powder for finishing optical parts and for lapping and polishing 

metals. The transverse parting characteristic of 

much corundum presents to the work a sharp, chisellike edge which scrapes rather than scratches the 

work and produces a smooth surface. When the abrasive wears, a flake spalls off so as to expose a new 

sharp chisel edge. Probably it is this characteristic 

that encourages a continuing small demand for 

corundum despite the fact that garnet, diamond, 

artificial aluminum oxide, and other abrasives can 

successfully substitute for all the uses to which 

corundum is now put. 

About 2,000 tons of corundum is imported each 

year, and about one-tenth of this is reexported as 

prepared grinding powder. For many years the 

source of supply was Rhodesia, but political considerations in mid-1968 cut off this supply, encouraging many users of corundum to convert immediately - and probably permanently - to artificial 

abrasives. South Africa has become the new source. 

It is perhaps a measure of the relative unimportance 

of corundum in our economy that the long-term 

Rhodesian source was cut off only a few months 

before the U.S. Government removed corundum 

from the list of strategic materials and offered for 

sale the last 2,000 tons of corundum in the strategic 

stockpile. 

The United States has no reserves of corundum, 

and the resources are poorly known. Not much more 

than 10,000 tons was produced between 1870 and 

1906 ; none has been produced since that time except for small test lots during the World Wars. 

Probably the ope area in the United States containing the largest amount of potential corundum 

or:e is that area embracing Clay, Macon, and Jackson Counties, N.C., and Towns and Rabun Counties, 

Ga., although corundum also is known in all of the 

Appalachian States, from Maine to Alabama, and 

in a few places in California, Montana, and Idaho. 

Deposits of corundum in the contact zone between 

peridotitic intrusive rocks and enclosing highly 

aluminous metamorphic rocks, especially those in 

Georgia and North Carolina, were the principal 

source of corundum in the United States. The genesis of these deposits has been debated by geologists 

for many years. Corundum also is a constituent of 

placer deposits and of more than 20 kinds of igneous rocks, including granite pegmatite, nepheline 

syenite, anorthosite, and gabbro. In some gneisses 

and schists, corundum makes up from 5 to 60 percent of the material in zones that range from a few 

inches to several tens of feet in width and that may 

extend several miles, although no such concentration currently represents an economic deposit. Panning would seem to be the method of choice for 

prospecting, and although perhaps not applicable 

to deposits in the United States, prospectors should 

be aware that peridotites rich in chromite generally 

contain no corundum, whereas those without chromite may. 

EMERY 

Emery is a gray to black granular material consisting of corundum and magnetite with admixed 

spinel, hematite, garnet, and other minerals. The 

proportion of some constituents ranges widely; 

some specimens are nearly pure corundum, others 

nearly pure magnetite, and still others nearly pure 

spinel. 

Synthetic abrasives have reduced the formerly 

multiple uses of emery to two. About 3 percent currently is made into coated abrasive sheets; the rest 

is used in nonskid pavements and stair treads. The 

true emery wheel has now become an antique curiosity. Only custom and economics encourage the 

continued use of emery because manufactured aluminum oxide grain probably would be superior for 

the same applications. Even granular magnetite, 

hematite, spinel, or garnet may substitute adequately, as indeed they probably have, judging 

from reported variations in the mineral content of 

emery ore used in the past~ 

Emery deposits are known in New York, Massachm~etts, Virginia, North Carolina, and Pennsylvania. Those in New York, a group of deposits 

about 3112 mi southeast of Peekskill and concentrated within an area of about 1 square mile, probably represent the largest single source in the United 

States. The U.S. Bureau of Mines estimated reserves 

of these deposits in 1955 at 60,000 tons, but since 

then the entire U.S. production of about 150,000 

tons has been from these deposits and production 

continues from a single mine at an annual rate of 

5-10 thousand tons. The extent of surface openings 

indicates that, with full development and the accommodation of several grades of ore, these deposits 

may well be capable of producing more than 10,000 
ABRASIVES 31 

tons per foot of depth to depths of many hundreds 

of feet. Overseas supplies have come from Greece 

and Turkey at an annual rate of from a few hundred 

tons to about 2,000 tons. Reserves in these countries 

aggregate 5-10 million tons and the resources probably amount to many millions of tons. Large deposits of emery are known in the Soviet Union, but 

this emery does not enter world trade. 

Emery deposits in Greece and Turkey occur as 

pods and lenses in metamorphosed limestone; those 

in the United States are in the margins of mafic 

intrusive rocks which are in contact with alumi:-

nous country rock. All probably result from contactmetamorphic processes, although geologic controversy very similar to that involving corundum 

deposits also has accompanied the study of deposits 

of emery. 

GARNET 

Garnet is the term applied to about 15 varieties 

of a complex silicate mineral which crystallizes in 

the cubic system, generally as rhombic dodecahedra. 

This form is nearly spherical and gave rise to the 

name garnet, derived from the Latin "granatus," 

meaning grainlike or seedlike. Common commercial garnet is almost entirely the variety almandite, 

a dark-red to dark-brownish-red iron aluminum 

silicate. 

Garnet currently has three major uses as an abrasive. (1) About 45 percent is used as a sandblast 

medium to clean an impart a textured surface to 

both ferrous and nonferrous metals in the shipbuilding, aircraft, and automotive industries, and to a 

much lesser extent for such other manufactures as 

home appliances, stone, and artworks. The tough 

round all uvial garnet crystals impart a pleasing 

work-hardened matte surface to these materials. 

(2) About 35 percent is used as crushed grit and 

powder to grind and polish lenses and other optical 

parts, to surface semiconductor materials, and to 

accomplish the intermediate grinding in the finishing of plate glass. The recent advent of the Pilkington, or "float," process of plate-glass manufacture, 

whereby a ribbon of hot glass is drawn across a bed 

of molten tin resulting in a finished surface of plateglass quality, will probably reduce substantially the 

future demand for crushed and sized garnet grit for 

glass-grinding purposes, currently about 4,000 tons 

per year. (3) About 20 percent is crushed and made 

into abrasive sheets. In this form it is used to dress 

rubber, plastics, leather, soft metals, and wood. 

The use of garnet as an abrasive is almost entirely American ; more than 95 percent of the garnet 

produced in the world is produced in the United 

States, and more than 80 percent is consumed here. 

Yet there are only two producing mines of consequence, and total annual production is only about 

20,000 tons. Spain, Portugal, India, and Canada 

have produced small quantities very occasionally. 

The garnet from New York State has an unusual 

structure, a closely spaced lamellar parting ordinarily not developed in garnet, that results in 

chisel-edged granules when the garnet is crushed, 

which scrape the work surface rather than scratch 

it. This property makes the garnet similar to corundum, for which it commonly substitutes. This garnet is unmatched as a tool for surfacing furniture 

woods or soft metals, or for skiving leather and 

rubber, and its use for grinding glass results in 

fewer scratches and a lower rejection rate than 

does use of other abrasives. Yet, garnet has no application in which it cannot be replaced by other 

appropriately prepared and adapted abrasives, ranging from sand, glass beads, and steel grit for sandblasting, to diamond powder for finishing optical 

parts. A continuing, even moderately increasing, 

use of garnet is probable, subject nearly entirely 

to changes in economics and technology. 

Garnet, as a source of commercial abrasives, occurs almost exclusively in metamorphic rocks and 

in placer deposits derived from them. Garnet-rich 

zones in gneisses and schists may contain 4-60 percent garnet, may be several hundreds of feet wide, 

and may extend for many miles. Many placers contain as much as 20 percent garnet, and very few 

beach, dune, glacial, and stream deposits throughout the world do not contain from a fraction of a 

percent to a few percent of garnet. The garnet easily 

could be saved by any of several simple mechanical 

or electrical methods of extraction, but it almost 

never is ; large quantities of garnet are lost every 

day in the production of sand and gravel from these 

deposits for. other purposes. Garnet deposits have 

been reported in more than half the States-all the 

States west of the Great Plains-and the Appalachian States from Maine to Georgia. The alluvial 

sandblast garnet recovered from Idaho comes from 

a single placer deposit estimated to contain 500,000 

tons of recoverable garnet. There are unmined 

placers in the Western States, and perhaps some 

undiscovered placers. The garnet with the lamellar 

parting currently being mined from a coarsely 

crystalline gneiss at North Creek, N.Y., is in a deposit which if fully developed could produce more 

than 7,000 tons of garnet per foot of depth to a 

depth perhaps in excess of 1,000 feet. Several other 

deposits of garnet with lamellar partings are reported elsewhere in northern New York, in New 
32 UNITED STATES MINERAL RESOURCES 

Hampshire, and in North Carolina. Those in North 

Carolina apparently are very large. N onlamellar 

garnet also is common in metamorphic rocks and 

in placer deposits in the Eastern States, particularly 

in the Adirondak Mountains of New York State. 

Many of these deposits have been little prospected, 

and the resources are not well known, but it is 

certain that each of a reasonably large number of 

deposits contains from half a million to many millions of tons of garnet. Overseas resources of garnet 

are unknown, inasmuch as garnet is little used outside the United States. 

SILICA SAND 

Silica sand, both crushed and uncrushed, is used 

in large quantities; one-half million tons is used in 

this country annually for grinding stone and glass, 

and more than a million tons for sandblast purposes. 

It is, or could be, produced in each of the 50 States 

by nearly any of the more than 5,000 producers of 

sand and gravel currently operating. Resources are 

large. (See chapter "Silica.") 

TRIPOLI 

Tripoli is fine-grained silica which remains as a 

bedded residuum of the weathering of siliceous limestone. It is roughly similar in characteristics and 

uses to rottenstone, mined in Pennsylvania from 

weathered siliceous shale, and to diatomite, bedded 

deposits of the siliceous remains of marine microorganisms. A combined total of about 40,000 tons 

of these materials is consumed each year as abrasives, mostly in scouring soaps and powders and in 

metal- and lacquer-polishing pastes. Large deposits 

of tripoli are known in Illinois, Missouri, Oklahoma, 

Tennessee, Georgia, Alabama, Arkansas, California, 

Texas, and Nevada. Deposits of diatomite are known 

in several Western States. (See chapter "Diatomite.") 

THE ARTIFICIAL ABRASIVES 

After the commercial introduction of artificial 

abrasives about 1900, the industry became almost 

immediately dominated by these products. The dominance is increasing even today. Aluminum oxide in 

particular found its principal application, among a 

host of other applications, in the rough grinding of 

ferrous metals, an operation formerly accomplished 

slowly and expensively by metalworking machinery. 

Nearly all subsequent research on artificial abrasives has been directed to the discovery of an abrasive even more efficient than aluminum oxide for 

grinding ferrous metals. None has been found, although large families of carbides, borides, nitrides, 

silicides, oxides, and even a few artificial silicates 

have been tried. A few abrasives useful for other 

purposes have been discovered, and research continues. 

Artificial diamond, as discussed above, was first 

produced in 1955. It is manufactured from a mixture of graphite and a catalyst of iron, manganese, 

chromium, cobalt, nickel, or other metal under conditions of high temperature and pressure, typically 

3,000°C., 70,000 bars of pressure, and several hours 

of time. Although available for less than 20 years, 

artificial diamond already infringes seriously on the 

market for natural industrial diamond, all of which 

must be imported. This trend is expected to accelerate in the years ahead. Artificial diamond itself 

may one day be challenged as an abrasive because 

artificial cubic boron nitride, invented in 1957 and 

manufactured in much the same way as diamond, 

has been demonstrated in grinding tests to abrade 

diamond as rapidly as does diamond. It also has the 

advantage of remaining stable at high temperatures, 

whereas diamond tends to revert to graphite at the 

temperatures often reached at the grinding surface, 

resulting in rapid ablation of the diamond in the 

abrasive wheel. Diamond also is difficult to incorporate in ceramic-bonded wheels because of hightemperature effects. 

Artificial aluminum oxide, chemically but not 

physically identical with corundum, is manufactured by fusing or sintering bauxite or intermediate 

products in an electric furnace. Annual production 

is more than 200,000 tons and requires about 

320,000 tons of bauxite, or about 2 percent of the 

annual consumption of bauxite in the United States. 

Ten to fifteen percent goes into nonabrasive applications, mostly refractory products. New techniques over the years have lowered the required 

alumina content of the furnace charge, previously 

60 percent, to less than 50 percent, and further 

technological changes are expected soon to allow 

alumina contents of only 35 percent, making available vast resources of syenitic and other aluminous 

rock for this purpose. 

Commercial production of silicon carbide is accomplished by the reaction of a mixture of silica 

sand and coke, preferably petroleum coke, in an 

electric furnace. The principal abrasive use of silicon carbide is in the wire sawing of stone, but the 

abrasive successfully substitutes in many operations 

to which hard natural abrasives also are put, including the skiving of rubber and leather, and it is 

the leading abrasive in the dressing of nonferrous 

metals. Nearly 200,000 tons of silicon carbide is 

produced each year in the United States, about half 

of which is used as an abrasive. Refractory appli-
ABRASIVES 33 

cations require most of the rest. 

Steel, as shot and grit, is used extensively as a 

sandblast medium and as pebbles in tumbling mills. 

More than 200,000 tons is produced for these purposes each year. This amount requires the furnace 

reduction of about 400,000 tons of iron ore. 

Other artificial abrasives are manufactured in 

relatively small amounts. Many are furnace products and are made in much the same manner as 

aluminum oxide and silicon carbide. Among these 

are zirconium oxide, cerium and other rare earth 

oxides, and rouge and crocus (iron oxide for polishing). Others are precipitates from aqueous solutions 

and several of these, including calcium carbonate 

and silica, duplicte the naturally occurring minerals 

and are used for the same purposes. 

POTENTIAL RESOURCES 

Resources of the several abrasive materials in the 

United States range from the infiinitesimal to quantities which for practical purposes approach the 

infinite. There are no known diamond deposits and 

little prospect of discovering any, but deposits of 

silica sand are literally underfoot in many parts of 

the country. The size of deposits of other abrasives 

lies between these extremes. 

Table 5 gives estimated tonnages for each of the 

TABLE 5.-Resources, in short tons, of abrasive materials in 

the United States 

Commodity 

Diamond --------- Corundum -------- Emery ----------- Garnet ----------- Triopli (and related 

materials) ------ Silica sand --------

Identified resources 1 

(including reserves 2) 

0 

125,000 

3,000,000 

14,000,000 

4,500,000,000 

Large 

Hypotbetieal resources a 

0 

>2,000,000 

>4,000,000 

>100,000,000 

>10,000,000,000 

Large 

1 Identified resources: specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. 2 Reserves: identified deposits from which minerals ean be extracted 

profitably with existing technology and under present economic conditions. 3 Hypothetieal resources: undiscovered mineral deposits, whether of 

recoverable or subeconomic grade, that are geologically predictable as existing in known districts. 

more significant abrasive materials occurring in the 

United States. Estimates of identified resources are 

based on the general premise that a tabular deposit, 

one with great length and depth relative to its width, 

should conservatively produce ore from a volume of 

rock that is six times the volume of an equidimensional quarry opened to the full width of the deposit. 

Most corundum and garnet and much emery characteristically occur as concentrations within lenticular zones in metamorphic rocks having these dimensions. Podlike deposits such as those formed marginal to intrusive bodies are estimated to produce 

ore to a depth equivalent to the longest surface 

dimension of an individual ore body of average size. 

Bedded deposits are estimated to produce half as 

much ore as is indicated by the lateral limits and 

the average thickness known from extensive outcrop, drill, or mining exploration. 

The apparent large quantities of identified and 

hypothetical resources of the several abrasive materials relative to their annual consumption makes 

an estimation of tonnages of speculative resources 

superfluous. 

SELECTED REFERENCES 

Chandler, H. P., 1960, Tripoli, in Industrial minerals and 

rocks [3d ed.] : Am. lnst. Mining, Metall., and Petroleum 

Engineers, p. 881-887. 

Coes, Loring, Jr., 1971, .Abrasives: New York, SpringerVerlag, 177 p. 

Cooper, J. D., 1970a, Corundum and emery, in Mineral facts 

and problems, 1970 ed.: U.S. Bur. Mines Bull. 650, p. 

939-951. 

--- 1970b, Garnet, in Mineral facts and problems, 1970 

ed.: U.S. Bur. Mines Bull. 650, p. 1001-1011. 

Eardley-Wilmot, V. L., 1928, Diatomite, its occurrence, preparation, and uses: Canada Dept. Mines, Pub. 691, 182 p. 

French, A. E., and Eilertsen, N. A., 1968, Abrasives, in 

Mineral resources of the Appalachian region: U.S. Geol. 

Survey Prof. Paper 580, p. 261-267. 

Friedman, G. M., 1956, The origin of spinel-emery deposits 

with particular reference to those of the Cortlandt Complex, New York: New York State Mus. Bull. 351, 68 p. 

Ladoo, R. B., 1960, Abrasives, in Industrial minerals and 

rocks [3d ed.]: Am. lnst. Mining, Metall., and Petroleum 

Engineers, p. 1-21. 

Larsen, E. S., 1928, A hydrothermal origin of corundum and 

albitite bodies: Econ. Geology, v. 23, no. 4, p. 398-433. 

Myers, W. M., and Anderson, C. 0., 1925, Garn3t, its mining, 

milling, and utilization: U.S. Bur. Mines Bull. 256, 54 p. 

Pratt, J. H., 1906, Corundum and its occurrence and distribution in the United States (a revised and enlarged edition of Bulletin 180) : U·S. Geol. Survey Bull. 269, 175 p. 

UNITED STATES MINERAL RESOURCES 

ALUMINUM AND BAUXITE 

By SAM H. PATTERSON and JoHN R. DYNI 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction ------___ ----------------------------

United States and world bauxite production --------

Byproducts -------------------------------------- Environmental considerations ---------------------

Geologic environment of bauxite -------------------

Resources ---------------------------------------

Bauxite resources ----------------------------

Other potential resources of aluminum ---------

Alunite ---------------------------------

Aluminum phosphate rock ----------------

Aluminous shale and slate ----------------

Dawsonite -------------------------------

High-alu~ina clays ----------------------

Igneous rocks ----------------------------

Saprolite --------------------------------

Coal aSh -------------------------------- Copper-leach solutions --------------------

Problems for research ---------------------------

Selected references -------------------------------

FIGURE 

7. Graph showing United States production and imports and world production of bauxite, 1928-

71 ----------------------------------------

TABLES 

6. Specifications for abrasive, chemical, and refracPage 

35 

35 

36 

37 

37 

37 

38 

38 

39 

39 

39 

40 

40 

41 

41 

41 

42 

42 

42 

43 

Page 

37 

Page 

tory grades of bauxite ---------------------- 36 

7. Chemical composition of bauxite resources in the 

Untted States ------------------------------ 38 

ABSTRACT OF CONCLUSIONS 

Imports of bauxite and alumina, mainly from Jamaica, 

Surinam, and Australia, supply approximately 87 percent of 

the United States requirements for manufacture of aluminum metal and certain refractories, abrasives, and chemicals. 

Bauxite mined in Arkansas, Georgia, and Alabama supplies 

the remaining 13 percent. Barring unforeseen political developments, the growing requirements of the aluminum industry in the United States will be met by imports of increasing amounts of aluminum metal and alumina rather 

than bauxite ore. 

Domestic resources of bauxite-approximately 40 million 

tons reserves and 250-300 million tons potential resourcesare inadequate to fulfill the long-term demand; however, the 

Nation has virtually inexhaustible potential resources of 

aluminous materials other than bauxite. High-alumina clays 

now seem the most promising of the potential alternate 

sources of aluminum. Dawsonite in the rich oil-shale deposit·s 

of Colorado is a possible source of aluminum that may be a 

recoverable byproduct of shale oil. Alunite, reportedly found 

in a large deposit in Utah, may be a possible source of 

aluminum and other products. Other less promising potential resourc·es include aluminous shale and slate, aluminum 

phosphate rock, igneous rocks, saprolite, coal ash, and copperleach solutions. 

Exploration for major high-grade bauxite deposits should 

continue. Favorable areas for exploration include parts of 

South America, Africa, Asia, and Australia. Use of improved 

analytical tools, such as the borehole neutron activation 

probe, could speed up exploration for new deposits and 

evaluation of known deposits. Geologic research is also 

needed on the nonbauxite sources of aluminum in the United 

States, inasmuch as the detailed geologic information available on the potential resources is inadequate. 

INTRODUCTION 

Aluminum is a silvery white ductile lightweight 

(specific gravity of 2. 7) metal having efficient electrical conductivity and resistance to oxidation. Because of its properties, abundance, and low cost, 

aluminum has become one of the most important 

metals in industry; only iron surpasses it in tonnages used. Major uses of the metal are in the construction industry and in the manufacture of aircraft, motor vehicles, electrical equipment and 

supplies, fabricated metal products, machinery, 

beverage cans, containers, and a wide variety of 

home-consumer products. Aluminum is essential to 

our standard of living and is a strategic commodity 

U.S. GEOL. SURVEY PROF. PAPER 820 

35 
36 UNITED STATES MINERAL RESOURCES 

for military defense. Plastics, wood, and other 

metals including copper, steel, lead, zinc, magnesium, 

and titanium could be substituted for some of the 

uses for aluminum. However none of these materials 

has all the properties of aluminum, and none offers 

much market competition for aluminum, except for 

a few specialized uses. Both alumina (the oxide of 

aluminum, Al20a) and bauxite (the major ore of 

aluminum) are used in the manufacture of refractories, abrasives, and chemicals. 

Bauxite is a complex impure mixture of aluminous minerals, chiefly aluminum hydroxides. Alumina content of most bauxites ranges from 35 to 

50 percent; the common impurities are quartz, kaolinite, and iron-oxide-bearing minerals. Bauxite 

ores, of which there are several types, are classified 

by mineral content, occurrence, use, and source. In 

recent years, about 88 percent of the bauxite and 

alumina consumed in the United States was used in 

making metal, 4 percent in refractories, 6 percent 

in chemical and related uses, and 2 percent in abrasives. 

Aluminum metal is made by extracting alumina 

from bauxite by the Bayer process and by reducing 

this oxide to metal electrolytically. In the Bayer 

process, bauxite is leached under pressure and heat 

by a caustic solution which converts the ore to a 

solution of sodium aluminate and red mud waste. 

From this solution, hydrated aluminum oxide is 

precipitated, washed, and calcined to obtain alumina. This alumina is then reduced to the metal by 

electrolysis of a hot molten solution of alumina and 

crolite, N aaAlF 6• Metallurgical-grade bauxite ranges 

from 35 to 55 percent Al20a. Depending on grade 

and type of ore, between 4. 7 and 7 short tons of 

bauxite are required to produce 2 tons of alumina, 

and 2 tons of this oxide are required to make 1 ton 

of aluminum metal. 

Bauxite used for manufacture of abrasives, refractories, and chemicals must meet more restrictive 

specifications as to aluminum, silicon, iron, and 

titanium contents than does metallurgical bauxite 

(table 6). Although the amount of bauxite used for 

purposes other than metal production is relatively 

TABLE 6.-Specifications, in percent, for abrasive, chemical, 

and refractory grades of bauxite 1 

Grade 

Dried: 

Abrasive ---- Min 55 Chemical ---- Min 55-&8 Refractory __ Min 59-61 

Calcined ------ 85·-90 

Max fi 2 Max 5-12 Max 1 5-5.5 3-6 

1 Modified from Stamper (1970, p. 440) 

Max 6 Max 2 

Max 2 

1.5-7.0 

Min 2.5 

Min 2.5 

3-4 

2 A major portion of the bauxite used by the U.S. chemical industry 

exceeds 15 percent Si02. 

small, these uses are of major importance to industry. For example, only 2 percent of U.S. bauxite 

consumption is used to manufacture aluminum 

oxide abrasives; yet this represents about half of 

all production of artificial abrasives and more than 

five times the total production of natural abrasives. 

The United States is dependent mostly on imports 

for its bauxite and alumina requirements. Excluding trade in alumina metal, the United States in 

1971 produced about 2 million long dry tons of 

bauxite, imported 13.7 million long tons of bauxite 

and 2.3 million short tons of alumina, and exported 

30,000 tons of bauxite, and 1.1 million tons of alumina. In that year, the United States consumed the 

equivalent of approximately 27 percent of the world 

production of bauxite and produced domestically 

only 12.5 percent of its requirements. Between 1967 

and 1970, imports of bauxite were from Jamaica 

(59 percent), Surinam (24 percent), and other 

countries (17 percent). Alumina imports during the 

same period came from Australia (52 percent), 

Surinam (24 percent), Jamaica (18 percent), and 

other countries (6 percent). 

UNITED STATES AND WORLD 

BAUXITE PRODUCTION 

Aluminum was extracted from bauxite in both 

France and England in the middle of the 19th 

century, but less than 50 tons of metal had been 

produced by 1885. Production increased at a rapid 

rate in the late 1800's; the yearly world demand for 

bauxite, however, did not reach 1 million tons until 

1917, during World War I. World production of 

bauxite dropped sharply after the war and reached 

a low of 334,000 tons in 1921. A little more than 1 

million tons was produced in 1923, and a yearly 

production of 2 million tons was first reached in 

1929. World production again dropped in the depression years of the early 1930's (fig. 7) but recovered in the last half of the decade and reached a 

sharp peak of more than 13 million tons in 1943. 

Production again slumped sharply after World 

War II as the economy changed to peacetime conditions and accumulated stocks were consumed. After 

recovering from this slump, world production 

reached 11 million tons in 1951 and has since remained on a sharply increasing trend, reaching 57 

million tons in 1970. 

Domestic production, including the World War I 

peak, remained below 1 million tons annually until 

very intensive mining was started in 1942 to meet 

World War II requirements; a record production 

of 6.2 million tons was reached in 1943 (fig. 7). 
ALUMINUM AND BAUXITE 87 

~g1-rrnnr""~~~~~"""~~~~~~ 

50 

~40 

e 30 

~ 20 

0 

..J 

u.. 10 

0 8 fl) 

z 6 

0 

~ 4 ..J 

~ 2 

1940 1950 1960 1970 

FIGURE 7.-United States production and imports and world 

production of bauxite, 1928-71 (1971 world production 

is inferred), compiled from U.S. Bureau of Mines Minerals 

Yearbooks and statistical data. 

Since that war, production has remained between 

1 and a little more than 2 million tons a year. 

The Arkansas district has produced more bauxite 

than all other districts in the United States combined. About 64 million tons was produced in Arkansas from 1896 through 1971. Production in all 

Southeastern States from 1889 through 1971 

amounted to only 3.6 million tons, dry basis. 

BYPRODUCTS 

A few metals and other byproducts are recovered 

in making aluminum. Gallium is recovered from 

Arkansas bauxite by one company and from bauxite 

in Hungary. Pig iron is produced from bauxite processed by the Pedersen method in Norway. Vanadium 

has been recovered from bauxite in France. Vanadium and chromium were produced from bauxite in 

Germany during World War II. Red mud, the waste 

product from the Bayer process, has been used as 

a soil conditioner to neutralize acid soils in Arkansas and as a red pigment in foreign countries. Phosphate and portland cement are coproducts of alumina recovered from nepheline syenite in the 

U.S.S.R. Some bauxite resources in the United 

States and large bauxite deposits elsewhere in the 

world contain substantial amounts of titanium. Although there has been considerable research on 

recovery of titanium from bauxites, its extraction 

has not yet proved to be profitable. 

ENVIRONMENTAL CONSIDERATIONS 

Like the other mineral and metal industries, the 

aluminum industry faces serious environmental 

problems. Those related to mining are primarily the 

reclamation of strip-mined land and the contamination of streams by sediment. Those related to recovery and use include (1) disposal of red-mud waste 

from alumina plants, (2) control of atmospheric 

contamination by dust and fumes containing fluorides, and surface-water contamination from electrolytic plants, (3) the control of sulfur in fuel for the 

generation of electricity, and (4) disposal and recycling of used metal. The industry is making significant progress on environmental problems, though 

improvements are still to be made. The reclamation 

of recently mined lands is efficient. In most plants, 

scrubbers are in operation to clean up gaseous effluents, monitoring systems are installed to check their 

continued efficiency, and water is treated to control 

toxicants. However, the big problem of disposal or 

profitable use of red mud remains without a satisfactory solution, and much improvement in the recycling of waste metal is needed. In 1970, approximately 3 billion aluminum beer- and soft-drink cans 

were made from 57,000 tons of aluminum. In that 

year, approximately 10 percent of the cans were 

recycled, and there was a modest increase the following year. Even if this marks the beginning of a 

trend, the problem of beer- and soft-drink-can litter 

control and disposal or reuse remains a monumental 

one. 

GEOLOGIC ENVIRONMENT OF BAUXITE 

Aluminum, surpassed in abundance only by oxygen and silicon in the crust of the earth, is a major 

constituent in many types of rocks. It occurs in 

nature only in combination with other elementsmostly with silicate minerals, the remainder with 

other compounds. Aluminum combined with oxygen 

and hydrogen makes up the minerals in bauxite 

deposits, and this is the form most commonly mined 

for metal. The principal minerals in bauxite are 

gibbsite, AI (OH) a; boehmite, AlO (OH); and diaspore, which has the same composition as boehmite 

but is denser and harder. Gibbsitic bauxites are 

designated the trihydrate type; boehmite- and 

diaspore-bearing bauxites are the monohydrate type. 

Trihydrate bauxites that have a low silica content 

(or low reactive-silica content) are the cheapest to 

process by the Bayer method. The extraction of 

alumina from monohydrate and mixed monohydratetrihydrate bauxites is more costly because higher 

temperatures and pressures and additional amounts 

of caustic soda are required. Lower metallurgical 

costs make it possible to utilize trihydrate bauxite 

of lower grade than the other types. 
38 UNITED STATES MINERAL RESOURCES 

Most of the bauxite deposits in the United States 

are composed chiefly of gibbsite; the principal impurity is kaolinite, (OH) sSi4Al4010• Jamaican 

bauxite, the leading source of our imports, is 

chiefly gibbsite but also contains some boehmite. 

Most deposits in Europe and several in Asia are 

composed chiefly of boehmite. Minor quantities of 

diaspore are present in several bauxite deposits in 

foreign countries and occur in refractory-clay deposits in Missouri and Pennsylvania. 

Bauxite minerals are formed mostly by weathering of aluminous rocks. Various deposits of bauxite 

in different parts of the world are known to have 

formed from virtually every type of rock that contains aluminum. Conditions favorable for the formation of bauxite are (1) warm tropical climate, 

(2) abundant rainfall, (3) aluminous parent rocks 

having high permeability and good subsurface 

drainage, and ( 4) long periods of tectonic stability 

that permit deep weathering and preservation of 

land surfaces. During weathering, the bauxite becomes enriched in aluminum by removal of most 

of the other elements in the parent rocks mainly by 

solution by subsurface water. Because of chemical 

weathering and removal of essential plant nutrients, 

soils developed on bauxite deposits commonly support a cover of undernourished, dwarfed vegetation. 

Useful guides in exploration for surficial bauxite 

are the recognition of old land surfaces and dwarfed 

vegetation ; such guides led to the discovery of the 

bauxite deposits in Oregon and Hawaii, as well as 

several very large deposits in other parts of the 

world. 

Several types of bauxite deposits occur in the 

United States. The major deposits in the Arkansas 

region are of Eocene age, and they were formed by 

weathering of nepheline syenite (Gordon and others, 

1958). Some deposits in this region are residual on 

the igneous rock; others have been transported and 

are interlayered with marine shale that was deposited in a sea that overlapped the syenite. The ironand titanium-bearing low-grade bauxites (table 7) 

in Washington (Livingston, 1966), Oregon (Corcoran and Libbey, 1956), and Hawaii (Patterson, 

1971) were formed from basalt lava flows. These 

deposits are of the laterite type and have origins 

.similar to the very large deposits occurring in thick 

residual soils in several tropical areas. The deposits 

in Washington and Oregon occur on flows of probable middle Miocene age, and the bauxite is thought 

to have formed chiefly in late Miocene time. Those 

in Hawaii formed mainly during the Pleistocene 

Epoch. Some bauxite deposits in the Appalachian 

region occur in areas of karst topography, and apparently they formed by leaching of fine-grained 

aluminous materials that accumulated in sink holes. 

These deposits are thought to be early Tertiary in 

age. 

TABLE 7.-Chemical composition, in percent, of bauxite resources in the United States 

Al20a 

Arkansas --------- 4()-60 

Oregon 1 ---------- 35.0 

Washington 1 ------ 38.8 

Kauai, Hawaii 1 ___ 25.9 

1 Average of several analyses. 

1->20 

6.7 

6.6 

4.7 

Fez<> a 

3->6 

31.5 

28 '1 39.4 

RESOURCES 

BAUXITE RESOURCES 

Loss on Ti02 ignition 

1-3 15--35 

6.5 20.2 

4.2 21.7 6.7 20-23 

Compared with world resources of metallurgicalgrade bauxite, the United States reserves and potential resources are very limited. The domestic 

reserves, which are in beds 8 or more feet thick in 

Arkansas, amount to approximately 40 million tons. 

Potential resources of metallurgical bauxite in the 

laterite deposits in Hawaii, Washington, and Oregon, and thin, deeply buried deposits in Arkansas, 

amount to 250 to 300 million tons. Some of the deposits in Washington and Oregon are as rich in 

alumina as bauxite mined in some countries, but it 

has not been established that alumina can be extracted profitably from this bauxite. With the development of a process of profitable extraction, as 

much as 100 million tons could be shifted from conditional resources to the reserve category, thereby 

increasing the reserves to 140 million tons. But even 

with this larger figure, the United States would 

have only about 1 percent of the world's bauxite 

reserves. 

World bauxite reserves were estimated in 1965 

by Patterson (1967) to be 5.8 billion tons and potential resources to be 9.6 billion tons. Since this 

estimate was made, very large deposits have been 

discovered in several countries, and trihydrate 

bauxite containing as little as 35 percent Al203 is 

now mined in Australia and elsewhere. As the result 

of the use of lower grade bauxite, much of that 

considered to be potential resources in 1965 now 

should be classified as reserves. The total world 

bauxite reserves are now probably 12-15 billion 

tons. Lack of reliable data precludes estimating 

potential bauxite resources, but these resources are 

undoubtedly much larger than the 1965 estimate. 

It is unlikely that new large deposits of metallurgical-grade bauxite will be discovered in the 

United States. Elsewhere, however, there are large 

unexplored areas in South America, Africa, Asia, 
ALUMINUM AND BAUXITE 39 

and Australia that seem favorable for discovery of 

major new deposits of metallurgical-grade bauxite. 

Reserves of bauxite for abrasives, refractories, 

and chemicals in the United States are approximately 5 million tons, and potential resources are 

about 25 million tons. These deposits are in Arkansas (Gordon and others, 1958) and in many small 

districts scattered throughout the Appalachian region and the Coastal Plain in Southeastern United 

States (Overstreet, 1964). Chemical-grade bauxite 

is mined in Arkansas; Andersonville, Ga. ; and the 

northwest Georgia districts. Refractory-grade bauxite is mined in Arkansas and in the districts at 

Eufaula, Ala., and Andersonville, Ga. Small quantities of refractory-grade bauxite are occasionally 

mined where lenses of bauxite are found during 

mining of kaolin in the extensive kaolin belt of 

Georgia. Much of the refractory-grade bauxite produced domestically is used for mullite-type refractory products because of its high silica content, and 

demand for such material is increasing. Abrasivegrade bauxite has been produced in the Arkansas 

district, but now most of it is imported in calcined 

form from Guyana and Surinam. 

Guyana and Surinam are now the principal 

sources of high-grade refractoFy bauxite for most 

of the world. D1,1ring the period of 1966--70, the 

United States imported yearly from 145,000 to 

237,000 long tons of bauxite, mainly for uses other 

than metal, from Guyana (Kurtz, 1971, p. 6) and 

from 16,000 to 48,000 long tons from Surinam. 

Some calcined abrasive-grade bauxite has been recently imported from the Weipa district in Australia, and calcined bauxite is reported to be available in the Republic of Guinea; however, the longrange potential of these sources is not yet clear. 

In the United States, possibilities remain for 

finding additional small deposits of bauxite for refractory and chemical uses in Arkansas and the 

Southeastern States. Such deposits are likely to be 

high in silica, and some will be deeply buried, but 

the search for these hypothetical deposits may become more profitable as domestic supplies diminish. 

Suggested areas for exploration are ( 1) beneath 

considerable cover downdip from the nepheline 

syenite body on which the Arkansas deposits were 

formed (Jespersen, 1964), and (2) in scattered 

areas in the southern Appalachian region, where 

sinkholes are abundant. 

OTHER POTENTIAL RESOURCES OF ALUMINUM 

Potential resources of aluminum other than bauxite comprise a variety of rocks and minerals, including alunite, aluminous shale and slate, aluminum 

phosphate rock, dawsonite, high-alumina clays, 

nepheline syenite, anorthosite, saprolite, coal ash, 

and aluminum-bearing copper-leach solutions. Alunite and nepheline syenite are being mined today in 

the U.S.S.R. for alumina and other products. Elsewhere in the world several of these resources have 

been investigated in considerable detail, but they 

are not mined because bauxite is available. The potential aluminum resources in the United States 

collectively amount to many billions of tons and are 

virtually inexhaustible. Their use will depend largely 

on costs of imported bauxite, alumina, and aluminum 

and on advances in technology that will make them 

competitive with imports. The United States could 

become self-sufficient in aluminum now if a profit 

in its production were not required. 

ALUNITE 

Alunite, KAls (S04) 2 (OH) 6' a white mineral containing 37 percent alumina, commonly occurs in 

veins, replacement bodies, and in disseminated form 

in altered volcanic rocks. The mineral has potential 

value for potash and sulfur as well as aluminum. 

Alunite is a present source of aluminum in the 

U.S.S.R., and an alunite processing plant is reportedly under construction in Mexico. In the United 

States, alunite was investigated through the pilotplant stage as an emergency source of aluminum 

during World War II. 

Recently, alunite deposits near Cedar City, Beaver 

County, Utah, were explored by two companies 

(Engineering and Mining Journal, 1971). The deposits are on lands under Federal potash permits in 

the Wah Wah Mountains. Four zones of alunitized 

Tertiary volcanic rocks, each more than 100 million 

tons of rock, have been reportedly found by extensive drilling. The deposits are said to be 35--45 

percent alunite, and the remainder is mostly quartz. 

Aluminum sulfate or alumina and potassium sulfate 

are the proposed products from this deposit (W. W. 

Walker, oral commun., May 1972). If this initial 

report on the size and grade of these deposits is 

confirmed, they are a large potential resource of 

aluminum, but whether or not this metal can be recovered profitably is yet to be determined. 

ALUMINUM PHOSPHATE ROCK 

The leached zone, 2--20 feet thick, occurring above 

and stripped off in mining of phosphate deposits in 

Florida, contains several aluminum phosphate minerals and minor quantities of uranium. The alumina 

content of this rock ranges from 4 to 20 percent, 

and the U3 0 8 content from 0.005 to 0.02 percent. 

These deposits in Florida extend over several hun-
40 UNITED STATES MINERAL RESOURCES 

dred square miles and were estimated to contain 

800 million tons of this low-grade rock; however, 

part of this theoretical resource of alumina has 

been lost in mining. 

Research has been carried on by industry and government organizations on the possibility of recovering alumina, uranium, and phosphate from these 

deposits and similar ones overseas. Some of the 

earlier efforts were sufficiently encouraging to generate the issuing of several U.S. and foreign patents, 

but no profitable extraction of aluminum has been 

achieved. 

ALUMINOUS SHALE AND SLATE 

Aluminous shale, containing 20-24 percent Alz03, 

and slate, some of which is considerably richer in 

alumina, are widely distributed throughout the 

United States. The most extensive aluminous shale 

units were formed from fine-grained marine sediments. Those in Central and Eastern United States 

are of Paleozoic age, and those in the High Plains 

and Rocky Mountain regions are of Cretaceous age. 

Most slates in Eastern United States occur in a belt 

extending from Maine to North Carolina, and they 

are of Paleozoic age. 

Shales have been investigated as possible sources 

of aluminum by several .State agencies and by industry. The North American Coal Co. built a pilot 

plant at Powhatan Point, Ohio, and tested the shaly 

roof stone above the Pittsburgh coal bed. This attempt at commercial production was unsuccessful. 

DAWSONITE 

Dawsonite, NaAl(OH)2C03, a colorless or white 

acid-soluble mineral, occurs in small needlelike 

crystalline aggregates or as fine-grained to microscopic crystals in several types of host rocks. Dawsonite contains, by weight, 35.4 percent Al203 or 

18.7 percent aluminum metal. When heated it loses 

hydroxyl water and carbon dioxide and forms watersoluble sodium aluminate. Until its discovery in the 

Tertiary oil-shale deposits of Colorado, dawsonite 

was a mineralogical curiosity found only at a few 

localities in the world (Smith and Milton, 1966; 

Loughnan and See, 1967). 

Large quantities of dawsonite and nahcolite (see 

discussion of nahcolite in chapter on "Evaporites 

and Brines") are present in the rich oil-shale deposits of the Tertiary Green River Formation in the 

Piceance Creek basin, northwestern Colorado. Dawsonite occurs as microscopic crystals disseminated 

throughout the oil shale in sequences as much as 

1,000 feet thick toward the center of the basin. The 

top of the dawsonite- and nahcolite-bearing oil shale 

in the central part of the basin ranges from about 

1,100 to 2,000 feet below the surface. The dawsonite 

content of the oil shale ranges from a few percent 

to at least 20 percent (Hite and Dyni, 1967). From 

an examination of well cuttings, DeVoto, Stevens, 

and Bloom ( 1970) identified a 500-foot-thick sequence of oil shale of potential commercial value in 

a 250-square-mile area in the northern part of the 

basin. The shale in this sequence contains a minimum of 1.5 percent acid-extractable aluminum 

(equivalent to 8 percent dawsonite), which amounts 

to a resource of about 19 billion short tons of equivalent dawsonite. In addition to the aluminum, the 

rock contains an average of about 30 gallons of 

shale oil per ton. 

Alumina for production of aluminum metal and 

sodium aluminate for use in water-pollution control 

are potential products of dawsonite in the Colorado 

oil-shale deposits (Hite and Dyni, 1967; Irvin Neilsen, written commun., 1972). Recovery of either 

product seems most feasible after the rock has been 

retorted for shale oil. During retorting, the dawsonite would be converted to sodium aluminate 

which could then be extracted by a water or caustic 

leach (Dyni, 1972; VanNordstrand, 1968). Aluminum hydroxide could be precipitated from the 

sodium aluminate solution, then calcined to form 

alumina. Additions of nahcolite to the oil shale 

before retorting might improve the recovery of 

sodium aluminate (Hite, 1969). Although the 

amount of extractable aluminum is very low to 

serve as a commercial source of aluminum, the costs 

of mining and processing the rock would be partly 

offset by coproduction of shale oil and nahcolite (or 

soda ash) from the same rock. Furthermore, extraction of sodium aluminate from retorted dawsonitebearing oil shale does not require the Bayer process 

which is necessary in processing bauxite for aluminum metal. 

The dawsonite-bearing oil-shale deposits in Colorado originated in an ancient closed-basin lake environment whose waters were rich in organic matter 

and sodium carbonate. Vast amounts of carbonate 

minerals including dawsonite, nahcolite, and dolomite were precipitated from strongly alkaline solutions by mechanisms that are as yet unclear. Dawsonite seems to be restricted to the Piceance Creek 

basin; it has been looked for but not found in the 

Green River Formation in Utah or Wyoming. Elsewhere in the world small amounts of dawsonite 

have been found in dikes at Montreal, Canada, in 

sandstone from the Permian Greta Coal Measures 

in Australia, in alluvial claystones of Pleistocene 

age in Olduvai Gorge, Tanzania, and in a few other 
ALUMINUM AND BAUXITE 41 

localities of minor importance. Possibly, oil-shale 

deposits of lacustrine origin elsewhere in the world 

have potential for content of dawsonite and other 

sodium carbonate minerals. 

HIGH-ALUMINA CLAYS 

High-alumina clays consisting mainly of kaolinite 

have long been considered as a possible source of 

aluminum. During the World War II emergency, the 

possibilities for extracting alumina from such clays 

were evaluated in pilot plants at Salem, Ore., and 

Harleyville, S. C. Clays of this type were used as a 

source of aluminum in Germany and Japan during 

that war and have been investigated as a source of 

aluminum in Poland, the U.S.S.R., South Africa, and 

elsewhere in recent years. High-alumina clays have 

long been considered by the U.S. Geological Survey 

and the U.S. Bureau of Mines to be the most favorable potential source of aluminum from nonbauxite 

rocks in the United States, because of their high 

aluminum content and their availability. A panel 

of academic and industrial experts in liaison with 

government officials recently r2affirmed this position (National Materials Advisory Board, 1970, 

p. 1). 

High-alumina kaolin and kaolinitic and refractory 

clays having alumina contents of 25-35 percent 

occur at many places in the United States (Patterson, 1967, p. 129-145; U.S. Bureau of Mines, 1967; 

chapter on "Clays"), mainly in sedimentary rocks 

of Pennsylvanian, Cretaceous, and Tertiary ages. 

Though the total resource of clays containing as 

much as 25 percent alumina is extremely large, the 

deposits that realistically can be considered to be 

major potential sources of aluminum are more limited. Those clays which are likely to be used for 

aluminum, if a breakthrough of the use of such 

materials is ever achieved, are likely to have rather 

restrictive characteristics; most particularly they 

will be high in grade, having average alumina contents of approximately 35 percent; and they will 

occur in very large deposits under geologic conditions permitting cheap strip mining and will be on 

lands owned by aluminum companies or on lands 

that can be acquired at a comparatively low cost. 

The principal limitation on the availability of highalumina clay is that most of the large high-grade 

deposits under light overburden are now owned by 

companies producing various grades of kaolin and 

refractory and ceramic clays, and the value of these 

deposits for these uses is greater than for recovery 

of aluminum. 

Areas where high-grade clay in quantities of 50 

million tons are likely to be available include (1) 

deposits associated with bauxite in Arkansas; (2) 

the extensive Georgia kaolin belt; and (3) a belt of 

Eocene clay including the Andersonville district, 

Georgia, and extending northeast and southwest 

from that belt. The total amount of high-alumina 

clay in the United States containing 25 percent 

Al203 or more and under no limits of availability, 

overburden, or mining costs may be as much as 10 

billion tons. 

IGNEOUS ROCKS 

Nepheline syenite and anorthosite are two igneous 

rocks that are potential sources of aluminum. 

Nepheline syenite is a medium- to coarse-grained 

soda-rich rock composed chiefly of nepheline, alkalic 

feldspars, and ferromagnesian minerals. In Arkansas, the alumina content of nepheline syenite ranges 

from 18 to 20 percent. Deposits of nepheline syenite 

occur in many other places in the United States and 

elsewhere in the world. A deposit of nepheline 

syenite in the Kola Peninsula, U.S.S.R., containing 

considerably more alumina than the Arkansas rock, 

has produced metal-grade alumina, fertilizer, fluorine, and cement for several years. A large new plant 

using similar rock in southern Siberia is also reported to be in production. 

Anorthosite, a medium- to coarse-grained igneous 

rock, is composed mostly of plagioclase feldspar and 

contains 23-28 percent alumina. The rock forms 

large intrusive masses of Precambrian age near 

Laramie, Wyo., in California, in New York, and in 

many other localities in the United States and elsewhere in the world. A pilot plant operated in the 

early 1950's by the U.S. Bureau of Mines tested a 

method of recovering metal-grade alumina and 

cement from Wyoming. This work proved alumina 

can be recovered from the rock, but not at currently 

competitive costs. In the summer of 1972, the Aluminum Company of America announced the purchase of a large deposit of anorthosite in Wyoming. 

Neither nepheline syenite nor anorthosite is likely 

to become a source of aluminum in the United States 

in the near future, although both constitute enormous low-grade resources amounting to billions of 

tons. 

SAPROLITE 

Saprolite is a rock whose original minerals are 

replaced by others during weathering but whose 

original textures and structures are preserved. The 

physical and chemical characteristics of these rocks 

are dependent on climate and drainage as well as 

the composition of the parent material. In the United 

States, saprolite deposits are extensive, amounting 
42 UNITED ST ATE.S MINERAL RESOURCES 

to many millions of tons in the Piedmont region 

that extends from southern Virginia through the 

western parts of South Carolina and North Carolina, 

and northern Georgia and into northeastern Alabama. Little is known about the composition of 

these saprolite deposits. Analysis of a few samples 

collected near Shelby, N.C., and Gaffney, S.C., found 

the saprolite to contain 25-36 percent alumina, 

partly in gibbsite but much in very fine grained 

aluminum silicate minerals. Probably much of the 

silica in these rocks would be reactive and deleterious in alumina processing. Other large saprolite 

deposits are associated with the low-grade bauxites 

in Hawaii, Washington, and Oregon. Saprolite also 

occurs at several other localities in the United 

States. 

Saprolite was investigated as a source of aluminum by several major aluminum companies during 

the 1950's. In 1970, large acreages were leased by 

a newly formed company to recover alumina from 

saprolite. 

COAL ASH 

Approximately 50 million tons of ash containing 

8-40 percent alumina is produced by burning coal 

each year in the United States. Coal ash is an 

unlikely present-day source of aluminum because 

sufficient quantities are not generated in any one 

locality, and the ash may have been heated to temperatures that would make the alumina difficult to 

extract. As a long-range resource, however, coal 

ash may have some potential. If future energy requirements necessitate the use of large amounts of 

high-sulfur coal in steam-electric generating plants, 

possibly alumina and sulfuric acid could be recoverable byproducts. 

COPPER-LEACH SOLUTIONS 

Recent consideration has been given to recovering 

alumina from acid solutions used to leach copper 

from mine dumps and low-grade copper deposits 

in the United States (National Materials Advisory 

Board, 1970, p. 57-60). Repeated cycling of these 

solutions increases the alumina content; one copper 

company estimated that the amount of leach solution it circulated daily contains 1,000 tons of alumina. Potential resources of as much as 2,000 tons 

of alumina per day are estimated to be available 

from operations of 14 copper mines in the United 

States. 

PROBLEMS FOR RESEARCH 

On the assumption of a politically stable period 

in the world, it seems likely that the growing demand in the future for aluminum in the United 

States will be met largely by imports. It is anticipated that the current trend of increasing imports 

of alumina and aluminum, rather than of bauxite, 

will continue. This condition could change if methods are developed for economic recovery of aluminum and coproducts from nonbauxite domestic 

sources. High-alumina clay, dawsonite-bearing oil 

shale, and possibly alunite seem to be the most 

promising nonbauxite domestic sources of aluminum. 

Continued research on the geology of bauxite deposits of the world is needed. This research should 

include exploration for additional major deposits, 

particularly in tropical areas, as well as continued 

investigations of the size, depth, thickness, grade, 

composition, impurities, and possible byproducts of 

known foreign deposits. 

New tools and methods to aid in prospecting and 

in the evaluation of bauxite deposits would indeed 

be useful. In the past, in the evaluation of deposits 

no substitute has been found for detailed augering 

or drilling and the analyzing of numerous samples. 

A breakthrough in expediting the analytical workload may have come recently when one company 

introduced a modern semimobile laboratory in the 

Amazon Basin bauxite region (Mining Engineering, 1971). This laboratory is reported to have an 

atomic-absorption spectrophotometer, photoelectric 

colorimeter, and a rotating heat-pressure digestion 

system. Another major aid in exploration may result from a neutron-activation probe developed by 

Allan B. Tanner, Robert M. Moxham, and Frank E. 

Senftle of the U.S. Geological Survey and J. A. 

Baicker of the Princeton Gamma Tech Corporation 

(Tanner and others, 1972). This probe, when lowered down a drill hole, will provide semiquantitative 

determinations of the aluminum in the wallrock. Information on the content of titani urn, iron, and 

other possible metallic byproducts in the bauxite 

might also be obtained by this method. 

Additional research and information are needed 

on domestic potential sources of aluminum and on 

the location, size, grade, and principal mineral and 

impurity contents in several high-alumina clay deposits. Detailed studies of the geology, mining, and 

metallurgy of the dawsonite-bearing oil-shale deposits in Colorado by the U.S. Geological Survey 

and the U.S. Bureau of Mines are continuing. If the 

reported large deposit of alunite in Utah is confirmed, geologic studies of this deposit and similar 

ones in the Western United States would be warranted. Much information related to costs of extracting alumina from non-bauxite materials is also 
ALUMINUM AND BAUXITE 43 

needed. This need is emphasized by the recommendation of the National Materials Advisory Board 

(1970, p. 1) that the U.S. Bureau of Mines, with 

financial help and cooperation of the aluminum producers, should select the best acid process for recovering aluminum from clay and build and operate 

an alumina plant to provide information on costs. 

SELECTED REFERENCES 

Bergquist, H. R., and Overstreet, E. F., 1965, Bauxite deposits of the Margerum district, Alabama: U.S. Geol. 

Survey Bull. 1199-D, 23 p. 

Clark, L. D., 1965, Bauxite deposits of the Springvale district, Georgia: U.S. Geol. Survey Bull. 1199-F, 24 p. 

Cloud, P. E., Jr., 1966, Bauxite deposits of the Anniston, Fort 

Payne, and Ashville areas, northeast Alabama: U.S. 

Geol. Survey Bull. 1199-0, 35 p. 

--- 1967, Geology and bauxite denosits of the Rock Run 

and Goshen Valley areas, northe~st Alabama: U.S. Geol. 

Survey Bull. 1199-N, 74 p. 

Conant, L. C., 1965, Bauxite and kaolin deposits of Mississippi exclusive of the Tippah-Benton district: U.S. Geol. 

Survey Bull. 1199-B, 70 p. 

Corcoran, R. E., and Libbey, F. W., 1956, Ferruginous 

bauxite deposits in the Salem Hills, Marion County, 

Oregon: Oregon Dept. Geology and Mineral Industries 

Bull. 46, 53 p. 

Denson, N. M., and Waage, K. M., 1966, Some bauxite and 

clay deposits in northeastern Alabama: U.S. Geol. Survey Bull. 1199-P, 27 p. 

Dunlap, J. C., Bergquist, H. R., Craig, L. C., and Overstreet, E. F., 1965, Bauxite deposits of Tennessee: U.S. 

Geol. Survey Bull. 1199-L, 37 p. 

DeVoto, R. H., Stevens, D. N., and Bloom, D. N., 1970, 

Dawsonite and gibbsite in the Green River Formation: 

Mines Mag., v. 60, no. 5, p. 17-21. 

Dyni, J. R., 1972, Process for extracting aluminum compounds from dawsonite and dawsonitic oil shale: U.S. 

Patent No. 3,642,433 [assigned to the Secretary of the 

Interior]. 

Engineering and Mining Journal, 1971, Colorado Central 

plans aluminum production from alunite: Eng. and Mining Jour., v. 172, no. 11, p. 172. 

Gordon, MacKenzie, Jr., Tracey, J. I., Jr., and Ellis, M. W., 

1958, Geology of the Arkansas bauxite region: U.S. 

Geol. Survey Prof. Paper 299, 268 p. 

Hite, R. J., 1969, Process for extracting aluminum values 

from oil shale: U.S. Patent No. 3,481,695 [assigned to 

the Secretary of the Interior]. 

Hite, R. J., and Dyni, J. R., 1967, Potential resources of 

dawsonite and nahcolite in the Piceance Creek basin, 

northwest Colorado: Colorado School Mines. Quart., v. 

62, no. 3, p. 25-38. 

Jespersen, Anna, 1964, Aeromagnetic prospecting for bauxite 

deposits in the Mississippi embayment, Arkansas and. 

Missouri: U.S. Geol. Survey Geophys. Inv. Map GP370. 

Kurtz, H. F., 1971, Bauxite: U.S. Bur. Mines Mineral Yearbook 1970, preprint, 13 p. 

Lang, W. B., Warren, W. C., Thompson, R. M., and Overstreet, E. F., 1965, Bauxite and kaolin deposits of the 

Irwinton district, Georgia: U.S. Geol. Survey Bull. 1199-

J, 26 p. 

Livingston, V. E., Jr., 1966, Geology and mineral resources 

of the Kelso-Cathlamet area, Cowlitz and Wahkiakum 

Counties, Washington: Washington Div. Mines and 

Geology Bull. 54, 110 p. 

Loughnan, F. C., and See, G. T., 1967, Dawsonite in the 

Greta Coal Measures at M us.wellbrook, New South 

Wales: Am. Mineralogist, v. 52, p. 1216-1219. 

Mining Engineering, 1971, Alcoa jungle lab in Brazil for 

aluminum exploration: Mining Eng., v. 23, no. 11, p. 6. 

National Materials Advisory Board, 1970, Processes for extracting alumina from nonbauxite ores: Natl. Materials 

Advisory Board Rept. 278, 88 p. 

Overstreet, E. F., 1964, Geology of the southeastern bauxite 

deposits: U.S. Geol. Survey Bull. 1199-A, 19 p. 

Patterson, S. H., 1967, Bauxite reserves and potential 

aluminum resources of the world: U.S. Geol. Survey 

Bull. 1228, 176 p. 

--- 1971, Investigations of ferruginous bauxite and other 

mineral resources on Kauai and a reconnaissance of 

ferruginous bauxite deposits on Maui, Hawaii: U.S. 

Geol. Survey Prof. Paper 656, 7 4 p. 

Smith, J. W., and Milton, Charles, 1966, Dawsonite in the 

Green River Formation of Colorado: Econ. Geology, v. 

61,no. 6,p. 1029-1042. 

Stamper, J. W., 1970, Aluminum, in Mineral facts and problems, 1970: U.S. Bur. Mines Bull. 650, p. 437-462. 

Tanner, A. B., Moxham, R. M., Senftle, F. E., and Baicker, 

J. A., 1972, A probe for neutron activation analysis in 

a drill hole using 252cr, and a Ge(Li) detector cooled 

by a melting cryogen: Nuclear Instruments and Methods 

100, no. 1, p. 1-7. 

Tourtelot, H. A., 1964, Bauxite deposits of the Tippah-Benton 

district, Mississippi: U.S. Geol. Survey Bull. 1199-C, 

31 p. 

U.S. Bureau of Mines, 1967, Potential sources of aluminum: 

U.S. Bur. Mines, Inf. Circ. 8335, 148 p. 

VanNordstrand, R. A., 1968, Process for the recovery of 

aluminum values from retorted shale and conversion of 

sodium aluminate to sodium aluminum carbonate hydroxide: U.S. Patent No. 3,389,975. 

Warren, W. C., Bridge, Josiah, and Overstreet, E. F., 1965, 

Bauxite deposits of Virginia: U.S. Geol. Survey Bull. 

1199-K, 17 p. 

Warren, W .C., and Clark, L. D., 196·5, Bauxite deposits of 

the Eufaula district, Alabama: U.S. Geol. Survey Bul. 

1199-E, 31 p. 

White, W. S., 1965, Bauxite deposits of the Warm Springs 

District, Meriwether County, Georgia: U.S. Geol. Survey Bull. 1199-I, 15 p. 

White, W. S., and Denson, N. M., 1966, Bauxite deposits of 

northwest Georgia, with a section on the Summerville 

area, by J. C. Dunlap and E. F. Overstreet: U.S. Geol. 

Survey Rull. 1199-M, 42 p. 

Zapp, A. D., 1965, Bauxite deposits of the Andersonville district, Georgia: U.S. Geol. Survey Bull. 1199-G, 37 p. 

Zapp, A. D., and Clark, L. D., 1965, Bauxite in areas adjacent to and between the Springvale and Andersonville 

districts, Georgia: U.S. Geol. Survey Bull. 1199-H, 10 p. 

UNITED STATES MINERAL RESOURCES 

ANTIMONY 

By M. H. MILLER 

CONTENTS 

Page 

Abstract of conclusions --------------------------- 45 

Introduction ------------------------------------- 45 

Exploitation ------------------------------------- 46 

Geologic environment ---------------------------- 47 

Geochemistry _______________________ ------ __ _ 47 

Mineralogy ---------------------------------- 47 

Types of deposits ---------------------------- 47 

Resources --------------------------------------- 48 

Identified and hypothetical resources ---------- 48 

Speculative resources ------------------------ 48 

Prospecting techniques --------------------------- 49 

Problems for research ---------------------------- 49 

Selected references ------------------------------- 49 

FIGURE 

Page 

8. Graph showing price and production of antimony 

in the United States, 1916-70 ---------------- 46 

TABLE 

Page 

8. Estimated world resources of antimony --------- 48 

ABSTRACT OF CONCLUSIO~S 

The United States consumes each year about 40 percent 

of the world's supply of primary antimony. Deposits in this 

country furnish only about 15 percent of the antimony consumed, and most of this is recovered as a byproduct from 

silver, copper, and lead-zinc ores, mainly in Idaho, and as 

antimonial lead from lead smelters; most of the antimony 

used is imported from the Republic of South Africa, Mexico, 

and Bolivia. Identified resources in the United States, here 

estimated to be 100,000 short tons, are in Western States, 

mainly Idaho, Nevada, Alaska, and Montana; principal identified world resources, estimated at 5,600,000 short tons, are 

in China, Bolivia, the U.S.S.R., Republic of South Africa, 

and Mexico. Future antimony resources may be developed 

from Mississippi Valley-type lead deposits and from certain 

base-metal deposits in the Eastern United States. The possibility of future production from these sources will hinge 

on the ability of lead smelters to continue operations and 

meet standards set to protect the environment. 

INTRODUCTION 

Antimony is a brittle silver-white metal that has 

a specific gravity of 6.6 and a melting point of 

630.5°C. It imparts strength, hardness, and corrosive resistance to alloys. 

Antimony is marketed as metal, oxide, antimonial 

lead, and sulfide. Metallic antimony is sold under 

brand names ; each brand name commonly represents metal with a guaranteed antimony content, 

and an allowable maximum content of arsenic and 

other minor constituents detrimental to many uses 

of antimony. 

The largest use of antimony in the United States 

is in the manufacture of storage batteries. Automobile batteries contain as much as 12 percent antimony, but most manufacturers now are using 4-6 

percent antimony alloyed with lead. Very high purity antimony metal (99.999+ percent pure) is used 

in intermetallic compounds for semiconductors and 

other chemical applications. Antimony is used as a 

hardening agent in metals used in chemical pumps, 

tank linings, roofing sheets, plumbing fixtures and 

pipes, cable sheaths, foil, and bullets. Antifriction 

bearings, type metal, solder, and decorative castings of Britannia metal and pewter also contain 

antimony. "Antimony black" is finely divided metallic antimony used in bronzing for metals and plaster 

casts. 

Antimony oxides are used in paints and plastics 

as a pigment and fire-retarding agent and in white 

ceramic enamels as an opacifying agent. With suitable stabilizers and coloring additives, antimony 

trioxide glass can be made opaque to all visible 

light except long-wave infrared rays. 

Antimony sulfides are used in the manufacture 

of ammunition primers, smoke generators, visual 

U.S. GEOL. SURVEY PROF. PAPER 820 

45 
46 UNITED STATES MINERAL RESOURCES 

range-finding shells, tracer bullets, and fireworks 

and as a vulcanizing agent in the rubber industry. 

A small amount of antimony sulfide is also used in 

friction matches. 

Organic antimony compounds are used in the 

treatment of certain parasitic diseases. Potassium 

antimonyl tartrate has been used as a nauseant and 

expectorant. 

U.S. consumption of primary antimony was about 

23 percent lower in 1970-71 than during the previous 4-year period. This may reflect consumer resistance to the high price level during 1970, but 

antimony prices in June 1971 were comparable to 

October-November 1969 prices, and prices continued the downtrend during the last half of 1971. 

More than 80 percent of the U.S. smelter output of 

primary antimony is derived from imported antimony ores and concentrates or byproduct antimony 

from foreign lead ores; domestic antimony ores 

account for about 7 percent and byproduct antimony from lead-silver ores accounts for 9 percent 

of the antimony produced. 

Other substances may be substituted for antimony 

in most uses, but substitutes may be in short supply or may be more expensive to use. Substitution 

is restricted by the necessity of making changes in 

production techniques and factory equipment. Mercury, titanium, lead, zinc, chromium, tin, and zirconium may substitute for antimony in paints, pigments, and enamels. Possible substitutes for 

antimony-hardened lead are tin, calcium, and 

dispersion-hardened lead; selected organic compounds have been accepted as alternative materials 

in flameproofing. 

Antimony is a strategic commodity because of its 

important military uses. Concern about future supply of antimony is increased by the dependency of 

the United States on imported ores and concentrates. 

The United States receives about 50 percent of its 

imported antimony ores from the Republic of South 

Africa; Mexico and Bolivia, important suppliers in 

the past, still account for about half the ore imports. 

EXPLOITATION 

Stibnite deposits and occurrences were discovered 

in Nevada as early as the 1860's, and some antimony 

ore was produced as early as 1865. Idaho's production started in the early 1890's. 

Military importance of antimony was first realized 

during World War I; the shortage resulting from 

military uses was eased to some extent by increased 

domestic production and imports from Bolivia. The 

price for antimony dropped from a high of 45 cents 

per pound in 1916 to a low of 4 cents per pound in 

1922. Expanded use of storage batteries in the automobile industry increased antimony consumption 

during the 1930's. (See fig. 8.) World War IIescalated the demand for antimony, and idle domestic 

mines were reopened and foreign mines expanded 

production. Secondary antimony recovered from 

scrap became a major supply source. 

(I) 

z 

0 

IIa: 

~ 5000 

(I) 

~~ ·04000 

~~ 

~~ 

g ~3000 O&L. 

00 

a: 

ll. 

w 2000 

z 

~ 

u; 1000 

:) 

Continued production 

Yellow Pine mine 

World W•r II 

> 

z 

0 

~ 

1-

z 

~ 

1.50 &L.(I) 

Oa: 

o.C: zj 1.00 =>o 20 

a:! 

0.50 :.; 

wC 

0.25 ~t; 

0.06 f~ 

w 

~ 

~ 

a: 

w 

> 

~ 

FIGURE 8.-Price and production of antimony in the United 

States, 1916-70. 

World War II antimony production peaked in 

1943 when U.S. mines produced 5,111 short tons of 

contained antimony, largely from the Yellow Pine 

mine of Idaho. Production peaked again in 1948 at 

the all-time high total from U.S. mines of 6,489 

short tons of contained antimony, again largely from 

the Yell ow Pine mine. This production peak reflects 

the continued production of antimony at the Yellow 

Pine mine after the high-grade tungsten-antimony 

ore was exhausted. In 1951, domestic production 

attained a minor peak of 3,472 short tons of contained antimony, probably paralleling increased 

military needs during the Korean War. Thus, the 

three production peaks occurred during one 10-year 

period, 1942-52. 

The price for imported antimony metal, at New 

York, reached a high of $4 per pound early in 1970, 

and the price for imported ore and concentrates, 60 

percent antimony, topped at $43-$45 per long-ton 

unit in June 1970. Peak prices of RMM ($1.76 per 

lb) and Lone Star ($1.77 per lb) metals produced 

I 

by NL Industries, Inc., at Laredo, Tex., were reached 

in April 1970, and they held at that level through 

August 1970. Production from mines in the United 
ANTIMONY 47 

States rose from 938 short tons of contained antimony in 1969 to 1,130 short tons in 1970 and then 

dipped to 992 short tons in 1971. In 1969, U.S. 

smelter production was 13,203 short tons of contained antimony as compared to 13,381 short tons 

in 1970 and 13,157 short tons in 1971. These statistics indicate that the amount of antimony mined in 

the United States and that produced by U.S. 

smelters are not greatly affected by price fluctuations. Mines reopened primarily for antimony could 

not reach a production stage soon enough to take 

advantage of the higher prices. Price levels during 

the first quarter of 1972 approximated those of the 

third quarter of 1969. 

Although antimony is toxic when taken internally, 

its production alone probably would not constitute 

a hazard to the environment. Lead smelters, where 

antimonial lead is recovered, may be detrimental to 

the environment, and many smelters cannot meet 

present-day emission standards. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

The abundance of antimony in the earth's crust 

ranges from 0.2 to 0.5 ppm (parts per million). In 

igneous rocks the abundance is 0.1-1 ppm. According to Vinogradov (1962), basalts contain the highest percentage of antimony, and Turekian and 

Wedepohl (1961) found that deep-sea clays contain 

1 ppm antimony. 

The chemical and physical properties of antimony 

are similar to those of arsenic and bismuth. Antimony is chalcophile in distribution and combines 

readily with sulfur and the preferred heavy metals 

lead, copper, and silver. Metallic minerals found in 

association with primary antimony minerals are 

pyrite, galena, sphalerite, chalcopyrite, arsenopyrite, pyrrhotite, gold, and silver; the common 

gangue minerals are quartz (predominantly), calcite, and barite. 

The amount of antimony found distributed 

through sedimentary rocks is very small, and the 

changes that anitmony undergoes in the weathering 

process are obscure. Antimony, like arsenic, tends 

to be concentrated in hydrolyzates, chiefly by adsorption on ferric hydroxide. Although the antimony 

content of sea water is beyond limits of detection 

by most analytical methods, small amounts have 

been reported in some marine animals and in ashes 

of seaweeds. Although data are lacking, it seems 

likely that during metamorphism much antimony in 

stibnite is quickly remobilized and moved through 

and into fissures, fractures, and brecciated zones, 

again forming low-temperature hydrothermal deposits. 

MINERALOGY 

Stibnite, Sb2S3, is the predominant ore of antimony; next in importance are valentinite, Sb203; 

senarmontite, Sb203; stibiconite, Sb204 · H20; bindheimite, Pb2Sb201 · nH20; and kermesite, 2Sb2S3 

· Sb203. Tetrahedrite, Cu8 Sb2S7, has become an important antimony ore, and jamesonite, Pb2Sb2S5, has 

been mined from deposits at Zimapan, Hidalgo, 

Mexico; Candelaria, Nev. ; and the Arabia district, 

Nevada. 

TYPES OF DEPOSITS 

Antimony occurs in a variety of deposits-epithermal veins, pegmatites, and replacement and hotspring deposits. Deposits of antimony range in age 

from Precambrian to Quaternary. Wang (1952, p. 

6-10) showed a rather complex classification of 

worldwide antimony deposits; White (1951; 1962) 

classified world deposits into two types, with gradations between these types ; one of these is mineralogically and structurally simple and the other 

complex. 

Simple antimony deposits consist principally of 

stibnite, or rarely, native antimony in a siliceous 

gangue, commonly with some pyrite and in places 

a little gold and small amounts of other metal sulfides, principally silver and mercury. The "manto" 

deposits of Mexico are of the simple type and consist of selective replacements of favorable limestone 

beds, generally overlain by shale. Most stibnite of 

the hypogene deposits is oxidized to one or more 

of the antimony oxides. Most deposits of Mexico, 

Bolivia, Peru, China, Republic of South Africa, 

Yugoslavia, Algeria, Hungary, Czechoslovakia, 

Italy, and Japan are of the simple type. 

Complex antimony deposits consist of stibnite 

associated with pyrite, arsenopyrite, cinnabar, or 

scheelite or of antimony sulfosalts with varying 

amounts of copper, lead, and silver as well as the 

common sulfides of these metals and zinc. Ores of 

the complex deposits generally are mined primarily 

for lead, gold, silver, zinc, or tungsten. Most of the 

antimony produced in the United States, Australia, 

and Canada is from complex deposits. 

Neither the simple antimony deposits nor the 

complex ones can be said to have affinity for a specific rock type, U.S. deposits range in age from Precambrian to Tertiary (White, 1962). Although many 

U.S. deposits are of Tertiary age, equally as many 

are of Mesozoic age, and about one-fifth of the deposits are of Paleozoic age. Deposits closely asso-
48 UNITED STATES MINERAL RESOURCES 

ciated with Mesozoic or Tertiary igneous rocks are 

about equally divided between dikes and lava flows 

and coarse-grained intrusive rocks, commonly granodiorite or quartz monzonite. The often-held view 

that antimony deposits are of Tertiary age and volcanic association is an oversimplification. 

Most antimony produced in the United States 

comes from the complex deposits, as a byproduct 

of the treatment of silver, lead, copper, and zinc 

ores. The deposits in the Coeur d'Alene district, 

Idaho, are outstanding examples of complex deposits. In the Yellow Pine district, Valley County, 

Idaho, another example of an area of complex ores, 

gold and tungsten were the principal metals, but 

with a high enough price antimony outvalues the 

other metals. For detailed information about specific U.S. deposits, see White (1951; 1962). 

Most antimony deposits presumably formed from 

hydrothermal solutions at relatively low temperature and shallow depth, which gave rise to filled 

fissures, joints, and irregular replacement masses. 

In places, antimony is disseminated through the 

wallrock alteration zone. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Estimated identified and hypothetical resources 

are summarized in table 8; these estimates are 

based on sparse data in files of the U.S. Geological 

Survey and a few published sources of information 

on the occurrence of antimony as a relatively minor 

constituent in ore deposits of major metals. Approximately 25 percent of the known U.S~ antimony resources is in scattered simple-type deposits, which 

are not of economic importance unless the p:fice for 

TABLE 8.-Estimated world resources of antimony, in short 

tons of metal 

[Figures are modified from data compiled by U.S. Bureau of Mines ex· cept where otherwise noted] 

Country 

United States ---------------- M,exico ---------------------- Bolivia ---------------------- Yugoslavia ------------------

Turkey ---------------------- Republic of South Africa ------

U.S.S.R. --------------------- China ----------------------- Thailand --------------------- Australia --------------------

Identified 

resources 1 

100,000 

200,000 

420,000 

100,000 

120,000 

300,000 

300,000 

3,800,000 

110,000 

150,000 

World total ------------ 5,600,000 

Hypothetical 

resources 2 

3 100,000 

1,500,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions 2 Hypothetical resources: Undiscovered mineral deposits, whether of 

recoverable or subeconomic grade, that are geologically predictable as existing in known districts. a Based on unpublished data in files of U.S. Geological Survey. 

ore or concentrates would triple or quadruple and 

stabilize at that level. Although 25 percent of the 

U.S. antimony resources is contained in the Yellow 

Pine district, little antimony has been produced since 

the Yellow Pine mine was closed in 1952. Ranchers 

Exploration and Development Corporation leased 

the Yell ow Pine mine and carried out a diamonddrilling program in 1970, but there is no indication 

that any ore was produced (B. F. Leonard, oral 

commun., 1972). At least 50 percent of the U.S. antimony resources is contained in known complex 

lead-silver-copper and gold ores. 

During the last 40 years, about four-fifths of U.S. 

mine production of antimony has come from Idaho. 

Reserves of ore in the Coeur d'Alene district are 

considered adquate for continuous operations for 

many years. 

The Fairbanks district, , Alaska, has produced 

about 2,500 tons of stibnite ore, and since 1936, 

when it began operations, the Stampede mine in the 

Kantishna district, Alaska, has produced about 2, 700 

tons of stibnite ore. About 75 percent of Alaska's 

antimony was produced before World War II. From 

1960 to 1971, about 100 tons of antimony was produced from Alaskan deposits, mainly the Stampede 

mine. Known Alaskan resources are estimated as 

nearly 10,000 tons of low-grade material (Berg 

and others, 1964). 

On the basis of scattered analyses, it is estimated 

that lead ores in southeastern Missouri, the TriState district, and the Upper Mississippi Valley may 

contain as much as 50,000 tons of antimony, here 

considered as a hypothetical resource. So far as is 

known, no antimony is now being recovered from 

these ores. 

SPECULATIVE RESOURCES 

Potential resources of antimony that may be 

mined in the future are tied directly to lead-silvercopper-zinc deposits like those from which most 

domestic antimony is recovered as a byproduct or 

coproduct. 

Antimony is present in some galenas from Mississippi Valley-type lead deposits (Allen Heyl, oral 

commun., 1972), and antimony is a constituent of 

some base-metal deposits in the Eastern United 

States. Apparently, fringe areas of some mineralized 

zones, such as in Nevada, show anomalous amounts 

of antimony; potential resources possibly exist 

there. When the United States can no longer import 

antimony in quantities to meet the needs, some additional domestic production may be obtainable from 

these base-metal deposits and from areas of known 

base-metal, tungsten, silver, and gold mineralization. 
ANTIMONY 49 

PROSPECTING TECHNIQUES 

Historically, very little prospecting has been directed solely toward antimony; probably most was 

incidental to prospecting for gold, silver, lead, or 

copper. In some instances, although antimony was 

not detected in sulfides or oxides of certain metal 

deposits, antimony has been recovered during smelting of the ores. Where antimony is recognized, 

prospectors have searched successfully for extensions of known deposits and for other deposits in 

or near known occurrences. 

Geochemical methods of determining antimony in 

soils and rocks have been tested in the laboratory 

and under field conditions (Ward and Lakin, 1954; 

Jardine, 1963; Ward and others, 1963). The field 

method described by Ward and Lakin (1954) was 

used successfully by Sainsbury (1957) in geochemical exploration for antimony in Alaska. 

PROBLEMS FOR RESEARCH 

Detailed geologic studies of the occurrence of 

antimony-bearing minerals in known deposits, especially those minerals in which antimony substitutes 

for another element, would broaden our base of 

knowledge and enhance the possibility of delineating areas that contain additional antimony resources. 

SELECTED REFERENCES 

Bailey, E. H., and Myers, W. B., 1942, Quicksilver and antimony deposits of the Stayton district, California: U.S. 

Geol. Survey Bull. 931-Q, p. 405-434. 

Berg, H. C., Eberlein, G. D., and MacKevett, E. M., Jr., 1964, 

Metallic and nonmetallic mineral resources-Metallic 

mineral resources, in Mineral and water resources of 

Alaska: U.S. 88th, Gong., 2d sess., p. 95-125. 

Brooks, D. B., 1965, Supply and competition in minor metals: 

Baltimore, Johns Hopkins Press (for Resources for the 

Future), 147 p. 

Colson, J. S., 1961, The geology of the Sunshine mine, in 

Guidebook to the geology of the Coeur d'Alene mining 

district: Idaho Bur. Mines and Geology Bull. 16, p. 

30-34. 

Cooper, J. R., 1951, Geology of the tungsten, antimony and 

gold deposits near Stibnite, Idaho: U.S. Geol. Survey 

Bull. 969-F, p. 151-197. 

Day, F. H., 1963, The chemical elements in nature: New 

York, Reinhold Pub. Corp., 372 p. 

Dickson, F. W., and Tunell, George, 1968, Mercury and antimony deposits associated with active hot springs in the 

Western United States, in Ore deposits of the United 

States, 1933-1967 (Graton-Sales Volume), v. 2: New 

York, Am. Inst. Mining, Metall., and Petroleum Engineers, p. 1673-1701. 

Erickson, R. L., and Marsh, S. P., 1971, Geochemical, aeromagnetic, and generalized geologic maps showing distribution and abundance of antimony and tungsten, 

Golconda and Iron Point quadrangles, Humboldt County, 

Nevada: U.S. Geol. Survey Mineral Inv. Field Studies 

Map MF-313 [1972]. 

Fryklund, V. C., Jr., 1964, Ore deposits of the Coeur d'Alene 

district, Shoshone County, Idaho: U.S. Geol. Survey 

Prof. Paper 445, 103 p. 

Hall, W. E., and Heyl, A. V., 1968, Distribution of minor 

elements in ore and host rock, Illinois-Kentucky fluorite 

district and Upper Mississippi Valley zinc-lead district: 

Econ. Geology, v. 63, p. 655-670. 

Hausen, D. M., and Kerr, P. F., 1968, Fine gold occurrence at 

Carlin, Nevada, in Ore d·eposits of the United States, 

1933-1967, (Graton-Sales Volume), v. 1: New York, 

Am. Inst. Mining, Metall., and Petroleum Engineers, p. 

908-940. 

Hobbs, S. W., Griggs, A. B., Wallace, R. E., and Campbell, 

A. B., 1965, Geology of the Coeur d'Alene district, Shoshone County, Idaho: U.S. Geol. Survey Prof. Paper 

478, 139 p. 

Jardine, M. A., 1963, Field and laboratory methods used by 

the Geological Survey of Canada in geochemical surveys 

-No. 4, a laboratory method for determining antimony 

in soils and rocks: Canada Geol. Survey Paper 63-29, 

11 p. 

Lawrence, E. F., 1963, Antimony deposits of Nevada: Nevada 

Bur. Mines Bull. 61, 248 p. 

Lessemann, R. H., 1965, The changing pace and pattern in 

the business of mining-antimony: Eng. and Mining 

Jour., v. 166, no. 2, p. 129-132. 

Li, K. C., 1953, Arsenic and antimony, Chap. 3 in Mathewson, 

C. H., ed., Modern uses of nonferrous metals [2d ed.]: 

New York, Am. Inst. Mining Metall. Engineers, p. 40-

53. 

Oiwa, Yasushi, Nordquist, C. G., and Lentz, 0. H., 1961, 

Antimony and tin, Chap. 9 in Mineral industries of Japan 

and southeast Asia: Colorado School Mines Quart., v. 

56,no.4,p. 295-302. 

Paone, James, 1970, Antimony, in Mineral facts and problems, 1970: U.S. Bur. Mines Bull. 650, p. 463-477. 

Parker, R. L., 1967, Composition of the Earth's crust, in 

Data of geochemistry [6th ed.]: U.S. Geol. Survey Prof. 

Paper 440-D, 19 p. 

Purdy, C. P., Jr., 1951, Antimony occurrences of Washington: Washington Dept. Conserv. Devel., Div. Mines and 

Geology Bull. 39, 186 p. 

Rankama, Kalervo, and Sahama, Th. G., 1950, Geochemistry: 

Chicago, Univ. Chicago Press, 911 p. 

Sainsbury, C. L., 1957, A geochemical exploration for antimony in southeastern Alaska: U.S. Geol. Survey Bull. 

1024-H, p. 163-178. 

Stafford, J. B., ed., 1970, Antimony profile, in Metal statistics, 

1970: New York, Am. Metal Market Co., p. 81-85. 

Turekian, K. K., and Wedepohl, K. H., 1961, Distribution of 

the elements in some major units of the earth's crust: 

Geol. Soc. America Bull., v. 72, p. 175-192. 

Vinogradov, A. P., 1962, Average contents of chemical elements in the principal types of igneous rocks of the 

earth's crust: Geokhimiya, no. 7, p. 555-571 (in Russian); translation in Geochemistry, no. 7, p. 641-664. 

Ward, F. N., and Lakin, H. W., 1954, Determinations of 

traces of antimony in soils and rocks: Anal. Chemistry, 

v. 26, no. 7, p. 1168. 

Ward, F. N., Lakin, H. W., Canney, F. C., and others, 1963, 
50 UNITED STATES MINERAL RESOURCES 

Analytical methods used in geochemical exploration by 

the U.S. Geological Survey: U.S. Geol. Survey Bull. 

1152, 100 p. 

Wang, C. Y., 1952, Antimony-its geology, metallurgy, industrial uses and economics: London, Charles Griffin 

and Co., 170 p. 

White, D. E., 19-40, Antimony deposits of a part of the 

Yellow Pine district, Valley County, Idaho: U.S. Geol. 

Survey Bull. 922-I, p. 247-279. 

--- 1951, Antimony resources of the world, Chap. 3 of 

Materials survey, antimony: U.S. Bur. Mines, 57 p. 

--- 1962, Antimony in the United States, exclusive of 

Alaska and Hawaii: U.S. Geol. Survey Mine'l'al Inv. Resource Map MR-20, scale 1:3,168,000. 
UNITED STATES MINERAL RESOURCES 

ARSENIC 

By J. L. GUALTIERI 

CONTENTS 

Page 

Abstract of conclusions -------------------------- 51 

Introduction ------------------------------------- 51 Exploitation _ ___ __ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ __ __ _ _ __ ___ 52 

Geologic environment ----------------------------- 52 

Geochemistry -------------------------------- 52 

Minerals ------------------------------------ 53 

Types of deposits --------------------------- 53 

Enargite-bearing copper-zinc-lead deposits _ 53 

Ars.enical pyritic copper deposits ---------- 54 

Native silver and nickel-cobalt arsenide deposits --------------------------------- 55 

Arsenical gold deposits ----------------------- 55 

Arsenic sulfide and arsenic sulfide gold deposits__ 56 

Arsenical tin deposits ------------------------ 57 

Other deposits ------------------------------- 58 

Resources --------------------------------------- 58 

Identified and hypothetical resources ----------- 58 

Sp·eculative resources ------------------------ 59 

Prospecting techniques --------------------------- 60 

Problems for research ---------------------------- 60 

Selected references ------------------------------- 60 

TABLES 

Page 

9. World identified and hypothetical resources of 

arsenic ----------------------------------- 58 

10. Types of arsenic deposits of the world --------- 59 

ABSTRACT OF CONCLUSIO~S 

Arsenic is used mostly in agriculture, where it is employed 

as an insecticide, pesticide, and herbicide. It has limited use 

in industry as an alloying agent and a chemical reagent. 

Current domestic consumption of ars·enic is about 20,000-

30,000 short tons per year, but domestic production fills only 

about a tenth of this. The rest is mostly supplied by other 

countries of the free world, chiefly Sweden, France, and 

Mexico. 

Arsenic is produced as a byproduct and occurs in several 

types of deposits: enargite-bearing copper-zinc-lead deposits, 

arsenical pyritic copper deposits, native silver and nickelcobalt arsenide deposits, arsenical gold deposits, arsenic sulfide and arsenic sulfide gold deposits, and arsenical tin deposits. 

U.S. and world identified resources of arsenic are herein 

estimated to be 1,300,000 short tons and 17,600,000 short 

tons, resp·ectively; these resources are more than sufficient 

to fill projected needs until the year 2000. Hypothetical resources for the United States and the world are estimated 

at 650,000 short tons and 14,300,000 short tons, respectively. 

Speculative resources of arsenic are estimated to be 10 

million short tons. Arsenic may be obtainable from organic 

shale of marine origin; where such shale is subjected to 

tectonic and metamorphic processes, contained metals may 

migrate to and concentrate in favorable structures. 

INTRODUCTION 

Elemental arsenic in its most stable form is a 

silver-gray metalloid, moderately hard but brittle 

and having a specific gravity of about 5.73. It rarely 

occurs naturally in its native state. 

Arsenic is chemically allied to a group of elements 

which includes nitrogen, phosphorus, antimony, and 

bismuth; but it is physically more like antimony and 

bismuth, which also have metallike qualities. 

Arsenic is important because of its toxic effect on 

living matter; its principal use is in agriculture 

where arsenic compounds function as insecticides, 

pesticides, and herbicides. Arsenic acid is used as 

a defoliant or dessicator to facilitate the mechanical 

harvesting of cotton. Organic arsenic compounds are 

used to control or to kill undesirable grasses and as 

parasite control agents in poultry and livestock. 

Other arsenic compounds are used as wood preservatives. 

Uses of arsenic in industry are minor compared 

with those in agriculture. Arsenic is used as a decolorizer in the manufacture of glass, and arsenic 

compounds are used as pigments in some enamels 

and as reagents in flotation processes for separating minerals. 

Metallurgically, arsenic is used as a hardener for 

lead in bearing metal, battery plates, and shot. It is 

U.S. GEOL. SURVEY PROF. PAPER 820 

51 
52 UNITED STATES MINERAL RESOURCES 

also alloyed with copper to give increased corrosion 

and erosion resistance and a higher annealing temperature. 

Potential uses of arsenic include the manufacture 

of gallium arsenide or gallium arsenide phosphate 

diodes, improved lead-antimony or lead-tin-antimony 

alloys, catalysts used in the formation of some 

organic compounds, and nucleating agents in 

ceramic manufacture. The potential uses of the element, however, are not expected to increase its 

consumption appreciably. 

Arsenic and arsenic compounds are important to 

the production of certain crops in countries that 

have developed advanced agricultural technologiesthe United States, Canada, the countries of western 

Europe, Australia, and New Zealand, and to a lesser 

degree, the U.S.S.R. and the countries of eastern 

Europe. Industrial-technological-scientific societies 

have developed only where manpower has been freed 

from the production of foods and textiles. The initial increases in agricultural productivity resulted 

from mechanization; later increases resulted from 

the use of chemical fertilizers and improved seed; 

and more recent increases resulted from the use of 

insecticides, pesticides, and herbicides. Insecticides, 

pesticides, and herbicides play an important role in 

achieving the standard of living now enjoyed by the 

advanced nations, and they undoubtedly will play an 

increasing role in advancing the standard of living 

of the emerging nations. 

Substitutes have been sought for arsenic compounds, not because arsenic is in short supply or is 

exepnsive, but because it is toxic to humans. In place 

of inorganic arsenic compounds, a group of chlorinated hydrocarbons and organic phosphorous compounds have been developed which are claimed to 

have lower toxicities for humans. Substitutes for 

arsenic used in industrial and metallurgical processes may in part be met by the chemically allied 

metalloids antimony and bismuth. 

Domestic consumption of arsenic fluctuates from 

about 20,000 to about 30,000 short tons per year. 

An estimate for 1968 shows that the United States 

consumed or stocked the equivalent of 26,200 short 

tons of arsenic. Of this amount, 2,900 tons (11 percent) came from domestic sources and 23,300 tons 

(89 percent) came from foreign sources, either in 

arsenic metal and compounds or in ores and concentrates. Of the imports, Sweden supplied 37 percent, Mexico 28 percent, and France 26 percent. 

Only about 40 tons (about 0.2 percent) came from 

the Communist world, although in 1967 shipments 

from this source exceeded 1,000 tons. 

The domestic output of arsenic is insufficient to 

meet current demand, although the United States 

has both the sufficient arsenic resources and the 

production facilities to meet demand. The increasing reliance on foreign sources, which has taken 

place over the last 25 years, is chiefly due to economics. 

EXPLOITATION 

Arsenic, because it is recovered as a byproduct, 

has had a history of exploitation different from that 

of most other commodities. It is removed from various ores during smelting, but its output is dependent 

upon several factors, including size, grade, and type 

of deposits, availability of smelter facilities, and 

price policies at custom smelters. Arsenic-rich segregates are refined at smelters with facilities for 

doing so. Where facilities are lacking or are idle, 

the segregates are stockpiled and shipped to other 

processing plants. Supplies have normally exceeded 

requirements and can be increased when necessary 

by activiating idle processing plants to recover 

arsenic from ores not ordinarily so treated. 

Significant arsenic production started around 

1900 and has increased steadily since then. Arsenic 

first was produced from arsenical gold deposits and 

later from other types of deposits. The arsenic-rich 

Boliden cooper deposit in Sweden started producing 

in 1926 and in large part made Sweden the world's 

foremost producer of arsenic. 

Environmental problems resulting from exploitation of arsenic-bearing deposits are similar to those 

of other deposits. Access roads, mining, milling, 

and smelting and the disposal of overburden material, waste rock, mill tailings, and slag all tend to 

disturb the original environment of any area. At 

best these disturbances can only be minimized, and 

then at some cost. With the final cessation of mining and allied activity, some operational areas can 

be restored to approximate original conditions but 

at considerable cost. 

Where arsenic in sulfide minerals is exposed to 

the atmosphere, as in the waste dumps of mines, 

soluble arsenates may be formed which can be a 

source of stream pollution. Smelters which treat 

arsenical sulfide ores can lose arsenic to the atmosphere in the form of arsenic oxides or arsine, 

AsH:~, although most of the arsenic volatilized in 

smelting and roasting forms a fine ash or dust which 

is arrested in the smelter stacks or Cottrell precipitators. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Arsenic is a relatively rare crustal element, con-
ARSENIC 53 

stituting about 2 ppm (parts per million) of igneous rocks (Onishi and Sandell, 1955) but 60 ppm 

or more of magmatic sulfide minerals (Ran kama and 

Sahama, 1950, p. 739). Geochemically, arsenic is 

similar to antimony and bismuth. All three elements 

combine with sulfur, selenium, and tellurium. They 

form sulfosalts, arsenides, and antimonides with 

var!ous heavy metals and show a preference for 

combining with copper, iron, nickel, and cobalt. 

Some sulfide ores contain varying amounts of 

arsenic, antimony, and bismuth. Research on the 

mineralogy of these elements is incomplete ; their 

presence has been established only in galena. 

Arsenic occurs sparingly in the early and main 

stages of magmatic crystallization. Early magnetite 

and hematite contain little arsenic, and although the 

early magmatic sulfide minerals contain relatively 

large amounts, the late magmatic sulfides are 

strongly enriched. Arsenic first occurs as a distinct 

mineral (arsenopyrite) during the pegmatitic stage, 

but in most minerals it develops in the pyrometasomatic and hydrothermal stages of magmatism. 

Arsenic tends to precipitate in extremely fine 

grained sedimentary materials that are made up of 

chemically undecomposed comminuted rock and 

insoluble rock residues derived through hydrolytic 

decomposition. It is especially concentrated in sediments that contain relatively large quantities of 

iron and manganese oxides, principally by adsorption on ferric hydroxide. Whereas as little as 4 ppm 

arsenic is found in bottom sediments of the Atlantic 

Ocean, as much as 65-650 ppm is found in ancient 

sedimentary iron ores. It is driven from iron-rich 

sediments through metamorphic processes. Arsenic 

is also precipitated with pyrite that was formed in 

carbonaceous oozes. More than 3,000 ppm of arsenic 

is reported in sedimentary pyrite. 

Arsenic forms the anion AsO.u which is isomorphous with the anion P04; consequently, arsenates substitute for phosphates and are present in 

both marine organisms and phosphate deposits. A 

small part of the arsenic in marine environments, 

however, escapes precipitation and remains in solution, possibly as an arsenite. 

MINERALS 

Arsenic occurs in more than two dozen minerals, 

but only a few are commonly found in ore deposits. 

The primary arsenic minerals are arsenopyrite 

(FeAsS), lollingite (FeAs2 ), smaltite (CoAsz), 

chloanthite (NiAsz), niccolite (NiAs), tennantite 

(Cu~-<AszS.-), enargite (Cu:~AsSJ, and proustite 

(Ag8AsS3). 

The supergene arsenic minerals are arsenolite 

(Asz03), mimetite (PbCl· Pb4As3012), olivenite 

( Cu3Asz0s · Cu ( 0 H) z) , realgar (AsS) , orpiment 

(AszO:J, scorodite (FeAs04 ·2Hz0), and pearceite 

(Ag9AsSs). 

TYPES OF DEPOSITS 

No ore deposit is currently being mined solely 

for arsenic, although in the past, a few deposits high 

in arsenic were so mined for brief periods. Arsenic 

occurs in various types of metalliferous deposits 

which are classed in their approximate order of 

importance on the basis of estimated past production. They are as follows : 

1. Enargite-bearing copper-zinc-lead deposits 

2. Arsenical pyritic copper deposits 

3. Native silver and nickel-cobalt arsenide deposits 

4. Arsenical gold deposits 

5. Arsenic sulfide and arsenic sulfide gold deposits 

6. Arsenical tin deposits 

7. Other deposits 

ENARGITE-BEARI~G COPPER-ZINC-LEAD DEPOSITS 

Enargite-bearing copper-zinc-lead deposits occur 

almost exclusively in orogenic belts in areas characterized either by granitic bodies or by volcanic 

rocks including vent deposits and mafic dikes and 

sills. Host rocks, in addition to granitic and volcanic rocks, include metasedimentary rocks of clastic 

origin and rarely carbonate rocks. 

Enargite-bearing copper-zinc-lead deposits have 

complex mineralogies. This is due in part to repetitive episodes of dissimilar mineralization, in part to 

supergene alteration, and in part to the location of 

some deposits in extremely arid climates where 

otherwise soluble minerals are stable. 

The more important minerals characteristic of 

the ores are enargite-famatinite, tetrahedrite, and 

pyrite, with quartz gangue; enargite-famatinite 

with native bismuth, argentian galena-sphalerite, 

tetrahedrite, pyrargyrite, and stephanite, with 

pyrite gangue; pyrite, enargite, tennantite, bornite, 

chalcocite, sphalerite, and a little chalcopyrite and 

covellite; and pyrite, chalcopyrite, sphalerite, galena, 

and lesser amounts of tetrahedrite and enargite. 

Supergene chalcocite is important in those deposits 

where near-surface copper was oxidized, leached, 

and redeposited at depth. In the oxidized zones of 

some deposits, native silver is important. 

Enargite is the only important arsenic-bearing 

mineral; arsenolite and scorodite are present in the 

oxidized zone of some deposits but are sparse. 

The deposits occur in veins and in massive blanket 

or lensoidal bodies. Vein deposits occur in sets of 

fractures or faults; some of the faults were active 
54 UNITED STATES MINERAL RESOURCES 

during mineralization. The evins may be hundreds 

to thousands of feet long, as much as several tens 

of feet thick, and widely spaced, or they may be 

relatively short, thin, and closely spaced. The veins 

are commonly curvilinear and from place to place 

change in strike and dip; some veins split to form 

one or more additional veins. 

The massive deposits occur in lenticular bodies 

measuring hundreds to thousands of feet in width 

and length and as much as 200 feet thick; they conform to controlling structures such as bedding and 

to the contacts between rock units. The vein deposits are structurally controlled, although most occur 

in granitic rock. They are in multiple sets of small 

faults or fractures, some of which may have been 

guided along a preexisting structural grain. Preferred mineralization of one set of fractures or 

faults over another may be due to availability of 

openings during the mineralization process. 

Some massive bodies measuring hundreds of feet 

in length and width occur along or associated with 

major faults. The Cerro de Pasco deposit of Peru is 

located along a thrust fault of regional extent, but 

the significance of the fault as a controlling factor 

is unknown. The upper plate is mineralized and 

encloses manto-type sulfide deposits. 

Enargite-bearing copper-zinc-lead deposits are 

among the largest ore deposits known. The deposit 

at Butte, Mont. (Meyer and others, 1968, p. 1395-

1403), from 1880 to 1964 produced 318,234,680 

pounds of arsenic compounds, although arsenic was 

not recovered during all this period. The tenor of 

mined copper over this period was about 21;2 percent; that of arsenic is estimated to have been about 

0.1 percent. Some of the other deposits of this type 

are, or will be when fully developed, comparable in 

size and tenor. 

Other important deposits are Chuquicamata, Chile 

(Taylor, 1935, p. 473-484), Cerro de Pasco (McLaughlin and others, 1935, p. 517-527) and Morococha, Peru (Graton and others, 1935, p. 528-544), 

and Lepanto, Republic of the Philippines (Kinkel 

and others, 1956). 

Enargite-bearing vein deposits are generally 

thought to be hydrothermal in origin and to have 

been derived from adjacent granitic plutons. 

The massive deposits were long considered to be 

sedimentary-syngenetic veins or lodes that were 

deposited by ascending solutions or by hydrothermal 

replacement of crushed or sheared zones. More recently, they have been considered to be of volcanicsyngenetic origin and to have been produced by 

base-metal-rich sulfide emanations emitted during 

submarine volcanism (Anderson, 1969). 

ARSENICAL PYRITIC COPPER DEPOSITS 

Arsenical pyritic copper deposits occur in Precambrian terranes associated with metasedimentary 

and metavolcanic rocks, in Precambrian magmatic 

granite, and in orogenic belts with carbonate rock. 

Host rocks include rhyolite or tuffaceous schist, biotite schist, chlorite or chlorite-sericite schist, andalusite, sericite schist, conglomerate, calcareous breccia, and limestone. 

The. metallic minerals include pyrite, chalcopyrite, 

pyrrhotite, arsenopyrite, sphalerite, galena, pyrargyrite, tetrahedrite or tennantite, and native gold; 

gangue minerals include quartz, tourmaline, dolomite, ankerite, and sericite. Bismuth minerals are 

present in some deposits. Arsenopyrite and tennantite are the only arsenic-bearing minerals; arsenopyrite occurs sparingly or abundantly and is either 

evenly distributed or concentrated in nodular 

masses; tennantite, although more evenly distributed 

in deposits in which it is present, is very minor. 

Arsenical pyritic copper deposits occur in massive 

tabular or lenticular bodies as much as several 

hundreds of feet long and at least 100 feet thick, 

or in pipelike masses several hundred feet in diameter and thousands of feet in vertical extent. Some 

deposits of this type seem to be controlled by steeply 

dipping shear zones or drag folds. They also occur 

consistently at or near the contacts of rock units. 

Deposits in foliated rocks follow the grain of the 

schistosity, a feature preserved in the ore; fractured or brecciated textures that were formed during mineralization are also displayed in the ore. 

The size of the deposits ranges from a few hundreds of tons to millions of tons. The Boliden mine 

of Sweden, now exhausted, produced 8,341,550 

metric tons of ore which contained 556,000 metric 

tons (620,000 short tons) of arsenic, an average of 

6.91 percent, in addition to 1.42 percent copper, 15.2 

grams per metric ton of gold, and 49 grams per 

metric ton of silver. Other deposits of this type 

which contained more copper (5-6 percent) contained only a fraction of 1 percent arsenic. 

In addition to the Boliden deposit (Grip and 

Wirstam, 1970), examples of this type include the 

Rammelsberg deposits in the Federal Republic of 

Germany (Lindgren and Irving, 1911), the United 

Verde mine in the Jerome area of Arizona (Lindgren, 1926, p. 32-35, 61-78; Anderson and Creasey, 

1958, p. 92), and several deposits on the island of 

Honshu, Japan (Kanehara, 1935, p. 688). 

Arsenical pyritic copper deposits have been considered epigenetic and to have formed by replacement; those in schistose rock, for example, display 

relic foliation inherited from the host. The miner-
ARSENIC 55 

alizing solutions were thought to be hypothermal, 

although no deposit could be traced with certainty 

to a magmatic source. More recently, the supracrustal host rocks appear to be the source of the 

metals ; the metals, mobilized by deep-level granitization, moved ahead of a migmatite front to accrete 

in favorable host structures or strata (Grip, 1960, 

p. 3-14) . A volcanic-syngenetic origin also has been 

suggested for deposits of this type. 

NATIVE SILVER AND NICKEL-COBALT 

ARSENIDE DEPOSITS 

Deposits containing native silver and arsenides 

of nickel and cobalt are numerous in Precambrian 

shield areas and in orogenic belts. In shield areas 

the deposits are associated with belts of volcanic 

and related intrusive rocks and with sedimentary 

rocks derived from volcanic rocks, whereas in orogenic belts the deposits appear to be associated with 

small igneous bodies that were intruded into a 

variety of sedimentary rocks. The host rocks are 

diabase, mafic and intermediate lavas, conglomerate, 

graywacke, quartzite, and metamorphosed and granitized sedimentary rocks. 

The major metallic minerals in these deposits are 

native silver, argentite, chalcopyrite, galena, pyrite, 

pyrrhotite, sphalerite, tetrahedrite, and native bismuth, accompanied by lesser amounts of proustite, 

pentlandite, polybasite, stephanite, and stromeyerite. 

Collectively important is the suite of arsenide, sulfide, sulfarsenide, and antimonide minerals which 

include smaltite-chloanthite (CoAs2-NiAs2), domeykite (Cu3As), safHorite (CoAs2), rammelsbergite 

( N iAs2), skutterudite ( CoAs3), gersdorfite ( N iAsS), 

cobaltite (CoAsS), glaucodot ( [Co,Fe]AsS), niccolite (NiAs), dyscrasite (Ag3Ss), and breithauptite 

(NiSb), as well as lollingite and arsenopyrite. Uraninite is present in a few of the deposits. 

Secondary minerals include the hydrous arsenates 

annabergite (NisAs20s·8H20), erythrite (Co3As20s 

· 8H20), and scorodite, as well as limonite and manganese oxide. The gangue minerals differ from deposit to deposit and include mainly calcite, dolomite, 

and quartz and lesser amounts of rhodochrosite, 

barite, and fluorite. 

Native silver and nickel-cobalt arsenide deposits 

commonly occur in braided vein systems in which 

the individual veins in general range in thickness 

from a fraction of an inch to a foot; a very few are 

as thick as 8 feet. The veins are commonly relatively 

short, extending only a few hundred feet along 

strike and dip, but some have been traced for 

thousands of feet. 

Some deposits in shield areas occur along extensive faults or fault-related fractures, but more commonly they are localized by more subtle features, 

such as fractures that developed parallel to the contacts of sills and other intruded rock bodies and 

along unconformities underlying locally deposited 

favorable host rocks. In orogenic belts native silver 

and nickel-cobalt arsenide deposits have formed at 

such sites as intersection of fracture veins with 

flat crushed zones in gneiss or in preferred host 

rocks such as slate. 

Native silver and nickel-cobalt arsenide deposits 

range widely in size and tenor ; individual veins 

have produced tens of thousands of tons of ore. 

Arsenic constitutes a significant part of the ore; 

carload lots of smelter-run material have run as 

high as 42 percent arsenic, but the average runs 

about 2-3 percent. 

Important producing areas include the Cobalt 

and Thunder Bay districts of Ontario, Canada 

(Lang and others, 1970, p. 210-215), the Annaberg 

and Schneeberg areas of the German Democratic 

Republic (Lindgren, 1933, p. 602-603), the Andreasberg area in the Harz Mountains of the Federal 

Republic of Germany (Lindgren, 1933, p. 601-602), 

and the Kongsberg district, Norway (Vokes, 1960, 

p. 14-16). 

Native silver and nickel-cobalt arsenide deposits 

originally were considered to be derived from diabase sills, either through differentiation and vein 

injection, or by diffusion and metasomatic fixation. 

It was later found, however, that some deposits are 

located where diabase sills are absent and that 

where deposits are located near sills, the sills were 

completely crystallized prior to vein formation. Recently, the restricted lateral and vertical extent of 

the veins has been interpreted to indicate that the 

metals were derived from the rocks either cut by the 

veins or in close proximity to the veins, rather than 

from a magmatic source. The only rocks sufficiently 

rich in copper, nickel, and cobalt to supply the metals 

are greenstone and black pyritic rock interbeded 

with greenstone. It is theorized that these metals and 

other relatively rare metals, including arsenic, migrated by diffusion through a static water medium 

to favorable structural or stratigraphic depositional 

sites (Lang and others, 1970). 

ARSENICAL GOLD DEPOSITS 

Arsenical gold deposits occur in the broad shield 

and lesser areas of Precambrian rock and in orogenic belts. 

The lithologic characteristics of the Precambrian 

terranes differ in detail but are alike in general. 

Precambrian arsenical gold deposits are mostly in 
56 UNITED STATES MINERAL RESOURCES 

or associated with felsic volcanic and related intrusive rocks including dacite, andesite, and basalt 

or their altered equivalents. A few are hosted in 

metamorphic rocks including quartzite and schist. 

The orogenic belts are mostly post-Precambrian 

sedimentary volcanic and metamorphic rocks which 

have been structurally deformed and intruded by 

great masses of granitic rock. Arsenical gold deposits in orogenic belts occur in a variety of sedimentary and volcanic rocks and are associated with 

felsic and intermediate intrusive rocks. 

Arsenical gold deposits commonly contain native 

gold in quartz and (or) sulfide minerals. Arsenic 

occurs only in arsenopyrite in most deposits, but in 

some deposits lollingite also occurs. Arsenopyrite is 

commonly accompanied by pyrite and (or) pyrrhotite, which together may be as much as ten times 

as abundant as arsenopyrite. Other sulfide minerals 

that may be present include chalcopyrite, galena, 

tetrahedrite, and sphalerite. Scheelite and wolframite occur rarely in some deposits. Sulfarsenide minerals are known but are extremely rare in arsenical 

gold deposits. 

Gangue minerals, except for quartz, which is generally present, differ from deposit to deposit and 

include ankerite, albite, and tourmaline. 

Most deposits occur as replacement veins in or 

around rock that has been fractured or sheared by 

faulting. Some deposits are simple in form and 

occur as single persistent veins that are planar or 

more commonly curvilinear and of even thickness, 

whereas others are complex and occur as swarms of 

lenticular veins, which extend short distances. Deposits which were initially simple in form but which 

underwent subsequent deformation occur in contorted pipelike or ribbonlike bodies, reflecting the 

complexity and intensity of deformation. Sulfide 

minerals in some deposits are evenly disseminated 

through the vein, whereas in others they are restricted to lenses or pods. 

Arsenical gold deposits characteristically are 

structurally controlled and commonly occur on or 

along fractured or sheared rock. Some, although 

obviously emplaced on fault-related structures, are 

more numerous where the structures transect a 

particular rock type such as schist, suggesting that 

the mineralizing process was sensitive to subtle differences in rock chemistry. 

The arsenic content of these deposits differs 

markedly ; most deposits within an area or district 

may contain but a fraction of a percent arsenic, 

whereas others within the same area or district may 

contain several percent arsenic. In some deposits 

the arsenic content is remarkably consistent, and 

the arsenic occurs in a fixed ratio with gold ; in 

others, the arsenic content diminishes or increases 

from place to place disproportionately to gold. 

Arsenical gold deposits may contain as much as 20 

percent arsenic, but the average content is no more 

than 1 percent. 

Arsenical gold deposits range from hundreds of 

tons to several hundred thousands of tons of ore. 

The Jardine mine, Montana, between 1879 and 1942, 

produced more than 7 million tons of ore from which 

9 million pounds of arsenic was obtained, although 

this production was for only 8 years of the mine's 

life. The average grade is estimated to be less than 

one-half of 1 percent. 

ARSENIC SULFIDE AND ARSENIC SULFIDE 

GOLD DEPOSITS 

Arsenic sulfide and arsenic sulfide gold deposits 

occur almost exclusively in orogenic belts and commonly are associated with Tertiary intrusive igneous 

or volcanic rocks. Arsenic and mercury sulfide minerals occur together in some deposits. Elsewhere the 

association is less intimate; deposits of arsenic, 

mercury, and antimony occur separately but display 

a regional zonal pattern which suggests a common 

genesis. Arsenic sulfide minerals are also abundant 

in some gold deposits. 

Host rocks include intermediate and felsic intrusive and volcanic rocks, volcanic sedimentary rocks 

such as tuffaceous sandstone, and limestone and 

noncarbonate clastic rocks or their metamorphic 

equivalents. 

Arsenic sulfide deposits are characterized by realgar and orpiment, almost to the total exclusion of 

other arsenic minerals. Some small vein deposits 

are composed entirely of one or the other of these 

minerals. Composite deposits of arsenic sulfide minerals and mercury contain stibnite, cinnabar, metacinnabar, calomel, and native mercury. Arsenic 

sulfide gold deposits have a more complicated mineralogy; in addition to realgar and orpiment, they 

contain pyrite, pyrrhotite, marcasite, arsenopyrite, 

chalcopyrite, scheelite, molybdenite, sphalerite, cinnabar, stibnite, native arsenic, and native gold. The 

gangue minerals include quartz, fluorite, barite, 

alunite, sericite, and leverrierite. 

Many arsenic sulfide deposits occur as veins that 

fill fractures and may be tens to hundreds of feet 

long but which are commonly narrow, generally a 

few inches to 1 foot thick. Other deposits occur in 

breccia zones which extend hundreds of feet along 

strike and dip and are as much as several feet 

thick. In these deposits, the arsenic sulfide minerals 
ARSENIC 57 

form a part of the cement around the breccia fragments. 

Arsenic sulfide gold deposits occur in vein systems 

that comprise numerous ore shoots. Such veins measure thousands of feet in length and several hundred 

feet along the dip, and range in thickness from a few 

feet to 200 feet. Lenses of realgar and stibnite as 

much as 20 feet long and 4 feet thick occur in some 

of the ore shoots. 

Both arsenic sulfide and arsenic sulfide gold deposits are controlled by such structural features as 

fractures, shear zones, or other fault-related structures. The deposits occur as fissure fillings and largescale replacements. In some deposits or in the deeper 

parts of some deposits, replacement was nonselective and all strata transected by the veins were 

affected, whereas elsewhere replacement was selective. Some deposits in volcanic terranes may have 

been concentrated along the contact of rocks of 

different permeability. 

Arsenic sulfide deposits are small and range from 

those which have produced a few tens of tons of ore 

to those which have produced a few thousands of 

tons. Some of.the ore contains as much as 20 percent 

arsenic but averages only a few percent. Arsenic sulfide gold deposits have yielded tens of thousands and 

hundreds of thousands of tons of ore; arsenic in 

these deposits was recovered as a byproduct and constituted a small fraction of the ore, averaging not 

more than 1 percent. 

Examples of arsenic sulfide deposits include several in the State of Washington (Shedd, 1924, p. 

51-55). The occurrence of arsenic sulfide minerals 

with mercury has been reported in Oregon (Brown 

and Waters, 1951, p. 234) and Alaska (Berg and 

Cobb, 1967, p. 89-94). Arsenic sulfide gold deposits 

are best exemplified in Nevada, where several deposits of this type have yielded byproduct arsenic 

(Hewitt, 1968, p. 872-873; Nolan, 1935, p. 111, 151-

156). 

Arsenic sulfide deposits are generally considered 

to have come from sources deep within the crust 

but to have been emplaced fairly close to the surface 

at low temperatures. Their occurrence near centers 

of volcanic activity reflects the common source of 

mineralizing solutions and flow rocks, both of which 

are assumed to be differentiates of the same magma 

(Lindgren, 1933, p. 455). 

ARSENICAL TIN DEPOSITS 

Arsenical tin deposits occur mostly in orogenic 

belts, but they occur sparsely in Precambrian terranes. The deposits are closely associated with granitic stocks or batholiths, are commonly emplaced 

in such bodies or close to their peripheries, and are 

most numerous near the cupolas or summit areas 

of the granitic bodies. 

Arsenical tin deposits also are emplaced in a 

variety of sedimentary rocks (sandstone, shale, and 

limestone), in metamorphic rocks (schist, gneiss, 

and slate) , and in older granitic rocks. No one host 

rock seems to be more favorable than another. 

The ore minerals commonly are cassiterite, native 

bismuth, bismuthinite, arsenopyrite, and wolframite 

and lesser amounts of chalcopyrite, pyrite, pyrrhotite, galena, and sphalerite. Hematite, magnetite, 

and ilmenite occur rarely. The gangue minerals are 

quartz, which is most abundant, fluorite, lepidolite, 

topaz, tourmaline, apatite, axinite, and, rarely, beryl 

or orthoclase. Cassiterite is the principal ore mineral. Arsenopyrite is the only arsenic mineral in 

this type of deposit. 

Arsenical tin deposits occur in veins and pipes. 

The veins occur in simple planar or undulous form. 

Some occur in braided systems ; others are very irregular and occur in stockworks. They may be as 

much as 3 miles long, as much as 3,000 feet invertical extent, and a few inches to several tens of 

feet thick. They formed by filling of open fissures 

and replacement of wallrock. 

The pipes are roughly circular in plan, range 

from several tens of feet to more than 100 feet in 

diameter, and are several hundreds of feet in vertical extent. The ore in some pipes is disseminated, 

and the walls are indefinite; in others, the contact 

of ore and wallrock is well defined. In some pipes, 

arsenopyrite occurs in segregated masses. 

Vein deposits of arsenical tin occur in fissures 

which formed in the chilled shell of congealing granitic plutons and extend into the adjoining country 

rock. Faulting took place along some of the fissures 

during mineralization, with the res:ult that composite 

veins developed. 

Some pipe deposits developed along shear zones or 

other structures, but other deposits do not appear 

to be located on preexisting structures. It is theorized they were emplaced explosively in the manner 

of diatremes and were initiated at points of incipient fissuring during a period of extraordinarily 

high pressure. 

The size of arsenical tin deposits ranges from 

hundreds of tons to hundreds of thousands of tons. 

The early mined veins, lodes, and pipes were of 

relatively high tenor, averaging several percent, but 

because of their depletion, larger but lower tenor 

deposits are now being worked. The arsenic content 

of the deposits ranges from a fraction of 1 percent 
58 UNITED STATES MINERAL RESOURCES 

to as much as 2 percent and is estimated to average 

not more than 0.2 percent. 

Examples of arsenical tin deposits include the 

Aberfoyle mine, Australia (Connolly, 1953), the 

Stavoren Fides tin mines, Republic of South Africa 

(Union of South Africa Department of Mines, 

Geology Survey, 1959), the Lost River mine, Alaska 

(Sainsbury, 1964, p. 25), and the mines of the 

Uncia area, Bolivia (Ahlfeld, 1931, p. 248). 

Tin and arsenical tin deposits are generally believed to be products of high-temperature solutions 

charged with fluorine and boron which acted as 

strong solvents for metals such as tin and tungsten. 

The solutions originally constituted a part of the 

magma, but as the magma cooled, they separated, 

and subsequently, where fissures developed in the 

chilled periphery of the magma body, they escaped. 

The escaping solutions reacted with the fissure walls 

in the chilled envelope and country rock to form 

deposits containing fluorine and boron minerals and 

cassiterite (Ferguson and Bateman, 1912). 

OTHER DEPOSITS 

Other types of arsenical deposits are known but 

are not promising as significant sources of arsenic. 

The types are arsenical quartz, silver, and lead-zinc 

deposits. 

Arsenical quartz deposits are commonly in veins 

composed of quartz with arsenopyrite and pyrite 

and, rarely, minor amounts of other sulfide minerals 

and gold. The arsenical quartz veins represent an 

early stage of a complex base- and precious-metal 

mineralization but commonly were emplaced separately from the main-stage ore. They are known in 

orogenic belts and Precambrian terranes. They are 

estimated to contain less than 1 percent arsenic. 

The arsenical silver deposits described in the literature occur in Precambrian schist in vein systems 

as much as 1 mile long and more than 1,000 feet 

wide. The ore includes silver sulfide and sulfosalts, 

pyrite, arsenopyrite, and very minor amounts of 

chalcopyrite and gold. The deposits occur in the 

Randsburg district of Kern and San Bernardino 

Counties, Calif. (Stewart, 1957, p. 529-530). Deposits of this type may average as much as a few 

tenths of 1 percent arsenic. 

Arsenical lead-zinc deposits are sparse and as a 

type are best characterized by the Sullivan mine in 

the Kootenay district of British Columbia (Schofield, 1915, p. 107-108, 131-133; Little and others, 

1968, p. 504-505). This deposit formed by replacement of argillitic beds in Precambrian quartzite. 

The ore minerals are galena, sphalerite, pyrite, pyrrhotite, magnetite, cassiterite, arsenopyrite, jamesonite, and boulangerite. The core of the deposit 

is composed of pyrite and pyrrhotite. Around the 

core is a zone relatively rich in lead, silver, tin, and 

arsenic, and outward from it is a zone rich in zinc 

and antimony. Deposits of this type, although large 

producers of base metals, are not sufficiently numerous or rich enough in arsenic to be considered a 

significant arsenic source ; they probably average 

less than one-half percent arsenic. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Arsenic resource estimates are based on a limited 

amount of data. Arsenic has been or is almost entirely obtained as a byproduct of gold, silver-nickelcobalt, copper, or copper-zinc-lead deposits. The 

content of arsenic in such deposits is, with few exceptions, only generally known. The arsenic is reclaimed from mill and smelter wastes, and production data are available from only a few deposits. 

Further, because arsenic is a byproduct, the estimate of arsenic resources is in part dependent on 

estimates of the resources of the primary commodities and, more importantly, on an understanding of 

the relation of arsenic to them. 

The data base, weak for arsenic resources within 

the United States, is even weaker for areas outside 

the United States and is almost nonexistent for 

countries of the Communist bloc. The resource data 

are shown in table 9. Resources are considered more 

TABLE 9.-World identified and hypothetical resourc.es of 

arsenic, in short tons 

United States ------------------ North America exclusive of 

United States ------------------ South America ------------------ Eurasia (including insular areas of southeastern Asia) ___ _ 

Africa -------------------------- Australia -----------------------

World total ----------------

Identified 

resources 1 

1,300,000 

500,000 

3,000,000 

10,100,000 

2,300,000 

400,000 

17,600,000 

Hypothetical 

resources 2 

650,000 

300,000 

2,700,000 

8,450,000 

1,850,000 

350,000 

14,300,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade and whose contained minerals may or may not be profitably recoverable with existing technology 

and economic conditions. 

2 Hypothetical resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that are geologically predictable as existing in known districts. 

than ample to fill the expected demands until the 

year 2000. 

The assumptions that serve as a basis of treatment are as follows : of the gold resources, 5 percent 

are considered to be arsenical and to have an average 

ratio of arsenic to gold of 2,000: 1 ; of the resources 

of copper and copper-zinc-lead, 15 percent are considered to be arsenical with a ratio of arsenic to 
ARSENIC 59 

copper of 1: 50 ; of the resources of cobalt, 3 percent are considered to be arsenical with an average 

ratio of arsenic to cobalt of 2: 1 ; and of the tin 

resources, 10 percent are considered to be arsenical 

with an average ratio of arsenic to tin of 10: 1. 

Several factors stemming from the relation of 

arsenic to primary metals are considered when calculating the various arsenic-metal ratios. For example, arsenic does not occur in placer deposits of 

gold or tin or in gold deposits hosted by Precambrian conglomeratic sandstone. Gold placer deposits 

can be disregarded for they are a relatively small 

source of gold and the absence of arsenic from them 

is of little account in the estimate, whereas tin 

placer deposits are an important source of tin and 

the absence of arsenic from them seriously affects 

the estimate. Gold deposits in ancient conglomeratic 

sandstone deposits are the most important source 

of gold, and the absence of arsenic from them drastically affects the estimate. The ratio of arsenic to 

cobalt was weighted to favor arsenic in order to 

account for the additional arsenic that is combined 

with nickel, copper, and iron in native silver and 

nickel-cobalt arsenide deposits. Lateritic deposits of 

nickel and cobalt are disregarded as sources of 

arsenic. Such deposits may have in part been derived from primary deposits of native silver and 

nickel-cobalt arsenides, but arsenic apparently escaped in the weathering process. 

The resource figures for arsenic shown herein 

were largely derived from data for gold, copper, and 

other base metals published in other chapters of this 

volume. Each of the continental areas is assumed to 

contain sufficient resources of some of the more 

important types of arsenic-bearing deposits so that 

general estimates accurate within an order of magnitude can be made. The hypothetical resources of 

arsenic are estimated to be equal to the total of 

identified resources of arsenic occurring with base 

metals plus one-third the identified resources of 

arsenic occurring with the gold. 

Arsenic is currently produced in about 25 countries. The types of arsenic-bearing deposits and the 

countries in which they occur are shown in table 10. 

SPECULATIVE RESOURCES 

Arsenic deposits which may form by the mobilization, concentration, and redeposition of arsenic in 

favorable geologic environments could be an additional resource of arsenic. 

Most of the arsenic or arsenical deposits that have 

been discussed here are types which were derived 

from magmatic or magma-related sources; a few, 

however, were derived from adjoining host rocks. 

TABLE 10.-Types of arsenic deposits of the world 

Type of deposit Areas 

Enargite-bearing copper- United States, Argentina, Chile, 

zinc-lead deposits. Peru, Mexico, Republic of the 

Philippines, Spain, Yugoslavia, 

U.S.S.R. 

Arsenical pyritic copper United States, Sweden, Federal 

deposits. Republic of Germany, Japan, 

France, U.S.S.R. 

Canada, Norway, German Democratic" Republic, Czechoslovakia. 

Native silver and nickelcobalt arsenide-bearing deposits. Arsenical gold deposits __ United States, Brazil, Canada, 

Republic of South Africa, 

Australia, U.S.S.R. 

United States, People's Republic 

of China. 

Arsenic sulfide and 

arsenic sulfide gold 

deposits. Arsenical tin deposits __ United States, Bolivia, Australia, 

Indonesia, Malaysia, Republic 

of South Africa. 

Studies of ancient rock terranes show that certain 

types of ore deposits are broadly related to certain 

rocks, and studies of sulfur isotopes indicate that 

metals in disseminated sulfide minerals in the surrounding rocks were the likely source of metals concentrated in the ore deposits. The metals were mobilized when sufficiently energized and then moved 

by diffusion through the rock and accumulated in 

favorable structures. 

Under local favorable conditions in areas where 

the rock has a high arsenic content, arsenic or 

arsenical deposits might be found. Geochemical 

studies show that shale averages 5-15 ppm arsenic 

and that sulfide-rich organic shale of marine origin 

contains even greater amounts. Although organicrich shale is widespread and has formed in many 

geologic periods, the number of ore deposits found 

in it is few. The few that have been found may have 

formed under exceptional circumstances in which 

metals became highly concentrated in sea water. 

Rather than investigate organic-rich shale units on 

a broad basis, efforts should be concentrated on 

areas that have been subjected either to extreme 

structural deformation and (or) to metamorphism 

or that have been intruded by large bodies of igneous rock. In such areas, the metals may have been 

mobilized and concentrated in favorable structural 

settings. These areas are likely to be regional in 

scope and to be recognizable from stratigraphic, 

structural, and other geologic relationships. Such 

areas include parts of depressed belts or geosynclines, which are the locales of organic-rich marine 

shale. Other such areas include ancient crystalline 

terranes where graphitic schist, the metamorphic 

equivalent of organic-rich shale, is present. 

The amount of arsenic in organic shale is estimated to total about 1011 tons; if as much as 0.01 

percent of this arsenic is concentrated in minable 
60 UNITED STATES MINERAL RESOURCES 

deposits, about 10 million tons should be a recoverable resource. 

PROSPECTING TECHNIQUES 

Arsenic has not been and is not a sought-after 

commodity; it is produced as a byproduct of other 

commodities-gold, silver, or copper-and consequently,, no prospecting endeavor has been aimed 

solely at finding it, although techniques suitable for 

finding other commodities are well suited for finding it. 

Some small arsenic deposits containing realgar or 

arsenopyrite were no doubt found by recognition of 

the ore minerals or their gossans in place, in float, 

or in stream gravels. The Boliden arsenical copper 

deposit in Sweden was found by an electrical geophysical method following the discovery of sulfide 

boulders in till which blanketed the region. Arsenic 

in soils and stream sediments may be detected by 

geochemical methods and has been used as a guide 

to other metals, including cobalt, tungsten, gold, 

and silver; as such, it can be used as a guide to 

arsenical metal deposits. Its mobility, however, is 

restricted by the presence of high iron in soils and 

stream sediments. 

PROBLEMS FOR RESEARCH 

Because arsenic historically has been sufficently 

abundant to meet human needs and has been obtained almost wholly as a byproduct of other commodities, it has not been intensively studied. The 

ever-persistent problem of supply of most other 

commodities will eventually include arsenic. Research is needed so that the geologic relations of 

arsenic can be better understood and guides can be 

found for the discovery of new deposits. 

Much fundamental background knowledge on 

arsenical deposits is needed. Arsenic minerals which 

occur in many ore deposits are reported only in a 

cursory manner, and only rarely are estimates of 

their proportions to the associated metals given. 

Also the relationship of arsenic to primary or host 

commodities needs additional study. Arsenic occurs 

randomly with several metals including gold, copper, and tin, but its occurrence with these metals 

is not fully understood. Further study might make 

possible more accurate predictions of the occurrence 

of arsenic with these metals on a districtwide or 

regionwide scale. 

SELECTED REFERENCES 

Ahlfeld, Frederick, 1931, The tin ores of Uncia-Lallagua, 

Bolivia: Econ. Geology, v. 16, no. 3, p. 241-257. 

Anderson, C. A., 1969, Massive sulfide deposits and volcanism: Econ. Geology, v. 64, no. 42, p. 129-146. 

Anderson, C. A., and Creasey, S. C., 1958, Geology and ore 

deposits of the Jerome area, Yavapai County, Arizona: 

U.s. Geol. Survey Prof. Paper 308, 185 p. 

Berg, H. C., and Cobb, E. H., 1967, Metalliferous lode deposits of Alaska: U.S. Geol. Survey Bull. 1246, 254 p. 

Brown, Randall, and Waters, A. C., 1951, Quicksilver deposits of the Bonanza-Nonpareil district, Douglas 

County, Oregon: U.S. Geol. Survey Bull. 955-F, p. 225-

251· 

Burbank, W. S., Matthews, A. F., and Mosier, McHenry, 

1947, Arsenic, in Hearings before a subcommittee of 

the committee on public lands: U.S. Senate, 80th Cong., 

1st sess., p. 214-216. 

Butler, B. S., Loughlin, G. F., Heikes, V. C., and others, 

1920, The ore deposits of Utah: u.s. Geol. Survey Prof. 

Paper 111, 672 p. 

Connolly, H. J. C., 1953, The Aberfoyle tin-wolfram mine, 

·in Geology of Australian ore deposits: Empire Mining 

and Metall. Cong., Australia and New Zealand, 5th, 

Melbourne 1953, v. 1, p. 1200-1208. 

Ferguson, E. H., and Bateman, A. H., 1912, Geologic features of tin deposits: Econ. Geology, v. 7, no. 3, P· 

209-262. 

Forman, F. G., 1953, Geological structure of the shield in 

southern Western Australia in relation to mineralization, in Geology of Australian ore deposits: Empire Mining and Metall. Cong., Australia and New Zealand, 5th, 

Melbourne 1953, v. 1, p. 65-77. 

Gair, J. E., 1962, Geology and ore deposits of the Nova Lima 

and Rio Acima quadrangles, Minas Gerais, Brazil: U.S. 

Geol. Survey Prof· Paper 341-A, 67 p. 

Graton, L. C., Burrell, H. C., and others, 1935, The Morococha 

district, 1935, in Copper resources of the world, v. 2: 

Internat. Geol. Cong., 16th, Washington, D.C. 1933, p. 

527-544. 

Grip, Erland, 1960, The Skellefte district and Laisvall area, 

in Grip, Erland, Quensel, Percy, Geijer, Per, and 

Ljunggren, Sven, Sulphide and iron ores of Vasterbotten and Lapland, northern Sweden: Internat. Geol· 

Cong., 21st, COpenhagen 1960, Guide to excursions A27 

and C22, p. 3-14. 

Grip, Erland, and Wirstam, A., 1970, The Boliden sulfide 

deposit-A review of goo-investigations carried out 

during the lifetime of the Boliden mine, Sweden, 1924-

1967: Sveriges Geol. Undersokning, Arsbok, v. 64, no. 

8, 68 p. 

Hewitt, W. P., 1968, Western Utah, eastern and central 

Nevada, in Ore deposits of the United States, 1933-

1967: Am. Inst. Mining, Metall., and Petroleum Engineers, v. 1, P· 857-885. 

Kanehara, Nobuyasu, 1935, Copper resources of Japan, in 

Copper resources of the world, v. 2: Internat. Geol. 

Cong., 16th, Washington, D.C. 1933, p. 687-700. 

Kinkel, A. R., Jr., Santos-Yiiigo, L. M., Samaniego, Sisenaudo, and Crispin, Oscar, 1956, Geology of Lepanto 

copper mine, in Copper deposits of the Philippines, pt· 

1: Philippines Bur. Mines, p. 17-50. 

Krauskopf, K. B., 1955, Sedimentary deposits of rare metals, 

in Pt. 1 of Bateman, A. M. ed., Economic geology, 50th 

anniversary volume, 1905-1955: Econ. Geology Pub. 

Co., p. 411-463. 

Lang, A. H., Goodwin, A. M., Mulligan, R., Whitmore, D. 

R. E., Gross, G. A., Boyle, R. W., Johnston, A. G., 
ARSENIC 61 

Chamberlain, J. A., and Rose, R. E., 1970, Economic 

minerals of the Canadian shield, in Geology and economic minerals of Can;:ula: Canada Geol. Survey, Econ. 

Geology Rept. 1, p. 153-226. 

Lansche, A. M., 1965, Arsenic, in Mineral facts and problems: U.S. Bur. Mines Bull. 630, p. 75-80. 

Lindgren, Waldemar, 1926, Ore deposits of the Jerome and 

Bradshaw Mountains quadrangles, Arizona: U.S. Geol. 

Survey Bull. 782, 192 p. 

--- 1933, Mineral deposits [4th ed.]: McGraw-Hill Book 

Co., 930 p. 

Lindgren, Waldemar, and Irving, John D., 1911, The origin 

of the Rammelsberg ore deposit: Econ. Geology, v. 6, 

no. 3, p. 303-313. 

Little, H. W., Belyea, H· C., Scott, D. F., Latour, B. A., and 

Douglas, R. J. W., 1968, Economic minerals of western 

Canada, in Geology and economic minerals of Canada: 

Canada Geol. Survey, Econ. Geology Rept. 1, p. 490-546. 

Lord, C. S., Hage, C. 0., and Stewart, J. S., 1967, The 

cordilleran region, in Geology and economic minerals of 

Canada [3d ed.]: Canada Dept. Mines and Resources, 

Econ. Geology, ser. 1, p. 220-310. 

McLaughlin, D. H., Bowditch, S. 1., and others, 1935, The 

Cerro de Pasco district, in Copper resources of the 

world, V· 2: Internat. Geol. Cong., 16th, Washington, 

D.C. 1-933, p. 516-531. 

Meyer, Charles, Shea, E. P;, Goddard, C. C., Jr., and others, 

1968, Ore deposits at Butte, Montana, in Ore deposits of 

the United States 1933-1967 (Graton-Sales volume), v. 

2: Am. Inst. Mining, Metall., and Petroleum Engineers, 

p. 1373-1416. 

Nolan, T. B., 1935, The Gold Hill mining district, Utah: 

U.S. Geol. Survey Prof Paper 177, 172 p. 

Onishi, Hiroshi, and Sandell, E. B., 1955, Geochemistry of 

arsenic: Geochim. et Cosmochim. Acta, v. 7, nos. 1-2, p. 

1-33· 

Paone, James, 1970, Arsenic, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 479-487. 

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry: 

Chicago, Univ. Chicago Press, 912 p. 

Renick, Abbott, 195·6, Arsenic, in Mineral facts and problems: U.S. Bur. Mines. Bull· 556, p. 67-68. 

Sainsbury, C. L., 1964, Geology of the Lost River mine area, 

Alaska: U.S. Geol. Survey Bull. 1129, 80 p, 

--- 1969, Tin resources of the world: U.S. Geol. Survey 

Bull· 1301, 55 p. 

Schofield, S. J ., 1915, Geology of the Cranbrook map area, 

British Columbia: Canada Geol. Survey Mem. 76, 245 p. 

Seager, G. F., 1944, Gold, arsenic, and tungsten deposits of 

the J ardine-Crevasse Mountain district, Park County, 

Montana: Montana Bur. Mines and Geology Mem. 23, 

111 p. 

Shedd, SolOn, 1924, The mineral resources of Washington : 

Washington, Div. Geology Bull. 30, 224 p. 

Stewart, R. M·, 1957, Silver, in Mineral commodities of California: California Div. Mines Bull. 176, p. 529-537. 

Taylor, A. V., Jr. ,1935, Ore deposits of Ghuquicamata, Chile, 

in Copper resources of the world, v. 2: Internat. Geol. 

Cong., 16th, Washington, D.C. 1933, p· 4 73-484. 

Union of South Africa Department of Mines, Geology Survey, 1959, The mineral resources of the Union of South 

Africa: Union of South Africa Govt. Printer, p. 180-

184. 

U.S. Bureau of Mines, 1971, Minor metals, in Minerals yearbook, 1969, v. 1, 2: U.S. Govt. Printing Office, p. 1175-

1176. 

Vokes, Frank, 1960, Mines in south and central Norway: Internat· Geol. Cong., 21st, Copenhagen 1960, Guide to 

excursion C10, 73 p. 

UNITED STATES MINERAL RESOURCES 

ASBESTOS 

By ANDREW F. SHRIDE 

CONTENTS 

Abstract of conclusions 

Introduction ------------------------------------- Definition and properties ---------------------

1Jses ---------------------------------------- Exploitation -------------------------------------

Geology -----------------------------------------

Modes of vein occurrence ---------------------

General settings -----------------------------

Ghrysotile deposits in massive serpentinite ____ _ 

Regional settings of principal North American deposits ---------------------------

Localizing factors ----------------------·--

Size, shape, and asbestos content ---------

Chrysotile deposits in limestone -----------------

Asbestos resources in North America --------------

Canada ------------------------------------- lJ nited States __________ -- __ ----- _ -- _____ ----

Mexico -------------------------------------- Prospecting techniques __ - __ ---- ___ - ----- __ -------

Problems for research ----------------------------

Selected references -------------------------------

FIGURE 

9. Graph showing world production, production 

from major sources, lJ.S. production and conPage 

63 

63 

64 

64 

65 

66 

66 

67 

67 

67 

68 

69 

69 

69 

69 

70 

71 

72 

72 

72 

Page 

sumption of asbestos, 1920-70 -------------- 66 

TABLE 

Page 

11. Chrysotile asbestos resources of North America_ 69 

ABSTRACT OF CONCLUSIO~S 

The fibrous silicate minerals grouped in commerce under 

the term "asbestos" are essential to modern technology in 

certain relatively low-volume uses. Asbestos-cement products 

consume 70 percent of world output, and expand-ed demand 

in this field is anticipated. 1Jniversally, asbestos-cement building materials are especially suited for new construction of 

housing and industrial plants; in industrial nations the 

asbestos-cement pipe for use in sewage and water systems 

is in particular demand. The 1Jnited States is the principal 

fabricator and consumer of asbestos products and currently 

imports 85 percent of the raw asbestos needed to sustain 

its large industry. 

Chrysotile asbestos constitutes 93 percent of world asbestos 

trade, and Canada has been the principal supplier of world 

needs since asbestos was first used on a large scale. Canada 

continues to have the largest res·erves of chrysotile, and its 

fields hold the greatest promise of any in the Americas for 

finding additional resources. Since World War II, the 

1J-S.S.R. has increased its chrysotile-asbestos-producing facilities and has found resources to approach those of Canada. 

Ninety percent of world resources of chrysotile are in 

Canada, Russia, and the nations of southern Africa. 

Crocidolite and amosite make up about 3% and 2% percent, respectively, of world asbestos commerce; anthophyllite, 

tremolite, and actinolite apparently make up only a fraction 

of 1 percent. Most of the world res·erves, and the only sources 

currently exploited, of crocidolite (blue) asbestos are in the 

Transvaal and Cape Provinces of the Republic of South 

Africa. The only source of amosite is in the Transvaal. 

Domestic resources of anthophyllite and tremolite, little used 

in the 1Jnited States, are apparently adequate for lJ.S. 

needs. 

INTRODUCTION 

The geologic potentials for asbestos resources 

most likely to be available for consumption in the 

United States during the next several decades are 

the prime concern of this report. Technologic aspects 

necessary to a general understanding of the asbestos 

industry are not discussed here except as required 

to define terminology peculiar to the commodity. For 

those who wish to delve further, review articles 

that cover all facets of the industry are cited; 

where available, recent reports that update the reviews are also noted. A selected bibliography of 

asbestos literature extant as of 1955 is available 

(Avery and others, 1958), as is a map showing the 

location of asbestos occurrences in the conterminous United States (Chidester and Shride, 1962). 

For general background two review articles by 

U.S. GEOL. SURVEY PROF. PAPER 820 

63 
64 UNITED STATES MINERAL RESOURCES 

Jenkins (1949, 1960), which are complementary in 

their coverage, are recommended. Condensed comparisons of worldwide scope of subjects such as 

mining and milling methods, grading and classification, and production and consumption trends have 

been furnished by Bowles (1959). Updated discussions of trade and use trends are available in two 

articles in Industrial Minerals (1970a, b). 

DEFINITION AND PROPERTIES 

"Asbestos" is a term applied in commerce to 

naturally fibrous silicates that are amenable to 

mechanical separation into fine filaments of considerable tensile strength and flexibility; these 

fibers have, by virtue of unique combinations of 

physical and chemical properties, a great variety 

of industrial uses. Manmade fibers and naturally 

occurring organic fibers do not possess the full range 

of properties inherent in asbastos, and thus-at 

best--can be substituted only partially for the mineral fibers ( Carroll-Porczynski, 1958) . Chrysotile, 

the fibrous form of serpentine, constitutes about 93 

percent of world asbestos production. The other 

five asbestiform minerals ordinarily used are amphiboles. In order of quantities consumed, they are: 

crocidolite and amosite, which respectively make up 

about 31f2 and 2112 percent of asbestos commerce; 

anthophyllite and tremolite which probably make 

up only a fraction of 1 percent of the asbestos used; 

in recent decades, actinolite, the least used, has 

seldom been given note in the trade. These use ratios 

mainly reflect desirable physical properties; crocidolite and amosite do have particular properties that 

would favor greater use if they occurred more universally and in larger amounts. 

The properties primarily of concern in evaluating 

asbestos as to ultimate use are: (1) flexibility, (2) 

length of fiber, (3) tensile strength, (4) chemical 

reactivity, (5) resistance to heat, (6) electrical 

conductance, and (7) filtration characteristics. (See 

Badollet, 1951 and 1953, for comparative properties 

of asbestos species.) The use of a given lot of asbestos is governed by acceptable properties which are 

determined largely by fiber length. The longest fibers 

demand the highest prices and the shorter grades 

progresively are lower in value. (In recent years 

soft chrysotile fibers 3,4-inch long have sold for 

$1,500-$1,600 per ton, whereas the shortest grades 

have brought $50-$100 per ton.) Thus, asbestos 

should be separated from the parent rock, fiberized, 

and classified by length with attention given to a 

minimum of breakage. 

By virtue of variations in physical properties, a 

given mineral is put to very different uses. Soft, 

silky chrysolite of adequate length fabricates into 

textiles. The same fiber, because it forms a slurry 

that can be dewatered only slowly, is unsuitable for 

processing as the binder in cement products. Harshness-that is, resilience like a broomstraw when 

flexed-makes chrysotile very unsuitable for textile 

use but greatly enhances the manufacture of chrysotile into asbestos-cement products. Some desirable 

combinations of properties are limited in occurrence. An example of strategic concern is textilequality chrysotile of low iron content for heatresistant electrical insulation. Physical characters 

ordinarily overlooked can be significant. Resources 

recently developed near Coalinga, Calif., are illustrative. For decades large parts of an extensive serpentine mass in this area had been recognized in 

the form of minutely sheared incoherent leathery 

flakes, quite lacking resemblance to typical asbestos 

ores. On appraisal in the late 1950's, the flaky material proved to contain high proportions of microscopic fibers, all of the shortest lengths ordinarily 

recovered in the processing of ordinary ores. Further, these fibers had special attributes of being 

superior in whiteness-thus being particularly 

suited as binders for floor tiles-and of capacity to 

absorb hydrocarbons. 

USES 

Asbestos is widely stated to be a constituent in at 

least 3,000 manufactured products. It is a particularly critical material in friction materials and in 

electrical insulation, where resistance to moisture, 

flexure fatigue, and abrasion and a capacity to 

absorb resins can be as important as heat and flame 

resistance. Asbestos is important as an abrasionand corrosion-resistant binder or reinforcing material in products made of rubber or plastic and mixed 

with lubricants or other compounds used in packings 

or gaskets, where an inert material is required owing to exposure to superheated steam, acids, alkalis, 

oil, or seawater. Laminated as paper or in textiles, 

it is fabricated into products that are immune to 

attack by fungus, bacteria, or vermin and that are 

not affected by alternate wetting and drying. Asbestos fibers can be finely divided; and, separated in 

optimum degrees, they are superior inert mediums 

for filtering gases and liquids. This partial listing 

only superficially indicates the many asbestosbearing products essential to our modern way of 

life; actually such products account for less than 

one-third of asbestos consumption. 

About 70 percent of U.S. and world consumption 

of asbestos is in asbestos-cement products. Indeed, 

the demand for shingles, roofing, wallboard, flat and 
AS·BESTOS 65 

corrugated sheets, and pipe is increasing more 

rapidly than that for other asbestos products. Since 

World War II, new asbestos-cement plants have been 

built throughout the world. Most of the lesser industrialized nations, as well as many of the emerging nations, now have manufacturing facilities. The 

lack of a domestic or nearby source of asbestos is 

no great deterent to this trend, because processed 

asbestos makes up only 15-20 perecnt of the locally 

finished product, which is competitive in cost for 

low-cost housing and is universally suitable as building material. In the United States, the demand for 

asbestos-cement pressure pipe, mainly for use in 

sewage and water systems, has increased even more 

rapidly than the need for other asbestos-cement 

products. The demand in Europe, where such pipe 

was used extensively long before it came into common use in the United States, is also increasing. 

Thus, the demand for the medium- to short-length 

chrysotile fibers (groups 4, 5, and 6-see Bowles, 

1959, or Jenkins, 1960, for summary of classifications commonly in use) and equivalent crocidolite 

and amosite fibers is bound to escalate wherever 

population or industrial expansion occurs. Demand 

in the United States is likely to keep pace, as long 

as per capita consumption of water increases and 

pollution control forces the construction of more 

sophisticated sewage disposal systems. 

Actually, perhaps at least half of the remaining 

30 percent of asbestos consumed is also keyed to the 

construction industry. In the United States, floor 

tiles account for 10 percent of consumption; paints, 

electrical insulation, steam-pipe coverings, and other 

low-volume uses probably account for several percent. 

EXPLOITATION 

Asbestos was first produced in Quebec in 1878, 

and within a few years this source dominated world 

production. The firm establishment of an asbestos 

fabricating industry and markets in America by 

1900 awakened interest in asbestos mining throughout the world. By 1910, notable asbestos-mining 

facilities had been established in the countries that 

since have become the centers of world production. 

Although asbestos occurrences are widely dispersed 

throughout the world, and mining is recorded at 

several widely separate localities on every continent 

except the polar landmasses, most of world production has been from three areas. In order of productivity these are: (1) Canada, (2) the U.S.S.R., 

and ( 3) the southern Africa fields centered mainly 

in Rhodesia and the Transvaal and the Cape Provinces of the Republic of South Africa, but with significant increments from one district in Swaziland. 

Before 1950, 90-95 percent of the reported world 

annual production was from these three areas. In 

1968, they furnished about 84 percent; the United 

States, Italy, and mainland China probably produced another 10 percent, and 17 other nations 

accounted for most of the remainder. 

The dominance of Canada in the asbestos trade is 

apparent in several ways. The largest asbestos mines 

and mills in the world are in Quebec; as a consequence, specification standards that affect commerce 

are in great part determined there. Before the mid1950's, more than half of world production was in 

Canada; and for several years, output from Canada 

exceeded 60 percent and even approached 70 percent 

of world supply. Despite a 65-percent jump in productivity since 1950, Canadian shipments have been 

increasing at a lower rate than total world production; consequently, Canada has accounted for about 

45 percent of the annual total in recent years. 

Canada consumes less than 5 p~rcent of its output, 

and in supplying raw asbestos to more than 80 

countries it accounts for 70-75 percent of world 

exports. Russia, the second largest producer and the 

only nation that is both a large producer and a 

large consumer, during recent years has exported 

about 15 percent of its production, mainly to eastern 

European nations. Until recently Rhodesia was the 

second largest exporter of asbestos to the Western 

World. 

The United States has long been the principal 

fabricator and consumer of asbestos products, but 

has always been dependent on imports of raw asbsetos to sustain its large industry. During many years 

prior to 1955, the United States consumed 45-55 

percent of world output and domestic sources supplied only 3-8 percent of annual requirements. With 

the larger scale production of short chrysotile from 

California that started in 1962, domestic production 

more than doubled and current annual output of 

125,000-130,000 tons represents about 15 percent 

of United States consumption. Before this increase, 

in terms of tonnage, 90-96 percent of United States 

imports was chrysotile asbestos from Canada, and 

these imports represented 70-75 percent of Canadian production. Thus, for a considerable time, as 

shown in figure 9, United States consumption was 

reflected in the Canadian production record. Before 

1950, Rhodesia furnished most of certain textile 

grades of chrysotile. 

The United States is wholly dependent-as are 

all nations-on the Transvaal for amosite asbestos 

and on the Transvaal and Cape Provinc~s of South 

Africa for all but a small part of crocidolite (blue) 
66 UNITED STATES MINERAL RESOURCES 

asbestos needs. The American asbestos-cement industry has become particularly reliant on crocidolite 

because a small content of these fibers blended with 

chrysotile facilitates manufacture. For several decades there was speculation that large resources of 

crocidolite existed in the remote Hammersley Range 

of Western Australia. The first significant mining 

of these deposits began in 1947; concurrently intensive exploration was done through large parts of an 

area about 200 miles long by 75 miles wide. Ore 

seams were found to be thin and not generally extensive, and continuity was difficult to predict. 

Crocidolite mining was recessed in 1966, apparently 

because the readily won resources had been largely 

depleted. Some 400,000 tons of crocidolite are outlined to be recovered when access and other circumstances are more favorable. Submarginal resources 

of crocidolite have been estimated at 2 million tons 

(Trendall and Blockley, 1970). Thus, some doubt 

exists that the Australian crocidolite resources can 

significantly supplement those of the Republic of 

South Africa. 

Since 1940, the increase in worldwide demand for 

asbestos has been exceptional ; more remarkable has 

been the ability of the industry to discover and 

rapidly develop resources to keep pace. These events 

are in part depicted on figute 9. Between 1940 and 

1950, U.S. consumption doubled, paralleling the 

world trend, then leveled to average about 750,000 

tons annually. With the impetus provided by the 

postwar escalation of production capacity and in 

view of the potential created by universal acceptance 

of asbestos-cement products, Canadian producers 

successfully searched out new markets and continued to increase production, thus breaking the longestablished pattern of production parallel with 

U.S. consumption. 

While Canada increased production by more than 

400 percent, from 375,000 tons in 1940 to 1,650,000 

tons in 1970, similar expansion occurred in the 

other major producing areas. Data for the U.S.S.R. 

are scant; therefore, the production record shown 

on figure 9 is incomplete. Nonetheless, the order of 

the increase in U.S.S.R. production, from 100,000 

tons in 1940 to 1,150,000 tons in 1970 is of the correct magnitude. With due allowance for exports, 

consumption of asbestos in the U.S.S.R. may have 

reached a par with U.S. consumption during the late 

1960's. Rhodesian production of chrysotile asbestos, 

about 58,000 tons in 1940, apparently tripled by the 

late 1960's. In the Republic of South Africa, where 

chrysotile makes up about 15 p~rcent, amosite about 

a third, and crocidolite something over half the output, production increased from 27,400 tons in 1940 

3~0r------+------~------+-----~------~ 

aooor------+------~------+-----~r-4---~ 

~2~r------+------~------+-------~----~ 

0 

IIa: 

0 

:I: 

Cl) 

u. 2000 r------+------~------+----+-~r-----~ 

0 

Canadian 

production 

"" 

Cl) 

0 

z 

c( 

Cl) 

:::> 

0 

:I: 1 ~ r------+------~-------tf-..l£.....--~r----=+~ 

1-

1930 1940 1950 1960 

, 

. I 

1970 

FIGURE 9.-World production, production from major sources, 

U.S. production and consumption of asbestos, 1920-70. 

to about 280,000 tons in 1970. South African output 

surpassed Rhodesia production for the first time in 

about 1950. Several nations that mined only small 

amounts of asbestos or mined only sporadically also 

have expanded production to significant tonnages in 

recent years. 

GEOLOGY 

MODES OF VE'IN OCCURRENCE 

Asbestos occurs as cross-fiber veins, in which the 

parallel fibers are about normal to the vein walls; 

as slip-fiber, in which fibers lie in near-parallel arrangement, commonly somewhat matted together, 

along the plane of the vein-commonly also an obvi-
ASBESTOS 67 

ous plane of slippage; or as mass-fiber, which is an 

aggregation of variously oriented fibers or stellate 

groups of radially arranged fibers. Most cross-fiber 

veins are split by one or more partings about parallel to vein walls; as a result, most of the fibers of 

this mode of occurrence are considerably shorter 

than vein width. Asbestos of the cross-fiber mode is 

the type most readily separated from enclosing rock 

and prepared for use. Slip-fibers may be of considerable length and flexibility, but commonly present 

difficulties in preparation. Chrysotile, crocidolite, 

and amosite occur mainly as the cross-fiber type. 

Some slip-fiber is found in most chrysotile deposits, 

and from a few it is the principal type recovered. 

The remaining asbestiform amphiboles-anthophyllite, tremolite, and actinolite-occur mainly as massfiber or slip-fiber, are least amenable to separation, 

and commonly are brittle or weak and therefore 

limited in use. The rare deposits that do include 

these minerals as strong flexible fibers in cross-fiber 

veins contain them in very small amounts. 

GENERAL SE'ITINGS 

Chrysotile asbestos the world over occurs in two 

geologic settings of different type. Chrysotile is 

won mainly from large stockworks of veins in serpentinized peridotite, pyroxenite, and dunite, collectively termed "serpentinites." From some of their 

prime occurrences these deposits can be termed the 

"Quebec type." Chrysotile asbestos is mined secondarily from deposits of the Arizona type, in which 

the veins are confined to thin serpentine layers in 

limestone. 

Anthophyllite and tremolite asbestos deposits occur in ultramafic intrusions and in associated greenstones and amphibolites; thus, their gross geologic 

setting parallels that of the principal chrysotile deposits. The deposits are small and erratic in distribution and in character of fibers. 

Crocidolite and amosite occur only in certain finegrained cherty ferruginous metasediments of the 

sort commonly designated "banded ironstones" or 

"banded iron formation." The banded' iron formations that host crocidolite occl!rrences are additionally distinctive in that aggregates of sodium-rich 

minerals occur in certain layers. Such geologic settings are known in only a few localities worldwide, 

and in still fewer places have geologic processes 

coincided in such a way as to bring about the formation of crocidolite and amosite ( Cilliers and Genis, 

1964). Locally in the northern Transvaal, amosite 

and crocidolite occur together (Cilliers, 1964). The 

only exploited deposit of crocidolite in the Western 

Hemisphere, and the only recognized potential 

source other than the South African and Australian 

occurrences previously mentioned, is in a remote 

part of east-central Bolivia. Reportedly, blue asbestos from Bolivia lacks tensile strength inherent in 

the crocidolite from other sources. 

CHRYSOTILE DEPOSITS IN MASSIVE SERPENTINITE 

REGIONAL SETTINGS OF PRINCIPAL 

NORTH AMERICAN DEPOSITS 

The zone of ultramafic rocks in the Appalachian 

belt of eastern North America is a prime example 

of the regional setting found wherever chrysotile 

deposits of the Quebec type exist. Hundreds of ultramafic intrusive masses, ranging from essentially 

concordant lenses and sills a few tens of feet wide 

and of no great length to thick irregular tabular or 

bulbous masses with maximum dimensions measurable in miles, are confined to a belt that is commonly 

less than 5 miles wide, that is only in a few places 

more than 25 miles wide, and that stretches northeast from Alabama to Newfoundland along a sinuous trace of more than 2,000 miles. This trace marks 

the site of an ancient fold mountain belt, which 

began as a eugeosynclinal trough that-starting in 

Late Ordovician time-accumulated a thick sequence· 

of sediments, which were indurated, were invaded 

by intrusive masses, and were complexly folded. 

The belt was terminated as mountain terrane in 

Middle Devonian time. 

The ultramafic rocks of this and other asbestosbearing belts are dominated by peridotite, but include much dunite and pyroxenite. These ultramafic 

r-ocks are commonly much altered to form serpentinites, and are intricately juxtaposed with basaltic 

volcanics, diabase, and gabbro to make up complexes 

that have been termed "ophiolites." The ophiolites 

of orogenic (mountain-forming) belts are generally 

designated as the "alpine type" (Thayer, 19.67). 

The genesis of the alpine-type ophiolites, and especially the mode of transport and emplacement of the 

serpentinites, long has been the subject of spirited 

debate; the debate has been accelerated particularly 

during the last decade with the rapid evolution of 

concepts of global tectonics. Early work(.rS regarded 

peridotite, pyroxenite, and dunite as rock types directly crystallized from a magma; the lack of associated thermal metamorphism and other magmatic 

features ultimately forced the conclusion that alpinetype serpentinites were emplaced in their present 

host rocks at low temperatures and probably in the 

solid state (for review, see Chidester, 1962). Recent 

hypotheses-in various versions-propose that serpentinites represent slabs of ultramfic mantle ripped 
68 UNITED STATES MINERAL RESOURCES 

from the base of the thin ocean crust and transported tectonically to be emplaced along margins 

of the continents. Coleman (1971) reviews such concepts; Bailey, Blake, and Jones (1970) discus pertinent ophiolites in California. Certain large alpinetype serpentinite masses are almost certainly sedimentary accumulations derived from tectonically 

transported mantle material (Lockwood, 1971). 

The restriction of asbestos-bearing terranes to 

short increments of the Appalachian belt is typical 

of most ophiolite belts. Veinlets of chrysotile may 

be seen sporadically in many ultramafic masses of 

the Appalachians. Until recently, the only minable 

concentrations were found along a 55-mile segment 

that trends northeast in the Eastern Townships of 

southeastern Quebec. (See Cooke, 1937 ; Riordon, 

1957.) Farther northeast, noteworthy prospects have 

been found; but only one major deposit, near Baie 

Verte on the north coast of Newfoundland, has been 

opened-and that only in the last decade. To the 

south, the Belvidere Mountain deposits of northern 

Vermont are the only minable deposits to lie outside 

the Eastern Townships, Quebec, interval. South in 

the Appalachian belt beyond Staten Island, N.Y., 

no chrysotile occurrances that would warrant more 

than cursory exploration seem to be present. 

A wholly separate ophiolite terrane of Precambrian age is exposed widely in eastern Ontario and 

extends eastward into western Quebec. Large-scale 

chrysotile asbestos production in Ontario began 

with opening of the Munro mine in 1950. Since then, 

widely separate serpentinite masses in this older 

terrane have been targets of much exploration and 

of mine development which is still current. 

A longer, much broader, and structurally more 

complex belt of ultramafic bodies, emplaced during 

Mesozoic time, crudely parallels the Pacific Coast 

of North America. The best known interval is in 

California where numerous small to very large serpentinite masses occur ( 1) in the Coast Ranges from 

southern part of the State to southwestern Oregon, 

(2) to the east of the Coast Ranges across the Great 

Valley of central California in the western foothills 

of the Sierra Nevada, and ( 3) and in especially wide 

exposures in the Klamath Mountains of northwestern California (Bailey and others, 1964). Serpentinites of a presumed offset extension of the belt 

occur in east-central Oregon. Next seen in scanty 

occurrences east of Puget Sound along the Cascades 

of northern Washington, the belt continues northnorthwest through central British Columbia and 

Yukon Territory to the vicinity of Dawson. Sub 

parallel to the British Columbia portion and 80-160 

miles west, along the panhandle of southeastern 

Alaska, is a separate noteworthy belt, 30 miles wide 

and almost 400 miles long, of zoned ultramafic bodies 

(Taylor and Noble, 1960). These bodies are little 

serpentinized and apparently lack chrysotile deposits. The continuation of the main belt in an arcuate trend northwest and perhaps west an undetermined distance into central Alaska is poorly known. 

As yet, only a few large deposits of asbestos have 

been recognized in the Pacific belt. 

LOCAliZING FACTORS 

The succession of geologic events (Cooke, 1937; 

Riordon, 1957) that culminated in the formation of 

chrysotile, deposits in southeastern Quebec is typical 

of events wherever large deposits occur. Two stages 

of serpentinization are recognized. The first stage 

was pervasive but incomplete and apparently occurred during initial cooling of magma or while 

solid ultramfic masses were being emplaced. Peridotite, which is the principal host for asbestos veins, 

and pyroxenite were only partly altered to serpentine; commonly, dunite segregations were converted 

rather thoroughly to serpentine. Much later, after 

or near the end of an episode of deformation that 

modified the structural disposition of the intrusive 

bodies, all ultramafic rocks in the vicinity of shear 

zones and associated faults and fractures were 

altered almost completely to serpentine. The stockworks of chrysotile veins that make up the deposits 

were formed during this second episode. A final episode of hydrothermal activity resulted in the formation of talc schist, steatite, and massive quartzcarbonate bodies. These materials are largely confined to major shear zones that transect the serpentinites and to sheared margins of the masses. 

In places, the asbestos was deleteriously altered by 

the talc~forming process. 

Most of the Quebec deposits border or contain 

small acidic intrusions which range from granite 

to albite syenite in composition. The parts of the 

ultramafic masses that border the granitic masses 

may be intricately fractured and thoroughly serpentinized. A few instances of chrysotile veining 

granite have been noted. These relations cause many 

investigators to believe that acid intrusions had a 

part in the genesis of chrysotile concentrations. This 

hypothesis is not universally upheld, however, probably because many chrysotile deposits exist that do 

not show obvious association to granite. 

The location, form, and size of individual chrysotile deposits in great part have been determined by 

the configuration of major faults and by the volume 

of peridotite affected by subsidiary faults and fractures; both of which in turn reflect the relative com-
ASBESTOS 69 

petencies of contiguous rock units. Riordon and 

others ( 1957) provide descriptions that permit comparisons of individual deposits. Major persistent 

shear zones in serpentinite are largely barren of 

asbestos; but stockworks of asbestos veins occupy 

intricately fractured rocks that border these shear 

zones. Similarly, thoroughly serpentinized aureoles 

adjacent to acid intrusions and completely altered 

dunite bodies tend to fail by shearing and flow; in 

response to the resultant stresses the more competent peridotites adjacent to these masses developed 

and sustaind complex networks of open fractures in 

which chrysotile was formed. Where peridotite 

masses have considerable breadth, the chrysotile 

deposits commonly hug a margin of the peridotite 

mass, reflecting again the tendency for optimum 

fracturing to occur where contrasts in rock competency exist. Several of the larger deposits occur 

where an irregularity in the plane between peridotite and host rock influenced the trend and distribution of faults. Others occur in "wedges" of fractured peridotite where throughgoing shear zones 

converge along strike or dip. 

SIZE, SHJAPE, AND ASBESTOS CONTENT 

Ore bodies are irregular in outline, may be erratic 

in asbestos content so that margins of ore bodies 

are sharp to ill defined, and range considerably in 

size. In Quebec, the minimum dimension of rudely 

ellipsoidal bodies is about 400 feet. Lenticular bodies 

are 200-2,500 feet thick and have maximum dimensions of 1,000-5,000 feet. Most of these bodies bottom at depths of 400-1,000 feet, but one major ore 

shoot extends to a depth of at least 1,800 feet. Individual deposits currently mined in Quebec originally contained 10-200 million tons of ore. A very 

exceptional deposit, the site of the Jeffrey mine 

with production capacity since the mid-1950's in 

excess of 500,000 tons of fiber per year, still has ore 

reserves on the order of 500 million tons. 

Asbestos content and quality vary. Most ore bodies 

are stockworks of cross-fiber veins; in some tabular 

bodies, veins, disposed in parallel, ribbon large parts 

of the serpentinized peridotite. Some cross-fiber 

veins are 6 inches or more thick, but all except a 

small proportion are less than 1;2 inch wide; ribbonvein occurrences in particular may average much 

less. Thus, one deposit may consistently yield short 

fibers; whereas another yields various lengths. Similarly, some deposits are rather uniform in quality of 

fiber; others contain both harsh and soft fibers. 

Deposits with an overall asbestos content of 11;2-2 

percent have been mined; some deposits locally have 

contents as high as 25 percent ; the typical occurrenee has an overall content of 5-7 percent. Thus 

the deposits are of sizes and proportions amenable 

to large-scale open-pit or underground mining methods, and in some instances only large-scale operations would permit the economic recovery of a 

range of variable ores. 

CHRYSOTILE DEPOSITS IN LIMESTONE 

The Arizona type of chrysotile deposit is made up 

of one or more tabular asbestos-bearing zones 6-8 

inches thick and of small areal extent. These tabular 

lenses were localized where cherty or otherwise siliceous magnesian li:mestones were metamorphosed 

adjacent to igneous intrusions-in most instances 

sill-form intrusions of gabbro or diabase. The 

Arizona-type deposits are mostly of small tonnage 

and are amenable to mining only by small-scale, 

high-cost methods; but the asbestos content of the 

ore is high, long fiber predominates, and low iron 

content is characteristic. Thus asbestos from the 

Arizona-type deposits can complement the short 

magnetite-rich chrysotile characteristic of most 

Quebec-type deposits. 

ASBESTOS RESOURCES IN NORTH AMERICA 

A review of exploration activities provides a 

basis for an optimistic view that many geologically 

favorable sites remain to be prospected and that 

known occurrences have not everywhere been widely 

or deeply enough explored. No attempt is made here 

to appraise asbestos resources outside North 

America. The following summation of the resources 

in the United States and contiguous areas (table 

11) is probably conservative. 

TABLE 11.-Chrysotile asbestos resources of North America, 

in short tons of fiber 

Canada ---------------- United States ----------

Mexico ----------------

Identified 

resources 1 

70,000,000 

3 3,700,000 

1,500,000 

Hypothetical 

resources 2 

35,000,000 

2,000,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained min· 

erals may or may not be profitably recoverable with existing technology 

and economic conditions. 2 Hypothetical resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that are geologically predictable as existing in known districts. a Exclusive of Group 7 resources in California, see under "United 

States." 

CANADA 

Canadian production prior to 1950 was almost 

exclusively from the Eastern Townships of Quebec. 

Since 1950 the volume of reserves outlined in Ontario, British Columbia, Yukon Territory, Newfoundland, and other parts of Quebec has increased 

steadily, and about 15 percent of Canadian production is from these sources. Considerable additions 

also have been made to the known reserves in the 
70 UNITED STATES MINERAL RESOURCES 

Eastern Townships, and this established district 

contains at least three-quarters of identified Canadian reserves. Much of the terrane encompassing 

the more recently exploited deposits is yet to be 

evaluated geologically. Pending determination that 

the later developed asbestos-bearing areas are as 

consistently geologically favorable as the Eastern 

Townships belt, the latter must continue to be regarded as the most promising area in the Americas 

for undiscovered resources. 

The first deposit opened in northern Ontario was 

depleted within 15 years, but other deposits in the 

general vicinity are taking its place, and continuing 

exploration provides promise for additional exploitable resources in that area. The Precambrian terrane that is host to these occurrences is structurally 

complex and commonly poorly exposed, and the potential asbestos deposits require rigorous geologic 

study and extensive drilling programs for evaluation. None of the Ontario occurrences have yet been 

shown to have the potential of the larger deposits 

of the Eastern Townships belt. 

Occurrences elsewhere in eastern Canada do show 

promise of sustaining large-scale operations. Significant reserves have been outlined in Maizerets 

Township and near Chibougamau, respectively about 

300 miles northwest and. north of Ottawa, and in a 

third deposit 800 miles farther north on the Ungava Peninsula. If viable mining operations materialize in these three widely separated localities 

in Quebec, they may well give the impetus to search 

out additional large resources in the Precambrian 

ultramfic terrane of the province. 

Soon after mining of the Advocate deposit, on the 

north coast of Newfoundland, began in 1963, a 

yield in excess of 60,000 tons of fiber annually was 

established. With expansion .of facilities, production 

of 100,000 tons annually is anticipated. The success 

of the Advocate development may spark continued 

prospecting of the many ultramfic bodies of Newfoundland. 

The discovery in 1950 of the Cassiar deposit on 

McDame Mountain in northern British Columbia, 

and subsequent rapid implementation of the mining 

operation-which started in 1953 despite problems 

such as rigorous climate, permafrost, and transportation logistics related to remote location-stimulated search for other deposits in the northern part 

of the Pacific Coast ultramafic belt. The Cassiar 

reserve, of some 25 million tons of ore with a content of 8-10 percent asbestos that mills free of 

magnetite and includes a high proportion of long 

fibers, has eliminated long-standing dependence on 

Rhodesia for strategic low-iron textile fibers. Comparable reserves were ultimately outlined at the 

Clinton Creek deposit, 65 miles northwest of Dawson City in the Yukon Territory and within 9 miles 

of the Alaskan border, and mining started in! 1968. 

The Cassiar and Clinton Creek mines furnished 

more than 10 percent of Canadian production in 

1969-70. West-northwest of the Clinton Creek deposit and as much as 80 miles into Alaska a few 

occurrences of chrysotile have been reported (Foster, 1969). That part of the ultramafic belt that 

extends through interior British Columbia, across 

Yukon Territory and perhaps 150 miles or more into 

the Yukon-Tanana upland of east-central Alaska is 

a prime target for much geophysical and geologic 

evaluation. 

UNITED STATES 

Prior to the early 1960's, about 80 percent of the 

asbestos produced in the United States had been 

mined from deposits on Belvidere Mountain, near 

Lowell in northern Vermont. Currently about 

40,000 tons of medium- to short-length chrysotile 

fibers are produced annually from those deposits. 

Reported reserves are more than 1 million tons of 

fiber. This remains the only locality in the Appalachian belt within the United States where minable 

concentrations of chrysotile asbestos are known or 

are likely to be found. Along the southern part of 

of the belt, particularly in western North Carolina 

(Conrad and others, 1963) and northeastern Georgia (Bowles, 1955, p. 25-26), many small deposits 

contain in aggregate an anthophyllite resource of 

more than 100,000 tons. 

Although the ultramafic rocks of California have 

been much prospected and intermittently yielded 

small quantities of asbestos after 1882, no mining 

operation of large scale was developed until 1962, 

when a plant with a capacity of 2,500 tons of ore 

per day began operation on a deposit near Copperopolis in Calaveras County. The unusual shortfiber deposits in eastern San Benito County and 

western Fresno County, northwest of Coalinga, also 

were first exploited in 1963. California immediately 

bzcame the principal asbestos-producing State and 

currently furnishes more than 75,000 tons of chrysotile fibers annually. 

The host for the occurrences near Coalinga is an 

intensely sheared mass of serpentinite 14 miles long 

and 4 miles wide. The chrysotile occurs as fibers 

largely indiscernible to the eye that are matted in 

leathery flakes along closely spaced shear planes. 

Chrysotile occurs extensively in this form in the 

southeastern half of the serpentinite mass. Fiber 

content is highly variable, but locally exceeds 50 
ASBESTOS 71 

percent; large ill-defined masses of the leathery 

material that will yield 20-25 percent fiber in the 

milling process is considered ore. Only fiber of Group 

7 grade is recovered. Obviously these occurrences 

cannot be evaluated by conventional techniques, and 

only a few sites in the sheared serpentine have been 

outlined as ore bodies. At least 100 million tons of 

flaky material amenable to processing occurs in 

masses of proportions suitable for mining. Conceivably, resources totaling several times this 

amount could occur in this 14-mile serpentinite 

mass. In nearby localities other serpentinite masses 

rather similar in character remain to be prospected. 

Obviously this is a significant resource, but of Group 

7 fiber only, and it will long be the prime source for 

certain California asbestos fabrication plants and 

may ultimately supply a much expanded industry. 

Because these resources are not typical of the content of fibers, and cannot be put to the wider range 

of uses represented in asbestos resources tabulated 

for other districts, they are not included in the 

foregoing tabulation of conventional asbestos resources available in the United States. 

Of more than 90 asbestos prospects reported in 

the serpentinites of California at least half are 

chrysotile occurrences (Wiebelt and Smith, 1959). 

About 30 are tremolite or anthophyllite occurrences. 

Intermittently, small tonnages of weak fiber that 

has limited use have been mined from some of the 

amphibole deposits, and occurrences of this type that 

remain cannot be expected individually to have more 

potential, in either volume or quality. Most of the 

little-known prospects for which the mineral species 

is not reported are likely mere mineralogic occurrences. Geologic settings with promise of hosting 

extensive chrysotile stockworks of the Quebec type 

are most numerous along the western foothills of 

the Sierra Nevada and in the Klamath Mountains, 

which is a northern outlier of the foothills belt. 

Among or in the vicinity of the chrysotile prospects 

of these areas, it is reasonable to anticipate that at 

least a few and perhaps several additional deposits 

comparable to the Copperopolis ore body will ultimately be discovered. The possibility of large stockworks of chrysotile in the serpentinite masses west 

of the Great Valley of California is certainly not to 

be overlooked, but relatively few of these appearfrom sparse information-to be promising in their 

geologic settings. 

In east-central Oregon, along the presumed offset 

continuation of the Pacific Coast ultramfic belt, 

exposures of serpentinite masses are sparse compared to the numbers and volume exposed in the 

California interval. Oregon is thus a less promising 

region to prospect. The most promising known eastern Oregon chrysotile occurrence has been explored 

by modern techniques, apparently without outlining 

significant amounts of asbestos. 

Other domestic occurrences of chrysotile in massive serpentinite receive intermittent attention as 

possible targets for prospecting. Most noteworthy 

among these are occurrences at various localities 

near the Kobuk River in northwestern Alaska 

(Bowles, 1955, p. 17) and scattered prospects in 

Wyoming opened during and before World War I 

(Beckwith, 1939). Past prospecting of the northwest Alaska occurrences was directed mainly toward 

determining mineral species and whether fibers of 

textile length existed. Most of the prospected occurrences are of short-fiber chrysotile; data available 

provide little hint as to whether or not any are 

potential targets for outlining extensive deposits. 

In the area prospected for chrysotile a few miles 

south of Casper, Wyo., rocks other than serpentinite 

make up the bulk of exposures ; many of the serp::mtinite exposures are barren of asbestos, and 

apparently none exhibit faces extensively veined by 

asbestos. It is not certain that any of these serpentine masses are large enough to contain an asbestos 

deposit of minable size. Serpentine masses south of 

Lander, Wyo., are moderately well exposed and 

obviously large enough to include minable stockworks of chrysotile; none of the present exposures 

contain enough asbestos to encourage mining, but 

chrysotile veining is widespread enough to suggest 

that the occurrence could be reassessed as a possible target for exploration by modern techniques. 

The chrysotile resources of Arizona are entirely 

in deposits of the limestone type.- At any given time, 

reserves estimated for the entire district aggregate 

only a few thousand tons. From considerations of 

geologic habit and regional distribution, an estimated 75,000 to 100,000 tons of fiber remains to be 

discovered within the depths at which these typically 

small deposits can be economically mined (Shride, 

1969). Those resources include a high proportion of 

long fiber. When available, as in the past, these 

resources will largely be marketed only for special 

uses. Chrysotile occurrences of the Arizona type 

known in the Panamint Mountains of eastern California and near Cliff Lake in the Madison Range of 

southwestern Montana are erratic in fiber distribution. They do not approach the Arizona deposits in 

quality of fibers or in continuity of the mineralized 

zones and cannot be regarded as recoverable resources. 

MEXICO 

The search for and mining of chrysotile asbestos 
72 UNITED STATES MINERAL RESOURCES 

is just beginning in Mexico. Two widely separated 

deposits contain the reported reserves. Until more 

is known of the settings of these occurrences, geologic projection of additional resources is not plausible. The expanding asbestos-cement product industry 

of Mexico will long have first call on any resources 

that can be discovered in that country. 

PROSPECTING TECHNIQUES 

Quebec-type chrysotile deposits are large enough 

targets to be searched out by geophysical techniques ; 

the magnetite ubiquitous in ultramfic terranes determines the prospecting method. Magnetite, most 

abundant in parts of the ultramfic complexes most 

intensely faulted, is thus a common constituent of 

asbestos veins and adjacent wallrock, where anomalous concentrations can be outlined by magnetic 

surveys. Major zones of shearing and bodies of serpentinized dunite, both likely to be barren of asbestos, can also be expected to exhibit strong magnetic 

anomalies. Therefore, interpretation of magnetic 

data is most effective when done with knowledge 

of the geologic habits of the ultramafics of a given 

area. Ground surveys have long been a prime 

method to outline potential asbestos-bearing zones 

(Low, 1951). Airborne magnetic surveys are especially effective for reconnaissance to locate serpentinite masses, and with moderate geologic ground 

control or local supplementation by ground magnetic 

surveys, airborne surveys can be used to outline 

geologic features of possible economic significance 

(Conn, 1970). 

PROBLEMS FOR RESEARCH 

The reasons for the restriction of large concentrations of chrysotile asbestos to certain very limited 

intervals in an alpine-type serpentine belt are not 

yet clear. Data of the sort that led to the recent 

recognition (Irwin, 1964) that serpentinites of the 

Klamath Mountains of northern California are 

somewhat older (and the subjects of a different tectonic history) than serpentinites contiguous to the 

west are possibly the kind of field data needed for 

future evaluations. In this instance the known 

chrysotile occurrences may be entirely restricted to 

the older serpentinites. 

The evolution of ideas on the tectonic emplacement of alpine-type serpentinites should be given 

close future attention for hints as to targets for 

asbestos exploration. The restriction of asbestos 

concentrations to only parts of the geosynclinal belts 

may be related to a certain sequence of structural 

events, or to optimum pressures or temperatures 

operative in one tectonic wedge and not in an adjacent mass. Appraisals are being made of the strength 

and ductility or brittle behavior characteristics of 

the various serpentinites. Certainly the degree of 

competence prevailing at the time when energy and 

solutions were available for the late (local) stage 

serpentinization was a vital factor in formation of 

a minable deposit. As a part of the "global tectonics" 

research, physical properties of the various occurrences of serpentinite may one day be accurately 

and readily defined ; these data and the techniques 

used in their determination should be given attention for practical application. As a potential secondary result of such studies, for instance, perhaps 

magnetic anomalies directly related to asbestos 

localization may be differentiated from magnetic 

phenomena that are not so related. 

SELECTED REFERENCES 

Avery, R. B., Conant, M. L., and Weissenborn, H. F., 1958, 

Selected annotated bibliography of asbestos resources in 

the United States and Canada: U.S. Geol. Survey Bull. 

1019-L, p. 817-865. 

Badollet, M. S., 1951, Asbestos, a mineral of unparalleled 

properties: Canadian Inst. Mining and Metallurgy 

Trans., v. 54, p. 151-160. 

-- 1953, Asbestos fibers-Production and usage: Canadian Inst. Mining Metall. Trans., v. 56, p. 247-249. 

Bailey, E. H., Irwin, W. P., and Jones, D. L., 1964, Franciscan and related rocks and their significance in the 

geology of western California: California Div. Mines and 

Geology Bull. 183, 177 p. 

Bailey, E. H., Blake, M. G., Jr., and Jones, D. L., 1970, Onland Mesozoic oceanic crust in California Coast Ranges, 

in Geological Survey research 1970: U.S. Geol. Survey 

Prof. Paper 700-C, p. C70-C81. 

Beckwith, R. H., 1939, Asbestos and chromite deposits of 

Wyoming: Econ. Geol., v. 34, no. 7, p. 812-843. 

Bowles, Oliver, 1955, The asbestos industry: U.S. Bur. Mines 

Bull. 552, 122 p. 

-- 1959, Asbestos-a materials survey: U.S. Bur. Mines 

Inf. Circ. 7880, 94 p. 

Carroll-Porczynski, C. Z., 1958, Inorganic fibers: New York, 

Academic Press Inc., p. 169-259. 

Chidester, A. H., 1962, Petrology and geochemistry of selected talc-bearing rocks and adjacent country rocks in 

north-central Vermont: U.S. Geol. Survey Prof. Paper 

345, 207 p. 

Chidester, A. H., and Shride, A. F., compilers, 1962, Asbestos 

in the United States (exclusive of Alaska and Hawaii): 

U.S. Geol. Survey Mineral Inv. Resource Map MR-17. 

Cilliers, J. J., leR., 1964, Amosite at the Penge asbestos 

mine, v. 2 of Haughton, S. H., ed., The geology of some 

ore deposits in southern Africa: Geol. Soc. South Africa, 

p. 579-591. 

Cilliers, J. J., leR., and Genis, J. H., 1964, Crocidolite asbestos 

in the Cape Province, v. 2 of Haughton, S. H., ed., The 

geology of some ore deposits in southern Africa: Geol. 

Soc. South Africa, p. 543-570. 

Coleman, R. G., 1971, Petrologic and geophysical nature of 

serpentinites: Geol. Soc. America Bull., v. 82, p. 897-

918. 
ASBESTOS 73 

Conn, H. M. K., 1970, Geophysics and asbestos exploration, 

in Mining and groundwater geophysics-1967: Canada 

Geol. Survey Econ. Geology Rept. 26, p. 485-491. 

Conrad, S. G., Wilson, W. F., Allen, E. P., and Wright, T, J., 

1963, Anthophyllite asbestos in North Carolina: North 

Carolina Dept. Conserv. and Devel. Div. Mineral Resources Bull. 77, 61 p. 

Cooke, H. C., 1987, Thetford, Disraeli, and the eastern half 

of Warwick map-areas, Quebec: Canada Geol. Survey 

Mem. 211, Pub. 2440, 160 p. 

Foster, H. L., 1969, Asbestos occurrence in the Eagle C-4 

quadrangle, Alaska: U.S. Geol. Survey Circ. 611, 7 p. 

Industrial Minerals, 1970a, Cement products the key to asbestos industry growth: Indus. Minerals (London), no. 

28, p. 9-17. 

--- 1970b, World asbestos industry: Indus. Minerals 

(London), no. 28, p. 17-29. 

Irwin, W. P., 1964, Late Mesozoic orogenies in the ultramafic 

belts of northwestern California and southwestern Oregon: U.S. Geol. Survey Prof. Paper 501-C, p. Cl-C9. 

Jenkins, G. F., 1949, Asbestos, in Industrial minerals and 

rocks, 2d ed.: New York, Am. Inst. Mining Metall. 

Engineers, p. 55-76. 

--- 1960, Asbestos, in Industrial minerals and rocks, 3d 

ed.: New York, Am. In st. Mining Me tall. Petroleum 

Engineers, p. 23-53. 

Lockwood, J. P., 1971, Sedimentary and gravity-slide emplacement of serpentine: Geol. Soc. American Bull., v. 

82, p. 919-936. 

Low, J. H., 1951, Magnetic prospecting methods in asbestos 

exploration [Quebec]: Canadian Inst. Mining Metallurgy 

Trans., v. 54, p. 888-395. 

Rice, S. J., 1963, California asbestos industry: California 

Div. Mines and Geology Mineral Inf. Service, v. 16, no. 

9, p. 1-7. 

Riordan, P. H., 1957, The structural environment of the 

Thetford-Black Lake asbestos deposits [Quebec]: Geol. 

Assoc. Canada Proc., v. 9, p, 83-93. 

Riordon, P. H., and others, 1957, Asbestos, in The geology of 

Canadian industrial mineral deposits: Sixth Commonwealth Mining and Metall. Cong., p. 3-53. 

Shride, A. F., 1969, Asbestos, in Mineral and water resources 

of Arizona: U.S. 90th Cong., 2d. sess., Senate Interior 

and Insular Affairs p. 303-311. 

Taylor, H. P., Jr., and Noble, J. A., 1960, Origin of the 

ultramafic complexes in southeastern Alaska: Internat. 

Geol. Cong., 21st, Copenhagen 1960, Rept. 13, p. 175-

187. 

Thayer, T. P., 1967, Chemical and structural relations of 

ultramafic and feldspathic rocks in alpine intrusive 

complexes, in Wyllie, D. J., ed., Ultramafic and related 

rocks: New York, John Wiley and Sons, p. 222-239. 

TrendaU, A. F., and Blockley, J. G., 1970, The iron formations of the Precambrian Hamersley Group, Western 

Australia, with special reference to the associated crocidolite: Geol. Survey Western Australia, Bull. 119, 

366 p. 

Wiebelt, F. J., and Smith, M. C., 1959, A reconnaissance of 

asbestos deposits in the serpentine belt of northern 

California: U.S. Bur. Mines Inf. Circ. 7860, 52 p. 

UNITED STATES MINERAL RESOURCES 

BARITE 

By DoNALD A. BRoBsT 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

Exploitation ------------------------------------- Geochemistry _________________________ --__ - _ ----_ 

Ore minerals of barium --------------------------

Types of deposits -------------------------------- Vein and cavity-filling deposits ---------------

Residual deposits ----------------------------

Bedded deposits -----------------------------

Resources --------------------------------------- Identified and hypothetical resources ----------

Speculative resources ------------------------

Prospecting techniques ---------------------------

Problems for research ----------------------------

Referenc·es cited ---------------------------------

FIGURE 

10. Barite, world production and U.S. production 

and consumption, 1919-71 -----------------

TABLES 

12. Barite, world production and U.S. production 

Page 

75 

75 

76 

77 

78 

78 

78 

79 

80 

81 

81 

82 

83 

83 

84 

Page 

77 

Page 

and imports, 1850-71 --------------------- 76 

13. Identifi·ed and hypothetical barite resources of 

the United States ------------------------ 81 

14. World resources of barite ------------------- 82 

ABSTRACT OF CONCLUSIO~S 

The world production of barite (BaSO,, barium sulfate) 

has increased from less than 1.5 million tons in 1945 to more 

than 4 million tons in 1970. The world's estimated total 

barite production from 1850 to 1971 amounted to nearly 92 

million tons, but nearly 75 percent of that total was mined 

between 1945 and 1971 and increasing use is forecast, particularly inasmuch as barite is vital to the petroleum industry, which in 1972 consumed 80 percent of the world's 

annual production. The United States is self-sufficient and 

should remain so, even with modestly increasing demands 

placed on its resources. 

Three major types of barite deposits are vein and cavityfilling, residual, and bedded deposits. The vein and cavityfilling deposits of the world constitute large resources of 

barite, much of which are recoverable as byproducts or coproducts. Residual deposits at shallow depths constitute a 

large resource in the United States. Bedded deposits of fetid 

black fine-grained barite·, commonly of high grade (50-95 

percent barite) , are abundant in siliceous sedimentary rocks 

of mid-Paleozoic age. The bedded deposits, probably of sedimentary origin, are a large part of the barite resources of 

the United States. Similar large deposits probably lie undiscovered in many parts of the world. 

The total of the world's barite resources in all categories 

is about 2 billion metric tons of barite, but only about 300 

million metric tons (15 percent) are identified resources, 

which are the sum of curr·ently minable ore (reserves) and 

lower grade material of subeconomic value now (conditional 

resources) . If future industrial demands are to be met, 

hypothetical and speculative resources will have to be converted to identified resources, and this will require continued geological research on barite and barium minerals. 

INTRODUCTION 

Barite (BaS04, barium sulfate) is extremely vital 

to the petroleum industry, which consumes much 

of the world's current annual production of about 

4 million tons, as a major ingredient of the heavy 

fluid, called mud, that is circulated in the rotary 

drilling of oil and gas wells. Barite also is a source 

for various barium compounds and barium metal 

whose uses also are nearly hidden among the technical complexities of modern industrial processes 

and products. 

In the United States, about 80 percent of the 1.5 

million tons of barite consumed annually is ground 

finely (90 percent, minus 325 mesh) for use in 

drilling mud, the circulation of which lubricates the 

drill stem, cools the drill bit, seals off the walls of 

the hole, removes cuttings, and confines the high oil 

and gas pressures met at depth. The latter feature 

aids in the prevention of gushers, thus reducing 

U.S. GEOL. SURVEY PROF. PAPER 820 

75 
76 UNITED STATES MINERAL RESOURCES 

waste of oil and gas resources and environmental 

pollution, as well as conserving the natural pressure 

for greater production and rate of recovery of the 

products in the reservoir rocks. Barite is particularly well suited for drilling mud because it is soft, 

heavy, chemically inert, and available in sufficient 

quantity at competitive prices throughout much of 

the world. Many heavy materials tried as substitutes for barite in drilling mud have been rejected 

simply because of excessive initial cost, because they 

react chemically in the system, or because they 

abrade pipes, pumps, and hole walls resulting in 

increased drilling costs. 

The remaining 20 percent of barite consumed 

annually in the United States goes chiefly into the 

manufacture of glass to add brilliance and clarity; 

into the wares of the paint and rubber industry 

principally as a pigment and filler; and into the 

chemical industry for the preparation of barium 

compounds. Barite is a common industrial filler, extender, and weighting agent. A survey of the uses 

of barium chemicals by the Food Machinery and 

Chemical Corp. (1961) listed more than 2,000 specific industrial applications in 17 major classifications. Among the newer developments are the use 

of barium titanate ceramics in the electronics industry and of barium f~rrate ceramics in permanent magnets. Barite, a good absorber of gamma 

radiations, has been used as an aggregate in concrete for shielding in atomic reactors, thereby reducing the amount of more expensive lead shielding 

otherwise needed. 

With energy requirements rising in the United 

States and throughout the world, there is every 

reason to believe that demand for mud-grade barite 

(92-94 percent BaS04 ) will continue at high levels, 

and even increase, as the search for oil and gas continues. Not only will more wells be drilled, but they 

will be deeper and they will extend into highpressure reservoirs requiring the use of more barite 

as the potential for blowouts and mud leakage increases. Other industrial uses of barite are sure to 

continue at accelerated rates as the population 

grows, as new nations industrialize, and as economies expand in the older industrial nations. Further 

information on uses, material specifications, economics, production, and outlook for future demand 

of barite has been given recently by Brobst (1970) 

and Lewis (1970). 

As the decade of the 1960's closed, nearly 1 million tons of barite was produced annually in the 

United States, chiefly in Missouri, Arkansas, Nevada, Georgia, and Tennessee. Another half million 

tons was imported annually from various countries, 

especially Canada, Mexico, Peru, Ireland, Greece, 

Yugoslavia, and Morocco. Current knowledge of the 

widely distributed domestic reserves of barite suggests that the United States could be self-sufficient 

in barite for some years, even at moderately increasing rates of consumption (Brobst, 1970, p. 11-12). 

EXPLOITATION 

Commercial demand for barite began about mid19th century when the United States and the nations of western Europe began to industrialize. 

Estimates of the world's barite production compiled 

from various sources are shown in table 12. Nearly 

TABLE 12.-Barite, world production and U.S. production and 

imports, in millions of short tons, 1850-71. 

[Compiled from U.S. Bur. Mines data and many other sources] 

World u.s. 

production production 

1850-1914 ----------- 1 6.5 1.2 

1915-18 ------------- 1.2 .7 

1919-44 ------------- 16.7 7.1 

1945-71 ------------- 67.5 23.5 

Total --------- 91.9 32.5 

1 Author's estimate: few foreign production data available. 2 2,500 short tons imported during this period. 

u.s. 

imports 

0.2 

20 

.9 

12.5 

13.6 

75 percent of the total world's barite production of 

nearly 92 million tons has been mined since 1945, 

and the United States has consumed 46 million tons 

(about half) of this amount. 

Figure 10 shows world production, U.S. production, and U.S. consumption (production plus imports) from 1919 to 1971. The three curves are 

almost parallel until 1959, after which barite consumption outside of the United States increased 

sharply because of an expanding world need for 

mud-grade barite. The peak between 1925 and 1930 

coincides with the period when barite was first used 

for drilling mud. 

From 1838 to 1971, the. residual deposits of the 

United States have yielded about 17 million tons of 

barite, the bedded deposits about 11.5 million tons, 

and the vein deposits about 4 million tons. Before 

1940, most of the U.S. barite production came from 

residual deposits, chiefly in Missouri, Tennessee, 

and Georgia. After 1940, the black bedded barite 

deposits of Arkansas came into production and 

within a few years the barite produced rivaled, and 

in some years exceeded, that of the great residual 

deposits of Missouri. The bedded deposits of Nevada 

have been worked since early in the 20th Century 

at rates that since 1960 have increased almost 

annually. 
BARITE 77 

~3000H-------~-----+------4---~H4------~ 

z 

0 

IIa:: 

~2~0H-------~-----+------4--1--~------~ 

~ 

u.. 

0 

~ 

~ 2~H-------r------+------~~~~------~ ~ 

~ 

::::> 

0 

::t 

1- 1500H-------~-----+------#-~~rn~~4-~ 

1930 1940 1950 1960 1970 

FIGURE 10.-Barite, world production and U.S. production 

and consumption, 1919-71. 1. Post-World War I dep·ression. 2. Barite drilling mud introduced and accepted. 3. 

Economic depression. 4. World War II. 5. World economic 

recession. 

Barite has been or could be produced as a byproduct or coproduct of some fluorspar, base and 

precious metal, and rare-earth deposits. These 

sources of barite have not been greatly utilized for 

many reasons. Some deposits are too far from 

markets, or the additional milling operation cannot 

be handled by existing mills. The barite is too 

irregularly disseminated in some deposits, and the 

demand for the major product too variable to guarantee the barite user a steady supply in others. 

Economic changes may bring much of this barite 

into future markets. 

Most of the barite mined in the United States has 

been mined in open pits. The mining of residual 

deposits has brought on the need to rehabilitate 

many acres of worked ground. In many areas of 

shallow residual deposits, rehabilitation is not difficult, but any costs will ultimately be paid by the 

consumer. 

GEOCHEMISTRY 

Recent estimates of the abundance of barium in 

the earth's crust (Parker, 1967; Lee and Yao, 1970) 

suggest that the value lies in the range of 300-500 

ppm (parts per million equals grams per metric ton ; 

1 ppm equals 0.0001 percent). In igneous rocks, the 

basalts contain as little as 100 ppm Ba; granites 

commonly contain 700-800 ppm Ba; syenites and 

some of the more potassic igneous rocks contain as 

much as 3,000-5,000 ppm Ba. The role of barium in 

the crystallization of igneous rocks has been discussed by Dunham and Han or ( 1967) . Among the 

sedimentary rocks, shale generally contains the most 

barium (500-1,000 ppm) and limestone contains 

the least (commonly less than 200 ppm) . The barium content of sandstone varies widely, from a few 

to several hundred parts per million. 

The large size of the barium ion in its common 

valence state· (Ba+2, 1.43 angstrom units) makes 

isomorphous substitution possible only with strontium (Sr+2 , 1.27) and generally not with the other 

members of the elements of Group 2A of the periodic 

table (Ca +z, 1.06; Mg+2 , 0.78). Among the other 

elements that occur with barium in nature, substitution is common only with potassium (K+, 1.33), 

but not with the smaller ions of N a, Fe, Mn, AI, and 

Si in their most common valence states. This explains why the potassium-rich igneous rocks contain the greatest amounts of barium. The barium 

commonly substitutes for potassium in the minerals 

of the feldspar and mica groups. 

Unlike many other common metals, the sulfide of 

barium is water soluble, the sulfate is virtually insoluble in distilled water, and, as the chloride the 

element is easily transportable. Barium, therefore, 

is mobilized, transported, and concentrated under 

different conditions from those which govern the 

course of many base and ferrous metals in the geochemical cycle. 

The geochemical cycle of barium begins with its 

arrival in the upper crust of the earth as a result 

of volcanic activity and the emplacement of intrusive igneous rocks and any attendant vein systems. 

The mechanical and chemical disintegration of igneous rocks releases barium to the sedimentary 

cycle through which it is carried seaward as fine 

particles of mineral material, or as ions absorbed 

on particles of clay size, or perhaps attached to 

negatively charged sols, such as Mn (OH) 4· In the 

sea, ionic barium will combine readily with available sulfate anions to form a precipitate of barium 
78 UNITED STATES MINERAL RESOURCES 

sulfate (barite), which accounts for the low concentration of barium in sea water. 

Connate brines of many sedimentary formations 

contain barium chloride (BaCl2) which on mixing 

with sulfate-rich waters will yield a precipitate of 

barite. This process has caused problems in oil field 

operations, notably in the Wilmington (Long Beach, 

Calif.) oil field (Gates and Caraway, 1967). 

The geochemistry of barium is complex. More information and many references are available in the 

works of Rankama and Sahama ( 1950), Graf 

(1960), and Friedman (1969). 

ORE MINERALS OF BARIUM 

Barite, the chief ore mineral of barium, when 

pure, has a specific gravity of 4.5, has a hardness 

of 3 on Mobs' scale (in which the hardness of a 

fingernail is about 1.5), and contains 58.8 percent 

barium and 41.2 percent sulfate. The mineral occurs 

in assorted colors, although shades of white to dark 

gray and black are common in commercial deposits. 

Barite crystallizes in the orthorhombic system and 

commonly forms prismatic or tabular crystals. Generally it is found in irregular masses, concretions, 

nodules, rosettelike aggregates, and in massive to 

laminated beds. Mine-run ores contain some inclusions and intergrowths of other minerals as well as 

small amounts of other elements (Brobst, 1958, p. 

80-81). Barite of vein and residual deposits commonly contains several percent strontium. 

Barite is most commonly associated with quartz, 

chert, jasperoid; calcite, dolomite, siderite, rhodochrosite, celestite; fluorite; and various sulfide minerals, such as pyrite, chalcopyrite, galena, sphalerite, 

and their oxidation products. Ferruginous clays 

make up a large part of residual deposits of barite. 

Barite is a common gangue mineral in many types 

of ore deposits, especially in veins that are mined 

principally for other commodities, including lead, 

zinc, gold, silver, fluorite, and rare-earth minerals. 

Barite is a common constituent of some siderite-rich 

iron deposits in Europe, but deposits of this type 

have not been found in the United States. 

Witherite (BaC03, barium carbonate, 69.6 percent Ba and 30.4 percent C03), a highly desirable 

source for the production of barium chemicals because of its solubility in hydrochloric acid, occurs 

as a minor accessory mineral in some barite deposits. Like barite, this mineral also crystallizes in the 

dipyramidal class of the orthorhombic system. 

Witherite has a hardness of 3-3.5 on Mobs' scale 

and a calculated specific gravity of 4.29. In the 

United States, only the El Portal mine, Mariposa 

County, Calif., has produced witherite in large 

amounts ; operations ended there about 1950. Nearly 

all the world's supply of witherite in 1972 came 

from the Settlingstones mine, N orthumberlandshire, 

England. Witherite is probably only a very small 

part of the barium resources of the world. 

~san bornite (BaSi205), which contains 50 percent 

bari urn, is of potential interest as a source of 

barium for chemicals because, unlike many silicate 

minerals, it is soluble in acid. The solubility permits 

the recovery of the barium by further chemical processing. The mineral, formerly considered rare, has 

been found in abundance associated with other 

barium silicate minerals in contact with metamorphic rocks, mostly quartzite, in roof pendants 

of the Sierra Nevada batholith in Fresno County, 

Calif. (Matthews and Alfors, 1962). The resource 

potential of sanbornite deposits is virtually unstudied. 

Barium occurs in other minerals, but in concentrations so low that none of the minerals are likely 

to be potential sources of the element. 

TYPE OF DEPOSITS 

Barite occurs in many geological environments 

in sedimentary, igneous, and metamorphic rocks. 

The geologic relations of three major types of commercial deposits, the vein and cavity-filling, the 

residual, and the bedded deposits, have been summarized by Brobst (1958). 

Some recent references to the geology of barite 

are given in this report; others are available in an 

annotated bibliography by Dean and Brobst ( 1955), 

and in a pamphlet included with a map (at a scale 

of 50 miles to the inch) which shows the size and 

distribution of deposits in the United States (Brobst, 

1965). A summary of the geology and reserves of 

barite deposits of the world (Brobst, 1970) also 

includes a bibliography of about 100 references to 

deposits outside the United States. 

VEIN AND CAVITY -FILLING DEPOSITS 

The vein and cavity-filling deposits are those in 

which barite and associated minerals occur along 

faults, gashes, joints, bedding planes, breccia zones, 

and solution channels and in various sink structures. 

The deposits in solution-channel and sink structures 

are most common in limestone. The host rocks are 

of Precambrian to Tertiary age in the United States. 

Many deposits in the Western States are associated 

with igneous rocks of Tertiary age, J~.lthough notable exceptions are vein deposits of barite and rareearth minerals associated with igneous rocks of 

Precambrian age at Mountain Pass, San Bernardino County, Calif., and in the Wet Mountains, 
BARITE 79 

Custer County, Colo. In most of the deposits in the 

Eastern and Midwestern States an association with 

igneous activity is not obvious. 

Most of the barite in veins and cavity fillings is 

dense and gray to white, and is associated with 

many other minerals including the minerals of the 

metallic ores as already mentioned. The grade of 

the barite ore varies by deposit and within deposits. 

The deposits commonly have sharp contacts with 

wallrocks; large-scale replacement of the host rocks 

by vein minerals is rare. Within individual districts, 

the deposits commonly are scattered and irregular, 

and range in thickness from a few inches to a few 

feet and in length from tens to hundreds of feet. 

Barite cementing of breccia along fault zones forms 

thin deposits of small extent in the eastern United 

States. On weathering, fault-breccia deposits may 

form bodies of residual ore. 

Barite deposits in collapse and sink structures 

are common in central Missouri where they are 

known as circle deposits, and in the Appalachian 

States. The deposits have yielded rich ore but the 

individual bodies tend to be small. On weathering, 

these deposits also form valuable bodies of residual 

ore. 

The barite and other minerals of the vein and 

cavity-filling deposits are typical of an epithermal 

suite precipitated from low-temperature solutions. 

Many geologists agree that most vein deposits containing barite in the Western States had such an 

origin. A hydrothermal origin also is postulated for 

many deposits in the midcontinent region and in the 

Eastern States where the term "telethermal" has 

been applied to indicate that the solutions traveled 

farther from their source, and therefore, were somewhat cooler than those generally termed "epithermal." Evidence has been accumulating in the past 

decade to suggest that some barite and minerals of 

base metals may form vein deposits from circulating ground waters (meteoric or supergene water). 

RESIDUAL DEPOSITS 

Residual barite deposits in unconsolidated material are formed by weathering from preexisting 

deposits. Many residual deposits of commercial interest lie within the clayey residuum derived from 

Cambrian and Ordovician limestone and dolomite, 

especially in southeastern Missouri (Brobst and 

Wagner, 1967) and the Appalachian region (Brobst 

and Hobbs, 1968). These include deposits in the 

major barite districts at Sweetwater, Tenn. (Maher, 

1970, p. 13) and Cartersville, Ga. (Kesler, 1950), 

and many lesser known districts in Alabama and 

Virginia. 

Most residual barite is white and is translucent 

to opaque; it occurs in discrete mammillary, fibrous, platy, or dense fine-grained irregular masses 

most of which range in longest dimension from 

about 1 to 6 inches. Small amounts of pyrite, galena, 

and sphalerite occur in or on some of the barite, 

and locally some lead and zinc may be minor byproducts of barite mining. Chert and jasperoid are 

common in many deposits. Incompletely weathered 

rock fragments, and red, yellow, or brown clay 

typically make up the rest of most deposits. 

The grade of the ores varies greatly, but commercial mining now requires a minimum of about 

220 pounds of recoverable barite per cubic yard of 

residuum. Much of the typical ore in major districts 

has 200-300 pounds of recoverable barite per cubic 

yard of residuum. 

Deposits in Washington County, Mo., are in residuum overlying bedrock 10-15 feet below the surface. The deposits at Cartersville, Ga., are in residuum that is as deep as 150 feet. Commercial 

deposits are commonly many acres in extent, but 

the shape of the residual deposit depends on the 

shape of the original deposit. Deposits derived from 

solution channels and vein systems tend to be 

elongate, and those derived from sink structures 

tend to be circular. 

Ribs or pillars of carbonate bedrock protrude upward into the residuum at many deposits. Some of 

the ribs contain veins filled with barite, fluorite, 

quartz, calcite, and locally some sulfide minerals 

including pyrite, chalcopyrite, galena, and sphalerite. In other deposits, only thin veinlets or disseminated lumps and pods of barite occur in the 

carbonate bedrock. The source of the barite in 

residual deposits generally has been assumed to be 

epigenetic (introduced) hydrothermal vein material 

left after the host rock has been chemically destroyed. 

Today's knowledge of mineralogy and crystallography suggests that any barium that was trapped 

in precipitating carbonate will fit into the lattice 

of aragonite, which seems to be a common primary 

precipitate of calcium carbonate. Because of the 

differences in ionic radii of the cations and the 

crystal structure, barium will not fit into the lattice 

of calcite or dolomite. Thus, when aragonite is converted to calcite or dolomite, any structurally included barium is expelled from the lattice. It seems 

reasonable to suppose that any sulfate present in 

the pore fluids might then fix the barium as barite 

in veinlets or nodules in the carbonate rocks. If the 

pore fluid is chloride-rich, and sulfate-poor, the 

expelled barium might be converted to the very 
80 UNITED STAT'ES· MINERAL RESOURCES 

soluble chloride, in which case the barium could be 

held in solution to be precipitated later, in place or 

elsewhere, as barite when sulfate ions became 

available. Connate water may play an important 

role in the redistribution of barium in the carbonate 

environment. The foregoing is perhaps an oversimplification of a complex chemical process, but it 

does offer an explanation of why calcite- and 

dolomite-rich rocks generally contain such small 

amounts of barium. Just as important perhaps is 

the largely unevaluated role of organisms, especially 

bacteria, in the mobilization and redistribution of 

elements such as barium in the sedimentary environment under conditions of low temperature and 

pressure. 

BEDDED DEPOSITS 

Bedded deposits include those in which barite 

occurs as a principal mineral or cementing agent 

in stratiform bodies in layered sequences of rock. 

The major deposits of commercial value in this 

group are bedded concentrations of fetid dark-gray 

to black fine-grained barite, some of which contain 

millions of tons of barite easily beneficiated for use 

in drilling mud and chemical plants. Deposits were 

being mined in 1972 in Arkansas, California, and 

Nevada. Geological details are available for some 

deposits in Arkansas, including the major deposit 

at Magnet Cove (Scull, 1958; Zimmermann and Amstutz, 1964) ; in Nevada, including deposits in the 

Toquima Range (Shawe and others, 1969) and the 

Shoshone Range (Ketner, 1965; Zim1nermann, 

1969) ; and in California, near Castella, Shasta 

County (Weber and Matthews, 1967). The bedded 

deposits and their origin are discussed in some de--

tail here because of the economic value of these 

deposits and the good potential for finding more of 

them in many parts of the world. 

Geologic features of the bedded deposits may be 

summarized briefly. The dark beds of barite are a 

few inches to 50 feet thick and extend over many 

acres. The beds commonly occur interbedded with 

dark chert and siliceous siltstone and shale. Some 

ore zones are more than 100 feet thick. Some individual beds of barite are massive, but more commonly the beds are laminated. The grains of barite 

generally are less than 0.1 mm in diameter. Barite 

nodules and rosettes make up a substantial part of 

some barite beds, and a smaller part of some silty 

or shaly beds. Some nodules have concentric rings 

of barite, and the rosettes have a radially bladed 

structure. Both structures suggest that room for 

free growth existed during deposition. Conglomeratic beds consisting of nodules and fragments of 

barite, chert, phosphate (apatite), and fragments 

of rock in a fine-grained matrix of barite have been 

found in the Toquima Range, Nev. (Shawe and 

others, 1969, p. 248). Many small-scale sedimentary 

textures and structures, as well as rhythmic alternations of beds have been described (Zimmermann 

and Amstutz, 1964; Zimmermann, 1969). 

Many beds of ore in these deposits consist of 50-

95 percent barite. The chief impurity is fine-grained 

quartz whose abundance is inverse to that of barite. 

Small amounts of clay and pyrite are common. Carbonate minerals are rare. Spectrographic analyses 

of many samples indicate that the environment of 

these barite deposits is extremely low in calcium 

and magnesium-the total of these two elements 

generally is less than 1 percent. The most abundant 

minor element is strontium; it occurs in amounts 

up to about 7,000 ppm. The trace element suite is 

limited, and the abundance of each element is unusually small as compared with the suite and abundance of the trace elements in vein deposits. Manganese and vanadium generally are each less than 

50 ppm. Cobalt, copper, chromium, nickel, yttrium, 

and zirconi urn each are less than 20 ppm. 

The beds of black bedded barite contain several 

percent organic matter and characteristically give 

off the odor of hydrogen sulfide (H2S) when struck 

with a hammer. The hydrogen sulfide is believed to 

be the product of the decay of organic matter and 

reduction of sulfate by anaerobic bacteria. Fatty 

acids, hydrocarbons, and other organic compounds 

(a geolipid fraction) have been extracted from samples collected in Arkansas, California, and Nevada 

(Miller and others, 1972). The fatty acids identified 

are considered to be biological markers for the 

cell walls of bacteria that probably once lived on 

or within the crystallizing barite masses. 

Rocks containing the black bedded deposits commonly are of mid-Paleozoic age even though they 

are widely scattered geographically. The relation is 

not fully understood, but is perhaps more than coincidental. Most of the deposits in Arkansas are of 

Devonian and Mississippian age ; those in California 

and Nevada are mostly of Devonian age, although 

some in Nevada may be of Ordovician age. Somewhat similar deposits at Meggen, Westphalia 

(Ehrenberg and others, 1954), and in the Saarland 

(Krebs, 1970) of western Germany also occur in 

Devonian rocks. 

Earlier workers have proposed that the black 

fetid beds of barite in Arkansas (Scull, 1958) and 

Nevada (Ketner, 1965) originated by replacement 

of carbonate rocks by barium-bearing hydrothermal 

solutions stemming from intrusive igneous activity. 
BARITE 81 

The appeal of this hypothesis is greatly reduced by 

(1) the absence of igneous rocks in the vicinity of 

many deposits, especially in western Arkansas, except for the Magnet Cove deposit; (2) the absence 

of anomalously large concentrations of such elements as copper, lead, zinc, silver, molybdenum, and 

mercury expected in and around hydrothermal ore 

deposits; and (3) the absence of abundant carbonate 

rock available for replacement in the formations 

that contain rich beds of barite. 

The black bedded barite deposits probably are of 

sedimentary origin, formed virtually at the same 

time as the enclosing rocks by organic and inorganic 

chemical processes of concentration and deposition. 

A sedimentary origin for the deposit at Magnet 

Cove, Ark., was postulated by Zimmermann and 

Amstutz (1964) from structural and textural evidence. Zimmermann (1969) later found similar features in the deposits of the Shoshone Range, Nev. 

Shawe, Poole, and Brobst (1969) proposed a sedimentary origin for the deposits in the Toquima 

Range, Nev., because of textural, structural, and 

chemical features, including the effects of contact 

metamorphism on the barite beds (coarsening of 

the grain size by recrystallization and bleaching of 

the dark color) from the emplacement of an igneous 

rock. 

The source of the barium in these deposits has 

not been established, although some hypotheses have 

been proposed. Sources in submarine volcanic emanations and springs were suggested for the barite 

and sulfide beds at Meggen, Germany (Ehrenberg 

and others, 1954). Hydrothermal solutions are considered by Dunham and Hanor (1967) to be the 

ultimate source of all barite deposits. A barium 

source in sea water, with extraction related to biological activity, was discussed by Shawe, Poole, and 

Brobst (1969). 

The recycling of bari urn from preexisting rocks 

should not be overlooked as a source of barium for 

these bedded deposits. Connate brines seem to be 

good concentrators and transporters of barium, as 

already observed in the discussion of residual deposits. Barium-rich chloride waters reaching sulfaterich marine or brackish water could mix locally to 

yield deposits of barite. If this mechanism functions 

in nature, the possibility of finding barite deposits at 

the sites of ancient or modern lakes and swamps containing sufficient sulfate, especially in coastal areas, 

must be considered seriously. 

White to clear barite occurs as a cement in some 

sandstones and conglomerates, such as the Pike 

Gravel, the basal formation of the Trinity Group of 

Cretaceous age in Howard and Sevier Counties, Ark. 

(Scull, 1958). The Pike Gravel marks the Cretaceous 

strandline and unconformably overlies folded rocks 

of Paleozoic age. About 20 miles to the north, the 

Paleozoic rocks contain deposits of black bedded 

barite, which perhaps are the source of the barium 

for the barite cement in the Pike Gravel. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

The identified and hypothetical resources of barite 

in the United States are listed by State and type of 

deposit in table 13. The identified resources include 

TABLE 13.-Identified and hypothetical barite resources of the 

United States, in thousands of short tons 

[ +, indicates present in small, but otherwise unknown, amounts] 

Identified resources 1 Hypothetical resources 2 

Bedded Residual Vein Bedded Residual Vein 

Alaska ----------- Washington ------- 500 

Idaho ------------ 500 Montana --------- California -------- 1,000 

Nevada ----------- 35,000 

Arizona ---------- New Mexico -------

Utah ------------ Colorado ---------- Oklahoma -------- 25 Texas ------------ Wisconsin --------- Missouri ----------- 15,000 

Arkansas --------- 10,000 

lllinois ----------- Kentucky --------- + Tennessee --------- 3,000 

Alabama ---------- 25 

Georgia ---------- 2,000 

5,000 

100 1,000 

100 1,000 

500 

5,000 5,000 

1,000 50,000 

1,000 

100 

100 

500 

100 

5,000 

50 

500 5,000 

5,000 

5,000 

5,500 + 

1,000 6,500 

500 

5,000 

10,000 

500 

500 

1,000 

25,000 

1,000 

1,000 

100 

100 

1,000 

100 

1,000 

2,000 

5,000 

6,000 

15,000 

South Carolina ____ 1,000 2,000 N?rt~ . Carolina ____ 200 1,000 

VIrginia ---------- 25 500 

Maryland 5 --------- + 5 5 

Pennsylvania ------ + 5 5 

Copneeticut ------- ----------------500 

Sub total 

(rounded) _ 47,000 20,000 31,700 62,000 17,500 72,800 

Total, all types (rounded) _ 99,000 152,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existing technology 

and economic conditions. 2 Hypothetical resources: Undiscovered mineral deposits, whether of 

recoverable or subeconomic grade, that are geologically predictable as existing in known districts. 

currently minable ore (reserves) and lower grade 

material of subeconomic value (conditional 'resources). 

Deposits of bedded barite in the identified resources include those within 500 feet of the surface 

whose ore contains at least 40 percent barite. Ores 

containing 40 to about 92 percent must be beneficiated to yield a product for drilling mud. Flotation 

techniques for concentrating these ores are in common use. Selective mining in many of the deposits 

yields substantial tonnages of barite that requires 

only grinding for use as drilling mud. 

Estimates of the identified resources of barite in 

residual deposits include materials to a depth of 
82 UNITED STATES MINERAL RESOURCES 

250 feet (most are much shallower) that contain 

more than 125 pounds of recoverable barite per cubic 

yard of residuum processed. This cutoff includes 

material that is subeconomic by the 1972 standards 

of about 220 pounds of barite per cubic yard of 

residuum. An identified resource of 1.9 million tons 

of barite is reported in 67 tailings ponds in the 

Washington County barite district, Missouri (Wharton, 1972, p. 55). 

Identified resources of vein material include ores 

in a wide variety of grades, with and without potential coproducts in deposits within 1,500 feet of 

the surface. The common coproducts are, or could 

be, one or more of the following: fluorspar and 

minerals of lead, zinc, silver, gold, and rare earths. 

Some of these barite ores must be literally rediscovered in known metal districts. In earlier times, 

bodies of mixed ore, especially of barite and fluorspar, were bypassed in mining because it was then 

impossible to beneficiate them economically. Techniques for the beneficiation of these mixed ores are 

now available. The estimates of resources also include some barite available by reprocessing mine 

dumps and tailings ponds. Parts of settling ponds 

at old washer plants in the Washington County 

district, Missouri contain as much as 35 percent 

fine-grained barite. 

Barite resources of Alaska have scarcely been 

evaluated, but are of considerable interest because 

of anticipated oil production on the Arctic slope. 

Vein deposits were mined in 1972 on Castle Island 

in the Petersburg region, and vein deposits in the 

Skagway area have been recently described by MacKevett ( 1971). A potential ore target for barite, 

fluorite, and metal sulfides has been identified near 

Nome on the Seward Peninsula (Brobst and others, 

1971). In northern Alaska, gray barite occurs in 

cherty rocks of Paleozoic age (Tailleur, 1970), and 

abundant barium occurs in shales of Mesozoic age 

that are rich in organic matter (Tourtelot and Tailleur, 1965). The distribution of the occurrences suggests that the Brooks Range might also contain 

barite deposits of commercial value. 

Hypothetical resources listed in· table 13 were estimated for each type of deposit using the same limiting depth as for the identified resources ; however, 

the cutoff for bedded deposits is reduced to 30 percent barite and for residual deposits to 75 pounds of 

recoverable barite per cubic yard of residuum processed. The grade of vein deposits included in this 

estimate varies as widely as in identified resources, 

but a favorable potential for coproducts is regarded 

as economically necessary for exploitation. 

A summary of the world's identified and hypothetical resources of barite is shown by continent 

in table 14. The identified resources are extrapolated 

TABLE 14.-World resources of barite in millions of metric 

tons 

Hypo the- SpeculaArea Identified 1 tical 2 tive 3 

North Ameriea -------- 118 180 400 

Central America and 

the West Indies ----- 2 5 10 

South America -------- 15 20 100 

Europe --------------- 75 85 220 

Africa ---------------- 38 50 200 

Asia ----------------- 52 50 300 

Oceania --------------- 10 10 50 

Totals ---------- 310 400 1,280 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existing technology 

and economic conditions. 2 Hypothetical resources: Undiscovered mineral deposits,. whether of re- coverable or subeconomic grade, that are geologically predictable as existing in known districts. 3 Speculative resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that may exist in unknown districts or in unrecognized or unconventional form. 

from world reserve data described and tabulated by 

Brobst ( 1970). Outside the United States, perhaps 

as much as 75 percent of the identified barite resources are in vein deposits, many of which are 

mined or are minable for multiproducts. The hypothetical resources are predicated on estimates for 

similar types of deposits in the United States. 

Barium-rich nodules have been found on great 

areas of the sea floor. The barite might eventually 

be recovered as a coproduct with other materials, 

notably manganese, although much remains to be 

done on the recovery and processing techniques. The 

resources probably are large, but they are as yet 

mostly unmeasured, and none are included in the 

total for identified resources of conventional deposits. 

Barite is associated with carbonatite in east 

Africa and probably elsewhere in the world, but the 

commercial potential of these deposits remains to 

be evaluated fully. 

In northern Honshu, Japan, layered volcanic rocks 

of Miocene age contain black ore (kuroko) consisting of economically recoverable amounts of pyrite, 

barite, copper, lead, zinc, silver, and ·gold. The 

geology and beneficiation of these ores have been 

described recently (Mining Engineering, 1969). 

Deposits similar to these also might occur in the 

Western United States and other countries in the 

circumpacific volcanic belt. Deposits of this type 

probably have not been sought in many places where 

potential for their discovery is good. 

SPECULATIVE RESOURCES 

The speculative resources, those of undiscovered 

districts, are large. 

It is highly probable that additional deposits of 

black bedded barite will be found in dark siliceous 
BARITE 83 

sequences of sedimentary rock of Paleozoic age in 

Arkansas, Nevada, and California. Some bedded 

deposits also might occur in the Ouachita Mountains 

of eastern Oklahoma. The potential for the discovery of bedded deposits of value in Alaska is great. 

The Appalachian region probably has never been 

explored for bedded deposits. The bedded deposits 

tend to be large but are easily overlooked. They are 

worthy targets for exploration in sedimentary rocks 

throughout the world. 

Undiscovered deposits of considerable size probably occur in the Appalachian region from Pennsylvania to Alabama in the residuum of Cambrian 

or Ordovician carbonate rocks. Additional districts 

the size of the Sweetwater district, Tennessee, and 

the Cartersville district, Georgia, probably are hidden in the region. Other new districts containing 

residual deposits of barite may be found in the midcontinent region in the residual mantles on baritebearing rocks. 

The speculative resources of barite in vein deposits are large. Much barite will become available 

as a coproduct from base-metal, rare-earth, and 

fluorspar veins. Discovery of at least one other fluorspar district containing large amounts in the midcontinental United States and similar to the IllinoisKentucky district seems probab~e. The discovery of 

additional rare-earth and barite deposits such as 

those in the Mountain Pass district, California, also 

is probable. 

The caprock and environs of the salt domes in the 

coastal areas of the Gulf of Mexico and other regions of the world might contain barite deposits. 

Abundant chloride and sulfate ions in connate 

waters in this environment enhance the possibilities 

for concentration of barite there. 

The world's speculative resources of barite are 

listed in table 14. Speculative resources of the United 

States are estimated to be about 250 million metric 

tons (1 short ton equals 0.91 metric ton) as compared with 400 million metric tons of barite for all 

North America. Speculative resources for Europe 

and North America are proportionally smaller as 

compared to their identified and hypothetical resources than are those for other regions of the 

world, because more intensive exploration has been 

done on those two continents and deposits are correspondingly less likely to remain undiscovered. 

PROSPECTING TECHNIQUES 

Sophisticated technical methods for prospecting 

barite deposits have not yet been developed, chiefly 

because new deposits have been fairly easy to find 

in known districts. The success of future prospecting will be increased if prospecting is guided by a 

knowledge of geologic associations and the role of 

barite in the sedimentary environment. Deposits 

should be sought in residuum overlying carbonaterich rocks, especially those of Cambrian or Ordovician age. Other areas of well-weathered rocks that 

have been hosts for veins or pods of barite also 

should be examined. The fetid black beds of barite 

occur abundantly in sequences of dark siliceous 

rocks of mid-Paleozoic age. The widespread, but 

probably mistaken, idea that the black bedded deposits must be of hydrothermal origin has diverted 

the attention of prospectors from search in sedimentary basins that lack intrusive igneous· rocks. 

Geochemical techniques may be helpful in prospecting for barite deposits because increased concentration of barium has been noticed in rocks enclosing barite-rich zones in Arkansas (Brobst and 

Ward, 1965). Gravimetric surveys have potential 

use in prospecting (Uhley and Scharon, 1954). 

PROBLEMS FOR RESEARCH 

Research on problems relating to the evaluation 

of barite resources has one focal point: to get the 

information necessary to convert hypothetical and 

speculative resources to identified resources, which 

is a fundamental reason for doing research on the 

geology of any mineral commodity. 

Further studies of the geochemistry of barium are 

needed to understand the processes at work in the 

mobilization, transportation, and concentration of 

barium, especially in the sedimentary environment. 

The role of connate water in the formation of barite 

deposits requires further examination. Barium is an 

abundant accessory element in the ash of n1any coals 

and in smne Alaskan oil shales; this fact suggests 

that factors leading to the concentration of the 

organic materials favor the concentration of barium. 

The function of organic materials and bacterial 

processes i.n precipitating barium is a virtually unexplored field and should be investigated. A question remains about the so-called residual barite deposits: Does the barite of these deposits become 

concentrated mechanically or are solution and redeposition of the barite also involved? The relation 

of bedded barite deposits to bedded phosphate deposits needs examination. New information about 

any of these subjects should help to define new areas 

and targets worthy of exploration for barite. 

The close association of barium minerals with 

those of fluorine, rare earths, manganese, lead, zinc, 

and precious metals in vein deposits should be 

studied further. The use of barium as a tracer in 

the search for deposits of other coexisting elements 
84 UNITED STATES MINERAL RESOURCES 

has not been tested thoroughly. 

Better conservation of barium would be possible 

if supplies of barite available as a coproduct were 

utilized more fully. Techniques also might be developed to extend known barite resources through 

the reuse of barite and barium products, almost none 

of which are recovered for reuse in today's salvage 

and recycling operations. 

REFERENCES CITED 

Brobst, D. A., 19•58, Barite resources of the United States: 

U.S. Geol. Survey Bull. 1072-B, p. 67-130. 

--- 1965, Barite in the United States: U.S. Geol. Survey 

Mineral Inv. Resources Map MR-43. 

--- 1970, Barite-world production, reserves and future 

prospects: U.S. Geol. Survey Bull. 1321, 46 p. 

Brobst, D. A., and Hobbs, R. G., 1968, Barite, in Mineral Resources of the Appalachian region: U.S. Geol. Survey 

Prof. Paper 580, p. 270-277. 

Brobst, D. A., Pinckney, D. M., and Sainsbury, C. L., 1971, 

Geology and geochemistry of the Sinuk River barite deposit, Seward Peninsula, Alaska, in Geological Survey 

research 1971: U.S. Geol. Survey Prof. Paper 750-D, p. 

D1-D8· 

Brobst, D. A., and Wagner, R. J., 1967, Barite, ·in Mineral 

and water resources of Missouri: Missouri Div. Geol. 

Survey and Water Resources [Rept.]t 2d ser., v. 43, p. 

99-106. 

Brobst, D. A., and Ward, F. N., 1965, A turbidimetric test 

for barium and its geologic application in Arkansas: 

Econ. Geology, v. 60, no. 5, p. 1020-1040. 

Dean, B. G., and Brobst, D. A., 1955, Annotated bibliography 

and index map of barite deposits in the United States: 

U.S. Geol. Survey Bull. 1019-C, p. 145-186. 

Dunham, A. C., and Hanor, J. S·, 1967, Controls on barite 

mineralization in the Western United States: Econ. 

Geology, v. 62, no. 1, p. 82-94. 

Ehrenberg, Hans, Pilger, Andreas, and Schroder, Fritz, 1954, 

Das Schwefelkies-Zinkblende-Schwerspatlager von Meggen (Westfalen) (Monographien der deutschen BleiZink-Erzlagerstatten 7) : Geol. J ahrb. Beihefte, no. 12, 

352 p. 

Food Machinery and Chemical Corp., 1961, Barium bibliography: New York, Food Machinery and Chemical Corp., 

Mineral Products Div., 433 p. 

Friedman, G. M., 1969, Trac·e elements as possible environmental indicators in carbonate sediments, in Friedman, 

G. M., ed., Depositional environments in carbonate rocks: 

Soc. Econ. Paleontologists and Mineralogists Spec. Publication 14, p. 193-198. 

Gates, G. L., and Caraway, W. H., 1967, Deposition of 

barium sulfate from sea water in oil-well rotary pumps: 

U.S. Bur. Mines Rept. Inv. 6960, 16 p. 

Graf, D. L., 1960, Minor element distribution, pt. 3 of Geochemistry of carbonate sediments and sedimentary carbonate rocks: Illinois State Geol. Survey Circ. 301, 71 p. 

Kesler, T. L., 1950, Geology and mineral deposits of the 

Cartersville district, Georgia: U.S. Geol. Survey Prof. 

Paper 224, 97 p. 

Ketner, K. B., 1965, Economic geology, in Gilluly, James, 

and Gates, Olcott, Tectonic and igneous geology of the 

northern Shoshone Range, Nevada: U.S. Geol. Survey 

Prof. Paper 465, p. 129-144. 

Krebs, Wolfgang, 1970, Nachweis von Oberdevon in Der 

Schwerspat-Grube Eisen (Saargebiet) und die Folgerungen fiir PaHiogeographie und Lagerstattenkunde 

des linksrheinischen Schiefergebirges: N eues J ahrb. 

Geologie u. Palaontologie Monatsh. J g. 1970, H. 8, p. 

465-480. 

Lee, Tan, and Yao, Chi-lung, 1970, Abundance of chemical 

elements in the earth's crust and its major tectonic 

units: lnternat. Geol. Review, v. 12, no. 7, p. 778-786. 

Lewis, R. W., 1970, Barium, in Mineral facts and problems 

1970: U.S. Bur. Mines Bull. 650, p. 865-877. 

MacKevett, E. M·, Jr., 1971, Analyses of samples and preliminary geologic summary of barite-silver-base metal 

deposits near Glacier Creek, Skagway B-4 quadrangle, 

southeastern Alaska: U.S. Geol. Survey open-file report, 

8 p. 

Maher, S. W., 1970, Barite resources of Tennessee: Tennessee Div. Geology Rept. lnv. 28, 40 p. 

Matthews, R. A., and Alfors, J. T., 1962, Sanbornite from 

Rush Greek, Fresno County [Calif.]: California Div. 

Mines and Geology, Mineral Inf. Service, v. 15, no. 6, 

p.1-3. 

Miller, R. E., Brobst, D. A., and Beck, P. C., 1972, The 

geology and organic geochemistry of black bedded barite 

[abs.]: Geol. Soc. America, Abstracts with programs, v. 

4, no. 7, p. 596. 

Mining Engineering, 1969, The black ore district of Hokuroku: Mining Eng., v. 21, no. 5, p. 60-65. 

Parker, R. L., 1967, Composition of the earth's crust: U.S. 

Geol. Survey Prof. Paper 440-D, 19 p. 

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry: 

Chicago, Ill., Chicago Univ. Press, p. 457-484. 

Scull, B. J., 1958, Origin and occurrence of barite in 

Arkansas: Arkansas Geol. and Conserv. Comm. Inf. Circ. 

18, 101 P· 

Shawe, D. R., Poole, F. G., and Brobst, D. A., 1969, Newly 

discovered bedded barite deposits in Northumberland 

Canyon, Nye County, Nevada: Econ. Geology, v. 64, no. 

3, p. 245-254. 

Tailleur, I. L., 1970, Lead-, zinc-, and barite-bearing samples 

from the western Brooks Range, Alaska: U.S. Geol. 

Survey open-file rept., 16 p. 

Tourtelot, H. A., and Tailleur, I. L., 1965, Oil yield and 

chemical composition of shale_ from northern Alaska: 

U.S. Geol. Survey open-file rept., 17 p. 

Uhley, R. P., and Scharon, LeRoy, 1954, Gravity surveys for 

residual barite deposits in Missouri: Mining Eng., v. 6, 

no. 1, p. 5·2-56. 

Weber, H. F., Jr., and Matthews, R. A., 1967, Prospecting 

for barite in Northern Shasta County [Calif.]: California Div. Mines and Geology Mineral Inf. Service, v. 

20, no. 9, p. 107-114. 

Wharton, H. M., 1972, Barite ore potential of four tailings 

ponds, Washington County barite district, Missouri: 

Missouri Geol. Survey and Water Resources Rept. Inv. 

53, 91 p. 

Zimmermann, R. A., 1969, Stratabound barite deposits in 

Nevada: Mineralium Deposita, v. 4, p. 401-409. 

Zimmermann, R. A., and Amstutz, G. C., 1964, Small scale 

sedimentary features in the Arkansas barite district, in 

Amstutz, G. C., ed., Developments in Sedimentology, v. 

2: New York, Elsevier Publ. Co., p. 157-163. 
UNITED STATES MINERAL RESOURCES 

BERYLLIUM 

By wALLACE R. GRIFFITIS 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------- Properties and uses of the metal --------------

Properties and uses of beryllium alloys --------

Properties and uses of the oxide --------------

Beryl as an industrial mineral ----------------

End uses of beryllium ------------------------

Secondary recovery -------------------------- Toxicity of beryllium and its compounds -------

History of production and consumption ------------

Future consumption --------------------------

Extractive methods --------------------------

Geologic environment ---------------------------- Geochemistry _________________ -- ____________ _ 

Minerals ------------------------------------

Types of beryllium deposits -------------------

Pegmatitic deposits ----------------------

Hydrothermal deposits -------------------

Hypothermal deposits ----------------

Mesothermal deposits -----------------

Epithermal deposits ------------------

Regional distribution of beryllium deposits _ 

Resources ---------------------------------------

Selected references -------------------------------

FIGURES 

11. Graph showing beryl ore imported and coosumed 

by U.S. industry, 1936-71 ------------------

12. Map showing areas of the conterminous United 

States in which beryllium deposits are most 

likely to be found -------------------------

TABLES 

15. End uses of beryllium in the United States, 1968 

16. Sources of beryl ore used in the industry of the 

United States ----------------------------- 17. Characteristics of beryllium minerals known to 

form large deposits ------------·-----------

18. Estimated resources of beryllium -------------

Page 

85 

85 

85 

86 

86 

86 

86 

86 

87 

87 

88 

88 

88 

88 

89 

89 

90 

91 

91 

91 

91 

91 

92 

93 

Page 

87 

92 

Page 

86 

88 

90 

92 

ABSTRACT OF CONCLUSIONS 

Beryllium metal is used in a variety of products in which 

its low density and other physical properties are particularly 

valuable. More than half the metal produced is used with 

copper in strong, fatigue-resistant alloys. Beryllium oxide 

and beryl are used in many ceramic and other products. The 

total amount used is small; less than 1,000 tons of beryllium was used in all forms in the year of highest consumption. The annual consumption may increase to as much as 

4,000 tons by the year 2000. 

About 95 percent of the beryllium ore used in the United 

States has been imported, three-fourths of it coming from 

Brazil, the Republic of South Africa, India, Argentina, and 

Mozambique. Significant domestic production began in 1969 

and probably will increase until it accounts for at least half 

the ore consumed. 

The resources of beryllium in known domestic deposits are 

estimated at 60,000 tons, and these can be increased by further exploration to become sufficient to supply our needs for 

many decades. 

INTRODUCTION 

The beryllium industry is both small and young 

as compared with most base-, ferrous-, and lightmetal industries. Beryllium thus is one of many 

minor commodities, one that has been rather highly 

publicized because of glamorous actual and potential 

uses in nuclear energy and manufacture of space 

vehicles. Nonetheless, many important uses for 

beryllium have developed during the 40 years since 

production began. The industry is shifting from 

complete dependence upon imported beryl concentrates derived from small pegmatitic deposits to 

the mining of large domestic nonpegmatitic deposits. 

Deposits containing 60,000 tons of metal-enough 

to satisfy national needs for several decades-were 

found in about 10 years. More deposits doubtless 

can be found if markets develop sufficiently to 

stimulate prospecting. 

PROPERTIES AND USES OF THE METAL 

Beryllium, with a specific gravity of 1.85, is one 

of the lightest metals stable in air. Like aluminum, 

U.S. GEOL. SURVEY PROF. PAPER 820 

85 
86 UNITED STATES MINERAL RESOURCES 

it develops a coherent oxide coating when exposed 

to air, which protects it from further oxidation and 

increases its apparent hardness. Unfortunately, 

oxygen-free beryllium metal is very difficult to prepare. Most metal in commerce contains nearly 2 

percent oxygen, which contributes to its brittleness. This brittleness requires production of articles 

by powder metallurgy and machining-a costly procedure-and limits reshaping by rolling or drawing. 

The high thermal conductivity, high melting point, 

high specific heat, low density, and rigidity of the 

metal make it useful in heat sinks and in specialized 

structural elements for aircraft and spacecraft. Its 

low neutron absorption and its emission of neutrons 

under appropriate gamma or alpha bombardment 

lead to uses in nuclear energy. In the early 1970's, 

nearly 20 percent of the beryllium extracted was 

used as the metal. 

PROPERTIES AND USES OF BERYLLIUM ALLOYS 

More than half the beryllium reduced from its 

ore is used in alloys, principally in beryllium-copper 

alloys containing about 2 percent beryllium and 

about 0.2 percent nickel or cobalt. These alloys have 

the greatest strength and wear resistance of any 

nonmagnetic material, with a tensile strength about 

twice that of hard-drawn iron and two-thirds that 

of mild steel. They also are excellent conductors of 

electricity and heat and are very resistant to corrosion. Below a temperature of about 300°F, they 

are much more resistant to fatigue than steel. They 

are much used in springs, electrical connectors, and 

many other specialized items. The use of the alloys 

in computers and other electrical equipment has 

resulted in greatly increased consumption during the 

last 20 years. 

Beryllium has been used in small amounts with 

nickel to make hardenable alloys with very high 

tensile strength that are usable at higher temperatures than copper alloys. 

In light alloys with aluminum and magnesium, 

beryllium can improve the properties or facilitate 

the production of the metal. Addition of 0.02 percent of beryllium to aluminum-magnesium alloys 

reduces reaction with green sand molds and improves oxidation resistance. It eliminates the need 

for elaborate precautions against burning of magnesium, inasmuch as the molten metal containing 

beryllium can be poured safely at a temperature of 

1,400°F. "Lockalloy," containing 62 percent beryllium and 38 percent aluminum, has some of the desirable properties of beryllium, is reasonably workable, 

and can be used at temperatures as high as 800°F. 

Various composite materials containing beryllium in 

nonbrittle matrices are strong and light. 

PROPERTIES AND USES OF THE OXIDE 

Beryllium oxide is the third major form in which 

beryllium is used. This oxide, with a high melting 

point, a high thermal conductivity, and very low 

electrical conductivity, can be used as an electrical 

insulator in applications where heat must be transferred or dissipated, as in power transistors. The 

high thermal conductivity results in high thermal 

shock resistance, which is important in special 

ceramics. These, and the nuclear properties, lead to 

the use of beryllium oxide in reactor fuel elements. 

BERYL AS AN INDUSTRIAL MINERAL 

In addition to the uses of beryllium that require 

extraction of the metal from its ore, there are many 

uses that are met by incorporating undecomposed 

beryl into an industrial product. These uses account 

for about one-tenth of the beryl ore used during the 

last 20 years. Some of these uses are chemicalthe addition of beryllium to a ceramic or glass mix; 

others rely upon one or more physical properties of 

the mineral beryl itself such as its structure, its 

thermal conductivity, or its ability to adhere to 

plastics. 

END USES OF BERYLLIUM 

The amount of beryllium used in various ways 

in the United States is summarized in table 15. 

TABLE 15.-End uses of beryllium in the United States, 1968 

[Data from Hcindl. 1970. p. 498] 

Use Short tons 

Nuclear applications ------------ 35 

Guided missiles and space vehicles 35 

Instruments -------------------- 45 

Switch gear ------------------- 90 

Welding equipment ------------- 40 

Electronic computers ----------- 40 

Radio and television equipment___ 25 

Other -------------------------- 38 

Total -------------------- 348 

SECONDARY RECOVERY 

Percent 

of total 

10 

10 

13 

26 

11 

11 

6 

13 

100 

Much recoverable beryllium scrap is produced in 

making articles out of beryllium metal. This is an 

inevitable result of the necessity of making blank 

or roughly formed pieces of metal by powder metallurgy, then machining the final product from them. 

Not much metal, however, can be salvaged from 

the final articles. Components of missiles and rockets 

are commonly destroyed in use, whereas those of 

manned capsules and orbiting observatories may be 
BERYLLIUM 87 

recoverable. Many beryllium aircraft parts can 

readily be salvaged; so can beryllium used in nuclear energy establishments, if it is not too strongly 

contaminated by radioactive substances. Berylliumcopper alloy is used mostly to make very small items 

and this beryllium generally cannot be salvaged. 

The same is to a large extent true of the beryllium 

in ceramic ware, whether high or low in BeO. 

TOXICITY OF BERYLLIUM AND ITS COMPOUNDS 

Much was written during the 1940's and 1950's 

about the toxicity of beryllium and its compounds. 

Subsequent studies have shown that the ores are not 

hazardous and that industrial products can be handled safely with reasonable precautions. The toxicity has caused few restrictions on its use, the most 

notable being its elimination from phosphors in 

fluorescent lamps and its exclusion from the fuel 

of most rockets. 

13,000 

HISTORY OF PRODUCTION AND 

CONSUMPTION 

The beryllium industry is rather new; commercial production began in the United States in 1932. 

Consumption increased steadily until 1943, as indicated in figure 11. After the World War II stimulus 

and the postwar slump, ore consumption increased 

rather steadily until about 1960, but since then it 

has not changed greatly. In most years imports of 

beryl ore have exceeded consumption, and stockpiles 

have accumulated. The opening of the beryllium 

mine near Delta, Utah, in 1969, and release of ore 

from the Federal stockpile are at least partly responsible for the relatively low imports in 1970 and 

1971. This proportion of imports probably will continue, with about half of the U.S. needs imported, 

I 

the other half produced domestically. Thus, increasing amounts of beryllium will be obtained from 

Purchases for 

Federal beryl 

1 

stockpile 

Unusually large~ 

Atomic Energy 

Commission 

purchases 

Aerospace 

12,000 program 

10,000 

9000 

(I) 8000 

z 

0 

II- 7000 

a: 

0 

I 

(I) 6000 

5000 

4000 

3000 

2000 

1000 

shipments from 1\ 

India and 1 \ 

Argentina I \ 

I \ 

I \ 

I \ 

I \ 

I \ 

1

\ I \ 

\ ' \ I \ I \ 

Imports"-I \ f \ 

( \..) \ 

I 

I 

!"'-' 

I 

I ....._Consumption 

I 

I 

9.888 tons 

released from 

Federal stockpile 

Aerospace program 

Vietnam War 

50 52 54 56 58 60 62 64 66 68 70 72 

FIGURE 11.-Beryl ore imported and consumed by U.S. industry, 1936-71. Nonberyl ore, recalculated to equivalent amounts 

of beryl ore, not important before 1969. Data from U.S. Bureau of Mines Minerals Yearbooks. 
88 UNITED STATES MINERAL RESOURCES 

nonberyl ores. Nonberyl ores were recalculated as 

equivalent amounts of beryl in preparing figure 11. 

There has otherwise been little change in the sources 

(table 16) since 1939, when Brazil first became a 

TABLE 16.-Sources of beryl ore used in the industry of the 

United States 

[Data from U.S. Bureau of Mines, 1953; 1953-69] 

Percent of total 

Country 

Brazil -------------------- Republic- of South Africa __ 

India -------------------- Argentina ---------------- Mozambique -------------- United States ------------

Zaire -------------------- Rhodesia ----------------- Kenya and Uganda -------

Australia ---------------- Malagasy Republic --------

Portugal -----------------

Other --------------------

Total tons beryl 

1936-51 

49 

10 

8 

12 

2 

10 

4 

4 

1 

(rounded) -------------- 32,000 

1952-59 

27 

11 

11 

15 

13 

5 

5 

7 

<1 

2 

2 

2 

<1 

98,000 

196G-68 

32 

5 

13 

10 

10 

4 

7 

3 

8 

5 

3 

<1 

<1 

161,000 

major exporter. One evident feature is the decreasing portion mined within the United States. 

FUTURE CONSUMPTION 

The history of beryllium use has been one of 

diversification. The metal has gone into many end 

products, no one of which has been a very large 

part of the total. The rate of growth, therefore, has 

been rather steady for many years, following an 

exponential curve; the major fluctuations result 

from sporadic government programs in armaments, 

nuclear energy, and space. The assured supply of 

raw material from Spor Mountain, Utah, doubtless 

will encourage the development of additional uses 

by potential consumers who lack confidence in a 

dependable supply of imported beryl ore. It is likely, 

even, that this new source of ore will stimulate uses 

sufficiently to bolster the market for beryL Consumption may well increase threefold or fourfold 

by the year 2000, with the use in that year of 

3,000-4,000 tons of beryllium in all forms. About 

4,500 tons of metal would then have been used of 

our total known domestic resources of about 60,000 

tons. Perhaps the use in light alloys-with aluminum and magnesium-will increase more than other 

uses. 

EXTRACTIVE METHODS 

To extract beryllium, beryl ore is heated, with or 

without fluxes, and then is leached to give an aqueous solution of beryllium fluoride or sulfate. In the 

United States, Kawecki-Berylco Industries sinter 

finely pulverized beryl with fluorides and sodium 

carbonate, then leach the sintered material with 

water to obtain a beryllium-fluoride solution from 

which beryllium hydroxide is precipitated. BrushWellman Co., in an alternate process, fuses lump 

beryl ore, quenches the melt, and leaches the beryllium with sulfuric acid. Ore can also be mixed with 

a carbonate flux, fused, then leached with sulfuric 

acid. The nonberyl ore from Spor Mountain, Utah, 

yields its beryllium upon leaching with sulfuric acid 

with no pretreatment. All these procedures can 

extract more than 90 percent of the beryllium in 

the ore. 

The different extraction methods are not equally 

applicable to all types of ore, and therefore are of 

significance in assessing the resource potential of 

various beryllium-rich materials. The fuse-quench 

method is well adapted to coarse beryl ore, but not 

to low-grade ore, nonberyl ore, or to fine-grained 

concentrates. The fluoride-sintering method requires 

fine grinding of ore and can readily handle flotation 

concentrates, even if the beryllium is contained in 

minerals other than beryl. Apatite and fluorite, 

which commonly accompany beryl in pegmatitic and 

hydrothermal deposits, respectively, reduce the extractability of beryllium by the fluoride method but 

not by carbonate fusion-sulfuric acid leach methods ; these methods may therefore come into use 

despite their comparatively high reagent costs. 

The novel extractive procedure developed for use 

with the ores of Spor Mountain, Utah, may be the 

precursor of markedly modified or new technologies 

for use on other nonpegmatitic ores. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Beryllium has one stable isotope, Be9

, which is 

the only one involved in industrial use and in most 

geochemical and geological processes. Three unstable 

isotopes, Be7, Be8 , and Be10, are produced by cosmicray interaction with the upper atmosphere. 

The beryllium content of the earth's crust is estimated to be 2-3.5 ppm (parts per million). All but 

a very small percentage of this metal is contained 

in the common rock-forming minerals and not in 

beryllium-rich minerals. This dispersal is caused by 

its ability to replace silicon-its ionic radius ( 0.31 

A) is near that of the silicon ion (0.41 A). However, because of the difference in charge ( +2 instead of +4), the difference in size, and the greater 

tendency of beryllium to form covalent bonds, the 
BERYLLIUM 89 

substitution of beryllium for silicon impairs the 

stability of a crystal's structure. Hence, beryllium 

is most concentrated in minerals whose structures 

are most tolerant of the resulting distortion. Plagioclase feldspar probably contains much of the earth's 

beryllium, but micas and clays are also important 

hosts. 

During the crystallization of a magma, beryllium 

becomes progressively more concentrated in the 

fluid as crystallization proceeds. One result of this 

is an increasing concentration of beryllium in successively younger rocks in genetically related suites. 

This enrichment reaches a point where beryllium 

minerals can form only in the presence of complexing agents, such as F- or C03 -z, that keep an unusually large proportion of the beryllium in the 

residual liquids. In igneous rocks the beryllium content therefore increases along with silica and alkali 

contents. The average content of beryllium in peridotite is less than 0.25 ppm, that of basalt and gabbro is about 0.5 ppm, and that of rhyolite and granite is about 5 ppm. Detailed study of each of these 

groups shows the relations to be complex. For example, in silicic rocks the beryllium content passes 

through a maximum as silica content increases. In 

addition, the average beryllium content of plutonic 

rocks is higher than that of volcanic rocks, perhaps 

reflecting the loss of beryllium in vapors during 

volcanism. 

The very coarse texture of pegmatites has made 

them difficult to sample for beryllium content, although the coarseness facilitates the determination 

in the field of the contents of beryl and other economic minerals. 

In a series of related pegmatites, the beryllium 

content can increase in successively intruded rocks 

to a maximum of about 180 ppm; it then remains 

rather uniform. This is apparently the maximum 

concentration that can be reached through magmatic processes in magmas of granitic composition. 

Much higher beryllium contents may characterize 

beryl-rich inner zones of pegmatite dikes, but averaging these with the larger beryl-poor outer zones 

shows that few, if any, bodies contain more than 

200 ppm overall, which corresponds to about onehalf of 1 percent beryl. This is the maximum grade 

that can be expected in large bodies of pegmatite. 

Most pegmatites contain much less and may average 

a few tons of parts per million of beryllium. 

Beryllium is very scarce in most hydrothermal 

deposits, generally constituting 1 ppm or less. Ores 

formed by replacement commonly contain about as 

much beryllium as the rock that was replaced. For 

example, most tactites in limestone contain less than 

1 ppm beryllium, and replacement veins in granite 

or gneiss commonly contain a few parts per million. 

Certain hydrothermal deposits are low in base and 

precious metals but are rich in beryllium. They generally contain fluorite, magnetite or hematite, carbonate minerals, zinc minerals, and if fluoritic, one 

or more metals that, like beryllium, form watersoluble fluoride complexes, such as tin, tungsten, 

bismuth, manganese, rare earths, titanium, or niobium. These metals are largely in oxygen compounds; sulfide minerals are rather uncommon. 

Beryllium is released from the rock-forming minerals as they weather, and is incorporated in clay 

minerals. Thereafter, it remains in clayey soil or 

is carried off in suspension in running water. Most 

coarse sedimentary materials-pebbles, sand, and 

derived rocks-have low beryllium contents, corresponding to that of the quartz that is generally the 

dominant component. Near beryllium deposits, 

coarse sediments may contain detrital particles of 

beryllium minerals, many of which are resistant to 

weathering. Industrial beryl, and gem chrysoberyl, 

phenakite, and euclase (AlBeSi04 (OH)) have been 

mined from such extremely local concentrations. 

Very little migration of beryllium takes place in 

solution in normal waters because the beryllium released upon weathering is quickly adsorbed by mineral particles. High acid or carbonate- or haliderich water can cause small-scale migration of berylli urn, but not on an economically important scale. 

The beryllium contents of r~cks change very little 

with metamorphism. Thus, most micaceous metamorphic rocks contain a few parts per million of 

beryllium, and quartzite and marble contain very 

little. 

MINERALS 

The only beryllium mineral that has had much 

economic importance is beryl, which has yielded 

nearly all the beryllium used in industry. Bertrandite, phenakite, helvite, chrysoberyl, and barylite are 

known to occur in moderately large deposits. The 

other 39 known beryllium minerals have been found 

in only small amounts. It is possible that some of 

them will become important, as bertrandite and 

barylite have. Twenty years ago bertrandite and 

barylite were thought to be very rare, but now they 

are known to ··form large bodies of present or potential economic value. The common or important 

minerals are shown in table 17. 

TYPES OF BERYLLIUM DEPOSITS 

Beryllium deposits can be divided into two broad 

categories: (1) pegmatitic, and (2) nonpegmatitic 
90 UNITED STATES MINERAL RESOURCES 

TABLE 17.-Characteristics .of berryllium minerals known to form large deposits 

Usual 

Mineral BeO content Hardness Specific (percent) gravity 

Beryl ( HeaAlllSi60ts) ------ 12-13.5 7.5 2.6 -2.9 

Bertrandite 42 6 2.6 

( B~Si201 ( OH) 2). 

Phenakite (Be:$i0,) 45 7.5 2.9 -3-0 

Chrysoberyl (AhBeO,) --- 19.8 8.5 3.5 -3.8 

Helvite 11-14 5.5-6.5 3.16-3.66 

( (Mn,Fe,Zn,) BesSis012S). 

Barylite (BaBe2Si207) ---- 16 7 4 

or hydrothermal. Each of these must be further subdivided: the pegmatitic into fine-grained unzoned 

deposits and coarse-grained zoned deposits; the 

hydrothermal deposits into several categories, in 

general conforming to Lindgren's classification of 

hypothermal, mesothermal, and epithermal. 

PEGMATITIC DEPOSITS 

The pegmatitic deposits that are significant as 

sources of beryllium minerals are composed of 

major amounts of quartz, sodic plagioclase, and 

microcline, with or without spodumene, muscovite, 

or lepidolite. The association of beryl with spodumene is close, and few spodumene-bearing pegmatites lack beryl. Muscovite is also a common associate of beryl, especially in nonlithian pegmatites. 

Commonly, however, the muscovite found with beryl 

will not yield sheet mica, which limits the production of beryl as a byproduct from mica mines. 

The fine-grained unzoned pegmatite dikes that 

have attracted most attention as potential sources 

of beryl are aggregates of albite, microcline, spodumene, quartz, beryl, and muscovite. These are moderately uniform in composition, differing from place 

to place mainly in the size and orientation of the 

mineral particles. Spodumene and microcline crystals range in maximum dimension from a fraction 

of an inch to a few feet, and lathlike crystals of 

spodumene may be parallel or random in orientation. Albite, quartz, muscovite, and beryl form a 

fine-grained matrix that surrounds the spodumene, 

microcline, and lumps of quartz. Fine-grained beryl, 

Associated minerals 

Common Size of 

colors grains Pegmatitic deposits Nonpegmatitie deposits 

White, <0.1 inch- Quartz, sodic Quartz, fluorite, 

pale 2 feet plagioclase, carbonates, iron 

blue, microcline, oxide minerals. or muscovite, 

green. spodumene. White __ <0.001-~ Beryl, quartz, Quartz, beryl, 

inch. feldspars. fluorites, car- bonates, iron 

oxide minerals. 

White __ <0.1-2 Beryl, quartz, Beryl, fluorite, 

inches. feldspars, topaz carbonates. 

fluorite, 

<0.1-2 

topaz. 

Green, Microcline, Fluorite, disapore, 

yel- inches. sodic plagio- tourmaline. 

low. clase, quartz, beryl, mica. 

Brown, <0.1-3 Feldspars, Quartz, fluorite, 

yel- inches. quartz, carbonates, iron 

low, fluorite. oxide minerals. 

gray. 

White, <0.1 inch. -------------- Quartz, albite, 

yel- carbonates, sodic 

low. amphiboles. 

generally white, constitutes about ¥2 percent of 

the pegmatite. 

These pegmatites are important sources of spodumene, scrap mica, and feldspar, but the small 

amount and fine grain size of the beryl have prevented its recovery, even in conjunction with flotation of the other minerals. 

Most zoned pegmatites are composed of the same 

minerals as the unzoned pegmatites. They differ in 

that the proportions of minerals and the textures 

of the rocks vary markedly from place to place in 

a dike, generally changing from the wall to the 

core of the pegmatite body. This internal structure 

of pegmatite dikes is uniform throughout the world. 

Near the walls the rock consists of plagioclase and 

quartz, with or without muscovite or microcline, 

and it has a very coarse granitic texture. Toward 

the center of the dike, this composition gives way 

to a zone of blocky microcline that may be monomineralic or may contain plagioclase and quartz 

interstitial to the microcline blocks. The center of 

the dike is occupied by a core of quartz. The margins of the quartz core are the loci of crystals of 

beryl ; some crystals are very large, 3 feet or more 

wide and 20 feet long. The beryl is not evenly distributed along the margins of the cores but is in 

pockets separated by barren rock. 

The much less common, but more spectacular, 

zoned lithian pegmatites usually have spodumenebearing zones between the microcline-rich zone and 

the quartz core. Many of these zones are rather 

similar in composition to the unzoned spodumene-
BERYLLIUM 91 

bearing pegmatites. The crystals of spodumene and 

beryl may be very large, which permits them to be 

recovered by hand sorting in rather simple mining 

operations. 

The coarse zoned pegmatites have yielded nearly 

all the beryl used in industry. 

HYDROTHERMAL DEPOSITS 

The hydrothermal deposits that are of most interest as actual or potential sources of beryllium 

ore are mainly hypothermal types formed at high 

temperature and at least moderate depth, and epithermal types formed at shallow depths. These deposits have provided a very small proportion of the 

total supply of ore but will become dominant in the 

near future. 

HYPOTHERMAL DEPOSITS 

Hypothermal deposits are generally quartz-rich 

moderately coarse-grained veins and beryl-bearing 

granite, both associated with greisen. In North 

America they are most commonly mined for tungsten, but a few have yielded tin minerals, and the 

ones near Lake George, Colo., were mined for beryl 

and bertrandite. Other examples of berylliumbearing hypothermal deposits are those near Lost 

River, Alaska; in the Bagdad area, Arizona; in the 

Mineral and Sheeprock Ranges, Utah; and in the 

Mount Wheeler and Eureka areas, Nevada. Most of 

these are veins in silicate rocks; a few, as in Nevada, 

are in carbonate rocks; and in the Sheeprock and 

Mineral Ranges beryl is dispersed in granite. 

Contact-metasomatic deposits are hypothermal 

replacement bodies in carbonate rocks, most commonly along or near contacts of intrusive rocks. 

They contain a wide variety of silicate minerals and, 

rather uncommonly, helvite. Much of the beryllium 

reported in these deposits is contained in idocrase 

or other minerals of low-beryllium content. The deposits at Iron Mountain, N. Mex., have been thoroughly studied. Others are at Iron Mountain, N.H., 

and in the Victorio Mountains, N. Mex. 

MESOTHERMAL DEPOSITS 

The mesothermal deposits that yield most of our 

lead, zinc, and copper are notably poor in beryllium. 

A little helvite has been found in deposits rich in 

rhodochrosite or rhodonite near Philipsburg, Mont., 

and Silverton, Colo., but these deposits show no 

promise as sources of beryllium. 

For convenience, the chrysoberyl deposits of the 

Seward Peninsula, Alaska, are included here, although they might also be grouped with the hypothermal deposits with which they are associated. 

These replacement bodies in limestone consist 

largely of very fine grained fluorite, diaspore, and 

chrysoberyl, and they lack silicate gangue minerals. 

They contain some of the largest known resources 

of beryllium and of fluorite and may form the basis 

for a multiproduct mining operation. 

EPITHERMAL DEPOSITS 

Concentrations of beryllium minerals in epithermal deposits were overlooked for many years because 

they are not closely associated with the famous 

gold- and silver-bearing sulfide deposits of this 

genetic type. Instead, they are in sulfide-poor altered 

rocks that contain small amounts of fluorite as th~ 

only readily recognizable economic mineral. The 

largest known beryllium deposits are the epithermal 

mantos at Spor Mountain, Utah, in which a rhyolite 

ash bed containing as much as 65 percent of limestone and dolomite in pebbles and cobbles was replaced by montmorillonite, silica, fluorite, adularia, 

and bertrandite. The ore is too fine grained to be 

beneficiated, but nearly all the beryllium can be 

leached from it with acid. A somewhat similar deposit is a few miles north of Iron Mountain, N. Mex. 

Large veins of quartz, calcite, adularia, and bertrandite cut monzonite in the Gold Hill district, 

Utah, and are unusual in that they contain no fluorite and are not in calcareous host rocks. 

REGIONAL DISTRIBUTION OF BERYLLIUM DEPOSITS 

Pegmatite deposits of Paleozoic age have been 

found along much of the Appalachian Mountains 

from Nova Scotia to central Alabama. Beryl is 

widespread in the northern Appalachians, but is 

largely restricted in the southern Appalachians to 

the tin-spodumene belt near Kings Mountain, N.C., 

the Amelia-Powhatan County area, Virginia, and 

the Troup County area, Georgia. Pegmatites of Precambrian age yield beryl in the Black Hills, S. Dak., 

northern Colorado, northern New Mexico, and 

south-central Wyoming. Beryl-bearing pegmatites 

are not as productive elsewhere in the west. 

N onpegmatitic deposits have an entirely different 

distribution. Most are in the block-faulted regions 

of the West, and a few are in strongly faulted areas 

in Alaska, the Mississippi Valley, and northern New 

England. The beryllium deposits are in, and probably are features of, fluorspar metallogenic provinces, especially in the West, where they commonly 

are associated with igneous rocks of middle or late 

Tertiary age. Many of the deposits are in limestone 

or dolomite. 
92 UNITED STATES MINERAL RESOURCES 

RESOURCES 

The only resources that have been reasonably well 

delineated in pegmatites are those in the fine-grained 

spodumene-bearing pegmatites that are being mined 

for lithium. These contain a very large amount of 

beryl; 800,000 tons has been estimated to be in the 

pegmatites of North and South Carolina alone. However, because of the low beryl content of the rock 

(about one-half of 1 percent) and its fine particle 

size, this beryl will not be economically recoverable. 

Hence, it is not included in the resource tabulation. 

TABLE lB.-Estimated resources of beryllium, in short tons 

of metal 

In known deposits In undiscovered deposits 

United States ---- Other countries __ _ 

Pegmatitie 

300 

600 

Nonpeg- Pegmatitie matitie 

60,000 600 

32,000 4,500 

Nonpegmatitie 

250,000 

400,000 

The coarse zoned pegmatites, on the other hand, 

contain beryl that is readily recoverable, but the 

known beryl resources are no more than 10,000 tons, 

because no exploration is done in advance of mining. 

The larger nonpegmatitic deposits are persistent 

enough to be explored thoroughly before mining and 

to yield fairly reliable resource estimates with minimal exploration. The three largest districts, Spor 

Mountain, Utah; Seward Peninsula, Alaska; and 

Gold Hill, Utah, account for most of the resources 

of beryllium in known nonpegmatitic deposits as 

given in table 18. 

The 60,000 tons of beryllium in nonpegmatitic 

deposits in the United States are in deposits discovered in a period of about 10 years, after which 

exploration abruptly ceased. Additional deposits 

doubtless remain to be discovered. These are assumed to contain about four times as much beryllium as the deposits that are now known. The following characteristics of major districts were used 

in evaluating potential future discoveries : most 

beryllium districts (1) are associated with highangle faults of regional extent, generally block 

faults; (2) are in fluorite metallogenic provinces; 

and (3) have calcareous rocks as the most favorable 

host for mineralization. Figure 12 shows areas that 

are most promising for additional exploration. It 

.._ ______ _ 

--,...,.... __ 

lt~ts,, : : --.... ........ ..__ ......... 

"Gr0 I ( -·--

l. " 1 \ ------r--·--------'~---.l'L..__ 

:::.~---) .. -:-~ ....... L·~· ...... \ ...... ou;-· - / ~--~--------------~ --------(i t! 

--.. -.._,~ I : I SOUTH DAkOTA : ...... ~ .. WISCONSI" 

/ -----.i I : I '--. 

/ ~ -··-·;··---~ .. ,OMING ~----·-··--·-~---,r-··-··-··-··"\...,_ .. --· 

le;:;Y I ! ' ~, '> 

(. ·~ '-·--r-··-··-.. _1_ ___ N[BRAS.. \ >.J \ \ OMIO j\.-• ,;•" •J" ~ \ ~'·• I l ·----------·-r :INoi•N•\ r· ~J '--, \:. CAL '.~ •••;• ; ~---··-··-··--·~•J \.. ILLINOIS \ •., fwEST ,.J 

IFo~N ' ~ ! COLORADO i \., \ ~ ,J •. -"-,~IRGIHIAj .. 

'• \ · · . · ·-, · .- • 1 ~~"G "V 

· \\ /----+------,.L __ ·:~·~---___1 ..... ·-.·-.:,_::i::=::C:.-~c~--:::~:. ~ ~ i ~----·-·j \-··-·--··- '?.j TENNESSEE .r·' -r-··---.,.,_., 

) •••• ••zoo• j j i OKLAHOMA \ { ---- -------r··.J.·-:..... soutH., __ 

I • : N£ .. MEXIco : l I ARKANSAS r l \ \. __ cAROLI ... 

··-- ~ ! I '---, .. ..,. •

1

• I ;;: ·

1 •• '·· t ·~.. ; ~-~ ............. --...... I ~ ' \ GEORGIA \ '·· ~ I 1 _] • ocABAMA \ • 

-....... __ ~-~\~~~--] ..... \.-----L.: \ _____ l__ ___ _. 

1·.. i LOUISIAN.A : •._n ··-~- i:•:•, • ~- ~~ ______ ........_ 

\ .,, \ 

\ .. ,_ 0 100 JOO JOO - KILOOIPUS I I I I I 

FIGURE 12.-Areas of the conterminous United States in which beryllium deposits are most likely to be found. 
BERYLLIUM 93 

should be emphasized that the diagnostic characteristics given above pertain to most, but not all districts. Beryllium districts may well be found that 

do not conform to these generalizations, but their 

potential cannot now be estimated. 

Beryllium minerals of hydrothermal deposits seldom can be recognized readily in the field, and the 

deposits themselves are likely to be covered by soil. 

Hence, they are most likely to be found by a study 

of regional geology, followed by geochemical surveys 

of the most promising areas. Resources now known 

are large, but small-scale search is justified for deposits that might be better economically than those 

that are now known. 

SELECTED REFERENCES 

Beus, A. A., 1966, Geochemistry of beryllium: San Francisco, 

W. H. Freeman and Co., 401 p. 

Cameron, E. N., Jahns, R. H., McNair, A. H., and Page, 

L. R., 1949, Internal structure of granitic pegmatites: 

Econ. Geology Mon. 2, 115 p. 

Everest, D. A., Napier, E., North, A. A., and Wells, R. A., 

1965, Economic assessment of four processes for the production of beryllium hydroxide from flotation concentrates: Inst. Mining and Metallurgy Trans., v. 74, (Bull. 

707) ' p. 869-895. 

Griffitts, W. R-, 1964, Beryllium resources of the tin-spodumene belt, North Carolina: U.S. Geol. Survey Circ. 309, 

12 p. 

Heindl, R. A., 1970, Beryllium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 489-501. 

Mulligan, Robert, 1968, Geology of Canadian beryllium deposits: Canada Geol. Survey Econ. Geology Rept. 23, 

109 p. 

Sainsbury, C. L., 1969, Geology and ore deposits of the 

central York Mountains, western Seward Peninsula, 

Alaska: U.S. Geol. Survey Bull. 1287, 101 p. 

Shawe, D. R., and Bernold, Stanley, 1966, Beryllium content 

of volcanic rocks: U.S. Geol. Survey Bull. 1214-C, 11 p· 

Staatz, M. H., and Carr, W. J., 1964, Geology and mineral 

deposits of the Thomas and Dugway Ranges, Juab and 

Tooele Counties, Utah: U.S. Geol. Survey Prof. Paper 

415, 188 p. 

Stokinger, H. E., 1966, Beryllium-its industrial hygiene aspects: New York, A cad. Press, 394 p. 

U.S. Bureau of Mines, 1953, Supply-demand position, in 

Materials survey-Beryllium: U.S. Govt. Printing Office, 

p. IV, 1-21. 

--- 1953-1969, Minerals yearbooks. 

UNITED STATES MINERAL RESOURCES 

BISMUTH 

By J. W. HAsLER, M. H. MILLER, and R. M. CHAPMAN 

CONTENTS 

Page 

Abstract of conclusions --------------------------- 95 

Introduction ------------------------------------- 95 

Exploitation ------------------------------------- 96 

Geologic environment ---------------------------- 96 

Geochemistry -------------------------------- 96 

Bismuth ores -------------------------------- 97 

Major sources --------------------------- 97 

Minor occurrences ----------------------- 97 

Resources --------------------------------------- 98 

Identified resources -------------------------- 98 

Hypothetical and speculative resources --------- 98 

Prospecting techniques --------------------------- 98 

Problems for research ---------------------------- 98 

References cited --~------------------------------ 98 

ABSTRACT OF CONCLUSIONS 

In the United S.tates, bismuth is largely a byproduct from 

ores of other metals with which it is associated, principally 

lead and copper. Lesser amounts of bismuth are found in 

molybdenum, gold, silver, tin, tungsten, and zinc ores. The 

United States consumes annually as much as four times the 

amount of bismuth recovered from domestic ores; thus, the 

United States must rely on imports for 50-75 percent of its 

supply. The three principal uses of bismuth in the United 

States at present are in the manufacture of pharmaceuticals 

(medicines and pearlescent cosmetics), low-melting alloys, 

and metallurgical additives. 

A continued supply of bismuth must come as a byproduct 

from the major producers of lead, zinc, and copper in the 

Western United States. Other potential sources in the United 

States are molybdenum and tungsten ores, coal ash from 

West Virginia coals, and oceanic manganese nodules. Bismuth is known to occur in lead deposits in the Appalachian 

Mountains from North Carolina to Maine. Host rocks include 

Precambrian dolomites west of the Adirondack Mountains 

in New York and Precambrian and Cambrian schists east of 

the Blue Ridge in North Carolina. Bismuth content of some 

metamorphic rocks in the Piedmont province is relatively 

high. Pegmatites in southeastern Pennsylvania and in western Maine commonly carry native bismuth and bismuthinite 

in small amounts. 

Should lead production be curtailed by continued closings 

of smelters, especially those with bismuth recovery units, the 

domestic supply of bismuth will be seriously affected; consequently, research and exploration for bismuth-bearing 

minerals should be continued. 

INTRODUCTION 

Bismuth is obtained largely as a byproduct from 

ores of other metals, principally lead and copper. 

Lesser amounts of bismuth are associated with molybdenum, cobalt, gold, silver, tin, tungsten, and 

zinc. Despite its quantitative scarcity, the frequency 

of occurrence of bismuth is remarkably high. The 

bismuth minerals bismite (Biz03) and bismuthinite 

(BizS3) are widely distributed in small quantities in 

ores throughout all the continents (Paone, 1970). 

Bismuth reserves in the United States are dependent 

on western U.S. lead reserves, which average about 

7 pounds bismuth per ton of lead (0.35 percent), or 

100 ppm (parts per million) bismuth in 3-percent 

lead ore (R. L. Erickson, written commun., 1972). 

Free-world countries known to have major bismuth reserves are Japan, 95,200,000 pounds; Mexico, 

25 million pounds ; and Peru, 20 million pounds. 

Bolivia, Canada, South Korea, France, and Yugoslavia together have a reserve of about 18 million 

pounds (U.S. Department of the Interior, 1972, p. 

24-26). 

The principal uses for bismuth are in low-melting 

alloys, in metallurgical additives for aluminum, carbon steel, and malleable iron, in pearlescent cosmetic pigments, in medicines, and in a variety of 

other smaller specialized applications. The largest 

single use of bismuth continues to be in the pharmaceutical field. 

Small quantities of bismuth compounds are used 

as an accelerating agent in the rubber vulcanizing 

process. A bismuth-cadmium alloy is used in the 

production of some selenium rectifiers, and a few 

thousand pounds of metal is consumed each year in 

the manufacture of bismuth-tellurium electronic 

U.S. GEOL. SURVEY PROF. PAPER 820 

95 
96 UNITED STATES MINERAL RESOURCES 

devices. Experimental uses and some laboratory 

reagent chemicals account for small additional quantities (Bancel, 1971). 

The future for bismuth seems good. However, 

much of the demand for bismuth depends somewhat 

on the state of health of the aircraft and automobile 

industries. These affect lead production, and increased lead production should normally increase 

bismuth production. 

The search for new and undiscovered sources of 

bismuth will correspond to the search for bismuth's 

associated metals, such as cobalt, copper, gold, lead, 

molybdenum, silver, tin, tungsten, and zinc. Ash 

from some coals contains as much as 0.003 percent 

bismuth, or 30 ppm (Goldschmidt, 1935). 

Estimated annual production of bismuth in the 

United States ranged from 590,000 pounds in 1962 

to approximately 850,000 pounds in 1971. These 

figures probably include some bismuth produced in 

the United States from foreign ores. The United 

States consumed from 2,175,038 to 3,199,321 pounds 

of bismuth metal annually during 1963-70; in 1971, 

consumption dropped to 1,648, 718 pounds. World 

bismuth production in 1971 (excluding People's Republic of China and U.S.S.R.) totaled 7,990,000 

pounds (Cook, 1972) . 

U.S. bismuth demand is forecast to increase at an 

annual rate of 3 percent, and the domestic consumption in the year 2000 is estimated to range from 3 

to 5.2 million pounds (Charlie Wyche, oral commun., 

1972). Though the supply of bismuth seems assured, 

exploration cutbacks, production problems (such as 

strikes, continued smelter closings, or mine fires), 

or nationalization of foreign mines may result in a 

reduction of much-needed imports as well as domestic production. The bismuth supply situation could 

then become most critical. 

EXPLOITATION 

Bismuth, a metallic element, was probably unknown to the Greeks and Romans; in the Middle 

Ages it became familiar but was frequently confused with other metals, such as tin, lead, antimony, 

and zinc. In the 15th century Basil Valentine referred to it as "wismit." About 1597, the efficacy of 

bismuth nitrate in treating intestinal disorders was 

discovered by Andreas Lebanius, and the element 

has been used for that purpose to the present. However, it was not until the 18th century that J. H. 

Pott, C. J. Geoffrey, and T. Bergman produced pure 

bismuth metal. Beginning in 1833 with the Pattison process for desilverization of lead bullion and 

attendant extraction of bismuth alloy, continued 

development and improvement of metallurgical 

processes for extraction and purification of bismuth 

have resulted in commercial availability of bismuth 

metal of 97.995 percent purity. 

Bismuth compounds were noted initially for their 

soothing effects on human digestive disorders and 

healing effects on wounds and sores. This property 

of bismuth was exploited in many medicinal and 

cosmetic preparations, and until 1930 some 90 percent of the bismuth used was for this purpose. The 

development of low-melting alloys has since resulted 

in a wide variety of industrial applications of bismuth alloys and chemical compounds such as metallurgical additives for aluminum, carbon steel, and 

malleable iron and in pearlescent pigments. The 

major current uses for metallic bismuth depend on 

its ability to impart fusibility and machinability to 

a variety of alloys. The United States consumes considerably more bismuth than is recovered from 

domestic ores and must therefore rely on imports 

for 50-75 percent of its supply (Persse, 1970). 

Major sources of imports in 1971 were Mexico, 

Japan, and Peru. Refinery production of bismuth in 

the United States is mainly from the American 

Smelting and Refining Co. in Omaha, Nebr.; U.S. 

Smelting, Refining, and Mining Co. at East Chicago, 

Ind. ; and Southern California Chemical Co., Los 

Nietos, Calif. 

Reductions in lead production and subsequent 

closures of any lead refining facilities will seriously 

affect the bismuth supply in the United States. Current environmental problems are having a serious 

impact on the domestic mining industry and will 

continue until such problems can be solved. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

The average bismuth content of the earth's crust 

is estimated at 0.1 ppm or one part in 10 million. 

Bismuth's abundance is reported to be highest in 

oceanic manganese nodules, where it ranges from 

0.5 to 24 ppm, and is next highest in silicic rocks, 

in which it ranges from 0.02 to 0.9 ppm (Michael 

Fleischer, written commun., 1970). Analyses from 

various sources indicate that the abundance of bismuth in coal ash may be as much as 0.003 percent, 

or 30 ppm (Goldschmidt, 1935). 

Bismuth, like arsenic and antimony, is chalcophile, 

and all three show a strong affinity for sulfur. Most 

bismuth-bearing minerals crystallize in late magmatic stages or are deposited by relatively hot hydrothermal solutions. Throughout the geochemical cycle, 

bismuth is comparatively readily precipitated as 

basic carbonate which forms during the hydrolytic 

decomposition of bismuth salts in aqueous solution. 
BISMUTH 97 

Bismuth, therefore, becomes concentrated in the 

hydrolyzates. Although the biological role is unknown, bismuth is known to occur in some marine 

organisms (Rankama and Sahama, 1950) . 

BISMUTH ORES 

Most bismuth produced in the United States is 

a byproduct of lead refineries which treat crude 

bullion, flue dust, and other metallurgical products. 

The bismuth content of ores and concentrates is 

generally so low that it is not reported in assays, 

even from mines known to be relatively rich in 

bismuth; thus the primary sources of bismuth are 

known only in a general way (Cooper, 1962). 

MAJOR SOURCES 

Hypogene deposits in the Western United States 

account for most of the domestic bismuth production. These deposits generally formed at high to 

medium temperatures, commonly within or near 

intrusive igneous rocks. A few small pockets of 

bismuth ore have been mined from pegmatite dikes, 

quartz veins, and contact-metamorphic deposits, but 

most of the bismuth occurs as a minor constituent 

of ores of silver, lead, zinc, copper, gold, tungsten, 

and molybdenum. Lead and lead-zinc ores that are 

high in bismuth also tend to be high in silver, gold, 

and commonly copper. A distinct association of bismuth with silver is apparent in some mines. 

Lead-zinc-silver replacement deposits in limestone 

have probably been the most important sources of 

bismuth in the United States. Deposits of this type 

occur at Leadville and Gilman, Colo. ; Tintic and 

Little Cottonwood, Utah; Darwin, Calif. ; and Patagonia, Ariz. In these deposits the bismuth occurs 

in the oxidized as well as in the sulfide ores. Primary bismuth minerals, where known, include bismuth sulfosalts of lead, silver, and copper, bismuthinite, and native bismuth. 

Complex lead-copper-silver-bismuth ores have 

been mined in the Red Mountain, Poughkeepsie 

Gulch, Upper Uncompahgre, Mineral Point, Engineer Mountain, and Lake City districts in the San 

Juan Mountains, Colo., and also in the Montezuma 

district in the Front Range, Colo. The ore bodies 

are small, but some are very rich in bismuth and 

precious metals. 

In the Coeur d'Alene district, Idaho, bismuth in 

recoverable amounts has been reported from the 

Sunshine mine and certain other mines in the 

"Silver Belt." Gold-bismuth ores are reported from 

gold deposits in Riverside County, Calif., and Grant 

County, N. Mex. Relatively abundant bismuth minerals are reported in complex gold ores of the Boise 

Basin district, Idaho; the Goldfield and Yellow Pine 

districts, Nevada; and the Argenta and Elkhorn 

districts, Montana. Lead and zinc ores and concentrates from deposits of the Mississippi Valley type 

contain no detectable bismuth. 

MINOR OCCURRENCES 

Bismuth minerals, generally in very minor quantities, have been reported in many gold-quartz veins 

in the southern Piedmont gold belt, which extends 

from northern Virginia southwestward to Alabama 

in the southeastern part of the United States. These 

deposits are of general interest only. 

Lead deposits from North Carolina to Maine contain 0.05 ppm to as much as 1 percent bismuth. The 

eastern lead deposits occur in the Appalachian 

Mountains and on the west side of the Adirondack 

Mountains in New York. All the deposits are in 

rocks that have been folded and faulted to a considerable extent. The host rocks include Precambrian dolomite on the west side of the Adirondacks, 

Precambrian or Cambrian schists in the districts 

east of the Blue Ridge in North Carolina and Virginia, lower Paleozoic dolomites west of the Blue 

Ridge in Tennessee and Virginia, Silurian conglomerates in southeastern New York, and both Precambrian granitic rocks and Triassic red beds and diabase in southeastern Pennsylvania. The Piedmont 

province is composed of Precambrian and highly 

metamorphosed Paleozoic rocks, relatively high in 

bismuth, whereas Triassic rocks are low in bismuth 

and high in antimony. Pegmatites in southeastern 

Pennsylvania and in western Maine commonly carry 

native bismuth and bismuthinite in small amounts. 

The spatial proximity of igneous intrusive rocks 

to which the deposits can be related genetically 

varies from district to district. Deposits in the western Adirondack Mountains are associated with 

Precambrian granite intrusives, and those east of 

the Blue Ridge occur near batholithic masses of 

granite to which a Devonian or late Paleozoic age 

has been ascribed. 

Native bismuth and other bismuth minerals are 

reported in placer gold deposits at many localities 

in Alaska and some localities in the southwestern 

and Rocky Mountain States. Bismuth minerals are 

said to be very abundant in the black sands in the 

Boise Basin district, Idaho, and some other localities, but bismuth is not known to have been recovered from these sources. 

Bismuth is reported to occur in uranium veins in 

the Ralston Buttes district, Jefferson County, Colo., 

and native bismuth and emplectite (CuBiS2) have 

been found in some deposits. A fairly clean handpicked sample of pitchblende from the Schwartz-
98 UNITED STATES MINERAL RESOURCES 

walder mine reportedly contained 1.5 percent bismuth. Bismuthinite, native bismuth, and their oxidation products are reported in uraniferous veins 

in the White Signal and Blackhawk districts, New 

Mexico. Bismuthinite and molybdenite are reported 

in a vein containing brannerite in Mono County, 

Calif. A brannerite-rich mill product from Climax, 

Colo., also is reported to contain bismuth, which 

occurs in the range of 10-100 ppm in the Climax 

molybdenum deposit. No bismuth is known to have 

been recovered from uranium deposits in the United 

States. 

The known bismuth deposits in Alaska are of 

minor importance and probably would not yield 

significant amounts of the metal. Vein deposits from 

which native bismuth and bismuthinite are reported 

include those along Charley Creek about 25 miles 

north of N orne; on Eva and Moose Creeks about 36 

miles south of Nenana ; on a headwater tributary 

of Fish Creek, about 15 miles northeast of Fairbanks ; and along No Grub and Caribou Creeks in 

the Salcha River drainage. In these veins, native 

bismuth and bismuthinite are commonly associated 

with sulfide minerals, and with graphite and scheelite, in gold-quartz veins within igneous and (or) 

metamorphic rocks. The veins are generally less than 

1 foot thick and commonly are localized by joint or 

foliation planes (Berg and others, 1964, p. 98; 

Cobb, 1970). 

RESOURCES 

IDENTIFIED RESOURCES 

Measured, indicated, and inferred reserves of 

domestic recoverable bismuth associated with copper, lead, and zinc ores in Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, and 

Utah are estimated at 26,400,000 pounds; in addition, potential bismuth resources in these ores are 

estimated at about 10 million pounds (Persse, 1970). 

There is a potential resource of some 200,000 

pounds of bismuth in domestic tungsten resources. 

However, only minor amounts of bismuth have been 

recovered from tungsten ores because the amount 

present seldom exceeds the maximum impurity allowance. Hence, its value would not offset the cost 

of recovery. 

HYPOTHETICAL AND SPECULATIVE RESOURCES 

The search for bismuth as an independent metal 

seems unfeasible because its association with lead, 

copper, molybdenum, tin, tungsten, and zinc will 

insure a bismuth supply, especially from the Western States. 

Hypothetical bismuth resources may exist in 

smelter products. However, throughout the history 

of lead smelting few analyses have been made specifically for bismuth, and major smelting companies 

have analyzed only sporadically for bismuth. 

Analyses of bismuth in coal and coal ash indicate 

a source of bismuth, but only a few scattered occurrences have been noted. Data available indicate 

that certain coals may contain approximately 1 

pound of bismuth in each 200 tons of coal. No 

technology has been developed for the removal 

of bismuth from coal or coal ash, and to our knowledge, no systematic studies are underway pertaining to the recovery of bismuth from coals. 

PROSPECTING TECHNIQUES 

Prospecting techniques that have had major roles 

in the discovery of new ore deposits, especially for 

copper, molybdenum, gold, silver, lead, and zinc, 

and indirectly for bismuth, are detailed geologic 

mapping, airborne and ground geophysics, geochemical exploration, drilling, and imagery. Probably little or no prospecting for bismuth has been 

done in the United States. 

PROBLEMS FOR RESEARCH 

The geology of bismuth, where it is known to 

occur with tungsten, molybdenum, oceanic manganese nodules, and coal, should be thoroughly investigated. In addition research needs to be done to 

ascertain potential bismuth resources in smelter 

products and coal ash and studies should be carried 

out on smelter byproducts to identify bismuth 

source areas in the United States. 

REFERENCES CITED 

Bancel, D. A., 1971, Bismuth: Eng. and Mining Jour., v. 

172, no. 3, p. 115-116. 

Berg, H. C., Eberlein, G. D., and MacKevett, E. M., Jr., 

1964, Metallic mineral resources [pt. of] Metallic and 

nonmetallic mineral resources, in Mineral and water resources of Alaska: U.S. Cong., 88th, 2d sess., Senate 

Comm. Interior and Insular Affairs, Comm. Print, p. 

95-125. 

Cobb, E. H., 1970, Bismuth occurrences in Alaska: U.S. Geol. 

Survey Mineral Resources Map MR-53. 

Cook, David, 1972, Bismuth: Eng. and Mining Jour., v. 173, 

no. 3, p. 99-101. 

Cooper, J. R., 1962, Bismuth in the United States: U.S. Geol. 

Survey Mineral Resources Map MR-22. 

Goldschmidt, V. M., 1935, Rare elements in coal ashes: Indus. 

Eng. Chern., v. 27, p. 1100-1102. 

Paone, James, 1970, Bismuth, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 503-513. 

Persse, F. H., 1970, Bismuth in the United States: U.S. 

Bur. Mines lnf. Circ. 8439, 25 p. 

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry: 

Chicago, Univ. Chicago Press, 912 p. 

U.S. Department of the Interior, 1972, First annual report of 

the Secretary of the Interior under the Mining and 

minerals policy act of 1970 (P.L. 91-63)-pt. 2, App.: 

[470] p. 
UNITED STATES MINERAL RESOURCES 

BITUMEN-BEARING ROCKS 

By w. B. CASHION 

CONTENTS 

Page 

Abstract of conclusions -------------------------- 99 

Introduction ------------------------------------- 99 

Exploitation ------------------------------------- 100 

Geologic environment ---------------------------- 100 

Resources --------------------------------------- 100 

Prospecting techniques --------------------------- 102 

Problems for research --------------------------- 102 

Selected references 

TABLE 

19. Deposits of bitumen-bearing rocks in the United 

States with resources of at least 1 million 

103 

Page 

barrels ---------------------------------- 101 

ABSTRACT OF CONCLUSIONS 

Bitumen-bearing rocks occur in many areas in the United 

States, but few deposits have been exploited or evaluated for 

their total energy potential. The evaluated deposits are a 

relatively small part of North American resources of bitumen-bearing rocks and probably will not contribute to U.S. 

energy needs before 1985. Studies of known but unappraised deposits, especially extensive subsurface tar sands, 

will greatly increase total resource ,estimates. Technological 

advancements are needed in tar-sand processing, especially 

for in situ recovery methods. 

INTRODUCTION 

Nonfluid petroleum occurs as interstitial deposits 

in numerous types of rock. These rocks and their 

associated hydrocarbons are commonly treated as 

one group, regardless of rock type, and have been 

referred to as tar sands, oil-impregnated rocks, 

asphalt-bearing rocks, oil sands, bitumen-bearing 

rocks, and petroleum-impregnated rocks. As used 

in this report, the term "bitumen-bearing rocks" 

is all-inclusive and, on the basis of information 

drawn from several reports, is defined as follows: 

Consolidated or unconsolidated rocks whose interstices contain viscous to semisolid to solid petroleum 

which in its natural state cannot be recovered by primary petroleum-recovery methods. This definition includes vein, dike, and asphalt~lake deposits as well 

as disseminated deposits, but it excludes pyrobitumens (such as coal and oil shale) and fluid bitumens. 

Nonfluid bitumen occurs principally as disseminated deposits in small pore spaces spread throughout rock material. Bitumen content may be as much 

as 20-25 percent by weight but is normally much 

less. Bodies of homogeneous semisolid to solid 

hydrocarbon, containing very little rock material, 

occur in vein, pod, and lake deposits. These occurrences make up a small part of the total resource. 

Relatively small deposits can be developed, however, because of the purity of the ore. 

Utilization of bitumen-bearing rocks in the 

United States has been chiefly in road building. Because of competition from refinery asphalt, the demand for native asphalt, supplied by bituminous 

sandstone and bituminous limestone, has not kept 

pace with the 20th-century surge in road construction. (See section "Exploitation.") Gilsonite is the 

only solid hydrocarbon produced in appreciable 

amounts. It is used in ink, paint, battery boxes, and 

numerous other manufactured items and is refined 

to produce high-quality ·coke and gasoline. 

The Athabaska tar sands in Canada are being 

mined and processed by GCOS (Great Canadian 

Oil Sands, Ltd.) to produce crude oil. GCOS is producing about 45,000 barrels of oil per day, and 

they plan to increase production. Other companies 

also plan to add new installations. 

In 1967, tar-sand deposits in Albania, Rumania, 

and Russia and an asphalt-lake deposit on the island 

of Trinidad were being exploited; in 1964 the La 

Brea, Trinidad, operation produced 189,246 tons of 

material (Phizackerley and Scott, 1967, p. 571). 

The United States possesses a rather small part 

U.S. GEOL. SURVEY PROF. PAPER 820 

99 
100 UNITED' STATES MINERAL RESOURCES 

of the world's resources of bitumen-bearing rocks. 

The/in situ bitumen in all U.S. deposits that have 

beet\ studied is here estimated to total a maximum 

of approximately 29 billion barrels (table 19). Numerous U.S. deposits need additional study. It should 

be noted, however, that any future estimate of 

energy in all bitumen-bearing rocks of the United 

States will probably be small compared to estimates 

for the remainder of the world. The estimate of 

world resources in major tar-sand deposits (those 

containing more than 15 million barrels of bitumen 

in situ) is 915.2 billion barrels (Phizackerley and 

Scott, 1967, p. 551). 

Although substantial tonnages of tar sand in the 

United States are available for producing crude oil, 

there seems to be little incentive to develop the deposits in the near future. The National Petroleum 

Council, in its assessment of future energy supplies 

and demands, has predicted that Canadian deposits 

will be the primary and probably the only North 

American source of tar-sand oil through the year 

1985 (Burk, 1971, p. 171). 

EXPLOITATION 

In many States, bituminous sandstone and bituminous limestone hav~ long been mined commercially for use as road material, but currently there 

is activity at only a few places. The demand for 

asphalt, although it has increased greatly in recent 

years, is being supplied mostly by refinery asphalt. 

In 1968, bituminous limestone was produced in Alabama and Texas, and bituminous sandstone was 

produced in Kentucky and Missouri. During 1948-

68, production of native asphalt and bitumens 

(bituminous sandstone, bituminous limestone, and 

gilsonite) increased from 1,136,126 to 1,786,840 

short tons, and during the same period, there was 

approximately a threefold increase in production 

of refinery asphalt and road oil (Redfield and 

Spencer, 1950; Kirby and Moore, 1969). 

Two basic production methods are used to recover 

the bitumen: ( 1) strip mining followed by extraction treatment and (2) in situ extraction. The first 

method recovers about 90 percent of the bitumen, 

and the second method 35-50 percent (Burk, 1971, 

p. 178). Mining and hot-water extraction method is 

being used in commercial development of the Athabaskan tar-sand deposits. The depths to which strip 

minjng is feasible are limited, however, and deeper 

deposits will require in situ recovery methods. Experimentation with in situ recovery has had only 

limited success. Some nonfluid bitumen deposits contain appreciable amounts of sulfur and certain 

metals that may, with proper treatment, be recovered profitably. 

Environmental problems that may be associated 

with a large-scale tar-sand development have not 

been studied extensively but in handling huge tonnages of material in a strip-mining operation some 

problems can be predicted, for example, water pollution, silting of streams, and unstable fill. In situ 

recovery has the advantage of not disturbing the 

surface, but the disadvantage of a lower bitumen 

recovery rate. 

GEOLOGIC ENVIRONMENT 

N onfluid bitumen deposits occur most abundantly 

in sandstone and limestone, in lesser amounts in 

other types of sedimentary rocks, and rarely in 

igneous and metamorphic rocks (commonly adj acent to petroliferous sedimentary source rocks) . 

Primary pore spaces in clastic rocks are host to 

more than 95 percent of the bitumen in deposits 

studied in detail. In secondary openings produced by 

weathering, solution, and structural movement, 

hydrocarbon deposits of gilsonite, ozocerite, and 

grahamite have been found. Gilsonite deposits 

in vertical veins in eastern Utah and western 

Colorado are the only sizable accumulations of 

solid hydrocarbons in the United States. 

Sedimentary rocks containing bitumen represent 

a variety of environments of deposition, including 

marine, nearshore, and fluvial. Most of the large 

bitumen-bearing sandstone deposits occur in estuarine or fresh-water rocks (Phizackerley and Scott, 

1967, p. 566), along basin margins where petroleumbearing beds have been tilted and brought to or 

near the surface. Some bitumen-bearing rocks occur 

adjacent to faults, joints, unconformities, brecciated 

zones, and other geologic features which allow 

gases and light oil fractions to escape from accumulations of liquid petroleum. 

The source and evolution of nonliquid bitumen 

evidently are not the same in all deposits. Studies 

of various deposits yield evidence to support all the 

following statements about the bitumen : ( 1) formed 

in situ, (2) migrated to present location, (3) a 

precursor of liquid petroleum, ( 4) a residue of 

liquid petroleum, (5) was deposited with the sediment, and (6) accumulated after deposition of 

sediments. 

RESOURCES 

Bitumen deposits in. the United States are numerous and some individual deposits are extensive, 

but the fragmental information available does not 
BITUMEN-BEARING ROCKS 101 

permit a detailed estimate of the total resources. 

Many deposits are characterized by extreme and 

abrupt vertical and lateral changes in bitumen content of the impregnated rock sequence. Evaluation 

requires closely spaced surface and subsurface data 

points, but in many areas it is not feasible to gather 

such data. Thickness, percentage of bitumen, lateral 

extent, and other characteristics of most of the 

deposits are poorly known. The larger deposits for 

which estimates have been made are given in table 

19. Appraisal of other known deposits will result in 

TABLE 19.-Deposits of bitumen-bearing rocks in the United 

States with resources of at least 1 million barrels 

[Sources of data: Ball Associates, Ltd. (1965-); Burk (1971) ] 

Age Name 

of deposit 

California 

Type 

of deposit 

Bliltumen 

resources 

(millions 

of barrels, 

rounded) 

Late Miocene Edna ____________ Sandstone ---------------141-166 

and early 

Pliocene. 

Do ---------South Casmalia ____ Diatomaceous mudstone 46 

and vein deposits. 

Do ---------North Casmalia ________ do ---------------------40 

Pliocene -------Sisquoc -----------Sandstone ----------------26-50 

Miocene _______ Santa Cruz ___________ do ---------------------10 

Pliocene and McKittrick ____________ do --------------------6-9 

Pleistocene. 

Miocene _______ Point Arena __________ do ----------------------1 

Kentucky 

Pennsylvanian _Kyrock area ------Sandstone -------------------18 

Do _________ Davis-Dismal area ______ do -------------------7-11 

Do _________ Bee Spring area _______ do ----------------------8 

New Mexico 

Triassic --------Santa Rosa _______ Sandstone -------------------67 

Texas 

Cretaceous -----Uvalde ___________ Limestone --------------124-141 

Permian and 

Triassic 

Utah 

Tar Sand Triangle _Sandstone ----------10,00Q-18,100 

Eocene ________ P. R. Springs _________ do --------------3,700-4,000 

Do _________ sunnyside ____________ do --------------2,000-3,000 

Triassic _______ Circle Cliffs ___________ do ------- _______ 1,00Q-1,300 

Cretaceous and Asphalt Ridge _________ do --------------1,00Q-1,200 

Oligocene. 

~~~~~c Do ---------Lake -=======~tte~~k Fork ____________ ============~~ do ~~~~~~~~~~~~~~~~~3~g:1~g ------------------15-20 

Do ---------Raven Ridge ----------do -----------------100-125 Do ---------Rim Rock _____________ do ___________________ 3o-35 

Total ---------------------- -------------------18,693-28,862 

an appreciable increase in the estimate of total resources. Collation of information from exploratory 

wells in the Rocky Mountain States that are known 

to contain extensive subsurface tar-sand deposits 

will add a major segment to the resource estimate. 

The major tar-sand deposits of the world (those 

with more than 15 million barrels of bitumen in 

situ) are estimated to contain 915.2 billion barrels 

of bitumen, of which about 710 billion barrels is 

attributed to Canada and 200 billion barrels to 

eastern Venezuela (Phizackerley and Scott, 1967, 

p. 551). Some other authors estimate that the eastern Venezuelan tar-sand resources are comparable 

to those of Canada, and Burk (1971, p. 174) mentioned that although deposits in Colombia have not 

been well defined, available information suggests 

the possible presence of almost a trillion barrels of 

bitumen in situ. Phizackerley and Scott (1967 p. 

570) stated that very little information is available 

concerning Russian tar sands, but that one Siberian 

deposit reportedly contains impregnated Permian 

sandstone in an area the same order of size as the 

Athabaskan deposits. 

Numerous reports deal with bitumen-bearing 

rocks in the United States, but few of these give 

data that can be used for resource estimates. Ball 

Associates, Ltd. ( 1965), in a survey of available 

data, listed 546 occurrences of bitumen-bearing 

rocks in 22 States, but scant data permit estimates 

of partial resources for only seven States. Readers 

who want details of individual deposits should consult the report of Ball Associates, Ltd. (1965) and 

a comprehensive annotated bibliography by Mullens 

and Roberts (1972). Brief descriptions of some of 

the more significant near-surface deposits, taken 

mostly from the report of Ball Associates, Ltd. 

(1965), follow. 

Alabama.-Bitumen is found in several beds of 

sandstone and limestone of Mississippian age within 

a northwest-trending band, about 70 miles long and 

8 miles wide, that extends across six counties in the 

northwestern part of Alabama. Some impregnated 

beds are as much as 20 feet thick, although most are 

less than 12 feet thick. Bitumen contents of as much 

as 15 percent by weight have been reported for 

assayed samples. The Alabama Geological Survey 

is studying the deposits. 

Alaska.-Many bitumen-bearing rocks and oil 

seeps in Alaska have been reported, but owing to 

the nature of the terrain and structural deformation, little is known of the extent or thickness of 

impregnated beds. 

California.-N early all bitumen deposits in California occur near the margins of sedimentary basins 

in rocks of Miocene and Pliocene age. The deposits 

are concentrated in the southwestern part of the 

State within 75 miles of the coast. Large tonnages 

are available in San Luis Obispo, Santa Barbara, 

Santa Cruz, and Kern Counties. In San Luis Obispo 

and Santa Barbara Counties, large deposits have 

been investigated for oil-mining possibilities, but 
102 UNITED STATES MINERAL RESOURC-ES 

thus far none have been developed commercially. 

In California, the bitumen resources in only seven 

deposits, the largest being in the Edna district, San 

Luis Obispo County, are about 300 million barrels. 

Kansas.-The principal deposits of bituminous 

rocks in Kansas are in the east-central and southeastern part of the State and are of Pennsylvanian 

age. The bitumen is in beds of porous sandstone and 

limestone in a stratigraphic sequence exposed across 

several counties in a band 15-40 miles wide. A core 

from an area in the southeastern part of the State 

shows a bitumen-impregnated sandstone 100 feet 

thick containing 65,000 barrels of oil per acre in 

situ. 

Kentucky.-In west-central Kentucky sizable deposits of bitumen-bearing rocks occur, and in a few 

counties of eastern Kentucky minor accumulations 

occur. The asphalt-bearing strata are predominantly 

sandstone of Pennsylvanian and Mississippian age 

and have reported bitumen content of as much as 

10 percent by weight. Estimates of bitumen resources for three areas in Kentucky are given in 

table 19. 

Missouri.-Known deposits of bitumen are widely 

distributed in 21 counties in western Missouri. The 

deposits occur in both sandstone and limestone of 

Mississippian and Pennsylvanian age, but mostly 

in Pennsylvanian sandstones. The impregnated rocks 

of Mississippian age are mostly limestones located 

in the zinc-lead mining area in the southwestern 

part of the State. Maximum reported thickness of 

impregnated rocks is 30 feet, and maximum bitumen content is 15 percent by weight. No bitumen 

resource estimates have been made for Missouri, 

although some deposits are known to be extensive. 

New . M exico.-One economically important tarsand deposit occurs in New Mexico, and that is in 

the Santa Rosa Sandstone (Triassic) in Guadalupe 

County. The bitumen-bearing zone is as much as 

60 feet thick and contains as much as 8 percent 

hydrocarbon by weight. A resource estimate for the 

Santa Rosa Sandstone is given in table 19. 

Oklahoma.-Ball Associates, Ltd. (1965, p. 227-

231) listed 80 areas containing petroleum-impregnated rock located in 21 Oklahoma counties. The 

largest deposits are in sandstones and limestones of 

Ordovician age in Murray County. The sandstone 

contains as much as 14 percent bitumen by weight. 

Other bitumen deposits are found in rocks ranging 

in age from Ordovician to Cretaceous. 

Texas.-Cretaceous rocks, in a northeast-trending 

area that extends across the middle one-third of 

Texas, contain most of the known bitumen deposits 

of the State. The largest deposits, in the Uvalde 

district (table 19), are in the Anacacho Limestone. 

The bitumen-bearing sequence is as much as 200 

feet thick, and its maximum hydrocarbon content 

is 20 percent by weight. 

Utah.-Outcrops of tar sand are found in many 

sections of eastern Utah. The largest outcrops are 

situated around the margin of the Uinta Basin and 

in a triangle-shaped area west of the confluence of 

the Green and Colorado Rivers. The deposits in the 

Uinta Basin are, for the most part, in rocks of Tertiary age. Some impregnated zones extend through 

several hundred feet of sandstone and related rocks. 

Asphaltic zones in the "Tar Sand Triangle" are extensive and are as much as 250 feet thick. They 

occur in rocks of Permian and Triassic age. The 

estimate of nonfluid bitumen in Utah has been 

greatly increased as a result of recent studies by the 

Utah Geological and Mineralogical Survey. 

Gilsonite is the only solid hydrocarbon produced 

in appreciable quantities. Utah has all the major 

deposits. The deposits are not large enough, however, to contribute greatly to the total energy needs 

of the United States. Original reserves of gilsonite 

are estimated to have been 45 million tons, and much 

ore has been mined from the widest veins. All operating mines are in Utah. 

PROSPECTING TECHNIQUES 

Discovery of most of the larger known occurrences 

of bitumen-bearing rocks has been due to visible 

indications of impregnations, such as discolored 

rocks and tar seeps. Other deposits have been found 

as a result of mineral-mining operations and exploratory drilling for oil and gas. Because there 

has been no rapid depletion of known tar-sand deposits, little attention has been given to developing 

sophisticated tools for prospecting. If the need 

arises for tar-sand exploration, some methods now 

employed in searching for liquid petroleum could 

be adapted to prospecting for nonliquid bitumen. In 

the near future, however, increases in the estimated 

amount of United States tar-sand resources will 

probably be a result of investigations of known 

deposits that have not been evaluated. 

PROBLEMS FOR RESEARCH 

Large reserves of relatively high-grade material 

occurring in a small area are required for largescale economic development of bitumen-bearing 

rocks. In North America, the Canadian tar sands 

are, by far, the deposits best suited for exploitation. 

Development of the Canadian deposits has brought 

great advancement in the technology used in mining 

and processing enormous tonnages of tar sand, but 
BITUMEN-BEARING ROCKS 103 

thus far the operation has had marginal economic 

success. 

Most in situ recovery experimentation has not 

been encouraging. Variations in bitumen content, 

physical properties, and water saturation of the 

rocks cause problems in establishing and maintaining proper underground communication and flow 

rate. 

Additional research is needed for improving in 

situ recovery methods and for determining those 

measures required to protect the environment during tar-sand development. Special attention should 

be given to deposits in arid climates inasmuch as 

a limited water supply could affect all phases of the 

development. 

SELECTED REFERENCES 

Abraham, Herbert, 1960, Asphalts and allied substancestheir occurrence, modes of production, uses in the arts, 

and methods of testing, v. 1, Historical review and 

natural raw materials [6th ed.]: Princeton, N. J., D. 

Van Nostrand Co., 370 p. 

Ball A·ssociates, Ltd., 1965, Surface and shallow oil-impregnated rocks and shallow oil fields in the United States: 

U.S. Bur. Mines Mon. 12, 375 p. 

Burk, R. 0., chm., 1971, Tar Sands Task Group report, Chap. 

12, in McLean, J. G., chm., U.S. energy outlook-an initial appraisal 1971-1985: Natl. Petroleum Council's 

Ci>mm. on U.S. Energy Outlook, Summ. Task Group 

Repts., v. 2, p. 171-182. 

Eldridge, G. H., 1901, The asphalt and bituminous rock deposits of the United States: U.S. Geol. Survey 22d Ann. 

Rept., pt. 1, p. 209-452. 

Kirby, J. G., and Moor·e, B. M., 1969, Crude petroleum and 

petroleum products, in U.S. Bur. Mines Minerals Yearbook 1968, v. 1-2, p. 809'-825. 

Mullens, M. C., and Roberts, A. E., 1972, S.elected annotated 

bibliography on asphalt-bearing rocks of the United 

States and Canada, to 1970: U.S. Geol. Survey Bull. 

1352, 218 p. 

Phizackerley, P. H., and Scott, L. 0., 1967, Major tar sand 

deposits of the world, in Drilling and production: World 

Petroleum Cong., 7th, Mexico 1967, Proc., v. 3, p. 551-

571. 

Redfield, A. H., and Spencer, S. J., 1950, Asphalt and related bitumens, in U.S. Bur. Mines Minerals Yearbook 

1948, p. 156-163. 

UNITED STATES MINERAL RESOURCES 

CADMIUM 

By HELMUTH WEDOW, JR. 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -- _----------_-- _ --------------------

Exploitation -------------------------------------

Geologic environment ----------------------------

Geochemistry --------------------------------

~inerals ------------------------------------

Ores ----------------------------------------

Resources ---------------------------------------

References cited ---------------------------------

TABLES 

20. Zinc and cadmium (!Ontents and zinc:cadmium 

Page 

105 

105 

106 

106 

106 

106 

107 

107 

109 

Pqe 

ratios in selected geologic materials --------- 107 

21. Cadmium content of sphalerite from selected 

U.S. and Canadian mining districts and regions ------------------------------------- 108 

22. Estimated identified and undiscovered cadmium 

resources of the United States and the world- 108 

23. Recoverable identified resources of cadmium in 

the United States, grouped by major geologic 

regions and compared with similarly classified 

zinc resources of these regions -------------- 109 

ABSTRACT OF CONCLUSIO:"'JS 

Cadmium, a trace metal similar to zinc in many ways but 

having a much lower crustal abundance, occurs as an impurity in zinc-bearing mineral's. It is used chiefly in the 

electroplating of fabricated steel products to obtain superior 

corrosion resistance; additional uses are in the manufacture 

of yellow and red pigments, vinyl plastics, phosphors for 

television picture tubes, and nickel-cadmium batteries. None 

of the few independent cadmium minerals currently known 

is sufficiently abundant to be mined as an ore. thus, all 

cadmium produced has been as a byproduct of zinc refining 

from sphalerite. World zinc concentrates are estimated to 

contain an average of about one-fourth of 1 percent cadmium, 

of which about 75 percent is generally recovered or can be 

recovered during zinc smelting and refining. 

Estimates of world cadmium resources place recoverable 

identified resources at more than 1.2 million metric tons, 

of which about one-fourth is in the United States. Total 

world recoverable and subeconomic resources, both identified 

and undiscovered, are estimated to be in excess of 18 million 

metric tons of contained cadmium. About one-sixth of these 

resources is in deposits believed to be exploitable under 

existing economic conditions. 

Many of the deposits containing the world's cadmium resources are the conventional zinc-bearing types, chiefly those 

known as massive sulfide and strata-bound. However, significant low-grade resources occur in phosphorites and such 

black metal-rich shales as the Kupferschiefer of central 

Europe, in which the Cd: Zn ratio is considerably higher 

than in the more conventional deposits. 

INTRODUCTION 

Cadmium 1s a silver-white soft, malleable metal, 

which with its compounds has a wide range of industrial uses. Its relative rarity and consequent high 

price, however, have prevented more extensive use 

inasmuch as it is in direct competition with its more 

abundant less expensive sister element, zinc. Cadmium metal has a specific gravity of 8.65, and its 

melting and boiling points are 321 oc and 765°C, 

respectively. The high luster on a freshly cut surface dulls rapidly with the formation of a thin, 

impervious coating of cadmium oxide, which is the 

most important characteristic of its use as a metal. 

All new commercial cadmium is obtained as a byproduct of zinc production, in which it is recovered 

from the fumes released by the roasting of zinc sulfide ores or from sludges generated during the purification of the sulfuric acid leachate of roasted zinc 

ore. Thus, most zinc producers also market cadmium. 

Cadmium is available in several forms. It can be 

cast as balls, ingots, slabs~ and other shapes, and also 

can be obtained as sticks, flakes, or sponge. Some 

producers also convert the molten metal directly to 

the oxide. For electroplating (see below) as much as 

0.05 percent lead and 0.033 percent zinc is permitted, 

whereas for certain other uses the allowable maxiU.S. GEOL. SURVEY PROF. PAPER 820 

105 
106 UNITED STATES MINERAL RESOURCES 

mums of zinc and lead are less. In addition, cadmium 

used in pigments requires a low content of thallium, 

and cadmium solders cannot contain even trace 

amounts of aluminum. 

The major use of cadmium is in the electroplating 

of fabricated steel products to give them superior 

corrosion resistance. Such electroplating uses about 

50 percent of the available metal. The metal is also 

used in low-melting-point alloys. The chief use of 

cadmium compounds is as pigments; cadmium sulfide, cadmium sulfoselenide, and lithopone generally 

account for the color range of yellow, orange, and 

red in corrosion-resistant paints. Cadmium stearate 

is used as a stabilizer in the production of some of 

the vinyl plastics. Cadmium phosphors are used widely in black-and-white television and as coatings for 

fluorescent tubes; these phosphors are also increasingly being used in color television for blue and green 

components. Cadmium nitrate is one of the chief 

components of the nickel-cadmium battery. Despite 

a variety of substitutes, cadmium is sufficiently 

superior to warrant continued use, and therefore 

most available supplies will be consumed. (See 

Heindl, 1970.) 

EXPLOITATION 

The industrial use of cadmium dates from the 

1870's, although the metal was first detected as an 

impurity in zinc ores as early as 1817. All commercial cadmium used in the latter part of the 19th century was produced from the ores of the Upper Silesian zinc-lead district, at that time in Germany but 

after World War I in Poland. The cumulative German, and hence total world production, in the 19th 

century amounted to about 115 mt (metric tons). 

The United States first began to extract cadmium 

from zinc ores of the Joplin district, Missouri, in 

1906 and since then has produced more than 150,000 

mt of this metal. Total world production of cadmium 

thus far in the 20th century has exceeded 320,000 

mt. The annual world production rate was 3112, 131/2, 

3,150, and 16,000 mt in 1882, 1900, 1935, and 1970, 

respectively. In comparison, the U.S. annual production rate was 6, 112, 1,800, and 4,300 mt in 1907, 

1917, 1935, and 1970, respectively. 

Because cadmium is recovered as a byproduct during the smelting and refining of zinc, its production 

is clearly a function of zinc production. (See chapter 

on "Zinc.") However, because cadmium is recovered 

at the smelter, world production more closely parallels zinc smelter production than mine production. 

Comparison of zinc production data with cadmium 

production data shows that the world has doubled its 

use of cadmium in the last 15 years, whet:eas its consumption of zinc has required about 20 years to 

double. This somewhat greater increase in the rate 

of cadmium production relative to that of zinc is due 

to the improvement of zinc-refining techniques and 

to the development of more efficient recovery methods. At the same time, some major zinc production 

has been shifted to ores somewhat richer in cadmium, as for example those of the Mississippi Valley 

type. These relations are clearly seen in shift of the 

Zn: Cd ratio of production data from values of more 

than 80,000 in the 1880's (the first decade of cadmium production) down to an average of about 525 for 

the 1930's, 340 for the 1940's, 350 for the 1950's, and 

310 for the 1960's. From the ratio for the 1960's 

(310) and on the assumption that the average zincbearing concentrate contains 55 percent zinc and 

that about 75 percent of cadmium in the concentrate 

is recovered, it is estimated that world zinc concentrates average about 0.24 percent cadmium. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Cadmium is the chemical element with atomic 

number 48. Cadmium has an atomic weight of 112.41, 

and eight stable isotopes in proportions as follows: 

Isotope Percent 

Cdtos ----------------------------- 1.22 

Cdtoe ----------------------------- .88 

Cd110 ----------------------------- 12.39 

Cd111 ----------------------------- 12.75 

Cd112 ----------------------------- 24.07 

Cd113 ------------------------------ 12.26 

CdlH --------------------------------- 28.86 

Cd118 

----------------------------- 7.58 

Cadmium has a valence of + 2 ~nd an ionic radius 

of 0.97 A. It belongs to Group IIb of the periodic 

system, along with zinc and mercury. Thus, cadmi urn is chemically very similar to these elements, 

a similarity that accounts for its relative concentration in zinc minerals despite a much larger ionic 

radius (0.97 A versus 0.74 A). However, cadmium is 

relatively more sulfophile than zinc and hence is 

relatively more concentrated in the later stages of 

magmatic differentiation and associated hydrothermal ores and even more so in the low-temperature 

reducing sedimentary environments. This relationship is clearly shown by the Zn: Cd ratios of various 

geologic materials given in table 20. 

MINERALS 

There are relatively few independent cadmium 

minerals. The native metal is unknown, and natural 

cadmium oxide (CdO) has been found only in Sardinia, as a coating on hemimorphite. Cadmium sulfide (CdS) occurs both as hawleyite, the cadmium 
CADMIUM 107 

TABLE 20.-Zinc and cadmium contents and zinc: cadmium ratios in selec.ted 

geologic materials 

Average metal content (ppm) Zn:Cd 

Geologie material Reference 

Crustal abundance ----------------------

Do ---------------------------------

Igneous rocks --------------------------

Do ---------------------------------

Magmatic sulfides ----------------------- Swedish sphalerites ---------------------

Estimated average world zinc concentrate_ 

Joplin sphalerites ----------------------- Southeastern U.S. sphalerites ------------ Permian phosphatic shale, Wyo ---------- Bentonites in Pierre Shale ---------------

Black shale ----------------------------

Kupferschiefer ore, Mansfeld district ___ _ 

Zn 

91 

40 

132 

8,500 

544,000 

550,000 

579,600 

609,000 

10,400 

110 

9,000 

analog of isometric sphalerite, and as greenockite, 

the cadmium analog of hexagonal wurtzite-sphalerite and wurtzite are the two crystalline varieties 

of zinc sulfide (ZnS). The anhydrous carbonate 

(CdCOa), otavite, is the cadmium analog of smithsonite (ZnCOa) and can occur as oriented overgrowths on zinc carbonate crystals. Otavite was first 

found at Tsumeb, near Otavi, South West Africa. 

The most common of the independent cadmium minerals is the sulfide, greenockite·. It occurs chiefly as a 

yellowish earthy film or coating on zinc minerals, 

mainly sphalerite, and rarely as crystals. These coatings form as a result of the low-temperature alteration of sphalerite, chiefly alteration due to 

weathering. 

ORES 

None of the independent cadmium minerals is 

abundant enough to be an ore mineral, although the 

presence of trace greenockite in slightly altered or 

oxidized sphalerite will slightly enhance the cadmium content of the zinc-bearing ores. The chief source 

of commercial cadmi urn is zinc ore, and cadmi urn is 

by far the major metallic byproduct recovered in the 

smelting of zinc concentrate and the refining of zinc 

metal. Thus, the major concentrations of cadmium 

reasonably well known today are in the sulfide zinc 

ores, although potential resources exist in other zinc 

ores and in other lesser known potential zinc concentrations. (See chapter on "Zinc.") 

The cadmium content of sphalerite is highly variable. This zinc sulfide, along with wurtzite, generally 

contains from less than 0.1 percent to 1 percent Cd 

and locally as much as several percent. The world 

ratio 

Cd 

0.2 455 Zn-"Crustal Abundance," this 

volume; Cd-Parker, 1967. 

.15 270 Tourtelot and others, 1964. 

.15 880 Rankama and Sahama, 1950. 

530 Sandell and Goldich, cited by Rank- ama and Sahama, 1950. 

20 425 Rankama and Sahama, 1950. 

1,700 320 Gabrielson, cited by Rankama and 

Sahama, 1950. 

2,400 230 "Zinc," this volume. 

3,580 162 Siebenthal, 1909. 

5,200 117 Maher and Fagan, 1970. 

200 52 Love, 1961. 

2.8 39 Tourtelot and others, 1964. 

10-30 Davidson, cited by Tourtelot and 

others, 1964. 

500 18 Cissarz and Moritz, cited by 

Rankama and Sahama, 1950. 

average for zinc concentrates, which are dominantly 

sphalerite, is estimated as 0.24 percent Cd in material 

containing 55 percent Zn (table 20). The range and 

average cadmium content of sphalerites from selected U.S. and Canadian zinc mines and a few other 

occurrences of significance are listed in table 21. 

Higher temperature sphalerites appear to contain 

less cadmium than those formed at lower temperatures. Some of the lower cadmium values may also 

be due to metamorphism-that is, cadmium is 

mobilized and more widely dispersed preferentially 

to zinc during metamorphism of a preexisting sulfide 

deposit. 

RESOURCES 

Cadmium resources are closely associated with 

zinc resources. If the Zn: Cd ratio of 455: 1 based on 

crustal abundances of these elements (table 20) is 

valid, then the amount of cadmium in the uppermost 

1 kilometer of the continental crust of the earth is 

about 750 x 109 mt of which about 44 X 109 mt is 

within this depth in the United States. Erickson (See 

chapter on "Crustal Abundance") estimates world 

and U.S. zinc reserve potentials as 3,400 X 106 and 

198 X 106 mt, respectively. If Erickson's zinc potentials are presumed to be chiefly in conventional sulfide ores, then similar cadmium reserve potentials, 

based on a Zn: Cd ratio of 230 for world zinc concentrates (table 20) can be estimated as a:pproximately 

15 x 106 and 0.86 x 106 mt for the world and the 

United States, respectively. 

Estimates of cadmium resources for the United 

States and the world for this report are listed in 

table 22. These estimates were prepared chiefly by 
108 UNITED STATES MINERAL RESOURCES 

TABLE 21.-Cadmium content, in percent, of sphalerite from selected U.S. and Canadian mining districts and regions 

Location 

Number of 

analyses Range Average Reference 

Balma~Edwards, N.Y --------------------------

Edwards, N.Y. --------------------------------- Franklin, N. J -------------------------------- Friedensville, Pa -------------------------------

Do -----------------------------------------

Timberville, ~~~~~~a~~ Va ~~-=============================== --------------------------------

Austinville, Do ----------------------------------------- Va __ --------- _..., ___________________ _ 

Austinville (and other occurrences in 

Cambrian rocks of southeastern U.S.). 

East Tennessee, Kingsport ores ------------------

Do ----------------------------------------- Ducktown, Tenn -------------------------------- Middle Tennessee veins -------------------------- Middle Kentucky veins ------------------------- Illinois-Kentucky fluorspar district --------------- Upper Mississippi Valley ------------------------

Tri-State -------------------------------------- Gilman, Colo ----------------------------------- Rocky Mountain region (U.S. except Butte) ------

Do ----------------------------------------- Butte, Mont ------------------------------------

Do ----------------------------------------- Coeur d'Alene, Idaho --------------------------- Metaline, Wash -------------------------------- Northport, Wash ------------------------------- Western Canada, chiefly British Columbia --------

Ontario and Quebec ---------------------------- Pine Point, Northwest Territories ----------------

1 Composite. 

•Not given. 

13 

1 

1 

1 

1 

3 

1 

2 

2 

12 

11 

6 

6 

1 

6 

37 

5 

6 

15 

1 

8 

5 

3 

3 

59 

2 

3 

118 

5 

4 

TABLE 22.-Estimated identified and undiscovered cadmium 

resources of the United States and the world 

[Values given are in thousands of metric tons of contained cadmium] 

UndisIdentified covered Total resources resources resources 

United States 

Recoverable ------------- Subeconomic ------------

Total -------------

295 

Rest of the world 

Recoverable ------------- Subeconomic ------------

Total -------------

950 

Total world 

Recoverable ------------- Subeconomic ------------

Total -------------

1,245 

400 695 

1,500 

2,195 

1,425 2,375 

14,000 

16,375 

1,825 3,070 

15,500 

18,570 

applying Zn: Cd ratios of various geologic materials 

(such as those in table 20) to the basic data from 

which zinc resources were estimated. (See "Zinc," 

this volume.) The proximity of the estimate of recoverable cadmium resources in the United States 

(695,000 mt, in table 22) to the reserve potential 

(860,000 mt) suggests that the United States may be 

0.08-0.15 

. 08- .16 

.25- .38 

.45-- .60 

.13- .18 

.08- .45 

.24- .48 . 25-- .80 

(1) 

(ll) 

(ll) 

. 38-1.40 

.04- .40 

.11- .71 

.1- .6 

.4 -1.0 . OX- .1 

. 2 - .2 

.10- .80 

.3- .6 

.1 - .7 . 2- .9 

.2- .3 

.06-- .15 

0.12 

.4 

.15 

.05 

. 20 

.12 

. 22 

. 32 

. 52 

.15 

. 18 

. 32 

.47 

.09 

1.3 

1.34 

.69 

. 17 

. 34 

. 22 

. 28 

. 58 

.1 

.2 

.40 

.45 

. 26 

.45 

. 22 

. 11 

Lenker, 1962. 

Warren and Thompson, 1945. 

Lenker, 1962. 

Callahan, 1968. 

Warren and Thompson, 1945 . Lenker, 1962 . Maher and Fagan, 1970 . Lenker, 1962 . Maher and Fagan, 1970 . Lenker, 1962. 

Maher and Fagan, 1970 . 

Lenker, 1962 . Maher and Fagan, 1970 . Do. 

Jolly and Heyl, 1968. 

Do. 

Hall and Heyl, 1968 . Do . Siebenthal, 1909 . Lenker, 1962 . Kaiser and others, 1954 . Warren and Thompson, 1945 . Kaiser and others, 1954 . Warren and Thompson, 1945 . Fryklund and Fletcher, 1956. 

Kaiser and others, 1954. 

Do . Warren and Thompson, 1945 . Do . Evans and others, 1968 . 

nearing its potential for cadmium associated with 

zinc ores as currently mined. On the other hand, the 

potential subeconomic resources, both identified and 

undiscovered, imply that there is no significant possible long-range shortage of cadmium from U.S. 

sources. The data in table 22 also indicate that world 

resources of cadmium, estimated at more than 18 

million mt, are probably more than adequate for future needs as currently projected. One likely source 

for the future may well be marine phosphorites from 

which both zinc and cadmium could be extracted during the preparation of superphosphate fertilizers, although small amounts of these elements are undoubtedly needed in the final fertilizer product as 

trace nutrients. 

Table 23 shows the distribution of recoverable 

identified cadmium resources of the United States by 

major geologic regions and compares these estimates 

with those for. zinc in the same regions. Also given 

are the approximate Zn:Cd ratios for the respective 

zinc and cadmium recoverable identified resources of 

these regions. The Zn: C<katio of 150 for the total of 

these U.S. resources indicates that the greater part 

of this country's zinc ores are in mineral deposits 

that contain relatively more cadmium than the estimated world average (Zn:Cd ratio 230, table 20). 
CADMIUM 109 

TABLE 23.-Recoverable identified resources of cadmium in 

the United States, grouped by major geologic regions and 

compared with similarly classified zinc resources of these 

regions 

[See also chapter on "Zinc"] 

Zinc Approxi- Cadmium content mate content of ores Zn:Cd of ores Region (X 103 mt) ratio (X 103 mt) 

Appalachian ---------- 16,400 200 82 

Mississippi Valley ----- 19,200 120 160 

Rocky Mountain ------ 7,300 180 41 

Pacific Coast --------- 2,100 170 12 

Total ---------- 45,000 1 150 295 

1 Average. 

Because of the geochemical similarity of zinc and 

cadmium, most deposits containing zinc also contain 

cadmium but in lesser to barely trace amounts. As 

indicated previously, cadmium is produced solely as 

a byproduct of zinc extraction and purification. For 

detail on the types of zinc deposits, their classification, and the prospecting techniques used in the 

search for them the reader is referred to the discussion of zinc resources in "Zinc," this volume. For 

additional information on the utilization and exploitation of cadmium, the reader is referred to 

Heindl (1970). 

REFERENCES CITED 

Callahan, W. H., 1968, Geology of the Friedensville zinc 

mine, Lehigh County, Pennsylvania, in Ridge, J. D., 

ed., Ore deposits of the United States 1933-1967 

(Graton Sales volume) v. 1: New York, Am. Inst. 

Mining, Metall., and Petroleum Engineers, p. 96--107. 

Evans, T. L., Cambell, F. A., and Krouse, H. R., 1968, A 

reconnaissance study of some western Canadian leadzinc deposits: Econ. Geology, v. 63, no. 4, p. 349-359. 

Fryklund, V. C., Jr., and Fletcher, J. D., 1956, Geochemistry 

of sphalerite from the Star mine, Coeur d'Alene district, Idaho: Econ. Geology, v. 51, no. 3, p. 223-247. 

Hall, W. E., and Heyl, A. V., 1968, Distribution of minor 

elements in ore and host rock, Illinois-Kentucky fluorite 

district and Upper Mississippi Valley zinc-lead district: 

Econ. Geology, v. 63, no. 6., p. 655-670. 

Heindl, R. A., 1970, Cadmium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 515-526. 

Jolly, J. L., and Heyl, A. V., 1968, Mercury and other trace 

elements in sphalerite and wall rocks from central 

Kentucky, Tennessee, and Appalachian zinc districts: 

U.S. Geol. Survey Bull. 1252-F, p. Fl-F29. 

Kaiser, E. P., Herring, B. F., and Rabbitt, J. C., 1954, Minor 

elements in some rocks, ores, and mill and smelter products: U.S. Geol. Survey TEI-415, 119 p., issued by the 

U.S. Atomic Energy Tech. lnf. Service, Oak Ridge, Tenn. 

Lenker, E. S., 1962, A trace element study of selected sulfide 

minerals from the eastern United States: Pennsylvania 

State Univ. Ph.D. Dissert., 151 p. 

Love, J. D., 1961, Vanadium and associated elements in the 

Phosphoria Formation in the Afton area, western Wyoming: U.S. Geol. Survey Prof. Paper 424-C, p. C279-

C282. 

Maher, S. W., and Fagan, J. M., 1970, Trace element content of some ore deposits in the Southeastern States: 

Tennessee Div. Geology Inf. Circ. 16, 1 chart. 

Parker, R~'L., 1967, Composition of the earth's crust, in Data 

of geochemistry, 6th ed.: U.S. Geol. Survey Prof. Paper 

440-D, p. Dl-D19. 

Rankama, Kalervo, and Sahama, Th. G., 1950, Geochemistry: 

Chicago, Chicago Univ. Press, 912 p. 

Siebenthal, C. E., 1909, Cadmium, in U.S. Geological Survey, 

Mineral resources of the United States, 1908: Washington, D.C., U.S. Govt. Printing Office, p. 793-803. 

Tourtelot, H. A., Huffman, Claude, Jr., and Rader, L. F., 

1964, Cadmium in samples of the Pierre Shale and some 

equivalent stratigraphic units, Great Plains region, in 

Short papers in geology and hydrology, 1964: U.S. Geol. 

Survey Prof. Paper 475-D, p. D73-D78. 

Warren, H. V., and Thompson, R. M., 1945, Sphalerites from 

western Canada: Econ. Geology, v. 40, no. 5, p. 309-

335. 

UNITED STATES MINERAL RESOURCES 

CHROMIUM 

By T. P. THAYER 

CONTENTS 

Page 

Abstract of e<>nclusions -------------------------- 111 

Introduction ------------------------------------- 111 

Exploitation ------------------------------------- 112 

Geologic environment ---------------------------- 112 

Mineralogy of chromite and chromite ores ----- 112 

Primary chromite deposits -------------------- 112 

Stratiform deposits ---------------------- 113 

Podiform deposits ----------------------- 115 

Disrupted stratiform deposits ------------- 115 

Genesis of primary chromite deposits ------ 116 

Secondary deposits and associated metals ------ 116 

Resources --------------------------------------- 116 

Identified resources -------------------------- 116 

Hypothetical and speculative resources --------- 119 

Exploration for chromite deposits ----------------- 119 

Problems for research ---------------------------- 120 

References cited --------------------------------- 120 

FIGURE 

13. Graph showing world production and U.S. consumption and production of chromite ore and 

relation of price to domestic production from 

Page 

1900 to 1970 ------------------------------ 113 

TABLE 

Page 

24. Estimated world reserves and resources of chromite ore by type and country -------------- 117 

ABSTRACT OF CONCLUSIO~S 

Although world reserves are large and resources of chromite ore are ample for the foreseeable future, domestic resources (excluding the national stockpile) are low grade and 

represent only about a 4- to 5-year supply. The outlook for 

substantially increasing domestic resources, even at several 

times present world prices, is not favorable. The thicker, 

minable parts of the Stillwater Complex in Montana, the 

principal domestic source, are e<>mplexly faulted and sheared 

off at depth. Although many podiform deposits must occur 

in serpentine along the Appalachian Mountains and Pacific 

Coast, most would be too small to mine at depths of 100 feet 

or more, even if means were available to locate them. A few 

relatively large podiform deposits probably are concealed 

at minable depths and might meet national needs for a few 

months at most. 

The principal North American resources other than those 

in the Stillwater Complex are in a similar complex in Manitoba and very large low-grade deposits in Greenland. Metallurgical research to improve recovery of chromium from the 

low-grade "ores" and acquisition of more information on 

the Greenland deposits are needed. The only minable chromite reserves in the Western Hemisphere are a few million 

tons in Brazil and perhaps some in Cuba. 

INTRODUCTION 

Chromium is one of the most important and indispensable industrial metals. It is best known as a 

silvery white, hard, and bright metal plating on steel 

or other material used for decoration or protection 

from corrosion. Such coatings, however, rarely exceed 0.00002 inch in thickness and use only relatively 

minor amounts of the metal. Over the 5 years 1966-

70, the United States consumed an average of 430,000 

tons of chromium annually; about 67 percent was 

used in ferroalloys, about 18 percent in high-temperature furnace linings, and 15 percent in chemicals, 

including plating. In relatively small amounts, 

chromium hardens and toughens steel and increases 

its resistance to corrosion, especially at high temperatures. Most stainless steel contains about 18 percent chromium, and some cutting tools and wearresisting alloys contain as much as 33 percent. The 

mineral chromite has some unique refractory uses. 

Although there are substitutes for chromium in 

many uses, such as titanium or aluminum for stainless steel and magnesite for chromite in refractories, 

no adequate substitutes have been, or are likely to be, 

found for chromium in some applications. 

U.S. GEOL. SURVEY PROF. PAPER 820 

111 
112 UNITED STATES MINERAL RESOURCES 

During the last 5 years, the United States has consumed about 7 million long tons of chromium ore, 

equal to about 28 percent of total world production, 

but it has mined none at all since 1962 (fig. 13). Our 

presumed resources are nearly all low grade; although theoretically they might last about 5 years 

at our present rate of consumption, they would be 

difficult to mine and expensive to use. Since 1962, our 

entire supply of chromite has been imported from the 

Eastern Hemisphere, and for the last 5 years about 

45 percent of the chromium we have used in metallurgy has been imported from the Soviet Union. 

EXPLOITATION 

The alltime production of chromite in the United 

States is about 1,850,000 long tons; of this total 

about 950,000 tons, all high-iron ore and concentrates, came from Montana. The remaining 900,000 

tons came almost entirely from podiform deposits in 

California, Oregon, Pennsylvania, Maryland, and 

Alaska. Since 1900, only in wartime has the United 

States produced more than 3,500 tons of chromite a 

year. During World War 1, the maximum domestic 

production of 82,430 long tons equaled less than half 

of consumption, and the gap between domestic production and consumption has widened ever since 

(fig. 13). Before 1940 all production was from podiform deposits, but since then, production of concentrates from the Stillwater Complex has predominated. Of 1,085,185 long tons produced during the 

Korean war for Government purchase programs, 

about 800,000 tons of Stillwater concentrates was 

stockpiled because of its low grade (38.5 percent 

Cr20a). Moreover, despite a base price of $115 a ton 

for standard lumpy metallurgical ore during the 

Korean war, the podiform deposits as a group yielded only about 24,700 tons a year. From the period 

1942--44 to the period 1952--57, an increase in price 

from $87 to $115 in 1954 constant dollars-a price 

increase of 32 percent-stimulated a rise in production of usable ore from podiform deposits by only 10 

percent (Materials Advisory Board, 1959, p. 44). 

Because the podiform deposits are small and most 

are in relatively inaccessible areas, no serious environmental problems are anticipated. Large-scale 

mining and milling operations at the Stillwater Complex, however, would entail large dumps and tailings 

ponds along the sides of a scenic part of the Stillwater River valley. 

GEOLOGIC ENVIRONMENT 

Chromium is a rock-forming element that is closely associated with magnesium and nickel in the ultramafic rocks peridotite, pyroxenite, and serpentine. 

From a normal range of 1,100-3,400 ppm (parts per 

million) and an average of about 1,800 ppm in ultramafic rocks, the content of chromium drops to about 

200 ppm in gabbro and basalt, and 5 ppm in granite. 

Chromium is concentrated with the clay fraction of 

sedimentary rocks, normally in amounts of less than 

100 ppm; but in phosphorites from Idaho, Wyoming, 

and Utah, it averages about 1,000 ppm (Michael 

Fleischer, written commun., 1972). 

MINERALOGY OF CHROMITE AND CHROMITE ORES 

The mineral chromite is the only commercial 

source of chromium and varies compositionally within wide limits permitted by the formula (Mg,Fe2+) 

(Cr,Al,Fe3+) 204. The Cr20a content of the pure mineral chromite ranges from about 15 to 64 percent, 

but directly usable ores, which are mixtures of 

chromite and silicate minerals, range from about 33 

to 55 percent Cr20a. Compositionally, three general 

kinds of chromite ore are recognized: (1) highchromium, which contains 46 percent or more Cr20a 

and has a Cr: Fe ratio of 2: 1 or more; (2) high-iron, 

which contains 40--46 percent Cr20a and has a Cr: Fe 

ratio of less than 2: 1; and (3) high-aluminum, which 

contains more than 20 percent Al20a, and more than 

60 percent Al20a and Cr20a combined. Although all 

three kinds are interchanged or blended for some 

uses, the high-chromium ores are used for metallurgy, and the high-aluminum ores mostly for refractories. Only high-iron ores are used for making 

chemicals, and they are also of major importance for 

making alloys and refractories. 

All chromite ores consist of mixtures of chromite 

and associated minerals that are waste or gangue. 

Massive lumpy ore that contains little gangue is preferred by industry for metallurgical and refractory 

uses. Natural deposits, however, range from massive 

or high grade to disseminated or low grade, and ore 

commonly grades from one to the other .. The lowgrade ores may be concentrated by simple washing 

if they are friable or by grinding and separating the 

chromite from gangue by various physical methods. 

In general, milling of primary ores containing less 

than 10 percent Cr20a (20 percent chromite) has not 

been successful. 

PRIMARY CHROMITE DEPOSITS 

Primary chromite deposits occur only in certain 

kinds of ultramafic or closely related anorthositic 

rocks (Thayer, 1971) and are of two major geologic 

types: stratiform (layered) and pod-shaped (Jackson, 1961 ; Thayer, 1960, 1964) . 
CHROMIUM 118 

z $100 

0 

~ 

(!) 

z 

0 $50 ...J 

a: $40 

w 

~ $30 

w 

~ $20 a: 

~ 

$10 

A-,.' 

Average value of domestic, " --..~-

, ... tl ores, excluding Stillwater, ~.' .., ! I I 

.. ,·. Mont., in 1954 dollars I ' 1952 Stillwater a !.'"' :, . "T 1---

I" ... ,.-- I I ,,, \ I! contr~ct p~ice 

- ' ' ,', ,'i~~ !·..," . .. I I I , ... , I I \ ~ ,., , ' '-, ,I ,, \ I j .. .. I \' r ., .. -, I ,, ,,.~ 

,I t : ... ,..--, .. : \ I 'rl' .. r ' , i 

/ \ I I '!I., \I I I 

r~/ \ " ~ I .., \ /'Average price'paid fo~ ,, I '-.... " · .... _, ,, ~ \I "- I domestic ores, excluding 

" 1 'I 'r-, ! ' Stillwater, Mont. 

I 

$8 " 

6000 

5000 

4000 

3000 

2000 

1000 

I T T v 

500 

400 

300 

200 

I .' ft. 

I\ I 1\1 / , v 7 7 

World production-"-/-\, /r \ 

1 

~Total U.S. 

11 consumption 

(/) 100 z 

0 

~ 

(!) 

z 50 0 

7 ~ '- y //// 

l-----,:1---f--+---J.'~-IJHIJ.+-_--+--+-----+------l---4J11r,a..concentrates~~/:,£'/,..:,.'/,..,·/.q.q. _ __,__---i I 1J V '///// 

If' f I v '/Y///~ 

...J 40 

u.. 

0 30 

(/) 

0 

z 20 

I\/ W~rldWar~ World War II..__~ ~~~ 

<{ 

(/) 

::::> 

0 

:I: 10 ~ // // 

'/// // '////. '/ '/// / '////. '/ 

I '//// '// V//// 

'//// v~ '///~ 1% 

~ ~ ~/~ r% 

/ ~ ~ ~ ~ 

~ ~ ~~ ~ t// 

~ 

~ ~ ~ ~ \~ H ~ ~ 1940 1950 1960 1970 

FIGURE 13.-World production and U.S. consumption and production of chromite ore and relation of price to domestic production from 1900 to 1970. Data from U.S. Geological Survey and from U.S. Bureau of Mines (1942-70). 

STRATIFORM DEPOSITS 

The stratiform deposits form layers in the lower 

parts of stratified igneous comJ:lexes of the Bushveld or Stillwater type ; they are characterized by 

great lateral extent and uniformity and by consistent 

positions within the host complexes. They contain 
114 UNITED STATES MINERAL RESOURCES 

more than 98 percent of the chromite resources of 

the world. The Steelpoort Main Seam in the Bushveld Complex in South Africa, for example, contains 

"reserves of merchantable ore conservatively estimated at half a billion tons" (Cameron and Desborough, 1969, p. 24). The chromite in stratiform 

deposits is predominantly of the high-iron type, but 

the high-chromium ores of the Great Dyke in 

Rhodesia are an outstanding exception. The regularity of the layering facilitates mining, even of thin 

seams, and is a reliable guide in prospecting. All the 

chromite-bearing layered complexes are geologically 

old, and in many the chromite layers have been dismembered by folding and faulting. Though mining 

may be difficult and expensive in highly deformed 

rocks, the layered structure usually can be used to 

guide exploration for sizable blocks of ore that have 

been separated. 

The chromite deposits in the Stillwater Complex 

in Montana, which contains about 80 percent of the 

chromium resources of the United States, are of the 

layered high-iron type. They occur in an east-west 

belt about 30 miles long by half a mile wide. Thirteen 

chromite-rich zones are known; they range in thickness from 1 inch to more than 12 feet; several can 

be traced laterally more· than 15 miles ; and one can 

be traced more than 25 miles. The layers dip from 

about 50° to vertical and "extend downward to great 

depths except where terminated by major faults" 

(Jackson, 1963, p. 58). Two of the up}:er zones were 

mined in the eastern part of the complex under U.S. 

Government purchase contracts during World War 

II and the Korean war. In the Benbow mine nearly 

65,000 long tons of concentrates averaging 41.5 percent Cr20s was recovered from a highly faulted vertical layer 4--5 feet thick (Materials Advisory Board, 

1959, p. 42). In the Mountain View area about 

830,000 long tons of concentrates averaging 38.5--

38.8 percent Cr20s was recovered from two layered 

zones which range in width from 2 to 16 feet and 

from 3 to 8 feet, respectively (Price, 1963, p. 1). 

Analogous to the Montana deposits are major deposits of the high-iron class in the layered Bird River 

complex in southeastern Manitoba, Canada. The complex has been folded to vertical and broken by numerous faults, and the probable total length of the 

chromite-bearing zone is 6-10 miles (Davies, 1958). 

Extensive layered chromite deposits in anorthosite 

near Fiskenaesset in southwestern Greenland may 

represent the largest potential resources of chromite in North America. The chromite occurs in layered 

zones that average 1.5--10 feet in thickness, reach a 

maximum of 65 feet, and consist of interlayered 

anorthosite and chromitite layers, usually 1,4-2¥2 

inches thick. The chromite layers have a minimum 

exposed length of 75 miles. The chromite mineral 

averages about 33 percent Cr20s, 0.9:1 in Cr:Fe 

ratio, and contains 0.2-0.5 percent V 20s, averaging 

about 0.3 percent. The average grade of rock in 

minable widths probably ranges from 15 to 25 percent Cr20s. Although the rocks have been intricately 

fclded, layers are favorably situated for mining over 

considerable areas. For example, it is estimated that 

one layer 3-22 feet thick along a strike length of 

4,600 feet contains a million tons of recoverable 

chromite or 350,000 tons of Cr20s and 3,000 tons of 

V20 5 • The chromite is exposed in completely bare 

outcrops near the coast; nearby fjords are deep, and 

Fiskenaesset harbor is accessible the year round 

(Ghisler and Windley, 1967). 

The tremendous resources of chromite in South 

Africa and Rhodesia are in two great layered complexes, the Bushveld and the Great Dyke, respectively. The Bushveld Complex is a rudely basin-shaped 

layered mass 26,000 square miles in extent. As many 

as 29 chromite layers or groups of layers occur in 

various segments of the chromite-bearing zone, 

which is exposed over a distance of more than 70 

miles along the eastern margin alone (Cameron and 

Desborough, 1969). Although some of the layers are 

less than 1 inch thick, several layers are of minable 

thickness and quality. The relation of ore reserves to 

geometry of deposits is illustrated by the Steelpoort 

Main Seam, mentioned earlier. If the inclined seam 

averages 40 inches in true thickness over a known 

distance of 40 miles and if the ore has a specific 

gravity of 4.2, each foot of ore below the outcrop 

represents 100,000 tons. In view of the 40-mile 

length, projecting only a mile downdip from the outcrop seems minimal but yields "half a billion tons" 

(Cameron and Desborough, 1969, p. 24). The total of 

6.1 billion .tons given for resources of the entire 

Bushveld Complex (Republic of South ,Africa) in 

table 24 is believed to be conservative. 

The Great Dyke in Rhodesia is a layered complex 

332 miles long by 3-6 miles wide. In cross section the 

Dyke is synclinal with dips of 20°-40° near the margins. Chromite layers occur over the entire length of 

the Dyke, and individual layers have been traced continuously the entire width, though they vary in number from 6 to 12 in different segments (Worst, 1960). 

The layers range in thickness from 2 to 18 inches, 

and nearly all the chromite is the high-chromium 

variety. Only layers 6 inches or more thick are mined 

below the outcrop; some of the thicker layers are 

mined more than 1,000 feet down the slope. 
CHROMIUM 115 

PODIFORM DEPOSITS 

The podiform chromite deposits are lenticular or 

rudely tabular pods, but some defy description as to 

form. They range in size from a few pounds to several million tons. Most pod deposits yield less than 

1,000 tons of ore each, but most of the production 

comes from ore bodies that contain 100,000 tons or 

more. Less than a dozen deposits that originally contained 1,000,000 tons or more are known. Most pod 

deposits are of the high-chromium type, but these 

deposits also are the only source of high-aluminum 

chromite. Podiform deposits occur in irregular peridotite masses or peridotite-gabbro complexes of the 

alpine type, which are restricted to mountain belts 

such as the Appalachians and Urals and to belts that 

surround most of the Pacific Ocean. Within many 

large complexes, the chromite deposits are localized, 

generally near contacts between peridotite and gabbro; but where there is no gabbro, deposits appear to 

be scattered at random. 

Podiform chromite deposits are scattered along the 

Pacific Coast of the United States from the Kenai 

Peninsula in southern Alaska to southern California 

and along the Appalachian Mountains from northern 

Vermont to Georgia. The principal concentrations of 

deposits or districts are in the Klamath Mountains in 

southwestern Oregon and northern California, in the 

western slopes of the Sierra Nevada, in the Coast 

Ranges of California, in eastern Oregon, and in the 

Maryland-Pennsylvania (State Line) district (Thayer and Miller, 1962; Thayer, 1966; Thayer and Ramp, 

1969). The largest single high-grade ore body probably was at the Woods mine in Pennsylvania, which 

yielded between 100,000 and 200,000 tons of lump 

ore before 1900 (Pearre and Heyl, 1960). Statistical 

analysis of recorded production from 456 mines in 

the United States between 1916 and 1953 has shown 

that of 517,000 long tons of ore shipped the largest 

20 mines provided about 72 percent, 42 mines yielded 

15.7 percent, and 394 mines yielded only 12.3 percent 

of the ore. These figures are believed to typify podiform deposits, and accordingly, they show that most 

deposits of this type are economically insignificant. 

The high-chromium chromite ores of the Eastern 

Hemisphere, except for the Great Dyke, are mostly 

in podiform deposits that are concentrated in three 

major tectonic belts: (1) the Ural Mountains, (2) 

the so-called Tethyan mountain chains between the 

Alps and Himalayas, and (3) around the western 

margin of the Pacific Ocean. The largest single welldescribed deposit is the Coto ore body in the Philippine Islands (Stoll, 1958), which originally contained 

about 15 million tons of high-aluminum chromite ore. 

The TiE~ bag hi mine in New Caledonia and the GOlolan 

ore body in Turkey each yielded more than a million 

tons of high-chromium chromite. The southern Ural 

Mountains appear to include the greatest known concentration of large podiform deposits in the world, 

but no modern figures on size of deposits are 

available. 

DISRUPTED STRATIFORM DEPOSITS 

Tectonic disruption and dismemberment of stratiform deposits have led to misidentification of those 

in some districts as podiform. Recognition of parts 

of a once-continuous stratiform sheet can provide an 

economic incentive for systematic exploration to find 

missing segments, whereas a similar program in a 

podiform chromite district could be financially ruinous. No large podiform deposits are known in Precambrian rocks, and no true stratiform deposits are 

known in rocks younger than about middle 

P:recambrian. 

Recent cooperative investigations by the U.S. Geological Survey and the Companhia de Pesquisa de 

Recursos Minerais and Departamento Nacional da 

Produ~ao Mineral, under the auspices of the U.S. 

Administration for International Development, have 

revealed that the chromite deposits near Campo Formoso, Bahia, formerly believed to be isolated blocks 

actually are segments of a highly faulted layered 

complex 10 to 11 miles long. Massive layers that 

range from about 1 to 6 feet in thickness are of highchromium (metallurgical) grade. Large amounts of 

high-iron chromite have been recovered by washing 

of disseminated ore that has been weathered irregularly to maximum depths of about 150 feet. Because a thick layer of debris from quartzite cliffs 

above the ore zone covers much of the area, the 

mines originally were located where this cover was 

thin. Determination by drilling that the deposits are 

semicontinuous under the debris has led to plans for 

production of 100,000--200,000 tons of ore a year 

(Mining Jour., 1972). Recent prospecting indicates 

that similar, although probably much smaller deposits, occur in the surrounding region. Podiform 

deposits, mostly of high-aluminum chromite, occur 

in small peridotite masses and in the Tocantins complex (Herbert, 1973; White and others, 1971) in central Goias along a north-south belt about 1,000 miles 

long. The lode deposits are small, and concentrations 

of residual chromite in soil have been the principal 

sources of production. Because exploration for 

chromite in Brazil is at an early stage, the estimates 

in table 24 are regarded as very tentative. The Bahia 

deposits are believed to have the largest minable 

reserves, by far, in the Western Hemisphere. 
116 UNITED STATES MINERAL RESOURCES 

GENESIS OF PRIMARY CHROMITE DEPOSITS 

All chromite of economic interest is believed to 

have been formed by crystallization from fluid magma essentially simultaneously with the associated 

silicates. Chromite and other minerals that crystallize early are denser than the magma, and the crystals, therefore, settle as they form and collect in 

layers on the floor of the magma chamber. In most 

stratiform complexes the layering and many delicate 

primary igneous and sedimentary features (Jackson, 

1961) are preserved intact despite metamorphism 

and deformation. Many podiform deposits also preserve settled textures, some identical with those in 

the stratiform deposits, but also some that are 

unique (Thayer, 1964, 1969). The similarities of the 

podiform and stratiform deposits indicate a common 

origin by crystal settling, but differences between 

them are attributed to crystallization of podiform 

deposits in the upper mantle, and of stratiform deposits in the crust where they are now. Intrusion of 

peridotite and chromite from the upper mantle into 

the upper crust by solid flowage at high temperature, 

probably over distances of many miles, is believed to 

have fragmented the original layering and imposed 

metamorphic features on the podiform deposits and 

their host rocks (Thayer, 1969). Some features of 

chromite deposits that were interpreted 30--40 years 

ago as evidence of hydrothermal origin are now attributed to alteration of primary magmatic minerals. 

SECONDARY DEPOSITS AND ASSOCIATED METALS 

Erosion of chromite-bearing rocks may form secondary deposits of two kinds, black sands and lateritic soils. Because chromite is heavy and resists 

weathering, it may accumulate as grains in black 

sands or soil to form placers. Under favorable tropical or subtropical conditions, solution of magnesium 

silicates from ultramafic rocks by ground water 

forms lateritic soils which contain as much as 50 percent iron, 2--4 percent Cr20a, 2-2.5 percent nickel, 

about a tenth as much cobalt as nickel, and some 

aluminum (Gross, 1970a, p. 27). Such ferruginous 

laterites are now being worked for nickel and cobalt 

in several countries and for iron ore in a few places, 

but economic recovery of the chromium has not been 

achieved. Chromite has been recovered from black 

sands in the United States and Japan on a relatively 

small scale, and from alluvial soil in Rhodesia by 

flotation on a large scale. 

No other minerals are mined with primary chromite, although platinum occurs with layered chromite 

deposits in some complexes in the Ural Mountains. 

Some gold and platinum have been mined from 

chromite-bearing beach sands along the Oregon 

coast (Griggs, 1945), but no other minerals have 

been recovered during operations for chromite 

(Thayer and Ramp, 1969). 

The second largest known chromium resource in 

the United States is in black-sand deposits in raised 

beaches along the southwestern coast of Oregon 

(Griggs, 1945). The black sand forms lenses and layers that range in thickness from a few inches to 42 

feet and in width from a few tens of feet to more 

than 1,000 feet, and are as much as a mile long. Depth 

of overburden is as much as 75 feet of sand, clay, and 

gravel. The chromite is associated with ilmenite, 

rutile, magnetite, and heavy silicates, all of which 

are hard to separate because of similar physical 

properties. Zircon in the deposits is of definite economic interest. The explored deposits that contain 5 

percent or more Cr20a approximate 2 million long 

tons. The concentrates would average about 40 percent Cr20a, with a Cr:Fe ratio of 1.6:1. 

RESOURCES 

IDENTIFIED RESOURCES 

A comparison of world production (fig. 13) and 

world resources of various categories (table 24) 

shows that chromite resources are ample for the 

foreseeable future. The only minable reserves in the 

Western Hemisphere, however, are in Brazil and 

Cuba. The figures for high-chromium chromite in the 

United States are postulated entirely on intensive 

exploration for extensions of known podiform ore 

bodies or new ore bodies in known districts under 

the stimulus of very high prices. Since 1918, mining 

of podiform deposits has been on a precarious basis; 

rarely have significant reserves been blocked out 

ahead of mining. The figures for high-iron presumed 

resources are based on an estimate of tonnages down 

to the level of the Stillwater River valley in the Stillwater Complex (Jackson, 1968) and in the Oregon 

black sands (Griggs, 1945) . The Canadian and Greenland deposits are lower in Cr20a content and higher 

in iron than most Stillwater chromite. Western Hemisphere reserves (excluding the U.S. national stockpile) and presumed resources exclusive of Greenland 

total about 25 million tons, possibly a 12- to 15-year 

supply for the countries in the region. 

Most of the Eastern Hemisphere resources is in 

the Bushveld and Great Dyke complexes in southern 

Africa, where labor is cheap and thin seams can be 

mined. The reserves of 1.05 billion tons for the Bushveld Complex are regarded as assured, although they 

have not actually been blocked. out (Cameron and 

Desborough, 1969). The estimate of Rhodesian reserves is based mainly on layers of minable thickness 
CHROMIUM 117 

TABLE 24.-Estimated world reserves and resourtJes of chromite ore by type and country 

(Thousands of long tons of shipping ores and concentrates. A, high-chromium ore. CnOa more than 46 percent, Cr:Fe more than 2:1. B, high-iron ore, Cn<>a 40-46 percent, Cr:Fe 1.5:1 to 2:1. B-, high-iron ore, Crl!Oa less than 40 percent. Cr:Fe 1.5:1 or less. c. high-aluminum ore, Al20a more than 20 percent, Al20a + Crl!Oa more than 60 percent; (C), amount not estimated. (S), layered or stratiform. (P), podshaped. (PI), placer, sub· 

ordinate. References cited are for subeeonomi;c resources in the United States and for reserves in the rest of the world; all other estimates are extrapolated by the author from reserve figures and the geology of the deposits and are intended only to indicate possible order of magnitude of 

potential ehromite resources] 

Hemisphere total -------

Total ------------------

See footnotes at ezad of table. 

Type of ore and deposit 

A;(P) 

B,B-; ( S, Pl) 

C;(P) 

A;(S) 

B;(S) 

C;(P) 

A;(P) 

B,B-;(S) 

A;(P) 

C;(P) 

B-;(S) 

A 

B 

Bc 

(other) 

--------------

A;(S) 

B;(S) 

A; (S, PI) 

B;(S) 

A;(P) 

B-;(S) 

C;(P) 

Identified resouree& 1 

Conditional 

Reserves 2 resources 1 

WESTERN HEMISPHERE 

United States 

None 8 350 

None7 5,000 

None 8 100 

Brazil 

2,500 3,000 

3,500 2,000 

100 150 

Canada 

100 

2,500 

Cuba 

100? 

250? 1,000? 

Greenland 

10,000 

Other 

200 

2,500 3,650 

3,500 

-------- 19,500 

350 1,200 

200 

6,350 24,550 

EASTERN HEMISPHERE 

Republic of South Africa 

50,000 50,000 

1,000,000 2,000,000 

Rhodesia 

500,0000 500,000 

50,000 50,000 

U.S.S.R. 

10,000 10,000 

1,000 2,000 

10,000 10,000 

Hypothetical ' and 

speculative 5 resources Reference and comments 

500 Modified from Thayer 

and Jackson (1957). 

2,000 

100 

l D. C. Hedlund, wri·tten 

5,000 commun., 1972. 

Estimate by author. 

D-avies (1958). 

5,000 

1,000 } Estimate by author 

10,000+ Ghisler and Windley (1967). 

200 Estimate by author. 

5,500 

} 17,000+ 

1,100 

200 

23,800+ 

Estimate by author. 

3,000,000+ Cameron and Desborough ( 1969). 

l Stanley (1961). 

500,000+ 

Worst (1960). 

l 25,000 Author's estimate. 
118 UNITED STATES MINERAL RESOURCES 

TABLE 24.-Estimated u:orld reserves and resources of chromite ore by type and country-Continued 

Hemisphere totals ------

Total ----------------- World total (rounded) _ 

Type of ore and deposit 

A,(C);(P) 

B;(S) 

A; (S,P( ?) ) 

B;(S) 

A;(P) 

C;(P) 

A;(S?) 

B; (S?) 

A;(P) 

A;(P) 

C;(P) 

A,(C); (P) 

B;(S) 

A 

B 

BC 

l 

Identified resources 1 

Hypothetical ' and 

Conditional speculative 5 resources Referenee and comments Reserves 2 

Turkey 

5,000 

Finland 

10,000 

India 

5,000 

2,000 

resources 3 

5,000 

5,000 

4,000 

2,000 

Philippine Republic 

700 500 

4,000 2,000 

Malagasy Republic 

4,000 

1,000 

Iran 

1,500 

Greece 

50 

50 

Other 

2,000 

577,250 

1,064,000 

1,000 

14,050 

1,656,300 

1,663,000 

3,000 

2,000 

1,000 

l 100 

2,000 

574,550 

2,060,000 

2,000 

12,050 

2,648,600 

2,675,000 

5,000 

10,000 

l 20,000 

1,000 

5,000 

l 7,500 

5,000 

250 

2,500 

} 8,581,250 

3,581,250 

3,600,000+ 

U J3. Bur. Mines 

(1968, v. 66, no. 4, 

p. 6.) 

Kujanpaa (1971, p. 

92). 

Ratio of A: B estimated by author. 

Balasundaram ( 1972, 

p. 47). 

Philippine Mining 

Yearbook ( 1971a, 

p. 26). 

Philippine Mining 

Yearbook (1971b, 

p. 54). 

U.S. Bur. Mines (1966, v. 62, no. 6, p. 9). 

U.S. Bur. Mines (1968, v. 65, no. 2, p. 4-6). 

Estimate by author. 

Estimate by author. 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may not be profitably recoverable with exist:ng technology and economic conditions. 2 Reserves: Identified deposits from which minerals can be extracted profitably with existing technology and under present economic conditions. 3 Conditional resources: Specific, identified mineral deposits whose contained minerals are not profitably recoverable with existing technology and 

economic conditions. 

' Hypothetical resources: Undiscovered mineral deposits, whether of recoverable or subeconomic grade, that are geologieal!y predictable as existing in known districts. 5 Speculative resources: Undiscovered minerd deposits, whether of recoverable or subeconomic gr:tda, that may exist in unknown districts or in 

unconventional form. 8 Excludes chromite ores or equivalent in national stockpile: Metallurgical ore and ore equivalent. 4,760,000 long tons. Refractory (high-aluminum) ore, 1,050,000 long tons. Inventory of stockpile materials as of Mar. 31, 1972, U.S. GenPral Services Administration. 7 Excludes chemical chromite in national stockpile, plus coneentrates stockpiled at Nye, Mont., 1,320,000 long tons total. 
C:HROMIUM 119 

in the Great Dyke which have been projected to 500 

feet below the surface but which are known to go 

much deeper (Stanley, 1961). Eastern Hemisphere 

reserves outside southern Africa are estimated at 

55-60 million tons, and conditional resources at 

about 50 million tons. Even excluding southern 

Africa, reserves and presumed resources of the Eastern Hemisphere appear to be about triple those of 

the Western Hemisphere. However, because most of 

these resources are in podiform or highly deformed 

stratiform deposits, the uncertainties of supply and 

costs of production can be expected to mount rapidly 

as identified resources are depleted. 

HYPOTHETICAL AND SPECULATIVE RESOURCES 

The probability of finding major new chromite districts is believed to be shrinking rapidly, except possibly in central Asia, where little information is 

available. In the last 20 years, major high-chromium 

rodiform deposits have been developed in two regions 

in Iran. The stratiform deposit at Kemi, Finland, 

with reserves of approximately 33 million tons of 

crude milling-grade high-iron ore, was discovered in 

1959 (Kahma and others, 1962) ; it represents a 

major new district that was discovered under glacial 

drift. The low-grade but potentially very important 

chromite deposits at Fiskenaesset in southwestern 

Greenland were discovered in 1964 during regional 

geologic mapping (Ghisler and Windley, 1967). The 

figures for hypothetical and speculative resource'S are 

predicated more on discoveries in known districts 

than on new districts. The figures for India and Malagasy assume that large segments of disrupted stratiform deposits will be found in laterite-covered areas 

or at depth. 

The universal presence of chromite as an accessory mineral in peridotite suggests a possibility of 

recovering it by large-scale mining of very low-grade 

rocks, as copper and molybdenum are mined from 

porphyry-type deposits. The analogy is not apt, however, for several reasons. In rock containing less than 

about 10 percent Cr203 or 20 percent chromite, because the chromite is fine grained and relatively soft, 

it slimes badly during the grinding necessary to free 

it from the silicates. Furthermore, flotation processes 

that work so well with sulfide ores present difficulties 

for chromite, an oxide (Batty and others, 1947; Sullivan and Stickney, 1960). Concentrates from lowgrade disseminated ores normally are considerably 

lower in chromium and richer in iron than highgrade massive ores (Jackson, 1968, p. 1510). 

Extensive deposits of iron-rich laterite blanket 

many peridotites in tropical and subtropical regions 

of the world. The laterite contains approximately 

40-50 percent iron, 0.5-3 percent chromium, 0.2-2.5 

percent combined nickel and cobalt, some aluminum, 

and 10-15 percent combined water (Gross, 1970a, 

p. 27). Only relatively small amounts of laterite are 

used as iron ore, although nickel is recovered from 

laterite on a large scale by hydrometallurgical processes in New Caledonia and Cuba. Recovery of all the 

metals presents difficult unsolved metallurgical problems. The laterites of Cuba alone have been estimated 

at 3 billion tons; at an average of 2 percent Cr203 

(1.4 percent Cr), they would contain 42,000,000 tons 

of chromium metal (Gross, 1970b, p. 250). Estimates 

of the potential chromium resources in laterite are 

not included in table 24 because of the low tenor of 

chromium, scarcity of essential data on tonnages, 

and the lack of technology for recovery. 

EXPLORATION FOR CHROMITE DEPOSITS 

Restriction of chromite deposits to the lower parts 

of very distinctive layered complexes and to peridotite of the alpine type (Thayer, 1971) sharply limits 

areas for prospecting. By virtue of its resistance to 

weathering, massive chromite, crops out or forms 

bouldery float and black sand that can be traced 

readily. In stratiform complexes the layered structure can be used as a guide to concealed deposits and 

faulted blocks or segments of ore. 

Prospecting for concealed podiform deposits generally has been disappointing. In large peridotitegabbro complexes, chromite deposits are concentrated within the peridotite near the gabbro, and 

thus the peridotite-gabbro contact can be used as a 

guide to the most promising ground (Flint and 

others, 1948; Rossman and others, 1959). Under almost ideal conditions of low relief in central Cuba, 

gravimeter surveys located some concealed deposits 

(Hammer and others, 1945), but in most areas high 

relief precludes use of this method. Magnetic surveys can outline areas of serpentine very accurately, 

but because most chromite is less magnetic than the 

host rocks, such surveys do not indicate concealed 

deposits. The high-iron stratiform deposits at Kemi, 

Finland, however, were traced under glacial till by a 

combination of magnetic and gravimetric surveys 

(Kahma and others, 1962). Seismic methods are not 

effective because most ore bodies are too small to 

detect and the host rock commonly is highly fractured and sheared. Known geochemical methods are 

not applicable because of presence of accessory 

chromite in all peridotite. With the exceptions noted, 

no substitute for detailed geological mapping and 

traditional means of underground exploration has 

been devised for finding concealed podiform chromite 

deposits. 
120 UNITED STATES MINERAL RESOURCES 

PROBLEMS FOR RESEARCH 

The fundamental problem of chromium supply for 

the United States is lack of domestic high-grade deposits and scarcity even of low-grade resources. 

Endeavors to expand the domestic resource base 

substantially would, it is believed, be very costly 

(Brantley, 1970, p. 260). Without access to South 

African, Rhodesian, and Russian. sources, we would 

have to be prepared to depend largely on low-grade 

high-iron chromite ores from the Stillwater Complex, from Canada, and from Greenland. This would 

entail major shifts and inefficiencies in metallurgy 

and for most other uses. 

Exploration for concealed podiform chromite deposits in the United States faces major problems and 

limitations. The first problem is the inability of 

known geophysical and geochemical methods to point 

to deposits concealed under very thin cover in areas 

of even moderate relief. The limitations are twofold: 

most podiform deposits are too small to be minable 

even at moderate depths, and in aggregate the few 

postulated relatively large deposits could only mitigate the national supply problem temporarily and at 

very high cost. 

Research on means to recover more chromium 

from scrap and from low-grade ores appears more 

promising than geological research on domestic resources. Stainless-steel scrap, other than mill scrap, 

in 1968 provided the equivalent of 51,000 tons of 

chromium, or about 12 percent as much as was imported in ore (Brantley, 1970, p. 252). Recovery of 

chromium from scrap presumably will increase with 

development of processes to dispose of solid waste in 

general. 

Development of processes to smelt the higher 

grades of Stillwater crude ore directly to FeCr alloy 

with local energy would avoid losses of 15--20 percent 

of contained Cr203 in milling (Thayer, 1962, p. 12) 

and could greatly reduce transportation costs to 

eastern consuming centers. Research aimed at adapting a process for direct smelting of high-iron chromite to stainless steel, announced in 1966 (Brantley, 

1970, p. 261), to treat crude Stillwater ores, would 

seem to be indicated. Though such a process cannot 

compete with recovery of chromium from African 

ores at present prices, increases in wages of African 

miners to equitable scales and increased production 

of FeCr in southern Africa for export could change 

the situation drastically. Investigations of the Greenland ores should consider the likelihood of separating 

chromite readily from anorthosite by sink-float 

methods, and recovery of the contained 0.3 percent 

of V205 (Ghisler and Windley, 1967). 

REFERENCES CITED 

Balasundaram, M. S., 1972, A review of the reserves and 

demand pattern of iron, manganese and chromite ores 

in India: Eastern Metals Review, Ann. No., v. 25, p. 39-

49. 

Batty, J. V., Mitchell, T. F., Havens, R., and Wells, R. R., 

194 7, Beneficiation of chromite ores from the western 

United s.tates: U.S. Bur. Mines, Rept. Inv. R. I. 4079, 

26p. 

Berbert, C. 0., 1973, Geologia geral dos complexos basicos 

e ultra-basicos de Goias: 24th Congresso Brasileiro de 

Geologia, Soc. Brasileira de Geologia (in press). 

Brantley, F. E., 1970, Chromium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 247-262. 

Cameron, E. N., and Desborough, G. A., 1969, Occurrence and 

characteristics of chromite deposits--eastern Bushveld 

Complex, in Wilson, H.D.B., ed., Magmatic ore deposits, 

a symposium: Econ. Geol. Mon. 4, p. 23-40. 

Davies, J. F., 1958, Chromite deposits of southeastern Manitoba: Canadian Mining Jour., v. 79, p. 112-114. 

Flint, D. E., Guild, P. W., and de Albear, J. F., 1948, 

Geology and chromite deposits of the Camagiiey District, Gamagiiey, Province, Cuba: U.S. Geol. Survey 

Bull. 954-B, p. 39-63. 

Ghisler, M., and Windley, B. F., 1967, The chromite deposits 

of the Fiskenaesset region, West Greenland: Geol. Survey Greenland, Rept. 12, 39 p. 

Griggs, A. B., 1945, Ghromite-bearing sands of the southern 

part of the coast of Oregon: U.S. Geol. Survey Bull. 

945-E, p. 113-150. 

Gross, G. A., 1970a, Nature and occurrence of iron ore deposits, in Survey of World iron ore resources, pt. 2: 

New York, United Nations, p. 13-31. 

Gross, G. A., 1970b, Iron ore deposits of Canada and the 

West Indies, in Survey of World iron ore resources, Pt. 

3: New York, United Nations, p. 237-252. 

Hammer, S., Nettleton, L. L., and Hastings, W. K., 1945, 

Gravimeter prospecting for chromite in Cuba: Geophysics, v. 10, p. 34-49. 

Jackson, E. D., 1961, Primary textures and mineral associations in the ultramafic zone of the Stillwater complex, 

Montana: U.S. Geol. Survey Prof. Paper 358, 106 p. 

-- 1963, Chromium, in Mineral and water resources of 

Montana: U.S. Cong., 88th, 1st sess., Senate Comm. Interior and Insular Affairs, p. 57-60. Also reprinted as 

Montana ~ur. Mines and Geology Spec. Pub. 28. 

-- 1968, The chromite deposits of the Stillwater Complex, Montana, in Ore deposits of the United States, 

1933-1697 (Graton-Sales Volume), v. 2: New York, Am. 

Inst. Mining, Metall. and Petroleum Engineers, p. 1495-

1510. 

Kahma, A., Siikarla, T., Veltheim, V., Vassjoki, 0., and 

Heikkinen, A., 1962, On the prospecting and geology of 

the Kemi chromite deposit, Finland: Finlande Comm. 

Geol. Bull. 194, 91 p. 

Kujanpaa, J., 1971, Maliesintyman geologia (Geology of 

the Kemi ore deposit) : Vuorimieslehti-Bergshantering, 

no. 2, 1971, p. 92-93 [translation in English by Outokumpu Oy]. 

Materials Advisory Board, 1959, Report of the Committee 

on Refractory Metals: Nat. Acad. Sci.-Nat. Research 

Council, Rept. MAB-154-M (1), v. 2, chap. 4, p. 23-47. 

Mining Journal, 1972, Brazilian chromite development: Mining Jour. (London), v. 278, p. 93. 
CHROMIUM 121 

Pearre, N. C., and Heyl, A. V., Jr., 1960, Chromite and 

other mineral deposits in serpentine rocks of the Piedmont Upland, Maryland, Pennsylvania, and Delaware: 

U.S. Geol. Survey Bull. 1082-K, p, 707-833. 

Philippine Mining Yearbook Company, 1971a, Acoje Mining 

Company: Philippine Mining Yearbook, v. 13, no. 17, p. 

26, 34. 

--- 197lb, Benguet Consolidated, Inc.: Philippine Mining Yearbook, v. 13, no. 17, p. 54, 56. 

Price, Paul M., 1963, Mining methods and costs Mouat Mine, 

American· Chrome Company, Stillwater County, Montana: U.S. Bur. Mines Inf. Circ. 8204, 58 p. 

Rossman, D. L., Fernandez, N. S., Fontanos, C. A., and 

Zepeda, Z. C., 1959, Chromite deposits on Insular Chromite Reservation Number One, Zambales_, Phillippines: 

Philippine Bur. Mines, Spec. Proj. Ser., Pub. 19, Chromite, 12 p. 

Stanley, R., 1961, Chromium in Southern Rhodesia: Southern Rhodesia Mines Dept., 21 p. 

Stoll, W. C., 1958, Geology and petrology of the Masinloc 

chromite deposit, Zambales, Luzon, Philippine Islands: 

Geol. Soc. America Bull., v. 69, p. 419-448. 

Sullivan, G. V., and Stickney, W. A., 1960, Flotation of 

Pacific Northwest chromite ores: U.S. Bur. Mines Rept. 

Inv. R. I. 5646, 14 p. 

Thayer, T. P., 1960, Some critical differences between Alpine-type and stratiform peridotite-gabbro complexes: 

lnternat. Geol. Cong., 21st, Copenhagen 1960, Rept. XIII, 

p. 247-259. 

--- 1962, Mineralogy and geology, World resources, in 

Materials survey-Chromium: U.S. Business and Defense Services Adm., chaps. 2 and 3, p. 3-25. 

--- 1964, Principal features and origin of podiform 

chromite deposits, and some observations on the Guleman-Soridag district, Turkey: Econ. Geology, v. 59, 

p. 1497-1524. 

--- 1966, Chromite, in Mineral and water resources of 

California: U.S. Cong., 89th, 2d sess., Senate Comm. 

Interior and Insular Affairs, pt. 1, p. 120-126. 

--- 1969, Gravity differentiation and magmatic re-emplacement of podiform chromite deposits, in Wilson, H. 

D. B., ed., Magmatic ore deposits, a symposium: Econ. 

Geology Mon. 4, p. 132-146. 

--- 1971, Authigenic, polygenic, and allogenic ultramafic 

and gabbroic rocks as hosts for magmatic ore deposits: 

Geol. Soc. Australia Spec. Pub. 3, p. 239-251. 

Thayer, T. P., and Jackson, E .D., 1957, Chromite reserves 

of the United States estimated: Dept. Interior Inf. 

Service Press Release, July 5, 1957, 3 p. 

Thayer, T. P., and Miller, M. H., 1962, Ghromite in the 

United States: U.S. Geol. Survey Mineral Inv. Resources 

Map MR-26 (with text). 

Thayer, T. P., and Ramp, Len, 1969, Chromite, in Mineral 

and water resources of Oregon: U.S. Cong., 90th, 2d 

sess., Senate Comm. Interior and Insular Affairs, p. 

108-116. 

U.S. Bureau of Mines, 1942-70, Chromium, in Minerals Yearbook, 1942-70, published annually. 

U.S. Bureau of Mines, 1966-1971, Chromium, in Mineral 

trade notes, 1966-71. 

White, R. W., Motta, J., and de Araujo, V. A., 1971, Platiniferous chromitite in the tocantins complex, Niquelandia, 

Goias, Brazil, in Geological Survey research 1971: U.S. 

Geol. Survey Prof. Paper 750-D, p. D26-D33. 

Worst, D. G., 1960, The great dyke of Southern Rhodesia: 

Southern Rhodesia Geol. Survey Bull., no. 4 7, 234 p. 

UNITED STATES MINERAL RESOURCES 

CLAYS 

By JoHN W. HosTERMAN 

CONTENTS 

Page 

Abstract of conclusions --------------------------- 123 

Introduction ------------------------------------- 123 

Kaolin ------------------------------------------ 125 

Ball clay ---------------------------------------- 126 

Fire clay --------------------------------------- 126 

Bentonite and fuller's earth ----------------------- 127 

Miscellaneous clay ------------------------------- 128 

Summary of resources --------------------------- 129 

Environmental considerations --------------------- 129 

Problems for research ---------------------------- 129 

Selected bibliography ____ _ _ _ _ _ _ __ _ _ __ __ __ __ __ ____ 130 

FIGURE 

14. Production of miscellaneous clay, fire clay, kaolin, bentonite, fuller's earth, and ball clay in 

Page 

the United S.tates, 1920-70 ----------------- 125 

TABLE 

Page 

25. Summary of clay resources of the United States 129 

ABSTRACT OF CONCLUSIO~S 

Clays are naturally occurring rocks composed of fine particles that are principally hydrous aluminum (or magnesium) 

silicates. They occur as deposits that are divided for commercial purposes into kaolin, ball clay, fire clay, bentonite, 

fuller's earth, and miscellaneous clay. Resources of clay deposits similar to those used currently are extremely large, 

except for those of high-grade ball clay and high-grade 

colloidal bentonite. The geologic profession could be of better service to the city, county, and State planners, the clay 

producers, and the consumers of a wide variety of clay 

products if geologists doing areal geologic mapping, particularly near metropolitan areas, were more aware of the 

economic potential of clay occurrences in the area being 

mapped. Attaining such awareness may require the making 

available the necessary equipment and procedures to evaluate 

the economic potential of the clay occurrence. 

INTRODUCTION 

Clay was first used in the United States by the 

Indians for making pottery. It has been used extensively as the building material for adobe, a sundried mixture of clayey loam, straw, and water since 

the time of the early Spanish settlers in the southwestern part of the country. Clay was first used in 

this country in 1585 to make building brick at the 

Raleigh settlement on Roanoke Island, N.C. Dr. 

Danial Coxe, an early governor of West New Jersey, 

was probably the first to make pottery in the Colonies, when he built a plant at Burlington, N.J., 

about 1685. White clay is reported to have been first 

mined by the Indians in western North Carolina ; 

and was exported to England in the early part of 

the 17th century. 

Clays are naturally occurring rocks, both unconsolidated and consolidated, composed of very fine 

particles of clay minerals that principally are layered hydrous aluminum (or magnesium) silicates 

but may contain varying amounts of iron, potassium, 

sodium, and other ions. All deposits of clay contain 

other minerals, and these impurities are rare in 

some deposits but abundant in others. The most 

common other minerals are quartz, mica, feldspar, 

iron oxides, and carbonates. Titanium-bearing minerals and gypsum are abundant in some deposits; 

organic matter, such as carbon or kerogen, is abundant in others. 

Most deposits of clay have as their major component, one of the following clay minerals: Kaolinite, 

halloysite, montmorillonite, palygorskite, and illite. 

Some clay deposits may contain one or more of these 

clay minerals as a minor constituent. The U.S. 

Bureau of Mines has classified clay deposits into 

U.S. GEOL. SURVEY PROF. PAPER 820 

123 
124 UNITED STATES MINERAL RESOURCES 

six categories both on the product rather than on the 

raw material. They are kaolin, ball clay, fire clay, 

bentonite, fuller's earth, and miscellaneous clay. 

Major difficulties are met in statistical records because different types of clay products are made from 

the same clay minerals. Kaolin, ball clay, and fire 

clay are composed chiefly of kaolinite, and all have 

the same properties, especially when fired. Bentonite 

consists primarily of montmorillonite. Fuller's earth 

may be composed of montmorillonite or palygorskite 

or both. Miscellaneous clay is composed of illite as 

the dominant mineral, particularly in the shales, but 

some deposits contain kaolinite and montmorillonite 

as the major constituents. 

The structural formula of kaolinite is (OH) s 

Si4Al401o, and its theoretical composition is 39.50 

percent Al20a, 46.54 percent Si02, and 13.96 percent H20. Other minerals of the kaolinite group 

are metahalloysite and its hydrated form halloysite. 

Metahalloysite has the same formula and composition as kaolinite, but halloysite contains two more 

molecules of water. Halloysite is more common than 

metahalloysite, but inasmuch as dehydration takes 

place at room temperature, halloysite converts irreversibly to metahalloysite which may be indistinguishable from kaolinite. Kaolinte is a potential 

source of aluminum because it contains as much as 

39 percent alumina. Furthermore, some kaolin deposits contain gibbsite (AI (OH) 3), and some fireclay deposits contain diaspore (AIO (OH)) or boehmite (AIO (OH)), which increases the alumina content of these deposits to between 40 and 70 percent. 

(See "Aluminum.") 

Kaolinite and halloysite are formed by hydrothermal, katamorphic (weathering in place), and 

sedimentary processes, either alone or in combination. Hydrothermal clay is formed by ascending hot 

solutions dissolving the country rock and precip~tating a mineral of the kaolinite group. These clays 

are sometimes associated with sulfide deposits. Residual clay is formed in place by the action of 

chemical weathering, a katamorphic process that 

alters minerals such as feldspars and muscovites to 

kaolinite or halloysite. In general, the residual clays 

are well crystallized and coarse grained. Deposits 

of unconsolidated sedimentary kaolinite are formed 

by the weathered debris being eroded, transported 

by streams, and deposited in fresh- or brackishwater lakes and lagoons. The kaolin deposits contain large flakes of well-~rystallized kaolinite, and 

the ball-clay deposits contain very fine flakes of 

poorly crystallized kaolinite and impurities of illite 

and (or) montmorillonite. The size and crystallinity 

of the kaolinite depend upon the source material, 

amount of breakup during transportation, and to 

some extent the amount of diagenesis or recrystallization after deposition. Deposits of consolidated 

sedimentary kaolinite are formed by the weathered 

debris being eroded, transported by streams, and 

deposited in swamps. After deposition, leaching by 

organic and carbonic acids removes iron, potassium, 

and other ions so that silica and alumina are concentrated, and then postdepositional diagenesis 

cause~ recrystallization of the kaolinite. Kaolinite 

formed in this manner occurs in deposits of fire 

clay or underclay which contain four types of clay 

differing primarily in the degree of crystallinity and 

the amount of impurities. The four types are plastic, 

semiflint, flint clay, and nodular flint. Plastic clay 

is composed of poorly crystallized kaolinite and contains illite as the major impurity; flint clay is composed of well-crystallized kaolinite and contains no 

impurities. Nodular flint clay is composed of wellcrystallized kaolinite and contains diaspore or boehmite, because advanced leaching has removed some 

silica and has concentrated alumina. 

Bentonite, by geologic definition, is a product of 

the devitrification and alteration of volcanic ash or 

tuff. The chemical alteration of the fine-grained ash 

that accumulated in a marine environment probably 

began while the ash was settling through the sea 

water. Most bentonites consist chiefly of montmorillonite (OH) 4Sis (Ala.a4Mgo.6s) 02o; however, some 

montmorillonite clays not formed from ash or tuff 

are still classified as bentonite under commercial 

usage of the term. 

Fuller's earth produced in the Attapulgus, Ga.-

Quincy, Fla. district is predominantly palygorskite 

(attapulgite), (OH2)4Mg5SisO~o·4H20; most of the 

fuller's earth produced from deposits elsewhere in 

the United States is montmorillonitic clay, and several of these deposits are actually bentonitic clays. 

The origin of palygorskite is speculative, but the 

general agreement is that it formed in sea water 

that had a high content of magnesium and silica. 

Evidence from samples taken from the bottom of 

the Atlantic Ocean indicates that palygorskite can 

form as a chemical precipitate from the reaction of 

hydrothermal solutions with sea water. 

Illite is the dominant mineral in the miscellaneous 

clay, especially in the shales, and its approximate 

formula is (OH)4K2(Si6·Al2)Al402o· Illite can be 

formed in many ways, but as the major constituent 

of shales, it is the result of weathered debris' being 

eroded, transported by streams, deposited in a nearshore marine environment, and subjected to diagenesis and lithification. 

Materials such as talc, silica, and calcium car-
(/) 

z 

0 

IIa: 

0 

J: 

(/) 

u.. 

0 

(/) 

0 

z 

<( 

(/) 

:> 

0 

J: 

1-

CLAYS 125 

bonate can be substituted for many kaolin end 

products; however, the comparatively low cost of 

clays gives them a decided advantage over most 

substitutes. Many construction products and raw 

materials can be substituted very effectively for 

brick, tile, and lightweight aggregate. A few of the 

major ones are concrete, stone, glass, metal, plastics, expanded slag, sintered fly ash, vinyl asbestos, 

and cork. 

In 1969, the United States produced 58,694,000 

short tons of clay, exported 1,574,000 short tons, 

and imported 82,000 short tons (Wells, 1971, p. 

287). The only clays imported in any large quantity 

were kaolin and ball clay, but all six types of clay 

were exported. Of the total clay production in 1969, 

miscellaneous clay accounted for 72 percent; fire 

clay, 12 percent; kaolin, 8 percent; bentonite, 5 percent; fuller's earth, 2 percent; and ball clay, 1 percent (fig. 14). 

In the United States, clay resources consisting of 

material similar to that used currently are large, 

but the clay deposits included in such resources may 

not be ideally located for potential markets. Information on clay resources in the rest of the world is 

100,000, I I I I I I I I I' I I I I I I I I I' I I I I I I I I I' I I I I I I I '_I_'~:~'-'~~ I~ 

; """''-, - ~,. ..... , 

~ Miscellaneous clay! ~ 

10,000~ ~· 

1920 1930 1940 1950 1960 1970 

FIGURE 14.-Production of miscellaneous clay, fire clay, kaolin, bentonite, fuller's earth, and ball clay in the United 

States, 1920-70. 

not complete, but undoubtedly these resources are 

enormous. 

KAOLIN 

The term "china clay" is somewhat synonymous 

with kaolin, particularly for the raw material used 

for ceramic products other than refractories. Kaolin 

is white and easily dispersible and can be fired at 

high temperatures without warping or changing 

color. It is used primarily for coating and filling 

paper, but other major uses are as fillers for products other than paper and refractories. Minor uses 

include pottery, dinnerware, stoneware, and white 

cement. Both kaolinite and halloysite are used in 

the petroleum industry as petroleum-cracking catalysts. Most kaolin is white, or nearly so, but shades 

of red, yellow, and brown are common. Most of it 

is plastic when wet, but some is hard and has flinty 

characteristics of homogeneity and conchoidal fracture. Although many kaolins are pure enough to be 

used in their natural state for many purposes, most 

kaolins are refined or are beneficiated by washing 

or by several other processes. 

Five tons of kaolin was mined near Franklin, 

N.C., and shipped to Josiah Wedgewood in England 

in 1767-68. Since that time, the demand for kaolin 

has increased so greatly that in 1970 production 

reached almost 5 million short tons valued at slightly 

more than $100 million. Georgia and South Carolina 

are the major producers of kaolin, and small quantities are produced in Alabama, California, Florida, 

Idaho, North Carolina, Pennsylvania, Texas, and 

Utah. Kaolin production has increased at a nearly 

constant rate during the past 50 years (fig. 14). 

The depression in the 1930's and the recessions since 

then have affected kaolin production less than any 

of the other types of clay. The average value per ton 

has increased from $5.75 in 1933 to $21.91 in 1968. 

This undoubtedly indicates that increasing demands 

for high-quality clay used for paper filler and paper 

coater have caused production costs to rise steadily. 

Reserves of kaolin in the Cretaceous and Tertiary 

rocks of the coastal plain of Georgia, Alabama, and 

Mississippi are estimated to be more than 300 million tons. Other deposits estimated to contain 1 

million tons of kaolin are scattered throughout the 

Appalachian region. The Nation's resources of kaolin, which contain a much higher percentage of impurities than the reserves, are estimated to be at 

least 5 billion tons. This includes the potentially 

recoverable kaolinite and halloysite found in saprolite in North Carolina, California, Washington, and 

Idaho, and the hydrothermal halloysite in Utah and 

Nevada. 
126 UNITED STATES MINERAL RESOURCES 

Byproducts-sand for use in making glass and 

muscovite for use in insulation and other products-are recovered from kaolin deposits in Latah 

County, Idaho, and muscovite is recovered near 

Spruce Pine, N.C., Sand for the glass industry is 

recovered from the kaolin deposit in Orange County, 

Calif. Bauxite is a minor byproduct of some of the 

kaolin deposits in the Coastal Plain of Georgia and 

Arkansas. 

BALL CLAY 

The term "ball clay" originates from an early 

English mining practice of rolling the highly plastic 

clay into balls weighing 30-50 pounds. The impurities found in ball clay are illite, montmorillonite, 

and carbonaceous matter. Quartz, as particles of 

silt and sand size, and iron oxide minerals are virtually absent from the best grade ball clays·. The 

color of most ball clay is nearly white, but some 

colors range from pink to brown and through shades 

of gray to black. The color after firing is almost 

white. Ball clays require between 40 and 65 percent 

water of plasticity to become workable; plasticity, 

toughness, high dry-green strength, and adhesion 

are the outstanding characteristics of ball clay. 

When fired, bali clay becomes dense and vitreous, 

and its deformation point is between 1670° and 

1765°C. Whiteware, floor and wall tile, and refractories account for most uses of ball clay, and building brick and paint filler account for minor uses. 

Ball clay was first mined in the United States in 

1860 near Paris, Tenn., but it was used only by the 

local pottery industry. Steady production of ball 

clay began in 1894 when Mr. I. Mandie shipped clay 

from western Tennessee to East Liverpool, Ohio. 

The production of ball clay in 1969 was 682,000 

short tons valued at $9.7 million. Tennessee, Kentucky, and Mississippi are the major producers, but 

very small quantities are produced in Maryland, 

Texas, and California. Production of ball clay has 

been increasing during the past 50 years (fig. 14) ; 

however, during the depression years of 1921 and 

1932-34, production was low, and the amount of 

ball clay produced yearly is lower now than any 

other clay commodity. The average value per ton 

has increased from $6.21 in 1933 to $14.25 in 1969. 

Lenses of ball clay are known to occur in the following sedimentary units : Wilcox and Claiborne 

Formations of Eocene age in Kentucky, Ripley 

Formation of Cretaceous age and Wilcox and Claiborne Groups of Eocene age in Tennessee, Fearn 

Springs Sand Member of the Nanafalia Formation 

and Claiborne Group of Eocene age in Mississippi, 

Wilcox Formation of Eocene age in Texas, and 

Potomac Group of Cretaceous age in Maryland. All 

these units are located in the Coastal Plain and 

Mississippi Embayment, and most of the best grade 

ball clays are shipped from the Mississippi Embayment area. 

Reserves of ball clay containing the lower percentages of quartz sand and silt are estimated to be 

about 4 million tons in Kentucky, Tennessee, and 

Mississippi. Resources of ball clay are estimated to 

be more than 50 million tons, but this total includes 

ball clay containing a percentage of sand and silt 

higher than that in the deposits now being mined. 

FIRE CLAY 

The term "fire clays" originated from their refractory property, the ability to be fired at high 

temperatures without warping. On the basis of their 

physical appearance, characteristics, and properties, 

fire clays can be divided into four categories : plastic 

clay, semiflint clay, flint clay, and nodular flint clay. 

The associated minerals are mainly quartz, siderite, 

feldspar, and rarely anatase. The color of fire clay, 

controlled primarily by the amount of carbonaceous 

matter, is mainly some shade of gray, but brown 

and black are common. The relative plasticity and 

hardness give a good indication of the refractoriness 

of each type. The flint and nodular clays have no 

plasticity and are the hardest and most refractory, 

deforming when fired at temperatures between 

1,745° and 1,805°C. The plastic clay is the most 

plastic and the softest, and it deforms when fired at 

1,620° to 1,670°C. Semiflint clay is intermediate in 

plasticity and hardness, and it deforms when fired 

at 1,670° to 1,745°C. The fired colors range from 

red to buff and gray. Fire clays are used in making 

refactories, structural brick, sewer pipe, pottery, 

stoneware, floor and wall tile, and cement and as 

fillers. 

The first production of fire clay in the United 

States was in New Jersey where fire clay was mined 

at Woodbridge in 1816 for shipment to Boston, 

Mass., and the first plant for making refractory 

products was built in 1825 at Salamander, N.J. 

Until1943, fire clay was the leading clay commodity 

(fig. 14), but since then, it has been second to the 

clays of the miscellaneous group. The demand for 

fire clay increased to a peak production of 11.8 

million short tons in 1957, and since then production has steadily declined to 7.2 million short tons 

in 1969. This decline is due to the major change by 

the steel industry from open-hearth furnaces to 

basic oxygen furnaces. The production of fire clay 
CLAYS 127 

will probably continue to decrease in the future. The 

major fire-clay-producing States are Alabama, California, Colorado, Illinois, Kentucky, Missouri, Ohio, 

Pennsylvania, Texas, and West Virginia. The minor 

producers are Arizona, Arkansas, Idaho, Indiana, 

Kansas, Maryland, Minnesota, Mississippi, New 

Jersey, New Mexico, Oklahoma, Oregon, Utah, 

and Washington. The average value per ton was a 

low of $2.35 in 1942 and a high of $5.29 in 1967. 

All deposits of fire clay are found in sedimentary 

rocks, and many of them are associated with coal 

beds. Much of the fire clay produced east of the 

Mississippi River is from the Lower Pennsylvanian 

sedimentary rocks; these clays are referred to as 

underclays because they almost invariably occur 

just below coal beds. Some kaolin called fire clay is 

mined from the Raritan Formation of Cretaceous 

age in New Jersey, from the Nanafalia Formation 

of Eocene age in Georgia and Alabama. West of 

the Mississippi River, fire clay occurs in beds and 

lenses of the Dakota Sandstone of Cretaceous age 

in at least six States. In Missouri, the clay is in the 

Cheltenham Clay of Wanless ( 1939) of Pennsylvanian age. In the Pacific Coast States and Idaho, 

fire clay occurs in Eocene sediments, the lone Formation in California being the most productive. 

The reserves of fire clay suitable for :use in lowand moderate-heat-duty refractories ar~ estimated 

at 1 billion tons, and for high-heat-duty refractories, 

flint and nodular flint clays, the reserves are estimated at about 500 million tons. Resources of fire 

clay are estimated at approximately 7 billion tons. 

If the future demands for fire clay decrease, the 

present production trend of fire clay will continue 

as shown (fig. 14); however, most of the decline 

will be in the demand for high-heat-duty refractory 

products, and the demand for low- and moderateheat-duty refractory products will remain constant 

and may increase in the future as the production of 

metals expands. 

In some areas where fire clay occurs as underclay, 

there is economic waste in the mining methods. 

Before World War II, almost all fire clay was mined 

by underground methods, and the coal was left because it made a better, safer roof than shale. Localally, the coal was mined from areas in the mine 

where the clay had been removed previously. Underground mining has become very costly, and for the 

past 10 years, fire clay has been almost exclusively 

strip mined. Now, the clay companies rarely mine 

any potentially economical coal as a coproduct, and 

the coal is wastefully placed on the spoil bank with 

the overburden by means of draglines, power shovels, and bulldozers. 

BENTONITE AND FULLER'S EARTH 

Bentonite and fuller's earth are clay commodities 

that are related either by mineral composition or 

by use. The term "fuller's earth" comes from its 

former use which was for cleaning or fulling wool 

by fullers. Both bentonite and fuller's earth have a 

wide variety of physical properties that make them 

suitable for many different uses and applications. 

Both are used in drilling muds, bentonite principally 

where fresh water is present in the rocks penetrated 

and palygorskite-type fuller's earth where salt 

water is present. The "sodium," "high swelli~g," or 

"Wyoming" -type bentonite has exchangeable sodium 

ions and when wetted with water will increase in 

volume 15-20 times. The "calcium," "low-swelling," 

or "southern" bentonite will not increase in volume 

when wetted with water. The swelling bentonite has 

excellent dry properties and is used for bonding 

foundry sand and iron-ore pellets. Most of the nonswelling bentonite has very good green-bond properties and is used in foundries employing the greenmold technique. Bentonite is also used in petroleum 

refining as a catalyst, and fuller's earth is sold for 

clarifying and processing mineral and vegetable 

oils. Some bentonite or fuller's earth is treated or 

"activated" with acid to improve its effectiveness 

in processing oil, and the activated clay is usually 

referred to as bleaching clay. A fuller's earth product termed "absorbent granules" is used for many 

purposes, such as an agent for absorbing oil, grease, 

and chemicals from floors, as an animal litter, and 

as a soil conditioner. Both fuller's earth and bentonite are used as carriers for insecticides and 

fungicides, and minor quantities of bentonite are 

sold for many other uses, such as sealing irrigation 

canals and reservoirs. 

The first shipment of bentonite for commercial 

purposes was made in 1888 from Rock Creek, Wyo., 

by William·· Taylor. Fuller's earth was first produced in the United States in 1891, when a bed of 

Tertiary clayey marl near Alexander, Ark., was 

mined. This clay, however, was used for only a very 

short time because it proved to be unsatisfactory. 

In 1893, fuller's earth was discovered through curiosity near Quincy, Fla., when an effort to burn 

brick proved unsuccessful. The production of both 

bentonite and fuller's earth has increased more or 

less steadily since the late 19th century. In 1969 

the production of bentonite reached 2.6 million short 

tons valued at $25.9 million, and the production of 

fuller's earth reached 984,000 short tons valued at 

$25.3 million. Wyoming, Mississippi, and Texas are 

the major bentonite-producing States, and Florida, 
128 UNITED STATES MINERAL RESOURCES 

Georgia, and Mississippi are the major fuller's 

earth-producing States. Bentonite production data 

(fig. 14) are available for only 40 years because 

before 1930 they were included in the miscellaneousclay category. The production data for fuller's earth 

for the past 50 years are shown in figure 14. The 

average value per ton of bentonite increased from 

$5.37 in 1936 to $11.83 in 1960 and then decreased 

to $9.82 in 1969. Some of this decrease in value 

during the 1960's was due to the increased demand 

for low-cost poor-quality bentonite as a bond in 

pelletizing fine-grained iron ores. The average value 

per ton of fuller's earth increased from $9.28 in 

1933 to $25.77 in 1969. Part of this increase in 

value took place in the 1960's when animal litter, 

sold in small quantities, became popular at the 

supermarkets. 

Much of the best grade "Wyoming" or "sodium" 

bentonite occurs in the Mowry Shale of Cretaceous 

age in Wyoming and South Dakota. The Clay Spur 

Bentonite bed, near the top of this formation in a 

belt surrounding the Black Hills, has been a major 

source of bentonite, and it still contains large reserves. Other beds in the Mowry Shale and younger 

formations have been mined in the vicinity of the 

Bighorn Mountains, Wyo. and at scattered localities in Montana. The "calcium" or "southern" bentonite of Cretaceous age is mined in Mississippi and 

Alabama. Extensive beds of "calcium" bentonite of 

Tertiary age have been the major sources of bentonite in Texas, Arizona, and California, and smaller 

deposits of "calcium" bentonite occur in all Western 

States. A unique magnesium and lithium-bearing 

high-swelling bentonite termed "hectorite" occurs 

near Hector, Calif., and at a locality in Arizona. 

Altered volcanic rock, consisting mainly of montmorillonite, is mined at a locality in Utah and sold 

as bentonite. Probably similar rock in other States 

is used as bentonite. 

Most fuller's earth deposits occur as beds in sedimentary rock, but some are hydrothermally altered 

volcanics. The deposits in southern Georgia and 

northern Florida that consist mainly of palygorskite 

and montmorillonite are in the Hawthorn Formation of Miocene age. Fuller's earth also oc.curs in 

this formation in central peninsular Florida and in 

the vicinity of Tampa, Fla. Significant tonnages of 

fuller's earth products are produced from the 

Twiggs Clay of Eocene age in middle Georgia. The 

Porters Creek Clay of Paleocene age, which contains enormous tonnages of fuller's earth, is mined 

at six localities. This formation extends from southeastern Missouri to southern Illinois, across the 

western part of Kentucky and Tennessee, across 

northeastern Mississippi, and well into Alabama. 

The clay in both the Twiggs Clay and the Porters 

Creek Clay consists chiefly of montmorillonite and 

poorly crystalline silica in the form of opal or cristobalite. Bentonite is mined at a few places in 

Texas, California, and elsewhere and is sold as 

fuller's earth. Altered volcanic rock consisting 

chiefly of montmorillonite is also mined in Utah and 

California and is sold as fuller's earth. 

Resources of all grades of both bentonite and 

fuller's earth are very large. The reserves of bentonite must be considered as at least 1 billion tons, 

and any estimate of presumed resources would be 

much greater than this figure. The estimate of 1 

billion tons includes large deposits of bentonite 

suitable for bonding iron-ore pellets, but it is classed 

as submarginal for uses such as drilling mud. The 

reserves of very high grade colloidal bentonite are 

limited, and deposits of this type are in demand. 

Resources of fuller's earth are tentatively estimated 

at 2 billion tons. Almost any figure, however, could 

be used here, if all the material equivalent to the 

grade of fuller's earth used in the past, but now 

considered submarginal is included. This would include much of the extensive Porters Creek Clay, the 

Twiggs Clay, thick opal claystone beds, and many 

scattered impure or low-grade bentonites. 

MISCELLANEOUS CLAY 

The term "miscellaneous clay" is used by the U.S. 

Bureau of Mines for clays and shales that do not 

fit any of the other five categories. The miscellaneous 

clay and shale may be any color. and may contain 

a large amount of impurities, but the color and 

impurities may give the clay the necessary properties to make the final product a salable item. Miscellaneous clays and shales are used chiefly in making fired products, but some are used in the unfired 

form. The unfired uses are as follows: Shale for 

filler in paint and asphalt; clay for abrasives, 

termed "rottenstone"; shale for "clay dummies" 

used to pack dynamite in blasting holes; and clay 

used for plugging oil and gas wells. These products 

are easily processed, requiring only drying, grinding, and bagging. Fired products made from miscellaneous clay and shale include face and structural 

brick, vitrified sewer pipe, drain tile, flue tile, conduits, pottery, and stoneware and floor, wall, and 

roofing tile. In addition to these uses, clay and shale 

are used in the manufacture of portland cement and 

lightweight aggregate. 

The demand for miscellaneous clay has increased 
CLAYS 129 

in the United States so that in 1969, 42.3 million 

short tons, valued at $63.3 million, of miscellaneous 

clay and shale was produced. Every State, except 

Alaska and Rhode Island, has produced miscellaneous clay products. The States producing over 1 

million tons in 1969 were Alabama, California, 

Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Mississippi, Missouri, New York, 

North Carolina, Ohio, Pennsylvania, South Carolina, Tennessee, Texas, and Virginia. Miscellaneous clay production increased tremendously in 

the 1944-46 period (fig. 14) because there was 

an increase in building construction following 

World War II. Before that time, clay production 

fluctuated considerably, but since then production 

has been steady. The average value per ton of miscellaneous clay was lowest at $0.72 in 1944 and 

highest at $2.91 in 1929, just before the depression. 

The average value per ton in 1969 was $1.49. 

Miscellaneous clay and shale occur in rocks ranging in age from Precambrian to Holocene and are 

formed by several different geologic processes. Rocks 

used for miscellaneous clay products include both 

fresh and weathered shale, weathered and fresh 

schist, slope wash and alluvium, loess, and ferruginous saprolite. Underclay beds and kaolin are also 

used in heavy-clay products, and some production of 

these clays is reported as miscellaneous clay by the 

U.S. Bureau of Mines. 

Reserves of miscellaneous clay and shale are 

enormous in many areas of the United States, but 

a few plants in or near metropolitan areas have 

raw-material-supply and air-pollution problems. 

The suburban spread of large cities, especially on 

the east coast, has engulfed a few brick and tile 

plants and their clay and shale resources. Some 

plants must be relocated or face increasing costs of 

transporting raw material, and other plants will 

have to install smoke and dust clarifiers. Future demands for products made from miscellaneous clay 

and shale can be expected to increase at the same 

rate as demands for the past two decades ( fig. 14). 

The demand for structural clay products should 

continue to grow, although competition from other 

building materials will also continue to increase. 

The demand for shale in making lightweight aggregate continues to increase and may replace much of 

the sand and gravel which are being depleted near 

some of the large eastern cities. 

Resources of miscellaneous clay and shale are virtually inexhaustible. The average value per ton is 

so low that the economics of land values, mining 

costs, production problems, transportation, market 

demands, and competition are much more important. 

SUMMARY OF RESOURCES 

A summary of the resources of the various types 

of clays is given in table 25. 

TABLE 25.-Summary of clay resources of the United States 

Type of clay 

Kaolin 

Do ----------

Reserves 1 

(tons) • 

>300 million _ 

Potential 

resources 1 

(tons) 

5 billion -----

Ball clay -------- 4 million -----

Do ---------- 50 million ___ _ 

Fire clay -------- 1 billion ------

Do ---------- 500 million ---

Do ---------- ------------- 7 billion ------ Bentonite ------- 1 billion ----- >1 billion ----

Fuller's earth ___ ------------ 2 billion ------

Miscellaneous 

clays. Enormous ---- Virtually inexhaustible. 

Remarks 

Chiefly in Georgia, 

Alabama, and 

Mississippi. Lower grade than reserves. Chiefly in Ken- tucky. Ten- nessee, and 

Mississippi. Lower grade than reserves. Refractories 

(low to medium 

duty). 

Refractories 

(high duty); 

flint and 

nodular flint 

clays. 

All grades. 

Limited re- serves of highgrade colloidal 

type. Chiefly 

in Wyoming, 

South Dakota, 

Mississippi, 

and Alabama. 

Chiefly in 

Georgia, Florida, Alabama, 

Kentucky, 

Tennessee, 

Mississippi, 

Missouri, 

Illinois, Texas, 

and California. 

Total probably 

greater. 

1 Reserves: Identified deposits from which minerals can be extracted 

profitably with existing technology and under present economic conditions. 2 Potential resources: Identified mineral deposits not profitably recover- able with existing technology and economic conditions and undiscovered 

mineral deposits whether of recoverable or subeconomic grade .. 

ENVIRONMENTAL CONSIDERATIONS 

Almost all clay deposits are mined from open pits; 

heavy equipment is used to remove the overburden 

and dig the clay. Surface mining destroys the beauty 

of the countryside and may pollute streams and 

rivers. Most States require clay producers to install 

settling ponds to prevent contaminiation of the 

streams; some States require open pits to be backfilled and covered with vegetation to restore the 

mined-out areas. Many older abandoned pits are, 

however, ugly scars detracting from the beauty of 

the countryside. Many clay-processing plants have 

installed, and others will be required to install, 

smoke- and dust-control systems to prevent atmospheric pollution. This, along with increased mining 

costs, will raise the future market prices of manufactured clay products. 

PROBLEMS FOR RESEARCH 

More geologic studies are needed related to clay 

deposits, especially bentonite and fuller's earth, and 
130 UNITED STATES MINERAL RESOURCES 

increased awareness is needed by the geologic profession of the value of clay deposits. The economic 

information needed on clay occurrences in areas 

currently being mapped are mineralogy, purity, 

thickness, areal distribution, overburden, and potential uses. Many geologic reports of areas containing clay deposits either have ignored those deposits or have given them cursory attention. To help 

in evaluating potential uses, clay-testing laboratories 

should be made available to the Federal and State 

geological surveys and to the public. 

SELECTED BIBLIOGRAPHY 

Bergquist, H. R., and Overstreet, E. F., 1965, Bauxite deposits of the Margerum district, Alabama: U.S. Geol. 

Survey Bull. 1199-D, 23 p. 

Calver, J. L., 1949, Florida kaolins and clays: Florida Geol. 

Survey Inf. Circ. 2, 59 p. 

Clark, L. D., 1965, Bauxite deposits of the Springvale district, Georgia: U.S. Geol. Survey Bull. 1199-F, 24 p. 

Cloud, P. E., Jr., 1966, Bauxite deposits of the Anniston, 

Fort Payne and Ashville areas, northeast Alabama: U.S. 

Geol. Survey Bull. 1199-0, 35 p. 

--- 1967, Geology and bauxit.e deposits of the Rock Run 

and Goshen Valley areas, northeast Alabama: U.S. Geol. 

Survey Bull. 1199-N, 74 p. 

Conant, L. C., 1965, Bauxite and kaolin deposits of Mississippi exclusive of the Tippah-Benton district: U.S. Geol. 

Survey Bull. 1199-B, 70 p. 

Cooper, J. D., 19701 Clays in Mineral facts and problems 

1970: U.S. Bur. Mines Bull. 650, p. 923-938. 

Denson, N. M., and Waage, K. M., 1966, Some bauxite and 

clay deposits in northeastern Alabama: U.S. Geol. Survey Bull. 1199-P, 27 p. 

Dunlap, J. C., Bergquist, H. R., Craig, L. C., and Overstreet, 

E. F., 1965, Bauxite deposits of Tennessee: U.S. Geol. 

Bull. 1199-L, 37 p. 

Grim, R. E., 1962, Applied clay mineralogy: New York and 

London, McGraw-Hill Co., 422 p. 

--- 1968, Clay mineralogy: New York and London, 

McGraw-Hill Co., 596 p. 

Harrison, J. L., 1961, Refractory clays of Indiana: Indiana 

Geol. Survey Prog. Rept., no. 24, 18 p. 

Hosterma.n, J. W., and Livingston, V. E., Jr., 1966, Clays, 

in Mineral and water resources of Washington: U.S. 

89th Cong., 2d sess., Senate Comm. Interior and Insular 

Affairs, p. 177-185. 

Hosterman, J. W., Patterson, S. H., Sweeney, J. W., and 

Hartwell, J. W., 1968, Clay, in Mineral resources of the 

Appalachian region: U.S. Geol. Survey Prof. Paper 580, 

p. 167-188. 

Hosterman, J. W., and Prater, L. S., 1964, Clays, in Mineral 

and water resources of Idaho: U.S. 88th Cong., 2d sess., 

Senate Comm. Interior and Insular Affairs, p. 51-57. 

Kelley, F. R., 1966, Clay, in Mineral and water resources of 

California, Pt. 1 : U.S. 89th Cong., 2d sess., Senate 

Comm. Interior and Insular Affairs, p. 12&-134 [repr. 

in California Div. Mines and Geology Bull. 191, p. 12&-

134]. 

Klinefelter, T. A., and Hamlin, H. P., 1957, Syllabus of clay 

testing: U.S. Bur. Mines Bull. 565, 67 p. 

Knechtel, M. M., and Weis, Paul, 1965, Nonfuel mineral resources of eas·tern Montana, except uranium, in Mineral 

potential of eastern Montana-A basis for future 

growth: U.S. 89th Cong., 1st sess., Senate Doc. 12, p. 

57-66 [repr. in Montana Bur. Mines and Geology Spec. 

Pub. 33, 1965]. 

Lang, W. B., Warren, W. C., Thompson, R. M., and Overstreet, E. F., 1965, Bauxite and kaolin deposits of the 

Irwinton district, Georgia: U.S. Geol. Survey Bull. 1199-

J, 26 p. 

Mark, Helen, 1963, High-alumina kaolinitic clay in the 

United States: U.S. Geol. Survey Mineral Inv. Resource Map MR-37. 

Mason, R. S., 1969, Clay, in Mineral and water resources of 

Oregon: U.S. 90th Cong., 2d sess., Senate Gomm. Interior 

and Insular Affairs, p. 200-205. 

Overstree.t, E. F., 1964, Geology of the southeastern bauxite 

deposits: U.S. Geol. Survey Bull. 1199-A, 19 p. 

Piartterson, S. H., 1964a, Clays, in Mineral and water resources of Golorado: U.S. 88th Cong., 2d sess., Senate 

Comm. Interior and Insular Affairs, p. 183-190. 

---1964b, Clays, in Mineral and water resources of Utah: 

U.S. 88th Cong., 2d ses.s., Senate Comm. Interior and 

Insular Affairs, p. 157-162. 

--- 1969, Clay, in Mineral and water resources of 

Arizona: U.S. 90th Cong., 2d sess., Senate Comm. Interior and Insular Affairs, p. 324-336 [repr. in Arizona 

Bur. Mines Bull. 180, p. 324-336]. 

Patterson, S. H., and Cox, E. J ., 1964, Clays, bentonite, and 

lightweight aggregate, in Mineral and water resources 

of South Dakota: U.S. 88th Cong., 2d sess., Senate 

Gomm. Interior and Insular Affairs, p. 105-112. 

Patterson, S. H., and Holmes, R. W., 1965, Clays, in Mineral 

and water resources of New Mexico: U.S. 89th Cong., 

1st sess., Senate Comm. Interior and Insular Affairs, p. 

312-322 [repr. in New Mexico Bur. Mines and Mineral 

Resources Bull. 87, p. 312-322]. 

Pence, F. K., DeBeck, H. 0., and Shurtz, R. F., 1948, Texas 

kaolins in the Wilcox Group: Texas Univ. Research Lab. 

in Ceramics, Rept. Inv. 1, 9 p. 

Sahinen, U. M., 1963a, Bentonite, in Mineral and water resourc-es of Montana: U.S. 88th Cong., 1st sess., Senate 

Comm. Interior and Insular Affairs, p. 5&-57. 

--- 1963b, Clays, in Mineral and water resources of Montana: U.S. 88th Cong., 1st sess., Senate Gomm. Interior 

and Insular Affairs, p. 60-62. 

Searight, W. V., Kisvarsanyi, E. B., Bush, A. L., and Patterson, S. H., 1967, Clay and shale, in Mineral and 

water resourc-es of Missouri: U.S. 90th Cong., 1st sess., 

Senate Doc. 19, p. 10&-124 [repr. in Missouri Div. Geol. 

Survey and Water Resourc.es, 2d ser., v. 43, p. 10&-124]. 

Smith, R. W., 1929, Sedimentary kaolins of the Coastal 

Plain of Georgia: Georgia Geol. Survey Bull. 44, 482 p. 

Tourtelot, H. A., 1964, Bauxite deposits of the TippahBenton district, Mississippi: U.S. Geol. Survey Bull. 

1199-C, 31 p. 

U.S. Bureau of Mines, 1920-32, Mineral resourc·es of the 

United States: Washington: U.S. Govt. Printing Office, 

ann. pubs. [continued by U.S. Bur. Mines Minerals 

Yearbook, 1932-68]. 

Wanless, H. R., 1939, Pennsylvanian correlations in the 

Eastern Interior and Appalachian coal fields: Geol. Soc. 

America Spec. Paper 17, p. 74-108. 
CLAYS 131 

Warren, W. C., Bridge, Josiah, and Overstreet, E. F., 1965, 

Bauxite deposits of Virginia: U.S. Geol. Survey Bull. 

1199-K, 17 p. 

Warren, W. C., and Clark, L. D., 1965, Bauxite deposits of 

the Eufaula district, Alabama: U.S. Geol. Survey Bull. 

1199-E, 31 p. 

Wells, J. R., 1971, Clays: U.S. Bur. Mines Yearbook, 1969, 

v. 1-2, p. 287-308. 

White, W. S., 1965, Bauxite deposits of the Warm Springs 

district, Meriweather County, Georgia: U.S. Geol. Survey Bull. 1199-I, 15 p. 

White, W. S., and Denson, N. M., 1966, Bauxite deposits of 

northwest Georgia, with a section on the Summerville 

area, by J. C. Dunlap and E. F. Overstreet: U.S. Geol. 

Survey Bull. 1199-M, 42 p. 

Zapp, A. D., 1965, Bauxite d·eposits of the Andersonville 

district, Georgia: U.S. Geol. Survey Bull. 1199-G, 37 p. 

Zapp, A. D., and Clark, L. D., 1965, Bauxite in areas adjacent 

to and between the Springvale and Andersonville districts, Georgia: U.S. Geol. Survey Bull. 1199;....H, 10 p. 

UNITED STATES MINERAL RESOURCES 

COAL 

By pAUL AVERITT 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------ Environment of coal accumulation ----------------

Rank of coal ------------------------------------

Grade of coal -----------------------------------

Sulfur -------------------------------------- Research on removal of sulfur ------------

Minor elements in coal -----------------------

United States coal resources ---------------------

Identified resources -------------------------- Distribution by selected categories ---------

Stripping coal resources -----------------

Hypothetical resources -----------------------

Speculative resources ------------------------

VVorld coal resources ----------------------------

References cited ---------------------------------

FIGURES 

15. Graph showing comparison on moist, mineralmatter-free basis of heat values and proximate analyses of coal of different ranks __ _ 

16. Graph showing approximate percentage distribution of original identified U.S. coal resources by major resource categories ------

17. Graph showing probable distribution of total 

estimated U.S. coal resources according to 

thickness of overburden ------------------

TABLES 

26. Distribution of identified United State-s coal resources according to rank and sulfur content_ 

27. Total estimated remaining coal resources of 

the United States, January 1, 1972 --------

28. Estimated total original coal resources of the 

world, by continents ---------------------

ABSTRACT OF CONCLUSIONS 

The estimated coal resources of the United States remaining in the ground as of January 1, 1972, totaled 3,224 billion 

Page tons. Of this large total, 1,581 billion tons, or 49 percent, is 

133 classed as identified, and 1,643 billion tons, or 51 percent, is 

133 classed as hypothetical. 

134 Stripping coal resources remaining in the ground as of 

134 January 1, 1968, totaled 118 billion tons, or about 7.5 percent 

134 of the identified resources. 

135 VVorld coal resources are estimated to total 16,830 billion 

135 tons, of which 9,500 billion tons is classed as identified, and 

136 7,330 billion tons is classed as hypothetical. The United 

136 States contains about one-fifth of estimated total world re138 sources. 

138 On a uniform Btu basis, U.S. coal resources are larger 

139 than the combined domestic resources of petroleum, natural 

139 gas, oil shale, and bituminous sandstone. The prolonged fu140 ture need for energy in ever-increasing quantitie-s, and the 

140 prospect of decreasing availability of and increased prices 

140 for petroleum and natural gas, have focused very -sharp atPage 

135 

138 

139 

Page 

135 

137 

140 

tention on coal as an alternative source of synthetic gas, 

liquid fuels, and lubricants. 

INTRODUCTION 

Coal is widespread and abundant in the United 

States. Coal-bearing rocks underlie about 13 percent 

of the land area of the 50 States, and are present 

in varying amounts in parts of 37 States (Trumbull, 1960; Barnes, 1961). The ready availability of 

coal has contributed substantially to the growth 

and industrial development of the nation. 

On any basis of analysis, U.S. resources of coal 

are larger than the combined resources of petroleum, 

natural gas, oil shale, and bituminous sandstone, 

but use of coal lags behind use of both petroleum 

and natural gas because these two fuels are cleaner 

to burn and easier to handle. In spite of this handicap, annual coal production in the United States 

ranges typically from 500 to 600 million tons. About 

10 percent of the annual production is exported, 

primarily to Japan, Canada, and western Europe. 

Of coal consumed annually in the United States, 

about 62 percent is used in the production of elecU.S. GEOL. SURVEY PROF. PAPER 820 

133 
134 UNITED STATES MINERAL RESOURCES 

tric power, 20 percent is used by the steel industry, 

16 percent by the manufacturing industry, and 2 

percent for all other purposes. Coal is also of great 

future value and importance as a subsidiary source 

of synthetic gas, liquid fuels, and lubricants. 

ENVIRONMENT OF COAL ACCUMULATION 

Coal is the compressed and altered residue of 

plants that grew in ancient fresh- or brackish-water 

swamps. As the plant remains accumulated they 

were transformed into peat; later they were altered 

by diagenesis (chemical and physical changes occurring before they became solidified), and still later 

by metamorphism (chemical and physical changes 

brought about by pressure and heat after they became solidified). Coal contains widely varying 

amounts of sand, silt, and mud that was washed 

into the peat swamps, and this admixed sediment 

forms the bulk of the ash of burned coal. The physical and chemical properties of coal and the coalification process have been described in considerable 

detail by Schopf (1948; 1956) and by Dapples and 

Hopkins (1969). 

The accumulation of peat requires a humid climate to support a rich growth of vegetation, and 

a high water table to permit prolonged accumulation of plant material in a reducing environment 

(See "Peat," this volume). Most of the large peat 

deposits of Pennsylvanian age that were the precursors of coal mined extensively in the Eastern 

and Central United States were formed near sea 

level-some in estuaries or coastal lagoons, others 

on large deltas or many coalescing deltas, others on 

low-lying, broad coastal plains. These features form 

characteristically in areas of gentle downwarping of 

the sea floor marginal to the edges of an eroding 

landmass. This topographically low position in an 

area of gentle downwarping permitted periodic 

transgressions of the sea. Some thick coal beds of 

very wide areal extent required a very large and 

wide coastal plain, a prolonged optimum rate of 

plant growth and accumulation, a slow rate of subsidence, and an equally slow encroachment of the 

sea over periods measured in_ centuries. 

The transgressive sea ultimately covered the peatforming swamp and terminated plant growth. The 

eroding landmass continued to supply sand, silt, 

and mud to the sea, and this material settled in 

layers over the submerged peat swamp. In time, 

depending in length on the rate of sedimentation, 

the depth of the transgressive sea, and the rate of 

subsidence, this sedimentary material built up new 

deltas, lagoons, and coastal plains conducive to the 

development of new, younger peat-forming swamps. 

This sequence of deposition was repeated many 

times by intermittent downwarping alone, but the 

sequence might have been prolonged, shortened, or 

terminated at any time by relatively minor movements of land relative to the sea floor. In the very 

delicate balance between sedimentation, subsidence, 

and uplift of the land, the sea also regressed from 

time to time. Peat swamps obviously formed during 

the regressive phase of the cycle, but these were 

subject to oxidation and are less commonly preserved. These cyclic repetitions of the conditions 

allowing the formation of coal are documented in 

many of the world's coal fields, but rarely as strikingly as in a sequence of several thousands of feet 

of sedimentary rock in West Virginia that contains 

117 coal beds of sufficient geologic and economic 

interest to have been described and named. 

Weight of the overlying sedimentary rock, heat 

produced by depth of burial, structural deformation, and time all contribute to the progressive compaction and devolatilization of peat to form the 

higher ranks of coal, which are discussed below. A 

subsequent major uplift of the land relative to the 

sea has raised the U.S. coal fields to their present 

positions, exposing them to erosion and to view, 

thereby permitting study and mine development. 

RANK OF COAL 

Coal is classified by rank according to the percentage of fixed carbon and heat content, calculated on a mineral-matter-free basis. As shown in 

figure 15, the percentage of fixed carbon and the 

heat content increase from lignite to low-volatile 

bituminous coal as the percentages of volatile matter and moisture decrease. These changes are primarily the result of depth and heat of burial, 

compaction, time, and structural deformation. Rank 

is thus a way of expressing the progressive metamorphism of coal. It is quite independent of grade, 

which is a way of expressing quality. 

As coals of different rank are adapted to different uses, rank is a major basis of differentiation in 

coal-resource calculations. In accompanying tables 

and figures, the coal resources are expressed in 

short tons. If arithmetic adjustments were made 

for the contained heat values, the distribution patterns would be changed somewhat because of the 

lower heat values of lignite and subbituminous coal. 

GRADE OF COAL 

Coal is classified by grade largely according to the 

content of ash, sulfur, and other deleterious constituents. Thus far in work on coal resources, a 

preliminary classification on the basis of sulfur 
COAL 135 

12.000t---------~'--t::1-----t:1--M----i/1------.t;1--l/1-----l/1 

/ 

100 M 0 I s tl:: _1. J.! JL _.E-- ---

~ ' 

/ ' --- --- ~ ~ / / 

- - 1--

p. ,. / / 

t-Il / 

\. E. / 

.. =-- '--- ...___ ~/; 

--- ~ r-~ -.! ~ 

~ .! // 

/ 

·~ ·e ~ ~ --- c r-~ ~ -! c - ID 

~~ r-i c '!' (,) .I! !!I i ·e c i ~~ ll jg i·e .,; :IE 

~e 0 

.~:i r-J r-'!" '!"~ .c::'!::' .C:'!::' .!I .a % ~ .!U' % :a % 

D c A ~ R B 0 N 

80 

/,-

FIGURE 15.-Comparison on moist, mineral-matter-free basis 

of heat values and proximate analyses of coal of different 

ranks. 

content has been made, but classification on the 

basis of ash content has not been made, because ash 

is a more highly variable component than sulfur. 

In recent years, information on trace elements in 

coal has increased somewhat, but classification according to trace-element content is not yet possible. 

SULFUR 

Sulfur is an undesirable element in coal. It lowers 

the quality of coke and of the resulting iron and 

steel products. It contributes to corrosion, to the 

formation of boiler deposits, and to air pollution. 

Its presence in spoil banks inhibits the growth of 

vegetation. As sulfuric acid, it is the main deleterious compound in acid mine waters, which contribute 

to stream pollution. 

The sulfur content of coal in the United States 

ranges from 0.2 to about 7.0 percent, but the average in all coal is 1.0-2.0 percent. Most of the sulfur, 

perhaps 40-80 percent, occurs as a constituent of 

pyrite and marcasite (FeS2). The remainder occurs 

as hydrous ferrous sulfate (FeS4•7H20), derived 

by weathering of pyrite, as gypsum (CaS04•2H20), 

and as organic sulfur in combination with the coalforming vegetal material (Walker and Hartner, 

1966). 

The percentage of sulfur and of pyritic sulfur is 

highest in bituminous coals of Pennsylvanian age 

in the Appalachian and Interior coal basins. The 

percentage is relatively low, generally less than 1 

percent, in subbituminous coal and lignite of the 

Rocky Mountain and Northern Great Plains regions. 

This relation is shown clearly in table 26. 

TABLE 26.-Distribution, in percent, of identified 1 United 

States coal resources according to rank and sulfur content • 

Sulfur content (In percent) 

Rank Low Medium Hich 

G-1 1.1-3.0 3+ 

Anthracite -------------- 97.1 2.9 

Bituminous coal 43~4 --------- 29.8 26.8 

Subbituminous coal ------ 99.6 .4 

Lignite ----------------- 90.7 9.3 

All ranks --------------- 65.0 15.0 20.0 

lidentified resources: Specific, idE:nti.fied mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existiq teehnolop 

and economic conditions. 1 From DeCarlo, Sheridan, and Murphy ( 1966). 

The conspicuously large percentage of low-sulfur 

coal in the United States, shown on the last line 

of table 26, is primarily due to the fact that the 

resources of low-sulfur subbituminous coal and lignite concentrated in the Rocky Mountain and Northern Great Plains regions represent about 54 percent 

of total identified resources. 

RESEARCH ON REMOVAL OF SULFUR 

Pyrite and marcasite have a high specific gravity, 

and most of this material can be removed from coal 

by various washing and cleaning procedures. The 

other forms of sulfur have lower specific gravities 

and are more intimately mixed with the coal, and 

consequently are less easily removed. Between 60 

and 65 percent of all coal mined in the United States 

is cleaned to remove pyritic and inert material before use. However, in spite of such large-scale cleaning, the average sulfur content of all coal used in 

the United States is still nearly 2 percent. 

Current efforts to reduce the sulfur content of 

coal and of flue gas take many forms: 

1. Much r~search is in progress on methods to remove S02 and S03 from flue gas. This can be 

done by several well-known chemical processes, 

and the technical problems inherent in the 

large-scale commercial application of chemical 

processes are likely to be solved in the near 

future. 

2. Meanwhile, the search for low-sulfur coal has 
136 UNITED STATES MINERAL RESOURCES 

been intensified, particularly in the Eastern 

States, and the use of lower-sulfur coal has 

been increased. A few older coal-burning utility plants in the Midwest have converted from 

high-sulfur local coal to low-sulfur Rocky 

Mountain coal. This substitution has required 

payment of transportation costs of $3-$5 per 

ton, and acceptance of the lower heat content 

of Rocky Mountain coal. Such high transportation costs obviously will intensify research 

efforts mentioned in item 1. 

3. Much research is in progress on methods to 

produce a high-Btu, sulfur-free gas from coal. 

This is also a technical possibility soon to be 

realized. It has the mult;iple advantages of 

lowering the costs of long-distance transportation of energy, of eliminating the sulfur 

problem, of augmenting declining resources 

of natural gas, of reducing dependence on 

foreign sources of oil and gas, and ultimately 

permitting use of high-sulfur eastern coal. 

4. Research on improved methods of producing 

electric power by nuclear fission and fusion 

is continuing. 

These varied avenues of approach suggest that 

the amount of sulfur .released to the atmosphere by 

the burning of coal will soon be greatly reduced. 

MINOR ELEMENTS IN COAL 

Coal contains small quantities of virtually all 

metallic and nonmetallic elements, that were introduced into the coal bed in one or all of four different ways: 

1. As inert material washed into the coal swamp 

at the time of plant accumulation. 

2. As a biochemical precipitate from the swamp 

water. 

3. As a minor constituent of the original plant 

cells. 

4. As a later addition, introduced after coal formation, primarily by ground water moving downward and laterally. 

When coal is burned, most of these elements are 

concentrated in the coal ash, but a few of the more 

volatile elements are emitted into the atmosphere. 

Coal ash is composed largely of the oxides of Si, AI, 

Fe, Ca, Mg, K, Na, and S, which typically make up 

93-98 percent of the total weight of the ash (Abernethy and others, 1969a). The remaining few percent of coal ash is made up of small individual 

amounts of many other elements, which differ in 

variety and quantity in different areas and beds. 

These elements are generally measured in parts per 

million or billion, and for this reason are termed 

minor elements, although they may not be minor 

elements in other contexts. 

The minor elements in coal are of considerable 

interest because some may become of future resource importance, and others may be pollutants. 

Most of the minor elements occur in coal in about 

the same concentration as their estimated concentration in the earth's crust, but 25-30 elements occur 

locally in greater concentration and these have received the most study. A few elements, notably U, 

Ge, As, B, and Be, occur locally in vastly greater 

concentrations than their estimated concentration 

in the earth's crust; others, including Ba, Bi, Co, 

Cu, Ga, La, Pb, L, Hg, Mo, Ni, Sc, Se, Ag, Sr, Sn, 

V, Y, Zn, and Zr, occur locally in appreciably greater 

concentrations. Other elements of interest that generally occur in lower concentrations than those 

listed above include Cr, Mn, P, Te, Tl, Ti, and W. 

It should be noted that the concentration of an 

element in excess of the estimated concentration in 

the earth's crust, although of great interest and 

geologic significance, does not necessarily imply an 

economic or paramarginal concentration, because 

that is determined by the concentration in typical 

commercial sources of the respective element. 

Reports by Abernethy and Gibson (1963); Abernethy, Peterson, and Gibson ( 1969a, b) ; Zubovic 

( 1966a, b) ; Zubovic, Sheffey, and Stadnichenko 

(1967); Zubovic, Stadnichenko, and Sheffey (1960a, 

b, c; 1961a, b; 1964; and 1966) ; and by Sun, 

Vasquez-Rosas, and Augenstein (1971) summarize 

available information concerning minor elements in 

coal. A selected bibliography on trace elements in 

coal, applicable primarily to U.S. coals, has been 

compiled by Averitt, Breger, Gluskoter, Swanson, 

and Zubovic (1972). 

UNITED STATES COAL RESOURCES 

The remaining coal resources of the United States 

as of January 1, 1972, are estimated to total 3,224 

billion tons. Of this large total, 1,581 billion tons, 

or 49 percent, has been identified on the basis of 

mapping and exploration, and the remainder of 

1,643 billion tons, or 51 percent, is classed as hypothetical because it has been determined by extrapolation of the data on identified resources into unmapped and unexplored areas. The distribution of 

this tonnage by State is given in table 27. 

The figures in table 27, and in subsequent tables 

and figures, express resources in the ground. The 

recoverability in coal mining ranges from 40 to 90 

percent, depending largely on the method of mining, 

but it is influenced by many other diverse factors 

such as the nature of the roof rock, joints, faults, 
COAL 137 

TABLE 27.-Total estimated remaining coal resources of the United States, January 1, 1972 

[In millions of short tons. Figures are for resources in the ground, about half of which may be considered recoverable. Includes beds of bituminous 

coal and anthracite 14 in. or more thick and beds of subbituminous coal and lignite 2% ft or more thick] 

State 

Alabama 

Alaska 

Arizona 

Arkansas 

Colorado 

Georgia 

Illinois ------- Indiana ------- Iowa 

Kansas-======== 

Kentucky 

Maryland 

Michigan 

Missouri ------- Montana ------ New Mexico 

North Carolina-=-

North Dakota __ Ohio --------- Oklahoma ----- Oregon 

Pennsylvania 

Rhode Island 

South Dakota -- Tennessee -----

Texas --------- Utah ---------

Virginia 

Washington -----

West Virginia __ 

Wyoming 

Other States ---

Total ----

Identified resources 1 

Overburden 0-3,000 ft 

Estimated identified resources remaining in the eround, Jan. 1, 1972 

SubBitumi- bitumi- Lignite nous coal nous coal 

13,342 0 2,000 

19,413 110,668 (') 6 21,246 (6) 0 

1,638 0 350 

62,339 18,242 0 

24 0 0 

139,124 0 0 

34,573 0 0 

6,509 0 0 

18,674 0 (8) 

64.842 0 0 

1,158 0 0 

205 0 0 

31,014 0 0 

2,299 131,855 87,521 

10,752 50,671 0 

110 0 0 

0 0 1150,630 

41,358 0 0 

3,281 0 (8) 

50 284 0 

56,759 0 0 

0 0 0 

0 0 2,031 

2,572 0 0 

6,048 0 6,824 

11 23,541 11 180 0 

9,352 0 0 

1,867 4,190 117 

100,628 0 0 

12,705 107,951 (2) 

13610 U32 154,6 

686,033 424,073 449,519 

Anthracite and 

semi- ToW 

anthracite 

0 15,342 

(5) 130,081 

0 21,246 

430 2,418 

78 80,659 

0 24 

0 139,124 

0 34,673 

0 6,509 

0 18,674 

0 64,842 

0 1,158 

0 205 

0 31,014 

0 221,675 

4 61,427 

0 110 

0 350,630 

0 41,368 

0 3,281 

0 334 

20,510 77,269 

(10) 

0 2,031 

0 2,572 

0 12,872 

0 11 23,721 

335 9,687 

5 6,179 

0 100,628 

0 120,656 

·o 688 

21,362 1,580,987 

Source of estimate 

Culbertson (1964); T. 

A. Simpson (written commun., 1972). Barnes (1951; 1967) 

Peirce and others 

(1970)1. 

Haley (1960) -------- Landis (1959) -------- Johnson (1946)7 ------

Simon (1965 )7 -------

Spencer (1953) ------- Landis (1965) ------- Schoewe (1952; 1958) 7 _ 

Huddle and others 

(1963). 

Averitt (1969) ------- Cohee and others 

(1950). 

Robertson (1971)1 ___ _ 

Combo and others 

(1949; 1950) 7. 

Read and others ( 1950) _ Reinemund ( 1949; 

1955). 

Brant (1953) -------- Brant and DeLong 

(1960). 

Trumbull (1957) ----- R. S. Mason (written commun., 1965)7. Reese and Sisler (1928); 

Arndt and others 

(1968)7. 

Toenges and others 

(1948). 

D. M. Brown (1952) 

Luther ( 1959; written commun., 1965). 

Mapel ( 1967) ; Perkins 

and Lonsdale (1955). 

Doelling 1970, 1971a, 

b, c, d, e, f, Doelling 

and Graham, ( 1970; 

1971); H. H. Doelling 

(written commun., 1971). 

Brown and others 

(1952). 

Beikman and others 

(1961). 

Headlee and Nolting (1940). 

Berryhill and others 

(1950; 1951). 

Total 

Hypothetical resources ll resources 

Over- Over- Over- Over• 

burden burden burden burden 

0-3,000 3,000- 0-6,000 0-6,000 

ft 6,000 ft ft 

ft 

Total 

Estimated estimated 

hypothe- identified 

tical re- and hyposources in thetical 

unmapped Estimated resources 

and un- hypothe- remainexplored tical re- Total ing in 

are~UJ rea- sources in estimated the 

sonably deeper hypothe- eround 

near the structural tical re- Jan. 1, 

surface 3 basins 3 sources !972 

20,000 6,000 26,000 41,342 

130,000 5,000 135,000 265,081 

0 0 0 21,246 

4,000 0 4,000 6,418 

146,000 146,000 291,000 371,659 

60 0 60 84 

100,000 0 100,000 239,124 

22,000 0 22,000 56,573 

14,000 0 14,000 20,1)()9 

4,000 0 4,000 22,674 

52,000 0 52,000 116,842 

400 0 400 1,558 

500 0 500 705 

18,200 0 18,200 49,214 

157,000 0 157,000 378,675 

27,000 21,000 48,000 109,427 

20 5 25 135 

180,000 0 180,000 530,630 

2,000 0 2,000 43,358 

20,000 10,000 30,000 33,281 

100 0 100 434 

9 10,000 0 10,000 87,269 

0 0 0 

1,000 0 1,000 3,031 

2,il00 0 2,000 4,572 

14,000 0 14,000 26,872 

12 21,000 35,000 66,000 79,721 

5,000 100 5,100 14,787 

30,000 15,000 45,000 51,179 

0 0 0 100,628 

325,000 100,000 425,000 545,656 

1,000 0 1,000 1,688 

1.306,280 337,105 1,643,385 3,224,372 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may not be profitably recoverab:e with existing, technology and economic conditions. 2 Hypothetical resources: Undiscovered mineral deposits, whether of recoverable or subeconom1c grade, that lire geologically predictable as existing in known district. 3 Estimates by H. M. Beikman (Washington), H. L. Berryhill, Jr. (Wyoming), R. A. Brant (Ohio and North Dakota), W. C. Culbertson 

(Alabama), H. H. Doelling (Utah), K J. Englund (Kentuckv and Virginia), B. R. Haley (Arkansas), E. R. Landis (Colorado and Iowa), E. T. 

Luther (Tennessee), R. S. Mason (Oregon), C. E Robinson (Missouri), J. A. Simon (Illinois), J. V. A. Trumbull (Oklahoma), C. E. Wier (Indiana), 

and the author for the remaining States. 

' Small resources of lignite included under subbituminous coal. 5 Small resources of anthracite in the Bering River field believed to be too badly crushed and faulted to be economically recoverable (Barnes, 1951). 8 Includes coal in the Dakota Formation of the Black Mesa field, some of which may be of subbituminous rank. Does not include small resources of 

thin and impure coal in the Deer Creek and Pinedale fields. 7 See other summary reports on coal resources in individual States as follows: Arizona (Averitt and O'Sullivan, 1969); Georgia (Butts and 

Gildersleeve, 1948; Sullivan, 1942); Illinois (Cady, 1952); Kansas (Abernathy and others, 1947); Mis'!louri (Hinds, 1913; Searight, 1967); eastern Montana (Averitt, 1965); Ohi(J (Struble and others, 1971); Oregon (Mason and Erwin, 1955; Mason, 1969); Pennsy1vania anthracite (Ashley, 1945; 

Ashmead, 1926; Rothrock, 1950); and Utah (Averitt, 1964). 8 Small resources of lignite in beds generally less than 30 in. thick. 9 From Ashley (1944). 10 Small resources of meta-anthracite in the Narragansett basin believed to be too graphitic and too badly crushed and faulted to be economically 

recoverable as fueL 11 Excludes coal in beds less than 4 ft thick. 12 Includes coal in beds 14 in. or more thick, of which 14,000 million tons is in beds 4 ft or more tbick. 

13 California, Idaho, Nebraska, and Nevada. u California and Idaho. 115 California, Idaho, Louisiana, and Mississippi. 
138 UNITED STATES MINERAL RESOURCES 

and the need to protect oil and gas wells and fields. 

From the long-term national point of view, average 

recoverability is probably about 50 percent. However, it is not desirable to report coal resource data 

on an arbitrary recoverable basis, because experience with most commodities has shown very significant long-term changes in what is regarded as 

economically recoverable. Coal in the ground is a 

more certain value that can be modified now or in 

the future by any recoverability factor deemed 

appropriate. 

IDENTIFIED RESOURCES 

DISTRIBUTION BY SELECTED CATEGORIES 

In addition to the distribution by rank of the 

identified resources of 1,581 billion tons as presented in table 27, about 60 percent of this total 

has been classified into additional categories according to the thickness of overburden, degree of reliability of estimates, and thickness of beds as shown 

in figure 16. This classified tonnage is fairly large 

and is widely distributed in 21 States; it is likely 

to be reasonably representative of the total identified tonnage. 

Overburden.-Figure 16 clearly shows the pro100 

58 

1-

z 

Lo.l 

~50 

Lo.l 

A. 

Thin 

34 

nounced concentration of identified resources in the 

0-1,000-foot overburden category. This concentration results in part from the fact that coal-bearing 

rocks are near the surface in most parts of the 

United States, and in part from the fact that progressively less information is available for the more 

deeply buried beds. Much of the tonnage classed as 

hypothetical in figure 17 is in the 1,000-2,000-foot 

and the 2,000-3,000-foot overburden categories. As 

exploration and development are carried to greater 

depth it is certain that the identified resources will 

be considerably increased by addition of tonnage in 

the deeper overburden categories. 

Degree of reliability of estimates.-Figure 16 also 

shows the progressive increase in tonnage from the 

measured to the inferred categories. In the 0-1,000-

foot overburden category, for example, 8 percent of 

the tonnage is classified as measured, 23 percent 

as indicated, and 58 percent as inferred. The same 

relation can be observed in the deeper overburden 

categories. The large percentage of inferred coal 

reflects merely distance from points of known information. Resources classified as "inferred" obviously 

exist, but the locations of such tonnage may differ 

slightly from those assumed to make the calculations. As mapping and exploration continue, the 

'ii 'ii~ 0 

8~ u 

.,~ 

c ~ .,. ::~.'!::: 

~ 0 ::I ... oc til o=: CCII 

::: .! c c ·e= A. • . ·e~ ::~-a 

(.J -c .Ec :a• j:ij«< . .a 

Thin 14-28 in 2lfz-5 ft 

28-42 in 5-10ft 

Thick More than More than 

42 in 10 ft 

FIGURE 16.-Approximate percentage distribution of original identified U.S. coal resources by major resource categories. 
COAL 139 

percentage of coal classified as measured and indicated will surely increase. 

Thickness of beds.-Coal in thick beds, 0-1,000 

feet below the surface comprises 4 percent measured, 

8 percent indicated, and 13 percent inferred, for a 

total of 25 percent of the identified resources shown 

in figure 16. This percentage, when applied to the 

total of 1,581 billion tons, is equivalent to nearly 

400 billion tons. This choice tonnage is in a thickness and overburden category comparable to that of 

coal now being mined, and is therefore of current 

and near-current economic interest. 

Coal in beds of intermediate thickness, 0-1,000 

feet below the surface, makes up 23 percent of the 

identified resources, and is equivalent to 350 billion 

tons. This tonnage is of less immediate economic 

interest than tonnage in the thicker beds. However, 

some coal in this thickness and overburden category 

is currently being mined, and the total must be 

considered a paramarginal resource that will become of increasing economic interest and importance 

in the future. 

Coal in thin beds, 0-1,000 feet below the surface, 

makes up 41 percent of the identified resources, and 

coal in all thickness categories, 1,000-3,000 feet 

below the surface, makes up the remaining 11 percent. This coal is of little current economic interest. 

The amount in any category or combination of 

categories can be derived from figure 16 by the 

procedure used above. 

STRIPPING COAL RESOURCES 

In a recently published study, the U.S. Bureau of 

Mines (1971) concluded that the remaining stripping coal resources of the United States as of January 1, 1968, totaled 118 billion tons. Of this total, 

__,- about 90 billion tons, or 80 percent, is within reach 

by present machinery and methods of mining, but 

only 45 billion tons is both available for use and 

economically recoverable. 

For purpose of comparison, the larger total of 

118 billion tons of stripping coal resources is 7.5 

percent of the total of 1,581 billion tons of remaining identified resources as reported in table 27. 

The 45 billion tons of potentially recoverable 

stripping coal includes 32 billion tons of low-sulfur 

coal (less than 1 percent) , 4 billion tons of medi urnsulfur coal (1-2 percent), and 9 billion tons of 

high-sulfur coal (more than 2 percent). 

HYPOTHETICAL RESOURCES 

The preceding analysis of the distribution of 

identified coal resources provides convincing evidence that unmapped and unexplored areas in 

known coal fields contain substantial additional resources that must be classed as hypothetical. The 

approximate magnitude of the additional hypothetical resources has been estimated by a process 

of extrapolation from nearby areas of identified 

resources, and estimates for each State are presented in separate columns in table 27. The total 

tonnage of hypothetical resources actually exceeds 

by a small amount the tonnage of identified resources. Figure 17 shows the percentage relation 

between identified and hypothetical resources in 

four overburden categories. 

100~----

50.5 

:~~~~~~HH 6 

EXPLANATION 

Mined 

-out 

rzJlJ 

Identified resources 

~!'!:!'!:~~ 

~::::::::::~ 

.;_:;.;:~:,&;;,;. 

Hypothetical resources 

FIGURE 17.-Probable distribution of total estimated U.S. 

coal resources according to thickness of overburden. 

Although large, the hypothetical resources are, 

for the most part,. relatively inaccessible for mining 

at present, and a more exact delineation of the 

magnitude, distribution, and future utility of such 

resources will require a substantial amount of detailed geologic mapping, exploration, and study over 

a long period. Nevertheless, the estimated hypothetical resources constitute an important part of 

the total resource that needs to be considered in 
140 UNITED STATES MINERAL RESOURCES 

future planning for the utilization of all energy 

resources. 

SPECULATIVE RESOURCES 

The resources presented in table 27 and discussed 

under the headings of identified and hypothetical 

resources represent total resources within limits 

established by the minimum thickness of coal beds 

and the maximum thickness of overburden. The 

major geologic features of the United States are 

known well enough to justify the statement that, 

in all probability, no major coal fields remain to be 

discovered. Hence the coal resources of the United 

States are all either identified or hypothetical. Because there are no undiscovered districts, there are 

no speculative resources. 

WORLD COAL RESOURCES 

The original identified coal resources of the world 

total about 9,500 billion tons, the additional hypothetical resources total about 7,330 billion tons, 

and the two categories combined total 16,830 billion 

tons. The distribution of this tonnage by continents 

is shown in table 28. 

TABLE 28.-Estimated total original coal resources of the 

world, by continents 1 

[In billions of short tons] 

Hypo the- Estimated 

Continent Identified tieal re- total rEIIOUree& J sources a resources 

Asia' ----------------- 5 7,000 4,000 8 11,000 

North America --------- 1,720 2,880 4,600 Europe --------------- 620 210 830 

Africa ---------------- 80 160 240 

Oceania --------------- 60 70 130 

South and Central 

America ------------ 20 10 30 

Total ----------- 5 9,500 7,330 8 16,830 

1 Original resout·ces in the ground in beds 12 in. or more thick and generally less than 4,000 ft below the surface, but includes small amounts between 4,000 and 6,000 ft. :I Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. 3 Hypothetical resources: Undiscovered mineral deposits, whether of 

recoverable or subeconomic grade, that are geologically predictable as existing in known districts. 

' Includes European U.S.S.R 5 Includes about 6,500 billion short tons in the U.S.S.R. 8 Includes about 9,500 billion short tons in the U.S.S.R. (Hodgkins, 1961, p. 6). 

The figures for the United States as shown in 

table 27 are included in the total for North America 

in table 28. On the basis of identified resources, the 

United States contains about one-sixth of world 

resources; on the basis of total resources, the United 

States contains about one-fifth of world resources. 

Table 28 shows clearly that Asia contains most 

of the world's total coal resources. This tonnage is 

concentrated in the U.S.S.R. and China, both of 

which are important coal-producing countries. The 

table also shows that the coal resources of Europe 

have been well established by mapping and exploration, and that estimates will not be greatly increased 

by future work. Finally, table 28 shows that Africa, 

Oceania, and South America contain small resources as compared with the rest of the world, but 

that the quantities assumed to be present are sufficient to justify continued exploration and development. (See Averitt, 1969, p. 81-85.) 

REFERENCES CITED 

Abernathy, G. E., Jewett, J. M., and Schoewe, W. H., 1947, 

Coal reserves in Kansas: Kansas Geol. Survey Bull. 70, 

pt. 1, 20 p. 

Abernethy, R. F., and Gibson, F. H., 1963, Rare elements in 

coal: U.S. Bur. Mines Inf. Girc. 8163, 69 p. 

Abernethy, R. F., Peterson, M. J., and Gibson, F. H., 1969a, 

Major ash constituents in United States coals: U.S. Bur. 

Mines Rept. Inv. 7240, 9 p. 

--- 1969b, Spectrochemical analysis of coal ash for trace 

elements: U.S. Bur. Mines Rept. Inv. 7281, 30 p. 

Arndt, H. H., Averitt, Paul, Dowd, James, Frendzel, D. J., 

and Gallo, P. A., 1968, Coal, in Mineral resources of the 

Appalachian region: U.S. Geol. Survey Prof. Paper 580, 

p. 102-133. 

Ashley, G. H., 1944, Mineral resources, Pt. 2 of Pennsylvania's mineral heritage: Pennsylvania Dept. Int. 

Affairs, p. 73--200. 

--- 1946, Anthracite reserves: Pennsylvania Topog. and 

Geol. Survey Prog. Rept. 130, 13 p. 

Ashmead, D. C., 1926, Anthracite losses and reserves in 

Pennsylvania: Pennsylvania Geol. Survey, 4th ser., Bull. 

M8, 71 p. 

Averitt, Paul, 1964, Coal, in Mineral and water resources of 

Utah: U.S. 88th Gong., 2d sess., Comm. Interior and Insular Affairs, p. 39-51 [reprinted in Bull. 73 of Utah 

Geol. and Mineralog. Survey]. 

--- 1965, Coal, in Mineral potential of eastern Mon,tanaa basis for future growth: U.S. 89th Gong., 1st sess., 

Comm. Interior and Insular Affairs, p. 9-25. 

--- 1969, Coal resources of the United States-January 

1, 1967: U.S. Geol. Survey Bull. 1275, 116 p. 

Averitt, Paul, Breger, I. A., Gluskoter, H. J., Swanson, V. 

E., and Zubovic, Peter, 1972, Minor elements in coala selected bibliography, July 1972, in Geological Survey 

research 1972: U.S. Geol. Survey Prof. Paper 800-D, 

p. D169-D171. 

Averitt, Paul, and O'Sullivan, R. B., 1969, Mineral fuels and 

associated resources--Coal, in Mineral and water resources of Arizona: U.S. 90th Cong., 2d sess. Comm. Interior and Insular Affairs, p. 59-69 [reprinted in 

Arizona Bur. Mines Bull. 180]. 

Barnes, F. F., 1951, A review of the geology and coal resources of the Bering River coal field, Alaska: U.S. 

Geol. Survey Circ. 146, 11 p. 

-- 1961, Coal fields of the United States-Sheet 2, 

Alaska: U.S. Geol. Survey Map, scale 1:5,000,000. 

--- 1967, Coal resources of Alaska: U.S. Geol. Survey 

Bull. 1242-B, p. Bl-B36. 

Beikman, H. M., Gower, H. D., and Dana, T. A. M., 1961, 

Coal reserves of Washington: Washington Div. Mines 

and Geology Bull. 4 7, 115 p. 
COAL 141 

Berryhill, H. L., Jr., Brown, D. M., Brown, Andrew, and 

Taylor, D. A., 1950, Coal resources of Wyoming: U.S. 

Geol. Survey Circ. 81, 78 p. 

Berryhill, H. L., Jr., Brown, D. M., Burns, R.N., and Combo, 

J. X., 1951, Coal resources map of Wyoming: U.S. Geol. 

Survey Coal Inv. Map C-6. 

Brant, R. A., 1953, Lignite resources of North Dakota: U.S. 

Geol. Survey Circ. 226, 78 p. 

Brant, R. A., and DeLong, R. M., Coal resources of Ohio: 

Ohio Div. Geol. Survey Bull. 58, 245 p. 

Brown, Andrew, Berryhill, H. L., Jr., Taylor, D. A., and 

Trumbull, J. V. A., 1952, Coal resources of Virginia: 

U.S. Geol. Survey Circ. 171, 57 p. 

Brown, D. M., 1952, Lignite resources of South Dakota: 

U.S. Geol. Survey Circ. 159, 18 p. 

Butts, Charles, and Gildersleeve, Benjamin, 1948, Geology 

and mineral resources of the Paleozoic area in northwest 

Georgia : Georgia Geol. Survey Bull. 54, 176 p. 

Cady, G. H., 1952, Minable coal reserves of Illinois: Illinois 

Geol. Survey Bull. 78, 138 p. 

Cohee, G. V., Burns, R. N., Brown, Andrew, Brant, R. A., 

and Wright, Dorothy, 1950, Coal resources of Michigan: 

U.S. Geol. Survey Circ. 77, 56 p. 

Combo, J. X., Brown, D. M., Pulver, H. F., and Taylor, D. 

A., 1949, Coal resources of Montana: U.S. Geol. Survey 

Circ. 53, 28 p. 

Combo, J. X., Holmes, C. N., and Christner, H. R., 1950, 

Map showing coal resources of Montana: U.S. Geol. 

Survey Coal Inv. Map C-2. 

Culbertson, W. C., 1964, Geology and coal resources of the 

coal-bearing rocks of Alabama: U.S. Geol. Survey Bull. 

1182-B, p. B1-B79. 

Dapples, E. C., and Hopkins, M. E., eds., 1969, Environments 

of coal deposition: Geol. Soc. America Spec. Pub. 114, 

204 p. 

DeCarlo, J. A., Sheridan, E. T., and Murphy, Z. E., 1966, 

Sulfur content of United States coals: U.S. Bur. Mines 

Inf. Circ. 8312, 44 pp. 

Doelling, H. H., 1970, Alton coal field: Utah Geol. and Mineralog. Survey open-file report, 64 p. 

--- 1971a, Wasatch Plateau coal field: Utah Geol. and 

Mineralog. Survey open-file report, 170 p. 

-- 1971b, Book Cliffs coal field: Utah Geol. and Mineralog. Survey open-file report, 185 p. 

--- 1971c, Emery coal field: Utah Geol. and Mineralog. 

Survey open-file report, 78 p. 

--- 1971d, Sevier-Sanpete, Goose Creek [and] Lost Creek 

coal fields: Utah Geol. and Mineralog. Survey open-file 

report, 84 p. 

--- 1971e, Henry Mountains [and] Kolob-Harmony coal 

fields: Utah Geol. and Mineralog. Survey open-file report, 160 p. 

--- 1971f, Coalville, Tabby Mountain, Henrys Fork, Sego, 

[and] LaSal-San Juan coal fields: Utah Geol. and Mineralog. Survey open-file report, 171 p. 

Doelling, H. H., and Graham, R. L., 1970, Kaiparowits 

Plateau coal field: Utah Geol. and Mineralog. Survey 

open-file report, 140 p. 

--- 1971, Vernal coal field: Utah Geol. and Mineralog. 

Survey open-file report, 88 p. 

Eavenson, H. N., 1942, The first century and a quarter of 

American coal industry: Baltimore, Md., Waverly Press, 

Inc., 701 p. 

Haley, B. R., 1960, Coal resources of Arkans·as, 1954: U.S. 

Geol. Survey Bull. 1072-P, p. 795-831. 

Headlee, A. J. W., and Nolting, J. P., Jr., 1940, Characteristics of minable coals of West Virginia: West Virginia 

Geol. Survey Rept., v. 13, 272 p. 

Jlinds, Henry, 1913, The coal deposits of Missouri: Missouri 

Bur. Geology and Mines, 2d ser., v. 11, 503 p. 

Hodgkins, J. A., 1961, Soviet power-Energy resources, production and potentials: Englewood Cliffs, N. J., PrenticeHall, Inc., 190 p. 

Huddle, J. W., Lyons, E. J., Smith, H. L., and Ferm, J. C., 

1963, Coal reserves of eastern Kentucky: U.S. Geol. 

Survey Bull. 1120,247 p. 

Johnson, V. H., 1946, Coal deposits on Sand and Lockout 

Mountains, Dade and Walker Counties, Georgia: U.S. 

Geol. Survey Coal Inv. Map. 

Landis, E. R., 1959, Coal resources of Colorado: U.S. Geol. 

Survey Bull. 1072-C, p. 131-232. 

--- 1965, Coal resources of Iowa: Iowa Geol. Survey 

Tech. Paper 4, 141 p. 

Luther, E. T., 1959, The coal reserves of Tennessee: Tennessee Div. Geology Bull. 63, 294 p. 

Mapel, W. J ., 1967, Bituminous coal resources of Texas: 

U.S. Geol. Survey Bull. 1242-D, p. D1-D28. 

Mason, R. S., 1969, Coal, in Mineral and water resources of 

Oregon: U.S. 90th Gong., 2d sess., Comm. Interior and 

Insular Affairs, p. 272-280. 

Mason, R. S., and Erwin, M. I., 1955~ Coal resources of 

Oregon: U.S. Geol. Survey Circ. 362, 7 p. 

Peirce, H. W., Keith, S. B., and Wilt, J. C., 1970, Coal, oil, 

natural gas, helium, and uranium in Arizona: Arizona 

Bur. Mines Bull. 182, 289 p. 

Perkins, J. M., and Lonsdale, J. T., 1955, Mineral resources 

of the Texas Coastal Plain [prelim. rept.]: Texas Univ. 

Bur. Econ. Geology Mineral Resources Circ. 38, 65 p. 

Read, C. B., Duffner, R. T., Wood, G. H., and Zapp, A. D., 

1950, Coal resources of New Mexico: U.S. Geol. Survey 

Circ. 89, 24 p. 

Reese, J. F., arid- Sisler, J. D., 1928, Coal resources, introductory volume, pt. 3 of Bituminous coal fields of Pennsylvania: Pennsylvania Geol. Survey, 4th ser., Bull. 

M6, 153 p. 

Reinemund, J. A., 1949, Geology of the Deep River coal 

field, Chatham, Lee, and Moore Counties, North Carolina: U.S. Geol. Survey Coal Inv. Map. 

--- 1955, Geology of the Deep River coal field, North 

Carolina: U.S. Geol. Survey Prof. Paper 246, 159 p. 

Robertson, C. E., 1971, Evaluation of Missouri's coal resources: Missouri Geol. Survey Rept. Inv. 48, 92 p. 

Rothrock, H. E., 1950, A summary and critique of the esti .. 

mates of Pennsylvania anthracite reserves, in Pennsylvania Acad. Sci., Symposium on mineral resources in 

Pennsylvania: Pennsylvania Acad. Sci. Proc., v. 24, p. 

192-197. 

Schoewe, W. H., 1952, Coal resources of the Cretaceous System (Dakota Formation) in central Kansas: Kansas 

Geol. Survey Bull. 96, pt. 2, p. 69-156. 

--- 1958, Economic geography; mineral resources, pt. 4 

of The geography of Kansas: Kansas Acad. Sci. Trans., 

v. 61, no. 4, p. 359-468 [1959]. 

Schopf, J. M., 1948, Variable coalification-the processes involved in coal formation: Econ. Geology, v. 43, no. 3, 

p. 207-225. 

--- 1956, A definition of coal: Econ. Geology, v. 51, no. 

6, p. 521-527. 
142 UNITED STATES MINERAL RESOURCES 

Searight, W. V., 1967, Coal, in Mineral and water resources 

of Missouri: U.S. 90th Cong., 1st sess., Senate Doc. 19, 

p. 235-243. 

Simon, J. A., 1965, Illinois pioneers in coal geology research: 

Coal Mining and Processing, v. 2, no. 8, p. 31-35. 

Spencer, F. D., 1953, Coal resources of Indiana: U.S. Geol. 

Survey Circ. 266, 42 p. [1954]. 

Struble, R. A., Collins, H. R., and Kohout, D. L., 1971, Deepcore investigation of low-sulfur coal possibilities in 

southeastern Ohio: Ohio Div. Geol. Survey Rept. Inv. 81, 

29 p. 

Sullivan, J. W., 1942, The geology of the Sand-Lookout 

Mountain area, northwest Georgia: Georgia Geol. Survey Inf. Circ. 15, 68 p. 

Eun, S. C., Vasquez-Rosas, H., and Augenstein, D., 1971, 

Pennsylvania anthracite refuse--a literaturP. survey on 

chemical elements in coal and coal refuse: Pennsylvania 

State Univ. Spec. Research Rept. SR-83, 72 p. 

Toenges, A. L., Turnbull, L. A., Neale, A., Schopf, J. M., 

Abernathy, R. F., and Quinn, A. W., 1948, Investigation 

of meta-anthracite in Newport and Providence Counties, 

Rhode Island; petrography, chemical characteristics, and 

geology of the deposits: U.S. Bur. Mines Rept. Inv. 

4276, 37 p. 

Trumbull, J. V. A., 1957, Coal resources of Oklahoma: U.S. 

Geol. Survey Bull. 1042-J, p. 307-382. 

--- 1960, Coal fields of the United States, exclusive of 

Alaska-Sheet 1: U.S. Geol. Survey Map, scale 

1:500,000. 

U.S. Bureau of Mines, 1924-1931, Mineral resources of the 

United States [annual volumes for the years indicated]: 

Washington, U.S. Govt. Printing Office. 

--- 1932-1970, Minerals yearbooks [annual volumes for 

the years indicated]: Washington, U.S. Govt. Printing 

Office. 

--- 1971, Strippable reserves of bituminous coal and 

lignite in the United States: U.S. Bur. Mines Inf. Circ. 

8531, 148 p. 

-- 1972, Weekly coal report 2853: Pittsburgh, U.S. Bur. 

Mines, 3 p. 

U.S. Geological Survey, 1886-1923, Mineral resources of the 

United S.tates [annual volumes for the years indicated]: 

Washington, U.S. Govt. Printing Office. 

Walker, F. E., and Hartner, F. E., 1966, Forms of sulfur 

in U.S. coals: U.S. Bur. Mines lnf. Circ. 8301, 51 p. 

Zubovic, Peter, 1966a, Physicochemical properties of certain 

minor elements as controlling factors in their distribution in coal, [Chap.] 13, in Gould, R. F., ed., Coal science-Am. Conf. Science, University Park, Pa., 1964: 

Washington, D. C., Am. Chern. Soc., Advances Chemistry 

Ser. 55, p. 211-231. 

--- 1966b, Minor element distribution in coal samples of 

the Interior Coal Province, [Chap.] 14, in Gould, R. F., 

ed., Coal science-Am. Conf. Science, University Park, 

Pa., 1964: Washington, D. C., Am. Chern. Soc., Advances Chemistry Ser. 55, p. 232-247. 

Zubovic, Peter, Sheffey, N. B., and Stadnichenko, Taisia, 

1967, Distribution of minor elements in some coals in 

the western and southwestern regions of the Interior 

Coal Province: U.S. Geol. Survey Bull. 1117-D, 33 p. 

Zubovic, Peter, Stadnichenko, Taisia, and Sheffey, N. B., 

1960a, Relation of the minor element content of coal 

to possible source rocks, in Short papers in the geological sciences : U.S. Geol. Survey Prof. Paper 400-B, p. 

B82-B84. 

--- 1960b, The association of some minor elements with 

organic and inorganic phases of coal, in Short papers 

in the geological sciences: U.S. Geol. Survey Prof. Paper 

400-B, p. B84-B87. 

--- 1960c, Comparative abundance of the minor elements 

in coals from different parts of the United States, in 

Short papers in the geological sciences: U.S. Geol. Survey Prof. Paper 400-B, p. B87-B88. 

--- 1961a, Chemical basis of minor-element associations 

in coal and other carbonaceous sediments, in Short 

papers in the geologic and- hydrologic sciences: U.S. 

Geol. Survey Prof. Paper 424-D, p. D345-D348. 

--- 1961b, Geochemistry of minor elements in coals of the 

Northern Great Plains coal province: U.S. Geol. Survey Bull. 1117-A, p. A1-A58. 

--- 1964, Distribution of minor elements, in coal beds of 

the Eastern Interior region: U.S. Geol. Survey Bull. 

1117-B, p. B1-B41. 

--- 1966, Distribution of minor elements in coals of the 

Appalachian region: U.S. Geol. Survey Bull. 1117-C, p. 

C1-C37. 
UNITED STATES MINERAL RESOURCES 

COBALT 

By JoHN S. VHAY, DoNALD A. BROBST, and ALLEN V. HEYL 

CONTENTS 

Page 

Abstract of conclusions -------------------------- 143 

Introduction ------------------------------------ 148 

Exploitation ------------------------------------ 144 

Geologic environment ---------------------------- 145 

Geochemistry -------------------------------- 145 

Cobalt minerals ----------------------------- 146 

Types of deposits ---------------------------- 146 

Hypogene deposits associated with mafic intrusive igneous rocks ------------------ 146 

Contact metamorphic deposits ------------- 147 

Lateritic deposits ------------------------ 148 

Massive sulfide deposits in metamorphic rocks 148 

Hydrothermal deposits ------------------- 149 

Strata-bound deposits -------------------- 150 

Chemical 'precipitates -------------------- 150 

Resources --------------------------------------- 150 

Identified resources -------------------------- 150 

Hypothetical resources ----------------------- 151 

Speculative resources ------------------------ 152 

Prospecting techniques --------------------------- 152 

Problems for research ---------------------------- 153 

References cited --------------------------------- 153 

TABLES 

Page 

29. World production of cobalt in 1969 _____ ._____ 144 

30. Average cobalt content of igneous rocks ------ 145 

31. Cobalt minerals ---------------------------- 146 

32. Identified resources of cobalt in the United 

States ----------------------------------- 150 

33. Identified resources of cobalt in the world ____ 151 

ABSTRACT OF CONCLUSIONS 

Cobalt is a hard, silvery white metal of strategic importance in the production of high-temperature alloys, permanent magnets, and tool steels. Currently the United States 

consumes about 15 million pounds of the world's annual 

cobalt production of 45 million pounds, but the domestic 

production, only about 3 million pounds, is derived from 

recycled scrap and the byproduct of iron mining in Pennsylvania. That the amount of cobalt mined annually in the 

United States is so small is more a function of economic and 

technological problems than the lack of ore deposits containing cobalt. Nearly all the cobalt that now reaches the world 

markets is the byproduct of mining sulfide ores of associated 

metals, chiefly copper, nickel, and iron in central Africa, 

Canada, and Finland. Large potential supplies of cobalt are 

in lateritic iron-nickel deposits of tropical regions. More 

than 1 billion pounds of cobalt is in the identified resources 

of the United States, chiefly in various types of deposits of 

sulfide ore in the Appalachian and midcontinent regions. Published data indicate that the identified cobalt resources of the 

world contain more than 9.9 billion pounds of the element. 

Additional large amounts of cobalt are in the manganese 

nodules of the sea floor. The world's hypothetical and speculative resources of cobalt likely amount to many more billions of pounds of metal. 

INTRODUCTION 

Cobalt (Co) is a hard, moderately malleable and 

ductile, strongly magnetic, silvery, white metal of 

great commercial importance in metallurgical applications. The major uses of cobalt in the United States 

are, in order of consumption : ( 1) high-temperature 

alloys, the superalloys, (2) permanent-magnet alloys, (3) cutting and wear-resistant alloys, (4) tool 

steels, ( 5) miscellaneous alloys, ( 6) pigments and 

driers for paint, ink, lacquer, and varnish, (7) 

ground-coat frit for enameling, (8) catalysts in the 

chemical and petrol~um industries, (9) ceramic 

glazes, ( 10) additives and supplements to sheep and 

cattle feed, and ( 11) as radioactive Co60 in several 

medical applications. 

In 1969 the United States consumed about 15 million pounds of the world's estimated production of 

45 million pounds of cobalt (table 29). Domestic 

sources provided only about 3 million pounds, derived from recycled scrap and as a moderate-yield 

byproduct from iron mines in southeastern Pennsylvania (DeHuff, 1971, p. 399). The remaining domestic needs of 12 million pounds were filled by imports 

from ores originating chiefly in Zaire, Canada, 

Morocco, and Zambia. 

U.S. GEOL. SURVEY PROF. PAPER 820 

143 
144 UNITED STATES MINERAL RESOURCES 

TABLE 29.-World production of cobalt in 1969' 

[From DeHuff (1971, p. 401). Short tons of contained cobalt; "'• estimate] 

Country 

Australia ---- ________________________ _ Canada _ ------_______________________ _ 

Cuba --------------------------------- Finland ------------------------------- Germany (lVest) ---------------------- 11orocco ------------------------------- U.S.S.R. ------------------------------ Zaire _________________ ---------------- Zambia __________________ ---___ - _____ _ 

Total ---------------------------

Production 

.. 330 

1,602 

1,700 

1,800 

864 

"'1,700 

"'1,650 

"'11,000 

1,650 

22,296 

1 Excluding Bulgaria, East Germany, Poland, and the United States. 

The great disparity between domestic production 

and consumption, particularly during periods of 

national emergency, is a matter of serious concern. 

This disparity may well increase in the future. According to Reno (1970, p. 270), the annual demand 

for cobalt in the United States in the year 2000 is 

estimated to be at least 18.6 million pounds and possibly as much as 30.5 million pounds. Most of this 

metal will have to be imported, with the attendant 

costs in foreign exchange, unless substitutes can be 

developed or available domestic sources can be 

utilized more efficiently. 

The forecast of cumulative demand for cobalt in 

the United States from 1968 to the year 2000 ranges 

from 520 to 670 million pounds (Reno, 1970, p. 273). 

The world's cumulative demand for cobalt for the 

same period ranges from 1,645 to 1,997 million 

pounds. The potential supply of primary cobalt in 

the world at current prices is more than 8-10 times 

the cumulative total of domestic demand and more 

than 2.5 times the cumulative total of world demand. 

This supply, however, is available only at a rate of 

40-50 million pounds per year, chiefly as a byproduct of nickel and copper mining. Supplies are thus 

tied to production of the major product, but production of these elements will also increase. Under current competitive economic conditions, future supplies will continue to come at no relative increase in 

current price (Reno, 1970, p. 273) from sulfide deposits in Zai:re, Canada, Morocco, and Zambia, and 

from the laterites of New Caledonia, Cuba, Indonesia, the Philippines, and other tropical lands. Beginning in 1954, however, the consumption of cobalt 

in other nations has increased at accelerating rates 

far in excess of that in the United States (Piedboeuf, 

1961, p. 3). The economic competition for available 

cobalt, especially under emergency conditions, perhaps will become greater in the future. 

Alleviation of the increasing demand for the production of cobalt may possibly be found in the discovery and development of acceptable substitutes and 

the increased recycling of scrap. So far as is known, 

however, many of the alternate materials proposed 

as substitutes for cobalt also are strategic industrial 

metals, including nickel, and for some applications, 

vanadium, molybdenum, tungsten, and chromium. 

No substitutes are known, however, for the use of 

cobalt in carbides and in some tool steels (Reno, 

1970, p. 269). In other applications, several organic 

and mineral catalysts and driers can be used in the 

place of cobalt, but only at a loss in effectiveness. 

The same is true of substitutes for Co60 as a source of 

gamma radiation. 

Few published data are currently available on the 

quantities of cobalt-bearing scrap that are recovered 

and reused in the United States. The quantity may 

be large, inasmuch as increasing volumes of cobaltbearing superalloy are being used and the service 

life of many of the products made from these alloys 

is relatively short. Permanent magnets are also a 

potential source of secondary cobalt. According to 

Reno (1970, p. 268), export statistics show that at 

least 1.5 million pounds of cobalt-bearing scrap is 

generated and shipped out of the United States 

annually. 

EXPLOITATION 

Cobalt is now produced primarily as a byproduct 

of the mining and metallurgical processing of copper, nickel, and silver ores. More than half the 

cobalt produced comes from the strata-bound deposits of copper in central Africa. Major production 

also comes from sulfide ores of copper, nickel, and 

iron associated with mafic rocks in Canada and Finland. Currently, only the mines at Bou Azzer, Morocco, are producing cobalt as a major product from 

vein deposits. 

In the United States some cobalt has been produced 

intermittently for more than 100 years. One of the 

principal early domestic sources of cobalt production 

was the Gap nickel mine, Lancaster County, Pa. 

Joseph Wharton operated the mine until 1893 and 

smelted the ore containing nickel, copper, and 0.1 

percent cobalt, at the Camden Nickel Works. Records 

indicate that a total of 143,499 pounds of cobalt oxide 

was produced from 1869 to 1893. Wharton's process 

for commercially recovering small amounts of cobalt 

from mixed sulfide ores in the mafic rocks served as 

a basis for some modern technology used in Canada 

and Europe. In the lead district of southeast Missouri, the Mine La Motte and Fredericktown areas 

also have been leading producers of cobalt-at least 

5.2 million pounds from 1844 to 1961. The Madison 

mine, near Fredericktown, produced 2.8 million 
COBALT 145 

pounds of cobalt for the national stockpile of strategic minerals. from 1954 to 1961 (Cornwall and 

Vhay, 1967, p. 70). 

About 400,000-600,000 pounds of cobalt is produced annually from pyrite as a byproduct of mining 

magnetite at Cornwall, Pa. (Andrews, 1962, p. 161). 

The mineral production from Cornwall and the 

Grace mine, near Morgantown, Pa., is now virtually 

the only primary source of domestic cobalt. 

Small amounts of cobalt were produced from the 

veins of the Blackbird district, Idaho, during World 

War I, and about 14 million pounds was produced 

from 1951 to 1959, when the mines closed. The mines 

were still inactive in 1972. According to Andrews 

( 1962, p. 162), the Magnesia Talc Co., at Burlington, 

Vt., has produced concentrates containing cobalt and 

nickel as a product in the froth flotation of talc. Not 

much information is available, but the concentrates 

are believed to contain 0.015 percent cobalt and 0.2 

percent nickel. 

Small production of cobalt has been reported from 

other places in earlier times-near Chatham, Conn., 

the Goodsprings and Table Mountain districts, N evada, and the Quartzburg district, Oregon. 

The production of cobalt from laterite ores has 

been small during the past few decades, but these 

deposits, which can be mined at relatively low cost 

by open-pit methods, are destined to become increasingly important. The cobaltiferous laterite, or asbolane, deposits of New Caledonia intermittently have 

been the leading world producers of cobalt. Although 

production from this source has been insignificant 

since 1911, the total cobalt reserves are estimated to 

be large and readily available for renewed production. In more recent years, chiefly since the beginning of World War II, cobalt has been recovered 

from laterite ores in Cuba. It is believed that with 

proper economic incentives this production can be 

increased substantially. Similar large deposits occur 

in the Philippines, Indonesia, the U.S.S.R., Western 

United States, Guatemala, and many other countries. 

The history of cobalt production clearly indicates 

that large ore deposits containing some small 

amounts of cobalt are widespread in the world, but 

virtually none are workable for cobalt content alone. 

The current utilization of the world's cobalt is primarily a matter of economics and technology, and 

not a question of geologic availability. 

Mining, smelting, and other environmental considerations in the production of cobalt are identical 

with those considered in the chapters of this volume 

dealing with iron, copper, and nickel. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Cobalt (atomic number, 27; atomic weight, 58.93) 

is a metallic element whose abundance in the earth's 

crust is estimated to be about 20 ppm (parts per 

million). It is a simple element consisting in terrestrial materials almost exclusively of the single stable 

nuclide Co59 except for minor traces of fission-produced and cosmic-ray-produced Co60 (Rankama, 

1963, p.· 393-394). In addition, nine radioisotopes of 

mass numbers 54-58 inclusive, and 60, 61, 62, and 

64, have been made artificially, of which Co60 is a 

highly important source of radioactivity (Rankama, 

1963, p. 393). The ionic radius of cobalt in sixfold 

coordination is 0.72A for Co2 + and 0.63A for Co3 +, 

closely similar to the ionic radii of Mg2 +, Mn4 +, 

Fe2 +, Fe3 +, Ni 2 +, and possibly Zn2 +, with all of 

which it is commonly associated in nature. 

The principal concentrations of cobalt are found 

in mafic and ultramafic igneous rocks. As shown in 

table 30, the cobalt content progressively decreases 

TABLE 30.-Average cobalt content of igneous rocks 

[Compiled by J. S. Vhay] 

Roek type 

(listed in order of 

increasing differentiation) 

Ultramafic rocks ------------

Gabbro --------------------- Basalt ---------------------

Diabase -------------------- Intermediate igneous rocks - _ 

Felsic rocks ----------------

Co Ni Ni/Co 

(ppm) (ppm) 

270 1,900 7 

51 133 2.6 

41 102 2.5 

31 65 2.3 

14 27 1.9 

5 5.7 1.1 

in a differentiation series from ultramafic to acidic 

rocks. The ratio of nickel to cqbalt also decreases 

during differentiation, chiefly because cobalt enters 

the lattice of early crystallizing magnesium silicates 

less readily than nickel, which has an ionic radius 

closer to magnesium. 

The concentrations of cobalt in sedimentary rocks 

are not well known, in part because of the past difficulty in analysis for the small amounts present in 

most types of rock. Average figures from a variety 

of sources indicate about 4 ppm Co in sandstone, 

6 ppm in carbonate rocks, and about 40 ppm for 

shale, clay, mudstone, and siltstone. Few analyses of 

cobalt in iron-rich sedimentary rocks are available; 

however, Krauskopf (1955) indicated a range of 

20-300 ppm. The cobalt content of phosphorite is 

reported between 2 and 50 ppm (Krauskopf, 1955). 

Somewhat higher concentrations are reported in 

sedimentary deposits that are rich in organic carbon. As much as 500 ppm cobalt has been reported 

in ashed carbonaceous shale, 148 ppm in ashed coal, 
146 UNITED STATES MINERAL RESOURCES 

490-3,280 ppm in ashed petroleum (Krayushkin and 

others, 1964), and as much as 90,000 ppm, or 9 percent, in ashed asphalt. 

During the formation of metamorphic rocks, apparently little movement and concentration of cobalt 

takes place. Thus, the cobalt content of different 

metamorphic rocks depends almost entirely on the 

amount of cobalt in the original igneous or sedimentary rock source. Metamorphic rocks derived from 

ultramafic and mafic rocks average about 100 ppm 

Co; in contrast, gneissic granite contains only 16 

ppm Co, and metasedimentary rocks average about 8 

ppm. An exception to the general stability of cobalt 

during metamorphism is involved with the proposed 

origin of the sulfide deposits at Thompson, Manitoba, 

described briefly in a subsequent section. 

Under oxidizing conditions, cobalt displays a 

strong tendency to concentrate with manganese 

(Rankama and Sahama, 1950, p. 650; Goldschmidt, 

1954, p. 627, 632-642 ; Mason, 1958, p. 17 4 ; Goldberg, 1954; and Krauskopf, 1955). Mero (1965), 

describing the widespread occurrence of manganese 

nodules on the bottom of the Pacific Ocean, pointed 

out that Mn02 precipitates as submicroscopic colloidal particles that "scavenge" any nickel, copper, 

cobalt, zinc, and molybdenum in the water. Cobalt is 

also abundant in residual soils derived from the deep 

weathering of manganiferous sedimentary rocks in 

a number of areas, particularly in the Eastern 

United States. 

The concentration of cobalt, particularly with 

manganese oxides, and the separation of cobalt from 

nickel are especially pronounced in laterite deposits 

that occur over deeply weathered mafic and ultramafic rocks in tropical areas where rainfall is abundant (Engineering and Mining Journal, 1968). During the weathering process, magnesia and silica are 

leached downward or are removed. Nickel also migrates downward, whereas iron, manganese, cobalt, 

and alumina are residually enriched near the surface (Banning and others, 1962; Hotz, 1961; McMillan and Davis, 1955; and Pecora, 1944). In New 

Caledonia, the cobalt occurs in nodules, lenses, and 

small veins of cobaltiferous wad, or asbolane, commonly in a matrix of red iron-rich clay that does not 

contain appreciable nickel (Andrews, 1962, p. 187). 

In Cuba, both nickel and cobalt commonly occur in 

the same ore bodies. 

COBALT MINERALS 

Cobalt is a major or important constituent of approximately 70 minerals (Andrews, 1962, p. 6-12), 

and is a minor or trace constituent of several hundred more, particularly those containing Ni, Fe2+, 

or Mn4+ (Fleischer, 1955). Minerals that are relatively high in cobalt and have been mined or concentrated for their cobalt content are listed in table 

31. In addition, 27 cobalt sulfides, selenides, sulfoTABLE 31.--Cobalt minerals 

Mineral Percent cobalt 

Linnaeite, C<>aS, --------------------58.0 (theoretical) 

Siegenite, (Co,Ni)aS, ----------------20.4-26.0 

Carrollite, (C02Cu) S, ---------------35.2-36.0 

Cobaltite, (Co,Fe) AsS ______________ 26.0-32.4 

Saffiorite, CO,Fe) As2 ----------------13.0-18.6 Glaucodot, (Co,Fe)AsS _____________ 12.0-31.6 

Skutterudite, (Co,Fe) As3 ____________ 10.9-20.9 . 

Heterogenite, CoO ( OH) -------------64.1 (theoretical) 

"Asbolite," (Manganese oxides + Co)- .5-5.0 

Erythrit.P, (Co,Ni)3(As04)2•8H20 ____ 18.7-26.3 

Gersdorffite, (Ni,Co)AsS ------------ (low) 

Pyrrhotite, (Fe,Ni,Co)x-lSx ---------- 1.00 (maximum) 

Pentlandite, (Fe,Ni,Co)DSs ----------- 1.50 (max!mum) Pyrite, (Fe,Ni,Co) S2 ________________ 13.00 (max~mum 

Sphalerite, Zn(Co) S ---------------- .30 (max~mum) Arsenopyrite, Fe(Co)AsS ----------- .38 (maxtmum) 

Manganese oxide minerals ----------- .10-1.00 (or more) 

salts, and hydrated sulfates and arsenates contain 

relatively large amounts of cobalt, but are generally 

of such rare occurrence as to have no commercial 

importance. (See Fleischer, 1955; Fryklund and 

Fletcher, 1956; and Burnham, 1959.) 

TYPES OF DEPOSITS 

Cobalt is recovered from mineral deposits both as 

a principal product and as a byproduct. Most of the 

world's supply of cobalt reaches the market as a byproduct of mining copper, nickel, and silver ores; 

smaller amounts are byproducts of iron, chromium, 

lead, zinc, urani urn, and manganese. In this discussion of cobalt deposits, the geology will be emphasized, but the geologic features of specific cobalt 

deposits will be reviewed only briefly. Further information and references to many deposits are available in works by Vhay (1952), Andrews (1962), and 

Cornwall (1966), and in other chapters in this volume about commodities with which cobalt is 

associated. 

Cobalt deposits may be classified geologically according to their environment of genesis or occurrence: (1) hypogene deposits associated with mafic 

intrusive igneous rocks; (2) contact metamorphic 

deposits also associated with mafic rocks; (3) lateritic (weathered) deposits; ( 4) massive sulfide 

deposits in metamorphic rocks, chiefly of volcanosedimentary origin ; ( 5) hydrothermal deposits of 

several varieties; (6) strata-bound deposits; and (7) 

deposits formed as chemical precipitates. 

HYPOGENE DEPOSITS ASSOCIATED W,ITH MAFIC 

INTRUSIVE IGNEOUS ROCKS 

Commercial bodies of massive and disseminated 
COBALT 147 

iron-nickel-copper sulfides containing cobalt are an 

important type of hypogene deposit associated with 

intrusive mafic igneous rocks. Large typical deposits 

of this kind occur in the famous Sudbury district of 

Ontario, where the ore has an average cobalt content 

of 0.07 percent (Andrews, 1962, p. 93). The suite of 

ore minerals consists of pyrrhotite, pentlandite, pyrite, marcasi~, magnetite, cobaltite, and gersdorffite in pods, lenses, veins, stringers, and disseminated 

grains in a layered sequence of norite, quartz diorite, micropegmatite, and rocks of transitional composition and texture. The igneous host rocks.of Precambrian age occur in an elliptical basin about 37 miles 

long and 17 miles wide. The ore deposits are large : 

A decade ago Andrews ( 1962, p. 93) reported proved 

reserves of more than 250 million tons of ore. The 

origin of these and similar deposits elsewhere in the 

world is complex and hotly debated. Cornwall ( 1966, 

p. 27-29) reviewed the hypotheses of origin ranging 

from segregation by differentiation in situ to hydrothermal deposition, and even to impact by meteorite. 

(See "Nickel.") More recently, Cheney and Lange 

(1967) have offered a summary of a process of sulfurization as an explanation of the origin of the Sudbury-type deposits of nickel and cobalt. 

Deposits of the Sudbury type, however, are not 

restricted to Canada. Indeed, similar deposits are 

known in the United States, and some have been 

known for a long time. The Gap nickel mine, Lancaster County, Pa., is in the base of a metamorphosed 

gabbroic intrusive body. The ore is nickel-copper 

sulfide minerals that contain 0.1-0.3 percent cobalt. 

An estimated 1 million tons of ore remains at the old 

mine. Large deposits of this type also occur near 

Union, Maine, and in the keel of the Moxie LakeMoosehead Lake gabbro body (Young, 1968, p. 129, 

134). The huge deposits of the Katahdin Iron Works 

area are in gabbro and norite where the cobalt content of much mineralized rock is 0.05-0.1 percent. 

Samples from several bodies of mafic rock in the 

Calais area, Maine, indicate a cobalt content of 0.1 

percent. 

Cobalt is associated with pyrrhotite deposits in 

mafic rocks in Connecticut, at West Torrington and 

in the Mount Prospect area near Litchfield ( Cameron, 1943), and in Massachusetts, at Dracut (Dennen, 

1943). At the Phillips mine and vicinity near Peekskill, N.Y., gabbro of Precambrian age has mineralized rock that contains 0.003-0.24 percent cobalt. 

Other deposits of this type are reported in Washington, Oregon, and California. 

Huge concentrations of copper-nickel sulfides occur in the lower part of the Duluth Gabbro Complex 

southeast of Ely, Minn. Samples from three drill 

cores contain 0.038 percent cobalt, 0.39 percent copper, and 0.14 percent nickel (Grosh and others, 

1955). It is now estimated that about 14 billion tons 

of rock containing 0.25 percent total copper and 

nickel occur in a southwest trend 35 miles long (P. 

K. Sims, Director, Minnesota Geol. Survey, written 

commun., Sept. 22, 1972). No cobalt values are available for the large tonnage reported, but if the entire 

deposit contains an average of 0.01 percent cobalt--

one-fourth of that reported in 1955-then about 3 

billion pounds of cobalt would be available. Current 

knowledge of thesE: deposits suggests that identified 

resources of 1 billion pounds of cobalt are a conservative estimate. 

The mafic rocks of the Stillwater Complex in Montana contain some bodies of a few million tons rich 

in nickeliferous sulfides (Cornwall, 1966, p. 45-46) 

that also contain small amounts of cobalt. 

Other cobaltiferous ores in large deposits are associated with mafic igneous rocks and metamorphic 

rocks in the Lynn Lake and Thompson-Moak Lake 

area, Manitoba. The deposits in the Thompson-Moak 

Lake area are of especial geologic interest because 

the nickel and cobalt probably were derived from 

peridotite and serpentine when they were metamorphosed at a temperature of at least 600°C to rocks 

of the garnet-amphibolite assemblage. Evidence suggests that sulfur was available in the hydrothermal 

solutions which deposited the mobilized nickel and 

cobalt in sulfide minerals, as first suggested by 

Michener (1957). If this process does indeed produce deposits of this type, peridotite bodies throughout the world could have valuable nickel-cobalt 

deposits if the bodies were sufficiently metamorphosed in an environment that had sulfur available. 

(See "Nickel"; also Cornwall, 1966, p. 20-23.) 

CONTACT MET AM ORPHIC DEPOSITS 

Deposits of magnetite, chalcopyrite, and cobaltiferous pyrite formed by contact metamorphism of 

carbonate rock by sills and dikes of diabase comprise 

an important type of cobalt deposit in the United 

States. Typical deposits are near Cornwall, Lebanon 

County, and Morgantown (the Grace mine), Berks 

County, Pa. These and many other deposits occur in 

the Triassic basin, an area about 75 miles long and 

5-20 miles wide· in southeastern Pennsylvania. At 

Cornwall, a discordant saucer-shaped body of diabase of Triassic age has silicated and mineralized adjacent carbonate rocks of Cambrian age. Recent 

descriptions of these commercially valuable iron 

deposits at Cornwall (Lapham, 1968) and Morgantown (Sims, 1968) indicate that the mine-run ore 

contains 0.02-0.056 percent cobalt, most of which is 
148 UNITED STATES MINERAL RESOURCES 

concentrated in a pyrite-rich separate that contains 

0.68-1.4 percent cobalt. About 75 percent of this 

cobalt is recovered and these mines are currently the 

major domestic source of cobalt. Some gold (1,700 oz 

in 1953) and silver also have been recovered from 

the pyrite concentrate at the Cornwall mine (Lapham, 1968, p. 79). The deposits in this region are 

large: The Cornwall mine alone has yielded nearly 

100 million tons of ore since 1742. 

LATERITIC DEPOSITS 

Laterite, a mantle of internally weathered soil 

from a few feet to more than 100 feet thick, is 

formed over large areas of low relief during long 

periods of intense weathering and erosion, chiefly in 

humid subtropical to tropical climates. The weathering of peridotite and serpentine bodies generally 

yields a laterite rich in iron, nickel, cobalt, and 

chromium. The lateritic deposits commonly underlie 

many hundreds to many thousands of acres, and 

individual deposits may contain millions of tons of 

ore. Commercially valuable deposits contain 40-50 

percent iron, 1-2 percent nickel, and 0.01-0.1 percent cobalt. Although the cobalt content of laterites 

is only one-tenth to one-fourteenth the nickel content, the cobalt can be recovered by chemical 

processing. 

Cobaltiferous laterite deposits, many of Tertiary 

age, are scattered over the world, and resources include billions of tons of ore. Lateritic ores in the 

United States occur chiefly in California, Oregon, 

and Washington, and probably to a lesser extent in 

North Carolina. One of the largest deposits, near 

Riddle, Oreg., has reserves of 16 million tons of ore 

containing 0.05 percent cobalt (Vhay, 1969, p. 120). 

Smaller deposits containing 0.16 percent cobalt occur 

in the Webster district, North Carolina (Cornwall 

and others, 1968, p. 325) . 

Major lateritic iron-nickel deposits of the world 

occur in eastern Cuba where more than 2 billion 

pounds of cobalt occur in ore with an average content of 0.1 percent cobalt, 1.39 percent nickel, 2.75 

percent chromium, and 38 percent iron (McMillan 

and Davis, 1955; Andrews, 1962, p. 149-150; Engineering and Mining Journal, 1968, p. 74). Other 

deposits of assorted sizes also occur in New Caledonia, the Solomon Islands, Indonesia, Australia, 

Philippines, Puerto Rico, Guatemala, Colombia, 

Venezuela, Brazil, U.S.S.R., Yugoslavia, Greece, and 

Malagasy Republic. 

Closely allied to lateritic deposits are those chiefly 

in the eastern and central parts of the United States 

that have been derived from the weathering of manganiferous sedimentary rock. The deposits tend to 

be small. The cobalt content is more variable than in 

many nickeliferous laterites. The White Oak mine, 

Tennessee, contains 0.37-2.28 percent cobalt; the 

deposit at Round Mountain, Va., contains 0.12-2.24 

percent cobalt; and the deposit at Rock Run, Ala., 

contains 0.05-4.8 percent cobalt. About 300,000 

pounds of cobalt occur in deposits of this type in the 

southern Appalachian Mountains (Pierce, 1944, p. 

270 ; Cornwall and others, 1968, p. 375). Manganese 

deposits of this type in Missouri contain over 1 million tons of ore in grade of 20 percent manganese 

and 0.5 percent cobalt at the contact of the Eminence 

and Gasconade Dolomites (Grawe, 1943). Cobalt 

also occurs in the manganese deposits of the Batesville district, Arkansas (Vhay, 1952). 

Pierce (1944, p. 268) reported that the greatest 

cobalt concentrations in the manganese deposits of 

the southeastern States occur in those deposits containing the lowest concentrations of manganese. Experimental work has been done by the U.S. Bureau 

of Mines on chemically treating these manganese 

ores. When such beneficiation does become economically feasible, some cobalt and other metals present 

in small amounts can be recovered. 

MASSIVE SULFIDE DEPOSITS IN METAMORPHIC ROCKS 

Deposits of massive sulfides consisting chiefly of 

pyrite and pyrrhotite (some containing small 

amounts of cobalt) occur in metamorphic rocks. The 

host rocks commonly have andesitic composition and 

are probably of volcano-sedimentary origin. (See 

"Copper.") These deposits generally are mined for 

their content of sulfur, iron, copper, and smaller 

amounts of zinc, nickel, and cobalt. 

Large massive sulfide deposits occur in the Blue 

Ridge and Piedmont provinces of the southeastern 

United States (Laurence, 1968, p. 162-164). The 

largest and best known of these deposits occur at 

Ducktown, Tenn. (Magee, 1968), where pyrite that 

contains 0.4-0.5 percent cobalt is reported by Cornwall, Vhay, and Frendzel (1968, p. 375). The cobalt 

currently is not recovered. The deposit at Sykesville, 

Md., contains base metals and some gold ; the average content of cobalt is 0.07 percent (Heyl and 

Pearre, 1965) ~ The en echelon bodies of primary 

pyrrhotite, chalcopyrite, and sphalerite along the 

20-mile trend of the Gossan Lead, Carrol and Grayson Counties, Va., contain about 0.01 percent cobalt. 

At least 16 other deposits believed to be of the Ducktown type have been mined or explored from Carroll 

County, Md., southward to Randolph County, Ala., 

according to Laurence (1968, p. 164). 
COBALT 149 

HYDROTHERMAL DEPOSITS 

Hydrothermal deposits (formed from heated solutions) locally have been important sources of cobalt, 

and some of them are the only deposits mined chiefly 

for this metal. The hydrothermal deposits may be 

subdivided into two major classes: (1) vein deposits, and (2) replacement deposits. 

In the United States, the vein deposits of the 

Blackbird district, Idaho, contain 1.6 percent copper, 

0.6 percent cobalt, and lesser amounts of nickel and 

precious metals (Vhay, 1964, p. 68). The aggregate 

tonnage of the ore in the district was reported in 

1959 to contain 15 million to as much as 225 million 

pounds of cobalt (Bilbrey, 1962, p. 27), equivalent 

to hypothetical resources in the classification of this 

report. In the Goodsprings district, Nevada, heterogenite forms envelopes around bodies of copper minerals. Large amounts of rock in many small bodies 

contain 0.3-0.5 percent cobalt (Vhay, 1952). Some 

cobalt occurs in the base metal veins of the Coeur 

d'Alene district, Idaho. Veins containing uranium, 

zinc, silver, nickel, and cobalt (0.09 percent) occur 

in the Blackhawk district, New Mexico ( Gillerman 

and Whitebread, 1956). Several thousands of tons 

of cobaltian manganese ores (0.01-0.5 percent cobalt) occur in the Luis Lopez hot springs deposits, 

New Mexico. In Connecticut, veins with cobalt occur 

at Great Hill; and at the Booth mine, north of 

Bridgeport, at least two bodies of pyrrhotite contain 

0.01 percent cobalt. 

In Canada, veins that contain as much as 10 percent cobalt occur in the great silver-arsenide deposits 

of the Cobalt-Gowganda region, Ontario (Berry, 

1971). Cobalt occurs with uranium in ore now produced in the Northwest Territories (Andrews, 1962, 

p. 99). 

Many veins containing an average of 1.2 percent 

cobalt with nickel, iron, and silver occur in the Bou 

Azzer area, Morocco, near the contact of serpentinite 

and diorite with granite and mica schist of Precambrian age (Orcel and Jouravsky, 1936). 

Hydrothermal replacement deposits containing 

cobalt minerals occur in the Bawdwin mine, Burma. 

The ore body consists of silver, lead, and zinc minerals that have replaced greatly sheared rhyolitic 

tuffs that are overlain and underlain by sedimentary 

rocks. The cobalt occurs in gersdorffite. The ore has 

an average grade of 0.5 percent cobalt, but during 

smelting of the ore the cobalt content is increased to 

3-4 percent in the nickel speiss (Sharma, 1944). At 

Outokumpu, Finland, large reserves in a copper-rich 

sulfide deposit contain 0.2 percent cobalt, chiefly in 

the mineral linnaeite. The ore minerals replace 

quartzite, serpentinite, and other rocks of the Karelian schist (Vahatolo, 1953). 

An extensive shear zone has been mineralized by 

small amounts of pyrite and sphalerite for at least 

15-20 miles along the east foot of Catoctin Mountain, 

Va. Surface samples from about a half dozen localities along the strike suggest that although the grade 

of sulfide minerals is low, the distribution of the 

minerals is uniform. The cobalt content is 0.007-

0.05 percent. 

The geologic features of deposits of the Mississippi 

Valley type have been summarized recently by Snyder (1968, p. 277-284). The deposits occur chiefly 

in carbonate rocks of Cambrian to Pennsylvanian 

age on the flanks of broad domes. The ore consists 

mostly of sulfides of lead, zinc, iron, and copper. Sulfides of cobalt and nickel occur in a few districts. 

Fluorite and barite are major minerals in some districts, and minor in others. Cadmium, silver, germani urn, and arsenic also are reported in some districts. All these ore materials probably were deposited from hydrothermal brines at temperatures 

not over 125°C. 

The cobalt and nickel content of the Mississippi 

Valley ores is of particular interest because of the 

records of past production. At the south end of the 

old lead belt, especially in the Fredericktown and 

Mine La Motte areas of southeast Missouri, cobalt 

and nickel sulfides (siegenite, millerite, bravoite, and 

several unidentified minerals) associated with chalcopyrite and sphalerite locally were abundant, especially in places where the mineralized dolomite of 

the Bonneterre Dolomite pinches out against the 

Precambrian rocks in the core of the St. Francois 

Mountains (Kline and others, 1961). Siegenite-rich 

ores were the source of the cobalt produced in the 

southeastern part of the old lead belt in the early 

days of mining, as well as from 1944 to 1961. 

The metal ratios in the ore of the Bonneterre--Flat 

River areas in the northern part of the old lead belt 

were estimated by Snyder and Gerdemann (1968, p. 

349). The data indicated that cobalt and nickel were, 

respectively, 20 and 40 times more abundant than 

silver, but only the silver was recovered. Nearly all 

the 300,000 Troy ounces of silver produced in Missouri in 1965 came from the Bonneterre--Flat River 

area of the southeast district (Kiilsgaard, 1967, p. 

71). 

Cobalt and nickel sulfides associated with chalcopyrite and sphalerite are locally abundant in the lead 

deposits of the Viburnum Trend now in production 

on the west side of the St. Francois Mountains. These 

deposits also occur in the Bonneterre Dolomite in a 

belt about 27 miles long and have an average min-
150 UNITED STATES MINERAL RESOURCES 

able thickness of 20 feet (Snyder and Gerdemann, 

1968, p. 334). The belt contains about 500 million 

tons of ore, if the average width of the minable zone 

is at least 150 feet ( Gerdemann and Myers, 1972, p. 

429). If the cobalt content of the raw ore is only 0.01 

percent cobalt, the belt contains a resource of about 

100 million pounds of cobalt. 

Cobalt also occurs in the Wisconsin zinc district 

that includes adjacent parts of Illinois and Iowa. 

These ores, also of the Mississippi Valley type, include several cobalt minerals associated with pyrite, 

sphalerite, and some galena and chalcopyrite. 

STR.A TA-BOUND DEPOSITS 

Strata-bound deposits show pronounced stratigraphic localization in rocks of many different ages. 

One metal typically dominates, generally copper, 

lead, or zinc, and it is accompanied by lesser amounts 

of nickel, cobalt, silver, cadmium, and other elements. The great copper-cobalt deposits of ZaireZambia are of this type; they occur in folded shale 

and dolomite that contain chalcopyrite, bornite, chalcocite, and a wide variety of other minerals, including linnaeite, carrollite, and others that contain 

cobalt. The ore bed, 20-80 feet thick, contains an 

average of 3.5 percent copper, but some ore contains 

2 percent copper and 2 percent cobalt. These deposits 

currently are the world's major source of cobalt 

(Robert, 1956). 

The copper-rich shales in the Kupferschiefer of 

central Europe formerly produced cobalt (Andrews, 

1962, p. 123). The cobalt, copper, lead, zinc, and 

silver in this stratigraphic unit is a large resource 

that currently is mostly of subeconomic value. 

CHEMICAL PRECIPITATES 

Chemically precipitated cobalt is associated with 

the manganese nodules on the sea floor. Mero (1965, 

p. 235) estimated that such nodules in the Pacific 

Ocean, containing an average of 0.35 percent cobalt, 

are a resource of 5.8 billion tons of cobalt. Copper, 

nickel, and cobalt occur together in an average ratio 

of 3:4: 1. Thus, cobalt produced from this source 

also would be a byproduct. (See also McKelvey and 

Wang, 1969.) 

RESOURCES 

The cobalt resources tabulated and discussed in 

this section have been selectively compiled from 

various published sources. Resources outside the 

United States were compiled only from the most 

readily available published data. Many of the details 

in the comprehensive compilations of world resources of cobalt by Vhay (1952) and Andrews 

(1962) have not been repeated here. 

The totals of resources include materials containing 0.01 percent or more cobalt and are expressed in 

millions of pounds of cobalt. Resources of this grade 

already have yielded some commercial cobalt. 

IDENTIFIED RESOURCES 

The identified resources of cobalt in the United 

States are summarized in table 32. Most of the cobalt 

resources of the United States potentially are available only as byproducts of mining for the more abundant elements in the ores. The small production of 

TABLE 32.-ldentijied resources 1 of cobalt in the 

United States 

[ + = some identified resources] 

Cobalt 

State (millions Remarks 

of pounds) 

Alaska --------- 125 Brady Glacier and other deposits ( MacKevett and 

others, 1971). 

Arkansas -------- + Batesville manganese district. 

California ------- 25 Chiefly laterite deposits 

( Hotz, 1966, p. 283). 

Idaho ----------- 50 Blackbird (Bilbrey, 1962, p. 

27) and Coeur d'Alene districts (Vhay, 1964, p. 8). 

Maine ---------- 130 Union and other deposits 

(Young, 1968), Katahdin 

Iron Works. 

Minnesota 1,000 Sulfide deposits in gabbro, Ely area (Grosh and others, 

1955). 

Missouri -------- 150 Southeast Missouri district 

(Kline and others, 1961), 

Viburnum Trend ( Gerde- mann and Myers, 1972). 

Montana -------- + Stillwater Complex, with 

chromium. 

Nevada --------- + Goodsprings district. 

New Mexico ----- 6 Blackhawk (Weber, 1965, p. 

207-209) and other districts. 

North Carolina __ 3 Chiefly laterite in the Webster 

district (Cornwall and 

others, 1968, p. 375). 

Oregon --------- 34 Chiefly laterite (Vhay, 1969, 

p. 116--120; Cornwall, 1966). 

Pennsylvania ---- 66 Contact metamorphic deposits in southeast region 

(Andrews, 1962, p. 161; 

Cornwall and others, 1968, 

p. 375). 

Tennessee ------- 40 Ducktown district (Magee, 

1968, p. 234) . 

Vermont -------- + Byproduct of talc operations 

(Andrews, 1962, p. 162; 

Vhay, 1952). 

Virginia -------- 25 Piedmont region; gossan lead 

and also includes Sykesville 

district, Carroll County, Md. 

Washington ----- 20 Chiefly lateritic ores (Vhay, 

1966, p. 116--125). 

Wisconsin ------- 10 Upper Mississippi Valley 

district, includes adjacent 

parts of Illinois and Iowa. 

Total ----- 1,684+ 

t Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. 
COBALT 151 

primary cobalt in the United States is more a function of economics and technological problems than 

the lack of ore deposits containing cobalt. 

The most thoroughly evaluated deposits of cobalt 

in the United States contain more than 1.6 billion 

pounds of cobalt. That amount may soon be increased 

as the full potential of the great copper-nickel deposits in the Ely area, Minnesota, is evaluated. 

Although the ·ores might be considered marginal, 

technology is available to recover metal from this 

type of deposit. Development work has begun, and 

cobalt from these deposits may well reach the market before that from previously known deposits. 

The mixed sulfide ores of the Mississippi Valley 

type are undoubtedly one of the great resources of 

cobalt and nickel in the United States. Reserves in 

the Madison mine, near Fredericktown, Mo., were 

estimated to contain another 14 million pounds of 

cobalt in 4.5 million tons of ore containing 0.16-

0.18 percent cobalt (Kline and others, 1961) . Most 

of these reserves and many other tons of cobalt resources on the east side of the St. Francois Mountains remain in the ground because old mining practices required that much of the ore with the highest 

cobalt content be left because of subsequent beneficiation and smelting problems. In 1949, it was 

estimated that 600.,000 pounds 9f cobalt was lost 

annually from the lead ore processed in the district 

(Vhay, 1952, p. 45). By October 1972, all mining 

operations in the old lead belt on the entire east side 

of the St. Francois Mountains had ceased. 

The world's identified resources of cobalt (table 

33) are largely in the lateritic ores of the tropical 

regions. Production of nickel from laterite is expected to double by 1980, making additional supplies 

of cobalt increasingly available from this source 

(Engineering and Mining Journal, 1968, p. 73). It 

is clear, however, that large amounts of cobalt will 

continue to become available from other types of 

deposits, especially the sulfide deposits associated 

with mafic igneous rocks, as at Sudbury, Ont., and 

in the Ely area, Minnesota, and the strata-bound 

deposits of central Africa. 

The minable reserves in the Bou Azzer area, Morocco, are now reported to be so small that mining 

may soon end (DeHuff, 1971, p. 401). 

Not included in the world's total of cobalt resources in table 33 are those in the less conventional 

and less well evaluated deposits of manganese nodules on the sea floor. Mero (1965, p. 235) estimated 

that the manganese nodules in the Pacific Ocean 

alone contain 5.8 billion tons ( 11.6 trillion pounds) 

of cobalt. 

TABLE 33.-ldentified resources 1 of cobalt in the world 

[ + = additional identified resources] 

Country 

Australia -------------------------

Brazil ---------------------------- Burma ---------------------------

Canada -------------------------- Colombia -------------------------

Cuba ----------------------------- Dominican Republic ---------------

Finland -------------------------- Guatemala ------------------------

Japan ---------------------------- ~orocco -------------------------- New Caledonia -------------------- New Guinea-Indonesia ------------- Philippines ____ - -------------------

Puerto Rico ----------------------- Solomon Island -------------------- Uganda -------------------------- U.S.A. ---------------------------

U.S.S.R. -------------------------- Venezuela _____ -------------------

Zaire ----------------------------- Zambia ---------------------------

Total ------------------------

Cobalt 

( mUiions of pounds) 

650 

20+ 

35 

550 

50 

2,312 

196 

50 

100 

6 

15 

850 

40 

350 

150 

50 

18 

1,684+ 

400 

132 

1,500 

766 

9,9·24 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing tech· 

nology and economic conditions. 

HYPOTHETICAL RESOURCES 

The world's hypothetical resources of cobalt are 

very large. Just as with the identified deposits, few 

of these deposits will be rich enough to mine for 

cobalt alone. Most of the world's future supplies of 

cobalt will reach the market as byproducts of other 

associated metals in greater demand, chiefly nickel, 

copper, iron, chromium, lead, zinc, precious metals, 

urani urn, and manganese. 

Hypothetical resources of cobalt in the United 

States probably amount to billions of pounds. Most 

of these resources are in various types of sulfide ore 

bodies. 

Large resources already are postulated for the 

partly evaluated deposits in the gabbro near Ely, 

Minn. If the cobalt content of 0.038 percent (Grosh 

and others, 1955) is indicative of the grade of large 

volumes of rocks, then as much as 12 billion pounds 

of cobalt may be in these deposits. 

The region around the Gap mine, Lancaster County, Pa., probably has not been prospected. The ore 

body at the Gap mine lies at the extreme west edge 

of an intrusive mafic complex containing an anorthositic core centered in the Coatesville area. Possibilities surely are favorable for the discovery of more 

deposits like the one at the Gap mine. 

Possibilities for the discovery of more bodies of 

ore in Alaska similar to those already identified 

should be excellent. Other plutons containing nickelcobalt-copper deposits may be found near some of 
152 UNITED STATES MINERAL RESOURCES 

those already mentioned in the New England States. 

Additional bodies of cobalt minerals associated 

with iron ore of contact metamorphic origin, such as 

those at Cornwall, Pa., probably lie hidden in southeastern Pennsylvania. Perhaps as many as two dozen 

bodies might occur at depth at the sites of magnetic 

anomalies in the region. The discovery of the hidden 

body that is now the Grace mine was facilitated by 

such data. 

The chances for finding more massive sulfide 

bodies of the Ducktown type seem good all through 

the Appalachian region, especially in the southern 

Piedmont and Blue Ridge provinces. 

Possibilities for the discovery of more ores of the 

Mississippi Valley type are good. The chances of 

such ore containing some cobalt and nickel seem 

favorable, because the ore already known in the midcontinental United States forms one of the world's 

great concentrations of metal sulfides, including 

cobalt and nickel, and two such cobalt-bearing districts, widely spaced, are known. Large deposits may 

still be found in extensions of known districts. The 

lead deposits of northern Arkansas might contain 

cobalt, especially indicated by the local bodies rich 

in pyrite. The known ore deposits may be the exposed parts of zoned districts in which the cobaltrich parts are still hidden beneath barren caprocks. 

Large new deposits of laterite probably will not be 

found in the United States. In niany tropical areas of 

the world, however, substantially large hypothetical 

(and speculative) resources will likely be found, 

especially in some of the more remote regions. 

More areas of sea bottom containing manganese 

nodules will be found and evaluated. When practical 

techniques for mining and extracting the metals 

from the nodules have been developed, large resources of cobalt will become available. 

SPECULATIVE RESOURCES 

The foregoing discussjons suggest that the speculative resources of cobalt in the United States and 

the rest of the world are large. 

Additional mafic and ultramafic rocks in the Appalachian and Cordilleran regions might be found 

containing valuable resources of cobalt. More massive sulfide bodies might be found at greater depth 

in Precambrian rocks of the Great Lakes region. 

Cobalt in commercial quantities might occur in large 

transverse veins in the copper region of the Upper 

Michigan Peninsula. In 1902 a shipment of arsenide 

minerals from the Mohawk mine went to the Camden Nickel Works and was "treated successfully" 

for cobalt, but records show no further production 

from that area. 

Deposits of the Cornwall type may well occur 

along the edges of the diabase intrusions in the Triassic trough in Virginia, Maryland, and New Jersey. 

The Triassic region of New Jersey may well have 

more sills and lopolithic bodies at depth that are in 

contact with Paleozoic carbonate rocks that were 

most favorable for the formation of large ore deposits. Replacement deposits might occur along the 

diabase contact of the Triassic trough of the Connecticut Valley. 

Additional districts containing cobalt-bearing sulfide ores of the Mississippi Valley type probably occur elsewhere in the United States and in the world. 

Geologic indications of such a district are exposed in 

the cobalt-bearing veins near Rossie, N.Y., and in 

nearby southern Ontario. These deposits do not seem 

to be related to the large zinc deposits of the BalmatEdwards district, New York. 

Metamorphic-hydrothermal deposits similar to 

those in the Thompson-Moak Lake district, Manitoba, probably occur elsewhere in the world. The 

possibilities are excellent in the great Precambrian 

Shield areas of Canada, Africa, Australia, and Eurasia for locating major ore districts of the Sudbury 

type, as has been shown by the many major discoveries since World War II. 

PROSPECTING TECHNIQUES 

Inasmuch as cobalt is produced chiefly as a byproduct of mining other ores, relatively little direct 

exploration for cobalt deposits has been needed or 

undertaken, except during domestic national emergencies when foreign supplies were restricted or unavailable. These exploration efforts generally have 

been directed toward careful examination of areas 

of known cobalt deposits and occurrences using conventional geologic, geophysical, and geochemical 

techniques. Pyrrhotite deposits are particularly easy 

to identify by known geophysical techniques, and 

cobalt is easy to identify with geochemical prospecting methOds. Techniques for determining trace 

amounts of cobalt are well known (Almond, 1953; 

Hawkes, 1957; Ward and others, 1963; Canney and 

Nowlan, 1964; Warren and others, 1964). Cobalt is 

more mobile than copper and may be useful as a 

pathfinder for deposits of associated elements (Canney and Wing, 1966). Biogeochemical prospecting 

for cobalt holds promise (Warren and Delavault, 

1957; Tooms and Jay, 1964). 

Applications of geochemical prospecting techniques have successfully found the extension of a 

vein in the Quartzburg district, Oregon, and outlined the Blacktail ore body as well as a large halo of 

cobalt in the Blackbird district, Idaho (Canney and 
COBALT 153 

others, 1953) . Methods are reported for special use 

in glacial areas (Koehler and others, 1954), in areas 

of deep soil in the tropics (Webb, 1958; Jay, 1959; 

Tooms and Webb, 1961), and in the study of secondary dispersion halos in the southern Ural Mountains of the U.S.S.R. (Makunina and others, 1962). 

PROBLEMS FOR RESEARCH 

Further geologic studies are needed on the minerals of cobalt and their genesis. Much needs to be 

learned about the mineralogy of cobalt so that better 

commercial separations and concentrations can be 

made in order to make better use of available resources of cobalt. The mineralogy of the sulfides of 

the Mississippi Valley type in Missouri has proved 

to be more complex than formerly realized and 

should be studied further. New and better technology is needed for the recovery of more valuable cobalt 

(currently selling for $1.85 per pound) from ores 

containing less valuable lead, zinc, and copper because loss of such valuable byproducts in mining, 

beneficiating, and smelting is not only a financial 

loss to the producer but, more importantly, may be 

an irretrievable loss of the material itself. A prime 

modern loss of cobalt is in the matte smelting of copper from deposits also containing lead and zinc, although techniques seem to have been available in the 

19th century to recover much of the nickel and 

cobalt in the matte. 

New technology needs to be developed to mine and 

recover cobalt and other metals from the manganese 

nodules on the sea floor. Methods developed in the 

laboratory to recover cobalt from supergene manganese oxides might be further advanced into commercial processes for cobalt recovery. 

Another economically significant economic breakthrough would be the development of processes to 

recover cobalt and nickel from silicate minerals of 

ultramafic rocks whose average composition includes 

0.027 percent cobalt and 0.19 percent nickel. Many 

cobaltiferous materials of potential commercial value 

contain less cobalt, but more nickel, than the average 

ultramafic rock. Dunite, because of its simple mineralogy, seems like a good material on which to 

begin intensive research. 

REFERENCES CITED 

Almond, Hy, 1953, Determination of trac·es of cobalt in soils: 

Anal. Chemistry, v. 25, p. 166-167. 

Andrews, R. W., 1962, Cobalt: Overseas Geol. Surveys, Mineral Resources Div. (London, Her Majesty's Stationery 

Office) , 222 p. 

Banning, L. H., Anable, W. F., Quicho, R. B., Hess, H. D., 

and Good, P. C., 1962, Metallic inventory of Philippine 

nickel ores: U.S. Bur. Mines Rept. Inv. 6063, 71 p. 

Berry, L. G., ed., 1971, The silver-arsenide deposits of the 

Cobalt-Gowganda Region, Ontario: Mineralog. Assoc. 

Canada, v. 11, pt. 1, 430 p. 

Bilbrey, J. H., 1962, Cobalt, a materials survey: U.S. Bur. 

Mines Inf. Circ. IC-1803, 140 p. 

Burnham, C. W., 1959, Metallogenic provinces of the southwestern United States and northern Mexico: New 

Mexico Bur. Mines and Mineral Resources Bull. 65, 76 

p. 

Cameron, E. N., 1943, Origin of sulfides in nickel deposits 

of Mount Prospect, Connecticut: Geol. Soc. America 

Bull., v. 54, no. 5, p. 651-686. 

Canney, F. C., Hawkes, H. E. Richmond, G. M., and Vhay, 

J. S., 1953, A preliminary report of geochemical investigations in the Blackbird district, Lemhi County, Idaho: 

U.S. Ge<>l. Survey open-file report, 20 p. 

Canney, F. C., and Nowlan, G. A., 1964, Determination of 

ammonium citrate-soluble cobalt in soils and sediments: 

Econ. Geology, v. 59, no. 7, p. 1361-1367. 

Canney, F. C., and Wing, L. A., 1966, Cobalt--Useful but 

neglected in geochemical prospecting: Econ. Geology, v. 

61, no. 1, p. 198-203. 

Cheney, E. S., and Lange, I. M., 1967, Evidence for sulfurization and the origin of some sudbury-type ores: Mineralium Deposit, v. 2, p. 80-94. 

Cornwall, H. R., 1966, Nickel deposits of North America: 

U.S. Ge<>l. Survey Bull. 1223, 62 p. 

Cornwall, H. R., and Vhay, J. S., 1967, Cobalt and nickel, 

in Mineral and water resources of Missouri: U.S. Cong., 

90th, 1st sess., Senate Doc. 19 (Missouri Div. Geol. Survey and Water Resources [Rept.l, 2d ser., v. 43), p. 

68-70. 

Cornwall, H. R., Vhay, J. S., and Frendzel, D. J., 1968, Cobalt and nickel, in U.S. Geol. Survey and U.S. Bur. 

Mines, Mineral resources of the Appalachian region: 

U.S. Geol. Survey Prof. Paper 580, p. 374-376. 

DeHuff, G. L., 1971, Cobalt, in Minerals yearbook 1969, v. 

1-2, Metals, minerals, and fuels: U.S. Bur. Mines, 

p. 397-402. 

Dennen, W. H., 1943, A nickel deposit near Dracut, Massachusetts: Econ. Geology, v. 38, no. 1, p. 25-55. 

Engineering and Mining Journal, 1968, Laterites-future 

source for nickel: Eng. and Mining Jour., v. 169, no. 

10, p. 73-84. 

Fleischer, Michael, 1955, Minor elements in some sulfide 

minerals, in pt. 2 of Bateman, A. M., ed., Economic 

Geology, 50th Anniversary volume: Urbana, Ill., Econ. 

Geology Pub. Co., p. 970-1024. 

Fryklund, V. C., Jr., and Fletcher, J. D., 1956, Geochemistry 

of sphalerite from the Star mine, Coeur d'Alene district, 

Idaho: Econ. Geology, v. 51, p. 223-247. 

Gerdemann, P. E., and Myers, H. E., 1972, Relationships of 

carbonate facies patterns to ore distribution and to ore 

genesis in the Southeast Missouri lead district: Econ. 

Geology, v. 67, no. 4, p. 426-433. 

Gillerman, Elliot, and Whitebread, D. H., 1956, Uraniumbearing nickel-cobalt-native silver deposits, Blackhawk 

district, Grant County, New Mexico: U.S. Geol. Survey 

Bull. 1000-K, p. 283-313. 

Goldberg, E. D., 1954, Chemical scavengers of the sea, [pt.] 

1 of Marine geochemistry: Jour. Geology, v. 62, no. 3, 

p. 249-265. 

Goldschmidt, V. M., 1954, Geochemistry: Oxford, Clarendon 

Press, 730 p. 
154 UNITED STATES MINERAL RESOURCES 

Grawe, 0. R., 1943, Manganese deposits of Missouri: Missouri Geol. Survey and Water Resources Bien. Rept., 

62d, App. 6, 77 p. 

Grosh, W. A., Pennington, J. W., Wasson, P. A., and Cooke, 

S. R. B., 1955, Investigation of copper-nickel mineralization in Kawishiwi River area, Lake County, Minnesota: U.S. Bur. Mines Rept. Inv. RI-5177, 18 p. 

Hawkes, H. E., Jr~ 1957, Principles of geochemical prospecting: U.S. Geol. Survey Bull. 1000-F, p. 225-335. 

Heyl, A. V., and Pearre, N. C., 1965, Copper-zinc-lead-ironcobalt and barite deposits in Piedmont upland of Maryland: Maryland Geol. Survey Bull. 28, 72 p. 

Holtz, P. E., 1961, Weathering of peridotite, southwest 

Oregon, in Geological Survey research 1961: U.S. Geol. 

Survey Prof. Paper 424-D, p. D327-D331. 

--- 1966, Nickel, in Mineral and water resources of 

California: California Div. Mines and Geology Bull. 

191, p. 279-284. 

Jay, J. R., 1959, Geochemical prospecting studies for cobalt 

and uranium in Northern Rhodesia: London Univ., 

Imperial Coli., Ph.D. thesis. 

Kiilsgaard, T. H., 1967, Silver, in Mineral and water resources of Missouri: U.S. Cong., 90th, 1st sess., Senate 

Doc. 19 Missouri Div. Geol. Survey and Water Resources 

[Rept.], 2d ser., v. 43, p. 70-72. 

Kline, H. D., Calhoun, W. A., and Reynolds, B. M., 1961, 

Mining and milling methods and costs, Madison Mine, 

National Lead Co., St. Louis Smelting and Refining Division, Madison County, Mo.: U.S. Bur. Mines lnf. 

Circ. IC-8028, 26 p. 

Koehler, G. F., Hostetler, P. B., and Holland, H. D., 1954, 

Geochemical prospecting at Cobalt, Ontario: Econ. 

Geology, v. 49, no. 4, p. 378-388. 

Krauskopf, K. B., 1955, Sedimentary deposits of rare metals, 

in pt. 1 of Bateman, A. M., ed.,: Economic geology, 50th 

Anniversary volume: Urbana, Ill., Econ. Geology Pub. 

Co., p. 411-463. 

Krayushkin, V. A., Kagakov, S. B., and Drabma, Y. M., 

1964, Vanadium, nickel, and other trace elements in the 

petroleums of the Bitkovskofield: Geochemistry, no. 4, 

p. 822-827. 

Lapham, D. M., 1968, Triassic magnetite and diabase at 

Cornwall, Pennsylvania, in Ridge, J. D., ed., Ore deposits of the United States 1933-1967 (Graton-Sales 

Volume) v. 1: Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 72-94. 

Laurence, R. A., 1968, Ore deposits of the Southern Appalachians, in Ridge, J. D., ed., Ore deposits of the 

United States, 1933-1967 (Graton-Sales Volume) v. 1: 

Am. Inst. Mining, Metall., and Petroleum Engineers, 

p. 155-168. 

MacKevett, E. M., Jr., Brew, D. A., Hawley, C. C., Huff, L. 

C., and Smith, J. G., 1971, Mineral resources of Glacier 

Bay National Monument, Alaska: U.S. Geol. Survey 

Prof. Paper 632, 90 p. 

Magee, Maurice, 1968, Geology and ore deposit of the Ducktown district, Tennessee, in Ridge, J. D., ed., Ore deposits of the United States 1933-1967 (Graton-Sales 

Volume) v. 1: Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 207-241. 

Makunina, A. A., Sorokina, E. P., and Buckovskii, E. S., 

1962, Secondary dispersion haloes in the southern Ural 

copper-cobalt deposit: Vopr. Geogr. Nauch. Sb. Mosk. 

Filiala geogr. Obshchestva SSSR, no. 49, p. 53-81. 

Mason, B. H., 1958, Principles of geochemistry: New York, 

John Wiley and Sons, 310 p. 

McKelvey, V. E., and Wang, F. H., 1969, Preliminary maps 

world subsea mineral resources: U.S. Geol. Survey Misc. 

Geol. Inv. Map 1-632. 

McMillan, W. D., and Davis, H. W., 1955, Nickel-cobalt resources of Cuba: U.S. Bur. Mines Rept. lnv. 5099, 86 p. 

Mero, J. L., 1965, The mineral resources of the sea: New 

York, Elsevier Publishing Co., 312 p. 

Michener, C. E., 1957, Genesis of mineral deposits and exploration: N atl. Advisory Comm. Research Geol. Sci., 

7th Ann. Rept. 1956-1957, p. 13-14. 

Orcel, Jean, and Jouravsky, G., 1936, Le minerai de cobalt 

de Bou Azzer (Maroc), sa composition mineralogique et 

sa structure: Cong. lnternat. Mines, Metallurgie, Geol. 

Appl., 7th, Paris 1935, Geol. v. 1, p. 207-216. 

Pecora, W. T., 1944, Nickel-silicate and associated nickelcobalt-manganese-oxide deposits near Sao Jose do Tocantins, Goiaz, Brazil: U.S. Geol. Survey Bull. 935-E, 

p. 247-305. 

Piedboeuf, Charles, 1961, The cobalt market-Production, 

uses, and consumption : Cobalt Inf. Center, Supp. to 

Cobalt no. 13, Dec. 1961, 9 p. 

Pierce, W. G., 1944, Cobalt-bearing manganese deposits of 

Alabama, Georgia, and Tennessee: U.S. Geol. Survey 

Bull. 940-J, p. 265-285. 

Rankama, Kalervo, 1963, Progres·s in isotope geology: New 

York and London, Interscience Publishers, Inc., 705 p. 

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry: 

Chicago, Ill., Univ. Chicago Press, 912 p. 

Reno, H. T., 1970, Cobalt, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 263-274. 

Robert, Maurice, 1956, Geologie et geographie du Katanga 

y compris I' etude des resources et de la mise en valeur: 

Brussels, Union Min. Haut-Katanga, 620 p. 

Sharma, N. L, 1944, Nickel and cobalt ores in India and 

Burma: Jour. Sci. and Indus. Research [New Delhi, 

India], v. 2, no. 2, p. 114-121. 

Sims, S. J ., 1968, The Grace mine magnetite deposit, Berks 

County, Pennsylvania, in Ridge, J. D., ed., Ore deposits, 

of the United States 1933-1967 (Graton-Sales Volume), 

v. 1: Am. Inst. Mining, Metall., and Petroleum Engineers, p. 108-124. 

Snyder, F. G., 1968, Geology and ore deposits of the midcontinent United States, in Ridge, J. D., ed., Ore deposits 

of the United States, 1933-1967 (Graton-Sales Volume), 

v. 1: Am. lnst. Mining, Metall., and Petroleum Engineers, p. 257-286. 

Snyder, F. G., and Gerdemann, P. E., 1968, Geology of the 

southeast Missouri lead district, in Ridge, J. D., ed., 

Ore deposits of the United States 1933-1967 (GratonSales Volume), v. 1: Am. Inst. Mining, Metall., and 

Petroleum Engineers, p. 326-358. 

Tooms, J. S., and Jay, J. R., 1964, The role of the biochemical 

cycle in the development of copper-cobalt anomalies in 

the freely drained soils of the Northern Rhodesian copperbelt: Econ. Geology, v. 59, no. 5, p. 826-834. 

Tooms, J. S., and Webb, J. S., 1961, Geochemical prospecting 

investigations in the Northern Rhodesian copperbelt: 

Econ. Geology, v. 56, no. 5, p. 815-846. 

Vahatolo, V. 0., 1953, On the geology of the Outokumpu ore 

deposit in Finland: Finlande Comm. Geol. Bull. 164, 

98 p. 
COBALT 155 

Vhay, J. S., 1952, Cobalt resources, Chap. 6 of Materials 

Survey-Cobalt: U.S. Bur. Mines, 56 p. 

--- 1964, Cobalt and nickel, in Mineral and water resources of Idaho: Idaho Bur. Mines and Geology, Spec. 

Rept. 1, p. 66--68. 

--- 1966, Nickel and cobalt, in Mineral and water resources of' Washington: U.S. Cong., 89th, 2d sess., Senate Comm. Interior and Insular Affairs, p. 116--125. 

--- 1969, Cobalt, in Mineral and water resources of 

Oregon: U.S. Cong., 9()th, 2d sess., Senate Comm. Interior and Insular Affairs, p. 116--120. 

Ward, F. N., Lakin, H. W., Canney, F. C., and others, 1963, 

Analytical methods used in geochemical exploration by 

the U.S. Geological Survey: U.S. Geol. Survey Bull. 1152, 

100 p. 

Warren, H. V., and Delavault, R. E., 1957, Biogeochemical 

prospecting for cobalt: Canada Royal Soc. Trans., 3d 

ser., v. 51, sec. 4, p. 33--37. 

Warren, H. V., Delavault, R. E .. , and Barakso, John, 1964, 

The role of arsenic as a pathfinder in biogeochemical 

prospecting: Econ. Geology, v. 59, no. 7, p. 1381-1385. 

Webb, J. S., 1958, Observations on geochemical exploration 

in tropical terrains: lnternat. Geol. Cong., 20th, Mexico 

D. F., 1956, Explor. Geochim, Symposium, v. 1, p. 143-

173. 

Weber, R. H., 1965, Nickel and cobalt, in Mineral and water 

resources of New Mexico: New Mexico Bur. Mines and 

Min. Res. Bull 87, p. 207-209. 

Young, R. S., 1968, Mineral exploration and development iii 

Maine, in Ridge, J. D., ed., Ore deposits in the United 

States, 1933-1967, (Graton-Sales Volume), v. 1,: Am. 

Inst. Mining, Metall., and Petroleum Enginers, p. 125-

139. 

UNITED STATES MINERAL RESOURCES 

CONSTRUCTION STONE 

By ROBERT A. LAURENCE 

CONTENTS 

Page 

)lbstract of conclusions --------------------------- 157 

Introduction ------------------------------------- 157 

Production and use ------------------------------ 157 

Distribution ----------··-··------------------------- 158 

Problems for research ---------------------------- 161 

Selected references ------------------------------- 161 

FIGURES 

18. Map showing lithologie provinces of the United 

States as related to occurrence and production 

Pa~e 

in 1969 of principal kinds of crushed stone __ 159 

19. Map showing lithologic provinces of the United 

States as related to occurrence and production 

in 1969 of principal kinds of dimension stone_ 160 

TABLES 

Page 

34. Production of stone, United States ----------- 158 

35. Production of stone in 1969, by types of stone, 

in the United States ---------------------- 161 

ABSTRACT OF CONCLUSIONS 

Domestic resources of stone for construction, both crushed 

and dimension stone, are adequate to provide for the expected demand indefinitely. Resource problems exist in localities of urbanization and industrial development and will 

increase, unless careful plans are made to reserve favorable 

areas for quarrying. Geologie mapping, especially of urban 

and suburban areas, can provide basic data for such planning. 

INTRODUCTION 

Stone is an essential mineral commodity in our 

modern_ industrialized society. It is especially important in building highways and railroads, but 

also has wide use in all phases of construction. 

"Stone," as a commercial term, includes all consolidated rock used for construction and roads, as 

well as that used in cement manufacture, in agriculture ("aglime," poultry grit), in chemical and metallurgical industries, and for roofing granules. For 

purposes of this chapter, only stone used for construction, monuments, and roads is considered. 

Other uses of stone are discussed in the appropriate 

chapters. 

Stone as a construction material may be further 

classified as crushed stone and dimension stone. 

Crushed stone is a term applied to rock that has 

been broken, crushed, or ground to smaller fragments after quarrying (Thrush, p. 284). Dimension 

stone is natural building stone that has been selected, trimmed, or cut to specified or indicated 

shapes or sizes (American Society for Testing and 

Materials, 1972, p. 103). 

Desirable properties of stone for use as crushed 

stone in construction are toughness, strength, abrasion resistance, low porosity and absorption, and 

absence of minerals, such as sulfides or chert which 

may deteriorate through weathering or by chemical 

reaction with certain types of cement. 

Desirable properties of dimension stone include 

those for crushed stone; in addition dimension 

stone must be free from fractures and other flaws 

so that it can be removed from the quarry in large 

blocks and then cut or shaped as desired. For most 

interior uses, dimension stone should be capable of 

taking a polish, and for both interior and exterior 

uses, the color and appearance of the exposed face 

are important characteristics. 

PRODUCTION AND USE 

According- to Cooper (1970, p. 1219), 

The stone industry is the largest nonfuel, nonmetallic mineral industry in the United States from the standpoint of 

total value of production and is second only to sand and 

gravel in volume produced. With exception of a few special 

varieties or qualities of dimension stone, the United States is 

U.S. GEOL. SURVEY PROF. P )lPER 820 

157 
158 UNITED STATES MINERAL RESOURCES 

entirely self-sufficient with respect to stone requirements. 

Volumewise, imports and exports are approximately equal, 

but the value of imports, about $20 million in 1968, is appromiately double that of exports. 

Use of dimension stone began when early man 

gave up nomadic life, and it flourished when early 

civilization built cities and temples. It is still an 

important industry-598 quarries produced $95 

million worth of dimension stone in the United 

States in 1970 (Division of Nonmetallic Minerals, 

1972, p. 141)-but United States productioh 'was 

highest in the 1920's, averaging about 4 million 

short tons annually between 1925 and 1930 (Currier, 1960, p. 15). Following a period of small production in the 1930's and early 1940's, production 

increased after World War II from less than 1 million short tons to 21f2 million short tons in 1955, but 

has declined slightly since then. 

The crushed stone industry began in England in 

about 1815 (Severinghaus, 1960, p. 285) and expanded rapidly after the invention of the mechanical rock crusher in 1858, especially during periods 

of extensive railroad and highway building. In 

1969, more than 4,500 quarries in the United States 

produced 861 million short tons of crushed stone 

(Wood and Carrales, 1970, p. 16), with a total 

value of $1 ¥a billion. 

The recent, rapid growth of our domestic stone 

industry is shown by table 34. These figures, from 

TABLE 34.-Production of stone, United States 

[All figurE!'! are in millions] 

1929 ___ Tonnage -----------

Value ------------- 1939 ___ Tonnage -----------

Value -------------- 1949 ___ Tonnage -----------

Value -------------- 1959 ___ Tonnage -----------

Value -------------- 1969 ___ Tonnage -----------

Value ------------- 1970---Tonnage ----------- Value --------------

Dimension Crt16hed stone stone 

4.7 

$70 

2.8 

$25 

1.8 

$52 

2.3 

$25 

1.9 

$99 

1.6 

$95 

98 

$94 

145 

$138 

222 

$289 

145 

$133 

861 

$1,326 878 $1,380 

Total 

(rounded) 

98 

$164 

147 

$158 

224 

$341 

147 

$158 

863 

$1,425 

875 

$1,475 

the U.S. Bureau of Mines Minerals Yearbooks, show 

the tremendous increase in production of crushed 

stone, chiefly caused by demands of expanded highway and other construction, and the gradual decline 

of the dimension stone industry as use of concrete 

and steel for structural materials increased. 

Imports in 1970 were valued at $35.7 million but 

amounted to only about 2.5 percent of the total 

value of stone consumed in the United States in 

that year. About 84 percent of the imported stone 

(by value) was dimension stone, chiefly marble from 

Italy and Portugal and granite from Canada and 

Italy. Total value of stone exports was $5.6 milliononly 0.004 percent of the year's production (Drake, 

1972). Prosperity of the stone industry does not 

depend on either exports or imports. 

Demand is expected to increase, over the next 30 

years, at an annual rate of 2.3--3.3 percent for dimension stone and 3.5-5.1 percent for crushed stone 

(Cooper, 1970, p. 1229). 

DISTRIBUTION 

Stone was produced in 1970 in all States except 

Delaware, and the total value of stone produced in 

the United States reached a new record high of 

$1.48 billion. More than 99 percent of the total 

quantity} with 93.5 percent of the total value, was 

crushed stone (Drake, 1972, p. 1). Stone was the 

principal mineral, by value, produced in eight States 

in 1970, was the second in 12 States, third in 10 

States, and fourth in three (Daugherty and Fahrney, 1972, p. 6). 

The eight most populous States produced 45 percent of the total output of stone, which represented 

40 percent of the total value in 1970. This reflects, 

of course, the importance of the cost of shipping or 

hauling stone from the quarry site to the place of 

use. Inasmuch as the present heavily populated areas 

will continue to be the principal areas of growth 

and construction, they will continue to be the leading consumers of construction materials, and a 

healthy and adequate stone industry must be maintained in and near all major population centers. 

Nearly three-fourths of all crushed stone produced 

in the United States in 1970 was shipped by truck 

(Drake, 1972, p. 15). After a very few miles, the 

cost of trucking can exceed the total of all other 

production costs of crushed stone. 

Most kinds of rock are suitable for use as crushed 

stone; as a result no area in the United States is far 

from an active or potential source of crushed stone. 

Distribution of these sources of stone is shown in 

figure 18. About 73 percent of the total output of 

crushed stone, which represents 67 percent of the 

total value, is limestone; traprock and granite are 

the other principal varieties produced (table 35). 

Distribution of types used for dimension stone is 

shown in figure 19. Granite is the leading variety 

representing 37 percent of the total output and 46 

percent of the total value ; limestone and sandstone 

are next in abundance (table 35). 

The principal competitor of and substitute for 

crushed stone is another ubiquitous mineral commodity, sand and gravel. It is commonly used as a 

substitute for stone in road construction and as 

concrete aggregate. Usually, the availability and 
) ........ __ ') ......... ___ ........ 

I '!'(-••. WA ,' : 

Sif I IVG I ( G 'orv I \ 

•, s i ~ 

"-------~ r : \\ -----J -, ·. I J ) G 

Of1 / G "··\ L fGorv .( L \, r 

G : S , r--- l. I ·--·-·t 

r ,' r IDA!io i . I : f -------.L I i ------,--. ____ i ' ' ....... i i j , ' t.._., 

( "'r~AoA j ·-;--

\ 5 i UTAif i \ '5 s : CA(fF \ L i L I 

G

OflrviA \ ' : \ , I 

l. \ L ' L 

ALASKA G l T 

•• HAWAII l T 

·----- PUERTO RICO Gl • --.-----r-----------, ~IVA • i ( i NORTH DAKOTA i ' . ~ _________________ ) _____ J ( 

~ SOUTH DAKOTA 

~· S l T 

r------------------...... ; 

; \ I NEBRASKA t l -!. ___ 1 L ) > 

1-

: '\·---

3

--··-·r ILLIIIOIS 

: ----------------' . .., \, l 

I \, ·-. s ' • \1 

i KANSAS \ MISSOURI : 

I L I l TG~-

s 

ro 

IOWA 

S \ i ----------.J T 

r \, r-) j --------------

\5 : 

i s \ s .,.'. 

-:-~--=~.-------------L--------- ~ \ I \ A 111z : .· orq J I s ' NEW i G ' S ----~; L / G 

'·--.... T j l ··...._ : T 

·-., I ----...!·-- PRovrNcEs ----.~. __ J \ \. 1. Atlantic and Gulf coastal plain deposits (Cretaceous, Tertiary, and Qua- • •• 

ternary sedimentary formations) 't 2. Eastern crystalline (eastern Appalachian belt, Piedmont belt, Adiron- \ 

dack Mountains, and New Enatand) \, 2a. Northern Maine, area of 1=hiefly Paleozoic sedimentary rocks with -•• 

scattered areas of intrusive crystalline rocks "-r 2b. Triaasic sandstone areas 

3. Great Plains-central lnterlor.-western Appalachian area of Paleozoic and 

Mesozoic sedimentary rocks, with a few scattered small areas of crys- talline rocks 

4. Lake Superior area of cryatalline rocks 

5. Cordilleran, Great Basin, and Pacific coastal belt of crystalline and sedi- mentary rocks, undifferentiated 

Boundaries are aeneralized, and based on "Geoloalc Map of the 

United States," U.S. Geolopcal Survey (1932) 

L 

s 

G 

T 

··---.. " 

\. 

I \ 

i OKLAHOMA \ 

I L : 

:- s I '-·· G : ............. "'"\. 

.... ...._ .. 

'•,'1 

\ 

··-, .. 

0 100 200 300 400 MILES 

0 100 200 300 400 KILOMETERS I I I I I 

,......-· 

FIGURE 18.-Lithologic provinces of the United States as related to occurrence and production in 

1969 of principal kinds of crushed: stone. Modified from Currier (1960). 

ROCK SYMBOLS 

Symbols denote States that reported 

production of the five major clas-

- of crushed stone and are placed within States and lltholoaic prov- Inces, but they do not Indicate 

locations of exploited deposita within States 

G Granite and related crystalline 

rocks L Limestone (noncrystalline) 

M Marble (Includes crystalline limestone sold u commercial marble) 

S Sandatone, includina quartlite T Tnprock 

(ITriaulc aandatone 

• Cryatalllne rocks 

0 

0 

z 

rll 

t-3 

~ 

Sl 

..... 

~ 

en 

t-3 

0 

z 

l.2:J 

f-& 

en 

CD 
)-----

} -----..__ , r--,- __ _ IV.q ,' : ' 51111

'~Gr I ( --------- •, ; o,., / \ -----r-----------, 

\. . \ .. : . -------------_j \ - • I ( . I l'I"'"A "'A • • 

OIIEGof'/ 

G 

s 

) .' ; NORTH DAKOTA i 

i ~, : : 

( l f- ----------------~ ; ··----r-- J ( .' ID.qko j ----- ' . 

----- - I : • SOUT,H DAKOTA f ·-----..L I ia-G s . ----- ,' Ot.r ! I r------ I s ,____________ j ,' : 7 I .... - ..... " .. ~ 

I I ;___ i \ IOWA 

: f'l£v 1

• ·-r-··-.. : NEBRASKA \. l \ .qD.q ' -L___ L ; 

.. s : ' l ! ---' \ "" 1 u T A k 1 : \------ ·r I , L I No I s 

C.qllf.' \ ,' S i ;-------------··--',? 3 \,, 0 11"' I • I 5 L ' c 0 l 0 R A D 0 I ·, .\ G .q \ : ' G , i ··1 

L .. L__ ! M~ i KANSAS \ MISSOURI :.._, 

S \ i ---------..1. L : L : L ~-, 

St \ f_,. /:-------------- _j_ ________ .:_ _________ \ ~nl'_ '.: \~-- ,' I r··- \( j I -------,1 r---------- )~ 

\ ' : I I s } •• AFIIzo,.,A j I ' : Sl <;' ----

/ s : NEW t.IEX/Co : ! • I ARKANSAS r 

J. I s I L '-·· : f - ------· ' G ' s ............. I 01. '·-..... i i ·---. l . 01. 

·-- I L ' G 1--------i "' "' ...... ___ i --- i l 1 ~ ~ ...... . -----!. ___ _. l •' - PROVINCES ----.J. __ J \ ', / :< 

I. Atlantic: and Gulf coastal plain deposits (Cretaceous, Tertiary, and Qua- \.,_ \ ( •• -'-··-. ternary sedimentary formations) \ 1 : 2. Eastern crystalline (eastern Appalachian belt, Piedmont belt, Adiron- ~ l : 

la. d~~~t~e~:n::~~:~.a:r!::;vc:~~~;n:~leozoic: sedimentary rocks with \ ···-,, 

scattered areas of intrusive crystalline rocks ·-,.- "\ 

lb. Triuaic: sandstone areas '. 3. Great Plaina-c:entral interior-western Appalachian area of Pilleozoic and '\. 

:==~~~dimentary rocks, with a few scattered small areas of crys- '\, 

4. Lake Superior area of crystalline rocks ', 

5. Cor:::~::;~:::!. ~-:~~if!~:n~~~~:t coastal belt of crystalline and sedi- \ •• 

Boundaries are aeneralized, and based on " Geotoaic: Map of the United States," U.S. Geotoaic:al Survey ( 1932) 

'·· 

? lcr> 2Cf 3Cf" •yo MILES 

0 100 200 300 •oo KILOMETERS I I I I I 

_,.......-· 

FIGURE 19.-Lithologic provinces of the United States as related to occurrence and production in 

1969 of principal kinds of dimension stone. Modified from Currier ( 1960). 

ROCK SYMBOLS 

Symbols denote States that reported 

production of the five major classes of dimension stones and are placed within States and lithologic 

provinces, but they do not indicate 

locations of exploited deposits 

within States 

G Granite and related crystalline 

rocks L Limestone (noncrystalline) 

M Marble (includes crystalline 

limestone sold as commercial marble) 

S Sandstone, including quartzite 

Sl Slate II Triuaic: sandstone 

.Crystalline rocks 

t-& 

0) 

0 

~ 

z 

.... 

1-3 

~ 

t:f 

00 

1-3 

> 1-3 

~ 

00 

1:!:: 

.... 

z 

~ 

~ t'4 

~ 00 

0 

~ 

~ 

0 

tzJ 

00 
CONSTRUCTION s·TONE 161 

TABLE 35.-Production of stone in1969, by types of stone, 

in the United States 

Percentage of total 

Type 

Crushed stone 

Limestone (including dolomite) __ 

Marble Granite ------------------------____ -- _.__ ______________ _ 

Sandstone (including quartzite) _ 

Traprock ---------------------- Other --------------------------

Total __ --_______ ----__ millionsDimension stone 

Granite ------------------------ Limestone (including dolomite) __ _ 

Marble ------------------------ Sandstone (including quartzite) _ 

Slate ------------------------·--

Other -------------------------

Total _________________ millionsTonnage 

73 

9 

.2 

3 

10 

4.8 

100 

861 

37 

31 

4 

17 

8 

3 

100 

1.873 

Value 

$67 

9 

2 

4 

11 

7 ---

100 

$1,326 

$46 

18 

13 

11 

9 

3 

100 

$99 

cost of transportation determine which of the two 

is used in any particular job; these qualifications 

depend upon local features. In areas which have 

been glaciated (for example, the Ohio Valley and 

the Great Lakes) or in coastal-plain areas, consolidate rock may be scarce or may be covered by unconsolidated materials, giving the latter products a 

competitive cost advantage. 

Other substitutes for crushed stone are manufactured aggregates, such as slag or expanded lightweight aggregates. 

Principal substitutes for dimension stone are precast concrete slabs or blocks (which may use either 

crushed stone, sand and gravel, or expanded shale 

as aggregate) , bricks, and glass or ceramic products. Use of dimension stone as a principal structural material has declined since the growth of 

structural steel construction, but many producers 

are now providing dimension stone in thin slabs or 

as composites, with concrete backing, for exterior 

use (Bliss, 1971), and a growing demand is anticipated. 

PROBLEMS FOR RESEARCH 

Although the United States is self-sufficient in 

resources of stone, local problems commonly result 

from lack of adequate planning to reserve the best 

areas for quarrying. Many communities expanded so 

rapidly during the 1950's and 1960's that potential 

quarry sites were surrounded, or in some cases covered, with urban development. Then, when existing 

quarries approached property lines, or encountered 

excessive water which increased the cost of deeper 

quarrying, the operators had difficulty in locating 

and developing a new site. Residents object to the 

noise, vibration, blasting, dust, and increased truck 

traffic associated with quarrying. To avoid this, operators have had to go to more distant sites, thereby 

increasing the cost of the delivered product. One 

alternative to this is underground quarying, which 

has the additional advantage of providing usable 

underground space after the rock has been removed. 

An example is a 1,500-acre tract in Kansas City, 

Mo., where the planned use as an underground storage area serves as a guide in the extraction of 

limestone (Missouri Geological Survey and Water 

Resources, 1970). 

In most areas, certain geologic formations provide the best source of stone for construction. If a 

geologic map of the area has been made, it is a 

simple matter to prepare a map showing areas of 

suitable quarry rock which should be preserved, and 

these could be of great assistance to zoning boards, 

planning commissions, and other nongeological 

groups who are faced with the problem of locating 

construction stone. 

SELECTED REFERENCES 

American Society for Testing and Materials, 1970, Annual 

book of ASTM standards, pt. 10: 620 p. 

--1972, Annual book of ASTM standards, pt. 12: 516 p. 

Barton, W. R., 1968, Dimension stone: U.S. Bur. Mines 

Inf. Circ. 8391, 147 p. 

Bliss, D. R., ("Bud"), 1971, The shape of things to come: 

Stone Mag., v. 91, no. 1, p. 6-9. 

Bowles, Oliver, 1939, The stone industries [2d ed.]: New 

York, McGraw-Hill Book Co., 519 p. 

-- 1956, Limestone and dolomite: U.S. Bur. Mines lnf. 

Circ. 7738, 29 p. 

-- 1960a, Dimension stone, in Gillson, J. L., ed., Industrial minerals and rocks [3d ed.]: Am. Inst. Mining 

Metall. and Petroleum Engineers, p. 321-337. 

-- 1906b, Slate, in Gillson, J. L., ed., Industrial minerals 

and rocks [3d ed.]: Am. Inst. Mining Metall. and Petroleum Engineers, p. 791-798. 

Cooper, J. D., 1970, Stone, in Mineral facts and problems, 

1970: U.S. Bur. Mines Bull. 650, p. 1219-1235. 

Currier, L. W., 1960, Geologic appraisal of dimension-stone 

deposits: U.S. Geol. Survey Bull. 1109, 78 p. 

Daugherty, Mary, and Fahrney, Nellie, 1972, Statistical 

summary U.S. Bur. Mines, preprint from 1970 Bureau of 

Mines Minerals Year book, 36 p. 

Division of Nonmetallic Minerals, U.S. Bureau of Mines, 

1972, Stone, in Commodity data summaries: U.S. Bur. 

Mines, p. 140-141. 

Drake, H. J., 1972, Stone: U.S. Bur. Mines, preprint from 

1970 Bureau of Mines Minerals Yearbook, 19 p. 
162 UNITED STATES MINERAL RESOURCES 

Missouri Geological Survey and Water Resources, 1970, 

[Storage]: Missouri mineral industry news, Rolla, Mo., 

v. 10, no. 5, p. 95. 

Sereringhaus, Nelson, 1900, Grushed S.tone, in Gillson, J. L., 

ed., Industrial minerals and rocks [3d ed.]: Am. Inst. 

Mining Metall. and Petroleum Engineers, p. 285-302. 

Stose, G. W., ed., 1932, Geologic map of the United States: 

U.S. Geol. Survey. 

Sweet, H. S., and Woods, K. B., 1942, A study of chert as a 

deleterious constituent in aggregates: Purdue Univ. 

Eng. Bull., v. 26, no. 5, 110 p. 

Thrush, P. W., ed., 1968, A dictionary of mining, mineral, 

and related terms: U.S. Bur. Mines, 1269 p~ 

Wood, S. 0., Jr., and Carrales, M., Jr., 1970, Stone: U.S. 

Bur. Mines, preprint from 1969 Bureau of Mines Minerals Yearbook, 21 p. 
UNITED STATES MINERAL RESOURCES 

COPPER 

By DENNIS P. Cox, RoBERT G. ScHMIDT, JAMES D. VINE, HAROLD KIRKEMO, 

ELIZABETH B. TouRTELOT, and l\1ICHAEL FLEISCHER 

CONTENTS 

Abstract of conclusions --------------------------

Properties, uses, and resources -------------------

Exploitation -------------------------------------

Geologic environment ----------------------------

Geochemistry and abundance -----------------

Geochemical cycle ------------------------

Mineralogy ----------------------------------

Types of deposits ---------------------------- Porphyry copper deposits and related types_ 

Porphyry copper deposits -------------

Veins, pipes, and replacement deposits __ 

Strata-bound deposits in sedimentary rocks_ 

The Kupferschiefer ------------------

The African copper belt --------------

Precambrian sedimentary copper deposits in the United States ----------

Precambrian sedimentary copper deposits in the U.S.S.R. --------------

Red-bed copper deposits --------------

Modern sea floor nodules ------------- Metal-rich sediments of the Red Sea __ _ 

Horizontal transport of secondary 

copper deposits --------------------

Mobilized deposits of probably sedimentary origin --------------------

Environments of deposition -----------

Size and grade characteristics --------

Massive sulfide deposits in volcanic rocks __ _ 

Copper in nickel ores --------------------

Native copper deposits of the Keweenaw type 

Miscellaneous types ----------------------

Resources --------------------------------------- Identified and hypothetical resources -----------

Speculative resources -------------------------

Subeconomic resources ------------------------

Prospecting techniques ---------------------------

Problems for research ------------------------

Selected references 

FIGURES 

Page 

163 

164 

165 

166 

166 

167 

168 

169 

169 

169 

171 

172 

173 

173 

174 

175 

175 

176 

17G 

21. Graph showing U.S. primary copper production, 1850-1970 -------------------------- 22. Graph showing size and grade characteristics 

36. 

37. 

38. 

39. 

40. 

41. 

of selected copp·er ore bodies ---------------

TABLES 

Copper supply and demand data, 1950-71, and 

projections for the year 2000 --------------

Copper content of various materials ----------

Minerals of copper; composition and environment of origin --------------------------- Identified and hypothetical copper resources --

Summary of speculative resources of copper __ 

Partial list of subeconomic (conditional) resources of copper -------------------------

ABSTRACT OF CONCLUSIONS 

Page 

166 

171 

Page 

165 

167 

168 

180 

183 

184 

About 70 percent of the world's identified copper resources 

can be grouped in the following geologic-geographic cate176 gories, listed in order of decreasing importance: porphyry 

177 

177 

178 

178 

179 

179 

180 

180 

180 

181 

183 

185 

186 

186 

copper deposits of Chile and Peru, porphyry copper deposits 

of the Southwestern United States (19 percent of the world 

total), sedimentary copper deposits of Za'ire and Zambia, 

and porphyry cop·per and sedimentary copper deposits of 

the U.S.S.R. Other important groups of identified resources 

include porphyry copper deposits in Oceania, in Mexico, and 

in western Canada and porphyry copper and sedimentary 

copper deposits in southeastern and central Europe, respectively. These and the remaining identified resources amount 

to 344 million tons of copper metal, sufficient to last for 50 

years at present rat.es of mine production. 

Hypothetical resources, or those not now known but 

suspected to be present near known deposits, will probably 

provide another 400 million tons of copper. Important reresources of this category are most likely to occur in the 

porphyry copper provinces of southeastern Arizona, western 

Canada, Chile, and Peru. Large sedimentary deposits will 

probably be found in Africa, the U.S.S.R., and the northern 

Page Rocky Mountains of the United States. Additional resources 

20. Graph showing U.S. supplies and uses of cop- in sea-floor manganese nodules also will probably be disper, 1950-71 ----------------------------- 165 covered. 

U.S. GEOL. SURVEY PROF. PAPER 820 

163 
164 UNITED STATES MINERAL RESOURCES 

It is possible to speculate that another 320 million tons of 

copper might be found in areas not yet prospected and 

in which important deposits are unknown. The most promising areas lie in the Basin and Range province of the United 

States, outside the known porphyry copper province; in the 

U.S.S.R. Far East where porphyry copper provinces may be 

found in Mesozoic fold belts and the younger island arc system; and in the Brazilian shield where major sedimentary 

copper deposits might be found. 

The aforementioned identified, hypothetical, and speculative categories refer to known or postulated ore deposits, 

minable under present economic and technological conditions. 

In addition to these are large conditional resources in 

porphyry copper, sedimentary copper, and igneous coppernickel deposits and in manganese nodules on the sea floor. 

At least 381 million tons of copper in ~uch subecooomic deposits can be identified or hypothesized. This copper may become available at some future period of high metal prices 

and (or) improved technology. 

A comparison of current U.S. and world production and 

the copper content of various copper deposits shows that 

the United States p·roduces enough copper to mine out an 

average-sized porphyry copper deposit each year. Maintaining a balance between deposits discovered and deposits 

mined out means that a great investment in geological, geochemical, and geophysical studies must be made and maintained in spite of short-~rm fluctuations in the price of 

copper. 

PROPER TIES, USES, AND RESOURCES 

Copper, one of the most useful and versatile 

metals, has been used by man perhaps longer than 

any other metal except gold. Its unique physical and 

mechanical properties are utilized both in its metallic state and in alloy with many other metals. Copper, chemical symbol Cu, has a hardness (Mohs' 

scale) of 2.5-3, a melting point of 1,083°C, a boiling point of 2,595°C, a density (annealed at 20°C) 

of 8.89, and an electrical resistivity at 20°C of 1.71. 

Its electrical conductivity in cross section and by 

weight is surpassed only by silver and by aluminum, 

respectively. 

High electrical and thermal conductivities, good 

resistance to corrosion, good ductility and malleability, high strength, lack of magnetism, and a 

pleasing red color are properties and characteristics 

of copper that find innumerable industrial applications. Copper and many of its alloys can be joined 

by welding, brazing, and soldering. It can be finished by plating and lacquering. 

The four traditional copper-base alloys, brass, 

bronze, nickel-silver, and cupronickel, contain no 

less than 40 percent copper, with the amount of 

copper not less than that of any other constituent. 

Copper also is used in many other alloys where it 

is not the major component. 

About half (53 percent) of the 1.5 million tons 

of copper used domestically in 1970 was for electrical applications, followed by 16 p~rcent in construction, 12 percent in industrial machinery, 8 percent in transportation, 6 percent in ordnance, and 

5 percent in other uses. 

Use of copper in all applications for which it is 

suited would exceed its available supply, but aluminum has substituted for copper in many applications. In the last two decades U.S. consumption of 

aluminum has more than tripled, while the use of 

copper increased only 15 percent. Although copper 

is virtually indispensable for some applications, 

aluminum serves satisfactorily as an alternate metal 

in many others, and often at lower cost. The relative capabilities of the two metals in their electrical 

conductor applications depend on their physical and 

mechanical properties. For example, an aluminum 

conductor weighs only 30 percent as much as a 

copper conductor of identical size, but an aluminum 

conductor has 1.64 times the electrical resistance of 

a copper conductor of equal size. Thus, for equal 

current-carrying capacity, an aluminum conductor 

weighs half as much as a copper conductor, but has 

a cross-sectional area 26 percent greater. 

Aluminum and stainless steel are used in place of 

copper for some applications in the building industry. Steel increasingly replaces brass in shell cases. 

The use of copper cladding proportionately requires 

less copper than would solid copper; copper now 

substitutes for silver in coins which have a copper 

core and a cupronickel cladding material. Printed 

electrical circuits and plastics have replaced copper 

in many applications. These shifts in the overall 

use pattern make more copper available for preferred uses. In spite of substitution, the continued 

use of a substantial part of our present copper requirement is needed to maintain or present living 

standard. 

The supply to meet .domestic demand is derived 

from U.S. mine production, secondary production 

(recovery of old scrap), imports, and withdrawals 

from industrial and Government stockpiles. The 

trends in supply and demand for copper during the 

period 1950-70 are illustrated in figure 20 and 

table 36. Other demand forecasts to the year 2000 

are discussed by Lowell (1970) and by Ageton and 

Greenspoon (1970). 

Copper is traded in a number of commercial 

classes-ore, concentrate, matte, blister, refined, and 

secondary-each with varying percentages of copper content. Because of the complexity in determining the total amount of copper used from all 

classes and the many demands of trade such as 

imports, exports, and stockpiles, the total demand 
COPPER 165 

3 

~CI) .z 

t-0 

Zl- 2 

w&L 

~0 

Ocn 

oz 

~0 1 .~ 

... ~ ;i o~~...:~= 

1950 

USES 

1955 1960 1965 1970 1950 CURRENT 

FIGURE 20.-U.S. supplies and uses of copper, 1950-71. (From U.S. Department of the Interior (1972). 

TABLE 36.-Copper supply and demand data, 1950-71, and 

projections for the year 2000, in thousands of short tons 

[Data from National Commission on Materials Policy (1972), U.S. De- partment of the Interior ( 1972), and U.S. Bureau of Mines (1970] 

Year Refined Old 

production scrap U.S. mines 

1950 ----------- 921 485 

1960 ----------- 1,121 429 

1970 ---------- 1,521 504 

1971 1 ---------- 1,400 450 

2000 3 ---------- 2,38(1 1,700 

1 Preliminary. 

2 Not available or estimated. 8 Unrefined. 

Total U.S. Rest of U S demand, ex- world mine net elusive of production 

imports new scrap 

491 

107 

155 

190 

(2) 

1,897 

1,657 

2,180 

2,040 

9,700 

1,851 

3,570 

4,847 

(2) 

(2) 

often is expressed as withdrawals or apparent consumption. 

With few exceptions, the United States has been 

a net importer of copper each year since 1939. Dependency on foreign sources of supply has ranged 

from a high of about 60 percent in 1945 and 1946 

to 6 percent in 1971. 

The major sources of copper imports in 1971 

were Canada, 37 percent; Peru, 29 percent; Chile, 

15 percent; and all other countries; 19 percent. 

Major destinations of copper exports in 1971 were 

West Germany, 26 percent; Italy, 11 percent; 

France, 10 percent; Canada, 9 percent; and all other 

countries, 44 percent. 

The sources of 1971 imports differ markedly from 

the sources for the 1967-70 period, when 27 percent 

originated in Chile, 23 percent in Canada, 21 percent in Peru, 7 percent in the Republic of South 

Africa, and 22 per from all other countries. The 

nationalization in 1971 of mines owned by U.S. 

firms in Chile disrupted world trade patterns in 

copper, as is evident from the preceding data. 

The possible effect of industrialization of developing countries on the world copper market is best 

illustrated by the Peoples Republic of China. Present 

per-capita copper consumption in China is about 

one-half pound per year, and many recent studies 

of the world metal situation have pointed to the 

impact of the increase that is sure to come with 

advancing industrialization in that and other populous, mostly agricultural, countries. Even though 

Chinese copper production may increase rapidly, 

consumption may well outrun it for many years, and 

China probably will become a major importer in the 

short term, though self-sufficiency may be possible 

at a future time. The 4-year agreement for Chinese 

purchase of copper from Chile is an example of this 

kind of change that is sure to have widespread effect 

on the world copper market. 

EXPLOITATION 

The introduction of new domestic sources of copper, important new developments, and other events 

having significant impact on the supply of copper 

are shown in relation to primary copper production 

in figure 21. 

Development of foreign deposits also has had its 

impact on the copper industry. The more economically important developments were the following : 

1912, Braden Copper Co. began operations in Chile. 

1916, Chile Copper Co. started production at Chuquicamata. 

1924, Katanga in Zaire (Congo) started production. 

1950, 1960's, Large deposits developed in Chile and 

Peru. Substantial production started and reserves 

added in Canada, Zambia, Zaire, Yugoslavia, 

Poland, Ireland, Finland, Bulgaria, U.S.S.R., 

Australia, and the Philippines. 

Among the foreign developments begun in the 

1960's and expected to be in production in the 1970's 

are those in Indonesia (West Irian), New Guinea 

(Manus Island, Bougainville), British Columbia, 

and Iran. 

Two factors of paramount importance to the copper industry are the grade of ore mined and the 

price per pound. The steady decline in average grade 

of domestic ore mined and the wide range in prices 

are evident in the following summary : 
166 UNITED STATES MINERAL RESOURCES 

1.8 

a: 

w 

Q. 

Q. 

0 

0 

0 

w 

z 

<t 

1-

z 1.1 0 

0 

u.. 

0 

(/) 0.9 z 

0 

1- 0.8 

1-

a: 

0 0.7 

I 

(/) 

u.. 0.6 

0 

(/) 0.5 

z 

0 

...J 0.4 ...J 

~ 0.3 

0.2 

0.1 

"' ... 

·;;; 

0 

Q. 

II 

"C 

> 

> J: 

Q. 

0 

Q. 

c 

0 

"C 

II 

Q. 

0 

'i 

> II 

"C 

Q 

c 

·c: 

·e 

... ·a 

c 

II 

Q. 

0 

0 

0 

01 

... 

"' "' 8 

0 

a. 

c 

0 

·;; 

• 0 

;: 

II 

> 

·;; 

u • 'i 

"' 0 

-

... 

Ill 

~ 

:E 

0 

~ 

\ 

Economic boom._, 

Recession 

1930's depression 

0 

r01 

... 

FIGURE 21.-U.S. primary copper production, 1850-1970. 

Notes indicate major new sources, developments, or events. 

Average annual price in cents per pound Average grade of Year Quoted refinery Equivalent ore mined 

1970 doUars (percent copper) 

1900 ---------- 16.19 63.5 4.0 

1910 ---------- 12.73 43.5 1.88 

1920 ---------- 17.45 30.0 1.63 

1930 ---------- 12.98 32.5 1.43 

1940 ---------- 11.29 29.5 1.20 

1950 ---------- 21.32 30.0 .89 

1955 ---------- 37.49 41.0 .83 

1960 ---------- 32.05 36.5 .73 

196·5 ---------- 35.02 39.9 .70 

1970 ---------- 58.20 58.2 .60 

Copper ores also contain other valuable recoverable metals, and many ores mined chiefly for other 

metals also contain recoverable copper. The 

coproduct-byproduct recovery of copper and associated metals from ores depends upon the quantity of 

metals present (grade) and the processes used in 

recovering the principal values. Copper production 

yields significant quantities of gold, silver, molybdenum, cobalt, zinc, lead, nickel, sulfur, tellurium, 

selenium, rhenium, palladium, platinum, arsenic, 

and iron. Seleni urn is an essential byproduct of copper production, and rhenium is obtained from the 

molybdenum in porphyry deposits. Cobalt is derived 

mainly from copper ores mined in Zaire. 

Several problems of major concern to copper producers relate to protecting environmental qualities 

while maintaining competitive costs. Copper smelters are under severe new or proposed restrictions 

on sulfur emission, requiring major capital investment for control equipment. This stress may result 

in the closing of some smelters and a shift to new 

methods of hydrometallurgy. Surface restoration is 

particularly difficult in copper mining because of 

the finely powdered state of mill tailings and the 

very high ratio of waste to produced metal. Water 

pollution by mine and mill waste is a problem, and 

particularly as many of the big copper deposits are 

in arid regions, obtaining adequate water supplies 

for mining and milling becomes more difficult. 

Several porphyry copper deposits in Arizona are 

now being worked by in-place leaching methods 

which greatly decrease the effect of copper extraction on the environment. The deposits are first cut 

by a system of tunnels, then fractured by explosive 

or hydraulic methods, and then leached by sulfuric 

acid introduced through pipes to the upper part of 

the deposit. The copper-rich fluids are withdrawn 

from the lowest levels of mine workings, pumped 

to the surface and the copper removed electrolytically. The main disadvantages of this method 

are that only 50-60 percent of the copper in the ore 

deposit can be recovered under present techniques, 

and that all of the byproduct metals, such as molybdenum, gold, and selenium, are left in the rock during the leaching process. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY AND ABUNDANCE 

Copper is a chemical element of group II-B of the 

periodic table; it has atomic number 29 and atomic 

weight 63.546, consisting of the isotopes 63Cu(69.09 

percent) and 65Cu (30.91 percent). It occurs in nature as the native element, as compounds of Cu+1 

(ionic radius 0.54 A) and Cu +2 (ionic radius 0.81 A 

for sixfold coordination). In the Cu+2 state, as 

shown particularly by naturally occurring sulfates 

and phosphates, it is isomorphous with Zn (0.83 A), 

Mg (0.80 A), and Fe+2 (0.69 A). In· sulfides, Cu+2 

is isomorphous with zinc (as in tetrahedrite), and 

Cu +1 with silver. Copper is a strongly sulfur-seeking 

(chalcophile) element, and it tends to be concentrated in sulfide deposits; in igneous rocks it occurs 

mainly as finely divided sulfides, principally chalcopyrite and bornite. 

Estimates of the abundance of copper in the con-
COPPER 167 

tinental crust have been reviewed by Parker (1967); 

most recent estimates are about 50 ppm (parts per 

million). As indicated in table 37, copper is conTABLE 37.-Copper content of various materials 

Copper content generally reported 

Type of material Range Average 

Igneous rocks (parts per million) 

Ultramafic rocks ---------------- 15 

Basaltic and gabbroic rocks ------ 30-160 90 

Andesites ----------------------- 35 

Granitic rocks ------------------ 5-30 15 

Sedimentary rocks (parts per million) 

Limestones ---------------------- Sandstones --------------------- Shales and clays ------------- __ _ 

Soils --------------------------- Phosphorites ___________________ _ 

Coals ---------------------------

1 10-20 

18-120 

2-100 

10-100 

2-40 

Waters (parts per billion) 

Sea VVater ---------------------- Surface waters ------------------

1 Pettijohn ( 1963). 

1-15 

.4-150 

4 

10 ( ?) 2 45 

20 

30 

15 

3 

5 ( ?) 

2 260 for deep-sea elays ( Turekian and Wedepohl, 1961); 660 average for 450 samples of deep-sea elay ( Landergren and Manheim, 1963). 

centrated in the igneous cycle in basaltic and gabbroic rocks. In these it is highest in the ferromagnesian minerals such as pyroxenes and biotite where 

it probably occurs mainly as minute grains of chalcopyrite (Goldschmidt, 1954, p. 182). 

During the crystallization of igneous rocks, copper and some other elements that do not fit readily 

into the structures of silicate minerals may be concentrated to form ore deposits. If the magma contains appreciable volatiles, copper may be dissolved 

and transported with these into veinlets or extensive vein systems. If, as in the case of some gabbroic rocks, the volatile content is low, copper may 

remain in the intrusion, concentrating as an immiscible copper sulfide fluid. 

The data on sea water indicate that less than 

0.1 percent of the copper carried to the ocean remains in solution, the remainder being precipitated-mainly with the clays, in part with manganese oxides, and in part removed by biota. Probably 

much, perhaps most, of the copper reported in surface waters is due to industrial contamination from 

metallurgical wastes, plating work, and so forth. 

Copper is found in at least trace amounts in 

nearly all sedimentary rocks. The averages for 

some common rocks are shown in table 37. The copper content of Lower Eocene nonmarine sandstones 

in the Rocky Mountain region was found to average 

11 ppm and, for individual basins, to range from 

5.2 to 29 ppm (Vine and Tourtelot, 1970a). Pelitic 

Belt rocks from the Mission Mountains Primitive 

Area, Mont., contain an average of 14 ppm copper, 

whereas similar rocks in the Pend Oreille, Idaho, 

area contain 6.8 ppm copper (Harrison and Grimes, 

1970, table 11). 

Copper is readily soluble and mobilized by oxidizing solutions; therefore, it concentrates in certain 

environments of deposition. Thus, marine clays and 

other fine-grained rocks tend to have more copper 

than coarse-grained rocks and limestones. Moreover, 

the average black shale contains about twice as much 

copper as the average shale, and some black shales 

rich in organic matter contain several hundred parts 

per million copper (Vine and Tourtelot, 1970b). 

Pelagic sediments contain significantly greater concentrations of copper than continental rocks. Landergren and Manheim ( 1963) reported 560 ppm 

copper as the average for 450 samples of deep-sea 

clay. Bostrom and Peterson (1966) found more than 

1,000 ppm copper and an enrichment of several 

heavy metals along the crest of the East Pacific rise. 

A metal-rich sediment associated with hot brine 

from the Atlantis II deep in the Red Sea is reported 

to contain 0.5 percent copper (Miller and others, 

1966). 

GEOCHEMICAL CYCLE 

Copper is introduced into the accessible part of 

the earth's crust from unknown deeper sources by 

igneous intrusions and by upward migrating fluids. 

Economic concentrations of the metal may result 

directly from these processes and from secondary 

effects of weathering, erosion, and sedimentation. 

Remobilization and reconcentration by numerous 

later stages of intrusion and by metamorphism may 

occur, and in addition ground water and deep connate waters may dissolve, transport, and redeposit 

copper to form younger ore deposits. Copper in 

oceanic basalt and copper carried to the sea in solution and deposited with oceanic sediments may be 

remobilized during subduction of oceanic crustal 

plates, and a part may ultimately be redeposited in 

continental crustal rocks above the subduction zone. 

The weathering of chalcopyrite readily oxidizes 

copper and releases it to ionic solution. A portion 

of this ionic copper may be adsorbed on organic 

matter, clay minerals, and iron oxide particles, and 

some of it probably reaches the sea in ionic form. 

According to Robert Ehrlich and T. A. Vogel (oral 

commun., 1972), the absence of much potassium is 

an important factor in the transport of copper as a 

complex with montmorillonite. The copper in solution in river waters ranges widely, but 0.010-0.015 

ppm is probably the general range for large rivers. 

Some copper is believed to have been transported 

to the Siberian U dokan deposits in detrital form 
168 UNITED STATES MINERAL RESOURCES 

(Bogdanov, 1968), and Ehrlich and Vogel (oral 

commun., 1972) suggested that some of the copper 

in the Nonesuch Shale was carried in this way. 

Because sea water contains only 0.003 ppm copper 

(Green, 1969), the discharge of an estimated 1X106 

tons new copper by streams each year must be balanced against various mechanisms that remove it. 

In reducing environments, copper is probably precipitated as the sulfide by sulfur-reducing bacteria 

or adsorbed on decaying humic organic matter. Copper also accumulates in some oxidizing environments, such as in manganese nodules and in pelagic 

muds where precipitation may occur as the oxide. 

The fate of copper in an evaporite environment is 

not understood. Some copper may be concentrated 

in residual brines and eventually squeezed into adjacent porous sediments and precipitated by reaction 

with hydrogen sulfide. Copper may also be trapped 

in connate pore waters in basins of nonmarine deposition. Precipitation would eventua!ly occur by reaction with hydrogen sulfide or organic matter, or 

as a carbonate, sulfate, silicate, or phosphate. The 

regional and stratigraphic association of stratabound copper ores with evaporites was described by 

Davidson (1965). 

billion years ago (Cloud, 1971) , the geochemical 

cycle for copper may have been significantly different. Primary copper sulfide minerals were probably 

sufficiently stable to survive weathering and redeposition as heavy minerals in detrital rocks. Subsequent exposure of buried sediment to oxygenated 

waters could have resulted in redistribution of the 

copper in chemically reactive environments within 

the sedimentary sequence, for example in beds rich 

in organic matter. 

MINERALOGY 

Copper occurs in at least 160 minerals. Table 38 

gives the name, composition, and general mode of 

occurrence of 20 of the more common ones. 

Prior to the evolution of a modern atmosphere 

containing about 20 percent oxygen some 1.2-1.4 

Chalcopyrite is by far the most abundant copper 

sulfide; bornite and chalcocite are next in abundance. 

The sulfarsenides enargite and tennantite and the 

sulfantimonides tetrahedrite and famatinite are 

generally rare, but each makes up major parts of 

at least one large ore body. The mineral digenite 

(Cu2-.7!S) is not shown in table 38, but it may be a 

major ore mineral. It is detected only by careful 

petrographic work or X-ray analysis and is generally reported as chalcocite. Native copper is abundant in certain types of deposits. 

Malachite, azurite, and chrysocolla are the most 

TABLE 38.-Minerals of copper; composition and environment of origin 

[o, major ore mineral; x, minor ore mineral] 

Name 

Native copper -------------- Chalcocite ------------------ Covellite ------------------- Bornite -------------------- Chalcopyrite --------------- Enargite ------------------- Cuprite -------------------- Malaehite ------------------

Tetrahedrite --------------- Tennantite ----------------- Famatinite ----------------- Stannite ------------------- Atacamite ------------------ Tenorite (melaconite) ------

Azurite -------------------- Chrysocolla ---------------- Brochantite ---------------- Antlerite ------------------ Chalcanthite --------------- Kroehnkite -----------------

Composition 

Major minerals 

Cu ------------------------ Cu2S ---------------------- CuS ----------------------- CuoFeS .. --------------------

CuFeS2 -------------------- CuaAsS, -------------------

Cu20 ---------------------- Cu2(0H)2(C0s) ------------

£ 

i 

~ P-4 

X 

0 

0 

Significant supplementary minerals 

.. "ttm s=E! 

·~ 

--a =· 

~2: 

0 

0 

0 

0 

(Cu,Fe)12Sb4Sa ------------- x (Cu,Fe)uAs,Sa ------------- x 

C~SbS, -------------------- X 

Cu2FeSnS, ----------------- x Cu2(0H)aCl ----------------

CuO ----------------------- Cua(OH)2(C0s)2 ------------ CuSiOs•2H20 --------------- Cu,(SO,) (OH)e ------------- Cua(SO,) (OH), ------------ CuS0,•5H20 ---------------- Na2Cu(S0,)2•2H20 ----------

t;-ot~ 

s~ ti.ljl 

.§S li 

0 

0 

X 

0 

.~~ 

m= 

~j 

=· 

~~ :>r~~ 

0 

0 

0 

X 

X 

X 

( ?) 

Secondary 

enrichments 

and secondary 

deposits 

= ~ ~:8 .... Cll 

El~ ~G G ~ 1111'4 "ttG q:lG 

·~ G~ ~s -= ))Jill ::.::~ ... ~s 

0 X X 

X 0 

0 

0 

0 

0 X 

0 

X 

0 

X 

0 

X 

0 

0 

X 
COPPER 169 

common minerals of the oxidized zone, and the 

bright colors of these minerals have been a guide to 

prospectors for thousands of years. 

TYPES OF DEPOSITS 

Most copper deposits fall into one of five major 

types. ( 1) The most important of these are the 

porphyry copper deposits and vein and replacement 

deposits; these account for almost two-thirds of the 

world's copper resources and are discussed together 

because of their common genetic association with 

felsic intrusive rocks. (2) A fourth of the world's 

identifiable copper resources is in sedimentary rocks, 

and ( 3) about 5 percent is in volcanic rocks as 

massive sulfide deposits. ( 4) Smaller portions of 

world resources are in nickel-copper ores formed by 

magmatic processes in mafic intrusives and ( 5) in 

native copper ores of the Keweenaw type. These 

types, as well as certain uncommon or unique types 

of deposits, are discussed in order of their relative 

importance as copper resources. 

PORPHYRY COPPER DEPOSITS AND RELATED TYPES 

Porphyry copper deposits and most of the important vein and replacement copper deposits are 

genetically associated with intrusions of felsic igneous rocks. The copper in these deposits is believed 

by some geologists (for example, Fournier, 1967) 

to be a primary constituent of the associated intrusion. A part of the copper is trapped in disseminated 

grains by the rapid crystallization of the magma, 

which in turn gives rise to the characteristic porphyritic texture of the intrusion. Another part of 

the copper is mobilized by water and other volatiles 

escaping from the hot congealed rock mass and is 

deposited in fractures in the intrusion and its wall 

rocks. A third part may escape completely from the 

intrusion and form vein and replacement deposits 

in nearby reactive host rocks. Thus porphyry copper 

deposits commonly occupy the central part of large 

or small mining districts containing vein and replacement deposits of copper, lead, zinc, silver, gold, 

iron, and manganese. 

PORPHYRY COPPER DEPOSITS 

An excellent review of the geology of porphyry 

copper deposits of the North American Southwest 

with detailed descriptions of 15 individual deposits 

was assembled by Titley and Hicks ( 1966). Sutherland-Brown (1969) and Sutherland-Brown, Cathro, 

Panteleyev, and Ney (1971) wrote excellent descriptions of deposits in British Columbia. 

Porphyry copper deposits are defined herein as 

deposits of disseminated copper sulfide that are in 

or near a felsic intrusive body; in most deposits, at 

least one facies of the intrusive is a porphyry. This 

definition does not include size, grade, or amenability to mass-mining methods because these factors 

restrict consideration of the similar but subeconomic occurrences that are so important to regional 

metallogenic studies. Lowell and Guilbert ( 1970) 

tabulated the geologic features of 27 major porphyry deposits, 18 of them in the North American 

Southwest, and arrived at a typical or average deposit. This hypothetical ore body is oval and pipelike, it measures 3,500 by 6,000 feet in plan, and 

it contains 150 million tons of ore averaging 0.8 

percent copper and 0.15 percent molybdenum. Ore 

below the zone of secondary enrichment contains 

on the average only 0.45 percent copper. On the 

average 70 percent of the ore body is in the intrusion, and 30 percent is in the country rock. Sulfide 

minerals in descending order of abundance are 

pyrite, chalcopyrite, molybdenite, and bornite. 

Supergene sulfides may form a higher grade zone 

of secondary enrichment. 

Porphyry copper deposits have petrologic associations that are dependent on their tectonic environment. Deposits formed on thick continental 

crust are usually associated with quartz monzonite, 

as in Arizona (Lowell and Guilbert, 1970). Deposits 

in island arcs are associated with quartz diorite, 

diorite, or granodiorite, as in Bougainville (Macnamara, 1968), the Philippines (Madamba, 1972; 

Loudon, 1972), and Puerto Rico (Cox, 1971). Similarly, British Columbia porphyry deposits of two 

distinct ages and of distinct petrologic affinities 

seem to be related to two types of crustal plate 

motion (Hodder and Hollister, 1972). Thus, deposits 

of Triassic and Jurassic age were formed during 

plate convergence as the North American plate 

moved westward over the Pacific plate; as the East 

Pacific rise drifted under the American plate, development of tensional structures in the continental 

crust and a new regimen of magmatic activity gave 

rise to the Cretaceous and Tertiary deposits. The 

deposits formed in the earlier cycle in a thin or 

poorly developed continental crust are associated 

either with syenite, monzonite, or fennite as at Stikeen and Copper Mountain or with quartz diorite 

and granodiorite as at Highland Valley. The later 

deposits that formed in a thicker continental crust 

are associated with quartz monzonite. 

Breccia pipes are present in 20 of the 27 deposits 

considered by Lowell and Guilbert (1970), and wide 

zones of closely and irregularly fractured rock 

(crackle zones) surround almost all the deposits. 

This last feature is a very useful one in the recognition of porphyry deposits in the field. 
170 UNITED STATES MINERAL RESOURCES 

Lowell and Guilbert (1970, p. 403-404) described 

the hydrothermal alteration of a typical deposit 

as forming in response to a "physical-geochemical 

continuum from low-temperature magmatic to 'conventional' hydrothermal conditions" in which hydrogen ion concentrations increase outward or with 

time. Where the country rock is homogeneous, a 

series of symmetrical, concentric shells of distinct 

hydrothermal mineral assemblages may be produced around the igneous intrusive. From the interior of the deposit outward, these are the potassic 

( quartz-K-feldspar-biotite), the phyllic (quartzsericite-pyrite), the argillic (quartz-kaolin-chloride), 

and the propylitic (chlorite-epidote-carbonateadularia and albite). 

Many factors limit or disrupt the symmetry of 

the model porphyry copper deposit. Lowell and Guilbert listed (1) a strong regional structural fabric, 

(2) heterogeneity of preore host rocks, (3) postore 

faulting and intrusion, and ( 4) different levels of 

erosion exposing the deposits. 

Titley (1972) drew attention to the profound 

effect of the country rock on the alteration mineralogy and on the form of the ore bodies. He distinguished "intrusion porphyry copper deposits" in 

which the ore body is mostly within the intrusive 

porphyry, from "wall rock porphyry copper deposits". in which the wallrock near a porphyry intrusion is altered and mineralized. Composites of 

these types are common. Titley emphasized that ore 

bodies in wallrocks may be just as valuable as those 

in intrusions and should not be overlooked because 

their alteration pattern does not follow the ideal 

model. 

Porphyry copper deposits of the Pacific and Caribbean islands exhibit alteration patterns that diverge sharply from the Lowell and Guilbert model. 

Biotite is the most common mineral in the potassic 

alteration facies, and K-feldspar is commonly lac-king, possibly because of the low availability of potassium in the intrusive quartz diorite and diorite 

porphyries and surrounding andesitic volcanic rocks. 

Propylitic alteration is widespread in these deposits, 

and in Puerto Rico it appears to follow an early 

period of biotitic alteration (Cox, 1971). 

Figure 22 shows the size and grade characteristics 

of various porphyry copper deposits. The Bingham 

deposit in Utah is the largest in the United States, 

with a production since 1904 of over 14 million tons 

of copper (Anaconda Copper Corp., annual reports). 

The field of 22 U.S. deposits in production in 1960 

has its center point at about 100 million tons at 

0.8 percent copper or about 800,000 tons of copper 

metal per deposit. 

A second field of eight U.S. and Canadian deposits 

brought into production in the last 10 years shows 

a downward trend in grade. At Sierrita, Ariz., the 

mining of ore averaging 0.34 percent copper is 

made possible by lower cost mining and processing 

methods. These new deposits contain on the average 

about 2 million tons of copper each. Likewise, porphyry deposits with byproduct molybdenum discovered in other parts of the world are being brought 

into production at average copper grades as low as 

0.18 percent (Brenda, British Columbia) and 0.3 

percent (Casino, British Columbia) (Peters, 1970). 

La Caridad, Mexico (Peters, 1970) and the combined San Manuel-Kalamazoo deposits, Arizona 

(Peters, 1970; Thomas, 1966, p. 139) are the largest of the new deposits, with about 7 million tons 

of copper each. 

Overshadowing these are the great Andean porphyry deposits of Chile and Peru. These deposits 

were brought into production with average grades 

of 1-2 percent, and the average of 11 deposits 

plotted is about 4 million tons of copper each. The 

El Teniente and Chuquicamata deposits in Chile, 

which would lie on the right side of this field in 

figure 22, are larger by at least an order of magnitude than the majority of North American porphyry 

deposits. It is obvious that the Andes represent a 

copper province of great wealth and that numerous 

other lower grade deposits await development. 

The principal byproduct metals of porphyry deposits are molybdenum, gold, and silver. King (see 

"Molybdenum" chapter) gives a range of MoS2 

values of 0.015-0.1 percent for porphyry copper deposits; Simons and Prinz (see "Gold" chapter) give 

a range of 0.001-0.025 ounce gold -per ton in copper 

deposits in general. An average silver value of 0.06 

oz per ton is given for 14 Arizona porphyry deposits 

by Heyl and others (see "Silver" chapter). Kesler 

( 1971) pointed out that continental porphyry deposits have higher molybdenum values and that 

island arc deposits have higher gold values and 

lower molybdenum values. Gold content of the 

Panguna deposit in Bougainville is 0.018 oz per ton; 

the Marcopper deposit in the Philippines contains 

0.001 oz per ton (Espie, 1971; Loudon, 1972). Molybdenum values in these deposits are negligible. 

Economically important trace amounts of selenium, tellurium, and rhenium are derived from copper and molybdenum concentrates from porphyry 

deposits. Pyrite concentrates are recovered for their 

use in sulfuric acid manufacture, and magnetite 

concentrates are recovered from some porphyry del 

posits such as Atlas in the Philippines (Madamba, 

1972). 
COPPER 171 

1-

z 

w 

u 

a: 

w 

CL 

~ 

w· 

a: 

0 

a: 

w 

:: 0.5 

0 

u 

IL 

0 

w 

0 

c{ 

a: 

CJ 

0.1 

0.05 

500 1000 

QUANTITY OF COPPER ORE, IN MILLIONS OF SHORT TONS 

FIGURE 22.-Size and grade characteristics of selected copper ore bodies. Diagonal lines show tons of copper metal per deposit; world and U.S. mine production of copper metal are shown for comparison by diagonal dashed lines. Data from 

unpublished compilation by A. R. Kinkel, Jr., and others and from Peters (1970). 

VEINS, PIPES, AND REPLACEMENT DEPOSITS 

Copper-rich veins, pipes, and replacement deposits may be localized in felsic plutonic rocks with 

local porphyry intrusions as at Butte, Mont. (Meyer 

and others, 1968) ; in favorable host rocks near a 

porphyry copper deposit as at Bingham, Utah, and 

Bisbee, Ariz.; or near barren felsic intrusive rocks 

as at Magma, Ariz. (Hammer and Peterson, 1968) 

or Mission, Ariz. (Kinnison, 1966). Veins are 

formed when metal-rich solutions, emanating from 

a crystallizing intrusion, deposit minerals in faults 

or fractures. They are tabular in form and may 

show mineral textures indicating growth of crystals 

in open cavities as well as replacement of wallrocks 

by copper minerals. Many veins show several generations of mineral deposition related to opening 

and reopening of fault zones by tectonic movements. 

Hydrothermal alteration envelopes may accompany the veins, indicating chemical reaction between wallrocks and mineral-rich solutions. Sales 

and Meyer (1949), in their monumental study of 

quartz-sulfide veins at Butte, Mont., described a 

sequence of alteration zones outward from the veins 

into the quartz monzonite wallrocks. The sequence 

is consistently sericite to kaolin to montmorillonite 

to fresh wallrock. Comparison of the chemical composition of these zones suggests diffusion of some 

ions from the rock into the vein and simultaneous 

migration of hydrogen ions into the wallrocks. There 
172 UNITED STATES MINERAL RESOURCES 

is a close similarity in mineralogy between largescale alteration zones extending outward from 

porphyry deposits and small-scale alteration zones 

successively enveloping sulfide veins. 

Ore pipes are rodlike in form as contrasted to 

tabular veins. They may form in fractured or brecciated rock at the intersections of faults or by explosive release of gases derived from intrusive 

magmas. These latter are called breccia pipes because of the broken rock associated with them. At 

many places copper deposits in breccia pipes show 

a close spatial and genetic relation to mineralized 

porphyry intrusions as at Cananea, Mexico (V elasco, 1966) or a close geographic relation to porphyry copper deposits as in the porphyry copper 

belt in Chile (Sillitoe and Sawkins, 1971). 

Replacement deposits form in reactive host rocks 

near the intrusive contacts or along mineral veins. 

These hosts may be sedimentary rocks such as limestone, dolomite, or calcareous sandstone or even 

diabase sills as at Ray, Ariz. (Metz and Rose, 1966). 

Replacement deposits tend to be tabular in form 

and may be roughly concordant with bedding. 

Though high in grade at some mines, when these 

deposits are removed as part of a large low-grade 

ore body they are generally regarded as part of 

the porphyry copper ore body, as at the Mission 

and Pima mines in Arizona. Mining of porphyry 

ore at Bingham, Utah, encroaches steadily on chalcopyrite replacement bodies in limestone beds to the 

west, and the distinction between ore in porphyry 

and ore in wallrocks becomes academic. 

Favorable host rocks for replacement deposits 

may have continuity over large areas, and the 

recognition of their stratigraphic position is of great 

importance in the search for new deposits. In Arizona, increasing attention is being paid to details 

of local stratigraphy in attempts to locate hidden 

replacement deposits (Eyde, 1972). 

Vein, pipe, and replacement ores have a more 

varied mineralogy than the porphyry deposits. Chalcopyrite and bornite are the most common hypogene 

minerals. Chalcocite and covellite may be present as 

hypogene minerals in addition to forming secondary 

enrichment blankets. At Butte, Mont. (Meyer and 

others, 1968), main-stage mineralization gave rise 

to veins of four distinct types : veins of the deeplevel chalcopyrite zone containing chalcopyrite, 

bornite, and tennantite; veins containing chalcociteenargite in the central zone; bornite-chalcocitechalcopyrite-enargite veins in the intermediate zone; 

and carbonate veins containing rhodochrosite, sphalerite, galena, and rhodonite in the peripheral zone. 

At the Magma mine in Arizona (Hammer and 

Peterson, 1968) vein ores contain chalcopyrite; 

bornite, enargite, tennantite, chalcocite, digenite, 

and sphalerite. Enargite predominates in the lower 

levels and gives way upward to tennantite, but 

sphalerite predominates in the upper levels. Digenite 

is present only in the lower levels. In the limestone 

replacement ores, chalcopyrite is predominant. 

Mineral zoning such as is exhibited at Butte and 

Magma is present to some extent in most vein and 

replacement deposits. In addition to this a larger 

scale mineral zoning has been noted around most 

mineral deposits related to felsic intrusive rocks. 

Lowell and Guilbert ( 1970) in their tabulation of 

27 porphyry copper deposits described some peripheral mineralization in all the deposits and arcuate 

clusters of small mines and prospects in 23 of the 

deposits. Most of these peripheral veins contain 

gold and silver values along with pyrite, chalcopyrite, sphalerite, specularite, enargite, famatinite, 

tetrahedrite, barite, and manganese and vanadium 

minerals. Recognition of a cluster of small veins as 

part of an outer zone surrounding a buried ore deposit may be an important step in the discovery of 

new copper resources. 

Vein and replacement deposits are difficult to 

characterize in terms of tonnage and grade. If the 

Butte district is considered as one deposit-and no 

criteria seem to exist as a basis on which to subdivide it into smaller deposits-the amount of contained copper metal is enormous, rivaling that of 

the largest Andean porphyry deposits. In the period 1880 to 1964 the Butte mines produced more 

than 8 million tons of copper (Meyer and others, 

1968). In Arizona, major vein and replacement deposits fall into a field (in fig. 22) with an average 

copper content of 350,000 tons of copper each. 

In general, copper resources in vein, pipe, and 

replacement deposits are small in comparison to 

those of the closely related porphyry copper deposits, and discoveries of new deposits similar to Butte 

or Magma have declined sharply in the last few 

decades. The relatively small size of the ore bodies 

and alteration envelopes makes these deposits difficult targets in areas of deep overburden. It is likely, 

however, that vein, pipe, and replacement ore bodies 

will be discovered incidentally in the search for 

porphyry deposits. 

STRATA-BOUND DEPOSITS IN SEDIMENTARY ROCKS 

Strata-bound deposits in sedimentary rocks include some of the world's largest sources of copper. 

The sedimentary deposits of Zai're and Zambia alone 

make up 15 percent (table 39) of the world's identified resources, and enormous deposits are known in 
COPPER 173 

the U.S.S.R. Deposits of this type represent the 

largest potential for discovery of new deposits. Not 

only are many of them difficult to recognize in the 

field, but the geologic controls of their origin are 

only beginning to be understood. 

A genetic classification of sedimentary copper deposits should distinguish ores formed by chemical 

or biological processes from those formed by mechanical processes; those deposited simultaneously 

with the enclosing sediment from those formed by 

later alteration; and those formed in a reducing 

environment from those formed in an oxidizing 

environment. However, these processes are not 

mutally exclusive, and the criteria for distinguishing them are frequently equivocal. Idealized descriptions of different types of sedimentary copper deposits presented below, followed by descriptions of 

several important deposits that may be combinations 

of types. 

Type 1.-Rocks of intermediate Precambrian age 

formed when atmospheric oxygen began to become 

abundant and to mobilize copper that was previously 

stable. These deposits may include copper reworked 

or leached out of earlier disseminated deposits. The 

deposits of the African copper belt and those in the 

Belt Supergroup of western Montana may be of 

this type. 

Type 2.-Syngenetic marine deposits formed on 

the sea floor by precipitation or adsorption on organic matter. These deposits should show a systematic relation to lithologic facies and may be characterized by lateral persistence within a bed or 

facies. Mineral textures are typical of sedimentary 

rocks and the deposits may contain other metals, 

such as uranium, vanadium, and silver, that could 

precipitate under similar conditions. The Kupferschiefer and equivalent formations in Europe may 

be of this type. 

Type 3.-Deposits formed by reaction of connate 

brines or meteoric ground water with chemically 

reactive strata such as black shale, sandstone containing carbonaceous matter, or carbonate rock. As 

discussed by Lindgren (1911), such deposits probably form during compaction and lithification and 

are localized by variations in permeability, structure, and chemical reactivity of the host strata. The 

deposits may be nonpersistent and highly variable 

in size, shape, grade, and texture of the ore. Typical 

ore is more coarse grained than syngenetic ore and 

may include local replacement of original framework 

grains. The associated metals are the same as found 

in syngenetic deposits. Favorable host rocks include 

nonmarine arkosic sandstones. The "red-bed" copper deposits near Cuba, N. Mex., are an example of 

this kind of deposit. The other types of deposits 

have probably been modified to some degree by the 

processes that form this type of deposit. 

THE KUPFERSCHIEFER 

The Permian Kupferschiefer of Mansfeld, in the 

German Democratic Republic, is a thin-bedded bituminous marine marl or shale about 50 centimeters 

thick containing copper, lead, zinc, and silver in economic concentrations and many other metals in 

unusually large amounts (Richter-Bernburg, 1941; 

Wedepohl, 1964, 1971). The equivalent Zechstein 

shales of Lower Silesia in Poland contain economic 

concentrations of copper in some areas and of lead 

in other areas (Haranczyk, 1970). Many Europeans 

regard the mineralization of the Kupferschiefer and 

equivalent units as syngenetic because the mineralization is confined to a thin stratigraphic unit and 

its distribution is related to lithologic facies 

(Richter-Bernburg, 1951). Most advocates of the 

syngenetic hypothesis also suggest some extraordinary way of concentrating greater than usual 

amounts of copper from sea water. Submarine mineral springs and erosion of older copper ores are 

among the sources suggested for the copper. More 

recently, Brongersma-Sanders ( 1968) suggested that 

heavy metals could be concentrated in black shales 

and phosphorites by upwelling nutrient-rich waters. 

Davidson (1964) rejected all the arguments for 

unusual environments of deposition in favor of an 

epigenetic episode of mineralization by saline ground 

waters derived from the Zechstein salt deposits 

overlying the Kupferschiefer, citing as an example 

the metal-rich thermal ground waters encountered 

in wells near the Salton Sea as potential mineralizing solutions. Wedepohl (1971, p. 272) suggested a 

correlation between the local metal content of the 

Kupferschiefer and the soluble trace metals in the 

Lower Permian red sandstones over which the Kupferschiefer sea transgressed. 

Much of the Kupferschiefer in West Germany is 

probably of submarginal grade, but there may be 

as much as several tens of millions of tons of rock 

with an average grade of 0.3 percent copper. 

THE AFRICAN COPPER BELT 

Nearly one-fifth of the world's production of copper comes from deposits in upper Precambrian sedimentary rocks that extend for about 300 miles 

across parts of Zambia and the Katanga province 

of Za'ire in Africa (U.S. Bur. Mines, 1970). These 

deposits are usually called "strata-bound copper 

deposits" because of some uncertainty as to their 

origin. Individual beds containing disseminated cop-
174 UNITED STATES MINERAL RESOURCES 

per sulfide minerals are persistent for many miles. 

The ore occurs in dark shales of the lower Roan 

Formation of the Katanga Supergroup. Most of the 

lower Roan Formation is made up of arkosic conglomerates and eolian sandstones overlying a granitic basement, but the dark shales of the main 

ore horizon also contain algal reefs. Thus, the ore 

horizon was probably deposited in a shallow restricted basin surrounded by algal reefs. An important feature suggestive of a syngenetic origin 

is the zonal arrangement of ore minerals within the 

ore formation parallel to the shoreline as it migrated back and forth with transgressions and regressions of the sea (Garlick, 1961, p. 155-160). 

The sequence proceeds from barren sediment along 

the shoreline through disseminated chalcocite, bornite, and chalcopyrite to pyrite in the same direction 

as the general flow of currents, as determined from 

crossbedding. However, the mineralized zone cuts 

stratigraphically upward through the succession 

from conglomerate to sandstone to argillite to impure dolomite. 

The later discovery by Malan (1964) that chalcopyrite occurs in narrow argillaceous interstices 

between stromatolite columns in algal reefs is also 

cited as evidence that copper was deposited at the 

time of sediment deposition, perhaps by sulfatereducing bacteria, or as a colloidal sulfate gel. Metal 

deposition in the copper, iron, and cobalt-bearing 

Chibuluma West ore body, Zambia, was syngenetic 

with sands and muds, according to Whyte and 

Green (1971) and could have been by (1) biogenic 

deposition of sulfides, (2) precipitation especially 

of iron and cobalt hydroxides by changes of pH 

where river waters entered the lake or branch of 

the sea, (3) detrital deposition of metalliferous 

minerals, or ( 4) by a combination of these methods. 

Many of the deposits in Za!re have been altered by 

supergene enrichment, and they produce secondary 

copper minerals and a variety of other elements 

from dolomitic beds. 

The very large resource of copper in the African 

copper belt may result from a combination of several important processes. If we assume that the 

deposits are syngenetic, they may have formed during the interval of Precambrian time when oxygen 

first became available in sufficient quantity to mobilize copper. Moreover, these deposits are at or 

near the base of a marine transgression which could 

mobilize copper in the underlying crystalline and 

nonmarine rocks in a manner suggested by W edepohl (1971, p. 272) for the Kupferschiefer. Common 

features of the African copper belt and the Kupferschiefer were discussed by Putzer (1972). 

The current rate of copper production from the 

African copper belt would suggest a known reserve 

of well over a billion tons of ore. Speculative resources may be several times as great. 

PRECAMBRIAN SEDIMENTARY COPPER DEPOSITS 

IN THE UNITED STATES 

At the White Pine district in Ontonogan County, 

Mich., copper occurs in the Nonesuch Shale of Precambrian Y age, especially in the basal parting 

shale bed (Ensign and others, 1968). About 5 percent of the U.S. copper production comes from this 

single bed which is 1-8 meters thick and contains 

anomalous copper over a distance of at least 250 

kilometers (160 miles) in the Upper Peninsula of 

Michigan and northern Wisconsin. Chalcocite is the 

principal sulfide mineral in the mineralized zone 

whereas pyrite is the characteristic sulfide in the 

upper part of the Nonesuch Shale. The richest copper occurs in the darkest carbonaceous siltstones, 

shales, and sandstones, where chalcocite grains 

ranging in size from 2 to 20 microns are disseminated interstitial to the framework grains. Although 

the mineralization is persistent in certain beds 

throughout the district, a crosscutting relation between ore and bedding on a regional scale and the 

absence of a characteristic copper-bearing lithologic 

facies distinguish this deposit from the African 

copper belt. Consequently, an epigenetic, but not 

magmatic, source for the copper seems most likely. 

However, Robert Ehrlich and T. A. Vogel stated 

(oral presentation at Institute on Lake Superior 

Geology, Houghton, Mich., May 4, 1972) that according to their interpretation, the copper in the Nonesuch Shale is syngenetic, with some diagenetic 

modification of the distribution. 

Strata-bound sedimentary copper deposits or.cur 

in Precambrian Y rocks of the Belt Supergroup in 

western Montana and adjacent parts of Idaho. Copper sulfides occur as disseminations, blebs, and 

veinlets in persistent beds of white fine-grained 

quartzite and siltite of the Revett Formation along 

a belt parallel to a broad domal feature formed 

before the close of Belt time. Anomalous amounts 

of copper are more widely known in green strata 

throughout the Belt basin. Most of the Belt rocks 

are feldspathic and contain variable amounts of 

mica (illite and sericite) plus chlorite in amounts 

inversely related to grain size. Anomalous amounts 

of silver and mercury are known to be associated 

with copper locally, but lead is known only in separate beds. The apparent relation between mineralization and a late Precambrian broad domal structure is suggestive of a diagenetic or early epigenetic 
COPPER 175 

ong1n for the copper (Harrison, 1972). Later recrystallization and metamorphism to the biotite 

zone reduced rock permeability and precludes the 

possibility of late epigenetic mineralization. 

Rocks of the Belt Supergroup, including the Revett Formation, may contain as much as 1 billion 

tons of ore with an average grade of 0.5-1.0 percent 

copper. Submarginal grade rocks with anomalous 

copper may be 10-100 times more abundant. Silver 

will be a valuable byproduct of the Belt ores when 

commercial exploitation begins. 

PRECAMBRIAN SEDIMENTARY COPPER DEPOSITS 

IN THE U.S.S.R. 

With an estimated reserve of at least 10 million 

tons of metallic copper (Sutulov, 1972, p. 10), the 

undeveloped sedimentary ores of Udokan in eastern 

Siberia (near 57° N., 117° E.) form one of the 

world's largest sedimentary copper deposits; Shank 

(1972, p. 88) reported that it may be the largest. 

The ores are mainly sedimentary and related to 

lithology, and the greatest ore concentrations occur 

in the 1,800-2,500-meter-thick Sakukan Formation 

within the 10,000-12,000 m Udokan Group of fine 

sandstone and siltstone and some thin lenses of 

carbonate (Bakun and others, 1958). The main layer 

within which ore masses occur is about 300 m thick, 

its top 250 m below the top of the Sakukan Formation. The top of a lesser ore-bearing layer is 1,250-

1,950 m stratigraphically beneath the main one. 

Despite the great thickness of the Udokan Series, 

deposition was in shallow water, or in a littoral 

and deltaic environment. 

The Udokan Series is considered by most geologists to be of Precambrian X age, but some geologists think it as young as Precambrian Z. Copper 

minerals were deposited with the sedimentary material or were diagenetic (Bogdanov, 1968). The 

copper is believed to have come from a Precambrian 

W shield area located to the northeast, containing 

anomalous quantities of copper. Part is believed to 

have been transported as fine clastic particles. 

The U dokan Series is folded into a big synclinal 

basin, irregularly oval in plan; the southwest limb 

is overturned, but folding is not complex. The entire series is slightly metamorphosed, and some of 

the rocks are now quartzites and phyllites. 

The main ores are disseminated chalcocite and 

bornite; there are also some chalcopyrite ores that 

are not associated with the preceding. Malachite, 

brochantite, and other secondary minerals are present in a restricted oxidized zone. Sphalerite, native 

silver, and molybdenite are rare in the deposit. Ore 

has been traced to depths of more than 1,500 m. 

Lyubimov (1966, p. 231) described the remote 

location and problems that face development in the 

Udokan Series. The region has severe climate, permafrost, and seismicity and an elevation of more 

than 1,000 m above sea level, but the high metal 

content of the ore and the possibility of open-pit 

mining probably will compensate for the high capital expenditures needed. 

RED-BED COPPER DEPOSITS 

Numerous deposits of copper are associated with 

red sandstone strata of late Paleozoic or early 

Mesozoic age, as described by Lindgren (1911). In 

the Southwestern United States, only a few of the 

deposits are large enough to be mined economically. 

Host rock strata, interbedded with red strata, are 

generally light gray to dark gray and may weather 

yellowish gray. Nonmarine feldspathic or arkosic 

sandstones containing carbonaceous matter are the 

most common host rocks. Such copper deposits are 

similar in size and shape to some of the well-known 

deposits of uranium and vanadium in sandstone, and 

transitional deposits containing all three metals 

exist. The copper deposits generally contain some 

silver, and at Silver Reef, Utah, silver values exceed those for copper. 

Near Cuba, N. Mex., the Nacimiento copper deposit, which occurs in the Agua Zarca Sandstone 

Member of the Chinle Formation, is a typical large 

red-bed copper deposit (Kaufman and others, 1972). 

Rich ore occurs as chalcocite, bornite, covellite, and 

secondary copper minerals, replacing fossil wood 

and forming halos around the wood. The deposit is 

clearly epigenetic, but appears to predate the major 

structural features of the area. In past years selective mining of rich chalcocite replacements of logs 

left much disseminated ore in the ground. The remaining disseminated and rich copper ore may be 

as much as several million tons in this area alone. 

The total speculative resources of copper in redbed copper deposits of the United States may be 

several hundreds of millions of tons of mineralized 

material. 

A second type of copper deposit generally included with red-bed copper deposits is represented 

by disseminated copper sulfide minerals currently 

mined from thin beds of gray shale in the Flowerpot Shale of Permian age in southern Kansas and 

western Oklahoma (Ham and Johnson, 1963; Johnson and Ham, 1972). The copper-bearing shales occur in a sequence that includes red sandstone, dolomite, gypsum, and shale and are facies equivalents 

of evaporite deposits including salt in western Kansas and in the Midland and Delaware basins of 
176 UNITED STATES MINERAL RESOURCES 

Texas and New Mexico. Like the Kupferschiefer of 

Europe, these deposits have lateral persistence 

within thin strata, which is commonly cited as evidence for a syngenetic origin. 

Strata-bound copper-bearing sandstones that occur in Carboniferous rocks of Dzhezkazgan in 

central Kazakhstan, U.S.S.R., are included here 

even though descriptions of these deposits indicate 

significant differences from our red-bed copper deposits. Copper sulfides with some lead occur in gray 

sandstone horizons interbedded with barren brown 

sandstones of shallow marine lagoonal and deltaic 

facies. As many as 27 zones of mineralized sandstone occur in 700 m of enclosing rock. The gray 

host rock is more calcareous and dolomitic than the 

associated barren rock. The primary ore consists of 

sandstone impregnated with bornite, chalcocite, 

chalcopyrite, and galena concordant with the lamination of the sandstone. The first stage of mineralization is probably syngenetic or diagenetic with the 

enclosing strata; it is cut by a second, epigenetic 

stage of copper-lead-zinc mineralization that forms 

intersecting veins, stockwork zones, and hydrothermal wallrock alteration. The ore-forming solutions may have been derived from basaltic magma 

at depth below the sea floor according to Shcherba 

(1971). These deposits were estimated to have a 

reserve of more than 3.5 million tons copper metal 

in ore containing 1.6 percent copper (Sutulov, 1967, 

p. 113). 

MODERN SEA FLOOR NODULES 

Extensive deposits of ferromanganese nodules 

now forming on the deep-sea floor in the major 

oceanic basins are examples of syngenetic copperbearing deposits that may become economic in the 

near future as technology progresses. Although the 

origin and mode of concentration of metals in these 

nodules are the subject of intense debate, there can 

be no question that the nodules represent syngenetic 

deposition. The copper content of the nodules varies 

regionally in the ocean basins ; the higher concentrations are normally on the west sides of the basins 

and between lats 10° N. and 10° S., 2,500--6,000 m 

below the surface. The nodules in the richer areas 

contain more than 25 percent manganese, as much 

as about 1.5 percent copper and nickel, and 0.25 

percent cobalt, as well as many other elements in 

smaller quantity. The copper ions are thought to 

be adsorbed on the manganese oxides; copper minerals have not been reported. These nodules are 

discussd in more detail in "Manganese" ; Mero 

( 1965) reported information as to distribution and 

quantity. 

METAL-RICH SEDIMENTS OF THE RED SEA 

In March 1964, during an oceanographic survey 

of the Red Sea, scientists aboard the RRS Discovery 

found hot brine in the Discovery Deep. Subsequent 

exploration has shown that underlying the hot brine 

are iron-rich, brine-saturated sediments at least 

10 m thick containing anomalous amounts of copper 

and zinc. The geology, chemistry, and physical properties of these sediments are discussed in detail in 

a collection of reports edited by Degens and Ross 

( 1969). Aside from the economic potential of these 

deposits (Bischoff and Manheim (1969) estimated 

50 million tons of brine-free sediment averaging 

1.3 percent copper), the greatest interest lies in the 

theoretical implications of these deposits with respect to the origin of sedimentary deposits elsewhere. James (1969) suggested that deep burial of 

deposits of this type and continued circulation of 

hot brine through them would result in re-solution 

of the base metals and lateral migration. He speculated that such migration would continue until the 

solutions reached the H2S-bearing reef limestones 

known to be laterally continuous with the metalrich sediments, there to precipitate as sulfide minerals. Such a model provides a basis for new 

appraisals of the theories of origin of many types 

of sedimentary base-metal deposits. Furthermore, 

since the hot brines which have introduced the 

metals to the sea floor appear to be related to continental rifting, a tectonic control for sedimentary 

deposits is suggested. If stratigraphic and paleotectonic studies of a region suggest rifting and deep 

basin filling, favorable host rocks along the flanks 

of the rift may· contain deposits of base-metal sulfides. 

HORIZONTAL TRANSPORT OF SECONDARY COPPER DEPOSITS 

A few localities are known where copper dissolved from sulfide-bearing rock as a part of the 

conventional surficial leaching has then traveled 

laterally and been deposited in a secondary zone that 

is not located above the primary sulfide. Perhaps 

this phenomenon is more common that is suspected, 

and consideration might be given to searching for 

such ores in the vicinity of subeconomic sulfide 

mineralization. 

Lateral transport and secondary deposition of 

copper has been described at the Emerald Isle mine, 

Wallapai mining district, Arizona (Dings, 1951, p. 

149-153), Jerome, Ariz. (Lindgren, 1926, p. 90-91), 

Chuquicamata, Chile (Newberg, 1967), GlobeMiami district, Arizona (Throop and Buseck, 1971), 

and Ray, Ariz. (Phillips and others, 1971). The 

transport distance at Chuquicamata was about 4 
COPPER 177 

kilometers. Most of the deposits are in Quaternary 

gravels, but some are in older rocks. 

MOBILIZED DEPOSITS OF PROBABLY SEDIMENTARY ORIGIN 

Two major deposits, Aitik in northern Sweden 

and Mount Isa in Queensland, Australia, contain 

copper ores that were probably sedimentary in origin but have been modified by metamorphism. The 

ores of the old White Pine mine, Michigan, were 

deposited by hydrothermal solutions, but the source 

of the metal was probably the nearby strata-bound 

copper present in the Nonesuch Shale, the ore of 

the present mine. Many other deposits may also fall 

into this general category, and classification is 

harder as modification has increased. 

The large low-grade copper deposit of Aitik, near 

Gallivare, Sweden, is in Precambrian gneisses, 

schists, and quartzites (Zweifel, 1972). The copper 

is in chalcopyrite and occurs with pyrite, magnetite, 

and pyrrhotite, mainly as disseminations and 

stringers. There was some hydrothermal alteration 

along with the mobilization of the sulfides. 

At Mount Isa, lead-zinc-silver ores form masses 

that are conformable with the bedding of the Precambrian Mount Isa Shale, but the generally associated copper ores are in shears, particularly where 

silica and dolomite have been introduced. Thus, the 

lead-zinc-silver ores are reasonably interpreted as 

syngenetic, but the origin of the copper sulfide ores 

is less certain. 

ENVIRONMENTS OF DEPOSITION 

An understanding of the origin and environment 

of deposition of sedimentary copper deposits has 

practical application in the search for new or hidden ore deposits. A search conducted in depositional 

environments comparable to those of known copper 

deposits should have a far greater chance for success 

than a random search. Environments worth consideration include depositional environments where 

syngenetic concentrations are optimum, as well as 

postdepositional environments where diagenetic or 

epigenetic concentration seem most likely, as follows: 

1. Deep marine basin sediments associated with 

midocean ridges or continental plate boundaries, such as the recent sediments along the 

crest of the East Pacific rise and sediments 

in association with the hot brine pools of the 

Red Sea. 

2. Continental-margin marine black shales associated with phosphorites, such as the Meade 

Peak Phosphatic Shale Member of the Phosphoria Formation of Permian age in western 

Wyoming. 

3. Shallow marine or estuarine shale associated 

with evaporites or nonmarine deposits, such 

as the Flowerpot Shale of Permian age in 

Oklahoma and the Kupferschiefer of Permian age in Germany and the equivalent 

Zechstein beds in Poland. 

4. Sandstone, shale, and carbonate rocks exposed 

to migrating saline ground waters, such as 

alkaline carbonated waters or chloride brines 

derived from subsurface solution of evaporites. Examples might be the "Speckled Sandstone" of probable Early Permian age in the 

Salt Range of Pakistan, the Flowerpot Shale 

of Permian age in Oklahoma, the Santa Rosa 

Sandstone of Triassic age in New Mexico, 

and the San Andres Limestone of Permian 

age in New Mexico. 

5. First-cycle sedimentary rocks in a restricted 

or closed basin, such as the Agua Zarca 

Sandstone Member of the Chinle Formation 

of Triassic age along the west flank of the 

Nacimiento Range, N. Mex. 

6. Pyritic shale associated with submarine volcanism, as perhaps the Nonesuch Shale of 

Precambrian Y age in Michigan and Wisconsin. 

7. Pyroclastic or porous carbonate-bearing rocks 

exposed to ground water from weathering 

copper-sulfide deposits, like the Apache Leap 

Tuff of Miocene age at the Inspiration mine, 

Arizona (Throop and Busek, 1971). 

8. Stratified rocks of mostly Precambrian Y age 

(800-1,600 million years), especially if they 

are first-cycle sediments deposited in shallowwater or restricted basin environments. Examples are the Revett Formation of the Belt 

Supergroup in northwestern Montana, and 

the Roan Formation of the Katanga Supergroup in the African copper belt. 

9. Basal transgressive marine rocks directly overlying deeply weathered crystalline rocks or 

first-cycle arkosic clastic strata, such as the 

Kupferschiefer of Permian age in central 

Europe and the Roan Formation of Precambrian age in the African copper belt. 

10. Porous strata updip and marginal to deeply 

buried volcanic rocks of basaltic to intermediate composition, as the amygdaloidal flow 

tops and conglomerate beds of the Portage 

Lake Volcanics and perhaps also the Nonesuch Shale, both of Precambrian Y age in 

the Upper Peninsula of Michigan. 
178 UNITED STAT'ES MINERAL RESOURCES 

11. Porous or chemically reactive strata, including 

lava flows and pyroclastic rocks, within or 

peripheral to rocks of the zeolite facies of 

low-grade metamorphism. Examples besides 

the Nonesuch Shale are the Sangre de 

Cristo Formation of Pennsylvanian and Permian age in southern Colorado and the 

Apache Leap Tuff at the Inspiration mine, 

Arizona. 

The environments described above are not all 

mutually exclusive; therefore, a coincidence of several may greatly increase the probability of finding significant copper mineralization .. 

SIZE AND GRADE CHARACTERISTICS 

Sedimentary deposits are difficult to characterize 

as to size. On the one hand, many separate mines 

are not in separate ore deposits but in parts of a 

continuously mineralized stratum, and on the other 

hand, very large tonnage figures have been mentioned for beds continuously mineralized over wide 

areas even though only a small part may be mined 

economically. In figure 22, a field of seven deposits 

in Za!re and Zambia has an average copper content 

of 4 million tons each in ore averaging 3.5 percent 

copper. Totals of production and reserves for both 

the White Pine and Keweenaw Point districts in 

Michigan amount to 7 or 8 million tons of metal 

for each deposit but in lower grade ore. Estimates 

for the Udokan deposit in the U.S.S.R. exceed 10 

million tons contained copper. 

MASSIVE SULFIDE DEPOSITS IN VOLCANIC ROCKS 

Copper is more abundant in basalt and andesite 

than in other igneous rocks. Under various conditions, this copper content may be concentrated to 

form·an ore deposit of distinctly different form from 

those associated with felsic intrusions. 

A small but locally important part of the world's 

copper resources is found in lavas and pyroclastic 

rocks laid down in the marine environment. These 

deposits are generally (1) stratiform or lenticular, 

and concordant with the bedding of the surrounding rocks, (2) of small lateral extent as compared 

to thickness, and ( 3) composed largely of sulfide 

minerals with small proportions of silicate gangue. 

Mineralogically the deposits consist mainly of 

pyrite and (or) pyrrhotite and varying amounts of 

chalcopyrite, sphalerite, and galena. The terms 

"massive sulfide," "cupriferous pyrite," or "massive 

pyrite" deposits have been used to identify this 

class. 

The last decade has been extremely productive in 

theories of origin of massive sulfide deposits. Recognition of metamorphic features in the North American deposits by Kinkel (1962) and Kalliokoski 

(1965) permitted the interpretation that their emplacement was earlier than the events that deformed 

them. Regional geologic studies such as those of 

Goodwin (1965) in the Noranda area, Quebec, made 

possible the views that the deposits were a part of 

the volcanic rock complexes that enclosed them and 

not a later superimposed feature. Detailed studies 

of Kuroko-type ores in Miocene tuffs of Japan (for 

example, Horikoshi, 1969) showed that these ores 

were formed on the sea floor during the last stages 

of an eruptive cycle. The equivalence of these deposits to the metamorphosed massive sulfides of 

older terranes had by this time become clear to 

many workers. 

Anderson (1969) presented a thorough review of 

the genesis of these deposits, and in 1970 the meeting of the International Mineralogical AssociationInternational Association on the Genesis of Ore 

Deposits in Japan brought together an outstanding 

group of papers on the subject. The description 

which follows is largely taken from papers by Tatsumi and Watanabe ( 1971) , Hutchinson and Searle 

(1971), and L. A. Clark (1971) in the proceedings 

of that meeting. 

Massive sulfide deposits that are undeformed by 

later orogenic activity exhibit a wide variety of 

textures and forms. Ore may be found in disseminations and stockworks or swarms of veins in highly 

propylitized lava. Above these may be found sulfide 

ore in cavities between pillows as at Cyprus. Massive sulfide bodies above the stockworks and vein 

swarms may show banding and colloform texture 

indicating deposition in open cavities or on the open 

sea floor. The ore may be intensely brecciated with 

interfragmental spaces filled with fine-grained 

sandy pyrite, and evidence exists for gravitational 

transport of blocks of ore, lava$ and soft bottom 

sediment downslope on the sea floor from the source 

of the deposit. Overlying the massive ore are bedded 

deposits rich in iron oxides, silica, and disseminated 

pyrite. These bedded deposits are thickest over the 

massive ore, and they thin abruptly laterally. 

The preceding features have given rise to the 

volcanic exhalative theory of origin. Metal-bearing 

solutions or vapors are thought to ascend rapidly 

through fractures in a submarine volcanic pile and 

to precipitate, partly in colloidal form, in nearsurface cavities and on the sea floor. Deposition of 

sulfides may temporarily seal the vent area, and 

the resulting increase of vapor pressure may cause 

the brecciation of previously deposited ore. Mixing 

of iron-rich solutions with oxygen-rich circulating 
COPPER 179 

sea water results in deposition of the overlying 

bedded siliceous ironstones. 

The source of metals for these deposits is the 

same magma that gives rise to the surrounding volcanic rocks. Different lava types give rise to deposits of different mineralogy. For example, pyritepyrrhotite-chalcopyrite deposits are commonly 

associated with mafic volcanics, and sphalerite- and 

galena-bearing deposits tend to be found with silicic 

volcanic rocks (Anderson, 1969). 

Copper-bearing massive sulfide deposits contain 

as much as 10 percent copper, with a mean in commercial ores of about 2.5 percent, and they range in 

size from a few hundred thousand tons to more than 

50 million tons. The wide range in production grade 

of copper is due in part to the variable content of 

zinc, lead, silver, and gold in these ores as well as 

the economics of recovery of sulfur and iron from 

them. 

COPPER IN NICKEL ORES 

Many of the commercial nickel deposits in mafic 

rocks throughout the world have copper associated 

with them, and this "byproduct copper" is an important contribution to the supply, especially in 

Canada and the U.S.S.R. These deposits are generally interpreted to have been formed by a magmatic-segregation process as a part of the intrusion 

of the bodies of mafic rock. 

The chalcopyrite-pentlandite ores related to mafic 

intrusives range in composition from mostly copper 

sulfides to mostly nickel sulfides, depending on the 

composition of the primary magma; the proportion 

of nickel increases roughly with maficity (T. P. 

Thayer, oral commun., 1972). In certain cumulate 

mafic bodies this may result In high-nickel sulfide 

at the base and more cupreous sulfide in higher 

strata (Thayer, 1971, p. 242). In these ores the 

sulfide has generally separated as an immiscible 

liquid, and the richest concentrations in these sulfurrich magmas formed when the sulfide separated before crystallization had gone very far. Many papers 

in Wilson (1969) deal with the origin of ores of 

this type. 

The most significant producer of copper from 

nickel-bearing mafic rocks is the Sudbury district 

of Ontario. In this area of complex geology, the 

ores, some stratiform and some crosscutting, are 

polygenic in relation to their enclosing rocks but 

were probably all derived initially as products of 

crystallization and the separation of a sulfide-rich 

dense liquid. Variation in the Ni: Cu ratio in different ore bodies makes it possible for a mining company to adapt the ratio in the ore produced to 

metal-market conditions. 

Besides the Sudbury district, nickel sulfide deposits containing appreciable quantities of copper 

are found as segregations in mafic intrusive bodies 

in Maine and New Brunswick, in Quebec, Manitoba, 

Saskatchewan, and particularly in the coastal crystalline belt of British Columbia and southeast 

Alaska. The copper-nickel ores of Norway, Sweden, 

Finland, and the Kola Peninsula, U.S.S.R., are 

mostly polygenic and complex. The nickel-coppercobalt ores of Noril'sk in _north-central Siberia are 

also an important source of copper for the U.S.S.R. 

Nickel ores in Precambrian ultramafic and mafic 

rocks in the newly discovered Kambalda district in 

Western Australia contain 0.25--0.57 percent copper. 

The deposits in Minnesota are in the Precambrian Duluth Gabbro Complex in the northern part 

of the State. Disseminated copper and nickel sulfides form discontinuous lenses and layers in the 

basal part of the gabbro complex. Recent studies 

show that although these deposits are not minable 

under present conditions, they represent a very important future copper resource (P. K. Sims, oral 

commun., 1972). 

NATIVE COPPER DEPOSITS OF THE KEWEENAW TYPE 

On the Keweenaw Peninsula, Mich., deposits of 

native copper occur in amygdaloidal flow tops and 

conglomerate beds in the Portage Lake Volcanics. 

These strata-bound and in part conglomerate-bedcontrolled ores are mostly interpreted to be epigenetic in origin and may have affinities to some 

strata-bound ores in sedimentary rocks. (Bateman 

(1950, p. 498) likened them to the sandstone ores 

of Corocoro, Bolivia.) The proximity in both space 

and time of ores in the Portage Lake rocks to the 

mineralized Nonesuch Shale, 350-6,000 feet (110-

1,850 m) above, also suggests this affinity. 

Opposing this reasoning are the widespread minor 

copper occurrences in basaltic rocks all over the 

world, suggesting that the copper was originally 

syngenetic but has been redistributed and concentrated to minable grades by later processes (Cornwall, 1956, p. 620) . 

More than 5 million tons of copper metal has 

been produced on the Keweenaw Peninsula since 

mining began in 1845, and although there is little 

activity in the district now, large ore reserves 

remain. 

Most of the copper is the native metal and was 

introduced into vesicles, fractures, and interstitial 

pore spaces after deformation of the rocks. Moreover, the copper deposits fit into a pattern of lowgrade regional metamorphic zoning of silicate min-
180 UNITED STATES MINERAL RESOURCES 

erals similar to the zeolite facies described by 

Coombs, Ellis, Fyfe, and Taylor (1959). The source 

of mineralizing solutions for the copper sulfide deposits in the Nonesuch Shale and the native copper 

deposits in the Portage Lake Volcanics may be 

essentially the same-namely, the 15,000-30,000 

feet of flood basalts at depth in the Lake Superior 

Basin (Ensign and others, 1968, p. 486). The 

copper-bearing solutions, according to White (1968, 

p. 322), may represent water driven from the voids 

and interstices of flow tops as the lava flows were 

crushed and metamorphosed in the axial region of 

the Lake Superior syncline, downdip from the present deposits. 

Other copper occurrences that resemble the Keweenaw type are the chalcocite-bearing Coppermine 

deposits in gently dipping basalt flows of Precambrian Y age in the Northwest Territories, Canada, 

and the native copper-cuprite-azurite-malachite 

ores in chloritized and epidotized mafic flows in -the 

Catoctin Formation (Precambrian Z) of Maryland 

and Virginia. Chilean copper deposits in terrestrial 

volcanic rocks such as Buena Esperanza (Ruiz and 

others, 1971) may be similar in origin to the Keweenaw type, although they lack native copper. Bornite, 

chalcocite, and chalcopyrite are found in amygdaloidal upper parts of andesite flows in these deposits. 

MISCELLANEOUS TYPES 

Some copper deposits of local and (or) historic 

importance differ significantly in form and rock 

association from those of the five major groups just 

described. Among these are small and very high 

grade chalcocite deposits such as Kennecott, Alaska, 

and Mountain City, Nev. (See fig. 22 for comparison with other types.) Nearby volcanic rocks have 

been called upon as a source of copper in these 

deposits (Coats and Stephens, 1968; E. M. MacKevett, written commun., 1972). The massive chalcopyrite lenses and veins of Matahambre, Cuba, 

appear to be unrelated to -either volcanic or intrusive rocks (R. A. Bradley, oral commun., 1972). The 

sulfide lenses in shears crosscutting anorthosite 

bodies at Chibougamau, Quebec, do not lend themselves to inclusion with any of the previously described types. 

Replacement ore bodies in carbonate rocks far 

from an igneous source, such as at Bornite-Ruby 

Creek, Alaska (Runnels, 1969), may be an important resource of copper. Numerous lodes of this 

type in a 450-mile belt along the south slope of the 

Brooks Range, Alaska, are believed to contain more 

than 10 million tons of copper metal. Small copper 

production (12,000 tons in 1970) from Missouri is 

a byproduct of the lead-zinc replacement bodies in 

carbonate rocks without igneous affiliation (Allen 

Heyl, oral commun., 1972). 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

About 70 percent of the world's identified copper 

resources fall into four distinct geologic-geographic 

groups. These are, in decreasing importance, porphyry copper deposits of Chile and Peru, porphyry 

copper deposits of the Southwestern United States, 

sedimentary copper deposits of Zaire and Zambia, 

and porphyry copper and sedimentary copper deposits of the U.S.S.R. Other important groups are 

the porphyry copper deposits in Oceania, in Mexico, 

and in western Canada and the porphyry copper 

and sedimentary copper deposits in southeastern and 

central Europe, respectively. Volcanogenic deposits 

and nickel-copper deposits in mafic intrusions, important as they may be to local economies, do not 

contribute significantly to the worldwide picture. 

Identified copper resources, given in table 39, are 

TABLE 39.-ldentified and hypothetical copper resources, in 

millions of short tons 

Area 

United States: 

Eastern ----------------- Western, except Alaska ---

Alaska ------------------

Canada ---------------------- Mexico ---------------------- Central America ------------- Antilles --------------------- South America --------------- Europe, excluding U.S.S.R. ----

Africa ----------------------- U.S.S.R. --------------------- Middle East-south Asia -------

China ----------------------- Oceania, including Japan ------

Australia --------------------

Total ------------------

Identified 1 Hypothetical 2 

10 5 

64 75 

2 20 

19 50 

18 20 

1 6 

2 1 

80 50 

25 20 

53 50 

39 50 

4 20 

3 ? 

21 30 

3 3 --------------------- 344 400 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. Based on all categories of reserve figures 

plus estimates where no figures are available. Amounts are tentative and 

accuracy will be refined in subsequent publications. 2 Hypothetical resources: Undiscovered mineral deposits, whether of 

recoverable or subeeonomie grade, that are geologically p~dietable as existing in known districts. Based generally on identified resource figures 

times a factor assigned according to geologie favorability of the region, extent of geologie mapping, and exp!oration. 

those for which a size estimate is available. All 

categories of reserve figures as well as estimates 

for deposits where no reserve figures are published 

have been combined to make up this identified resource. These figures should be ,regarded as tentative, and considerable refinement of their accuracy 

should be expected in subsequent publications. They 

are derived from unpublished resource compilations 

made by A. R. Kinkel and others in the early 1960's, 

with additions and subtractions based on new dis-
COPPER 181 

coveries and estimated mine production, respectively. Low-grade deposits are not included here but 

are discussed under "Subeconomic Resources" of 

this chapter. 

Hypothetical resources given in table 39 are those 

that have not been found but whose existence is 

suspected, as in concealed parts of known mineral 

districts, in projections of incompletely explored 

mineral belts, and in areas near important isolated 

new discoveries that suggest the possibility of a 

future mining district. The largest hypothetical reserves are in the Western United States, South 

America, Africa, and the U.S.S.R., all areas of 

favorable geologic setting and much recent successful exploration. 

Hypothetical resources in the Western United 

States comprise the concealed deposits under basin 

fill in the major porphyry copper regions, a possible 

new porphyry copper province in the Absaroka 

Range of Wyoming, and the great resources of sedimentary copper in the Belt Supergroup of Idaho and 

Montana. Alaskan hypothetical resources are based 

on favorable evaluation of porphyry deposits in 

eastern Alaska and of replacement deposits in carbonate rocks on the south slope of the Brooks Range. 

Canadian hypothetical resources are in British 

Columbia and Yukon Territory. South American 

resources are in the Andes of Chile, Peru, Ecuador, 

and Argentina, and the estimate is probably conservative. African hypothetical resources are in the 

copper belt region and in the Precambrian rocks of 

southwest Africa. U.S.S.R. hypothetical resources 

are large, and the estimate of 50 million tons may be 

conservative; the resources comprise undiscovered 

porphyry deposits in the Kazakhstan and Uzbekstan 

regions and copper-bearing sedimentary strata in 

several areas. Another area where future discovery 

of important copper porphyry deposits can be reasonably expected is in the central Iranian volcanic 

belt northwest from the known porphyry occurrences near Kerman through the area near Hamadan and Tabriz and then westward across northern 

Turkey. In this area some types of copper mineralization related to intrusions have been reported by 

Superceanu. (1971, p. 395). The areas of copper 

prospects in northeastern and east-central Iran that 

may have potential for large copper deposits are 

discussed under "Speculative Resources." 

The identified resources in the United States, 76 

million tons of copper metal, are enough to last the 

country 45 years at the constant-use rate of 1.7 

million tons per year; the world identified resource 

of 344 million tons will last 50 years at the rate of 

6.9 million tons per year. At the same use rates, 

hypothetical resources add 60 years supply to the 

United States and 58 years supply to the world. 

SPECULATIVE RESOURCES 

During the last decade many new mineral provinces and districts were discovered and developed. 

Important examples of these are the porphyry copper deposits of the Canadian cordillera, the Southwest Pacific, and Iran. These areas had previously 

received little attention, and deposits of the porphyry type were thought to be limited mostly to 

Southwestern North America and the Andes. Similarly, sedimentary copper deposits, previou~ly considered as rather unique occurrences, have been discovered in the Western United States and in eastern 

U.S.S.R. The development of these new provinces 

has drastically increased. the resources. 

There is considerable likelihood of finding even 

more new copper provinces g~ven the new knowledge 

of copper metallogeny and perhaps aided by the 

same combination of economic boom and high metal 

prices that existed in the last decade. Future discoveries of porphyry copper and sedimentary copper deposits are more likely to have a major impact 

on the world's copper resources, and these types 

will receive the greatest attention. Unfortunately, 

not enough is known of the stratigraphic and paleotectonic controls of sedimentary copper deposits to 

be able to point to many areas with potential resources of this type. 

In the United States, the greatest likelihood of 

new discoveries lies in the Southwest. In Arizona, 

the search for new porphyry copper deposits has 

been concentrated in the southeastern part of the 

State because of the greater number of known deposits and because more is known about the geology, 

geophysics, and geochemistry. Most of the southwestern, western, and northwestern parts of the 

Basin and Range province has not been evaluated 

adequately in reconnaissance, much less in detaill. 

Adequate geologic maps exist for only a few widely 

separated areas. The reasons for this are many and 

include inaccessibility, restricted access to military 

bombing ranges and Indian reservations, and inhospitable climate. Nevertheless, from what is 

known, these are pristine· exploration areas, and 

must be considered to contain many copper deposits. 

On the basis of a simple comparison with the concentration of copper deposits in southeastern Arizona, and generally favorable regional geology, an 

order of magnitude of 108 tons is estimated for 

these areas. 

Elsewhere in the Western United States, the 

Mountain City copper deposit in Elko County, Nev., 
182 UNITED STATES MINERAL RESOURCES 

which yielded over 100,000 tons of copper in ore 

averaging nearly 10 percent, is believed to have been 

derived from the nearby metavolcanic rocks of the 

Nelson Formation of Late Mississippian age (Coats 

and Stephens 1968). Volcanic rocks of Mississippian 

to Permian age are widespread in northwestern 

Nevada, and these and nearby sedimentary rocks 

offer numerous prospecting targets for high-grade 

copper deposits (Hewitt, 1968). 

Metal-rich brines in the Salton Sea area of southern California and the Boleo copper deposits in 

Pliocene rocks in Baja California, Mexico, suggest 

a prospecting area. Upper Tertiary to Holocene 

rocks and sediments in and along both sides of the 

Gulf of California rift zone and its northern projection in the Salton trough may have been or may be 

in the process of being mineralized by metal-rich 

solutions rising through this rift zone. 

In the Appalachian Mountains, the possibility of 

finding large porphyry copper deposits of Paleozoic 

age is intriguing. Ore-bearing porphyries are believed to be emplaced only at relatively high levels 

in the crust, during the final or postorogenic stages 

of a tectonic cycle. Thus pre-Mesozoic fold belts 

contain few of these deposits, because erosion in 

these areas has progressed to the point where most 

of the upper part of the crust has been removed. 

Special conditions, however, such as the deep burial 

and preservation of rocks of an early tectonic cycle 

by geosynclinal deposits of a later cycle, may result 

in the preservation of some older porphyry-type 

deposits such as at Catheart Mountain in Maine and 

those of the U.S.S.R. in central Asia. 

Guild (1971) and Sillitoe (1972) discussed the 

relationship between porphyry copper deposits and 

the boundaries of major crustal plates and concluded that many deposits are related to the process 

of magma generation along the subduction zone 

where one crustal plate slides beneath another. 

Porphyry copper deposits tend to occur along the 

concave side of arc-trench systems resulting from 

the process of subduction. Recognition of ancient 

crustal-plate boundaries of this type would enable 

us to outline episubduction regions where porphyry 

copper deposits might occur. The Piedmont Province 

of the Appalachian Mountains may be such a region. 

H. L. James ("The Metallogenic Concept," Presidential address. Soc. Economic Geologists, Nov. 13, 

1970, unpub. rept.) pointed out that this province 

has an arrangement of ore-bearing zones suggesting and eastward-dipping subduction zone. If porphyry copper deposits still are preserved they would 

lie in the Piedmont near the present _edge of the 

Coastal Plain. Copper, lead, and zinc have been 

noted in several old mines forming a trend extending 400 miles northeastward from central Georgia 

to the North Carolina-Virginia boundary. Within 

this trend, several low-grade disseminated coppermolybdenum occurrences have been explored by 

drilling programs in recent years. Porphyritic intrusive rock has been reported from only the Magruder mine area in Lincoln County, Ga., but geologic reports on the old gold mines and prospects 

are mostly sketchy and limited to descriptions of 

the veins and the closely associated rocks. Some of 

the mines and prospects are reported to have areas 

of abundant disseminated pyrite. 

In southwestern Alaska and the Aleutian Islands, 

geologic conditions similar to those of the Southwest 

Pacific permit the possibility of discovery of porphyry copper deposits. Quartz diorite intrusions 

and wide areas of disseminated pyrite described on 

Amchitka Island (Powers and others, 1960, p. 539, 

541) suggest that in at least one locality a favorable environment exists for porphyry copper prospecting. Projection of the porphyry copper provinces 

of British Columbia and Yukon Territory into central Alaska suggests that large resources might be 

found there. 

In the Antilles, an extensive copper province is 

suggested by the occurrence of porphyry copper 

dep-osits in Puerto Rico. The Puerto Rican deposits 

were formed during a period of vulcanism and intrusion in the early Tertiary (Barabas, 1971) and 

are overlapped by middle and upper Tertiary 

coastal plain carbonate rocks. A small molybdenum 

prospect in an Eocene pluton in the Virgin Islands 

(Ratte, 1971) suggests an eastward extension of 

this mineral province. In the limestone Caribbees, 

lower Tertiary plutonic rocks are exposed on St. 

Martin and Antigua. Hydrothermally altered rocks 

in_ St. Martin, Guadeloupe, Martinique, and other 

islands suggest interesting drilling targets, some of 

which were being explored by private companies 

during 1971. It is possible that another million tons 

of copper might be discovered in these islands, but 

land-use conflicts between mining and tourism may 

make their recovery in the near future doubtful. 

West of Puerto Rico the lower Tertiary mineral 

province is interrupted. Volcanic rocks and potentially productive intrusive bodies are absent in the 

lower Tertiary sequence of Santo Domingo. However in the Montagnes Noires of Haiti, the Blue 

Mountains of Jamaica, and the southern Oriente 

Province of Cuba, lower Tertiary volcanic rocks are 

present. Quartz-bearing intrusive rocks and alteration zones that may be present in these areas represent high-priority targets for porphyry copper 
COPPER 183 

exploration. 

In western Colombia, quartz diorite intrusions of 

probable middle Tertiary age in the Sierra Occidental (Irving, 1971) suggest a large region where 

porphyry deposits might be found. Recent geochemical investigations by U.S. Geological Survey 

and Colombian government geologists have revealed 

strong copper anomalies in one of these intrusions 

in the north end of the Sierra (E. M. Irving, oral 

commun., 1972). 

In Panama, recently discovered porphyry copper 

deposits related to upper Tertiary volcanic rocks 

(Ferencic, 1970; Dengo and others, 1969) suggest 

a wide province with potential mineralization. 

Economically important copper deposits are unknown in the Precambrian shields of South 

America, but the region is vast, nearly unpopulated, 

and difficult of access. In Brazil, the recent highway 

construction and westward pioneering movement 

and accompanying geologic and geochemical exploration may yield copper resources of great size. Not 

enough is known of the geology of this region to 

do more than speculate on the possibility of major 

sedimentary copper deposits of the Zaire-Zambia 

type or smaller deposits of the Tsumeb type. 

In western Europe and northwest Africa, porphyry copper deposits of late Paleozoic age may be 

preserved. These could be products of a Paleozoic 

subduction zone resulting from the collision of the 

European-African and the American crustal plates. 

Goosens (1971) suggested the possibility of porphyry copper occurrences in western Africa. 

The Alborz Mountains of northern Iran, with numerous small copper occurrences, may be a long 

extension of the copper-molybdenum porphyry province in Soviet Armenia. The areas of volcanosedimentary complex northeast of the Dasht-e-Lut 

in eastern Iran and in the northern part of the 

Chagai District in Pakistan, both areas of some late 

volcanism, are favorable areas for the occurrence 

of very young (Pliocene-Pleistocene) porphyries. 

One untested porphyry at Saindak in the Chagai 

District was described (Schmidt, 1968), and one 

prospect in east-central Iran, that at Gazu, was 

described in a way suggesting a porphyrylike deposit (Bazin and Hubner, 1969, p. 107-108). 

Mesozoic fold belts of the Soviet Far East probably contain large porphyry copper deposits. The 

Koryak Peninsula would be the logical beginning 

for the search for these because of the apparent 

continuity of cordilleran-type structures into this 

area. Younger deposits may occur along the KurileKamchatka-Aleutian arc-trench system. 

Recent discovery of porphyry copper deposits in 

the Philippines, Solomon Islands, and Borneo suggests that all the island arc areas in the Western 

Pacific, especially the Indonesian islands, might be 

potential prospecting ground. 

A region of abundant felsic volcanic rocks in 

northeastern China and eastern Mongolia would 

seem to have potential for significant copperporphyry and massive sulfide deposits. Other ranges 

besides the Ch'i-lien-shan, especially in northern 

Tsinghai Province, might contain significant massive sulfide copper deposits. There is also considerable potential for sedimentary copper deposits in 

many parts of this large country. We do not know 

enough about recent Chinese geologic literature to 

speculate on extensions of the environment of the 

copper porphyry of Chung-t'iao-shan in Shansi 

Province. 

The Tasman geosynclinal belt in eastern Australia 

contains many copper occurrences and major deposits of the massive sulfide type. Late Paleozoic 

felsic intrusions in this belt may contain large resources of the porphyry copper type. 

Table 40 summarizes our estimate of the amount 

TABLE 40.-Summary of speculative resources, in millions 

of tons, of copper 1 

Basin and Range porphyry copper ------------ 100 

Alaska porphyry copper --------------------- 10 

Other Western United States possibilities, 

Appalachian Mountains porphyry copper, 

and Antilles porphyry copper -------------- 10 

Central America-Colombia porphyry copper___ 10 

Brazilian shield sedimentary copper ----------- 50 

Western Europe-northwest Africa porphyry 

copper ------------------------------------ 10 Middle East porphyry copper ----------------- 10 

U.S.S.R. Far East and Kurile-Kamchatka arc__ 100 

China -------------------------------------- (?) Australia ----------------------------------- 10 

Indonesia ----------------------------------- 10 

Total --------------------------------- 320 1 Speculative resources: Undiscovered mineral deposits, whether of re• coverable or subeconomic grade, that may exist in unknown districts or in unrecogni.zed or unconventional form. Based mostly on estimates of 

geologic favorability and extent of geologic mapping. 

of copper that might be contained in these untapped 

districts and provinces. The figures are at best a 

guess and may be in error by as much as 100 

percent. 

SUBECONOMIC RESOURCES 

Lowell (1970) estimated that in the upper mile of 

the earth's crust there are about 3X1015 tons of 

copper. The recoverable identified, hypothetical, and 

speculative ore deposits discussed in the previous 

section make up a small fraction of this amount. 

Another fraction, su beconomic resources, comprise 

bodies of mineralized rock containing copper in 

amounts considerably higher than crustal abun-
184 UNITED STATES MINERAL RESOURCES 

dance but lower than could be mined under present 

economic and technological conditions. Subeconomic 

resources may be either identified or hypothetical, 

but inasmuch as data on grade and tonnage of subeconomic deposits are rarely available, no distinction 

is made between these categories. Subeconomic 

speculative resources represent such a high degree 

of uncertainty that they cannot be given numerical 

values. The lower limit of copper content of deposits in the· subeconomic category depends on one's 

personal expectations of revolutionary advances in 

mineral recovery and mining methods. Copper will 

ultimately be mined at lower grades than most other 

metals because recovery is facilitated by its tendency to occur as minute sulfide grains rather than 

in silicates. However, adverse effects on the environment and the magnitude of the labor and power 

requirements mitigate against the creation of huge 

open-pit mines in rocks containing only a few 

hundred parts per million of copper. 

Table 41 gives some of the identified and hypoTABLE 41.-Partiallist of subeconomic (conditional) resources, in millions of tons, of copper 1 

Locality 

Western United States --------

Do --------------------- Eastern United States --------

Do --------------------- Sea floor ------------------- Western Canada ------------- South America, Andes --------

Africa ----------------------

Europe ---------------------

Total ---------------------

Type of 

deposit 

Porphyry copper ----

Sedimentary -------- Sedimentary ------- Copper-nickel ------- Nodules · ----------- Porphyry copper ___ _ 

___ do ------------- Sedimentary --------

___ do -------------

Copper 

resources 

20 

20? 

11 

60 

50 (4o-60) 20 

100 

50 

50 

381 

1 Conditional resources: Specific, identified mineral deposits whose con- tained minerals are not profitably recoverable with existing technology and economic conditions. 

thetical subeconomic resources that may become 

economically important in the future. 

In the United States, conditional resources.in porphyry copper deposits are probably very large. 

Lowell (1970, p. 69) predicted that average grades 

in open-pit copper mines will decline to 0.25 percent 

by the year 2000. In-place leaching of deposits of 

even lower grade may soon become economical. In 

addition, some large deposits such as at Safford, 

Ariz., are too deep or too irregularly distributed to 

permit profitable mining at the present time but 

may become minable in the near future. An estimate 

of the hypothetical su beconomic resources in porphyry copper deposits averaging 0.25 percent copper requires some knowledge of the frequency of 

such deposits compared with deposits of minable 

grade. Moreover, to predict the increase in reserves 

of known deposits in response to a drop in average 

ore grades requires some knowledge of the rate at 

which copper content falls off with distance outward 

from boundaries of porphyry copper ore bodies. If 

the slope of the curve of copper plotted against 

distance outward is steep for most deposits, decreases in average grade will have little effect on 

reserves. Inasmuch as these data are not available, 

we are reduced to making the simple assumption 

that there are at least as many deposits averaging 

0.1-0.4 percent as there are deposits of currently 

minable grade. The discovery and development of 

this additional 7-8 billion tons of material in the 

western porphyry copper provinces with average 

grades of about 0.25 percent would yield about 20 

million tons of additional copper. 

Large conditional resources in sedimentary copper deposits in the United States are difficult to 

evaluate. Geologically, sedimentary deposits pass 

from economic ores to subeconomic resources when 

the beds in which the copper minerals occur become 

too thin or become separated by thick beds of barren 

rock. Also, some beds may have engineering characteristics that make mining dangerous or expensive, or a steeply dipping copper-bearing bed may 

reach depths that are beyond the reach of presentday underground mining practice. Nevertheless, the 

copper in certain sedimentary deposits is known to 

be continuous at fairly constant grade for great 

distances. 

The Nonesuch Shale at White Pine, Mich., is such 

a deposit. W. S. White (oral commun., 1972) estimated that 11 million tons of copper metal exists 

in currently subeconomic mineralized beds. The 

sedimentary copper deposits recently being explored 

in the Belt Supergroup of Montana and Idaho probably contain large conditional resources, but no information is yet available on their minable reserves. 

The copper-nickel deposits in the Duluth Gabbro 

Complex in Minnesota represent a large conditional 

resource. P. K. Sims (oral commun., 1972) estimated that 14 billion tons of mineralized rock exists 

along the lower contact of the gabbro body. This 

material has a lower cutoff of 0.25 percent and an 

average grade of 0.58 percent combined copper 

nickel. Assuming a 3 to 1 copper-nickel ratio, these 

deposits contain slightly more than 60 million tons 

of copper metal. Some of this copper is desseminated in bodies as large as 100 million tons and may 

soon become amenable to mass-mining methods, according to Sims. 

Summing up these large conditional resources 

(table 41) gives a total of 111 million tons of copper 

which may at some time become available in the 

United States. 

Among the world's most important conditional 

resources are those of the sea floor. These comprise 
COPPER 185 

copper-bearing manganese nodules of the ocean 

basins and brine-associated metal-rich bottom sediments of the Red Sea. On the basis of Mero's (1965) 

estimates of copper content and abundance of ocean 

floor manganese nodules (see also "Manganese"), 

we estimate that 40-60 million tons of copper may 

be available from this source. Development of these 

resources depends on the accurate determination of 

their size, research and development on economical 

mining and metallurgical methods, and settlement 

of the international-legal problems of ownership. 

Elsewhere in the world, reasonable assumptions 

on which to base estimates of presumed resources 

become increasingly difficult to make. In the Andes, 

where porphyry copper deposits are large and are 

mined at much higher grade than those in the 

United States and Canada, there must exist very 

large subeconomic resources. The sedimentary deposits of Zaire and Zambia probably also contain 

very large amounts of copper in thin or deeply 

buried beds. A doubling of the copper reserves of 

these areas is not difficult to imagine when modern 

low-cost mining methods are established and (or) 

world copper prices rise. 

Wedepohl (1971) gave 30-100 million tons as the 

probable copper content of the Kupferschiefer in 

Germany. Economic deposits are largely depleted, 

and this resource lies in thin or deeply buried beds. 

PROSPECTING TECHNIQUES 

We must assume that most easy-to-find copper 

deposits in the populated regions of the world have 

now been discovered. For all except some remote 

areas, new discoveries are more difficult to make 

and indirect methods of prospecting are being used 

increasingly to find copper and other metals. From 

now on, our success in finding new and especially 

hidden deposits will greatly depend on our ability 

to develop new methods of detecting concealed ores. 

Some prospecting techniques can be applied to a 

wide variety of ores, but others are only for specific 

targets. Geochemical reconnaissance is often the first 

step in prospecting and usually seeks several metals 

that may be dispersed from any kind of ore deposit. 

Stream sediment sampling, described by Hawkes 

and Webb (1962), is the most effective reconnaissance method in many terranes. Refinements of this 

method, such as improved statistical analysis of 

data and sampling of certain mineral species (for 

example, magnetite), have had some success. Detailed study of anomalous areas and outlining of 

drilling targets are usually accomplished by soil 

sampling and analysis. In tropical areas copper can 

be mostly leached from soils overlying the deposits, 

but Learned and Boissen (1972) showed that over 

porphyry copper deposits, traces of gold associated 

with chalcopyrite remain in the soil and that the 

deposit may be outlined by the gold anomaly over 

it. In glaciated regions, ore fragments in boulder 

trains have been studied in hope of tracing them to 

their source; sulfide fragments were followed for 

50 km in the discovery of the Outokumpu ores of 

eastern Finland. 

Rocks containing widely disseminated pyrite associated with copper porphyry deposits, in combination with other effects of hydrothermal alteration, weather in the desert environment to produce 

a large color anomaly, "distinguished by brownish 

to greenish coloration, bleaching and variegated 

iron staining" (Jerome, 1966, p. 82-83). In some 

localities large red-brown areas ("red thumbs") 

have developed near the ore bodies as at Bisbee, 

San Manuel, and Banner-Pima-Mission, all in Arizona. Recognition of the "red thumb" area from an 

aircraft played an important part in the exploration 

of the La Caridad deposit, Mexico. The areas of 

color anomaly may be hundreds of meters to several 

kilometers in size and might be recognizable on 

colored aerial photography (Schmidt, 1968, p. 60). 

They also form target areas large enough to be 

sought from instrumented satellites; tests of the 

detection of a porphyry ore body in a desert area 

are planned for the Earth Resources Technology 

Satellite A. 

Preliminary experiments have been made to compare the spectral reflectance from trees in soil over 

a sulfide mineral deposit with reflectance from trees 

of the same species on nearby unmineralized soil 

(Canney, 1970). Early results of tests made on a 

disseminated copper-molybdenum deposit in Maine 

have been encouraging. 

Geophysical methods of many types are suitable 

for copper prospecting, but they are much more 

specific for certain types of ore. Aeromagnetic surveys are used to outline bodies of mafic rocks which 

may contain massive sulfide or magmatic-segregation deposits or to indicate areas of weakly magnetic 

hydrothermal alteration or highly magnetic skarn 

mineralization associated with porphyry deposits. 

The use of geophysical methods in the search for 

copper porphyry deposits was discussed by Brant 

(1966) and Sumner (1970). The potassic alteration that accompanies porphyry copper deposits can, 

theoretically, be detectable by modern airborne 

gamma-radiation surveys (Moxham and others, 

1965). Electromagnetic surveys by ground or air 

are used in outlining massive sulfide deposits; 

induced-potential surveys are effective in locating 
186 UNITED STATES MINERAL RESOURCES 

porphyries and other types of rocks that contain 

disseminated sulfides. The use of geophysical methods in the search for massive sulfide ores is discussed 

by several authors in Morley ( 1970). 

Recent developments in geochemistry and geophysics have made it possible to recover more information from diamond drilling than simply the 

geology and copper assays of the core. Cheaper and 

rapid analytical methods, principally in spectroscopy, have made it more feasible to analyze large 

numbers of samples for many elements. Slight variation in trace-element composition may be caused by 

metals dispersed outward from an ore body not 

intersected by the hole. Similarly, down-hole geophysical instruments of many types have been 

perfected, enabling the geologist to extend his 

knowledge many feet beyond the walls of the drill 

hole. 

PROBLEMS FOR RESEARCH 

Figure 22 shows the relationship between the size 

and grade of ore deposits and copper production. 

Annual U.S. production is about equivalent to a 

deposit the size of Sierrita in Arizona, and annual 

world production is about equal to a La Caridad 

deposit or an average Zaire-Zambian sedimentary 

deposit. It is important to know if we are mining 

our copper deposits faster than we are finding them. 

During the last 10 years, U.S. mine production was 

about 13 million tons of copper (table 36) . New 

porphyry copper deposits discovered and (or) 

brought into production during this 10-year period, 

listed by Peters ( 1970), will yield slightly more than 

14 million tons of copper. Assuming that several 

million tons of copper is known in other, less important types of deposits and in some large but 

unannounced discoveries, it appears that, in the 

United States, exploration and development are 

ahead of production by a small margin. Worldwide 

exploration and development lead mine production 

by at least 28 percent, again using Peters' list of 

discoveries. 

The last decade was notable for intense exploration activity in response to favorable political conditions and high copper prices. Moreover, economic 

geologists experienced a renaissance in geologic 

theory during this period, in which new approaches 

to problems of geochemistry, igneous and sedimentary petrology, and tectonics were found and applied 

to ore deposits. However exploration geology is 

very sensitive to economic cycles, and there is reason to believe that this period of activity is over, at 

least temporarily (Colen, 1972). This stop-and-start 

exploration activity is extremely wasteful of human 

energy, and if we are to satisfy the long-term demand for metal in a future world in which ore 

deposits become increasingly more difficult to find, 

new ways of organizing exploration activities must 

be sought, especially long-range planning. 

Copper is a commodity for which a permanent 

worldwide shortage is not easily foreseeable, but 

even though the hypothetical and speculative resources may be very jarge, an enormous amount of 

geologic field work, analysis, and even intuition will 

be required to transform these resources into proven 

reserves. At the same time we must continue to 

develop our scientific knowledge in order to replace 

outdated exploration ideas with new ones. 

On the geological side of resource study, the need 

for geologic and geophysical maps as a base for mineral exploration cannot be overemphasized. More 

specifically, additional efforts must be applied to 

mapping and other geologic studies of those parts 

of the United States that have the highest mineral 

potential. Southeastern Arizona is probably the 

richest copper province in the world, yet geologic 

mapping at a scale of 1: 62,500 is complete for only 

27 percent of the area, and nearly half the province 

is unmapped. 

Large-scale metallogenic maps might be an effective exploration tool in southeastern Arizona to 

detect the presence of deposits concealed beneath 

younger volcanic and sedimentary rocks. 

Lowell and Guilbert ( 1970) and others pointed 

out that almost all porphyry copper deposits have 

a peripheral zone of small veins of base and precious 

metals, manganese carbonates, and barite that may 

extend outward for several miles from the deposit. 

Careful mapping of these veins, including even the 

smallest mineral occurrences, and careful classification of them according to various mineralogic, structural, textural, and genetic schemes may direct the 

exploration geologist to blind porphyry ore bodies 

or to those covered by later deposits. This mapping 

should be done at scales of 1: 125,000 or greater 

depending on the complexity of the geology and 

spacing of the data points. Trace-element analyses 

of the veins and of mineral separates from them 

such as biotite or chlorite may aid in the interpretation. Studies of salinity and temperature of formation of fluid inclusions in the vein materials may 

show the geologist the direction toward the source 

of the mineralizing solutions. 

SELECTED REFERENCES 

Ageton, R. W., and Greenspoon, G. N., 1970, Copper, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 

535-553. 
COPPER 187 

Anderson, C. A., 1969, Massive sulfide deposits and volcanism: Econ. Geology, v. 64, p. 129-146. 

Bakun, N. N., Volodin, R. N.; Krendele·v, F. P., 1958, 

Osnovnyye osobennosti geologicheskogo stroyeniya U dokanskogo mestorozhdeniya medistykh peschanikov i 

napravleniye yego dal'neyshey razvedki (Principal 

characteristics of the geologic structure of the U dokan 

cupriferous sandstone deposit and the direction of subsequent exploration work there) : Russia Ministerstvo 

vysshego obrazovaniya Izvestiya vysshikh uchebuykh 

zavedeniy, Geologiya i razvedka, n. 5. 

Barabas, A. H., 1971, K-Ar dating of ign·eous events and 

porphyry copper mineralization in west central Puerto 

Rico [abs.] : Econ. Geology, v. 66, p. 977. 

Bateman, A. M., 1950, Economic mineral deposits [2d ed.] : 

New York, John Wiley and Sons, 916 p. 

Bazin, Dominique and Hubner, Helmuth, 1969, Copper deposits in Iran: Iran Geol. Survey Rept. 13, 232 p. 

Bischoff, J. L., and Manheim, F. T., 1969, Economic potential of the Red Sea heavy metal deposits, in Degens, E. 

T., and Ross, D. A., eds., HCYt brines and recent heavy 

metal deposits in the Red Sea: New York, SpringerVerlag, Inc., p. 535-541. 

Bogdanov, Yu. V., 1968, Usloviya formirovaniya medistykh 

otlozheniy v rayone U dokanskogo mestorozhdeniya 

(Conditions of formation of cupriferous rocks in the 

area of the U dokan deposit) : Akad. nauk SSSR Kom. 

po osadochnym porodam i Otdeleniye nauk o Zemle. 

Geokhimiya osadochnykh porod i rud, p. 375-385. 

Bostom, Kurt, and Peterson, M. N. A., 1966, Precipitates 

from hydrothermal exhalations on the East Pacific Rise: 

Econ. Geology, v. 61, p. 1258-1265. 

Brant, A. A., 1966, Geophysics in the exploration for Arizona 

porphyry coppers, in Geology of the porphyry copper 

deposits, southwestern North America: Tucson, Ariz., 

Univ. Arizona Press, p. 87-110. 

Brongersma-Sanders, Margaretha, 1968, On the geographical association of strata-bound ore deposits with evaporites: Mineralium Deposita, v. 3, no. 3, p. 286-291. 

Canney, F. C., 1970, Remote detection of geochemical soil 

anomalies, in Earth resources aircraft program, status 

review: U.S. Natl. Aeronautics and Space Adm., v. 1, 

p. 7-1-7-8. 

Clark, A. L., 1971, Strata-bound sulfides in the Precambrian 

Belt Supergroup, Northern Idaho and Northwestern 

Montana: Soc. Mining Geology Japan, Spec. Issue 3, 

p. 261-267. 

Clark, L. A., 1971, Volcanogenic ores-comparison of cupriferous pyrite deposits and Japanese Kuroko deposits: 

Soc. Mining Geology Japan, Spec. Issue 3, p. 206-215. 

Cloud, P. J., 1971, The primitive Earth, Chap. 11 in Glass, 

I. G., Smith, P. J., and Wilson, R. C. L., eds., Understanding the Earth, a reader in the Earth sciences: 

Sussex, England, Artemis Press (for Open File Univ. 

Press), p. 150-155. 

Coats, R. R., and Stephens, E. C., 1968, Mountain City copper mine, Elko County, Nevada, in Ore deposits of the 

United States, 1933-1967 (Graton-Sales volume), v. 2: 

Am. Inst. Mining, Metall., and Petroleum Engineers, p. 

1074-1101. 

Colen, H. R., 1972, Exploration in 1971-a study in dec·eleration: Mining Cong. Jour., v. 58, no. 2, p. 90-93. 

Coombs, D. S., Ellis, A. J., Fyfe, W. S., and Taylor, A .M., 

1959, The zeolite facies, with comments on the interpretation of hydrothermal syntheses: Geochim. et Cosmochim. Acta, v. 17, p. 53-107. 

Cornwall, H. R., 1956, A summary of ideas on the origin of 

native copper deposits: Econ. Geology, v. 51, no. 7, p. 

615-631. 

Cox, D. P., 1971, Puerto Rican porphyry copper deposits, 

petrology and alteration [abs.]: Caribbean Geol. Conf., 

6th, Porlarmar, Venezuela 1971, Program. 

Davidson, C. F., 1964, Uniformitarianism and ore genesis: 

Mining Mag. (London), v. 110, no. 3, p. 176-185; no. 4, 

p. 244-253. 

--- 1965, A possible mode of origin of strata-bound copper ores: Econ. Geology, v. 60, p. 942-954. 

Degens, E. T., and Ross, D. A., eds., 1969, Hot brines and 

recent heavy metal deposits in the Red Sea: New York, 

Springer-Verlag, Inc., 600 p. 

Dengo, Gabriel; Levy, Enrique; Bohnenberger, Otto; Caballeros, R., 1969, Mapa Metalogenetico de America Central, 

1:2,000,000: Inst. Centroamericano Inv. y Tecnologia 

Indus. Pubs. Geol. 

Dings, M. G., 1951, The Wallapai mining district, Cerbat 

Mountains, Mohave County, Arizona: U.S. Geol. Survey 

Bull. 978-E, p. 123-163. 

Ensign, C. 0., Jr., White, W. S., Wright, J. C., Patrick, J. 

L., Leone, R. J., Hathaway, D. J., Trammell, J. W., 

Fritts, J. J., and Wright, T. L., 1968, Copper deposits 

in the Nonesuch Shale, White Pine, Michigan in Ore 

deposits of the United States, 1933-1967 (Graton-Sales 

volume), v. 1: Am. Inst. Mining, Metall., and Petroleum 

Engine·ers, p. 460-488. 

Espie, F. F., 1971, The Bougainville copper project: Australasian Inst. Mining and Metallurgy Proc., no. 238. 

Everett, F. D., and Bennett, H. J., 1967, Evaluation of domestic reserves and pCYtential sources of ores containing 

copper, lead, zinc, and associated metals: U.S. Bur. 

Mines Inf. Circ. 8325. 

Eyde, T. H., 1972, Stratigraphy is a sometimes overlooked 

guide to porphyry coppers: Mining Eng., Apr. 1972, p. 

40-42. 

Ferencic, Ante, 1970, Porphyry copper mineralization in 

Panama: Mineralium Deposita, v. 5, p. 383-389. 

Fournier, R. 0., 1967, The porphyry copper deposit exposed 

in the Liberty open-pit mine near Ely, Nevada; pt. 1, 

Syngenetic formation: Econ. Geology, v. 62, p. 57-81. 

Garlick, W. G., 1961, The syngenetic theory, in F. Mendelsohn, ed., Geology of the Northern Rhodesian Copperbelt: London, Macdonald, 523 p. 

Goldschmidt, V. M., 1954, Geochemistry: Oxford, Clarendon 

Press, 730 p. 

Goodwin, A. M., 1965, Mineralized volcanic complexes in the 

Porcupine-Kirkland Lake-Noranda Region, Canada: 

Econ. Geology, v. 50, p. 955-971. 

Goosens, P. J., 1971, L·es gisements du type "porphyry copper" (Deposits of the porphyry type) : Mines Metall., 

no. 3661, p. 218-220. 

Green, Jack, 1969, Abundances and distribution of elements: 

Douglas Advanced Research Labs., Huntington Beach, 

Calif., Research Commun. 91, 80 p. 

Guild, P. W., 1971, Metallogeny-a key to exploration: Mining Eng., v. 23, p. 69-72. 

Ham, W. E., and Johnson, K. S., 1963, Copper in the Flowerpot Shale (Permian) of the Creta area, Jackson County, 

Oklahoma: Oklahoma Geol. Survey 64, 32 p., ill us. and 
188 UNITED STATES MINERAL RESOURCES 

geol. map (19·64). (Summary prepared for release Aug. 

1, 19·63.) 

Hammer, D. F., and Peterson, D. W., 1968, Geology of the 

Magma Mine area, Arizona, in Ore deposits of the 

United States, 1933-1967 (Graton-Sales volume), v. 2: 

Am. Inst. Mining, Metall., and Petroleum Engineers, 

p. 1282-1310. 

Haran~zyk, Czeslaw, 1970, Zechstein lead-bearing shales in 

the Foresudetian monocline in Poland: Econ. Geology, 

v. 65, p. 481-495. 

Harrison, J. E., 1972, Precambrian Belt basin of northwestern United States-its geometry, sedimentation and copper occurrences: Geol. Soc. America Bull., v. 83, p. 

1215-1240. 

Harrison, J. E., and Grimes, D. J., 1970, Mineralogy and 

geochemistry of some Belt rocks, Montana and Idaho: 

U.S. Geol. Survey Bull. 1312-0, p. 01-049. 

Hawkes, H. E., and Webb, J. S., 1962, Geochemistry in 

mineral exploration: New York, Harper and Row, 415 p. 

Hewitt, W. P., 1968, Western Utah, eastern and central 

Nevada, in Ore deposits of the United States, 1933-1967 

(Graton-Sales volume), v. 1: Am. Inst. Mining, Metall., 

and Petroleum Engineers, p. 857-885. 

Hodder, R. W., and Hollister, V. F., 1972, Structural features of porphyry copper deposits and the tectonic evolution of continents: Canadian Inst. Mining and Metallurgy Trans., v. 75, p. 23-27. 

Horikoshi, Ei, 1969, Volcanic activity related to the formation of the Kuroko type deposits in the Kosaka district: 

Mineralium Deposita, v. 4, p. 321-345. 

Hutchinson, R. W., and Searle, D. L., 1971, Stratabound 

pyrite deposits in Cyprus and relations to other sulfide 

ores: Soc. Mining· Geology Japan, Spec. Issue 3, p. 198-

205. 

Irving, E. M., 1971, La evolucion estructural de los Andes 

mas septentrional de Colombia: Inst. Nac. Inv. Geol. 

Mineras, Bol. Geol., v. 19, no. 2, 89 p. 

James, H. L., 1969, Comparison between Red Sea deposits 

and older ironstone and iron formation, in Degens, E. 

T., and Ross, D. A., eds., Hot brines and recent heavy 

metal deposits in the Red Sea: New York, Springer-Verlag, Inc., p. 525-532. 

Jerome, S. E., 1966, Some features pertinent in exploration 

of porphyry copper deposits, in Geology of the porphyry 

copper deposits, southwestern North America: Tucson, 

Ariz., Univ. Arizona Press, p. 75-85. 

Johnson, K. S., and Ham, W. E., 1972, Permian copper-shale 

deposits of southwestern Oklahoma [abs.]: Geol. Soc. 

America Abs. with Programs, v. 4, no. 7, p. 555. 

Kalliokoski, Jorma, 1965, Metamorphic features in North 

American massive sulfide deposits: Econ. Geology, v. 

60, no. 3,' p. 485-505. 

Kaufman, W. H., Schumacher, 0. L., and Woodward, L. A., 

1972, Stratiform copper mineralization in the Nacimiento region, New Mexico: New Mexico Bur. Mines 

and Mineral Resources Target Expl. Rept. E-1. 

Kesler, S. E., 1971, Cu-Mo-Au abundances in island arc and 

continental porphyry copper deposits [abs.]: Econ. 

Geology, v. 66, no. 6, p. 979. 

Kinkel, A. R., Jr., 1962, The Ore Knob massive sulfide copper 

deposit, North Carolina-an example of recrystallized 

ore: Econ. Geology, v. 57, p. 1116-1121. 

Kinnison, J. E., 1966, The Mission copper deposit, Arizona, 

in Geology of the porphyry copper deposits, southwestern North America: Tucson, Ariz., Univ. Arizona Press, 

p. 281-287. 

Landergren, V. S., and Manheim, F. T., 1963, fiber die 

Abhangigkeit der Verteilung von Schwermetallen von 

der Fazies (on the relationship of the distribution of 

the trace metals in facies) (in German ; English abs.) : 

Fortschr. Geologie Rheinland. u. Westfalen, v. 10, p. 

173-192. 

Learned, R. E., and Boissen, R., 1972, Gold a useful pathfinder element for porphyry exploration in Puerto Rico 

[abs.]: Internat. Geochem. Explor. Symposium, 4th, 

London 1972, Handb. 

Lindgren, Waldemar, 1911, Copper, silver, lead, vanadium, 

and uranium ores in sandstone and shale: Econ. Geology, 

v.6,no.6,p. 568-581. 

--- 1926, Ore deposits of the Jerome and Bradshaw 

Mountains quadrangles, Arizona: U.S. Geol. Survey 

Bull. 782, 192 p. 

Loudon, A. G., 1972, Marcopper disseminated copper deposit, Philippines [preprint]: Am. Inst. Mining, Metall., 

and Petroleum Engineers, and Mining and Metall. Inst. 

Japan, May 24-27 mtg. Tokyo, 8 p. 

Lowell, J. D., 1970, Copper resources in 1970: Mining Eng., 

v. 22, no. 4, p. 67-73. 

Lowell, J. D., and Guilbert, J .M., 1970, Lateral and vertical 

alteration-mineralization zoning in porphyry ore deposits: Econ. Geology, v. 65, p. 373-408. 

Lyubimov, I. M., 1966, Poleznyye iskopayemyye SSSR (Economic minerals of the USSR): "Prosveshcheniye" 

Press, Moscow, 253 p. 

McMahon, A. D., 1965, Copper, a materials survey: U.S. 

Bur. Mines Inf. Circ. 8225, 339 p. 

Macnamara, P. M., 1968, Rock types and mineralization at 

Panguna porphyry copper prospect, Upper Kaverong 

Valley, Bougainville Island: Australasian Inst. Mining 

and Metallurgy Proc., no. 228, p. 71-79. 

Madamba, F. A., 1972, Geology and mineralization of the 

Atlas-Cebu disseminated copper deposits [preprint]: 

Am. Inst. Mining, Metall., and Petroleum Engineers, 

and Mining and Metall. Inst. Japan, May 24-27 mtgs., 

Tokyo, 9 p. 

Malan, S. P., 1964, Stromatolites and other algal structures 

at Mufulira, Northern Rhodesia: Econ. Geology, v. 59, 

p. 397-415. 

Mero, J. L., 1965, The mineral resources of the sea: Amsterdam, Elsevier Publishing Co., 312 p. 

Metz, R. A., and Rose, A. W., 1966, Geology of the Ray copper 

deposit, Ray, Arizona, in Geology of the porphyry copper 

deposits, southwestern North America: Tucson, Ariz., 

Univ. Arizona Press, p. 177-188. 

Meyer, Charles, Shea, E. P., Goddard, C. C., Jr., (and 

others), 1968, Ore deposits at Butte, Montana, in Ore 

deposits of the United States, 1933-1967 (Graton-Sales 

volume), v. 2: Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 1373-1416. 

Miller, A. R., Densmore, C. D., Degens, E. T., Hathaway, 

J. C., Manheim, F. T., McFarlin, P. F., Pocklington, R., 

and Jokela, A., 1966, Hot brines and recent iron deposits in deeps of the Red Sea: Geochim. et Cosmochim. 

Acta, v. 30, p. 341-359. 

Morley, L. W., ed., 1970, Mining and groundwater geophysics 

1967: Canada Dept. Energy, Mines and Resources, 

Ottawa, 722 p. 

Moxham, R. M., Foote, R. S., and Bunker, C. M., 1965, 
COPPER 189 

Gamma-ray spectrometer studies of hydrothermally altered rocks: Econ. Geology, v. 60, no. 4, p. 653-671. 

National Commission on Materials Policy, 1972, Towards a 

national materials policy, basic data and issues, an interim report, April 1972: Washington, D. C., U.S. Govt. 

Printing Office, 63 p. 

Newberg, D. W., 1967, Geochemical implications of chrysocolla-bearing alluvial gravels: Econ. Geology, v. 62, no. 

7, p. 932-956. 

Parker, R. L., 1967, Composition of the Earth's crust, Chap. 

D of Fleischer, Michael, ed., Data of geochemistry [6th 

ed.]: U.S. Geol. Survey Prof. Paper 440-D, 19 p. 

Peters, W. C., 1970, Some geological comparisons--Recent 

porphyry copper discoveries: Mining Cong. Jour., Oct. 

1970, p. 28-32. 

Pettijohn, F. J., 1963, Chemical composition of sandstonesexcluding carbonate and volcanic sands, Chap. S of 

Fleischer, Michael, ed., Data of geochemistry [6th ed.]: 

U.S. Geol. Survey Prof. Paper 440-S, 19 p. 

Phillips, C. H., Cornwall, H. R., and Rubin, Meyer, 1971, A 

Holocene ore body of copper oxides and carbonates at 

Ray, Arizona: Econ. Geology, v. 66, no. 3, p. 495-498. 

Powers, H. A., Coats, R. R., and Nelson, W. H., 1960, Geology 

and submarine phys.iography of Amchitka Island, 

Alaska: U.S. Geol. Survey Bull. 1028-P, p. 521-554. 

Putzer, Hannfrit, 1972, Kupferschiefer in Zambia und Mitteleuropa, ein palaogeographischer Vergleich: Geol. 

Jahrb. (Hanover), v. 90, p. 415-430. 

Ratte, C. A., 1971, Mineralogy, host rock alteration and 

fracture pattern at Mine Hill and Copper Mine Point, 

Virgin Gorda, British W es·t Indies: Caribbean Geol. 

Conf., 6th, Porlamar, Venezuela, Program. 

Richter-Bernburg, Gerhard, 1941, Geologische Gesetzmassigkeiten in der Metallfuhrung des Kupferschiefers ( Geological laws in the mineralization of the Kupferschiefer) 

(in German): Arkiv fur Lagerstattenforschung, no. 73, 

61 p. 

--- 1951, Zwei beitrag zu fazies, tektonik und Kupferfuhrung des Zechsteins. I. Waldeck, II. Nordusudeten. 

(Two studies of the facies, tectonics, and copper content of the Zechstein-1. Waldeck, 2. northern Sudeten) 

(in German): Geol. Jahrb., v. 65, p. 145-212. 

Ruiz, C., Aguilar, A., Egert, E., Espinosa, W., Peebles, F., 

Quezada, R., Serrane, M., 1971 Strata-bound copper sulfide deposits of Chile: Soc. Mining Geology Japan, Spec. 

Issue 3, p. 252-260. 

Runnels, D. D., 1969, The mineralogy and sulfur isotopes of 

the Ruby Creek copper prospect, Bornite, Alaska: Econ. 

Geology, v. 64, p. 75-90. 

Sales, R. H., and Meyer, Charles, 1949, Results from preliminary studies of vein formation at Butte, Montana: 

Econ. Geology, v. 44, no. 6, p. 465-484. 

Schmidt, R. G., 1968, Exploration possibilities in the western 

Chagai District, West Pakistan: Econ. Geology, v. 63, 

p. 51-60. 

Shank, R. J., 1972, Copper, in 1971 Mineral industry review: Canadian Mining Jour., v. 93, no. 2, p. 79-89. 

Shcherba, G. N., 1971, The stratiform deposits of Kazakhstan: Soc. Mining Geology Japan, Spec. Issue 3, p. 172-

177 (Proc. IMA-IAGOD meetings, 1970). 

Sillitoe, R. H., 1972, A plate-tectonic model for the origin 

of porphyry copper deposits: Econ. Geology, v. 67, p. 

184-197. 

Sillitoe, R. H., and Sawkins, F. J ., 1971, Geologic, mineralogic 

and fluid inclusion studies relating to the origin of 

copper-bearing tourmaline brecca pipes, Chile: Econ. 

Geology, v. 66, p. 1028-1041. 

Sumner, J. S., 1970, Geophysical aspects of porphyry copper 

deposits: in L. W. Morley, ed., Mining and groundwater 

geophysics, 1967: Canada Dept. Energy, Mines and Resources, p. 322-335. 

Superceanu, C. I., 1971, The eastern Mediterranian-Iranian 

alpine copper-molybdenum belt: Soc. Mining Geol. 

Japan, Spec. Issue 3, p. 393-398. 

Sutherland-Brown, A., 1969, Mineralization in British 

Columbia and the copper and molybdenum deposits : 

Canadian Mining and Metall. Bull., v. 62, no. 681, p. 

26-40. 

Sutherland-Brown, A., Cathro, R. J., Panteleyev, A., and 

Ney, C. S., 1971, Metallogeny of the Canadian Cordillera: Canadian Mining and Metall. Bull., v. 64, no. 

709,p.37-61. 

Sutulov, Alexander, 1967, Copper production in Russia: Univ. 

Concepcion, Concepcion, Chile, 220 p. 

--- 1972, Copper in the communist world: World Minerals and Metals, no. 6, p. 9-13. 

Tatsumi, T., and Watanabe, T., 1971, Geological environment 

of formation of Kuroko-type deposits: Soc. Mining 

Geology Japan, Spec. Issue 3, p. 216-220. 

Thayer, T. P., 1971, Authigenic, polygenic, and allogenic ultramafic and gabbroic rocks as hosts for magmatic ore 

deposits: Geol. Soc. Australia, Spec. Pub. 3, p. 239-251. 

Thomas, L. A., 1966, Geology of the San Manuel ore body, 

in Geology of the porphyry copper deposits southwestern 

North America: Tucson, Ariz., Univ. Arizona Press, p. 

133-142. 

Throop, A. H., and Buseck, P. R., 1971, Nature and origin 

of black chrysocolla at the Inspiration mine, Arizona: 

Econ. Geology, v. 66, p. 1168-1175. 

Titley, S. R., 1972, Intrusion, and wall rock, porphyry copper 

deposits: Econ. Geology, v. 67, p. 122-123. 

Titley, S. R., and Hicks, C. L., eds., 1966, Geology of the 

porphyry copper deposits, southwestern North America: 

Univ. Arizona Press, Tucson, Ariz., 287 p. 

Turekian, K. K., and W edepohl, K. H., 1961, Distribution of 

the elements in some major units of the Earth's crust: 

Geol. Soc. America Bull., v. 72, no. 2, p. 175-192. 

U.S. Bureau of Mines, 1970, World review of copper: U.S. 

Bur. Mines Minerals Yearbook, 1969, p. 42. 

U.S. Department of the Interior, 1972, First annual report 

of the Secretary of the Interior under the Mining and 

Minerals Policy Act of 1970, March 1972: 142 p., ap.p. 

Velasco, J. R., 1966, Geology of the Cananea district, in 

Geology of the porphyry copper deposits, southwestern 

North America: Tucson, Ariz., Univ. Arizona Press, p. 

245-250. 

Vine, J. D., and Tourtelot, E. B., 1970a, Preliminary geochemical and petrographic analysis of lower Eocene 

fluvial sandstones in the Rocky Mountain region, in 

Wyoming Geol. Assoc. Guidebook 22d Ann. Field Conf., 

Wyoming Sandstones Symposium: p. 251-263. 

--- 1970b, Geochemistry of black shale deposits-a summary report: Econ. Geology, v. 65, no. 3, p. 253-272. 

Wedepohl, K. H., 1964, Untersuchungen am Kupferschiefer 

in Nordwestdeutschland; Ein Beitrag zur Deutung der 

Genese bituminoser Sedimente (Investigation of the 

Kupferschiefer in northwest Germany; a contribution 

to the genesis of bituminous sediments) (in German; 
190 UNITED STATES MINERAL RESOURCES 

English abs.): Geochim. et Cosmochim. Acta, v. 28, p. 

305-364. 

--- 1971, "Kupferschiefer" as a prototype of syngenetic 

sedimentary ore deposits: Japan Soc. Mining Geology, 

Spec. Issue 3, p. 268-273 (Proc. IMA-IAGOD meetings, 

1970). 

'White, W. S., 1968, The native-copper deposits of northern 

Michigan, in Ore deposits of the United States, 1933-

1967 (Graton-Sales volume) v. 1: Am. Inst. Mining, 

Metall., and Petroleum Engineers, p. 303-325. 

Whyte, R. J., and Green, Margaret, 1971, Geology and paleogeography of Chibuluma west ore body, Zambian Copperbelt: Econ. Geology, v. 66, p. 400-424. 

Wilson, H. D. B., ed., 1969, Magmatic ore deposits: Econ. 

Geology Monograph 4. 

Zweifel, Hans, 1972, Geology of the Aitik copper deposit: 

Internat. Geol. Cong., 24th, Montreal 1972, sec. 4 (mineral deposits), p. 463-473. 
UNITED STATES MINERAL RESOURCES 

DIATOMITE 

By DAVID L. DURHAM 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

Uses --------------------------------------------

Production --------------------------------------

Geologic environment ----------------------------

Prospecting techniques ---------------------------

~ources ---------------------------------------

Problems for research ----------------------------

References cited ---------------------------------

FIGURE 

Page 

191 

191 

192 

192 

192 

193 

194 

194 

194 

spines, and bristles; the combined area of holes in 

the frustules generally ranges from 10-30 percent 

of the total area (Lewin and Guillard, 1963, p. 378). 

Many valuable properties of the rock depend upon 

the aggregate effect of the microscopically complex 

and chemically inert diatom frustules. Papers by 

Conger (1951), Lewin and Guillard (1963), Lohman (1960), and Patrick and Reimer (1966) include much general information about diatoms. 

Although the opaline silica of dead diatoms is 

soluble in most natural waters, the rate of solution 

is slow enough that siliceous diatom remains can 

accumulate under favorable conditions to form the 

substance of diatomaceous sediments and rocks. 

23. Graph showing estimated diatomite production, 1948-68 ----------------------------

Page Rock composed almost entirely of diatom frustules 

generally is called diatomite; the term implies ma193 terial of commercial quality. Although unconsolidated diatomaceous sediments are not properly 

ABSTRACT OF CONCLUSIONS 

Diatomite is a rock made of microscopic poro:us shells of 

silica. Its principal domestic US·e is as a filtering material, for 

purifying water and various food proc·essing and industrial 

fluids; other diverse uses include fillers, construction and 

insulating materials, and mild abrasives. United States and 

world resources of crude diatomite are adequate for the 

foreseeable future, but the need for diatomite near markets 

and for particular purposes encourages development of new 

sources for the material. Studies that relate the geologic 

setting and history of diatomite to the occurrenc·e and properties of the rock can help locate important und·eveloped deposits. 

INTRODUCTION 

classified by the rock name "diatomite", both the 

rock and the sediments are considered together as 

a commodity because they both are sources of diatom products. The names "diatomaceous mudstone", "diatomaceous siltstone", and "diatomaceous 

shale" describe rocks that contain diatom remains 

along with a considerable amount of other sedimentary material; these rocks are of less commercial interest than the more nearly pure diatomite. 

The names "diatomaceous earth" and "kieselguhr" 

are synonymous with the term "diatomite"; the 

names "moler" and "moler earth" apply to impure 

diatomite produced in Denmark. The names "infusorial earth" and "tripoli" are used improperly for 

Diatomite is a sedimentary rock composed mainly diatomite. Numerous trade names identify the diof the siliceous remains of diatoms, which are atomite products of particular manufacturing comsingle-celled aquatic organisms that generally are panies. Papers by Calvert (1966), Conger (1942), 

classed as algae. Diatoms depend upon a form of and Lisitsyn (1967) describe the accumulation of 

photosynthesis ; consequently they flourish only in diatomaceous sediments; papers by Cummins 

sunlit waters. They develop frustules, or shells, of (1960), Eardley-Wilmot (1928), and Williamson 

amorphous opaline silica (Si02 •nH20) that com- (1966), and an article in Industrial Minerals (1969) 

monly are complexly perforated and bear ribs, summarize data on diatomite. 

U.S. GEOL. SURVEY PROF. PAPER 820 

191 
192 UNITED STATES MINERAL RESOURCES 

The most conspicuous features of diatomite are 

the light weight, high porosity, and whiteness of 

the material. Scanning electron microscope photographs of diatomite show plainly the fine aggregate 

stru~ture responsible for many remarkable properties of the rock (Gillott, 1969, p. 104). Dry blocks 

of crude diatomite have an apparent density of 

20-40 pounQ.s per· cubic foot, only about half that 

of water, although the specific gravity of the opaline 

silica of diatom frustules is about twice that of 

water. Dry diatomite powder has an apparent 

density of only 5-16 pounds per cubic foot. Diatomite is highly porous, and the porosity increases with 

increasing temperature up to about 700°C. It has 

low thermal conductivity and the melting point 

ranges from about 1,400° to 1, 750°C; certain impurities lower the melting point considerably. The 

rock can absorb 11;2-3 times its weight of water; 

the absorptive capacity is increased when the combined water of the opaline silica is driven off by 

calcination. Diatom products also have useful adsorptive properties (Anderson and others, 1947). 

Diatomite has a dull earthy luster and generally is 

white or nearly white, although both impurities and 

water content affect the color. Diatomite ranges 

from massive to finely laminated and, ordinarily, 

it is easily friable. The opaline silica of diatoms has 

a hardness of 4-6 on the Mobs scale, but the rock 

itself has an apparent hardness of only 1.5 

Chemical analyses of diatomite generally show 70-

90 percent Si02, 2-10 percent Al20a, and variable 

but small percentages of Fe20a, FeO, Ti02, P 20s, 

CaO, MgO, Na20, and K20 (Cressman, 1962, table 

3 ; Cummins, 1960, table 1). 

The physical properties of diatomite vary considerably from one deposit to another and may vary 

from bed to bed in a single deposit. The varieties 

and commercial grades of diatomite depend mainly 

on ( 1) the kind and amount of impurities in the 

crude material, and (2) the aggregate effect of the 

shape, size, arrangement, and relative proportions 

of the constituent diatoms. The commercial value 

of diatomite generally is affected adversely by impurities such as clay, volcanic ash, sand, carbonate, 

and organic matter. Also, the commercial quality 

of the material is lessened if the constituent diatom 

frustules are crushed or broken. 

USES 

Diatomite has hundreds of specific uses in 10 

principal categories: (1) filters, (2) fillers (see 

"Pigments and Fillers"), (3) insulating materials, 

(4) mild abrasives, (5) absorbents, (6) catalyst 

carriers, (7) reactive-silica source, (8) structural 

materials (see "Lightweight Aggregates"), (9) 

additive or pozzolan for concrete, and (10) conditioner or anti caking agent. The first category, filters, 

accounts for more than half of the diatomite consumed in the United States-58 percent in 1969 

(West, 1971, table 2). Processed diatomite is an 

especially effective filter aid, or fine powder, that is 

mixed with a liquid to be filtered; the filter aid 

forms a continuously building porous cake on the 

filter medium and retards clogging of the filter 

pores by trapping impurities. The suitability of 

diatomite for filtration depends largely on the shapes 

and sizes of the constituent diatoms. Diatomite that 

contains a substantial percentage of long hairlike 

diatoms together with fragments of discoid diatoms 

generally is best for retention of fine impurities 

while allowing a high rate of flow; rock of this 

type is mainly of marine origin. Diatomite has a 

role in the purification and clarification of a host of 

chemicals, beverages, foods, pharmaceuticals, and 

other liquids. Its use in water purification expanded 

greatly following development of diatomite filters 

for military use during World War II. 

The chemical inertness of diatomite (readily soluble only in hydrofluoric acid and strongly alkaline 

solutions) makes the material especially useful as 

a filler, extender, or diluent in many products, including paints, papers, insecticides, plastics, and 

fertilizers. This second category of uses accounts 

for about 20 percent of the diatomite consumed in 

the United States (West, 1971, table 2). 

PRODUCTION 

The United States leads the world in diatomite 

production-followed by the U.S.S.R., Denmark, 

France, West Germany, and Italy-and is the dominant producer of filtration-quality material (West, 

1971). Both the United States and world production 

increased during the 20-year period 1949-68 (fig. 

23). The United States exports substantial amounts 

of prepared diatomite-176,000 short tons in 1969, 

valued at $13,510,000 (West, 1971, table 4)-

mainly filtration-grade material. Although transportation is a major factor in the cost of diatomite 

products, high-quality filter-aid material is exported 

regularly from the Western United States to European and other distant markets. United States imports of diatomite are small-47 short tons in 1969 

(West, 1971, p. 484). 

GEOLOGIC ENVIRONMENT 

Diatoms are one of the chief agents by which 

silica is removed from solution in marine and fresh 

waters ; their role as consumers of dissolved silica 
DIATOMITE 198 

z· 

0 

j: 

(J 

::> 

Q 

0 

C[ 

CL 

FIGURE 23.-Es·timated diatomite production, 1948-68, 

adapted from production figures and estimates by the 

U.S. Bureau of Mines (1968-71). The pronounced upturn 

in the world production curve between 1966 and 1960 

mainly reflects increased production figures for Denmark 

and France and larger production estimates for the 

U.S.S.R. 

and the concentration of biogenous silica in their 

accumulated remains at:e major factors in the silica 

balance of most water bodies. Diatoms live in nearly 

all aquatic environments, but they form thick pure 

deposits only where they flourish for a considerable 

time away from contaminating sediment sources. 

Preservation of the siliceous parts of diatoms may 

be favored in sediments high in organic matter 

(Berger, 1970, p. 1387) ; also, the inclusion of diatoms in fecal pellets may enhance the chance of 

preservation of diatom frustules because the membrane that encases a pellet protects the frustules 

from dissolution, and the pellets speed the fall of 

frustules through the water column (Schrader, 1971, 

p. 56-57). 

Because diatoms growing in abundance soon deplete the silica supply of near-surface water, sustained diatom production depends on continued 

renewal of silica-rich water to the surface. The 

interaction of many factors determines the abundance of diatoms at any particular place and time, 

but commonly diatoms proliferate in marine areas 

of upwelling, in lakes on volcanic terranes, and in 

lakes in areas that had Quaternary glaciers. Although marine diatomite commonly is associated 

with volcanic rocks (Bramlette, 1946, p. 39; Khvorova, 1968, p. 111; Taliaferro, 1933, p. 36), at some 

places oceanic circulation alone supplies sufficient 

silica to account for thick accumulations of diatomaceous sediments without requiring introduction of 

additional silica from nearby volcanism (Calvert, 

1966, p. 593). The beneficial effects of an ash fall 

on the diatom population of a modern lake have 

been shown (Kurenkov, 1966, p. 429), but silica 

seldom is a limiting factor in diatom production in 

lakes except during intensive diatom blooms 

( Schelske and Stoermer, 1971, p. 423). Papers by 

Gregor (1968), Grill (1970), Harriss (1966), 

Krauskopf (1956), and Siever (1957) consider the 

role of biogenic silica in maintaining the silica concentration of natural waters. 

Marine diatoms occur in rocks as old as Mesozoic, 

but with some notable exceptions (Hanna, 1927), 

thick deposits of marine diatomite are middle Tertiary or younger. Nonmarine diatoms occur in rocks 

as old as late Eocene (Lohman and Andrews, 1968), 

but most nonmarine diatomite deposits are late 

Tertiary or Quaternary. The lack of more ancient 

diatomaceous rocks may be due partly to conversion 

of the opaline silica of diatom frustules to other 

forms of silica (Ernst and Calvert, 1969, p. 131). 

Marine Tertiary porcelaneous rocks that occur in 

great thicknesses in California almost certainly 

represent altered diatomaceous rocks (Bramlette, 

1946, p. 50; Lohman, 1960, p. 184-185). 

Economic diatomite deposits are of three main 

types : ( 1) marine rocks that accumulated near continental margins, (2) nonmarine rocks that formed 

in lakes or marshes, and ( 3) sediments in modern 

lakes, marshes, and bogs. Diatomite deposits near 

Lompoc, Calif. (Industrial Minerals, 1969, p. 14-16, 

17, 37; Mulryan, 1936), exemplify the first type; 

this material formed in a shallow-marine environment in late Tertiary time. Similar marine diatomite 

deposits occur elsewhere in coastal California, and 

less pure marine deposits occur extensively in Maryland and Virginia. Diatomite deposits that formed 

in lakes or marshes in Nevada, Oregon, Washington, 

and eastern California represent the second type, 

and diatomaceous sediments in modern lakes, 

marshes, and bogs in Florida, New Hampshire, and 

New York (Conger, 1939) belong to the third type. 

Modern marine sediments are a potential fourth 

source of diatoms. 

PROSPECTING TECHNIQUES 

Prospecting for diatomite involves first outlining 

of areas that contain stratigraphic sequences likely 

to include diatomaceous strata-for example, the 

Tertiary and Quaternary lake basins of the Western 

United States, or the Miocene marine basins of 

coastal California-followed by examination of outcrop sections in these areas. After diatomite is 

found, the initial reconnaissance is followed by 
194 UNITED STATES MINERAL RESOURCES 

trenching and drilling to determine the size of the 

deposit. Local high-precision surface gravity surveys 

may be a promising tool for delineating concealed 

deposits under some circumstances. Because the diatomite in a deposit may vary considerably, especially from bed to bed, a deposit must be sampled 

carefully throughout its thickness to determine the 

quality and potential use of the material. Microscopic examination of the rock may be necessary to 

distinguish diatomite from volcanic ash or from 

some porcelaneous rocks. 

RESOURCES 

Diatomite resources are difficult to describe because diatomaceous rocks underlie large areas and 

include strata of various qualities; even the resources of California, the principal producing area 

in the United States, have never been computed 

and classified according to grade. However, diatomite resources of the United States obviously are 

more than sufficient for many years to come, even 

allowing for a steady increase in diatomite production. The abundance of the material is evident, for 

example, if the deposit controlled by one diatomiteproducing company at Lompoc, Calif., is CQJlsidered. 

This deposit has been described as covering an area 

of 3-4 square miles and being workable to a depth 

of 700 feet (Industrial Minerals, 1969, p. 14), 

which suggests that it could supply world needs for 

diatomite at the current rate of consumption for 

several hundred years. On the other hand, factors 

such as proximity to markets and suitability of the 

material for specific uses enter into the evaluation 

of diatomite resources; the location and quality of 

diatomite deposits seem to be greater factors in the 

economics of diatomite production than is the 

amount of material available. 

PROBLEMS FOR RESEARCH 

The areal and geologic occurrences of diatomite 

generally are well known, but conditions that affect 

the thickness and quality of deposits are imperfectly 

understood. Postdepositional circumstances that 

affect the quality of diatomite also are uncertain. 

Clearly, geologic work on diatomite should involve 

not only the location and classification of deposits, 

but also should relate the physical features of diatomite to the geologic history of the rock to aid 

in the discovery of deposits for particular purposes. 

REFERENCES CITED 

Anderson, R. B., and others, 1947, Kieselguhrs, suitability as 

carriers in catalysts: Ind. and Eng. Chemistry, v. 39, 

no. 12, p. 1618-1628. 

Berger, W. H., 1970, Biogenous deep-sea sediments-Fractionation by deep-sea circulation: Geol. Soc. America 

Bull., v. 81, no. 5, p. 1385-1401. 

Bramlette, M. N., 1946, The Monterey Formation of California and the origin of its siliceous rocks: U.S. Geol. 

Survey Prof. Paper 212, 57 p. 

Calvert, S. E., 1966, Accumulation of diatomaceous silica in 

the sediments of the Gulf of California: Geol. Soc. 

America Bull., v. 77, no. 6, p. 569-596. 

Conger, P. S., 1939, Origin and utilization of diatomaceous 

peat deposits: Sci. Monthly, v. 49, no. 6, p. 509-523. 

--- 1942, Accumulation of diatomaceous deposits: Jour. 

Sed. Petrology, v. 12, no. 2, p. 55-66. 

--- 1951, Diatoms: Sci. Monthly, v. 73, no. 5, p. 315-

323. 

Cressman, E. R., 1962, Nondetrital siliceous sediments, in 

Data of geochemistry, 6th edition: U.S. Geol. Survey 

Prof. Paper 440-T, p. T1-T23. 

Cummins, A. B., 1960, Diatomite, in Industrial minerals and 

rocks, [3d ed.]: New York, Am. Inst. Mining, Metall., 

and Petroleum Engineers, p. 303-319. 

Eardley-Wilmot, V. L., 1928, Diatomite, its occurrence, 

preparation, and uses: Canada Dept. Mines, Mines 

Branch, Pub. 691, 182 p. 

Ernst, W. G., and Oalvert, S. E., 1969, An experimental study 

of the recrystallization of porcelanite and its bearing 

on the origin of some bedded cherts: Am. Jour. Sci., v. 

267-A (Schairer volume), p. 114-133. 

Gillott, J. E., 1969, Study of the fabric of fine-grained sediments with the scanning electron microscope: Jour. Sed. 

Petrology, v. 39, no. 1, p. 90-105. 

Gregor, Bryan, 1968, Silica balance of the ocean: Nature, 

v.219,no. 5152,p. 360-361. 

Grill, E. V., 1970, A mathematical model for the marine dissolved silicate cycle: Deep-Sea Research, v. 17, no. 2, 

p. 245-266. 

Hanna, G. D., 1927, Cretaceous diatoms from California: 

California Acad. Sci. Occasional Paper, v. 13, 48 p. 

Harriss, R. C., 1966, Biological buffering of oceanic silica: 

Nature, v. 212, no. 5059, p. 275-276. 

Industrial Minerals, 1969, Diatomite--its production, uses, 

and potential: Indus. Minerals, no. 18, p. 9-17, 19, 21, 

23-27, 37. 

Khvorova, I. V., 1968, Geosynclinal siliceous rocks and some 

problems of their origin: Internat. Geol. Cong., 23d, 

Czechoslovakia 1968, Rept., sec. 8, p. 105-112. 

Krauskopf, K. B., 1956, Dissolution and precipitation of 

silica at low temperatures : Geochim. et Cosmochim. 

Acta, v. 10, no. 1, p. 1-26. 

Kurenkov, I. I., 1966, The influence of volcanic ashfall on 

biological processes in a lake: Limnology and Oceanography,v. 11,no. 3,p. 426-429. 

Lewin, J. C., and Guillard, R. R. L., 1963, Diatoms: Ann. 

Rev. Microbiology, v. 17, p. 373-414. 

Lisitsyn, A. P., 1967, Basic relationships in distribution of 

modern siliceous sediments and their connection with 

climatic zonation: Internat. Geology Rev. v. 9, no. 5, 

p. 631-652; no. 6, p. 842-865; no. 7, p. 980-1004; no. 8, 

p. 1114-1130. 

Lohman, K. E., 1960, The ubiquitous diatom-A brief survey 

of the present state of knowledge: Am. Jour. Sci., v. 

258-A (Bradley volume), p. 180-191. 

Lohman, K. E., and Andrews, G. W., 1968, Late Eocene 

nonmarine diatoms from t.~e Beaver Divide area, Fre-
DIATOMITE 196 

mont County, Wyoming: U.S. Geol. Survey Prof. Paper 

593-E, 26 p. 

Mulryan, Henry, 1936, Geology, mining and processing of 

diatomite at Lompoc, Santa Barbara County, California: 

California Jour. Mines and Geology, v. 32, no. 2, p. 133-

166. 

Patrick, Ruth, and Reimer, C. W., 1966, The diatoms of the 

United States exclusive of Alaska and Hawaii, v. 1: 

Acad. Nat. Sci., Philadelphia, Mon. 13, 688 p. 

Schelske, C. L., and Stoermer, E. F., 1971, Eutrophication, 

silica depletion, and predicted changes in algal quality 

in Lake Michigan: Science, v. 173, no. 3995, p. 423-

424. 

Schrader, Hans-Joachim, 1971, Fecal pellets-Role in sedimentation of pelagic diatoms: Science, v. 174, no. 4004, 

p. 55-57. 

Siever, Raymond, 1957, The silica budget in the sedimentary 

cycle: Am. Mineralogist, v. 42, nos. 11-12, p. 821-841. 

Taliaferro, N. L., 1933, The relation of volcanism to diatomaceous and associated siliceous sediments: California Univ. Pubs., Dept. Geol. Sciences Bull., v. 23, no. 

1, p. 1-56. 

U. S. Bureau Mines, 19·58-71, Minerals Yearbook [annual 

volumes for the years 1954-1969]: Washington, D. C. 

West, J. M., 1971, Diatomite, in Metals, minerals, and fuels: 

U.S. Bur. Mines Minerals yearbook 1969, v. 1 and 2, 

p. 483-485. 

Williamson, D. R., 1966, Exploration for diatomites: Colorado School Mines Mineral Industries Bull., v. 9, no. 3, 

p. 1-14. 

UNITED STATES MINERAL RESOURCES 

EVAPORITES AND BRINES 

By GEORGE I. SMITH, CHARLES L. JONES, WILLIAM c. CULBERTSON, 

GEoRGE E. ERICKSEN, and JOHN R. DYNI 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction ------------------------------------- Geologic setting of evaporite and brine deposits ___ _ 

Marine evaporites -------------------------------

~onmarine evaporites ----------------------------

Brines ------------------------------------------ Known resources of evaporites and brines ----------

Potassium compounds ------------------------ Salt _______________________________________ _ 

Gypsum and anhydrite -----------------------

Sodium carbonate ----------------------------

Sodium sulfate ------------------------------

Boron minerals ------------------------------

~itrates ------------------------------------ Strontium _ ---------------------------------- Bromine --- ____ ---__________________________ _ 

Iodine -------------------------------------- Calcium chloride -----------------------------

Magnesium compounds ----------------------- Undiscovered resources of evaporites and brines ___ _ 

Marine evaporites ----------------------------

~onmarine evaporites ------------------------

Brines -------------------------------------- Summary of U.S. resources __ 

Problems for research -----=--==================== 

References cited ---------------------------------

FIGURE 

24. Map showing marine evaporite deposits of the 

United s.tates -----------------------------

Page 

197 

197 

198 

198 

202 

202 

203 

203 

204 

205 

206 

207 

207 

208 

208 

209 

209 

209 

210 

210 

210 

212 

213 

213 

213 

214 

Page 

199 

ABSTRACT OF CONCLUSIONS 

Commodities derived from evaporite and brine depos.its include potassium and magnesium compounds, salt, gypsum and 

anhydrite, calcium chloride, sodium carbonate and sulfate 

nitrates, boron, strontium, bromine, and iodine. World and 

national resources of most evaporite minerals are very large. 

Some of these resources are adequate for a few centuries at 

present rates of consumption; others are adequate for 

thousands of years ; still others are virtually unlimited. 

Very probably within the next several hundred or few 

thousand years, no evaporite resources will be exhausted or 

will increase greatly in cost. 

Evaporite resources of the United States are large. Unlimited supplies of nitrates, bromine, and magnesium are 

available from air and sea water. Resources of salt and 

sodium carbonate appear adequate for thousands of years 

at present consumption rates. Known supplies of gypsum and 

anhydrite, sodium sulfate, borates, strontium, iodine, and 

calcium chloride should be adequate for hundreds of years. 

Known domestic resources of potassium compounds may be 

exhausted in 100 years at present consumption rates, but 

Canadian resources are l;Ufficient to fulfill requirements of 

~ orth America for thousands of years. 

At present world consumption rates, known world resources of potassium salts in marine evaporites are adequate 

for 5,000 years, and resources of salt, gypsum, magnesium, 

and calcium chloride are virtually unlimited. ~onmarine 

evaporites provide known resources of sodium carbonate 

adequate for thousands of years, sodium sulfate and strontium for hundreds to thousands of years, and borates, nitrates, and iodine for hundreds of years. Brines from wells, 

lakes, and the ocean provide resources of iodine, bromine, 

and calcium chloride adequate for hundreds of years. Sea 

water and air are unlimited and currently are practical 

sources of magnesium and nitrogen. 

INTRODUCTION 

Evaporites and brines are the main source of sevT ABLES eral industrial and agricultural minerals important 

to the U.S. economy. Their aggregate annual value is 

about two-thirds of a billion dollars. Some of the 

Page • I . 

42. Marine evaporite deposits of the United States__ 200 m1nera s are Important because of properties at43. Evaporite and brine resources of the United tributable to one element in the compound, others 

States ------------------------------------ 213 because of the properties of the compound itself. The 

U.S. GEOL. SURVEY PROF. PAPER 820 

197 
198 UNITED STATE'S MINERAL RESOURCES 

valuable components of nearly all of these materials 

were at one time dissolved in large bodies of water. 

Their present geologic settings reflect the one or 

more processes by which those dissolved components 

were concentrated or crystallized into deposits that 

can, or might be, commercially exploited. 

Some of the commodities described in this chapter 

come from more than one type of evaporite or brine 

deposit. The largest quantities, however, generally 

come from one of three types of deposits that have 

fundamentally similar geologic histories. Potassium 

compounds, salt, gypsum, and anhydrite mostly come 

from sediments formed by the evaporation of sea 

water during the geologic past. Sodium carbonate, 

sulfate, borate, nitrate, and some iodine and strontium compounds come from sediments and near-surface brines formed by the evaporation of inland 

bodies of water. Bromine, iodine, calcium chloride, 

magnesium, and magnesium compounds are mostly 

extracted from brines derived from sea water, wells, 

a~ inland salt lakes. Lithium is also extracted from 

brines, but is discussed in a separate chapter. 

The existing quantities of evaporites and brines 

provide theoretical resources that are much larger 

than the amounts that.are likely to ever be used. It is 

difficult, however, to predict this limit. This is true 

of all commodities, but some unusual factors are 

involved in assessing commodities extracted from 

evaporites and brines. One factor is that some commodities can be derived from both evaporites and 

brines. Future resources of these commodities are 

thus represented by extremely diverse forms of 

"ore" which may vary in grade by one or two orders 

of magnitude. Obviously, they require quite different 

technologies for processing and therefore very different bases for projecting future use. Brines, in 

essence, are very low grade ore bodies that are exploitable only because they are very large and can be 

inexpensively processed. Many brines contain less 

than 5 percent of the desired substance, and some 

contain only a few tenths or hundredths of a percent. Solid salts, in contrast, are generally mined 

from very high grade ore bodies; operating potash 

mines normally extract ore containing more than 20 

percent potassium mineral, and salt, sodium carbonate, and borate mines normally extract ore that is 

75-95 percent mineral. 

Another reason that resources of commodities obtained from evaporite and brine deposits are difficult 

to assess is that the price is determined largely by 

the cost of transporting the commodities to markets. 

Deposits nearest rail and highway systems now have 

an advantage over those that are more remote ; deposits near seaports have advantages over all others 

in shipping to some domestic and most international 

markets. Proximity to markets and efficiency of 

transportation will probably remain important factors in the economic potential of most deposits, but 

. consideration of these factors is beyond the scope of 

this study so cannot be included in its conclusions. 

Still other uncertainties must be considered in the 

evaluation of the resources of certain commodities. 

Some are compounds, not elements, and new technological developments may provide ways in which 

some of them can be synthesized from abundant and 

low-cost sources of their ingredients. Still others are 

present in significant amounts in sea water, and new 

processes may someday allow them to be extracted 

from it ; sea water would then be an unlimited source 

of those commodities. 

In the following discussion, the geologic settings of 

evaporite and brine deposits are first outlined. Commodities derived from evaporites and brines are then 

described individually so that their uses, production, 

economics, geologic settings, and known resources 

can be outlined. Speculation follows as to the outlook 

for existing but undiscovered resources of geologically related commodities; future resources are discussed in genetically related groups because evaluation of them is based more on their general character and on the prevalence of broadly favorable 

areas than on specific targets. Salient problems and 

examples of the research necessary to help solve 

them are suggested in the final section. 

GEOLOGIC SETTING OF EVAPORITE AND 

BRINE DEPOSITS 

The deposits that serve as sources of commodities 

derived from evaporites and brines are grouped in 

this chapter both by the geologic setting in which 

they originated and by their present form. Crystalline deposits are separated into two groups according 

to their marine or nonmarine origin ; surface and 

subsurface waters containing unusual quantities of 

valuable inorganic components are combined into a 

group called brines, regardless of their probable geologic origin. Although deposits within each group differ in many respects, they have features in common. 

The following summaries emphasize the common features but also note some of the differences. 

MARINE EVAPORITES 

The group of sedimentary rocks known as marine 

evaporites consists of halite, gypsum, anhydrite, and 

commonly some interbeds of limestone and dolomite. 

Some limestone and either gypsum or anhydrite are 

present in all major and many minor evaporite basins 

of the United States (fig. 24, table 42) ; halite and 
)'-~~ 

} ~"~~~"l~~~~-

W~sH,~G i ( ,, rotv : ~ 

I \ 

'----------------~ : \. / 

) <-, 

\ --1 1... ._ ___ __,,l r·· 

/ 'DAHo j 

/ i ----,. _______ i. 

·0 

/ --r·---;~---- I ---1 / 0 0 : 

~.oo 0 

Ofi<Go~y 

,'0 fv<vADA ~~ 

\ ' -. I CA(IFoFitviA \ \\ ' 

nO:::. , 

\) (/\_ 

~ 

EXPLANATION 

0 Gypsum-anhydrite deposit 

~ Halite and gypsum-anhydrite deposits 

m Poly halite, halite, and gypsum-anhydrite deposits 

~ Sylvite-carnallite-langbeinite, polyhalite, halite, and 

gypsum-anhydrite deposits 

( ..

\ 

\ -·-----( 

1 I -...... 

~-----------~ 

--------....... ? \...,_..----

\ DOWA "1 ~ ~J i \ 

1-- -·--·· ' \ 1 AN A', 

-~----':\-,.---~.) ~ IVbLLiNOIS 'liND \ 

'· '-.. . \'' ': \. ~ r· .. I MISSOURI : .J • : .. ._. ~.. / 

1 ' (' ~E TUCK" 

~~~~"-'>-..~~~'-.."+-l------~ ~-- - ----- ~-----------, r-:' .. --r----

\ 

i 

0 100 200 300 400 MILES 

0 100 200 300 400 KILOMETERS 

FIGURE 24.-Marine evaporite deposits of the United States. 

tzJ 

< 

> "0 

0 

~ ..... 

~ 

tzJ 

00 

> z 

tj 

~ 

~ ..... 

z 

tzJ 

til 

U) '""" 

U) 
200 UNITED STATES MINERAL RESOURCES 

TABLE 42.-Marine evaporite deposits of the United StatBB 

[Evaporite minerals are gypsum, G; anhydrite, A; halite, H; polyhalite, P; and the bittern salts of potassium and magnesium (chiefly sylvite, carnallite, and langbeinite), S. Thicknesses are approximate and include nonevaporite rocks] 

Aae and unit or formation 

Tertiary: 

Muddy Creek Formation ----------------------

Evaporite-bearing rocks, undifferentiated ------- Gypsum-bearing rocks, undifferentiated --------

Cedar Keys Limestone ------------·------------ Cretaceous : Gypsum-bearing rocks, undifferentiated 

Beds of Trinity, Fredericksburg, and 

Washita age. 

Ferry Lake Anhydrite ------------------------- Hell to Finish Formation of Zeller (1968, 1965) __ 

Cretaceous (1) or Jurassic (1) : 

Fort Pierce Formation ------------------------ Jurassic: 

Todilto Limestone -----------------------------

Malone Formation ----------------------------- Minas Viejas Group of Mexico ---------------- Buckner Formation --------------------------- Werner Formation and Louann Salt 

(Jurassic age uncertain). 

Curtis, Summerville, and Wanakah Formations ..• 

Preuss Sandstone ------------------------------

Carmel Formation ---------------------------- Arapien Shale ---------------------------------

Twin Creek Limestone ··------------------------

Piper Formation ------------------------------ Gypsum Spring Formation --------------------

Triassic: 

Gypsum-bearing rocks, undifferentiated -------

Moenkopi Formation 

Triassic and Permian: 

Goose Egg Formation 

Spearfish Formation ---------------------------

Triassic(?) and Permian: 

Lykins Formation ----------------------------- Permian: 

Rustler, Salado, and Castile Formations -------

Artesia Group ---------------------------------

Artesia Group -------------------------------- San Andres Limestone -------------------------

Blaine Formation ------------------------------

Briggs Formation ----------------------------- Pequop and Loray Formations of Steele (1960) __ 

Undifferentiated saline-bearing rocks of 

Permian age. 

Kaibab Limestone -----------------------------

Toroweap Formation --------------------------

Opeehe Shale ----------------------------------

Yeso Formation -------------------------------

Clear Fork Group and Flowerpot Shale -------

Epitaph Dolomite and equivalents 

Wichita and Wellington Formations ---------} 

Hennessey end Ninnescah Shales ------------ Stone Corral Formation --------------------- Abo Formation ------------··-------------------

Supai Formation ------------------------------ Pakoon Limestone of McNair (1951) ----------

Easly Creek Shale ----------------------------- Permian ( T) : 

Fort Dodae Gypsum of MeGee (1884) ----------

Evaporite 

minerals present 

G A H P S 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X X 

X 

Thickness 

(feet) Area 

1,200 Western Arizona shelf (western Arizona, 

southern Nevada). 

2,000+ Central Arizona --------------------------- 400 Various places in Coast Rance and Mohave 

.Uesert (southern and central California). 

1,000 South Florida shelf (Floricja) --------------

100(1) Western Arizona shelf (southern Nevada) --

4,200 Florida shelf (Florida) ---------------------

200 Gulf Region (eastern Texas to Alabama) 

100(1) Northwestern shelf of Chihuahua trou&'h 

(southwestern New Mexico). 

1,800 

100 

25 

1,500 

150 

4,000+ 

150 

700 

150 

200-r 

100 

125 

125 

600 

300 

400 

150 

4,100 

1,100 

1,100 

1,000 

300 

600 

500 

800 

300 

400 

250 

1,000 

1,500 

300 

800 

200 

1,000 

200 

20 

50 

South Florida shelf (Florida) -------------

Lacustrine{?) basin (northwestern 

New Mexico). 

Chihuahua trough (western Texas) -------- Rio Grande embayment (southern Texas) --- Gulf region (eastern Texas to Alabama) ---- Gulf region (Texas to Alabama and Florida 

Panhandle). 

Utah shelf (central and southwestern Utah 

and western Colorado). 

Western Wyoming-Idaho trough (northern 

Utah, southeastern Idaho, and south- western Wyoming). 

Utah shelf (central and southwestern Utah) •• 

Utah shelf (central Utah) ------------------

Western Wyoming trough (Wyomiq and 

Idaho). Northern Rocky Mountain shelf (Montana)--

Williston basin and southwestern shelf 

(:Montana. North and South Dakota, 

and Wyomiq). 

Cordilleran eugeosyncline (northwestern 

Nevada, central-eastern Oregon, and western Idaho). 

Western Arizona shelf (southwestern Utah, 

northwestern Arizona, and southern 

Nevada). 

Northwestern shelf of Denver basin (Wyom- ing and Colorado). 

Williston basin (Montana and North and 

Sguth Dakota). 

West side of the Denver basin (Colorado) 

Southern Permian basin (New Mexico and 

Texas). Northern and western shelf of Delaware basin 

(New Mexico). 

Eastern shelf of Permian basin (Texas) 

Central Permian basin (Texas and New 

Mexico). Northern and eastern Permian and Anadarko 

basins (Kansas, Oklahoma, and Texas). 

Diablo platform (Texas) ------------------- Cordilleran mio&'eo&YDcline (eastern Nevada 

and western Utah). 

Western Arizona shelf (western Arizona and 

southern California). 

Western Arizona shelf (southern Nevada, 

southwestern Utah, and western Arizona). 

Western Arizona shelf (southern Nevada, 

southwestern Utah, and western Arizona). 

Williston basin (Montana and North and 

South Dakota). 

Northwestern shelf of Delaware basin 

(New Mexico). Northern and central Permian basin (Kansas, 

Oklahoma, Texas, and Colorado). 

Sonoran trough (southeast Arizona and 

southwestern New Mexico). 

{

Northern and central Permian basin and 

Anadarko basin (Kansas, Nebraska, Colorado, and Olkahoma). 

Northwestern shelf of Delaware basin 

(New Mexico). 

Shelf (east-central Arizona) -------------'"- Western Arizona shelf (southern Nevada) -- Northern Permian basin (Kansas) ----------

Northeastern shelf of Forest City 

basin (Iowa). 

Evaporite 

mineral 

recovered 

Gypsum. 

Halite. 

Gypsum. 

Gypsum. 

---------- Gypsum, 

halite. 

Gypsum. 

Gypsum. 

Gypsum. 

Gypsum. 

Gypsum. 

Sylvite, halite. 

Gypsum. 

Gypsum. 

Halite, 

upsum. 

CiiP;.;;;_--

Gypsum. 
EVAPORITES AND BRINES 201 

TABLE 42.-Marine evaporite deposits of the United States-Continued 

Evaporite 

minerals present Age and unit or formation 

G A H P S 

Permian and Pennsylvanian: 

Minnelusa Formation -------------------------- X X X 

Wells Formation ------------------------------ X 

Panther Seep Formation ---------------------- X X 

Pennsylvanian: 

Hermosa Formation -------------------------- X X X 

Eagle Valley Evaporite ------------------------ X 

.Mississippian or younger: 

Gypsum-bearing rocks, undifferentiated --------- X 

.Mississippian: 

Big Snowy Group (of formation rank in SW X 

.Montana and Idaho). 

Otter Formation ---------------------------- X 

Kibbey Formation --------------------------- X 

Charles Formation ----------------------------

Warsaw and St. Louis Limestones ------------- X 

St. Louis Limestone --------------------------- X 

.Maccrady Shale ------------------------------- X 

.Michigan Formation ------------··------------- X 

Devonian: 

Three Forks Formation and Potlatch Anhydrite_ 

Souris River Formation -----------------------

Prairie Formation ---------------------------- X 

Cedar Valley and Wapsipinicon Limestones ----- X 

Detroit River Group (of formation rank in X 

Indiana according to Shaver and others, 1970). 

Silurian: 

Salin!l Formation -----------------------P·----- X 

Silurian and Ordovician: 

Interlake Formation ---------------------------

Ordovician: 

Red River, Stony Mountain, and Stonewall of 

Kindle (1914) Formations. 

Joachim Dolomite equivalent ------------------ Precambrian: 

Grenville Series ------------------------------- X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

X 

potassium minerals are present in some. Evaporites 

typically form stratified rock units that extend tens 

and even hundreds of miles and attain thicknesses of 

several thousand feet (Pierce and Rich, 1962; Withington, 1962). Many deposits occupy areas that were 

part of the continental shelf and that extend into 

areas that were part of an adjacent synclinal trough. 

Locally, along the continental margin and elsewhere, 

great masses of halite and associated evaporites have 

intruded overlying sedimentary strata to form salt 

domes and other diapiric structures. Both bedded and 

domal deposits of marine evaporites are known to 

contain potassium ores, and they are also important 

sources of gypsum, anhydrite, salt, sulfur, and other 

commodities (Stewart, 1963; Braitsch, 1971). 

All marine evaporites are thought to have been 

formed by evaporation of sea water in barred basins 

Thickness 

(feet) 

450 

100 

100 

6,000 

Area 

Denver and Williston basins (Colorado, 

Nebraska, North and South Dakota, 

and Montana). 

Southeastern ldaho and northern Utah ------ Oro Grande basin (southern New Mexico) ---

Evaporite 

mineral 

recovered 

Paradox basin (Colorado and Utah) --------- Sylvite, halite. 

1,000 Eagle basin (western Colorado) ------------

00 (?) Cordilleran eugeosyncline (Chichagof Island, 

Alaska) . 

50 

50 

200 

800 

125 

200 

2GO(?) 

400 

480 

200 

600 

300 

1,100 

4,000 

50 

200 

85 

200 

Northern Rocky Mountain shelf (.Montana, 

Idaho, and Wyoming). 

Williston basin and Northern Rocky .Mountain shelf (.Montana and North and South 

Dakota). 

Williston basin and Northern Rocky Mountain shelf (.Montana and North and South 

Dakota). 

Williston basin and Northern Rocky Mountain shelf (.Montana and North and South 

Dakota). 

Northeastern shelf of Forest City basin 

(Iowa). 

Dlinois basin (Indiana, Dlinois, and 

Kentucky). 

Gypaum. 

Do. 

Appalachian basin (Virginia) -------------- Gypsum, halite • .Michigan basin (.Michigan) ---------------- Gypsum . 

Northern Rocky .Mountain shelf (.Montana) __ Williston basin (Montana and North and 

South Dakota). 

Williston basin (Montana and North and 

South Dakota). 

Northeastern shelf of Forest City 

basin (Iowa) . .Michigan basin (.Michigan, Ohio, and 

Indiana). 

Appalachian and .Michigan basins (New 

York, Pennsylvania, West Virginia, 

Ohio, and .Michigan). 

Williston basin (.Montana and North and 

South Dakota). 

Williston basin (Montana and North and 

South Dakota). 

Illinois basin (Dlinois) --------------------

Northwestern Adirondack .Mountains (New 

York). 

(Halite and 

sylvite re- covered in 

Canadian 

section of 

basin). 

Gypsum. 

Halite . 

Gypsum, 

halite. 

or on broad shelf areas where circulation was restricted. The dominant rocks formed in this manner 

were limestone, dolomite, gypsum or anhydrite, 

halite, and the rocks containing potassium minerals. 

Within most evaporite basins, these rocks are arranged in broad belts or facies that reflect the changing depositional environment between open sea and 

land ; limestone or dolomite facies lie in the areas 

that contained the least saline water, and they grade 

into gypsum or anhydrite facies, then to halite 

facies, in areas that contained successively more 

saline waters. Red beds commonly represent the 

nearshore accumulation of clastics. Economic concentrations of potassium minerals represent the final 

stage of evaporite deposition and wherever present 

lie within the halite facies (Mattox and others, 1968; 

Hite, 1970). 
202 UNITED STATES MINERAL RESOURCES 

Examples representing virtually all possible distributions of evaporite facies are found in evaporite 

basins of the United States. Potassium minerals 

typically occupy only a small part of a basin and are 

relatively rare; only 7 of the 69 marine evaporite 

deposits listed in table 42 are known to contain 

potassium minerals. Halite facies are found in 28 of 

the 69 deposits listed in that table. Gypsum or anhydrite facies are found in all. 

NONMARINE EVAPORITES 

Nonmarine evaporite deposits include near-surface 

saline minerals (and associated brines) in Quaternary dry lakes, and bedded crystalline deposits in 

continental Tertiary formations. Pre-Tertiary deposits are known, but are rare and much less important. All are geologically similar in that they 

formed by evaporation of lakes in closed basins. The 

geologic requirements for such deposits are: (1) 

development of a closed basin that prevents the components dissolved in the waters from escaping to the 

sea, and (2) an original mixture of dissolved components that evolves by means of successive crystallizations into a concentrated brine that precipitates 

valuable salts. 

Basins having no external drainage are mostly 

rroducts of faulting or warping. To persist, they 

require a tectonic setting that will either lower the 

floor of the basin faster than sedimentation can raise 

it or elevate barriers across possible outlets faster 

than erosion can destroy them. Most, but not all, 

closed basins today are in arid or semiarid areas 

where sedimentation rates are low. Comparable 

basins in the geologic past probably had a similar 

climatic setting. 

For valuable evaporite deposits to form in a closed 

basin, however, enough water must have flowed into 

the basin to introduce large quantities of salts. This 

requirement greatly limits the number of highly 

favorable environments because arid basins generally 

receive large volumes of water only where they adjoin high mountain ranges or are the terminus of 

integrated drainages from adjacent less arid regions. 

Even when these conditions are satisfied, most 

waters will not evolve through natural evaporation 

into a lake containing a valuable mix of components. 

The most favorable source waters for a sodium carbonate deposit, for example, come from springs or 

from rivers draining volcanic terrane, although metamorphic and some other igneous terranes are suitable. Apparently a sodium carbonate lake cannot be 

formed by evaporation of calci urn bicarbonate waters from limestone terrane, of sulfate waters from 

sulfide deposits, or of chloride waters from marine 

evaporites (Eugster, 1971, p. B46). 

The minerals deposited depend upon the composition and temperature of the brine at the time of 

crystallization. Normally, saline minerals are formed 

in a sequence that is determined by their solubility 

in the particular chemical and physical environment 

provided by the lake. Studies of sodium carbonate 

deposits, for example, find that these minerals generally crystallize after the calcium-bearing minerals 

and before the sodium sulfate and chloride minerals, 

although the sequence varies. The species of carbonate mineral formed depends on the partial pressure 

of dissolved C02 in the brine. If the brine is in equilibrium with the partial pressure of C02 in the atmosphere, trona (Na2C03·NaHC03·2H20) is formed; 

if the partial pressure is higher because of organic 

activity, nahcolite (NaHC03) is formed; if lower, 

natron (Na2C03 · NaH20) is formed (Bradley and 

Eugster, 1969). Because of diagenesis after burial, 

the carbonate mineral constituting the final deposit 

tends to reflect the C02 pressures in the accumulating bed of minerals rather than in the open lake 

waters. 

BRINES 

Many of the brines that are exploited commercially 

contain abnormally large amounts of bromine, iodine, 

calcium chloride, and magnesium. The geologic 

processes that result in such brines have long been 

debated and are not well understood today. Probably 

several processes were operative inasmuch as the 

brines come from diverse geologic settings; some of 

the brines are pore waters in oil fields, some are 

deep-well brines from marine salines or rocks peripheral to them, some are from thermal springs or 

wells, and some are surface or subsurface brines that 

were associated with Quaternary salt lakes or seas. 

The geologically old and deep-well brines were probably produced chiefly during diagenesis by the interaction of pore fluids with clays and possibly with 

other components of clastic rocks that act as ionic 

filters; some of the fluids may have originally been 

sea water of normal salinity although most were 

probably bitterns from marine evaporites (White, 

1957, 1965; White and others, 1963; Rittenhouse, 

1967; Collins and others, 1967). Quaternary brines 

that contain abnormally large amounts of bromine 

and other substances are products of natural evaporation of dilute river and spring waters that mostly 

originally had unusually high ratios of these components (Bentor, 1961; Livingstone, 1963; Jones, 

1966; Hardie and Eugster, 1970). 
EVAPORITES AND BRINES 203 

KNOWN RESOURCES OF EVAPORITES 

AND BRINES 

POTASSIUM COMPOUNDS 

Potassium (commonly referred to as its oxide, 

"potash," K20) is a plant nutrient that is essential 

to maintain and expand food production for both 

man and animal. About 95 percent of the potassium 

compounds produced in the world are used as fertilizers ; the remaining 5 percent are used in manufacturing drugs, dyes, and chemical reagents (U.S. 

Bur. Mines, 1970). Polyhalite (2CaS04 · K2S04 · MgS04 

·2H20) deposits in New Mexico and Texas are not 

now used, but may someday be, as a combination soil 

conditioner and fertilizer; coarsely ground polyhalite 

in contact with water forms solutions containing 

potassium, magnesium, and sulfate, and leaves gypsum as a soil-conditioning residue. 

World production of potassium compounds in 

1970-71 was equivalent to 17.8 million tons of K20, 

and production capacity is considerably larger. Eastern Europe supplied 37 percent of this quantity; 

North America, 31 percent; Western Europe, 27 percent ; and South America, Africa, and Asia, the balance. Countries providing major sources are the 

U.S.S.R., East Germany, West Germany, France, 

Canada, and the United States. Israel, Spain, Italy, 

China, Chile, and Congo (Brazzaville) provided smaller amounts. Potash-producing facilities are under 

development in Australia and the United Kingdom 

(Eilertsen, 1971 ; Lewis, 1970b; British Sulphur 

Corp., 1971). 

In the United States in 1970, potassium compounds 

were produced by 13 companies which operated 

rlants in five States. About 87 percent of production 

in the United States comes from crystalline deposits 

in southeastern New Mexico and eastern Utah; the 

remaining 13 percent comes largely from brine operations in northwestern Utah, California, and Michigan. Production declined from a maximum of 3.3 

million tons of K20 equivalent valued at $122 million 

in 1966 to 2.7 million tons valued at about $71 million 

in 1970 (Lewis, 1970b). This decline is expected to 

continue as the domestic industry faces serious problems of dwindling reserves of high-grade ores and 

loss of markets to Canadian sources of supply. 

Sources of potassium compounds in the United 

States and elsewhere in the world are of hvo main 

types: (1) crystalline deposits of saline rocks of 

marine origin containing sylvite, langbeinite, andrelated potassium minerals, and (2) concentrated 

brines from wells or in relict lakes and lacustrine 

sediments of continental origin in arid regions. The 

crystalline deposits are by far the richest in potassiurn and the simplest to exploit; the concentrated 

brines are lower grade but generally allow production 

of other substances such as sodium carbonate, sodium sulfate, borates, magnesium, lithium, or bromine 

as coproducts of the potassium compounds. 

Most potassium ores in marine evaporite deposits 

have the potassium concentrated in sylvite (KCl) or 

a potassium-magnesium mineral, and all occur within the sodium-rich (halite) facies of evaporite deposits. Although not now considered ore, large and 

nea.rly pure deposits of the potassium mineral polyhalite (K2MgCa2 (S04) 4 · 2H20) occur in or near the 

calcium-rich facies of evaporite deposits. In North 

America, polyhalite deposits occur only in southeastern New Mexico and western Texas near the 

boundary of the halite and anhydrite facies. 

The greatest concentrations of sylvite in most 

ev~porite basins are in tabular bodies that may be 

pnmary or replacement in origin. Such deposits are 

mostly tens of feet thick and several square miles 

in area, and generally contain at least twice as much 

halite as sylvite. Smaller concentrations of sylvite 

(or carnallite) occur in markedly dis·cordant replacement lenses and veins that contain little or no halite. 

Both types of concentrations ordinarily have sharp, 

clear-cut boundaries (Jones and Madsen, 1968). 

Brines are also a source of potassium compounds 

in the United States. Most productive brines are from 

inland lakes but some are from deep wells. Most allow production of other commodities along with the 

potassium salts so that the costs of processing are 

shared, a practice that contributes to the commercial 

feasibility of such low-grade sources of the element. 

In other respects, however, brin~s that yield potassium have little else in common, either geologically or 

chemically. Production from California is from alkaline near-surface brines in an upper Quaternary saline deposit; Utah production is from nearly neutral 

surface waters of a saline lake; Michigan production 

is from acidic deep-well brines; production from 

Israel is from brines in the Dead Sea. 

Exploration for potassium deposits is difficult because the deposits are soluble and consequently do 

not crop out at the surface. Before extensive drilling 

for petroleum, potassium deposits were mostly encountered accidentally in mines being worked for 

salt. Analysis of near-surface brines from relict lakes 

has been used with some success to locate exploitable 

deposits in arid regions, but it has not been used 

with success elsewhere. Analysis of cuttings, cores, 

and gamma-ray and other logs from exploratory 

boreholes drilled primarily for petroleum has been 

responsible for most potash discoveries in recent 
204 UNITED STAT'ES MINERAL RESOURCES 

years, and the recognized association of petroleum 

and evaporites means that a high percentage of 

basins favorable for evaporites in North America 

have been explored by oil companies (Buzzalini and 

others, 1969). The potash deposits in southeastern 

New Mexico, eastern Utah, and southern Saskatchewan-mines which now supply roughly one-third of 

all the world output of potassium compounds-were 

discovered in this way. 

Many geologic guides to the locations of concealed 

potassium salts and other evaporites are available. 

Preliminary evaluation techniques include reconstructing from geologic maps and other sources the 

climatic, topographic, hydrologic, and geochemical 

environments that existed at the time the sedimentary rocks in the particular basin were deposited. 

Arid climatic belts that favor deposition of evaporites tend to occupy the same part of the globe, and 

raleomagnetic and other techniques allow the geographic positions of depositional basins relative to 

these belts to be reconstructed. Sedimentary rock 

units that are most favorable for evaporites are 

those that were deposited at latitudes favorable for 

arid climates. Many other characteristics and constituents of sedimentary rocks indicate the climate 

that prevailed during sedimentation ; for instance, 

certain organisms and chemical reactions are temperature sensitive, and microfossils or other organic 

materials, stable isotope percentages, and mineralogy may therefore give data as to water temperature. 

Still other prospecting techniques depend on interpretational refinements of many kinds of field data. 

Within favorable climatic belts, environments capable of forming marine evaporite deposits were the 

nearly enclosed basins and shallow shelf areas that 

lay between the open sea and the landmasses. Systematic geologic mapping furnishes data essential to 

th~ reconstruction of paleogeographic environment. 

Processes involved in chemical sedimentation and diagensis are also becoming better understood. Once 

an evaporite body has been found, numerous exploratory techniques can expedite the location of highgrade potassium deposits. Evaporite mineral facies 

have a fairly predictable pattern, and variations in 

the quantities of certain trace elements such as 

bromine can indicate areas and horizons of maximum 

promise. 

At present production levels, potash reserves 

available in crystalline deposits and brines within the 

United States are sufficiently large to last at least 

100 years. The very large deposits of Canada, however, are so close to the United States that costs of 

transporting supplies from these deposits are not 

excessive; inasmuch as one-half of the world reserves 

and resources are in Canada, resources adequate for 

thousands of years will continue to be available from 

areas close to U.S. consumers. Potential resources of 

the United States also are large and include submarginal crystalline deposits, sea water, and potassiumbearing silicate rocks (British Sulphur Corp., 1966). 

World reserves and potential resources of potassium compounds are enormous. Estimates of quantities in known deposits exceed 100 billion tons of 

K20; this represents more than a 5,000-year world 

supply at present consumption rates (Colorado 

School of Mines, 1967). Hypothetical and undiscovered deposits increase the total probable resources to 

a larger quantity, but as noted later, this increase 

may not be great. 

SALT 

Among the marine evaporites, salt (the common 

term for both the commodity and rock composed entirely of halite, NaCI) is by far the most valuable 

mineral resource, ranking with coal, limestone, iron, 

and sulfur, as a basic industrial raw material. It is 

used as a source of sodium, chlorine, soda ash, hydrochloric acid, caustic soda, and other compounds indispensable in the manufacture of many other products and chemical reagents. Salt itself is important 

in the production and preservation of foodstuffs as 

well as for animal feed, water softening, snow and 

ice removal, and roadbed stabilization (Hibpshman, 

1971). Underground cavities created artificially in 

rock salt deposits are used to store petroleum products and to dispose of industrial wastes ; the resource 

value of some salt deposits may be determined more 

by the possible storage capacity than by the need 

for the salt that was removed to provide that capacity (Pierce and Rich, 1962). 

In the United States, leader of world production of 

salt, more than 45 million tons of salt with a value of 

more than $285 million was produced in 1970 by 54 

companies, which operated 99 plants in 17 States. 

China, the U.S.S.R., Germany, and the United Kingdom are the other major producers. Australia has 

had the greatest recent increase in production 

(Jacoby, 1972). Past growth of the industry has been 

steady, and the future outlook is for an annual 

growth of from 3 to 5 percent. 

The principal methods of producing salt in the 

United States are (1) solution mining, (2) underground mining, and (3) evaporation of natural brines 

and sea water. About 70 percent of the salt produced 

in the United States is extracted from natural or 

synthetic brines or sea water; 30 percent is mined 

as a solid (Kaufmann, 1960). 

Subsurface deposits of rock salt are the principal 
EVAPORITES AND BRINES 205 

source of salt in the United States. About half of 

the production is from salt domes, and most of the 

balance from stratified marine evaporites. Boreholes 

show that stratified halite deposits occur in most 

major evaporite basins and a few minor basins that 

are distributed through 24 of the 50 States. The 

deposits are typically extensive and thick, and tend 

to be superposed one above the other over wide areas 

(fig. 24 and table 42). Few domes or beds are pure 

salt, but their salt content may exceed 98 percent; 

dolomite, shale, anhydrite, and other evaporites are 

usually found as impurities. Individual beds in stratifield rock salt range in thickness from a fraction of 

an inch to several hundred feet, and they are both 

massive and laminated. Salt domes have very complex internal structures. 

Salt is also produced in the United States from salt 

lakes in the arid Western States and by solar evaporation of sea water. Unpurified salt scraped from dry 

lakes normally contains small amounts of other components that limit its use or require purification. 

Nearly pure salt is produced by solar evaporation of 

lake brines and sea water, but the process requires 

an arid climate and large flat areas for evaporation 

ponds (VerPlanck, 1958). 

Domestic resources of salt are virtually unlimited 

(Lefond, 1969). Huge bedrock resources are known 

in the Northeastern, Southeastern, and Central 

Western States (fig. 24); salt lakes and solar evaporated sea salt are close to populated areas of the 

west coast states. 

Salt resources of the rest of the world are also 

virtually unlimited. About 15 percent of the earth's 

continental areas are underlain by beds of marine 

salt (Kozary and others, 1968) that can be extracted 

by excavation or solution mining as the need arises. 

Even greater quantities could be extracted from sea 

water. This conclusion does not mean that salt will 

be extracted from sursurface layers or adjacent seas 

by all countries that have these resources, because 

the economics of producing and transporting the 

product will remain dominant. What it does mean is 

that requirements can be met if necessary for even 

remotely foreseeable future demands. 

GYPSUM AND ANHYDRITE 

Gypsum (CaS04 ·2H20) and anhydrite (CaS04) 

are common evaporite minerals widely used in the 

construction industry and agriculture. Gypsum, by 

far the more important of the two, is used to retard 

setting time in portland cement and as an agricultural soil conditioner and fertilizer. In addition, gypsum is calcined for use as plaster for construction 

and industrial purposes, and for manufacturing wallboard and other prefabrication products widely used 

in the building industries. Anhydrite is interchangeable to a limited extent with gypsum for use as a soil 

conditioner. In Europe and elsewhere, anhydrite has 

had moderate use in manufacturing sulfuric acid and 

ammonium sulfate. 

For more than a decade, the United States has produced annually about 25 percent of the world gypsum 

supply, and at the same time it has been dependent 

on foreign sources for about one-third of its gypsum 

supply. Domestic production for the. past 10 years 

has ranged between 9.4 and 10.7 million tons per 

year, with its annual value ranging mostly between 

$35 and $40 million. Imports, chiefly from Canada, 

Jamaica, and Mexico, have averaged almost 5.6 million tons per year (Ashizawa, 1971). Approximately 

50 percent of the domestic gypsum supply comes 

from mines and quarries in Michigan, Iowa, Texas, 

and California ; the remainder is from mining operations in 17 States. Both the domestic production and 

the imports of gypsum are very sensitive to the 

demands of the construction industry, and they 

respond rapidly to any change in the activity of this 

industry (Schroeder, 1970). 

Both gypsum and anhydrite occur widely and 

abundantly in virtually all marine evaporite basins 

(Withington, 1962). Gypsum normally predominates 

over anhydrite at or near the surface and grades into 

anhydrite at depths ranging from a few feet to a few 

hundred feet. Geological evidence indicates that some 

near-surface gypsum was formed by hydration of 

primary or secondary anhydrite where meteoric 

ground and surface water came in contact with anhydrite. The depth of complete hydration is important in exploitation because the presence of more 

than a few percent anhydrite renders gypsum unfit 

for many purposes. 

Some gypsum is mined from deposits formed in 

continental basins by the evaporation of nonmarine 

waters. Most of these deposits probably originated as 

gypsum, and their lack of deep burial has kept anhydrite from forming. Most nonmarine deposits are 

smaller than marine deposits but tend to be nearer 

the surface. 

Domestic reserves and resources of gypsum are 

plentiful but are unevenly distributed. They are concentrated in the eastern Great Lakes region, the central midcontinent region, the Rocky Mountain belt 

from Canada to Mexico, and the southern California 

and Nevada region. Like salt, beds of gypsum also 

underlie an appreciable part of the earth's continents ; but unlike salt, they cannot be mined by solu1 

tion and must therefore lie near the surface to be 

extracted at low cost. Nevertheless, available quanti-
206 UNITED STATES MINERAL RESOURCES 

ties are very large and adequate for centuries to 

come. Synthetic gypsum is produced as a byproduct 

of the manufacture of several other compounds, but 

the economics of production probably will prevent 

these sources from being exploited solely for the 

value of the gypsum. 

SODIUM CARBON ATE 

Sodium carbonate (Na2COa, which is known industrially as "soda ash") is an important industrial 

chemical because of its own chemical properties, and 

because of its use in the manufacture of other compounds such as sodium bicarbonate, sodium hydroxide, and sodium nitrate. In 1970 the United States 

consumed 6.8 million tons of sodi urn carbonate and 

exported an additional 0.3 million tons. Present 

domestic consumption is as follows: 50 percent for 

manufacture of glass, 40 percent for making other 

chemicals, 8 percent in paper and pulp manufacture, 

and 2 percent in miscellaneous uses such as soap, 

detergents, and water softeners (MacMillan, 1970d; 

Lansche, 1971b). A potentially large use of one of its 

derivatives, sodium bicarbonate (NaHCO:~), is as a 

cleanser of sulfur dioxide from stack gases of powerrlants. 

Most of the sodium caJ:bonate and bicarbonate now 

produced in the United States is manufactured from 

sodium chloride, ammonia, and carbon dioxide by the 

Solvay process, but this production is gradually declining because of the high cost of new plants and 

rollution problems. This chapter discusses natural 

deposits whose 1971 production was valued at $56 

million and constituted 38 percent of the U.S. total. 

Before 1950, sodium carbonate from natural sources 

in California supplied only about 6 percent of U.S. 

needs. In that year, however, production commenced 

from an immense deposit of bedded trona (Na2COa 

· NaHCOa ·2H20) in southwestern Wyoming. By 

1970, this deposit furnished about one-third of the 

Nation's sodium carbonate. It will probably become 

the major domestic source within a few years; planned increases in the mining and refining capacity of 

three plants producing from the Wyoming deposit 

would raise annual production to about 5 million tons 

of sodium carbonate (70 percent of present consumption) and a possible fourth plant would raise production even further. 

Core drilling is virtually required in prospecting 

for natural sodium carbonate and other saline deposits. All valuable saline minerals are soluble and 

so are rarely exposed in outcrop, but some geologic 

indications help narrow the target before drilling 

(Smith, 1966c; Culbertson, 1971). For example, 

sodium carbonate minerals dissolved from outcrops 

may be indicated by identifiable cavities or pseudomorphs, a high sodium carbonate content in ground 

or surface water may indicate concealed deposits 

undergoing such solution, and certain lithologic textures and less soluble evaporite minerals in outcropping rocks may indicate nearby buried salines. 

Gamma-ray, neutron, sonic, and density geophysical 

logs from oil and gas test holes generally indicate the 

presence of any trona layers that were penetrated, 

although it is difficult to distinguish them from some 

other evaporites. 

The domestic resources of sodium carbonate are 

immense. Not only are tn:,re nearly inexhaustible 

supplies of salt and limestone from which sodium 

carbonate could be manufactured by the Solvay 

process, but the trona deposits in the Green River 

Formation of Eocene age in southwestern Wyoming 

that are now being mined would supply the Nation's 

needs for more than 3,000 years at the present rate 

of consumption. These deposits underlie an area of 

about 1,300 square miles at depths of 400-3,500 feet 

(Bradley and Eugster, 1969; Culbertson, 1971). Resources of trona in beds more than 3 feet thick total 

about 85 billion tons; some beds, however, locally 

contain halite as an impurity. Between 30 and 40 

billion tons of trona are contained in halite-free beds 

more than 6 feet thick. Marlstone and oil-shale beds 

between the trona beds contain submarginal resources in the form of disseminated sodium carbonate minerals such as shortite (Na2C03 · 2CaCOa) and 

northupite (Na2COa · NaCl· MgCOa). 

In northwestern Colorado, the Green River Formation contains additional resources of sodium carbonate in the form of nahcolite (NaHCOa). These 

resources add substantially to the nation's supply. 

The mineral occurs as lenses, nodules, and beds in a 

thick sequence of rich oil shale that also contains 

large amounts of dawsonite and some halite. Nahcolite·-bearing oil shale, 100 or more feet thick, underlies an area of about 255 square miles in the northern 

part of the Piceance Creek basin at depths of 1,100-

2,000 feet. The average nahcolite content in representative core holes ranges from 13 to 26 weight percent. The area is estimated to contain 32 billion tons 

of nahcolite, making this the second largest sodium 

carbonate deposit known in the world (Trudell and 

others, 1970; Dyni and others, 1970). Nahcolite is a 

potential source of soda ash, but it may also gain use 

in its natural form as a chemical agent for removing 

oxides of sulfur and nitrogen from hot industrial 

stack gases and as a low -cost means of increasing 

the yield of alumina from interbedded dawsonitebearing oil shales with which the nahcolite necessarily would be mined. 
EVAPORITES AND BRINES 207 

Searles and Owens Lakes. Calif., contain amounts 

of sodium carbonate smaller than those in Colorado. 

The deposits are of Quaternary age and consist of 

porous crystalline bodies saturated with brines 

(Smith, G. I., 1966a). They are estimated by us to 

contain about 700 million tons of sodium carbonate. 

Some sodium carbonate occurs in numerous small 

playa lakes in the Western United States; the resource potential of these deposits probably does not 

exceed 200 million tons (Garrett and Phillips, 1960). 

Production of sodium carbonate from natural 

sources also comes from the trona deposits of Lake 

Magadi, Kenya (Eugster, 1970). The lake generates 

new trona at about the same rate as present annual 

production (150,000-200,000 tons). Other sodium 

carbonate lakes in the rift valleys of eastern Africa 

contain large but unknown amounts of additional 

material. Deposits of unknown, but probably small, 

size occur also in South America, eastern Europe, 

the U.S.S.R., central Africa, China, and India. 

SODIUM SULFATE 

Sodium sulfate (Na2S04, known also as "salt 

cake"), is produced in the United States from natural brines and as a byproduct of certain manufacturing processes. About 1.5 million tons is produced 

annually of which 46 percent, valued at $12.5 million, comes from natural sources in California, Utah, 

Texas, and Wyoming (Lansche, 1971b; MacMillan, 

1970d). The kraft paper industry consumes nearly 

75 percent of U.S. production whereas the glass, 

c~ramic glaze, detergent, and other industries consume the balance (Goudge and Tompkins, 1960). 

California sodium sulfate production from natural 

sources comes from subsurface Pleistocene brines in 

Searles Lake; Utah production is from the brines in 

Great Salt Lake; Texas production is from subsurface brines; and Wyoming production is from surface crusts on dry lakes. Canadian production, which 

is about equal to U.S. production from natural 

sources, comes from salt lakes in Saskatchewan. All 

deposits are in arid to semiarid environments. The 

presence of sodium sulfate in a closed basin is a 

result of several geologic controls, especially the 

chemicatsomposition of rocks and soils within the 

drainage area and the composition of mineral springs 

that discharge into the basin. Extraction processes 

can be relatively simple because of the marked influence of temperature on the solubility of sodium 

sulfate at temperatures below 32°C (Rueffel, 1970). 

Resources of sodium sulfate are large. Searles 

Lake, Calif., is estimated by us to contain 400 million tons, a 600-year supply at present rates of U.S. 

] consumption from natural sources. Great Salt Lake 

contains about 30 million tons, and both solid and 

brine deposits are known in 10 other States in the 

United States. Canadian deposits contain about 60 

million tons. Production has come also from several 

countries in Europe and South America, and a 

single deposit in the U.S.S.R. contains an estimated 

2 billion tons (Goudge and Tompkins, 1960). 

BORON MINERALS 

Boron minerals mined in the United States in 1970 

supplied more than 60 percent of world needs. Production totaled about 1 million short tons of ore 

which contained about 560,000 tons of B203; value of 

the ore was approximately $85 million (Kistler, 

1972). All domestic production came from California; small deposits in Nevada and Oregon are unmined (Smith, W. C., 1960, 1962). Foreign production came mostly from Turkey with smaller amounts 

coming from Italy, Argentina, and probably China 

and the U.S.S.R. 

Boron mineral consumption by the United States 

was about 35 percent of world production. Consumption was largely by the manufacturers of glass, glass 

fiber, enamel, chemical and agricultural products, 

soaps and detergents, abrasives, gasoline additives, 

fire-retardants, metal alloys, and other industries 

(West, 1971). Annual growth in U.S. consumption 

over the next quarter century is estimated to be 3.5-

4.6 percent, with greater growth possible (MacMillan, 1970a). 

Boron minerals being mined today occur chiefly as 

deposits in nonmarine Cenozoic rocks. Production at 

Boron, Calif., comes from a thic-k, slightly deformed 

lacustrine deposit of middle Tertiary age that contains borax (Na2B407 ·10H20) and kernite (Na2B407 

·4H20) (Barnard and Kistler, 1966). The near lack 

of other evaporite components in the deposit indicates that it was formed from lake waters unusually 

rich in sodium borate, but the existence of comparable deposits in Turkey and Argentina show that this 

setting is not unique. Production near Death Valley, 

Calif., consists mostly of calcium borates (such as 

colemanite) from deformed upper Cenozoic mudstone and sandstone deposited in a depression ancestral to Death Valley (McAllister, 1970). Sodium 

borate production from Searles Lake, Calif., comes 

from brines pumped from the interstices of mineralogically complex salt layers beneath the dry lake 

surface; the salts are an upper Quaternary deposit 

formed by desiccation of a succession of large Pleistocene lakes (Smith, G. I., 1966c). Less is known of 

the geologic setting of major deposits in other :t:arts 
208 UNITED STATES MINERAL RESOURCES 

of the world, but available data suggest that most 

deposits are in areas characterized by above-average 

amounts of boron in spring waters and sediments and 

are in Cenozoic nonmarine basins formed by tectonic 

processes. 

Prospecting for boron minerals starts with the 

identification of basins that were, during the geologic past, favorable for the accumulation of boraterich waters. Some basins and their sediments are 

undeformed whereas others are folded, faulted, partly eroded, and concealed to an extent that their 

original shape can be inferred only by geologic reconstruction. Exploration generally requires drilling. 

Sodium borate minerals (for example, borax) are 

soluble and therefore are soon leached from outcrops 

except in very arid regions. Calcium borate minerals 

(for example, colemanite) and sodium-calcium borates (for example, ulexite) are less soluble but are 

not well preserved in outcrop. 

Reserves and known resources of borates are large. 

One published estimate of world indicated reserves 

is 72 million short tons B20s; one-half of this is in 

domestic deposits and one-sixth is in Turkish deposits (MacMillan, 1970a, p. 882). Conservative estimates of the sodium borate reserves in California 

alone show that they are sufficient for 300 years at 

present domestic consumption rates and 100 years at 

present world consumption rates (Smith, W. C., 

1966). Recently discovered Turkish sodium borate 

reserves increase this supply fivefold (Industrial 

Minerals, 1970). Calcium borate reserves in California, Turkey, and South America further add to 

the supply. At present consumption rates, world reserves and known resources thus are adequate for 

many hundreds and possibly thousands of years. The 

geologic settings of boron deposits are relatively well 

understood, and prospecting during the last decade 

for new deposits has been correspondingly effective. 

New deposits are likely to be found if economic incentive exists, and world resources might ultimately 

be increased 2-10 times. 

NITRATES 

Nitrogen compounds are essential to modem industry and agriculture. Production of nitrogen compounds by "fixation" of nitrogen from the atmosphere began during World War I and now accounts 

for all United States, and nearly all world, production of nitrogen compounds. In 1968, world production was 35.4 million tons of contained nitrogen, and 

U.S. production was 10.1 million tons (Lorenz, 1971). 

Nitrogen from the atmosphere will supply world 

needs for the foreseeable future. For nearly 100 

years before World War I, however, the chief source 

of fixed nitrogen was the Chilean nitrate caliche 

deposits, and even today no comparable source of 

.solid nitrates is known in the world. The source of 

nitrates before discovery of the Chilean deposits was 

animal wastes. The Chilean deposits are still being 

exploited but production is small; in 1968, NaNOs 

and KNOa production from there was equivalent to 

0.12 million tons of nitrogen (Lewis, 1970a). Nevertheless, their importance as a potential resource is 

large, and they supply other valuable coproducts. 

Caliche layers containing nitrates are extensive in 

the Atacama Desert of northern Chile and are 

known to occur in the coastal desert of Peru as far 

north of Arequipa. The caliche layer is at or near 

the surface and generally is 3-12 feet thick. Evaporite minerals occur as cementing material in regolith 

(the cement commonly makes up about a third of 

the caliche) and as veins and impregnations in bedrock. The principal minerals are soda-niter (NaNos), 

halite (NaCl), and several sulfate minerals; the 

deposits are unique in also containing iodate 

minerals. 

Reserves of Chilean nitrate ore containing 7 percent (present cutoff grade) or more NaNOs are estimated to be about 2.5 billion tons. Contained in this 

ore are an estimated 220 million tons of NaNOs, 1 

million tons of iodine, 9 million tons of B20s, and substantial amounts of less valuable components. Caliche that is similar but contains less than 7 percent 

NaNOs is even more widespread in northern Chile 

and probable resources are more than 25 billion tons. 

STRONTIUM 

Strontium and its compounds are used chiefly for 

pyrotechnics and similar purposes that utilize the 

red coloration of its flame, but some is used for 

vacuum tubes, greases, ceramics, color television 

tube glass, and other purposes. In 1968, about 6,500 

tons of strontium was consumed in the United States. 

Most production comes from celestite (SrS04), although strontianite (SrCOs) is locally abundant. 

Current production of strontium minerals comes 

chiefly from Mexico and the United Kingdom. The 

United States has sources of strontium, but all present consumers utilize imported ore (Park, 1971). 

Bedded deposits of celestite and strontianite in 

California were mined during World Wars I and 

II. They consist of concretionary layers of the minerals in Cenozoic lacustrine deposits made up chiefly 

of tuff and shale. Both celestite and strontianite 

deposits contain gypsum and some include halite; 

the strontianite beds are also associated with limestone. The stronti urn minerals formed largely by 

replacement of preexisting clastic sediments, but 
EVAPORITES AND BRINES 209 

some may have been part of the original sediment. 

Deposits in 11 other States are mostly replacement, 

vein, disseminated, or vuggy occurrences in older 

rocks (Durrell, 1953; Schreck and Arundale, 1959). 

Resources in the United States have been estimated at 3.5 million tons of rock containing 85 percent or more SrS04. World resources are probably 

many times larger. Brines containing several thousand parts l>er million strontium exist and might 

also be utilized. At present rates of consumption, 

the U.S. resources of celestite and strontianite represent a 500-year world supply (Schreck and Arundale, 1959; Handsman, 1970). Very little prospecting for strontium minerals have been carried out 

in the United States or elsewhere. An extensive program could probably increase U.S. resources fourfold. 

BROMINE 

Annual production of bromine in the United 

States is almost 400 million pounds valued at $88 

million. This constitutes more than three-fourths of 

world production. Most bromine is used in gasoline 

additives although some is needed for fire extinguishers, flame retardants, and other uses (MacMillan, 1970b). Inasmuch as present consumption 

of bromine largely reflects its use as a gasoline 

additive, future consumption in the United States 

is uncertain. Public concern over air pollution could 

result in a greatly curtailed use of lead in gasolines ; 

the use of lead creates the need for ethylene dibromide as an additive. 

All U.S. production comes from brines. Five plants 

in Michigan and five in Arkansas use brines from 

deep wells ; one plant in California uses brines from 

Searles Lake. Production of bromine from sea water 

ceased in 1969, but the sea provides the United 

States with an unlimtied resource (Olson, 1971). 

Well brines that allow production mostly contain 

more than 1,000 parts per million bromine. Typical 

samples of brines from producing wells in Michigan 

contain 1,300-2,900 ppm bromine (White and others, 

1963, table 13) ; California brines that allow production of bromine as a byproduct contain about 850 

ppm (Bixler and Sawyer, 1957) ; sea water contains 

about 65 ppm but this can be concentrated to 1,750 

ppm by solar evaporation before processing (Ver 

Planck, 1957). 

Resources of bromine are virtually unlimited. 

Sea water provides a source that is almost economic today, and deep-well brines now in use are 

available in large volume. Bittern salts and interstitial brines in marine evaporite bodies have bromine concentrations similar to those in the best 

deep-well brines. 

IODINE 

Iodine is used primarily in the manufacture of 

photographic chemicals, disinfectants, and pharmaceutical preparations. During World War I, it was 

extracted from seaweed on the west coast of the 

United States. Subsequently, in this country, it was 

derived chiefly from oil-well brines in Louisiana and 

California. Present production of iodine comes 

chiefly from gas-well brines in the Chiba Peninsula 

of Japan (5,092 tons in 1969) and from nitrate ores 

of northern Chile (2,700 tons). Imports in 1969 

from these countries, which supply most U.S. requirements, were about 2,900 tons valued at $5.7 

million (Park, 1971). Annual production of iodine 

from brines at Midland, Mich., is probably about 

150 tons (MacMillan, 1970c). 

The Chilean nitrate deposits contain 200-600 ppm 

iodine, only part of which is recovered. Iodine occurs in the minerals lautarite (Ca (lOa) 2), brtiggenite (Ca(IOa)2·H20), and dietzeite (Ca(I03 )2 

(Cr04)), and probably as a contaminant in other 

saline minerals of the deposits. High-iodine brines 

of oil fields and other deep wells are characteristically chloride brines in which the iodine occurs in 

concentrations ranging from 35 to 135 ppm ; bromine is commonly present in similar concentrations 

(White and others, 1963; Collins and others, 1967). 

Reserves and resources of iodine in brines and 

nitrate deposits currently being exploited are at 

least 1.5 million tons, of which the Chilean nitrate 

deposits account for more than 1 million tons. Potential resources in these and other iodine-rich 

brines are several times as large; potential resources 

in the United States are probably several hundred 

thousand tons. 

CALCIUM CHLORIDE 

Calcium chloride is sold as crystals and as a dense 

brine. Its largest single market is for highway 

deicing, but dust control, concrete treatment, and 

other uses require major amounts. About one-third 

of the calcium chloride produced in the United 

States is a synthetic byproduct of sodium carbonate 

derived by the Solvay process; two-thirds comes 

from natural brines which in 1970 were processed 

by five plants in Michigan and two in California. 

Average annual production between 1965 and 1969 

from natural sources was valued at $13 million 

(Babcock, 1964; Lansche, 1971a). 

Oil-field and other deep-well brines rich in calcium chloride are generally low in carbonate and 
210 UNITED STATE'S ,MINERAL RESOURCES 

sulfate and high in ammonia and total solids (White 

and others, 1963, p. 9, tables 13, 16, 29). They come 

from diverse geologic settings and areas, and their 

origin is not clear. Lake brines with comparable 

compositions occur in still other environments 

(Smith, G. I., 1966b). 

Resources of calcium chloride in the world are 

large and, for practical purposes, nearly inexhaustible. Production in the United States is now limited 

primarily to the number of wells drilled in known 

favorable areas, but these and new wells could 

almost certainly supply domestic needs for at least 

100 years. Billions of tons of calcium and magnesium chloride are available from tachyhydrite 

bodies in Brazil and western Africa (Ivanov, 1969; 

Hite, 1972; Wardlaw, 1972). This amount represents thousands of years supply at present world 

consumption rates. 

MAGNESIUM COMPOUNDS 

Magnesium and its compounds are produced from 

bedrock deposits, natural and synthetic brines, and 

sea water. The principal minerals mined for their 

magnesia (MgO) content are magnesite (MgCOa), 

brucite (Mg(OH)z), and dolomite (MgCa(COa)z); 

deposits of these minerals are discussed in "Magnesian Refractories" and "Limestone and Dolomite." 

Most of the domestic and ~orld production consists 

of magnesium metal or one of several grades of 

magnesia, although some is in the form of magnesium hydroxide, magnesium sulfate, magnesium 

trisilicate, and magnesium chloride. Magnesium 

metal is used extensively in aircraft manufacturing 

and other purposes for which its light weight is a 

factor, and magnesia is used chiefly as a refactory 

for the steel and other basic industries (Comstock, 

1963; Lewis and Cammarota, 1971; Paone, 1970). 

Many industrialized nations produce magnesium 

and magnesia from the sea that borders them. In 

the United States, magnesium and its compounds 

were produced in 1970 from deep-well brines in 

Michigan and from sea water in five States. The 

deep-well brines in Michigan supplied most of production. Facilities for extraction of magnesium compounds from Great Salt Lake brines are 'being constructed. Extraction of magnesium from sea water 

or brine also requires calcined limestone or dolomite, 

the latter yielding magnesium in quantities about 

equal to that from sea water. 

The geologic environments of the raw materials 

used in this industry are extremely diverse. Dolomite and magnesite occur widely and were deposited 

in a variety of environments. Magnesium in usable 

concentrations is found in many surface and sub~ 

surface brines that are dominated by sulfate or 

chloride anions and that are deficient in carbonate. 

Evaporite deposits containing billions of tons of 

tachyhydrite (2MgC12 • CaC12 ·12Hz0) in Brazil and 

western Africa represent possible magnesium resources (Ivanov, 1969; Hite, 1972; Wardlaw, 1972). 

For practical purposes, the U.S. and world resources 

of magnesium and magnesium compounds in brines 

and sea water are unlimited, and bedrock resources 

are large. 

UNDISCOVERED RESOURCES OF EVAPORITES 

AND BRINES 

MARINE EVAPORITES 

The ultimate supply of commodities derived from 

marine evaporites is theoretically limited only by the 

existing volume of such deposits. That volume is 

huge. Deposits of marine evaporites tend to be 

hundreds of feet thick, and Kozary, Dunlap, and 

Humphrey (1968) showed that about 25 percent of 

the world's continental area is underlain by one or 

more of them. 

This known area of evaporites may be nearly all 

the total area that exists. This surprising conclusion stems from the fact that the area climatically 

favorable for the formation of marine evaporites 

at any given time in the earth's history is limited; 

calculations based on these limits plus reasonable 

geologic assumptions as to areas that might also by 

physiographically favorable allow one to approximate the maximum area of evaporites that could 

have formed since the close of Precambrian time. 

One such calculation, described below, shows that 

maximum area to be about 60 percent of the earth's 

surface. However, after subtracting areas representing reasonable guesses of the area of nondeposition 

and loss due to erosion, the remainder barely accounts for the evaporite bodies now known. Less 

conservative, but still reasonable, assumptions fail 

to account for all known deposits. Alternative models 

are virtually limited to those that increase the depositional area, and experimentation has shown that 

geologically reasonable alternatives that make substantial differences in the conclusion are difficult to 

find. For this reason, the conclusion regarding the 

small number of undiscovered evaporite bodies 

seems sound and not likely to be wrong by any 

factor approaching an order of magnitude. A more 

detailed explanation of calculating procedures and 

assumptions follows. 

Virtually all marine evaporites apparently formed 

where warm arid climates prevailed along coasts 

or in large embayments connected with the sea. 
EVAPORITES AND BRINES 211 

Warm and arid coastal regions today are mostly in 

the zones of trade winds (zones of nearly constant 

wind direction) that lie between about 10° and 35°, 

both north and south of the equator. The arid coasts 

are where the trade winds blow from the land toward the sea. At least since Precambrian time, 

trade-wind belts probably have had about the same 

size and global distribution; they are products of 

the interaction between solar energy and the spinning earth and its atmosphere, and it is reasonable 

to postulate that the output of solar energy, the 

earth's spin and the physical properties of the 

atmosphere have been nearly constant during that 

period. These 25°-wide trade-wind belts make up 

about 40 percent of the global surface. If one assumes that two landmasses lay astride these belts, 

each with a 5°-Wide (about 300 miles) evaporiteforming basin along the entire shoreline that is in 

the trade-wind belt, about 1 percent of the globe 

would be accumulating evaporites. If, in the geologic past, the number of continental landmasses 

astride the trade-wind belts averaged two, and if 

the configurations of the coastlines changed every 

10 million years sufficiently for new portions of the 

earth's surface to begin accumulating evaporites, 

there could have been as many as 60 different accumulations of this size in the 600 million years since 

the close of Precambrian time. This mea}1s that 

about 45 percent of the globe could have at one time 

been the site of evaporite deposition. 

This maximum possible area does not seem to be 

large enough. Considering the near absence of 

present-day evaporite-forming basins, it seem likely 

that on the average, far less than half of the climatically favorable sites in the past were likely to 

be occupied by basins that produced evaporites. 

Furthermore, very probably at least half of onceformed evaporites have been eroded or dissolved. 

Finally, one must consider that the area of known 

evaporites would substantially exceed 8 percent of 

the earth's surface if none of the evaporite deposits 

overlapped. Conceivably, other environments than 

those considered in this model have produced major 

quantities of marine evaporites, but available geologic evidence seems more consistent with this model 

than any other. For these reasons, the numbers us3d 

in the above model calculation probably could be 

changed substantially and still not account for the 

known areas of marine evaporite deposits. Numbers 

and assumptions that would lead to the conclusion 

that areas of undiscovered evaporites are large 

would require even more drastic departures from 

what seems geologically reasonable. 

The only alternative assumption that seems to be 

reasonable for this calculation is that the areas of 

accumulating evaporites were commonly much 

larger than postulated because in some respects, 

past environments differed intrinsically from those 

of the present. It is difficulty to envision larger areas 

of global aridity caused by wider trade-wind belts, 

but very possibly areas of inland seas were much 

larger than now known. Available evidence indicates that many of the world's present continental 

areas were originally part of a single landmass and 

that the present continents evolved by the slow 

spreading of individual masses away from this 

center. As they spread, nearly landlocked inland 

seas may have evolved to become sites of evaporite 

deposition that were much larger than any now 

known. Such a phenomenon could explain the apparent overabundance of marine evaporite bodies, 

but still does not necessarily imply that a large 

number of evaporite bodies are undiscovered. 

If one accepts the above lines of reasoning, it 

follows that the likelihood of finding many large 

new deposits of marine evaporites is small. This 

means that estimates of resources in known deposits can be considered nearly equivalent to ultimate resources. An estimate of these figures follows. 

If 25 percent of the world's 57 million square miles 

of continental area is underlain by evaporite deposits, and the average deposit contains 300 feet 

of evaporites, 0.8 million cubic miles of evaporites 

exist. (The average of the maximum thickness of 

deposits listed in table 42 is 750 feet; the deposits 

are estimated to contain 20 percent impurity and 

to have average thicknesses that are half their maximum thickness.) An independent- estimate of this 

volume by Ronov (1968, fig. 3) concludes that approximately 0.9 million cubic miles of evaporites 

are in the earth's sedimentary shell, with about 70 

percent of this volume in relatively near-surface 

deposits formed in platform environments and the 

remainder formed in geosynclinal environments. 

Most evaporites consist of gypsum, anhydrite, or 

halite; thus, a volume of 0.8 million cubic miles 

means that about 10l6 tons of these components 

exist. 

An estimate by us (based on well-explored portions of U.S. deposits) suggests that about 0.002 

percent of an average marine deposit consists of 

potassium mineral concentrations, although this has 

to be a very approximate number. Applying this 

figure to the 0.8 million cubic miles of evaporites in 

the world suggests that about 160 billion tons of 

KCl containing 100 billion tons of K20 is concentrated in such bodies. This is very close to the 

amount inferred to exist in known deposits and 
212 UNITED STATES MINERAL RESOURGES 

tends to support the inference that most of the 

earth's evaporite and potash deposits have already 

been discovered. No doubt some deposits remain unknown, but the above calculation strongly implies 

that the number is not large. 

In the United States, all marine evaporite deposits represent possible sources of potassium cornpounds, salt, and gypsum. Figure 24 shows that 

about 35 percent of the 3 million square miles that 

make up the 48 adjoining States is underlain by 

evaporites, and calculations like those used for 

estimating world resources indicate that about 8 

billion tons of K20 equivalent could be contained in 

these deposits. This amount is about 20 times 

greater than estimates of known U.S. resources and 

suggests that several large undiscovered deposits 

may exist. 

In summary, it is not likely in the foreseeable 

future that potassium compounds, salt, or gypsum 

will become the sole target of expensive exploration programs because of dwindling world supplies. 

Enormous quantities are now known although their 

global distribution is uneven. However, there is 

strong incentive to keep costs of these substances 

low because their costs influence the price of a very 

large number of other products. Furthermore, strategic reasons, balance of payment problems, differences in quality of the product from different 

sources, and potential profits stemming from attractively priced transportation to large or growing 

markets remain as strong incentives for exploration. 

New and exploitable resources may well be discovered as a result of these stimuli. 

NONMARINE EVAPORITES 

Ultimate resources of commodities derived from 

continental evaporites-deposits formed by the 

evaporation of inland bodies of water-are less 

easily evaluated than are resources of marine 

evaporites. Requirements for an environment favorable for the deposition of continental evaporites are 

a semiarid to arid climate that will produce a high 

evaporation rate, a closed basin having internal 

drainage, and a source of large quantities of water 

having the proper ratio of dissolved components. 

Evaporation rates high enough to keep closed basins 

from filling and overflowing exist today in areas 

that mostly lie between lats 45° N. and 45° S.; the 

sizes and locations of basins within such areas, 

however, are variable. Closed basins receive large 

inflow where they adjoin high mountains or upland 

areas ; the high mountains or uplands extract most 

of the moisture from passing airmasses, and the 

closed basins downwind from the mountains are 

arid because they have been deprived of this moisture. Extensive faulting and warping are the geological processes required to create both the basins 

and the mountains. 

Areas known to contain large volumes of nonmarine sedimentary rocks that were deposited in 

closed basins between the 45 o parallels represent a 

subordinate part of the world's surface. Most known 

continental evaporite dep9sits are Cenozoic, and 

some evaporite assemblages are favored by drainage from a volcanic rock environment whereas 

others are favored by drainage from other types of 

terrane; these factors provide further guidance to 

areas that should be considered during exploration 

for deposits and in estimating undiscovered resources. 

In the United States, virtually all areas that have 

had a long history of internal drainage are west of 

the Rocky Mountains, although several basins having more brief histories of interior drainage lie in 

the Great Plains. In the area between the Wasatch 

Range and the Sierra Nevada, more than 100 closed 

basins are large enough to have contained Jakes 

during the Pleistocene, and probably 5-10 times 

this number of closed basins existed during one part 

or another of Cenozoic time. Between 500 and 1,000 

such basins may therefore have formed in that area, 

and the sediments deposited in perhaps half are now 

preserved. Of these basins, less than 10 percent have 

been adequately prospected. If remaining basins 

were tested and a 1-percent success 1 resulted, two 

to five basins would be found to contain evaporite 

deposits. Although such deposits might be profitable, 

the degree of increase to resources would depend on 

the minerals they contain; salt, potash, sodium carbonate, or magnesium deposits would probably not 

greatly change the resource outlook, but deposits 

containing other possible components might. Discovery of new deposits in favorable areas in other 

parts of the world is even more likely because these 

parts have been less explored; western China and 

adjacent parts of Afghanistan and the U.S.S.R., 

Iran, Turkey, western Central and South America, 

and eastern Africa all have probably had Cenozoic 

geologic histories similar to the Western United 

States. If those areas together contain 10 times as 

many basins as the Western United States, it seems 

likely that 20-50 major deposits of continental 

1 A basis used by some mining companies for budgeting mineral ex- ploration programs in geologically favorable areas is to spend up to 1 percent of the value of the anticipated ore body. This figure is com- monly justified by citing past experience, which shows that there is about a 10 percent chance of success in finding an ore body that would allow at least a 10 percent profit. The 1 percent chance of success used in the 

present calculation results from an estimate that only 10 percent of the 

basins in this area are geologically favorab~e. and that 10 percent of 

them-1 percent of the total number-would contain a deposit. 
EVAPORITES AND BRINES 213 

evaporites remain to be discovered in the world. 

These might increase world resources of their components by 1 to 2 orders of magnitude above resources in known deposits. 

BRINES 

Sea water, lakes, seas, and many shallow subsurface brines have known compositions. They are not, 

therefore, "undiscovered," but they do represent 

potential resources because processes capable of 

extracting selected dissolved components at a profit 

may someday be developed. Those bodies contain 

large to virtually unlimited quantities of several 

commodities. New extraction processes for many 

substances are not likely to be developed out of 

world necessity inasmuch as known reserves and 

resources appear adequate for hundreds or thousands of years. Some may be developed, however, 

as new techniques allow some chemicals to be extracted more cheaply or closer to markets. 

Deep subsurface brines contain very large quantities of dissolved substances, but few basins outside of known or potential petroleum and gas fields 

have been explored. The geologic factors controlling 

the distribution of valuable brines are not well understood and the number of unexplored basins containing valuable brines cannot be reliably estimated. In 

some areas, the amount of brine now extracted is 

controlled by pet:·oleum production. More could be 

extracted if necessary, but the quantity cannot be 

evaluated although it is known to be large. 

SUMMARY OF U.S. RESOURCES 

Evaporite resources of the United States, expressed as years supply at current rates of consumption are shown in table 43. Although known 

domestic resources of potassium compounds are 

relatively low, Canadian resources are sufficient to 

fulfill requirements of North America for thousands 

of years. 

PROBLEMS FOR RESEARCH 

The abundance of evaporite and brine resources 

means that no shortage is impending. Continuing 

effort should be made toward finding new and more 

economic deposits, however, because they would 

supply large quantities of the basic chemicals required in industry and agriculture, and their cost 

would be an important factor in the price consumers pay for many products. For this reason it is 

imperative to have not only resources, but resources 

that would permit these chemicals to be produced 

and transported to the consumer at low cost. The 

main problems posed by resources derived from 

evaporites and brines are that the costs of some are 

TABLE 43.-Evaporite and brine resources of the 

United States 

[Expressed as years supply at current rates of domestic consumption] 

Commodity 

Undiscovered re- Identified resources 1 sources ( Hypothe-

(Reserves 2 and sub- tical a and speculaeconomic deposits) tive ' resources) 

Potassium compounds ___ 100 years ______ Virtually 

inexhaustible. 

Salt -------------------1,000+ years ___ Do. 

Gypsum and anhydrite __ 500+ years ---- Do. 

Sodium carbonate ------6,000 years ____ 5,000 years. 

Sodium sulfate ---------700 years ______ 2,000 years. 

Borates ----------------300 years ______ 1,000 years. 

Nitrates ---------------Unlimited Unlimited (air). 

(air). 

Strontium --------------500 years ______ 2,000 years. 

Bromine ---------------Unlimited Unlimited 

(sea water). (sea water). 

Iodine -----------------100 years ______ 5{)0 years. Calcium chloride ________ 100+ years ____ 1,000+ years. 

Magnesium ------------Unlimited Unlimited 

(sea water). (sea water). 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existing technology 

and economic conditions. 3 Reserves: Identified deposits from which minerals can be extracted 

profitably with existing technology and under present economic conditions. 3 Hypothetical resources: Undiscovered mineral deposits, whether of 

recoverable or subeconomic grade, that are geologically predictable as existing in known districts. 4 Speculative resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that may exist in unknown districts or in unrecognized or unconventional form. 

undesirably high today and costs of others are likely 

to increase in the future. These problems are results 

of the uneven geographic distribution of deposits 

throughout the United States and the world, and 

the increasingly low-grade ores and the more complex and expensive extraction processes needed to 

utilize them. Discovery of new and more inexpensively processed deposits is needed. The abundance 

of known deposits of marine evaporites. minimizes 

the need to find new ones, and efforts should be 

concentrated on locating the more valuable concentrations of minerals within the known deposits. In 

contrast, a large percentage of the world's deposits 

of nonmarine evaporites ·and brines are undiscovered, and extensive programs of geologic study and 

drilling will be needed to find them. 

Important to the geologic understanding of evaporite and brine deposits are a knowledge of (1) the 

variations in past positions of global climatic belts, 

(2) the times of past fluctuations in global climatic 

character, (3) the processes involved in the concentration and crystallization of evaporite components from waters, and (4) the mechanics of 

diagenesis that affect solids and brines both immediately and long after burial. Major obstacles to 

the finding and development of new evaporite resources stem from our imperfect understanding of 

these phenomena, and research leading to an improved understanding is essential. 
214 UNITED STATES MINERAL RESOURCES 

Almost every subdivision of earth sciences has 

contributed techniques useful in prospecting for 

evaporites. It is, in fact, this variety in disciplines 

that makes it difficult for exploration groups to 

utilize known techniques effectively because so few 

groups include members that have facility in all 

fields. All subdivisions of the sciences also have 

great promise of developing new techniques. New 

geochemical methods, for example, may well enhance our ability to reconstruct salinity gradients 

within evaporite-bearing basins. Variations in the 

bromine content in halite of marine origin provide 

an established technique, but far less work has 

been done on the distribution of other elements that 

reflect salinity as they change concentration in 

minerals associated with evaporite bodies. Such 

changes might be indicated by variations in the concentration of strontium as it proxies for calcium in 

minerals such as limestone, dolomite, gypsum, and 

anhydrite ; by shifts in the isotopic ratios of both 

hydrogen and oxygen in the water of liquid inclusions which may reflect changes in evaporationinduced salinity of crystallizing brines ; or by variations in the 0 18 in the sulfate ion of gypsum and 

anhydrite which may change during evaporation of 

the parent brine yet be less affected by diagenesis 

than most other ions oi radical components. 

Also needed are more complete studies of evaporite deposits in the process of being formed. Few 

marine deposits are forming today, and none has 

been examined in all ways that are desirable. More 

nonmarine deposits than marine are being formed 

today, and immediate studies of many are needed 

because these evaporites may not repeat their depositional cycle. 

Perhaps the least understood geologic phenomena 

related to evaporites and brines are the roles and 

mechanisms of diagenesis. Almost immediately after 

deposition, some changes in mineral composition 

and form occur that stern from changes in the surrounding chemical and physical conditions relative 

to those extant at the site of original crystallization. 

Other changes occur later-for example, as deeper 

burial increases load pressures, as tectonic and other 

forces alter the hydraulic regimes that control the 

migration of interstitial brines, as time allows metastable assemblages of minerals to convert to thermodynamically stable assemblages, and as clay, 

organic, and other substances that act as ionic filters 

change the compositions of brines passing through 

them. Field studies of these problems have been 

made, but progress is difficult because so much of 

the evidence has been destroyed or is not available 

from existing drill cores. Laboratory studies are 

difficult because so many of the reactions are slow. 

Future research should be more fruitful because the 

problems are becoming better defined and new techniques are becoming available, but much remains 

to be done. 

REFERENCES CITED 

Ashizawa, R. V., 1971, Gypsum, in U.S. Bur. Mines Minerals 

Yearbook 1969: v. 1-2, p. 547-553. 

Babcock, C. 0., 1964, Calcium and calcium compounds, in 

U.S. Bur. Mines Minerals Yearbook 1963: v. 1, p. 341-

346. 

Barnard, R. M., and Kistler, R. B., 1966, Stratigraphic and 

structural evolution of the Kramer sodium borate ore 

body, Boron, California, in Rau, J. L., ed., 2d Symposium 

on salt: Cleveland, Northern Ohio Geol. Soc., Inc., p. 

133-150. 

Bentor, Y. K., 1961, Some geochemical aspects of the Dead 

Sea and the question of its age: Geochim. et Cosmochim. 

Acta, v. 25, no. 4, p. 239-260. 

Bixler, G. H., and Sawyer, D. L., 1957, Boron chemicals 

from Searles Lake brines: Indus. and Eng. Chemistry, 

v. 49, p. 322-333. 

Bradley, W. H., and Eugster, H. P., 1969, Geochemistry and 

paleolimnology of the trona deposits and associated 

authigenic minerals of the Green River Formation of 

Wyoming: U.S. Geol. Survey Prof. Paper 496-B, 71 p. 

Braitsch, Otto, 1971, Salt deposits, their origin and composition: New York, Heidelberg, and Berlin, SpringerVerlag, 297 p. 

British Sulphur Corporation, 1966, World survey of potash: 

Wrexham, Wales, Cambrian Press Ltd., 93 p. 

--- 1971, Statistical supplement, raw materials supply I 

demand, 1970-fertilizer supply/demand 1970/71: London, Stat. Suppl. no. 4, p. 14-15. 

Buzzalini, A. D., Adler, F. J., and Jodry, R. L., spec. eds., 

1969, Evaporites and petroleum: Am. Assoc. Petroleum 

Geologists Bull., v. 53, no. 4, p. 775-1032. 

Collins, A. G., Zelinski, W. P., and Pearson, C. A., 1967, 

Bromide and iodide in oilfield brines in some Tertiary 

and Cretaceous formations in Mississippi and Alabama: 

U.S. Bur. Mines Rept. Inv. 6959, 27 p. 

Colorado School of Mines, 1967, Potash: Mineral Indus. 

Bull., v. 10, no. 3, 18 p. 

Comstock, H: .. B., 1963, Magnesium and magnesium compounds: A materials survey: U.S. Bur. Mines Inf. Circ. 

8201, 128 p. 

Culbertson, W. C., 1971, Stratigraphy of the trona deposits 

in the Green River Formation, southwest Wyoming, in 

Contributions to Geology, v. 10, no. 1, Trona Issue: 

Laramie, Wyo., Wyoming Univ., p. 15-23. 

Durrell, Cordell, 1953, Geological investigations of strontium 

deposits in southern California: California Div. Mines 

Spec. Rept. 32, 48 p. 

Dyni, J. R., Rite, R. J., and Raup, 0. B., 1970, Lacustrine 

deposits of bromine-bearing halite, Green River Formation, northwestern Colorado, in Rau, J. L., and Dell wig, 

J. L., eds., 3d Symposium on salt: Cleveland, Northern 

Ohio Geol. Soc., Inc., p. 166-180. 

Eilertsen, D. E., 1971, Potash, in U.S. Bur. Mines Minerals 

Yearbook, 1969: v. 1-2, p. 933-946. 

Eugster, H. P., 1970, Chemistry and origin of the brines of 
EVAPORITES AND BRINES 215 

Lake Magadi, Kenya: Mineralog. Soc. America Spec. 

Paper 3, p. 213-235. 

--- 1971, Origin and deposition of trona, in Contributions to Geology, v. 10, no. 1, Trona Issue: Laramie, 

Wyo., Wyoming Univ., p. 49-56. 

Garrett, D. E., and Phillips, J. F., 1960, Sodium carbonate 

from natural sourc·es in the United States, in Industrial 

minerals and rocks: Am. Inst. Mining, Metall., Petroleum Engineers, p. 799-808. 

Goudge, M. F., and Tompkins, R. V., 1960, Sodium sulfate 

from natural sources, in Industrial minerals and rocks: 

Am. Inst. Mining, Metall., Petroleum Engineers, p. 809-

814. 

Handsman, M. A., 1970, Strontium, in Mineral facts and 

problems: U.S. Bur. Mines Bull. 650, p. 1237-1245. 

Hardie, L. W., and Eugster, H. P., 1970, The evolution of 

closed-basin brines: Mineralog. Soc. America Spec. 

Paper 3, p. 273-290. 

Hibpshman, M. H., 1971, Salt, in U.S. Bur. Mines Minerals 

Yearbook 1969: v. 1-2, p. 959-968. 

Hite, R. J ., 1970, Shelf carbonate sedimentation controlled 

by salinity in the Paradox basin, southeast Utah, in 

Rau, J. L., and Dell wig, J. L., eds., 3d Symposium 

on salt: Cleveland, Northern Ohio Geol. Soc. Inc., v. 1, 

p. 48-66. 

--- 1972, Potassium and magnesium in Cretaceous evaporites of northeast Brazil [abs.]: Am. Assoc. Petroleum Geologists Bull., v. 56, no. 3, p. 627. 

Industrial Minerals, 1970, Sodium borate reserves subject 

of new proposals: Indus. Minerals, no. 35, p. 32. 

Ivanov, A. A., 1969, Developed and undeveloped potash deposits in Africa: Lithology and Minerals Resources, 

no. 2, p. 187-195. 

Jacoby, C. H., 1972, Salt: Mining Eng., v. 24, no. 1, p. 52-

53. 

Jones, B. F., 1966, Geochemical evolution of closed basin 

water in the western Great Basin, in Rau, J. L., ed., 2d 

Symposium on salt: Cleveland, Northern Ohio Geol. Soc., 

Inc., p. 181-200. 

Jones, C. L., and Madsen, B. M., 1968, Evaporite geology of 

fifth ore zone, Carlsbad district, southeastern New 

Mexico: U.S. Geol. Survey Bull. 1252-B, 21 p. 

Kaufmann, D. W., 1960, Sodium chloride-The production 

and properties of salt and brine: Am. Chern. Mongraph Ser., no. 145, 743 p. 

Kistler, R. B., 1972, Boron: 1971 Industrial Minerals Review: Mining Eng., v. 24, no. 1, p. 36-37. 

Kozary, M. T., Dunlap, J. C., and Humphrey, W. E., 1968, 

Incidence of saline deposits in geologic time, in Mattox, 

R. B., and others, eds., Saline deposits: Geol. Soc. 

America Spec. Paper 88, p. 43-45. 

Lansche, A. M., 1971a, Calcium and calcium compounds, in 

U.S. Bur. Mines Minerals Yearbook 1969: v. 1-2, p. 

241-243. 

--- 1971b, Sodium and sodium compounds, in U.S. Bur. 

Mines Minerals Yearbook 1969: v. 1-2, p. 1015-1018. 

Lefond, S. J., 1969, Handbook of world salt resources: New 

York, Plenum Press, 384 p. 

Lewis, J. R., and Cammarota, V. A., Jr., 1971, Magnesium 

compounds, in U.S. Bur. Mines Minerals Yearbook 1969: 

v. 1-2, p. 665-672. 

Lewis, R. W., 1970a, Nitrogen, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 1099-1115. 

--- 1970b, Potassium, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 1157-1170. 

Livingstone, D. A., 1963, Chemical composition of rivers 

and lakes: U.S. Geol. Survey Prof. Paper 440-G, 64 p. 

Lorenz, W. C., 1971, Nitrogen, in U.S. Bur. Mines Minerals 

Yearbook 1969: v. 1-2, p. 775-782. 

McAllister, J. F., 1970, Geology of the Furnace Creek borate 

area, Death Valley, lnyo County, California: California 

Div. Mines and Geology Map Sheet 14, 9 p. 

MacMillan, R. T., 1970a, Boron, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 879-891. 

--- 1970b, Bromine, in Mineral facts and problems: U.S. 

Bur. Mines Bull 650, p. 893-901. 

--- 1970c, Iodine, in Mineral facts and problems: U.S. 

Bur. Mines Bull. 650, p. 1049-1058. 

--- 1070d, Sodium, in Mineral facts and problems: U.S. 

Bur. Mines Bull. 650, p. 1201-1217. 

Mattox, R. B., Holser, W. T., Ode, Helmer, Mcintire, W. L., 

Short, N. M., Taylor, R. E., and Van Siclen, D. C., spec. 

eds., 1968, Saline deposits-A symposium based on 

papers from the International Conference on Saline Deposits, Houston, Texas, 1962: Geol. Soc. America Spec. 

Paper 88, 701 p. 

Olson, K. S., 1971, Bromine, in U.S. Bur. Mines Minerals 

Yearbook, 1969: v. 1-2, p. 231-234. 

Paone, James, 1970, Magnesium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 621-638. 

Park, W. G., 1971, Minor nonmetals, in U.S. Bur. Mines Minerals Yearbook 1969: v. 1-2, p. 1187-1194. 

Pierce, W. G., and Rich, E. 1., 1962, Summary of rock salt 

deposits in the United States as possible storage sites 

for radioactive waste materials: U.S. Geol. Survey Bull. 

1148, 91 p. 

Rittenhouse, Gordon, 1967, Bromine in oil-field waters and its 

use in determining possibilities of origin of these 

waters: Am. Assoc. Petroleum Geologists Bull., v. 51, 

no. 12,p. 2430-2440. 

Ronov, A. B., 1968, Probable changes in the composition of 

sea water during the course of geological time: Sedimentology, v. 10, p. 25-43. 

Rueffel, P. G., 1970, Natural sodium sulfate in North 

America, in Rau, J. L., and Hellwig, J. L., eds., 3d 

Symposium on salt: Cleveland, Northern Ohio Geol. 

Soc., Inc., p. 429-451. 

Schreck, A. E., and Arundale, J. C., 1959, Strontium: A materials survey: U.S. Bur. Mines Inf. Circ. 7933, 45 p. 

Schroeder, H. J., 1970, Gypsum, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 1039-1048. 

Smith, G. I., 1966a, Sodium carbonate, in Mineral resources, 

pt. 1 of Mineral and water resources of California: U.S. 

89th Cong., 2d sess., Senate Comm. Interior and Insular 

Affairs, p. 385-389. 

--- 1966b, Calcium Chloride, in Mineral resources, pt. 1 

of Mineral and water resources of California: U.S. 89th 

Cong., 2d sess., Senate Comm. Interior and Insular 

Affairs, p. 117-119. 

--- 1966c, Geology of Searles Lake-A guide to prospecting for buried continental salines, in Rau, J. L., ed., 2d 

Symposium on salt: Cleveland, Northern Ohio Geol. 

Soc., Inc., p. 167-180. 

Smith, W. C., 1960, Borax and borates, pt. I, in Industrial 

Minerals and Rocks: Am. Inst. Mining, Metall., Petroleum Engineers, p. 103-118. 
216 UNITED STATES MINERAL RESOURCES 

--- 1962, Borate in the United States, exclusive of Alaska 

and Hawaii: U.S. Geol. Survey Mineral Inv. Resource 

Map MR-14. 

--- 1966, Borax and other boron compounds, in Mineral 

resources, pt. 1 of Mineral and water resources of California: U.S. 89th Cong., 2d sess., Senate Comm. Interior 

and Insular Affairs, p. 104-111. 

Stewart, F. H., 1963, Marine evaporites, in Fleischer, Michael, 

ed., Data of geochemistry [6th ed.]: U.S. Geol. Survey 

Prof. Paper 440-Y, 53 p. 

Trudell, L. G., Beard, T. N., and Smith, J. W., 1970, Green 

River Formation lithology and oil-shale correlations in 

the Piceance Creek basin, Colorado: U.S. Bur. Mines 

Rept. Inv. 7357, 14 p. 

U.S. Bureau of Mines, 1970, The United States position and 

outlook in potash: U.S. Bur. Mines Inf. Circ. 8487, 47 p. 

Ver Planck, W. E., 1957, Bromine, in Mineral commodities of 

California: California Div. Mines Bull. 176, p. 95. 

--- 1958, Salt in California: California Div. Mines Bull. 

175, 168 p. [ 1957]. 

Wardlaw, N. C., 1972, Unusual marine evaporites with salts 

of calcium and magnesium chloride in Cretaceous basins 

of Sergipe, Brazil: Econ. Geology, v. 67, p. 156-168. 

West, J. M., 1971, Boron, in U.S. Bur. Mines Minerals Yearbook 1969: v. 1-2, p. 225-230. 

White, D. E., 1957, Magmatic, connate, and metamorphic 

Waters: Geol. Soc. America Bull., v. 68, p. 1659-1682. 

--- 1965, Saline waters of sedimentary rocks: Am. Assoc. 

Petroleum Geologists Mem. No. 4, p. 342-366. 

White, D. E., Hem, J. D., and Waring, G. A., 1963, Chemical 

composition of subsurface waters, in Fleischer, Michael, 

ed., Data of geochemistry [6th ed.]: U.S. Geol. Survey 

Prof. Paper 440-F, 67 p. 

Withington, C. F., 1962, Gypsum and anhydrite in the 

United States, exclusive of Alaska and Hawaii: U.S. 

Geol. Survey Mineral Inv. Resource Map MR-33. 
UNITED STATES MINERAL RESOURCES 

FELDSPAR 

By FRANK G. LEsuRE 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------- Use and economic importance --------------------

Exploitation -------------------------------------

Geologic occurrence ------------------------------

Resources --------------------------------------- Identified and hypothetical resources ----------

Speculative resources ------------------------

Problems for research --------------------------- Selected references --___ ---__ ----_______________ _ 

FIGURE 

25. Graph showing, crude feldspar sold or u~ed by 

producers in the United States, 1900-70, compared with imports of nepheline syenite, 

1937-70 ---------------------------------

ABSTRACT OF CONCLUSIONS 

Page 

217 

217 

217 

219 

220 

221 

221 

221 

221 

222 

Page 

217 

Feldspar is the general name for an important group of 

aluminum silicate minerals used primarily in the glass and 

ceramic industries. Although consumption in the United 

States has more than doubled since 1940, domestic ~erves 

and resources are considered adequate for anticipated demand. Transportation costs are a major factor in the delivered price of feldspar and contribute to the use of substitutes where available. Research problems involve identifying potential source~ nearer to consumers. Demand for 

feldspar in the United States by the year 2000 is expected 

to be three to five times present production. This demand 

is in large part based on the increasing use of container 

glass and will depend partly on the recycling of bottle glass 

and the continued increase in the use of throwaway bottles. 

INTRODUCTION 

and constitute nearly 60 percent of many igneous 

rocks. The principal potassium feldspars, orthoclase 

and microcline, have the same chemical composition 

(KAlSisOs), but different crystal forms. The sodiumcalcium feldspars, called plagioclase, form a complete series of minerals ranging from pure 

NaAlSisOs (albite) to pure CaAl2Sis08 (anorthite). 

The plagioclase minerals between albite and anorthite in order of decreasing sodium content and increasing calcium content are oligoclase, andesine, 

labradorite, and bytownite. Most natural orthoclase 

and microcline contain 10-25 percent NaAlSiaOs, 

and most plagioclase contains 5-15 percent KAlSisOs. 

Intergrowths of orthoclase or microcline with albite 

are called perthite and they are a common constituent of pegmatites. 

Producers and consumers know feldspar as a beneficiated mixture composed of feldspar minerals with 

ideally less than 5 percent but sometimes as much as 

20 percent of quartz, and minor quantities of other 

minerals. Perthitic microcline (potash spar), albite 

(soda spar), and oligoclase (soda-lime spar) are the 

principal types of feldspar mined in the United 

States. 

USE AND ECONOMIC IMPORTANCE 

From 1955 to 1970, about 55 percent of the feldspar sold in the United States was used in glass, 31 

percent in pottery, 4 percent in enamel, and 10 percent in soaps, abrasives, mineral fillers, welding-rod 

coatings, and other miscellaneous uses. Feldspar is 

a source of alumina, soda, and potash for glass. The 

alumina improves workability, retards devitrification, and increases the chemical stability of the finished product. Iron oxide, a coloring agent, is the 

most common undesirable impurity in glass-grade 

Feldspar is the general name for a group of an- feldspars. The maximum acceptable iron-oxide conhydrous aluminum silicate minerals that contain tent of feldspar for flint glass is 0.1 percent, but as 

varying amounts of potassium, sodium, and calcium. much as 0.5 percent is acceptable for green or amber 

The feldspars are important rock-forming minerals glass. Minerals too refractory to melt at temperau.s. GEOL. SURVEY PROF. PAPER 820 

217 
218 UNITED STATES MINERAL RESOURCES 

tures used in glass manufacture are undesirable 

impurities because unmelted fragments appear as 

flaws in finished glass. Specifications for most glass 

manufacture require the feldspar to be ground to 

minus 20 or 30 mesh and not more than 10-20 percent to be ground to minus 140 mesh. Minor amounts 

of feldspar were used in glass as early as 1895 but 

its use in container glass was generally adopted by 

major producers in 1924 and became standard industry practice about 1935. Use of feldspar in the flatglass industry was standard by 1940. A little more 

than 110 pounds of feldspar is used in an average 

ton of glass containers and slightly less than 100 

pounds in a ton of flat glass. 

Feldspar is useful in ceramic batches because it 

fuses at lower temperatures than most of the other 

ingredients, and as a result, it cements crystalline 

phases in some types of ceramic bodies and acts as a 

flux in physicochemical reactions of crystalline 

phases in whiteware. The feldspar, which imparts 

strength, toughness, and durability to the finished 

product, makes up 10-35 percent of the body and 

30-50 percent of the glaze in many types of ceramics. 

The ratio of potash to soda in the feldspar affects the 

firing characteristics, and in general, high-potash 

material is preferred. Feldspar products are available with potash-to-soda ratios varying from 5 to 1 

to less than 1 to 1. A maximum iron-oxide content of 

0.1 percent, specified limit for silica, and absence of 

dark mineral particles are also required. Feldspar 

for most ceramic use is ground to minus 200 mesh. It 

has been used as a separate ingredient in ceramics in 

China since the Tang dynasty (A.D. 621-945) and 

in Europe since the 18th century (Burgess, 1949, p. 

349). 

Uses of feldspar other than in glass and ceramics 

are few, and consumption is small, but use as a 

mineral filler, especially in latex, is growing. The 

most important other uses are in abrasives and 

scouring soaps because of physical properties such 

as cleavage, hardness, and white color. Excellent 

cleavage in two directions provides sharp edges; but 

feldspar hardness, being less than that of glass, 

minimizes damage to glass and glazed whiteware by 

scratching. Feldspar is also used in electric weldingrod coatings as a source of potassium to improve arc 

characteristics and to serve as a flux. It has been 

used in roofing granules and poultry grit and for 

other crushed-stone uses. 

In recent years, various materials have been used 

in the glass and ceramic industries as substitutes for 

feldspar. Chief among these are nepheline syenite, 

aplite, talc, pyrophyllite, electric furnace slag, and 

lithospar. Most nepheline syenites contain too much 

iron oxide for use in glass, but a deposit in Ontario, 

Canada, that is low in iron is mined extensively for 

this purpose. "Aplite" in the glass trade is the name 

for a mixture of plagioclase and microcline produced 

in Amherst and Nelson Counties, Va., by flotation 

methods from anorthosite. Talc replaces feldspar in 

dinnerware and wall tile; pyrophyllite is used instead of feldspar in enamels and wall tile. Electricfurnace slag is used as a substitute source of 

alumina for glass, and lithospar is a naturally occurring mixture of spodumene and feldspar used as a 

flux. 

The United States is or could be self-sufficient in 

feldspar production. In 1970 we imported 3,247 long 

tons, mostly from Canada, and exported about 5,000 

long tons. Reserves are large, and until recently the 

industry operated at only 50-percent capacity. Less 

than 1 percent of the feldspar used in the United 

States is imported, but large amounts of nepheline 

syenite, as a substitute for feldspar in glass and 

ceramics, are imported from Canada. These shipments began in 1936, and in recent years they have 

increased more rapidly than domestic feldspar production (fig. 25). The U.S. production of feldspar 

Ul 

2 

0 

IC) 

z 

0 

.J 

u.. 

0 

~ z 

c{ 

Ul 

:::> 

~ 200 1-

1910 1920 1930 1940 1970 

FIGURE 25.-Crude feldspar sold or used by producers in the 

United States, 1900-1970, compared with imports of 

nepheline syenite 1937-1970. Derivation of domestic feldspar is shown for 1955-70. Data from U.S. Geol. Survey 

and U.S. Bur. Mines, Mineral Resources of the U.S. 

and Minerals Yearbook, 1900-70. 

was about 28 percent of the estimated world production in 1970 (Wells, 1972, p. 2). 
FEL.DSPAR 219 

Principal production of feldspar in the res of the 

world in 1970 is in Europe, close to large arkets 

for glass and ceramics. Major producers a e West 

Germany, the Soviet Union, Italy, France a d Norway; smaller production came from Finland Spain, 

Yugoslavia, Poland, Sweden, and Portugal. In Africa, 

the major producers are the Republic o South 

Africa and Ethiopia; in Asia, Japan, the Phi ippines, 

India, and Korea; in the Western Hem sphere, 

Mexico, Argentina, and Colombia. 

The forecast demand for feldspar in the United 

States in the year 2000, based on a projected growth 

rate of gross national product, is 2-3 milli n tons 

(Cooper and Wells, 1970, p. 983). Demand or feldspar will fluctuate mostly with demand f r glass 

containers, flat glass, and pottery. If a si nificant 

amount of bottle glass is recycled or if th use of 

throwaway bottles decreases, feldspar ne ds will 

decrease. 

EXPLOITATION 

Feldspar was first mined in the United S ates in 

1825. The mineral came from pegmatite b dies in 

Connecticut and was shipped to England fo use in 

ceramics (DuBois, 1940, p. 207). Principal production from 1853 to 1910 was from Connectic t, New 

York, Maine, Pennsylvania, and Maryland. though 

there is a legend that the Indians mined nd sold 

semikaolinized feldspar from western Nort Carolina before 17 44, the first recorded shipme t from 

that State was made in 1911. Within sever I years 

North Carolina became a major producer of eldspar 

and has for many years accounted for at le st half 

of the annual U.S. production. In recent ye rs California, Connecticut, South Carolina, Geor ia, and 

South Dakota have been our other import t feldspar producers. Production fluctuates from year to 

year, but it has in general steadily increas d since 

1940, when use of feldspar in glass became 

(fig. 25). 

Most of the feldspar produced in the Unit States 

until 1946 consisted primarily of perthite a d oligoclase hand-cobbed from coarse-grained peg atites. 

In 1936, the U.S. Bureau of Mines began an investigation of the concentration of feldspar y table 

agglomeration and flotation (O'Meara and others, 

1939). The first commercial plant to produce eldspar 

for glass by flotation began operation a Kona, 

Mitchell County, N.C., in 1946. Use of flotat'on permitted low-cost mining of finer grained p gmatite 

and granite and expanded the potential so rces of 

raw material. Quartz and flake mica are co monly 

byproducts of flotation feldspar. Some flotat on feldspar is also produced as a coproduct in the mining 

of lithium-rich pegmatites, especially in North Carolina. Recent studies by the U.S. Bureau of Mines 

and others have shown the practicability of producing feldspar, quartz, and mica concentrates from 

granitic rocks (Hill and others, 1969) and of utilizing tailings from feldspar plants in North Carolina 

(Redeker, 1970). 

In 1970, about 57 percent of the feldspar used in 

the United States was taken from flotation concentrates, 8 percent was hand sorted, and 35 percent 

was from feldspar-silica mixtures (Wells, 1972, p. 

2). In 1955, these figures were 40, 45, and 15 percent, respectively (fig. 25). 

Feldspar is mined by open-pit and underground 

methods. Most of the mines producing ore for beneficiation are open pits using power equipment and 

yielding 300--800 tons per day. Selective mining is 

done in zoned pegmatites, usually at a rate of less 

than 100 tons a day. The broken rock is sorted by 

hand during loading or on a picking belt. Feldspar 

has also been produced as a byproduct of sheet-mica 

mining, which requires the broken rock to be sorted 

and moved by hand. The number of small producers 

using hand-cobbing methods is decreasing as labor 

and material costs increase; in 1971, only four mills 

in the United States were using hand-cobbed ore. 

Details of the mining, beneficiation, and marketing 

of feldspar are given by Castle and Gillson (1960), 

Cooper and Wells (1970), and Feitler (1967). 

The average price of crude feldspar per long ton 

was $14.87 in 1970 and $9.51 in 1960 (Wells, 1972, 

p. 2). The average price of ground feldspar per 

short ton was $14.60 in 1970 and $13.40 in 1960. 

Prices quoted for ground feldspar for December 

1970 were as follows: North Carolina 20 mesh, flotation, $11.00; 200 mesh, flotation, $20.50--$26.00 

(Engineering and Mining Journal, 1970). 

Transportation cost is an important element in 

marketing feldspar for glass because the delivered 

cost per unit of alumina plus alkalies is the basis 

for determining relative value of competing feldspar 

products. Nepheline syenite from Canada has an 

advantage over feldspar from Southern United 

States in the glass markets of parts of New York, 

New Jersey, Pennsylvania, and Ohio because of its 

greater content of alumina plus alkalies and because 

of more favorable freight rates. The ceramic industry, however, is more concerned with a particular 

feldspar and its effect on the delicate balance of 

ceran1ic mix, plant operation, and product quality. 

In general, one feldspar product cannot be substituted for another in a ceramic mix without extensive 

tests. A ceramic feldspar is sometimes shipped past 
220 UNITED STATES MINERAL RESOURCES 

another producing plant to a consumer who would 

rather pay more freight than change suppliers. 

Environmental problems of feldspar mining are 

standard for a nonmetallic mineral mined by openpit methods. Large dumps may be avoided by better 

coproduct or byproduct recovery, especially of quartz 

sand, mica, or feldspar-silica mixtures. Dust hazards 

also can be avoided. Some open pits may be utilized 

for lakes or reservoirs ; the impounded water should 

generally be clear because sources of feldspar usually 

lack sulfide minerals that produce acid nrine waters. 

GEOLOGIC OCCURRENCE 

Commercial deposits of feldspar are found in some 

pegmatites, many granites and related igneous rocks, 

and certain beach sands and alluvium. Most pegmatites are light-colored coarsely crystalline igneous 

rocks, which are found as lenticular or tabular bodies 

in metamorphic rocks or in large granitic intrusions. 

Individual mineral grains and crystals range in 

length from less than 1 inch to many feet. Pegmatite 

bodies vary in size from small pods and veins to 

large masses hundreds of feet thick and thousands 

of feet long. Feldspar, quartz, and mica are the most 

common minerals present, but many rare and unusual minerals are found in some deposits. In many 

pegmatite bodies the minerals are somewhat evenly 

distributed throughout, but in others the minerals 

are segregated into certain layers or parts of the 

body, called zones. These zones can sometimes be 

selectively mined to recover the desired minerals by 

hand sorting and are, therefore, important economically. Most of the feldspar produced in the United 

States before 1946 was perthite, which commonly is 

abundant as very large crystals in the intermediate 

zones or cores of zoned pegmatite bodies. 

The principal pegmatite districts in the United 

States are in New England, especially Maine, New 

Hampshire, and Connecticut, in the Appalachian 

Piedmont from Virginia to Alabama, and in the 

Blue Ridge Mountains in North Carolina and Georgia. Smaller districts are in the Black Hills of South 

Dakota, the Front Range of Colorado, several areas 

in northern New Mexico, western Arizona, and 

southern California ; minor districts are in Nevada, 

Montana, Wyoming, Idaho, and Washington (Cameron and others, 1949; Jahns, 1955). 

Granite and related igneous rocks are composed 

of one or two kinds of alkalic feldspar ; quartz ; and 

minor amounts of various other minerals, mainly 

muscovite, biotite, hornblende, or rarely pyroxene. 

Feldspar content ranges from 50 to 70 percent, and 

grain size from less than one-fourth inch to about 

an inch. Deposits range from small masses measured 

in feet to very large masses measured in miles. 

Granitic rocks such as alaskite, that contain only 

small amounts of ferromagnesian minerals, locally 

are mined in bulk and a mixture of potassium and 

sodium feldspar recovered by milling and flotation. 

Mixtures of feldspar and quartz are also produced as 

byproducts of granite quarrying. 

Granites are common igneous rocks that occur 

widely in the crystalline terranes of the world. Large 

granitic bodies in the United States are scattered 

throughout New England ; the older Appalachians 

from New York to Alabama; the Llano area, Texas ; 

northern Wis·consin and adjacent Michigan; northern Minnesota; the St. Francois Mountains, Mo. ; the 

Black Hills of South Dakota; the Rocky Mountains 

from New Mexico to Wyoming; and in isolated 

mountain ranges of Arizona, Utah, and Nevada. 

Large batholithic intrusions are in California, Idaho, 

Montana, and Washington. 

Feldspathic beach sands and alluvial deposits may 

be rich enough to be mined for their feldspar content. The dune sands of Pacific Grove, Monterey 

County, Calif., which have been worked extensively, 

contain about 53 percent quartz, 46 percent feldspar, and less than 1 percent other minerals in an 

area about 6 miles long and 1 mile wide. Alluvial 

deposits along the Mississippi, Illinois, Wabash, and 

Ohio Rivers and dune and beach sands of Pleistocene 

age in Illinois contain 5--25 percent feldspar, 2-12 

percent feldspathic rock fragments, 60-80 percent 

quartz, and some chert and heavy minerals. The 

alluvial sand3 are in low river terraces, in present 

channels, and in sandbars (Hunter, 1965). Similar 

deposits along the Kansas, Arkansas, Little Arkansas and Republican Rivers in Kansas contain as 

much as 27 percent feldspar. 

Authigenic potash feldspar has been reported 

from many sedimentary rocks of various lithologies 

and ages (Sheppard and Gude, 1965, p. 6). Feldspar 

content may range from less than 10 percent in 

some shales and siltstones to as much as 90 percent 

in some tuffaceous beds. Recent work on Cenozoic 

tuffs in saline lake beds in California, Oregon, Nevada, and Arizona has shown a definite zonal pattern 

to these deposits (Sheppard and Gude, 1968; Sheppard and Walker, 1969). At the margins of former 

lakes, most of the tuff beds contain unaltered glass 

and grade into a zeolite facies toward the middle 

of the lakes; however, near the centers of the lakes 

in areas of higher salinity nearly pure beds of 

potash feldspar are found. The deposits studied to 

date contain more iron and are finer-grained than 

is desired for glass feldspar. The tuff beds, however, are 2-8 feet thick and may cover tens of square 
FELDSPAR 221 

miles and so significant tonnages of nearly pure 

potash feldspar may be present in California in the 

Barstow Formation of Miocene Age, San Bernardino 

County, and in Lake Tecopa, Inyo County (Sheppard 

and Gude, 1965, 1968). 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Identified and hypothetical resources of feldspar 

in the United States are large enough to meet any 

anticipated demand, but quantitative data are not 

available for calculations on reserves. A recent estimate by the Bureau of Mines (Cooper and Wells~ 

1970, p. 985) of our feldspar reserves is 500 million 

long tons of material similar to that being mined in 

1970. Reserves in the Spruce Pine district of North 

Carolina alone exceed 200 million tons of material 

within 50 feet of the surface (Brobst, 1962, p. A15). 

Immense hypothetical resources of feldspar exist in 

granitic rocks exposed in the igneous and metamorphic terranes of the United States and many 

other countries. Although almost any granite can 

be used, those that contain few ferromagnesian 

minerals, such as the alaskite of Spruce Pine, N.C., 

are the most satisfactory. The average granite body 

is generally thousands of feet to several miles wide 

and may contain 60 percent or more feldspar plus 

potential byproduct quartz and flake mica. 

Reserves and resources of feldspar in pegmatites 

are difficult to estimate. Many deposits of high-grade 

potash feldspar in zoned pegmatites have been 

worked out, but most of these were in pegmatite 

bodies exposed at the surface. It is safe to assume 

that the present surface is a random sample of 

what exists at shallow depths, less than 500 feet, 

and therefore our undiscovered resources of feldspar in zoned :(:egmatites not exposed but within 

minable depth are equal to the amount already 

mined, that is, more than 8 million tons. Prospecting 

for these deposits will not be easy, but detailed geologic mapping, geophysical techniques, drilling, and 

possibly geochemical methods can be used. Because 

of the availability of resources of fine-grained feldspar and the low prices of crude ore, the additional 

expense in exploring for more zoned pegmatites is 

probably not justified at this time. 

Domestic and foreign reserves and resources of 

feldspar in feldspathic sands are also large. Such 

deposits may contain from 20 to at least 50 percent 

feldspar, at least 50 percent quartz, and only minor 

amounts of other minerals. Deposits may cover many 

acres or even square miles. Unlike nearly all other 

mineral deposits, alluvial sands dredged from stream 

channels are renewable. Such deposits are becoming more desirable, not only because they can be 

mined inexpensively, but also because they can be 

used as feldspar-silica mixtures with very little 

beneficiation. A few deposits of this type have been 

studied and several are being mined, but many more 

probably exist. Recent mapping by the U.S. Geological Survey in southern Delaware and adjacent 

Maryland has outlined a large outcrop area of the 

Beaverdam Sand, a feldspathic marine sand of Pleistocene age (J.P. Owens, written commun., 1972). 

Preliminary studies indicate a feldspar content as 

high as 50 percent of equal amounts of plagioclase 

and microcline. The sand has a known thickness of 

80-90 feet and is exposed in an area of about 1,800 

square miles. 

Resources of authigenic feldspar are very large, 

but until further study is made of the uses of such 

material, these deposits are only a potential resource. 

SPECULATIVE RESOURCES 

Identified and hypothetical resources of feldspar 

are so large that little thought has been given to 

speculative resources. The basic types of igneous 

feldspar deposits, the coarse-grained feldspar in pegmatite and the finer grained in granite, occur in 

igneous and metamorphic terranes, most of which 

are probably identified in much of the world. A few 

additional districts may be found in areas not yet 

mapped. The distribution of detrital and authigenic 

feldspar in sediments is not so well known, and the 

possibility of discovery of new districts is probably 

greater than for the igneous deposits~ Speculative 

resources of both types are probably large, but 

prospecting and resource study will be concentrated 

more on the known districts or in areas nearest to 

markets because of the high cost of transportation 

and the low value of the commodity. 

PROBLEMS FOR RESEARCH 

Even though existing sources of feldspar are large, 

continued evaluation of potential sources should be 

made during regional geologic mapping. Because 

transportation costs make up a major part of the 

delivered cost of feldspar, the most pressing need 

in the United States is for discovery of supplies 

closer to consuming areas, especially in the Central 

States. Possible sources in that area-in feldspathic 

sands and granites-have been outlined, but additional work is needed on technical feasibility, economic evaluation of markets, and byproduct recovery. Geologic mapping may outline additional or 

more economic sources in the Central States. 
222 UNITED STATES MINERAL RESOURCES 

SELECTED REFERENCES 

Brobst, D. A., 1962, Geology of the Spruce Pine district, 

Avery, Mitchell, and Yanc.eyCounties, North Carolina: 

U.S. Geol. Survey Bull. 1122-A, p. A1-A26. 

Brown,- W. R., 1962, Mica and feldspar deposits of Virginia: 

Virginia Div. Mineral Resources, Mineral Resources 

Rept. 3, 195 p. 

Burgess, B. C., 1949, Feldspar, in Industrial Minerals and 

Rocks, [2d ed.]: New York, Am. Inst. Mining, Metall. 

Engineers, p. 345-373. 

Cameron, E. N., Jahns, R. H., McNair, A. H., and Page, 

L. R., 1949, Internal structure of granitic pegrnatites: 

Econ. Geology Mon. 2, 115 p. 

Castle, J. E., and Gillson, J. L., 1960, Feldspar, nepheline 

syenite, and aplite, in Industrial Minerals and Rocks, 

[3d ed.]: New York, Am. Inst. Mining, Metall. and 

Petroleum Engineers, p. 339-362. 

Cooper, J. D., and Wells, J. R., 1970, Feldspar, in Mineral 

facts and problems: U.S. Bur. Mines, Bull. 650, p. 977-

988. 

DuBois, H. B., 1940, Development and growth of the feldspar 

industry: Am. Ceramic Soc. Bull., v. 19, no. 6, p. 206-

213. 

Engineering and Mining Journal, 1970, Nonmetallic minerals, 

in Miscellaneous Metals: Eng. and Mining Jour., v. 

171, p. 22-28. 

Feitler, S. A., 1967, Feld·spar resources and marketing in 

eastern United States: U.S. Bur. Mines Inf. Circ. 8310, 

41 p. 

Hill, T. E., Jr., Kenworthy, H., Ritchey, R. A., and Gerard, 

J. A., 1969, Separation of feldspar, quartz, and mica from 

granite: U.S. Bur. Mines Rept. Inv. 7245, 25 p. 

Hunter, R. E., 1965, Feldspar in Illinois sands-a further 

study: Illinois State Geol. Survey Circ. 391, 19 p. 

Jahns, R. H., 1955. The study of pegrnatites, in pt. 2 of Bateman, A. M., ed., Economic Geology, 50th anniversary 

volume, Urbana, Ill., Economic Geology Pub Co., p. 

1025-1130. 

Norton, J. J., and Page, L. R., 1956, Methods used ro determine grade and reserves of pegrnatites: Mining Engineering, v. 8, no. 4, p. 401-414. 

O'Meara, R. G., Norman, J. E., and Hammond, W. F., 1939, 

Froth flotation and agglomerate tabling of feldspar: 

Am. Ceramic Soc. Bull., v. 18, no. 8, p. 286-292. 

Parker, J. M., III, 1948, New Jersey's potential feldspar 

resource·s: Rutgers Univ. Bur. Mine.ral Research, Bull. 

5, pt. 1, 66 p. 

--- 1950, Feldspar and mica deposits of Southeastern 

United States, in Snyder, F. G., ed., Symposium on 

mineral resources of the Southeastern United States: 

Knoxville, Tenn., Tennessee Univ. Press, p. 42-48. 

Redeker, I. H., 1970, North Carolina feldspar flotation and 

solutions to waste disposal problems [abs.] : Mining 

Eng., v. 22, no. 1, p. 42; preprint for AIME annual 

meeting no. 7-H-83, 17 p. 

Sheppard, R. A., and Gude, A. J ., 3d., 1965, Potash feldspar 

of possible economic value in the Barstow Formation, 

San Bern:ardino County, California: U.S. Geol. Survey 

Circ. 500, 7 p. 

--- 1968, Distribution and genesis of authigenic silicate 

minerals in tuffs _of Pl·eistocene Lake Tecopa, lnyo 

County, California: U.S. Geol. Survey Prof. Paper 597, 

38 p. 

Sheppard, R. A., and Walker G. W., 1969, Potassium feldspar 

in Mineral and water resources of Oregon: U.S. 90th 

Gong., 2d sess., Senate Comm. Interior and Insular 

Affairs, p. 268-272. 

Trauffer, W. E., 1965, Georgia crushed granite firm makes 

feldspar-quartz by-p·roduct: Pit and Quarry, v. 58, no. 

2, p. 97-100. 

Wells, J. R., 1972, Feldspar, nepheline syenite and aplite, 

in Minerals Yearbook, 1970, v. 1, Metals minerals and 

fuels: U.S. Bur. Mines, 8 p. (preprint). 
UNITED STATES MINERAL RESOURCES 

FLUORINE 

By R. G. WoRL, R. E. VAN ALSTINE, and D. R. SHAWE 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------

Exploitation -------------------------------------

Geologic environn1ent -----------------------------

Geochemistry -------------------------------- Fluorine deposits associated with igneous rocks _ 

Fluorine deposits associated with sedin1entary 

rocks--------------------------------------

Fluorine deposits associated with metamorphic 

rocks -------------------------------------- Fluorine in hydrothermal deposits -------------

Resources --------------------------------------- Identified and hypothetical resources -----------

Speculative resources -------------------------

Prospecting techniques ---------------------------

Problems for research ---------------------------- References cited 

FIGURE 

26. Graph showing world production, 1913-70, U.S. 

production, 1900-70, and U.S. consumption, 

Page 

223 

223 

224 

224 

224 

226 

227 

228 

228 

230 

230 

231 

232 

233 

233 

Page 

1911-70, of fluorspar ---------------------- 225 

TABLE 

Page 

44. Estimated fluorspar resources of the world ___ 230 

ABSTRACT OF CO~CLUSIONS 

Fluorine is used by industry mainly as fluorspar (CaF2) 

for flux in steel making; as synthetic cryolite (NaaAlF6) and 

alun1inum fluoride in the manufacture of aluminum n1etal; 

and as fluorocarbons in refrigerants, aerosol propellants, 

solvents, and many other compounds. Fluorine consumption 

in the United States and the world has increased greatly 

since World War II, while fluorine production in the United 

States has remained static. The United States produces only 

20 percent of its requirement at the present. 

Fluorine in nature is dominantly in the combined form 

and tends to concentrate in specific geologic environments. 

Preferred igneous associations are silicic and alkalic extrusives and intrusives, con1plex pegmatites, carbonatites, and 

contact aureoles of these. Sedimentary rocks containing concentrations of fluorine are volcaniclastic, lacustrine, evaporite, marine carbonate, and marine phosphorite beds. Major 

concentrations of fluorine occur in hydrothermal fluorspar 

deposits. Hydrothermal deposits are distributed among a 

wide variety of geologic environments in the form of veins, 

mantos, stratiform beds, pipes, stockworks, and alteration 

zones. 

Commercial sources of fluorine to date have been dominantly hydrothermal deposits of fluorsp·ar. Additional sources 

in the future will be as byproducrts from ores of other commodities, as coproducts of multicommodity ores, and from 

fluorine deposits other than hydrothermal. A major future 

source of fluorine will be as a byproduct of the processing 

of phosphate rock, because fluorapatite (Cas(P04,C0a)2F) 

is the major component of phosphate rock. 

World reserves of fluorspar (50 percent CaF2) are estimated to be 190 million short tons, of which 25 million are 

in the United States. Speculative resources of fluorine in 

the world are probably very large. 

INTRODUCTION 

Fluorine, a versatile element, is widely used in 

many industries and will probably remain in great 

demand in the future. Present and potential sources 

of fluorine are the major fluorine-bearing minerals 

fluorite, cryolite, fluorapatite, and topaz. In this 

report attention will be given mainly to fluorspar, 

the ore of the mineral fluorite, until recently virtually the only commercial source of fluorine. Synthetic cryolite now has commercial value, but with 

minor exceptions, other fluorine-bearing minerals 

have not had commercial value. 

Fluorspar is marketed in three grades; acid, 

ceramic, and metallurgical (Hodge, 1971, p. 10). 

Acid-grade fluorspar contains a minimum of 97 percent CaF2 and a maximum of 1.5 percent Si02. Limits are commonly placed on other common impurities-CaC03, sulfide sulfur or total sulfur, iron, 

lead, zinc, and phosphorus. Ceramic-grade fluorspar 

U.S. GEOL. SURVEY PROF. PAPER 820 

223 
224 UNITED STATES MINERAL RESOURCES 

varies according to consumer demands but generally 

contains 85-96 percent CaF 2 and has limits on Si02, 

CaC03, Fe203, sulfide sulfur, lead, and zinc. Metallurgical-grade fluorspar (metspar) is commonly 

listed in market quotations as 60, 70, and 72.5 effective CaF 2 units ; effective CaF 2 unit is a measure 

obtained by multiplying the Si02 content of the ore 

by 2.5 and subtracting this figure from the CaF 2 

content of the ore. Specifications for metspar usually 

set maximum limits of 0.3 percent sulfide sulfur and 

0.25-0.5 percent lead. Consumers desire metspar in 

the form of lumps or gravel having no fines and a 

maximum size of about 2 inches. Pellets and briquets 

made from fines and flotation concentrates are now 

replacing lump and gravel metspar in the United 

States. It is significant from an economic standpoint 

that metspar is used virtually as it occurs in nature, 

ftuorite (CaF2) plus impurities. 

Fluorspar as a flux in steel making accounts for 

33 percent of the U.S. fluorine demand; fluorspar 

as an iron foundry flux, a nonferrous metals flux, 

and an additive in electrometallurgy accounts for 

8 percent. Several possible substitutes for fluorspar 

in steel fluxing have been tried, including calcium 

chloride, bauxite and colemanite (hydrated borate 

of calcium). None of these appears to be usable on 

a large scale, but a concentrated effort is being 

made by the steel industry to develop a usable synthetic flux. 

Cryolite (Na3A1Fe) and synthetic aluminum fluoride are essential in the manufacture of aluminum 

metal. Most cryolite used is synthetic and is made 

by combining caustic soda, alumina, and hydrofluoric acid, or is prepared from waste solutions 

containing 15-25 percent fluosilicic acid recovered 

in manufacture of superphosphate. 

Natural or synthetic cryolite is the major flux 

used in reducing alumina to aluminum metal in 

electrolytic cells, and this use accounted for about 

18 percent of the U.S. fluorine demand in 1968. Not 

all the fluorine is lost in this process, and progress 

is being made in recovering some of the fluorine 

volatilized or wasted. This practice may reduce 

slightly the acid-grade fluorspar requirement from 

the present 135 pounds per ton of aluminum produced. The use of lithium carbonate as an additive 

in aluminum manufacture also seems tO' reduce the 

fluorine consumption. 

Fluorine consumed in the United States is mainly 

in the form of fluorspar, 44 percent; hydrofluoric 

acid (fluorocarbons), 35 percent; hydrofluoric acid 

(cryolite), 18 percent; and fluosilicates, 3 percent 

(MacMillan, 1970, p. 993). The production of fluorocarbon compounds has only recently reached its 

present consumption level and will probably remain 

a major consumer of fluorine for some time. Fluorocarbon compounds are used in many ways-refrigerants, aerosol propellants, solvents, and special-use 

plastics-and demand for fluorine is expanding 

rapidly as new uses of these unique compounds are 

developed. Fluorocarbons conceivably could be replaced in part by liquid nitrogen and compressed 

gaseous nitrogen, which are readily available now 

as byproducts of liquid-oxygen production. Fluorine 

used in the ceramic, glass, welding-rod, and enamel 

industries constituted about 6 percent of the U.S. 

fluorine demand in 1968. 

In 1970 the United States accounted for about 6 

percent of the world's production of fluorspar but 

consumed 30 percent of this production. Thus in 

that year the United States produced only 20 percent of the fluorspar it consumed; the other 80 percent was imported mainly from Mexico, Spain, and 

Italy. In the recent past the United States produced 

only 15 percent of its consumption of fluorine; the 

1970 increase probably reflects in part the release 

by the U.S. Government of large amounts of stockpiled acid-grade fluorspar. 

EXPLOITATION 

Until recently, fluorspar was virtually the only 

source of fluorine, and it will probably remain the 

major source in the near future. A relatively minor 

amount of the fluorine consumed is at present being 

recovered from the processing of phosphate rock, 

which, along with other byproduct and coproduct 

sources, will become increasingly important in the 

future. Though data are not readily available, the 

amounts of byproducts recovered from fluorspar 

mining in the past apparently were not significant. 

Sulfide concentrates-mainly lead, zinc, and silverare recovered in some operations, and barite is recovered as a coproduct in a few operations. 

Since World War II (fig. 26) world fluorspar production and U.S. fluorspar consumption have increased greatly, whereas U.S. production has 

remained nearly static. The great increase in fluorspar consumption reflects the worldwide increased 

production of steel and aluminum and the utilization of fluorocarbons in many new industries. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Fluorine (atomic number 9, atomic weight 19) 

consists of a single isotope occurring in nature 

mostly as a singly charged anion, F-, but also occasionally as a compound of complex anions, such 

as (BF 4) -. Fluorine is a gaseous element, and large 
FLUORINE 225 

4500 

4000 

0:: 

<t: 

ll. 

(/) 

0:: 3500 0 

::::> 

...I 

LL 

~ 3000 

0 

.... 

.... 

0:: 

0 

:I: 

(/) 

LL 

0 

(/) 

0 

z 

<t: 

C/) 

::::> 

0 

:I: 

.... 

2500 

2000 

1500 

0~~~----~----~~---L----~~~~--_j 

1900 1910 1920 1930 1940 1950 1960 1970 

FIGURE 26.-World production, 1913-70, U.S. production, 

1900-70, and U.S. consumption, 1911-70, of fluorspar 

(CaF,). 

amounts of gaseous fluorine are given off in some 

active volcanie areas. Most fluorine in nature, however, is found combined in solid form. The radius 

of the fluoride ion F- (1.33 A) is very close to that 

of the hydroxyl ion (OH)- (1.33 A) and the oxygen 

ion 0-2 (1.32 A), and with proper valence conditions, diadochic substitution of F- for (OH)- or 

0-2 is relatively simple. Fluorine in the lithosphere 

therefore is tied up as an essential element in fluoride minerals or as a substitute in other minerals, 

mainly silicates and phosphates. Fluorite, CaF 2, is 

geologically the most abundant and economically the 

most important fluoride. Some other fluorides of 

possible economic significance are cryolite, N aaAlF 6 ; 

sellaite, MgF2; villiaumite, NaF; and bastnaesite, 

(Ce,La) (COa) F, whereas other, still less common 

fluorides will probably be of little economic significance in the future. Fluorine occurs in many silicate minerals, including tourmaline, topaz, and the 

micas phlogopite, zinnwaldite, lepidolite and biotite, 

and in the phosphates monazite, xenotime, fluorapatite, and amblygonite. Fluorapatite, Ca5 (P04,COa)aF, 

and topaz, Al2Si04 (F,OH) 2, are of economic significance. 

The organic chemistry of fluorine in terms of 

fluorosis and fluorocarbons is well understood; the 

geochemistry of fluorine is not. The distribution of 

fluorine in the earth's crust can be noted but not adequately explained. Crustal abundance is difficult to 

determine. Fleischer and Robinson (1963, p. 67) 

reported a value of 650 ppm (parts per million) 

fluorine for the average content of the continental 

rocks of the earth's crust. They also gave the following mean values, in parts per million, for various 

rock types: basalt, 360; andesite, 210; rhyolite, 480; 

phonolite, 930; gabbro and diabase, 420; granite and 

granodiorite, 870 ; alkalic rocks, 1,000 ; limestone, 

220; dolomite, 260 ; sandstone and graywacke, 180; 

shale, 800 ; oceanic sediment, 730 ; and soil, 285. The 

geochemical cycle of fluorine and the problems associated with fluorine determinations were discussed 

by Fleischer and Robinson (1963) and Barth 

(1947). 

Although fluorine is widespread throughout the 

lithosphere, biosphere, and hydrosphere, it tends to 

be concentrated in fairly specific environments. In 

igneous activity fluorine is considered as a characteristic component of the volatile phase of magmatic 

differentiation. More specifically fluorine is concentrated in alkalic and silicic hypabyssal and extrusive rocks and related hydrothermal deposits, in 

complex pegmatites, in carbonatites, and in alteration zones, including greisens, associated with alkalic, silicic and carbonatite intrusive rocks. 

Fluorine becomes concentrated in sedimentary environments largely by precipitation as fluorite, other 

fluorides, or fluorapatite during accumulation of the 

sediments or during their subsequent diagenesis. 

These minerals are not common as detrital components of the rocks. Five general groups of sedimentary deposits contain concentrations of fluorine: 

volcaniclastic, lacustrine, evaporite, marine carbonate, and marine phosphate beds. 

Fluorine is a common but variable constituent of 

gases and waters of volcanic origin, mainly as HF 

but also as F 2, SiF4' and H2SiF s· Volcanic exhalations contribute large quantities of fluorine to the 

surface environment. For example, Zies ( 1929) estimated that at one time the Valley of Ten Thousand 

Smokes, Alaska, was releasing HF at the rate of 

200,000 tons annually. 

The fluoride content of ground water ranges from 

zero to a maximum recorded value of 67.2 ppm, and 

few waters contain more than 10 ppm. Large areas 

of the world, however, locally have ground waters 

containing more than 1.5 ppm F. The fluoride content of ground water depends in part upon the 

nature of the bedrock. Alkalic igneous rocks, dolo-
226 UNITED STATES MINERAL RESOURCES 

mites, phosphorites, and, especially, ' volcanic glass 

give rise to high fluoride waters. 

Surface waters vary greatly in fluoride content 

depending upon source of the water and amount of 

rainfall, the fluoride content generally being higher 

in dry periods. Fleischer and Robinson (1963) gave 

0.2 ppm as the average fluoride content of rivers. 

This figure also is probably close to that for freshwater lakes. Highly saline lakes, on the other hand, 

have much higher fluoride contents: 14 ppm is reported for Great Salt Lake, Utah, and as much as 

1,627 ppm for lakes in Kenya. 

Individual species of plants contain variable quantities of fluorine depending upon the amounts they 

need for growth and the amounts available in the 

soil or air. Some plants can be classed as fluorine 

accumulators, and some plants increase in fluorine 

content with age. Other plants accumulate fluorine 

from the air only. All these factors must be considered if fluorine in plants is to be used in exploration for ore deposits. 

Fluorine deposits of past and present significance, 

of probable future significance, and of possible future significance are classified into the following 

four groups, which, although they overlap and intergrade somewhat, provide a convenient basis for 

further discussion. 

1. Fluorine deposits associated with igneous rocks. 

Includes disseminated deposits, deposits in 

pegmatite and carbonatite, and deposits in contact aureoles. 

2. Fluorine deposits associated with sedimentary 

rocks. Includes those in volcaniclastic and lacustrine sedimentary rocks and those in evaporite, marine carbonate, and phosphorite rocks. 

3. Fluorine deposits associated with regionally 

metamorphosed rocks. 

4. Fluorine in hydrothermal (hot water) deposits. 

Includes those in veins and mantos, in pipes 

and stockworks, and in zones of alteration. 

FLUORINE DEPOSITS ASSOCIATED WITH 

IGNEOUS ROCKS 

Fluorine deposits associated with igneous rocks 

contain fluorine minerals that are considered to be 

genetically related to the igneous rocks. These deposits include accessory fluorine minerals disseminated through the igneous rock and fluorine minerals 

in pegmatites, carbonatites, and contact aureoles of 

intrusive rocks. Fluorine-bearing igneous rocks of 

possible future economic significance are hypabyssal bodies and extrusive rocks, generally of alkalic 

or silicic-alkalic composition, and plutonic rocks of 

silicic composition. Topaz and fluorite occur in some 

silicic volcanic rocks of the Western United States 

(Shawe, 1966, p. C209), where they are dispersed 

through the rock and concentrated within vugs .. 

Stocks of alkalic rocks in the Western United States 

and in many other parts of the world contain fluorite 

and, in places, topaz as accessory minerals. Fluorite 

also is a common constituent of batholithic rocks of 

granite composition in South Africa, Newfoundland 

(Van Alstine, 1944), the United States, Eastern 

Mongolia (Khasin and Kalenov, 1965), and many 

other parts of the world. Although large amounts of 

fluorine occur in these rocks, the tenor is low, generally less than 2 percent CaF 2• 

Some pegmatites and carbonatites are mined for 

their fluorine content. Pegmatites commonly contain 

local concentrations of fluorite and other fluorides, 

but not in large volume. Most fluorite mined from 

pegmatites has been used as specimens or for optical 

purposes. However, the fluorspar deposits at Crystal 

Mountain, Mont., and the cryolite deposits at Ivigtut, Greenland, are both considered to be almost 

monomineralic pegmatites. The Crystal Mountain 

deposits are mainly fluorite but have minor amounts 

of biotite, quartz, feldspar, sphene, rare-earth-bearing apatite, amphibole, fergusonite, thorianite, and 

thortveitite (Parker and Havens, 1963). This deposit is exceedingly rich and has yielded a substantial amount of fluorspar since production began in 

1952. The deposit at Ivigtut, Greenland, is largely 

cryolite but also contains complex fluorides, fluorite, 

microcline, topaz, columbite, siderite, sphalerite, 

galena, and chalcopyrite. 

Carbonatite complexes are notably enriched in 

fluorine, which is mostly dispersed through the rock 

in silicates and apatite. Economic fluorine deposits 

associated with carbonatite complexes are contactzone deposits and late-stage hydrothermal veins. 

Deposits at Okorusu in South West Africa and at 

Amba Dongar, India, are of this type (Deans and 

others, 1972). Apatite-bearing carbonatite rock is 

the principal source of phosphate in southern and 

eastern Africa. The apatite rocks, of which there are 

considerable reserves, contain 1-3 percent fluorine 

(Deans, 1966, p. 393). Apatite-bearing carbonatite 

rock near J acupiranga, Sao Paulo, Brazil, being 

mined for phosphate, contains 4-5 percent fluorine 

(Abreu, 1960, p. 123), and apatite-bearing carbonatite rocks in the U.S.S.R. are a present source of 

fluorine; the fluorine is recovered as a byproduct of 

fertilizer production. Carbonatite at Mountain Pass, 

Calif., contains at least 1 percent fluorine, mostly in 

bastnaesite (Olson and others, 1954). 

Fluorite, topaz, and apatite are common minerals 

in contact aureoles around many intrusive bodies, 
FLUORINE 227 

mainly silicic and alkalic rocks and carbonatite complexes. The fluorine minerals occur in tactite and in 

posttactite hydrothermal veins and replacement 

bodies. Contact-zone fluorspar deposits, mined in 

Korea and Japan, are generally small podlike bodies 

about 20 meters long, 10-15 meters wide, and 10 

meters high. The deposits in Korea are replacement 

bodies in limestone at the contact with younger 

"granites" and are of two types: a low-temperature 

type consisting mainly of fluorite, quartz, and coarsely crystalline calcite, and a high-temperature type 

consisting of epidote and calc-silicates in addition to 

fluorite, quartz, and calcite (Gallagher, 1963, p. 93). 

Both types contain some sulfides. 

Fluorspar deposits associated with the Okorusu 

complex in South West Africa are veins and replacement bodies in the contact aureole of carbonatite 

intrusives. At Amba Dongar, India, the main economic concentrations of fluorite occur as veins and 

replacement bodies in carbonate wallrock around 

late-stage ankeritic carbonatite intrusives which are 

also fluorite-bearing (Deans and others, 1972, p. 

B6) . Fine-grained cherty quartz and minor amounts 

of barite, dickite, galena, pyrite, and chalcopyrite 

are associated with fluorite at Amba Dongar. Metasomatic phlogopite rocks around carbonatite plugs 

in Zambia, Malawi, and Rhodesia contain anomalous 

amounts of fluorine. The fluorine in these dull-gray 

rocks is contained largely in fluor-phlogopite, but 

some occurs in sellaite (Deans and others, 1972, 

p. B6). 

FLUORINE DEPOSITS ASSOCIATED WITH 

SEDIMENTARY ROCKS 

Some fluorine deposits in sedimentary rocks appear to be genetically related to the enclosing sediments, but some of the deposits may be of hydrothermal or metasomatic origin. They occur in volcaniclastic sedimentary rocks; lacustrine deposits; 

and evaporite, marine-carbonate, and marine-phosphate rocks. Fluorine minerals generally do not occur in detrital accumulations of economic value. 

Although volcanic ash commonly contains fluorine 

in glass shards and absorbed on tephra, commercial 

or potential deposits of fluorine in volcaniclastic 

sedimentary rocks seem to be either disseminated 

deposits of probable hydrothermal origin or interbedded deposits of lacustrine origin. Fluorite-beryllium deposits in altered volcaniclastic sedimentary 

rocks near Spor Mountain, Utah, described later in 

this chapter, are considered to be of hydrothermal 

origin. Fluorspar deposits near Rome, Italy, and 

Rome, Oreg., are lacustrine deposits interbedded 

with volcaniclastic sedimentary rocks. 

Fluorspar deposits in unconsolidated tuffs near 

Rome, Italy, are lenses composed of finely crystalline 

fluorite, barite, calcite, dolomite, apatite, opal, and 

chalcedonic quartz and minor amounts of detrital 

minerals and volcanic glass. The fluorite content of 

some zones averages 55 percent. These lenses are 

thought to be sedimentary deposits of chemical 

origin formed in lake basins that were subject to 

emanations of hydrothermal fluids rich in fluorine, 

calcium, barium, strontium, silicon, sulfur, and 

phosphorus (Spada, 1969). 

Near Rome, Oreg., fluorite occurs as submicroscopic, nearly spherical grains in tuff, tuffaceous 

mudstone, and mudstone of Tertiary lacustrine deposits. Fluorite content is generally less than 5 percent but is as much as 16 percent in some zones. 

According to Sheppard and Gude ( 1969, p. D69) the 

"fluorite probably formed during diagenesis in sediments that had been deposited in an alkaline, saline 

lake." 

Some lacustrine brines and evaporites contain concentrations of fluorine; the best examples are the 

brines and recent evaporites of lakes in the rift valleys of Africa, where lake waters contain as much 

as 1,627 ppm fluorine. The evaporite sequence of 

Lake Magadi, Kenya, composed largely of trona, 

locally contains as much as 22 percent villiaumite 

(NaF), and fluorite is common throughout much of 

the sequence (Sheppard and Gude, 1969, V· D73). 

In the U.S.S.R., possible economic concentrations 

of fluorine in marine carbonates and evaporites of 

the Permian Preurals have been noted (Abramovich 

and Nechayev, 1960). Fluorite occurs as a fine dissemination and as crystalline aggregates in vugs in 

dolomitized limestone. The CaF 2 content of some 

zones exceeds 30 percent. In the United States a 

minor occurrence in Permian <;folomitic limestones of 

the Rocky Mountains contains 12-15 percent CaF 2• 

In marine carbonates of the U.S.S.R., as noted by 

Kazakov and Sokol ova ( 1950), fluorite is related to 

the saline facies of relict basins, mainly to dolomite, 

dolomitized limestones, gypsum, redrocks, anhydrite, 

potassium and magnesium salts, and celestite. According to them (p. 68 of the English translation) 

the fluorite was precipitated from sea water that 

had been concentrated three to four times, and continued to precipitate from the brine in a dying sea 

basin where potassium salts and borates were being 

deposited. 

The ore mineral of sedimentary phosphate rock is 

carbonate fluorapatite with ratio ofF to P20s about 

1 to 10. Phosphate rock contains as much as 4 percent F and 40 percent P 20s, although lower grade 

deposits are now mined for their phosphate content. 
228 UNITED STATES MINERAL RESOURCES 

Plants in eight countries are recovering fluorine as a 

byproduct (Wood, 1972). The fluorine in phosphate 

rock could have been part of the original precipitate, 

or, inasmuch as calcium phosphate or calcium 

hydroxy-phosphate can collect fluorine from very 

dilute solutions, it could have been introduced later. 

(See also the chapter in this volume entitled 

"Phosphates.") 

FLUORINE DEPOSITS ASSOCIATED WITH 

MET AM ORPHIC ROCKS 

Topaz and tourmaline are common in metamorphic rocks and may represent future sources of 

fluorine. For example, a Precambrian topaz-quartzsillimanite gneiss in the central part of the Front 

Range, Colo., contains major amounts of topaz 

(Sheridan and others, 1968). This unit, part of a 

high-grade metamorphic gneiss and granitic plutonic 

complex, is 11-100 feet thick and crops out along 

strike for 7,000 feet. Three composite chip samples 

of this unit were found to contain 67, 23, and 36 

weight percent topaz and 4.2, 3.9, and 2.2 weight 

percent rutile. The gneiss may warrant investigation 

as an ore of rutile, especially since it might also yield 

topaz or topaz and sillimanite as byproducts (Sheridan and others, 1968). 

FLUORINE IN HYDROTHERMAL DEPOSITS 

Historically, the dominant commercial sources of 

fluorine have been fluorspar deposits of hydrothermal origin. Hydrothermal fluorspar occurs in a wide 

variety of types of deposits formed in many geologic 

environments under a wide range of physical-chemical conditions. Fluorite is generally the only fluorine 

mineral in these deposits, and its abundance ranges 

from nearly 100 percent down to trace amounts. 

Other common minerals are quartz, chalcedonic 

quartz, opal, barite, manganese oxides, calcite, clay 

minerals, and lead and zinc sulfides. The following 

elements are commonly, but not universally, present 

in these deposits, and at many places they are in 

trace amounts only: silver, gold, beryllium, iron, 

manganese, molybdenum, lead, the rare earths, tin, 

tellurium, uranium, vanadium, tungsten, and zinc 

(Worl, 1971). Hydrothermal fluorite occurs in almost any type of host rock but especially in carbonate, silicic igneous, and silicic metamorphic rocks. 

The form of hydrothermal fluorspar deposits is 

the standard ~sis for their classification. Most 

common forms are veins and mantos, which are 

abundant in well-defined regions of the world. Individual veins range in thickness from millimeters to 

several meters and are as much as several kilometers 

in length. Fluorspar mantos, or blanketlike replacements of rock, are generally confined to marine carbonate rocks and commonly extend outward from 

veins. Mantos are irregular lenticular or wedgeshaped bodies and are not layered concordantly within a stratigraphic sequence. Fluorspar in many veins 

and mantos is characterized by monomineralic banding, crustification, and mammillary textures. Massive crystalline material, breccias, and fine-grained 

earthy material are also common. Most fluorspar 

veins and mantos contain at least 35 percent CaF 2 ; 

many contain at least 70 percent CaF 2 ; and some 

contain as much as 98 percent CaF 2• 

Although host-rock compositions were important 

in localizing many individual deposits, regional 

structures controlled the location of most hydrothermal fluorspar districts. Fluorite veins and mantos in 

many areas are confined to large faults and subordinate fissures of deep-seated regional tensional nature, as in India (Deans and others, 1972), in 

Eastern Mongolia (Khasin and Kalenov, 1965), in 

the Western United States (Worl, 1971), and along 

the rift valleys of Africa. Regional domes and arches 

helped localize fluorspar mineralization in the Illinois-Kentucky district of the United States (Heyl 

and Brock, 1961) and in the North Pennine ore field 

of the United Kingdom (Sawkins, 1966). Hydrothermal fluorspar veins and mantos have been documented all over the world, some of the best known 

occurring in Mexico (Van Alstine, 1961), the 

United States (Grogan and Bradbury, 1968), Spain 

(Marin and deLis, 1945), Brazil (Abreu, 1960), 

South Africa (DeKun, 1965), the U.S.S.R. (U.S. 

Bur. Mines, 1958), Korea (Gallagher, 1963), Canada 

(Van Alstine, 1944), Italy (Spada, 1969), France 

(Chermette, 1960), Pakistan (Bakr, 1965), and 

Thailand (Gardner and Smith, 1965). 

Some districts characterized by veins and mantos 

contain individual hydrothermal fluorspar deposits 

best described as stockworks and pipelike bodies. 

Fluorspar pipes mined in the Thomas Range, Utah, 

and near Beatty, Nev., are circular to elliptical in 

plan and range in diameter from 5 to about 45 

meters (Peters, 1958, p. 672). Much of the fluorspar 

at Jamestown, Colo., and the Buffalo mine, Union of 

South Africa (DeKun, 1965, p. 409), is in the form 

of stockworks of veins and veinlets. Fluorspar pipes 

and stockworks commonly occur at fault intersections and are generally associated with stocks and 

hypabyssal bodies of igneous rock. Fluorspar production from Jamestown, Colo., has been from breccias containing 50-90 percent CaF 2 within the stockwork. Fluorspar in stockworks generally is diffused 

through large bodies of rock so that the ore grade is 
FLUORINE 229 

low, but the reserves may be substantial. 

In the Western United States many areas of hydrothermally altered volcanic rock, agglomerates, volcaniclastic sediments, and unconsolidated clastic 

sediments contain dispersed fluorite. The fluoriteberyllium deposits near Spor Mountain, Utah, and 

the Honey Comb Hills, Utah, are good examples 

(McAnulty and Levinson, 1964). Altered water-laid 

tuff near Spor Mountain, Utah, contains commercial 

amounts of beryllium and about 4 percent CaF z. 

Microscopic fluorite occurs dispersed through altered 

tuff and in a fine-grained intergrowth with opal and 

chalcedony in nodules as much as 30 centimeters in 

diameter. Part of the fluorite in these deposits probably represents redeposition of fluorine leached from 

the included volcanic ash. However, much of the 

fluorine, along with beryllium, gallium, lead, lithium, 

niobium, cesium, and yttrium, seems to have been 

introduced with laterally spreading hydrothermal 

solutions (Staatz and Griffitts, 1961; D. A. Lindsey, 

oral cornrnun., 1972). 

Hydrothermal fluorspar deposits in general 

formed under a wide range of conditions, from high 

pressure and temperature at depth to low pressure 

and temperature near the surface, and were precipitated from solutions of varied chemical composition. Nevertheless, each individual deposit formed 

under a relatively small range of conditions. Fluorite 

at the Tyrny-Auz skarn complex, North Caucasus, 

U.S.S.R., formed from pneurnatolytic and hydrothermal solutions at temperatures in excess of 500° 

C. The initial hydrothermal solutions were highly 

supercharged with chlorides and fluorides of sodium, 

potassium, calcium, and other elements (Lesnyak, 

1965, p. 484). At Jamestown, Colo., fluorite in a 

stockwork next to an alkalic intrusive formed from 

solutions that varied in composition with time and 

space. The main-stage fluids were highly saline (26-

32 percent equivalent NaCl) and near 350°C, though 

the fluids at times were alternately supersaline, COz 

rich, or relatively dilute and cool (J. T. Nash and 

C. G. Cunningham, oral cornrnun., 1972). Fluorite in 

veins not closely associated with igneous rocks in 

southern New Mexico formed from solutions that 

changed with time. As the temperature decreased 

from about 200°C to about 140°C over several substages of deposition, the salinity increased from 

about 10 percent equivalent NaCl to about 15 percent 

equivalent NaCl (Roedder and others, 1968, p. 336). 

Fluorite in banded and crustified epithermal veins, 

common throughout the world, formed from very 

dilute solutions at temperatures ranging from 50° 

to 200°C (Errnakov, 1965, p. 197; Steven, 1960, p. 

410). The nature of near-surface fluorite deposits, 

such as at Spor Mountain, Utah, suggests that the 

fluorite must have been deposited from very dilute 

and low-temperature (50°-100°C) solutions. Stratiform lead-zinc-fluorine-barium deposits of the English Pennines and the Illinois-Kentucky district were 

formed from relatively high-salinity solutions (20 

percent equivalent N aCl) at temperatures ranging 

from 75° to 200°C (Sawkins, 1966, p. 385). 

Many fluorine deposits can be attributed to late 

stages of igneous activity. The solutions depositing 

the fluorine in many places seem to have had a common source with the magmas that formed related 

fluorine-bearing igneous bodies and carbonatite complexes. The common source was probably a differentiating magma deep in the crust or a zone of fractionation in the upper mantle. The partitioning of 

fluorine between the hydrothermal solutions and the 

late siliceous magma must have been nearly equal. 

The source of the ore-forming solutions for some 

fluorine deposits, such as the stratiform deposits of 

the English Pennines and the Illinois-Kentucky district, is much debated. Most workers agree that these 

deposits formed from slow-moving, relatively hot 

(75°-200°C), dense, sodium-calcium-chlorine-fluorine brines containing abundant organic matter. 

Davidson (1966) suggested that the brines were de-

. rived from the diagenesis of overlying evaporites 

and that they concentrated their metals from the 

limestone and other rocks traversed. Dunham 

(1966), pointing to the low sodium/potassium ratios 

of the brines, as little as 6 : 1, compared with 39 : 1 

for normal sea water, suggested that the relative 

enrichment in potassium appears to rule out purely 

connate solutions as the source of the brines. He 

preferred nonevaporitic connate water, reinforced 

by juvenile fluids associated with an igneous heat 

source below, as the origin of ore-forming brines. 

Grogan and Bradbury (1968) suggested that the 

brines were magmatic, connate, and meteoric in 

origin, and that the fluorine and metals were of magmatic origin. 

Probably in most fluorine deposits the materials 

making up the ore-forming solution carne from more 

than one source. The ultimate source of the fluorine 

needed to form the deposits is generally unknown; 

the relationship of fluorine deposits to major structures points to a deep-seated origin. Still, the regional distribution of fluorine in the Western United 

States through geologic time suggests that once a 

specific region becomes enriched in fluorine, it remains so through several geologic cycles and episodes 

of mineralization (Peters, 1958, p. 685). 
230 UNITED STATES MINERAL RESOURCES 

RESOURCES TABLE 44.-Estimated fluorspar resources of the world 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Fluorspar deposits, although generally small, are 

relatively abundant and widespread throughout the 

world. The world's known reserves are adequate to 

meet the current demand, especially as fluorspar 

prices rise; improved mining and processing techniques have increased reserves substantially over 

earlier estimates. The beneficiation of fluorite-barite 

ores, now profitable in the United States, United 

Kingdom, Italy, Spain, and Tunisia, has extended 

world reserves. Fluorspar is currently one of the 

most sought-after industrial minerals, and deposits 

continue to be discovered in many countries. The 

most recently found deposits are chiefly in the 

United States, Mexico, Argentina, Brazil, United 

Kingdom, France, Spain, Italy, Thailand, India, and 

southern Africa. 

Fluorspar resources are chiefly in shallow, lowtemperature, hydrothermal vein, pipe, and manto or 

stratiform deposits; however, an increasingly important source of fluorspar will be as a coproduct of 

mining and processing certain ores of iron, lead, 

zinc, bismuth, tungsten, molybdenum, tin, beryllium, 

and rare earths that contain fluorite as a minor constituent. In the United States it is now profitable to 

mine ores containing as little as 15-20 percent CaF 2 

if they have sufficient lead or zinc values to compensate for the low fluorite content. Molybdenum deposits of the Western United States, such as at 

Questa, N. Mex., contain fluorite; and although the 

percentage is small, the large tonnages of rock 

processed may warrant extraction of fluorite. Contact replacement iron-ore deposits in the Iron 

Springs district, Iron County, Utah, contain fluorapatite. Although the fluorine content is less than 1 

percent, fluorine is being extracted during processing of this ore for its iron content. Environmental 

considerations in the future, in fact, may demand the 

recovery of fluorine during ore processing so that it 

is not released into surficial material, the atmosphere, or surface waters. More and more fluorspar 

will be recovered elsewhere from mine dumps and 

tailings resulting from the working of some metalliferous deposits, as is now being done in Mexico, the 

United Kingdom, and Spain. 

The estimate of the world's resources of fluorspar 

ore in table 44 is based largely on published information. The figures are rounded, but they indicate 

orders of magnitude. This new total for the estimated fluorspar resources of the world, 190 million 

tons, agrees well with recent estimates of 150 million tonf' by Chermette ( 1968) and 182 million tons 

[Millions of short tons of exude ore. The ratio of crude fluorspar ore to processed fluorspar recovered is about 3: 1 1 

Area 

United States -------------------- Mexico - __ -- ____ - _- _------_ -------

Canada -------------------------- Europe3 ------------------------- Africa' -------------------------- Asia 5 

---------------------------

South America 6 ------------------

Australia ------------------------

Total ----------------------

Identified 

resources 1 

25 

25 

10 

62 

39 

25 

3 

1 

190 

Hypothetical 

resources 2 

45 

50 

15 

84 

310 

62 

6 

1 

573 

1 Chiefly exploitable economic ore containing 35 percent or more CaF2 or equivalent in combined fluorspar and metal values. The average 

CaF2 content is about 50 percent. Includes some subeeonomic material. 2 Some material of ore grade, but much rock is exploitable only under more favorable economic or technologic conditions. Deposits htcompletely 

known because few subeconomic fluorspar deposits have been explored. a Chi~fly France, Germany, Italy, Spain, United Kingdom, and U.S.S:R· 

' Chiefly Kenya, Morocco, Mozambique, Rhodesia, South West Africa, 

Tunisia, and Union of South Africa. 5 Chiefly China, India, Korea, and Thailand. 6 Chiefly Argentina and Brazil. 

by the U.S. Bureau of Mines (Wood, 1972). Each of 

the two countries with the largest resources of 

fluorspar, Mexico and the United States, has about 

25 million tons. 

A previous detailed reserve estimate (Van Alstine, 

1956) for fluorspar deposits of the United States 

showed 22.5 million tons of commercial ore and about 

12 million tons of lower grade material containing 

15-35 percent CaF2. As a result of mining and discoveries since 1956, the identified resources in the 

United States are now estimated at about 25 million tons, largely in Illinois, Kentucky, Texas, New 

Mexico, Nevada, Utah, Colorado, Idaho, Montana, 

and Alaska. Nearly all of this resource is believed 

amenable to processing into acid- and metallurgicalgrade products, the latter grade especially by pelletizing flotation concentrates. 

As European fluorspar consumption continues to 

increase, the substantial exports from Italy and 

Spain to the United States probably will not be 

available. This situation should make the mining of 

even more low-grade resources profitable· and should 

stimulate further domestic exploration. Detailed information is lacking on which to base accurate estimates of hypothetical resources of most low-grade 

fluorspar deposits in foreign countries. 

Marine phosphate rock, by far the world's largest 

fluorine resource, generally contains about 3 percent 

fluorine. Resources of phosphate rock in the United 

States are chiefly in Florida, North Carolina, Tennessee, Utah, Wyoming, Idaho, and Montana. Reserves there are about 10 billion tons of phosphate 

rock, and hypothetical resources have been estimated 

at more than 60 billion tons; the latter class represents a potential fluorine resource of about 2 billion 

tons and is equivalent to about 4 billion tons of 
FLUORINE 231 

fluorspar. Similar deposits of phosphate rock, with 

estimated reserves totaling more than 10 billion tons 

and enormous hypothetical resources, occur mainly 

in Morocco, Tunisia, Algeria, Turkey, U.S.S.R., Peru, 

China, North Vietnam, and Australia. Potentially 

several hundred thousand tons of fluorine annually 

could be obtained as a byproduct of phosphate production in the United States. The estimated quantity 

of fluorine discarded or lost during the processing 

of phosphate rock in the United States approximates 

the annual fluorspar imports into the United States 

(Blake and others, 1971). In recent years more than 

100,000 tons of hydrofluosilicic acid was recovered 

in the United States during the manufacture of 

superphosphates and was used mostly for water 

fluoridation; however, some of this acid is now processed further into aluminum fluoride and synthetic 

cryolite for the aluminum industry and into fluosilicates. Fluorine from phosphate rock for the aluminum industry will become more competitive with 

fluorspar in the next few years, as fluorspar prices 

rise, as the demand grows, and as the phosphate 

industry strives to control environmental pollution 

near processing plants by recovering the fluorine. 

Industrial plants in the United States, Mexico, 

Canada, U.S.S.R., Austria, Rumania, India, and 

Japan now use waste hydrofluosilicic acid from the 

processing of phosphate rock, and other plants are 

planned for France, West Germany, Switzerland, 

and Australia. (See also the chapter on "Phosphate 

Deposits" in this volume.) 

Topaz, although rarely concentrated, occurs in 

probable commercial quantity and grade in at least 

two localities in the United States. At the old 

Brewer gold mine in South Carolina, reserves were 

estimated at about 100,000 tons of schist averaging 

approximately 15 percent topaz and about 1,200 tons 

of topaz in adjacent placer deposits that contain 

1-24 percent topaz. The hypothetical resources at 

this deposit are estimated at about 800,000 tons of 

ore. In the Front Range, Colo., a lens in Precambrian 

gneiss containing about 15 percent topaz was estimated to constitute a reserve of about 600,000 tons 

of topaz-bearing rock. The hypothetical resources of 

this topaz-bearing rock are estimated to be about 

250,000 tons for every 100 feet of depth. 

Bastnaesite in carbonatite at Mountain Pass, 

Calif., is a potential resource of fluorine. This rareearth mineral contains about 7 percent fluorine and 

constitutes 5-15 percent of the carbonatite rock. 

On the basis of an estimated 100 million tons of 

potential ore at Mountain Pass (Olson and others, 

1954), about 1 million tons of fluorine is estimated 

as a potential byproduct of rare-earth extraction. 

SPECULATIVE RESOURCES 

Exploration for and evaluation of fluorine resources must be based upon the geology and geochemistry of fluorine. The important geologic parameters are regional tensional faults or other deepseated structures, alkalic and silicic igneous rocks, 

carbonatites, and hydrothermal activity-including 

hot springs. Fluorine is apparently very mobile in 

geologic settings characterized by these parameters, 

and in addition to forming deposits directly related 

to those features, it also has moved into other geologic environments associated in time and space to 

form deposits there. For example, fluorine mobilized 

by exhalations or weathering has been transferred 

from the alkalic igneous rocks and carbonatites 

along the African rift structures into the lake brines, 

to be concentrated in evaporites of the rift valleys. 

Fluorine-bearing solutions genetically related to the 

important geologic parameters have permeated 

country rock, such as the altered and mineralized 

volcaniclastic sedimentary rocks of the Western 

United States; have replaced receptive country 

rocks, as in the Illinois-Kentucky district; and have 

filled subsidiary fractures, in places some distance 

from the igneous activity and major structures, as 

in many smaller fluorspar districts of the Western 

United States. 

The important geologic parameters listed above 

define environments and processes in which fluorine 

was available in abnormal amounts in some part of 

the system and in which it could be mobilized and 

transported into concentrations of economic interest. 

Geologic processes in other environments also have 

acted to concentrate minor amounts of fluorine (of 

the order of crustal abundance) into deposits of 

economic interest, as in the precipitation of fluorapatite from sea water. 

These principles assure us that numerous possibilities exist for the discovery of new resources of 

fluorine. The best possibilities are undiscovered but 

geologically predictable fluorine districts ; known 

small, but high grade, deposits; and very large lowgrade multicommodity ores. At this time it is impossible to give a quantitative indication of speculative resources, other than that they are probably 

very large. 

In the United States new fluorspar districts might 

be found northwest of the important IllinoisKentucky district in carbonate rocks beneath the 

cover of Pennsylvanian rocks, and also northeast of 

this district toward Ohio and the Michigan basin 

beneath Pleistocene cover where fluorite occurrences 

are known in Silurian and Devonian dolomites. Similarly the Paleozoic carbonate rocks of central Tennes-
232 UNITED STATES MINERAL RESOURCES 

see and Kentucky are widely mineralized with fluorite, as shown in recent drilling, and may contain 

other commercial deposits. Large, but lower grade, 

stratiform fluorspar deposits in carbonate rocks, like 

those worked in the United States, France, U.S.S.R., 

and southern Africa, probably will be popular targets for exploration. In the Western United States 

fluorspar deposits undoubtedly underlie parts of the 

widespread cover of Tertiary and Quarternary sedimentary and volcanic rocks. Cenozoic tuffaceous lake 

beds in the Western United States, Italy, and southern Africa contain fluorite, some of commercial interest, and other occurrences of this type of finegrained fluorite may have been overlooked. Some 

fluorspar deposits of the Western United States are 

related genetically to areas of silicic volcanic rocks, 

namely the Big Bend subprovince of Texas; the N acimiento subprovince of Arizona, New Mexico, and 

Colorado; and the Shoshone province of Nevada, 

Utah, Idaho, and Montana. Other areas with relatively high fluorine content in volcanic rocks might 

be worthy of further prospecting, especially southeastern Idaho, northwestern Wyoming, and northwestern Utah. In west-central Utah, topaz is disseminated in volcanic rocks, and commercial fluorspar 

deposits are distributed around the southern and 

western periphery of a caldera. Only a third of the 

caldera is exposed; the remainder, which is covered 

by rhyolite flows or alluvium, may contain undiscovered deposits (Shawe, 1972, p. B76-B77). A tectonic 

unit consisting of the Rio Grande trough in New 

Mexico, and its northern extension through Colorado, Wyoming, and Montana, is especially rich in 

fluorspar deposits and should be explored further. 

Deposits of syngenetic fluorite associated with gypsum and limestone are reported from Permian marine evaporites in the Big Horn Mountains, Wyo. ; 

similar extensive deposits are known in the Permian of U.S.S.R., and other equivalent evaporites 

should be investigated for deposits of fluorite. 

Large deposits of fluorapatite in marine phosphate 

rock probably exist beneath the sea in Tertiary 

coastal plain sediments extending east from deposits 

in North and South Carolina and Florida. Fluorine 

is recovered from huge deposits of fluorapatite in 

alkalic rocks of U.S.S.R., and other deposits of this 

type may be found and profitably explored elsewhere. 

Probably millions of tons of topaz-bearing rock 

are yet to be discovered in widespread metamorphic 

terranes throughout the world. Because cryolite, 

NasAlFs, is a rare mineral, it probably will not be 

an important source of fluorine; the world's only 

known commercial deposit of natural cryolite, in 

Greenland, has been depleted. Sodium fluoride has 

been found in saline lake beds in Tanganyika and 

may some day be a source of fluorine. 

Some brines, volcanic gases, fumaroles, and hot 

springs with relatively high fluorine contents may 

suggest fluorine-rich provinces in which deposits of 

fluorspar, phosphate rock, or other fluorine materials 

should be sought. Deep sea sediments, which have 

more fluorine than most other marine sediments 

except phosphate rock, contain about 0.07 percent 

fluorine; these types of sediments and sea water itself, which has about 0.0001 percent fluorine, may 

be sources of fluorine in the distant future. 

Numerous high-grade but small deposits of fluorspar, such as those of the Western United States, 

might be utilized. This use would require better 

techniques of locating and evaluating small pods of 

fluorspar and the use of portable extraction and 

processing equipment. Even though this type of 

mining may not be feasible now in the Western 

United States, because of high labor costs and land 

problems, it might be elsewhere in the world. 

Very large low-grade multicommodity ores offer 

potential fluorine resources. These include deposits 

in which fluorine, mainly in the form of fluorite, is 

associated with metallic minerals (see discussions 

of geochemistry and exploitation) and those in 

which it is associated with or contained in other 

minerals of commercial interest, such as barite, 

bastnaesite, apatite, zeolites, and feldspars. It may 

be possible in the future to process such multicommodity ores, in which no single commodity is of 

high enough grade to be commercial. 

PROSPECTING TECHNIQUES 

Fluorspar deposits commonly have been found by 

identification of fluorite in outcrops and surficial materials. The durability of fluorite during weathering 

and the high fluorine content of the mineral suggest 

that some geochemical methods might be useful in 

prospecting for fluorspar. Nevertheless, geochemistry has not been widely used, in part because of the 

lack of rapid analytical procedures for determining, 

with the necessary reliability and low cost, the fluorine contents of samples. 

A fluorine halo could be meaningless in fluorine 

exploration, inasmuch as fluorine is widely dispersed in many mineralized and altered areas other 

than those containing fluorine-rich deposits. Pathfinder elements can be used as a guide to some fluorine mineralization. To use this guide, however, 

requires considerable geologic knowledge of the area 

being surveyed. This approach avoids the problem 

of low-level fluorine analysis but will be successful 

only where the pathfinder element is consistently 
FLUORINE 233 

associated with fluorine deposits. Friedrich and 

Pltiger (1971) found that lead, zinc, and mercury 

contents of soils were useful guides in exploring for 

fluorite in Spain and that mercury was useful in the 

Wolsendorf district, Germany. If fluorite contains 

uranium minerals, as in the Thomas Range, Utah, 

and Jamestown, Colo., scintillation counters or 

Geiger counters might be helpful in prospecting for 

fluorspar. 

Recent work in western North America has shown 

that fluorite deposits can effectively be sought by 

geochemical and heavy-mineral techniques. Fluorite 

persists for long distances during transport in the 

sediment of streams and can be concentrated therefrom with the gold pan. A systematic heavy-mineral 

survey near Winston, N. Mex., during 1970, by H. V. 

Alminas and K. C. Watts (oral commun., 1971), 

showed that fluorite is plentiful in sediment near two 

major subparallel north-trending faults, near the 

intersection of which an independent operator recently found a large fluorspar deposit. 

Geochemical exploration investigations in the 

Browns Canyon district, Colorado, by Van Alstine 

(1965) showed that fluorine is found in abnormal 

concentrations in residual soil directly above and 

downslope from the principal vein and in alluvium 

downstream from the vein. The abundance of fluorine in those places may be due in part to the semiarid climate of the area. Van Alstine also pointed out 

that abundant biotite and hornblende increase fluorine values over that attributed to fluorite because of 

the fluorine content of the dark minerals. This problem is avoided by determining content of fluorite 

instead of fluorine. 

Neither heavy-mineral nor geochemical prospecting methods for fluorite and fluorine have been well 

developed for fluorspar districts in humid regions. 

Geochemical studies of stream sediment and soils 

were found to be useful in prospecting for fluorine in 

the H wanggangri region, Korea (Sang Kyu Yun and 

others, 1970). 

Geophysical techniques have been utilized to some 

degree in evaluating mineralized areas that have 

fluorine potential. Electrical methods have been successful in outlining faults, some of which contain 

fluorspar (Hubbert, 1944), and alteration zones associated with fluorspar veins (Johnson, 1971). The 

refraction seismic method has been used as an indirect means of exploring for fluorspar in southern 

Illinois (Johnson, 1957). In general, it seems impracticable or impossible to detect minable bodies 

directly by methods of geophysical prospecting. The 

value of geophysical techniques is in finding locally 

mineralized faults, dikes, and altered zones, which 

then require geologic evaluation to determine fluorine potential. 

PROBLEMS FOR RESEARCH 

The distribution of fluorine in nature is only partly understood, and more research is needed on the 

geology and geochemical cycle of fluorine, especially 

on the partitioning of fluorine in geologic processes. 

Our present knowledge is not advanced enough even 

to adequately estimate crustal abundance, much less 

to accurately estimate resources. The fluorine content of igneous rocks serves as an excellent guide to 

potential fluorine deposits in the vicinity of such 

rocks ; and yet, fluorine is commonly not determined 

in igneous rock analyses. Fluorine determinations 

should be made routinely in all chemical analyses of 

igneous rocks. 

New techniques are needed to explore for and to 

evaluate fluorine deposits. Geochemical investigations of the fluorine content of rocks, soils, plants, 

and waters hold some promise as an exploration 

technique. However, for geochemical exploration to 

be useful, a quick, reliable, and inexpensive method 

of testing for fluorine needs to be developed. 

Utilization of potential low-grade multicommodity 

ores as fluorine resources will require refinement and 

improvement of mining and processing techniques. 

Many of these low-grade deposits are very fine 

grained, and the fluorine minerals are intimately 

intergrown with other minerals, such as chalcedonic 

quartz, so that separation of the fluorine minerals is 

difficult. 

REFERENCES CITED 

Abramovich, Yu. A., and Nechayev, Yu. A., 1960, Authigenic 

fluorite in Kungurian deposits of the Permian Preurals: 

Doklady Akad. Nauk SSSR, v. 130, p. 1288-1289. 

Abreu, S. F., 1960, Recursos minerais de Brasil: Rio de 

Janeiro, Inst. Nac. de Technologia, v. 1, 471 p. 

Bakr, M. A., 1965, Fluorspar deposits of Pakistan: Pakistan 

Geol. Survey Rec., v. 16, pt. 2, 5 p. 

Barth, T. F. W., 1947, On the geochemical cycle of fluorine: 

Jour. Geology, v. 55, no. 5, p. 420-426. 

Blake, H. E., Jr., Thomas, W. S., Moser, K. W., Reuss, J. L., 

and Dolezal, H., 1971, Utilization of waste fluosilicic 

acid: U.S. Bur. Mines Rept. Inv. 7502, 60 p, 

Chermette, A., 1960, Les resources de la France en spath 

flour: Bur. Recherches Geol. et Minieres, no. 1, 56 p. 

-- 1968, Le marche du spath-fluor dans le monde: Extrait des Mines et Metallurgie, Paris, Mai a Decembre, 

14 p. 

Davidson, C. F., 1966, Some genetic relationships between 

ore deposits and evaporites: Inst. Mining and Metallurgy 

Trans., see. B, v. 75, Bull. 717, p. B216-B225. 

Deans, T ., 1966, Economic mineralogy of African carbonatites, in Tuttle, 0. F., and Gittins, J., eds., Carbonatities: 

New York, lntersci. Publishers (John Wiley & Sons), 

p. 385-416. 
234 UNITED STATES MINERAL RESOURCES 

Deans, T., Sukheswala, R. N., Sethna, S. F., and Vilad.kar, 

S. G., 1972, Metasomatic feldspar rocks (potash fenites) 

associated with the fluoride deposits and carbonatites of 

Amba Dongar Gujarat, India: Inst. Mining and Metallurgy Trans., sec. B, v. 75, Bull. 717, p. B1-B9. 

DeKun, Nicolas, 1965, The mineral resources of Africa: 

Elsevier Publishing Co., 7 40 p. 

Dunham, K. C., 1966, Role of juvenile solutions, connate 

waters and evaporitic brines in the genesis of lead-zincfluorine-barium deposits: Inst. Mining and Metallurgy 

Trans., sec. B, v. 75, Bull. 717, p. B226-B231. 

Ermakov, N. P., 1965, on temperatures of formation of some 

fluorite deposits in Central Asia and in Transbaykalia, 

in Ermakov, N. P., and others, Research on the nature of 

mineral forming solutions: New York, Pergamon Press, 

p. 458-484. 

Fleischer, Michael, and Robinson, W. D., 1963, 8ome problems 

of the geochemistry of fluorine: Royal Soc. Canada Spec. 

Paper 6, p. 58-75. 

Friedrich, G. H., and Pliiger, W. L., 1971, Geochemical prosspecting for baryte and fluorite deposits: Canadian Inst. 

Mining and Metallurgy Spec. Pub. 11, p. 151-156. 

Gallagher, David, 19·63, Nonmetallics and miscellaneous 

metals, v. 4A of Mineral resources of Korea: Mining Br., 

Industry and Mining Div., USOM, Korea (in cooperation with Korean Geol. Survey), p. 86-121. 

Gardner, L. S., and Smith, R. M., 1965, Fluorspar deposits 

of Thailand: Thailand Dept. Mineral Resources Rept. 

Inv. 10, 42 p. 

Grogan, R. M., 1960, Fluorspar and cryolite, in Industrial 

minerals and rocks, 3d ed.: Am. Inst. Mining Metall. 

and Petroleum Engineers, p. 363-382. 

Grogan, R. M., and Bradbury, J. C., 1968, Fluorite-zinc-lead 

deposits of the Illinois-Kentucky mining districts, in 

Ridge, J. D., ed., Ore deposits of the United States, 1933-

1967 (Graton Sales Volume): Am. Inst. Mining Metall. 

and Petroleum Engineers, pt. 3, chap. 19, p. 370-399. 

Heyl, A. V., and Brock, M. R., 1961, Structural framework 

of the Illinois-Kentucky mining district and its relation 

to mineral deposits, in Short papers in the geologic and 

hydrologic sciences: U.S. Geol. Survey Prof. Paper 424-

D, p. D3-D6. 

Hodge, B. L., 1971, Fluorspar-A world review: Industrial 

Minerals, Sept. 1971, no. 48, p. 9-29. 

Hubbert, M. K., 1944, An exploratory study of faults in the 

Cave-In-Rock and Rosiclare districts by the earth-resistivity method, pt. 2 of Geological and geophysical survey of fluorspar areas in Hardin County, Illinois: U.S. 

Geol. Survey Bull. 942, p. 73-147. 

Johnson, G. R., 1971, Preliminary results of I. P. resistivity 

surveys in the Northgate district, Colorado: U.S. Geol. 

Survey open-file rept., 18 p. 

Johnson, R. B., 1957, Refraction seismic investigations, Rosiclare fluorspar district, Illinois: Illinois Geol. Survey 

Circ. 231, 15 p. 

Kazakov, A. V., and Sokolova, E. I., 1950, Usloviya obrazovaniya flyuorita v osadochnykh porodakh (flynoritovaya 

sistems) [Conditions of the formation of fluorite in sedimentary rocks]: Akad. Nauk SSSR Geol. Inst. Trudy, v. 

114, geol. se,r. 40, p. 22-64 [English translation, U.S. 

Geol. Survey Trace Elements Inv. Rept. TEI-186, 76 p., 

1951]. 

Khasin, R. A., and Kalenov, A. D., 1965, Distribution patterns of fluorite mineralization in eastern Mongolia: 

Doklady Akad. Nauk SSSR, v. 164, p. 115-117. 

Lesnyak, V. F., 1965, Mineralothermometric research at the 

Tyrny-Auz skarn-ore complex, North Caucasus, in 

Yermakov, N. P., and others, Research on the nature of 

mineral-forming solutions: New York, Pergamon Press, 

p. 458-489. 

MacMillan, R. T., 1970, Fluorite, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 989-1000. 

Marin, Augustin, and deLis, Bertram, 1945, Minas de fluori 

de Osar (Gerona): Madrid, Mineroria y Metallurgia, 

no. 56, p. 1-9. 

McAnulty, W. N., and Levinson, A. A., 1964, Rare alkali and 

beryllium mineralization in volcanic tuffs, Honey Comb 

Hills, Juab County, Utah: Econ. Geology, v. 59, no. 5, 

p. 768-774. 

Olson, J. C., Shawe, D. R., Pray, L. C., and 8harp, W. N., 

1954, Rare-earth mineral deposits of the Mountain Pass 

district, San Bernardino County, California: U.S. Geol. 

Survey Prof. Paper 261, 75 p. 

Parker, R. L., and Havens, R. G., 1963, Thortveitite associated with fluorite, Ravalli County, Montana, in 

Geological Survey research 1963: U.S. Geol. Survey 

Prof. Paper 475-B, p. B10-Bll. 

Peters, W. C., 1958, Geologic characteristics of fluorspar deposits in the western United States: Econ. Geology, v. 

53, p. 663-688. 

Roedder, Edwin, Heyl, A. V., and Creel, J. P., 1968, Environment of ore deposition at the Mex-Tex deposits, 

Hansonburg district, New Mexico, from studies of fluid 

inclusions: Econ. Geology, v. 63, p. 336-348. 

Sang Kyu Yun, Hyo Joon Seo, Sahng Yup Kim, Jae Sang 

Cho, and Nam Iue Hong, 1970, Detailed geochemical exploration for Mo-W and CaF2 in Hwanggangri region, 

Republic of Korea: Seminar on methods and techniques 

of geochem. explor. in the humid tropical environment, 

2d, Peradeniya, Ceylon, Doc. GSM (2) /107, 9 p. 

Sawkins, F. J., 1966, Ore genesis in the North Pennine ore 

field, in the light of fluid inclusion studies: Econ. 

Geology, v. 61, p. 385-401. 

Shawe, D. R., 1966, Arizona-New Mexico and Nevada-Utah 

beryllium belts, in Geological Survey research 1966: U.S. 

Geol. Survey Prof. Paper 550-C, p. C206-C213. 

--- 1972, Reconnaissance geology and mineral potential 

of Thomas, Keg, and Desert calderas, central Juab 

County, Utah, in Geological Survey research 1972: U.S. 

Geol. Survey Prof. Paper 800-B, p. B67-B77. 

Sheppard, R. A., and Gude, A. J ., 1969, Authigenic fluorite 

in Pliocene lacustrine rocks near Rome, Malheur 

County, Oregon, in Geological Survey research 1969: 

U.S. Geol. Survey Prof. Paper 650-D, p. D69-D74. 

Sheridan, D. M., Taylor, R. B., and Marsh, S. P., 1968, Rutile 

and topaz in Precambrian gneiss, Jefferson and Clear 

Creek Counties, Colorado: U.S. Geol. Survey Circ. 567, 

7 p. 

Spada, Aldo, 1969, 11 giceimento di fluorite e baritina 

esalative-sedimentarie (facies) lacustre, in tes calate 

nei sedimenti piroclastici delle zone de Castel Giuliano, 

in Prov. di Roma: "L'Industria Min.," v. 20, 37 p. 

Staatz, M. H., and Griffitts, W. R., 1961, Beryllium-bearing 

tuff in the Thomas Range, Juab County, Utah: Econ. 

Geology, v. 56, p. 941-950. 

Steven, T. A., 1960, Geology and fluorspar deposits, Northgate district, Colorado: U.S. Geol. Survey Bull. 1082-F, 

p. 323-422. 
FLUORINE 235 

U.S. Bur. Mines, 1958, Fluorspar-U.S.S.R.: Mineral Trade 

Notes, v. 46, no. 2, p. 22-33. 

Van Alstine, R. E., 1944, The fluorspar deposits of St. 

Lawrence, Newfoundland: Econ. Geology, v. 39, no. 2, 

p. 109-132. 

--- 1956, Fluorspar reserves of the United States estimated: U.S. Geol. Survey Press Release, Nov. 23, 1956, 

3 p. 

--- 1961, Investigation of the principal fluorspar districts 

of Mexico, in Short papers in the geologic and hydrologic 

sciences: U.S. Geol. Survey Prof. Paper 424-C, p. C212-

C215. 

--- 1965, Geochemical prospecting in the Browns Canyon 

fluorspar district, Chaffee County, Colorado, in Geological Survey Research 1965: U.S. Geol. Survey Prof. 

Paper 525-D, p. D59-D64. 

Wood, H. B., 1972, Fluorspar: Eng. and Mining Jour., v. 

173,no. 3,151-153. 

W orl, R. G., 1971, Spatial and time distributions of fluorite 

occurrences in western U.S. [abs.]: Mining Eng., v. 

23, no. 12, p. 80. 

Zies, E. G., 1929, The acid gases contributed to the sea during volcanic activity, pt. 2 of The Valley of Ten Thousand Smokes: Natl. Geog. Soc. Contr. Tech. Papers, v. 

1, no. 4, p. 62-66. 

UNITED STATES MINERAL RESOURCES 

GALLIUM, GERMANIUM, AND INDIUM 

By RoBERT A. WEEKS 

CONTENTS 

Page 

Abstract of conclusions -------------------------- 237 

Introduction ------------------------------------- 237 

Principal uses ------------------------------- 238 

Alternate materials -------------------------- 238 

Problems in development of commercial uses --- 239 

Resource availability ------------------------- 239 

Exploitation ------------------------------------- 240 

Relation to other coproducts or byproducts ----- 241 

Environmental relationship ------------------- 241 

Geologic environment ----------------------------- 241 

Geochemistry -------------------------------- 241 

Abundance ---------------------------------- 242 

Ore minerals -------------------------------- 242 

Types of ores ------------------------------- 243 

Sulfide ores ----------------------------- 243 

Bauxite --------------------------------- 244 

Coal deposits ---------------------------- 244 

Resources --------------------------------------- 244 

Reserves ------------------------------------ 245 

Potential resources -------------------------- 245 

Prospecting techniques --------------------------- 245 

Problems and needs for additional research -------- 246 · 

Selected bibliography ---------------------------- 246 

TABLES 

Page 

45. Selected properties of gallium, germanium, and 

indium ---------------------------------- 238 

46. Estimated production, price, and apparent demand for gallium, germanium, and indium __ 239 

47. Gallium, germanium, and indium contents of 

various materials ------------------------ 241 

48. Gallium, germanium, and indium contents of 

selected ore minerals and of reported gallium, 

germanium, and indium minerals ---------- 243 

ABSTRACT OF CONCLUSIONS 

Known exploited sources of gallium, germanium, and indium are largely the ores of zinc and aluminum, from which 

they are recovered as minor byproducts. Potential additional 

sources are copper ores, tin ores, and combustion products 

of coal. The high cost of recovery and refining of gallium, 

germanium, and indium limits their use to relatively small 

quantities, mainly in transistors, diodes, and other electronic 

devices. 

The geologic potential for finding deposits that could be exploited solely for their gallium, germanium, or indium content is very small. The potential for discovery of ore·s of other 

metals from which gallium, germanium, or indium could be 

recovered is significant. The potential for recovery of gallium 

and germanium from coal ash, flue dust, and stack gases in 

industrial plants consuming large quantities of coal is large. 

INTRODUCTION 

Gallium, germanium, and indium are three relatively rare metallic elements that occur in accessory 

or trace amounts in many rocks and minerals, including some in ores of other metals. Commercial 

recovery of these minor metals is, at present, entirely as a byproduct in the processing of major 

metallic ores, primarily zinc and aluminum, and to 

a lesser extent copper and lead. 

There are no known deposits in which these metals 

are sufficiently concentrated that they are apt to be 

the principal product sought. None of them occur 

as native elements, and they are essential components in only a few very rare minerals. Their total 

value is small or even negligible in relation to the 

value of the principal metals with which they are 

associated. They are deleterious impurities and must 

be removed in refining the major metal. The complex technology for their recovery is economically 

feasible only if, at some stage in the processing of 

the major metal, the minor metal or metals become 

concentrated in a separable phase. The costs of their 

separation and purification are significant, and so 

recovery is limited to the amount of each that can 

be marketed. A further problem associated with such 

potential byproduct materials concerns the lack of 

data about the variability of specific individual ore 

sources, inasmuch as the processing plants do not 

normally maintain records for such minor constituU.S. GEOL. SURVEY PROF. PAPER 820 

237 
238 UNITED STATES MINERAL RESOURCES 

ents. The varied concentration of these byproduct 

materials in their primary ores is significant, although it is secondary in importance to the technology employed in processing the primary materials, inasmuch as the technology is what determines 

whether the initial gallium, germanium, and indium 

contents are concentrated or dissipated. 

The principal physical and chemical properties of 

the three elements are listed in table 45. Gallium is 

notable for its low melting point and long liquid 

range and its expansion upon solidifying. Germanium 

also expands upon solidifying but is more notable for 

its high electrical resistivity in ultrapure form. Indium also melts at a low temperature but is notable 

for its softness and malleability. 

TABLE 45.-Selected properties of gallium, germanium, and 

indium 

Element ---------- Gallium 

Atomic number ____ 31 

Atomic weight ---- 69.72 

Stable isotopes and, 69 (60.1) their abundance 71 (39.9) 

(percent). 

Germanium 

32 

72.60 

70 (20.9) 72 (27.6) 73 (7.7) 74 (36.4) 76 (7_4) 

Melting point ( ° C)_ 29.78 937 

Boiling point ( o C)_ 2,403 2,840 

Density (g cm-3 ) __ 5.904 (solid) at 5.323 (solid) at 

29.6°C. 25°C. 6.095 (liquid) at 5.589 (liquid) 

29.8°C. 5.445 at 1,000° c. Expansion on so'idi- 3.2 6 fying (percent). 

Specific resistance 0.38•10-' at 0°C 60 at 27°C (ohm-em). 

49 

114.6 

Indium 

113 (4.2) 115 (95.8) 

156.2 

2,323 

7.31 at 20° C. 

9•10-8 at 20°C. 

60e10-R at 937°C 29•10-8 at 

156.4°C. Color ------------ Bluish white ___ Silvery white __ Lustrous bluish 

Hardness --------- Soft, ductile ___ Brittle, nonValence (most com- mon shown in italic). 

ductile. 

4, 8, 2 4. 2 

PRINCIPAL USES 

white. 

Malleable, 

ductile. 

8, 2, 1 

The principal uses for gallium, germanium, and 

indium are as ingredients in transistors, diodes, and 

rectifiers, which are basic electronic components 

used in a wide variety of communications and control systems. The importance of these tiny devices 

in modern technology is difficult to overestimatethey perform the functions that formerly required 

vacuum tubes, but they do so with greater reliability, very small power consumption, negligible heat 

loss, extended durability, ruggedness, and compactness. Without these so-called solid state devices, the 

present generation of large computers would not 

have been feasible, because of the space, power requirements, and heat generated by an equivalent 

number of vacuum tubes. The amount of gallium, 

germanium, or indium used in each individual transistor or diode is quite small, but the very large 

number of such devices now being manufactured 

provides a significant market for these little-known 

materials. 

Gallium, in addition to being used in these semiconductor devices, is used to modify other semiconductor materials, to form leads for transistor 

connections, and to provide a device that emits visible light as an indicator in various instruments. As 

an alloying ingredient, gallium forms a number of 

low-melting alloys of potential use. It also has 

potential application as a catalyst and in fluorescent 

materials. 

Germanium is used dominantly in single-crystal 

high-purity form in the manufacture of transistors, 

diodes, and rectifiers. A typical transistor contains 

a wafer of germanium alloy 4 square millimeters in 

area and about 0.2 millimeters thick, whereas a 

diode is only about one-fourth as large, and rectifier 

crystals may be much larger. The weight of a transistor wafer is a few thousandths of a gram. In addition to major applications in communications and 

computers, germanium semiconductor devices have 

considerable use in nuclear radiation detection instruments. Germanium also is used in infrared equipment and in special optical glass. As an alloying 

ingredient, it increases hardness and improves rolling properties in alloys with copper, aluminum, and 

magnesium. It is used in gold solders and in jewelry 

manufacture. It is a constituent in several phosphors and has been used as a catalyst in polyester 

textile manufacturing. 

Indium is used as a desired impurity in germanium and silicon transistors, as a solder for transistor leads, and in the fabrication of transistors, 

thermistors, and optical devices. It has been used 

in low-melting alloys and as a bearing alloy. It is 

used as a gasket material in aerospace hardware, 

as a sealant for glass-to-metal and glass-to-glass 

joints, in dental alloys, and in jewelry and silverware alloys to keep metals bright. Proposed uses 

include colorants for glass and as catalysts in 

petroleum refining. 

ALTERN ATE MATERIALS 

Silicon in high-purity form is an alternate and 

less expensive material that competes extensively 

with germanium in the fabrication of transistors 

and diodes, and selenium and tellurium are used in 

rectifiers. Gallium, germanium, and indium can be 

used to some extent in substitution each for the 

other material. The specific characteristics of each, 

however, are unique in some applications, and therefore, complete substitution is not likely. 
GALLIUM, GERMANIUM, AND INDIUM 239 

PROBLEMS IN DEVELOPMENT OF COMMERCIAL USES 

The dispersed nature of the occurrences of gallium, germanium, and indium delayed the identification of these elements in to the latter part of the 

19th century. The complex technology needed to 

recover each of them from dispersed sources has 

kept their prices at reasonably high levels. Their 

presence in ores of other metals is generally in such 

small quantities that they are not routinely analyzed 

for in commercial ore assays, nor has there been any 

reward to the producer for the gallium, germanium, 

or indium content of his ores. 

Conventional treatment of these ores tends to 

eliminate the small content of the three metals as 

an inconspicuous part ·of the waste products. No 

major toxic effects have been reported from any of 

the three elements, so no special handling has been 

required to remove them from waste products. Each 

of these factors contributes to the overall situation 

that at present exists, in which the lack of a major 

supply precludes uses that would require significant 

tonnages of any of these metals, and conversely, 

the lack of a demand for significant tonnages precludes an intensive search for major additional 

sources of these metals. 

The present industry recovers and refines only 

enough of each metal to satisfy existing markets, 

largely because the cost of refining is high and substantially equal to the market price. The recovery 

and refining processes are typically conducted as 

batch processes and for the most part have not 

operated on a full-time basis. In short, the recovery 

and refining of gallium, germanium, and indium 

have not been a major profit or operating factor in 

any operations to date. 

Published data on production of the three materials have been limited by the relatively small 

number of producers. Table 46 presents estimated 

data, based on published sources, to provide some 

idea of the present extent of production. 

RESOURCE AVAILABILITY 

Gallium, germanium, and indium are so dispersed 

in nature that no deposits are known that could be 

exploited solely for their recovery. The commercial 

sources for these elements in the United States at 

present are as byproducts from the processing of 

zinc ores and, additionally for gallium, processing 

of aluminum ores. In the United Kingdom, germanium and gallium are recovered by processing fly-ash 

TABLE 46.-Estimated production, price, and apparent demand for gallium, germanium, and indium 

Production (kg) 

Price per gram Apparent U.S. demand Year Gallium Gennanium Indium (k&') 

u.s. World 1 u.s. World u.s. World Ga Ge In Ga Ge J;n 

1926 8 

1930's +150/yr $50.00 

1941 220 42 <5 650 $5.00 $1.00 

43 <10 <50 1,850 .50 44 <10 <50 2,565 .35 

45 <10 <50 1,785 .25 

46 <10 51}-.-500 300 .072 

47 <10 435 .072 

48 90 500 380 4.50 .072 

49 0 1,705 .072 

1950 3,910 4.50 .072 

51 90 4,765 -3.5o .072 

52 0 .77 .072 

53 10,000 3.25 .072 

54 3.25 .072 

55 

>3~35 3.25 .072 

56 32,000 3.25 .072 

57 3.25 .072 20~00 58 27,150 .072 

59 90 3 50,001}-.- .32 .072 

75,000 

1960 24,500 .295 .072 

61 18,150 .295 .072 

62 16,780 .295 .072 

63 9,070 .95- .25 .072 

1.40 

64 9,070 68,945 .25 .07-4 

65 13,610 .252 .088 66 13,610 .17 .088 67 13,610 -62~2-00 .17 .088 

68 100- 800- 9,525 54,750 .60- .17 .08 200- 47,200 17,100 

300 1,000 1.75 400 

69 13,610 85,275 .185 .08 

1970 12,700 84,370 .271 .08 71 12,250 88,000 .75 293 .08 

1 Total world production to 1965 about 5 tons. a 4-year annual average, 1959-62. 2 10-year annual average, 1958-67. 
240 UNITED STATES MINERAL RESOURCES 

from the combustion of coal. Additional potential 

sources of recovery exist in the processing of copper and lead ores and possibly in the processing of 

ores of other metals, including tin, tungsten, molybdenum, and arsenic. 

The major resource problem therefore involves 

not so much the geologic occurrences of the three 

metals as the fate of the three metals during the 

processing of the ores for their major components. 

From the scattered data on occurrence, apparently 

relatively little of the gallium, germanium, and indium potentially recoverable is now being obtained. 

Estimates of the germanium content of zinc ores, 

for example, suggest that potential resources are 

adequate to support a several-fold increase in annual 

production and the additional potential resources in 

coal would permit further expansion of production. 

Potential for recovery of additional gallium is also 

quite large, and the potential for indium is appreciable. 

EXPLOITATION 

Gallium, germanium, and indium have had similar 

histories. About half a century elapsed between the 

time they were first identified and the time that 

first commercial uses for them were developed. The 

growth in specific uses of the elements was undoubtedly retarded by the lack of natural sources 

of ores containing appreciable concentrations and 

by the relative difficulty of refining each of them 

from dispersed sources. Systematic study of their 

physical and chemical properties and investigation 

of their compounds and alloys are still progressing; 

thus, additional new uses will undoubtedly be found. 

Recovery of indium on a semicommercial scale 

began in the 1920's for use as a precious-metal alloying agent to enhance brightness and retard tarnish. 

Additional uses developed in special bearing-metal 

alloys in the 1940's, but until the development of 

uses in semiconductor devices about 1952 the demand was not particularly steady. Similarly, germanium was not recovered in significant quantities 

until the early 1940's, when its use in electronic 

rectifiers led to initial commercial-scale production. 

With the development of transistors, beginning 

about 1948, germanium consumption increased 

greatly, and it continued to increase steadily through 

1960, when there was a sharp decline in consumption 

because of competition from silicon and because of 

improvements in fabricating techniques. Gallium 

production began in 1943 with most of the few kilograms produced being used in research. With the 

development of semiconductor devices, production 

grew in the late 1940's and early 1950's to about 90 

kg (kilograms) a year and has apparently stayed at 

about that level since then, with 1968 production 

estimated to be in the range of 100-300 kg. The 

present commercial production of each of the three 

elements is substantially smaller than might be 

achieved if there were larger markets. Recovery and 

refining are expensive; therefore, only the amounts 

that can be marketed are processed. The amounts recovered are obtained from several different intermediate products in the processing of ores of other 

metals. These starting materials in the recovery of 

the three metals generally represent the highest concentrations of gallium, germanium, or indium that 

can be obtained at some point in the production line 

where a separation can be made conveniently. 

The principal products in which appreciable gallium, germanium, and indium are concentrated are 

recovered by roasting zinc sulfide ores to produce 

crude zinc oxide and by further roasting this with 

salt to separate the volatile chlorides of germanium, 

gallium, cadmium, and indium from the zinc. These 

chlorides are collected by electrostatic precipitation 

and purified by complex distillation, chemical treatment, and electrolytic separation. 

In addition, the drosses, slags, and anode slimes 

in other smelting and refining processes can be used 

as starting materials, especially the materials that 

are associated with the recovery from zinc of other 

byproduct metals such as cadmium, lead, and tin. 

Gallium is also recovered from the leaching solutions 

used to make alumina from bauxite. At some stage 

in the caustic leaching cycle the solution builds up 

an equilibrium concentration of gallium (about 0.1 

g per liter) which can be recovered by precipitation 

with carbon dioxide, filtration, -and complex separation followed by electrolysis. 

The complex chemical and physical processes used 

to separate and concentrate these metals have been 

developed primarily to operate on specific starting 

materials available to individual companies. For the 

most part, these starting materials are selected because they have the highest initial concentration of 

one or more potentially salable byproducts and because the particular starting materials can be conveniently acquired. Very few data are published on 

the trace-metals content of potential interest for 

other possible off-products at various stages of 

smelting and refining. 

Judging from geochemical data on their germanium and indium contents, some copper ores, especially those containing enargite, bornite, tennantite, 

and tetrahedrite, would seem to be of particular interest as sources of these metals. The distribution of 

such trace metals in various stages of concentrating, 
GALLIUM, GERMANIUM, AND INDIUM 241 

smelting, and refining have not been described in 

detail. 

RELATION TO OTHER COPRODUCTS OR BYPRODUCTS 

The interrelationship of these minor byproduct 

metals to other byproduct or coproduct metals is of 

particular interest. For example, the refining of cadmium from zinc plant residues offers an additional 

stage of processing in which germanium and indium 

may be volatilized and partly separated from other 

metals into an enriched product. Similarly, in the 

re-treatment of lead-bearing wastes in the refining 

of zinc, several metals, such as tin, bismuth, and 

indium, are concentrated in the dross skimmed from 

lead bullion. Recovery of these minor constituents 

and further separation account for most of the 

Canadian production of indium. 

The economic viability of production of these 

minor metals from a particular source is not easily 

determinable. With limited markets, the search for 

additional sources has not been intensive. The recovery and separation methods have not yet been 

simplified to the extent that any one technique 

could be incorporated as a step in a continuous 

smelting or refining process. 

ENVIRONMENTAL RELATIONSHIP 

Both gallium and germanium, in limited amounts, 

are apparently taken up by plants. A germanium 

concentration of 10 ppm (parts per million) in the 

ash is r~ported to be the toxic limit for plants under 

experimental conditions. There are no reported occurrences of natural concentrations of germanium in 

soils above toxic limits. No toxicity in plants has 

been established for gallium or indium. Gallium is 

reported to be found in concentrations of 0.1-0.2 

ppm in plant ash and has been detected in vegetable 

foodstuff and hens' eggs. No adverse environmental 

factors have been directly attributed to any of the 

three elements, although indium and its compounds 

have toxic properties to humans if ingested in large 

quantities, and massive ingestion of gallium compounds is also toxic. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

All three elements are among the "dispersed" 

elements that tend not to form distinct minerals 

of their own, but to proxy for other major elements 

in most rocks and minerals. 

Gallium is closely coordinated geochemically with 

aluminum, with which it is associated. Its ionic 

radius is 0.70 A in sixfold coordination (valence 

+3), permitting relatively easy substitution for 

aluminum (ionic radius 0.61 A). This association 

accounts for the thorough dispersal of gallium as a 

trace constituent in most igneous and sedimentary 

rocks, as shown in table 47. It also accounts for the 

relatively higher concentration of gallium in bauxite 

and other aluminous rocks. Gallium is also concentrated in sulfide minerals, especially the zinc sulfide 

minerals sphalerite (ZnS) and wurtzite ( [Zn,Fe] S), 

in which concentrations of as much as 0.5 percent 

gallium have been reported. The concentration of 

gallium is reported to be higher in sulfide minerals 

formed at lower temperatures. Gallium is apparently 

absorbed by the organic matter in some plants and 

becomes concentrated in coal beds. 

Germanium is closely coordinated with silicon and 

tin, and it can proxy for these elements in the 

crystal lattices of appropriate minerals. Germanium 

is distributed rather uniformly among the silicate 

minerals of most rocks. It is notably concentrated 

in topaz (as much as 700 ppm) and, to a lesser 

extent, in cassiterite, garnet, and micas from rocks 

rich in fluorine, such as some granite pegmatites 

TABLE 47.-Gallium, germanium, and indium contents of various materials 

Material 

Continental crust ----------------------- Igneous rocks: 

Ultramafic -------------------------- Basaltic --------------·------------- Intermediate ------------------------ Silicic -----------------------------

Alkalic ---------------------------- Sedimentary rocks: 

Limestones ------------------------- Sandstones ------------------------- Shales and clayS --------------------

Bauxites ---------------------------

Waters: Coal ------------------------------

Ground water ---------------------- Hot springs ------------------------

Rivers -----------·------------------ Sea water --------------------------

[Crust and rocks, parts per million; waters, parts per billion] 

Gallium 

Usual range 

1-5 

9-20 

1~23 

14-30 

18-70 

3-20 

7-50 

2~100 

Average 

18 

2 

15 

16 

19 

40 

4 

8 

20 

60 

7 

Germanium 

Usual range Average 

0.7- 1.5 

.8- 3.2 

1.2- 6 .5- 4.7 .9- 3.5 

~ .8 

o- 3.5 o- 3.9 1.~ 3.6 1 -150 

~ 24 .4- 44 

.03- .11 

1.5 

1 

1.3 

1.6 

1.6 

1.4 

.4 

.8(?) 

2.2 

2 

5.5 

.3(?) 10 .05 

.06 

Indium 

Usual range 

0.01-0.3 

.01- .3 .01- .9 

.02- .5 .01- .3 

.03- .2 .01- .7 .03- .2 

Average 

0.14 

.07 

.1 

.17 

.16 

.07 

.01 

.06 

.1 

.08 
242 UNITED STATES MINERAL RESOURCES 

and greisens. Germanium is appreciably concentrated 

in sulfide minerals, particularly sphalerite and wurtzite, which commonly contain 0.01-0.05 percent ger· 

manium and have been reported to contain as much 

as 0.5 percent germanium. Enargite (Cu3AsS4) commonly contains 0.01-0.1 percent germanium. Ger. 

manium is absorbed by the organic matter in plants 

and becomes concentrated in coal beds, especially in 

the uppermost and lowermost layers in a coal se· 

quence. In weathering, germanium apparently enters 

the clay minerals and is slightly concentrated in 

shales. 

Indium is not closely coordinated with any major 

element, and its distribution in nature is less well 

known. It has some association with tin, for which 

it apparently can proxy. It is a rare element, and 

notable concentrations are mainly limited to occurrences in sulfide minerals, especially sphalerite, 

which commonly contains 10-20 ppm and has been 

reported to contain as much as 1 percent indium in 

some specimens. Some copper-bearing minerals, particularly chalcopyrite and tetrahedrite, also have 

indium contents ranging from a few parts per million to 1,500 ppm. 

ABUNDANCE 

As shown in table 47, the estimated abundance of 

these three elements in rocks of the continental crust 

ranges from 18 ppm for gallium to 0.14 ppm for 

indium. Gallium is thus slightly less abundant than 

cobalt and considerably more abundant than various 

much better known metals such as tin, molybdenum, 

cadmium, and silver. Germanium, with an average 

abundance of 1.5 ppm, is as abundant as molybdenum and tin. Indium is slightly more abundant than 

silver. The fact that none of the three elements 

forms its own minerals, except in a few rare deposits, 

is largely a function of the chemical nature of the 

elements that permits them to substitute in trace 

amounts for other elements in a variety of common 

minerals. 

Gallium in igneous rocks tends to occur in larger 

amounts in the more aluminous rocks, and within 

individual intrusions it is more concentrated in the 

later formed aluminous minerals. Highest concentrations are found in pegmatites, where gallium is 

most abundant in muscovite. Gallium tends to follow 

aluminum in the processes of weathering, although 

it may be slightly more mobile in normal soil-profile 

development. In the development of bauxite, however, the relative concentration of gallium increases 

with respect to aluminum. In sedimentary rocks only 

shales and clays tend to accumulate gallium. In 

metamorphic rocks there does appear to be a significant migration of gallium, although data are 

sparse. Gallium does not enter the biologic cycle to 

a significant extent, but it is taken up by some 

plants, where it is a minor component, presumably 

in an organic complex. 

Germanium in igneous rocks is slightly more abundant in the silicic and intermediate rocks and is 

especially more abundant in the rocks developed in 

the late pegmatitic and pneumatolytic stages. In 

such rocks fluorine apparently provides a mechanism to transport and concentrate germanium into 

such minerals as topaz and cassiterite. In the weathering cycle, germanium is not notably concentrated 

in most processes but may be partly removed by 

surface waters. The bulk of the germanium content 

remains and is most likely in the clay minerals. The 

germanium content in living plants never exceeds 

10 ppm in their ash, which is reported to be the 

toxic level in plants. The germanium content of coals 

ranges from a few parts per million to several hundred parts per million and is irregularly distributed 

laterally within individual coal beds and vertically 

within coal seams. Highest germanium contents are 

typically found in either the uppermost or lowermost layers. The germanium content is predominantly bound to the organic matter, coals with lowest 

ash content having the highest germanium content. 

Fly ash from coal combustion may contain as much 

as several percent germanium. 

Very sparse data are available to indicate the distribution of indium. In igneous rocks it is slightly 

more abundant in intermediate and silicic rocks than 

in basaltic or alkalic rocks. It is notably concentrated only in pneumatolytic and hydrothermal 

stages. In sedimentary rocks it may be slightly concentrated in clays and shales. Data are insufficient 

to categorize its occurrence in metamorphic rocks, 

although slight enhancement of the indium content 

is suggested. Indium is not reported to be concentrated in plant ash or in coal. 

ORE MINERALS 

Gallium, germanium, and indium are concentrated 

in sulfide minerals, especially the zinc sulfide sphalerite. Table 48 lists the principal ore minerals that 

have been reported to contain appreciable amounts 

of any of the three elements, and where data exist, 

it gives some idea of both the range and the typical 

contents- of these elements. The table also lists the 

rare minerals containing any of the three elements 

as essential components. 

Of these rare minerals, most have been found 

mainly in studies of a single deposit, that at Tsumeb 

in South West Africa. 
GALLIUM, GERMANIUM, AND INDIUM 243 

TABLE 48.-Gallium, germanium, and indium contents of selected ore minerals and of reported gallium, germanium, and 

indium minerals 

Mineral name and composition Gallium Germanium Indium 

Ore minerals (ppm) 

Sphalerite, ZnS ---------------------- Galena, PbS ------------------------ Chalcopyrite, CuFeS2 -----------------

Enargite, CusAsS! -------------------- Bornite, CusFeS4 ---------------------

Tennantite, Cul2AsfS1a ---------------- Tetrahedrite, Cu12SbfS1a ---------------

Covellite, CuS ----------------------- Chalcocite, Cu2S ---------------------

Pyrite, FeS2 ------------------------

Molybdenite, MoS2 ------------------- Stannite, llu2FeSnSt ------------------ Cas!literite, Sn02 --------------------- Wolframite, (Fe,Mn)WOt ------------- Arsenopyrite, FeAsS -----------------

Range 

1-10,000 

0- 600 

0- 100 

0- 100 

0- 60 

Median 

40-60 

Range 

I) -1,850 

0 - 10 

0.6- 900 

10 -5,000 

0 -1,000 

0 -5,000 0 - 500 

0 - 40 

0 - 30 

0 - 100 

2 - 10 6 - 20 5 - 200 

1 - 60 

Median 

100-600 

10- 40 

10- 80 

10 

Range 

0.5-10,000 

0.5- 100 

0 - 1,600 

0 - 100 1 - 1,000 

0.1- 160 

0 - 500 

0 - 100 0 - 50 

5 - 1,500 

0.6-13,500 

0 - 16 

0.3- 20 

Median 

40 

20 

so::5oo 

22 

0- 10 

3 

Galliu~ minerals (percent) 

Gallite, CuGaS2 ---------------------- Sohngeite, Ga(OH)a ------------------

36 

49.6 

Germanium minerals (percent) 

Argyrodite, AgsGeSe ------------------ Germanite, Cua(Ge,Fe)S. -------------- Renierite, ( Cu,Fe,Ge,Zn) S ------------ Briarite, Cu2(Fe,Zn)GeS• -------------

Stottite, FeGe(OH)6 ------------------ Fleiseberite, PbaGe(S0,)2(0H)6e3H20 __ _ 

Itoite, PbaGe(S04)202(0H)2 ----------- Schaurteite, CaaGe(S04)2(0H)6e3H20 __ _ 

1.85 

0.65 

0-2.2 

0.7 

7 6.2-11.4 

5.9- 9.6 

13.7-16.9 

29 

6.7 Not available 

14.8 

0.15 

Indium minerals (percent) 

Indite, FeiD2S4 ----------------------- Requesite, CulnS2 -------------------- Sakuralite, (Cu,Zn,Fe)a(ln,Sn)S• ------

Dzhalindite, ln(OH)a -----------------

As shown in table 48, sphalerite is the mineral in 

which all three elements tend to be most concentrated. The exact nature of their incorporation into 

the crystal lattice of sphalerite is not fully known, 

but there do not appear to be distinct solid phases 

of the sulfides of any of the three elements, and each 

element is apparently able to proxy for zinc in the 

limited amounts found. There is some evidence that 

germanium and gallium contents are highest in the 

low-temperature varieties of sphalerite and that indium content is highest in medium-temperature 

varieties of sphalerite. Thus, zinc ores from lowtemperature deposits such as the upper Mississippi 

Valley and Tri-State districts tend to have among 

the highest reported gallium and germanium contents but not the highest indium content. 

Other sulfide minerals that have major concentrations of germanium are chalcopyrite, bornite, enargite, and tennantite. Major concentrations of indium 

have been reported in cassiterite, especially in the 

"wood tin" variety, in which the concentration may 

typically exceed 0.5 percent indium. Stannite, another tin-bearing mineral, also has been reported to 

contain significant indium concentrations. 

TYPES OF ORES 

59.3 

46.3-47.8 

17 -23 Not available 

The present major sources of gallium, germanium, 

and indium are zinc and bauxite ores, which are 

more fully described in the chapters on zinc and 

aluminum resources. 

SULFIDE ORES 

Far too few data are available to indicate the 

variation in distribution of any of the three elements 

in s~ecific zinc deposits or within districts or broader 

regions. The sparse data suggest that there may be 

geologic provinces in which one or all of these elements are relatively more abundant in the intermediate to silicic igneous rocks, and that late-stage 

pneumatolytic and hydrothermal deposits associated 

with these rocks might be correspondingly enriched. 

The relatively higher gallium and germanium content noted in sphalerites formed at lower temperatures indicates a beginning of attempts to unravel 

the specific distribution patterns for these elements. 

The geologic environment most favorable for large 

zinc sulfide ore deposits is in sedimentary sequences 

which include carbonate rock strata that have been 

permeated by mineralizing solutions. The source of 
244 UNITED STATES MINERAL RESOURCES 

mineralizing solutions for some deposits is clearly 

associated with nearby igneous intrusions. For a 

significant number of major districts, however, the 

source of mineralizing solutions is equivocal. The 

Mississippi Valley and the Tri-State districts, in 

which gallium and germanium are relatively highly 

concentrated, are included in the group of deposits 

which have no closely associated intrusive bodies. 

The unique Tsumeb deposit in South West Africa is 

a pipelike body cutting a dolomitic sequence; it consists of a core of aplitic or pseudoaplitic rock surrounded by a shell of replaced carbonate rock containing lead, copper, and zinc sulfides with sparse 

amounts of germanite and renierite intergrown with 

galena and tennantite. 

From the sparse data available, the occurrence of 

gallium, germanium, and indium in sulfide deposits 

is governed by their ability to coprecipitate with zinc 

in environments favorable to metal sulfide deposition. Apparently the concentration of gallium, germanium, and indium in mineralizing solutions is 

small, and in only a few deposits, notably at 

Tsumeb, has the concentration exceeded the maximum level at which they are able to enter the crystal 

lattice of sphalerite and other sulfide minerals. 

In addition to occurring in zinc deposits, germanium is notably concentrated in some sulfide ores 

of copper, especially in deposits containing enargite, 

bornite, or tennantite, such as those at Butte, Montana; Chuquicamata, Chile; Cerro de Pasco, Morococha, Quiruvilca, and Casapalca, Peru; and Bor, 

Yugoslavia. The germanium content of enargite 

typically may be higher than it is in many zinc 

deposits. Complex sulfide copper ores containing tin, 

antimony, and arsenic, as well as many tin ores such 

as those in Bolivia, contain significant indium and 

some germanium and gallium. Lead ores and complex lead-zinc-copper ores also may be potential 

sources. These ores of metals other than zinc in 

general have not provided major sources for recovery of germanium or gallium but have been the 

source of some indium production. 

BAUXITE 

Gallium is also concentrated in bauxite, which 

forms through intensive weathering of different 

kinds of aluminous rocks. For the Arkansas bauxite 

deposits, a slight increase in the gallium-aluminum 

ratio during bauxitization has been shown in comparing a series of analyses of fresh nepheline syenite, partly bauxitized rock, and high-grade pisolitic bauxite. This increase has been attributed to 

the lower solubility of gallium hydroxide compared 

with aluminum under reducing conditions. Typical 

gallium contents of bauxites range from 20 to 100 

ppm, the higher values being found in bauxites developed from granitic and alkalic rocks. There are no 

systematic studies of the lateral variation of gallium 

content in bauxite deposits, but the few data available suggest that lateral variation could be very 

slight. 

In the less intensely weathered high-alumina clays 

that have been considered as potential resources of 

aluminum, the gallium content is generally in the 

range of 30-60 ppm. 

COAL DEPOSITS 

Germanium and gallium both are found in very 

small concentrations in living plants, but no specific 

function has been attributed to their presence. Plant 

residues typically show some enrichment in both 

elements. The germanium and gallium content of 

many coal beds is notably high and is greatest in 

the uppermost or lowermost parts of individual coal 

seams. The germanium content of coal typically 

ranges from a few to a few hundred parts per million, and it may increase to a few tenths of a percent in the ashes formed by combustion of the coal. 

Gallium content in coals is not as variable, but it 

also increases from a few tens of parts per million 

in most coals to a tenth of a percent or more in 

selected combustion products. 

The variability of germanium content in coal 

seams is largely attributed to the reaction of complex humic acid hydroxyl groups with germaniumbearing water in such a way that any germanium 

released by plant decay or entering from outside 

the coal-forming environment is promptly incorporated or adsorbed in the organic complex. The gallium content presumably is similarly enhanced during coalification. The higher content of both metals 

in the upper and lower parts of coal seams is attributed to the greater volume of water passing through 

or adjacent to these parts of the coal beds during 

their formation because of the low permeability of 

the enclosing clayey strata. 

RESOURCES 

The known reserves of gallium, germanium, and 

indium are closely associated with currently exploited zinc and aluminum ores and with coal deposits that are supplying fuel to a few power plants 

in Great Britain. Additional potential resources are 

known, but much of the ore from which these metals 

might be recovered currently is processed without 

separation of these minor constituents. The extent 

of recovery in the future depends both on better 

recovery technology and on increased demand for 
GALLIUM, GERMANIUM, AND INDIUM 245 

the three metals. Ores of metals other than zinc 

and aluminum, especially some copper and tin ores, 

appear to have interesting concentrations of one or 

all of these metals and might become important 

sources. Recovery of germanium and some gallium 

from industrial coal ash, flue dusts, and stack gas 

is feasible and would increase the recoverable recoverable resources of these two metals significantly. 

RESERVES 

The U.S. Bureau of Mines has estimated the recoverable supplies to the year 2000 for these three 

metals, on the basis of 1968 technology and prices, 

and projected demands for the major metals with 

which they are associated, as follows: 

Gallium: 

Total potential in bauxite 

and zinc ores likely to be 

produced to year 2000 ___ _ 

Recoverable --------------- Germanium: recoverable from 

lead-zinc ores -------------

Additional potential, assuming 

recovery from coal consumed in industrial plants _ 

Indium: recoverable from 

lead-zinc ores (assumes 

some increase in zinc 

United States World 

(kg) (kg) 

2,700,000 Not available 

27,000 Not available 

375,000 1,360,000 

545,000 4,500,000 

prices) --------------------- 1,460,000 3,360,000 

These estimates are necessarily conservative in 

that present low recovery ratios have been used 

and no new technology is assumed. Some uncertainties have been introduced in these figures by the 

closing of several older U.S. zinc smelters in the 

:r:eriod 1970-72, which resulted in the reduction of 

domestic zinc smelting capacity by as much as a 

third. The figures provide at least the order of 

magnitude for amounts of the three metals that 

may be obtained in the next few decades at expected 

prices and using present technology. The figures 

suggest that any potential new uses requiring large 

amounts might require an associated increase in 

production through better technology or exploitation 

of additional sources. 

POTENTIAL RESOURCES 

On the basis of a simplistic assumption that all 

sphalerites contain gallium, germanium, and indium 

and that the estimated zinc reserves are all present 

as sphalerite, calculation of the amount of these 

three metals using median figures given in table 48 

suggests that about 2 million kg of gallium, 13.5 

million kg of germanium, and 1.8 million kg of 

indium might be contained in the recoverable portion of identified U.S. zinc resources described in 

the zinc chapter of this volume. If presumed identified resources are also included, these figures would 

be approximately three times larger. World identified recoverable zinc resources would contain on the 

order of 10 million kg of gallium, 70 million kg of 

germanium and 9 million kg of indium. 

About 2,400,000 kg of gallium may be present in 

identified domestic bauxite resources, and 12-18 

million kg of gallium in potential domestic resources. 

World resources of gallium contained in bauxite are 

probably on the order of 50 times larger than the 

domestic resources just cited. 

The amounts of gallium and germanium that 

might be contained in coal combustion products are 

less easily estimated, but the U.S. Bureau of Mines 

estimate suggests about 500,000 kg of germanium 

could be obtained from coal used in U.S. industrial 

plants, with a world figure at about 10 times that 

amount. 

The potential for recovery from ores of other 

metals has not been enumerated. At least for germanium, the content in identified domestic copper 

ores containing significant enargite, tetrahedrite, 

and tennatite might exceed 160,000 kg. On a world 

basis, the gallium, germanium, and indium contents 

of copper and tin ores are too poorly known to estimate their additional potential. 

PROSPECTING TECHNIQUES 

Prospecting techniques for each of the major resources with which gallium, germanium, and indium 

are associated are described elsewhere in this volume 

and will not be repeated. Even if major new uses for 

one or all of these elements were to be developed 

that would require greatly expanded production and 

associated price increases, there is very little geologic probability of finding ores that will be exploited solely for their gallium, germanium, or indium contents. 

Much information needs to be obtained and natural distribution patterns need to be defined before 

specific guides can be determined for each element. 

Their geochemistry is still imperfectly understood, 

especially the variability of each within specific 

deposits and the range of variability in different 

geologic settings. The accumulation and analysis of 

such data is the next logical step in establishing a 

better basis for identifying favorable deposits and 

estimating resource availability. 
246 UNITED STATES MINERAL RESOURCES 

PROBLEMS AND NEEDS FOR ADDITIONAL 

RESEARCH 

Resource studies of minor byproduct metals are 

limited by inadequate data. Although data have been 

published on germanium production in recent years, 

no production data are available for gallium and 

indium. Specific identity of original sources of byproduct materials is not maintained for these three 

metals. 

The data on geologic distribution of these trace 

metals have not been systematically assembled; 

therefore, distributional patterns in individual de-

:rosits are not well known, and regional variations 

have not been established. To the extent that commercial recovery of these materials might be feasible from sources other than those currently being 

exploited, much research is needed to establish the 

natural distribution pattern. 

The most promising areas of research would seem 

to be in studying the distribution of these trace 

metals in zinc and copper ore deposits and in making 

a systematic compilation of the metals' regional 

variations. 

In the broader area of commercial recovery, there 

appears to be significant concentration of these 

metals that might be recovered in the processing of 

other ores, particularly copper ores. Search for concentration of these metals in various smelting and 

refining products of all , metallic sulfide ores is 

needed. 

SELECTED BIBLIOGRAPHY 

Gorey, R. C., Myers, J. W., Schwartz, C. H., Gibson, F. H., 

and Colbassani, P. J., 1959, Occurrence and determination of germanium in coal ash from power plants: U.S. 

Bur. Mines Bull. 575, 68 p. 

Fleischer, Michael, and Harder, J. 0., 1948, The occurrence 

of germanium: U.S. Geol. Survey Trace Elements Inv. 

Rept. TEI-7, 25 p. 

Goldschmidt, V. M., 1954, Geochemistry: Oxford, Clarendon 

Press, 730 p. 

Gordon, Mackenzie, Jr., and Murata, K. J., 1952, Minor elements in Arkansas bauxite: E.con. Geology, v. 47, no. 

2, p. 169-179. 

Greenspoon, G. N., 1970, Indium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 595-602. 

Harner, H. R., 1961, Germanium, in Rare metals handbook 

[2d ed.]: New York, Reinhold Pub. Corp., p. 188-197. 

Kaiser, E. P., Herring, B. F., and Rabbitt, J. C., 1954, Minor 

elements in some rocks, ores, and mill and smelter products: U.S. Geol. Survey Trace Elements Inv. Rept. 

TEI-415, 119 p. 

Mills, J. R., King, R. A., and White, C. E. T., 1961, Indium, 

in Rare metals handbook [2d ed.]: New York, Reinhold 

Pub. Corp., p. 220-238. 

Paone, J ., 1970, Germanium, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 563-571. 

Sclar, C. B., and Geier, B. H., 1957, Paragenetic relationships 

of germanite and renierite from Tsumeb, Southwest 

Africa: Econ. Geology, v. 52, p. 612-631. 

Shaw, D. M., 1957, The geochemistry of gallium, indium, 

thallium-a review, [chap.] 6 in Ahrens, L. H., and 

oth·ers, eds., Physics and chemistry of the earth: New 

York, McGraw-Hill Book Co., v. 2, p. 164-211. 

Songina, 0. A., 1970, Rare metals [3d ed.] (translated from 

Russian by J. Schmorak): Israel Program for Sci. 

Translation, available from U.S. Dept. CommerC£, NTIS 

No. TT 70-50021, 442 p. 

Stadnichenko, T. M., Murata, K. J., Zubovic, Peter, and 

Hufschmidt, E. L., 1953, Concentration of germanium 

in the ash of American coals: U.S. Geol. Survey Circ. 

272, 34 p. 

Stampe·r, J. W., 1970, Gallium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 555-561. 

Thompson, A. P., 1961, Gallium, in Rare metals handbook 

[2d ed.]: New York, Reinhold Pub. Corp., p. 178-187. 

Wedepohl, K. H., 1970, Germanium, in Wedepohl, K. H., ed., 

Handbook of geochemistry: Berlin, Springer-Verlag, v. 

11-1, ch. 32. 

Zubovic, Peter, Sheffey, N. B., and Stadnichenko, Taisia, 

1967, Distribution of minor elements in some coals in 

the western and southwestern regions of the Interior 

coal province: U.S. Geol. Survey Bull. 1117-D, 33 p. 

Zubovic, Peter, Stadnichenko, Taisia, and Sheffey, N. B., 

1961, Geochemistry of miner elements in coals of the 

Northern Great Plains coal province: U.S. Geol. Survey 

Bull. 1117-A, 58 p. 

--- 1964, Distribution of minor elements in coal beds of 

the Eastern Interior region: U.S. Geol. Survey Bull. 

1117-B, 41 p. 

--- 1966, Distribution of minor elements in coal beds of 

the Appalachian region: U.S. Geol. Survey Bull. 1117-

C, 37 p. 
UNITED STATES MINERAL RESOURCES 

GEM STONES 

By ROBERT E. THADEN 

CONTENTS 

Page 

Abstract of conclusions -------------------------- 247 

Introduction ------------------------------------ 247 

Exploitation ------------------------------------- 248 

Geologic environment ---------------------------- 248 

United States occurrences ------------------------ 249 

United States production ------------------------- 250 

Imports and exports ----------------------------- 250 

Selected references ------------------------------- 250 

ABSTRACT OF CO~CLUSIONS 

Gem stones are mineral substances, other than metals, 

that are attractive enough for use in personal adornment or 

as small household objects. More than 230 mineral species 

are, or have been, us,ed as gem stones at one or another 

stage of man's cultural history. Gem stones ideally possess 

beauty, durability, and rarity, but the value of a stone may 

be enhanced considerably by masterful cutting. Diamond, 

sapphire, ruby, and emerald generally are considered precious stones; all other gem stones generally are considered 

semi-precious. Neither imitation nor synthetic gems have 

infringed seriously on the market for natural stones, nor 

are they likely to do so. Gem stones occur in most of the 

major geologic environments, but they do not form ore deposits in the normal sense. Since 1935, the mining of gem 

stones in the United States has been almost entirely a recreational activity of mineral collectors and hobbyists. The 

annual value of such gem production has risen from half a 

million dollars in 1952 to nearly $3 million in 1972. A little 

over $500 million a year is spent for importing gems, mostly 

cut and uncut diamonds, and about $200 million worth of 

cut diamonds and synthetic gems are exported annually. 

INTRODUCTION 

Gem stones are mineral substances, other than 

metals, that are attractive enough for use in personal 

adornment or as small household objects such as 

book ends, pin boxes, and statuettes. Gem stones are 

mostly, but not exclusively, of inorganic origin. 

Some vegetable substances, such as amber, and the 

cannel, anthracite, and jet varieties of coal are ineluded, as well as some organically precipitated 

mineral materials, especially pearl and coral. 

A large number of minerals have been used as gem 

stones at one or another stage of man's cultural history, mostly depending on availability or fashion. 

An inventory of more than 230 mineral species that 

now have or have had currency as gems-nearly onetenth of all known minerals (Fleischer, 1971)-can 

easily be compiled from published lists of gems and 

gem localities (Ball, 1931; Jahns, 1960; Schlegel, 

1957; French, 1968). 

Ideally a gem stone should possess beauty, durability, and rarity. Beauty, of course, is in the eye of 

the beholder and varies with the individual and with 

the culture in which he lives. Beauty is based on an 

appreciation of certain attributes of the stone-its 

color, clarity, optical dispersion, index of refraction, 

and perfection of chatoyant zones, to name a few. 

Durability encompasses other physical properties including chiefly resistance to scratching, which is a 

measure of innate hardness; resistance to cleavage 

and fracture; and insolubility. Rarity appeals to 

human exclusiveness and perhaps for this reason 

usually is the principal control over the value assigned to stones. Rarity, however, can act in the 

opposite manner; Jahns (1960) has stated that some 

stones, even those having all the other desirable attributes, are so rare as to be undependable in supply, 

to be virtually unknown, and therefore to command 

no market. Examples given by Jahns include the 

beautiful oil-green and reddish-brown strongly 

dichroic andalusite, and transparent phenakite, 

euclase, and staurolite. Others also could be namedtransparent cassiterite, brazilianite, and lapis lazuli. 

Some stones are a matter of national pride and are 

far more expensive in their country of origin than 

elsewhere. Alexandrite (chrysoberyl) from the 

U.S.S.R. is the prime example. 

Another characteristic, independent of the physical properties important in determining the value of 

U.S. GEOL. SURVEY PROF. PAPER 820 

247 
248 UNITED STATES MINERAL RESOURCES 

the stone, is the "make," a measure of the degree to 

which the lapidary has enhanced the physical characteristics of a stone. Enhancement is accomplished 

by orienting, proportioning, accurately shaping or 

faceting, and polishing the gem to display most effectively its optical properties in an esthetically 

satisfying form. 

Almost no gem stones meet the ideal definition 

that requires beauty, durability, and rarity; and 

some have no redeeming virtue but beauty. It is obvious, then, why those few stones-diamond, sapphire, 

ruby, and emerald-that have these three qualities 

to a high degree always have commanded a high 

price and always have been thought of as precious 

stones, in contrast to others considered to be only 

semiprecious. At certain times and places opal, chrysoberyl, and even pearl, turquoise, and amber also 

have been considered precious stones, largely on the 

basis of their rarity. Pearl and turquoise are now 

reasonably abundant and therefore reasonably inexpensive. On the other hand, vanishingly small supplies of stones of exceptional size and quality allow 

ruby and Uralian alexandrite to command prices far 

in excess of that asked for diamond of the same 

weight. Other stones increase in price faster than 

can be accounted for by inflation, increasing rarity, 

or national pride. Aquamarine and tanzanite (a variety of zoisite), for instance, have risen rapidly in 

price recently in some parts of the world, apparently 

very largely in response to changes in style of personal ornamentation-that is, in response to fad. 

The exhaustion of ancient mining areas, the discovery of new deposits, shifting tastes, development of 

synthetic stones, and changes in pattern of transportation and marketing have combined to break down 

these distinctions ; so the tendency is for all gem 

materials now simply to be known as precious stones. 

EXPLOITATION 

A very large fraction of all the gem materials ever 

produced is still in existence because of the inherent 

durability of stone, however soft, and the care normally lavished on costly artifacts. With the constant 

discovery of new gem deposits, it might be expected 

that the supply eventually would satisfy the market. 

But the market constantly grows, along with world 

population and affluence, and the attendant social 

and political unrest puts an additional premium on 

gems, for they constitute an easily portable and concentrated form of wealth. The price of any gemmaterial is not likely to drop except over the short term. 

Neither imitation nor synthetic gem stones have 

infringed seriously on the market for natural stones, 

nor are they likely to do so in the future,~ in spite of 

the already wide variety and crystalline perfection of 

these materials and the nearly frantic research to 

produce others. Ruby, sapphire, spinel, rutile, emerald, garnets, lapis lazuli, greenockite, diamond, and 

a number of other gems have been synthesized. Soma 

of these, in both colored and colorless forms, together with several natural gems and other synthetic 

materials such as strontium titanate and yttriumaluminum garnet (YAG), are marketed as inexpensive substitutes for natural diamond. Colored glass 

and imitation pearls, of course, fill the need for costume jewelry. Like Rembrandt originals, however, 

natural gem stones will always be assured a market 

because of the exclusiveness of rarity and genuineness, regardless of the disparity in price between 

them and their substitutes. 

Persistent commercial production of gem stones at 

a profit by a private corporation is a rarity anywhere in the world. The rich diamond pipes of Africa 

and the alluvial diamond deposits in Africa and in 

Brazil are significant exceptions. The profitability of 

government-owned mines, such as the emerald mines 

of Colombia and West Pakistan and the diamond 

deposits of Soviet Siberia, is not known. It is a fact, 

however, that the privately operated Chivor emerald 

mines in Colombia are now idle, perhaps in part 

because a reported large fraction of production was 

lost through pilferage and never reached the company's vaults. Commercial ventures to produce sapphire and ruby in Burma and in the Yogo Gulch area 

of Montana were short lived, as was the attempt to 

produce diamonds from the kimberlite pipes at Murphreesboro, Ark., and the same is true at many 

other places throughout the world. The small size 

·and diffuse nature of most deposits of gem materials 

seem to make them amenable to exploitation only by 

the individual miner or small group, often a family, 

many of whom mine stones only intermittently and 

by relatively unsophisticated methods. Yet the bulk 

of all gem stones exclusive of diamond and emerald 

are produced in this manner, whether they come 

from _the pegmatites of the Malagasy Republic, 

Brazil, Maine, or California, or from the alluvial 

deposits of Burma, Ceylon, or Idaho. 

GEOLOGIC ENVIRONMENT 

It is no tautology to say that gem stones are rare 

because they are not plentiful. They do not form 

"ore" deposits in the normal sense. The very precise 

environmental conditions required to produce gem 

stones, any gem stones, are unusual in the context of 

the large scale and constantly changing chemicalthermal-dynamic systems in which all minerals are 

formed. Gems, when present at all, generally are 
GEM STONES 249 

scattered sparsely throughout a large body of rock, 

or have crystallized as small aggregates or fill veins 

and small cavities. Even placer concentrations tend 

to be small-a few stones in each of several bedrock 

cracks, potholes, or gravel lenses in a streambed. The 

average grade of the richest diamond pipes in Africa 

is about 1 part diamond in 40 million parts "ore," 

and because much diamond is not of gem quality, the 

average stone in a woman's engagement ring is the 

product of the removal and processing of 200-400 

million times its volume of rock. 

Gem stones occur in most of the major geologic 

environments. Each environment produces a characteristic suite of gem materials, although many 

gems occur in more than one environment. 

The igneous rocks are the source of the greatest 

value of gems each year largely because the kimberlites in Africa (see chapter on "Abrasives") yield 

most of the world's diamonds. Other mafic igneous 

rocks yield ruby, sapphire, garnet, and peridot, and 

probably also, at least in some places, jadeite and 

nephrite. Granitic igneous rocks, particularly the 

coarsely crystalline pods and tabular bodies called 

pegmatites, and coarsely crystalline fillings of miarolitic cavities, probably contain a wider variety of 

gem stones than any other rock type. Quartz, tourmaline, topaz, apatite, spodumene, and beryl (including emerald) , in all their varieties and colors, as 

well as zoisite, garnet, chrysoberyl, sphene, spinel, 

and zircon, are characteristic of pegmatites and igneous cavity fillings. 

Metamorphic rocks ate the source of ruby, saphphire, garnet, and emerald. The schists and gneisses 

also contain andalusite, actinolite, chrysoberyl, zolsite, topaz, jadeite, and nephrite, whereas the additional suite of gem stones characterizing the marbles 

and related calcareous metamorphic rocks includes 

rhodonite, !azurite, epidote, cordierite, apatite, axinite, and tourmaline. Contact-metamorphosed rocks 

are likely to be more productive of a variety of gem 

materials than those that have been regionally metamorphosed; the igneous rock bodies nearby supply 

fluid emanations containing the constituents needed 

to form some of the gem minerals. 

Aqueous solutions, both the hot solutions derived 

from plutonic igneous bodies or from volcanic activity and the relatively cold solutions that percolate 

downward into the rocks from the surface of the 

earth, are the source of a rich variety of gem materials which precipitate in cracks, fissures, and 

voids or replace preexisting materials. Some gems 

precipitate only from waters that are at least reasonably hot; examples are euclase, citrine quartz, 

imperial topaz, emerald, and benitoite. Other gems 

can precipitate from aqueous solutions having a wide 

ranges of temperature-cacoxinite and amethyst, 

for example, as well as opal, pumpellyite, datolite, 

thomsonite and the other zeolites, hematite, tourmaline, some topaz, and certain garnets. Cold-water 

solutions descending through the rocks are the 

source of most agate, jasper, petrified wood and 

bone, and tigereye and other forms of cryptocrystalline quartz, and they also supply the oxygen needed 

to alter preexisting mineral materials to such gem 

materials as malachite and -turquoise. 

When a primary deposit of gem stones is weathered deeply, as is common in many parts of the 

world, the gems are left behind in a clayey matrix 

from which miners can easily wash them. Nearly all 

mining of gem-bearing rock is confined to the weathered zone because of the difficulty of freeing gems 

from fresh rock without shattering them. 

A placer deposit is formed when wind or water 

removes clayey matrix from a weathered gem-bearing rock body leaving the gems concentrated. Placers 

generally are far richer than the original sources 

because of the concentration process and because the 

imperfect gem stones tend to be eliminated by breakage, leaving behind the gems of exceptional quality. 

UNITED STATES OCCURRENCES 

Nearly 100 different mineral species have been 

mined and marketed in the United States as gem 

stones, and every state has contributed to this market. Most deposits consist of "semiprecious" stones. 

Even quasi-gem materials such as banded rhyolite, 

porphyritic andesite, clusters of marcasite crystals, 

and fossil trilobites have commercial value in the 

fabrication of pins, broaches, tie slides, and similar 

items. The United States also has produced diamond 

from Arkansas and ruby and sapphire from Montana and the Appalachian States, especially North 

Carolina; North Carolina also continues to produce 

an occasional emerald. Maine was at one time known 

for its commercial production of colored tourmalines 

and beryl. Large quantities of pink tourmaline from 

the Pala district of California were sent to China in 

the early part of this century. Wyoming and California continue to produce large quantities of the 

jade minerals, but production from vast jade fields 

in the Kobuk River region of Alaska is just beginning. Benitoite is known to occur nowhere in the 

world except in California, and the rhodolite garnets of North Carolina and the pumpellyite amygdules from the western end of Lake Superior are, as 

far as is known, unique. 

Large deposits of the more valuable gem materials 

that can be and have been mined for centuries such 
250 UNITED STATES MINERAL RESOURCES 

as the abundant pegmatites of Brazil and the Malagasy Republic, or the extensive placer deposits of 

southern Asia, are not known in the United States. 

The few American deposits which produced ruby, 

sapphire, emerald, beryl, and tourmalines commercially ceased doing so years ago. Since about 1935 

the production of gem stones in the United States 

has been restricted very largely to turquoise, jadeite, 

nephrite, opal, aventurine, and the cryptocrystalline 

silica minerals agate, petrified wood, ·~halcedony, 

chrysoprase, and jasper. In total value the silica minerals overwhelm all the others. Nearly all the gem 

stone production of the last 40 years has come from 

Texas and the States west of the Great Plains, but it 

is impractical to enumerate here all of the gem stone 

localities of even the Western States. 

UNITED STATES PRODUCTION 

The mining of gem stones in the United States 

since about 1935 has been almost entirely a recreational activity of mineral collectors and hobbyists. 

Estimates of the number of individuals in recent 

years whose entire income is derived from gem 

stones mined by themselves have ranged from only 

8 to about 30. This is not to say that the proprietors 

of roadside rock shops buy all of their stock from 

others. Rock shops are abundant in areas rich in gem 

materials, and the operators tend to specialize in the 

local gem commodities, most of which they gather 

themselves. Owners of properties containing gem 

materials, rather than doing the mining themselves, 

sometimes charge hobbyists for the privilege of collecting gem stones. Diamond in Arkansas, opal in 

Idaho, and agate in Oregon and Washington are 

mined by hobbyist under this type of "fee digging" 

arrangement. it is not usually, however, the value 

of the stones produced and sold in an area or the 

generally small fees collected by property owners 

that are the most significant contributions to the 

local economy of areas productive of gem stones; 

rather, it is the cost-of-living expenses of the hobbyists while afield. Moreover, with the growing popularity of lapidary work and of "rock hounding" 

among all age groups in the United States, and with 

the steadily increasing number of older people, many 

of whom are retired and have time available to pursue the hobby, both gem production and the economy 

of gem-producing areas are likely to increase substantially in the future. It is not paradoxical, therefore, that the United States, which has no major 

gem stone deposits and no organized gem-producing 

industry, still has been able to increase the value of 

its gem production from half a million dollars in 

1952 to nearly $3 million in 1972; the annual value of 

gem stones produced 20 years hence probably will be 

several times $3 million. 

IMPORTS AND EXPORTS 

The United States is a large importer of gems, 

mostly the "precious" stones diamond and emerald, 

of which the United States has only minuscule domestic production. Diamond once made up nearly 95 

percent of all gem imports; and although it has now 

dropped to about 80 percent, current import of cut 

diamond is about $200 million annually, and import 

of uncut diamond is about $300 million. Cut emerald 

is imported at a rate of about $10 million annually, 

and in some recent years the import of synthetic 

stones has been nearly this much. Pearls and other 

gem materials, including imitation stones, constitute 

only a few percent of the value of all gems imported. 

The value of gem stones exported from the United 

States is about $200 million per year. The reexport 

of diamond, cut in this country from imported uncut stones, accounts for much of this, but an increasing percentage is made up of synthetic stones. There 

is also a small but steadily increasing export of 

natural domestic gem materials to Germany, Taiwan, and elsewhere for fabrication. Principal among 

these materials are turquoise and the jade minerals, 

as well as quantities of massive actinolite, pink dolomite, banded rhyolite, and other ornamental stones. 

SELECTED REFERENCES 

Ball, S., H., 19?.2, The geologic and geographic occurrence of 

precious stones: Econ. Geology, v. 17, no. 7, p. 575-601. 

-- 1931, Historical notes on gem mining: Econ. Geology, 

v. 26, no. 7, p. 691-738. 

-- 1935, A historical study of precious stone valuation 

and prices: Econ. Geology, v. 30, no. 6, p. 630-642. 

-- 1949, Precious stones, in Industrial minerals and 

rocks [2d ed.]: Am. Inst. Mining and Metall. Engineers, New York, p. 714-747. 

Bauer, M. H., 1896, Edelsteinkunde (English translation, 

1904, by L. J. Spencer): Reprinted 1968 by Dover Publications, New York, 627 p. ( 2 vol.). 

Comstock, H. B., 1970, Gem stones, in Mineral facts and 

problems: U.S. Bur. Mines Bull. 650, p. 1013-1023. 

Fleischer, Michael, 1971, Glossary of mineral species, 1971: 

Mineralogical Record, Bowie, Maryland, 103 p,, appendix. 

French, A. E., 1968, Gem-stone, mineral, and fossil collecting, in Mineral resources of the Appalachian region: 

U.S. Geol. Survey Prof. Paper 580, p. 288-302. 

Jahns, R. H., 1960, Gem stones and allied materials, in Industrial minerals and rocks [3d ed.]: Am. Inst. Mining 

Metall., and Petroleum Engineers, New York, p. 383-

441. 

Petkof, Benjamin, 1965, Gem stones, in Mineral facts and 

problems: U.S. Bur. Mines Bull. 630, p. 361-377. 

Schlegel, D. M., 1957, Gem stones of the United States: 

U.S. Geol. Survey Bull. 1042-G, p. 203-253. 
UNITED STATES MINERAL RESOURCES 

GEOTHERMAL RESOURCES 

By L. 1. p. MUFFLER 

CONTENTS 

~bstract of conclusions ---------------------------

Introduction ------------------------------------- Exploitation -------------------------------------

Environmental considerations ----------------

Geologic Environments ---------------------------

Resources and probletns --------------------------

Prospecting techniques ---------------------------

References cited ---------------------------------

FIGURES 

27. Graph showing growth of geothermal generating 

capacity by countries, 1900-72 --------------

28. Graph showing weight percent of steatn produced 

by flashing water at various temperatures __ 

TABLE 

49. Principal utilization (other than for electricity) 

of geothermal resources --------------------

ABSTRACT OF CONCLUSIONS 

Page 

251 

251 

252 

253 

254 

254 

258 

259 

Page 

252 

255 

Page 

253 

The geothertnal resource base is defined as all the heat 

above 15°C in the earth's crust, but only a stnall part of this 

resource base can properly be considered as a resource. The 

magnitude of the geothermal resource depends on the evaluation of many physical, technological, econotnic, environtnental, 

and governmental factors. The physical factors that control 

the distribution of heat at depth can be evaluated, at least 

rudely. More tenuous are the assutnptions of technology, economics, and governtnental policy. These assumptions are critical to geothermal resource estimation, and differences 

among thetn are in great part responsible for the vast range 

in tnagnitude among different geothermal resource estimates. 

Utilization of a greater proportion of the geothertnal resource base depends on achieving one or tnore of the following items: 

1. Technological advances that would allow electrical generation frotn low-temperature reservoirs. 

2. Breakthroughs in drilling technology that would permit 

low-cost drilling of holes to depths greater than 3 kin. 

3. Developtnent of techniques of artificial stitnulation that 

would increase the productivity of geothermal reservoirs. 

4. Expansion of the use of low-grade geothermal resources 

for such purposes as space heating, product processing, 

agriculture, and desalination. 

INTRODUCTION 

Geothermal energy, in the broadest sense, is the 

natural heat of the earth. Temperatures in the 

earth rise with increasing depth. At the base of 

the continental crust (25-50 km), temperatures 

range from 200°C to 1,000°C (Lachenbruch, 1970) ; 

at the center of the earth (6,371 km), they range 

perhaps from 3,500°C to 4,500°C. Most of the earth's 

heat is far too deeply buried ever to be tapped by 

man. Although drilling has reached 7112 km and may 

some day reach 15-20 km, the depths from which 

heat might be extracted profitably are unlikely to 

be greater than 10 km. Even in this outer 10 km, 

most of the geothermal heat is far too diffuse ever 

to be recovered economically (White, 1965). Consequently, most of the heat within the earth, even at 

depths of less than 10 km, cannot be considered an 

energy resource. 

Geothermal energy, however, does have potential 

economic significance where heat is concentrated 

into restricted volumes in a manner analogous to 

the concentration of valuable metals into ore deposits or of oil into commercial petroleum reservoirs. At present, economically significant concentrations of geothermal energy occur where elevated 

temperatures are found in permeable rocks at depths 

less than 3 km. The thermal energy is stored both 

in the solid rock and in water and steam that fill 

pores and fractures. This water and steam serve to 

transfer the heat from the rock to a well and thence 

U.S. GEOL. SURVEY PROF. PAPER 820 

251 
252 UNITED STATES MINERAL RESOURCES 

to the ground surface. Under present technology, 

rocks with too few pores, or with pores that are not 

connected, do not constitute an economic geothermal 

reservoir, however hot the rocks may be. 

Water in a geothermal system also serves as the 

medium by which heat is transferred from a deep 

igneous source to a shallow geothermal reservoir at 

depths shallow enough to be tapped by drill holes. 

Geothermal reservoirs are located in the upflowing 

parts of major water convection systems. Cool rainwater percolates underground from areas that may 

consist of tens to thousands of square kilometers. 

At depths of 2-6 km, the water is heated by contact 

with hot rocks (in turn probably in contact with 

molten rock). The water expands upon heating and 

then moves buoyantly upward in a column of relatively restricted cross-sectional area (1-50 km2 ). 

The driving force of these large circulation systems 

300 

200 

100 

en 

1::300 

c( 

;: 

c( 200 

(!) 

w 

:::i: 100 

~ 

> 0 

1- 200 0 

is gravity, effective because of the density difference 

between cold downward-moving recharge water and 

hot, upward-moving geothermal water. 

EXPLOITATION 

The primary use of geothermal resource to date 

is for the generation of electricity (fig. 27). Under 

existing technology, geothermal steam (after separation of any associated water) is expanded into a 

low-pres~ure (5-7 bar) turbine which drives a conventional electrical generator. Geothermal heat is 

also used directly (table 49) in the heating and airconditioning of buildings, in the heating of hothouses and soil for agricultural purposes, and in 

product processing. In addition, warm waters from 

springs and wells are widely used for bathing, recreational, and therapeutic purposes, particularly in 

central Europe and in Japan (Komagata and others. 

U.S.A. 

c( 

~ NEW ZEALAND 

c( 100 

0 

..J 

c( 0 

2 ,:c a: 

1-

0 

w 

JAPAN l ..J ,:c w MEXICO 

I l 

100[ 

0 

U.S.S.R. J 

,:c ICELAND J 

1900 1910 1920 1930 1940 1950 1960 1970 

FIGURE 27.-Growth of geothermal generating capacity by countries 1900-72. Sources-Italy: [Italy] ENEL, [1970]. U.S.A.: 

Bruce (1971). New Zealand: McKenzie and Smith (1968); Smith (1970). Japan: Hayashida and Ezima (in press); Mori 

(in press). Mexico: Alonso-Espinosa and others (1968). U.S.S.R.: Tikhonov and Dvorov (1970); Facca (in press). Iceland: Ragnars and others (1970). 
GEOTHERMAL RESOURCES 253 

TABLE 49.-Princ.ipal utilization. (other than for electricity) of geothermal resources 

Use Country Loealitiea Quantity Reference 

Space heating --------- Iceland --------- Reykjavik 1.08X10U cal )'1'""1 in 1969 ····------·· P&lmason and Zoip (1970). 

Hungary -------

Hveragerdi, Selfosa, Saud&rkrokur, 8.8X1011 cal yr-1 in 1969 --······-·-·- Olafsfjordur, and Dalvfk. 

Various localities -------------------- Peak load 3.9X10U cal hr-1

: "Optimal useful production eapaclty''=1.1X 

Do. 

Boldiz&r (1970). 

1016 cal yr-1• 

U.S.S.R -------- Caucausus Mountains, Kazakhstan, 

Kamchatka. Uncertain but larce ------········-··· Makarenko and 

others (in press), 

Sukharev and 

others (in pr818). 

and Tikhonov and 

Dvorov (in press). 

New Zealand --- United Statea --- Rotorua -------------------------···- -950 wella ........................... . Burrows (1970). 

Klamath Peterson and Groh Falls, Oreg ----------------- -3X101ll cal yr-1 ---··-·----------·--- (1967). 

Boise, Idaho -····---------------------- Capability of 1-2x1oa gal )'1'""1 of 

75°C. water. ~ig (1970). 

Air conditionine ------- New Zealand __ _ Rotorua ----------------------------- 5.8 X lOS cal hr-1 heat input to LiBr absorption unit. 

Reynolds ( in press) • 

Agricultural heatine P&lmason and Zoiga --- Iceland --------- Hveragerdi -------------------------- >9.oX1~ m• of greenhouse in 1960; 5.3X101• cal 71'""1 in 1969. (1970). 

U.S.S.R -------- Various localities -------------------- 2X1()7 mJ of greenhouse in 1969 ------ Dragone and Rumi 

(in press). 

Hungary ------- Japan ----------

____ do ------------------------------ -4 X 1011 m~ of greenhouse in 1969 __ Boldiz&r ( 1970) • Komagata and others 

(1970). •••• do ------------------------------ -2X1~ mZ of greenhouse -----------

Italy -----------

United State& -- Product processing: 

Castelnuovo ------------------------- 3X108 m• of greenhouse -------------

Lakeview, Oreg ---··----------------- 2.3X108 m2 of greenhouse ----------·-

Dragone and Rumi 

(in press). 

Head (1970). 

Paper ------------- New Zealand __ _ Kawerau • --------·------------------ -9X101' cal )'1'""1 

-·-------······----·- Calculated from Smith ( 1970, table 

10). 

Diatomite --------- Iceland --------- N&mafjall --------------------------- -2X101' cal yr-1 ------·--·----------- Ragnars and otheta (1970, table 3). 

Salt ------··-------- Japan ---------- Shikabe, Hokkaido ------------------- 150 tons yr-1 of salt recovered from sea Komagata and 

water. others (1970). 

Byproduct&: 

Dry ice ----------- United Statea --- Imperial Valley, Calif ----·----------- >1.84 X 101 m• of COs between 1934 and Muffter and White 

1943. (1968). 

Boron ------------- Calcium chloride --- Italy ----------- United State& --- Larderello ---------------------··----- Large production from 1810 to 1966 -- Imperial Valley, Calif ---------------- Uncertain but small ------------------

1970). Geothermal energy has potential use in 

refrigeration and freeze drying (Einarsson, 1970), 

and some geothermal fluids contain potentially valuable byproducts, such as potassium, lithium, calcium, and other metals (White, 1968). 

Production of fresh water by self-desalination of 

geothermal fluids has been proposed for the Imperial 

Valley in Southern California (Rex, 1968, 1971b) 

and for the El Tatio geothermal field in northern 

Chile (Barnea, 1971). Evaluation of the geothermal 

desalination potential of the Imperial Valley is being 

carried out jointly by the U.S. Bureau of Reclamation and the Office of Saline Water (U.S. Bur. Reclamation, 1972). The quantities of geothermal water 

in storage in the Imperial Valley are large (Dutcher 

and others, 1972). If geothermal desalination proves 

to be technologically and economically feasible, the 

waters of the Imperial Valley may prove to be a 

significant augmentation to the fresh water supply 

of the southwest United States. 

ENVIRONMENTAL CONSIDERATIONS 

Considerable attention has been drawn to geothermal resources as an electrical generating mode 

that can have a relatively small effect on the environment. Geothermal energy does not produce 

atmospheric particulate pollutants as do fossil-fuel 

plants, and it has no potential for radioactive pollution. Geothermal modes of generating electricity do 

share with fossil-fuel and nuclear modes the potential for thermal pollution; indeed, the amount of 

waste heat per unit of electricity generated is higher 

for geothermal than for either nuclear or fossil-fuel 

modes, owing to the low turbine efficiencies at the 

low geothermal steam pressures. Geothermal effluents, as well as being warm, commonly are mineralized and thus present a chemical pollution hazard 

to surface or ground waters. Accordingly, most if 

not all proposed geothermal developments in the 

United States plan to dispose of unwanted effluent 

by reinjection into the geothermal reservoir. 

Other insults to the environment that are inherent 

in geothermal development are in large part ~ontrollable at reasonable costs. These include noise 

(drilling, testing, and production), gaseous emissions (particularly H2S), and industrial scars. Intensive geothermal exploitation may cause subsidence, due either to fluid withdrawal (Hunt, 1970) 

or to thermal contraction of rock as heat is withdrawn. Reinjection of water in fault zones may 

increase the incidence of earthquakes, by a mechanism similar to that demonstrated for the Rocky 
254 UNITED STATES MINERAL RESOURCES 

Mountain Arsenal well in Colorado by Healy, Rubey, 

Griggs, and Raleigh (1968). 

Bowen ( 1973) correctly pointed out that "To 

understand properly the impact of the production 

of electric power on the environment, it is necessary 

to evaluate more than just the power plant, whether 

it is geothermal, nuclear, or fossil fueled; the entire 

fuel cycle from mining, processing, transportation, 

and the disposal of spent wastes must be considered." When viewed in this light, the environmental 

impact of geothermal generation does indeed appear 

to be minor compared with fossil-fuel or nuclear 

generation. The environmental impact of geothermal generation is restricted to the generating site, 

whereas much of the environmental impact of other 

modes of generating takes place at other sites 

(mines, processing plants, disposal sites) and is 

commonly neglected in the evaluation of environmental impact of a power plant. 

GEOLOGIC ENVIRONMENTS 

Geothermal reservoirs are the "hot spots" of 

larger regions where the flow of heat from depth in 

the earth is about 11;2-5 times the worldwide average of 1.5X10- 6 calories per square centimeter per 

secoruL_ Such regions of high heat flow commonly 

are zonesm young volcanism and mountain building and are localized along the margins of major 

crustal plates (Muffler and White, 1972, fig·. 1). 

These margins are zones where either new material 

from the mantle is being added to the crust or 

crustal material is being dragged downward and 

"consumed" in the mantle. In both situations, molten 

rock is generated at depth and moves buoyantly 

upward into the crust. The resultant pods of igneous 

rock provide the heat that is then transferred by 

conduction to the convecting systems of meteoric 

water. 

There are two major types of geothermal systems: (1) hot water (White, 1970, 1973) and (2) 

vapor dominated ("dry steam") (White and others, 

1971 ; Truesdell and White, 1973 ; White, 1973). In 

a hot-water geothermal system, the fluid in the rock 

at depth is water alone. Steam is produced by boiling 

as the fluid moves up a well to the surface, and a 

mixture of steam and water is produced at the surface; the water must be removed from the steam 

before the steam is fed to a turbine. Vapor-dominated geothermal systems, on the other hand, contain both water and steam in the reservoir at depth. 

With decrease in pressure upon production, heat 

contained in the rock dries the fluids first to saturated and then to superheated steam, which can be 

piped directly into a turbine. Among geothermal 

systems discovered to date, hot-water systems are 

perhaps 20 times as common as vapor-dominated 

systems (White, 1970). 

Potentially recoverable geothermal resources also 

occur in some regions where the normal heat flow 

of the earth is trapped by insulating impermeable 

clay beds in a rapidly subsiding geosyncline. For 

example, along the gulf coast of the United States, 

temperatures of 150°C-273°C are found at depths 

of 4-7 km in geopressured zones (Jones, 1970). 

Waters in these geopressured zones are not circulating meteoric water; they are produced by compaction and dehydration of the sediments themselves. 

RESOURCES AND PROBLEMS 

Estimates of the geothermal resources of the 

United States and of the world differ by as much as 

six orders of magnitude. White (1965, p. 14) stated 

that "existing worldwide utilization equivalent to 

about 1 million kw * * * probably can be increased 

at least 10 times [that is, to 104 Mw] under present 

economic conditions and maintained for at least 50 

years." Banwell (1967, p. 155) estimated a potential heat production of 2X109 kg-cal/sec from geothermal energy associated with "Pacific type volcanism." At 14 percent thermal efficiency, this rate 

of heat production could sustain electrical generating capacity of about 106 Mw. Rex (1971a, p. 54) 

stated that he and his colleagues " * * * are estimating the western [conterminous] U.S. geothermal 

potential from 105 to 107 megawatts." White (1965) 

and Muffler and White (1972) estimated that the 

world geothermal resource to a depth of 3 km for 

electrical generation by proven techniques is approximately 2 X 1019 calories (equivalent to 58,000 

Mw for 50 yr). Rex (1972a) stated that" * * * the 

present recoverable [geothermal] resource for the 

western third of the continental United States, excluding Alaska, is of the order of 108 megawattcenturies. This figure could be expanded by another 

factor of 10 by the inclusion of the eastern twothirds of the United States and another factor of 

10 [that is, to 1010 megawatt-centuries] by improvements in technology." 1 John Banwell and Tsvi Meidav (oral presentation, Ann. Mtg. Am. Assoc. Adv. 

Sci., Philadelphia, 1971 ; ms. supplied by Tsvi Meidav) stated that "The geothermal energy reserves 

of the world are orders of magnitude greater than 

the total reserve of any other form of fossil energy." 

The wide variance among these resource estimates 

reflects several factors-predominantly, the defini1 If one assumes 14 percent thennal efficiency (as in Rex, 1972b), this 

electricity is produced from 4.93 X 11)26 cal. or approximately eight times the 

estimate of White (1965, p. 2) for the total heat stored under the 

United States to a depth of 10 km. 
GEOTHERMAL RESOURCES 255 

tion of the term "resources" as used by the respective authors. Schurr and Netschert (1960, p. 297) 

stated: 

The "resources" of a mineral raw material may be defined 

according to any technical and economic criteria that may 

be considered relevant and appropriate. The resources consist of that part of the resource base (including reserves) 

which seem likely to become available given certain technologic and economic conditions. * * * Whether any particular definition of resources is us·eful depends on the context 

in which i.t is to be used and the possibility and need for 

expressing it quantitatively. It is essential in any event 

that an explicit definition always be given in conjunction with 

the use of the term. 

Particularly for geothermal resources, it accordingly is incumbent upon any author to define his 

usage of "resources" and to state explicitly his assumptions. Most authors are seriously remiss in this 

regard, and their resource estimates must therefore 

be viewed with skepticism. 

The "resource base" was defined by Schurr and 

Netschert (1960, p. 297) as all of a given material 

present in the earth's crust, whether its existence 

is known or unknown and regardless of cost considerations. For geothermal resources, the "resource 

base" is therefore all of the heat in the earth's crust, 

presumably measured from ooK (= -273.15°C). 

For obvious practical reasons, heat below mean surface temperature of the earth (about 15°C) is excluded from consideration, and the geothermal resource base may be considered as all heat above 

15°C in the earth's crust. Quantification of the geothermal resource base depends on the definition of 

the term "crust," the estimate of the dimensions 

of the crust, the three-dimensional distribution of 

temperature within the crust at any particular 

moment, and the heat flux between the mantle and 

the crust and between the crust and the atmosphere. 

What proportion of the geothermal resource base 

should be considered as a resource? This proportion 

depends on evaluation of the following factors, many 

of which are interdependent: 

1. Depth of extraction, which is dependent on the 

technology and economics assumed. White 

(1965) gives estimates of geothermal resources to depths of 3 km, the deepest geothermal well drilled to date, and 10 km, the deepest 

well likely to be drilled in the foreseeable 

future. 

2. Three-dimensional temperature distribution to 

the depth assumed. 

3. Specific heat distribution; a convenient approximation presented by White ( 1965) is based 

on the fact that most earth materials have 

nearly equal volumetric specific heats. 

4. Porosity, effective porosity, specific yield, and 

permeability. 

5. Physical state of the fluid in the reservoir ( water or steam). 

6. Available technology. 

7. Economics of various possible uses. 

8. Governmental policy with respect to societal 

needs, environmental constraints, and availability of other forms of energy. 

Many physical factors that control the distribution of heat to any given depth can be evaluated, 

at least rudely (White, 1965, 1973; Banwell, 1967; 

Rex, 1971b; Muffler and White, 1972). More tenuous are the assumptions of technology, economics, 

and governmental policy. These assumptions are 

critical to geothermal resource estimation, and differences (explicit or implicit) among them are in 

great part responsible for the vast range in magnitude among geothermal resource estimates. 

Geothermal reserves (defined as those resources 

recoverable at present at costs competitive with 

alternative forms of energy) are clearly limited if 

one considers only generation of electricity. For the 

generation of electricity using proved and demonstrated technology, the geothermal reservoir must 

have a temperature of at least 180°C; at lower 

temperatures the quantity of flash steam is inadequate (fig. 28). Reservoirs at this or higher temperature, at recoverable depths, and with adequate 

350 

u 

0 

300 ~ 

....-- v 

/ 

v 

v w· 

a: 

::::> 

1-

ct 250 

a: 

w 

Q.. 

:::?! 

w 

1- 200 

/ 

v 

/ Flashed to 

4.46 bars 

150 I/ 

0 10 20 30 40 50 60 70 

STEAM, IN WEIGHT PERCENT 

FIGURE 28.-Weight percent of steam produced by flashing 

water at various temperatures to a turbine inlet pressure 

of 50 lb in-2 gauge (James, in press). Graph calculated 

from data given in tables 1 and 2 of Keenan and others 

(1969). 
256 UNITED STATES MINERAL RESOURCES 

productivity are unlikely to be abundant. White 

(1965) estimated resources recoverable as electricity to 3 km to be 2 X 1019 calories (=2.32X1018 

kwhr). This energy is less than one ten-millionth of 

the total amount of heat above 15°C in the outer 

10 km of the earth (White, 1965, p. 2). 

Utilization of a greater proportion of the heat 

stored in the outer 10 km of the earth depends on 

achieving one or more of the following items : 

1. Technological advances that would allow electrical generation from low-temperature reservoirs. 

2. Breakthroughs in drilling technology that would 

permit low-cost drilling of holes to depths 

greater than 3 km. 

3. Development of techniques of artificial stimulation that would increase the productivity of 

geothermal reservoirs. 

4. Expansion of the use of low-grade geothermal 

resources for such purposes as space heating, 

product processing, agriculture, and desalination. 

Several of these breakthroughs may occur in the 

reasonably near future ; if they do, the recoverable 

resource estimates of White (1965) will have to be 

revised upward to reflect the major changes in 

basic assumptions. Four possible breakthroughs deserve specific mention : 

1. Much attention is currently being paid to the 

possible generation of electricity from lowtemperature geothermal waters, using a system whereby the geothermal heat is used in a 

heat exchanger to boil a secondary fluid such as 

isobutane or freon. This low-boiling fluid (as a 

gas) drives a turbine, is condensed, and then 

returns to the heat exchanger (Jonsson and 

others, 1969). A generating unit based on the 

heat-exchange principle and using intake water at 81 oc is reported to be in pilot operation 

at Paratunka, Kamchatka, U.S.S.R. (Facca, 

in press). U.S. industry interest in this generating mode is high (Anderson, 1973), although no pilot or prototype plant has yet 

been built. 

2. Successful demonstration of the technical feasibility of geothermal self-desalination (U.S. 

Bur. Reclamation, 1972) could greatly enhance the economic position of geothermal 

resources. Particularly in water-short parts 

of the world, geothermal energy may be the 

preferable energy source for desalination, 

either of the geothermal brine itself or of other 

saline waters near the geothermal development. 

3. Research at the L.A. ~L (Los Alamos Scientific 

Laboratory) has r~.ently been focused on the 

development of a nuclear drill that would bore 

holes in rock by progressive melting rather 

than by chipping, abrading, or spalling 

(Smith, 1971). If development of this "nuclear subterrene" is successful and its use is 

relatively inexpensive, extraction of geothermal energy from depths as much as 10 km 

:p1ay become feasible. 

4. One possible application of the nuclear subterrene proposed by LASL is to drill to depths 

greater than 5 km in regions where temperatures may be abnormally high but where permeability is low. LASL proposes to hydrofac 

the hot rock to increase permeability and 

expects that extraction of heat by water circulated through the crack will result in 

thermal-stress cracking and a continuously 

enlarging crack system (Aamodt and Smith, 

1973; Harlow and Pracht, 1972). Geothermal 

reservoir stimulation by various methods (including nuclear devices) was recently the subject of a symposium of the American Nuclear 

Society (Kruger and Otte, 1973). 

Another confusing aspect of geothermal resource 

estimation involves the units of energy in which 

the estimates are expressed by various authors. 

Geothermal energy is heat, and the resource and 

reserve estimates therefore should be expressed in 

calories, joules, or Btu's. But historically the major 

use of geothermal energy has been ~,o generate electricity, and resource estimates commonly have been 

expressed in units of electrical energy · (kilowatthours or megawatt-years) or in terms of installed 

electrical capacity (kilowatts or megawatts). In 

converting from calories to kilowatt-hours, however, one cannot blindly use the energy conversion 

factors given in standard tables (for example, 

Handbook of Chemistry and Physics). These conversion factors, although mathematically and physically accurate, do not take into account the thermodynamic inefficiencies in converting heat to 

electricity via a turbine and generator. For example, in units 3 and 4 at The Geysers, Calif. (a vapordominated geothermal system), only 14.3 percent 

of the energy delivered to the turbine is actually 

converted to electricity (Bruce, 1971). Almost all 

the remaining 85.7 percent is discharged as heat 

to the atmosphere, with only a small fraction of 

heat being returned to the reservoir in condensate 

from the cooling towers. 

The best fossil-fuel generating plants in the 

United States have a thermal efficiency of about 
GEOTHERMAL RESOURCES 257 

40 percent; the best nuclear plants, about 33 percent (U.S. Library of Congress, 1970). The relatively high efficiencies of these generating modes 

compared with geothermal modes are mainly due 

to the much higher temperatures and pressures of 

steam input. 

Any system that generates electricity from heat 

has an efficiency limited by the second law of thermodynamics. An ideal ( Carnot) engine will have a 

thermal efficiency equal to 1-(T1/T2), where T1 is 

the final temperature, in degrees Kelvin, and T2 is 

the initial temperature, in degrees Kelvin (Hossli, 

1969). Thus, for geothermal generation (as at The 

Geysers) where T1 = 80°F (299.8°K) and T2 == 

355°F (452.6°K) (Barton, 1972, fig. 4), the maximum theoretical efficiency is [1-(299.8/452.6)] 

(100) == 33.9 percent. For a fossil-fuel plant at T1 

= 100°F (311 °K) and T2 == 1,000°F (811 °K), the 

maximum theoretical efficiency would be 61.6 percent. 

The overall generating efficiency of an installation 

at a hot-water geothermal field is even less, owing 

to the fact that under existing technology only the 

steam can be utilized in a turbine. In a hot-water 

system at 260°C (like Wairakei, New Zealand), the 

fluid delivered to the power plant at a turbine inlet 

pressure of 50 lb in-2 gauge (4.46 bar absolute) is 

by weight 24 percent steam and 76 percent water. 

Fifty-nine percent of the produced heat is in the 

steam, and 41 percent, in the water. Accordingly, 

the overall thermal efficiency of a 260°C hot-water 

geothermal installation is approximately (59 percent) (14.3 percent) ::::.:::: 8 percent. 

Geothermal resources cannot be expressed in kilowatts or megawatts unless the assumed life of the 

system and the plant factor (for geothermal generation usually assumed to be 8,000 hr yr-1) are 

also specified. Kilowatts and megawatts are units 

of electrical capacity, not electrical energy, and thus 

are a function of not only the size of the geothermal resource but also the rate of production. The 

rate of production depends on the economics of the 

particular situation; production has to be held to a 

level that will allow the capital facilities to be 

amortized before the field is exhausted. The largest 

geothermal field imaginable presumably could be 

exhausted in 1 year, at prohibitive economics. More 

reasonable assumptions for field life fall between 

25 and 50 years. 

Even if one restricts resource discussion to heat 

and thus avoids the possible ambiguity of electrical 

units, one must be careful to specify whether the 

heat considered is total heat in a specified volume 

of ground, heat in the fluid phase only, heat that 

actually can be extracted from the ground, or heat 

actually delivered to a turbine. 

To illustrate these differences, consider a hypothetical hot-water geothermal system to a depth of 

3 km, with temperatures controlled by the boilingpoint curve to a base temperature of 260°C. I 

assume a rock particle density of 2.6 g cm- 3

, a rock 

specific heat of 0.2 cal g-1 oc-I, and all calculations 

referred to 15°C. Using steam table data (Keenan 

and others, 1969) and the boiling-point curve for 

pure water at sea level (Haas, 1971), one can calculate incrementally that the heat contained in the 

geothermal system at temperatures less than 260°C 

(that is, at depths shallower than 0.5518 km) is 

6.3 x 1016 cal km - 2. The heat stored at 260°C from 

0.5518 to 3.0 km is 34.0 x 1016 cal km - 2. Therefore, 

the total heat in the geothermal system above 15°C 

is approximately 40.3 X 1016 cal km-2. 

The amount of heat remaining after exploitation 

perhaps can be approximated by assuming that the 

geothermal system drops to a base temperature of 

180°C; the calculations are similar to those just 

shown. The heat withdrawn during exploitation is 

then the difference between the heat at the initial 

state (40.3 X 1016 cal km-2) and the heat at the 

final (depleted) state (28.5 X 1016 cal km-2), or 

11.8 X 1016 cal km-2. This figure is undoubtedly too 

high, perhaps by a factor of 2, owing to inefficient 

extraction because of impermeable rock, insufficient 

number of drill holes, and drilling spacing that is 

not optimum. Therefore, the heat actually delivered 

to the surface wells will be approximately 5.9 X 

1016 cal km-2, about 15 percent of the heat actually 

stored in the initial geothermal system above 15°C. 

Taking into account the 14.3 percent thermal efficiency of generation and the heat wasted in hot 

water ( 41 percent), we find that only 1 percent of 

the heat contained in this hot-water geothermal 

system can be converted into electricity. 

The amount of heat and water recharge assumed 

to enter the system from greater depths should also 

be specified in the estimation of the geothermal 

resources or reserves of any area. Calculations such 

as the above do not take into account the possibility 

of recharge, and therefore give only a minimum 

figure for the heat that may ultimately be derived 

from a geothermal system. At Wairakei, New Zealand, recharge is significant. Hunt (1970), using 

precise gravity and leveling techniques at various 

times during exploitation of the field, has shown 

that about 20 percent of the water drawn off from 

the Wairakei field from 1961 to 1967 was replaced 

by recharge. Although recharge is clearly a significant factor in geothermal reserve estimations, its 
258 UNITED STATES MINERAL RESOURCES 

quantitative importance cannot be evaluated without 

making some estimate of the rate of exploitation of 

the reservoir. If exploitation is very rapid, recharge 

will have little significance, but if exploitation is 

very slow, recharge will be significant; thus, establishment of a steady balance between extraction and 

recharge (both heat and water) may permit the 

geothermal system to be exploited indefinitely. 

The ~eothermal resources of the world, therefore, 

lie somewhere between 2X 1019 cal (White's 1965 

estimate of potential reserves to 3 km recoverable 

as equivalent electrical energy using present technology) and 5-10X1025 cal (calculated from Rex, 

1972a). Of these geothermal resources, perhaps 

5-10 percent are in the United States (White, 1965). 

The differences among the various resource estimates will not be resolved until there is (a) better 

knowledge of the distribution of geothermal energy 

in the earth's crust, (b) clarification of the technological limitations upon geothermal resource exploitation, and (c) definition of uses. 

PROSPECTING TECHNIQUES 

The first step in reconnaissance geothermal exploration involves outlining broad regions where 

the heat flow is significantly greater than 1.5X10- 6 

cal cm- 2 sec- 1 (for example, Sass and others, 

1971). Most of these regions of high heat flow are 

in zones of young volcanism and tectonic activity, 

and most are characterized by abundant hot springs. 

Techniques for identifying potentially economic 

concentrations of geothermal energy within broad 

regions of high heat flow are not well developed. 

Important considerations include distribution of hot 

springs, evaluation of volcanological and tectonic 

setting, and chemical analysis of hot-spring fluids. 

In particular, the content of silica (Fournier and 

Rowe, 1966) and the ratios of sodium, potassium, 

and calcium (Fournier and Truesdell, 1973) provide 

information about the minimum subsurface temperature to be expected. 

Several geophysical techniques have proved useful 

in the final delineation of geothermal targets (Combs 

and Muffler, 1973; Banwell, in press). Of these 

techniques, perhaps the most unambiguous is the 

direct measurement of temperature gradients at 

depths of 25-100 meters (Combs, 1971; Burgassi 

and others, 1970). Temperature measurements at 

shallower depths, however, can be very misleading, 

owing primarily to the effects of seasonal changes 

in temperature and to the shallow movement of 

ground water (Banwell, in press). Thermal infrared surveys detect surface temperature anomalies, 

but these anomalies can be caused by many factors 

other than geothermal heat flow (Ban well, in press ; 

Watson and others, 1971). 

Several techniques that measure the electrical 

conductivity at depth have had great success in geothermal exploration. The conductivity at depth 

varies directly with temperature, porosity, salinity 

of interstitial fluid, and content of clays and zeolites. All these factors tend to be higher within 

good geothermal reservoirs than in the surrounding 

ground, and consequently the electrical conductivity in these geothermal reservoirs is relatively high. 

Electrical conductivity at depth can be measured 

by electrical (galvanic) or electromagnetic (inductive) methods. Among the electrical techniques, only 

direct-current methods are reliable, owing to skin 

effects attendant to alternating-current methods; 

direct-current electrical arrays commonly used are 

Wenner, Schlumberger, and dipole-bipole (Banwell 

and Macdonald, 1965; Hatherton and others, 1966; 

Risk and others, 1970; Macdonald and Muffler, 

1972; Zohdy and others, 1973). Electromagnetic 

methods ( audiofrequency magnetotellurics, electromagnetic coil surveys, and loop-loop or wire-loop 

induction surveys) have certain theoretical advantages (Keller, 1970; Harthill, 1971) and are becoming more widely used. 

Passive seismic methods are proving of use in 

locating fractured and permeable zones in geothermal areas. Microearthquakes at relatively shallow 

focal depths are concentrated along fracture or fault 

zones in many geothermal areas (Ward, 1972 ; Ward 

and Bjornsson, 1971; Hamilton and Muffler, 1972). 

In addition, some geothermal areas appear to have 

a high level of seismic ground noise (Whiteford, 

1970) ; analysis of the areal distribution of this 

noise may outline prospective zones of geothermal 

production (Goforth and others, 1972). 

Several other geophysical techniques have proved 

useful in special circumstances. Gravity surveys 

may in some areas define positive anomalies that 

are caused by alteration or metamorphism of subsurface rock (Hochstein and Hunt, 1970; Biehler, 

1971), but in other areas they may define a negative anomaly that may represent an intrusive mass 

at depth (Calif. Div. Mines and Geology, 1966). 

Magnetic surveys in some areas define negative 

anomalies that are caused by alteration of magnetite to pyrite (Studt, 1964), but in other areas they 

define positive magnetic anomalies that are caused 

by intrusions of magnetic igneous rock (Griscom 

and Muffler, 1971). Active (explosion) seismology 

is useful in defining subsurface geologic structure 

(Hochstein and Hunt, 1970; Hayakawa, 1970), and 

analysis of seismic attenuation across geothermal 
GEOTHERMAL RESOURCES 259 

areas may someday become useful in geothermal 

exploration (Hochstein and Hunt, 1970). 

REFERENCES CITED 

Aamodt, Lee, and Smith, Morton, 1973, Induction and growth 

of fractures in hot rock, in Kruger, Paul, and Otte, Carel, 

eds., Geothermal energy-resources, p·roduction, stimulation: Stanford Univ. Press (in press). 

Alonso-Espinosa, H., Fernandez, G., and Guiza, J., 1968, 

Power generation in Mexico from geothermal energy: 

7th world power conference at Moscow, U.S.S.R. 

Anderson, J. H., 1973, Economic power from geothermal 

heat, in Kruger, Paul, and Otte, Carel, eds., Geothermal 

energy-resources, production, stimulation: Stanford 

Univ. Press (in press). 

Banwell, C. J., 1967, Geothermal power: Impact of Science 

on Society (UNESCO), v. 17, no. 2, p. 149-166. 

--- (in press), Geophysical techniques in geothermal ex-· 

ploration: Geothermics, Spec. Issue 2, v. 1. 

Banwell, C. J., and Macdonald, W. J. P., 1965, Resistivity 

surveying in New Zealand thermal areas: Commonwealth 

Mining and Me.tall. Cong., 8th, Australia and New Zea-· 

land, 1965, New Zealand Section, paper no. 213, p. 1-7. 

Barnea, Joseph, 1971, Multipurpose exploration and development of geothermal resources: Natural Resources Forum 

(United Nations), v. 1, no. 1, p. 55-58. 

Barton, D. B., 1972, The Geysers power plant-a dry steam 

geothermal facility, in Anderson, D. N., and A~tel, L. 

H., eds., Geothermal Resources Council Conf., 1st, El 

Centro, Calif., 1972, Compendium of first day papers; 

Davis, Calif., Geothermal Resources Council, p. 27-38. 

Biehler, Shawn, 1971, Gravity studies in the Imperial Valley, 

in Cooperative geological-geophysical-geochemical investigations of geothermal resources in the Imperial Valley area of California: California Univ. Riverside, July 

1, 1971, p. 29-42. 

Boldiza.r, T., 1970, Geothermal energy production from porous 

sediments in Hungary: Geothermics, Spec. Issue 2, v. 1, 

pt. 1, p. 99-109. 

Bowen, R. G., 1973, Environmental effects of producing electric power from geothermal resources, in Kruger, Paul, 

and Otte, Carel, eds., 1972, Geothermal energy-re·-

sources, production, stimulation: Stanford Univ. Press 

(in press). 

Bruce, A. W., 1971, Geothermal power--on line: Northwest 

Conference on Geothermal Power, 1st, Olympia, Wash., 

1971, Washington Div. Mines and Geology, Proc. 

Burgassi, P. D., Ceron, P., Ferrara, G. C., Sestini, G., and 

Toro, B., 1970, Geothermal gradient and heat flow in 

the Radicofani region (east of Monte Amiata, Italy): 

Geothermics, Spec. Issue 2, v. 2, pt. 1, p. 443-449. 

Burrows, W., (in press), Geothermal energy resources for 

heating and associated applications in Rotorua and surrounding areas: Geothermics, Spec. Issue 2, v. 2, pt. 

2. 

California Division of Mines and Geology, 1966, Gravity map 

of Geysers area: California Mineral lnf. Service, v. 19, 

no. 9, p. 148-149. 

Combs, J., 1971, Heat flow and geothermal resource estimates for the Imperial Valley, in Cooperative geological-geophysical-geochemical investigations of geothermal 

resources in the Imperial Valley area of California: 

California Univ. Riverside, July 1, 1971, p. 5-28. 

Combs, Jim, and Muffler, L. J. P., 1973, Exploration for 

geothermal resources, in Kruger, Paul, and Otte, Carel, 

eds., Geothermal energy-resources, production, stimulation: Stanford Univ. Press (in press). 

Dragone, G., and Rumi, 0., in press, Pilot greenhouse for the 

utilization of low-temperature waters: Geothermics, 

Spec. Issue 2, v. 2, pt. 2. 

Dutcher, L. C., Hardt, W. F., and Moyle, W. R., Jr., 1972, 

Preliminary appraisal of ground water in storage in the 

Imperial Valley area, California: U.S. Geol. Survey Circ. 

659, 57 p. 

Facca, G., (in press), General report on the status of world 

geothermal development: Geothermics, Spec. Issue 2, 

v.l. 

Fournier, R. 0., and Rowe, J. J., 1966, Estimation of underground temperatures from the silica content of water 

from hot springs and wet-steam wells: Am. Jour. Sci., 

v. 264, p. 685-697. 

Fournier, R. 0., and Truesdell, A. H., 1973, An empirical 

Na-K-Ca geothermometer for natural waters: Geochim. 

et Cosmochim. Acta (in press) . 

Goforth, T. T., Douze, E. J., and Sorrells, G. C., 1972, 

Seismic noise measurements in a geothermal area: 

Geophys. Prosp., v. 20, p. 76-82. 

Griscom, Andrew, and Muffler, L. J. P., 1971, Aeromagnetic 

map and interpretation of the Salton Sea geothermal 

area, California: U.S. Geol. Survey Geophys. Inv. Map 

GP-754. 

Haas, J. L., Jr., 1971, The effect of salinity on the maximum thermal gradient of a hydrothermal system at 

hydrostatic pressure: Eoon. Geology, v. 66, p. 9·40--9·46. 

Hamilton, R. M., and Muffler, L. J. P., 1972, Microearthquakes at The Geysers geothermal area, California: 

Jour. Geophys. Research, v. 77, no. 11, p. 2081-2086. 

Harlow, F. H., and Pracht, W. E., 1972, A theoretical study 

of geothermal energy extraction: Jour. Geophys. Research,v. 77, p. 7038-7048. 

Harthill, Norman, 1971, Geophysical prospecting for geothermal energy: Mines Mag., v. 6, no. 6, p. 13-18. 

Hatherton, T., Macdonald, W. J.P., and Thompson, G. E. K., 

1966, Geophysical methods in geothermal prospecting in 

New Zealand: Bull. Volcano!., v. 29, p. 485-497. 

Hayakawa, M., 1970, The study of underground structure 

and geophysical state in geothermal areas by seismic 

exploration: Geothermics, Spec. Issue 2, v. 2, pt. 1, p. 

347-357. 

Hayashida, 1., and Ezima, Y. (in press )

1 Development of 

Otake geothermal fi·eld: Geothermics, Spec. Issue 2, v. 

2, pt. 2. 

Head, Jon, 1970, Geothermal energy for greenhouse heating: 

Ore Bin, v. 32, no. 9, p. 182-183. 

Healy, J. H., Rubey, W. W., Griggs, D. T., and Raleigh, C. 

B., 1968, The Denver earthquakes: Science, v. 161, no. 

3848,p. 1301-1310. 

Hochstein, M. P., and Hunt, T. M., 1970, Seismic, gravity, 

and magnetic studies, Broadlands geothermal field, New 

Zealand: Geothermics, Spec. Issue 2, v. 2, pt. 1, p. 333-

346. 

Hossli, Walter, 1969, S.team turbines: Sci. American, v. 220, 

no. 4, p. 100-110. 

Hunt, T. M., 1970, Gravity changes at Wairakei geothermal 

field, New Zealand: Geol. Soc. America Bull., v. 81, p. 

529-536. 

[Italy] ENEL, [1970], Larderello and Monte Amiata-Electric Power by Endogenous Steam: Rome, En:te N azionale 
260 UNITED STATES MINERAL RESOURCES 

L'Energia Elettrica, n.p. 

James, R. (in press), Power station strategy: Geothermics, 

Spec. Issue 2, v. 2, pt. 2. 

Jones, P. H., 1970, Geothermal resources of the northern 

Gulf of Mexico basin: Geothermics, Spec. Issue 2, v. 2, 

pt. 1, p. 14-26. 

Jonsson, V. K., Taylor, A. J., and Gharmichael, A. D., 1969, 

Optimisation of geothermal power plant by use of Freon 

vapour cycle: Timarit VFI, 1.-2. hefti, arg., p. 2-18. 

Keenan, J. H., Keyes, F. G., Hill, P. G., and Moore, J. G., 

1969, Steam tables-thermodynamic properties of water 

including vapor, liquid, and solid phases (International 

edition-metric units): New York, John Wiley & Sons, 

Inc., 162 p. 

Keller, G. V., 1970, Induction methods in prospecting for 

hot water: Geothermics, Spec. Issue 2, v. 2, pt. 1, p. 

318-332. 

Koenig, J., 1970, Geothermal exploration in the western 

United States: Geothermics, Spec. Issue 2, v. 2, pt. 1, 

p. 1-13. 

Komagata, S., Iga, H., Nakamura, H., and Minohara, Y., 

1970, The status of geothermal utilization in Japan: 

Geothermics, Spec. Issue 2, v. 2, pt. 1, p. 1's5-196. 

Kruger, Paul, and Otte, Carel, eds., 1973, Geothermal energy 

-resources, production, stimulation: Stanford Univ. 

Press (in press) . 

Lachenbruch, A. H., 1970, Crustal temperature and heat 

production-implications of the linear heat-flow relation: Jour. Geophys. Research, v. 75, no. 17, p. 3291 ..... 

3300. 

Macdonald, W. J. P., and Muffler, L. J. P., 1972, Recent 

geophysical exploration of the Kawerau geothermal 

field, North Island, New Zealand: New Zealand Jour. 

Geology and Geophysics, v. 15, p. 303-317. 

McKenzie, G. R., and Smith, J. H., 1968, Progress of geothermal development in New Zealand: World Power 

Conf., 7th, Moscow, 1968 Proc., p. 1-1 to 1-3-2. 

Makarenko, F. A., Mavritsky, B. F., Lokchine, B. A., and 

Kononov, V. 1., (in press), Geothermal resources of the 

USSR and prospects for their practical use: Geothermics, Spec. Issue 2, v. 2, pt. 2. 

Mori, Y. (in press), Exploitation of Matsukawa geothermal 

area: Geothermics, Spec. Issue 2, v. 2, pt. 2. 

Muffler, L. J. P., and White, D. E., 1968, Origin of COa in 

the Salton Sea geothermal system, southeastern California, U.S.A., in Genesis of mineral and thermal waters: 

Internat. Geol. Cong., 23d, Prague 1968, Rept., v. 17, p. 

185-194~ 

--- 1972, Geothermal energy: Sci. Teacher, v. 39, no. 3, 

p. 40-43. 

Palmason, G., and Zoega, J., 1970, Geothermal energy developments in Iceland 1960-69: Geothermics, Spec. Issue 

2, v. 2, pt. 1, p. 73-76. 

Peterson, N. V., and Groh, E. A., 1967, Geothermal potential 

of the Klamath Falls area, Oregon-a preliminary 

study: Ore Bin, v. 29, no. 11, p. 209-232. 

Ragnars, K., Saemundsson, K., Benediktsson, S., and Einarsson, S.S., 1970, Development of the Namafjall Area, 

Northern Iceland: Geothermios, Spec. Issue 2, v. 2, pt. 

1, p. 925-935. 

Rex, R. W ., 1968, Investigation of the geothermal potential 

of the lower Colorado River basin, phase 1-the Imperial Valley project: Inst. Geophys. Planetary Physics, 

California Univ. Riverside, 15 p. 

--- 1971a, Geothermal energy-the neglected energy option: Sci. and Public Affairs, Bull. Atomic Scientists, 

v. 27, no. 8, p. 52-56. 

--- 1971b, Geothermal resources in the Imperial Valley, 

in Seckler, David, ed., California Water-a study in resource management: California Univ. Berkeley Press, 

348 p. 

--- 1972a, Geothermal energy in the United States, 

March, 1972: California Univ. Riverside, Education Research Service, Inst. Geophys. and Planetary Phys. 

Contr. 72-9, 4 p. 

--- 1972b, Geothermal energy-its potential role in the 

national energy picture, April 1972: California Univ. 

Riverside, Education Research Service, Inst. Geophys. 

and Planetary Phys. Contr. 72-10, 8 p. 

Reynolds, G., in press, Cooling with geothermal heat: Geothermics, Spec. Issue 2, v. 2, pt. 2. 

Risk, G. F., Macdonald, W. J. P., and Dawson, G. B., 1970, 

D.C. resistivity surveys of the Broadlands geothermal 

region, New Zealand: Geothermics, Spec. Issue 2, v. 

2, pt. 1, p. 287-294.~ 

Sass, J. H., Lachen:bruch, A. H., and Munroe, R. J., 1971, 

Thermal conductivity of rocks from measurements on 

fragments and its application to heat-flow determinations: Jour. Geophys. Research, v. 76, p. 3391-3401. 

Schurr, S. H., and Netschert, B. G., 1960, Energy in the 

American Economy, 1850-1975: Baltimore, The Johns 

Hopkins Press, 77 4 p. 

Smith, J. H., 1970, Geothermal development in New Zealand: 

Geothermics, Spec. Issue 2, v. 2, pt. 1, p. 232-247. 

Smith, M. C., ed., 1971, A preliminary study of the nuclear 

subterrene: Los Alamos Sci. Lab. LA-4547, 62 p. 

Sukharev, G. M., Vlasova, S. P., and Taranukha, Y. K., in 

press, The utilization of thermal waters of the developed 

oil deposits of the Caucasus: Geothermics~ Spec. Issue 

2, v. 2, pt. 2. 

Tikhonov, A. N., and Dvorov, I. M. (in press), Development of 

research and utilization of geothermal resources in the 

U.S.S.R.: Geothermics, Spec. Issue 2, v. 2, pt. 2. 

Truesdell, A. H., and White, D. E., 1973, Production of superheated steam from vapor-dominated geothermal reservoirs containing liquid water: (in press). 

U.S. Bureau of Reclamation, 1972, Geothermal resource investigations, Imperial Valley, California, January 1972-

developmental concepts: U. S. Bur. Reclamation, 58 p. 

U. S. Library of Congress, 1970, The economy, energy, and 

environment: U.S. Lib. Cong., Legislative Ref. Service, 

Environmental Policy Div., 131 p. 

Ward, P. L., 1972, Microearthquakes-prospecting tool and 

possible hazard in the development of geothermal resources: Geothermios, v. 1, p. 3-12. 

Ward, P. L., and Bjornsson, Sveinbjorn, 1971, Microearthquakes, swarms, and the geothermal areas of Iceland: 

Jour. Geophys. Research, v. 76, no. 17, p. 3953-39·82. 

Watson, Kenneth, Rowan, L. C., and Offield, T. W., 1971, 

Application of thermal modeling in the geologic interpretation of IR images: Internat. Symposium on Remote 

Sensing of Environment, 7th, Willow Run Lab., Michigan Univ. 1971, Proc., p. 2017-2041. 

White, D. E., 1965, Geothermal energy: U. S. Geol. Survey 

Circ. 519, 17 p. 

--- 1968, Environments of generation of some base--metal 

ore deposits: Econ. Geology, v. 63, p. 301-335. 

--- (in press), Geochemistry applied to the discovery, 
GEOTHERMAL RESOURC.ES 261 

evaluation, and exploitation of geothermal energy resources: Geothermics, Spec. Issue 2, v. 1. 

--- 1973, Characteristics of geothermal resources and 

problems of utilization, in Kruger, Paul, and Otte, Carel, 

eds., Geothermal energy-resources, production, stimulation: Stanford Univ. Press (in press). 

White, D. E., Muffler, L. J. P., and Truesdell, A. H., 1971, 

Vapor-dominated hydrothermal systems compared with 

hot-water systems: Econ. Geology, v. 66, no. 1, p. 75-97. 

Whiteford, P. C., 1970, Ground movement in the Waiotapu 

geothermal region, New Zealand: Geothermics, Sp·ec. 

Issue 2, v. 2, pt. 1, p. 478-486. 

Zohdy, A. A. R., Anderson, L.A., and Muffler, L. J. P., 1973, 

Resistivity, induced polarization and self potential surveys of a vapor-dominated geothermal system: Geophysics (in press) . 

UNITED STATES MINERAL RESOURCES 

GOLD 

By FRANK S. SIMONS and WILLIAM C. PRINZ 

CONTENTS 

Page 

Abstract of conclusions -------------------------- 263 

Introduction ------------------------------------- 26~ 

Uses -------------------------------------------- 264 

Exploitation ------------------------------------- 265 

Geologic environment ----------------------------- 266 

Geochemistry -------------------------------- 266 

~ineralogy ---------------------------------- ~67 Types of gold deposits ----------------------- 267 

Gold-quartz lodes ------------------------ 267 

Epithermal ("bonanza") deposits ---------- 268 

Young placers --------------------------- 268 

Ancient (fossil) placers ----------------- 26!;1 

~arine placers -------------------------- 270 

Deposits of disseminated gold ------------- 270 

Byproduct gold -------------------------- 271 

Reserves and resources -------------------------- 271 

Prospecting techniques --------------------------- 273 

Problems for research ---------------------------- 273 

References cited --------------------------------- 274 

FIGURES 

P~ge 

29. Graph showing world gold production, 1890-

1970 ------------------------------------- 265 

30. Graph s.howing United States gold production, 

1930-70, and consumption, 1951-70 -------- 265 

TABLES 

Page 

50. Equivalent weights and measures for gold ____ 264 

51. Reserves and resource.s of gold in the world 

as estimated in several sources of data _____ 271 

ABSTRACT OF CONCLUSIONS 

~ost of the world's gold reserv.es, estimated at 1 billion 

ounces, are in South Africa, and that country will continue 

to produce two-thirds of the world's gold for many years. 

The U.S.S.R. is thought to have a large part of the remainder, and no other country has more than a few percent 

of the reserv·es. Official world gold currency reserves are 

about 1.3 billion ounces, and a some·what smaller amount is 

hoarded; both rese-rves and hoards may become sources of 

industrial gold, the first by gov·ernment decision, the second 

by a sufficient rise in the price of gold. 

United States nonmonetary consumption of gold has been 

three to four times dome,stic production for s·everal years, 

and the United States is unlikely to become self-sufficient in 

gold in the foreseeaMe future. United States gold reserves 

of a few tens of millions of ounces are mainly in the Homestake (S. Dak.) and Oarlin and Cortez (Nev.) gold deposits 

and in copper deposits, such as Bingham, Utah, which produce byproduct gold. U.S. gold resources are large but in 

general very low grade, and most placer deposits pose insurmountable technologic problems at present. Deposits as 

yet undiscovered that are most likely to provide new gold 

production are those of disseminated gold, similar to Carlin 

and Cortez, which were overlooked in early prospecting. 

INTRODUCTION 

Gold is a yellow metal that has a density of 19.3 

grams per cubic centimeter (nearly twice that of 

lead and exceeded only by some of the platinum 

metals and rhenium) and that is soft, very malleable 

and easily shaped, and highly resistant to corrosion 

and tarnish. Because of its workability, beauty, durability, and common occurrence as native metal, gold 

was one of the first metals used by man. Over the 

centuries it has been a principal medium of international monetary exchange, and its physical properties have made it prized for jewelry and other adornments. Gold has traditionally been equated with 

wealth, and the lore of lost gold mines and hidden 

pirate hoards cannot be matched by that of any 

other commodity. Even today gold is sought by the 

weekend prospector in the hope of striking it rich, 

as a very few of his predecessors did a century ago. 

Gold is known to have been mined in substantial 

amounts for at least 6,000 years, probably first in 

Egypt, where gold objects appeared as early as 4,000 

B.C. (Sutherland, 1960, p. 25). Various estimates of 

the amount of gold mined since the discovery of 

U.S. GEOL. SURVEY PROF. PAPER 820 

263 
UNITE.D STATES MINERAL RESOURCES 

America converge at about 2.5 billion ounces (see 

table 50 for weights and measure) (Wise, 1964, p. 

TABLE 50.-Equivalent weights and measures for gold 

[All data in this report are in Troy ounces or metric units, 

such as grams or tons. g, grams; dwt, pennyweights; oz, ounces; ppm, parts per million; ppb, parts per billion] 

WEIGHTS AND MEASURES 

Weight or measure Equi1Jalent 

1 Troy ounce ----------------- 31.1 g 20 dwt 

1 metric ton ------------------ 106 g 32,150 oz 1.1 short ton 

1 ppm ------------------------ 1 g per ton 

0.032 oz per ton 

1 ppb ------------------------ 0.001 g per ton 

PRICES 

Price per ounce 

$35 ---------------------------------- 40 ---------------------------------- 45 ---------------------------------- 60 ---------------------------------- 70 ---------------------------------- 100 ----------------------------------

Value of 1 g 

$1.12 

1.29 

1.45 

1.61 

2.24 

3.22 

9; Green, 1968, p. 14; Kavanagh, 1968, p. 553; Park, 

1968, p. 121; Ageton, 1970, p. 574), and a reasonable 

guess about earlier production leads to an estimated 

total production through world history of about 3 

billion ounces (Kavanagh, 1968, p. 553). Because of 

its indestructibility, intrinsic value, and appeal, gold 

endures. Some undoubtedly was lost in sunken ships, 

some has been entombed· with its owners, and some 

was hidden by people long dead, but a very large 

part of all that was ever produced probably can be 

accounted for. Official monetary reserves are about 

1.3 billion ounces (U.S. News & World Report, 1972, 

p. 21). The difference between this amount and the 

estimated world total production is about 1. 7 billion 

ounces; this figure, less whatever gold has been 

irretrievably lost, gives an order of magnitude for 

the quantity of gold in jewelry, coin collections, museums, church adornments, electronic equipment, 

capitol domes, teeth, and, above all, hoards in the 

form of bars or coins. The amount is enormous, but 

some perspective may be gained from the realization 

that during 1966-68 alone, all newly mined gold, 

about 120 million ounces exclusive of the U.S.S.R., 

plus about 66 million ounces from non-Communist 

official reserves-that is, a total of 186 million 

ounces-passed into private holdings (Hoyt, 1971, p. 

522, 538). Between 1941 and 1968, an estimated 550 

million ounces of gold came under private control 

(Busschau, 1967, p. 21; Park, 1968, p. 114). Park 

(1968, p. 121-122) estimated that nearly 550 million ounces of gold are held in hoards alone. By way 

of contrast, U.S. monetary reserves of gold at the 

end of 1971 totaled only 291.6 million ounces (U.S. 

Dept. Interior, 1972, app. 1, p. 103). 

USES 

Gold has traditionally been the principal medium 

of international monetary exchange, but its role has 

undergon~ profound change in recent years. From 

1934 to 1972 the United States maintained full convertibility of the dollar to gold at a fixed rate of $35 

per ounce. Increasing balance-of-payments deficits 

starting after World War II, and rising industrial 

consumption of gold, caused a steady drain on U.S. 

monetary reserves of gold. In March 1968, agreement was reached among seven major monetary 

nations (Belgium, Great Britain, Italy, Netherlands, 

Switzerland, United States, and West Germany) to 

discontinue open-market buying or selling of gold 

but to continue intergovernment transactions at the 

same price of $35 per ounce. As a result of this 

agreement, the U.S. Treasury stopped selling gold 

for industrial use, thus slowing down the drain on 

official reserves. However, the balance-of-payments 

deficits continued, and on August 16, 1971, the U.S. 

Government suspended convertibility. On December 

18, 1971, the Group of Ten nations (the same countries as above, less Switzerland and plus Canada, 

France, Japan, and Sweden) agreed to raise the 

official price of gold to $38 per ounce, and this agreement was signed by the President of the United 

States on April 3, 1972. After establishment of a 

free market for gold in 1968, the price fluctuated between $35 and $45 per ounce until early 1972, when 

the price started to rise sharply, and it reached $70 

per ounce in early August 1972. These events are 

certain to have a significant effect on the future 

monetary role of gold, but their full impact cannot 

be predicted at this time. 

Gold has a long history of use in the manufacture 

of jewelry and related articles and in dentistry, and 

more recently it has achieved wide industrial use, 

particularly in the electronics and computer industries. U.S. consumption of gold in industry and the 

arts has been 6-7 million ounces annually during 

1967-72, and in 1971 it was distributed as follows: 

jewelry and arts, 60 percent; dentistry, 11 percent; 

industry, 29 percent (U.S. Bur. Mines, 1972, p. 60). 

All these nonmonetary uses of gold are rising steadily-in the arts and dentistry because of population 

growth and increasing affluence, and in industry for 

fabrication of semiconductors, printed circuits, connectors, and other microcomponents for computer 

and space application. Nonmonetary use of gold in 

the rest of the world is estimated at three to four 

times that of the United States, but distribution of 

consumption among various uses is not accurately 

known. 
GOLD 265 

Gold has no entirely suitable substitute for any of 

its major uses. Platinum is a substitute in jewelry 

but is more costly and lacks the color and appeal of 

gold ; silver is not sufficiently tarnish resistant. Various stainless alloys are usable in dentistry but are 

more difficult to fabricate. Silver can be substituted 

in many electronics applications but is much less corrosion resistant and somewhat less ductile. Nevertheless, gold can be replaced or its use deferred in 

all its main areas of utilization, and in this sense it 

is not as vital an industrial commodity as, for instance, copper. 

EXPLOITATION 

World gold production is dominated by a single 

country, the Republic of South Africa (fig. 29). 

100 

80 

60 

40 ~ 

/ \ / - (f) 

w 

(J 20 

z 

::> 

0 

IL. 10 

0 9 

(f) 8 

z 7 

0 6 

...1 5 

...1 4 

~ 3 

2 

~public";;: ............. 

~ v World 

v '\ v South Africa, :/ I 

I h/~ I I 

L / I"' 1/ / USSRy..; I United States • ·- I :::/.' I ,? ~\ ,--1,..,' 

/) ~J \ ~, ~\ .... f -----~ "~ 

A_ I \ 

t-......_ . .t.K- l/ II \\/ Ca~ada--\ 

7 I ··.,Canadaj \ \ I \'i-i'-' I ~ l/ a ., USSR \ / United States J' ' ..... 1 

1890 1900 1910 1920 1930 1940 1950 1960 1970 

FIGURE 29.-World gold production, 1890-1970. Data for 

U.S.S.R. are from U.S. sources; production since 1936 is 

estimated. E·stimates from European and South African 

sources for annual production of U.S.S.R. since about 1945 

are higher than those shown and range from 7 to 10 million ounces or more. 

South Africa has produced about 37 percent of the 

estimated 2.5 billion ounces of gold mined since the 

discovery of America, and in the last decade it has 

annually produced about two-thirds of the world 

total output. Current production from that country 

is about 31 million ounces of gold annually. By contrast, only three other countries produced more than 

a million ounces in 1970: the U.S.S.R., 6.5 million 

ounces (estimated); Canada, 2.3 million ounces; and 

the United States, 1.8 million ounces. Other countries that produce more than 100,000 ounces of gold 

annually are, in approximate decreasing order of 

output, Australia, Ghana, Philippines, Rhodesia, 

Japan, Colombia, Nicaragua, Brazil, Mexico, Zaire, 

Peru, India, and Fiji Islands. 

Gold production of the Communist nations can 

only be estimated because figures are not released 

by them ; Russian production, for instance, has not 

been officially reported since 1936. The U.S.S.R. is 

known to be a major gold producer, and for much of 

the 19th century it led the world in gold output. 

From the discovery of America until 1970, production from the U.S.S.R. is estimated between 290 and 

350 million ounces, approximately the same as that 

of the United States (315 million oz) (Emmons, 

1937, p. 329; U.S. Bur. Mines, 1932-71; Busschau, 

1967, p. 21). North Korea is estimated to produce 

160,000 ounces annually, and mainland China, 

50,000-60,000 ounces annually. Bulgaria, Czechoslovakia, Hungary, and Rumania are minor producers. 

U.S. estimates of annual U.S.S.R. gold production 

made from 1940 to 1963 showed a gradual increase 

from about 4 million ounces in the early 1940's to a 

high of 12.5 million ounces in 1963. In 1964 these 

estimates were drastically revised downward to a 

low of 3.2 million ounces in 1943 and a high of only 

4.4 million ounces in 1963 (U.S. Bur. Mines, 1965, 

p. 530-531; Green, 1968, p. 75-76). Production from 

the U.S.S.R. during 1967-72 has been estimated by 

the U.S. Bureau of Mines at 5-7 million ounces 

annually, and some other estimates have been as 

much as 50 percent higher. Russian sales of gold 

ranged from 2 to 16 million ounces annually during 

1950-65, and in the period 1963-65 they averaged 

more than 14 million ounces per year (Busschau, 

1967, p. 21). From 1966 to 1970, very little gold 

was sold by Russia, but gold sales were resumed in 

1971. 

U.S. gold production for the last 25 years has generally been 1.5-2 million ounces annually (fig. 30). 

7 

(I) 

w 

061-----------------~/-----1 

z 

::> 

0 4 .__ __ _,._ 

IL. 

0 

~ 3 

0 

3 2 

i 

0 

1930 1935 19«1 19416 1960 1966 1960 1965 1970 

FIGURE 30.-U.S. gold production, 1930-70-from lode, placer, 

and byproduct sources-and U.S. gold consumption, 1951-70. 
266 UNITED STATES MINERAL RESOURCES 

About 60 percent of current U.S. production comes 

from lode deposits, and 40 percent is a byproduct 

from the refining of other metals, principally copper. Placer deposits, once a major source of gold in 

the United States, are now only a very minor source. 

In recent years, consumption of gold in the United 

States has been three to four times domestic production of new gold. The difference between the amount 

consumed and the amount produced is made up by 

reclaimed scrap gold (2.3-3 million oz annually (U. 

S. Bur. Mines, 1972, p. 60)), by releases from U.S. 

Treasury stocks (until1968), and by imports, mainly from Canada. The United States thus is far from 

being self-sufficient in gold, and it is unlikely to become so in the foreseeable future. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Gold is a rare element-at least 70 of the naturally 

occurring elements are more abundant, most of them 

at least an order of magnitude more abundant, than 

gold (Rankama and Sahama, 1950, p. 39-40; Mason, 

1966, p. 45-46; Krauskopf, 1967, p. 639-640 ; Lee 

and Yao, 1970, p. 782). 

Estimates of abundance of gold in the earth's 

crust made during the last 50 years range from 

0.001 ppm (parts per million) to 0.006 ppm; as 

analytical methods have improved, earlier estimates 

have been reduced. A reasonable estimate of crustal 

abundance based on modern analyses is 0.003-0.004 

ppm, or about 1 g (gram) per 300 metric tons 

(Jones, 1968, p. 3; Lee and Yao, 1970, p. 782). Gold 

is more abundant in mafic than in felsic igneous 

rocks (Gottfried and others, 1972, p. 8, 21) and 

apparently is somewhat more abundant in sedimentary than in igneous rocks and in sandstone than in 

other sedimentary rocks, although data are sparse 

(Jones, 1969). 

Gold is much more abundant in the iron-rich meteorites than in rocks of the earth's crust, as shown 

by the following data from Jones (1968, p. 1-3). The 

iron meteorites, or siderites, contain as much as 8 

ppm gold, but the average ranges from 0.67 to 1.3 

ppm, or 150-300 times as much as the earth's crust. 

The siderolites, or stony iron meteorites, contain 

about the same amount of gold as the siderites. The 

chondritic stony meteorites contain 0.15-0.27 ppm 

gold, 40-70 times as much as crustal rocks, whereas 

achondritic meteorites have about the same gold 

content as the earth's crust. The earth's core is believed to be chemically similar to the iron meteorites, and the earth's mantle, similar to the chondritic 

stony meteorites; so most of the earth's gold is 

probably locked up below the earth's crust. However, rocks that are believed to have been part of 

the mantle and that are now exposed at the earth's 

surface do not show notable enrichment in gold ; the 

most iron rich of these, the dunites, contain only 

about twice the average gold content of the crust 

(Jones, 1969, p. 15, tables 4, 5). 

The abundance of gold in the oceans appears to 

vary appreciably from ocean to ocean and within a 

given ocean; two recent estimates of average gold 

content are 0.011 ppb (part per billion) (1 g per 

90,000 tons of sea water) (Rosenbaum and others, 

1969) and 0.05 ppb (1 g per 20,000 tons of sea 

water) (Jones, 1970, p. 1-3). 

Bedrock deposits of gold that have been mined 

profitably have contained gold in amounts ranging 

from 0.05 to 1 ounce or more per ton, but the average 

gold content appears to be in the range of 0.3-0.5 

ounce per ton. Ore being mined at present at the 

three largest gold mines in the United States (Homestake, S. Dak.; Carlin and Cortez, Nev.) averages 

about 0.3 ounce per ton, or about 10 ppm. This gold 

content represents a concentration of 2,500-3,000 

times the average crustal abundance. This ratio of 

concentration, which is in a very general way a 

measure of the likelihood of occurrence of an economic concentration of an element (the higher the 

ratio of concentration, the less the likelihood that 

concentrations of the requisite size and grade will be 

formed), is one of the highest needed to produce an 

economic mineral deposit. 

In ore deposits, gold is commonly associated with 

pyrite and sulfide minerals of silver and copper even 

though it does not form a separate sulfide mineral. 

All gold ores contain some silver, many ores that are 

predominantly of silver contain appreciable quantities of gold, and copper ores produce the bulk of byproduct gold. 

Gold deposits are found in so great a variety of 

rocks as to almost preclude generalizations about 

association of gold with particular rock types. Nevertheless, gold deposits occur more commonly with 

felsic or intermediate igneous rocks than with mafic 

or ultramafic types, and more commonly in siliceous 

or aluminous sedimentary or metamorphic types 

than in carbonate rocks (however, the host rock at 

the recently discovered Carlin and Cortez gold deposits in Nevada is a silty dolomitic limestone) . 

Gold is extremely inert in natural environments 

at the earth's surface, and during weathering and 

decomposition of rocks it is little affected. Thus, it 

may be residually concentrated at the weathering 

site or transported in the native state and concentrated locally along with other highly resistant min-
GOLD 267 

erals in placer deposits. Gold is soluble in hydrochloric acid in the presence of manganese dioxide 

but is appreciably so only at concentrations of acid 

so high as to occur only rarely in nature (Krauskopf, 1967,p. 523-526). 

MINERALOGY 

Gold occurs mainly as native metal, always alloyed 

with variable amounts of silver and other metals, 

mainly copper and iron. Other than native gold, the 

only important gold minerals are the tellurides, composed of gold or gold plus silver, copper, or lead combined with tellurium; calaverite (AuTe2) and sylvanite ((Au,Ag]Te2) are the most common of these 

minerals. Other gold minerals are rare. Gold also 

occurs in small amounts in many minerals, generally 

less than 5 ppm in sulfide minerals, and less than 1 

ppm in other minerals ; however, as much as 500 

ppm has been reported from sphalerite (zinc sulfide) (Jones and Fleischer, 1969, p. 11). 

TYPES OF GOLD DEPOSITS 

Gold occurs in many and varied geologic environments, which are grouped into seven broad categories in this report. 

Historically, the most productive general types of 

deposits have been gold-quartz lodes and a subcategory of these, the epithermal ("bonanza") deposits 

(mainly in the North American Cordilleran region); 

geologically young placers; and ancient (fossil) 

placers. Other types are marine placers; bedrock 

deposits of disseminated gold, a type represented by 

several recent discoveries in Nevada; and deposits of 

other metals or minerals which produce gold only as 

a byproduct (Internat. Geol. Cong., 1930; Lindgren, 

1933; Emmons, 1937; Cooke, 1946; Canadian Inst. 

Mining and Metall., 1948; Bateman, 1950; Commonwealth Mining and Metall. Cong., 6th, 1957; Commonwealth Mining and Metall. Cong., 8th, 1965; De 

Kun, 1965; Koschmann and Bergendahl, 1968; Canada Geol. Survey, 1970; Park and MacDiarmid, 1970; 

Roberts and others, 1971). 

GOLD-QUARTZ LODES 

Examples of gold-quartz lodes are Mother LodeGrass Valley, Calif.; Homestake, S. Dak.; Central 

City, Colo.; Alaska Juneau-Treadwell, Alaska; Porcupine and Kirkland Lake-Larder Lake, Ontario, 

Canada; Morro Velho, Minas Gerais, Brazil ; Kolar, 

Mysore, India; Kalgoorlie, Western Australia; Bendigo-Ballarat, Victoria, Australia; Ashanti, Ghana; 

the Bulawayo and Hartley belts, Rhodesia; and the 

Kilo and Moto districts, Zaire. This category comprises a wide variety of deposits, but these are essentially hydrothermal veins of quartz and gold that 

either replace wallrock (Homestake) or fill open 

spaces along fracture zones (Mother Lode). They 

were formed at great depths below the earth's surface and persist to depths of thousands of feet below 

the present surface, and most of them are enclosed 

in Precambrian rocks and are of Precambrian age. 

Alteration of wallrocks ranges from slight (Homestake) to widespread and pervasive (Alaska Juneau). The gold content of ores mined ranges from 

about 0.3 to about 0.6 ounce per ton; only rarely has 

much ore containing more than 0.6 ounce per ton 

been found, and conversely in only a few mines has 

ore containing as little as 0.1 ounce per ton been 

mined profitably. 

The size of the gold-quartz lodes varies greatly, 

and data on individual deposits or mines are difficult 

to obtain for many of the great gold-mining districts. Many mines have produced at least 1 million 

ounces (North Star and Empire mines, Grass Valley, 

Calif.); an appreciable number have yielded 2-5 

million ounces (Alaska Juneau; Brownhill-Oroya 

and probably several other mines at Kalgoorlie, as 

well as at Bendigo and Ballarat, Australia); a few 

have produced 5-20 million ounces (Hollinger, Mcintyre, and Dome mines, Porcupine, Ontario ; Kirkland 

Lake zone, including the Lake Shore and other mines, 

Kirkland Lake, Ontario; Kerr-Addison mine at 

Larder Lake, Ontario; Morro Velho, Brazil); and at 

least two have produced more than 20 million ounces 

(Homestake, S. Dak., and Kolar, India). Homestake 

is the most productive lode gold mine in the world 

and has a total production of about 30 million ounces 

since its discovery in 1876. It is of interest to note, 

however, that the total output of the Homestake 

mine is about equal to 1 year's production at present 

rates from the Witwatersrand district (fossil placer) of South Africa. 

The percentage of world gold production attributable to these deposits is difficult to estimate. Most of 

their production probably has come during the 20th 

century, although some of them, particularly the 

California deposits, were mined before 1900, and a 

few, such as Kolar, India, may have been worked 

2,000 years ago or more. These lode deposits have 

accounted for perhaps 25 percent of the world's gold 

production since' 1900, and in 1969 they yielded 20-

25 percent of the world output. They have produced 

about 25-30 percent of all the gold mined in the 

United States, and since 1950 they have produced 

nearly one-half of the U.S. gold output. 

Their future importance appears easier to assess. 

Production from these deposits is fairly steady in 

the United States, Brazil, and India; is decreasing in 
268 UNITED STATES MINERAL RESOURCES 

Canada and Australia; and does not appear to be 

rising appreciably in any country. Although several 

new mines opened in Canada during the last 10 

years, and other new deposits are likely to be found 

there and elsewhere, the general trend of output is 

downward. 

All the examples cited except Alaska JuneauTreadwell, Mother Lode-Grass Valley, and BendigoBallarat are in Precambrian rocks, mainly metamorphosed volcanic and sedimentary rocks of the greenstone-granite association, and many of the Siberian 

lode gold deposits are also in Precambrian rocks. 

Precambrian terrane appears to be favorable for this 

type of gold deposit, and it is likely that most new 

finds will be in areas of Precambrian rocks, such as 

the Canadian, Brazil-Guyanan, and African-Arabian 

shields. 

EPITHERMAL ("BONANZA") DEPOSITS 

Examples of the "bonanza" deposits of the North 

American Cordillera are Goldfield, Virginia City, 

and Tonopah, Nev.; Cripple Creek, Telluride, Silverton, and Ouray, Colo. ; .and El Oro, Pachuca, and 

Guanajuato, Mexico. Geologically similar deposits 

occur in Transylvania (Rumania), Nicaragua, the 

Philippines, New Zealanq, and Japan. These deposits 

are hydrothermal veins of quartz, carbonate minerals, barite, and fluorite containing gold or gold 

tellurides and variable but commonly large amounts 

of silver relative to gold. They were emplaced mainly 

by filling of open spaces, and most of them are in 

highly altered volcanic rocks of Tertiary age. They 

were formed within a few thousand feet of the present surface and persist to depths of only a few 

thousand feet at most, generally much less. The gold 

content of ore mined is extremely variable; some ore 

at Goldfield contained 20 ounces of gold per ton, but 

most ore in these deposits probably contained 0.5-1 

ounce of gold per ton, somewhat more than the goldquartz lodes. 

The "bonanza" deposits, although they generally 

persist only to relatively shallow depths, may contain very large amounts of gold and silver. Cripple 

Creek, Colo., produced about 19 million ounces of 

gold, and the Comstock district at Virginia City, 

Nev., produced 8.5 million ounces, as well as more 

than 200 million ounces of silver. Other sizable deposits include Goldfield, Nev. (4.2 million oz); Telluride, Colo. ( 4 million oz plus more than 63 million 

oz of silver) ; Tonopah, Nev. (1.9 million oz plus 

more than 100 million oz of silver); Waihi (4 million oz) and Thames (1.5 million oz) in the Hauraki 

region, North Island, New Zealand; and El Oro, 

Mexico (2 million oz). 

Gold deposits of this general type probably have 

been mined for thousands of years, first in Egypt 

and the Balkans. In the United States their exploitation dates from around 1860, and from then until 

the 1920's they were a major source of gold. Four 

deposits alone-Cripple Creek, Virginia City, Goldfield, and Telluride-have produced more than onetenth of all United States gold, and from 1860 to 

1920 they accounted for nearly one-fifth of United 

States gold production. 

Very little gold is produced at present from "bonanza" deposits, and practically none, in the United 

States. Despite much effort in the United States 

during the past half century, no new deposit or significant extension of a known deposit has been discovered. Inasmuch as these deposits are probably 

the most easily discoverable type of bedrock gold 

deposit, it. appears unlikely that they will be a 

significant factor in future gold production. 

YOUNG PLACERS 

Examples of young placers are deposits along the 

American, Feather, and Yuba Rivers in the Sierra 

Nevada of California; along Alder Gulch at Virginia 

City, Mont.; on the Yukon River at Fairbanks, 

Alaska, and on and near the beach at N orne, Alaska; 

at Klondike in the Yukon Territory of Canada; in 

the upper Lena, Yenisey, and Amur Rivers in Siberia; and along the east flank of the Andes Mountains in Bolivia, Peru, Ecuador, and Colombia. The 

Tertiary placers of the Sierra Nevada and the geologically similar placers at Ballarat, Australia, as 

well as the Upper Cretaceous to lower Tertiary auriferous conglomerates of northwestern Wyoming are 

also placed in this group; they are older and more 

consolidated than the typical young placers, but they 

are more similar to the young than to the fossil 

placers. 

The young placer deposits are composed primarily 

of unconsolidated or semiconsolidated sand and 

gravel that contain very small amounts of native 

gold and other heavy minerals. Most are stream 

deposits and occur along present stream valleys or 

on benches or terraces of preexisting streams. Much 

less commonly, they are beach deposits, as at Nome, 

Alaska, or are residual deposits, such as those in 

the saprolite (deeply weathered rock) of the southeastern United States. The deposits contain from a 

few cents to several dollars worth of gold per cubic 

yard (1 cu yd of gravel weighs about 1.5 tons, and 

a very rich placer deposit would thus contain only 

a few grams of gold per ton of gravel). The largest 

placers yielded several million ounces of gold ; most 

placers, however, were much smaller. 
GOLD 269 

Placer deposits were easy to find and easy to mine; 

consequently they were discovered early and were 

a very important source of gold in the ancient world 

and indeed as late as the 19th century. Their contribution to total world production cannot be estimated closely, but it probably is between one-fourth 

and one-third of the total, or somewhere between 

750 million and 1 billion ounces. 

Since the beginning of gold mining in the United 

States, placer deposits have yielded about 114 million ounces of gold, or about 36 percent of all gold 

mined. Of this amount, about 68 million ounces have 

come from the Sierra Nevada placers of Californiaabout 53-54 million ounces from young placers and 

14--15 million ounces from Tertiary placers (Merwin, 

1968). Other large U.S. placer deposits include those 

of Fairbanks, Alaska (7.2 million oz), Nome, Alaska 

(3.5 million oz), Virginia City, Mont. (2.5 million 

oz), and Boise Basin, Idaho (2.3 million oz) (Koschmann and Bergendahl, 1968). 

Production from placer mines has been declining 

for many years, and at present the mines yield significant amounts of gold only in the U.S.S.R. and 

Colombia; they probably account for 5--10 percent of 

the world production. Placer gold production in the 

United States in 1969 was only 25,418 ounces, a little 

more than 1 percent of the total U.S. output. The 

reasons for this decline are varied-ease of discovery 

and exploitation and consequent early exhaustion, 

increasing costs of operations, and, particularly in 

the United States, environmental problems such as 

water pollution and siltation. 

Placer deposits are not expected to be a significant 

factor in future U.S. gold production. The country 

has been so well explored that probably no large 

deposits remain undiscovered. Moreover, regulations 

dealing with stream pollution and water use will 

probably become more stringent rather than less so. 

Both these factors make it most unlikely that the 

current downward trend in placer production will 

be reversed. Worldwide, the situation appears similar to that in the United States. In Colombia, placer 

production has been significant, but it has been declining gradually and was less than 200,000 ounces 

in 1969, or only about half the output of 10 years 

ago. Little is known about production of placer gold 

from the U.S.S.R. in recent years; perhaps 50 percent of the total production of 290-350 million 

ounces (estimated) has come from placers, but the 

percentage derived from these deposits at present 

is not known. Other formerly productive placers are 

either virtually exhausted (Egypt, Spain, Australia, 

Canada) or are being worked on a much reduced 

scale (Brazil, Peru, Bolivia) . 

ANCIENT (FOSSIL) PLACERS 

Examples of ancient (fossil) placers are the Witwatersrand district, Republic of South Africa; Tarkwa, Ghana; and the Serra de Jacobina, Bahia, Brazil. These deposits are placers that formed in the 

geologically distant past (all examples are of Precambrian age) and have been lithified to conglomerate to become part of the bedrock; they may thus 

be termed "fossil placers" in the same sense as the 

remains of organisms found in rocks are called 

fossils. These conglomerates consist of small wellrounded pebbles of quartz embedded in a matrix of 

pyrite and micaceous minerals. In addition, they contain a large suite of heavy and resistant minerals, 

the most valuable of which are gold, uraninite, and 

platinum-group metals. The conglomerates were laid 

down originally on the earth's surface, but they 

were buried and are now tilted to varying degrees. 

The individual conglomerate beds generally are only 

a few feet thick but have lateral extents measured 

in miles and are known to reach depths of more 

than 2 miles below the earth's surface. Their gold 

content ranges from 0.2 to 0.8 ounce per ton; the 

average grade of gold ore milled in the Witwatersrand district between 1893 and 1969 was about 0.35 

ounce per ton (Chamber of Mines of South Africa, 

1969, p. 60), at Tarkwa the ore averages 0.2 ounce 

per ton (De Kun, 1965, p. 91), and at Jacobina the 

gold content of ore mined is about 0.5 ounce per ton 

(Gross, 1968, p. 272). 

Although the Jacobina deposits were mined as 

early as the 17th century, this type of deposit did 

not produce any appreciable part of the world's gold 

until discovery of the Witwatersrand district in 

1886. Since then this great district has become an 

increasingly important source of gold, and since 

1954 it has produced more than one-half of the 

world's gold output exclusive of the U.S.S.R. It 

seems safe to say that no other single mining district has dominated the world output of a mineral 

commodity so completely and for so long as the Rand 

has dominated gold production ; in 1970, for example, 67 percent of the world's newly mined gold 

came from Rand mines. 

The future importance of the fossil placer deposits 

can hardly be overestimated. The very large reserves-about 600 million ounces according to several recent estimates (Gold Producers Comm., 

1967 ( ?) , p. 41; Kavanagh, 1968, p. 557; U.S. Bur. 

Mines, 1972, p. 61) -of the Witwatersrand indicate 

that the district will continue to be the principal 

source of the world's gold for many years, even 

though some dire predictions about the life of the 

district, based on a fixed price of $35 per ounce for 
UNITED STATES MINERAL RESOURCES 

gold, have been made during the last 5 years (World 

Mining, 1967). No fossil placer gold district even 

approaching the size of the Rand has been discovered anywhere in the world, but it seems at least 

possible that some of the ancient shield areasCanadian, Brazil-Guyanan, or African-Arabian, in 

particular-may contain other extensive gold-bearing conglomerates. Indeed, geologically similar uranium-bearing conglomerates were discovered at Blind 

River (or Elliot Lake), Ontario, Canada, in 1949, but 

these contain only minor amounts of gold (Roscoe, 

1957; Bateman, 1958). No fossil placer deposits have 

been found in the United States, and extensive fieldwork done in recent years indicates that none are 

likely to be exposed at the present surface. 

MARINE PLACERS 

Examples of marine placer deposits that have 

yielded significant production are lacking. Sediment 

on the ocean floor in several parts of the world is 

known to contain small amounts of gold. Most of 

this gold was derived from the land, transported by 

streams to the ocean basins, and deposited with 

clastic sediments on the ocean floor. Some appears 

to have been derived from the reworking of goldbearing rocks and sediments on the sea floor. None 

of these deposits is being mined at present, and the 

only reported production of gold from a marine 

placer is a small amount recovered as a byproduct 

of tin dredging in Malaysia. 

The largest known gold-bearing area on the sea 

floor is in the northern Bering Sea, where concentrations of 30-100 ppb have been found over a very 

broad area including Norton Sound along the south 

edge of Seward Peninsula in Alaska (U.S. Geol. Survey, 1968, p. A79; 1969, p. 30). On the continental 

shelf off Oregon and northern California, concentrations of gold ranging from 10 to 390 ppb have been 

found in several areas (Moore and Silver, 1968). 

These deposits are believed to have formed at or 

near sea level during a lower stand of the sea. 

Marine placer deposits of tin are exploited on a 

large scale in Malaysia, Thailand, and Indonesia, but 

these placers contain only negligible amounts of 

gold; a small production o.f gold is reported from 

West Malaysia. Beach sand deposits of the titanium 

minerals ilmenite and rutile in Australia, and similar deposits of ilmenite in Ceylon, also are mined 

on a large scale, but these apparently contain no 

recoverable gold. 

The future importance of marine gold placers such 

as those of the Bering Sea is difficult to assess but 

would appear to be minor. The volume of material 

available is large, but the gold content is very low, 

and operating conditions are severe. 

DEPOSITS OF DISSEMINATED GOLD 

Examples of deposits of gold disseminated in bedrock are Carlin (Hardie, 1966), Cortez (Wells and 

others, 1969), Getchell (Erickson and others, 1964), 

and Gold Acres (Wrucke and others, 1968), all in 

Nevada (Roberts and others, 1971). These appear to 

be a new major type of gold occurrence, although 

deposits geologically somewhat similar to them have 

long been known, such as Mercur, Utah (Butler, and 

others, 1920, p. 382--395), and Bald Mountain, Deadwood, and others, South Dakota (Irving, 1904, p. 

111-162; Connolly and O'Harra, 1929, p. 142-171). 

All these deposits were brought into production 

after 1935, and Cortez was discovered in 1966. The 

deposits consist of very fine grained gold (0.01-10 

microns, or 0.00001-0.010 mm) disseminated in silty 

and carbonaceous dolomitic limestone; at both Carlin and Cortez the host rock is of Silurian age. Gold 

is accompanied by silica, a little pyrite and other 

sulfide minerals, and barite. The ore was formed by 

hydrothermal replacement of the host rock. It contains about 0.3 ounce of gold per ton and very little 

silver, generally less than 10 percent of the amount 

of gold, as well as a characteristic suite of trace 

elements-arsenic, antimony, mercury, and, less 

commonly, tungsten. Some of the deposits are of 

Tertiary age, and others may be slightly older; the 

Carlin deposit has not been dated closely but presumably is within the same age range. 

Because only a few deposits of disseminated gold 

have been discovered, little is known about the 

amount of gold this type of deposit may contain. 

Both the Carlin and the Cortez deposits contain more 

t:han 1 million ounces of gold, and the Getchell mine 

has yielded nearly 0.5 million ounces. 

These deposits have produced only a tiny fraction 

of U.S. or world gold; from 1936 to 1969, they 

yielded slightly more than 2 million ounces, less than 

3 percent of U.S. production during that period. 

However, they have become an increasingly important contributor to United States output, and in 

1969 the Carlin and Cortez mines alone accounted 

for about 22 percent of U.S. production. 

The future importance of this type of deposit is 

difficult to assess on a worldwide basis, but for the 

United States it is likely to be great. Because of the 

very fine grained nature of their gold, these deposits 

went largely unrecognized during the great wave of 

prospecting in the last half of the 19th century and 

the early 20th century, and the deposits that were 

discovered were too low grade to be attractive. The 

discovery of two major deposits, Carlin and Cortez, 
GOLD 271 

in the 1960's encourages belief in the existence of 

other unrecognized deposits. The geologic environment of these deposits is still not completely understood but is the subject of much current research; 

for instance, the geochemical similarity between 

these deposits and certain modern hot-spring deposits in New Zealand that contain as much as 85 ppm 

gold and 500 ppm silver has been noted recently by 

Weissberg (1969). Enough is known, however, to 

indicate that very large areas underlain by favorable host rocks remain untested ; the most likely 

area for further discoveries is the Antler orogenic 

belt in central Nevada and its inferred extension in 

southern Idaho north of the Snake River Plain 

(Roberts, 1960, 1966). 

BYPRODUCT GOLD 

Gold is a common minor constituent of base-metal 

ores and may be recovered when these ores are 

smelted and refined. Such ores, although data on 

their gold content are very sparse, appear to contain 

0.001-0.025 ounce per ton (0.04-0.9 ppm). Despite 

the very low gold content, gold production from 

these deposits is significant because of the large 

tonnages mined each year. Currently, byproduct 

gold accounts for 40 percent of the total United 

States gold output, and 19 of the 25 largest goldproducing mines in the United States yield gold only 

as a byproduct (Hoyt, 1971, p. 533). Of the byproduct production, 80 percent is from copper ore, and 

the rest is principally from complex ores of lead, 

zinc, and copper. Salt Lake County, Utah, which 

contains the large open-pit copper mine at Bingham, 

yielded more than half of the byproduct gold produced in the United States in 1969. 

Precise figures on the worldwide production of byproduct gold are not available, but this source probably accounts for 5-10 percent of the total world 

output. Byproduct gold constitutes a significant 

part-15 percent or more--of the production from 

several major gold-producing countries, including 

Australia, Canada, Japan, Nicaragua, Peru, and the 

Philippines. 

In recent years, byproduct gold has been a steady 

source of supply in the United States, and it is 

expected to continue to be so into the future. Any 

change in production will be controlled largely by 

output of copper and, to a lesser extent, of lead and 

zinc. Changes in the price of gold will have a negligible effect on production from this source. Similar 

considerations apply to byproduct gold output in the 

rest of the world. 

RESERVES AND RESOURCES 

Many estimates of U.S. and world reserves and 

resources of gold have been made, and a few are 

given in table 51. World reserves of gold total about 

1 billion ounces, of which 60 percent is in South 

Africa. At the present rate of production, world reserves would be exhausted in 20-25 years. U.S. gold 

reserves are 50-80 million ounces, about half of 

which are in byproduct ores. The remainder are 

mostly in disseminated and lode deposits. 

In addition to reserves of gold in the ground, 

large amounts are held by governments and banks 

as official reserves and by speculators and other 

private holders. Government and bank holdings total 

1.3 billion ounces, of which about 292 million ounces 

was in the U.S. Treasury at the end of 1971. The 

quantity of gold in the hands of speculators and 

others, although difficult to estimate, is probably of 

the order of 1 billion ounces. Clearly, the reserves 

of gold already mined are considerably larger than 

those of unmined gold. 

The U.S. gold resources shown in table 51 are 

mostly conditional resources. Hypothetical and 

TABLE 51.-Reserves 1 and potential resources • of gold (in millions of ounces) ·in the world as estimated in several sources 

of data 

A' B c D 

Source of dataa ------------------------------------------ Reserv.es Potential 

resources Reserves Reserves Reserves Potential 

resources 

8 United 53 '~244 States ------------------------------------- 6 9 399 50 82 

300 

1 

600 

South Africa ------------------------------------- } } 600 

Canada ------------------------------------------- 25 

Australia ----------------------------------------- 950 10 

Other non-Communist countries -------------------- 83 

Communist countries (excluding Yugoslavia) ------- 200 -------------------------------------------------- World 353 844 total --------------------------------- 1,000 1,000 1 Reserves: Identified deposits from which minerals can be ex- tracted profitably with existing technology and under present economic 

conditions. 11 Potential resources: Identified mineral deposits not profitably re- coverable with existing technology and economic conditions, and undiscovered mineral deposits whether of recoverable or subeconomic grade. a A, U.S. Bur. Mines (1967, p. 5); B. U.S. Geol. Survey (1968, p. 

A13); C, Ageton (1970, p. 577); and D, U.S. Bur. Mines (1972, p. 61). ~ Exclusive of byproduct gold. 6 Producible at $36 per ounce. 8 Producible at 1968 price-about $40 per ounce. Includes 3() million ounces of byproduct gold. 7 Producible at prices up to $145 per ounce. Includes 30 million ounces of byproduct gold. 
272 UNITED STATES MINERAL RESOURCES 

speculative resources cannot be estimated as accurately as reserves, but these resources are probably 

large compared with current U.S. gold production 

or consumption but small compared with total world 

reserves. The largest potential resources of gold in 

the United States are in Tertiary or Cretaceous 

placer deposits or auriferous conglomerates, followed in decreasing order of magnitude by disseminated, lode, "bonanza," and other placer deposits. 

The Tertiary-Cretaceous placer deposits of the 

United States represent a very large resource of 

gold, but at the present time they are not economic 

to mine. The auriferous conglomerates of northwestern Wyoming contain 35-200 ppb gold in a 

volume exceeding 50 cubic miles, and they probably 

contain several hundred million ounces of gold ( 6-

10 yr production from the Witwatersrand) (Antweiler and Love, 1967) . The Tertiary placers of the 

Sierra Nevada have an estimated 3-4 billion cubic 

yards of gravel containing 20-30 million ounces of 

gold (Merwin, 1968, p. 2). In both areas, formidable 

and, for the foreseeable future, probably insurmountable technologic and legal problems militate against 

utilization of these resources. 

Deposits of disseminated gold-the so-called 

Carlin-type deposits-probably contain the second 

largest domestic resources of gold and almost certainly the largest undiscovered resources of grade 

high enough to be mined at the present price of 

gold or even at a substantially higher price. The 

two largest deposits were discovered as late as the 

1960's, and others may well have been missed by 

earlier prospectors. The area of possible occurrence 

of favorable host rocks, principally in north-central 

Nevada, is large, and the known deposits contain 

enough gold--one-half million ounces or more 

apiece-to make discovery of others rewarding. 

Undiscovered resources of gold undoubtedly remain to be found in the lode- and "bonanza" -type 

deposits, but the amount is probably small compared 

with that in the disseminated deposits. The lode and 

"bonanza" deposits have been sought for many 

years, and most of them discoverable with present 

exploration techniques probably have been found. 

The lode deposits occur principally in rocks of Precambrian age, rocks which have a complex geologic 

history. Each year our knowledge of the geology of 

these rocks is improving, and this in time should 

lead to development of guides that will increase 

chances for discovery of new deposits. For the 

"bonanza"-type deposits, a better understanding of 

the geochemistry of the extensive alteration halo 

that envelops these deposits might provide a useful 

tool for recognizing the outer fringes of the halo 

over a concealed deposit. However, much effort has 

been expended toward these ends in recent years, 

but so far no new discoveries have been reported. 

Gold resources of young placer deposits must be 

small ; these deposits are easy to find and have been 

extensively mined, and the likelihood that any 

young placer of significant size remains undiscovered 

is very slight. Moreover, the increasingly strict legal 

restraints on placer mining because of water pollution problems inherent in this kind of mining are 

discouraging to further prospecting. 

Inasmuch as gold may be recoverable even at very 

low concentrations, materials containing gold in 

amounts near crustal abundance should perhaps be 

considered as potential future resources. Such materials would include, for instance, sea floor sediment such as in the Bering Sea, or sea water itself, 

both of which presumably contain enormous quantities of gold. However, the concentration of gold in 

both is far too low for economic recoverability at 

present, and in fact, the average concentration of 

gold in sea water is so minute as to exclude it from 

serious consideration as a potential source in the 

foreseeable future. (At a medium concentration of 

0.03 ppb, and with gold at $70 per oz, the gold in a 

metric ton of sea water would be worth $.0000639; 

expressed in another way, the amount of sea water 

that would have to be processed to extract 1 oz of 

gold, assuming a concentration of 0.03 ppb and 

complete recovery, would be approximately 1 million 

m3

-enough water to flood two football fields to a 

depth of 100m.) 

Not enough is known about uneconomic and undiscovered gold resources outside the United States 

to permit an estimate of their magnitude at this 

time. The one figure shown in table 51 (col. C) for 

gold resources outside the United States represents 

mainly deposits that are considered reserves by other 

authorities. It seems clear, however, as noted previously, that the most favorable areas for discovery 

of new deposits of the two types that historically 

have been the most productive-the gold-quartz 

lodes and the fossil placers-are those of Precambrian rocks, particularly rocks in the approximate 

age range of 1.6-2.7 billion years. Rocks in this age 

group are hosts for all the major Precambrian gold 

deposits of the world-Witwatersrand, Homestake, 

Kolar, Porcupine, Kirkland Lake-Larder Lake, Kalgoorlie, Tarkwa, and probably Morro Velho. Precambrian rocks constitute the Canadian, BrazilianGuyana, African-Arabian, Australian, and Indian 

shields and are exposed over extensive areas in 

Siberia. In the United States, Precambrian rocks 

older than about 1.6 billion years are not widely 
GOLD 273 

exposed. Their main areas of outcrop are in the 

eastern ranges of the Rocky Mountains in New 

Mexico, Colorado, Wyoming, and Montana; in the 

Black Hills in South Dakota; and in northern Michigan, Wisconsin, and Minnesota around the west end 

of Lake Superior. Smaller areas are scattered 

through Arizona, southern Nevada, and southeastern California. 

PROSPECTING TECHNIQUES 

Because of the nature of gold-its high density, 

its resistance to tarnish and hence its high visibility, 

and its distinctive color-the most useful field tool 

in the search for gold deposits has been the gold pan, 

with which gold can be recognized immediately if it 

is in large enough particles. The gold pan is still a 

useful implement, but it is unreliable for detecting 

gold tellurides or extremely fine grained gold such 

as characterizes the Carlin-type deposits. For measurement of unseen gold in rock samples, the fire 

assay has until recently been the standard method. 

However, the fire assay is both costly and time consuming and has been supplanted to a large degree 

by atomic absorption spectrophotometry, a rapid 

and economical method that can detect as little as 

20 ppb gold in a sample. This method has made possible the routine analysis of large numbers of samples and thus has greatly facilitated exploration for 

gold. 

PROBLEMS FOR RESEARCH 

Early in 1966, the U.S. Geological Survey undertook a large research program, the Heavy Metals 

Program, to tackle many of the geologic problems 

related to gold. This program is no longer in existtence, but research is being continued on many important problems as part of the Geological Survey's 

mineral-resource program. 

A principal geologic problem related to U.S. gold 

deposits is the geologic and geochemical nature of 

the disseminated (Carlin-type) deposits. Inasmuch 

as these deposits probably represent the largest relatively high grade gold resource of the United States, 

further research on them would appear to have a 

high possible payoff. Much is already known about 

the geologic setting and geochemical makeup of 

these deposits, and they are the subject of continuing research. Nevertheless, no new discoveries have 

been reported since Cortez, Nev., in 1966. Is some 

vital clue perhaps being overlooked? 

The greatest gold-producing district in the world 

is the Witwatersrand. Counterparts of the Precambrian gold-uranium placer deposits of the Rand seem 

to be very rare, and none even remotely ~omparable 

in productivity has been found. What critical combination of geologic factors was operative in the 

formation of these deposits? If this question could 

be answered satisfactorily, would it be possible to 

predict where and when other such combinations 

might have occurred in the geologic past? 

Very large amounts of gold must have been eroded 

from the Precambrian deposits of the Canadian 

Shield in Ontario and Quebec, yet very little gold 

has beeJl found in younger rocks overlying the shield 

along its southern edge even though they were extensively sampled in the Heavy Metals Program. 

Are there other more likely places where this gold 

might have been concentrated? 

The high concentration of major gold deposits in 

rocks of intermediate Precambrian age (2,700-

1,600 million years) has already been noted. Many 

of these deposits are in rocks of, or related to, the 

so-called greenstone-granite association (districts in 

Ontario and Quebec, Canada; Kalgoorlie, Australia; 

Kolar, India; Rhodesia). Do the auriferous greenstone-granite terranes have any geochemical peculiarities that would distinguish them from lithologically similar but barren terranes? 

Broad alteration halos surround "bonanza"-type 

gold deposits. Much is being done to characterize 

these halos chemically and to determine the chemical 

and mineralogic changes that occur during the formation of a halo and its subsequent weathering. Will 

it be possible to distinguish a halo associated with 

an ore deposit from one in barren rock? 

Gold deposits occur in mountain ranges at or near 

enough to the surface to be detected with existing 

exploration tools. But what of these deposits that 

undoubtedly occur in adjacent valleys beneath a 

thick cover of younger sediment? Can exploration 

tools be developed to detect them'! Measurement of 

the mercury content of air, which is higher over 

certain types of ore deposits, holds promise. Are 

there other elements that might be useful? 

A group of related problems concerns the distribution of gold in rocks. Considerable information is 

available on the gold content of various rock types 

and minerals and of bedrock ores, but many gaps in 

knowledge remain. For instance, there seem to be 

three points, or relatively narrow ranges of points, 

in the spectrum of gold concentrations: (1) crustal 

abundance of 0.003-0.004 ppm; (2) gold content of 

the lowest grade gold ore mined in modern times 

(Alaska Juneau mine, average grade of ore only 

about 0.04 oz per ton, or a little more than 1 ppm) 

and of the porphyry copper deposits, which yield 

gold as a byproduct (0.001-0.018 oz per ton, or 

0.04-0.6 ppm) ; and (3) gold content of ore being 
274 UNITED STATES MINERAL RESOURCES 

mined at gold mines throughout the world (0.3-0.5 

oz per ton, or 10-17 ppm). Is any appreciable percentage of the total gold in the accessible parts of 

the earth's crust present in concentrations intermediate between those of porphyry copper ore and 

currently minable gold ore, say 1-5 ppm, or is there 

a real gap in the concentration range between these 

two grades of ore, rather than only an apparent one 

created by mining economics? A corollary question 

concerns the distribution of gold near deposits of 

gold and other metals: is gold confined largely to 

the deposits themselves or does it decrease gradually 

away from the deposits; that is, does a gold-enriched 

halo or "assay wall" commonly bound a gold-bearing 

deposit? 

Other gaps in knowledge include the mode of occurrence of gold in minerals, especially those of 

mafic rocks, and the distribution of gold in porphyry 

copper deposits and their wallrocks. 

A final problem, for the most part not a geologic 

one, concerns the lack of up-to-date information on 

the gold resources of the U.S.S.R. Although Russia 

has the second largest gold production in the world 

and is believed to have substantial reserves and resources, almost nothing has been published on its 

production, reserves, resources, or economics since 

the midthirties. If, as some analysts believe, industrial demand for gold has already reached the current level of production, or will do so in the near 

future, then Russian output may play an important 

role in determining both the price of gold and its 

degree of utilization. 

REFERENCES CITED 

Ageton, R. W., 1970, Gold, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 573-585. 

Antweiler, J. C., and Love, J. D., 1967, Gold-bearing sedimentary rocks in northwest Wyoming-a preliminary report: U.S. Geol. Survey Circ. 541, 12 p. 

Bateman, A. M., 1950, Economic mineral deposits [2d ed.] : 

New York, John Wiley & Sons, Inc., 916 p. 

Bateman, J. D., 1958, Uranium-bearing auriferous reefs at 

Jacobina, Brazil: ECQn. Geology, v. 53, p. 417-425. 

Busschau, W. J., 1967, Future trends in world gold production: Mining Survey, no. 61, Sept. 1967, p. 17-21. 

Butler, B. S., Loughlin, G. F., Heikes, V. C., and others, 

1920, The ore deposits of Utah: .U.S. Geol. Survey Prof. 

Paper 111, 672 p. 

Canada Geological Survey, 1970, Geology and economic minerals of Canada [5-th ed.], R. J. W. Douglas, ed.: Econ. 

Geology Rept. 1, v. 1, 838 p.; v. 2. 

Canadian Institute of Mining and Metallurgy, 1948, Structural geology of Canadian ore deposits: Montreal, Mercury Press, Ltd., 948 p. 

Chamber of Mines of South Africa, 1969, 80th annual report, 1969 : Johannesburg, South Africa, 64 p. 

Commonwealth Mining and Metallurgical Congress, 6th, 

Canada, 1957, Structural geology of Canadian ore deposits, 524 p. 

Commonwealth Mining and Metallurgical Congress, 8th, 

Australia and New Zealand, 19·65, Geology of Australian 

ore deposits, v. 1 [2d ed.]: Melbourne, 547 p. 

Connolly, J. P., and O'Harra, C. C., 1929, The mineral wealth 

of the Black Hills: South Dakota School Mines Bull. 

16,418 p. 

Cooke, H. C., 1946, Canadian lode gold areas (Summary account): Canada Dept. Mines and Resources, Econ. 

Geology Ser. no. 15, 86 p. 

DeKun, Nicolas, 1965, The mineral resources of Africa: 

Amsterdam, Elsevier Pub. Co., 7 40 p. 

Emmons, W. H., 1937, Gold deposits of the world: New York, 

McGraw-Hill Book Co., 562 p. 

Erickson, R. L., Marranzino, A. P., Oda, Uteana, and Janes, 

W. W., 1964, Geochemical exploration near the Getchell 

mine, Humboldt County, Nevada: U.S. Geol. Survey 

Bull. 1198-A, 26 p. 

Gold Producers Committee, 1967 ( ?) , The outlook for gold 

mining-the role of the gold mining industry in the 

future economy of South Africa: Gold Producer's Committee, Ghamber of Mines, Transvaal and Orange Free 

State, 63 p. 

Gottfried, David, Rowe, J. J ., Tilling, R. L., 1972, Distribution of gold in igneous rocks: U.S. Geol. Survey 

Prof. Paper 727, 42 p. 

Green, Timothy, 1968, The world of gold: New York, Walker 

and Go., 242 p. 

Gross, W. H., 1968, Evidence for a modified placer origin for 

auriferous conglomerates, Canavieiras mine, Jacobina, 

Brazil: Econ. Geology, v. 63, p. 271-276. 

Hardie, B. S., 1966, Carlin gold mine, Lynn district, Nevada: 

Nevada Bur. Mines Rept. 13, pt. A, p. 73-83. 

Hoyt, C. D., 1971, Gold, in U.S. Bur. Mines Minerals Yearbook 1969, v. 1-2, p. 521-538. 

International Geological Congress, 1930, The gold resources 

of the world: Internat. Geol. Gong., 15th, Pretoria, 1929, 

457 p. 

Irving, J. D., 1904, Economic resources of the Black Hills, 

with contributions by S. F. Emmons and T. A. J aggar, 

Jr.: U.S. Geol. Survey Prof. Paper 26, 222 p. 

Jones, R. S., 1968, Gold in meteorites and in the earth's 

crust: U.S. Geol. Survey Circ. 603, 4 p. 

--- 1969, Gold in igneous, sedimentary, and metamorphic 

rocks: U.S. Geol. Survey Circ. 610, 28 p. 

--- 1970, Gold content of water, plants, and animals: 

U.S. Geol. Survey Circ. 625, 15 p. 

Jones, R. S., and Fleischer, Michael, 1969, Gold in minerals 

and the composition of native gold: U.S. Geol. Survey 

Circ. 612, 17 p. 

Kavanagh, P. M., 1968, Have 6,000 yeavs of gold mining exhausted the World's gold reserves?: Canadian Mining 

and Metall. Bull., v. 61, no. 672, p. 553-558. 

Koschmann, A. H., and Bergendahl, M. H., 1968, Principal 

gold-producing districts of the United States: U.S. 

Geol. Survey Prof. Paper 610, 283 p. 

Krauskopf, K. B., 1967, Introduction to geochemistry: New 

York, McGraw-Hill Book Co., 721 p. 

Lee, Tan, and Yao, Chi-Lung, 19·70, Abundance of chemical 

elements in the earth's crust and its major tectonic units: 

Internat. Geology Rev., v. 12, no. 7, p. 778-786. 

Lindgren, Waldemar, 1933, Mineral deposits [4th ed.]: New 

York, McGraw-Hill Book Co., 930 p. 
GOLD 275 

Mason, Brian, 1966, Principles of geochemistry [3d ed.]: 

New York, John Wiley & Sons, Inc., 329 p. 

Merwin, R. W., 1968, Gold resources in the Tertiary gravels 

of California: U.S. Bur. Mines Tech. Prog. Rept., 14 p. 

Moore, G. W., and SHver, E. A., 1968, Gold distribution on 

the se.a floor off the Klamath Mountains, California: U.S. 

Geol. Survey Circ. 605, 9 p. 

Park, C. F., Jr., 1968, Affluence in jeopardy: San Francisco, 

Freeman, Cooper and Co., 368 p. 

Park, C. F.,. Jr., and MacDiarmid, R. A., 1970, Ore deposits 

[2d ed.]: San Francisco, W. H. Freeman & Co., 522 p. 

Rankama, Kalervo, and Saha.ma, T. G., 1950, Geochemistry: 

Chicago, Chicago Univ. Press, 912 p. 

Roberts, R. J., 1960, Alinement of mining districts in northcentral Nevada, in Short papers in the geological sciences: U.S. Geol. Survey Prof. Paper 400-B, p. B17-B19. 

--- 1966, Metallogenic provinces and mineral belts in 

Nevada: Nevada Bur. Mines Rept. 13, pt. A, p. 47-72. 

Roberts, R. J ., Radtke, A. S., and Coats, R. R., 1971, Goldbearing deposits in north-central Nevada and southwestern Idaho: Econ. Geology, v. 66, p. 14-33. 

Roscoe, S. M., 1957, Geology and uranium deposits, Quirke 

Lake-Elliot Lake, Blind River area, Ontario: Ganada 

Geol. Survey Paper 56-7, 21 p. 

Rosenbaum, J. B., May, J. T., and Riley, J. M., 1969, Gold 

in sea water-fact or fancy: Soc. Mining Engineers 

Preprint 69-AS-82, Am. lnst. Mining, Metall., and Petroleum Engineers Ann. Mtg., Washington, D. C. 1969, 

9 p. 

Sutherland, C. H. V., 1960, Gold-its beauty, power, and 

allure: London, McGraw-Hill Book Co., 196 p. 

U.S. Bureau of Mines, 1932-1971, Minerals yearbook, 1931-

1969. 

--- 1967, Production potential of known gold deposits in 

the United States: U.S. Bur. Mines Inf. Circ. 8331, 24 p. 

--- 1972, Commodity data summaries: January 19·72. 

U.S. Department of the Interior, 1972, First annual report 

of the Secretary of the Interior under the Mining and 

Minerals Policy Act of 19·70 (P.L. 91-631), Pt. 2-

Appendices: U.S. Govt. Printing Office, March 1972. 

U.S. Geological Survey, 1968, Geological Survey research 

1968: U.S. Geol. Survey Prof. Paper 600-A, 371 p. 

-- 1969, U.S. Geological Survey Heavy Metals Program progress report 1968-Field studies: U.S. Geol. 

Survey Circ. 621, 35 p. 

U.S. News & World Report, 1972, Is the dollar headed for 

more trouble: U.S. News & World Rept., July 10, 1972, 

p. 20-23. 

Weissberg, B. G., 1969, Gold-silver ore--grade precipitates 

from New Zealand thermal waters: Econ. Geology, v. 

64, p. 95-108. 

Wells, J. D., Stoiser, L. R., and Elliott, J. E., 1969, Geology 

and geochemistry of the Cortez gold deposit, Nevada: 

Econ. Geology, v. 64, p. 526-537. 

Wise, E. M., 1964, Gold-recovery, properties, and applications: Princeton, D. Van Nostrand Co., 367 p. 

World Mining, 1967, Witwatersrand gold-the challenge of 

inflation: v. 3, no. 2, p. 12-17. 

Wrucke, C. T., Armbrustmacher, T. J., and Hessin, T. D., 

1968, Distribution of gold, silver, and other metals 

near Gold Acres and Tenabo, Lander County, Nevada: 

U.S. Geol. Survey Circ. 589, 6 p. 

UNITED STATES MINERAL RESOURCES 

GRAPHITE 

By pAUL L. WEIS 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------- Exploitation -------------------------------------

Geologie environment ----------------------------

Geochemistr,y --------------------------------

Geology ------------------------------------- Vein graphite ---------------------------

Flake graphite --------------------------

Amorphous graphite ---------------------

Resources --------------------------------------- Identified and hypothetical resources ----------

Speculative resources ------------------------

Prospecting -------------------------------------- Problems for research ---------------------------

Selected references ------------------------------

FIGURE 

31. Graph showing U.S. consumption of graphite, 

Page 

277 

277 

279 

280 

280 

280 

280 

280 

281 

281 

281 

282 

282 

282 

283 

Page 

1910-69 ---------------------------------- 279 

TABLES 

Page 

52. Consumption, by uses, of natural graphite in 

the United States in 1969 ---------------- 278 

53. Tonnage and value of 1969 U.S. imports for 

consumption of natural graphite, by countries ------------------------------------ 278 

54. Identified resources of graphite of the United 

States ----------------------------------- 281 55. Identified and hypothetical graphite resources 

of the world ---------------------------- 282 

ABSTRACT OF CONCLUSIONS 

Within the last 20 years technology and attitudes in the 

graphite industry have changed significantly. In 1950 the 

domestic industry demanded natural graphite from only a 

few sources and strongly resisted substitutions. Since 1960, 

the price of raw graphite has risen because of steadily increasing costs of labor at the source areas abroad and the 

more recent devaluation of the dollar in the world market. 

Today, new technology has shown that these old preferences 

need not be so rigorously applied. Domestic consumption of 

generally more costly synthetic graphite has increased and 

by 1969 was seven times that of natural graphite. 

This combination of technical and economic factors has 

generated renewed interest in domestic graphite deposits 

whose total resources are greater than 10 million tons. ·Except for one active mine in Texas, no domestic resources of 

graphite currently seem competitive with foreign sources. 

Flake graphite deposits in Alabama, New York, and Pennsylvania are probably too low grade to mine now. Flake 

and amorphous deposits in Alaska are too remote, and vein 

deposits in Montana are too small to be of commercial value 

soon. 

The likelihood of finding richer, larger, or more favorably 

located domestic deposits seems slight. 

INTRODUCTION 

The graphite industry is one of the Nation's 

smallest mineral industries. The total sales of natural graphite in the domestic industry were less than 

$61/2 million in 1969; however, the unique physical 

and chemical properties of graphite make it irreplaceable in some uses. The importance of graphite 

to the national economy is therefore difficult to define precis.ely, but is far greater than the annual 

dollar value of commercial sales would appear to 

indicate. 

Graphite is pure crystalline carbon; it is steel gray 

and has a hardness of 1 to 2, specific gravity of 2.1 

to 2.3, and excellent cleavage. It is sectile, flexible, 

and a good conductor of heat and electricity. Graphite is also extremely inert to most chemical reagents, 

including hydrofluoric acid and boiling aqua regia. 

At temperatures above 600°C graphite decomposes 

slowly in an oxidizing atmosphere, but if protected 

by a nonoxidizing atmosphere or an inert coating, it 

remains stable to 3,500°C. 

U.S. GEOL. SURVEY PROF. PAPER 820 

277 
278 UNITED STATES MINERAL RESOURCES 

Nat ural graphite occurs in three geologic environments, and the distinctive qualities of the graphite 

in each give rise to three categories of commercial 

deposits. 

1. Veins consisting of 75-100 percent graphite are 

of commercial value, but they are only found 

in a few places where they cut igneous and 

metamorphic rocks, commonly of Precambrian 

age. The graphite is marketed as "lump and 

chip," "crystalline lump," or "amorphous 

lump," in various classes depending on particle 

size and purity. 

2. "Flake graphite" is the commercial designation 

for graphite that occurs as flakes disseminated 

through layers of metamorphosed carbonaceous sedimentary rocks. Commercial deposits 

contain from about 8 to more than 20 percent 

graphite. The thickness, toughness, density, 

size, and shape of the flakes vary by the deposit. 

3. "Amorphous graphite" is a commercial designation for any massive, very fine grained graphite, most of which comes from thermally metamorphosed beds of coal. Deposits of commercial value generally contain at least 80 percent 

graphite. 

Industrial uses of graphite depend upon the characteristics of the three natural graphite types. Finegrained, relatively low cost "amorphous" graphite is 

used extensively for foundry facings, certain refractories, and as a source of carbon in steelmaking. 

Flake graphite is prized for high-quality lubricants 

and for high-quality crucibles and refractory ware. 

"Amorphous lump," or vein graphite, is also used 

in lubricants and refractory ware but is especially 

desired for carbon brushes in electric motors. The 

uses of the graphite consumed in the United States 

in 1969 are summarized in table 52. 

The industrial importance of the three types of 

natural graphite is reflected in the tonnage of U.S. 

imports shown in table 53. Amorphous graphite, 

chiefly from Mexico, has averaged about 80-85 percent of total imports. Shipments from Madagascar 

and Ceylon in recent years have been on the order 

of 4,500 and 2,500 tons, respectively. Although the 

proportion of Ceylon graphite classified as crystalline lump and lump and chip (vein type) is not clear, 

it probably amounts to less than 50 tons per year in 

recent years. 

The only domestic graphite mine now ac-tive, that 

at Burnet, Tex., produces flake graphite. Deposits 

of similar material, however, occur in many other 

places in the United States, chiefly in Alabama, 

Alaska, New York, Pennsylvania, and other places 

TABLE 52.-Consumption, by uses, of natural graphite in the 

United States in 1969 

Use Short tons Value 

(thousands) 

Batteries -------------------- (1) (1) 

Bearings -------------------- 104 $51,307 

Brake linings ---------------- 1,066 368,998 

Carbon brushes -------------- 588 285,869 Crucibles, retorts, stoppers, 

sleeves, and nozzles -------- 4,639 780,793 

Foundry facings ------------- 8,028 1,017,221 

Lubricants ------------------- 2,702 492,316 

Packings -------------------- 409 182,983 

Paints and polishes ----------- 182 27,997 

Pencils ---------------------- 2,190 666,095 

Refractories ----------------- 5,554 735,419 

Rubber ---------------------- 225 73,054 

Steelmaking ----------------- 6,624 578,386 

Other 2 ---------------------- 4,853 1,093,359 ------------------- Total ----------------- 37,164 6,353,797 

1 Withheld to avoid disclosing individual company confidential data; in· 

cluded in "Other." ll Includes adhesives, ehemieal equipment and processes, electronic prod· 

'nets, gray iron castings, powdered-metal parts, small packages, specialties, and batteries. Data from U.S. Bur. Mines. 

TABLE 53.-Tonnage and 11alue of1969 U.S. imports for consumption of natural graphite, by countries 

[Data from U.S. Bureau of Mines] 

Country 

Total 

Value 

Short tons (thousands) 

Austria -------------------------- 20 $2 Ceylon --------------------------- 3,517 402 

France -------------------------- 16 9 

Germany, West ------------------- 1,535 246 

Hong Kong ---------------------- 337 8 

Italy ---------------------------- 18 8 

Korea, South -------------------- 618 17 

Malagasy Republic --------------- 5,042 507 

Mexico -------------------------- 43,269 876 

Norway ------------------------- 4,037 334 

Sweden -------------------------- 44 4 

Switzerland ---------------------- 6 2 

United Kingdom ----------------- 20 4 ---------------- Total ---------------------- 58,479 2,419 

in Texas. Deposits of vein graphite occur in Montana and New York, and deposits of amorphous 

graphite occur in Rhode Island, New Mexico, and 

Colorado. The unproductive deposits are not economically competitive with foreign sources of natural graphite. 

Natural graphite now faces competition from synthetic graphite, marketed as "artificial graphite." 

The commercial name is a misnomer insofar as it 

implies an imitation, because the product is really 

crystalline graphite produced in high-temperature 

furnaces from petroleum coke or other forms of 

amorphous carbon. Synthetic graphite is a product 

of high purity, but it tends to be finer grained, less 

dense, and more expensive than most natural flake 

graphite. Synthetic graphite can be substituted to 

some degree in all of the uses of natural graphite, 
GRAPHITE 279 

though its higher cost makes it noncompetitive for 

some uses. Synthetic graphite, however, is the only 

product that is pure enough for use in moderator 

rods in nuclear reactors. It is also used in electrodes 

for electrosmelting and in anodes for the electrochemical industry. Total consumption of synthetic 

graphite in the United States has increased steadily 

over the last 20 years and in 1969 was 225,500 tons, 

almost seven times the total tonnage of natural 

graphite consumed. The use of synthetic graphite in 

future industrial markets undoubtedly will affect the 

mining of natural graphite. 

Other details of the economic aspects of the graphite industry are given by Lewis (1970). 

EXPLOITATION 

Graphite production in the United States began 

between 1644 and 1648 at Sturbridge, Mass., but 

between that time and about 1850, production, which 

carne from scattered operations in New England, 

New York, and New Jersey, apparently was small 

and sporadic. During the period 1850-1900, deposits 

in New York, New Jersey, Alabama, Pennsylvania, 

Michigan, Texas, California, Nevada, and Rhode 

Island were explored and developed, and a domestic 

graphite industry carne into being. From the 1850's 

to 1900, the mines of the Joseph Dixon Co. near 

Ticonderoga and Lake George, N.Y., were the principal domestic source of flake graphite, but around 

1900, Alabama and eastern Pennsylvania began intermittent production of substantial amounts of 

flake graphite. In 1911, Alabama took first place as 

a producer of flake graphite and maintained that 

position until after World War II. From about 1946 

to 1954, Texas and Alabama produced nearly equal 

amounts of flake graphite. By the end of 1954, all 

flake graphite production had stopped. After a short 

lapse, production in Texas resumed in 1955 and has 

continued to the present at the Southwest Graphite 

Co. mine in Burnet County. 

Amorphous graphite was apparently first mined 

in quantity from deposits in Rhode Island, North 

Carolina, California, and Nevada, then later in 

Michigan, Wisconsin, and other States. By the end 

of 1954, only one deposit of amorphous graphite in 

Rhode Island was being mined. Tonnage and quality 

of the deposits in these States are both lower than 

the Mexican sources that have supplied a large part 

of our needs since World War I. 

A high proportion of the annual consumption of 

natural graphite in the United States is by the ferrous and nonferrous metals industries where it is 

used for foundry facings, carburizing, and a wide 

variety of refractory ware. Total consumption and, 

to a lesser degree, total imports therefore, approximately reflect the general level of prosperity and 

industrial productivity in the United States (fig. 31). 

en 

z 

0 

1-

~ 

0 

en 

0 

z 

c( 

en 

:> 

0 

I: 

1-

80 

60 

0 

1910 

Total imports plus 

total U.S. production, 

all types 

1920 1930 

Total U.S. consumption, 

all types (includes some synthetic graphite) 

1940 1950 1960 1969 

FIGURE 31.-U.S. consumption of graphite, 1910-69. 

Industrial activity during World War I caused graphite production and imports to reach a record high; 

the great depression of the 1930's caused them to 

reach a record low. World War II, the postwar boom 

of the 1950's, and the Korean and Viet Narn Wars 

also caused peaks in graphite consumption. The general recession of 1949, intensified by disastrous 

strikes in the coal and steel industries, marks the 

deepest low since the early 1930's. 

The data shown in figure 31 also reflect one of 

the major problems of the prospective U.S. producer-that of fluctuation of graphite consumption. 

Since 1949, U.S. annual consumption has ranged 

from 15,000 to 52,000 tons, a difference of more 

than 340 percent. Only with bravery and optimism 

can capital and effort be invested in a business that 

fluctuates so widely and unpredictably. 

Until recently there has been strong resistance by 

industry to graphite from any but long-established 

foreign sources, notably the Malagasy Republic for 

flake, Ceylon for both flake and vein, and Mexico 

and Korea for amorphous graphite. Several reasons 

account for the favored position that foreign graphite commanded. Supplier's formulas for refractory 

ware were based on trial and error. Certain graphite 

plus certain clay plus certain mixing and annealing 

gave products with a long life. Changes in ingredients or preparation methods shortened the life of 

the product, thus changes in formulas were strongly 

resisted. Uses of lubricating flake demanded coarserather than fine-grained material, a preference favoring Malagasy flake over others. Finally, many overseas suppliers had been in business long enough to 

have demonstrated their ability to maintain quality 

and provide reliable delivery at prices well below 
280 UNITED STATES MINERAL RESOURCES 

that of most domestic producers. Since about 1960, 

however, technological changes and increased prices 

for raw graphite have changed the attitudes of importers and suppliers. Development of the silicon 

carbide-graphite crucible, which can use graphite 

from almost any source, is an example of improved 

technology. The net result is that domestic deposits, 

particularly those of flake graphite, look much more 

attractive now than they did in the 1950's or 1960's. 

GEOLOGIC ENVIRONMENT 

The form, oc.currence, mineralogy, origin, and distribution of natural graphite have been discussed 

in considerable detail elsewhere (Cameron and W eis, 

1960, p. 206-208; 241-249) and will be described 

only briefly here. 

GEOCHEMISTRY 

Carbon is 11th in abundance among the elements 

that form the earth's crust, but the crustal abundance of carbon bears little relationship to the abundance or distribution of graphite. Most of the carbon 

in the crust of the earth-probably 80-90 percentis in carbonate rocks, and most of the remaining 

carbon occurs in living or fossil organic matter or 

in the atmosphere as C02 ; probably less than onehalf of 1 percent of the carbon in the earth's crust 

occurs in elemental form, as amorphous carbon, 

graphite, or diamond. 

Carbon's behavior in the geochemical cycle depends largely on its form. More than 95 percent of 

the earth's carbon occurs as C02 or its compounds, 

and most of the remainder occurs as one of the 

hundreds of organic hydrocarbons. These compounds 

have characteristic geochemical cycles that are unlike that of elemental carbon. 

Carbon that occurs as graphite came at least in 

part from organic material. Once in the form of 

graphite, it is likely to remain unchanged. In most 

chemical environments, graphite is one of the most 

inert substances known to man. Acids, bases, oxidizing and reducing environments alike leave it unchanged. Only at temperatures greater than about 

600°C in an oxidizing environment does it slowly 

change to C02. Under surface weathering conditions 

it remains unchanged. Metamorphism tends to recrystallize graphite to coarser grains. The graphite 

cycle tends to become a closed system once the 

mineral is formed. 

The cycle of erosion, transportation, deposition, 

and metamorphism tends to disseminate graphite, 

rather than to concentrate it. There are no workable 

sedimentary deposits of graphite. Economic deposits 

of flake or amorphous graphite occur only where 

concentrations of nongraphitic carbon have been 

metamorphosed. 

GEOLOGY 

VEIN GRAPHITE 

Vein deposits of graphite are fracture fillings that 

contain 75-100 percent graphitic carbon. Crustification is common, with coarse, platy, or needlelike 

interlocking crystals apparently grown inward from 

both walls. Mineral impurities include quartz, feldspar, pyrite, pyroxene, apatite, and calcite. Veins 

range from thin films to massive bodies more than 

10 feet in thickness. Some extend along strike for 

thousands of feet, and some have been mined downdip for more than 1,500 feet. The veins cut both 

igneous and metamorphic rocks, generally of Precambrian age. 

Vein graphite deposits are known near Crown 

Point, N.Y., and in the Dillon area, Montana, but 

the only economically important world supply is 

from Ceylon. 

The agents of transport and precipitation of carbon that lead to the formation of graphite veins are 

not understood. Some geologists have suggested that 

the veins are hydrothermal ; others, that they are 

pneumatolytic. Neither the hydrothermal nor the 

pneumatolytic hypothesis has enough supporting 

field evidence to enable one to make a final choice. 

FLAKE GRAPHITE 

Flake graphite of commercial size is derived from 

carbonaceous material in sedimentary rocks that 

have metamorphosed at least to garnet grade. The 

resulting gneisses and schists are the hosts for all 

deposits of flake graphite. The grade of the deposit 

is dependent on the carbon content of the original 

sedimentary rocks. Graphitic metasedimentary rocks 

contain from a trace to as much as 90 percent flake 

graphite, but most of these gneisses and schists contain less than 3 percent graphitic carbon. Distribution of the graphite in flakes, that may range from 

1 to more than 250 millimeters in diameter, generally is more uniform along strike and dip than from 

one layer to another. 

Impurities in flake graphite are the common minerals of high-grade metasedimentary rocks, especially quartz, feldspars, mica, amphibole, and garnet. 

The suite of' gangue minerals is an important economic consideration. Most of these minerals are 

easily separated from the graphite. Mica is a notable exception, especially when intergrown with 

graphite, a common relation in many flake deposits. 

The separation of these minerals becomes extremely 
GRAPHITE 281 

difficult if fine grinding is necessary because the 

mica becomes coated with a film of graphite and is 

collected along with the graphite, and the grade of 

the graphite concentrate is thereby lowered. Marketable concentrates generally contain 85 percent or 

more graphite. 

Probably the largest deposits of flake graphite in 

the United States occur in gneiss and schist in the 

Kigluaik Range on the Seward Peninsula, Alaska. 

The graphitic rocks are exposed for 60 miles along 

strike, and many layers containing about 10 percent 

graphite are more than 25 feet thick. Within these 

layers are lenses and pods containing 50--60 percent 

graphite, part of which is coarse flake. Most of these 

lenses and pods are 1/2-11/2 feet thick and 10--20 

feet long, but some are as much as 6 feet thick and 

100 feet long. Within parts of the range, in the zone 

of graphitic schist, these high-grade pods are estimated to make up 25 percent of the rock (Coats, 

1944). 

Deposits of flake graphite in the United States 

have been mined in Alabama, Alaska, New York, 

Pennsylvania, and Texas. 

The world's most economically important flake 

deposits now in production are in Malagasy Republic, where layers 10--100 feet thick contain 10-20 

percent graphite. Much of the ore is intensely weathered and requires only a simple wash to produce a 

concentrate containing 85-92 percent graphite. Other 

important foreign deposits of flake graphite are in 

Austria, Norway, Russia, and China. 

AMORPHOUS GRAPHITE 

Amorphous graphite, formed by thermal metamorphism of coal beds, is massive and cryptocrystalline. The size, grade, and mineral impurities in the 

deposit depend on the characteristics of the original 

coal seam. Major deposits being mined today generally contain at least 85 percent graphitic carbon. 

The material is dried, shipped, and used without 

beneficiation. Operations are successful only if large 

quantities of material of reliable quality can be 

supplied at low cost. The most important single 

factor in marketing amorphous graphite today is 

transportation cost. 

In the United States, small amorphous graphite 

deposits are known in Rhode Island, near Raton, 

N. Mex., and near Chaffee, Colo. Major free-world 

sources are Sonora, Mexico, and Korea. 

RESOURCES 

The graphite resources of the world are undoubtedly great, but their extent is unknown. Reserves 

are known for a number of operating mines, but reasonable estimates of potential resources probably 

are not available for a single major graphite district 

in the world. The principal reason is that graphite 

is a relatively abundant and widespread mineral, 

and known deposits in many areas far exceed current or foreseeable demands, making it understandably difficult to generate interest in making careful 

resource estimates. As of 1972, deposits containing 

a total of many hundreds of millions of tons are 

known, and total world resources may be many times 

that amount. 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

The identified resources of graphite in the United 

States as of 1960 are summarized in table 54. So 

TABLE 54.-ldentified resources of graphite of the 

United States 1 

[Summarized from Cameron and Weis (1960, p. 252)] 

District 

Dillon, Mont ---------

AJaska -------------- Alabama ------------ New York ----------- Pennsylvania -------- Southwest Texas -----

Type of 

deposit 

Vein ----------- Flake, vein ( ?) __ 

Flake ---------- ___ do ---------- ___ do ----------

___ do ----------

Recoverable 

graphite (tons) 

<5,000 

> 10,000,000 

>300,000 

>250,000 

>10,000 

50,000 ± 

1 Identified resources are specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. 

little prospecting and mining has been done since 

1960 that these estimates of recoverable graphite 

have not yet been improved. 

Most of the graphitic rocks of Alabama, New 

York, and Pennsylvania contain less than 5 percent 

graphite, although a few contain as much as 10 

percent. The location and ease of mining these 

deposits suggest that a modest increase in the price 

of raw graphite might herald the start or resumption of commercial production in these States, especially Alabama. The largest domestic graphite deposits occur in the gneiss and schist in the Kigluaik 

Range of the Seward Peninsula, Alaska (Coats, 

1944). These deposits are higher grade than those 

in the eastern United States, but the greater distance from markets and the greater difficulty of 

mining them will retard their commercial development. 

The world's identified and hypothetical resources 

of graphite are summarized in table 55. 

The best known provinces of vein graphite deposits are in Montana and Ceylon where the veins cut 

Precambrian gneiss and igneous rocks. Further 

search in these areas may reveal additional deposits. 

The graphitic metamorphic rocks of the Kigluaik 

Range, Alaska, have been intruded by igneous rocks, 
282 UNITED STATES MINERAL RESOURCES 

TABLE 55.-ldentified 1 and hypothetical' graphite resources 

of the world 

Locality Quantity 

Rock containing at least 4 percent graphitic carbon as flake graphite 

North America: 

Canada ------------->1 million tons. United States --------Millions of tons. South America: 

Argentina -----------A million tons ( ?) 

Brazil --------------Millions of tons. Europe: 

Austria -------------Hundreds of thousands of tons. Finland -------------Less than 1 million tons. 

France -------------- Do. West Germany _______ Several million tons. 

Italy -----~---------A few hundred thousand tons. 

Norway ------------- Do. 

Spain --------------- Do. 

Sweden -------------Tens of millions of tons. Asia: U.S.S.R. ____________ Hundreds of millions of tons. Ceylon ______________ Hundreds of thousands of tons. 

China _______________ Probably at least millions of tons. India _______________ Hundreds of thousands of tons. Japan ______________ A million tons(?) 

Korea -------------Many millions of tons. Turkey -------------Tens of thousands of tons(?) 

Africa: 

Kenya --------------Hundreds of thousands of tons. Malagasy Republic ____ Many hundreds of millions of tons, in many 

districts, in an area 100 by 600 miles. 

Tanzania ____________ Hundreds of thousands of tons(?) 

Uganda _____________ Small. 

Zambia _____________ Possibly millions of tons. 

Australia: 

South Australia ______ Possibly millions of tons. 

Amorphous graphite in deposita containing about 85 percent graphitic carbon 

North America: Canada _____________ Considerable graphite in eastern Canada ia 

too fine grained to be marketed as flake. 

Total reserves may be several million tons, 

mostly low grade. Mexico _____________ Hundreds of millions of tons, containing 8(}-

85 percent graphite. United States ________ A few thousand tons of 8(}-85 percent graphEurope: 

ite. Byproduct fine material from flake 

graphite deposits-possibly several thousands 

of tons. Alaska-byproduct, millions of tons that would 

require upgrading. 

Austria -------------Hundreds of millions of tons. Czechoslovakia -------Millions of tons. West Germany _______ Hundreds of thousands of tons. 

Sweden -------------Two hundred million tons. Asia: 

U.S.S.R. ------------Tens of millions of tons. Good quality. 

China --------------Probably many millions of tons, possibly 

many tens of millions of tons. Hong Kong ----------Thousands or tens of thousands of tons. India ---------------Possibly thousands of tons. Japan --------------Tens of thousands of tons. Korea ---------------Hundreds of millions of tons. Africa: 

Morocco ------------A few million tons. Southwest Africa -----Thousands of tons(?) 

Australia: 

Queensland ----------Millions of tons. 

Vein graphite in veins consisting of at least 90 percent graphite 

United States ___________ Less than 10,000 tons. Brazil __________________ Occurrences are reported. Details are unavailable. U.S.S.R. ________________ Large deposits are reported west of Irkutsk, 

in eastern Siberia. 

Ceylon -----------------The major world supply of vein-type graph• ite is believed to be here. Total reserves are only estimates from millions of tons to possibly tens or hundreds of millions of tons. China ------------------Vein-type deposits are reported. Reserves may 

range from thousands to millions of tons. 

1 Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be 

profitably recoverable with existing technology and economic conditions. 2 Undiscovered mineral deposits, whether of recoverable or subeeonomic 

grade, that are geologieally predictable as existing in known districts. 

and this area should be explored for possible deposits 

of vein graphite. Few details are known about the 

veins of graphite reported in China, the U.S.S.R., 

and Brazil, and their commercial potential is still 

mostly unevaluated. 

SPECULATIVE RESOURCES 

The geology of the Eastern United States is so 

well known that the likelihood of finding new deposits of flake graphite closer to market is very 

small. Igneous activity in the coal fields of the 

United States either did not occur or was of a scale 

small enough to preclude the chances of finding 

amorphous graphite deposits of commercial size and 

grade. Certainly none found are likely to rival the 

size and grade of the great deposits of Sonora, 

Mexico. 

PROSPECTING 

The simplest and most effective means of finding 

graphite is to look for it in outcrops and residual 

soil. Because of its chemical inertness, graphite 

remains completely unaltered in weathered material; 

and the dark, lustrous flakes are conspicuous in 

surface soil. 

As in prospecting for any mineral, a knowledge 

of areal geology of the area is the first step in 

prospecting for graphite. Flake graphite occurs only 

in metamorphic rocks-commercial sizes generally 

in schists and gneisses of garnet grade or higher or 

in marbles associated with other metasediments. 

Amorphous graphite forms only by thermal metamorphism of coal ; therefore, areas to prospect are 

those where coal-bearing sediments may have been 

intruded by igneous rock. Vein graphite is so rare 

and its origin is so poorly understood that it is 

difficult to characterize the most favorable places to 

prospect. Most known graphite veins cut Precambrian igneous and metamorph-ic rocks, although a 

few are known to be in younger metamorphic rocks 

as well. 

PROBLEMS FOR RESEARCH 

Little effort with modern tools has gone into the 

geologic study of graphite deposits in the United 

States recently, chiefly because most of the known 

deposits were considered noncommercial, reasonably priced graphite has been available continuously 

from foreign sources, and synthetic graphite has 

acquired a large share of the market. Better techniques to beneficiate the low-grade ores are needed 

if a domestic industry is to be viable. Studies on 

the nature of formation of graphite veins might 

aid considerably the science of ore deposits as well 

as the search for more graphite deposits. The role 

of organic matter in metamorphism and hydrothermal ore deposits is not well understood. 
GRAPHITE 

SELECTED REFERENCES 

[Annotations of selected items] 

Alling, H. L., 1917, The Adirondack graphite deposits: New 

York State Mus. Bull. 199, 150 p. Excellent detailed 

descriptions of individual deposits. 

Armstrong, F. C., and Full, R. P., 1946, Geologic map of the 

Crystal Graphite mine, Beaverhead County, Montana: 

U.S. Geol. Survey open-file map. 

Bascom, Florence, and Beach, L. M., 1922, Graphite and History of graphite mining in Pennsylvania, in Nonmetals, 

pt. 2 of Mineral Resources of the United States, 1919: 

U.S. Geol. Survey, p. 309-324. 

Bascom, Florence, and Stose, G. W., 1938, Geology and mineral resources of the Honeybrook and Phoenixville quadrangles, Pennsylvania: U.S. Geol. Survey Bull. 891, 

145 p. 

Bastin, E. S., 1912, The graphite deposits of Ceylon, with 

a description of a similar graphite deposit near Dillon, 

Montana: Econ. Geology, v. 7, p. 419-443. 

Cameron, E. N., and Weis, P. L., 1960, Strategic graphitea survey: U.S. Geol. Survey Bull. 1082-E, p. 201-321. 

Detailed description of mineralogy, uses, history of production, and geology of major U.S. graphite deposits. 

Extensive references. 

Chelf, Carl, 1943, Graphite in Llano County, Texas: Texas 

Univ. Bur. Econ. Geology Mineral Resources Circ. 57, 

10 p. Includes bibliography on Texas graphite. 

Cirkel, Fritz, 1907, Graphite-its properties, occurrence, refining, and uses : Ottawa, Canadian Dept. Mines, 307 p. 

An old but still very useful and comprehensive general 

treatise. 

Coats, R. R., 1944, Graphite deposits on the north side o:f the 

Kigluaik Mountains, Seward Peninsula, Alaska: U.S. 

Geol. Survey open-file rept., 10 p. 

Ford, R. B., 1954, Occurrence and origin of the graphite deposits near Dillon, Montana: Econ. Geology, v. 49, p. 

31-43. 

Harrington, G. L., 1919, Graphite mining in the Seward 

Peninsula: U.S. Geol. Survey Bull. 692-G, p. 363-:367. 

Hopkins, D. M., 1963, Geology of the Imuruk Lake :a.rea, 

Seward Peninsula, Alaska: U.S. Geol. Survey Bull. 1141-

C, 101 p. 

Jones, W. B., 1929, Summary report on graphite in Alabu.ma: 

Alabama Geol. Survey Circ. 9, 29 p. 

Lewis, R. W., 1970, Graphite (natural), in Mineral facts and 

problems: U.S. Bur. Mines Bull. 650, p. 1025-1038. 

Miller, B. L., 1912, Graphite deposits of Pennsylvania: Pennsylvania Topog. and Geol. Survey Rept. 6, 147 p. Detailed descriptions of Pennsylvania mining methodls. 

Moffit, F. H., 1913, Geology of the Nome and Grand Central 

quadrangles, Alaska: U.S. Geol. Survey Bull. 533, 1:37 p. 

Paige, Sidney, 1911, Mineral resources of the Llano-Burnet 

region, Texas: U.S. Geol. Survey Geol. Atlas, Folio 183, 

16 p. 

Pallister, H. D., and Thoenin, J. R., 1948, Flake graphite and 

vanadium investigations in Clay, Coosa, and Chilton 

Counties, Alabama: U.S. Bur. Mines Rept. Inv. ·1366, 

84 p. 

U.S. Bureau of Mines, 1971, Metals, minerals, and fuels, v. 

1-2 of Minerals Yearbook 1969: Washington, U.S. Govt. 

Printing Office, 1194 p. 

UNITED STATES MINERAL RESOURCES 

HELIUM 

By DwiGHT E. WARD and ARTHUR P. PIERCE 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction __ ---__ ---__ ------------------------- Geologic environment ______ -- __________ - __ --------

Resources --------------------------------------- Identified and hypothetical resources -----------

Speculative resources ------------------------

Problems for research ----------------------------

References cited ---------------------------------

FIGURE 

Page 

285 

285 

286 

287 

287 

288 

289 

290 

Billions of cubic feet of helium are being wasted annually 

in the production of natural gas from which the helium is 

not removed. Better and cheaper methods of helium recovery 

are needed to save this helium for the future. 

INTRODUCTION 

Helium, a lightweight, inert gas, is an end product of the radioactive decay of uranium and thorium 

in rocks. In World War I, the first attempts were 

made to obtain helium from natural gas for use in 

lighter-than-air craft, but it was not until World 

War II that this use was realized on a large scale. 

The abundant and dependable supply developed during World War II has made helium available for 

Page various uses that now overshadow military needs. 

32. Graph showing helium sales in the United The properties of lightness and inertness have made 

States, 1920-70 --------------------------

TABLE 

286 helium useful in the space exploration program, the 

largest user. Either or both of these properties have 

made helium useful in creating controlled atmospheres for welding certain metals and for growing 

56. Some known deposits of helium in the United 

States and Ganada -----------------------

Page crystals, for various other industrial processes, for 

use in chromatography, for heat transfer in nuclear 

ABSTRACT OF CONCLUSIONS 

289 reactors, for leak detection, for breathing mixtures, 

and for various laboratory researches. In cryogenics 

research and engineering, liquid helium is used to 

Helium, because of its light weight, chemical inertness, and 

very low temperature in liquid form, is important in space 

exploration, industry, and research. It is recovered as a byproduct from natural gas used for fuel and has not been a 

tE.r~ for independent exploration. 

This situation will change, however, when the few large 

gas fields that now supply most of the helium are exhausted, 

unless comparable deposits are found. Natural gases with 

little or no fuel value but appreciable amounts of helium 

occur in various places in the Rocky Mountain region, but 

their potential for supplying helium needs of the future is 

unknown. 

Inasmuch as helium originates from uranium and thorium 

derived from igneous rocks, accumulations are not necessarily limited to areas where oil and gas are found. Uraniummining areas and volcanic and geothermal areas of the 

Western United States have untested potential for helium 

accumulation. 

obtain temperatures near absolute zero. 

Assuming that helium will continue to be available 

in large volumes at reasonable cost, all the previously 

mentioned uses are expected to increase in the future, and new uses will probably appear. One potential use is as a coolant in power transmission, 

where conductors at the temperature of liquid helium 

become superconductors, thereby increasing the 

efficiency of power transmission lines. In power 

generation by nuclear fusion, envisioned for the 

future, thermonuclear reactions may be confined by 

magnetic fields produced by high-intensity superconducting magnets which will use liquid helium for 

a refrigerant. The nuclear power industry could 

become a limited source of helium from the disintegration of nuclear fuels. 

U.S. GEOL. StJRVEY PROF. PAPER 820 

285 
286 UNITED STATES MINERAL RESOURCES 

The United States, because of its early development of natural-gas resources for fuel, was the first 

country to find large resources of helium, which is 

present in natural gas in trace to small amounts, 

along with other nonflammable gases such as nitrogen, carbon dioxide, and argon. When the natural 

gas is liquefied, the helium remains a gas and is 

recovered as crude helium for further refinement. 

Much of the growth in the use of helium in the 

United States was due to its availability at reasonable prices from the huge natural-gas fields of the 

Texas and Oklahoma Panhandles and southwestern 

Kansas. 

From 1950 to 1968, annual use of helium in the 

United States increased more than tenfold, from 81 

to 842 million cubic feet (fig. 32) (Lipper, 1965, p. 

1~rr-----~------~----~----~----~ 

0 9oor-----------------------------~~ 

0 ~~----------------------------- z 0 1- 700 1----------------------------

::; _,w w 600 1--------------------------- - u. 600 1--------------------------- ~u 

z iii 400 1------------------------ - :l 300 1----------------------- w·u 

~ 200 

_, 100 t---------------1-----

g 50~.--------- 1930 19410 1950 1960 1970 

FIGURE 32.-Helium sales in the United States, 1920-70. 

Adapted from Seibel (1968, fig. 8). 

437 ; 1970, p. 84). In 1968, in addition to the 842 

million cubic feet of helium sold in the United States, 

about 25 million cubic feet was exported, and 3,988 

million cubic feet was pumped into underground 

storage as part of the government's long-range conservation program (Lipper, 1970, p. 84). Helium not 

separated from natural gas when the gas is withdrawn for fuel is lost to the atmosphere. Helium 

pumped underground and stored will assure a future 

supply, possibly for several decades after the natural 

gas has been exhausted. 

In 1968, use of helium outside the United States 

was probably not more than 100-150 million cubic 

feet. Canada supplied about 3 percent of the freeworld supply from one recovery plant in Saskatchewan (Lipper, 1970, p. 79). In 1969, France began 

recovering helium from natural gas supplied by the 

Netherlands, and the U.S.S.R. produced 70 million 

cubic feet of helium. 

The United States has the largest known reserves 

of helium, which, at the present level and rate of 

use, are expected to supply the Nation's needs until 

at least the end of this century. Intensive exploration for and development of natural-gas resources, 

which have begun outside the United States only 

within the last decade or two, doubtless will lead 

to discovery of new helium resources as well. 

GEOLOGIC ENVIRONMENT 

Although helium is of great cosmic abundance, 

second only to hydrogen, it is one of the rarer elements of the earth. Uranium and thorium are radioactive elements that are present in trace amounts 

in all rocks, but they are most abundant in the 

accessory and iron-rich varietal minerals of granitic igneous rocks and in dark shaly marine sedimentary rocks (Clark, 1966, p. 522-540). During 

the radioactive decay sequences in which these 

elements are transformed to lead, each alpha particle given off becomes a stable helium atom (Rutherford and Royds, 1909): 

uzss ______ 8He4+Pbzos 

uzs5 ______ 7He4+PbzoT 

Thzsz _____ 6He4+Pbzos 

Almost all the helium atoms in natural gas are 

of the heavier He4 isotope (atomic weight, 4); the 

lighter He3 isotope (atomic weight, 3) occurs only 

in trace amounts and is thought to originate from 

tritium, the radioactive isotope of hydrogen (Aldrich and Nier, 1948). He3 is about 10 times more 

abundant in helium in the atmosphere than in 

helium in natural gas and is produced by various 

actions of cosmic rays and by auroral precipitation 

of solar wind plasma (Johnson and Axford, 1969, 

p. 2436). Helium atoms, because of their low atomic 

weights, are able to escape from the earth's atmosphere to outer space, and as a result their average 

concentration in the atmosphere is only 4 or 5 

parts per million. 

Studies of the amounts of radiogenic helium in 

minerals, natural gas, and the atmosphere suggest 

that less than half the helium formed in rocks is 

retained in the mineral structures ; the remainder 

is either dissolved in interstitial fluids, entrapped 

with other natural gases as a gaseous phase in rocks, 

or lost to the atmosphere (Hurley, 1954; Damon and 

Kulp, 1958). 

The helium that is distributed in sedimentary 

rocks probably migrates through porous aquifers 

either as a gas or in the connate waters, or it travels 

along fractures. Some of it may have leaked into 

sedimentary rocks from deep crystalline rocks that 

underlie the sedimentary strata. Much of it is probably first dissolved as a trace constituent in connate 

waters from which it was expelled as the water 
HELIUM 287 

moved upward into traps in the sedimentary column. 

Concentrations of helium found by drilling occur 

mixed with other kinds of natural gas, particularly 

the hydrocarbon gases, nitrogen, and carbon dioxide. 

Helium in concentrations higher than that of the 

atmosphere has also been found in the firedamp of 

many coal mines, in gases from mineral springs, in 

volcanic gases, and in gases from glacial till and 

other shallow sources. 

Many natural-gas fields have been tested for 

helium by the U.S. Bureau of Mines (Anderson and 

Hinson, 1951; Boone, 1958; Munnerlyn and Miller, 

1963; Miller and Norrell, 1964a, 1964b, 1965; Moore, 

Miller, and Shrewsbury, 1966; Moore and Shrewsbury, 1966, 1967, 1968; Cardwell and Benton, 1970a, 

1970b, 1971). The analyses indicate that in general 

the concentration of helium in gas fields increases 

with geologic age of the reservoir rocks (Pierce, 

1960). Gas with more than 0.3 percent helium occurs 

mostly in geologically old rocks, generally of Paleozoic age, and less extensively in younger rocks. 

Dobbin ( 1968) briefly described the occurrences 

of helium and other nonflammable natural gases that 

have been found in the United States and Canada, 

and Jodry and Henneman (1968) reported on the 

occurrence, origin, and other aspects of helium. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

All helium recovered in the United States except 

that from gas fields in the Shiprock area of northwestern New Mexico (discontinued in 1969) and 

from the Pinta Dome field near Navajo, Ariz., has 

come from Kansas and the panhandle areas of 

Oklahoma and Texas. Recovery has been from gases 

with helium content of 0.3 percent or more, the minimum content considered economically feasible to 

recover with present technology (Lipper, 1970, p. 

82). 

So long as natural gas continues to be produced 

in quantity, helium-rich gas fields will continue to 

be the main source of helium as a byproduct. According to U.S. Bureau of Mines estimates (Thomasson, 1971, p. 4), at the end of 1970 at least 80 percent of proved helium reserves of 154 billion cubic 

feet in gases containing 0.3 percent or more of 

helium were in the five fields-Hugoton, Panhandle, 

Greenwood, Keyes, and Cliffside (table 56)-that 

now produce most of the helium. The remaining 

proved reserves are in 83 scattered fields in Arizona, 

Colorado, Kansas, Montana, New Mexico, Oklahoma, 

Texas, Utah, Wyoming, and West Virginia. In most 

of these fields the helium is not recovered as the gas 

is withdrawn for fuel. 

The reserves of natural gas of the United States 

and Canada are reported annually by the American 

Gas Association and the Canadian Petroleum Association, respectively. The Potential Gas Agency publishes biennial estimates of the potential gas supply 

that is as yet undiscovered. Using the 1968 figures 

of these organizations for average helium content 

of gases in the various regions, Lipper (1970, p. 

82) estimated total helium resources of the United 

States at about 935 billion cubic feet. He divided 

this figure into 250 billion cubic feet of proved reserves, 155 billion probable, 220 billion possible, and 

310 billion speculative. The average helium content 

on which these figures are based ranges from 0.006 

percent in the gulf coast of Louisiana and Texas, 

where gas reserves and potential are large, to 0.278 

percent in a seven-State area extending from Minnesota and Michigan southward to Missouri, where 

natural-gas reserves and potential are small. 

The extent of helium resources outside North 

America is mostly unknown because the natural gas 

resources are not well known. Significant discoveries have been reported in Canada, Africa, the Middle East, and the U.S.S.R.; however, commercial 

production from these countries is small. On the 

basis of a geologic comparison of the sedimentary 

rocks of the world with those of the United States, 

Hendricks (1965) estimated the possible ultimate 

discoveries of natural-gas resources of the sedimentary basins of land areas and their bordering 

continental shelves. Assuming that these gas resources contain amounts of helium comparable to 

those of the United States, on a volume-for-volume 

basis, an estimate of possible ultimate discoveries 

of helium outside the United States is nearly seven 

times that of the United States, which is estimated 

to have more than 1 trillion cubic feet. The estimate for the United States, however, includes the 

Hugoton, Panhandle, and adjacent gas fields with 

huge gas volume and large helium content. Gas 

fields of comparable size occur elsewhere, but thus 

far none have been reported with comparable helium 

content. Therefore, such an estimate of world helium 

resources, at this stage, is highly optimistic. 

How much of the discoverable resources of natural 

gas and helium might be economically recoverable 

depends on economic, geological, and geographical 

factors, which, for the present, are mostly unknown. 

For example, liquefied natural gas (LNG) is now 

becoming an important export from countries with 

large gas resources. The liquefaction process leaves 

a residual gas enriched in helium. This helium can 

be recovered and sold if there is sufficient market 

demand. 
288 UNITED STATES MINERAL RESOURCES 

SPECULATIVE RESOURCES 

Helium, although now supplied as a byproduct of 

natural-gas fuel, originates from different source 

materials and therefore is not necessarily limited to 

oil and gas areas. Because of the extensive exploration for natural gas for fuel and because helium 

needs are being satisfied from known gas fields, a 

separate search for helium has not been necessary. 

When the few large gas fields that now supply most 

of the country's helium needs are exhausted, helium 

may cease to be a byproduct of natural gas and may 

become a target for direct exploration. If this haPpens, then some of the gas deposits in Paleozoic 

rocks in the Rocky Mountain region that have such 

high content of nitrogen or carbon dioxide as to 

be unsatisfactory for fuel may become economically 

valuable for their helium content. The extent of 

these gas deposits is not known because most developers do not explore beyond the original discovery well. Three such deposits, the Woodside and 

Harley Domes of Utah and the Model Dome of 

Colorado, have been set aside as helium reserves. A 

fourth deposit of this type, the Tip Top field occurs 

in western Wyoming. Only the Pinta Dome field in 

Arizona is producing gas solely for its helium content. The remaining gas in the field is mostly 

nitrogen. 

Regions within which deposits of nonfuel gases 

are known cover at least 20,000 square miles. Lipper 

(1970, p. 83) reported that about 8 percent of the 

known domestic helium reserves (in gases containing more than 0.3 percent helium) is in gases that 

are noncombustible or that have such low heating 

value that they are not salable as fuel. The extent 

of these nonfuel gases is unexplored in large areas. 

Sedimentary rocks derived from the erosion of 

igneous rocks may be sources of helium because of 

the uranium and thorium content of the sediments. 

(See chapter on "Nuclear fuels.") Helium atoms, 

because of their very small size and light weight, 

are able to migrate through very small pore spaces 

and fractures to reach traps where other natural 

gases accumulate. 

The minute amounts of uranium and thorium 

present in rocks and the long time required for their 

radioactive decay indicate that time is an important 

factor in the accumulation of helium deposits. Hydrocarbon gases form comparatively quickly, and 

the greatest volumes have been found in Tertiary 

and Cretaceous rocks. Helium concentrations, on the 

other hand, are largest in the Paleozoic rocks. Some 

of the gas fields of the United States and Canada 

which contain comparatively high percentages of 

helium are listed in table 56. 

The information in table 56 suggests the following potential source rocks and localities, both within 

and outside oil and gas areas, in which future exploration for helium may hold promise. 

1. Black shales and other dark-colored sedimentary 

rocks having comparatively high radioactivity 

and of large extent and volume could generate 

helium that would be trapped in overlying 

rocks, particularly in rocks of Paleozoic age. 

Examples of such possible source rocks are 

the Pennsylvanian Heebner Shale Member of 

the Oread Limestone in shales of the Pennsylvanian Cherokee Group in Kansas and equivalents in Oklahoma and the Devonian and Mississippian Chattanooga Shale and equivalents 

of the midcontinent region. Gamma-ray logs 

of these rocks reveal high radioactivity. 

2. Granitic rocks of basement highs and "granite 

wash" derived from these highs are the probable sources of helium in the Panhandle and 

Otis-Albert gas fields (table 56). Little natural 

gas has been found north and northeast of the 

Central Kansas uplift, but study of the basement rock map of the United States (Bayley 

and Muehlberger, 1968) suggests that this 

would be a good area in which to look for gas 

with appreciable helium content. Although gas 

deposits in this area apparently would not be 

large and the gases from them might have 

little or no value as fuel, they would be found 

at comparatively shallow depths. 

3. Igneous rocks apparently are the source of 

helium in the gas fields of New Mexico and 

Arizona listed in table 56. This apparent 

source suggests that other areas of igneous 

activity, which were very extensive in the 

Western United States, may also have helium 

resources both in natural gas deposits and in 

geothermal areas. In many areas, exploration 

and development of geothermal sources of 

energy are receiving much attention, and in 

some of the areas the fluids and gases may be 

abnormally high in helium. 

Most of the gas fields listed in table 56 are on or 

near the highest parts of uplifts. The largest accumulations of helium in the United States are in 

structurally high areas around the southern, western, and northern margins of the Anadarko basin 

of Oklahoma. Natural-gas fields occur also in structurally lower parts of the basin, but these do not 

contain large amounts of helium. Contours of the 

basement surface on the basement rock map of the 

United States (Bayley and Muehlberger, 1968) de-
HELIUM 289 

TABLE 56.-Some known deposits of helium in the United States and Canada 

Field (except last 

State or province entry, whieh is Age and name of host roek 

Coneen tration (percent) Geologie associations 

a well) He Ns COs Possible source rocks Remarks 

Large reserves 1 (1 trillion cubic feet or more of natural gas) 

Kansas. Oklahoma, Hugoton __________ Permian (Wolfcampian) HerTexas. ington and Krider Limestone 

Members of N olans Limestone, Winfield and Fort Riley 

Limestones and Towanda 

Limestone "Member of Doyle Shale and equivalents. Texas ------------Panhandle ________ Permian (Wolfcampian) equivalent to Herington and Krider 

Limestone Members of Nolana 

Limestone and Winfield and. 

Fort Riley Limestones. 

Pennsylvanian granite wash. 

Kansas ___________ Greenwood --------Pennsylvanian (Virgilian) Topeka Limestone and (Missourian) Lansing Group. 

Oklahoma _________ Keyes ------------Pennsylvanian (Morrowan) 

Keyes sand of subsurface 

usage. 

0.3-1.9 

.1-2.2 

.4- .7 

.3-2.7 

11.1-41.4 

3.4-54.7 

3.9-28.3 

9.6-33.3 

0.1- 1.7 Dark shales of the 

Permian section. 

o-11. 7 Uraniferous asphal- tite and basement 

igneous roeks. 

o- 3.1 Roeks equivalent to Heebner Shale Mbr 

of Oread Ls below 

reservoir beds. · .1-16.8 Dark shales of Mor- rowan age. 

Hugoton embayment 

of the Anadarko 

basin. ' 

On AmarilloWichita uplift. 

Adjacent to the west edge of Huaoton 

field. 

On the Cimarron 

uplift updip from 

Greenwood field. 

Moderate or small reserves 1 (less than 1 trillion cubic feet of natural gas) 

Texas ____________ Cliffside __________ Permian (Wolfcampian) equiva- 1.7-1.8 23.0--25.2 0.4- 0.8 Uraniferous asphal- tite in reservoir 

roeks. 

On the Amarillo 

lent to Herington and Krider uplift. 

Limestone Members of N olans 

Limestone. Kansas ___________ Otis-Albert ________ Cambrian-Ordovician basal 

sand (Cambrian Reagan{T) 

Sandstone). Colorado __________ Model Dome -------Permian Lyons(?) Sandstone __ 

New Mexico _______ Hogback ----------Pennsylvanian Hermosa Formation. 

Rattlesnake -------Mississippian Leadville Lime- stone and Devonian Ouray Limestone. 

Arizona __________ Pinta Dome -------Permian Coconino Sandstone __ 

Utah _____________ Lisbon -----------Mississippian Leadville Limestone. 

1.2-2.3 9.1-31.0 

6.7-8.3 75.7-77.9 

1.4-8.0 16.5-79.9 

7.5-8.0 71.3-76.6 

5.6-9.8 86.3-93.7 

.3-1.1 6.7-17.7 

.1- .4 

13.9-14.8 

.1-20.3 

1.9- 8.8 

o- .9 

21.1-31.3 

Precambrian granite, 

schist and quartzite. 

Precambrian crystalline roeks. 

Deep-seated igneous 

intrusion. 

___ do ------------

On Central Kansas 

uplift. 

On Apishapa uplift. 

Volcanic neeks and 

dikes in the area. Do. 

___ do ------------ Igneous plugs and 

Mississippian and 

Devonian shales 

and Pennsylvanian 

Molas Formation 

and regolith. 

dikes in the area. Gas in Pennsylvanian Hermosa Formation has very little He. 

Harley Dome ______ Jurassic Entrada Sandstone __ 7.0 84.5 1.0 Precambrian rocks _ On Uncompahgre 

uplift. 

30.0 ___ do ------------ On San Rafael 

Swell. 

Woodside Dome ____ Permian Coconino SandstQne __ 1.3 64.0 

Wyoming _________ Tip Top __________ Ordovician Bighorn Dolomite __ .8 6.5 85.5 ___ do ------------ From one well that 

penetrates thrust 

plate. 

.7 ___ do ------------ Fault and fractures on west flank. 

Montana _________ Cabin Creek _______ Cambrian sandstone ____ ,....____ .4 89.8 

SW. Saskatchewan, Wilhelm well 1-9 ___ Cambrian siltstone and mud- 1.o-2.0 96.0 

Canada. stone. ___ do ------------ Gas at 200 ft above 

Precambrian 

erosion surface. 

1 Identified deposita from whieh gas can be extracted profitably with existing technology and under present economic conditions. 

fine broad areas of uplift in much of the country 

where helium might be expected to accumulate. 

The principal submarginal resources of helium are 

in the earth's atmosphere, where the average helium 

content is about 5 ppm (Rankama and. Sahama, 

1950). Even at this low concentration, the total 

quantity in the atmosphere is about 690 trillion 

cubic feet. 

PROBLEMS FOR RESEARCH 

Analyses of the uranium and thorium content of 

igneous and metamorphic rocks underlying the sedimentary rock section would be useful in identifying 

the sources and explaining the distribution of helium 

in natural gases. The basement rock map of the 

United States (Bayley and Muehlberger, 1968) 

shows the locations of wells that have penetrated 

the sedimentary rocks to the basement. 

The many thousands of analyses of natural-gas 

samples made and published by the U.S. Bureau of 

Mines since World War I are a store of data that 

lends itself to a statistical approach in the investigation of the origin, occurrence, and distribution of 

helium. 

In gases unsuitable for fuel because of high nitrogen or carbon dioxide content, evaluation of helium 

resources is a problem because of lack of further 

drilling after the original discovery wells. Such 

gases represent some of the best potential resources, 

and proved reserves of helium possibly could be 

established with further drilling. 

In much natural gas used as fuel, helium is not 

being recovered and thus is wasted. Most helium is 

now recovered in big plants located where a large 

flow of pipeline gas from an extensive producing 

area can be diverted through the plant. If a better 
290 UNITED STATES MINERAL RESOURCES 

and cheaper method could be found for recovering 

helium, then smaller plants could be built in scattered gas fields to recover helium that is now being 

wasted. 

REFERENCES CITED 

Aldrich, L. T., and Nier, A. 0., 1948, The occurrence of He3 

in natural sources of helium: Phys. Rev., v. 74, no. 11, p. 

1590-1594. 

Anderson, C. C., and Hinson, H. H., 19·51, Helium-bearing 

natural gases of the United States: U.S. Bur. Mines 

Bull. 486, 141 p. 

Bayley, R. W., and Muehlberger, W. R., compilers, 1968, 

Basement rock map of the United States (exclusive of 

Alaska and Hawaii): U.S. Geol. Survey, 2 sheets, scale 

1:2,500,000. 

Boone, W. J., Jr., 1958, Helium-bearing natural gases of the 

United States: U.S. Bur. Mines Bull. 576, supp. to Bull. 

486, 117 p. 

Cardwell, L. E., and Benton, L. F., 1970a, Analyses of natural 

gases, 1968: U.S. Bur. Mines Inf. Circ. 8443, 169 p. 

--- 1970b, Analyses of natural gases, 1969: U.S. Bur. 

Mines Inf. Circ. 84 75, 134 p. 

--- 1971, Analyses of natural gases, 1970: U.S. Bur. 

Mines Inf. Circ. 8518, 130 p. 

Clark, S. P., Jr., 1966, Handbook of physical constants: Geol. 

Soc. America Mem. 97, 587 p. 

Damon, P. E., and Kulp, J. L., 1958, Inert gases and the 

evolution of the atmosphere: Geochim. et Cosmochim. 

Acta, v. 13, p. 280-292. 

Dobbin, C. E., 1968, Geology of natural gases rich in helium, 

nitrogen, carbon dioxide, and hydrogen sulfide, in N atural gases of North America: Am. Assoc. Petroleum 

Geologists Mem. 9, p. 1957-1969. 

Hendricks, T. A., 1965, Resources of oil, gas, and natural gas 

liquids in the United States and the world: U.S. Geol. 

Survey Circ. 522, 20 p. 

Hurley, P. M., 1954, The helium age method and the distribution and migration of helium in rocks, in Faul, Henry, 

ed., Nuclear geology-a symposium: New York, John 

Wiley & Sons, p. 301-328. 

Jodry, R. L., and Henneman, A. B., 1968, Helium, in Natural 

gases of North America: Am. Assoc. Petroleum Geologists Mem. 9, p. 1970-1982. 

Johnson, H. E., and Axford, W. 1., 1969, Production and loss 

of He3 in the earth's atmosphere: Jour. Geophys. Research, v. 74, p. 2433-2438. 

Lipper, H. W., 1965, Helium, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 630, p. 429-440. 

--- 1970, Helium, in Mineral facts and problems: U.S. 

Bur. Mines Bull. 650, p. 79-95. 

Miller, R. D., and Norrell, G. P., 1964a, Analyses of natural 

gases of the United States, 1961: U.S. Bur. Mines lnf. 

Circ. 8221, 148 p. 

--- 1964b, Analyses of natural gases of the United 

States, 1962: U.S. Bur. Mines Inf. Circ. 8239, 120 p. 

--- 1965, Analyses of natural gases of the United States, 

1963: U.S. Bur. Mines Inf. Circ. 8241, 102 p. 

Moore, B. J., Miller, R. D., and Shrewsbury, R. D., 1966, 

Analyses of natural gases of the United States, 1964: 

U.S. Bur. Mines Inf. Circ. 8302, 144 p. 

Moore, B. J., and Shrewsbury, R. D., 1966, Analyses of 

natural gases of the United States, 1965: U.S. Bur. 

Mines Inf. Circ. 8316, 181 p. 

--- 1967, Analyses of natural gases, 1966: U.S. Bur. 

Mines Inf. Circ. 8356, 130 p. 

--- 1968, Analyses of natural gases, 1967: U.S. Bur. 

Mines Inf. Circ. 8395, 187 p. 

Munnerlyn, R. D., and Miller, R. D., 1963, Helium-bearing 

natural gases of the United States: U.S. Bur. Mines 

Bull. 617, 2nd supp. to Bull. 486, 93 p. 

Pierce, A. P., 1960, Studies of helium and associated natural 

gases, in Short papers in the geological sciences: U.S. 

Geol. Survey Prof. Paper 400-B, p. B77-B79. 

Rankama, K. K., and Sahama, T. G., 1950, Geochemistry: 

Chicago, Univ. Chicago Pres·s, 912 p. 

Rutherford, E., and Royds, T., 1909, The nature of the alpha 

particle from radioactive substances: Philos. Mag., ser. 

6, v. 17, p. 281-286. 

Seibel, C. W ., 1968, Helium-Child of the sun: Lawrence, 

Kans., Univ. Kansas Press, 138 p. 

--- 1969, Helium from rare to well done, in Helium Symposia proceedings in 1968-A hundred years of helium: 

U.S. Bur. Mines Inf. Circ. 8417, p. 229-241. 

Thomasson, E. M., 1971, Helium, in Minerals yearbook for 

1970 [preprint]: U.S. Bur. Mines, 4 p. 
UNITED STATES MINERAL RESOURCES 

IRON 

By HARRY KLEMIC, HAROLD L. jAMEs, and G. DoNALD EBERLEIN 

CONTENTS 

Abstract of conclusions --------------------------- Introduction ______ . ______________________________ _ 

Exploitation -------------------------------------

Byproducts and coproducts -------------------

Environmental problems ----------------------

Geologic environment ----------------------------

Ore minerals --------------------------------

Classification of deposits ---------------------

Bedded sedimentary deposits --------------

Banded iron-formations ---------------

Ironstones --------------------------- Mi·scellaneous sedimentary deposits ___ _ 

Deposits related directly to igneous activity_ 

Magmatic segregations ---------------

Pyrometasomatic deposits ------------

Deposits formed by hydrothermal solutions __ 

Replacement deposits in nonferruginous 

rocks ----------------------------- Enrichments of preexisting ferruginous 

rocks ----------------------------- Deposits produced by surface or near-surface 

enrichment ----------------------------

Laterites ---------------------------- Enrichments of preexisting low-grade 

ores -------------------------------

Summary of types of deposits -------------

Resources --------------------------------------- Identified reserves and resources --------------

Hypothetical resources -----------------------

Speculative resources ------------------------

Exploration -------------------------------------

Problems for research ---------------------------

Selected references ------------------------------

FIGURES 

33-38. Graphs: 

33. Steel production in the United 

States, 1951-71 ---------------- 34. World production and world trade 

>n iron ore since 1951 ----------

Page 

291 

292 

294 

296 

296 

297 

297 

297 

298 

298 

299 

299 

300 

300 

300 

301 

301 

301 

302 

302 

302 

302 

302 

302 

304 

304 

304 

305 

306 

Page 

292 

293 

33-38. Graphs-Continued: 

35. U.S. iron-ore consumption, production, and imports for consumption 

in the period 1951-71 ----------- 36. Sources and amounts of iron ore imported to the United States, 1961-

71 ---------------------------- 37. Value of United States imports and 

Page 

293 

294 

exports of iron ore, 1951-71 ---- 294 

38. Iron-ore production in the United 

States and in the Lake Superior 

region of the United States, 1875-

1971 -------------------------- 295 

TABLES 

Page 

57. Principal features of the iron-formation facies- 298 

58. Summary description of categories of iron ore_ 3()3 

59. World iron-ore resources -------------------- 303 

60. The identified iron-ore resources of the United 

States ----------------------------------- 304 

ABSTRACT OF CONCLUSIONS 

Iron is the principal metal employed in modern industrial 

civilization and is indispensable to everyday living. Annual 

world production of iron ore is approximately 750 million 

long tons. The United States produces more than 80 million 

tons of iron ore per year, of which about 80 percent is from 

the Lake Superior region. World trade in iron ore is nearly 

300 million tons per year and is highly competitive. The 

United States has sufficient res·erves and potential resources 

of iron ore to meet its needs for many decades but imports 

about one-third of the iron ore it consumes. Most of the imports are from Canada and South America. 

The principal iron-ore minerals are the iron oxides-magnetite, hematite, and goethite. Bedded sedimentary deposits 

of these minerals in Precambrian banded iron-formations 

containing 30 percent or more of iron are the principal 

sources of iron ore. The six major continents contain vast 

known iron-ore resources. Identified world resources of iron 

ore, including reserves, exceed 780,000 million tons. Iron-ore 

reserves in the United States are about 9,000 million tons, 

and total identified U.S. iron-ore resources, including reS·erves, are 100,600 million tons. These are mainly in the 

U.S. GEOL. SURVEY PROF. PAPER 820 

291 
292 UNITED STATES MINERAL RESOURCES 

Lake Superior region, in low-grade ores that require beneficiation and agglomeration to make them usable. 

Research is needed to appraise the economic potential of 

domestic iron-ore deposits, to develop better techniques for 

utilizing low-grade ores, and to minimize environmental 

problems resulting from mining and processing the ores. 

INTRODUCTION 

Iron is the principal metal employed in modern 

industrial civilization. It is an abundant and readily 

extractable gray metal that has a favorable combination of physical characteristics such as hardness, strength, and durability combined with properties that make possible its fabrication into a 

myriad of useful forms. Alloying of iron and other 

elements to form steels, in which one or more of 

the desirable properties of iron are greatly enhanced, has greatly extended the usefulness of the 

metal. In addition to its many applications in metallic form as steel, iron is combined chemically with 

many other elements to produce many useful compounds. 

The history of man in terms of use of materials 

has progressed from the stone age through the 

bronze age through the iron age, and even though 

the present period is sometimes referred to as the 

atomic age, iron in the form of steel still is a basic 

necessity in the technological fabric of nations. 

The industrially developed nations of the world 

could not maintain their present high standards of 

living without the continued production and use of 

large quantities of iron and steel products. Nations 

are ranked in industrial development partly on the 

basis of total production and per capita consumption 

of steel. The higher levels in standard of living 

toward which the peoples of developing nations 

strive involve ever-increasing use of steel. 

Iron and steel have become indispensable in our 

everyday living. They are used in structural components, transportation equipment, tools, containers, 

fasteners, pigments, and many other materials. A 

measure of the sustained use of steel in' our economy 

is indicated by the records of steel production in 

the United States during the past two decades as 

shown in figure 33. 

This graph tells only part of the story, for it does 

not indicate steel imports. Large cumulative quantities of iron and steel products are being used in 

the form of durable items such as bridges, building 

frames, pipelines, railroads, wire, and countless 

other items that perform their functions for decades 

or longer. 

Although other materials, such as wood, aluminum, and plastics, are and may continue to be used 

as substitutes for steel in some items of manufacen 

z 

0 

~ 

~ 115~-----+~----4-----~~----~------4 

0 

I: 

en 

~ 

0 

~ 1o5r--r+-~--~--4-----~r-----~----__, 

Q 

..J 

..J 

~ 

75~~~~~~~~~~~~~~~~~~ 

1951 1955 1959 1963 1967 1971 

FIGURE 33.-Steel production in the United States, 1951-71. 

Data from U.S. Bureau of Mines Minerals Yearbooks 

(1951-70) and Commodity Data Summaries (1972). 

ture, there are no practical substitutes for iron and 

iron alloys-steel-for a broad spectrum of purposes. The development of special varieties of steel, 

however, has reduced the amount of steel needed 

for many purposes. Stronger steel for structural 

purposes, such as in building frames and bridges, 

provides equal or greater strength with less material 

than ordinary steel, and corrosion-resistant steels 

used in place of ordinary steels have extended the 

period of usefulness of other items. The recycling 

of scrap metal has also reduced the amount of primary metal required to meet demand. Consumption 

of iron and steel scrap in the United States in 1971 

was estimated to be more than 80 million short tons 

(U.S. Bur. Mines, 1972). 

World production of iron ore has trebled during 

the past two decades, rising from 250 million long 

tons in 1950 to approximately 750 million tons in 

1971, as shown in figure 34. Also shown in figure 

34 is world trade in iron ore, which has more than 

doubled since 1955. During the same period annual 

domestic production of iron ore in the United States 

has fluctuated between about 60 million tons and 
IRON 293 

(I) 

z 

0 

~ 

C) 

z 

0 

..J 

u. 

0 

(I) 

z 

0 

:::i 

..J 

~ 

800 

700 

600 

500 

.00 

300 I-""" 

200 

100 

0 

1951 

I I I I I I I I I I I I I I I 

r--

L/ 

I 

/,......' l 

World I 

iron ore 

production 11 ,....__,_ / 

/ 

I 

/,L~ 

~/ 

-' 

;'\I J I 

/' 

/ 

1/ ,.-/ 

World trade 

In iron or~ :/ 

,_..,.... ,.., ........ .....,, ~-

I I I I I I I I 1 L 1 I I I I 

1955 1959 1963 1967 1971 

FIGURE 34.-World production and world trade in iron ore 

since 1951. Data from Institute of Geological Sciences 

( 1971) and from U.S. Bureau of Mines Minerals Yearbooks (1951-70) and Commodity Data Summaries (1972). 

118 million tons and in recent years has been between 80 and 90 million tons. This is considerably 

lower than it was two decades ago, despite an increase of nearly 20 percent in domestic consumption. 

A considerable amount of the world trade in iron 

ore has resulted from the investment of American 

capital overseas. This has helped to provide the 

United States with a continuing supply of highgrade, low-cost iron ore, but it has also enabled 

other nations to obtain assured supplies and to 

produce fabricated products that compete effectively 

with American goods, both in the domestic market 

and in foreign markets that formerly were dependent on U.S. sources. 

For many years the United States led the world 

in iron-ore and steel production. However, in 1958, 

the Soviet Union surpassed the United States in 

annual iron-ore production, and in recent years its 

production has been almost double that of the United 

States, (U.S. Bur. Mines Minerals Yearbooks 1958-

70). Similarly, the United States led the world in 

steel production until 1971, when it was surpassed 

by the Soviet Union (Deily, 1972). Japan's steel 

production has risen to a level equal to 80 percent 

of that of the United States. The steel industry in 

the Soviet Union is based wholly upon domestic 

resources. In contrast, that of Japan is almost entirely dependent upon imports of both iron ore and 

fuel, yet Japan is a net exporter of steel products 

to the United States. 

The United States has sufficient reserves and potential resources of iron ore and has the productive 

capacity to meet its needs for iron and steel for 

many decades. However, for economic and other 

reasons, the United States is a net importer of finished steel and iron ores. The domestic consumption, 

production, amounts produced in the Lake Superior 

region of the United States, and imports of iron ore 

for consumption in the United States in the period 

1951-71 are shown in figure 35. 

(I) 

z 

0 

1-

~ so~~~,r~~~~~--_,~-----r----~ 0 

..J 

u. ..,~ ,-, 

0 / ' .,' ' 

~ 60 t-----+--__..__;r-+---;----r--<-/'.._-Production 

from 

..J Lake Superior 

..J region 

~ _.-- •• 1 -- , .. ' ... ,· ...... ' 40t------~------+------4~,~--~------~ 

,'"-Imports # • ·ll.. ,-- ,,"· · .... ,·· •, ,' 

•' ·~ ',1 

20~----:~------+-----~------~----~ 

...... 

o~~~-L-L~~~L-~~~~~~~~~ 

1951 1955 1959 1963 1967 1971 

FIGURE 35.-U.S. iron-ore consumption, production, and imports for consumption in the period 1951-71. Data from 

U.S. Bureau of Mines Minerals Yearbooks (1951-70) and 

Commodity Data Summaries (1972) and Wimpfen (1971). 
294 UNITED STATES MINERAL RESOURCES 

In recent years approximately one-third of the 

iron ore consumed in the United States has been 

imported (Wimpfen, 1971). About 50 percent has 

come from Canada, about 40 percent from South 

America, 5 percent from Africa, and the remainder 

from Australia, western Europe (mostly from Sweden), Asia, and Oceania. No iron ore is imported 

from the eastern European countries or from eastern continental Asia. The sources and quantities of 

imports of iron ore to the United States during the 

past decade are indicated in figure 36. 

en 

z 

0 

.... 

0 

z 

0 

..J 

u.. 

0 

en 

z 

0 

..J 

..J 

j 

50 I I I I I I 

45 

Total U.S. imports-............. ~ 

( 1\ V\ I 

~ 

40 

35 

I North America 

(almost entirely Canada) 

30 

25 

/ 

v...-, II "" .......... -....... 1", 

I ",;' I 

20 

~-, // -.... 

" venezuela - 15 

South America 

10 

Peru r--

Chile ~ 

Brazil :-:------

/--1-------- Africa ........... __ 

A (mostly Liberia) . .,..!, Europe (mostly Australia 

5 

t--r.- Norway and Sweden)~---- -f-_1-.rr.:=- ~ --- -...J:-__.,____l -k--t. -~L------- 1 0 

1961 1963 1965 1967 1969 1971 

FIGURE 36.-Sources and amounts of iron ore imported to 

the United States, 1961-71. Data from Institute of Geological Sciences (1971) and from U.S. Bureau of Mines Minerals Yearbooks (1961-70) and Commodity Data Summaries (1972). 

Canada, Venezuela, Liberia, Chile, Peru, Sweden, 

and more recently Australia, have been substantial 

suppliers of iron ore to the United States. The 

value of iron ore imported to the United States has 

exceeded 400 million dollars per year in recent years, 

while the value of iron ore exported from the United 

States has been less than 70 million dollars per year, 

as shown in figure 37. 

~r-,-,-,-,--.-.-.-.-.-r-r-r-r~~~~~ 

360r-----~-------+-------H------~----~ 

en 

a: 300 ~ 

..J 

..J 

0 

0 

u.. 

0 240 

en 

z 

0 

..J 

..J 

j 180 

Exports 

~ -...J \ 

o~~~~~~~~-L~~~~~~~~~~ 

1951 1955 1959 1963 1967 1971 

FIGURE 37.-Value of United States imports and exports of 

iron ore, 1951-71. Data from U.S. Bureau of Mines Minerals Yearbooks (1951-70) and Commodity Data Summaries (1972). 

EXPLOITATION 

Iron ore has been produced in 45 of the 50 States 

of the United States (Dutton, 1955; United Nations, 

1970; see also data in U.S. Bur. Mines Minerals 

Yearbooks 1932-70 and U.S. Geol. Survey and U.S. 

Bur. Mines Mineral Resources of the United States 

1882-1931). Only Kansas, Louisiana, Nebraska, 

North Dakota, and Hawaii have no record of ironore production. 
IRON 295 

Iron furnaces were built in Virginia and Massachusetts in the 1600's, and before the Civil War 

furnaces using local iron ores were producing in 

most of the Eastern States, as reported in early volumes of Mineral Resources of the United States. 

Quantitative data on production for the early period 

of American history are scarce, but in 1854, production of iron was about 657,000 tons. This probably 

required approximately 1.5 million tons of ore. 

Iron-ore production increased slowly prior to the 

Civil War, but between 1870 and 1917, it more than 

doubled in each 15-year period. Annual production 

has reflected trends in the business cycle and periods of high wartime demand, as indicated in 

figure 38. 

The rate of growth of domestic iron-ore production has been greatly changed by the increase in 

imports, as shown in figure 35. 

The significance of iron-ore production in the Lake 

Superior region is evident in the record of ore shipments. Production from the Marquette iron Range 

began in 1854, from the Menominee Range in 1877, 

and from the Gogebic Range in 1884; by 1890 the 

120 

110 

100 

90 

~ 80 

0 

~ 

~ 70 

0 

..J 

u..60 

0 

en 

! 

i 

A I 

f\ 

.. J; 

z T 

I ' J: \ '• -I 

~ 

Lake Superior mines furnished 56 percent of the 

total output. The first shipments from the Mesabi 

Range were in 1893, and with a few years the Mesabi Range attained a position of dominance that 

has been maintained to the present. By 1907, 80 

percent of the national production was from the 

Lake Superior region. Total production through 

1970 from this region exceeded 4,000 million tons, 

two-thirds of which was from the Mesabi Range. 

Iron-ore shipments in the United States since 1910 

have exceeded 4,350 million tons, of which about 81 

percent has been produced and shipped from the 

Lake Superior region (Aim and Trethewey, 1971; 

Am. Iron Ore Assoc., 1970; see also data in U.S. 

Bur. Mines Minerals Yearbooks 1932-70 and U.S. 

Geol. Survey and U.S. Bur. Mines Mineral Resources 

of the United States 1910-31). The Southeastern 

States produced about 8 percent, the Western States 

about 6 percent, the Northeastern States about 4 

percent, and the rest of the United States about 1 

percent. 

Prior to about 1950, most of the material mined 

and shipped from the Lake Superior region was of 

A I 

1\ u ~I l\ A~ ' v 

I 

:, I 

··, vI\,, ( I \ I' It ~v~~ 

! , j r \,•I 

I 

't'~l ': u I ~ j I ~,I ~~ I "I• 

A},\ I' ' . 

I 'I·~ II ~\ / 

/ I I I I 

II ,, I I I II / , J f I ., I •-' I 

~v ,, II I I I I 

1\ /\ I I II I I 1 ~/I 

I I \J I II I I I ' . z 

050 

~ V,\f,, ,V/ ~~,· I I 

•J1{ I I I \ i I I I '1 ~ I I' I ! I I I , ~v~ ': ~I ·~/ I I 

I I ' I I ±: f ld ' I I I 

I I 

~ I •' I ) ,, Total U.S. 1 production/ 1 

f I ~ 

I 

/ 

J/ Lake f/ "\.) 1 Superior 

," region 

~ v---.. I _, , ....... ,,. ~ 

...... "'"- , ---

..J 

2 40 

30 

20 

10 

0 

1875 1880 1885 1890 1895 1900 1905 1910 1915 1920 1925 1930 1935 1940 1945 1950 1955 1960 1965 19701971 

FIGURE 38.-Iron-ore production in the United States and in the Lake Superior region of the United States, 1875-1971. 

Data from U.S. Geological Surv-ey and U.S. Bureau of Mines Mineral Resources of the United States (1882-1931) and 

from U.S. Bureau of Mines Minerals Yearbooks (1932-70) and Commodity Data Summaries (1972). 
296 UNITED STATES MINERAL RESOURCES 

direct-shipping ores or of ores that had been beneficiated by simple washing techniques (Dutton, 

1955). As a result of continued large-scale production, resources of direct-shipping ore were rapidly 

becoming depleted, and efforts were made to obtain 

alternate sources of ore. Imports were increased 

rapidly during the 1950's. Since 1964 imports have 

exceeded 40 million tons per year, as shown in 

figure 36. 

During the 1950's, however, the Lake Superior 

iron mining industry underwent a technological 

revolution with the development of processes for 

large-scale treatment of low-grade material to produce high-grade agglomerates. The agglomerates, 

principally in the form of pellets, are ideal furnace 

feed. The net result has been displacement of directshipping ore by pelletized concentrates produced 

from low-grade ores. Jet-drilling, autogenous oregrinding, magnetic concentration and flotation, and 

pelletizing now are common practice not only for 

low-grade ores but also for those of higher grade. 

The successful research that led to these developments has vastly increased the reserves of minable 

ore not only in the Lake Superior region but also 

throughout the world. 

BYPRODUCTS AND COPRODUCTS 

The banded iron-formations that make up the 

bulk of the iron resources of the world generally do 

not contain significant amounts of byproduct or coproduct other than manganiferous iron ore. 

Other types of iron deposits, however-particularly those related to igneous activity, some deposits 

related to surface and near-surface enrichment, and 

iron-rich placer deposits-commonly contain recoverable or potentially recoverable materials in addition to iron (Dutton, 1955; United Nations, 1970). 

These are gold, silver, copper, cobalt, titanium, tin, 

manganese, chromium, nickel, vanadium, zinc, sulfur, phosphates, rare earths, aluminum, fluorine, 

beryllium, uranium, thorium, and zirconium. In the 

United States, gold, silver, copper, and cobalt are 

recovered from iron ore in Pennsylvania and titanium from deposits in New York; phosphate minerals are potentially recoverable from iron deposits 

in New York and Missouri. Some of these phosphate 

minerals also contain rare earths, uranium, and 

thorium. Titanium is recovered from iron sands in 

Japan, vanadium from iron deposits in -South Africa 

and Peru, and phosphates from deposits in Sweden. 

Tin may be recoverable from iron deposits in Malaysia and nickel, chromium, and aluminum from 

lateritic deposits in several tropical areas. Iron has 

been recovered from nickel ores in Canada and from 

sulfide-rich copper deposits in the Western United 

States. Zircon and associated titanium minerals have 

been recovered from iron-rich sands in Italy. 

In addition to the metal and mineral byproducts 

and coproducts, the waste rock from mining and the 

tailings from ore beneficiation plants are valuable 

resources in some areas such as the Northeastern 

United States. They are used for road metal and for 

fill for construction purposes, and sand- and gravelsized materials from some of these plants have been 

used in making concrete. 

ENVIRONMENTAL PROBLEMS 

The mining and processing of iron, as with other 

metals required to sustain the economy, have undesirable environmental consequences. Those specifically associated with iron are chiefly factors of 

scale : the mines and recovery plants are huge, 

transportation systems are complex, and furnaces 

and steel mills are major industries in themselves. 

Most of the iron ore produced in the United States 

is extracted from open pits, which in the Mesabi 

district are a mile or more wide, many miles long, 

and several hundred feet deep. The tonnage of 

waste material produced in stripping operations 

commonly is two to three times that of the ore 

mined, and this mass must be disposed of. In the 

past, most of the waste has simply been accumulated 

in great unsightly piles adjacent to the mining operation. This spoil could, however, either be returned 

to mined-out areas or distributed in a beneficial 

manner. Part of the waste may be processed as 

low-grade ore. 

The pits themselves, after mining ceases, have 

the potential for environmental enhancement, since 

most will fill with water and thus become manmade 

lakes. To make these lakes usable for recreational 

and other purposes, however, the bounding walls 

would have to be reduced to a stabilized configuration to protect against hazardous slumping and to 

provide access. The cost would be substantial, and 

careful planning before and during the mining 

operation would be necessary. The added cost would 

place the domestic industry at a competitive disadvantage with less restrained foreign producers, 

but at the national level it would yield lasting benefits to the present and future population of the 

eountry. 

Perhaps a more difficult problem is posed by disposal of the large amounts (more than 50 million 

tons per year) of finely ground waste (fines) produced in the United States in the extraction process 

whereby taconite containing about 30 percent iron 

is concentrated to a product containing 60 percent 
IRON 297 

or more iron. The traditional method is to deposit 

this waste, which initially is in the form of a slurry, 

in settling ponds. The waste itself is not chemically 

reactive-it consists mainly of quartz-but because 

of the fine grain size the settled material effectively 

chokes off organic life. No satisfactory alternative 

for large-scale disposal or utilization of this material 

has yet been devised, and the problem deserves intensive research. 

GEOLOGIC ENVIRONMENT 

Iron is one of the more abundant and ubiquitous 

elements in the earth's crust. Common sedimentary 

rocks contain 2-3 percent iron and basalt and gabbro contain about 8.5 percent; the average content 

of crustal rocks is about 5 percent. Rock mined economically ranges in iron content from about 20 

percent to 69 percent, so the concentration factor 

("concentration clarke") relating crustal abundance 

to minable ore is very low-4-14, as compared with 

factors of 102 or 103 for elements such as manganese, 

chromium, copper, and lead (James, 1966). 

The ability of iron to exist in more than one 

valence state, coupled with its general abundance, 

accounts for the presence of iron minerals in deposits of widely different character and associations. 

The geochemical cycle of iron is complex, but it is 

reasonably well known and contains may points at 

which the element can be trapped to form significant 

concentrations. Economically minable deposits are 

formed by magmatic segregation, hydrothermal 

replacement, direct sedimentation and diagenesis, 

and weathering processes at the surface and in the 

subsurface. 

ORE MINERALS 

Nearly 300 minerals contain iron as an essential 

component, but only about six of them can be classed 

as ore minerals, and of these only the oxidesmagnetite, hematite, and goethite (limonite) -are 

of major importance (Gross, 1965; James, 1966; 

United Nations, 1970). Siderite (the iron carbonate), pyrite and pyrrhotite (iron sulfides), and 

chamosite (an iron silicate) are mined locally, but 

deposits of these minerals are at present of minor 

economic significance. Ilmenite, the iron-titanium 

oxide, is a potential source of byproduct iron, but 

it cannot be classed at this time as an iron-ore 

mineral. 

The ore minerals are listed as follows : 

Magnetite (Fes04) .-Black, strongly magnetic. 

Iron content, 72.4 percent. Principal ore mineral of 

those parts of Precambrian banded iron-formations 

mined as taconite; associated with quartz and generally minor amounts of iron carbonate and iron 

silicates. Principal ore mineral of replacement deposits, in which associated minerals vary with type 

of deposit but commonly include specularite, pyrite, 

and pyrrhotite, and silicates such as garnet and 

actinolite. 

Hematite (Fe20s) .-Black (if coarse) to red (if 

fine) , depending upon grain size; virtually nonmagnetic. Iron content, 70 percent. As specularite, a 

common and locally important ore mineral with 

magnetite in taconite and in replacement deposits. 

As red iron oxide, a principal constituent of secondary (direct-shipping and semi taconite) deposits 

in Precambrian iron-formations, associated with 

goethite (limonite), and in younger sedimentary 

oolitic ironstones, associated with goethite, calcite, 

and clastic quartz. 

Goethite (Fe20s · H20) .-Yellow to dark brown, 

commonly soft and earthy, may be hard and brittle; 

nonmagnetic. Iron content, about 60 percent. 

Limonite is the general term applied to earthy or 

impure goethite. Principal constituent of ores originating by surface or near-surface weathering processes, as in laterites; associated minerals mainly 

hematite and clay minerals. 

Siderite (FeCOs) .-Gray, but exposed material 

quickly acquires tan or reddish color owing to surface oxidation ; nonmagnetic. Iron content of pure 

mineral is 48 percent, but in most siderite the iron 

is replaced by significant amounts of manganese, 

calcium, or magnesium. A major constituent of Precambrian iron-formations and of some younger 

ironstones, but in North America mined as an iron 

ore only in the Michipicoten district of Ontario, 

where it is associated with pyrite. 

Pyrite (FeS2) and pyrrhotite (Fe1-a1S).-Yellow, 

with metallic luster; pyrrhotite is weakly magnetic. 

Pyrite is a principal mineral in the relatively scarce 

sulfide facies of Precambrian iron-formations and 

younger ironstones; mined as an iron ore in North 

America only in the Michipicoten district of Ontario (see above). Surface oxidation of pyrite and 

pyrrhotite bodies gives rise to deposits of iron oxides that have been mined locally. 

Chamosite ( (Mg,Fe,Al) s (Si,Al) 4014 (OH) s). -

Greenish, fine-grained, chloritelike; nonmagnetic. 

Major constituent of post-Precambrian oolitic ironstones; locally mined as ore in Europe, associated 

with siderite and goethite. 

CLASSIFICATION OF DEPOSITS 

The ores of iron fall into four main categories, 

based on mode of origin (James, 1966). The genetic 

classification outlined below is basically geologic 
298 UNITED STATES MINERAL RESOURCES 

rather than economic, but it does, however, provide 

a practical means of grouping characteristics such 

as mineralogy, tonnage-grade factor, form, and projection in depth, that are of prime importance to 

assessment of resource potential. The major categories, together with the more significant subdivisions, are listed as follows and are discussed in 

more detail in succeeding paragraphs. 

I. Bedded sedimentary deposits : 

A. Banded iron-formations, almost exclusively 

Precambrian. 

B. Ironstones, mainly post-Precambrian. 

C. Miscellaneous sedimentary deposits, including "black band" siderite, bog iron, 

and clastic accumulations. 

II. Deposits related directly to igneous activity: 

A. Magmatic segregations. 

B. Pyrometasomatic deposits. 

III. Deposits formed by hydrothermal solutions : 

A. Replacement deposits in nonferruginous 

rocks. 

B. Enrichments of preexisting ferruginous 

rocks. 

IV. Deposits produced by surface or near-surface 

enrichment: 

A. Laterites. 

B. Enrichments of low-grade ores. 

BEDDED SEDIMENTARY DEPOSITS (I) 

The principal concentrations of iron in the earth's 

crust are products of chemical sedimentation, which 

have been modified by wave and current action, by 

chemical and mineralogic changes that take place 

below the depositional interface (diagenesis) , and 

by mineralogic changes induced by heat and pressure in burial environments. 

BANDED IRON-FORMATIONS (I-A} 

Banded iron-formations occur as sedimentary 

units in Precambrian rocks throughout the world. 

They constitute the greatest single source of iron 

now being mined and contain the largest potential 

resources. The rock has been defined as follows: 

"a chemical sediment, typically thin bedded or laminated, containing 15 percent or more iron of sedimentary origin, commonly but not necessarily containing layers of chert." In some iron-formations 

the iron is in the form of carbonate ( siderite, with 

an appreciable content of manganese, magnesium, 

and calcium) or silicate (greenalite, minnesotaite, 

stilpnomelane), and in rare occurrences it is in the 

form of sulfide (pyrite). The most distinctiye and 

economically most significant rock type, however, 

consists of iron oxides (magnetite or hematite) and 

chert (or its recrystallized equivalent) in alternating thin layers, with an iron content commonly in 

the range of 25 to 40 percent. Each of the sedimentary facies-oxide, carbonate, silicate, sulfidehas the distinctive aspects of mineralogy, total iron 

content, and structure that are summarized in 

table 57. 

TABLE 57.-Principalfeatures of the iron-formatimfacies (modified from James, 1966) 

Silicate Oxide 

Sulfide Carbonate 

Nongranular Granular Magnetite-banded Hematite-banded 

Lithology --- Laminated to thin- Thin-bedded to Laminated light- Massive dark- Dark, thin-bedded Thin-bedded to 

banded black py- laminated rock green to greenish- green rock with to irregularly irregularly bedded 

ritie carbonaceous consisting of black rock. Chert irregular bedding bedded rock eon- rock consisting of 

slate. Chert rare. alternating layers rare. marked by layers sisting of layers of alternate layers of 

of gray chert and of chert and magnetite alter- crystalline hematite 

carbonate. mapetite. nating with layers and gray chert or of dark chert, reddish jasper. areen silicates, or silicates plus 

carbonate. 

Principal iron Pyrite ----------- Iron-rich carbonate _ Iron silicate Iron silicate Magnetite --------- Crystalline 

mineral. ( minnesotaite, (greenalite, hematite. 

stilpnomelane, minnesotaite, 

chlorite). stllpnomelane). 

Subsidiary Carbonate Pyrite, stilpnome- Carbonate, Magnetite, Gl'eeJlalite, Magnetite iron min- ( Greenalite) . lane, minnesotaite, magnetite. carbonate, minnesotaite, (carbonate). 

erals (rarer magnetite aematite. stllpnomelane, minerals in (hematite). carbonate, 

paren- hematite 

thesis). (pyrite). 

Typical range 

in content 15-25 2o-ao 2o-30 2o-ao 26-35 ao-40 

of metallic 

iron, in 

percent. 

Distinctive Graphitic --------- Stylolites common -- Laminated Granule-bearing ---- Strongly magnetic - Locally oolitic. 

features. structure. 

Environment Strongly reducing, Reducing --------- Variable, but Mildly oxidizing Mildly oxidizing to Strongly oxidizina. 

of origin. anaerobic. typically mildly to mildly reducing. mildly reducing. 

reducing. 
IRON 299 

Many iron-formations have undergone conditions 

of higher temperature and pressure (metamorphism) which have changed preexisting minerals to 

silicates such as grunerite, pyroxene, and olivine 

and which have resulted in coarsening of grain size 

of quartz, magnetite, and hematite. Oxide facies of 

iron-formation that has been so metamorphosed is 

the most suitable as a low-grade ore (taconite) because the iron oxides are more readily concentrated 

by milling. In contrast, the more weakly metamorphosed carbonate and silicate facies, generally not 

usable at the present time in the United States as 

low-grade ore, are more susceptible to alteration by 

surface and ground waters and commonly give rise 

to ore bodies of soft limonite and hematite (directshipping ores) and to deposits classed in the Lake 

Superior region as "wash ores" or "semi-taconite" 

(Dutton, 1955; United Nations, 1970). 

Chemically, the iron-formations are marked by 

extraordinarily low contents of alumina, sodium, 

potassium, and minor elements. Iron and silica generally dominate, but in some districts, notably the 

Cuyuna district of Minnesota, the manganese content is several percent (Dutton, 1955). 

The banded iron-formations commonly are exposed as steeply to moderately dipping beds in belts 

a few miles to several tens of miles long (Gross, 

1965). A few, such as those in Labrador, are in 

belts several hundreds of miles long. Thicknesses 

commonly are on the order of a few hundred feet 

but range from less than 25 to more than 2,000 feet. 

With some prominent exceptions, notably the Mesabi Range of Minnesota and the Hamersley Range 

of Australia, the iron-formations are tightly, and 

often very complexly, folded. Dips generally are 60° 

or more, a fact of considerable importance to economic assessment. Aggregate tonnages of rock containing 20 percent or more iron are enormous, but 

factors such as location, mineralogy, and structure 

are of profound importance in assessment of actual 

potential. 

Prominent examples of this class of iron deposits 

are the iron ranges of the Lake Superior region of 

the United States-Mesabi, Cuyuna, Gogebic, Marquette, and Menominee; the Michipicoten, Lake 

Albanel-Mistassini, and Labrador districts of 

Canada ; the Quadrilatero Ferrifero of Brazil ; the 

Krivoi Rog and Kursk districts of Russia; and the 

Hamersley Range of Australia (James, 1966; United 

Nations, 1970). 

IRONSTONES (I·B) 

The strata classed as ironstones contain iron in 

grades comparable to or greater than that of Precambrian banded iron-formations-that is, in the 

general range of 20-40 percent--but they differ 

profoundly in many ways, notably in much younger 

age, in the absence of interlayered chert, and in the 

much smaller dimensions (James, 1966) . 

Considerable variety exists within the class, but 

the most common type is thick-bedded rock consisting of small pellets ( ooliths) of limonite, hematite, or chamosite in a matrix of chamosite, siderite, 

or calcite. Grains of clastic quartz and fossil fragments form the cores of many ooliths and are dispersed in the matrix, and the acceptability as an 

ore depends in part on the relative amounts of 

quartz and calcite. Rock containing abundant calcite 

may be self-fluxing, whereas content of abundant 

quartz is deleterious. Phosphate minerals are also 

common contaminants in ironstones. As with banded 

iron-formations, ironstones may be divided into oxide, carbonate, silicate, and sulfide facies, depending 

upon the dominant iron mineral. The rocks originate 

as chemical sediments, but the oolite types--economically the most important--have been profoundly modified by wave action and transport so 

that chemically heterogeneous assemblages of 

limonite (or hematite), chamosite, and siderite are 

common. 

Thicknesses of ironstone formations range from 

at least a foot to several tens of feet. Beds tend to 

be lenticular on a scale of a few thousand feet or a 

few miles, but a belt of deposits having approximately the same age may continue for hundreds of 

miles, as for example those in the Clinton Formation of Silurian age that extend from Alabama to 

New York. In general, thicknesses and lateral extents of ironstones are an order of magnitude less 

than those of banded iron-formations, consequently 

potential tonnages probably are less than 1 percent 

of those contained in the older rocks. 

Because of the prime importance of location, ease 

of beneficiation, and local near-surface enrichment, 

many ironstones have been and are being mined. 

The relative importance of these ores in world production, however, is decreasing. The most important 

region of economic extraction was in northern 

Europe-England, France, Luxembourg, and Germany-where the ironstones of Jurassic age have 

been mined for generations. In North America, the 

most important examples have been the Clinton ores 

of Silurian age in the Birmingham district of Alabama and the W abana ores of Ordovician age in 

Newfoundland (United Nations, 1970). 

MISCELLANEOUS SEDIMENTARY DEPOSITS (I·C) 

Iron has been extracted in the past from a variety 
300 UNITED ST'A TES MINERAL RESOURCES 

of sedimentary rocks other than banded ironformation and ironstone, but these are of little 

present or potential importance. Bog-iron deposits, 

which are accumulations of iron oxides in swampy 

areas or shallow lakes in northern latitudes, have 

been mined in northern Europe and North America 

(James, 1966). 

"Black band" and "clay band" are deposits of 

siderite that occur as thin layers in coal sequences; 

they once were mined extensively in Great Britain. 

Possibly of greater potential significance are clastic 

accumulations of iron minerals (black sands) such 

as occur in southeastern Alaska and New Zealand ; 

these, however, typically contain abundant ilmenite, 

the iron-titanium oxide, and recovery of iron depends upon the economic feasibility of separation 

and recovery of titanium (United Nations. 1970). 

DEPOSITS RELATED DIRECTLY TO IGNEOUS ACTIVITY (II) 

Iron may be concentrated during crystallization 

of igneous rocks in several ways: (1) as a constituent of early formed minerals such as ilmenite that 

may have settled to the base of the magma chamber, (2) as a late-stage magmatic fraction from 

which iron minerals are precipitated after most 

other constituents have crystallized, and (3) as a 

constituent of fluids (gases and aqueous liquids) 

that escape the magma chamber and deposit iron 

minerals in surrounding rocks (James, 1966). The 

first two constitute category II-A; the third (and 

quantitatively probably most important), category 

11-B. 

MAGMATIC SEGREGATIONS (II-A) 

Magmatic segregations of iron fall into two main 

groups : titaniferous and nontitaniferous. 

The titaniferous ores occur as layers and segregations in gabbro, pyroxenite, and anorthosite. The 

deposits in gabbro and pyroxenite commonly are 

crudely layered lenses of magnetite, ilmenite, and 

silicates such as pyroxene. Content of iron generally is about 20 percent, and that of titanium is 

2 percent or more. Many of these deposits, particularly in Alaska, are of considerable thickness and 

extent, but as with the titaniferous black sands referred to previously, their significance as potential 

sources of iron hinges largely on the feasibility of 

separating iron from titanium economically (United 

Nations, 1970) . Most of the ores occurring in anorthosite are of quite different character. These are 

irregular masses and dikes of coarse-grained ilmenite, magnetite or specularite, feldspar, ulvospinel 

(Fe2Ti04), and rutile (Ti02), often in complex 

intergrowths on a microscopic scale. Deposits are 

abundant in the belt of Precambrian anorthosite 

bodies that extends from upper New York State 

northward into Quebec and Labrador. The iron content of some deposits, such as the one at Allard 

Lake, Quebec, is about 40 percent, but the ore is 

exploited primarily for titanium and iron recovered 

as a byproduct. 

Nontitaniferous magmatic segregations are not 

abundant in North America, but they form the 

great ore bodies of the Kiruna, Rektor, and other 

districts of northern and central Sweden (United 

Nations, 1970). These Swedish deposits occur within 

syenite porphyry and quartz porphyry as massive 

sheets or irregular veinlike masses composed of 

magnetite and minor amounts of hematite. The main 

body at Kiruna is a steeply dipping sheet several 

hundred feet thick and at least 14,000 feet long. The 

iron content is 60-65 percent. Phosphorus content 

is high, commonly 1-2 percent, and this may have 

been a significant factor in the evident ability of a 

concentrated iron fluid to separate, remain molten, 

and ultimately intrude solidified parts of the parent 

igneous body. 

The important ore bodies of Precambrian age in 

Missouri, such as those at Pea Ridge and Pilot Knob, 

are similar in occurrence and association to the 

Kiruna deposit and are so classed in this report. 

Some marginal parts of these ore bodies, however, 

show indications of hydrothermal activity, and there 

may well be all gradations between a purely magmatic concentration and a high-temperature hydrothermal transfer of iron to form replacement ore 

deposits in peripheral rocks. 

PYROMETASOMATIC DEPOSITS (II-B) 

This category encompasses a rather wide variety 

of deposits that have· igneous (presumably genetic) 

associations ranging from diabase to syenite. 

The typical pyrometasomatic or contact metamorphic deposits are replacements, most commonly 

in limestone, at or near a contact with the parent 

igneous rock. An important group in the United 

States is related to Triassic diabase sills that occur 

in a belt that extends intermittently from Connecticut to South Carolina. The known deposits of iron 

ore, however, are restricted to a 75-mile segment 

that centers at Cornwall, Pa. (Carr and others, 

1967). The deposit at Cornwall, which has been 

mined since 1792, is the type example; here the ore 

occurs in two separate bodies replacing limestone 

of Cambrian age (Dutton, 1955). The ore bodies are 

tabular masses about 100 feet thick and half a mile 

to a mile long, and they extend downdip for as much 

as 2,400 feet. The ore contains about 40 percent iron 
IRON 301 

as magnetite, which is associated with sulfides, 

among which pyrite and chalcopyrite are dominant. 

Actinolite and chlorite are the chief gangue minerals. Copper, silver, gold, and cobalt are recovered 

as byproducts (United Nations, 1970). Elsewhere in 

Pennsylvania, similar ore deposits are found in Precambrian marble and in Triassic limestone conglomerate in each case in close proximity to a sheet of 

diabase. The relationship between diabase, limestone, and ore is incontrovertible, but the precise 

origin of the ore-forming fluids is less evident. 

Pyrometasomatic ore bodies related to quartz 

monzonite are fairly common in the Rocky Mountain region of the United States, and some are of 

large dimensions (Carr and others, 1967; United 

Nations, 1970). The mined deposits of the Iron 

Springs district, Utah, occur at or near the contacts 

of laccolithic bodies of quartz monzonite of Tertiary 

age with limestone of Jurassic age. Dimensions are 

on the order of a thousand feet in strike and dip 

length, with thicknesses of as much as 230 feet. The 

iron content is about 50 percent, and the iron is in 

the form of magnetite. Gangue minerals include 

phlogopite and fine-grained calc-silicates, and significant amounts of apatite; phosphorus content is 

as much as 5 percent in places and averages 0.2 

percent. The ore was deposited by fluids emanating 

from the intrusive quartz monzonite. 

DEPOSITS FORMED BY HYDROTHERMAL SOLUTIONS (III) 

Many iron deposits are hydrothermal in originthat is, they were deposited by heated aqueous fluids. 

These fluids may have originated from relatively 

distant bodies of crystallizing magma, or they may 

simply represent waters of any origin that have 

circulated at depth to acquire the necessary heat. 

Similarly, the iron may be of primary origin from 

a magma, or it may have been leached from rocks 

being traversed by the solutions. The deposits of 

hydrothermal origin can be divided into two general groups: those in which the iron has been derived from a distant source, then transported and 

deposited in virtually nonferruginous rocks ; and 

those in which the ores represent a further concentration of iron in rocks that are themselves relatively iron rich. 

REPLACEMENT DEPOSITS IN NONFERRUGINOUS ROCKS (111-A) 

Deposits of small to medium size are common in 

areas of relatively recent magmatic activity, as in 

the Western United States, and a genetic relation 

generally is inferred. Most occur as pods, veins, and 

lenses in volcanic rocks, brecciated igneous rocks, 

and limestone (Carr and others, 1967; Dutton, 1955 ; 

United Nations, 1970). Magnetite and hematite are 

the typical ore minerals and occur mainly in association with pyrite and chalcopyrite, but some veins 

and bedding replacements consist wholly or largely 

of siderite. The largest production in the Western 

States-several million tons-from deposits of this 

category has been from the Buena Vista Hills district of Nevada. Here the ore occurs as irregular 

bodies of magnetite and hematite in metavolcanic 

rocks and diorite of probable Jurassic age. The host 

rocks are extensively altered to scapolite, a distinctly 

unusual feature in ore deposits of this type. Individual ore bodies in the Nevada deposits have maximum strike and dip lengths of several hundred feet, 

and widths rarely exceed 100 feet. 

An unusual group of deposits assigned to this 

category is that of Precambrian age in New York 

and New Jersey (Carr and others, 1967). The ore 

bodies are tabular to pencillike masses of magnetite 

and hematite oriented along the dominant linear 

structure of the enclosing gneiss. The largest known 

ore body is at the Benson mine, New York, on the 

overturned flank and keel of a syncline; it has been 

mined for a strike length of 2¥2 miles and has been 

traced magnetically for an additional 5 miles. Mining widths are several hundred feet. Ores of this 

group of deposits commonly are relatively lo1V 

grade; the ore at the Benson mine averages about 

23 percent iron, and contacts with the country rock 

are gradational. Gangue minerals are dominantly 

those of the enclosing gneiss: quartz, potassium 

feldspar, sillimanite, garnet, and ferromagnesian 

minerals. Some of the ore contains appreciable 

amounts of titanium minerals. Structurally, these 

deposits have features in common with those of 

category III-B (see below), but no convincing evidence for an original bed of iron-rich rock has been 

presented; if one existed, the high titanium content 

suggests that it was deposited as a black sand rather 

than as a chemically precipitated sedimentary ironformation. 

ENRICHMENTS OF PREEXISTING FERRUGINOUS ROCKS (111-B) 

In several places in the world, most notably in the 

Quadrilatero Ferrifero of Brazil, very large deposits of high-grade ore occur within beds of Precambrian iron-formation (United Nations, 1970). The 

ore consists of crystalline hematite (specularite) 

with minor magnetite, locally with retention of the 

thinly layered structure of the original iron-formation. Some of the ore is loose and friable. The iron 

content approaches 70 percent, the theoretical content of pure hematite, and reserves exceed a billion 

tons. The deposits are believed to have originated by 
302 UNITED STATES MINERAL RESOURCES 

hydrothermal replacement of silica layers along favorable structures in the enclosing iron-formation, 

but the source of the solution is unknown. Deposits 

of similar character occur in Liberia, Mauretania, 

India, Australia, and in the now dormant Vermilion 

district of Minnesota. 

DEPOSITS PRODUCED BY SURFACE OR NEAR-SURFACE 

ENRICHMENT (IV) 

Many iron deposits owe their origin to surface or 

near-surface enrichment of rocks of lesser iron content. Preexisting iron-bearing minerals are attacked 

by surface and ground waters, and the iron is 

altered to limonite and hematite, often with the loss 

of other elements in solution. In localities where 

surface erosion is minor, or where the oxidation 

occurs below the surface, the result is a progressive 

concentration of iron oxides. Many of these residual 

deposits have been mined in the past, and some 

that are of major economic or potentially economic 

importance remain. 

Two general groupings are convenient: Laterites, 

which are characteristic products of weathering in 

humid tropical climate, and residual enrichments of 

lower-grade iron deposits. 

LATERITES (IV-A} 

The process of lateritization is one of deep chemical weathering under tropical conditions with alternating wet and dry seasons. The nature of the product varies with that of the underlying rock; bauxite, 

for example, is produced by lateritization of rock 

high in alumina relative to quartz and iron minerals. The iron-rich laterites most commonly are 

derived from serpentine, as in Cuba and the Philippine Islands (Dutton, 1955; United Nations, 1970). 

The material is porous and brown, and it may accumulate to depths of many tens of feet. Surface areas 

are measured in square miles, and so the potential 

tonnage is very large. The dominant ore mineral is 

limonite (impure goethite), and the iron content of 

the rock commonly is 40--50 percent. Nickel, cobalt, 

and chromium also are concentrated in laterite. The 

major impurity is elay which, along with chromium, 

cobalt, and nickel, inhibits the greater use of laterite 

as an iron ore. Many iron-rich laterites now are 

being mined for nickel alone, but future improvement of metallurgical techniques may result in 

greater use of laterite as an iron ore, with nickel 

and cobalt, and possibly chromium, as coproducts. 

ENRICHMENTS OF PREEXISTING LOW-GRADE ORES (IV-B) 

Most of the iron ore used in the world to date has 

been produced from deposits arising from the nearsurface enrichment of lower grade material. Before 

the development of a method for processing taconites, virtually all the production from districts 

such as the Mesabi in the United States and Krivoi 

Rog in Russia was of soft limonite and hematite. 

These direct-shipping ores, with iron contents of 

50-60 percent, and the so-called wash ores and 

semitaconite of the Lake Superior region are products of deep residual enrichment of primary ironformation, in which oxidation of ferrous minerals 

was accompanied by partial to complete leaching 

and replacement of chert (James, 1966). The enrichment extends to considerable depths in many 

parts of the world-commonly to many hundreds of 

feet and in some districts to as much as 5,000 feet. 

The deposits have yielded immense amounts of ore; 

the Lake Superior districts alone have produced 

more than 3 billion tons (Aim and Trethewey, 1971; 

see also data in U.S. Bur. Mines Minerals Yearbooks 1932-1970 and U.S. Geol. Survey and U.S. 

Bur. Mines Mineral Resources of the United States 

1882-1931). 

Many other examples exist of ores that are products of enrichment. The famous Bilbao deposits of 

Spain consist of massive limonite and hematite derived by enrichment of preexisting siderite bodies 

(United Nations, 1970). The brown ores of Texas 

and the southeastern United States were formed by 

oxidation and enrichment of Tertiary strata containing siderite and glauconite. The hard ores of 

the Marquette district of Michigan, which occur at 

the top of the Negaunee Iron-formation, probably 

represent in part a former enrichment and in part 

a clastic accumulation, now profoundly modified by 

metamorphism. 

SUMMARY OF TYPES OF DEPOSITS 

Table 58 presents a general summary description 

of types of iron-ore deposits. Characteristics such 

as iron content and form vary widely in each type, 

but the descriptions given apply reasonably well to 

the major deposits. 

RESOURCES 

IDENTIFIED RESERVES AND RESOURCES 

Vast quantities of iron-ore resources are known 

to exist throughout the world. A recent survey of 

world iron-ore resources by the United Nations 

( 1970) indicated world reserves totaling approximately 250,000 million metric tons and an additional 530,000 million tons of potential iron-ore resources. The estimated iron-ore resources of various 

parts of the world, slightly modified from the 

amounts listed above, are shown in table 59. 
Subdivision and 

location of typical 

example 

1-A. Banded iron-formation: 

IRON 

TABLE 58.-Summary description of categories of iron ore 

A venae 

of 

typical 

Principal iron min.erals iron Form of exploited deposits eon tent (percent) 

I. Sedimentary deposits 

Present 

importance 

Resource potential 

United 

Statea World 

303 

Labrador ------------- Magnetite, hematite, 33 Bed hundreds of feet thick, Major Enormous -- Enormous. 

siderite, iron silicates. 

1-B. Ironstone: 

Birmingham, Ala. ------ Limonite, hematite, 

siderite, chamosite. 

1-C. Miscellaneous (bog iron, black band siderite, black sands) : Limonite, siderite, 

magnetite, ilmenite. 

30 

tens of miles in strike length. 

Beds tens of feet thiek, miles in 

strike length. 

Various ----------------------

Minor Medium ---- Large. 

Negligible -- Small ------ Small. 

II. Deposits related directly to igneous activity 

11-A. Magmatic segregations: 

Kiruna, Sweden -------- Magnetite 66 

11-B. Pyrometasomatic deposits: 

Cornwall, Pa. ---------- Magnetite, hematite ------ 46 

Tabular bodies, hundreds of feet 

thick, many thousands of feet 

long. 

Tabular to podlike deposits, a few hundred feetthick, a few 

thousands of feet long. 

Modest ----- Medium ---- Medium. 

___ do ------ Large ------ Do. 

III. Deposits formed by hydrothermal solutions 

III-A. Replacement deposits in nonferruginous roeks: 

Buena Vista, Nev. ------ Magnetite, hematite, 

siderite. 

III-B. Enrichments of preexisting ferruginous rocks: 

Minas Gerais, Brazil --- Specular hematite, 

minor magnetite. 

30 

68 

Irregular pods, lenses, stockworks; veins. 

Tabular bodies parallel or subparallel to bedding of enelosing 

iron-formation. Thickness up to several hundred feet. 

Minor ------ Small ------ Small. 

Modest ----- Negligible __ Medium. 

IV. Deposits produced by surface or near-surface enrichment 

IV-A. Laterite: 

Cuba ----------------- Limonite, hematite ------ 46 Blankets tens of feet thick, tens or hundreds of square miles 

in area. 

Minor ------ Small ------ Large. 

IV-B. Secondary enrichments of low-grade iron deposits: 

Lake Superior (direct- Limonite, hematite ------ shipping and wash 66 

ores). 

Blankets to sacklike bodies, 

dimensions in hundreds to thousands of feet. Most 

restricted to depth of a few 

hundred feet below surface, 

but Lake Superior deposits extend to several thousand 

feet. 

Major ------ Large ------ Do. 

TABLE 59.-World iron-ore resources, in millions of metric 

tons, figures rounded (United Nations, 1970) 

Country, region, or continent 

United States ----------- North America exclusive of 

United States (mostly 

Reserves 1 

9,000 

Identified resources, 2 

including reserves 

101,000 

Canada) -------------- 36,000 126,000 

South America ---------- 34,000 94,000 

Europe ----------------- 21,000 34,000 

Africa ------------------ 7,000 31,000 Australia and 

New Zealand --------- 17,000 8 17,000+ 

Asia ------------------- 17,000 72,000 

U.S.S.R. ---------------- 111,000 304,000 ----------------------------- Total ------------- 25·2,000 779,000+ 

1 Reserves: Identified deposits from which minerals can be extracted 

profitably with existing technology and under present economic conditions. 2 Identified Resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may not be profitably recoverable with existing technology and 

economic conditions. 3 Mostly high-grade ores; vastly greater quantities of lower grade ironformations are known but have not been assessed. 

The amounts listed as reserves include large 

qua.ntities of low-grade ores as well as high-grade 

ores. Therefore the tonnages listed for the various 

continents or regions are not directly comparable in 

terms of iron content. Nevertheless, the total reserve figures, even reduced by two-thirds to compensate for a ratio as low as 3 tons of crude ore to 

1 ton of shipping-grade concentrate from taconite 

ores, represent more than 100 years' supply at recent world iron-ore production rates of nearly 750 

million tons per year. The total crude-ore resources, 

including reserves, represent more than 300 times 

the recent annual production of shipping-grade ore. 

At least four nations in the world-U.S.S.R., 

Canada, Brazil, and Australia-have ore reserves 

in excess of 10 billion tons each. Nine-United 

States, India, France, Peoples Republic of China, 

Sweden, United Kingdom, Federal Republic of Germany, South Africa, and Venezuela-have reserves 

of .more than 1 billion tons each. Other nations 

which have substantial iron-ore reserves in production and which have exported more than 500,000 

tons a year in recent years are Angola, Chile, Korea 

(south), Liberia, Malaysia, Morocco, Norway, Peru, 
304 UNITED S·TATES MINERAL RESOURCES 

Philippine Republic, Sierra Leone, Spain, and Tunisia. 

The identified iron-ore resources of the United 

States are shown in table 60. 

TABLE 60.-The identified iron-ore resources of the United 

States, in millions of metric tons (United Nations, 1970) 

[Figures rounded. Include estimates for some deposits for which precise data are not available] 

Region Reserves 1 

Identified re- sources 2 ( re- serves + ~ tential ores) 

Lake Superior -------------- 6,500 78,000 

Northeastern ---------------- 200 1,400 

Southeastern ---------------- 100 9,400 

Central-Gulf ---------------- 600 700 

Central-western ------------- 1,100 2,300 

Western -------------------- 600 1,200 

Alaska --------------------- 6,600 

Hawaii --------------------- 1,000 -------------------- Total ----------------- 9,100 100,600 

1 Reserves: Identified deposits from which minerals can be extracted 

profitably with existing technology and under present economic con- ditions. 2 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. 

HYPOTHETICAL RESOURCES 

Because of the great amounts of identified ironore resources, no attempt is made to estimate quantities of hypothetical iron-ore resources beyond 

stating that they are enormous. The identified ironore resources in the world are a sampling of the 

surface and near-surface parts of the geologically 

explored land areas of the earth. Most of the identified resource material is within half a mile of the 

surface of the earth. It is reasonable to expect that 

in many areas the zone between a depth of half a 

mile and 1 mile beneath the surface will ~ontain 

hypothetical resources proportional in amount to 

the near-surface identified quantities. This concept 

is especially applicable to the great expanses of 

Precambrian iron-formation and younger ironstone 

formations that exist on all the continents. It also 

applies to areas in which deposits are the results of 

processes related to magmatic activity. Allowance 

must be made, however, for some deposits that are 

not resources because they did not undergo surficial 

enrichment and also for some flat-lying iron-formations that do not extend to depths of more than 

half a mile. 

In North America, and in the geologically explored parts of other continents, bedded Precambrian sedimentary iron-formations and younger 

sedimentary ironstone deposits extend for lengths 

totaling hundreds of miles (United Nations, 1970). 

Undoubtedly these formations, in many areas, maintain their basic characteristics for considerable distances in the subsurface. In view of the existence 

of very large quantities of identified iron-ore resources, and because setting upper limits to the 

amounts of hypothetical iron-ore resources would 

involve many questionable assumptions, detailed 

estimates of the existing quantities of hypothetical 

iron-ore resources can have little meaning. Factors 

such as the amounts of ore that must be left in 

place as mine pillars and physical limitations upon 

depths to which mining activities can be carried on 

in various types of rock impose limitations upon 

the practical estimation of hypothetical resources at 

great depths. Advances in the state of the art of 

mining can extend the depths to which ore can be 

mined, but can also extend the competitive exploitation of low-grade shallow ore deposits. 

SPECULATIVE RESOURCES 

Although speculative iron-ore resources are impossible to quantify in any meaningful way, they 

are worthy of consideration. In the past two decades 

most of the identified iron-ore resources of Australia 

became known, and Australia has become one of 

the major iron-ore producing nations (lnst. Geol. 

Sci., 1971; United Nations, 1970). Similarly, large 

high-grade deposits, measuring in thousands of millions of tons, have been identified in recent years in 

Brazil. Large areas in South America, Africa, Asia, 

and Antarctica remain to be explored geologically. 

On the other continents large areas in which Precambrian basement rocks are under a relatively 

thin cover of younger rocks offer possibilities for 

the discovery of major iron deposits. Manganeseand iron-rich nodules and other sediments on the 

sea floor remain to be assessed as potential resources. 

In the United States, the most promising regions 

for iron-ore discovery have largely been identified 

and at least partially explored. The principal need 

is to obtain more detailed information concerning 

these regions. Because most of the major iron deposits or iron-bearing formations have associated 

magnetic anomalies, major programs of aeromagnetic surveying to delineate the zones of magnetic 

rocks and potential ore bodies should be continued. 

Such surveys have been made for many areas and 

have proved to be successful. In some cases further 

geologic studies and interpretations of the magnetic and geological data are needed. 

EXPLORATION 

Exploration for iron ores differs significantly 

from that involved in the search for most other 

metals, in part because of the low value of ore--
IRON 

less than 1 cent a pound-and the general abundance 

of deposits, and in part because most ores are magnetic or have some surface expression and hence 

are comparatively easy to discover. 

In unexplored areas, now relatively few in the 

United States, the primary tool in the search for 

new deposits is the airborne magnetometer. Surveys 

can be made rapidly and inexpensively; an area of 

1,000 square miles can be adequately searched at a 

cost less than $20,000. Once favorable areas are 

located, detailed geologic mapping and ground magnetic surveys, possibly supplemented by gravity surveys, serve to delineate target areas for drilling. 

Most exploration in the United States except that 

for buried magmatic, pyrometasomatic, or hydrothermal deposits, is directed not toward discovery 

but toward definition of deposits that meet the economic criteria of geologic location, large size, suitability for low-cost mining and beneficiation~ and 

low content of objectionable impurities. The major 

developments of the past 20 years in the United 

States and Canada and many that are anticipated 

in the future concern the bedded iron-formations 

(taconites) in the Lake Superior and the Rocky 

Mountain regions. The location and extent of virtually all such deposits probably are now known, 

but intensive geologic mapping, drilling, and sampling are necessary to appraise the actual economic 

potential. Investments for a major taconite mine and 

processing plant are so large that a minimum proved 

reserve of about 100 million tons of minable lowgrade ore commonly is required. 

Exploration for buried high-grade deposits of 

magmatic, pyrometasomatic, or hydrothermal origins presents problems more analogous to those encountered in base-metal exploration. The deposits 

are likely to be irregular in form and size, and they 

lack the geologic predictability of bedded ores. 

Nevertheless, those within a few thousand feet of 

the surface generally will yield measurable aeromagnetic anomalies that provide a basis for restricting 

the area in which detailed geologic and ground magnetometer surveys are needed for definition of 

drilling targets. 

The geologic and geophysical techniques are used 

to select targets, but physical sampling and analyses 

of samples are required to prove the existence of a 

mineral deposit of economic value. Such sampling 

commonly involves drilling to obtain representative 

specimens of the ore from locations sufficiently 

spaced so as to give a three-dimensional view of the 

ore zone and thus locate a volume large enough to 

meet the minimum size requirements for an economically minable deposit. Additional drilling and 

sampling may be done to determine the existence 

of greater quantities of ore for larger scale operations, to determine the limits of the ore zone, for 

planning of mining techniques and pit design, and 

for selection of plant sites that will not interfere 

with the extraction of the ore. Additional factors 

particularly applicable to the economic evaluation 

of iron-ore deposits have recently been discussed by 

Ohle (1972). 

PROBLEMS FOR RESEARCH 

Specific regions that ought to be studied or reappraised geologically are : ( 1) Parts of the Adirondack Mountains area of northern New York, for 

titaniferous and nontitaniferous iron deposits; (2) 

selected parts of the Lake Superior region, particularly the South Cuyuna Range and adjoining areas, 

for iron-formation in the subsurface; (3) the Cebolla Creek area, Colorado, for titaniferous deposits; 

( 4) iron-ore districts in southwestern Utah, for 

magnetite and hematite deposits; ( 5) iron-ore districts in parts of Nevada, for magnetite and hematite deposits; and (6) the Iliamna Lake area in 

southwestern Alaska, for titaniferous magnetite 

deposits. Some of these areas have been reconnoitered or studied in more detail by private investigators, but sufficient data for the appraisal of 

their iron-ore resource potential are not publicly 

available. The fact that some areas have been investigated in the past does not eliminate the possibilities for significant discoveries in these areas. 

Perhaps the most meaningful studies, from the 

long-range point of view, would be those directed 

toward the objective of utilizing the entire ironrich parts of major iron-formations such as the 

Biwabik Iron-formation in Minnesota (Dutton, 

1955). Such studies would involve sampling, mineralogic investigation~, beneficiation tests, and experimentation directed toward new iron-ore smelting 

techniques. In many places only selected parts of 

the iron-formation are mined as ore, and large 

quantities of iron-rich rock must be moved in order 

to recover the selected parts. For example, the magnetic taconite layer mined may represent only about 

150 feet of a total thickness of 500 feet or more of 

iron-formation. In places, as much as 550 feet of the 

iron-formation contains more than 23 percent in 

total iron. Such material would contain about 335 

million tons of iron per square mile in a layer 550 

feet thick. 

The need to minimize environmental problems 

resulting from mining and processing ores, while 

assuring adequate domestic supplies of iron ore, 

gives added incentive to efforts toward use of more 
306 UNITED s.T'A TES MINERAL RESOURCES 

of the total iron in the iron-formation of the Lake 

Superior region. Processes applicable to utilization 

of iron in silicates and carbonate as well as in 

oxides in the Biwabik Iron-formation of the Mesabi Range would be applicable to iron-formations 

of other districts in the Lake Superior region and 

elsewhere in the world. If the cost advantage that 

would be derived from centering more of the nation's production in these large deposits would offset any possible increases in costs of processing the 

bulk iron-formations, the Lake Superior region could 

supply much of the nation's expected needs for iron 

for centuries (Michelson and others, 1970; Roberts 

and Crago, 1948). Thus, the requirements for land 

areas for iron mining and associated beneficiation, 

waste disposal, and transportation facilities would 

be minimized if more of the iron in the Lake Superior iron-formations were utilized. 

The potential iron-ore resources in manganeseiron-rich nodules on the sea floors may be worthy 

of further investigation because of the possibility 

that many other valuable products could be extracted from the nodules. These include manganese, 

copper, nickel, cobalt, zirconium, and titanium. The 

nodules, however, are probably only of minor potential value for iron. 

SELECTED REFERENCES 

Aim, M. R., and Trethewey, W. D., 19·71, Mining directory 

issue: Minnesota Univ. Bull., v. 74, no. 7, 245 p. 

American Iron Ore Association, 1970, Iron ore, 1970: Cleveland, Ohio, Am. Iron Ore Assoc., 127 p. 

Carr, M. S., Guild, P. W., and Wright, W. B., 1967, Iron in 

the United States: U.S. Geol. Survey Mineral Inv. Resource Map MR-51 (with 20 p. text). 

Deily, R. L., 1972, Iron ore and steel : Eng. and Mining 

Jour., v. 173, no. 3, p. 94-97. 

Dutton, C. E., 1955, Iron-ore deposits of North America and 

the West Indies, in United Nations, Department of Economic and Social Affairs, Survey of world iron ore resources: New York, United Nations, p. 179-208, 

Gross, G. A., 1965, General geology and evaluation of iron 

deposi•ts : Canada Geol. Survey Econ, Geology Rept. 22, 

v. 1, 181 p. 

Institute of Geological Sciences, Mineral Resources Division, 

1971, Statistical summary of the mineral industryWorld production, exports and imports, 1964-1969: 

London, Her Majesty's Stationery Office, p. 147-174. 

James, H. L., 1966, Chemistry of the iron-rich sedimentary 

rocks: U.S. Geol. Survey Prof. Paper 440-W, 61 p. 

Michelson, R. W ., Polta, J. J ., and Peterson, Prin, 1970, 

Evaluating the economic availability of Mesabi Range 

taconite iron ores with computerized models: U.S. Bur. 

Mines Inf. Circ. 8480, 99 p. 

Ohle, E. L., 1972, Evaluation of iron ore deposits: Eeon. 

Geology, v. 67, no. 7, p. 953-964. 

Roberts, H. M., and Crago, W. H., 1948, Reserves and the 

competitive position of Lake Superior iron ores: Minneapolis, 9th Ann. Mining Symposium, p. 1-15. 

United Nations, Department of Economic and Social Affairs, 

1970, Survey of world iron ore resources: New York, 

United Nations, 479 p. 

U.S. Bureau of Mines, 1972, Commodity data summariesIron sections: p. 72-76. 

---[published annually]. Minerals yearbook. 

Wimpfen, S. P., 19'71, Iron and steel imports: Skillings 

Mining Rev., v. 60, no. 10, p. 1, 8-10. 
UNITED STATES MINERAL RESOURCES 

KYANITE AND RELATED MINERALS 

By GILBERT H. EsPENSHADE 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------- Exploitation -------------------------------------

Geologic environment ----------------------------

Resources --------------------------------------- United States resources of kyanite-group minerals --------------------------------- Deposits of micaceous schist and gneiss ----

Quartzose deposits ------------------------ Byproduct sources of kyanite-group minerals 

Foreign resources of kyanite-group minerals ___ _ 

Speculative resources ------------------------

Problems for research ----------------------------

References cited ---------------------------------

TABLES 

61. E·stimated United States demand for kyanite 

and synthetic mullite --------------------- 62. United States resources of kyanite and related 

minerals ---------------------------------

ABSTRACT OF CONCLUSIONS 

Page 

307 

307 

308 

308 

309 

309 

309 

310 

310 

310 

310 

311 

311 

studies and sampling of deposits of the kyanite-group minerals are needed in order to appraise their economic potential. 

INTRODUCTION 

Kyanite and related minerals (known as the 

kyanite or sillimanite group) are high-alumina minerals used in the manufacture of. high-quality refractory materials and other ceramic products. The 

most abundant are kyanite, sillimanite, and andalusite, all having the same chemical composition, 

Al2SiOs (also written Al203 · Si02), but different 

physical properties. Dumortierite (containing boron) 

and topaz (containing fluorine) have similar composition but are much scarcer. Each of these minerals 

has been produced in the United States, but since 

1950, production has been mostly of kyanite, accompanied by small amounts of andalusite and sillimanite. An excellent comprehensive review of the 

Page properties, treatment, and industrial uses of these 

308 minerals and the geology of the deposits has been 

309 

given by Varley (1965). 

When these minerals are heated to very high temperatures, the new compounds mullite (3Al203 

·2Si02) and silica glass are formed. Mullite can also 

be made from various materials that contain alumina 

Kyanite and related minerals are high-alumina silicates (Al2Q 3 ) and silica (Si02), such as mixtures of aluused mainly in the manufacture of refractory linings for 

metallurgical and other types of furnaces. Domestic produc- mina, kaolin, and kyanite, alumina and kaolin, 

tion currently exceeds consumption, and considerable ton- bauxite and kaolin, or alumina and silica sand; this 

nages are exported. Enormous resources of these minerals product is kn.own as synthetic mullite[(Cooper, 1970,P. 

exist in the United States; this should permit the increase 1060-1061). Mullite retains its strength and stability 

in production that will be needed to meet the demand ex- at high temperatures for long periods of time and 

pected during the next 25 years. Production now comes large- ly from kyanite-quartz deposits in the Southeastern States; has become very widely used as a refractory makyanite and sillimanite are also recovered as a byproduct terial in the metallurgical industry (Foster, 1960; 

from Florida ilmenite sands. Resources of deposits of these Klinefelter and Cooper, 1961, p. 3-6; Varley, 1965). 

two types are very large but make up no more than 5 per- The refractory properties are improved as the mulcent of our total resources. The remaining 95 percent or lite content of the material is increased. more is in deposits of micaceous schist and gneiss, mostly The United States is now the largest producer in the Appalachian Mountain system and in Idaho. None of 

these deposits is now being mined, but profitable mining of and consumer of kyanite and synthetic mullite. Dosome may eventually be possible. More detailed geologic mestic demand for kyanite and synthetic mullite in 

U.S. GEOL. SURVEY PROF. PAPER 820 

307 
308 UNITED STATES MINERAL RESOURCES 

1968 was estimated at about 120,000 short tons, and 

exports were about 20,000 tons ; total value of the 

production was about $10.7 million. The demand in 

1968 by different industries and the possible demand 

in the year 2000 (table 61) were estimated by 

TABLE 61.-Estimated United States demand for kyanite and 

synthetic mullite 

Industry 

or use 

Iron and steel ----------- Nonferrous meta.ls -------- Boiler furnaces -----------

Glass ------------------- Other. uses ---------------

Total --------------

Estimated demand (short tons) 

1968 2000 ----

60,000 

36,000 

6,000 

17,000 

12,000 

120,000 

Low High 

126,000 

130,000 

26,000 

60,000 

40,000 

380,000 

300,000 

196,000 

40,000 

140,000 

200,000 

876,000 

Cooper (1970, p. 1066-1069). 

According to Cooper, the major trend in the use 

of these materials as refractories in the next 25 

years probably will be to replace other types of 

refractories in metallurgical, glass, and boiler furnaces. Important nonrefractory uses may also be 

developed, such as the manufacture of aluminumsilicon alloys, floor and wall tile, spinnable mullite 

fibers, and blown-wool refractory insulations. 

Before 1951, the United States imported more 

kyanite than it produced because the massive ore 

("strategic kyanite") from India and Kenya was 

required as an essential component in making the 

best high-alumina refractory bricks. The fine-grained 

kyanite concentrate produced from domestic disseminated ore is more suitable for other purposes. 

Manufacture of synthetic mullite began in 1951, and 

its use has practically eliminated the need for imported massive kyanite. 

The increased demand expected in the United 

States for kyanite-group minerals during the next 

25 years can be supplied from our very large domestic resources. All domestic production for many years 

has come from mines in the Southeastern States ; 

production from these mines can be increased, and 

probably several new mines can be opened at other 

deposits in the region. The increased demand for 

kyanite expected in the Western States could probably be met by mining some of the deposits in 

Idaho, California, or New Mexico. Expansion of synthetic mullite production might require increased 

imports of bauxite or alumina, but this need would 

be very small in comparison to the large quantities 

of bauxite and alumina imported by the aluminum 

industry. The trend of exports of kyanite and synthetic mullite from the United States over the next 

25 years is difficult to forecast because foreign production will doubtless increase, and trade patterns 

may change considerably. 

EXPLOITATION 

Domestic mining> of the kyanite-group minerals 

began in the 1920's when kyanite was mined at 

Baker Mountain, Va., Ogilby, Calif., and Petaca, N. 

Mex.; andalusite at White Mountain, Calif.; and 

dumortierite at Oreana, Nev. Other deposits of 

various types were mined or prospected between 

1930 and 1950. Since 1950, nearly all production has 

come from kyanite-quartz deposits at Baker Mountain and Willis Mountain, Va., Graves Mountain, 

Ga., and Henry Knob, S.C.; mining at Henry Knob 

ceased in 1969. Byproduct recovery of kyanite and 

sillimanite began in 1968 from Florida sands processed for ilmenite and other heavy minerals. Various 

aspects of domestic mining operations have been 

discussed by Espenshade and Potter (1960), Foster 

(1960),.Klinefelter and Cooper (1961), and Cooper 

(1970). 

United States production of kyanite has increased 

steadily since 1940 when it was 4,241 short tons. 

By 1950, it was about 15,400 short tons, and in 

1960, about 33,000 short tons (Varley, 1965, p. 30). 

Cooper (1970, p. 1066) stated that it was about 

100,000 short tons in 1968. 

GEOLOGIC ENVIRONMENT 

Kyanite, sillimanite, and andalusite are very common in many parts of the world in aluminous metamorphic rocks which have undergone the deformation and increased temperatures that accompany 

mountain building. Each of the Al2SiOs minerals 

forms under certain distinctive ranges of temperature and pressure. Kyanite typically forms in schists 

and gneisses at fairly high temperatures and pressures, under conditions of strong regional or dynamic metamorphism. Andalusite forms at lower 

pressure and is very common in the hot zones of contact (or thermal) metamorphism surrounding large 

intrusions of granite or gabbro. Sillimanite forms 

at higher temperatures during both regional and 

contact metamorphism. Mullite is a very rare mineral formed naturally at temperatures even higher 

than sillimanite. Topaz and dumortierite are much 

less common than the Al2SiOs minerals. They are 

most abundant in quartzose deposits, some of which 

appear to be hydrothermally altered volcanic rock. 

The Al2SiOs minerals are principally contained in 

micaceous schists and gneisses which underlie many 

square miles in some regions. Kyanite and sillimanite 

are more abundant than andalusite in these deposits. 

The content of these minerals may be as much as 
KYANITE AND RELATED MINERALS 309 

40 percent, but generally is less than 15 percent. 

Their distribution may be very irregular because of 

variable alumina content of the original beds or 

layers and the subsequent strong deformation of 

the layered rock. Usually only one of the Al2Si05 

minerals is present, but two of them occur together 

at some places, and all three have been found together at a few places. 

Another important but less common type of deposit consists of quartzose rock that contains one or 

more of the kyanite-group minerals in association 

with various other aluminous minerals and quartz. 

These quartzose deposits generally have a higher 

content of Al2SiOs minerals (commonly more than 

20 percent) than do the micaceous schists and 

gneisses, but they are much smaller in size. Kyanite 

is usually more abundant in the quartzose deposits 

than are other minerals of the group. 

The kyanite-group minerals also occur in quartz 

veins and pegmatites but in relatively small amounts. 

These minerals are very resistant to weathering 

and erosion and may accumulate in abundance in 

the soils overlying the source rocks. Subsequently, 

the Al2SiOs minerals are concentrated in stream and 

river alluvium; later in the cycle of sediment transport, they may be preserved in beach sands along 

with other resistant minerals such as quartz, zircon, 

monazite, staurolite, and the titanium minerals 

ilmenite and rutile. 

RESOURCES 

UNITED STATES RESOURCES OF KYANITEGROUP MINERALS 

The Al2SiOs minerals occur in nearly every large 

area of metamorphic rocks in the country (Espenshade, 1961, 1962; Varley, 1965). The kyanite-group 

minerals have been found in bedrock at innumerable 

places in at least 30 States (Grametbauer, 1959). At 

many places, no more than a few percent of these 

minerals is contained in the rock, too little to be of 

economic interest. Only those deposits that contain 

at least 10 percent of the Al2SiOs minerals are of 

potential economic value. All domestic resources are 

of the disseminated type of ore in which the kyanite 

minerals must be separated from quartz, mica, and 

other minerals by beneficiation. 

Domestic resources of the kyanite-group minerals 

are summarized in table 62 according to three types 

of deposits. Enormous amounts of the Al2SiOs minerals are contained in micaceous schists and gneiss, 

but such deposits typically have lower contents of 

these minerals than do the quartzose deposits and 

have produced only a few percent of the total doTABLE 62.-United States resources of kyanite and related 

minerals 

[Short tons of contained kyanite-group minerals] 

Type of deposit 

Deposits of micaceous 

schist and gneiss ----------- Quartzose deposits ----------- Byproduct or potential 

byproduct from deposits 

mined for other minerals ---

Resources 

Identified t 

960,000,000 

33,300,000 

13,600,000 

Hypothetical I 

1,000,000,000 

11,000,000 

26,000,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be eva uated as to extent and grade, and whose contained minrals may or may not be profitably recoverable with existing technology 

and economic conditions. 2 Hypothetical resources: Undiscovered mineral deposits. whether of 

recoverable or subeeonomic grade, that are geologically predictable as existing in known districts. 

mestic output of these minerals. Probably at least 

95 percent of total production has come from quartzose deposits, although these deposits contain no 

more than 5 percent of our resources. 

The data used in estimating these resources are 

generally better for the quartzose deposits and byproduct sources than for the deposits of micaceous 

schist and gneiss. For identified resources, the 

minimum grade (except for byproduct sources) has 

been taken as 10 percent content of kyanite-group 

minerals; estimates of open-cut mining depths range 

from 50 feet to several hundred feet. Estimates of 

hypothetical resources are based on extensions of 

known deposits or districts in depth or in area. None 

of the micaceous schist and gneiss deposits included 

in table 62 is now being mined, but profitable mining of some may become possible within the next 

25 years. Deposits of sillimanite schist containing 

finely fibrous sillimanite ( "fibrolite") are not included in the resource estimate because of the 

difficulty in making a clean and efficient separation 

of this variety of sillimanite. 

DEPOSITS OF MICACEOUS SCHIST AND GNE.ISS 

Kyanite and sillimanite are widely distributed in 

micaceous schist and gneiss in the Appalachian 

mountain system from Maine to Alabama. Andalusite in such rocks is much more restricted in occurrence and is found principally in New England. General distribution of the Al2SiOs minerals in the 

Appalachians was shown on a map by Morgan 

(1972); distribution in New England has also been 

given (Doll and others, 1961; Hussey and others, 

1967; and Thompson and Norton, 1968); distribution in parts of the southern Appalachians was 

given by Overstreet and others (1968), Carpenter 

(1970), and Hadley and Nelson (1971). The principal 

Appalachian deposits of micaceous schist and gneiss 

included in table 62 are kyanite-garnet-mica 

gneisses near New Hartford, Conn. (R. W. Schnabel, 

written commun., Apr. 1972); similar gneiss and 
310 UNITED STATES MINERAL RESOURCES 

schist near Spruce Pine, N.C. (Brobst, 1962), 

Clarkesville, Ga., and other areas in the Blue Ridge; 

andalusite in the contact zones of gabbroic and granitic plutons in central Maine (Espenshade and 

Boudette, 1967); and sillimanite schist in Hart 

County, Ga. (Teague, 1950). 

The AlzSiOs minerals are also widely distributed 

in micaceous schist and gneiss in Idaho, Montana, 

Colorado, the Black Hills, S.Dak., the Sierra Nevada, 

Calif., and parts of Washington (Thorsen, 1966) and 

Oregon. However, the only deposits that are large 

enough and rich enough to be regarded as important resources are the kyanite-sillimanite deposit 

at W oodrat Mountain and the kyanite-andalusite 

deposit at Goat Mountain, Idaho (Hietanen, 1956; 

Van Noy and others, 1970). 

QUARTZOSE DEPOSITS 

The principal quartzose deposits of kyanite-group 

minerals are in the southern Piedmont (Hurst, 1959 ; 

Espenshade and Potter, 1960). Nearly all domestic 

kyanite production since 1950 has come from mines 

at Willis Mountain and Baker Mountain, Va., at 

Henry Knob in the Kings Mountain district, N.C. 

and S.C., and at Graves Mountain, Ga. Most resources of quartzose deposits are at these localities 

and in other kyanite-quartz deposits in the Piedmont. Smaller deposits containing other minerals of 

the kyanite group that are also included in table 62 

are sillimanite-quartz deposits in the Kings Mountain district and some andalusite-pyrophyllite-quartz 

deposits in North Carolina. 

Quartzose deposits of kyanite-group minerals in 

the Western States are much smaller than those in 

the Southeastern States. Such deposits are found in 

New Mexico in the Picuris Range and the Petaca 

district (Montgomery, 1953; Corey, 1960). An 

unusual deposit of topaz, sillimanite, and rutile in 

quartzose gneiss occurs in the Front Range of Colorado (Sheridan and others, 1968). In California, 

kyanite has been mined from quartzose deposits 

near Ogilby, Imperial County (Henshaw, 1942), and 

andalusite has been mined at White Mountain, Mono 

County (Wright, 1957). Dumortierite and andalusite were once mined from quartzose deposits in 

altered rhyolite near Oreana, Nev. (Kerr and Jenney, 1935). 

BYPRODUCT SOURCES OF KYA~ITE-GROUP MINERALS 

Kyanite and sillimanite occur in small amounts 

in the sands mined for ilmenite and other heavy 

minerals in Florida, Georgia, and New Jersey; they 

have been recovered from the Florida sands since 

1968 (Browning and others, 1956; Markewicz, 1969; 

Cooper, 1970). These minerals are also present in 

very small amounts along with other heavy minerals 

in the pebble phosphate deposits of Florida ; none of 

the heavy minerals has been recovered, but Stow 

(1968) estimated that about 200,000 short tons of 

heavy minerals (containing about 16 percent kyanite 

and sillimanite) are discarded yearly from the phosphate mining operations. Topaz occurs in the molybdenum ore at Climax, Colo. (Wallace and others, 

1968) and is a potential byproduct. 

FOREIGN RESOURCES OF KYANITE-GROUP MINERALS 

According to Varley (1965), the minerals of the 

kyanite group are widely distributed in many countries ; the principal deposits of economic value are 

the quartzose type, as in the United States. Many 

foreign quartzose deposits contain massive segregations of the AlzSiOs minerals, which in places have 

accumulated as loose boulders and fragments in the 

surficial residuum. Such massive ore is easily mined 

and requires little or no beneficiation, in contrast to 

domestic disseminated ores. 

India has been the principal foreign producer of 

AlzSiOs minerals since the 1920's, mostly massive 

kyanite from Lapsa Buru, Singhbhum, Bihar, and 

massive sillimanite from Assam and Madhya Pradesh. Sillimanite was once recovered from ilmenite 

beach placers in Kerala and Madras. The Republic 

of South Africa has also been a major producer for 

many years, mining andalusite from river placers 

in the Marico district, Transvaal, and sillimanitecorundum from near Pella, Namaqualand. Kenya 

was an important producer of both massive kyanite 

and kyanite concentrates from 1943 to 1960. Massive kyanite has also been produced from South 

West Africa, Bechuanaland, Rhodesia, and Nyasaland. Sillimanite and small amounts of kyanite and 

andalusite have been produced in Australia since the 

1930's. In the U.S.S.R., andalusite has been produced 

on a large scale from quartzose deposits in Kazakhstan; important deposits of kyanite occur on the 

Kola Peninsula and of sillimanite, in eastern Siberia. 

Cooper (1970, p. 1062) estimated that foreign reserves amount to 82,500,000 tons, mainly in the 

U.S.S.R., the Republic of South Africa, Canada, and 

India. Resources in the sense used here are clearly 

far larger and must be enormous in the case of the 

U.S.S.R., India, and some African countries. The 

data, howeve:r; are not adequate for a reliable estimate of foreign resources. 

SPECULATIVE RESOURCES 

The AlzSi05 minerals are so common in metamorphic rocks that they will be continually discovered as geologic mapping progresses in metamorphic terranes in the United States and other 
KYANITE AND RELATED MINERALS 311 

countries. Probably some of these deposits will be 

rich enough and large enough to be of potential 

economic value, but many will be too low in grade 

for exploitation in the next 25 years. Resources in 

undiscovered deposits and districts in the United 

States are doubtless enormous and may exceed our 

identified and hypothetical resources. 

PROBLEMS FOR RESEARCH 

The information available about grade and size 

of many deposits of the kyanite-group minerals is 

insufficient for meaningful economic appraisals because the economic potential of a deposit is difficult 

to assess by conventional geologic studies. As the 

Al2Si05 minerals are highly resistant to weathering 

and erosion, high-grade rock is commonly better 

exposed than low-grade rock, and consequently a 

deposit may appear much richer than it actually is. 

Detailed mapping and sampling are necessary to 

determine the extent of high-grade and low-grade 

rock. A careful preliminary evaluation by these 

means will be very useful to economic geologists as 

a guide to deposits which may deserve more exploration. 

REFERENCES CITED 

Brobst, 1). A., 1962, Geology of the Spruce Pine district, 

Avery, Mitchell, and Yancey Counties, North Carolina: 

U.S. Geol. Survey Bull. 1122-A, 26 p. 

Browning, J. S., Clemmons, B. H., and McVay, T. L., 1956, 

Recovery of kyanite and sillimanite from Florida beach 

sands: U.S. Bur. Mines Rept. Inv. 5274, 12 p. 

Carpenter, R. H., 1970, Metamorphic history of the Blue 

Ridge province of Tennessee and North Carolina: Geol. 

Soc. America Bull., v. 81, no. 3, p. 749-761. 

Cooper, J. D., 1970, Kyanite and related minerals, in Mineral 

facts and problems: U.S. Bur. Mines Bull. 650, p. 1059-

1072. 

Corey, A. F., 1960, Kyanite occurrences in the Petaca district, Rio Arriba County, New Mexico: New Mexico 

Bur. Mines and Mineral Resources Bull. 47, 70 p. 

Doll, G. G., Cady, W. M., Thompson, J. B., Jr., and Billings, 

M. P., compilers and eds., 1961, Centennial geologic map 

of Vermont: Montpelier, Vt., Vermont Geol. Survey, 

scale 1:250,000. 

Espenshade, G. H., 1961, Resources, chap. 3 in Klinefelter, 

T. A., and Cooper, J. D., Kyanite-A materials survey: 

U.S. Bur. Mines Inf. Circ. 8040, p. 8-19. 

Espenshade, G. H., 1962, Pyrophyllite, and kyanite and related minerals in the United States, exclusive of Alaska 

and Hawaii: U.S. Geol. Survey Min. Inv. Resources 

Map MR-18, scale 1 :3,168,000. 

Espenshade, G. H., and Boudette, E. L., 1967, Geology and 

petrology of the Greenville quadrangle, Piscataquis and 

Somerset Counties, Maine: U.S. Geol. Survey Bull. 

1241-F, 60 p. 

Espenshade, G. H., and Potter, D. B., 1960, Kyanite, sillimanite, and andalusite deposits of the Southeastern 

States: U.S. Geol. Survey Prof. Paper 336, 121 p. 

Foster, W. R., 1960, The sillimanite group-kyanite, andalusite, sillimanite, dumortierite, and topaz, in Gillson, J. L., 

ed., Industrial minerals and rocks: New York, Am. Inst. 

Mining, Metall., and Petroleum Engineers, p. 773-789. 

Grametbauer, A. B., 1959, Selected bibliography of andalusite, kyanite, sillimanite, dumortierite, topaz, and pyrophyllite in the United States: U.S. Geol. Survey Bull. 

1019-N, p. 973-1046. 

Hadley, J. B., and Nelson, A. E., 1971, Geologic map of the 

Knoxville quadrangle, North Carolina, Tennessee, and 

S~uth Carolina: U.S. Geol. Survey Misc. Geol. Inv. Map 

1-654, s<~ale 1 :250,000. 

Henshaw, P. C., 1942, Geology and mineral deposits of the 

Cargo Muchacho Mountains, Imperial County, Calif.: 

California Jour. Mines and Geology, v. 38, no. 2, p. 

147-196 .. 

Hietanen, Anna, 1956, Kyanite, andalusite, and sillimanite 

in the schist in the Boehls Butte quadrangle, Idaho: Am. 

Mineralogist, v. 41, no. 1-2, p. 1-27. 

Hurst, V. J., 1959, The geology and mineralogy of Graves 

Mountain, Georgia: Georgia Geol. Survey Bull. 68, 33 p. 

Hussey, A. M., Chapman, C. A., Doyle, R. G., Osberg, P. H., 

Pavlides, Louis, and Warner, Jeffrey, compilers, 1967, 

Preliminary geologic map of Maine: Augusta, Maine, 

Maine Geol. Survey, ·scale 1:500,000. 

Kerr, P. F., and Jenney, C. P., 1935, The dumortierite-andalusite mineralization at Oreana, Nevada: Econ. Geology, 

v. 30,no. 3,p. 287-300. 

Klinefelter, T. A., and Cooper, J. D., 1961, Kyanite-A materials survey: U.S. Bur. Mines Inf. Circ. 8040, 55 p. 

Markewicz, F. J., 1969, Ilmenite deposits of the New Jersey 

Coastal Plain, in Subitzky, Seymour, ed., Geology of 

selected areas in New Jersey and eastern Pennsylvania 

and guidebook of excursions: New Brunswick, N. J., 

Rutgers Univ. Press, p. 363-382. 

Montgomery, Arthur, 1953, Pre-Cambrian geology of the 

Picuris Range, north-central New Mexico: New Mexico 

Bur. Mines Bull. 30, 89 p. 

Morgan, B. A., 1972, Metamorphic map of the Appalachians: 

U.S. Geol. Survey Misc. Geol. Inv. Map I-724, scale 

1 :2,500,000. 

Overstreet, W. C., White, A. M., Whitlow, J. W., Theobald, 

P. K., Jr., Caldwell, D. W., and Guppels, N. P., 1968, 

Fluvial monazite deposits in the Southeastern United 

States: U.S. Geol. Survey Prof. Paper 568, 85 p. 

Sheridan, D. M., Taylor, R. B., and Marsh, S. P., 1968, 

Rutile and topaz in Precambrian gneiss, Jefferson and 

Clear Creek Counties, Colorado: U.S. Geol. Survey Circ. 

567, 7 p. 

Stow, S. H., 1968, The heavy minerals of the Bone Valley 

Formation and their potential value: Econ. Geology, 

v. 63, no. 8, p. 973-975. 

Teague, K. H., 1950, Sillimanite in the Southeast: Mining 

Eng., v. 187, no. 7, p. 785-789. 

Thompson, J. B., Jr., and Norton, S. A., 1968, Paleozoic regional metamorphism in New England and adjacent 

areas, in Zen, E-an and others, eds., Studies of Appalachian geology, northern and maritime: New York, lntersci. Publishers (John Wiley & Sons), p. 319-328. 

Thorsen, G. W., 1966, High-alumina refractory materials, in 

Mineral and water resources of Washington: U.S. Cong., 

89th, 2d sess., Senate Comm. on Interior and Insular 

Affairs, Comm. Print, p. 219-224. 
312 UNITED STATE.S MINERAL RESOURCES 

U.S. Bureau of Mines, 1954-1972, Minerals Yearbook, 1951-

1970: Washington, D.C., U.S. Govt. Printing Office (annual publication). 

Van Noy, R. M., Petersen, N. S., and Gray, J. J., 1970, 

Kyanite resources in the Northwestern United States: 

U.S. Bur. Mines Rept. Inv. 7426, 81 p. 

Varley, E. R., 1965, Sillimanite--Andalusite, kyanite, sillimanite: London, Overseas Geol. Surveys, Mineral Resources Div., 165 p. 

Wallace, S. R., Muncaster, N. K., Jonson, D. G., Mackenzie, 

W. B., Bookstrom, A. A., and Surface, V. E., 1968, 

Multiple intrusion and mineralization at Climax, Colorado, in v. 1 of Ore deposits of the United States, 1933-

1967 (Graton-Sales Volume): New York, Am. Inst. 

Mining, Metall.,. and Petroleum Engineers, p. 605-640. 

Wright, L. A., 1957, Kyanite, andalusite, and related minerals, in Wright, L.A., ed., Mineral commodities of California: California Div. Mines Bull. 176, p. 275-280. 
UNITED STATES MINERAL RESOURCES 

LEAD 

By H. T. MoRRIS, ALLEN V. HEYL, and RoBERT B. HALL 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction ------------------------------------·- Ancient uses _______________________________ _ 

]dodern uses --------------------------------- Outlook ____________________________________ _ 

Exploitation ____________________________________ _ 

Geologic environment ----------------------------- Geochemistry _______________________________ _ 

Ore mineralogy ------------------------------

Types of deposits ----------------------------

Strata-bound deposits of syngenetic origin __ 

Strata-bound deposits of epigenetic origin __ 

Volcano-sedimentary deposits -------------

Replacement deposits --------------------

Veins ----------------------------------- Contact pyrometasomatic deposits ---------

Resources ---------------------------------------

Reserves ------------------------------------

Conditional resources -------------------------

Hypothetical resources -----------------------

Speculative resources ------------------------- Prospecting techniques __________________________ _ 

Problems for research ----------------------------

References cited ---------------------------------

FIGURE 

39. Production of primary lead in the world and in 

the United States, 1830-1971, and consumption of lead, including scrap, in the United 

States, 1918-71 ----------------------------

TABLES 

63. World mine production of lead in 1969, by countries ------------------------------------- 64. Lead consumption in the United States, by products, in 1969 ------~-----------------------

65. Estimate of world reserves of lead, by regions or 

countries ---------------------------------

ABSTRACT OF CONCLUSIONS 

Lead has been used by man for approximately 6,000 years; 

Page it is now the fifth most important metal of trade in our in313 dustrialized economy. Lead occurs in a wide variety of ore 

313 deposits that are mined in more than 40 countries on all 

313 the continents except Antarctica. The world reserves are 

314 here estimated to exceed 140 million short tons of lead con315 tained in ores, equivalent to a 31-year supply at the 1971 

315 world rate of consumption. The reserves of the United States 

317 are estimated to constitute 38,185,000 short tons of lead; 

317 average annual domestic consumption during the period 

317 1961-70 was 1,240,000 short tons, of which about 43 percent 

318 was recycled scrap. The outlook for the continuing discovery 

318 of additional reserves and resources at a rate that exceeds 

319 consumption is believed to be excellent; many of these un321 discovered ore deposits are assumed to be comparable in 

322 tonnage and grade with known ore bodies. 

323 Conditional resources of conventional types but low grades 

324 are contained in strata-bound, massive sulfide, and. other 

325 kinds of deposits in several areas of the United States. 

325 Conditional resources of unconventional types are contained 

326 in lead-bearing manganese nodules on the sea floors, in the 

327 Kupferschiefer and related strata of Europe, in the Belt 

327 Supergroup of the Northwest United States, and in sediment 

327 in thermal deeps of the Red Sea and other oceanic areas. 

329 These conditional resources may total as much as 1.5 bil329 lion tons of lead, most of which is in the manganese 

Page 

316 

Page 

314 

315 

325 

nodules. Hypothetical and speculative resources together may 

equal half again as much as the known world reserves. 

INTRODUCTION 

ANCIENT USES 

The earliest uses of lead greatly antedate the 

earliest uses of iron, and lead, with copper and 

silver, may have been one of the first metals smelted 

from sulfide or oxidized ores. Because of its relatively common occurrence, the simplicity of its 

metallurgical reduction, its high density and low 

fusibility, and its softness and malleability, lead was 

used by many ancient peoples. As early as 3800 B.C. 

it was used by an artisan or priest to fashion a 

figurine that was discovered at the site of the Temple of Osiris at Abydos, in upper Egypt (Mitman, 

1922, p. 596). During the succeeding centuries, it 

U.S. GEOL. SURVEY PROF. PAPER 820 

313 
314 UNITED STATES MINERAL RESOURCES 

was commonly recovered with silver and used increasingly by the Egyptians, Cretans, Babylonians, 

and other ancient people in castings, as pottery 

glaze, as sheets and solder, and as an additive to 

bronze. In 2000 B.C. the Chinese were using lead 

coinage, and about the same time the Babylonians 

were employing soldered lead sheets as roofing for 

temples and public buildings among other uses. 

Some of this lead was probably obtainf~d in trade 

with the Hittites in Asia Minor, who had discovered the technique of smelting iron. By about 1600 

B.C., the Phoenicians, who established a farflung 

commerce in many commodities, had developed lead 

mines in Cyprus, Greece, Sardinia, and Spain. The 

ancient Britons bartered lead ores for products of 

the East brought by the Phoenician seafarers, and 

this trade was maintained and expanded with the 

Carthaginians and other seafarers who succeeded 

them. 

Lead was used extensively by the Greeks and 

Romans. The mines of Laurium, near Athens, among 

others, supplied the Greeks with silver to finance 

their wars and with lead for construction of their 

cities. The segments, or "drums," of the fluted columns that characterize Greek architecture are 

pinned together by iron rods fitted into sockets that 

were filled with molten lead. Lead was also used for 

slip-joint pipes that are remarkably similar to modern soil pipe and was used in coinage, in the production of bronze, and in the arts. Lead compounds 

were widely used as pigments and cosmetics by both 

the Romans and the Greeks and in ointments and 

salves. The Romans extended the mining of argentiferous lead ores into Yugoslavia, Rumania, France, 

Belgium, and Turkey, chiefly in a search for evergreater amounts of silver to finance their conquests 

and enrich Rome. Traces of Roman mining activities are still evident in these countries as well as in 

Italy, Sardinia, and Spain, where lead objects are 

occasionally found during the course of modern 

mining and archaeological activities. In Britain, for 

example, lead pipes of the Roman era still carry 

water at the hot-spring area of Bath. 

Many of the mines that were originally developed 

in all of those countries by the Phoenicians and 

Romans as well as other mines developed in Germany during the Dark Ages after the collapse of 

the Roman Empire are still important sources of 

lead in modern world trade and technology. 

MODERN USES 

In the present industrial economy of the world, 

lead is the fifth-ranking metal of trade and consumption after iron and steel, aluminum, copper, 

and zinc. Of the total world mine production in 

1969, 3,523,401 short tons (table 63), the United 

TABLE 63.-World mine production of lead in 1969, by 

countries 

[NA, not available. Data from U.S. Bureau of Mines Minerals Yearbook, 

1971] 

North America: 

Canada -------------------------------- Guatemala -----------------------------

llonduras ------------------------------ Mexico -------------------------------- Uni,ted States -------------------------- South America: Argentina ____________________________ _ 

Bolivia --------------------------------

Brazil --------------------------------- Chile Colombia ---------------------------------- _____________________________ _ 

Peru ---------------------------------- Europe: 

Austria -------------------------------- Bulgaria _____________________________ _ 

Czechoslovakia -------------------------

Finland -------------------------------- France -------------------------------- Germany: 

East ------------------------------ VVest ------------------------------ Greece --------------------------------- Ireland -------------------------------- Italy _____ - __ --------------------------

Norvvay -------------------------------- Poland -------------------------------- Portugal _________ ---- __ -- ____ ---------

Roumania -----------------------------

Spain ---------------------------------- Svveden -------------------------------- U.S.S.R. ------------------------------- United Kingdom ----------------------- Yugoslavia _______ ------ ___ ---------- __ _ 

Africa: 

Algeria -------------------------------- Congo (Brazzaville) --------------------

Morocco ------------------------------- Nigeria -------------------------------- Southvvest Africa ---------------------- Tunisia --------------------------------

Zambia -------------------------------- Asia: 

Burma -------------------------------- China, mainland ------------------------

India ---------------------------------- Iran ---------------------------------- Japan ------------------ ------------- Korea.: 

North ----------------------------- South ----------------------------- Philippines ----------------------------- Thailand ________ - _____ ---- __ --__ --__ --

Turkey -------------------------------- Oceania: 

Australia ------------------------------

Total (listed figures only) 

8 Estimated. 

1 Recoverable. 

2 Smelter production. 

Short tons 

330,781 1

314 

15,255 

188,378 

1

509,013 

35,000 

8

27,819 

30,416 

906 

451 1

179,592 

7,500 8

90,940 •8,ooo 

5,019 8

33,400 

8

13,000 

43,335 

9,458 8

63,700 

•39,700 

8

3,500 

54,000 

•2,170 8244 000 

76:700 

8

79,000 

490,000 

•3,300 

135,600 

•7,200 

•NA 

77,832 

1

66,634 2816,500 2825,350 

•9,900 

·uo,ooo 

2,239 

•26,400 

70,037 

8

77,000 

18,163 

74 

2,094 

2,440 

490,891 

3,523,401 

States production was 509,013 short tons, or 14.4 

percent. In contrast, the consumption in the United 

States of lead from all sources, including scrap, was 
LEAD 315 

1,389,358 short tons, 39.4 percent of the world's primary mine production (table 64) . 

TABLE 64.-Lead consumption in the United States, by 

products, in 1969 

[Data from U.S. Bureau of Mines Minerals Yearbook, 1971] 

Metal products: 

Ammunition --------------------------- Bearing metals -------------------------

Brass and bronze ----------------------- CabJe covering ------------------------- Casting metals ------------------------- Caulking lead -------------------------- Collapsible tubes -----------------------

F~l ----------------------------------- Pipes, traps, and bends -----------------

Sheet lead -----------------------------

Solder --------------------------------- Storage batteries: 

Battery grids, posts, etc ------------- Battery oxides ---------------------

Terne metal --------------------------- Type metal -·---------------------------

Total --------------------------------

Pigments: 

White lead ----------------------------- Red lead and litharge -------------------

Pigment colors ------------------------- Other (incl. leaded zinc oxide, etc) _____ _ 

Total --------------------------------

Chemicals: 

Gasoline antiknock additive ------------- Miscellaneous chemicals ________________ _ 

Total. ____ ---------------------------

Miscellaneous uses: Annealing ________________ -- _------ __ --

Galvanizing ----------------------------

Lead plating --------------------------- Weights and ballast --------------------

Total --------------------------------

Other, unclassified uses ---------------------

Grand total 1 -------------------------

Short tons 

79,233 

17,406 

21,512 

54,203 

9,918 

44,857 

12,484 

5,881 

19,407 

25,818 

72,626 

280,386 

302,160 

1,583 

25,660 

973,134 

6,617 

79,898 

14,670 

1,201 

102,386 

271,128 

602 

271,730 

4,252 

1,797 

406 

17,366 

23,821 

18,287 

1,389,358 

1 Includes lead that went directly from scrap to fabricated products. 

The consumption of lead in the United States is 

dominated by its use in storage batteries and leaded 

gasoline and in the construction industry, as shown 

in table 64. Other important but apparently diminishing uses are in pigments, cable sheathing, type 

metal, and ammunition. It is significant to note, 

however, that only the lead used in paint pigments 

and ammunition and in tetraethyl lead fluids and 

other chemical compounds is nonrecoverable. Much 

of the lead used for other purposes, particularly as 

grids in storage batteries, is recyclable and eventually returns to the market in the form of scrap. 

From 1951 to 1971, the consumption of lead in 

the United States increased from 1,185,000 short 

tons to 1,380,000 short tons, an increase of 16.5 percent, whereas increase in world consumption, from 

approximately 2,170,000 short tons to approximately 

4,563,000 short tons, was 110 percent (U.S. Bur. 

Mines unpub. data, 1972). The burgeoning world 

consumption of lead as compared with United States 

consumption is attributed to the expanding use of 

passenger automobiles, trucks, and other modes of 

transportation and to the growth of the communications industry throughout the world, especially 

in Europe and Japan. 

OUTLOOK 

According to the U.S. Bureau of Mines survey 

(Paone, 1970, p. 615), projection of population 

growth statistics, consumption data, and other 

factors to the year 2000 indicate a continuing increase in the United States demand for lead in the 

production of storage batteries, leaded gasoline, 

bearings, and possibly in the construction industry; 

in contrast, only moderate to small increases are 

forecast for the use of lead in small-arms ammunition, insecticides, packaging, and radiation shields, 

and decreases are anticipated in the printing industry and in the manufacture of paint pigments. As 

noted by Paone (1970, p. 615), the U.S. demand for 

lead for storage batteries and leaded gasoline may 

be expected to triple or quadruple during the next 

30 years, whereas the demand for other uses is 

expected to show only a fractional increase or an 

actual decrease. The current antipollution standards, 

if rigorously applied during this interval, undoubtedly will substantially modify the projected increase 

for leaded gasoline through the greater use of diesel 

engines, gas turbines, and electric vehicles and by 

the continued development of low-lead or lead-free 

high-octane gasolines. Similarly, the successful development of lightweight sodium-sulfur and lithiumor sodium-water batteries may substantially diminish the demand for the heavier, le!itd-acid batteries 

despite the expected increase in the total number 

of accessorized automobiles and trucks and electric 

vehicles by the year 2000. 

All things considered, the large domestic resources 

of lead appear to be adequate to supply an increasingly larger proportion of the needs of the United 

States, at least to the year 2000, despite the rapidly 

expanding consumption of the rest of the world. 

EXPLOITATION 

Production of primary lead in the world and in 

the United States and the United States consumption of lead from all sources are summarized in 

figure 39. It is estimated, in part using data presented by Smith (1929), that world production 

from prehistoric time to 1969 was about 151,162,000 
316 UNITED STATES MINERAL RESOURCES 

(I) 

z 

0 

~ 

~ 

a: 

0 

:I: 

4 

3 

(I) 2 

"" 0 

(I) 

z 

0 

J 

.J 

i 

4 

3 

(/) 

z 

0 

~ 

(.J 

a: 

~ 

w 

2 ::! 

0 "" 

(I) 

z 

Q 

.J 

.J 

0 0 

1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 

FIGURE 39.-Production of primary lead in the world and in the United States, 1830-1971, and consumption of lead, including scrap, in the United States, 1918-71. Data from U.S. Geological Survey, U.S. Bureau of Mines, and American 

Bureau of Metal Statistics. 

short tons. Of this amount, less than 5 million tons 

is estimated to have been produced prior to 1800, 

25,167,000 tons from 1801 to 1900, and 120,995,000 

tons from 1901 to 1969. Production during the next 

decade will certainly exceed the production of the 

entire 19th century. 

The significant variations in the production curves 

of lead for both the United States and the world are 

largely related to political and economic factors 

rather than to the discovery of large ore deposits 

or to technological advancements in mining, milling, 

or smelting. The effects of major events on world 

production of lead include: (1) a leveling of production during World War I, (2) a small decline 

during the postwar economic recession of 1919-21 

followed by a steep rise in production, (3) a second 

decline during the depression years of the early 

1930's, also followed by a steep rise, and ( 4) a 

third major decline, essentially coincident with 

World War II, followed by a rise in production that 

has been relatively unbroken since 1946. The United 

States production through 1940 in general shows the 

same perturbations as the world production but 

differs in some respects. During the period 1916-

18, a slight increase in production reflects increased 

U.S. exports, presumably to the warring nations of 

western Europe. The decade of prosperity between 

the economic recessions of 1920 and 1930 did not 

result in a rise in U.S. production comparable in 

magnitude to the rise in world production; during 

this interval the United States became a significant 

importer of lead. After the depression years of the 

1930's our highest domestic production was onethird less than in the best predepression years, and 

production generally declined from 1942 to 1962, 

largely as a result of depletion of many of our 

major deposits. Since 1962, approximately the time 

of the first production from the new mines in the 

Viburnum area of southeast Missouri, U.S. production has increased; by 1970 it had reached 572,000 

tons. 

The current and future discovery and exploitation 

of lead deposits throughout the world will undoubtedly continue to be controlled more by economic, 

political, and environmental considerations than by 

technological advances. In recent decades such advances have more than offset the losses in production resulting from the exhaustion of many small 
LEAD 817 

high-grade deposits, particularly those that produced lead as a coproduct with silver and other 

metals. These advances include the development of 

high-volume mining and milling techniques that 

have allowed the profitable exploitation of large 

low-grade disseminated ore bodies ; the successful 

application of new techniques of continuous smelting of intimately mixed zinc and lead ores; the 

recovery ~f byproduct lead concentrate from the 

milling of massive sulfide ores in Sweden, Japan, 

and elsewhere ; and, most importantly, the continued discovery and development of conventional types 

of ore bodies. Certain trends, however, tend to indicate a softening demand for lead in the future, 

particularly in the United States and Western 

Europe. These trends include severe limitations on 

the permissible levels of sulfur dioxide, lead oxide, 

and other emissions from smelters ; significant reductions in the lead content of high-octane gasoline; 

the virtual elimination of lead oxides in paint;· and 

the substitution of other substances for the lead 

used in cable sheathing, type metal, and other applications. Whether or not increased consumption 

of lead in some uses (such as batteries) will offset 

declining consumption in other uses (such as tetraethyl lead gasoline additive) over the near term is 

difficult to predict. It seems certain, however, that 

world production and consumption of newly mined 

lead will increase over the long term, but eventually 

must decline as the primary sources approach exhaustion and the recycling of scrap lead increases. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Lead is a chemical element of atomic number 82. 

The atomic weight varies because of variations in 

isotope composition which are due to unequal incorporation of radiogenic lead, the product of 

atomic decomposition of both uranium and thorium. 

Common lead of isotopic composition Pb204 1.5 percent, Pb206 23.6 percent, Pb207 22.6 percent, and 

Pb208 52.3 percent has an atomic weight of 207.2. 

Lead occurs in nature rarely as the metallic element 

and in the quadrivalent state but predominantly in 

the divalent state with an ionic radius of 1.26 A 

for sixfold coordination. Commonly it diadochically 

replaces Ba +2 (1.44 A), Sr+2 (1.21 A), and K +1 

(1.46 A) in the lattice of certain silicates, phosphates, and other minerals. 

Lead is the 34th most abundant element in the 

lithosphere, averaging about 15 ppm (parts per 

million) . In crustal abundance, it ranks not only 

below copper and zinc but also below such less common and even rare elements as yttrium, neodymium, 

lanthanum, and possibly gallium (Mason, 1958, p. 

44). In igneous rocks it ranges in concentration 

from approximately 5 ppm in gabbro and related 

rocks to 10 ppm in oceanic crust and approximately 

20 ppm in granite. Typical concentrations in sedimentary rocks range from an average of 7 ppm in 

sandstone and 9 ppm in carbonate rocks to 20 ppm 

in shales; deep-sea clays reportedly average 80 ppm 

(Turekian and Wedepohl, 1961, table 2). Inasmuch 

as lead ores of minimum minable grade average 

about 4 percent, they represent a concentration factor of 2,600 times the average crustal composition, 

or about 2,000 times the average concentration in 

granite. 

Lead appears to be chiefly siderophile, according 

to Rankama and Sahama (1950, p. 729-730), although it may also be chalcophile; in the lithosphere 

it shows a rather pronounced affinity for sulfur and 

also for oxygen. Lead is essentially absent as an 

early magmatic sulfide and is particularly enriched 

in pneumatolytic and hydrothermal solutions genetically associated with quartz-bearing igneous 

rocks. It is the major constituent of more than 200 

known minerals. 

In primary ore deposits, lead oc·curs predominantlJl 

as the sulfide. During weathering, this sulfide is slowly oxidized to lead sulfate, a process that is facilitated by the concurrent oxidation of the commonly 

associated pyrite to ferric sulfate, which acts as an 

oxidizing agent. The lead sulfate, which is only moderately soluble, and therefore relatively stable, is in 

turn converted by the action of carbon dioxide or 

soluble bicarbonates to the even more stable lead 

carbonate, which is the most chemically resistant 

lead compound in the zone of oxidation. Other rarer 

compounds that may be formed in the oxidation 

zone include arsenates, chlorides, vanadates, phosphates, chromates, and molybdates. In time even the 

stable lead carbonate is physically disaggregated or 

is taken into solution as the moderately soluble lead 

bicarbonate and finds its way to the sea. 

ORE MINERALOGY 

In the wide variety of lead-producing deposits 

throughout the world, the overwhelmingly dominant 

ore mineral is galena (PbS). This metallic, steel-gray 

mineral with perfect cubic cleavage is one of the 

most widely distributed and easily recognized ore 

minerals. Very commonly it contains silver, usually 

as occluded blebs of argentite (Ag2S), argentiferous 

tetrahedrite (3[Cu · Ag]2S·Sb2Ss), and similar minerals; it becomes silver ore when the value of silver 

exceeds that of the contained lead. Near the surface, 
318 UNITED STATES MINERAL RESOURCES 

many of the galena ore bodies are altered to cerussite (PbCOa), anglesite (PbS04), pyromorphite 

(Pb4[PbCl] [P04]a), and other minerals, but commercial ores consisting chiefly of these secondary minerals now represent only a small fraction of the total 

volume of lead ores currently being produced. A 

great many other metallic lead minerals have been 

recognized, including many silver-, copper-, bismuth-, 

and antimony-bearing sulfosalts that are important 

sources of silver and other metals. Only rarely are 

these minerals found in concentrations large enough 

to produce a significant quantity of lead. 

The primary metallic minerals most commonly associated with galena include pyrite (FeS2), sphalerite (ZnS), chalcopyrite (CuFeS2), tetrahedrite 

(SCu2S·Sb2Sa) or tennantite (SCu2S·As2Sa), argentite, bournonite (3PbS · Cu2S · Sb2S3), and other sulfosalts, and, locally, marcasite (FeS2) and pyrrhotite 

(Fe7Ss). Sphalerite, in particular, is such a common 

associate of galena that sphalerite-free galena ore 

bodies and galena-free sphalerite ore bodies are rare. 

The primary gangue minerals found in lead deposits 

include quartz in various forms; calcite, dolomite, 

and other carbonates; barite; and fluorite. Some of 

these minerals, as well as many of the associated 

minor metallic minerals, commonly are recovered as 

coproducts and byproducts. 

TYPES OF DEPOSITS 

The ore bodies in which galena is a major or arecoverable minor constituent have been deposited in 

a wide variety of physical and chemical environments. They are most effectively classified on the 

basis of their geologic occurrence as: (1) stratabound deposits of syngenetic origin, (2) stratabound or stratiform deposits of epigenetic origin, (3) 

volcano-sedimentary deposits and their metamorphic 

equivalents, ( 4) replacement deposits, including mantos, (5) veins, and (6) contact pyrometasomatic 

deposits in the aureoles of granitic plutons. As with 

other types of classification systems, the above 

scheme is not wholly satisfactory, inasmuch as one 

type of deposit-such as a vein-may gradually assume the characteristics of another type-such as a 

replacement deposit. Also, there is much disagreement among geologists and geochemists as to the 

genesis of many ore bodies, rarticularly the stratabound deposits, which may have either a syngenetic 

or an epigenetic origin. As pointed out by Brown 

(1970, p. 108), it is remarkable that so many wellqualified authorities can examine the same set of 

facts about the strata-bound ore bodies and reach 

such widely different conclusions as to their genesis. 

In recent years, however, studies of fluid inclusions 

and of lead, sulfur, and oxygen isotopes and their 

ratios in various deposits of unquestioned origin appear to have helped resolve questions of the origin of 

some previously enigmatic ore bodies. (NOTE.-Usage of the terms "strata-bound" and "stratiform" in 

this chapter is somewhat different from usage in 

some other chapters.) 

STRATA-BOUND DEPOSITS OF SYNGENETIC ORIGIN 

The largest and most productive lead deposits are 

those that are apparently restricted to one or more 

sedimentary rock units, chiefly limestone, dolomite, 

or shale. Many of these deposits underlie areas exceeding several square kilometers and are, in fact, 

merely the richer parts of broadly mineralized terranes that extend for many hundreds or even thousands of square kilometers. Detailed studies commonly reveal that these deposits may be further 

divided into two general types: those in which the 

ore minerals were deposited syngenetically with the 

enclosing sediments or formed shortly afterward as 

a result of diagenetic processes and those in which 

the ore minerals chiefly occur in secondary features 

and commonly are enclosed within aureoles of secondary dolomitization or some other form of postdiagenetic alteration. Although deposits of the latter 

type have many features in common with the replacement deposits, particularly the mantos, they 

generally differ in the absence of any clear evidence 

of their association with igneous rocks. These epigenetic deposits are discussed separately. 

The strata-bound ores of syngenetic origin are 

typified by the "Kupferschiefer" bed, near the base 

of the Zechstein Formation, which is currently being 

mined in East Germany in the area of Mansfeld, 

Richelsdorf, and Sangerhausen and in Poland in the 

Subsudetic syncline. This layer of bituminous shale 

is commonly 1 meter or less thick; it locally overlies 

a patchy marine conglomerate, the first stratum 

deposited· in the Upper Permian basin of central 

Germany, and underlies a sequence containing limestone, gypsum, halite, and sandstone. It is reportedly 

mineralized over an area of 4,560 square kilometers 

(Bauchau, 1971, p. 5). The ore minerals are finely 

disseminated through the shale and consist predominantly of bornite, chalcocite, galena, sphalerite, 

and tetrahedrite. Accessory elements include nickel, 

cobalt, selenium, vanadium, molybdenum, and silver. 

There are virtually no gangue minerals except for 

wispy veinlets of barite and gypsum. Here and there 

the Kupferschiefer is cut by small faults, and near 

them the bed may be either enriched or impoverished 

in the metals; locally, some of these faults contain 
LEAD 319 

secondary ore minerals and have been mined as 

lodes. 

The general grade of the Kupfers·chiefer bed that 

has been mined for its copper content is 2-3 percent 

copper, 1.3 percent zinc, about 1.5 percent lead, and 

approximately 4 ounces per short ton silver. Elsewhere, the content of zinc and lead is higher, as at 

Uftrungen, where the bed averages 2.5 percent lead 

and 1.7 percent zinc (Deans, 1950, p. 343). Overall, 

the Kupferschiefer may contain an average zinc and 

lead concentration more than 10 times higher than 

that of copper (Wedepohl, 1971, p. 269). 

The genesis of the Kupferschiefer has been the 

subject of much controversy. Most geologists who 

have studied the deposits favor a syngenetic origin 

because of the virtual restriction of the ore minerals 

to a thin stratum that is rich in organic carbon, 

the fine dissemination of the ore minerals, the apparent bacterial origin of the contained sulfur, the 

patterns of both vertical and regional zonation of the 

ore metals, and the wide occurrence of ore minerals 

in correlative units in western Poland, western Germany, and northeast England. According to RichterBernburg (1941), however, the metals occur in the 

Kupferschiefer in such great volume that they could 

not have been derived entirely from the denudation 

of ore deposits in the surrounding landmasses during 

the short time available for deposition of the thin ore 

bed. He suggested that they were enriched over a 

long period of time in deep-lying ground water, which 

later rose to mingle with the early Zechstein sea. 

Wedepohl (1971), in a more recent study, favored 

the gradual deposition of metals in the anoxic bottom 

waters of the Kupferschiefer sea as it transgressed 

over a peneplane cut into red-be~ country rocks. He 

further stated that time factorff' and the occurrence 

of the main ore-bearing zones at the margins of the 

Kupferschiefer sea virtually rule out an origin from 

submarine springs of cryptovolcanic affinity. 

Although other possibly syngenetic strata-bound 

deposits of copper are not uncommon, particularly in 

south-central Africa, lead-bearing deposits of unquestioned syngenetic origin are rare. Strata-bound 

deposits of lead minerals in the Precambrian Belt 

Supergroup of northern Idaho and northwestern 

Montana have recently been described by Clark 

(1971). In this area, the somewhat better explored 

strata-bound copper deposits-whose origin is still 

in debate (see "Copper" chapter)-are locally overlain by zones of galena-impregnated rock that contain as much as 6 percent of lead. Unlike the Kupferschiefer, the host rocks are most commonly carbonate-rich quartzite and siltite, and zinc minerals are 

rare to absent. Deposits that are closely similar to 

the separated strata-bound copper and lead deposits 

of the Belt Supergroup have been described at Dzhezkazgan in central Kazakhstan by Shcherba (1971, p. 

173--174). It should also be noted that many stratabound deposits in Europe and northern Africa, considered by European geologists to be syngenetic, 

have many of the characteristics of the stratiform 

epigenetic deposits described in the following section. 

(See Brown, 1970.) 

STRATA-BOUND DEPOSITS OF EPIGENETIC ORIGIN 

Ore deposits that are essentially restricted to one 

or a few well-defined tabular stratigraphic units, 

chiefly limestone or dolomite, but which are clearly 

younger than the lithification of the host rocks and 

are not obviously related to any jgneous rocks, account for most of the lead that has been produced 

in the world or is known as reserves (Bauchau, 1971, 

p. 9). For some of these deposits, the widely used 

term "strata-bound" may be misleading. As noted by 

Brown (1970, p. 104), the ores occur mainly in certain preferred horizons or strata, and most are sufficiently conformable to bedding to be described as 

stratiform; as the ore bodies commonly occur in 

several formations of different ages, however, they 

also may be closely related to cross-breaking fractures, breccia pipes, and other tectonic features. 

In general, the most common host rocks of the 

epigenetic stratiform deposits are shallow-water 

marine carbonate rocks. In many areas they are most 

heavily mineralized near the rims of the sedimentary 

basins, adjacent to domelike positive areas, at facies 

contacts within the basins, or near unconformities 

within the basin strata. The minerals of the deposits 

consist predominantly of galena, sphalerite, and pyrite or marcasite. In some mines chalcopyrite, siegenite ([Co,Ni]aS.i), and other sulfides are present, and 

nickel, cobalt, and copper, as well as cadmium, silver, 

and germanium, are recovered as byproduct metals. 

In many deposits, the ore consists predominantly of 

either galena or sphalerite. In some deposits in the 

Kentucky-Illinois, central Kentucky, and central 

Tennessee districts, barite or fluorite are major coproduct constituents, but elsewhere the gangue minerals commonly include only calcite, dolomite, and 

jasperoid. 

The epigenetic stratiform deposits are typically 

flat lying, although in central Kazakhstan and elsewhere subsequent tectonic activity may have compressed some of them into folds or tilted them steeply within fault blocks. The ore bodies are characteristically large and commonly are localized by stratigraphic pinch-out zones, by masses of breccia of 

diverse origin, by zones of minor faults and frac-
320 UNITED STATES MINERAL RESOURCES 

tures, or by bioherms and associated sedimentary 

and organic features. Typically, ore does not occur 

on faults of large displacement, although it commonly occurs adjacent to them. The prevalent occurrence 

of the ore bodies in carbonate rocks is probably related to the tendency of these rocks to fracture 

readily and to produce breccias, to develop zones of 

secondary porosity and even karst environments during periods of preore ground-water movement, and 

to be highly soluble and reactive. Many individual 

ore bodies form runs of ore that are several hundred 

feet wide and 100-200 feet high and have been followed for a mile or more, each containing several 

million tons of ore. In the Southeast Missouri lead 

district the average grade of ore in the epigenetic 

stratiform deposits is 3-8 percent lead, 0.5-1 percent 

zinc, and 0.10 percent copper; nickel, cobalt, cadmium, silver, germanium, and indium are present in 

minor amounts. In northeastern Morocco, similar 

deposits contain 5-7 percent lead in the form of 

galena and also contain sphalerite, chalcopyrite, and 

secondary dolomite. 

A few of the larger and better known districts containing strata-bound deposits of epigenetic origin 

include the Southeast Missouri (Snyder and Gerdemann, 1968), Tri-State (McKnight and Fischer, 

1970; Brockie and others, 1968), Upper Mississippi 

Valley (Heyl, 1968), and Metaline (Dings and Whitebread, 1965) districts in the United States, the Pine 

Point deposit in Canada (Campbell, 1967), Laisvall 

in Sweden (Grip, 1950, p. 367-369), MechernichMaubach and other districts in West Germany (Behrend, 1950), Silesia-Cracow in Poland (Galkiewicz, 

1967; Gruszczyk, 1967), Touissit-Bou Beker and other areas in Morocco (Agard, 1967; Jouravsky and 

others, 1950), and Mirgalimsai, Kazakhstan ( Shcherba, 1971, p. 173). Other countries that contain epigenetic strata-bound lead deposits include Spain, 

France, Belgium, Austria, Italy, and Tunisia. Similar 

districts here believed to have emerging and potential 

importance as lead-producing areas in the United 

States include the Kentucky-Illinois and central Kentucky districts and the recently discovered central 

Tennessee district. Older districts of the same general type that may continue to be important sources 

of lead include the Alpine lead-zinc deposits of 

Europe and the lead and zinc deposits of the Appalachian Valley of the Eastern United States. 

Continuing detailed studies of the epigenetic 

stratiform deposits throughout the world indicate 

that although these deposits are similar in size and 

geological character, they differ in important geochemical details. In general, they may be divided into 

three types: (1) the Upper Mississippi Valley type, 

(2) the Alpine type, and (3) the stratiform or stratabound deposits of normal replacement origin. The 

Mississippi Valley type deposits are named from the 

extensive lead and zinc ore bodies in the Tri-State, 

Southeast Missouri, Upper Mississippi Valley, and 

other districts in the Central United States but are 

also recognized in Europe and elsewhere. As stressed 

by Brown (1970, p. 116-117), they are characterized 

by isotopically anomalous lead of the J-type, which 

contains an excess of the three radiogenic components Pb206, Pb207, and Pb208, indicating a "future" 

age. In ore bodies from which an appreciable number 

of analyses are available, the J-type lead has a fairly 

wide range in its isotopic character, indicating that 

the solutions from which it was deposited were not 

magmatic in origin. Isotopic analyses of the sulfur in 

the Mississippi Valley type deposits show that it is 

within the range of sulfur of biogenic origin, the sulfur of connate brines, and normal depositional sulfides in sedimentary rocks. 

Studies of fluid inclusions in the sulfide and gangue 

minerals of the Mississippi Valley type ore bodies 

suggest that they were deposited from metal-rich 

brines of moderate salinity at temperatures of 70°-

150°C. These brines are of the Na-Ca-Cl type--

about five to 10 times as concentrated as sea waterand closely resemble the connate waters found in oil 

fields in adjacent sedimentary basins. The source of 

the metals is unknown; the sources favored by most 

geologists who have worked in the Mississippi Valley 

districts are the rocks and saline deposits of the 

sedimentary basins or, in particular, the igneous and 

metamorphic rocks of the crystalline basement beneath the ore-bearing strata. The tendency for many 

of the deposits to be localized in stratigraphic traps 

on the flanks of broad domes suggests that during a 

period of minor tectonic deformation, connate brines 

containing metals and other components of the ore 

bodies that had been leached from adjacent rocks 

migrated upward along new and preexisting conduits. Ore deposition then followed as a result of 

chemical and physical changes in the brines when 

they reached the sites of ore deposition. 

The Alpine lead deposits are similar in many respects to the Mississippi Valley type deposits but 

differ from them in containing B-type lead, whose 

isotope composition indicates an age older than that 

of the rocks and structures that enclose the ore 

bodies. As noted by Brown (1965, p. 65), the isotope 

composition of the lead in a large number of stratiform deposits in central Europe indicates an essentially uniform Devonian age, although the ore bodies 

occur in strata ranging in age from Devonian to Triassic. Such leads may have been carried by connate 
LEAD 321 

fluids that percolated through the older Paleozoic 

strata and later were mixed with a minor proportion 

of younger lead derived from the host rocks or the 

prevailing oceans at the date of deposition (Brown, 

1970, p. 109). The specific origin of the metals in 

these deposits and, their environment of deposition 

are the subject of much vigorous debate among European geologists, some of whom favor a syngenetic or 

a meteoric origin for the deposits. 

Strata-bound or stratiform deposits that closely 

resemble the Mississippi Valley- and Alpine-type dep-osits but contain lead whose apparent isotopic age 

is the same as the apparent age of ore deposition, 

constitute the third class of strata-bound epigenetic 

deposits. These ore bodies are genetically similar to 

the vein and replacement deposits described in the 

following sections. An example of such a deposit is 

Pine Point in Canada, which contains lead from a 

homogeneous source with model age of about 2.50-

275 million years, appreciably younger than the 

Devonian host rocks (Cumming and Robertson, 

1969). Additional examples may be found among the 

Appalachian Valley lead and zinc deposits of east 

Tennessee, Virginia, and Pennsylvania and in other 

stratiform deposits in other parts of the world. 

VOLCANO-SEDIMENTARY DEPOSITS 

The second most productive deposits of lead and 

zinc are lenticular bodies of massive sulfides that are 

conformable or semiconformable with interstratified 

volcanic, volcano-sedimentary, and sedimentary 

rocks. These deposits range from the relatively little 

deformed Kuroko deposits of Miocene age in Japan 

to the recrystallized massive deposits of Paleozoic 

and Precambrian ages in metamorphic rocks in other 

parts of the world. Some of these latter deposits form 

the largest individual concentrations of metal sulfides yet discovered. 

The unmetamorphosed volcano-sedimentary, or 

Kuroko, deposits of Japan are massive pods and 

lenses of various sizes composed of intimate mixtures of sphalerite, galena, some chalcopyrite, accessory sulfosalt minerals, barite, and gypsum (Kinoshita, 1931; Horikoshi, 1969). Byproducts of gold, 

silver, tin, tungsten, arsenic, barite, and other elements are recovered locally. The deposits occur chiefly in shale, sandstone, green tuff, and other clastic 

volcano-sedimentary rocks of Miocene age. Many 

show a zonal arrangement with lead- and zinc-rich 

ore (kuroko) in the center, chalcopyrite- and pyriterich ore (oko) forming an intermediate zone, and 

silica-rich pyrite ore (kieko) forming an irregular 

outer zone next to gypsum-rich altered country rock 

(Japan Geol. Survey, 1960, p. 141). The deposits are 

essentially parallel to the stratification of the enclosing volcano-sedimentary rocks, but many are obviously replacement deposits and are surrounded by 

envelopes of altered rocks. One of the larger ore 

bodies, the Matsumine, is more than 1,000 meters 

long, 500 meters wide, and 30 meters thick and 

originally contained 30,000,000 metric tons of ore. 

The grade of this ore body is estimated to be 2--2.5 

percent copper, 1 percent lead, 3.5 percent zinc, and 

17-24 percent sulfur (Maruyama and Sa to, 1970, p. 

177) . Other minable Kuroko deposits range downward in size to the Suehiro ore body, 50 meters long, 

40 meters wide, and 30 meters thick, which contains 

about 40,000 metric tons of ore that averages 4.7 percent copper, 1.7 percent lead, 3.8 percent zinc, and 

20.2 percent sulfur (Maruyama and Sato, 1970, p. 

177). Some parts of many Kuroko ore bodies, however, consist essentially of massive galena and marmatitic sphalerite. 

Geologic and mineralogic relations indicate that 

the Kuroko ore bodies were formed by submarine 

exhalative processes during the geosynclinal accumulation of their country rocks. They are most commonly found as replacements of water-laid tuffs and 

similar rocks beneath caprocks of lava on the flanks 

of domes that are cored by rhyolite intrusions. Some 

of the deposits merge downward with veins and 

stockworks that may represent the conduits for the 

relatively low temperature mineralizing solutions 

that formed the massive ore bodies. 

Deposits somewhat similar to the Kuroko deposits 

have been described at Atasu and Achisai in Kazakhstan by Shcherba (1971, p. 172-17 4). 

Massive sulfide deposits in metamorphic rocks 

have many features in common with the Kuroko deposits including large size, common association with 

volcanic rocks, strata.. bound or stratiform character, 

simple mineralogy with abundant iron sulfide, and an 

absence of obvious structural localization. Some of 

them differ from the Kuroko deposits in containing 

somewhat higher concentrations of lead and zinc, 

and in being somewhat coarser textured; both features may be attributable to recrystallization during 

metamorphism. It is possible that many of these 

deposits are large replacement bodies that were emplaced long after lithification, uplift, and even metamorphism of the country rock. However, a submarine-exhalative origin is suggested by their 

apparent concordant nature, their independence from 

faults and other structural features, and the common 

absence of nearby intrusive bodies. 

As a group, the massive sulfide deposits in metamorphic rocks range in size from small pods containing only a few tons or less to enormous bodies con-
322 UNITED STATES MINERAL RESOURCES 

taining more than 100 million tons. The ore is 

commonly fine grained, consisting of intimate aggregates of pyrite or pyrrhotite, sphalerite, galena, 

and chalcopyrite, with minor or subordinate amounts 

of quartz, sericite, chlorite minerals, ankerite, and 

other carbonate minerals. Host rocks include argillite, metavolcanic rocks, schists of various mineral 

associations, shale, and carbonate rocks. In folded 

terranes, the ore bodies are typically, but not invariably, found on the limbs of folds. In such widely 

separated places as Bathurst, New Brunswick, 

Jerome, Ariz., and Broken Hill, New South Wales, 

the ore bodies are intimately associated with metamorphosed quartz porphyry. 

As typified by the Bathurst deposits, individual 

ore lenses may be 3,000 feet or more long and as 

much as 250 feet wide and may extend to depths 

greater than 1, 700 feet. Zones of en echelon ore 

lenses in the Bathurst area are nearly a mile long 

(Gates, 1971, p. 113). The grade of the larger concentrations of lead and zinc ores in the irregularly 

zoned Brunswick and Heath Steele ore bodies is 

close to 3-3.5 percent lead and 8. 75 percent zinc; 

copper, silver, and gold are also recovered. Additional examples of volcano-sedimentary deposits in 

metamorphic rocks include numerous mines in Norway (Vokes, 1962), Sweden (Kautsky, 1957), 

U.S.S.R. (Smirnow, 1960), especially Leninogorsk 

and adjacent areas (Nekhoroshev, 1941), and elsewhere (Anderson, 1969). Other great massive ore 

deposits of the world, such as Mount Isa and Broken 

Hill in Australia, Rammelsberg and Meggen in West 

Germany, Kidd Creek and Sullivan in Canada, and 

Ducktown in the United States, may have originated 

as volcano-sedimentary deposits, but conclusive evidence of their origin has not been established or may 

have been obliterated by metamorphism, recrystallization, or subsequent tectonism. 

REPLACEMENT DEPOSITS 

The third most productive source of primary lead 

is hydrothermal replacement ore deposits that are 

commonly associated with postorogenic intrusions 

of intermediate to acid composition. Most commonly 

these deposits occur in such readily soluble rocks as 

limestone and dolomite, but they also occur in 

quartzite and shale and in igneous and metamorphic 

rocks. They range in size from insignificant pods 

to extensive masses like the Cerro de Pasco ore body 

in Peru, which may have originally contained more 

than 2.3 million tons of galena, 6 million tons of 

sphalerite, and 100 million tons of pyrite, and significant amounts of other hydrothermal minerals 

(recalculated from Peterson, 1965, p. 446). In most 

of the replacement deposits the dominant lead mineral is galena, which is associated with sphalerite, 

chalcopyrite, and pyrite. In many deposits, silver, 

arsenic, antimony, and cadmium are also abundant, 

giving rise to a great variety of arsenides, antimonides, and sulfosalts. Oxidation, which locally 

extends to considerable depth, results in a still 

greater variety of minerals and commonly aids in 

the enrichment of some lead ore by the solution and 

migration of more soluble constituents. 

The form and size of replacement ore bodies are 

largely ~etermined by the chemical character of 

their host rocks and the geologic structures that 

localize the deposits. In less readily soluble igneous 

and metamorphic rocks and in quartzite and other 

refractory sedimentary rocks, replacement deposits 

commonly assume, wholly or partly, the form of 

such structural features as tabular fault and shear 

zones, pipe-shaped masses of intrusion breccia, flatlying beds or layers of porous tuff, agglomerate, and 

similar rocks, or podlike masses of breccia of diverse 

origin. In the more soluble carbonate rocks, the replacement deposits similarly assume the general 

character of the localizing structural or stratigraphic feature, but they also typically extend irregularly and unpredictably along a variety of minor 

or obscure features, producing ore bodies that are 

highly irregular and branching. In gently dipping, 

relatively unfractured carbonate rocks, particularly 

in central Mexico and central Colorado, the replacement bodies form flat-lying tabular bodies and nearhorizontal pipelike bodies-both called mantos; 

these bodies commonly extend outward along one 

or more selected horizons from vertical columns or 

chimneys of ore that are several hundred feet high, 

which may or may not be localized by recognizable 

fractures (Prescott, 1926). Most of the important 

replacement deposits contain a few hundred thousand to a few million tons of ore. Many of them are 

small, but some exceed 100 million tons. The grade 

is commonly of the order of 10-30 percent of lead 

and zinc combined, 3-5 percent copper, 5-50 ounces 

per ton silver, and a few hundredths of an ounce of 

gold per ton. Some deposits show a pronounced 

vertical or lateral zonation of the metals. 

Examples of some of the more important massive 

replacement ore deposits include Tintic, Utah (Morris, 1968), Bingham, Utah (Rubright and Hart, 

1968), Gilman, Colo. (Tweto and Lovering, 1947), 

Leadville, Colo. (Emmons and others, 1927; Tweto, 

1968), central Mexico (Prescott, 1926), central 

Peru (Peterson, 1965), Sardinia, Italy (Novarese, 

1950), Trepca, Yugoslavia (Forgan, 1950), Cartagena, Spain (Pavilion, 1969), Tsumeb, South West 
LEAD 828 

Africa (Tsumeb Corp. Ltd., 1961), Turlan, U.S.S.R. 

(Knyazev, 1954), and many others. Deposits of 

doubtful replacement origin include the Broken Hill, 

Mount Isa, and Hilton ore deposits in Australia, the 

Sullivan ore body in Canada, and one or more of the 

massive sulfide deposits in the metamorphic terranes pf Scandinavia. 

The1 environments of deposition of hydrothermal 

replacement deposits range from high pressures and 

essentially magmatic temperatures to low temperatures and a few atmospheres of pressure. Studies 

of fluid inclusions, isotopic ratios, and the stability 

fields of minerals and mineral associations indicate 

that the highly productive limestone replacement ore 

bodies were deposited from brines of moderate 

density at temperatures ranging from 175°C to 

500°C and at pressures of 140 to 400 atmospheres. 

Commonly the terminal phases of ore deposition 

show relatively low temperatures. Prospecting for 

these ore bodies in areas where they are entirely 

concealed is often expensive, frustrating, and unrewarding. 

VEINS 

Tabular or sheetlike masses of ores that occupy 

a fracture or sets of fractures are perhaps the most 

widespread and best known type of ore deposit. In 

past centuries they have been the principal source 

of lead ores, and today they are the chief type of 

deposit being mined in several highly productive 

mining districts, including the famous Coeur d'Alene 

district of Idaho. Veins are found in all types of 

rocks, assuming all possible attitudes and directions. 

The simplest veins are those in which the ore and 

gangue minerals partly or wholly occupy the original open spaces along a fracture. Filled veins completely occupy a fracture, commonly leaving no 

residual masses of country rock; many of them are 

banded, and some show evidence of rebrecciation 

and renewal of ore deposition. Replacement veins, 

which generally occur in limestone and other reactive rocks, so extensively replace their walls that 

the character of the localizing fracture is commonly 

obliterated and the veins become indistinguishable 

from massive replacement deposits. In most districts, veins occur in groups or systems of subparallel trend, in which individual veins branch and 

divide, commonly joining with adjacent veins by 

means of diagonal structures. They range in width 

from narrow seams to exceptional deposits that are 

50 feet or more wide. Networks of narrow, short 

veins, or close-spaced "horsetail" vein systems 

locally are mined as stockworks or compound lodes. 

Persistent veins follow faults of moderate to large 

displacement; in the Harz Mountains, Germany, 

some of the lead-bearing veins are traceable for 12 

miles, and in the Silverton area, Colorado, single 

ore-bearing fissures are 5 miles or more in length 

(Lindgren, 1933, p. 164). The vertical extent of 

most veins is generally less than their length. Some 

disappear within a few tens of feet below the surface; others have been followed downdip for as much 

as 10,000-11,000 feet. Because of greatly increased 

operating costs at depth and the relatively small 

volume of ore in most ore shoots, only those basemetal veins with a high proportion of gold or silver 

can be mined below 2,000-3,000 feet. 

Few veins contain ore of minable grade for their 

entire length or depth. The ore minerals are concentrated in ore shoots, which may be enclosed in 

halos of low-grade material or separated by 

stretches of barren gangue minerals. The shoots 

have a wide range of size, shape, and continuity, 

ranging from small bunches or kidneys to great 

vertical or horizontal sheets, or to narrow vertical 

pipes. They may occur at places where there is a 

change in the strike or dip of the vein or in the 

character of the wallrocks, or at vein intersections. 

Recognition of such habits is useful in exploring for 

new ore shoots, although more subtle factors related to changes in the temperature, pressure, and 

chemistry may have been predominant in the precipitation of the ore metals. In the Coeur d'Alene 

district of Idaho, the highly productive Star-Morning ore shoot has a dip length of 6, 700 feet, a strike 

length of about 4,000 feet, and a maximum width of 

about 50 feet (Hobbs and Fryklund, 1968, p. 1426). 

In contrast, the lead ore shoots in the North Pennine district of England, which are localized at the 

traces of relatively thin beds of hard limestone and 

sandstone along the vein, are as much as 3,000 feet 

in length but extend only 65 feet from top to base 

although they are locally connected with other overlying and underlying horizontal ribbon ore shoots 

by steep pipe-shaped ore shoots as much as 585 feet 

long (Dunham, 1949, p. 77-78). 

In mineralogy and grade, the lead-producing ore 

shoots in veins are similar to the replacement and 

other type of ore bodies. The dominant minerals are 

galena and sphalerite and pyrite. In some deposits, 

argentiferous tetrahedrite, chalcopyrite, silver-lead 

sulfosalts, and, rarely, cobalt, nickel, and uranium 

minerals are also important. Gangue minerals commonly include quartz, siderite, calcite, barite, and 

fluorite. The grade of ore ranges from a few percent to as much as 50 percent or more combined 

lead and zinc. As indicated, many lead-producing 

veins are mined chiefly for their content of silver 
324 UNITED STATES MINERAL RESOURCES 

and other metals, or for fluorite, barite, or calcite. 

In addition to the great Coeur d'Alene district of 

Idaho and the North Pennine district of England, 

other examples of highly productive vein-type lead 

deposits include the classic districts of Clausthal, 

West Germany, Freiberg, East Germany, and Pribram, Czechoslovakia (Berg, 1927), Santa Barbara, 

Fresnillo, and Taxco in Mexico (Gonzales Reyna, 

1950), Morococha, Casapalca, San Cristobal, and 

others in Peru (Peterson, 1965), Butte, Mont. 

(Meyer and others, 1968), Montevecchio, Italy 

(Zuffardi, 1950), and many others. It should be 

noted, however, that some districts that are well 

known for other types of lead deposits, such as the 

Tintic, Park City, Leadville, and Pioche districts 

of the United States, and a great many others, also 

contain vein deposits of considerable importance. 

The apparent environments of deposition of leadbearing veins are generally as widely. varying as 

the depositional environments of replacement deposits. They range in character from high-temperature veins containing galena in association with 

tourmaline (Knopf, 1913) and with garnet, hedenbergite, actinolite, fluorite, and quartz (Spurr and 

Garrey, 1908) to crustified epithermal veins that 

were deposited at low temperatures and shallow 

depths, commonly in association with fluorite, calcite, and quartz. The extreme temperature range 

may extend fr~m 50°C to 550°C, and the pressure 

range from 1 to 1,000 atmospheres or more. Some 

veins, such as those of the Kentucky-Illinois fluorspar and lead district and possibly those of the 

North Penn:lne district of England (Dunham, 1949), 

are classified with the Mississippi Valley type 

deposits. 

CONTACT PYR.OMETASOMATIC DEPOSITS 

Although the irregular or pod-form lead deposits 

that occur in the aureoles of granitic plutons may 

have importance locally, particularly in Japan, they 

are relatively unimportant in terms of gross production. These deposits are localized chiefly in limy 

or dolomitic rocks that have become bleached, recrystallized, and silicated by solutions that were 

associated with intrusions of intermediate composition. Some deposits also occur in calcareous shales, 

tuffs, and sandstones. In general the contact deposits range in form from tabular bodies and masses 

of unpredictable shape to veins. The more common 

metallic minerals include galena, typically less abundant than iron-rich sphalerite, chalcopyrite, pyrite, 

pyrrhotite, arsenopyrite, and magnetite. In some 

deposits, bismuth, molybdenum, and tungsten minerals and native gold may also be present. The 

gangue minerals include diopside, hedenbergite, garnet, fluorite, epidote, actinolite, ilvaite, tremolite, 

quartz, and a variety of other silicates. 

The deposits range in size from insignificant 

veins and lenses to large pods, one of which, at the 

Kamioka mine, Japan, is 850 feet long, 230 feet 

wide, and has been proven to a depth of 1,575 feet 

(Japan Geol. Survey, 1960, p. 182). This mine 

annually produces more than 1.5 million metric tons 

of ore containing 1.12 percent lead, 5.80 percent 

zinc, and 0.84 ounce per ton of silver. A somewhat 

similar but relatively lead-poor ore body in the 

Central district, New Mexico, 2,500 feet long, 30 

feet wide, and 80 feet high (Lasky and Hoagland, 

1950, p. 106), contained sphalerite and small 

amounts of galena and chalcopyrite, in association 

with andradite, salite, hedenbergite, ilvaite, and 

other minerals (Hernon and Jones, 1968, p. 1229). 

The average grade of this ore was probably close to 

14 percent zinc, 0.13 percent lead, 6.19 percent iron, 

and 10.19 percent sulfur (Lasky and Hoagland, 

1950, p. 106). Other contact pyrometasomatic de-

' posits that produce lead include the Chichibu, Nakatatsu, Obori, and other deposits of Japan (Japan 

Geol. Survey, 1960, p. 180--183), Tetyukhe in Siberia (Grigor'yev, 1936), Parroquia-Magistral and 

La Sirena in Mexico (Gonzalez Reyna, 1950), Falun, 

Garpenberg, Saxberget, Stollberg, Ammeberg, and 

other mines in Sweden (Magnussen, 1950), Trep~ 

in Yugoslavia (Forgan, 1950), and possibly the 

Darwin mine in California (Hall and MacKevett, 

1962). In some of these deposits lead is merely a 

coproduct or byproduct of zinc, copper, silver, or 

other metal. 

The spatial and temporal relations of contact 

pyrometasomatic ore deposits with nearby intrusions indicate that hot, metal-enriched solutions rose 

steeply within the fractured margins of the plutons 

and spread laterally into the fractured and brecciated wallrocks. Where these wallrocks consisted of 

argillaceous and arenaceous limestone and dolomite, 

they were commonly converted to skarn and were 

also locally replaced by sulfide minerals and magnetite. The intimate association of galena, sphalerite, chalcopyrite, and other sulfide and oxide minerals with anhydrous garnet and pyroxene minerals 

and the thermodynamic stability of these metallic 

minerals above 600°C (Holland, 1965, p. 1140--1147) 

both indicate a depositional environment with 

temperatures and pressures not far below the solidification temperatures and pressure of the associated 

igneous rocks. These temperatures and pressures 

are above the critical constants for water, indicating 

deposition from supercritical solutions. It is recog-
LEAD 325 

nized, however, that the temperatures diminished 

with time and that some copper-zinc-lead deposits 

in contact zones are hydrothermal rather than pneumatolytic in origin. 

RESOURCES 

RESERVES 

The reserves of lead contained in ores in known 

mines and districts in the world are here estimated 

to be about 141 million short tons, the equivalent 

of a 31-year supply at the 1971 rate of consumption, 

or a 22-year supply, not including recycled scrap, 

if an average annual increase in consumption of 3 

percent is assumed. 

These reserves are found on all of the continents 

except Antarctica, occurring in more than 40 countries, as shown in table 65. The greatest concentration of lead reserves is in the Southeast Missouri 

lead district; Weigel (1965, p. 77) estimates a 

potential of 30 million tons of contained lead for 

the Viburnum area alone. Other areas containing 

significant concentrations include south-central British Columbia and east-central New Brunswick in 

Canada, central Mexico, central Peru, the Bal~an 

nations in Europe, the Kazakhstan and TransBaikal areas, U.S.S.R., and in particular, central, 

north-central, and other parts of Australia. 

The estimate of reserves presented in table 65 

compares with an estimate of 50 million tons of 

measured and indicated ore and a possibly equivalent amount of inferred ore made a decade ago by 

Callaway (1962, p. 2). The difference between the 

two figures possibly reflects in part a more conservative approach by the U.S. Bureau of Mines as 

compared with the Geological Survey, but it should 

be noted that Callaway's data preceded the discovery 

and development of enormous lead deposits in southeast Missouri, north-central Australia, Roumania, 

and elsewhere during the past 10 years. Recent 

unpublished Bureau of Mines estimates of the 

measured and indicated reserves of lead in the 

world are much closer to the estimates presented 

here. 

The data presented in table 65 have been assembled chiefly from such sources as: Published estimates of tonnage and grade of ore reserves of specific mines and districts, which were based originally 

on physical exploration and geologically permissive 

extensions of known ore bodies, estimates made from 

narrative descriptions of the general size, character, and grade of less well developed deposits, and 

10-, 20-, or 30-year projections of production data 

from long-term lead-producing countries for which 

specific reserve data or mine descriptions are not 

available. The validity and accuracy of these data 

are thus contingent upon a number of factors, including: The degree to which some ore bodies, particularly those of the irregular limestone replacement type, are accurately delineated more than a 

few years in advance of mining; the extent of current knowledge of the geology and ore habits within 

TABLE 65.-Estimate of world reserves 1 of lead, by regions or countries 

[In thousands of short tons] 

North America: 

Canada: 

Yukon ------------------------- 3,500 Northwest Territories ---------- 1,250 

British Columbia --------------- 5,000 

Saskatchewan-Manitoba --------- 200 

Ontario ------------------------ 400 

New Brunswick --------------- 4,500 

Newfoundland ----------------- 300 

Other ------------------------- 700 

Total, Canada ---------------- 15,850 

United States: 

Northeast Washington --------- 150 

Coeur d'Alene district --------- 1,500 

Butte district ------------------ 500 

Great Basin -------------------- 2,500 

Rocky Mountains -------------- 1,000 

Tri-State ---------------------- 250 

Southeast Missouri ------------- 30,000 Upper Mississippi Valley ------ 1,000 

Kentucky-Dlinois --------------- 30 

East Tennessee ----------------- 10 

Austinvffie district ------------ 100 

Northern New York ----------- 45 

Appalachian Massive: 

Sulfide Belt ------------------ 100 

Other -------------------------- 1,000 

Total, United States --------- 39,185 

Greenland ----------------------- 70 

Total, North America -------- 54,105 

Central America: 

Mexico -------------------------- 4,500 

Honduras ------------------------ 250 

Other ---------------------------- 100 

Total, Central America --------- 4,850 

South America: 

Argentina ------------------------ 1,000 

Bolivia -------------------------- 800 

Brazil --------------------------- 750 

ChDe ---------------------------- 100 

Colombia ------------------------- 25 

Peru ---------------------------- 3,500 

Total, South America ---------- 6,175 

Europe: 

Austria ------------------------- 175 

Bulgaria ------------------------- 3,500 

East Germany ------------------- 500 

Finland -------------------------- 100 

France --------------------------- 700 

Greece --------------------------- 300 

Ireland -------------------------- 2,000 

Italy ---------------------------- 1,000 

Norway -------------------------- 100 

Poland -------------------------- 2,500 

Rumania -----··------------------- 500 

Spain ---------------------------- 2,750 

Sweden -------------------------- 2,500 

West Germany ------------------- 4,500 

Yugoslavia ----------------------- 3,000 

Other --------------------------- 500 

Total, Europe ----------------- 24,625 

Africa: 

Algeria -------------------------- flO 

Moroeeo ------------------------- 1,500 South West Africa --------------- 1,500 

Tanzania ------------------------ 100 

Tunisia -------------------------- 400 

Zambia -------------------------- 750 O~er --------------------------- 200 

Total, Africa ------------------ 5,200 

Asia: 

Burma -------------------------- 750 

China ---------------------------- 3,000 

India ---------------------------- 125 

Iran ----------------------------- 2,000 

Japan --------------------------- 1,200 

North Korea -------------------- 1,800 

RuBBia (U.S.S.R.) --------------- 18,000 

South Korea --------------------- 500 

Thailand ------------------------- 20 

Turkey -------------------------- 100 

Total, Asia -------------------- 27,495 

Oceania: 

Australia ------------------------ 18,500 

World total ------------------ 140,950 

1 Reserves: Identified deposits from which minerals can be extracted profitably with existing technology and under present economic conditions. 
326 UNITED STATES MINERAL RESOURCES 

specific districts ; the common practice of maintaining secrecy about the development of new ore reserves or the loss of established reserves; and 

political and economic factors leading to a paucity 

of data from Communist nations such as China and 

the U.S.S.R. These factors may result in a margin 

of error of as much as 25 percent for some countries, 

but it should be noted that virtually all past estimates have erred in being considerably smaller than 

subsequent estimates based on more complete data 

and that most of the larger reserves are contained 

in deposits that are either well explored by drilling 

or extensively developed in operating mines. 

In estimating lead reserves, price-cost and other 

economic factors should be consirlered together with 

technological advances in mining, milling, and smelting practices. The data of table 65 include all lowgrade ores that can be mined at the currently prevailing relatively high price of lead. Decreasing 

prices and increasing costs will diminish ore reserves, and some of these ore reserves may be 

irretrievably lost if the higher grade parts of the 

deposits are mined, thereby eliminating the possibility of blending ores to produce acceptable mill 

feeds. Conversely, a price increase, or more expectably, technological advances that substantially 

reduce mining and milling costs or permit the utilization of complex ores,.can abruptly increase apparent ore reserves by the inclusion of large tonnages 

of lead-bearing materials formerly considered to 

be unprofitable. In this category, in addition to 

conventional ores of subeconomic grade, are large 

volumes of lead-bearing slags, mill tailings, and 

mine wastes that are not considered in this report. 

CONDITIONAL RESOURCES 

Lead deposits of subeconomic grade have been 

recognized and explored to various degrees throughout the world, both on land and in the ocean basins. 

These deposits include not only conventional ore 

bodies that are similar to productive deposits except for a lower grade, but also unconventional deposits that previously have not been mined. The 

total quantity of lead in these presumed resources 

is not accurately known, but estimates of their 

contained metal-disregarding the potentially large 

problems inherent in achieving reasonable mining 

and metallurgical recoveries-may range as high as 

1.5 billion tons of lead. 

The predominant resource of low-grade leadbearing material in this category is the manganese 

nodules that occur in considerable volume on parts 

of the ocean floor and on the beds of some freshwater lakes. Although these nodules are considered 

to be of potential value chiefly as a source of manganese, nickel, copper, and cobalt, they contain an 

average of about 0.10 percent of lead, which may 

be recovered in some of the hydrometallurgical 

processes now being investigated. Mero ( 1965) estimates 1.656 trillion tons of nodules for the Pacific 

Basin alone. These nodules contain an average of 

0.09 percent of lead, approximately 1.3 billion tons. 

Over large areas where the nodules are particularly rich in nickel, copper, and cobalt, and where 

they presumably would be mined first, the average 

lead content is 0.18-0.30 percent and thus would be 

an important early coproduct. Similar deposits occur in the Atlantic and other oceans and in parts of 

Lake Michigan. Although mining and metallurgical 

reduction techniques are currently under investigation, no attempts at commercial exploitation have 

yet been made, and a question may be raised as to 

the validity of considering the nodules a mineral 

resource in the conventional sense at this time. 

An example of another large but more conventional resource of subeconomic lead-bearing material 

is the famous Kupferschiefer and adjacent beds of 

the Zechstein and equivalent formations of Europe 

(Deans, 1950). Although this formation is best 

known and once was widely mined in East Germany 

for copper, it is believed to contain far greater 

quantities of lead and zinc, some of which was recovered as coproducts and byproducts. According 

to generalized estimates by Richter-Bernburg 

(1941), the portion of the Zechstein Formation 

extending between Magdeburg and Richelsdorf in 

East Germany alone may contain as much as 100-

150 million tons of lead and 200-250 million tons of 

zinc as compared with only 50 million tons of copper. 

However, mining is not feasible under current economic conditions because of the limited thickness of 

the ore-bearing stratum, the relatively low tenor of 

the ore, the depth of large parts of the ore bed, 

and other factors. Mineral-bearing parts of the 

same stratigraphic unit also extend into West Germany, Poland, where it is currently being mined 

for copper, silver, and other metals, and northeastern England ; the total quantity of their contained 

lead is not known but is probably much less than in 

East Germany. 

Similar, but less well known, syngenetic deposits 

are currently being studied in the Belt Supergroup 

of northern Idaho and northwestern Montana. Preliminary estimates based on initial, incomplete 

surveys indicate a potential of 1 million tons or 

more of contained lead. However, the mining of 

adjacent and more valuable copper ore bodies may 
LEAD 327 

result in a loss of the lead resources (A. L. Clark, 

oral commun., 1972). 

Known and partly explored lead deposits of presumably large size also occur in strata-bound ore 

bodies in central Tennessee, central and southcentral Missouri, northern Arkansas, central Texas, 

northeast Washington, and central Kentucky in the 

United States; in several areas in western Canada; 

in central Europe; in North Africa; and in the 

U.S.S.R. Other low-grade deposits are known in 

several mining districts in the Rocky Mountains and 

Great Basin, and in numerous districts that contain 

vein and replacement deposits in other parts of the 

world. Similarly, many low-grade, lead-bearing massive sulfide deposits in the Eastern United States 

have not been fully explored or developed, at least 

during recent decades, and some may contain significant recoverable resources. Eventual exploration 

and development of some of these low-grade deposits are expected to disclose, from time to time, sections that are of fairly high grade. 

Another conditional, but perhaps unconventional 

resource of lead and other metals is the mineralized 

sediments that occur in the thermal deeps of the 

Red Sea basin (Degens and Ross, 1969). According 

to Bischoff and Manheim (1969, p. 535), the uppermost 10 meters of the Atlantis Deep in this basin 

contains 50 million metric tons of mineral-bearing 

sediment containing 3.4 percent of zinc, 1.3 percent 

of copper, 0.10 percent of lead, and about 1.6 

ounces per ton of silver. The adjacent Discovery 

and Chain Deeps contain similar sediments of lower 

concentration, and presumably other undiscovered 

thermal areas in the world's ocean basins are the 

sites of metal-enriched sediments. Like the manganese nodules, exploitation of these deposits will 

pose many problems. 

HYPOTHETICAL RESOURCES 

Throughout the history of mining and exploration, 

only a few of the larger mining districts have been 

totally worked out and abandoned. Successive generations, armed with new concepts, new techniques, 

and new-found optimism, have successfully redeveloped old mines and discovered new deposits that 

were somehow overlooked by their predecessors. In 

many areas throughout the world, small or unimportant districts have also been developed into major producers. With the passage of time, mining 

has been carried to greater and greater depths, and 

new, totally concealed ore shoots and even centers 

of ore deposition have been discovered. Areas that 

hold promise for the discovery of new ore centers 

in active or formerly active mining districts inelude, among many examples, the central plateau 

of Mexico, the cordillera of Peru and adjacent countries, the districts of Kazakhstan that are undergoing accelerated development, and even the classic 

districts of Europe, United States, and Canada. 

Like the "Identified Resources," the "Hypothetical 

Resources" include ores that are technologically 

recoverable as well as those that are subeconomic. 

Any attempt to quantify the amount of lead that 

may' be contained in them would be perilous, but it 

may be generally estimated to be equal to half or 

more of the known world reserves. 

SPECULATIVE RESOURCES 

The volume of recoverable and subeconomic lead 

ores in undiscovered districts cannot be estimated, 

but they may equal or exceed all of the reserves currently known throughout the world. During the past 

few decades, new mines and ore centers that rank 

among the largest that are known have been discovered in Canada, Australia, United States, and 

other countries throughout the world. These deposits occur in a variety of geologic terranes, but had 

remained undiscovered because they were totally 

concealed by barren rocks or because insignificant 

exposures did not indicate their true size or grade. 

Inasmuch as vast areas of possible mineral-bearing 

rocks underlie glacial debris in North America, 

Europe, and Asia, deep soil and other surficial deposits in the tropic, temperate, and arid regions of 

the world, and even the marine waters of the continental shelves, it is certain that similar deposits 

will continue to be discovered during the indefinite 

future. Many of these deposits are amenable to discovery through geophysical and geochemical exploration; others, such as those that are thoroughly oxidized or deeply buried, will be discovered only as a 

result of imaginative geologic analysis and courageous physical exploration. Inasmuch as lead deposits are widely distributed in many different geologic environments throughout the world, such 

geologic analysis will be applied most successfully 

to specific types of lead deposits in specific geologic 

terranes. As in the past, it will be chiefly based on 

continuing studies of the genesis of ore deposits and 

the features that determine their distribution and 

localization in the earth's crust, and it must be 

coupled with a willingness to consider and test 

pioneering concepts of ore deposition and distribution. 

PROSPECTING TECHNIQUES 

The principal new discoveries of lead deposits 

like most other types of mineral deposits, have been 
328 UNITED STATES MINERAL RESOURGES 

made mainly in existing mining districts through 

direct physical exploration of undeveloped areas 

that are geologically similar to the environments of 

the known ore deposits. In previously unproductive 

but geologically favorable terranes and in small or 

relatively inactive districts, the preliminary techniques of exploration employed in advance of drilling, shaft sinking, or drifting are less direct and 

may be divided into three categories: geologic, geochemical, and geophysical. TheEte techniques may be 

used separately or in any combination or sequence. 

Prior to World War II and the era of accelerated 

exploration that followed it, some new discoveries 

were chance finds or were made through serendipitous observations during unrelated efforts. As noted 

by McKinstry (1948, p. 413), however, such lucky 

accidents often make entertaining anecdotes but are 

not the source of many mine discoveries. Most modern discoveries result from scientifically directed 

prospecting, a costly undertaking. 

Geologic techniques for prospecting for lead deposits range in magnitude from the regional delineation of mineral belts, greenstone belts, and other 

metavolcanic terranes and areas of domal uplift on 

cratonic platforms to the solution of the problem 

of fault displacement of part of a minor ore bodyall based on geologic mapping at appropriate scales. 

Features to be recognized and evaluated, especially 

in the search for concealed deposits or deposits 

with unimpressive surface manifestations, are structural and stratigraphic localization of ore, chemical 

and mineralogical changes in the adjacent wall rocks, 

zonation, and temperature and pressure regimes. 

Among many examples of mineral discoveries based 

largely on geologic reasoning are the lead deposits 

of the Viburnum area, Missouri, the lead and zinc 

deposits of central Tennessee, and on a smaller scale, 

the polymetallic Bulldog Mountain mine, Creede district, Colorado (Steven and Ratte, 1960; Cox, 1965). 

Geochemical exploration is generally used in conjunction with geologic studies in several ways: to 

help eliminate unmineralized tracts within broad 

areas that are geologically favorable, to identify 

halos of dispersed metals in rocks or in residual surficial deposits above and adjacent to concealed deposits, to delineate the source areas of ore-metal 

dispersion trains in transported materials such as 

stream sediments and glacial till, and to determine 

possible patterns of compositional zonation of known 

deposits or groups of deposits. The techniques used 

include chemical, spectrographic, radiometric, and 

atomic-absorption analysis, heavy-mineral dispersion 

studies, and analysis of geobotanical relations 

(Hawkes, 1957). Examples of lead-producing mines 

that were discovered, at least in part, by geochemical 

techniques, include among others the Laisvall, Rakkejaur, and other deposits in Sweden (Grip, 1953), 

the Burgin deposit, Utah (Bush and others, 1960), 

and the Tynagh ore body in Ireland (Clark, 1965). 

Geophysical prospecting techniques are based on 

certain physical characteristics of ore minerals, ore 

bodies, or ore host rocks that contrast with their 

enclosing country rocks and may be detected, measured, and evaluated rapidly, cheaply, and usually at 

some distance from the body being sought or through 

a concealing cover. Such characteristics include density, magnetism, electrical conductivity, radioactivity, and seismic response. In the search for metallic 

mineral deposits, including galena. ore bodies and 

especially polymetallic sulfide deposits containing 

galena in association with high proportions of pyrite 

and pyrrhotite, the most successful methods during 

the past decade or so have been airborne magnetic 

and electromagnetic surveys that establish the position, size, and trend of anomalies over large areas of 

till-, forest-, or swamP-covered terrane, followed by 

detailed ground surveys that employ other geophysical, geochemical, and geologic techniques. These 

methods have been especially successful in the Precambrian shield areas of the world where large 

massive sulfide deposits are concealed beneath a relatively thin cover of surficial material. The aeromagnetic surveys delineate greenstone belts, intrusive 

bodies, major faults, and other geologic features that 

are commonly concealed. The electromagnetic (EM) 

, systems are then used to create a low-frequency inductive field in the vicinity of the low-flying aircraft, 

inducing eddy currents in the conductive ore bodies; 

the secondary fields radiating from the conductive 

bodies are then detected by receivers. The application of EM techniques has been greatly enhanced in 

recent years by the development of rapid dataprocessing equipment coupled directly to the transmitting and receiving equipment. Other techniques 

that may be used concurrently with airborne magnetic and electromagnetic methods include infrared 

and radar imagery, color and multiband photography, and side-viewing radar. 

Geophysical techniques used on the ground in the 

evaluation of anomalies discovered by airborne methods include a variety of EM systems that are similar 

to the airborne EM systems, the long-established and 

widely used induced polarization (IP) methods, and 

the audiofrequency magnetic (AFMAG) method, 

which utilizes natural currents of the earth that arise 

chiefly from thunderstorm activity in the equatorial 

regions. Locally, resistivity and self-potential methods also continue to be used. Each of these systems 
LEAD 829 

may be somewhat limited, or have special applications, when used in the search for specific types of 

ore bodies. In general, the surface EM systems have 

been most successfully applied in the exploration for 

massive sulfides beneath thin glacial overburden; the 

IP systems are widely used in the exploration for 

disseminated ·sulfides of the porphyry copper or Mississippi Valley types, although disseminated barren 

pyrite·, graphite, and some clay minerals also give IP 

responses. The AFMAG system is useful in locating 

deep conductive features and can be used to trace 

major faults and belts of rocks that have a wide 

range of conductivity. 

Many important lead-producing deposits have been 

discovered as a result of geophysical prospecting. 

These include the Brunswick, Heath Steele, Kidd 

Creek, and many others in eastern Canada, the Lady 

Evelyn in northern Australia, the Gortdrum and 

Silvermines deposits in Ireland, deposits in the Skellefte area, Sweden, the Vihanti district in Finland 

and others (for a more complete list see Pemberton, 

1966, and other sources). 

PROBLEMS FOR RESEARCH 

The reserves and identified world resources of lead, 

unlike resources of many other mineral commodities, 

appear to be adequate for the foreseeable future. 

Despite an accelerating rate of consumption since 

World War II, these reserves and resources have not 

only kept pace with extraction but have been substantially increased as a result of highly successful 

exploration in many countries. Enormous submarginal resources have been recognized in the ocean basins 

in the form of heavy-metal-rich manganese nodules, 

which eventually may become a competitive source 

of lead. It would appear that the main problems concerning lead are related not so much to the availability of resources as to mining, processing, and use 

of lead in our modern mechanized society. As these 

aspects are beyond the scope of this paper, they are 

noted here only briefly. 

Of chief concern is the toxicity of lead to humans, 

resulting in a variety of health hazards, particularly 

in the urban environment, and the resultant loss of 

markets for some lead products as selected uses of 

lead are restricted or prohibited. For example, recent 

legislation has virtually eliminated the use of lead 

pigments in interior paints and greatly restricted 

their use in many exterior and industrial applications. 

Similarly, legislative action has been directed toward 

reducing or eliminating lead in high-octane gasoline. 

Although such action may be required to bring about 

the adoption and use of some catalytic exhaust-control devices and to prevent atmospheric contamination, the advantages of tetraethyllead in controlling 

the burning rate of gasoline in high-compression 

engines, which greatly decreases the consumption of 

gasoline under conditions of constant performance, 

may force the adoption of smog-reducing exhaust 

systems that are compatible with at least a small 

quantity of lead in most gasolines, or that remove 

lead along with carbon monoxide, nitrogen oxides, 

and unburned hydrocarbons. Other factors leading to 

decreased use of lead include the expanding use of 

plastic cable sheaths and caulking compounds and 

the use of alternate compounds in solder, type metal, 

and coatings. 

Despite these restrictions on the use of lead, increased consumption is anticipated as a result of the 

accelerating use of automobiles and trucks throughout the world, the development of battery-operated 

vehicles for delivery and commuter transport, the 

growing demand for lead as an additive to improve 

the machinability of steel, brass, and other alloys, 

and the small but possibly increasing use as radiation shielding that will be required in the wider 

adoption of atomic energy. 

More directly related to the problems of reserves 

and resources are the many difficulties inherent in 

utilization of fine-grained, complexly intergrown 

massive ores that constitute an important part of 

the reserves of lead and other metals in southeastern 

Canada, Eastern United States, Japan, and elsewhere. Despite many attempts, some of these ores 

have not been amenable to processing efficiently or 

profitably by conventional milling and smelting techniques. Continued development of chemical oreprocessing methods and of continuous-smelting techniques that do not require clean separation of galena, 

sphalerite, pyrite, and copper sulfide minerals should 

lead to greater development of these massive sulfide 

ore bodies. 

REFERENCES CITED 

Agard, J., 1967, Conclusions genetiqu~, tirees de l'etude 

d-es gites strataformes de plomb, zinc, baryte, dans les 

formations carbonatees du Maroc, in Brown, J. S., ed., 

Genesis of strataform lead-zinc-barite-fluorite deposits 

(Mississippi Valley type deposits)-A symposium, New 

York 1966: Econ. Geology Mon. 3, p. 31~321. 

Anderson, C. A., 1969, Massive sulfide deposits and volcanism: 

Econ. Geology, v. 64, no. 2, p. 129-146. 

Bauchau, Christian, 1971, Essai de typologie quantitative des 

gisements de plomb et de zinc avec la repartition de 

l'argent: Bur. Recherches Geol. et Minieres Bull., sec. 

2, no. 3, p. 1-72; no. 4, p. 1-47. 

Behrend, Von F., 1950, Die Blei-und Zinkerz Fiihrenden 

lmpragnations Lagerstatten im Buntsandstein am 

Nordrand der Eifel und ihre Entstehung, in Dunham, 
330 LEAD 

K. C., ed., The geology, paragenesis and reserves of the 

ores of lead and zinc: Internat. Geol. Cong., 18th, London 

1948, rept., pt. 7, p. 325-339. 

Berg, G., 19·27, Zonal distribution of ore deposits in central 

Europe: Econ. Geology, v. 22, no. 2, p. 113-132. 

Bischoff, J. L., and Manheim, F. T., 1969, Economic potential 

of the Red Sea heavy-metal deposits, in Degens, E. T., 

and Ross, D. A., eds., Hot brines and recent heavy metal 

deposits in the Red Sea: New York, Springer-Verlag, 

p. 535-549. 

Brockie, D. C., Hare, E. H., Jr., and Dingess, P. R., 1968, 

The geology and ore deposits of the Tri-State district of 

Missouri, Kansas, and Oklahoma, in v. 1 of Ridge, J. D., 

ed., Ore deposits of the United States, 1933-67-The 

Graton-Sales Volume: New York, Am. Inst. Mining, 

Metall., and Petroleum Engineers, p. 400-430. 

Brown J. S., 1965, Oceanic lead isotopes and ore genesis: 

Econ. Geology, v. 60, p. 47-68. 

--- 1970, Mississippi Valley type lead-zinc ores-A review and sequel to the "Behre Symposium": Mineralium 

Deposita, v. 5, p. 103-119. 

Brown, J. S., ed., 1967, Genesis of stratiform lead-zinc-baritefluorite deposits (Mississippi Valley type deposits)-A 

symposium, New York, 1966: Econ. Geology Mon. 3, 

443 p. 

Bush, J. B., Cook, D. R., Lovering, T. S., and Morris, H. T., 

1960, The Chief Oxide-Burgin area discoveries, East 

Tintic district, Utah-a case history: Econ. Geology,v. 

55, nos. 6 and 7, p.1116-1147, 1507-1540. 

Callaway, H. M., 1962, Lead-a materials survey: U.S. Bur. 

Mines lnf. Circ. 8083, 194 p. 

Campbell, Neil, 1967, Tectonics, reefs, and stratiform leadzinc deposits of the Pine Point area, Canada, in Brown, 

J. S., ed., Genesis of stratiform lead-zinc-barite-fluorite 

deposits (Mississippi Valley type deposits)-A symposium, New York, 1966: Econ. Geology Mon. 3, p. 59-

70. 

Clark, A. L., 1971, Strata-bound copper sulfides in the Precambrian Belt Supergroup, northern Idaho and northwestern Montana: [Proc. IMA-IAGOD mtg., 1970 

IAGOD vol.] Soc. Mining Geol. Japan Spec. Issue 3, p. 

261-267. 

Clark, G. R., 1965, Exploration and geology: Canadian Mining Jour., v. 86, no. 12, p. 58-61. 

Cox, M. W., 1965, Geologic theory leads to ore at Creede 

[Colorado]: Eng. and Mining Jour., v. 166, no. 9, p. 6. 

Cumming, G. L., and Robertson, D. K., 1969, Isotopic composition of lead from the Pine Point deposit: Econ. 

Geology, v. 64, p. 731-732. 

Deans, T., 1950, The Kupferschiefer and the associated leadzinc mineralization in the Permian of Silesia, Germany, 

and England, in Dunham, K. C., ed., The geology, paragenesis, and reserves of lead and zinc: lnternat. Geol. 

Cong., 18th, London, 194·8, rept., pt. 7, p. 340'--35·2. 

Degens, E. T., and Ross, D. A., eds., 1969, Hot brines and 

recent heavy metal deposits in the Read Sea: New York, 

Springer-Verlag, 600 p. 

Dings, M. C., and Whitebread, D. H., 1965, Geology and ore 

deposits of the Metaline zinc-lead district, Pend Oreille 

County, Washington: U.S. Geol. Survey Prof. Paper 

489, 109 p. 

Dunham, K. C., 1949, Geology of the Northern Pennine orefield: Great Britain Geol. Survey Mem., v. 1, 357 p. 

Emmons, S. F., Irving, J. D., and Loughlin, G. F., 1927, 

Geology and ore deposits of the Leadville mmmg district, Colorado: U.S. Geol. Survey Prof. Paper 148, 

368 p. 

Forgan, C. B., 1950, Ore deposits at the Stantrg lead-zinc 

mine [Yugoslavia], in Dunham, K. G., ed., The geology, 

paragenesis, and reserves of the ores of lead and zinc: 

Internat. Geol. Cong., 18th, London, 1948, rept., pt. 7, 

p. 290-307. 

Galkiewicz, Tadeusz, 1967, Genesis of Silesian-Cracovian 

zinc-lead deposits, in Brown, J. S., ed., Genesis of stratiform lead-zinc-barite-fluorite deposits (Mississippi Valley type deposits)-A symposium, New York, 1966: 

Econ. Geology Mon. 3, p. 156-168. 

Gates, W. G., 1971, Geology and geological aides to production 

at the Heath Steele mine: AIME World Symposium on 

Mining and Metallurgy of Lead and Zinc [St. Louis], p. 

108-122. 

Gonzalez Reyna, J., 1950, Geologia, paragene~is y reservas 

de los yacimi·entos de plomo y zinc de Mexico, in Dunham, 

K. G., ed., The geology, paragenesis, and reserves of the 

ores of lead and zinc: Internat. Geol. Cong., 18th, London, 19·48, rept., pt. 7, p. 121-141. 

Grigor'yev, I. F., 1936, Pervichnye rudy Tetyukhe i ikh 

genezis [The primary ores of Tetyukhe and their 

genesis]: Akad. Nauk SSSR Izv. Ser. Geol., no. 1, 1936. 

Grip, Erland, 1950, Lead and zinc deposits in northern 

Sweden, in Dunham, K. C., ed., The geology, paragenesis, 

and reserves of lead and zinc: lnternat. Geol; Cong., 

18th, London, 1948, rept., pt. 7, p. 362-370. 

--- 1953, Tracing of glacial boulders as an aid to ore 

prospecting in Sweden: Econ. Geology, v. 48, no. 8, p. 

715-725. 

Gruszczyk, Hubert, 1967, The genesis of .the Silesian-Cracow 

deposits of lead-zinc ores, in Brown, J. S., ed., Genesis 

of stratiform lead-zinc-barite-fluorite deposits ( Mississippi Valley type deposits)-A symposium, New York, 

1966: Econ. Geology Mon. 3, p. 169-177. 

Hall, W. E., and MacKevett, E. M., Jr., 1962, Geology and 

ore deposits of the Darwin quadrangle, Inyo County, 

California: U.S. Geol. Survey Prof. Paper 368, 87 p. 

[1963]. 

Hawkes, H. E., Jr., 1957, Principles of geochemical prospecting: U.S. Geol. Survey Bull. 1000-F, p. 225-355. 

Hernon, R. M., and Jones, W. R., 1968, Ore deposits of the 

Central mining district, Grant County, New Mexico, in 

v. 2 of Ridge, J. D., ed., Ore deposits of the United 

States, 1933-1967-The Graton-Sales Volume: New 

York, Am. Inst. Mining, Metall., and Petroleum Engineers, p. 1211-1238. 

Heyl, A. V., 1968, The Upper Mississippi Valley base-metal 

district, in v. 1 of Ridge, J. D., ed., Ore deposits of the 

United States, 1933-1967-The Graton-Sales Volume: 

New York, Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 431-459. 

--- 1969, Some aspects of genesis of zinc-lead-baritefluorite deposits in the Mississippi Valley, U.S.A.: Inst. 

Mining and Metallurgy Trans., sec. B, v. 78, Bull. 756, 

p. B148-B160. 

Hobbs, S. W., and Fryklund, V. C., Jr., 1968, The Coeur 

d'Alene district, Idaho, in v. 2 of Ridge, J. D., ed., Ore 

deposits of the United States, 1933-1967-The GratonSales Volume: New York, Am. Inst. Mining, Metall., 

and Petroleum Engineers, p, 1417-1435. 

Holland, H. D., 1965, Some applications of thermochemical 
UNITED STATES MINERAL RESOURCES 831 

data to problems of ore deposits-[pt.] 2, Mineral assemblages and the composition of ore forming fluids: 

Eoon. Geology, v. 60, no. 6, p. 1101-1166. 

Horikoshi, Ei, 1969, Volcanic activity related to the formation of the kuroko-type deposits in the Kosaka district, 

Japan: Mineralium Deposita, v. 4, no. 4, p. 321-345. 

Japan Geological Survey, 1960, Geology and mineral resources of Japan [2d ed.]: Japan Dai-Nippon Printing 

Co., Ltd., 304 p. [various paginations]. 

Jouravsky, G., Permingeat, F., Bouladon, J., and Agard, J., 

1950, Deux types de gisements de plomb au Maroc 

Francais, in Dunham, K. C., ed., The geology, paragenesis, and reserves of the ores of lead and zinc: Internat. Geol. Gong., 18th, London 1948, rept., pt. 7, p. 

222-233. 

Kautsky, Gunnar, 1957, Ein Beitrag zur stratigraphie und 

dem Bau des Skelleftefeldes, Novschweden: Sveriges 

Geol. Undersokning Arsb., 49, no. 3, (Geol. Survey 

Sweden, ser. C., no. 543) , 65 p. 

Kinoshita, Kameki, 1931, On the "Kuroko" (black ore) deposits: Japanese Jour. Geology and Geography, v. 8, no. 

4, p. 281-352. 

Knopf, Adolph, 1913, The tourmalinic silv·er-lead type of 

ore deposit: Econ. Geology, v. 8, p. 105-119. 

Knyazev, I. I., 1954, Gidrothermal'no izmenennye karbonatnye porody [The hydrothermal alteration of carbonate vocks], in Kurek, N. N., ed., Izmenennye 

okolorudnye porody i ikh poiskovoe znachenie: V ses. 

Nauchno-Issled. Geol. Inst. Trudy, 272 p. 

Lasky, S. G., and Hoagland, A. D., 1950, Central mining 

district, New Mexico, in Dunham, K. C., ed., The geology, 

paragenesis, and reserves of the ores of lead and zinc: 

Internat. Geol. Cong., 18th, London, 1948, rep·t., pt. 7, 

p. 97-110. 

Lindgren, Waldemar, 1933, Mineral deposits [4th ed.]: New 

York and London, McGraw-Hill Book Co., 930 p. 

Magnusson, N. H., 1950, Zinc and lead deposits of central 

Sweden, in Dunham, K. C., ed., The geology, paragenesis, and reserves of lead and zinc: Internat. Geol. 

Cong., 18th, London 1948, rept., pt. 7, p. 371-379. 

Maruyama, Sadao, and Sato, Noritaka, 1970, Geology and 

exploration of the kuroko deposits in Japan, in Rausch, 

D. 0., and Mariacher, B. C., eds., Mining and concentrating of lead and zinc, v. 1 of Lead and zinc: 

New York, Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 171-194. 

Mason, B. H., 1958, Principles of geochemistry [2d ed.]: 

New York, John Wiley & Sons, Inc., 276 p. 

McKinstry, H. E., 1948, Mining geology: New York, Prentice-Hall, Inc., 680 p. 

McKnight, E. T., and Fischer, R. P., 1970, Geology of the 

Picher field, Oklahoma and Kansas: U.S. Geol. Survey Prof. Paper 588, 165 p. 

Mero, J. L., 1962, Ocean-floor manganese nodules: Econ. 

Geology, v. 57, no. 5, p. 747-767. 

--- 1965, The mineral resourc·es of the sea: Amsterdam, 

Elsevier Publishing Co., 312 p. 

Meyer, Charles, Shea, E. P., Goddard, C. C., Jr., Zeihen, L. 

G., Guilbert, J. M., Miller, R. N., McAleer, J. F., Brox, 

G. B., Ingersoll, R. G., Jr., Burns, G. J., and Wigal, 

Thomas, 1968, Ore deposits at Butte, Montana, in v. 2 of 

Ridge, J. D., ed., Ore deposits of the United States, 

1933-1967-The Graton-Sales Volume: New York, Am. 

Inst. Mining, Metall., and Petroleum Engineers, p. 1373-

1416. 

Mitman, C. W., 1922, Lead, in Annual report of the Board 

of Regents of the Smithsonian Institution, 1921: Washington, U.S. Govt. Printing Office, p. 595-614. 

Morris, H. T., 1968, The main Tintic district, Utah, in v. 2 

of Ridge, J. D., ed., Ore deposits of the United States, 

1933-1967-The Graton-Sales Volume: New York, Am. 

Inst. Mining, Metall., and Petroleum Engineers, p. 1043-

1073. 

Nekhoroshev, V. P., 1941, Zony smyatiya rudnogo Altaya 

[Crushed zones of Rudnyy Altai]: Akad. Nauk SSSR 

Izv. Ser. Geol. 

Novarese, V., 1950, I giacimenti piombo zinciferi della 

Sardegna, in Dunham, K. G., ed., The geology, paragenesis, and reserves of the ores of lead and zinc: Intern at. Geol. Cong., 18th, London, 1948, rept., pt. 7, p. 

251-256. 

Paone, James, 1970, Lead, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 603-620. 

Pavilion, Marie-Jose, 1969, Les mineralisations plombozinciferes de Carthagene ( Cordilleres betiques, Espagne) : Mineralium Deposita (Berlin), v. 4, no. 4, p. 

368-385. 

Pemberton, R. H., 1966, World geophys"ical discoveries bolster future mineral needs: Eng. and Mining Jour., v. 

167, no. 4, p. 85-88. 

Peterson, Ulrich, 1965, Regional geology and major ore deposits of central Peru: Econ. Geology, v. 60, no. 3, p. 

p. 407-476. 

Prescott, Basil, 1926, The underlying principles of the limestone replacement deposits of the Mexican province-! 

and II: Eng. and Mining Jour., v. 122, no. 7, p. 246-253; 

no. 8, p. 289-296. 

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry: 

Chicago, Univ. Chicago Press, 912 p. 

Richter-Bernburg, Gerhard, 1941, Geologische Gesetzmassigkeiten in der Metallfiihrung des Kupferschiefers: 

Lagerstattenforschung ( R·eichstelle fiir Bodenforschung) N.F., no. 73, 61 p. 

Rubright, R. D., and Hart, 0. J., 1968, Non-porphyry ores 

of the Bingham district, Utah, in v. 1 of Ridge, J. D., 

ed., Ore deposits of the United States, 1933-1967-The 

Graton-Sales Volume: New York, Am. Inst. Mining, 

Metall., and Petroleum Engineers, p. 886-907. 

Shcherba, G. N., 1971, The stratiform deposits of Kazakhstan: [Proc. IMA-IAGOD mtg., 1970 IAGOD vol.J Soc. 

Mining Geol. Japan, Spec. Issue 3, p. 172-177. 

Smirnow, W. 1., 1960, fiber die moglichen exhalativen und 

·exhalativ-s·edimentaren Kiesvorkommen in der Sowjetunion: Freiberger Forschungshefte, C 79 Lagerstattenkund·e, p. 62-66. 

Smith, L. A., 1929, Summarized data of lead production: 

U.S. Bur. Mines Econ. Paper 5, 44 p. 

Snyder, F. G., and Gerdemann, P. E., 1968, Geology of the 

Southeast Missouri lead district, in v. 1 of Ridge, J. D., 

ed., Ore deposits of the United States, 1933-1967-The 

Graton-Sales Volume: New York, Am. Inst. Mining, 

Metall., and Petroleum Engineers, p. 326-358. 

Spurr, J. E., and Garrey, G. H., 1908, Ore deposits of the 

Velardeiia district, Mexico: Econ. Geology, v. 3, no. 7, 

p. 688-725. 

Steven, T. A., and Ratte, J. C., 1960, Relation of mineraliza-
382 LEAD 

tion to caldera subsidence in the Creede district, San 

Juan Mountains, Colorado, in Geological Survey research 

1960: U.S. Geol. Survey Prof. Paper 400-B, p. B14-

B17. 

Tsumeb Corp. Ltd., 1961, Geology, mining methods, and 

metallurgical practice at Tsumeb-Geology by G. 

SOhnge: Commonwealth Mining and Metallurgical Cong., 

7th, trans., South African Inst. Mining and Metallurgy, 

v. 1, p. 159-179. 

Turekian, K. K., and Wedepohl, K. H,, 1961, Distribution of 

the elements in some major units of the Earth's crust: 

Geol. Soc. America Bull., v. 72, no. 2, p. 175-191. 

Tweto, Ogden, 1968, Leadville district, Colorado, in v. 1 of 

Ridge, J.D., ed., Ore deposits of the United States, 1933-

1967-The Graton-Sales Volume: New York, Am. Inst. 

Mining, Metall., and Petroleum Engineers, p. 681-705. 

Tweto, Ogden, and Lovering, T. S., 1947, The Gilman district, Eagle County, in Vanderwilt, J. W., and others, 

Mineral resources of Colorado: Denver, Mineral Resources Board, p. 378-387. 

U.S. Bureau of Mines, 1971, Metals, minerals, and fuels, 

v. 1-11 of Minerals Yearbook 1969: Washington, U.S. 

Govt. Printing Office, 1,194 p. 

Vokes, F. M., 1962, Mineral paragenesis of the massive sulfide ore bodies of the Caledonides of Norway: Eeon. 

Geology, v. 57, no. 6, p. 890-903. 

Wedepohl, K. H., 1971, "Kupferschiefer" as a prototype of 

syngenetic sedimentary ore deposits: [ Proe. IMAIAGOD mtg., 1970 IAGOD vol.] Soc. Mining Geol. Japan, 

Spec. Issue 3, p. 268-273. 

Weigel, W. W., 1965, The inside story of Missouri's exploration boom, pt. 1: Eng. and Mining Jour., v. 166, no. 11, 

p. 77-86, 170, 172; pt. 2, no. 12, p. 81-83, 161-162. 

Zuffardi, P., 1950, 11 giacimento piombo-zincifero de Monteveechio, Sardgena, in Dunham, K. C., ed., The geology, 

paragenesis, and reserves of the ores of lead and zinc: 

lnternat. Geol. Cong., 18th, London 1948, rept., pt. 7, p. 

266--276. 
UNITED STATES MINERAL RESOURCES 

LIGHTWEIGHT AGGREGATES 

CONTENTS 

Abstract of conclusions --------------------------

Fore~rd --------------------------------------- Structural lightweight aggregates -----------------

Introduction --------------------------------- Exploitation ---------------------------------

Clays, shales, and slates ---------------------

Volcanic rocks ------------------------------

Scoria and volcanic cinder ----------------

Pumice and pumicite ---------------------

Diatomite -----------------------------------

Other materials ------------------------------

Ultralightweight aggre,gates ----------------------

Introduction --------------------------------- Exploitation ---------------------------------

Volcanic rocks -------------------------------

Perlite ----------------------------------

Pumicite --------------------------------

Vermiculite ----------------------------------

Selected references -------------------------------

40. 

41. 

42. 

FIGURES 

Graph showing production of materials used as 

structural lightweight aggregates in the 

United States, 1940-60 ------------------- Triangular diagram showing comparative composition of bloating and nonbloating argilla,.. 

ceous rocks ------------------------------ Graph showing production of materials used as 

ultralightweight aggregates in the United 

Sta~, 1935-70 --------------------------

TABLES 

By A. L. BusH 

Page 

333 

333 

335 

335 

335 

338 

341 

342 

343 

345 

345 

345 

345 

346 

347 

347 

348 

348 

351 

Page 

336 

340 

346 

ABSTRACT OF CONCLUSIONS 

The United States is adequately supplied with both structural lightweight aggregates (scoria, volcanic cinder, pumice 

and pumicite, expandable clays, shales and slates, diatomite, 

expanded blast-furnace slag, and fly and bottom ash) and 

ultralightweight aggregates (expanded perlite, expanded 

pumicite, and exfoliated vermiculite). The aggregates are 

low unit value, high place value materials, partly because 

large quantities are available and partly because normalweight (sand and gravel) and synthetic aggregates are 

stiff competition. However, they have high place value, in as 

much as transportation costs largely determine whether they 

are used. 

Recoverable reserves of expanded clays, shales, and slates 

are equivalent to about half the cumulative output needed 

through the year 2000. For the same period, scoria, cinder, 

pumice, and pumicite reserves are at least twice the estimated demand, and perlite reserves seem to be at least as 

large, and vermiculite reserves somewhat larger than their 

respective demands. 

Virtually no export or import markets exist for the lightweight aggregates. Along the eastern seaboard, oceanic 

freight rates allow competition between pumice from western 

domestic sources and pumice imported mostly from the Mediterranean area, but only a few hundred thousand tons per 

year are involved. For similar reasons, a few thousand tons 

of vermiculite are imported annually from the Republic of 

South Africa. A few thousand tons of domestic perlite are 

exported to Canada per year. 

The prospects for converting hypothetical and speculative 

resources of clays, shales, scoria, cinder, pumice, and pumicite to recoverable reserves are excellent. For perlite and 

vermiculite, the prospects are good. 

FOREWORD 

Many materials serve primarily as lightweight 

aggregates for concretes and plasters, but some of 

them find even more use as construction materials 

in their own right, as components in manufacturing 

processes or in end products, or as aids of various 

Pa~re kinds in agriculture. Some are used for their physical 66• Cl:~~:ti:~~:~Jsro~~~e_s-~:-~i~~t:~i~~:-~~~ 334 properties alone, but for most the chemical prop.. 

67. Comparative composition of expansible clays, erties also are significant. Some are used with only 

shales, and slates ------------------------ 338 minimal processing, such as crushing and grading, 

68. Comparative composition of volcanic glasses __ 341 but others require fairly complex and sophisticated 

U.S. GEOL. SURVEY PROF. PAPER 820 

833 
334 UNITED STATES MINERAL RESOURCES 

treatment. Many are mineral raw materials, others 

are waste or synthetic products, and some are organic materials. A brief look at the array of materials and at some of their properties is given in 

table 66. Several of the materials touched on in this 

chapter are also discussed in other chapters. (See 

"Abrasives," "Clays," "Diatomite," "Pigments and 

Fillers," "Magnesian Refractories," and "Silica 

Sand.") 

are in the 35- to 60-pound range and those used for 

non-load-bearing purposes are in the 5- to 20-pound 

range ( ultralightweight aggregates). 

The distinction between normal-weight and lightweight aggregates is made at about 75 lb per cu ft 

(pounds per cubic foot) for loose graded aggregate. 

Most lightweight aggregates weigh considerably 

less ; generally those used for structural purposes 

Expanded clays and shales make up more than 

70 percent by weight of the structural lightweight 

aggregates used annually, with the remainder divided among expanded slate, scoria, expanded slag, 

and fly ash at about 6, 7, 15, and 2 percent, respectively. The production data for clays and shales are 

commingled and cannot be separated satisfactorily, 

but about half of all the aggregate seems to be 

made from expanded shale. 

Vermiculite and perlite are the most used ultralightweight materials, each with about one-third 

TABLE 66.-Classijication and properties of lightweight aggregate materials 

Composition (welcht percent) 

Texture 

( unexpanded) Expanaion 

needed 

Prodaeta of u:ploain YOieaniun 

Texture 

(expanded) 

Pumice -------- SUicic -------------- Frothy, very vesicular. 

None On chanced 

Pumicite ------ ---do --------------- Porous -------- ---do ---do 

Scoria --------- Basic 

Perlite -------- SUicic .(lb0:2-6) 

Clinkerlike, 

very vesicular. 

Fractured, 

onionakin 

partings. 

---do --------------- ---do 

To X 6; about 1,(00°F. Cellular, frothy spheres. 

Obsidian ------- SUicic (lb0:<2) ----- Dense class, eonehoidal 

fracture. 

To about X 6: 1,,00°- ---do ---------- 1,5000F. 

Clays, shales, 

slates. 

Wide ranee; silty, ealeareous, carbona- ceous, ferrucinous. 

Diatomite ------ Si02, close to 100, may be clayey, petrolif· erous. 

Vermiculite Hydrated macnesium-

( Bydrobiotite). iron-aluminum 

Blast-furnace 

alae. 

Fl:r aab, 

bottom ash, 

eoke breeze. 

Cindera -------

Plastic beads 

and foams. 

Foam inc 

eompounda. 

Rice hulls, 

wheat bulla, 

sawdust, 

wood fibers. 

silicates; varies 

eonaiderahl:r. 

Best alae is 

Si0J=36-38; 

CaO+AbOa==,H7; 

low MgO. FeO, S. 

Wide ranees: SiOs+ 

AbOa+ Fel!Os:>70, 

McO:<Ii; SOa:<s: 

alkalies: <1.6. 

---do ---------------

Polyurethane, polystyrene, 

polyvin:rl ehloride. 

Aluminum powder, 

vin:rl resina. 

Bl!OL 

01'1r&nic -------------

Dense, may be 

fissile. 

Depoelta of HdimentaQ' orqin 

To X 2-3 at about 

1,800°-2,200°F. 

Cellular, fairl:r 

uniform. 

Porous, ma:r be friable. None --------------- Cellular ---------

Alteration of male silicate aainerala 

Mieaeeous ------ To X 8-16 at about 

2,000°F. 

Aeeordionlike 

Byprodaeta of aauafaetarinc proe ..... 

Liquid slag ---- About X 3 at ambient 

temperature. 

Extremely fine 

crained. 

Cellular, 

nonuniform. 

None 

None 

Cellular, fairl:r 

uniform. 

Cellular ---------

Unchanced ------

Synthetie ud aaiaeellueoaa aaateriala 

Does not apply _ Various temperatures, 

reaetiona. 

---do --------- ---do 

Fibrous, 

eellular. 

None 

Cellular. 

uniform spheres. 

Does not apply --

Unchanced ------

Weicht 

(lb per cu ft) Remarks 

3o-60 

60-'70 

36-76 

6-16 

26-80 

Blocks and fracmenta 

of coherent class. 

Shards of class; vel")' 

fine crained; very 

low stt-encth: ex• pansible. Tephra aa bombs and 

lapilli; vesiculated zones in lava flows. 

Low strength; hich 

permeabUity to sur- face area ratio; 

ultralicht. 

Do. 

3o-60 Kiln or sinter product; 

cood strencth; red ores least likely to expand. ~60 Coproduct of ealeininc 

for filter aid produets. 

6-15 Supercene alteration of 

86-60 

86-66 

biotite, pblogopite. hornblende, diopside, 

aucite, olivine, ehlorite, serpentine; low 

•tt-encth: ultralicht. 

Zinc and phosphate smelter slap have 

also been used aue- cesafully. 

Ash from burninc pul- verized eoal: aintered to eause agclomeration. 

From burninc of pea· size or Iarcer eoal, 

eoke. 

<16 Many patented teehnf· 

ques and appliea· tiona. 

Various ----Does not substitute for acereaate: lowers density by adding voida. 

No data ----Generally low strencth: 

very minor usace. 
LIGHTWEIGHT AGGREGATES 335 

share of the market for aggregates. Pumice-pumicite 

and diatomite claim the remaining third in about 

a 10:1 ratio. The production data for pumice, pumicite, scoria, and volcanic cinders are so commingled 

and the terms are applied so unspecifically in regard 

to uses that only the broadest guess can be made; 

the ratio for pumice-pumicite may be low by a factor 

of 3. 

All in all, about 13.5 million short tons of rock 

was used in 1970 for structural lightweight aggregates, and perhaps as much as one-half million short 

tons was used for ultralightweight aggregates for 

non-load-bearing concretes, plaster insulation board, 

and loose fill insulation. Their values after processing 

for final use were about $71 million and $14 million, 

respectively. As these materials also have other 

applications, their annual production value for all 

uses was somewhat greater for the structural lightweights, about $7 4 million, and much greater for 

the ultralightweights, about $78 million; we have 

an overall value, then, of more than $150 million 

per year. 

The natural subdivision of the lightweight aggregates into those used for structural purposes and 

those used in non-load-bearing applications will be 

followed in this chapter. 

STRUCTURAL UGHTWEIGHT AGGREGATES 

INTRODUCTION 

Despite their varied origin, the aggregates suitable for structural purposes have several characteristics in common : they are porous, ideally highly 

so ; they are permeable, ideally poorly so ; and the 

pore walls are relatively thick, as compared with 

the diameter of the voids. This last characteristic 

gives the aggregates fairly high compressive 

strengths. The porosity of all aggregates results 

from heat treatment-natural (volcanic) heat for 

the scoria; intentional rotary kilning or horizontal 

furnace sintering for the expanded clays, shales, 

and slates; and unavoidable heat in blast furnaces 

for the slags and in coal-fired steam power plants 

for the fly ash. 

Because of their porus but fairly impermeable 

texture, the lightweight aggregates are both thermal and acoustic insulators. These properties make 

the aggregates desirable for bulk use in floor and 

roof fill, and they are an added advantage in concretes where the primary reason for the use of these 

aggregates is weight reduction. 

Compressive strength that can be obtained for 

concrete made with these aggregates ranges from 

perhaps 1,200 psi (pounds per square inch) to more 

than 6,000 psi, depending upon the proportions of 

sand, cement, aggregate, and water. Higher strength 

and increased weight go hand in hand; for example, 

a scoria aggregate concrete at 1,200 psi weighs 

about 60 lb per cu ft, whereas a sintered expanded 

shale concrete at about 6,000 psi weighs about 120 

lb per cu ft. In this broad range of strengths, the 

lightweight aggregate concretes can be used for fill, 

bridge decks, shell walls, concrete floors, concrete 

frames using precast, prestressed, or posttensioned 

girders, precast tilt-up units, poured barge and ship 

hulls, and lightweight masonry blocks. In bulk form 

the aggregates are used as railroad ballast, as highway and embankment fill, and in the surface course 

of bituminous paving mixtures. 

Structural lightweight aggregates and concretes 

play an important though not indispensable role in 

urbanized, industrialized nations. They enhance efficiency-they allow buildings to be made higher, 

their steel framework to be more fire resistant, and 

their floors and ceilings to be better insulants. They 

contribute to more economical use of funds, materials, and time, inasmuch as concrete can be 

pumped higher and farther from a single location; 

plates, girders, and shell walls can be mass produced 

off site; and additional thermal and acoustic insulation can be reduced. On the esthetic level, the lightweight aggregates and concretes allow innovative, 

experimental construction and design. 

The United States is by far the largest producer 

and consumer of structural lightweight aggregates. 

Inasmuch as domestic supplies are abundant and 

the materials have low unit value but high place 

value-that is, transportation costs largely govern 

whether the materials can be used-there are virtually no import or export markets. To all intents, 

the country is self-sufficient in these commodities. 

Production data for pumice reveal some imports 

used for lightweight block, but in 1970 less than 

400,000 tons was imported for all purposes, as compared with more than 8 million tons of domestic 

lightweight aggregates used in lightweight block. 

Overall, imports make up less than 2 percent of the 

structural lightweight aggregates market. Almost 

all this usage was along the eastern seaboard, where 

marine freight rates allowed competition with pumiee from domestic western sources. 

EXPLOITATION 

Pumice first was used as a lightweight construction material by the Romans about the beginning 

of the Christian era, but because production data 

are somewhat sketchy between then and about 1940, 

only the production trends since 1940 are really of 
336 

en 

z~z Oce:o 

~z-

~~t> 0:~::> 

0::>0: 

~mt; 

u.enz oWO >o 

:g~:t zow 

ce:_,z 

en_,o: 

=>ce:o 

~-u. 

~ 

100,000 

90,000 

80,000 

70,000 

60,000 

50,000 

40,000 

30,000 

20,000 

10,000 

9000 

8000 

7000 

6000 

5000 

4000 

3000 

2000 

1000 

900 

800 

700 

600 

500 

400 

300 

200 

100 

90 

80 

70 

60 

50 

40 

30 

20 

/\ 

/ \ 

\ 

\ 

\ 

\...-""" 

/ 

I I 

/~ i I ~ \...=..---' 

I 

I 

I -, I 

: \ I 

I ' . I \ I I , 

" 

I I I I 

UNITED STATES MINERAL RESOURCES 

T T T T T I I I I I I I I l 100 

~ 

------ ---- New construction """"" - (In dol~~ .....-

/~ 

/ 

( v Total output 

c __,.,. 

B_ 

./ ~- - I ~ 1---- - ---- 10 

I / , 

I ~ Clav, shale slate ..... ..,... - / .,~ 

/ / 

/ - / ~ / - Pumice~ --------, 

Sla97"1 ------ .,../. -·-. - ~· ,-- .>..,.~ _ _... ......... .................. ,'" ~, j-' ... 'v/ .... / 

/-......... / 

Pumice in concrete-,.__ .... ........ /. , 

, ' , / I , .... _.,.. ... _, / / , ,· '· -- __ .., 

! .-1-6 I __ ,.., ...... / 

I ~---lT '~'/ .... 

; /,' ./ "" 

·' /// 

! ,(,' IJ /.' ,: 1950 1955 1960 1965 1!:17 0 

I I I 

, 

I Pumice without cinder~ 

I 

I /' I -,.;;;.. 7' 1 .....;,: ... I \ 000 , - ' , '· I ' / '· / \ I \ .i\ ....,...,., '\··' \J \ / \ y / \/., 

I I I I I I I I I I I l l I J I I I I 10 1 00 

1940 1945 1950 1955 1960 1965 1970 

en 

z 

0 

~ 

~ 

0: 

0 

z 

en 

u. 

0 

U) 

0 

z 

c( 

U) 

::> 

0 

z 

~ 

FIGURE 40.-Production of materials used as structural lightweight aggregates in the United States, 1940-70. 

New coutruction.-Value of total new construction, exclusive of maintenance and repair; data from Statistical Abstracts 

of the United States, 1940-70. 

Total output.-Tonnage of all materials used as structural lightweight aggregates: A, Estimate in Rock Products, v. 60, no. 

1, p. 83, 1962. B, Estimate by R. A. Grancher in Rock Products, v. 72, no. 12, p. 62, 1969 (lacks data for slate, 1960-

63). C, Estimate by Harvey Smith in Mining Engineering, v. 24, no. 1, p. 53,1972. 
LIGHTWEIGHT AGGREGATES 337 

significance. Cinders from coal-fired furnaces and 

boilers were used throughout the country for the 

production of cinder block from the late 1800's 

through World War II ; conversion to gas- and oilfired installations and to the use of pulverized coal 

has effectively removed the source of the material, 

and it now constitutes a very small resource. Fly 

ash and bottom ash, the residues of pulverized-coal 

combustion, are used as aggregates and pozzolans 

and will supply an increasing amount over the next 

several years to the aggregate market. Expanded 

clay and shale aggregates in lightweight concrete 

were used as early as World War I in concrete ships, 

and there was a small market (small, partly owing 

to patent restrictions) for the lightweight aggregates through the end of World War II. A rapid increase in number of plants and production of expanded clay and shales began in about 1947 (fig. 40) 

with the expiration of patents on the rotary kiln 

(Hayde) process. Data before 1953 are incomplete 

but suggest that production tripled from 1947 to 

1953 and tripled again between 1953 and 1956. Production and consumption of "pumice" and expanded 

iron blast-furnace slag increased very rapidly in 

the period 1945-50 (fig. 40), as a part of the postwar construction boom. Since 1956 overall production 

of the structural lightweight aggregates has reflected construction trends fairly closely, although 

some deviations from trend in production of pumice 

and a long-term decline in production of expanded 

slag have occurred. 

A fairly steady increase (with some minor fluctuations) in the total amount of pumice produced 

since 1957 conceals sharp periodic (1-2 years) 

variations in the amounts classed as "volcanic 

cinder" (fig. 40); inconsistency in classification 

probably causes the variation, rather than actual 

selective production. Deviations in trend between 

total pumice and pumice used as concrete aggregate 

and admixtur-e are real, however, and reflect the 

responsiveness of the lightweight concrete-block 

market to construction activity in the residential 

and light industrial fields. Since 1953 the production of all pumice has more than doubled, whereas 

its use in concrete has increased more slowly and 

has virtually leveled off since 1958-59, fluctuating 

about 10 percent around the million-ton-per-year 

level. During the same period use of pumice as 

railroad ballast decreased, but its use for road construction very markedly increased. 

Expanded slag production peaked between 1955 

and 1958, and it has slowly declined since then, 

hovering at about 2-2¥2 million tons per year. Significant short-term decreases reflect both market 

conditions, as in 1961, 1968, and 1970, and nonmarket influences, as in the prolonged steel strike 

of 1959, which cut off supplies of molten slag. Overall, the decline represents a- loss of markets to 

competitive products, particularly the expanded and 

sintered clays, shales, and slates. Sources of slag 

predominantly are iron blast furnaces, which are in 

only a few areas of the country. Suitable sources 

of clay, shale, and slate are widespread ; new facilities have been brought into production to compete 

with slag in market areas close to the furnaces, as 

well as in the peripheral areas where slag use a 

marginal operation. Usage of fly ash in some of 

the slag-production areas has also contributed to 

the decline. 

In common with other extractive industries that 

produce materials at the earth's surface, the lightweight-aggregate industry is faced with the environmental problems inherent in open-cast mining, in 

the control of fine materials formed in the manufacturing process, in the destructive consumption 

of water in some processes, and in the degradation 

of water quality in other processes. None of these 

problems is insuperable; all involve extra expense 

in production, in a highly competitive market with 

commonly slender profit margins. As low-unit-value 

high-place-value commodities, raw-material sources 

and production sites have to be as close together 

as possible, and both have to be as centrally located 

to the market area as possible. Consumption of 

structural aggregates. is mostly in urban areas; 

environmental impacts and conflicts are increased 

because they take place close to where many people 

live. One further complication; in some areas the 

Clay, shale, slate.-Total production of kilned and sintered aggregate: 1948-55, J. W. Roberts, Solite Corp., oral commun., 

Feb. 14, 1960; 1956-70, U.S. Bur. Mines Minerals Yearbooks, and A. L. Bush, U.S. Geol. Survey. 

Slag.-Ex_panded blast-furnace slag, does not include zinc and phosphate smelter slags; U.S. Bur. Mines Minerals Yearbooks. 

Pumice.-Total tonnage of pumice and pumicite, 1940-70, and of scoria and volcanic cinder, 1953-70; U.S. Bur. Mines 

Minerals Yearbooks. 

Pumice in concrete.-Tonnage used as concrete admixture and additive, excludes scoria and volcanic cin~r before 1953; 

U.S. Bur. Mines Minerals Yearbooks. 

Pumice without cinder.-Tonnage of pumice and pumicite, exclusive of scoria and volcanic cinder, 1953-70; U.S. Bur. Mines 

Minerals Yearbooks. 
338 UNITED STATES MINERAL RESOURCES 

raw material must be extracted before the area is 

irretrievably lost to preclusive uses, such as industrial plants, high-rise buildings, and residential 

construction. 

CLAYS, SHALES, AND SLATES 

Many varieties of clays, shales, and slates, of 

diverse origins, expand somewhat on heating to 

about 2,000°F (1,100°C). Basically, all clays, shales, 

and slates are chemically and, to some extent, mineralogically similar-they differ mostly in their 

physical characteristics. Lightweight aggregates are 

used only for their physical properties, and it is 

their chemical similarity that makes all of them 

amenable to thermal expansion. Table 67 presents 

several representative chemical analyses for the 

argillaceous rocks that have been tested for use as 

lightweight aggregate. The range in composition is 

wide for each of the three materials, and all three 

ranges largely overlap. Unfortunately, the analyses 

of rocks that expand suitaby, that expand inadequately, or that do not expand, all fall in these same 

ranges. 

The basic requirement for expansion of an argillaceous rock is a source of gas within the raw material, but several other physical characteristics are 

required for full suitability. Sufficient gas must form 

to cause a full bloat, in the temperature range where 

the material is pyroplastic (melted enough to be 

viscous), so that the gas can be trapped; there must 

be enough vitrification, at a high enough viscosity, 

so that most of the gas can be held in small, evenly 

distributed pores ; and the temperature range between softening and liquefaction must be large 

enough (about 100°F) that the bloating can be controlled in large-scale commercial production. Economical production is had at kiln or sinter temperatures between 1,800° and 2,200°F (1,000°-1,200°C), 

although temperatures can be as low as 1,600°F 

(870°C) or as high as 2,400°F (1,300°C). 

There is little agreement on the relative importance of the number of possible sources for the gas 

evolved within the raw material. Conventional wisdom in the early days of the industry held that. the 

argillaceous rocks had to have a significant organic 

content, although the amount varied with the practitioner. However, laboratory investigation of the 

evolved gases showed that many materials with very 

little total carbon expanded better than those with 

an appreciable amount (Austin and others, 1942; 

Sullivan and others, 1942)-to perhaps 1.5 percentand that C02, S02, and H20 all played a part in the 

bloating. Riley's (1951) research indicated that 

thermal destruction of hematite, pyrite, and dolomite provided both C02 and S02 in amount sufficient 

for bloating without recourse to organic , carbon. 

Ehlers and Richardson (1958) emphasized the role 

of C02 derived by the heating of calcite, dolomite, 

and ankerite in the argillaceous rocks, and subsequent more effective entrapment in illite than in 

kaolinite (kaolinite fuses at a higher temperature 

than illite). They deemphasized the role of iron in 

gas liberation, considering it to be of possible significance only where hematite exceeded 5 percent of 

TABLE 67.-Compa,rative composition of ezpansible clays, shales, and slates 

Clay 

Sample -------------------

SiOa ------------- AhOa ------------ Fe:!Oa ------------

FeD ------------- MgO -------------

CaO ------------- N~ ------------ ~ ------------- TiOa ------------- Loss on ia'nitfon ---

Total -------

COa ------------- C (organic) ------

HaO + ----------- H.o- ------------

8 ---------------- Other ------------

1 Total iron. 

1 

53.00 

20.74 

4.27 

2.30 

1.82 

.66 

.51 

8.4 

1.06 

•iii:7j .82 

.78 

7.15 

2.81 

.04 

•.98 

a Total of all constituent.. 

2 8 

61.80 36.7 

16.88 25 8 1 9.68 2.65 

.13 

.06 1.22 

1.27 10.7 

2.09 .26 

.67 8.4 

1.17 .57 

to~:~~ •too.oi 

2.98 

.72 

4.68 

4.28 

.08 

'7.89 

a PsOs, 0.67; MnO, 0.11; CI, 0.15; F, 0.10. 

'PsOs, 7.8; F, 0.59. 

49.00 

24.67 

5.44 

6.79 

2.36 

.49 

.7.& 

8.50 

8.16 

100.15 

.98 

.87 

.79 

Shale 

& 

65.01 

17.07 

2.15 

3.38 

1.89 

.70 

1.33 

2.59 

5.69 

99.81 

.21 

.so 

.64 

6 

69.00 

11.60 

6.37 

1.07 

1.58 

.32 

.95 

3.00 

.80 

5.U 

11101.20 

.37 

.85 

.51 

.044 

SAMPLE LOCATIONS AND REFERENCES 

1. Pennsylvania (Roen and Hosterman, 1969, sample Ro-R-1b). 

2. New South Wales, Australia (Hill and Crook, 1960, sample 4). 

8. Florida (Conley and others, 1948, sample 10). 

4. IDinoiB (White, 1960, sample 1415). 

5. IDinoiB (White, 1960, sample 1334A). 

6. Pennsylvania (Root, 1968, sample 10). 

7. Florida (Conley and others, 1948, sample 8). 

8. Pennsylvania (Conley, 1942, sample 1). 

9. New South Wales, Australia (Hill and Crook, 1960, sample 18). 

7 

64.6 

12.9 

1.72 

4.17 

136 

1.29 

1.28 

5.9 

1.10 

1 100.00 

3.47 

.54 

1.18 

.41 

.08 

Slate 

8 

54.00 

17.80 

1 6.65 

8.82 

4.68 

.76 

2.28 

.73 

4.87 

'100.18 

4.21 

1.34 

9 

57.86 

18.95 

1 7.12 

8.69 

8.02 

.61 

2.24 

.78 

5.98 

99.75 

2.96 
LIGHTWEIGHT AGGREGATES 339 

the rock. Meanwhile, Gervids (1957) admitted that 

carbonates, sulfides, sulfates, and oxides could all 

participate in the gas-forming process but asserted 

that the gas was formed at temperatures ( 550°-

825°C) well below the rock-softening level (1,050°-

1,1500C). He suggested that only the dehydroxylation of micas and amphiboles could account for the 

bloating, inasmuch as these reactions occurred at 

rock-softening temperatures. Hill and Crook (1960, 

p. 382) specifically refuted this contention, stating 

that it was intrinsically "improbable because the 

dehydroxylation temperature is considerably lower 

than the bloating temperature * * * ," and they 

very strongly emphasized the role of the reduction 

of ferric to ferrous oxide, with the oxygen evolved 

as the cause of the bloating. Chopra, Lal, and Ramachandran (1964) decided that both organic matter 

and calcium carbonate produced the gas that does 

the bloating, and that hydroxyl water, entrapped 

pore air, and ferric oxide were not significant contributors. Donnelly, Brennan, and Peacock (1968) 

concluded that iron oxide and water reacted with 

carbon (as little as 0.1 percent) to produce carbon 

monoxide, carbon dioxide, and a little hydrogen and 

that the decomposition of carbonates does not contribute to the bloating. This brief history suggests 

(1) that the divergence of opinion as to what causes 

bloating is considerable, (2) that no single factor 

is most important, and (3) that insufficient consideration has been given to the possible effects of the 

suggested reactions operating simultaneously, at 

least as far as the production of gas is concerned. 

Riley (1951) investigated the combinations of 

constituents that apparently acted as fluxes and 

affected pyroplastic conditions at the appropriate 

temperatures for gas formation and retention. In 

plotting the distribution of some 85 chemical 

analyses of bloating and nonbloating clays and 

shales in terms of their Si02, Al20a, and combined 

Fe20a, FeO, CaO, MgO, and (K, Na) 20 (flux) content, he was able to define a range of compositions 

that included most of the bloatable materials and 

excluded most of the nonbloatable materials. That 

range was about Si02, 52--80 percent; Al20a, 11-25 

percent; and combined fluxes, 10-25 percent (fig. 

41). Additional investigations since 1951 have shown 

that this bloating range is less reliable than it first 

seemed to be, but it is a useful guideline. As examples, White (1960) showed that the range had to be 

extended in the direction of higher Al20a and lower 

flux contents, whereas Sweeney and Hamlin (1965a) 

had to extend the range to a higher flux content 

(fig. 41). At the same time, more materials previously considered to be nonbloatable were included 

in the bloating range. 

Laboratory methods for evaluating raw materials 

have been described by Conley, Wilson, Klinefelter, 

and others (1948), Klinefelter and Hamlin (1957), 

and Hamlin and Templin (1962). The ultimate evaluation is how the material expands in a commercial 

operation; for this determination to be made, several tons of material may need to be run. 

To distinguish between favorable and unfavorable 

rocks in the field is difficult because so many different argillaceous rocks have been found to be suitable. Burnett (1964) suggested that field estimates 

be made of the content of iron, alkali, carbonate, 

organic carbon, and silt. Because too much of any 

of these constituents can cause the bloating range 

to be too narrow, the firing temperature to be too 

high, or the expanded product to be too heavy, an 

overabundance can serve as a negative criterion. 

There are no really positive field criteria. Illitic and 

montmorillonitic sediments seem to be more consistently favorable than kaolinitic ones. The darker 

colored clays, shales, and slates (green, gray, black) 

are more suitable than the light colored (particularly 

red) ones, especially if they have a moderate content of dispersed organic carbon. In general, unweathered materials are more suitable than weathered ones. Common or brick clay is more suitable 

both physically and economically than flint or ball 

clay. Thinly fissile shales and slates tend to expand 

unidimensionally, which is undesirable. Most of 

these features tend to vary more greatly in short 

vertical intervals across the sedimentary section 

than laterally along the sedimentary units, but 

lateral variation is enough that units unsuitable at 

one point may be eminently suitable a few hundreds 

of yards to a few miles away. 

In addition to the materials that can be made to 

expand, argillaceous rocks can be ground, mixed 

wth combustible materials-such as ground coaland sintered to produce lightweight aggregates. 

The mass becomes pyroplastic, or cohesive, and voids 

are left as the combustibles are burned out; some 

bloating may occur, but it is incidental to the sintering. Inasmuch as units that may not bloat of 

themselves can thus be used for lightweight aggregate, classifications of argillaceous rocks as unfit is 

unwise unless the rocks have been tested and found 

unsuitable for both processes. 

Marine, littoral, lacustrine, and fluviatile clays 

and shales, and slates derived from them, are all 

possible raw materials. They occur in formations 

that range in thickness from a few feet to more 

than 1 thousand feet and in age from Precambrian 

to Holocene, and they are distributed throughout 
340 UNITED STATES MINERAL RESOURCES 

0 

0 

e / 

/. e 0 

I 

I o o 

I 

I Oa 

• 

\ 60 

,., 

0 \ •• 

\ L\ 

\ .· 

\ 

50~----~~----~~----~~----~~----~~----~~----~~----~~----~~----~50 

Al 1 0 3 40 30 20 10 Fe1 0 3 , FeO, S 

CaO, MgO, P2 0 5 

Na2 0, K 2 0, N02 

EXPLANATION 

Reference 

Riley (1951) 

White (1960) 

Bloater 

e 

Nonbloater 

0 

• 

Sweeney and Hamlin (1965a) • 0 

FIGURE 41.--Comparative composition of bloating and nonbloating argillaceous rocks. 

the continental United States. The list of suitable 

rocks in the Appalachian region as given by Bush 

and Sweeney (1968) illustrates the number and 

variety available and is probably not complete. 

The sheer volume of suitable rocks make reserve 

and resource problems somewhat different from 

those for most mineral commodities. The distinctions 

among proved, probable, and possible reserves are 

somewhat blurred, inasmuch as the principles of 

stratigraphic continuity allow for projection of the 

favorable unit for unusually great distances beyond 

points of observation, but the amount of accuracy 

in the calculation. of tonnage is fair. In most mineral deposits, paramarginal and submarginal reserves are in lower grade, larger tonnage masses 

for which a complex interplay of costs determines 

profitability. In this situation the entire rock mass 

is the ore, changes in processing technology are seldom involved, and transportation costs are usually 

the determining element in separating recoverable, 

paramarginal, and submarginal reserves. The distinction between hypothetical and speculative re-
LIGHTWEIGHT AGGREGATES 341 

sources is similarly blurred, for the concept of deposits in mining districts really does not apply to 

the distribution of argillaceous rocks throughout the 

United States. Geologic mapping in the United 

States, at scales adequate to identify the presence 

of argillaceous rocks, is sufficiently complete to virtually rule out the possibility of finding additional 

units. What remains to be found are those deposits 

that would be classed as submarginal or, at best, 

as paramarginal. 

Reserves of expandable clays, shales, and slates 

are so large that they can be relied upon to satisfy 

the Nation's needs for many years. If those needs 

are projected from 1970 through 2000, starting with 

the estimated actual 1970 production of slightly 

more than 10 million tons and projecting an annual 

growth rate of 5 percent, the cumulative production 

is about 670 million tons. That figure, though impressive, is seen in better perspective if it is allocated among the 36 States that produced lightweight 

aggregates in 1970-an average per State of about 

18¥2 million tons, or the mining of about 13 standard mining claims to a depth of a little less than 

20 feet. Put another way, cumulative production 

through the year 2000 will represent about onemillionth of the tonnage of argillaceous rocks in the 

48 contiguous States to a depth of 20 feet below 

the surface. 

For a number of reasons the sum of recoverable 

reserves cannot be stated with much accuracy, but 

a reasonable estimate can still be made, based on 

other than strictly geologic reasoning. Between 70 

and 85 processing plants (both kiln and sinter) have 

been in operation annually over the period 1965-70. 

Plant investments are large, ranging from several 

hundred thousand dollars to more than $1 million. 

Average annual production in 1970 was about 

150,000 tons. Plant amortization requirements over 

about a 10-year period suggest the need for an 

average raw-material reserve of about 1.5 million 

tons per plant, about the equivalent of a standardsize mining claim quarried to a depth of 20 feet. In 

view of the stratigraphic characteristics of the argillaceous rocks, this is a very plausible estimate 

for almost any of the processing sites. As a rule of 

thumb, roughly equal amounts can be assigned to 

the proved, probable, and possible reserves, perhaps 

about 115 million tons each, or a rounded total of 

recoverable reserves in the presently known deposits 

of about 350 million tons. The sum of all reserves 

plus hypothetical and speeulative resources is many 

times that of the recoverable reserves. 

VOLCANIC ROCKS 

Various volcanic rocks are suitable for use as 

lightweight aggregates ; all are glasses, and they 

range in composition from mafic to silicic. Scoria., 

volcanic cinder, pumice, and pumicite make moderate- to low-strength structural aggregates, whereas 

expanded perlite and expanded pumicite are ultralightweight materials. The chemical composition of 

the glasses (table 68) faithfully mirrors that of 

TABLE 68.-Comparative compositicm of volca:nic glasses 

[Tr., traee; ND, not determined; NA not applieable] 

Pumieite Pumiee Perlite Obsidian Scoria 

Sample -------------------- 2 3 4 6 6 7 8 9 10 11 12 13 14 16 16 

Si011 -------------------- 73.32 71.98 68.43 72.3 60.10 67.50 69.47 70.38 73.20 67.05 72.75 7(.(1 73.38 72.93 6.0.90 44.6 

AI !lOa ------------------- 10.76 10.94 12.94 11.8 13.66 12.96 13.48 16.82 12.17 1(.91 13.34 13.33 13.69 16.63 18.24 24.6 

Fei!Oa ------------------- 1.66 1.93 1.22 1.7 3.30 2.32 1.43 1.60 .76 .92 1.12 .08 1.84 1.20 7.77 8.3 

FeO -------------------- 1.42 .30 1.48 1 .89 .86 .13 

TiO:a -i.7i -------------------- 1.36 • 33 .6 Tr • .60 .26 .13 .34 1 .13 .06 .12 

CaO -------------------- .53 2.14 1.17 1.0 4.96 1.06 1.13 1.66 1.08 2.44 1.13 1.90 1.38 1.31 9.58 6,, 

MgO -------------------- .23 .16 .22 .3 .72 .01 .20 .48 .13 .66 8 .19 .43 .37 .18 5.73 2.0 

K:aO 6.30 6.94 2.16 '5.' .68 2.41 1.70 4.10 6.16 3.04 15 4.22 4.30 4.22 3.87 2,.20 6.2 

Na:aa-:::::::::::::::::::: 2.27 2.08 3.60 '2.7 2.00 9.89 6.68 3.70 3.12 ,,16 6 3.01 2.99 3.92 3.47 4.90 8.6 

P:a011 Tr. Tr. ND -;.12 -(os .02 .12 .08 .23 .08 

SOa, so,:-s-:::::::::::::: ND 0 11 1.83 8 .03 

MnO -------------------- -,~78 .14 • 08 Tr • .06 .02 

Other 10 .12 Loss mi"i~iii<;;-----------· 

(also total HIIO) -------- 3.93 4.61 9.81 4.3 12.87 8.17 6.60 3.62 8.62 4.86 4.08 .62 .89 .36 .98 .8 

Total -------------- 99.36 100.00 100.22 NA 100.16 99.94 99.92 102.08 99.76 99.96 NA 99.16 99.69 NA 102.04 NA 

1 Average of four analyses. 0 SOa. 1 Average of 14 anal)'Bes. 7 so .. a Average of 16 analyses. as. 

' Average of 40 analyses. • COs. 0.81; Ob, 0.4'7. 1 Averaee of 20 analyses. 10Cb. 

SAMPLE LOCATIONS AND REFERENCES 

1. Sample JV-6, Pearlette ash, Kansas (Carey and others, 19&2). 

2. Sample NNV-1B, Calvert Ash Bed of Ogallala Formation, Kansas 

(Carey and others, 1962). 

3. Pumieite at Shoshone, Calif. (Chesterman, 1956). 

4. Average of 54 analyses, Kansas (Bauleke, 1962). 

6. Mono County, Calif. (Chesterman, 1966). 

6. Italy (Talmage and Wooton, 1937). 

7. Mount Taylor, N.Mex. (Talmage and Wotton, 1937). 

8. Average of 80 analyses (Kine. 1948). 

9. Soeorro deposit, New Mexieo (Weber, 1963). 

10. Desehutes deposit, Oregon (King, 1948). 

11. Average of 21 analyses: 11 from King (1948); 10 from Anderson, 

Selvig, Baur, Colbassani, and Bank (1966). 

12. Shirataki, Japan (Yagi, 1966). 

13. Glass Mountain, Calif. (Chesterman, 1966). 

14. Average of three anal)'Bes, Orearon and California (Ki~~~r, 1948). 

16. Red Cinder Mountain, Calif. (Chesterman, 1966). 

16. Averqe of six anal)'Bes, Idaho (Asher, 1966). 
UNITED STATES MINERAL RESOURCES 

their crystalline counterparts ; scoria and cinder are 

like basalts (and basaltic andesites), and pumice, 

pumicite, and perlite are like granites and rhyolites. 

Contained water in basalts is little different from 

that in scoria and cinder, but the difference between 

that in the granitic rocks and that in silicic glassy 

rocks is significant. It is this excess of water that 

allows the perlites and pumicites to be thermally 

expanded. In a general way, the viscosity of the 

extruded rock melt varies directly with the Si02, 

N a20, and K20 content and inversely with the Fe20a, 

FeO, CaO, and MgO content; thus, whereas the mafic 

rocks are more fluid, the silicic rocks are more likely 

to retain gases. 

SCORIA AND VOLCANIC CINDER 

Scoria and volcanic cinder are cellular, frothy 

products of explosive volcanism-erupted as tephra 

(blocks, bombs, lapilli, and gravel) or lava flows 

from mafic magmas. Much of the material is forcefully ejected from the vent, vesiculating in the air 

as the volcanic gases (mostly water) expand and are 

entrapped by the rapid cooling of the relatively fluid 

lava. Scoria also develops where the gases are entrapped by rapid cooling at the surface of the flows ; 

it may then be broken into blocks and irregular 

fragments by continued movement of the flows. 

There is a fairly wide range in vesicle size (particularly in the ejecta, most of which have dense fused 

surfaces) and in the thickness of the cell walls, 

which results in a considerable variation in the 

density of the rocks. The distinction between scoria 

and volcanic cinder is an arbitrary one of size; 

cinder is the material less than 1 inch (about 2.5 

em) in largest dimension. Characteristically, mafic 

ejecta are fairly heavy and are not thrown long distances from the vent; they form cinder cones 

around the vent that are generally a few thousand 

to several thousand feet in diameter and several 

hundred feet in height. In contrast, mafic lava flows 

(basalt or basaltic andesite) tend to be fluid, several 

hundred feet to tens of miles in lateral extent, and 

a few feet to several tens of feet thick. The flows are 

seldom abundantly scoriaceous throughout; most of 

vesicular zones are confined to the upper few feet of 

the flow and are highly variable in their development. 

Most of the deposits of scoria and volcanic cinder 

are geologically youthful, in Quaternary or upper 

Tertiary terranes ( < 1-11 m.y. old), and some are 

only a few thousand years old. Many mafic extrusive rocks are latecomers in the volcanic sequence 

and, thus, are less likely to be buried deeply enough 

to survive prolonged erosion. In addition, the ejecta 

seldom make well-consolidated resistant lithologic 

units because the individual blocks, bombs, and 

lapilli do not weld together consistently. They are 

easily eroded and, in humid climates, are subject to· 

rapid chemical weathering. Although the ejecta 

enter readily into the sedimentary cycle, they are 

not persistent in it. They lack sufficient resistance 

to abrasion to survive reworking for very long in 

the moderate-energy environment needed to move 

them to protected sites where they can be preserved. 

Mafic vesicular volcanic rocks are widely distributed throughout the Western United States, including Hawaii and Alaska, but are missing from the 

Central and Eastern States. Deposits of scoria and 

cinder are known in every State west of the 104th 

meridian, and production was recorded in 1969 or 

1970 from all States but Alaska. Arizona, Oregon, 

California, Hawaii, and New Mexico are the .. largest 

producers, generally in that order; however, in 1970 

Oregon was first. The ranking in production does 

not always reflect the relative amounts of scoria 

and cinder available, in part because production is 

determined by competition and the size of the 

market within economic range of the deposits and 

in part because the reporting of production includes 

pumice and pumicite. In the States west of 104°, 

nearly all the metropolitan districts with a core 

city of at least 50,000 people and most cities of at 

least 25,000 are within about 100 miles of deposits 

of scoria or cinder, but not all can be served ec(}-

nomically from them. 

Estimating the recoverable reserves of scoria and 

cinder is an exercise in very short term prediction, 

for production is extremely sensitive to the state of 

the construction industry, and pits can be and are 

shut down quickly. For example, Meisinger (1972) 

reported the closing in 1970 of 48 operations of the 

171 that were open in 1969. His figures are for all 

pumice, pumicite, scoria and cinder operations, but 

inasmuch as 85 percent of the total production was 

cinder, it..seems reasonable to assume that most of 

the closed operations were also for scoria or cinder. 

Although the more than 25 percent drop in operations resulted in only a 15. percent drop in output 

from 1969, it might represent either a larger or 

smaller decrease from the 1969 recoverable reserves, for when an operation closes, all its recoverable reserves, by definition, become at least paramarginal. 

For scoria and cinder, the economic criteria that 

separate recoverable from paramarginal and submarginal reserves are primarily the level of activity 

of the construction industry and competition from 

expanded clays, shales, and slates. Other materials, 
LIGHTWEIGHT AGGREGATES 343 

like expanded slag and fly ash, are not significant 

competitors in the Western States. The stumbling 

block is usually the cost of transportation, and this 

cost almost invariably cannot be decreased. For 

most commodities the grade of the ore enters into 

the criteria, and new techniques of recovery may 

convert protore into ore. These criteria are not 

particularly applicable to any of the nonmetallic 

deposits, where the whole rock mass is the ore. Volcanic ejecta have already undergone a crude form 

of aerial classification that has substantially separated vesiculated from dense rock. Only a small 

additional tonnage could be won at any deposit by 

separating vesiculated rock from predominantly 

dense rock. In deposits that are scoriaceous zones 

in flowrock, more intermingling of vesiculated and 

dense rock occurs, but even here the additional tonnage to be gained is small, and the cost of winning 

it comparatively high. In summary, these paramarginal resources are not significant. 

An order of magnitude can be established, although not from strictly geologic evidence, for both 

the recoverable reserves and the identified resources. 

For example, many cinder cones have basal diameters greater than 2,000 feet, and angles of slope· 

(determined by the angle of repose for fragmental 

volcanic material) that range from 30° to 40° (Colton, 1964). For a cone that has a 2,000-foot base 

diameter, a crater lip 425 feet above the base, and 

a crater 500 feet in diameter at the lip, the angle 

of slope is less than 30°, well within the angle of 

repose. Depending on the density of the scoria, 

which can range from 1,000 to 1,500 lb per cu yd 

(pounds per cubic yard), such a cone could contain 

from 10 to 15 million tons. One such cone, then, can 

contain from three to six times the entire U.S. 

production of volcanic cinder, 2,656,000 tons for 

1970 (Meisinger, 1972, p. 965). An assumption seems 

reasonable that 25--30 of the operating pits in 1970 

(there were more than 100 in all) were in cinder 

cones of this size in the 10 or more States where 

scoria was produced; as a result, recoverable reserves that year were between 250 and 450 million 

tons in just those deposits. In the category of paramarginal resources, economically recoverable at 1.5 

times the present price (McKelvey, 1972), there are 

probably a similar number of deposits and tonnages 

and, also, a similar quantity in the submarginal resources. Identified resources can be thought of as 1 

billion tons, plus or minus 25 percent. 

Let us put it in another kind of perspective. If we 

assume that 3 million tons of scoria and cinder was 

produced in 1970 and that an annual growth rate 

of 5 percent persists through the year 2000, we 

shall have need for a cumulative output of about 200 

million tons. That appears to be significantly less 

than the recoverable reserves in the cinder cones 

being mined in 1970. 

The category of hypothetical resources requires a 

different approach, for basically the search is not 

for hidden deposits but for unmapped ones. By 1972 

the location of most of the cinder cones and mafic 

lava flows in the conterminous United States probably had been depicted on some sort of geologic 

map at some kind of scale. Knowledge of the sizes 

and volumes of these cones and flows and of the 

ratio of vesicular to dense rock within them is what 

is required to convert their status to one of the 

reserve classes. The distribution of the deposits that 

make up the identified resources suggests that there 

may be at least an equal number for which information on size is lacking, and, on that basis, the hypothetical resources can be estimated to be on the 

order of 1 billion tons, as well. 

Speculative resources require a further exercise 

of the imagination. Higgs (1949) estimated that 

Cenozoic extrusive rocks in the conterminous United 

States covered 8.368 percent of the land surface. 

In the absence of other estimates on the ratio of 

mafic to silicic extrusives at the surface, and for 

ease of estimation, let us assume that mafic rocks 

cover only 1 percent of the surface and that they 

average about 50 feet thick. Let us further assume 

that 1 percent of this volume is scoriaceous. This is 

equivalent to about 3 cubic miles of scoria, or about 

9 billion tons. The potential reserves and hypothetical resources listed above can be adequately 

accommodated within this total resource. 

PUMICE AND PUMICITE 

Pumice and pumicite a~e the silicic extrusive 

equivalents of scoria and volcanic cinder but are 

lighter in color, of lower density, and more highly 

cellulated. In pumice the voids may be spherical, 

ovoid, tubular or irregular; the cell walls are commonly very thin ; and the rock is light enough to 

float. If sufficient gas and steam are available during explosive extrusion, the pumiceous froth is very 

commonly shattered, and the shards and finer fragments form pumicite (volcanic ash). The range in 

composition (table 68) is from rhyolitic to dacitic, 

andesitic, and even basaltic, but most pumices are 

in the rhyolite-dacite range. The higher viscosity of 

the silicic rock melts generally leads to more violent 

extrusion, and the lower density pumice and pumicite are thrown much farther from the vents than 

the scoria and cinder; many pumicite deposits are 

several hundred miles from their sources. 
UNITED STATES MINERAL RESOURCES 

Deposits of pumice and pumicite occur in a larger 

variety of forms than do scoria and cinder. A very 

common form is an air-fall blanket, semiconcentric 

to a crater source vent or broadly fan-shaped lateral 

to fissure vents and more extensively developed 

along the prevailing wind directions. Pumice cones 

along fissure vents are also numerous. Very large 

volumes occur in ash-flow tuffs and in the upper 

parts of rhyolite and "obsidian" domes. Any of 

these deposits is subject to rapid erosion, reworking, 

and consequent redeposition as stream or lake sediments. Thicknesses range from a tenth of an inch 

to many tens of feet, and areal extents range from 

a few square feet to tens of square miles ; therefore, 

volumes may be a few tons or many hundred 

thousand tons. Ash-fall deposits are more likely to 

be interbedded with other sediments than are ash 

flows, and reworked and redeposited materials very 

commonly are interbedded. 

In contrast with ash falls, most ash flows are 

unsorted, heterogeneous mixtures of pumice and 

ash, the pumice occurring in fragments and blocks 

as much as perhaps 8 or 10 feet in maximum dimension. Commonly, ash flows were hot enough and 

cooled slowly enough to weld and to cause the 

pumice to soften to the point of collapse, so that 

dense glassy zones in the central or lower part of 

the flow were formed. Ash flows are crudely sorted, 

with most of the larger blocks and fragments close 

to the source and successively finer materials at 

greater distances ; the finest ash may be carried for 

hundreds of miles. Some ash falls also retained 

enough heat to weld and to form glassy zones. Where 

ash and pumice fall directly on standing bodies of 

water, and where reworked material is deposited in 

quiet water, an inverted graded bedding may occur. 

The finest material has the greatest density and 

settles first, whereas coarser material is vesicular, 

floats longer, and is deposited last. 

Pumice deposits occur in all the Western States 

from the Rocky Mountains to the Pacific Ocean, 

and pumicite deposits are in Texas, Oklahoma, Kansas, North and South Dakota, and Nebraska nearly 

as far east as the Missouri River. In 1970 pumice or 

pumicite was produced in every Western State but 

Montana, and in Hawaii as well. Oregon and California were probably the leading producers of 

pumice, and Kansas was the leader in pumicite. 

Production statistics are so grouped that accurate 

data for each rock type cannot be determined. 

Prediction of the resources base for pumice and 

pumicite presents many of the same problems as 

for scoria and volcanic cinder. Any figure for recoverable reserves reflects wide annual variations 

in the number of operating mines and no accurate 

census has ever been kept of producers grouped by 

product. In part, the extreme increases and decreases in annual tonnage (fig. 40) reflect this imprecise classification, but they also suggest that 

many of the operations were marginal anc;l that 

what were recoverable reserves one day were 

paramarginal the next. Since 1957, except for 

1963 and 1964, the overall trend has been toward 

smaller production. But because most pumice and 

pumicite is used in the construction industry, the 

long-term-consumption trend will be a growth rate 

similar to that for construction. On the basis of the 

1960-70 average annual output of slightly more than 

600,000 tons and the previously used annual growth 

rate of 5 percent, cumulative production through 

the year 2000 will be about 40 million tons. 

Recoverable reserves can be estimated only within 

very broad limits. In 1970 some 30 mines operated 

in the conterminous United States. Although the 

range in deposit size seems to be fairly large, a 

conservative estimate suggests that many occurrences have dimensions of 500 by 1,000 by 10 feet. 

Bulk densities range from 850 lb per cu yd for 

pumice to 1,750 lb per cu yd for pumicite; tonnage 

for the sample deposit lies between about 80,000 and 

160,000 tons. Thus, the 1970 level of operations 

might entail between 2¥2 and 5 million tons of rock 

as recoverable reserves, ignoring all past production. 

Estimating paramarginal and submarginal resources 

each at twice the recoverable reserves is acceptable 

(see estimate of the total resource below) so that 

the identified resources can be thought of as a minimum of 25 million tons, more than half the amount 

needed through the year 2000. 

The total resource can be approximated on the 

same basis as that for scoria and volcanic cinder, 

using Higgs' (1949) estimate (8.368 percent) of 

extrusive rocks at land surface in the Western 

States. Higgs' method excludes all volcanic ash in 

the States east of the Rocky Mountains, however. 

Again no reliable estimates of the relative amounts 

of silicic, intermediate, and mafic volcanic rocks are 

available, but a general feeling among geologists 

indicates that intermediate rocks predominated in 

the early and middle Cenozoic and that both silicic 

and mafic rocks were abundant in the late Cenozoic, 

the mafiic rocks possibly having been more abundant. Basic rocks were assumed to occupy 1 percent 

of the surface for the scoria estimate; here, let us 

assume 0.1 percent coverage and an average thickness of 10 feet for the silicic rocks; let us further 

assume that 1 percent of this volume is pumice or 

pumicite. These parameters would seem to be almost 
LIGHTWEIGHT AGGREGATES 845 

minimal. On the basis of these assumptions the 

total resource is between 150 and 300 million tons, 

exclusive of the volcanic ash of the Great Plains. 

Pumicite deposits on the Great Plains are numerous and vary greatly in size; Ham (1949) reported 

one in Oklahoma to contain about 10 million cubic 

yards (perhaps 7-8 million tons). He estimated a 

total of about 20 million cubic yards in known deposits; by our definitions this 20 million cubic yards 

would be ·considered an identified resource of about 

17-18 million tons. Carey, Frye, Plummer, and 

Swineford (1952) estimated about 20 million tons 

for known deposits in Kansas, which we would also 

class as identified resources. Data are lacking for 

Nebraska, but on the basis of past production and 

the distribution of the deposits, a tonnage on the 

same order of magnitude as Kansas and Oklahoma 

is reasonable. A conservative estimate for all the 

Great Plains States may be taken as 50-60 million 

tons of identified resources, and perhaps the same 

amount for hypothetical and speculative resources 

combined; the total resource may be thought of as 

about 100-150 million tons. 

DIATOMITE 

Although diatomite has been and is used as a 

lightweight aggregate, the usage seldom exceeds a 

few tens of thousands of tons per year and is not 

a significant factor in the reserve and resource position of the United States. In general, its value for 

other uses, such as filter aids, is far too great to 

justify its utilization as a low-cost aggregate. Only 

in a very few special cases can diatomite be used 

economically, and then it is generally as a byproduct 

from the treatment of the material for its more 

specialized roles. Information on distribution, geologic habit, and resources are in the chapter 

"Diatomite." 

OTHER MATERIALS 

Expanded blast-furnace slag and fly ash are a 

significant part of the supply of structural lightweight aggregates in the heavily industrialized 

Great Lakes and Pennsylvania areas and in Alabama, Colorado, California, and North Carolina. 

Expanded slag production ranged from about 21/2 

million tons per year during the period 1960-70 

(fig. 40). Expanded slag is only a fraction of the 

slag produced annually; it is likely to be ample to 

meet any demand for many years. Fly ash production (which includes bottom ash) in 1970 was more 

than 35 million tons and was widely distributed 

throughout the country with only about 4 million 

tons being utilized in any way. Lightweight aggregate production of sintered fly ash totaled about 

260,000 tons and was confined to the Detroit, Mich., 

Pittsburgh, Pa., and Charlotte, N.C., areas. 

There appears to be an obvious market potential 

for both expanded slag and fly ash-perhaps a little 

more favorable for the ash-because the coalburning power-generating stations are widely distributed and the country's increasing demands for 

energy probably entail the construction of more 

plants. 

ULTRALIGHTWEIGHT AGGREGATES 

INTRODUCTION 

The natural ultralightweight aggregates are perlite, pumicite, and vermiculite; the first two are 

products of dominantly silicic· volcanism (see section on "Pumice and Pumicite"), whereas vermiculite is a low-temperature alteration product of ultramafic igneous and metamorphic rocks. High-temperature heating is required of all three crude ores 

to cause expansion and to develop the vesicularity 

that gives the materials their desirable attributes. 

Properly treated, all three materials develop high 

porosity but low permeability and have very thin 

cell walls. Thus, they make excellent thermal and 

acoustic insulators, but their compressive strength 

is low. Concretes and plasters using them as aggregates have strengths from 100 psi to about 2,290 

psi; the more cement used, the greater the strength 

and the greater the weight. The materials are very 

well employed in fireproof plasters, in concrete curtain walls, floor fills, and roof decks, in concrete 

refractory and insulating walls in bake ovens, and 

in decorative, non-load-bearing blocks and facings 

(Schroeder, 1970a, b). In loose fill or bulk form they 

are primarily used for insulation, both thermal and 

acoustic, but significant amounts are used as inert 

carriers and extenders in horticultural products and 

in manufacturing processes. 

As with the structural lightweight aggregates, 

the ultralightweights . are not indispensable; synthetic materials (polystyrene beads, polyurethane 

foams, foamed phenolic resins) can be substituted 

in some applications; lightweight concretes and 

plasters can be made by air entrapment through the 

use of aluminous foaming compounds; foamed glass 

can be used for some special requirements. In general, however, the use of expanded natural materials 

is more economic and less complicated in preparation and use. 

The United States produces all the perlite and 

pumicite that it consumes and has ample material 

to export, but, because of the low unit value of 

crude perlite, only a few thousand tons is exported 

annually-all of it to expanders in Canada. No 
346 UNITED STATES MINERAL RESOURCES 

pumicite is exported. Almost all the vermiculite used 

in the United States is produced domestically, but 

along the eastern seaboard, oceanic freight rates 

allow some vermiculite to be imported economically 

from the Republic of South Africa. In 1970 the 

United States was the world's largest producer of 

crude vermiculite, at about 285,000 tons, and South 

Africa was second, with about 134,000 tons (Fulkerson, 1972). The most Tecent import data are for 

1969, when about 6,500 tons entered the United 

States; this was equivalent to a little more than 2 

percent of the domestic production. 

EXPLOITATION 

The production histories of vermiculite and perlite are broadly similar in their early periods, and 

are very closely related since about 1955 (fig. 42). 

Vermiculite was first produced in Colorado in 1913, 

but the first significant sustained production began 

in Montana in 1925, with about 100 tons of crude 

ore. The growth rate was rapid, but the tonnages 

were small to 1937 (about 27,000 tons in 1937). 

The rate then became more gradual, but tonnage 

increased to about 200,000 tons in 1950, and then 

growth was slow but steady to about 300,000 tons 

in 1969 and 1970. Perlite production began after 

World War II and about 5,000 tons of crude ore was 

produced in 1946; output rose rapidly to about 

150,000 tons in 1951, and growth has continued at 

a slower but steady rate to more than 450,000 tons 

in 1969 and 1970. Since 1955 the annual increases 

and decreases in production of crude vermiculite and 

crude perlite virtually parallel each other, with the 

production of perlite about 150,000 tons greater 

than that of vermiculite. Consumption of expanded 

perlite has varied more than that of exfoliated ver1000 I I I I I I I I I I I I I I I l I 1 1 1 J J 1 L ..J.-... lOO ~ ~ ~r---------~---------+----------+---------~-----------~--------~~~~--~ 

700r---------1----------+----------+---------~----------~-----=~~~----------~ 

600j--------j--------t--------r--------t-----~~~~----~--~r-------~ 

~r---------~---------+----------+---------~----~~~--~--------~-------=~ 

4001------+------ _,/ P - -----:::= I d New construction ~ l er •t~ c~ ~,......- '---./"" 

300 (in dollers) Y ~ __ ,. -1--- ~ ~ ~ 

~~---~---~-~~--~-~-~-~~~,~~~~~~-~------~, I ~a: 100 /\ (-:_;~~,; ~~,;;t.~:.:-·----- ~~ 0 Z 90 

~r----------~~----~,----+,~~,I~----I~'I~---------+----------~---------+--------~ ' I , I 10 00 j~ 

~ 70~-----~~~----~~~--~,~,~+-,----~,7~t==========t==========t==========t=========j ~ 0 60 I r \. ~ • / 1'#--/+----------+---------i----------+--------1 LL W ~ 50!1 :·.. -~ / '/ oz 

c I ,. / II ~g z 40r---------1--,~-~/-+-----~~~-+---------~--------~----------~--------~ 2> 

<{ I , I ..J..J 

~ ~ ;' ..JZ 0 /'" I jDO 

z I ', ""_, ~ 

~ ~~~~---=-~-~--4----------+-----~--~----------~--------~----------~--------~ w 

~ermiculite, crude tPerlite, expanded ~ I ~ I 

10~·---------4----------+---~-----+----------~--------~----------~--------~ 

9r---------~---------+--~n~----+---------~----------~-------~--------~ 8 J 

7r---------,_ ________ -+--~~~-----+----------~--------~----------~--------~ II 6r---------,_ ________ -+-.~H~-------+----------~--------~----------~--------~ 5r---------,_ ________ -+~~------+---------~----------~--------~-------~ 

4~L-IL-I~I~I~~~--~IL-IL-I~~'~I~IL-L-IL-~I~I~IL-L-IL-~1~1~1--~IL-~I~I~J--I~L-~I~I~I--~1 

1935 1940 1945 1950 1955 1960 1965 1970 

FIGURE 42.-Production of materials used as ultralightweight aggregates in the United States, 1935-70; U.S. Bureau of 

Mines Minerals Yearbooks. 

New construction.-Value of total new construction, exclusive of maintenance and repair; data from Statistical Abstracts 

of the United States, 1935-70. 

Perlite, crude.-Total crude ore sold and used by producers. 

Perlite, expanded.-Total produced. 

Vermiculite, crude-Total crude ore sold and used by producers. 

Vermiculite, exfoliated.-Total produced. 
LIGHTWEIGHT AGGREGATES 347 

miculite, in part reflecting the dominance of the 

vermiculite market by a single company, and in part 

reflecting the movement of perlite into the filteraids field at the same time as a decrease in perlite 

use in concretes and plasters. 

Perlite, pumicite, and vermiculite share the common problems of open-cast mining, but because 

many of the deposits are located in remote or 

sparsely populated areas, public concern with the 

mining operations has been minimal to date (1972). 

That is not true of the processing plants. Large 

amounts of fines are produced in the grinding circuits in the processing of perlite, and additional 

amounts are produced in the explosive expansion 

("popping") of perlite and pumicite. Their disposal 

is a problem from several aspects. Because both 

rna terials are glasses, the fines are pointed, sharp 

slivers and shards. Dust control is a major problem, both in preventing and alleviating pollution 

beyond the limits of the plant itself and in protecting plant workers from respiratory injuries and diseases. These problems are not so severe for vermiculite, which yields thin flakes to the fines; where wet 

classification methods are used, the disposal of 

vermiculite slimes presents other difficulties. 

VOLCANIC ROCKS 

PERLITE 

Obsidian, perlite, and pitchstone are volcanic 

glasses of generally silicic composition and are the 

equivalents of rhyolites, rhyodacites, trachytes, or 

latites. Among themselves, they differ chemically 

primarily in water content; obsidian has no more 

than 2 percent H20, perlite has 2-5 percent, and 

pitchstone has more than 5 percent. The general 

range of composition (table 68) is Si02 from 70 to 75 

percent and Al203 from about 10 to 15 percent. The 

water content seems to be the only chemical 

component critical to expansion, and even then 

obsidians with as little as 0.2 percent H20 are 

reported to have expanded satisfactorily (King, 

1948). Originally, perlite meant a glassy rock characterized by concentric cracks, the "peri" (from the 

German "Perlstein") referring either to the resemblance of broken-out fragments to pearls or to the 

pearly luster of the surfaces. Today's commercial 

usage includes any glassy rock (except pumicite), 

regardless of composition or origin, that can be 

made to expand by heating to about 2,000°F 

(1,100°C). Most commercial perlites fit the petrographic definition that emphasizes a 2- to 5-percent 

water content. 

Many of the traditional applications of perlite are 

in the construction field, but an increasing percentage of the annual production over the past several 

years has gone into filter aids (1964, 15 percent; 

1970, 23 percent). Diatomite is the principal material used in filtration, but perlite seems to be 

making significant inroads into the market. In the 

construction field the principal competition comes 

from exfoliated vermiculite; in 1970 some 200,000 

tons of perlite and 180,000 tons of vermiculite were 

used. Schroeder (1970a) gave a rather detailed discussion of perlite processing, marketing, uses, and 

substitutes. 

Perlite is found in three major associations ; in 

glassy zones in welded ash-flow tuffs, in lava flows 

from volcanic domes, and in the wall zones of felsitic intrusive plugs and dikes. Smith (1960) has 

described the central zone of dense welding in a 

simple cooling unit of an ash flow as a glass with 

virtually no porosity, composed of completely collapsed pumice and ash, and bordered successively, 

both above and below, by a zone of partial welding 

and a zone of no welding. Sparse phenocrysts of 

feldspar, quartz, biotite, and hornblende may be 

present in all the zones. Ash flows may be deposited 

before cooling of an underlying one has proceeded 

very far; as a result, composite cooling units may 

result. In these, the zones of dense welding may 

coalesce, and the intermediate zones of partial welding and no welding are obliterated. In such a stack 

of flows, very thick densely welded zones of glass 

can develop. Characteristically, the welded zones 

pass laterally into zones of devitrification toward 

the central area of the cooling unit; thus, a zone of 

glass borders and envelops a zone of felsitic tuff. 

However, if cooling is sufficiently rapid to prevent 

crystallization, the glass may be preserved for some 

millions of year. Preservation of glasses, regardless 

of origin, is increasingly rare from the Pliocene 

back to the beginning of the Tertiary and is very 

rare in rocks older than that. 

The glass that develops in flows and in volcanic 

domes represents the rapidly cooled lava liquid, 

rather than collapsed pumice. Glass develops near 

the surface of the flow or dome and may be rolled 

under as the flow advances. In the process it may 

be brecciated, remelted, and annealed. As the flow 

comes to a stop, a zone of glass can be near its 

1 surface and near its base, and if cooling is rapid 

I 

enough the zones may coalesce to make a flow that 

. is virtually all glass. As with the ash-flow units, 

I the glass may pass laterally into a felsitic central 

I zone. In a somewhat analogous manner, a selvage 

1 of rapidly chilled glass can be formed at the con-
348 UNITED STATES MINERAL RESOURCES 

tact of a dike or plug with the country rock; in this 

type of occurrence the glass apparently devitrifies 

most rapidly. 

Perlite very commonly surrounds cores of obsidian, and there is a full range of occurrences from 

obsidian containing a minor amount of perlite along 

a network of fractures, through nearly equal 

amounts of perlite and obsidian, to complete perlite. 

Most obsidian cores range from about 1 inch in 

diameter to microscopic. Ross and Smith (1955) discovered a very marked, abrupt contra::~t in water 

content between the obsidian cores (a few tenths of 

1 percent) and the surrounding perlite (2-5 percent). They attributed the contrast to hydration 

of the glass after emplacement, on the basis of 

marked differences in the indices of refraction between obsidian and perlite and the relative ease of 

dehydration of perlite below 600°C as compared 

with dehydration of obsidian between 800° and 

1,000°C. They suggested that the water in obsidian 

was · pristine and that the water in perlite represented hydration from snow, rain, and ground 

water. Investigations of the deuterium content of 

the water in obsidian and perlite by Smith and 

Friedman (1957) and Friedman and Smith (1958) 

showed that most of the water in perlite was indeed of meteoric origin. These conclusions and the 

increasing devitrification of glass with increasing 

age are of importance to the consideration of perlite 

resources. 

As with the other volcanic glasses, perlite is 

widely distributed throughout the western conterminous United States (Jaster, 1956). In 1970 the 

production of crude ore came from New Mexico (87 

percent), Arizona, California, Nevada, Colorado, 

Idaho, and Utah. A very few deposits have had 

short-term production in Oregon and Texas ; other 

deposits are known in Montana, Wyoming, and 

Washington. 

Basic data on which to build a detailed estimate 

of the recoverable reserves of perlite in the United 

States are lacking. Simply, from the broad geologic 

knowledge of the very large volumes of extrusive 

rocks available, no shortage is foreseeable. As an 

example, some 600,000 tons of crude perlite was 

produced in 1970, and about 420,000 tons of expanded perlite was consumed, a ratio of about 1.5 

tons of crude for 1 ton of expanded. The perlite 

industry is moving toward less dependence on the 

construction industry, and so an annual growth rate 

(6 percent) should be assumed that can take into 

account consumption in additional new, and perhaps 

more rapidly growing, fields. Through the year 2000, 

the cumulative need for crude perlite production will 

total about 48 million tons. Schilling (1960, p. 108) 

estimated that in north-central New Mexico alone 

"There is over 100 million tons-probably several 

hundred million tons-of readily minable, commercial-grade perlite in the No Agua deposit." This is 

the district which produced nearly all the perlite 

mined in 1970. Even if this estimate should be an 

order of magnitude too large, a single district can 

apparently furnish at least one-fourth of the anticipated demand. 

Numerous sizable deposits also are present in 

California (Chesterman, 1957, 1966), Arizona, Nevada, and elsewhere in New Mexico, all with reserves 

that appear to be in millions or tens of millions of 

tons. Other large deposits, but fewer, are present in 

Colorado (Bush, 1951, 1964), Utah, and Idaho. No 

quantitative data are available to estimate the 

amounts of paramarginal and submarginal resources, 

but the paramarginal resources (determined more 

by costs of stripping and transportation than by 

lower expansibility or greater dilution) are likely 

of the same order of magnitude as the reserves, 

whereas the submarginal resources are considerably 

smaller. Using the same approach as for pumice and 

pumicite, the total resource can be approximated 

very conservatively at about 650 million tons. 

The hydration of silicic volcanic glass by meteoric 

water raises the problem of how far the glasses are 

hydrated inward from their margins. The extent is 

surely a function of the thickness and permeability 

of the overlying rocks and of the structure, texture, 

and attitude of the host rocks. In the absence of 

data on the extent of hydration, any reserve or 

resources estimate must be considered to be a 

maximum. 

PUMICITE 

Laboratory investigations by the Oklahoma Geological Survey in 1944 revealed that pumicite was 

capable of considerable expansion upon heating in 

excess of 1,100°C (Burwell, 1949). Additional investigations by the Kansas Geological Survey in the 

1960's provided many more data on temperatures 

and strengths and suggested industrial uses as filter 

aids and ultralightweight construction materials 

(Bauleke, 1962; Hardy and others, 1965). Discussion of geologic habit, reserves, and resources is 

given in the section on "Pumice and Pumicite." 

VERMICULITE 

In contrast with all the other naturally occurring 

lightweight aggregate materials, vermiculite is a 

single mineral rather than an assemblage of minerals. The rocks that are suitable for use as lightweight aggregates are abundant materials that oc-
LIGHTWEIGHT AGGREGATES 349 

cur in common geologic terranes, although they may 

not be ubiquitously distributed. The varieties of 

Cenozoic extrusive rocks previously described are 

good examples; they occur in a great many localites throughout the western conterminous United 

States. In searching for recoverable reserves of vermiculite, however, one must find a suitable host 

rock, then the site where it is in the proper geochemical environment, and then the specific areas 

where alteration has produced the mineral in the 

concentration needed to be useful. For vermiculite, 

the search must start with an understanding of the 

mineral and its origin. 

Mineralogically, vermiculite is a micaceous, hydrated magnesium iron aluminum sheet silicate, of 

variable composition, composed of a basic unit 

formed of two tetrahedral silicate sheets which face 

each other and which are joined by an octahedral 

sheet that contains the aluminum and iron (Grim, 

1962) . This configuration is also the basic structural 

unit of a single mica layer; the micas are built up 

by a repetitive stack of these layers. Each layer, 

on its upper and lower surfaces, has regularly arranged "holes" that overlap corresponding sites on 

overlying layers. In biotite, potassium atoms occupy 

these sites, and their electronic charges help to hold 

the layers together. In vermiculite, only some of the 

sites are occupied, and these only by magnesium, 

but a double layer of water molecules also is present 

in these interlayer regions. 

Commercially, "vermiculite" includes any micaceous mineral that is capable of expansion, regardless of its chemical composition or the regularity of 

its crystal structure. Pure vermiculite can be expanded (exfoliated) up to 30 times its original 

thickness when heated to about 1,600° -2,000°F 

(870° -1,100°C), impure varieties expand less. The 

exfoliation results from the flash conversion of the 

interlayer water molecules into steam ; the mineral 

develops a high degree of porosity as the layers are 

forced apart into an accordionlike structure. The 

resulting material is easily compressed along the 

line of expansion, but it has moderate strength in 

other directions. Schroeder ( 1970b) has listed many 

of the uses of exfoliated vermiculite; most are connected with the construction industry, which in 1970 

consumed more than 80 percent of the output, about 

equally divided between aggregates for concrete, 

cement, and plaster, and insulating uses, mostly as 

loose fill. 

Vermiculite is an alteration product of a variety 

of mafic minerals ; it has not been found as a primary rock constituent. The geologic literature has 

many descriptions of vermiculite derived from biotite, phlogopite, diopside, tremolite, augite, hornblende, olivine, chlorite, and serpentine. The alteration may have included an intermediate biotite or 

chlorite stage, for X-ray diffraction studies of the 

vermiculite reveal it to be interlayered with biotite 

or chlorite, although macroscopic and microscopic 

examination may show no biotite or chlorite elsewhere in the rock. Biotite is the common parent 

mineral, and the similarity of the biotite and vermiculite crystal structures permits an intimate interlayering on a molecular scale in a seri~s that ideally 

extends either regularly or irregularly from pure 

biotite through 1: 1 biotite-vermiculite to pure vermiculite. In a general way, varieties in the series 

from perhaps 10-50 percent vermiculite are called 

hydrobiotite. The alteration has been considered to 

be hydrothermal (Prindle and others, 1935 ; Leighton, 1954) or supergene (Murdock and Hunter, 1946; 

Roy and Romo, 1957; Bassett, 1959) and partly both 

(Boettcher, 1966). The character of the alteration 

has a major impact on the resources of vermiculite. 

Almost all vermiculite deposits are associated with 

mafic and ultramafic rocks, both igneous and metamorphic, that have been intruded by silicic and in 

many instances by alkalic igneous rocks, and in 

some instances by carbonatites. They can be broadly 

grouped in three different types, but there are strong 

points of similarity among all the classes: (1) large 

ultramafic intrusives, such as pyroxenite plutons, 

sometimes zoned, that are cut by syenites or alkalic 

granites and by carbonitic rocks and pegmatites 

(examples are deposits at Libby, Mont., and Phalaborwa, Republic of South Africa); (2) small to large 

ultramafic intrusives, such as dunites and unzoned 

pyroxenites and peridotites, that are cut by pegmatites and syenitic or granitic intrusive rocks (examples are deposits in the Blue Ridge region of the 

Southeastern United States) ; and (3) ultramafic 

metamorphic rocks (usually amphibolite schists that 

commonly are layered) that may have originally 

been igneous rocks, sometimes cut by or in contact 

with pyroxenites or peridotites, and cut by pegmatites (examples are deposits in the Enoree district, 

South Carolina, and most of the deposits in Colorado, Wyoming, and Texas). With the major excePtion of the deposit at Libby, almost all the vermiculite deposits in the world appear to be in rocks of 

Precambrian age. 

The world's largest vermiculite deposit at Libby, 

Mont., is a zoned pyroxenite pluton of middle Cretaceous age that cuts Precambrian sedimentary 

rocks of the Belt Supergroup (Boettcher, 1967)-a 

type 1 deposit. The pluton has a core of biotitite in 

a mass of biotite pyroxenite. A shell (like a ring 
350 UNITED STATES MINERAL RESOURCES 

dike) of magnetite pyroxenite intruded the zone of States are of this type, in the Enoree and Enoreeweakness at the contact of the biotite pyroxenite Waldrep districts of South Carolina, where many 

with the country rocks. A younger mass of syenite deposits have contained 20,000 to 50,000 tons of ore, 

cut both the magnetite and the biotite pyroxenite, and some as much as 100,000 tons of ore. In these 

and alkalic syenite dikes cut the biotitite core. districts, weathering is so intense that rock types 

Fenitized Belt rocks and a small nepheline syenite are difficult to identify and the contact relations are 

mass nearby suggest the presence of a carbonatitic very obscure. Hunter (1950) suggested that the 

mass at depth. Biotite in the biotite pyroxenite, and vermiculite developed by deep weathering of biotite 

to a small extent in the magnetite pyroxenite, is from lenses of pyroxenite in contact with biotite 

altered to hydro biotite and vermiculite; the biotite gneiss and schist. Only fragments of pyroxenite 

of the dense core is virtually unaltered. have been found in the deposits; the pyroxenite 

Boettcher (1966) concluded that the hydrobiotite bodies may have been metamorphosed to amphibolite 

is the result of high-temperature alteration (pre- schists, which have been mapped in the Enoree area 

sumably hydrothermal), whereas the vermiculite is by McClure (1963). All the deposits are cut by 

the result of surficial alteration by circulating stringers of pegmatite, and small masses of "granground water. The evidence for hydrothermal altera- ite" have been reported. Hunter (1950) described 

tion is not conclusive to me ; a definite answer will vermiculite lenses 450 feet long and 150 feet wide, 

probably not be gained until hydrobiotite is found with a depth to unaltered biotite of about 80 feet; 

below the level of ground-water circulation. A fairty these dimensions suggest pluglike bodies rather than 

intensive search of the literature has not turned up l dikes or layered rocks, but most of the deposits have 

any such occurrences. The Mining Journal (1952) length-width rations of 5:1 or greater-consistent 

reported that vermiculite had been proved by drill- with favorable zones in layered rocks. 

ing to a depth of 800 feet; as the deposit is located The most numerous deposits, but also those with 

in mountainous terrain and underlies a ridge with the smallest amounts of vermiculite, are in the 

from 800 to 1,200 feet of relief on three sides, it is layered metamorphic rock (type 3). Characteristicvery possible that the vermiculite from the bottom ally, the deposits are in biotite schists, amphibolite 

of the 800-foot hole was still in the zone of circulat- schists, or mica-amphibolite schists, and are cut by 

ing ground water, the zone of surficial alteration. pegmatites. The deposits are only a few feet thick, 

Many hundreds of thousands of tons of vermiculite although they may be several hundred long, and the 

have been produced from this deposit since mining depth of weathering is usually no more than a few 

began about 1925, and the deposit is far from tens of feet. Ore content usually ranges from a few 

depleted. hundred tons to several thousand tons. Hagner 

Vermiculite in the dunite-type (type 2) deposits (1944) described several deposits of this type in 

of the Blue Ridge province also is found only in the Wyoming, and Clabaugh and Barnes (1959) did so 

zone of weathering. It occurs in veins and lenses for Texas. Descriptions of deposits in other States 

along the commonly serpentinized contact of dunite are given in publications liPted in "Selected Referand pyroxenite bodies with the metamorphic country ences." 

rocks and with crosscutting pegmatites, and along In general, the geologic relations of all the types 

fractures within the bodies. The largest deposits are of deposits suggest that pyroxenes ( diopside and 

at the contacts, but the highest concentrations are augite), amphiboles (hornblende and tremolite), and 

along the internal fractures. Where the country rock olivine in the ultramafic rocks were altered by soloalso is mafic (hornblende gneiss or biotite schist), tions and volatiles from intrusive syenites, carbonathe vermiculite may occur on both sides of the con- tites, and pegmatites (supplying mostly OH); and 

tact. In these deposits, vermiculite typically occurs biotite, phlogopite, serpentine, and chlorite were 

in lenses that are as much as 4--5 feet thick and formed. Supergene alteration by circulating ground 

50--60 feet long. A few lenses are 20 feet thick and waters later removed the alkalis, redistributed magmore than 100 feet long (Hunter, 1950). nesium, and added H20 as interlayer water moleThere is considerable variety among the deposits cules to form vermiculite. The position of 1: 1 reguin the layered metamorphic rocks (type 3). Some larly interstratified hydrobiotite in the sequence is 

of the amphibolite and biotite schists may have been not certain (Boettcher, 1966), but I believe that it, 

sedimentary rocks, others intrusive or extrusive too, is a supergene alteration product. 

rocks, but all deposits are characterized by granitic In order of significance, the vermiculite deposits 

or syenit.ic crosscutting pegmatites. The deposits in of the United States are in Montana (almost twothe second most important group in the United thirds of the United States production), the Inner 
LIGHTWEIGHT AGGREGATES 351 

Piedmont province of South Carolina (one-third of 

the production), the Blue Ridge province in Virginia, North Carolina, South Carolina, and Georgia, 

and scattered deposits in Wyoming, Texas, Colorado, 

California, Nevada, Arizona, Washington, and Oregon. The almost invariable association of vermiculite with Precambrian rocks allows Hawaii and virtually all the central part of the country from the 

Rocky Mountains east to the Blue Ridge to be dismissed from consideration, except possibly the 

Wichita Mountains and the Ozark Mountains. 

All the recoverable reserves of vermiculite in the 

United States are in one deposit in Montana and in 

several deposits in the Enoree and Enoree-Waldrep 

districts of South Carolina. Inasmuch as almost all 

of them are controlled by a single company, and the 

rest by two other companies, it is not appropriate to 

publish a quantitative estimate. However, in 1952 

a mining publication in London (Mining Jour., 1952) 

estimated that reserves at the Libby deposit ranged 

from 25 to 100 million tons. No grade was given, so 

the amount of vermiculite mineral that was available 

is uncertain. As a measure of the United States 

position, we can again estimate the cumulative output needed to satisfy the demand through the year 

2000, using a 5-percent rate for the annual growth. 

Based on the 1970 production (Fulkerson, 1972) of 

about 285,000 tons of crude and 220,000 tons of 

exfoliated vermiculite, about 19 million tons of crude 

will be required. Since 1952 about 4.3 million tons 

of crude has been produced from all U.S. deposits. 

The total is less than the smaller estimate for the 

Libby deposit as published in 1952. 

The remainder of the identified resources of vermiculite must be classed as submarginal, for it is 

unlikely that any of the other known deposits can 

be brought into operation at 1.5 times the present 

price. They are too small, or too low grade, or too 

poorly located to be able to compete at that price ; 

thus, they cannot be considered paramarginal reserves. The total tonnage that can be estimated as 

submarginal reserves is on the order of 2-3 million 

tons in North and South Carolina, Texas, Wyoming, 

Colorado, and Nevada. 

Hypothetical resources in the known districts are 

probably on the order of 11/2-2 million tons-it is 

unlikely that a new Libby will be found in the 

known districts, but discovery of new deposits of 

the Enoree type can be expected. It is also unlikely 

that there is only one Libby deposit in the conterminous United States, and so a projection of 25 to 

100 million tons in the classification of speculative 

resources seems reasonable. 

Where and how are the hypothetical and speculative resources to be f~und? Most of the hypothetical 

resources, in deposits of the 20,000- to 100,000-ton 

size, are likely to come from deposits of the Enoree 

type in the Inner Piedmont region of South Carolina. Possibly a combination of airborne and ground 

geophysical surveys and detailed geologic mapping 

can locate these deposits. We should be able to 

distinguish the zones of ultramafic rocks from the 

granitic rocks by airborne magnetic surveys, and 

possibly we may be able to identify magnetic anomalies the size of the target vermiculite deposits. At 

present there are virtually no guides to favorable 

ground and ore deposits, other than the relationship 

to ultramafic rocks. 

Deposits of the Libby size, which would contain 

most of the speculative resources, have geologic 

relations that are intriguing and encouraging for 

additional discoveries. The association of ultramafic 

plutons with syenites, alkalic rocks, and carbonatites 

is too common to be happenstance; the association 

of these rocks is known from several deposits in the 

United States (Rocky Boy, Mont.; Gem ParkMcClure Mountain and Powderhorn, Colo.), in the 

U.S.S.R., and, in particular, in many parts of the 

African continent. Several generalized clues to 

places where these rocks may be found together 

are ( 1) the rocks are usually in Precambrian terranes, (2) they may be related to Precambrian 

structural trends, (3) they may exhibit significant 

magnetic anomalies, and ( 4) they may be characterized by ring-dike structures. 

Several problems deserve investigation. What is 

the environment in which mafic minerals are altered 

to vermiculite? What are the temperature-pressure 

conditions and the role of solutions and volatiles 

from pegmatites, alkalic rocks, and carbonatites? 

What is the mineralogenic sequence-the need for 

formation of a micaceous mineral as an intermediate step between diospide and vermiculite, for example? What role does the composition of the 

ground water play in the formation of vermiculite, 

and what climatic factors affect the alteration, and 

in what way? In a broader context, where the 

answers are· of importance to resources besides vermiculite, what are the guides to the localization of 

ultramafic rocks, of syenites and carbonatites and 

other alkalic rocks? 

SELECTED REFERENCES 

Aase, J. H., 1967, Lightweight aggregates-Expansion propties of selected Michigan shales: U.S. Bur. Mines Rept. 

Inv. 7055, 23 p. 

Anderson, F. G., Selvig, W. A., Baur, G. S., Colbassani, P. J., 

and Bank, W., 1956, Composition of perlite: U.S. Bur. 

Mines Rept. Inv. 5199, 13 p. 
352 UNITED STATES MINERAL RESOURCES 

Asher, R. R., 1964, Stone and construction materials, in Mineral and water resources of Idaho: U.S. 88th Cong., 2d 

sess., Senate Committee on Interior and Insular Affairs, 

Comm. Print., p. 200-211. 

--- 1965, Volcanic construction materials in Idaho: Idaho 

Bur. Mines and Geology Pamph. 135, 150 p. 

Austin, C. R., Nunes, J. L., and Sullivan, J. D., 1942, Basic 

factors involved in the bloating of clays: Mining Technology, v. 6, no. 4 [Am. Inst. Mining and Metall. Engineers Tech. Pub. 1486], 11 p. 

Barbour, E. H., 1916, Nebraska pumicite: Nebraska Geol. 

Survey,v. 4,pt.27,p.357-401. 

Bassett, W. A., 1959, The origin of the vermiculite deposit at 

Libby, Montana: Am. Mineralogist, v. 44, no. 3-4, p. 

282-299. 

Bauleke, M. P., 1962, What's new in volcanic ash for industry?: Kansas Geol. Survey Bull. 157, pt. 3, 19 p. 

Boettcher, A. L., 1966, Vermiculite, hydrobiotite, and biotite 

in the Rainy Creek igneous complex near Libby, Montana: Clay Minerals, v. 66, no. 4, p. 283-296. 

--- 1967, The Rainy Creek alkaline-ultramafic igneous 

complex near Libby, Montana: Jour. Geology, v. 75, 

no. 5, p. 526-553. 

Bowen, C. H., 19·55, Lightweight aggregates in Ohio: Ohio 

State Univ. Expt. Sta. News Eng., v. 27, no. 2, p. 18-21. 

Brown, L. F., Jr., 1959, A review of Pennsylvanian clay 

mineral industries, north-central Texas: Texas Univ. 

Bur. Econ. Geology Mineral Resources Circ. 39, 10 p. 

Brownell, W. E., Broughton, J. G., and Peterson, R. B., 1951, 

The clay and shales of New York State: Albany, New 

York State Dept. Commerce, 349 p. 

Burnett, J. L., 1964, Prospecting for expansible shale: Mining Eng., v. 16, no. 1, p. 50-51. 

--- 1966, Shale, expansible, in Mineral and water resources of California: U.S. 89th Cong., 2d sess., Senate 

Comm. on Interior and Insular Affairs, Comm. Print. 

(California Div. Mines and Geology Bull. 191), p. 374-

380. 

Burwell, A. L., 1949, Cellular products from Oklahoma volcanic ash: Oklahoma Geol. Survey Circ. 27, 89 p. 

--- 1954, Lightweight aggregate from certain Oklahoma 

shales: Oklahoma Geol. Survey Mineral Rept. 24, 20 p. 

Bush, A. L., 1951, Sources of lightweight aggregates in 

Colorado: Colorado Sci. Soc. Proc., v. 15, no. 8, p. 305-

368. 

--- 1964, Lightweight aggregates, in Mineral and water 

resources of Colorado: U.S. 88th Cong., 2d sess., Senate 

Comm. Interior and Insular Affairs, Comm. Print., p. 

197-202. 

--- 1967, Lightweight aggregate, in Mineral and water 

resources of Missouri: U.S. 90th Cong., 1st sess., Senate 

Doc. 19 (Missouri Div. Geol. Survey and Water Resources [Rept.], 2d ser., v. 43), p. 155-157. 

Bush, A. L., and Sweeney, J. W., 1968, Lightweight aggregates, in Mineral resources of the Appalachian region: U.S. Geol. Survey Prof. Paper 580, p. 210-224. 

Caldwell, D. W., 1959, Glacial lake and marine clays of the 

Farmington area, Maine-Origin and possible use as 

lightweight aggregate: Maine Geol. Survey Spec. Geol. 

Studies, no. 3, 48 p. 

Carey, J. S., Frye, J. C., Plummer, Norman, and Swineford, 

Ada, 1952, Kansas volcanic ash resources: Kansas Geol. 

Survey Bull. 96, pt. 1, 68 p. 

Chesterman, C. W. ,1956, Pumice, pumicite, and volcanic 

cinders in California: California Div. Mines Bull. 174, p. 

3-99. 

--- 1957, Volcanic lightweight aggregates of Western 

United States: Internat. Geol. Cong., 20th, Mexico, D.F., 

1956, sec. 1, Vulcanologia del cenozoico, v. 1, p. 205-229. 

--- 1966, Pumice, pumicite, perlite, and volcanic cinders, 

in Mineral and water resources of California: U.S. 89th 

2d sess., Senate Comm. on Interior and Insular Affairs, 

Comm. Print. (California Div. Mines and Geology Bull. 

191) , p. 336-341. 

Chopra, S. K., Lal, Kishan, and Ramachandran, V. S., 1964, 

Gas producing agents in the production of lightweight 

aggregates: Jour. Appl. Chemistry (London), v. 14, 

no. 5, p. 181-185. 

Clabaugh, S. E., and Barnes, V. E., 1959, Vermiculite in 

central Texas: Texas Univ. Bur. Econ. Geology Rept. 

Inv. 40, 32 p. 

Cole, W. A., and Zetterstrom, J. D., 1954, Investigation of 

lightweight aggregates in North and South Dakota: 

U.S. Bur. Mines Rept. lnv. 5065, 43 p. 

Colton, H. S., 1964, Collapsed cinder cones in the San Francisco Mountains, in Contributions to the geology of 

northern Arizona: Mus. Northern Arizona Bull. 40, p. 

1-4. 

Conley, J. E., 1942, Waste slate as a raw material source 

of lightweight aggregates: Mining Technology, v. 6, 

no. 5 [Am. Inst. Mining and Metall. Engineers Tech 

Pub. 1512], 6 p. 

Conley, J. E. Wilson, Hewitt, Klinefelter, T. A., and others, 

1948, Production of lightweight concrete aggregates 

from clays, shales, slates, and other materials: U.S. 

Bur. Mines Rept. Inv. 4401, -121 p. 

De Munck, V. C., 1956, Possibilities for lightweight aggregate 

for concrete near Great Falls, Montana: Montana Bur. 

Mines and Geology lnf. Circ. 12, 11 p. 

Diamond, W. G., Early, T. R., and Robertson, H. F., 1964, 

Expanded clay and shale lightweight aggregate industry in the South-central United States: U.S. Bur. 

Mines lnf. Circ. 8233, 50 p. 

Dixon, L. H., 1967, Test data and evaluation of miscellaneous 

clays: Louisiana Geol. Survey Clay Resources Bull. 1, 

107 p. 

Dixon, L. H., and Tyrrell, M. E., 1969, Occurrence, test data, 

and evaluation of clay for making lightweight aggregate: Louisiana Geological Survey Clay Resources Bull. 

2, 145 p. 

Donnelly, R. P., Brennan, L. J., and Peacock, B., 1968, 

Mechanism of bloating of clays and shales: Australian 

Chern. Processing and Engineering, v. 21, no. 1, p. 8-

15. 

Eckhart, R. A., and Plafker, ~rge, 1959, Haydite raw materials in the Kings River, Sutton, and Lawing areas, 

Alaska: U.S. Geol. Survey Bull. 1039-C, p. 33-65. 

Ehlers, E. G., and Richardson, J. H., 1958, Mineralogical 

factors involved in the formation of lightweight aggregates, pt. 2 of Everhart, J. 0., and others, A study of 

lightweight aggregates: Ohio State Univ. Eng. Expt. 

Sta. Bull. 169, p. 24-44. 

Elston, W. E., 1967, Summary of the mineral resources of 

Bernalillo, Sandoval, and Sante Fe Counties, New 

Mexico (exclusive of oil and gas): New Mexico Bur. 

Mines and Mineral Resources Bull. 81, 81 p. 

Everhart, J. 0., Ehlers, E. G., and Johnson, E. G., 1958, The 
LIGHTWEIGHT AGGREGATES 353 

sampling and evaluation program, in Everhart, J. 0., 

and others, A study of lightweight aggregates: Ohio 

State Univ. Eng. Expt. Sta. Bull. 169, v. 27, no. 3, 

p.l-23. 

Fisher, W. L., and Garner, L. E., 1965, Clay and clay materials, in Fisher, W. L., Rock and mineral resources of 

east Texas: Texas Univ. Bur. Econ. Geology Rept. 

Inv. 54, p. 79-179. 

Foster, R. W., 1966, Sources for lightweight state aggregate 

in New Mexico: New Mexico Bur. Mines and Mineral 

Resources Bull. 88, 86 p. 

Friedman, Irving, and Smith, R. L., 1958, The deuterium 

content of water in some volcanic glasses: Geochim. et 

Cosmochim. Acta, v. 15, p. 218-228. 

Fulkerson, F. B., 1972, Vermiculite: U.S. Bur. Mines Minerals Yearbook, 1970, v. 1, p. 1171-1173. 

Gemmill, Paul, 1964, Perlite, in Mineral and water resources 

of Nevada: U.S. 88th Cong., 2d sess., Senate Doc. 87, p. 

230-235. 

Gervids, I. A., 1957, Keramzit (Investigation of its technology): Nauchno Soobshchenie, Nauchno-Issled. Inst. 

Novykh Stroitel. Materialov, Keramzit, p. 7-75. 

Greene, R. C., Walker, G. W., and Corcoran, R. E., 1972, 

Geologic map of the Burns quadrangle, Oregon: U.S. 

Geol. Survey Misc. Geol. Inv. Map I-680. 

Grim, R. E., 1962, Applied clay mineralogy: New York, 

McGraw-Hill Book Co., p. 20-37. 

Grosh, W. A., and Hamlin, H. P., 1963, Lightweight aggregates-Expansion properties of clays, shales, and 

argillites of Minnesota: U.S. Bur. Mines Rept. Inv. 

6313,30 p. 

Gustafson, Fred D., 1949, The mining, milling, and processing of perlite: Am. Inst. Mining and Metall. Engineers 

Trans., v. 184, p. 313-316. 

Hagner, A. F., 1944, Wyoming vermiculite deposits: Wyoming Geol. Survey Bull. 34, 4 7 p. 

Ham, W. E., 1949, Volcanic ash deposits in Oklahoma, in 

Burwell, A. L., Cellular products from Oklahoma volcanic ash: Oklahoma Geol. Survey Circ. 27, p. 42-81. 

Hamlin, H. P., and Templin, George, 1962, Evaluating raw 

materials for rotary-kiln production of lightweight aggregate: U.S. Bur. Mines Inf. Circ. 8122, 23 p. 

Hammer, D. F., Webster, R. N., and Lamb, D. C., 1962, 

Some geologic features of the Superior area, Pinal 

County, Arizona: New Mexico Geol. Soc. Guidebook 

13th Ann. Field Conf., p. 148-153. 

Hardy, R. G., 1966, Inventory of Kansas industrial minerals: 

Kansas Geol. Survey Mineral Resources Notes, no. 1, 

p.l-8. 

Hardy, R. G., Bauleke, M. P., Hornbaker, A. L., Hess, W. 

R., and Hladik, W. B., 1965, Kansas industrial mineral 

development-A feasibility study for the production of 

filter aids from Kansas volcanic ash: Kansas Geol. Survey Spec. Distrib. Pub. 19, 34 p. 

Hatmaker, Paul, 1932, Pumice and pumicite: U.S. Bur. 

Mines Inf. Circ. 6560, 23 p. 

Hickman, R. C., and Hamlin, H. P., 1964, Ceramic clay investigations in Alachua, Clay, and Putnam Counties, 

Florida: Florida Geol. Survey Inf. Circ. 46, 41 p. 

Higgs, D. V., 1949, Quantitative areal geology of the United 

States: Am. Jour. Sci., v. 247, no. 8, p. 575-583. 

Hill, R. D., and Crook, D. N., 1960, Some causes of bloating 

in expanded clay and shale aggregates: Australian 

Jour. Appl. Sci., v. 11, no. 3, p. 374-384. 

Hollenbeck, R. P., and Tyrrell, M. E., 1968, Shales for lightweight aggregate in Appalachian region, Kentucky and 

Tennessee: U.S. Bur. Mines Rept. Inv. 7129, 54 p. 

--- 1969, Raw materials for lightweight aggregate in 

Appalachian region, Alabama and Georgia: U.S. Bur. 

Mines Rept. Inv. 7244, 21 p. 

Horton, R. C., 1964a, Pumice, pumicite, and volcanic cinders, 

in Mineral and water resources of Nevada: U.S. 88th 

Cong., 2d sess., Senate Doc. 87, p. 237-240. 

--- Compiler, 1964b, Industrial minerals of Nevada: 

Nevada Bur. Mines Map 27, 1:1,000,000. 

Hosterman, J. W., 1966, Clays, in Mineral and water resources of Washington: U.S. 89th Cong., 2d sess., Senate 

Comm. on Interior and Insular Affairs, Comm. Print., 

p. 183-185. 

Hubbard, C. R., 1955, A survey of the mineral resources of 

Idaho: Id·aho Bur. Mines and Geology Pamph. 105, 74 

p. 

Hunter, C. E., 1950, Vermiculite of the southeastern states, 

in Snyder, F. G., ed., Symposium on mineral resources 

of the Southeastern United States: Knoxville Tennessee 

Univ. Press, p. 120-127. 

Huntting, M. T., 1966, Pumice, pumicite, volcanic cinders, 

and perlite, in Mineral and water resources of Washington: U.S. 89th Cong., 2d sess., Senate Comm. on Interior 

and Insular Affairs, Comm. Print., p. 240-245. 

Jaster, M. C., 1956, Perlite resources of the United States: 

U.S. Geol. Survey Bull. 1027-I, p. 375-403. 

Karsten, Andrew, 1956, Characteristics and behavior of certain South Dakota shales under expansion to produce 

lightweight aggregate: South Dakota Nat. Resources 

Comm. 34 p. • 

Keith, S. B., 1969a, Basalt and related rocks. in Mineral and 

water resources of Arizona: U.S. 90th Cong., 2d sess., 

Senate Comm. on Interior and Insular Affairs, Comm. 

Print. (Arizona Bur. Mines Bull. 180), p. 315-320. 

--- 1969b, Pumice and pumicite, in Mineral and water 

resources of Arizona: U.S. 90th Cong., 2d sess., Senate 

Comm. on Interior and Insular Affairs, Comm. Print. 

(Arizona Bur. Mines Bull. 180), p. 407-412. 

Kiersch, G. A., 1955, Construction materials-Geology, evaluation and uses, with sections on Mineral Resources, 

Navajo-Hopi Indian Reservations, Arizona-Utah, by J. C. 

Haff and H. W. Pierce: Tucson, Arizona Univ. Press, 

v. 3, 81 p. 

King, C. R., 1948, Pumice and perlite as industrial minerals 

in California: California Jour. Mines and Geology, v. 

44,no.3,p. 293-319. 

Klinefelter, T. A., and Hamlin, H. P., 1957, Syllabus of 

clay testing: U.S. Bur. Mines Bull. 565, p. 39-41. 

Knechtel, M. M., Hamlin, H. P., and Hosterman, J. W., 

1966, Expandable clay in St. Marys Formation of southern Maryland: Maryland Geol. Survey Rept. Inv. 4, 

17 p. 

Knechtel, M. M., and Hosterman, J. W., 1960, Bloating clay 

in Miocene strata of Maryland, New Jersey, and Virginia: U.S. Geol. Survey Prof. Paper 400-B, p. B59-

B62. 

Knechtel, M. M., Larrabee, D. M., Fischer, E. C., and others, 

compilers, 1948, Map showing construction materials 

and nonmetallic, mineral resources of Montana: U.S. 

Geol. Survey Missouri River Basin Studies 11. 

Kulp, J. L., and Brobst, D. A., 1954, Notes on the dunite 

and the geochemistry of vermiculite at the Day Book 
UNITED STATES MINERAL RESOURCES 

dunite deposit, Yancey County, North Carolina: Econ. 

Geology, v. 49, no. 2, p. 211-220. 

Lee, K. Y., Petsch, B. C., Rothrock, E. P., and Agnew, A. F., 

1961, Possible expanded shale resourees near Yankton, 

South Dakota: South Dakota Geol. Survey Mineral Resources Inv. Map 1. 

Leighton, F. B., 1954, Origin of vermiculite deposits, southern Virgin Mountains, Nevada [abs.]: Geol. Soc. America 

Bull., v. 65, no. 12, pt. 2, p. 1277. 

--- 1967, Gold Butte vermiculite deposits, Clark O>unty, 

Nevada: Nevada Bur. Mines Rept. 16, 18 p. 

Lodding William, 1956, Raw materials for lightweight aggregate production in New Jersey: Rutgers Univ. Bur. 

Mineral Research Bull. 7, 160 p. 

Lugn, A. L., 1935, The Pleistocene geology of Nebraska: 

Nebraska Geol. Survey Bull. 10 2d ser., p. 132-134. 

McClure, W. C., 1963, Geology of the Enoree area, South 

Carolina: South Carolina Univ. unpub. M.S. thesis, 39 

p. 

McGrain, Preston, 1957, Sources of shale in Kentucky for 

lightweight aggregate production: Kentucky Geol. Survey Rept. Inv. 12, ser. 9, 23 p. 

--- 1958, Sources of shale in Kentucky for lightweight 

aggregate production No. 2: Kentucky Geol. Survey 

Rept. Inv. 15, ser. 9, 30 p. 

McKelvey, V. E., 1972, Mineral resource estimates and public policy: Am. Scientist, v. 60, no. 1, p. 32-40. 

Mapel, W. J., and Hail, W. J., Jr., 1959, Tertiary geology 

of the Goose Creek district, Cassia County, Idaho, Box 

Elder County, Utah, and Elko County, Nevada: U.S. 

Geol. Survey Bull. 1055-H, p. 217-254 [1960]. 

Mason, R. S., 1969, Stone, in Mineral and water resources of 

Oregon: U.S. 90th Cong., 2d sess., Senate Comm. on 

Interior and Insular Affairs, Comm. Print., p. 261-265. 

Maxwell, R. A., 1962, Mineral resourees of south Texas: 

Texas Univ. Bur. Eoon. Geology Rept. Inv. 43, 140 p. 

Meisinger, A. C., 1972, Pumice: U.S. Bur. Mines Minerals 

Yearbook, 1970, p. 965-969. 

Mining Journal, 1952, The vermiculite industry: v. 738, no. 

6091, p. 499. 

Murdock, T. G., and Hunter, C. E., 1946, The vermiculite deposits of North Carolina: North Carolina Div. Mineral 

Resources Bull. 50, 44 p. 

Murray, H. H., and Smith, J. M., 1958, Lightweight aggregate potentialities of some Indiana shales: Indiana 

Dept. Conserv. Rept. Press 12, 42 p. 

Olson, R. H., 1964, Vermiculite, in Mineral and water resources of Nevada: U.S. 88th Cong., 2d sess., Senate 

Doc. 87, p. 260-262. 

O'Neill, B. J., Jr., and others, 1965, Properties and uses of 

Pennsylvania shales and clays: Pennsylvania Topog. and 

Geol. Survey Mineral Resources Rept. M51, 448 p. 

Osterwald, F. W., Osterwald, D. B., Long, J. S., Jr., and 

Wilson, W. H., 1959, Mineral resources of Wyoming: 

Wyoming Geol. Survey Bull. 50, 259 p. 

Pallister, H. D., Hastings, E. L., and Daniel, T. W., Jr., 

1964, Clay and shale for lightweight aggregate in Alabama: Alabama Geol. Survey Circ. 26, 45 p. 

Parks, W. S., McLeod, C. A., and Wehr, A. G., 1964, Survey 

of lightweight aggregate materials of Mississippi: 

Mississippi Geol. Econ. and Topog. Survey Bull. 103, 

115 p. 

Patterson, S. H., and Cox, E. J ., 1964, Clays, bentonite, and 

lightweight aggregate, in Mineral and water resources 

of South Dakota: U.S. 88th Cong., 2d sess., Senate 

Comm. on Interior and Insular Affairs, Comm. Print., 

p. 105-112. 

Pierce, H. W., 1969, Perlite, in Mineral and water resources 

of Arizona: U.S. 90th Cong., 2d sess., Senate Comm. on 

Interior and Insular Affairs, Comm. Print. (Arizona 

Bur. Mines Bull. 180), p. 403-407. 

Plafker, George, and Berg, H. C., 1964, Nonmetallic mineral resources, in Mineral and water resources of Alaska: 

U.S. 88th Cong., 2d sess., Senate Comm. on Interior and 

Insular Affairs, Comm. Print., p. 145-146. 

Plummer, H., and Hladik, W. B., 1951, The manufacture of 

lightweight concrete aggregate from Kansas clays and 

shales: Kansas Geol. Survey Bull. 91, p. 1-100. 

Prindle, L. M., and others, 1935, Kyanite and vermiculite deposits of Georgia: Georgia Geol. Survey Bull. 46, p. 

41-46. 

Prokopovich, N., and Schwartz, G. M., 1957, Preliminary 

survey of bloating clays and shales in Minnesota: Minnesota Geol. Survey Summary Rept. 10, 69 p. 

Riley, C. M., 1951, Relation of chemical properties to the 

bloating of clays: Am. Ceramic Soc. Jour., v. 34, no. 

4, p. 121-128. 

Roberts, M. J., 19·58, Bloated clay aggregate-Its production 

and marketing potential in Florida: Florida Univ. Eng. 

Prog. Bull. Ser. 98, v. 12, no. 6, 51 p. 

Robinson, G. D., and Marvin, R. F., 1967, Upper Cretaceous 

volcanic glass from western Montana: Geol. Soc. Am. 

Bull., v. 78, no. 5, p. 601-608. 

Roen, J. B., and Hosterman, J. W., 1969, Analyses and potential uses of selected shales and clays, Greene County, 

Pennsylvania: Pennsylvania Geol. Survey Inf. Circ. 67, 

4th ser., p. 17. 

Root, S. I., 1968, Geology and mineral resources of southeastern Franklin County, Pennsylvania: Pennsylvania 

Geol. Survey Atlas 119, 4th ser., 118 p. 

Ross, C. S., and Smith, R. L., 1955, Water and other volatiles 

in volcanic glasses: Am. Mineralogist, v. 40, nos. 11, 

12, p. 1071-1089. 

Roy, Rustum, and Romo, L. A., 1957, New data on vermiculite, pt. 1 of Weathering studies: Jour. Geology, v. 

65, no. 6, p. 603-610. 

Sahinen, U. M., 1963. Clays, in Mineral and water resources 

of Montana: U.S. 88th Cong., 1st sess., Senate Comm. 

on Interior and Insular Affairs, Comm. Print., p. 60-62. 

Schilling, J. H., 1960, Mineral resources of Taos County, 

New Mexico: New Mexico Bur. Mines and Mineral Resources Bull. 71, 124 p. 

Schroeder, H. J., 1970a, Perlite, in Mineral facts and problems, 1970: U.S. Bur. Mines Bull. 650, p. 1129-1137. 

--- 197()b, Vermiculite, in Mineral facts and problems, 

1970: U.S. Bur. Mines Bull. 650, p. 1283-1291. 

Sharps, T. I., 1961, Perlite in Colorado and other Western 

States: Colorado School Mines Mineral Industries Bull., 

v. 4, no. 6, 16 p. 

Smith, C. E., 1963, Lightweight aggregate industry in Virginia: Virginia Minerals, v. 9, no. 3, p. 1-6. 

Smith, R. L., 1960, Zones and zonal variations in welded 

ash flows: U.S. Geol. Survey Prof. Paper 354-F, p. 

149-159 [1961]. 

Smith, R. L., and Friedman, Irving, 1957, Origin of water 

in some volcanic glass [abs.]: Geol. Soc. Americ·a Bull., 

v. 68, no. 12, p. 1730. 

Staley, W. W., 1962, The Oneida perlite deposit: Idaho Bur. 
LIGHTWEIGHT AGGREGATES 355 

Mines and Geology Mineral Resources Rept. 9, 7 p. 

Stuckey, J. L., 1965, North Oarolina-Its geology and mineral resources: North Carolina Dept. Conserv. and 

Devel., 550 p. 

Sullivan, J. D., Austin, C. R., and Rogers, E. J ., 1942, Expanded clay products: Am. Inst. Mining and Metall. 

Engineers Tech. Pub. 1485, 10 p. 

Sweeney, J. W., and Hamlin, H. P., 1964, Lightweight aggregates-Expansion properties of selected Iowa shales, 

clays, and loess: U.S. Bur. Mines Rept. Inv. 6393, 33 p. 

--- 1965a, Lightweight aggregates-Expansion properties of selected Illinois shales and clays: U.S. Bur. Mines 

Rept. Inv. 6614, 34 p. 

--- 1965b, Lightweight aggregates-Expansion properties of selected Indiana shales: U.S. Bur. Mines Rept. 

Inv. 6574, 28 p. 

Talmage, S. B., and Wootton, T. P., 1937, The nonmetallic 

mineral resources of New Mexico and their economic 

features (exclusive of fuels): New Mexico Bur. Mines 

and Mineral Resources Bull. 12, p. 135-137. 

Temple, A. K., and Grogan, R. M., 1965, Carbonatite and 

related alkalic rocks at Powderhorn, Colorado: Econ. 

Geology, v. 60, no. 4, p. 672-692. 

Trefethen, J. M., 1955, Lightweight aggregate in Maine, in 

Report of the State Geologist, 1953-1954: Maine Devel. 

Comm., p. 83-85. 

Van Horn, Richard, 1964, Lightweight aggregate, in Mineral and water resources of Utah: U.S. 88th Cong., 2d 

sess., Senate Comm. on Interior and Insular Affairs, 

Comm. Print., p. 185-188. 

Varley, E. R., 1952, Vermiculite: London, Colonial Geor. 

Surveys, Mineral Resources Div., 70 p. 

Wagner, N. S., 1969, Perlite, pumice, pumicite, and cinders, 

in Mineral and water resources of Oregon: U.S. 90th 

Cong., 2d sess., Senate Comm. on Interior and Insular 

Affairs, Comm. Print., p. 222-228. 

Weber, R. H., 1963, Geologic features of the Socorro perlite 

deposits, in New Mexico Geol. Soc. Guidebook 14th Ann. 

Field Qonf., 1963-Socorro region: New Mexico Bur. 

Mines and Mineral Resources, p. 144-145. 

--- 1965, Lightweight aggregates, in Mineral and water 

resources of New Mexico: U.S. 89th Cong., 1st sess., 

Senate Comm. on Interior and Insular Affairs, Comm. 

Print~, p. 332-344. 

Weis, P. L., 1963, Vermiculite, in Mineral and water resources of Montana: U.S. 88th Cong., 1st sess., Senate 

Comm. on Interior and Insular Affairs, Comm. Print., p. 

127-128. 

White, W. A., 1960, Lightweight aggregate from Illinois 

shales: Illinois Geol. Survey Circ. 290, 29 p. 

White, W. A., and O'Brien, N. R., 1964, Illinois clay resources for lightweight ceramic block: Illinois Geol. Survey Circ. 371, 15 p. 

Williamson, D. R., and Burgin, Lorraine, 1960, Pumice and 

pumicite: Colorado School Mines Mineral Industries 

Bull., v. 3, no. 3, p. 1-12. 

Wright, L. A., Chesterman, C. W., and Norman, L. A., Jr., 

1954, Occurrence and use of nonmetallic commodities in 

southern California: California Div. Mines Bull. 170, 

chap. 8, pt. 7, p. 59-74. 

Yagi, K., 1966, Experimental study on pumice and obsidian: 

Bull. Volcano!., 2d ser., v. 29, p. 559--571. 

UNITED STATES MINERAL RESOURCES 

LIMESTONE AND DOLOMITE 

By HARoLD A. HUBBARD and GEORGE E. ERICKSEN 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

Definitions ----------------------------------

Production, uses, and desirable properties ----------

Construction stone ---------------------------

Portland cement ------------·-----------------

Fluxes --------------------------------------

Lime --------------------------------------- Refractory dolomite -------------------------

Agricultural limestone -----------------------

Other uses ------------------------------------

Geologic environments ---------------------------

Distribution and resources ------------------------

Problems for research ----------------------------

Selected references --------------·-----------------

FIGURE 

43. Graph showing production and use of limestone 

stone and dolomite. For uses in which the chemical properties are important, substitutes are few, generally scarce, 

and more costly. Because limestone and dolomite are abunPage dant, the price at the mine is low, and shipping costs con357 stitute a major part of the price to the consumer. About 

357 two-thirds of the limestone and dolomite mined in the 

358 United States is used because of its physical properties, 

358 chiefly in construction as aggregate and fill and for re359 lated purposes, but a small amount is also used as an in359 dustrial filler. The remainder is used because of its chemical 

360 properties as a raw material in the production of portland 

360 cement, lime, alkali, calcium carbide, and glass; for flux in 

360 metallurgy; for agricultural purposes; and for a large 

360 number of minor purposes. 

360 The largest resources of high-purity limestone and dolo360 mite in the United States are in the central and eastern 

361 parts of the country, but details of the distribution of such 

363 stone are incompletely known. Consequently, some potentially 

363 valuable deposits are endangered by urban spread and by 

Page 

zoning regulations that restrict or prevent quarrying in 

populous areas. 

INTRODUCTION 

and dolomite in the United States, 1950-69__ 359 

Limestone and dolomite, commonly referred to as 

carbonate rocks, are among the world's most widely 

used mineral commodities and are essential to modern industrial society. Huge quantities of these rocks 

are consumed annually in construction, in agriculture, and by the chemical and metallurgical industries. The total value of limestone and dolomite extracted annually is exceeded by that of only a few 

mineral commodities-sand and gravel, petroleum, 

and coal. Limestone and dolomite used for their 

physical properties, chiefly for construction purposes, occur in extremely large quantities on all the 

continents and constitute at least 10 percent of the 

near-surface rock of the continents. Large quantities of limestone are used in the manufacture of 

cement; the rock suitable for this purpose may be 

rather impure but is widespread and abundant, 

though less so than the limestone used in construction. High-calcium limestone and high-purity dolomite, which are needed for chemical and metallurgical purposes, are much less widespread and abunTABLES 

Page 

69. Principal sources and some potential sources of 

high-calcium limestone in the United States_ 362 

70. Principal sources and some potential sources of 

high-purity dolomite in the United States ___ 363 

ABSTRACT OF CONCLUSIONS 

Limestone and dolomite are at or near the earth's surface 

over at least 10 percent of the continental areas, and the 

resources are extremely large. However, high-purity stone 

suitable for chemical and metallurgical use is restricted in 

extent, but its resources are larg4~, also. For uses in which 

physical properties of the rock are important, as in construction, many kinds of rock can be substituted for limeU.S. GEOL. SURVEY PROF. PAPER 820 

357 
358 UNITED STATES MINERAL RESOURCES 

dant. Resources of these rocks are restricted to small 

parts of the continents. This chapter emphasizes 

limestone and dolomite that are used for their 

chemical properties ; uses for construction are described in the chapter "Construction Stone." Magnesite, another carbonate rock, consists of the mineral magnesite, MgC03, and is used mostly as a 

refractory material. Magnesite is discussed in the 

chapter "Magnesian Refractories." 

Distribution, characteristics, and uses of limestone 

and dolomite are discussed in many reports. The 

U.S. Bureau of Mines "Minerals Yearbooks" and 

"Mineral Facts and Problems" give information 

about production and use. Recent data about chemistry and technology are discussed in "Mineral Facts 

and Problems" (U.S. Bureau of Mines, 1970) and by 

Boynton (1967). New information about depositional 

environments and origin of limestone and dolomitethe result of intensive investigations during the 

last 20 years-aids the search for high-purity limestone and dolomite. Among recent reports giving 

such information are those in the symposia edited 

by Chilingar, Bissell, and Fairbridge (1967a), Friedman (1969), and Pray and Murray (1965). Summary 

information about the distribution of limestone and 

dolomite in the United States was presented by Gillson (1960, p. 148-183). Ericksen and Cox (1968) 

discussed distribution of carbonate rocks in the 

Appalachian region. 

DEFINITIONS 

Limestone and dolomite are rocks composed, respectively, of the minerals calcite, CaC03, and dolomite, CaMg(C03) 2; however, both limestone and 

dolomite commonly are called limestone by the industry, and intermediate varieties are not distinguished. Some newly deposited limestone consists 

chiefly of the mineral aragonite, which has the same 

composition as calcite but a different crystal structure. The aragonite structure is unstable, and with 

time aragonite gradually changes to calcite. Commonly, both calcite and dolomite occur in the same 

rock, but generally one predominates in any one 

layer or stratigraphic unit. A complete gradation 

between limestone and dolomite is uncommon. 

The value and use of carbonate rocks are determined by their composition. High-calcium limestone 

and high-purity dolomite have a great variety of 

uses in the chemical and metallurgical industries 

and are by far the most valuable of these rocks. 

High-calcium limestone is defined here as consisting 

of at least 97 percent CaC03 by weight, but many 

writers use 95 percent as a defining limit (Ericksen 

and Cox, 1968, p. 227). High-purity dolomite has at 

least 87.5 percent CaMg(C03)2 (40 percent MgCOg). 

Pure dolomite, CaMg(C03)2, consists of 45.7 percent 

MgC03 by weight. Cement limestone may contain a 

considerable amount of clastic impurities if they are 

relatively uniformly distrib1:1ted throughout the rock 

and provides the alumina and silica needed for portland cement. Cement limestone must contain less 

than 6.5 percent dolomite because raw materials for 

portland cement cannot contain more than 3 percent 

MgC03 ; the specifications for portland cement permit no more than 5 percent MgO. During the manufacture of cement, C02 is lost from CaMg(C03) 2, 

causing relative enrichment of the magnesium in 

the finished product (Boynton, 1957, p. 98). 

Carbonate rocks containing· more than 25 percent 

fine clastic material are unsuitable for any use except as fill for construction. Chert in crushed stone 

to be used as concrete aggregate is undesirable 

because the chert may react with the cement, and 

the resulting chemical compounds might weaken the 

concrete and cause spalling. 

PRODUCTION, USES, AND DESIRABLE 

PROPERTIES 

The present consumption of limestone is immense; 

more than 628 million tons of limestone and dolomite was used in the United States in 1969 (fig. 43). 

Although essential to industry, limestone and dolomite are among the cheapest of the mineral commodities-the average price of crushed limestone 

and dolomite at domestic quarries was $1.46 per ton 

in 1969. Commonly, a user pays more for shipping 

the limestone than for the rock itself. For example, 

the M. W. Kellogg Co. (1972, p. 13) reported the 

following freight rates for crushed stone in the 

United States, expressed in cents per ton-mile: 

truck, 5-10 (at 10 miles) to 2-5 (at 100 miles) ; 

rail, 4.5-6 (at 10 miles) to 0.75-1.5 (at 250 miles) ; 

and water (barge or ship), 0.9-1.5 (at 20 miles) to 

0.25-0.50 (at 500 miles). Because of shipping costs, 

limestone of relatively poor quality may be used in 

preference to better quality limestone that must be 

shipped in from a- greater distance. For example, the 

Vanport Limestone is mined in western Pennsylvania, eastern Ohio, and northern West Virginia 

for use in nearby steel plants, even though it contains only 90-95 percent CaC03 instead of the 95 

percent or more CaC03 usually required for flux. 

Most limestone and dolomite is produced from 

open pits or quarries ranging from tens to a few 

hundreds of feet in depth. Relatively small amounts 

of stone, chiefly high-purity material, are produced 

from room-and-pillar underground mines, most of 

which are less than 500 feet deep. Open-pit mining 
LIMESTONE AND DOLOMITE 359 

1000 

900 I I I I I I I I I I I I I I I 

800 

700 

600 ...----- -- 500 ~ - - 400 --------- _,...,--

Cl) 300 z ~ --- 'tJ 

• Q 

c 0 

.... v- Aggregate, fill, road metal, and railroad ballast • 

.&:. 

.... 

a: 

0 200 ~ u,-

£. 

I 

Cl) • u. 

0 ~ ~ - - ~ .. 

0 

Cll 

Cl) 

z 

0 Portland cement !,-

• ...1 

...1 100 ~ 90 

~ 80 

z· 70 

0 

- ~ u 

- - _, 

~ - ""' ....... _..,....- Q• 

..... ~_,.-- c ,·-

.--------- Lime ~ - ~- ---- Q. .' 

j: 60 u 

::> 

c 50 

• Flux ,rr. 1 

0 

a: 

~ 40 - _....., - / ~ - "" / ----- / 

I 

30 I 

I 

Agriculture I .! .... ! , o:~ 

' r::: - - .,.'0,._ 20 v -

"" ~ ~ I 3§~--

~ - - - Q:lllt .= ... _g 

Other 

t: ~ ... 

goe; 

c!-o£ ~ 

I I I I I I I I I I I l I I r 

1955 1960 1965 1969 

FIGURE 43.-Production and use of limestone and dolomite in the United S~tes, 19~69. Data from U.S. Bureau of Mines 

"Minerals Yearbook." 

and crushing and screening of rock are noisy and 

dusty operations and, hence, are commonly curtailed 

or banned in populous areas. 

CONSTRUCTION STONE 

Nearly two-thirds of all limestone produced in 

the United States in 1969 was used in construction, 

chiefly as aggregate, fill, and road metal. The stone 

for these purposes must be clean, hard, strong, and 

free of soft or friable material ; it should break into 

irregular but nearly equidimensional fragments; 

road metal should also be resistant to abrasion and 

have low porosity. Concrete aggregates should be 

low in reactive materials such as alkalis, soluble 

sulfides, and certain types of silica, particularly 

chert, that weaken concrete or even cause it to disintegrate. Many rocks are interchangeable with 

limestone for construction purposes. 

PORTLAND CEMENT 

Portland cement manufacture consumed about 15 

percent of limestone production in the United States 

in 1969. Portland cement is a complex mixture of 

calcium silicate, calcium aluminate, and calcium 

aluminoferrite made by fusing a finely ground mixture of limestone and aluminous and siliceous rna-
360 UNITED STATES MINERAL RESOURCES 

terials, such as shale and silica sand (Ericksen and 

Thomson, 1968, p. 165). Suitable limestone contains 

as much as 25 percent clay and sand, generally not 

more than 6.5 percent dolomite, less than 0.5 percent 

phosphorous pentoxide, and only very small amounts 

of sulfur. In the Chicago, Pittsburgh, and Birmingham steel-producing areas, blast-furnace slag is 

used for making cement; on the Gulf Coast and in 

California, large deposits of sea shells are used as 

the source of CaCOa. Cement made with slag and 

shells, however, accounts for only a small part of 

the total production. 

FLUXES 

Flux for blast and open-hearth furnaces consumed 

about 5 percent of carbonate rocks produced in the 

United States in 1969. During smelting, the magnesia (MgO) and lime ( CaO) of these rocks combine 

with impurities, such as silica and alumina, to form 

a liquid slag that separates from the molten metal. 

About half the limestone used for tlux comes from 

Michigan, and about 20 percent from Ohio, and 20 

percent from Pennsylvania (U.S. Bur. Mines, 1953-

1971, Minerals Yearbooks for 1950 to 1969). Limestone suitable for blast-furnace flux ranges from 

high-calcium limestone to calcareous dolomite containing as much as 31 percent MgCOa and not more 

than 5 percent silica, 2 percent Al20a, and 0.05 percent sulfur (Dever and McGrain, 1969, table 22). 

It should contain at least 95 percent total carbonate; 

however, where the transportation cost of such stone 

is high, lower grade stone may be used. Limestone 

for open-hearth furnaces should contain at least 97 

percent CaCOa, less than 3 percent silica, less than 

1.5 percent Al20a, and low sulfur. Limestone suitable for fluxing nonferrous metals is similar to 

high-calcium limestone suitable for blast-furnace 

flux. 

LIME 

Lime manufacture consumed about 5 percent of 

the limestone produced in the United States in 1969. 

Lime is calcium oxide or calcium and magnesium 

oxide made by calcining (heating) limestone or dolomite to drive off the carbon dioxide. About onethird of the manufactured lime is used in metallurgy 

for smelting and for concentration or beneficiation 

of metalliferous ores, another third is used by the 

chemical industry, and the remainder is used in 

many ways, principally for water softening, pulp 

and paper manufacture, sugar manufacture, and 

sewage and waste treatment. Limestone suitable 

for high-calcium lime contains at least 97 percent 

CaCOa. Low-magnesium lime contains 6-40 percent 

MgCOa, whereas high-magnesium lime contains more 

than 40 percent MgCOa ; both types should have less 

than 3 percent noncarbonate impurities. 

REFRACTORY DOLOMITE 

Dead-burned or refractory dolomite, a fairly 

stable lime made by calcining dolomite at especially 

high temperature, used about one-half a percent of 

the carbonate rocks produced in 1969 in the United 

States. It is used chiefly for lining and patching of 

linings of open-hearth steel furnaces. Dolomite for 

this purpose should contain more than 37.5 percent 

MgCOa and at least 97 percent total carbonate 

minerals. 

AGRICULTURAL LIMESTONE 

Agricultural limestone consumed about 4 percent 

of the limestone produced in the United States in 

1969. Agricultural limestone must have a calcium 

carbonate equivalent value of 80 or more. Pure limestone has a value of 100 and pure dolomite 108.6. 

(Dolomite has a larger value because magnesium is 

lighter than calcium.) 

OTHER USES 

About 8 percent of the limestone produced in the 

United States in 1969 had a wide variety of uses, 

each too small to be shown in figure 43. Among 

these are for alkali works, about 0.5 percent; glass 

manufacture, about 0.15 percent; and limestone 

sand, about 1.5 percent. Some other uses were not 

tabulated by the U.S. Bureau of Mines in 1969 but 

in past years have consumed comparable amounts of 

limestone. These include the manufacture of calcium carbide, beet sugar, pulp and paper, and industrial filler (whiting), and uses as pulverized limestone or dust that is applied to walls, roofs, and 

floors of coal mines to prevent or check coal-dust 

explosions, and as filter beds for water purification. 

The requirements for these uses vary, but, in general, limestone with a CaCOa content of at least 97 

percent is required. 

Limestone and dolomite probably will continue to 

be consumed in increasing quantities in the future 

and undoubtedly, new uses, particularly for highpurity stone, will become important. 

GEOLOGIC ENVIRONMENTS 

Limestone and dolomite form in a variety of environments, but they generally accumulate in warm 

shallow marine water. High-calcium limestone 

forms in those areas of free circulation with the 

open sea that are free of clastic sediments from 

nearby streams. Dolomite, however, is chiefly a rock 

of secondary origin, formed during diagenesis of 

limestone by partial replacement of CaCOa with 

MgCOa to form the mineral dolomite. 
LIMESTONE AND DOLOMITE 361 

Most limestone is a lithified mixture of detrital 

grains and lime mud. The grains include whole and 

broken fossils, pellets of mud, and oolites composed 

of concentric layers of calcite precipitated around 

a nucleus. A complete gradation occurs between 

limestone composed entirely of grains and limestone 

composed entirely of limy mud. The mud is composed of chemically precipitated calcite and aragonite and tiny calcareous fragments from organisms. 

The carbonate sediments respond to marine currents 

as do land-derived noncarbonate sediments, and 

some limestone layers are finely laminated and show 

graded bedding or even crossbedding. 

Reef limestone is formed in place as rigid frameworks build up by colonial organisms, such as corals, 

bryozoa, and algae. Organic reefs form only under 

ideal conditions of clear shallow marine water, warm 

temperatures, and abundant food supply. Large reefs 

can form only where the water depth slowly increases. Detrital materials, including fragments 

eroded from the reef by wave action and shells of 

noncolonial organisms, accumulate around the reef 

and commonly make up a much greater volume than 

the rigid reef rock. 

Dolomite forms in some places where sea water 

evaporates and also forms indirectly as a partial 

replacement of calcite in limestone by magnesium 

from calcium-depleted brines of evaporated sea 

water percolating through limestone. Today, dolomite forms on broad, nearly level flats just above 

the level of high tide. These flats are intermittently 

flooded by sea water, during either spring tides or 

storms, and some of the water remains on the flats 

after the flooding. The water collects in small depressions where evaporation takes place, and various minerals may precipitate as the brine becomes 

more saline. Gypsum (CaS04 ·2H20), the first mineral to precipitate, depletes the brine in calcium, 

causing a change in the ratio of magnesium to calcium from 5: 1 in normal sea water to as much as 

50: 1. Dolomite forms by reaction of the magnesiumenriched brines with formerly deposited calcite and 

aragonite. Seasonal rainfalls may bring about a concentration or purification of the dolomite by dissolving impurities deposited by the brine; for example, 

gypsum, which is more soluble than dolomite, is 

thus preferentially dissolved and returned to the 

ocean. Dolomite also occurs in some evaporite sequences that were deposited in broad shallow seas 

of nearly stagnant or very slowly circulating water 

in an arid climate. In such shallow seas a salinity 

gradient developed, whereby the salinity increased 

as the distance from the open ocean increased. 

DISTRmUTION AND RESOURCES 

Limestone and dolomite occur in most parts of 

the world and have formed throughout geologic 

time, but they are notably more abundant in rocks 

formed after shell-secreting organisms became 

abundant about 500 million years ago. Limestone 

and dolomite formations are widespread in the 

United States, and nearly every State has deposits 

adequate for construction and other uses that do 

not require chemically pure stone. High-calcium 

limestone and high-purity dolomite make up only a 

small fraction of all limestone and dolomite formations, and they occur in restricted areas. But even 

so, some high-purity carbonate formations are widespread, occurring in minable thicknesses nearly continuously over areas of many hundreds or even 

thousands of square miles. Although these nearly 

pure rocks are far less widely distributed than impure carbonate rocks, the resources are large and 

are sufficient to supply the growing needs of the 

Nation for hundreds or even thousands of years at 

anticipated rates of consumption. 

The most extensive stratigraphic units of limestone and dolomite of the United States were deposited in the Paleozoic Era, when North America 

was extensively covered by shallow seas. Carbonate 

rocks make up a significant part of the thickness of 

the Paleozoic sedimentary sequence. Exploitable 

limestone and dolomite formations occur most extensively in the slightly deformed rocks of the midcontinent-especially in Kentucky, Tennessee, Missouri, and the States adjacent to the Great Lakes. 

Formations exposed in the folded and faulted parts 

of Appalachian and Rocky Mountains tend to be 

linear bands parallel to regional geologic structure 

and, thus, are more restricted in area. However, 

some parts of these mountainous areas, as in the 

Appalachian Plateaus and the plateau regions of 

the Western United States, are relatively undeformed and the nearly flat-lying units are at minable depths over wide areas. 

Only a few formations will ultimately be the 

principal sources of high-calcium limestone and 

high-purity dolomite. The greatest quantities of 

high-calcium limestone occur in widely distributed 

formations of Mississippian age (table 69), whereas 

the greatest quantities of high-purity dolomite occur in formations of Ordovician and Silurian ages 

(table 70). Smaller deposits of high-quality limestone and dolomite occur in formations of other 

ages, and many formations that are chiefly impure 

rock locally contain minable deposits of high-purity 

limestone or dolomite. Some Ordovician formations 
362 UNITED STATES MINERAL RESOURCES 

TABLE 69.-Principal sources and some potential sources of high-calc.ium limestone in the United States 

Principal areas of occurrence of 

Geolocie age Stratigraphie unit high-calcium limestone 

Eastern and Central United States 

Tertiary ------------------Ocala Limestone -----------Northwestern peninsula, Florida. 

Pennsylvanian ------------Vanport Limestone (also Western Pennsylvania, northern West a member of the Virginia, eastern Ohio. 

Alleghany Formation). 

Mississip'Dian -------------Greenbrier Limestone ------Northern West Virginia, southwestern 

Virginia. 

Bangor Limestone ---------Northern Alabama, northern Georgia. Maxville Limestone _______ Eastern Ohio. 

Ste. Genevieve Limestone __ Eastern Tennessee, northern Alabama, 

Kentucky, Indiana. 

Girkin Formation (former- Western Kentucky, northern Alabama. 

ly Gasper Formation). St. Louis Limestone _______ Missouri, Illinois. 

Salem Limestone ----------Southern Indiana. 

Warsaw Limestone ________ Southern Indiana, Kentucky, northern 

Alabama. 

Boone Formation __________ Northern Arkansas. 

Devonian -----------------Helderberg Group _________ New York. 

Jeffersonville Limestone ___ Kentucky, southern Indiana. 

Traverse Formation, as Michigan, Indiana. 

used by Shaver and 

others ( 1970) , or Group. 

Cedar Valley Limestone Southeastern Minnesota. as used by Thiel and 

Schwartz (1941). 

Rogers City Formation ____ Northeastern Michigan. 

Dundee Formation -------- Do. 

Columbus Limestone _______ North-central Ohio. 

Ordovician ----------------Holston Limes.tone ________ Eastern Tennessee, southwestern Virginia. 

New Market Limestone ----Southwestern Virginia. 

Newala Limestone ---------Northern Alabama. 

Valentine Member of Central Pennsylvania. 

Curtin Limestone of 

Kay (1943). 

Annville Limestone --------Southeastern Pennsylvania. Trenton Limestone ________ New York. 

Galena Dolomite and Minnesota, Illinois, Wisconsin. 

Platteville Limestone. 

Cambrian ----------------Tomstown Formation ______ Panhandle of West Virginia. 

Western United States 

Quaternary ---------------Shell beds ________________ Southern California coast and Texas coast. 

Tertiary ------------------Sierra Blanca Limestone ___ Southwestern California. 

Vaqueros Formation ------- Do. 

Martinez Formation ------- Do. 

Cretaceous ----------------Mural Limestone ----------Southeastern Arizona. 

Edwards Limestone --------Central and western Texas. 

Tertiary to Jurassic -------Franciscan Formation and Coastal Range and California and southmetamorphic rocks of western Oregon. nearly equivalent age 

(limestone occurs as lenticular bodies) . Jurassic ( ?) ---------------Limestone of Kings Southern Alaska. 

River area. Triassic ------------------Limestone of Snake Southwestern Idaho. 

River area. Trias~ic and Permian ------Isolated limestone deposits __ Northeastern Oregon. 

Permian ------------------Ingleside Formation -------North-central Colorado. 

Permian to Mississippian ___ White Knob Limestone and Southeastern Idaho. 

Wells Formation. 

Carboniferous(?) ---------Oro Grande Formation ____ Central southern California. 

Pennsylvanian or Limestone lenses in Southwestern Oregon. Mississippian. metasediments. 

Mississippian -------------Madison Group -----------Western parts of Montana, Wyoming, and 

Colorado; southeastern Idaho, and northeastern Utah. 

Escabrosa Limestone ------Southeastern Arizona. 

Redwall Limestone --------Northern Arizona. 

Devonian -----------------Crystal Pass Limestone Southern Nevada. 

Member of the Sultan 

Limestone. 

Silurian ------------------St. Clair Limestone ________ Central and eastern Oklahoma. 

Heceta Limestone ---------Southeastern Alaska. 

Ordovician ----------------Fernvale Limestone _______ central and eastern Oklahoma. 

Cambrian -----------------Meagher Limestone --------Western Montana. 

Paleozoic (undi1fer- Limestone of Pico Blanco. __ Southern coast of California. 

entiated). · 
LIMESTONE AND DOLOMITE 363 

TABLE 70.-Principal sources and some potential sources of high-purity dolomite in the United States 

Geologie aee Stratigraphie unit 

l>rineipal areas of oeeurrenee of 

high-purity dolomite 

Eastern and Central United States 

Devonian -----------------Geneva Dolomite __________ Southeastern Indiana. 

Silurian ------------------Niagara G.roup, Lime- Wisconsin, Illinois, Michigan, Indiana, 

stone, or Dolomite. Ohio, Pennsylvania, New York. 

Ordovician ________________ Galena Dolomite ---------- Northern Illinois. 

Cambrian -----------------Tomstown Formation ------Western Maryland, western Virginia, and 

eastern panhandle of West Virginia. Shady Dolomite ___________ Eastern Tennessee, southwestern Virginia. Ketona Dolomite __________ Northern Alabama. 

Western United States 

Mississippian _____________ Monte Cristo Dolomite or Southern Nevada. 

Limestone. 

Devonian -----------------Water Canyon Formation __ Northern Utah. 

Silurian __________________ Laketown Dolomite --------Southeastern Idaho, northern Utah. 

Fusselman Dolomite -------South-central and wes·tern New Mexico. Ordovician ________________ Bighorn Dolomite or Western Wyoming. 

Limestone. 

Fish Haven Dolomite ______ Northern Utah. 

Cambrian ________________ Hasmark Formation or Western Montana. 

Dolomite. 

Royer Dolomite ___________ Southern Oklahoma. 

contain deposits having exceptionally high calcite 

content-the Holston Limestone of eastern Tennessee, the Valentine Member of the Curtin Formation 

of central Pennsylvania (one of the purest limestones in the United States), and the New Market 

Limestone of western and southwestern Virginia. 

In the eastern panhandle of West Virginia, the 

Tomstown Formation contains units of high-calcium 

limestone and high-purity dolomite, both of which 

are intensively exploited. The chief source of highpurity dolomite in the United States is the Niagara 

Group (table 70) in western Ohio. 

PROBLEMS FOR RESEARCH 

Although the United States is self-sufficient in 

limestone and dolomite and reserves of these rocks 

are immense, the reserves of chemically pure limestone and dolomite are limited and decreasing because some deposits are being mined out, users continue to make more stringent specifications, land 

underlain by high-purity carbonate rocks is being 

preempted for other uses, and zoning regulations 

restrict or prevent quarry operations in populous 

areas. The cost of high-calcium limestone will increase as thick, near-surface layers close to the industrial centers are mined out. Future production 

increasingly will depend on selective mining of relatively thin layers of limestone, underground mining, 

and mining from deposits distant from industrial 

centers. High-calcium limestone resources are more 

endangered by urban spread than almost any other 

mineral resource, except perhaps for sand and 

gravel, and the need to identify and protect areas 

of high-calcium limestone for future use is pressing. 

Future supply of high-purity dolomite in the 

United States is less of a problem than that of 

high-calcium limestone because far less high-purity 

dolomite is required by industry. Furthermore, immense resources of high-purity dolomite occur in 

the Great Lakes region, near eastern industrial centers where most dolomite is used. The extensive 

high-purity dolomite of the Niagara Group (table 

70) is an example. Resources of high-purity dolomite in the United States should be adequate for 

thousands of years. Shipping costs will continue to 

be a major factor in the future sources of supply 

of high-purity limestone and dolomite, particularly 

in the Western United States. These costs will rise 

as more distant sources are exploited, which probably will bring about the use of less pure stone 

nearer the user. 

Although much general information about potential resources and distribution of chemically pure 

limestone and dolomite in the United States is available, detailed information about the chemistry and 

the distribution of high-quality stone in most formations is relatively sparse. Systematic study of these 

formations should be undertaken to identify favorable areas that can be protected from urban spread 

and thus assure an adequate supply of inexpensive 

stone in the future. 

SELECTED REFERENCES 

Boynton, R. S., 1967, Chemistry and technology of lime and 

limestone: New York, Intersci. Pubs., 499 p. 

Chilingar, G. V., Bissell, H. J., and Fairbridge, R. W., eds., 

1967a, Carbonate rocks-Origin, occurrence and classification, [v.] 9A of Developments in sedimentology: New 

York, Elsevier Publishing Co., 471 p. 

-- 1967b, Carbonate rocks-Physical and chemical aspects, [v.] 9B of Developments in sedimentology: New 

York, Elsevier Publishing Co., 413 p. 
UNITED STATES MINERAL RESOURCES 

Dever, G. R., Jr., and McGrain, Preston, 1969, High-calcium 

and low-magnesium limestone resources in the region of 

the lower Cumberland, Tennessee, and Ohio Valleys, 

western Kentucky: Kentucky Geol. Survey Bull. 5, 

ser. 10, 192 p. 

Ericksen, G. E., and Cox, D. P., 1968, Limestone and dolomite, in Mineral resources of the Appalachian region: 

U.S. Geol. Survey Prof. Paper 580, p. 227-252. 

Ericksen, G. E., and Thomson, R. D., 1968, Cement, in Mineral resources of the Appalachian region: U.S. Geol. 

Survey Prof. Paper 580, p. 163-167. 

Friedman, G. M., ed., 1969, Depositional environments in 

carbonate rocks-A symposium: Soc. Econ. Paleontologists and .Mineralogists Spec. Pub. 14, 209 p. 

Gillson, J. L., 1960, [chapters on] Carbonate rocks, Cement 

materials, Lime, Mineral fillers, and Mineral wool, in 

Industrial minerals and rocks: New York, Am. Inst. 

Mining, Metall., and Petroleum Engineers, p. 123-241, 

497-519,567-584,595-604. 

Ham, W. E., 1962, Classification of carbonate rocks-A symposium: Am. Assoc. Petroleum Geologists Mem. 1, 279 p. 

Kay, G. M., 1943, Chemical lime in central Pennsylvania: 

Econ. Geology, v. 38, no. 3, p. 188-203. 

M. W. Kellogg Co., 1972, Availability of limestone and dolomites-Task #1 final report: Environmental Proteetion 

Agency, Office of Air Programs, Control Systems Div. 

Contract CPA 70-68, 185 p. 

Pray, L. C., and Murray, R. C., eds., 1960, Dolomitization 

and limestone diagenesis-A symposium: Soc. Econ. 

Paleontologists and Mineralogists Spec. Pub. 13, 180 p. 

Shaver, R. H., and others, 1970, Compendium of rock-unit 

stratigraphy in Indiana: Indiana Geol. Survey. Bull. 

43', 229 p. 

Thiel, G. A., and Schwartz, G. M., 1941, Subsurface structure 

of the Paleozoic rocks of southeastern Minnesota: Geol. 

Soc. America Bull., v. 52, no. 1, p. 49-60. 

U.S. Bureau of Mines, 1953-71, [chapters on] Cement, Lime, 

and Stone, in Minerals Yearbooks, 1950 to 1969: Washington, U.S. Govt. Printing Office. 

--- 1970, [chapters on] Calcium and Stone, in Mineral 

facts and problems: U.S. Bur. Mines Bull. 650, p. 903-

912, 1219-1235. 
UNITED STATES MINERAL RESOURCES 

LITHIUM, CESIUM, AND RUBIDIUMTHE RARE ALKALI METALS 

By jAMES 1. NORTON 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Lithium ----------------------------------------- Lithium deposits in pegmatites ---------------

Geology ---------------------------------

ndineralogy ------------------------------

Petrogenesis ----------------------------- Crystallization of lithium-rich pegmatite -------------------------------

Origin of pegmatitic magma ----------

Lithium pegmatite localities --------------

lJnited States ------------------------

Canada -----------------------------

South America ----------------------

Africa ------------------------------

Eurasia ----------------------------- Australia __________________________ _ 

Lithium in brines ----------------------------

Other lithium deposits -----------------------

Exploration and mining ---------------------

Reserves and resources ----------------------

Resources in pegmatites ------------------

lJnited States -----------------------

Canada -----------------------------

Africa ------------------------------ Eurasia, Australia, and South America_ 

Resources in brines ---------------------- Summary of lithium reserves and resources_ 

Cesium -----------------------------------------

Geology -------------------------------------

Production ----------------------------------

Reserves and resources ----------------------

Rubidium ---------------------------------------

Research suggested ------------------------------

Selected references -------------------------------

TABLES 

71. Crustal abundance of rare alkali metals ___ _ 

72. Composition of lithium minerals mined from 

pegmatites -------------------------------

73. Lithium resources --------------------------

Page 

365 

365 

366 

367 

367 

367 

368 

368 

368 

369 

369 

369 

370 

370 

370 

370 

370 

371 

371 

372 

372 

372 

373 

373 

374 

374 

375 

375 

375 

376 

376 

376 

377 

377 

Page 

366 

367 

372 

ABSTRACT OF CONCLUSIONS 

Lithium, cesium, and rubidium, though rare in comparison 

with sodium and potassium, are abundant relative to the apparent commercial need for them. Lithium and cesium both 

form independent minerals in pegrnatites. Lithium production from brines has increased so greatly in recent years 

that it has taken much of the market away from pegmatitic 

lithium. Rubidium forms no known independent minerals but 

exists chiefly as a substitute for potassium, especially in 

minerals formed late in the crystallization of pegmatites. 

ndost commercial rubidium and some cesium have been obtained as byproducts of processing lepidolite. 

The world's proved and probable reserves of lithium, most 

of which are in the 1Jnited States, are 1,200,000 tons, or 

about 400 times the 1970 consumption. Additional resources 

in known lithium regions are about 10 million tons, and 

even this large figure probably could be increased many 

times by intensive search throughout the world. 

World cesium reserves are 100,000 tons, which also is 

vastly greater than consumption and probably much less 

than could be found if needed. For rubidium, meaningful 

resource estimates cannot be made, but surely the supply obtainable at current prices is plentiful. 

To prepare for new uses frequently proposed, especially 

uses of lithium, knowledge of the geology of rocks and 

waters that are enriched in rare alkalis should be increased. 

INTRODUCTION 

The alkali metals include, in addition to the abundant elements sodium and potassium, four much 

rarer members-lithium, cesium, rubidium, and 

francium. Lithium, atomic number 3, has been mined 

and used since the latter part of the 19th century, 

and by the 1950's it had become the basis for an 

industry of moderate size. Cesium and rubidium, 

atomic numbers 55 and 37, respectively, have never 

been used in quantities of more than a few thousand 

pounds per year, virtually all of which is a byproduct 

from lithium mining. Cesium in the mineral pollucite does occur in deposits that would be minable 

for cesium alone if the market were larger, though 

even in these deposits cesium is a byproduct in the 

sense that it is generally found during exploration 

lJ.S. GEOL. SlJRVEY PROF. PAPER 820 

365 
366 UNIT'ED STATES MINERAL RESOURCES 

or mining for lithium minerals. Rubidium is not 

known to form any minerals of its own and occurs 

only as a minor constituent in minerals of other 

kinds, especially potassium minerals, and thus appears destined to continue as a byproduct. Francium, 

atomic number 87, is virtually nonexistent and may 

be disregarded in any discussion of mineral resources. 

The phrase "rare alkalis" is to some degree misleading. The known quantities of lithium and cesium, 

and probably also rubidium, obtainable under economic conditions resembling those of the present or 

the recent past are far greater than the amounts 

needed for current use or even for any but the most 

fanciful uses predicted for corning decades. New discoveries have often made supplies available to the 

market long before a demand for the supplies materialized. Publicity about these discoveries, which 

too frequently magnifies evidence that uses of these 

commodities will increase, tends to put the merit of 

even good deposits in question when after some years 

they have still not been mined, for the fact that the 

shortcoming lies not in the supply but in the demand may go unrecognized. The adequacy of lithium 

reserves to support new uses has been questioned 

even in recent years. Yet it was known two decades 

ago, and has been stated in the published record 

since at least 1955~ that lithium reserves are enormous and that large additional reserves could almost 

certainly be discovered, as in fact they have been 

in the intervening years. 

The geologic distribution of lithium, cesium, and 

rubidium is in many respects parallel to the distribution of the common alkali metals sodium and potassium, which is expectable from their chemical 

similarities. All the principal lithium minerals, as 

well as the cesium mineral pollucite, are obtained 

from granitic pegmatite, which is a generally coarsegrained rock consisting chiefly of sodic and potassic 

feldspars, quartz, and muscovite. Most of the rubidium and some cesium used commercially have 

been extracted from residues of the processing of 

lepidolite, a lithium-rich mica of pegmatite. Lithium 

from brines, which have long been a modest source, 

has in recent years come to dominate the market. 

Crustal-abundance estimates in table 71 show 

TABLE 71.-Crustal abundance, in parts per million, of rare 

alkali metals 

[Data from Heier and Billings (1970)] 

Rubidium Lithium Cesium 

Upper continental erust ---------- Lower continental erust ---------- Continental erust ---------------- Oeeanie erust -------------------

Crust --------------------------

110 

16 

48 

2.5 

37 

20 

10 

13 

10 

1Z 

' 3 ' 1 

' 

rubidium as the most common of the rare alkalis, 

lithium as a distant second, and cesium as very 

meager. The abundance of rubidium may surprise 

those whose chief acquaintance with rare alkalis is 

through knowledge of industry patterns or awareness of the absence of deposits comparable to those 

of lithium and cesium. Rubidium seems to substitute 

so readily for potassium in minerals that it is never 

greatly concentrated in nature, whereas lithium and 

cesium are less able to proxy for other elements and 

thus must under some conditions form independent 

minerals. Granitic rocks are the predominant host 

of all the rare alkalis. During weathering and sedimentation, rubidium and lithium, and probably 

cesium as well, are for the most part dispersed in 

clays. All deposits that have been economic sources 

of rare alkalis formed either in the pegmatite phase 

of granitic activity or through the development of 

unusual varieties of brine. 

UTmUM 

Lithium is by far the most economically important 

of the rare alkalis, and for this reason it will be 

discussed first and at greatest length. 

Most users of lithium products purchase lithium 

in the form of manufactured chemical compound~, 

of which the most common are the carbonate, hydroxide, bromide, chloride, hypochlorite, and stearate, and butyl lithium. Lithium metal and alloys are 

also produced. Lepidolite and petalite and lesser 

quantities of other lithium minerals go directly into 

some kinds of glass and ceramics. Additional uses 

of lithium products are in grease, in the manufacturing of air-conditioning systems and alkaline storage batteries, in fluxes for welding and brazing, and 

in metallurgy. 

Two of the more frequently mentioned potential 

uses for lithium could someday cause a very great 

increase in demand. One is for anodes and as a 

constituent of the electrolyte in storage batteries to 

power electric automobiles. The other is as an 

energy source, to breed tritium for fusion reactions. 

The United States is generally self sufficient in 

lithium and will remain so under any likely future 

circumstances. The only shortage is in lepidolite and 

petalite for glass and ceramics, and substitution may 

be practicable for some of these uses. Unfortunately, 

domestic production figures have not been published 

for many years, and few export figures are available; thus, it is impossible to calculate relationships 

among production, consumption, imports, and exports. 

Lithium was obtained chiefly from pegmatites 

throughout most of the history of the industry, 
LITHIUM, CESIUM, AND RUBIDIUM 367 

though after 1938 a sizable supply came from brine 

at Searles Lake, Calif. In 1966, however, production 

started from brine at Silver Peak, Nev., and this 

deposit seems to have become the world's largest 

source of lithium. Certain clays are also known to be 

enriched in lithium, but no attempt has ever been 

made to mine them. 

LITHIUM DEPOSITS IN PEGMATITES 

GEOLOGY 

Pegmatites containing lithium minerals can be 

divided into two categories: (1) deposits of spodumene in which there is so little change in the composition or texture of the rock from one place to 

another that it can be said to be virtually homogeneous; and (2) deposits of spodumene or other 

lithium minerals that are segregated into a series 

of zones of different composition or texture, in places 

accompanied by replacement bodies and fracturefilling units. 

The Foote Mineral Co.'s deposit at Kings Mountain, N. C., stands out as the best example of a 

homogeneous lithium-rich pegmatite. Kesler (1961) 

showed that the mineral content, in weight percent, 

is : spodumene, 20 percent; quartz, 32 percent; albite, 

27 percent; microcline, 14 percent; muscovite, 6 

percent; and other minerals, 1 percent. Crystals of 

spodumene and microcline are as much as 3 feet 

long, but most are less than 1 foot long. The other 

minerals are all finer grained. The deposit consists 

of many irregularly shaped, interfingering bodies, 

some large and some small; yet, the only noticeable 

inhomogeneity is the absence of spodumene and 

microcline within a few inches of some contacts, 

where a narrow wall zone consists of quartz, albite, 

and muscovite. 

Many spodumene-rich pegmatites have a more 

conspicuous wall zone of this same kind and are 

assigned to the zoned category, though actually they 

may differ only slightly from the homogeneous pegmatites. The Beecher No. 2 pegmatite in the Black 

Hills, S. Dak., has a well-defined wall zone barren 

of lithium minerals, but otherwise it resembles the 

homogeneous pegmatites at Kings Mountain in its 

composition and texture, and also in its structural 

irregularities. It is rightfully called a zoned pegmatite, but it can be regarded as being gradational 

between the homogeneous pegmatites and the complexly zoned pegmatites. 

Some lithium pegmatites contain many zones, of 

whieh one or several may contain lithium minerals. 

The Bob Ingersoll No. 1 pegmatite in the Black 

Hills has been a major source of lepidolite from its 

innermost zone and contains amblygonite in another 

zone; yet it carries no lithium minerals in the four 

remaining zones. On the other hand, the nearby 

Etta pegmatite contains spodumene throughout the 

three largest zones; only the narrow wall zone and 

the small quartz core are barren. 

MINERALOGY 

Spodumene is by far the most abundant lithium 

mineral of pegmatites. Other important minerals 

are lepidolite and petalite. Additional minerals from 

which lithium has been obtained are amblygonite 

and eucryptite. Table 72 shows the chemical formulas and Li20 contents of these minerals. 

TABLE 72.--Composition, in weight percent, of lithium minerals mined from pegmatites 

Mineral Formula 

Spodumene ___ LiAJSisOs 

Lepidolite ----KLi2AISit01oFr Petalite ______ LiAISitOlo 

Amblyconite __ LiAlPOt ( F ,OR) 

Eueryptite ___ LiAISiOt 

Maximum theore- LbO content tieal content of of commercial 

LitO concentrates 

8.0 

7.7 

4.9 

10.2 

11.9 

4 -7.& 8 -4.& 

8.6-4.71 

7.&-9.& 

6.6--6.6 I 

1 Formula for polylitbionitc end member. Natural lepidolite baa "arioue 

proportions of muscovite molecule. 1 For Bikita, Rhodesia (Cooper, D. G., 1964, p. 460) 

Spodumene is invariably accompanied by quartz, 

and, except in the inner zones of a few zoned pegmatites, it is also accompanied by feldspar. Ordinarily spodumene constitutes between 20 and 25 

percent of the rock mined, whether in a homogeneous pegmatite or in a zone of a zoned pegmatite. 

All deposits that have been successfully mined carry 

at least 1.0 percent Li20. 

Lepidolite (lithium-rich mica) ranks as an important source of lithium mainly because of its 

abundance at Bikita, Rhodesia, but it also has been 

mined at several other localities. It occurs mainly in 

the central part of zoned pegmatites, where its chief 

associates are albite and quartz. 

Petalite has been found in very few places, but 

where it does occur, it commonly is abundant. Virtually no petalite has been found in the United 

States. Descriptions of such foreign deposits as the 

one at Bikita, Rhodesia (Cooper, 1964), show that 

the petalite is mainly in intermediate zones of zoned 

pegmatites, where it is associated with quartz, feldspar, and spodumene. Eucryptite is common as an 

alteration product of spodumene at Bikita, though 

very rare elsewhere. 

Amblygonite is widely distributed in pegmatites, 

but rarely if ever does it form as much as 10 percent 

of any sizable body of rock. It has been mined chiefly 

from very coarse grained parts of certain zoned pegmatites that yielded crystals large enough to be 

concentrated by hand. Its large lithium content made 
368 UNIT'ED STATES MINERAL RESOURCES 

it the favored source, and at times the dominant 

source, of lithium in early years of the industry, 

but in recent decades its share of the market has 

been small. 

Other lithium-bearing minerals in pegmatites are 

zinnwaldite and allied micas, triphylite-lithiophilite 

and similar phosphates, and bikitaite. None of these 

have been commercially important sources of lithium, nor are any likely to become important in the 

future. 

PETROGENESIS 

CRYSTALLIZATION OF LITHIUM-RICH PEGMATITE 

How lithium pegmatites crystallize has been 

greatly elucidated by the experimental work of 

Stewart (1960, 1963, and written communs.). The 

geochemical development of lithium pegmatites has 

the remarkable result that in deposits of spodumene, 

petalite, or lepidolite the grade is rarely much lower 

than 1.0 percent or much greater than 2.0 percent 

Li20. Stewart has found that the system albitequartz-spodumene-water has a thermal minimum 

(analogous to the well-known granite minimum) at 

a composition characteristic of homogeneous spodumene pegmatites and of feldspar-quartz-spodumene 

zones of zoned pegmatites. The magma may at the 

outset pt·ecipitate only quartz and feldspar, forming 

the spodumene-free units observed in the outermost 

parts of many spodumene pegmatites, but when the 

lithium concentration of the melt reaches that of 

the thermal minimum, a lithium mineral will begin 

to be precipitated. Ordinarily the lithium mineral 

will be spodumene, which crystallizes from the melt 

at low temperatures and high pressures. Under lower 

pressure (PB2o less than about 2,000 bars) the 

liquidus does not reach the low temperature of 

spodumene crystallization, and the higher temperature mineral, petalite, must crystallize from the 

melt. Not uncommonly, as the solidified pegmatite 

becomes cooler, the petalite changes to spodumene 

plus quartz. 

As crystallization from the melt proceeds, the 

composition must remain feldspathic and have an 

Li20 content of no more than about 2 percent. Yet 

inner zones of some pegmatites are exceedingly 

quartzose, and a few inner units contain more than 

2 percent Li20. Stewart discovered that the solids 

dissolved in the gas coexisting with the melt are 

highly siliceous. He thus attributes quartzose inner 

zones and also units of abnormally high lithium content to precipitation from the gas. 

Hydrothermal investigations by Munoz ( 1971) 

show that lepidolite is stable only at low temperatures in pegmatitic mineral assemblages and that it 

can form by subsolidus reaction of spodumene and 

potassic feldspar in the presence of a fluorine-bearing 

aqueous gas. Textural and structural relations of 

some lepidolite to spodumene and microcline at many 

localities indicate that it does indeed form by replacement during cooling of pegmatite. Yet most 

lepidolite is in the innermost zone of the pegmatite, 

quite separate from any zone containing other lithium minerals. Though such lepidolite zones have a 

very disordered texture, with abundant veining and 

corrosion features, they lack evidence of preexisting lithium minerals. The core of the Bikita pegmatite has quartz as the principal associate of lepidolite and may have crystallized directly from the 

siliceous gas described by Stewart. In other pegmatites, however, feldspar is abundant in the lepidolite 

core, and its origin thus becomes implausible as a 

product either of the gas or of the silicate melt. 

Nevertheless, if lepidolite can form at low temperatures by subsolidus reactions as a replacement mineral in outer zones, then it should also be stable as 

a direct precipitate of whatever residual fluid remains at these temperatures trapped in the center 

of the pegmatite. 

ORIGIN OF PEGMATITIC MAGMA 

How a lithium-rich magma is generated can be 

stated in generalities but with few details. Localities containing pegmatites ordinarily also contain 

granite of approximately the same age that is universally regarded as the source of the pegmatitic 

fluid or in some other way closely related to it. The 

granites that accompany pegmatites-, being. of low 

calcium content and in some instances having virtually no calcium at all, are probably formed by 

melting of calcium-poor sediments rather than by 

fractionation of basic magmas. If so, then only 

where lithium is available in the zone of the melting-presumably from clays that have been carried 

to great depths-can lithium pegmatites result, 

which would account for the absence of lithium 

minerals in many pegmatite regions. 

How granites, which rarely contain much more 

than 100 ppm (parts per million) lithium, can generate pegmatitic magma of generally granitic composition but with several thousand parts per million 

lithium is a formidable question. In the Georgia 

Lake area, Ontario (Pye, 1965, p. 52-54), and in 

the Black Hills of South Dakota, the granite near 

lithium pegmatites tends to be of higher lithium 

content than elsewhere. This might be viewed as 

implying that the granitic magma fractionated to 

produce a lithium-rich magma were it not that 
LITHIUM, CESIUM, AND RUBIDIUM 369 

pegmatites as a rule contain either a great amount 

of lithium or virtually none at all ; very small areas 

can contain both kinds, with few or no pegmatites 

of intermediate lithium content. This bimodal distribution indicates that the process of forming a 

lithium-rich magma involves more than simple concentration of lithium in granitic magma. D. B. 

Stewart (oral communs.), who has pondered this 

problem at length, has suggested that minerals of 

the granite, some of which can carry many hundreds 

of parts per million lithium, returned their lithium 

to the residual melt during reactions at a late stage 

of magmatic crystallization. Whether a pocket of 

residual melt could be in contact with, or have access 

to, enough of the solidified granite to obtain the 

requisite amount of lithium, and why it should 

seldom if ever crystallize in place but instead be 

expelled to crystallize elsewhere, are questions that 

diminish the attractiveness of this ingenious proposal. 

That the lithium-rich magma was derived from 

granite magma, by processes not now understood, 

remains likely, but it is by no means a certainty. 

An alternate possibility is that lithium-rich magma 

formed in the zone of anatexis, independently of the 

granite magma, from partial melting of metasediments enriched in lithium. This origin is particularly 

appealing for large pegmatites, such as those at 

Kings Mountain, N. C., which have the same composition as at the minimum melting temperature in 

the feldspar-quartz-spodumene system. If a body 

of magma thus formed retains its individuality during upward movement, it becomes a lithium-rich 

pegmatite; if it merges with nearby granite magma, 

the result is granite with a somewhat higher than 

normal lithium content. 

LITHIUM PEGMATITE LOCALITIES 

The known lithium deposits of the world are 

numerous and widely distributed, but only a few 

have been economically important. The outstanding 

deposits are at Kings Mountain, N. C. ; Barraute, 

Quebec; and Bikita, Rhodesia; and in the Karibib 

and Warmbad districts of South West Africa. Many 

other localities are known to be promising. Production figures presented by Schreck (1961, tables 9-

12) provide a means of gaging the amount of lithium 

mining during past years at places throughout the 

world. 

UNITED STATES 

The dominant lithium district in the United States 

is Kings Mountain, N. C., where an area about 25 

miles long contains many spodumene-rich pegmatites. The largest of these deposits, owned and mined 

by the Foote Mineral Co., has been described in 

detail by Kesler (1961). 

Other areas in the United States contain pegmatites that are rich in lithium but too small to compete with equally rich but much larger deposits in 

North Carolina. The foremost among these areas is 

the Black Hills of South Dakota, which was the 

main source of lithium in the United States before 

the 1950's. All the production of the Black Hills has 

been from relatively small well-zoned pegmatites. 

The chief lithium mineral is spodumene, but the 

output includes a moderate quantity of lepidolite 

and most of the amblygonite mined in the United 

States. Lepidolite has also been extracted at the 

Harding mine near Dixon, N. Mex.; at the Stewart 

mine in the Pala district, California; and at the 

Brown Derby mine in the Quartz Creek district, 

Colorado. Other lithium pegmatites, most of which 

contain spodumene as the lithium mineral, have been 

found in Arizona, Wyoming, Massachusetts, New 

Hampshire, and Maine. 

CANADA 

The Quebec Lithium Corp.'s spodumene mine at 

Barraute, near Val d'Or, Quebec, is the most important of the known deposits in Canada and is the 

only one with a record of large production. The 

several pegmatites in this mine are virtually onzoned and consist mainly of albite, quartz, and 

spodumene. 

The Tanco pegmatite (named from the Tantalum 

Mining Corp. of Canada, Ltd.) at Bernie Lake, near 

Lac du Bonnet, southeast Manitoba, which was 

earlier known as the Chemalloy and still earlier as 

the Montgary pegmatite, has drawn widespread 

attention as a potentially important source of 

lithium. This is a well-zoned pegmatite in which 

spodumene is the predominant lithium mineral but 

in which lepidolite is also abundant (Hutchinsoit, 

1959; Wright, 1963; Howe and Rowntree, 1966) and 

petalite is present (Cerny and Ferguson, 1972). 

For the many other lithium pegmatites that have 

been discovered in Canada, Mulligan (1965) is the 

most comprehensive source of information. The Val 

d'Or region, Quebec, and the region near Bernie 

Lake, Manitoba, have attracted the greatest interest 

and contain many of the deposits. Pegmatites at 

Georgia Lake (Pye, 1965) and at several other localities in western Ontario carry spodumene. An extensive area near Yellowknife, Northwest Territories, 

has long been known to have lithium pegmatites, 

some of which are well zoned (Mulligan, 1965, p. 

85-87). Furthermore, in broad areas of the Cana-
370 UNITED STATES MINERAL RESOURCES 

dian Shield, largely covered by glacial drift, it seems 

unlikely that more than a modest fraction of the 

existing lithium pegmatites have been found. 

SOUTH AMERICA 

Pegmatites in northeastern Brazil have been 

mined for both spodumene and amblygonite. The 

production, though small, is enough to encourage 

hope that more can be found. 

Argentina is the only other South American 

country that has been a source of lithium, but 

whether its pegmatites have a significant potential 

is questionable. 

AFRICA 

Lithium pegmatites have been found in so many 

parts of Africa that only the outstanding localities 

can be mentioned here. The Bikita pegmatite in 

Rhodesia is preeminent. Cooper (1964) and Martin 

(1964) described this as a well-zoned pegmatite, 

5,400 feet long, that contains abundant lepidolite 

and petalite and lesser quantities of spodumene, 

amblygonite, and eucryptite. The only other localities with a notable record of production are the 

Karibib and Warm bad districts, South. West Africa, 

which contain zoned pegmatites described by Cameron (1955) that have been sources of lepidolite, 

petalite, and amblygonite. The Manono tin deposits, 

Republic of the Congo (Zaire), have attracted interest as potential sources of lithium. These deposits 

are in two pegmatites, each said to be 3.5 miles long 

and 150-2,500 feet wide and to contain 10-25 percent spodumene (Kesler, 1960, p. 527). 

EURASIA 

Lithium pegmatites are known in many parts of 

Europe and Asia, but none of the deposits have a 

record of large production nor is there published 

evidence for large reserves. The chief localities are 

in Czechoslovakia, France, East Germany, Portugal, 

Spain, Sweden, Soviet Union, India, and Korea. The 

best known of the western European deposits is the 

Varutrask pegmatite in northern Sweden, which 

contains lepidolite, petalite, spodumene, and amblygonite ( Quensel, 1952, p. 53-55). France and 

Portugal have each produced more than 4,000 tons 

of lepidolite (Schreck, 1961, table 9). In the U.S.S.R., 

deposits on Kola Peninsula and in the Altai Mountains may be important, but available published data 

are not adequate for evaluating them. 

AUSTRALIA 

Several pegmatite districts in Australia are known 

to have lithium minerals, and the very small production may not be an accurate measure of the 

potential. Western Australia contains most of the 

known occurrences. Spodumene, amblygonite, lepidolite, and petalite have all been reported (Noakes, 

1946, p. 9-12). 

LITHIUM IN BRINES 

Lithium has been obtained since 1938 from subsurface brine at Searles Lake, Calif., and since 1966 

from another dry lake at Silver Peak, Nev. The 

Silver Peak deposit has become a very large supplier of lithium, probably the world's largest, but 

production figures are unpublished. 

At Searles Lake the lithium is from an operation 

in which potassium chloride and sodium carbonate, 

sulfate, and borate are the main products. The brine 

contains about 0.015 percent Li20 (Ryan, 1951, 

table 1), or 70 ppm lithium, which is extracted as 

dilithium sodium phosphate that contains about 21 

percent Li20. 

At Silver Peak, according to Barrett and O'Neill 

(1970), the brine contains 300 ppm lithium and 

10-15 percent other dissolved constituents, of which 

chlorine and sodium are by far the most abundant. 

Lithium is the sole product. The well field from 

which the brine is obtained extends over an area of 

about 2 square miles, but the entire playa covers 

about 32 square miles. Clays, silts, sands, and 

evaporites are saturated with brine to a depth of 

at least 600 feet and possibly to 1,500 feet. I. A. 

Kunasz, in a 1970 Pennsylvania University doctorate 

thesis, "Geology and Geochemistry of the Lithium 

Deposit in Clayton Valley, Esmeralda County, Nevada," showed that the playa sediments have abundant hectorite obtained by erosion from nearby tuff. 

The hectorite was probably formed originally by 

hydrothermal alteration along a fault. Lithium of 

the brine, according to Kunasz, was leached from the 

tuff, and additional lithium may have been contributed by hot springs at the periphery of the 

basin. 

The development of the Silver Peak locality has, 

by putting substance into what previously was only 

a promise, greatly increased interest in lithium of 

brines. Earlier analyses of saline deposits either 

indicated no more than teasing amounts of lithium, 

which implied that nothing better than byproduct 

lithium, as at Searles Lake, would ever be found, 

or were themselves of dubious validity (Norton and 

Schlegel, 1955, p. 340). An additional source of production has now been developed at Great Salt Lake 

(Indus. Minerals, Dec. 1971, p. 37), which contains 

about 60 ppm lithium that is extracted together 

with magnesium. The Salton Sea geothermal brine 
LITHIUM, CESIUM, AND RUBIDIUM 371 

has been found to contain 210 ppm lithium in addition to a wide variety of other potentially valuable 

constituents (White, 1968, table 1). Observations 

by Helen L. Cannon (written commun., 1972) indicate concentrations of lithium in several closed 

basins in Nevada and California, especially those 

surrounded by volcanic rocks. 

Foreign localities have as yet received little attention. Chong (1971, p. 26) has found that lithium 

is concentrated in subsurface potassic brine in the 

Salar de Atacama of northern Chile. Though analyses are unpublished, the average grade is reported 

to be 2,000 ppm lithium (Mining Jour., June 26, 

1970, p. 597; Guillermo Chong, written commun., 

Aug. 21, 1972). This seems too high to be accepted 

without confirmation but is nonetheless an indication that lithium-rich brines exist in western South 

America as in western North America. 

All these lithium-rich brines are associated with 

continental sediments. Analyses of marine evaporites are invariably discouraging. 

OTHER LITHIUM DEPOSITS 

Fragmentary evidence has been cited from time 

to time to show that there may be other deposits of 

potential commercial value (Norton and Schlegel, 

1955, p. 332-333, 336-337, and 341). Hectorite (a 

magnesium-rich bentonite) at Hector, Calif. contains about 1 percent Li20 (Ames and others, 1958, 

table 3). Other clay deposits, which contain 0.2--0.5 

percent Li20, have been recorded near Amboy, Calif. 

(Foshag and Woodford, 1936, table 1, p. 241), Kirkland, Ariz. (Norton, 1965), and Spor Mountain, Utah 

(Shawe and others, 1964). Kesler (1960, p. 524) 

mentioned an average content of 0.5-1 percent Li20 

in the shaly matrix of borate deposits at Boron, 

Calif. During study of zeolitic tuffs in lake beds of 

the southwestern States, R. A. Sheppard (written 

commun., 1972) found that lithium not infrequently 

attains levels of several hundred parts per million 

in montmorillonoid clay minerals, especially in saline 

environments; a nearly pure separate of saponite 

from Pleistocene Lake Tecopa, Calif., has 0.34 percent Li20. Tardy, Krempp, and Trauth (1972) recorded the lithium contents of many additional clays. 

Whether any metamorphic rocks or hydrothermal 

veins contain enough lithium to attract interest is 

unknown. The mineral ephesite, a sodium-rich margarite detected in emery deposits in Turkey and in 

manganese deposits in South Africa, contains as 

much as 3.85 percent Li20 (Schaller and others, 

1967, p. 1692), but so far as known, it is a rare 

mineral. 

EXPLORATION AND MINING 

Though sporadic production was recorded from a 

few localities in the 1880's and 1890's, the world's 

first lithium mining of consequence began in 1898 

at the Etta mine, Keystone, S. Dak. For the next 

40 years, the chief sources were small mines in 

which spodumene, amblygonite, and lepidolite were 

recovered by hand sorting. During this period, production of lithium minerals in the United States was 

generally less than 2,000 tons annually; but in five 

of these years it exceeded 4,000 tons, and in 1920, 

a record year, the production was 11,696 tons, 

valued at $173,002 (Schreck, 1961, table 10), which 

probably contained about 250 tons of lithium. During these early years, the Etta mine was the largest 

individual source of lithium, and the only other important sources were the Harding mine, Dixon, N. 

Mex. ; the Stewart mine, Pala, Calif.; and the Tin 

Mountain mine, west of Custer, S. Dak. Domestic 

production during this period was far greater than 

production from other countries. · 

The first important change came in 1938, when 

the American Potash and Chemical Corp. began 

producing lithium at Searles Lake, Calif. This 

marked the beginning of a period in which large, 

fully mechanized operations took the place of stnall 

mines that depended on hand sorting. 

Expanding use during World War II caused the 

production of lithium minerals to reach a new peak 

in 1944, when 13,319 tons was produced in the 

United States and 17,169 tons was produced in the 

entire world (Schreck, 1961, table 9). This large 

production was made possible by the introduction 

of mineral dressing techniques, especially by the 

Solvay Process Co. at Kings Mountain, N. C. 

A sharp postwar slump, which lasted until 1950, 

was followed by the tremendous increase in production of the 1950's that soon far surpassed all previous records. The greatest incentive was the purchase of lithium hydroxide by the U.S. Atomic 

Energy Commission. By 1954, domestic output was 

37,830 tons of lithiurn minerals, containing 1,142 

tons of lithium; and world production was 102,763 

tons (Schreck, 1961, tables 9 and 10). Domestic production figures have not been published since 1954. 

For other parts of the world, however, production in 

the latter years of the 1950's was record setting, 

reaching a maximum in 1957, when the total was 

about 170,000 tons of lithium minerals and concentrates (Schreck, 1961, tables 9 and 11), which probably contained about 3,500 tons of lithium. If, as 

seems likely, domestic production also increased 

after 1954, the world's maximum output, in 1957 
372 UNITED STATES MINERAL RESOURCES 

or within a year or two thereafter, was probably 

between 5,000 and 6,000 tons of lithium. 

Three mines furnished most of the world's lithium 

during this period. One was the spodumene mine at 

Kings Mountain, N. C. operated by the Foote Mineral Co., which processed its own ores. Another was 

the spodumene mine of the Quebec Lithium Corp. at 

Barraute, Quebec; its concentrates were processed 

by the Lithium Corp. of America at Bessemer City, 

N. C. The third was the mine of Bikita Minerals 

(Pvt.), Ltd., at Bikita, Rhodesia; lepidolite concentrates from this mine were processed by American 

Lithium Chemicals, Inc., at San Antonio, Tex. 

The rate of production dropped greatly in 1960, 

when the last of Atomic Energy Commission contracts expired, but it was still large by the standards of the years prior to 1953. The principal raw 

material sources continued for several years to be 

the same as in the 1950's, but the processing and 

marketing patterns changed. 

Another milestone came in 1966 when production 

began from Silver Peak and an accompanying price 

reduction not only encouraged increased consumption but also led the Quebec Lithium Corp. to withdraw from the market. Luckenbach (1972, p. 115) 

estimated that domestic consumption, expressed as 

LiCOa, increased from 14,490,000 pounds (1,360 tons 

Li) in 1966 to 20,000,000 pounds (1,880 tons Li) in 

1970. Corresponding figures for the world were 

20,790,000 pounds (1,950 tons Li) in 1966 and 

32,500,000 pounds (3,050 tons Li) in 1970. Although 

consumption diminished in 1971, the trend indicates 

that the industry will in a few years pass the record 

set in the 1950's. 

RESERVES AND RESOURCES 

Reserves of lithium have long been known to be 

enormous relative to annual consumption, and with 

the opening of the Silver Peak deposit the reported 

reserve figures have become astronomic. Most of 

the known supply and most of the consumption of 

lithium are in the United States. There is little reason to believe that the large size of reserves in the 

United States means anything except that the search 

for lithium has been most intense near home; the 

rest of the world may be as well endowed with 

lithium as the United States. It may seem surprising 

that efforts have been expended to find much more 

lithium than is likely to be used for many decades. 

The explanation is not that efforts have been wasted 

but that many lithium deposits are disproportionately large relative to their market and have resources that can be readily estimated from the data 

acquired during exploration and development of 

even a small mine. 

Table 73 shows total world resource figures in 

TABLE 78.-Litkium resources, in short tons 

Locality 

Kings Mountain, N. C --------------- Blaek Hills, S. Dak ------------------ Other pegmatite districts of th.!! 

United States --------------------- Silver Peak, Nev., brine -------------- Salton Sea, Calif., geothermal brine -----

Searles Lake, Calif ------------------

United States, total (rounded) ----

Barraute, Quebee -------------------- Bernie Lake, Manitoba --------------- Other resources in Canada ------------

Canada, total ------------------

Bikita, Rhodesia ---------------------

South lVest Africa ------------------- Other resources in Africa ------------

Africa, total -------------------

South America brines ----------------

lVorld total (rounded) ---------

Identified resources 1 

P088ible 

Proved reserves and and 

probable eondi· reserves 2 tiona! re- sources a 

486,000 (II) 

10,000 

6oo:OOo 1,000 

2,000,000 

1,100,000 

10,000 30,000 

1,000,000 3,100,000 

84,000 

46,000 

200.000 

129,000 200,000 

90,000 

4,000 

94,000 

(1) 

1,200,000 3,300,000 

Hypotbetical re- sources' 

1,000,000 

2,500,000 

3,500.000 

1,000,000 

1,000,000 

1,00_!,000 

1,000,000 

1,000,00~ 

6,600,000 

1 Speeifie, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existing technology and economic conditions. ll Identified deposits from which minerals can be extracted profitably 

with existing technology and under present eeonomie conditions. a Speeifie, identified mineral deposits whose contained minerals are not profitably recoverable with existing technology and economic conditions. 

'Undiscovered mineral deposits, whether of recoverable or subeeonomie 

grade, that are geologically predictable as existing in known districts. 11 Included in hypothetical resources. 

three categories: ( 1) proved and probable reserves, 

(2) possible reserves and conditional resources, and 

(3) hypothetical resources. All the proved and probable reserves are backed by persuasive evidence that 

they exist and that they can be mined profitably 

under conditions prevailing now or in the recent 

past. Possible reserves are included with conditional 

resources because there is doubt about how to categorize many deposits. Many unexplored spodumene 

deposits, for example, have a grade equal to that at 

existing mines, and thus would ordinarily be regarded as having possible reserves; but because it 

is questionable whether a new spodumene mine could 

now be developed and operated profitably in competition with brines, these resources perhaps should 

be downgraded to conditional. 

RESOURCES IN PEGMA TITES 

UNITED STATES 

Virtually all the domestic reserves of pegmatitic 

lithium, and a very large part of the world's reserves, are at Kings Mountain, N.C. 

Kesler (1960, p. 525, and 1961, table 3) reported 

that measured (equivalent to proved) reserves in 

the main part of the Foote Mineral Co.'s deposit on 

June 30, 1959, were 20,746,297 tons of ore carrying 

1.53 percent Li20, which amounts to 147,000 tons 

of lithium. Additional reserves, but in the indicated 
LITHIUM, CESIUM, AND RUBIDIUM 373 

(probable) category, were reported at the same time 

as 15,769,075 tons, presumably of the same grade 

(Kesler, 1960, p. 525), which adds 112,000 tons of 

lithium to the total. Elsewhere in the Kings Mountain district, the Lithium Corp. of America holds 

reserves that were reported as of May 20, 1963 

(Clarke, F. F., written commun., 1963), to amount 

to 37 million tons at 1.32 percent Li20, or 227,000 

tons of lithium. 

Kesler (1960, p. 525) reported that the total reserves of the Kings Mountain district probably 

exceed all published estimates. The largest of the 

estimates is equivalent to 600,000 tons of lithium 

(Norton and Schlegel, 1955, table 5). These reserves 

were almost entirely in the inferred (possible) category, yet they are not much greater than the proved 

and probable reserves of 486,000 tons that have 

since been demonstrated. Certainly enough lithium 

to make up the difference is in the many small 

spodumene pegmatites of the region and in unexplored parts of the known large deposits. It is not 

unreasonable to suppose also that the district has 

additional large bodies of spodumene pegmatite, 

perhaps at great depth, perhaps even near the surface. The total of possible reserves, conditional resources, and hypothetical resources may well be 

placed at twice the known reserves, or about 1 million tons of lithium. 

Of the many localities elsewhere in the United 

States that contain lithium pegmatites, only the 

Black Hills, S. Dak., is known to have a significant 

quantity of lithium minerals, and the estimate there 

is only about 10,000 tons of lithium (Norton, 1964, 

p. 130). Because lithium mining has been dormant 

in the Black Hills for many years owing to the area's 

inability to compete with mines elsewhere, its 

lithium should be classified as a conditional resource. 

An estimate of hypothetical resources for the Black 

Hills or other localities in the United States would 

be trivial in comparison with the estimate for Kings 

Mountain. 

CANADA 

The best known deposits in Canada are at the 

Quebec Lithium mine, Barraute, Quebec, and the 

Tanco deposit, Bernie Lake, Manitoba. The Quebec 

Lithium resarves are 15 million tons containing 1.2 

percent Li20, or 84,000 tons of lithium, according 

to the account by Mulligan (1965, p. 46), who apparently preferred these figures to somewhat larger 

figures published elsewhere. At the Tanco deposit, 

Howe and Rowntree (1966, p. 210) placed lepidolite 

reserves at 107,700 tons with 2.24 percent Li20 and 

spodumene reserves at 4, 727,263 tons with 2.01 percent Li20, excluding ore that would have to be left 

as a pillar unless the lake were drained. These figures indicate a total of 45,000 tons of lithium in 

the Tanco mine. 

Reserve estimates have been published for many 

other deposits in Canada. None of them have been 

mined, nor do any seem as attractive as the Quebec 

Lithium or the Tanco deposits, one of which was 

closed in the face of competition from Silver Peak 

and the other after many years of effort has yet to 

produce lithium. In these circumstances, the other 

Canadian deposits seem most suitably classified as 

conditional resources. Pye (1965, p. 26) has tabulated data from the Georgia Lake area, Ontario, 

that indicate a total of 62,000 tons of lithium. For 

other areas in Canada, Mulligan (1965, table 6) compiled estimates that amount to 84,000 tons of lithium. Quite surely there is additional lithium at 

Barraute, Quebec, where only the ore within 600 

feet of the main shaft to a depth of 850 feet is included in the Quebec Lithium reserves nor should 

the ore excluded as a pillar at the Tanco deposit, 

which has 22,000 tons of lithium, be left wholly out 

of account. For the Yellowknife region, Mulligan 

(1965, p. 89) preferred to quote none of the existing 

reserve estimates but instead remarked that there 

is a "reserve of many millions of tons of material 

comparable to that developed elsewhere." Taken 

altogether, the existing information points to conditional resources of at least 200,000 tons of lithium 

in Canada. 

The vigorous prospecting for lithium in Canada 

during the 1950's resulted in the recognition of a 

great number of deposits. Mulligan (1965, table 6) 

listed 67 known deposits and lithium localities. Yet, 

in the absence of successful lithium mining, except 

at Barraute, Quebec, enthusiasm quickly waned. It 

may be surmised that exploration thus far has discovered only a fraction of the total amount of lithium actually available. An estimate of hypothetical 

resources amounting to 1 million tons of lithium 

seems plausible. 

AFRICA 

The two principal sources in Africa have been the 

Bikita pegmatite, Rhodesia, and the Karibib and 

Warmbad districts, South West Africa. Symons 

(1961, p. 145--148) reported that on December 31, 

1960, the reserves (here converted to short tons) at 

Bikita were 6,700,000 tons of various categories of 

material containing an average of 2.90 percent Li20, 

or 90,000 tons of lithium. For South West Africa, 

Kesler (1960, p. 527) estimated "about 350,000 tons 

of crude lepidolite ores mostly containing 20 to 50 
374 UNITED STATES MINERAL RESOURCES 

percent recoverable lepidolite, and about 200,000 tons 

of crude petalite ores of somewhat higher yield." 

These figures suggest a total of about 4,000 tons of 

lithium. 

No published data appear to be available to calculate resources in the Manono deposits, Republic of 

the Congo, though the quantity seems to be immense 

(Kesler, 1960, p. 527). Eilertsen (1965, p. 534) mentioned deposits in the Republic of Mali that have 

8,000 tons of lithium. In several other African countries lithium minerals have been mined or the existence of lithium pegmatites has been noted. The hypothetical resources of Africa may be estimated at 

1 million tons of lithium. 

EURASIA, AUSTRALIA, AND SOUTH AMERICA 

Noakes (1946) recorded resources amounting to 

1,000 tons of lithium in western Australia, and 

Eilertsen (1965, p. 534) mentioned 4,000 tons in 

the same region. Lithium pegmatites in South 

America and Eurasia, though numerous and widespread, seem not to be large, or at least no published statement to the contrary has been noticed. 

The U.S.S.R. has at least a few deposits and has 

recently exported lithium compounds (Luckenbach, 

1970, p. 83), though not in sufficient abundance to 

suggest that the country has any truly large mine. 

The identified resources throughout the vast regions of Eurasia, South America, and Australia 

seem too small to take into account in this report, 

and there are no grounds at all for estimating 

hypothetical resources. This is not to say, however, 

that sizable resources will not ultimately be discovered. 

RESOURCES IN BRINES 

The key to any estimate of the overall lithium 

resources in brines is the Silver Peak deposit, 

N evadaJ for which the Foote Mineral Co. reported 

reserves of 5--10 billion pounds of lithium (Foote 

Mineral Co., 1967, p. 24 ; Luckenbach, 1968) . Details of how these reserve figures were computed 

have not been published, but enough numerical data 

are available so that with only a few assumptions 

the calculations can be approximately duplicated. 

Barrett and O'Neill (1970, p. 47) provided figures of 

32 square miles for the area of the playa, 600 feet 

for the minimum thickness of the brine-bearing 

body, and 300 ppm for the content of lithium in the 

brine. Using these data and guessing that the brine 

occupies 40 percent of the volume and has a density 

of 1.1, one finds after making the appropriate calculations that the quantity of lithium approaches 5 

billion pounds. It thus appears that the Foote 5-10 

billion estimate applies to the entire 32-square-mile 

basin, and that the lower figure is to the known 

depth of brine in existing wells and the higher 

figure is to the probable average depth of the bottom 

of the basin. The grade apparently was assumed to 

be constant throughout the basin, and no estimate 

was made of how far the lithium content can be 

depleted before the grade becomes too low for profitable operation. The quantity, if any, of lithium that 

is being added to the brine from lithium-bearing clay 

and nearby hot springs, which would enlarge the 

reserves, seems to be regarded as too small to take 

into account. 

With this background, it is possible to place the 

reserves and resources in categories. Probably 

500,000 tons of lithium (20 percent of 5 billion 

pounds) in and near existing wells over a thickness 

of 600 feet can be called proved and probable reserves. Another 2 million tons of lithium at the 

same depth extending outward to the borders of 

the basin can be called possible reserves or conditional resources. The remaining 2,500,000 tons (or 

5 billion pounds) of lithium seems best categorized 

as hypothetical resources. 

For Searles Lake, Calif., published data have been 

used to make one estimate of 75,000 tons of Li20 

(Kesler, 1960, p. 524) and another of 90,000 tons 

of Li20 (Norton and Schlegel, 1955, p. 346-347), 

or about 40,000 tons of lithium. Because lithium is 

only one of many products from Searles Lake, the 

question of how much of it will be extracted depends 

on the outlook for the rest of the operation. Production is about 100 tons of lithium annually (Smith 

and Irwin, 1966, p. 234). If, at the present rate of 

operation, the deposit has a life of 100 years, which 

seems as good an estimate as any that can be made 

from the host of figures available, then the ultimate 

output of lithium will be 10,000 tons. This amount 

can be labeled reserves, and the remaining 30,000 

tons known in the deposit can be called conditional 

resources. 

The few other lithium brines that have been 

identified have yielded very large resource estimates. 

Conditional resources of 1,100,000 tons of lithium 

are in the Salton Sea geothermal brine, which contains several other constituents of potential economic value (White, 1968, p. 313). The Salar de 

Atacama, Chile, is said to have 1,200,000 tons of 

lithium (Mining Jour., June 26, 1970, p. 597). Guillermo Chong (written commun., Aug. 21, 1972) 

confirms this estimate but says that an exploration 

program is now starting. Until this exploration is 

completed and the extraordinarily high supposed 

content of 2,000 ppm lithium is substantiated, the 
LITHIUM, CESIUM, AND RUBIDIUM 375 

potential of this deposit seems best combined with 

that of other lithium brines that may exist in South 

America to make an estimate of 1 million tons of 

hypothetical resources. 

Great Salt Lake and probably other saline lakes 

in the world contain enormous quantities of lithium. 

Such lakes are omitted from table 73 because, unlike the other deposits included in the table, they 

are far more important for other purposes than as 

mineral deposits, and the likelihood is small that 

their lithium, which is at a very low grade, will be 

extracted in large quantity for a long time, if ever. 

SUMMARY OF LITHIUM RESERVES AND RESOURCES 

Table 73 shows that the world has proved and 

probable reserves of 1,200,000 tons of lithium plus 

nearly 10 million tons of possible reserves, conditional resources, and hypothetical resources. The 

proved and probable reserves alone would last the 

world 400 years at the 1970 rate of consumption. 

Most of the vast quantities of lithium itemized in 

table 73 are in the United States, which suggests 

that much larger resources exist but remain undetected in foreign countries. By multiplying domestic 

resources by 16.0, which is approximately the ratio of 

the world's land area to that of the United States, 

one finds that world totals can probaby be brought 

to a level of 120 million 'tons of lithium. If domestic 

resources are in fact greater than shown in table 

73, which is likely, and if the rest of the world does 

have proportionately as much lithium as the United 

States, which is also likely, then the actual world 

total is even larger. Any new discoveries are most 

likely to be made in localities with pegmatitic rocks 

in Canada, South America, Africa, and Australia, 

and in brines of western North and South America 

or geologically similar regions elsewhere. 

Lithium-resource estimates by this author have 

sometimes been called conservative. They are in fact 

neither conservative nor liberal, but are merely the 

largest that can be projected from existing data. 

The real meaning of table 73 is that resources of 

lithium, in deposits comparable to those that have 

been mined, are virtually unlimited relative to any 

likely demand. If a truly large demand for lithium 

ever arises-for example, for batteries for electric 

automobiles or for nuclear-power generation, which, 

however inevitable their development may be, will 

not necessarily use much lithium-then the search 

for high-quality lithium deposits will be renewed, 

and resource figures will skyrocket even further. 

Prudence would, of course, require that deposits be 

identified and their reserves determined before any 

such large use actually begins. 

CESIUM 

Cesium, though of low abundance in the earth's 

crust, has large reservoirs relative to its exceedingly small consumption. Most of the production 

and nearly all the known reserves are attributable 

to the Bikita pegmatite in Rhodesia, a few pegmatites in South West Africa, and the Tanco pegmatite, Manitoba. 

Uses that have most commonly been mentioned 

are in research and development of ionic engines for 

space travel and thermionic power generation, 

which thus far at least has also been associated 

chiefly with space flights. Otherwise the use of 

cesium is in infrared lamps, photomultiplier tubes, 

scintillation crystals, pharmaceuticals, and certain 

chemical processes (Heindl, 1970, p. 530) . 

GEOLOGY 

Cesium is most abundant in zoned pegmatites, a 

few of which contain astonishingly large and rich 

deposits. It is also concentrated in natural brines 

during crystallization of salts from sea water, but 

reaches a maximum of only 20 ppm in the last precipitates, sylvite and carnallite (Michael Fleischer, 

written commun., 1972). Two analyses of the Salton 

Sea geothermal brine show 14 and 20 ppm cesium 

(White, 1968, table 1). If any brines are 

known to have greater concentrations of cesium, 

the facts seem not to have been published. 

In pegmatites the most abundant (and for practical purposes, the only) cesium mineral is pollucite, 

( Cs,N a) AlSi20s, which in commercial concentrates 

generally contains somewhat more than 20 percent 

Cs20. Analyzed pure pollucite from the Tanco pegmatite, which has the largest reserves, contains 

36.2 percent Cs20 (Nickel, 1961, p. 6). Handsorted 

material, because it is contaminated by quartz which 

resembles pollucite, has about 28 percent Cs20 in 

the Tanco deposit (Hutchinson, 1959, p. 1534) and 

about 25 percent at Bikita (Cooper, 1964, p. 451). 

Other cesium-rich minerals include uncommon forms 

of beryl (as much as 9.5 percent Cs20), cesium 

kupletskite, avogadrite, and the rare borate rhodizite (Michael Fleischer, written commun., 1972). 

Pollucite deposits have a conspicuous association 

with lithium pegmatites that contain lepidolite and 

petalite. The Bikita and Tanco pegmatites have the 

world's two largest lepidolite deposits and also the 

two largest pollucite deposits. Similarly in South 

West Africa, though the published record is not so 

clearcut on the subject, the pegmatites with lepidolite and petalite seem also to be the source of 

pollucite. In both the Bikita and the Tanco pegmatites. most of the pollucite is in a single large and 
376 UNITED STATES MINERAL RESOURCES 

very rich lenticular unit on the hanging-wall side 

of the pegmatite, generally well removed from the 

lepidolite core and surrounded by a spodumene-rich 

intermediate zone containing petalite (Cooper, 1964, 

p. 450-451 and figs. 3, 6, and 7; Martin, 1964, p. 

124 and pl. 8; Hutchinson, 1959, p. 1534 and figs. 

2 and 5; Wright, 1963, p. 936 and pl. 1; Crouse and 

~erny, 1972, figs. 3 and 4). 

PRODUCTION 

Production and consumption figures for cesium 

are rarely published. Howe and Rowntree (1966, p. 

211) say that the United States in 1964 used about 

8 short tons of cesium salts and somewhat more 

than 3,000 pounds of cesium metal. In 1970, the 

United States imported 5,129 pounds of cesium compounds plus an unstated quantity of pollucite, and 

the U.S.S.R. imported 200 tons of pollucite containing about 40 tons of cesium (Kurtz, 1972). From 

these figures, the world's consumption now and in 

the immediate future may be gaged at only a few 

tons of cesium annually. Prices are high; the 5,129 

pounds of cesium products imported in 1970 were 

valued at $189,056 (Kurtz, 1972), or about $37 

per pound. 

The principal source has been the Bikita pegmatite, mainly from pollucite but also as a byproduct 

of the extraction of lithium from lepidolite, which 

resulted in an alkali carbonate residue containing 

about 2 percent cesium. South West Africa has been 

the other source in recent years, and Mozambique 

has also yielded cesium (Howe and Rowntree, 1966, 

p. 211). Only about 100 tons of pollucite has been 

mined in the United States, mostly from the Tin 

Mountain pegmatite, Black Hills, S. Dak., but also 

from Oxford County, Maine. All these sources are 

likely to be dwarfed by the Tanco deposit during 

any expansion of the cesium market unless a now 

unanticipated source of cesium (for example, as a 

byproduct of brine processing) makes an appearance. 

RESERVES AND RESOURCES 

ReserVes of the Tanco deposit have most recently 

been placed at 293,863 tons of pollucite with 23.67 

percent Cs20, or 66,000 tons of cesium (Mining 

Engineering, April 1962, p. 18). At Bikita the dimensions of the pollucite body, as furnished by 

Martin (1964, p. 124 and pl. 8), imply about 25,000 

tons of cesi urn. Reserves in South West Africa may 

also be sizable, but elsewhere in the world the known 

amount of poilu cite is negligible. Nevertheless, the 

world's total reserves may be placed at very close 

to 100,000 tons of cesium, which is virtually infinite 

relative to the trivial annual consumption or to 

anticipated demand. 

Estimates of conditional or hypothetical resources 

are not worthwhile in the absence of data and in 

the absence of any predictable need for a larger 

quantity of cesium. If one makes the plausible assumption that the ratio between cesium reserves 

and proved and probable reserves of lithium in pegmatites (about 1: 7) will remain approximately the 

same as additional lithium deposits are developed, 

the world has resources of several hundred thousand 

tons of cesium. 

RUBIDIUM 

Rubidium resources cannot be appraised in the 

same way as lithium or cesium resources because no 

rubidium minerals or rubidium-rich waters have 

been found or seem likely to be found, and all rubidium recovered is byproduct. The amount of 

rubidium available suffices for the small demand, 

and probably other byproduct sources could be 

tapped to increase the supply without much effect 

on prices. 

Consumption figures for rubidium are unpublished 

but apparently are even smaller than for cesium, 

which in some uses serves the same purpose as 

rubidium. Consumption is mainly in research and 

development, but rubidium is also used in vacuum 

tubes, photocells, and medicine (Heindl, 1970, p. 

700-702). The main source in recent years has been 

the alkali carbonate residue of the lepidolite plant 

formerly at San Antonio, Tex., the stock of which 

has not yet been exhausted, but it is also a byproduct of the processing of pollucite (Heindl, 1970, p. 

700). 

The apparent absence of independent rubidium 

minerals is attributable to chemical properties which 

enable rubidium to substitute for potassium, a 

ubiquitous constituent not only of granites and clays, 

which have the highest average contents of rubidium 

(Heier and Billings, 1970), but also of pegmatites 

and evaporites, which are commonly enriched in 

rubidium. According to Michael Fleischer (written 

commun., 1972) the rubidium content of pegmatite 

minerals is as much as 3.0 percent in microcline, 

2.1 percent in muscovite, 4.1 percent in biotite, 4.5 

percent in lepidolite, and 0.85 percent in pollucite; 

minerals of the Tanco pegmatite reach or exceed 

these maximums (Nickel, 1961, tables 1 and 4; Petr 

Cerny, written commun., 1972). Among evaporite 

minerals, the rubidium content is at most about 0.2 

percent in sylvite and carnallite (Michael Fleischer, 

written commun., 1972). Because both sylvite and 

carnallite are formed in the last stages of crystalli-
LITHIUM, CESIUM, AND RUBIDIUM 377 

zation of oceanic salts, it is clear that rubidium increases in concentration in the brine until very 

nearly the end. The same applies as granite progresses to pegmatite, and the increase doubtless 

continues to the late stages of crystallization of at 

least some pegmatites, especially those containing 

lepidolite and pollucite. 

Exhaustion of the stock of alkali carbonate remaining from lepidolite processing at San Antonio 

will necessitate finding another source of rubidium. 

This is not likely to be difficult if the demand continues small and the price high. Development of any 

new large-magnitude use, beyond what can be supplied from byproduct sources, will require search 

for new deposits, which in all likelihood can be 

found somewhere among the wide range of natural 

substances containing concentrations of alkalis. A 

discovery of rubidium-rich pegmatites in Manitoba 

(Jambor and Potter, 1967) indicates that grades of 

at least 1.0 percent Rb20 are possible. The large 

body of analytical data acquired throughout the 

world in making rubidium-strontium age determinations probably would provide useful leads to where 

rubidium deposits might be found. At present, however, data pointing to potential rubidium deposits, 

as well as data about future demand for rubidium, 

and in what chemical form it might be used, are so 

sparse that it is fruitless to attempt to estimate 

resources. 

RESEARCH SUGGESTED 

Because supplies of lithium, cesium, and probably 

rubidium are large relative to their market, there 

is no urgent need to find new resources. New uses 

for these elements are seriously considered from 

time to time, and some of these uses could ultimately 

create a large demand. To prepare for this eventuality, it would be prudent to learn more about 

which rocks and waters have concentrations of these 

elements and to identify the processes that cause 

these concentrations, so that search for new deposits can, at any future time, be intelligently planned. 

Geochemical investigations to date have been directed mainly at rocks, minerals, and waters that 

contain only slight amounts of these elements rather 

than at those likely to become economically productive, but they provide a basis for studies that 

can clarify how deposits form and where they might 

be found. 

A desirable objective of future research is to facilitate the discovery of higher grade lithium deposits 

than those now known, so as to diminish cost of production-or, on the other hand, to show that no such 

deposits are likely to be found and all plans must be 

based on present costs. Lithium is unusual among 

mineral commodities in that the known resources in 

deposits of modest but minable grade are enormous, 

yet resources in truly high-grade deposits have never 

been found. This suggests that sizable high-grade 

deposits do in fact exist but have been overlooked. 

SELECTED REFERENCES 

Ames, L. L., Jr., Sand, L. B., and Goldich, S. S., 1958, A 

contribution on the Hector, California, bentonite deposit: Econ. Geology, v. 53, no. 1, p. 22-37. 

Barrett, W. T., and O'Neill, B. J., Jr., 1970, Recovery of 

lithium from saline brines using solar evaporation, in 

Third Symposium on Salt, v. 2: Cleveland, Ohio, Northern Ohio Geol. Soc., p. 47-50. 

Broadhurst, S. D., 1956, Lithium resources of North Carolina: North Carolina Div. Mineral Resources Inf. Circ. 

15, 37 p. 

Cameron, E. N., 1955, Occurrence of mineral deposits in the 

pegmatites of the Karibib-Omaruru and Orange River 

areas of South West Africa: Mining Eng., v. 7, no. 9, 

p. 867-874. 

~erny, Petr, and Turnock, A. C., 1971, Pegmatites of southeastern Manitoba: Geol. Assoc. Canada Spec. Paper 9, 

p. 119-127. 

~erny, Petr, and Ferguson, R. B., 1972, Petalite and spodumene relations in the Taneo pegmatite, Bernie Lake, 

Manitoba: Canadian Mineralogist, v. 11, pt. 3, p. 660-

678. 

Chong D., Guillermo, 1971, Depositos salinos en el norte de 

Chile y el Salar de Atacama: Geoehile, no. 3, p. 13-27. 

Cooper, D. G., 1964, The geology of the Bikita pegmatite, in 

The geology of some ore deposits in southern Africa, v. 

2: Geol. Soc. South Africa, p. 441-461. 

Crouse, R. A., and ~erny, Petr, 1972, Geology and paragenesis of the Tanco pegmatite, Bernie Lake, Manitoba: 

Canadian Mineralogist, v. 11, pt. 3, p. 591-608. 

Cummings, A. M., 1970, Lithium, in Mineral facts and problems, 1970: U.S. Bur. Mines Bull. 650, p. 1073-1081. 

Eilertsen, D. E., 1965, Lithium, in Mineral facts and problems, 1965: U.S.._ Bur. Mines Bull. 630, p. 631-536. 

Foote Mineral Company, 1967, Is there enough lithium?: 

Foote Prints, v. 36, p. 23-24. 

Foshag, W. F., and Woodford, A. 0., 1936, Bentonitic 

magnesian clay mineral from California: Am. Mineralogist, v. 21, no. 4, p. 238-244. 

Gough, W. C., and Eastlund, B. J., 1971, The prospects of 

fusion power: Sci. American, v. 224, no. 2, p. 50-64. 

Heier, K. S., ar.d Billings, G. K., 1970, Lithium, rubidium, 

cesium, in Handbook of geochemistry: Springer-Verlag, 

v. 2-1, chapters 3, 37, and 55. 

Heindl, R. A., 1970, Cesium, in Mineral facts and problems, 

1970: U.S. Bur. Mines Bull. 660, p. 627-534. 

-- 1970, Rubidium, in Mineral facts and problems, 1970: 

U.S. Bur. Mines Bull. 660, p. 69.7-7Q4. 

Horstman, E. L., 1957, The distribution of lithium, rubidium, 

and caesium in igneous and sedimentary rocks: Geochim. 

et Cosmochim. Acta, v. 12, nos. 1-2, p. 1-28. 

Howe, A. C. A., and Rowntree, J. C., 1967, Geology and economic significance of the Bernie Lake pegmatite: Can. 

Mining and Metall. Bull., v. 60, p. 207-212. 
378 UNITED STATES MINERAL RESOURCES 

Hutchinson, R. W., 1959, Geology of the Montgary pegmatite 

[Manib>ba] : Econ. Geology, v. 54, no. 8, p. 1525-1542. 

Jambor, J. L., and Potter, R. R., 1967, Rubidium-bearing 

dykes, Gods River area, Manitoba: Geol. Survey of 

Canad·a Paper 67-15, 7 p. 

Kesler, T. L., 1960, Lithium raw materials, in Industrial 

minerals and rocks [3d ed.]: Am. Inst. Mining, Metall., 

and Petroleum Engineers, p. 521-531. 

--- 1961, Exploration of the Kings Mountain pegmatites: 

Mining Eng., v. 13, no. 9, p. 1062-1068. 

Kunasz, I. A., 1971, Geology and geochemistry of the lithium 

deposits in Clayton Valley, Esmeralda Ccunty [abs.]. 

Dissert. Abs., v. 32. no. 1, p. 379B. 

Kurtz, H. E., 1972, Cesium and rubidium, in. U.S. Bur. Mines 

Minerals Yearbook 1970: v. 1, p. 1215-1226. 

Luckenbach, W. F., 1968, Lithium: Eng. and Mining Jour., 

v. 169, no. 3, p. 125. 

--- 19·70, Lithium: Eng. and Mining Jour., v. 171, no. 3, 

p. 82-84. 

--- 1972, Lithium: Eng. and Mining Jour., v. 173, no. 3, 

p. 115-116. 

McKelvey, V. E., and Duncan, D. C., 1967, United States and 

world resources of energy, in Symposium on the development of petroleum resources of Asia and the Far East, 

3d, Proc.: United Nations Mineral Resources Development Ser., no. 26, v. 2, p. 9-16. 

Martin, H. J., 1964, The Bikita Tinfield, in Wilson, J. F., The 

geology of the country around Fort Victoria: Southern 

Rhodesia Geol. Survey Bull. 58, p. 114-132. 

Mulligan, Robert, 1965, Geology of Canadian lithium deposits: Canada Geol. Survey Econ. Geology Rept. 21, 

131 p. 

Munoz, J. L., 1971, Hydrothermal stability relations of synthetic lepidolite: Am. Mineralogist, v. 56, p. 2069-2087. 

Nickel, E. H., 1961, The mineralogy of the Bernie Lake 

pegmatite, southeastern Manitoba: Canada Dept. Mines 

• and Tech. Surveys, Mines Br., Tech. Bull. TB20, 38 p. 

Noakes, L. C., 1946, Lithium: Australia Mineral Resources 

Survey, Mineral Resources of Australia, Summary Rept. 

25,17 p. 

Norton, J. J., 1964, Nonmetallic and industrial mineral resources-Pegmatite minerals, in Mineral and water resources of South Dakota: U.S. 88th Cong., 2d sess., 

Senate Comm. Interior and Insular Affairs Comm. Print 

(South Dakota Geol. Survey Bull. 16), p. 112-133. 

--- 1965, Lithium-bearing bentonite deposit, Yavapai 

County, Arizona, in Geological Survey research 1965: 

U.S. Geol. Survey Prof. Paper 525-D, p. D163-D166. 

Norton, J. J., and Schlegel, D. M., 1955, Lithium resources 

of North America: U.S. Geol. Survey Bull. 1027-G, p. 

325-350. 

O'Neill, B. J., Kunasz, I. H., and Wright, L. A., 1969, The 

lithium production curve-a measure of many things: 

Earth and Mineral Sci., v. 38, no. 6, p. 45-48. 

'Pye, E. G., 1965, Geology and lithium deposits of Georgia 

Lake area, District of Thunder Bay: Ontario Dept. 

Mines Geol. Rept. 31,113 p. 

Quensel, Percy, 1938, Minerals of the Varutrisk ~gmatite, 

[pt.] I, Pollucite, its vein material and alteration products: Geol. Foren, Stockholm Forb., v. 60, p. 612-634. 

--- 1952, The paragenesis of Varutrisk pegmatite 

[Sweden]: Geol. Mag., v. 89, no. 1, p. 49-60. 

Ryan, J. E., 1951, Industrial salts-production at Searles 

Lake [Calif.]: Min-ing Eng., v. 3, no. 5, p. 447-452. 

Schaller, W. T., Carron, M. K., and Fleischer, Michael, 1967, 

Ephesite, Na(LiAl:~) (Al,Si.) Oto(OH)., a trioctahedral 

member of the margarite group, and related brittle 

miea·s: Am. Mineralogist, v. 52, p. 1689-1696. 

Schreck, A. E., 1961, Lithium-a materials survey: U.S. Bur. 

Mines lnf. Circ. 8053, 80 p. 

Shawe, D. R., Mountjoy, Wayne, and Duke, Walter, 1964, 

Lithium associated with beryllium in rhyolitic tuff at 

Spor Mountain, western Juab County, Utah, in Geological Survey research 1964: U.S. Geol. Survey Prof. 

Paper 501-C, p. C86-C87. 

Smith, G. 1., and Irwin, W. P., 1966, Lithium, in Mineral resources of California: U.S. 89th Cong., 2d sess., Senate 

Comm.. Interior and Insular Affairs Comm. Print (California Div. Mines and Geology Bull. 191), p. 233-235. 

Stewart, D. B., 1960, The system LiAlSiO,-NaAlSiaOs-H.O 

at 2,000 bars, in Minerals and genesis of pegmatites: 

Internat. Geol. Cong., 21st, Copenhagen, 1960, Rept., pt. 

17' p. 15-30. 

--- 1963, Petrogenesis and mineral assemblages of 

lithium-rich pegmatites [abs.]: Geol. Soc. America Spec. 

Paper 76, p. 159. 

Symons, Ralph, 1961, Operation at Bikita Minerals (Private), Ltd., Southern Rhodesia: Inst. Mining and 

Metallurgy (London) Bull., no. 661, p. 129-172. 

Tardy, Yves, Krempp, Gerard, and Trauth, Norbert, 1972, Le 

lithium dans les mineraux argileux des sediments et des 

sols: Geoehim. et Cosmochim. Acta, v. 36, p. 397-412. 

White, D. E., 1968, Environments of generation of some 

base-metal ore deposits: Econ. Geology, v. 63, no. 4, p. 

301-335. 

Wininger, D. G., 1972, Lithium, in U.S. Bur. Mines Minerals 

Yearbook 1970: v. 1, p. 1230-1231. 

Wright, C. M., 1963, Geology and origin of pollucite-bearing 

Montgary Pegmatite, Manitoba: Geol. Soc. America 

Bull., v. 74, no. 7, p. 919-945. 
UNITED STATES MINERAL RESOURCES 

MAGNESIAN REFRACTORIES 

By ALFRED J. BoDENLos and T. P. THAYER 

CONTENTS 

Page 

Abstract of conclusions -------------------------- 379 

Introduction ------------------------------------ 379 

Exploitation __ --__ - ------------------------------ 380 

Geology ----------------------------------------- 381 

Mineral deposits ----------------------------- 381 

Magnesite ------------------------------- 381 

Prospecting ------------------------- 382 

Genesis ----------------------------- 382 

Brucite --------------------------------- 382 

Olivine ---------------------------------- 382 

Other sources ------------------------------- 382 

Resources --------------------------------------- 383 

Identified and hypothetical resources ---------- 383 

Speculative resources ------------------------ 383 

Problems for research ---------------------------- 383 

Selected references ------------------------------- 384 

FIGURE 

Page 

44. Diagram showing use of the principal raw materials of magnesium --------------------- 380 

ABSTRACT OF CONCLUSIONS 

Magnesium-bearing compounds are processed into hightemperature refractories, indispensable as linings in modern 

steel furnaces; chemicals; and magnesium, the lightest of 

structural metals. They are derived from minerals, brines, 

and sea water. 

Resources from which magnesium-bearing compounds may 

be recovered range in size from large to practically unlimited 

and are globally widespread. Identified resources of magnesite throughout the world total 12 billion tons, and those 

of brucite several million tons. Resources of dolomite, forsterite, and the magnesium-bearing evaporite minerals are 

enormous; magnesium-bearing brines must constitute a resource of billions of tons ; and the resource contained in sea 

water is practically unlimited. The magnesium industry is 

highly competitive, and more costly sources, such as evaporite 

minerals, are little used. The bulk of magnesium-bearing 

compound-s and the metal are recovered in the United States 

from sea water, brines, and dolomite, and elsewhere in the 

world from magnesite. 

Magnesite deposits still are being sought, particularly 

those low in lime content. Opportunity for discovering such 

deposits in the United States is judged to be small, but is 

somewhat better in other parts of the world. 

INTRODUCTION 

Magnesium comnounds are used to prepare refractories and chemicals; high-temperature refractories are indispensable as linings in modern steel 

furnaces and in certain parts of base-metal smelters, 

and reactive magnesium chemicals have many wellestablished industrial and pharmaceutical uses. 

Magnesium is the lightest of the structural metals 

and is used either as the pure metal or as an alloy' 

wherever weight is a critical factor; magnesium 

competes with aluminum for these purposes to the 

extent that its higher price will allow. Magnesium 

metal also is used as a reductant in the extraction 

of titanium and certain other metals and as an 

oxygen scavenger; it is an important military incendiary material (Comstock, 1963 ; and Paone, 

1970). 

Magnesium-bearing raw materials are abundant, 

geographically widespread, and strongly competitive 

in world markets ; they consist of minerals and 

brines of various geological origins (Davis, 1957 ; 

Birch and Wicken, 1951; and Wicken, 1960). This 

chapter, however, deals principally with the resources of magnesite, brucite, and olivine. Resources 

of dolomite, evaporites, and brines are described in 

other chapters of this volume. 

Uses of the principal raw materials are shown 

in figure 44. 

Magnesite and brucite, when calcined at low temperature (1,600°F) yield reactive or caustic-calcined 

magnesia that is used to make chemicals and cements. Magnesite and dolomite when calcined at 

high temperatures (3,000°F --4,000°F) yield inert 

U.S. GEOL. SURVEY PROF. PAPER 820 

379 
380 UNITED STATES MINERAL RESOURCE.S 

Brucite Magnesite Seawater, brines 

Mg(OH) 2 MgC0 3 precipitated Mg(OH) 2 

Refractories 

lb 

Chemicals Metal 

I~ >< 

Forsterite 

(MgFe) 2 Si04 

Dolomite 

CaCO 3 · MgCO 3 

Evaporite minerals 

FIGURE 44.-Use of the principal raw materials of 

magnesium. 

oxides (dead-burned magnesite, periclase, and deadburned dolomite) used to make refractories. Sea 

water and magnesium-rich brines are treated with 

lime or caustic-calcined dolomite to precipitate magnesium hydroxide, which can be converted either to 

chemicals or refractories or to magnesium chloride, 

from which the metal can be extracted in electrolytic cells. When heated with ferrosilicon, causticcalcined dolomite yields magnesium metal. Byproduct magnesium bitterns resulting from treatment 

of evaporite minerals are used to prepare magnesium oxide and have been used in the past in 

electrolytic cells to recover the metal. Forsterite 

molded into brick is fired at 3,000°F to produce a 

refractory that is inert to certain flue dusts and 

gasses, and when ground, the mineral forms a superior foundry molding sand. 

The United States is virtually self-sufficient in 

magnesium-bearing raw materials, although its resources of low-cost low .. lime magnesite are small; 

the country is a net exporter of magnesium metal 

and a net importer of magnesium compounds. 

EXPLOITATION 

Mining of magnesite deposits began in California 

in 1886, in Washington in 1916, and in Nevada in 

1937; it ended in California in 1950 and in Washington in 1968. The large-scale use of calcined dolomite as a refractory began during World War I, 

and mining of brucite in Nevada began in 1934. 

Recovery of magnesium metal from deep-well Michigan brines began in 1916; sea-water recovery of 

magnesium oxide for metal production began in 

1940, and in subsequent years sea-water magnesia 

supplanted magnesite as the prime source of refractory raw material. Magnesium metal was extracted 

from dolomite and magnesite on a large scale during World War II, but its recqvery from these 

sources ceased in the following years. Deep-well 

magnesium brines in Texas were developed in 1970, 

and the brines of Great Salt Lake, Utah, were under 

development in 1972 by two companies for the recovery of magnesium compounds and the metal. 

Forsterite, the magnesium-rich variety of olivine, 

has been mined in North Carolina since 1933, and 

in Washington since 1956. 

Since World War II, dolomite has provided the 

largest single source of magnesium-bearing compounds in the United States. More than 2 million 

short tons of dead-burned dolomite was produced 

annually in the midsixties, but changes in steelmaking reduced its consumption to 1 million tons in 

1971 ; another several hundred thousand tons of 

caustic-calcined dolomite is used annually to precipitate magnesium hydroxide from sea water and 

brines. Reported production of magnesite reached a 

peak in 1956, when 690,000 short tons of crude 

magnesite was produced. Since then, production has 

not been reported, but in 1972 the Washington deposits were not mined, and therefore the production 

for that year was probably less than in 1969. About 

1 million tons of brucite was mined from the N evada deposits during 1934--66, but annual rates of 

production are not reported. Olivine production 

similarly is not reported but probably is on the 

order of several tens of thousands of tons per year. 

Under categories currently reported by the U.S. 

Bureau of Mines, refractory magnesia sold and used 

by producers totaled 627,000 short tons in 1971 and 

802,000 sho1t tons in 1970; shipments of causticcalcined and specified magnesias (exclusive of magnesia used in manufacture of the metal) totaled 

102,000 short tons in 1971 and 122,000 short tons 

in 1970. Magnesium metal production was 123,000 

short tons in 1971, continuing a rising trend of the 

previous several years. Figures on the amounts of 

magnesium compounds obtained from sea water, 

deeP-seated brines, magnesite, and brucite are not 

available (Chin, 1971a, b) . 

Outside the United States, about 12 million tons 

of magnesite is mined annually; most is from deposits of crystalline magnesite, but more than 1 

million tons is from deposits of bone magnesite. The 

consumption of bone magnesite has been increasing 

in recent years because this refractory possesses 

high strength and is resistant to high temperatures, 

properties desirable in the linings of basic-oxygen 

steel furnaces. 

About 120,000 tons of magnesium metal is produced annually outside the United States. Rated 

capacity of plants recovering magnesia from sea 

water outside the United States totals 1.1 million 
MAGNESIAN REFRACTORIES 381 

tons, and that of plants recovering magnesia from 

inland lakes, 200,000 tons (Industrial Minerals, 

1970). 

GEOLOGY 

Magnesium is the eighth most abundant of the 

elements in the earth's crust; it averages 2.09 percent by weight of all igneous rocks. Magnesium 

makes up about 0.13 percent of sea water; during 

evaporation, it precipitates at an early stage, largely 

with carbonate minerals, but it also precipitates at 

the end stages, in bittern minerals. Magnesium carbonate also precipitates during evaporation from 

certain inland lakes. 

MINERAL DEPOSITS 

This chapter deals largely with resources of magnesite, brucite, and olivine; resources of dolomite, 

evaporite minerals, and brines are described elsewhere in this volume. 

MAGNESITE 

Magnesite occurs mainly in four types of deposits: 

as crystalline masses replacing dolomite, as impure 

crystalline masses replacing ultramafic rocks, as 

cryptocrystalline masses in ultramafic rocks, and as 

sedimentary beds and lenses. 

Crystalline magnesite deposits in dolomite.-Accumulations of crystalline magnesite occur as massive lenses, stockworks, or disseminations in dolomite or in limestone locally altered to dolomite. 

Crystalline magnesite is light gray, gray, brown, 

pink, or red, and its grain size ranges from 0.5 to 

20.0 mm. Its chief impurities are calcium, contained 

within the lattice of magnesite grains or within included dolomite grains; iron, contained either in 

breunnerite (ferroan magnesite) or as disseminated 

specularite; silica, as quartz veins or as impregnations of quartz and chalcedony ; and silicate minerals such as talc, tremolite, anthophyllite, or enstatite, occurring in individual grains or in veins 

or lenses. Igneous dikes or stocks commonly cut 

magnesite lenses. 

Crystalline magnesite deposits range in size from 

pockets containing a few tens of thousands of tons 

to irregular to lenticular b_odies containing more 

than 100 million tons. Impurities may range from 

about 2 to 20 percent, excluding blocks rendered 

unminable by veins of silica or silicate minerals or 

by igneous dikes. Grade is as critical as size in de--

termining the worth of any given deposit, particularly for magnesite used in the manufacture of highpurity refractories. There is little market for magnesite containing more than 4 percent CaO. 

Only two districts in the United States contain 

large deposits of crystalline magnesite: one at 

Gabbs, Nev., and the other in Stevens County, Wash. 

Small occurrences are known in New Mexico and 

Texas (Vitaliano and Callaghan, 1956; Vitaliano 

and Cleveland, 1966; Schilling, 1968; and Bennett, 

1941, 1943). 

Crystalline magnesite deposits in ultramafic 

rocks.-Magnesite mixed with talc and with or 

without quartz occurs as lenses replacing dunite or 

serpentinized dunite. Deposits of this type are as 

variable in size as those in dolomite. They form 

massive lenses or occur as shells around ultramafic 

bodies. The only crystalline magnesite deposits in 

ultramafic rocks in the United States are found in 

north-central Vermont. These deposits consist of 

gray to faintly greenish gray rock, in which the 

magnesite occurs as grains or clusters of grains 

ranging from 0.01 to 30.0 mm in diameter in a 

matrix of fine-grained talc. Proportions of magnesite to talc in these deposits range from 38:62 to 

50: 50; the magnesite is low in lime but contains 

several percent iron ; the rock as a whole also contains magnetite as an accessory mineral. A deposit 

near Timmins, in Ontario, Canada, contains 48-72 

percent magnesite, 6-20 percent talc, and 11-21 

percent quartz (Chidester, 1962; and Griffis, 1972). 

Cryptocrystalline magnesite deposits.-Cryptocrystalline magnesite, also known as bone magnesite, 

occurs as nodules, veins, and stockworks in serpentinized zones of ultramafic rocks; it also is 

found as small deposits in tuffs. Bone magnesite 

resembles unglazed porcelain and generally is dead 

white but locally is tinted gray, green, or pink. 

Impurities include serpentine, enclosed in or bordering nodules and associated vein minerals, as well 

as opal, chalcedony, several hydrated magnesium 

silicate minerals, and rarely calcite or dolomite. 

Bone magnesite itself may contain traces to small 

percentages of lime and iron. 

Bone-magnesite deposits tend to be much smaller 

than crystalline deposits ; the largest group of veins 

in the United States, at Red Mountain, Calif., originally contained about 1 million tons of magnesite. 

Individual veins range from a few feet to hundreds 

of feet in length and depth, and from fractions of 

an inch to tens of feet in width. The wider veins 

tend to consist of separate magnesite nodules in 

serpentine. 

Most bone-magnesite deposits occur in ultramafic 

rocks in California, but several are known in Oregon and Pennsylvania. Deposits of bone magnesite 

replace bedded rhyolitic tuff in eastern Nevada 

(Davis, 1957; Bodenlos, 1950a; and Vitaliano, 

1951). 
382 UNITED STATES MINERAL RESOURCES 

Sedimentary magnesite.-Sedimentary magnesite 

is a brown to gray carbonate rock which probably 

formed by evaporation. Individual beds may cover 

several tens of acres and range in thickness from 

inches to several feet. Such magnesite is interbedded with dolomite, clastic rocks, or strata of volcanic origin. Although the grade of some sedimentary magnesite is high, the thin beds cannot be 

mined economically. Deposits are limited to several 

States in the Southwest (Rubey and Callaghan, 

1936; and Vitaliano, 1950). 

PROSPECTING 

Deposits of crystalline magnesite may be overlooked because magnesite differs from crystalline 

dolomite only slightly in luster and specific gravity. 

In some deposits, magnesite is more resistant to 

weathering than dolomite and hence forms bolder 

outcrops. Weathered surfaces may differ slightly in 

color from the weathered surfaces of dolomite. Talcbearing crystalline carbonate rocks should be 

checked for magnesite, although talc also occurs in 

dolomite. Chemical or mineralogical tests thus may 

be needed to identify new prospects. 

Crystalline carbonate masses in ultramafic rocks, 

particularly if mixed with talc, probably consist of 

magnesite; such material weathers shades of rusty 

brown owing to its contained iron. 

Bone magnesite forms highly distinctive deadwhite outcrops and float, perhaps associated with 

chalcedony and opal, which contrast like whitewash 

against the somber shades of the host ultramafic 

terrane. 

Sedimentary magnesite perhaps is the most difficult type of magnesite deposit to recognize, because 

it has no clearly distinguishing physical features or 

characteristic geological associations. 

GENESIS 

Most carbon dioxide needed to form magnesite 

deposits probably was derived from deep-seated igneous sources, although some may have been furnished through thermal dissociation of underlying 

carbonate rocks ; a very small amount may have 

been carried by ground water. Ultramafic rocks 

furnished the magnesia now found in their contained magnesite deposits, but the source of magnesia in crystalline deposits in dolomite is less 

certain. One hypothesis proposes that the magnesia 

was produced during thermal dissociation of underlying dolomite. Another hypothesis suggests that 

crystalline magnesite deposits are metamorphosed, 

recrystallized lenses of sedimentary magnesite, but 

this hypothesis does not explain the obvious replacement nature of many if not most crystalline deposits (Faust and Callaghan, 1948; Schilling, 1968; 

Vitaliano and Cleveland, 1966; Bodenlos, 1950a, 

1954; and Lovering, 1969). 

Sedimentary magnesite in the southwestern States 

formed in closed basins and therefore is of evaporite origin. 

BRUCITE 

Brucite [Mg(OH2)] in minable concentrations 

rarely is found. Two such deposits are associated 

with magnesite at Gabbs, Nev.; there the mineral 

occurs as lenses of massive white to light-brown 

material resembling old-fashioned laundry soap, 

which is soft enough to scratch with the fingernail. 

Impurities include veinlets and grains of dolomite, 

magnesite, talc, forsterite, and periclase; the deposits also are cut by igneous dikes. The deposits 

lie close to a stock of granodiorite postdating magnesite deposition, suggesting that the intrusive 

locally drove off carbon dioxide in magnesite and 

formed magnesium hydroxide. 

Besides the Gabbs occurrence, brucite has been 

found within the United States, in small amounts 

only in New Mexico (Schilling, 1968; Davis, 1957) 

and Arizona (Ericksen, 1969). 

OLIVINE 

Olivine [ (MgFe) 2 SiO.] is a common mineral in 

quartz-free igneous rocks;· its magnesium-rich variety, forsterite, forms the rock called dunite. Forsterite alters readily to serpentine minerals; thus, 

masses of fresh dunite are not common. Within the 

United States, fresh dunite makes up most of the 

Twin Sisters Mountains, east of Bellingham, Wash., 

and it occurs as smaller masses in North Carolina 

and Georgia (Stuckey, 1965; Moen, 1969). 

OTHER SOURCES 

Deep-well brines in Michigan and in other States 

have provided recoverable magnesium compounds, 

and the brines of Great Salt Lake are under development for the same purpose. (See "Evaporites and 

Brines.") Magnesium compounds are extracted from 

sea water in recovery plants on the Atlantic, Pacific, 

and Gulf coasts, the annual rated capacity of which 

in 1970 was 570,000 tons MgO. Dolomite is quarried 

in various States. Dolomite used to recover magnesium metal formerly was quarried in Connecticut, 

New York, Ohio, Michigan, Mississippi, and Washington. Deposits of evaporite minerals in New 

Mexico remain largely untapped as a source of 

magnesium-bearing compounds. 
MAGNESIAN REFRACTORIES 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Magnesium resources in sea water are practically 

unlimited, and those in magnesium-bearing evaporites, dolomite, and dunite are enormous. Magnesium 

resources contained in interior saline lakes and seas 

must total billions of tons, and it is judged that 

deep-well brines contain large tonnages of magnesium salts. Identified resources in the magnesite 

deposits of the world total 12 billion tons; those in 

the brucite deposits of the world, several million 

tons. 

The apparent reserve of magnesite of the United 

States in 1970 was placed at 65 million tons (Paone, 

1970), about equal to the national reserve in 1960 

(Comstock, 1963). Data are not available to determine what fractions lie in recoverable and subeconomic resources, but probably less than half of the 

identified resource is commercially recoverable under 

present prices and required grades. Hypothetical 

resources are limited to unexplored magnesite at 

depth below known deposits. Perhaps 20 million 

tons of subeconomic resources seems a reasonable 

estimate. 

Recoverable resources of magnesium chloride in 

Great Salt Lake are said to exceed 600 million tons. 

Resources of fresh dunite in Washington State total 

billions of tons, and those in North Carolina total 

more than 200 million tons. Recoverable resources 

of brucite remaining in the Nevada deposits are 

said to be small, probably not more than 1-2 million 

tons. At least an additional several tens of millions 

tons of magnesite constitutes a subeconomic resource within the magnesite-talc deposits in Vermont. 

A recent compilation set the apparent world reserve of magnesite at 9.4 billion tons, exclusive of 

small reserves in several countries (Paone, 1970). 

To this should be added 300 million tons of crystalline magnesite in Brazil (Bodenlos, 1950b, 1954); 

240 million tons of magnesite in the Sudan (Whiteman, 1971); 100 million tons of magnesite in 

Canada, which consist of magnesite-talc-quartz rock 

replacing dunite; and 2,000 million tons of talc-rich 

magnesite at Savinsk, in eastern Siberia, the host 

rock of which is unreported (Industrial Minerals, 

1970). Total identified resources consist largely of 

crystalline magnesite associated with dolomite; but 

at least 1 billion tons consists of crystalline magnesite replacing dunite, and perhaps more if the 

Siberian occurrence lies in such rock. Identified resources of bone magnesite are not well known, but 

older compilations indicate that they are on the 

order of several tens of millions of tons. N otwithstanding, bone magnesite is at present being mined 

at a rate of more than 1 million tons per year, so it 

is likely that past resource estimates of bone magnesite were conservative. 

Although magnesium-bearing evaporite minerals 

are not covered in this chapter, the tachyhydrite 

deposits of Sergipe, Brazil, must be cited as a large 

new resource; R. J. Hite reported that the upper 

zone alone contains about 4 billion metric tons of 

the mineral, equivalent to 380 million tons of magnesium metal (U.S. Geol. Survey, 1970, p. A216; 

Wardlaw, 1972). Similar deposits also have been 

found in Gabon and Zaire, Africa. Tachyhydrite 

(CaMg2Cl6 • H20) is so soluble, even in drilling 

brines, that its occurrence may have been overlooked 

in other evaporite sequences. 

SPECULATIVE RESOURCES 

Crystalline magnesite deposits are not common. 

Areas favorable for their occurrence are carbonate 

rocks near igneous intrusions, which in the United 

States were thoroughly searched without success 

during World War II. Probably nearly all deposits 

of crystalline magnesite in Europe have been found, 

but undiscovered deposits undoubtedly exist on 

other continents. Because such deposits tend to be 

large, any one discovery could add from tens to 

hundreds of millions of tons to the world's resources. 

Crystalline and bone magnesite deposits in ultramafic rocks are globally widespread. Bone magnesite 

outcrops are conspicuous; therefore, most nearsurface deposits probably have been found, even in 

remote areas. Ore bodies undoubtedly exist that do 

not crop out; targets for exploration should include 

serpentinized shear zones in relatively unaltered 

masses of peridotite, particularly where the serpentine is veined by chalcedony or opal. Deposits of 

crystalline magnesite in ultramafic rocks evidently 

are very rare, but most seem to be very large although low in grade. Undoubtedly more will be discovered. in those parts of the world not yet fully 

geologically mapped. 

PROBLEMS FOR RESEARCH 

Industrial technology successfully developed 

methods to recover magnesium-bearing compounds 

and the metal from a wide variety of natural resources. Efforts are continuing to produce stronger 

refractories, to increase the efficiency of recovery 

processes, and to develop new magnesium-bearing 

alloys. 

The geology of magnesium-bearing mineral deposits is reasonably well known. Not enough is 

known, however, about the genesis of deep-seated 

magnesium-rich brines. The world's resources of 
UNITED STATES MINERAL RESOURCES 

bone magnesite should be reappraised in view of 

current demand for that raw material as a deadburned refractory. 

SELECTED REFERENCES 

Bennett, W. A. G., 1941, Preliminary report on magnesite deposits of Stevens County, Wash.: Washington Dept. 

Conserv. and Devel., Div. Geology Rept. Inv. 5, 25 p. 

--- 1943, Character and tonnage of the Turk magnesite 

deposit: Washington Dept. Conserv. and Devel., Div. 

Geology Rept. lnv. 7, 22 p. 

Birch, R. E., and Wicken, 0. M., 1951, Magnesite and related minerals, in Industrial minerals and rocks [2d 

ed.] : Am. Inst. Mining, Metall., and Petroleum Engineers, p. 521-541. 

Bodenlos, A. J., 1950a, Geology of the Red Mountain magnesite district, Santa Clara and Stanislaus Counties, 

Calif.: California Jour. Mines and Geology, v. 46, no. 2 

p. 223-278. 

--- 1950b, Magnesite deposits of central Ceara, Brazil: 

U.S. Geol. Survey Bull. 962-C p. 121-153. 

--- 1954, Magnesite deposits in the Serra das Eguas, 

Brumado, Bahia, Brazil: U.S. Geol. Survey Bull. 975-C, 

p. 87-170. 

Chidester, A. H., 1962, Petrology and geochemistry of selected talebearing ultramafic rocks and adjacent country 

rocks in north-central Vermont: U.S. Geol. Survey Prof. 

Paper 345, 207 p. 

Chin, E., 1971a, Magnesium compounds: U.S. Bur. Mines 

Minerals Yearbook, 1971, preprint, 8 p. 

--- 1971b, Magnesium: U.S. Bur. Mines Minerals Yearbook, 1971, preprint, 6 p. 

Comstock, H. B., 1963, Magnesium and magnesium compounds: U.S. Bur. Mines Inf. Circ. 8201, 128 p. 

Davis, R. E., 1957, Magnesium resources of the United States 

-a geolDgic summary and annotated bibliography to 

1953: U.S. Geol. Survey Bull. 1019-E, p. 373-515. 

Ericksen, G. E., 1969, Brucite and magnesite, in Mineral and 

water resources of Arizona: U.S. 90th Cong., 2d sess., 

p. 320-324. 

Faust, G. T., and Callaghan, Eugene, 1948, Mineralogy and 

petrology of the Currant Creek magnesite deposits and 

associated rocks of Nevada: Geol. Soc. America Bull. 

v. 59, p. 11-74. 

Griffis, Robert, 1.972, Genesis of a magnesite deposit, Deloro 

Twp., Ontario: Econ. Geology Bull. v. 67, no. 1, p. 63-71. 

Industrial Minerals, 1970, Magnesite-rapid growth from 

new producers: Indus. Minerals, no. 39, p. 9-31. 

Lovering, T. S., 1969, The origin of hydrothermal and low 

temperature dolomite: Eoon. Geology Bull., v. 64, no. 7, 

p. 743-754. 

Moen, W. S., 1969, Mines and mineral deposits of Whatcom 

County, Washington: Washington Div. Mines and 

Geology Bull. 57, 134 p. 

Paone, James, 1970, Magnesium, in Minerals facts and problems: U.S. Bur. Mines Bull. 650, p. 621-638. 

Rubey, W. W., and Callaghan, Eugene, 1936, Magnesite and 

brucite, in Hewett, D. F., and others, Mineral resources 

of ,the region around Boulder Dam: U.S. Geol. Survey 

Bull. 871, p. 113-144. 

Schilling J. H., 1968, The Gabbs magnesite-brucite deposit, 

Nye County, Nevada, in Ore deposits of the United 

States, 1933-1967 (Graton-Sales volume): Am. Inst. 

Mining, Metall., and Petroleum Engineers, p. 1608-

1622. 

Stuckey, J. L., 1965, North Carolina-.-its geology and mineral resources: North Carolina Dept. Conserv ., Devel., 

550 p. 

U.S. Geological Survey, 1970, Geologic and hydrologic investigations in other countries-Brazil, in Geological 

Survey research 1970: U.S. Geol. Survey Prof. Paper 

700-A, p. A215-216. 

Vitaliano, C. J ., 1950, Needles magnesite deposit, San Bernardino County, Calif.: California Jour. Mines and 

Geology, v. 46, p. 357-382. 

--- 1951, Magnesium-mineral resources of the Currant 

Creek district, Nevada: U.S. Geol. Survey Bull. 978-A, 

p. 1-25. 

Vi.taliano, C. J., and Callaghan, Eugene, 1956, Geologic map 

of the Gabbs magnesite and brucite deposits, Nye 

County, Nevada: U.S. Geol. Survey Mineral Inv. Field 

Studies Map MF -35. 

Vitaliano, C. J ., and Cleveland, J. H., 1966, Magnesium 

mineralization, Gabbs, Nevada in Forum on geology of 

industrial minerals, 2d, Proc., A symposium on geology 

of cement raw materials: Bloomington, Indiana Univ., 

p. 173-197. 

Wardlaw, N. C., 1972, Unusual marine evaporites with salts 

of calcium and magnesium chloride in Cretaceous basins 

of Sergipe, Brazil: Econ. Geology Bull. v. 67, no. 2, p. 

156-168. 

Whiteman, A. J., 1971, The geology of the Sudan Republic: 

Oxford, Clarendon Press, 290 p. 

Wicken, 0. M., 1960, Magnesite and related minerals, in Industrial min~rals and· rocks [3d ed.]: Am. Inst. Mining 

Metal!., and Petroleum Engineers, p. 533--544. 
UNITED STATES MINERAL RESOURCES 

MANGANESE 

By JoHN VAN N. DoRR, II, MAx D. CRITTENDEN, JR., and RoNALD G. WoRL 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction ------------------------------------- Exploitation ____________________________________ _ 

Geologic environment ____________________________ _ 

Geochemistry and crustal abundance ----------

Types of manganese deposits -----------------

Manganese minerals ----------------------

Sedimentary deposits ---------------------

Manganese nodules ----------------------

Volcanogene deposits ---------------------

Hypogene deposits -----------------------

Resources --------------------------------------- Identified and hypothetical resources ----------

Reserves -------------------------------- Conditional resources --------------------

Hypothetical resources -------------------

Speculative resources ------------------------

Prospecting techniques ---------------------------

Problems for research ----------------------------

General problems ---------------------------- Needs for new prospecting techniques ---------

Technological problems -----------------------

Selected references -------------------------------

45. 

FIGURE 

Domestic manganese ore production (metallurgical grade), 1943-63, distributed according to 

sources of output -------------------------

TABLES 

Page 

385 

385 

386 

387 

387 

389 

389 

389 

390 

391 

392 

393 

393 

393 

393 

394 

394 

396 

396 

396 

397 

398 

398 

Page 

ABSTRACT OF CONCLUSIONS 

Known minable reserves and known resources of manganese are very large in relation to world consumption but 

are very irregularly distributed throughout the world. The 

United States has virtually no domestic reserves and its 

known resources are both very low grade and refractory to 

economic concentration. The principal hopes of finding domestic reserves or resources of conventional types may lie 

in ( 1) finding the source of the manganese of the Pierre 

Shale, conceivably buried under Pleistocene sedimentary 

rocks in central or western Minnesota or adjacent areas; (2) 

finding another Molango-type deposit by careful analysis of 

the distribution of manganese in certain miogeosynclinal 

carbonate rocks; or (3) finding the source of the high manganese concentrations in the Salton Sea brines. Much more 

promising modes of relieving dependence on foreign sources 

are by vigorously attempting to perfect techniques of effectively exploiting sea-fl.oor nodules and by dissolving legal 

impediments to large-scale investment in subsea mining. 

Maintenance of an adequate national stockpile is essential. 

With respect to world resources, efforts should be made to 

explore the sedimentary high-grade manganese carbonate 

bodies, which through weathering have given rise to overlying rich supergene oxide deposits, in order to establish 

the tonnage and grade of material that will be available for 

use when oxide deposits are depleted; the tonnage is probably great. There is some possibility that deposits without 

the oxidized cap might be found in eugeosynclinal belts in 

the North American Shield areas. 

INTRODUCTION 

Manganese, a metal rarely seen in elemental form, 

is essential in two ways to the manufacture of steel: 

386 (1) used as a scavenger in molten steel, it combines 

with sulfur and oxygen, which make steel brittle, and 

removes them as part of the slag; (2) used as an 

alloy, it makes stool more resistant to shock or abraPage sion. It is used also in the chemical industry and, in 

74. Production, imports, and consumption of man- dioxide form, as a depolarizer in dry batteries. More 

75. 

76. 

77. 

ganese ore and concentrates and ferroman- than 90 percent of the consumption in the United 

ganese, 1966, 1970, and 1971 --------------- 386 Common manganese minerals _______________ _._ 389 Stattebs is by the steel industry, and no substitute has 

World manganese resources ------------------ 393 ye een found despite much effort. About 13-20 

Major identified manganese resources of the pounds of manganese is consumed per ton of steel 

United States ----------------------------- 394 manufactured; therefore the element is essential to 

U.S. GEOL. SURVEY PROF. PAPER 820 

885 
386 UNITED STATES MINERAL RESOURCES 

the whole industrial capacity of the world. When we 

can do without steel, we can do without manganese. 

Manganese is introduced in the steel-making process primarily as the alloy ferromanganese (about 78 

percent Mn, 15-18 percent Fe), as spiegeleisen 

(about 15-20 percent Mn, the rest largely Fe), as 

silicomanganese (about 66 percent Mn, 12-20 percent Si), or as manganese metal added to the converter of whatever type may be used or to the ladle. 

Ferromanganese, which accounts for more than 75 

percent of consumption, is made by smelting an ore 

with a Mn/Fe ratio of 7: 1 or greater. For a succinct 

discussion of the consumption, uses, and processes 

involved in the manganese industry, the reader is 

referred to the manganese chapter in the U.S. Bureau of Mines publication "Mineral Facts and Problems" (Sheridan, 1970). 

The United States is now completely dependent 

upon foreign sources of manganese, for the last 

domestic manganese mine closed in 1970. 

Salient data from U.S. Bureau of Mines Minerals 

Yearbooks on domestic and world production of manganese ores and domestic consumption of ferromanganese and imports of these materials are given in 

table 74. 

TABLE 74.-Production, imports, and consumption of manganese ore and concentrates and ferromanganese, 1966, 

1970, and 1971, in millions of short tons 

Ore and concentrates: Domestic production, >35 percent Mn ___ _ 

World production, >30 percent Mn ----- Imports, >35 percent Mn ------------~-

Ferromanganese: 

Domestic consumption ------------------ Imports for consumption ----------------

1966 1970 1971 

0.014 0.005 0 

19.1 19.2 20.4 

2.6 1.7 1.9 

1.0 

.25 

1.0 

.29 

.9 

.24 

Principal suppliers of manganese ore to the United 

States in 1971 were (in order of importance): Brazil, 

Gabon, Republic of South Africa, Za!re (ex-Kinshasa 

Congo), and Ghana. Principal suppliers of ferromanganese were the Republic of South Africa, France, 

and India, in that order. In 1970, manganese ore was 

produced by 40 countries, of which 11 produced 96 

percent, six produced 84 percent, and three produced 

63 percent. With the exception of a few hundred tons 

of ferromanganese imported from Yugoslavia, none 

of the U.S. manganese supply in 1971 came from the 

socialist countries. 

EXPLOITATION 

The necessity for manganese in the steel-making 

process to avoid brittleness in the steel was recognized in 1856 by Mushet, whose discovery made the 

Bessemer converter practical. Since then, increasing 

world production of manganese has closely paralleled 

that of steel. In the middle of the 19th century, the 

United States was largely self-sufficient in manganese. Major deposits were found in the U.S.S.R., 

Brazil, and India in the late 19th century, and large 

deposits were found in Africa, Brazil, Cuba, and 

Mexico in subsequent decades. The most recent significant discoveries were those in Amapa, Brazil 

( > 30 million tons), and the Kalahari basin, South 

Africa ( >3,000 million tons), in the 1940's, in Gabon 

(200 million tons) in the 1950's, and at Groote Eylandt in Australia (about 75 million tons) in the 

1960's; the carbonate deposits of Molango, Mexico 

( > 15 million tons), were also discovered in the 

1960's. Despite unparalleled consumption since World 

War II, known reserves of commercial-grade ore are 

now far greater than at any time in the past ; the 

grade of the ore used is nearly as high as it ever was, 

and· the price is lower in constant dollars than for 

many years. 

Production from various sources in the United 

States in the 20 years _from 1943 to 1963, the period 

of maximum production, is shown in figure 45. It 

should. be remembered that the curve entitled "Lowgrade purchases for stockpile" represents noncommercial manganiferous material, most of which contained 15-17 percent manganese, that was then and 

is still unusable as a source of manganese without 

concentration. This production, the carlot purchases, 

1~r------+------+-----V (I) 

z .... oz 

.... w 140 

........ CE:z o8 120 

z 

cnw 

IL. ID 100 Oz 

cnc( 

~~ 80 

c(c( 

~~ ~ QIL. 

zO 

.... 40 

20 

0 

Mangan"• ore production 

(as defined by U.S. Bureau 

of Min") 

/ 

Production at commercial pric ... 

(All. below the dashed line produced 

by The Anaconda Company) 

1943 1945 1947 1949 1951 1953 1955 1957 1959 1961 1963 

FIGURE 45.-Domestic manganese ore production (metallurgical grade), 1943-63, distributed according to sources of 

output. Modified from Brooks ( 1966, p. 75). 
MANGANESE 387 

and the Nevada production for stockpile, the latter 

two of commercial grade, were heavily subsidized. 

The declining production before the subsidy ended 

clearly indicated that most known deposits were uneconomic even at the subsidized prices. No important 

domestic discoveries have been made since, and 

domestic production since 1963 has been very small, 

largely from Montana and New Mexico. 

Much metallurgical research has been done in the 

United States and Canada to make feasible the extraction of manganese from the low-grade ores of 

those countries and from slag piles from open-hearth 

furnaces; techniques are available to do this at a 

price two to five times the present world price for 

manganese. 

Most manganese ore now produced in the world 

comes from large open-pit mines; underground mines 

still produce in countries with low wage s·cales or 

where the ore zone is thick, permitting efficient 

underground operation, as at Molango, Mexico, and 

in the Chiatura field in the U.S.S.R. Mining methods 

are standard. Concentration in most areas consists of 

relatively simple washing, screening, or jigging to 

remove clay, sand, or other contaminants. Hand sorting, however, still exists in some mines in South 

Africa and India. The first pelletization plant for 

fine ore is scheduled to begin producing in Brazil in 

1972; heretofore such fine material has been stockpiled, sintered, nodulized, or discarded, as lumpy ore 

is needed in ferromanganese production. 

Except for the manganese carbonate mines in Montana and a few small mines in the Western United 

States in which base or precious metals were coproducts or in which the manganese was a byproduct, 

most manganese mines are exploited only for that 

metal. In the future, when the mining of manganese 

nodules from the sea floor becomes technologically 

and economically feasible, copper, nickel, and cobalt 

will certainly be produced as well as manganese. Extraction of the valuable metals would probably be by 

hydrometallurgical and electrolytic techniques. 

As in all mining operations where there is no legal 

obligation or economic stimulus for preservation of 

the environment, manganese mining results in mine 

dumps, tailings piles, rapid erosion of mined-out 

areas, and large pits. Except for increased sediment 

load and siltation, manganese mining does not cause 

water pollution. 

The only environment-restoration effort seen by 

the senior author in visits to hundreds of manganese 

mines on four continents was being carried on at the 

enormous Nikopol open-pit mines in the U.S.S.R. 

There the rich black topsoil of the Ukraine was careI 

fully removed, the sterile rock overburden replaced 

after the underlying manganese bed had been extracted, and the topsoil replaced. After 3 to 4 years, 

orchards or grain were planted and seemingly throve. 

Lakes, which had been landscaped, had formed in 

some of the older unrestored large pits. Clubhouses 

had been built, and the lakes were used for outboard 

motorboats, water sports, and fishing by the miners 

and their families. Thus, the land was withdrawn 

from productive agriculture only for about 5 or 6 

years and theretofore-absent recreational facilities 

were developed. Well over 100 million tons of material is moved each year in these mines. The geology 

of the Nikopol area makes such restoration relatively easy, and the fertility of the soil makes 

restoration economic for an integrated economy. 

The reduction of manganese ore to ferromanganese is commonly accompanied by much air pollution 

unless special equ~pment is installed to prevent this. 

Fumes high in Mn02 are said to be very toxic and to 

cause a high incidence of respiratory disease. 

Extraction of deep-sea nodules should cause little 

if any significant damage to the envidonment; in 

fact, the bottom water that is brought to the surface in hydraulic mining is higher in nutrients and 

will support a more numerous and broader flora and 

fauna than the surface water. Properly planned hydrometallurgical extraction should cause no serious 

pollution problems. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY AND CRUSTAL ABUNDANCE 

Manganese (Mn) constitutes about 0.1 percent of 

the earth's crust and is the 12th most abundant element. It is more abundant in mafic rocks, averaging 

about 0.16 percent, and less abundant in granitic 

rocks, averaging perhaps 0.06 percent. Deposits that 

were economic at 1971 prices contained between 25 

and 50 percent manganese; thus the element must 

have been concentrated by natural processes 250-

500 times the normal background to form an economic ore deposit. 

The geochemical characteristics of manganese are 

very similar in many ways to those of iron ; therefore some manganese deposits are closely related to 

iron deposits, and some contain considerable quantities of iron. 

Manganese commonly occurs in nature in three 

valence states: +2, +3, +4. The ionic radius of 

bivalent manganese is close to that of bivalent iron 

and calcium; manganese ions may substitute for 

iron ions in ferrous minerals. Indeed, almost all the 
388 UNITED STATES MINERAL RESOURCES 

manganese in igneous rocks occurs in such diadochic 

substitutions, largely in mafic minerals. True manganese minerals are most rare in such rocks. Mafic 

minerals break down readily under weathering, and 

the contained ionic manganese is liberated. Under 

reducing or near-neutral conditions, bivalent manganese is relatively soluble and is commonly transported by subsurface or surface waters to sites 

where for some reason the waters have higher oxygen content. There the mnaganese may be deposited 

at higher valences in the relatively insoluble oxide 

form. Given proper conditions, the manganese may 

also be deposited in bivalent carbonate form. Bivalent manganese may also substitute for the calcium ion in limestone or dolomite, forming manganoan limestone or dolomite or deposits of even 

more complex manganiferous carbonate minerals. 

Volcanic rocks subjected to large-scale alteration, 

such as molten lava extruded into relatively shallow 

sea water or solid volcanics altered by hydrothermal 

solutions, may also lose considerable quantities of 

manganese by destruction of mafic minerals. The 

manganiferous solutions may then transport the 

manganese to sites where the ambient conditions 

abruptly change because of variations in wallrock, 

redox potential, intermixing ground water, rapid 

cooling, or other factors. There the manganese may 

be precipitated in veins, replacement deposits, or 

hot-spring deposits, or, in marine or lacustrine 

basins, as sedimentary deposits. 

Manganese derived from cooling magma tends to 

concentrate in pneumatolytic and hydrothermal 

solutions. Pegmatites locally contain a widely varying suite of complex manganiferous minerals of no 

economic interest as a source of manganese. In 

veins and replacement deposits of magmatic origin 

deposited at relatively low temperatures, manganese 

as the carbonate or silicate may replace wallrocks 

or form the gangue of precious- and base-metal 

deposits, as at Leadville, Colo., Pioche, Nev., and 

Philipsburg, Mont. In many localities the manganese 

occurs in zones outside the main center of base- or 

precious-metal deposition. The manganese so deposited may be produced as a byproduct or coproduct of the base-metal mining, as at Butte, Mont. 

Low-temperature veins of manganese oxide are also 

formed from such solutions, but these are of minor 

economic significance. 

Manganese may be carried to lakes or the sea in 

ionic solution or in colloidal or very finely particulate form. Certain bacteria precipitate manganese 

as part of their life cycle, and bog and some lake 

deposits apparently are due to such organic action. 

Other lake or basin deposits are apparently due to 

sudden increases in the oxygen content of the water, 

typically in near-shore environments, resulting in 

long narrow deposits of manganese oxides closely 

related to facies changes of the host sedimentary 

rocks. Manganese that reaches the sea may be doposited in a platform or near-shore environment, 

either as rather pure manganese oxide mixed to a 

greater or lesser extent with detrital terrigenous 

sediments, or as manganese carbonate or complex 

manganese-calcium-magnesium carbonate minerals 

if the' environment is more reducing. 

The exact environmental conditions causing the 

deposition of such sedimentary manganese in any 

particular spot have never been satisfactorily explained. We know the general mechanism and environment of deposition but not the localizing factors ; that is, we often know how a deposit was 

formed but not why it was formed in a particular 

spot and not in some other spot. This is a critical 

question for the economic geologist. 

Many deposits of sedimentary and other origins 

are in rocks later subjected to metamorphism. If 

the original deposits are relatively pure oxides or 

carbonates, they remain generally unchanged; if 

intermixed alumina and silica are available, the 

original manganese reacts with them to form bodies 

of recrystallized manganese oxide or carbonate with 

some intermixed manganiferous silicates. Examples 

are the oxide deposits of the Central Provinces of 

India and the manganese carbonate bodies of Ghana 

and Brazil. If the original deposit is high in intermixed alumina and silica, all the original manganese 

carbonate or oxide reacts with the impurities to 

produce extensive zones of manganese silicates, 

called gondite, useless for industrial purposes and 

from which only small and low-grade secondary 

deposits form. 

In the deep sea, and locally at the intermediate 

depths, where sedimentation of detrital and organic 

material is very slow, nodules containing from about 

10 to 35 percent manganese and from 5 to 35 percent iron cover extensive areas. Some believe that 

most of the manganese in these nodules is derived 

ultimately from terrigenous sources; others believe 

that contributions from submarine volcanic activity 

are large. The manganese in these nodules commonly 

occurs as complex oxide minerals. These nodules 

may be the ultimate sink for the manganese and 

iron and some other metals introduced into the sea 

water from rivers and submarine volcanics. Their 

equivalent has not been recognized in land deposits, 

but their included metals may be recycled as sea-bed 

deposits which are carried to great depths in the. 

mantle in subduction zones and there are melted to 
MANGANESE 389 

form new igneous rocks with associated ore bodies, 

completing and renewing the geochemical cycle. 

Thus may be explained the association of volcanogene manganese with volcanic rocks ringing the 

Pacific. 

To summarize, the manganese in the earth's ore 

deposits originated from manganiferous mafic minerals in igneous rocks or from magmas, being released by weathering and hydrothermal alteration 

of those minerals or by fluids driven off from the 

crystallizing magma. The manganese was carried to 

the site of deposition in very dilute solution and 

was there deposited in significant concentration because abrupt change of the environment rendered 

the dissolved manganese insoluble. Changes in the 

oxidation-reduction potential were probably the most 

important control in the precipitation of manganese. 

There is reason to believe that biologic agents were 

involved in deposition of major carbonate-facies 

manganiferous sedimentary deposits, but there is 

no evidence of this for major oxide-facies deposits. 

Much disagreement exists as to the relative importance of the various sources of manganese discussed above; the enormous size of the major sedimentary deposits strains the capacity of direct contribution from volcanic or magmatic sources. The 

lack of volcanic rock closely associated with such 

major deposits makes the weathering of igneous 

rock a more likely source of manganese for the 

larger deposits. The manganese in the higher grade 

deposits has in many instances been through at 

least two stages of natural concentration: (1) its 

original deposition and (2) subsequent weathering 

of low grade deposits, particularly the carbonates, 

that removed dilutents. 

TYPES OF MANGANESE DEPOSITS 

Primary manganese deposits may be classified 

into three types-sedimentary (including sea-floor 

nodules), volcanogene, and hypogene-that to some 

extent are intergradational. All are modified to 

greater or lesser extent by supergene processes; in 

oxide form, manganese is less soluble than many 

other elements and is concentrated in the zone of 

weathering. 

MANGANESE MINERALS 

Table 75 shows the more common manganese minerals formed in these various environments. 

SEDIMENTARY DEPOSITS 

A distinction must be made between sedimentary 

deposits of manganese laid down as carbonates and 

TABLE 75.-Common manganese minerals 

[Supergene mineralogy essentially the same regardless of type or origin 

of protore except possibly nsutite] 

Supergene minerals 

Pyrolusite 1 

Cryptomelane 1 

Psilomelane 1 

Coronadite 1 

Nsutite 1 (carbonate source) 

Birnessite 1 

Todorokite 1 

Chalcophanite 2 

Manganite2 

Lithophorite 2 

Metamorphic minerals 

[Metamorphic mineralogy is largely dependent on metamorphic grade 

and rock composition. Many oxides and rhodochrosite remain intact 

during metamorphism in environments low in AI and Si. Many primary 

oxides stable in low-grade metamorphism]) 

Manganite 2? I Bixbyite 3 (all grades) 

Braunite a (all grades) 

Hollandite 3 (all grades) 

Hausmannite 3 (higher grades) 

Jacobsite 3 (higher grades) I 

Rhodochrosite 4 

Rhodonite 5 

Spessarite • Tephroite 5 (higher grades) 

Other Mn silicates s 

Hypogene Minerals 

Pyrolusite 1 

Cryptomelane 1 

Psilomelane 1 

Birnessite 17 

Coronadite t 

Hollandite3 

Braunite a 

Jacobsite 3 

Hausmannite a Rhodochrosite 4 

Mn-Fe-Mg-Ca carbonates 

Black calcite 4 

Rhodonite 5 

Volcanogene minerals 

Pyrolusite 1? 

Psilomelane 1? Braunite a 

Hausmannite a Rhodochrosite 4 

Mn-Fe-Ca carbonates 

Neotocite 5 

Bementite 5 

Mn silicates 

Sedimentary minerals 

Pyrolusite 1 

Cryptomelane 1 

Psilomelane u 

Birnessite 1* 

Todorokite 1* 

Manganite2 

1 Higher oxide. 

2 Hydroxide. 

s Medium and lower oxide. 4 Carbonate. 

Braunite a Rhodochrosite 4 

Mn-Fe-Mg-Ca carbonates 

Black calcite 4 

Mn in lattice of magnetite and Fe silicates and carbonates 

5 Silicate. 6 Other. 

*Nodule minerals. 

those deposited as oxides. In all instances for which 

data are available, major deposits of high- and 

medium-grade primary manganese carbonate are 

known to be closely associated with carbonaceous 

or graphitic rocks, often rather clayey, indicating 

a strongly or moderately reducing sedimentary environment, in many examples in closed basins. Primary oxide deposits, on the other hand, are more 

commonly associated with coarser clastic sediments 

with little or no free or organic carbon, indicating 

nearshore and strongly oxidizing conditions with 

relatively free circulation of water. The Ukrainian 

deposits in the U.S.S.R. are unique in that the intertonguing transition from oxide facies to carbonate 

facies can be observed to occur basinward over 

distances ranging from some hundreds of meters 

to a few kilometers. In Precambrian and lower 

Paleozoic rocks, sedimentary manganese deposits 

may be closely associated in space and time with 

iron-formation; oxide-facies manganese deposits 

may be interbedded with oxide-facies iron-formation, whereas the carbonate-facies deposits tend to 

be separated stratigraphically (as at Moanda, 
390 UNITED ST'ATES MINERAL RESOURCES 

Gabon) or spatially (as in Minas Gerais, Brazil) 

from the (usually) carbonate-facies iron-formation. 

Most large sedimentary deposits of manganese 

were deposited in sea water, as indicated by fossils 

and associated rocks. Many smaller deposits, generally oxide facies, were formed near the shores of 

fresh-water lakes, as indicated by fossils (Autlan, 

Mexico, and some deposits in Chile). Some sedimentary manganese oxide deposits are closely associated with gypsum and may well have formed near 

the shores of closed evaporite basins (Three Kids, 

Nev.; Lucifer, Mexico; and possibly some Chilean 

deposits). 

The most favorable host rocks for carbonate-facies 

sedimentary manganese deposits seem to be eugeosynclinal sediments with associated tuffaceous and 

limy rocks or platform limestones or dolomites, deposited in local sea-floor depressions. The deposits 

in the eugeosynclinal sediments are. commonly composed of rhodochrosite and to varying degrees are 

diluted by clastic rocks, whereas those deposited 

with platform or miogeosynclinal carbonates commonly contain manganoan calcite or dolomite or 

complex calci um-magnesi urn-manganese carbonates 

and are rarely diluted by clastic sediments. The 

large deposits of very low grade manganoan carbonate rock, containing from half a percent to a few 

percent manganese, are commonly miogeosynclinal 

or platform deposits and do not characteristically 

contain free carbon. Carbonate-facies iron-formation 

may locally contain several percent manganese, 

probably present as manganoan siderite. 

Sedimentary deposits are characteristically stratiform and have widely varying degrees of lenticularity. In many places, particularly the oxide deposits, these lenses are much longer than wide. Some 

extend for many kilometers, as in the Ukraine and 

in the Kalahari Basin, South Africa, but more commonly the lenses are a few hundred meters to a 

few kilometers long and a few tens of meters to a 

kilometer or more wide. In many deposits the 

manganese is in a single bed; in others, such as 

Chiatura, U.S.S.R., and Urucum, Brazil, the manganese is in several separated beds. Thickness of 

the beds ranges from a hairline to about 30 meters ; 

except in the Kalahari field, few ore-grade primary 

oxide beds are more than 3 meters thick. High-grade 

carbonate beds tend to be thicker but to be smaller 

in areal extent. Low-grade manganoan dolomite or 

limestone may be very thick and very extensive. 

The grade of the sedimentary manganese deposits 

also varies widely. Few unenriched oxide beds contain more than 50 percent Mn ; more contain between 

40 and 50 percent, and probably most contain between 25 and 40 percent Mn before beneficiation. 

Few beds containing less than 25 percent Mn are 

now mined. The carbonate beds are lower grade 

because manganese carbonate contains only 4 7.8 

percent Mn at theoretical purity, which is rarely 

found ; 35 percent Mn is considered to be high grade 

for manganese carbonate in place, and most beds 

contain between 15 and 30 percent Mn. 

Workable sedimentary manganese oxide deposits 

range upward in size from a few tens of thousands 

of tons. There are many such deposits with less than 

a million tons, a substantial number with reserves 

between 1 million and 10 million tons, several with 

reserves between 10 million and 200 million tons, 

and three known areas with even larger reserves, 

ranging into the billions of tons. The Ukranian and 

the Kalahari deposits each are known to exceed 3 

billion tons, and indications are that they may be 

several times this size, there is no economic incentive 

to prove such larger reserves. 

No really large deposits of carbonate-facies manganese ores of ore grade are now known, but exploration of such bodies has rarely penetrated far 

below the zone of weathering, and this resource is 

poorly known. High-grade oxide ore resulting from 

the weathering of such beds rarely occurs in bodies 

of more than 50 million tons, the most productive 

districts being the N suta deposit in Ghana, the 

Serra do N avio deposits in Amapa and the Meridional deposits in Minas Gerais, Brazil, and the 

Kisenge deposits in Zaire. The Moanda deposit in 

Gabon, by far the largest of this type yet discovered, 

has reserves of about 200 million tons of high-grade 

secondary oxide ore. In many but not all such deposits, it may be presumed that the resource of unaltered manganese carbonate at least equals the tonnage of oxide formed from it. 

MANGANESE NODULES 

An enormous potential future source not only of 

manganese but also copper, cobalt, and nickel is on 

the ocean floors in the form of discrete nodules, 

locally welded together to form a pavement. Despite 

much research into the nature, composition, and 

distribution of these nodules, particularly since 

sophisticated cmneras and light sources permitted 

photographing the sea floor, our knowledge of this 

resource is in its infancy. In the last decade several 

tens of millions of dollars have been spent by industry and some governments in locating favorable 

areas and in an attempt to develop modes of submarine mining and extraction of the valuable metals 

from the nodules. Within a decade or less, if political 

obstacles can be overcome, economic extraction 
MANGANESE 391 

might well become practical. Several major American and foreign companies and governments are now 

engaged in scientific and technological research 

toward this goal. 

Extensive areas of the ocean floor have concentrations of nodules that range from a . few millimeters to several tens of centimeters in diameter 

and are roughly spherical to ellipsoidal. The nodules 

are composed of roughly concentric layers of material of varying composition, largely oxides of iron 

and manganese, deposited around nuclei of broken 

nodules, fragments of volcanic ejecta or other clastic material, and, rarely, fossils. It is estimated that 

these nodules grow at the rate of 1-5 mm per million 

years. 

Nodules are most abundant and highest in tenor 

in parts of the oceans that receive minimal contributions of sediments ; these are the deeper parts, 

ranging from about 2,500 meters to about 6,000 

meters in depth. Lower-grade deposits are found in 

great abundance on the Blake Plateau, off Florida, 

at much shallower depth. Although nodules buried 

in the sediments of the bottom are found, the first 

30 em down from the interface is believed to contain about 65 percent of the useful material; the 

deposits should be envisioned as very widespread 

but very thin accumulations of consolidated nodules 

resting in and on a usually unconsolidated and very 

fine clay matrix. 

The metallic content of the nodules varies widely 

from ocean to ocean, regionally and to some extent 

systematically within the individual oceans, and 

from place to place within the regions. Variations 

in nodule population may be very abrupt. Various 

authors have presented generalized information on 

composition and population, but the detailed data 

on which mining plans and resource calculations 

can be based, resulting from prospecting in progress, 

are not publicly available. It is understood, however, that areas, each of 2,600 square kilometers or 

more, have been located in which the nodules average more than 25 percent Mn, 1.0 percent Cu, 1.0 

percent Ni, and 0.25 percent Co, with smaller values 

in other metals. The iron is not economically recoverable. At 1972 prices, the value of the metals in 

such nodules would be more than $150 per dry ton. 

The richer areas may contain about 13,500 tons per 

square kilometer or even much more; the average 

in deposits of minable size would probably be significantly less. Although astronomical figures as to 

the total tonnage of nodules on the sea floor have 

been published, resources in areas having a minable 

population of nodules are probably far less, but still 

undoubtedly very large. Extraction of the metals 

from the nodules demands innovative metallurgical 

practice; dredging of the nodules from great depths 

demands innovative mining practice. 

The genesis of these manganiferous nodules is 

hotly debated. Some oceanographers believe that the 

metallic content is derived from submarine volcanism or alteration of submarine volcanic rocks; 

others, that it comes from reactions in the upper 

part of the sediments by which the metals are released during diagenesis of the sediments; and still 

others, that the metals are derived by subaerial 

weathering of the continental masses, being transported to the ocean basins by rivers, and to the sites 

of deposition by ocean currents. The presence of extensive deposits on the Blake Plateau on a limestone 

substrate, far from volcanic activity, suggests the 

third theory as the preferred model there. However, 

a sole source for all the deposits does not seem required. 

VOLCANOGENE DEPOSITS 

Bcause many small-scale and some medium..:scale 

deposits of manganese are closely related in space 

and time to volcanism, the conclusion that such 

deposits are somehow genetically related to volcanism seems unavoidable. There is no general agreement as to the mechanism by which the manganese 

has been separated from the volcanic material and 

concentrated ; several processes may be involved. 

This uncertainty, as well as the wide variation in 

types of deposits (ranging from clearly sedimentary 

to vein-type deposits) that are closely related to 

volcanism, makes use of the term "volcanogene" 

appropriate. This type of deposit is gradational both 

with the sedimentary type already discussed and 

with the hypogene type discussed below, and no 

clear-cut separation can be made. 

Volcanogene deposits are closely associated with 

volcanic rocks, of both pyroclastic and flow origin, 

and either subaerial or submarine. In many instances the pyroclastic rocks have been deposited in 

lakes or the sea and are closely associated with 

clastic and chemical sediments or with limestone. 

Major volcanic piles, such as those in eastern Cuba 

or the Olympic Peninsula in Washington, are favored sites for this type of deposit. Peculiarly, although such piles may have a maximum thickness 

of thousands of meters, the manganese deposits in 

many of them are confined to widespread zones a 

few meters to a hundred meters thick, indicating 

that the concentration of manganese by volcanic 

processes or from the volcanic rocks was not a 

continuing and normal process but demanded special conditions, the nature of which remains uncer-
392 UNITED STATES MINERAL RESOURCES 

tain. The depth of the water into which submarine 

volcanics were extruded may be one governing factor, for below a certain depth the confining water 

pressure is so high that included volatiles in the 

molten lava cannot readily escape. 

Because many volcanic piles and extensive areas 

of volcanic rock contain no concentrations of manganese, the mere presence of volcanic rocks is no 

indicator of potential manganese discoveries. Characteristically, however, if one manganese deposit is 

found in such rocks, many others will be found in 

the same general area. Commonly, one or two deposits will be much larger and (or) higher grade 

than the others. Although deposits are known from 

continental volcanic rocks, the more important deposits are found in a marine or lacustrine environment, as in Mexico, Chile, and Cuba, and thus are 

really sedimentary deposits, in the strict sense of 

that term. 

Volcanogene deposits are commonly but not exclusively composed of the oxide minerals, and the 

mineralogy is usually somewhat more complex than 

that found in unmetamorphosed sedimentary deposits without volcanic affiliation. Replacement of 

the diluting clastic and pyroclastic fragments in the 

ore horizon by manganese minerals is common; this 

seems to be a diagenetic feature in many places but 

may also be the result of supergene or hypogene 

alteration. In many such deposits, chert in small to 

rather large lenses accompanies, underlies, or overlies the manganiferous material, which here may be 

the hydrous manganese silicates bementite and 

neotocite. These manganese silicates are not ore 

minerals. 

Deposits large enough to be economically interesting are commonly either sharply lenticular or stratiform; the larger ones are stratiform. Numerous but 

normally very small deposits may be associated with 

altered volcanic rocks and spilites. The volcanogene 

deposits interfinger with tuffaceous and (or) calcareous sediments or cherty and j aspery rocks. 

Local unconformities and abrupt lithologic changes 

in the host· rocks are common. 

Reserves in volcanogene deposits are characteristically small to medium in size. Very few deposits 

contain more than a million tons of recoverable ore, 

the largest probably being the Charco Redondo deposit in Cuba, which has produced about 5 million 

tons, and the Autlan deposits in Mexico, which produced about 4 million tons before exhaustion. Both 

are stratiform deposits. 

With some notable exceptions, such as the Crescent mine in the Olympic Peninsula, most such 

deposits are medium grade, and the ore must be 

concentrated before shipment. 

As with many other types of ore deposits, the 

localization of volcanogene deposits is apparently 

caused by relatively abrupt and localized changes 

in the nature or environment of the fluids which 

brought the manganese to the site of deposition. 

For deposits such as those in the Olympic Peninsula, the interface between the hot lava and the sea 

water into which it was extruded was the site of 

an abrupt change, and the manganese was deposited at and near that interface. For deposits such 

as Charco Redondo, the manganese evidently was 

transported some distance and deposited in a sedimentary environment with limestone and waterlaid tuff. 

The sources of the manganese deposited in such 

bodies may be either fluids evolved from the magma 

at depth during volcanism, or, in small deposits such 

as those in the Olympic Peninsula, perhaps the alteration of the rock as it reacted with the sea water. 

HYPOGENE DEPOSITS 

Myriad small and a few medium-sized deposits of 

manganese ores are of hypogene origin-that is, 

they were deposited directly from warm fluids rising from sources deep in the earth. Some of these 

deposits merge into the volcanogene type, and it is 

impossible to be sure how closely they are related 

genetically to the volcanic rocks that enclose them. 

They also merge into the sedimentary type in that 

the fluids that brought the manganese into the basins in which sedimentary ore deposits formed by 

the normal sedimentary processes are thought, in 

some instances, to have been thermal waters. 

The hypogene deposits occu-r in the same structural setting as the base- and precious-metal deposits with which they are often associated. Most are 

related to intrusive rocks, about which they are 

zonally arranged. They may take the form of veins, 

as at Butte, Mont., or replacement deposits in limestone or dolomite, as at Philipsburg, Mont. Another 

type, more abundant in the Basin and Range province of the United States and Mexico, is the vein 

deposit, predominantly in volcanic rocks. A few 

minor deposits are in the aprons of hot springs. 

Most of the vein deposits formed at relatively low 

temperatures. In most, the manganese is in oxide 

form, but in a few it is in carbonate form. The few 

known occurrences of manganese sulfide are typically in veins. The replacement deposits may be in 

either oxide or carbonate form ; carbonate deposits 

have commonly been oxidized at and near the surface 

by supergene action. 

Few vein deposits have been followed to consid-
MANGANESE 393 

erable depths ; nearly all die out or change their 

nature at depths of a few tens of meters to a few 

hundred meters. Many veins reveal strongly increasing percentages of hematite or barite with depth, 

indicating a zonal pattern. A number of deposits in 

brecciated volcanic rocks consist of myriad small 

thin veinlets of nearly pure manganese oxide lining 

fractures in the host rocks. 

Replacement deposits of manganese carbonate are 

commonly in limestone or dolomite and tend to 

form tabular or pipelike shoots and irregular pods 

adjacent to faults or other conduits by which mineralizing solutions gained access to host rocks. Permeability of the host rock is a major control; therefore brecciated zones are favored. Replacement on 

a large scale is apparently confined to the more calcareous rocks, although tuffaceous rocks are replaced 

locally. Hypogene manganese oxide deposits are 

more generally confined to veins, generally filling 

fissures but in some instances replacing fault gouge, 

breccia, or other particularly permeable zones in 

host rocks of various types. 

The vein deposits of manganese in the United 

States, Mexico, and Morocco have yielded a small 

tonnage of relatively high grade ore for many years. 

Locally such ore is rather low grade in the vein but 

can be hand sorted or mechanically concentrated to 

bring it to merchantable grade. Few such deposits 

yield as much as 100,000 tons; most contain a few 

tens to thousands of tons of salable ore. The replacement deposits may be much larger but generally are 

lower in grade, as at Leadville, Pioche, and Philipsburg. 

The hypogene ores are deposited from thermal 

fluids originating at depth in the earth. Undoubtedly 

some of these fluids are derived from crystallizing 

magma; others are probably heated ground waters 

that derived their metallic content while circulating 

through and altering preexisting rocks of diverse 

origin. As the fluids approach the surface, changes 

in their environment and chemistry make the manganese insoluble and it deposits on the conduit walls 

or, if the chemistry is favorable, replaces the wallrocks. Experience has shown that there is little 

likelihood of finding significant hypogene oxide deposits at depths of more than a hundred meters or 

so; carbonate deposits may be found at greater 

depths, usually associated with deposits of other 

metals. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

There is no lack of identified manganese resources 

in the world today, but these resources are so distributed that only one industrialized country, the 

U.S.S.R., is not almost completely dependent on 

imports for its supply. Table 76 gives the general 

TABLE 76.-World manganese ore resources, in millions of 

tcms 

Conditional Hypothetical 

Country Reserves 1 resources 2 resourees 3 

North America: 

Canada 0 196 

Cuba ----------- 1(1) 3(?) 

United States --ioou> -- 0 961 

Mexico 15;;t; 50;;t;(T) 200(!) 

North America, 

total ------- 16± 1,210;!;; 300(1) 

Africa: 

South Africa --- 3,000 3,000(?) 2,000(?) 

Gabon --------- 200 40(?) 

Zaire ---------- 6(?) 30(1) 10(1) 

Upper Volta ---i (?) 25(1) 

Egypt ---------- 1 

Morocco -------- 1(?) 

Ghana 1 --6on> 

Africa, total -- 3,208 3,116 2:o&ocn 

Europe, except 

USSR. 2(?) 1(1) 10(f) 

Australia and 

Oceania. 100 60(?) 50(?) 

USSR Europe and 

Asia). 3,000 3,000(?) 3,000(?) 

Asia: 60(?) India ---------- 35 65 

China oT-'A;i~:-- 30(?) 50(?) 100(?) 

Rest 100(?) except USSR. 6(?) 

Asia (excluding USSR), 

total. 70 115 250(?) 

South America: 

Brazll 160(?) --------- 100 50 

Bolivia 2(?) 10(?) 50(?) 

Chlle ----------- 1 10(?) 

South America, 210(?) total. 103 60 

Sea floor nodules • __ 200+ (?) &,ooo+ <?> 

Rounded total_ -6,500 -7,700 -10,000 

1 Identified deposits from which minerals can be extracted profitably 

with existing technology and under present economic conditions. 2 Specific, identified mineral deposits whose contained minerals are not profitably recoverable with existing technology and economic conditions. a Undiscovered mineral deposits, whether of recoverable or subeconomic 

grade, that are geologically predictable as existing in known districts. 

picture; firm data are available for few countries, 

and the figures presented are personal estimates 

based on evaluation of many sources, published and 

unpublished. Queried figures are particularly weak 

and could be wrong by an order of magnitude. Grade 

of most resources and of ore ranges from 25 to 50 

percent manganese. 

RESERNES 

Reserves are in bodies or districts being mined 

today. This category includes proved, indicated, and 

inferred reserves. 

CONDITIONAL RESOURCES 

Examples of conditional resources are the enormous deposits of manganiferous material deep in 

the Kalahari basin in South Africa that have been 

cut by a few deep drill holes. Very large easily accessible deposits are also available there, and accordingly exploitation of the deep beds in the foreseeable 

future is unlikely. Similarly, the sedimentary manganese carbonate deposits, ranging from 20 to 36 
394 UNITED STATES MINERAL RESOURCES 

percent Mn, underlying the supergene oxide ores in 

Ghana, Brazil, and elsewhere are considered as conditional resources. Figures on the size of such bodies 

are very gross estimates indeed, for none have been 

explored to depth. Low-grade bodies of manganiferous rocks such as those at Artillery Peak, Ariz., and 

Aroostook County, Maine, are here included, although they probably will never be used. Also included are the Tambao deposits in Upper Volta, 

constituting 9 million tons of 50 percent Mn oxide 

ore plus pos.sibly a greater amount of high-grade 

manganese carbonate, now without transportation 

facilities. 

HYPOTHETICAL RESOURCES 

Included as hypothetical resources are some deposits about which too little is known to include 

them as identified resources, . such as some reported 

in eastern Bolivia and western Brazil ; that such 

deposits exist is known, but details of size and grade 

are not accurate enough to include the resource as 

identified. Similarly, a large area of the southern 

Ukraine is underlain by manganese deposits like 

those mined at Nikopol ; their presence is said to be 

indicated by widely scattered drilling, but the possible extent and grade of the whole resource are unknown, and given the enormous known reserve, there 

is no incentive to establish those facts. Clearly, estimates of such resources can be scarcely more than 

informed guesses-and not very well informed at 

that. 

The assumptions on which these estimates are 

based are: ( 1) sedimentary manganese deposits laid 

down in a shelf or platform environment may be very 

extensive, and (2) the possible extent may be judged 

from the continuity of the geologic environment as 

witnessed by the associated rocks, even though the 

manganiferous layer(s) are buried beneath younger 

rocks. Thus the Molango manganiferous zone is 

known for some 80 kilometers along strike, although 

it is below present ore grade for most of that distance. Who can say what might be revealed by 

exploration back from the outcrop, which is a fortuitous sample of a much more extensive manganiferous zone. 

Sedimentary deposits in small tectonic basins, 

such as some of the Moroccan deposits, cannot be 

thus extrapolated, nor can the spotty and relatively 

small hypogene or volcanogene deposits. Similarly, 

although small deposits of manganese oxide formed 

by the weathering of manganiferous dolomite or 

limestone, such as those along the west foot of the 

Blue Ridge in the Appalachians, remain to be discovered, what will be the cost and the expectable economic return? Such small deposits are not here 

included. Some districts with residual ore of this 

type, such as the Postmasburg district in South 

Africa, have produced millions of tons although 

known reserves probably never exceeded half a million tons and are here included on the basis of past 

productivity. 

The sea-floor nodules, of course, will represent a 

great resource of manganese and some other metals 

when problems of extraction, metallurgical treatment, and legal status have been solved. The true 

extent of this resource is not yet even approximatly 

known, but exploration is continuing, and the resource may well eventually reach billions to tens of 

billions of minable tons. Resource data on nodules 

given in table 76 are subject to gross modification. 

Table 77 gives details of resources and grade of 

known significant deposits of manganiferous rock 

TABLE 77.-Major identified manganese resources 1 of the 

United States 

[In millions of long tons. Data slightly modified from Pavlides, (in Hewett 

and others, 1956, p. 214) ] 

District 

Cuyuna Range, Minn 

Aroostook County, Maine ---- Chamberlain, S. Dak -------- Artillery Peak, Ariz ----------

Pioche, Nev ------------------ Leadville, Colo ---------------

Total ------------------

Average 

Raw grade Contained 

material (percent Mn Mn) 

450 5 22.5 

280 9 25.2 

69 15.5 10.7 

156 4 6.2 

3 10 0.3 3 15 0.5 

961 6.8 65.4 

1 Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be 

profitably recoverable with existing technology and economic conditions. 

that have been considered as potential sources of 

manganese in the United States. These deposits are 

included in the identified rsources shown in table 76. 

Brooks (1966, p. 70-92) ably discussed the technical and economic problems involved in developing 

these domestic deposits; to the authors' knowledge, 

no breakthroughs ha.ve been made in the metallurgical problems since Brooks' analysis was made. Because capacity of the high-grade ore producers in 

Brazil, Gabon, South Africa, and Australia was being 

greatly increased in 1971-72, it is doubtful that the 

world price of manganese in constant dollars will rise 

significantly in the near future; the price is lower 

now in constant dollars than for many years. Accordingly, there is now little stimulus to search for 

and develop the hypothetical resources here discussed 

or the speculative resources discussed below. 

SPECULATIVE RESOURCES 

Speculative resources are impossible to quantify. 

Manganese deposits of usable mineralogy, size, and 

grade are too sporadically distributed to permit 
MANGANESE 395 

sound generalizations as to how much might be present in given areas or volumes of rock. Perhaps this 

section should be entitled "Guidelines for future 

prospecting" rather than "Speculative resources." 

Presumably, future prospecting will be for medium- to large-scale deposits; when compared with 

potential reward, the expense of looking for small 

deposits is prohibitive. In terms of national security, 

only those deposits that can make a significant contribution to requirements are worth considering; the 

long lead time in developing significant production 

emphasizes the need for an adequate stockpile. 

For Jurassic and younger deposits, the few volcanogene deposits of economically interesting size 

and grade are all near the leading edge of the moving 

tectonic plates, and therefore this type of deposit 

should be sought in that environment. The large 

higher grade sedimentary deposits in this age range, 

however, are all either on the trailing edge of the 

continental plates or on intracontinental platforms. 

We cannot yet make similar informed generalizations 

about pre-Jurassic sedimentary deposits, for the 

former configurations of the tectonic plates have not 

been deciphered. Many of the older sedimentary 

oxide deposits were clearly formed in a platform 

environment. 

In the United States, the largest concentration of 

manganese is in the carbonate nodules and the enclosing manganiferous rocks of the Cretaceous 

Pierre Shale in South Dakota. (The resource estimate in table 77 is based on rock with less than 1f2 : 1 

stripping ratio; the manganiferous beds are very 

much more extensive. This resource is essentially 

unworkable at present because of mining, ore dressing, and metallurgical problems; development would 

perforce hasten silting of important reservoirs.) The 

source of this enormous quantity of manganese is 

still unknown. Precambrian iron-formation is in 

many localities accompanied by or closely associated 

in time and in space with concentrations of manganese. Some of the iron-formations in the Lake 

Superior region, notably the Cuyuna range, are highly manganiferous. Although most bedrock in central 

and western Minnesota is now hidden by Pleistocene 

glacial deposits, it is known that underlying rocks 

cause magnetic anomalies and also that a long erosional interval with semitropical or tropical climate 

took place there during Cretaceous time. The authors 

think that the manganese in the Pierre Shale may 

have been derived by intensive chemical weathering, 

during the Cretaceous Period, of now-buried manganiferous iron-formations or manganese deposits in 

central or western Minnesota or contiguous areas to 

the south. The Cretaceous weathering episode may 

also have created man.ganese oxide concentrations at 

that weathering surface. It is of course possible that 

Pleistocene glaciation may have scoured away such 

supposed surficial concentrations, which in unglaciated terrane occur on topographic highs. 

It is also possible that Precambrian sedimentary 

deposits of manganese carbonate such as those that 

gave rise to secondary oxide deposits in Africa, Asia, 

and South America were present in eugeosynclinal 

rocks of the Precambrian shields of North America; 

such deposits are now known in several other Precambrian shields. The characteristically high 

graphite content of the wallrocks of such deposits 

might be utilized in geophysical prospecting if cover 

were not too thick. 

Finding of the so-far unique Molango deposit in 

Mexico raises question as. to whether a similar deposit might be present in miogeosynclinal environments in the United States. The gray manganiferous 

rock at Molango looks like most somewhat-organic 

limestones and could easily be overlooked; it was 

discovered during development of small bodies· of 

secondary manganese oxide formed from it by 

weathering. Most analyses of limestone· made in the 

United States do not determine the manganese content of the rock, and our knowledge of the manganese distribution in limestone in the country is 

spotty and incomplete. Several carbonate formations 

in the United States are known to be slightly manganiferous, notably the Shady Dolomite in the Eastern Appalachians. This formation has never been 

systematically sampled, mainly because it crops out 

poorly and is in many places covered by debris from 

other formations. By careful sampling, patterns of 

manganese distribution in this or other manganiferous carbonate formations might be found, and another Molango might be located. A careful regional 

study of the Molango area to discover the controls 

of manganese deposition there would be helpful. 

An area of the North American continent that 

might carry a significant deposit of high-grade manganese oxide is the part of California and northwestern Mexico where the Pacific Rise intersects the 

continent at the head of the Gulf of California. In 

Pliocene time the Lucifer manganese deposit (and 

also the adjacent Boleo copper deposit) in Mexico 

formed in a basin, probably closed, beside or on this 

rift zone. The Colorado River has dumped enormous 

quantities of more recent sediment on this part of 

the continent, and wells to tap thermal fluids in these 

sediments in the Salton Sea area and areas to the 

south in Mexico have brought to the surface steam 

and water at high temperature and pressure highly 

charged with mineral salts, including manganese; 
396 UNITED STATES MINERAL RESOURCES 

the metal content of the steam and water is much 

higher in California than in Mexico. The source of 

these metals, which is still unknown, might be the 

sediments themselves, or underlying rocks, or magmatic bodies at depth. A careful study of the distribution of manganese in the fluids and the· direction 

of their movement might lead to prospecting guides. 

Such a hypothetical deposit would, of course be very 

expensive to find and more so to develop, as it would 

involve underground mining in difficult conditions. 

On other continents, the most logical and promising areas are those in which Precambrian eugeosynclinal rocks have been exposed to one or more 

cycles of erosion and where remnants of ancient erosion surfaces are still preserved. All the significant 

secondary manganese oxide deposits that formed by 

weathering of primary sedimentary manganese carbonate deposits are in erosional remnants of such 

ancient surfaces. In west and central Africa, rocks of 

Birrimian age are the most favorable and are widely 

distributed in the western and central parts of the 

continent. In equatorial Africa, the Francevillian 

rocks are also favorable. It would be surprising if all 

the significant deposits have already been found. 

In South America the rain forest of the Amazon 

region to the north and south of the central zone of 

Paleozoic and younger rocks is possibly the most 

favorable area; the eugeosynclinal Precambrian 

rocks in the middle and headwater areas of the 

north-flowing tributaries are also very favorable. 

Many occurrences of manganese ores have been located in these areas; probably, commercial deposits 

will be found, there too on remnants of ancient 

erosional surfaces. The recent discovery of very extensive areas of oxide-facies iron-formation south of 

the Amazon increases the possibility of discovery of 

manganese or manganiferous iron ore associated 

with these rocks. 

In western Brazil and eastern Bolivia at about 20° 

south latitude, the large known reserves of bedded 

manganese oxide ore associated with lower Paleozoic 

oxide-facies iron-formation might be radically increased by more detailed subsurface exploration, not 

necessarily in the places now known to contain manganese. Here the nearshore facies of the J acadigo 

Series is perhaps the prime target for exploration. 

The known manganese beds are lenticular, although 

individual lenses may be several square kilometers in 

extent, and concealed lenses or lenses cropping out 

obscurely may be of very significant size. 

In India the major manganese deposits are metamorphosed primary oxide sediments in lenses of 

considerable extent. They have not been explored by 

drilling, and deep drilling probaby will reveal a considerable tonnage of high-grade ore. The economic 

viability of the deep ore will depend on increased 

world prices, as such ore will be expensive to extract. India is a manganese-rich province, with deposits of different kinds, largely of sedimentary 

origin. It would be surprising if further discoveries 

were not made. 

PROSPECTING TECHNIQUES 

Prospecting for manganese deposits has been carried on by the classical method of looking for surface 

indications of manganese oxide. This approach is 

very usable in areas of outcrop and residual soil because manganese oxide is relatively immobile under 

most surface and near-surface conditions and because manganese carbonate oxidizes readily to manganese oxide under near-surface conditions. 

The high but variable background content of manganese in all rocks, soils, waters, and plants makes 

geochemical methods difficult, if not unusable. Use of 

other elements as pathfinders to manganese deposits 

is hazardous, mainly because most large sedimentary 

deposits are free of trace elements suitable for this 

use. Plants may be useful in future manganese 

exploration. Presence of certain plants, at least locally in the Eastern United States and the Katanga, is 

indicative of a manganese-rich environment (Cannon, 1971, p. 245). 

The common association of graphite and organic 

carbon with sedimentary manganese carbonate deposits would cause anomalous electrical reactions ; 

therefore induced polarization (IP) and other electrical geophysical methods should be able to detect 

the carbonaceous wallrocks where these have not 

been too highly altered. In tropical zones, however, 

the carbonaceous material is normally oxidized to 

some depth, so the electrical methods would be applicable only in areas of slight surface alteration. 

Once signs of a manganese deposit are located 

visually, then drilling, test pitting, and exploration 

of the deposit by adits or shafts are essential to 

establish the size and grade, for the surficial expression of a deposit may be deceptively large and high 

grade. 

PROBLEMS FOR RESEARCH 

GENERAL PROBLEMS 

1. The most important problem involved in manganese supply for the United States today is the continuing maintenance of an adequate stockpile of 

ferromanganese alloys or high-grade manganese ore 

so that this country will never again be subject to 

stringent and industrially crippling shortages caused 
MANGANESE 397 

by interruption, either political or military, of the 

supply of this essential raw material, all of which is 

now imported. 

2. From the viewpoint of raw-materials supply, 

the most promising development would be the successful winning of nodules from the sea floor and 

extraction of the contained metals. This would insure not only a greatly increased resource of manganese but also a significant increment in the supply 

of nickel, cobalt, and copper-also metals for which 

the United States is dependent on imports. Large 

investments are needed to bridge the gap between 

promising research and pilot-plant operations and 

industrial-scale application, but the legal status of 

deep-sea mining must be resolved before large-scale 

private investment can be secure. 

3. Should a decision be reached to attempt to make 

this country more self-sufficient in manganese supply from conventional sources, greatly expanded 

metallurgical research would be necessary to tap 

known submarginal identified resources as well as 

geological research to locate the hypothetical and 

speculative resources already discussed. 

4. Continuing research into the geological habitat of manganese, causes of concentration into large 

economic deposits, and the geochemistry of the element can only make the search for conventional and 

nonconventional sources more fruitful and increase 

the supply available to our industry and civilization. 

Because most of the large-scale concentrations and 

all of the high-grade concentrations of economic 

size are outside the United States, much of the 

needed research must be carried out overseas. Judging from past successes and their impact on the 

supply situation during the last two decades, investment in such research is sound. Specifically, thorough subsurface investigations of at least one of 

the large carbonate sedimentary bodies, such as 

N suta, Ghana, or Serra do N avio, Brazil, should be 

undertaken to establish the geological habits and 

expectable reserves of this type of manganese ore. 

Such a study probably would have to be subsidized; 

at present there is little economic justification for 

a company to undertake research of this type independently because of the abundance of high-grade 

oxide ores in the world. Results must be published. 

NEEDS FOR NEW PROSPECTING TECHNIQUES 

Because manganese oxide is very resistant to 

weathering and usually crops out or is found as 

concretionary or detrital pebbles or boulders in 

residual soils overlying significant bodies, prospecting in areas of residual soils is relatively simple. 

In areas of transported soils or debris and in areas 

of glacial moraine, loess, or other transported surficial material, or under unconformities, there may 

be no surface sign of underlying bodies. Geochemical 

prospecting is much handicapped by the widespread 

presence of manganese in the earth's crust and the 

ease with which it is precipitated from solutions 

under near-surface conditions ; positive anomalies 

are, accordingly, much more common than ore deposits and, by themselves, are relatively meaningless. 

Except for a rare magnetic mineral, manganese 

oxide deposits have no particularly distinguishing 

geophysical characteristics that would selectively 

locate concentrations. Manganese minerals have 

relatively high specific gravity, but many nearsurface secondary deposits have so many voids that 

gravimetric techniques would have only moderate 

chance of success, although in certain environments 

the technique has been successfully used (Rowston, 

1965). Carbonate-facies sedimentary manganese 

deposits are in most places closely associated with 

a high free-carbon content in the wallrocks, and 

this can be detected under slight or moderate cover 

by certain electrical methods of prospecting. Unfortunately, many carbonaceous rocks are not associated 

with manganese deposits, and unless positive indication of the presence of manganese at depth is 

available, the method is nondiagnostic. In driftcovered areas a combination of geochemical prospecting followed by geophysical investigation in the 

neighborhood of major anomalies might help locate 

large bodies of manganese carbonate, but to the 

authors' knowledge this dual approach has not been 

attempted and may not be practical. Large manganese carbonate sedimentary bodies are known in 

many tropical shield areas and may be present but 

undiscovered in shield areas in northern latitudes. 

These bodies have hitherto not been exploration 

targets for economic reasons ; the oxide is the preferred ore. 

In South Africa, Australia, and the Eastern 

United States, certain plants have been shown to 

concentrate manganese in their leaves and (or) 

twigs. To the authors' knowledge, no extensive research has been done on the general applicability 

of biogeochemical prospecting to manganese-ore 

finding; and therefore this is a promising avenue 

for future systematic research, to determine whether 

variation in manganese content of plants is a function of generic type, climate, or soil environment. 

A better understanding of the exact sedimentary 

conditions and environment causing large-scale 

deposition of relative pure manganese minerals in 

the specific spots in which they are found seems 

prerequisite to evolving new prospecting techniques. 
398 UNITED STATES MIN~RAL RESOURCES 

The general principles are to a large extent known ; 

the reasons why deposits are where they are have 

not yet been pinpointed and need much closer study 

and research. 

TECHNOLOGICAL PROBLEMS 

Manganese carbonate when intimately intermixed 

with calcite or dolomite or other similar contaminants is difficult to concentrate; similarly, much 

manganese oxide ore is so intimately mixed with 

iron minerals or calcite that the constituents cannot be economically separated by known means. 

Manganese minerals such as cryptomelane, kutnahorite, and braunite inherently contain other elements that cannot be mechanically separated. However, by calcining to drive off carbon dioxide, ores 

containing much carbonate may be radically upgraded, and ores containing potassium, aluminum, 

or iron in deleterious amounts can be made usable 

by mixing with other ores containing less of these 

elements. Certain elements, such as phosphorus, 

arsenic, and potassium, are highly deleterious when 

they occur in amounts above defined limits. 

The manganese nodules on the ocean floor contain important quantities of copper, cobalt, and 

nickel, which must be recovered to make nodule 

mining economic. Several hydrometallurgical processes have been tried, and one company claims to 

have solved the problem on an economic basis in 

pilot-plant studies. Should this be correct, the techniques might be adaptable to recovery of manganese 

from some of the low-grade resources on land. 

SELECTED REFERENCES 

Alexandrov, E. A., 1965, Problems of genesis of sedimentary 

manganese deposits: Ann Arbor, Mich., University 

Microfilms, Inc., 369 p. 

Borchert, H., 19·70, On the ore-deposition and geochemistry 

of manganese: Mineralium Deposita, v. 5, no. 3, p. 300-

317. 

Brooks, D. B., 1966, Low-grade and nonconventional sources 

of manganese: Washington, Resources for the Future, 

Inc., 123 p. 

Cannon, H. L., 1971, The use of plant indicators in ground 

water surveys, geological mapping, and mineral prospecting: Taxon, v. 20, no. 2/3, p. 227-256. 

Cdttenden, M. D., and Pavlides, Louis, 1962, Manganese in 

the United States: U.S. Geol. Survey Min. Inv. Resource Map MR-23. 

De la Hunty, L. E., 1963, The geology of the manganese deposits of Western Australia: Western Australia Geol. 

Survey Bull. 116, 123 p. 

De Villiers, P. R., 1970, The geology and mineralogy of the 

Kalahari manganese-field north of Sishen, Cape Province: South Africa Geol. Survey, Dept. Mines, Pretoria, 

Mem. 59, 84 p. 

Dorr, J. V. N., II, 1968, Primary manganese ores: Soc. 

Brasileira Geol. XXII Congresso, Belo Horizonte, v. 22, 

12 p. 

Dorr, J. V. N., II, Coelho, I. S., and Horen, Arthur, 1956, 

The manganese deposits of Minas Gerais, Brazil: Internat. Geol. Cong., 20th, Mexico, Symposium del manganeso, v. 3, p. 279-346. 

Gomes Juarez, D., 1961, Estudio geologico de la Mina de San 

Francisco localizada en Autlan, Eso. de Jalisoo: Unpub. 

engineer's thesis, U.N.A.M., Mexico, 83 p. 

Hewett, D. F., 1966, Stratified deposits of the oxides and 

carbonates of manganese: Econ. Geology, v. 61, p. 431-

461. 

Hewett, D. F., Crittenden, M. D., Pavlides, Louis, and de 

Huff, G. L., 1956, Manganese deposits of the United 

States: Internat. Geol. Cong., 20th, Mexico, Symposium 

del manganeso, v. 3, p. 169-230. 

Krauskopf, K. B., 1967, Introduction to geochemistry: New 

York. McGraw-Hill Book Co., 721 p. 

--- 1972, Geochemistry of micronutrients, in Micronutrients in agriculture: Soil Science Soc. America, Madison Wise., p. 7-40. 

McKelvey, V. E., and Wang, F. F. H., 1969, World subsea 

mineral resources: U.S. Geol. Survey Misc. Geol. Inv. 

Map 1-632, 4 sheets, 17 p. 

Mero, J. L., 1965, The mineral resources of the sea: New 

York, Elsevier, 312 p. 

Park, C. F., 1946, Spilite and manganese problems of the 

Olympic Peninsula, Washington: Am. Jour. Sci. v. 244, 

p. 305-323. 

Perfilev, B. V., Gabe, D. R., Galperina, A. M., Rabinovitcb, 

V. A. Sapotnitskii, A. A., Sherman, E. E., and Troshanov, E. P., 1965, Applied capillary microscopy-The 

role of microorganisms in the formation of iron-manganese deposits : New York, Consultants Bureau, 120 p. 

[Translated from Russian) 

Pinto, M. da Silva, 1961, Minerio de Manganes no Brazilsuprimento interno e export~ao: Geologia e Metalurgia, Centro Moraes Rego., Sao Paulo, bol. 23, p. 62-

179. 

Rowston, D. L., 1965, Gravity survey of manganese deposits 

in the M t. Sidney-Woodie-Woodie area, Pilbara gold 

field: Geol. Survey Western Australia Ann. Rept. for 

1964, p. 49-51. 

Sapozhnikov, D. G., ed., 1970, Manganese deposits of the 

Soviet Union, in Proceedings of the conference on principal genetic types and the geochemistry of manganese 

deposits in the U.S.S.R.: Israel Program for Scientific 

Translations, Jerusalem 522 p. 

Scarpelli, Wilson, 1966, Aspectos geneticos e metamorficos 

das rochas do Distrito de Serra do Navio, Territorio 

Federal do Amapa, Brazil, in Anais da VI Conferencia 

Geologica das Guianas: Departmento N ac. da Produ~ao 

Mineral, Div. Geol. Mineral., Avulso 41, Rio de Janeiro, 

p. 37-57. 

Sheridan, E. T., 1970, Manganese, in Mineral facts and problems: U. S. Bur. Mines Bull. 650, p. 315-331. 

Simons, F. S., and Straczek, J. A., 1958, Geology of the 

manganese deposits of Cuba: U.S. Geol. Survey Bull. 

1057,289 p. 

Smith, W. C., and Gebert, H. W., 1970, Manganese at Groote 

Eylandt, Australia: Inst. Mining and Metallurgy Proc., 

Ninth Commonwealth Mining and Metallurgy Congress, 

1969, London, v. 2, p. 585-604. 
MANGANESE 399 

Straczek, J. A., Subramanyam, M. R., Naraya-Naswami, S., 

Shukla, K. D., Vemban, N. A., Chakravarty, S. C., and 

Ventkatesh, V., 1956, Manganese ore d·eposits of Madhya 

Pradesh, India: Internat. Geol. Cong., 20th, Mexico, 

Symposium del manganeso, v. 4, p. 63-96. 

Taliaferro, N. L., and Hudson, F. S., 1943, Genesis of the 

manganese deposits of the Coast Ranges of California: 

California Div. Mines Bull. 125, p. 217-275. 

Varentsov, I. M., 1964, Sedimentary manganese ores: Amsterdam, Elsevier, 119 p. 

Weber, Fran~is, 1969, Une Serie precambrienne de Gabon: 

Sedimentologie, geochimie, relations avec les gites 

mineraux associes: Unpub. doctoral thesis, Unive:rsite de 

Strasbourg, France, v. 1 and 2, 367 p. 

Zantop, Half, 1969, Trace element distribution in manganese 

oxides and iron oxides from the San Francisco manganese deposit, Jalisco, Mexico: Stanford, Calif., Stanford Univ. unpub. doctoral thesis, 161 p. 

UNITED STATES MINERAL RESOURCES 

MERCURY 

By E. H. BAILEY, A. L. CLARK, and R. M. SMITH 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Uses ---------------------------------------- Size and importance of the industry -----------

Exploitation -------------------------------------

]dining ------------------------------------- Production _________________________________ _ 

Prices and tariffs ---------------------------

Outlook ------------------------------------- Geologic environment -----------------------------

Basic geochemistry ---------------------------

Ore deposits ---------------------------------

Resources ---------------------------------------

Identified resources --------------------------

Speculative resources ------------------------

Prospecting techniques ---------------------------

Problems for research ----------------------------

References --------------------------------------

FIGURES 

46. Graph showing mercury production and prices, 

1850-1971 ------------------------------- 47. Graph showing demand and domestic supply of 

mercury in the United States, 1850-1971 __ _ 

48. ]dap showing relation of mercury deposits of 

the world to post-Jurassic subduction zones49. Map showing relation of mercury deposits of 

California to the Coast Range thrust -------

TABLES 

78. Uses and consumption of mercury in the United 

States ----------------------------------- 79. Mercury produced in the United States ------

80. Mercury supply and demand in the United 

States ----------------------------------- 81. Mercury content of various natural subs·tances_ 

82. Identified mercury resources of the world ----

83. Identified mercury resources of the United 

States -----------------------------------

Page 

401 

401 

402 

402 

402 

402 

403 

405 

405 

405 

405 

40·7 

409 

409 

409 

411 

411 

413 

Page 

404 

406 

410 

412 

Page 

402 

403 

405 

407 

409 

409 

ABSTRACT OF CONCLUSIONS 

Mercury has several thousand uses, for many of which no 

substitution is practical or desirable. The annual world production is nearly 300,000 flasks (76 lb each), and the U.S. 

production in recent years has been less than one-tenth of 

this amount. In contrast, the United States, to supply its industrial base, has required about one-third of the world production. 

In the past few years in the United States, concern over 

mercury poisoning and pollution has led to legal restrictions, 

reduced consumption, drastic drop in the price of mercury, 

and closing of most mercury mines. The geologic outlook for 

new domestic discoveries of ores rich enough to be competitive in the world market is poor, although there is some 

possibility in the less explored parts of southwest Alaska. 

Correlation of occurrences with elements of the "new global 

tectonic" framework suggests that areas of the Southwest 

Pacific will be found to contain undiscovered deposits. 

Additional domestic research is needed to determine the 

quantity and mode of occurrence of mercury in the lithosphere, how mercury migrates under geologic processes, how 

mercury is converted to the highly toxic organic compounds, 

what are tolerance levels, and how to eliminate or inactivate 

mercury in already polluted areas. Other research directed 

toward recovery of mercury from mine and plant wastes 

would benefit the environment and add to the supply needed 

by the United States. 

INTRODUCTION 

Mercury is the only metallic element that at ordinary temperatures is a fluid, which together with 

its silvery color has led to its being commonly called 

quicksilver. It has many uses, most of which are 

for technologically advanced applications, and therefore it is in greatest demand in the most industrialized countries. The United States years ago 

produced more than enough mercury to supply its 

needs, but now it consumes one-third of the world 

production while producing less than one-tenth of 

the world supply.1 Much of the U.S. requirement is 

met by imports, but the total dollar value of the 

U.S. mercury consumption is relatively small, 

amounting to $40 million in 1969 and only $15 

1 All statistical data regarding production and consumption for the 

period since 1932 are from records compiled by the U. S. Bureau of 

Mines. 

U.S. GEOL. SURVEY PROF. PAPER 820 

401 
UNITED STATES MINERAL RESOURCES 

million in 1971. When this report was prepared in 

mid-1972, all major mercury mines in the United 

States had drastically curtailed or ceased production because of the low price of mercury brought 

about by concern over mercury pollution. 

USES 

In addition to being fluid at normal temperatures, 

mercury possesses a unique combination of properties, such as high surface tension, linear thermal 

ex~~nsion, good electrical conductivity, high density, 

ability to alloy readily, and tendency to form very 

toxic compounds. These properties make mercury 

useful in a great variety of processes and products. 

Some uses, such as in thermometers or mercury 

switches, require minute amounts in each apparatus, 

but ?thers, such as in chlorine-caustic soda plants, 

require several tons. Amounts and trends by categories are shown in table 78. Note that the two 

largest uses, electrical apparatus (mostly batteries) 

and catalysts (chlorine manufacture), together have 

accounted for about half the U.S. consumption in 

recent years, and uses dependent on the toxicity of 

mercury compounds have amounted to another quarter of the consumption. For a detailed review of 

uses and projected trends for the United States, 

see reports by the National Research Council ( 1969) 

and by Greenspoon ( 1970). 

Metallic mercury of 99.9-percent purity is generally recovered by a distillation process at the 

mine site, and it is bottled and marketed directly in 

standard steel flasks containing 76 pounds (about 

2.5 liters or 2. 7 quarts) of the liquid metal. For 

some uses, it is redistilled to achieve greater purity 

and redistributed in glass, plastic, or earthenware 

bottles containing from 4 ounces to 10 pounds. 

Mercurial compounds are nowhere made at the mine 

but are manufactured from refined mercury metal. 

TABLE 78.-Uses and consumption of mercury in the United 

States 

[Thousands of flasks} 

Agriculture (germicides fungicides 

A~~~~~i~n-(~~j~;~~~-b~f~;;~19-00) _______ _ 

Cauuys~: ------

Chlor.ine-caustic soda (started 1937) ------ Plastics, res~ns, acetic acid, other chemicalsDental preparations ----- __ Electrical apparatus (mostJy -b~t;ri~T------

Felt manufacture (none since 1943) --------- Instruments, industrial, control ------------

i~~~rc!:~·bl:!u~:cap~-(~~~;-si~;;-i956) ____ _ 

Pa!nt, a~tifouling (mostly ship bottoms) -=== 

Pamt, mildew proofing Paper and pulp manufact;;_;;-(~i~icid;)-----­

Pharmaceuticals ----- ----- Vermilion (none since 1944)----------------

0ther, concealed, unknown _::::=.::=.:=.::::: 

Total 

1942 1951 1970 1971 

1.5 7.7 

.2 .2 

.5 1.5 

3.3 2.6 

2.1 1.6 

5.5 13.2 • 2 0 6.6 10.4 

.3 .5 

7.8 .5 1.2 2.5 

0 0 

0 0 

8.1 2.8 .2 0 2 12.2 13.3 

1.8 1 1.5 .2 0 

15.0 12.3 

2.2 1.1 

2.3 2.4 

16.0 16.9 

0 0 

4.8 4 

1.8 .18 0 0 

.2 .4 

10.1 8.2 

.2 .002 

.7 .7 

0 0 2 6.3 2.3 

49.7 56.8 61.5 52.5 

~ Includes ~ungicid~ and bactericides for industrial use. Includes mstallation and expansion of chlorine-caustic -s~ )llmfa. 

Substitutes for mercury have been found in many 

formerly important mercury uses, and very little 

mercury is now used for amalgamation (largest use 

in 1870's), antisyphilitics (largest use in 1917), 

munitions, detonators (fulminate), felt manufacture, pattern making, paper manufacture, vermilion, 

fireworks, and cosmetics. In some other major uses, 

substitutes could be used but would result in sacrificing quality of the product or economy of manufacture, or both. For example, in the manufacture 

of chlorine-caustic soda, a diaphragm cell can be 

used instead of the mercury electrolytic cell, but it 

yields a product of lower purity at a higher cost, 

which ultimately affects the price of nylon, rayon, 

petroleum products, aluminum, detergents, and 

many other consumer items. However, for many 

uses, such as batteries, mercury lamps, wall 

switches, thermostats, barometers, manometers, 

thermometers, pressure gages, and laboratory uses, 

substitution is impractical and undesirable. For 

agricultural uses and paint, substitution may in the 

future be practical as nonmercurial germicides and 

fungicides having selective toxicity are discovered. 

SIZE AND IMPORTANCE OF THE INDUSTRY 

World production of mercury reached an all-time 

high in 1969 of 290,000 flasks, valued at about $159 

million. U.S. mercury production in the same year 

was 29,640 flasks, valued at about $15 million, or 

0.02 percent of the $7.2 billion of national income 

generated by mining. The importance of the mercury 

industry, however, outweighs its relative size. About 

300 U.S. companies use primary mercury, and another 400 that use redistilled mercury account for 

about 20 percent of the total U.S. consumption. Almost everyone safely uses a little mercury every 

day, and without it we would be forced to use inferior products made at increased cost. It is classified by the U.S. Government as a strategic commodity, essential to the economy. Financial assistance in 

exploration for new mercury deposits is provided 

by the Government through the U.S. Geological Survey, Office of Mineral~ Exploration. Of the 36 eligible commodities, mercury is one of nine eligible for 

assistance of 75 percent of the allowable costs of 

exploration, as compared with 50 percent for the 

others . 

EXPLOITATION 

MINING 

By most mining standards, mercury mines are 

all small. The largest probably is the New Almaden 

mine in California, where about 30 miles of horizontal underground workings were driven for ex-
MERCURY 

ploration or development over a hundred-year period. To avoid high labor costs, in the past 30 years 

a diligent search has been made in the UnitEd States 

for large low-grade surficial deposits, but the only 

really major deposit that has been mined ·by openpit methods is tmat of the Sulphur Bank ntine also 

in California, which was discovered 100 yenrs ago. 

Mining and recovery costs at mercury mines vary 

so widely that averages seriously oversim]plify the 

picture. At open-pit mines, ore containing :~pounds 

of mercury per ton ($5 per ton in 1963) has been 

successfully treated, but concurrently some underground mines have lost money on ore conbl~ining 10 

pounds per ton. In 1970 the Quinn River mine (formerly Cordero) in Nevada closed when the price 

fell below $425 a flask, and in 1972 the ma.j or New 

Idria mine in California was closed when the price 

fell below $160 a flask. For compJ~,rative ])urposes, 

the best guides to costs are price-production curves 

(fig. 46). At any given price, some mines lose 

money, others break even, and only a few make a 

profit. Average costs generally approach average 

prices within a few percent. 

PRODUCTION 

Total world production during this century has 

ranged from 65,000 flasks in 1933 to 290,000 flasks 

in 1969 (fig. 46). Probably nearly 1,000 mines ir. 

the world have each produced more than 1.00 flasks 

of mercury, but three-fourths of the world production has come from only six mines or distJricts. 

Domestic primary production fluctuates wildly in 

response to short-term variations of a few hundred 

percent in price. The peak U.S. production, almost 

80,000 flasks, was in 1877. Since then, the domestic 

industry has undergone a half dozen cycles of stimulated production, in response to higher prices, followed by collapse, on the heels of lower prices. By 

1943, under war-time conditions, production had 

risen from the less than 10,000 flasks produced 10 

years before to almost 52,000 flasks. By 1950, production had again dropped, to a new low of 5,000 

flasks. After another cycle, production rose in 1969 

to 29,000 flasks in response to all-time high prices. 

Our production through the years has come from 

over 300 mines in 11 States (table 79); however, 

just as is true for world production, three-fourths 

of the domestic output has come from six mines, 

all of which are in California. 

The U.S. proportion of world production, with 

generally rising demand, has declined from more 

than 60 percent in 1877 to less than 3 percent in 

1950 and 6 percent in 1971. The proportion of U.S. 

consumption coming from domestic mines reached 

a low of 9 percent in 1950 but rose to 33 percent in 

1971. This seeming improvement, however, is the 

result of temporary curtailment of consumption because of pollution problems and does not reflect 

increased production. 

Secondary production of mercury in the United 

States, first reported in 1946, has become increasingly important in helping to make up the difference between U.S. requirements and mine production. Most of the mercury reclaimed is from electrolytic cells, mercury boilers, discarded inP.truments, 

battery scrap, dental amalgam, and electrolytic, 

oxide, and acetate sludges. Secondary recovery is 

made by six processors and four scrap dealers in 

TABLE 79.-Mere?A:ry produced in the United States, by States 

[nub of 76 lbl 

State 

Primary (from mines) : 

AJaska ---------------- Arizona ---------------

Arkanaaa -------------- California -------------

Idaho ----------------- Nevada ---------------- New York ------------

Oregon ---------------- Texas ----------------- Utah ----------------- Washincton -----------

l'int 

production 

1928 

1908 

1981 

1860 

1917 

1903 

196! 

1870's 

1899 

Earl3• 1880's 

1916 

Total primary -------------··-----

Annual number of produeina 

mines --------------------··----- Annual averacea of mercury 

recovered (lb per ton of ore) ··-----

Secondary ---------------- 1946 

1860-1949 

4,650 

6,034 

11,404 

2,623,873 

14.731 

72,996 

89,284 

146,666 

3,497 

6,604 

2,978,727 

1-197 

735-4.9 

11,055! 

1960-69 

16,919 

819 

1fo:793 

14,268 

46,245 

13;629 

1,552 

20 

196o-69 

14,151 

1,43! 

350 

163,042 

7,927 

54,422 

280 

4,779 

1,885 

----~, 

204,235 248,309 

16-147 48-149 

9.3-6.4 13.6-4.1 

47,430 •94,459 

1 Alaska, Arkanaaa, Texas, and We.ahineton, 2,454 ftaaka in 1970. 2 AJaska, Arkansas, New York, ONcon, and Texas, 1,748 ftaaka in 1971. • Includes GSA releases 1963-71. 

1970 

(1) 

-{i)-

18,693 1,038 

4,909 

28 

274 

(1) 

-(i)-

27,296 

79 

4.8 

1971 

17,627 

60 

a 8,051 a 16,666 
UNITED STATES MINERAL RESOURCES 

PRODUCTION, IN FLASKS OF 76 POUNDS MAJOR DETERMINANTS, U.S. 

PRODUCTION (EXCEPT PRICE) 

0 50,000 100,000 150,000 200,000 250,000 300,000 1850r---~--~--~----~--~--~--~--~----~--~------~ New Almaden-first U.S. production 

1890 

1910 

1920 

1940 

1950 

New ldria discovered 

New Almaden closed-litigation 

Avg. mining cost per ton of ore, $170 

Avg. grade of ore, 279 lb per ton 

New Almaden deep ore discovered 

Scott furnace invented 

Avg. grade of ore, 47 lb per ton 

New Almaden "almost exhausted" 

Avg. mining cost per ton of ore, $9 

Tex.s-flrst production 

Nevada-first production 

United States becomes 

a net importer of mercury 

Herreshoff furnace adopted 

Oregon-first sustained production 

Rotary furnace successful 

New ldria closed-litigation 

Avg. grade of ore, 10 lb per ton 

Arkansas-first production 

The only years when production 

was reported from all 1 0 states 

Avg. mining cost per ton of ore, $13 

Secondary production reported 

Index of metal-mining expenses, 74 

Secondary production increased 

Index of metal-mining expenses, 100 

{Government assistance, exploration 

J Avg. o•ade of o.e. 7.6 lb pe• ton 

Index of metal-mining expenses, 114 

Avg. grade of ore, 4.8 lb per ton 

1980 ~--~--1~o~o--~---2~o~o--~---300~--~---40~o--~---so~o---L---so~o 

AVERAGE ANNUAL U.S. PRICE PER FLASK, IN CURRENT DOLLARS 

FIGURE 46.-Mereury production and prU:es, 1850-1971. From U.S. Bureau of Mines Minerals Yearbooks. 
MERCURY 

TABLE 80.-Mercury supply and demand in the United States 

[Thousands of flasks] 

185o-1949 1950-59 196H9 1970 1971 

Mine production (started 1850) ------------- 2,979 204 248 27.3 17.6 

Secondary production (started 1946) --------- 47 1 94 1 8.1 216.7 

21.7 29.7 Imports (started 1868) ---------------------_____ 50_5 ___ 2_31 ______ _ 

57.1 64.0 Total supply ------------------------- =====75=6===5=73======= 

61.5 52.5 

4.7 27.2 Consumption (no record before 1867) __ ------- 515 7g~ 

Exports (started 1864) ---------------------______ 7 _________ _ 

66.2 59.7 Total demand ------------------------=====52=2===7=20======== 

Surplus or deficit --------------·------- 234 -147 -9.1 4.3 

1 Includes GSA sales of 72,366 flasks ill 1965-69 and 701 flasks in 1970. 2 Includes GSA exports of 5,700 flasks to AID. 

the United States. Official figures compiled by the 

U.S. Bureau of Mines (table 80) are smnewhat 

confusing because sales and releases of primary 

mercury from the Government stockpile by the General Services Administration are included under 

secondary recovery. In 1964 these releases included 

7,000 flasks to other Government agencies and 

10,000 flasks to the Department of Health, Education, and Welfare for donation to more than 3,000 

hospitals and schools. In 1971 there were no GSA 

sales, but 5, 700 flasks were transferred to the 

Agency for International Development for shipment 

to India. 

PRICES AND TARIFFS 

The U.S. price has averaged as low as $28.56 a 

flask, in 1883, and as high as $570.75, in 1965 ; but 

it reached an intraweekly all-time high of lp775 on 

July 1, 1965 (fig. 46). When this report was prepared in mid-1972, the price was only $165 n flask. 

The world (London) price is generally lower 

than the New York price by roughly the atlllount of 

the U.S. tariff, but monthly averages range from 

about $80 lower to $35 higher. 

There are no special federal taxes on tnercury 

production, although some States impose a tax on 

the proceeds of all mines. An import tariff of $19 

per flask in effect since 1922 was reduced to $15.20 

on January 1, 1969, to $12.92 on January l, 1970, 

and to $11.40 on January 1, 1971. A deple:tion allowance for new domestic discoveries of 15 percent 

since 1932 was increased to 23 percent under the 

Internal Revenue Code of 1954 and has continued 

through 1971. The allowance is limited to 50 percent of net income. 

OUTLOOK 

Until just before World War I the United States 

produced more mercury than it consumed (fig. 47). 

Ever since, it has relied to greater or le~ser degree 

on imports to supplement domestic mine production, 

except during the World War II period, when, with 

high prices and some Government support, domestic 

mines virtually :filled the U.S. requirements. It has 

been generally felt that if the price of mercury were 

high enough, United States mining could supply all 

domestic needs, although production response to the 

increased price would lag 2-4 years behind the price 

increase. In 1965 the price rose to unprecedented 

levels, but the mine production response peaked in 

1969 at about 29,000 flasks, which was only onethird of the domestic consumption. It has become 

obvious that, as predicted (Bailey and Smith, 1964), 

the U.S. supply of known, or even suspected, mercury ore of grade competitive on the world market 

is entirely inadequate to meet domestic needs. The 

current outlook for discovery of large high-grade 

deposits in the conterminous United States is unpromising, but in less explored southwestern Alaska 

major discoveries may be possible. 

As a result of concern about pollution, the demand for mercury in the United States has diminished considerably, but concurrently the price has 

fallen so low that domestic mine production will 

not supply even the reduced demand. 

Until higher grade foreign deposits are depleted-which, it is estimated, will not be for at 

least 25 more years at Almaden, Spain-the United 

States will remain a net importer of mercury, owing to the low grade of ore available and the relatively high cost of mining it. However, the maintenance of some domestic industry, even if for no 

other reason than to provide a bargaining base, is 

highly desirable. 

GEOLOGIC ENVIRONMENT 

BASIC GEOCHEMISTRY 

A little mercury occurs in almost all natural substances-rocks, soils, water, air, and both animal 

and vegetable organisms-but analytical techniques 

sufficiently sensitive to measure the minute amounts 

involved have been perfected only recently. AI-
1860 

1870 

1880 

1890 

1900 

1910 

1920 

1930 

1940 

1950 

1960 

1970 

UNITED S·TATES MINERAL RESOURCES 

PRODUCTION, IN FLASKS OF 76 POUNDS 

20,000 40,000 60.000 80,000 

Total domestic supply ..._ __ ....... (includes secondary 

production 1946-71, 

General Services 

Administration 

releases1963-71) 

MAJOR DETERMINANTS 

OF DEMAND 

Civil War 

Hydraulic gold mining, California 

Silver mining, Nevada 

Mercury-vapor lamp invented 

World War I 

Postwar depression 

Mercury boiler invented 

Industrial expansion 

World depression 

Electrolytic cell developed 

(Chlorine-caustic soda) 

World War II 

Mercury dry cell developed 

Korean War 

Atomic power plants started 

Strategic stockpile 

Electrical apparatus, 

chlorine-caustic soda 

} 

Chlorine-caustic soda, new plants 

Pollution regulations 

FIGURE 47.-Dern.and and domestic supply of mercury in the United States, 1850-1971. From U.S. Bureau of Mines Minerals 

Yearbooks. 
MERCURY 

though there is much variation, typical amounts 

can be given (table 81). 

The average mercury content of continenUl~l rocks 

has been calculated at about 80 ppb (parts per billion) (Taylor, 1964), and a similar figure was calculated for the earth's crust (Saukov, 1946). More 

recent work (Ehmann and Lovering, 196~') suggests that these values may be a little too large, but 

they are certainly the right order of magnitude. In 

contrast, the content of a minable mercury ore deposit must be at least 2 pounds to the ton, or 

1,000,000 ppb (0.1 percent), representing a mercury concentration 10,000 times greater than the 

usual content of most rocks. 

For additional details regarding the occurrence 

of mercury compounds in nature and their behavior during the weathering cycle, see Tunell 

(1970). 

TABLE 81.-Mercury content of various natural substances 

[Most data from U.S. Geol. Survey (1970)] 

Igneous rocks: 

Peridotite, dunite, basalt ----------- Andesite, granite ------------------- Sedimentary rocks: 

Sandstone -------------------------- Shale ------------------------------ Limestone _ --_----------------------

Coal ------------------------------- Metamorphic rocks ---------------------

Soil ------------------------------------ Natural fluids: 

Itain lVater ------------------------- River lV&ter ------------------------ Ocean lVater ------------------------ Petroleum -------------------------- Air -------------------------------- Organisms: 

Plants -----------------------------

Fish ------------------------------- Mammals --------------------------

ORE DEPOSITS 

Parts JM!l' billion 

5 - 20 

15 - 100 

20 - 75 

100 - 1,000 

15 - 50 

10 - 1,000 

20 - 200 

10 - 100 

.Jl 

.03- 1 

2,000 -20,000 

.01 

<500 

20 - 200 

<20 

All major mercury deposits are mined for their 

mercury content alone, and all contain the red mercuric sulfide, cinnabar, as the chief ore 1nineral. 

Liquid mercury metal and a black mercuric sulfide, 

metacinnabar, are locally of some econornic importance, and in one medium-size deposit a tnercuryantimony sulfide, livingstonite, was the main ore 

mineral. The more than a dozen other knovm mercury minerals are relatively rare and inconsequential as sources of mercury. 

Within the past few years, mercury has b~n produced as a byproduct at the Gortdrum copper mine 

in Ireland (1,300 flasks per yr), the Rudnalrly zinccopper mine in Czechoslovakia (1,000 flasks per yr), 

and the Carlin gold mine in Nevada ( 60 fl~~sks per 

yr) . Cinnabar has been identified at all of these 

deposits, but other minerals probably also contain 

small amounts of mercury. The St. Joe Minerals 

Corp. smelter in Monaca, Pa., also recovers mercury (300 flasks per yr) from zinc concentrates 

from deposits in New York, but the mercurybearing mineral is unknown. 

Silica and carbonate minerals are the common 

introduced gangue minerals in mercury deposits, 

but pyrite and marcasite may be abundant in deposits formed in iron-bearing rocks. Stibnite is rare 

but is more common than orpiment. Other metals, 

such as gold, silver, or base metals, are generally 

present in only trace amounts. An exception, however, is a base-metal assemblage containing mercurian tetrahedrite, from which mercury has been 

recovered in a few places. 

The ore-forming mercury minerals, and introduced gangue minerals, are deposited from hot solutions at temperatures from perhaps 50°C to 200°C, 

and they thus form relatively low-temperature, epithermal deposits (White, 1967; Tunell, 1970). The 

deposits are characteristically shallow, and in the 

United States only half a dozen have been mined at 

depths greater than 1,000 feet. Even in the major 

mercury deposits of the world, ores have not been 

mined more than about 2,000 feet below the surface, although at the largest, the rich Almaden mine 

in Spain, ore is reported to have been drilled at 

depths of 3,000 feet. The greatest depth at which 

cinnabar has been found is reported to be 5,900 

feet, in a well drilled for geothermal steam in the 

Geyser area, Sonoma County, Calif. (G. H. Gaul, 

written commun., Feb. 22, 1969). 

Mercury ore deposits have doubtless been formed 

throughout geologic time; but owing to their shallowness, those deposited long ago have been either 

eroded away or covered over so they cannot be seen. 

Very young deposits, still uneroded and uncovered, 

constitute the discoverable and minable ore bodies. 

Because they were deposited in preexisting rocks, 

almost any kind of rock might be the host, though 

some varieties have unusually favorable chemical or 

physical properties. However, the distribution of 

mercury deposits about the world is restricted because the volcanic and tectonic activity responsible 

for generating the heated pregnant solutions that 

deposited the mercury has in recent time taken 

place only in limited belts (Bailey, 1959). One 

highly productive belt extends northward along the 

western part of South and North America, passes 

through central Alaska, extends southward through 

Japan, then turns westward across central China 

and through the southern part of the Soviet Union 

and Europe. Other shorter and much less productive 

belts extend from New Zealand up through Papua-
- UNITED STATES MINERAL RESOURCES 

New Guinea and along the Indonesia-Sumatra arc. 

(See fig. 48). Although the deposits are in belts of 

volcanic activity, many major ore bodies are remote 

from any young volcanic rocks. 

The six most productive mines or districts, and 

their approximate production, are: 

Almaden, Spain -------------------- ldria, Yugoslavia ------------------- Monte Amiata, Italy ---------------- Santa Barbara, Peru --------------- New Almaden, Calif ---------------- New Idria, Calif -------------------

Flasks 

7,500,000 

3,000,000 

2,000,000 

1,500,000 

1,100,000 

600,000 

Very brief descriptions of the geology of these 

most important deposits will serve to show the diversity of occurrence that characterizes mercury 

deposits. 

The famous Almaden mine, which has yielded 

about one-third of the world production, is in an 

area of folded and faulted shale, limestone, and 

quartzite of Ordovician to Devonian age (Mamen, 

1971). Igneous rocks are represented in the mine 

area by narrow diabase dikes; the nearest major 

intrusive is a granite batholith 25 kilometers away. 

The ore bodies occur in three parallel vertical 

quartzite beds that from the surface to a depth of 

at least 750 meters are extensively replaced by cinnabar and locally impregnated with native mercury. 

The most productive bed is 30 feet thick, and a 

central zone about 10 feet thick contains in some 

places more than 10 percent mercury. The minable 

strike length is over 1,000 feet on the 17th level. 

Average grade of ore treated is about 2 percent. 

The ldria mine in northwestern Yugoslavia lies 

in a thick sequence of sedimentary rocks ranging 

in age from Carboniferous to Eocene and occurring 

in four superposed thrust sheets (Mlakar, 1964). 

Most of the ore is formed by cinnabar that has replaced Permian and Triassic dolomite, but some 

occurs in shale or sandstone. Individual ore bodies 

are large, many having a plan area of over 20,000 

square feet and extending through a vertical interval of 200 feet. Ore has been mined to a depth of 

1,300 feet. In recent years, an ingenious solution of 

a fault problem led to the discovery of a wholly new 

major ore zone offset 2 miles from that which has 

been mined for the past 450 years. Because only 

sparse native mercury occurred in the uppermost 

thrust plate and rich cinnabar occurred in the plate 

below, it has been suggested that the ore was formed 

in Triassic time, before the thrust faulting, and 

thereafter was protected from erosion by being covered by the overthrust plate. The near-surface native mercury is believed to be the result of postore 

and postthrust upward migration of vapor from the 

main ore body. The grade of ore processed ranges 

from 0.1 to 0.2 percent. 

The major mine of the Monte Amiata district, 

central Italy, is the San Salvatore, which is on the 

lower slopes of Monte Amiata volcano (Eckel, 1948). 

The rocks below the lava are much deformed and 

broken beds of Eocene limestone and shale. Ore 

bodies of detrital cinnabar occur in curious solution caves in limestone, which are widest just beneath the lava and taper downward to narrow roots 

several hundred feet below the contact. The ore 

bodies were formed by rising hot solutions that first 

deposited cinnabar just below the contact and later 

dissolved the limestone, releasing the cinnabar to 

accumulate in the caves. Other, deeper primary ore 

bodies consist of cinnabar coatings on broken limestone and shale. The grade of ore treated is about 

0.4 percent. 

The Santa Barbara mine, high in the Andes near 

Huancavelica, Peru, once rivaled Almaden, Spain, 

in production but has had only minor production in 

the past century. Mesozoic limestone, sandstone, and 

shale are overlain by a great pile of Tertiary volcanic rocks and intruded by volcanic breccia. Tabular ore bodies occurred through a depth range of 

about 1,000 feet in places where cinnabar filled pore 

spaces or fractures in sandstone or voids in volcanic breccia. The average grade was about 2 percent, though ore mined in recent years is much 

leaner. 

The New Almaden mine in California (Bailey and 

Everhart, 1964) is the greatest mercury producer 

in North America, but most of its yield came prior 

to World War I. In the mine area, folded and faulted 

Mesozoic eugeosynclinal sedimentary and volcanic 

rocks are intruded by serpentine, which in Tertiary 

time was altered along its margins to silicacarbonate rock. Rich ore occurs where silicacarbonate rock was replaced by cinnabar along steep 

parallel fractures, and large ore bodies were found 

from the surface to depths of about 2,000 feet. The 

grade of all ore recovered through the life of the 

mine is about 4 percent. 

The New Idria mine in central California (Linn, 

1968) is the second most productive mercury mine 

in North America and was a major producer until 

the spring of 1972. The mine is near the northern 

margin of a pluglike mass of serpentine that has 

arched upward and pierced through a thick Cretaceous shale-sandstone sequence. Steeply dipping 

shale near the serpentine has been rendered brittle 

through induration, and subsequently shattered. 

Most ore bodies occur where cinnabar alone fills the 

fractures or coats their walls, but some cinnabar and 
MERCURY 

metacinnabar occur in thick carbonate veins. The 

largest ore shoot in shale was 300 feet long, 25-

150 feet wide, and 800 feet high. Ore mined. in the 

early days contained 10 percent cinnabar, hut for 

the past 30 years, mined ore has averaged less than 

1 percent. 

These deposits have in common cinnabar as the 

major ore mineral and comparatively shallow depth, 

but little else. Some are in sedimentary roc]<s such 

as limestone, quartzite, or shale, and some are in 

volcanic breccia or altered serpentine. Some: major 

ore bodies have been formed by replacement,, others 

by open-space filling, and others by both, an.d some 

are a result of detrital concentration. The thousand 

or so smaller deposits not described in this report 

likewise show a diversity of mineralization, host 

rocks, rock alteration, and structural locali:~ation. 

RESOURCES 

IDENTIFIED RESOURCES 

At most mercury mines, no effort has been made 

to ascertain the ultimate reserve of the deposit in 

advance of exploitation, and at few mines is enough 

ore blocked out for more than 1 year of op~~ration. 

Major exceptions are at some of the larger foreign 

deposits, such as Almaden or ldria, but even at these 

no attempt is made to learn in advance the complete 

resource. In the Soviet Union, much effort is expended in trying to determine the ultimate reserves 

before mining, with only indifferent success for 

mercury deposits, but all reserve figures are closely 

guarded. Hence, no one knows the total resE:rves or 

resources of the major mercury deposits of the 

world, and only estimates based on product:[on records and familiarity with the geologic habitB of the 

ore can be made. On this basis, we have estimated 

the resources of known areas by countrie8 or by 

groups of countries (table 82). 

TABLE 82.-Identified mercury resources of the u·orld J 

[Given in thousands of flasks in ore minable at price per flask mdicated] 

United States --------------

Canada --------------------- !dexico --------------------- South America -------------""' 

Spain ---------------------- Italy ----------------------- Yugoslavia ----------------- Czechoslovakia -------------- Africa ---------------------- Japan ----------------------

Turkey --------------------- Philippines -----------------

U.S.S.R. -------------------- Communist China -----------

Total -----------------

$400 $1,t)00 

170 

200 

300 

50 

2,500 

750 

1,000 

15 

30 

60 

60 

50 

1,000 

1,000 

7,185 

•l90 

•lOO 

'700 

:JOO 

6,1)00 

2,noo 

2,000 

30 

60 

:wo 

:~00 

~00 

3,·~00 

1,500 

17,[)80 

1 Identified resources: Specific, identified mineral deposits tltat may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may not be profitably recoverable with existing technology and 

economic conditions. 

Estimates by States, made on a similar basis but 

with greater familiarity with the deposits, are given 

in table 83. 

TABLE 83.-ldentified merc.ury resou.rces o.f the United States, 

by States J 

[Given in thousands of flasks in ore minable at price per flask indicated] 

Alaska --------------------- Arizona ___ ---------------_-

Arkansas ------------------- Califomia ------------------

Idaho ---------------------- Nevada --------------------- New York-------------------

Oregon ---------------------

Texas ---------------------- Utah ----------------------- VVashington -----------------

Total -----------------

$400 

25 

1 

100 

10 

20 

5 

5 

4 

170 

$1,000 

100 

6 

1 

300 

25 

30 

5 

10 

10 

1 

2 

490 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may not be profitably recoverable with existing technology and 

economic conditions. 

A word of caution seems required in the use of 

these numbers, especially those for the United 

States. Although these estimates are for ore i~ 

known ore-bearing areas, they do not represent 

known ore. At $400 a flask, even if the ore were 

minable once it had been found, the cost of finding 

it might be excessive. Thus, while U.S. mines offer 

a potential at this price, few will be reopened or 

explored by other means until the price is higher or 

is expected to go higher. For other estimates of 

resources at various prices, see U.S. Bureau of Mines 

(1965). 

SPECULATIVE RESOURCES 

Masses of rock containing concentrations of mercury rich enough and large enough to form minable, 

or even near-minable, ore deposits are exceedingly 

rare. The surface area underlain by known mercury 

ore throughout the world probably does not exceed 

50 square kilometers, which is about one threemillionth, or 0.00003 percent, of the earth's land 

area. In considering the mercury potential of the 

world, or in the search for new mineralized areas, 

the economic geologist concerns himself with the 

question of what parts of the remaining 99.99997 

percent might be underlain by mercury ore. We expect we are searching for places comparable in size 

to known ore bodies, which in proportion are even 

smaller than the proverbial needle in a haystack. 

Origin and geologic occurrence of known deposits 

provide the best clues about where to look and the 

best data for predicting the potential of unexplored 

areas. 

During the past century, geologists , noting the 

global distribution of mercury deposits about the 

Pacific, with a branch extending westward from 
20" o· 

o·1- I 

20"1 \ I 

20" 40" 60" so• 100" 120" 140° 160" 180" 160" 140° 120" 100" 

...._, ~ J...._ ,~~:~;,;-__ ' ,..._ 

• [ ' ] •·•·•• '' ?['Z: I \ I ¥-. ·dllt'l~l I I• I I l ,_ -·"•'·"·······:•::::·~·····:'''''':~ I 

\.••••J.''':i"i,.-1 J..,,.,, - I \ I I .Kt:'''''''':'':?''''lt~'] __ - I'"~ '!1" ·::)· I :··p . I I 1 ucuuaaal \Wf~'''~'''l'}'X?k'::• 

---- ...____ ' . -

" 

TECTONIC SYMBOLS EXPLANATION 

--i- Spreading axis and transform fault 

'--'--1 Subduction zone. Hachures on overthrust side 

Plate margin of uncertain character 

. 

MERCURY DEPOSITS 

~ Belt of productive deposits 

A Major deposit mentioned in text 

e Productive deposit 

X Small deposit or occurrence 

FIGURE 48.-Relation of mercury deposita of the world to pos.~Jurassic subduction zones. 

I -..-·:;:;:~:;:~~::. 

''"""'I 

I 

• .... 

0 

c:: 

z 

~ 

1-3 

l;l;2 

t::l 

rJl 

1-3 

> 1-3 

l;l;2 

00 

tl: 

~ 

z 

l;l;2 

~ 

> 

~ 

~ 

l;l;2 

00 

0 

c:: 

~ 

n 

lllj 

00 
MERCURY 411 

southern China through sQUthern U.S.S.R. to the 

Alpine belt of southern Europe (Bailey, 195!l'), have 

correlated their distribution with a general 'l'ertiary 

belt of volcanoes referred to as the "belt of fire." 

In the past 6 years, geologists have recognized the 

relation of major tectonism and volcanism to moving crustal pl~tes and have developed the revolutionary "new global tectonics" (Heirtzlt~r and 

others, 1968; LePichon, 1968). Comparison of the 

occurrence of mercury deposits with the new global 

elements (fig. 48) shows that most deposits occur 

on the continentward side of post-Jurassic subduction zones. Especially, they are localized where 

oceanic crust and its accompanying trough deposits 

are swept downward beneath the margins of blocks 

of continental crust. This suggests that the mercury originally contained in the marginal eugeosynclinal sediments, or perhaps even in oceanic 

crustal material, has been distilled out of the 

downward-plunging plate and emplaced at a higher, 

cooler level along or above the subduction zone. 

Additional search in the less explored partf:~ of the 

world lying close to such subduction zones, such as 

in Indonesia, on Kamchatka, or in the Papua-Fiji 

belt, should find entirely new mercury districts. 

In the main mercury belt of the United States, 

which trends through the California Coast Ranges 

and has yielded 85 percent of the U.S. production, 

global tectonic relations also apply in a striking and 

significant fashion. As shown in figure 49, virtually 

all the productive deposits lie close t;o, and generally just below, the Coast Range thrust, which is 

a major late Mesozoic subduction zone (Bailey and 

others, 1970). This major structure provides an 

unusually fine guide to where to look for m~()re ore, 

but through the past 100 years, the part of California indicated to be most favorable has been so 

well explored that the discovery of new tnercury 

deposits of significant size cannot be expectEd. 

The use of principles of global tectonics indicates 

areas to be explored for new mercury deposits, and 

new ones will probably be found along the f~~vorable 

belts. Considering the rate of discovery of the past 

100 years, it seems likely that even with better 

geologic guides and exploration techniques, the 

amount of mercury discovered in new districts will 

not equal the amount consumed. Most of the undiscovered resources will come from new ore bodies to 

be found in districts now being exploited. 

PROSPECTING TECHNIQUES 

The most widely used, and most successful, prospecting technique has been simple panning of stream 

sediments or slope debris. Most standard geophysical 

methods have been tried, but they do not seem to 

be generally applicable to the search for mercury 

deposits. In recent years, various geochemical exploration techniques have been used with some success. Stream sediment sampling has been done by 

Clark and others ( 1970a, b, c, and 1971), and soil 

sampling has been widely used. Shacklette (1965) 

has applied geobotanical methods, and McCarthy, 

Vaughn, Learned, and Meuschke (1969) have shown 

that determination of mercury vapor in soil or air 

over deposits is useful for locating mercury or some 

base-metal deposits. Recent refinements of methods 

for measuring trace amounts of mercury have made 

geochemical methods of prospecting more reliable 

and useful (Barringer, 1966; Dinnin and Worthing, 

1966; Hinkle and others, 1966; Vaughn, 1967; Manning (1970), Plimmer and Klingebiel, 1971; Weissberg, 1971). 

PROBLEMS FOR RESEARCH 

The immediate problems of mercury supply for 

the United States are chiefly nongeologic. For many 

years the domestic mercury-mining industry has 

had difficulty competing with foreign producers who 

have such rich ores and cheap labor that they can 

undersell U.S. producers, thus closing down U.S. 

mines. Intensive exploration might find a new rich 

ore body in the United States, but the chances of 

such a discovery are small. The problems of utilizing our lower grade ores are well known and need 

no discussion here. However, in the past 5 years a 

new problem has been introduced-that of the undesirable effects of mercury pollution-and much 

research is needed to evaluate properly the degree 

of mercury pollution brought about by industrialization and its effects. 

Both mercury liquid and vapor, as well as nearly 

all compounds of mercury, are toxic; fortunate 

exceptions are the most common ore minerals, the 

mercuric sulfides. Mercury poisoning has been recognized for centuries and has been guarded against 

by both mercury mining and utilizing industries. 

Recently, it has become a concern, partly because 

of public awareness regarding general environmental deterioration, and partly because recent improvements in detection and measurement techniques have for the first time allowed accurate 

determination of low-level mercury contamination. 

In addition, the increased use of mercurial germicides and the more numerous chlorine-caustic soda 

plants discharging mercurial waste into lakes and 

rivers have led to identified cases of mercury poisoning of birds, fishes, and humans (Goldwater, 1971; 

Wallace and others, 1971). 
41Z 

0 

UNITED STATES MINERAL RESOURCES 

EXPLANATION 

Contact 

I ! .... 1 

Coast Range thrust,. a late Mesozoic or early Tertiary subduction zone 

Dotted where concealed. Hachures on overthrust side 

Major strike slip fault or fault 

zone 

Dashed where inferred; dotted 

where concealed 

MERCURY DEPOSITS 

.. 

New 

Major deposit mentioned in text 

Less productive • deposit 

50 100 MILES 

0 50 100 KILOMETERS 

EXPLANATION 

Rocks younger than 

Coast Range thrust 

!•:·:·:·:·:·:·:·:·:·} .......... 

::::::::::::::::::: 

Rocks of Great Valley sequence 

lying above Coast Range thrust 

Eugeosynclinal ( Franciscan) 

rocks lying beneath Coast 

Range thrust 

Older, generally metamorphosed 

rocks and late Mesozoic granitic rocks 

FIGUltE 49.-Relation of mercury deposits of Califomia to the Coast Range thrust. 
MERCURY 413 

In the early 1950's, in Sweden and Finland, population declines of seed-eating birds were traced to 

methyl mercury used as seed dressing for the prevention of plant diseases, and similar declines 

among birds living on fish from waters contaminated 

by methyl mercury were also found. Sweden banned 

the use of mercurials in seed dressing in 1966, and 

the sale of fish from about 40 lakes in 1967. Also, in 

Iraq (1956), West Pakistan (1961) and Guatemala 

( 1963), humans were poisoned by eating seed grain 

treated with mercurial fungicides. 

In Japan, between 1953 and 1960, 110 people were 

poisoned by eating fish from Minamata Bay, which 

was contaminated by methyl mercury in waste 

water from a plastics plant; subsequently, 52 deaths 

were reported. Fishing was prohibited, and mercury 

was eliminated from the discharge. In Niigata, 

Japan, in 1965, five deaths resulted from 26 cases 

of mercury poisoning; the people poisoned had been 

eating fish containing as much as 20 ppm (parts 

per million) mercury as often as three times a day. 

The plant to which discharges were traced was 

closed. 

In the United States in 1969, several members of 

a farm family in Alamagordo, N ~Mex., were poisoned by eating pork from hogs that had been fed 

seed grain treated with a fungicide containing 

mercury. 

In Canada in 1970, walleye pike in Lake St. Clair 

were found to contain as much as 7 ppm mercury. 

The mercury was traced to the discharges from two 

chlor-alkali plants--one at Sarnia, Ontario, and the 

other in Michigan-and commercial fishing in the 

lake was prohibited. In the United States in late 

1970, food testing revealed 0.18 to 2.4 ppm mercury 

in swordfish and as much as 1.12 ppm in 138 samples of canned tuna tested. Both were removed from 

the markets (21fs million cans of tuna), but tuna 

was later declared safe to eat. Subsequently, analyses of seven museum specimens of tuna caught between 1878 and 1909, and of one swordfish caught 

in 1946, showed mercury in about the same amount 

(0.13 to 1.27 ppm) as specimens caught in 1971. 

By mid-1972, the use of 12 pesticides was prohibited, registration of 48 mercury compounds used 

for algaecides, slimicides, and commercial laundering was suspended, and use of 750 other compounds 

was conditionally cancelled. Proposed mercuryemission standards would prohibit the release into 

the atmosphere of more than 5 pounds per 24-hour 

period, which would be difficult for a large mercury 

furnace plant to meet (Federal Register, 1971). 

More research is needed to ascertain the quantities of mercury in various environments-in the lithosphere, the reaction of mercury minerals in the 

weathering and transportation cycle, the formation 

of the easily assimilated toxic organic mercury 

compounds, the distribution of mercury in the biological food chain, and human tolerance levels. 

Other research should be directed toward improved techniques for recovery of mercury not only 

from ores but especially from industrial wastes. 

Such research could simultaneously improve the 

environment and provide some of the mercury 

needed by our highly industrialized society. 

REFERENCES 

Bailey, E. H., 1959, Resources, chap. 3 of Pennington, J. W., 

Mercury-a materials survey: U.S. Bur. Mines Inf. 

Circ. 7941, p. 11-27. 

Bailey, E. H., Blake, M. C., and Jones, D. L., 1970, On-land 

Mesozoic oceanic crust in California, in Geological Survey research 1970: U.S. Geol. Survey Prof. Paper 700-C, 

p. C70-C81. 

Bailey, E. H., and Everhart, D. L., 1964, Geology and quicksilver deposits of the New Almaden district, Santa Clara 

County, California: U.S. Geol. Survey Prof. Paper 360, 

206 p. 

Bailey, E. H., and· Smith, R. M., 1964, Mercury-Its occurrence and economic trends: U.S. Geol. Survey Circ. 496, 

11 p. 

Barringer, A. R., 1966, Interference-free spectrometer for 

high-sensitivity mercury analyses of soils, rocks and 

air: Inst. Mining and Metallurgy Trans., sec. B, v. 75, 

p. B120-B124. 

Clark, A. L., Condon, W. H., Hoare, J. M., and Sorg, D. H., 

1970a, Analyses of rock and stream-sediment samples 

from the Taylor Mountains A-6 and southern part of 

Taylor Mountains B-6 quad•rangles, Alaska: U.S. Geol. 

Survey open-file report. 

--1970b, Analyses of rock and stream-sediment samples 

from the northern part of the Taylor Moun-tains B-6 

quadrangle, Alaska: U.S. Geol. Survey open-file report. 

-- 1970c, Analyses of rock and stream-sediment samples 

from the Taylor Mountains C-8 quadrangle, Alaska: 

U.S. Geol. Survey open-file report. 

Clark, A. L., Sorg, D. H., Condon, W. H., and Hoare, J. M., 

1971, Analyses of stream-sediment samples from the 

Taylor Mountain D-8 quadrangle, Alaska: U.S. Geol. 

Survey open-file report. 

Dinnin, J. I., and Worthing, H. W ., 1966, Determination of 

microquantities of mercury in sulfide ores by Penfield 

tube-dithizone and semiquantitative spectrographic 

methods, in Geological Survey research 1966: U.S. Geol. 

Survey Prof. Paper 550-C, p. C220-C223. 

Eckel, E. B., 1948, Mercury industry in Italy: Am. Inst. 

Mining Engineers Tech. Pub. 2292, p. 285-307; discussion, Am. Inst. Mining Engineers Tech. Pub. 2474, p. 

3-5. 

Ehmann, W. D., and Lovering, J. F., 1967, The abundance 

of mercury in meteorites and rocks by neutron activation analysis: Geoehim. et Cosmochim. Acta, v. 31, p. 

357-376. 

Federal Register, 1971, National emission standards for 

hazardous air pollutants-Proposed Standards for asbestos, beryllium, mercury: Federal Register, v. 36, no. 

234, p. 23239-23256. 
414 UNITED STATES MINERAL RESOURCES 

Goldwater, L. J., 1971, MercU'ry in the environment: Sci. 

Am., v. 224, no. 5, p. 15-21. 

Greenspoon, G. N., 1970, Mercury, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 639-652. 

Heirtzler, J. R., Dickson, G. 0., Herron, E. M., and Pittman, 

W. C., 3d, 1968, Marine magnetic anomalies, geomagnetic field reversals, and motions of the ocean floor and 

continents: Jour. Geophys, Research, v. 73, no. 6, p. 

2119-2136. 

Hinkle, Margaret, Wo Leong, K.am, and Ward, F. N ., 1966, 

Field determination of nanogram quantities of mercury 

in soils and rocks, in Geological Survey research 1966: 

U.S. Geol. Survey Prof. Paper 550-B, p. B135-B137. 

LePichon, Xavier, 1968, Sea-floor spreading and continental 

drift: Jour. Geophys. Research, v. 73, no. 12, p. 3661-

3697. 

Linn, R. K., 1968, New Idria mining district, in Ridge, J. D., 

ed., Ore deposits of the United States, 1933-1967, The 

Graton-Sales volume: New York, Am. Inst. Mining, 

Metall., and Petroleum Engineers, v. 2, p. 1623-1649. 

McCarthy, J. H., Jr., Vaughn, W. W., Leamed, R. E., and 

Meuschke, J. L., 1969, Mercury in soil gas and air-A 

potential tool in mineral exploration: U.S. Geol. Survey 

Circ. 609, 16 p. 

Mamen, C., 1971, Almaden-Quicksilver cen.tre of the world: 

Canadian Mining Jour., v. 92, no. 1, p. 40-43. 

Manning, D. C., 1970, Non-flame methods for mercury determination by atomic absorption-A review: Atomic Absorption Newsletter, v. 9, no. 5, p. 97-99. 

Mlakar, Ivan, 1964, The role of postmineralization tectonics 

in the search for new mineralized zones in the Idria 

area: Rudarsko-Metalurski Zbornik, no. 1, p. 19-25. 

National Research Council, 1969, Trend·s in usage of mercury: N atl. Materials Advisory Board Pub. NMAB--258, 

37p. 

Plimmer, J. R., and Klingebiel, U. I., 1971, Hyperfine Zeeman e:ffect atomic absorption spectrometer for mercury; 

Science, v. 174, p. 404-408. 

Saukov, A. A., 1946, Geochemistry of mercury: Akad. Nauk 

SSSR Geol. Inst. Trudy 78, p. 1-129. [In Russian] 

Shacklette, H. T., 1965, Bryophytes associated with mineral 

deposits and solutions in Alaska: U.S. Geol. Survey Bull. 

1198-C, 18 p. 

Taylor, S. R., 1964, Abundance of chemical elements in the 

continental crust; a new table: Geochim. et Cosmochim. 

Acta, v. 28, p. 1273-1285. 

Tunell, G., 1970, Mercury in Handbook of Geochemistry: Berlin, Springer-Verlag, v. 11/2, p. 80-B-1 to 80-M-5. 

U.S. Bureau of Mines, 1965, Mercury potential of the United 

States: U.S. Bur. Mines Inf. Circ. 8252, 376 p. 

U.S. Geological Survey, 1970, Mercury in the environment: 

U.S. Geol. Survey Prof. Paper 713, 67 p. 

Vaughn, W. W., 1967, A simple mercury vapor detector for 

geochemical prospecting: U.S. Geol. Survey Circ. 540, 

8 p. 

Wallace, R. A., Fulkerson, William, Shults, W. D., and Lyon, 

W. S., 1971, Mercury in the environment-the human 

element: U.S. Atomic Energy Comm. Oak Ridge Natl. 

Lab., ORNL NSF-EP-1, 61 p. 

Weissberg, B. G., 1971, Determination of mercury in soils 

by flameless atomic absorption spectrometry: Econ. 

Geology, v. 66, no. 7, p. 1042-1047. 

White, D. E., 1967, Mercury and base-metal deposits with 

associated thermal and mineral waters, in Bames, H. L., 

ed., Geochemistry of hydrothermal ore deposits: New 

York, Holt, Rinehart and Winston, Inc., p. 575-631. 
UNITED STATES MINERAL RESOURCES 

MICA 

By FRANK G. LESURE 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------- Types and uses of mica --------------------------

Sheet mica ----------------------------------

Scrap mica ---------------------------------- Exploitation -------------------------------------

Mining and preparation --------------------------

Prices ------------------------------------------- Geologic features of mica deposits -----------------

Pegmatites ----------------------------------

Phlogopite deposits --------------------------

Scrap- and flake-mica deposits ----------------

Resources --------------------------------------- Identified and hypothetical resources ----------

Speculative resources -------------------------

Prospecting techniques ---------------------------

Problems for research ----------------------------

Selected references -------------------------------

FIGURES 

50. Graph showing production of sheet mica in the 

United States compared with imports of 

sheet mica, 1900-70 ---------------------- 61. Graph showing production of scrap mica in the 

United States, 1900-70, compared with that 

in the rest of the world, 1925-70 ----------

TABLE 

84. Sheet mica on hand in all U. S. Government inventories, as reported by General Services 

Page 

415 

415 

415 

416 

416 

416 

417 

418 

418 

418 

419 

419 

420 

420 

421 

421 

422 

422 

Page 

417 

418 

Page 

Administration, March 31, 1972 ------------ 420 

ABSTRACT OF CONCLUSIONS 

Sheet mica has been an important s·trategic mineral used 

in electrical appliances, vacuum tubes, capacitors, and various other electrical and nonelectrical products. The United 

States has not been self-sufficient in sheet-mica production 

since before the turn of the 20th century and has imported supplies to meet half to all of its need·s, mostly from 

India, Brazil, and Malagasy Republic. Sheet-mica uses are 

declining with advancing technology and introduction of 

substitutes. Although the United States has undiscovered 

and paramarginal resources of sheet mica, the high cost of 

the necessary hand labor involved in mining and preparation of sheet mica deters exploration, development, or further mining. 

Average United States scrap-mica production is increasing, but reserves and resources are adequate for foreseeable 

demand. The United States is self sufficient in flake-mica 

production and is a net exporter of ground mica. 

INTRODUCTION 

Mica is the general group name for several complex hydrous aluminum silicate minerals. The principal mica minerals are muscovite (white mica), 

biotite (black mica), and phlogopite (amber mica). 

All have a perfect basal cleavage and form crystals 

that can be split into thin sheets having various 

degrees of transparency, toughness, flexibility, and 

elasticity. The micas are common minerals in igneous, metamorphic, and some sedimentary rocks. 

Muscovite is the most important commercial mica 

in the United States. Phlogopite is generally inferior 

to muscovite except in uses that require resistance 

to high temperature: muscovite breaks down at 

temperatures of more than 500°C, whereas phlogopite is relatively stable up to 1,000°C. Biotite is 

inferior to muscovite and phlogopite and has little 

commercial value. 

TYPES AND USES OF MICA 

Two types of mica are sold : sheet mica, which 

must be relatively flat, free from most defects, and 

large enough to be cut into pieces at least 1 square 

inch; and scrap mica, which is all mica that does 

not meet sheet-mica specifications and that is generally ground to a powder. Small sheets of untrimmed mica of poorer quality that can be punched 

or trimmed into disks at least 1 inch in diameter 

U.S. GEOL. SURVEY PROF. PAPER 820 

415 
411 UNITED STATES MINERAL RESOURCES 

are classified as punch mica and are included in the 

general term ''sheet mica." Built-up mica made 

from very thin sheets and reconstituted mica made 

from scrap can be substituted for larger sheet 

mica for some uses. 

SHEET MICA 

Sheet mica is an important dielectric and insulating material used in the manufacture of electronic 

and electrical equipment, such as electronic vacuum 

tubes for radio and television, capacitors, motors, 

transformers, generators, and electrical appliances. 

Nonelectric uses include shields for high-temperature steam-gage glasses, regulator diaphragms, and 

in years gone by, stove windows and lamp chimneys. 

The value of sheet mica depends on the color, size, 

structure, and quality of the natural crystals. Quality of sheet mica varies widely within and between 

mica districts and even within a single deposit or 

mica-rich shoot. 

A variety of synthetic materials-such as built-up 

mica, r-econstituted and glass-bonded mica, organic 

polymers, and synthetic mica-and alternate materials-suc:h as alumina ceramics, fused quartz, and 

talc-are replacing sheet mica in some uses. Technological developments, such as miniaturization of 

circuits and solid-state electronics, also reduce the 

need for sheet mica. 

Muscovite in sheets as thin as paper is generally 

colorless, but thicker sheets may range from red or 

yellow brown to greenish brown or green. Reddish 

brown or ruby mica is generally thought to be of 

slightly better quality and brings a higher price 

than the other varieties of mica. 

The best sheet mica is clear, flat, and free of 

mineral inclusions and structural defects. Mica that 

contains inclusions or impurities is called stained 

mica. Primary impurities are air bubbles, mottling, 

and mineral intergrowths; secondary impurities are 

air creep, clay, iron oxide and manganese oxide inclusions, and organic or vegetable stain. 

Structural defects of the mica crystals are also 

of primary and secondary origins. The most common primary defects are reeves and wedge structure. Reeves are lines, striations, or shallow corrugations that lie in the plane of the cleavage. Where 

two sets of reeves intersect at an angle of nearly 

60°, the resulting mica is said to have "A" structure. 

Wedge structure is caused by interlayering of sheets 

of unequal size. Some muscovite crystals, or books, 

have discontinuous sheets, partial intergrowth of 

sheets, or internal distortions and do not split freely. 

These books, termed "locky," or "tangled," are used 

only for scrap. Secondary structural defects include 

bending, cracking, twisting, and ruling, all caused 

by deformation of the mica after crystallization. 

Ruling is a secondary cleavage that cuts the basal 

cleavage at an angle of nearly 67°. 

Crude books of mica must be at least 2 inches 

across to yield trimmed sheet mica. The average 

commercial book is about 5 inches across and about 

1f5 to lh as thick as it is wide. In some deposits 

books measuring 8 to 12 inches are common. Some 

larger books as much as several feet across and 

weighing 50-300 pounds have been found. 

SCRAP MICA 

Many pegmatite deposits contain only scraPquality mica, and a large amount of scrap is produced during the mining, trimming, and fabricating of sheet mica. Such scrap is of high quality and 

is in great demand for making mica paper or reconstituted mica. Scrap mica obtained from clay or 

feldspar deposits or from mica schists is generally 

finely divided and is often called flake mica. 

Scrap mica from sheet operations, from .scrap 

mining, and from clay and feldspar mining may be 

blended before grinding to either dry-ground or 

wet-ground mica. Wet-ground mica is produced in 

chaser mills using wooden grinding surfaces. The 

finished product is usually white and has a greasy 

ungent feel and a pronounced sheen (Broadhurst 

and Hash, 1953, p. 9). Individual particles are 

highly polished and have smooth edges. Particle 

size generally ranges from 80 to 325 mesh. Wetground mica is used chiefly in the manufacture of 

wallpaper, rubber goods, and paint. 

Dry-ground mica is produced in rod mills, hammer mills, cage disintegrators, and various types of 

attrition mills (Skow, 1962, p. 89). The product is 

a flat white powder having little luster; individual 

particles have rough edges and little polish. Particle 

size ranges from 20 to 250 mesh. Some special micronized mica has particle sizes of 1,000-3,000 mesh, 

or 5-2<f microns. Dry-ground mica is used chiefly 

in the manufacture of rolled roofing or asphalt 

shingles, wallboard or joint cement, oil-well drilling 

mud, paint, rubber goods, plastic, and welding rods. 

The value of scrap mica depends on color and freedom from impurities. Various other mineral fillers 

can substitute for ground mica in most uses. Synthetic fluorophlogopite can substitute for scrap in 

reconstituted mica (Shell and Ivey, 1969, p. 214). 

EXPLOITATION 

Mica was mined in North Carolina, Virginia, and 

Alabama by the Indians more than a thousand years 

before the coming of the white man (Prufer, 1964, 
MICA 

p. 90), but modem mica-mining began in New 

Hampshire in 1803 and in North Carolina in 1867. 

The grinding of scrap mica began in a small way in 

North Carolina about 1870 (Broadhurst and Hash, 

1953, p. 13) and grew rapidly after 1890. 

In the United States, mica has been produced 

mostly in the Blue Ridge Mountains of North Carolina and in the Piedmont from Virginia to Alabama. 

Next in importance have been the New England 

States of New Hampshire, Maine, and Connecticut, 

and then the Black Hills of South Dakota. Smaller 

amounts have been produced in Colorado, Idaho, and 

10,000,000 

1,000,000 

U.S. Imports of 

sheet mica 

417 

o.u Sheet mica sold 

1\ Incomplete / 1 or used by pro. 1 duc:ers In the 

i\ 1 1 ~\ • " '\ 1

1 1

1 /nlted SUtes ' I •' a , ... •'/ "'' " ' ' \

1 I 1\ 1 I I \ 1 1 I 

" I I 1 I \ ,' \, 1 \ \ II 1 

l I '/ 1 1 I 1 •• ! ..... I 

fl) New Mexico, and minor production is reported from a 

z Arizona, California, Montana, Nevada, and Wyo- :l 

I L

1 ' I ' ,, " 

Us I f .. mports o '' l' '• \t \I , 11 

sheet mica , 1 11 

ming. A few deposits are known in Maryland, Mas- 2 

sachusetts, Minnesota, New Jersey, New York, 

Pennsylvania, Texas, Utah, Vermont, and Washington. North Carolina has been the principal producer of sheet mica and produces yearly 50-60 

percent of the domestic scrap mica. 

100,000 

',, 

"' lt I• I 

I 

I 

I 

I 

I 

I 

I 

: t, ::I Because of the high cost of hand labor, the 

United States produces only a small amount of its 

domestic needs for sheet mica and relies on imports 

from India, Brazil, and Malagasy Republic for its 

principal requirements (fig. 50). In 1970, no production of sheet mica was reported in the United 

States for the first time in over 100 years, and it is 

unlikely that there will be much future production. 

U.S. imports of sheet mica have declined since 1950 

because of the impact of improved technology and 

the availability of substitutes. In 1971, the Indian 

Government announced its decision to take over 

mica exports as of January 1972; the effects of this 

decision on the industry are not known. 

The United States is the major producer (fig. 51) 

and consumer of scrap mica, including flake mica. 

Increased use of scrap probably depends on increased needs in housing for rolled roofing, joint 

cement, and paint. 

North Carolina is the principal producer of scrap 

mica. Other States producing scrap in 1970 included 

Alabama, Arizona, Colorado, Connecticut, Georgia, 

New Hampshire, New Mexico, South Carolina, and 

South Dakota. Production for the rest of the world 

is mostly waste from the mining of sheet mica in 

India, Brazil, and Malagasy Republic. 

MINING AND PREPARATION 

Sheet-mica mining methods are simple and sometimes primitive. Most of the mines are small and 

shallow and require a minimum of equipment. Openpit methods are used where possible, but most deposits are mined to some extent in underground 

workings that are generally irregular and follow 

10,000 Ill 

I I ' ~ I 

No production in 1970 ' 

FIGURE 50.-Production of sheet mica in the United States 

compared with imports of sheet mica, 1900-70. Data from 

U.S. Geological Survey and U.S. Bureau of Mines, Mineral 

Resources of the United States and Minerals Yearbook, 

1900-70. 

the mica in rich shoots or from one rich pocket to 

another. Drilling and blasting must be done carefully to avoid damage to the mica. After a blast, 

crystals of mica are handpicked from broken rock. 

Large rocks are broken with sledges, and both 

waste and mica are usually hoisted to the surface. 

Because of the handwork involved, mining costs are 

high in relation to the average amount of sheet mica 

found in most deposits. Inefficiency and waste are 

common in mica mining. Handcobbed feldspar is 

sometimes recovered as a byproduct. 

Processing of sheet mica requires extensive hand 

labor in cobbing or removing dirt or,xock from the 

books, in rifting or splitting the books into thin 

sheets, and in trimming broken edges and imperfections from the sheets. Complete quantitative data 

are not available, but recovery of good trimmed mica 

from crude mica ranges from 2 to 8 percent for the 

average mine and is as much as 19 percent from 

good-quality crude mica in a few mines (Urban, 

1932; Amos, 1959, table 1, p. 33). 
UNITED STATES MINERAL RESOURCES 

en 

~100r-----------------------------~rlL~~ IIa: 

~ BOr---------------------------~----~~ en 

u.. 

0 Scrap mica, United States 

~ sor-------------------------~-------+~ 

z 

c( 

en 

:> 

0 40r---------------------+-~*-------~~ I 

1-

FIGURE 51.-Production of scrap mica in the United States, 

1900-70, compared with that in the rest of the world, 

1925-70. Data from U.S. Geological Survey and U.S. 

Bureau of Mines, Mineral Resources of the United States 

and Minerals Yearbook, 1900-70. 

Details of the preparation and classification of 

mica and trade practices of the industry are too 

elaborate to discuss here, but they have been described well by Rajgarhia (1951), Skow (1962), 

Montague (1960), Jahns and Lancaster (1950), 

and Wierum and others (1938). 

Most deposits of scrap mica must be deeply weathered so that they can be mined in bulk with power 

equipment and the ore can be washed and screened 

to recover the mica. The content of recoverable 

mica ranges from 3 to 20 percent. In simple washing plant operations, mica smaller than 8 mesh is 

not recovered readily; but through the use of spiral 

methods of concentration, better recovery is possible (Broadhurst and Hash, 1953, p. 6; Skow, 1962, 

p. 86). 

PRICFS 

The selling price of mica ranges from only a few 

cents per pound for punch or scrap to many dollars 

a pound for large sheets of the best quality. In 1970, 

prices for sheet mica ranged from $0.85 a pound 

for sheets 1¥2 inches across to $8.00 a pound for 

sheets 8 inches or more across. Punch mica brought 

$0.07-$0.12 a pound. Scrap mica generally brought 

$30-$40 per short ton. Ground mica prices were 

$0.02-$0.04 a pound for dry-ground mica and 

$0.075-$0.095 a pound for wet-ground mica. 

GEOLOGIC FEATURES OF MICA DEPOSITS 

Sheet-muscovite deposits occur in coarse-grained 

igneous rocks called pegmatites; scrap-mica deposits are found in pegmatites, granite, and micarich metamorphic rocks. Phlogopite deposits are in 

pyroxenite layers in marble or gneiss. 

PEGMATITES 

Most pegmatites are light-colored coarsely crystalline igneous rocks, commonly found as dikes or sills 

in metamorphic rocks or in large granitic intrusions. Individual mineral grains and crystals range 

in length from less than 1 inch to many feet, and 

a large variation in grain size within a single pegmatite body is common. 

Pegmatites range from small pods and thin seams 

to large masses hundreds of feet thick and thousands of feet long. In general, they are tabular or 

lenticular bodies. Some pinch and swell along strike 

or downdip, or both. Most lenticular bodies are discoidal, but some bodies are best described as tonguelike or pipelike. In some pegmatite districts, most 

of the deposits are concordant with the foliation of 

the enclosing country rock ; in others, most are discordant bodies in joints or faults. Branching, folded, 

or irregular bodies may be present in areas of complex structure. Most elongate bodies and minor 

bulges or rolls in concordant pegmatites are generally parallel to the plunge of minor structural 

features in the country rock. 

Pegmatites are composed mostly of feldspar, 

quartz, and mica but may contain accessory minerals such as garnet, tourmaline, apatite, and beryl 

and unusual or rare minerals of many types. The 

many and unusual minerals found in some pegmatites make pegmatites favorite collecting sites for 

mineralogists and rockhounds. 

Plagioclase is generally the most common feldspar in muscovite-rich pegmatite. Perthite or perthitic microcline, an intergrowth of plagioclase and 

microcline feldspars, is generally present and may 

be abundant in some pegmatites. The feldspars are 

discussed in greater detail in a separate chapter. 

Book mica in commercially mined pegmatite generally constitutes 2-6 percent of the rock. Local 

rich shoots or pockets might have as much as 40 

percent muscovite, but large volumes of pegmatite 

have no more than 2 percent. 

The minerals in many pegmatites are almost 
MICA 419 

evenly distributed throughout, but in other pegmatites the minerals are segregated into certain layers 

or parts of the body called zones. At places, these 

zones can be mined selectively to recover the desired 

minerals by hand sorting and are, therefore, important economically. In general, zones are successive shells, complete or incomplete, that commonly 

reflect the shape or structure of the whole pegmatite body. Where best developed, the zones are concentric about an innermost zone, or core, and according to accepted practice, the zones from the 

outermost one inward to the core are called border 

zone, wall zone, intermediate zones, and core. 

Border zones are generally thin fine-grained selvages of quartz-mica-feldspar pegmatite; wall zones 

are of similar composition but are coarser grained. 

Intermediate zones may contain mixtures of several 

minerals or virtually all one mineral, usually feldspar. Most cores are a single mineral--commonly 

quartz or potash feldspar. The best quality and 

greatest concentration of sheet muscovite are commonly in the wall zone; less important concentrations are in intermediate zones and the core margin. 

In poorly zoned pegmatite, muscovite is scattered 

throughout the rock. 

-- The principal mica pegmatite districts in the 

United States are in New England (Cameron and 

others, 1954), the Southeastern Piedmont from Virginia to Alabama (Jahns and others, 1952), the 

Blue Ridge Mountains in North Carolina (Lesure, 

1968), the Black Hills of South Dakota (Page and 

'lthers, 1953), and northern New Mexico (Jahns, 

1946) . Less important districts are in Idaho and 

Montana (Stoll, 1950), Colorado and Wyoming 

(Hanley and others, 1950), Nevada (Olson and 

Hinrichs, 1960), and California (Lesure, 1966). In 

India, the most important mica pegmatite districts 

are in Bihar, Madras, and Rajasthan (Skow, 1962; 

Rajgarhia, 1951). In Brazil, the important mica 

pegmatite districts are in Minas Gerais (Pecora 

and others, 1950). Important mica pegmatite districts are also known in Argentina, parts of Africa, 

the Soviet Union, and China (Skow, 1962). 

The origin of pegmatites has been studied by 

hundreds of workers for more than 100 years. 

Jahns (1955) gives an extensive bibliography of 

these studies. Recent reports (Jahns and Tuttle, 

1963; Jahns and Burnham, 1969) stress the origin 

of granitic pegmatite from crystallization of granitic magma in place in virtually a closed system 

with little or no wallrock alteration. In many districts, like the Black Hills of South Dakota, the 

spatial relationship between pegmatite and large 

masses of granite indicates the same or a similar 

source. In other areas, like parts of the Blue Ridge 

Mountains of North Carolina, no close relationship 

to granitic masses is evident, but the mica pegmatites are restricted to areas where regional metamorphism has reached at least kyanite or sillimanite 

grade. 

PHLOGOPITE DEPOSITS 

According to Hoadley (1960, p. 45), the occurrences and distribution of phlogopite deposits are 

everywhere similar. Known deposits are in areas of 

metamorphosed sedimentary rocks intruded by 

masses of pegmatite-rich granitic rocks. The phlogopite deposits commonly are in veins or irregular 

pockets in diopsidic pyroxenite interlayered with 

or cutting marble or gneiss. The pyroxenite may be 

normal intrusive mafic igneous rock or a contact 

metamorphic alteration of crystalline carbonate by 

solutions from granitic magma. The phlogopite deposits may also have formed by contact metamorphism at about the same time as the surrounding 

pyroxenite. The principal resources of phlogopite 

are in the Malagasy Republic (Murdock, 1963, p. 

124-129); minor deposits are found in Canada 

(Hoadley, 1960), Mexico (Larrabee, 1946), Ceylon, 

and the Soviet Union (Skow, 1962). The United 

States has no commercial phlogopite deposits. 

SCRAP- AND FLAKE-MICA DEPOSITS 

The original source of scrap mica was the waste 

from sheet-mica mining and preparation, hence the 

name scrap. About 1910, however, demand for scrap 

had increased so much that mica deposits containing poor quality sheet or smaller sizes were being 

mined for just the scrap content. Today in Spruce 

Pine, N.C., which produces nearly half the scrap 

mica mined in the United States, deeply weathered 

alaskite bodies containing 10-20 percent muscovite 

are mined for fine-grained scrap mica or flake mica. 

In such deposits, depths to unweathered rock may 

be 50-100 feet for areas of several acres. Some deposits are mined for clay, and the mica is recovered 

as a byproduct; some are mined for mica, and the 

clay generally is lost in the washing process. Unweathered alaskite is mined for feldspar, and mica 

is recovered as a byproduct. 

Flake mica can also be recovered from muscovite 

schist, a rock found in many metamorphic terranes. 

Such deposits may be a few tens or hundreds of 

feet thick and many miles long. Mica content can 

range from a few percent to at least 90 percent. 
UNITED STATES MINERAL RESOURCES 

Many other minerals are commonly present, including quartz, feldspar, garnet, kyanite, and graphite. 

Most mica schist was originally fine-grained siltstone or shale, which was subjected to at least 

medium-grade regional metamorphism. 

Where slightly weathered, mica schist can be 

easily mined. Recent work by the U.S. Bureau of 

Mines (Browning and Bennett, 1965; Adair and 

Browning, 1969) has developed methods of concentrating good-quality flake mica from mica schist. 

Preliminary studies in North Carolina indicate that 

the percentage of mica in schist ore is about four 

times as high as that of mica ores now being mined, 

and a flow sheet was developed that would make 

mica-schist products competitive in the present 

market (Lewis and others, 1971). 

Another type of flake-mica deposit mined in Lancaster County, S.C., is very fine grained and claylike. The original rock, apparently a volcanic ash 

or tuff, has been altered to a mixture of sericite 

(fine-grained muscovite) and quartz. The rock is 

easily mined and requires minimum preparation for 

sale as a mineral filler. 

Muscovite is one of the more stable rock-forming 

minerals and under ideal conditions will be concentrated in sediments. Such a deposit of detrital 

mica in Holocene sediments was mined in Davy 

Crockett Lake, Greene County, Tenn., from 1956 

to 1960. The conditions of formation of this deposit 

are unusual; the lake is downstream from the washing and grinding plants of the Spruce Pine pegmatite district, and fine mica, which was lost in mining and processing of clay, feldspar, and scrap mica, 

collected in the headwaters of the lake. Similar deposits may occur elsewhere in the· world where 

weathered metamorphic and igneous rocks are being 

eroded. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Few quantitative data are available to estimate 

reserves or resources of sheet mica. Most of the 

deposits mined to date were found by testing surface outcrops. Some mines have reached depths of 

300-400 feet in the United States and as much as 

800 feet in India. If the present surface is considered a random sample of what occurs at depth, then 

many pegmatites in the world do not crop out but 

are still within mining depth (less than 500 ft). On 

this basis, conditional and hypothetical resources of 

sheet mica in the United States probably are at 

least equal to the amount already mined-that is, 

about 75 million pounds of sheet mica in deposits 

similar to those mined but not exposed at the surface in the principal mica pegmatite districts mentioned previously. Unless the economics of sheetmica mining change radically, little of this hypothetical mica will ever be looked for or mined. In 

case of a national emergency, initial demand for 

sheet mica will be filled by the Government stock 

piles (table 84). 

TABLE 84.-Sheet mica, on ha,'IU/, in a,U U.S. Government inventories, fl,8 reported by GeneraJ, Services Administration, 

March 81, 1971 

[ Clauifleation: block mica, minimum thicknesa of 0.007 in. and minimum 

usable area of 1 aq in.; film mice, variable thicknesses rancinc from 

0.0012 to 0.004 in. and minimum usable area same as block miea; 

splittmgs, maximum thickness of 0.0012 in. and minimum usable area, for top qualities, of 0.076 sq in. (Skow, 1962, p. 4)] 

Clcssijicction Wright (poaflds) 

Muscovite block, stained and better ---------------------- 10,648,007 

Muscovite bloek, nonstockpile grade --------------------- 3,603,422 

Muscovite fllm, 1st and 2d qualities ---------------------- 1,468,340 

Muscovite fllm, nonstoekpile lfl"&de ----------------------- 640 

Muscovite splittinaa ----------------------------------- 37,630,606 

Phloeopite block -------------------------------------- 16.721 

Phloeopite block, nonstockpile grade -------------------- 137,217 

Phloeopfte splittinp ----------------------------------- 4,669,27.& 

Resources of sheet mica also occur similarly in 

many countries throughout the world. Some of these 

are Canada, Guatemala, Argentina, Bolivia, Colombia, Austria, France, Norway, Rumania, the Soviet 

Union, Burma, China, Australia, and several small 

districts in Africa. The major resources of sheet 

muscovite, however, are in India and Brazil, and 

the major resources of phlogopite are in the Malagasy Republic. No quantitative data are available 

to estimate reserves or resources of sheet mica in 

these countries, but the resources in the Bihar and 

Madras areas of India are probably very large. 

Resources in Brazil, West Africa, Rajasthan area 

of India, and the Lake Baikal and Sayan Upland 

areas of the Soviet Union are large (Skow, 1962, 

p. 42). Resources in the other countries are small 

to moderate. 

A few data are available to estimate resources of 

scrap mica. Although mica-rich zones in some pegmatite bodies may contain as much as 40 percent 

mica, the largest resources of scrap mica are in 

mica schists that may contain as much as 90 percent mica and in muscovite granites that contain 

10-20 percent. Using a conservative figure of 40 

percent mica, the average mica schist would contain 

1,450 tons of mica per acre-foot of outcrop area. 

Mica schist formations are typically measured in 

tens or hundreds of feet in outcrop width and miles 

in outcrop length. Muscovite granites like the alaskite of Spruce Pine, N.C., or the granite of Stone 

Mountain, Ga., are principally a source of feldspar 

but contain 350-700 tons of byproduct or coproduct 

mica per acre-foot and have outcrops measured in 

many acres or square miles. Assuming a mining 

depth of 100 feet, the resources of scrap mica per 
MICA 421 

acre of schist would be 145,000 tons and of granite, 

35,000 tons. 

In areas where geologic and mining data are available, good estimates of resources can be made. Thus, 

reserves of primary scrap or flake mica in the 

Spruce Pine district have been estimated as 45-50 

million tons in material similar to that currently 

being mined (Brobst, 1962, p. 15-16). Conditional 

and hypothetical resources of scrap mica in that 

district may be several times greater than reserves. 

Hypothetical resources of scrap mica in mica schist, 

weathered pegmatite, and granite in the rest of the 

Blue Ridge Mountains and Piedmont in the southeastern States must equal or be many times greater 

than the reserves in the Spruce Pine district. 

Similarly immense hypothetical resources of scrap 

mica are present in pegmatites, granites, and mica 

schist in metamorphic and igneous terranes in New 

England; the Black Hills of South Dakota; the 

district seem poor. Speculative resources of sheet 

mica, therefore, are probably not large. 

In contrast to speculative resources of sheet mica, 

those of flake mica are probably large. Large areas 

of metamorphic rock known to exist throughout the 

world have not been studied in enough detail to 

outline mica schist deposits that might be a source 

of flake mica. Deposits of hydrothermally altered 

rock containing fine-grained muscovite like that 

being mined in South Carolina may be widespread 

but have not been evaluated as a mica resource. 

Deposits of detrital mica similar to that mined in 

Davy Crockett Lake, Tenn., represent another type 

not exploited to any great extent. All such deposits 

may be very widespread and may represent large 

speculative resources of flake mica. 

PROSPECTING TECHNIQUES 

Llano area of Texas; the Rocky Mountains ; isolated Most sheet-mica mines are in pegmatites that 

mountains in Arizona, Utah, and Nevada; parts of were found because they were exposed at the surCalifornia; and other areas of the United States. face. Chips of coarse mica in the soil, exposures of 

However, projected annual demand in the United massive quartz, or white clay weathered from a 

States for flake mica by the year 2000 ranges from feldspar-rich zone are good signs of a potentially 

280,000 to 550,000 tons (Petkof, 1970, p. 1096) ; mica-bearing pegmatite. Prospecting consists of 

thus, the resources of just the Spruce Pine district trenching, digging shallow pits, or sinking shafts 

seem adequate to meet the expected demand for or inclines in a pegmatite. The pegmatite is tested 

years to come. for mica concentrations along the contacts with 

World resources of scrap mica in pegmatite, mica wallrocks or in the different zones. In the past 20 

schist, and granite are probably at least of the years some drilling has been done, but generally, 

same order of magnitude as the U.S. resources. drilling only proves the presence or absence of pegProduction of scrap mica outside the United States matite and reveals little about any mica that it may 

has come mostly from mine scrap, and deposits of contain. Only by mining a large enough sample of 

flake mica are largely undeveloped. Scrap-mica re- mica-bearing pegmatite can the miner establish, 

serves and resources in India must be very large; from the size, quantity, and quality of the mica, 

about 10 million tons of scrap were heaped near l feasibility of development of the pegmatite. Geomines and factories in 1965 (W. R. Griffitts, written logic mapping to determine structure and metacommun.). The other sheet-mica-producing countries morphic grade of the country rock may help outmust have similar supplies of scrap because world line potential areas for prospecting. Most sheetdemand has generally been much less than United mica-bearing pegmatites not in granitic rocks are 

States demand. in metasedimentary rocks that are products of 

SPECULATIVE RESOURCES 

Even less can be said about speculative resources 

of sheet mica than about reserves and hypothetical 

resources. Commercial sheet muscovite is found 

only in pegmatite deposits, and most of the pegmatite districts in the world have probably been 

found. The chances of finding a large previously 

undiscovered district seem negligible because pegmatite minerals are coarse grained and so unusual 

that they are not easily ignored. The distribution 

of phlogopite deposits is probably less well known, 

but again, chances of finding a .large undiscovered 

medium- to high-grade (kyanite- or sillimanitegrade) regional metamorphism. If there has been 

later deformation, the pegmatite may contain mica 

that is deformed and good only for scrap. Mapping 

and detailed study of pegmatites begun during 

World War II proved that reserves and resources 

can be calculated in zoned pegmatites if the geologic 

details are known (Cameron and others, 1949 ; 

Jahns, 1955; Norton and Page, 1956). Stl)dy of the 

use of geophysical or geochemical techniques in 

looking for concealed deposits should be made. Small 

positive geochemical anomalies of various trace elements have been found in gneiss and schist within 
UNITED STATES MINERAL RESOURCES 

5-50 meters of pegmatite that is rich in potash 

feldspar and mica (Shmakin and others, 1971). 

Most prospecting is still done by prospectors who 

have developed their own criteria for finding mica 

through years of experience. The success of the 

Indian mica industry is in part the result of low 

labor costs that have permitted intensive and continued prospecting for new deposits by individual 

prospectors. For every 100 pegmatites that the Indians find, however, only two or three prove rich 

enough to develop for commercial mining (Rajgarhia, 1951, p. 49). This ratio of productive to 

nonproductive pegmatites seems applicable to the 

world supplies. 

PROBLEMS FOR RESEARCH 

The principal problems of the mica industry are 

the high cost of hand labor needed for mining and 

processing of sheet mica and the increasing use of 

substitutes or decreasing need for sheet mica because of improved technology. The U.S. Bureau of 

Mines forecasts a drastic reduction in sheet mica 

needs by the year 2000 (Petkof, 1970, p. 1093), 

and there is little reason to believe that sheet-mica 

mining will ever again be important in the United 

States. With the decrease in mining and processing 

of sheet mica, the amount of high-quality scrap will 

also decrease. Increased use of synthetic mica as a 

substitute for coarser scrap in reconstituted mica 

can be expected. Large supplies of high-quality scrap 

probably will be available from India as long as the 

sheet-mica industry is active there. In the United 

States, a need for scrap- or flake-mica sources closer 

to the active industry could be met by continued 

evaluation of mica schist deposits that are outlined 

by regional geologic mapping. 

SELECTED REFERENCES 

Adair, R. B., and Browning, J. S., 1969, Flotation of muscovite for Alabama graphite-mica schist ore: U.S. Bur. 

Mines Rept. Inv. Rl-7273, 7 p. 

Amos, D. H., 1959, DMEA project blossoms into best U.S. 

mica mine: Mining World, v. 21, no. 11, p. 30-34. 

Broadhurst, S. D., and Hash, L. J., 1953, The scrap mica resources of North Carolina: North Carolina Div. Mineral 

Resources Bull. 66, 66 p. 

Brobst, D. A., 1962, Geology of the Spruce Pine district, 

Avery, Mitchell, and Yancey Counties, North Carolina: 

U.S. Geol. Survey Bull. 1122-A, 26 p. 

Brown, W. R., 1962, Mica and feldspar deposits of Virginia: 

Virginia Div. Mineral Resources Rept. 3, 195 p. 

Browning, J. S., and Bennett, P. E., 1965, Flotation of California mica ore: U.S. Bur. Mines Rept. Inv. Rl-6668, 

7 p. 

Cameron, E. N., Jahns, R. H., McNair, A. H., and Page, 

L. R., 1949, Internal structure of granitic pegmatites: 

Econ. Geology Mon. 2, 115 p. 

Cameron, E. N., and others, 1954, Pegmatite investigations, 

1942-45, New England: U.S. Geol. Survey Prof. Paper 

225,352 p. 

Clark, G. H., 1921, Mica deposits of Alabama: Alabama Geol. 

Survey Bull. 24 ,115 p. 

Furcron, A. S., and Teague, K. H., 1943, Mica-bearing pegmatites of Georgia: Georgia Geol. Survey Bull. 48, 192 p. 

Hanley, J. B., Heinrich, E. W., and Page, L. R., 1950, Pegmatite investigatioDB in Colorado, Wyoming, and Utah, 

1942-44: U.S. Geol. Survey Prof. Paper 227, 125 p. 

Hoadley, J. W., 1960, Mica deposits of Canada: Canada Geol. 

Survey Econ. Geol. Ser., no. 19, 141 p. 

Jahns, R. H., 1946, Mica deposits of the Petaca district, 

Rio Arriba County, N. Mex.: New Mexico Bur. Mines 

Mineral Resources Bull. 25, 289 p. 

Jahns, R. H., 1955, The study of pegmatites: Eoon. Geology 

50th Anniversary Volume, pt. 2, p. 1025-1130. 

Jahns, R. H., and Burnham, C. W., 1969, A model for the 

derivation and crystallization of granitic pegmatite, pt. 

1 of Experimental studies of pegmatite genesis: Econ. 

Geology, v. 64, no. 8, p. 843-864. 

Jahns, R. H., and Lancaster, F. W., 1950, Physical characteristics of commercial sheet muscovite in the southeastern United States: U.S. Geol. Survey Prof. Paper 225, 

110 p. 

Jahns, R. H., and Tuttle, 0. F., 1963, Layered pegmatiteaplite intrusives: Mineralog. Soc. America Spec. Paper 

1, p. 78-92. 

Jahns, R. H., and others, 1952, Mica deposits of the southeastern Piedmont: U.S. Geol. Survey Prof. Paper 248, 

462 p. 

Larrabee, D. M., 1946, The phlogopite industry of Oaxaca, 

Mexico, in Mineraias metalicos e niio metalica, 1• 

Com.: Cong. Panam. Engenharia Minas e Geologia, 2°, 

Rio de Janeiro, Anais, v. 2, p. 353-368, Petr6polis, 

Brazil, Oct. 1946. 

Lesure, F. G., 1966, Mica, in Mineral and water resources 

of California: U.S. Cong., 89th, 2d Sess., Comm. Interior 

and Insular Affairs, Comm. Print. (California Div. 

Mines and Geology Bull. 191), p. 254-258. 

Lesure, F. G., 1968, Mica deposits of the Blue Ridge in 

North Carolina: U.S. Geol. Survey Prof. Paper 577, 

124 p. 

Lewis, R. M., Bundy, J. L., and Wiener, L. S., 1971, Beneficiation and geologic evaluation of North Carolina mica 

schist: North Carolina State Univ., School of Engineering Bull. 86, 52 p. 

Montague, S. A., 1960, Mica, in Industrial minerals and rocks 

[3d ed.]: New York, Am. Inst. Mining, Metall., and 

Petroleum Engineers, p. 551-566. 

Murdock, T. G., 1963, Mineral resources of the Malagasy 

Republic: U.S. Bur. Mines lnf. Circ. IC-8196, 147 p. 

Norton, J. J., and Page, L. R., 1956, Methods used to determine grade and reserves of pegmatites: Mining Eng., v. 

8, no. 4, p, 401-414. 

Olson, J. C., 1944, Economic geology of the Spruce Pine 

pegmatite district, North Carolina: North Carolina Div. 

Mineral Resources Bull. 43, 67 p. 

Olson, J. C., and Hinrichs, E. N., 1960, Beryl-bearing pegmatites in the Ruby Mountains and other areas in 

Nevada and northwestern Arizona: U.S. Geol. Survey 

Bull. 1082-D, p. 135-200. 
MICA 423 

Page, L. R., and others, 1953, Pegmatite investigations, 1942-

46, Black Hills, South Dakota: U.S. Geol. Survey Prof. 

Paper 247, 228 p. 

Pecora, W. T., and others, 1960, Mica deposits in Minas 

Gerais, Brazil: U.S. Geol. Survey Bull. 964-C, p. 206-

306. 

Petkof, Benjamin, 1970, Mica, in Mineral facts and problems: U.S. Bur. Mines Bull. 660, p. 1083-1098. 

Petkof, Benjamin, 1972, Mica, in Minerals yearbook, 1970, v. 

1, Metals, minerals, and fuels: U.S. Bur. Mines preprint, 

8 p. 

Prufer, 0. H., 1964, The Hopewell cult: Sci. American, v. 

211, no. 6, p. 90-102. 

Rajgarhia, Chand Mull, 1961, Mining, processing, and uses 

of Indian mica: New York, McGraw-Hill Book Co., 

388 p. 

Shell, H. R., and lvey, K. H., 1969, Fluorine micas: U.S. 

Bur. Mines Bull. 647, 291 p. 

Shmakin, B. M., Makryghina, V. A., Glebov, M.P., and 

Zagorsky, V. Y., 1971, Use of petrographical-geochemical 

prospecting method for the discovery of hidden muscovite deposits in different geological environments, in 

Geochemical exploration, Proc. 3d Intemat. Geochem. 

Expl. Symposium, Toronto, Apr. 16-18, 1970: Canadian 

Inst. Mining and Metallurgy Spec. Vol. 11, p. 391-393. 

Skow, M. L., 1962, Mica, a materials survey: U.S. Bur. Mines 

lnf. Circ. IC-8126, 240 p. 

Sterrett, D. B., 1923, Mica deposits of the United States: 

U.S. Geol. Survey Bull. 740, 342 p. 

Stoll, W. C., 1960, Mica and beryl pegmatites in Idaho and 

Montana: U.S. Geol. Survey Prof. Paper 229, 64 p. 

Tan, Li-Ping, 1966, Major pegmatite deposits of New York 

State: New York State Mus. and Sci. Service Bull. 408, 

138 p. 

Urban, H. M., 1932, Mica-mining methods, costs and recoveries at No. 10 and No. 21 mines of the Spruce Pine 

Mica Co., Spruce Pine, North Carolina: U.S. Bur. Mines 

Inf. Circ. IC-6616, 16 p. 

Wierum, H. F., and others, 1938, The mica industry: U.S. 

Tariff Comm. Rept. 130, 2d ser., 166 p. 

UNITED STATES MINERAL RESOURCES 

MOLYBDENUM 

By R. U. KING, D. R. SHAWE, and E. M. MAcKEVErr, Ja. 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction ------------------------------------- Exploitation -------------------------------------

Geologic environment ----------------------------

~emistry --------------------------------

!dineralogy ----------------------------------

Types of deposits ---------------------------- Porphyry deposits -----------------------

Climax, Colorado --------------------

Urad-Henderson, Colorado ------------

Questa, New Mexico -----------------

Contact-metamorphic deposits -------------

Quartz veins ----------------------------

PegT:natites ------------------------------ Bedded deposits in sedimentary rocks ------

Resources --------------,------------------------ Identified and hypothetical resources -----------

Speculative resources ------------------------

Prospecting -------------------------------------

Problems for research ----------------------------

Selected bibliography -----------------------------

FIGURE 

52. Map showing location· of molybdenum resources 

in and near Colorado and north em New 

!dexico in relation to various geologic paraPage 

425 

425 

426 

427 

427 

427 

427 

427 

428 

429 

429 

429 

429 

429 

430 

430 

430 

431 

433 

434 

434 

Page 

meters ---------------------------------- 432 

TABLE 

Page 

85. Estimated magnitude of world resources of 

molybdenum ----------------------------- 431 

ABSTRACT OF CONCLUSIONS 

!dolybdenum, a rare metal widely dispersed in the rocks 

of the earth's crust, occupies an essential place in today's 

highly sophisticated industries. 

World production of molybdenum is about 200 million 

pounds per year, of whieh about 60 percent is produced in 

the United States. Identified resources amounting to about 

17.5 million tons of molybdenum in the United States and 

about 32 million tons in the world and occurring both as the 

primary metal sulfide in large low-grade porphyry molybdenum deposits and as a subsidiary metal sulfide in large lowgrade porphyry copper deposits, seem adequate to supply 

world needs for the forseeable future. 

To assure economic availability of these resources and to 

discover additional resources that surely will be needed if 

world demand continues to escalate and if environmental 

problems should tend to restrict the commercial development 

of resources, employment of our most sophisticated exploration techniques will be essential. Successful prediction or" the 

location of undiscovered molybdenum resources will depend 

upon an understanding of the genetic relationship of molyddenum to associated magmatic rocks, the environments in 

which these magmatic rocks were emplaced, and the role of 

plate tectonics in developing favorable environments and 

mechanisms for the generation and emplacement of molybdenum-carrying rocks. 

INTRODUCTION 

Molybdenum, discovered in the last 1770's, is a 

metal of fairly recent entry into the commercial 

market, having come into significant use during the 

1920's as a result of extensive metallurgical research 

into its alloying properties and as a result of the 

establishment at Climax, Colo., of proved reserves 

sufficient to supply world demand for many years 

at a reasonable price. Its importance as an alloying 

metal is due chiefly to the increase in hardness, 

toughness, and resistance to corrosion and wear at 

elevated temperatures that it imparts to iron, steel, 

and stainless steel. 

Molybdenum is a silvery-gray metal having a 

high specific gravity (10.2)-slightly higher than 

copper-and a melting point of 2,620°C-the fifth 

highest melting point of all metals. It is ductile and 

has a hardness of about 200 V.P.N. (Vickers Pyramid Number) and its coefficient of thermal expansion is among the lowest of metals. It is resistant 

U.S. GEOL. SURVEY PROF. PAPER 820 

425 
426 UNITED STATES MINERAL RE.SOURCES 

to acids and oxidation at ordinary temperatures. It 

has a high thermal conductivity and good electrical 

conductivity. 

The principal uses of molybdenum are in the iron 

and steel industries with 70 percent of the apparent 

consumption going into high-speed, tool, stainless, 

and low-alloy construction steels and 20 percent 

going into special alloys and castings ; the remaining 10 percent is used as molybdenum metal and in 

pigment, catalysts, agriculture, chemicals, and 

lubricants. 

It must be evident from the above list of uses 

that molybdenum is an essential metal in a highly 

sophisticated industrialized nation such as the 

United States and that it is equally essential in 

other industrially developed countries. The extent 

to which our present living standards depend on 

the ready availability and constant supply of molybdenum may be illustrated by an example of 

molybdenum utilization in the automotive industry: 

10 million units yearly production consumes more 

than 2 million pounds of molybdenum, a significant 

consumption despite the small weight of molybdenum used per unit. 

Without molybdenum as an alloying metal, superstrength steel as used in heavy construction such 

as modern skyscrapers and bridges would be more 

costly, and in some instances the increased weight 

needed for equivalent strengths would render certain construction patterns unmanageable. 

Molybdenum can substitute for tungsten, vanadium, chromium, columbium, tantalum, nickel, and 

boron. Each substitution is a matter of cost-availability to obtain certain desired qualities in the finished product. 

Molybdenum is virtually the sole metal commodity 

of which the United States is a net exporter. Domestic production in 1970 was just over 110 million 

pounds of molybdenum, or two-thirds of the free 

world production. Domestic consumption, on the 

other hand, is about 50 million pounds ; the United 

States annually exports about 55 million pounds of 

molybdenum in various forms such as molybdenite 

concentrates, molybdenum trioxide, and ferromolybdenum to more than 20 other nations. 

EXPLOITATION 

Recorded world production of molybdenum began 

just after 1900, when about 100 short tons of the 

metal was produced, approximately half of which 

came from Australia and Norway and half from the 

United States (Fischer and King, 1964). Through 

the years, molybdenum has been produced, at one 

time or another, in some 30 countries around the 

world. The major part, Jlowever, has come from 

nine countries: the United States, Chile, Canada, 

Japan, Korea, Norway, Mexico, the U.S.S.R., and 

China. 

The United States currently supplies about 60 

percent of the world's total molybdenum; Canada, 

about 15 percent; the U.S.S.R. and China, about 

15 percent; and all other producing countries, 10 

percent. 

World production of molybdenum increased from 

about 300,000 pounds per year in 1906 to 3 million 

pounds per year in 1932, a tenfold increase during 

this 26-year period. The next tenfold increase occurred within a 5-year period in the 1930's, as a 

result of a major increase in United States production brought about chiefly by the initiation of largescale mining by block caving of the Climax ore 

body in Colorado. Production increased sharply during W o_rld War II to a high point in 1943 of 70 

million pounds of molybdenum and then decreased 

rapidly to about 24 million pounds in 1946, remaining at this level until 1949 owing to the low level of 

demand that followed the end of hostilities. Since 

1949 a relatively uniform and consistent increase 

in the annual rate of production, interrupted only 

by recession in 1958 and work stoppages in 1962, 

has continued to the present, at which time about 

200 million pounds of molybdenum is produced 

annually. 

Until 1936, domestic production of molybdenum 

was as a main product of molybdenum ores. In 

1936, at the Bingham, Utah, porphyry copper mine, 

recovery of molybdenum as a byproduct was begun; 

today about one-quarter of the United States production of molybdenum is obtained as a byproduct 

of copper mining, and at least half of the world 

production of molybdenum is obtained as a byproduct or coproduct of copper mining operations. 

For many years the famous Climax molybdenite 

mine in Colorado was the only known porphyry 

molybdenum deposit in the world; but in 1957, the 

Questa molybdenite deposit in New Mexico was 

recognized to have many characteristics of a 

stockwork-type ore body, and intensive exploration 

confirmed the presence of a large tonnage of lowgrade molybdenite ore. In 1966, open-pit mining of 

the disseminated ore body at Questa began, and by 

1969, the annual production of molybdenum was 

more than 10 million pounds. In British Columbia, 

several porphyry molybdenum and copper-molybdenum deposits were developed, and in 1966, molybdenum output from British Columbia's mines 

amounted to 20 million pounds. 

Early in the 1960's, intensive exploration was 
MOLYBDENUM 427 

undertaken at the Urad-Henderson porphyry molybdenite deposits in Colorado. Production at the 

Urad mine began in 1967 at an annual rate of about 

3 million pounds of molybdenum. In 1966, American 

Metal Climax, Inc., announced reserves of more than 

300 million tons of ore in its Henderson deposit, 

some 2,000 feet below the Urad ore body, at a grade 

of 0.49 percent molybdenite. The company expects 

to put this mine into production by the late 1970's 

Only at Climax, Colo., has the recovery of associated minerals in a porphyry-type molybdenum deposit so far been successful; tungsten (huebnerite), 

pyrite, topaz, uranium (brannerite), monazite, tin 

(cassiterite), and molybdenum oxide have been recovered as byproducts. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 1 

Molybdenum is a metallic element of Group Vlb 

of the periodic table and has atomic number 42, 

atomic weight 95.94, and occurs as six isotopes. In 

nature it has valences of +4 and +6 in molyhydrates and possibly rarely has valences in the +3 

and +5 states. Molybdenum is a rare element, its 

abundance in continental crustal rocks being generally given as 1 to 1.5 ppm. It is rather uniformly 

distributed among the igneous rocks but averages 

slightly higher in basaltic rocks than in granitic 

rocks. · 

Chemically, molybdenum can function both as a 

metal and as a nonmetal. In the geochemical cycle 

it becomes concentrated in shales, clays, and phosphorites; in these rocks, there is a positive correlation between the content of molybdenum and the 

content of organic carbon. Molybdenum is also concentrated in coal and petroleum. Of the molybdenum 

that is supplied to ocean waters, virtually all is 

precipitated either mainly with the clay minerals 

or partly in hydrous manganese oxides. 

Man's activities contribute molybdenum to the 

environment in mining, in metallurgical processing, 

in the addition of phosphate fertilizers to the soil, 

and in the conversion of coal and oil to provide for 

his various energy needs. 

MINERALOGY 

Molybdenum does not occur in nature in its free 

or native state but is found only in combination 

with other elements, such as sulfur, oxygen, tungsten, lead, uranium, iron, magnesium, cobalt, vanadium, bismuth, and calcium. The most common 

molybdenum minerals are molybdenite (molybdenum 

1 From material provided by Michael Fleischer. written eommun .• 1972. 

disulfide, MoS2), powellite (calcium molybdate, 

CaMo04), wulfenite (lead molybdate, PbMo04), 

ferrimolybdite (FeMoOa · H20), ilsemannite (molybdenum oxysulfate), and jordisite (amorphous 

molybdenum disulfide). Of these, only molybdenite, 

ferrimolybdite, and jordisite are of current economic importance. Some molybdenum has been recovered in the past, however, from wulfenite- and 

powellite-bearing ores. As the demand for molybdenum continues to rise, powellite, ferrimolybdite, 

and jordisite may be looked upon as possible source 

materials. 

TYPES OF DEPOSITS 

Molybdenum deposits are of five genetic types : 

( 1) porphyry or disseminated deposits including 

stockworks and breccia pipes in which metallic sulfides are dispersed through relatively large volumes 

of altered and fractured rock, (2) contact-metamorphic zones and tactite bodies of silicated limestone adjacent to intrusive granitic rocks, (3) 

quartz veins, (4) pegmatites and aplite dikes, and 

( 5) bedded deposits in sedimentary rocks. 

PORPHYRY DEPOSITS 

Probably more than 95 percent of the world's 

supply of molybdenum has been obtained from porphyry molybdenum or porphyry copper-molybdenum 

deposits. In these deposits primary copper sulfides 

and (or) molybdenite occur as disseminated grains 

and in stockworks of quartz veins and veinlets in 

fractured or brecciated, hydrothermally altered 

granitic intrusive rocks and in the intruded igneous 

or sedimentary country rocks. 

Favorable host intrusive rocks with which the 

ore minerals are generally assumed to be genetically 

related range from intermediate to acidic and include diorite, quartz monzonite, and granite, and 

their porphyritic equivalents. Metalization commonly took place both in the host intrusive and in 

the surrounding or overlying country rock. 

In the porphyry molybdenum deposits, molybdenite is characteristically the sole ore mineral. Molybdenite commonly is accompanied by pyrite, 

fluorite, and small amounts of tungsten, tin, lead, 

and zinc minerals. In contrast, the porphyry-copper 

or copper-molybdenum deposits contain only small 

amounts of molybdenum, and in these, the molybdenum is of economic significance only because of 

the recoverable copper content. The primary copper 

mineral is chalcopyrite, which is intimately associated with pyrite. 

The porphyry or disseminated deposits are commonly considered to be pipe-shaped bodies, circular 
428 UNITED STATES MINERAL RESOURCES 

or oval in plan and with steeply dipping sides. In 

nature, however, the deposits are more likely to be 

in complex forms, such as domal, funnel-shaped, 

arcuate, and annular bodies (Brown, 1969; James, 

1971). 

Almost invariably one or more major faults pass 

through or close to the ore bodies. Evidence of both 

preore and postore movement is abundant in these 

faults, ~nd localization of the ore bodies along major 

faults is an accepted hypothesis. Intensive, widespread and continued fracturing of host intrusives 

and of enclosing country rocks is characteristic. 

The average mineral content of porphyry-type 

deposits ranges from 0.1 to 0.5 percent molybdenite 

in molybdenum porphyries, and from about 0.015 

to 0.1 percent molybdenite in copper-molybdenum 

porphyries. Currently minable porphyry deposits 

range in size from a few hundred feet to several 

thousant feet in horizontal dimension and may 

extend to depths of several thousand feet. Fractures 

and hydrothermally altered rocks extend many hundreds of feet outward beyond the limits of minable 

ore, decreasing in intensity outward from the central zone. 

Three-fourths of the world's reserves of molybdenum are in the Western Cordillera of North and 

South America, the mountainous region along the 

western part of these continents. These reserves 

consist of large low-grade disseminated deposits of 

hydrothermal origin that occur in clusters throughout the length of the Cordillera. They are typical 

porphyry deposits, genetically associated with intrusive rocks of acidic to intermediate composition 

in areas of intense volcanism and complex tectonic 

history. The period of ore deposition extended from 

Late Triassic to middle Tertiary. 

The remaining one-fourth of the world's reserves 

of molybdenum are distributed among the U.S.S.R., 

parts of Europe, southwestern Asia, and southeastern Asia including China, the islands of the South 

Pacific, and Australia; the U.S.S.R. reserves account for at least half of this fraction. 

Porphyry or stockwork deposits that yield molybdenum alone or as the chief metal are known to 

occur principally in Alaska, British Columbia, and 

in the Rocky Mountain region of the United States 

(Clark, 1970) ; porphyry copper-molybdenum deposits from which molybdenum is obtained as a 

byproduct occur over the entire length of the Western Cordillera from Alaska to Argentina, and in 

other parts of the world (Eimon, 1970). 

The Climax and Urad-Henderson deposits in 

Colorado and the Questa deposit in New Mexico are 

described here as three examples that illustrate the 

typical porphyry molybdenum ore deposits, their 

geological relationships, and the resources connected 

with this type of deposit. Comprehensive descriptions of the porphyry copper-molybdenum deposits 

in southwestern North America are given by Titley 

and Hicks ( 1966) , and of those in the Western 

Hemisphere by Ridge (1972). 

CLIMAX, COLORADO 

For many years ( 1930-55), the Climax molybdenum deposit at Fremont Pass, about 100 miles 

west of Denver, Colo., was unique in that it was 

the only known porphyry molybdenum deposit in 

the world. Large-scale bulk mining of the disseminated ore body began in the mid-1930's, about 20 

years after its discovery and after the mining from 

near the top of the deposit of small tonnages of 

high-grade zones that contained from % to 1 percent molybdenite (Butler and Vanderwilt, 1933). 

The Climax mine, operated by the Climax Molybdenum Co. division of American Metal Climax, Inc., 

exploits one of the three largest known molybdenum 

stockwork deposits in the United States if not in 

the world. The two other deposits of equivalent size 

and character are the Questa molybdenum deposit 

in northeastern New Mexico (Molybdenum Corp. of 

America), and the Urad-Henderson molybdenum 

deposit at Empire, Colo. (Climax Molybdenum Co.). 

The Climax deposit has, according to the company's 

annual report, reserves amounting to about 500 

million tons of molybdenum ore which contain over 

2 billion pounds of molybdenum, sufficient to sustain 

the present rate of production through the remainder of this century. 

The deposit consists of a complex dome-shaped 

mass of fractured, silicified, and mineralized Precambrian granite, gneiss, and schist that generally 

overlies a composite porphyry stock of quartz monzonite to granite composition, middle Tertiary in 

age. Molybdenite associated with quartz, pyrite, 

fluorite, topaz and lesser amounts of tungsten, scandium, titanium, and tin minerals is dispersed in 

fracture fillings, in veinlets, and as minute flakes 

throughout the fractured host rocks forming a lowgrade (0.05 to 0.5 percent Mo) ore body of several 

thousand feet in smallest dimension. Several commodities, such as tungsten, pyrite, and tin, are recovered aB byproducts. Climax has become a leading United States producer of tungsten in recent 

years. A small tonnage of monazite has been recovered in the past, as has a small amount of topaz. 

According to company reports, more than 150 million tons of ore had been mined from the Climax 

deposit by 1972. The ore deposit has not yet been 
MOLYBDENUM 

delineated completely and the possibility therefore 

exists that additional reserves may be discovered 

that will at least in part replace reserves currently 

being mined. Detailed descriptions of the geology 

of the Climax area and of the deposit were given 

by Vanderwilt and King (1955) and Wallace, Baker, 

Johnson, and MacKenzie (1960). 

URAD-HENDERSON, COLORADO 

The Urad-Henderson porphyry molybdenum deposit near Empire, about 50 miles west of Denver, 

is a prime example of the discovery and development of a huge deposit as a result of careful and 

exhaustive geologic study and the use of modern 

exploration techniques. The Urad ore body, known 

for many years, was first developed on high-grade 

quartz-pyrite-molybdenite fissures and fracture 

zones, from which about half a million pounds of 

molybdenum was produced during the early part 

of the century and in the 1940's. The Urad molybdenite ore body is localized in a zone of fractured 

and altered granite around the southern margin of 

a composite granite porphyry stock (Carpenter, 

1960, p. 321) of middle Tertiary age. Molybdenite 

also occurs in veinlets and as disseminations in the 

altered and fractur~ granite between the fracture 

zones and fissures, forming a massive porphyry type 

body of many millions of tons of molybdenite ore 

containing from 0.3 to 0.5 percent molybdenite. 

About 2,000 feet below the Urad ore body, and 

separated from it by altered rocks that contain only 

traces of molybdenite, is the Henderson molybdenite 

ore body. According to the Climax Molybdenum 

Co., reserves in the Henderson ore body amount to 

over 300 million tons at a grade of 0.49 percent 

molybdenite. Very few geological data have been 

published on the Henderson deposit, but it is a 

typical porphyry or stockwork deposit. The mine is 

expected to be brought into production late in the 

1970's, with a planned milling capacity of 50,000 

tons per day. 

QUESTA, NEW MEXICO 

Molybdenite at Questa occurs in massive quartz 

veins, in a stockwork of discontinuous veinlets, and 

as fine disseminated ftakes in a hydrothermally 

altered and fractured zone several thousand feet 

wide. The quartz-molybdenite veins exploited during the earlier development period, as well as the 

stockwork molybdenite, lie along the contact of a 

composite intrusive body of granite and the overlying andesitic volcanic rocks. Molybdenite is the 

only mineral of economic importance in the deposit 

although rhodochrosite, ftuorite, and a little chalcopyrite are present. The grade of the ore body is 

low, averaging only about 0.1 percent molybdenum. 

According to company reports, more than a quarter 

of a billion tons of ore has been developed at the 

property. Despite its low grade, the Questa deposit 

promises to be one of the major domestic sources 

of molybdenum for many years. 

CONTACT -METAMOR.PHIC DEPOSITS 

In the molybdenum-bearing contact-metamorphic 

deposits (tactites and skarns), molybdenite is commonly associated with scheelite, bismuthinite, or 

copper sulfides in zones of silicated limestone near 

granitic intrusive rocks. Molybdenite also occurs 

alone in contact-metamorphic deposits. The Pine 

Creek mine in California is an example of the contact type of deposit from which molybdenum and 

tungsten have been recovered as coproducts since 

1939 (Bateman, 1956). 

Significant amounts of molybdenum also occur in 

contact-metamorphic deposits in the northeastern 

Caucasus of the U.S.S.R., in China, and in Morocco 

(Kruschov, 1959). The molybdenite deposits of the 

Knaben mine in Norway are in quartz-rich amphibolitic gneisses of probable sedimentary origin and 

may be included in this category. The ore ranges 

from 0.1 to 0.2 percent molybdenite, and although 

production from the deposit has been persistent for 

many years, it has been relatively small. 

QUARTZ VEINS 

Quartz veins containing molybdenite are widely 

distributed throughout the world. Early production 

about 1900 was made from the relatively high grade 

deposits of this type. A prime example of vein type 

bodies is found at the Questa molybdenite deposit 

at Red River, N. Mex., where small tonnages of 

molybdenite were produced between the 1920's and 

the mid-1950's from high-grade quartz-pyrite mollybdenite gash veins along the contact between a 

sodic granite and overlying andesitic volcanic rocks. 

The molybdenite content of the veins ranged from 

1 to 30 percent molybdenite. Not until the late 

1950's was it discovered that the veins were associated with mineralized rocks having the characteristics and potential for a large low-grade porphyrytype molybdenite ore body associated with a composite granite stock. 

PEGMATITES 

Commonly, pegmatite bodies and aplite dikes contain molybdenite among many other metallic and 
430 UNITED STATES MINERAL RESOURCES 

nonmetallic @onstituents. The molybdenite is generally coarsely crystalline, occurring as rosettes or 

thick books and aggregates of flakes, which are 

erratically distributed in the host rocks. Although 

much specimen material of ex(!ellent quality can be 

obtained from this type of deposit, few deposits 

have been of economic interest owing to the characteristically small tonnage available and the erratic 

distribution of molybdenite. Notable among the pegmatite-type deposits that have yielded significant 

quantities of erratically disseminated molybdenum 

are those at Val d'Or and Preissac, in eastern Quebec, where molybdenite is associated with bismuth 

in pegmatite bodies and greisen zones (Vokes, 

1963). 

BEDDED DEPOSITS IN SEDIMENTARY ROCKS 

Although molybdenum is concentrated in coals, 

shales, and phosphorites, no molybdenum of economic grade has been found in these rocks. Only in 

certain lignitic sandstone beds of southwestern 

North Dakota, northwestern South Dakota, and 

eastern Montana, and in some arkosic sandstone 

beds in the badlands of southwestern South Dakota 

and northeastern Utah, has the molybdenum content approached ore grade (0.1 to 0.2 percent Mo) 

in deposits thick enough to be minable. 

In the United States, molybdenum is associated 

in significant amounts with some of the bedded 

sandstone uranium deposits in Arizona, Wyoming, 

South Dakota, New Mexico, and Utah, and in the 

Gulf Coast region of Texas. Similar occurrences undoubtedly exist in other parts of the world, but 

published data are not readily available on these 

deposits. The molybdenum is in the minerals jordisite and ilsemannite and is present in amounts 

ranging from a few parts per million to more than 

0.5 percent. It is irregularly distributed with respect 

to the uranium ore bodies, commonly occurring 

along or some distance from the outer margins of 

the ore bodies rather than within them. Ordinarily 

the small amount of molybdenum present in this 

type of ore deposit is detrimental because the molybdenum interferes with the recovery of uranium 

and must be segregated out of the circuits during 

milling processes. However, where the uranium deposits are of sufficient size and the molybdenum 

content is significant, a valuable byproduct may 

exist. According to the U.S. Bureau of Mines, 

molybdenum has been recovered from composites 

of uranium ores and ash residues of some uraniumbearing lignites from South Dakota and New 

Mexico. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

About half the world's identifieti resources of 

molybdenum are in the United States, and of these 

resources, about 75 percent occur in deposits where 

molybdenum is the principal metal sought. The other 

half of the world's identified resources are distributed among more than 30 countries around the 

world. These resources occur as large bodies of 

fairly· uniformly mineralized rock containing more 

than 500 ppm (parts per million) (0.05 percent) of 

molybdenum if no other valuable metal is present 

in significant amounts, or more than 50 ppm ( 0.005 

percent) of molybdenum if molybdenum is not the 

primary metal sought. 

Most of the identified resources of molybdenum 

are in the disseminated or porphyry-type deposits 

of the Colorado Mineral Belt, the Sangre de Cristo 

Range in New Mexico, and the Basin and Range 

province of the southwestern United States; the 

Interior Belt of British Columbia, Canada; the Andean Cordillera of Peru and Chile; and the Ural 

and Altai Mountains of the U.S.S.R. (table 85). 

Many of these deposits have been explored only to 

a minimal extent, and the metal contents appear to 

be lower than current ore grades-molybdenum in 

porphyry molybdenum deposits in the order of 

0.01 to 0.1 percent and copper in porphyry coppermolybdenum deposits in the order of 0.1 to 0.2 

percent-too low to be profitably mined under 

present conditions. 

The magnitude of the identified resources of molybdenum can only be partly estimated directly from 

published data and statistics,_ because of the large 

fraction that is associated with copper resources. 

Clearly a sizable part of the discussion of the resources of molybdenum must therefore be based on 

geologic and geochemical information. 

Large quantities of molybdenum probably are 

still hidden in areas of known deposits, as extensions of mining districts or mineral belts, and occur 

in deposits similar in geologic character and grade 

to those already known. Such hypothetical resources 

are predicted on the basis of known distributions 

of geologic environments favorable for molybdenum 

deposits and on the basis of our current understanding of the processes of deposition of molybdenum 

deposits. The bulk of hypothetical resources thus 

estimated amounts to about 1 billion tons of molybdenum, a large part of which appears to be equally 

divided between the United States and the U.S.S.R. 

Table 85 is a summary of the estimated world 

resources of molybdenum. 
MOLYBDENUM 431 

TABLE 85.-Estimated magnitude, in millions of pounds, 

of world resources of molybdenum 

Area 

North America: 

Canada: 

British Columbia ----- Quebec --------···------ Subtotal _______________ ._ 

Greenland ---------------- Uni.ted States: 

Alaska --------------- Arizona -------------- Colorado -------------

Idaho ---------------- Maine --------------- Montana ------------- Nevada -------------- New Mexico ---------- North Carolina -------

Texas ---------------- Utah ---------------- VVashington ---------- VVyoming ------------

Subtotal ---------------

Puerto Rico --------------

Identified 

resources 1 

8,000 

2,000 

10,000 

200 

1,000 

2,000 

20,000 

1,000 

100 

1,000 

500 

8,000 

100 

100 

1,000 

200 

100 

35,100 

500 

Mexico ------------------- =~~= 

Central America ----------

1,000 

1,000 

Total ------------------ South America: 

Argentina ---------------- Columbia ----------------- Ecuador -----------------

Chi~ --------------------- Peru ---------------------

Total ------------------ Europe: 

Bulgaria ----------------- Rumania ----------------- Spain -------------------- Yugoslavia ---------------

Total ------------------ Africa: 

!dorocco ------------------ Sierra Leone -------------

Total ------------------ Asia: 

Burma -------------------

China -------------------- India -------------------- Iran --------------------- Japan -------------------- U.S.S.R. ----------------- Thailand ----------------- Vietnam ------------------

Total ------------------ Antarctica -------------------

Australia -------------------- Oceania: 

Borneo ------------------- Bougainville -------------- New Guinea -------------- Philippines ---------------

Total ------------------

47,800 

100 

100 

100 

5,500 

1,300 

7,100 

100 

100 

100 

1,000 

1,300 

50 

50 

100 

100 

1,000 

50 

100 

100 

5,000 

50 

50 

6,450 

50 

100 

30 

40 

30 

100 

200 

VVorld total ------------------ ===::=::::=:=:::::===.::== 8 63,100 

Hypothetical 

resources 2 

---------

--------- 10 li 

---------

---------

---------

---------

---------

---------

---------

---------

---------

---------

---------

---------

---------

--------- 10' 

---------

---------

--------- 10' 

---------

---------

---------

---------

--------- 10 11 

---------

---------

---------

--------- 10' 

---------

--------- 10 2 

---------

---------

---------

---------

---------

---------

---------

--------- 10' 

10 2 

10 I 

---------

---------

---------

--------- 10' 

'2.2 X 10 1 

1 Identified resources are specific, identified mineral deposits that 

may or may not be evaluated as to extent and grade, and whose eon• tained minerals may or may not be profitably recoverable with existing technology and economic conditions. 2 Hypothetical resources are undiscovered mineral deposits, whether of 

recoverable or subeeonomic grade, that are geologically predictable as existing in known districts. a Equal to 31,650,000 tons. ' Equal to 1.1 billion tons. 

SPECULATIVE RESOURCES 

Speculation as to worldwide distribution and magnitude of molybdenum resources necessarily must 

be based on geologic relationships of the deposits 

that are best documented and most clearly understood. Domestic deposits offer the best information 

in this regard; consequently models based largely on 

occurrences in the United States and the Western 

Hemisphere as described under "Porphyry Deposits" 

are used to infer speculative resources. 

World molybdenum resources are likely to be divided somewhat equally between deposits that contain molybdenum as the primary metal and those 

in which molybdenum is expected to be a byproduct 

or coproduct. Porphyry-molybdenum and porphyrycopper deposits are expected to contain by far the 

bulk of molybdenum resources. 

Porphyry-molybdenum or porphyry-copper deposits are individual mineral deposits associated with 

stocklike intrusives, breccia structures, and faults. 

Distribution of this type of deposit worldwide, 

therefore, should be related to the distribution of 

certain major geologic features: 

1. The deposits are found in belts of CretaceousTertiary tectonic activity that were disturbed 

by subsequent igneous activity (Eimon, 1970). 

They occur along the cordillera of North and 

South America, the Alpide belt (Sillitoe, 

1972), the Iranian orogenic belt, the south 

Pacific Arc, and in the Ural and Altai Mountains of the U.S.S.R. 

2. They are associated mostly with intrusive activity that ranges in age from Triassic to 

mid-Tertiary (Sillitoe, 1972). 

3. They occur in intrusive rocks of intermediate to 

acid composition ; porphyry molybdenum deposits tend to be associated with granitic intrusives and porphyry copper-molybdenum deposits with instrusives of intermediate composition. 

4. The molybdenum deposits commonly occur in 

clusters or groups of 5 to 20 miles in radius 

(King, 1970). 

5. Porphyry deposits are commonly found in areas 

of gravity and magnetic lows; porphyry molybdenum deposits related to Tertiary silicic 

intrusives tend to occur in regional gravity 

lows. 

6. Molybdenum deposits are commonly alined in 

major structural belts and at intersections of 

structural belts (Noble, 1970). 

7. The intrusive rocks and commonly the intruded 

rocks show evidence of local and regional frac-
432 UNITED STATES MINERAL RESOURCES 

turing of an intense nature and of long duration (Rehrig and Heidrick, 1972). 

8. The deposits are associated with intrusives of a 

complex nature showing evidence of multiple 

intrusion events (Wallace and others, 1968). 

9. Intense hydrothermal alteration of host intrusive as well as of country rocks with an accompanying variety of accessory minerals is 

a trademark of porphyry deposits (Vanderwilt and King, 1955). 

Using a combination of some of the geologic features just described, we have estimated speculative 

resources of molybdenum in and near the State of 

109° 108° 41or-- rI 

I 

I 0 

I 

I 40l 

I 

I 

I 

I 39l 

I 

I 

I 0 .. I 

38°1-

I 

Colorado as an example. 

The known molybdenum occurrences in and near 

Colorado occur in clusters that are shown in figure 

52. These clusters of molybdenum deposits are 

closely associated with area.S of principal middle 

Tertiary silicic intrusive activity. The molybdenum 

occurrences and associated intrusives are spatially 

related to major gravity lows, also shown in 

figure 52. 

Three of the clusters of molybdenum occurrences 

contain the major porphyry molybdenum deposits 

at Henderson, at Climax, and at Questa. Some evidence suggests that the other clusters shown may 

104° 

----,--- ------, 

EXPLANATION 

-250 milligals -300 milHpls 

Bouguer gravity contours 

(from Woollard and Joesting, 1964)_ 

,_.-

\..' 

Limits of principal tertiary intrusive 

activity 

0 

Ouster of known molybdenum occurrences 

+ 

Major molybdenum deposit 

I 

I 

I 

I 

I 

1 

I 

I 

I 

I 

I 

l 

' I 

I 

I 

., 

50 

I 

0 

I 

50 MILES 

I I 

I 

I 

__L.fOLORADO 

1

. 

_____ _1 -- NEW MEXICO 

OKLAHOMA 

I 

I 

r-:;:;A~-

FIGURE 52.-Map showing location of molybdenum resources in Colorado and northern New Mexico in relation to various 

geologic parameters. 
MOLYBDENUM 

also contain major molybdenum deposits, though 

perhaps not all of minable grade. For example, the 

cluster of occurrences next southwest of the Climax 

cluster has been drilled by exploration companies 

for many years, and although no minable deposit 

has been discovered, a phenomenal amount of widely 

dispersed molybdenum has been revealed, probably 

greater in amount than is contained in the Climax 

deposit itself (Ogden Tweto, oral commun., 1972). 

From a geological standpoint, but not an economic 

standpoint at this time, this cluster contains a major 

molybdenum deposit. 

Molybdenum deposits known in the San Juan 

Mountains in southwestern Colorado occur largely 

in the volcanic pile overlying the intrusive bodies 

that form the roots of the present San Juan volcanic field. Deposits in central Colorado in the main 

segment of the Colorado Mineral Belt are associated with intrusive bodies that represent the rootzone of a volcanic field now largely stripped away 

by erosion. If major molybdenum deposits occur in 

the San Juan field, presumably they lie at depth in 

the root-zone of the present volcanic pile, analogous 

to the central Colorado deposits. Occurrences known 

at the surface in the San Juan field are likely "leakages" from deeper seated deposits. The geological 

probability of major· molybdenum deposits at depth 

in the San Juan Mountains seems good, although 

the economics of mining them, even if they could 

be found now, are at present unfavorable. 

The three known major molybdenum deposits in 

and near Colorado have produced or contain unmined resources estimated at 5 X 109 lbs molybdenum 

each. Returning to the earlier conclusion that each 

of the 10 clusters of molybdenum occurrences shown 

on the map likely contains a major molybdenum 

deposit, we can estimate a total resource for the map 

area of roughly 5 X 1010 lb molybdenum, occurring 

in the vicinity of surface occurrences of molybdenum. 

By making further assumptions that volcanic and 

other young rocks in the San Juan Mountains and 

in the vicinity of Questa may cover unknown clusters of molybdenum occurrences and that the spacing of clusters of molybdenum occurrences in the 

root-zone of a middle Tertiary igneous province is 

similar to that shown in the central Colorado part 

of the Colorado Mineral Belt where a root-zone is 

exposed, it is logical to infer the presence of additional unknown clusters in the San Juan Mountains 

and in the vicinity of Questa. Such unknown clusters 

may nearly equal in number those already known 

at the surface, judged from the areas of possible 

molybdenum occurrence implied by the outlines of 

gravity lows and of middle Tertiary intrusive activity shown on the map. If this assumption is correct, perhaps about 20 major molybdenum deposits 

exist in and near Colorado, representing a total 

resource of roughly 1011 lb molybdenum. 

PROSPECTING 

The search for molybdenum is facilitated by the 

physical properties of molybdenite as well as by the 

geochemical characteristics of the element. Molybdenite does not oxidize readily, and because of its 

bright silvery gray color and a strong platy c:cystal 

habit, it can be seen by eye in concentrations 

amounting to less than 100 ppm in light-colored 

rocks. Molybdenum is a mobile element and is both 

sulfophile and oxyphile. These characteristics work 

both for and against the prospector. In chemically 

acid environments, · as in the presence of pyrite, 

molybdenite commonly is fixed in place, chiefly as 

ferrimolybdite, a recognizable molybdenum mineral, but also very commonly is attached to ironbearing clay minerals, and to goethite and other 

limonitic minerals, in which forms it is not ordinarily recognizable. Fortunately, molybdenum in 

its six-valence oxidation state is amenable to inexpensive and rapid detection by qualitative and 

semiquantitative chemical and spectroscopic methods that have threshold sensitivities in the parts 

per million range, approaching and even reaching 

crustal-abundance values of molybdenum. In chemically less acid environments or in alkaline environments, molybdenite may convert to ilsemannite, a 

water-soluble blue efflorescence. 

Because the economically significant molybdenum 

deposits of today, and probably of the foreseeable 

future, are the large volume stockworks and 

porphyry-type deposits related to fractured and 

hydrothermally altered granitic intrusive rocks, 

various geophysical techniques are useful prospecting methods (Sumner, 1969). Anomalously low 

magnetism may be detected as a result of the removal of magnetite during hydrothermal alteration 

of host intrusives, and low gravitational anomalies 

due to large intrusive stocks of granitic rocks may 

be measurable. 

In terranes that are characterized by large volumes of silicic intrusive rocks as young as Tertiary 

in age, such as the Western Cordillera of the United 

States, low regional gravity values are closely correlated with distribution of the young silicic rocks; 

because molybdenum seems to be preferentially 

concentrated around silicic intrusives of Tertiary 

age in this region, major regional gravity lows reflect regions favorable for molybdenum deposits. In 
UNITED STATES MINERAL RESOURCES 

terranes characterized by large volumes of silicic 

rocks older than Tertiary, such as Britich Columbia, 

low regional gravity values are not correlated 

closely with the distribution of the silicic rocks; 

inansmuch as molybdenum is associated principally 

with Mesozoic intrusives in British Columbia, major 

regional gravity lows do not correlate closely with 

regions of known molybdenum deposits. 

Residual heat in intrusive rocks, heat from exothermal weathering of sulfides, and differences in 

vegetative cover due to metal concentration and 

alteration may be detected by airborne infrared 

imagery techniques, but these methods are not adequately developed to date to be highly useful in 

exploration. Geochemical and biochemical sampling 

of vegetative cover, soils, rocks, and water have 

been used to delineate general target areas of molybdenum concentration at and near ground surface. 

PROBLEMS FOR RESEARCH 

Because economic exploitation of molybdenum 

today requires that large tonnages of ore be mined 

and processed, large surface areas will be disturbed 

whether mining be done by underground methods 

or by open-pit methods; and because of the low 

mineral content of the ores, large surface areas will 

be needed for disposal of the residual waste materials. Molybdenum exploitation therefore is subject to the same or similar environmental problems 

as any large-scale operations, whether it be strip 

mining of coal, stone quarrying, mining of beachsand deposits, or opencut mining of iron, aluminum, 

and copper. 

Successful prediction of the location of presently 

unknown molybdenum deposits will come mostly 

from improved understanding of ( 1) the genetic 

connection between molybdenum (as well as associated elements) and the magmatic rocks around 

which molybdenum deposits formed, (2) the environments in which the magmatic rocks were generated and emplaced,_ and (3) the role of plate tectonics in developing favorable environments for 

generation and emplacement of molybdenumcarrying magmatic rocks. 

SELECTED BIBUOGRAPHY 

Anderson, C. A., 1969, Copper, in Mineral and water resources of Arizona: Arizona Bur. Mines Bull. 180, p. 

117-156. 

Anderson, C. A., Scholz, E. A., and Strobell, J. D., Jr., 1955, 

Geology and ore deposits of the Bagdad area, Yavapai 

County, Arizona, U.S. Geol. Survey Prof. Paper 278, 

103 p. 

Aubry, J., and Malaprade, L., 1959, Molylidene, in Pascal, 

Paul, ed., Nouveau traite de chimie minerale: Paris, 

Masson et Cie. Editeurs, v. 14, p. 663--745. 

Bateman, P. C., 1956, Economic geology of the Bishop tungsten, district, California: California Div. Mines Spec. 

Rept. 47,87 p. 

Bauer, H. L., Jr., Cooper, J. J., and Breitrick, R. A., 1960, 

Porphyry copper deposits in the Robinson mining district, White Pine County, Nevada, in Geology of east 

central Nevada: lntermtn. Assoc. Petroleum Geologists, 

11th Ann. Field Conf., 1960 Guidebook, p. 220-228. 

Bieniewski, C. L., 1970, Demand and supply of molybdenum 

in the United States: U.S. Bur. Mines Inf. Circ. 8446, 

61 p. 

Brown, A. S., 1969, Mineralization in British Columbia and 

the copper and molybdenum deposits: Canadian Inst. 

Mining and Metallurgy, and Mining Soc. Nova Scotia 

Trans., v. 72, p. 1-15. 

Bryner, Leonid, 1969, Ore deposits of the Philippines-An 

introduction to their geology: Econ. Geology, v. 64, p. 

644-666. 

Bugge, Arne, 1963, Norges molybdenforekomster: Norges 

Geol. Undersokelse [Shr.] NR 217, 134 p. 

Butler, B. S., and Vanderwilt, J. W., 1933, The Climax 

molybdenum deposit, Colorado: U.S. Geol. Survey BulL 

846-C, p. 195-237. 

Carpenter, R. H., 1960, Urad deposit, in Molybdenum, chap. 

4 of Del Rio, S. M., ed., Mineral. resources of Colorado, 

First sequel: Denver, Colorado Mineral Resources Board, 

p. 321-325. 

Clark, K. F., 1970, Characteristics of disseminated molybdenum deposits in the Western Cordillera of North 

America: New York, Am. Inst. Mining, Metall. and 

Petroleum Engineers, preprint 70-1-90, 16 p. 

Cobb, E. H., 1960, Molybdenum, tin, and tungsten occurrences 

in Alaska: U.S. Geol. Survey Mineral Inv. Resources 

Map MR-10. 

Creasey, S. C., 1954, Geology of the Starr Molybdenum mine, 

Okanogan County, Washington, in Purdy, C. P., Jr., 

Molybdenum occurrences of Washington: Washington 

Div. Mines and Geology Rept. Inv. 18, p. 51-62. 

-- 1957, Geology and resources, in Mcinnis, Wilmer, 

Molybdenum, material survey: U.S. Bur. Mines Inf. Circ. 

7784, p. 7-15-

-- 1959, Some phase relations in the hydrothermally altered rocks of porphyry copper deposits~ Econ. Geology, 

v. 54,no.3,p.351-373. 

De Geoffroy, J., and Wignall, T. K. ,1972, A statistical study 

of geological characteristics of porphyry coppermolybdenum deposits in the Cordilleran Belt-application to the rating of porphyry deposits: Econ. Geology, v. 

67, no. 5, p. 656-668. 

Eimon, P., 1970, Fifty years-Worldwide porphyry copper discoveries: Tucson, Ariz., 50th Anniversary Soc. Econ. 

Geologists, 7 p. 

Engel, A. E. J., Engel, C. G., and Havens, R. G., 1965, Chemical characteristics of oceanic basalts and the upper 

mantle: Geol. Soc. America Bull., 'v. 76, no. 7, p. 719-

734. 

Fischer, R. P., and King, R. U., 1964, Trends in the consumption and supply of molybdenum and vanadium: 

New York, Am. In-st. Mining, Metall. and Petroleum 

Engineers, preprint 64 K-2, 18 p. 

Huntting, M. T., 195S, Metallie minerals, Pt. 2 of, Inventory 

of Washington minerals: Washington Div. Mines and 

Geology Bull. 37, v. 1, 428 p. 
MOLYBDENUM 435 

Ishihara, S., 1971, Major molybdenite deposits and related 

granitic rocks: Geol. Survey Japan Rept. 239, 178 p. 

James, A. H., 1971, Hypothetical diagrams of several 

porphyry copper deposits: Econ. Geology, v. 66, no. 7, 

p. 43-47. 

King, R. U., 1966, Molybdenum, in Mineral and water resources of New Mexico: New Mexico Bur. Mines and 

Mineral Resources Bull. 87, p. 201-20·7. 

--- 1966, Molybdenum, in Mineral and water resources of 

Washington: U.S. Cong. 89th, 2d sess., Comm. Interior 

and Insular Affairs, Comm. Print, p. 109-116. 

--- 1969, Molybdenum and rhenium, in Mineral and water 

resources of Arizona: Arizona Bur. Mines Bull. 180, p. 

230-238. 

--- 1970, Molybdenum in the United States: U.S. Geol. 

Survey Mineral Inv. Resource Rept. MR-66. 

Kirkemo, Harold, Anderson, C. A., and Creasey, S. C., 1966, 

Investigations of molybdenum deposits in the conterminous United States, 1942-60: U.S. Geol. Survey Bull. 

1182-E, 90 p. 

Kruschov, N. A., 1969, Classification of molybdenum deposits, 

in Geology of ore deposits: Acad. Sci. USSR, no. 6, p. 

62-67. 

Kuroda, P. K., and Sandell, S. B., 1954, The geochemistry 

of molybdenum: Geoehim. et Cosmoehim. Acta, p. 36-63. 

Lowell, J. D., and Guilbert, J. M., 1970, Lateral and vertical 

alteration-mineralization zoning in porphyry ore deposits: Econ. Geology, v. 66, no. 4, p. 373-408. 

MacKevett, E. M., Jr., Brew, D. A., Hawley, C. C., Huff, 

L. C., and Smith, J. G., 1971, Mineral resources of 

Glacier Bay National Monument, Alaska: U.S. Geol. 

Survey Prof. Paper 632, 90 p. 

Ney, C. S., 1966, Distribution and genesis of copper deposits 

in British Columbia, in A symposium on the tectonic 

history and mineral deposits of the western cordillera, 

Vancouver, B. C., 1964: Canadian Inst. Mining and 

Metallurgy Spec. Vol. 8, p. 296-303. 

Noble, J. A., 1970, Metal provinces of the western United 

States: Geol. Soc. America Bul., v. 81, p. 1607-1624. 

Purdy, C. P., Jr., 1954, Molybdenum occurrences of Washington: Washington Div. Mines and Geology Rept. Inv. 

18, 118 p. 

Rechenberg, H. P., 1960, Molybdan, v. 12, of Die metallischen 

Rohstoffe: Stuttgart, Ferdinand Enki Verlag, p. 128. 

Rehrig, W. A., and Heidrick, T. L., 1972, Regional fracturing in Laramide stocks of Arizona and its relationship 

to porphyry copper mineralization: Eeon. Geology, v. 

67, no. 2, p. 198-213. 

Ridge, J. D., ed., 1968, Ore deposits of the United States 

1933-1967 (Graton-Sales volume), v. 2: New York, Am. 

Inst. Mining Metall. and Petroleum Engineers, p. 992-

1880. 

--- 1972, Annotated bibliographies of mineral deposits in 

the Western Hemisphere: Geol. Soc. America Mem. 

131, 681 p. 

Roedder, Edwin, 1971, Fluid inclusion studies on the 

porphyry-type ore deposits at Bingham, Utah, Butte, 

Montana, and Climax, Colorado: Econ. Geology, v. 66, 

no. 1, p. 98-120. 

Rose, A. W., 1970, Zonal relations of wallroek alteration and 

sulfide distribution at porphyry copper deposits : Econ. 

Geology, v. 66, no. 8, p. 920-936. 

Sauchelli, Vincent, 1969, Trace elements in agriculture: New 

York, Van Nostrand Reinhold Co., 248 p. 

Schilling, J. H., 1964, Molybdenum, in Mineral and water resources of Nevada: U.S. Cong., 88th, 2d sess., Senate 

Doe. 87; Nevada Bur. Mines Bull. 66, p. 124-132. 

Sillitoe, R. H., 1972, A plate tectonic model for the origin 

of porphyry copper deposits: Econ. Geology, v. 67, no. 

2, p. 184-197. 

Stringham, Bronson, 1968, Relationship of ore to porphyry 

in the Basin and Range province, U.S.A.: Eeon. Geology, 

v. 63,no.7,p. 806-822. 

Sumner, J. S., 1969, Geophysical aspects of porphyry copper 

deposits, in Morley, L. W., ed., Mining and groundwater 

geophysics, 1967-Canadian Centennial Conference on 

Mining and Groundwater Geophysics, Proe., Niagara 

Falls, Canada, 1967: Canada Geol. Survey Econ. Geology 

Rept.26,p.322-335. 

Sutulov, A., 1962, Molybdenum: Santiago, Ohile, University 

of Concepcion, 214 p. 

--- 1967, Copper production in Russia: Santiago, Chile, 

University of Concepcion, 220 p. 

Titley, S. R., and Hicks, C. L., eds., 1966, Geology of the 

porphyry copper deposits, southwestern North America: 

Tucson, Ariz., Arizona Univ. Press, [Wilson volume], 

287 p. 

Vanderwilt, J. W., and King, R. U., 1956, Hydrothermal alteration at the Climax molybdenite deposit: Am. Inst. 

Mining Engineers Trans., v. 202, p. 41-63. 

Vokes, F. M., 1963, Molybdenum deposits of Canada: Canada 

· Geol. Survey Econ. Geology Rept. 20, 332 p. 

Wallace, S. R., Baker, R. C., Jonson, D. C., and MacKenzie, 

W. B., 1960, Geology of the Climax molybdenite deposit 

-a progress report, in Rocky Mtn. Assoc. Geologists, 

Guide to the geology of Colorado: Geol. Soc. America, 

Mtn. Assoc. Geologists, and Colorado Sci. Soc., p. 238-

262. 

Wallace, S. R., Muncaster, N. K., Jonson, D. C., MacKenzie, 

W. B., Bookstrom, A. A., and Surface, V. E., 1968, 

Multiple intrusion and mineralization at Climax, Colorado, Chap. 29 of Pt. 6, Colorado Rockies, in Ridge, J. 

D., ed., Ore deposits of the United States, 1933-1967 

(Graton-Sales volume) v. 1 : New York, Am. Inst. Mining, Metall. and Petroleum Engineers, p. 606-640. 

Woollard, G. P., and Joesting, H. R., 1964, Bouguer gravity 

anomaly map of the United States: American Geophysical Union, Special Committee for the geophysical and 

geological study of the continents, and U.S. Geol. Survey, unnumbered map, 2 sheets. 

UNITED STATES MINERAL RESOURCES 

NICKEL 

By HENRY R. CoRNWALL 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Exploitation problems ----------------------------

Geologic environment ----------------------------

Geochemistry --------------------------------

Nickel minerals ------------------------------

Types of deposits ----------------------------

Sulfide deposits --------------------------

Nickeliferous laterite deposits ------------- Resources ______________ -~- ______________________ _ 

Identified resources ---·-----------------------

Speculative resources ------------------------

Prospecting techniques ---------------------------

Problems for research ---------------------------

References cited ---------------------------------

TABLES 

86. Nickel minerals -----------------------------

87. World nickel-sulfide resources ----------------

88. World nickel-laterite resources ---------------

ABSTRACT OF CONCLUSIONS 

Page 

437 

437 

438 

438 

438 

438 

439 

439 

440 

440 

440 

441 

442 

442 

442 

Page 

438 

440 

441 

At the present time the free world requirement of nearly 

1 billion pounds of nickel per year is supplied from deposits 

of nickel sulfides, mostly in Canada, and of nickel laterites, 

mainly in New Caledonia. World resources from these types 

of deposits are estimated to total 70 million tons (140 billion pounds) of nickel in 7 billion tons of material averaging about 1 percent nickel. An additional 7 billion tons 

averaging 0.2 percent nickel, or 14 million tons of nickel, is 

estimated for sulfid·e deposits in the United States. The 

0.2-0.4 percent of nickel universally disseminated in peridotites and serpentinites throughout the world amounts to a 

figure several orders of magnitude greater than 70 million 

tons, as does the quantity of nickel contained in deep-sea 

mangenese nodules; but new technological developments will 

be required to recover nickel successfully from these two 

types of occurrence. The discovery in 1949 at Thompson, 

Manitoba, of a major new type of nickel sulfide deposit suggests the possibility that similar deposits may exist elsewhere in the world. 

INTRODUCTION 

Nickel is vital to the economic welfare and security of the United States, as it is also to the 

other industrial nations of the world. This is illustrated by examining the uses of nickel. In 1970 

(U.S. Bureau of MinP.s, 1970, Minerals Yearbook) 

the United States consumption was: 

Use 

Steel ----------------------------------- Super alloys ---------------------------- Nickel-copper alloys --------------------- Permanent magnet alloys ----------------- Other nickel alloys ----------------------

Cast irons ------------------------------ Electroplating ________ --___ -----------_ --

Chemicals ------------------------------

Other -----------------------------------

Total -----------------------------

Ccn&BUmption (million 

pounds) 

124 

23 

13 

5 

71 

10 

50 

2 

14 

312 

Free world consumption (Metals Week, Jan. 3, 

1972) in 1970 and 1971, by area, was as follows: 

Ccn&BUmption 

(million pounds) 

Area 1970 1971 

Western Europe and United Kingdom__ 376 327 

United States ---------------------- 330 273 

Japan ----------------------------- 202 172 

Canada ---------------------------- 33 24 

Australia -------------------------- 9 9 

Other ----------------------------- 25 20 

Total ------------------------ 975 825 

The United States obtains most of its nickel from 

foreign sources-mainly Canada. Since 1966 the 

primary production of nickel in the United States 

has averaged 26 million pounds per year. The remainder of the nickel consumed has come almost 

entirely from Canada. The United States is thus 

almost completely dependent on foreign sources of 

nickel under present economic conditions. 

U.S. GEOL. SURVEY PROF. PAPER 820 

437 
438 UNITED STATES MINERAL RESOURCES 

EXPLOITATION PROBLEMS 

Exploitation problems in nickel mining and processing are in part the same as or similar to those 

for copper. Air pollution is a major problem around 

the smelters, and it is likely that strict controls on 

·smoke exhalations will soon be enforced throughout 

the United States. Most other countries are less concerned with air pollution at the present time, but 

demands for stricter control are also increasing in 

those countries. 

Another major consideration, particularly applicable to some areas of large potential laterite development, is that the political climate of some 

countries is not conducive to huge long-term investment (hundreds of millions of dollars) and a long 

development period ( 5 years or more for a large 

operation). 

The cost and difficulty of recovering nickel-bearing 

nodules from mid-ocean depths of 3,500-4,500 

meters are major problems. Furthermore, suitable 

refining methods have yet to be demonstrated. The 

availability of large and relatively low-cost sources 

of the component metals on land also reduces incentive to their development. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Nickel is widespread in nature and is estimated 

to be the fifth most abundant element of the earth. 

Estimates of the nickel content of the earth's crust 

range from 0.008 to 0.02 weight percent (Fleischer, 

1953). Ultramafic igneous rocks-dunite, peridotite, 

and pyroxenite--contain the most nickel, 0.1-0.3 

percent; Vinogradov (1956) estimated the average 

nickel content of these rocks to be 0.12 percent. His 

estimates for other rock types are: mafic igneous 

rocks (basalt, gabbro, norite, and related rocks), 

0.016 percent; neutral igneous rocks (diorite and 

andesite), 0.0055 percent; silicic igneous rocks 

(granite, rhyolite, and related rocks), 0.0008 percent ; and sedimentary rocks (clay and shale) , 

0.0095 percent. 

A generally accepted theory is that the core of 

the earth, 4,300 miles in diameter, has a composition similar to that of iron meteorites, most of which 

are kamacite-native iron with a nickel content of 

almost 7 percent. Inasmuch as the margin of the core 

is 1,800 miles below the earth's surface, this vast 

amount of nickel will probably never become available to man. The crust of the earth (about 10 miles 

thick), from which man must obtain the nickel he 

needs, contains only 0.003 percent of the total nickel 

in the earth, as computed from data given by Mason 

( 1958, p. 44, 50). 

The mantle, lying between the crust and the core 

of the earth, is nearly 1,800 miles thick and is believed to be peridotitic. Rocks of this ultramafic 

zone, like similar rocks exposed at the surface, may 

contain 0.1-0.3 percent nickel. Because the mantle 

makes up more than two-thirds of the total mass 

of the earth, it probably contains a large quantity 

of nickel. 

The peridotite and related mafic rocks that have 

intruded the crust of the earth, and are in part 

exposed at the surface, probably have been derived 

largely from the mantle. Furthermore, most of the 

known nickel ore deposits are closely associated 

with mafic and ultramafic intrusive rocks, and the 

nickel in the ore bodies was probably derived either 

from the intrusives themselves or from similar rocks 

at depth. Thus the original source of most of the 

nickel ore bodies found in North America and elsewhere in the world was probably the mantle. 

NICKEL MINERALS 

The nickel minerals are given in table 86. The 

nickel-iron sulfide pentlandite [ (Fe,Ni) 9Ss] is the 

principal present economic source of nickel, and 

garnierite (nickel-magnesium hydrosilicate) is next 

in economic importance. Garnierit~also called 

nickel gymnite, genthite, noumeite, and nepouit~ 

TABLE 86.-Nickel minerals 

Mineral 

Native nickel-iron ___ _ 

Pentlandite ---------- Bravoite ------------

Violarite ------------ Vaesite ------------- Polydymite ---------- Millerite ------------

Heazlewoodite ------- Siegenite ------------ Linnaeite ------------ Gersdorflite ---------- Niccolite ------------ Rammelsbergite ------ Chloanthite ---------- Smaltite ------------ Skutterudite --------- Maucherite ---------- Breithauptite -------- Ullmannite ---------- Parkerite ------------ Annabergite ---------

Morenosite ---------- Zaratite -------------

Garnierite -----------

Formula 

NiaFe 

(Fe,Ni)eSs 

(Fe,Ni)Sa 

NiaS2 

(Ni,Co)aS~ 

( Co,Fe,Ni) .s~ 

NiAsS 

NiAs 

NiAs2 

(Ni,Co)Asa-.. ( Co,Ni) Asa-.. (Co,Ni)Asa 

NiuASs 

NiSb 

NiSbS 

NiaBi2Sa 

Nia(As0,):~·8H:O 

NiS0,·7H:O 

NiCoa·2Ni(OH)2 ·4H~~O 

Nickel-magne- sium hydrosilica.te 

Occurrence 

Rare. 

Common. 

Minor; 

secondary. 

Do. 

Rare. 

Do. 

Minor; 

secondary. 

Rare. 

Minor. 

Do. 

Do. 

Do. 

Rare. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Do. 

Rare; 

secondary. 

Do. 

Do. 

Common; 

secondary. 
NICKEL 439 

is not a true mineral but rather a mixture of nickel 

serpentine, nickel talc, and possibly other silicates. 

Besides the nickel mnierals given in table 86, 

nickel occurs in minor amounts in pyrrhotite 

(Fel-xS) and pyrite (FeS2), particularly where 

these sulfides are associated with mafic or ultramafic 

rocks. In most of these occurrences the total amount 

of included nickel is less than 1 percent. Nickel may 

replace iron to a considerable extent in these minerals, but substantial amounts may also be present 

as intergrowths of pentlandite or other nickel sulfides. Native terrestrial iron also contains nickel, 

ranging in amounts from 2 to 75 percent, but such 

native nickel-iron is rare; it occurs in basalts and 

carbonaceous sediments and with limonite and organic matter in petrified wood. The most important 

occurrence of native terrestrial iron is on Disko 

Island, Greenland, where it occurs in basalt as particles and, in places, as masses as large as 20 tons. 

TYPES OF DEPOSITS 

Sulfide deposits are by far the most important 

present source of nickel, in regard to both quantity 

of nickel and number of deposits. In 1964 two sulfide districts in Canada were producing about 80 

percent of the free world total ; one of these, the 

Sudbury district, has produced more than half the 

total world supply since about 1905. In recent years, 

however, major deposits have been discovered in 

other parts of the world, particularly in Australia 

and South Africa, as well as two large but very low 

grade deposits in the United States. 

Another type of deposit, in which sulfides (together with arsenides of nickel, cobalt, and copper) 

occur in hydrothermal veins, has been found in both 

Canada and the United States, but these deposits 

are small and unimportant as sources of nickel. 

Important nickel deposits are found in the lateritic mantles formed by the weathering of peridotite, 

include dunite, pyroxenite, and serpentinite, mostly 

in tropical and subtropical climates. The weathering 

of fresh peridotite has yielded nickel-silicate laterites in which the hydrosilicate garnierite is the 

principal nickel mineral. These deposits contain 

more than 1.5 percent nickel. Large deposits of this 

type occur in New Caledonia, and medium to large 

deposits occur in Indonesia, Venezuela, Brazil, 

United States (Oregon), and elsewhere. The weathering of serpentinite (serpentinized peridotite) has 

also formed nickeliferous iron laterite that averages 

0.9-1.4 percent nickel. Large deposits of this type 

occur in Cuba and the Philippines, and medium to 

large deposits occur in Indonesia, the U.S.S.R., the 

Western United States, Guatemala, and other localities. 

Recent oceanographic research has revealed the 

presence of vast deposits of nickel-bearing manganese-oxide nodules on deep ocean floors, particularly 

in the Pacific Ocean. The nodules contain 0.1-1.1 

percent nickel as well as somewhat lesser amounts 

of copper and cobalt. 

Most of the nickel deposits of the world that were 

known as of 1950 were shown by the U.S. Bureau 

of Mines (1952, fig. V-1), but since then, major deposits have been discovered in the United States, 

Canada, Australia, Guatemala, Colombia, and South 

Africa. 

SULFIDE DEPOSITS 

The nickel-bearing sulfide deposits typically consist predominantly of pyrrhotite (Fe1-11,S) and 

associated pentlandite [ (Fe,Ni) 9Ss] and chalcopyrite (CuFeS2). Many of the deposits contain 

minor but recoverable amounts of platinum metals, 

cobalt, and selenium. These deposits occur in or near 

peridotite or norite intrusions and are generally 

considered to be genetically related to them. The 

sulfides occur as disseminations, massive bodies, or 

veins and stringers in the igneous rocks. Some of 

the masive ores contain fragments of the host rock. 

The individual ore bodies are normally elongate, 

lenticular, or sheetlike and may extend for hundreds 

or thousands of feet. 

Many deposits occur at or near the base of peridotite or norite intrusives and are particularly well 

formed in local hollows or reentrants along the 

basal contacts. Magmatic segregation is considered 

by many geologists to have been the mechanism by 

which these deposits were formed ; immiscible liquid 

sulfide droplets were segregated from the parent 

mafic or ultramafic magma at an early stage of 

crystallization, settling downward and coalescing to 

form a sulfide zone at the base of the intrusive. The 

evidence in favor of this mechanism seems to be 

strongest in many small deposits associated with 

relatively small intrusives. For some larger deposits, although the mode of occurrence is similar, the 

origin is disputed ; typical of these are the large 

deposits in the Sudbury district, Ontario, Canada, 

which occur along the base of a basin-shaped or 

funnellike norite intrusive. Hawley (1962) has recently summarized the case for origin of these deposits by magmatic segregation. Others (for example, Yates, 1948) support a theory of epigenetic 

origin-introduction of the sulfides into the norite 

contact zone by hydrothermal solutions that migrated from depth. Different theories of origin have 
440 UNITED STATES MINERAL RESOURCES 

been proposed, and are summarized by Cornwall 

(1966). 

Other nickel-bearing sulfide deposits occur along 

faults or shear zones ; these are clearly epigenetic 

and the place of deposition was structurally controlled. 

NICKELIFEROUS LATERITE DEPOSITS 

Laterite has formed over large areas during long 

periods of intensive weathering and erosion, mainly 

in tropical to subtropical climates, where stable 

landmasses have gradually been reduced to almost 

flat featureless peneplains. Such a period of erosion 

took place during Tertiary time in many parts of 

the world. Where the rock exposed at the surface 

was peridotite (composed essentially of olivine and 

pyroxene), dunite (all olivine), pyroxenite (all 

pyroxene), or serpentinite (serpentinized peridotite), and laterite that was developed is almost invariably rich in iron and nickel. 

The laterite formed from the weathering of serpentinite is richest in iron, generally containing 

45-55 percent. The nickel content of this laterite 

commonly averages about 1 percent, ranging from 

about 0.9 to 1.3 percent for large volumes of material. These deposits are called nickeliferous iron laterite. The mode of occurrence of the nickel in this 

laterite is not known; most likely the nickel is included in the goethite, limonite, and serpentine 

minerals, which are the major constituents. Huge 

deposits of nickeliferous iron laterite, similar to 

those in Cuba, the Philippines, and Indonesia, are 

not known in North America, but several smaller 

deposits have been thoroughly explored in California, Oregon, and Washington. 

The other type of nickeliferous laterite is known 

as the nickel-silicate type, because a significant 

part of the nickel occurs either as the hydrosilicate 

garnierite or as nickel-bearing talc or antigorite. 

This laterite has formed from the weathering of 

fresh peridotite, dunite, and, to a lesser degree, 

pyroxenite. The iron content is less than 30 percent 

in most laterite of this type; the Si02 content, 

which is very low in the iron laterite, may be as 

much as 30 percent; and the nickel content exceeds 

1.5 percent and averages about 1.6 percent for large 

tonnages. The largest known deposits of nickelsilicate laterite occur in New Caledonia and Indonesia. A moderately large deposit occurs in the 

United States at Riddle, Oreg. 

RESOURCES 

IDENTIFIED RESOURCES 

This discussion considers first the world sulfide 

resources and second the world laterite resources 

of nickel. The basic figures are given in tables 87 

and 88 and are considered conservative. The United 

States resources are given by States; resources of 

other nations are listed by country. 

The United States sulfide resources are quite large 

(6.9 billion tons) but low grade (0.21 percent Ni). 

The very large estimate of nickel in the Duluth 

Gabbro near Ely, Minn., is based on data recently 

released by the Minnesota Geological Survey (P. K. 

Sims, written commun., 1972). Canadian reserves 

of minable ore are the world's largest with probably 

close to 2 billion tons of material that can be mined 

under present economic conditions. Australia probably has great potential for increasing the present 

estimate of 400 million tons and the yearly production rate is growing rapidly. South Africa also has 

potential for greater than the 200 million tons estimated here. U.S.S.R. tonnage is probably greater 

than 100 million, but grade is probably less than 

0.6 percent nickel. 

TABLE 87.-World nickel-sulfide identified resources 

[Identified resources are specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions] 

Area 

United States: 

California ------------------

Colorado -------------------- M?ntana; (Stillwater) 1 ______ _ 

M1ssoun -------------------

Nevada --------------------- Pennsylvania (Gap) ---------

VVashington ----------------- Minnesota (Ely) 2 -----------

Alaska, Brady Glacie·r ------- Yakobi Island ----------- Funter Bay ------------

Maine ----------------------

Total (0.21 percent 

Ni avg) ----------------

Canada: 

Thompson district: 

Thompson mine --------- Mystery Lake deposit ---- Moak Lake deposit ------

Others -----------------

Total (1.0 percent 

Ni avg) ------------

Sudbury district -------------

Other Canadian ------------- Other Canadian ------------- South Africa -------------------

Norway ------------------------- Burma ------------------------- Australia ----------------------- Australia -----------------------

U.S.S.R. ------------------------

1 Also contains 0.25 percent Cu. 2 Also contains 0.64 percent Cu. 

Ni Tons of ore (percent) 

100,000 1.6 

70,000 .8 

150,000,000 .25 

10,000,000 .5 

30,000 .3 

800,000 .7 

100,000 .9 

6,500,000,000 .21 

200,000,000 .26 

20,000,000 .3 

600,000 .35 

10,00(),000 1 

6,900,000,000 

150,000,000 3.0 

200,000,000 .45 

400,000,000 .7 

250,000,000 1 

1,000,000,000 

400,000,000 1.5 

100,000,000 1.5 

200,000,000 .2 

200,000,000 1 

2,000,000 1 

25,000,000 .3 

300,000,000 .6 

100,000,000 1.6 

100,000,000 .6 
NIGKEL 441 

TABLE 88.-World nickel-laterite identified resources 

[Identified resources are specific, identified mineral deposits that may or may not· be evaluated as to extent and grade, and whose contained minerals may or may not be profitab!y recoverable with existing technology 

and economic conditions] 

Area 

Philippine Islands ---------------

Indonesia ----------------------- Australia -----------------------

Solomon Islands ----------------- New Caledonia ------------------

~alagasy -----------------------

Cuba --------------------------- Dominican Republic ------------- Guatemala ---------------------- Venezuela (Lorna Hierro) -------- Colombia (Cerro ~atoso) _______ _ 

Brazil -------------------------- Puerto Rico ---------------------

Greece -------------------------- U.S.S.R. ------------------------ Yugoslavia --------------------- United States: 

Nickel ~ountain (Riddle), 

Oreg -------------------- Northern California and rest of 

Oregon ------------------- Washington ( Cle Elurn, 

Blewett) ------------------ North Carolina --------------

Tons of ore 

1,000,000,000 

500,000,000 

100,000,000 

100,000,000 

500,000,000 

2,000,000 

2,000,000,000 

70,000,000 

100,000,000 

60,000,000 

40,000,000 

20,000,000 

100,000,000 

2,000,000 

100,000,000 

20,000,000 

10,000,000 

55,000,000 

30,000,000 

5,000,000 

Nl 

(percent) 

0.8 

.9 

1.2 

1.2 

1.8 

2 

1 

1.5 

1.5 

1.6 

2.5 

2 

.9 

1.7 

1.5 

1 

1.5 

.75 

.5 

1 

The world nickel laterite resources (table 88) 

include areas that have only recently been explored, such as the Solomon Islands, Colombia, and 

Australia, but most of the remainder have been 

known for many years, particularly the larger resources. The United States laterite estimate of 100 

million tons probably will not be greatly increased, 

and the individual laterite bodies that it comprises 

are small. A number of companies have been and 

are currently negotiating with local governments for 

operating concessions in the Philippines, Indonesia, 

New Caledonia, Colombia, and Venezuela, and development has been delayed by such negotiations 

and difficulties of financing in areas where the risk 

appears high. 

In a few areas the laterite estimates are probably 

quite accurate; in others, when large-scale mining 

starts, renewed exploration probably will substantially increase the resource estimates, such as in 

Indonesia, Australia, and Colombia. 

Another very large nickel resource, recently described by McKelvey and Wang (1969), occurs on 

the deep floor of the Pacfiic Ocean in the form of 

manganese-oxide nodules. The nodules cover 20-50 

percent of the bottom in large areas of the northeast, central, and southern Pacific. In addition to 

dominant manganese and iron, the nodules contain 

copper, nickel, and cobalt, with an average ratio of 

3:4:1. Nickel content ranges from 0.1 to 1.1 percent, but large deposits appear to contain· 0.8-1.1 

percent. Estimates of the size of the nodule deposits 

range from 90 billion to 1. 7 trillion tons ; thus for 

a liberal estimate, a resource of 1. 7 trillion tons of 

nodules averaging 0.95 percent nickel would contain 16 billion tons of nickel. However, the amount 

in deposits of suitable quality, abundance, and environmental setting to warrant dredging is likely to 

be much smaller. 

SPECULATIVE RESOURCES 

The discovery of the Thompson district, Manitoba, in 1949, and particularly the discovery of the 

Thompson mine in 1956, revealed a new type of 

nickel-sulfide deposit. Data collected by the company 

geologists indicated that the nickel was derived 

from peridotite and serpentinite where metamorphosed to a garnet-amphibolite-sillimanite assembage, indicating a temperature of 600°C or higher. 

Unmetamorphosed peridotites in the area (as elsewhere in the world) contain 0.25-0.3 percent nickel; 

metamorphosed peridotite (metaperidotites) in the 

area contain significantly less. There is evidence 

that sulfur was available in hydrothermal solutions 

during metamorphism-metamorphosed iron-formation in the area has been partly converted to pyrrhotite (Fe1 _xS). In such an environment it is 

possible or even probable that nickel was mobolized 

by hydrothermal solutions during metamorphism 

and deposited at present sites as the sulfide (pentlandite), as first proposed by Michener (1957). 

If this mechanism for the formation of the 

Thompson deposits is valid, peridotites throughout 

the world could have associated nickel-sulfide deposits where sufficiently metamorphosed in an environment where sulfur was available-for example, 

in proximity to black shales, which commonly contain sulfur in disseminated pyrite. 

Another possibility that would make vast quantities of nickel available would be the development 

of new metallurgical techniques to produce nickel 

from peridotites and serpentinites. Large bodies of 

these rocks occur in certain areas of the world, including both Eastern and Western United States, 

and they universally contain 0.2-0.4 percent nickel. 

The nickel is probably included chiefly in the lattices 

of the silicate minerals (mainly olivine and serpentine), but no method is now available for extracting 

it economically. 

As shown in table 87, conservative estimates of 

world nickel resources are about 2 billion tons of 

sulfide averaging 1.0 percent nickel and 7 billion 

tons averaging more than 0.2 percent nickel. For 

nickel laterites (table 88) , the figure is about 5 

billion tons averaging about 1.0 percent nickel. The 
442 VNITED STATES MINERAL RESOURCES 

sulfide estimates might be doubled by new discoveries; the laterite estimate probably will not be as 

greatly expanded. 

As mentioned above, if a practical method is 

found to extract the 0.2-0.4 percent of nickel universally disseminated through peridotites and serpentinites, vast amounts of nickel will become available. The total of estimates given in the preceding 

paragraph would be increased by several orders of 

magnitude. The potential size of nickel resources in 

unknown areas of deep-sea manganese nodules could 

be enormous. 

PROSPECTING TECHNIQUES 

Prospecting and exploration techniques are quite 

different for the sulfide-, laterite-, and nodule-types 

of nickel deposits. Prospecting for nickel sulfides 

can be well illustrated by briefly describing the 

methods used by Inco (International Nickel Co. of 

Canada, Ltd.) in their discovery of the major 

Thompson district in Manitoba in 1956. Geologists 

first studied aerial photos to find major structural 

lineaments and bodies of favorable rocks such as 

ultramafics with which nickel deposits are known 

to be associated. Such a lineament was discovered 

trending southwest from Hudson Bay through the 

Thompson area. The area was then flown with airborne magnetometer and electromagnetic equipment. 

Areas of coincidence of high magnetic anomalies 

and high electromagnetic conductivity were selected 

for exploration by diamond drilling. This drilling 

led to the discovery of two very large deposits of 

low-grade disseminated nickel sulfides in serpentinized peridotite intrusives. Attention was then 

turned to electromagnetic conductors that coincide 

with small magnetic anomalies. Such drilling resulted in the discovery of the Thompson deposit of 

nickel and iron sulfides in biotite schist that averages 3 percent nickel and extends for 31/2 miles 

laterally and over 2,000 feet vertically. 

Prospecting for nickel laterites involves first the 

identification of large laterite (intensely weathered 

saprolitic soils) areas overlying ultramafic rocks. 

Most of the large nickel or nickel-iron laterites have 

probably been found ; they occur in or near the 

tropics and lie on Tertiary erosion surfaces. The 

first step in the search for such laterites is the 

delineation of old erosion surfaces in favorable 

areas. Then the areas of ultramafic rocks are outlined and the most promising selected for sampling 

on 500-foot or smaller centers. Sampling is done by 

augering or by digging pits. Nickel, iron, and magnesium determinations are made for 1- to 5-foot 

lengths in each hole. Thus areas of ore grade (commonly those of higher than 1 percent nickel) are 

delineated. 

Nickel-bearing manganese nodules on the deep 

ocean floor are explored by dredging and bottom 

photography. 

PROBLEMS FOR RESEARCH 

Problems of developing potential nickel resources 

come under three headings : scientific, technological, 

and political. 

Research on the origin of the metamorphosed 

ultramafic deposits (Thompson type) would almost 

certainly pay dividends in the form of new discoveries. How does the nickel occur in these p~ridotites, 

and what happens to it during metamorphism? 

What are the most favorable environmental factors 

for the formation of this type of deposit? What 

criteria can be used in searching for similar deposits elsewhere in the world? 

The technological breakthrough of greatest potential value would be development of a technology 

for the extraction of nickel that is universally present in peridotites and serpentinites in small but 

abnormal amounts. For ocean-bottom manganese 

nodules, the cost and difficulty of recovery from 

mid-ocean depths of 3,500-4,500 meters are major 

problems. The separation and refinement of the 

nickel and other metals from the nodules also poses 

a metallurgical problem that has not yet been resolved. 

REFERENCES CITED 

Cornwall, H. R., 1966, Nickel deposits of North America: 

U.S. Geol. Survey Bull. 1223, 62 p. 

Fleischer, Michael, 1953, Recent estimates of the abundances 

of the elements in the earth's crust: U.S. Geol. Survey 

Circ. 285, 7 p. 

Hawley, J. E., 1962, The Sudbury ores, their mineralogy and 

origin-Pt. 3, Interpretations-The history and origin 

of the Sudbury ores: Canadian Mineralogist, v. 7, pt. 

1, p. 146-207. 

McKelvey·, V. E., and Wang; F. F. H., 1969, World subsea 

mineral resources: U.S. Geol. Survey Misc. Geol. Inv. 

Map 1-632-A, 17 p. 

Mason, B. H., 1958, Principles of geochemistry: New York, 

John Wiley and Sons (2d ed.), 310 p. 

Michener, C. E., 1957, Genesis of mineral deposits and exploration: Canada Natl. Advisory Comm. Research Geol. 

Sci. Ann. Rept., 7th, 1956-57, p. 13-14. 

U.S. Bureau of Mines, 1952, Materials surveys on nickel, 

1950: Washington, U.S. Govt. Printing Office, 301 p. 

Vinogradov, A. P., 1956, The regularity of distribution of 

chemical elements in the earth's crust: Geochemistry 

( Geokhimiya) , no. 1, p. 1-43 (English ed.) . 

Yates, A. B., 1948, Properties of International Nickel Company of Canada [Sudbury area, Ontario] in Canadian 

lnst. Mining and Metallurgy, Geol. Div., Structural 

geology of Canadian ore deposits, Jubilee Volume, p. 

596-617. 
UNITED STATES MINERAL RESOURCES 

NIOBIUM (COLUMBIUM) AND TANTALUM 

By RAYMOND L. PARKER and JoHN W. ADAMS 

CONTENTS 

Abstract of conclusions -------------------------

Introduction ------------------------------------ Exploitation ____ -----_ --------------------------

Environmental problems ---------------------

Geologic environment ---------------------------- Geochemistry __ - ___________ - __ - __ --_-- _- _ ---- Minerals _________________ ----______ --_____ --

Types of deposits ---------------------------

Alkalic rock complexes -------------------

Nepheline syenites ------------------

Carbonatites __ - _____ - _--------------

Granitic rocks ---------------------------

PegTnatites ------------------------------ Placer deposits --------------------------

Resources ---------------------------------------

Identified resources --------------------------

Undiscovered resources ----------------------

Prospecting techniques ---------------------------

Problems for research --------------------------- References 

FIGURE 

53. Graph showing world production and U.S. imports of niobium-tantalum concentrates, 1937-

71 --------------------------------------

TABLES 

89. Reserves of niobium and tantalum ----------

90. Conditional resources of niobium and tantalum_ 

91. Unevaluated resources of niobium and tantalum 

92. Summary of identified resources of niobium 

and tantalum in the world ----------------

ABSTRACT OF CONCLUSIONS 

Page 

443 

443 

444 

445 

445 

445 

446 

446 

446 

446 

447 

448 

448 

449 

450 

450 

452 

452 

453 

453 

Page , 

444 

Page 

450 

451 

451 

452 

Niobium (columbium) and tantalum have become important metals in modern technology because of their metallurgical, electronic, chemical, and nuclear uses. Both metals 

occur in nature almost entirely as single isotopes Nb113 and 

Ta181 and are present in the earth's crust in estimated abundance of 20 ppm (parts per million) and 2 ppm respectively. 

Niobium and tantalum have strong geochemical coherence 

and occur together in most rocks and minerals; however, 

some rock types such as nepheline syenite and earbonaqtes 

contain niobium in great preponderance over tantalum. These 

elements occur in ·minerals chiefly as oxides and multiple 

oxides, hydroxides, a few silicates, and one borate; more 

than 90 mineral species are known. 

Ore concentrations of niobium and tantalum occur in 

carbonatites and other rocks of alkalic complexes, certain 

types of granite, pegTnatites, placers, and resi®al deposits. 

Most of the known deposits of niobium are found in carbonatites and those of tantalum are contained in pegmatites and placers. Most of the world's resources of niobium 

and tantalum lie outside the United States, and consequently these metals are almost entirely imported. Known resources within the United States could be utilized during 

times of national emergency but cannot at present compete 

with the larger and :higher grade foreign deposits. On a 

worldwide basis, resources of niobium are more than adequate to supply the projected needs to the year 2000, but 

resources of tantalum barely meet these projected needs. 

Geologic research is needed to expl'ore the pos•sibilities of the 

existence of new types of tantalum deposits. 

INTRODUCTION 

Niobium (columbium) 1 and tantalum are two 

similar metals that have become increasingly important in modern technology because of physical 

properties that are useful in certain metallurgical, 

electronic, chemical, and nuclear applications. These 

metals were discovered in 1801-02, but for more 

than a century and a quarter no practical use was 

found for them. Commercial usage of niobium began 

about 1930 when it was first used as an alloying 

element in steel. Tantalum, although used to a minor 

degree in the chemical and electrical industries in 

the 1920's, was not extensively used until 1940 when 

it became an important material for capacitors. Both 

metals have been in strategically short supply at 

various times during and since World War II. 

t Niobium (Nb) is the preferred name in chemistry and most other 

sciences and was officially adopted by the International Union of Pure 

and Applied Chemistry in 1960. The name columbium is still used to 

some extent in metallurgy and mineral trades. 

U.S. GEOL. SURVEY PROF. PAPER 820 

448 
UNITED STATES MINERAL RESOURCE.S 

Niobium is utilized chiefly in the form of ferrocolumbium as an alloying element in carbon and 

alloy steel, stainless steel, and superalloys. Of prominence in recent years has been the inclusion of 

niobium in high-strength low-alloy steels that are 

used in the 'construction of large buildings, pipelines, 

and machinery and structures where savings in 

weight and increased durability and strength are 

important factors. Niobium is added as a grain 

refiner and stabilizer in some stainless steels and 

variously improves the corrosion resistance, weldability, or formability of the material. Niobium is 

a common alloying addition to nickel-, iron-, or 

cobalt-based superalloys that have use in hightemperature and high-strength applications such as 

gas-turbine components and hot-gas ducting in aircraft. For example, niobium-based alloys are used 

in rocket engines and superconductors, and unalloyed 

niobium is used in currently classified nuclear applications, mainly in mill-product form. 

More than half of the tantalum produced is used 

in the electronics industry, largely in the manufacture of capacitors and rectifiers. The remainder goes 

into the production of superalloys in high-temperature corrosion-resistant applications in aerospace 

vehicles, into tantalum carbide for high-temperature 

cutting tools, and into tantalum metal for a variety 

of corrosion-resistant usages such as prosthetic devices, chemical processing equipment, and liquidmetal containment apparatus. 

Because niobium is principally used as a ferroalloy 

element in steel, its consumption is tied closely to 

the activities of the steel industry; a cutback in 

steel production is reflected in a low consumption of 

niobium. The consumption of tantalum is related 

chiefly to the level of production in the electronics 

industry. 

In many applications vanadium can be substituted 

for niobium although some substitutions result in 

deficiencies in certain mechanical properties such as 

weldability in high-strength steel. Tantalum and 

titanium are possible substitutes for niobium in 

superalloys. 

Aluminum and ceramic materials can be substituted for tantalum in capacitors, with corresponding tradeoffs among such things as durability, cost, 

and size of units. Molybdenum and tungsten are 

sometimes substituted for tantalum used in chemical 

environments, and they may be actually superior in 

some applications where halogens and halides are 

involved; however, unlike tantalum, both have poor 

weldability characteristics. 

Except for material released from the government stockpile, the United States has imported all 

its niobium and tantalum since 1959. Some domestic 

deposits are known and have been variably explored, 

developed, or exploited, but none are commercially 

productive at the present time. These metals are 

imported mostly in the form of mineral concentrates 

chiefly from Brazil, Canada, and Nigeria and other 

African countries and in processed material in the 

form of ferrocolumbium from Brazil and of tantalum-bearing tin smelter slags from Malaysia. 

EXPLOITATION 

Limited demand for niobium and tantalum began 

in the first quarter of the 20th century and a low 

consumption continued until the World War II 

period at which time critical shortages of both 

niobium and tantalum developed (fig. 5~). Tempo50.-~-----------,-----------.----------~ 

45~------------------------------------~ 

40~------------------------------------4-4 

35r-----------------------------------~~ 

(/) 

~aor-----------------------------------~--4 

:> 

0 

Q. 

025~----------------------------------~--4 

(/) 

z 

0 

...J 

...J20r-------------------------------~~--~ 

:E 

15r-------------------------------~~--~ 

1950 1960 1970 

FIGURE 53.-World production and U.S. imports of niobiumtantalum concentrates, 1937-71. Data from U.S. Bureau 

Mines (1938--72). Note: F·errocolumbium included in import data for 1964-68. Comparable d.ata not available for 

1970-71. One pound ferrocolumbium arbitrarily considered 

equivalent to 2 pounds niobium ore concentrate. 
NIOBIUM (COLUMBIUM) AND TANTALUM 

rary allocation controls were applied to the use of 

these. metals, and some concentrates were airlifted 

to help alleviate the shortage which could not be 

met by domestic production. The increased need for 

these metals was caused by the increased use of 

niobium in high-temperature steel alloys and the 

use of tantalum as a catalyst in the manufacture 

of synthetic rubber. 

A se«;ond period of critical shortage occurred in 

the early 1950's during the Korean conflict when 

niobium-bearing steel alloys were required in the 

greatly increased manufacturing of jet engines. At 

this time the United States instituted a guaranteed 

purchase program that promoted exploration, discovery, and production of niobium in both domestic 

and foreign deposits. The program resulted in the 

discovery of numerous large low-grade carbonatite 

deposits and some large placer deposits. One of these, 

the Bear Valley, Idaho, placer deposit, has been the 

site of the dominant and the only significantly largevolume niobium-tantalum production in the United 

States. This production ceased in 1959 because government purchase contracts were fulfilled at that 

time. 

In the subsequent 10 years, production and consumption of niobium and tantalum generally followed the trend in production of steel which showed 

a general gradual increase, and niobium-tantalum 

consumption of the United States accounted for the 

largest proportion of the world production. However, during the last few years prior to 1972, as 

illustrated in figure 53, this relation has changed 

markedly, with the U.S. consumption of niobium, 

though increasing, greatly overshadowed by the 

much greater rate of increase in world production. 

The increased rate of world production is attributed 

to the rapidly expanding use of niobium in the manufacture of high-strength low-alloy steels by modern 

steel-manufacturing facilities in Japan and Western 

Europe. 

ENVIRONMENTAL PROBLEMS 

Mining operations for niobium and tantalum have 

no known unique features that affect the environment differently from the mining of many other 

ores. Open-pit mining of carbonatites presents the 

problems of large excavations and extensive waste 

disposal which in populated regions are offensive to 

view and may affect local property values. Placer 

mining and dredging of niobium-tantalum minerals 

requires the restoration of placered ground and also 

requires the application of measures to control the 

added mud and silt in the draining streams. Niobiumtantalum minerals themselves are not pollutants, 

and drainage waters from mines should not be degrading to the environment. 

Niobium and tantalum are not hazardous metals; 

stack exhaust fumes, gases, and dust from extraction plants are easily controlled and offer no known 

health hazards or uncontrollable environmental 

problems. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Niobium is a chemical element with atomic number 41 and atomic weight 92.91 ; tantalum has atomic 

number 73 and atomic weight 180.95. In nature both 

elements consist almost entirely of single isotopes 

Nb93 and Ta181 (Strominger and others, 1958), with 

Ta 180 accounting for only 0.01 percent of that element (Evans and others, 1955; White and others, 

1955). 

Niobium and tantalum have strong geochemical 

coherence ; that is, they are closely associated and 

found together in most rocks and minerals in which 

they occur. Great preponderance of one element over 

the other rarely occurs in some rocks such as nepheline syenite (niobium-rich) or lithium-bearing pegmatites (tantalum-rich). The principal reasons for 

coherence are similar ionic radii and identical 

valence states (Nb+5 =0.69 A and Ta +5 =0.68 A). 

Both elements are lithophilic, showing strong affinity 

for oxygen and being enriched in the earth's crust 

(Rankama and Sahama, 1950). Niobium is also enriched in some carbonatites and kimberlites that are 

considered to be of mantle derivation. 

The crustal abundance of niobium is considered 

by modern estimates to be about 20 ppm (parts per 

million) and of tantalum, to be about 2 ppm (summarized by Parker and Fleischer, 1968). The abundance is variable both in members of the same rock 

type in different localities and in different rock types. 

In general, however, lowest values of niobium and 

tantalum are found in some ultramafic rocks (not 

related to alkalic complexes) and some of the highest 

values of niobium are found in alkalic granites, 

nepheline syenites and related ultramafic rocks, pegmatites, and carbonatites. Highest contents of tantalum occur in albitized granites and pegmatites 

that are late-stage differentiates of granitic batholiths. Worthy of note is the fact that many carbonatite niobium deposits have very low contents of 

tantalum. 

The small amounts of niobium and tantalum that 

are dispersed in ordinary magmatic rocks are chiefly 

present as "camouflaged" elements in iron- and irontitanium-bearing minerals, to a certain extent in 

zirconium minerals, and rarely as discrete minerals 
UNITED STATES MINERAL RESOURCES 

of niobium and tantalum. Where present in many 

rock-forming minerals, the niobium and tantalum 

are in limited substitution for titanium, tin, tungsten, and zirconium. 

MINERALS 

A glossary of niobium and tantalum minerals 

given by Parker and Fleischer (1968) shows that 

niobium and tantalum minerals are chiefly oxides, 

multiple oxides, and hydroxides, as well as a few 

silicates and one borate. More than 90 species are 

known; the most important ore minerals and their 

chemical compositions are listed below: 

Columbitetantalite ----- (Fe,Mn) (Nb,Ta)20A 

Euxenite ------- (Y,Ca,Ce,U,Th) (Nb,Ti,Ta)20o 

Fergusonite ____ (Y,Er,Ce,Fe) (Nb,Ta,Ti) 04 

Ixiolite -------- (Ta,Nb,Sn,Fe,Mn)40s 

Loparite 

(variety of 

perovskite) __ ( Ce,N a,Ca) 2 ( Ti,Nb) 20e 

Microlite ------- (Na,Ca)2T~(O,OH,F)7 

Murmanite -----N~(Ti,Nb)2 Si20o•nH20 

Pandaite ------- (Ba,Sr) (Nb,Ti) (0,0H)7 

Pyrochlore ----- (Na,CI:l)2Nb2(0,0H,F)7 

Samarskite ---- (Y,Er,Ce,U,Ca,Fe,Pb,Th) (Nb,Ta, Ti,SnhOe 

Wodginite ------ (Ta,Nb,Sn,Mn,Fe)te082 

TYPES OF DEPOSITS 

Ore concentrations of niobium and tantalum occur 

in certain types of magmatic rocks and endogenic 

derivatives of those rocks. Commercial deposits have 

been found in various related rocks of alkalic complexes, such as nepheline syenites and carbonatites, 

certain granites, pegmatites, and placers. Some lowgrade, widely disseminated, unexploited deposits of 

niobium occur in riebeckite granite and in bauxite 

derived from nepheline syenite. 

ALKALIC ROCK COMPLEXES 

NEPHELINE SYENITES 

Nepheline-bearing syenites are among the types 

of rocks that may be greatly enriched in niobium 

and tantalum, particularly in their late phases such 

as pegmatites, albitized zones, and some carbonatites. Nepheline syenites are found in alkalic rock 

provinces throughout the world but are best known 

from their many occurrences in the U.S.S.R. where, 

according to Es'kova (1960), they constitute 1 percent of the exposed igneous rocks. In eight of the 

prominent nepheline syenite massifs of the U.S.S.R., 

the average niobium content ranges from 100 to 900 

ppm, and the average tantalum content ranges from 

12.0 to 20.5 ppm (Parker and Fleischer, 1968). 

On the basis of chemical and mineralogical differences, there appear to be two distinct types of 

nepheline syenites, which have been given the distinguishing terms "agpaitic" and "miaskitic." As 

originally proposed by Ussing (1911), the agpaitic 

type is characterized by an excess of alkalies 

(K20+Na20) over alumina, in contrast to the "common" type in which this ratio is 1 or less. The 

agpaitic type is also characterized by the presence 

of complex zirconium- and chlorine-bearing minerals 

and sodic amphiboles and pyroxenes and by the 

general absence of calcite. Because of their enrichment in typical "rest elements" and in volatiles 

such as F, Cl, and H20, agpaitic nepheline syenites 

have a compositional resemblance to pegmatites 

(Sorensen, 1960). The "common" or miaskitic nepheline syenite, in addition to having the lower alkalialumina ratio, differs from the agpaitic type in 

mineral assemblage by containing more of the common rock-forming species, such as biotite, augite, 

hornblende, sphene, and apatite, and fewer of the 

rare minerals of complex chemistry that are found 

in the agpaitic type. These and other characteristics 

of the two types, as well as some notable occurrences, are described by Heinrich (1966, p. 19.). 

Although both agpaitic and miaskitic syenites may 

be enriched in niobium and tantalum, they differ in 

the kind and number of minerals in which these 

elements occur. In agpaitic syenites and their derivatives, these two elements are largely fixed in titanium and zirconium minerals, many of which are rare 

species (Es'kova, 1960). In the miaskitic type, some 

of these minerals may be present, but there is a 

greater tendency for the formation of independent 

niobium-tantalum minerals such as pyrochlore, particularly in the late magmatic and postmagmatic 

derivatives. 

Niobium- and tantalum-bearing agpaitic rocks 

make up much of the great Lovozero alkali massif 

. in the Kola Peninsula, U.S.S.R., and have been 

described in detail by Vlasov, Kuz'menko, and Es'-

kova (1959). The massif as a whole contains about 

900 ppm niobium and 70 ppm tantalum, but the content of these elements varies not only among the 

various differentiates but also within the layered 

rock units themselves, as for example, in porphyritic 

lujarvrite, which may contain 0.03-0.92 percent 

(Nb,Ta)205. 

The principal niobium mineral in the Lovozero 

complex is loparite, a member of the perovskite 

group which contains about 12 percent (Nb,Ta) 205. 

It is found to some extent in all the rocks of the 

complex but is most abundant where differentiation 

has been greatest, particularly in the base of urtite 

(nepheline-rich syenite) layers and the top of the 

underlying trachytic nepheline syenite. Niobium and 

tantalum are major constituents of several other 
NIOBIUM (COLUMBIUM) AND TANTALUM 

minerals of the complex in addition to loparite and 

are also present in minor amounts in many more. 

Another important area of niobium mineralization is the llimaussaq complex in southwest Greenland where agpaitic nepheline syenites are overlain 

by lavas, gabbros, anorthosites, and augite syenite. 

All the rocks contain niobium minerals, chiefly pyrochlore and members of the epistolite-murmanite 

group, in shear zones and hydrothermal veins. The 

agpaitic rocks contain 500-1,500 ppm Nb205 and 

15--60 ppm Ta205. The niobium content of the rocks 

of the .complex increases from the preagpaitic rocks 

to the agpaitic rocks and further to the late hydrothermal veins (Hansen, 1968). 

Alkalic complexes dominated by agpaitic rocks are 

found at various other places in the world, including 

the United States, but so far as is known, only those 

in the Kola Peninsula, U.S.S.R., have been economically exploited for niobium. Economic deposits are 

chiefly in the more numerous complexes of dominantly miaskitic rocks which are more favorable for 

the development of carbonatite bodies and veins. 

Although there are some exceptions (Sorensen, 

1960), the miaskitic types are characterized by far 

less of the numerous zirconium-titanium minerals 

in which much of the niobium and tantalum in the 

agpaites is dispersed and are more apt to contain 

the niobium and tantalum in richer and more economically interesting species, notably pyrochlore, in 

minable concentrations in their related carbonatites. 

Nepheline syenite bodies containing about 200 

ppm niobium are the source rocks of the bauxite 

deposits of Pulaski and Saline Counties, Ark. Investigation of the trace-element content of the bauxite 

showed that a significant enrichment in niobium had 

taken place, the bauxite containing about 2.5 times 

the amount of niobium present in the parent rock 

(Gordon and Murata, 1952 ; Fleischer and others, 

1952). Niobium in the syenite appears to be largely 

contained in accessory sphene which during bauxitization was altered to various other titanium minerals, chiefly ilmenite, which then became the principal carriers of niobium in the bauxite. The niobium 

enrichment parallels that of alumina, suggesting 

that the concentration was entirely residual. 

CARBONATITES 

Carbonatite bodies contain the most extensive 

known world resources of niobium. They commonly 

are found in the interior parts of alkalic intrusive 

complexes which contain a wide variety of rock types 

ranging from nepheline syenite to alkalic gabbro 

and pyroxenite. Many of these complexes are circular in plan (though some are not) and the constituting rocks including the carbonatites commonly 

are arranged in arcuate, radial, or irregular discordant mass~es within the complexes. Some carbonatites are found intruding unrelated country 

rocks, but most of the occurrences can be associated 

with nearby alkalic rocks. 

Carbonatites and associated alkalic rocks range 

widely in age from Precambrian to Holocene and 

are npt confined to any particular geologic period. 

Some complexes are linked to volcanic activity at the 

earth's surface, and actual carbonatite lavas are 

recorded at Oldoinyo Lengai in Tanzania (Tanganyika). Others not obviously related to any known 

extrusive rocks represent complexes exposed at 

deeper levels in the crust by a combination of erosion and geologic structure. 

Carbonatites and related alkalic rock complexes 

are for the most part restricted to the stable parts 

of the continent. This distribution is true for Africa, 

South America, North America, and Eurasia. Some 

complexes tend to cluster along major crustal breaks 

such as the African rifts, whereas some show little 

relation to identifiable structures. 

Carbonatites have been intensively explored over 

the world primarily in the search for niobium, and 

considerable information is now available on their 

nature and composition. Many carbonatites have 

been shown to contain deposits of one or more of 

the following metals or mineral commodities: Niolbium, rare earths, cop·per, nickel, titanium, thorium, 

uranium, vermiculite, fluorite, zirconium, barite, 

apatite, and strontium. The carbonatite itself ranges 

from iron- and magnesium-bearing carbonates to 

nearly pure calcite, and some of this material is 

marketed for agricultural and other purposes. Some 

carbonatites conceivably could be exploited profitably for the collective recovery of more than one 

commodity, whereas on an individual basis the commodities might be marginal or submarginal economically. 

Explored niobium deposits in carbonatites contain immense reserves of niobium. The grades range 

from below 0.2 percent Nb205 to more than several 

percent. Some of the largest deposits exceed 8 million tons of Nb205 which occurs in the carbonati-tes 

chiefly as the mineral pyrochlore. 

Some representative niobium-bearing carbonatites 

in various parts of the world are listed below: 

Iron Hill, Colo. -------------Temple and Grogan (1965). 

Gem Park, Colo. ____________ Parker and Sharp (1970). 

Oka, Quebec -----------------Gold (1966). 

Axara, Brazil ---------------de Souza and Castro (1968). 

Fen, Norway ---------------- Saether (1957). 
UNITED STATES MINERAL RESOURCES 

Lueshe, Congo ---------------Wambeke (1965). 

Sukulu, Uganda _____________ Davies (1956). 

Kaiserstiihl, Gennany --------Wambeke and others (1964). 

Although some disagreement exists on the origin 

of carbonatites, prevailing opinion is that they are 

intimately related to alkalic rocks including kimberlites and that they probably originated from material 

derived at great depth, possibly within the mantle 

(Heinrich, 1966). 

GRANITIC ROCKS 

Niobium and tantalum are present in most granitic 

rocks in trace amounts in iron- and iron-titaniumbearing minerals and to some extent in zirconium 

minerals. A few rare granites contain columbite, 

euxenite, fergusonite, or pyrochlore as accessory 

minerals to the extent that economic concentrations 

of these minerals may develop through the weathering of the rocks either in residual deposits or in 

placers. 

The Jos Plateau in central Nigeria is an important 

producer of columbite which is obtained in part from 

alluvial and eluvial concentrations from Precambrian 

pegmatites, but mainly from alluvial deposits and 

saprolite derived from biotite granites. These granites are part of an igneous complex of possible 

Jurassic age (Black and Girod, 1970) known as the 

Jos-Bokuru Younger Granite complex which occupies an area of more than 100 square miles. The 

complex includes gabbros, porphyries, rhyolites, biotite granite bodies, and riebeckite granite (Mackay 

and others, 1949). Several phases of the biotite 

granite, all of which contain accessory columbite, 

have been recognized. The Rayfield-Gona and Forum 

phases are the richest and contain an average of 

0.4 pound columbite per ton, and as much as several 

pounds per ton are found in local concentrations 

(Williams and others, 1956). Columbite is also an 

accessory mineral in the Lunyo albite granite in 

Uganda (Knorring, 1960). Other accessory minerals 

in this rock include magnetite, cassiterite, zircon, 

thorogummite, fluorite, and pyrite. Columbite granites may not result entirely from magmatic processes 

but may involve autometasomatic processes resembling greisenization in which calcium is removed 

from plagioclase and iron, titanium, niobium, and 

tantalum are removed from biotite. These elements 

are recombined to form fluorite, magnetite, and 

columbite (Parker and Fleischer, 1968). 

Euxenite-bearing granitic rocks (quartz monzonite or quartz diorite) in the Idaho batholith contain from a trace to 0.05 pound of euxenite per cubic 

yard and with their related pegm.atites are the 

apparent source of the euxenite placer deposits in 

Bear Valley, Idaho (Mackin and Schmidt, 1956). A 

fergusonite granodiorite in the Nang-ling Range in 

southern mainland China has been described by 

Wang (1964). From the English summary of Wang's 

report (Lee, 1970, p. 22), the fergusonite is most 

abundant in the marginal zone of the granodiorite. 

Fergusonite granite has also been found in the basin 

of the Gava Say River in the U.S.S.R. (Parker and 

Fleischer, 1968). 

Pyrochlore granites are highly alkalic rocks composed principally of microperthite, sodic plagioclase, 

quartz, sodic amphibole, and sodic pyroxene. Pyrochlore is present in the Mount Rosa Granite, a 

riebeckite granite in the Pikes Peak area, Colorado 

(Gross and Heinrich, 1965), and in a riebeckite 

granite pha.se of the J os-Bokuru complex in Nigeria. 

The pyrochlore content of the Nigerian granite from 

one occurrence was estimated to be about 0. 7 percent (Mackay and others, 1949, p. 79). 

PEGMATITES 

Pegmatites are a type of igneous rock generally 

considered to represent the crystalline product of 

residual magmatic fluids and as such may contain 

concentrations of a number of rare elements whose 

properties inhibited their entry into minerals of 

earlier formed rocks. Pegmatites are commonly of 

granitic composition, but pegmatitic phases of other 

rocks, such as syenites, are found in some districts. 

A characteristic of pegmatites is the large but 

extremely variable grain size of the constituent 

minerals. Some pegmatites contain roughly concentric layers or zones of contrasting mineral assemblages, while others are unzoned with an essentially 

random distribution of minerals. 

Pegmatites were for many years the major source 

of niobium and tantalum, and whereas niobium is 

now obtained largely from carbonatites, pegmatites 

still remain the dominant primary source of tantalum. These elements may be present in pegmatites, 

either in one or more of a large number of independent minerals of which columbite-tantalite is the 

most common or in the structure of such carrier 

minerals as micas, garnets, tourmaline, ilmenite, or 

zircon. Certain types of pegmatites seem to be more 

intensely mineralized· with niobium and tantalum 

than others. These are commonly the complexly 

zoned pegmatites characterized by abundant albite 

and a strong development of lithium and beryllium 

minerals. 

The tendency for pegmatite minerals to occur in 

large crystals and to be localized in distinct zones 

has favored the recovery of niobium-tantalum minerals from deposits that would otherwise be unminable. Pegmatites in tropical areas may also be deeply 
NIOBIUM (COLUMBIUM) AND TANTALUM "' 

weathered, so that some of the heavy resistate 

minerals may be recovered from the saprolite by 

simple placer-type methods. 

Columbite-tantalite and other niobium-tantalum 

minerals occur in pegmatites throughout the world, 

but only a few deposits have been sufficiently rich 

to be mined solely for these minerals, and they are 

more commonly a coproduct or byproduct of mica, 

beryl, or cassiterite operations. In the United States, 

intermittent recovery of niobium-tantalum minerals, 

chiefly columbite, has been made from almost all 

areas where pegmatites are found (Barton, 1962). 

The Harding pegmatite, in Taos County, N. Mex., 

was an important source of tantalum during World 

War II and supplied about 3 tons of micro lite concentrates during a brief period when tantalum was 

in very short supply (Montgomery, 1947). By 1946, 

about 17,200 pounds of microlite had been produced 

from the deposit (Berliner, 1949). The unusual concentration of tantalum in the pegmatite is thought 

by Montgomery (1950) to have been derived from a 

genetically related granite in which tantalum is 

largely concentrated in sphene. 

The present major source of tantalum in North 

America is a pegmatite, the Bernie Lake deposit in 

southeastern Manitoba, that has been estimated to 

contain about 2 million tons of ore containing 0.23 

percent Ta20s (Howe, 1968). Like the Harding pegmatite, it is a complexly zoned deposit containing 

lithium and beryllium as well as tantalum and 

niobium. The principal ore mineral at Bernie Lake 

is the uncommon mineral wodginite which occurs 

mainly in a potassium feldspar-muscovite-quartzberyl zone lying below the quartz core (Grice and 

others, 1971). 

PLACER DEPOSITS 

Concentrations of niobium and tantalum minerals 

in various types of placer and residual deposits have 

been significant sources of these elements. Individual 

deposits of these types commonly are small but may 

be sufficiently numerous in a local area to constitute 

an economically important district. , 

Resistate heavy minerals such as columbite or 

tantalite, when released from their host rock by 

weathering, may accumulate essentially in place and 

become enriched in the rock debris by chemical and 

mechanical removal of other less durable and lighter 

weight minerals. Such accumulations in eluvium may 

constitute economic deposits minable by placer 

methods. 

Transport and redeposition by running water can 

form concentrations of niobium and tantalum minerals in alluvial placers, the richest being in or near 

the source area at some site where the velocity of 

the water is reduced to the point where the heavymineral grains can no longer be transported. This 

reduction of velocity can result from many factors 

largely related to the geomorphic history of the 

terrain. 

Heavy-mineral concentrations formed along sea 

beaches by wave action are important sources of 

monazite, zircon, and rutile. Niobium and tantalum 

minerals, however, are rarely reported from these 

placers, but it is quite probably that unsuspected 

niobium enrichment either from independent niobium minerals or from carrier minerals would be 

found by analytical studies of sea-beach concentrates. 

Consolidated equivalents of sea-beach placers are 

found in sedimentary rocks ; notable are those of 

Cretaceous age in Wyoming and other western 

States. Some of these fossil placers are large enough 

to constitute possible future sources of titanium, zirconium, and rare earths. A niobium-bearing opaque 

radioactive mineral found in the Wyoming deposits 

and tentatively identified as euxenite could be a coproduct of these placers if they were exploited 

(Houston and Murphy, 1962). 

The most important placer deposit of niobium and 

tantalum known in the United States is at Bear 

Valley, Valley County, Idaho. The placer was mined 

from 1955 through 1959 by two dredges with a combined capacity of 8,000 cubic yards per day, and 

during the period of operation 1,050,000 pounds of 

combined niobium and tantalum oxide was produced from the euxenite and subordinate columbite 

recovered from the deposit (Barton, 1962). It has 

been estimated that there is sufficient unmined 

ground to permit 30 years' mining at the same rate 

of operation (Mining World, 1958). 

The placer area is in a glaciated valley in the granitic rocks of the Idaho batholith ; the richest placers, 

which have been partially mined, are in the upper 

part of the valley where the source of the valuable 

minerals is thought to be a 6-square-mile area of 

quartz diorite and associated pegmatites (Mackin 

and Schmidt, 1956). The euxenite content of the 

quartz diorite is very irregular and may range from 

a trace to 0.05 pound per cubic yard; this has been 

enriched to about 1 pound per cubic yard in the 

placers, where the euxenite is accompanied by a 

large suite of other heavy minerals, some of which, 

with their estimated tenor in pounds per cubic yard, 

are as follows: Columbite (0.2), ilmenite (20), magnetite (5), zircon (0.05), garnet (5), and monazite 

(0.5). 

During the processing of the placer sands, euxen-
UNITED STATES MINERAL RESOURCES 

ite, columbite, and monazite were the principal products, and ilmenite, magnetite, zircon, and garnet 

were the stockpiled byproducts (Dayton, 1958). 

ods of glaciation (Mackin and Schmidt, 1956). 

The euxenite placers of Bear Valley are thought 

to be the result of a fortuitous combination of the 

following factors: (1) Local concentrations of the 

mineral in the quartz diorite and pegmatites, (2) 

sufficient disintegration of the host rock to free the 

minerals, (3) the action of Pleistocene glaciers 

which dammed the local drainage and led to the 

accumulation of valley fill, and ( 4) quickened downslope movement of enriched mantle during the periOther placer deposits in Idaho, particularly the 

Dismal Swamp deposit in Elmore County, contain 

niobium and tantalum minerals (Armstrong, 1957; 

Savage, 1961), but none of these are known to be 

comparable in size or grade to those at Bear Valley. 

RESOURCES 

IDENTIFIED RESOURCES 

The most extensive resources of niobium and 

tantalum (tables 89, 90, and 91) are found in Brazil, 

Canada, and several African countries. Known reTABLE 89.-Reserves of niobium and tantalum 

[Reserves: Identified deposits from which minerals ean be extracted profitably with existing technology and under present economic conditions] 

Locality 

Canada: 

Lake Nippissing, Ontario ----------------- _ Lakner Lake, Ontario ----------------------- Chapleau, Ontario -------------------------

Ore 

(tons) 

North America 

5,000,000 

50,000,000 

20,000,000 

15,000,000 

James Bay, Ontario ------------------------ 40,000,000 

St. Honore, Quebec ------------------------- 100,000,000 

Oka, Quebec ------------------------------- 225,000,000 

Bernie Lake, Manitoba ---------------------- 1,900,000 

Bugaboo Creek, British Columbia ------------ C) 

Total ------------------------------------------------- United States: 

Iron Hill, Colo. ---------------------------- 40,000,000 

Bear Valley, Idaho ------------------------- (

3

) 

Harding mine, N. Mex. --------------------- 100,000 

Total -------------------------------------------------

South America 

Brazil: 

Araxa ------------------------------------- 300,000,000 

Tapira ------------------------------------- 10,000,000 Tantalite deposits -------------------------- -------------

Total ------------------------------------------------- Other: 

French Guiana (tantalite) ------------------ 300,000 

Guyana (tantalite) ------------------------- -------------

Total -------------------------------------------------

Europe 

Germany: Kaiserstuhl -------------------------- 750,000 

Norway: S-ve ---------------------------------- 61,000,000 

Total -------------------------------------------------

Africa 

Congo: 

Lueshe ------------------------------------ 30,000,000 Bingo ------------------------------------- 7,100,000 

Columbite-tantalite ------------------------- -------------

Kenya: Mrima Hill ---------------------------- 56,000,000 

50,000,000 

Nigeria: 

Kaffo Valley ------------------------------- 140,000,000 

Jos Plateau --------------------------------------------- Uganda: Sukulu ------------------------------- 200,000,000 

Malawi: Ilomba -------------------------------- 100,000 

Total -------------------------------------------------

Grade 

(percent) 

0.7 

.26 

.5 

.3 

.52 

.5 

.35 

.23 

(2) 

.25 

(') 

.1 

3.0 

.5 

.4 

0.5 

0.2-0.5 

1.34 

2.4-3.6 

.67 

.7 

.26 

.25 

. 33 

Nb205 content Ta2011 content (tons) (tons) 

35,000 

130,000 

100,000 

45,000 

208,000 

500,000 

787,500 

-------- 5,100 

1,810,600 

100,000 

8,000 

--------

108,000 

9,000,000 

50,000 

--------

9,050,000 

500 

500 

3,750 

138,500 

142,250 

402,000 

198,000 

50,000 

375,200 

350,000 

364,000 

100,000 

500,000 

300 

2,744,500 

4,370 

4,370 

2,000 

100 

2,100 

4,000 

4,000 

1,200 

250 

1,450 

50,000 

10,000 

60,000 

1 66 million eu yd. 2 0.1 lb per cu yd. a 200,000,000 cu yd. • Estimated euxenite content, 1 lb per cu yd. 

Type of 

deposit 

Garbonatite. 

Do. 

Do. 

Do. 

Do. 

Do. 

Pegmatite. 

Placer. 

Carbonatite. 

Placer. 

Pegmatite. 

Carbonatite. 

Do. 

Pegmatite. 

Do. 

Do. 

Carbonatite. 

Do. 

Do. 

Do. 

Pegmatiteplacer. 

Carbonatite. 

Granite. 

Placer. 

Carbonatite. 

Pyroxenite . 
NIOBIUM (COLUMBIUM) AND TANTALUM 451 

TABLE 90.--Conditional resources of niobium and tantalum 

[Conditional resources: Specific, identified mineral deposits whose contained minerals are not profitably recoverable with existing technology and 

economic conditions] 

Locality 

North America (United States): 

Type of 

deposit 

Ore 

(tons) 

Grade 

(percent) 

Nb!!O&> content (tons) 

Ta!!O&> content (tons) 

Bauxite deposits, Arkansas ___ Byproduct 54,000,000 0.05-0.15 

.08 

55,100 

10,000 

potential. 

Magnet Cove, Ark -----------Carbonatite __ 12,000,000 

Africa: 

Nigeria: Jos Plateau -------- ------------- C) Malawi: Chilwa Island -------Residual Several million .21 

Other :

2 South America, Africa, 

Asia, and Europe. 

material. 

1 Several hundred million tons of ore is inferred. 

Several-thousand Several-thousand 

2 Tin smelter slags; based on estimated 1970 production times 10; exclusive of U.S.S.R. 

TABLE 91.-Unevaluated resources of niobium and tantalum 

Locality Type of 

deposit 

North America (United States): 

Gem Park, Golo --------------------Carbonatite. 

Potash Sulfur Springs, Ark --------- Do. 

Rocky Boy, Mont ------------------- Do. 

Europe: 

Finland: Sokli --------------------- Do. Portugal (tin-tantalite) _____________ Pegmatite and 

Africa: placers. 

Tanzania: Oldonyo Dili ------------- Carbonatite. 

North Rhodesia: 

Feira District ------------------ Do. 

Nkumbwa Hill ----------------- Do. 

South Rhodesia: 

Bikita ------------------------- Pegmatites. Darowa ------------------------Carbonatite. 

Gabon: Columbite-tantalite ---------- Pegmatites. South West Africa: 

Orange River .area -------------- Do. 

Karabib-Omaruru area ---------- Do. 

Zambia: 

Nkombwa ----------------------Carbonatite. 

Kaluwe ------------------------ Do. 

Malagasy Republic -----------------Pegmatite. 

Mozambique ----------------------- Do. 

Republic of South Africa: Glenover __ Carbonatite. 

Asia: 

Malaya ---------------------------- Pegmatites and 

placers. 

Thailand: Phang Ngo --------------Placer. India: Ambadongar ________________ carbonatite. 

Australia: Western Australia ----------- Pegmatites and 

placers. 

sources of these elements in the United States are 

relatively small. The United States as a major consumer of these elements must therefore look to 

these foreign sources for its present and near-future 

supply. 

In the past, small amounts of niobium and tantalum were produced from the numerous pegmatite 

districts in the United States, commonly as byproducts of mining for mica, beryl, and lithium minerals; 

This small and erratic source of niobium and tantalum is rather insignificant when compared to the 

large pyrochlore deposits now supplying most of the 

niobium markets. 

The most significant resources of niobium in the 

United States are contained in carbonatites at Iron 

Hill and Gem Park, Colo. ; Rocky Boy, Mont. ; and 

Magnet Cove and Potash Sulfur Springs, Ark. ; in 

euxenite placer deposits at Bear Valley, Idaho; and 

in the bauxite deposits of Arkansas. Minor tantalum 

resources are also contained in the placer deposits 

of Bear Valley, Idaho, and in pegmatites widely distributed in the United State·s but especially at the 

Harding mine, N. Mex. 

Three of the carbonatites are not sufficiently explored to be included in the computation of reserves, 

and one (Magnet Cove) is of lower grade than that 

of deposits now considered minable. The Arkansas 

bauxite deposits contain 0.05-0.15 percent Nb205 

and constitute a major potential resource, but recovery of the niobium, although it can be made 

during the processing of the bauxite, is unprofitable 

under present market conditions. 

At least half of the evaluated domestic deposits, 

therefore, are of much lower grade than those considered as commercial sources and must be classed 

as resources rather than reserves. Such deposits, 

however, remain strategically important and could 

be utilized in times of national emergency. 

Distinction between world deposits that constitute 

reserves and those that are conditional resources 

cannot be made on a strict tonnage and grade basis. 

Deposits shown as reserves (table 89) include some 

which are now being mined as well as others which 

would appear to be minable but which are not now 

com:r;etitive with the larger and richer deposits. The 

resources shown in table 90 are largely carbonatites 

that are known to contain niobium minerals but are 

otherwise unevaluated. Also listed in table 90 are 

some evaluated deposits of grade of 0.2 percent or 

below, which are considered subeconomic at the 

present time. 

The identified resources of niobium and tantalum 

of the world (exclusive of U.S.S.R. and Iron Curtain 

countries) are summarized in table 92. 
UNITED s·TATES MINERAL RESOURCES 

TABLE 92.-Summary of identified resources of niobium and 

tantalum in the world 

[Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existing technoloey 

and economic conditions 1 

Nb205 content Ta205 content (tons) (tons) 

Reserves 1 (see table 89): 

North America ----------- 1,918,600 6,470 

South America ----------- 9,050,500 5,450 

Europe ------------------ 142,250 

Africa ------------------- 2,744,500 60,000 

Total reserves --------- 13,855,850 71,920 

Total reserves rounded ___ --- _- 14,000,000 72,000 

Total conditional 2 resources (see text) ----------------- 14,000,000 72,000 

Total identified resources 28,000,000 144,000 

1 Reserves: Identified deposits from which minerals ean be extracted 

profitably with existing technology and under present economic conditions. 2 Conditional resources: Specific, identified mineral deposits whose con- tained minerals are not profitably recoverable with existing technology 

and economic conditions. 

About 14 million tons can be identified as a minimal figure for reserves of Nb205 in deposits in the 

world, and similarly a figure of 73,000 tons is minimal for r-eserves of Ta205. Additional resources of 

probable lower grade exist at many of the explored 

deposits as unevaluated protore bedrock beneath 

some surficial weathered deposits in some carbonatite 

complexes and in some weathered pegmatite and 

granite deposits. Some deposits also contain lower 

grade material that was not included in reserve 

calculations because it was below the grade of material being considered at the time of evaluation, 

and some deposits have been identified as containing 

niobium and tantalum minerals but have not been 

sufficiently explored or evaluated. These materials 

in these deposits all constitute conditional resources. 

The distribution and extent of known low-grade or 

unevaluated deposits suggest that such conditional 

resources are at least equal to the computed reserves 

or 14,000,000 tons Nb205 and 70,000 tons Ta205. 

UNDISCOVERED RESOURCES 

Undiscovered resources no doubt occur as blind 

ore bodies in known carbonatites or as ore bodies in 

undiscovered carbonatites in known carbonatite 

provinces. These hypothetical . resources will continue to be discovered through continuing geologic 

and exploration activities and constitute probably 

several times the amount of currently known 

resources. 

Some undiscovered resources termed speculative 

resources might lie in undiscovered carbonatite 

provinces or in new geochemical and geologic environments for these elements. For example, until 

the post-World War II era, commercial niobium 

deposits were considered to be restricted to pegmatites and related placers ; the discovery of lowgrade large-tonnage carbonatite-pyrochlore deposits, 

hoW!ever, changed the whole resource picture for 

niobium. 

One might speculate that such a low-grade largetonnage type of source lies undiscovered for tantalum and that additional new types of sources exist 

for niobium. Conceivably, unknown fossil placers 

exist that are large low-grade resources. Discoveries 

of such resources will depend on future scientific 

and technological advancements in exploration and 

geologic knowledge in order to discover the deposits 

that lie beneath great areas of volcanics, younger 

sedimentary rocks, and unconsolidated materials. 

PROSPECTING TECHNIQUES 

Inasmuch as alkalic-rock complexes and associated carbonatites at the present time are the chief 

targets for large low-grade niobium deposits, their 

recognition is the first step in exploration. Recognition has been made in the process of geologic maPping, through aerial observation and photography, 

and through geophysical surveying. The common 

circular plan and concentric arrangement of rocks 

constituting alkalic complexes can be distinguished 

and rock types can be identified by the usual 

geologic-mapping techniques, and these discordant 

structures are sometimes evident on aerial photographs in areas of surface exposure. 

Where these structures are covered with overburden or younger rocks, their magnetite content can 

be a factor in their detection. Both airborne and 

ground magnetic surveys have been employed to 

successfully detect magnetic anomalies, some of 

which have been shown to be caused by carbonatite 

niobium deposits. The natural association of niobium with uranium and thorium makes radiation 

detectors a useful exploration tool. Many occurrences 

of niobium have been found with the aid of these 

detectors, and new improved airborne radiometric 

detectors have great potential for prospecting. Seismic surveying and gravity measuring techniques 

have proved useful where information on depth of 

overburden or information on differences in rock 

densities was desired. Future prospecting methods 

no doubt will employ combinations of these techniques, both airborne and on the surface, to outline 

the basic targets for exploration. 

Once the target is identified, it must be evaluated 

by conventional exploration procedures. Niobium 

and tantalum minerals are not easily identified, and 

niobium and tantalum are not easily detected with-
NIOBIUM (COLUMBIUM) AND TANTALUM 

out special means because of their insolubility in 

most solutions and their refractory nature. Qualitative and quantitative chemical determinative procedures have been developed for niobium and have 

been used in the field. Such chemical procedures 

have not been satisfactorily developed to conveniently detect tantalum. The capacity to analyze large 

numbers of samples at the site has been demonstrated by Grimes and Marranzino (1968), utilizing 

truck-mounted spectrographic equipment, and this 

method has been effective for rapid determination 

of niobium. Similar rapid analyses for both niobium 

and tantalum can be accomplished in the laboratory 

by X-ray fluorescence spectroscopy. 

PROBLEMS FOR RESEARCH 

One of the basic problems relating to niobium and 

tantalum is the lack of domestic selfsuffi.ciency in 

resources of these elements in the United States. 

The United States is the world's largest single consumer, but these commodities are almost entirely 

imported. On a worldwide basis, supplies of niobium 

are more than adequate for projected needs to the 

year 2000 (Griffith, 1970) with chief sources in 

Brazil, Canada, and the African continent. 

Tantalum resources also are very limited in the 

United States, and ores are wholly imported from 

Brazil, Canada, and certain African countries. Even 

on a worldwide basis, the known resources of tantalum are not large, and this fact has served to limit 

industrial use of the metal and to discourage research on new applications. Pegmatites and placers 

are the only known commercial sources of this metal, 

and low-grade large-tonnage commercial deposits 

have yet to be discovered. 

Geologic research is needed to explore the possibilities of the existence of additional types of tantalum deposits. Such research has been hampered in 

the past by the lack of accurate abundance and analytical data on tantalum that in turn is a result of 

the lack of availability of suffi.cienijy senslitiv·e 

analytical techniques. Only neutron-activation analysis and elaborate chemical analysis currently are 

capable of detecting tantalum at the low values at 

which it is present in ordinary rocks. Research in 

new analytical techniques should receive first priority in any research effort directed toward discovery 

of additional resources of tantalum. 

REFERENCES 

Armstrong, F. C., 1957, Dismal Swamp placer deposit, Elmore County, Idaho: U.S. Geol. Survey Bull. 1042-K, 

p. 383-392. 

Barton, W. R., 1962, Columbium and tantalum, a materials 

survey: U.S. Bur. Mines lnf. Circ. 8120, 110 p. 

Berliner, M. H., 1949, Investigation of the Harding tantalumlithium deposits, Taos County, New Mexico: U.S. Bur. 

Mines Rept. lnv. 4607, 7 p. 

Black, R., and Girod, M., 1970, Late Paleozoic to Recent 

igneous activity in West Africa and its relationship to 

basement structure, in Clyford, T. N., and Gass, I. G., 

eds., African magmatism and tectonics: Darien, Conn., 

Hafner Publishing Co., p. 185-210. 

Davies, K. A., 1956, The geology of part of southe·ast Uganda 

with special reference to the alkaline complexes: Uganda 

Geol. Survey Mem. 8, 76 p. 

Dayton, S. H., 1958, Radioactive black sand is yielding 

columbite concentrate at Idaho mill: Mining World, v. 

20, no. 6, p. 3~1. 

de Souza, J. M., and Castro, L. 0., 1968, Geologia do deposito 

de terras rares, niobio e uranio da Area Zero, Araxa 

(MG): Soc. Brasileira Geologia Cong. 22d, Anais, p. 

97-102. 

Es'kova, E. M., 1960, The geochemistry of niobium and tantalum in nepheline syenites of the U.S.S.R.: lnternat. Geol. 

Cong., 21st, Copenhagen 1960, Papers of Soviet geologists, v. 1, Geochemical cycles (in Russian), p. 101-109. 

Evans, J. E'., Joki, E. G., and Smith, R. R., 1955, Evidence 

for a second naturally occurring isotope in tantalum: 

Phys. Rev., v. 97, 2d ser., p. 565-566. 

Fleischer, Michael, Murata, K. J., Fletcher, J. D., and Narten, 

P. F., 1952, Geochemical association of niobium (columbium) and titanium and its geologic and economic significance: U.S. Geol. Survey Circ. 225, 13 p. 

Gold, D. P., 1966, The minerals of the Oka carbonatite and 

alkaline complex, Oka, Quebec: lnternat. Mineralog. 

Assoc. Gen. Mtg., 4th, New Delhi 1964, Papers and 

Proc., Mineralog. Soc. India, IMA v., p. 109-125. 

Gordon, Mackenzie, Jr., and Murata, K. J., 1952, Minor elements in Arkansas bauxite: Econ. Geology, v. 47, no. 2, 

p. 169-179. 

Grice, J. D., Cerny,, Peter, Ferguson, R. B., an<! Tumock, 

A. C., 1971, Mineralogy and paragenesis of wodginite, 

tantalite, and pseudoixiolite from the Tanco (Chemalloy) 

pegmatite, Bernie Lake, Manitoba [abs.]: Canadian 

Mineralogist, v. 10, pt. 5, p. 913-914. 

Griffith, R. F., 1970, Columbium, in Mineral facts and problems, 1970: U.S. Bur. Mines Bull. 650, p. 275-288. 

Grimes, D. J., and Marranzino, A. P., 1968, Direct-current 

arc and alternating-current spark emission spectrographic field methods for the semiquantitative analysis 

of geologic materials: U.S. Geol. Survey Circ. 591, 6 p. 

GroSJS, E. B., and Heinrich, E. W., 1965, Petrology and 

mineralogy of the Mount Rosa area, El Paso and Teller 

Counties, Colorado--[Pt.] 1, The granites: Am. Mineralogist, v. 50, no. 9, p. 1273-1295. 

Hansen, John, 1968, Niobium mineralization in the Ilimaussaq 

alkaline complex, South-west Gre·enland: lnternat. Geol. 

Cong., 23d, Prague 1968, Endogenous ore deposits, Proc., 

sec. 7, p. 263-273. 

Heinrich, E. W., 1966, The geology of carbonatites: Chicago, 

Rand MeN ally and Co., 555 p. 

Houston, R. S., and Murphy, J. F., 1962, Titaniferous black 

sandstone deposits of Wyoming: Wyoming Geol. Survey 

Bull. 49, 120 p. 

Howe, A. C. A., 1968, Canada's firs.t tantalum producer: Westem Miner, v. 41, no. 12, p. 39-49. 

Knorring, Oleg von, 1960, Some geochemical aspects of a 

columbite-bearing soda granite from southeast Uganda: 

Nature, v. 188, no. 4746, p. 204-206. 
454 UNITED STATES MINERAL RESOURCES 

Lee, K. Y., 1970, Some rare-element mineral deposits in 

Mainland China: U.S. Geol. Survey Bull. 1312-N, 34 p. 

Mackay, R. A., Greenwood, R., and Rockingham, J. E., 19·49, 

Geology of the Plateau tin fields-resurv·ey 1945-1948: 

Nigeria Geol. Survey Bull. 19, 80 p. 

Mackin, J. H., and Schmidt, D. L., 1956, Uranium- and 

thorium-bearing minerals in placer deposits in Idaho, in 

Page, L. R., Stocking, H. E., and Smith, H. B.~ compilers, 

1956, Contributions to the geology of uranium and 

thorium by the United States Geological Survey and 

Atomic Energy Commission for the United Nations International Conference on Peaceful Uses of Atomic Energy, 

Geneva, Switzerland, 1955: U.S. Geol. Survey Prof. 

Paper 300, p. 375-380. 

Mining World, 1958, Idaho placer is eource of 99 percent of 

U.S. columbium-tantalum output: Mining World, v. 20, 

no. 1, p. 38-43, 62. 

Montgomery, Arthur, 1947, War production at the Harding 

Mine, in Benjovsky, T. D., Contributions of New Me,Oco's mineral industry to World War II: New Mexico 

Bur. Mines and Mineral Resources Bull. 27, p. 33-36. 

---1950, Geochemistry of tantalum in the Harding pegmatite, Taos County, New Mexico: Am. Mineralogist, v. 

35, p. 853-856. 

Parker, R. L., and Fleischer, Michael, 1968, Geochemistry of 

niobium and tantalum: U.S. Geol. Survey Prof. Paper 

611, 43 p. 

Parker, R. L., and Sharp; W. N., 1970, Mafic-ultramafic igneous rocks and associated carbonatites of the Gem 

Park complex, Custer and Fremont Counties, Colorado: 

U.S. Geol. Survey Prof. Paper 649, 24 p. 

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry: 

Chicago, Univ. Chicago Press, 911 p. 

Saether, Egil, 1957, The alkaline rock province of the Fen 

area in southern Norway: Norske Videnskab. Selskab 

Skr., no. 1, 150 p. 

Savage, C. N ., 1961, Economic geology of central Idaho 

blacksand placers: Idaho Bur. Mines and Geology Bull. 

17, 160 p. 

Sj~~rensen, Henning, 1960, On the agpaitic rocks: lnternat. 

Geol. Cong., 2l•st, Copenhagen 1960, Proc., pt. 13, Petrographic provinces, igneous and metamorphic rocks, p. 

319-327. 

Strominger, D., Hollander, J. M., and Seaborg, G. T., 1958, 

Table of isotopes: Rev. Modern Physics, v. 30, p. 585-904. 

Temple, A. K., and Grogan, R. M., 1965, Carbonatite and 

related alkalic rocks at Powderhorn, Colorado: Econ. 

Geology, v. 60, p. 672-692. 

U.S. Bureau Mines, 1938-72, Minerals yearbook [annual 

volumes for the years 1937-1971]. 

UsE.ing, N. V., 1911, Geology of the country around Julianehaab, Greenland: Medd. om Grfllnland, v. 38, 368 p. 

Vlasov, K. A., Kuz'menko, M. V., and Es'kova, E. M., 195-9, 

The Lovozero alkaline massif: Moscow, lzdatel'stvo 

Akad. Nauk SSSR, 623 p. (in Russian); translation, 

New York, Hafner Publishing Co., 1966, 627 p. 

Wambeke, L. van, 1965, A study of some niobium-bearing 

minerals of the Luesche carbonatite deposit (Kivu, Republic of Congo): Brussels, European Atomic Energy 

Community-Euratom, EUR 2110 e, 31 p. 

Wambeke, L. van, Brinck, J .W. Deutzmann, W., Gonfiantini, 

R., Hubaux, A., Metais, D., Omenetto, P., Tongiorgi, E., 

Verfaillie, G., Weber, K., and Wimmenauer, W., 1964, 

Les rockes alcalines et les carbonatites du Kaiserstuhl: 

Brussels, European Atomic Energy Community-Euratom, EUR 1827 d, e, f, 231 p. 

Wang, T. F., 1964, Petrologic characteristics of fergusonite 

granite in Nan-ling (in Chinese): K'o Hsiieh T'ung Pao 

(Scientia) 1964, no. 5, p. 449-452. 

White, F. A., Collins, T. L., Jr., and Rourke, F. M., 1955, New 

naturally occurring isotope of tantalum: Phys. Rev., v. 

97' p. 566-567. 

Williams, F. A., M·eehan, J. A., Paulo, K. L., John, T. U., 

and Rushton, H. G., 1956, Economic geology of the decomposed columbite-bearing granites, Jos Plateau, Nigeria: Econ. Geology, v. 51, no. 4, p. 303-332. 
UNITED STATES MINERAL RESOURCES 

NUCLEAR FUELS 

By WARREN I. FINCH, ARTHUR P. BuTLER, JR., FRANK C. ARMsTRONG, 

ALBERT E. WEISSENBORN, MoRTIMER H. STAATZ, and JERRY C. OLsoN 

CONTENTS 

Introduction -------------------------------------

Uranium ---------------------------------------- Abstract of conclusions -----------------------

Introduction ---------------------------------

Exploitation ---------------------------------

Geologic environment -------------------------

Geochemical cycle ------------------------

llineralogy ------------------------------ Types of deposits ------------------------

Peneconcordant deposits --------------

Deposits in quartz-pebble conglomerates 

Vein deposits ------------------------

Other epigenetic deposits -------------

Uraniferous igneous rocks ------------

Uraniferous phosphatic rocks ---------

Uraniferous marine black shales ------

Resources ----------------------------------- Identified and hypothetical resources -------

Recoverable resources ----------------

Conditional resources ----------------

Speculative resources ---------------------

Prospecting techniques -----------------------

Problems for research ------------------------

References cited -----------------------------

Thorium ----------------------------------------

Abstract of conclusions ----------------------- Introduction _________________________ ---____ _ 

Exploitation ---------------------------------

Geologic environment ------------------------

Geochemistry ----------------------------

Ore minerals and associated minerals ------

Types of deposits ------------------------

Veins -------------------------------

Placers ------------------------------ Deposits in sedimentary rocks --------

Concentrations in metamorphic and 

igneous rocks ---------------------

Resources -----------------------------------

Identified resources ---------------------- Hypothetical and speculative resources ___ _ 

Prospecting techniques -----------------------

Research needed on domestic thorium resources_ 

References cited -----------------------------

Page 

455 

456 

456 

456 

457 

459 

459 

459 

460 

460 

460 

461 

461 

461 

462 

462 

462 

462 

462 

464 

466 

466 

467 

467 

468 

468 

468 

469 

471 

471 

471 

471 

472 

472 

472 

472 

473 

473 

473 

475 

475 

475 

FIGURES 

Page 

54. Graph showing projected domestic uranium requirements, 1972-2010 -------------------- 456 

55. Graph showing uranium production, 1948-71, 

from United States and other countries ---- 458 

56. Graph showing production of monazite, 1887-

1970 ------------------------------------- 470 

TABLES 

93. Identified uranium resources 

94. Identified thorium resources 

INTRODUCTION 

By WARREN I. 'FINCH 

Page 

463 

474 

The increasing demand for ene1~.~,. throughout the 

world and the decreasing resources oi ·~! ;~!tnic fuels 

place the nuclear fuels, uranium and thorium, in the 

spotlight of future energy sources. Technologically, 

uranium's role is well established, but thorium's 

future use as a fuel is less certain. 

Thorium is about three times more abundant in 

the earth's crust than uranium. In igneous rocks the 

two elements are closely associated with each other; 

in the sedimentary cycle, however, they mostly part 

ways. The primary thorium minerals are resistant 

to oxidation, and weather out to form economically 

important placers. Thorium does not tend to enter 

the regimen of ground and meteoric water, rarely 

forms secondary minerals, and thus occurs in far 

fewer geologic environments than uranium. The 

primary uranium minerals, except those in which 

uranium substitutes for thorium, are easily oxidized. 

The most important placer concentrations of primary 

uranium minerals are those that are believed to have 

formed under nearly oxygen-free reducing atmosU.S. GEOL. SURVEY PROF. PAPER 820 

455 
456 UNITED STATES MINERAL RESOURCES 

pheric conditions in early Precambrian time. Uranium is very mobile in ground and meteoric water 

systems and reconstitutes into deposits in many 

kinds of rocks and environments. Uranium forms a 

great variety of minerals, many of which form rich 

concentrations, of higher grade than thorium, that 

are economically attractive. The ultimate resource 

of thorium, however, is greater than that of 

uranium. 

URANIUM 

By WARREN I. FINCH, ARTHUR P. BUTLER, JR., 

FRANK C. ARMSTRONG, and ALBERT E. WEISSENBORN 

ABSTRACT OF CONCLUSIONS 

Uranium is an important energy resource, and even though 

the demand for its use in nuclear-powered electrical generators was only moderate in 1972, near-future needs are expected to be very great. In the United States, large exploitable deposits are found chiefly in sandstone and associated 

rocks. In other parts of the world, large deposits are mainly 

in quartz-pebble conglomerate of early Precambrian age and 

in veins. Domestic resources recoverable at present prices 

totaled about 273,000 tons of UaOs at the end of 1971, and the 

total for all countries reporting resources is about 1.6 million tons of UaOs. These supplies are sufficient to last into 

the 1980's. Needs beyond 1980 are so great that tremendous 

efforts in exploration, and research in o~finding techniques, will be required to discover new recoverable resources. Identified low-grade paramarginal and submarginal 

resources in marine phosphorite and black shales and in 

igneous rocks are very large, but to obtain significant supplies of uranium from these sources would require mining 

and treating vast quantities of rock, disrupting large areas 

of ground at high unit costs. 

INTRODUCTION 

Uranium is a silvery white metal that consists of 

the three semistable radioactive isotopes U238' U235' 

and U234• It is an important energy source because 

fission of isotope U235 releases large amounts of 

energy. This readily fissionable nuclide constitutes 

only about 0.7 percent of natural uranium. The isotope U238 makes up most of the remaining 99.3 percent and the third, U234, only about 0.005 percent. 

U238 is not readily fissionable, but it is fertile material that under neutron bombardment converts to 

plutonium-239, which is fissionable. 

Prior to 1942, uranium was used chiefly for coloring glass and ceramic glazes. An ample supply was 

obtained by recovering some uranium from ores 

mined at first for radium and later for vanadium. 

In 1942, controlled nuclear fission was demonstrated, 

and uranium had two new and vastly more important 

uses: as an explosive by the military and as a source 

of heat to produce steam for generating electricity. 

With continued development of nuclear reactors to 

generate electricity, uranium is destined to become 

one of the principal energy sources for the world, 

for even "in today's light water reactors without 

plutonium recycle, in which less than one percent of 

the total potential heat content is made available, 

a pound of UaOs produces the heat equivalent of 

about eight tons of coal" (Johnson, 1972). 

Military uses for explosives stimulated search for 

uranium that by 1956 yielded a surplus of that element. In the 1960's, nuclear reactors for generating 

electricity were developed from the experimental 

stage to the commercial stage. By December 1971, 

domestic nuclear-powered electric plant capacity was 

about 10 million kw (kilowatts) (nearly 3 percent 

of the total U.S. electric utility capacity of 357 

million kw); about 45.8 million kw capacity was 

being built, and about 51.6 million kw was ordered 

(U.S. Atomic Energy Commission, 1972a). The domestic electric power need is growing at a rate of 

7--8 percent per year, and the nuclear share is expected to grow at a faster and increasing rate, so 

it is predicted that in the year 2000 nuclear plants 

will provide about 60 percent of the total electrical 

power (U.S. Department Interior, 1972). 

Although the demand for electricity generated by 

nuclear energy is expected to increase significantly 

for many years, technological developments may 

ultimately permit a decrease in the amount of uranium required to generate the needed electricity. If 

fast-breeder reactors are developed by the mid1980's, annual domestic uranium requirements are 

expected to peak about 1990 at about 100,000 short 

tons of UaOs, about 10 times the 1972 requirement 

(solid line, fig. 54), after which they will decline 

gradually to about the same level as in 1972 as the 

currently used nonbreeder reactors are phased out 

150,0001---------------------7"'1 

(/) 

z 

~ 125,0001---------------.,£-.-------1 

..... 

~ 100,000 1--------------:::±--~:...__---------1 

z 

(/) 75,0001---------+---,.tL-------3o,-------l z 

0

• 50,000 

.., 

:> 25,0001-----2fll'-~----------~~ 

OL--~-~--L-~-~-~~-L-~ 

1970 1980 1990 2000 2010 

FIGURE 54.-Projected domestic annual uranium requirements, 1972-2010, using light-water reactors (LWR) and 

high-temperature gas-cooled reactors (HTGR) only, relative to changeover to fast-breeder reactors (LMFBR) 

in 1986 (Johnson, 1972). 
NUCLEAR FUELS 457 

owing to obsolescence. If, on the other hand, fastbreeder reactors are not successfully developed, uranium requirements will continue to increase, as 

shown by the dashed line on figure 54. 

The identified domestic recoverable resources of 

273,000 short tons UaOs as of December 31, 1971, 

can supply domestic requirements into the early 

1980's. After that time, uranium requirements probably cannot be satisfied merely by finding new ore 

bodies in the known mining districts, but will require 

the discovery of new districts. This task poses a 

great challenge to industry. Guides to new districts 

are urgently needed. 

The world nuclear electric capacity was about 

18,000 MWE (megawatts electrical) in January 

1969 and is expected to grow to between 230,000 and 

330,000 MWE by 1980, according to the European 

Nuclear Energy Agency and International Atomic 

Energy Agency (1969, p. 19). Total cumulative 

world uranium demand for the period 1970-80 is 

estimated at 563,000-739,000 short tons of UaOs, 

and world demand of 73,000-106,000 short tons is 

anticipated in 1980. 

Thermal and nuclide pollution from nuclear reactors are serious problems that challenge technical 

ingenuity and affect the cost of nuclear electric 

power. The half-lives of some nuclides require safe 

disposal or storage for 10,000-500,000 years. 

EXPLOITATION 

Uranium was discovered in 1789 by Marten Klaproth in pitchblende from a mine in Germany. The 

element was first isolated in 1842. Radioactivity was 

discovered in 1896, and radium, a daughte1· of uranium decay, was discovered by the Curies and Bemont in 1898 in pitchblende from J oachymov 

(Joachimsthal), Czechoslovakia, where the mineral 

had been known since 1727. In the early 1900's, 

radium became important in medical therapy. This 

led to the search for uranium ore as a source for 

radium. The first important sources of radium outside Czechoslovakia were the uranium-vanadium 

sandstone deposits in western Colorado and eastern 

Utah from which about 275,000 tons of ore was 

produced during the period 1898-1923. This ore 

yielded about 200 grams of radium, 2,000 tons of 

vanadium, and a small but indeterminate amount of 

uranium; most of the uranium went into the tailings (Fischer, 1968). 

In 1923, the U.S. deposits were supplanted as the 

source of radium by the large and rich Shinkolobwe 

vein deposit in the Belgian Congo. In 1933, production began from another vein deposit, the Eldorado 

at Port Radium, Northwest Territories, Canada, and 

thereafter the market was shared by Canada and 

the Belgian Congo. Only minor amounts of domestic 

uranium-vanadium sandstone ore were mined from 

1924-1935. 

In 1936, mining of the uranium-vanadium ores 

increased markedly owing to increased demand for 

vanadium. In anticipation of the development of 

controlled nuclear fission, the United States in 1940 

began to recover uranium from tailings discarded 

during radium and vanadium operations, and by the 

end of 1947 a total of 1,440 tons of UaOs had been 

produced (U.S. Atomic Energy Commission, 1959). 

In addition, the United States procured about 10,150 

tons of U aOs from outside sources, mainly Canada 

and the Belgian Congo. Prior to 1940, the total production from all world sources was slightly more 

than 7,500 tons of U aOs. 

To meet military needs, the U.S. Atomic Energy 

Commission established in 1948 a domestic minimum price schedule that induded bonus payments 

for discovery and production of high-grade ore. The 

base price was raised in 1951. These incentives 

brought about the first large-scale mining of 

uranium-vanadium ores solely for uranium, and led 

to the discovery of many large deposits not only in 

the Colorado Plateau region, but also in Washington, 

Wyoming, South Dakota, and Texas. By 1956 it was 

clear that the newly discovered domestic and foreign 

resources of uranium were adequate for military 

needs as well as for its experimental use in nuclear 

reactors for producing electricity. Accordingly, the 

U.S. Atomic Energy Commission announced in 1956 

that after March 31, 1962, a price of $8 per pound 

for UaOs concentrate would replace the original price 

schedules. Later they announced that ore discovered 

after November 24, 1958, would not be purchased 

under any of the existing price schedules, and that 

if it were purchased at all, each sale would be 

individually negotiat~. In 1959, the U.S. Atomic 

Energy Commission relinquished its options to continue foreign purchases and in 1962, proposed to 

stretch out domestic purchases. 

Annual domestic production reached a maximum 

of 18,800 tons of U aOs in 1960, whereas world production peaked at more than 44,000 tons in 1959 

(fig. 55). Both domestic and world production declined to lows of about 10,000 and 19,000 tons, respectively, in 1966. In 1964 and 1965 actual demands 

and predicted future demands for nuclear powerplants stimulated new exploration and mining, which 

resulted in increased production in 1967. This rejuvenation was short-lived, however, because predicted 

demands did not materialize, owing partly to delay 

of reactor deliveries and partly to public concern 
458 UNITED STATES MINERAL RESOURCES 

45 

30 

U) 

z 

0 

~ 

~ 

a: 

0 

~ 

U) 25 u.. 

0 

U) 

0 

z 

c{ 

U) 

::J 

0 20 :I: 

~ 

z 

o· 

::J ... 

15 France and overseas affiliates 

Republic of South Africa 

FIGURE 55.-Uranium production, 1948-71, from the United States, Canada, Republic of South Africa, France and African 

affiliates, Belgian Congo (now Zaire), Australia, and other countries including Argentina and Sweden in most years, and 

Finland, West Germany, Portugal, and Spain in some years after 1956. Data from U.S. Atomic Energy Commission 

(1959), European Nuclear Energy Agency and International Atomic Energy Agency (1969, table 2), U.S. Bureau of 

Mines (1949-1972), and Williams (1971). 
NUCLEAR FUELS 459 

over safety and pollution hazards, and production 

leveled off in 1970 and 1971. Recently, concern over 

dwindling domestic oil and gas resources has increased new orders for nuclear reactors, and demand for uranium is expected to increase for many 

years. 

Domestic production in the period 1948-71 totaled 

229,913 short tons of Us08 , and reported world production, about 493,000 tons. 

The chief source of domestic production was sandstone ores from the Colorado Plateau, Wyoming 

basins, and the Texas Coastal Plain ; only about 5 

percent came from vein and other deposits, mainly 

in Washington and Colorado. Small byproduct 

amounts came from copper leach solutions and from 

the processing of marine phosphorite to produce 

treble super phosphate (Bieniewski and others, 1971, 

p. 9). The phosphorite processing is significant because of the large resource in marine phosphorites. 

Outside the United States, sandstone ores are not 

an important source of uranium. Vein deposits are 

the. chief uranium sources in Australia, the Congo, 

and France; Precambrian quartz-pebble conglomerates contain very large uranium reserves in South 

Africa and Canada. 

Environmental problems in exploiting uranium 

deposits are those common to all milling, open-pit, 

and underground mining operations ; an additional 

problem is the presence of radon gas in mines and 

tailings. Nuclear reactors produce plutonium, which 

is a hazardous material that requires very careful 

handling. They also produce radioactive wastes as 

well as large amounts of waste heat that require 

careful disposal. Nuclear plants, however, do not 

pollute the atmosphere as do oil- gas- and coalfueled generators. The radioactive pollution hazards 

of nuclear reactors are not of the continuous type, 

but rather those of accidental spillage, seepage, fire, 

and explosion. With proper safeguards, nuclear powerplants affect the environment less than fossilfueled types. 

GEOLOGIC ENVIRONMENT 

GEOCHEMICAL CYCLE 

The uranium content of the crust of the earth is 

about 2 ppm (parts per million) and that of granitic 

rocks is about 4 ppm. Uranium originates in magmas 

where it is mostly in the tetravalent state. As 

magma crystallizes, the large size of the tetravalent 

uranium ion prevents it from entering the crystal 

lattices of common rock-forming minerals except as 

minor occlusions; instead part of it is deposited in 

an intergranular film on rock-forming minerals, 

enters accessory minerals, or forms its own minerals. The remaining uranium is concentrated in late 

magmatic differentiates, where some uranium forms 

its own minerals in pegmatites and veins. In veins, 

iron is commonly associated with uranium, and in 

some places copper, lead, zinc, molybdenum, and 

cobalt accompany uranium. 

The accessory uranium-bearing minerals of igneous rocks generally resist oxidation, and weather 

out to' be washed into detrital sediments, or under 

special circumstances, to become concentrated in 

placers, some of which contain appreciable uranium. 

On the other hand, the uranium-bearing films that 

form on minerals in igneous rocks and the uranium 

minerals in pegmatites and veins oxidize readily, 

and water-soluble hexavalent uranium is released 

to surface and ground waters. As these waters circulate through sediment some uranium may be absorbed by clay minerals and carbonaceous matter, 

and some is precipitated chemically or by evaporation. Reduction of hexavalent uranium to the tetravalent state and its subsequent precipitation from 

ground water is the mechanism by which the uranium deposits in sandstones are thought to have 

been formed. Iron is univer.sally precipitated with 

uranium in this part of its geochemical cycle, and in 

some places copper, molybdenum, selenium, and chromium are similarly precipitated. Uranium-bearing 

waters also escape to the ocean where uranium may 

be precipitated with phosphatic sediments, taken up 

by organisms, or absorbed by carbonaceous mud. In 

the virtually oxygen-free atmosphere of early Precambrian time, it is postulated that uraninite from 

pegmatites and veins did not oxidize but rather 

formed placer concentrations, commonly with gold 

and thorium-bearing minerals. 

MINERALOGY 

Uranium in unoxidized black ores is tetravalent 

and in most such deposits it occurs in the minerals 

uraninite (U02) and coffinite [U(Si04)1-a.r(OH)4a.r] 

with pyrite as a common gangue mineral. The multiple oxides brannerite (oxide of uranium, titanium, 

thorium, rare earths, and other elements) and davidite (oxide of titanium, iron, and uranium) are the 

main uranium minerals in a few unoxidized ores. 

Tetravalent uranium substitutes for thorium and 

other elements in minerals such as monazite, uranothorite, multiple oxides of niobium, and tantalum, 

and for calcium in carbonate fluorapatite. It also occurs in unidentified organic compounds in many coaly 

rocks and marine black shales. 

Under oxidizing conditions tetravalent uranium 

changes to hexavalent uranium and forms oxide, 
460 UNITED STATES MINERAL RESOURCES 

vanadate, arsenate, silicate, sulfate, and carbonate 

compounds, most of which are hydrous and many of 

which are bright yellow or green. The vanadates, 

carnotite and tyuyamunite, are the most common 

and abundant. 

TYPES OF DEPOSITS 

Although anomalous uranium concentrations are 

widespread, concentrations of uranium that make 

minable deposits, ranging from about 400 to 2,500 

times crustal abundance, are not common. Most 

identified resources are in a few kinds of rocks and 

geologic environments. The principal domestic recoverable resources occur as peneconcordant masses 

in continental and marginal marine sandstone and 

associated rocks. A small part is in coaly rocks and 

nonmarine limestone. Less than 2 percent of domestic resources occur in veins. Identified paramarginal 

and submarginal resources are chiefly in marine 

phosphorite and black shale and in igneous rocks. 

Some major foreign resources are in Precambrian 

quartz-pebble conglomerate. 

PENECONCORDANT DEPOSITS 

Peneconcordant deposits are widely distributed in 

the United States ; they are es~ially numerous in 

some western States (Butler and others, 1962) . 

Typically these deposits occur in sandstone lenses 

that are interbedded with mudstone. These strata 

accumulated under fluvial, lacustrine, and nearshore marine conditions in cratonic or marginal cratonic environments. Most of the host sandstone beds 

are quartzose and were derived from older sedimentary rocks; some, however, are arkosic and were 

derived mainly from granitic rocks. Volcanic ash is 

present in some of the host sandstone beds and is 

common in overlying and interbedded mudstone. 

Nearly all of the host sandstone beds contain carbonized plant matter or organic residues. The host 

beds range in age from late Paleozoic to Tertiary, 

but in any given area all or nearly all of the deposits 

are in one or a few favored stratigraphic units. 

Uraninite and coffinite are the primary uranium 

ore minerals ; carnotite and other secondary minerals 

are ore minerals in some deposits. The ore minerals 

mainly occupy the pore spaces of the sandstone, but 

in places they replace the sand grains or the carbonized plant fossils. The average grade of the ore 

mined ranged from about 0.15 to 0.30 percent UaOs; 

0.08 percent UaOs is a common grade cutoff for min-

-ing and little material below 0.08 percent is mined. 

Ore bodies range in size from small masses containing a few tons of ore to those containing more than 

10 million tons. They occur in two distinct geometric 

forms: tabular bodies that are nearly concordant 

with the gross sedimentary structures of the host 

sandstone and roll bodies that are crescent-shaped 

and discordant to bedding in cross section and 

elongate in plan, with their long axes nearly con- · 

cordant to bedding. The tabular deposits are discrete 

masses and tend to be clustered in favorable areas a 

few miles across ; they are enclosed in reduced sandstone. The roll deposits are scattered along crescentshaped interfaces between oxidized sandstone on the 

concave sides and reduced sandstone on the convex 

sides ; in a given mining district an interface may 

extend for several miles and localize several ore 

bodies. Large deposits representative of the tabular 

type occur in the San Juan Basin, N.Mex. (Hilpert, 

1969) and the Uravan mineral belt, Colorado (Motica, 1968); deposits representative of the roll type 

occur in the Shirley Basin, Wyo. (Harshman, 1968) 

and the Texas Coastal Plain (Eargle and others, 

1971). 

Many hypotheses have been proposed for the genesis of the deposits (Finch, 1967, table 8). Most 

geologists now think that the uranium was derived 

by leaching-either from volcanic glass within or 

overlying the host rock or from granitic terranes 

exposed along the margins of the sedimentary basins. Uranium was transported in ground water in 

the hexavalent state and precipitated under reducing conditions. Carbonaceous matter, H2S gas, and 

transient sulfite derived from oxidation of preore 

pyrite are materials that have been cited as reductants that caused precipitation. Roll-type deposits 

apparently form at a dynamic interface between 

oxidizing and reducing conditions, that moves down 

the regional dip leaving altered (oxidized) host rock 

in its wake. In contrast, tabular deposits are wholly 

enclosed in reduced rock which in places may be 

completely surrounded by oxidized rock that is not 

in contact with ore. 

DEPOSITS IN QUARTZ-PEBBLE CONGLOMERATES 

Uranium-bearing Precambrian quartz-pebble conglomerates were deposited under deltaic or fluvial 

conditions in shallow: basins in cratonic or marginal 

cratonic environments more than 2.3 billion years 

ago. It is postulated that in the nearly oxygen-free 

reducing atmosphere of early Precambrian time, 

rounded and polished detrital grains of uraninite and 

pyrite accumulated with the more typical detrital 

placer minerals. Although locally the placer forms 

of some uraninite and pyrite grains were later modified, both minerals are generally coextensive with 

conglomerate beds or coarse parts of conglomerates. 

The deposits are very large and extensive. In the 
NUCLEAR FUELS 461 

Blind River-Elliot Lake district, Canada, deposits 

containing uraninite and brannerite are 7-15 feet 

thick and from hundreds of feet to 2 miles across, 

and contain more than 5 million tons of ore. Minable grade averages 0.12-0.16 percent UaOs; gold 

values are 0.02-0.03 ounce per ton. The thoriumuranium ratio is 1:4 to 1:3 and some thorium has 

been recovered as a byproduct. In the Witwatersrand, South Africa, the deposits are larger and more 

extensive than at Blind River-Elliot Lake, but their 

uranium content is lower, generally 0.03-0.07 percent UaOs. Uranium is produced mainly as a byproduct of gold mining and locally as a coproduct. Ore 

minerals are uraninite with minor amounts of brannerite. Thorium is not recovered because of the 

small amount in the ore. Possibly similar deposits of 

undetermined magnitude have recently been identified in Precambrian rocks near Belo Horizonte, Brazil (L. A. Moura, Commissao Nacional de Energia 

Nuclear, Brazil, oral commun., 1972). 

VEIN DEPOSITS 

Uranium-bearing veins are fissure fillings in faults, 

joints, and fracture zones; they occur in many kinds 

of rocks ranging from Precambrian to Tertiary in 

age, and in diverse geologic settings. Ore occurs as 

tabular bodies, irregular stockworks, pipelike masses 

at fracture intersections, and in mineralized gouge 

and breccia. Chief types of alteration associated with 

uranium veins are sericitic, argillic, chloritic, and 

hematitic. Individual veins are a few inches to several feet wide and extend along strike and downdip 

as much as several hundred feet ; these combine to 

form vein s-ystems which extend as much as 1,300 

feet below the surface in the United States and 

5,000 feet in Canada and which contain 10 tons to 

millions of tons of ore. Average mined grade ranges 

from 0.10 to 1.0 percent Ua08 • Deposits in which 

base-metal sulfides constitute appreciable to major 

amounts of the ore include the large deposits at 

Shinkolobwe, Zaire (formerly Belgian Congo) and 

at Port Radium, Northwest Territories, Canada, both 

now depleted; and the moderate-sized deposits at 

J oachymov, Czechoslovakia, and at the Schwartzwalder mine, Colorado (Walker and others, 1963). 

Pyrite is the only abundant sulfide in the very large 

deposits at Beaverlodge Saskatchewan, Canada. 

Fluorite is a characteristic component of the moderate-sized deposits at Marysvale, Utah. 

At Bancroft, Ontario, Canada, uraninite-thorite 

veins and irregular pods cut and replace bodies of 

unzoned granitic pegmatite and form fairly large 

deposits (Robinson and Hewitt, 1958). They contain 

an average of about 0.1 percent U aOs and 0.025-0.2 

percent Th.02. 

Veins are thought to have been deposited from 

hydrothermal solutions derived by differentiation of 

magmas. Uranium-bearing veins in the United States 

formed mainly during Late Cretaceous to late Tertiary time. 

OTHER EPIGENETIC DEPOSITS 

A few major epigenetic deposits do not fit into the 

preceding groups. The Midnite mine, Washington, is 

in Precambrian metasedimentary rocks along their 

contacts with Cretaceous granite. Individual ore 

bodies are as much as 200 feet wide, 700 feet long, 

and more than 150 feet thick. The average mined 

grade is about 0.23 percent U aOs. The deposit probably was formed shortly after granitic intrusion, by 

hydrothermal solutions directed along favorable 

zones adjacent to the intrusive contact (Becraft and 

Weis, 1963). At the Ross Adams mine in southeastern Alaska, numerous uraninite- and thoriumbearing veinlets cut peralkaline granite in which 

abundant uranothorite and uranoan thorianite occur 

as late crystallizing accessory minerals (MacKevett, 

1963). This deposit has yielded about 70,000 tons of 

ore that averaged more than 0.60 percent UaOs. Although the uranium-thorium ratio is about 1: 1, 

thorium has not been recovered. 

Deposits in this miscellaneous group in foreign 

areas include: ( 1) A several-million-ton irregular 

pipelike body of uraninite and uranophane disseminated in brecciated syenitic rock at the Gunnar mine, 

Beaverlodge area, Saskatchewan, Canada, (2) a subhorizontal, irregular, tabular body of mineralized 

metamorphic rock at Rabbit Lake, Saskatchewan 

(H. W. Little, Geol. Survey of Canada, oral commun., 

1972), and (3) probably the Nabarlek, Jim Jim, and 

Ranger deposits in older Precambrian rocks discovered recently in the Northern Territory, Australia. 

URANIFEROUS IGNEOUS ROCKS 

In the United States, only small amounts of uranium have been mined from pegmatites, most of which 

are the zoned type. 

Aside from pegmatites, a few igneous rock bodies 

contain anomalous concentrations of uranium as an 

indigenous constituent. The biotite phase of the Conway Granite of Triassic or Jurassic age in central 

New Hampshire contains an average of 0.0015 percent UaOs over a 300-square-mile area. It also contains about 0.0064 percent Th02. (See under Thorium in this chapter.) 

Bodies of a variety of uraniferous igneous rocks 

in other countries are mostly smaller but richer in 

uranium than the Conway granite. They include 
462 UNITED STATES MINERAL RESOURCES 

pyrochlore-bearing alkalic rocks at Araxa, Brazil, 

and in Ontario, Canada (Rowe, 1958); sodalite foyaite and nepheline syenite near J ulianehaab, Greenland (Bondam and Sorensen, 1958); riebeckite 

granite in Nigeria; and alaskitic rock near Rossing, 

South West Africa. 

URANIFEROUS PHOSPHATIC ROCKS 

Most phosphatic rocks are uraniferous and their 

uranium content generally increases with the phosphate content. Marine phosphorite is the dominant 

source of phosphate and constitutes a 'very large 

resource of urani urn. In such rocks, geosynclinal 

facies tend to be more uraniferous than platform 

facies. Uraniferous marine phosphorite deposits, 

commonly 5-10 feet thick, underlie hundreds of 

square miles, and their uranium content generally 

ranges from 0.007 to 0.07 percent UaOs. Phosphorite 

beds in the Phosphoria Formation of Permian age 

underlie 135,000 square miles of Idaho, Montana, 

Utah, and Wyoming (McKelvey and Carswell, 1956). 

Their uranium content ranges from 0.001 to 0.075 

percent U aOs, but beds more than 3 feet thick and 

with more than 31 percent P205 generally average 

0.012-0.024 percent U a08 • Prosphorite in the Bone 

Valley Formation of Pliocene age in the land-pebble 

phosphate field in Florida ranges in thickness from 

6 to 7 feet over several hundred square miles and 

averages 0.012-0.024 percent UaOs and 20-30 percent P205 (Altschuler and others, 1956)·. Uranium 

in marine phosphorite deposits was probably deposited from sea water during sedimentation, or in 

some places possibly later by downward percolating 

ground water. 

Large portions of extensive deposits of marine 

phosphorite in countries along the Mediterranean 

Sea from Morocco to Israel contain at least 0.01 percent UaOs (Davidson and Atkin, 1953). Near Recife, 

Brazil, deposits of phosphorite somewhat like those 

in Florida yield phosphate products that contain 0.02 

percent U aOs. Phosphorite that fills large depressions 

formed by solution of dolomite in Central African 

Republic are also uncommonly rich in uranium 

(Mabile, 1968). Deposits of aluminum phosphate in 

Senegal and Nigeria are also uraniferous. Marine 

phosphorite of Cambrian age in the Kara-Tau Mountains, Kazakhstan, U.S.S.R., resemble the Phosphoria Formation and are probably uraniferous. 

URANIFEROUS MARINE BLACK SHALES 

Many marine black shales rich in organic matter 

contain minor amounts of uranium that was deposited under anaerobic conditions with the organic 

fraction of the shale during sedimentation in shallow epicontinental seas. Most of the identified domestic black shale resources are in the upper member of 

the Chattanooga Shale of Late Devonian and Early 

Mississippian age in central Tennessee and adjacent 

Kentucky and Alabama (Swanson, 1961). This member is 12-18 feet thick over an area of about 4,000 

square miles, and averages about 0.007 percent UaOs. 

Moreover, the Chattanooga and its correlatives 

underlie about. 800,000 square miles extending from 

eastern Tennessee to Texas and Montana; its uranium-bearing strata average about 40 feet in thickness 

and about 0.0035 percent U aOs in grade. In Sweden, 

black shale of Late Cambrian and Ordovician age, 

which is 9-18 feet thick, is unusually rich in uranium and averages about 0.03 percent UaOs (Svenke, 

1956). Radioactive shale of the same age in the 

U.S.S.R. near the Baltic Sea may not be as rich as 

that in Sweden, but no modern determinations of its 

uranium content have been announced. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Both identified and hypothetical uranium resources can be divided into three subclasses: (1) 

recoverable resources, those that can be extracted 

profitably under 1972 economic conditions, (2) paramarginal resources, here defined as those that might 

be extracted profitably with a 50-percent to 5-fold 

increase in the price of UaOs, and (3) submarginal 

resources, those that require more than a 5-fold price 

increase. Nearly all of the domestic recoverable resources can be produced as a sole or principal product of mining operations, but they represent only a 

small fraction of the total identified resources. Most 

of the much larger paramarginal and submarginal 

resources are not likely to become major sources of 

uranium in the near future-either because the technology of extraction is costly or unsolved, because 

limits on land use might restrict mining large volumes of material, or because the most nearly economically recoverable uranium can be obtained only 

as a byproduct. 

RECOVERABLE RESOURCES 

The identified recoverable resources in the United 

States totaled 273,000 tons of UaOs, as of December 

31, 1971 (table 93) and are in rock averaging about 

0.22 percent U3 0 8 (4lb. UaOs per ton). Of this total, 

more than 99 percent-270,800 tons--is in peneconcordant deposits in sandstone and related rocks, and 

the remaining 2,200 tons is in veins and other types 

of deposits. About 50 percent of these resources is in 

northwestern New Mexico, about 35 percent in Wyoming, about 5 percent in Texas, about 3 percent 
NUCLEAR FUELS (63 

TABLE 93.-Identified uranium resourc.ea in the United States and other countries that have reported resources 

[Identified resources are speeifie, identified mineral deposita that may or may not be evaluated as to extent and lrl"&de, and whose contained minerals may or may not be profitably recoverable with existing teehno:ogy and eeonornie conditions] 

Loeality 

United States: western States ---------------------------

Canada: 

Blind River -Elliot Lake, Wollaston Lake, Bancroft, 

Beaverlodge. 

Elliot Lake ----------------------------------------

Mexico: Chihuahua (Aldama) and other States ----------

Argentina: Salta, Mendoza ------------------------------

f''' uf deposit 

Peneconeordant in 

sandstone, 'Vein. 

Precambrian con- glomerate, veins, 

and other types. Precambrian con- glomerate. 

Peneconcordant in 

sandstone, vein. 

Sandstone. 

France: Vendee, Limousin, Forez, Morvan ---------------- ___ do 

Portugal: Viseu (Urgeirica), Nisa, Guarda --------------- ___ do 

Spain: Ciudad Rod.rigo (Salamanca), Andujar ------------ ___ do ------------

Sweden: Vastergotland (Billingen), Niirke --------------- Marine black shale. 

Other Europe: West Germany, Italy, Turkey, Yugoslavia __ Vein, peneconcordant in sandstone. 

Central Africa Republic: Bakouma ---------------------- Phosphatic-filling karst in Precambrian dolomite. 

Gabon: Mounana (Franceville), Mikouloungou ----------- Structural con- trolled dissemination in Precambrian sandstone. 

Niger: Arlit ------------------------------------------- Peneconcordant in 

sandstone. 

Azelick. Madaouela --------------------------------- South Africa, South West Africa: Witwatersrand, Rossing __ 

Australia: Mary Kathleen, Alligator Rivers area (Nabarlek, 

Jim Jim, Ranger), Frome Lake. 

India: Jaduguda, Bihar ---------------------------------

___ do ------------ Precambrian con- glomerate, 

igneous rock. 

Vein and other 

types. 

Vein. 

Japan: Ningyo-Toge ------------------------------------ Peneconcordant(?) in Miocene and 

Total --------------------------------------------

Pliocene con- conglomerate. 

Grade 

(percent 

UaOs) 

0.22 

>.10 

<.10 

>.10 

>.10 

>.10 

>.10 

>.10 

. 03 

>.10 

.-.10 

>.10 

.29 

>.10 

<.10 

>.10 

.06-.07 

.06 

Short 

tons 

UaOa 

273,000 

230,000 

130,000 

2,380 

9,000 

66,400 

9,500 

11,000 

350,000 

6,500 

19,500 

19,500 

26,000 

13,100 

300,000 

100,000 

36,000 

4,000 

------ 1,605,880 

Souree of data 

U.S. Atomic Energy 

Comm. (1972b). 

Sherman ( 1972). 

Sherman (1972). 

Sherman ( 1970) . 

European Nuclear 

Energy Agency 

and International 

Atomic Energy Agency ( 1969). 

Sherman (1972). 

European Nuclear 

Energy Agency 

and International 

Atomic Energy 

Agency ( 1969). 

European Nuclear 

Energy Agency 

and International 

Atomic Energy Agency (1969). 

Sherman (1972) • European Nuclear 

Energy Agency 

and International 

Atomic Energy Agency (1969). 

Sherman (1972) • 

Sherman (1972). 

Sherman (1972). 

Sherman (1969). 

Sherman (1972). 

Sherman (1971). 

Mining Journal 

(1971). 

European Nuclear 

Energy Agency 

(1965). 

each in Colorado and Utah, and the rest in a few 

other Western States. 

These identified recoverable resources, plus several thousand tons of U aOs that might be recovered 

each year as a minor byproduct from phosphate rock 

and some copper ores, are adequate to satisfy estimated domestic requirements to the early 1980's, 

and most of these resources will be mined by that 

time. 

Recoverable uranium resources outside the United 

States listed in table 93 are largely in Precambrian 

conglomerate and in vein and related types. Most of 

these deposits average more than 0.10 percent UaOs 

and may be mined for their uranium content alone. 

Sweden recovers uranium from black shale deposits 

having an uncommonly high grade for black shale of 

0.03 percent UaOs (table 93). In the Witwatersrand, 

South Africa, uranium is a byproduct or coproduct 
464 UNITED STATES MINERAL RESOURCES 

of gold mining. Part of the African resources are 

probably paramarginal because of their remote 

location. 

The total identified recoverable uranium resources of countries listed in table 93 is about 1.6 

million tons of U aOs, which is enough to supply the 

estimated world demand until the late 1980's. 

Uranium resources in the U.S.S.R., China, and 

some other Asiatic and eastern European nations 

not listed in table 93 occur in deposits similar to 

those found in North America. Data on identified 

resources for these areas are not available. It is 

known, however, that in the U.S.S.R., peneconcordant uranium deposits occur in unspecified localities, 

and uranium-bearing veins occur in the Ukrainian 

region and elsewhere. 

Domestic hypothetical recoverable resources are 

estimated to total about twice the identified recoverable resources, or about 500,000 tons. If these resources are found by continued exploration and are 

mined, as expected, they will satisfy the estimated 

domestic requirements only until the early 1990's. 

After that, the domestic requirements, which will 

gradually decrease if the fast-breeder reactors are 

developed or will continue to increase if they are not, 

will have to be satisfied by importing much of the 

uranium needed or by mining much lower grade 

uranium resources at a high unit cost. 

CONDITIONAL RESOURCES 

Peneconcordant sandstone deposits and vein deposits contain about 200,000 tons of U a08 classified 

as identified paramarginal resources. These resources, which are too lean to be mined at present 

prices, are mostly adjacent to minable ore bodies 

where they would be bypassed in mining, and subordinately in separate deposits. The material adjacent to minable ore bodies would be very costly to 

recover by conventional mining methods after mine 

openings are abandoned and caved ; perhaps, however, techniques of solution mining can be developed 

to recover some of this uranium at moderate cost. 

Alternately, a scheme to subsidize the extraction and 

stockpiling of the low-grade material that is being 

bypassed in current mining operations might be justifiable to conserve a resource that will be much 

needed in the future. 

Other conditional resources consist of small 

amounts of uranium concentrated in certain types of 

rocks that are moderately abundant, and although 

the amount of uranium in a single ton of these rocks 

is small, the total amount of uranium contained in 

them is indeed large. The uranium in such rocks 

should be considered in appraising uranium resources, provided some of the factors limiting its 

availability are appreciated. These factors are chiefly 

price, technology, and byproduct status. 

Where the amount of uranium per ton of rock is 

small, the recovered U aOs is necessarily expensive. 

Such high-cost uranium must compete with possible 

substitutes, including less expensive uranium from 

domestic or foreign sources, thorium, and fossil 

fuels. The abundance of coal, gas, and oil as alternate 

fuels for the generation of electricity in the short 

term and the possible increase in use of thorium in 

nuclear reactors (see "Thorium") will effectively 

limit the price that will be paid for uranium. Consequently many domestic low-grade uranium deposits 

will not be a source of uranium in abundance for 

many decades to come. 

Whether much of the uranium in low-grade deposits becomes an available resource depends heavily 

on developments in metallurgical and other technology. For some types of deposits the technology of 

recovery has not yet been developed; from others 

the uranium can be recovered but only at considerable expense. The development of new recovery 

methods and the improvement in the efficiency of 

others will determine how soon and how much of the 

low-grade deposits become an available resource. 

The supply of uranium recovered as a byproduct 

in the production of another commodity is determined by the amount of the prime commodity produced. It can be increased only as the markets for 

the prime commodity expand. 

Factors such as the foregoing, which limit availability of conditional resources, must be borne in 

mind in connection with the ensuing discussion of 

the large low-grade uranium resources in the United 

States. 

Marine phosphorites in the United States contain 

large uranium resources. The Phosphoria Formation in Idaho and adjacent States is estimated to 

contain identified paramarginal resources of about 

700,000 short tons of UaOs in rock with an average 

grade of not less than 0.012 percent UaOs (0.24 lb 

UaOs per ton) and not less than 31 percent P205 (V. 

E. McKelvey, written commun., 1951). Identified 

paramarginal resources in the Bone Valley Formation in Florida are estimated to be about 300,000 

short tons of U aOs in phosphate rock products of 

about the same grade as in the Phosphoria (Altschuler and others, 1956; J. B. Cathcart, written 

commun., 1951). Additional marine phosphorites in 

Idaho and North Carolina are estimated to contain 

identified submarginal resources of about 5 million 

short tons of U aOs in rock whose grade ranges from 

about 0.006 to about 0.012 percent UaOs (0.12-0.24 
NUCLEAR F-UELS 465 

lb UaOs per ton) (V. E. McKelvey, written commun., 

1951 ; J. B. Cathcart, written commun., 1965) . 

Domestic hypothetical paramarginal uranium resources in marine phosphorite are estimated at about 

250,000 short tons of UaOs, and submarginal, about 

1 million short tons, both mostly in western States. 

A very small amount of the total resources in phosphorite can be obtained at moderate cost as a byproduct of making fertilizer, but to obtain more 

uranium would require mining and treating this 

rock principally for uranium; unit costs would be 

high and vast quantities of rock would have to be 

moved to obtain a significant amount of uranium. 

Phosphorite deposits are being mined for phosphate but their contained uranium is not being recovered. Uranium in rock that is used to make elemental phosphorus by the electric furnace method 

goes mostly into the silicate slag. A process for recovering uranium from the slag has not been developed. Most of the uranium in phosphorite that is 

used to make fertilizer by the wet-process phosphoric 

acid method stays in the fertilizer and is lost as a 

resource when the fertilizer is used. Marine phosphorite from Florida was the source of about 500 

tons of U aOs recovered between 1953 and 1961 as a 

minor byproduct from phosphoric acid made by the 

wet-process method. Recovery was discontinued because of costs uncompetitive with uranium from 

sandstone ores. Bieniewski, Persse, and Brauch 

( 1971) estimated that, if Florida phosphate rock 

containing 0.012 percent UaOs were treated by the 

wet-process method at the expected rate of fertilizer 

production, about 85,000 tons of UaOs could be recovered between 1971 and 2000 at a cost of slightly 

more than $10 per pound. 

Residues of copper smelting are also a potential 

source of byproduct uranium at about the same cost 

as that from phosphate rock. Bieniewski, Persse, and 

Brauch ( 1971) estimated that about 30,000 tons of 

UaOs could be recovered during the next 30 years by 

leaching residues containing 0.0001-0.0012 percent 

UaOs. Although byproduct uranium recovered in 

manufacturing fertilizer and from smelter residues 

would help to meet requirements, the amount that 

could be obtained most economically is limited by the 

production rate of the principal commodities. 

Marine black shales are a common rock, and they 

generally contain low concentrations of uranium. Of 

all the black shale beds of minable thickness that 

have been sampled in the United States, the Chattanooga Shale in eastern Ti!nnessee contains the highest concentration of uranium, but only 0.007 percent 

UaOs (0.14 lb UaOs per ton). It represents a submarginal resource of about 7 million tons of U aOs, 

but to obtain any significant part of this resource 

would require mining vast areas by open-cut and 

underground methods; unit costs would obviously be 

high. More than twice as much uranium is present 

in this formation in other parts of Tennessee and 

adjacent States, but at concentrations only about 

half that in eastern Tennessee. Even more uranium 

is present in the Chattanooga and its correlatives in 

the midcontinent where they are deeply buried, but 

the uranium content of these rocks is leaner, and less 

well defined, than it is in the more restricted areas. 

Most igneous rocks contain a little uranium, representing the order of crustal abundance-0.0002-

0.0004 percent UaOs-but some bodies of igneous 

rock are appreciably richer and thus might qualify 

as a potential resource. Of the igneous bodies that 

have been sampled in the United States, those of 

syenite and associated pegmatite in the Bearpaw 

Mountains, Mont., and the Conway Granite in New 

Hampshire are favorable examples. Those rocks in 

the Bearpaw Mountains are in relatively small 

bodies, but they average 0.05 percent UaOs (1lb per 

ton), and are estimated to contain a paramarginal 

resource of about 12,500 tons U aOs. The Conway 

Granite is exposed over an area of about 300 square 

miles and contains 0.001-0.003 percent UaOs (0.02-

0.06 lb per ton). This body of granite to a depth of 

1,000 feet (representing almost 50 cubic miles of 

rock) is estimated to contain about 7112 million short 

tons of UaOs. Hypothetical uranium resources in 

igneous rocks have not been estimated. 

If bodies of rock like the phosphate deposits, black 

shales, or igneous rocks are ever seriously considered as possible sources of domestic uranium, it 

might be possible to develop recovery processes to 

extract other useful commodities along with uranium, which might reduce to some extent the unit cost 

of the urani urn recovered. Nevertheless, if significant quantities of uranium are sought from these 

sources, vast quantities of rock would have to be 

mined and treated, which would require much energy and would temporarily disrupt large areas of 

ground. 

No attempt is made here to evaluate worldwide 

conditional uranium resources in phosphorites and 

black shales; they are known to be very large. 

Hypothetical resource figures are not available for 

most nations outside the United States. However, in 

view of the wide occurrence of deposits akin to those 

in North America, it is postulated that in areas of 

continental size the uranium resources bear the same 

relation to the size of the area as the uranium resources of North America bear to its area. 

Sea water contains 0.00015-0.0016 ppm uranium. 
(66 UNITED STATE~ MINERAL RESOURCES 

Although that is a low concentration, the total 

amount of uranium in sea water is very large (European Nuclear Energy Agency, 1965). It seems reasonable to suppose that a small amount of byproduct 

uranium will be recovered in the near future from 

desalination plants or from plants recovering magnesium from sea water. 

SPECULATIVE RESOURCES 

Domestic speculative resources consist of ( 1) new 

districts containing types of uranium deposits found 

elsewhere in the United States, (2) types of deposits 

known only elsewhere in the world, and (3) new 

types of deposits. 

The margins and locally the axial parts of sedimentary basins, particularly those containing sediments derived from either granitic terranes or volcanic ash, are favorable targets in the search for 

new uranium districts. These basins may be either 

intermontane such as in Wyoming, or of the gulf 

type as exemplified by the coastal plain in Texas 

where shoreline-facies rocks contain major deposits. 

Although both of these basins are Tertiary in age, 

analogs in older rocks, especially Cretaceous, ought 

to be equally favorable. 

Unconformities related to paleokarst topography 

may be favorable sites for occurrence of large uranium deposits. Two types of deposits are known in this 

setting. A large deposit of Cretaceous uraniumbearing phosphatic rock reportedly fills paleokarst 

developed in Precambrian dolomite in Bakouma, 

Central African Republic, and small deposits of 

tyuyamunite-bearing breccia occur in cavities related to karst developed on the Madison Limestone 

in the Pryor Mountains, Mont. Exploration here and 

elsewhere in this environment may be fruitful. 

Ancient, 2.0-2.4 b.y. (billion years) old, Precambrian quartz-pebble conglomerates analogous to 

those that contain the Witwatersrand and Blind 

River-Elliot Lake uranium deposits do not crop out 

in the United States. This type of rock might be 

present, however, somewhere in the deep subsurface of North and South Dakota and the east half of 

Montana, where, according to Goldicb, Lidiak, 

Hedge, and Walthall (1966), the ancient continental 

crust was formed more than 2.5 b.y. ago. 

Theoretical considerations and the description of 

the Rossing deposit in South West Africa suggest 

that there may be "porphyry" uranium deposits 

similar to porphyry copper and molybdenum deposits. Porphyry uranium deposits would be late 

magmatic differentiates-for example, alaskites and 

associated pegmatites-and would be easiest to 

recognize in arid or semiarid regions. 

PROSPECTING TECHNIQUES 

Radiation counters are the commonest tools used 

in prospecting for uranium. They are of two main 

types: ( 1) Geiger counters, which are normally 

portable and are designed to count y radiation alone, 

and {3 plus y radiation, and (2) scintillometers, 

which count only y radiation and which may be portable, carborne, or airborne. Scintillometers are more 

sensitive and respond faster than Geiger counters. 

If uranium only is present and is in equilibrium with 

all the daughter products of its radioactive decay, 

both types of instruments may be calibrated to indicate uranium content. However, if the uranium is 

not in equilibrium, they may indicate either more or 

less uranium than is present. In places where uranium has been leached but its daughter products remain, it is possible to detect radiation where there is 

little or no uranium. Conversely, recently deposited 

uranium that is too young (less than 500,000 years 

old) to be in radioactive equilibrium, emits so little 

{3 and y radiation that a deposit may contain more 

uranium than is indicated by its {3 and y count. 

Standard Geiger counters and scintillometers cannot 

distinguish uranium from thorium, or from naturally occurring radioactive potassium-40. 

Radiation counters are also used in drill-hole exploration. Only y radiation can be detected in drill 

holes because {3 particles lack the energy to pass 

through the water which is usually in the hole or 

through the walls of the detecting instrument. Scintillometers are used to probe drill holes because of 

their greater sensitivity and faster response. Resistivity and spontaneous potential surveys of drill 

holes are also customarily run. These two geophysical methods do not indicate uranium directly, but 

can be interpreted to distinguish sandstone from 

shale and to indicate relative porosity. The identification of shale at the site of a small y anomaly strongly suggests that the anomaly is caused by potassium40 in the shale. 

Airborne radiometric surveys using the total count 

method have proved useful in prospecting for uranium. In this method the scintillometer records total y 

radiation and does not discriminate between uranium, thorium, and potassium-40 sources. Total count 

anomalies have to be ground checked to determine if 

uranium causes the anomaly. Airborne gamma-ray 

spectrometry, which has been developed in recent 

years, distinguishes between uranium, thorium, and 

potassium-40 by measuring y radiations at particular energy levels. Thus, the strong y-emitting 

daughters of U238 and Th232, Bi214 and Tl208, respectively, are used to distinguish uranium and thorium; 
NUCLEAR FUELS 467 

they spectrum of potassium-40 is used for potassium-40. 

Other direct methods that have been used in prospecting for uranium are water analyses and geochemical sampling of soil and colluvium. Anomalously large amounts of uranium in water have led to the 

discovery of a few deposits, but in most places water 

analyses have not been a successful prospecting tool. 

Many natural waters contain anomalous amounts of 

uranium even though no uranium deposits are 

known in the vicinity. 

Under development is an indirect technique that 

uses the Eh and pH_ of water to evaluate sandstone 

aquifers and to locate favorable areas for exploration. If oxidation-reduction interfaces are important 

factors in the formation of uranium deposits in sandstone, then with further development and refinements this technique may be a useful exploration 

tool. 

Radon, an alpha-emitting gas and one of the 

daughter products of uranium, has been used as an 

indirect aid in prospecting for uranium. Scintillometers and alpha-sensitive film have been used to 

detect its presence. 

The indirect method of magnetic prospecting has 

been used without much success in looking for uranium deposits in continental sandstones. If the uranium were concentrated in stream channels and were 

associated with heavy detrital minerals, particularly 

magnetite, then the magnetic method might be a 

useful tool. 

PROBLEMS FOR RESEARCH 

The sedimentary framework of basins containing 

major uranium deposits in sandstone formations 

should be studied in order to develop new guides for 

finding new districts in these and other basins. Particular effort should be made to determine: (1) The 

original boundaries and configuration of basins, 

especially any intraformational basins within thick 

sequences of rocks, (2) the location, relief, and 

rock types of bordering uplands, (3) the diagnostic 

characteristics of the proximal, midfan, and distal 

rock facies between the margins and center of basins, (4) the ancient and modern hydrologic conditions, and ( 5) the postsedimentary histories. 

The differences and similarities between tabular 

deposits, such as found in the Colorado Plateau region, and roll-type deposits, found in Wyoming Tertiary basins, should be studied. Comparative studies 

of alteration patterns and the sedimentary framework of each type are needed. Colorado Plateau deposits should be examined for possible evidence of 

vestiges of roll-type bodies that may have been 

developed at an early stage in the formation of the 

ore bodies. If evidence of early ore bodies is found, 

then redistribution of uranium during compaction, 

consolidation, and lithification of the host rock 

should be investigated. Results of the study could 

guide exploration for and aid resource evaluation of 

undiscovered districts in the Plateau region, and 

especially in Mesozoic and Paleozoic rocks elsewhere. 

The geology of uranium-bearing veins in the 

United States should be studied in the hope of increasing our relatively small resources of this type. 

Knowledge of the geology and distribution of the 

large vein deposits in Canada may aid this research. 

Continued research is needed on the development 

of cheaper methods of extraction of uranium from 

paramarginal and submarginal resources in marine 

phosphorite and black shale and igneous rocks. 

The applicability of geochemical and other methods for prospecting and exploring for uranium 

should be improved by additional research. 

REFERENCES CITED 

Altschuler, Z. S., Jaffe, E. B., and Cuttitta, Frank, 1956, The 

aluminum phosphate zone of the Bone Valley Formation, Florida, and its uranium deposits, in Page, L. R., 

Stocking, H. E., and Smith, H. B., compilers, Contributions to the geology of uranium and thorium by the 

United States Geological Survey and Atomic Energy 

COmmission for the United Nations International Conference on Peaceful Uses of Atomic Energy, Geneva, 

Switzerland, 1955: U.S. Geol. Survey Prof. Paper 300, 

p. 483-487. 

Becraft, G. E., and Weis, P. L., 1963, Geology and mineral 

deposits of the Turtle Lake quadrangle, Washington: 

U.S. Geol. Survey Bull. 1131, 73 p. 

Bieniewski, C. L., Persse, F. H., and Brauch, E. F., 1971, 

Availability of uranium at various prices from resources 

in the United States: U.S. Bur. Mines Inf. Circ. 8501, 

92 p. 

Bondam, Jan, and Sorensen, Henning, 1958, Uraniferous 

nepheline syenites and related rocks in the Ilimaussaq 

area, J ulianehaab District, Southwest Greenland, in 

United Nations, Survey of raw material resources: Internat. Conf. Peaceful Uses Atomic Energy, 2d, Geneva, 

1958, Proc., v. 2, p. 555-5·59. 

Butler, A. P., Jr., Finch, W. 1., and Twenhofel, W. S., 1962, 

Epigenetic uranium deposits in the United States, exclusive of Alaska and Hawaii: U.S. Geol. Survey Mineral Inv. Resource Map MR-21, 42 p. 

Davidson, C. F., and Atkin, D., 1953, On the occurrence of 

uranium in phosphate rock: Internat. Geol. Con g., 19th, 

Algiers 1952, Comptes rendus, sec. 11, p. 13-31. 

Eargle, D. H., Hinds, G. W., and Weeks, A. M. D., 1971, 

Uranium geology and mines~ South Texas, in Houston 

Geol. Soc. Field trip, Houston, Texas, 1971 : Houston 

Geol. Soc., 59 p., 1 pl. 

European Nucle·ar Energy Agency, 1965, World uranium and 

thorium resources: Paris, France, Organization for 

Econ. Coop. and Devel., 22 p. 

European Nuclear Energy Agency and International Atomic 
468 UNITED STATES MINERAL RESOURCES 

Energy Agency, 1969, Uranium, production and short 

term demand, January 1969: Paris, France, Organization for Eeon. Coop. and Devel., 29 p. 

Finch, W. I., 1967, Geology of epigenetic uranium deposits 

in sandstone in the United s.tates: U.S. Geol. Survey 

Prof. Paper 538, 121 p. 

Fischer, R. P., H~68, The uranium and vanadium deposits of 

the Colorado Plateau region, in Ore deposits of the 

United States, 1933-1967 (Graton-Sales Volume), v. 1: 

New York, Am. In st. Mining, Metall. and Petroleum 

Engineers, p. 735-746. 

Goldich, S. S., Lidiak, E. G., Hedge, C. E., and Walthall, F. 

G., 1966, Geochronology of the midcontinent region, 

United States-[Pt.] 2, Northern area: Jour. Geophys. 

Research, v. 71, no. 22, p. 5389-5408. 

Harshman, E. N., 1968, Uranium deposits of the Shirley 

Basin, Wyoming, in Ore deposits of the United States, 

1933-1967 (Graton-Sales Volume), v. 1: New York, Am. 

Inst. Mining, Metall. and Petroleum Engineers, p. 849-

856. 

Hilpert, L. S., 1969, Uranium resources of northwestern 

New Mexico: U.S. Geol. Survey Prof. Paper 603, 166 p. 

Johnson, W. E., 1972, Status of the uranium producing industry: Mining Cong. Jour., v. 58, no. 2, p. 59-64. 

Mabile, J., 1968, Long-range trend for uranium: Atlanta, 

Ga., Southern Interstate Nuclear Board, Conf. on 

nuclear fuel exploration for power reactors, Proc. 

MacKevett, E. M., Jr., 1963, Geology and ore deposits of the 

Bokan Mountain uranium-thorium area, southeastern 

Alaska: U.S. Geol. Survey Bull. 1154, 125 p. 

McKelvey, V. E., and Carswell, L. D., 1956, Uranium in the 

Phosphoria formation, in Page, L. R., Stocking, H. E., 

and Smith, H. B., compilers, Contributions to the geology 

of uranium and thorium by the United States Geological 

Survey and Atomic Commission for the United Nations 

International Conference on Peaceful Uses of Atomic 

Energy, Geneva, Switzerland, 1955: U.S. Geol. Survey 

Prof. Paper 300, p. 483-487. 

Mining Journal, 1971, India, Recent mineral discoveries: 

Mining Jour., v. 277, no. 7111, p. 507. 

Motica, J. E., 1968, Geology and uranium-vanadium deposits 

in the Uravan mineral belt, southwestern Colorado, in 

Ore deposits of the United States, 1933-1967 (GratonSales Volume), v. 1: New York, Am. Inst. Mining, 

Metall. and Petroleum Engineers, p. 805-813. 

Robinson, S. C., and Hewitt, D. F., 1958, Uranium deposits 

of Bancroft region, Ontario, in United Nations, Survey 

of raw material resources: Internat. Conf. Peaceful 

Uses Atomic Energy, 2d, Geneva, 1958, Proc., v. 2, p. 

498-501. 

Rowe, R. B., 1958, Niobium (columbium) deposits of Canada: 

Canada Geol. Survey, Econ. Geol. ser. 18, 108 p. 

Sherman, J. T., 1969, Uranium: Eng. and Mining Jour., v. 

170, no. 3, p. 104-108. 

--- 1970, Uranium: Eng. and Mining Jour., v. 171, no. 

3, p. 92-96. 

--- 1971, Uranium: Eng. and Mining Jour., v. 172, no. 

3, p, 108-111. 

--- 1972, Uranium: Eng. and Mining Jour., v. 173, no. 

3, p. 140-143. 

Svenke, Erik, 19·56, The occurrence of uranium and thorium 

in Sweden, in United Nations, Geology of uranium and 

thorium: Internat. Conf. Peaceful Uses Atomic Energy, 

Geneva 1955, Proc., v. 6, p. 198-199. 

Swanson, V. E., 1961, Geology and geochemistry of uranium 

in marine black shales, a review: U.S. Geol. Survey 

Prof. Paper 356-C, p. 67-112. 

U.S. Atomic Energy Commission, 1959, U.S. uranium concentrate procurement statistics for 1949-1959 made public by AE·C: U.S. Atomic Energy Comm. Press Release 

B-166, Sept. 23, 2 p. 

--- 1972a, Status of nuclear powerplants: U.S. Atomic 

Energy Comm. Press Release 589, Jan. 17, 1 p. 

--- 1972b, Statistical data of the uranium industry, January 1, 1972: U.S. Atomic Energy Comm. GJ0-100, 63 p. 

U.S. Bureau of Mines, 1949-72, Minerals Yearbook (annual 

volumes). 

U.S. Department Interior, 1972, United States energy, a 

summary review: Washington, D. C., 72 p. 

Walker, G. W., Osterwald, F. W., and Adams, J. W., 1963, 

Geology of uranium-bearing veins in the conterminous 

United States: U.S. Geol. Survey Prof. Paper 455_, 

146 p. 

Williams, R. M., 1971, Uranium and thorium, in Canadian 

Minerals Yearbook 1971: Canada Dept. Energy, Mines 

and Resources Mineral Resources Br., preprint 51. 16 p. 

THORIUM 

By MORTIMER H. STAATZ and JERRY C. OLSON 

ABSTRACT OF CONCLUSIONS 

Although the current demand for thorium is small, future 

needs may be large as a fuel for nuclear generators. The 

occurrence of thorium is widespread, and large deposits are 

found in beach and fluviatile placers, veins, sedimentary 

rocks, alkalic igneous rocks, and carbonatites. Thorium has 

been produced principally from monazite from beach and 

fluviatile placers, although in the 1950's and early 1960's 

monazite from a unique vein in South Africa was the chief 

source. In the early 1970's monazite was recovered principally 

as a byproduct of titanium or tin mining in India, Brazil, 

Australia, and Malaysia. A large thorium resource in the 

conglomerates at the Elliot Lake uranium mines, Canada, 

could become an important byproduct if demand increases. 

Thorium resources are not well known because of the small 

demand, but are sufficient for many years in the future. The 

development of a viable domestic thorium mining industry is 

dependent on a large enough increase in demand to exceed 

the amount obtainable as byproducts from other types of deposits. 

INTRODUCTION 

Thorium is a heavy, ductile, silver-gray metal 

that, like uranium, is the parent of a series of radioactive decay products, ending in a stable isotope of 

lead. 

Current demand for thorium is small, and in 1968 

was only about 125 tons of Th02 (Stevens, 1969, p. 

1068). Of this amount, 50 percent was used in making gas mantles, 30 percent in magnesium alloys, 

10 percent in dispersion-hardened metals, and the 

rest in specialized refractories, polishing compounds, 

electronic devices, and chemicals. The demand for 

industrial uses, although small, will continue inasmuch as satisfactory alternate materials are not 
NUCLEAR FUELS 469 

known for most of thorium's uses, especially in gas 

mantles and in alloys (Shortt, 1970, p. 209). Being 

radioactive, thorium has considerable potential as a 

nuclear fuel. It cannot, however, be used directly in 

a nuclear reaction, because it does not contain fissionable isotopes to start the reaction; bombardment by 

neutrons from fissionable U235 converts thorium to 

fissionable U233. Five types of thorium-cycle reactor 

systems have been investigated by the U.S. Atomic 

Energy Commission (Stevens, 1969, p. 1072). The 

farthest advanced of these is the HTGR (hightemperature gas-cooled reactor). A 40-MWE (megawatts electrical) prototype of the HTG R was put 

into operation by Philadelphia Electric at Peachbottom, Pa., in 1966. The first reactor designed specially 

for commercial use is near Platteville, Colo., where 

Public Service Co. of Colorado has a 330 MWE 

HTGR that is expected to start producing electricity 

in April1973. Four other HTGR reactors have been 

ordered-two of 770 MWE by Delmarva Power and 

Light Co. and two of 1,100 MWE by Philadelphia 

Electric. The HTGR has a number of technical advantages over the uranium reactors now in use-it 

is more efficient to operate, runs on cheaper fuel, 

and produces less thermal pollution. The Public 

Service Co. of Colorado's HTGR will have an efficiency of 39 percent, which is on a par with the 

best coal-operated electric generators and is better 

than the best uranium generators in use in 1971, 

which have 34 percent efficiency. 

EXPLOITATION 

Thorium was discovered by Berzelius in 1828, but 

the first real demand for the element was created 

after Carl Auer von W elsbach invented the thoriated 

incandescent gas mantle in 1891. The only common 

thorium mineral known at that time was monazite. 

Although monazite is also a principal source of rare 

earths, monazite production from 1895 to 1921 (fig. 

56) reflects the demand for Th02 and minor amounts 

of Ce02 used in the gas mantle industry (Olson and 

Overstreet, 1964, p. 3). Monazite production in the 

United States prior to 1909 came principally from 

stream placers in North and South Carolina, and 

about equalled the country's demand. The rest of 

the world production came chiefly from beach placers 

in Brazil. From 1912 to 1945 the large beach placers 

in India produced a major part of the world's monazite. After 1920 the use of Th02 in gas mantles declined (fig. 56), and the little monazite produced between 1921 and 1934 was used largely for its rare 

earth content. Before World War II, uses and production of both rare earths and thorium increased. 

Because thorium is a radioactive material, India and 

Brazil nationalized their monazite deposits in 1946 

and 1951, respectively, and restricted monazite exports during the period in which the United States 

was building up its stockpiles. The difference in 

demand was taken up by monazite from beach 

placers chiefly in Australia, Malaysia, South Korea, 

Indonesia, United States, and Malagasy, and from a 

unique vein deposit in South Africa. Both India and 

Brazil resumed monazite mining, but separated the 

thorium and rare earths from the monazite in local 

plants. The thorium was not exported, but foreign 

markets were sought for the rare earths (Overstreet, 1967, p. 10). During the 1950's and 1960's 

monazite was mainly a byproduct of titanium (ilmenite or rutile) mining in Australia, India, and 

United States and of tin in Malaysia and Indonesia. 

The only nonplacer monazite mined came from a 

vein 13 feet thick exposed for 900 feet on the Steenkampskraal farm in Cape Province, South Africa 

(Pike, 1958, p. 92). This vein consists of 80 percent 

monazite and apatite, and veins of this type have 

not been reported elsewhere. About 51,100 tons of 

monazite were shipped from this property between 

1952 and 1959 to Lindsay Chemical Co. in the United 

States and 8,000 tons in 1962 and 1963 to American 

Potash and Chemical Corp. Because of production 

from this mine, South Africa largely dominated the 

monazite market during these periods (fig. 56), but 

at present it is shut down. 

Data on the amount of ThOz actually obtained 

from monazite production during various years are 

not always obtainable, for two principal reasons. 

One is that the amount of Th02 ranges from 0 to 

31.5 percent in various monazites (Overstreet, 1967, 

p. 1), or from about 3.5 to 9.0 percent in commercial 

monazite concentrates (Parker and Baroch, 1971, 

p. 67). The Th02 content of monazite from each 

geographical area, however, commonly falls within 

relatively short ranges. The other principal reason 

is that in some years, such as the late 1960's, monazite is sold principally for its rare earth content, and 

the amount of Th02 actually produced is not known. 

Monazite was practically the only source of thorium prior to 1953. Since that time thorium has also 

been recovered as a byproduct from the following 

two types of uranium ores: 

1. In Malagasy, from 1953 to 1968, relatively small, 

rich uranothorianite deposits yielded 4,170 

short tons of concentrates that averaged about 

60 percent Th02 (Parker and Baroch, 1971, p. 

68). These concentrates were produced principally by the French Atomic Energy Commission and shipped to France. This amount of 

Th02 is about twice the amount used in the 
470 UNITED STATES MINERAL RESOURCES 

16,000 

15,000 

14,000 

13,000 

12,000 

11,000 

~ 10,000 

0 

1-

1-

a: 9000 

0 

I 

Cl) 

!: 8000 

w' 

1-

;::;; 7000 

<( 

z 

0 

':!! 6000 

5000 

4000 

3000 

2000 

1000 

0 0 

N 

en 

It) 

N 

en 

It) 

(") 

en 

World production 

South Africa production 

0 

" en 

FIGURE 56.-United States, South African, and world production of monazite, 1887-1970. Data for 1887-1947 from Olson 

and Overstreet (1964, fig. 1); 1948-70, from U.S. Bureau of Mines (1950-72). 

United States from 1947 through 1968 for 

nonenergy uses. 

2. Near Elliot Lake, Canada, thorium was first recovered from Precambrian uranium-bearing 

conglomerates in 1959, from ore containing 

about 0.05 percent Th02 (Williams, 1969, p. 

487). The thorium was recovered from eftluent 

solutions by ion exchange following the removal of the uranium, and was precipitated as 

a concentrate that contained 25-40 percent 

Th02. The Th02 was recovered from only a 

small part of the uranium ore mined. Thorium 

shipments in Canada in the period 1966-69 

contained a total of about 186 tons of Th02, 

only a small part of the capacities of the mills, 

but lack of market caused production to cease 

in 1968. Most of the concentrates were shipped 

to Thorium Ltd. in Great Britain, although 

some was shipped to the United States and 

some was used in Canada for making thorium 

metal. 

In 1957, 132 tons of thorium-bearing ores was re-
NUCLEAR FUELS 471 

covered principally from pegmatites; and in 1958, 

650 tons of thorite concentrate was obtained from 

thorite-bearing quartz-carbonate veins in Colorado 

(Kelly, 1962, p. 3). 

The principal placers that have been mined for 

monazite in the southeastern United States are small 

fluvial placers in the Piedmont of North and South 

Carolina. The value of the land for agricultural purposes is commonly greater than for monazite placer 

mining. The changes in land use and the small size 

of many of the deposits deter the operation of most 

fluvial placers. In some of the larger beach placers 

from South Carolina to northern Florida, the value 

of residential property would deter their use as 

beach placers. For example, Hilton Head Island, 

S. C., where 8,266,000 tons of heavy minerals containing approximately 2,880,000 tons of ilmenite and 

94,600 tons of monazite were reported (McCauley, 

1960, p. 5-6), is covered by many fine estates, golf 

course, and summer residences. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Recent estimates of the thori urn content of the 

earth's crust range from about 6 to 13 ppm. Most of 

the thorium is widely disseminated in small quantities which vary in amount in different rocks. In its 

geochemical cycle, thorium becomes concentrated 

during several episodes, for example: 

1. In magmatic intrusion and differentiation, because of its relatively large ionic radius and 

high valence thorium tends to become concentrated in the residual solutions as crystallization progresses. Thus it is most abundant in 

the younger members of rock series such as 

granitic and alkalic rocks and other rocks 

formed from residual magmatic fluids. The 

thorium content of granitic rocks that aPproach true granite in composition is likely to 

be higher than that of granodiorite or quartz 

monzonite, and it is notably high in some small 

alkalic rock complexes with which carbonatite 

and fenite are associated. During magmatic 

and metamorphic processes, therefore, thorium may be concentrated in veins, carbonatite, pegmatite, and certain alkalic rocks, 

granites, and metamorphic rocks. 

2. In magmatic and metamorphic phases, the type 

and grade of metamorphism are factors in 

determining whether monazite, the principal 

ore mineral of thorium, is formed, and in determining the thorium content of the monazite. Thus the higher grade metamorphic and 

related igneous terranes are the best source 

areas for monazite with a high thorium content. 

3. During weathering and erosion, monazite tends 

to remain as detrital grains owing to its insolubility and high specific gravity. The weathered mantle thus becomes enriched in this and 

other residual heavy minerals, which gradually move downslope and downstream, forming 

local placer concentrations. Monazite and other 

heavy minerals that reach the sea are deposited chiefly near shore at the mouths of 

rivers, but some thorium is also adsorbed on 

clay minerals during weathering and becomes 

disseminated in clayey sediments. During 

weathering and erosion, therefore, thorium 

may be concentrated in residual, stream (valley) placer, or beach placer deposits. Detrital 

mineral deposits formed in these ways may 

also be preserved in ancient sedimentary rocks 

under proper conditions, or on erosion of them 

the monazite may be reconcentrated to form 

rich, second-generation placer deposits. 

ORE MINERALS AND ASSOCIATED MINERALS 

The chief ore minerals of thorium are monazite 

[ (Ce,La,Nd,Th) P04], thorite, (ThSi04), uranothorite, and brannerite (a multiple oxide of Ti, U, Ca, 

Fe, Th, and Y) . Other thorium-bearing minerals 

present in some deposits include allanite; multiple 

oxides such as euxenite, samarskite, fergusonite, and 

betafite; and thorianite (Th02). Thorium is commonly associated, in minerals and in deposits, with 

the rare earths, niobium, titanium, and zirconium; 

thorium may occur with these elements as important 

coproducts or byproducts. In placer deposits, potential source minerals for thorium include monazite 

and several thorium-bearing multiple-oxide minerals. 

In veins or lodes the principal thorium-bearing minerals are thorite, monazite, and uranothorianite, and 

less commonly allanite, brockite, and brannerite. 

Thorium-bearing pyrochlore is found in some carbonatiteR. 

TYPES OF DEPOSITS 

Thorium concentrations of possible economic interest occur in the following types of deposits: (1) 

Veins, (2) beach and stream placers and residual 

deposits, (3) deposits in sedimentary rocks-ancient 

placer deposits, thorium-bearing dolomite (as found 

in Canada)', and conglomerates or quartzites enriched in thorium and in some places uranium (as 

at Elliot Lake, Ontario), and ( 4) concentrations in 

igneous and metamorphic rocks, mostly of low grade, 

which include carbonatite, fenite, dikes or layers of 

alkalic igneous rock, thorium-rich granite, pegma-
472 UNITED STATES MINERAL RESOURCES 

tite, pegmatitic migmatite, and thorium-rich zones 

in metamorphic rock. 

VEIN~ 

Three types of thorium veins are known. First are 

the unique monazite-apatite veins of South Africa 

that have been the principal producers, but are 

largely depleted. The second type comprises uranothorite or uranothorianite deposits in Malagasy 

and on Bokan Mountain, Alaska; these also are 

largely depleted. The third type consists of veins 

composed chiefly of fine-grained quartz, potassium 

feldspar, and iron oxide. The most abundant thorium 

mineral in these veins is thorite, but monazite, allanite, or brockite are common in some places. Veins of 

this type are known at 13 localities in the United 

States. The veins are from a few feet to 5,000 feet 

long and many are 1-2 feet thick. They occur in 

steeply dipping fractures that cut across the structure of the host rocks; many are brecciated. In many 

areas the veins are adjacent to alkalic complexes and 

carbonatites. The veins formed from highly mobile 

fluids at low temperatures, and hence may be as 

much at 20 miles from their probable source. 

The grade of the veins is commonly erratic, but 

many contain an average of several tenths of a 

percent thorium. A few veins, such as those in the 

Wet Mountains, Colo. (Christman and others, 1959, 

p. 522 and 530), and at Hall Mountain, Idaho (Staatz, 

1972, p. 247), may contain several percent thorium. 

The rare-earth content of the veins may equal or 

exceed the thorium content. Inasmuch as the grain 

size is small and the iron oxide may be abundant, 

separation of thorium minerals by standard phyflical 

methods is difficult. 

PLACERS 

In many countries, monazite is a common accessory mineral in placer deposits that were formed 

from the debris of metamorphic and granitic rocks. 

Many of these placer deposits are formed on active 

beaches, where the monazite and other heavy minerals are concentrated in a narrow belt along the 

shoreward facies. Many placer deposits are extensive; some are more than 10 miles long and onequarter mile wide. Some placer deposits occur in 

partly indurated beach sediments that now lie landward of the active beaches. 

In tropical areas, where weathering has been extensive and penetrated deeply, beach placers may 

contain more than 50 percent heavy minerals that 

consist chiefly of ilmenite or magnetite, although 

garnet, zircon, rutile, sillimanite, cassiterite, or 

monazite may also be sufficiently abundant to be 

economically important. The monazite, however, generally occurs in minor amounts compared to many 

of the other minerals. The Th02 content of monazite 

in these deposits is highly variable, and commonly 

ranges from 3.5 to 9.0 percent (Parker and Baroch, 

1971, p. 67), but the Th02 content of the monazite 

from any one deposit or area is fairly constant. 

Stream placers are smaller and tend to be less 

uniform in composition than beach placers, and 

therefore must be of higher unit value to be worked 

successfully. Monazite generally is the principal and 

only thorium mineral in these deposits, but other 

thorium minerals are found in a few places. The 

principal thorium mineral is euxenite in the placers 

at Bear Valley, Idaho, and uranothorite in the Hailey 

area, Idaho (Mackin and Schmidt, 1956). 

DEPOSITS IN SEDIMENTARY ROCKS 

Some sedimentary rocks consist chiefly of indurated p!acer sediments, such as those of fossil beach 

deposits. In some of these deposits, the sorting and 

concentration of the valuable minerals has been 

more complete than in others. In some of these 

deposits especially in sandstone and conglomerate, 

the heavy minerals tend to be dispersed, but even 

here they have been concentrated because the softer 

or more brittle minerals have been ground finer and 

carried farther away. Monazite is commonly the only 

thorium-bearing mineral found, but near Elliot Lake, 

Canada, it occurs with brannerite and uraninite 

(Roscoe and Steacy, 1958, p. 482). The latter two 

minerals, important sources of uranium, are found 

in conglomerates in ancient Precambrian rocks. 

Indurated sedimentary rocks require grinding to 

liberate the thorium minerals-unless they contain 

an important coproduct, such as uranium, they are 

not likely to be mined until the less expensive 

unconsolidated placers are largely exhausted. 

CONCENTRATIONS IN METAMORPHIC AND IGNEOUS ROCKS 

Thorium minerals are found in some metamorphic 

and igneous rocks. Monazite is especially widespread 

in metamorphic rocks of garnet to sillimanite grade. 

In a few small areas, such as near Central City, Colo. 

(Young and Sims, 1961), and in southern Music 

Valley, California (Evans, 1964), monazite and 

xenotime are concentrated, but the deposits are too 

small to mine. 

Thorium minerals are commonly associated with 

potassic igneous rocks, especially granitic and alkalic complexes. Also related to these igneous rocks 

are bodies of carbonatite, which commonly contain 

several valuable minerals. Thorium occurs in some 

such carbonatites; for example, it might be recov-
NUCLEAR FUELS 473 

ered as a byproduct of rare-earth mining at Mountain Pass, Calif.; of niobium mining at Araxa, Brazil; 

or of copper mining at Palabora, South Africa. 

Most granite contains an average of 0.0025 percent thorium, but granite with a greater content of 

thorium could be a potential low-grade resource. The 

Conway Granite underlies a large area in New Hampshire and, in addition to uranium, contains more than 

twice as much thorium as the average value already 

cited (Adams and others, 1962, p. 1903). The granites of the Tokovskii complex in the U.S.S.R. contain four times the average thorium content of 

granite (Filippov and Komlev, 1959, p. 541). 

RESOURCES 

IDENTIFIED RESOURCES 

The resources of thorium are not well known, owing in part to the small demand in relation to available supply. The increased use of thorium for generating electricity, however, has stimulated interest 

in resources. Because the amount of byproduct Th02 

recovered throughout the world in 1972 was more 

than sufficient to meet current needs, deposits in 

which thorium is the principal element cannot be 

mined at a profit. 

The present known resources of Th02 in the 

United States as given in table 94 include resources 

recoverable as byproducts as well as both high- and 

low-grade nonbyproduct resources. The only minable reserves at present are some of the Atlantic 

Coast beach placers, where monazite is produced as 

a rather minor byproduct of titanium mining. Resources of beach placers along the Atlantic coast include 15,600 tons of Th02 estimated to be in monazite in the sands in Florida, on Hilton Head 

Island, S.C., and in some of the ancient beach 

placers near Folkston, Ga. 

The United States has large resources (table 94) 

of thorium in relatively high-grade veins-those 

containing more than 0.1 percent Th02. The W~roming and Michigan resources, which occur in detrital 

monazite in conglomerates, are too low-grade for 

recovery to be feasible until higher grade and easierto-handle ores such as placers and veins have been 

depleted. These conglomerates are nonuraniferous, 

and thorium cannot be recovered from them as a 

byproduct as it can in the uraniferous conglomerates 

at Elliot Lake, Canada. A large potential source of 

thorium is in the low-grade deposit of granite near 

Conway, N.H. This granite, the Triassic or Jurassic 

Conway Granite which has an average grade of 

0.0064 percent Th02, underlies an area of about 307 

square miles (Adams and others, 1962, p. 1903), and 

could be mined at a cost of about $50-$100 per pound 

of Th02 (Brown and others, 1963, p. 6-11). More 

than half of the world's identified resources of thorium are in beach placers, principally in India (table 

94) . The total resources of thorium in beach placers 

are undoubtedly larger, inasmuch as in some countries, such as Brazil, Australia, and Malaysia, only 

part of the beach placers has been evaluated. Furthermore, present-day beach placers are being 

formed continually, and in some areas new placers 

may form several years after the old one has been 

worked out. 

Carbonatites are also an important resource of 

thorium, containing more than ·one-sixth of. the 

evaluated thorium resources potentially recoverable 

as a byproduct (table 94). Thorium can:be recovered 

as a byproduct of copper and uranium mining at 

Palabora, South Africa, and of niobium and rare 

earths at Araxa, Brazil. About 40 percent of the 

known resources of thorium potentially recoverable 

primarily as a byproduct is in the uranium deposits 

in the Elliot Lake district in Canada. As these deposits are being actively mined for uranium, only a 

separate circuit need be added to the mill waste after 

the precipitation of the uranium in order to recover 

a thorium-rich concentrate. 

The largest known resources are in Greenland, 

where several square miles of lujavrite, a variety of 

nepheline syenite, contains 200 ppm to several tenths 

percent thorium and a half to a quarter as much 

uranium. The cost of recovery of either element, 

however, would be high. 

Although the identified resources of thorium are 

small compared to those of many other metals, they 

are large compared to the amounts of thorium used 

in the past. Known resources are about 10,000 times 

greater than the amount used in 1968. The general 

use of thorium in reactors would, however, greatly 

enlarge the demand for this element, hence the appraisal of potential resources becomes important. 

HYPOTHETICAL AND SPECULATIVE RESOURCES 

Beach placers have been and will continue to be 

major sources of thorium. Resources in some places 

will probably be increased as additional areas of 

known monazite-bearing sand are evaluated. Thus, a 

favorable area for finding new placers is below the 

water level, off present beaches, where seaward extensions of known placers could be mined under 

somewhat more difficult conditions. McKelvey ( 1968, 

p. 40) estimated the monazite content in undiscovered marginal offshore deposits on the U.S. continental shelf to be about 4 million tons. Even larger 

off-shore deposits probably occur in Australia, 

Brazil, and India. 
474 UNITED STATES MINERAL RESOURC'ES 

TABLE 94.-Identified thorium resources 

[Identified resources are specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may not be profitably recoverable with existing technology and economic conditions] 

Loeality1 

United States: 

Atlantic coast ----------------------- North and South Carolina -------------

Type of deposit 

Beach placer. 

Fluviatile placer. 

Idaho and Montana ------------------- ___ do 

Lemhi Pass district, Idaho and Montana_ Veins. 

Wet Mountains, Golo ----------------- ___ do ------------ Powderhorn district, Colo ------------- ___ do ------------

Thousands of short tons ThOs 

Recover- Recoverable priable marily for ThO:t of 

primarily grade88 byproduct or >O.l <O.l 

coproduct percent percent 

16 

Principal published reference 

McCauley (1960, p. 1). 

56 Overstreet, Theobald, and 

Whitlow (1959, p. 713-714). 

2 

100.0 

4.5 

1.5 

.5 

38 

U.S. Atomic Energy Comm. 

(1969, p. 127). 

Mountain Pass district, California ------ ___ do -----------·- ---do -------------------------------- Carbonatite. 28 

Palmer area, Michigan ---------------- Conglomerate. 

Bald Mountain, Wyo ----------------- ___ do ------------

46 Olson and Overstreet ( 1964, 

p. 37). 

2 Borrowman and Rosenbaum 

(1962, p. 2). 

Total, United States ---------------- 46 106.5 142 

Australia -------------------------------- Beach placers. Brazil: 

Atlantic coast ------------------------ ___ do ------------

50 

20 

Griffith (1964, p. 106). 

Stamper and Chin (1970, 

Morro de Ferro, Minas Gerais ---------

Araxa, Minas Gerais ------------------ Canada: Elliot Lake, Ontario -------------

Greenland: southwest part ----------------

India; various areas, including Kerala, Bihar, 

West Bengal ---------------------------

Kenya: Mrima Hill, Mombasa area --------

Korea -----------------------------------

Alkalic rock 

complex. 

Carbonatite. 

Conglomerate. 

Alkalic rock 

complex. 

Placers. 

Carbonatite. 

Fluviatile and 

130 

2 580 

450 

21 

6 

14.0 

750 

p. 685). 

Wedow (1967, p. 30) 

Guimaraes (1957). 

Griffith an.d Roscoe ( 1964, p. 

11). 

European Nuclear Energy 

Agency ( 1967, p. 13). 

Bhola and others ( 1965, p. 

93). 

Davidson (1956, p. 206). 

Olson and Overstreet ( 1964, 

Malagasy Republic .t: Fort Dauphin area __ _ beach placers. p. 32-33). 

Murdock (1963). 

Malaysia -------------------------------- Malawi ----------------------------------

Beach placers. 

Placers. 

Fluviatile and 

10 

20 

10 

Shortt (1970, p. 207). 

Bowie (1959). 

South Africa 1 : Palabora, Transvaal -------- Uganda: Sukulu, Eastern Province --------- United Arab Republic: Nile delta ----------

beach placers. Pike (1958, p. 94). 

Davidson (1956, p. 206). 

Higazy and N agui.b ( 1958). 

Carbonatite. 

___ do ------------

75 

2 

Fluviatile and 10 

W'eSt Africa: Nigeria, Sierra Leone -------- beach placer. 

Placers. 15 Bowie (1959). 

Total world identified resources ------ 1,435 120.5 902 

1 Not shown, because of inadequate data, are resources in Argentina, Ceylon, parts of Malag88y Republic, Norway, South Mrica (Steenkampskraal 

monazite veins), Uruguay, U.S.S.R., and several other countries. 2 Includes some hypothetical resources, which are undiscovered mineral deposits, whether of recoverable or subeconomic grade, that are geologically 

predictable 88 existing in known districts. 

Knowledge of certain factors in the formation and 

concentration of monazite can aid in the search for 

undiscovered placers. Monazite commonly forms by 

recrystallization during metamorphism, and the 

thorium content of the monazite increases with the 

grade of metamorphism (Overstreet, 1967). Monazite weathered from metamorphic rocks is concentrated in the near-shore sediments laid down in the 

ocean. If these sediments are raised above sea level 

and are in turn eroded, monazite may be reconcentrated. Beaches in which the monazite has gone 

through more than one cycle of erosion and deposition, in general, have greater concentrations of monazite than those that have gone through only one 

cycle. Furthermore, more monazite is freed from 

rocks where the enclosing minerals are thoroughly 

weathered-for example, in warm, humid climates. 

In arid climates the rocks do not weather as deeply, 

and in the far north the monazite in the sediments 

may be dispersed by glaciation. In the search for new 

monazite beaches, effort should be concentrated in 

areas in subtropical or tropical climates that have 
NUCLEAR FUELS 475 

high-grade metamorphic rocks inland and Tertiary 

or Cretaceous clastic rocks along the coastline. 

Additional resources of thorium will also be found 

in vein deposits in areas that have not been thoroughly prospected because of lack of demand for 

thori urn. Undiscovered resources exist both in known 

districts at untested depths (hypothetical resources), 

and in areas where no thorium deposits have yet 

been found (speculative resources). Districts containing vein deposits, such as Lemhi Pass, IdahoMontana, Hall Mountain, Idaho, and the Wet Mountains, Colo., have had little subsurface exploration 

and parts of the areas are covered by thin Quaternary deposits. Exploration in these areas will undoubtedly discover many new deposits, and additional exploration at depth may well increase resources 

several times over those now known in veins. The 

origin of many thorium vein deposits is related to the 

formation of alkalic stocks and their associated carbonatites. Hence, prospecting within a radius of 

about 20 miles from known alkalic stocks well may 

locate new thorium vein districts. 

PROSPECTING TECHNIQUES 

Methods of prospecting for thorium vary according to type of deposit and other factors. The most 

useful methods rely on the radioactivity of thorium. 

Geiger and scintillation counters have been widely 

used in detection and appraisal of thorium deposits. 

Abnormal radioactivity can also be detected with a 

gamma-ray spectrometer, and the content of thorium, potassium, and uranium daughter products can 

be measured in a few minutes with this instrument. 

Except for the radioactivity methods, thorium 

prospecting is carried out by traditional techniques 

of examination and sampling of favorable terrane. 

Panning for heavy minerals is particularly useful in 

areas where placer concentrations occur. Methods of 

exploration by panning and churn drilling of placer 

deposits in Idaho, North and South Carolina, and 

other States have been described by Kline (1952). 

Water sampling has not been used for thorium deposits because of the low solubility of thorium in 

ground water, lakes, and rivers. Sampling of stream 

sediments has been tested by Staatz, Bunker, and 

Bush (1971) in the Len1hi Pass district where its 

usefulness is quite limited. 

Because of the limited market for thorium, very 

few deposits have been explored at depth by drilling 

or underground excavations. Radioactivity methods 

penetrate only a very thin surface layer, hence in 

most areas the extent and grade of deposits at depth 

are conjectural. 

RESEARCH NEEDED ON DOMESTIC 

THORIUM RESOURCES 

The United States will probably continue to obtain 

the greater part of its thorium needs, at least for 

the next few years, from foreign sources. Embargoes by several principal producing countries tend 

to diminish this supply greatly. These embargoes, 

coupled with the very likely large growth in demand, 

would shift some of the interest from foreign to domestic sources. The most easily available resources 

of thorium in the United States are beach placers in 

Florida and Georgia mined for their titanium content, but the monazite recoverable is limited not only 

by the size and grade of the deposits but by the demand for titanium. 

A larger and still untapped U.S. resource is the 

thorium veins of the West. Complete reserve estimates are needed on the veins in each district 

(length, thickness, depth, and average grade) . Information is needed on the relation of these veins to 

regional faulting and to alkalic intrusives and on 

their ages, mineralogy, total rare earth content, and 

on the relative distribution of the various rare 

earths to one another in the veins. 

Small amounts of thorium also occur in carbonatites in the United States. Additional study of the 

mineralogy and chemistry of these deposits would 

help to determine the amount and recoverability of 

thorium, possibly as a byproduct of rare earths or 

niobium. 

Definition of thorium-rich metallogenic provinces, 

by the grouping of deposits or districts and the thorium content of various rocks, should aid in outlining 

target areas for future prospecting. 

REFERENCES CITED 

Adams, J. A. S., Kline, M .C., Richardson, K. A., and Rogers, 

J. J. W., 1962, The Conway Granite of New Hampshire 

as a major low-grade thorium resource: Natl. Acad. 

Sci. Proc., v. 48, p. 1898-1905. 

Bhola, K. L., Dar, K. K., Rama Rao, Y. N., Suri, S. C., and 

Mehta, N. R., 1965, A review of uranium and thorium 

deposits in India, in International Conference on Peaceful Uses of Atomic Energy, 3d, Geneva, 1964, Proc., v. 

12, Nuclear fuels-[Pt.] 3, Raw materials: New York, 

United Nations, p. 86-93. 

Borrowman, S. R., and Rosenbaum, J. B., 1962, Recovery 

of thorium from a Wyoming ore: U.S. Bur. Mines Rept. 

Inv. 5917, 8 p. 

Bowie, S. H. U., 1959, The uranium and thorium resources 

of the Commonwealth: Royal Soc. Arts Jour., v. 107, 

p. 704-715. 

Brown, K. P., Hurst, F. J., Grouse, D. J., and Arnold, W. D., 

1963, Review of thorium reserves in granitic rock and 

processing of thorium ores: U.S. Atomic Energy Comm., 

Oak Ridge Natl. Lab., ORNL-3495, OC-26, 25 p. 

Christman, R. A., Brock, M. R., Pearson, R. C., and Singe-
476 UNITED STATES MINERAL RESOURCES 

wald, Q. D., 1959, Geology and thorium deposits of the 

Wet Mountains, Colorado-a progress report: U.S. Geol. 

Survey Bull. 1072-H, p. 491-535. 

Davidson, C. F., 1956, The economic geology of thorium: 

Mining Mag. [London], v. 94, no. 4, p. 167-208. 

European Nuclear Energy Agency, 1967, Uranium resources, 

revised estimates: Paris, France, Organization for Econ. 

Coop. and Devel., 23 p. 

Evans, J. R., 1964, Xenotime mineralization in the southern 

Music Valley area, Riverside County, California: Calif. 

Div. Mines and Geology, Special Rept. 79, 24 p. 

Filippov, M. S., and Komlev, L. V., 1959, Uranium and 

thorium in granitoids of the Middle Dnepr region: 

Geochemistry, no. 5, p. 535-549. 

Griffith, J. W., 1964, Uranium: Canadian Mining Jour., v. 

85,no.2,p. 104-106. 

Griffith, J. W., and Roscoe, S. M., 1964, Canadian resources 

of uranium and thorium: Canada Dept. Mines and Tech. 

Surveys, Mineral Inf. Bull. MR 77, 12 p. 

Guimaraes, Djalma, 1957, Relatoria sobre a Jazida de 

Pirocloro de Barreiro, Araxa, Minas Gerais: Div. de 

Fomento da Produ~ao Mineral, Belo Horizonte, 1957, 

Bull. 103, 87 p. 

Higazy, R. A., and Naguib, A. G., 1958, Study of Egyptian 

monazite-bearing black sands, in International Conference Peaceful Uses of Atomic Energy, 2d, Geneva, 1958, 

Proc., v. 2, Survey of raw material resources: New 

York, United Nations, p. 658-662. 

Kelly, F. J., 1962, Technological and economic problems of 

rare-earth-metal and thorium resources in Colorado, 

New Mexico, and Wyoming: U.S. Bur. Mines Inf. Circ. 

8124, 38 p. 

Kline, M. H., 1952, Evaluation of monazite placer deposits: 

U.S. Atomic Energy Comm. Rept. RM0-908, 16 p. 

Mackin, J. H., and Schmidt, D. L., 1956, Uranium- and 

thorium-bearing minerals in placer deposits ~n Idaho, in 

Page, L. R., Stocking, H. E., and Smith, H. B., compilers, 

Contributions tO the geology of uranium and thorium by 

the United States Geological Survey and Atomic Energy 

Commission for the United Nations International Conference on Peaceful Uses of Atomic Energy, Geneva, 

Switzerland, 1955: U.S. Geol. Survey Prof. Paper 300, 

p. 375-380. 

McCauley, C. K., 1960, Exploration for heavy minerals on 

Hilton Head Island, South Carolina: South Carolina 

Devel. Board, Div. Geology Bull. 26, 13 p. 

McKelvey, V. E., 1968, Mineral potential of the submerged 

parts of the U.S.: Ocean Industry, v. 3, no. 9, p. 37-43. 

Murdock, T. G., 1963, Mineral resources of the Malagasy Republic: U.S. Bur. Mines Inf. Circ. 8196, 147 p. 

Olson, J. C., and Overstreet, W. C., 1964, Geologic distribution and resources of thorium: U.S. Geol. Survey Bull. 

1204,61 p. 

Overstreet, W. C., 1967, The geologic occurrence of monazite: 

U.S. Geol. Survey Prof. Paper 530, 327 p. 

Overstreet, W. C., Theobald, P. K., Jr., and Whitlow, J. W., 

1959, Thorium and uranium resources in monazite deposits of the western Piedmont, North and South Carolina: Mining Eng., v. 11, no. 7, p. 709-714. 

Parker, J. G., and Baroch, C. T., 1971, The rare-earth elements, yttrium, and thorium-a materials survey: U.S. 

Bur. Mines Inf. Circ. 8476, 92 p. 

Pike, D. R., 1958, T'horium and rare-earth bearing minerals 

in South Africa, in International Conference on Peaceful Uses of Atomic Energy, 2d, Geneva, 1958, Proc., 

v. 2, Survey of raw materials: New York, United Nations, p. 91-96. 

Roscoe, S. M., and Steacy, H. R., 1958, On the geology and 

radioactive deposits of Blind River Region, in Interna ... 

tional Conference on the Peaceful Uses of Atomic 

Energy, 2d, Geneva, 1958, Proc., v. 2, Survey of raw 

materials: New York, United Nations, p. 475-483. 

Shortt, C. E., 1970, Thorium, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 203-218. 

Staatz, M. H., 1972, Thorium-rich veins of Hall Mountain 

in northernmost Idaho: Econ. Geology, v. 67, no. 2, p. 

240-248. 

Staatz, M. H., Bunker, C. M., and Bush, C. A., 1971, Geochemical prospecting for thorium veins by streamsediment sampling, Lemhi Pass quadrangle, Idaho and 

Montana, in Geological Survey research 1971: U.S. Geol. 

Survey Prof. Paper 750-C, p. C136-C140. 

Stamper, J. W., and Chin, Edmond, 1970, Rare-earth elements, in Mineral facts and problems: U.S. Bur. Mines 

Bull. 650, p. 681-696. 

Stevens, R. F., Jr., 1969, Thorium, in U.S. Bureau of Mines, 

Minerals yearbook, 1968: Washington, U.S. Govt. Printing Office, v. 1-2, p. 1067-1072. 

U.S. Atomic Energy Commission, 1969, The use of thorium 

in nuclear power reactors: U.S. Atomic Energy Comm., 

WASH 1097, UC-80, 144 p. 

U.S. Bur. Mines, 1950-72, Minerals yearbook (annual 

volumes). 

Wedow, Helmuth, Jr., 1967, The Morro do Ferro thorium 

and rare-earth ore deposit, P~os de Caldas district, 

Brazil: U.S. Geol. Survey Bull. 1185-D, 34 p. 

Williams, R. M., 1969, Uranium and thorium, in Canadian 

Minerals Yearbook 1967: Canada Dept. Energy, Mines 

and Resources Mineral Resources Br. Mineral Rept. 17, 

p. 479-489. 

Young, E. J., and Sims, P. K., 1961, Petrography and origin 

of xenotime and monazite concentrations, Central City 

district, Colorado: U.S. Geol. Survey Bull. 1032-F, p. 

273-297. 
UNITED STATES MINERAL RESOURCES 

OIL AND GAS 

By T. H. McCuLLOH 

CONTENTS 

Abstract ---------------------------------------- Introduction ____________________________________ _ 

The problem --------------------------------

Geologic setting -----------------------------

Producible hydrocarbon assessment ----------------

Fluid hydrocarbons from sedimentary organic 

detritus --------------------------------------- Petroleum migration and entrapment --------------

Petroleum and natural gas resources --------------

Selected references ------------------------------

57. 

58. 

59. 

60. 

61. 

FIGURES 

Graph showing age-dependent variations in the 

averag~ content of organic carbon in sedimentary rocks from the Russian Platform and 

the United States -------------------------

Graph showing age-dependent variations in produced and proven reserves of oil and gas for 

the United States and the world ------------

Diagram showing selected diagnostic and critical 

steps in the genesis and migration of petroleum 

and natural gas from sedimentary organic 

matter ----------------------------------- Graph showing estimates of ultimate producible 

oil resources (and ultimate oil in place) of the 

United States, in relation to records of cumulative production plus proved reserves from 1900 

through 1972 ----------------------------- Graph showing United States and world crude 

oil production and proved reserves in relation 

to selected important developments in petroleum exploration technology ----------------

ABSTRACT 

Page 

477 

477 

477 

478 

480 

484 

485 

487 

493 

Page 

479 

482 

pressures great enough to actuate mechanisms of hydrocarbon expulsion and migration require basinal burial to 

depths of 1,500 feet or more. Wherever fluid hydrocarbons 

migrating toward the surface are interrupted and trapped, 

oil and gas reservoirs occur. 

Organic carbon, hydrocarbons, and producible hydrocarbon 

accumulations are distributed extremely unevenly in the 

United States and the world. They are practically restricted 

to sedimentary rocks and are much more abundant in geologically young strata than in old. Producible hydrocarbons occur with greatest frequency and in greatest volume at depths 

shallower than 10,000 feet, and a very small percentage of 

all known accumulations contains a very large percentage 

of all proved reserves. A few regions (notably the Middle 

East) contain a disproportionate share of the world reserves. 

All estimates of petroleum and natural gas resources depend upon prior exploration results and are unreliable. 

Changing economic incentives, technologic advances, enlarged prospecting areas, and creative thinking all increase 

exploration effectiveness. 

INTRODUCTION 

THE PROBLEM 

What are the ultimate potential United States and 

world resources of petroleum and natural gas, both 

those discovered and those waiting to be found? 

488 Where are they? What part of them can be found 

and exploited economically? What fraction of the 

total was originally within the territorial limits of 

the United States? How much of that fraction lies 

491 beneath the continental shelves-and where? To 

what extent will the United States be dependent in 

the future on imported petroleum, and how can we 

492 be assured of an economical supply? What should 

be the national goal and policy toward encouraging 

domestic exploration on land and beneath the 

continental shelves? What part of our national 

Thermal "cracking'' of part of the biogenic organic de- research and investment capability should be devoted 

tritus interred in fine-grained subaqueous sediment releases 

hydrocarbon compounds that form petroleum and natural gas. to programs ai:r:ned at utilizing coal resources or 

Rapid nearshore marine deposition favors accumulation and nuclear "fuels" more fully in the future in place of 

preservation of such sedimentary organic matter. Tempera- petroleum and natural gas? Should special incentures high enough for cracking to begin and compactional tives be provided to support conservative but ecoU.S. GEOL. SURVEY PROF. PAPER 820 

477 
478 UNITED STATES MINERAL RESOURCES 

nomically marginal operation of "stripper wells," of 

"tight gas reservoirs," of secondary recovery 

operations? 

The answers to these questions, and myriads like 

them, are of the utmost concern or importance today 

to business leaders, industrialists, economists, politicians, international strategists, and military planners. To an important extent, the answers stem 

from geological, geophysical, and geostatistical research and investigations. Whether such questions 

are answered correctly or incorrectly, the life of 

every citizen living in the United States in the 

year 2000 will be affected profoundly by the actions 

that are being taken now on the basis of the answers 

available. The very long lead times required to discover and develop wholly new petroleum and natural 

gas reserves requires that planning be done now to 

fill needs anticipated or projected for the last decade 

of the 20th century (Hartley, 1969; Harvey, 1970; 

Moody, 1970) . Even longer lead times are needed 

to plan, finance, and conduct research into new and 

improved methods of seeking the hard-to-find deposits of hydrocarbons that will be needed by future 

generations. 

GEOLOGIC SETTING 

Petroleum ("rock oil"). and natural gas ("earth 

gas") are mixtures or solutions of raw chemicals. 

They are natural fluids composed predominantly of 

compounds of hydrogen and carbon. The simplest 

of these compounds is methane, the principal constitutent of natural gases. More complex hydrocarbon compounds of higher molecular weights that 

have been identified as constituents of petroleum 

number in the many hundreds, but about half of the 

weight of average crude oil consists of light hydrocarbon compounds containing from three to 14 

carbon atoms per molecule. Many semi-independent 

lines of evidence indicate that these natural hydrocarbon chemicals are of ultimately biological origin .. 

The most compelling evidence is the overwhelmingly 

predominant tendency for both the fluid hydrocarbons and associated organic matter to occur in 

sedimentary rocks, especially in those of marine and 

lacustrine origin that were deposited rapidly in 

basins or depositional centers. Posthumous organic 

detritus interred in subaqueous sediment is the 

starting material from which these scarce and valuable fugitive raw chemicals were derived. 

Hydrocarbon compounds are virtually ubiquitous 

in differing amounts at and near the surface of the 

earth and in the rocks and pore fluids beneath the 

surface. Small quantities occur in living protoplasm 

(from a few parts per million on a dry weight basis 

in most higher organized living matter to a few 

thousand parts per million in some plankton and 

microorganisms), mostly of compounds having 15 

carbon atoms or more per molecule. Even in the 

atmosphere, trace amounts occur near biological 

sources, in coal mines, at oil and gas seepages, at 

some volcanogenic vents, and in association with 

dust particles. Small quantities make up part of the 

few milligrams of dissolved organic substances per 

liter of average sea water, and minute amounts 

occur in some meteorites and in a few places even 

within the crystals of coarse-grained igneous rocks. 

But by far the greatest proportion of the hydrocarbons in the earth occurs in sediments and sedimentary rocks. 

Organic carbon and hydrocarbons are distributed 

extremely unevenly in the earth's sedimentary 

mantle. In Holocene sediments, they are generally 

most abundant in marine silt and clay deposited 

rapidly in basins or depressions on or at the edg~ 

of continental shelves. They decline in abundance 

as grain size increases and are least abundant in 

coarse-grained sediments. They are present even in 

nonmarine deposits, but at generally much lower 

levels, and are abundantly present there only in 

lacustrine deposits, especially those that are 

hypersaline. 

The average content of organic carbon in Holocene marine clastic sediments of continental derivation was long ago recognized to be about 1.4 percent (Trask, 1937, p. 149; Trask, assisted by others, 

1932, p. 249). Subsequent investigations confirm 

this as a rough approximation but also suggest that 

the complicating effects of basin size, continental 

shelf width, basin morphology, and hydrodynamic 

and hydrobiological features render any "average" 

figure of little use (compare for example, Emery, 

1960, tables 12 and 27, and Bordovskiy, 1965, p. 

37-44). Hydrocarbons are associated with the organic matter of Holocene marine sediments in the 

lipid (or "bitumen") fraction. According to Trask, 

assisted by others (1932), the mean "bitumen" content of such sediments is 0.06 percent, and the data 

of many authors show that the ether-extractable 

content of individual samples, although quite variable, is directly proportional to total organic carbon, therefore being generally highest in quickly 

buried pelitic sediments. These early findings of 

Trask have also been supported by subsequent investigations (Smith, 1956; Bordovskiy, 1965, p. 57-

68) but with the addition of such important details 

as the facts that such "bitumens" consist of about 

65 percent asphaltenes and about 10 percent oils 

(0.005 to 0.015 percent of dry sediment) and that 
OIL AND GAS 479 

molecules having odd numbers of carbon atoms 

conspicuously predominate among the heavy normal 

paraffins (Bray and Evans, 1961). 

The great bulk of the organic carbon that occurs 

in sedimentary rocks, like the total organic matter 

and most of the hydrocarbons, is disseminated in 

low concentrations through large rock volumes. On 

the basis of many tens of thousands of rock samples 

(Trask, 1937, p. 149; Trask and Patnode, 1942; 

Ronov, 1958; Hunt, 1962; Gehmen, 1962), the organic carbon contents of unmetamorphosed sedimentary rocks are known to range between a high 

of 1.77 percent (average) for coastal-marine shales 

of petroliferous regions and a low of 0.15 percent 

(average) for nonmarine carbonate rocks of nonpetroliferous areas. The data of Trask and Patnode 

(1942) and especially of Ronov (Ronov and others, 

1965, p. 330; Ronov, 1968, fig. 7; 1958, figs. 1 and 2) 

show that the distribution of organic carbon in 

sedimentary rocks is not at all constant through 

geologic time. Instead, a long-term increase from 

very low concentrations in young Precambrian clay 

strata of the Russian Platform (0.08 percent organic 

carbon for 700-million-year-old Sinian strata) to 

high concentrations in Mesozoic and Cretaceous 

clays (0.41 percent organic carbon) is attributed 

by Ronov and his coworkers ". . . to the overall 

increase in the total mass of living substances in 

the biosphere." Major fluctuations in this long-term 

increase have been demonstrated (Ronov, 1958, 

table 2 and figs. 1 and 2) from data from the Russian 

Platform and the United States (Trask and Patnode, 1942). Figure 57 summarizes these data and 

emphasizes the remarkable parallelism between the 

Russian and the U.S. stratigraphic averages. Tappan and Loeblich (1970), calling attention to the 

worldwide contemporaneity of such geochemical 

fluctuations with important marine and terrestrial 

biologic events, suggested that changes in the quantitative distribution of marine phytoplankton are 

the fundamental causative link connecting such 

otherwise apparently unrelated correlations (see 

also House, 1963). 

Knowledge about the uneven distribution of total 

organic carbon in sediments of different grain sizes 

and depositional environments and in sedimentary 

rocks of different regions and ages is both sketchy 

and problematic ; but it is vastly more complete and 

satisfactory than knowledge about the hydrocarbon 

compound whose carbon forms but a minute part 

of the organic carbon. The relatively small quantities of hydrocarbon compounds, their mobility and 

physicochemical lability, and the relative newness 

of many of the analytical procedures and equipment 

1- 1.6 

z 

w 

(J 

a: 

w 

A. 

1-

J: 

CJ 1.0 iii 

~ 

~ 

z· 

0 

CD 

a: 

<( 0.6 (J 

(J 

z 

<( 

CJ 

a: 

0 

01 

0 

en 

Ill 

c: 0 c: 0 i c:oc: .. IIIC: uou ... <11 :ii ... (') ·! (;;·~ :I Nta ~; ~-~ 5 ... ~ ~ • ·u 

·:; E N'~ :I 0 ,f I E E 0 Jl a; Gl ~ ..:: ~ ~ 'C 'i: A. 0 0 .8 Gl (J ct ~ 

AGE: GEOLOGIC AND RADIOMETRIC 

(NUMBERS ARE MILLIONS OF YEARS BEFORE PRESENT) 

u 0 '2 

0 

c: 

Gl 

(J 

F'IGURE 57.-Age-dependent variations in the average content of organic carbon in sedimentary rocks from the Russian Platform and the United States. Adapted from Ronov 

( 1958, figs. 1 and 2.). 

needed for quick reliable quantitative determinations 

of most of them, combine with the enormous scope 

of the undertaking to be more conducive to ignorance than to knowledge. 

Hydrocarbon compounds have been identified from 

some of the oldest Precambrian strata (3-billionyear-old Fig Tree shale of the Swaziland System, 

South Africa) and, among others, from unmeta .. 

morphosed carbonaceous middle Precambrian undoubted microfossiliferous chert (1.9-billion-yearold Gunflint Iron Formation, Ontario, Canada). 

However, critical investigations of the origins of 

these compounds (aromatic hydrocarbons in the 

older shale and normal alkanes and saturated and 

unsaturated fatty acids in the younger chert) indicate that the hydrocarbons are present because of 

contamination that possibly is quite recent. They 

are neither indigeneous nor syngenetic with the 

mainly indigenous carbonaceous materials (Hoering, 1967, p. 99-100; Abelson and Hare, 1968; Smith 

and others, 1970; Nagy, 1970). As Hoering (1967, 

p. 105) so clearly stated in his remarkably farsighted treatment of such problems of hydrocarbon 

contamination, "Vast quantities of geologically 

younger petroleums are a part of our present environment and can appear in unsuspected places." 

However, the detection of chemically stable metalloporphyrins in an extract of 1.1-billion-year-old 

Nonesuch shale from northern Michigan (Barghoorn and others, 1965) points clearly to a biogenic 

origin for the organic matter from which this relic 
480 UNITED STATES MINERAL RESOURCES 

of photosynthetic organisms was derived (Treibs, 

1936; Orr and others, 1958; Dunning, 1963). Furthermore, the evolution of an impressive series of 

alkanes (methane through pentane) by low temperature pyrolysis from ether-insoluble organic matter (kerogen) extracted from this same stratum 

(Hoering, 1967, p. 97 and table 4) indicates that the 

seepage petroleum (first reported by White and 

Wright, 1954) from the White Pine Copper mine is 

almost certainly younger Precambrian in age, and 

the Nonesuch shale is its ancient source rock. Carbon isotope ratios from the soluble and the insoluble 

fractions of the Nonesuch organic matter are almost 

identical and diagnostically biosynthetic (Hoering, 

1967, table 8) and further strengthen this conclusion. Negative results were reported by Hoering 

from his attempts to detect optical activity (ro~ 

tion in the Nonesuch petroleum by " ... a factor of 

50 less than has been reported from Paleozoic 

petroleums.") The likelihood that polycyclic, saturated hydrocarbons are responsible for some of the 

optical rotation so characteristic of younger petroleums (Oakwood and others, 1952 ; Hills and others, 

1970) and that sterols are precursors of such com~ 

pounds takes on special interest in view of the fact 

that anaerobic organisms do not produce highly 

unsaturated fatty acids or sterols (Bloch, 1965). 

Many other occurrences have been reported (Vassoyevich and others, 1971; Murray, 1965) of possible, probable, and undoubted Precambrian hydrocarbons from many .localities in the world, but none 

is as thoroughly documented by pertinent observational and analytical detail as the occurrence in the 

Nonesuch shale. Of these other occurrences, the 

oldest that appears to be fairly certainly indigenous 

is 1.2 b.y. (saturated paraffinic compounds extracted 

from "Muhos shale" of the Jotnian series, FinlandHoering, 1967, p. 98-100), and most are from 

youngest Precambrian rocks. Of further interest is 

the fact that only one undoubtedly Precambrian 

occurrence has resulted in commercial hydrocarbon 

production ; that of gas, condensate, and oil from 

the late Proterozoic multizone Markovo field in the 

Irkutsk part of the western Siberian AngaraTunguska basin (Vassoyevich and others, 1971, p. 

412-413). Commercial petroleum and natural gas 

are almost exclusively products of sedimentary rocks 

deposited during only the last one-eighth to onefourth of the earth's history, that part during which 

an atmosphere rich in oxygen prevailed and during 

which complex multicellular organisms developed. 

Carbon is the stuff of life ! 

The evidence has been summarized which indicates that hydrocarbon compounds are quite scarce 

in rocks of Precambrian age, even those relatively 

rich in organic carbon and kerogen, and that fluid 

hydrocarbons (commercially producible or. not) are 

extremely rare in such strata and are restricted thus 

far to rocks of late Proterozoic age. It is self evident, then, that most of the earth's hydrocarbons 

must occur in rocks of Phanerozoic age and in Holocene sediment (plus the biosphere and hydrosphere). 

Qualitatively at least, the long-term increase in 

organic carbon concentrations of clays of the Russian Platform appears to be paralleled by a worldwide increase in hydrocarbon concentrations from 

late Precambrian to Mesozoic and Tertiary rocks. 

Whether these relationships result primarily from 

temporal variations in the primary productivity of 

the ancient biosphere, or whether other timedependent factors intervene and override, such as 

diagenetic (metamorphic) modifications of the hydrocarbon precursors in sedimentary organic matter or erosional, structural, or thermal events that 

reduce sedimentary rock volume, rock porosity, or 

the effectiveness of hydrocarbon traps, remains to 

be examined quantitatively Quantitative: data are 

needed regarding variations in the hydrocarbon concentrations of Phanerozoic rocks as a function of 

geologic age and depth of burial (thermal history). 

Unfortunately, only a start has been made toward 

that goal, and that only coincidentally as a result of 

commercial prospecting for petroleum and natural 

gas. 

PRODUCffiLE HYDROCARBON ASSESSMENT 

Compared with the tremendous efforts that have 

been expended in the industrial search for commercially producible fluid hydrocarbons (especially in 

the United States and elsewhere in North America), 

the previously mentioned efforts to assess the organic carbon contents of sedimentary rocks, impressive and valuable as they are, are completely 

overshadowed. In the United States alone, more than 

2,222,300 wells, totalling 7 billion feet of hole in 

all (R. F. Meyer, oral commun., Jan. 25, 1973), 

have been drilled in the search for petroleum and 

natural gas. Most of those holes were located after 

much deliberation, on the basis of substantial scientific and technical data expertly evaluated. They 

were drilled either to exploit hydrocarbon reservoirs 

ah~eady known to exist from prior exploratory drilling, or as "wildcats" with the specific objective of 

evaluating scientific hypotheses advanced by technical advisors who suggested the possibility of finding abnormally rich concentrations of hydrocarbons; 

concentrations large enough and sufficiently energized that part of the crude chemicals could be pro-
OIL AND GAS 481 

duced profitably to the surface. The results of such 

endeavors can be regarded in a sense as a rockhydrocarbon assessment of sorts ; not of the total 

hydrocarbon content of sedimentary rocks of all 

types, but a sampling of that fraction of the total 

organic matter which was mobilized sufficiently at 

one time or another to have been expelled from its 

source stratum and enabled to migrate through permeable pathways toward regions of lowered pressure (ultimately the atmosphere), and to be trapped 

along the way to accumulate more-or-less temporarily in a producible and findable reservoir. 

The industrial search for commercial hydrocarbons has not been a random search, except locally 

to a minor degree. Therefore, the results of the 

search cannot be treated in all regards as data 

gathered randomly or according to some consciously 

designed sampling scheme. For example, rocks at 

great depth have been prospected much less thoroughly than rocks at shallower depths because of 

economic considerations. (Shallow reservoirs have 

been easier to find and cheaper to exploit, and shallow discoveries provided sufficient production to 

serve the needs of the United States until recently.) 

Similarly, reservoirs associated with structural 

traps, especially anticlinal traps, have been subject 

to a more diligent search than a variety of other 

more subtly-trapped accumulations because exploration techniques thus far available are best suited to 

structural mapping. In attempting to use the statistical data resulting from the search for petroleum 

and natural gas, limitations (or sampling bias) such 

as these should be kept in mind. 

Limitations of another sort should be explicitly 

recognized. To a very large extent, the most reliably 

useful data available from drilling for hydrocarbons 

are the records of the amounts and kinds of fluids 

produced. These have been measured. Less reliable 

and much more difficult to interpret are estimates 

of the producible "proved ·reserves," or of the 

amounts of crude oil or natural gas "initially in 

place" in a reservoir or field. Such estimates depend 

not only upon interpretations of a variety of difficult geologic and engineering measurements, but 

also in part upon assessments of variable economic 

factors. "Cumulative production" plus "proved reserves" constitute that fraction that is known or 

judged to be economically and physically extractable of the hydrocarbons "initially in place" in a 

reservoir. Statistical data from the United States 

indicate that currently an average of 30 percent of 

the "oil in place" and 80 percent of the "gas in 

place" are economically extractable (Moore, 1970a, 

p. 133; Elkins, 1971). Keeping these limitations in 

mind, let us examine the data available from drilling and production. 

Cumulative production of crude oil through 1971 

was 264 billion barrels for the world and 97 billion 

barrels from the United States. Proved reserves for 

the world and the United States are 632 and 38 1 

billion barrels, respectively (see fig. 61). World and 

U.S. cumulative production for natural gas are 620 

and 415 trillion cubic feet, respectively, and proved 

reserves are 1, 725 and 279 trillion cubic feet, respectively. When dissected and examined in detail, 

these figures reveal that the known commercially 

producible hydrocarbons in the world and the United 

States are distributed extremely unevenly, but according to the following general and important 

regularities. 

Of overriding importance is the fact that a very 

large percentage of the total oil (and gas) occurs 

in a very small percentage of all known accumulations. More than 85 percent of the world's hydrocarbon production plus reserves occur in less than 

5 percent (238 fields) of all producing accumulations. Even more remarkable, 65 percent of the 

hydrocarbons (petroleum and gas) occursin slightly 

over 1 percent of all fields-the 55 "supergiants" 

(a billion barrels or a trillion cubic feet or more; 

Halbouty and others, 1970; Klemme, 1971), and an 

astounding 15 percent occurs in only two immense 

accumulations in the Middle East region ( Ghawar 

field in Saudi Arabia and Burgan field in Kuwait). 

In smaller areas similar conclusions hold. For example, Halbouty ( 1968) showed that of the 22,898 

oil and gas fields in the United States as of January 

1, 1968, only 308 (1.33 percent) will yield about 60 

percent of the presently estimated ultimately producible hydrocarbons. The importance of this tendency was first clearly stated by Heald ( 1950, p. 

15). "If we are concerned with our future, we will 

study the record of major discoveries, the distribution of major fields, the geological conditions under 

which they exist, and will strive to recognize the 

areas wherein major discoveries are now unlikely 

or impossible as well as those in which major fields 

may be." 

Almost equal in importance to the tendency for 

a few accumulations to contain most of the producible hydrocarbons is the tendency for those hydrocarbons to occur with greatest frequency and 

abundance in geologically young rocks. Halbouty 

and others (1970) provide the most recent data that 

show how the world's known oil and gas are dist Estimate by American Petroleum Institute. S. P. Sehweinfurth, U.S. 

Geological Survey, estimates U.S. proved reserves at 45 billion barrels 

(oral eommun., Feb. 9, 1973). 
482 UNITED STATES MINERAL RESOURCES 

tributed according to the age of the reservoir rocks. 

Their data (fig. 58) show 29 percent to be Cenozoic 

(0-74 m.y.b.p. (million years before present)), 57 

percent to be Mesozoic ( 7 4-200 m.y. b. p.) , 8 percent 

to be Permian (200-225 m.y.b.p.), and less than 6 

percent to be pre-Permian in age. For comparison, 

Radchenko ( 1968, table 50) gives, on the basis of 

"data up to 1960," 49.4, 21.5, 4.7, and 24.4, respectively, as the percentages of total world cumulative 

production for the same four stratigraphic intervals. 

Current estimates for the United States yield percentages that are significantly different from either 

set of world percentages (fig. 58). The percentages 

of known producible hydrocarbons from U.S. reser60 

50 

ui 

~~ a:,... 

wen 

(I)-

wz 

a: C) 40 

o=> 

wo 

>a: O:I: a:t-

~z 

00 

:>- ...JI-

~u 

z=> 30 00 _o 

t-a: 

u~ 

:>...J 

Oc( Ota:o 

~~-

Zu.. 

oo 

ID 20 a: I- c(Z 

uw 

ou 

a: a: ow 

>~ :I: 

10 

0 74 

u ·a 

N 

0 

; 

~ 

200 

Total world 

"' 5:u 

'""C 

~0 c 

O"C 

.cc ._IV 

l3 

510 

voir rocks of both Cenozoic and Paleozoic ages are 

much higher than the world percentages, and that 

for Mesozoic reservoirs are much lower. These differences reflect the strong influence of the vast 

reserves in the Middle East (more than 62 percent 

of the world reserves), a large part of which are in 

reservoirs of Mesozoic age. Considering only production and reserves from "giant" fields outside the 

Persian Gulf region, Tertiary, Mesozoic, and Paleozoic rocks contain 40, 39, and 21 percent, respectively, of the total producible reserves. As offshore 

exploration and development in the United States 

continue, the U.S. percentages for Cenozoic and 

Mesozoic hydrocarbons will doubtless increase at 

0 

United States :0 

( 15 percent of world total) ·o; ~ 

c 

~ 

= 'ii 

c 

2 

74 200 510 

RADIOMETRIC AGE 

(MILLIONS OF YEARS BEFORE PRESENT) 

FIGURE 58.-Age-dependent variations in produced and proven reserves of oil and gas for the United States and the world. 
OIL AND GAS 483 

the expense of the percentage of Paleozoic oil and 

gas because of the volumetric predominance of 

Cenozoic and Mesozoic marine strata beneath all 

U.S. continental shelves (Weeks, 1971, p. 99; Gilluly 

and others, 1970, especially p. 368). The fivefold 

larger average volume of geologically very young 

pools than pools in most Mesozoic and Paleozoic 

rocks (Hopkins, 1950, fig. 4) is of importance in 

relation to this fact. 

Not only the relative amounts, but also to some 

degree the chemical and physical characteristics of 

crude oils depend systematically upon the geologic 

age of the rocks in which they occur. Statistical 

comparisons of crude oil properties from U.S. fields 

(and a few Venezuelan and Canadian fields) over 

a wide range of geologic ages and depths (Hopkins, 

1950, fig. 1; McNab and others, 1952; Biederman, 

1965) show beyond doubt that petroleums of low 

density occur with greater frequency in Paleozoic 

rocks and that those of high density make up the 

greatest proportion of crudes in Tertiary rocks. 

Furthermore, the older crude oils show a clear tendency toward a higher percentage content of low 

molecular weight fractions and a low content of 

oxygen- and nitrogen-containing materials. The 

young crude oils contain appreciable amounts of 

oxygen- and nitrogen-containing compounds, more 

like the organic precursors from which they evolved. 

Evidently, a progressive time-dependent evolution 

or maturation occurs from dense crude oils rich in 

large cyclic compounds, forming early and tending 

to occur in young sedimentary rocks, to less dense 

crude oils composed of more paraffinic compounds 

of lower molecular weights and more characteristic 

of older rocks. Perhaps this is why 50 percent of 

the hydrocarbons reservoired in U.S. "giant" fields 

of Paleozoic age are gas (Halbouty and others, 

1970, p. 532). However, hydrocarbon composition 

is influenced strongly not only by the length of time 

it has had to mature, but also by the depth ( temperature) to which it has been subjected, and to 

some extent by compositional characteristics of the 

source materials (Martin and others, 1963; Dean 

and Whitehead, 1964; Hedberg, 1968) ; thus, simplified interpretations of compositional data are generally risky and equivocal. 

The influence of depth of occurrence on hydrocarbon composition has long been recognized 

(White, 1915; Barton, 1934; Hopkins, 1950; MeN ab 

and others, 1952; Biederman, 1965; Landes, 1967). 

Hudson ( 1963, p. 133) emphatically underscored the 

empirical fact that commercial quantities of crude 

oil do not occur in the United States at depths 

greater than about 20,000 feet and are unlikely to 

occur deeper than about 16,000 feet. Phase relations among the compounds of petroleum and natural gas indicate that only the simple hydrocarbon 

compounds in a gaseous phase can exist at temperatures and pressures prevalent at depths of about 

20,000 feet or more (Halbouty and others, 1970, p. 

533). At shallower depths (and lower temperatures) 

than those beyond which hydrocarbons do not persist as liquid petroleums, other depth-dependent 

variations .in petroleum composition occur. Specific 

gravity of deep crude oil is statistically lower than 

that of shallow oil of the same age, and the deeper 

crude oil contains higher proportions of lower 

molecular weight compounds (McNab and others, 

1952, p. 2558-2560). Thus, it appears clear that the 

higher temperatures imposed by great depth of 

burial affect petroleum maturation and hydrocarbon 

alteration in much the same way as do extended 

periods of time. This in turn poses several questions 

of fundamental and practical importance, such as : 

Through what depth range are earth temperatures 

appropriate to cause thermal disintegration of the 

disseminated organic matter in sedimentary rocks 

to form liquid and gaseous hydrocarbon compounds? 

How do such thermal disintegration processes affect 

the residual organic matter (both the kerogen and 

the solvent-soluble fraction) left behind dispersed 

through the rock? By what mechanisms do newlyformed fluid hydrocarbons migrate from minute 

interstitial capillary openings in fine-grained rocks 

into units permeable enough to serve as reservoir 

rocks? What is the fate of relatively immature dense 

petroleum, containing minor proportions of low 

molecular weight compounds, if subjected to elevated temperatures attendant upon subsidence and 

deep burial of an initially shallow accumulation? 

A very large amount of work has been done in the 

search for answers to these questions and still only 

partial answers exist. Let us defer further consideration of the questions until more of the pertinent 

facts have been summarized. 

Just as petroleum quality (composition) is distinctively dependent upon reservoir depth so, for 

discovered hydrocarbons, is petroleum quantity. In 

his pioneer treatment of the exceptional importance 

of exceptionally large hydrocarbon accumulations, 

Heald ( 1950, p. 19-20) explicitly recognized that 

most petroleum and gas occurs in reservoirs at 

depths shallower than 10,000 feet. He stated, "If 

history is a dependable guide, the existence of producible oil or gas at a depth of not more than 6,500 

feet, is almost a prerequisite if a major field is to 

be opened." On the basis of worldwide production 

statistics available through 1960, Radchenko (1965, 
484 UNITED STATES MINERAL RESOURCES 

p. 213 of 1968 translation) calculated the following 

percentages of petroleum production volume according to depth ranges for all fields. 

Depth 

(meters) 

<500 

500-1,000 

1,000-1,500 

>1,500 

(feet) 

<1,640 -------------- 1,640-3,280 ---------- 3,280-4,920 ----------

>4,920 --------------

Production 

(percent of 

total volume) 

6.9 

32.3 

26.1 

34.7 

Virtually two-thirds of all oil produced up to 1960 

came from reservoirs shallower than 1,500 meters. 

For the 45 North American oil fields recognized as 

containing ultimate recoverable reserves of 500 

million barrels or more (Moody and others, 1970, p. 

11 and fig. 11) and comprising "35 percent of the 

continent's total ultimate recovery," the average 

reservoir depth peaks sharply at about 4,000 feet 

(averaged on the basis of volume of ultimately 

recoverable reserves), and almost no reservoirs lie 

below 14,000 feet. These and like statistics, based 

on a great deal of exploratory drilling and production, lead one to conclude that most, if not all, commercially producible crude oil reservoirs occur at 

depths shallower than 20,000 feet and that more 

than one-half of the ultimate petroleum production 

of the world will come from depths shallower than 

10,000 feet (and possibly from depths shallower 

than 5,000 feet). 

The reasons for such findings obviously are of 

the greatest possible practical importance, and they 

are to be found above all in the fact that total 

porosities of clastic sedimentary rocks, including 

reservoir sandstones, diminish regularly with increasing depth because of gravitational consolidation following burial (Athy, 1930; Hedberg, 1936; 

Dallmus, 1958; Maxwell, 1964; Atwater and Miller, 

1965; McCulloh, 1967). "This decrease in porosity 

. . . is the most important single factor controlling 

the amount of oil or gas in place per unit volume of 

sandstone reservoir rock" in the Tertiary strata of 

the United States Gulf Coast region (Atwater and 

Miller, 1965). Lithology, geologic age, and variations in geothermal regime are some of the complicating factors, but notwithstanding these, porosities of most clastic rocks approach limiting values 

close to 5 percent at depths of 10,000 to 20,000 

feet, whereas average resorvoir porosities in excess 

of 30 percent are possible (and commonplace in 

young sedimentary rocks) at depths shallower than 

4,000 feet (McCulloh, 1967, fig. 4). Shallow depths, 

high sandstone porosities, large reservoir volumes, 

and large hydrocarbon reserves (and production) all 

go together. Porosities of reservoir rocks of other 

lithologies follow more complicated rules, and it 

would be of considerable interest to determine 

whether or not petroleum from other than sandstone 

reservoir rocks predominates in the fraction produced from depths greater than 10,000 feet. 

The data have been reviewed which show that 

petroleum and natural gas are distributed extremely 

unevenly through the earth's sedimentary mantle. 

Most of the commercially producible volumes of 

hydrocarbons that have been discovered to date 

occur in Tertiary and Mesozoic marine strata; more 

than half occurs in Mesozoic and Tertiary reservoirs of the Persian Gulf region. Between one-half 

and two-thirds of the petroleum occurs in reservoirs 

less than 10,000 feet deep, and essentially all commercial oil production is from depths shallower than 

20,000 feet. Crude petroleum composition depends 

statistically upon depth and geologic age and only 

to a minor extent on original depositional environment. Shallow or young oil tends to be dense and 

chemically complex and exhibits strong similarities 

to altered biogenic precursors found in young nonlithified sediments. Deep or old oil tends to be light, 

chemically simple, and has a high content of low 

molecular weight paraffinic compounds. Reservoirs 

at depths of 20,000 feet and more contain gas only, 

although there is a gradual downward transition 

from deep accumulations of crude oil rich in dissolved "gas" and gasoline fractions, through reservoirs containing natural gas liquids (NGL), to 

natural gas reservoirs in which only minor quantities of higher molecular weight compounds occur. 

If meaningful prognostic predictions are to be made 

of where and in what amounts producible accumulations of petroleum and natural gas may occur, one 

must recognize not only that the distribution of 

fluid hydrocarbons in sedimentary rocks and basins 

is extremely uneven (although subject to certain 

broad general patterns) , but a substantial understanding of the underlying physical and chemical 

reasons for their uneven distribution is needed. We 

must have an understanding of the nature of the 

processes by which organic detritus interred in 

sediment is transformed to protopetroleum and 

thence to fluid hydrocarbons capable of migration, 

and of the chemical and physical processes by which 

such mobilized hydrocarbons are expelled from 

source rocks and trapped during their migrations 

to form commercial accumulations. 

FLUID HYDROCARBONS FROM 

SEDIMENTARY ORGANIC DETRITUS 

Laboratory pyrolysis experiments (Hunt, 1962; 

Abelson, 1964) and extraction experiments (Welte, 

1966) performed on kerogen-bearing rock indicate 
OIL AND GAS 485 

that saturated paraffins and aromatic hydrocarbons 

are released from kerogen when heated and are 

removable in solution in hot oil-field brine. Field 

observations of the stages in the progressive diagenesis and metamorphism of coals and particulate 

coaly matter contained in sediments buried to different depths, and from which hydrocarbons have 

been expelled, provide one means for gauging that 

potentially fluid hydrocarbons are released during 

natural thermal diagenetic transformations of organic matter (White, 1915; Teichmiiller, 1958; 

Brooks, 1970) through a wide range of depths, from 

probably less than 5,000 feet to almost certainly 

more than 15,000 feet, depending upon local geothermal gradients and duration of maturation conditions. Such conclusions have been reached independently by comparing presumably related reservoir and source rock hydrocarbon compositions 

(Baker, E. G., 1962) coupled with observations of 

depth-dependent variations in ratios of hydrocarbon 

carbon to total noncarbonate organic carbon (Philippi, 1957 and 1965). They are in excellent quantitative agreement also with some results of studies 

of depth-dependent variations in gross composition 

of dispersed organic and bituminous matter in nonreservoir strata (Larskaya and Zhabrev, 1964; 

Neruchev, 1964). Together with interpretations of 

systematic relations observed among the distinctive 

carbon isotopic compositions of natural organic substances (including natural gases, petroleum gases, 

specific petroleum fractions, whole petroleums, solid 

hydrocarbons, asphaltenes and tars, kerogen, coals, 

and unaltered biogenic materials), these results suggest that progressive low-temperature decomposition or thermal cracking of protopetroleum, composed importantly of high molecular weight compounds derived in substantial part from. plant lipids, 

accounts for all the chemical relationships thus far 

observed (Silverman and Epstein, 1958; Silverman, 

1964; Frank and Sackett, 1968; Vinogradov and 

Galimov, 1970; among others). Further research 

on the kerogen fraction of fine-grained interstitial 

organic matter of sedimentary rocks is badly needed 

to help clarify in very young and very old sedimentary rocks both the shallow and deep limits of 

depth (temperature) at which diagenesis makes 

parents of organic precursors of fluid hydrocarbons. 

Such research would probably be facilitated by applying electron spin resonance and infrared spectroscopic techniques in the search for additional 

reliable compositional data, especially C/H ratios 

(Marchand and others, 1969), that the coal studies 1 

have suggested may be important temperature in-~ 

dices. More research is also needed on the observable effects of later thermal alteration or destruction 

of petroleum which accumulated during an earlier 

episode of hydrocarbon release and migration in a 

reservoir at shallow or moderate depth. Sufficient 

evidence is available now to say that even mature 

petroleum rich in paraffinic compounds of relatively 

low molecular weight undergoes further thermal 

cracking if subjected to sufficiently high temperatures (Evans and others, 1971, p. 151-153) and 

would break down ultimately to highly fugacious 

methane on the one hand and solid graphitic carbon 

on the other. These are also the ultimate products 

of thermal degradation of the insoluble organic residues that remain in nonreservoir strata, or for that 

matter of coal. 

The metalloporphyrins of many crude oils are not 

only evidence of a biological origin for the petroleums, but they also set a limit on the temperature 

at which the transformation from sedimentary organic detritus to petroleum constituents occurs. 

Green porphyrin pigments, decay derivatives of 

chlorophyll, are commonly present in fine-grained 

marine and lake sediments. Through a series of 

hydrogenation and decarboxylation steps, sediment 

porphyrins may be diagenetically altered to metalloporphyrins containing vanadium or nickel such 

as occur in petroleum. The thermal stability of such 

compounds is such that they do not survive at temperatures above 200°C (Welte, 1965, p. 2257), and 

they thus set an upper limit on the temperature of 

the transformation process responsible for their 

presence in a petroleum. Unfortunately, there is no 

certainty that all constituents of a crude oil originated at the same time or place or at the same 

temperature. It would be a matter of some interest, however, to attempt to determine the depth of 

disappearance of metalloporphyrins from crude oils 

of widely differing depths (but confined to particular stratigraphic horizons) , as a means of determining whether or not the various crude oils represent fractions of one or more phases of petroleum 

genesis. 

PETROLEUM MIGRATION AND ENTRAPMENT 

Once formed, fluid hydrocarbons must be expelled 

from the capillary pores of the fine-grained organicrich source rocks before migration, entrapment, and 

accumulation can occur in shallower permeable reservoir rocks. The expulsion mechanism is not well 

understood, although it probably is complex. Expulsion may occur simply because of differential 

capillary pressure exerted because of two-phase 

fluid saturation of adjacent rocks of differing capillary sizes (Washburne, 1915, especially p. 832-834; 
486 UNITED STATES MINERAL RESOURCES 

Hubbert, 1953, p. 1979; Gussow, 1954, p. 821). 

Alternatively, hydrocarbons may dissolve in hot 

aqueous pore waters under pressure, either directly 

(Uspenskii, 1962, p. 1161; McAuliffe, 1966; Meinchein, 1959) or with the solubilizing assistance of 

organic "soaps" (Baker, D. R., 1962). In either case, 

porosity reduction because of gravitational compaction through continuing subsidence and loading 

(sedimentation) tends to express the pore waters 

and their dissolved or emulsified hydrocarbons from 

the finer grained and less permeable source rocks 

into coarser grained and more permeable (and porous) carrier and reservoir beds (Athy, 1930; Hedberg, 1936; Uspenskii, 1962, p. 1163; Philipp and 

others, 1963; Magara, 1969). Thermal recrystallization and dehydration (diagenesis or eometamorphism of clays or other hydrous mineral phases) 

in source rocks depressed to depths of thousands of 

meters provide further opportunities for flushing of 

dissolved or suspended hydrocarbons (Burst, 1969; 

Magara, 1969) into reservoir rocks or carrier beds. 

The underground temperature gradient in sediments 

and sedimentary rocks favors the "primary migration" of oil from source beds by stimulating dehydration reactions in the clay minerals which tend 

to decrease mineral adsorption capabilities in deeper 

levels (Snarskiy, 1962), by providing a temperaturedependent adsorption gradient favoring movement 

of hydrocarbons from regions of higher to regions 

of lower temperature (Watts, 1963), by stimulating 

upward diffusion along the temperature gradient 

(Watts, 1963; Witherspoon and Saraf, 1964), and 

by establishing local inter-pore or inter-bed pressure 

gradients because of the large volumetric expansion 

of hydrocarbons, as compared to water or brine, 

subjected to a temperature increase (McCulloh, 

1967). 

In a subsiding depositional basin, a number of 

processes all work hand in hand. These include 

physical depression of petroleum source rocks, augmentation of rock temperature, chemical transformation of organic precursors to hydrocarbon constituents of petroleum and natural gas, loading and 

gravitational rock compaction with attendant reduction of pore space, and the establishment of temperature and pressure gradients along which expressed pore water and entrained or diffused 

mobile hydrocarbons tend to migrate toward the 

surface. The greater the depth, the higher the temperature and the simpler (molecularly) the mobile 

(liquid or gaseous) hydrocarbon phases that are in 

thermal equilibrium with the environment. The 

greater the depth, the higher also the confining 

pressure, and the greater the tendency of thermally 

energized (and potentially greatly expandable) mobile hydrocarbon phases to escape to lower pressure 

regions. No wonder that for many years courts of 

law in the United States classed oil and gas as 

"fugacious minerals" or "minerals ferae naturae"-

wild beast minerals (Hedberg, 1971, p. 15). 

"Primary migration" apparently can begin when 

suitable source rocks have been depressed to a depth 

of 500-600 meters or more (Philipp and others, 

1963; Welte, 1965, p. 2263), although considerable 

evidence suggests that about 1 kilometer may be a 

more general upper limit (Welte, 1972, p. 122). 

During basin subsidence, an oil source rock can 

undergo progressive geochemical development during which an evolutionary series of hydrocarbons 

are generated under gradually higher temperature 

conditions. "Primary migration" of these hydrocarbons proceeds at least as long as gravitational compaction continues to reduce source rock porosity and 

diagenetic alteration of clays continues to release 

unbound water for expulsion. "Primary migration" 

merges into "secondary migration," in which hydrocarbons expelled from fine-grained source rocks 

begin to move more freely through coarser-grained 

carrier beds (or fractures) having physical characteristics of reservoir rocks. If permeable avenues 

exist to permit the expressed fluids egress directly to 

the surface, the hydrocarbons escape more-or-less directly. If, on the other hand, the carrier beds provide no direct or unimpeded avenue of escape to 

the atmosphere, the ultimate dumping ground for 

all mobilized hydrocarbons, trapping occurs in regions of minimum pressure along potential paths 

toward the surface, and petroleum or natural gas 

accumulations are formed. Throughout the migration process, no matter what the mechanism, the 

tendency for the migrating fluids is to attain the 

most stable state (generally the lowest level of potential energy) possible. This tendency is consistent 

with the expulsion of fluid hydrocarbons from finegrained source rocks and with their migration 

across strata or through carrier beds or fractures 

toward the surface from deep regions of higher 

temperature and greater confining pressure. The 

tendency is also consistent with aggregation of hydrocarbons into accumulations in local regions of 

lower pressure where they displace all but films of 

the water in the rock pores; with long-continued 

slow leakage of hydrocarbons (selectively the lowmolecular weight compounds) from large accumulations; and with the well-known propensity for oil 

and gas wells to "blow out" or "go wild," releasing 

their "minerals ferae naturae" abruptly (and with 

potential destructiveness) to the atmosphere. 
OIL AND GAS 487 

Entrapment of fluid hydrocarbons occurs wherever their tendency to escape to the atmosphere is 

interrupted or significantly impeded by any impervious or relatively impermeable barrier having a 

geometry suitable to hydrocarbon aggregation and 

accumulation, rather than to diversion. Both static 

(lithologic or mineralogic) and dynamic (hydrodynamic) barriers are effective, and an almost infinite 

variety of reservoir "traps" (McCullough, 1934) 

occur, the classical example of which, the anticlinal 

dome, consists of an upfolded (inverted cup-shaped) 

stratum of a porous permeable reservoir rock capped 

by a layer of shale, anhydrite, or other rock relatively impermeable to penetration by or transmission of large hydrocarbon molecules. Petroleum or 

natural gas constituents migrating gravitationally 

up-dip along natural escape routes through the permeable stratum are diverted toward the locus of 

minimum fluid pressure at the dome crest where they 

tend to be trapped and aggregate to form an anticlinal "pool" or reservoir. No attempt is made here to 

describe the myriads of other kinds of "traps" that 

have been recognized (Levorsen, 1954, p. 138-282). 

Any region of porous and permeable rock is a 

"trap" if it is connected more or less directly with 

pathways along which hydrocarbon fluids migrate 

(or once migrated), either in aqueous solution or 

as discrete intergranular filaments, droplets, globules, or slugs, and if it is enveloped or sealed up-dip 

(downstream from a potential viewpoint) by a 

barrier that prohibits hydrocarbon escape. When a 

petroleum or natural gas accumulation is opened by 

drilling, the fugacious hydrocarbon contents are permitted to resume their journey to the atmosphere. 

There they are ultimately oxidized, one way or 

another, to carbon dioxide and water, thereby bringing to completion the cycle that began (in some 

instances hundreds of millions of years earlier) 

with photosynthetic fixation of carbon in the organic compounds of living plants. The ultimate fate 

of most hydrocarbon accumulations that are not 

opened by drilling is to very slowly leak their contents to the surface (hence the historical importance to petroleum exploration of surface seepages, 

and the continuing efforts to understand surface 

geochemical anomalies and to develop practical geochemical prospecting methods (Pirson, 1970, p. 

208-239; Armstrong and Heemstra, 1972)). Other 

accumulations are opened by erosion at the surface 

following tectonic uplift, oxidized gradually through 

the actions of oxygenated waters circulating from 

the surface, or degraded by bacterial decay (World 

Oil, 1972). Doubtless the relative scarcity of geologically ancient petroleums is partly due to their 

fugitive nature in relation to the abundant opportunities for escape through geologic time. Possibly 

the fivefold to fifteenfold greater average volume of 

Pliocene than older reservoirs in the United States 

(Hopkins, 1950, fig. 4) is thus explainable. 

Figure 59 is an attempt to portray diagrammatically, but semiquantitatively, a few of the more conspicuous or diagnostic steps in the evolution of fluid 

hydrocarbons (such as comprise petroleum and 

natural gas) from organic debris interred in sediment and subjected to progressively higher temperatures upon burial in a subsiding basin. 

PETROLEUM AND NATURAL GAS RESOURCES 

Oil and gas fields are effective hydrocarbon traps 

that have been discovered through human resourcefulness. In general, those traps that have been discovered are those that are conspicuous (from the 

viewpoint of the host of exploration techniques that 

have been invented and employed), are of very large 

size, or are located in regions that have undergone 

thorough prospecting. Remaining to be discovered 

are innumerable small reservoirs, large reservoirs 

that are inconspicuous (when subjected to the exploration techniques available), and traps of all 

sizes in regions that have not yet been prospected 

thoroughly or at all. 

Who can say what the undiscovered resources of 

petroleum and natural gas are of the world or the 

United States? What are the incentives for seeking 

still more sophisticated and effective methods of 

exploring for undiscovered traps? In considering 

these questions one must keep in mind that not all 

subsurface hydrocarbon accumulations are worth 

finding. For every accumulation that can be found 

and produced economically, there are doubtless many 

accumulations of such small size that the volumes 

of hydrocarbons producible are insufficient to repay 

the costs of finding (including as they do the very 

great costs of drilling and completing the well, the 

high costs of exploration, and of all other efforts 

associated with such a technologic exercise). Under 

these circumstances it is obvious that small shifts 

in the supply I demand ratio for petroleum and 

natural gas bring about substantial shifts in numbers of accumulations and volumes of hydrocarbons 

from the paramarginal to the recoverable category. 

Similar effects are brought about by incremental 

improvements in exploration or exploitation technology. One must also keep in mind in considering 

these questions that the purposeful discovery of 

fluid hydrocarbons is a human endeavor, and one 

in which people have not been long engaged. Very 

large areas of the earth, especially portions of the 
488 UNITED STATES MINERAL RESOURCES 

SOURCE ROCKS RESERVOIR ROCKS .. II .. -&, 

0 -------Deposttaonal Su.uace l f 

Biogenic detritus contains -' No entrapment I 

minor hydrocarbQns with ,-

1 

I 

-100 

5-

20-

1--400 

more than 15 C atoms per I ~,- molecule ~-------

Cuttings gas- -, I I & 

Kerogen is ___ mainly methane -:::-d Gas-mostly methane I I .:2 

- paleyellow- _Mainly''wet"-~-------------- I 1,! 

II 

1 

4oximate taon 

threshold 

temperature 

for 

activalarge-~ C'IP. Jr 

scale kerogen Cs' I breakdown --

I I 

Y~w ~ I 1 

I ~ 

Crude oils-with or without gas caps 

and 

natural ps (ranging 

from methane to wet gas rich in gasoline fractions) 

I I 

I = Is~.~ I 0 >. :::1 u"' 

-~ ·=·51~c:5 

I :! :!·a o 8~ 

~ ~s e~~ 

I 

2 

lil~[1 I I :::2e 

Brown ·;;·;;I f8 f I ~ ~ ·;; ... ·;; 

I ~~,!:i! I -- ~ ;! 

I ~ l 1

1 

dl Crude oils-rich in low 

molecular weight par- I c~i>< .rr .... Dark rrown I Rough lower limit of co~cial crude oil ~ulation!._ 

I c~ ..... :r·"' 

i ~..:::.:~::•" ib~--·---------------

1 I Gas-containing little 

Black dissolved petroleum 

and I increasingly ] g 

graphl itic ~ ~ I ________________ _ ~:; I 

I ~~ I I __ Metalloporphyrins _ 8 :a ... 

I lower limit 5 e-..! I I ~~8 ... ~ :lq 

~e~l Gas-mostly methane 

I 

w:; 

40-

It 

ri 

..... 35-

~ 

i 

~ (1.1 

:1 30-

0 

at: 

!-o 

(1.1 

c 

100 ~ 

~ 25-

ri 

~ 

ti 

:1 

50 < 2i 

~ 

at: 

~ 20-

~ 

..J 

< :c 

(1.1 

~ 

c 

< 

at: 

25 ~ < 

:1 

::J 

:1 

>< 

< :1 

15-

~ 111:1 

< 

111:1 

0 

f 

10-

25~---------------------------LL-~----------------------------~------~ 

§ 

It 

r-: 

I.Q 

~ 

.t:! 

~ :::1 

'd 

! 

!-o 

z 

~ 

CJ 

at: 

~ 

A. 

~ 

>=' !: 

(1.1 

0 

at: 

~ 

at: 

~ at: 

~ (1.1 

~ 

at: 

~ 

z 

(1.1 

~ 

Q 

z 

< (1.1 

~ 

c 

< 

at: 

~ 

> 

< 

:1 

::J 

:1 

>< 

< :1 

~ 

..J 

111:1 

< 

111:1 

0 

f 

FIGURE 59.-Selected diagnostic and critical steps in the genesis and migration of petroleum and natural gas from sedimentary organic matter. 
OIL AND GAS 489 

seabed, have yet to be adequately explored geologically (Weeks, 1971). Our techniques for identifying hydrocarbon traps, or even those areas that 

especially favor hydrocarbon accumulation, are very 

imperfect. On both counts, the results of petroleum 

exploration to date serve as an inadequate baseline 

upon which to project results of future exploration. 

Nevertheless, the results of past exploration provide 

the most reliable single guide that we have. 

A decision must be made at the outset as to what 

will be an acceptable minimal sample unit or baseline if one is to attempt to use results of past exploration as a guide to future projections. For 

example, if one were to estimate the ultimate recoverable hydrocarbon resources of the United 

States on the basis of the productivity per square 

mile of surface area (or per cubic mile of sedimentary rock volume) of either the immensely productive Los Angeles Basin or the totally unproductive Imperial Basin, both Cenozoic basins of 

Southern California, the results in each case would 

be grossly in error. In the same way, estimations 

for unexplored regions would almost certainly be in 

error if the regional historical statistical data from 

either the aberrantly rich sedimentary areas or 

volumes of the Middle East or the exceptionally 

impoverished ones of Italy and the Adriatic Sea 

were to be used as guides. Out of ignorance and 

limited capability, one is tempted in such efforts to 

select the base unit to be an area as thoroughly 

explored and as large and diverse as possible, 

thereby hoping that an average of such extreme 

results as those from the Los Angeles and the Imperial Basins will somehow result and give a more 

meaningful blend. As a practical matter, one works 

with what is available, recognizing as he does that 

a fruitful field for further research awaits significant attack, and knowing that one thing needed is 

a sound measure of the frequency distribution of 

hydrocarbon productivity per unit of rock volume 

for a large enough number of depositional basins 

to provide a population curve representative for the 

world. There are few "Los Angeles Basins" in the 

world, and probably not many "Imperial Basins." 

Somewhere between these two extremes is the peak 

of a geologically composite population curve statistically applicable to totally unexplored basins and 

applicable with measured discrimination to geophysically analyzed basins or those only partly 

explored by drilling. 

The conterminous United States ("lower 48"), because of its political and economic unity, its comparatively long and intensive history of petroleum 

exploration and exploitation, its relatively large size 

(5.3 percent of the continental area of the earth), 

its large volume of Phanerozoic rocks (estimated 

to be 60X106 km3 by Gilluly and others (1970) ), and 

its great geological diversity provides " ... the most 

meaningful statistical sample for appraising possible ultimate potential" (Hendricks, 1965, p. 3). By 

starting with the quantity of petroleum found in the 

conterminous United States to the year 1961 and 

"the fraction of the potentially productive rocks 

that [had] been explored to [that] date," and by 

estimating the incidence of oil in the unexplored 

fraction " ... as determined by comparison with 

the explored part," Hendricks arrived at an estimate of 1,600 billion barrels of oil originally in place 

for the "lower 48." He estimated further (p. 9) that 

a total of 1,000 billion of those barrels could be found 

if economic incentives were sufficient to stimulate 

additional thorough but profitable exploration, and 

that 400 billion barrels would be ultimately recoverable (of which 68 billion barrels had been produced through 1961, and 97 billion today). By contrast, starting with the same basic historical records 

and data, but using a method of mathematical analysis that is in his words intrinsically ". . . comparatively insensitive to error in the estimates of [ ultimate cumulative production] ... ," Hubbert in a 

series of papers (1956, 1962, 1966, 1967) concluded 

that the amount of ultimately recoverable petroleum 

in the United States is between 150 billion barrels 

for the conterminous states and about 200 billion 

barrels for the entire continental United States (including Alaska and the outer continental shelves) . 

Hubbert's method is one of integral logistic curve 

fitting. It is related only statistically to rocks and 

geologic parameters, and to those only through a 

variety of economic and technologic factors. Supposing that human beings will be doing in the future 

as they have in the past, so far as petroleum exploration is concern~ both technologically and from 

an investment viewpoint, Hubbert's approach is 

unassailable. 

Hendricks was neither the only nor the first person to attempt to estimate undiscovered petroleum 

resources of the United States through an analysis 

of unexplored rocks based on analogy with historical 

results in explored areas. Twenty-three years earlier, 

Pratt (1942) published estimates of the ultimately 

discoverable and (presumably) producible petroleum 

resources of the United States and the world of 

100 billion and 500 billion barrels, respectively. The 

Pratt figures came from estimates made by Eugene 

Stebinger and L. G. Weeks" ... based on studies ... 

made of the records of past discoveries and of the 

nature and extent of sedimentary basins over the 
490 UNITED STATES MINERAL RESOURCES 

earth, which had yielded or appeared likely to yield 

oil" (Pratt, 1951, p. 9). De Golyer (1951, p. 9) 

criticized the Stebinger-Weeks-Pratt methods and 

assumptions in the following terms, "any hypothesis 

of equal expectation of minable oil by volume or 

area of sediments over large areas presupposes that 

the effects of all these processes will average about 

the same or, in case of inequalities that they will 

compensate." Of the figures themselves, De Golyer 

wrote, "They may be too high. They may be too low. 

I do not know. I am inclined to think that Pratt's 

original estimate of 100 billion bbl for the United 

States may be too low even if we add 13 billion bbl 

for the continental shelves .... " Inasmuch as cumulative production for the United States is today 

above 97 billion barrels, with 38 billion barrels more 

already categorized as "proved reserves" capable of 

economic extraction under current technology, the 

Stebinger-Weeks-Pratt estimation of 1942 was obviously an underestimation. The comparative success of a subsequent basically similar partial projection (Hopkins, 1950) leads one to ask, can we 

tell at this time th~t Hendrick's 1965 estimation of 

400 billion barrels is an overestimation? 

Although Hubbert's predictive (or projective) 

analytical procedure and results are perhaps more 

widely publicized than others, he is by no means 

the only scientist to have applied this method. Arps, 

Mortada, and Smith (1970) and Moore (1970a, b), 

provide examples of predictions made recently using 

similar mathematical analytical techniques which 

give somewhat divergent results; 165 billion barrels of "proved ultimate recovery discovered" 

(Arps and others, 1970, fig. 4) or 353 billion barrels 

(or 60 percent recoverable of 587 billion barrels of 

oil originally in place in the United States are predicted as discoverable; Moore, 1970~ fig. F-1} Does 

Moore know something that Hubbert does not to 

cause his projection to be so much higher (353 

billion versus 200 billion barrels; or versus 165 

billion in the case of Arps) ? I think not. The projective techniques employed are all probably equally 

sound and the same basic data were entered into 

each projection. There is simply enough latitude in 

the method that such divergent results all lie within 

the range of valid results. More importantly, these 

divergences are a measure of the adequacy of the 

projective baseline, which is no doubt subject to 

further evolutionary change as economic incentives 

enlarge, as competitive pressures force improvements in conservative efficiency, and as technologic 

advances permit improved and expanded exploration (greater ability to discover smaller and less 

conspicuous traps and to exploit a larger part of 

the resource base and a larger part of the prospective rocks). Speaking of the annual world oil discovery rate in a similar context, Warmen (1971, p. 

97) wrote, "for a curve with such violent fluctuations, it is not possible to carry out meaningful 

mathematical analysis." Needless to say, future 

changes in the baseline will inevitably be enlargements. 

For the sake of easy comparison at a glance, all 

of the more authoritative estimates of future and 

ultimately producible petroleum for the United 

States have been brought together in figure 60 and 

plotted as a function of their date of publication. 

Plotted also is the gross curve of production plus 

cumulative discoveries. The reader will note that 

the many more or less independent projections 

show a great deal of scatter (divergences such as 

those among the projections of Arps, Hubbert, and 

Moore), and that they tend to grow with the passage 

of time in a fashion that more-or-less parallels the 

growth of the curve of cumulative production plus 

reserves. Both the scatter and the tendency to grow 

are meaningful. They reflect the fact that the area 

under consideration has not remained constant 

through time-new producing regions and areas 

have been brought into the picture through combinations of business enterprise, economic pressures 

of many sorts, technologic advances, and exploitation effectiveness. There is considerable room for 

continuation of this evolutionary advancement--in 

all respects. Much of the United States continental 

shelf is unexplored. Who can say at this time that 

another "Los Angeles Basin" doesn't wait for discovery and exploitation beneath the waters of the 

Southern California Borderland (Emery, 1960)? 

Who knows that there is not another "Middle East," 

for example, beneath the continental margin off the 

southern Atlantic coast of the United States, with 

another "Ghawar" accumulation (the largest single 

oilfield, yet discovered in the world) containing another "75 billion barrels of producible reserves" 

(Arabian American Oil Company, 1959; Halbouty 

and others, 1970)? The onshore-offshore region 

south of Cape Hatteras has much in common geologically with the onshore-offshore region of Saudi 

Arabia, including a very thick section of structurally simple sedimentary rocks of the same ages and 

similar lithologies beneath a very large area. Prior 

to discovery by the drill and subsequent development, Ghawar field was not a particularly conspicuous prospect or structure, either from surface 

geologic mapping or geophysical interpretation 

(Arabian American Oil Company, 1959, especially 

p. 437 and p. 440-443) . Does anyone know that 
"%.1 

l5 

~ ~ 

0 

~ e 

I 

g, 

e. 

a: 

s 

;. 

't;j 

e; 

t:l.. 

~ 

s: 

(b' 

~ 

a 

ttl 

0 

~ 

'1 'C (') 

6"~ 

ttl-

'C Sl' 

~ :::3 <t:l.. 

~E ttl e (t) a. ~ ~ 

m s. 1-b-

'1 .... s ~ 

~ ~ 

~~ m 

)> 

g~ :II 

s:-a '1 

0 a:. ~ d) 

~ 

~~ (0 .... 

~[ 00 

it 

$ 

s· 

[ 

~ 

~-

S" 

d1 

g 

'1 

~ 

Sa 

g 

[ 

~ 

~-

'C 

a 

~ 

g 

~ 0 

~ 

I6v 

PETROLEUM, IN BILLIONS OF BARRELS 

Logarithmic scale 

1\.J w .. ~ _o 1\.J w .. U"' 0 0 0 ~-- 1\.J w .. U"' 0 0 0 ~ ~ 8 8 8 8 8 8 8 8 8 0 8 

~ 

0 

co 

~ 

co 

~ 

'R 

0 

co 

~ 

~ 0 

co 

..., 

0 

~ 

(;}-------~Day, 1909, p. 35 ~ <!r- -1!1 

~~ m _ .... 

... "C~ g' g' .... ::l 

~ 3' ~ 0 

~3 -· 3 3' 

~; ~ c: c: ~ ~ m 

&3 (II (II X 

["' ~ ~ "0 -(II c: r- -· CT (II"' c: :::~< 0 ::!. ;:; ;:; )> 

... -· :::3 3' 3' z (11 ... C» )> x!!!. ; ~ C» 

..... n· (II ; -4 N. 2. "C 0 0 (II 

~ c: 0 

- z ::l ;:; ~ 5' C» 3' c: 

3 n "C 

~ ~ a iii (II iD n 

(II 

r!r-- -1!1 Shaw, 1919, p. 481 

C» .()_.. iD ~ a\.® U.S. Geol. Survey, 1922 

~ ... \ 

"~· "'o'? 

Pratt, 1942 

~-+ (U.S. conterminous land area only) 

I 

I 

I 

I 

I 

1 

Weeks, 1948, p. 1094 

~ (U.S. conterminous land area only) I 

~Pratt, 1950, p. 149-151 , Land 

1B52, P\259 

\ 

® <!r-----~----® 

~ 

Egloff, 1952, p. 193 

\ Pogue and Hill, 1956, p. 24-25 'y Pratt, 1956, p.94 

.~ ® U.S. Dept. of Interior, 1956, p.82 

''@-.Hill and others, 1957, p.27 

@-..._Oil and Gas Jour.,1958 

.• 1 Hubbert-:-\!) Weeks, 1959 

1959 1!1-- -i1 U.S. Dept. of 

(;}-- --- ~app, 1961 Interior, 1960, 

\(;}-- -1!1 Moore, 1962 (total U.S.) P. 21-22 

\' -......... 

®---® \_Oil and Gas Jour--...1964, p. 71 

HendTicks, 1965 ~----------'1!., Hendricks and 

Hubbert,1966;0iland GasJour.,\1966-;® (.!r--{!1~~-----------~ Schweinfurth, 

Hubbert, 1967 ~ r""iMoore, 1966 '\1966 (unpublished) 

Elliott and Linden, 1968, p. 138: ® \ 

Hubbert,F969 ~ : ®-Maori, 1970-h------{!J Schweinfurth,1969 

Arps and others, 19 70 • ~ ~ -i!l 

• Natl. Petroleum 

Hubbert, 1970 Council,1970, p. 104 

SYD GNV '110 
Offshore development water depths 

-1 I I I ~ FEET 50 100 200 300 

Seismic l ------------ Reflection Tape recording Digital 

methods 

------- Refraction ~ 

_ _ _ _ _ _ Gravimeter I Underwater I Seagoing ~ 

Geopotential 

methods 

_ _ _ Torsion balance 1 

Pendulum ------------------------4 

Magnetometry 1 Airborne ~ 

I -

Geophysical well logging 

___ Surface geologic ------ __ __ Aerial photography 

mapping 

----------- Core drilling 

Seepage ___________ Geochemical prospecting 

--~~~---~ -------------~ 

Data compiled from public sources, particularly 

National Petroleum Council Committee on 

Effects of New Technology, 1967 

~ 

World proved reserves 

10 

-~ 9 

(I) 

_, 

w 

a: 

a: 8 c{ 

al 

LL 

0 

(I) 

z 

0 

7 ::::i 

_, 

al 

LL 

0 

(I) 

ss 

a: 

0 

z 

:::::> 

:I: 

z 5-

z 

0 

~ u 

:::::> 

0 

40 

a: 

~ 

0 

z 

c{ 

(I) 

3 w 

> 

a: 

w 

(I) 

w 

a: 

_, 2-0 

w 

0 

:::::> 

a: 

u 

I F. ~ ~ Unitad ~tates prove? reser~es I l l I I Ill l I I I I I I l I I I I I I,±=;~. I I I I I I I I 17, I I I I I I: '• I I I I, I I,, I 10 

1900 1910 

YEAR U.S. exploratory drilling peak 

FIGURE 61.-United States and world crude oil production and proved reserves in relation to selected important developments in petroleum exploration 

technology. 

~ 

~ 

~ 

d 

z 

...... 

~ 

t.%J 

t;1 

rJl 

~ 

> 

~ 

t;rj 

rJl 

a= 

...... 

z 

t.%J 

~ 

> t"'f 

~ 

t.%J 

00 

0 

d 

~ 

0 

t.%J 

00 
OIL AND GAS 498 

another such inconspicuous "supergiant" does not 

lie beneath the Blake Plateau, or someplace else 

within the territorial limits of the United States? 

Although it is extremely difficult to envision circumstances which would make the United States 

ever again economically self-sufficient in oil and gas 

(see fig. 61), until we know that the last accumulation is discovered, should we trust the estimates 

of future producible oil, no matter how elegantly 

prepared or firmly stated? To discover petroleum 

and new petroleum provinces requires an open mind, 

a desire to explore, a positive and adventurous attitude, a gambling spirit, and a will to win. Last but 

far from least, although only the drill bit can finally 

prove the presence of oil, "oil must be sought first 

of all in our minds" (Pratt, 1942, p. 49). 

SELECTED REFERENCES 

Abelson, P. H., 1964, Organic geochemistry and the formation of petroleum: 6th World Petroleum Con g. Proc., 

1963, Frankfurt/Main, Sec. 1, p. 397-407. 

Abelson, P. H., and Hare, P. E., 1968, Recent origin of amino 

acids in the Gunflint Chert: Geol. Soc. America, Program 

with abs., 1968 Ann. mtg., p. 2. 

Arabian American Oil Company, 1959, Ghawar oil field, 

Saudi Arabia: Am. Assoc. Petroleum Geologists Bull., 

v.43,no.2, p. 434-454. 

Armstrong, F. E., and Heemstra, R. J., 1972, Radiometries 

proposed for exploration: Oil and Gas Jour., June 5, 

1972, p. 88-91 and 97. 

Arps, J. J., Mortada, M., and Smith, A. E., 1970, Relationship 

between proved reserves and exploratory effort: Soc. 

Petroleum Engineers, SPE paper 2995. 

Athy, L. F., 1930, Density, porosity, and compaction of sedimentary rocks: Am. Assoc. Petroleum Geologists Bull., 

v. 14,no. 1,p. 1-24. 

Atwater, G. 1., and Miller, E. E., 1965, The effect of decrease in porosity with depth on future development of 

oil and gas reserves in south Louisiana [abs.]: Am. 

Assoc. Petroleum Geologists Bull., v. 49, no. 3, p. 334. 

Baker, D. R., 1962, Organic geochemistry of Cherokee Group 

in southeastern Kansas and northeastern Oklahoma: Am. 

Assoc. Petroleum Geologists Bull., v. 46, no. 9, p. 1621-

1642. 

Baker, E. G., 1962, Distribution of hydrocarbons in petroleum: Am. Assoc. Petroleum Geologists Bull., v. 46, no. 

1, p. 76-84. 

Barghoorn, E. S., Meinschein, W. G., and Schopf, J. W., 

1965, Paleobiology of a Precambrian shale: Science, v. 

148, p. 461-472. 

Barton, D. C., 1934, Natural history of the Gulf Coast crude 

oil, in Wrather, W. E., and Lahee, F. H., eds., Problems of petroleum geology: Tulsa, Okla., Am. Assoc. 

Petroleum Geologists, p. 109-155. 

Biederman, E. W., Jr., 1965, Crude Oil composition-a clue 

to migration: World Oil, v. 161, no. 7, p. 78-82. 

Bloch, K., 1965, The biological synthesis of cholesterol: Science,v. 150,p. 19-28. 

Bordovskiy, 0. K., 1965, Accumulation and transformation of 

organic substance in marine sediments: Marine Geology, 

v.3,no. 1-2,p. 33-82. 

Bray, E. E., and Evans, E. D., 1961, Distribution of n-paraffins as a clue to recognition of source beds: Geochim. 

et Cosmochim. Acta, v. 22, no. 1, p. 2-15. 

Brooks, J. D., 1970, The use of coals as indicators of the 

occurrence of oil and gas: Australian Petroleum Explor. 

Assoc. Jour. p. 35-40. 

Brooks, J. D., and Smith, J. W., 1967, The diagenesis of 

plant lipids during the formation of coal, petroleum and 

natural gas; I, Changes in the n-paraffin hydrocarbons: 

Geochim. et Cosmochim. Acta, v. 31, p. 2389-2397. 

--- 1969, The diagenesis of plant lipids during the formation of coal, petroleum and natural gas; II, Coalification and the formation of oil and gas in the Gippsland 

basin: Geochim. et Cosmochim. Acta, v. 33, no. 10, p. 

1183-1194. 

Burst, J. F., 1969, Diagenesis of Gulf Coast clayey sediments and its possible relation to petroleum migration: 

Am. Assoc. Petroleum Geologists Bull., v. 53, no. 1, p. 

73-93. 

Dallmus, K. F., 1958, Mechanics of basin evolution and its 

relation to the habitat of oil in the basin, in Weeks, L. 

G., ed., Habitat of oil-a symposium: Tulsa, Okla., Am. 

Assoc. Petroleum Geologists, p. 883-931. 

Day, D. T., 1909, The petroleum resources of the U.S., in 

Papers on the conservation of mineral resources: U.S. 

Geol. Survey Bull. 394, p. 30-61. 

Dean, R. A., and Whitehead, E. V., 1964, The composition 

of high boiling petroleum distillates and residues: 6th 

World Petroleum Cong., Proc., 1963, Frankfurt/Main, 

Sec. V, p. 261-279, Hamburg. 

De Golyer, E., 1951, On the estimation of undiscovered oil 

reserves: Jour. Petroleum Technology, Jan. 1951, p. 9-

10. 

Dunning, H. N., 1963, Geochemistry of organic pigments, 

Chap. 9 in Breger, I. A., ed., Organic Geochemistry: 

New York, Macmillan Co., p. 367-430. 

Eglinton, Geoffrey, Hamilton, R. J., Raphael, R. A., and 

Gonzalez, A. G., 1962, Hydrocarbon constituents of the 

wax coatings of plant leaves: Nature [London], v. 193, 

p. 739-742. 

Egloff, Gustav, 1952, Oil and gas as industrial raw materials, in Resources for freedom, Volume IV, The promise of technology: Washington, D. C., The President's 

Materials Policy Comm., v. IV, p. 193-204. 

Elkins, L. E., 1971, Oil recovery-past trends, future expectations, and t~echnological requirements: Am. Petroleum Inst. Div. of Production, Preprint. 

Elliott, M. A., and Linden, H. R., 1968, A new analysis of 

U.S. natural gas supplies: Jour. Petroleum Technology, 

v. 20 [Feb. 1968], p. 135-141. 

Emery, K. 0., 1960, The sea off southern California, a modern 

habitat of petroleum: New York, John Wiley and Sons, 

366. 

Evans, S. R., Rogers, M. A., and Bailey, N. J. L., 1971, 

Evolution and alternation of petroleum in western 

Canada: Chern. Geology, p. 147-170. 

Frank, D. J., and Sackett, W. M., 1968, Kinetic isotope 

effects during thermal cracking of hydrocarbons [abs.]: 

Geol. Soc. Am. Spec. Paper, 1969. 

Gehman, H. M., Jr., 1962, Organic matter in limestones: 

Geochim. et Cosmochim. Acta, v. 26, p. 885-897. 

Gilluly, James, Reed, J. C., Jr., and Cady, W. M., 1970, 

Sedimentary volumes and their significance: Geol. Soc. 

America Bull., v. 81, p. 353-376. 
494 UNITED STATES MINERAL RESOURCES 

Gussow, W. C., 1954, Differential entrapment of oil and gasa fundamental principle: Am. Assoc. Petroleum Geologists Bull., v. 38, no. 5, p. 816-853. 

Halbouty, M. T., 1968, Giant oil and gas fields in United 

States: Am. Assoc. Petroleum Geologists Bull., v. 52, 

no. 7, p. 1115-1151. 

Halbouty, M. T., Meyerhoff, A., Dott, R., King, R. E., and 

Klemme, H. D., 1970, World's giant oil and gas fields; 

geologic factors affecting their formation, and basin 

classification, in Halbouty, M. T., ed., Geology of giant 

petroleum fields: Am. Asoc. Petroleum Geologists Mem. 

14, p. 502-555. 

Hartley, Sir Harold, 1969, The future of world energy: 

New Scientist, Nov. 13, 1969, p. 3-5. 

Harvey, Hugh, 1970, Challenges facing the petroleum indus.try to the year 2000: an appraisal: Fuel, v. 49, no. 4, 

p. 357-374. 

Heald, K. C., 1950, Major oil fields of the United States 

and Canada: Geol. Assoc. Canada Proc., 1950, v. 3, 

p. 13-25. 

Hedberg, H. D., 1936, Gravitational compaction of clays and 

shales: Am. Jour. Sci., 5th ser., v. 31, no. 184, p. 241-

287. 

--- 1968, Significance of high-wax oils with respect to 

genesis of petroleum: Am. Assoc. Petroleum Geologists 

Bull., v. 52, no. 5, p. 736-750. 

--- 1971, Petroleum and progress in geology: Geol. Soc. 

London Jour., v. 127, p. 3-16. 

Hendricks, T. A., 1965, Resources of oil, gas, and naturalgas liquids in the United States and the world: U.S. 

Geol. Survey Circ. 522, p. 1-20. 

Hendricks, T. A., and Schweinfurth, S. P., 1966, The United 

States resource base 6f petroleum: U.S. Department of 

Interior, unpub. memo., Sept. 14, 1966. 

Hill, K. E., Hammar, H. D., and Winger, J. G., 1957, Future 

growth of the world petroleum industry: New York, 

The Chase Manhattan Bank, 44 p. 

Hills, I. R., Smith, G. W., and Whitehead, E. V., 19·70, Hydrocarbons from fossil fuels and their relationship with 

living organisms: Inst. Petroleum Jour., v. 56, no. 549, 

p. 127-137. 

Hoering, T. C., 1967, The organic geochemistry of Precambrian rocks, in Abelson, P. H., ed., Researches in 

geochemistry, V. 2: New York, John Wiley and Sons, p. 

87-111. 

Hopkins, G. R., 1950, A projection of oil discovery-1949-

1965: Jour. Petroleum Technology, June 1950, sec. 2, 

p, 6-10. 

House, M. R., 1963, Bursts in evolution: Adv. Sci., v. 19, no. 

82, p. 499-507. 

Hubbert, M. K., 1953, Entrapment of oil under hydrodynamic 

conditions: Am. Assoc. Petroleum Geologists Bull., v. 

37, no. 8, p. 1954-2026. 

--- 1956, Nuclear energy and the fossil fuels: New York, 

Am. Petroleum Institute, Drilling and Production Practice (1956), p. 7-25. 

--- 1959, Techniques of production with application to 

the petroleum industry: Houston, Texas Shell Devel. 

Company Explor. and Production Reserves Div. Pub. 

204, 32 p. and figs. 

--- 1962, Energy resources: Natl. Acad. Sci.-Natl. Research Council Pub. 1000-D, 141 p. 

--- 1966, M. King Hubbert's reply to J. M. Ryan: Jour. 

Petroleum Technology, February, p. 284-286. 

--- 1967, Degree of advancement of petroleum exploration in United States: Am. Assoc. Petroleum Geologists 

Bull., v. 51, no. 11, p. 2207-2227. 

--- 1969, Energy resources in Resources and man: Natl. 

Acad. Sci.-N atl. Research Council, Comm. on Resources 

and Man, p. 157-242. 

--- 1971, The energy resources of the earth: Sci. American [Sept. 1971], p. 61-70. 

Hudson, H. K., 1963, Is the "song of plenty" a siren song?: 

Oil and Gas Jour., v. 61, no. 24, p. 131-136. 

Hunt, J. M., 1962, Geochemical data on organic matter in 

sediments: Internat. Sci. Oil Conf. Proc., Budapest, preprint. 

King, R. E., 1969, Oil and gas exploration and production in 

the Soviet Union, in The exploration for petroleum in 

Europe and north Africa: London, Inst. of Petroleum, 

p. 181-190. 

Klemme, H. D., 1971, What giants and their basins have in 

common: Oil and Gas Jour., March 1, 1971, v. 69, no. 9, 

p. 85-99. 

Landes, K. K., 1967, Eometamorphism, and oil and gas in 

time and space: Am. Assoc. Petroleum Geologists Bull., 

v. 51, no. 6,p. 828-841. 

Larskaya, Ye. S., and Zhabrev, D. V., 1964, Effects of stratal 

temperatures and pressures on the composition of dispersed organic matter (from the example of the Mesozoic Cenozoic deposits of the western Ciscaspian region) : 

Akad. Nauk SSSR Doklady, v. 157, no. 4, p. 897-900 

(English translation in Geochemistry) . 

Levorsen, A. I., 1954, Geology of petroleum: San Francisco, 

W. H. Freeman and Co., 703 p. 

McAuliffe, C., 1966, Solubility in water of paraffin, cycloparaffin, olefin, acetylene, cycloolefin, and aromatic hydrocarbons: Jour. Phys. Chemistry, v. 70, no. 4, p. 

1267-1275. 

McCullough, E. H., 1934, Structural influence on the accumulation of petroleum in California; Problems of petroleum 

geology: Am. Assoc. Petroleum Geologists, Tulsa, 

Okla., p. 253-307. 

McCulloh, T. H., 1967, Mass properties of sedimentary rocks 

and gravimetric effects of petroleum and natural-gas 

reservoirs: U.S. Geol. Survey Prof. Paper 528-A, p. AlA50. 

McNab, J. G., Smith, P. V., Jr., and Betts, R. L., 1952, The 

evolution of petroleum: Indus. and Eng. Chemistry, v. 

44,no. 11,p. 2556-2563. 

Magara, K., 1969, Upward and downward migrations of 

fluids in the subsurface: Bull. Canadian Petroleum 

Geology, v. 17, no. 1, p. 20-46. 

Marchand, P., Libert, P., and Gombaz, A., 1969, Essai de 

caracterisation physico-chimique de la diagenese de 

quelques roches organiques "biologiquement homogenes": 

Rev. de L'institut Francais du Petrole, v. 24, no. 1, p. 

3-20. 

Martin, R. L., Winters, J. C., and Williams, J. A., 1963, Distribution of n-paraffins in crude oils and their implications to origin of petroleum: Nature, v. 199, p. 110-113. 

Maxwell, J. C., 1964, Influence of depth, temperature, and 

geologic age on porosity of quartzose sandstone: Am. 

Assoc. Petroleum Geologists Bull., v. 48, no. 5, p. 697-

709. 

Meinschein, W. G., 1959, Origin of petroleum: Am. Assoc. 

Petroleum Geologists Bull., v. 43, no. 5, p. 925-943. 

Moody, J. D., 1970, Petroleum demands of future decades: 
OIL AND GAS 495 

Am. Assoc. Petroleum Geologists BulL, v. 54, no. 12, p. 

2239-2245. 

Moody, J. D., Mooney~ J. W., and Spivak, J., 1970, Giant oil 

fields of North America, in Halbouty, M. T., ed., Geology 

of giant petroleum fields: Am. Assoc. Petroleum Geologists Mem. 14, p. 8-17. 

Moore, C. L., 1962, Method for evaluating United States 

crude oil resources and projecting domestic crude oil 

availability: Washington, D. C., U.S. Dept. of Interior, 

Office of Oil and Gas, 112 p. 

--- 1966, Projections of U.S. petroleum supply to 1980: 

Washington, D.C., U.S. Dept. of Interior, Office of Oil 

and Gas, 13 p. 

--- 1970a, Analysis and projection of historic patterns 

of U.S. crude oil and natural gas, in Future petroleum 

provinces of the United States-A Summary: Natl. 

Petroleum Council [July 1970], p. 133-138. 

--- 1970b, Analysis and projection of historic patterns of 

U.S. crude oil and natural gas, appendix F in Cram, 

I. H., ed., Future petroleum provinces of the United 

States-Their geology and potential: Am. Assoc. Petroleum Geologists Mem. 15, v. 1, p. 50-54. 

Murray, G. E., 1965, Indigenous Precambrian petroleum?: 

Am. Assoc. Petroleum Geologists Bull., v. 49, no. 1, p. 

3-21. 

Nagy, Bartholomew, 1970, Porosity and permeability of the 

early Precambrian Onverwacht chert; origin of the hydrocarbon content: Geochim. et Cosmochim. Acta, v. 34, 

no. 4, p. 525-527. 

National Petroleum Council, 1970, Future petroleum provinces of the United States : N atl. Petroleum Council 

Comm. on Possible Future Petroleum Provinces of the 

u.s., p. 1-138. 

National Petroleum Council Committee on Effects of New 

Technology, 1967, Impact of new technology on the 

U.S. petroleum industry 1946-1965: Washington, D.C., 

N atl. Petroleum Council. 

Neruchev, S. G., 1964, Changes in the composition of the 

autochthonous bitumoids of the organic matter in argillaceous rocks as effected by factors of metamorphism and 

oil extraction: Akad. Nauk SSSR Doklady, v. 157, no. 

4, p. 901-903 (English translation in Geochemistry). 

Oakwood, T. S., Shriver, D. S., Fall, H. H., McAleer, W. J., 

and Wunz, P. R., 1952, Op.tical activity of petroleum: 

Indus. and Eng. Chemistry, v. 44, p. 2568-2570. 

Oil and Gas Journal, 1958, [May 19, 1958], p. 114. 

--- 1964, Crude surplus expected through 1975: Oil and 

Gas Jour., Feb. 24, 19·64, p. 70-71. 

--- 1966, An expert gives a geological approach to reserve ultimate: Oil and Gas Jour., v. 64, no. 34 [Aug. 

22, 1966]' p. 150-151. 

Orr, W. L., Emery, K. 0., and Grady, J. R., 1958, Preservation of chlorophyll derivations in sediments off southern 

California: Am. Assoc. Petrol·eum Geologists Bull., v. 

42, no. 5, p. 925-962. 

Perrodon, Alain, 1966, Geologie du petrole: Paris, Presses 

Univ. France, 440 p. 

Philipp, W., Drong, H. J., Fiichtbauer, H., Haddenhorst, H. 

G., and Jankowsky, W., 1963, Zur Geschichte der Migration im Gifhorner Trog: Erdol u. Kohle-ErdgosPetrochemie, v. 16, p. 456-468. 

Philippi, G. 1., 1957, Identification of oil-source beds by 

chemical means: 20th Int. Geol. Gong., Mexico 1956, sec. 

3, p. 25-38. 

--- 1965, On the depth, time and mechanism of petroleum 

generation: Geochim. et Cosmochim. Acta, v. 29, p. 1021-

1049. 

Pirson, S. J ., 1970, Geologic well log analysis: Houston, 

Texas, Gulf Publishing Co., 370 p. 

Pogue, J. E., and Hill, K. E., 1956, Future growth and 

financial requirements of the world petroleum industry: 

New York, Petroleum Dept., The Chase Manhattan 

Bank, 39 p. 

Pratt, W. E., 1942, Oil in the earth: Kansas Univ. Press, 

105 p. 

--- 1950, The earth's petroleum resources, in Fanning, 

L., M., ed., Our oil resources: New York, McGraw-Hill 

Book Co., Inc., p. 137-153. 

--- 1951, On the estimation of undiscovered oil reserves: 

Jour. Petroleum Technology, April issue, p. 9-10. 

Pratt, Wallace E., 1956, The impact of the peaceful uses of 

atomic energy on the petroleum industry: Background 

material for the R.ept. of the Panel on the Impact of 

the Peaceful Uses of Atomic Energy to the Joint Committee on Atomic Energy, v. 2, January, p. 94. 

Radchenko, 0. A., 1968, Geochemical regularities in the distribution of the oil-bearing regions of the world: 

Jerusalem, Israel Program for Sci. Translations Ltd., 

312 p. 

Ronov, A. B., 1958, Organic carbon in sedimentary rocks (in 

relation to the presence of petroleum) : Geochemistry, 

no. 5, p. 510-536. 

--- 1968, Probable changes in the composition of sea 

water during the course of geologic time: Sedimentology, 

v. 10, no. 1, p. 25-43. 

Ronov, A. B., Mikhaylovskaya, M. S., and Solodkova, I. 1., 

1965, The evolution of the chemical and mineral compositions of sandy rocks: Geochemistry Internat., v. 2, p. 

318-371. 

Schultz, P. R., 1952, What is the future of petroleum discovery?: Oil and Gas Jour., July 28, 1952, p. 258-259, 

295-300. 

Schweinfurth, S. P., 1969, in McKelvey, V. E., Wang, F. H., 

Schweinfurth, S. P., and Overstreet, W. C., Potential 

mineral resources of the United States continental shelf 

in Public Land Law Review Commission Study of Outer 

Continental Shelf Lands of the United States, v. 4 (Append_ic·es) : available from N atl. Tech. In f. Service, U.S. 

Dept. of Commerce, Springfield, Virginia 22151. 

Shaw, E. W., 1919, The income and expense of natural gas 

production: Natural Gas Assoc. America, Proc., 14th 

Ann. Mtg., May 19-22, p. 479-503. 

Silverman, S. R., 1964, Investigations of petroleum origin 

and evolution mechanisms by carbon isotope studies, in 

Craig, Miller, and Wasserburg, eds., Isotope and Cosmic 

Geochemistry: Amsterdam, North-Holland Publishing 

Co., p. 92-102. 

Silverman, S. R., and Epstein, S., 1958, Carbon isotopic 

compositions of petroleums and other sedimentary organic materials: Am. Assoc. Petroleum Geologists Bull., 

v.42,no. 5,p. 998-1012. 

Smith, J. W., Schopf, J. W., and Kaplan, I. R., 1970, Extractable organic matter in Precambrian cherts: Geochim. et Cosmochim. Acta, v. 34, no. 6, p. 659-675. 

Smith, P. V., 1956, Hydrocarbons in Recent marine sediments. 

Smith, P. V., Jr., 1954, Studies on origin of petroleum--occurrence of hydrocarbons in recent s·ediments: Am. Assoc. 

Petroleum Geologists Bull., v. 38, no. 3, p. 377-404. 
496 UNITED STATES· MINERAL RESOURCES 

Snarskiy, A. N., 1962, Primary migration of oil: Petroleum 

Geology, v. 6, no. 11, p. 700-703 (of English translation). 

Tappan, Helen, and Loeblich, A. R., Jr., 1970, Geobiologic implications of fossil phytoplankton evolution and timespace distribution: Geol. Soc. America Spec. Paper 127, 

p. 247-340. 

Teichmiiller, Marlies, 1958, Metamorphisme du charbon et 

prospection du petrole: Rev. Industrie Minerale, Spec. 

issue, p. 99-113. 

Trask, P. D., 1937, Inferences about the origin of oil as indicated by the composition of the organic constituents 

of sediments: U.S. Geol. Survey, Prof. Paper 186-H, p. 

147-157. 

Trask, P. D., assisted by, Hammar, H. E., and Wu, C. C., 

1932, Origin and environment of source sediments of 

petroleum: Houston, Texas, American Petroleum Inst. 

323 p. 

Trask, P. D., and Patnode, H. W., 1942, Source beds of 

petroleum: Tulsa, Okla., Am. Assoc. Petroleum Geologists, 561 p. 

Treibs, A., 1936, Chlorophyll-und Haminderivate in organischen Mineralstoffen: Angew. Chemie, Bd. 49, p. 682-

686. 

U.S. Department of Interior, 1956, Impact of the peaceful 

uses of atomic energy on the coal, oil and natural-gas 

industries: Background material for the Rept. of the 

Panel on the Impact of the Peaceful Uses of Atomic 

Ene-rgy to the Joint Comm. on Atomic Energy, v. 2, 

January, p. 82. 

--- 1960, Resources of coal, petroleum, natural gas, oil 

shale, and tar sands in the United States and allied and 

neutral countries: Joint Comm. on Atomic Energy, U.S. 

Cong., March 1960, p. 1-43. 

U.S. Geological Survey, 1922, The oil supply of the U.S.: 

Am. Assoc. Petroleum Geologists Bull., v. 6, no. 1, p. 

42-46. 

Uspenskii, V. A., 1962, The geochemistry of processes of 

primary oil migration: Geochemistry. no, 12, p. 1157-

1178. 

Vassoyevich, N. B., Vysotskiy, I. V., Sokolov, B. A., and 

Tatarenko, Y e. I., 1971, Oil-gas potential of Late Precambrian deposits: Internat. Geology Rev., v. 13, no. 3, 

p. 407-418. 

Vinograd6v, A. P., and Galimov, E. M., 1970, Carbon isotopes 

and the origin of petroleum: Geochemistry Internat. v. 

7, no. 2, p. 217-235. 

Warman, H. R., 1971, Future problems in petroleum exploration: Petroleum Rev., March 1971, p. 96-101. 

Washburne, C. W., 1915, The capillary concentration of gas 

and oil: American In st. Mining Engineers Trans., v. 

50, p. 829-842. 

Watts, H., 1963, The possible role of adsorption and diffusion in the accumulation of crude petroleum deposits; a 

hypothesis: Geochim. et Cosmochim. Acta, v. 27, p. 925-

928. 

Weeks, L. G., 1948, Highlights on 1947 developments in 

foreign petroleum fields: Am. Assoc. Petroleum Geologists Bull., v. 32, no. 6, p. 1093-1160. 

--- 1971, World offshore scene in rapid change: Oil and 

Gas Jour., v. 69, no. 50, p. 91-94 and 99. 

Weeks, Lewis G., 1959, Where will energy come from in 

2059: Petroleum Engineer, v. XXXI, no. 9, August 1959. 

Welte, D. H., 1965, Relation between petroleum and source 

rock: Am. Assoc. Petroleum Geologists Bull., v. 49, no. 

12, p. 2246-2268. 

--- 1966, Extraktions experimente an bituminosen 

Gesteinen: Geochim. et Cosmochim. Acta. 

--- 1972, Petroleum exploration and organic geochemistry: Jour. Geochem. Explor. v. 1, p. 117-136. 

White, C. D., 1915, Some relations in origin between coal 

and petroleum: Washington Acad. Sci. Jour., v. 5, p. 

189-212. 

White, W. S., and Wright, J. C., 1954, The White Pine 

copper deposit, Ontonagon County, M·ichigan: Econ. 

Geology, v. 49, p. 675-716. 

Witherspoon, P. A., and Saraf, D. N., 1964, Diffusion of 

methane, ethane, propane and n-butane in water, in 

Hobson, G. D., and Louis, M. C., eds., Advances in organic geochemistry: Pergamon Press, p. 259. 

World Oil, 1972, Bacteria have destroyed 10 percent of 

world's crude: World Oil, Feb. 1, 1972, p. 2~29. 

Zapp, A. D., 1961, World petroleum resources, in Domestic 

and world resources of fossil fuels, radioactive minerals, 

and geothermal energy: Prelim. repts. prepared by 

members of the U.S. Geological Survey for the National 

Resources Subcommittee of the Federal Science Council, 

Nov. 28, 1961, 9 p. 
UNITED STATES MINERAL RESOURCES 

OIL SHALE 

By WILLIAM C. CuLBERTSON and JANET K. PITMAN 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------ Oil-shale deposits in the United States -------------

Lacustrine oil-shale deposits ------------------

Marine black shale deposits ------------------

Shale associated with coal beds ---------------

Resources --------------------------------------- Identified and hypothetical resources of shale oil 

Green River Formation ------------------

Chattanooga Shale and equivalent formations --------------------------------- Other shale deposits ---------------------

Foreign oil-shale deposits ----------------

Speculative resources ------------------------

Prospecting techniques ---------------------------

Problems for research ---------------------------- Selected references 

TABLES 

95. Shale-oil resources of the United States, in billions of barre1s, by grad·e (oil yield) of oil 

Page 

497 

497 

498 

498 

499 

499 

500 

500 

500 

500 

501 

501 

501 

502 

502 

503 

Page 

shale ----------------------------------- 500 

96. Shale-oil resources of the world (excluding the 

United States) in billions of barrels, by grade 

(oil yield) of oil shale -------------------- 501 

ABSTRACT OF CONCLUSIONS 

Oil shale, a fine-grained sedimentary rock containing in-

'Eoluble organic matter that yields substantial amounts of 

oil by destructive distillation, occurs in large volumes 

throughout the United States and the world, and constitutes 

an enormous resources of oil. Identified resources of shale 

oil in the United States total about 2 trillion barrels o.f oil 

in shale that yields an average of 15 or more gallons of oil 

per ton, most of which is in the lacustrine rocks of the 

Eocene Green River Formation of Colorado, Utah, and Wyoming. Although no oil is being produced from oil shale in 

the United States, it seems likely that oil from high-yield 

shales will be needed in the near future to supplement other 

sources of energy. It is estimated that 0.42 trillion barrels 

of oil are in oil shale that yields 30 or more gallons of oil 

per ton, 85 percent of which is in western Colorado. Minerals locally associated with the rich oil shale may yield 

recoverable sodium carbonate, sodium bicarbonate, or 

aluminum. 

Marine black shales occur in many parts of the United 

States and form an immense, but low-grade resource of 

shale oil. The better parts of these deposits generally yield 

only 10-15 gallons of oil per ton, but hydrogenation or similar techniques may increase the yield by 50 to 100 percent. 

Another widespread resource of shale oil may be the carbonaceous shales associated with coal beds. The total resources of shale oil to depths of 20,000 feet may total 26 

trillion barrels in low-yield shales and 1.3 trillion barrels 

in high-yield shales. 

INTRODUCTION 

Oil shale is a fine-grained sedimentary rock containing organic matter that has the property of yielding substantial amounts of oil when heated in a 

closed retort (destructive distillation) but that is 

mostly insoluble in ordinary petroleum solvents. The 

United States has tremendous quantities of oil shade, 

principally in the Green River Formation in Colorado, Utah, and Wyoming. These three States contain identified resources of about 1.8 trillion barrels 

of oil in oil shale that yields an average of 15 or more 

gallons per ton. However, no oil-shale venture has 

been a commercial success in the United States in the 

last 100 years, despite. the fact that other countries 

of the world have for many years burned oil shale as 

a fuel, or have produced oil or combustible gas from 

the shale. The principal reason for the lack of success is the abundant supplie-s of lower cost oil, gas, 

and coal that this country has developed. The rising 

demand for energy, however, may soon require the 

development of this abundant energy resource to 

supplement the dwindling supplies of other fo-ssil 

fuels. 

Duncan and Swanson (1965, p. 5) have estimated 

that about 400 million barrels of oil have been produced from oil shale in foreign countries prior to 

U.S. GEOL. SURVEY PROF. PAPER 820 

497 
UNITED STATES MINERAL RESOURCES 

1961, principally in Scotland, Estonia (U.S.S.R.), 

and Manchuria (China). Oil-shale deposits in France, 

Sweden, Germany, Spain, South Africa, and Australia have also been mined on a modest scale, and 

a new shale-oil operation is scheduled to begin in 

1972 in Brazil. 

In the United States, experiments in the production of oil and gas from oil shale have been conducted since 1850. Most early experiments were 

brief, ineffective efforts, but since 1944 pilot plants 

have been intermittently operated either by the U.S. 

Bureau of Mines ( 1944-56) or by private industry 

(1957-72) in the western Colorado oil-shale deposits. 

These pilot plants retorted oil shale that had been 

mined underground by conventional methods. In 

1966, the U.S. Bureau of Mines estimated the cost of 

producing shale oil by this method at about $3 a barrel (Schramm, 1970, p. 192). In 1970, the National 

Petroleum Council (1972) also evaluated this method 

and estimated that each barrel of oil with a heat 

value of 5.4 million Btu would cost between $4.30 and 

$5.30 at the plant site. This estimate assumed a plant 

p·roducing 100,000 barrels of oil a day (initial investment of $500 million) that used only the richer, more 

accessible oil shale (oil shale yielding 30-35 gallons 

of oil per ton, in zones more than 30 feet thick, within 1,500 ft of the surface) . This cost compares unfavorably with the present price of crude oil, which 

is about $3.50 a barrel. It is probable, however, that 

the value of coproducts of shale oil, such as aluminum 

or sodium bicarbonate, or advancements in technology, or increases in the price of crude oil, will n1ake 

shale oil competitive with crude oil in the near 

future. 

The possibility of heating the oil shale underground and pumping the oil to surface (in situ retorting) has been investigated by private industry 

in western Colorado, and by the U.S. Bureau of 

Mines in southwest Wyoming (Schramm, 1970• p. 

188). Many technical problems remain to be solved, 

but this method holds promise as a way to obtain the 

oil with little harm to the environment. 

Synthetic gas can be produced from oil shale, but 

the cost of converting the organic matter to highquality gas suitable for mixing with natural pipeline 

gas would appear to be greater per unit of contained 

energy. For example, it would cost $0.50 per million 

Btu to convert oil to gas. 

OIL-SHALE DEPOSITS IN THE UNITED STATES 

Oil shale occurs in many parts of the country in 

rocks ranging in age from Ordovician to Tertiary. 

Oil-shale deposits can be divided into three typesshale in lacustrine rocks, marine shales, and the 

shales associated with coal beds. 

LACUSTRINE OIL-SHALE DEPOSITS 

The principal oil-shale deposit of lacustrine origin 

is in the Green River Formation of Eocene age, 

which underlies about 17,000 square miles in Colorado, Utah, and Wyoming. Other small lacustrine 

deposits of Tertiary age containing oil shale have 

been reported in the intermontane basins of Montana, Nevada, Idaho, and California, but they rem~!_n_ 

unexrplored. 

The Green River Formation consists of oil shale 

interbedded with varying amounts of tuff, siltstone, 

sandstone, claystone, and locally with halite, trona, 

or nahcolite. The formation ranges in maximum 

thickness from a few feet to several thousand feet 

and intertongues laterally with the predominantly 

fluvial beds of the Wasatch Formation. The Green 

River Formation was originally deposited principally from two large Eocene lakes, one lying south of 

the Uinta Mountains and the other lying north and 

east. It is now preserved in seven basins-the Uinta 

Basin in Utah, the Piceance Creek and Sand Wash 

basins in Colorado, and the Green River, Great Divide, Washakie, and Fossil basins of Wyoming. 

In the Piceance Creek deposit (Donnell and Blair, 

1970 · Donnell, 1961), the Parachute Creek Member 

of th~ Green River contains up to 2,000 feet of oil 

shale in alternating rich and lean beds. Some of these 

rich beds are very persistent; the Mahogany zone, 

for example, underlies more than 2,000 square miles 

in Colorado and Utah. The oil shale is thickest and 

richest in the north-central part of the Piceance 

Creek basin, where it also contains nodules, lenses, 

and beds of nahcolite (NaHCOa) and halite (NaCl), 

and disseminated crystals of dawsonite [NaAl (OH2) 

CO a]. Nahcolite is potentially valuable as a source of 

sodium carbonate or sodium bicarbonate, and dawsonite as a source of aluminum. Toward the margins 

of the basin, the oil-shale sequence becomes progressively thinner and leaner, intertonguing with sandstone and siltstone. 

In the Uinta Basin (Cashion, 1967), the Green 

River Formation is similar to that in the Piceance 

Creek basin, but the oil-shale sequence is thinner and 

leaner and does not contain significant amounts of 

saline minerals. In the Green River Basin, oil shale 

occurs in thin, but widespread units in the Tipton 

Shale, Wilkins Peak, and Laney Members of the 

Green River (Culbertson, 1972; Bradley, 1964). The 

Wilkins Peak Member locally contains thick beds of 

trona (Na2C03 •NaHCOa•2H20) and halite, and disseminated crystals of shortite (Na2COa•2GaCOa), 
OIL SHALE 499 

and other saline minerals, as well as thin zones of 

uraniferous phosphate, but the oil-shale beds in this 

sequence are so thin that they rarely constitute a 

resource where the trona and halite predominate. In 

the Washakie basin the richest oil shale is in the 

Laney Member of the Green Riv·er Formation (Roehler, 1969). The Wilkins Peak Member here is free of 

saline minerals and has been replaced in part by 

fluvial beds of the Wasatch Formation. The Tipton 

Shale Member is widespread, but available data indicate that its oil shale is lean. 

In the Great Divide and Sand Wash basins, the 

Green River Formation is similar to that of the 

Washakie basin, but the oil shales are generally low 

grade. In the Fossil basin the Green River Formation was presumably deposited from a small lake 

separate from the main Green River lakes. The oilshale sequence is thin and mostly low grade. 

The oil shale of the Green River Formation is a 

dense, tough marlstone that is generally well laminated and ranges in color from tan to dark brown or 

olive-brown to brownish black. According to Bradley 

( 1970, p. 985), the organic fraction is derived from 

"microscopic algae, and other microorganisms, that 

grew and accumulated in the central parts of large, 

shallow lakes that existed under a sub-tropical climate," and from "wind-blown, or water horne, pollens and waxy spores." The inorganic fraction consists predominantly of dolomite and calcite with 

varying amounts of quartz, feldspar, analcime, clay, 

and pyrite. The mineralogy and the variation in mineral composition of the oil shale in the Piceance 

Creek basin, Colorado, are described in detail by 

Brobst and Tucker (1973). 

The sites of deposition of the oil shale we·re very 

fiat. The lakes weTe large in area and the relatively 

shallow water ranged from fresh to highly alkaline. 

The surrounding highlands contributed clastic sediment to the margins of the lake, but during most of 

their history little or none of the clastic material was 

carried into the central part of the lakes. Conditions 

were such that algae grew abundantly on the surface 

of the lake, and their remains were preserved in the 

bottom sediments. 

The basins sank slowly, and at irregular rates, 

causing the centers of deposition of oil shale to shift 

during Eocene time. In general, the areas were tectonically quiescent during deposition and for millions 

of years after the sediments were buried. Subsequently, uplift caus·ed local tilting and erosion of 

these beds. 

MARINE BLACK SHALE DEPOSITS 

Black shale deposits of marine origin which underlie large areas in most of the United States consist 

of two main types. The platform-type marine black 

shales were formed in shallow seas on continental 

platforms where circulation of water near the sea 

floor was restricted. Characteristically, the platform 

shales may be several hundred feet thick, but the oilshale zones are thin and persistent, ranging in thickness from a few feet to a few tens of feet (Duncan, 

1967, p. 661). Although few of them have a high oil 

yield, they underlie such large areas throughout the 

world that their resources of shale oil are larger than 

that of any other type of deposit. Geosynclinal marine shales were formed in subsiding geosynclinal 

basins, and are associated with limestone, phosphate 

rock, and chert in assemblages much thicker than the 

platform type. Some deposits of this type, such as 

Miocene shales in California, yield significant 

amounts of oil. 

The organic matter, which gives marine black 

shales their characteristic color, contains relatively 

little hydrogen, and therefore only a small percent 

of the organic matter converts to oil. According to 

Swanson (1960, p. 28), the organic matte·r is of two 

types: sapropelic (derived from algae, spore, pollen, 

etc.) and humic (derived from cellulose, lignin, and 

analogous woody parts) . The inorganic fraction predominantly consists of quartz and clay minerals, although some shales contain carbonate. Many shales 

also contain small amounts of uranium, vanadium, 

and other metals, and phosphate. 

A well-known ·example of the platform-type shale 

is the marine black shale of Late Devonian and Early 

Mississippian age that underlies more than 2·50,000 

square miles in Eastern and Central United States. 

It is known principally as the Chattanooga Shale in 

the Central United States, but the names New Albany, Ohio, Antrim, Mountain Glen, and Woodford 

Shales refer to approximate stratigraphic equivalents else·where of the Chattanooga Shale. The black 

shale generally ranges from 0 to 100 feet in thickness, its average oil yield is about 5 gallons per ton 

of shale, and its average uranium content is 0.003 

percent (Swanson, 1960, p. 7). 

SHALES ASSOCIATED WITH COAL BEDS 

Cartbonaceous shales associated with coal beds are 

of two types: thin persistent beds deposited in a 

shallow marine environment and beds deposited in a 

swampy, nonmarine environment that are limited in 

extent and exhibit considerable lateral variation in 

organic content. In the Appalachian coal province, 

the Pennsylvanian rocks. contain mostly nonmarine 

carbonaceous shales that have been reported to yield 

from 1 to 100 gallons of oil per ton, but most yield 
500 UNITED STATES MINERAL RESOURCES 

less than 10 gallons of oil per ton. The richest beds 

-the cannel shales-are thin and of small extent. In 

the Interior coal province, the Pennsylvanian rocks 

contain numerous marine shales, persistent across 

thousands of square miles, Swanson (1960, p. 16) 

reported that about 40 distinct shale units occur in 

eastern Kansas and northeastern Oklahoma, but 

most of them are thin and yield 5-10 gallons of oil 

per ton. In Illinois, the oil yield of 114 samples from 

30 marine shales ranged from 0 to 40 gallons of oil 

per ton, but 88 percent yielded less than 15 gallons 

of oil per ton. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

OF SHALE OIL 

Identified shale-oil resources are those deposits for 

which sufficient data are availalble to establish the 

magnitude and oil yield within reasonable limits. 

Hypothetical resources are resources in possible extensions of identified deposits or in nearby deposits, 

in vthich the approximate magnitude of the oil-shale 

deposit is known, but whose oil yield is inferred from 

scant evidence. 

GREE~ RIVER FORMATION 

The minimum thickness and grade of oil shale used 

by the U.S. Geological Survey in classifying public 

lands as valuable for oil shale of the Green River 

Formation is about equal to a sequence 15 feet thick, 

yielding an average of 15 gallons of oil per ton, but 

sequences yielding as little as 10 gallons per ton are 

included when computing the average yield of a thick 

sequence of oil shale. On this basis, the identified 

resources of the Green River Formation in Colorado, 

Utah, and Wyoming are estimated to total 1.8 trillion barrels of oil (table 95). Most of these identified 

resources ( 1.2 trillion barrels) are contained in the 

Piceance Creek basin of Colorado (Donnell, 1964; 

Donnell and Blair, 1970). The Uinta Basin of Utah 

is estimated to contain about 0.32 trillion barrels of 

oil (Cashion, 1964), and recent core data indicate 

that the Green River and Washakie basins of Wyoming together contain a similar amount. 

Apparently none of these resources can be considered as economically recoverable now. However, 

a modest increase in the price of oil may make oil 

shale yielding an average of 30 or more gallons of oil 

per ton competitive with crude oil, so resources of 

this grade were calculated. Resources in high-grade 

shale, in zones more than 100 feet thick, total 418 

billion barrels of oil (table 95) , or nearly one-quarter 

of the identified resources of 1.8 trillion barrels. The 

major part of these high-grade resources ( 355 bilTABLE 95.-Shale-oil resourc.es of the United States, in billions of barrels, by graile (oil yield) of oil shale 

[All resource figures except those for the Green River ForJ?l&tion are adapted from Duncan and Swanson, 1965, table 2; Ne, not estimated] 

Deposit 

Green River Formation, 

Colorado, Utah, 

and Wyoming ------------ Chatt nooga Shale and 

equivalent formations, 

Central and Eastern United States 

Marine ------------ shale, Alaska ------- Other shale deposits ---------

Identifiedl Hypothetical 2 Speculative 3 

25-100 10--25 25-100 16-25 25-100 10-25 

gal/ gal/ gal/ gal/ gal/ gal/ ton ton ton ton ton ton 

4 418 1,400 60 600 ---- ----

800 s~~!1 200 ---- ---- Small 250 200 ---- ---- ---- Small Ne Ne 600 23,000 

Total ---------------- '418 1,600 300 1,600 600 23,000 

1 Identified resources: Specific, identified mineral deposits that rna~ or may not be evaluated as to extent and grade, and . whost; ~ntamed 

minerals may or may not be profitably recoverable With exiSting technology and economic c•mditions. 2 Hypothetical resources: Undiscovered mineral deposits, w~ether of 

recoverable or subeconomic grade, that are geologically predictable as existing in known districts. a Speculative resources: Undiscovered miner&;l ~eposits, whet~er • of 

recoverable or subeconomic grade, that may exist 1D unknown districts or in unrecognized or unconventional for"?. . . , 4 The 25-100 gal/ton category is considered virtually equiva_ent to the 

category "average of 30 or more gallons per ton" 

lion bbl) is in the Piceance Creek basin of Colorado; 

the remainder is in the eastern part of the Uinta 

Basin of Utah (50 billion) and in the southeastern 

part of the Green River Basin of Wyoming (13 billion). About 80 percent of these resources (325 billion) has been well evaluated by core drilling; the 

remainder is based on data which are sparse, or less 

reliable. Because conservative estimates of thickness 

and grade were used in areas where data were 

sparse, it is possible that the drilling of more core 

holes will require an upward revision of these resource figures. 

The hypothetical resources of the Green River 

Formation are estimated to total about 650 billion 

barrels of oil, of which perhaps 50 billion barrels are 

in oil shales yielding 25-100 gallons of oil per ton. 

The synthetic-gas potential of oil shales of the 

Green River Formation has been investigated by the 

Institute of Gas Technology. Their data indicate that 

by using different processing methods, high-quality 

synthetic gas could be produced at the rate of 100 

cubic feet of gas for each gallon of shale oil that 

could be produced by a conventional retort, or 4,200 

cubic feet for each barrel of shale oil. Thus, the 

Green River Formation could he the source of an 

enormous amount of gas, instead of oil, if so desired. 

CHATTANOOGA SHALE AND EQUIVALENT FORMATIONS 

Most of the marine black shales in the United 

States yield so little oil hy conventional retorting 

(1-15 gallons of oil per ton) that it is difficult to 

consider them an economical resource of oil even for 

the distant future on this basis alone. However, many 

of the marine black shales have a high organic con-
OIL SHALE 501 

tent, and as a result 10-gallon-per-ton shale, when 

treated by alternative methods such as hydrogenation or synthetic gas in a retort, can be made to yield 

15-20 gallons of light oil per ton, or alternatively 

1,700-2,600 cubic feet of high-quality synthetic gas. 

A minimum thickness and grade of 5 feet of shale 

yielding an average of 10 gallons of oil per ton by 

conventional retort was adopted by Duncan and 

Swanson (1965, p. 13) for computing oil shale resources. The identified resources of 200 billion barrels of oil (table 95) are in formations of Devonian 

and Mississippian age in the Central and Eastern 

United States. (See Duncan and Swanson, 1965, fig. 

2.) They include resources in the central part of the 

eastern Highland Rim of Tennessee, where the Gassaway Member of the Chattanooga Shale averages 

15 feet in thickness, yields an average of 10 gallons 

of oil per ton, and contains an average of 0.006 percent uranium (Conant and Stansfield, 1968). Areas 

of New Albany Shale in Indiana and Kentucky include black shale zones 20-100 feet thick that yield 

an average of 10-12 gallons per ton and contain the 

major part of the resources. 

The hypothetical resources in the unexplored or 

little-sampled parts of this very widespread unit are 

estimated to total about 800 billion barrels of oil 

(Duncan and Swanson, 1965, p. 14). 

OTHER SHALE DEPOSITS 

In Alaska, oil shales are contained in rocks of 

mostly marine origin which underlie large areas in 

the north. These sequences range in age from Mississippian through Early Cretaceous, and consist 

dominantly of black shale, chert, and black organic 

limestone, except for the Cretaceous rocks which are 

dominantly sandstone and conglomerate (Donnell, 

Tailleur, and Tourtelot, 1967; Duncan and Swanson, 

1965, p. 14). Most of the area is complexly faulted 

and folded, and good exposures are rare in ~he 

tundra-covered slopes. Near the Nation River in 

eastern Alaska, outcropping Upper Triassic oil shale 

that is locally 200 feet thick is reported to yield 

about 30 gallons of oil per ton. On the north slope of 

the Brooks Range, exposures of Upper Triassic 

through Lower Cretaceous shale contain thin zones, 

less than 5 feet thick, of oil shale that yields as much 

as 160 gallons of oil per ton. Other zones, 20 feet or 

more thick, are known to yield an average of 15 

gallons of oil per ton. These shales also contain unusually high concentrations of trace elements such as 

silver, gold, and merucry. Because of the lack of 

data, identified resources of oil shale are extremely 

small, but Duncan and Swanson ( 1965, p. 14) estimated that hypothetical resources total ahout 450 

billion barrels of oil, of which about 250 billion barrels would be in high-grade oil shale. 

Beds of oil shale associated with coal are numerous in the United States, but they are generally thin 

and lean, or of small extent. Identified resourcesthose in carefully appraised deposits-are small. Hypothetical resources may be large. 

FOREIGN OIL-SHALE DEPOSITS 

Oil-shale deposits of Cambrian to Cenozoic age 

are abundant throughout the world in all types of 

depositional environments. The identified resources 

of shale oil in areas outside the United States total 

about 1.1 trillion barrels of oil (table 96). Most of 

the resources are in a few large groups of marine 

platform shale deposits, such as the Irati Formation 

of Permian age in Brazil, the Cambrian and Ordovician marine shale deposits in northern Europe and 

northern Asia, and the Jurassic deposits of western 

Europe and the Russian Platform, and in one large 

lacustrine deposit, the Triassic oil shales of central 

Africa (Duncan and Swanson, 1965; Duncan, 1967). 

Hypothetical resources total about 7.3 trillion barrels 

of oil, principally in the Irati Formation of Brazil, 

and in the Cambrian marine shale of northern Asia. 

Reviews of world occurrences are summarized by 

Duncan and Swanson (1965), Duncan (1967), and 

Smith, Smith, and Kommes ( 1959) ; deposits in the 

U.S.S.R. are described by Kotlukov (1968), and 

those in Brazil by Padula (1969). 

TABLE 96.-Shale-oil 'resources of the world (excluding the 

United Sta.tes) in billions of barrels, by grade (oil yield) 

of oil shale 

[All numbers are rounded; Ne, not estimated; from Duncan and Swanson 

1965, table 3] 

Identified 1 Hypothetical 2 Speculative a 

25-100 

Continents gal 

per 

ton 

Africa ------------------- 100 Asia --------------------- 90' Australia and New Zealand __ Small 

Europe ------------------- 70 North America (excluding 

United States) ---------- Small 

South TAmerica ------------ ..S.ntall 

otal --------------- 260 

10-25 25-100 10-25 25-100 gal gal gal gal per per per per 

ton ton ton ton 

Small Ne Ne 4,000 

14 2 3,700 5,400 

1 Ne Ne 1,000 

6 100 200 1,200 

Small 50 100 1,000 

. 80Q. N__e __ .u!W_. _.J.Q()_O. 

820 150 7,200 14,600 

10-25 

gal 

per 

ton 

80,000 

110,000 

20,000 

26,000 

23,000 

36..QQO 

295,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. 2 Hypothetical resources: Undiscovered mineral deposits, whether of 

recoverable or subeconomic grade, that are geologically predictable as existing in known districts. a Speculative resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that may exist in unknown districts or in unrecognized or 'Unconventional form. 

SPECULATIVE RESOURCES 

Speculative resources of shale oil in undiscovered 

deposits of shale were calculated by Duncan and 

Swanson (1965, p. 7) as follows: 
502 UNITED STATES MINERAL RESOURCES 

The United States is calculated to contain about 

2.4 million cubic miles of sedimentary rocks to a 

depth of 20,000 feet, of which 0:5 percent is assumed 

to be shale containing 10-65 percent organic matter 

and yielding 10-100 gallons of oil per ton. The total 

yield of oil is calculated to be about 28 trillion barrels., of which about 5 percent is assumed to be from 

shale yielding 25-100 gallons of oil per ton. From 

these figures are subtracted the identified and hypothetical resources to obtain the speculative resources. 

Similar calculations were made to obtain the speculative resource figures shown in table 96. 

Marine black shales are the primary source of the 

speculative shale-oil resources because they occur in 

large volumes in sedimentary basins all over the 

United States. Ordovician shales in New York, Illinois, Iowa, and Nevada are known to contain units 

that yield 10-25 gallons of oil per ton (Duncan and 

Swanson, 1965, p. 15). Permian deposits of black 

shale at some places contain 10-20 percent organic 

matter, but most samples yield little oil. In southwestern Montana, a Permian black shale may yield 

10-15 gallons of oil per ton in a 600-square-mile area. 

In California, Miocene marine shales underlie an 

area of 3,000 square miles and samples show a range 

in yield from 3-30 gallons of oil per ton. 

Carbonaceous shales associated with coal beds constitute a potentially large resource of shale oil because they occur throughout much of the United 

States. Duncan and Swanson (1965, table 2) estimated that these shales may yield 310 billion barrels 

of oil, of which 60 billion barrels would be from 

higher grade oil shale (25-100 gallons of oil per ton). 

Lacustrine deposits seem to be the best prospect 

for finding new shale-oil resources in high-yield oil 

shale because the best deposits currently kncwn are 

in the lacustrine Green River Formation of Eocene 

age. It is unlikely that any other deposit of the 

magnitude of the Green River Formation exists in 

the United States, because it required a unique set 

of conditions persisting for millions of years in extremely large shallow lakes. However, small highgrade deposits may be present in the numerous unexplored lacustrine deposits of Tertiary age in the 

Western United States (Feth, 1963), particularly in 

Montana, Nevada, and Wyoming (Duncan and Swanson, 1965, p. 16). 

PROSPECTING TECHNIQUES 

Oil shales can usually be recognized on the outcrop by their texture, color, and low specific gravity, 

but the evaluation of an oil-shale deposit requires 

core drilling to obtain unweathered samples that are 

representative of the buried deposit. Other techniques are available for use in a preliminary evaluation of a possible oil-shale deposit. If wells have been 

drilled through the deposit for other purposes, such 

as petroleum exploration, the cuttings of these wells 

can indicate the presence or absence of good oil 

shale. Geophysical logs of wells, such as sonic or 

density logs, can be used in some places in predicting 

the probable oil yield of the shales in the sedimentary sequence (Bardsley and Algermissen, 1963). 

For many years the U.S. Bureau of Mines has attempted to evaluate the oil-shale resources of the 

Green River Formation in Colorado, Utah, and Wyoming by collecting and assaying cuttings of wells. 

They were generally successful in indicating the 

boundaries of the oil-shale deposit and the approximate magnitude of the resources, but they found 

that individual sample sets could not be relied upon 

because of the possibility of contamination, or accidental enrichment, of the cuttings. 

In lacustrine deposits the richest oil shale is deposited in the center of the lakes, so a geologic 

evaluation of the outcropping rocks in a basin may 

point the way to the location of the depositional 

center of the deposit, and thus narrow the area of 

intensive search. 

PROBLEMS FOR RESEARCH 

Oil shale in the green River Formation contains a 

wide variety of unusual minerals but the amount 

and number are imperfectly known. Much exploration and research is needed to identify the minerals, 

to calculate the amount and extent of potentially 

valuable minerals, and to investigate the feasibility 

of recovering them as coproducts or byproducts in 

a commercial oil-shale mining and retorting operation. 

Research is also needed in solving the technological problems of extracting the oil at low cost 

and at minimum damage to the environment. Environmental problems associated with the extraction 

of shale oil by conventional retorting are magnified 

because of the large volume of rock that would be 

processed in a commercial operation. A plant producing 100,000 barrels of oil per day would probably 

mine about 130,000 tons of shale per day, and would 

require the disposal of a similar amount of spent 

shale. One problem would be to prevent the contamination of streams either by saline water encountered in mining, or by leaching of salts from 

spent shale. Other problems include the disposing 

of the spent shale and the revegetating of the spent 

shale if it is disposed of on the surface. 
OIL SHALE 503 

SELECTED REFERENCES 

Bardsley, S. R., and Algermissen, S. T., 1963, Evaluating oil 

shale by log analysis: Colorado School Mines Quart., 

v. 58, no 4, p. 178-184. 

Bradley, W. H., 1964, Geology of the Gre·en River Formation 

and associated Eocene rocks in southwestern Wyoming 

and adjacent parts of Colorado and Utah: U.S. Geol. 

Survey Prof. Paper 496-A, 86 p. 

1970, Green River oil shale-concept of origin 

extended: Geol. Soc. America Bull., v. 81, p. 985-1000. 

Brobst, D. A., and Tucker, J. D., 1973, X-ray mineralogy of 

the Parachute Creek Member, Green River Formation, 

in the northern Piceance Creek basin Colorado: U.S. 

Geol. Survey Prof. Paper 803. (In press.) 

CaEhion, W. B., 1964, The distribution and quality of oil 

shale in the Green River Formation of the Uinta Basin, 

Utah-Colorado, in Geological Survey Research 1964: U.S. 

Geol. Survey Prof. Paper 501-D, p. D86-D89. 

----- 1967, Geology and fuel resources of the Green 

River Formation, southeastern Uinta Basin, Utah and 

Colorado: U.S. Geol. Survey Prof. Paper 548, 48 p. 

Cashion, W. B., and Donnell, J. R., 1968, Oil shale and related deposits of Lake Uinta (Eocene), northwestern 

Colorado and northeastern Utah, U.S.A., [preprint] in 

United Nations symposium on the development and 

utilization of oil-shale reEources, sec. 1, 13 p. 

Conant, L. C., and Stansfield, R. G., 19,68, Oil shale, in 

U.S. Geological Survey and U.S. Bureau of Mines, Mineral resources of the Appalachian region: U.S. Geol. 

Survey Prof. Paper 580, p. 133-136. 

Culbertson, W. C., 1972, Oil shale in the Green River Formation, Green River basin, Wyoming: Mtn. Geologist, v. 9, 

nos. 2 and 3, p. 183-187. 

Donnell, J. R., 1961, Tertiary geology and oil-shale resources 

of the Piceance Creek basin between the Colorado and 

White Rivers, northwestern Colorado: U.S. Geol. Survey 

Bull. 1082-L, 57 p. 

----- 1964, Mineral fuels and associated resourcesOil shale, in Mineral and water resources of Colorado: 

U.S. Cong., 88th, 2d sess., p. 67-73. 

Donnell, J. R., and Blair, R. W., 1970, Resources appraisal 

of three rich oil-shale zones in the Green River Formation, Piceance Creek basin, Colorado: Colorado School 

Mines Quart., v. 65, no. 4, p. 73-87. 

Donnell, J. R., Culbertson, W. C., and Cashion, W. B., 1967, 

Oil shale in the Green River Formation: in World 

Petroleum Cong., 7th, Proc., v. 3, p. 699-702. 

Donnell, J. R., Tailleur, I. L., and Tourtelot, H. A., 1967, 

Alaskan oil shale, in Fourth symposium on oil shale: 

Colorado School Mines Quart., v. 62, no. 3, p. 39-43. 

Duncan, D. C., 1967, Geologic setting of oil-shale deposits 

and world prospects, in World Petroleum Gong. 7th, 

Proc., v. 3, p. 659-667. 

Duncan, D. C., and Swanson, V. E., 1965, Organic-rich shale 

of the United States and world land areas: U.S. Geol. 

Survey Circ. 523, 30 p. 

Feth, J. H., 1963, Tertiary lake deposits in western conterminous United States: Science, v. 139, no. 3550, p. 

107-110. 

Kotlukov, V. A., 1968, Geology and proEpects of studies of 

oil shale in the USSR, [preprint] in United Nations 

symposium on the development and utilization of oilshale l"e'sourc-es, s:ec. 1, 24 p. 

Linden, H. R., Tsaros, C. L., Feldkirchner, H. F., and Huebler, 

J., 1968, Pipeline gas from oil shale, [preprint] in 

United Nations symposium on the development and 

utilization of oil shale, sec. 3, 32 p. 

National Petroleum Council, 1972, An initial appraisal by the 

Oil Shale TaEk Group, 1971-1985, Supplementary report 

of a study titled U.S. Energy Outlook: An initial appraisal 1971-1985. 

Padula, V. T., 1969, Oil shale of the Permian Irati Formation, Brazil: Am. Assoc. Petroleum Geologists Bull., v. 

53, p. 591-602. 

Roehler, H. W ., 1969, Stratigraphy and oil-shale deposits of 

Eocene rocks in the Washakie basin, Wyoming, in 

Symposium on Tertiary rocks of Wyoming: Wyoming 

Geol. Assoc. Guidebook, 21st Field Conf., p. 197-206. 

Schramm, L. W., 1970, Oil Ehale, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 183-202. 

Serebryannikov, N. D., 1968, Production of town gas from 

oil shale, [preprint] in United Nations symposium on 

the development and utilization of oil-shale resources, 

sec. 3, 24 p. 

Smith, H. N., Smith, J. W., and Kommes, W. C., 1959, Petrographic examination and chemical analyses for several 

foreign oil shales: U.S. Bur. Mines Rept. Inv. 5504, 34 p. 

Swanson, V. E., 1960, Oil yield and uranium content of black 

shales: U.S. Geol. Survey Prof. Paper 356-A, 44 p. 

UNITED STATES MINERAL RESOURCES 

PEAT 

By CoRNELIA C. CAMERON 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

Classification ------------------------------------

The world peat industry -------------------------

The U.S. peat industry ---------------------------

Peat deposits ------------------------------------ Geologic and physiographic factors that control quality and quantity ------------------------------- Resource potential and outlook --------------------

References cited ---------------------------------

FIGURE 

Page 

505 

505 

506 

507 

507 

510 

511 

512 

513 

Page 

62. Ma.p showing peat mines in operation in 1971 __ 508 

TABLES 

Page 

97. Location of the world's peat resources, 1963___ 507 

98. World peat production in 1970 --------------- 507 

99. Peat produced in the United States in 1970, by 

type ------------------------------------ 509 

100. Production and commercial sales of peat in the 

United 8tates, by States, 1970 ------------ 509 

101. Peat moss imported for consumption in the 

United States, by grade and by country, 1970 509 

102. Commercial sales of peat produced in the 

United States, in 1970, by use ------------- 510 

103. Approximate magnitude of potential resources 

of peat estimated for each State ----------- 512 

ABSTRACT OF CONCLUSIONS 

Peat is no longer used as fuel in the United States. It is 

used for agricultural and horticultural purposes, and a demand is appearing for its use in environmental control. The 

physical characteristics of peat that are important to modern 

uses are related to the geologic and physiographic S·ettings 

of the deposits; therefore, research on methods of prospecting for peat focuses on establishing geologic controls for the 

types of peat defined in the classification adopted by the 

American Society for Testing and Materials in 1969. This 

new classification is designed principally to characterize different types of peat by means of such physical properties as 

amount, kind, and size of fibers and quantity of ash. One or 

more types of peat occur in all but about 8 of the 50 States 

in magnitudes ranging from hundreds of thousands to tens 

of billions of tons. 

The demand for specific physical qualities in peat related 

to modern uses and to standards for sales is largely respon-

.sible for national consumption of more peat than is produced 

domestically. In 1970, more than 525,000 tons of air-dried 

peat was produced and sold in the United States for almost 

$6,000,000 and 283,211 tons valued at $13,502,000 was imported, chiefly from Canada and West Germany. The forecast range of U.S. demand for peat in the year 2000 is from 

1,200,000 to 2,400,000 short tons. 

INTRODUCTION 

Peat consists of partly decayed vegetable matter, 

inorganic minerals, and water in varying proportions, the usual being 10 percent solid matter to 90 

percent water. Depending upon the amount of water 

contained, peat ranges from 0.1 to 1.6 in specific 

gravity and weighs 7-65 pounds per cubic foot. 

Hardly any two peat deposits contain material having the same physical properties. Differences are due 

mostly to the variety of plants from which peat is 

formed and to differences in climate, age of the 

deposit, water-level regime, and quantity of sediment deposited during accumulation of peat. Color 

ranges from light yellow through various shades of 

brown to jet black, the color representing a measure 

of the degree of decomposition of the peat. Peat 

that is newly exposed or has been well protected 

from the air is usually light yellow or brown. Welldecomposed humified peat is jet black. On drying 

in the air, most peat becomes lighter in color, except 

for very light varieties, which usually change to 

dark brown or black after being shredded and dried. 

One of the chief substances formed by plants 

during their growth is cellulose which consists 

largely of carbon, hydrogen, and oxygen. If plant 

debris falls upon drained soil, it is vigorously atU.S. GEOL. SURVEY PROF. PAPER 820 

505 
506 UNITED S~TATES MINERAL RESOURCES 

tacked by fungi and bacteria, and the carbon and 

hydrogen of the cellulose unite with atmospheric 

oxygen and with each other to form carbon dioxide, 

water, and marsh gas. If oxidation is unhampered, 

the organic material will disappear in a relatively 

short time. If, however, the plant falls into water or 

upon water-saturated soil where atmospheric oxygen is largely excluded, decay is slow, and if the 

plant debris becomes buried, a large proportion of 

the fixed oxygen is retained, and peat is formed. 

By this means, peat, which essentially has the composition Cs2H12024, forms from cellulose (Cr2H12o06o) 

by the elimination of hydrogen and oxygen as water 

(H20), carbon and oxygen as carbon dioxide (C02), 

and carbon and hydrogen as methane (CH4) (Soper 

and Osbon, 1922, p. 6-7). 

Peat is formed in swamps, bogs, or marshes under 

conditions favorable to the profuse growth of plants 

and to the accumulation of plant debris without 

complete decomposition by bacterial and chemical 

action. Climate, topography, and changes in position 

of the water table are the chief factors governing 

the formation and preservation of peat deposits. 

The quality of peat is determined by several factors. The rate and type of water inflow and drainage 

control the amount of inorganic material such as 

silt, sand, and gravel. Fluctuation of the water table 

permits air to come in contact with wet peat and 

causes rapid decomposition, leading to partial or 

complete destruction of plant fibers. Such fluctuation is greatest near streams and drainage ditches. 

If surface conditions are unchanged, carbonization 

is largely arrested, and peat forms; it may continue 

to exist indefinitely as peat unless the land is drained 

and decomposition begins, or unless it is deeply 

buried beneath sediments and subjected to pressure 

and heat to form coal. 

CLASSIFICATION 

For statistical purposes the U.S. Bureau of Mines 

has classified peat into three general types--moss 

peat, reed-sedge peat, and peat humus. Peat of 

sphagnum, hypnum, and other moss types is classified as moss peat, whereas peat of reed-sedge, shrub, 

and tree groups is classified as reed-sedge peat. Any 

peat so decomposed that the botanical identity is 

lost is classified as peat humus. This classification, 

however, does not adequately identify peat according to properties demanded by modern industry, 

properties which are based on the use of peat as a 

soil conditioner and horticultural material. 

Chief among these desirable properties is waterholding capacity, or the ability to reabsorb water 

after initial drying, like a sponge. Water-holding 

capacity, which is measured in percentage by weight, 

depends upon botanical character, the degree of 

decomposition, and the extent to which peat has 

dried. Ash content, also measured· in percentage by 

weight, consists of the solids remaining after a test 

portion of dry peat has been heated at 550°C. Ash 

content is therefore the reciprocal of organic content 

valuable to peat use. Fiber content refers to the 

proportion of stem, leaf, or other plant fragments 

between the sizes of 0.15 and 12.7 mm. 

To meet the need for a classification designed 

principally to characterize different types of peat 

on the basis of these and other useful properties, 

such as acidity and moisture content, a new classification was proposed by the American Society for 

Testing and Materials Committee D-29 Subcomrnittee I (Farnham, 1968); this classification was 

adopted in the form of ASTM Designation D2607-

69 (Am. Soc. Testing and Materials, 1969). According to this standard, "the term peat refers only to 

organic matter of geological origin, excluding coal, 

formed from dead plant remains in water and in 

the absence of air. It occurs in a bog, swampland, 

or marsh, and has an ash content not exceeding 25 

percent by dry weight." The classification lists five 

major plant types according to genesis and fiber 

content. Percentages of fiber are based on ovendried weight at 105°C., not on volume. The five 

types are: (1) Sphagnum moss peat, in which the 

oven-dried peat contains a minimum of 662;3 percent 

recognizable Sphagnum moss fiber; (2) Hypnum 

moss peat, in which the oven-dried peat contains a 

minimum of 33¥3 percent fiber, of which at least 

half is Hypnum moss fibers; (3) Reed-sedge peat, 

in which oven-dried peat contains a minimum of 

33¥3 percent fiber, of which at least half is reedsedge and other non-moss fibers; ( 4) Peat humus, 

in which oven-dried peat contains less than 33¥3 

percent fiber; and (5) Other peat, which includes all 

other forms of peat· not classified in ASTM Designation D2607-69. 

As part of the research leading to the formulation of this new classification, analyses were 

made of 191 representative samples of peat sold in 

the United States (Farnham, 1968, p. 89). Sphagnum 

moss peat samples had the highest fiber contents 

and generally the lowest ash content and pH. Also, 

except for a few artificially dried materials, the 

water-holding capacities were well over 1,000 percent. The hypnum moss peat samples were much less 

acid but had slightly higher ash contents. Reed-sedge 

peat samples differed in pH and ash contents and 

had medium fiber contents and water-holding capacities. Peat humus samples were very low in fiber 
PEAT 507 

content and water-holding capacity, a condition 

which is indicative of a high degree of decomposition. 

THE WORLD PEAT INDUSTRY 

Peat bogs are estimated to make up about 375 

million acres of the world's land surface. (Tibbetts, 

1968, p. 8). Almost 80 percent of this peatland is 

within the boundaries of the U.S.S.R., Finland, and 

Canada, more than 60 percent being in the U.S.S.R. 

alone. According to information available in 1963, 

the rest of the world's resources are largely in the 

United States, East and West Germany, Great 

Britain and Ireland, Sweden, Poland, Indonesia, Norway, Cuba, Japan, Denmark, Italy, and France (table 

97). 

TABLE 97.-Location of the world's peat resources, 1969 

[Souree: Tibbetts, 1968] 

Pef'centage 

of wMld f'eBOUf'CeB 

u.s~s.R. --------------------------- so.8 

Finland ---------------------------- 9.5 

Canada ---------------------------- 9.1 

U.S.A. ----------------------------- 5.0 

Gennany (East &·West) ------------- 3.5 

Great Britain and Ireland ------------ 3.5 

Sweden ---------------------------- 3.4 

Poland ----------------------------- 2.3 

Indonesia -------------------------- 0.9 

Norway ---------------------------- .7 

Cuba ------------------------------- .3 

Japan ----------------------------- .2 

Denmark -------------------------- .08 

Italy ------------------------------ .08 

France ---------------------------- .08 

Other countries --------------------- .56 

On the basis of available information, the U.S.S.R. 

accounts for 95 percent of the world's peat production, which was estimated in 1970 to be more than 

217 million short tons per year, an increase of 7 

percent over the estimated world output for 1969 

(Sheridan, 1971b). Production by countries in that 

year is listed in table 98. Although fourth in world 

production after the U.S.S.R., Ireland, and West Germany, the United States produced only 0.2 percent 

of the world total in that year. 

Only about 32 percent of the world's peat production is used for fuel, much of this being used for 

the generation of electric power, chiefly in the 

U.S.S.R. and Ireland. The generating capacity of 

present peat-fired power plants in Ireland is 387.5 

megawatts. Some peat is used in West Germany 

and Finland for fuel, but this use is declining. 

Most of the remaining 68 percent of the world's 

peat production is used for agricultural purposes; 

various grades of peat are produced for the amelioration of mineral soils. Other uses of peat include 

TABLE 98.-World peat production in 1970 

[Source: Sheridan, 1971b] 

U.S.S.R. -------------------------- Ireland --------------------------- West Gennany -------------------- United States --------------------- Netherlands ----------------------- Canada --------------------------- Finland --------------------------- Sweden --------------------------- France --------------------------- Japan ---------------------------- F.lungary ------------------------- Israel ---------------------------- Poland --------------------------- Norway -------------------------- ]{orea ---------------------------- Denmark ------------------------- Total ------+----------------

Thousand 

shMt 

tons 

206,462 

7,566 

1,467 

517 

440 

317 

255 

138 

80 

80 

72 

22 

22 

17 

10 

6 

217,471 

horticultural applications, as in the United States, 

Canada, and most countries of Europe; the manufacture of thermal insulating materials and chemicals in the U.S.S.R.; the making of peat planting 

pots in Norway, Denmark, Ireland, Czechoslovakia, 

Poland, and Japan; the production of activated carbon in the Netherlands; the distilling of whisky in 

Scotland; and uses in health spas, curative water, 

cosmetics, and tonics in Austria. 

THE U.S. PEAT INDUSTRY 

The use of peat in the United States for agricultural purposes began about 1904, when 12 companies produced a few thousand tons of peat annually. 

By 1971, peat was being extracted at 122 operations, 

where 120 companies produced 516,825 short tons 

(Sheridan, 1971a). In 1971, peat was produced in 

24 States (see fig. 62), but 8 States bordering the 

Great Lakes had more than half the active pits. 

Michigan, with 20 had the largest number of operations, followed by Colorado, with 15; Ohio and Pennsylvania, with 11 each; Washington, with 9; and· 

Florida and Minnesota, with 8 each. Thirty-seven 

plants produced moss peat, 39 plants produced reedsedge peat, and 33 plants produced humus. In addition to plants producing these types of peat, 13 

plants produced two or all three types. Peat produced in the United States in 1970, by types, is 

shown in table 99. 

Commercial sales of peat for 1970 totaled 525,603 

short tons valued at $5,986,000, averaging $11.39 

per ton (Sheridan, 1971a). Table 99 shows production of peat by types, and table 100 shows production 

and sal~s of peat by States in 1970. In addition, 

283,211 short tons valued at $13,502,000 were imported, chiefly from Canada and West Germany, as 

shown in table 101. 
* Alaska falls in the highest order of magnitude. 

Hawaii falls in the lowest order of magnitude 

--------------)-----.------

i 

i Morv r"' 1q NORTH DAKOTA 

~ ··-----·------ ------------~ I I 

: i 

--- ! j-------------------,., 

,. ______ ,_____ : \ 

: y-- I "'""' , I : : ! -- : I ---•----, \ 

SOUTH DAKOTA 

I 

I : 1---------- ' ------~, \ 

( ... .,, ' ' ' 

· I I I 

\ ' '" ' "'"' ' •, i i i 

\\ ;L_____ -----r~·-=:.-------------~-------- . , I I "'""''' , \ r- , : i 

\~ I ! ' 

/ ' ' "'"" I ' "------~ .. -.......... ---~, I j ' I : ! ---'"' I i ,........_ : 0 

EXPLANATION ',,'' .. , ! -----.!:-------.. -- '----~--1 Tonnage magnitude within State * 

Hundreds of thousands ( I 05 ) 

Millions (I 06 ) 

Tens of millions (107 ) 

Hundreds of millions (I 08 ) 

Billions (109 ) 

Tens of billions (I 010 ) 

Location of peat mine 

Reliability: Good from Maine to Minnesota and 

Florida 

Fair for onshore coastal areas and 

Western States 

Poor for offshore coastal areas 

TEXAS 

0 100 200 300 400 MILES 

0 100 200 300 400 KILOMETERS I •• 1 I I I 

FIGURE 62 .-Peat mines in operation in 1971 and estimated resources in short tons of air-dried peat suitable for commercial use. 

~ 

~ 

z 

~ 

1-3 

tzJ 

t1 

~ 

> 1-3 

tzJ 

tJl 

a: 

~ 

z 

tzJ 

~ 

~ 

~ 

tzJ 

00 

0 

c::: 

~ 

c 

tzJ 

00 
PEAT 

TABLE 99.-Peat produced in the United States in 1970, by type 

[In short tons. Source: U.S. Bur. Mines; Sheridan, 1971b] 

Processed 

Type Unprepared Shredded Kiln-dried Shredded and 

only only kiln-dried 

Moss ----------------- 48,718 79,161 2,135 

Reed-sedge ------------ 26,486 223,374 750 

Humus --------------- 41,925 90,633 3,643 

Total ----------- 117,129 393,168 4,393 2,135 

Total 

130,014 

250,610 

136,201 

516,825 

TABLE 100.-Production and commercial sales of peat in the United States, 

by States, 1970 

[W, withheld to avoid disclosing individual company confidential data; included in total. 

Source: U.S. Bur. Mines; Sheridan, 1971b] 

Commeroial sales 

Active Production Value 

State plants (short tons) 

Short tons Total Averqe 

(thousands) per ton 

California ------------ 3 9,792 9,792 w w 

Colorado ------------- 1 15 34,240 34,499 $210 $6.08 

Florida -------------- 8 45,743 45,742 304 6.65 

Georgia -------------- 1 432 432 w w 

Idaho ---------------- 1 w w w w 

Illinois --------------- 6 w w w w 

Indiana -------------- 5 w w w w 

Iowa ----------------- 2 w w w w 

Maine ---------------- 23 1,223 1,000 39 39.00 

Maryland ------------ 2 4,588 3,633 47 12.94 

Massachusetts -------- 1 2,000 2,000 30 15.00 

Michigan ------------- 1 20 156,699 166,950 1,896 11.36 

Minnesota ------------ 8 13,948 13,377 335 25.04 

Montana ------------- 1 w w w w 

New Jersey ----------- 4 45,260 45,260 557 12.30 

New Mexico ---------- 1 500 500 7 13.00 

New York ------------ 5 15,325 14,525 145 9.98 

North D-akota --------- 1 w w w w 

Ohio ----------------- 11 6,357 6,357 95 14.94 

Pennsylvania --------- 11 49,284 43,793 517 11.81 

South Carolina -------- 1 w VT w w 

Vermont ------------- 1 338 244 6 24.59 

W~hin!fton ---------- 9 16,625 16,625 71 4.27 

Wt·sconsm ------------ 2 1,581 1,650 w w 

Total ---------- 122 516,825 525,603 5,986 11.39 

1 Excludes one plant which had sales, but no production. ll Includes one plant which had production, but no sales. 

TABLE 101.-Peat moss imported for consumption in the United States, 

by grade and by country, 1970 

[Source: U.S. Bur. Mines; Sheridan, 1971b] 

Poultry and stable 

grade Fertilizer grade Total 

Oountry 

Short Value Short Value Short Value tons (thousands) tons (thousands) tons (thousands) 

Belgium-Luxembourg 

Canada -------------------- Finland -------------------- Germany, West ------------- Ireland -------------------- Japan --------------------- Mexico -------------------- Norway ------------------- Poland --------------------- Spain ---------------------- Sweden -------------------- United Kingdom ------------

Total ----------------

1 Less than ¥.a unit. 

1,679 

7 

86 

4 

6 

$94 

(1) 

3 

3 

4 

22 

267,944 

9,919 

960 

30 

24 

7 

1,950 

7 

449 

117 

(1) 

$12,792 

429 

46 

2 

1 

4 

88 

5 

22 

9 

22 C> 

269,623 $12,886 

7 (1) 

10,005 432 

964 49 

30 2 

24 1 

13 8 

1,950 88 

7 5 

449 22 

117 9 ----------------------------------------------------- 1,782 104 281,429 13,398 283,211 13,502 

509 
510 UNITED STATES MINERAL RESOURCES 

All humus and reed-sedge and some moss peat 

production is from surface pits, and most operations 

use conventional types of excavating and earthmoving machinery, including bulldozers, draglines, 

and front-end loaders in drained bogs, and clamshells 

and dredges for submerged deposits. Use of specialized machines for cutting sphagnum moss is 

replacing the ancient practice of hand cutting sphagnum moss blocks, especially in large bogs in Maine. 

Peat is prepared for sale by shredding and screening; some is dried artificially. 

Before 1955, most domestic peat was sold locally 

in bulk, but since then, large quantities have been 

packaged and distributed to all parts of the United 

States. Prices of domestic peat vary greatly; in 

general, the sales value depends chiefly on the type 

of peat, the degree of processing, and whether the 

peat is sold in bulk or packages. In 1970, the average value of bulk peat was $8.13 per ton, $0.46 more 

than the average value of bulk peat sold in 1969. 

Packaged peat, however, declined in average value 

from $17.60 per ton in 1969 to $14.51 per ton in 

1970. Commercial sales of peat in the United States 

in 1970 are shown in table 102. 

TABLE 102.-Commercial sales of peat produced in tke United States in 1970, by use 

[Source: U.S. Bur. Mines; Sheridan, 1971b] 

In bulk In packages Total 1 

Quantity Quantity Quantity 

Use (Short tons, Value (Short tons, Value (Short tons, Value 

thousands) (thousands) thousandfl) (thousands) thousands) (thousands) 

Soil improvement ------------ 193 $1,616 257 $3,421 450 $5,038 

Potting soils ----------------- 14 118 6 221 20 338 

Packing flowers, shrubs, etc. __ 40 298 2 37 42 336 

Seed inoculant --------------- 3 206 2 206 

Jdushroom beds -------------- 3 29 C> (1) 3 29 

Earthworm culture ---------- 1 9 (1) 2 1 11 

Jdixed fertilizers ------------- 6 27 6 27 

Total 11 

---------------- 258 2,098 268 3,888 526 5,986 

1 Less than % unit. • Data may not add to totals shown because of independent rounding. 

Although the average value of imported peat is 

more than three times that of domestically produced packaged peat, the two are not comparable 

because they are assigned at different marketing 

levels. Also, imported peat has different physical 

properties and is usually sold by volume rather than 

by weight. Each 100 pounds of typicalair-dried imported peat measures approximately 12 bushels, 

whereas the same quantity of a typical domestic 

peat measures 3 or 4 bushels. Only a few U.S. peat 

operators produce peat with properties similar to 

those of the imported type. 

The quantity of peat imported into the United 

States in 1970 decreased 6 percent from that imported in 1969, mainly because of decreased shipments from Canada. European shipments to the 

United States decreased 9 percent, mainly because 

of the smaller quantities shipped from Ireland and 

Poland. Shipments from West Germany supplied 

almost three-fourths of the peat imported from 

Europe. 

PEAT DEPOSITS 

Soper and Osbon (1922) recognized three general 

types of peat deposits, according to topography. 

These include the filled basin, in which peat accumulates in marshes, ponds, and lakes; the built-up 

deposit and its corollary, the climbing bog, in which 

peat forms on flat or gently sloping moist areas not 

covered with water; and the composite area consisting of built-up peat underlain by peat of the 

filled-basin type. 

The filled-basin type is predominant. Beginning 

at the center of basins filled with water and proceeding shoreward, the usual sequence of vegetation 

is algae, pondweeds, water lilies, bullrushes, and 

amphibious sedges. Sphagnum and heath shrubs 

sometimes grow on the marginal zones and are 

abundant on the quaki"ng bogs of the Northern 

States. Adjoining zones of vegetation usually overlap, and some zones may be absent. Unless the 

water is shallow enough to permit plants to take 

root, fine-grained algal peat is normally at the bottom of filled-basin deposits and is overlain by strata 

of reed, sedge, and grass peat. Fire, drought, and 

drainage, however, may prevent formation of successive growth and decay of plant associations, and 

changes in the surface water from alkaline to acid 

may also affect composition of flora. 

Salt-marsh peat fills basins in much the same 

manner as fresh-water peat but differs from it 

somewhat in character. Because few seed plants 

tolerate salt water, the number of plant varieties in 

salt marshes is small. Salt-marsh peat is composed 
PEAT 511 

of salt-marsh grasses, rushes, and sedges. In some 

of the coastal marshes, salt-marsh peat is underlain 

by peat of fresh-water origin, indicating subsidence 

of part of the coast. 

Built-up deposits consist of moss and heath, overlain by tamarack-spruce in the north and by gumcypress in parts of the Atlantic and Gulf coastal 

regions. The ground water level, although it may 

never rise above the surface, is progressively elevated as the peat collects. Surface conditions are 

little changed from year to year; hence, built-up 

bogs are relatively homogeneous. 

When a basin is filled with peat to the level of the 

surrounding country, it is mature, and if moisture 

is sufficient, the build-up process begins ; the deposit 

develops as if it had originated on a relatively level 

land surface not covered with peat. The result is 

a composite peat deposit which may accumulate to 

a thickness of many feet above the former level of 

the basin. Composite areas are recognized by marked 

changes in the character of the peat where the 

pondweeds, water lilies, and sedges were displaced 

by moss and heath plants. 

As the formation of peat depends upon many 

factors, the rate of its accumulation varies widely 

from place to place and from year to year. If climate, 

topography, and vegetation are favorable, peat forms 

rapidly, as in a few sphagnum bogs along the coasts 

of Maine and Alaska, but if one of these factors 

becomes relatively unfavorable, the rate of accumulation is retarded or brought to a stop, or destruction 

of the deposit may set in. Most if not all peat deposits that formed during the Pleistocene were 

erased by weathering or erosion, so that the present 

deposits, all of Holocene age, may lie on truncated 

remnants of older cycles of peat development. An 

age of about 13,000-14,000 years is about the maximum for a commercial peat deposit. Unlike timber 

stands, most peat deposits in the United States are 

not renewable. 

The major peat deposits in the conterminous 

United States occur (1) north of the 41st parallel 

and east of the 97th meridian in all the New England 

States, Illinois, Indiana, Iowa, Michigan, Minnesota, 

New Jersey, New York, Ohio, Pennsylvania, and 

Wisconsin; (2) in the Atlantic and Gulf coastal 

regions; and (3) in the western mountains and 

coastal areas including parts of Washington, Idaho, 

Montana, Oregon, California, Wyoming, Utah, Colorado, Arizona, and New Mexico. 

In the northeastern and north-central region, peat 

has accumulated chiefly in former lakes and ponds 

in glacial terrain. Built-up deposits of sphagnum 

moss peat are largely restricted to the cool humid 

northern parts of the Midwest and New England. 

The Atlantic and Gulf coastal regions are characterized by many salt- and fresh-water marshes and 

swamps ; the peat deposits occur principally in 

valleys and lagoons on a gradually subsiding coastal 

plain. This peat is made up mostly of salt-marsh 

grasses and other salt-water plants. However, many 

deposits also have an underlayer of peat formed 

from fresh-water plants. This layer was deposited 

before the basin was invaded by salt water. 

Peat deposits of the West (Jennings, 1966, p. 288; 

Cameron, 1968; Huntting, 1966; Savage, 1964) are 

in basins in glaciated mountains and plains, in tidal 

plains, and in river plains. 

The cool moist climate and irregular terrain of 

Alaska favor the formation of all types of deposits, 

but especially the built-up sphagnum moss type. 

Small pockets of peat occur in high volcanic uplands 

in Hawaii. 

GEOLOGIC AND PHYSIOGRAPHIC FACTORS 

THAT CONTROL QUALITY AND QUANTITY 

The minimum size of a peat deposit worth exploiting in the United States differs from place to place. 

In the glaciated areas of the North, West and 

Northwest, and in broad coastal marshes elsewhere, 

peat deposits now exploited are at least 10 acres in 

areal extent and have at least a 5-foot thickness of 

commercial-quality peat. Tonnage in peat deposits 

is calculated on the basis of 200 tons of air-dried 

peat per acre-foot. 

On the basis of these criteria, high-quality sphagnum moss peat may be expected in large raised bogs 

in New England, especially in Maine, and in northern Minnesota. Most of the peat in the United States, 

however, is reed-sedge, humus, and other types deposited largely in basins. The quality and quantity 

of these deposits are dependent upon constant factors such as size, shape, and composition of the 

depression containing the deposit, and upon varying 

factors such as climate and surface- and groundwater drainage. Cameron (1970a, b, c), working in 

the glaciated areas of Pennsylvania and New York 

and the unglaciated uplands of West Virginia, Maryland, and Pennsylvania, listed relationships of these 

factors significant to resource potential of peat deposits as follows: 

1. Peat deposits enclosed within a bedrock basin 

tend to have a higher percentage of fibers longer 

than 0.15 mm than those deposits surrounded by 

unconsolidated material. Relationship of peat quality to kind of material composing the surrounding 

area and the walls of the depression in which accumulation of peat took place involves several aspects, 
512 UNITED S·TATES MINERAL RESOURCES 

such as water-transmitting characteristics, solubility, resistance to erosion, and degree of weathering 

of the material next to the peat. 

2. Within unconsolidated material, peat deposits 

larger than several acres in areal extent tend to 

have lower ash content and a higher percentage of 

fibers longer than 0.15 mm than do similar smaller 

deposits. 

3. Peat deposits in depressions with high steep 

walls tend to be thicker than deposits in depressions 

with low gently sloping walls. Steep walls favor 

rapid build-up of marsh-type vegetation above the 

original pond-surface level and at the same time 

delay development, along the margins of the depression, of soil conditions that initiate transgression of 

a forest, which slows and eventually stops peat 

formation. 

4. Peat deposits accumulated in depressions with 

high steep stable walls are apt to have lower ash 

content than deposits in depressions with unstable 

walls. 

5. Peat deposits in depressions having small 

drainage basins tend to contain less clay, sand, and 

silt than do deposits in depressions having larger 

drainage basins. The ratio of effective drainage area 

to area of peat accumulation in more than 100 deposits in northeastern Pennsylvania showed that if 

the sediment-producing area is more than 10 times 

the size of the area of peat accumulation, the ash 

content of the peat is apt to be greater than 25 

percent. 

6. Peat deposits accumulating in a cool, moist 

climate are thicker and have lower ash content than 

deposits accumulating in a cool, dry climate. Humidity is the controlling factor in growth of peatproducing plants and preservation of plant structures. 

7. Peat deposits protected topographically from 

stream flooding are apt to have lower ash content 

than deposits subject to flooding. Two common 

causes of flooding are increased precipitation and 

ponding resulting from landslides or beaver activity. 

8. Peat deposits subject to water-table fluctuation 

caused by (a) artificial drainage, (b) drainage 

caused by breaching of dams on adjacent streams, 

or (c) lumbering operations and extensive forest 

fires, which extinguish springs and seeps, have 

higher ash content and a lower percentage of fibers 

longer than 0.15 mm than do deposits not subject 

to water-table fluctuation. This is because a deposit 

saturated with ground water is relatively free from 

aerobic bacterial activity which decays vegetable 

matter. When the water table falls, permitting oxygen to enter the deposit, decay increases ash content by destroying plant fibers. 

RESOURCE POTENTIAL AND OUTLOOK 

The latest nationwide study of the occurrence and 

use of peat was by Soper and Osbon in 1922 ; emphasis was on potential use as fuel, and deposits were 

not appraised with the restrictive criteria of present 

use. Moreover, since 1922, many peat deposits have 

been destroyed, and many new areas probably containing much peat have been made accessible by 

modern roads. Therefore, the 14 billion tons estimated by Soper and Osbon is no longer realistic for 

peat that meets the ash and fiber-size specifications 

of modern uses. Measurement of such resources in 

unexploited deposits is only just beginning. The 

data on figure 82 and table 103, although based on 

very scanty quantitative information and little 

known geologic and physiographic controls, are an 

attempt to approximate the magnitude of potential 

resources for each State. 

TABLE 103.-Approximate magnitude of potential resources 1 

of peat estimated for each State 

[Distribution shown on fig. d] 

State 

Short tons of 

air-dried peat 

Del~w~n:· Hawaii, Maryland, North Dakota, West 

V1rg1n1a ---------------------------------- 10 5 

Illinois, Iowa, Rhode Island, South Dakota ------ 10 8 

Alabama, Arizona, Connecticut, Indiana, Louisiana, Massachusetts, Missi-ssippi, New Hampshire, New Jersey, New Mexico, Ohio, Pennsylvania, Texas, Vermont ---------------------- 10 7 

California, Colorado, Georgia, Idaho, M.aine, 

Montana, New York, North Carolina, Oregon, 

South Carolina, Utah, Virginia, Washington, 

Wyoming ---------------------------------- 10 8 

Florida, Michigan, Wisconsin ------------------ 10 9 

Alaska, Minnesota ---------------------------- 10 10 

1 Potential resources: Identified mineral deposits not profitably recov- erable with existing technology and economic conditions, and undiscovered mineral deposits whether of recoverable or subeconomic grade. 

Refinements in prospecting for deposits in these 

States will result from close coordination of physicalproperty requirements, given in the recent ASTM 

peat classification, with the geologic and physiographic factors that control quality and quantity. 

Although the present physical-property requirements are largely for agricultural uses, they are 

much the same as those for the growing use of 

peat in environmental control. For example, D'Hennezel and Coupal (1972) have shown that moss peat, 

because of its very high water-holding capacity, can 

be used on a large scale in combating pollution 

caused by oil spills from offshore drilling and from 

freighters and barges. 

Extensive research by the Department of Chemical Engineering of the University of Sherbrooke, 

Quebec, Canada, has revealed the high efficiency of 
PEAT 513 

moss peat in the filtration of pigments and dyes in 

wastes from textile plants, and of mercury and other 

metals in wastes from other industrial plants; moss 

peat is 20 to 30 times cheaper than activated charcoal presently used as a filtering agent. 

Moss peat can now be used for the manufacture 

of activated carbon, as a binder for pelletizing ironore concentrates, and for manufacture of concretes 

used as lightweight thermal and sound insulators. 

Decarlo (1970) forecasted that the national demand for peat for the year 2000 will reach 1,200,000 

to 2,400,000 short tons. 

REFERENCES CITED 

American Society for Testing and Materials, 1969, D2607-69, 

Standard classification of peats, mosses, humus, and related products: Philadelphia, Pa., 1 p. 

Cameron, C. C., 1968, Peat in Mineral and water resources of 

Oregon; U.S. Cong., 90th, 2d Sess., Comm. Interior and 

Insular Affairs, Comm. Print, p. 218-222. 

1970a, Peat deposits of northeastern Pennsylvania: U.S .Geol. Survey Bull. 1317-A, 90 p. 

---- 1970b, Peat deposits of southeastern New York: 

U.S. Geol. Survey Bull. 1317-B, 32 p. 

---- 1970c, Peat resources of the unglaciated uplands 

along the Alleghany structural front in West Virginia, 

Maryland, and Pennsylvania: U.S. Geol. Survey Prof. 

Paper 700-D, p. D153-D161. 

D'Hennezel, F., and Coupal, B., 1972, Peat moss: A natural 

absorbent for oil spills: CIM Bull., v. 65, no. 717, p. 

51-53. 

Decarlo, J. A., 1970, Peat in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 137-146. 

Farnham, R. S., 1968, Classification system for commercial 

peat: Internat. Peat Cong., 3d, Quebec, Canada, Proc., 

p. 85-90. 

Huntting, M. T., 1966, Peat in Mineral and water resources 

of Washington: U.S. Cong., 89th, 2d Sess., Comm. Interior and Insular affairs, Comm. Print, p. 235-240. 

Jennings, C. W ., 1966, Peat, in Mineral and water resources 

of California: U.S. Cong., 89th, 2d Sess., Comm. Interior and Insular Affairs, Comm. Print (California 

Div. Mines and Geology Bull. AI), p. 288-291. 

Savage, C. N., 1964, Mineral resources-Peat, in Mineral 

and water resources of Idaho: U.S. Cong., 88th, 2d Sess., 

Comm. Interior and Insular Affairs, Comm. Print, p. 

143-145. 

Sheridan, E. T., 1971a, Peat producers annual, U.S. Bur. 

Mines: Washington, D.C., U.S. Govt. Printing Office, 

9 p. 

·---- 1971b, Peat, in U.S. Bur. Mines, Minerals Yearbook, 1970: Washington, D.C., U.S. Govt. Printing Office, 

preprint, p. 1-8. 

Soper, E. N., and Osbon, C. C., 1922, The occurrence and uses 

of peat in the United States: U.S. Geol. Survey Bull. 

728, 207 p. 

Tibbetts, T. E., 1968, Peat resources of the world-A review: 

Internat. Peat Cong., 3d, Quebec, Canada, Proc. p. 8-9. 

UNITED STATES MINERAL RESOURCES 

PHOSPHATE DEPOSITS 

By jAMEs B. CATHCART and R. A. GULBRANDSEN 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Exploitation ------------------------------------- Geochemistry ___________ --________ - _ -------------

Types of deposits --------------------------------

Igneous apatites -----------------------------

Guano and related deposits -------------------

Sedimentary phosphorite ----------------------

Deposits caused by divergence upwelling of 

sea water ----------------------------- Deposits formed in warm currents along 

eastern coasts ------------------------- Deposits formed on stable shelves or in continental interiors ----------------------

Concentration and enrichment of marine deposits --------------------------------- Other types of phosphate deposits -------------

Resources --------------------------------------- Identified and hypothetical resources -----------

Sedimentary phosphorite -----------------

lJnited States ------------------------

Latin America ----------------------

Africa and the Near East ------------

Asia -------------------------------- Australia ----------------------------

Guano and related deposits ---------------

Igneous apatites -------------------------

Speculative resources -------------------------

Prospecting techniques ---------------------------

Problems for research ---------------------------- Selected bibliography ____________________________ _ 

TABLES 

ABSTRACT OF CONCLUSIONS 

Phosphorus, an element essential to plant growth, is found 

in igneous apatite, guano or related deposits, and marine 

Page phosphorite. Most of the lJnited States' and the world's 

515 reserves and resources are in the marine phosphorite de515 posits which also account for about 75 percent of the total 

516 production. 

517 Marine phosphorite deposits, known throughout the world 

517 in rocks ranging in age from Precambrian to Holocene, 

517 form in basins away from sources of abundant clastic ma518 terial in warm latitudes in areas of upwelling water. 

518 Because most of the sedimentary basins are known and 

phosphate occurs in many of them, resources are classed as 

518 identified or as hypothetical. ·speculative resources form only 

a minor part of the total. However, identified resources of 

519 the world are measured in billions of tons of contained 

phosphorus and hypothetical resources are probably many 

519 times as great. 

A major factor of concern is the transportation of a bulk, 

520 low-value product to areas of use. Many problems, however, 

520 remain to be solved, particularly in the accurate delineation 

520 of reserves in the large areas of probable hypothetical re520 sources and in the mining and beneficiation of deeply buried 

520 and low-grade resources. 

520 Environmental problems attendant upon open-pit mining 

522 and chemical processing must be solved. Failure to solve 

522 these problems in the lJnited States may lead to drastic 

522 changes in the traditional supply patterns of phosphate rock 

522 in the world. 

522 Phosphate rock contains abundant fluorine and potentially 

522 economically recoverable amounts of vanadium, uranium, 

522 and the rare earths. Trace metals necessary to plant growth, 

523 such as boron, copper, molybdenum, manganese, and zinc are 

523 present in phosphate rock, are removed during chemical 

525 processing, and are readded to make a complete fertilizer. 

Chemical research on problems of recovery of minor elements 

and the retention in chemical fertilizer of the trace metals 

is needed. 

INTRODUCTION 

Page Phosphorus is one of the three elements vital to 

104. Marketed production of phosphate rock in the plant growth, but it tends to be less abundant than 

lJnited States in each lOth year of the period the other two (nitrogen and potassium), particularly 

1870 to 1970, and total production through in soils that have been extensively cropped or in 

105. p~:s~hat;-~~~~~~;-~f-th~-u~it;d--S;;~;-==== :~~ tropical soils that are thoroughly leached by acid 

106. World phosphate resources ------------------ 521 ground water. 

U.S. GEOL. SURVEY PROF. PAPER 820 

515 
516 UNITED STATES MINERAL RESOURCES 

About 70 percent of the domestic consumption of 

phosphate rock is in fertilizers, and the major use 

will continue to be in fertilizers because there is no 

substitute for phosphorus as a plant food element. 

Other uses are many; they include animal feed supplement, detergent, electroplating and polishing of 

metals, insecticides, medicines, and incendiary 

bombs. 

Phosphate fertilizers are used extensively in the 

developed countries, but are used sparingly or not at 

all in some of the less developed countries. Production of agricultural materials is limited by deficiency 

in plant nutrients, and chemical fertilizers, including 

phosphorus, are vital to the production of adequate 

food in the world. 

Phosphorus is found in minable concentrations in 

three principal environments-guano or deposits derived from guano, igneous apatites, and marine phosphate deposits. Other types of concentrations such 

as phosphatized rock, residual phosphate, and river 

pebble deposits are secondarily derived. 

All types of deposits are found in the United States 

and are widely distributed areally and geologically. 

Occurrences of phosphate rock are known from almost all geologic eras from Precambrian to Cenozoic, 

and in almost all of the States, but in 1971, phosphate 

rock was produced only from Ordovician rocks in 

Tennessee and Alabama; from Permian rocks in 

Idaho, Montana, Utah, and Wyoming; and from 

Miocene and Pliocene rocks in Florida and North 

Carolina. Some production from the Miocene of California is included in the totals for the Western 

States. Production in 1971 was about 38 million 

short tons, of which 83 percent was from Florida 

and North Carolina, 11 percent from the Western 

States, and 6 percent from Tennessee. About 27 million tons was used domestically ; the rest was 

exported. 

Reserves of phosphate rock in Florida, North 

Carolina, and the Western States are measured in 

billions of tons in each area ; Tennessee reserves are 

in millions of tons. These reserves can supply domestic demands for scores or hundreds of years, but 

political, economic, and ecological demands may 

radically alter the traditional supply patterns in the 

United States, and at some time in the future the 

supply of phosphate rock to the eastern seaboard 

may possibly come from foreign sources. 

World production of phosphate rock in 1970 was 

about 94 million tons. About 75 percent of the production came from marine phosphorite, 17 percent 

from igneous apatite, and the rest from guanoderived deposits. The United States produced about 

40 percent, the U.S.S.R. about 20 percent, and North 

Africa about 20 percent. 

Reserves of phosphate rock in the world are measured in scores of billions of tons and resources are 

equally vast. Most of the reserves and resources are 

in the marine phosphorites ; reserves in igneous apatite are large but account for only a small percentage 

of the total and those in guano or guano-derived 

deposits are limited. 

EXPLOITATION 

The first record of phosphate rock mining was in 

1847 when a few tons of nodules ("coprolites") were 

produced from Pliocene beds near Suffolk in England ; mining of igneous apatite began in 1851 in 

Norway. Mining of rock phosphate began after the 

discovery of Leibig and Lawes that bones and phosphate rock treated with sulfuric acid increased crop 

response. 

The first mining of rock phosphate in North America was of pegmatite apatite in Canada that started 

in about 1863; mining in the United States began in 

1867, when a few tons of South Carolina phosphate 

rock was produced. By 1870, production in the United 

States had reached 65,000 tons (table 104). Production of phosphate from Florida began in 1888, in 

Tennessee in 1894, and in the Western States in 1906. 

The maximum production of phosphate from South 

Carolina coincided with the start of production from 

Florida (table 104). The coincidence was due to the 

lower costs of producing from the much more extensive Florida deposits, and the increased Florida production eventually brought about the closing of the 

mines in South Carolina. 

Tennessee production is mostly from residual 

"brown rock" deposits and has steadily increased 

from 1894 to about 1965, except for a slight decline 

in the depression years of the 1930's. For the past 

several years, the rate of increase of production from 

Tennessee has lessened and production in 1970 was 

slightly less than production in 1969. 

The first production of phosphate rock in Florida 

was a few thousand tons in 1888. Rate of production 

increased rapidly and by 1920 was 3 million tons per 

year. The rate of production decreased during the 

depression and war years of the 1930's and 1940's, 

and then increased rapidly; as a result by 1970 the 

production was 31 million tons. Production has 

leveled off in the last few years; 1969 and 1970 

showed slight decreases from the maximum year 

1968, but 1971 showed a slight increase. 

Production of phosphate from the Western United 

States began in 1906 and has increased steadily to 
PHOSPHATE DEPOSITS 517 

TABLE 104.-Marketed production of phosphate rock in the United States in each 10th year of 

the period of 1870 to 1970 and total production through 1971 

[In thousands of long tons. Data from U.S. Geological Survey "Mineral Resources of the United States" and U.S. 

Bureau of Mines "Minerals Yearbook"] 

Year 

1870 ------------- 1880 ------------- 1890 ------------- 1900 ------------- 1910 ------------- 1920 ------------- 1930 ------------- 1940 ------------- 1950 ------------- 1960 ------------- 1970 ------------- Total production 

through 

1971 ---------

South 

Carolina 

65 

190 

464 

329 

180 

44 

---------

---------

---------

---------

---------

13,358 

Florida 

----------

----------47 

706 

2,068 

3,369 

3,749 

2,845 

8,068 

13,251 

2 31,278 

494,896 

Tennessee 

---------

---------

--------- 454 

393 

621 

61'1 

994 

1,384 

1,927 

3 3,163 

79,983 

Western 

States 

---------

---------

---------

---------10 

56 

67 

163 

783 

3,024 

'4,297 

66,3,34 

Others 1 Total 

65 

190 

511 

1 1,490 

5 2,656 

13 4,103 

3,927 

4,002 

10,253 

18,202 

38,739 

207 654,778 

1 Alabama, Arkansas, and Pennsylvania in 1900; Arkansas in 1910; Kentucky in 1920. 2 Includes north Florida and North Carolina in 1970. 3 Includes Alabama in 1970. 

' Includes California in 1970. 

more than 4 million tons in 1970. Production has 

leveled off somewhat in the last several years because 

of the general soft market for phosphate rock. 

The total production of phosphate in the United 

States has almost doubled in each succeeding decade 

since 1870 (table 104), except for the depression and 

war years, and by 1970 production had reached 38 

million tons. 

Total production of phosphate rock in the United 

States is about 654 million tons through 1971-76 

percent from Florida, 12 percent from Tennessee, 10 

percent from the Western States, and 2 percent from 

South Carolina. 

GEOCHEMISTRY 

Phosphorus is widely distributed in the earth's 

crust, which contains about 0.23 percent P205. Most 

of the phosphorus occurs in minerals of the apatite 

group Ca1o (P04,C03) s (F,OH,Cl) 2· The structure of 

apatite is such that small amounts of V04, As204, and 

S04 substitute for P04, and Na, Sr, U, Th, and the 

rare earths may substitute for Ca. 

Apatite is relatively insoluble in alkaline or neutral waters, and its solubility increases as acidity increases and temperature decreases. Thus, although 

apatite may be residually concentrated in the first 

stages of weathering, it eventually breaks down. 

Some of the phosphate may be redeposited locally. 

In limestone terranes, apatite is again formed; in 

igneous terranes, iron and aluminum phosphates 

(variscite and strengite) are formed; and in clay 

soils, aluminum phosphates (wavellite and crandallite) are formed. 

Phosphorus is carried to the sea as phosphate minerals adsorbed on iron or aluminum hydroxides or 

clays, in particulate or dissolved organic compounds, 

or in solution. 

The ocean is nearly saturated with phosphate, but 

the phosphate content of the ocean is not uniform. 

Deep cold water contains about 0.3 ppm P04 and 

warm surface water contains about 0.01 ppm. In the 

ocean, cold, nutrient-rich waters may be brought to 

the surface in several ways-by divergence upwelling, dynamic upwelling, turbulence, and convection. 

The solubility of phosphate in upwelling waters decreases as temperature and pH increase near the surface, and apatite may then be precipitated by organic 

or inorganic processes. Phosphorites and the accompanying rocks in the environment of upwellingblack shale, chert, and limestone-are depositional 

products from sea waters that change in composition 

as the result of physical, chemical, and biologic 

processes. 

TYPES OF DEPOSITS 

Minable concentrations of phosphate are found in 

igneous rocks, as sedimentary phosphorite, and as 

guano, or in deposits derived from guano. The term 

"phosphate rock" is applied to any rock that contains 

more than about 20 percent P 205. "Phosphorite" is 

equivalent, but is usually applied only to marine 

phosphate rocks. 

IGNEOUS APATITES 

Apatite occurs as intrusive masses or sheets, as 

hydrothermal veins or disseminated replacements, as 

marginal differentiations, or as pegmatites. Largest 

are the intrusive masses, which are commonly as-
518 UNITED STATES MINERAL RESOURCES 

sociated with alkaline igneous rocks including carbonatite, ijolite, nepheline syenite, and pyroxenite. 

The larger deposits in the world are in the Kola 

Peninsula (U.S.S.R.), eastern Uganda and Palabora 

in Africa, and Araxa and J acupiranga in Brazil. 

Reserves in individual deposits are measured in 

scores to hundreds of millions of tons. The phosphate 

mineral is a fluorapatite. P 205 contents are as high as 

36 percent, and weathering may form apatite-rich 

residual deposits overlying the surface of calcitic or 

dolomitic source rocks. 

Other forms of igneous apatite deposits are smaller and are lower in P 205 content. Examples in the 

United States include the ilmenite-apatite deposits 

of Virginia and the apatite-magnetite marginal 

deposits of the eastern Adirondacks. None of the 

deposits in the United States are being mined, and 

reserves and resources of this type of material are 

very small as compared with total resources of phosphate rock. 

About 17 percent of the world's production of 

phosphate is from deposits of igneous apatite; most 

of this is from the Kola Peninsula and Palabora. 

GUANO AND RELATED DEPOSITS 

All large accumulations of guano are formed at the 

surface by sea birds. Smaller quantities are formed 

in caves principally by bats. Reserves in most 

deposits are measured in thousands or hundreds of 

thousands of tons. The mineralogy of guano de;;osits 

is complex inasmuch as it depends on the amount of 

leaching by surface waters. Slightly decomposed deposits consist of ammonium and alkali oxalates, 

sulfates, and nitrates, and magnesium and ammonium-magne·sium phosphates. Decomposed guano consists chiefly of calcium phosphates-monetite and 

whitlockite. 

In areas of even slight rainfall, the soluble phosphate of guano is carried downward and replaces or 

alters the underlying rock. Apatite is the mineral 

formed where the underlying rock is limestone, and, 

over geologic time, deposits measuring scores of 

millions of tons have been formed on some of the 

islands of the western Pacific. Aluminum or aluminum-iron phosphates (strengite .and variscite) are 

formed where the underlying rock is volcanic. Deposits are known in several parts of the world (Malpelo Island, Colombia), but reserves are limited and 

processing costs are high. 

Guano has been mined from caves in various parts 

of the United States, but reserves and resources are 

negligible and world resources are small. Production 

of guano, largely from renewable sources, measured 

in terms of its phosphate content, is less than 1 percent of the total production of phosphate i~ the 

world. 

Guano-derived deposits, particularly those in the 

western Pacific account for almost 5 percent of the 

world's production of phosphate. Reserves are measured in millions of tons. 

SEDIMENTARY PHOSPHORITE 

About 75 percent of the world's production of 

phosphate rock is from deposits of marine phosphorite. The richest and largest of these deposits 

form in warm latitudes, mostly between the 4oth 

parallels and in areas of upwelling caused by divergence. These areas are in the tradewind belts on the 

west coasts of the continents or in mediterranean 

seas along the equatorial side of the basin. 

Significant concentrations also form along the 

west sides of poleward-moving warm currents along 

the eastern coasts of continents. In these areas 

there are cool coastal countercurrents, such as along 

the eastern coast of the United States. 

DF.POSITS CAUSED BY DIVERGENCE UP.WELLING 

OF SEA WATER 

Deposits caused by divergence upwelling are 

characterized by a suite of rocks that consists, in a 

shoreward direction, of black shale, phosphatic shale, 

phosphorite, dolomite, chert or diatomite, and saline 

deposits and red or light-colored sandstone or shale. 

The rocks grade laterally into one another, and be-

' cause of lateral shifts in environment due to epeirogenic movements, the sequence may also be repeated 

vertically. The thickest accumulations of phosphorite form in areas of geosynclinal subsidence where 

clastic sedimentation is at a minimum ; that is, a 

miogeosynclinal environment. Phosphorites are also 

found in the eugeosynclines, but are so mixed with 

the thick shale, chert, and volcanic materials of the 

eugeosyncline that thick high-grade deposits are not 

known and are unlikely. 

The phosphate in these rocks is carbonaceous and 

consists of pellets, some nodules, and minor phosphatized bone material and shell. The pellets may 

have formed by direct precipitation or by diagenesis, 

and some are certainly replaced calcite (as for example, the phosphatized shell material). Individual 

beds may be several feet thick and contain 30 percent or more P 205 , and the beds may extend over 

hundreds of square miles. Phosphorite that was 

formed on the adjacent stable continental shelf area 

is generally associated with chert, calcareous chert, 

and light-colored sandstone and shale. The phosphate 

consists of nodules, pellets, and abundant phosphatized shell and bone material ; phosphatic sandstone 
PHOSPHATE DEPOSITS 519 

is a common textural type. Individual beds tend to 

be thinner than in the geosynclinal environment, but 

some beds thicken locally. P205 contents are generally between 20 and 30 percent. 

Examples in the United States of phosphorite 

deposited from upwelling water caused by divergence include the Permian Phosphoria Formation 

of the Western United States, the Miocene Monterey Formation of California, the Mississippian 

and Triassic deposits of Northern Alaska, and the 

Mississippian deposits of Utah. The very large deposits of Kara Tau in the U.S.S.R., the Miocene deposits of the Sechura Desert in Peru, the Cretaceous 

of Colombia, the Cambrian of Australia, and the 

extensive deposits of Cretaceous and Eocene age in 

Western and Northern Africa and the Middle East 

are also of this type. 

DEPOSITS FORMED IN WARM CURRENTS 

ALONG EASTERN COASTS 

Phosphorites formed in warm currents along the 

eastern coasts of continents consist of phosphatic 

limestone or sandstone. Black shale and chert are 

not found with these deposits, although some diatomaceous material may be present. The deposits are 

generally lower in amount of phosphate per unit 

area than are the miogeosynclinal deposits. The 

most important deposits of this type are those of 

the Eastern United States-Florida, Georgia, and 

North Carolina. Phosphate in the Upper Cretaceous 

Gramame Formation near Recife in Brazil is another example. 

Deposits of this type are economic only when they 

have been reworked by submarine currents, subjected to weathering, or both. Most deposits of this 

type must be further upgraded by some method of 

baneficiation after mining to provide an economic 

product. 

The deposits along the eastern coast of the United 

States are of middle Miocene age and extend from 

southern Florida to southern Virginia. The richest 

deposits are found in basins of structural lows on 

the flanks of domes that were rising at the time of 

phosphate deposition. The phosphorite may have 

been deposited by dynamic upwelling or by the cool 

countercurrent associated with the warm density 

current. Turbulence caused by the divergence of the 

cool coastal current due to the rising positive area 

may have assisted in deposition. 

Concentrations of organic growth and nutrients 

are found near the mouths of large rivers or in 

estuaries in which the outflow of surface waters is 

replaced by a countercurrent of sea water. Decaying organic material sinks and is trapped in the 

inflowing sea water. Nutrients may accumulate in 

the system, and the estuaries may thus have a 

higher phosphate content than adjacent river or 

sea water. 

Such a process may account for the fact that the 

richer phosphate deposits in the Eastern United 

States are in the bays or basins (some of which may 

have been estuaries). At least this process may 

initiate precipitation. A combination of processes 

probably was operative during the formation of the 

phosphate deposits of the Eastern United States. 

Deposits of phosphate in eugeosynclinal sediments, associated with chert, shale, and limestone, 

have been found in Nevada. The phosphate beds are 

thin and low in P 205 content and are not likely to 

be an economic source of phosphate rock in the 

forseeable future. 

DEPOSITS FORMED ON STABLE SHELVES 

OR IN CONTINENTAL INTERIORS 

The marine phosphate deposits that form on the 

stable shelf or in the continental interior are associated with limestone, dolomite, shale, and glauconitic sandstone. The phosphate is in the form of 

nodules or grains that are large with respect to the 

matrix in which they are found. Individual beds are 

only a few feet thick, but commonly several beds 

contain phosphate. The phosphate beds contain from 

5 to 15 percent P 205, but the nodules may contain 

as much as 35 percent. 

Examples of deposits of this type in the United 

States include beds in the Maquoketa Shale of Ordovician age in Illinois, Iowa, and Wisconsin ; several 

formations of Ordovician age in Minnesota and 

Arkansas; the Oriskany Sandstone of Devonian age 

in New York, Pennsylvania, and Virginia; sandstone of Mississippian age in Tennessee and Arkansas ; black shale of Pennsylvanian age in Kansas, 

Missouri, and Oklahoma; shale of Pennsylvanian 

age in Arkansas ; several beds of Cretaceous age in 

Alabama, Mississippi, Georgia, and Texas, associated with limestone; and beds of Cretaceous and 

Paleocene age in Texas, Tennessee, Alabama, and 

Mississippi, and the northern Atlantic Coastal Plain, 

associated with glauconite. 

Some of the beds have been mined-for example, 

Mississippian sandstone of Tennessee, called "bluerock," and the Ordovician Cason Shale and Pennsylvanian Hale Formation in Arkansas-but production was small. Reserves are small and resources 

are at best moderate, but these types of deposits 

could serve as local sources of phosphate rock in the 

future. 
520 UNITED STATES MINERAL RESOURCES 

CONCENTRATION AND ENRICHMENT 

OF MARINE DEPOSITS 

The richest of the marine deposits have been concentrated or enriched by secondary processes. For 

example, the deposits in the Bone Valley Formation 

of Florida were formed by submarine reworking of 

a phosphate-rich residuum. Leaching related to 

Pleistocene and modern weathering has further upgraded the deposits. The occurrence of phosphate 

gravels at unconformities is caused by weathering 

and reworking. 

River-pebble deposits occur as bars and in the 

flood plains of streams that drain phosphate areas 

in Florida, Georgia, and South Carolina. The 

streams concentrate coarse-grained phosphate particles because of their size and specific gravity. 

Fine-grained phosphate particles, quartz sand, and 

clay are carried downstream, and the river-pebble 

deposits consist of coarse-grained phosphate nodules 

and quartz grains. The phosphate particles are low 

in P 205 content because of leaching by the acid 

waters of the stream. 

Chemical weathering of phosphatic limestone in 

a humid climate results in the removal of the soluble calcium carbonate and the consequent enrichment and concentration of the phosphate. The 

"brown rock" phosphates of Tennessee and Kentucky are examples. Individual deposits are not 

large but they are grouped in such a way that the 

mined material can be hauled to a central recovery 

, plant. The composition of the phosphate particles 

and their mineralogy are about the same as the 

composition and mineralogy of the marine phosphorite from which they were derived. 

The apatite mineral of sedimentary rocks is taken 

into solution by acid ground water, and P205 may 

be precipitated if the solutions pass through 

aluminum- or iron-bearing rocks or through limestone. Secondary deposits in limestone areas, such 

as the white rock of Tennessee and the hardrock of 

Florida, consist of phosphate incrustations or irregular replacement. The P 205 content depends on 

the degree of replacement; some replacement deposits are very high in phosphate content. Deposits 

are irregular in shape and are generally small. 

OTHER TYPES OF PHOSPHATE DEPOSITS 

Other sources of phosphate include bone piles, 

glauconite, and phosphatic iron ores that yield a 

basic slag in the Bessemer or basic open-hearth 

manufacture of steel. Bone piles are no longer an 

important source of phosphate. Glauconite (green 

sand) contains both K20 and P 205 and has some 

use as a fertilizer; reserves and resources in the 

Cretaceous and Paleocene of the Atlantic Coastal 

Plain are very large. Phosphatic iron ore includes 

marine deposits like the Red Mountain Formation 

of Alabama as well as apatite-magnetite deposits. 

Basic slag (Thomas Meal) made in processing these 

ores contains about 8 percent P 205, and is used as 

a fertilizer. 

Phosphatic lake beds of Eocene age are known 

from intermontane basins of Wyoming and Utah. 

The beds that contain phosphate range in thickness 

from less than 1 to about 6 feet and contain an 

average of about 2 percent P 205. The maximum 

P 205 is about 19 percent. 

RESOURCES 

IDEN'I11FIED AND HYPOTHETICAL RESOURCES 

Phosphorite deposits are known throughout the 

world and throughout the geologic column from the 

Precambrian to the Holocene. Data for tonnages of 

identified phosphorite in tables 105 and 106 are 

from all possible sources. Most of the figures for 

the United States are from unpublished data of the 

U.S. Geological Survey, including information from 

R. L. Detterman (written commun., 1972) for 

Alaska. Tonnages are computed in different ways 

for different deposits in the United States. For the 

unconsolidated phosphate sands of the Atlantic 

Coastal Plain, they are computed on the basis of 

recoverable product that contains a given percent 

BPL (bone phosphate of lime). In Tennessee, reserves are computed as tons of rock that contain 

a certain percent P, and in the Western United 

States tonnage is phosphate rock, in the ground, of 

a given percent P205. Percent P20s times 2.185 

equals percent BPL [equals Caa (P04) 2J, and percent P 205 times 0.436 equals percent P. 

Tonnages for the United States shown in table 

105 are in metric tons of rock that contain more 

than 24 percent P 205, and total tons -for the Eastern 

and Western United States are changed to metric 

tons of percent P to conform with the tonnage figures for other countries of the world in table 106. 

Tonnage estimates are fairly good for the United 

States, Africa, the Near East, and the Pacific 

Islands, but it is almost certain that the estimates 

are low, and perhaps very low, for Latin America 

and Australia. The resource estimates for Asia are 

probably low because of lack of detailed data, particularly for China. 

SEDIMENTARY PHOSPHORITE 

UNITED STATES 

Hypothetical resources for the United States 

shown in table 105 are those for which reasonable 
PHOSPHATE DEPOSITS 521 

TABLE 105.-Phosphate resources of the United States 

[In metric tons of rocks containing more than 24 percent P20s] 

Identified Hypothetical resources 1 resources 2 

~stern lJirlted States 

Atlantic Coastal Plain: 

Florida (Polk, Hills- 1.6 X 109 700 X 106 

borough). 

Florida (Manatee, Hardee, 500 X 108 1 X 109 

DeSoto). 

North Florida-South 300 X 106 1.5 X 109 

Georgia. 

River pebble ------------- 50 X 101 

Hardrock --------------- 50 X 106 1 X 109 

North Georgia ----------- 1.6 X 109 

South Carolina ----------- 500 X 106 

North Carolina ---------- 2 X 109 9 X 109 

Total Atlantic Coastal 4.4 X 1011 15.3 X 109 

Plain (rounded) . Tennesse, Kentucky, Alabama_ 80 X 106 100 X 106 

Others (Arkansas, Iowa) _____ 26 X 106 16 X 106 

Total phosphate re- 4.5 X 109 15.4 X 109 

sources, Eastern 

lJnited States. 

Total, tons of phosphorus. 0.59 X 109 1.69 X 109 

Western lJnited States 

Idaho, Montana, Utah, 

Wyoming (Phosphoria 

Formation). 

lJtah (Mississippian rocks) __ 

Alaska ---------------------- Others (Nevada, California) __ 

Total, phosphate re- sources, Western 

lJnited States. 

6.0 X 109 

6.0 X 109 

8.7 X 109 

16 X 106 

1 X 10~ 

106 

9.7 X 109 

Total, tons of phosphorus. 0. 78 X 109 1.02 X 109 

=================== Grand total, tons 1.4 X 109 2.7 X 109 

of phosphorus. 

1 Identified resources: Specific, identified mineral deposits that may or ~Y not be evaluated as to extent and grade, and whose contained 

malmerals may or may not be profitably recoverable with existing tech- n ogy and economic conditions. 2 Hypothetical resources: Undiscovered mineral deposits, whether of rec;o~era~le or sub~OJ?-Omic grade, that are geologically predictable as exiStmg m known districts. 

TABLE 106.-World phosphate 'resources 

[Metric tons of pereent phosphorus] 

Identified 

resources 1 

Hypothetical 

resources 2 

United States ------------------- 1.4 X 109 2.7 X 109 

Africa: Sedimentary ------------ 3.5 X 109 6 X 10° 

Igneous -------------------- 15 X 106 15 X 106 

Near East --------------------- .13 X 109 .6 X 109 

Latin America: Sedimentary ____ 80 X 106 .2 X 109 

Igneous -------------------- 13 X 106 10 X 106 

Guano --------------------- 5 X 106 Nil 

Asia: Sedimentary -------------- .2 X 109 .5 X 10" 

Igneous -------------------- .2 X 109 .2 X 10' 

Australia ---------------------- .2 X 109 1 X 109 

Pacific Islands ------------------ 6 X 106 3 X 106 

------------------- Total (rounded) ---------- 6 X 109 9 X 109 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existing technology 

and economic conditions. 2 Hypothetical resources: Undiscovered mineral deposits whether of 

recoverable or subeeonomie grade, that are geologically predictable as 

existill&' in known districts. 

amounts could be assigned. Additional hypothetical 

resources are probably large. Although all these resources are hypothetical, those not enumerated in 

table 105 are of a lower order of precision in terms 

of tonnage and are deeply buried, low in grade, or 

contain deleterious gangue minera]s, and as a result 

they pose such different mining and processing 

problems that it seems logical to discuss them separately. 

The principal additional hypothetical resource for 

the Western United States is contained in the 

Phosphoria Formation. Extrapolation of average 

thickness and phosphorus content over the entire 

area underlain by the Phosphoria indicates a total 

potential resource of about 16 X 109 tons of P. Of 

this amount, about 2 X 109 tons is represented by 

the identified and hypothetical resources shown in 

table 105. Subtracting this 2 X 109 tons from the 

total potential of 16 X 109 tons leaves about 14 X 

109 tons of P that may be considered to be an additional hypothetical resource in the Phosphoria Formation. Of this latter amount, 5 X 109 tons contains 

more than 24 percent P z05; 6 X 109 tons contains 

from 10 to 23 percent Pz05, and the rest consists of 

resources of low value. This resource will require 

new mining and processing techniques. 

Additional hypothetical resources in the Eastern 

United States can be divided into sandy phosphorite 

of the Florida and North Carolina type and phosphatic carbonate rock such as the Hawthorn Formation of Florida. Phosphatic carbonate rock may contain scores to hundreds of billions of tons of phosphate particles, and as much as 10 X 109 tons of P. 

This material cannot be mined or processed with 

present methods. 

Sandy phosphorite deposits of th2 Atlantic 

Coastal Plain are known from central Florida to 

North Carolina, and additional undiscovered deposits may be present in the subsurface as far north 

as Virginia. Deposits that are not known are completely and perhaps deeply buried; resources may 

aggregate billions of tons of pellets and hundreds 

of millions of tons of phosphorus. 

In northern Alaska, hundreds of square miles are 

probably underlain by phosphorite, and the total 

tonnage represented would be billions of tons of 

rock that contain at least 10 percent Pz05, and thus, 

hundreds of millions of tons of phosphorus. 

Large resources of phosphate rock exist offshore, 

but close to the shoreline, in the Pacific Ocean from 

southern California to southern Baja California and 

in the Atlantic Ocean from North Carolina to 

southern Florida. 

Phosphate is present as very coarse nodules in 
522 UNITED STATES MINERAL RESOURCES 

thin beds of shales and limestones in rocks of Ordovician, Devonian, Pennsylvanian, Permian, and 

Cretaceous ages in the midcontinent area of the 

United States. Phosphate particles are also concentrated as lag gravels at unconformities in this area. 

Although the amount of phosphate per unit area is 

small, the aggregate amount of phosphate most be 

large, and it is possible that some of these rocks 

may be mined as local sources of phosphate in the 

future. 

LATIN AMERICA 

Large tonnages of phosphate are known in the 

Jurassic of Peru and the Cretaceous of Colombia. 

The phosphate-bearing rocks may extend through 

Peru, Bolivia, and Ecuador into Colombia, and the 

deposits in most of this area represent a large hypothetical resource. Miocene rocks of the Sechura area 

in Peru and in Falcon State in Venezuela contain 

phosphorite deposits. The Miocene rocks of the western and northern coasts of South America should 

be examined to determine if additional resources 

are present. Along the Pacific Coast of Colombia the 

Miocene rocks are so thick that discovery of economic phosphate is not likely, but Miocene rocks in 

Ecuador and Peru and the northern coast, particularly in Venezuela, are thinner and may contain 

additional resources. 

Deposits of the Florida type may be present in 

Upper Cretaceous and Tertiary rocks on the east 

coasts of continents. Deposits of this type occur in 

Cretaceous rocks of the Recife area in Brazil, but 

the potential is small because of the small area 

underlain by marine Cretaceous rocks. Deposits 

may also be present in Upper Cretaceous and Tertiary rocks along the present east coast of South 

America in Argentina. 

AFRICA AND THE NEAR EAST 

A very large area including much of the northern 

half of West Africa and all of North Africa and 

the contiguous parts of the Near East (Israel, Jordan, Saudi Arabia, Turkey, etc.), is a sedimentary 

basin in which the identified and hypothetical resources of phosphate are extremely large. The potential of this area is enormous. Deposits have been 

found in recent years in almost all parts of the 

sedimentary basin that have been examined. As 

details of the stratigraphy, structure, and paleogeography are worked out, additional deposits will 

probably be found. No tonnage figures have been 

computed, but the total resources must be much 

larger than the numbers shown on table 106. 

ASIA 

Not a great deal of specific information is available on this part of the world, but it is known 

that large sedimentary basins that contain rocks 

ranging in age from Cambrian to Cretaceous contain phosphorite deposits, and it is likely that exploration will uncover additional large reserves. The 

potential for this area is great. 

AUSTRALIA 

Australia has identified and hypothetical resources 

of phosphate of Cambrian age in a large sedimentary 

basin in the interior of the continent. The total resources in this basin probably are extremely large--

several times the combined total of the identified 

and hypothetical resources shown in table 106. 

GUANO AND RELATED DEPOSITS 

Little hope remains for finding additional resources of the guano type of deposit such as typify 

the Pacific Islands. All the Pacific Islands have 

been searched, and although additional reserves may 

be found they will, in all probability, be small. 

IGNEOUS APATITES 

Additional resources of igneous apatite are at best 

moderate, particularly in comparison with the total 

resources of the sedimentary phosphorites. Reserves 

in undiscovered alkaline rock suites probably will 

be hundreds of millions of tons in maximum size; 

many will be much smaller. Reserves of this type 

might be utilized as local sources in the future, and 

the possibilities of finding deposits of apatite should 

not be overlooked. 

SPECULATIVE RESOURCES 

Very little in the way of truly speculative resources of phosphate remain to be found. We can 

refine ideas and theories of the formation of marine 

phosphorite, but the positions of the shelf, craton, 

sedimentary basins, and geosynclines are known at 

least in broad outline for most periods of geologic 

time throughout the world. Not all the prospective 

areas have been searched for phosphate, and sedimentary basins where phosphate is known have not 

all been thoroughly and exhaustively studied. New 

deposits, then, remain to be discovered but all are 

considered to belong to the hypothetical class rather 

than the speculative. The total amount of phosphate 

rock in the world, as identified or hypothetical, is 

potentially so enormous that the assumption that 

truly speculative resources are small has little 

meaning. 
PHOS·PHATE DEPOSITS 523 

Truly speculative resources may be present in 

Precambrian rocks as metamorphosed marine phosphorite. Precambrian phosphorite deposits are 

known in several parts of the world and a study of 

the Precambrian should be made to determine the 

location of possible sedimentary basins. These basins 

should then be studied to determine if phosphorite 

deposits are present. 

PROSPECTING TECHNiqUES 

The geologic relations discussed earlier are the 

basis for prospecting, particularly in the outlining 

of large areas that are worthy of further examination. 

Exploratory work should be concentrated on the 

search for marine phosphorite deposits. Deposits are 

very large; for example, it is estimated that phosphate in the Phosphoria Formation was deposited 

over an area of 135,000 square miles, and the potential resources, therefore, are correspondingly 

vast. 

Most marine phosphorites were deposited in basins of deposition in miogeosynclines or in subsiding areas on the adjacent relatively stable platform, 

and deposits have been classified as either geosynclinal or platform type. The first step in prospecting is to identify the large marine sedimentary 

basins of deposition. 

The second step is to determine whether any 

phosphate is present in the rocks of the basin. The 

typical suite of rocks associated with the deposits 

of phosphorite in the miogeosyncline is an invaluable aid to prospecting. The recognition of the black 

shale-chert-carbonate sequence in samples collected 

from oil exploration is a valuable clue to the location of a phosphorite deposit. Sandstone and lightcolored shale and siltstone are much more abundant 

in the platform facies, but chert, calcareous chert, 

siliceous shale, and some carbonate rock are also 

present. 

Phosphorite is not a very distinctive rock and can 

be overlooked or misidentified. Most phosphorites 

contain rounded to ovoid structureless sand-size 

pellets. Phosphatized bone fragments, fecal pellets, 

and fish and sharks' teeth are frequently found in 

phosphorites, and glauconite is a common accessory 

mineral. Any pelletal rock, particularly one that 

contains bone or teeth fragments, is worthy of 

further examination. Higher grade phosphorites 

may have a bluish-gray coating (phosphate bloom) 

on weathered surfaces, and high-grade phosphorite 

may also be distinguished by a fairly high specific 

gravity. 

Phosphorite deposits are found where the rate of 

deposition of other clastic material is at a minimum. 

The phosphorite sequence, therefore, tends to be 

thin when compared with sedimentary sequences 

deposited elsewhere at the same time. 

In a given basin of deposition, the phosphorite 

tends to be concentrated at one stratigraphic position, although the phosphorite facies may transgress 

time. 

Phosphorite deposits may be structurally controlled. For example, phosphorite of the platform 

facies is deposited in structural basins on the flanks 

of domes or anticlines that were rising at the time 

of deposition. Structural controls, other than the 

broad geosynclinal basin, may determine the site of 

deposition in the deeper parts of the basin. 

All marine phosphorites contain uranium in 

amounts that are high enough so that these rocks 

can be identified by gamma-ray well logging and 

even by aerial radiometric reconnaissance. Anomalous amounts of uranium are present in acid streams 

that drain phosphatic terranes, and in covered areas, 

such as the coastal plains of the United States, the 

presence of uranium in stream waters may be a 

clue to the presence of a phosphate deposit. 

Large deposits of igneous apatite are related to 

alkalic rocks, particularly to carbonatites, and these 

rocks are related to the large rift zones. Many carbonatite deposits are now known; several contain 

large apatite deposits. All carbonatites and areas 

where they may be present should be examined for 

phosphate. 

The only guano deposits that remain to be found 

are probably very small bat guano deposits in caves. 

Guano-related deposits, particularly those on arid 

coasts where there is modern dynamic upwelling of 

water, may remain to be found, and the possibilities 

should not be overlooked. 

PROBLEMS FOR RESEARCH 

Research is needed on a variety of problems that 

can be classified as recovery of byproducts, waste 

disposal, mining and processing, and geological. 

Minor elements that might be recovered as byproducts include fluorine, vanadium, uranium, scandium, and the rare earths. Marine phosphorites, 

because of their vast tonnages, constitute significant resources of these elements. Pure apatite contains from 3.5 to 4 percent F ; phosphorites probably average about 3 percent. All marine phosphorites contain uranium, probably substituting for 

calcium in the apatite lattice, in amounts ranging 

from 0.005 to as much as 0.05 percent; the average 

is about 0.01 percent. The rare earths (lanthanides 
524 UNITED STATES MINERAL RESOURCES 

and yttrium) form a solid solution in the structure 

of apatite and make up from 0.01 to 0.1 percent by 

weight of marine apatite. Vanadium probably is 

concentrated in the organic material associated with 

phosphorites; the average vanadium content of 

phosphate rock in the Phosphoria Formation is 

about 0.03 percent and in Florida phosphate is 0.01 

percent or less. 

All these minor elements, except scandium, have 

been or are being recovered from phosphoric acid 

made by the wet process, and vanadium is now recovered in the course of thermal processing. Because 

only about one-fourth of the phosphate rock mined 

is made into phosphoric acid, the maximum recovery 

of the minor elements can only be about 25 percent. 

The probability of the recovery of scandium from 

this source seems remote. Research is needed to develop better methods of recovery of all these elements. 

Recovery of some of the elements is related to 

reduction in air and water pollution. Fluorine, released in part as a gas in the chemical processing, 

cannot be allowed to escape in the effluent. Fluorine 

in the gas effluents is being controlled, but not all is 

being recovered. Research on methods of recovery 

of byproducts may lead to cleaner air and water 

effluents. 

Solid wastes formed in processing, particularly 

the slime (-200 mesh) fraction from the deposits 

on the Atlantic Coastal Plain, cannot be dumped 

into streams and are currently impounded in dams. 

Breaks do occur, causing water pollution. The slime 

fraction is a potentially valuable fertilizer, and research on control, disposal, and possible utilization 

of the slime fraction is of utmost importance. 

All open-pit mining, chemical processing, and disposal of mining and chemical wastes are now and 

will be increasingly regulated by clean air and water 

laws and by land reclamation laws. The phosphate 

mining and processing companies are reclaiming 

land in Florida and Tennessee and are working to 

solve problems of air and water pollution, but additional research is certainly needed. If there is any 

significant air or water pollution or ruining of land 

by mining in the future, legislation could force phosphate mining companies out of business and drastically change the export-import balance of phosphate trade. 

Mining of phosphate rock is geared to shallow 

open pits and to underground mining above entry 

level. To utilize much of the hypothetical resources 

in the United States, new or different mining methods will have to be devised, and processing methods 

to recover the phosphate particles will also have to 

be changed. Much of the hypothetical resource is 

carbonate rock containing phosphate pellets, and the 

recovery methods currently used are not effective. 

Although minable reserves are sufficient for many 

years, the beginning of research on mining and 

processing problems should not wait until these reserves are nearly exhausted, but should be started 

promptly. 

An additional set of chemical problems has to do 

with the amount and kind of trace metals present 

in phosphate rock. Certain minor elements are necessary for plant growth; among these are boron, 

copper, manganese, molybdenum, and zinc. These 

elements are all present in marine phosphorites, but 

are removed during chemical processing, only to be 

readded to the chemical fertilizer in about the same 

amount that was removed. Research is needed on 

methods of retaining these minor elements in 

chemical processing of phosphate rock. 

Geologic problems are related particularly to the 

discovery of new ore deposits of high grade. The 

hypothesis that marine phosphorites were deposited 

in miogeosynclines at some distance from the 

source of clastic sediment and only at low latitudes 

has proved workable. Each miogeosynclinal basin 

should be investigated particularly with respect to 

plate tectonics and the paleolatitude of the basin at 

the time of phosphate deposition. Thus, a knowledge 

of paleogeography, paleolatitude, paleocurrents and 

wind directions, and structure within the basin at 

the time of deposition is all important in determining the locus of possible phosphorite deposition. 

For deposits on the east coasts of continentsthe Florida-type deposits-again a knowledge of 

structure, geography, and current and wind directions is important. These deposits are likely to be 

buried, and any geologic parameters that might be 

used to reduce the size of the target area to be 

drilled are of great importance. 

Much remains to be learned about the chemistry 

of deposition of marine phosphorites. Phosphate 

may be precipitated chemically and biologically. The 

source of the phosphate might be ocean water itself, 

rivers entering the ocean, estuaries, the phosphatic 

bodies of fish and animals, or volcanic emanations 

onto the ocean floor, or some combination of all of 

these. The marine phosphorites are large; they contain billions of tons of phosphorus, and whatever 

the source, the phosphorus has to be available over 

long periods of time. 

Problems of reserves would not appear to be important, in view of the extremely large identified 

tonnages, but phosphate is a low-unit-value commodity and shipping costs can put the material out 
PHOSPHATE DEPOSITS 525 

of reach economically, particularly to farmers in 

developing countries. Thera are, therefore, problems 

of developing resources in the countries where phosphatic fertilizer is needed. 

SELECTED BIBLIOGRAPHY 

Altschuler, Z. S., Cathcart, J. B., and Young, E. J., 1964, 

Geology and geochemistry of the Bone Valley Formation and its phosphate deposits: Geol. Soc. America 

Ann. Mtg., Miami Beach, 1964, Guidebook field trip 6, 

68 p. 

British Sulphur Corporation, 1964, A world survey of phosphate deposits (2d ed.): London, The British Sulphur 

Corp., Ltd., 206 p. 

Bushinskii, G. I., 1966, Drevnie fosferity Azii i ikh genezis 

[Old phosphorites of Asia and their genesis]: Akad. 

Nauk SSSR, Geol. Inst. Moskva. 

Cathcart, J. B., 1963, Economic geology of the Keysville 

quadrangle, Florida: U.S. Geol. Survey Bull. 1128, 82 p. 

D'Anglejan, B. F., 1967, Origin of marine phosphorite off 

Baja California, Mexico: Marine Geology, v. 5, no. 1, 

p. 15-44. 

Furlow, J. W., 1969, Stratigraphy and economic geology of 

the eastern Chatham County phosphate deposit: Georgia 

Geol. Survey Bull. 82, 40 p. 

Gulbrandsen, R. A., 1966, Chemical composition of phospherites of the Phosphoria Formation : Geochim. et Cosmochim. Acta, v. 3, p. 769-778. 

--- 1969, Physical and chemical factors in the formation 

of marine apatite: Econ. Geology, v. 64, no. 4, p. 365-

382. 

Harrington, J. W., Ward, D. E., and McKelvey, V. E., 1966, 

Sources of fertilizer material in South America, a preliminary study: U.S. Geol. Survey Bull. 1240, 66 p. 

Jacob, K. D., 1953, Phosphate resources and processing facilities, in Jacob, K. D., ed., Fertilizer technology and 

resourc·es: New York, Acad. Press, Agronomy Mon., v. 

3, p. 117-166. 

Kazakov, A. V., 1937, The phosphorite facies and the genesis 

of phosphorites: USSR Sci. Inst. Fertilizers and Insectofungicides, Trans. 142, p. 95-113. 

Kimrey, J. 0., 1965, Description of the Pungo River Formation in Beaufort County, North Carolina: North Carolina Dept. Conserv. and Devel. Div. Mineral Resources 

Bull. 79, 131 p. 

Lewis, R. W., 1970, Phosphorus, in U.S. Bur. Mines, Mineral 

facts and problems: U.S. Bur. Mines Bull. 650, p. 1139-

1155. 

Love, J. D., 1964, Uraniferous phosphatic lake beds of Eocene 

age in intermontane basins of Wyoming and Utah: U.S. 

Geol. Survey Prof. Paper 474-E, 66 p. 

Mansfield, G. R., 1942, Phosphate resources of Florida: U.S. 

GeQl. Survey Bull. 934, 82 p. 

McKelvey, V. E., 1967, Phosphate deposits: U.S. Geol. Survey Bull. 1252~ 21 p. 

McKelvey, V. E., Cathcart, J. B., Altschuler, Z. S., Swanson, 

R. W., and Buck, K. L., 1953, Domestic phosphate deposits, in Pierre, W. H., and Norman, A. G., eds., Soil 

and fertilizer phosphorus in crop nutrition: New York, 

Acad. Press, Agronomy Mon., v. 4, p. 347-376. 

McKelvey, V. E., Swanson, R. W., and Sheldon, R. P., 1953, 

The Permian phosphorite deposits, Western United 

States: Internat. Geol. Cong., 19th, Algiers, 1952, Comptes Rendus, sec. 11, pt. 11, p. 45-64. 

Pevear, D. R., 1966, The estuarine formation of the United 

States Atlantic Coastal Plain phosphate: Econ. Geology, 

v. 61, no. 2, p. 251-255. 

Ruhlman, E. R., 1958, Phosphate rocks, mining, beneficiation 

and marketing: U.S. Bur. Mines lnf. Circ. 7814, 33 p. 

Sheldon, R. P., 1964, Paleolatitudinal and paleogeographic 

distribution of phosphorite: U.S. Geol. Survey Prof. 

Paper 501-C, p. C106-C113. 

Smith, R. W., and Whitlatch, G. 1., 1940, The phosphate 

resources of Tennessee: Tennessee Div. Geology Bull. 

48, 444 p. 

United Nations Economic Commission for Asia and the Far 

East, 1968, Proceedings of the seminar on sources of 

mineral raw materials for the fertilizer industry in Asia 

and the Far East: Mineral Resources Devel. Ser. 32, 

392 p. 

Waggaman, W. H., and Ruhlman, E. R., 1960, Processing 

and utilization, Pt. 2 of Phosphate rock: U.S. Bur. 

Mines Inf. Circ. 7951, 36 p. 

UNITED STATES MINERAL RESOURCES 

PIGMENTS AND FILLERS 

By c. ERVIN BROWN 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Terminology ------------------------------------

~atural pigxnents --------------------------------

Iron oxide pigxnents ------------------------- Iron oxide pigment market in the United States __ 

Competitive material -------------------------

Prospecting and field tests --------------------

Resources of iron oxides for pigments ---------

Miscellaneous pigxnents --------------------------

Manufactured pigments --------------------------

Zinc pigxnents -------------------------------

Titanium dioxide ----------------------------

Carbon black --------------------------------

Outlook for pigxnents -----------------------------

Mineral fillers ----------------------------------

Industrial filler uses and requirements ------------

Asphalt or bituminous compositions -----------

Paint ---------------------------------------

Plastics -------------------------------------

Rubber -------------------------------------

Paper -------------------------------------- Pesticides -----------------------------

Other uses ---------------------------------- Filler minerals __ -------------------------------- Wollastonite --------------------------------- Miscellaneous fillers _ _ _ _ _ _ _ 

Outlook for fillers -----------==-=----------------

Selected references ---------------================ 

FIGURE 

63. Graph showing consumption trends of seven 

major mineral fillers in the United States 

1957-69 ---------------------------------~ 

TABLES 

107. Approximate composition of earth pigxnents, in 

percent ----------------------------------

Page 

527 

528 

528 

528 

528 

529 

529 

529 

530 

530 

530 

530 

530 

531 

531 

531 

532 

532 

532 

532 

532 

532 

533 

583 

533 

535 

535 

535 

535 

Page 

533 

Page 

528 

Page 

108. ~atural iron oxide pigxnent colors and sources- 529 

109. Properties, value, and industrial utilization of 

the principal mineral fillers used in the 

United States in 1969 -------------------- 534 

ABSTRACT OF CONCLUSIONS 

Mineral fillers are finely ground, generally white, mineral 

or rock additives that impart necessary or desirable physical 

properties to a product. Mineral pigxnents are mineral-derived powders added for the sole purpose of giving color. 

The functions of fillers and pigxnents overlap inasmuch as 

one of the common purposes of a filler is coloring. 

The principal natural pigments are iron oxides, mainly 

hematite and limonite, that include various quantities of 

clay and some manganese dioxide. Production of natural 

iron oxide pigments is small and is decreasing and is being 

replaced by produc·tion of synthetic iron oxide from proces·ses using scrap iron, or copperas from Ti02 production. 

The manufacture of pigxnents from zinc ore, from rutile 

and ilmenite, and from petroleum products is a major industry. Zinc oxide is the principal zinc pigxnent made from 

zinc ore. Manufacture of zinc oxide consumed 16 percent 

of zinc mine production in 1969, and the consumption trend 

is growing. Manufacture of Ti02 pigxnent from ilmenite 

and rutile is the main use of these minerals and consumed 

96 percent of titanium ore production in 1969 .. Production 

of carbon black as a pigment and rubber reinf:orcing agent 

consumed more than 98,000 million cubic feet "of natural 

gas and 524 million gallons of liquid hydrocarbon. Together 

the value in sales of these three manufactured pigments in 

1969 totaled $426 million. 

Mineral fillers are made from many rocks and minerals, 

but kaolin, lime·stone, and talc make up about 84 percent 

of the total consumption. Fillers are essential components 

in paint, paper, plastics, pesticides, rubber, roofing, and 

fertilizer. Many fillers can be substituted for each other, 

but some have unique properties needed by c·ertain products. 

The use of wollastonite as a filler is a recent innovation. 

More than 15 rocks or minerals are commonly used as fillers, 

and in 1969 more than 7,000,000 short tons of fillers valued 

at more than $350 million was used in the United States. 

Consumption of pigments and fillers is intimately tied to 

the needs of a complex industrial society. The demand for 

these materials is expected to grow. R·esource data for the 

basic ingredients of many pigxnent and filler commodities 

are given in other chapters of this volume. 

U.S. GEOL. SURVEY PROF. PAPER 820 

527 
528 UNITED STATES MINERAL RESOURCES 

INTRODUCTION 

This report reviews the rocks, minerals, and fuels 

consumed in the United States for the production 

of pigments and fillers. It discusses ( 1) only the 

pigments made directly from minerals, metallic ores, 

and carbon black, made from gas and oil, and (2) 

only rock- and mineral-based fillers. Most natural 

mineral pigments and fillers are processed simply 

by grinding to very fine sizes. In addition some are 

calcined, and colored pigments are finished by mixing with white pigments to obtain desired tints. 

Other pigments are manufactured from metallic 

ores by chemical processes, and carbon black is produced from gas and oil by incomplete combustion 

or petrochemical methods. 

TERMINOWGY 

Fillers in the simplest sense are powders that are 

added to substances for some useful purpose. Although mineral fillers originally were intended to 

act mainly as adulterants and substitutes for more 

expensive compounds, their principal function now 

is to give some desirable or necessary property to a 

product. Commonly one of the many functions of 

fillers is to add color. Therefore, the functional field 

of fillers overlaps that of pigments, which in the 

purest sense are insoluble powders added only to 

color or tint. Because of the coloring function of 

fillers, some users refer to them as pigments. For 

example, in the rubber industry the finely divided 

clay and carbon black acting as reinforcing agents 

are called "rubber pigments," even though coloring 

is not necessarily their function. A recent paper 

(Kollonitsch and others, 1970a, b), in which the 

market for many mineral fillers is discussed, calls 

them "functional mineral pigments," distinct from 

"primary pigments" whose only function is coloring. 

The paper industry, a major consumer of fillers, 

calls them "fillers" or "coaters" depending upon 

whether the filler is "loaded" among the fibers of 

the paper sheet or is used as a surface coating. The 

paint industry uses fillers to help form the paint 

film and to extend or spread out the more expensive 

pigments and hence calls fillers "extenders." The 

pesticide and fertilizer industries use the inert but 

absorbent qualities of some fillers to dilute and 

carry the chemicals and hence call them "carriers." 

This carrier-chemical combination in turn is diluted 

further for field application by fillers known as 

"diluents." 

In order to avoid confusion, mineral filler as used 

in this report is synonymous with the special terms 

just mentioned and is a finely ground and generally 

inert rock or mineral powder added to give desirable or necessary physical properties to a finished 

product. A mineral pigment as used in this report 

is an insoluble powder added only for the purpose 

of imparting color, tint, or opacity to a finished 

product. By these definitions, a pigment is a onepurpose filler serving only to color. 

NATURAL PIGMENTS 

A comprehensive survey of the iron oxide pigment 

market in the United States and Great Britain recently appeared in the periodical "Industrial Minerals" ( 1971a). The principal previous study of 

mineral pigments was by Siegel ( 1960) . Much of 

the information in the following paragraphs is from 

these sources. 

Mining of pigments was one of the earliest mineral industries of primitive man and in America 

was done extensively by the Indians. Most notable 

among the mineral pigments are the earth colors 

produced by iron oxides. Some other mineral pigments are ultramarine from lapis lazuli, green 

earth from weathered basaltic tuffs, and a very unstable blue from azurite. Alteration of the latter 

might be responsible for the now green skies in 

some old Italian paintings (Ladoo and Myers, 1951). 

Most pigments now are produced synthetically 

from ores or metals or as byproduc,ts of other processes. The only important production of mineral 

pigment is from the natural iron oxides because 

they are inexpensive and available, although the 

market for these too is threatened by synthetic iron 

oxides because the consi~tency of color and particle 

size from synthetic iron oxides are more easily 

controlled. Increasing use of organic dyes has also 

cut deep inroads in the natural pigment market. 

IRON OXIDE PIGMENTS 

The principal iron oxide pigments are ochers, 

siennas, and umbers. Compositions vary widely, but 

limonite and hematite are the principal coloring 

agents. Mixed with these are various quantities of 

manganese oxide, clay, and in the case of Vandyke 

brown, organic material in the form of humates. 

Table 107 gives the approximate composition of 

earth pigments. 

TABLE 107.-Appro~ima.te composition of earth pigments, 

in percent 

[Adapted from Siegel, 1960] 

Fe.Oa ------------------- SiOa -------------------- AlsOa -------------------

MnOs ------------------- H.O loss on ignition -----

1 Small pereentace. 

Ocher 

17-60 

35-50 

10-40 

10-12 

Sienna 

25-75 

10-35 

10-20 

(1) 

16-20 

Umber 

37-60. 

16-35 

3--13 

11-23 

10-15 
PIGMENTS AND FILLERS 529 

Even though gradation of shades between ochers, 

siennas, and umbers is complete, the natural iron 

oxides can be conveniently classified according to 

their colors. Table 108 lists their properties, sources, 

and uses. 

TABLE 108.-N atural iron oxide pigment colors and sources 

Colors Trade 

names 

Principal 

world 

sources 

United 

States 

sources Oomment 

Yellow and Yellow ocher. South Africa; Cartersville, Permanent. 

yellow- Roman France. Ga. H~ry. opaque. 

brown. ocher. Va .• Chinese Eastern 

yellow. Pa. 

Red and Persian red. Ormuz Island. Mather iron Permanent. 

red-brown. Spanish Persian mine. opaque. red. Glilf; J aen. Marquette 

Spain. County. · Mich. 

Brown _____ Raw umber. Cyprus _____ Imported ___ Permanent 

named for colors; Raw 

Umbria. umber is 

Italy. calcined to remove or- ganic ma- terial and to oxidize the 

ferrous oxide to Fe20a and 

produce burnt 

umber. 

Dark brown -Burnt umber ____ do ______ Imported --- Do. 

Dark yellow- Raw sienna _Sienna, Italy_Imported; Transparent. 

brown. (ochers therefore can from be used for 

Georgia staining; raw are some- sienna caltimes called cined to pro- sienna). duce burnt 

sienna. Bright 

reddish 

brown. 

Burnt sienna ____ do ---------do ------ Do. 

Brown-black _Vandyke 

brown. ----------- ----------- Contains 

humates; fades to gray when 

exposed to bright light. 

Micaceous iron oxide, a pigment not included in 

tables 107 or 108, is a special-purpose pigment used 

to make anticorrosive paint and is not used for its 

color. Austria is the principal source, and about 

8,000 tons per year is mined from large continuous 

deposits. An unspecified quantity is imported by 

the United States, although this type of paint is not 

commonly used here (Am. Paint Jour., 1970). In 

England, some railway bridges painted in 1944 with 

this pigment have not rusted except where scratched 

by the inevitable graffiti (Indus. Minerals, 1971a) . 

Most mining of iron oxide pigments in the United 

States is on a small scale. The largest production 

is from the Mather mine in Marquette County, upper Michigan, where it is a coproduct of iron mining. About 25,000 tons of hematite, about 1 percent 

of the annual mine production, is produced there 

for the pigment, paint, and chemical industries. 

Other production is from small mining operations 

mainly in Georgia, Virginia, and Pennsylvania. The 

deposits in these States are limonite and ocherous 

material that has been leached from pyrite-bearing 

sedimentary rocks and redeposited by ground water 

in fractures or in the residual soil. Deposits in 

Georgia are in fractures and fault zones in Cambrian quartzites; and in eastern Pennsylavnia, 

residual deposits are associated with Paleozoic limestones and quartzites. The deposits of residual 

limonite in Virginia are in two belts, one along the 

west slope of the Blue Ridge Mountains and the 

other associated with Cambrian quartzites in Pulaski County (Siegel, 1960). These deposits at one 

time were the sites of small-scale iron-mining operations, but now they produce only pigment. 

IRON OXIDE PIGMENT MARKET IN -THE 

UNITED STATES 

Although the demand for pigments is increasing, 

the sale of natural iron oxides for pigments is declining. In 1969, finished pigments in the amount of 

142,900 short tons valued at $32.3 million were sold ; 

in 1970, sale of 40,800 short tons of crude natural 

1 pigments was $362,000. Imports of refined and synthetic iron oxides were 33,431 short tons, close to 

the amount of mine production in the United States 

(Fisher, 1969). Synthetic iron oxides are taking an 

increasingly large share of the world market. Imports into the United States include about half synthetic material. 

COMPETITIVE MATERIAL 

Although synthetic iron oxide pigment has replaced natural iron oxide in much of the market, 

the use of the natural material continues steadily 

in some areas. The synthetic material is produced 

mainly in two ways-one, by precipitation of ferrous hydroxide from an iron salt solution; and the 

other, by calcination of hydrated ferrous sulfate 

(copperas) . The first process uses scrap iron as a 

raw material, and the second uses byproduct ferrous sulfate from the production of titanium dioxide 

from ilmenite. No iron ore is used as raw material 

by the synthetic iron oxide industry. West Germany 

leads the world in this industry with exports alone 

totaling 125,600 short tons in 1970 (Indus. Minerals, 

1971a). The United States produced 70,507 short 

tons in 1969. Not all synthetic iron oxide goes to 

the pigment industry ; an unspecified amount is used 

to produce ferrites which are increasingly being 

used for their magnetic and electrical properties. 

PROSPECTING AND FIELD TESTS 

Almost any ocherous soil, vein, or deeply colored 

red, yellow, or brown sedimentary rock is potentially an iron oxide pigment. Most of these deposits 

are diluted with clay and other impurities; consequently their tinting strength is low. A simple test 

in the field for tinting strength is to grind the rna-
530 UNITED STATES MINERAL RESOURCES 

terial in a mortar and mix it with 10-20 times its 

weight of powdered ZnO and then to compare with 

commercial pigments treated similarly to disclose 

the tinting strength. Dilution with white ZnO is 

called "letting down" the pigment and is done to 

obtain desired shades in finished pigments. Another 

test is to determine the effect of particle size on the 

color. Each pigment has an optimum particle size, 

close to 1 micron, below which light scattering 

causes some undertones to be lost. On the other hand 

particle size above 2 microns causes a rough paint 

film. Tests for other properties, such as oil absorption, hiding power, and mass color are also important and are described by Siegel ( 1960). 

RESOURCES OF IRON OXIDES FOR PIGMENTS 

Because synthetic and byproduct iron oxides are 

rapidly replacing the use of natural oxides, speculation here about resources of the natural oxides 

that are discussed in the iron chapter of this volume 

is probably not significant. However, it is well to 

remember that red and yellow ocherous materials, 

such as in gossans, have a market, if they occur in 

sufficient quantity to be recovered easily. Ladoo and 

Myers ( 1951, p. 348) describe an operation jn 

which pigment is extracted from acid coal-mine 

drainage: 

. . . In Pennsylvania, where pigment recovery is attempted, 

logs and rocks are placed in the discharge of mine waters 

pumped from the mine. These obstacles agitate the water 

and aerate the solution, introducing oxygen and thereby 

accelerating the precipitation of the iron oxide. Economical 

recovery can be obtained only where there is a substantial 

tonnage within a few hundred feet of sufficient thickness 

to permit movement by ordinary shoveling . . . The yellow 

mud is shoveled from the stream, which may be diverted, or 

in some cases from the floor of the mine tunnel, with care 

to avoid contamination by soil or coal . . . 

Acid mine drainage charged with iron salts is 

one of the many pollution problems facing us today. 

Perhaps a more efficient process than that described 

above of aerating and recovering the precipitate 

from such water might provide a salable resource 

while aiding in cleaning the streams of iron in 

these problem areas. 

MISCELLANEOUS PIGMENTS 

Graphite, magnetite, and some carbonaceous slates 

have been used for black pigments, but the market 

for these materials as pigments is very small, with 

graphite the leading commodity. In 1969, graphite 

in the amount of 182 tons valued at $28,000 was 

consumed for paints and polishes. Magnetite is one 

of the few minerals that grinds to a black powder, 

but statistics on its current consumption as a pigment are not available. 

MANUFACTURED PIGMENTS 

Zinc ores, ilmenite and rutile, and fossil fuels are 

used as raw materials in the production of ZnO, 

Ti02, and carbon black, respectively-all major 

pigments. 

ZINC PIGMENTS 

Production of zinc compounds used for pigments 

in 1969 consumed 120,700 short tons of zinc ore of 

which 89,900 tons was domestic and represented 16 

percent of total zinc mine production in the United 

States. The percentage used for pigments has been 

steadily increasing, and this use should continue as 

an important market for zinc ores. 

The principal zinc compounds used as pigments 

are zinc oxide, zinc chloride, zinc sulfate, leaded 

zinc oxide, and lithopone, a coprecipitate of zinc 

sulfide and barium sulfate. Shipments of zinc oxide 

and zinc sulfate, produced mainly from zinc ore, 

have increased sharply as zinc oxide production has 

increased since 1960. The other zinc compounds are 

produced mainly from slab zinc and scrap and as 

byproducts. Consumption of zinc pigments other 

than zinc oxide and zinc sulfate is decreasing 

(Moulds, 1969). 

Zinc oxide is used mainly in the manufacture of 

white rubber products such as white sidewall tires . 

The rubber industry consumed 116,000 tons of zinc 

oxide in 1969, representing 53 percent of lead-free 

zinc oxide production (Moulds, 1969). The manufacture of photosensitive copying paper consumed 

27,600 tons of zinc oxide, and the manufacture of 

paint, particularly alkyd-latex paint used 25,200 

tons. Other zinc compounds used as pigments were 

consumed mainly by the paint industry. 

The total value of zinc pigments produced in the 

United States from zinc ores in 1969 was about 

$77.5 million out of about $80 million for zinc pigments from all zinc materials. During the year the 

United States imported an additional 23,500 tons 

of zinc pigments, an increase over previous years, 

and_ these imports were valued at $4.5 million 

(Moulds, 1969). Resources and other aspects of the 

zinc industry are discussed in the chapter of this 

volume on zinc. 

TITANIUM DIOXIDE 

Titanium dioxide, a very important pigment, is 

made from ilmenite, rutile, and titanium slag that 

is the residue after smelting ilmenite. All titanium 

dioxide for use as pigment is recrystallized after 

chemical treatment of the mineral concentrates. 

The resulting Ti02 is synthetic rutile or anatase or 

a mixture of the two. Both have very high reflect-
PIGMENT'S AND FILLERS 531 

ance; and because of rutile's high index of refraction, the rutile-type pigm~nt has a very high opacity 

or hiding power, making it valuable for paint or as 

a paper coating. 

Titanium dioxide for pigment ·is the principal 

product of titanium ores in the United States. Of 

1.29 million tons of concentrates mined in 1970, 

1.24 million tons or 96 percent was made into titanium pigments. The paint and paper industries consumed 76 percent of this and the remainder was 

divided among rubber, floor covering, textiles, ink, 

ceramics, and plastics manufacture and exports. 

The value of titanium pigments shipped in 1969 

was $333 million for 652,000 short tons (Noe, 1970); 

data for 1970 are not available. Other aspects of 

titanium and its resources are covered in the chapter of this volume on titanium. 

CARBON BLACK 

Carbon black is a nearly pure micron-sized carbon produced from natural gas or liquid petroleum 

by incomplete combustion or by thermal decomposition under carefully controlled conditions that determine the particle size, structure, and physical 

properties. Although carbon black is virtually a 

black pigment, its main use is as a reinforcing agent 

in tire rubber. As a pigment, it is used in ink and 

paint. The plastics industry used only a small 

amount of carbon black to color plastics until it 

was discovered that a larger percentage greatly improved the resistance of polyethylene to becoming 

brittle from sunlight aging. Now as much as 50 

percent carbon black is added to polyethylene cable 

coverings for this purpose (Kelley and Harper, 

1970, p. 66), another example of the overlapping 

functions of pigments and fillers. 

A direct relation exists between the expanding 

rubber industry and the growing consumption of 

carbon black. Other uses of carbon black, especially 

in inks and paints, do not show a similar increase 

in growth. Production of carbon black in 1969 was 

1.48 million short tons valued at $215 million. About 

98,251 million cubic feet of natural gas and 524.4 

million gallons of liquid hydrocarbons were consumed in its production. A process having an efficiency of 1-5 percent and using natural gas to produce "channel blacks" is giving way to much more 

efficient processes as the price of natural gas climbs 

(Kelley and Harper, 1970). Exports in 1969 were 

98,100 tons of carbon black, which represented a 

25.4 percent decrease from 1968 despite increased 

foreign production of tires. Expansion of U.S.-

owned and foreign-owned carbon black companies 

close to sources of foreign gas and oil accounts for 

this decrease in our exports (Kelley, 1969, p. 247). 

Imports in 1969 were 3,000 tons of specialty carbon 

blacks. 

OUTLOOK FOR PIGMENTS 

The demand for pigments is directly related to 

the manufacture of paint, printing inks, and coloring matter for rubber and plastics. These products 

are all voraciously consumed by a suburbia- and 

automobile-oriented society such as that of the 

United States. The demand for pigments will grow 

as population and gross national product increase. 

The demand for natural mineral pigments, such 

as iron oxide, however, is being supplanted by synthetic pigments because consistency of the manufactured product is more easily controlled. This 

trend toward the synthetic probably will continue 

although the market for good natural pigments will 

undoubtedly continue. Recovery on a large scale of 

iron oxide pigments as a byproduct of treatment of 

acid mine water is an intriguing possibility for the 

future. 

Production of ZnO, Ti02, and carbon black is 

increasing, and because these pigments are basic in 

the manufacture of paints, rubber, and plastics their 

demand will expand with the national growth. 

MINERAL FILLERS 

Mineral fillers are finely ground, generally inert 

rock or mineral additives used for the purpose of 

giving necessary or desirable physical properties to 

a finished product. Almost any rock could be pulverized and serve some of the many functions of a 

filler; however, several rocks and minerals satisfy 

the rigid physical specifications of filler products 

particularly well and are the backbone of mineral 

filler consumption, which reached 7 million tons in 

1969. The principal filler materials are kaolin, limestone, diatomite, carbon black, talc, asbestos, mica, 

barite, fuller's earth, pyrophyllite, and wollastonite. 

Many of these have specific properties, such as the 

fibrous particle shape of asbestos, that makes them 

uniquely suited for certain uses. Others, however, 

such as kaolin, talc, and pyrophyllite, can be substituted for each other for some purposes ; their use 

than also depends on availability, transportation, 

and cost of mining and beneficiation. Because of 

these additional factors and the ability of some filler 

minerals to be substituted for others, attention 

should be paid by geologists, working in districts 

with convenient transportation to industrial parts 

of the country, to the potential suitability of whitegrinding fairly soft, chemically inert rocks and 

minerals for use as mineral fillers. 
532 UNITED STATES MINERAL RESOURCES 

INDUSTRIAL FILLER USES AND 

REQUIREMENTS 

Of the varied industries using mineral fillers, each 

has specific requirements for the fillers it consumes. 

Much of the following information on the use of 

fillers was obtained from Cummins ( 1960). 

ASPHALT OR BITUMINOUS COMPOSITIONS 

Fillers are used in asphalt composition for road 

paving, roofing, reservoir linings, tile, joint sealers, 

battery boxes, and many other products to increase 

the viscosity, melting point, resistance to mechanical 

stress, hardness, or resistance to weathering. In 

many products the filler is loaded to nearly 50 percent, and in items such a8 asphalt tile, filler is the 

major component. In asphalt products the filler particles form an interlocking skeletal lattice which 

provides high viscosity and strength. Therefore, 

fibrous or platy particle shape is a more important 

property of the filler for asphalt products than are 

color and smoothness. 

PAINT 

Fillers used in paint are known as extenders because they hold more expensive pigments in suspension and upon drying form the paint film which 

supports and spreads out the pigment. Here the desirable mineral properties are platy or fibrous particle shape, smoothness and extreme fineness, high 

reflectance, and low oil absorption. The latter is important because most paints use oil and resins as 

vehicles, and therefore more pigment filler can be 

used per volume of oil and drying time is reduced if 

the oil is not absorbed by the filler particles. Desirable qualities sought through the proper choice of extender are consistency of film formation, film toughness, resistance to weathering, flatness, opacity, and 

a reduction of costs through using less prime pigment. Generally a mixture of extenders is used in 

order to get the desired paint qualities. With the 

increased use of water-based latex paints some consideration is given to the alkalinity of the filler in 

order to increase corrosion resistance. Most fillers 

are inert, but some, such as wollastonite, produce 

alkaline suspensions (Andrews, 1970), which are 

desirable to decrease "rusting through" of nail heads 

and rusting of paint cans and are compatible with 

pigments that would react if used in low pH suspension. Uniform fineness of particles is extremely 

important for paint extenders, because coarse particles show on thin paint films. For most uses, fillers 

must pass a 325-mesh screen, but as paint extenders 

they are ground to micron sizes, and techniques to 

grind particles finer are actively sought. 

PLASTICS 

Plastic floor tile has long been a major consumer 

of asbestos and other fillers. Inasmuch as the plastics industry is rapidly expanding and developing 

new products, many more types of mineral fillers 

are being used. The consumption of talc, wollastonite, and other fillers is rapidly expanding for this 

use because of the strength, electrical and heat resistance, and whiteness of these fillers. Carbon 

black is used to increase resistance of polyethylene 

to sunlight aging although it was used initially as 

a pigment. Properties desired from fillers in plastics 

are color, strength, electrical and heat resistance, 

increased melting point, stiffness, decreased brittleness, and low shrinkage. Many plastic products contain nearly 50 percent filler, which is responsible 

for most of the physical properties of the products. 

RUBBER 

The rubber industry is a major consumer of fillers 

used as reinforcing agents to increase tear resistance, abrasion resistance, stiffness, heat dissipation, 

and electrical resistance and to intensify color. Much 

research has been done by the rubber industry to 

understand the actual physical function of filler 

particles in rubber (Huber Corp., 1955; Cummins, 

1960). Particle size required for rubber fillers demands nearly 100 percent passing through a 325-

mesh screen. Grit particles tend to cause tearing 

and excess wear of cutting and extruding equipment. 

The percentage of loading fillers depends upon the 

desired quality of the finished rubber product, and 

a wide range up to more than 50 percent is common. 

For white rubber products color is important, and 

barite, zinc oxide, and titanium oxide are used with 

kaolin. Barite is also used to increase specific gravity, as in rubber mallets. Carbon black is the major 

reinforcing pigment used by the rubber industry. 

Kaolin also is an important rubber filler and is used 

to increase hardness and abrasion resistance. Very 

fine grained kaolin produces hard rubber, hence is 

known as "hard clay." "Soft clay," a coarser clay, 

allows rubber to remain soft. 

PAPER 

Another major consumer of fillers is the paper 

industry. This industry uses mineral fillers in two 

ways, one as a fill~r or loader, in which filler mixed 

with bonding agents fills the voids between the felted 

cellulose and textile fibers to be rolled out as the 

paper sheet, and the other as a surfacing material 

or coating where whiteness, opacity, and gloss are 

desired. Pigments and mineral fillers, for example 

flux-calcined diatomite with Ti02, are often used in 
PIGMENT'S AND FILLERS 533 

combination for coating. In this combination, the 

diatomite is a pigment extender (Cummins, 1960) . 

Chalk and Harris ( 1968) give a thorough discussion 

of the uses of mineral fillers by the paper industry. 

PESTICIDES 

Mineral fillers are used as diluents and carriers 

for insecticides and fungicides. Because the toxic 

elements cannot be distributed efficiently or effectively in the concentrated form, they must be diluted 

in liquids or dusts to insure proper distribution and 

a concentration that will not have deleterious effects 

on the host, yet will destroy the harmful organisms. 

The toxic chemicals are first mixed with a mineral 

powder known as a carrier to make a concentrate 

that is simple to store, ship, and handle prior to use 

in the field. Mineral fillers suitable for carrier use, 

like diatomite, fuller's earth, and some clays, are 

highly absorptive. These must be dispersible in 

liquids for sprays and must be inert and compatible 

with the toxicant involved. Fineness and low abrasiveness are important to avoid clogging and excess 

wear of nozzles. 

This carrier-pesticide mixture usually is further 

diluted for application from aircraft or ground 

equipment. The filler used for this application is 

known as a diluent. It must be of fine particle size 

and have low abrasiveness but need not be highly 

absorptive like the carrier. A good pesticide carrier 

also acts as a grinding aid in preparation of some 

pesticides, and as a conditioning agent for the 

diluent, so that dust is free flowing but will stick 

to the plant surface for maximum exposure to the 

harmful organisms (Cummins, 1960) . 

One interesting aspect of diluents and carriers is 

that some mineral dusts cause very high mortality 

rates on some insects and larvae when applied even 

without the toxic chemicals. Apparently these mineral dusts clog the digestive and respiratory systems 

(Huber Corp., 1955). 

OTHER USES 

Much mineral filler is used as a carrier and diluent 

for fertilizer, for most of the same reasons as in 

pesticides. Fillers also have miscellaneous uses in 

adhesives, joint cement, and many other products, 

each of which demands specific physical properties 

of the filler. 

FILLER MINERAlS 

Cummins (1960, tables 1 and 2) listed 19 minerals 

and mineral products, not including wollastonite, 

that commonly are used for fillers in the United 

States. Table 109 is an adaptation of his table 1 

showing major uses for the principal filler minerals. 

Resources and the export-import relation for most 

of these minerals are discussed in other chapters in 

this volurne and consequently are not discussed here. 

Pumicite, rock dusts, slate, and vermiculite are included by Cummins, but are excluded here because 

they are minor fillers or because very few data are 

available concerning their production and consumption. Further information about vermiculite is in 

the chapter on light-weight aggregates in this volume. Some fillers, such as rock dusts, are byproducts 

of other milling or mining activities. 

Excluding carbon black, 55 percent of the total 

tonnage of minerals or rocks consumed as fillers is 

kaolin. Limestone ranks second with 23 percent and 

of the remaining 22 percent, talc leads with 6 percent of the consumption, and many minor fillers 

make up the remaining 16 percent. 

The trends of domestic demand for seven major 

fillers for the past 12 years are shown in figure 63. 

Kaolin, fuller's earth, and talc show increasing 

~~----~-----.-----.------~----~~----~ 

4000 

3000 

--

LIMESTONE (Method of reporting 

date changed in 1958) 

KAOLIN ---- ........ ---- --____ ..,.,. 

10L-----~-----L----~------~----~----~ 

1957 1959 1961 1963 1965 1967 1969 

FIGURE ~.-Consumption trends of seven major mineral 

fillers in the United States, 1957-69. 
UNITED STATES MINERAL RESOURCES 

TABLE 109.-Properties, value, and industrial utilization of the princ.ipal mineral fillers used in the United States in 1969 

[ X, percentage unknown] 

Distribution by end. use (in percent, if known) 

Percent- Approxi- Approximate 

tonage used 

in United 

States for 

ftller (in 

age of mate Mineral total com- value (in Distinguishing 

ftller rnodity thous- properties Remarks 

consump- ands of 

thousands of 

tons) 

tion dollars) 

Asbestos -------- >75 X 

Barite ---------- 75 20 

Bentonite and 7 

other claya, ex- cluding fuller's 

earth and kaolin. 

Carbon black ---- X1 90 ± 5 

Diatomite ------- X X X X X 

Fuller's earth --- - - - 95 

Gypsum -------- X - X - X 

Kaolin --------- 4 12 75 3 <1 2 

Limestone ------- X X X X X 

Mica, ground ---- 37 9 x2 <1 52 

Perlite ---------- X - X 

Pyrophyllite ----- X X X X 

Silica, ground ___ X X X 

Tale ----------- 47 7 16 16 X 8 

Wollastonite ----- X X X 

Total ------ -

1 Used as a pigment. 

2 Used in wallpaper. 

X 25 

5 4 

93 0.5 

X P5 

X 20 

5 20 

4 66 

X 5 

X 62 

X 

X 65± 

X Small 

X 40 

25± 

consumption as fillers ; consumption of barite as a 

filler has decreased in the last few years after it 

showed a spectacular increase starting in about 

1960. As a filler, diatomite has experienced no increased demand, and mica has a very erratic demand. Limestone, which along with kaolin is the 

major filler, has had a strong decrease in demand 

as a filler, although information is incomplete be20,000 

>4,000 

500 

200,000 

7,200 

5,000 

Nearly all uses based on fibrous nature. 

Highest density ftller; 

inert, light colored. 

Absorbent ----------

Extremely fine particle 

size; only black filler. Inert or reactive opaline silica dependIng upon whether 

calcined; skeletal 

silica particles. 

Absorbent: cost low 

3,000± Low cost; soft ------

67,500 

22,000 

5,100 

220 

White, low oil absorption; abundant, low cost. 

High brightness; low 

oil absorption; 

availability good and cost low. 

Micaceous structure; 

high dielectric 

strength, spangled 

sheen to wallpaper. 

Light-weight; vesicular structure. 

1,000± Inert, soft, high 

brightness. 

14,000 

200 

350,000 

Hardness; low oil 

absorption. 

Inert, soft, high 

brightness; some varieties fibrous or platy. 

White, acicular-fibrous; 

low oll absorption; 

alkaline suspension. 

200 Filler uses take mainly 

"fines" and "shorts." 

(See "Asbestos" chapter.) 66 About 81) percent of the 

world's annual production 

is used for heavy drilling 

mud. (See "Barite" 

chapter.) 

28 Not an important ftller; 

mainly an insecticide dilu- ent. (See "Clay" chapter.) 

1,480 Excellent rubber reinforcing 

agent. Also a pigment. 

120 Used in raw state, milled or calcined for ftllers. Large reserves. (See "Diatomite" 

chapter.) 

187 Mainly used for ftoor sweeping compound, rotary drilling muds, and deoolorizing 

agent. (See "Clay" 

chapter.) 

100± Minor ftller mineral; used raw or calcined. (See 

"Evaporites and brines" 

chapter.) 

3,164 Most important ftller mineral, 

principal paper ftller, important rubber ftller. (See 

"Clay" chapter.) 

1,300 Cheapest ftller; has low oll 

absorption and good color. 

Main ftller for putty, caulking, and sealants. (See 

"Limestone and Dolomite" 

chapter.) 79 Scrap mica, including some phlogopite and biotite. Mica 

and;.' se'rieite schists are re- sources. (See "Mica" 

chapter.) 

5 Not an important filler. 

Mainly used for plaster and concrete aggregate and 

filtering aid. (See "LightWeight Aggregate" 

chapter.) 111 Statistics reported with tale 

in U.S. Bur. Mines Year- books; about 27,000 tons used for ceramics. For paint extender in deck 

paints, for high abrasive use. 350 Some grades contain much 

tremolite, anthophyllite, or serpentine. (See "Tale" 

chapter.) 

5 Mainly used in ceramics; 

7,200 

newest important filler 

mineral. 

cause the U.S. Bureau of Mines since 1967 has 

reported limestone data differently, and the 1969 

figure for limestone as a filler (Kollonitsch and 

others, 1970a) is not explained. 

Although most filler minerals are discussed elsewhere in this volume, wollastonite, a mineral relatively new to the filler industry, is not discussed 

elsewhere and is reported on here. 
PIGMENT'S AND FILLERS 535 

WOLLASTONITE 

Wollastonite (CaSiOs) an acicular white mineral, 

is used mainly for wall tile and other ceramic products. It is an excellent ceramic material in that it 

can be fired rapidly because no H20 or C02 must be 

driven off. The resulting ceramic does not absorb 

water and is resistant to thermal shock and brittleness. Although wollastonite is mainly used by the 

ceramic industry, its use as a filler is becoming 

much more common. The finished filler is brilliantly 

white, fibrous, and an excellent paint extender because its fibrous character suspends the pigment 

and prevents the accumulation of hard sediment in 

the paint can. Wollastonite also forms a strong paint 

film that weathers well. The filler is chemically 

stable, and suspensions of wollastonite are alkaline 

with a pH of about 10 (Andrews, 1970). This alkalinity has an advantage in paints like polyvinyl 

acetate that decompose in time, forming acetic acid. 

The alkaline suspension neutralizes the acid and 

prevents corrosion of the paint can. 

The rubber industry uses wollastonite as a semireinforcing filler in nonblack rubber goods. The 

plastics industry uses it in thermosetting and thermoplastic casein resins and in asphalt and vinyl 

floor tiles. Wollastonite filler has high opacity and 

has been experimented with as a filler and coater 

for paper. For these uses, however, it apparently 

cannot compete with kaolin, which is less expensive. 

Most wollastonite is found in contact metamorphic 

zones between calcareous and intrusive rocks. In the 

United States it was mined for mineral wool as 

early as the 1930's from a small deposit in Kern 

County, Calif. A much larger deposit at Willsboro, 

N.Y., along the contact of the anorthosite mass in 

the northeastern part of the Adirondack Mountains, 

was developed in the early 1950's, and material 

mined from there since 1953 is used in an everincreasing number of products. Total world production of wollastonite has been not over 50,000 

tons, and four-fifths of this has come from the New 

York deposit. The other principal producers are 

Mexico and Finland. Andrews (1970) has a complete and comprehensive report on wollastonite, its 

uses, and resources throughout the world. The periodical "Industrial Minerals" (1969b, and Whitmer, 

1969) also presented a thorough study of wollastonite. 

Although most of the U.S. production of wollastonite is from the deposit in New York, the mineral 

is still mined in Riverside County, Calif., where 

recovery is mainly for decorative stone. In 1966, 

however, some mining for industrial wollastonite 

was begun from the California deposits, but production since then apparently has been small. 

Arizona, Nevada, Utah, and the Virgin Islands 

are also cited by Andrews (1970) as containing 

notable occurrences of wollastonite. 

World identified resources of wollastonite amount 

to more than 60 million tons, and hypothetical resources are three times that according to Andrews 

(1970, p. 2). An appraisal of resources by nations 

has not been made. 

MISCELLANEOUS FILLERS 

Several other minerals and rocks such as Portland cement, gypsum, rock dust, ground slate, and 

phosphorite are locally and occasionally used as 

fillers. A small quantity of feldspar also has been 

used in the past few years as an extender in paint 

and a filler in rubber. 

OUTLOOK FOR FILLERS 

The market for mineral fillers is intimately dependent on the needs of a complex industrial society. 

The demand has steadily grown and should continue 

as a result of expansion of paper, plastics, paint, 

rubber, and other industries. No great spurts have 

occurred in the consumption of any one filler, and 

in fact consumption of some has declined ; nevertheless, the overall demand has continued with many 

small advances as new products and uses are devised. 

This steady growth in demand will undoubtedly 

continue in the United States. Because industries 

requiring fillers generally seek a local source for 

filler material to avoid high transportation costs, 

any light-colored inert rocks with low-cost transportation to industrial areas should be evaluated 

for their potential use as a filler to help satisfy 

this expanding demand. 

SELECTED REFERENCES 

American Paint Journal, 1970, Micaceous iron oxide: Am. 

Paint Jour., v. 54, June 22, 1970, p. 68-81. 

Andrews, R. W., 1970, Wollastonite: London, Inst. Geol. Sci., 

114 p. 

Chalk, Raymond, and Harris, G. R., 1968, Pulp and paper 

process minerals: Canadian Inst. Mining and Metallurgy 

Bull., v. 61, no. 680, p. 1427-1437. 

Cummins, A. B., 1960, Mineral fillers, in Industrial minerals 

and rocks, 3d ed: New York, Am. Inst. Mining, Metall., 

and Petroleum Engineers, p. 567-584. 

Fisher, W. L., 1965, Rock and mineral resources of East 

Texas: Bur. Econ. Geology, Texas Univ. Rept. Inv., 54, 

p. 287-294. 

Fisher, F. L., 1969, Iron oxide pigments, in Minerals yearbook, 1969: U.S. Bur. Mines, p. 613-616. 

Huber Corporation, 1955, Kaolin clays and their industrial 

uses: New York, J. M. Huber Corp., 214 p. 

Industrial Minerals, 1968, Talc-mineral with a multitude of 

uses: London, Indus. Minerals, no. 5, February, p. 9-16. 
536 UNITED STATES MINERAL RESOURCES 

1969a, Diatomite: its production, uses and potential: London, . Indus. Minerals, no. 18, March, p. 9-

27. 

----- 1969b, Wollastonite comes of age: London, Indus. 

Minerals, no. 19, April, p. 8-13. 

1970, Need for high TiO:~ feed for pigments: 

London, Indus. Minerals, no. 35, August, p. 38-39. 

1971a, Iron oxide pigments: London, Indus. 

Minerals, no. 50, November, p. 9-19. 

----- 1971b, Kaolin in the USA: London, Indus. Minerals, no. 5':1., December, p. 9-30. 

----- 1972, Calcium carbonate--natural chalk whiting; 

ground limestone; and precipitated calcium carbonate: 

London, Indus. Minerals, no. 54, March, p. 9-17. 

Key, W. W., 1965, Mineral fillers for the California pesticide 

industry: U.S. Bur. Mines Inf. Circ. 8260, 39 p. 

Kelley, C. W., 1969, Carbon black, in Minerals yearbook, 

1969: U.S. Bur. Mines, p. 245-254. 

Kelley, C. W., and Harper, W. B., 1970, Carbon, in Mineral facts and problems, 1970 ed.: U.S. Bur. Mines Bull. 

650, p. 63-77. 

Kollonitsch, Valerie, Kliff, E. F., and Kline, C. H., 1970a, 

Functional pigments, pt. 1 : London: Indus. Minerals, no. 

38, November, p. 35-40. 

----- 1970b, Functional pigments, pt. 2: London, Indus. 

Minerals, no. 39, December, p. 46-51. 

Ladoo, R. B., and Myers, W. M., 1951, Nonmetallic minerals, 

2d ed.: New York, McGraw-Hill, 605 p. 

Moulds, D. E., 1969, Zinc, in Minerals yearbook, 1969: U.S. 

Bur. Mines, p. 1143-1168. 

Noe, F. E., 1970, Titanium, in Minerals yearbook, 1970: U.S. 

Bur. Mines [preprint], 13 p. 

Siegel, Alfred, 1960, Mineral pigments, in Industrial minerals and rocks, 3d ed.: New York, Am. Inst. Mining, 

Metall., and Petroleum Engineers, p. 585-593. 

Stipp, H. E., 1970, Iron oxide pigments, in Minerals yearbook, 1970: U.S. Bur. Mines [preprint], 4 p. 

Watkins, T. C., Norton, L. B., Weidhass, D. E., and Brann, 

J. L., Jr., 1955, Handbook of insecticide dust, dilutents, 

and carriers, 2d ed. : Caldwell, N.J., Dorland Books, 150 

p. 

Whitmer, M .T., 1969, Versatile wollastonite: London, Indus. 

Minerals, no. 19, April, p. 16-20. 

Wilson, Hewitt, 1933, Iron oxide mineral pigments of the 

United States: U.S. Bur. Mines Bull. 370, 198 p. 
UNITED STATES MINERAL RESOURCES 

PLATINUM-GROUP METALS 

By NoRMAN J PAGE} ALLEN L. CLARK} GEORGE A. DESBOROUGH 

and RAYMOND L. PARKER 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Exploitation -------------------------------------

Geologic environment ---------------------------- Geoehemistry _______________________________ _ 

Major minerals of the platinum elements ------

Classification of deposits ---------------------

Stratiform complexes ---------------------

Concentric complexes --------------------

Alpine complexes ------------------------

Other mafic-rock environments ------------

Placers ---------------------------------- Minor occurrences ------------------------

Resources --------------------------------------- Identified and hypothetical resources -----------

Speculative resources -------------------------

Prospecting techniques ---------------------------

Problems for research ----------------------------

References cited ---------------------------------

TABLES 

110. Principal minerals and domestic occurrences --

111. Composition, in weight percent, of ferroplatinum ------------------------------------- 112. Identified, hypothetical, and speculative resources ---------------------------------- 113. Concentrations of platinum, palladium, rhodium, and iridium, southeastern Alaska ----

114. Correlations of maximum platinum-palladium 

concentrations, southeastern Alaska --------

ABSTRACT OF CONCLUSIO~S 

Page 

537 

537 

537 

538 

538 

538 

538 

539 

540 

540 

540 

540 

540 

541 

541 

542 

543 

544 

544 

Page 

539 

540 

541 

542 

543 

The United States produces only 1-2 percent of the platnum metals that it uses and is therefore virtually totally 

dependent upon foreign supplies; accordingly, the hypothetical and speculative resources in Alaska, Montana, California, Oregon, and Washington are of some interest for 

possible future platinum production. More precise evaluation of these resources will not be possible without improved 

analytical techniques for the platinum-group metals at concentrations less than 10 parts per million. The current lack 

of such techniques greatly hinders geological, geochemical, 

petrological, and mineralogical research necessary to evaluate the potential platinum resources. 

INTRODUCTION 

Platinum, palladium, iridium, osmium, rhodium, 

and ruthenium are the platinum-group metals. Platinum and palladium are the most abundant of this 

group, but all these metals are essential to modem 

industry where their applications are based on their 

catalytic properties, electrical conductivity, and resistance to chemical corrosion, heat, and oxidation. 

About 1.3 million ounces per year of platinum-group 

metals (Ageton and Ryan, 1970) are consumed in 

the United States (1) by electrical manufacturers as 

electrical contacts in high-precision instruments and 

insoluble anodes for metallurgical processing ; (2) 

by the chemical industry as catalytic gauze for oxidation of ammonia and the manufacture of nitric 

acid; (3) in petroleum refining as a catalyst to produce high-octane gasoline; ( 4) in dental and medical 

devices; (5) in decorative arts and jewelry; and (6) 

as spinnerettes used in manufacturing glass and synthetic fibers. 

The United States produces only 1-2 percent of the 

platinum metals that it uses and is therefore almost 

totally dependent upon foreign supplies. The major 

sources are the Republic of South Africa, U.S.S.R., 

Canada, and Colombia. 

EXPLOITATION 

Platinum metals have a long and somewhat erratic 

history of exploitation beginning in the 7th Century 

B.C. when a single forged grain of platinum was used 

as a hieroglyphic character by an Egyptian artisan 

to decorate an etui. It was reported to have been used 

U.S. GEOL. SURVEY PROF. PAPER 820 

537 
538 UNITED STATES MINERAL RESOURCES 

by Indians in Colombia before the arrival of the 

Spanish. Although Colombian placers were first described by Scaliger (1557, p. 323-324), mining of 

them did not begin until 1778, soon after the first 

chemical work on platinum was done. Until 1823, 

Colombia was the only source of platinum metals, but 

soon after the 1822 discovery of phittinum in placers 

in the Ural Mountains, Russia became the world's 

greatest producer, which it has remained except 

during 1936-61. 

Platinum placers were mined as early as 1885 in 

Canada, but lode deposits were not mined for platinum until 1919, when platinum metals began to be 

recovered from the nickel-copper deposits of the Sudbury district. By 1936, Canada had become the principal producer. In 1923 platinum lodes were discovered in Transvaal, Republic of South Africa, and 

in the following year in the Bushveld Complex. By 

1956 and 1957, output from these lodes outstripped 

Canadian production. Russia ranked third for a long 

time, but as the Uralian placers became depleted, 

lodes were found in Siberia that by 1961 again raised 

Russian output to first rank, with the Bushveld and 

Transvaal second and Canada third. In 1929, platinum placers were discovered in Alaska, and since 

1934, Alaska has ranked fifth in world production, 

and Colombia fourth. The Witwatersrand district, 

South Africa, a producer of osmiridium, ranks sixth. 

Through most of the first quarter of the 20th 

Century, placer deposits furnished the world's supply. The discovery of lodes in South Africa, Canada, 

and Siberia so altered the situation that in 1971 

these three countries produced more than 98 percent 

of the world's output. Production records have not 

been accurately kept, but production has amounted 

to about 63,685,000 ounces through 1971. 

The geologic occurrence of platinum-group metals 

as lodes or placers dictates that copper, nickel, gold, 

silver, and chromium will be either coproducts or byproducts in the recovery of the platinum metals and 

that platinum will be largely a byproduct. For example, about 1 ounce of platinum-group metals is 

recovered for each 35 tons of copper produced (Ageton and Ryan, 1970) from domestic ores. Because a 

larger part of the domestic production is a byproduct 

of copper mining, environmental e·ffects or problems 

mainly are those directly related to the mining 

and refining of copper. Indeed, a suggested use of 

platinum catalysts is as a potential pollution control 

of nitrogen oxide fumes. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

The crustal abundance of the platinum-group 

metals (Wright and Fleischer, 1965) is poorly 

known, owing to the low concentration of these elements and inaccurate analytical techniques. Mason 

(1958) estimated crustal abundances as follows: Pt, 

5 ppb; Pd, 10 ppb; and Ir, Os, Rh, and Ru, 1 ppb each. 

Useful equivalents are: 1 ppb (part per billion) = 

0.001 ppm (part per million) = 0.000032 oz per ton 

(troy ounce per ton). 

The complex, unique, but poorly known chemical 

nature of the platinum-group elements in geologic 

environments prohibits accurate generalizations regarding their distribution and geochemical cycle. 

The highest concentrations of the platinum elements 

are generally in igneous rocks that formed at high 

temperatures, an indication that the platinum metals 

are indigenous to the earth's mantle. Certain conditions of high temperature and (or) high sulfur partial pressure may result in mobilization and concentration of the platinum-group elements. Because of 

their high specific gravity, the platinum metals are 

concentrated by surficial or hydrologic processes to 

form placer deposits. 

MAJOR MINERALS OF THE PLATINUM ELEMENTS 

The platinum metals are major constituents of 

several metallic alloys and a number of minerals with 

anions of sulfur, arsenic, antimony, bismuth, and 

tellurium. As Wright and Fleischer (1965) listed 

most of the known platinum minerals and references 

to their mineralogy, this re~ort considers only those 

in domestic occurrences (table 110). With the exception of occurrences in the Stillwater Complex, Montana, virtually all the known platinum-group minerals in the United States come from placers, in 

which the material ranges from microscopic-size 

grains to nuggets several centimeters in the largest 

dimension. Mertie (1940, p. 72) observed that most 

nuggets and grains are composed of two or more 

minerals intergrown to form the grains, and recent 

microscopic and electron microprobe studies have 

validated this observation. 

CLASSIFICATION OF DEPOSITS 

The major workable deposits of platinum metals 

occur with nickel-copper and copper lodes associated 

with mafi·c and ultramafic rocks and as platinum alloys in placers. Mafic and ultramafic rocks form at 

least three distinctive types of igneous complexes 

(Jackson and Thayer, 1972) : (1) Stratiformfloored, tabular complexes consisting of vertical 

repetitions of well-layered rock sequences with cumulus textures, that are intrusive into Precambrian 

shields or into basaltic terranes of any age; (2) 

Concentric-roughly cylindrical, zoned complexes 
PLATINUM-GROUP METALS 539 

TABLE 110.-Principal minerals and domestic occurrences of 

the platinum-group metals identified by electron mic,roprobe or X-ray diffraction analysis 

Name or approximate 

composition 

Locality 

Alloys or metals 

Ferroplatinum (Pt, Fe, Ir, 

Os, Ru, Rh, Pd, Cu, Ni). 

Iridium-ruthenium-osmium _ 

Osmium ------------------- Osmium-iridium -----------

Goodnews Bay, Alaska __ _ Humbodlt County, Calif __ 

Trinity River, Calif ------

Stillwater, Mont ---------

Port Orford, Oreg ------- Goodnews Bay, Alaska __ _ 

Humboldt County, Calif __ 

Trinity River, Calif -----

Goodnews Bay, Alaska __ _ Goodnews Bay, Alaska __ _ 

Beegum Creek, Calif ---- Hay Fork Creek, Calif __ Humboldt County, Calif __ Antelope-Pony dist., Madi- son County, Mont. 

Port Orford, Oreg ------

Sulfides 

Laurite, (Ru, Ir, Os)S2 -·- Goodnews Bay, Alaska __ _ 

Port Orford, Oreg ------- Stillwater, Mont ---------

Erlichmanite, OsS2 -------- Trinity River, Calif ____ _ 

Cooperite, PtS ------------ Humboldt County, Calif __ 

Stillwater, Mont --------- Unnamed, (Ir, Rh, Pd) S __ Goodnews Bay, Alaska __ _ 

Arsenides and antimonides 

Mertieite, Pt5(Sb,As)2 ----- Goodnews Bay, Alaska __ _ 

Sperrylite, PtAs2 ---------- Humboldt County, Calif __ 

Stillwater, Mont ---------

Goodnews Bay, Alaska __ _ 

Rodian sperrylite, (Pt, Humboldt County, Calif __ Rh, Ni, Pd) (As, 8)2. 

Osarsite, (Os, Ru(AsS) ____ Gold Bluff, Calif ---------

Reference 

This study. Do. Snetsinger 

(1971a). 

Page ( 1971); 

Page and 

others 

(1971). 

This study. 

Leonard and 

others 

(1969). 

This study. 

Snetsinger 

(1971a). 

This study. Do. Spencer (1971). 

Do. 

This study. Do. 

Do. 

Leonard and 

others 

(1969). 

This study. 

Page (1971); 

Leonard and 

others 

(1969). 

Snetsinger 

(1971b). 

This study. Do. This study. 

Desborough and 

others 

(1972). 

This study. 

Howland and 

others 

(1936). 

J. B. Mertie, 

Jr., (written commun., 

1972). 

This study. 

Snetsinger 

(1972'). 

consisting of layers formed by sedimentary, metamorphic, and igneous processes, that are intruded 

into metamorphic rocks of eugeosynclinal orogenic 

belts; and (3) Alpine-irregularly shaped discordant 

complexes consisting of dis·cordant lenticular layers 

of rocks with tectonite fabrics, that are tectonically 

emplaced in eugeosynclinal orogenic belts and island 

arcs. 

Layered deposits or contact-metamorphic deposits 

associated with stratiform and concentric complexes 

are the major sites of platinum-lode deposits. Examples are the Merensky Reef in the stratiform 

Bushveld Complex, South Africa (Cousins, 1969), 

and the deposit of the Noril'sk district, Siberia 

(Mertie, 1969), which could be classified as a concentric mafic complex. 

Platinum placers consist of unconsolidated alluvial 

deposits in present or ancient stream valleys, terraces, beaches, deltas, and glaciofluvial outwash, and 

in lithified placers of similar origin. The placer 

metals are commonly derived from mafic and ultramafic rocks, but may come from nearby sources in 

sedimentary rocks, having ultimately been derived 

from mafic and ultramafic rocks during a previous 

erosion cycle. As the densities and sizes of platinum 

alloys are generally similar to those of alluvial gold, 

some platinum metals, when present, are recovered 

from gold placers. 

A domestic source of platinum-group metals is as 

a byproduct of refining copper from porphyry and 

other copper deposits and from lode and placer gold 

deposits, although the grade is extremely low. Other 

minor lode sources are in copper-gold contact-metamorphic deposits, copper deposits associated with 

syenitic rocks, and gold-quartz veins. Relatively 

small potential deposits exist domestically; such ores 

represent only a minor platinum resource, but serve 

to indicate the range of geologic environments. 

STRATIFORM COMPLEXES 

The Stillwater Complex (Hess, 1960; Jones and 

others, 1960; Jackson, 1961; Page and Nokleberg, 

1970) of Precambrian age in southwestern Montana 

contains several potential platinum lodes. Platinum, 

palladium, and rhodium are concentrated in the 

chromitite zones, but individual samples vary widely 

in contents and ratios of these three platinum metals 

(Page and others, 1969; 1971). The lowermost 

chromitite, the A zone, averages 0.10 oz/ton and 

attains a maximum known value of 0.60 oz/ton of 

Pt + Pd + Rh. Stibiopalladinite, sperry lite, cooperite, 

platinum-iron alloy, and laurite are the only platinum 

minerals identified (Page, 1971) ; they occur as inclusions (average diameter 5-10J.L) in chromite and 

in interstitial sulfides. Chromium shows the strongest correlation with platinum metals, V a moderate 

correlation, and Ni, Co, and Cu a lower correlation. 

Platinum metals occur in the greatest amounts 

where the oxidation ratio of chromite is lowest. This 

relation suggests that less oxidizing conditions 

favoring crystallization of chromite also favored the 

concentration of platinum metals from the magma. 

Platinum metals, though in lesser amounts, also occur below the A zone in the basal zone and are 

associated with massive and disseminated coppernickel sulfides. Small amounts of platinum metals 

have also been reported from disseminated sulfide 
540 UNITED ST'A TES MINERAL RESOURCES 

layers in the upper gabbroic rocks of the complex 

(Howland and others, 1936; Page and Jackson, 1967; 

Page and others, 1969). 

CONCENTRIC COMPLEXES 

The concentrically zoned ultramafic complexes and 

associated mafic bodies of southeastern Alaska contain only one known platinum lode, developed by the 

Salt Chuck mine. Both platinum and palladium were 

recovered as a byproduct of copper mining. The ore 

minerals occur as small masses and disseminations 

in pyroxenite, gabbro, and gabbro pegmatite (Mertie, 

1969, p. 76). The platinum metals are closely associated with bornite and chalcopyrite. The form in 

which the platinum metals occur is not known, but 

sperrylite has been identified in one specimen. 

Potential platinum lodes may exist within the concentrically zoned ultramafics, as shown by anomalous 

concentrations of platinum as high as 29 ppm in the 

chromite-bearing dunite core of the ultramafic complex at Union Bay. 

ALPINE COMPLEXES 

Alpine complexes may or may not represent potential platinum resources, judged on relatively few 

modern analyses. Eighteen dunites and harzburgites 

from Burro Mountain, Calif., average 12.8 ppb Pt, 

3.7 ppb Pd, and <5 ppb Rh (Loney and others, 1971). 

Analyses of dunites and harzburgites from Red 

Mountain and New Idria in California, and of similar 

rocks from Twin Sisters and Cypress Island in Washington, average <10 ppb Pt, <4 ppb Pd, and 

< 5 ppb Rh. Chromites from these occurrences average slightly higher-36 ppb Pt, 10 ppb Pd, and 9.5 

ppb Rh (Page, 1969). 

OTHER MAFIC-ROCK ENVIRONMENTS 

Minor platinum-metal deposits associated with 

copper, nickel, and gold in mafic and ultramafic rocks 

are probably insignificant in terms of platinum-metal 

resources but illustrate other environments where 

platinum metals are found. For example, deposits in 

the Bunkerville district, Nevada (Beal, 1965), have 

a reported range in grade of 0.14 to 0.25 oz/ton. 

Another example is in the Revais Creek district, 

Montana, where 0.23-0.54 ppm Pt and 0.10-0.79 ppm 

Pd (eight samples from the Copper King deposit) are 

found in a gold-silver-copper ore that consists of 

chalcocite, bornite, and chalcopyrite. The ore is in a 

hornblende gabbro dike and in the Ravalli Group 

(Precambrian) that it intrudes. The Rambler and 

Centennial mines, Wyoming, produced a small 

amount of platinum-group metals with a grade 

between 1 and 1.3 oz/ton from deposits of irregular 

shape in mafic igneous and metamorphic rocks (Mertie, 1969; Theobald and Thompson, 1968). 

PLACERS 

Platinum-group metals occur in many placers 

within the United States. Minor amounts of the 

platinum group have been recovered from the gold 

dredges of California and from the gold placers of 

Oregon, Washington, Montana, Idaho (Logan, 1919), 

and Alaska, but significant amounts have been produced only from the placers of the Goodnews Bay 

district, Alaska. 

Platinum-metal-bearing place·rs of the Goodnews 

Bay mining district occur in two paystreaks in the 

valley of the Salmon River (Mertie, 1969, p. 80). 

Total production from 1927 to 1969 is believed to 

have been considerably more than half a million troy 

ounces, with a maximum output exceeding 30,000 

ounces in 1938 (Mertie, 1969, p. 79). The weighted 

mean percentages of metals mined from 1936 to 1970 

are 82.31 percent platinum, 11.28 iridium, 2.15 osmium, 0.17 ruthenium, 1.29 rhodium, 0.38 palladium, 

and 2.24 gold. 

The platinum metals of these placers are contained 

mainly in two alloys. The major alloy is ferroplatinum; microprobe analyses by G. A. Desborough gave 

the results shown in table 111. The minor alloy conTABLE 111.-Composition, in weight percent, of ferroplatinum 

in 50 placer grains from Goodnews Bay, Alaska 

Mean (standard deviation) Range 

Pt -------------------------- Fe -------------------------- Ir -------------------------- Rh -------------------------- Pd -------------------------- Cu -------------------------- Os --------------------------

Ru --------------------------

86.1 (1.8) 

9.3 (.6) 

2.26 (1.70) 

.9 (.5) 

.65 (.3) 

.7 (.3) 

.3 (.3) 

.1 

82.7-88.6 

8.2-11.2 

.1- 2.0 

.1- 2.0 

.1- 1.4 

.1- 1.1 

.1- .8 

.1- .1 

sists dominantly of iridium and osmium, with small 

amounts of platinum, and still smaller amounts of 

ruthenium and rhodium. In addition to these two 

alloys, minute amounts of five platinum mineralscooperite, laurite, sperrylite, mertieite, and a yetunnamed iridium-palladium sulfide (table 111)-

have been identified. 

MINOR OCCURRENCES 

Platinum metals are associated with alkalic intrusive rocks (syenites) that have copper mineralization, but very little is known about this environment. The Copper Hill mine, La Plata mining district, Colorado (Eckel, 1949), is in an ore zone of 

chalcopyrite that contains platinum and palladium. 
PLATINUM-GROUP METALS 541 

(A recent analysis of chalcopyrite-bearing dump material by L. T. Riley and 0. M. Parker, U.S. Geol. Survey, gives 0.37 ppm Pt and 0.45 ppm Pd.) Analyses 

by the U.S. Bureau of Mines from samples in the 

small area immediately surrounding the glory hole 

of the Copper Hill mine averaged 1.87 percent Cu, 

0.49 ounce Ag, and 0.005 ounce platinum metals. 

Other recognized minerals are hematite, magnetite, 

pyrite, garnet, ankerite, quartz, and fluorite. The 

ore zone seems to be the result of intense late-stage 

fracturing and subsequent replacement of the rock 

with orthoclase and ore minerals, mainly chalcopyrite, in a highly sericitized and feldspathized 

porphyry. 

Another chalcopyrite deposit, in a syenite near 

Cooke City, Mont., contains 0.5 to 10 ppm Pt, 0.15 

to 3 ppm Pd, and as much as 0.04 ppm Rh (U.S. Geol. 

Survey, 1971). This deposit also is associated with 

widespread potassium metasomatism and veining of 

potassium feldspar. 

The Boss mine, Nevada (Hewett, 1931), is a typical example of the gold-quartz association. (For other examples, see Mertie, 1969.) About 1,000 ounces 

of platinum metals were recovered from a pipeshaped gold-copper-quartz deposit in a minor fault 

zone. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Identified and hypothetical resources estimates are 

given in table 112. The numbers of ounces of platinum-group metals should be viewed with extreme 

caution and recognized as estimates of order of magnitude. Total known and potential platinum-group 

metal resources obviously must not exceed the total 

production to date and the amount in the earth's 

crust. The lower limit is 63,685,000 ounces ; the upper limit, using Poldervaart's (1955) estimated mass 

of the earth's crust and Mason's (1958) average 

abundance of platinum-group metals, must be much 

less than 1.5 x 1016 ounces. Ageton and Ryan (1970) 

estimated the world reserves at 424 million ouncesprobably a conservative estimate. 

The estimates of subeconomic resources of platinum-group metals in the concentric zoned ultramafic 

complexes of Alaska are based on published reserves 

of 500 X 106 tons of titaniferous magnetite at the 

Klukwan deposit (averaging 0.0027 oz per ton platinum metals) and 500 x 106 tons of titaniferous magnetite at the Snettisham deposit (average 0.0027 oz 

per ton platinum metals). Additional areas of titaniferous magnetite associated with both of the bodies 

have a total potential of 3.5 x 109 tons (averaging 

0.0027 oz per ton platinum metals). 

TABLE 112.-Identijied, hypothetical, and speculative resources 

of platinum-group metals, in million troy ounces 

IDENTIFIED RESOURCES 1 

Summary data from Ageton and Ryan (1970) 

World (total) --------------------------------- 424 

United States (total) -------------------------- 3 

Goodnews Bay, Alaska ----------- .3 

Salt Chuck, Alaska --------------- .012 

South Africa ---------------------------------- 200 

U.S.S.R. --------------------------------------- 200 

Canada --------------------------------------- 16 

Colombia -------------------------------------- 5 

Data from various sources 

Alaska: 

Snettisham -------------------------------- 4.55 

Klukwan ---------------------------------- 7.55 

Goodnews Bay ----------------------------- 6.8 

Lodes ------------------------ 1.3 

~:i~he_s_======================= 5:g Lituya Bay beaches ------------------------ .06 

Gold placers ------------------------------- .016 

Porphyry copper -------------------------- .06 

Copper deposits ---------------------------- .002 

Montana, Stillwater Complex: 

Basal zone -------------------------------- 2.4 

Chromites --------------------------------- 2.2 

California, Tertiary gravels -------------------- .008 

Western United States, porphyry copper -------- 2 .002 

United States, minor occurrences --------------- .002 

South Africa, Bushveld Complex ---------------- 656 

Rhodesia, Great Dyke -------------------------- 1 100 

South Africa. Witwatersrand ------------------- 3 .075 

HYPOTHETICAL RESOURCES' 

Alaska: 

Concentric complexes ----------------------- 35 

Porphyry copper -------------------------- Gold deposits ------------------------------ Montana, Stillwater Complex: Basal zone -------- Conterminous United States: 

.15 

.032 

150 

Gold placers ------------------------------- Chromite deposits, excluding Stillwater 

Complex --------------------------------

SPECULATIVE RESOURCES 5 

Alaska: 

Continental shelf -------------------------- 4 

Kenai-Chugach ultramafic belt -------------- ? 

Fairbanks-Livingood ultrafafic belt ---------- ? 

Southeastern Alaska ultramafic belt --------- ? 

Porphyry copper, Alaska Range ------------- ? 

Alkalic rocks, Seward Peninsula ------------ ? 

California-Oregon-Washington: 

Continental shelf -------------------------- ? 

Beaches ----------------------------------- ? 

Antarctica, Dufek intrusive --------------------- ? 

Brazil, Goias serpentine belt -------------------- ? 

Worldwide: 

Syenitic and alkalic rocks ------------------ ? 

Basaltic rocks ----------------------------- ? 

.057 

.002 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with present technology. 2 From Ageton and Ryan (1970). 3 Based on Ageton's (1970) reserve estimates of gold for South Africa 

and on Cousins' ( 1972) ratio of osmiridium to gold produced. ~ Hypothetical resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that are geologically predictable as existing in known districts. 3 Speculative resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that may exist in unknown districts or in unrecognized or unconventional form. 
542 UNITED STATES MINERAL RESOURCES 

The estimates of identified platinum-group metals 

in the basal zone of the Stillwater Complex, Montana, 

are based on published reserves (Dayton, 1971) of 

ore tonnages and the existence of a 25-mile-long 

zone, averaging 300 feet in width and workable on 

the average to 2,000 feet downdip with a probable 

average of 0.5 ppm platinum-group metals. Similar 

estimates were made for the chromitite, using average platinum-group-metal content of the A, G, and 

H zones. 

The 250-mile-long Merensky Reef of the Bushveld 

Complex, South Africa, has been mined locally downdip 6,000 feet, with an average stoping thickness of 

28.5 inches (Mertie, 1969). The grade ranges from 

0.25 to 0.35 oz per ton. If a grade of 0.25 oz per ton 

persists throughout the reef's extent and the reef 

were mined to 10,000 feet, about 656 million ounces 

of platinum-group metals would be available in addition to the 200 million ounces estimated by Ageton 

and Ryan (1970, p. 657). Mertie (1969) implied that 

only 70 miles of reef could be productive under present economic conditions, and so our estimate represents a large proportion of subeconomic resources. 

The other area of identified resources is in the 

Goodnews Bay mining district and the contiguous 

offshore areas. Exploration there by mining companies has shown the presence of anomalous 

amounts of platinum metals in Goodnews Bay and in 

the beaches and offshore sediments. A recent study 

by Allen L. Clark (unpub. data) defined anomalous 

platinum-metal zones within the nearby Red Mountain ultramafic mass. 

The hypothetical resources (table 112) of Alaska 

are large, primarily because all the ultramafic bodies 

studied to date (Clark and Greenwood, 1972) contain 

anomalous amounts of platinum (table 113). In addiTABLE 113.-Concentrations, in parts per million, of platinum, 

palladium, rhodium, and iridium, southeastern Alaska 

Name of area 

Duke Island ----------- Union Bay -----··------ B!ashke Islands ------

Salt Chuck ------------ Klukwan --------------

Pt cone. Pd cone. Rh cone. Ir cone. 

Max. Ave. Max. Ave. Max. Max. 

0.200 0.037 0.140 0.033 0.010 29.000 .093 .200 .023 .062 0.215 .020 .010 .020 .010 .160 .057 2.900 1.010 .100 .046 .100 .040 

tion, the concentrically zoned complexes of southeastern Alaska are geologically very similar to the 

platiniferous bodies of the Ural Mountains, Russia, 

and therefore may have a comparable potential. One 

ultramafic body at the Salt Chuck mine yielded a 

large amount of platinum and palladium as a byproduct of copper mining, indicating the likelihood of 

undiscovered economic concentrations. 

Other belts of ultramafic rocks exist in Alaska, 

and where studied, have all been found to contain 

anomalous amounts of platinum metals. Frequently, 

placer mining for gold has recovered small amounts 

of platinum metals from streams draining these 

ultramafic belts. 

T. P. Thayer (U.S. Geol. Survey, 1957) estimated 

chromite reserves in alpine ultramafic rocks and in 

beach sands in Oregon, California, and Washington ; 

these deposits, in turn, are estimated to contain 0.03 

ppm platinum-group metals and could, then, yield 

1,660 hypothetical ounces of platinum-group metals 

as a byproduct. 

The U.S. Bureau of Mines ( 1967) estimated the 

potential production of gold from placers in California, Oregon, Washington, and Montana as 

81,068,000 ounces. Comparison of gold and platinum 

production figures and estimates by Logan (1919) 

and Pardee ( 1934) suggests that for each ounce of 

gold about 0.0007 of an ounce of platinum-group 

metal is recovered. This suggests that there are 

57,000 ounces of potential platinum metals in these 

placers. 

SPECULATIVE RESOURCES 

Limited knowledge of the geochemistry and geologic environments of platinum metals raakes it difficult to speculate about potential resources. With the 

assumption that platinum metals are derived from 

the mantle, then one may speculate that any igneous 

rocks that have a direct known or postulated origin 

in the mantle may contain resources of platinum 

metals (table 112). Ore deposits associated with 

some basalts or with some types of alkalic rocks and 

their associates-for example, carbonatites-might 

be worth investigating for platinum potential. Of 

course, known but unexplored stratiform mafic and 

ultramafic complexes, such as the Dufek in Antarctica (Ford, 1970), and known but inadequately explored belts of ultramafic rocks, such as the central 

Gohis Precambrian serpentine belt in Brazil (White 

and others, 1971), would have to be included as 

speculative resources. As noted by Wright and 

Fleischer (1965), platinum metals are sometimes 

concentrated by late-stage magmatic and hydrothermal processes and therefore pegmatites may be a 

potential source of platinum. 

After erosion and weathering, platinum metals apparently act in two ways: (1) as heavy minerals and 

(2) by dissolving. Any locality in which heavy minerals are concentrated from potential platinum-bearing terranes, and localities where salines are found 

in drainage basins draining potential platinum ter-
PLATINUM-GROUP METALS 543 

ranes should be investigated as speculative residences of platinum me·tals. 

More specifically, integration of regional geologic 

trends and the minor occurrences of platinum-group 

metals throughout the gold placers of Alaska allows 

one to speculate that large resources of platinum 

metals exist in Alaska. If such resources exist, they 

will be associated with three major ultramafic rock 

belts, a major porphyry copper province, and the 

alkalic rocks of the Seward Peninsula. 

The three major ultramafic belts-the Southeastern Alaska, Kenai-Chugach, and Fairbanks-Livingood belts-are only partly explored, and new 

ultramafic areas will undoubtedly be found in each 

of these three belts. In addition, large areas of 

Alaska, at present unmapped, may contain additional 

ultramafic belts. Therefore, with the high potential 

for undiscovered ultramafic host rocks and the wide 

areal distribution of platinum metals in placer deposits associated with the ultramafic belts, the 

potential for large platinum metal resources is very 

high. 

The common occurrence of platinum metals with 

porphyry copper deposits indicates that potentially 

large resources of platinum metals may exist 

throughout the 500-mile extent of the Alaska Range. 

Locally within the Alaska Range, porphyry copper 

deposits exist, and the potential for the discovery of 

several new districts is very good. 

A belt of alkalic rocks approximately 200 miles 

long exists in the eastern Seward Peninsula. To date 

no analyses for platinum metals have been made, but 

the potential of this area is very high, in light of 

platinum metals associated with similar types of 

rocks. 

PROSPECTING TECHNIQUES 

Prospecting for platinum metals has been, and 

continues to be, rather intuitive. Perhaps the most 

successful approach has been to look for placer accumulations of platinum metals by standard panning 

techniques and then attempt to find the lode source. 

After location of the lode source, normally a mafic or 

ultramafic body, prospecting has been concentrated 

on locating the oxide- and sulfide-rich zones with 

which the platinum metals are commonly associated. 

Recent work by Clark and Greenwood (1972) on 

the zoned ultramafics of southern and southeastern 

Alaska has shown strong correlations of platinum 

and palladium with specific major and trace elements 

and rock types (table 114). Although the correlations are consistent within an individual complex, 

they differ between complexes. Similar correlations 

TABLE 114.-Correlations of maximum platinum-palladium 

concentrations, soutkeastern Alaska 

EJements 

showing 

Name of Associated positive 

area Host rock oxide or correlasulfide tion 

with Pt 

and Pd 

Duke Island ---- Hornblendite ------- Magnetite, Fe, V 

chalcopyrite. 

Union Bay ----- Dunite ------------- Chromite, Fe, Cr 

magnetite. 

Blashke Islands .. Hornblendite ------- Magnetite, Fe, Ni 

chalcopyrite. 

Salt Chuck ----- Pyroxenite, gabbro, Bornite, Cu 

gabbro P.,egmatite. chalcopyrite. 

Klukwan ------- Pyroxenite --------- Magnetite, Fe, v 

ilmenite 

between rock and mineral types and trace elements 

were noted by Page, Riley, and Haffty (1969; 1971). 

Analytical studies have also shown that the stratiform and concentric ultramafic complexes are more 

likely to contain platinum lodes than the alpine type. 

Therefore, once a favorable type of ultramafic body 

has been defined, the following procedure is most 

effective: (1) sample and analyze all rock and mineral phases for platinum metals and associated trace 

major elements such as Fe, Cr, Ni, V, Ti, and Cu; 

(2) establish correlations between platinum metals 

and rock elements; and (3) define and sample areas 

with highest correlation parameters as probable lode 

sources. When utilizing this technique, it should be 

remembered that the lode zone being sought is normally very thin, even though it may extend for a 

long distance. Therefore any sampling done perpendicular to the layering must be close spaced. 

Recent studies by Cousins (1969, 1972) and Fuchs 

(1972) show that both platinum and palladium may 

be readily leached in the zone of weathering in source 

rocks as well as in placers. This fact suggests that 

regional geochemical prospecting techniques designed to locate soluble and transported platinum and 

palladium may be an effective way to locate potential platinum metal lode sources. Soil sampling for 

platinum metal lodes may also be effective if one 

looks for the more stable platinum metals such as 

Os, Rh, lr, and Ru. An attempt was made by Rudolph 

and Moore (1972) to define lode sources using geobotanical prospecting ; they reported that species of 

Eritrichium chamissonis, DC. contained up to 4.8 

ppm platinum collected from the Red Mountain ultramafic mass at Goodnews Bay, Alaska. Other attempts to use this method have been unsuccessful (J. 

B. Mertie, written commun., 1972). 

Platinum metals do, however, occur in many diverse geologic settings, particularly with copper 

deposits, and the techniques of exploration for these 
544 UNITED STATES MINERAL RESOURCES 

other deposits should be indirectly applicable in the 

search for potential platinum resources. 

PROBLEMS FOR RESEARCH 

Whereas base metals can be located by geochemical 

prospecting of stream sediments and soils and by 

geobotanical and geophysical methods, the discovery 

of platinum metals nearly always requires a direct 

chemical analysis of samples of the ore deposit. 

Nevertheless no laboratories can yet provide accurate 

results for all six platinum-group elements using a 

single analytical method, when these metals are present at concentrations less than 10 ppm. Methods do 

exist for Pt, Pd, and Rh down to the low part-perbillion range (Haffty and Riley, 1968). 

Indirect techniques needed to help locate platinum 

metals will require research into the chemical and 

physical behavior of platinum metals in the weathering and transportation cycles. Research on the geophysical parameters of platiniferous zones in known 

occurrences is also necessary as a prelude to developing useful geophysical prospecting techniques. Traceelement studies of platinum metals are also necessary 

to define pathfinder elements. 

A complete study of the nature and behavior of 

platinum metals should also be undertaken with the 

purpose of defining presumably unknown geological 

environments where these metals may be found. 

REFERENCES CITED 

Ageton, R. W., 1970, Gold, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 573-585. 

Ageton, R. W., and Ryan, J.P., 1970, Platinum-group metals, 

in Mineral facts and problems: U.S. Bur. Mines Bull. 

650, p. 653-669. 

Beal, L. H., 1965, Geology and mineral deposits of the 

Bunkerville mining district, Clark County, Nevada: 

Nevada Bur .Mines Bull. 63, 96 p. 

Clark ,A. L., and Greenwood, W. R., 1972, Geochemistry and 

distribution of platinum-group metals in mafic to ultramafic complexes of southern and southeastern Alaska, 

in Geological Survey research 1972: U.S. Geol. Survey 

Prof. Paper 800-C, p. C157-C160. 

t'Jousins, C. A., 1969, The Merensky Reef of the Bushveld 

Igneous Complex, in Wilson, H. D. B., ed., Magmatic ore 

deposits-a symposium: Econ. Geology Mon, 4. p. 239-

251. 

--- 1972, Platinoids in the Witwatersrand system: Univ. 

Witwatersrand, J ohannesberg, South Africa. [Read at 

Symposium on the Analytical Chemistry of the Platinum-group Metals]. 

Dayton, Stan, 1971, Hot air over Stillwater. Profile of a 

hearing on mineral entry: Eng. Mining Jour., v. 172, 

no. 10, p. 75-84. 

Desborough, G. A., Finney, J. J., and Leonard, B. F., 1972, 

Mertieite, a new palladium mineral from Goodnews Bay, 

Alaska: Am. Mineralogist. (In press.) 

Eckel, E. B., 1949, Geology and ore deposits of the La Plata 

district, Colorado: U.S. Geol. Survey Prof. Paper 219, 

179 p. 

Ford, A. B., 1970, Development of the layered series and 

capping granophyre of the Dufek Intrusion of Antarctica, in Visser, D. J. L., and von Gruenewalt, G., eds., 

Symposium on the Bushveld Igneous Complex and other 

layered intrusions: Geol. Soc. South Africa Spec. Pub. 

1, p. 511-531. 

Fuchs, W. A., 1972, Geochemical behavior of platinum, 

palladium, and associated elements in the weathering 

cycle in the Stillwater Complex, Montana: Pennsylvania 

State University M.S. thesis, 92 p. 

Haffty, Joseph, and Riley, L. B., 1968, Determination of 

palladium, platinum, and rhodium in geologic materials 

by fire-assay and emission spectrography: Talanta, v. 

15, p. 111-117. 

Hess, H. H., 1960, Stillwater igneous complex, Montana, a 

quantitative mineralogical study: Geol. Soc. America 

Mem. 80, 230 p. 

Hewett, D. F., 1931, Geology and ore deposits of the Goodsprings quadrangle, Nevada: U.S. Geol. Survey Prof. 

Paper 162, 172 p. 

Howland, A. L., Peoples, J. W., and Sampson, Edward, 1936, 

The Stillwater igneous complex and associated occurrences of nickel and platinum metals: Montana Bur. 

Mines Misc. Contr. 7, 15 p. 

Jackson, E. D., 1961, Primary textures and mineral associations in the ultramafic zone of the Stillwater Complex, 

Montana: U.S. Geol. Survey Prof. Paper 358, 106 p. 

Jackson, E. D., and Thayer, T. P., 1972, Some criteria for 

distinguishing between stratiform, concentric, and alpine peridotite-gabbro complexes: lnternat. Geol. Cong. 

24th Sess., Montreal, Canada. (In press.) 

Jones, W. R., Peoples, J. W., and Howland, A. L., 1960, 

Igneous and tectonic structures of the Stillwater Complex, Montana: U.S. Geol. Survey Bull. 1071-H, p. 

H281-H335. 

Leonard, B. F., Desborough, G. A., and Page, N. J., 1969, 

Ore microscopy and chemical composition of some !aurites: Am. Mineralogist, v. 54, p. 1330-1346. 

Logan, C. A., 1919, Platinum and allied metals in California: 

California Div. Mines and Geology Bull. 85, 120 p. 

Loney, R. A., Himmelberg, G. R., and Coleman, R. G., 1971, 

Structure and petrology of the alpine-type peridotite at 

Burro Mountain, California, U.S.A.: Jour. Petrology, 

v. 12, no. 2, p. 245-309. 

Mason, Brian, 1958, Principles of geochemistry [2d ed.]: 

New York, John Wiley and Sons, 310 p. 

Mertie, J. B., Jr., 1940, The Goodnews platinum deposits, 

Alaska: U.S. Geol. Survey Bull. 918, 97 p. 

--- 1969, Economic geology of the platinum metals: U.S. 

Geol. Survey Prof. Paper 630, 120 p. 

Page, N. J., 1969, Platinum content of ultramafic rocks, in 

U.S. Geological Survey Heavy Metals program progress 

report 1968-topical studies: U.S. Geol. Survey Circ. 622, 

p. 5. 

--- 1971, Sulfide minerals in the G and H ehromitite 

zones in the Stillwater Complex, Montana: U.S. Geol. 

Survey Prof. Paper 694, 20 p. 

Page, N. J., and Jackson, E. D., 1967, Preliminary report 

on sulfide and platinum-group mineral in the chromitites 

of the Stillwater Complex, Montana, in Geological Survey research 1967: U.S. Geol. Survey Prof. Paper 575-D, 

p. D123-D126. 
PLATINUM-GROUP METALS 545 

Page, N.J., and Nokleberg, W. J., 1970, Preliminary geologic 

map of the Stillwater Complex, Montana: U.S. Geol. 

Survey open-file report. 

Page, N.J., Riley, L. B., and Haffty, Joseph, 1969, Platinum, 

palladium, and rhodium analyses of ultramafic and 

mafic rocks from the Stillwater Complex, Montana: U.S. 

Geol. Survey Circ. 624, 12 p. 

--- 1971, Lateral and vertical variation of platinum, 

palladium and rhodium in the Stillwater Complex, 

Montana: Geol. Soc. America, Rocky Mountain Sec., 

Abs. with Programs, v. 3, no. 6, p. 401. 

Pardee, J .T., 1934, Beach placers of the Oregon Coast: U.S. 

Geol. Survey Circ. 8, 41 p. 

Poldervaart, Arie, 1955, Chemistry of the earth's crust, in 

Poldervaart, Arie, ed., Crust of the earth: Geol. Soc. 

America Special Paper 62, p. 119-144. 

Rudolph, W. W., and Moore, J. R., 1972, A new and strange 

prospecting guide: Alaska Construction and Oil, v. 13, 

no. 2, p. 40-42. 

Scaliger, J. C., 1557, Exotericarum exercitationum Liber XV 

de Sublititate ad Heironymum Canadanum, apud Cladium Marnium et haeredes Joannis Aubrii, Francofurti, 

p. 323-324. 

Snetsinger, K. G., 1971a, A platinum-metal nugget from 

Trinity County, California: Am. Mineralogist, v. 56, p. 

1101-1105. 

--- 1971b, Erlichmanite (OsS1:), A new mineral: Am. 

Mineralogist, v. 56, p. 1501-1506. 

--- 1972, Osarsite, a new osmium-rutherrium sulfarsenide 

from California: Am. Mineralogist. (In press.) 

Spencer. C. H., Jr., 1971, Statistical correlation of platinum 

metals with heavy minerals in stream sediments of the 

Klamath Mountains, California: California, San Jose 

State College M. S. thesis, 62 p. 

Theobald, P. K,. Jr., and Thompson, C. E., 1968, Platinum 

and associated elements at the New Rambler mine and 

vicinity, Albany and Carbon Counties, Wyoming: U.S. 

Geol. Survey Circ. 607, 14 p. 

U.S. Bureau of Mines, 1967, Production potential of known 

gold deposits in the United States: U.S. Bur. Mines 

Inf. Circ. 8331, 24 p. 

U.S. Geological Survey, 1957, Ghromite reserves of the 

United States estimated: U.S. Geol. Survey Press Release, July 5, 1957. 

--- 1971, Platinum at Cooke City, Montana, in Geological 

Survey research 1971: U.S. Geol. Survey Prof. Paper 

750-A, p. A36 [1972]. 

White, R. W., Motta, Jorge, and de Araujo, V. A., 1971, 

Platiniferous chromitite in the Tocantins complex, 

Niquelandia, Goias, Brazil, in Geological Survey research 1971: U.S. Geol. Survey Prof. Paper 750-D, p. 

D26-D33. 

Wright, T. L., and Fleischer, Michael, 1965, Geochemistry of 

the platinum metals: U.S. Geol. Survey Bull. 1214-A, 

p. A1-A24. 

UNITED STATES MINERAL RESOURCES 

RARE-EARTH ELEMENTS 

By JoHN W. ADAMS and MoRTIMER H. STAATZ 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

lJses ---------------------------------------- Availability _ ---- ____ -------- __ ---- __ --------

Geologic environment -----------------------------

Geochemistry --------------------------------

~ineralogy ----------------------------------

Types of deposits ----------------------------

Resources ---------------------------------------

Present situation ----------------------------

Potential resources --------------------------

Pr.ospecting techniques ---------------------------

Problems for research ----------------------------

Selected references -------------------------------

FIGURE 

64. Graph showing crustal abundance of rare-earth 

Some members of the group are relatively abundant in 

the earth's crust, but minable concentrations are uncommon. 

Bastnaesite, a rare-earth fluocarbonate, and monazite, a 

Page rare-earth phosphate, are the two important ore minerals. 

547 Bastnaesite is mined extensively from carbonatite in Cali54 7 fornia, and monazite is recovered largely from placer de548 posits in various parts of the world. The rare earths are 

548 present in many other minerals, either as essential con54~ stituents or as substituted constituents. Apatite is a com549 mon host of the substituted constituents and is a source of 

550 rare earths as a byproduct of fertilizer manufacture in 

551 Europe. 

552 The large reserves of bastnaesite in California make the 

552 lJnited States self-sufficient in the lanthanide elements, but 

552 no such high-grade source of yttrium is known. Potential 

554 domestic resources capable of meeting projected require554 ments, however, are available. 

555 

INTRODUCTION 

Page 

elements ---------------------------------- 549 

The rare-earth group of metals, also called the 

lanthanide elements, comprises 15 elements having 

atomic numbers 57 through 71. These are lanthanum 

(La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), 

TABLES 

Page 

115. Rare-earth content of various rock types _____ 549 

116. A partial listing of rare-earth-bearing minerals 550 

117. Identified sources of the rare earths and some 

potential rare-earth deposits of the world ___ 553 

ABSTRACT OF CONCLUSIO~S 

The rare-earth metals, which include yttrium and the 

lanthanides, consist of a group of geochemically related elements that have become of increasing economic interest, 

largely on the basis of their physical rather than their 

chemical properties. Their greatest present use is in petroleum-cracking catalysts, but they are also extensively used 

in the glass and ceramics industries, in iron and steel production, and in the manufacture of electronic devices. 

europium (Eu), gadolinium (Gd), terbium (Tb), 

dysprosium (Dy), holmium (Ho), erbium (Er), 

thulium (Tm), ytterbium (Yb), and lutetium (Lu). 

One of these, promethium, is best known as an artificially produced element, although its occurrence 

in minute trace amounts in natural materials has 

been reported. In addition to the lanthanides, yttrium (Y), with atomic number 39, is generally 

classed with the rare earths because of its chemical 

similarities and geochemical affinities. The rareearth group is divided into the cerium subgroup, or 

"light" rare earths, which consists of the first seven 

lanthanide elements listed (lanthanum through 

europium), and the yttrium subgroup, or "heavy" 

rare earths, which consists of yttrium and the last 

eight lanthanide elements listed (gadolinium through 

lutetium). 

lJ.S. GEOL. SlJRVEY PROF. PAPER 820 

547 
548 UNITED STATES MINERAL RESOURCES 

USES 

The rare earths are the basis for a small but increasingly important industry that had its origin 

about 100 years ago when rare earths were used as 

a minor constituent in thorium gas mantles. The 

annual domestic consumption of rare-earth oxides 

is now more than 10,000 tons, compared with about 

2,000 tons a decade ago. Most of the rare earths 

used are in the form of oxides, chlorides, or fluorides 

of one or more of the major members of the cerium 

subgroup-that is, cerium, lanthanum, neodymium, 

and praseodymium-derived from bastnaesite or 

monazite ores. Yttrium and the less abundant lanthanides, notably europium, are used to a lesser 

extent but, because of their higher cost, contribute 

disproportionately in dollar value to the industry. 

Yttrium has been extracted from several source 

materials including residues from the processing of 

Idaho euxenite for niobium, Canadium uranium 

ores, monazite, and xenotime. The rarer lanthanides 

may be obtained from bastnaesite ores or from any 

of the sources of yttrium just mentioned. 

Uses for the rare earths are diverse and are based 

largely on the physical rather than the chemical 

properties of the group. The major use at present is 

in petroleum-cracking catalysts, in which rare earths 

replace sodium in a synthetic zeolite structure. 

Adoption of this type of catalyst began about 1964 

and has contributed greatly to the expansion of the 

rare-earth industry. Next in importance is the use 

of rare earths in the glass and ceramic industries, 

where they are used in the form of oxides, chlorides, 

or fluorides for a variety of purposes, including 

polishing materials, opacifiers, colorizers, and decolorizers, and as inhibitors of radiation coloration 

in television-tube glass. Rare earths are used in 

both ferrous and nonferrous metallurgy, sparking 

alloys, and carbon-arc electrodes. Research into the 

properties of individual rare-earth elements has led 

to many new uses within the past decade. These 

have been based largely on their optical and luminescent characteristics related to their unusual 

atomic structure. Applications are in phosphors for 

color-television tubes and high-intensity lighting, 

in lasers, and in synthetic rare-earth garnets for 

microwave systems. Permanent magnets of exceptionally high coercive strength are being made using 

intermetallic compounds of rare earths and cobalt, 

of which SmCo5 appears to be the most promising. 

These and other uses of the rare earths are more 

fully discussed by Parker and Baroch ( 1971) and 

by Cannon (1972). 

New uses for rare earths undoubtedly will follow 

technological advances in many fields, and by the 

same token, some present uses will become obsolete. 

Research into catalysts for automobile exhaust 

emission control has indicated that compounds of 

rare-earth elements and certain transition elements, 

notably the compound LaCoOs, hold considerable 

promise (Libby, 1971). Adoption of such catalysts 

would, of course, create an unprecedented demand 

for the rare earths, as well as for cobalt. Another 

potential application of rare earths that could 

greatly increase their usage is in the removal of 

phosphates from wastewater. Discharge of phosphate-bearing wastewater into streams and lakes is 

a major cause of the "death" of bodies of water 

through eutrophication, and only a small percentage 

of the phosphate is removed by present watertreatment plants. A method that offers almost complete removal by precipitation as a rare-earth phosphate was described by Recht, Ghassemi, and 

Kleber (1970). 

AVAILABILITY 

The rare earths are comparative newcomers 

among the elements used by industry, and the extent 

to which they are employed by a country reflects to 

some extent the degree of sophistication of its technology. If rare earths were to become unavailable, 

the effect on our present standard of living would 

not be catastrophic because, in most applications, 

the rare earths are merely replacing other materials 

that are less effective for the particular purpose. 

Without rare earths we would have inferior color 

television, camera lenses, and cigarette-lighter flints ; 

far more serious might be the effects felt in the 

fields of glass manufacture, communications, ceramics, and the iron and steel industry, and less gasoline would be produced per barrel of crude oil. 

Since the development of the bastnaesite deposit 

at Mountain Pass, Calif., the United States has 

become largely self-sufficient in rare-earth resources. 

Bastnaesite, however, is a cerium subgroup mineral, and it contains only a very small percentage 

of yttrium and the yttrium subgroup lanthanides. 

Recent demands for these elements, notably yttrium, 

have been met by their extraction from (1) residues from the processing of Idaho euxenite for 

niobium, (2) monazite from beach placer deposits, 

which is chiefly imported, and (3) residues from 

Canadian uranium mills. Of these, the Idaho residues are now exhausted, and the recovery of rare 

earths by Canadian uranium mills has been discontinued. The present requirements for yttrium are 

small, however, and appear to be adequately met by 

stocks on hand and by existing sources. The United 

States, therefore, is a potential exporter of the light 
RARE-EARTH ELEMENTS 549 

rare earths and an importer of the heavy rare 

earths, although the latter role is one of economics 

rather than one of necessity, inasmuch as large 

undeveloped resources of yttri urn are present in 

domestic deposits, particularly in apatite-magnetite 

bodies and western phosphate rocks. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

The lanthanides and yttrium are lithophilic elements and are most commonly found as phosphates, 

carbonates, or silicates. In the geologic environment 

they are commonly trivalent with the exceptions of 

cerium, which may be in a Ce+4 state, and europium, 

which may be present as Eu +2• The lanthanides are 

unique in their electronic arrangement in that with 

increase in atomic number, electrons are added to 

an inner ( 4f) level rather than to outer levels. This 

arrangement results in the general chemical similarity of elements in the group, but it also gives them 

some unusual physical properties. One consequence 

of inner-level backfilling is the so-called lanthanide 

contraction, a progressive decrease in the ionic 

radius of the trivalent lanthanide ions from lanthanum to lutetium. Ionic-radius relationships are very 

important in rare-earth geochemistry in that they 

are fundamental to ·natural mechanisms by which 

the elements in this rather cohesive group may become separated from one another. These mechanisms, which depend on ionic size, basicity differences, 

coordination effects, solubility characteristics, and 

stability of complexes, are able, individually or collectively, to effect a natural fractionation of the 

rare earths to a remarkable degree (Adams, 1969). 

The actual abundance and distribution patterns 

of the lanthanides and yttri urn in terrestrial and 

extraterrestrial materials have been the subject of 

much recent research facilitated by the use of 

activation-analysis techniques (Haskin and others, 

1966; Herrmann, 1970). From the analytical data 

many attempts have been made to estimate the 

rare-earth content and distribution both in the 

whole earth and in its several crustal units, of which 

the continental crust has the greatest significance 

when we are considering the resources and geochemistry of the elements in the accessible parts of 

the earth. Taylor's (1964) abundance data for the 

rare earths in the continental crust are plotted in 

figure 64 to show their distribution pattern. J udging from Taylor's estimates and those of Lee and 

Yao (1965), the average rare-earth content of the 

continental crust is somewhat less than 200 ppm 

(parts per million). 

.c. 

.v 

(Atomic number 39) 

.Pr 

.sm Gd 

------·~ Dy Er Yb lEu •~•-

.Tb w ... •-~-· 'Im...,__ LlJ 0 

60 62 64 66 68 70 

59 63 65 67 69 71 

INCREASING ATOMIC NUMBER~ 

FIGURE 64.-Crustal abundance of the rare-earth elements. 

Even-odd pairs of elements are arranged in increasing 

atomic number along the abscissa of the graph, and 

abundance, in parts per million, is plotted along the 

ordinate. The upper curve connects lanthanides of even 

atomic number; the lower, their odd-numbered neighbors. 

Yttrium has been arbitrarily placed with dysprosium and 

holmium because of their similarity in ionic radii. 

The rare-earth content and distribution pattern 

of the different rock types vary considerably. Haskin and Frey (1966, p. 310) noted that the absolute 

rare-earth content of intrusive rocks generally increases from ultramafic rocks, through mafic and 

intermediate rocks, to the silicic granites. Various 

sedimentary rock types, although they may differ 

appreciably in their total rare-earth content, show 

mutually similar distribution patterns, which indicates that fractionation is minimal during sedimentation. 

Table 115 shows the rare-earth content of various 

TABLE 115.-Rare-earth content of various rock types 

[From Haskin and Frey, 1966] 

Rock type 

North American shales 

Ocean sediments ------------- Graywackes ----------------- Carbonate-bearing sedimentary 

rocks. 

Number 

of samples 

Composite 

of 40. 

8 

5 

8 

Sandstones ------------------ 5 

Basalt ----------------------Composite 

Granite (G-1) 1 -------------- C) 

Russian granites ------------- 3 

Gabbros --------------------- 3 1 Wesberly, R.I. 2 Number of samples not known. 

Rare-earth content (ppm) 

235 

102-271 

70-195 

16-159 

52-126 

174 

334 

225-475 

28-123 
550 UNITED STATES MINERAL RESOURCES 

rock types from the data of Haskin and Frey (1966). 

Even this limited sampling illustrates that the 

amount of rare earths present can vary widely 

within a single rock type. Rare-earth contents 

greater than those shown in the table have been 

found in both sedimentary and igneous rocks ; marine phosphorites, for example, commonly have a 

high rare-earth content, and some granites and 

syenites may contain more than 1,000 ppm. 

A significant part of the rare-earth content of 

rocks may be present in "carrier" minerals such as 

apatite, sphene, zircon, and the ferromagnesian 

minerals. Plagioclase feldspar may be enriched in 

europium (Haskin and Frey, 1966, p. 313). These 

minerals, as well as the specific rare-earth minerals, 

contain preferential rare-earth assemblages which 

may vary with their geologic environment (Fleischer and Altschuler, 1969). 

When rare-earth minerals are liberated from their 

host rocks by weathering, they may accumulate in 

the soil or be transported from their original site 

by running water. Heavy, resistate minerals such 

as monazite may accumulate in fluviatile or seabeach placers or become incorporated in sediments 

depositing offshore. As the minerals are largely 

insoluble under surface-weathering conditions, there 

is very little release of rare-earth ions for the development of secondary minerals. 

An interesting geochemical cycle for monazite 

was proposed by Overstreet (1960, 1967) to explain its relative abundance in highly metamorphosed rocks, and its virtual absence in those where 

the grade of metamorphism was low. He suggested 

that detrital monazite in the original sediment becomes unstable during initial metamorphism and 

breaks down, the rare earths entering other structures. As the intensity of metamorphism increases, 

monazite is again formed and reaches its maximum 

abundance in rocks that have undergone the most 

intense metamorphism. Monazite commonly contains 3-8 percent of thorium, and, as noted by 

Overstreet, the thorium content is also influenced 

by the degree of metamorphism, being greatest in 

monazite from the most highly metamorphosed 

rocks. 

MINERALOGY 

The rare earths are essential constituents of over 

100 mineral species and are present through substitution in many more. Only a few, however, have 

been found in sufficient concentration to be used 

solely as rare-earth ores ; some others are recovered 

primarily for one or more other elements, with rare 

earths as a byproduct. 

A partial list of rare-earth-bearing minerals and 

their general compositions is given in table 116. 

Of these, monazite and bastnaesite are the most im..: 

portant by virtue of their abundance, high rareearth content, and amenability to processing and 

are the two basic ore minerals used by industry. 

Xenotime, the yttrium phosphate, is also used, but 

to a minor extent. Byproduct rare earths have been 

produced from apatite in Finland, euxenite in the 

United States, loparite in the U.S.S.R., and from 

uraninite and brannerite in Canada. 

Monazite is a common accessory mineral in some 

igneous and metamorphic rocks and in ancient and 

modern placers. Most economic concentrations of 

TABLE 116.-A partial list of rare-earth-bearing minerals 

Mineral Composition 

Oxides: 

Cerianite --------------- ______ Ce02. 

Fluorides: 

Fluocerite -------------------- ( Ce,La) Fa. 

Fluorite, cerian (yttrocerite) _CaF2 + dominantly Ce subgroup. 

Fluorite, yttrian (yttrofluorite) _CaF~ + dominantly Y subgroup. 

Carbonates and fluocarbonates: 

Ancylite --------------------- ( Ce,La)4 ( Sr,Ca) a( COa) 7(0H) 4·8H20. 

Bastniisite -------------------CeFCOa. 

Doverite ___ ------ ___ ---------CaY ( COa) 2F. 

Parisite ------------ __________ 2CeFCOa· CaCOa. 

Synchisite --------------------CeFCOa· CaCOa. 

Silicates: 

Allanite ---------------------- (Ca,Ce,Th)2(AJ,Fe,Mg)3·Sia012· (OH). 

Cenosite ----------------------Ca2 ( CeY) 2Si4012COaH20. 

Cerite . ----------------------- ( Ce,Ca )2Si ( O,OH) s. Gadolinite ___ --------------- __ Be2FeY2Si2010. 

Huttonite ------------------ __ ThSi04. 

Stillwellite ------------------- (Ce,La,Ca) BSiOs. 

Thalenite ----.. ---------------Y2Sb01. Thorite ______ ------ ___ ··-- ____ ThSi04. 

Thortveitite ------------------ (Sc2YhSi201. Phosphates: Apatite t _____________________ Ca5(P04)aF. 

Brockite --------------------- ( Ca,Th,Ce) PO•·H20. 

Floren cite ------------------ __ Ce,A' P04) 2( OH )8. 

1 May contain rare-earth elements. 2 Cerian varieties known. 3 Cerian and thorian varieties known. 

Mineral Composition 

Phosphates-continued: 

Monazite --------------------- ( Ce,La,Th,Y) P04. 

Rhabdophane ---------··------- ( Ce,Y) P04· H20. 

Weinschenkite ---------------- YP0,·2H20. 

Xenotime --------------------YP04. 

Multiple oxides containing columbium (niobium), 

tantalum, and titanium: 

Brannerite ------------------- (U,Ca,Fe,Th,Y)aTisOte. 

Eschynite-priorite series: 

Eschynite ---------------- (Ce,Ca,Fe,Th) (Ti,Nb)20e. 

Priorite ------------------ (Y,Er,Ca,Fe,Th) (Ti,Nb)20e. 

Euxenite-polycrase series: 

Euxenite ----------------- (Y,Ca,Ce,U,Th) (Nb,Ta,Ti)20e. 

Polycrase ----------------- (Y,Ca,Ce,U,Th) (Ti,Nb,Ta)20e. 

Fergusonite-formanite series: 

Fergusonite -------------- (Y,Er,U,Th) (Nb,Ta,Ti)04. 

Formanite --------------- (Y,Er,U,Th) (Ta,Nb)04. 

Loparite --------------------- (Ce,Na,Ca) (Ti,Nb)20e. 

Perovskite 2 ------------------ CaTiOa. 

Pyrochlore-microlite series: 

Betafite . ----------------- (U,Ca) (Nb,Ta,Ti)aOg·nH20. 

Microlite 3 --------------- (Na,Ca)2Ta20e(O,OH,F). Pyrochlore _______________ NaCaNb20aF. 

Samarskite ------------------- (Y,Er,Ce,U,Fe,Th) (Nb,Ta)20e. 

Yttrotantalite ---------------- (Fe,Y,U,Ca) (Ta,Nb,Zr,Sn)04. 
RARE-EARTH ELEMENTS 551 

monazite are in placers, but a few have been found 

in carbonatites and veins. Monazite, in addition to 

having been a major source of rare earths, has been 

the principal source of thorium. Its Th02 content is 

variable but is commonly in the 5-10 percent range. 

Although dominantly a mineral of the light rare 

earths, monazite generally has a higher content of 

yttrium and the heavy lanthanides than does bastnaesite. 

Bastnaesite is a relatively rare mineral, and its 

use as an ore is largely the result of its concentrations in a very few large deposits, the most important of which is the carbonatite body at Mountain Pass, Calif. (Olson and others, 1954). Bastnaesite may also occur in veins, contact-metamorphic zones, and pegmatites, and as a rare accessory 

mineral in igneous rocks. 

Xenotime, the yttrium phosphate, is found in the 

same environments as monazite, but is usually much 

less abundant. 

Apatite, though not a rare-earth mineral, may 

incorporate these elements through substitution, 

commonly to the extent of less than half a percent 

of the total oxides but occasionally much higher. 

The light rare earths are usually dominant, although some apatites contain yttrium in excess of 

cerium (Cruft, 1966). The relationships between 

the rare-earth distribution in apatite and its geologic environment have been discussed by Fleischer 

and Altschuler ( 1969). Apatite is important as a 

potential source of rare earths, inasmuch as millions 

of tons of apatite-bearing rock are processed annually for the production of fertilizer materials. 

A large proportion of rare-earth minerals is 

known only from minor occurrences, chiefly in pegmatites, but almost any one of these minerals may 

become important through the discovery of some 

new or long-unrecognized deposit. 

TYPES OF DEPOSITS 

Primary concentrations of rare-earth-bearing 

minerals are found in a wide variety of geologic 

environments, such as veins, gneisses and migmatites, skarns, pegmatites, and alkalic rock complexes 

and related carbonatites. Only a very few of these 

primary deposits have been mined successfully for 

rare earths alone. Notable exceptions are the vein 

deposits in Burundi in Central Africa, which produced more than 2,300 tons of bastnaesite between 

1947 and 1956, and the bastnaesite deposit in carbonatite at Mountain Pass, Calif., which is probably 

the largest known rare-earth concentration. Some 

primary deposits have been exploited for other commodities, with rare earths as a b~product. These 

include the monazite-apatite vein at Steenskampskraal in the Republic of South Africa (Pike, 1958), 

mined primarily for thorium, and apatite deposits 

in the U.S.S.R. and Finland, where rare earths are 

recovered from apatite processed for its phosphate 

content. 

Unconsolidated secondary deposits-including seabeach placers, river valley (fluviatile) placers, and 

deltaic deposits-represent by far the largest number of minable concentrations of rare-earth minerals 

and include many of the world's important sources. 

Monazite is the most common rare-earth mineral 

found in the placers, where it is invariably associated with other stable heavy minerals, such as 

zircon, garnet, magnetite, ilmenite, rutile, sphene, 

and xenotime. Sea-beach placers, notably those of 

Brazil and the west coast of India, have been the 

largest monazite producers. In the United States, 

fluviatile placers in the Southeastern States and in 

Idaho have been mined for monazite. A deltaic deposit at the mouth of the Nile has been worked 

sporadically. Some placers may be mined for monazite alone, but in many operations monazite is a 

byproduct or coproduct of placers that are worked 

primarily for zircon or for the titanium minerals 

ilmenite or rutile. Rare-earth minerals other than 

monazite generally are not recovered from placers. 

In the period 1956-59, however, the multiple-oxide 

mineral euxenite was mined, together with monazite 

and other heavy minerals, from fluviatile placers at 

Bear Valley, Idaho, primarily for niobium, but with 

an important amount of yttrium and heavy lanthanides as byproducts. Recovery of xenotime, an 

yttrium phosphate mineral, has recently been initiated as a byproduct of the tin placer mining in 

Malaysia. 

Most consolidated sedimentary rocks have a very 

low rare-earth content, but with some important 

exceptions-phosphorites, fossil placers, and certain 

ancient conglomerates. The phosphorites, such as 

units in the Phosphoria Formation in the Western 

United States, represent vast resources of rare 

earths that are contained largely in apatite. Fossil 

placers-for example, those found in Upper Cretaceous sandstones in several Western States--commonly contain" monazite, together with ilmenite, zircon, and other heavy minerals. The conglomerate 

type, as exemplified by the Huronian conglomerates 

of the Blind River area, Ontario, are mined extensively for uranium contained in the minerals brannerite and uraninite; monazite is also present in the 

ore. Recovery of yttrium oxide was begun in 1965 

as a byproduct of uranium processing and continued 

as late as 1970. Although the ores have been esti-
552 UNITED STATES MINERAL RESOURCES 

mated to contain only 0.057 percent total rare-earth 

oxides (Jackson, 1968, p. 381), the production of 

yttrium oxide averaged more than 100,000 pounds 

per year during the 3-year period 1967-69. 

RESOURCES 

PRESENT SITUATION 

·The rare-earth industry in the United States is 

based largely on two main sources of raw materials-the bastnaesite deposit at Mountain Pass, 

Calif., and imported ores, chiefly monazite, from 

Australia and Malaysia. At times, these have been 

supplemented by unusual source materials, such as 

byproduct yttrium-rich residues from Idaho euxenite 

and Canadian uranium mills. Inasmuch as such 

sources have been ample to supply the 10,000 or so 

tons of rare-earth oxides now consumed annually 

in the United States, there is little incentive at present to search for and develop new deposits or to 

recover byproduct rare earths. 

By the year 2000, the annual domestic requirements may be nearly 25,000 short tons for lanthanide oxides and about 180 short tons (compared with 

the present requirements of about 30 tons) for 

yttrium oxide, as estimated by Stamper and Chin 

(1970, p. 692, 801). The lanthanide requirements 

probably can be met easily from sources that are 

now being used, but the estimated sixfold increase 

in. yttrium demand might necessitate its extraction 

from sources in the United States that have never 

been used. Reactivation of yttrium recovery from 

Blind River uranium mills can be anticipated, together with some increase over former production. 

POTENTIAL RESOURCES 

The foregoing discussion of types of rare-earth 

deposits will give some indication of the variety of 

environments in which the rare earths are likely to 

occur. Environments most favorable for the discovery of concentrations that could be mined solely for 

rare earths are very limited and are primarily carbonatites and placers. Concentrations in gneisses 

and migmatites so far discovered are currently of 

marginal value but may eventually become significant--particularly those containing xenotime, as at 

Music Valley, Calif. (Evans, 1964). When rare 

earths are considered as byproducts or coproducts, 

the field of potential producers is greatly expanded 

and will include many additional carbonatites and 

placers, both modern and fossil, thorite-bearing vein 

deposits, apatite-bearing magnetite deposits, and 

phosphatic rocks. Barite is a potential coproduct in 

some rare-earth deposits, such as those at Mountain 

Pass, Calif. 

Many carbonatites and related rocks in alkalic 

complexes contain large tonnages of rare earths, 

not only in dominantly rare-earth species, as at 

Mountain Pass, but as proxying elements in other 

valuable minerals, such as the niobium ore pyrochlore and the phosphate ore apatite. In at least one 

foreign country, rare earths are currently being 

produced as a byproduct in the processing of apatite 

for fertilizer materials. 

The apatite common in metasomatic magnetite 

deposits is generally high in rare earths, and such 

deposits are likely future sources of these elements, 

inasmuch as the apatite must be separated from the 

magnetite prior to smelting. Dumps at Mineville, 

N.Y., and Iron Mountain, Utah, contain large quantities of apatite; the Mineville apatite contains about 

11 percent total rare earths (McKeown and Klemic, 

1956, p. 6), and the apatite from Iron Mountain 

contains about 3 percent. Increases in the use of 

rare earths will make their recovery from this type 

of deposit feasible. 

Another even larger untapped resource lies in the 

sedimentary phosphatic rocks, where the rare earths 

are also present in apatite. Such rocks are likely to 

be a much lower grade source of rare earths than 

apatite concentrates from carbonatites or iron deposits, but greatly exceed these in tonnage. Altschuler, Berman, and Cuttitta (1967) pointed out 

that in the national production of wet-process phosphoric acid in 1964, roughly 3,500 tons of elemental 

rare earths was made available by the solution of 

6 million tons of apatite. This exceeded by more 

than 1,000 tons the domestic production of rareearth oxides from bastnaesite and monazite ores 

during the same year. Altschuler's study of the 

feasibility of rare-earth extraction from phosphorites was based largely on phosphorite of the Bone 

Valley Formation in Florida, which has an elemental 

rare-earth content of about 0.06 percent. Higher 

rare-earth values were reported by Gulbrandsen 

( 1966) for the phosphorites of the Phosphoria Formation in the Western United States; his average 

values for the Retort and Meade Peak Phosphatic 

Shale Members are 0.1 percent yttrium, 0.03 percent 

each for lanthanum and neodymium, and 0.001-

0.003 percent ytterbium. Other rare earths were not 

included in the analyses. On the basis of these values, 

the 4 million or so tons of phosphate rock mined 

annually from the Retort and Meade Peak Members 

could contain ~s much as 4,000 tons of yttrium alone, 

more than 100 times the present demand. Reserves 

of phosphate rock in the United States are on the 

order of billions of tons. (See chapter entitled "Phosphate Deposits.") In the processing of phosphorites, 
RARE-EARTH ELEMENTS 553 

only about one-third of the tonnage used is put in 

solution by acids for manufacture of phosphoric 

acid, and this is the only part of the phosphate rock 

from which the rare earths are liberated; thus, any 

contemplated recovery would have to be made from 

this material. 

Many current or potential sources of rare earths 

throughout the world are shown in table 117, toTABLE 117.-ldentified resources 1 of tke rare earths and s.ome potential rare-earth deposits of tke world 

Country 

Canada ------------

United States ------

Brazil 

Uruguay -----------

Bolivia -------------

U.S.S.R. -----------

Nigeria ------------

U.A.R. (Egypt) ----

Burundi ------------

Malawi 

Kenya 

Tanzania -----------

Republic of South 

Africa. 

Zaire (formerly 

Republic of the 

Congo). Malagasy Republic __ 

India --------------

Ceylon -------------

Deposit 

Blind River-Elliott Lake_ 

Oka -------------------

St. Honore ------------

Mountain Pass, Calif __ 

Music Valley, Calif ___ _ 

Idaho-Montana placers, 

includes Bear Valley, 

Idaho. 

Lemhi Pass, Idaho-Mont. 

Mineral Hill district, 

Idaho-Mont. 

Bald Mountain, Wyo 

Wet Mountains, Colo ---

Powderhorn district, 

Colo. 

Gallinas Mountains, 

N.Mex. 

North and South 

Carolinas, and so forth 

(Piedmont area). 

Hilton Head Island, S.C .. 

Mineville, N.Y ---------

Dover, N.J ------------

Atlantic coast beaches 

and some inland areas. 

Morro do Ferro --------

Araxa -----------------

Atlantida 

Llallagua area --------

Kola area -------------

Kyshtym area (Vishnevye Mountain). 

Plateau Province ------

Nile delta --------------

Karonge mine ----------

Kangankunde Hill -----

Mrima (Jombo) :. _____ _ 

Panda Hill (Mbeya) ---

Glenover ---------------

Steenskampskraal ------

Shinkolobwe 

Ft. Dauphin area ------ Chiefly in Kerala ------- Bihar and west -------- Chiefly west and 

northeast coasts. 

See footnotes at end of table. 

Type 

Conglomerate 

Carbonatite --------

----do 

----dO 

Metamorphic rocks _ 

Placers -------------

Thorite veins -------

Carbonatite veins ---

Conglomerate 

Thorite veins 

Thorite veins and 

carbonatite. 

Veins --------------

Stream placers, 

flood plains. 

Beach placers ------ Magnetite deposit ---

----do -------------

Beach and fluviatile 

placers. 

Alkalic complex ----

Carbonatite ---------

Beach placers ------

Veins 

Alkalic rocks and 

carbonatite. 

Alkalic rocks, 

placers. 

Placers -------------

Fluviatile placers ---

Veins --------------

Carbonatite and 

residual soils. 

Alkalic complex 

and carbonatite. 

Carbonatite ---------

Carbonatite ---------

Vein ---------------

____ do 

Placers ------------ Beach placers ------} Alluvial placers ---- Beach placers ------

Rare-earth oxides z (tons) 

1,200,000 

Not evaluated ------

80,000 

5,000,000 

Not evaluated ------ 147,600 

84,000 

Not evaluated ------

15,000 

1,750 

4,000 

Not evaluated ------

600,000 

60,000 

Not evaluated ------

••.• do 

180,000 

300,000 

90,000 

288 

Not evaluated ------

6,800,000 

Not reported -------

____ do 

120,000 

Not reported -------

68,000 

300,000 

Not reported -------

____ do 

9,000 

Not reported -------

60,000 

3,000,000 

6,000 

Remarks 

Potential byproduct of 

U; some has been 

produced. 

Potential byproduct of 

Nb. 

•••• do -----------------

Reserve in bastnaesite ore. Xenotime and monazite_ 

Monazite and euxenite __ 

Potential coproduct Th •• 

Monazite, thorite, 

ancylite. 

Monazite --------------

Potential coproduct Th. 

•••• do -----------------

Bastnaesite with 

fluorite. 

Monazite, minor .xenotime 

in numerous scattered 

deposits. 

Monazite -------------- Rare-earths in apatite, 

minor bastnaesite. 

Bastnaesite, doverite, 

xenotime. 

Monazite ---------------

Allanite, bastnaesite __ _ 

Potential byproduct Nb 

and apatite(?). 

Monazite. Represents one sampled area. Monazite, minor xeno- time in tin veins. 

Apatite, loparite. Tonnage based on potential byproduct from 

apatite processing. 

Apatite, cerite, bastnaesite, allanite. 

Apatite contains 0.29-

3.3 percent rare earths. 

Small production from 

tin placers. 

Monazite. Intermittent 

production. 

Bastnaesite. Intermittent 

production. 

Monazite --------------

Monazite; pyrocblore __ _ 

Potential byproduct Nb 

and apatite. 

Synchisite, monazite ---

Monazite. Has had large production. 

Monazite --------------

Monazite -------------- Monazite -------------- ----do ----------------- Monazite. Tonnage 

given is from one northeast coast deposit. 

References 

Shenk ( 1971); 

Griffith and Roscoe 

(1964). 

Rowe (1958); U.S. 

Bur. Mines ( 1963). 

Vallee and Dubuc 

(1970). 

Parker ( 1965). 

Evans (1964) • Eilertsen and Lamb 

(1956). 

U.S. Atomic Energy 

Commission 

( 1969); Staatz and 

others (1972) . Anderson (1958). 

Borrowman and 

Rosenbaum (1962). 

Christman and 

others (1959); 

Staatz and Conklin 

(1966). 

Olson and Wallace 

(1956); J. c. 

Olson ( unpub. data). 

Perhac and Heinrich 

(1964). 

Overstreet and others 

(11*51*). 

McCauley (1960). 

McKeown and 

Klemic (1956). 

Klemic and others 

(1962). 

Parker (1965). 

Roser and others 

(1964). 

Do. 

Bogert (1959). 

Gordon (1944). 

British Sulphur 

Corporation, Ltd. 

(1971). 

Zil'bermints (1929); 

Ganzeev and others 

(1966). 

Mackay and others 

(1949). 

Higazy and Naguib 

(1958). 

Thoreau and others 

(1958). 

Deans ( 1966) . 

Do. 

Fawley and James 

( 1955); Davidson 

(1956); Fick and 

Van der Heyde (1959). 

V erwoerd (1963). 

Pike (1958); U.S. 

Bur. Mines (1964). 

Derriks and Vaes 

(1956). 

Murdock (1963). 

Wadia (1956). 

Parker ( 1965). 

Davidson ( 1956). 
554 UNITED STATES MINERAL RESOURCES 

TABLE 117.-Identified resources 1 of the rare earths and some potential rare-earth depo·sits of the world-Continued 

Country Deposit Type 

Malaysia ----------- Various ---------------- Placers -------------

Indonesia ----------- ----do ----------------- ____ do -------------

Taiwan ------------ Coastal areas ---------- Beach placers ------ Korea -------------- Various ---------------- Stream and beach 

placers. 

Australia ----------- ____ do ----------------- Beach placers -------

Total 

(rounded). 

Mary Kathleen --------- Contact metamorphic_ 

Radium Hill ----------- Veins --------------

Rareo-ea.rth oxides 2 

(tons) 

Not reported -------

____ do 

6,000 

54,900 

480,000 

Not reported -------

____ do -------------

18,666,000 

Remarks 

Monazite, xenotime. 

Byproduct of Sn. 

Monazite --------------

____ do ----------------- Monazite. Tonnage from 

evaluated deposits 

only. 

Monazite -------------- Allanite, stillwellite in 

U deposit. 

Brannerite -------------

References 

Do. 

Olson and Over- street ( 1964). 

Shen ( 1965). 

Olson and Over- street ( 1964). 

Parker (1965) . Matheson and Searl 

(1956). 

Barrie ( 1965) . 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may not be profitably recoverable with existing technology and economic conditions. 2 Monazite assumed to contain 60 percent and euxenite 15 percent rare-earth oxides. 

gether with data on their reserves or resources, 

where such information is available. For some deposits the rare-earth tonnage has been derived indirectly from data in the cited references. The total 

resource potential, more than 181;2 million tons, 

does not include the resources of rare earths in the 

sedimentary phosphatic rocks but does include the 

igneous apatite of the Kola Peninsula. 

Only a fraction of this rare-earth potential can 

likely be recovered. Some deposits, such as many of 

the monazite placers in the Southeastern United 

States, either are too small to be worked or are on 

land too valuable for other purposes to be mined. 

Where rare earths are a potential byproduct, as in 

deposits mined for uranium, niobium, or phosphate, 

there will be no recovery without sufficient demand. 

PROSPECTING TECHNIQUES 

The discovery of rare-earth deposits is likely to 

be an accidental adjunct to the search for radioactive materials. This was true of the Mountain Pass 

bastnaesite deposit, where a local radioactivity 

anomaly due to thorite attracted the attention of 

prospectors. Numerous other rare-earth occurrences, 

for the most part uneconomic, were found during 

the period when the use of portable radiationdetecting instruments became commonplace. Many 

of these discoveries were made because of the radioactivity of monazite, which normally contains several percent thorium. Bastnaesite, however, is not 

itself appreciably radioactive, and where it is largely 

unaccompanied by thorium or uranium minerals, as 

in the Gallinas Mountains, N. Mex. (Perhac and 

Heinrich, 1964), radioactivity is of little value in 

prospecting. 

Lanthanide ions-notably those of neodymium, 

praseodymium, erbium, and holmium-produce absorption bands in the spectrum of light transmitted 

by many of the minerals in which they are present. 

These bands are easily seen with a hand spectroscope or microspectroscope when the mineral is 

illuminated by a strong source of white light 

(Adams, 1965). Samples can be examined in the 

field using sunlight, but they can be examined more 

effectively in the laboratory. The mineral grains 

must be sufficiently translucent to transmit some 

light, as is commonly true of bastnaesite, monazite, 

and xenotime. The use of this technique in the 

examination of panned concentrates was suggested 

by Mertie (1954). 

The recognition of cerium subgroup minerals by 

the use of unfiltered light from an ultraviolet lamp 

has been described by Murata and Bastron (1956). 

The emerald green shown by the minerals is due 

to the absorption of certain wavelengths of light 

by neodymi urn and praseodymi urn and is a very 

useful preliminary test for bastnaesite, monazite, 

and some other nonopaque rare-earth minerals. 

Many rare-earth-bearings materials are not recognizable by mineralogical examination, particularly 

when these elements are present in carrier minerals 

such as apatite, sphene, zircon, or thorite. For such 

rocks some analytical method such as X-ray fluorescence or emission spectrography (Parker and Baroch, 1971) must be used. 

PROBLEMS FOR RESEARCH 

Although known resources of rare earths are 

large, they undoubtedly can be increased by continued investigation of geologic materials in all 

parts of the world. Some potential domestic sources 

are not evaluated, and many others remain to be 

discovered. Resources in the apatite of phosphorites 

and iron deposits are impressive but are of little 

value until economic methods of recovery are developed, and research in this field is needed in 

anticipation of their eventual use. This is also true 

for the resources in thorite veins, where the rare 

earths may be an important coproduct. (See "Thorium" in chapter on "Nuclear fuels.") 
RARE-EARTH ELEMENTS 555 

A major problem in the rare-earth field, however, 

is not one of scarcity of raw materials, but rather 

of developing a better balance in the utilization of 

all the rare-earth elements normally recoverable 

from the ores. The ore minerals bastnaesite and 

monazite contain the individual rare earths in characteristic, though somewhat variable, proportions, 

with cerium subgroup elements predominant. Thus, 

a ton of bastnaesite may contain about 700 pounds 

of cerium oxide but only l1j2 pounds of europium 

oxide. These relationships, which are established by 

the natural distribution of the elements in the ores, 

cause no problems when the demand for mixed or 

separated elements is roughly proportional to their 

abundance. If, however, an unusual demand arises 

for one specific element, as for europium, its extraction can result in the unavoidable production of 

other lanthanides in excess of existing requirements. 

Increased uses for the more abundant rare earths 

and significant uses for some of the scarce ones 

would be of great value in stabilizing the industry, 

and it is in the discovery of these uses that further 

research is needed. 

SELECTED REFERENCES 

Adams, J. W., 1965, The visible region absorption spectra of 

rare-earth minerals: Am. Mineralogist, v. 50, nos. 3, 4, 

p. 356-366. 

--- 1969, Distribution of lanthanides in minerals, in 

Geological Survey research 1969: U.S. Geol. Survey 

Prof. Paper 650-C, p. C38-C44. 

Altschuler, Z. S., Berman, Sol, and Cuttitta, Frank, 1967, 

Rare earths in phosphorites-Geochemistry and potential recovery, in Geological Survey research 1967: U.S. 

Geol. Survey Prof. Paper 575-B, p. B1-B9. 

Anderson, A. L., 1958, Uranium, thorium, columbium, and 

rare-earth deposits in the Salmon region, Lemhi County, 

Idaho: Idaho Bur. Mines and Geology Pam ph. 115, 81 p. 

Barrie, J., 1965, Rare earths, in McLeod, I. R., ed., Australian 

mineral industry-The mineral deposits: Australian 

Bur. Mineral Resources, Geology and Geophysics Bull. 

72, p. 515-521. 

Bhola, K. L., Dar, K. K., Rama Rao, Y. N., Suri Sastri, C., 

and Mehta, N. R., 1965, A review of uranium and 

thorium deposits in India, in Nuclear fuels-Raw materials: United Nations Internat. Conf. on Peaceful Uses 

of Atomic Energy, 3d, Geneva, Switzerland, 1964, Proc., 

Paper 752, v. 12, p. 86-93. 

Bogert, J. R., 1959, Uruguay's beaches show heavy mineral 

concentrations: Mining World, v. 21, no. 8, p. 48-49. 

Borrowman, S. R., and Rosenbaum, J. B., 1962, Recovery of 

thorium from a Wyoming ore: U.S. Bur. Mines Rept. 

Inv. 5917, 8 p. 

British Sulphur Corporation, Ltd., 1971, World survey of 

phosphate deposits, 3d ed.: London, British Sulphur 

Corp., Ltd., 180 p. 

Cannon, J. G., 1972, Rare earths: Eng. and Mining Jour., 

v. 173, no. 3, p. 1g'7, 196, 198, 200. 

Christman, R. A., Heyman, A. M., Dellwig, L. F., and Gott, 

G. B., 1959, Thorium investigations, 1950-1952, Wet 

Mountains, Colorado: U.S. Geol. Survey Circ. 290, 40 p. 

Cruft, E. F., 1966, Minor elements in igneous and metamorphic apatite: Geochim. et Gosmochim. Acta, v. 30, no. 

4, p. 375-398. 

Davidson, C. F., 1956, The economic geology of thorium: 

London, Mining Mag., v. 94, no. 4, p. 197-208. 

Deans, Thomas, 1966, Economic mineralogy of African carbonatites, in Tuttle, 0. F., and Gittens, J ., eds., Carbonatites: New York, lnterscience Publishers, p. 385-

413. 

Derriks, J. J ., and V aes, J. F., 1956, The Shinkolobwe uranium deposit-Current status of our geologic and 

metallogenic knowledge, in Geology of uranium and 

thorium: United Nations Internat. Conf. on Peaceful 

Uses of Atomic Energy, Geneva, Switzerland, 1955, 

Proc., v. 6, p. 94-128. 

Eilertsen, D. E., and Lamb, F. D., compilers, 1956, A comprehensive report of exploration by the Bureau of Mines 

for thorium and radioactive black mineral deposits: 

U.S. Bur. Mines RME-3140, issued by U.S. Atomic 

Energy Comm. Tech. Inf. Service, Oak Ridge, Tenn., 

46 p. 

Evans, J. R., 1964, Xenotime mineralization in the southern 

Music Valley area, Riverside County, California: California Div. Mines and Geology Spec. Rept. 79, 24 p. 

Fawley, A. P., and James, T. C., 1955, A pyrochlore 

(columbium) carbonatite, southern Tanganyika: Econ. 

Geology, v. 50, p. 571-585. 

Fick, L. J., and Van der Heyde, C., 1959, Additional data on 

the geology of the Mbeya carbonatite: Econ. Geology, 

v. 54, p. 842-872. 

Fleischer, Michael, and Altschuler, Z. S., 1969, The relationship of the rare-earth composition of minerals to geologic 

environment: Geochim. et Cosmochim. Acta, v. 33, no. 

6, p. 725-732. 

Ganzeev, A. A., Efimov, A. F., and Mukhitdinov, G. N., 

Rare-earth elements in the Vishnevye Gory apatites (in 

Russian) : Geokhimiya, no. 3, p. 353-357; translated in 

Geochemistry Internat., v. 3, p. 275-279 (1966). 

Gordon, S. G., 1944, The mineralogy of the tin mines of 

Cerro de Llallagua, Bolivia: Acad. Nat. Sci. Philadelphia 

Proc., v. 96, p. 279-359. 

Griffith, J. W., and Roscoe, S. M., 1964, Canadian resources 

of uranium and thorium: Canada Dept. Mines and Tech. 

Surveys, Mineral Resources Div., Mineral Inf. Bull. 

MR-77, 12 p. 

Gulbrandsen, R. A., 1966, Chemical composition of phosphorites of the Phosphoria Formation: Geochim. et Cosmochim. Acta, v. 30, no. 8, p. 769-778. 

Haskin, L. A., and Frey, F. A., 1966, Dispersed and not-sorare earths: Science, v. 152, no. 3720, p. 299-314. 

Haskin, L.A., Frey, F. A., Schmitt, R. A., and Smith, R. H., 

1966, Meteoric, solar, and terrestrial rare-earth distributions, in Physics and chemistry of the earth, v. 7: New 

York, Pergamon Press, p. 167-321. 

Herrmann, A. G., 1970, Yttrium and lanthanides, in Wedepohl, K. H., ed., Handbook of geochemistry, Part 2: New 

York, Springer-Verlag., v. 2. 

Higazy, R. A., and Naguib, A. G., 1958, A study of the 

Egyptian monazite-bearing black sands: United Nations Internat. Conf. on Peaceful Uses of Atomic 

Energy, Geneva, Switzerland, Sept. 1-13, 1958, Proc., 

v. 2, paper 1486, p. 658-662. 

Jackson, W. H., 1968, Rare-earth elements, in Canadian 
556 UNITED STATES MINERAL RESOURCES 

mineral yearbook 1966: Canada Dept. Energy, Mines 

and Resources Mineral Rept. 15, p. 379-382. 

Klemic, Harry, Heyl, A. V., Taylor, A. R., and Stone, Jerome, 

1962, Radioactive rare-earth deposits at Scrub Oaks 

mine, Morris County, New Jersey: U.S. Geol. Survey 

Bull. 1082-B, p. 29-60. 

Lee, Tan, and Yao, Chi-Lung, 1965, Abundance of chemical 

elements in the earth's crust and its major tectonic 

units [in Chinese]: Acta Geol. Sinica, v. 45, no. 1, p. 

82-91; translated in lnternat. Geology Rev., v. 12, no. 

7, p. 778-786 (1970). 

Libby, W. F., 1971, Promising catalyst for au.to exhaust: 

Science, v. 171, no. 3970, p. 499-500. 

McCauley, C. K., 1960, Exploration for heavy minerals on 

Hilton Head Island, South Carolina: South Carolina Div. 

Geology Bull. 26, 13 p. 

Mackay, R. A., Greenwood, R., and Rockingham, J. E., 1949, 

Geology of the Plateau tinfields-Resurvey 1945-49: 

Nigerian Geol. Survey Bull. 19, 80 p. 

McKeown, F. A., and Klemic, Harry, 1956, Rare-earth-bearing apatite at Mineville, Essex County, New York: U.S. 

Geol. Survey Bull. 1046-B, 23 p. 

Matheson, R. S., and Searl, R. A., 1956, Mary Kathleen 

uranium deposit, Mt. Isa-Cloncurry district, Queensland, 

Australia: Econ. Geology, v. 51, p. 528-540. 

Mertie, J. B., Jr., 1954, The gold pan-A neglected geologic 

tool: Econ. Geology, v. 49, p. 639-651. 

Murata, K. J., and Bastron, Harry, 1956, Convenient method 

for recognizing nonopaque cerium minerals: Science, v. 

123, no. 3203,p. 888-889. 

Murdock, T. G., 1963, Mineral resources of the Malagasy 

Republic: U.S. Bur. Mines Inf. Circ. 8196, 147 p. 

Olson, J. C., and Overstreet, W. C., 1964, Geologic distribution and resources of thorium: U.S. Geol. Survey Bull. 

1204, 61 p. 

Olson, J. C., Shawe, D. R., Pray, L. C., and Sharp, W. N., 

1954, Rare-earth mineral deposits of the Mountain Pass 

district, San Bernardino County, Caiifornia: U.S. Geol. 

Survey Prof. Paper 261, 75 p. 

Olson, J. C., and Wallace, S. R., 1956, Thorium and rareearth minerals in the Powderhorn district, Gunnison 

County, Colorado: U.S. Geol. Survey Bull. 1027-0, p. 

693-723. 

Overstreet, W. C., 1960, Metamorphic grade and the abundance of Th02 in monazite, in Short papers in the geological sciences: U.S. Geol. Survey Prof. Paper 400-B, p. 

B55-B67. 

--- 1967, The geologic occurrence of monazite: U.S. Geol. 

Survey Prof. Paper 530, 327 p. 

Overstreet, W. C., Theobald, P. K., Jr., and Whitlow, J. W., 

1959, Thorium and uranium resources in monazite 

placers of the western Piedmont, North and South Carolina: Mining Eng., v. 11, no. 7, p. 709-714. 

Parker, J. G., 1965, Rare-earth elements, in Mineral facts 

and problems, 1965 ed.: U.S. Bur. Mines Bull. 630, p. 

753-768. 

Parker, J. G., and Baroch, C. T., 1971, The rare-earth elements, yttrium, and thorium, with a chapter on Resources by J. W. Adams: U.S. Bur. Mines lnf. Circ. 

8476, 92 p. 

Perhac, R. M., and Heinrich, E. W., 1964, Fluorite-bastnaesite deposits of the Gallinas Mountains, New Mexico, 

and bastnaesite paragenesis: Econ. Geology, v. 59, p. 

226-239. 

Pike, D. R., 1958, Thorium and rare-earth-bearing minerals 

in South Africa, in Survey of raw materials resources: 

United Nations lnternat. Conf. on Peaceful Uses of 

Atomic Energy, 2d, Geneva, Switzerland, 1958, Proc., 

v. 2, p. 91-96. 

Recht, H. L., Ghassemi, Masood, and Kleber, E. V., 1970, A 

new use for rare earths: Rare Earth Research Conf., 

8th, Reno, Nev., 1970, Proc., v. 2, p. 774-787. 

Roser, F. X., Kegel, G., and Cullen, T. L., 1964, Radiogeology 

of some high-background areas in Brazil, in Adams, J. 

A. S., and Lowder, W. M., eds., The natural radiation 

environment: Chicago Univ. Press (for Rice Univ.), p. 

855-762. 

Rowe, R. B., 1958, Niobium (columbium) deposits of Canada: 

Canada Geol. Survey Econ. Geology Rept. 18, 108 p. 

Shen, Jin-Tai, 1956, Exploration of monazite and associated 

minerals in the Province of Taiwan, China, in Geology 

of uranium and thorium: United Nations lnternat. Conf. 

on Peaceful Uses of Atomic Energy, Geneva, Switzerland, 1955, Proc., v. 6, p. 147-151. 

Shenk, R. L., 1971, Rare earths, in Canadian minerals yeatbook 1969: Canada Dept. Energy, Mines and Resources 

Mineral Rept. 19, p. 421-424. 

Staatz, M. H., and Conklin, N. M., 1966, Rare-earth thorium 

carbonate veins of the Road Gulch area, northern Wet 

Mountains, Colorado, in Geological Surv·ey research 

1966: U.S. Geol. Survey Prof. Paper 550-B, p. B130-

B134. 

Staatz, M. H., Shaw, V. E., and Wahlberg, J. S., 1972, Occurrence and distribution of rare earths in the Lemhi 

Pass thorium veins, Idaho and Montana: Econ. Geology, 

v. 67,no. l,p. 72-82. 

Stamper, J. W., and Chin, Edmond, 1970, Rare-earth elements [and] Yttrium, in Mineral facts and problems, 

1970 ed.: U.S. Bur. Mines Bull. 650, p. 681-696; 795-

804. 

Taylor, S. R., 1964, Abundance of chemical elements in the 

continental crust-A new table: Geochim. et Cosmochim 

Acta, v. 28, no. 8, p. 1273-1285. 

Thoreau, J., Aderca, B., and Van Wambeke, L., 1958, Le 

gisement de terres rares de la Karonge (Urundi): Acad. 

Royale Sci. Colon. Bull. Seances, v. 4, p. 684-715. 

U.S. Atomic Energy Commission, 1969, The use of thorium 

in nuclear power reactors: WASH 1097, UC-80, 144 p. 

U.S. Bureau of Mines, 1963, Columbium: Mineral Trade 

Notes, v. 56, no. 3, p. 11. 

--- 1964, Monazite: Mineral Trade Notes, v. 58, no. 1, 

p. 28-29. 

Vallee, Marcel, and Dubuc, Fernand, 1970, The St. Honore 

carbonatite deposit, Quebec: Canadian Inst. Mining and 

Metallurgy Trans., v. 73, p. 346-356. 

Verwoerd, W. J., 1963, Rare-earth minerals in South African 

carbonatites: South Africa Geol. Survey Ann. Rept., v. 

2, p. 119-135. 

Wadia, D. N., 1956, Natural occurrences of uranium and 

thorium in India, in Geology of uranium and thorium: 

United Nations Internat. Conf. on Peaceful Uses of 

Atomic Energy, Geneva, Switzerland, 1955, Proc., v. 6, 

p. 163-166. 

Zil'bermints, V. A., 1929, Sur le gisement de cerite, de 

bastnaesite, et d'un mineral noveau, le lessingite, dans 

le district minier de Kychtym (Oural): Akad. Nauk 

SSSR Doklady, Comptes Rendus [ser.] A, p. 55-60. 
UNITED STATES MINERAL RESOURCES 

RHENIUM 

By R. u. KING 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

Us·es ----------------------------------------

Exploitati(}n -------------------------------------

Resources ---------------------------------------

Problems for research ----------------------------

Selected bibliography ----------------------------

ABSTRACT OF CONCLUSIONS 

Page 

557 

557 

557 

558 

558 

558 

559 

Rhenium, a rare element that has only recently come into 

significant industrial use, has properties excellently suited 

for application as a refractory metal, as an alloying element, 

in high-temperature thermocouples, in electronic components, 

and as a catalyst in petroleum refining. Rhenium is obtained from molybdenite that is recovered as a byproduct 

of copper production, and the supply of rhenium, as well as 

the world resources of rhenium is therefore closely tied in 

with the world's resources of molybdenum in porphyry copper 

deposits. 

Identified U.S. resources of rhenium are estimated to be 

about 10,000 short tons, and world resources on the order of 

30,000 short tons. Although other sources may exist, they 

are not known to be significant. 

INTRODUCTION 

It has been found in significant concentrations only 

in association with molybdenite. 

Rhenium, atomic number 75, is a heavy transition metal that can form an extensive series of compounds that include the widest range of valences of 

any element, from -1 to +7. Rhenium is placed in 

column 7B of the periodic table, below manganese 

and technetium, adjacent to tungsten and the platinum metals, and diagonally below molybdenum. It 

has a marked affinity for sulfur, as does molybdenum. The association with molybdenum is marked, 

but there is evidence of only a slight association 

with manganese, the platinum metals, and tungsten 

(Fleischer, 1959). Unique features of rhenium 

chemistry are the unusually high volatility of the 

heptoxide and the high solubility of the heptoxide 

in water and oxygenated solvents. 

Various figures are given in the literature for the 

abundance of rhenium in the earth's crust, ranging 

from 0.5 to 10 parts per billion. 

USES 

The principal uses of rhenium are as an alloying 

element in specialty metals, in high-temperature 

thermocouples, in filaments of mass spectrographs 

and ion gages, in electronic and electrical control 

Rhenium, one of the rarest and most dispersed of devices, flash lamp filaments, metallic coatings, heat-, 

the metallic elements, has been intensively studied wear-, and corrosion-resistant alloys, and as a catasince its discovery in 1925. Rhenium metal is silvery lyst in petroleum refining to produce high-octane 

gray and has a melting point of about 3,180°C, the gasoline (Shimamoto, 1972). Its high melting point 

second highest of all metals (after tungsten). It and module of elasticity and its heat-stable crystalhas a density of 21 grams per cubic centimeter, the line structure make rhenium an excellent refractory 

fourth heaviest of the metals; it is almost as heavy metal. 

as platinum. It is ductile, extremely hard, and high In view of the current attention being placed 

in tensile strength. Wrought rhenium metal resists upon environmental pollution, particularly as reoxidation, but rhenium in powder form oxidizes lated to modern gasoline-powered transportation, 

readily at the moderate temperature of 150°C. Rhe- the beneficial properties of rhenium as a catalyst in 

nium does not occur in its native or pure state but the petroleum-refining industry may make it of 

only in combination with other elements, and no great national importance in the very near future. 

definite rhenium minerals have yet been identified. High-octane gasoline is produced more economically 

U.S. GEOL. SURVEY PROF. PAPER 820 

557 
558 UNITED STATES MINERAL RESOURCES 

by the use of bimetallic catalysts, such as platinumrhenium. Rhenium does not substitute for platinum 

in the refining (rheniforming) process, but acts as 

a promoter for the platinum catalyst. 

EXPLOITATION 

Rhenium is produced only in connection with the 

industrial practice of roasting of molybdenite concentrates that contain about 100 to 2,000 ppm (parts 

per million) rhenium (Churchward and Rosenbaum, 

1963). Such concentrates are almost exclusively 

those that are prepared as a byproduct from the 

mining of the porphyry copper-molybdenum ores of 

British Columbia, Western United States, Mexico, 

Peru, Chile, and Russia. 

In the United States, current production of rhenium, totaling only a few tons per year, comes from 

its recovery from flue dusts that accumulate during 

the conversion of byproduct molybdenite concentrates to molybdenum trioxide. 

Current technology permits recovery of rhenium 

from those deposits in which the rhenium content 

of the molybdenite is at least 100 ppm. 

Earliest recorded commercial production of rhenium was in 1930 when small amounts of the metal 

were recovered from copper smelter wastes at 

Mansfeld, Germany. 

In the U.S. rhenium production began in 1942 at 

the University of Tennessee, with the recovery there 

of a few hundred pounds from smelter flue ducts 

from the Miami Cooper Co.'s plant in Arizona; 

sizable production did not begin until 1954 when 

the Kennecott Copper Corp. began to recover rhenium from some of the copper-molybdenum ores. 

Annual production of rhenium increased markedly 

during the early 1960's from about 1,000 pounds in 

1962 to about 4,000 pounds i:h 1966, according to 

annual reports of the U.S. Bureau of Mines. 

In 1960 the world's recoverable reserves of rhenium were estimated to be greater than 500 tons, 

U.S. reserves amounting to about 65 percent of the 

total. World production in 1965 was about 5,000 

pounds· of rhenium. The price of rhenium has 

ranged widely over the years, from $400 to $800 

a pound. 

RESOURCES 

The principal rhenium resources consist of trace 

amounts occurring in the molybdenite that accompanies the copper ores of porphyry copper deposits. 

Rhenium is also present in the molybdenite of the 

porphyry molybdenum deposits, in contact-metamorphic tungsten-molybdenum deposits, molybdenum-bearing pegmatites, and molybdenite-bearing 

quartz veins. It also occurs with molybdenum and 

uranium in bedded deposits in sandstone, in bituminous copper-bearing shales, in vanadiferous black 

shales, and in cupriferous sandstone deposits. 

The molybdenites of porphyry copper deposits 

contain from about 100 to 3,000 ppm rhenium, several times that in other types of deposits. Although 

notable exceptions are known, in which rhenium 

concentrations exceed 2,000 ppm, these exceptions 

represent deposits containing tonnages too small to 

be of economic significance under present conditions 

(Peterson and others, 1959). 

Identified resources of rhenium in porphyry copper deposits are estimated to be about 10,000 short 

tons in the United States and on the order of 30,000 

short tons in the entire world. These estimates are 

calculated from the identified resources of _molybdenite in porphyry copper deposits as detailed in 

"Molybdenum" of this volume, assuming an average rhenium content of 800 ppm in the molybdenite 

( == 1,333 ppm Re in Mo) of such deposits. 

Because the only known readily available source 

of rhenium is molybdenite, speculation as to addi;.. 

tional resources must be related to molybdenum 

resources. Nongeological factors, however, may operate independently of the relation of rhenium to 

molybdenum, to add significantly to the rhenium 

resource base. ·Such factors include potential improvement in the technology of recovery, which may 

make it possible to profitably recover rhenium from 

the very large resources of molybdenite in the molybdenum porphyry deposits; improvements in 

process metallurgy; and discoveries of new uses, 

which may reduce costs of end products, with resulting increase in demand for rhenium and possible 

increase in its price. Owing to these factors and to 

the variability of the rhenium content in molybdenite, any attempt at present to quantify the hypothetical and speculative resources of rhenium would 

have very little meaning. 

PROBLEMS FOR RESEARCH 

Considerable variation in rhenium content of 

molybdenite from different parts of a deposit has 

recently been noted. Determining average values 

for rhenium in molybdenite in large deposits requires analysis of many samples, still a timeconsuming and expensive process ; the only alternative today is to depend on analyses of mill concentrates for these average values. Fu:r:ther research 

into analytical techniques seems warranted in order 

to permit adequate sampling of the large low-grade 

porphyry deposits, to delineate variations of rhenium in molybdenite, and to obtain better under-
RHENIUM 559 

standing of zonal distribution of rhenium in coppermolybdenum deposits. 

Rhenium minerals have not yet been isolated, 

with the possible exception of a rhenium copper 

sulfide from Russian deposits; moreover, the structural relation of rhenium in molybdenite is not well 

understood. Research into these aspects of rhenium 

mineralogy seems warranted. 

SELECTED BIBUOGRAPHY 

Churchward, P. E., and Rosenbaum, J. B., 1963, Sources and 

recovery methods for rhenium; U.S. Bur. Mines Rept. 

Inv. 6246, 16 p. 

Colton, Ray, 1965, The chemistry of rhenium and technitium: 

London, Interscience Publishers, 185 p. 

Druce, J. G. F., 1948, Rhenium: Cambridge Univ. Press., 92 p. 

Fleischer, Michael, 1959, The geochemistry of rhenium, with 

special reference to its occurrence in molybdenite~ Econ. 

Geology, v. 54, p. 1406-1413. 

Hirt, B., Tiltow, G. R., Herr, W., and Hoffmeister, W., 1963, 

The half-life of 187Re, in Geiss, J., and Goldberg, E. D., 

eds., Earth science and meteoritics: Amsterdam, NorthHolland Publishing Co., p. 273-280. 

Hiskey, C. F., and Meloche, V. W., 1940, Determination of 

rhenium in molybdenite minerals: Indus. and Eng. 

Chemistry, v. 12, no. 9, p. 503-506. 

Kuznetsova, V. V., and Saukov, A. A., 1961, Possible forms 

of occurrence of molybdenum and rhenium in the coals 

of middle Asia: Geochemistry, no. 9, p. 822-829. 

Lebedev, K. B., 1962, The chemistry of rhenium: London, 

Butterworths, 105 p. 

Morgan, J. W., and Lovering, J. F., 1967, Rhenium and 

osmium abundances in some igneous and metamorphic 

rocks: Earth and Planetary Sci. Letters, v. 3, p. 219-

224. 

Morgan, J. W., Lovering, J. F., and Ford, R. J., 1968, Rhenium and nonradiogenic osmium in Australian molybdenites and other sulfide minerals by neutron-activation analysis: Geol. Soc. Australia Jour., v. 15, pt. 2, p. 

189-194. 

Morris, D. F. C., and Fifield, F. W., 1961, The determination of rhenium in rocks by neutron-activiation analysis: 

Talanta, Northern Ireland, Pergamon Press, v. 8, p. 

612-618. 

Peterson, R. G., Hamilton, J. C., and Myers, A. T., 1959, An 

occurrence of rhenium associated with uraninite in 

Coconino County, Arizona: Econ. Geology, v. 54, p. 

254-267. 

Shimamoto, K. 0., 1973, Availability of rhenium in the 

United States: U.S. Bur. Mines Inf. Circ. 8573, 37 p. 

Sims, C. T., Wyler, E. N., Gaines, G. B., and Rosenbaum, 

D. M., 1956, A survey of the literature on rhenium: Battelle Memorial Inst., Wright Air Development Center, 

Ohio, WADC Tech. Rept. 56-319, 224 p. [1957]. 

Solt, M. W., Wahlberg, J. S., and Myers, A. T., 1969, Determination of rhenium in molybdenite by X-ray fluorescence: Talanta, Northern Ireland, Pergamon Press, v. 

16, p. 37-43. 

Songina, 0. A., 1970, Rare metals [3d ed.] translated from 

lzdatel'stvo Metallurgiya, Moskva, 1964: Israel Program for Scientific Translations, available from Natl. 

Tech. Information Service, U.S. Dept. Commerce, S·pringfield, Va. 22151, p. 1-32. 

Sutulov, Alexander, 1970, Molybdenum and rhenium recovery from porphyry coppers: Chile, Concepcion Univ., 

259 p. 

Trilabat, S. M., 1959, Rhenium, in Pascal, P., ed., Nouveau 

Traite de Chemie Minerale: Paris, Masson et Cie., v. 

16, p. 1097-1179. 

Vlasov, K. A., ed., 1966, Geochemistry and mineralogy of 

rare elements and genetic types of their deposits : 

U.S.S.R. Acad Science, v. 1, p. 607-633; v. 2, p. 765-768; 

v. 3,p. 581-583. ' 

UNITED STATES MINERAL RESOURCES 

SAND AND GRAVEL 

By WARREN YEEND 

CONTENTS 

Page 

Abstract of conclusions --------------------------- 561 

Introduction ------------------------------------- 561 

Geologic environments and their distribution ------- 562 

Potential resources ------------------------------ 562 

Exploration techniques --------------------------- 563 

Problems for research ---------------------------- 564 

References -------------------------------------- 565 

ABSTRACT OF CONCLUSIONS 

The sand and gravrel industry is the largest nonfuel mineral industry in terms of volume, in the United States. Although the United States currently produces enough sand 

and gravel to supply its requirements, it is predicted that 

by A.D. 2000 the domestic resources accessible at 1968 prices 

will barely meet the demand. 

The most important commercial sources of sand and gravel 

are river channels and glaciated terrain. However, as these 

sources become depleted, marine and lake environments could 

become important. 

Deposits in all areas are located by conventional field mapping with the aid of geophysical techniques, such as seismic 

refraction and reflection and resistivity surveys. 

A current major problem facing industry is land-use conflict where land containing potentially rich sand and gravel 

resources is at present more valuable for building development and is thus removed from future mineral production. 

Planning resulting in effective multiple use of the mineralrich land would allow for the recovtery of sand and gravel 

prior to urbanization. 

Additional sand and gravel now noneconomic may be 

made available through development of low-cost transportation from remote deposits or by the establishment of a 

workable two-way (back haul) exchange system. 

INTRODUCTION 

The sand and gravel industry is the largest nonfuel mineral industry, in terms of volume, in the 

United States. Although this commodity possesses 

the lowest average unit value of all the mineral 

commodities ($1.11 per ton in 1968), its total production value in 1970 was approximately $1.1 billion, surpassed by only a few mineral commodities. 

The construction industry accounts for 96 percent of all domestic consumption of sand and gravel, 

the principal uses being concrete aggregate, bituminous mixes, and fill. 

At present the United States is entirely selfsufficient and produces enough sand and gravel to 

supply all domestic requirements. However, because 

of the continual increasing cost of land, equipment, 

and personnel, as well as widespread zoning and 

environmental limitations, the outlook for the industry is uncertain and not without problems. Domestic resources now accessible at 1968 prices are 

barely adequate to meet the maximum cumulative 

forecast demand of 66 billion tons by the year 2000 

(Cooper, 1970). Transportation costs severely limit 

international trade in sand and gravel; thus, it is 

not surprising that less than 1 percent of the sand 

and gravel used in the United States is imported. 

Domestic production of sand and gravel in 1970 

was 943.9 million short tons, 43 percent of which 

was produced in seven States-California, Michigan, Ohio, Minnesota, Illinois, Wisconsin, and New 

York. Of the 100 largest sand and gravel operations 

in the United States, almost all are near the large 

population centers. The San Francisco Bay and Los 

Angeles areas account for 27 of the 100 largest 

operations. Most of the remainder are east of the 

Mississippi River in the Northern States, where the 

bulk of the population of the country is centered. 

Fortunately, much of this area falls within the 

glaciated area of the United States, which is a rich 

source area for sand and gravel deposits. 

Although there seems to be an increasing need, 

the demand for this commodity has, in the past, 

fluctuated locally as a function of construction of 

large public works projects, such as dams, freeways, 

and aqueducts. Such construction consumes by far 

the greatest tonnages of sand and gravel. A prediction of future need, therefore, hinges on a preU.S. GEOL. SURVEY PROF. PAPER 820 

561 
562 UNITED STATES MINERAL RESOURCES 

diction of future public-works projects. As the 

Nation becomes urbanized with a high population 

density, the need for more public-financed dams and 

highway projects may decrease. New forms of mass 

transit and housing structures, however, will place 

increased demands on the sand and gravel industry. 

GEOLOGIC ENVIRONMENTS AND THEIR 

DISTRffiUTION 

Sand and gravel are unconsolidated rocks and 

minerals ranging in size from silt (0.0039 mm) to 

boulders, formed by the breakdown, erosion, and 

transport of bedrock by ice, water, and wind. The 

precise definition and specifications for sand and 

gravel are extremely variable and commonly so 

complex that generalization is difficult. However, 

gravel generally has an upper size limit of 31;2 

inches in diameter and a lower limit of one-fourth 

of an inch, and sand particles are 1/4-1/16 of an 

inch in diameter (Industrial classification of the 

American Society for Testing and Materials). 

Ideally, a commercial deposit contains 60 percent 

gravel and 40 percent sand (Goldman, 1961). This 

provides ample coarse material to crush for road 

base or bituminous aggregate, and sand in the correct sizes and proportions for use in concrete. In 

addition, the aggregate used for concrete should be 

essentially free of clay, silt, mica, organic matter, 

chemical salts, and surface coatings. 

The primary commercial sources of sand and 

gravel are along existing or ancient river channels 

and in glaciated terranes; marine and lake environments have been less important source areas. Water 

is the sculpturing, sorting, cleansing, and transporting agent that is responsible for the flood-plain, 

outwash-plain, stream-terrace, alluvial-fan, esker, 

kame, delta, and moraine deposits that form the 

principal commercial deposits of sand and gravel. 

Windblown deposits locally are of minor economic 

importance. 

The sand- and gravel-rich geologic environments 

differ throughout the United States. The distribution of the most abundant deposit types on a 

countrywide geographic basis is as follows : Northern States, glacial outwash and till; Atlantic and 

Gulf Coast States, marine terraces; Southeastern 

and South Central States, river deposits; Mountain 

States, stream and fan deposits; Great Plains, 

stream deposits ; and Pacific Coast States, alluvial 

fans, river deposits, river terraces, beaches, and 

dunes. 

California leads all other States in sand and 

gravel production, of which 75 percent of the sand 

and gravel is produced from stream deposits. The 

huge alluvial-fan deposits in both the San Francisco 

and Los Angeles areas are the main sources of sand 

and gravel, but stream-channel deposits are also 

widely exploited. The stream deposits throughout 

the State are important sources for sand and gravel 

primarily because of their widespread availability, 

but other factors, such as thin overburden, nearness 

to water necessary for processing, and yearly replenishment by spring flooding, are important. The 

average particle size changes along a river channel, 

generally providing a variety of differently sized 

material for specific needs. The natural abrasive 

action prevalent during stream transport removes 

the nonresistant particles and concentrates the durable ones. Stream-produced subrounded to wellrounded particles are particularly de~irable for use 

in concrete. 

Glaciofluvial deposits, eskers, kames, and outwash 

provide the bulk of the sand and gravel in the Midwestern and Northeastern States. These deposits 

are favorable sources for sand and gravel because 

they are common and widespread, possess little 

deleterious material, and are generally free of overburden. 

In 1964 only 3 percent of the United States production of sand and gravel (including shell deposits) 

came from the ocean floor (Emery, 1966). As land 

sources are exhausted or removed from production 

for various reasons, the offshore deposits will probably be more extensively exploited. 

Bedded pre-Quaternary semiconsolidated sandstones and conglomerates deposited in ancient alluvial, lake, or marine environments have rarely been 

used as sources for sand and gravel. This type of 

deposit, while having a potential advantage of almost 

unlimited tonnages, has such disadvantages as thick 

overburden, high content of weathered, friable particles, high percentage of clay, and enough induration to require crushing. The use of such deposits 

is currently limited, although the Pliocene Kern 

River Formation in southern California has been 

utilized as a sand and gravel source (Goldman and 

Klein, 1961). 

POTENTIAL RESOURCES 

The estimated potential resource of sand and 

gravel in the United States is of little value unless 

costs of production are considered. A bulk tonnage 

not only would be difficult to estimate, but also 

would be meaningless without an economic frame 

of reference. Considerations, such as location, tonnage, quality, accessibility, and economic availability to markets, must be included in meaningful 

evaluations. In the near future shortages of sand 
SAN·D AND GRAVEL 563 

and gravel will result from uneven distribution of 

deposits, depletion of local deposits, urban encroachment, increased cost of property acquisition, and 

higher transportation costs (Sheridan, 1967). 

Goldman ( 1966, p. 369), an authority on sand and 

gravel in California, stated that "there are no undiscovered deposits near the metropolitan areas that 

can be developed to meet demand * * *. The State 

faces depletion of its major sources within the next 

3 decades unless sand and gravel deposits can be 

set aside as natural resource zones for future use." 

Thus, it may become necessary to import sand and 

gravel from beyond the present economic limit of 

50 miles. Consequently, we are faced with the task 

of correctly and effectively utilizing the known deposits. This will, in large part, be controlled by the 

zoning and planning officials of city governments. 

The geologist's role, therefore, may be merely to 

draw attention to the limits of the deposits and to 

point out that these deposits are the total resource 

existing within the economic radius of the population center. 

Crushed rock materials other than the conventional unconsolidated river and glacial deposits are 

potential sources that should be considered ; however, they have been neglected for specific reasons. 

Hard-rock mine dumps are potential resources of 

aggregate; however, although such material has 

had some use as road base, it is generally unsuitable 

for concrete aggregate because it lacks proper size 

and gradation and contains harmful sulfide minerals (Goldman, 1956). Artificially crushed stone is 

also useful for road base where angular shape is 

desirable, but when crushed stone is used in concrete, more cement is required, and more care is 

necessary in mixing and pouring than with conventional gravel. In the Tucson, Ariz., area, however, 

it has been forecast that "probably within 10 years 

coarse aggregate will be supplemented by broken 

and crushed rock quarried from nearby mountains" 

(Williams 1967). 

Dredge tailings generally consist of coarse gravel 

overlying fine-grained material, from which it is 

costly to obtain a "good blend"; however, many of 

these deposits are an excellent source of coarse 

aggregate. 

Pre-Quaternary rocks may be potentially useful 

but are generally too firmly cemented or contain too 

much weathered clayey material (Goldman, 1956). 

Marine and lake environments may offer some of 

the best potential source areas. Such environments 

should be target areas in a search for large blankettype aggregate deposits. Much of the continental 

shelf from New England to New Jersey is mantled 

by sand associated with lesser amounts of gravel 

"* * * in a quantity probably sufficient to constitute 

an economic asset" (Schlee, 1968). As the population continues to increase along the east coast 

(Washington, D.C.-Boston), demand for offshore 

supplies of sand and gravel will markedly increase 

(Emery, 1966). 

The underwater Great Lakes sand and gravel deposits continue to grow in importance as upland 

sources diminish by depletion, zoning, and high 

transportation costs. Large quantities of high-grade 

aggregate are already being extracted in western 

Lake Erie and along the Lake Ontario and Erie 

shorelines (Woodrow and others, 1971) . 

EXPLORATION TECHNIQUES 

Surface geologic mapping is perhaps the simplest 

and most common method by which sand and gravel 

deposits are located. Data are gathered by geological 

examination of streambanks, roadcuts, excavations 

for building foundations, and any other natural or 

manmade exposure of surficial material. With the 

aid of aerial photographs and topographic maps, 

and a knowledge of the types of landforms commonly underlain by sand and gravel, the geologist 

can pinpoint potential resource areas for detailed 

field examinations. After a deposit is located, the 

geologist must determine thickness, lateral extent, 

possible tonnage, and overburden depth, and he 

must collect representative samples for specific determinations. Records of drill holes from oil, gas, 

or water wells can be used when available to give 

valuable information in the subsurface dimension, 

particularly pertaining to the thickness of sand and 

gravel deposits. 

In the absence of drilling data, information about 

the depth and lateral extent of sand and gravel can 

be obtained with the aid of several different geophysical tools. Seismic refraction is a particularly 

sensitive niethod for determining depths and thickness of sand and gravel in certain geologic situations 

(Peterson and others, 1968). This method works 

best where less dense materials (sand and gravel) 

overlie denser materials (bedrock or fill). If a very 

dense overburden overlies an aggregate source, the 

presence of the aggregate is not likely to be determined by use of the seismic method because the 

shock waves will be diffused downward into lesf 

dense material. In areas of shallow bedrock, shallo" 

seismic devices employing a sledge hammer or firecrackers rather than a dynamite charge can be used 

(Criner, 1966). 

Another geophysical method used to determine 

thickness of sand and gravel is electrical resistivity. 
564 UNITED STATES MINERAL RESOURCES 

The method is generally used to measure texture; 

thus, bedrock would normally have a high resistivity compared with overlying unconsolidated materials. By using different electrode spacings, it is 

possible to "probe" to various depths and obtain a 

general idea of depths and thickness of layered units 

overlying bedrock. The method has been used successfully in a wide range of geologic environments 

and is a much cheaper way to obtain subsurface information than drilling (Bruce and Lundberg, 1964; 

Peterson and others, 1968). 

Surface samples and bottom photographs provide 

the best data for locating sand and gravel in offshore marine environments, although vibrocoring 

or drilling supplemented by seismic-reflection profiles are needed for determination of thickness 

(Emery, 1966). Seismic profiles across the continental shelf on the east coast show that a fairly 

uniform covering of sand and some gravel a few 

meters thick is present on the ocean floor (Schlee, 

1968). 

PROBLEMS FOR RESEARCH 

The sand and gravel industry, like many of the 

mineral industries, is currently beset with a wide 

variety of source and utilization problems. The major problem centers on land-use conflicts where land 

containing potentially rich sand and gravel resources 

is found to be more valuable for other uses and is 

removed from mineral production. 

A great deal more sand and gravel is being covered by manmade structures than is being produced 

for consumption (Cooper, 1970). A report on the 

Denver, Colo., area disclosed that four times as 

much aggregate has been lost through expansion 

of the city and suburbs into areas containing potential usable sand and gravel deposits than had 

been consumed in construction (Sheridan, 1967). 

The situation is probably similar in many other 

metropolitan areas in the United States. The millions of cubic yards of sand and gravel lost annually could be made available with better planning. 

Areas adjacent to large population centers should 

receive high priority in locating and preserving 

future sand and gravel resources. 

The heavily populated and urbanized Middle Atlantic, New England, and Pacific Coast States present the most immediate problems with respect to 

sand and gravel resources because of (1) the rapid 

depletion of currently operated deposits, (2) the 

covering of potential resources by urban structures, 

and (3) opposition to environmental disturbance 

that might result from sand and gravel operations. 

If we are going to have sand and gravel for use, 

more efficient multiple use of the land will be required. Numerous examples of beneficial multiple 

land use are demonstrated in the metropolitan Denver, Colo., area (Sheridan, 1967). Initially, the sandand gravel-rich lands were used for agriculture. 

Later, sand .and gravel were extracted, and the 

mined-out areas were subsequently used or are 

now serving as critically needed sanitary land-fill 

sites (garbage dumps). When the land is restored 

to a usable profile and grade, it is reclaimed in one 

of many ways, such as building sites for industrial 

and commercial structures, shopping centers, or 

churches, or as sites for recreational facilities, 

streets, freeways, or parking lots. "The conversion 

has been so complete and successful that, at many 

locations, nothing remains to indicate that the relatively temporary extractive operation existed" 

(Sheridan, 1967). More of these successful multipleland-use projects are needed as vast acreages of 

sand and gravel have been lost to production by 

the rapid urban sprawl. Equally large deposits remain, however, in urban areas from which, with 

thoughtful planning, the mineral potential can be 

realized while still preserving the land for later 

use. Several fairly detailed studies of site utilization and rehabilitation practices for sand and gravel 

operations have been made (Schellie and Rogier, 

1963; Johnson, 1966; Bauer, 1965; Ahearn, 1964). 

The widespread implementation of these practices 

is needed. 

Environmental limitations are factors that must 

be considered in the location and development of 

sand and gravel deposits. The effects of traffic, 

smoke, dust, noise, vibration, perils of excavation 

or ponds, hazards of mining equipment, depression 

of property values, unsightliness, water pollution, 

and lowering water table· must be determined prior 

to the mining. 

The threat to animal and plant life, streambed 

and runoff changes, and local flooding are problems 

associated with the dredging of sand and gravel 

that put limits on the location and type of deposits 

which can be used. 

Large quantities of water are needed for processing most sand and gravel deposits, and the availability of abundant, cheap water is becoming a factor in the location of plants. 

Local problems of the sand and gravel industry 

vary in different geographic areas. In the Tucson, 

Ariz., area, for example, problems are principally 

those of (1) the thinness (8-10 ft) of the gravel 

beds, (2) presence of caliche, which cements the 

gravel and is a deleterious material, (3) inadequate 

supplies of water, (4) thick overburden, and (5) 
SAND AND GRAVEL 565 

hot weather causing rapid setting of cement, thus 

requiring a short haul limitation for mixed cement 

(Williams, 1967). 

Many of the major problems associated with the 

industry could be eliminated if a cheap means of 

transporting sand and gravel were available. Transportation costs of this large-volume, low-unit-value 

commodity limit the distance the deposit can be 

from the market and still be economical. In California, this distance is roughly 40 to 50 miles (Goldman, 1968), and in Oregon, less than 20 miles 

(Schlicker, 1969). In some areas where the "back 

haul" can be utilized for some other commodity, 

the distance increases, as in the Denver area, where 

sand and gravel are back-hauled as much as 160 

miles east of the city by Kansas grain trucks (Sheridan, 1967). 

Perhaps the key to the future of the industry is 

to develop a cheap form of transportation to and 

from the metropolitan centers. What do the people 

in the metropolitan areas have in excess that they 

would like to get rid of in exchange for sand and 

gravel? Garbage! Perhaps unit trains could be used 

to exchange garbage for sand and gravel in sparsely 

populated areas. The garbage could be used as backfill, thus producing little noticeable change on the 

shape of the landscape. 

REFERENCES 

Ahearn, V. P., Jr., 1964, Land use planning and the sand 

and gravel produced: Silver Spring, Md., Natl. Sand 

and Gravel Assoc. 

Bauer, A. M., 1965, Simultaneous excavation and rehabilitation of sand and gravel sites: Silver Spring, Md., Natl. 

Sand and Gravel Assoc. 

Bruce, R. L., and Lundberg, B. E., 1964, Evaluation of exploration methods for coarse aggregate in eastern South 

Dakota: South Dakota Geol. Survey Rept. Inv. 95, 84 p. 

Cooper, J. P., 1970, Sand and gravel, in Mineral facts and 

problems: U.S. Bur. Mines Bull. 650, p. 1185-1199. 

Criner, J. H., 1966, Seismic surveying with firecrackers-A 

modification of the sledgehammer method, in Geological 

Survey research 1966: U.S. Geol. Survey Prof. Paper_ 

650-B, p. B104-B107. 

Emery, K. 0., 1966, Geological methods for locating mineral 

deposits on the ocean floor, in Exploiting the oceans: 

Marine Technology Soc. Conf. Exhibit, 2d Ann., Trans., 

p. 24-43. 

Goldman, H. B., 1956, Sand and gravel for concrete aggregate: California Jour. Mines and Geology, v. 52, no. 1, 

p. 79-104. 

--- 1961, Sand and gravel in California-Part A, Northern California: California Div. Mines and Geology Bull. 

180-A, 38 p. 

--- 1966, Sand and gravel, in Mineral and water resources 

of California: California Div. Mines and Geology Bull. 

191, p. 361-369. 

--- 1968, Sand and gravel in California-Part B, Central California: California Div. Mines and Geology Bull. 

180-B, 58 p. 

Goldman, H. B., and Klein, I. E., 1961, Sand and gravel resources of the Kern River near Bakersfield, California: 

California Div. Mines and Geology Spec. Rept. 70, 33 p. 

Johnson, Craig, 1966, Practical operating procedures for 

progressive rehabilitation of sand and gravel sites: 

Silver Spring, Md., N atl. Sand and Gravel Assoc. 

Peterson, D. W., Yeepd, W. E., Oliver, H. W., Mattick, R. 

E., 1968, Tertiary gold-bearing channel gravel in northern Nevada County, California: U.S. Geol. Survey Cire. 

566,22 p. 

Schellie, K. L., and Rogier, D. A., 1963, Site utilization and 

rehabilitation practices for sand and gravel operations: 

Silver Spring, Md., Natl. Sand and Gravel Assoc., 80 p. 

Schlee, John, 1968, Sand and gravel on the continental shelf 

off the Northeastern United States: U.S. Geol. Survey 

Circ. 602, 9 p. 

Schlickler, H. G., 1969, Sand and gravel, in Mineral and 

water resources of Oregon: U.S. 91st Cong., 1st sess., 

Comm. Interior and Insular Affairs, Comm. Print., p. 

233-237. 

Sheridan, M. J., 1967, Urbanization and its impact on the 

mineral aggregate industry in the Denver, Colorado, 

area: U.S. Bur. Mines lnf. Circ. 8320, 58 p. 

Williams, F. E., 1967, Urbanization and the mineral aggregate industry, Tucson, Arizona, area: U.S. Bur. Mines 

Inf. Circ. 8318, 23 p. 

Woodrow, D. L., Lewis, T. L., and Sutton, R. G., 1971, 

Lake Ontario as a source of sand: Rock Products, v. 

74, no. 4, p. 72-73. 

UNITED STATES MINERAL RESOURCES 

SCANDIUM 

By JoHN W. ADAMs 

CONTENTS 

Page 

Abstract of conclusions --------------------------- 567 

Introduction ------------------------------------- 567 

Geologic environment ----------------------------- 567 

Geochemistry -------------------------------- 567 

~ineralogy ---------------------------------- 568 

Types of deposits ---------------------------- 568 

Pegmatites ------------------------------ 568 

Greisen and vein deposits ---------------- 569 

Variscite deposits ----------------------- 569 

Enrichments in other materials ----------- 569 

Resources --------------------------------------- 569 

Problems for research ---------------------------- 570 

References cited --------------------------------- 570 

ABSTRACT OF CONCLUSIO~S 

Scandium is a rare metal that at present has only minor 

industrial applications. Geochemically, it is a highly dispersed element that occurs chiefly in trace amounts in the 

ferromagnesian minerals of igneous rocks. Scandium may 

he concentrated in pegmatites, some of which have been 

mined for thortveitite, one of the few independent scandium 

minerals. It may also be present in anomalously high amounts 

in some phosphate deposits and tungsten ores. Some scandium has been produced from domestic and foreign uranium 

ores in mills where it accumulated in residues that developed 

during the extraction of uranium. Scandium apparently is 

not being recovered from any source at the present time, but 

if demand were to increas·e, the element could be obtaiood 

again as a byproduct of uranium-ore processing as well as 

from certain tungsten ores and phosphatic rocks. 

INTRODUCTION 

Scandium (Sc) is a soft silvery metal that was 

discovered in 1879 but was not prepared in its 

metallic form until 1937. It has atomic number 21 

and is trivalent. It is sometimes included as a member of the rare-earth group but differs markedly 

from the rare earths in its geochemical behavior. 

Scandium is a commodity whose statistics of production and demand are quoted in grams rather than 

tons. Until a few years ago, its sole and very limited commercial use was as a tracer of fluid flow in 

oil wells. This purpose requires the irradiation of 

natural Sc45 in a nuclear reactor to produce the 

radioactive isotope Sc46 , which has a half life of 

84 days. Recently, however, a new application for 

scandium has been found in high-intensity lampsthe metal produces light in a more balanced color 

range. Several thousand grams of scandi urn are now 

used in these lamps annually (U.S. Bur. Mines, 

1971). 

Scandium is an expensive metal owing to both 

the cost of extraction and the very limited demand. 

In the past, it has been obtained almost exclusively 

from the rare mineral thortveitite, a scandiumyttrium silicate mined in Norway and Madagascar, 

but since 1960 its chief source has been waste products from certain uranium mills that use an organophosphate solvent· extraction process for uranium recovery (Ross and Rosenbaum, 1962). 

Scandium has not been produced from uranium 

mills in the United States for several years, and 

the limited demand has been met from producers' 

stockpiles or from imports from Canada and Australia (U.S. Bur. Mines, 1971). 

Should the need for scandium increase drastically, 

it could be produced from several possible sources, 

but its price would probably always be high if lowgrade raw materials had to be used. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Scandium tends to be dispersed like the rareearth elements, but it is dispersed to an even greater 

degree. Its crustal abundance has been variously 

estimated to be 5-30 ppm (parts per million) 

(Fryklund and Fleischer, 1963; Parker, 1967), 

about that of some lanthanide elements, but much 

greater than that of such familiar elements as antimony, mercury, molybdenum, and silver, which are 

more readily available owing to their tendency to 

U.S. GEOL. SURVEY PROF. PAPER 820 

567 
568 UNITED STATES MINERAL RESOURCES 

accumulate in enormously high concentrations in 

localized sites. 

Most of the scandium in the earth's crust is contained in igneous rocks, where it is largely a trace 

constituent of the ferromagnesian minerals. These 

minerals may commonly contain 5-100 ppm Sc20 3 

(Frondel, 1968, p. 122). Pyroxenes, hornblende, and 

biotite are the usual hosts for scandium; therefore, 

rocks rich in these minerals, notably the mafic rocks, 

will have the highest scandium contents. Analyses 

of 76 samples of igneous and sedimentary rocks, 

including nine composite samples, reported by Norman and Haskin (1968), showed that the highest 

scandium contents (30-40 ppm) are in basalts and 

gabbros and the lowest (about 1 ppm) in nepheline 

syenites and limestones. 

Scandium in the ferromagnesian minerals apparently substitutes for iron in sites occupied by either 

(Fe+3

,Al) or (Fe+2,Mg). Scandium can also form 

limited solid solution with Y +a, AI, the heavy lanthanides Er+a to Yb+3 , Ti+\ Sn+\ Zr+4, and W+6 

in certain geochemical environments. Where scandium is substituting for higher valence ions, such 

as Ti+4 or W+6

, a complex coupling mechanism involving (Nb,Ta) +s and Fe+a may be required for 

charge balances in some minerals (Frondel, 1968). 

MINERALOGY 

Scandium is an essential constituent of very few 

minerals and these are all very rare species. These 

minerals are: 

Thortveitite ------------ (Sc,Y) Si.~07 Sterrettite (Kolbeckite) _Sc(P0,)2H20 

Bazzite ----------------Bea ( Sc,Al) 2SieOts 

Magbasite --------------KBa(Al,Sc) (Mg,Fe)eSie020FJ 

Many additional minerals may contain scandium 

in amounts that range from a few to thousands parts 

per million through substitution by one or more of 

the mechanisms mentioned above. In addition to 

being found in the ferromagnesian minerals, scandium is found in multiple-oxide minerals of the 

rare earths, columbite, wolframite, cassiterite, beryl, 

garnet, muscovite, and aluminum phosphate minerals. The scandium contents of these and many 

other minerals have been reported by Neumann 

(1961), Borisenko (1963), Vlasov (1964), Phan, 

Foissey, Kerjean, Moatti, and Schieltz (1967), 

Frondel, I to, and Montgomery ( 1968), and Frondel 

(1970a,b). Inasmuch as several of the minerals 

that are scandium carriers are also important ores 

of other elements, byproduct recovery is a distinct 

possibility. 

TYPES OF DEPOSITS 

PEGMATITES 

Granitic pegmatites have so far been the only 

source of the high-grade scandium ore mineral 

thortveitite. Thortveitite-bearing pegmatites, known 

from only a few places in the world, have been 

mined for scandium in the lveland-Evje district in 

Norway and in Madagascar. 

In Norway, at least 10 pegmatites have produced 

thortveitite, but the aggregate recovery by 1961 was 

only about 50,000 grams (Neumann, 1961). The 

Befanomo pegmatite in Madagascar, apparently exhausted by 1955, supplied 38,000 grams (Murdock, 

1963, p. 101). 

Neumann's (1961) study of the Norwegian pegmatites shows that most of the scandium is contained in iron minerals, chiefly biotite and ilmenite, 

and that minerals from dikes in which thortveitite 

is present are richer in scandium than those from 

dikes without thortveitite. Neumann suggested that 

a deficiency of divalent iron, for which scandium 

commonly proxies, would favor the development of 

thortveitite in a pegmatite. 

Quite similar observations were made by Phan, 

Foissy, Kerjean, Moatti, and Schieltz (1967) from 

their work on Madagascar pegmatites. They noted 

that one rarely finds a rich scandium mineral if the 

associated minerals are scandium poor and that one 

can observe in the majority of mineral deposits the 

following decreasing order of tenor : Thortveitite, 

niobium-tantalum minerals (metamict minerals, 

columbite-tantalite, ilmenorutile), muscovite, garnet, beryl, and tourmaline. 

The only known occurrence of thortveitite in the 

United States is in the Crystal Mountain fluorite 

deposit in Montana (Parker and Havens, 1963). 

This deposit, described by Taber (1952, 1953) and 

by Weis, Armstrong, and Rosenblum (1958), consists of tabular bodies of fluorite in coarse-grained 

biotite granite that contains xenoliths of biotitequartz-plagioclase 1neiss, hornblende-plagioclase 

gneiss, and pegmatitic granite. Gangue minerals in 

the fluorspar are altered feldspar, sericite, quartz, 

and biotite. Massive quartz overlies the west outcrop (Geach, 1963). Radioactive zones, such as described by Weis, Armstrong, and Rosenblum ( 1958, 

p. 20), lie along the margins of the fluorite bodies. 

These zones consist largely of dark-purple fluorite 

and contain considerable biotite. Accessory minerals 

include sphene, quartz, oligoclase, apatite, green 

amphibole, fergusonite, thorianite ( ?) , and thortveitite (Parker and Havens, 1963). 

Limited geologic information on the Crystal 

Mountain deposit suggests a magmatic origin. One 
SCANDIUM 569 

might speculate further that the pegmatite is actually unusual. If it is unusual, the massive quartz 

body mentioned by Geach ( 1963) would be an asymmetric core, the fluorite bodies an intermediate zone, 

and the radioactive layers the wall zone. 

The Crystal Mountain deposit has been actively 

mined for fluorspar since 1952, but there is no indication that thortveitite or other minerals have been 

recovered. 

The influence of host rock on the scandium content of pegmatites has been long considered and is 

discussed by Neumann (1961) and Phan, Foissy, 

Kerjean, Moatti, and Schieltz (1967). Amphibolebearing rocks seem definitely favorable for scandium 

pegmatites, but an amphibolite host rock is no assurance that a pegmatite will be enriched in scandium. 

GREISEN AND VEIN DEPOSITS 

Metasomatic deposits containing minerals of 

tungsten, tin, or beryllium in association with 

quartz, muscovite, topaz, or tourmaline are found in 

or near granitic bodies from which they, and related high-temperature veins, presumably were derived. These deposits, called greisens, are apt to 

contain minerals with anomalously high scandium 

content. According to Borisenko ( 1963), the main 

scandium carriers in greisens are wolframite, cassiterite, beryl, and micas. 

Wolframite is commonly the richest in scandium 

of the greisen minerals and may contain up to 0.4 

percent Sc20a, although the average content is considerably lower. Where wolframite occurs in both 

greisen and associated high-temperature veins, the 

scandium content of the wolframite may differ. In 

the Lake George area, Colorado (Hawley, 1969), 

wolframite from greisen contained 0.3 percent scandium as compared to 0.07 percent in wolframite 

from a quartz vein in greisenized wallrock. 

Scandium enrichment is uncommon in deposits 

that would be considered normal hydrothermal veins, 

and even wolframite and cassiterite from these veins 

generally do not contain more than 0.005 percent 

Sc20a (Vlasov, 1964). Ross and Rosenbaum (1962), 

however, give an analysis of Colorado ferberite 

(FeW04) ore, presumably from the low-temperature 

hydrothermal veins of Boulder County, that shows 

a scandium content of 0.01 percent. 

V ARISCITE DEPOSITS 

Sterrettite, one of the few minerals in which 

scandium is a major component, occurs sparsely in 

a highly brecciated zone in limestone at Fairfield, 

Utah. It is associated with a large suite of phosphate 

minerals of which variscite, Al(P04) 2·2H20, and 

crandallite, CaAI (P04) 2 ( OH) 5 • H20, are the most 

common. 

In addition to its occurrence in sterrettite, scandium has been found in the associated phosphate 

minerals, notably crandallite and variscite, which 

contain from 0.01 to 0.8 weight percent Sc20a. A 

small amount of scandium oxide was produced from 

4,000 pounds of crude ore from the limestone deposit. The ore contained crandallite, variscite, chert, 

and limonitic clay and averaged 0.10 percent Sc20a 

(Fronde} and others, 1968). 

The deposit at Fairfield is thought to have formed 

under near-surface conditions by the precipitation 

of phosphate dissolved by ground water from the 

overlying Phosphoria Formation (Larsen, 1942). 

The average scandium content of the Phosphoria is 

0.001 percent (Gulbrandsen, 1966), but analyses of 

phosphatic shale from the Fairfield area were found 

by Ross and Rosenbaum (1962) to contain as much 

as 0.05 percent scandium. 

Anomalous amounts of scandium have been found 

in variscite deposits in the Western United States; 

the origin of the deposits and their relationship to 

the Phosphoria Formation seems to be quite similar 

to the origin and relationship of the Fairfield deposit (Frondel and others, 1968), which is the 

richest deposit found so far. 

ENRICHMENTS IN OTHER MATERIALS 

Scandium in concentrations greatly above crustal 

abundance has been found in many geologic materials and mill products, including coals, titaniferous 

magnetite ores, bauxites, nickeliferous laterites, and 

some placer deposits (Ross and Rosenbaum, 1962; 

Vlasov, 1964). None of these sources may be said 

to constitute a scandium deposit, but some may be 

considered potential sources of scandium as a byproduct of other commodities. 

RESOURCES 

If an important use developed for scandium that 

would require tons rather than grams or kilograms 

of the metal annually, what would be the most 

logical source? Considering the amount of thortveitite produced from pegmatites in Norway and Madagascar, pegmatite sources would be inadequate. 

Variscite deposits, such as at Fairfield, Utah, might 

supply a few pounds, but soon they would be exhausted. It is reasonable, therefore, to consider the 

lower grade deposits from which scandium might 

be produced as a byproduct. Tungsten ore concentrates, including concentrates of wolframite, huebnerite, and ferberite, are one important possible 

source. According to annual reports of the Climax 
570 UNITED STATES MINERAL RESOURCES 

Molybdenum Co., more than 1,000,000 pounds of 

tungsten concentrates, containing 0.05-0.08 percent 

scandium, are produced annually as a byproduct of 

molybdenum recovery at Climax, Colo. Work by the 

U.S. Bureau of Mines (Ross and Schack, 1965) has 

shown that about 85 percent of this scandium is 

recoverable at a cost relatively modest in relation 

to the value of scandium. The tungsten ore recovered from this one deposit could thus supply 400-

700 pounds of scandium annually. 

Uranium deposits, even though they may have a 

very low scandium content, are potential sources, 

and indeed some scandium has been recovered from 

uranium mills in the United States and Australia. 

Recovery of scandium is made possible by its accumulation in an iron sludge produced in mills which 

use an organophosphate process for extraction of 

uranium. This sludge, which may contain 0.1-0.2 

percent scandium (Ross and Rosenbaum, 1962), can 

be treated by methods described by Lash and Ross 

(1961) and Ross and Schack (1965) to produce 

scandium oxide. Some scandium was produced commercially from sludge at a uranium mill in Utah, 

but recovery was discontinued after 1964. Scandium 

was recovered in Australia from Radium Hill uranium ores. Baroch (1970) stated that uranium ores 

are the best potential source of scandium, and that 

as much as 30 pounds a day could be produced from 

the domestic uranium mills, which were then using 

the acid leach and clear liquor process. 

Phosphorites are another potential source of scandium. Like the rare earths, scandium is released 

from the phosphate ore during the wet-process production of phosphoric acid. Altschuler, Berman, and 

Cuttitta (1967) have estimated that 16 short tons 

of scandium was available for recovery from the 

phosphoric acid produced from Florida phosphorites 

in 1964. The phosphorites represent a very large 

resource of scandium; there are possibly several 

hundreds of thousands of tons in the world's phosphate deposits (Eilertsen, 1965), but the probability of its recovery from this source seems remote. 

The future sources of scandium will undoubtedly 

be ores of other mineral commodities from which 

scandium can be recovered as a byproduct. This 

byproduct status thus ties the resources of scandium 

, directly to those of uranium, tungsten, and phosphate rock, which are discussed in separate chapters 

of this report. 

PROBLEMS FOR RESEARCH 

The scandium that is now available as a byproduct 

but not recovered is irrevocably lost. Under the 

economic conditions of 1972, it is not likely that any 

recovery of byproduct scandium will be made unless 

the demand increases. There is, however, no reason 

why a few tons of scandium could not be produced 

annually at less than market value from raw materials now processed in industry. Research into applications for scandium is therefore needed to utilize, 

rather than lose, the scandium that is currently 

available. The search for concentrations of the element should continue, not only in natural materials, 

but also in the waste products of the mineral industry. 

REFERENCES CITED 

Altschuler, Z. S., Berman, Sol, and Cuttitta, Frank, 1967, 

Rare earths in phosphorites--Geochemistry and potential recovery, in Geological Survey research 1967: U.S. 

Geol. Survey Prof. Paper 575-B, p. Bl-B9. 

Baroch, C. T., 1970, Scandium, in Mineral facts and problems, 1970 ed.: U.S. Bur. Mines Bull. 650, p. 705-711. 

Borisenko, L. F., 1963, Scandium, its geochemistry and mineralogy: New York, Consultants Bur., 78 p. 

Eilertsen, D. E., 1965, Scandium, in Mineral facts and problems, 1965 ed.: U.S .Bur. Mines Bull. 630, p. 789-792. 

Fronde!, Clifford, 1968, Crystal chemistry of scandium as 

a trace element in minerals: Zeitsehr. Kristallographie, 

v. 127, p. 121-138. 

-- 1970a, Scandium contents of ore and skam minerals 

at Franklin, New Jersey: Am. Mineralogist, v. 55, p. 

1051-1054. 

-- 1970b, Scandium-rich minerals from rhyolitle in the 

Thomas Range, Utah: Am. Mineralogist, v. 55, p. 1058-

1060. 

Fronde!, Clifford, Ito, Jun, and Montgomery, Arthur, 1968, 

Scandium content of some aluminum phosphates: Am. 

Mineralogist, v. 53, nos. 7-8, p. 1223-1231. . 

Fryklund, V. C., Jr., and Fleischer, Michael, 1963, The 

abundance of scandium in volcanic rocks, a preliminary 

estimate: Geochim. et Cosmochim. Acta, v. 27, no. 6, p. 

643-664. 

Geach, R. D., 1963, Fluorspar, in Mineral and water resources 

of Montana: U.S. 88th Cong., 1st. sess., Senate Comm. 

Interior and Insular Affairs, p. 65-67. 

Gulbrandsen, R. A., 1966, Chemical composition of phosphorites of the Phosphoria Formation: Geoehim. et Cosmochim. Acta, v. 30, no. 8, p. 769-778. 

Hawley, C. C., 1969, Geology and beryllium deposits of the 

Lake George (or Badger Flats) beryllium area, Park 

and Jefferson Counties, Colorado: U.S. Geol. Survey 

Prof. Paper 608-A, 44 p. 

Larsen, E. S., 3d, 1942, The mineralogy and paragenesis of 

the variscite nodules from near Fairfield, Utah, Pt. 3: 

Am. Mineralogist, v. 27, no. 6, p. 441-451. 

Lash, L. D., and Ross, J. R., 1961, Scandium recovery from 

uranium solutions: Jour. Metals, v. 13, no. 8, p. 555-

558. 

Murdock, T. G., 1963, Mineral resources of the Malagasy 

Republic: U.S. Bur. Mines Inf. Circ. 8196, 147 p. 

Neumann, Henrich, 1961, The scandium content of some 

Norwegian minerals and the formation of thortveitite, 

a reconnaissance survey: Norsk. Geol. Tidsskr., v. 41, 

p. 197-210. 
SCANDIUM 571 

Norman, J. C., and Haskin, L. A., 1968, The geochemistry 

of Se-A comparison to the rare earths and Fe: Geochim. et Cosmochim. Acta, v. 32, no. 1, p. 93-108. 

Parker, R. L., 1967, Composition of the earth's crust, chap. 

D of Fleischer, Michael, ed., Data of geochemistry (6th. 

ed.): U.S. Geol. Survey Prof. Paper 440-D, 19' p. 

Parker, R. L., and Havens, R. G., 1963, Thortveitite associated with fluorite, Ravalli County, Montana, in Geological Survey research 1963: U.S. Geol. Survey Prof. 

Paper 475-B, p. B10-B11. 

Phan, K. D., Foissy, B., Kerjean, M., Moatti, J ., and 

Schieltz, J. C., 1967, Le scandium dans les mineraux et 

1es roches encaissants de certaines pegmatites malgaches: Bur. Recherches Geol. et Minieres Bull., no. 3, 

p. 77-97. 

Ross, J. R., and Rosenbaum, J. B., 1962, Reconnaissance of 

scandium sources and recovery of scandium from uranium mill solutions: U.S. Bur. Mines Rept. Inv. 6064, 

16 p. 

Ross, J. R., and Schack, C. H., 1965, Recovery of scandium 

from uranium plant iron sludge and from wolframite 

concentrates: U.S. Bur. Mines Rept. Inv. 6580, 22 p. 

Taber, J. W., 1952, Crystal Mountain fluorite deposits, 

Ravalli County, Montana: U.S. Bur. Mines Rept. Inv. 

4916, 8 p. 

--- 1953, Montana's Crystal Mountain fluorite deposit is 

big and high grade: Mining World, v. 15, no. 7, p. 43-

46. 

Vlasov, K. A., ed., 1964, Geochemistry of rare elements, v. 

1 of Geochemistry and mineralogy of rare elements and 

genetic types of their deposits (in Russian): Moscow, 

Publishing house "Nauka," 704 p., 1964; translated by 

Israel Program for Scientific Translations, Jerusalem, 

688 p., 1966. 

Weis, P. L., Armstrong, F. C., and Rosenblum, Samuel, 1958, 

Reconnaissance for radioactive minerals in Washington, Idaho, and western Montana, 1952-1955: U.S. Geol. 

Survey Bull. 1074-B, p. 7-48. 

U.S. Bureau of Mintes, 1971, Scandium, in Minor metals: 

Bur. Mines Minerals Yearbook 1970, preprint, p. 10-11. 

UNITED STATES MINERAL RESOURCES 

SELENIUM 

By H. W. LAKIN and D. F. DAVIDSON 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Uses ------------------------------------------- Geochemical cycle --------------------------------

Crustal abundance ------------------------------- Resources ______________________________________ _ 

Selected references -------------------------------

118. 

119. 

TABLES 

Selenium resources potentially available in 

identified resources of copper ores, lead ores, 

pyrite, and coal of the United States and the 

rest of the world -------------------------

Selenium content of annual coal consumption at 

five operating and five proposed powerplants 

in Western United States -----------------

ABSTRACT OF CONCLUSIO~S 

Page 

573 

573 

573 

574 

575 

575 

576 

Page 

575 

576 

The present demand for selenium is less than the amount 

available as a byproduct from the copper industry. Two 

factors, however, may result in a severe shortage of selenium 

INTRODUCTION 

Selenium was discovered in 1817 by J. J. Berzelius 

and J. G. Gahn in a red sediment found in sulfuric 

acid prepared from the sulfur recovered from pyrite 

mined at Fahlun, Sweden. 

It is a nonmetallic element, of atomic number 34 

and atomic weight 78.96, which exists at normal 

temperatures in two crystalline forms and two 

amorphous forms. The metastable monoclinic structural form is red, melts at 144o,c, has a specific gravity of 4.42, and changes to a ·hexagonal crystal struc• 

ture when heated. The stable hexagonal form is 

black, melts at 220°C, has a specific gravity of 4.82, 

and conducts electricity-the conductivity increases 

as much as a thousandfold during exposure to light. 

A black vitreous amorphous form is obtained by 

quick chilling of molten selenium. The red amorphous 

form is obtained by reduction of selenious acid to 

elemental selenium with sulfur dioxide or other reductant. It turns black on standing. 

Of the 1.1 million pounds of selenium used in the 

United States in 1968, about 40 percent was imported, principally from Canada. 

USES 

in the United States in the future. In situ leaching of copper Selenium is commonly marketed as elemental 

from its ores leaves the associated selenium undissolved in 

the waste rock resulting from the process. Thus, as the use selenium in the form of powder, pellet, and stick in 

of the leaching process increases at the expense of smelting, grades varying from 97.00 to 99.99 percent selenium, 

the supply of selenium will decrease. A second and more im- but it is alsoavailable in pellets as very pure seleniportant factor is the probable increasing use of selenium as um-99.999 + percent Se. About 40 percent of the 

a soil additive to provide enough selenium in the diet of selenium currently consumed in the United States is 

domestic animals to insure good health. It is anticipated high-purity grade (99.95-99.9 percent selenium), that this use will require a minimum of 10 times the present 

annual production of selenium. and it is used in electrostatic printing, rectifiers, 

Identified resources of copper in the United States are exposure meters, photoelectric cells, and optical 

estimated to contain about 52 million pounds of recoverable lenses. 

selenium. About seven times the current annual domestic Nearly 30 percent of the annual consumption goes 

consumption of 1.1 million pounds of selenium is contained into the manufacture of glass, in which the selenium 

in the coal burned per year in the United States. Thus the 

most promising source for a greatly increased supply of is used to eliminate the greenish tinge caused by iron 

selenium is as a byproduct for coal-burning powerplants. impurities. In larger quantities selenium gives a 

U.S. GEOL. SURVEY PROF. PAPER 820 

573 
574 UNITED STATES MINERAL RESOURCES 

desirable pink tinge to glass, and in still larger quantities yields a ruby-red glass. Although the principal 

use of selenium in flat glass is to decolorize, more 

than 100,000 pounds of selenium per year is used to 

produce "black" glass that is used as an outer surface in many modern office buildings. 

The manufacture of inorganic pigments, principally cadmium sulfoselenide, accounts for about 14 percent of the annual consumption of selenium. These 

pigments have good light stability and heat resistance and are used in plastics, paints, enamels, inks, 

and rubber. 

The remainder of the selenium is consumed in 

many diverse applications. For example, selenium 

added to stainless steels improves their machining 

characteristics. Selenium compounds are used as vulcanizing agents in rubber products to promote resistance to oxidation and abrasion, and in oils to obtain 

exceptional antioxidant properties. Selenium and its 

compounds are used in many catalytic reactions in 

the preparation of drugs and hydrogenated oils. The 

element also finds use in fungicides, bactericides, 

parasiticides, herbicides, and insect repellents and in 

photographic photosensitizers, phosphorescents, and 

luminescents. A rather exhaustive listing of uses 

may be found in the materials survey by Lansche 

(1967). 

An anticipated very large demand for selenium results from the discovery in 1957 that selenium is 

required in the nutrition of animals, including man. 

In New Zealand, the addition of selenium to soils to 

increase the selenium content of forage crops is not 

only legal but widely done. The use of selenium in 

fertilizers will probably be legalized in most countries in the near future. 

The adverse effects on the economy caused by 

selenium deficiency are summarized by Oldfield 

(1971) : 

Widespread field occurrence of white muscle disease in lambs 

and calves, myopathy of the gizzard and heart in turkeys, 

exudative diathesis in chicks, and liv·er necrosis in swine, 

together with depression of growth and decreased efficiency 

of feed utilization that result from selenium d·eficiency in 

commercial feeds, represent heavy economic losses to poultry 

and livestock producers in many part of the United States. 

Selenium deficiency diseases with resultant economic 

losses have also been reported in Canada, New Zealand, Australia, Scotland, Finland, Sweden, Denmark, France, Germany, Greece, Turkey, and Russia. 

At dietary levels below 0.04 ppm (parts per million) 

selenium, domestic animals suffer from seleniumdeficiency diseases; dietary levels of 1 ppm selenium 

are completely safe ; dietary levels above 4 ppm 

selenium cause domestic animals to suffer from 

selenium-toxicity diseases. 

Selenium as sodium selenite can be added safely 

and profitably at the rate of 1-2 pounds per acre once 

every 5 years in areas where forage crops are deficient in selenium. It is estimated that 12.5 million 

pounds of selenium per year would be required to 

treat the most severely selenium deficient areas of 

the United States; this figure is based on a rate of 

application of 1.5 pounds of selenium as sodium 

selenite once every 5 years. To reach an optimum 

nutritional level of selenium in forage crops in the 

United States, 25 million pounds of selenium would 

be needed annually. This consumption would be more 

than 20 times the amount of selenium used in the 

United States in 1968. 

More selenium would probably be used in industry, 

especially in steel and glass manufacture, if the supply and price were stable. 

GEOCHEMICAL CYCLE 

Selenium and its compounds H2Se and Se02 are 

sufficiently volatile to accompany sulfur in volcanic 

gases. It has been estimated that approximately 2 

pounds of selenium per square yard has been deposited on the earth's surface by volcanic gases. 

Through this process, seleni urn tends to become a 

dispersed element, but other geologic processes tend 

to concentrate it. 

Selenium associated with intrusives accompanies 

sulfur into sulfide minerals. The ionic radius of Se- 2 

is 1.98 A and that of S-2 is 1.84 A; thus Se-2 can 

substitute for S-2 in many sulfide minerals. The 

high-temperature sulfides, pyrrhotite and pentlandite, have a sulfur-selenium ratio of 7,000, a valu.e 

near that given by Goldschmidt and Strock for the 

crustal abundance estimate. In sulfide minerals from 

the mines of the Fahlun area in northern Sweden, 

the order of decreasing selenium content is galena, 

chalcopyrite, arsenopyrite, sphalerite, pyrite, and 

pyrrhotite. The order varies, however, in other areas. 

In porphyry copper ore containing 0.5 percent copper, the selenium content is 2.5 ppm. In these ores, 

copper is enriched over its crustal abundance 100 

times, but selenium is enriched only 50 times. 

In weathering, selenium and sulfur tend to be 

separated, in large part because selenium becomes 

fixed in insoluble basic ferric selenites. Only in an 

alkaline oxidizing environment is selenium oxidized 

to the soluble selenate form; sulfur, however, is even 

more readily oxidized to highly soluble sulfate and is 

carried away in surface and ground waters. As a 

result, selenium is present neither in sulfate deposits 

nor in sedimentary sulfur deposits. 

In contrast to the separation of selenium and sulfur in weathering processes, the two elements travel 
SELENIUM 575 

together in biological processes. Selenium replaces 

sulfur in amino acids; it is taken up by plants and 

concentrated by some species to a level which can 

produce toxic effects on animals that eat the plants 

(Lakin, 1972). 

The substitution of selenium for sulfur in biological processes and its reduction to selenides by 

anaerobic microorganisms often leads to the presence 

of selenium in pyrite contained in black shales and 

coal. Selenium is found in pyrite in some unweathered sedimentary rocks and may be found in concentrations many times its crustal abundance in 

ores rich in organic matter. Highly organic shales 

may contain as much as 1,500 ppm selenium in 

selected samples and as much as 20 ppm over expanses of thousands of miles. Phosphorites may contain as much as 300 ppm selenium and are almost 

without exception enriched above crustal abundance. 

Brimstones may contain as much as 20 ppm se!enium. 

Coals of the United States average 3.3 ppm (Pillay 

and others, 1969). The selenium content of soils 

varies widely, from less than 0.1 ppm to as much as 

1,200 ppm. 

High concentrations of selenium, to about 1 percent, occur in or with sandstone-type uranium 

deposits and other similar metal deposits in sedimentary rocks. The selenium is often found in the 

form of elemental selenium and sometimes as selenide minerals. 

Relatively high concentrations (in hundreds of 

rarts per million) occur in tuffs, or tuffaceous rocks, 

and concentrations of several percent are known in 

mercury and antimony deposits. 

CRUSTAL ABUNDANCE 

The abundance of selenium in the earth's crust is 

still poorly known owing to lack of adequate data. 

Sindeeva (1964) gave a crustal abundance of 0.14 

ppm selenium for rocks of the U.S.S.R. on the basis 

of the analysis of 18 samples. Brunfelt and Steinnes 

(1967) found an average of 0.04 ppm selenium in 

eight standard rock samples provided by the U.S. 

Geological Survey. Wells (1967) reported an average 

of 0.6 ppm selenium in 20 volcanic ash samples from 

New Zealand and 0.4 ppm in lava flows. 

Goldschmidt and Strock (1935) estimated that the 

sulfur-selenium ratio in sulfides is about 6,000 and 

that the crustal abundance of sulfur is 520 ppm. 

Dividing 520 by 6,000 gave a figure of 0.09 ppm for 

the estimated crustal abundance of selenium. This 

figure was accepted until 1961 when Turekian and 

Wedepohl (1961) revised the crustal abundance of 

sulfur downward to 300 ppm and, by using the Goldschmidt and Strock ratio, obtained an estimated 

crustal abundance for selenium of 0.05 ppm. 

RESOURCES 

Selenium is obtained primarily as a byproduct of 

copper refining; 90 percent of the production in the 

United States is derived from the anode mud deposited during electrolytic refining of copper. Blister 

copper contains an average of 0.05 percent selenium, 

or 1 pound of selenium per ton of copper, but actual 

recovery of selenium ranges from 0.4 to 0.75 pounds 

per ton of copper. Thus the production of selenium in 

the United States, and in most of the world, is directly related to the production of copper. In situ le·aching processes for the recove·ry of copper do not 

result in selenium recovery, and the increasing use 

of these processes could reduce the supply of selenium materially. Other countries with major potential resources of selenium are those with major potential resources of copper: Chile, U.S.S.R., Zambia, 

Peru, Zai're, Canada, and Mexico (Ageton, 1970; see 

also "Copper" chapter). Minor amounts of selenium 

are recovered from lead and pyrite ores. 

Resources of selenium estimated to be potentially 

available in the identified resources of copper, lead, 

pyrite, and coal in the United States and in the rest 

of the world are shown in table 118. 

TABLE 118.-Selenium resources, in thousands of pounds, potentially available in identified resources 1 of copper ores, 

lead ores, pyrite, and c.oal of the United States and the 

rest of the world 

Source 2 

Copper ores 3 ----------------

Lead ores ------------------- Pyrite ___ -------------------

Coal ------------------------

United 

States 

52,000 

880 

560 

4,740,000 

Other 

countries 

169,000 

2,350 

7,840 

23,760,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained min• 

erals may or may not be profitably recoverable with existing technology 

and economic conditions. 2 Identified resources from respective chapters of this volume, except 

for pyrite which is from Lewis ( 1970). 3 Assuming 65 percent recovery of selinum. 

In electrolytic refining of blister copper, about 65 

percent of the contained selenium is recovered from 

the slime residue. Using the ratio of 0.65 pound of 

selenium per ton of copper produced, we estimate a 

total of 52 million pounds of selenium available in 

identified copper resources of the United States, and 

169 million pounds available in identified copper 

resources of the rest of the world. 

Less than 10 percent of the present production of 

selenium is recovered from lead ores. If it is assumed 

that galena contains an average of 10 ppm selenium 
576 UNITE.D STATES. MINERAL RESOURCES 

and the world lead reserves are 140 million tons 

(see "Lead" chapter), there is a resource of selenium of 3.2 million pounds in lead ores. 

Selenium production from the burning of pyrite 

for sulfur is at present small. The world supply of 

sulfur in the form of pyrite is estimated to be 375 

million long tons (Lewis, 1970). Assuming an average value of 10 ppm selenium in pyrite, there is a 

reserve of 8.4 million pounds of selenium contained 

in pyrite. 

The average content of selenium in coal is at least 

1.5 ppm. Coal resources in the United States are 

estimated to be 1,580,000 million tons (rounded) and 

their estimated selenium resource should be 2.37 

million tons. Thus, coal contains the major resource 

for selenium if it can be recovered. 

The average selenium content of 86 samples of 

United States coal from 20 States as given by Pillay, 

Thomas, and Kaminski (1969) was 3.36 ppm. Eastern coals were higher in selenium content than coals 

from west of the Mississippi River. Table 119 gives 

TABLE 119.-Selenium content of annua.l coal consumption 

a.t five operating and five proposed powerplants in Western 

United States 

[Data from Swanson, 1972] 

Location 

Operating powerplants: 

Annual 

oon,sumption of 

coal 

(milllions 

of tons) 

Four Corners, N. Mex --------- 7 

Cholla, Ariz ------------------- .4 

Mohave, Nev ----------------- 6.7 Hayden, Colo -------------------- 6.25 Naughtcn, Wyo -----·---------- 2.6 Powerplants planned or under construction: 

San Juan, N. Mex ------------- 3.5 

Navajo, Ariz ------------------ 8.3 Kaiparowits, Utah ------------ 15 Huntington Canyon, Utah _____ 1 

Jim Bridger, Wyo ------------- 3.8 

Selenium 

content 

of ooa.l 

(parts 

per 

million) 

2.0 

2.3 

1.6 

1.2 

.7 

2.2 

1.6 

1.7 

1.7 

1.5 

Total 

selenium 

content 

of annual 

coal con- sumption 

(PQunds) 

28,000 

1,800 

21,500 

15,000 

3,600 

15,400 

26.500 

51,000 

3,400 

11,400 

Total ---------------------- --5-4.-5--------- 177,600 

Average ------------------- 1.65 

the average selenium content of coal used in five 

existing powerplants and of the coals proposed for 

use in five powerplants planned or under construction, together with the tonnages used or projected. 

The average selenium content of these coals is 1.65 

ppm. The total selenium in the 54.5 million tons of 

·coal that will be burned in 1 year in these ten powerplants is 177,600 pounds, which amounts to onesixth of the selenium used in the United States in 

1968. The estimated annual release of selenium from 

the combustion of coal in the United States is about 

8 million pounds. The portion of this selenium that 

escapes into the atmosphere is in, or is rapidly converted to, the form of elemental selenium and is not 

available to plants or biosystems. 

Selenium is enriched in sandstone-type uranium 

ores and in phosphate rocks mined for their phosphate content. Although some of these ores are relatively high in selenium, they constitute a small 

source of selenium and have not been exploited for 

selenium. 

SELECTED REFERENCES 

Ageton, R. W., 1970, Selenium, in Mineral facts and Problems: U.S. Bur. Mines Bull. 650, p. 713-721. 

Brunf.elt, A. 0., and Steinnes, E., 1967, Determination of 

s·elenium in standard rocks by neutron activation analysis: Geochim. et Cosmochim. Acta, v. 31, p. 283-285. 

Fleischer, Michael, 1955, Minor elements in some sulfide 

minerals, in pt. 2 of Bateman, A. M., ed., Economic 

geology, 50th anniversary volume: Urbana, Ill., Economic Geology Pub. Co., p. 970-1024. 

Goldschmidt, V. M., and Strock, L. W., 1935, Zur Geochemie 

des Selens II: Nachr. Gesell. Wiss. GOttingen, Abh., 

Math.-Phys. Kl IV, v. 1, p. 123-143. 

Lakin, H. W., 1972, Selenium accumulation in soils and its 

absorption by plants and animals: Geol. Soc. America 

Bull., v. 83, no. 1, p. 181-190. 

--- 1973, Selenium in our environment, in Symposium on 

trace elements in the environment: Am. Chern. Soc., 

Advances in Chemistry Ser. (in press). 

Lakin, H. W., and Davidson, D. F., 1967, The relation of the 

geochemistry of selenium to its occurrence in soils, 

chap. 3 of Selenium in biomedicine-Internat. Symposium, 1st, Oregon State Univ., 1966: Westport, Gonn., 

The A VI Pub Co., Inc., p. 27-56. 

Lansche, A. M., 1967, Selenium and tellurium, a materials 

survey, with a chapter on Resources by David F. Davidson: U.S. Bur. Mines lnf. Circ. 8340, 56 p, 

Lewis, R. W., 1970, Sulfur, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 1247-1265. 

Oldfield, J. E., chm., 1971 Selenium in nutrition: Natl. Acad. 

Sci., 79 p. 

Pillay, K. K. S., Thomas, C. C., Jr., and Kaminski, J. W., 

1969, Neutron activation analysis of the selenium content of fossil fuels: Nuclear Applications and Technology, v. 7, no. 5, p. 478-483. 

Sindeeva, N. Dl, 1964, Mineralogy and types of deposits of 

selenium and tellurium [translation from Russian]: 

New York, Interscience Publishers, 363 p. 

Swanson, V .E., 1972, Composition and trace-element content of coal and power plant ash, pt. 2 in Appendix J 

of Southwest Energy Study: U.S. Geol. Survey open-file 

report, 61 p. 

Turekian, K. K., and Wedepohl, K. H., 1961, Distribution of 

the elements in some major units of the Earth's crust: 

Geol. Soc. America Bull., v. 72, no. 2, p. 175-192. 

Wells, N., 1967, Selenium content of soil-forming rocks: 

New Zealand Jour. Geology and Geophysics, v. 10, no. 

1, p. 198-208. 
UNITED STATES MINERAL RESOURCES 

SILICA SAND 

By KEITH B. KETNER 

CONTENTS 

Psge 

Abstract of conclusions -------------------------- 577 

Introduction ------------------------------------- 577 

Exploitation ------------------------------------- 578 

Geologic environment ----------------------------- 578 

Resources --------------------------------------- 579 

Problems for research ---------------------------- 579 

Selected references ------------------------------- 580 

FIGURE 

PagE' 

65. Graph showing production of silica sand in the 

United States, 1930-70 -------------------- 578 

ABSTRACT OF CONCLUSIONS 

Silica-sand formations and the quartz sandstones from 

which silica sand and silicon are mainly derived are abundantly distributed throughout the United States and the 

world. Although the use of silica-sand, principally in the 

glass and metallurgical industries, is rapidly increasing, 

shortages that might cause heavy reliance on imports are 

not likely. Problems are caused if urban development preempts the surface over valuable silica sand deposits and if 

abandoned sandpits are left in a useless condition. Urban 

planners can solve the first problem by restricting important 

sand deposits from other long-term uses, and industry can 

solve the second by contouring the disturbed surface for 

productive or recreational use. More detailed geologic investigations in urban areas are needed to precisely delineate 

silica-sand deposits in advance of urban development. 

INTRODUCTION 

Natural sands can be composed of siliceous rock 

fragments and various silica-bearing minerals, but 

the term "silica sand" is generally understood to 

mean sand composed almost entirely of Si02 in the 

form of mineral quartz. This type of sand is also 

called special or industrial sand. Cemented silica 

sand is called quartz sandstone or quartzite. Some 

quartz sandstones can be easily broken down to their 

original state of loose sand either because they were 

never very firmly cemented or because the cement 

has been almost entirely dissolved by weathering 

processes. Sandstones softened by weathering are a 

principal source of silica sand. Silica sand can be 

made by crushing and grinding hard quartz sandstones or quartzites, but the result tends to be more 

expensive than natural sands. 

Silica sand of extraordinary purity is required in 

the manufacture of clear glass and sand of moderately high purity is required in the manufacture of 

brown or green glass and in certain uses, such as 

sandblasting, glass grinding, water filtration, railroad traction, and oil-well rejuvenation. Silica sand 

of moderately high purity with a natural or added 

bonding material is used in making metallurgical 

molds and furnace linings. Ground silica sand is a 

major component of ceramic ware. The use of 

siliceous raw materials as a source of metallic silicon is not treated here but is discussed by Brantley 

(1970). 

The glass and metallurgical industries consume 

more than 20 million tons of silica sand per year, 

and other users consume about 10 million tons. The 

rate of consumption is increasing rapidly. 

Certain relatively expensive natural and artificial 

aluminous abrasives can be substituted for quartz 

in blasting sand and glass-grinding sand, but for 

other uses no satisfactory substitute for high-silica 

sand has been found. 

The quartz content of many impure sands can be 

raised by beneficiation-the elimination of undesirable impurities such as clay, rock fragments, and 

iron-bearing minerals. Beneficiation techniques are 

well known and to some extent are in current use. 

These include screening, washing with water, leaching with acid, flotation, and various methods that 

take advantage of differences in specific gravity 

between quartz and some of the contaminating 

U.S. GEOL. SURVEY PROF. PAPER 820 

577 
578 UNITED STATES MINERAL RESOURCES 

grains. The impurities in some sands are themselves 

valuable when isolated, and their sale can help pay 

for the cost of beneficiation. Among these are clay 

and zircon. 

Silica sand and sandstone are common rocks of 

worldwide distribution. Inevitably, any large country that has a varied and representative geologic 

terrane such as the United States has a large share 

of these, and the chance that other nations will 

have deposits distinctly superior to those in the 

United States is negligibly small. Because of the 

large resources of silica-rich sand and the opportunities for substitution and for beneficiation of lowgrade deposits, the United States should be selfsufficient in silica sand for an indefinite period of 

time, notwithstanding the fact that a little silica 

sand is imported occasionally from foreign countries. Importation is the result of very low sea 

freight rates as compared to the overland freight 

rates from domestic sources, and it does not reflect 

adversely on either the quantity or quality of domestic sands. 

EXPLOITATION 

The annual production of silica sand increased 

rapidly between the depression year 1932 and 1944, 

fluctuated around 17 million tons until 1961, and 

then shot upward. In 1970, the last year for which 

complete figures are available, production was about 

30 million tons, of which one-third was glass sand 

and one-third was molding sand (fig. 65) . The current rate of increase is about 1 million tons per year. 

GEOLOGIC ENVIRONMENT 

High-silica sands are the products of especially 

long continued or often-repeated cycles of weathering, abrasion, and winnowing. The hardness and 

chemical inertness of quartz work in its favor to 

form a concentrated quartz sand deposit after almost all other minerals have been reduced to powder 

and wafted away. The most extensive and purest 

silica sands were formed in shallow seas. Less extensive and generally less pure deposits were formed 

as dunes along the shorelines of lakes and the sea, 

as dunes of desert regions, and as beds and flood 

plains of streams. 

Silica-sand deposits have formed in all geologic 

periods. Some of the oldest deposits, those of Precambrian age, are very large and very pure but are 

generally too distant from markets or are too well 

cemented to compete at present with silica sand 

from other sources. Many lower Paleozoic deposits 

are uniquely widespread and pure. For example, the 

30~------~--------,--------.--------. 

25 

en20 

z 

0 

IIa: 

0 

I 

en 

u..15 

0 

en 

z 

0 

...J 

...J 

~10 

5 

Glass, 

molding, 

grinding, 

blasting, 

furnace, 

traction, and 

filter sand 

*Comparable figures for 

the years prior to 1959 

not available. 

oL-------~---------L--------~------~ 

1930 1940 1950 1960 1970 

FIGURE 65.-Production of silica sand in the United States, 

19·30-70. Source of data: U.S. Bureau of Mines. 

St. Peter Sandstone and related deposits which extend from Wisconsin and Michigan to Oklahoma, an 

area of more than 300,000 square miles, are composed principally of nearly pure quartz. The Eureka 

Quartzite and equivalent deposits which extend from 

Idaho to southern California, an area of more than 

100,000 square miles, are likewise composed of 

nearly pure quartz. Analyses of the Eureka Quartzite indicate that the silica content generally ranges 

from 95 to 99 percent. The principal commercial 

deposits of the United States are in locally decemented parts of lower Paleozoic marine sandstones. 

The process of decementation by which hard sandstone is converted to weakly coherent sand is not 

well understood, but it is probably the result of local 

near-surface weathering. 

Although many silica sands deposited since early 

Paleozoic time are widespread and some are very 

pure, none of them rival those of the early Paleozoic age in extent and purity. Upper Paleozoic sand-
SILICA SAND 579 

stone in the eastern interior region and upper Mesozoic deposits on the east coast are exploited to some 

extent, but most outcropping silica sandstones deposited in late Paleozoic and Mesozoic times are located in the western interior States far from industrial users and are therefore not intensively exploited. Marine deposits and dune sands of Cenozoic 

age are important sources of silica sand along both 

east and west coasts. 

RESOURCES 

Silica sand and sandstone are among the more 

common sedimentary formations cropping out in the 

United States and, in general, their stratigraphic 

positions, extent, thicknesses, and the areas of outcrop are among the better known aspects of geology. 

This is true because silica-rich stratigraphic units 

generally form conspicuous outcrops, and because 

some have been investigated as possible oil reservoirs or aquifers. It is unlikely that important silica 

sand and sandstone units, completely unknown previously, remain to be discovered. Therefore, in a 

sense, almost all silica sand and sandstone units can 

be regarded as "identified" rather than as "undiscovered" resources. Parts of these identified resources can be allocated to the category of "reserves." These parts are where certain favorable 

geologic features fortuitously have combined with 

favorable geographic circumstances to yield deposits 

workable under present economic conditions. Favorable geologic features include chemical purity, uniform grain size, friability, amenabiliy to beneficiation, and proximity to the surface. The favorable 

geographic circumstances are proximity to markets 

and to transportation facilities. 

Identified resources of silica sand are virtually 

inexhaustible, and reserves are very large in relation to demand. Known deposits can satisfy national 

demands at reasonable cost for centuries. 

PROBLEMS FOR RESEARCH 

Although the United States silica-sand resources 

are so large that they are unlikely to be depleted 

by normal use, a large proportion of the most 

favorably located deposits may be precluded from 

exploitation by shortsighted public policies. 

Society's mistakes in this respect can be either 

unconscious or deliberate--unconscious when residential developments are allowed to spread over 

valuable sand deposits and deliberate when landuse laws are invoked to prohibit exploitation of 

known deposits in urban areas. The result of preclusion is not that we will run out of silica sand, 

but that costs will increase as a result of having to 

confine mining to areas remote from industrial users 

and the ultimate consumers. 

Sand and sandstone deposits capable of yielding 

high-quality silica sand should be identified and precisely delineated on geologic maps--especially on 

large-scale maps of urban regions. Geologic maps 

exist for many urban areas, but workable silica-sand 

deposits are specially designated on only a few of 

these. Precise location of all deposits in urban regions would permit orderly planning for the most 

beneficial use of land underlain by silica-sand deposits. 

If geologic reports are to be of maximum utility 

for the identification of silica-sand deposits, they 

must include more quantitative data on the physical 

attributes of the deposits. Geologic descriptions of 

sandy stratigraphic units commonly stress only 

those features that can be seen with a hand lens or 

microscope. These include grain size, sorting, nature of the cement, proportions of constituent minerals, and the roundness or angularity of the grains. 

In some reports, care is taken to measure these 

features quantitatively, but rarely do geologists 

make enough quantitative observations to permit 

descriptions of the stratigraphic and regional 

(three-dimensional) variations in these features. 

Moreover, general geologic descriptions almost 

never include important physical features such as 

coherence and the various factors involved in amenability to beneficiation. 

Much of the popular opposition to mining in urban areas lies in the unsightly, dangerous, and useless condition of mined-out areas. Methods for restoring abandoned pits to esthetically acceptable 

appearance and productive or recreational use 

should be developed. Most abandoned pits soon fill 

partially with water. If the banks are sloped and 

suitably planted and maintained, these ponds can 

be converted at moderate cost to parks or recreational and wildlife areas. 

Although the large resources of silica sand are 

capable of supporting a rapidly increasing production of disposable glass products (specifically, 

throwaway bottles), there are valid and pressing 

reasons for conservational practices. Wasteful consumption will lead inevitably to earlier depletion of 

nearby high-grade silica-sand deposits and earlier 

shifts by producers to more distant or lower grade 

deposits. The direct effect of these shifts will be 

higher priced glass and more damage to the land 

surface. The indirect effects will be more pollution 

in manufacture and, ultimately, more problems in 

disposing of the product after use. 
580 UNITED STATES MINERAL RESOURCES 

SELECTED REFERENCES 

Brantley, F. E., 1970, Silicon, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 369-384. 

Clark, W. B., and Carlson, D. W., 1956, Quartzite and quartz, 

in Wright, L. A., ed., Mineral commodities of California: 

California Div. Mines Bull. 176, p. 463-466. 

Gay, T. E., Jr., 1956, Specialty sands, in Wright, L. A., ed., 

Mineral commodities of California: California Div. 

Mines Bull. 176, p. 547-564. 

Jaster, M. C., 1957, Seleeted annotated bibliography of highgrade silica of the United States and Canada, through 

December 1954: U.S. Geol. Survey Bull. 1019-H, p. 

609-673. 

Martens, J. H. C., 1956, Industrial sands of New Jersey: 

Rutgers Univ. Bur. Mineral Research Bull. 6, 259 p. 

Murphy, T. D., 1960, Silica sand and pebble, in Gillson, J. 

L., ed., Industrial minerals and rocks: Am. Inst. Mining., Metall. and Petroleum Engineers, p. 763-772. 

Pettijohn, F. J., 1957, Sedimentary rocks [2d ed.]: New 

York, Harper and Brothers, 718 p. 

Pettijohn, F. J., Potter, P. E., and Siever, Raymond, 1965, 

Geology of sand and sandstone: Indiana Geol. Survey 

Field Conf. Guidebook, 207 p. 
UNITED STATES MINERAL RESOURCES 

SILVER 

By ALLEN v. HEYL, w. E. HALL, ALBERT E. WEISSENBORN, H. K. STAGER, 

W. P. PuFFETT, and BRUCE L. REED 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Exploitation ---------------------------· ---------

Geologic environment ----------------------------

Geochemistry --------------------------------

~ineralogy ----------------------------------

Types of deposits ----------------------------

Byproduct silver ------------------------

Porphyry copper deposits ------------

Copper-zinc-lead replacement deposits 

and vein clusters ------------------

Massive sulfide deposits --------------

Lead-zinc repl~cement deposits -------

Mississippi Valley- and Alpine-type lead, 

zinc, and fluorspar deposits and related deposits ---------------------

Copper deposits in sandstones and shales 

Native copper deposits ---------------

Gold deposits in veins, conglomerates, 

and placers ------------------------ Nickel and magnetite deposits --------

Silver as a major constituent ------------- Epithermal veins, lodes, and pipes ___ _ 

Epithermal disseminated and breccia 

deposits --------------------------- Epithermal silver-manganese deposits _ 

Epithermal silver-lead-zinc replacement 

deposits --------------------------- Epithermal silver-copper-barite deposits 

Mesothermal silver-base metal veins 

Mesothermal cobalt-silver, cobalturaninite-silver, and cobalt-silverzeolite deposits --------------------

Sandstone silver deposits -------------

Sea-floor muds and hot-spring deposits _ 

Resources --------------------------------------- Identified resources --------------------------

Hypothetical resources -----------------------

Speculative resources ------------------------

Problems for research ---------------------------

Selected references ------------------------------

Page 

581 

582 

584 

584 

584 

586 

587 

587 

587 

588 

588 

589 

590 

590 

591 

591 

592 

592 

592 

593 

593 

594 

594 

594 

595 

595 

595 

596 

596 

597 

597 

599 

600 

FIGURE 

Page 

66. Graph showing exploitation of silver in the 

United States --------------------------- 585 

120. 

121. 

122. 

123. 

124. 

125. 

TABLES 

The principal uses of silver ------------------

Mine production of recoverable silver, 1965 and 

1969, in the United States, by States -------

World mine production of silver, 1969, by 

countries _______ -- _____ - _-- _ -------------

Estimated free-world silver consumption and 

new mine production, 1949-70 -------------

Silver resources in the United States --------

Silver reserves of United States and free 

world ------------------------------------

ABSTRACT OF CO~CLUSIONS 

Page 

582 

582 

583 

583 

596 

596 

Silver is a major industrial metal in which a major worldwide imbalance of more than 100 million ounces per year 

exists between production and consumption. The silve1· used 

in photography alone in the United States is greater than 

our annual production, and most of this silver is not recovered for reuse. The deficit between domestic production 

and consumption formerly was partly filled by withdrawal 

from the U.S. Treasury silver reserves, but these reserves 

are now depleted. During the next decade this deficit must 

be filled by liquidation of private holdings, reclaimed silver, 

imports, increasing new production, or by use of substitutes 

for silver. 

Identified resources of silver in the United States comprise 

an estimated 1,440 million troy ounces economically recoverable at present prices (reserves) and an estimated 750 million ounces in material nearly commercial in grade ( conditional resources). Other conditional resources that might become recoverable at significantly higher prices are roughly 

estimated to be of about the same magnitude as the present 

reserves. Only about 35 percent of the identified resources is 

in deposits that would yield silver as the main product; the 

remaining 65 percent would be recovered as a byproduct 

U.S. GEOL. SURVEY PROF. PAPER 820 

581 
582 UNITED STATES MINERAL RESOURCES 

of mining copper, le•ad, zinc, and gold deposits, and its production is thus largely dependent on the production of these 

metals. For this reason, the imbalance between domestic 

production and consumption of silver is markedly increased 

by the permanent closure of one-third of our domestic lead 

and zinc ·smelters. 

Silver production could be increased by the discovery and 

development of new silver resources. Among the better possibilities are several kinds of copper-silver deposits such as 

the northern Idaho-Montana disseminated copper deposits, 

new porphyry copper deposits, and massive copper-zinc sulfides. Increased prices would encourage development of potential resources in low-grade disseminated silver and coppersilver sandstone deposits and in copper shales, would encourage the reopening of silver-bearing native copper deposits in Michigan, and would encourage the search for manganese-silver and other epithermal silver deposits which 

could help fill the short-term gap. New environmentally 

clean smelters and wet recovery methods are needed and 

must be developed and built as quickly as possible. 

INTRODUCTION 

Silver is a critical element in our national economy, 

and one in which our nation and the free world are 

confronted with a long-range problem of serious 

imbalance between consumption and new production. 

Silver is comparatively rare in the earth's crust, 

being the 67th element in order of natural abundance, but minerals containing it occur in small 

quantities widely distributed throughout the world 

in many different types of deposits. The physical 

properties of silver make it desirable for a wide 

range of uses for which adequate low-cost substitutes are very difficult to find. It is exceptionally 

ductile and malleable, it has the highest electrical 

and thermal conductivity of all metals, its compounds are extremely photosensitive, and it is stable 

in air and water except for tarnishing readily when 

exposed to sulfur compounds. 

Silver was one of the first metals known to man, 

and was used for ornaments and utensils made from 

native silver as early as 3000-2500 B.C. (Ageton, 

1970, p. 723). It has been used as a precious metal 

and as a monetary medium and basis of wealth for 

more than 2,000 years. It was used extensively for 

coinage until the late 1960's when such use was discontinued by the United States and most other 

countries, except for commemorative coins, because 

of the serious imbalance between consumption and 

new production. The principal uses of silver are 

listed in table 120. 

Annual mine production of silver in the United 

States in recent years has been a fairly stable 32-43 

million troy ounces of recoverable silver (Hoyt, 1971, 

p. 1006). In 1969 almost 42 million ounces was produced, which was valued at more than $75 million, 

an average price of $1.79 per troy ounce (Hoyt, 

TABLE 120.-Principal uses of silver 

[Data from U.S. Bur. Mines (1970, p. 1007)] 

Percentage 

Photographic materials ------------------- Electrical and electronic products ----------

Sterling ware ----------------------------

Electroplated ware ----------------------- Brazing wares --------------------------- Other, including dental and medical products, 

catalysts, bearings, and jewelry --------

29 

22 

20 

10 

10 

9 

1971, p. 997) . Since then the price had decreased 

markedly, but by October 1972 had risen to $1.80 

per troy ounce. Table 121 gives the mine production 

TABLE 121.-Mine production, in troy ounces, of recoverable 

silver, 1965 and 1969, in the United States, by States 

State 

[From U.S. Bur. Mines (1970, v, I-II, p. 1006)] 

1965 

Alaska ------------------ Arizona ----------------- California ----------------

Colorado ----------------- Idaho ------------------- Kentucky ---------------- Maine ----·--------------- M!chiga~ ---------------- Missoun -----------------

Montana ----------------- Nevada ------------------ New Mexico ------------- New York --------------

Oklahoma ---------------- Oregon ------------------ Pennsylvania ------------- South Dakota ------------

Tennessee ----------------

Utah -------------------- VVashington -------------- VVyonilng ----------------

Total --------------

7,673 

6,095,285 

196,787 

2,051,105 

18,456,809 

1,931 

457,851 

299,522 

5,207,031 

507,113 

287,472 

11,441 2 358,477 

8,801 

(2) 

128,971 

94,142 

5,635,570 

(2) 

52 

39,806,033 

1969 

2,030 

6,141,022 

491,927 

2,598,563 

18,929,697 

1 319,718 

1,009,022 

1,442,090 

3,429,314 

884,155 

465,591 

31,755 

C) 

4,749 

C> 

124,497 

78,614 

5,953,567 C> C> 

41,906,311 

1 Production of Maine, Oklahoma, Pennsylvania, Washington, e.nd 

Wyoming combined to avoid disclosing individual company-confidential 

data. 2 Production of Oklahoma, Pennsylvania, and Washington combined to avoid disclosing individual company-confidential data. 

of recoverable silver for 1969 in the United States. 

By far the most important silver-producing State is 

Idaho-mostly from the Coeur d'Alene districtfollowed by Arizona, Utah, Montana, Colorado, then 

by the two midwestern States of Missouri and Michigan which have markedly increased their production. 

Michigan and Missouri now produce more silver per 

year than several western "silver" States such as 

Nevada, New Mexico, South Dakota, and California. 

Idaho production for 1972 was seriously reduced as 

a result of the May 1972 fire in the Sunshine mine. 

The world production of silver in 1969 is given in 

table 122. The largest producers of silver were 

Mexico, mostly from epithermal veins and replacement deposits, and Canada, where the probable largest single source of silver is the Kidd Creek massive 

sulfide zinc-copper-silver mine at Timmins, Ontario, 

which has produced between 12 and 14 million troy 

ounces per year since 1968. 
SILVER 583 

TABLE 122.-Preliminary report of world mine production of 

silver, 1969, by .countries J 

[Data from U.S. Bur. Kines (1870, p. 1010). The letter ••e" precedlq ftaura indicate. estimated] 

SDver 

(thousand Country • troy ounces) 

North and Central America: 

Canada ---------------------------------- 41,929 

Haiti -----------------------------------e 17 

Honduras ------------------------------- 3,905 

~exico ---------------------------------- 42,904 

Nicaragua ------------------------------- 247 

lJnited States ---------------------------- 41,906 South America: 

Argentina ------------------------------- 2,820 

Bolivia ---------------------------------- 6,013 

Brazil ----------------------------------- 357 

Chile ------------------------------------ 3,133 

Colombia -------------------------------- 77 

Ecuador -------------------------------- 82 

Peru ------------------------------------ 34,147 Europe: 

Austria --------------------------------- 129 Czechoslovakia __________________________ e 1,100 

Finland --------------------------------- 625 

France (mine output) -------------------- 2,000 Germany: 

East -------------------------------e 4,800 

VVest ------------------------------e 2,000 

Greece ---------------------------------- 258 

Ireland (mine output) ------------------e 1,866 

Italy ------------------------------------ 1,832 Poland ---------------------------------e 165 

Portugal (mine output) ----------------- 339 

Rumania -------------------------------e 800 

Spain 3 ---------------------------------e 1,700 

Sweden (mine output) ------------------- 3,683 

lJ.S.S.R. --------------------------------e 37,000 

Yugoslavia ------------------------------ 3,456 Africa: 

Algeria --------------------------------e 100 

Congo (Kinshasa) ----------------------e 1,896 

Ghana ---------------------------------- 3 

Kenya ---------------------------------- 2 ~oroeco --------------------------------- 861 South Africa, Republic of ---------------- 3,335 

South-VVest Africa, Territory of' --------- 1,273 Tanzan,ia _ _ _ _ __ _ __ _ __ _ _ _ _ _ _ _ __ __ _ _ __ __ __ _ 2 

Tunisia --------------------------------e 47 

Zambi,a 11 --------------------------------e 768 

TABLE 122.-Preliminary report of world mine production of 

ailver, 1969, by countries J-Continued 

Country• 

SDver 

(thousand 

troy ounces) 

Asia: 

Burma ---------------------------------e 1,000 

Ohina, mainland ------------------------e 860 

India ----------------------------------- 127 

Indonesia -------------------------------- 316 

Japan ------------------------~--------- 10,804 Korea: 

North --------------------------------e 700 

South -----------·---------------------- 906 

Philippines ------------------------------ 1,561 

Taiwan ---------------------------------- 81 Oceania: 

Australia -------------------------------

Fiji ------------------------------------- New Guinea and Papua ------------------ New Zealand ----------------------------

24,667 

38 

17 

7 

Total 8 ----------------------------288,601 1 Recoverable content of ores and concentrates produced unless otherwise noted. ll Silver is also produced in Bulgaria, Guatemala, Hungary, New Zealand, Thailand, Turkey. and Southern Rhodesia and in several other 

African countries. Quantities are insignificant or not reported. a Smelter and (or) refinery production. 

' Recoverable content of Tsumeb Corp. Ltd. concentrates, as reported for year ending June 30. 15 Includes recovery from copper refinery sludges. 11 Total is of li&ted fieures only. 

Domestic production of silver in 1969 was about 

42 million ounces, but industrial use during the same 

period was about 142 million ounces, leaving a 

deficit of 100 million ounces; the free world deficit 

was 124 million ounces (table 123). The marked 

deficiency of new supplies of silver compared to increased industrial demand, which has nearly doubled 

for the free world since 1958, has caused major 

changes in patterns of usage and has forced increases in the price of silver. Until 1971, the deficit 

in the new supply was balanced by withdrawal of 

silver stocks from the U.S. Treasury and from sevTABLE 123.-Estimated free-world silver consumption and new mine production, 1949-70 1 

[Millions of fine troy ounces.From: U.S. Treasury Department staff study of silver and coinage, 1965; 1970 Yearbook of the American Bur. Metal Statistics; and U.S. Bur. Mines (195o-71)] 

Consumption in Consumption Total New mine arts and industry in eoinase consumption production Free 

world 

Period or year Free surplus 

Total world Total Total or deficit 

USA free USA except- USA free USA free excluding 

world ins USA world world coinage 

1949-52 (average) -------------- 101.1 153.1 36.5 48.2 137.6 237.8 38.8 173.9 + 20.8 

1953-57 (average) -------------- 97.8 190.1 37.5 36.0 135.3 263.6 37.7 191.0 + 0.9 

1958 --------------------------- 85.5 190.5 38.2 41.3 123.7 270.0 34.1 205.8 + 15.3 

1959 --------------------------- 101.0 212.9 41.4 45.0 142.4 299.3 31.2 188.4 - 24.5 

1960 --------------------------- 102.0 224.6 46.0 57.9 148.0 328.5 30.8 206.9 - 17.7 

1961 ---------------------------- 105.5 239.5 55.9 81.2 161.4 376.6 34.8 203.0 - 36.5 

1962 ---------------------------- 110.4 247.8 77.4 50.2 187.8 375.4 36.8 206.9 - 40.9 

1963 ---------------------------- 110.0 252.2 111.5 55.5 221.5 419.2 35.2 213.8 - 38.4 

1964 ---------------------------- 123.0 285.9 203.0 61.5 326.0 550.4 36.3 215.5 - 70.4 

1965 --------------------------- 137.0 336.0 320.3 60.8 457.3 717.7 39.0 214.8 -121.8 

1966 ---------------------------- 150.0 355.1 53.8 75.7 203.8 484.6 42.5 222.2 -132.9 

1967 --------------------------- 145.0 346.8 43.9 61.4 188.9 452.1 31.0 212.8 -134.0 

1968 ---------------------------- 145.0 349.6 37.0 52.3 182.0 438.9 31.7 223.8 -125.8 

1969 ---------------------------- 142.0 364.4 19.4 36.3 161.4 420.1 42.1 240.3 -124.1 

1970 ---------------------------- 135.0 357.6 .7 39.6 135.7 397.9 44.1 254.0 -103.0 
584 UNITED STATES MINERAL RESOURCES 

eral varieties of hoarded and reclaimed silver. The 

U.S. Treasury stocks totaled 2.1 billion ounces in 

1958, but have since been depleted by transfer to 

stockpile, redemption of silver certificates, and sales. 

This depletion of Treasury silver stocks has increased our dependence upon newly mined silver, 

liquidation of private holdings of silver, and reclaimed silver. Much of the hoarded silver is in coins 

that have much greater value to coin collectors and 

speculators than their metal content, unless the price 

of silver markedly increases. The supply gap of 

newly mined silver to silver consumption is worldwide, not just domestic, and a large increase in 

reclaimed silver, release of hoarded silver, and in 

silver substitutes will be necessary to fill the expected gap within the next decade unless new silver 

resources are developed. To emphasize current silver 

needs, the present annual consumption of silver in 

photography alone is 10 million troy ounces greater 

than the domestic production prior to the recent 

decline in mining of western silver-lead ores. Even 

assuming an increasing replacement of silver by 

substitutes in the next 30 years, our needs for photography alone will probably increase by 21;2 times 

by the year 2000, to more than 100 million troy 

ounces per year (Ageton, 1970, p. 734). 

EXPLOITATION 

Silver has become a major industriaLmetal and is 

wi\tely used in the arts. Figure 66 shows the annual 

U.S. production, consumption, and average price 

from 1860 to 1972. The more-than 100 million ounces 

per year gap between U.S. production and consumption is apparent even after the main use of silver for 

coinage ceased. A smaller but similar gap exists between world production and consumption. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Silver is a chalcophile element; that is, it will 

combine with sulfur or related anions rather than 

form silicate minerals. It has a valence of + 1 and 

an ionic radius of Ag+ 1.13 A. Thus silver is similar 

in size and valence to copper (Cu+, 0.96 A) and may 

substitute for it in various minerals. 

The crustal abundance of silver estimated to be 

0.07 ppm (parts per million) (Vinogradov, 1962). It 

is most abundant in basalt (0.1 ppm) and igneous 

rocks of intermediate composition (andesite and 

diorite, 0.07 ppm), and slightly less in ultramafic 

rocks (0.05 ppm) and felsic granites (0.05 ppm). Ore 

deposits in which silver is mined as a major component are most often associated with igneous rocks 

of intermediate composition. The silver-lead limestone replacement deposits that occur so extensively 

in the Western United States are localized near intrusive bodies of quartz monzonite and granodiorite. 

The rich epithermal silver deposits such as Tonopah 

and Comstock in Nevada are associated with andesite 

flows and shallow intrusives or with rhyolite, and 

the rich silver-cobalt ores at Cobalt, Ontario, and 

the silver ores at Gowganda, Ontario, and Kongsberg, Norway, are spatially and probably genetically 

related to diabase intrusives. 

Of the world's total production of silver, about 

75 percent is a byproduct or coproduct of base-metal 

ores. In base-metal ores, silver generally has an 

affinity for galena > chalcopyrite > sphalerite, and 

the fractionation of silver between coexisting galena 

and sphalerite ranges from 50:1 to 100:1. Galena is 

commonly highly argentiferous. Electron microprobe work on Darwin, Calif., galenas by G. K. 

Czamanske (oral commun., 1972) indicates approximately 0.2 percent (about 60 troy ounces per short 

ton) can be present in galena with no microinclusions. Experimental studies at elevated temperatures 

have shown complete solid solutions in the systems 

AgSbS2-2PbS (miargyrite-galena), AgBiS2-2PbS 

(matildite-galena), and AgBiS2-AgMiSe2 (matilditeselenium analog) (Wernick, 1960; Van Hook, 1960). 

Natural galenas from Darwin, Calif., have been 

analyzed that contained as much as 3.79 percent 

silver and 7.86 percent bismuth (Hall, 1971, p. 122). 

Ag+ and Sb3+ or BP+ thus may form a coupled substitution for 2Pb2 + in galena at the elevated temperatures of formation of mesothermal ore deposits 

(about 350°C). Malakhov (1969) tabulated the antimony and bismuth contents of 204 galenas and 

found· that low Sb: Bi ratios are characteristic of 

high-temperature galena and that high ratios of 

Sb: Bi are characteristic of low-temperature galena. 

In a few lead-zinc deposits, silver is concentrated 

in sphalerite rather than galena. In the southeast 

Missouri lead belt, sphalerite contains as much as 

45 ounces of silver per ton, probably in solid solution 

with sphalerite, whereas galena contains about 1 

ounce of silver per ton (Hall and Heyl, 1968; Taylor 

and Radtke, 1969). The geochemical controls for the 

rare concentration of silver in sphalerite rather than 

galena are not yet understood. 

Silver commonly is greatly enriched in the zone 

of oxidation, over that in the primary ore, which 

accounts for many of the shallow bonanza silver 

deposits that were mined during the latter part of 

the last century. Only a small part of the primary 

ore in these deposits was economically minable. 

Morris and Lovering (1952, p. 698) found at the 

Tintic Standard mine (Utah) that silver migrates 
SILVER 

150r-----------------------------------------------------------------------------------------------~ 

(/) 

w 

u 

z 

::> 

0 

> 

0 

0: 

1- 100 

w 

z 

u: 

u. 

0 

(/) 

z 

Q 

_I 

_I 

~ 

~ 

z' 

0 

;:: 

u 

::> 

0 

0 

0: 

~ 

50 

0 

1860 

Period of 

bonanza ore 

production in 

Western U.S. 

1870 1880 1890 

Beginning 

recovery of 

byproduct 

silver 

1900 

Exhaustion of 

near-surface 

bonanza 

deposits 

U.S. arts and 

industrial 

consumption 

10 

FIGURE 66.-Exploitation of the silver in the United States. 

1. Comstock lode, Nevada, discovered; 

2. Authorization for coinage of silver dollars; 

3. U.S. Treasury act to purchase silver; 

4. Purchasing act repealed and sharp price drop; 

5. Tonopah, Nevada, discovered; 

6. Production began from porphyry copper deposits; 

7. Peak from early silver and silver-gold mines and coinage demand of World War I allies; 

8. Heavy Chinese buying; 

9. Treasury began purchasing silver as monetary backing. Development Silver Belt, Idaho; 

10. World War II; 

11. Treasury began withdrawal of bullion reserve; 

12. Cessation use of silver for coinage; 

13. U.S. Treasury directed to purchase domestic silver at 90 lhc and authorized to sell at 91e; 

14. U.S. Treasury sales stabilizes price at 91c; 

15. Cessation of U.S. Treasury sales; 

16. Exhaustion of U.S. Treasury bullion reserve. Modified from McKnight (unpub. data, 1962). 

Era of byproduct 

and coproduct 

silver 

Deficit of 

new production 

585 
586 UNITED STATES MINERAL RESOURCES 

no more than several feet in limestone and dolomite 

host rocks but that it is as mobile as zinc in unreactive host rocks such as quartzite and shale. In oxidized lead-silver limestone replacement deposits 

silver commonly occurs as cerargyrite (AgCl), embolite (AgClBr), native silver, sooty argentite 

(Ag2S) or acanthite (,BAg2S), the ruby silvers 

(proustite, pyrargyrite), silver-bearing lead sulfate, 

argentian plumbojarosite, argentiferous anglesite, 

silver-bearing lead carbonate (argentiferous cerussite), various hydrous argentiferous lead-manganese 

oxides (for example, argentian todorokite), and silver sulfide minerals or sulfosalts precipitated by 

reaction of silver-bearing solutions with primary sulfide minerals. This supergene enriched ore may carry 

hundreds or thousands of ounces of silver per ton 

of ore, but one will be disappointed if one expects 

such values to continue downward into the primary 

ore. 

MINERALOGY 

There are few active mines in the United States 

whose principal product is silver. Most silver is 

obtained as a byproduct or coproduct from ores of 

copper, lead, zinc, gold, manganese, cobalt, nickel, 

or uranium. There are, however, all gradations from 

deposits that are mined chiefly for silver to those 

in which silver is a minor byproduct. 

The principal silver minerals are as follows: 

Native elements and alloys: 

Electrum _______ (Ag, Au) 

Silver __________ Ag 

Carbonate: 

Cerussite ___ PbCoa, commonly silver-bearing 

Sulfides, sulfosalts, selenides, and tellurides : 

Andorite ______________ PbAgSbaS6 

Acanthite -------------f3Ag2S Argentite _____________ Ag2S 

Diaphorite ____________ PbzAgaSbaSs 

Dyscrasite ____________ AgaSb 

Fizelyite ______________ pb5Ag2SbsS1s 

Galena (argentiferous) _ (Pb,Ag) S 

Hessite _______________ Ag2Te 

Matildite ______________ AgBiS2 

Miargyrite ____________ AgSbS2 

Naumannite ___________ Ag2Se 

Pearceite ______________ Agt6AszSll 

Petzite ________________ AgaAuTe2 

Proustite --------------(Ag,Cu) 16Sb2S11 

Polybasite _____________ AgaAsSa 

Pyrargyrite ___________ AgaSbSa 

Stephanite ____________ Ag 5SbS4 

Stromeyerite __________ CuAgS 

Sylvanite _____________ Ag2AU2Tes 

Tennantite (argentiferous) -------------(Cu,Fe,Ag) 12As4S1a 

Tetrahedrite (argentiferous) _____________ (Cu,Fe,Ag) 12Sb4S1a 

Halides: 

Bromyrite ____________ _A.gBr 

Cerargyrite ___________ AgCl 

Embolite ______________ Ag(Cl,Br) 

Iodyrite _______________ Agi 

Oxides: 

Aurorite __ (Ag2Ba,Ca,Pb,K2CuMn + 2) Mn +407 

•SH20 

Argentian 

todorokite ____ (Ag2K2Ca,Ba,Na,Cu,Pb) Mn +409 

•SH20 

Silver-bearing lead-manganese oxides 

Sulfates: 

Anglesite ___ PbSo4, commonly silver-bearing 

Argentian 

plumbojarosite --(Pb,Ag) Fe6 (S04) 4 (OH) 12 

Argentajarosite --Ag2Fe6 (S04) 4 (OH) 12 

Where silver is a byproduct or coproduct it may 

occur either as discrete silver minerals or it may 

substitute for other metals in minerals of basemetal ores. Argentiferous tetrahedrite and tennantite are exceptionally rich in silver in some basemetal deposits, and either one may be the economically important ore mineral. In many lead-silver deposits, silver occurs in tiny inclusions of argentite, 

tetrahedrite, tennantite, or other silver-antimony or 

silver-bismuth sulfosalts in ~gentian galena. Silver 

may also occur in solid solution in galena. Some 

galena may be relatively free of silver but accompanied by silver-rich sphalerite, chalcopyrite, and 

pyrite as in the southeast Missouri lead district 

(Hall and Heyl, 1968, p. 666). Some sphalerite enriched in silver contains inclusions of argentian 

tennantite. 

Most newly mined gold contains some alloyed 

silver, the quantity ranging from a trace to as much 

as 60 percent. Gold from the Mother Lode Belt of 

California commonly contains 10-20 percent silver ; 

that from the Homestake mine in South Dakota an 

average of 20 percent. The epithermal preciousmetal deposits commonly contain the highest proportion of silver to gold, such as in the Comstock 

Lode of Nevada. 

Placer gold contains less silver than the gold in 

the lode from which it was derived. Placer gold in 

California commonly contains 2-7 percent silver, as 

much as an order of magnitude less than that in the 
SILVER 587 

lodes from which it was derived. The difference has 

generally been explained as loss of silver during 

weathering, but Mertie ( 1940) suggested that in 

part it may be due to a primary difference between 

the gold in deep-seated parts of the lode and that 

in the apical part from which the placer gold was 

derived. 

In addition to silver alloyed with gold, appreciable 

quantities of silver minerals occur in many gold 

deposits. Such primary gold deposits grade in many 

places into predominantly silver deposits, with an 

increase in silver-bearing minerals such as native 

silver, tetrahedrite, tennantite, argentite, hessite, 

pearceite, polybasite, pyrargyrite, proustite, and 

argentian galena. 

Hypogene manganese-silver deposits are widely 

known. Most commonly they are silver-lead sulfide 

deposits with associated manganosiderite, such as 

at Leadville, Colo., or with associated rhodochrosite, 

such as at Phillipsburg, Mont. D. F. Hewett and his 

associates recently recognized another type of hypogene manganese-silver deposit, which consists of 

black silver- and manganese-bearing calcite or of 

silver-bearing manganese oxides (Hewett, 1964, 

1968; Hewett and others, 1963; Hewett and Radtke, 

1967; Radtke and others, 1967; and Smith, 1970). 

In the black calcites, the silver is in intergrowths 

and inclusions of argentian chalcophanite (aurorite), 

argentian todorokite, and silver-bearing lead-manganese oxides. The deposits on Treasure Hill, Hamilton, 

Nev., have this mineralogy. 

TYPES OF DEPOSITS 

Types of silver deposits are described here under 

two broad categories: mineral deposits with byproduct and coproduct silver and mineral deposits 

with silver as a major constituent. Most of the free 

world's silver comes from deposits of the first category. 

BYPRODUCT SILVER 

Silver is an important byproduct in (1) porphyry 

copper deposits, (2) copper-zinc-lead replacement 

deposits and vein clusters, and (3) massive sulfide 

deposits; these three types of deposits account for 

29 percent of domestic and 20 percent of Canadian 

silver production. Other types of deposits in which 

silver is important as a byproduct are (4) lead-zinc 

replacement deposits, (5) Mississippi Valley- and 

Alpine-type lead, zinc, and fluorspar deposits and 

related deposits, ( 6) copper deposits in sandstones 

and shales, (7) native copper deposits, (8) gold deposits in veins, conglomerates, and placers, and (9) 

nickel and magnetite deposits. 

These deposits are discussed in this chapter primarily insofar as they relate to production and 

resources of silver; for more detailed information 

the reader is referred to the respective chapters on 

copper, zinc, lead, and gold. 

PORPHYRY COPPER DEPOSITS 

Porphyry copper deposits· are a major source of 

silver in the United States and supply approximately 

20 percent of the domestic production. They are an 

important source of silver in Chile and to a lesser 

extent in northern Mexico. Porphyry copper deposits originally were defined as disseminated copper mineralization in felsic porphyritic intrusive 

bodies, but the term has been broadened generally 

to include all large, low-grade epigenetic hypogene 

copper, copper-molybdenum, and molybdenum deposits that can be mass-mined (Titley and Hicks, 

1966; see also chapter on "Copper"). Although the 

percentage of silver in the ore is very low-about 

0.01-0.1 ounce of silver per ton of ore-the total 

amount of silver that is recovered is very significant 

because of the vast tonnages mined. The porphyry 

molybdenum deposits, on the other hand, are virtually free of silver except for trace amounts. During 1970, the Bingham open-pit mine in Utah, a 

copper-molybdenum deposit, was the fifth largest 

silver producer in the United States, with an output 

of 2.6 million ounces of silver from 40 million tons 

of ore, or 0.065 of an ounce of silver recovered per 

ton of ore (Lindstrom, 1971). Arizona contains the 

largest known concentration of porphyry copper 

deposits. Fourteen such deposits average 0.06 of an 

ounce of silver recovered per ton of ore (8 ounces 

of silver per ton of copper) . Known "predicted" resources of porphyry copper deposits in Arizona are 

estimated to be 80 million tons of copper (A. F. 

Shride, oral commun., 1972) from which an estimated 640 million ounces of silver can be recovered. 

In recent years, porphyry copper deposits that contain silver have been found in Puerto Rico; in Maine 

near Jackman, along the Quebec border; in British 

Columbia; and in Panama. The deposits in Puerto 

Rico are relatively lean in silver and contain only a 

few parts per million of silver per ton of ore (D. P. 

Cox, oral commun., 1972). Most are not yet being 

mined. Porphyry copper deposits and copper-molybdenum deposits are now in production in British 

Columbia. Porphyry copper deposits in Chile annually yield about 31;2 million troy ounces of silver. 

Similar deposits in Peru also produce silver. The 

newly discovered porphyry copper deposits in Irian, 

Bougainville, New Guinea, and Iran will probably 
588 UNITED STATES MINERAL RESOURCES 

constitute important new silver sources in the 

future. 

Few porphyry copper deposits are known in Asia 

and Africa, and none are known or developed in 

Europe. Extensive low-grade porphyry copper deposits in the Balkhash-Kourmadskiy area of the 

eastern part of the U.S.S.R. contain silver, but only 

the shallow enriched zones are productive at present. A small but rich porphyry-type copper deposit 

is being mined in syenitic rocks and carbonatite at 

Palabora, northeast Transvaal, Republic of South 

Africa. 

COPPER-ZINC-LEAD REPLACEMENT DEPOSITS 

AND VEIN CLUSTERS 

Silver is an important byproduct or coproduct of 

some copper-zinc-lead replacement deposits such as 

at Butte, Mont., and in the Johnson Camp, Turquoise, 

Banner, and Superior districts, Arizona. In these, 

the copper generally is in a central zone which is 

surrounded by low-temperature zones of galena and 

sphalerite. At Butte, a peripheral zone contains 

manganese. Silver is enriched in the peripheral zones 

compared with the central copper zone. The ore 

bodies may be veins; irregular, pipe-shaped, or 

bedded replacements; or stockworks. The predominant primary copper mineral is chalcopyrite, although bornite, chalcocite, covellite, djurleite, and 

enargite are important minerals at Butte. 

Butte yielded more than 644 million ounces of 

silver between 1880 and 1964-the second largest 

producer of silver, after Coeur d'Alene, in the United 

States. The ore occurs in veins within the Boulder 

batholith, with a central zone of copper deposits, an 

intermediate zone of copper-zinc deposits, and a 

peripheral zone with zinc, lead, silver, and manganese d~posits (Meyer and others, 1968). Total 

production of silver at Butte has averaged about 2 

ounces per ton of ore mined, about half of which is 

from the central Berkeley Copper Pit, the remainder 

from the outer part of the intermediate zone or 

from the silver-rich copper-zinc-lead peripheral zone. 

Total production at Butte has averaged about 1 

ounce of silver for each percent copper, and current 

production is about 0.3 of an ounce of silver for 

each percent copper (Meyer and others, 1968, p. 

1376). 

The copper and copper-zinc replacement deposits 

in Arizona are mainly in limestone or altered limestone host rock near granitic intrusive bodies. The 

Magma mine has consistently produced 300,000 to 

1 million ounces of silver annually from ore that 

has averaged 1.93 ounces per ton (Hammer and 

Peterson, 1968, p. 1286), largely from the steep, 

east-striking Magma vein. This vein has been developed over a strike length of 10,000 feet and to a 

depth of 4,900 feet. 

The Kennecott copper mine in the Copper River 

region, Alaska, produced about 12 million ounces of 

silver during almost continuous operation from 1911 

to 1938. The copper ores, which contained 14 to 16 

ounces of silver per ton, occurred in replacement 

veins, in irregular massive replacements, and in 

stockworks in partly dolomitic beds in the Chitistone 

Limestone of Triassic age, which overlies thick 

copper-bearing basalts. The copper and silver was 

mainly in chalcocite and covellite (Bateman and 

McLaughlin, 1932). 

At Gilman, Colo., copper-silver-gold ores fill fractures, coat vugs, and replace early massive pyrite 

bodies in chimneys at the lower end of mantos. The 

ores average 3.5 percent copper, 18.7 ounces of 

silver, 0.08 of an ounce of gold per ton. 

In the southern part of the Tintic district in 

Utah, copper-silver-zinc-lead deposits include fissure 

veins and wallrock replacements of enargite, sphalerite, and silver minerals near Silver City, and the 

great replacement pipes and mantos of copperarsenic-silver ores in the southern parts of the 

Mammoth mine. 

In the Eastern United States, ores of this type 

are uncommon, and but few are known. The Barrett 

prospect, East Pembroke, Maine, is a stockwork of 

copper-zinc-silver ore in metavolcanic rocks. In the 

Linganore district of the Maryland Piedmont, chalcopyrite and bornite containing some silver, and 

locally argentian galena and sphalerite, are in veins 

and replace marble along contacts with metavolcanics. 

MASSIVE SUFIDE DEPOSITS 

The term "massive sulfide" as used here follows 

the definition of Anderson and Creasey (1958, p. 

96): " * * * deposits consisting of a granular aggregate of sulfide minerals such as pyrite, chalcopyrite, 

sphalerite, and galena, with little or no visible 

gangue minerals." Many contain pyrrhotite, magnetite, arsenopyrite, tetrahedrite, and barite, and 

many contain silver and gold as important byproducts. The geology and genesis of massive sulfides 

related to volcanic belts has been discussed by Anderson (1969), and is summarized in the "Copper" 

chapter of this volume. 

Massive sulfide deposits are of tremendous worldwide commercial importance as sources of silver and 

base metals in Canada, Japan, Ireland, Cyprus, Australia, U.S.S.R., Spain, Sweden, Philippines, Turkey, 

West Germany, and Norway. Some of the largest 
SILVER 589 

productive mines in North America that supply 

silver as a byproduct are massive sulfide deposits. 

They are abundant in the following regions : ( 1) 

The Appalachian region of the United States and 

Canada (Bathurst, New Brunswick; Buchans and 

Tilt Cove, Newfoundland ; Maine and Vermont ; 

Ducktown, Tenn.) (Kinkel, 1967; Heyl and Bozion, 

1971) ; (2) the Precambrian Shield of eastern and 

central Canada (Kidd Creek, Timmins, Ont.; Noranda, Quebec) , including the Adirondack uplift in 

New York and the Wisconsin dome in Wisconsin and 

Michigan; (3) the Pacific coast region of California 

(Kinkel and Hall, 1952), British Columbia, and 

Alaska; and ( 4) the Basin and Range province and 

Rocky Mountains (Iron King, Bagdad, and Jerome, 

Ariz. (Anderson, 1969), Pecos, N. Mex., and the 

Sedalia mine, Colorado) . 

At the United Verde mine, Jerome, Ariz., ·57 million ounces of silver was recovered between 1883 

and 1952 (Anderson and Creasey, 1958, p. 101). This 

represents 2112 ounces of silver per ton of ore, or 31 

ounces of silver per ton of copper. The Iron Mountain mine, in the West Shasta district, California, 

was first mined for silver in the gossan, which 

locally averaged about 8 ounces of silver per ton of 

ore; the primary ore contained less than 1 ounce of 

silver per ton (Kinkel anti Albers, 1951, p. 8). The 

massive sulfide deposits with substantial amounts 

of sphalerite and galena carry more silver than the 

pyrite-chalcopyrite ore. At the Iron King mine, 

Arizona, the ore averaged 4 ounces of silver, 2.2 

percent lead, and 6.4 percent zinc (Anderson and 

Creasey, 1958, p. 155). At the Mammoth mine, California, the massive sulfide ore that was mined for 

copper contained 2.2 ounces of silver whereas the 

ore mined for zinc averaged 5.8 ounces of silver per 

ton (Kinkel and Hall, 1952, p. 6). 

LEAD-ZINC REPLACEMENT DEPOSITS 

Lead-zinc replacement ore deposits are one of the 

principal sources of silver. Most argentiferous leadzinc replacement deposits formed from hydrothermal solutions of deep-seated origin at the margin of 

or within intrusive bodies of granitic to dioritic 

composition. In the margins of the intrusive bodies, 

limestone is a particularly favorable host rock, but 

quartzite, argillite, and schist also host major deposits. Many deposits are localized near or within 

the intrusive by structural features such as a favorable bed near a feeder fissure, a fracture or fissure, 

a brecciated zone near the intrusive, or a favorable 

bed in a roll in the structure. Especially favorable 

geologic settings are found near Mesozoic and Tertiary instrusives in the circum-Pacific belt and near 

Tertiary intrusives in the Great Basin and Rocky 

Mountains, eastern Canada, and central Europe. 

Much of the rich silver ore is produced from leadsilver-zinc replacement deposits in limestone. These 

include such famous camps as Park City and Tintic, 

Utah; Leadville and Red Cliff, Colo.; Silver City and 

Magdalena, N. Mex.; Eureka, Nev.; and Cerro de 

Pasco and Casapulca, Peru. The bedded replacement 

deposits at Park City are in many places contiguous 

with vein deposits that occupy feeder fissures in 

which the ore solutions moved. Silver-rich lode deposits were ex:rloited in the early years of the district. The Ontario lode provided high-grade silver 

ore over a strike length of approximately 5,000 feet 

and to a depth of 1,300 feet (Barnes and Simos, 

1968, p. 1116). Where the vein is in the Weber 

Quartzite, it contains high-grade ore, but in the 

underlying limestone the ore is discontinuous and 

lower grade. Extensive bedded limestone replacement ore bodies are found in the overlying Park City 

Formation; these deposits have been the major 

source of production since the early exploitation of 

the high-grade lodes. The Jenney limestone bed of 

economic usage, which is 100 feet above the Weber 

Quartzite-Park City Formation contact, is the host 

rock for most of the large bedded deposits (Garmoe 

and Erickson, 1968, p. 34). It was mineralized over 

a strike length of more than 6,000 feet, with a maximum width of 150 feet, and ranged in thickness 

from 25 to at least 100 feet. The ore averaged 25.3 

ounces per ton of silver, 14 percent lead, and 12 

percent zinc. 

At Tintic, Utah, much of the ore mined during 

the early history of the district averaged 30-40 

ounces of silver per ton (Lindgren and Loughlin, 

1919, p. 105-112) and some of it assayed more than 

100 ounces per ton. At Darwin, Calif., much of the 

near-surface primary ore averaged 50 ounces of silver per ton whereas the deeper replacement ore 

averaged about 6 ounces per ton (Hall and MacKevett, 1962). Oxidation and supergene enrichment 

of these argentiferous galena ores produced the shallow-depth bonanza ore bodies that were mined during the latter part of the 19th century. 

Lead-zinc deposits with appreciable silver occur 

in quartzite, argillaceous rocks, and schist, as veins 

or veinlike replacements along steep fissures or in 

fractures along bedding. Veins of this type constitute much of the formerly productive mineral belt 

of Colorado, particularly in the Montezuma, Idaho 

Springs, and Silver Plume districts, where they occur 

in fault zones in Precambrian gneisses (Lovering 

and Goddard, 1950, p. 138-178). 
590 UNITED STATES MINERAL RESOURCES 

MISSISSIPPI VALLEY- AND ALPINE-TYPE LEAD, ZINC, AND 

FLUORSPAR DEPOSITS AND RELATED DEPOSITS 

The Mississippi Valley-type districts contain epigenetic, low-temperature, hydrothermal deposits of 

galena, sphalerite, and pyrite, and locally fluorite, 

barite, chalcopyrite, calcite, and cobalt minerals. 

These deposits have been productive in lead, zinc, 

fluorite, and barite, and some have produced copper, 

silver, cobalt, and nickel as byproducts. The lead in 

the galena is of the radiogenic Joplin type (J-type). 

Brown (1970) has prepared an excellent summary 

of the geology and characteristics of the Mississippi 

Valley-type and related deposits. At present, about 

2 million ounces of silver per year is produced from 

the southeast Missouri district, which makes it one 

of the major silver-producing districts in the United 

States. Most of the silver is recovered from sphalerite, from some of the chalcopyrite, and from a silverlean galena. Silver is not recovered from other sulfides, such as pyrite, although locally they contain 

some silver. 

Silver is present in small amounts in both sphalerite and galena in the Upper Mississippi Valley district. Analyses of 29 sphalerite samples range from 

0.03 to 10 oz of silver per ton and average 0.7 oz 

per ton (Bradbury, 1961; Hall and Heyl, 1968). 

Analyses of 33 samples of galena range from 0.05 

to 3 oz of silver per ton and average 0.58 of an 

ounce per ton. 

Silver is recovered from some of the galena concentrates in the Illinois-Kentucky district, where 

silver in galena ranges from 15 ounces per ton of 

concentrates in Illinois to about 5 ounces per ton in 

western Kentucky (Hall and Heyl, 1968). In many 

veins, fluorite ores were mined, and galena and 

sphalerite-rich ores remain. Only traces of silver 

are known in the rest of the Mississippi Valley-type 

districts, but in many of them almost nothing is 

known of the silver content of minerals. 

The Appalachian Valley zinc deposits contain 

little lead. Where galena is present, it contains 

some silver in the range of 1-2 ounces per ton; the 

lead in it is not notably radiogenic. Silver has been 

recovered from the deposits in the Embreeville, 

Tenn., and Austinville, Va., districts. 

In many respects the lead-zinc deposits of the Alps 

in eastern France, Austria, northern Italy, and 

Yugoslavia resemble the Appalachian Valley zinc 

deposits except that in the Alps the galena is much 

more abundant than sphalerite. In all of these countries some silver in the galena is recovered as a 

byproduct, but the deposits are not notably rich in 

silver. The lead isotopes in the ga)ena are notably 

radiogenic in thorium lead (B-type). 

Ore deposits in the Metaline district of northeastern Washington occur as large, irregular replacement bodies in the Middle Cambrian Metaline Limestone. Sphalerite and galena are the ore minerals ; 

chief gangue minerals are jasperoid, dolomite, coarse 

calcite, and pyrite. Practically all the zinc and lead 

has been mined from an irregular zone near the top 

of the Metaline Limestone known as the "Josephine 

horizon., that is characterized by widespread brecciation. Other zinciferous zones are known in the 

Metaline Limestone but have not been exploited. 

Production from the district for the last few years 

has been at the rate of about 200,000 tons annually 

with a grade of 2.31 percent zinc, 0.85 percent lead, 

and 0.036 of an ounce of silver per ton. Total production of silver through 1969 amounts to 657,109 

ounces. The potential resources of the "Josephine 

horizon" may be as much as 1.2 million tons of 

lead, 3.4 million tons of zinc, and 5.3 million ounces 

of silver (Weissenborn, 1966). 

Somewhat similar deposits are found immediately 

to the west in Stevens County, Wash. As at Metaline, 

the deposits form replacement bodies in the Middle 

Cambrian Metaline Limestone; zinc predominates 

over lead ; and the silver content of the replacement 

deposits is low but the total silver production is 

substantial-incomplete data suggest that it 

amounts to about 600,000 ounces. 

COPPER DEPOSITS IN SANDSTONES AND SHALES 

Blankets or lenses of disseminated copper ores, 

in places with associated silver, and less commonly 

with lead, zinc, cobalt, vanadium, and uranium, are 

found throughout the world in marine and continental shallow-water sandstones and shales. Most 

of these deposits have no apparent association with 

igneous rocks. The silver is mostly in chalcocite, 

djurleite, argentite, bornite, and chalcopyrite, and 

their oxidation products, but some is native silver. 

Some of the deposits are very large, such as the 

upper Precambrian stratiform blanket deposits in 

shale near White Pine, Mich., and the Permian 

carbonaceous copper shales of Mansfeld (Germany), 

Poland, and the U.S.S.R. Copper shales in Poland 

contain 80-750 ppm silver. Copper shales near Kornberg, West Germany, contain about 1.5 percent 

copper and 10 ppm silver. Copper shales at White 

Pine contain more silver than those at Kornberg. 

The resources of White Pine are very large; more 

than a million ounces of silver per year is currently 

produced as a byproduct of the White Pine deposits, 

in addition to the silver needed to produce the White 

Pine silver-bearing Lake-brand copper, which contains 12 ounces or more of silver per ton. A much 
SILVER 591 

smaller quantity of silver comes from southwestern 

Oklahoma deposits. 

Lenticular, bedded, and roll deposits of disseminated chalcocite and pyrite, that locally contain 

uranium and vanadium minerals, occur in sandstones, mostly of Mesozoic age, in eastern New 

Mexico, southeastern Colorado, and in the Colorado 

Plateau province of Colorado, New Mexico, Utah, 

and Arizona (Fischer, 1937). Similar deposits are 

known in northeastern Utah, southern Idaho, and 

northeastern Pennsylvania. Most of these deposits 

are lean in silver, but contain small quantities in 

ores that have been mined for their copper content. 

Silver might be recovered from such ores in the 

future. 

Disseminated chalcocite, bornite, covellite, and 

chalcopyrite, locally with a little native copper and 

silver, occur in beds, veins, breccia zones, and along 

dikes in sandstones of Triassic age in Connecticut, 

New Jersey, Pennsylvania, Maryland, and Virginia, 

and in the Cashin mine in southwestern Colorado 

(Emmons, 1906), and in nearby deposits in Utah. 

The existence of possible economic concentrations 

of copper in beds of the Precambrian Belt Supergroup has been generally recognized only recently. 

(See chapter on "Copper.") One deposit has been 

developed to the point where it could be mined when 

desired, and other prospects are in various stages of 

exploration. These deposits are said to average about 

1 percent copper and to contain about 2 ounces of 

silver per ton for each percent of copper. Much work 

remains to be done before any realistic forecast can 

be made of the silver resources of the Belt Basin. 

They obviously could constitute an important resource of both silver and copper. Company exploration geologists stated (A. E. Weissenborn, oral 

commun., 1971) that the expected size of individual 

deposits may be as much as 60-100 million tons. 

NATIVE COPPER DEPOSITS 

Very large deposits of native copper and associated native silver occur in amygdaloidal basalt 

flows and conglomerates on the Keweenaw Peninsula, northern Michigan ; probably they were deposited by heated chloride-rich brines that rose 

updip from beneath the present location of Lake 

Superior (White, 1968). The deposits have been 

productive from prehistoric times until 1970, when 

the last mines were closed after having yielded 

nearly 5.4 million tons of copper and a very substantial quantity of silver. Most of the silver production was not recorded, however, because it was 

retained in the "Lake copper" produced, which contains as much as 8 ounces of silver per ton. The 

remaining resources in this district are very large, 

but mostly low grade, and are awaiting better metal 

prices and improved mining and recovery methods. 

GOLD DEPOSITS IN VEINS} CONGLOMERATES} AND PLACERS 

Silver is alloyed with gold in all precious-metal 

deposits. The amount of silver is indicated by the 

fineness of the gold, which is the proportion of gold 

to silver expressed in parts per thousand (thus, for 

example, "900 fine" means a gold to silver ratio of 

9:1, or 10 percent silver). Mesothermal and hypothermal gold-quartz veins generally have more gold 

than silver, whereas the epithermal precious-metal 

and the shale and sandstone deposits have more silver than gold. 

Gold-quartz veins are found extensively in metamorphic terranes around the world: in Western 

United States and Alaska; in the Precambrian shield 

of Canada and the United States; at Victoria, Australia; and in the Precambrian areas of South 

Africa, the Ural Mountains, the Austrian Alps, 

Brazil, India, and Siberia. 

The most extensive gold-quartz veins in the United 

States are in California along the belt of Mesozoic 

granitic rocks. The most productive was the Mother 

Lode Belt, which extends for a distance of 130 miles 

on the west side of the Sierra Nevada batholith in 

a folded belt of metamorphosed Paleozoic and Mesozoic volcanic and sedimentary rocks. The Mother 

Lode is a vein system with individual veins as much 

as 1 to 2 miles long; some veins have been mined 

5,000 to 10,000 feet down the dip. 

The gold-quartz veins in the Kirkland Lake and 

Porcupine districts in the Canadian Shield have 

many similarities to the Mother Lode veins. They 

occur in tightly folded Keewatin andesite and basalt 

flows, and the mineralogy of the veins is simple. The 

silver to gold ratios range from 0.11 to 0.25. 

The Homestake mine, South Dakota, produced 

approximately 28 million ounces of gold and 61;2 

million ounces of silver between 1878 and 1965, a 

gross of nearly $1 billion at today's prices (A. L. 

Slaughter, in Ridge, 1968, p. 1437). The ore occurs 

as a replacement of isoclinally folded Precambrian 

Homestake Formation (Hosted and Wright, 1923), 

and consists of several percent of pyrrhotite, arsenopyrite, and pyrite in a calcite-quartz-chlorite-ankerite gangue. 

Other important deposits of gold-quartz veins in 

the United States that have yielded byproduct silver 

include those in the Colorado mineral belt, the Appalachian Piedmont gold belts in the southeastern 

United States, the Neihart district, Montana, Mogollon district, New Mexico, Wallapai district, Arizona, 

the London vein system, Alma district, Colorado, and 
592 UNITED STATES MINERAL RESOURCES 

the Gold Mountain quartz veins in Tertiary tuffaceous sediments, pyroclastics, flows, and associated 

intrusives in the Republic district of Washington 

have yielded about 7112 million ounces of silver as a 

byproduct of gold mining. Epithermal gold-quartz 

veins in silicified zones in the Paleocene Swauk Formation at Wenatchee, Wash., have also yielded considerable byproduct silver. 

Gold-bearing conglomerate deposits in the Witwatersrand district, Transvaal, South Africa, have 

yielded more gold than the total gold produced in 

Alaska, California, and Colorado. Similar conglomerates have been mined in West Africa at Tarkwa 

and Abosso. The fineness of the gold in two Witwatersrand mines ranges predominantly from 750 

to 925 (Von Rahden, 1965, p. 983). 

All placer gold contains byproduct silver, although 

the amounts in the gold are much smaller than in the 

nearby lodes, and the total quantity per placer is 

small. The placers on the west side of the · Sierra 

Nevada, and near Fairbanks, Alaska, and the Yukon, 

Canada, however, have yielded appreciable quantities of silver. Future production of large amounts of 

silver from gold placers is unlikely because of the 

low grade of the remaining gravels and because of 

environmental considerations. 

NICKEL AND MAGNETITE DEPOSITS 

About a million ounces of silver is produced annually from the nickel ore bodies at Sudbury, Ontario. (See chapter on "Nickel.") The silver occurs 

in small amounts in chalcopyrite, and in galena of 

the mineralogically more complex "offset deposits," 

which are probably hydrothermal. Production is expected to continue for many years. 

At Cornwall and Morgantown, Pa., silver is recovered as a byproduct, along with gold, copper, and 

cobalt, from high-temperature hydrothermal magnetite deposits. (See chapter on "Iron.") The silver 

occurs in small quantities in chalcopyrite that is 

common in the ores. A small but steady output has 

come from these deposits for many years. Although 

Cornwall is approaching exhaustion, Morgantown is 

a major new mine and is expected to continue 

production. 

SILVER AS A MAJOR CONSTITUENT 

Mineral deposits in which silver is the main constituent include a wide variety of types, and they 

constituted some of the most productive deposits in 

the notable districts that were mined in the 19th 

century. They are no longer very productive except 

in a few major districts. These silver-rich deposits 

are (1) epithermal veins, lodes, and pipes, (2) epithermal disseminated and breccia deposits, (3) epithermal silver-manganese deposits, ( 4) epithermal 

silver-lead-zinc replacement deposits, ( 5) epithermal silver-copper-barite deposits, ( 6) mesothermal 

silver-lead-zinc-copper deposits, (7) mesothermal 

cobalt-silver, cobalt-uraninite-silver, and cobaltsilver-zeolite deposits, (8) sandstone silver deposits, 

and (9) sea-floor muds and hot-spring deposits. 

EPITHERMAL VEINS} LODES} AND PIPES 

Epithermal veins, lodes, and pipes form within a 

few thousand feet of the surface, under slight load, 

and generally in brittle rocks where open fractures 

and cavities are abundant. They are formed by 

deposition of silver-bearing minerals from hot ascending solutions in areas of volcanic activity. The 

presence of anomalous amounts of arsenic, antimony, mercury, bismuth, tellurium, and selenium 

are good geochemical indicators of favorable areas 

for prospecting and exploration. They are distinguished from mesothermal and hypothermal 

deposits by small grain size, open cavities, crustification, banding, and comb structures. They most commonly occur in Tertiary volcanic flows or tuffs, 

generally andesitic to rhyolitic in composition, or in 

fault fissures between these and other rocks. Only 

rarely do they occur in basalt, or in the underlying 

or adjacent rocks of plutonic or sedimentary origin. 

The common ore minerals are argentite, pyrargyrite, polybasite, and other complex silver sulfosalts, 

argentiferous tetrahedrite, argentiferous galena, and 

sphalerite. Most of the deposits contain gold, either 

free or alloyed with silver as electrum, and basemetal sulfides that are seldom of economic importance. Many of the deposits contain cerargyrite 

and native silver as secondary minerals in the zone 

of oxidation. The gangue minerals include quartz, 

and typically less abundant adularia, calcite, dolomite, barite, and fluorite, and rarely, rhodochrosite 

and rhodonite. Wallrock alteration is generally well 

developed and marked by abundant kaolin, chlorite, 

carbonate minerals, and pyrite, and locally by sericite or zeolites. The ore bodies commonly occur as 

shoots or chimneys of richly mineralized vein material surrounded by lower grade ore or barren gangue minerals. They are generally confined to fault 

fissures and other fractures but may locally extend 

into the wallrocks. The ore bodies range widely in 

size and grade; some have been mined continuously 

for strike lengths of several thousands of feet, and 

have yielded ore that contained from a few ounces 

to many thousands of ounces of silver per ton. Few 

deposits are known to extend to depths of more than 
SILVER 593 

2,000 feet below the surface, and most are confined 

to less than 1,000 feet below the outcrop. 

The most famous epithermal silver deposit in the 

United States, and perhaps the world, is the Comstock Lode in western Nevada (Becker, 1882; Bastin, 1922; Gianella, 1936; Thompson, 1956). This 

great deposit yielded nearly a half billion dollars in 

gold and silver from ore bodies along a strike length 

of about 3 miles and to a depth of more than 2,000 

feet. Another notable epithermal vein deposit is the 

Hornsilver, in the San Francisco district of Utah 

(Butler, 1913). This giant vein of silver-bearing 

galena, sphalerite, argentite, pyrargyrite, and chalcopyrite lies in a large fault between Tertiary 

quartz-latite flows on the east and lower Paleozoic 

limestone on the west. The vein was rich in silver, 

lead, and gold where partly oxidized near the surface; as in many epithermal veins, the productive 

part extended to only about 1,000 feet. Other notable 

epithermal vein deposits in the United States are 

those at Tonopah (Nolan, 1935) and Austin (Ross, 

1953), Nev.; Mojave (Tucker, 1935) and Randsburg 

(Hulin, 1925), Calif.; and the Mogollon district, , 

New Mexico (Anderson, 1957). Many of the rich 

silver deposits of Mexico and the Andes belong to 

this type. The eastern part of the Harz vein district in West Germany contains epithermal silverlead veins with a wide variety of silver minerals. 

Epithermal precious- and base-metal veins and 

lodes in Tertiary andesitic breccia of the San Juan 

Mountains of Colorado contain both silver and gold. 

Major silver-producing mines are still active in the 

Telluride-Sneffels district, near Silverton, and at 

Creede, where the host rocks are mostly felsic volcanic rocks. Most of the deposits in the San Juan 

Mountains are within or near the margins of giant 

calderas (Steven, 1968). At Creede, a new vein system recently opened up by the Homestake Mining 

Co. contains an unusual native silver and copper sulfide ore. Farther north this vein probably grades 

into very coarse grained, vuggy, argentiferous 

galena, sphalerite, and copper minerals similar to 

the Holy Moses, OK, and Amethyst veins to the east 

(Steven and Ratte, 1965). 

In the Silver Cliff and Querida districts of southcentral Colorado, breccia pipes in rhyolite are cemented by rich crusts of galena, sphalerite, various 

silver minerals, free gold, and gold tellurides. The 

best known deposits are those of the Bassick and 

Geyser mines. Nearby is the Bull Domingo pipe with 

mineralogically similar ore that cements a Tertiary 

breccia formed in Precambrian rocks. The deposits 

are small, but locally rich. Near Silver Cliff, a volcanic basin is covered by a blanket of altered rhyolite with many small intersecting silver veins. 

Beneath part of the district is a large, low-grade, 

epithermal porphyry-type silver-lead-zinc-copper 

deposit which is a resource for the future. 

EPITHERMAL DISSEMINATED AND BRECCIA DEPOSITS 

The large deposit at Calico, in southeastern California (Wright and others, 1953), has yielded about 

$20 million in silver from barite veins along faults 

and from rich pockets of cerargyrite, embolite, and 

native silver in shattered volcanic rocks and lake 

beds of Miocene age. Few of the deposits extend to 

depths greater than 200 feet. Exploration in 1966 

indicated a disseminated silver deposit containing 

many millions of tons of low-grade silver-bearing 

material in faulted and brecciated sedimentary rocks 

of late Miocene age along the Calico fault zone. 

The Monitor district, California, also has lowgrade disseminated silver in braided fissure zones in 

altered andesite of Miocene-Pliocene age. The silver 

occurs as argentite, polybasite, and pyrargyrite. 

Similar deposits are reported in Nevada and Arizona. 

Silver-antimony-lead-bearing epithermal jasperaid reefs that replace limestone were mined in the 

Taylor and Success districts east of Ely, Nev. 

(Drewes, 1967). Similar ores, of silver, occur in 

jasperoid mantos in the Vipont district in the northwest corner of Utah. Many other small deposits of 

this type are known in Colorado, Utah, and Nevada. 

EPITHERMAL SILVER-MANGANESE DEPOSITS 

Silver-rich manganese carbonate, manganiferous 

black calcite, and manganese oxide deposits, occurring as veins in layered volcanic rocks and as replacement deposits in limestone, were briefly productive in the United States. The best known districts are Lake Valley, N. Mex.; Pioche, Tybo, and 

White Pine, Nev.; Escalante, southwestern Utah; 

Tombstone. and Aquila, Ariz. ; Silver Cliff, Colo. ; and 

Modoc, Calif. In these and numerous other similar 

districts in the west, the silver mineral mined was 

cerargyrite that occurred in small near-surface deposits; the hypogene silver minerals were not determined in most deposits (Hewett and others, 1965; 

Hewett and Radtke, 1967). The most recently developed deposit of this type is in the Escalante district 

near Modena, Utah. Here a large tonnage of 10- to. 

15-ounce silver-manganese ore has been developed in 

a large vein of manganese oxides, fluorite, black calcite, vanadinite, pyromorphite, descloizite, and 

wulfenite; the vein, in rhyolite, extends below the 

shallow water table without sulfides. In the White 

Pine district, Nevada, the cerargyite ores are worked 

out, but aurorite, argentian todorokite, and hydrous 
594 UNITED STATES MINERAL RESOURCES 

silver-bearing lead-manganese oxides have been 

identified from black silver-bearing manganiferous . 

calcite samples (Radtke and others, 1967). 

One of the richest of the oxidized silver-manganese deposits was mined in the Lake Valley district, 

New Mexico, from 1878 to 1893, during which time 

it yielded 5 million ounces of silver (Jicha, 1954, p. 

71) . Half of the silver came from one stope where 

the silver occurred in cerargyrite and one 4-foot face 

averaged 15,000 ounces of silver per ton. Lower 

grade silver ore consisted of silver-bearing manganese and iron oxides in cherty limestone. The nature 

of the primary ore is not known inasmuch as all the 

mined ore was manganese oxides and silver chlorite 

in limestone; only a small amount of galena, almost 

completely oxidized, was found. Sulfide cavities are 

uncommon. 

EPITHERMAL SILVER-LEAD-ZINC REPLACEMENT DEPOSITS 

Epithermal silver-lead-zinc replacement deposits 

are not common, but a few have been very productive. One of the largest and most productive districts 

with such deposits is Aspen, Colo., where large veins 

and replacements along bedding-plane faults and 

cross faults in Mississippian carbonate rocks contain 

large, rich, pocketlike hypogene ore bodies of barite, 

pearceite, and native silver near the surface. In 

places these bodies grade into fine-grained colloform 

silver-rich galena and sphalerite. Other silver replacement deposits occur at Eureka and Cortez, 

Nev.; Tombstone, Ariz.; Hermosa and Kingston, N. 

Mex. ; and Shafter, Tex. 

Variants of this type are the Tertiary volcanic 

breccia pipes or chimneys of silver, gold, lead, zinc, 

copper, and tungsten ores that formerly were productive in the Red Mountain district in the core of 

the Silverton caldera of the San Juan Mountains, 

Colo. (Burbank and Luedke, 1968). The ore was deposited at shallow depth and replaces the breccia, or 

it forms cylindrical replacement envelopes around 

the pipes along the contact with wallrocks and fills 

the interstices. These epithermal ores are rich in 

silver and copper, and in places include pipes of 

shallow-depth high-temperature deposits containing 

heubnerite. The best silver ore consists mostly of 

stromeyerite and bornite. 

At Mercur, Utah, the Carlin-type very fine grained 

limestone-shale gold-arsenic replacement ores grade 

into silver ores geologically similar to the Carlin, 

Nev., gold ores. The first mining was for silver, and 

the gold ore was found after the highest grade silver 

ore had been mined out and the camp abandoned for 

a decade (Gilluly, 1932). 

EPITHERMAL SILVER-cOPPER-BARITE DEPOSITS 

Rich silver-copper-barite deposits of Triassic age 

were found in the 1960's at Walton, Nova Scotia 

(Boyle, 1963; 1972). At the surface, pipe deposits 

were mined for barite and manganese. Subsequent 

deep drilling for barite revealed deposits, beneath 

the barite in the same pipe, that consist of chalcocite 

and at least 10 other copper and silver sulfide minerals. Similar barite deposits with silver-bearing 

chalcocite are known in the Triassic shales of the 

Connecticut Valley. Hewett (1968) suggested that 

the Walton deposit is a type of silver occurrence that 

might be expected beneath the manganese-silver ores 

previously mined. 

MESOTHERMAL SILVER-BASE METAL VEINS 

The Coeur d'Alene district of Idaho is the country's leading silver producer, one of the few active 

mining districts in the world in which a significant 

part of the ores are mined chiefly for their silver 

content. Through 1968 its mines have yielded approximately 754,300,000 ounces of silver, 7,010,000 

short tons of lead, 2,555,000 short tons of zinc, and 

125,000 short tons of copper, in addition to substantial amounts of cadmium and antimony. The 

total value of the metals produced exceeds $2.3 

billion. 

The ore is in replacement veins in weakly metamorphosed argillites, siltites, and quartzites of the 

Precambrian Belt Supergroup. Coeur d'Alene ore 

shoots are characteristically longer in vertical dimension than in horizontal dimension. Ore has been 

mined over a vertical range of 8,000 feet. Many ore 

shoots have been bottomed, but others continue 

below the lowest mine levels, with no evidence to 

suggest their bottom limit. The principal producing 

mines are found in two groups, one north of the 

Osborn fault, the other south of the fault. The eastern part of the southern group is known as the 

"Silver Belt" because of the higher silver content of 

the ore. 

In most mines in the Silver Belt, the ore averages 

about 25 ounces of silver per ton and 0.75 percent 

copper. In the other mines the combined lead-zinc 

content averages 10-12 percent, and the silver content is variable. 

The Chewelah district, which has been the leading 

producer of silver in Stevens County, Wash., is in an 

entirely different geologic setting from the Coeur 

d'Alene district. The silver is in braided quartzcarbonate veins in shear zones in argillite of the Belt 

Supergroup. Chalcopyrite is the principal ore mineral. All the mines are within 2 miles of outcrops of 

the Flowery Trail Granodiorite (Clark and Miller, 
SILVER 595 

1968). The district has yielded 1,747,000 ounces of 

silver and 5,350 tons of copper, mostly from the 

United Copper mine. The mines have been idle for 

many years, and it is unlikely that mining will be 

resumed under present or foreseeable conditions. 

MESOTHERMAL COBALT-SILVER, COBALT-URANINITE SILVER, 

AND COBALT-SILVER-ZEOLITE DEPOSITS 

The cobalt-silver veins of Cobalt, Ontario, have 

yielded about 500 million ounces of silver to date, 

and several mines have been revived in recent years. 

The deposits occur in thin, short, vertical veins in 

diabase sills about 1,000 feet thick. The main minerals are native silver, cobalt, nickel and iron arsenides, arsenic sulfides, dolomite, and calcite. Some 

galena, chalcopyrite, pyrite, sphalerite, pyrrhotite, 

and tetrahedrite are present. Typical high-grade ore 

averages 10 percent silver, 9 percent cobalt, 6 percent nickel, and 39 percent arsenic (Jones, 1953, p. 

18) . The origin of the silver veins is controversial. 

Many believe the silver source was in the magma 

that gave rise to the diabase. Others suggest the ore 

minerals or metals were derived from sedimentary 

rocks interbedded in the greenstones. 

Similar deposits on the east shore of Great Bear 

Lake, northwestern Canada, contain native silver, 

cobalt and nickel arsenides, chalcopyrite, some uraninite, and bismuth, in thin quartz veins. The principal economic mineral in some veins is uraninite, and 

in others, native silver. Gangue is altered host rock, 

quartz, carbonates, and hematite. Five stages of 

mineralization have been recognized; pitchblende is 

part of an early stage and native silver is part of the 

latest stage. 

The Echo Bay mine, opened in 1964, has produced 

nearly 16 million ounces of silver. In 1971, this mine 

produced about 2.5 million ounces of silver and 

650,000 pounds of copper. Mill heads average 70 

ounces of silver per ton and 0.95 percent copper 

(Northern Miner, Jan. 6, 1972). Four large masses, 

largely of silver, that weighed 1,620, 800, 412, and 

344 pounds were mined in August 1971; the largest 

mass contained about 70 percent silver. 

Deposits somewhat similar to those at Great Bear 

Lake were formerly quite productive at Kongsberg, 

Norway; and at Andreasberg, Annaberg, and 

Schneeberg in Saxony, Germany. These deposits contain native silver, silver sulfides, cobalt, bismuth, 

and nickel arsenide associated with lead and zinc 

sulfides. Uraninite is much less abundant in these 

deposits than at Great Bear Lake although locally 

the veins are enriched in uraninite. Zeolites, barite, 

fluorite, calcite, and ankerite are the main gangue 

minerals. The veins at Schneeberg are ore bearing 

in metamorphic clay-slates but are impoverished in 

the underlying granite. The veins are multistage: 

the nickel-cobalt-bismuth ores are associated with an 

early stage ; uraninite with an intermediate stage; 

and silver with a late stage. 

SANDSTONE SILVER DEPOSITS 

Silver chloride deposits disseminated in sandstone 

occur in southern Utah at Silver Reef (Proctor, 

1953) . Small ones are also found to the southwest 

near St. George. The mines, which were productive 

for about 20 years in the late 19th century, yielded 

nearly 8 million ounces of silver. 

The deposits are a silver-rich variant of the Colorado Plateau sandstone uranium deposits and the 

sandstone copper-silver deposits previously described (Fischer, 1937). Most of the Silver Reef 

deposits contain some copper and, locally, some 

uranium and vanadium. The ore bodies are restricted to the Silver Reef Sandstone Member (of 

Proctor, 1953) of the Upper Triassic Chinle Formation and occur in blankets and lenses on the limbs 

and nose of a major anticline. The ore bodies were 

emplaced prior to anticlinal folding. They tend to be 

richest in carbonaceous trash pockets and in crossbedded sandstone beds and lenticular channels. The 

silver is mostly in cerargyrite, but it occurs locally as 

native silver. Associated minerals are malachite, 

azurite, and locally carnotite. Trace-element studies 

indicate that silver bromides are probably also present. The ore minerals are essentially invisible and 

occur as micrograins cementing the sandstone 

grains, and as thin gray crusts on lignite. Pyritic 

concretions, now altered to limonite, locally are especially rich in silver. The ores were worked to the 

water level and the mines closed. Little exploration 

was done below the water table, although the geology 

suggests that unoxidized ore, similar in grade to the 

oxidized ore, should be present. Little search has 

been made for similar ores elsewhere in the Colorado 

Plateau. 

SEA-FLOOR MUDS AND HOT-SPRING DEPOSITS 

Mineralized sea-floor muds of the Red Sea contain 

lead, zinc, and iron sulfides, and some silver in lenticular blankets in local basins (De gens and Ross, 

1969). They are being deposited by heated brines 

rising through the sea floor in the central part of the 

Red Sea. The blankets, which are very large, are 

examples of mineral deposits being deposited at 

present by hydrothermal solutions. Such deposits 

may ultimately form massive sulfide blankets such 

as those at Meggen, West Germany. 

Near Niland, Calif., close to the Salton Sea, a very 
596 UNITED STATES MINERAL RESOURCES 

concentrated brine with an unusually high content 

of potassium, lithium, and heavy-metals was tapped 

by a deep well that was drilled for geothermal power (White and others, 1963, p. 919-922). Evaporated 

residue of a deep water stream sample indicates the 

original water contains 1,000 ppm manganese, 2 ppm 

silver, 100 ppm lead, 500 ppm zinc, and 20 ppm copper. Dark material deposited in the discharge pipe 

from the well contained a high concentration of copper and silver. Such silver-bearing fluids might 

deposit their metal content to form syngenetic silver deposits in such closed saline basins as the Salton 

Sea. 

RESOURCES 

IDENTIFIED RESOURCES 

Listed in table 124 are our estimates of silver 

reserves and identified resources of material nearly 

commercial in grade and of hypothetical silver resources (undiscovered but geologically probable 

TABLE 124.-Silver resources (in troy ounces in ores) in the 

United States 

Type of deposit 

Identified 

resources1 

Hypothetical 

resources2 

Deposits in which silver is a byproduct 

Porphyry copper deposits ____ 741,000,000 725,000,000 

Copper-zinc-lead repiacemen ts 

and veins and copper-bear- ing sandstones and shales __ 

Massive sulfide deposits ------ Lead-zinc replacement deposits 

Mississippi Valley-type deposits 

Alpine-type zinc deposits in Valley and Ridge province ___ _ 

Native copper deposits ------ Gold veins and placers ______ _ 

Other types -----------------

398,000,000 1,585,000,000 

8,000,000 81,000,000 

170,000,000 235,000,000 

54,000,000 50,000,000 

200,000 

50,000,000 

5,000,000 

2,000,000 

200,000 

500,000,000 

35,000,000 

2,000,000 

Total ----------------- 1,428,200,000 3,213,200,000 

Deposits in which silver is the main product 

Epithermal veins, lodes, and 

pipes --------------------- Epithermal disseminated and 

breccia deposits ----------- Epithermal manganese and barite 

deposits ------------------ Epithermal replacement deposits 

and mesothermal veins with 

lead and zinc ------------- Mesotbermal cobalt-uraninitesilver deposits ------------- Sandstone silver deposits ____ _ 

Total -----------------

Total byproduct plus 

main product silver 

128,000,000 93,000,000 

_12,000,000 11,000,000 

18,000,000 18,000,000 

605,000,000 69,000,000 

0 1,000,000 

2,000,000 10,000,000 

765,000,000 202,000,000 

resources ----------- 2,193,000,000 3,415,000,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

mi,nerals may or may not be profitably recoverable with existing technology and economic condition~. 2 Hypothetical resources: Undiscovered mineral deposits, whether of 

recoverable or subeconomic grade, that are geologically predictable as existing in known districts. 

resources in known districts) in the United States. 

They are subdivided by geologic type of deposit as 

previously described. 

The total of identified resources is about 2.2 billion troy ounces, half again as large as the reserve of 

1.4 billion ounces estimated in 1968 (table 125). The 

difference between these two estimates is attributed 

TABLE 125.-Silver reserves/ in millions of troy ounces, of 

United States and free world' 

United States --------------- Free world (including U.S.) __ 

Silver reserves 

Measured 

and Inferred 

indicated ore Total ore 

590 

3,200 

850 

2,200 

1,440 

5,400 

t Reserves: Identified deposits from which minerals can be extracted 

profitably with existing technology and under present economic conditions. 2 Compiled in 1968 by E. T. McKnight and T. H. Kiilsgaard, U.S. 

Geological Survey, from all available published data, records of govern- ment agencies, data provided by mining company personnel and by 

minerals attaches, and annual reports of mining companies, based on materials considered economically exploitable at or near 1965-68 metal 

prices. 

partly to the discovery of the large disseminated 

silver-copper deposits in the Precambrian Belt 

Supergroup in northern Idaho and western Montana, 

which at present constitute a conditional resource, 

and partly to the increased potential resources in 

porphyry copper deposits. We have not attempted to 

estimate conditional resources in detail, but such 

resources that might become recoverable with a 

threefold to fourfold increase in the price of silver 

are roughly estimated to be of about the same magnitude as the present reserves. 

Hypothetical resources are based on geologic evidence for assumed continuations or repetitions of 

deposits in similar geologic settings. 

The identified resources of byproduct silver are 

nearly twice those of silver as the main product, and 

the hypothetical resources of byproduct silver are 

more than 15 times those of silver as the main product. By far the greatest silver resources are in 

porphyry copper deposits, massive sulfides, and copper-zinc-lead veins and replacement deposits, but 

very large identified resources are contained in the 

silver-rich lead veins and replacements such as those 

in the Coeur d'Alene district, Idaho ; in the lead-zincsilver replacement ores such as those at Leadville, 

Colo.; and in silver-bearing epithermal veins, lodes, 

and pipes similar to those in the San Juan Mountains 

of Colorado. Resources in the southeast Missouri 

district are surprisingly large, because although the 

percentage of silver in the ores is small, the tonnages of ore are immense. The small hypothetical 

resources of silver in ores in which it is a main 
SILVER 597 

product reflect the fact that most such deposits are 

restricted to shallow depth, and thus have small 

vertical extents. 

Silver consumption in the United States and in 

the world will probably continue to greatly exceed 

the newly mined supply, because silver is, and will 

continue to be, a byproduct or coproduct of copper, 

lead, zinc, and gold ores, and therefore its supply 

depends largely upon the production of these metals. 

In the future, silver will probably be produced more 

from the many types of copper deposits and from 

zinc-rich, lead-lean massive sulfides than from the 

silver-lead-zinc replacement and gold deposits that 

supplied most of the silver in the 20th century. The 

marked decline in western silver-lead and zinc production will continue because the high-cost western 

mines and smelters cannot compete with eastern ore 

until new, more efficient mining and recovery methods are commercially developed (which will take atl 

least 5-10 years), and until the price of silver is high 

enough to assure that the western silver industry 

will once more be competitive. A rise in the silver 

price would aid the opening of low-grade disseminated silver deposits such as those at Calico, Calif. 

Opening of more porphyry copper deposits and of 

large, recently developed silver-bearing copper deposits in sandstone and _shale, such as the disseminated copper-silver deposits of Idaho, Montana, 

Michigan, Oklahoma, and New Mexico, will partly 

fill the gap. 

Imported silver comes largely from Canada, 

Mexico, Peru, Ireland, and Australia. Most of the 

Canadian deposits are copper- or zinc-rich massive 

sulfides, silver deposits, gold deposits, or porphyries. 

The Mexican deposits are largely silver-rich epithermal and replacement deposits and copper porphyries. Those in Peru are copper porphyries and 

silver-lead deposits. The deposits in Australia and 

Ireland are largely massive sulfides. Increased production from these foreign deposits to obtain more 

silver in the immediate future will seriously affect 

our balance of payments and the present balance 

between supply and demand of base metals. 

HYPOTHETICAL RESOURCES 

The potential resources of silver will be increased 

substantially when economic conditions will justify 

exploration for large, low-grade deposits. 

Stratabound copper deposits may be a very large 

worldwide potential resource of silver that is not yet 

widely exploited except in Poland, East Germany, 

and Michigan. The existence of possible economic 

concentrations of copper and silver in the sandstones 

and shales of the Precambrian Belt Supergroup in 

Montana and Idaho, for example, has been recognized only recently. An enormous potential resource 

with more than 0.2 percent copper and 0.4 of an 

ounce of silver per ton is suggested by current investigations of the Belt Supergroup, and a hypothetical resource of 1 billion ounces of silver is 

possible. In addition, anomalous amounts of copper 

are known in sedimentary or low-grade metasedimentary rocks of Belt age in Africa, Australia, Russia, and Canada (Harrison, 1972, p. 1232). The 

southwest Oklahoma copper shales are known to 

extend at depth throughout most of the Anadarko 

Basin, eastward across much of Oklahoma, and 

northward into Kansas, and to grade into silver-rich 

deposits in southeastern Oklahoma. The sandstone 

silver deposits of Silver Reef, Utah, are probably a 

variant of the Colorado Plateau uranium and copperuranium deposits, many of which contain some silver. New sources are probable among the hundreds 

of uranium prospects not rich enough to be mined, 

where silver is a trace element and copper is common. The Silver Reef ore minerals are so nearly 

invisible that new deposits will not be found without 

careful sampling and analysis. Small sandstone silver deposits are known elsewhere in southwest Utah, 

indicating that Silver Reef is not unique. 

Massive sulfides, which are the source of so much 

of the world's base- and precious-metal ores, are 

abundant in the Appalachian Mountains. Under 

favorable economic conditions, many new commercial ore bodies can probably be found by prospecting 

and following prospects along known belts of metavolcanic rocks. A similar possibility for new deposits 

exists in the Precambrian of the Basin and Range 

province, outward from the well-known deposits in 

Arizona into central New Mexico, and northward 

into Colorado and southern Wyoming. These three 

States have large areas of exposed Precambrian 

rocks that contain many small massive sulfide deposits which have been largely overlooked because of 

the nearby Laramide and Tertiary deposits. The 

Sierra Nevada foothills in California and the northern California Shasta deposits are similar promising 

areas to search. A point worth remembering is that 

in 1950 the great massive sulfide deposits of Bathhurst (New Brunswick), Gaspe (Quebec), Timmins 

(Ontario) , and Newfoundland were unknown, but 

their presence was marked by small, nearly forgotten prospects of sulfide, which had been discounted 

and ignored by exploration geologists for many 

years. 

SPECULATIVE RESOURCES 

The United States, including Alaska and Puerto 
598 UNITED STATES MINERAL RESOURCES 

Rico, probably contains more silver-bearing deposits 

than almost any other nation in the world, and is one 

of the most favorable of nations for potential discovery of new deposits. The search for new deposits 

should be nationwide and not just restricted to the 

West. Perhaps one of the greatest silver anomalies 

in the United States is in southeast Missouri, and 

the Appalachian Mountain belt contains many silver 

occurrences of many geologic varieties. Large parts 

of Alaska are favorable for silver deposits, but the 

limited accessibility has discouraged intensive exploration. The Western United States has so many 

districts that it is still considered prime "prospecting ground." 

Perhaps one of the most promising of the speculative resources which includes silver is the possibility that massive sulfides of the Japanese Kuroko 

type may occur in the young volcanic belt of the 

Aleutian Island chain of western Alaska, and along 

the adjacent mainland. Geologically, this volcanic 

region is almost ideal for Kuroko-type volcanogenic 

massive sulfide deposits, and such deposits should be 

present somewhere in this long chain of islands. 

The geology of the German and Polish copper 

shales should be studied as examples in the search 

for similar shales in the United States. The European shales lie in a Permian saline basin with permeable sandstones above and below. Beneath them in 

the basins are thick salt, potash, and gypsum-anhydrite beds. During deposition the basins were shallow and were surrounded by subdued metamorphic 

uplands that contained many mineral deposits. The 

copper shales are in thin beds (6-8 in. thick) of 

black carbonaceous shale that are mineralogically 

zoned and that grade laterally into lead-, zinc-, and 

silver-rich strata. Copper shales containing silver 

are now mined in southwest Oklahoma. Similar copper shales may occur unrecognized in many other 

places in the United States where shallow, nearly 

closed basins previously existed. 

More than half the Basin and Range province is 

covered by alluvial deposits; many of the basins are 

largely pediment surfaces with thin gravel covers, 

beneath which much of the geology is similar to that 

of the adjacent mountain ranges. Many different 

kinds of silver-bearing deposits could exist in these 

basins at shallow depths. Exploration problems to be 

solved are much like those of glacial drift-covered 

shield areas. At present, geochemical prospecting is 

one of the best tools for finding them. 

Large Precambrian shield regions are covered by 

thin glacial deposits and thin Paleozoic sedimentary 

covers in northern New York, central and northern 

Wisconsin, upper Michigan, northern Minnesota, 

and eastern South Dakota. For years the geology of 

central and northern Wisconsin was shown as a 

great green undifferentiated area on the State geologic map because of the thick glacial cover and the 

sparseness of outcrops. This map (now being replaced) did not show the detailed and meticulous 

unpublished surveys of the geology completed prior 

to 1920. Dutton and Bradley (1970), in cooperation 

with the Wisconsin Geological and Natural History 

Survey, compiled maps and field-checked the outcrops indicated by the old unpublished notes. Several 

metavolcanic belts were delineated, and in them, 

large massive sulfide copper deposits have been 

found. Similarly, detailed mapping by Brown (1970) 

located a small deposit of sphalerite in a marble 

belt west of Balmat, N.Y., in the same rock as the 

major Balmat-Edwards zinc-lead deposits. Outcrops 

of the Balmat and Edwards ore bodies were quite 

small and not very promising ( J. S. Brown, oral 

commun. to Heyl, 1967). Discoveries of similar small 

outcrops of mineral deposits in the region could lead 

to the discovery of major new ore bodies. Similar 

studies are warranted in the other Precambrian 

shield areas of the United States. 

The Carlin-type epithermal gold deposits are nearly unrecognizable in the outcrop, as no gossans 

exist in the slightly altered limestones. At Mercur, 

Utah, a similar deposit produced much gold ore, but 

also some silver ore. Carlin-type epithermal silver 

ores may occur elsewhere in Utah, Nevada, Arizona, 

and New Mexico. They can be found only by careful 

geochemical analysis of slightly altered limestones 

and shales. 

Because of the major importance of porphyry 

copper deposits as a source of silver, the reader is 

referred to the excellent discussion of speculative 

resources of porphyry copper in the "Copper" chaPter of this volume. Almost all outcropping deposits 

in the Western United States have probably been 

tested, but the recent discovery at Catheart Mountain, Maine, suggests that a whole new eastern belt 

of porphyry copper deposits is possible in the Appalachian Mountain belt from Newfoundland to Alabama ; and recent discoveries in Puerto Rico and 

Panama point to new regions of possible discoveries 

in the Caribbean. 

The andesitic belts of the Unitad States should be 

geologically mapped and reexamined for silverbearing deposits. Ancient Precambrian belts of the 

West and Midwest should be located beneath glacial 

drift and the thin capping of Paleozoic sedimentary 

rocks. The use of statistical geochemical prospecting, 

geologic drilling, and the tracing of glacial boulder 

trains are also suggested. Where this has recently 
SILVER 599 

been done, as in north-central Wisconsin, some important discoveries have been made. 

During the 1960's, a large, low-grade disseminated 

silver deposit was explored by drilling and trenching 

in faulted areas in the Miocene Barstow Formation 

and in the formation at Burcham in southern California. The exploration work indicates the potential 

for large, low-grade silver deposits that could be 

mined at low cost in the vicinity of the former 

bonanza epithermal deposits. Such deposits may 

occur in other places in the West and they constitute 

a potential for large-scale mining during periods of 

good silver prices. 

The sandstone silver deposits at Silver Reef, Utah, 

were worked only to the ground-water table. If they 

are variants of the Colorado Plateau uranium deposits, as the geology indicates, the deposits could 

change into primary silver sulfide ore below the 

water table. The mineralogy and form of this hypothetical primary ore is unknown, but if it is similar 

to Plateau uranium ores, it should be in blankets and 

rolls, should be similar in grade to the ore above the 

water table, and should be concentrated in fluvial 

channels near pyrite concretions and carbonaceous 

trash pockets. 

The discovery of many mixed base- and preciousmetal massive sulfide deposits in Ireland in the 

1960's indicates a strong possibility that similar 

ores occur in the almost identical geologic setting 

along trend in Scotland and northern England. Similarly, if continental drift and ocean-floor spreading 

is a valid concept, Newfoundland should have many 

more lead-zinc-silver massive sulfides than have 

already been found. Boulders of massive sulfide ore 

are common in the glacial drift derived from the 

interior of the island. 

The work of Hewett and his associates (Hewett, 

1968; Hewett and others, 1965; Hewett and Radtke, 

1967) on primary epithermal manganese-calcite and 

manganese-silver deposits has indicated the likelihood of finding silver ores under many of the western (and some Appalachian) epithermal manganese 

oxide deposits. Similarly the Walton, Nova Scotia, 

barite deposits change to silver-copper-barite ores at 

depth. This change indicates that all eastern Triassic barite, as well as all copper and manganese 

deposits in the United States, should be reexamined 

with a similar possibility in mind. 

Another potential source of silver and base metals 

is the mineralized sediments that occur in thermal 

deeps, such as the Red Sea basin (De gens and Ross, 

1969). According to Bischoff and Manheim ( 1969, 

p. 535), the uppermost 10 meters of the Atlantic 

Deep in the Red Sea contains 50 million tons of 

mineral-bearing sediment averaging 1.6 ounces of 

silver, 3.4 percent lead, 1.3 percent copper, and 0.10 

percent zinc. Old basins that had similar hot-spring 

activity, such as the Mississippi River embayment of 

the Coastal Plain and the Salton Sea region in the 

Gulf of California, should be reexamined for possibilities of similar deposits. 

PROBLEMS FOR RESEARCH 

Without question, major new resources of silver 

can be located and developed in the United States if 

the need increases, if prices for silver and other 

metals improve, and if the general industrial climate 

is favorable for the production of silver. The present 

decline in silver production will probably continue 

for years, however, until new, more efficient mining 

methods and cleaner recovery methods are developed. 

The smelters that have closed, or are about to close, 

are old and obsolete, and are almost impossible to 

bring up to present environmental-control standards. 

New wet methods and bacterial recovery methods 

may be part of the answer to cleaner recovery methods, if the silver is recovered along with base metals, 

but some of the answer must be in new smelters in 

which controls for fumes and ash are built in when 

the plant is constructed. A tall stack to catch the 

dust and disperse the fumes is no longer a sufficient 

control. 

The recent emphasis in mining methods has been 

on mass production from huge open pits that are 

largely permanently destructive to large acreages of 

land in the West, even if partly reclaimed. Yet some 

of the largest, most efficient, lowest cost mines in the 

country are underground operations, which if properly planned have much fewer permanent environmental problems. Further improvements and breakthroughs are needed in techniques of underground 

mining, and the surface plants should be made attractive and relatively permanent, as they are in 

most European countries and in Japan. 

The mineralogy and accepted natural occurrences 

of silver should be reevaluated. Silver minerals are 

notably difficult to identify in the field and by the 

. older mineralogic methods. In part, this is because 

they commonly occur in microscopic-size crusts, 

grains, and inclusions. Silver-free and silver-rich 

types of sphalerite, galena, tetrahedrite, and copper 

sulfides look alike. Analysis is commonly the only 

way to determine the presence of silver, and sensitive methods like atomic absorption or the electron 

microprobe must be used to detect trace amounts. 

Traditionally, ores rich in galena, chalcopyrite, 

tetrahedrite, and mixed complex sulfide and sulfosalt 

ores are analyzed for silver, whereas sphalerite, 
600 UNITED STATES MINERAL RESOURCES 

pyrite, smithsonite, and chalcocite ores are not generally so analyzed. Silver-rich sphalerite is mined 

in southeast Missouri and in the Nigadoo mine in 

the Bathurst district of New Brunswick; silver-rich 

chalcocite is mined at White Pine, Mich., and is common in the sandstone chalcocite ores of Connecticut 

and near Walton, Nova Scotia. Silver-rich pyrite was 

thrown on the dumps of the Milan massive sulfide 

mine in New Hampshire; silver-rich smithsonite 

ores were found in several districts in Colorado, 

Utah, Nevada, and California, but the silver was 

seldom recovered because the silver content was not 

recognized. Analyses for silver should be made in 

these and in many other common minerals from the 

waste material in old mining districts as well as in 

all new discoveries. 

Minerals bearing silver, such as the manganese 

oxides, or chlorides, iodides, and bromides, have been 

automatically classed as supergene minerals wherever found. Hewett (1968) has shown that hypogene silver-manganese oxide minerals are common 

at one locality, and they have been identified elsewhere in the West (Hildebrand, 1967). Cerargyrite, 

embolite, and other silver halides theoretically could 

be deposited as hypogene minerals as well as supergene; these minerals are notably difficult to identify. 

They might occur in closed lake basins where chloride brines are present to precipitate silver from silver-bearing hot-spring solutions, such as those found 

at the edge of the Salton Sea in southern California. 

As the lead·-zinc industry becomes increasingly 

dependent on eastern low-cost silver-lean lead and 

zinc, silver production will probably depend increasingly on copper-silver deposits of the several types 

and upon silver-rich ores in which silver is the main 

product. With the gap increasing between silver 

production and consumption, another search for epithermal silver deposits is probably warranted, using 

the newly developed geochemical and geophysical 

prospecting techniques. 

The recovery of more byproducts will help support production of marginal ores. Valuable elements 

now wasted, such as manganese, bismuth, germanium, tellurium, and tin, as well as silver might 

be recovered by new and better metallurgical 

techniques. 

SELECTED REFERENCES 

Ageton, R. W., 1970, Silver, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 723-737. 

Anderson, C. A., 1969, Massive sulfide deposits and volcanism: Eeon. Geology, v. 64, no. 2, p. 129-146. 

Anderson, C. A., and Creasey, S. C., 1958, Geology and ore 

deposits of the Jerome area, Yavapai County, Arizona: 

U.S. Geol. Survey Prof. Paper 308, 185 p. 

Anderson, E. C., 1957, The metal resources of New Mexico 

and their economic features through 1954 : New Mexico 

Bur. Mines and Mineral Resources Bull. 39, 183 p. 

Baehau, Christian, 1971, Essai de typologie quantitative des 

gisements de plomb et de zinc avec Ia repartition de 

l'argent: Bur. Recherche de Geol. et Mineralogie, thesis, 

Univ. de Lausanne, Faeulte des Sci. 116 p. 

Banistu, D' Arey, and Knostman, R. W., 1969, Silver in the 

United States: U.S. Bur. Mines Inf. Cire. 8427. 

Barnes, M. P., and Simos, J. G., 1968, Ore deposits of the 

Park City district with a contribution on the M.ayflower 

lode, in Ridge, J. D., ed., Ore deposits of the United 

States 1933-1967, Graton-Sales Volume, v. 2: Am. Inst. 

Mining, Metall., and Petroleum Engineers, p. 1102-1126. 

Bastin, E. S., 1922, Bonanza ores of the Comstock lode, 

Virginia City, Nevada: U.S. Geol. Survey Bull. 735, p. 

41-63. 

Bateman, A.M., and McLaughlin, D. H., 1932, Geology of the 

ore deposits of Kennecott, Alaska: Eoon. Geology, v. 27, 

no. 2, p. 291-306. 

Beeker, G. F., 1882, Geology of the Comstock lode and 

Washoe district: U.S. Geol. Survey Mon. 3, 422 p. 

Bischoff, J. L., and Manheim, F. T., 1969, Economic potential 

of the Red Sea heavy metal deposits, in Degens, E. T ., 

and Ross, D. A., eds., Hot brines and recent heavy metal 

deposits in the Red Sea: New York, Springer-Verlag, 

p. 535-541. 

Boutwell, J. M., 1933, Excursion 4, Park City mining district: Internat. Geol. Cong. Guidebook 17, p. 69-81. 

Boyle, R. W., 1963, The geochemistry of silver and its deposits: Canada Geol. Survey Bull. 160. 

-- 1972, The geology, geochemistry, and origin of the 

barite, manganese, and lead-zinc-copper-silver deposits 

of the W alton-Cheverie area, Nova Scotia: Canada Geol. 

Survey Bull. 166, 181 p. 

Bradbury, J. C., 1961, Mineralogy and the question of zoning, 

northwestern Illinois zinc-lead district: Econ. Geology, 

v. 56, no. 1, p. 132-148. 

Brown, J. S., 1970, Mississippi Valley type lead-zinc ores: 

Mineralium deposita, v. 5, p. 103-119. 

Burbank, W. S., and Luedke, R. G., 1968, Geology and ore 

deposits of the western San Juan Mountains, Colorado, 

in Ridge, J. D., ed., Ore deposits of the United States 

1933-1967, Graton Sales Volume, v. 1: Am. Inst. Mining, 

Metall., and Petroleum Engineers, p. 714-733. 

Butler, B. S., 1913, Geology and ore deposits of the San 

Francisco and adjacent districts, Utah: U.S. Geol. Survey Prof. Paper 80, 212 p. 

Cannon, R. S., Jr., Pierce, A. P., Antweiler, J. C., and Buck, 

K. L., 1961, The data of lead isotope geology related to 

problems of ore genesis: Econ. Geology, v. 56, no. 1, p. 

1-38. 

Clark, L. D., and Miller, F. K., 1968, Preliminary geologic 

map of the Chewelah Mountain quadrangle, Stevens 

County, Washington: Washington Div. Mines and 

Geology, Geol. Map GM-5. 

Cox, M. W., 1968, Van Stone mine area (le·ad-zine), Stevens 

County, Washington, in Ridge, J. E., ed., Ore deposits 

of the United States 1933-1967, Graton-Sales Volume, 

v. 2: Am. Inst. Mining, Metall., and Petroleum Engineers, p. 1511-1519. 

Creasey, S. C., and Granger, A. E., 1953, Geologie map of 

the Lake Valley manganese district, Sierra County, New 
SILVER 601 

Mexico: U.S. Geol. Survey Mineral Inv. Field Studies 

Map MF-9. 

Degens, E. T ., and Ross, D. A., eds., 1969, Hot brines and 

recent heavy metal deposits in the Red Sea: New York, 

Springer-Verlag, 600 p. 

Dings, M. G., and Whitebread, D. H., 1965, Geology and ore 

deposits of the Metaline zinc-lead district, Pend Oreille 

County, Washington: U.S. Geol. Survey Prof. Paper 

489, 109 p. 

Domaas, F. B., associate ed., 1969, Kidd Creek-a huge 

mining success in Ontario: Eng. and Mining Jour., v. 

170,no.4,p. 87-108. 

Drewes, Harald, 1967, Geology of the Connors Pass quadrangle, Schell Creek Range, east-central Nevada: U.S. 

Geol. Survey Prof. Paper 557, 93 p. 

Dutton, C. E., and Bradley, R. E., 1970, Lithologic, geophysical, and mineral commodity maps of Precambrian rocks 

in Wisconsin: U.S. Geol. Survey Misc. Geologic lnv. 

Map 1-631. 

Edwards, A. B., 1953, Geology of Australian ore deposits: 

Empire Mining and Metall. Cong., 5th, Australia and 

New Zealand, v. 1. 

Emmons, W. H., 1906, The Cashin mine, Montrose County, 

Colorado: U.S. Geol. Survey Bull. 285, p. 125-128. 

Ensign, C. 0., Jr., White, W. S., J. C., Patrick, J. L., Leone, 

R. J., Hathaway, D. J., Trammell, J. W., Fritts, J. J., 

and Wright, T. L., 1968, Copper deposits in the Nonesuch Shale, White Pine, Michigan, in Ridge, J. D., ed., 

Ore deposits of the United States 1933-1967, GratonSales Volume, v. 1: Am. Inst. Mining, Metall., and 

Petroleum Engineers, p. 461-488. 

Fischer, R. P., 1937, Sedimentary deposits of copper, vanadium-uranium, and silver in southwestern United States: 

Econ. Geology, v. 32, no. 7, p. 906-951. 

Fryklund, V. C., Jr., 1964, Ore deposits of the Coeur d'Alene 

district, Shoshone County, Idaho: U.S. Geol. Survey 

Prof. Paper 445, 103 p. 

Garmoe, W. J., and Erickson, A. J., Jr., 1968, Ore depos·its 

of the Park City district, in Park City district, Utah: 

Utah Geol. Soc., Guidebook to the Geology of Utah, no. 

22, p. 30-39. 

Gianella, V. P., 1936, Geology of Silver City district and the 

southern portion of the Comstock lode, Nevada: Nevada 

Univ. Bull. v. 30, no. 9, 105 p. 

Gilluly, James, 1932, Geology and ore deposits of the Stockton and Fairfield quadrangles, Utah: U.S. Geol. Survey 

Prof. Paper 173, 107 p. 

Granger, H. C., and Warren, C. G., 1969, Unstable sulfur 

compounds and the origin of roll-type uranium deposits: 

Econ. Geology, v. 64, no. 2, p. 160-171. 

Hall, W. E., 1971, Minor element content of the sulfide minerals, Darwin lead-silver-zinc mine, Inyo County, California: Soc. Mining Geol. Japan, Spec. Issue 2, p. 119-

126. 

Hall, W. E., and Heyl, A. V., 1968, Distribution of minor 

elements in ore and host rock, Illinois-Kentucky fluorite 

district and Upper Mississippi Valley zinc-lead district: 

Econ. Geology, v. 63, no. 6, p. 655-670. 

Hall, W. E., and MacKevett, E. M., Jr., 1962, Geology and 

ore deposits of the Darwin Quadrangle, Inyo County, 

California: U.S. Geol. Survey Prof. Paper 368, 87 p. 

Hammer, D. F., and Peterson, D. W., 1968, Geology of the 

Magma mine area, Arizona, in Ridge, J. D., ed., Ore deposits of the United States 1933-1967, Graton-Sales 

Volume, v. 2: Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 1282-1310. 

Harrison, J. E., 1972, Precambrian Belt basin of northwestern United States-Its geometry, sedimentation, and 

copper occurrences: Geol. Soc. America Bull. v. 83, no. 

5, p. 1215-1240. 

Hewett, D. F., 1964, Veins of hypogene manganese oxide 

minerals in the southwestern United States: Econ. 

Geology, v. 59, no. 8, p. 1429-1472. 

--- 1968, Silver in veins of hypogene manganese oxides: 

U.S. Geol. Survey Circ. 553, 9 p. 

--- 1972, Manganite, hausmannite, braunite-Features, 

modes of origin: Econ. Geology, v. 67, no. 1, p. 83-102. 

Hewett, D. F., Fleischer, Michael, and Conklin, Nancy, 1963, 

Deposits of the manganese oxides-Sup·plement: Econ. 

Geology, v. 58, no. 1, p. 1-51. 

Hewett, D. F., and Radtke, A. S., 1967, Silver-bearing black 

calcite in western mining districts: Econ. Geology, v. 62, 

no.1,p. 1-21. 

Hewett, D. F., Radtke, A. S., and Taylor, Charles, 1965, Black 

calcite--A source of silver?: Mining Cong. Jour., v. 51, 

no. 6, p. 78. 

Heyl, A. V., 1969, Some aspects of genesis of zinc-lead-baritefluorite deposits in the Mississippi Valley, U.S.A., in Applied earth science: Inst. Mining and Metall., Sec. B 

Trans., v. 78, no. 4, p. B148-B160. 

Heyl, A. V., Jr., and Bozion, C. N., 1971, Some little-known 

types of mas·sive sulfide deposits in the Appalachian region, U.S.A.: Soc. Mining Geol. Japan, Spec. Issue 3, 

p. 52-59. 

Hildebrand, F. A., 1967, Silver-bearing manganese oxide at 

Silver Cliffs, Colo., in Geological Survey research 1967: 

U.S. Geol. Survey Prof. Paper 575-A, p. A6. 

Hosted, J. 0., and Wright, L. B., 1923, Geology of the Homestake ore bodies and the Lead area of South Dakota: 

Eng. and Mining Jour.-Press, v. 115, nos. 18 and 19, p. 

783-799,836-843. 

Hoyt, C. D., 1971, Silver, in Minerals yearbook 1969, v. 1, 2, 

Metals, minerals, and fuels: U.S. Bur. Mines, p. 997-

1010. 

Hulin, C. D., 1925, Geology and ore deposits of the Randsburg quadrangle, Oalifornia: California State Mining 

Bur. Bull. 95, 152 p. 

Jicha, H. L., Jr., 1954, Geology and mineral deposits of Lake 

Valley quadrangle, Grant, Luna, and Sierra Counties, 

New Mexico: New Mexico Bur. Mines and Mineral Resources Bull. 37, 93 p. 

Jones, W. A., (and others), 1953, Geology and ore deposits 

of the Porcupine mining district, Ontario, in Geol. Soc. 

America, Guidebook Toronto Field Trip, no. 9, 31 p. 

Kesten, S. N., 1970, The Van Stone mine, Stevens County, 

Washington, in Weissenborn, A. E., ed., Lead-zinc deposits in the Kootenay Arc, northeastern Washington 

and adjacent British Columbia: Washington Div. Mines 

and Geology Bull. 61, p. 123. 

Kiilsgaard, T. H., Hayes, W. C., and Heyl, A. V., 1967, Lead 

zinc, in Mineral and water resources of Missouri: U.S. 

90th Cong., 1st sess., Senate Doc. 19, p. 41-72. 

Kinkel, A. R., Jr., 1967, The Ore Knob copper deposit, North 

Carolina, and other massive sulfide deposits of the Ap-

.palachians: U.S. Geol. Survey Prof. Paper 558, 58 p. 

Kinkel, A. R., Jr., and Albers, J. P., 1951, Geology of the 

massive sulfide deposits at Iron Mountain, Shasta County, Calif.: California Div. Mines Spec. Rept. 14, 19 p. 
602 UNITED STATES MINERAL RESOURCES 

Kinkel, A. R., Jr., and Hall, W. E., 1952, Geology of the 

Mammoth mine, Shasta County, Calif.: Oalifornia Div. 

Mines Spec. Rept. 28, 15 p. 

Kinkel, A. R., Jr., Hall, W. E., and Albers, J. P., 1956, 

Geology and base-metal deposits of West Shasta copperzinc district, Shasta County, California: U.S. Geol. Survey Prof. Paper 285, 153 p. 

Knopf, Adolf, 1929, The Mother Lode system of California: 

U.S. Geol. Survey Prof. Paper 157, 88 p. 

Lindgren, Waldemar, 1933, Mineral deposits, 4th ed.: New 

York, McGraw-Hill, 930 p. 

Lindgren, Waldemar, and Loughlin, G. F., 1919, Geology and 

ore deposits of the Tintic mining district: U.S. Geol. 

Survey Prof. Paper 107, 282 p. 

Lindstrom, Philip, 1971, How about silver?: Mining World, 

v.24,no.9,p. 18-21. 

--- 1971, Silver, production and markets: Western Miner, 

p. 42-45. 

Lovering, T. S., and Goddard, E. N., 19·50, Geology and ore 

deposits of the Front Range, Colorado: U.S. Geol. Survey Prof. Paper 223, 319 p. 

Malakhov, A. A., 1969, Bismuth and antimony in galenas 

as indicators of some conditions of ore formation: 

Geokhimiya, no. 11, p. 1283-1296. (Translated from 

Russian.) 

McConnel, R. H., and Anderson, R. A., 1968, The Metaline 

district, Washington, in Ridge, J. D., ed., Ore deposits 

of the United States 1933-1967, Graton-Sales Volume, 

v. 2: Am. Inst. Mining, Metall., and Petroleum Engineers, p. 1460-1480. 

McKnight, E. T., and Fischer, R. P., 1970, Geology and ore 

deposits of the Picher Field, Oklahoma and K·ansas: 

U.S. Geol. Survey Prof. Paper 588, 165 p. 

Mertie, J. B., Jr., 1940, Placer gold in Alaska: Washington 

Acad. Sci. Jour., v. 30, no. 3, p. 93-124. 

Meyer, Charles, Shea, E. P., Goliard, C. C., Jr., Zeihen, L. 

G., Guilbert, J. M., Miller, R. N., McAleer, J. F., Broy, 

G. P., Ingersoll, R. G., Jr., Burns, G. J., and Wigal, 

Thomas, 1968, Ore deposits at Butte, Montana, in Ridge, 

J. D., ed., Ore deposits of the United States 1933-1967, 

Graton-Sales Volume, v. 2: Am. Inst. Mining, Metall., 

and Petroleum Engineers, p. 1373-1416. 

Morris, H. T., and Lovering, T. S., 1952, Supergene and 

hydrothermal dispersion of heavy metals in wall rocks 

near ore bodies, Tintic district, Utah: Econ. Geology, 

v. 47, no. 7, p. 685-716. 

Nolan, T. B., 19·35, The Gold Hill mining district, Utah: 

U.S. Geol. Survey Prof. Paper 177, 172 p. 

Park, C. F., Jr., and Cannon, R. S., Jr., 1943, Geology and 

ore deposits of the Metaline quadrangle, Washington: 

U.S. Geol. Survey Prof. Paper 202, 81 p. 

Parker, R. C., 1967, Composition of the earth's crust, Chap. 

D of Data of geochemistry, 6th ed.: U.S. Geol. Survey 

Prof. Paper 440-D, 17 p. 

Proctor, P. D., 1953, Geology of the Silver Reef (Harrisburg) 

mining district, Washington County, Utah: Utah Geol. 

and Mineralog. Survey Bull. 44, 169 p. 

Radabaugh, R. E., Merchant, J. S., and Brown, J. M., 1968, 

Geology and ore deposits of the Gilman (Red Cliff, 

Battle Mountain) district, Eagle County, Colorado, in 

Ridge, J. D., ed., Ore deposits of the United States 1933-

1967, Graton-Sales Volume, v. 1: Am. Inst. Mining, 

Metall., and Petroleum Engineers, p. 641-664. 

Radtke, A. S., Taylor, C. M., and Hewett, D. F., 1967, 

Aurorite, argentian todorokite, and hydrous silver-bearing lead manganese oxide: Econ. Geology, v. 62, no. 2, 

p. 186-206. 

Ridge, J. D., ed., 1968, Ore deposits of the United States 

1933-1967, Graton-Sales Volume: Am. Inst. Mining, 

Metall., and Petroleum Engineers, 1880 p. 

Ross, C. P., 19·53, The geology and ore deposits of the Reese 

River district, Lander County, Nevada: U.S. Geol. 

Survey Bull. 997, 132 p. 

Ryan, J. P., 1965, Silver, in Mineral facts and problems: U.S. 

Bur. Mines Bull. 630, p. 809-821. 

Salsbury, M. H., Kerns, W. H., Fulkerson, F. B., and 

Branner, G. C., Marketing ores and concentrates of gold, 

silver, copper, lead, and zinc in the United States: U.S. 

Bur. Mines Inf. Circ. 8207, 150 p. 

Schmidt-Fellner, A., 1972, Silver: Eng. and Mining Jour., 

v. 173, no. 3, p. 165-166 and 181. 

Sinclair, A. J., 1966, Anomalous leads from the Kootenay 

arc, British Columbia, in A symposium on the tectonic 

history and mineral deposits of the western Cordillera, 

Vancouver, B. C. 1964: Canadian Inst. Mining and 

Metall. Spec. Volume 8, p. 249-262. 

Smith, R. M., 1970, Treasure Hill reinterpreted: Econ. 

Geol~,v. 65,no. 5,p. 538-540. 

Steven, T. A., 1968, Ore deposits in the central San Juan 

Mountains, Colorado, in Ridge, J. D., ed., Ore deposits 

of the United States 1933-1967, Graton-Sales Volume, 

v. 1: Am. lnst. Mining, Metall., and Petroleum Engineers, p. 706-713. 

Steven, T. A., and Ratte, J. C., 1965, Geology and structural 

control of ore deposition in the Creede district, San 

Juan Mountains, Colorado: U.S. Geol. Survey Prof. 

Paper 487,87 p. 

Taylor, C. M., and Radtke, A. S., 1969, Micromineralogy of 

silver-bearing sphalerite from Flat River, Missouri: 

Econ. Geology, v. 64, no. 3, p. 306-318. 

Thompson, G. A., 1956, Geology of the Virginia City quadrangle, Nevada: U.S. Geol. Survey Bull. 1042-C, p. 45-

77. 

Thomson, J. E., 1950, Geology of the main ore zone at Kirkland Lake-introduction and general description: 

Ontario Dept. Mines Ann. Rept. 1948, v. 57, pt. 5, p. 

55-103. 

Titley, S. R., and Hicks, G. L., eds., 1966, Geology of the 

porphyry copper deposits, southwestern North America: 

Tucson, Arizona Univ. Press, 287 p. 

Tucker, W. B., 1935, Mining activity at Soledad Mountain 

and Middle Buttes, Mojave mining district, Kern County, 

Californi•a: California Jour. Mines and Geology, v. 31, 

no. 4, p. 465-485. 

Tweto, Ogden, 1968, Geologic setting and interrelationships 

of mineral deposits in the mountain province of Colorado 

and south-central Wyoming, in Ridge, J. D., ed., Ore 

deposits of the United States 1933-1967, Graton-Sales 

Volume, v. 1: Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 551-588. 

U.S. Bureau of Mines, 1932-70, Minerals yearbook annual 

public·ations for the years 1931-69 Washington, U.S. 

Govt. Printing Office. 

Van Hook, H. J., 1960, The ternary system Ag2S-Bi2Ss-PbS: 

Econ. Geology, v. 55, no. 9, p. 759-788. 

Vinogradov, A. P., 1962, Average contents of chemical elements in the principal types of igneous rocks of the 

earth's crust: Geochemistry, no. 7, p. 641-664. 
SILVER 603 

Von Rahden, H. V. R., 1965, Apparent fineness values of gold 

from two Witwatersrand gold mines: Econ. Geology, v. 

60, no. 5, p. 980-997. 

Weissenborn, A. E., 1966. Silver, lead, and zinc, in Mineral 

and water resources of Washington: U.S. 89th Cong., 2d 

sess., Comm. Print, p. 125-141. 

Wernick, J. H., 1960, Constitution of the AgSbS:r-PbS, 

AgBiS:r-PbS, and AgBiS:r-AgBiSe systems: Am. Mineralogist, v. 45, p. 591-598. 

White, D. E., Anderson, E. T., and Grubbs, D. K., 1963, Geothermal brine well-Mile-deep hole may top ore-bearing 

magmatic water and rocks undergoing metamorphism: 

Science, v. 139, p. 919-922. 

White, W. S., 1968, The native-copper deposits of northern 

Michigan, in Ridge, J. D., ed., Ore deposits of the United 

States 1933-1967, Graton-Sales Volume, v. 1: Am. Inst. 

Mining, Metall., and Petroleum Engineers, p. 303-325. 

Wright, L. A., and others, 1953, Mines and mineral deposits 

of San Bernardino County, California: California Jour. 

Mines and Geol-ogy, v. 49, no. 1-2, p. 49-192. 

UNITED STATES MINERAL RESOURCES 

SULFUR 

By ALFRED J. BoDEN Los 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

Exploitation -------------------------------------

Geologic environment ---------------------------- Geochemistry _______________________________ _ 

The inorganic cycle ----------------------

The organic cycle ------------------------

Atmospheric circulation ------------------

Deposits and recoverable accumulations --------

Inorganic sulfur -------------------------

Volcanic deposits --------------------

Hydrothermal sulfide deposits ---------

Gypsum -----------------------------

Organic sulfur -------------------------- Elemental sulfur deposits ----------------

Gulf coast --------------------------

VVest Texas ------------------------- Sulfur-forming reactions -------------

Sulfur accumulations in hydrocarbons -----

Sulfur accumulations in coal --------------

Resources --------------------------------------- The United States ---------------------------

Recovery --------------------------------

Canada and ~exico --------------------------

Other countries ------------------------------ Prospecting for elemental sulfur deposits ----------

Problems for research ---------------------------

References --------------------------------------

FIGURES 

67. Graph showing total sulfur production and pr(\-

duction, imports, and exports of elemental 

sulfur of the United States, 1900-70 -------

68. Graph showing production of sulfur contained 

in pyrites, recovered from petroleum and 

natural gas, and recovered from base-metal 

ores, 1900-70 ----------------------------

Page 

605 

605 

606 

607 

607 

607 

608 

609 

609 

609 

609 

609 

610 

610 

610 

610 

611 

612 

612 

613 

613 

613 

615 

615 

616 

617 

617 

617 

Page 

607 

608 

TABLES 

Page 

126. Identified, hypothetical, and speculative sulfur 

resources of the United States ------------- 613 

127. Sulfur resources of Canada and ~exico ----- 614 

ABSTR:ACT OF CONCLUSIONS 

Sulfur, an element in wide industrial use, currently is 

mined or recovered in the United States from elemental sulfur deposits associated with evaporites, from sulfur-bearing 

petroleum and natural gas, and from sulfide ores. The element also occurs as a constituent in bedded gypsum and 

anhydrite, coal, tar sands, and oil shale, as well as in 

volcanic deposists, none of which is being used at present 

as a domestic source of sulfur. Reserves are appreciable and 

resources are vast, not only in the United States but in 

many other parts of the world. 

Elemental sulfur is formed as a product of anaerobic 

bacterial activity wherever both sulfate ions and organic 

material are abund•ant; therefore, areas of potential sulfur 

discovery include anhydrite units in any petroliferous 

evaporite basins. ~ost accumulations of petroleum and 

natural gas high in sulfur content also are found in evaporite basins. Sulfide ores, in contrast, occur in a wide variety 

of rocks in all parts of the world. Volcanic sulfur occurs 

mostly in the circum-Pacific belt, but it also has been found 

in volcanoes extending from the ~editerranean to the Himalaya ~ountains. 

~ost countries contain sulfur-bearing accumulations in one 

form or another, but few contain large deposits of elemental 

sulfur. The extraction of sulfur from such accumulations in 

any given country depends largely upon recovery costs, 

which must be competitive with the prevailing world price 

of elemental sulfur. 

INTRODUCTION 

Sulfur, a soft yellow mineral that melts at ll3°C, 

has broad industrial use. Most sulfur is used in the 

manufacture of sulphuric acid, and only a relatively 

small amount is used in elemental form, as sulfur 

dioxide, or as carbon disulfide. The world's sulfur 

U.S. GEOL. SURVEY PROF. PAPER 820 

605 
606 UNITED S,TATES MINERAL RESOURCES 

reserves and resources are irregularly distributed; 

the commodity, therefore, moves in large tonnages 

in international trade (Ambrose, 1965; Lewis, 1970; 

Lundy, 1949; and Fogarty and Mollison, 1960). 

In approximate order of increasing cost of mining 

or recovery, the following raw materials provide 

most of the world's sulfur and sulfuric acid supply: 

1. Elemental sulfur deposits in evaporite rocks. 

2. Hydrogen sulfide contained in sour natural 

gas. 

3. Organic sulfur compounds contained in 

petroleum. 

4. Massive deposits of pyrite. 

5. Elemental sulfur deposits in volcanic rocks. 

6. Ores of metallic sulfide minerals ( Cu, Zn, Pb, 

Ni, Mo). 

Additional large resources of sulfur occur in the following minerals or compounds : 

7. Beds of the calcium sulfate minerals, anhydrite and gypsum. 

8. Organic sulfur compounds in tar sands. 

9. Organic sulfur compounds and pyrite in coal 

beds. 

10. Organic sulfur compounds and pyrite in oil 

shale and shale-rich organic matter. 

Approximately one-quarter each comes from elemental sulfur, massive pyrite, and sulfur in oil and 

gas. Only the elemental deposits in evaporites or in 

volcanic rocks are mined solely for their contained 

sulfur. Pyrite deposits can be mined for their sulfur, 

as the chief product or as coproducts or byproducts 

from the production of iron and other metals. Sulfur 

is recoverable from all the other types of deposits 

only as a byproduct or coproduct that can be used 

directly in acid manufacture or converted to elemental sulfur for shipment elsewhere. Sulfur contained in the last seven types of raw materials, however, commonly is lost to the atmosphere either during processing or through use of the primary 

product. 

Sulfur and its chemical compounds are used in 

virtually every segment of the world's industrial and 

agricultural complexes, as shown by the almost perfect parallelism between the Federal Reserve Board 

index of U.S. industrial production and the sulfur 

demand index (Landsberg and others, 1963). Principal uses in the United States are in the manufacture of soluble fertilizers, synthetic fibers, plastics, 

papers, pigments, explosives, petroleum products, 

drugs, and insecticides ; sulfur compounds also are 

used to leach ores and recover metals, vulcanize rubber, and condition soils. The physical properties of 

elemental sulfur, including its low thermal conductivity, high strength, and resistance to acids, suggest 

potential uses as a versatile construction material 

(Vroom, 1971). Sulfur should be applied to soils in 

far greater quantities in many parts of the world to 

balance chronic sulfur deficiencies. 

Sulfuric acid can be replaced by other common 

acids in many processes, but its low price makes 

large-scale substitution unlikely. 

The United States has an adequate reserve of lowcost sulfur minerals and compounds and large to 

great resources of moderate- to high-cost sulfurbearing compounds. In recent years, production, at 

about 9 million long tons, has exceeded consumption, 

the balance accumulating in producers stocks. Since 

World War II, the amount of sulfur rescovered from 

natural gas and petroleum has been increasing 

steadily, and present efforts to maintain cleaner air 

will result in even greater recovery of sulfur from 

all sources. 

EXPLOITATION 

It is anticipated that U.S. consumption of sulfur 

will grow at a rate of 4-5 percent per year, reaching 

perhaps 30 million tons annually by the year 2000, 

or about three times the present rate (Hazleton, 

1970; Lewis, 1970). 

The earliest demand for sulfur in the United 

States was met by imports of pyrite for acid manufacture and of Sicilian sulfur for nonacid uses. 

Shortly after 1900, Frasch mining of caprock sulfur 

deposits became commercially successful; and in the 

following years, plants also were constructed to 

recover sulfuric acid from pyrite deposits and basemetal ores. The United States became self-sufficient 

in sulfur supply during World War I. Between World 

War I and World War II, most domestic sulfuricacid plants were converted to use elemental sulfur 

as primary feed. Following World War II, sulfur 

was recovered in increasingly larger amounts from 

sour natural gas and from petroleum. Currently, 

base-metals smelters are installing units to recover 

larger amounts of sulfuric acid from flue gases. (See 

figs. 67 and 68.) 

The United States was the major exporter of elemental sulfur to the free world from World War I 

until the 1950's, when new sources were developed 

elsewhere: caprock deposits in Mexico (1954), elemental sulfur recovered from sour natural gas in 

France (1958) and in Canada (1960), and sulfur 

deposits in evaporites in Poland (1968). Since 1960, 

sulfur or sulfuric acid has been recovered in increasing amounts from new units in oil refineries in all 

parts of the world. The United States consequently 

lost its position as the sole exporter of elemental 
SULFUR 

10.----------.----------~----------~--------~----------~----------~---------. 

9~--~~~--~~~~~~ 

8 t-t------t------t------t------~f------..1/~ A . I L 

~ : ~-----------+--------+----------+--------+----------J~~---}- \/ v I 

(!) Total U.S.~ / \ I 

~ production , 1 \ '\ / 

..J ~ - ..... J \ o/ \ ! 

0 5 /·/'-1 Elemental.-\~/ ~.j-------1 en 1 sulfur 

Z I production 

Q 4~--------+----------+-----------+----------+----~·'---1----------~--------~ j 1\ I ,J 

~ 1~v/ ~ L_\ l-------1-----------~--------_, / \ fl --t- I 

/~ ~/1/\ \//1 v (\ A I I \ I 

2~--------+--------~~--.~\~ ~I ! __ ~_· ~---------+----------~---+--~~ 

~~~JMl ---;)// Exports, 1 r--./v ---~ / \/ \/- elemental~~ 1',.-

t-------------+---11~\.__..,_ ~ /f ' v r/ 1 - ~ 

sulfur I --~..L I 

II\......._, I ~~ Imports, ,.i"" WI , __ .. / elemental-y ... - I 

I / sulfur 1 

0 - / - ___./ ,.;_/ 

3 

1900 1910 1920 1930 1940 1950 1960 1970 

607 

FIGURE 67.-Total sulfur production and production, imports, and exports of elemental sulfur of the United States, 1900-

70. Data from U.S. Bureau of Mines. 

sulfur and faced increasing competition for its domestic markets from Mexican and Canadian suppliers. By 1968, U.S. exports and imports were about in 

balance. 

The present excess of free-world productive capacity probably will be balanced in about a decade by 

the steady rise in the demand for sulfur. During this 

period, however, competition for markets will be 

intense and sulfur prices will be low. After a balance 

is achieved, sulfur will be recovered in larger 

amounts from sources now classed as subeconomic, 

including perhaps those in coal, gypsum, tar sands, 

and oil shale. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

The average sulfur content of igneous rocks is 520 

ppm (parts per million), 13th in order of abundance 

among all elements. In molten rock, sulfur occurs as 

the sulfide ion and combines most readily with metallie ions, but it also combines with available hydrogen 

or oxygen. Sedimentary racks contain larger 

amounts of sulfur: sandstone averages 2,000 ppm, 

shale 2,600 ppm, and limestone 1,100 ppm. In the 

presence of abundant oxygen, the sulfide ion is oxidized to the sulfate ion, in which form it is contained 

in the hydrosphere. Sulfur is necessary in trace 

amounts to all plant and animal life and is constantly being absorbed and released during biologic 

cycles. Sulfur thus circulates in both inorganic and 

organic cycles and is both ubiquitous and mobile in 

all parts of the lithosphere, hydrosphere, atmosphere, and biosphere (Rankama and Sahama, 1950). 

THE INORGANIC CYCLE 

Sulfur is brought into the earth's crust by molten 

rock rising from the mantle and combines near the 

surface with iron and other metallic elements to 

form the common sulfide minerals or, if oxygen is 

available, to form sulfates. Where molten rock 

reaches the surface to erupt volcanically, its sulfur 
608 UNITED STATES MINERAL RESOURCES 

(/) 

z 

0 

1.6 

1.4 

1.2 

.,_ 1 0 

(!) • 

z 

0 

..J 

~ 0.8 

Cl) 

z 

0 

:::i 0.6 ..J 

~ 

0.4 

~I 

Sulfur recovered 

from pyrite\ 

Sulfur recovered ~-

from~ ~,.-v ~ores r\ __ , 

~ 

I 1/ 

I 

I 

/ 

,/. 

I 

I 

I 

I 

Sulfur recovered I 

from hydrocarbc rs)/ 

I 

II 

j 

I 

/ 

I 

I 

I A/ / 

/ ........ _)'J ..... 

r ~-v- v/ '\ \_..../ 

~ ~ / 

~__,.--- I' ,-.-- I 

-~ ~----~ 

0.2 

0 

1900 1920 1930 1940 1950 1960 1970 

FIGURE 68.-Production of sulfur contained in pyrites, recovered from petroleum and natural gas, and recovered from basemetal ores, United States, 1900-70. Data from U.S. Bureau of Mines. 

may ( 1) combine with hydrogen and be expelled 

into the atmosphere as hydrogen sulfide gas, (2) 

combine with oxygen and be expelled as sulfur dioxide gas (the two gases can react and produce elemental sulfur), or (3) combine with metals and 

form metallic sulfides. 

Exposure to atmospheric oxygen breaks down 

most sulfide minerals to relatively soluble sulfate 

minerals. Ground and surface waters leach the sulfate minerals and carry their salts to the sea, where 

the sulfate ion has accumulated in a concentration of 

2,650ppm. 

Where restricted arms of the sea spread over continents during periods of aridity, sea water evaporates and becomes increasingly saline, resulting in 

successive precipitation of calcium carbonate as 

limestone, calcium sulfate as gypsum, and sodium 

chloride as common salt. Owing to seasonal and 

longer range climatic variations, alternating layers 

of the different evaporites may precipitate. Vast 

amounts of calcium sulfate as gypsum have been 

withdrawn from the sea in the course of geologic 

times (Borchert and Muir, 1964). 

THE ORGANIC CYCLE 

Sulfur is an essential constituent of certain proteins and fats needed by plants and animals; plants 

utilize it as sulfate ions from soils, ground water, or 

sea water. Animals obtain their sulfur from water 

or by consuming plants or other animals. Upon death 

and decay, the reduced sulfur is released; on land it 

enters soils or humic compounds or is emitted into 

the atmosphere; in seas, it reenters the sea water. 

The cycle is balanced in the sea, but on the land, 

sulfur is lost both to the atmosphere and to the sea 

through the leaching of soil and humins by surface 

waters. 

Bacteria use sulfur compounds in metabolism; 

some bacteria reduce sulfates, others oxidize sulfides 

either to sulfates or to elemental sulfur, and still 

others oxidize elemental sulfur (Davis, 1967). In 

aerated environments the bacterial sulfur cycle tends 

to be complete and balanced, but in anaerobic environments the reactions result in only reduction of 

sulfate ions. The reduction of sulfate is accomplished 

largely by one species, Desulfovibrio desulfricans, an 

anaerobe found in stagnant marsh waters, tidal flats, 

oxygen-deficient bottom waters of seas and oceans 

and in ground water, oil field brines, and petroleum, 

to depths as great as 5,000 feet below land surfaces. 

This anaerobe is limited to environments having 

temperatures less than 165°F. 

Desulfovibrio uses dead organic matter, be it 
SULFUR 609 

plant, wood, or animal, and both liquid and gaseous 

hydrocarbons as a source of carbon and hydrogen; 

at the same time it uses sulfate ions to provide it 

with oxygen and sulfur. It expels waste carbon dioxide and hydrogen sulfide. It thus converts sulfate 

waters to carbonate waters and should calcium be 

available a biogenic variety of limestone may be 

generated. The hydrogen sulfide can leak into the 

atmosphere, be retained in rocks at depth, combine 

with organic material to form organic sulfur molecules, or combine with available metallic ions to form 

sulfide minerals. 

The activities of sulfate-reducing bacteria are 

probably responsible for most of the iron sulfide 

minerals in sedimentary rocks of all ages. They 

probably generated most of the sulfur compounds in 

petroleum, asphalt, kerogen, and coal, and the hydrogen sulfide contained in sour natural gas (Thode and 

Monster, 1965). The tonnage of sulfur in the world's 

beds of gypsum and anhydrite may be exceeded by 

the total tonnage of sulfur in other sedimentary 

rocks and fossil fuels. The hydrogen sulfide now being generated by sulfate reducers provides a major 

source of the sulfur compounds emitted into the 

atmosphere. 

Biogenic hydrogen sulfide also has formed several 

types of ore deposits. It has been suggested that 

bacteria generated the hydrogen sulfide that reduced 

soluble salts and precipitated minable concentrations 

of uranium. Where these bacteria had a source of 

hydrocarbons and ample anhydrite rock, they created masses of biogenic limestone impregnated with 

elemental sulfur, which form the principal elemental 

sulfur deposits of the world. 

ATMOSPHERIC CIRCULATION 

Sulfur compounds are constantly circulating in 

lithosphere, the biosphere, the atmosphere, and the 

hydrosphere. Some 550 million tons of sulfur compounds, calculated as sulfate-ion equivalent, are 

thought to be emitted into the atmosphere and returned to the earth's surface annually (Kellogg and 

others, 1972). A comparable tonnage of dissolved 

sulfate is carried annually by the world's rivers to 

the oceans. 

More than half the sulfur emitted into the atmosphere results from biologic decay, and about onequarter each is attributed to windblown sea salt 

and to manmade pollution ; only some 2 million tons 

of sulfate-ion equivalent is attributed to volcanic 

activity. About 60 percent of the total emission, some 

330 million tons, is thought to fall back on the 

world's landmasses. Atmospheric fallout of sulfur 

compounds replenishes the sulfur supply needed by 

plants, but it settles unevenly on landmasses. The 

available statistics also indicate that substantially 

more sulfur is being carried by streams and rivers 

to the seas than is being replenished by atmospheric 

fallout. Soils in many parts of the world thus are 

being depleted of the sulfur needed to sustain optimum plant growth. 

DEPOSITS AND RECOVERABLE ACCUMULATIONS 

INORGANIC SULFUR 

Excluding the very small tonnage of elemental sulfur extracted from volcanic deposits and an even 

smaller tonnage extracted for only a brief period 

from one gypsum deposit, sulfur in deposits of inorganic origin has been recovered in the United 

States only as a byproduct or a coproduct of the 

mining and smelting of the sulfide ores of metallic 

minerals. 

VOLCANIC DEPOSITS 

Gases and acids escaping from volcanoes convert 

silicate minerals of lava and ash to clay, silica, and 

sulfate minerals. Any reaction between escaping 

hydrogen sulfide and sulfur dioxide produces elemental sulfur, which is deposited as replacements, 

impregnations, and vein fillings in such altered material. The resulting sulfur-bearing masses are apt 

to be irregular in size, shape, and grade. The gangue 

of altered material must be removed, a relatively 

costly process , so volcanic sulfur is mined in the 

United States only when the price of sulfur is high. 

Pyrite is generated in volcanic vents by a reaction 

between hydrogen sulfide and iron. Pyrite may be 

deposited as disseminations or masses in the altered 

rock and is minable as a sulfur ore in some parts of 

the world. 

Elemental sulfur also is deposited by hot 

springs, probably the result of near-surface oxidation of hydrogen sulfide emissions. Gangue consists 

of altered rock and various minerals precipitated by 

the springs. Most such deposits are low in grade and 

have rarely been mined. 

Volcanic deposits of sulfur are known in California, western Nevada, and Alaska, and hot-spring 

deposits occur in various Western States. 

HYDROTHERMAL SULFIDE DEPOSITS 

When molten rocks crystallize at depth, some of 

their metals and sulfur are concentrated in hydrothermal solutions and ultimately deposited as disseminations, masses, or veins either within or outside the cooling masses, thus forming sulfide ore deposits of copper, molybdenum, lead, zinc, and other 

metals. During the smelting of such ores, the sulfide 

is converted into gaseous sulfur dioxide which, with 
610 UNITED STATES MINERAL RESOURCES 

appropriate smelting techniques and installations, 

can be recovered and converted to sulfuric acid or, 

at a greater cost, to elemental sulfur. Sulfide ore 

--deposits thus are actual or potential sources of recoverable sulfur compounds. 

The geology of metallic-sulfide deposits is described in other chapters of this volume, but mention 

should be made here of masses of pyrite and pyrrhotite deposited from hydrothermal solutions, generally containing only small amounts of metals other 

than iron. In some parts of the world, such iron sulfides are roasted to provide sulfur dioxide used in 

sulfuric-acid manufacture; iron and any accompanying metals may be recovered as coproducts. Only one 

such mass of pyrite in the United States (Ducktown,. 

Tenn.) is exploited as a large supplier of sulfuric 

acid, but it contains sufficient values of copper and 

other metals to be classed as a base-metal deposit 

(Kinkel and others, 1968). The resources of sulfur 

contained in other masses of pyrite that have little 

or no base metals occur mainly in Eastern States, 

less commonly in Western States, and in Alaska (Espenshade and Broedel, 1952). The deposits are relatively large and probably will be utilized after lower 

cost sources of sulfur are exhausted. 

GYPSUM 

Gypsum deposited during the evaporation of sea 

water forms beds that may contain layers of calcite 

or dolomite, and may contain beds of clay, silt, or 

sand derived from surrounding arid lands. When 

buried, gypsum (CaS04•2H20) loses its water of 

crystallization and is converted to anhydrite 

(CaS04). In contact with ground water, anhydrite 

reconverts to gypsum. The transformation has been 

noted at depths ranging from several tens of feet to 

about 1,000 feet. 

Gypsum and anhydrite are widespread in the 

United States. (See chapter on "Evaporites and 

Brines".) Reserves and resources are vast, but it is 

not known what fraction is sufficiently pure to be 

used as a raw material for production of sulfuric 

acid or elemental sulfur. The one plant designed to 

produce elemental sulfur from gypsum, near Van 

Horn, Tex., was supplied from a large reserve of 

very pure gypsum, virtually free of interbedded carbonates and clastic material. The explored block, still 

nearly intact, is in the upper part of the Castile Gypsum, a unit of Permian age in the Delaware Basin of 

west Texas (Jones, 1954; and Adams, 1969). 

The cost of converting gypsum or anhydrite to sulfuric acid or elemental sulfur is well above the cost 

of mining elemental sulfur or recovering sulfur from 

hydrocarbons or metallic ores. It can nonetheless be 

a future source of our sulfur supply after lower cost 

raw materials now available are mined out. 

ORGANIC SULFUR 

The conversion of sulfate ions to sulfide ions by 

anaerobic bacteria produced the chief sources of sulfur now minable at lowest cost, particularly the elemental sulfur deposits in accumulations of evaporite, 

the organic sulfur contained in petroleum, and the 

hydrogen sulfide associated with sour natural gas. 

Even greater tonnages of sulfur compounds of the 

same derivation are locked in coal, oil shale, and tar 

sands (Theobald and others, 1972; and Duncan and 

Swanson, 1965) . 

ELEMENTAL SULFUR DEPOSITS 

Bacterial attack on anhydrite produces lenses of 

limestone impregnated with elemental sulfur. Such 

deposits are formed in two stages: the first resulting 

in the formation of masses of porous, vuggy mediumgrained gray limestone and the second in the formation of coarsely crystalline white calcite and elemental sulfur deposited within the pores and openings in the limestone (Hanna, 1934). Very small 

amounts of selenite, barite, and celestite may be 

deposited later. The reactions theoretically produce 

1 ton of sulfur for every 3 tons of calcite, or an ore 

containing nearly 25 percent sulfur, but no limestone lenses contain this theoretical amount because 

hydrogen sulfide is so highly mobile and tends to 

escape from its zone of generation. The grade, porosity, and permeability of deposits differ over a substantial range. 

Elemental sulfur deposits of this type are associated with anhydrite caprocks of probable Cenozoic 

age overlying salt diapirs in the gulf coast and also 

occur in widespread sequences of anhydrite of Permian age in west Texas. In both areas, deposits range 

from small pockets containing several thousand tons 

to large accumulations containing tens of millions of 

tons of sulfur. The Boling Dome deposit, Texas, the 

largest in the gulf coast, underlies an area of 1,500 

acres and has yielded 70 million tons of sulfur to 

date; the Culbertson property deposit, the largest in 

west Texas, is said to contain about 80 million tons 

of sulfur underlying an area of 1,200 acres. The 

depth of minable sulfur deposits has ranged from 

400 to 3,200 feet. Some 30 deposits are known in the 

gulf coast, many of them mined out, and perhaps 10 

have been found as the result of recent exploration 

in west Texas (Hawkins and Jirik, 1966; Ellison, 

1971; and Zimmerman and Thomas, 1969). Twelve 

such deposits currently being mined supply about 75 

percent of the sulfur produced in the United States. 
SULFUR 611 

A specific sequence of geologic events must take 

place, and specific geologic conditions must be met 

before sulfur deposits can form; should any one element be missing, sulfur mineralization will not occur. Both in the gulf coast and in west Texas, the 

basic conditions needed for sulfur mineralization are 

( 1) solution of evaporite minerals, forming porous 

ground, (2) migration of petroleum into the prepared ground, (3) generation and retention of hydrogen sulfide gas within the formation, and ( 4) 

oxidation of the hydrogen sulfide to elemental sulfur. The required geologic steps differ between the 

gulf coast and west Texas, as described in the following paragraphs. 

GULF COAST 

Preparation of the ground in the gulf coast entailed formation of lenses of anyhdrite over the 

upper surfaces of salt diapirs, which consist of impure rock salt containing only several percent anhydrite. Ground water dissolved the salt at the upper 

surfaces of the diapiric masses, permitting residual 

accmumlation and subsequent lithification of the less 

soluble anhydrite. Anhydrite accumulated in appreciable thicknesses only where aquifers intersected 

the apexes of salt diapirs and where the rate of upward flow of rock salt was equalled by the rate of 

salt solution, providing stable surfaces upon which 

the anhydrite could accumulate. Conditions favoring caprock development differed widely, inasmuch 

as anhydrite lenses range in thickness from a few 

feet to more than 1,000 feet; more than one-third of 

the 190 diapirs in the gulf coast are overlain by less 

than 200 feet of anhydrite, thicknesses inadequate 

to permit formation of sulfur deposits of commercial size (Taylor, 1938: Goldman, 1952; Murray, 

1961; Halbouty, 1967; Bodenlos, 1970). 

During their intrusion, salt masses dragged surrounding strata upward and produced structures 

favoring migration of hydrocarbons toward the 

diapirs. Hydrocarbons entered most, but not all, 

caprocks partly because oil sands do not underlie the 

entire diapiric province, and partly because petroleum was too tightly held in peripheral traps to have 

escaped in quantity. As a result, biogenic limestone 

produced by bacterial attack overlies anhydrite as 

lenses ranging from a few to hundreds of feet in 

thickness. 

Hydrogen sulfide was retained and oxidized to elemental sulfur only where host caprocks were overlain by thick beds of impermeable clay or mudstone. 

Caprocks barren of sulfur are overlain either by 

thin beds of clay or directly by porous sandstone, 

which permitted hydrogen sulfide to escape. 

The incidence of sulfur deposits in the gulf coast 

indicates how infrequently all steps leading to their 

generation are met. Of the 190 salt diapirs in the 

gulf coast, the caprocks of only 18 contained ore 

bodies yielding more than 1 million tons of sulfur; 

another three or bodies opened more recently undoubtedly contain ore bodies of substantial size. 

Although the structures produced by intrusion of 

salt diapirs favor migration of ground water and 

hydrocarbons toward the salt masses, the critical 

factors' needed to produce sulfur deposits seem to be 

stratigraphic-permeable strata are needed up to 

the apexes of diapers to permit the flow of fluids, 

whereas impermeable strata are needed above caprocks to retain hydrogen sulfide. It seems unlikely 

that sulfur deposits can form in stratigraphic sequences uniformly coarse grained or uniformly fine 

grained and impermeable. 

WEST TEXAS 

The sulfur deposits in west Texas occur in thick 

extensive units of bedded anhydrite of evaporite 

origin that underlie the entire Delaware Basin and 

adjacent platforms. As bedded anhydrite is one of 

the least permeable of rocks, greatly inhibiting 

movement of ground water and hydrocarbons, 

ground was prepared for sulfur mineralization by a 

sequence of events differing from that in the gulf 

coast. Evidently all deposits in west Texas were 

formed in lenses or chimneys of anhydrite collapse 

breccia, so it seems probable that ground water 

moved upward along joints or faults from underlying aquifers and dissolved anhydrite at the base of 

the evaporite units. This solution process produced 

an underground, cavernous karst system, into which 

overlying anhydrite collapsed. Hydrocarbons ascending along the same fissures from underlying oil 

sands then penetrated the breccias, and the broken 

anhydrite was altered through bacterial activity to 

a fine- to medium-grained gray limestone. Thereafter, white calcite and elemental sulfur were deposited in the breccia voids and in the pores of the 

gray limestone (Davis and Kirkland, 1970; Hinds 

and Cunningham, 1970; McNeal and Hemenway, 

1972). 

Some mineralized breccia masses are confined to 

the lowermost parts of the anhydrite units, but 

others extend as chimneys completely through them, 

impinging against overlying carbonate or clastic 

beds. Chimneys breaking through anhydrite units 

exposed at the surface produced swallow holes that 

diverted surface drainage, and the voids in the breccia became clogged with very fine to coarse-grained 

alluvium. In the west Texas deposits, the seals 
612 UNITED STATES MINERAL RESOURCES 

needed to retain hydrogen sulfide in breccia masses 

until the gas was oxidized to elemental sulfur differ 

from deposit to deposit, consisting either of overlying anhydrite, overlying impervious strata, or of 

alluvial clay and silt within the breccia masses. Notwithstanding, many limestone breccia masses are 

barren of sulfur, indicating that they were not 

sealed against loss of hydrogen sulfide gas. 

The location of west Texas sulfur deposits seems 

to have been controlled largely by structure. Deposits lying near the southwest side of the Central 

Basin Platform occur in anticlinal highs, whereas 

those in the western part of the Delaware Basin 

seem to occur along or near lineaments that may 

represent faults of small displacement. Notwithstanding, no clear-cut controls have been found that 

satisfactorily explain the location of the huge deposit in Culbertson County. 

SULFUR-FORMING REACTIONS 

Regarding the chemical reactions that produced 

the deposits, it is generally agreed that anaerobic 

bacteria reduced the sulfate ions of anhydrite. Views 

differ, however, on the manner in which hydrogen 

sulfide is oxidized to elemental sulfur. Three possible reactions have been proposed: (1) inorganic reaction between the gas and calcium sulfate molecules: (2) oxidation of the gas by free oxygen carried in ground water; and (3) oxidation of the gas 

by sulfide-oxidizing bacteria (Feely and Kulp, 1957 ; 

Davis and others, 1970; and Ivanov, 1968). With 

particular regard to sulfur deposits in the gulf 

coast, the second proposal seems to be unfeasible 

because ground waters there are nearly devoid of 

free oxygen ; the required volumes of water would 

flush out the accumulated hydrogen sulfide before 

oxidizing any appreciable amount of that gas. Nor 

does it seem likely that aerobic, sulfur-oxidizing 

bacteria could coexist with anaerobic bacteria in 

the oxygen-deficient, hydrogen sulfide-saturated 

solutions contained in cap rock. It thus seems that 

an inorganic reaction between hydrogen sulfide and 

calcium sulfate would be the most likely to occur. 

Although this reaction can proceed thermodynamically only at slow rates, it produces both sulfur and 

a small amount of calcite, which in fact are deposited together during the second stage of mineralization. 

SULFUR ACCUMULATIONS IN HYDROCARBO~S 

Bacterial attack upon sulfate ions in stagnant 

waters produces hydrogen sulfide that can combine 

with organic matter in the associated sediments; 

the sulfur-bearing molecules can then be incorporrated into hydrocarbons formed from such parent 

material. Most crude oils, tar sands, asphalts, and 

organic-rich shales therefore contain sulfur even if 

only in low concentrations. The sulfur content of 

petroleum can range from traces to as much as 14 

percent, although crude oil containing more than 5 

percent sulfur is relatively uncommon. Two-thirds 

of the petroleum produced in the United States contains less than 1 percent sulfur, and only about 

one-tenth contains more than 2 percent sulfur (McKinney and Shelton, 1967). 

The geologic conditions leading to the wide range 

of sulfur in hydrocarbons are not well known. It 

can be assumed that coarser grained sediments will 

retain less hydrogen sulfide than finer grained sediments. The concentration of sulfate ions available 

for reduction also can differ, being lowest in seas 

near the mouths of large rivers and highest in basins 

undergoing evaporation. Still another variable is the 

iron content of source beds and connate waters, 

which will determine how much hydrogen sulfi4e will 

be withdrawn from the system as iron sulfide. All 

these variables probably played a part in determining how much sulfur was incorporated into the 

parent material of any given crude oil. 

As petroleum matured and migrated, heavier 

sulfur-bearing molecules could have been filtered 

out and hydrogen sulfide perhaps was generated as 

constituent molecules were reconstituted, both 

mechanisms leading to a reduction of sulfur content 

of the liquid fraction. Variations in sulfur content 

also have been noted within given oil pools, but in 

the aggregate all such changes can only modify the 

amount of sulfur originally accumulating with the 

parent organic material. 

The sulfur in tar sands is probably higher than 

the original concentration if it can be assumed that 

liquid and gaseous fractions containing less sulfur 

migrated elsewhere, whereas the sulfur in shales 

rich in organic matter must be that generated in 

place. 

Theories of origin for hydrogen sulfide in natural 

gas are diverse. Hydrogen sulfide and methane can 

be generated simultaneously in fresh-water swamps, 

for example, and perhaps both gases were distilled 

together as sulfur-bearing petroleum underwent 

chemical reconstitution at high pressures and temperatures. Sulfate ground water coming in contact 

with petroleum activates anaerobic bacteria and results in generation of hydrogen sulfide, and the 

same reactions can take place where petroleum is 

trapped under beds of anhydrite. Although most 

sour natural gas contains only a few percent hydrogen sulfide, some contains more than 80 percent of 
SULFUR 613 

that gas, undoubtedly the result of long-extended 

contact between petroleum and anhydrite. 

SULFUR ACCUMULATIONS IN COAL 

Reactions already described also occurred in 

swamps sufficiently stagnant to preserve as peat the 

organic matter contained in plants and trees, at the 

original sites of our present lignite and coal beds. 

Anaeorbic bacteria reduced any available sulfate 

ions and emitted hydrogen sulfide, which combined 

with organic material or was deposited as pyrite. 

Sulfur from this source augmented the traces of 

sulfur originally contained in the plant matter. In 

coal low in sulfur, the element largely is in organic 

molecules, whereas in coal high in sulfur, the element largely is in pyrite or marcasite. U.S. coals 

contain sulfur that ranges in amount from a trace 

to 7 percent (DeCarlo and others, 1966; Walker and 

Hartner, 1966). 

Most swamps in which coal formed in the United 

States lay close to sea level , so the slightest changes 

in levels produced widespread marint! transgressions 

or regressions, either bringing in an abundant supply of sulfate ions in sea water or bringing in fresh 

waters from land. Williams and Keith (1963) suggested that swamps transgressed by seas resulted 

in coals higher in sulfur than those which lay in 

areas of subsequent marine regression. Because sea 

water contains very little iron, only 2-20 parts per 

billion, marine transgression in itself cannot produce 

coal with high pyrite content; sources of iron from 

hinterlands behind coal-forming swamps also seem 

to be needed. It appears to be more than coincidental 

that most of our high-sulfur coals, those of Pennsylvanian age in the Illinois and midcontinent fields, 

were closest geographically to the iron-formations 

and iron deposits of Wisconsin, Michigan, and Minnesota. Conversely, coals lowest in sulfur content, 

those in our western fields, seem to have been deposited in environments in which seas were excluded 

by offshore bars and concurrently were at some distance from any terrane high in iron. 

RESOURCES 

The world's total resources of s·ulfur are vast, but 

only a fraction is minable or recoverable now at 

competitive prices (Hazleton, 1970; Ambrose, 1965; 

Lewis, 1970; British Sulphur Corp., 1966; President's 

Materials Policy Comm., 1952; Little, 1966). The 

previous estimates of the world's sulfur resources 

have differed widely for many reasons, including the 

factors discussed in the previous section on the 

geology of the deposits, and because of the lack of 

data on ore deposits in the remoter parts of the 

world. 

Estimates of identified, hypothetical, and speculative resources of sulfur in various types of deposits in the United States, Canada, and Mexico are 

compiled in tables 126 and 127. The compilation of 

the data for the United States is more detailed than 

that for Canada and Mexico. Only the more economically important accumulations of sulfur elsewhere in the world are cited in the following discussion. 

THE UNITED STATES 

The identified sulfur resources of the United 

States are divided into three categories: (1) recoverable, those accumulations that can be mined 

or recovered at prices less than $25 per long ton, 

TABLE 126.-Identified 1

, hypothetical', and speculative 1 sulfur resources of the United States 

[In millions of long tons; +.some resources, but amount not estimated] 

Identified resources Hypo- Speeula· Source Recover- Para- Sub- thetieal tive Total 

able mareinal mareinal Subtotal resources resources 

1. Elemental sulfur deposits in evaporites 150 40 10 200 100 150 450 

2. Hydrogen sulfide in sour natural gas --------- 10 5 15 '185 200 

3. Organic sulfur in petroleum ----------------- 10 25 220 255 '1,000 1,255 4. Pyrite deposits ----------------------------- 10 30 60 100 20 20 140 

5. Elemental sulfur in volcanic rocks ----------- 10 20 30 + + 30 

6. Sulfur contained in metallic sulfides ---------- 20 40 40 100 100 200 400 

7. Gypsum ----------------------------------- 150 7,050 7,200 1,800 9,000 8. Organic sulfur in tar sands ----------------- 10 10 10 

9. Organic sulfur and pyrites in coal ----------- 21,400 21,400 '19,600 41,000 10. Organic sulfur and pyrites in oil shale and 

shale rich in organic matter --------------- + + + + 81,000 

Total ------------------------------------ 200 300 28,810 29,310 22,805 370 133,485 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may not be profitably recoverable with existing technology and economic conditions. . . 2 Hypothetical resources: Undis<'overed mineral deposits, whether of rE:coverable or subeconomic grade, that are geologically predictable as exisbne 

in known districts. 3 Speculative resources: Undiscovered mineral deposits, whether of recoverable or subeconomic grade, that may exist in unknown districts or in un- recognized or unconventional form. 

' Includes some speculative resources. 
614 UNITED STATES MINERAL RESOURCES 

TABLE 127.-Sulfur resources of Canada and Me~ico 

[In millions of Ion&' tons 1 

Source 

Canada 

Hypothetieal2 and 

Mexico 

Hypo thetical• and 

Identified speeula- Total speculareBources t tive 3 re- Identified tive a re- sources resources 1 sourcEB Total 

1. Elemental sulfur deposits in evaporites ------- 80 50 130 

2. Hydrogen sulfide in sour natural gas --------- 140 185 

3. Organic sulfur in petroleum ----------------- 5 (') 

325 

5 

50 

5 (') 5 6 4. Pyrite deposits ----------------------------- 25 25 50 5 25 25 

5. Elemental sulfur in volcanic rocks ----------- 5 5 

6. Sulfur cont•ained in metallic sulfides ---------- 35 100 135 25 40 65 

7. Gypsum ----------------------------------- (a) e> 

8. Organic sulfur in tar sands ------------------ 40 1,800 

(6) (11) 

9. Organic sulfur and pyrites in coal ----------- ( (') (') 11 ) (8) 

10. Or.ganic sul.fur in oil shale and shale rich 

1,840 

m orgamc matter ------------------------ (11) (II) 

----------------------------------------------------- Total ------------------------------------ 245 2,110 2,355 140 115 255 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals 

may or may. not be profitably recoverable with existing technology and economic conditions. • 2 Hypoth-:tt~l resources: Undiscovered mineral deposits, whether of recoverable or sbueconomic grade, that are geologically predictable as existing m known districts. 3 Speculative resources: Undiscovered mineral deposits, whether of recoverable or subeconomie grade, that may exist in unknown districts or in 

unrecognized or unconventional form. 

'Not known; resources probably small. 5 Including pyrite in base-metal deposits. 11 Not known; resources probably lara-e. 

f.o.b. gulf coast ports; (2) paramarginal, those available at prices between $25 and $35; and (3) submarginal, those estimated to be available at prices 

higher than $35 per ton. Hypothetical and speculative resources are comparable to those are defined 

throughout this volume. Comments on each of the 

principal accumulations follow. 

1. Identified resources of elemental sulfur in 

evaporites cannot be estimated accurately because operating companies do not release reserve 

data. It is judged, however, that some 200 million tons of sulfur remains in the known deposits, 100 million tons each in the gulf coast 

and in the west Texas occurrences. Of the total 2. 

of 200 million tons, some 40 million tons is 

thought to be minable only when the price of 

sulfur approaches $35 a ton, and another 10 

million tons is thought to be minable only when 

the price exceeds $35 a ton. Another 100 million 

tons of sulfur, which may be found in west 

Texas, is shown in table 126 as part of hypothetical resources. 

In the United States, anhydrite occurs in 

many petroliferous sedimentary basins, includ- 3. 

ing the Michigan, Williston, Paradox, and Permian basins; anhydrite also occurs at great 

depths in the gulf coast geosyncline. Elemental 

sulfur deposits could have formed in all or any 

of these areas, and one can speculate that at 

least 100 million tons of sulfur ultimately will 

be discovered in them. 

The possibilities for further discovery of elemental sulfur deposits in anhydrite caprocks 

overlying salt diapirs are somewhat more limited because of the diverse geological processes 

and conditions required in their generation. Salt 

diapirs are common structures known on all 

continents and continental shelves in many parts 

of the world (McKelvey and Wang, 1970) , yet 

only in the gulf coast of the United States and 

Mexico have deposits of commercial size been 

found in caprocks. It can be anticipated that 

several more sulfur deposits, containing perhaps 50 million tons of sulfur, will be found in 

the offshore extension of the gulf coast belt of 

the United States. 

Hydrogen sulfide in natural gas yielded about 

30,000 tons of sulfur per trillion cubic feet of 

produced gas in 1971. Using this ratio, some 

15 million tons of sulfur is estimated to remain 

in the identified resources of natural gas (Theobald and others, 1972). Another 65 million 

tons may occur in recoverable undiscovered 

resources, and 120 million tons, in the submarginal undiscovered resources (combined as 

185 tons of hypothetical resources in table 126). 

Each billion barrels of petroleum in the United 

States reserve contains nearly 1 million tons of 

sulfur (U.S. Bur. Mines, 1971), a ratio which 

indicates that some 10 million tons of sulfur is 

contained in the recoverable petroleum and 245 

million tons in the petroleum that can only be 

extracted with difficulty. Another 1 billion tons 

of sulfur may occur in the undiscovered petroleum resoruces, of which 20 percent is a recoverable resource and 80 percent is a subeconomic 
4. 

5. 

6. 

7. 

8. 

9. 

SULFUR 615 

resource. The preceding calculations were restricted to the petroleum in the conterminous 

United States, inasmuch as petroleum under the 

continental shelves and in Alaska is so low in 

sulfur that a resource in such oil should not 

be postulated. 

Of the 100 million tons of sulfur contained in 

the identified resource of pyrite, 10 million tons 

arbitrarily is assigned to the recoverable fraction, and the balance, to the subeconomic resources. The President's Materials Policy Commission (1952) considered that some 30 million 

tons of sulfur, contained as pyritic gangue in 

base-metal ores, constitutes a resource. Although much of that pyrite will be rejected 

with tailings in nonrecoverable form, it is 

judged that 20 million tons of this sulfur eventually could be recovered, and this amount is 

included with the submarginal resources of 

pyrite deposits shown in table 126. Another 40 

million tons may occur in extensions of known 

districts and in areas as yet unexplored. 

The 30 million tons of subeconomic resources of 

sulfur in volcanic rocks cited for many years is 

probably still a reasonable estimate. Hypothetical and speculative resources are judged to be 

very small. 

Resources of sulfur contained in sulfide ores 

of base metals are calculated from estimates 

presented in other chapters of this volume. A 

nominal recoverable resource of 20 million tons 

is predicated on recovery efforts prior to present statutory requirements for cleaner air. 

Much of the subeconomic identified resources, 

some 80 million tons, will be recovered regardless of cost because of antipollution regulations. 

Gypsum resources are nearly 50 billion tons, 

the sulfur content of which constitutes an 

identified resource of about 7 billion tons, and 

a hypothetical resource of nearly 2 billion tons. 

Of this amount, 150 million tons of very pure 

gypsum has been blocked out as raw material 

for sulfur production. At present this constitutes a paramarginal resource. Huge anhydrite 

resources, many times greater than gypsum 

resources, are not included in the accompanying 

tabulation. 

Tar sands are said to contain an identified submarginal resource of 10 million tons of sulfur. 

The aggregate tonnage of sulfur contained in 

coal is enormous. Resources of all classes are 

estimated to be 41 billion tons, but none is recoverable at present prices of sulfur. In table 

126, the hypothetical sulfur resource in coal is 

predicated on undiscovered coal lying at less 

than 6,000 feet depth. 

10. Shales rich in organic matter, eventually exploitable as sources of liquid or gaseous hydrocarbons, contain at least 1 billion tons of sulfur 

in the oil shale of the northern Rocky Mountains, and 80 billion tons in the black shales of 

Devonian and Mississippian age in the Eastern 

and Central United States. The entire resource 

is subeconomic ; no attempt is made here to 

differentiate between identified and hypothetical 

resources. 

RECOVERY 

Recovery of sulfur from resources depends upon 

the state of the technology, upon the cost of extraction, and now also upon statutory requirements limiting sulfur emissions into the atmosphere. The 

resource data already presented must thus be qualified as follows: 

Frasch mining recovers 75-92 percent of the sulfur contained in the ground, depending on the technological efficiency of the operating companies and 

on the geological characteristics of given ore bodies. 

Recovery of sulfur from natural gas exceeds 95 

percent of the contained hydrogen sulfide, but only 

about 80 percent of the natural gas is recoverable 

from the ground. Recovery of sulfur from petroleum 

has been averaging 15-20 percent, and less than 

half the petroleum in the ground is recoverable under current technology. Recovery of the sulfur contained in pyrites is relatively high and that of sulfur 

in volcanic deposits reasonably high, both probably 

greater than 75 percent. Recovery of the sulfur 

contained in base-metal ores has been relatively low 

in the past, but should increase markedly in the 

coming years. Experience in the extraction of sulfur 

from gypsum, tar sands, and oil shale is yet too 

limited to indicate how efficient recovery will be. 

Little sulfur is recovered from petroleum in the 

United States. The low sulfur content of most U.S. 

oils has made extraction of sulfur during petroleum 

refining seem neither necessary nor economically 

important. The same is true with other deposits of 

hydrocarbons and with low-sulfur coal. About 30 

percent of the bituminous coal of the United States 

contains less than 1 percent sulfur. 

CANADA AND MEXICO 

Canada and Mexico ar·e among the leading producers of elemental sulfur. Canada recovers the 

element from hydrogen sulfide in natural gas and 

Mexico from caprock deposits. The sulfur in Canadian natural gas is an indicated resource of 140 
616 UNITED STATES MINERAL RESOURCES 

million tons (Cote, 1971), that in Mexican caprocks 

an indicated resource of 80 million tons (table 127). 

Both countries also are well endowed with deposits 

of base-metal sulfides and with bedded gypsum from 

which sulfur can be recovered. Canada also has vast 

resources of tar sands, whose bitumens contain an 

average of 4.5 percent by weight of sulfur, which 

amounts to a multibillion ton resource of sulfur. 

The 40 million tons shown in table 127 as the identified sulfur resources of the Canadian tar sands is 

that sulfur currently available for extraction in 

existing processing facilities. Some petroleum in 

southeastern Mexico contains enough sulfur to warrant its recovery during refining. 

The hypothetical and speculative resource data 

shown in table 127 summarize those resources whose 

discovery can be reasonably expected in known mineral districts and petroliferous areas and in untested 

regions. The postulated resource of 1,800 million tons 

of sulfur in tar sands should perhaps be listed partly 

as a subeconomic identified resource. Speculative resources of sulfur in Mexico include an estimated 50 

million tons of elemental sulfur in caprocks on salt 

diapirs in the southeastern part of the country. 

These deposits will be similar to those known in the 

gulf coast of the United States. 

OTHER COUNTRIES 

Sulfur resources outside of North America also 

are vast ; apparent reserves totaling nearly 2 billion 

tons have been estimated recently by Lewis (1970). 

Only the most notable concentrations are cited in 

the following brief discussion. 

1. Elemental sulfur deposits containing an identified resource of 100 million tons occur in 

bedded anhydrite of Miocene age in southern 

Poland. The belt of anhydrite extends into the 

U.S.S.R., where other sulfur deposits probably occur. Although the belt in the U.S.S.R. 

is not now petroliferous, hydrocarbons in the 

past evidently leaked upward into it at many 

places. The greatest potential for discovery 

of elemental sulfur outside the United States 

is in the Middle East, where the world's 

greatest accumulations of hydrocarbons coincide with extensive anhydrite beds. In Iraq, 

one deposit of elemental sulfur in anhydrite 

of Miocene age contains an identified resource 

of 200 million tons of sulfur. Most of the 

readily available sulfur in the bedded evaporites of Sicily has been mined. 

The salt diapirs of northern Europe and of 

the Middle East seem to be barren of sulfur 

deposits. Possibilities exist for caprock suifur mineralization in the northern Caspian 

area and northern Siberia in the U.S.S.R., 

perhaps over the diapirs lying under the Persian Gulf and under the North Sea, and over 

those diapers in the Canadian Arctic Islands. 

Neither the Canadian nor the North Sea areas 

would favor low-cost exploitation of any sulfur discovered. 

2. Hydrogen sulfide amenable to extraction from 

sour natural gas is moderately abundant in 

France and in eastern Europe, but the largest 

resource of such sulfur is in the Middle East, 

where about 500 million tons occurs in the 

very large natural gas resources. 

3. The petroleum of the Middle East perhaps contains about 300 million tons of sulfur, and 

that of Venezuela at least 30 million tons. 

4. Resources of sulfur in pyrite deposits are large 

and widespread. At least 500 million tons of 

sulfur occurs in Spanish deposits and perhaps 

an equivalent amount may occur in the pyrite 

deposits elsewhere in Europe. Such resources 

also are abundant in South America, the Middle East, Africa, and Australia. 

5. Elemental sulfur in volcanic rocks in the circumPacific belt provides a resource totaling 100-

200 million tons. Japan and Chile have most 

of these resources. Pyrite in volcanic deposits 

in this region also constitutes a large resource. 

6. Outside North America, at least 200 millon tons 

of sulfur occur in the known base-metal sulfide deposits scattered on all other continents. 

Pyrite included in these ores also constitutes 

an appreciable resource of sulfur. 

7. Anhydrite and gypsum underlie large areas on 

every continent (McKelvey and Wang, 1970) 

and form an almost unlimited resource of 

sulfur. 

8. Tar sands are abundant in Venezuela, but the 

tonnage of their sulfur never has been calculated. 

9. Extrapolating the average sulfur content of 

coal in the United States to that in coal outside North America, it would seem that at 

least 180 billion tons of sulfur occurs in the 

coal on other continents. 

10. Oil shale and shale rich in organic matter seem 

to contain at least as much sulfur as does 

coal ; therefore, the sulfur resources in such 

accumulations outside North America could 

reach several hundred billion tons. 

Lastly, sea water contains sulfate ions in low 
SULFUR 617 

concentrations but provides a virtually unlimited 

sulfur resource. 

In summary, the world position on sulfur resources 

is good and will sustain rates of production many 

times higher than present rates without strain. 

PROSPECTING FOR ELEMENTAL 

SULFUR DEPOSITS 

Most caprock sulfur deposits were discovered 

through wildcat drilling in search for oil, but some 

were found by either wildcat or systematic drilling 

in search for sulfur. Geophysical prospecting to date 

has not been effective in locating sulfur deposits, 

although it can be used to located caprock of unspecified composition. 

It has long been known that on the gulf coast, 

acid soil, known as sour dirt, occurs over known 

caprocks ; such soil is acidified by leakage of hydrogen sulfide from below. This geochemical evidence 

was instrumental in locating several caprock oil 

fields and also provided the first clue to the presence 

of a sulfur deposit in Boling Dome, Tex. (Haynes, 

1942). Acid soil, hydrogen sulfide emissions, and 

sulfuric acid springs also are known in west Texas 

but do not necessarily coincide with underlying sulfur deposits. They cannot be infallible geochemical 

indicators of sulfur deposits simply because they 

show only that hydrogen sulfide was generated, not 

that it was retained and oxidized to sulfur at depth. 

Regional stratigraphic features in the gulf coast 

region and local structural features in the Delaware 

Basin of west Texas could be applied to a greater 

extent in exploration for sulfur. Particularly on the 

outer continental shelf, study of stratigraphy could 

be applied to block out favorable and unfavorable 

areas for generation and retention of hydrogen sulfide within caprocks. Study of faulting in the Delaware Basin may lead to targets overlooked in previous exploration programs. 

PROBLEMS FOR RESEARCH 

Geological problems still to be resolved include 

determination of all the factors leading to the accumulation of sulfur in coal, petroleum, natural gas, 

and shale rich in organic matter. The various hypotheses advanced to date need to be tested and 

evaluated over sufficiently broad areas to determine 

their validity and hence their usefulness in exploring for low-sulfur coal or, if sulfur is being sought, 

for fossil fuels high in that element. 

A related geological problem needing further study 

is the generation in coal mines of sulfuric acid, a 

troublesome pollutant in streams traversing coalmining districts. A fuller understanding of the 

natural processes involved will lead to better methods of controlling acid generation. 

Perhaps more research has been devoted to methods of recovering sulfur or removing it as an unwanted element than to the recovery of any one 

other mineral commodity. The wide variety of raw 

materials now yielding sulfur as a byproduct attests 

to the past successes of these efforts. Research is 

continuing, nevertheless, to reduce the costs or to 

increase the efficiency of sulfur recovery processes 

applying to several of these raw materials. Major 

research efforts now are being directed to the problem of removing sulfur from coal. Techniques are 

being studied for removal of pyrite before ignition 

of the coal, removal of sulfur dioxide from stack 

gases, with or without the recovery of the sulfur itself, and removal and recovery of sulfur from coal as 

it is being gasified or liquified. Until these techniques 

are perfected, much coal must remain in the ground 

because it contains too much sulfur to meet cleanair requirements. 

The present excess sulfur production, particularly 

in Canada, is stimulating research on new uses that 

will exploit the unique physical properties of sulfur. 

The element is remarkably low in thermal and electrical conductivity, completely inert to attack by 

acids, impervious to water, and it has high strength 

at normal ambient temperatures ; it is easily applied 

and workable when plasticized or in molten fortn, and 

it hardens quickly. It thus promises to be a versatile 

construction material. 

REFERENCES 

Adams, J. E., 1969, Semi-cyclicity in the Castile evaporite, 

in Cyclic sedimentation in the Permian Basin-Symposium, Midland, Tex., 1967: West Texas Geol. Soc. Pub. 

69-56, p. 197-203. 

Ambrose, P. M., 1965, Sulfur and pyrites, in Mineral facts 

and problems, 1965 ed.: U.S. Bur. Mines Bull. 630, p. 

901-917. 

Bodenlos, A. J., 1970, Cap-rock development and salt-stock 

movement, in Geology and technology of Gulf Coast 

salt-A symposium: Baton Rouge, School of Geoscience, 

Louisiana State Univ., p. 73-86c. 

Borchert, Hermann, and Muir, R. 0., 1964, Salt depositsThe origin, metamorphism and deformation of evaporites: London, Princeton, N. J., Toronto, D. Van 

Nostrand Co., 338 p. 

British Sulphur Corp., Ltd., 1966, World survey of sulphur 

resources: London, British Sulphur Corp., 135 p. 

Cote, P. R., 1971, Sulphur, in Canadian minerals yearbook, 

1969; Canada Dept. Energy, Mines and Resources 

Mineral Resources Div., Mineral Rept., p. 485-496. 

Davis, J. B., 1967, Petroleum microbiology: Amsterdam, 

London, New York, Elsevier Pub. Co., 604 p. 

Davis, J. B., and Kirkland, D. W., 1970, Native sulfur deposition in the Castile Formation, Culberson County, Texas: 

Econ. Geology, v. 65, no. 2, p. 107-121. 
618 UNITED S.TATES MINERAL RESOURCES 

Davis, J. B. Stanley, J. P., and Custard, H. C., 1970, Evidence against oxidation of hydrogen sulfide by sulfate 

ions to produce elemental sulfur in salt domes: Am. 

Assoc. Petroleum Geologists Bull., v. 54, no. 12, p. 2444-

2447. 

DeCarlo, J. A., Sheridan, E. T., and Murphy, Z. E., 1966, 

Sulfur content of United States coals: U.S. Bur. Mines 

lnf. Girc. 8312, 44 p. 

Duncan, D. C., and Swanson, V. E., 1965, Organic-rich shale 

of the United States and world land areas: U.S. Geol. 

Survey Circ. 523, 30 p. 

Ellison, S. P., Jr., 1971, Sulfur in Texas: Texas Univ. Bur. 

Econ. Geology, Handbook 2, 48 p. 

Espenshade, G. H., and Broedel, C. H., 1952, Annotated 

bibliography and index map of sulfur and deposits in 

the United States and Alaska: U.S. Geol. Survey Circ. 

157, 48 p. 

Feely, H. W., and Kulp, J. L., 1957, Origin of Gulf Coast 

salt-dome sulphur deposits: Am. Assoc. Petroleum 

Geologists Bull., v. 41, no. 8, p. 1802-1853. 

Fogarty, C. F., and Mollison, R. D., 1960, Sulfur and 

pyrites, in Industrial minerals and rocks, 3d ed.: Am. 

Inst. Mining Metall; and Petroleum Engineers, p. 819-

833. 

Goldman, M. I., 1952, Deformation, metamorphism, and mineralization in gypsum-anhydrite cap rock, Sulphur salt 

dome, Louisiana: Geol. Soc. America Mem. 50, 167 p. 

Halbouty, M. T., 1967, Salt domes-Gulf region, United 

States and Mexico: Houston, Tex., Gulf Pub. Co., 425 p. 

Hanna, M. A., 1934, Geology of the Gulf Coast salt domes, 

in Problems of petrol~um geology (Sidney Powers memorial Volume): Tulsa, Okla., Am. Assoc. Petroleum Geologists, p. 629-678. 

Hawkins, M. E., and Jirik, C. J., 1966, Salt domes in Texas, 

Louisiana, Mississippi, Alabama, and offshore tidelands-A survey: U.S. Bur. Mines lnf. Circ. 8313, 78 p. 

Haynes, Williams, 1942, The stone that burns; the story 

of the American sulfur industry: New York, D. Van 

Nostrand Co., 345 p. 

Hazelton, J. E., 1970, The economics of the sulphur industry: 

Baltimore, Md., The Johns Hopkins Press, 172 p. ; published for Resources for the Future, Inc. (Washington, 

D. C.). 

Hinds, J. S., and Cunningham, R. R., 1970, Elemental sulfur 

in Eddy County, New Mexico: U.S. Geol. Survey Circ. 

628, 13 p. 

Ivanov, M. V., 1968, Microbiological processes in the formation of sulfur deposits: Jerusalem, Israel Program for 

Sci. Translations, IPST. no. 1850, 298 p. Pub. for U.S. 

Dept. Agriculture and N atl. Sci. Found. 

Jones, C. L., 1954, The occurrences and distribution of potassium minerals in southeastern New Mexico, in New 

Mexico Geol. Soc. Guidebook, 5th Field Conf., southeastern New Mexico, p. 107-112. 

Kellogg, W. W., Cadle, R. D., Allen, E. R., Lazrus, A. L., 

and Martell, E. A., 1972, The sulfur cycle: Science, v. 

175,no. 4022,p. 587-595. 

Kinkel, A. A., Jr., Feitler, S. A., and Hobbs, R. G., 1968, 

Copper and sulfur, in Mineral resources of the Appalachian region: U.S. Geol. Survey Prof. Paper 580, p. 377-

385. 

Landsberg, H. H., Fischman, L. L., and Fisher, J. L., 1963, 

Resources in America's future--Patterns of requirements and avaHabilities, 1960-2000: Baltimore, Johns 

Hopkins Press, 1017 p.; published for Resources for the 

Future, Inc. (Was·hington, D. C). 

Lewis, R. W., 1970, Sulfur, in Minerals facts and problems, 

1970 ed.: U.S. Bur. Mines Bull. 650, p. 1247-1265. 

Little, Arthur D., Inc., Service to Management Program, 

1966, The Free World sulfur outlook: Cambridge, Mass., 

Arthur D. Little, Inc., 51 p. 

Lundy, W. T., 1949, Sulphur and pyrites, in Industrial minerals and rocks, Am. Inst. Mining Metall. Engineers, p. 

989-1017. 

McKelvey, V. E., and Wang, F. F. H., 1970, World Subsea 

mineral resources, preliminary maps: U.S. Geol. Survey 

Misc. Geol. Inv. Map 1-632. 

McKinney, C. M., and Shelton, E. M., 1967, Sulfur content 

of crude oils of the free world: U.S. Bur. Mines Rept. 

Inv. 7059, 36 p. 

McNeal, R. P., and Hemenway, G. A., 1972, Geology of Fort 

Stockton sulfur mine Pecos County, Texas: Am. Assoc. 

Petroleum Geologists Bull., v. 56, no. 1, p. 26-37. 

Murray, G. E., 1961, Geology of the Atlantic and Gulf Coastal 

province of North America: New York, Harper and 

Brothers, 692 p. 

President's Materials Policy Commission, 1952, Sulfur, in 

Resources for freedom: v. 2, p. 83-87. 

Rankama, Kalervo, and Sahama, Th. G., 1950, Geochemistry: 

Chicago, Univ. Chicago Press, 912 p. 

Taylor, R. E., 1938, Origin of the cap rock of Louisiana salt 

plugs: Louisiana Geol. Survey Geol. Bull. 11, 191 p. 

Theobald, P. K., Schweinfurth, S. P., and Duncan, D. C., 

1972, Energy Resources of the United States: U.S. Geol. 

Survey Circ. 650, 27 p. 

Thode, H. G., and Monster, Jan, 1965, Sulfur-isotope geochemistry of petroleum, evaporites, and ancient seas, 

in Fluids in subsurface environments, a symposium: 

Am. Assoc. Petroleum Geologists Mem. 4, p. 367-377. 

U.S. Bureau of Mines, 1971, Oil availability by sulfur levels: 

U.S. Bur. Mines, prepared for the Environmental Protection Agency, 209 p. 

Vroom, A. H., 1971, Sulphur utilization, a challenge and an 

opportunity, 2d ed.: Natl. Research Council Canada, 

NRC 12241, 80 p. 

Walker, F. E., and Hartner, F. E., 1966, Forms of sulfur in 

U.S. coals: U.S. Bur. Mines lnf. Circ. 8301, 51 p. 

Williams, E. G., and Keith, M. L., 1963, Relationship between 

sulfur in coals and the occurrence of marine roof beds: 

Econ. Geology Bull., v. 58, p. 720-729. 

Zimmerman, J. B., and Thomas, Eugene, 1969, Sulfur in 

West Texas-Its geology and economics: Texas Univ. 

Bur. Econ. Geology Geol. Circ. 69-2, 35 p. 
UNITED STATES MINERAL RESOURCES 

TALC 

By c. ERVIN BROWN 

CONTENTS 

Page 

Abstract of conclusions --------------------------- 619 

Introduction ------------------------------------- 619 

Mineralogy and physical properties ------------ 620 

Uses ---------------------------------------- 620 

Competitive minerals ------------------------- 621 

Exploitation _______________________ -------------- 622 

Byproducts and coproducts -------------------- 622 

Environmental problems ---------------------- 622 

Geologic environment ----------------------------- 623 

Talc from regionally metamorphosed dolomite __ 623 

Talc deposits formed from ultramafic and mafic 

igneous rocks ------------------------------ 623 

Talc deposits formed by contact metamorphism of 

dolomitic sediments ___________ - __ ---- __ ---- 624 

Resources --------------------------------------- 624 

Identified and hypothetical resources ----------- 624 

Speculative resources ------------------------- 624 

Prospecting techniques --------------------------- 625 

Problems for research ---------------------------- 625 

References cited --------------------------------- 625 

FIGURES 

Page 

69. Graph showing production and use of talc and 

soapstone in the United States, 1950-70 ____ 621 

70. Graph showing U.S. consumption of talc, soapstone, and pyrophyllite, 1910-70 ----------- 622 

TABLE 

Page 

128. Talc and soapstone sold or used by producers 

in the United States, by uses -------------- 620 

ABSTRACT OF CONCLUSIO~S 

Talc as mined and used industrially is a rock containing 

a mixture of magnesium-rich silicates and ranging in mineral composition from pure talc to predominant tremolite. 

Other minerals commonly present in talc rock are serpentine, 

diopside, anthophyllite, and chlorite and less abundantly the 

carbonates calcite, dolomite, and magnesite. 

Industrial talc is used in the pulverized form as a ceramic 

base for floor and wall tile; a paint extender; a filler for rubber, paper, plastics, roofing, and many other products; a 

diluent or carrier for pesticides; and a polishing or dusting 

agent. 

Talc is mined from metamorphosed dolomitic and quar~ 

zos,e sedimentary rocks or from hydrothermally altered 

ultramafic and mafic rocks. The main producing areas are in 

the eastern States from New England to Alabama and 

in the west in California, Nevada, Montana, and Texas. 

In 1969 and 1970, total consumption was over a million 

tons-double that of 20 years ago. The projected demand 

for the year 2,000 ranges from 2.28 to 3.36 million tons. 

Resources of talc are large and should be adequate to meet 

this demand, although deposits meeting the rigid chemical 

and physical specifications of some consumer industries are 

relatively scarce. Although all talc mining districts contain known reserves and have a good to excellent potential 

for the discovery of additional reserves, the great bulk of 

reserves are in New York and Vermont. 

Most industrial areas of the United States are fairly 

close to a source of industrial talc, except for the industries 

of the midcontinent. There, shipping charges are a much 

larger part of the cost of talc because most supplies are 

shipped from Montana and Texas. Areas of metamorphic 

rocks in Wisconsin and Michigan could contain talc deposits more favorably located for the midcontinent market. 

INTROUUCTION 

The purposes of this report are to present a current picture of the resources of industrial talc in the 

United States and to assess the potential for additional resources. A talc resource study by Chidester, 

Engel, and Wright (1964) is the latest extensive 

account giving detailed descriptions of many of the 

talc deposits in the United States and a discussion of 

all talc-producing districts. Subsequent studies have 

been published for deposits in Alabama (Neathery, 

1968; Neathery and others, 1967), California 

(Wright, 1968), and New York (Brown, 1969). Bibliographies of talc in the United States are available 

in works of Engel and Wright (1960) and Merrill 

U.S. GEOL. SURVEY PROF. PAPER 820 

619 
620 UNITED STATES MINERAL RESOURCES 

(1963), and a map locating all talc-mining areas was 

published by Chidester and Worthington (1962). 

MINERALOGY AND PHYSICAL PROPERTIES 

Talc is a hydrous magnesium silicate mineral with 

the theoretical formula H2Mg3 (Si03) 4· As used industrially, however, the term "talc" refers to a rock 

composed mainly of magnesium-rich silicate minerals and having the mineral talc as an important 

constituent. Mineral content of industrial talc can 

range from pure talc to predominantly tremolite. 

Minerals other than talc that are most commonly present in industrial tales are serpentine 

(H4Mg3Si09), chlorite (hydrous Mg-Fe-Al silicate), 

tremolite (Ca2Mg5H2(Si03)s), anthophyllite 

( (Mg,Fe) 1 (OH) 2Sis022), and diopside ( CaMg 

(Si03) 2) ; less commonly present are quartz (Si02), 

calcite (CaC03), dolomite (CaMg(C03) 2), and magnesite (MgC03). Pyrophyllite, an aluminum silicate 

(Al2Si4010 (OH) 2) closely related to talc in structure, 

properties, and uses, is generally lumped with talc 

and soapstone in production and consumption statistics, but it is not included in this discussion. 

The constituents of industrial talc differ considerably in physical and mineralogic properties, consequently, rocks having different mineral proportions vary accordingly in their properties. The 

mineral talc is extremely soft and slippery, having 

a hardness of 1 on the Mobs scale; and because of 

a strong basal cleavage, it is flaky. The associated 

tremolite and anthophyllite have a hardness of 5 

to 6 and when ground produce a fibrous powder 

because of their prismatic cleavage. Other minerals, 

such as serpentine, vary in hardness and in shape 

of pulverized particles. Most of the major constituent minerals of industrial talc are chemically inert 

and generally grind to a white powder and have 

high dielectric constants, therefore, these minerals 

naturally occuring in varying proportions produce 

inert light-colored rocks with a range of hardness 

and particle shape when pulverized, making industrial talc an unusually versatile and widely used 

mineral product. 

USES 

Industrial talc is used where certain combinations 

of the following properties are desired : Extreme 

whiteness when powdered or fired, softness or 

smoothness, fibrous or flaky particle shape, various 

degrees of oil absorption, chemical inertness, high 

fusion point, low water absorption and shrinkage 

when fired as a ceramic body, low electrical and 

thermal conductivity, good retention as fillers, and 

ease of grinding to extreme fineness (Industrial 

Minerals, 1968). 

Talc in the form of soapstone has been used since 

prehistoric times for carved cooking utensils ; current uses of talc are intimately tied to the demands 

of a complex industrial society. It is important to 

the manufacturing and building industries, and 

periodic fluctuations in consumption are directly 

related to the economic conditions of those industries. 

Talc is used as a ceramic base material for wall 

and floor tile; as a filler by the plastic, paper, roofing, and rubber, industries; as a paint extender; and 

as an insecticide diluent and carrier. Other special 

uses are diverse, ranging from a polish for rice, 

wood turnings, nails, and white shoes to a dusting 

powder for salami. In the massive form of soapstone, it is cut for laboratory table tops and sinks, 

steel-marking crayons, and blocks for art carvings. 

High-frequency ceramic insulator shapes are machined and fired from another massive variety 

known as block steatite, and block talc is machined 

and fired for burner nozzles. Talc and soapstone 

sold or used in the United States in 1969 and 1970 

are listed by use in table 128. Figure 69 shows conTABLE 128.-Talc and soapstone sold or used by producers in 

the United States, by uses 

[In short tons. From Wells (197G)] 

Use 

Ceramics ______________________ _ 

Insecticides ---------------------

Paint --------------------------- Paper -------------------------- Roofing ------------------------- Rubber ------------------------- Textile ------------------------- Toilet preparations --------------

Other1 -------------------------

Total ---------------------

1969 

245,704 

53,722 

166,170 

54,554 

30,526 

24,464 

7,974 

12,235 

279,168 

874,517 

197'0 

228,595 

33,697 

154,265 

52,328 

44,997 

28,348 

6,187 

13,721 

289,644 

851,782 

1 Includes asphalt filler, crayons, exports, fertilizer, ftoor and wall tile, 

foundry facings, insulated wire and cable, joint cement, plastics, rice 

polishing, and miscellaneous products. 

sumption of talc by the major consuming industries 

during 1950-70. Talc used for ceramic wall tiles 

and extender in paint now accounts for half of the 

annual consumption. The roofing, paper, insecticide, 

and rubber industries together consume an additional quarter, and the many miscellaneous special 

uses account for the remainder. The only recent 

outstanding increase in the consumption of talc is 

in the "other uses" category in figure 69. This curve 

since 1966 shows an exponential growth which I 

attribute to the use of talc as a filler pigment in 

white plastic insulation, containers, and sheeting. 
TALC 621 

fJ) 

z 

0 

._ 

._ 

II 

300 

250 

0 200 J: 

fJ) 

~ 

0 

fJ) 

~ 150 

~ fJ) 

:::::> 

0 

J: 

._ 

100 

50 

1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 

FIGURE 69.-Talc and soapstone produced and used by major consuming industries in the United States, 1950-1970. Other 

uses include asphalt filler, crayons, exports, fertilizer, floor and wall tile, foundry facings, electrical insulation, joint 

cement, plastics, rice polishing, textile coating, toilet preparations, and miscellany. 

The United States has abundant reserves and resources of talc, but is deficient in certain grades 

such as block steatite used for high-frequency insulators, and cosmetic talc. In 1970, imports of talc 

were 29,988 short tons, and exports were about 

105,000 tons. Use of flotation and magnetic separation methods in the processing of talc has made us 

less dependent on imports for cosmetic-grade talc, 

although in 1970 imports of cosmetic-grade talc 

from Italy were markedly increased. Phosphatebonded synthetic "lava" talc and die-formed steatite 

is being increasingly substituted for block steatite 

for ceramic insulator needs; however, a residual 

demand for block steatite for high-frequency insulators will probably continue. 

COMPETITIVE MINERALS 

Many minerals are competitive with talc for 

ceramic and filler uses. Kaolin is commonly used as 

a base for wall tile, but such clay-base tile absorbs 

water and expands causing the glaze to craze (Gaskins, 1952). Addition of a certain amount of talc to 

the base material alleviates this condition and improves translucency and toughness of the tile. Another important competitive use of kaolin is as paper 

filler and coater. Ground limestone is substituted 

for talc as a paint pigment extender, but it is 

reactive and does not have the scaly and fibrous 

particle shape of talc that aids in both coating 

and holding pigment in suspension. Wollastonite 

(CaSiO;{) has most of the good qualities of talc and 

is directly competitive in the ceramic and paint industries (Andrews, 1970). However, reserves of 

wollastonite are relatively small in the United 

States, and this mineral is now mined only in Essex 

County, N.Y., and in Riverside and Inyo Counties, 

Calif. Synthetic molded laboratory work surfaces 

are increasingly being used as a substitute for 

sawed soapstone slabs. Some of the synthetic material probably contains talc as a filler, and the 

overall tonnage of talc consumption may therefore 

not be seriously decreased, but a much less expensive form of industrial talc will be consumed. 

Pyrophyllite, a mineral with physical properties 
622 UNITED STATES MINERAL RESOURCES 

similar to talc, has many of the same uses as talc 

and is in fact generally included with talc in resource studies. In the United States it is produced 

in North Carolina and California (Espenshade, 

1962), and in the past 10 years pyrophyllite consumption averaged about 13 percent of talc consumption. Resources of pyrophyllite are much less 

extensive than those of talc, so although its substitutability for talc is high, its percentage of the 

industrial talc market probably will not increase 

significantly. 

EXPLOITATION 

Talc was used by the Indians and early settlers 

for cooking utensils carved from soapstone that 

occurred mainly in altered ultramafic bodies. Mining 

of talc and soapstone deposits for other uses began 

in some districts in the early 1800's, but because 

industrial talc is tied closely to the demands of a 

modern industrial society, extensive mining has 

occurred only in about the past 50 years. Figure 70 

1200 

1000 

en 

z ~ 

0 ftl 

1- ~ 

1- 800 a: 

0 - :I: -

~ en ., u.. 600 ~ 

0 ~ 

en 0 

0 ~ ~ z ., .q: 400 ~ en 

::> Data not 0 available :I: 

1-

200 

0 

1910 1920 1930 1940 1950 1960 1970 

FIGURE 70.-United States consumption of talc, soapstone, 

and pyrophyllite, 1910-70. 

shows the consumption curve for talc, soapstone, 

and pyrophyllite during 1910-70. The figures are 

from the Bureau of Mines yearbooks, and the included pyrophyllite ranges from 10 to 15 percent 

of the total. The graph shows increases during national emergencies and other fluctuations owing to 

changing economic conditions of industry during 

more normal periods. The overall slope of the curve 

is straight and steep. 

Because of the diversity of uses for industrial 

talc, total consumption increases steadily, even when 

demand for individual consumer products fluctuates 

drastically. As technology develops new products, 

such as the widespread use of plastic insulation in 

place of rubber, the demand for talc as a filler may 

continue because both plastic and rubber require an 

inert mineral filler. Likewise, increasing use of talc 

as a base by the ceramic industry since about 1955 

has offset decreased consumption by the rubber and 

insecticide industries (fig. 69), and the booming 

use of white plastic by our society has apparently 

caused an increase in talc consumption as a white 

filler. Other, more sophisticated uses are being developed; for example talc reduced to minus 50-

millimicron particle size was used in a patented 

method by which an electrically insulating surface 

layer can be induced by electrophoresis on the exterior of an article that in itself is electrically conducting (Wells, 1970, p. 7). 

BYPRODUCTS AND COPRODUCTS 

Talc mining generally produces no byproducts. 

Because of the great variety of talc grades required 

by different consumers, selective mining, milling, 

and laboratory control results in high recovery of 

numerous marketable grades from most deposits. 

In effect, the many grades of industrial talc are 

coproducts. Bilbrey (1962, p. 22) reported that a 

cobalt-nickel concentrate was a byproduct of talc 

flotation in Vermont for a few years in the 1940's. 

The U.S. Bureau of Mines "Minerals Year books, 

1940-43" indicate a total sale of 109 tons of concentrate containing 1.16 percent cobalt and 12.7 percent nickel. Other potential byproducts are anthophyllite asbestos at Dadeville, Ala. (Neathery and 

others, 1967), and magnesite from Johnson, Vt. 

(Cooper and Hartwell, 1970). 

The recent discovery of scheelite in soapstone 

deposits in Madison County, N.C., raises the possibility of coproduction from these deposits. (See 

"Tungsten.") 

ENVIRONMENTAL PROBLEMS 

Mining of industrial talc is from both underground and opencut mines. Inasmuch as recovery is 

higher than that in mining for vein minerals, far 

less of the landscape is disrupted by the operation, 

and waste piles are relatively small. Only a few 

operations, such as at Johnson, Vt., use flotation 

methods for mineral separation; therefore, most 

talc mining does not have tailings ponds. 

One environmental problem does confront the 

industry, however; research mainly by a group in 
TALC 623 

Mt. Sinai School of Medicine in New York City has 

shown a positive correlation between incidence of 

lung disease and working with or near asbestos 

without safety precautions (New York Academy of 

Sciences, 1965). Because many of the talc deposits 

mined in the United States contain asbestiform 

tremolite and anthophyllite, emission-control standards will undoubtedly be established for mining and 

milling them. The tremolite and anthophyllite content of talc used as a cosmetic or for food processing, such as polishing rice or dusting salami, also 

will probably be carefully monitored, as will that 

in talc used as a carrier for pesticide dusts. 

GEOLOGIC ENVIRONMENT 

Talc and soapstone deposits of commercial importance occur mainly in metamorphosed dolomite 

and altered ultramafic igneous rocks. These rocks 

and contained talc deposits are present in metamorphosed terranes throughout the world. In the 

United States, talc is found in the older Appalachians and Piedmont from New England to Alabama in the east and in California, Nevada, Washington, and Montana in the west (Chidester and 

Worthington, 1962). Important deposits also occur 

in Texas, but most of the Central United States, 

from the Appalachians to the Rocky Mountains, lack 

a convenient source of industrial talc. 

TALC FROM REGIONALLY METAMORPHOSED 

DOLOMITE 

Dolomites with ascociated siliceous sediments can 

be metamorphosed to form talc. In many deposits 

derived from sedimentary dolomite and silica, talc 

forms as a final retrograde hydrothermal phase 

from earlier magnesian silicates such as tremolite, 

forsterite, and diopside. These three minerals result from high-grade metamorphism with the addition of silica and limited water. Retrograde alteration of the earlier minerals to talc and serpentine 

is accomplished hydrothermally with the release of 

calcite and C02. 

Most of the major talc deposits in the United 

States are in metamorphosed dolomite; this type 

accounts for more than half the total production. 

The largest producers in the country are mines on 

such deposits in St. Lawrence County, N.Y., where 

talc, tremolite, and serpentine rocks occur in Precambrian carbonate and siliceous sedimentary rocks. 

The talc zones are stratigraphic units that have 

been tectonically swelled in axial parts of folds and 

at places are pinched out on fold limbs. Shearing has 

played a major role in the development of talc schist 

zones. 

Similar talc deposits are in the Murphy Marble 

belt of North Carolina, the Dillon-Ennis district of 

southwestern Montana, and the Inyo and Panamint 

Ranges of California. The deposits in North Carolina 

are lens shaped and follow a zone of quartzose dolomitic marble. Some of the North Carolina talc is 

exceptionally white, and locally massive varieties 

are sawed for steel-marking crayons. The deposits 

in Montana are rather large but require considerable selective mining and sorting because of interlayered unaltered wallrock. The Montana deposits 

and those in the Inyo and Panamint Ranges of California provide some rock of steatite or near-steatite 

grade. 

Deposits in the Chatsworth district of Georgia and 

the Allamoore district of Texas, also formed from 

metasedimentary rocks, are not so closely related to 

dolomitic parent rocks. These deposits are associated 

with phyllites, schists, and quartzites, and required 

extensive metasomatism for their development. 

The Winterboro deposits in Talladega County, 

Ala., occur in or as residual deposits derived from 

Cambrian and Ordovician dolomite that is relatively 

unmetamorphosed. The talc is virtually unfoliated 

and preserves the crystallinity of the parent rock 

(Wedow and Sweeney, 1968). These deposits should 

be studied further because of their low metamorphic 

grade. Possibly they result from prograde metamorphism, with talc being the highest grade mineral produced, in contrast to other deposits in which 

retrograde metamorphism was important. 

TALC DEPOSITS FORMED FROM ULTRAMAFIC 

AND MAFIC IGNEOUS ROCKS 

Talc deposits associated with serpentinized ultramafic rocks occur in regionally metamorphosed and 

folded sedimentary and volcanic rocks such as those 

in the older Appalachian Mountains and Piedmont 

in a belt from New England to Alabama (Larrabee, 

1966, 1971). These deposits generally occur as rinds 

on serpentine bodies but in places have completely 

replaced them. Some deposits occur where sodic 

pegmatites intrude serpentine. Steatitization, the 

formation of talc-rich-rock, was accomplished by 

either of two processes-the metasomatic reaction 

between serpentinite and introduced C02 or a metamorphic reaction between serpentinite and siliceous 

country rock. These two processes, though independent, can work together. Generally, the deposits 

formed mainly by C02 metasomatism have an abundance of talc-carbonate rock; and where metamorphic reaction was important, talc rock is dominant. 

The largest producing talc mines in altered ultramafic rocks are in Vermont; many similar but 
624 UNITED STATES MINERAL RESOURCES 

smaller deposits have been mined in the eastern 

serpentine belts and in California, Texas, and other 

States. 

Talc deposits that formed by intrusion of sodic 

pegmatites into serpentinite are mined in Harford 

County, Md. (Pearre and Heyl, 1960, p. 795). Apparently the igneous intrusions provided solution 

and heat for the reaction with serpentinite to produce a thin contact-zone rind of vermiculite and 

actinolite, and farther into the country rock, an 

irregular zone of massive talc rock. 

Some talc deposits were formed by pervasive 

steatitization of mafic rocks associated with ultramafic rocks. At Schuyler, Va., tabylar or lenticular 

bodies of hypersthene gabbro have been altered to 

greenish-gray soapstone (Hess, 1933). Steatitization 

here is related either to regional metamorphism or 

to igneous activity deep in the crust. The altered 

rock consists of varying proportions of amphibole, 

chlorite, carbonate, talc, and magnetite and therefore varies from hard to soft. The rock is tough 

because of an interlocked felted texture of the minerals and is desirable for sawed shapes such as 

laboratory tables and sinks. 

TALC DEPOSITS FORMED BY CONTACT 

METAMORPHISM OF DOLOMITIC SEDIMENTS 

Granite plutons and diabase dikes that intrude 

favorable dolomitic strata provided the heat and 

solutions for the steatitization of the sedimentary 

rocks, and in some places granite itself has been 

replaced by talc. Southern California contains excellent examples of talc deposits formed by such 

contact metamorphism. A mining district that extends from the Panamint Range eastward across 

southern Death Valley to the Kingston Range in 

lnyo and San Bernardino Counties contains talc 

deposits that occur mainly along the upper contacts 

of diabase sills with cherty dolomite of Precambrian 

age. These ore bodies average 10-25 feet in width 

and are 1,000 feet to at least 1 mile in length. Most 

of the talc produced in California comes from them. 

Wright (1968) presented a detailed description of 

more than 40 deposits in this district. 

Talc deposits of northeastern San Bernardino 

County in the Silver Lake-Yucca Grove district are 

genetically associated with -granitic plutons. The 

deposits occur as lenses in a terrane composed of 

lower Precambrian metasedimentary and intrusive 

rocks. Dolomitic strata were selectively tremolitized 

when granitic rocks were emplaced nearby. Subsequently, during retrograde metamorphism, the 

tremolite was altered to talc schist along the borders 

of the deposits. The industrial talc in these deposits 

is snowy white and medium to coarse grained. 

Minable talc bodies are about 10 feet wide and as 

much as 800 feet long (Chidester and others, 1964, 

p. 25). 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

The United States is self-sufficient in most grades 

of talc and soapstone. In the past, we have imported 

most of our block steatite and cosmetic-grade talc. 

Because of technical refinements in the use of 

phosphate-bonded domestic ground talc of steatite 

grade and die-formed steatite as a substitute for 

insulator forms machined from block steatite, we 

are no longer dependent on foreign supplies, and 

stockpiled material probably will be sold. About half 

the cosmetic-grade talc consumed (Industrial minerals, 1971) is still imported, but selective-flotation 

techniques using domestic talc have eliminated much 

of our dependence on foreign sources. 

Chidester, Engel, and Wright (1964) estimated 

our identified resources at a minimum of 89 million 

tons, with the possibility of additional discoveries 

being good to excellent in all mining districts. Resources should be adequate to meet the demands for 

many decades. The Bureau of Mines, in its Commodity Data Summary of January 1972, estimated 

United States reserves at 150 million tons and world 

reserves at 360 million tons. Projected demand for 

talc in the United States for the year 2,000 by the 

U.S. Bureau of Mines is 2.28 to 3.36 million tons 

(Cooper and Hartwell, 1970). Worldwide demand 

for talc is increasing faster than demand in the 

United States as societies become more complex, but 

the world's identified resources appear adequate to 

meet demand. 

SPECULATIVE RESOURCES 

Most talc deposits are found in areas of highgrade or contact metamorphism. The deposits in 

Talledega County, Ala., however, are in relatively 

unmetamorphosed Cambrian and Ordovician dolomite. Similar dolomites exist at many other places 

in the United States. The Alabama deposits should 

be carefully studied to determine their genesis so 

that similar deposits might be predicted elsewhere. 

Many areas of dolomitic marble in the southeastern 

Piedmont, such as the Wakefield and Cockeysville 

Marbles in Maryland, might contain talc deposits. 

Another intriguing possibility is the dolomite and 

marble units in areas of Precambrian rocks in Wisconsin and Michigan. For example, the Randville 

Dolomite in Dickinson County, Mich., locally consists of white tremolitic marble (James and others, 
TALC 625 

1961, p. 128), although this formation at most places 

is not metamorphosed. This area is particularly important as a potential source of industrial talc because of its proximity to the industrial areas of the 

Middle West, which are hundreds of miles from all 

current sources of talc. 

PROSPECTING TECHNIQUES 

Detailed geologic mapping is currently the best 

technique in prospecting for industrial talc. For 

deposits derived from dolomite, the stratigraphy and 

structure must be known in order to predict the 

occurrence of talc zones in the subsurface; for instance, previously unknown deposits were recently 

identified in the town of DeKalb in St. Lawrence 

County, N.Y., through use of 1: 12,000-scale geologic mapping (Brown, 1969; Bannerman, 1972). 

Although these deposits are exposed at the surface, 

estimation of continuation to depth can only be attempted through an understanding of the geologic 

structure. Where talc is a product of contact metamorphism, such as along the diabase sills in the 

southern Death Valley region, detailed knowledge 

of the location of dolomitic sediments and diabase 

sills is important for the location of talcose zones 

and prediction of their continuation in the subsurface. For deposits formed from ultramafic rocks, 

too, detailed geologic mapping is important. Geophysical methods, mainly magnetic, can be applied 

to help locate the parent ultramafic rock. Detailed 

geologic mapping and drilling then are needed to 

find talcose zones. 

For most of the ceramic and filler grades of talc, 

the consumer industries have rigid chemical and 

physical specifications for the milled rock. Therefore, 

after a deposit is located, considerable careful testing of chemical and physical properties is required 

to ascertain the minable parts of a deposit. 

PROBLEMS FOR RESEARCH 

Even though the resources of talc in the United 

States are large, restrictive specifications of color 

and other properties make many deposits unusable 

for high-priced grades of talc. Sampling and laboratory testing of all known talc deposits would establish the quality and marketability of known resources. As already discussed, new deposits are 

likely to be found primarily as a result of detailed 

mapping in geologically favorable terranes. A program of concurrent field and laboratory research is 

at present being conducted by the North Carolina 

Department of Conservation and Development for 

deposits in Madison County, N.C. (L. S. Wiener, 

written commun., 1972), and a similar study recently was completed for Tallapoosa and Chamber 

Counties, Ala. (Neathery, 1968). 

Industrial talc is an extremely versatile mineral 

product, and new uses are continually being found. 

Close cooperation between the research laboratories 

of the manfacturers and those of the mining companies could probably develop even more functional 

grades of talc depending on the demands of new 

products. Research on new pulverizing techniques 

capable of producing submicron particle sizes would 

help in opening new markets, as consumers seem to 

desire ever finer material despite the high costs. 

High reflectance or whiteness is a required quality of industrial talc used in the ceramic, paint, 

paper, and a few other industries. During the quest 

for this higher priced product, much subgrade rock 

is discarded. Some of the waste could be sold locally 

for mineral filler not requiring white rock, such as 

in rubber, roofing, insecticide, and some dusting applications. Some progress has apparently been made 

in improving the color of off-white talc (Wells, 

1970). More research in this field is needed. 

REFERENCES CITED 

[Extensive bibliographies on talc were published in 1960 (Engel and 

Wright), 1963 (Merrill) and 1964 (Chidester and others)] 

Andrews, R. W., 1970, Wollastonite: London, Inst. Geol. 

Sciences, Natural Environment Research Council, 114 p. 

Bannerman, H. M., 1972, Geologic map of the RichvilleBigelow area, St. Lawrence County, New York: U.S. 

Geol. Survey Misc. Geol. Inv. Map, Ml-664. 

Bilbrey, J. H., 1962, Cobalt, a materials survey: U.S. Bur. 

Mines Inf. Circ. 8103, 140 p. 

Brown, C. E., 1969, New talc deposit in St. Lawrence County, 

New York: U.S. Geol. Survey Bull. 1272-D, 13 p. 

Chidester, A. H., Engel, A. E. J., and Wright, L. A., 1964, 

Talc resources of the United States: U.S. Geol. Survey 

Bull. 1167, 61 p. 

Chidester, A. H., and Worthington, H. W., 1962, Talc and 

soapstone in the United States, exclusive of Alaska and 

Hawaii: U.S. Geol. Survey Mineral Inv. Map MR-31. 

Cooper, J. D., and Hart~ell, J. W., 1970, Talc, soapstone, 

and pyrophyllite, in Mineral facts and problems: U.S. 

Bur. Mines Bull. 650, p. 1267-1281. 

Engel, A. E. J., and Wright, L. A., 1960, Talc and soapstone, in Industrial minerals and rocks [3d ed.]: New 

York, Am. Inst. Mining, Metall., and Petroleum Engineers, p. 835-850. 

Espenshade, G. H., 1962, Pyrophyllite, and kyanite and related minerals in the United States: U.S. Geol. Survey 

Mineral lnv. Resources Map MR-18. 

Gaskins, W. W., 1952, Historical background development 

on use of talc in ceramic bodies : Am. Ceramic Soc. Bull., 

v. 31,no. 10,p. 392-395. 

Hess, H. H., 1933, Hydrothermal metamorphism of an ultrabasic intrusive at Schuyler, Virginia: Am. Jour. Sci., 

5th ser., v. 26, no. 154, p. 317. 

Industrial Minerals, 1968, Talc-Mineral with a multitude 

of uses: Indus. Min. (London), no. 5, Feb., p. 9-16. 
626 UNITED STATES MINERAL RESOURCES 

1971, Talc in the USA: Indus. Min. (London), no. 

41, Feb., p. 39-50. 

James, H. L., Clark, L. D., Lamey, C. A., and Pe.ttijohn, F. 

J., 1961, Geology of central Dickinson County, Michigan: 

U.S. Geol. Survey Prof. Paper 310, 176 p. 

Kollonitsch, Valerie, Kliff, E. J., and Kline, C. H., 19·70, Functional pigments, pt. 2: Indus. Min. (London), no. 39, 

Dec., p. 46-51. 

Larrabee, D. M., 1966, Map showing distribution of ultramafic and intrusive mafic rocks from northern New Jersey to eastern Alabama: U.S. Geol. Survey Misc. Geol. 

Inv. Map MI-4 76. 

--- 1971, Map showing distribution of ultramafic and 

intrusive mafic rocks from New York to Maine: U.S. 

Geol. Survey Misc. Geol. Inv. Map Ml-676. 

Merrill, C. W., 1963, S.elected bibliography of talc in the 

United States: U.S. Geol. Survey Bull. 1182-C, 26 p. 

Neathery, T. L., 1968, Talc and anthophyllite asbestos deposits in Tallapoosa and Chambers Counties, Alabama: 

Geol. Survey of Alabama Bull. 90, 98 p. 

Neathery, T. L., LeVan, H. P., Ahrenholz, H. W., and 

O'Neill, J. F., 1967, Talc and asbestos at Dadeville, 

Alabama: U.S. Bur. Mines Rept. Inv. 7045, 57 p. 

New York Academy of Sciences, 1965, Biological effects of 

asbestos: New York Acad. Sci. Annals, v. 132, art. 1, 

p. 1-766. 

Pearre, N. C., and Heyl, A. V., Jr., 1960, Chromite and other 

mineral deposits in serpentine rocks the Piedmont Upland, Maryland, Pennsylvania, and Delaware: U.S. Geol. 

Survey Bull. 1082-K, p. 707-833. 

Wedow, Helmuth, Jr., and Sweeney, J. W., 1968, Talc, soapstone, pyrophyllite, and sericite schist, in Mineral resources of the Ap·palachian Region: U.S. Geol. Survey 

Prof. Paper 580, p. 355-3.61. 

Wells, R. J., 1970, Talc soapstone and pyrophyllite: U.S. 

Bur. Mines Mineral Yearbook for 1970 (preprint), 7 p. 

Wright, L.A., 1968, Talc deposits of the Southern Death Valley-Kingston Range region, California: California Div. 

Mines and Geology Spec. Rept. 95, 79 p. 
UNITED STATES MINERAL RESOURCES 

TELLURIUM 

By D. F. DAVIDSON and H. W. LAKIN 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Uses -------------------------------------------

Crustal abundance ------------------------------- Geochemistry ___________________________________ _ 

Resources __ --- _ ---------------------------------

References _____ - _ --------------------------------

TABLES 

129. T-ellurium resources potentially available in 

identified resources of copper ores, lead ores, 

Page 

627 

627 

627 

628 

628 

629 

630 

Page 

coal, and oceanic manganiferous nodules __ 629 

130. Tellurium content of annual coal consumption 

at four operating powerplants in Western 

United States ---------------------------- 630 

ABSTRACT OF CONCLUSIONS 

The present demand for tellurium is less than the amount 

available as a byproduct from the copper and lead industries. 

A shortage of tellurium could develop as a result of a 

chan~ in the processes of recovery of copper from its ores. 

In-place leaching of copper from its ores leaves the associated tellurium undissolved in the waste rock resulting 

from the process. Thus, as the use of the leaching process 

increases at the expense of smelting, the supply of tellurium 

will decrease. 

Identified resources of copper in the United States are 

estimated to contain about 13.5 million pounds of recoverable tellurium. Tellurium may be recovered as a byproduct 

in burning of coal in huge powerplants, paying in part for 

environme.ntal improvement. The major resource of tellurium 

is found in manganese oxide nodules on the ocean floors. 

INTRODUCTION 

Tellurium was discovered in a complex group of 

gold telluride minerals in the ores of Transylvania 

by F. J. Muller von Reichenstein in 1782. It is characteristic of tellurium to form its own minerals in 

metallic sulfide deposits, although it is very rare. 

Tellurium is a nonmetallic element; its atomic 

number is 52 and atomic weight 127.6; and it exists 

in eight stable isotopes. It has a specific gravity of 

6~24 and melts at 452°C. Tellurium can be obtained 

in an amorphous or a crystalline form. Amorphous 

tellurium is brown to black and is produced by reduction of tellurium solutions. Crystalline tellurium 

has a trigonal structure, is grayish white, lustrous, 

and brittle, and is produced by casting the molten 

element. In a thin film, tellurium is dull purple; its 

vapor is orange yellow. 

USES 

Tellurium is marketed as a steel-gray powder, 

and in slabs, tablets, and sticks. The usual commercial grade is about 99.7 percent tellurium with 

selenium and copper as the principal impurities. 

Grades of 99.99+ and 99.999+ percent tellurium 

are available. About 18 percent of the tellurium produced is sold as copper tell uri urn alloys ( 40-50 percent tellurium) and ferrotellurium (50-58 percent 

tellurium) (Lausche, 1967). 

About 80 percent of the 221,000 pounds of tellurium used in the United States in 1968 went into 

the primary metal industries. Low-carbon steels 

containing 0.02-0.2 percent tellurium have better 

machinability. Tellurium is also used in iron or 

steel to reduce the adsorption of nitrogen, to act 

as a weak deoxidizer, and to minimize pinhole porosity. Less than 1 percent tellurium in copper improves machining properties of the copper without 

effecting the electrical conductivity or hot working 

properties of the metal. Lead containing 0.05 percent of tellurium has added resistance to corrosion. 

The rubber industry accounted for about 10 percent of the tellurium used in the United States in 

1968. Tellurium is used both as the element and as 

tellurium diethyldithiocarbamate in synthetic and 

U.S. GEOL. SURVEY PROF. PAPER 820 

627 
628 UNITE-D STATES MINERAL RESOURCES 

natural rubbers to increase the resistance to heat 

and abrasion, to decrease vulcanization time, and 

to improve the aging properties of the elastomer. 

The remaining 10 percent of the tellurium 

consumed in 1968 goes into many diverse but important uses. Tellurium is used as a catalyst in 

oxidation, hydrogenation, dehydrogenation, chlorination, dechlorination, hydroxylation, and phenol 

condensation. Noteworthy properties of tellurium 

catalysts are selectivity, good yield, and resistance 

to poisoning. Tellurium has been used as a colorant 

in ultramarine, black, blue, red, and brown glasses 

and ceramics. Organic tellurides have been used as 

antioxidants for lubricants, greases, hydraulic 

fluids, and hydrocarbon fuels. Tellurium compounds 

are used as antimicrobial and therapeutic agents. 

Cyclotelluropentane-3, 5-diones, and various derivatives are very powerful germicides. Tellurium has 

been used in the treatment of leprosy with good 

results. Tellurium dioxide suspensions are effective 

in the treatment of seborrheic dermatitis of the 

scalp. Tellurium is also used in blasting caps, batteries, thermoelectric devices, solar cells, infrared 

windows, and semiconductor devices. 

Selenium may be used as a substitute for tellurium in metallurgy, ceramics, rubber, and thermoelectric devices. Lead may be used to achieve machinability in steel and thus replace tellurium. 

CRUSTAL ABUNDANCE 

The crustal abundance of tellurium is unknown. 

The element is so rare that analytical methods have 

not been devised with sufficient sensitivity to determine tellurium in igneous rocks with adequate 

reliability. Efforts have been made to estimate the 

abundance of tellurium on the basis of seleniumtelluri urn ratios in materials containing enough of 

both elements to be measured, but this gives rise to 

a second-generation error because the abundance 

of selenium is arrived at similarly by use of sulfurselenium ratios. Recent estimates of the abundance 

of tellurium are 0.001, 0.002, and O.OOX ppm (parts 

per million). The selenium-tellurium ratio in copper 

produced from porphyry copper deposits in the 

United States is 1 to 0.4, or 2.5 to 1 ; the. same ratio 

for Sudbury ores of Canada is 15. Using 0.05 ppm 

as the crustal abundance of selenium, the ratio of 

2.5 gives 0.02 ppm tellurium for the U.S. porphyry 

copper ores and 0.003 ppm tellurium for the 

pyrrhotite-chalcopyrite-pentlandite ores of Sudbury. 

This divergence in the selenium-tellurium ratios is 

indicative of fundamental differences in the geochemistry of these elements. 

GEOCHEMISTRY 

Sulfur, selenium, and tellurium belong to the same 

family of elements; their physical and chemical 

properties change progressively from the low atomic 

weight sulfur through selenium to tellurium. An 

example of how progressive change in physical 

properties can affect dispersion of these elements 

in volcanism is found in the boiling points of pertinent chemical forms. The boiling points of sulfur, 

selenium and tellurium are 444°, 688°, and 1,390°C 

respectively. Hydrogen sulfide is a stable gas at 

ambient temperature; hydrogen selenide decomposes in moist air to give selenium and water; 

hydrogen telluride is even less stable than hydrogen 

selenide. Whereas sulfur dioxide is a relatively 

stable gas at ambient temperatures, both selenium 

and tellurium dioxides are solids that sublime at 

317° and 450°C respectively. It is evident from 

these differences in the three elements that sulfur 

is very mobile and may be carried in the atmosphere 

great distances. In contrast, tellurium will be found 

close to the volcanic source. 

Differences in ionic radii materially alter the distribution of tellurium from the distribution of sulfur and selenium. The ionic radius of S- 2 is 1.84 A, 

of Se- 2 1.98 A, and of Te-z 2.21 A. Selenium can 

readily substitute for sulfur in sulfide minerals but 

the tellurium ion is too large to replace sulfur. 

Consequently selenium occurs in sulfide minerals and 

selenide minerals in isomorphous association with 

sulfide minerals, whereas tellurium forms its own 

minerals as tellurides. 

The minimum radius ratio 

(

radius of cation ) 0.414 

radius of anion 

for stability of coordinated octahedrons with a ligancy number of 6 (Pauling, 1960, p. 544-545) permits the metals gold, silver, bismuth, mercury, 

platinum, palladium, and lead to form stable crystalline tellurides, whereas tellurides of zinc, copper, 

nickel, and iron are less stable. The metals goldlead listed above, with very large ionic radii, cannot 

readily substitute in sulfid~s of zinc, copper, nickel, 

and iron, nor can tellurium substitute for sulfur; 

consequently, the rare metals gold, silver, bismuth, 

mercury, platinum, and palladium tend to accumulate in residual ore fluids and to crystallize as telluridea after most of the sulfide minerals have crystallized. This sequence appears to occur in early magmatic sulfide deposits of the Sudbury (Canada) and 

Merensky Reef (Africa) types in which platinum, 

palladium, and bismuth tellurides are conspicuous, 

as well as in the late-stage, low-temperature hydro-
TELLURIUM 629 

thermal deposits of the telluride ores of Boulder 

County, Colo., in which gold and silver tellurides are 

abundant (Kingston, 1966; Kelly and Goddard, 

1969). 

Sindeeva (1964) observed that tellurium forms 

its own minerals in many diverse types of ore deposits. In lead-zinc deposits she reported that tellurium concentrates in galena in microscopic segregations of altaite (PbTe) and hessite (AgTe). The 

tellurium in copper deposits is associated with chalcopyrite and may occur as microscopic segregations 

of hessite inasmuch as there is more silver in such 

ore than required to accommodate all of the tellurium usually found in the ore (Cooper, 1971, table 

2-1, p. 15). 

In the zone of active oxidation at or near the 

surface, tellurium is readily oxidized to tellurites 

(TeOa-2) from tellurides (Te-2) throughout the 

normal pH range (3-8). At relatively high, but 

feasible, oxidation potentials, tellurites are oxidized 

to tellurates (TeO. - 2) in alkaline environments (pH 

6-8.5). This oxidation is verified by minerals consisting of ferric tellurite Fe2 (TeOa) a and lead, bismuth, ferrous, and mercurous tellurates. The ready 

oxidation of tellurides gives rise to the dispersal 

of tellurium in ground water, from predominantly 

telluride deposits. 

In acid environments produced by the oxidation 

of pyrite, tellurium is captured in the iron oxide 

gossans, presumably as basic ferric tellurites. Gossans have been found that contain as much as 1 

percent tellurium. 

Tellurium is not known to be essential for animal 

or plant life. It occurs in minute quantities in plants 

and animals but below concentrations that are 

readily measured. To illustrate, a limber pine 

(Pinus ftexilus) was found to contain 0.05 ppm 

tellurium in twigs, 0.012 ppm in bark, and < 0.005 

ppm in the wood (Hubert, 1971). This tree was collected in the Cripple Creek mining district, Colorado, where the ore consisted of gold tellurides and 

where soils are unusually rich in tellurium; the soil 

in which it grew contained 0.5 ppm tellurium to a 

depth of 24 inches and 1 ppm tellurium in the 24-

to 30-inch layer. 

No tellurium has been found in phosphate deposits, Colorado Plateau uranium deposits, sedimentary 

sulfur, or sedimentary sulfides. Tellurium is found 

in the fly ash (as much as 0.2 ppm) of the powerplants burning coal. The selenium-tellurium ratio 

in coal used in certain southwestern U.S. powerplants ranges from 50 to 100. This ratio indicates 

a depletion of tellurium with respect to selenium. 

Although inadequate analytical methods hamper 

studies of these materials it is easily established 

that the selenium-tellurium ratio is much larger in 

organic-rich sedimentary materials than in their 

assumed crustal abundance. One must conclude that 

in the weathering processes, tellurium is dispersed 

and is not reconcentrated again as selenium is in 

biosinks. 

RESOURCES 

Tellurium is obtained primarily as a byproduct of 

copper refining; 80 percent of the production in the 

United States is derived from the anode mud deposited during electrolytic refining of copper. Blister 

copper contains an average of 0.02 percent tellurium 

or 0.4 of a pound of tellurium per ton of copper, but 

actual recovery of tellurium is about 0.17 of a pound 

per ton of copper. Thus, the production of tellurium 

in the United States, and in most of the world, is 

directly related to the production of copper. In-place 

leaching processes for the recovery of copper do not 

result in tellurium recovery, and the increasing use 

of these processes could reduce the supply of tellurium materially. Other countries with major potential resources of tellurium are those with major 

potential resources of copper: Chile, U.S.S.R., Zambia, Peru, Zaire, Canada, and Mexico (Ageton, 

1970; see also "Copper" chapter). Substantial 

amounts of tellurium are recovered from lead ores. 

Resources of tellurium estimated to be potentially 

available in the identified resources of copper, lead, 

and coal in the United States and in other countries 

together with the tellurium available in oceanic manganiferous nodules are shown in table 129. 

In electrolytic refining of blister copper about 42 

percent of the contained tellurium is recovered from 

the slime residue. Using the ratio of 0.17 of a 

pound of tellurium per ton of copper produced, we 

estimate a total of 13.5 million pounds of tellurium 

available in identified copper resources of the United 

States, and 43.9 million pounds available in identified copper resources of the rest of the world. 

Refining of lead ores accounts for about 20 percent of the present production of tellurium or oneTABLE 129.-Tellurium re3-ources (in thousands of pounds) 

potentially available in identified resources 1 of copper ores, 

lead ores, coal, and oceanic manganiferous nodules 

Source 2 

Copper ores 3 -----------------

Lead ores -------------------- Coal ------------------------- Oceanic manganiferous nodules_ 

United States Other countries 

13,500 43,900 

3,000 10,000 

4 7,400 237,600 

1,980,000 

1 Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained min· 

erals may or may not be profitably recoverable with existing technology 

and economic conditions. 2 Identified resources from respective chapters of this volume. a Assuming 42-percent recovery of tellurium. 
630 UNITED STATES MINERAL RESOURCES 

fourth of the tellurium from copper resources. The 

values for tellurium from lead ores given in table 

129 are about one-fourth of the resources from 

copper ores. On the basis of 140 million tons of 

lead, this estimate requires 1.3 pounds of tellurium 

per ton of lead ; the estimate is probably high. 

The average content of tellurium in coal is taken 

at one-hundredth of the selenium estimate or 0.015 

ppm (parts per million) tellurium; this value is 

probably low, but is significant as a reserve because 

tellurium would be recoverable with selenium. In 

table 130 the average tellurium content of coal used 

TABLE 130.-Tellurium content (in pounds) of annual coal 

consumption (in millions of tons) at four operating powerplants in Western United States 

[Data from U.S. Geol. Survey. 1972] 

Location of powerplants 

Four Corners, N. Mex -------

Gholla, Ariz ---------------- Mohave, Nev --------------- Hayden, Colo ---------------

Annual 

consumption coal 

(in millions tons) 

7.0 

.4 

6.7 

6.25 

Total 

tellurium 

Calculated content of 

Te 1 con- annual eoal tent coal consump- (in ppm) tion (in 

0.025 

.002 

.013 

.006 

pounds) 

350.0 

1.6 

187.2 

75.0 

1 Calculated from tellurium in fly ash and fly ash = 0. 75 total ash. 

in four operating powerplants in Western United 

States is given, together with the tonnages used per 

year. The calculated tellurium content ranges from 

0.002 to 0.025 ppm, and we find 613.8 pounds of 

tellurium in 20.35 million tons of coal ; in the same 

coal we found 66,300 pounds of selenium which 

gives a ratio of about 100 selenium to 1 tellurium. 

Using this ratio the estimated annual release of 

tellurium from the combustion of coal in the United 

States is about 80,000 pounds. All, or virtually all, 

of this tellurium would be contained in the fly ash. 

Tellurium is enriched in oceanic manganese oxide 

nodules. The median tellurium content of 12 samples from diverse locations in the Pacific and Indian 

Oceans is 30 ppm (Lakin and others, 1963). If it is 

assumed that manganese oxide nodules contain only 

10 ppm tellurium and we have an estimated 90 

billion tons of nodules, then there is a potential 

resource of 1,980 million pounds of tellurium in 

these ocean deposits. 

REFERENCES 

Ageton, R. W., 1970, 'Dellurium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 739-747. 

Cooper, W. C., ed., 1971, Tellurium: New York, Van Nostrand Reinhold Co., 437 p. 

Hubert, A. E., 1971, A sensitive method for the determination of tellurium in vegetation, in Geological Survey research 1971, U.S. Geol. Survey Prof. Paper 750-D, p. 

D162-D164. 

Kelly, W. C., and Goddard, E. N., 1969 Telluride ores of 

Boulder County, Colorado: Geol. Soc. America Mem. 

w~~7~ · Kingston, G. A., 1966, The occurrence of platinoid bismuthotellurides in the Merensky Reef at Rustenburg platinum 

mine in the western Bushveld: Mineralog. Mag., v. 35, 

p. 815-834. 

Lakin, H. W., Thompson, C. E., and Davidson, D. F., 1963, 

Tellurium content of marine manganese oxides and other 

manganese oxides: Science, v. 142, no. 3599, p. 1568-

1569. 

Lauscbe, A. M., 1967, Selenium and tellurium, a material 

survey (with a chapter on resources by D. F. Davidson): 

U.S. Bur. Mines Inf. Circ. 8340, 56 p. 

Pauling, Linus, 1960, The nature of the chemical bond: 

Ithaca, N. Y., Cornell Univ. Press, 644 p. 

Sindeeva, N. D., 1964, Mineralogy and types of deposits of 

seltenium and tellurium: Intersci. Publishers, New York, 

N.Y., 363 p. 

U. S. Geol. Survey, 1972, Composition and trace element content of coal and powerplant ash, Pt. 2 in App. J of Southwest Energy Study: U.S. Geol. Survey open-file report, 

61 p. 

632 UNITE.D STATES MINERAL RESOURCES 

linings in aluminum smelters is improved by the 

addition of thallium. Thallium is also used to modify 

the pore size of molecular sieves by partial cation 

exchange. Thallium has extensive electronic applications, being used in the construction of photoelectric cells and exposure meters to detect infrared 

radiation, particularly in military communication 

systems. It is used as an integral part of scintillation spectrometers, in thallium-activated sodium 

iodide crystals, where it reduces background noise 

in the detection of gamma radiation and in measuring high-energy electrons for X-rays. The performance of rectifiers is also improved by utilization of 

a selenium-thallium alloy in the cathodes. Thallium 

is used in electrical resistors and superconductors, 

in tungsten filaments and radiation sources in 

X-ray fluorescence, and in the production of illuminated phosphors. The inclusion of thallium in mercury vapor lamps has increased their service life 

and almost doubled their illumination output. It has 

also been tested in lamps producing radiation in the 

suntan range. The refractive index of optical glass 

is increased by the inclusion of thallium. It is also 

used with other metals and as an oxide to glaze semiconductors, capacitors, printed circuits, and other 

electronic devices to protect them from atmospheric 

deterioration and contamination. As a catalyst in 

electroplating, thallium improves the adherence and 

uniformity of gold coatings on semiconductor devices. Technological advances have been made in 

the use of thallium in alloys for low-temperature 

thermometry. Thallium has also been utilized in 

explosives as TINa, in medicine to treat· ringworm, 

and in agriculture. In experiments conducted in 

Russia, Kolotova and Kharitonova (1970) found 

germination and leaf growth were promoted in seeds 

soaked with 0.001 percent Tl2S04 solution, resulting 

in a 13-percent increase in corn yield and a 43-

percent increase in carrot yield. A solution of 0.05 

percent is toxic. 

Current application and use for thallium are wide 

but limited; U.S. domestic production can exceed 

demand, and immediate reserves are substantial. 

Thus, thallium is not a high-priority material and 

no government-sponsored stockpiles exist. To some 

extent, current use and demand for thallium are 

limited by the need for additional comprehensive 

research into its complete chemical and physical 

properties and into its utilization potential. Lee 

(1971) expects its future industrial use to be one 

of a reaction intermediate in various syntheses, utilizing to advantage the oxidizing power of Tl +a 

and the stability of many Tl + 1 derivatives. The 

highly toxic nature of thallium salts is a deterrent 

to its use, and adequate substitutes are available 

for some of its present applications, particularly in 

rodenticides and insecticides and in electronics. 

Hence, the national and world economic importance 

of thallium is relatively low. Possibly, however, new 

technological advances in the use of thallium and 

its compounds will change this situation. Furthermore, the variable abundance of thallium in specific 

minerals may prove a valuable index to the economic 

potential of mineralized areas for other commodities. 

World production of zinc ores containing thallium 

is adequate for the current demand. It is doubtful, 

however, that any substantial future or sudden need 

for thallium could be met by increased processing of 

residues and flue dusts from the smelters and (or) 

by improving the recovery factor. This fact implies 

that alternative sources of thallium must be established soon. 

Present estimates of the world consumption of 

thallium are as much as 15 short tons annually, of 

which the U.S. requirements are given as 3.25 tons. 

The United States now refines enough thallium to 

meet domestic demand, although an estimated 50 

percent is obtained from zinc ores imported from 

Canada. U.S. imports of zinc ores containing thallium 

are mostly from Canada ; lesser amounts are from 

Mexico, Peru, Australia, and other countries. The 

current shutdown of domestic smelters, however in 

conjunction with expanded smelting capacity in 

Canada, Mexico, Australia, and Japan, may soon 

change the sufficiency of domestically refined 

thallium metal to complete dependence on imported 

sources. 

EXPLOITATION 

The first recorded use of thallium salts was in 

medicine in 1896. In 1919 thallium salts were used 

in the manufacture of photosensitive cells. In 1920 

they were used as a rat poison in Germany, and in 

1925 the principal worldwide use of thallium salts 

became that of a rodent poison and insecticide in 

the form of thallium sulfate, ~n extremely toxic, 

odorless, and tasteless chemical. This practice was 

curtailed in the United States by a 1965 Federal 

ruling, because of the extreme toxicity of thallium 

salts to humans. Lee (1971) stated that thallium 

sulfate is a cumulative poison which may be absorbed by the skin. A human lethal dose is about 

1.75 grams, death occurring in a few days through 

respiratory failure after convulsions and delirium. 

The sparsity of characteristic thallium minerals 

and its highly dispersed nature have prevented 

thallium from being found in concentrations of sufficient magnitude to be mined as the principal ore 
THALLIUM 633 

material. As a group, potassium-rich silicates contain the greatest and most consistent amounts of 

thallium, but these minerals have little or no commercial value in the metallurgical processing industry at this time. Thus, as Greenspoon (1970) stated, 

the exploitation of thallium is an integral function 

of zinc production and demand. To date, world consumption of thallium has been less than the amount 

that could be produced as a byproduct from basemetal sulfides. 

Except for two periods of marked increase in 

demand, one in the late-middle 1950's and one in 

the early-middle 1960's, U.S. consumption of thallium has been relatively stable, approximating 4,000 

pounds annually. Greenspoon (1970), however, indicated that the 1968 demand for thallium had risen 

to 6,500 pounds. She gave values of annual peak 

demand for thallium in the mid-1950's at approximately 14,000 pounds and in the mid-1960's at some 

9,000 pounds. The 1950's demand probably resulted 

from increased research using radiation equipment 

and from sophistication of military defense systems, 

particularly infrared detection. The increased demand in the mid-1960's may have been due to the 

conversion of domestic electronic equipment to solid 

state and increased use of thallium in or associated 

with electronic components. The sudden drop following this increase in demand was probably due to the 

Federal curtailment on the use of thallium as a 

rodenticide. From 1964 to 1968 no thallium was produced in the United States, presumably because 

processed reserves were sufficient to meet requirements. Thus, production is sporadic. It is likely that 

industrial plants that use thallium buy sufficient 

amounts at any one time to last several years. As a 

consequence, production/time curves are erratic and 

of no meaningful significance. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Thallium, atomic number 81, atomic weight 204.39, 

occurs next to lead in the periodic table and the two 

metals exhibit similar physical properties. There are 

two naturally occurring stable isotopes of thallium, 

Tl203 and Tl205, their relative abundances being given 

as 29.46 and 70.54 percent respectively. Thallium 

metal is bluish white to silvery white and, like lead, 

is soft and malleable. Unlike lead, however, a freshcut surface of thallium metal will develop a thick 

oxide coating in several weeks. The density of 

thallium is 11.85 g/cm:J at 20°C, the melting point 

is 303°C, and the boiling point is 1,457°C. Thallium 

metal occurs with three crystal lattice modifications: 

below 230°C it is hexagonal close-packed, above 

230°C it is body-centered cubic, and at high pressures it is face-centered cubic, the triple point being 

at 110°C and 30 kilobars. 

Shannon and Prewitt (1969) gave the following 

ionic radii for thallium in various coordination 

polyhedra. 

Tl+ll 

Coordination No. 

VI 

VIII 

XII 

VI 

VIII 

Ionic 

radius (A) 

1.50 

1.60 

1.76 

.88 

1.00 

Thallium was placed in group III of the periodic 

table by Mendeleev, under boron, aluminum, gallium, 

and indium. Thallium has three electrons in its 

outer valence shell and the maximum positive valence state attained is Tl +\ by donation of the two 

outer 6s2 and single 6p1 electrons to coordinating 

anions. The thallic state is generally attained under 

highly oxidizing conditions. The single. 6p1 electron, 

however, is much more readily donated than the 

two 6s2 electrons, so that under more normal endogene processes, thallium is preferably in the monovalent Tl + 1 or thallous state. Thallous (Tl + 1 ) salts 

are generally highly volatile. 

In the monovalent state, thallium has unique 

chemical and physical pro~erties, resembling both 

lead and the alkali metals potassium, rubidium, and 

cesium. Thus, thallium is both a chalcophile and a 

lithophile element, and under certain conditions 

displays considerable siderophilic affinities. As a 

consequence it is widely dispersed in the earth's 

crust. Vlasov (1964, p. 491-680 of English translation) stated that thallium metal closely resembles 

lead in density, melting point, electrical conductivity, 

hardness, atomic volume, radius, and thermal stability. Like lead and other chalcophile elements, 

thallium is also diamagnetic. Similarly, monovalent 

thallium resembles the alkali metals potassium, rubidium, and cesium of the lithophile group in both 

physical and chemical properties. It replaces K + 1 

by isomorphous substitution in silicates such as the 

alkali feldspars and micas, and in some minerals 

such as pollucite it is thought to replace Rb+ 1 and 

Cs+ 1 (Ahrens, 1947a). Several authors have attempted, with limited success, to establish Rb/Tl 

and K/Tl ratios on basic through acidic and pegmatitic igneous rocks. In some instances there is a 

suggestion of a direct linear relationship between 

rubidium and thallium (Ahrens, 1948) and the suggestion of an inverse linear relationship between 

potassium and thallium. 
634 UNITED STATES MINERAL RESOURCES 

The crustal abundance of thallium is low, approximating 1 ppm (part per million). Estimates of the 

average crustal abundance of thalli urn range from 

3 ppm (Ahrens, 1947b) to values as low as 0.1 ppm 

(Noddack and Noddack, 1934). An average value 

for all estimates approximates 1 ppm, which is in 

agreement with the values of 1.3 ppm given by 

Shaw (1952, 1957) and of 1-1.1 ppm by Ivanov (in 

Vlasov, 1964). Although the abundance of thallium 

is extremely low, it is in excess of the crustal abundances of elements such as mercury, silver, and gold. 

Unlike these elements, however, thallium rarely 

concentrates into specific minerals. Several characteristic thallium sulfide, selenide, and oxide minerals occur in nature, but they are extremely rare; 

most thallium occurs as a trace element in other 

minerals. 

The occurrence and concentration of thallium appear to be functions of genetic environment and 

elemental association. These conditions, in turn, are 

governed by chemical affinity, atomic size, valency, 

and temperature and pressure. 

DISTRIBUTION IN MINERALS AND ROCKS 

The main source of thallium metal is sulfide ore, 

mined primarily for base metals such as lead and 

zinc that yield thalliwn as a byproduct. The thallium 

content of these sulfides ranges from 10,000 ppm to 

nondetectable amounts. The most consistent occurrence of thallium is in the structure of the alkali 

feldspars and some micas, in which values range 

from 600 ppm to nondetectable amounts ; these silicate minerals have little or no present economic 

significance. 

Vlasov (1964) noted that although thallium occurs 

in sphalerite, pyrite, marcasite, chalcopyrite, pyrrhotite, and other sulfide minerals, it is particularly 

concentrated in the colloform varieties. Thus it may 

be possible to explain the wide variation of thallium 

content in specific sulfide minerals in terms of temperature and pressure--those sulfides formed from 

a crystallizing melt generally being low in thallium, 

and those formed from colloidal suspensions under 

lower temperatures and pressures generally being 

enriched in thallium, with intermediate variations 

between these end members. 

Because of chemical affinity, size, and valency, 

thallium associates with silicate minerals rich in the 

alkali metals potassium, rubidium, and cesium. The 

isomorphous substitution of thallium for potassium 

is readily attained in the alkali feldspars and in the 

micas where potassium is contained as the relatively 

loosely bound, high coordinated interlayer cation. 

Hence their thallium content may be quite high, in 

the hundreds of parts per million, especially in the 

later-stage pegmatitic alkali feldspars and micas. 

In minerals of sedimentary origin, many manganese hydroxides contain concentrations of thallium 

with values as high as 2,300 ppm. Substantial thallium content has also been recorded in pyrites of 

sedimentary origin, particularly those associated 

with coal beds. 

Thallium is widely dispersed in rocks, but its distribution is controlled by its general restriction to 

the sulfide and alkali-rich silicate rock-forming minerals. Thus its concentration in ultrabasic rocks is 

very low, less than 1 ppm, increasing gradually 

through intermediate to acidic and pegmatitic rocks 

to concentrations greater than 1 ppm. Thallium appears to increase in direct relationship to an increase 

in alkali feldspars and potassium-rich micas. In 

particular, it is noted to concentrate in the later 

stage, lower temperature pegmatites and aplites. 

The relationship of thallium to metamorphic rocks 

is poorly understood. On the basis of characteristic 

mineral assemblages, particularly those rich in the 

alkali metals, it would appear logical for thallium to 

decrease with increasing metamorphic grade in an 

open system. 

In the sedimentary cycle, the behavior of thallium 

is complex. Thallium may occur in a detrital grain 

of the original host mineral, such as a feldspar or 

mica. It may also occur as a constituent of those 

minerals formed in the sedimentary environmentin highly oxidizing conditions incorporated into 

manganese hydroxides, in reducing conditions as a 

sulfide in colloidal pyrite, and in a marine environment preferentially absorbed by colloidal clays and 

shales. 

Thus thallium values range from 6 ppm, recorded 

in a shale, to nondetectable values in carbonate 

rocks. 

RESOURCES 

World reserves and potential resources of thallium 

(table 131) were calculated from respective commodity reserve and resource estimates prepared for 

this volume (except for iron sulfides, which were 

based on U.S. Bureau of Mines estimates), using 

thallium contents of 2.2 ppm in zinc sulfides, 2 ppm 

in lead sulfides, 0.25 ppm in iron sulfides, 0.75 ppm 

in coal ash, and 10 ppm in manganese nodulesfactors computed from recently processed analytical 

data of a study of the distribution and occurrence 

of thallium in rocks and minerals. 

The United States is potentially self-sufficient in 

thallium resources, the reserves contained in zinc, 

lead, and iron sulfides being 266 short tons, and 
THALLIUM 635 

TABLE 131.-World reserves and potential resources of 

thallium, in short tons 

Reserves: Identified deposits from which minerals can be extracted profitably with existing technology and under present economic conditions. Potential resources: Identified mineral deposits not profitably recover- able wtth existing technology and economic conditions, and undis- covered mineral deposits whether of recoverable or subeconomic grade. 

Identified resources: Specific, tdentified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existing technology 

and economic conditions. Hypothetkal resources: Undiscovered mineral deposits, whether of re- coverab'e or subeconomic grade, that are geologically predictable as existing in known districts. 

Source __________ _ 

U.S.A. ------------------ Other North American ___ _ 

South America -----·-------

Europe ------------------ Russia ------------------ Asia -------------------- Australasia -------------- Africa ------·------------

World total 

Reserves 

Zinc 

sulfide 

165 

143 

59 

198 

106 

70 

77 

51 

869 

Lead 

sulfide 

88 

48 

14 

58 

42 

24 

44 

12 

330 

Potential resources 

Iron 

sulfide 

13 

15 

26 

50 

40 

36 

1 

10 

191 

All 

sulfide 

266 

206 

99 

306 

188 

130 

122 

73 

1,390 

In zinc sulfide, worldwide -------------------------------- 17,818 In lead sulfide, worldwide ---------------------------------- 3,944 In oceanic manganese nodules _____________________________ 9,900,000 

In coal ash from identified coal resources: 

U.S.A. ---------------------------------119,000 Other North American ------------- ______ 11,000 

South America -------------------------- 1,500 

Europe ---------------------------------- 47,000 

!~i:ia--=================================4g~:ggg Australasia -------------------------- ___ 4,500 

Africa --------------------------------- 6,000 

Total coal ash, identified resources ------------- ____ 715,000 

In coal ash from hypothetical coal resources ------------------- 550,000 

resources contained in coal ash being 119,000 tons. 

The coal ash, however, is a highly dispersed source 

and probably most thallium will continue to be obtained as a byproduct from zinc ores. No published 

data could be found on the recovery factors attained 

in the processing of thallium from the flue dust and 

residues of base-metal smelting. Previous authors 

have inferred the recovery factors to be low. Converting the total 1968 U.S. smelter production of 

zinc to sulfide, calculating the hypothetical thallium 

amount this sulfide should contain, and then comparing this value with the estimated amount of 

thallium actually extracted in 1968, produces a 

recovery factor of approximately 75 percent. This is 

considered a realistic value and a minimum if the 

assumed average thallium content of zinc sulfide 

at 2.2 ppm is correct. It is certainly not low, as 

previously stated. 

U.S. recoverable thallium reserves from zinc sulfides, employing present technology, are estimated 

at 124 tons, and from all sulfides, 200 tons. At a 

domestic consumption rate of 3.25 tons annually, 

the supply is sufficient for 38 and 62 years respectively. The present supply of thallium-bearing zinc 

ores slightly exceeds the requirements for thallium 

metal, and unprocessed residues containing thallium 

are being stockpiled by the industry. Any unforeseen increase in the demand for thallium, however, 

would command that alternative sources other than 

zinc sulfides be considered. In this respect the vast 

potential of coal ash and sea floor manganese nodules 

is important. 

The United States refines approximately 20 percent of the world's output of thallium metal to meet 

domestic requirements. This percentage must surely 

decrease with continuation of the current trend 

toward closing of domestic smelters and expansion 

of zinc-smelting facilities in Canada, Mexico, Australia, and Japan, together with the capability of 

extracting thallium as a byproduct. 

Total world reserves of thallium contained in zinc 

sulfide reserves are estimated at 869 tons, of which 

650 tons is recoverable with a 75 percent recovery 

factor. At an estimated world consumption rate of 

15 tons annually, the supply is sufficient for 43 years. 

Projected world reserves of thallium from all sulfide sources, 1,390 tons, will be exhausted in 70 

years under the same conditions. Total world thallium resources contained in coal ash from identified 

coal resources are estimated at 715,000 tons, and in 

sea-floor manganese nodules a massive 9.9 million 

tons. Increased discovery of sulfide deposits will proportionately increase thallium reserves, and potential 

resources are very high, particularly in relatively 

unexplored areas. In addition, the inclusion as speculative resources of the thallium contained in pegmatitic feldspars and micas, which could be recovered should the need arise, produces vast potential 

resources. 

PROBLEMS FOR RESEARCH 

Research is needed to improve our quantitative 

understanding of thallium distribution in minerals 

and rocks. Alternate sources for the recovery of 

thallium metal, such as sea-floor manganese nodules 

and coal ash, must be delineated to cover anticipated 

and sudden unforeseen future demands. 

Although thallium is widely distributed in the 

earth's crust, it is concentrated in, or has an affinity 

for, certain mineral species. There is evidence to 

suggest that its concentration in these minerals 

is temperature and pressure controlled. Thus, its 

variable abundance in specific index minerals must 

be studied and modeled over known mineralized 

deposits and rock suites of genetically different 

origins. It may then be possible to evaluate the potential of mineralized areas for other commodities, 

on the basis of the distribution and amount of 

thallium that is present. 
636 UNITED STATES MINERAL RESOURCES 

REFERENCES CITED 

Ahrens, L. H., 1947a, Analysis of the minor constituents in 

pollucite: Am. Mineralogist, v. 32, p. 44-51. 

--- 1947b, The abundance of thallium in the earth's crust: 

Science, v. 106, p. 268. 

--- 1948, The unique association of thallium and rubidium 

in minerals: Jour. Geology, v. 56, p. 578-590. 

Greenspoon, G. N., 1970, Thallium, in Mineral facts and problems, 1970 ed.: U.S. Bur. Mines, Bull. 650, p. 749-758. 

Kolotova, S. 8., and Kharitonova, N. I., 1970, Effect of 

thallium on plants [abs.]: Chern. Abs., v. 76, no. 1, p. 

261, 2855a. 

Lee, A. G., 1971, The chemistry of thallium: Amsterdam/ 

London/New York, Elsevier, 336 p. 

Noddack, I., and Noddack, W., 1934, Die geochemischen 

Verteilungskoeffizienten der Elemente: Svensk Kern. 

Tidskr., v. 46, p. 173-200. 

Shannon, R. D., and Prewitt, C. T., 1969, Effective ionic 

radii in oxid·es and fluorides: Acta Cryst., v. 25, p. 925-

946. 

Shaw, D. M., 1952, The geochemistry of thallium: Geochim. 

et Cosmochim. Acta, v. 2, no. 2, p. 118-154. 

--- 1957, The geochemistry of gallium, indium, thalliuma review [Chap.] 6 in Physics and chemistry of the 

earth: v. 2 of Ahrens, L. H., and others, eds., New 

York, Pergamon Press, p. 164-211. 

Vlasov, K. A., ed., 1964, Geochemistry of rare elements, v. 

1 of Geochemistry and mineralogy of rare elements and 

genetic types of their deposits [in Russian]: Moscow, 

Publishing House "Nauka," 704 p. [Translation, Israel 

Program for Sci. Translations, Jerusalem, 688 p., 1966.] 
UNITED STATES MINERAL RESOURCES 

TIN 

By C. L. SAINSBURY and BRucE L. REED 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

lJses ----------------------------------------

Supply -------------------------------------- Exploitation -------------------------------------

Relation to byproducts -----------------------

Environmental problems ---------------------

Geologic environment ----------------------------

~chentistry --------------------------------

Geochemical cycle ----------------------------

Tin minerals --------------------------------

Types of deposits ----------------------------

Lode deposits -----------------------------

Pegmatite deposits ----------------------- Pneumatolytic-hydrothermal deposits _____ _ 

Subvolcanic or tin-silver deposits ---------

Disseminated deposits -------------------

Contact-metamorphic deposits -------------

Fumarole deposits -----------------------

Placer deposits ----------------------------

Residual placers -------------------------

Eluvial (slope) placers -------------------

Alluvial (stream) placers -----------------

Marine placers --------------------------

Fossil placers ----------------------------

Resources ---------------------------------------

Identified resources --------------------------

Hypothetical resources -----------------------

Speculative resources ------------------------

Prospecting techniques ---------------------------

Problems for research ---------------------------

References cited ---------------------------------

FIGURE 

71. Diagram showing geochemical cycle of tin __ _ 

TABLES 

132. Ionic radii and electronegativity of ions similar 

to Sn2+ and Sn'+ -------------------------

Page 

637 

637 

638 

638 

639 

639 

640 

640 

640 

641 

642 

643 

643 

643 

643 

643 

643 

643 

644 

644 

644 

644 

644 

644 

645 

645 

645 

645 

646 

648 

650 

651 

Page 

642 

Page 

640 

Page 

133. Range and average contents of tin in various 

materials -------------------------------- 641 

134. The more common tin minerals -------------- 642 

135. Tin reserves and resources of the world ------ 646 

ABSTRACT OF CONCLUSIONS 

The lJ ni ted States consumes almost 30 percent of the free 

world's annual production of primary tin. Nearly half this 

amount is used in the manufacture of tinplate, principally 

for tin cans; the other main uses are in solders, bearing 

alloys, bronze, chemicals, and coatings other than tinplate. 

Many of these uses could be met by substitutes such as tinfree steel, aluminum, or plastics. 

Current lJ.S. tin production, as a byproduct of molybdenum 

mining in Colorado, is negligible. The strategic stockpile is 

sufficient to guarantee against a sudden shortage of primary 

tin for essential uses, but at the current rate of consumption even this supply would be depleted in a little more 

than 4 years. Domestic reserves of tin, mainly in Alaska, 

would provide only about three-fourths of a year's supply, 

conditional resources about the same, and hypothetical and 

speculative resources about 2 years' supply; thus, it seems 

clear that the lJ nited States must continue to depend on 

tin imports for most of its needs. The largest foreign conditional and undiscovered resources are in southeastern Asia, 

Brazil, China, Bolivia, and Zaire. The worldwide geologic 

association of tin with acid granitic rocks and rhyolites is 

so well marked that speculation as to the likelihood of finding major tin resources in new geologic environments is 

without redeeming value. 

INTRODUCTION 

Tin metal has two modifications: "white" tin of 

tetragonal crystal symmetry and specific gravity of 

7.31, and "gray" tin of cubic symmetry and specific 

gravity of 5.75 (Lange, 1961). Below a temperature 

of 13.2°C, white tin changes to gray tin and crumbles to a powdery mass. Alloying tin with any other 

metal prevents this change from white to gray tin; 

hence, tin is seldom if ever used in pure elemental 

form. Tin is nontoxic, is easily melted, and has a 

low coefficient of friction. Although tin metal is 

soluble in strong acids, tin as plating is rendered 

U.S. GEOL. SURVEY PROF. PAPER 820 

637 
638 UNITED STATES MINERAL RESOURCES 

inert toward weak acids, bases, air, and other corrosive agents by the formation of a thin film of tin 

oxide. Probably the most important property of tin 

is its extreme fluidity in the molten state and thus 

its ability to wet many other metals and alloys. 

The fluidity and excellent wetting characteristics 

lead to its most important use as tinplate, which 

accounts for nearly 50 percent of the tin used in 

the United States. 

USES 

The six principal use categories of tin, in decreasing order of importance, are tinplate, solders, bearing alloys, bronze, chemicals, and coatings other 

than tinplate. In the highly developed countries, the 

principal use of tin is as a coating on steel plate for 

use in the manufacture of tin cans. Although aluminum, plastics, and tin-free steel (steel with a very 

thin coating of chromium) are capturing a large 

share yearly of established can production in these 

nations, tin is normally used in cans produced in the 

newly developing nations. These two factors roughly 

balance each other; as a result, the total yearly 

world consumption of tin in tinplate increases only 

slightly. 

Because of a strong and sustained research program funded by contributions of the tin-producing 

nations to the Tin Research Institute (Fraser Road, 

Greenford, Middlesex, England), new uses of tin 

are established almost yearly, offsetting active 

trends toward the substitution of aluminum and 

plastics for tin. Only a few of the new uses are 

mentioned here ; the interested reader is referred 

to the "Quarterly Review" of the Tin Research Institute and to the various minerals yearbooks of the 

U.S. Bureau of Mines. 

One of the fastest growing new uses of tin is in 

the production of organotin chemicals. These are 

chemicals in which quadrivalent tin is linked to three 

hydrogen atoms and to an "X Group," which includes 

OH, Br, Cl, I, acetate, alkenyl, alkanoyloxy, or more 

complex derivatives. These organotin chemicals 

have proved to be very effective pesticides, fungicides, and wood preservatives and have relatively 

low toxicity. Between 1950 and 1968, production of 

organotin compounds rose from 50 tons to.more than 

10,000 tons, largely because of research· initiated 

worldwide by the Tin Research Institute. A very 

rapid rise in use of organotin compounds has resulted from their use as a stabilizing agent in polyvinylchlorides (PVC). Organotins have proved effective in preventing discoloration and embrittlement 

\?f clear PVC. Because of its low toxicity, PVC stabilized with organotins may be legally used in packaging of foodstuffs. 

Within the automotive industry, tin continues its 

long-established uses in bearings, bronzes, solders, 

body fillings (to smooth joins and contours), terneplate for gasoline tanks, and pewter parts. In addition, tin is being added to cast-iron or cast-steel 

parts to improve their machinability and is being 

used as an additive in sintering of iron powders. 

Much of the safety glass now used is made by the 

new technique of floating liquid glass on a molten 

bath of tin metal. 

In keeping with the space- and nuclear-age technology, an alloy of tin and niobium has been found 

to be a highly superior superconductor. Such a 

superconductor, consisting of more than 20 km of 

niobium-tin ribbon wound on a wheel of 5-foot diameter, when activated in liquid helium will produce a 

magnetic field so strong that the entire assembly 

will float in space in its own magnetic field. This 

extreme magnetic field will be used to trap a highenergy plasma of electrons and ions produced by 

thermonuclear fusion. This energy source and trapping arrangement ultimately may supply unlimited 

quantities of cheap electric power. 

Finally, mention should be made of the irreplaceable low-fusing-point eutectic alloys of tin with 

elements such as bismuth or antimony. These are 

bright, silvery, nontarnishing alloys which can be 

melted and remelted with negligible loss to oxide 

films. One such alloy, consisting of tin, bismuth, 

cadmium, lead, and indium, melts at 47°C. Such 

alloys are indispensable in automatic fire-control 

systems; in machining of fragile parts, which are 

cast in low-melting temperature alloys and machined to shape, after which the alloy is melted 

away; and in engineering research. 

In spite of loss of some established markets, such 

as tin foil, new uses of tin are likely to more than 

offset these losses, and tin consumption is not likely 

to decrease in the foreseeable future. 

SUPPLY 

U.S. consumption of primary tin-about 57,000 

tons in 1968-is about 30 percent of the free world's 

mine output, which in 1968 amounted to about 

182,000 tons. About 90 percent of the world's tin is 

produced by seven countries. In 1970, Malaysia furnished 63 percent of tin imported into the United 

States; Thailand furnished 30 percent, and five other 

nations-Australia, Brazil, Indonesia, Nigeria, and 

the United Kingdom-combined to furnish the remaining 7 percent. 

Because the United States consumes almost 30 
TIN 639 

percent of the free world's primary tin but produces virtually none, tin remains within the strategic category established by the U.S. Government. 

Because of this strategic category, a large stockpile 

of tin was accumulated by the Defense Production 

Administration during the 1950's. This stockpile 

contains a required strategic reserve of 232,000 long 

tons of tin. About 20,000 long tons of tin has been 

declared surplus from the stockpile and is gradually 

being disposed of by the General Services Administration. 

Although tin is not produced within the United 

States, the strategic stockpile is sufficient to guarantee against a sudden shortage of tin for essential 

uses. Moreover, because the tin-producing countries 

are scattered widely throughout the world and across 

many types of political boundaries, loss of production from one area can be compensated for within 

a few years by increased production from other 

areas. Historically, tin has been available for all 

peace-time uses, and in fact it has often been in 

excess supply. Because many of the uses of tin 

could be met by substitutes, such as tin-free steel, 

lacquered cans for foods, and aluminum or plastics, 

tin can be considered at least partly replaceable in 

the world's technology. 

EXPLOITATION 

A discussion of tin would not be complete without mention of the fact that of all the mineral commodities in world trade, tin is unique in being regulated by international agreements, imposed by the 

International Tin Council. This organization is composed of members of most of the major producing 

and consumer countries. Producing nations contribute funds to the Council; these funds are used to 

create a buffer stock of tin which is disposed of or 

acquired by the Buffer Stock Manager, who must 

buy or sell tin as the world market price goes below 

or above predetermined prices. In times of oversupply, the Tin Council may impose production 

quotas which must be adhered to by the signatory 

producing countries .The actions of the International 

Tin Council serve to prevent violent price fluctuations 

and to insure an orderly flow of tin in the world 

markets. Because of the resemblance of the Tin 

Council to an international cartel, the United States 

is not a member. 

Tin has been a standard metal of commerce at 

least since the late Bronze Age (3500-3200 B.C.). 

In such a long-lived world trade, diverse cultures 

have been brought into contact, thus modifying 

many of the historical cultures. For instance, the 

Phoenicians regularly transported tjn from Cornwall (England) into world markets, the tin being 

furnished in large part from old alluvial placers. The 

bronze made from tin was used in all metal tools 

including weaponry for innumerable centuries. Few, 

if any, other metals have played such an important 

continuing part through the development of human 

civilization. 

Since the beginning of historical times, tin has 

been available except when major wars or other 

political events have temporarily disrupted its usual 

flow. Perhaps never has tin been in jeopardy because 

of exhaustion of minable reserves, but political 

events have played the major part in all disruptions. 

For instance, between 1954 and 1959, production 

from Indonesia, the Congo, and Bolivia fell 25,000 

tons, creating a shortfall which raised tin prices to 

an all-time high. This loss was entirely political and 

was alleviated by increased production in Malaysia, 

Thailand, and Australia. When Indonesian production is reestablished to the 1954 level, an excess of 

tin will be produced. In fact, Indonesian tin probably 

will replace some Malaysian tin, if necessary, as a 

result of imposition of production quotas. 

New discoveries of major tin fields also have been 

important in maintaining world reserves. The deposits in the Congo were discovered in 1938, and 

reserves there must yet be largely unexplored. 

Within the past 10 years, the discovery and development of the Rondonian deposits in Brazil have 

added significantly to world production and very 

significantly to world reserves. After World War II, 

large new deposits were found in Siberia; these are 

sufficiently productive to satisfy the growing Soviet 

tin needs. To date, no major tin-bearing area of the 

world can be said to be totally exhausted, as proved 

by the reestablishment of a significant production 

in Cornwall, long thought of as being exhausted. 

RELATION TO BYPRODUCTS 

With each technological improvement in beneficiation, older deposits are returned to production, and 

new demands for byproducts have elevated large 

tonnages of tin ores from the category of resources 

to reserves. For instance, the tin which may ultimately be won during the mining of the Lost River 

fluorite-tin-tungsten-beryllium deposits in Alaska 

could amount to as much as 40,000 long tons of tin. 

Most of this tin was considered a submarginal resource until the price of fluorspar rose sufficiently to 

place large tonnages of rock containing tin, fluorite, 

tungsten, and some base metals into the reserve 

category. In the future, other large deposits, in 

which tin is only one of several valuable commodities, will undoubtedly be brought into production. 
640 UNITED STATES MINERAL RESOURCES 

In other established mining areas, certain byproducts and coproducts have played an important 

part in the establishment and life of tin mines. 

Many placer mines produce important amounts of 

columbite-tantalite (Nigeria) ; others produce significant amounts of rare-earth minerals and thorium. 

Often, the economic feasibility of an operation will 

depend upon the byproducts. Unfortunately, such 

mines are subject to closure by major discoveries of 

deposits that contain the associated byproducts. 

With the discovery of the large rare-earth deposits 

at Mountain Pass, Calif., much of the market was 

lost to byproduct monazite and other minerals containing rare earths that formerly were recovered 

commercially from tin placers. The capture of the 

niobium market by pyrochlore from the Canadian 

deposits seriously reduced the economic potential of 

the placers of Nigeria, which historically had produced a salable columbite-tantalite concentrate. 

In some lode deposits, cassiterite is accompanied 

by several valuable potential coproducts or byproducts, especially lead, zinc, silver, uranium, bismuth, 

cadmium, tungsten, and fluorite, but most such byproducts are not yet marketable. One advantage of 

complex ores, which helps offset expensive beneficiation, is that prices of all commodities are unlikely 

to be depressed simultaneously. 

Practically all the tin recovered in North America 

is produced as a byproduct. The lead-zinc mine at 

Sullivan, British Columbia, has produced over 

10,000 tons of tin as a byproduct, and some tin is 

recovered from the molybdenum mine at Climax, 

Colo. Of perhaps greater significance is the silver 

recovered from the complex Bolivian ores. In other 

mines, as at the San Antonio mine, Mexico, the silver 

produced has been as valuable as the tin. The large 

Kochiu tin fields of China were originally opened 

for their silver content. 

In short, a certain amount of the tin produced in 

the world is dependent upon the value of the byproducts, but as the bulk of the tin is produced 

from placers with limited production of salable byproducts, it is unlikely that byproducts will greatly 

influence future tin production. 

ENVIRONMENTAL PROBLEMS 

By its nature, placer mining tends to reshape or 

destroy valuable lands along river courses. Without 

planned rehabilitation, placer tailings are useless for 

agriculture, but in Malaysia, dredge pools have in 

places been converted to fish hatcheries and fish 

farms. Nevertheless, in places such as the Kinta 

Valley, the richest tin placers lie beneath the most 

productive farmlands. In such areas, land-use planning far ahead of current operations is required for 

extraction of the tin. In other areas, such as Bolivia, 

lode mines are in lands virtually useless for agriculture. That development of new lode mines need not 

interfere with other land uses is illustrated by the 

successful reopening of the South Crofty mine in 

Cornwall, England, certainly one of the most scenic 

areas on earth. 

As noted by Heindl (1970, p. 767), "Industrial tin 

operations, because of the relatively high unit value 

of the product and the size of the operations, are 

not important contributors to industrial pollution. 

Primary tin-smelting operations discharge SO:r 

containing gas from a 250-foot stack." At present, 

no tin smelters are in operation in the United States, 

and no smelter-gas problem from tin ores exists. 

In Southeast Asia, where the greatest tin reserves 

and resources are found, many of the tin placers are 

beneath sea water, and no conflicting land-use problems exist. The same can be said for the Siberian 

placers beneath the Arctic tundra. At present, there 

is little likelihood that land-use conflicts or environmental issues can seriously curtail world tin production. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 1 

Tin is an element of atomic number 50 and atomic 

weight 118.70, consisting of the isotopes, in percent, 

Sn112, 0.95; Sn114, 0.65; Sn115, 0.34; Sn116, 14.24; 

Sn117, 7.57; Sn118, 24.01; Sn119, 8.58; Sn120, 32.97; 

Sn122 , 4.71; and Sn12\ 5.98-one of the more complex 

isotopic compositions known. Tin has two common 

valences, +2 and +4, with ionic radii respectively 

of 0.93 A and 0.71 A. Table 132, modified from Borchert and Dybek (1960), shows the ionic radii and 

electronegativity of the more common ions with 

which tin is associated. Tin also is amphoteric, forming either acids or bases. Because of its similarity 

TABLE 132.-lonic radii and elec.tronegativity of ions similar 

to Sn2+ and Sn•+ 

Ionic Ion radius ( i) 

Sn2+ --------------- 0.93 

Ca2+ ----------- .99 

Cd2

+ ----------- .97 

Fe2+ ----------- .83 

Sn'+ --------------- .71 

Ti'+ ------------ .68 

Fe3+ ------------ .67 

M~+ ----------- .78 

Sc3+ ----------- .83 

Electronegativity (e) 

1.65 

1.00 

1.50 

1.65 

1.80 

1.60 

1.80 

1.20 

1.30 

iXe 

1.535 

.99 

1.47 

1.37 

1.33 

1.088 

1.206 

.936 

1.079 

1 Modified from a statement prepared by Michael Fleischer, U.S. 

Geological Survey. 
TIN 641 

to other common metallic ions, tin may proxy for 

these ions in common minerals or may form tin analogs of common minerals. Thus tin may be dispersed 

in minerals containing iron, titanium, or calciumfor example, in biotite (up to several hundred parts 

per million), rutile (900 ppm), or andradite garnet 

(up to 1.7 percent). A good example of a tin analog is the mineral malayaite (CaSnSi0 5 ), in which 

tin replaces titanium in the mineral sphene. Malayaite is found in contact-metamorphic skarns (El 

Sharkawi, 1966). It has long been known that magnetite from skarns near tin deposits commonly 

contains tin in anomalous amounts, and recently 

Desborough and Sainsbury (1970) showed that cassiterite from the Lost River tin deposits, Alaska, 

has exsolved from magnetite. Thus the iron-tin 

association is well established. 

The crustal abundance of tin is in the range of 

2-3 ppm (parts per million). Work by several investigators on meteorites (Goldschmidt and Peters, 

1933; Onishi and Sandell, 1957; Borchert and Dybek, 1960) has shown that the nickel-iron phase 

contains an average of 100 ppm tin, whereas the 

chondritic phase contains about 5 ppm and the 

troilite phase about 15 ppm. This suggests that a 

primary enrichment occurred in the nickel-iron phase 

in the earth's core. During the magmatic differentiation of the crust, tin is progressively concentrated 

in the more acid differentiates, as shown in table 133. 

TABLE 133.-Range and average contents of tin in various 

materials 

[Values in parts per million except where noted] 

Material 

Igneous rocks 

Ultramafic rocks ------------------ Basaltic rocks -------------------- Intermediate rocks ---------------- Silicic rocks ----------------------

Greisens -------------------------- Alkalic rocks _____________________ _ 

Usual range reported 

0.1-1.3 

0-8 

0-10 

<1-15 

780-7,800 

8-39 

Sedimentary rocks 

Average 

0.6 

1.1 

1.4 

3.5 

Limestones --·--------------------- --------- 0.2? 

Sandstones ----------------------- --------- .4? 

Shales and clays ------------------ 1-20 6 

Soils ---------------------Mostly__ 0-10 8? 

Phosphorite ----------------------- 0-15 

Other materials 

Ground waters ___ parts per billion__ 0-30 <1 

Oceans .---------------------do____ 0.3-1.2 H?t sprmgs _________________ do____ 0.1-1 

A1r, urban areas_nanograms/cu m__ 3-300 

Within sedimentary rocks, the amount and distribution of tin is imperfectly known, although 

some shales may contain as much tin as tin-rich 

granites (table 133). However, no sedimentary rocks 

are known that are enriched in tin to such a degree 

as to approach commercial ore. 

Of all the metals found in epigenetic deposits, tin 

shows perhaps the most clear-cut relation to a single 

rock type-almost all primary tin lodes are associated with biotite or biotite-muscovite granites, or 

their extrusive equivalents. This imposes certain 

parameters on rampant speculation about the genesis of tin deposits. Whatever the genesis, it has 

something to do with geochemical, physicochemical, 

or petrochemical processes that are peculiar to granites. This is discussed briefly in the later section on 

genesis. 

GEOCHEMICAL CYCLE 

The knowledge of the geochemistry of tin is based 

largely on comparison of different types of analyses 

of different rocks and different types of deposits, 

from widely disp·ersed areas of the world. Before 

the geochemical cycle of tin can be understood fully, 

many more studies on complete rock suites, ores, and 

minerals from single districts are needed. The work 

of Butler (1953) in Cornwall is valuable in tracing 

tin through the weathering cycle. Data have been 

assembled, but only in preliminary form, from the 

Lost River area, Alaska (Sainsbury and others, 

1968), and are summarized in figure 71. (For detailed descriptions of the tin deposits and regional 

geologic setting, see Knopf, 1908, and Sainsbury, 

1964b and 1969.) This tin-bearing area is typical of 

the sulfide-cassiterite type of high-temperature deposit, but unusual in that it includ€'s large deposits 

of fluorite, containing beryllium in economic 

amounts which are zoned about the tin deposits. 

Several significant observations should be made 

about figure 71: (1) Tin is greatly concentrated in 

the granites relative to the limestone and shale 

through which the granites penetrated. (2) The 

heavy-mineral fraction of the granite unquestionably is the clearest indicator of associated tin deposits, although the biotite also contains a high 

amount of tin. ( 3) Tin is slightly concentrated in 

the hornfels zones around the granite, and is highly 

concentrated in all the individual minerals separated 

from the tin and beryllium lodes, clearly recording 

a common genesis. ( 4) Soils (over limestone) are 

greatly enriched in tin over the ore deposits, and the 

tundra plants over ore bodies clearly are enriched 

in tin. ( 5) Bulk stream sediments are enriched in 

tin downstream from tin deposits. (Water was not 

analyzed.) 

More studies, and in greater detail, of this type 

are needed to establish criteria required for making 

valid geochemical comparisons in divers·e areas of 
642 UNITED STATES MINERAL RESOURCES 

Tin deposits 

Fluorite 580 

Arsenopyrite 900 

Dark cassiterite 

Topaz 190 

Quartz 90 

Plagioclase 50 

Orthoclase 4 7 

Biotite 250 

Quartz <40 

>3.3 sp gr 2250 

Bulk granite 20 

FIGURE 71.-Geochemical cycle of tin, western Seward Peninsula, Alaska. Number indicates maximum concentration, in 

parts per million. For granite the concentration is the average of five samples: for individual minerals in granite it is 

the average of three samples. In plants, the concentrations vary with plant type; value shown is the maximum observed 

gain over the corresponding soil. (From Sainsbury, Hamilton, and Huffman, 1968, pl. 2.) 

the world and for formulating dependable exploration techniques. In another area near the Lost River 

district, where cassiterite in placers is associated 

with quartz-cassiterite veins not accompanied by sulfides, bulk stream sediments were devoid of geochemical anomalies, even though overlying a buried 

placer. Only panned concentrates revealed the presence of the lodes (Sainsbury and others, 1970). 

TIN .MINERALS 

Cassiterite (Sn02) contributes almost all the tin 

of industry, although small amounts are recovered 

from tin-sulfide minerals, such as stannite, cylindrite, and teallite. The more common tin minerals 

are listed in table 134. This list is restricted to tin 

minerals containing oxygen or sulfur ; tin also forms 

TABLE 134.-The more common tin minerals 

Name Composition 

Geographic 

occurrence 

Argyrodite _______ AgsGeSn6 -------------Bolivia. 

Arandisite ________ Complex tin silicate __ SouAtfh. West 

rica. 

Berndtite _________ Beta SnS2 ------------ Do. 

Cassiterite ________ Sn02 -----------------Worldwide. 

Canfieldite ________ Ag8SnSe --------------Bolivia, 

Tasmania. 

Colusite __________ Cua(As,Sn,V,Fe,Te) S! _Montana. 

Cylindrite ________ PbaSn,Sb2Su __________ Bolivia, 

Tasmania. 

Franckeite _______ pb5SnaSh2Su ---------- Do. 
TIN 643 

TABLE 134.-The more common tin minerals-Continued 

Name Composition 

Geographic 

occurrence 

Herzenbergite _____ SnS ------------------Bolivia. 

Hielmite ---------Y,Fe,Mn,Ca,Sn-niobate_ Sweden. 

Hochschildite _____ PbSnOa•nH20 _________ Bolivia. 

Hulsite ___________ l2(Fe,Mg) 0•2Fe20a• Alaska. 

lSn02• 3B20a•2H20. 

Malayaite ________ caSnSiOs _____________ Malaya, 

Cornwall. 

Mawsonite --------Cuu.sFe12.sSn10.4Saa ------Tasmania. 

Native tin --------Sn ___________________ New South 

. . Wales. 

N1ger1te ----------Complex tin silicate ___ South West 

Africa. 

Nordenskioldine ___ ca,Sn (BOa) 2 __________ Norway, 

South West 

Africa. 

Ottemannite ------ Sn2Sa ________________ Bolivia. 

Paigeite __________ 30Fe0•5Fe20a•1Sn02• Alaska. 

6B20a•5H20. 

Renierite ---------Cua( Ge,Fe,Sn,Zn) S4 ___ ( ?) 

Soren~enite - _-- _-- N a4SnBe2Si601s ( 0 H), __ Greenland. 

Stanmte ----------Cu2FeSnS1 ------------Worldwide. 

Stokesite ---------Ca,Sn ( SiaOo) •2H20 ____ Cornwall. 

Sukulaite ---------Ta2Sn207 _____________ Norway. 

Teallite ----------PhSnS2 ---------------Bolivia. Thoreaulith -- _____ Sn Ta20, ______________ Congo. 

Varlamoffite ------H2SnOa --------------- Do. 

compounds with tellurium and selenium, but only at 

high temperatures and pressures, and no such minerals are known to occur in nature. Only in Bolivia 

are many of the sulfide minerals present in sufficient 

amounts to be recovered, and their recovery requires 

a complex hydrometallurgical treatment. Stannite is 

found in many tin-sulfide deposits, and small 

amounts are recovered. Of all the coproducts or byproducts produced, tungsten is probably the most 

important. 

TYPES OF DEPOSITS 

Tin is produced from six different types of lode 

deposits, and from placer deposits. 

LODE DEPOSITS 

Lode tin deposits can be classified into six distinct 

types, following the classification of Ahlfeld 

(1958) : (1) pegmatite deposits, (2) pneumatolytichydrothermal deposits, (3) subvolcanic or tin-silver 

deposits, ( 4) disseminated deposits, (5) contactmetamorphic deposits, and ( 6) fumarole deposits. 

PEGMATITE DEPOSITS 

Tin-bearing pegmatites are generally associated 

with granitic rocks and contain cassiterite (Sn02 ), 

as well as other uncommon, valuable minerals such 

as columbite-tantalite, beryl, or spodumene. Most 

productive pegmatites are in areas of deep tropical 

weathering, which permits the economic exploitation of pegmatites that contain less than 0.4 percent 

tin. Some pegmatites are very large, contain cassiterite throughout, and constitute major reserves of 

tin; one example is the Manono pegmatite in the 

Democratic Republic of the Congo, which is 10 

kilometers long and 100-400 meters wide. 

PNEUMATOLYTIC-HYDROTHERMAL DEPOSITS 

Most of the major lode tin deposits of the world 

(those of Bolivia excepted) are of the pneumatolytic- hydrothermal type. (This distinction of the Bolivian type of deposit from what may be called the 

Cornwall type may not be valid. The authors here 

are following most other workers, who consider them 

in separate categories.) Lodes are near or in biotite 

or two-mica granite and form replacement deposits 

or fissure fillings in diverse types of country rock. 

Owing to a regional zonation commonly displayed, 

deposits vary widely in mineralogy. In or near granite, lodes typically contain cassiterite in greisen 

(quartz-mica rock) or quartz-topaz-tourmaline rock 

that also contains wolframite and many base-metal 

sulfides. Farther from the granite, some lodes contain stannite (CuzFeSnS4), base-metal sulfides, and 

silver; in some places, the deposit may be valued 

principally for the silver content. Some individual 

deposits are very large, such as the Dalcoath lode 

in Cornwall, England, which produced 80,000 tons of 

tin (Dines, 1956). 

SUBVOLCANIC OR TIN-SILVER DEPOSITS 

The subvolcanic or tin-silver type of deposit is 

exemplified by the mineralogically complex and very 

rich deposits of Bolivia, where bonanza tin lodes 

also contain large amounts of silver. Deposition in 

a near-surface environment led to strong telescoping 

of the deposits and to mineralogical complexity, 

which creates a p·roblem in the recovery of tin. Rare 

tin-bearing minerals, such as teallite, herzenbergite, 

cylindrite, and canfieldite, are common in these deposits. Individual mines in such deposits have produced enormous amounts of tin; one mine at Llallagua, Bolivia, produced over 500,000 tons (Ahlfeld, 

1936). 

DISSEMINATED DEPOSITS 

In these deposits, cassiterite in small amounts is 

disseminated widely in altered granite, especially in 

border zones or parts changed by addition of tourmaline, topaz, or fluorite. Although only a few disseminated deposits are worked commercially at present, erosion of such lodes (particularly border zones 

of granites) has resulted in large and rich placer 

deposits (Southeast Asia and elsewhere). 

CONTACT-METAMORPHIC DEPOSITS 

Contact-metamorphic deposits are fairly uncom-
644 UNITED STATES MINERAL RESOURCES 

mon and generally consist of cassiterite or malayar 

ite in tactites near granite (Cornwall). The minerals customarily associated are magnetite, garnet, 

pyroxene, fluorite, tourmaline, various sulfide minerals, and, in the Lost River area, Alaska, beryllium 

minerals (Sainsbury, 1964a). The grade is generally 

less than 0.5 percent tin, but hirge tonnages and potential byproduct recovery of base metals, beryllium, and fluorite may give added importance to 

such deposits when other tin supplies dwindle. 

FUMAROLE DEPOSITS 

The term "fumarole deposits" was used by Ahlfeld (1958) to describe small but widespread deposits that form fracture fillings i11 Tertiary lavas. The 

fracture fillings contain cassiterite generally intergrown with specular hematite, and minute grains of 

cassiterite are distributed in kaolinized wall rock 

along veins. A few deposits are mined commercially, 

on a small scale. Placers derived from the erosion 

of such veins are mined in Mexico, New Mexico, and 

Argentina. 

PLACER DEPOSITS 

Worldwide, placer deposits are more productive 

and more cheaply mined than lode deposits; they 

furnish, therefore, most of the commercial production. Cassiterite, the main tin mineral of commerce, 

is both heavy and chemically resistant ; consequently, it forms large placers or residual concentrations. Placers can be conveniently classed as 

residual, eluvial (slope), alluvial (stream), marine, 

and fossil placers. 

RESIDUAL PLACERS 

Residual placers form in place over a bedrock 

source of cassiterite by the chemical decay and removal of the rock minerals. At places, such as Kitololo in the Democratic Republ.ic of the Congo, residual placers-~ downward into weathered lodes 

and are mined either as placers or as open-pit lodes. 

In a truly residual placer, the enriched zone contains 

not only heavy minerals such as cassiterite and 

columbite-tantalite but also chemically resistant 

light minerals such as beryl. In Indonesia, residual 

placers commonly are cemented tightly by hydrous 

iron oxides, forming the "kaksa" of industry, which 

must be crushed to free the cassite-rite. 

ELUVIAL (SLOPE) PLACERS 

Eluvial placers are formed by the chemical decay 

of tin-bearing rocks and the gravity s·eparation of 

cassiterite and other heavy resistates as the decayed 

mantle moves downslope under the influence of 

sheetwash, gravity, and, locally, frost action. Such 

placers grade imperceptibly into residual placers upslope, and often into alluvial (stream) placers downslope. Because of active gravity sorting, some eluvial placers are richer than residual placers; many, 

however, contain coarse rubble, and, in cold regions 

(Alaska and Siberia), fragments of unoxidized deleterious constituents such as arsenopyrite. 

ALLUVIAL (STREAM) PLACERS 

Alluvial placers, by far the largest and richest 

placers, furnish most commercial tin. In 1964, almost 60 percent of the world's tin production came 

from alluvial placers in Southeast Asia (Shelton, 

1965). Other major producing placer areas are in 

Nigeria and in the newly developed tin fields in the 

Territory of Rondonia, Brazil (Brazil Div. Fomento 

Prod. Mineral, 1964). Alluvial placers occupy both 

modern and fossil streambeds, and the distribution 

of tin is dependent upon the location of the source 

areas and the hydraulics of running water. The best 

placers are formed near lodes in sections of streams 

where the velocity is sufficient to result in good 

gravity separation but not enough so that the channel is swept clean. A type of location proved to be 

especially favorable for placer tin is a long stream 

that flows parallel to the margin of a tin-bearing 

granite. 

In Southeast Asia, stream placers formed seaward of present shorelines when sea level was eustatically lowered periodically during the Pleistocene. These stream placers now lie beneath sea 

water ; they are mined by seagoing dredges. In Rondonia, Brazil, some placers lie in areas so low that 

sea water covered them during certain interglacial 

periods when sea level stood much higher than at 

present. Elsewhere in the world, as in Cornwall and 

Tasmania, both lode and placer deposits occur 

within areas which have fluctuated between land and 

sea bottom during Pleistocene climatic changes ; 

placers in such areas may have characteristics of 

both marine and alluvial deposits. 

Owing to the long exposure to air and water and to 

good gravity separation, tin concentrates produced 

from alluvial placers are relatively free of deleterious constituents and may contain as much as 70 

percent tin; as such, they constitute prime smelter 

concentrates. 

MARINE PLACERS 

Most marine placers are beach placers or inundated beach placers. They form where a marine 

shoreline inte-rsects or transgresses either a stream 

valley containing alluvial cassiterite or a bedrock 

source of tin. Although a true beach placer norm-
TIN 645 

ally has a large length-to-width ratio, a placer of 

transgressive origin may consist of a sheet of heavy 

minerals buried beneath marine sediments (Australia). Placers of this type have yielded large 

amounts of cassiterite in Indonesia (Bangka and 

Billiton Islands) and will continue to do so. 

FOSSIL PLACERS 

Any or all of the preceding four types of placers 

may become fossil placers by burial beneath younger 

sediments or lava. Uplift and renewed erosion along 

disrupted drainages may expose such placers irregularly, and second-cycle alluvial placers may be generated (Nigeria). Depending in part on the geologic 

age, the gravels of some fossil placers may be lithified to such an extent that they must be mined by 

lode-mining methods. In others, major postdepositional changes, such as partial solution of cassiterite, may affect the value. 

RESOURCES 

IDENTIFIED RESOURCES 

Tin resources of the world were computed by 

Robertson (1965); his figures were incorporated 

with some modifications and additions into a report 

by Sainsbury (1969). These two reports contain the 

facts and presumptions of the calculations of reserves and brief descriptions of the main tin-producing deposits of the world. 

In the present report, new calculations have been 

made, principally to accommodate this volume's 

classification of undiscovered resources in both 

known and unknown districts. Such geologic calculations require a bold and optimistic approach, and 

new figures are presented herein (table 135) . Factors which can be used to estimate undiscovered 

resources are largely geologic and partly intuitive 

and include: 

1. History of production. 

2. Rapid rise of reserve figures in newly discovered 

districts, such as Rondonia, in Brazil. 

3. Potential favorability of parts of the world in 

which even basic geologic mapping is lacking. 

4. Unexpected new developments in old districts, 

such as the major ore bodies opened recently 

in Cornwall. 

5. Comparison of tonnages mined in countries having a long production history, such as Malaysia, 

with other countries having a substantial production but with higher grade known reserves, 

such as Indonesia and Thailand. 

When these factors are applied optimistically, the 

potential resources of tin in undiscovered districts 

seem to be large, and reserves and resources in 

known districts are increased substantially over the 

previous estimates by Robertson (1965) and Sainsbury (1969). 

The tin reserves and resources of China, Russia, 

and other Communist countries cannot be assessed 

accurately from published data. Even the International Tin Council has not attempted a tabular summary. For this report, however, we have estimated 

the magnitude of tin reserves and resources of China 

and Russia. 

As can be seen from table 135, all the identified 

tin resources lie within the established tin-producing 

countries. The figures given for these resources do 

not differ greatly from those of the previous resource calculations mentioned above. In this report, 

inferred reserves for countries with revived mining 

of substantial amounts of tin, such as England or 

Australia, are assumed to be equal to or greater than 

their measured and indicated reserves. In other 

countries, such as Zaire (the Congo) and Thailand, 

inferred reserves must be much greater than the 

figures for measured and indicated ore. 

Probably the greatest departure from earlier 

reserve estimates is the assignment of substantial 

proved and inferred reserves for England and Australia and greater inferred reserves for Indonesia 

and Thailand. The greater inferred reserves for Indonesia and Thailand are based directly upon a comparison of grade of material being mined by dredges. 

Inasmuch as the tin-producing areas in Thailand, 

Malaysia, and Indonesia are roughly comparable in 

size, a large amount of tin will no doubt be mined in 

Thailand and Indonesia before the grade of their 

alluvial deposits drops to that being mined today in 

Malaysia. 

Because classes of reserves in this report differ 

from those in all previous reports, no direct comparison can be made beyond the figures for identified 

resources, which roughly correspond to the total in 

categories historically called measured, indicated, 

and inferred. 

HYPOTHETICAL RESOURCES 

Evaluation of hypothetical resources can be based 

in part on the past mining history of an area. 

Countries such as Malaysia and Indonesia, which 

have produced large amounts of tin for nearly a 

hundred years and which can expand their production greatly if a slight price increase and an adequate market warrant, are going to continue to 

produce tin for nearly as long as they have already 

done. Other countries, such as Nigeria, have wellknown limiting factors which suggest that they may 

not be able to produce for extended periods of time. 

Hence, their subeconomic resources must be smaller. 
646 UNITED STATES MINERAL RESOURCES 

TABLE 135.-Tin reserves and resources of the world, in long tons of tin metal 

Reserves: Identified deposits from which minerals can be extracted 

profitably with existing technology and under present economic con· ditions. 

Conditional t-esources: Specific, identified mineral deposits whose con· tained minerals are not profitably recoverable with existing technology and economic conditions. 

Country Reserves Measured 

Hypothetical resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that are geologically predictable as existing in known districts. 

Speculative resources: Undiscovered mineral deposits, whether of recover· able or subeconomic grade, that may exist in unknown districts or in 

unrecognized or unconventional fot"m. 

Conditional resources Undiscovered resources 

plus Inferred Paramarginal Submarginal Hypothetical Speculative 

indicated 

North America: 

U.S.A. -----------------------

Canada ----------------------- Mexico -----------------------

8,435 

10,000 

1,000 

33,100 

10,000 

5,000 

14,000 

43,000 

14,000 

40,000 70,000 

200,000 

47,700 

Total 19,435 48,100 14,000 57,000 40,000 317,700 

South America: 

Bolivia ----------------------- 485,000 500,000 

Brazil ------------------------ 300,000 300,000 1,074,000 -------- 1,000,000 

500,000 1,250,000 

1,674,000 

Argentina -------------------- 3,000 3,000 -------- -------- -------- 7,000 ----------------------------------------------------------------------- Total ------------------- 788,000 803,000 1,074,000 500,000 2,924,000 1,007,000 

Europe: 

England ---------------------- 128,700 128,700 -------- 600.000 

Spain and Portugal ----------- 15,000 15,000 -------- 150~000 

425,000 

750,000 

France ----------------------- -------- 4,000 ________ 4,000 ----------------------------------------------------------------------- Total ------------------- 143,700 147,700 -------- 754,000 1,175,000 ============================================================== Asia, Non-Communist: 

Indonesia 1 

-------------------- 500,000 1,860,000 540,000 540,000 

Malaysia --------------------- 600,000 230,000 -------- 1,000,000 1,500,000 1,000,000 

Thailand 2 -------------------- 217,000 1,000,000 1,860,000 -------- 1,500,000 1,000,000 

Burma ----------------------- 250,000 250,000 -------- -------- 250,000 250,000 

Other countries --------------- 17,500 90,000 -------- -------- -------- 100,000 ---------------------------------------------------------------------- Total ------------------- 1,584,500 3,430,000 2,400,000 1,540,000 3,250,000 2,350,000 

Africa: 

~~r:~ia--====================== 138,000 138,000 100,000 3 500,000 

Other countries 4 --------------

65,000 130,000 1,000,000 -------- -------- 1,000,000 

117,000 117,000 -------- 22,000 -------- 330,000 

Total ------------------- 320,000 385,000 1,000,000 122,000 500,000 1,330,000 ====~========~====~~========~===================== 

Australia and Tasmania ----------- 94,330 94,000 100,000 100,000 100,000 500,000 

Chinas --------------------------- 500,000 1,000,000 1,000,000 1,000,000 1,000,000 1,000,000 

U.S.S.R. 5 ------------------------- 200,000 420,000 300,000 300,000 300,000 1,000,000 ==================================================~=== 

World total ----------------- 3,649,965 6,327,800 5,888,000 4,373,000 9,289,000 7,504,700 

1 Inferred reserves in Indonesia are greatly expanded over the estimate 

of Sainsbury ( 1969) on the basis of grade of placer deposits being 

dredged currently in Malay&ia and Indonesia. Present grade of Indonesia 

dredge ground is about 0.62 lbs per cu yd, somewhat higher than that 

dredged in Malaysia in 1947. Hence, before grade in Indonesian placers 

falls to the level of current grades in Malaysia, as much tin will be 

produced from Indonesian placers as was produced in Malaysia between 

1937 and 1971, or about 1,860,000 long tons. 

SPECULATIVE RESOURCES 

In assessing the possibility of finding new districts, several factors unique to tin must be considered. These are: 

1. Tin has been mined and used throughout the 

world for thousands of years, and whatever 

major tin deposits exist in regions settled or 

penetrated by civilized peoples have probably 

been discovered. Conversely, entire new districts might still be found in remoter regions, 

as attested by the recent discovery of a major 

district (Rondonia) in western Brazil. 

2. Each discovery of new tin deposits merely reinforces the fact that deposits containing eco2 The same computation used for Indonesia was applied for Thailand on the assumption that the stanniferous areas were equal to those of 

Malaysia. a In old channels buried under volcanic rocks. 4 Republic of South Africa, South West Africa, Southern Rhodesia, 

Cameroons, Burundi-Urundi, and the north African countries. 5 These are classed as no better than educated guesses. 

nomic amounts of tin are invariably similar to 

those deposits which have been mined for 

thousands of years. One cannot, therefore, even 

validly speculate that new types of deposits 

will be found for tin, such as have been found 

recently for beryllium (Spor Mountain, Utah; 

Lost River, Alaska) or for gold (Carlin and 

Cortez, Nev.). 

3. Many of the great mining districts of the world 

were found by Cornish miners who left Cornwall after her mining industry collapsed, and 

who migrated all over the world. In their 

search for gold, diamonds, or base metals, these 

miners are unlikely to have overlooked major 
TIN 647 

tin deposits in areas they penetrated. 

4. Finally, with the possible exception of commercial deposits of chromite, tin displays such a 

well-marked geologic association-with acid 

granitic rocks or rhyolite-that speculation as 

to the finding of major tin reserves and resources in entirely new geologic environments 

is without any redeeming value; it is like 

speculation as to the possibility of the seventh 

dimension, and the planning of structures 

based upon the speculative existence of it. 

In assembling the table of undiscovered resources, 

it has been assumed that but a few new tin deposits 

will be found. For instance, the estimate of U.S. 

resources includes the assumption that tin deposits 

may be found on the Aleutian Islands, whose geology 

is roughly comparable to the Japanese Islands, which 

have produced moderate amounts of lode tin. Some 

tin deposits may be found in the southern Alaska 

Range, where placer tin has long been known and 

where Reed and Elliot (1970) have found tin anomalies in stream sediments near biotite granites. Analyses of placer concentrates collected between 1900 

and 1954 from many Alaskan streams have shown 

that noteworthy tin occurs in numerous localities 

where tin deposits are not known (J. C. Hamilton, 

written commun., 1972). Tin-bearing lodes may be 

found, but no major new districts are believed likely 

to exist near such areas. In Canada, perhaps a few 

more mines similar to the Sullivan will be found, as 

will be more mines similar to the Mount Pleasant in 

eastern Canada. But speculation about the finding 

of large reserves in North America faces one rigid 

fact-there are no known large tin deposits, lode or 

placer, even in areas with favorable rock types. 

Again, most of these areas have been panned by the 

gold seekers. 

On the basis of the above factors, one cannot 

reasonably expect to find speculative resources of 

any magnitude in the United States, and areas favorable for new deposits in North America are virtually limited to areas such as the Canadian Shield 

or the rhyolite areas of Mexico. Such deposits likely 

will be small. 

In South America, areas may remain in Rondonia, 

possibly even in easternmost Bolivia, in which many 

new deposits similar to those now known may be 

found. This leads to large speculative resources in 

South America. Inasmuch as the large Rondonian 

deposits occur in and near Precambrian granites, 

one can speculate that the Precambrian Shield areas 

in the Guianas and eastern Colombia may also 

contain tin deposits. Perhaps a field even as large 

as the Nigerian tin fields could exist there. Elsewhere in South America, speculative placer resources 

in Bolivia would exist near some lode tin deposits 

and hypothetical resources would be in deeper, unknown ore bodies in known districts. 

In Europe, there is little likelihood for the discovery of large new districts. However, it is assumed that at least 10 more Wheal Jones, or South 

Croftys, will ultimately be found in the old established Cornish mining district. In Spain and Portugal, because of the favorable geology, the known 

deposits~ and the archaic state of mining and exploration, large amounts of tin are assumed to 

remain in unknown deposits. Nowhere else in Europe 

can one postulate substantial tin resources, even in 

the Erzgebirge, because the intensive exploration 

and mining by the Germans during World War II 

have exhausted that possibility. 

In Asia, the long history of mining, the great extent of the placer deposits, and the remoteness of 

much of the jungle country probably insure that 

new lode and placer deposits will be found. Large 

reserves undoubtedly lie offshore on the Sunda Shelf 

and ultimately will be found and mined. Tin will be 

found in Burma, perhaps mostly associated with 

tungsten deposits, but most of this tin will be in 

the known tin belt. 

Because of the remoteness, the jungle cover, and 

the relative recency of the discovery of the tin 

fields of Zaire, both sufficient area and favorable 

geology indicate the possibility for discovery of another tin field the size of the Nigerian field. In 

northern Africa, the scattered known deposits, associated with biotite granite, the remoteness of the 

area, and the poor state of geologic knowledge all 

suggest that tin deposits may be found there. 

In Australia, the rapid resurgence of tin mining 

since 1965 proves that new deposits will be found, 

principally in Tasmania and possibly in Western 

Australia. 

In Communist China, it is assumed that new deposits will be found in the remote ranges of the 

Himalayas, as well as in known districts, when 

modern mining and exploration techniques become 

available, but elsewhere in China the long occupancy by civilized people who have used tin suggests 

that major new districts probably will not be found. 

In the U.S.S.R., tin deposits not yet known probably exist in the tundra-covered areas of Siberia 

and in the Magadan area of eastern Siberia, for 

numerous deposits have been found in these areas 

since World War II. Despite the large number of 

Soviet geologists actively employed in economic 

geology, it is unlikely that Asiatic Russia has yet 

been adequately explored, though it is unlikely, too, 
648 UNITED STATES MINERAL RESOURCES 

that large new tin districts will be found. 

Resources which may exist in Antarctica and 

Greenland are not considered because data on which 

to base realistic evaluations are not available. 

The grand total of all the reserves and resources 

listed above is about 37 million long tons of tin. 

This is sufficient to sustain a world consumption of 

200,000 long tons of tin per year for about 185 years. 

PROSPECTING TECHNIQUES 

Before discussing the methods used in searching 

for tin deposits, the authors would like to repeat 

two statements made by K. F. G. Hosking at the 

First International Symposium on Tin, in London, 

in 1967 (Hosking, 1967, p. 269). 

Sound prospecting programmes designed to locate new 

primary tin deposits are usually based, to no small degree, 

on the designers' views concerning the relationship between 

such deposits and granitic rocks. 

* * * * * 

As far as possible the writer has refrained from discussing those questions of relationship which require consideration of the sources of granite magmas, granitising agents 

and ore-forming ones, and theories of the nature of these 

agents and of the chemistry of ore genesis. He has adopted 

this line of action becaus·e he believes that a good exploration program must be based essentially on facts, and that 

a program founded largely on theoretical concepts, however sophisticated the latter may appear to be, is little 

better than one which requires only that a blind-folded person should stick a pin in a map in order to find a tin deposit. 

Following somewhat along the lines above quoted, 

the authors are here confining their discussion to 

the accepted exploration techniques. These techniques are based in part on application of concepts 

that were originally theoretical but have been "stabilized" by a long history of facts. 

In regional exploration, analyses of major tectonic and petrologic features are of great value. 

Because of the obvious relation of all known tin 

deposits to acid granitic rocks, tectonic elements 

that localize such granitic rocks are considered ; 

these elements vary from major mountain ranges 

with granitic cores, subjacent volcanic rocks, and 

extrusive rhyolites to isolated stocks and bosses of 

proper composition. Certain factors may then be 

evaluated for localizing favorable ground within the 

larger elements; these factors may be grouped 

under two broad categories: tectonic and geochemical. 

Numerous authors have noted that the apical 

parts of granitic masses, as well as the margins, are 

especially favorable for the occurrence of tin deposits. Hosking (1967, 1969, 1972) holds that these 

apical parts, which he calls "cusps," are of great, 

almost overriding, importance in localizing tin deposits. Other authors (Stemprok, 1967; Sainsbury, 

1969; Dines, 1956) are inclined to consider that 

postgranite fractures of both regional and local 

extent are of great importance in localizing the 

larger and richer lode ore shoots of some of the 

world's tin districts. When one studies the descriptions of the great lode mining districts of the world, 

one cannot escape the conclusion that most rich veins 

are localized along fractures which formed long after 

the consolidation of the enclosing granite. Where 

great tin lodes are mined within great expanses of 

granite, such as in Cornwall, in veins that (1) conform to regional fracture patterns which cut the 

granites, and (2) may lie entirely blind thousands 

of feet below the present surface (which itself is an 

unknown distance below the original apical part of 

the granites) as at South Crofty mine in Cornwall, 

then it is extremely difficult to relate the tin to 

"cusps" (cupolas?) on the original surface of the 

granite. Even Hosking himself pointed out that regional fracture patterns have localized deposits in 

Cornwall (Hosking, 1967, p. 297). 

The margins of granites, however, have been 

proved to be especially favorable places for the occurrence of placer deposits, especially where streams 

have followed long distances along such margins. 

Stemprok (1967) showed that margins of granitic 

rocks in the Erzgebirge in Czechoslovakia are enriched in tin, and he related this enrichment to the 

escape of volatiles from deeper parts of the granite 

mass along joints and fractures in the shell of the 

granite. Sainsbury (1964b) has shown that even 

though the main tin-tungsten-beryllium-fluorite lode 

at Lost River, Alaska, lies generally above the apex 

of the granite (thus supporting Hosking's views), 

the main tin lodes are along faulted dikes intruded 

along faults of a regional set which cut the granites 

and postdate them by an appreciable time. An enrichment of tin in the marginal shell of the granite 

is related to small veinlets localized in the cooling 

joints of the granite. Again, Stemprok and Sulcek 

(1969) have shown that tin-bearing granites in the 

Krusne hory Mountains of Czechoslovakia have 

marked alteration along flat-lying zones at great 

depths in the granite. The Bolivian deposits are 

localized near subjacent porphyry intrusions, but 

they lie along veins that pass downward out of and 

beyond some of the porphyry intrusives. 

A reasonable conclusion is that tin deposits of 

large tonnage and low grade may be directly related 

to the "bleeding off" of volatiles above cupolas 

("cusps") of granites or along the fractured regions 

of such intrusives but that the large and rich veins 
TIN 649 

are localized in faults and fractures that postdate 

the intrusives and may or may not have any relationship to "cusps." 

Hence, in regional exploration of granitic terranes, a study of the major fracture patterns is 

invaluable. It is especially valuable to determine 

whether regional faults or fractures followed the 

intrusion of the granites closely enough in time to 

allow for the cooling of the shells of the intrusives, 

entrapment of volatile elements in deeper parts of 

the granites, and then rupture of these deep parts 

by major fractures while volatiles were still able 

to escape at high temperature. 

Once a favorable granitic terrane is recognized, 

can one use the petrogenic characteristics of the 

granites to give a dependable clue as to whether 

tin deposits are likely to be associated? The literature upon this subject is voluminous and in large 

part contradictory. For a good discussion, see Hosking (1967), who rather effectively showed that to 

date the only infallible indication of a granite that 

is favorable for tin deposits is the known presence 

of tin deposits! On the other hand, Beus (1969, p. 

70) has shown, by a statistical treatment of data 

obtained by analyses of both bulk granite and biotite, that statistically significant variations are 

found between granites of nonstanniferous regions 

and granites of stanniferous regions, as well as 

between biotites from such granites, in certain areas 

in Russia. Beus' figures show that 98 percent of 

samples from granites of nontin-bearing provinces 

must contain less than 10 ppm tin, whereas only 

12 percent of samples from granites of stanniferous 

areas contain less than 10 ppm tin. However, we 

must still face the fact that the determination that 

a granite (or granites) contains a high amount of 

tin (more than 100 ppm) is still no guarantee that 

a single workable tin lode will be found in or near 

that granite. 

A further problem encountered in the search for 

tin deposits using the geochemical and petrologic 

features of granites is that the analytical methods 

used by different workers are not directly comparable and give wide variations in tin values for a 

single rock, and that the degree of freshness, possible deuteric alteration, and classification of the rocks 

investigated are seldom standardized by scouting of 

several workers. 

Following a suggestion at the First International 

Technical Conference on Tin in London in 1967, and 

after additional discussion at the Second International Technical Conference on Tin in Bangkok in 

1969, a cooperative program was set up to have 

analyses and petrologic descriptions made of the 

same granites (in fact, sawed slabs of a single large 

piece of granite were to be used in the laboratories) 

to determine just how many variations would be 

found. Results obtained to date show that analyses 

and study by three different geological surveys have 

resulted in wide variations in tin content, as well as 

different classifications, for identical pieces of two 

Alaskan tin-granites. Results of continuing studies 

will be reported in an International Symposium to 

be held in Europe in 1974 (Dr. Miroslav Stemprok, 

Ustredni Ustav Geologicky, Malostranske Nam 19, 

Praha, Czechoslovakia). 

In the geochemical prospecting of an area presumed to contain tin deposits, the standard techniques of panning of stream gravels and collection 

of stream sediments are used-and this cannot be 

overemphasized-but they do not always give comparable results! Because cassiterite, the main ore 

mineral of tin, is both heavy and chemically stable 

in the surface environment, panned concentrates 

from streams are a necessity in searching for tin 

deposits. Near the nonsulfide types of tin deposits 

no geochemical anomalies will be found in stream 

sediments, especially in the finer grained fraction. 

Varlamoff (1969) has shown that in the Congo only 

panned concentrates will reveal tin anomalies. Brundin (1969) has shown that in geochemical prospecting in Sweden, in glaciated areas, heavy-mineral 

concentrates were necessary in searching for deposits containing scheelite, cassiterite, and wolframite, and also served in finding ores of sulfide minerals containing base metals. Sainsbury, Hudson, 

Kachadoorian, and Richards (1970) documented an 

area in Alaska where a stream-sediment survey 

using -80 mesh or -40 mesh fractions of total 

stream sediments failed entirely to disclose tin 

placers (and associated base-metal lode deposits), 

whereas panned concentrates, irrespective of the 

concentration ratio achieved by panning, were infallible in tracking down the source area for the 

tin in placers. 

Where tin deposits of the sulfide-cassiterite type 

occur, stream sediments are useful indicators of 

such ore deposits. In the surface environment, stannite breaks down to varlamoffite, an earthy friable 

tin mineral which is easily incorporated into finegrained sediments. Because many other ore elements 

are found in sulfide-cassiterite deposits, tin may be 

accompanied in stream sediments by such elements 

as copper, lead, zinc, silver, tungsten, beryllium, bismuth, arsenic, and antimony, even in the clay-size 

or -80 mesh fraction. Typical values obtained in 

-40 mesh stream sediments downstream from a 

sulfide-cassiterite lode in northwestern Alaska are, 
650 UNITED STATES MINERAL RESOURCES 

in parts per million: Be=41, Sn=1,100, W =70, 

Cu=150, Pb=150, Zn=300, As=3,000, Li=3,000. 

Soils developed over weakly mineralized limestones 

near the ore bodies gave maximum values, in parts 

per million, of Be=270, Cu=610, Pb=2,100, Zn= 

5,000, and Sn=1,500, representing enrichment factors respectively for the above elements of > 180, 

76, >210, >50, and 500 as compared to nearby soils 

over unmineralized bedrock (Sainsbury and others, 

1968). Because many base-metal sulfide deposits contain some tin in sulfide minerals such as chalcopyrite, 

or discrete tin-sulfide minerals, tin values in the 

range 10-40 ppm may be found in stream sediments 

nearby, but they do not indicate tin lodes. In assessing small tin anomalies, it is valuable to consider 

the associated elements lithium, boron, and bismuth, which generally are associated with tin deposits. 

For a more complete discussion of pitfalls to 

avoid in prospecting for tin lodes, see Hosking 

(1965), as well as the numerous papers presented 

at the First and Second International Technical 

Conferences on Tin (lnternat. Tin Council, 1968, 

1969). These volumes give excellent data on searching for both lode and placer tin deposits in various 

parts of the world. 

Most sulfide-cassiterite tin deposits, except possibly those in Bolivia, are associated with large 

amounts of minerals containing fluorine and boron, 

especially fluorite and tourmaline. Therefore, all 

granites of potentially stanniferous areas which are 

fluoritized or tourmalinized should be carefully investigated. In fact, the worldwide association of 

cassiterite with fluorine or boron is sufficiently close 

that most workers are agreed that tin leaves the 

parent magma as tin complexes of fluorine and 

boron. It is immaterial whether we know exactly 

how these complexes form, or how they leave the 

magma; the association of tin and fluorine or boron 

still is a useful prospecting tool. 

PROBLEMS FOR RESEARCH 

The geology of lode tin deposits is well understood; the genesis of tin deposits and tin-granite 

remains a fertile field of debate, speculation, and 

little fact. Much of the recent information on the 

origin of tin-granites is of questionable value because of sampling and analytical difficulties, and the 

senior author questions whether fundamental laws 

will ever be shown to exist to explain the so-called 

tin-granites. With respect to the actual search for 

tin deposits, the efforts required to collect large 

suites of rocks, treat them in the laboratory, analyze 

them, and manipulate the results by complex mathematical mechanisms might well be less effective in 

finding ore than a similar amount of time, money, 

and effort invested in actual prospecting of known 

stanniferous areas. But no doubt geologists and geochemists will continue such investigations. 

With respect to scientific studies, several areas of 

total ignorance are at once apparent. For instance, 

no information is available on the isotopic composition of tin in tin deposits. Such data are needed, 

though they may never lead to discovery of an ore 

body. Laboratory experiments are needed to duplicate the transfer of the numerous elements found 

together in tin deposits. Because the deposits in 

rhyolite are clearly formed during the crystallization of the magma, studies of fluid inclusions in 

these deposits would be invaluable. 

The authors are unaware of any studies currently 

in progress that would apply isotopic studies of 

oxygen and sulfur to the problem of genesis of 

different types of tin deposits. The very exhaustive 

and important study of the Bolivian tin deposits 

by Kelly and Turneaure (1970) suggests that of 

all the numerous tools available to study the temperature of formation of tin deposits, as well as 

the composition of the ore-forming fluids, fluidinclusion studies are by far the most usable. Their 

study should provide a model for much more work 

like theirs-detailed, factual, and with arguments 

based upon the observed facts. That the ore-forming 

solutions were high-temperature (to 560°C) highly 

saline solutions that probably boiled at times will 

not but please hydrothermalists. And the added 

conclusions of Kelly and Turneaure that 

"The Bolivian province has provided an ideal testing ground for numerous laboratory geothermometers that have been proposed in recent years. The 

results obtained with the various sulfide thermometers have been generally disappointing and hardly 

justify the time invested." 

will certainly disturb the "laboratory economic 

geologist" and delight the field economic geologist. 

If their conclusion is true, cannot one validly ask 

"If such rigidly controlled laboratory experiments 

cannot provide dependable data on even the temperature of deposition of tin deposits, how shall we 

ever discover (and prove) the method of generation 

of a tin-rich magma?" 

One last and troubling problem in petrogenesis 

needs mention. The alkalic rocks in many parts of 

the world contain tin in amounts equal to or greater 

than the so-called tin-granites, yet no commercial 

tin lodes are ever associated with them. In a way, 

this fact refutes the possibility that the tin granites 

derive their tin from the surrounding rocks invaded 
• 

TIN 651 

by the magma or that tin deposits are formed by 

circulating meteoric waters which set up a circulation cell about the intrusive, leaching metals from 

the surrounding· rocks, transferring them in or 

alongside the intrusive and then redepositing them 

as the economic tin deposits. If such a mode of 

origin for tin deposits is to be seriously entertained, 

first must come a valid answer as to why tin-rich 

syenites, or other alkalic rocks which often rise 

through continental crust similar to the tin granites, 

do not have associated tin deposits. Research on this 

problem is much needed. 

REFERENCES CITED 

Ahlfeld, Friedrich, 1936, The Bolivian tin belt: Econ. 

Geology, v. 31, no. 1, p. 48-72. 

--- 1958, Zinn und Wolfram, pt. 2 of Die metallischen 

Rohstoffe: Stuttgart, Ferdinand Enke, 212 p. 

Beus, A. A., 1969, Geochemical criteria for assessment of 

the mineral potential of igneous rock series during reconnaissance exploration: Colorado School Mines Quart., 

v. 64, no. 1, p. 67-74. 

Borchert, Hermann, and Dybek, Josef, 1960, Zur Geochemie 

des Zinns: Chemie der Erde, v. 20, p. 137-154. 

Brazil Divisao de Fomento da Produ~ao Mineral, 1964, 

Pesquisa de cassiterita no Territorio Federal de 

Rondonia: Brazil Div. Fomento Produ~ao Mineral 

A vulso 88, 61 p. 

Brundin, N. H., 1969, Some experiences in geochemical and 

heavy mineral prospecting: Colorado School Mines 

Quart., v. 64, no. 1, p. 89-94. 

Butler, J. R., 1953, The geochemistry and mineralogy of rock 

weathering: (1) The Lizard area, Cornwall: Geochim. 

et Cosmochim. Acta, v. 4, p. 157-178. 

Desborough, G. A., and Sainsbury, C. L., 1970, Cassiterite 

as an exsolution product in magnetite, Lost River tin 

mine, Alaska: Econ. Geology, v. 65, p. 1004-1007. 

Dines, H. G., 1956, The metalliferous mining region of southwest England: Great Britain Geol. Survey Mem., v. 1, 

508 p. 

El Sharkawi, N. A. H., and Dearman, W. R., 1966, Tinbearing skarns from the northwest border 0f the Dartmoor granite, Devonshire, England: Econ. Geology, v. 

61,no. 2, p. 362-369. 

Goldschmidt, V. M., and Peters, Cl., 1933, Zur Kenntnis der 

Troilit-Knollen der Meteoriten, ein Beitrag zur Geochemie von Chrom, Nickel und Zinn [Note on the composition of troilite nodules of meteorites and its bearing on the distribution of chromium, nickel, and tin in 

the earth]: Akad. Wiss. Gottingen Nachr., Math.-Phys. 

Kl., no. 3, p. 278-287. 

Heindl, R. A., 1970, Tin, in Mineral facts and problems: U.S. 

Bur. Mines Bull. 650, p. 759-771. 

Hosking, K. F. G., 1965, The search for tin: Mining Mag., 

v. 113, no. 4,p. 261-273. 

--- 1967, The relationship between primary deposits [of 

tinJ and granitic rocks-Internat. Tin Council, First 

Technical Conference on Tin, Haymarket House, 28 

Haymarket, London: Wijland and Leiteritz p. 267-

311. 

--- 1969, The nature of the primary tin ores of southwest of England: International Tin Council, Seeond 

Technical Conference on Tin, Haymarket House, 28 

Haymarket, London. 

--- 1972, Primary tin mineralization of west Malaysia; 

Regional conference on the geology of southeast Asia, 

in Harte, N. S., ed., Abstracts of papers: Geol. Soc. 

Malaysia, annex to Newsletter No. 34, p. 24-28. 

International Tin Council, 1968, A technical conference on 

tin, v. 1, 2, p. 1-641. 

--- 1969, A second technical conference on tin, v. 1-3, p. 

1-1258. 

Kelly, W. C., and Turneaure, F. S., 1970, Mineralogy, 

paragenesis and geothermometry of the tin and tungsten deposits of the eastern Andes, Bolivia: Econ. 

Geology, v. 65, no. 6, p. 609-680. 

Knopf, Adolph, 1908, Geology of the Seward Peninsula tin 

deposits, Alaska: U.S. Geol. Survey Bull. 358, 71 p. 

Lange, N. A., 1961, Handbook of chemistry [10th ed.]: New 

York, McGraw-Hill Book Co., 1969 p. 

Onishi, Hiroshi, and Sandell, E. B., 1957, Meteoritic and 

terrestrial abundance of tin : Geochim. et Cosmochim. 

Acta, v. 12, no. 3, p. 262-270. 

Reed, B. L., and Elliot, R. L., 1970, Reconnaissance geologic 

map, analyses of bedrock and stream sediment samples, 

and an aeromagnetic map of parts of southern Alaska 

Range: U.S. Geol. Survey open-file report, 145 p. 

Robertson, W. A., 1965, Report on the world tin position 

with projections for 1965 and 1970: London, Internat. 

Tin Council, 160 p. 

Sainsbury, C. L., 1964a, Association of beryllium with tin 

deposits rich in fluorite: Econ. Geology, v. 59, no. 5, 

p. 920-926. 

--- 1964b, Geology of the Lost River mine area, Alaska: 

U.S. Geol. Survey Bull. 1129, 80 p. 

--- 1969, Tin resources of the world: U.S. Geol. Survey 

Bull. 1301, 55 p. 

Sainsbury, C. L., Hamilton, J. C., and Huffman, Claude, Jr., 

1968, Geochemical cycle of selected trace elements in the 

tin-tungsten-beryllium district, western Seward Peninsula, Alaska: U.S. Geol. Survey Bull. 1242-F, p. FlF42. 

Sainsbury, C. L., Hudson, T. L., Kachadoorian, Reuben, and 

Richards, Thomas, 1970, Geology, mineral deposits, and 

geochemical and radiometric anomalies, Serpentine Hot 

Springs area, Seward Peninsula, Alaska: U.S. Geol. 

Survey Bull. 1312-H, 19 p. 

Shelton, J. E., 1965, Tin: U.S. Bur. Mines Minerals Yearbook, 1964,v. 1, p. 1057-1073. 

Stemprok, Miroslav, 1967, Genetische Probleme der ZinnW olfram-Vererzung im Erzgebirge: Mineralium Deposita 2, p. 102-118. 

~temprok, Miroslav, and Sulcek, Zdenek, 1969, Geochemical 

profile through an or,e-bearing lithium granite: Econ. 

Geology, v. 64, no. 4, p. 395-404. 

Varlamoff, Nicolas, 1969, The bearing of tin minerals and 

ores in the weathering zone and the possibility of geochemical exploration for tin: Colorado School Mines 

Quart., v. 64, no. 1, p. 4 79-495. 
• 
UNITED STATES MINERAL RESOURCES 

TITANIUM 

By HARRY KLEMIC, SHERMAN P. MARSH, and MARGARET CooPER 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction ------------------------------------- Exploitation -------------------------------------

Prices, value of imports ----------------------

Byproducts and coproducts -------------------

Environmental problems ---------------------

Geologic environment ----------------------------

Geochemistry --------------------------------

Titanium-rich minerals ----------------------

Primary rutile deposits -----------------------

Secondary rutile deposits ---------------------

Primary ilmenite deposits --------------------

Secondary ilmenite deposits -------------------

Resources --------------------------------------- Identified titanium resources ------------------

Hypothetical resources -----------------------

Speculative resources -------------------------

Exploration -------------------------------------

Problems for research ---------------------------- References cited ---------------------------------

FIGURE 

72. Graph showing ilmenite concentrate production 

for the world and the United States, and 

titanium slag production for Canada, 1951-

71 ---------------------------------------

Page 

653 

653 

656 

656 

656 

657 

657 

657 

658 

658 

659 

659 

659 

660 

660 

661 

662 

663 

663 

664 

Page 

655 

ABSTRACT OF CONCLUSIONS 

Titanium is an abundant element that is principally useful in the modern industrial technology of affluent societies. 

Titanium metal and alloys are used in the aerospace and 

chemical industries, and titanium dioxide is used in the 

welding-rod and pigment industries. Rutile (Ti02), ilmenite 

(FeTiOa), and titanium slag made from ilmenite are the 

principal raw materials from which purified titanium products are extracted. The Kroll method, involving reduction 

of titanium tetrachloride in an inert atmosphere, is used to 

obtain metallic titanium. 

The United States is dependent almost entirely upon foreign sources, mostly Australia, for rutile, but has substantial reserves and production of ilmenite. In 1970, U.S. demand for titanium was 490,000 short tons, and annual demand is expected to exceed 1 million short tons by the year 

2000. U.S. and world identified resources are estimated to 

be about 298 million and 2,000 million short tons of Ti02, 

respectively. Reserves of titanium in the United States in 

1970 were estimated to be about 25 million short tons of 

Ti02, mostly in ilmenite. 

Rutile, ilmenite, and other titanium-rich minerals occur 

in primary deposits in igneous and metamorphic rocks and 

in secondary-type sedimentary deposits, especially placer 

sands. Research is needed to find new domestic titanium deposits and processes for extracting titanium and other valuable coproducts from complex ores. Environmental problems 

may limit the mining of some titanium deposits. 

INTRODUCTION 

Titanium is an abundant element that has become 

TABLES significantly useful industrially to man only within 

the past 100 years. Its principal uses are related to 

136. 

137. 

138. 

139. 

140. 

141. 

142. 

143. 

144. 

Page requirements and wants of modern industrial techWorld production of rutile, 1969-71 ---------- 655 

U.S. consumption of titanium concentrates, 1970 655 nology and affluent societies. 

U.S. imports of the titanium concentrates, Titanium is a silver-gray metal that crystallizes 

ilmenite and rutile, 1967-71 --------------- 656 in the hexagonal system below 882°C and in the 

Principal titanium-rich minerals ------------- 658 cubic system above 882°C; it has a density of 4.5, 

Identified titanium resources in the United which is only 75 percent of the density of steel 

Id!!::~:d -tit~~i~~-;;; ~-r~~;-~f-th;-~~~~d-=== ::~ (Barksdale, 1966). At low temperatures titanium 

Identified world resources of rutile ----------- 661 and its alloys compare favorably in strength with 

World reserves of titanium ------------------ 661 some steels. At higher temperatures to 800°C, the 

Hypothetical world resources of titanium ____ 662 strength-weight ratio of titanium is more favorable, 

U.S. GEOL. SURVEY PROF. PAPER 820 

653 
654 UNITED STATES MINERAL RESOURCES 

but above 800°C it weakens considerably, and above 

1,3oooc it absorbs gases from the atmosphere and 

becomes brittle. This latter characteristic makes it 

necessary to utilize inert atmospheres or a vacuum 

in high-temperature processing or fabrication operations. Titanium metal has better corrosion resistance than stainless steel to sea water and other 

systems in which chloride ions are present. It is 

heavier than aluminum alloys but is much stronger 

and more chemically inert than aluminum. 

Titanium metal is widely used in the aerospace 

industries and in the chemical industry (Miller, 

1957; Stamper, 1970). In aircraft and spacecraft 

structural components, where strength to weight 

ratios are of great importance, the use of titanium 

alloys has grown rapidly. In the aircraft engine 

industry titanium alloys are used for parts requiring strength at high temperatures. In the chemical 

industry, where protection against corrosion is 

necessary, tubing, valves, pumps, and other plant 

components made of titanium alloys are widely 

used. 

Titanium dioxides have properties of whiteness, 

opacity, and chemical inertness that make them 

especially suitable for use as pigments in paints and 

other surface coatings and in plastics (Miller, 1957; 

Stamper, 1970). Titanium dioxides have another 

important use, as welding-rod coatings, where they 

protect the surfaces of the weld from unwanted 

reaction with the atmosphere during welding. Other 

uses of titanium dioxides are in the manufacture of 

mineral fibers, in ceramic components for electronic 

equipment, in alloys, and in carbides. 

Because the uses of titanium have evolved so 

recently, titanium and titaniferous materials are 

substitutes replacing other more commonly utilized 

materials. The production of titanium metal and 

titanium compounds of high purity involves complex and costly industrial processes, so these materials now are utilized as substitutes in the few 

applications where advantages are gained in performance or cost. 

Unprocessed titaniferous magnetite ores are used 

in minor amounts as heavy aggregates because of 

their density. 

The principal raw materials for the production 

of titanium metal and titanium products are (1) 

titanium ores, containing the minerals ilmenite 

(FeTi03), its alteration product leucoxene, and 

rutile (Ti02) ; and (2) titanium slag made by smelting ilmenite ores (Lawthers, 1957). Ilmenite and 

associated leucoxene are more abundant than rutile 

and are produced in many countries, including the 

United States (Lawthers and Mark, 1957; Lynd, 

1960). Rutile, however, is available in the United 

States only in deposits that are economically marginal or submarginal, and the United States, at 

present, is almost wholly dependent upon foreign 

sources for this material. 

Two principal processes employed in converting 

titanium raw materials to purified usable titanium 

products are the chloride and sulfate processes 

(Barksdale, 1966). Rutile is the raw material that 

is preferred for the chloride process, which involves 

the production of titanium tetrachloride, a highly 

reactive liquid that must be handled under inert 

conditions. The titanium tetrachloride is converted 

to titanium dioxide of the rutile type or to titanium 

metal. Ilmenite, leucoxene (ilmenite with a high 

titanium content), and titanium slag can also be 

used in the chloride process. 

In the sulfate process, either ilmenite (Temple, 

1966) or titanium slag is treated with sulfuric acid 

to yield solutions from which iron sulfates produced 

from iron in the ore are precipitated, and the 

titanium remaining in the solution is then extracted 

by precipitation. The titanium may be in two different forms of titanium dioxide, anatase or rutile, 

both suitable for use as pigments. 

Ti tani urn metal is prepared commercially by the 

Kroll method (Stamper, 1970), which involves the 

reduction of titanium tetrachloride by metallic magnesium in an inert atmosphere and the formation 

of titanium sponge metal. Titanium sponge metal is 

melted in a vacuum to prevent reaction with gases 

in the atmosphere and is processed into titanium 

ingots. 

The United States, as a leading industrial nation, 

is a major producer and consumer of titanium 

metal and welding rods ; and as an affluent society 

it produces and utilizes great quantities of pigments, as reported in U.S. Bureau of Mines "Minerals Yearbooks, 1950-70." It is one of the major consumers of titanium raw materials as well as one of 

the major producers of ilmenite. World and U.S. 

production of ilmenite concentrates and Canadian 

production of titanium slag in the last two decades 

are shown in figure 72. 

Production of rutile in recent years has been limited to only a few countries. Information available 

for rutile production in the world in recent years, 

as reported in U.S. Bureau of Mines "Minerals Yearbook, 1970" and "Commodity Data Summaries, 

1972," is shown in table 136. 

Closure of a mine in Sierra Leone in 1971 reduced world production of rutile by nearly 10 percent, leaving Australia as the only major rutileproducing country. 
TITANIUM 655 

4000 I I I I lr 

I 

I 

3600 

3200 

2800 

(I) 

z 

0 

.... 2400 

.... 

t[ 

0 

:I 

(I) 

~ 2000 0 

(I) 

0 

z 

<( 

(I) 

::> 

0 1600 

:I 

.... 

I 

I 

(\-' 

(v I 

"World 

I 

1200 I _ _j 

United v----... ......-...... Stay ;( 

v/\'v· 

r-- / \ 

VCanada 

/ 

/ 

r--_,~ (Ti slag) r--/ }.~ I 

/ \ ........ 

...... "' / 

v 

;-,. / " 

800 

400 

0 ~/l I I I I 

1951 53 1955 57 1959 61 1963 65 1967 69 1971 

FIGURE 72.-llmenite concentrate production for the world 

and the United States, and titanium slag production for 

Canada, 1951-71. Data from U.S. Bureau of Mines ''Minerals Yearbooks, 1950-70," and "Commodity Data Summaries, 1972." 

TABLE 136.-World production, in short tons, of rutile, 

1969-71 

Country 

Australia ---------- Sierra Leone ______ _ 

India --------------

Ceylon ------------- South Africa -------

1969 

399,100 

31,379 

2,751 

3,036 

543 

1970 

405,735 

48,593 

2,756 

3,000 

Not 

Brazil ------------- 10 available 

1971 (estimated) 

410,000 

12,000 

Undistributed ---------------------------- 8,000 

Total -------- 436,819 460,084 430,000 

The consumption of titanium concentrates in the 

United States exceeds domestic production. In 1970, 

the United States consumed titanium concentrates 

as shown in table 137 (U.S. Bur. Mines, 1972). 

TABLE 137.-U.S. consumption, in short tons, of titanium 

concentrates, 1970 

Ilmenite --------------- Titanium slag ---------

Rutile -----------------

Gross weight 

968,926 

129,247 

188,290 

Total estimated Ti02 -----------

Ti02 content (estimated) 

517,256 

91,639 

180,642 

789,537 

In terms of the element titanium, consumption 

in the United States in 1970 was about 491,000 

short tons. Of this, approximately 325,000 tons was 

from ilmenite, 106,800 tons from rutile, and 58,800 

tons from titanium slag, and the remainder from 

imported titanium sponge, waste, and scrap, as reported in U.S. Bureau of Mines "Minerals Yearbook, 

1970." 

The specific amounts of titanium used for production of various titanium products are not disclosed 

in order to protect data that are company confidential. However, the production capacity of the 

three companies that make titanium sponge metal 

in the United States is about 25,000 tons per year, 

and about 24,300 tons of titanium ingot, including 

alloys, was produced in 1970. Nearly 95 percent of 

the titanium metal consumed in the United States 

is used in the aircraft and spacecraft industry. Most 

of the remaining 5 percent is used in chemical industries and in steel making. Titanium pigment 

production, in terms of contained TiOz, in 1970 was 

about 650,000 short tons, and more than 15,000 tons 

of TiOz was used in the production of 212,000 tons 

of welding rods, as reported in US. Bureau of Mines 

"Minerals Yearbook, 1970." 

Although the greater part of the titanium consumed in the United States is in the form of pigment, the uses of titanium metal and titanium dioxide in the form of rutile are considered to be of 

strategic importance, and the Government maintains stockpiles of these materials. In December 

1969, the Office of Emergency Preparedness established stockpile objectives of 100,000 short tons of 

rutile and 33,500 tons of titanium sponge metal. At 

the end of May 1972, stockpile deficits for rutile 

were 43,475 tons and for titanium sponge metal, 

6,999 tons (Kirkemo, Harold, oral commun., 1972). 

Financial assistance for exploration for rutile, 

available from the U.S. Geological Survey, Office of 

Mineral Exploration, was set at 75-percent Government participation in 1967 (Stamper, 1970). 
656 UNITED STATES MINERAL RESOURCES 

U.S. consumption of titanium raw materials 

greatly exceeds domestic production. The deficit is 

made up by imports, largely from Australia. U.S. 

imports of titanium concentrates in recent years are 

listed in table 138. 

TABLE 138.-U.S. Imports, in short tons, of the titanium 

concentrates, ilmenite and rutile, 1967-71 

[NA, not available; e, estimate. Data from U.S. Bur. Mines "Minerals 

Yearbooks, 1967-70" and "Commodity Data Summaries, 1972"] 

Source 1967 1968 1969 1970 1971 

Ilmenite 

Australia ---------- 60,689 45,196 28,524 96,123 NA 

Canada (Ti slag) --- 147,216 132,958 82,329 134,996 NA 

Other countries ----- 1 NA 

Total ------------ 207,906 178,154 110,853 231,119 150,000e 

Rutile 

Australia ---------- 153,768 171,847 176,550 223,407 200,000+e 

Sierra Leone ------- 13,129 1,348 26,442 19,682 NA 

Canada ------------ 1,171 262 180 NA 

Other countries ----- 203 1,673 NA 

Total ------------ 167,100 174,366 204,927 243,269 200,ooo+e 

The United States has large reserves of ilmenite 

and modest potential resources of rutile. However, 

competition from foreign sources, the relatively low 

grade of some domestic deposits, the relatively high 

cost of production from such deposits, and other 

factors have prevented the development of production capability to satisfy domestic needs. Specifically, 

the availability of rutile from foreign sources has, 

to some extent, delayed the development of additional facilities for production of synthetic rutile 

from ilmenite-derived titanium dioxides utilizing 

domestic ores. 

EXPLOITATION 

Within the last two decades, 1951-70, there has 

been more than a four-fold increase in world production of primary titanium-from less than 

400,000 short tons in 1950 to 1.78 million tons in 

1970 (U.S. Bur. Mines, 1972). During this period, 

demand for primary titanium in the United States 

more than doubled, reaching about 490,000 short 

tons in 1970. Titanium scrap consumption in 1969 

was 22,800 tons (Gray and Mcilroy, 1971). Demand 

for titanium in the United States is expected to be 

between 1.1 million short tons and 2.6 million short 

tons by the year 2000. 

The greater demand for titanium has increased 

demand for rutile, which is the preferred raw material for production of titanium metal or pigments. 

Because rutile supplies in deposits of economic 

grade are limited and production has risen, greater 

reserves are needed to meet future demand. Interest has increased in developing improved processes 

for upgrading ilmenite and for processing it to produce titanium products. 

The mining of rutile and ilmenite from placer 

sand deposits involves the excavation and handling 

of unconsolidated material, and relatively low grade 

placers can be worked profitably. Monazite-zirconilmenite deposits containing as little as 3-4 percent 

heavy minerals have been worked; these contained 

0.5-1.5 percent Ti02. Other deposits having various 

mixtures of the minerals monazite, zircon, ilmenite, 

leucoxene, rutile, garnet, and staurolite are worked 

in Florida and New Jersey. The heavy minerals are 

concentrated and then separated by use of Humphrey spirals and electromagnetic and electrostatic 

separators (Quirk and Eilertsen, 1963). 

Mining of primary ilmenite deposits such as those 

at Tahawus, N. Y., involves drilling, blasting, and 

crushing of hard-rock ore, followed by fine grinding, 

magnetic separation, and hydraulic classification. 

The cost of these operations is high, but the crude 

ore contains about 16 percent Ti02, which is upgraded to concentrates containing 45 percent Ti02. 

In addition to the titanium concentrate, magnetite 

ore containing 56 percent iron is recovered. The 

ilmenite ores also contain 0.24 percent vanadium 

pentoxide (V20 5 ), which is a potentially recoverable valuable constituent. (See chapter on "Vanadium.") 

PRICES, VALUE OF IMPORTS 

The prices of some titanium raw materials and 

of some titanium products are indicated in the following list taken from data compiled from published sources for 1970 (Noe, 1972). 

Specification of material 

Ilmenite, domestic (60 percent Ti02), 

per short ton ------------------------ Ilmenite, imported (54 percent Ti02), 

per long ton -------------------------- Rutile, imported (96 percent Ti02), 

per long ton ------------------------- Titanium slag, imported (about 70 percent 

Ti02), per long ton -------------------

Rutile grade titanium dioxide, per pound __ 

Titanium sponge, domestic, per pound ----

Titanium sponge, imported (from Japan 

and Britain), per pound --------------

Price 

$30.00- $35.00 

20.00- 21.00 

160.00- 185.00 

45.00 

.26-- .27 

1.32 

1.20- 1.25 

The value of imported rutile in 1970 was $19.8 

million, and the combined value of imported ilmenite and titanium slag was $6.4 million. Unwrought 

titanium metal waste and scrap valued at $10.5 

million were also imported in 1970. 

BYPRODUCTS AND COPRODUCTS 

Titanium deposits in various parts of the world 

commonly are worked for more than one product. 
TITANIUM 657 

In some places, titanium minerals are merely byproducts, and the exploitation of the deposits is dependent upon market conditions for the other 

minerals. 

The major byproducts and coproducts recovered 

from titaniferous ores are iron-ore concentrates, 

monazite, and zircon. Vanadium is obtained from 

some titaniferous ores and is potentially recoverable 

from many primary ilmenite deposits (Jones, 1965). 

Potential coproducts from secondary deposits resulting from lateritic weathering of the primary minerals are iron ores, aluminum ores, and nickel, 

cobalt, and chromium concentrates. 

In deposits of rutile such as those near Evergreen, 

Colo., topaz is a possible coproduct. 

Rutile has been recovered from deposits worked 

for gold, diamonds, platinum, and tin. Other heavy 

minerals which contain columbium, tantalum, uranium, and rare earths are potential byproducts of 

titanium. 

It is likely that future titanium mining and processing will involve increased recovery of coproduct 

and byproduct materials. 

ENVIRONMENTAL PROBLEMS 

Environmental problems related to titanium production are physical hazards, land despoilment, and 

pollution, which are the same as those related to 

other types of metal mining, processing, and fabrication. Mining of primary deposits produces opencut pits and underground workings in which falling 

rock, landslides, or land subsidence present direct 

physical dangers. These dangers, however, can be 

minimized by taking ordinary but at times costly 

precautions. Land despoilment in the mining of 

secondary deposits in particular can be a major 

problem. Large areas along beaches and in terrace 

deposits away from shorelines may be excavated. 

These can be reclaimed by releveling in many 

places, if the deposits are sufficiently valuable that 

the costs of reclaiming the land can be covered by 

the profits derived from mining. Some lands, however, have high surface values, particularly in inhabited and recreational areas, and deposits in such 

places may not be minable. Pollution by particulate 

matter, such as sand and silt in streams and along 

some shores, may be difficult or impossible to control 

if some deposits are mined. Another major problem 

is the disposal of large quantities of sulfates and 

other chemicals that accumulate in waste products 

that result from the chemical processing of titanium 

ores. 

In present and future mining and processing of 

titanium ores, the environmental problems require 

a great deal of consideration if the operations are 

to be conducted profitably. In many places, deposits 

may not be mined or mining may be curtailed because of conflicting environmental considerations. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Titanium is the ninth most abundant element, following oxygen, silicon, aluminum, iron, calcium, 

magnesium, sodium, and potassium, which make up 

more than 98 percent of the earth's crust. The remaining 84 elements are commonly considered to be 

trace elements. 

Titanium is a lithophile element and has a strong 

affinity for oxygen. It is in group IVA of the periodic table, along with zirconium and hafnium. 

Titanium, zirconium, and hafnium have approximately the same abundance ratio (Ti: Zr: Hf== 

1,000: 50: 1) in igneous rocks, in silicate meteorites, 

and in the solar atmosphere (Rankama and Sahama, 1950) . 

Because titanium is strongly lithophilic, it concentrates in stony matter of the "slag crust" of the 

earth as well as in the stony matter of meteorites 

(Goldschmidt, 1954, p. 409). Oceanic crust and continental crust contain about 8,100 ppm (parts per 

million) and 5,300 ppm titanium, respectively (Lee 

and Yao, 1970). It forms oxides and oxy-salts and 

has no tendency to concentrate in metallic iron or 

to form sulfides. Titanium tends to be incorporated 

in ilmenite (FeTiOa) and sphene (CaTiSi05). The 

greatest abundance of titanium is in subsilicic rocks, 

including mafic and alkalic rocks, or is associated 

with anorthosites. The abundance of titanium in 

different rock types in percent is (Vinogradov, 

1962) : stony meteorites, 0.05; ultramafic rocks, 

0.03; mafic rocks, 0.9; intermediate rocks, 0.8; felsic 

rocks, 0.23 ; and sediments, 0.45. 

The behavior of titanium in magmatic crystallization is complicated and depends on such factors as 

the initial titanium content of the magma, the 

chemical activities of iron, silicon, and aluminum, 

the partial pressure of oxygen, and the temperature 

of crystallization. Thus, in some magmas titanium 

will enter silicate minerals at high temperatures 

rather than form oxides (Verhoogen, 1962). 

Titanium commonly occurs in clinopyroxenes, 

olivine, biotite, amphibole, and sphene. In crystallizing magmas, Ti-Fe oxides will form in two ways : 

( 1) by direct precipitation of ilmenite or ilmenitehematite solid solution or ulvospinel-magnetite 

solid solution ; the earliest formed oxides will have 

the highest Ti/Fe ratios; (2) by breakdown of 
658 UNITED STATES MINERAL RESOURCES 

iron-bearing pyroxenes at low oxygen pressures to 

form ilmenite and iron-free pyroxene. 

Because of its strong affinity for oxygen, most of 

the titanium in the lithosphere is in oxide minerals. 

The three common titanium minerals are ilmenite, 

rutile, and sphene; of these, ilmenite is by far the 

most common, accounting for more than 90 percent 

of the titaniferous constituents of igneous rocks. In 

some igneous rocks where rapid crystallization has 

occurred, the titanium has combined with magnetite to form titanium-magnetite; titanium is also 

present in minor amounts in many other minerals. 

TITANIUM-RICH MINERALS 

Rutile is one of three titanium dioxide minerals 

but has somewhat different physical characteristics 

from anatase ( octahedrite) and brookite, the other 

two dioxides. Some physical characteristics of these 

and other titanium-rich minerals are listed in table 

139. The percentage of titanium dioxide in these 

minerals is a measure of the percentage of titanium 

dioxide that can be obtained in concentrates of each 

of these minerals. Their high specific gravities indicate that they can be separated from more common 

light minerals by gravity methods. The indices of 

refraction of the three varieties of titanium dioxide 

minerals are a measure of the opacity of these 

crystalline forms. This is of importance in their use 

as pigments, as "covering power" of the pigment is 

related to the opacity of its constituents. White pigments of high opacity and high degree of chemical 

inertness can be made from rutile and anatase. 

The principal titanium minerals form primarily 

as products of the crystallization of igneous magmas 

and as recrystallization products in metamorphic 

rocks. Rutile deposits occur as local concentrations 

in igneous and metamorphic rocks, in veins associated with igneous and metamorphic rocks, and as 

concentrations in sedimentary rocks and unconsolidated sediments derived from the weathering of 

rutile-bearing rocks. 

PRIMARY RUTILE DEPOSITS 

Rutile occurs primarily in alkalic igneous rocks, 

in alkalic noritic-anorthositic complexes, and in granitic and syenitic veins and pegmatites. It is also 

formed in aluminum-rich high-grade metamorphic 

rocks and in high- and low-grade metamorphosed 

mafic and ultramafic rocks. All economic primary 

rutile deposits are in the noritic-anorthositic complexes. Few primary rutile deposits are of economic 

value, however, and most primary rutile is recovered as a product of ilmenite mining. 

At Kragero, Norway, rutile occurs in an aplite 

dike associated with gabbro that contains an average of 5-10 percent rutile. In the United States, in 

Amherst and Nelson Counties, Va. (Hillhouse, 1960; 

Ross, 1941), rutile occurs as an abundant mineral 

in dikelike or lenticular bodies of nelsonite, an 

ilmenite-apatite-rutile-rich rock, associated with 

a larger body of anorthosite. Some of the nelsonite 

contains as much as 60 percent rutile. Rutile also 

occurs in the anorthosite as disseminated grains 

averaging 4-5 percent of the rock and in quartzrutile stringers containing as much as 30 percent 

rutile. Rutile has been mined from nelsonite dikes 

adjacent to, and disseminations in, anorthosite at 

Roseland, Va. (Peterson, 1966). It has also been 

produced from an alkalic igneous complex at Magnet Cove, Ark. ( Fryklund and Holbrook, 1950). In 

the Magnet Cove area, rutile and brookite occur in 

association with novaculite and aegirine phonolite 

porphyry. The rutile in that area is in carbonatefeldspar veins that cut the porphyry, and the brookite occurs as crystals in quartzite masses embedded 

in the novaculite. Chloritic ultramafic rock in Harford County, Md., contains about 5 percent rutile in 

association with abundant magnetite, apatite, and 

ilmenite, on the flank of a serpentinized ultramafic 

body (Herz and Valentine, 1970). 

In Mexico, rutile is associated with anorthosite at 

Pluma Hidalgo, Oaxaca (Roy, 1970a) ; and in 

Canada, rutile occurs in ilmenite-rich anorthosite 

in the St. Urbain area, Quebec (Rose, 1969). 

Potentially economic deposits of rutile occur near 

Evergreen in the Front Range of Colorado as fine 

disseminations in fluorine-metasomatized lightTABLE 139-Principal titanium-rich minerals 

[ Leucoxene, an alteration product of other titanium minerals; contains more than 60 percent Ti02. Data from Deer and others ( 1962): Lawthers 

(1957)] 

Ti02 percentage Range of Mineral Formula Theoretical Specific indices of Cl')'!Stal maximum Minimum gravity refraction system 

Anatase _______________ Ti02 100 98.2 3.90 2.488-2.561 Tetragonal. Brookite _______________ Ti02 100 98.8 4.14 2.583-2.700 Orthorhombic. 

Rutile _________________ Ti02 100 45.7 4.21 2.612-2.899 Tetragonal. Ilmenite _______________ FeTiOa 52.7 46.2 4.72 ---------- Hexagonal. Perovskite _____________ CaTiOa 58.9 38.7 4.01 2.30-2.37 ( Pseudoisometric, 

Sphene ________________ CaTiSiOs 40.8 33.7 

monoclinic?) 

3.4-3.56 1.900-2.034 Monoclinic. 
TITANIUM. 659 

colored high-grade gneiss (Sheridan and others, 

1968). These deposits are thought to have been 

originally laterites or bauxites that contained resistant titanium minerals. The rutile forms about 

2-4 percent of the gneiss. 

SECONDARY RUTILE DEPOSITS 

Secondary deposits of rutile derived from the 

weathering of primary occurrences of rutile are the 

most important types of rutile deposits currently 

mined. These consist mainly of marine placer sands, 

stream sands and gravels, and lag saprolite deposits. 

Rutile, having a specific gravity greater than 4.0, is 

concentrated in placers with other heavy minerals 

by wave and stream action, in loose sands along 

coastal areas and along streams. In addition to 

deposits along modern shores, important quantities 

of rutile are contained in buried placers in terraces 

inland from present shorelines. Such deposits commonly have other valuable heavy minerals such as 

ilmenite and zircon, and some heavy-mineral deposits, in which monazite is the most abundant and 

the most important heavy mineral, also contain 

significant amounts of rutile. Similar deposits probably occur in offshore areas near coasts where shoreline rutile deposits indicate availability of suitable 

types of sediments. Formerly commercial deposits 

in lag saprolite deposits derived from weathering 

of titanium-bearing rock are present in Amherst 

and Nelson Counties, Va. (Fish, 1962; Herz and 

others, 1970), as well as in Hanover County. The 

Magnet Cove, Ark., rutile deposits also include some 

occurrences of the saprolitic type. 

PRIMARY ILMENITE DEPOSITS 

Some of the more important and currently economic primary ilmenite deposits are in the U.S.S.R., 

the United States, Canada, and Norway (Lawthers, 

1957; Peterson, 1966; Rose, 1969; Roy, 1970a). In 

the limen Mountains (part of the Ural Mountains) 

of the U.S.S.R. (Lawthers, 1957), large economic 

deposits of ilmenite and titaniferous magnetite also 

contain important amounts of vanadium. The 

titanium-iron ores there measure in the hundreds 

of millions of tons. Other ilmenite deposits in the 

U.S.S.R. are known in the Kola Peninsula and in 

the Ukraine. In the United States, ilmenite-magnetite deposits in gabbro and anorthosite at Tahawus, 

Essex County, N. Y. (Peterson, 1966) are a major 

source of titanium. Economic deposits of ilmenite, 

hematite, and magnetite occur as segregated masses 

in gabbro and anorthosite in the Tellnes deposit, 

Norway, and high-grade ilmenite ores in amphibolite at the Otanmaki deposit in Finland (Paakkonen, 1956) are mined. Important commercial deposits of ilmenite, magnetite, and rutile in gabbroanorthosite are worked in the St. Urbain area, Quebec, Canada. Large deposits of ilmenite and titaniferous magnetite in the Bushveld Complex of South 

Africa are important for their vanadium content. 

SECONDARY ILMENITE DEPOSITS 

Most titanium minerals are relatively resistant 

to weathering and are commonly found in resistate 

sediments. Ilmenite forms most of the economic 

secondary deposits of titanium; these deposits are 

placer sands that occur throughout the world: In 

general, they are in areas peripheral to regions 

having host rocks containing primary titanium mineral deposits. During the weathering of ilmenite, 

iron is released and titanium forms a simple dioxide, leucoxene, which is commonly present in placers. 

The placer deposits of ilmenite, rutile, and leucoxene commonly contain other heavy minerals, such 

as zircon and monazite, in significant amounts. 

Placer deposits of ilmenite and other titanium 

minerals occur along present-day beaches where 

wave action sorts and concentrates the heavy minerals, and in deltas and along streams where heavy 

minerals settle from the slower moving water. Fossil placers of ilmenite in sedimentary rocks are also 

known where similar mechanisms in the past have 

concentrated the heavy minerals. Some placer deposits have been derived from older detrital deposits. The coastal areas of all the inhabited continents 

have significant ilmenite placer deposits. Important 

deposits in the United States are in northern Florida 

and near Lakehurst, N. J. 

Fossil placer deposits in the United States near 

Highland and Starke, Fla., are at present being 

mined for ilmenite, rutile, and zircon, which were 

originally derived from the crystalline rocks of the 

Piedmont area (Pirkle and Yoho, 1970). At Lakehurst, N. J., a fossil placer of ilmenite is being 

mined from heavy-mineral lenses in sediments of 

Cretaceous and Tertiary ages. Reworking has concentrated the heavy minerals into an economic deposit (Markewicz, 1969). 

Australia is the leading producer of titanium minerals with a production of 0.98 million tons of ilmenite in 1970 (Lynd, 1972) from the coastal sands 

of Western Australia. Rutile, zircon, ~onazite, and 

ilmenite are also recovered from deposits on the 

coast of Queensland and New South Wales. In 1970, 

Australia produced 405,735 short tons of rutile, 

about 89 percent of world production (Lynd, 1972). 

New Zealand also has large resources of coastal 

black-sand deposits of ilmenite, which are currently 
660 UNITED STATES MINERAL RESOURCES 

being investigated (Lynd, 1972). In Brazil, a deposit 

of beach sand was mined for ilmenite in southern 

Bahia (Roy, 1970b). 

Other secondary titanium occurrences are concentrations of titanium dioxide in residual deposits 

formed by lateritic weathering of titaniferous rocks, 

many in areas having tropical climates. Titanium 

in the common rock-forming silicate minerals is 

hydrolyzed upon weathering and carried into the 

hydrolyzates (bauxites and other laterites) where 

it forms oxide minerals (Rankama and Sahama, 

1950). Goldschmidt (1954) stated that the compounds in which this titanium occurs are not known 

but that the titanium may be present as amorphous 

or finely crystalline titanium dioxide. These lateritic deposits are not of commercial value at present 

but are widespread in Hawaii and elsewhere. A 

major nontropical occurrence is found in the lateritic ferruginous bauxites from the Columbia River 

Basalt in Oregon, which contain 3.5 million short 

tons of Ti02 (Herz, 1969). 

RESOURCES 

IDENTIFIED TITANIUM RESOURCES 

The identified titanium resources in the United 

States, in terms of contained Ti02, are about 298 

million short tons. The distribution of these resources by States is shown in table 140. 

TABLE 140.-Identified titanium resources, in thousands of 

short tons, in the United States 

[NA, not available. Data from Herz (1969); Hillhouse (1960.); Peterson 

(1966); Stamper (1970)] 

State 

Alabama -------------------------------- Alaska ---------------------------------- Arkansas -------------------------------- California ------------------------------- Colorado --------------------------------

Florida ---------------------------------

Idaho ~~:If-================================= -----------------------------------

Montana Minnesota _______________________________ -------------------------------_ 

New Jersey ----------------------------- New Mexico ----------------------------- New York ------------------------------

Oklahoma North Carolina -------------------------- ______________________________ _ 

Oregon ---------------------------------- Rhode Island ---------------------------- South Carolina --------------------------

~~~ni;--================================ VVashington ------------------------------ VVyoming --------------------------------

Total -----------------------------

Ti02 

143 

127,000 

70 

840 

673 

20,615 

NA 

51,434 

315 

14,414 

270 

12,500 

609 

23,960 

71 

4,941 

3,500 

686 

2,716 

188 

12,000 

890 

20,000 

297,835 

The data given in this tabulation are only an 

approximation, because the source material upon 

which the estimates are based is incomplete and 

some of the data have not been corrected for 

amounts depleted by mining. 

In the States of Florida, Georgia, New Jersey, 

New York, Virginia, North Carolina, and South 

Carolina, where secondary or primary deposits have 

been mined for titanium minerals, identified resources are estimated to be about 72 million tons 

of contained Ti02. Titanium reserves in the United 

States were estimated by the U.S. Bureau of Mines 

in 1970 (Stamper, 1970) to be about 25.5 million 

short tons of Ti02, most of which is in ilmenite. 

Reserves of rutile included in this figure were reported to be 500,000 tons, but inasmuch as rutile 

production in the United States has virtually ceased, 

this rutile may be more realistically considered to 

be only a conditional resource. 

The identified titanium resources of the world, 

in terms of Ti02, are about 2,000 million short tons. 

Distribution of these resources is listed in table 141. 

TABLE 141.-Identified titanium resourc.es, in thousands of 

short tons, of the world 

[Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained minerals may or may not be profitably recoverable with existing technology 

and economic conditions. Data from Herz (1969); HiUhouse (1960); 

Lawthers (1954, 1957); Peterson (1966); Stamper (1970); United Nations 

(1970); U.S. Bur. Mines "Mineral Trade Notes, 1950-70," "Minerals 

Yearbooks, 1950-70," and "Commodity Data Summaries, 1972;" Williams 

(1965)] 

Continent and country 

North America: 

United States -------------------------- 297,835 

Canada -------------------------------- 397,374 

Mexico -------------------------------- 4,812 

Costa Rica ---------------------------- 1,390 ---- Total ------------------------------- 701,411 

South America: 

Argentina ----------------------------- Brazil --------------------------------- Guyana -------------------------------- Uruguay -------------------------------

Total --------------------------------

Australia and New Zealand: 

Australia ------------------------------ New Zealand ---------------------------

Total --------------------------------

Europe: 

Finland ------------------------------- France -------------------------------- Norway ------------------------------- Sweden· ___ -----------------------------

U.S.S.R. -------------------------------

Total 

Africa: 

Angola -------------------------------- Dahomey ----___ - ----------------------- Madagascar (Malagasy Republic) --------

Mauretania ----------------------------

Mozambique ----------------------------

Senegal ------------------------------- Sierra Leone -------~-------------------

3,114 

4,525 

18,548 

912 

27,099 

15,068 

42,130 

57,198 

6,750 

3,208 

43,836 

24,728 

73,404 

151,926 

331 

15 

1,045 

144 

5,884 

3,440 

2,490 
TITANIUM 661 

TABLE 141.-ldentijied titanium resources, in thousands of 

short tons, of the world-Continued 

Continent and country 

Africa-Continued: 

South African Republic ----------------- South West Africa --------------------- Spanish Sahara ------------------------

Tanzania ------------------------------ Uganda -------------------------------- United Arab Republic ------------------- Upper Volta ---------------------------

Total --------------------------------

Asia: 

761,384 

5 

8,819 

6,449 

5,156 

16,660 

6,614 

818,436 

Burma -------------------------------- 678 

Ceylon --------------------------------- 2,849 

China, People's Republic ---------------- 744 

Taiwan -------------------------------- 27 

India ---------------------------------- 196,726 

Indonesia ------------------------------ 1,819 

Japan --------------------------------- 9,052 

Korea --------------------------------- 826 

Malaysia ------------------------------ 82 

North Vietnam ------------------------- 4 

Pakistan ------------------------------- 849 

Philippines ----------------------------- 807 

Saudi Arabia -------------------------- 69 

Thailand ------------------------------- 8 

Total -------------------------------- 214,540 

World total -------------------------- 1,970,610 

The amounts listed are considered to be very conservative, because quantitative estimates of the 

potential titanium resources in many of the large 

complexes of mafic rock in various parts of the 

world are not included. 

Because rutile is the preferred raw material for 

the chemical extraction of titanium in commercial 

practice, the resources of rutile are worthy of consideration separately, even though they are included 

in the titanium resources listed in table 141. Identified resources of rutile in some principal primary 

and secondary deposits are listed in table 142. 

Although the identified titanium resources of the 

world are large, less than 10 percent of these resources can be considered as titanium reserves. 

Recent estimates made by the U.S. Bureau of Mines 

(Stamper, 1970) of world reserves of titanium show 

nearly 147 million short tons of contained titanium, 

which is equivalent to about 247 million tons of 

Ti02. The distribution of these reserves is shown 

in table 143. As for total identified resources, the 

reserve data are considered to be very incomplete. 

HYPOTHETICAL RESOURCES 

Hypothetical resources of titanium are large, but 

difficult to quantify. Because the estimates of identified resources for the world include more than 90 

percent potential ores in known districts and less 

than 10 percent reserves, those estimates, to some 

degree, may include some hypothetical ores. Some 

TABLE 142.-Identijied world resources, in thousands of 

short tons, of rutile 

[Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained min· 

erals may or may not be profitably recoverable with existing technology 

and economic conditions. Data from Barksdale ( 1966); Hillhouse ( 1960); 

Lawthers (1954, 1957); Lynd (1972); Peterson (1966); Rose (1969); 

Stamper (1970); U.S. Bur. Mines "Mineral Trade Notes, 195Q-70" and 

"Minerals Yearbooks, 1950-70"] 

Country 

Canada: 

St. Urbain -------------------------- United States: 

Amherst and Nelson Counties, Va, ___ _ 

Magnet Cove, Ark. ------------------ South Carolina monazite belt --------- Florida and Georgia deposits --------- Mexico: 

Rutile 

300 

450- 1,150 

500 

1,100 

650 

Pluma Hidalgo, Oaxaca -------------- 5,000-25,000 

Brazil: 

Paranaiba delta, State <>f Maranhao __ 

State of Sergipe --------------------- Uruguay: 

Aguas Dulces ----------------------- Argentina: 

Buenos Aires Pr<>vince --------------- Sierra Leone: 

500 

300 

27.2 

1.9 

Bonthe (Sherbro) area -------------- 1,500-30,000 

Cameroons: 

Yaounde River ---------------------- Senegal: 

Goast north of Dakar ---------------- South Africa: 

Orange Free State -~-----------------

Natal ------------------------------- South West Africa : 

Area north of Karibib --------------- U.S.S.R.: 

Ukraine __________ ----_------------- India: 

Kerala State ------------------------ Ceylon: 

Pulmoddai and Kokkilai area ---------- Australia: 

Eneabba, west coast <>f 

C) 

100 

500 

170 

5 

100 

300 

Western Australia ----------------- 3 1,000 

C<>ast of Queensland -----------------------·} 6,900 

Goast of New South Wales ------------------

1 Past production data available, but no reserve data. 2 Data incomplete. a Undeveloped. 

TABLE 143.-World reserves, in thousands of short tons, of 

titanium 

[Reserves: Identified deposits from which minerals can be extracted profitably with existing technology and under present economic conditions. Data from Stamper (1970)] 

Titanium Titanium 

Country Ilmenite equivalent Rutile equivalent 

United States ---------- 100,000 25,000 500 250 

Australia -------------- 20,000 5,000 4,000 2,000 

Canada ---------------- 100,000 25,000 300 250 

Ceylon ---------------- 5,000 1,250 500 150 

India ------------------ 60,000 15,000 100 50 

Norway --------------- 120,000 30,000 

Sierra Leone ----------- 3,000 1,500 

U.S.S.R. --------------- 100,000 25,000 300 150 

United Arab Republic ___ 40,000 10,000 

Others 1 ---------------- 25,000 6,250 

Total ------------ 570,000 142,500 8,700 4,350 

1 Comprise Finland, mainland China, Malaysia, Japan, Spain, and 

Brazil. 

coastal areas, into which extensions of deposits of 

titaniferous sands can be projected, are excluded 
662 UNITED STATES MINERAL RESOURCES 

from consideration because of the probable environmental damage to scenic and recreational areas that 

would result from mining. In sparsely inhabited 

areas, especially in developing nations, such considerations may not be deterrents to mining. Political considerations in the developing nations may 

temporarily have a great influence on mining 

activity. 

Placer deposits in some coastal areas are partially renewable over periods of years or decades 

because of continuous reworking of the sands by 

waves and currents. The grade of the deposits decreases as the sands are mined repeatedly. 

Deposits such as the titaniferous magnetite 

bodies and the titaniferous gabbros in the State of 

New York are irregular in form, and their projection to greater depths or in lateral directions can 

be done with reasonable certainty only for individual deposits. They can, however, be considered 

collectively as being representative of the concentrations of titanium in their host rocks to a specified depth. Inasmuch as the concentrations of titanium in deposits of this type are not related to 

enrichment relative to the present surface, the quantity of titanium in such concentrations for each 

additional increment of depth should tend to average near the amount that exists in the shallow zone. 

For example, if nearly 24 million short tons of Ti02 

has been identified in the upper1nost 500 feet of the 

districts that have been explored in New York, it 

is likely that an equivalent amount will exist between depths of 500 and 1,000 feet in these districts. 

Hypothetical resources of titanium in the United 

States are estimated to be about 155 million short 

tons Ti02. This quantity represents only a 53-percent 

addition to the identified titanium resources, and 

most of this increase is for primary-type ilmenite 

deposits. Among these, magnetite-ilmenite deposits 

of northern New York and eastern Minnesota are 

high-grade deposits, favorably located with respect 

to markets. Very large low-grade magnetite-ilmenite 

deposits in Alaska are distant from markets but are 

along the coast and are accessible. Primary ilmeniterutile deposits in Virginia and their associated 

placer deposits are also favorably located geographically, but competitive land-use considerations could 

render the placers unavailable. Primary magnetiteilmenite deposits in Wyoming may contain large 

hypothetical resources. Placer deposits in Florida, 

Georgia, South Carolina, North Carolina, and New 

Jersey contain large tonnages of hypothetical resources of titanium. Some of these are also important for monazite, zircon, and other heavy 

minerals. 

Any attempt to assign quantitative estimates to 

hypothetical resources of titanium must be made 

with the recognition that the resource data are incomplete. Hypothetical resources based on modest 

projections of identified resources and on interpretations of the extent of exploration effort and production records for certain regions are shown in 

table 144. 

TABLE 144.-Hypothetical 'World resources, in millions of 

short tons, of titanium 

[Hypothetical resources: Undiscovered mineral deposits, whether of re- coverable or subeconomic grade, that are geologically predictable as existing in known districts] 

Continent Ti02 

North America -------------------------- 400 

South America --------------------------- 200 

Australia and New Zealand -------------- 100 

Europe ---------------------------------- 200 

Africa ---------------------------------- 500 

Asia ------------------------------------ 200 

Total 1,600 

SPECULATIVE RESOURCES 

Speculative resources of titanium are very great. 

Ilmenite is a common mineral in mafic and ultramafic rocks such as those of the Bushveld Complex 

of South Africa, in anorthosites of the Canadian 

Shield, and in similar rocks of Precambrian shield 

areas of each continent. Many tens of billions of 

tons of such rocks containing a few percent of 

ilmenite are within a depth of less than 1 mile beneath the surface of the earth, and exploration of 

these great rock units should disclose large bodies 

having higher than average amounts of ilmenite. 

Bauxite and other lateritic deposits containing 

aluminum, iron, chromium, cobalt, nickel, and a few 

percent Ti02 are also potential sources of titanium. 

Lithified placer deposits in sedimentary rocks, such 

as the extensive black sand deposits in the Upper 

Cretaceous formations of Wyoming and also present in Arizona, New Mexico, Utah, Colorado, Idaho, 

and Montana (Dow and Batty, 1961; Houston and 

Murphy, 1962), indicate the possibility of significant resources of titanium minerals in sandstone 

deposits. Metamorphic equivalents of similar 

titanium-rich sedimentary rocks and of some mafic 

plutonic rocks offer additional possibilities for titanium ores. Offshore placer deposits paralleling 

known coastal placer deposits and placer deposits 

along coasts where the shallow marine sediments 

were derived from titaniferous rocks should contain concentrations of titanium minerals equivalent 

to those in shoreline placers or in terrace deposits 

in raised beaches (McKelvey and Wang, 1969). In 

many parts of the world the areas favorable for 
TITANIUM 663 

offshore titanium placer deposits are large in comparison with the areas of shoreline placer deposits, 

and the potential resources therefore are large. If 

mining of sea-floor manganese nodules becomes a 

practical source of metals, as suggested by Mero 

(1965), another source of titanium as a byproduct 

would be developed. New techniques for economic 

development of this potential source of metals will 

determine the possibility of such mining becoming 

commercial in operation. 

Quantitative estimates of the world's speculative 

resources of titanium, in terms of contained Ti02, 

are given below: (Speculative resources are undiscovered mineral deposits, whether of recoverable or 

subeconomic grade, that may exist in unknown districts or in unrecognized or unconventional form.) 

Type of deposit Size 

Primary: 

Ilmenite, magnetite, 

rutile, anatase, 

brookite, perovskite, 

and sphene in igneous 

and metamorphic rocks _______________ Large (tens of billions of tons). 

Secondary: 

Unconsolidated placers. 

Consolidated placers 

in fairly unmetamorphosed sedimentary rocks ___ _.. __ Intermediate (billions of tons). 

Residual: 

Lateritic and saprolitic 

concentrations in 

surficial zones ______ Small (hundreds of millions 

Sea-floor nodules: of tons). 

Iron- and manganeserich nodules con- taining minor amounts 

of titanium _________ Small. 

EXPLORATION 

Exploration for titanium deposits has been directed largely toward the discovery of well-known 

types of primary deposits, such as the occurrences 

of ilmenite and titaniferous magnetite in association with mafic and ultramafic rocks, or toward the 

discovery of secondary deposits of titaniferous 

heavy minerals in placers. Background geologic 

information concerning the occurrence of favorable 

host rocks or known mineral occurrences is used to 

provide a basis for selecting target areas for exploration. Because most primary ilmenite deposits 

contain large amounts of magnetite, these deposits 

have associated magnetic anomalies. Such anomalies 

are detected by aeromagnetic surveying, and after 

anomalous areas are located, they are studied in 

more detail by ground magnetic surveys, gravity 

surveys, and detailed geologic mapping. Titaniferous 

magnetite deposits commonly have somewhat more 

complex magnetic anomalies than those associated 

with most nontitaniferous magnetitic iron deposits 

and thus require sophisticated geophysical interpretations. High-grade ilmenite deposits have higher 

densities than their host rocks and are therefore 

detectable by the gravity anomalies that reflect the 

differences in density between the ore deposits and 

their host rocks. Combined magnetic and gravity 

data interpreted in conjunction with other geologic 

data are used to pinpoint target areas for drilling 

and sampling. The sampling and the analyses of 

the samples provide the basis for evaluation of deposits that are discovered. 

In exploration for placer deposits, coastal areas, 

known areas of fossil placers, and terrace deposits 

along streams are sampled, and heavy-mineral concentrates from the samples are analyzed to determine their mineral and chemical compositions. 

Wherever possible, interpretations are made of 

sedimentary features, such as ancient stream channels, beaches, offshore bars, and sand dunes. Other 

sedimentary parameters used are grain size and 

composition; these make it possible to reconstruct 

the probable conditions of deposition and concentration of heavy minerals and to determine the 

probable extent of favorable concentrations of the 

minerals sought. 

Many placer concentrations of heavy minerals 

contain radioactive minerals. Such deposits can be 

detected by aerial or ground radiometric surveys, 

provided that the deposits are not covered by too 

great a thickness of overburden. Aerial albedo surveys will probably be used more in the United States 

as quantitative albedo measurements become feasible. 

Once the favorable target areas are located, they 

must be tested by sampling in order to determine 

the economic potential of the deposits. The samples 

must be analyzed, and factors such as the quantity 

and quality of the recoverable ore and the ratio of 

overburden to ore must be determined. 

PROBLEMS FOR RESEARCH 

The cost of processing the abundant titanium mineral, ilmenite, to obtain usable titanium dioxide or 

titani urn metal is so much higher than that of processing natural rutile that despite its relative scarcity 

and higher cost in world markets, rutile is preferred 

as a source of titanium. So long as rutile is obtainable from foreign sources at lower cost than that 

produced in the United States, domestic rutile deposits of lower grade and higher production cost 

are noncompetitive. Geologic exploration is needed 

to find large and higher grade domestic rutile de-
664 UNITED STATES MINERAL RESOURCES 

posits. Such exploration can be guided by known 

geologic data or by development of new geologic 

and mineralogic concepts that will make it possible 

to discover previously unrecognized types of deposits. Extensive sampling and analyses-of many rocktypes are needed to obtain additional background 

data on the occurrence and distribution of titanium, 

not only in ilmenite and rutile but also in sphene, 

perovskite, and other titanium minerals. 

Geologic search for titani urn resources might be 

based upon a reexamination of analytical and geologic data that are already available for many large 

rock units and upon reinterpretation of possible geologic environments in which titanium may be concentrated. For example, search could be made for 

sedimentary deposits containing titanium minerals 

that had been primary segregates in the eroded 

upper parts of the Stillwater Complex in Montana 

or of other major gabbroic and anorthositic rock 

units, such as the Duluth Gabbro in Minnesota. Such 

studies of sedimentary rocks in the U.S.S.R. have 

related heavy-mineral concentrations in rock formations of various ages to the source rocks and to 

erosional and depositional histories of the sediments (Gurvich and others, 1965). Greater use 

might be made of data available from drilling for 

oil and gas, not only for knowledge of depositional 

environments of titanium but also for information 

concerning the mineralogical composition of sedimentary rocks. 

The portion of the titanium industry that is 

equipped to use ilmenite or other minerals rather 

than rutile can be expected to increase in view of 

the abundance of ilmenite and the relative scarcity 

of rutile. This change is likely to be slow, but, as 

in the case of the iron-ore industry turning to 

taconite ores, in the long run the titanium mineral 

processing industry may find it profitable to place 

greater emphasis on the use of the abundant· titanium raw material ilmenite. 

The current small market for titanium is a limiting factor in the development of large low-grade 

deposits of ilmenite and of improved methods for 

extracting the titanium from such ores. This is also 

true for possible multiproduct ores such as laterites. 

The separation of the major mineral industries into 

those producing iron, aluminum, titanium, and other 

metals has not favored the development of mineral 

beneficiation of complex multiproduct ores, but such 

development is needed. A specific example in which 

this development could affect the titanium industry 

is the future utilization of the titanium and many 

other components of sea-floor manganese nodules 

(McKelvey and Wang, 1969; Mero, 1965). The technology needed for recovery of sea-floor nodules involves a large increase in scale of dredging over 

that currently done for finer grained materials in 

shallow waters. Separation of the metallic components of the nodules into usable and marketable 

products is a chemical or metallurgical problem. 

Both chemical and metallurgical research are 

needed to improve methods of processing mineral 

raw materials in general, because such improvements. result in great additions to the quantities of 

useful mineral resources. The excess of titaniferous 

magnetite concentrates obtained from primary ilmenite ores might be converted to usable iron ore, 

and an increase in recovery of ilmenite might be 

achieved by improved mineral beneficiation methods. 

REFERENCES CITED 

Barksdale, Jelks, 1966, Titanium, it·s occurrence, chemistry, 

and technology [2d ed.]: New York, Ronald Press, 691 p. 

Deer, W. A., Howie, R. A., and Zussman, J., 1962, Rockforming minerals-V. 5, Non-silicates: New York, John 

Wiley and Sons, 371 p. 

Dow, V. T., and Batty, J. V., 1961, Reconnaissance of titaniferous sandstone deposits of Utah, Wyoming, New 

Mexico, and Colorado: U.S. Bur. Mines Rept. Inv. 5860, 

52 p. 

Fish, G. E.~r., 1962, Titanium resources of Nelson and 

Amherst Counties, Virginia-[Pt.] 1, Saprolite ores: 

U.S. Bur. Mines Rept. Inv. 6094, 44 p. 

Fryklund, V. C., Jr., and Holbrook, D. F., 1950, Titanium 

ore deposits of Hot Spring County, Arkansas: Arkansas 

Resources and Devel. Comm., Div. Geology Bull. 16, 

173 p. 

Goldschmidt, V. M., 1954, Geochemistry: Oxford, Clarendon 

Press, 730 p. 

Gray, J. J., and Mcilroy, Paul, 1971, A survey of the secondary titanium market: U.S. Bur. Mines lnf. Circ. 8532, 

17 p. 

Gurvich, S. 1., Kazarinov, L. N., and Khmara, N. V., 1965, 

Drevnie redkometal'no-ti,tanovye rossypi, metody ikh 

poiskov i otsenki [Early rare-metal and titanium placers 

-Prospecting and valuation methods]: Moscow, Izdatel. 

Nedra, 170 p., 1964; English translation (partial), U.S. 

Joint Pubs. Research Service Rept. 31,066, 84 p. 

Herz, Norman, 1969, Titanium, in Mineral and water resources of Oregon: U.S. Cong., 90th, 2d sess., Senate 

Comm. Interior and Insular Affairs, Comm. Print; 

Oregon Dept. Geology and Mineral Indus. Bull. 64, p. 

172-175. 

Herz, Norman, and Valentine, L. B., 1970, Rutile in the 

Harford County, Maryland,. serpentinite belt, in Geological Survey research 1970: U.S. Geol. Survey Prof. Paper 

700-C, p. C43-C48. 

Herz, Norman, Valentine, L. B., and lberall, E. R., 1970, 

Rutile and ilmenite placer deposits, Roseland district, 

Nelson and Amherst Counties, Virginia: U.S. Geol. 

Survey Bull. 1312-F, p. F1-F19. 

Hillhouse, D. N., 1960, Geology of the Piney River-Roseland 

titanium area, Nelson and Amherst Counties, Virginia: 

Virginia Polytech. Inst. Ph.D. dissertation; [abs.] in 

Dissert. Abs., v. 25, no. 10, p. 5861, 1965. 
TITANIUM 665 

Houston, R. S., and Murphy, J. F., 1962, Titaniferous black 

sandstone deposits of Wyoming: Wyoming Geol. Survey Bull. 49, 120 p. 

Jones, W. R., 1965, Vanadium deposits of Western Australia, 

in McAndrew, John, ed., Geology of Australian ore deposits [2d ed.]-Commonwealth Mining and Metall. 

Cong., 8th, Australia and New Zealand 1965: Melbourne, 

Australia, Australasian Inst. Mining and Metallurgy 

Pub., v. 1, p. 154-155. 

Lawthers, Robert, 1954, Titanium resources of the world: 

U.S. Geol. Survey open-file report, 283 p. 

--- 1957, Titanium, a materials survey, by Miller, J. A.-

Chap. 2, Mineralogy and geology of titanium deposits; 

Chap. 3, Resources; Chap. 4, Prospecting, mining and 

beneficiation: U.S. Bur. Mines Inf. Circ. 7791, p. 23-58. 

Lawthers, Robert, and Mark, H. R., 1957, Bibliography of 

titanium deposits of the world: U.S. Geol. Survey Bull. 

1019-G, p. 543-608. 

Lee, Tan, and Yao, Chi-lung, 1970, Abundance of chemical 

elements in the earth's crust and its major tectonic 

units: Internat. Geology Rev., v. 12, p. 778-786. 

Lynd, L. E., 1960, Titanium, in Industrial minerals and rocks 

[3d ed.]: New York, Am. Inst. Mining, Metall., and 

Petroleum Engineers, p. 851-880. 

--- 1972, Titanium: Mining Eng., v. 24, no. 1, p. 56-57. 

Markewicz, F. E., 1969, Ilmenite deposits of the New Jersey 

Coastal Plain, Field Trip 6, in Geology of selected areas 

in New Jersey and eastern Pennsylvania and guidebook 

of excursions-Geol. Soc. America, Ann. Mtg., Atlantic 

City, N. J., 1969: New Brunswick, N. J., Rutgers Univ. 

Press, p. 363-382. 

McKelvey, V. E., and Wang, F. F. H., 1969, World subsea 

mineral resources: U.S. Geol. Survey Misc. Geol. Inv. 

Map I-632, 17 p., 4 maps. 

Mero, J. L., 1965, The mineral resources of the sea: Amsterdam, Elsevier Publishing Co., 312 p. 

Miller, J. A., 1957, Titanium, a materials survey: U.S. Bur. 

Mines Inf. Circ. 7791, 202 p. 

Noe, F. E., 1972, Titanium: U.S. Bur Mines Minerals Yearbook, 1970, v. 1, p. 1109-1121. 

Paakkonen, Veikko, 1956, Otanmaki, the ilmenite-magnetite 

ore field in Finland: Finlande Comm. Geol. Bull. 171, 

71 p. 

Peterson, E. C., 1966, Titanium resources of the United 

States: U.S. Bur. Mines Inf. Circ. 8290, 65 p. 

Pirkle, E. C., and Yoho, W. H., 1970, The heavy mineral ore 

body of Trail Ridge, Florida: Econ. Geology, v. 65, no. 

1, p. 17-30. 

Quirk, Richard, and Eilertsen, N. A., 1963, Methods and 

costs of exploration and pilot plant testing of ilmenitebearing sands, Lakehurst mine, the Glidden Co., Ocean 

County, New Jersey: U.S. Bur. Mines Inf. Circ. 8197, 

68 p. 

Rankama, Kalervo, and Sahama, Th. G., 1950, Geochemistry: 

Chicago Univ. Press, 912 p. 

Rose, E. R., 1969, Geology of titanium and titaniferous deposits of Canada: Canada Geol. Survey Econ. Geology 

Rept. 25, 177 p. 

Ross, C. S., 1941, Occurrence and origin of the titanium deposits of Nelson and Amherst Counties, Virginia: 

U.S. Geol. Survey Prof. Paper 198, 59 p. 

Roy, B. C., 1970a, Titanium-Pt. 1: Jour. Mines, Metals, 

and Fuels, v. 18, no. 9, p. 315-321. 

--- 1970b, Titanium-Pt. 2: Jour. Mines, Metals, and 

Fuels, v. 18, no. 10, p. 350-360. 

Sheridan, D. M., Taylor, R. B., and Marsh, S. P., 1968, 

Rutile and topaz in Precambrian gneiss, Jefferson and 

Clear Creek Counties, Colorado: U.S. Geol. Survey Circ. 

567, 7 p. 

Stamper, J. W., 1970, Titanium, in Mineral facts and problems, 1970: U.S. Bur. Mines Bull. 650, p. 773-794. 

Temple, A. K., 1966, Alteration of ilmenite: Econ. Geology, 

v. 61, no. 4, p. 695-714. 

United Nations, Department Economic and Social Affairs, 

1970, Survey of world iron ore resources-Occurrence 

and appraisal: New York, United Nations, 479 p. 

U.S. Bureau of Mines, 1950-70, Mineral Trade Notes. 

---1950-70, Minerals Yearbooks. 

--- 1972, Commodity data summaries (ilmenite, rutile, 

and titanium sections) : p. 68-69, 126-127, 154-155. 

Verhoogen, John, 1962, Distribution of titanium between silicates and oxides in igneous rocks : Am. Jour. Sci., v. 

260,no. 3,p. 211-220. 

Vinogradov, A. P., 1962, Average contents of chemical elements in the principal types of igneous rocks of the 

earth's crust: Geochemistry, no. 7, p. 641-664. 

Williams, G. J., 1965, Iron- and titanium-bearing minerals, 

[Chap.] 9, in Williams, G. J., and New Zealand Geological Survey, Economic geology of New Zealand-Commonwealth Mining and Metall. Cong., 8th, Australia 

and New Zealand 1965: Melbourne, Australia, Australasian Inst. Mining and Metallurgy Pub., v. 4, p. 127-142. 

UNITED STATES MINERAL RESOURCES 

TUNGSTEN 

By S. WARREN HOBBS and JAMES E. ELLIOTT 

CONTENTS 

Abstract of conclusions --------------------------

Introduction -------------------------------------

Exploitation -------------------------------------

Geologic environment ----------------------------

Geochemistry --------_---------------.-------

~ineralogy ---------------------------------- Types of deposits ----------------------------

Contact-metamorphic deposits -------------

Tungsten-bearing vein deposits ------------

Stockwork and related deposits ------------

Other modes of occurrence ----------------

Resources --------------------------------------- Identified and hypothetical resources -----------

Speculative resources ------------------------

Prospecting techniques ---------------------------

Problems for research ----------------------------

References cited --------------------------------- General references 

FIGURE 

73. Graph showing U.S. production and price of 

tungsten, 1900-1971 -----------------------

TABLES 

145. ~inerals of tungsten -----------------------

146. Geology and reserves of principal tungsten deposits of the world -----------------------

ABSTRACT OF CONCLUSIONS 

Page 

667 

667 

668 

668 

668 

670 

671 

671 

672 

673 

674 

675 

675 

675 

676 

677 

678 

678 

veins, and stockworks. A close genetic association between 

igneous rock and ore is strongly suggested by the localization of many ore bodies of these kinds within or adjacent 

to the roof zones of major intrusive bodies, or close to 

cupolas, stocks, and bosses. 

U.S. tungsten reserves in known deposits or their geologically reasonable extensions are estimated at 15 million short 

ton units (1 short ton unit=20 pounds WOa). This is about 

6.8 percent of known world reserves, of which approximately 

60 percent are in China. Subeconomic resources in identified 

or geologically plausible deposits in the United States are 

conservatively estim~ted to contain two to three times the 

reserves. Covered areas in the United States probably contain concealed deposits that are comparable in grade and 

total tonnage to those now known. 

The United States has the potential for adequate tungsten 

production into the foreseeable future, provided it is willing 

to pay the price of essential research, extensive exploration, 

and the processing of high-cost low-grade ores. 

INTRODUCTION 

Tungsten in its pure form is a silver-gray or tinwhite metal of high specific gravity (19.35) whose 

usefulness is related directly to its special or unique 

physical and mechanical properties: the metal has, 

Page next to carbon, the highest melting point of all the 

elements (3,400°C) ; its tensile strength (maximum 669 of 590,000 lbs per sq in.) is the highest of all metals; 

and its high heat of sublimation, low compressibility, 

and low coefficient of thermal expansion are further 

attributes of impo~ance in certain applications. 

Page These fundamental properties are due to the nature 

671 of the crystalline lattice of tungsten atoms. Tungsten 

is one of the so-·called transition metals which arf 

676 characterized by incompleted "d" levels in the elec 

tronic configuration surrounding the nucleus. It apparently has the optimum number of vacancies in 

the fifth "d" level to establish an exceptionally 

Most of the major tungsten deposits of the world have a strong interatomic bonding that explains, at least 

close spatial and genetic association with granitic intrusive qualitatively, the metal's exceptional properties. 

rocks or their related porphyries. Although several very The major uses of tungsten relate not only to the 

diverse modes of occurrence are recognized, more than 95 

percent of all tungsten production has come from three types special characteristics of the metal itself but also to 

of deposits: contact-metamorphic deposits (tactites), quartz the properties that it imparts to its compounds and 

U.S. GEOL. SURVEY PROF. PAPER 820 

667 
668 UNITED STATES MINERAL RESOURCES 

its alloys-extreme hardness, the ability to retain 

hardness and strength at elevated temperatures, high 

tensile strength, adequate electrical conductivity, and 

high wear resistance. The basic forms in which tungsten is consumed are, in approximate percentages, as 

follows: tungsten carbide, 45 ; alloy steels, 25; nonferrous alloys, 11; tungsten and tungsten-base alloys, 

18 ; chemicals and others, 1 to 2. These various tungsten materials have important and in some cases 

very specific application in the production of metalworking machinery, tool steel, construction and mining machinery, drill bits, turbines, rocket nozzles, 

structural material in nuclear and space applications, 

transportation equipment (including tire studs), 

electrical equipment, lamp filaments, high-temperature thermocouples, inorganic chemicals for use in 

dyes, inks, glass, and luminous pigments, and other 

minor items. More detailed information is given by 

Griffith (1970). 

Tungsten, because of its properties, has many uses 

that are basic to a modern, rapidly diversifying technology; consequently, the metal will continue to be 

an increasingly important, if not critical, commodity 

of worldwide importance. Accelerated industrial expansion and new applications predicate an increasing 

domestic demand for tungsten, which can be met 

only by discovery of pew deposits, by the processing 

of lower-grade source materials at higher cost, by 

increased imports from abroad, or by the recycling 

of tungsten from scrap. An unsatisfactory alternative to an adequate supply is substitution of other 

metals for tungsten in some end-use applications. 

Molybdenum is substituted for tungsten in tool steels 

and high-temperature nonferrous alloys even though 

these products have a lower melting point, lower 

hardness at red heat, and a tendency to decarburize. 

Titanium carbide combined with molybdenum, nickel, 

or cobalt has gained acceptance in cutting tools ; 

other materials such as aluminum oxides and industrial diamonds can be substituted in certain applications. In many lesser uses such as filaments for 

electric lamps no adequate substitutes are now 

available. 

U.S. production of tungsten ore has varied widely, 

and although production peaks have occasionally exceeded consumption lows, the country has, on the 

average over the past 20 years, produced only about 

75 percent of its demand. As a result, the United 

States is a net importer of concentrates, mostly from 

Canada, Australia, Bolivia, Peru, Portugal, and South 

Korea. Of the known and estimated world reserves 

approximating 220 million units WOa (one unit 

equals 1 percent per ton, or 20 pounds WOa containing 15.862 pounds tungsten metal) , about 80 percent 

is estimated to be in Communist countries-60 percent in southeastern China and 20 percent in North 

Korea and the U.S.S.R. The impact of the Chinese 

reserves and potential production is the major unknown factor in predicting worldwide tungsten 

markets. 

EXPLOITATION 

Tungsten mining in the United States began on a 

very small scale in 1898 with production from pegmatites in Connecticut and South Dakota and from 

quartz veins in Arizona. The history of production 

from 1900 to the present has seen wide fluctuations, 

with short periods of high productivity stimulated 

by high prices during periods of national emergencies or special Government production incentive programs, followed by drastic cutbacks to lower levels. 

Figure 73 shows curves of production and unit price 

for the period 1900-1971. The three peaks on the 

production curve represent the effects of World Wars 

I and II and of the Government stockpile purchase 

program during the Korean War. Since 1960, annual 

production has fluctuated only moderately, and since 

1965, it has been stabilized in the range of 400 

thousand to 500 thousand units, largely as the result 

of the U.S. policy to sell tungsten from Government 

stockpiles at a fixed price. 

The relation of the price to production (fig. 73) is 

revealing as to future domestic supplies. Three times 

in the past 60 years, critical demands for tungsten 

have been met by domestic production, which suggests that the Nation has a relatively high tungsten 

t:otential. This is not a low-cost potential, however, 

when compared to other producing areas in the 

world, nor is it an indefinite potential; but under a 

price incentive, tungsten can be produced in quantity. 

A U.S. Bureau of Mines tungsten-availability report 

(Larson and others, 1971) documents this situation. 

The production of tungsten as a coproduct or byproduct in various mining operations is discussed 

later in this chapter. Such sources of supply will 

likely increase with the continued exploitation of 

large-volume, low-grade ore bodies. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

There is a paucity of data for many aspects of the 

geochemical behavior of tungsten, and many of the 

older data (pr~1946) are probably in error because 

of an earlier lack of methods to analyze accurately 

for small amounts of tungsten in common rocks and 

minerals. Only in recent years have these problems 

been largely overcome, and data are becoming available from which a better understanding of the geo-
TUNGSTEN 669 

1400r-------~---------.---------.---------.--------~--------~--------~~70 

1200 60 

0 

~ 

Cl) 

t2 

:::> o"' 

z 1000 50~ 

0 

t- !:: t- z a: :::> 

0 

I z Cl) 0 

t- ~ 

0 800 40 ten ( a: 

0 0 

z 

:I: 

<( I Cl) 

Cl) a: :::> w 0 Q,. 

:I: Cl) 

t- 600 30a:: 

~ <( 

-' 

-' 

z· 0 

0 0 

(.) 

t- ~ 

:::> w· 0 400 0 20 ~ 

a: a: Q,. Q,. 

z 

w 

tCl) 

(!) 

z 

:::> 200 t- 10 

FIGURE 73.-United States production and price of tungsten, 1900-1971 

chemistry of tungsten will emerge. The following 

information is based primarily on recent compilations 

of the geochemistry of tungsten by Krauskopf 

(1970) and Barabanov (1971). 

Tungsten (W) is one of the rarer elements in the 

earth's crust. The average crustal abundance of 

tungsten has been estimated at 1-1.3 ppm (parts per 

million). Of all igneous rocks, those of granitic affinities contain the most tungsten (average 1.5 ppm). 

Mafic rocks have a somewhat lower range of 0.5-1.0 

ppm and ultramafic rocks the lowest (0.1-0.8 ppm) 

(Krauskopf, 1970). Sedimentary rocks have an average tungsten content estimated at 1-2 ppm, the 

amount in clastic sediments generally being higher 

than that in carbonate rocks. The few data for metamorphic rocks are too fragmentary to substantiate 

any general conclusions. 

Meager data suggest that the content of tungsten 

in natural waters is extremely low. Such low values 

are compatible with the general insolubility of tungsten minerals as well as with the strong tendency for 

any dissolved tungsten to be adsorbed on iron and 

manganese oxides. The average tungsten content 

of sea water is probably near 0.0001 ppb (parts per 

billion). Lakes and stre·ams probably contain much 

less than 1 ppb. In acid mine waters associated with 

tungsten ore deposits, values are as much as 100 ppb 

tungsten. Exceptionally high values of 40-64 ppm 

tungsten are re·ported for the brine·s of Searles Lake, 

Calif. In hot spring waters, tungsten content may 

reach a few hundred parts per billion. 

In general, the content of tungsten in common 

rock-forming minerals is low. Quartz and feldspar 

generally have less than 2 ppm, and mica, the rich-
670 UNITED STATES MINERAL RESOURCES 

est, may contain from 5 to 50 ppm. The accessory 

iron-oxide and titanium minerals may have tungsten 

values greater than 10 ppm, and the content of tungsten in niobium-tantalum minerals may reach 1 percent or more, owing to the substitution of W+6 for 

Nb+5 and Ta+5

• The hypogene manganese-oxide minerals psilomelane and cryptomelane locally contain 

large amounts of tungsten. 

Tungsten is one of the Group VI elements in the 

periodic table and has atomic number 7 4 and an 

atomic weight of 184. It is a lithophile element in terrestrial environments and occurs in nature as W+4 

(ionic radius 0.70 A) and W+6 (ionic radius 0.62 A). 

The closest relative of tungsten, molybdenum, has 

similar ionic radii and electro-negativities, the same 

valences in natural materials, and about the same 

abundance in the earth's crust. Other geochemically 

similar elements are niobium and tantalum, close 

neighbors of tungsten in the periodic table. 

Separation of molybdenum and tungsten in natural environments occurs because of the tendency of 

molybdenum to form the sulfide, molybdenite, and 

· tungsten to form the tungstates, scheelite and 

wolframite. 

The geochemical cycle of tungsten begins with the 

formation of a tungsten deposit by processes related 

to magmatism. In a crystallizing magma, the tungsten gradually becomes concentrated in the residual 

fluids as either volatile compounds (not quantitatively appreciable, according to thermodynamic calculations) or soluble components of the water-rich phase. 

Experimental evidence indicates that tungsten is 

carried in ore-forming solutions chiefly as tungstate 

ion, tungstic acid, sodium tungstate, or a heteropolyacid, the relative amounts of these being controlled 

by temperature, pH, and the silica content of the 

solutions (Krauskopf, 1970). At a critical stage of 

physical conditions and of solution and wallrock 

chemistry, tungsten is precipitated as either wolframite or scheelite; which tungsten mineral forms is 

controlled by relative amounts and activity of iron, 

manganese, calcium, carbon dioxide, and fluorine. 

During weathering of a tungsten deposit, most of 

the wolframite and scheelite enter surface waters as 

detritus because both are fairly insoluble in the pH 

range of these waters. The high specific gravities and 

insolubilities of wolframite and scheelite predispose 

their accumulation in eluvial and alluvial placers 

from which some production has been made, but 

these are not a significant source of tungsten at present. The brittleness of these minerals causes them 

to break down during transport into very fine particles which are dispersed as fine sediment and thus 

lost within relatively short distances. 

Narrow tungsten "halos" in soils around ore deposits suggest some mobility of the metal in nearsurface waters. Secondary enrichment of tungsten 

is known, but is minor and very local. Alkaline solutions probably have little effect on tungsten minerals; the influence of organic matter is uncertain. 

Tungsten minerals are slowly attacked by acid surface waters and the released tungsten is thought to 

be partly dissolved as HW04- and partly converted 

to some form of tungstic oxide ( tungstite, hydrotungstite, ferritungstite). Some of the tungsten in 

solution may be removed by adsorption on oxides of 

iron and manganese. The part remaining in solution 

is stable as polytungstate ions such as 6H(W04)-

and (HW6021) - 5 and heteropolyacids such as H8Si 

(W201) 6 having silicon as the central atom in the 

complex. The concentration in natural waters is 

generally very low. Much of the tungsten is eventually dispersed in sedimentary rocks in amounts 

about the same as in igneous rocks. Enrichment may 

occasionally occur in ferruginous sandstone and 

shale. In soils tungsten is slightly enriched in the B 

horizon or lower A horizon and may form halos 

around ore deposits. 

Almost nothing is known about the biogeochemistry of tungsten. Some indication of enrichment in 

plants in mineralized zones has been documented. 

There is little information on black shales, but high 

values for graphitic phyllites and schists in Uganda, 

Ruanda, and India suggest a syngenetic sedimentary 

origin of the tungsten and a correlation with carbon 

content. An important biogeochemical role is unlikely, since tungsten in more than traces is poisonous 

to most organisms. 

The behavior of tungsten in metamorphic processes is unknown. It has been speculated that tungsten occurring in minute amounts in ordinary rocks 

may be mobilized by fluids generated during metamorphism and transported long distances to be deposited where the solutions change character. Thus, 

some investigators have suggested that most tungsten deposits, even those intimately associated with 

granites, are derived by metamorphic processes from 

the small accumulation of tungsten in sediments. 

MINERALOGY 

Although more than 20 species of tungsten-bearing minerals are known, only members of the wolframite group and scheelite are important as ore minerals. Many are very rare in occurrence and several 

have been described from only one locality. Only the 

more common minerals are listed in table 145. 

In many deposits throughout the world, tungsten 

occurs with minerals of other commodities. In the 
TUNGSTEN 671 

TABLE 145.-Minerals of tungsten 

Name Composition 

Wolframite group: Huebnerite ___ Mn W04 

Wolframite ___ (Fe,Mn) WO, 

Ferberite ----- FeW04 

Scheelite --------- CaWO, 

Powellite --------- Ca(Mo,W)04(W0a 

to about 10 percent) 

Stolzite ----------- PbW04 

Tungstite --------- H2W04 

Cuprotungstite ____ Cu2W04(0H)2 

Relative 

abundance 

Common. 

Major. 

Common. 

Major. 

Common. 

Uncommon. 

Common. 

Uncommon. 

principal tungsten mine in the United States, the 

tungsten is a coproduct with molybdenum and copper; but in the second largest producer, tungsten is 

a byproduct of molybdenum mining. Ore minerals of 

other commodities that commonly occur in the tungsten deposits of the world are· molybdenite (MoS2), 

cassiterite (Sn02), chalcopyrite (CuFeS2), bismuthinite (Bi2S3), native bismuth (Bi), and fluorite 

( CaF 2). In a few places in the United States, tetrahedrite (8Cu2S · Sb2S3) and sphalerite (ZnS) are coproducts. 

TYPES OF DEPOSITS 

Concentrations of tungsten occur in a wide variety 

of geologic environments that range from hightemperature, deep-seated deposits to those deposited 

at the surface from relatively low-temperature hot 

springs. In addition, tungsten has been recovered 

from placers and is known to exist in significant 

though as yet-uneconomic amounts in the brines of 

Searles Lake, Calif. The principal types of occurrence from which most production has come are 

contact-metamorphic deposits (tactites), hydrothermal veins, and stockworks and related porphyrymolybdenum deposits. Other deposits that have been 

productive or represent significant resources either 

are variants of these major types or result from 

special geologic situations. These include pegmatites, 

iron-manganese-bearing hot-spring deposits, replacements of various host rocks under special conditions, 

placer deposits, and the Searles Lake brines. 

CONTACT-METAMORPHIC DEPOSITS 

Tactite, one of the products of contact metamorphism, is the principal commercial source of tungsten 

in the United States and is second only to quartz 

veins as a commercial source on a worldwide basis. 

Tactites are the products of high-temperature replacement and recrystallization of pure or impure 

limestone or dolomite at or near the contact of intrusive igneous rocks. The resulting dark-colored 

deposits, comprising various combinations of such 

dark calc-silicate minerals as garnet (usually almandine or andradite), epidote, hedenbergite, and hornblende, together with magnetite and some quartz and 

calcite, are usually conspicuous in contrast to the 

lighter-colored granitic rocks or the sedimentary sequence into which the granite was intruded. The 

name "tactite" was applied to deposits of this type 

by Hess (1919) and is analogous in a broad sense to 

the Swedish term "skarn." 

Contact-metamorphic deposits have been produced 

by two basic processes-simple thermal metamorphism of impure carbonate strata, and additive metamorphism of either pure or impure carbonate layers 

wherein at least part of the material essential to the 

deposit is added from the magma. Presumably, both 

processes are active in the formation of tactites, and 

essential materials added are principally iron and 

silica with lesser amounts of aluminum manganese, 

and possibly some magnesium. Locally, significant 

amounts of tungsten, molybdenum, copper, zinc, sulfur, and fluorine are added-usually at a late stage. 

Determination of which major elements have been 

added and in what amounts is often difficult unless 

the tactite zone can be traced along strike into the 

unaltered strata where the original composition can 

be determined. However, the presence of one or 

more of the metallic elements, and of sulfur, fluorine, 

or boron, is considered to be indicative of additive 

processes. 

Tungsten, where introduced into tactites, occurs 

only as scheelite or molybdenum-bearing scheelite. 

Magnetite is usually present and may be abundant as 

at the Long mine, Pershing County, Nev., and the 

Old Hickory mine, Milford County, Utah. Pyrite, 

pyrrhotite, molybdenite, sphalerite, chalcopyrite·, 

tetrahedrite, stibnite, and bornite are formed at a 

late stage in some deposits, and fluorite, usually present, is locally abundant as at Darwin, Calif., and 

Tern Piute, Nev. 

In most places, tactites form distinctive, sharply 

bounded bodies whose shape and distribution are 

controlled by many factors but mainly by the contact 

of an intrusive body which usually forms one wall, by 

favorable composition of the invaded host rock, and 

by the structural relations of the strata to the contact. Tactite developed along conformable contacts 

tends to form tabular bodies parallel to the contact 

that seldom maintain a uniform width and vary from 

a few inches to many feet. Where a contact crosses 

bedding, beds more favorable lithologically may be 

replaced outward from the contact for greater distances than less favorable ones-in some instances 

for more than a thousand feet. Steep beds may be 

replaced for considerable vertical extent, the tactite 
672 UNITED STATES MINERAL RESOURCES 

pitching along the intersections of favorable beds 

with the intrusive. In some places, as at Tern Piute, 

Nev., ore-bearing tactite having no exposed contact 

with igneous rock has formed in layers parallel to a 

contact but is separated from it by several hundred 

feet of barren strata. Irregularities in igneous contacts and premineralization faults provide traps as 

well as channelways for mineralizing solutions that 

result in major local enlargements of tactite bodies. 

At the Pine Creek mine, Calif., and. at the Nevada 

Scheelite mine, Mineral County, Nev., overhangs of 

the granite contact are associated with enlarged and 

enriched ore bodies. Also at the Pine Creek mine, as 

at the Riley mine in the Osgood Range, Humboldt 

County, Nev., plunging troughlike curvatures of the 

intrusive contact are occupied by enlarged ore shoots. 

Roof pendants and inclusions of calcareous sedimentary rocks in plutonic rocks may be converted to 

tactite bodies that range in size from only a few feet 

in all dimensions to others that measure hundreds 

of feet. Large pendants like the one at Pine Creek, 

Calif., which is 7 miles long and nearly a mile wide, 

contain a variety of rock types, only some of which 

are replaced by tactite. 

Scheelite is seldom uniformly distributed in tactite, and many tactite bodies, perhaps most, contain 

none at all. In many mines, scheelite occurs in fairly 

well defined shoots or is more concentrated along 

certain bands in the tactite than in others. The vertical range may be as great as that of the tactite itself or may be restricted by such factors as permeability, fracturing, channeling of the ore-bearing 

solutions, and other local controls. 

Scheelite-bearing tactite deposits range in size 

from small isolated pods scattered along a contact to 

massive bodies which may comprise millions of tons. 

The content of W03 in tactite deposits is generally 

low. Parts of the Humboldt ore· body at Mill City, 

Nev., contained 10 percent W03 but the entire body 

averaged about 1 percent. A few smaller mines in 

California and Nevada yielded ore averaging between 

1 and 2 percent, but these are the exception. Most 

productive mines contain between 0.5 and 1.0 percent and a few properties, during periods of high 

prices and under conditions of inexpensive mining, 

produced concentrates from tactite containing as 

little as 0.3 percent wo3. 

Major production of tungsten from tactite deposits 

in the United States has come from the Pine Creek 

mine, Inyo County, Calif. (Bateman, 1965; Gray and 

others, 1968); the Mill City district, Pershing County, Nev.; various deposits in the Osgood Range, Humboldt County, Nev. (Hobbs and Clabaugh, 1946; Hotz 

and Willden, 1964) ; and the Brownes Lakes and 

Calvert Creek deposits in Beaverhead County, Mont. 

Numerous other deposits, particularly in the Sierra 

Nevada of California and in western Nevada, have 

produced lesser but cumulatively very significant 

amounts of concentrates. 

Major occurrences of tungsten-producing tactite 

outside the United States occur at the Flat River 

area in the Northwest Territories, Canada, on King 

Island, Tasmania, and in South Korea. 

TU~GSTEN-REARING VEIN DEPOSITS 

Tungsten-bearing quartz veins are widely distributed and account for more than three-fourths of 

the known world reserves of the metal. The great 

bulk of these reserves, however, are concentrated in 

the extensive tungsten province of southeastern 

China. As with the tactite deposits, most of the productive veins are associated spatially and probably 

genetically with plutonic rocks of granitic composition and usually occur near their contacts-either 

within border zones of the plutons or, more generally, in the adjacent intruded terrane. In contrast 

with environments favorable for tactites, however, 

the host rock associated with such veins generally 

contains little, if any, carbonate. Shale, siltstone, 

and quartzite or their metamorphic equivalents, as 

well as igneous rocks, either older than the parent 

intrusive or forming the border zones of the parent 

intrusive itself, are favorable hosts for the deposition of tungsten in quartz veins. Exceptions to this 

general rule are the quartz-scheelite veins cutting 

carbonate beds in the Minerva district, Nevada, and 

calcite-scheelite veins and stockworks in the Cherry 

Creek district and the Snake Range, Nev. 

Most tungsten veins are mineralogically simple 

and consist of quartz with scheelite and (or) one of 

the wolframite series and minor amounts of other 

minerals. Scheelite is the only ore mineral in the 

quartz-calcite veins at Atolia, Calif., which occur in 

quartz monzonite, and at the Minerva district, 

Nevada, where veins cut carbonate beds. Ferberite 

is the predominant mineral in veins of the famous 

Boulder tungsten district, Colorado, which carry 

only minor amounts of scheelite. Huebnerite is the 

dominant mineral at the Ima mine, Idaho, and at 

the Hamme district, North Carolina, although some 

scheelite occurs in both places. In some veins both 

scheelite and wolframite occur in nearly equal 

amounts. Other minerals such as sphalerite, galena, 

chalcopyrite, tetrahedrite, and arsenopyrite occur 

in large enough amounts in some deposits to be 

recovered as byproducts. Pyrite, pyrrhotite, molybdenite, fluorite, rhodochrosite and some feldspar 

may be present as gangue minerals. In many dis-
TUNGSTEN 673 

tricts quartz veins that are mined primarily for 

other metals-especially gold-contain scheelite as 

a sporadically distributed secondary component. The 

Mother Lode of California, the Murray district, 

Idaho, and the Jardine district, Montana, are examples. 

Tungsten-quartz veins are similar in most respects 

to typical hydrothermal vein deposits. They are 

tabular bodies that vary greatly in length, width, 

and depth. Although some vein zones extend for 

thousands of feet, the individual component veins 

tend to pinch and swell or to be arranged as a 

series of echelon lenticular segments both along 

strike and downdip. The attitude of the veins depends largely on the local structural environment. 

Most known occurrences tend to dip steeply, but a 

few are controlled by nearly flat joint systems in 

igneous terrane. 

Tungsten minerals in veins are usually localized 

in ore shoots. These shoots, as well as the veins 

themselves, are controlled by general factors of 

temperature, pressure, chemical composition of 

mineralizing solutions, available channelways for 

solutions, the sequence of mineral formation, and 

the local effect of structure and type of country 

rock. Quartz-tungsten veins are, as a rule, spatially 

very closely related to the contacts of igneous intrusive rocks and notably to the roof zones of such 

intrusions. This relation is illustrated by the notuncommon association of major districts with small 

plutons as at Boriana, Ariz., and the Ima mine, 

Idaho, which are probably in cupolas of larger subjacent masses, and the alinement of major vein 

zones with granite-cored anticlinal ridges as in the 

Chinese deposits. Tungsten ore shoots in quartz 

veins range from small isolated pockets of scheelite 

or wolframite to nearly continuously mineralized 

vein material that may measure a thousand feet or 

more on strike and downdip. Such extensive ore 

shoots are the exception in the United States, however, and most individual shoots have a vertical 

range of less than 500 feet. Cumulatively, the echelon ore bodies both at the Ima mine, Idaho, and in 

the Hamme district, North Carolina, extend well 

beyond a depth of 1,000 feet. In most occurrences, 

however, the ore shoots are small and even though 

the vein itself may be extensive, the concentrations 

of tungsten minerals within it are widely and 

erratically dispersed. Such "pockety" habit is commonplace and makes exploitation difficult. The 

thickness of tungsten veins varies as widely as do 

length and depth, but the economically minable size 

depends as much on grade, attitude, and other physical factors as on actual extent. For example, a 

l-inch-thick vein of pure ferberite (60 percent W03) 

in the Boulder district, Colorado, was mined ; elsewhere, shoots averaging less than 1 percent across 

15 feet or more of vein material have been worked. 

The average grade for all productive tungsten vein 

deposits in the United States is probably close to 1 

percent. Major productive vein deposits in the 

United States are at Boriana, Ariz., Atolia, Calif., 

Boulder district, Colorado, Ima, Idaho, and Hamme, 

North Carolina. Numerous smaller deposits are 

widely scattered in Arizona, Nevada, Colorado, 

Washington, Idaho, and Montana. 

STOCKWORK AND RELATED DEPOSITS 

Deposits of tungsten minerals as fracture fillings 

and replacements in stockworks and breccia zones 

are known at several places in the United States. 

These occurrences, though comprising varied host 

rocks, mineral associations, shape; size, and grade, 

have at least two common prerequisites of origina source of hydrothermal solutions with suitable 

access channelways, and suitable sites of deposition 

prepared through intimate fracturing, brecciation, 

or shearing of the host terrane. In most deposits of 

this kind (except the closely related porphyrymolybdenum occurrences), scheelite is the only 

tungsten mineral. Where breccias and stockworks 

were formed in carbonate rocks, the composition of 

the host undoubtedly was a major factor in the 

deposition of the scheelite. Similar chemical controls 

may have been an important, even if subordinate, 

factor in other environments. 

At Henderson Gulch, Mont., parts of a highly 

fractured granitic body are mineralized along fracture planes by iron sulfides- with some gold and 

scheelite. A small amount of gold and scheelite has 

been recovered from placer deposits downstream 

from this occurrence although the source rock itself has so far proved to be too low-grade for mining. At the Goat Creek property near Thompson 

Falls, Mont., an elliptical area of moderately fractured and · altered nearly horizontal sedimentary 

rocks of the Wallace Formation of the Precambrian 

Belt Supergroup carries thin seams and veinlets of 

iron sulfides, molybdenite, and some scheelite. This 

occurrence, located on the crest of a broad anticline, 

coincides with a strong, nearly circular aeromagnetic anomaly that has been interpreted to reflect 

a buried stock at some unknown depth. Although 

this deposit has not yet been proved economically 

feasible, it illustrates a mode of occurrence that 

may have future potential either here or elsewhere. 

Small calcite-scheelite replacement pipes and 

stockworks have been mined in Nevada and Cali-
674 UNITED STATES MINERAL RESOURCES 

fornia. These deposits, though locally high grade, 

are small and appear to be related to more extensive vein deposits in the same area. 

Huebnerite occurs in small amounts disseminated 

through large volumes of the porphyry-molybdenum 

ore body of the Climax Molybdenum Co. at Climax, 

Colo. Although the grade of the tungsten is only a 

few hundredths of 1 percent and thus is far below 

the economic cutoff for tungsten alone, the huebnerite is recovered as a byproduct of the very large 

scale mining for molybdenum and has become a very 

significant source of domestic supply; in 1970, Climax was second only to Pine Creek, Calif., in United 

States production of tungsten. The geologic evolution of the Climax stock and the sequence of mineralization are extremely complex and have been 

well documented in the literature (Wall ace and 

others, 1968). The composite Climax stock was intruded into Precambrian schist and gneisses and 

comprises four separate intrusions, each of which 

had its own associated hydrothermal event. The first 

three of these produced large stockwork ore bodies 

and associated alteration zones that cap and flank 

each intrusive body. The positioning of these separate intrusions in the same area has led to much 

overlapping and juxtaposition of ore zones. Each 

mineralizing episode, however, produced a generally 

consistent pattern of ore distribution with a molybdenum-rich zone overlain by a zone with low molybdenum but anomalous amounts of huebnerite and 

pyrite. The upper, currently producing molybdenum 

ore body is overlapped by one of the tungstenbearing halos. 

The Climax deposit is the only one of this kind 

in the United States from which byproduct tungsten 

is recovered. However, the reported association of 

tungsten minerals with geologically similar deposits, 

not only in Colorado but also in New Brunswick, 

Canada, raises the potential for this type of occurrence to become an increasingly important source of 

future supply. 

OTHER MODES OF OCCURRENCE 

Pegmatites containing scheelite or wolframite or 

both are found in many parts of the world, and in 

many places are closely associated with tungstenbearing quartz veins near the contacts of intrusive 

bodies. For the most part, the deposits are small 

and because of their irregular and generally pockety 

nature are difficult to exploit. A relatively insignificant percentage of the world production has come 

from pegmatites. The only important tungstenbearing pegmatites in the United States, those at 

the Oreana mine, Pershing County, Nev., were 

largely mined out in the 1940's. Other occurrences 

with very minor production are in the southern 

Black Hills of South Dakota and at Silver Hill near 

Spokane, Wash. 

The mushroom-shaped scheelite ore body of the 

Yellow Pine mine, Idaho, was a replacement of brecciated quartz monzonite near a major shear zone 

(Cooper, 1951) . The gangue comprised crushed 

country rock replaced by fine orthoclase and quartz. 

Early-formed gold, pyrite, and arsenopyrite were 

followed by scheelite and subsequently by stibnite 

with some silver. This ore body, which produced 

about 826,900 units WOa during 1941-45, has been 

mined out. 

The replacement of a bed of sandy dolomite in 

the northern Black Hills of South Dakota by wolframite accompanied by gold, barite, and a little 

scheelite and stibnite is apparently unique in the 

United States (Runner and Hartmann, 1918). 

Several manganese- and iron-oxide deposits of 

hot-spring origin in the Western United States contain significant amounts of tungsten in a form still 

unidentified but apparently closely associated with 

the oxide minerals. These deposits, formed at or 

very near the surface, comprise various mixtures of 

manganese and iron oxides in surficial alluvial 

materials, as hot-spring aprons, or as near-surface 

veins. Only the large deposits at Golconda, Nev., 

where tungsten-bearing oxides impregnate Pleistocene continental fanglomerate, contained enough 

tungsten to be exploited (Kerr, 1940). 

Anomalous amounts of tungsten have been reported from other hot-spring deposits as well as 

from epithermal manganese-bearing veins in Nevada, Oregon, New Mexico, and Bolivia. Many others 

probably exist, but because of their usual small size 

and the metallurgical problems they pose, they will 

probably always represent a very small part of 

world resources. 

Commercial concentrations of tungsten minerals 

in stream placers are rare and are generally restricted to areas close to abundant coarse-grained 

source material as in the Atolia-Randsburg district, 

California. A small amount of fine-grained scheelite 

was recovered as a coproduct with gold from placers 

that were dredged for several miles in Henderson 

Gulch, Mont., downstream from the mineralized 

stockwork deposit previously described. Small 

amounts of wolframite have been recovered from 

eluvial material in the Germania district, Stevens 

County, Wash. 

Significantly larger amounts of placer tungsten 

are reported to have been recovered from eluvial 

and stream placers in the great Chinese tungsten 
TUNGSTEN 675 

province and from the extension of this province 

into Indochina. 

A small but anomalous amount of WOa is present in the saline brines of Searles Lake (Carpenter 

and Garrett, 1959) and, to a lesser extent, in Owens 

Lake, both of which are a part of the Pleistocene 

Owens River interior drainage system in eastern 

California. The drainage area includes the eastern 

slope of the Sierra Nevada and the tungsten deposits of the Bishop region-from which much of the 

tungsten in the brines was probably leached. Numerous springs, at least one of which is known to 

carry anomalous amounts of tungsten today, may 

also have contributed to the total tungsten that 

collected in the lakes at the time of the throughgoing Pleistocene drainage. 

Tungsten in Searles Lake occurs as a solute, 

probably as a complex ion, in the brines in the 

amount of about 0.007 percent (70 ppm) W03. Although the amount is low:, and no efficient extraction method has yet been designed, these brines must 

be considered a major resource for future consideration, because the large volume of brines contains 

approximately 8.5 million units W03-more than 

half the known reserves of the United States. 

RESOURCES 

IDENTIFIED AND HYPOTHETICAL RESOURCES 

Reserves of tungsten in the United States are 

estimated to be nearly 15 million short ton units 

WOa in ore containing more than 0.3 percent W03 • 

This is about 6.5 percent of an estimated world 

reserve total of 230 million units. Nearly two-thirds 

of the U.S. reserves occurs as scheelite in tactite 

deposits located principally in California, Nevada, 

and Montana. Other tactite occurrences are located 

in Utah, Arizona, Washington, and Idaho. Most of 

the remaining one-third of the reserves is found as 

ferberite, wolframite, and huebnerite in quartz veins 

in Arizona, Idaho, Colorado, and North Carolina 

and as huebnerite in the Climax porphyry-molybdenum deposit of Colorado. 

An illuminating aspect of the resource potential 

for tungsten in the United States is the fact that 

since 1955 the total United States reserves have 

remained stable or have increased significantlyespecially in recent years. This has occurred in spite 

of the very high rate of production in the mid1950's and the industry's relatively depressed condition since then. Presumably this fact reflects new 

discoveries during periods of active exploration and 

exploitation as well as significant extension of reserves in the few major mines that have produced 

more or less continuously. 

In addition to its reserves, the United States has 

numerous deposits containing less than 0.3 percent 

WOa that may be considered as conditional resources. Most of these resources are in tactites and 

stockworks, and they are estimated to total two 

to three times the known U.S. reserves. The 8.5 

million units WOa in Searles Lake brines is an additional conditional resource. 

An extrapolation of identified resources into the 

realm of hypothetical ore bodies may reasonably be 

attempted on the basis of our knowledge of regional 

distribution, modes of occurrence, and geochemical 

association. Those parts of the Western United 

States from which most of our tungsten has been 

produced include vast areas covered by surficial 

debris and Tertiary sedimentary or volcanic rocks 

that undoubtedly conceal deposits at least equal in 

volume to, if not greatly exceeding, known deposits. 

Also, the proved association of important amounts 

of tungsten with molybdenum in porphyry-molybdenum deposits presages the discovery of others of 

this type, especially in Colorado. No real measure 

of tungsten recovery irom this source in other parts 

of the country is yet available, but because of the 

tremendously large molybdenum resources estimated for deposits of this kind, the potential for 

tungsten byproduct recovery is proportionately 

large. 

More than 90 percent of the world's known tungsten reserves are outside the United States, with 

60 percent in southeastern China. Table 146 summarizes the general reserve estimates and geologic 

characteristics of the major tungsten-producing 

countries of the world. Reserve figures are estimates 

only, and those for Communist countries, where information is outdated, inadequate, and difficult to 

evaluate, are far less reliable than those for the 

free world. 

SPECULATIVE RESOURCES 

The worldwide pattern of tungsten distribution, 

combined with the known geologic conditions related to its localization, leads to broad speculation 

of ultimate potential which can reasonably be extended an order of magnitude beyond the identified 

and hypothetical world resources. 

The localization of many of the major tungsten 

districts of the world in a broad circum-Pacific belt 

extending from South America through the United 

States, Canada, Alaska, and down the eastern coast 

of Asia into Australia and Tasmania, marks this 

zone as one in which other deposits or districts may 

very likely be found. The discovery and extensive 

production from contact-metamorphic deposits in 
676 UNITED STATES MINERAL RESOURCES 

TABLE 146.-Geology and reserves of principal tungsten deposits of tke world 

Country 

Reserves 1 

(millions 

of short ton units 

N ortb America: 

Canada ---------

United States --

South America: 

Bolivia ---------

Brazil ----------

Europe: 

Portugal 

U.S.S.R. 

Asia: 

Burma 

China 

North Korea __ _ 

South Korea ___ _ 

Malaysia --------

Australia -----------

W03 ) 

30.0 

15.0 

5.5 

2.5 

1.4 

30.0 

4.4 

132.3 

15.7 

6.4 

2.0 

4.8 

Major deposit 

types 

Contact metaso· matic. 

Contact metaso- matic, stockwork veins, 

quartz veins. 

Quartz veins ___ _ 

Contact metaso- matic, quartz 

veins. 

Quartz veins ___ _ 

Contact metaso- matic, quartz 

veins. 

Quartz vein.s ----

----do ----------

----do ----------

Contact metaso- matic, stockwork veins, • quartz veins. 

Quartz veins, contact 

metasomatic. 

Contact metaso- matic quartz 

veins. 

Tungsten 

minerals 

(major 

mineral 

italized) 

Scheelite --------

Sckeelite, wolframite, ferberite, 

huebnerite. 

Wolframite, 

scheelite. 

Sckeelite, wolframite. 

Wolframite, 

scheelite. 

Sckeelite, wolframite. 

Wolframite, 

scheelite. 

Wolframite -----

Wolframite, 

sebeelite. 

Sckeelite, wolframite. 

Wolframite, 

scheelite. 

Wolframite, 

sebeelite. 

Major 

associated 

minerals 

of other 

commodities 

Chalcopyrite ----

Molybdenite, 

chalcopyrite. 

Cassiterite, 

sphalerite, 

stannite, chalcopyrite, 

fluorite, bismuth minerals. 

Molybdenite, bism,utite. 

Cassiterite, 

ebalcopyrite, 

sphalerite, 

galena, fluorite. 

Molybdenite, 

powellite, bismuth minerals, 

fluorite, 

cassiterite, 

sulfides. 

Cassiterite, minor 

sulfides. 

Cassiterite, bismuth minerals, 

Dl<llybdenite, 

chalcopyrite. Chalcopyrite, 

fluorite. 

Molybdenite, chalcopyrite. 

Cassiterite, minor 

sulfides, fluorite. 

Cassiterite, 

molybdenite, 

bismuth minerals, fluorite. 

Host rocks 

Paleozoic lime- stone. Limestone, 

granitic and 

metasedimentary rockB. 

Paleozoic sedimentary rocks, 

Cretaceous to Tertiary sedimentary and 

volcanic rocks. 

Precambrian cal- careous rocks 

in mica schists. 

Granite and 

metamorphic 

rocks. 

Various metasedimentary rocks. 

Sedimentary 

rocks. 

Paleozoic and 

Mesozoic sedimentary rocks 

and granite. Phyllite, mica 

schist, gneiss. Metasedimentary 

rocks and 

granite. 

Paleozoic and 

Mesozoic sedimentary, volcanic, and 

metamorphic 

rocks. 

Sedimentary, 

metasedimentary rocks and 

granite. 

.1\ssociated igneous rocks 

Olassification 

Quartz mon- zonite. 

Quartz mon· zonite to granite. 

Dacite to quartz lati·te. 

Granite ---------

•••• do ----------

•••• do ----------

•••• do 

____ do 

____ do ----------

____ do ----------

•••• do ----------

•••• do -·----··-· 

Age 

Cretaceous. 

Late Paleozoic, Jurassic to Cretaceous, 

Tertiary. 

Late Jurassic, 

late Tertiary. 

Precambrian. 

Late 

Paleozoic. 

Late Paleo- cene to Eocene. 

Mesozoic(?). 

Late Jurassic. 

Cretaceous. 

Do. 

Mesozoic. 

Late 

Paleozoic. 

1 Identified deposits from which minerals can be extracted profitably with existing technology and under present economic conditions. 

the Yukon within the last 20 years is a specific 

example. In other parts of the world, tungsten, presumed to be of Precambrian age, is widely scattered in parts of the Brazilian, African, and Canadian Shield areas, as well as in the Precambrian 

crystalline cores of the Rocky Mountains of Colorado and Wyoming. Although mostly small as now 

known, these deposits are indicative of a time-andplace relation that once thoroughly understood 

might lead to the discovery and exploitation of significant amounts of tungsten ore. The association 

of tungsten with porphyry-molybdenum deposits in 

Colorado is well known and such association is 

suggested in other areas as well. In contrast, the 

association of tungsten with porphyry copper deposits is thought to be rare or is undetermined, in 

spite of the fact that these deposits are strikingly 

similar in mode of occurrence and origin to the 

molybdenum-bearing porphyries. Recovery of tungsten as a byproduct from some of the porphyry 

copper operations is a speculative possibility. 

PROSPECTING TECHNIQUES 

Many early discoveries of tungsten deposits were 

made from the recognition of scheelite and wolframite, accompanying other heavy . minerals, in 

panned concentrates collected in the search for gold 

and other precious metals. In outcrop, wolframite, 

as black bladed crystals in quartz veins, was easily 

identified, but scheelite, because of its similarity in 

color and luster to quartz and feldspar, was often 

overlooked. Panning is still a very useful technique 

for tracing tungsten to its source. Development of a 

portable shortwave ultraviolet light during the 

1930's greatly stimulated the search for scheelite, 

which fluoresces a bright blue-white to creamyyellow at this wavelength. The degree of yellow 

fluorescence is controlled by the amount of molybdenum in the mineral structure. A person experienced in the use of this technique can detect very 
TUNGSTEN 677 

small amounts of scheelite and estimate grade quite 

accurately. Most discoveries of workable tungstenbearing tactite deposits in the United States were 

made by use of this method through systematic 

scanning of recognized tactite zones. 

Geophysical methods are particularly applicable 

to the selection of geologic environments in which 

tungsten deposits might logically exist, but no direct 

measurements of the tungsten content can be made 

by these techniques. Broad regional studies by means 

of airborne magnetic and radiometric surveys and 

regional gravity measurements are useful in identifying variously anomalous rock bodies that are 

known to relate to possible environments of ore 

deposition. Such measurements have located igneous 

contacts, have provided data on location and depth 

of buried plutons and cupolas, have delineated 

tungsten-associated granites (as in the Kazakhstan 

region of the U.S.S.R.) that have relatively low 

magnetic field intensity and high radioactivity, and 

have helped define such regional structures as the 

Colorado Mineral Belt, whose intrusive igneous 

masses are reflected in low gravity anomalies even 

though the associated molybdenum-tungsten mineralization is not so reflected. 

Detailed geophysics may apply directly to the detection of ore zones, individual ore bodies, or promising environments. Many tactites that contain 

magnetite and (or) pyrrhotite are responsive to 

magnetic methods of detection; those with high sulfide contents respond to various electrical techniques; and detailed gravimetry may usefully refine 

the location, size, and depth of small plutons or the 

configuration of significant contacts. 

Geochemical surveys, though used sparingly in 

the United States to date, can be useful for future 

tungsten exploration. The simplest and perhaps most 

useful technique is the panning and analysis of 

stream sediments. Because of their high specific 

gravity and low solubility, tungsten minerals tend 

to concentrate as resistate fractions in streambeds, 

and the systematic sampling of stream sediments 

will often identify anomalous drainage basins and 

pinpoint source areas. The sampling and analysis 

of individual plutons of an intrusive complex has 

shown that, in some instances, plutons associated 

with tungsten mineralization contain anomalous 

amounts of tungsten and associated elements. This 

technique, even though not specific for individual 

deposits, does narrow the target for the application 

of other methods. 

Tungsten, because of its low chemical mobility 

under weathering conditions, generally produces 

geochemical anomalies of only limited range surrounding the source material. Analysis for indicator 

elements such as fluorine, arsenic, and (or) phosphorus that have greater mobility and are commonly 

associated with tungsten deposits may, in some circumstances, be more useful because of the wider 

halos they produce in rocks, soils, and (or) plants. 

In some special circumstances, other metallic elements commonly associated with tungsten such as 

molybdenum, copper, bismuth, antimony, and tin, 

may be used as indicators. 

PROBLEMS FOR RESEARCH 

Much has been learned about tungsten deposits 

from long experience with them. The application of 

empirical data has identified the common modes of 

occurrence, the effects of local geologic controls, the 

general geologic environment, associated minerals, 

general distribution, and other characteristics, and 

it has been useful in the discovery of new deposits 

and even new districts. There are limits, however, 

to this approach and a full evaluation of the resource potential of tungsten must await the answers 

to many basic questions : Why is tungsten found in 

some geologic provinces and not in others? Why is 

it associated with igneous rocks of certain composition or of certain ages? Why is it frequently 

pockety and erratic in distribution? Why has it been 

deposited over such a wide range of temperaturepressure conditions? Why is it deposited as scheelite 

in one place and wolframite in another? These are 

but a few questions, most of which relate to tungsten's geochemistry-its distribution in the earth's 

crust and the processes by which it is concentrated 

into ore deposits. 

Answers to these and other pertinent questions 

can come only from basic research that should, 

ideally, combine geologic mapping and sampling of 

carefully selected field areas with detailed laboratory 

work on the mineralogy and chemistry of all related geologic components. One of the key restraints 

in this approach has been the inability to analyze 

with accuracy for small amounts of tungsten (less 

than 10 ppm) in rocks and minerals. It is hoped 

that the refinements in techniques already made or 

being developed will lower the level of accurate detection into the parts-per-billion range. Such refined 

measurements may lead, for example, to the identification of source rocks, the delineation of channels 

of migration of ore-bearing solutions, or the recognition of dispersion halos of buried ore bodies. 

Many prospecting techniques have been used in the 

search for tungsten, but new approaches are needed 

and undoubtedly will be developed. Immediate help 
678 UNITED STATES MINERAL RESOURCES 

is available, however, through the more imaginative 

use of known techniques especially for the identification of favorable environments in covered areas. 

Intensive application of various geophysical methods 

to locate contact zones or buried stocks and cupolas, 

with which many tungsten deposits are associated, 

is an approach that should prove fruitful. 

Technological problems in recovery of tungsten 

from ore have been as varied as the modes of 

occurrence. Where ore minerals are coarse grained 

and the gangue has low specific gravity, the problem 

is minimal; in tactites where the gangue minerals 

are nearly as heavy as the ore minerals, recovery 

is more difficult and still inefficient; in special occurrences, as at Golconda, expensive chemical processes must be used that can recover only a part of 

the contained metal ; and for some occurrences, as 

at Searles Lake, no economic process has yet been 

devised for recovery. Most of the scheelite recovered 

from tactite deposits contains several percent calcium molybdate (powellite) in its molecular structure, and for many uses, the scheelite must be purified by chemical treatment to remove the molybdenum. Byproduct recovery from very low grade 

material is usually extremely inefficient, and new 

techniques to improve such recovery may also be 

applicable to the recovery of 111uch of the tungsten 

that has been lost or is still being lost in the tailings 

piles of tungsten mills. 

REFERENCES CITED 

Barabanov, V. F., 1971, Geochemistry of tungsten: Internat. 

Geology Rev., v. 13, p. 332-344. 

Bateman, P. C., 1965, Geology and tungsten mineralization 

of the Bishop district, California: U.S. Geol. Survey 

Prof. Paper 470, 208 p. 

Carpenter, L. G., and Garrett, D. E., 1959, Tungsten in 

Searles Lake: Mining Eng., v. 11, no. 3, p. 301-303. 

Cooper, J. R., 1951, Geology of the tungsten, antimony, and 

gold deposits near Stibnite, Idaho: U.S. Geol. Survey 

Bull. 969-F, p. 151-197. 

Gray, R. F., Hoffman, V. J., Bagan, R. J., and McKinley, H. 

L., 1968, Bishop tungsten district, California, in Ore deposits of the United States, 1933-1967 (Graton-Sales 

Volume), v. 2: New York, Am. Inst. Mining, Metall. 

and Petroleum Engineers, p. 1531-1554. 

Griffith, R. F., 1970, Tungsten, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 399-415. 

Hess, F. L., 1919, Tactite, the product of contact metamorphism: Am. Jour. Sci., 4th ser., v. 48, p. 377-378. 

Hobhs, S. W., and Clabaugh, S. E., 1946, Tungsten deposits 

of the Osgood Range, Humboldt County, Nevada: Nevada 

Bur. Mines Bull., v. 40, no. 5, Geology and Mining Ser. 

44, 32 p. 

Hotz, P. E., and Willden, Ronald, 1964, Geology and mineral 

deposits of the Osgood Mountains quadrangle, Humboldt County, Nevada: U.S. Geol. Survey Prof. Paper 

431, 128 p. 

Kerr, P. F., 1940, Tungsten-bearing manganese deposit at 

Golconda, Nevada: Geol. Soc. America Bull., v. 51, no. 9, 

p. 1359-1389. 

Krauskopf, K. B., 1970, Tungsten (wolfram), section in 

Wedepohl, K. H., ed., Handbook of geochemistry, V. II/ 

2: Berlin, Heidelberg, New York, Springer-Verlag, p. 

74-B to 74-0. 

Larson, L. P., and others, 1971, Availability of tungsten at 

various prices from resources in the United States: 

U.S. Bur. Mines Inf. Circ. 8500, 65 p. 

Runner, J. J., and Hartmann, M. L., 1918, The occurrence, 

chemistry, metallurgy and uses of tungsten: South 

Dakota School Mines Bull. 12, 264 p. 

Wallace, S. R., Muncaster, N. K., Jonson, D. C., Mackenzie, 

W. B., Bookstrom, A. A., and Surface, V. E., 1968, Multiple intrusion and mineralization at Climax, Colorado, 

in Ore deposits of the United States, 1933-1967 (GratonSales Volume), v. 1: New York, Am. Inst. Mining, 

Metall. and Petroleum Engineers, p. 605-640. 

GENERAL REFERENCES 

Kerr, P. F., 1946, Tungsten mineralization in the United 

States: Geol. Soc. America Mem. 15, 241 p. 

Li, K. C., and Wang, C. Y., 1955, Tungsten-its history, 

geology, ore-dressing, metallurgy, chemistry, analysis, 

applications, and economics [3d ed.]: Am. Chern. Soc. 

Mon. 94, 506 p. 

Lemmon, D. M., and Tweto, 0. L., compilers, 1962, Tungsten 

in the United States, exclusive of Alaska and Hawaii: 

U.S. Geol. Survey Mineral Inv. Resource Map MR-25. 
UNITED STATES MINERAL RESOURCES 

VANADIUM 

By R. P. FISCHER 

CONTENTS 

Abstract of conclusions --------------------------

Introduction ------------------------------------- Production _______________________ ---- ____ ----- __ 

Geographic sources of vanadium --------------

Geologic sources of vanadium -----------------

Geologic environment ---------------------------- Geochemistry _______________________________ _ 

Vanadium minerals -------------------------- Vanadium deposits ______________ -------- ____ _ 

Deposits of magmatic origin -------------

Titaniferous magnetite deposits -------

Nontitaniferous magnetite deposits ___ _ 

Vanadium-bearing hydrothermal vein 

deposits ------------------------------- Epigenetic deposits -----------------------

Vanadate deposits -------------------

Deposits in sandstone ----------------

Asphaltite deposits ----------------------

Deposits associated with alkalic 

igneous complexes --------------------- R.esources ______________________________________ _ 

Reserves in productive deposits ---------------

Potential resources in unproductive deposits ___ _ 

Prospecting techniques ---------------------------

Problems for research ----------------------------

References cited ---------------------------------

FIGURES 

7 4. Graph shoVIring principal uses of vanadium consumed in the United States, 1955-70 _____ _ 

75. Generaliz·ed graph showing the principal geographic sources of vanadium, 1910-70 _____ _ 

76. Generalized graph showing the principal geologic types of deposits from which vanadium 

was recovered, 1910-70 --------------------

TABLE 

147. Vanadium reserves in the principal sources of 

vanadium, 1970 --------------------------

Page 

679 

679 

680 

680 

680 

681 

681 

682 

682 

682 

682 

683 

683 

683 

683 

683 

684 

684 

684 

684 

684 

686 

687 

687 

Page 

680 

681 

681 

Page 

685 

ABSTRACT OF CONCLUSIONS 

Vanadium is used mainly as an alloy agent in steel. Its 

domestic consumption increased rapidly during the 1960's, 

and a growth rate of demand higher than that of any other 

ferrous mineral has been predicted to the year 2000. Foreign 

uses, consumption, and predicted requirements have a similar 

pattern. 

Predicted domestic requirements to the year 2000 exceed 

the estimated amount of vanadium available from productive domestic sources by about 300,000 to 400,000 short tons. 

Domestic resources in magnetite deposits and in carbonaceous 

shales are adequate to furnish this d·eficient vanadium, but 

they can do so only if domestic metallurgical practices are 

modified or new ones are developed. 

Foreign reserves in productive titaniferous magnetite deposits and resources in known but unproductive deposits of 

this type are adequate to satisfy world requirements for 

vanadium in the foreseeable future; these deposits occur in 

many countries, but the largest are in Australia, Canada, 

South Africa, and the U.S.S.R. Large resources also occur 

in vanadiferous shales in various parts of the world; those 

in Australia and the U.S.S.R. are perhaps more apt to become productive. Small but significant amounts of vanadium 

will be recovered from other iron ores, phosphate rock, petroleum residues, and other byproduct sources. 

Although vanadium resources are large, vanadium supplies large enough to satisfy requirements are not necessarily 

secure, because so much vanadium is recoverable only as a 

byproduct of operations for other commodities. 

INTRODUCTION 

Vanadium (V) has the atomic number of 23 and 

the atomic weight of 50.95. It is a bright silver-white 

to steel-gray metal, with a melting point of about 

1,900°C. Its specific gravity is 5.87 at 15°C. It alloys 

with several other metals. 

About 80 percent of the vanadium consumed domestically has been used as an alloy in steel (fig. 69) ; 

foreign usage is similar. Vanadium is added mainly 

to toughen and strengthen steel and to control its 

grain size (National Materials Advisory Board, 1970; 

Busch, 1961; Griffith, 1970). In vanadium-bearing 

tool steels, the amount used ranges from about 0.5 to 

4 percent V, and it is commonly used in varying comU.S. GEOL. SURVEY PROF. PAPER 820 

679 
680 UNITED STATES MINERAL RESOURCES 

FIGURE 74 .-Principal uses of the vanadium consumed in the 

United States, 1955-70. Data from U.S. Bureau of Mines 

"Minerals Yearbook" published annually. 

binations with chromium, niobium, molybdenum, 

nickel, and tungsten; a limited de:gree of substitution 

among these metals is possible but not usually practiced. The class "Other alloy steels" shown in figure 

74 mainly comprises the "high strength-low alloy 

steels" (HSLA) that are used principally for highpressure pipelines and construction purposes ; the 

use of this type of steel, and the consumption of 

vanadium in it, has increased appreciably since the 

early 1960's. Generally, only 0.02-0.1 percent V is 

used in most of these steels, but it increases the yield 

point from about 35,000 psi (pounds per square inch) 

to the range of 50,000-65,000 psi. Niobium is used 

with vanadium in some of these HSLA steels, and it 

can be substituted for vanadium to a considerable 

extent if desirable from the standpoint of price or 

supply of these two alloy metals ; other alloy metals 

can also be used with vanadium or as substitutes for 

it in some steels. A small amount of vanadium is 

used, along with other alloying metals, in cast irons 

made for special purposes. In the future an appreciable increase in the use of vanadium in the continuous casting of steel billets is possible but not likely; 

in this practice, vanadium is used along with, or 

partly in substitution for, aluminum and (or) 

niobium. 

Vanadium as an alloying agent in nonferrous 

metals is used chiefly with titanium in the aerospace 

field, an application that is expected to increase 

significantly in the future. Vanadium has numerous 

uses in the chemical industry, especially as a catalyst. Vanadium metal, with several other metals 

added as alloys, is a candidate for use in the nuclear 

industry as a fuel-cladding material for advanced 

liquid-metal-cooled fast-breeding reactors; other candidates for this application are stainless steels and 

molybdenum- and cobalt-base alloys. If vanadium is 

ultimately selected, vanadium requirements after 

about 1985 would be large. 

From the 1940's until about 1960, the United 

States was the world's principal producer of vanadium, and it enjoyed a moderate export market. In 

recent years, domestic production has remained fairly constant, at about 6,000 short tons V yearly, but 

consumption has increased and now about equals 

production ; some exporting has continued but is 

about equaled by imports. Future domestic requirements are expected to increase appreciably (National Materials Advisory Board, 1970). Griffith (1970, 

table 2) predicted domestic demand in the year 2000 

to range from 25,500 to 37,500 short tons V, projected on the basis of an estimated growth rate of 

demand higher than that of any other ferrous mineral. (For comparative figures of the predicted 

growth rate of demand for the ferrous minerals see 

table 1, p. 245, U.S. Bureau of Mines (1970) .) Using 

this predicted growth rate of demand, Griffith (1970) 

estimated cumulative domestic requirements in the 

1968-2000 period to range from 420,000 to 520,000 

short tons V; he also estimated known reserves in 

productive domestic sources to total only 115,000 

short tons of recoverable vanadium, which indicates 

an appreciable domestic deficiency. New domestic 

sources will have to be developed or imports increased to meet this deficiency. 

PRODUCTION 

GEOGRAPHIC SOURCES OF VANADIUM 

Figure 75 is a generalized graph showing vanadium production for every tenth year from 1910 to 

1970. A limited and probably desultory U.S.S.R. production in the 1930's and 1940's is not plotted. Other 

countries are known to have produced vanadium, but 

production figures are generally not available, and a 

category of "other" is not shown on the graph. In 

1970 this "other" production probably amounted to 

1,000-2,000 short tons V, most of which came from 

Canada, Chile, several European countries, and 

Japan. This "other" category was not significant in 

earlier years except during World War II, when Germany and Japan recovered appreciable vanadium, 

probably in the order of 3,000 short tons V yearly for 

a few years. 

GEOLOGIC SOURCES OF VANADIUM 

Figure 76 is a generalized graph showing the 

geologic types of deposits that yielded the vanadium 

production shown in figure 75. The category "Sandstone and others" represents vanadium production in 

the United States; about 90 percent of the total U.S. 

production during 1910-70 is from sandstone deposits, a very small part from vanadate ores, and the 
VANADIUM 681 

V) 

z 

0 

IIa: 

0 

:I: 

V) 10 u. 

0 

V) 

0 

z 

~ V) 

:::> 

0 

:I: 

1-

1910 1930 1950 1970 

FIGURE 75 .-Generalized graph showing the principal geographic sources of vanadium, 1910-70. Data from published figures of U.S. Geological Survey (1910 and 1920) 

and U.S. Bureau of Mines, except U.S.S.R. data for 1960 

and 1970, which are estimates by the writer. 

~ 

:::> 

0 

~ 

~20 

> 

. 

V) 

z 

0 

IIa: 

0 

~10 

u. 

0 

V) 

0 

z 

c{ 

V) 

:::> 

0 

:I: 

.... o-F====~====~~~~----~----~-----4-

1910 1930 1950 1970 

FIGURE 76 .-Generalized graph showing the principal geologic 

types of deposits from which vanadium was recovered, 

1910-70. Compilation by author, based on data in figure 75. 

rest is from phosphate rock and the deposit in 

Arkansas described below. The category "Iron 

deposits" is wholly from titaniferous magnetite 

deposits. The vanadium produced in 1970 from countries other than those shown in figure 75 (see "Geographic Sources of Vanadium") was derived from 

iron ores, the residue of petroleum refining, the soot 

and ash from furnaces burning crude oil, the sludge 

derived from the Bayer process of making alumina, 

and other waste products. 

About 75 percent of the reporte.d and estimated 

1970 vanadium production shown in figure 76 was 

derived from iron (titaniferous magnetite) deposits. 

Output from this source became significant in the 

1950's and large in the 1960's, reflecting the inability 

of the traditional high-grade sources to satisfy the 

increasing requirements for vanadium. This situation 

is analogous to that of the copper industry about 50 

years ago, when copper requirements exceeded the 

capacity of the high-grade sources, mainly vein deposits, to meet the demands, and the large-tonnage, 

low-grade porphyry copper deposits were developed 

as the principal geologic source of copper. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Vanadium is considered to be a minor element, but 

it is a rather abundant one. Its crustal abundance is 

in the order of 100-150 ppm (parts per million), 

about twice that of copper and zinc and 10 times that 

of lead. It is one of the lithophile elements that occur 

mainly in silicate rocks, but it does not form an important part of any common rock-forming mineral. 

It also has a biophile tendency, so it accumulates in 

some environments rich in organic materials. V anadium occurs in three valence states in nature; 3-

and 4-valent vanadium are rather insoluble in aqueous solutions, but 5-valent vanadium is relatively 

soluble. 

Geologically, vanadium is a rather well-disciplined 

element-it has a well-defined geochemical cycle, and 

it accumulates in only a small number of geologic 

situations, where its habits and grade range are 

reasonably consistent. 

In igneous rocks, vanadium occurs mainly in the 

insoluble 3-valent state and substitutes for iron and 

perhaps aluminum in iron and ferromagnesian minerals. It is most abundant in the mafic igneous rocks 

(about 200 ppm), less abundant in the ultramafic and 

intermediate rocks (about 50 ppm), and sparse in the 

silicic ones (about 25 ppm). Vanadium is concentrated in magmatic magnetite deposits, especially 

those that are titaniferous, and commonly ranges 

from 1,000 to 5,000 ppm in these deposits.· 

Because most of the vanadium in magmas is in the 

insoluble 3-valent state, not much vanadium is available for hydrothermal transport ; hence, only a little 

(10-100 ppm V) occurs in most hydrothermal ore 

deposits. However, many titanium-bearing vein deposits and some gold-quartz veins, especially those 

with gold-telluride minerals, contain some vanadium, 

commonly about 1,000 ppm. 

During weathering of igneous rocks in humid climates, much of the vanadium in the ferromagnesian 
682 UNITED STATES MINERAL RESOURCES 

minerals apparently goes into the clay minerals that 

are formed, but it remains in the 3-valent state or 

oxidizes to the 4-valent state, both of which are relatively insoluble. If erosion is insignificant but chemical leaching is intensive, the residual material may 

be enriched in vanadium, as are some bauxites and 

laterites, which commonly contain about 500 ppm V. 

If, on the other hand, the clay minerals are removed 

by erosion, most of the vanadium must stay with 

these clay minerals during transport to places where 

they accumulate as sedimentary rocks, for argillaceous sediments commonly contain about as much 

vanadium as do igneous rocks, whereas sandstones 

contain only about 20 ppm V and limestones about 

10 ppm. 

During the weathering of igneous, residual, or 

sedimentary rocks, some vanadium oxidizes to the 

5-valent state, especially in the intensive oxidizing 

conditions of arid climates. In this state the vanadium goes into surface or ground-water solutions and 

remains in solution over a wide range of acidity and 

alkalinity. It can be precipitated from solution and 

locally concentrated in rocks under the following 

three general conditions: 

1. By reaction with hydroxides of aluminum or 

ferric iron. This process forms or enriches the vanadium concentration in some bauxites and residual 

or sedimentary iron ores, some of which contain 

about 500 ppm. 

2. By reaction with cations of heavy metals, such 

as copper, lead, and zinc. This process forms the epigenetic vanadate minerals in the oxidized zones of 

base-metal deposits. The vanadium concentrations 

range from a trace to several thousand parts per 

million V. 

3. By reduction in the presence of organic material 

or biogenetically generated H2S. If the vanadiumbearing solutions are moving through rocks, epigenetic ore deposits such as those in sandstone in 

the Colorado Plateau region can be formed. On the 

other hand, if the vanadium is carried to the seas by 

surface waters, it can concentrate syngenetically in 

phosphorites that are rich in organic material, and in 

carbonaceous shales ; some of these shales contain as 

much as 5,000 ppm V. Furthermore, if the organic 

materials in these shales are converted to liquid 

hydrocarbons, the vanadium can be moved as a dissolved constituent; some crude oils contain as much 

as several hundred parts per million V. Vanadium accumulates in the ashes of these oils, and also in the 

asphaltic residues resulting from natural or industrial distillation of these oils, and these materials 

have been used as commercial sources of vanadium. 

VANADIUM MINERALS 

Fischer and Ohl (1970) listed the names of 110 

vanadium minerals, but only some 60 of these are 

generally accepted by mineralogical authorities ; the 

rest are considered to be inadequately des<rribed or 

unneeded synonyms. Of the accepted vanadi urn minerals, most are scarce. The important ore minerals 

are listed below ; however, most of the vanadium 

being produced currently is recovered from ores or 

materials in which no specific vanadium ore mineral 

is recognized. 

Carnotite: K2(UOt)2(V04)2•3H20. A secondary mineral 

in surface and near-surface deposits of vanadium and uranium in sandstone; especially common in the Colorado Plateau 

region. 

Coul8onite: (Fe,V)a04. A primary ~neral exsolved from 

magnetite in some titaniferous magnetite deposits; also with 

magnetite in nontitaniferous magnetite deposits in Nevada. 

Descloizite-mottramite 8 erie 8 : PbZn (V04) OH-PbCu 

(V04) OH. Includes araeoxene, chileite, cuprodesclozite, dechenite, eusynchite, psittacinite, ramirite, schaffnerite, and 

vanadite. Secondary minerals in the oxidized parts of basemetal deposits; common in deposits in arid climates. 

Montro8eite: (V,F,e) O•OH. A primary mineral, mostly in 

deposits in sandstone; common but nowhere abundant. 

Patronite: VS4. A primary mineral in the asphaltite-vein 

deposit at Mina Ragra, Peru. 

Ro8coelite: Near K(V,Al)aSiaOlo(OHh A primary mineral, 

common and abundant in vanadium deposits in sandstone, 

sparse to moderate in some gold-quartz veins. 

Vanadinite: Pbs(V04)aCl. A secondary mineral in the 

oxidized parts of some base-metal deposits. 

VANADIUM DEPOSITS 

DEPOSITS OF MAGMATIC ORIGIN 

TIT ANIFEROUS MAGNETITE DEPOSITS 

Vanadium-bearing titaniferous magnetite deposits 

are associated with mafic and related igneous rocks, 

most commonly anorthosite and gabbro. These rocks 

occur in thick stratiform sheets or complex intrusive 

bodies and are of deep-seated origin; most of those 

exposed are in continental shield areas and are of 

Precambrian age; only a few are younger. Magnetite 

and ilmenite are the principal ore minerals, but some 

hematite is present in some deposits. These minerals 

occur in medium- to fine-grained intergrowths and 

in exsolution and solid-solution relations. Small blebs 

and exsolution blades of coulsonite have been recognized in magnetite in a few deposits, but no vanadium 

mineral has been identified in most deposits; almost 

always, however, vanadium is more abundant in the 

magnetite (magnetic) concentrates of these deposits 

than in the ilmenite concentrates. Ore gr::~.des in productive deposits vary widely: 16-60 percent Fe, 1.5-

38 percent Ti02, and 0.1-2 percent V 205. Small but 

varied amounts of chromium, copper, and nickel occur in these deposits; phosphorus is generally sparse. 
VANADIUM 683 

The ore minerals crystallized with the silicate minerals from the magma, and commonly they occur 

disseminated in large masses of rock or were segregated by crystal settling into extensive lenses or 

layers as much as several feet thick. Some bodies of 

magnetite and ilmenite occur as plugs, dikes, and 

irregularly shaped masses that presumably were 

injected into these forms when conditions caused 

remeltirtg of these minerals in places where they 

originally crystallized. Deposits vary widely in size 

-from those too small to be mined to those that consist of several billion tons of ore containing several 

million tons of vanadium. 

NONTIT ANIFEROUS MAGNETITE DEPOSITS 

Nontitaniferous magnetite deposits, by arbitrary 

definition, contain less than about 1 percent Ti02. 

They also generally contain less vanadium but more 

phosphorus than do the titaniferous magnetite deposits-commonly 0.1 to about 0.5 percent V20 5 and 

more than 0.1 percent P. Their geologic habits are 

less consistent than those of the titaniferous magnetite deposits; some of them are derived from mafic 

igneous rocks but others are associated with igneous 

rocks of intermediate or syenitic composition, and 

some deposits are apparently wholly magmatic 

whereas others have the characteristics of contact 

or hydrothermal replacement bodies. Magnetite, the 

principal ore mineral in these deposits, occurs in disseminated or massive bodies; the iron content ranges 

from about 30 to 60 percent Fe. Apatite is present in 

the deposits rich in phosphorus. 

VANADIUM-BEARING HYDROTHERMAL VEl~ DEPOSITS 

Vanadium is sparse in typical hydrothermal vein 

deposits except those containing titanium minerals 

and some containing gold. A few tenths percent V 205 

is common in the titanium minerals ilmenite, rutile, 

and brookite, and also in the uranium-titanium-iron 

mineral davidite, where these minerals occur in 

veins. N olanite ( Fe4 V 1o023, Fe3 V s018) is intergrown 

with ilmenite and other vein minerals in the uranium-bearing veins in the Goldfields district, Saskatchewan, Canada (Robinson, 1955). In some goldquartz veins, especially those containing goldtelluride minerals, roscoelite, the vanadium-bearing 

mica, is conspicuous. The roscoelite is finely intergrown with quartz and other gangue minerals, and 

in places it forms small aggregates along the vein 

walls. The vanadium content of these veins is assumed to be low, although no grade data have been 

found except for the Kekionga-Magnolia vein, Magnolia district, Colorado, where "a moderate tonnage 

averaging 2 percent vanadium oxide was blocked 

out" (Lovering and Goddard, 1950, p. 234). 

EPIGENETIC DEPOSITS 

VANADATE DEPOSITS 

Vanadates of lead, zinc, and copper ( vanadinite 

and minerals of the descloizite-mottramite series) 

are common in the oxidized zones of base-metal 

deposits, especially in areas of arid climate and deep 

oxidation. These minerals form crusts and partly fill 

cavities in the altered and leached material of the 

primary base-metal sulfide veins and replacement 

bodies. The vanadate ore bodies are irregular in 

shape and varied in size and grade ; most are rather 

small and low in grade. Carbonate rocks are the host 

to most deposits, but some deposits are in silicic 

igneous rocks. It is generally assumed that the vanadium was introduced by oxidizing ground waters 

from remote sources because the vanadium contents 

of the primary sulfide deposits and the country rocks 

are virtually nil. 

DEPOSITS IN SANDSTONE 

Vanadium deposits in sandstone have been the 

principal source of this metal until recent years; 

similar but unimportant deposits are known in limestone and shaly sandstone. Typically, the productive 

deposits occur in stream-laid sandstone lenses several tens of feet thick and 1 mile to several miles 

wide, interbedded with mudstone of flood..Jplain or 

lacustrine origin. These beds accumulated on broad 

alluvial plains or fans, and all are of late Paleozoic 

age or younger, probably coincident with the evolutionary development of land plants ; coalified fossil 

plant material is present in most deposits. A few 

productive deposits are in beds of clean sandstone of 

eolian origin. 

Varied amounts of uranium and copper are associated with vanadium in these deposits. The principal primary ore minerals are silicates and oxides of 

both vanadium (mainly roscoelite and montroseite) 

and uranium (coffinite and uraninite) and the common sulfides of copper; carnotite is the principal 

secondary vanadium-uranium mineral. These minerals chiefly fill the pores of the sandstone, but they 

also partly replace the sand grains and the plant 

fossils. Ore grades are commonly 1-2 percent V 205, 

0.05-0.25 percent U 308, and a trace to 1 percent Cu. 

Some ore bodies are irregular in shape, but most of 

them are tabular; they average only a few feet in 

thickness and lie nearly parallel to the bedding of the 

host rock. Ore bodies range in size from a few tons 

of ore to more than a million tons. Individual deposits are discrete bodies and are separated from 

neighboring deposits by barren sandstone; nevertheless, deposits tend to be clustered in patches of 

ground a few miles across and to recur in a favored 
684 UNITED STATES MINERAL RESOURCES 

stratigraphic zone over broad areas. It is generally 

assumed that the vanadium and associated metals 

were introduced by ground waters moving along the 

sandstone host beds to places where an adequate 

reducing environment existed; coalified plant material and H2S generated by bacteria feeding on the 

plant material likely were the reducing agents. 

ASPHAL TITE DEPOSITS 

The trace amounts of vanadium in crude oils tend 

to accumulate in the natural asphalts and related 

materials that are the residues or natural distillation 

products of crude oils. Many asphaltites contain 

about 1 percent V 205, and some have yielded samples 

reported to contain appreciably more vanadium. 

One asphaltite deposit, that at Mina Ragra, Peru 

(McKinstry, 1957), has been intensively exploited 

for vanadium; this deposit was mined from 1907 to 

1955 and was the world's principal source of vanadium in the early 1900's. Unoxidiz€d ore in this 

deposit consisted of quisqueite (a hydrocarbon), 

coke, and pa.tronite (a vanadium sulfide). Vanadates 

and vanadium oxide minerals formed +:he nearsurface oxidized ore, some of which was fabulously 

rich, containing as much as 40 percent V 205. Country rock at Mina Ragra comprises shalf' and thinbedded limestone of Cretaceous age. These rocks 

were invaded by igneous dikes and were cut by numerous faults. The ore minerals and associated material occupy a fracture and permeate the adjoining 

shale, forming a lens-shaped body, about 50 feet wide 

and several hundred feet long at the surface, which 

bottomed at a depth of about 250 feet. The high concentration of vanadium in this deposit may be due 

to intensive distillation of the original asphaltite and 

perhaps to a local transfer of vanadium from the 

country rock by thermal solutions. 

DEPOSITS ASSOCIATED WITH 

ALKALIC IGNEOUS COMPLEXES 

The recently developed vanadium deposit at Wilson Springs, Ark., is at the contact of the Potash 

Sulfur Springs alkalic intrusive complex (Hollingsworth, 1967). The vanadium ore, which contains 

about 1 percent V 205, occurs as poorly defined 

bodies in irregular masses of argillic altered rock of 

both the igneous intrusion and the bordering sedimentary strata. For mining control, ore bodies are 

delimited by assaying samples; recognizable vanadium minerals are sparse. A similar deposit occurs at 

the contact of the nearby Magnet Cove alkalic complex (Reed, 1949). 

Because of the intensive alteration of the host 

rocks and deep weathering in the area, the genesis of 

these deposits is not yet clearly established; ultimately, these deposits may be classified as either 

contact metasomatic or hydrothermal. But regardless of the mode of concentration, the significant 

factor in the origin of these deposits may be their 

association with alkalic igneous complexes. Although 

this association has not been recognized by most 

students of the geochemical distribution of vanadium, anomalous amounts of vanadi urn are reported in 

analyses of samples from numerous alkalic igneous 

complexes in various parts of the world. Magnetite 

and titanium minerals, especially ilmenite, are common in many alkalic intrusives, and vanadium is 

commonly associated with these minerals in the 

magmatic stage and to some extent in hydrothermal 

deposits. If these ideas are correct, alkalic intrusives 

should be searched more frequently for vanadium 

deposits. Exploration probably will be difficult, however, for the vanadium probably will not occur in 

visually recognizable minerals. 

RESOURCES 

World resources of vanadium in known deposits 

are very large (Fischer, 1961). They amount to millions of short tons V, representing hundreds of 

years' supply at the current rate of consumption. 

Only a few known deposits, however, are rich 

enough in vanadium to be worked for this metal 

alone. Most of the vanadium resources are in deposits from which vanadium is being, and will be, 

recovered as a coproduct or byproduct. Some productive sources contain only trace amounts of vanadium, which is recovered only as a minor byproduct from waste materials. 

RESERVES IN PRODUCTIVE DEPOSITS 

Significant data on the major and most of the 

minor sources of vanadium in 1970 are summarized 

in table 147. This table shows the known reserves in 

certain deposits, and it also illustrates the diverse 

geologic ·materials from which vanadium can be recovered and the ranges in grade of these rna terials, 

factors that are important in estimating future production and potential resources in unproductive 

deposits. 

POTENTIAL RESOURCES IN UNPRODUCTIVE 

DEPOSITS 

Large vanadium resources occur in known but unproductive deposits similar to those from which 

vanadium is being recovered. (In this discussion, 

"large" implies more than about 1,000,000 short tons 

V, "moderate" from about 100,000 to 1,000,000 short 

tons, and "small" less than about 100,000 short tons.) 

Large resources also occur in carbonaceous shale 
VANADIUM 685 

TABLE 147.-Vanadium reserves in the principal sources of vanadium, 1970 

Country and 

deposit or source 

United States: 

Geologic type 

of deposit or source Commodities 

recovered 

V20o 

grade 

(percent) 

Reserves 1 

Ore 

(millions of Vanadium 

short tons) (short tons) 

Principal 

source of data~ 

Colorado Plateau 

Wilson Springs, ArkSandstone ------ U, V ----------------- ±1.5 5 40,000 Griffith (1970). 

Undetermined V -------------------- 1 5 

(Large) 

30,000 Do. 

Idaho -------------- Phosphate ------ P, V ------------------ .2-.3 3 45,000 Do. 

South-West Africa: 

Otavi district ------- Vanadate ------ Cu, Ph, Zn, V --------- .7 1.6 6,250 South West Africa 

Co., Ltd., Annual 

report, 1970. 

South Africa: 

Bushveld complex Titaniferous 

magnetite. Fe, V ----------------- 1.5-2 '212 2,000,000 Nel and Luyt (1964). 

Finland: 

Otanmaki ---------- Norway: 

Rodsand ----------- U.S.S.R.: 

Mount Kachkanar 5 _ 

Chile: 

El Romeral --------

Canada: 

___ do ---------- Fe, Ti, V 

---do 

_ __ do 

N ontitaniferous 

magnetite. 

Fe, Ti, V 

Fe, V 

Fe, V 

.47 55 

.5 11 

. 10-.12 13,500 

. 3-.4 80 

140,000 Marelle (1970). 

31,000 Do. 

8,000,000 Sokolov (1970) . 

150,000 Alvarado (1970) . 

Oil refinery -------- Crude oil ------- Petroleum products, V __ 

France: 6 ----------- Bauxite -------- AI, V ----------------- Japan: ----------------- Ilmenite sands __ Ti02, V ---------------

.02 

.1 

.1-.2 

(Large) 

(Large) 

(Large) 

? DeHuff (1965). 

? Taylor (1971). 

? DeHuff (1971). 

1 Identified deposits from which minerals can be extracted profitably with existing technology and under present economic conditions. 2 For additional information on the geology and resources of these deposits, see references cited by Fischer and Obi (1970). ~Vanadium estimated by Griffith (1970) tbat will be recovered from ferrophosphorus slags derived from making elemental phosphorus from Idaho 

phosphate rock during the 1968-2000 period 4 Marelle and Abdulla (1970) reported 200 million metric tons of measured, indicated, and inferred reserves and 1,800 million metric tons of po- tential ores, totaling 2,200 million short tons of total resources; if the average grade of this material is 1.7 percent V20;;, as seems likely, the total 

vanadium resources amount to about 20,000,000 short tons V. 5 Some vanadium may have been recovered from the titaniferous magnetite ores at Kusinkoe and Pervouralskoe and perhaps from other iron deposits in the U.S.S.R. in 1970 (Polyakov, 1959). 6 Some vanadium may also have been recovered from bauxite in other European countries. 

beds, from which vanadium has not been recovered 

commercially. But because many of these unproductive deposits are not developed or even extensively 

explored, accurate resource appraisals are not possible. Furtermore, many of the known but unproductive deposits are not readily amenable to present 

metallurgical practices, and most of these deposits 

would yield vanadium only as a byproduct. For these 

reasons, it is not possible, except for a few deposits, 

to predict which ones are most likely to become productive in the foreseeable future. 

Titaniferous magnetite deposits in the United 

States contain large resources of vanadium; those in 

Alaska (Klemic, 1970; Wells and Thorne, 1953), 

Wyoming (Dow, 1961), and New York (Balsley, 

1943) are the larger and more promising ones. Large 

resources of the same type occur in Canada (Rose, 

1969, 1970), U.S.S.R. (Yudin and Zak, 1971; Sokolov, 1970), Republic of South Africa (seB footnote 

4, table 147), Australia (Jones, 1965; Daniels, 1967; 

Hockley, 1971), and perhaps mainland China (Nishiwaki, 1970; Hsing, 1959). Of the unproductive titaniferous magnetite deposits, those in the Singhbhum area, Bihar and Orissa, India, seem to be the 

most favorable to yield vanadium as the principal 

product; ore reserves total about 20,000,000 tons and 

perhaps average about 2 percent V205 (Roy, 1969). 

Vanadium might be recoverable from the deposits at 

Lake Sanford, N.Y., and Allard Lake and St. Urbain, 

Quebec, Canada, that are being mined for titanium. 

Nontitaniferous magnetite deposits being mined 

for iron ore at Buena Vista Hills, Nev. (Reeves and 

Kral, 1955; Radtke, 1962), and the Savage River 

area, Tasmania, Australia (Evoy, 1970), contain 

about 0.3-0.5 percent V 205, about that in the deposit 

at El Romeral, Chile (table 147), from which vanadium is being recovered. Vanadium resources in 

the deposits at Buena Vista Hills and Savage River 

are moderate. Although the vanadium content of the 

nontitaniferous magnetite deposits in the Kiruna and 

Gallivare districts, Sweden, is only 0.1-0.2 percent 

V20 5, these deposits contain a large resource of 

vanadium. 

During World War II, Germany recovered considerable vanadium from sedimentary iron ores in 

northwestern Europe that contain only 0.02-0.2 

percent V205 (Fischer, 1946). Although vanadium 

recovery from these ores presumably is not economically feasible under present conditions, the wartime operations show that recovery is technologically 

possible; hence, these deposits and similar ones qualify as a vanadium resource. The reserves of the 
686 UNITED STATES MINERAL RESOURCES 

minette-type iron ores of northern Franc~, Western 

Germany, and central England are large (Marelle, 

1970), and probaJbly each area contains a moderate 

to large resource of vanadium. Three similar deposits in the U.S.S.R.-Ayatskoe (0.1 percent V205), 

Lisakovskoe (0.1 percent V205), and Kerch (0.05 

percent V205) (Sokolov, 1970; Bardin, 1957)-each 

contain large iron-ore reserves (Sokolov, 1970) and 

moderate to large vanadium resources. Although vanadi urn probably is not being recovered from these 

ores, Slotvinskii-Sidak and Liakishev (1970, p. 202) 

stated: "Large vanadium reserves are concentrated 

in the iron ores of Lisakovskoe, Kerchinskoe, Ayatskoe, and other deposits. Thus, in projected amount 

of recovery of ores of the Lisakovskoe deposit, some 

tens of thousands of tons of vanadium pentoxide 

will be recovered in the iron concentrate (with 48-

50 percent Fe and 0.15-0.25 percent V 20 5) ." 

Magnetite and ilmenite sands commonly contain 

0.1-0.5 percent V205; those rich in mat.rnetite, especially those derived from titaniferous magnetite 

deposits, are the ones generally richer in vanadium. 

Some of these sand deposits occur along streams, but 

most of them are on b€aches. They occur in many 

parts of the world, and some of them contain large 

reserves of the black minerals and small to moderate 

resources of vanadi urn. Japan is recovering some 

vanadium from waste sulfuric acid derived from producing titanium dioxide from ilmenite sands (DeHuff, 1971). During World War II Japan recovered 

vanadium and titanium from magnetite-rich beach 

sand utilized principally as a source of iron. Perhaps 

the sand deposits that offer the greatest potential for 

vanadium production are those in New Zealand that 

are now being exploited for iron (Ridley, 1968). 

These deposits contain several hundred million tons 

of sand, the concentrates of which contain 53-60 percent Fe, 8-10 percent Ti02, and 0.3-0.5 percent V20 5 

(Fyfe, 1952). 

Potential resources of vanadi urn in undiscovered 

de~osits in sandstone in the Colorado Plateau region, 

United States, are probably small; likely they do not 

much exceed known reserves (table 147). Similar 

deposits of vanadium with uranium in sandstone are 

known in other parts of the United States and in 

some foreign countries, notably the U.S.S.R., Gabon, 

Argentina, and Australia, but generally these deposits have a lower vanadium content than the vanadium-rich deposits of the Colorado Plateau, and 

therefore they do not seem to offer a significant vanadium potential. 

Occurrences of vanadate minerals are widespread, 

especially in arid parts of the world, but accumulations of these minerals in amounts necessary for 

mining are few; resources are judged to be negligible compared to other geologic ty.pes of vanadium 

deposits. 

Many crude oils contain little or no vanadium, but 

some, especially the asphalt-base oils, contain up to 

several hundred parts per million V (Whisman and 

Cotton, 1971). Although it would hardly be conventional to classify an oil pool as a vanadium deposit, 

industrial and natural residues of petroleum are, 

nevertheless, commercial sources of vanadium and 

they might become more significant sources in the 

future. Vanadium is recovered from the ash and soot 

of oil .. burning furnaces and from refinery residues ; 

pollution-control practices may enhance the chance 

of recovery from these sources in the future. The 

recovery of vanadium from the residue of refining 

Athabaska tar sand, Alberta, Canada, has been proposed (Oil and Gas Journal, 1967) ; although these 

sands contain only about 240 ppm V, the quantity of 

material being processed could yield annually about 

a quarter of the current North American vanadium 

requirements. Similar deposits, if exploited for 

petroleum products, could also be sources of vanadium. The vanadium-bearing asphaltite deposit at 

Mina Ragra, Peru, was the richest vanadium deposit 

known, and it had yielded about one-fourth of the 

world's total vanadium output by the time it was 

mined out in 1955. No other sizable asphaltite deposit 

of comparable grade is known, but many deposits 

containing about 1 percent V 205 have been reported, 

especially in Peru (Larson and Welker, 1947) and 

Argentina (Wright, 1940). 

Certain carbonaceous shales, oil shales, phosphatic shales, and graphitic schists contain 0.2 to 

nearly 1 percent V205; higher grade samples are 

also reported. Some of the vanadium-bearing shale 

deposits are tens of feet thick and cover broad areas 

-obviously these deposits contain enormous tonnages of rock and represent large resources of vanadium. References to many carbonaceous shale 

deposits are given by Tourtelot (1970) and by 

Fischer and Ohl (1970). Notable examples of these 

shales occur in Idaho and adjoining States (Fischer, 

1961), in Kazakhstan, U.S.S.R. (Ankinovich, 1961), 

in the high Andes of Peru (Larson and Welker, 

1947), and in Queensland, Australia (Taylor, 1971). 

PROSPECTING TECHNIQUES 

The basic tools for prospecting for vanadium are 

a knowledge of the geologic types of deposits in 

which vanadium is apt to occur and a knowledge of 

the geologic habits and mineral associations of such 

deposits. The vanadium ore minerals in the vana-
VANADIUM 687 

date deposits and in the deposits in sandstone are 

visually recognizable in the field, and of course the 

presence of associated uranium in the sandstone 

deposits is readily detected by its radioactivity. The 

presence of vanadium in iron deposits much be determined by analysis, even though the principal ore 

minerals in these deposits can be recognized visually. Analyses are also generally needed to detect the 

presence of vanadium in phosphate rock, carbonaceous shale, and asphaltite, although in places 

recognizable vanadium minerals develop on the 

weathered outcrops of these deposits. Generally, vanadium is not amenable to geochemical exploration 

techniques of sampling soils and stream sediments, 

as are the base metals and some other metals, because vanadium is not so readily soluble and because 

it has a high background content in many types of 

rocks. 

PROBLEMS FOR RESEARCH 

The demand for vanadium is expected to increase 

appreciably. World resources of vanadium are very 

large, but most of the raw materials containing these 

resources will yield vanadium only as a byproduct, 

commonly a minor one, and so output of vanadium is 

largely dependent on the requirements for other 

commodities and on technological practices that 

permit the recovery of small amounts of vanadium. 

Domestic requirements for vanadium are expected 

to exceed domestic output. In order to avoid dependence on foreign supplies, new vanadium deposits 

must be found or the means must be developed to 

recover byproduct vanadium profitably from known 

sources. Potentially recoverable vanadium is currently being lost from some operations that mine 

magnetite and phosphate rock and some that refine 

or burn crude oil. 

REFERENCES CITED 

Alvadaro, Benjamin, 1970, Iron ore deposits of South 

America, in Survey of world iron ore resources: New 

York, United Nation Dept. Econ. and Social Affairs, p. 

302-380. 

Ankinovich, S. G., 1961, Lower Paleozoic vanadiferous basin 

of the northern Tyan-Shan and the western part of central Kazakhstan, Pt. 1 [in Russian]: Alma-Ata, Kazakh, 

SSR, Akad. N auk Kazakh. SSR, Izdatel., 270 p. 

Balsley, J. R., Jr., 1943, Vanadium-bearing magnetiteilmenite deposits near Lake Sanford, Essex County, New 

York: U.S. Geol. Survey Bull. 940-D, p. 99-123. 

Bardin, I. P., ed., 1957, Zhelezorudnaya baza chernoy metallurgii SSSR [The iron-ore base of the ferrous-metallurgy 

industry of the U.S.S.R.]: Moscow, Izdvo Akademiya 

Nauk SSSR, Mezhvedomstrennaya Postoyanaya Komissiya po Zhelezu, 565, p.; excerpts translated 4 Dec. 1958, 

202 p., JPRS/DC-393. OTS $3.50. (See Tech. Translations, v. 1, p. 261, 1959). 

Busch, P. M., 1961, Vanadium, a materials survey: U.S. 

Bur. Mines lnf. Circ. 8060, 95 p. 

Daniels, J. L., 1967, Subdivision of the Giles Complex, Central Australia: Western Australia Geol. Survey Ann. 

Rept. 1966, p. 58-62. 

DeHuff, G. L., 1965, Vanadium, in Minerals Yearbook, 1964: 

U.S. Bur. Mines, v. 1, p. 1141-1149. 

DeHuff, G. L., 1971, Vanadium, in Minerals Yearbook, 1969: 

U.S. Bur. Mines, v. 1-2, p. 1131-1137. 

Dow, V. T., 1961, Magnetite and ilmenite resources, Iron 

Mountain area, Albany County, WyQming: U.S. Bur. 

Mines Inf. Circ. 8037, 133 p. 

Evoy, E. F., 1970, Iron ore deposits of Australia, New Zealand and New Caledonia, in Survey of world iron ore 

resources: New York, United Nations Dept. Econ. and 

Social Affairs, p. 207-236. 

Fischer, R. P., 1946, German iron ores yield vanadium: Am. 

Inst. Mining Metall. Engineers, Tech. Pub. 2070, 5 p. 

Fischer, R. P., 1961, [Vanadium] Resources, Chap. 4, of 

Busch, P. M., Vanadium, a materials survey: U.S. Bur. 

Mines Inf. Circ. 8060, p. 33-41. 

Fischer, R. P., and Ohl, J. P., 1970, Bi•bliography on the 

geology and resources of vanadium to 1968: U.S. Geol. 

Survey Bull. 1316, 168 p. 

Fyfe, H. E., 1952, The iron ore resources of New Zealand 

[in English]: Internat. Geol. Cong. 19th, Algiers 1952, 

Symposium sur les gisements de fer du monde, v. 2, p. 

589-594. 

Griffith, R. F., 1970, Vanadium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 417-430. 

Hockley, J. J., 1971, Occurrence and geological significance 

of layered stratiform intrusion in the Yilgarn Block, 

Western Australia: Nature, v. 232, no. 5308, p. 252-

253. 

Hollingsworth, J. S., 19·67, Geology of the Wilson Springs 

vanadium deposits, Garland County, Arkansas, in Geol. 

Soc. America Guidebook Field Conf., Central Arkansas, 

economic geology and petrology, Nov. 18-19, 1967: 

Arkansas Geol. Comm., p. 22-28. 

Hsing, Feng-Ming, 1959, Genesis of the titanomagnetite deposits of Panchihua [in Chinese]: Ti-chih lun-p'ing, v. 

19, p. 421-425; Chern. Abs., v. 54, col. 6421, 1960. 

Jones, W. R., 1965, Vanadium deposits of Western Australia, 

in Madigan, R. T., ed., Geology of Australian ore deposits: Commonwealth Mining and Metall. Cong., 8th, 

Aust:r~alia and New Zealand, 1965, v. 1, 2d ed., p. 154-

155. 

Klemic, Harry, 1970, Iron ore deposits of the United States 

of America, Puerto Rico, Mexico and Central America, 

in Survey of world iron ore resources: New York, United 

Nations Dept. Econ. and Social Affairs, p. 411-477. 

Larson, C. B., and Welker, K. K., 1947, Vanadium resources 

of Peru: U.S. Bur. Mines Mineral Trade Notes, v. 25, 

no. 1, Spec. Suppl. 16, 58 p. 

Lovering, T. S., and Goddard, E. N., 1950, Geology and ore 

deposits of the Front Range, Colorado: U.S. Geol. Survey Prof. Paper 223, 319 p. 

Marelle, Andre, 1970, Iron ore deposits of Europe, in Survey of world iron ore resources: New York, United N ations Dept. Econ. and Social Affairs, p. 270-301. 

Marelle, Andre, and Abdulla, M. A., 1970, Iron ore deposits 

of Africa, in Survey of world iron ore resources: New 

York, United Nations Dept. Econ. and Social Affairs, p. 

62-101. 
688 UNITED STATES MINERAL RESOURCES 

McKinstry, Hugh, 1957, [Review of] El vanadio en el Peru, 

by Silvio Hernandez Aquije: Eeon. Geology, v. 53, no. 3, 

p. 324-325. 

National Materials Advisory Board, Division of Engineering, National Research Council, 1970, Trends in the use 

of vanadium-Report of the Panel on Vanadium, Committee on Technical Aspects of Critical and Strategic 

Materials: Natl. Acad. Sci.-Natl. Acad. Engineering 

Pub. NMAB-267, 46 p. 

Nel, H. J., and Luyt, J. F. M., 1964, Vanadium-rich magnetite seams of the Bushveld igneous complex, South Africa 

[abs.]: Econ. Geology, v. 59, no. 7, p. 1416. 

Nishiwaki, Ghikao, 1970, Iron ore deposits of the Middle 

East, Asia and the Far East, in Survey of world iron 

ore resources: New York, United Nations Dept. Econ. 

and Social Affairs, p. 102-206. 

Oil and Gas Journal, 1967, Athabasca crude to hit pipeline 

soon: Oil and Gas Jour., v. 65, no. 41, p. 76-77. 

Polyakov, A. Yu., 1959, Osnovy metallurgii vanadiya [Principles of the metallurgy of vanadium]: Moscow, U.S.S.R., 

Gos. Lauchn.-Tekh. Izdatel. Lit po Chernoy i Tsvetnoy, 

Met., 137 p.; summary by V. P. Sokoloff, in U.S. Bur. 

Mines Mineral Trade Notes, v. 53, no. 5, p. 48-50, 1961. 

Radtke, A. S., 1962, Coulsonite, FeV20,, a spinel-type mineral 

from Lovelock, Nevada: Am. Mineralogist, v. 47, nos. 

ll-12, p. 1284-1291. 

Reed, D. F., 1949, Investigation of Christy titanium deposit, 

Hot Springs County, Arkansas: U.S. Bur. Mines Rept. 

Inv. 4592, 10 p. 

Reeves, R. G., and Kral, V. E., 1955, Geology and iron ore 

deposits of the Buena· Vista Hills, Churchill and Pershing Countries, Nevada, Pt. A of Iron ore deposits of 

Nevada: Nevada Bur. Mines Bull. 53, p. 1-32. 

Ridley, J. W., 1968, The development of New Zealand ironsands: [London], Mining Mag., v. 119, no. 1, p. 4-5, 7, 

9, 11, 13. 

Robinson, S. C., 1955, Mineralogy of uranium deposits, Goldfields, Saskatchewan [Canada]: Canada Geol. Survey 

Bull. 31, 128 p. 

Rose, E. R., 1969, Geology of titanium and titaniferous deposits of Canada: Canada Geol. Survey Econ. Geology 

Rept. 25, 177 p. 

--- 1970, The ferride element content of titaniferous 

magnitite in Canada: Canada Geol. Survey Paper 69-54, 

9 p. 

Roy, B. C., 1969, Vanadium: Jour. Mines, Metals and Fuels, 

v. 17,no. 11,p. 381-388. 

Slotvinskii-Sidak, N. P., and Liakishev, N. P., 1970, Nekotorye voprosy prozvodstva vanadii v SSSR [Some problems of vanadium production in the U.S.S.R.]: Sbornik 

trudov Tsentral'nyi Nauchno Issled. Inst. Chernoi 

Metallurgii, no. 75, p. 202-205; English translation 

available only f.rom N atl. Tech. lnf. Service, U.S. Dept. 

Commerce, Springfield, Va. 22151. 

Sokolov, G. A., 1970, Iron ore deposits of the Union of 

Soviet Socialist Republics, in Survey of world iron ore 

resources: New York, United Nations, Dept. Econ. and 

Social Affairs, p. 381-410. 

Taylor, H. A., Jr., 1971, Vanadium, in Minerals Yearbook, 

1970: U.S. Bur. Mines, 7 p. (In press.) 

Tourtelot, E. B., 1970, Selected annotated bibliography of 

minor-element content of marine black shales and related sedimentary rocks, 1930-65: U.S. Geol. Survey 

Bull. 1293, 118 p. 

U.S. Bureau of Mines, 1970, Ferrous minerals, in Mineral 

facts and problems: U.S. Bur. Mines Bull. 650, p. 2~3-

430. 

Wells, R. R., and Thorne, R. L.,. 1953, Concentration of 

Klukwan, Alaska, magnetite ore: U.S. Bur. Mines Rept. 

4984, 15 p. 

Whisman, M. L., and Cotton, F. 0., 1971, Bumines data 

promise help in identifying petroleum-spill sources: Oil 

and Gas Jour., v. 69, no. 52, p. 111-113. 

Wright, C. W., 1940, Mineral resources, production, and 

trade of Argentina: U.S. Bur. Mines Foreign Minerals 

Quart., v. 3, no. 3, 52 p. 

Yudin, B. A., and Zak, S. 1., 1971, Titanium deposits of 

northwestern USSR (eastern part of Baltic Shield): 

Internat. Geology Rev., v. 13, no. 6, p. 864-872; translated from Titanovyye mestorozhdeniya Severo-Zapada 

SSR (Vostochnaya chast' Baltiyskogo schita): Sovetskaya Geologiya 1970, no. 9, p. 138-147, 1970. 
UNITED STATES MINERAL RESOURCES 

ZEOLITES IN SEDIMENTARY ROCKS 

By RICHARD A. SHEPPARD 

CONTENTS 

Page 

Abstract of conclus·ions -------------------------- 689 

Introduction ------------------------------------ 689 

Exploitation ------------------------------------- 690 

Geologic environment ---------------------------- 690 

Prospecting techniques --------------------------- 692 

Potential resources ------------------------------- 693 

Research needed --------------------------------- 693 

References -------------------------------------- 694 

TABLE 

Page 

148. Zeolites reported from sedimentary rocks ____ 691 

ABSTRACT OF CONCLUSIONS 

Zeolites are among the most common authigenic silicate 

minerals in s·edimentary rocks; they occur in rocks that are 

diverse in age, lithology, and depositional environment. 

Zeolites are particularly common in Cenozoic sedimentary 

rocks that originally contained abundant silicic vitric material. Most zeolites in sedimentary rocks formed during 

diagenesis by the reaction of volcanic glass with interstitial 

water which originated as either meteoric water or connate 

water of a saline, alkaline lake. Although about 20 different 

zeolites have been reported from sedimentary rocks, only 

analcime, chabazite, clinoptilolite, erionite, ferrierite, heulandite, laumontite, mordenite, and phillipsite commonly 

make up the major part of zeolitic rocks. Nearly monomineralic beds of zeolites are known, but most zeolite rocks also 

contain clay minerals, silica minerals, and feldspars of 

authigenic origin. 

Production of natural zeolites in the United States is 

currently only several hundred tons per year. The abundance 

and variety of zeolite deposits in the United States, the 

unique properties of the zeolites, and the seemingly low 

cost of mining suggest potential uses in many industrial and 

agricultural proc·esses. Chemical and structural modifications of the natural materials could further increase their 

potential. When new markets for zeolites are developed, the 

United States will not only be s·elf-sufficient but will probably become a major exporter. 

The total of identified, hypothetical, and speculative resources of zeolites in the United States is conservatively 

estimated at more than 10 trillion tons. Total resources of 

zeolites in the res•t of the world have not yet really begun to 

to be cataloged. 

INTRODUCTION 

Zeolites-crystalline hydrated aluminosilicates of 

the alkalis and alkaline earths-are important rockforming constituents in sedimentary rocks and are 

potentially valuable industrial minerals. They have 

a framework structure that encloses interconnected 

cavities occupied by the relatively large cations and 

water molecules. The cations, chiefly sodium, potassium, and calcium, and the water have considerable 

freedom of movement within the structure and give 

the zeolite their cation-exchange and reversibledehydration properties. Some zeolites have essential 

contents of barium, strontium, or magnesium. The 

basic structure of all zeolites consists of (Si,Al) 04 

tetrahedra wherein each oxygen is shared between 

two tetrahedra; thus, the atomic ratio 0: (Si+Al) 

is 2. The net negative charge of the structure is 

balanced by the cations. The porous framework of 

the zeolites enables them to act as molecular sieves 

for the separation of molecular mixtures according 

to the size and shape of the molecular compounds. 

More than 30 distinct species of zeolites occur in 

nature. Numerous zeolites have also been synthesized, but many of these have no natural counterparts. Most zeolites have a specific gravity of 2.0-

2.3 and indices of refraction of 1.44-1.52. Zeolites 

rich in barium or strontium commonly have higher 

specific gravities and indices of refraction. Because 

the zeolites have similar physical properties, X-ray 

diffraction techniques are generally used for identification. 

Synthetic zeolites have been produced commercially in the United States since the early 1950's. 

These synthetic zeolites are used principally as catalysts, selective sorbents, and desiccants; they are 

U.S. GEOL. SURVEY PROF. PAPER 820 

689 
690 UNITEn STATES MINERAL RESOURCES 

now utilized in about 90 percent of the petroleum 

catalytic cracking installations and have greatly 

increased the recovery of gasoline. Natural zeolites, 

however, have found only limited use in this country. 

Clinoptilolite is used to remove cesium from radioactive wastes (Brown, 1962), and chabazite is used 

to desiccate mildly acidic natural gas. Zeolitic tuff 

has been used as a pozzolan in cement. 

In Japan, on the other hand, zeolites have been 

extensively mined and utilized since their discovery 

there in sedimentary deposits in 1949. Clinoptilolite 

and mordenite are the only zeolites currently mined 

in Japan, and they are utilized chiefly in the fields 

of agriculture and animal husbandry. Minato and 

Utada (1969) described the following uses: Desiccant for gases, separator of oxygen from air, adsorbent for obnoxious odors in farm yards, filler and 

whitening agent for paper, and a soil conditioner to 

increase the effectiveness of chemical fertilizers. 

More clinoptilolite is mined in Japan for the last 

use listed than for any of the others. 

Some of the natural zeolites may find applications 

in pollution control. For example, laboratory and 

pilot-plant studies by Pacific Northwest Laboratory, 

Battelle Memorial Institute, Richland, Wash. (Mercer and others, 1970), indicate that clinoptilolite is 

effective in the removal of ammonia from wastewater. Also, recent studies suggest that mordenite 

may be suitable for the removal of S02 from stack 

gases. 

The United States is self-sufficient with respect 

to the present fledgling zeolite industry. Because of 

the large potential zeolite resources and the diverse 

zeolite mineralogy, the United States will not only 

remain self-sufficient when new markets develop but 

will probably become a major exporter. 

EXPLOITATION 

Production figures have not been published for 

natural zeolites in the United States; however, small 

tonnages were mined from upper Cenozoic tuffs. 

Several hundred tons of chabazite, clinoptilolite, and 

erionite have been mined each year since the mid1960's; the mined deposits are near Bowie, Ariz., 

near Hector, Calif., and in Jersey Valley, Nev., respectively. 

Exploration and sampling of bedded zeolite deposits by commercial organizations have been active 

since the late 1950's in Arizona, California, Nevada, 

Oregon, Texas, and Wyoming. The exploration 

peaked in the early 1960's, when the search concentrated on natural molecular-sieve zeolites that 

might compete with the synthetic zeolites. Since 

1970, exploration has accelerated again. This time 

the emphasis is on the location of zeolite deposits 

suitable for pollution-control processes. 

Japan is probably the world's leading producer of 

natural zeolites. Since the mid-1960's, Japan has had 

an annual production of about 100,000 tons. About 

half of this production is from one mine, at Itaya, 

Honshu. Clinoptilolite and mordenite are the only 

zeolites currently mined in Japan. 

GEOLOGIC ENVIRONMENT 

Zeolites have been known since the mid-1750's, 

and they occur in rocks that are diverse in age, 

lithology, and geologic setting. Zeolites have been 

recognized in sedimentary deposits since 1891, when 

Murray and Renard (1891) described phillipsite in 

deep-sea deposits. Prior to the early 1950's, however, 

most zeolite occurrences were reported from fractured fillings and vesicle fillings in igneous rocks, 

particularly in basaltic rocks. Most of the large 

attractive zeolite specimens in museum collections 

were obtained from igneous rocks. In recent years, 

zeolites have been recognized as important rockforming constituents in low-grade metamorphic 

rocks and in a variety of sedimentary rocks (Hay, 

1966). The zeolites in sedimentary rocks are very 

finely crystalline and do not appeal to mineral collectors; however, deposits of this type are voluminous and have great economic potential. The remainder of this chapter summarizes those zeolite 

resources in sedimentary deposits. 

Of the more than 400 published reports that describe zeolites in sedimentary rocks throughout the 

world, more than 75 percent were published in the 

last dozen years. The factors chiefly responsible for 

this recent surge of reports are (1) the widespread 

use of X-ray powder diffraction techniques in the 

study of fine-grained sedimentary rocks, (2) the 

exploration for zeolite deposits suitable for commercial use, and (3) the early review papers by 

Coombs, Ellis, Fyfe, and Taylor (1959) and Deffeyes (1959), both of which emphasized the widespread and relatively common occurrences of diagenetic or authigenic zeolites in sedimentary rocks. 

Zeolites are among the most common authigenic 

silicate minerals that occur in sedimentary rocks, 

and they have formed in sedimentary rocks of diverse lithology, age, and depositional environment. 

Those zeolites given in table 148 have been reported 

from sedimentary rocks; however, some, such as 

faujasite, gismondine, gonnardite, scolecite, and 

thomsonite, generally occur in trace amounts and are 

rarely reported. Only nine zeolites commonly make 

up the major part of zeolitic rocks. These are analcime, chabazite, clinoptilolite, erionite, ferrierite, 
ZEOLITES 691 

TABLE 148.-Zeolites reported from sedimentary rocks 

Zeolite Formula 

Analcime -------------- NaAISi20s•H20 

Chabazite --------------· ( Ca,Na2) Al2Si4012•6H20 

Clinoptilolite ----------- (NB-2,K2,Ca) 3AlsSiao072•24H20 

Epistilbite ------------- ( Ca,Na2) aAlsSits04s•16H20 

Erionite ---------------· (Na2,K2,Ca)4o5Al9Si27072•27H20 

Faujasite --------------· ( Na2,Ca) MsAla.sSis.s02t•16H20 

Ferrierite --------------· (K,Na) 2 (Mg,Ca) 2AlaSiao072•l8H20 

Gismondine ------------· (Ca,Na2,K2)4AlsSis032•16H20 Gonnardite _____________ .Na2CaAI4Sis02o•5H20 

Harmotome ------------· (Ba,Na2)2Al4Sit2032•12H20 

Heulandite ------------- (Ca,Na2)4AlsSi2s072•24H20 Laumontite ____________ .Ca4AJ~Sitn04~·16H20 

Mordenite --------------· (Na2,K2,Ga) Al2Sito024•7H20 

Natrolite ______________ .Na4Al4Sia02o•4H20 

Phillipsite -------------· (K2,Na2,Ca) 2Al4Si12032•12H20 Scolecite _______________ .Ca2Al4Sis020•6H20 

Stilbite ----------------· ( Ca,Na2) 4AlsSi2s0,2•28H20 

Thomsonite ------------·NaCa2AlsSis02o•6H20 

Wairakite --------------CaAI2SL012•2H20 

Yugawaralite ----------·CaA12S.iaOta•4H20 

heulandite, laumontite, mordenite, and phillipsite. 

Analcime and clinoptilolite are by far the most 

abundant zeolites in the sedimentary rocks. All nine 

of these common zeolites in sedimentary rocks show 

a considerable range in Si :AI ratios and cation contents. Except for heulandite and laumontite, they 

are generally alkalic and more siliceous than their 

counterparts that occur in mafic igneous rocks. Summaries of their chemistry are given by Deer, Howie, 

and Zussman (1963), Hay (1966), Sheppard (1971), 

and Utada (1970). 

Most zeolites in sedimentary deposits formed after 

burial of the enclosing sediments by the reaction of 

aluminosilicate materials with the pore water. Silicic 

volcanic glass is the aluminosilicate material that 

most commonly served as a precursor for the zeolites, although materials such as clay minerals, feldspars, feldspathoids, nad gels also have reacted 

locally to form zeolites. Hay (1966) showed that 

authigenic zeolites and associated silicate minerals 

can be correlated with the following factors: (1) 

composition, grain size, permeability, and age of the 

host rocks, (2) composition of the pore water including pH, salinity, and proportion of dissolved ions, and 

(3) depth of burial of the host rock. Except for 

laumontite and possibly some heulandite, the common zeolites generally occur in tuffaceous sedimentary rocks that have not been deeply buried or 

exposed to hydrothermal solutions. 

Classification of the diverse zeolitic sedimentary 

rocks is difficult, but the following tenuous classification is based on geologic setting and is offered as 

a basis for further discussion: ( 1) hydrothermal, 

(2) burial metamorphic, (3) weathering, ( 4) open 

system, and (5) closed system. The hydrothermal 

type includes those zeolites associated with metallic 

deposits such as those at the East Tintic district, 

Utah (Lovering and Shepard, 1960), and especially 

with hot-spring deposits. Well-known examples of 

the latter are at Yellowstone National Park, Wyo. 

(Fenner, 1936; Honda and Muffler, 1970), Wairakei, 

New Zealand (Steiner, 1953, 1955), and Onikobe, 

Japan (Seki and others, 1969). Zeolites of geothermal areas commonly show a vertical zonation, and 

the downward succession of mineral assemblages 

seems to correlate with an increase in temperature. 

At Wairakei and Onikobe, for example, the downward succession is characterized by mordenite, laumontite, and then wairakite. 

Zeolites of the burial metamorphic type were 

originally recognized by Coombs (1954) in Triassic 

sedimentary rocks of the Southland syncline, New 

Zealand. Coombs, Ellis, Fyfe, and Taylor (1959) 

demonstrated a vertical zonation of mineral assemblages that is characterized by a downward succession of clinoptilolite-heulandite-analcime, laumontite-albite, and then prehnite-pumpellyite-albite. 

Rocks rich in prehnite and pumpellyite commonly 

grade downward into rocks typical of the greenschist metamorphic facies. Locally, a zone rich in 

wairakite occurs between the laumontite-albite and 

prehnite-pumpellyite-albite zones or overlaps these 

zones. The zeolites and associated silicate minerals 

of the burial metamorphic type commonly occur in 

marine volcaniclastic strata that are more than 

10,000 feet thick and locally are as much as 40,000 

feet thick. The vertical succession of mineral assemblages is one of decreasing hydration with depth and 

is generally thought to be temperature dependent; 

however, chemical variables may prove to be equally 

important. Besides occurrences in New Zealand, zeolitic rocks of the burial metamorphic type have been 

recognized in Australia (Packham and Crook, 1960), 

Puerto Rico (OtaJora, 1964), U.S.S.R. (Kossovskaya 

and Shutov, 1963), Japan (Seki, 1969; Utada, 1970), 

British Columbia, Canada (Surdam, 1968), and the 

United States. Laumontite-bearing rocks of the 

burial metamorphic type occur in central Oregon 

(Dickinson, 1962; Brown and Thayer, 1963), in 

Mount Rainier National Park, 'Vash. (Fiske and 

others, 1963), and near Cache Creek, Calif. (Dickinson and others, 1969). 

Zeolites of the weathering type are volumetrically 

rather minor, but many deposits have probably been 

overlooked. Analcime was recently reported from 

alkaline, saline soils of the eastern San Joaquin 

Valley, Cailf. (Baldar and Whittig, 1968). The analcime was detected to a depth of about 4 feet, and 

its abundance decreased with depth. Hay (1963a) 

recognized analcime, chabazite, natrolite, and phil-
692 UNITED ·STATES MINERAL RESOURCES 

lipsite in alkaline, saline soil profiles at Olduvai 

Gorge, Tanzania. Surface concentrations of analcime 

were also reported in reddish, root-marked claystones 

on the Luboi Plain, Kenya (Hay, 1970). 

The most voluminous and potentially valuable zeolite deposits belong to the open- and closed-system 

types. The terms, "open system" and "closed system,'· are used in a hydrologic sense rather than in 

a thermodynamic sense. Deposits of the open-system 

type formed by the reaction of volcanic glass with 

subsurface water that originated as meteoric water. 

The original volcanic material commonly was deposited in marine or fluviatile environments or was 

air laid on the land surface. Deposits of the closedsystem type formed by the reaction of volcanic glass 

with the ·connate water trapped during sedimentation in a saline, alkaline lake. 

Deposits of the open-system type commonly 

formed in thick tuffaceous strata and show a vertical zonation of authigenic silicate minerals. Hay 

(1963b) proposed hydrolysis and solution of silicic 

glass by subsurface water to account for the formation of clinoptilolite in tuff and tuffaceous claystone 

in the lower part of the Tertiary John Day Formation in central Oregon. The upper part of the formation contains unaltered glass or montmorillonite. 

The authigenic mineral zonation is more complex 

in the Tertiary tuffs at the Nevada Test Site (Hoover, 1968). An upper zone consists of unaltered 

glass with local concentrations of chabazite and clay 

minerals. Zeoli tic tuff continues downward . for as 

much as 6,000 feet and is characterized by a downward succession of zones rich in clinoptilolite, mordenite, and then analcime. The zeolite zones of the 

open-system type commonly cut across stratigraphic 

boundaries. 

Zeolite deposits of the closed-system type formed 

during diagenesis in alkaline, saline lakes, commonly of the sodium carbonate-bicarbonate variety. 

Brine of this composition generally has a pH greater 

than 9, which probably accounts for the relatively 

rapid solution of vitric material and precipitation of 

zeolites. The authigenic silicate mineralogy can be 

correlated with the salinity in deposits of the closedsystem type. The Pleistocene deposits of Lake Tecopa, Calif. (Sheppard and Gude, 1968), are characteristic of the closed-system type. Vitric material 

is unaltered or partly altered to clay minerals in 

tuff deposited in fresh water near the lake shore and 

inlets; however, the tuffs consist of zeolites where 

deposited in moderately saline water and of potassium feldspar where deposited in the highly saline 

and alkaline water of the central part of the basin. 

Thus, individual tuffs show a lateral zonation in a 

basinward direction of unaltered glass to zeolites 

and then to potassium feldspar. Zeolitic tuffs at 

Lake Tecopa consist chiefly of phillipsite, clinoptilolite, and erionite. Chabazite is a minor constituent of tuffs at Lake Tecopa, but it is locally the 

major constituent in zeolitic tuffs of other saline 

lacustrine deposits. In some deposits of the closedsystem type, such as the Miocene Barstow Formation of California (Sheppard and Gude, 1969) and 

the Eocene Green River Formation of Wyoming 

(Surdam and Parker, 1972) a zone of analcime separates the other zeolites from the zone of potassium 

feldspar. In addition to clay minerals, zeolites, and 

potassium feldspar, deposits of the closed-system 

type locally contain opal or chalcedony, searlesite 

(NaBSi206•H20), fluorite (CaF2), or dawsonite 

(NaAl (C03) (OH) 2) of authigenic origin. 

PROSPECTING TECHNIQUFS 

Prospecting for bedded zeolite deposits is difficult 

because the zeolites are finely crystalline and resemble bedded diatomite, feldspar, or bentonite in the 

field. Zeolitic tuffs generally have an earthy luster 

and are resistant. Although some zeolitic tuffs are 

pastel shades of yellow, brown, red, or green, many 

are white or pale gray. If the zeolitic tuff is nearly 

monomineralic, certain gross physical properties of 

the rock may aid field recognition (Sheppard and 

Gude, 1969, p. 17-18). Utilizing the ion-exchange 

and molecular-sieve properties of zeolites, Helfferich 

(1964) designed a "field" test for the recognition 

of zeolites. Helfferich's test distinguishes zeolites 

from clay minerals, feldspars, and volcanic glass, 

but the test will not identify the zeolite species. My 

experience with Helfferich's test suggests that it is 

better suited to the laboratory than to the field. 

X-ray powder diffraction analysis of bulk samples 

is the technique generally used for identification of 

the zeolites in sedimentary rocks. This method also 

permits ·a semiquantitative estimate of the abundance of zeolites and associated minerals in the samples. Tuffaceous strata are sampled, and then the 

sample-s are brought to the laboratory for examination by X-ray diffraction. Fresh tuff is generally 

distinguishable from altered tuff in the field, so only 

the altered parts of the tuffaceous rocks are sampled 

in both vertical and lateral directions. Once zeolites 

have been identified by X-ray diffraction, an additional detailed sampling is necessary to ascertain 

the distribution and abundance of the zeolites and 

associated authigenic minerals. Inasmuch as the 

samples must be returned to the laboratory for X-ray 

study, the availability of a truck-mounted X-ray 

diffractometer unit, suitable for field use, would 
ZEOLITES 693 

facilitate the location of favorable targets and provide a guide for a meaningful sampling program. 

POTENTIAL RESOURCES 

Evaluation of zeolite resources is hampered by 

the paucity of data on the extent and grade of the 

identified deposits. Although more than 100 occurrences of zeolites in sedimentary rocks of the United 

States have been recorded (Sheppard, 1971), information such as the grade, mineralogy, and vertical 

and lateral extent of the zeolitic rock and the thickness of overburden are lacking except for several 

deposits. The occurrence of zeolites in a certain sedimentary unit is commonly recognized from the examination of only one sample. Nevertheless, very 

large tonnages of zeolitic tuff of high purity are 

known from the Cenozoic deposits of the Western 

United States and the Gulf Coastal Plain. 

The only published estimate of zeolite resources 

in the United States was made by Deffeyes (1968), 

who estimated that about 120 million tons of clinoptilolite, chabazite, erionite, mordenite, and phillipsite 

occur in near-surface deposits of the Basin and 

Range province. This estimate is probably conservative for the zeolite deposits of the Basin and Range 

province, and the potential zeolite resources of the 

United States is probably several orders of magnitude greater. If the restraints of grade and depth 

of overburden are ignored, the total of identified, 

hypothetical, and speculative zeolite resources in the 

United States is conservatively estimated at 10 trillion tons. The nine common zeolites listed in approximate order of decreasing abundance are 

clinoptilolite (including heulandite), analcime, mordenite, erionite, phillipsite, chabazite, laumontite, 

and ferrierite. The United States probably has the 

world's largest potential resources of high-grade 

chabazite, erionite, and phillipsite. The only highgrade deposits of ferrierite in the world have been 

reported from central Nevada (Regis, 1970). 

If an estimate of zeolite resources in the United 

States is difficult to make, a meaningful estimate of 

zeolite resources for the other countries of the world 

is impossible to make. Zeolites have been reported in 

sedimentary rocks from many other countries, and 

their occurrences were summarized by Hay (1966) 

and Iijima and Utada (1966). However, no resource 

estimates have been published. In addition to the 

foreign zeolite deposits mentioned in these summaries and those foreign deposits mentioned previously in this chapter, apparently extensive and 

relatively high grade zeolite deposits occur in France 

(Esteoule and others, 1971), Germany-(F. A. MumPton, written commun., 1972), Italy (Sersale, 1960; 

Alietti and Ferrarese, 1967; Alietti, 1970), Yugoslavia (Stojanovic, 1968), Hungary (Nemecz and 

Varju, 1962), and Bulgaria (Alexiev, 1968). Most of 

the occurrences are in Cenozoic tuffaceous rocks, 

and the major zeolite is clinoptilolite. 

Additional deposits of zeolites will undoubtedly be 

discovered in the Western United States and in other 

countries of the world. Zeolites can form from a 

variety of aluminosilicate materials during diagenesis, providing the interstitial water has a relatively 

high pH and high concentration of alkalis. The 

purest zeolite deposits, however, form from volcanic 

ash that lacks crystal and rock fragments. In the 

Western Hemisphere, zeolites have not been reported 

from countries south of the United States except 

Argentina. An examination of upper Mesozoic and 

Cenozoic tuffaceous rocks will probably reveal large 

zeolite deposits in Mexico and many of the countries 

of Central America and western South America. 

Future exploration will also probably identify bedded 

zeolite deposits in the volcanic terranes of southern 

Europe, eastern Africa, and southern Asia. 

RESEARCH NEEDED 

The genesis of zeolites in sedimentary rocks is 

understood in general terms; however, several problems merit additional study. Phillipsite and clinoptilolite are the chief zeolites in young deep-sea 

deposits, but the relative importance of the precursor materials and the interstitial fluids in their 

formation is unknown. Tuffs of originally rhyolitic 

composition in deposits of alkaline, saline lakes characteristically contain a variety of zeolite minerals, 

but the factors that control which particular zeolite 

forms are poorly understood. Low-temperature experimental studies combined with studies of the zeolites and associated interstitial fluids in Holocene 

tuffs presently undergoing alteration may provide 

some answers. Another problem that warrants investigation is the relationship of the chemistry of a 

certain zeolite species to the geologic setting of the 

host rock. 

Other research of a technological nature that deserves consideration is (1) development of techniques for the separation Qf zeolites from the gangue, 

(2) development of techniques for the separation of 

one zeolite from another, and (3) chemical or structural modifications of natural zeolites to increase 

their usefulness. Natural zeolites or zeolitic rocks 

will undoubtedly be used in many industrial and 

agricultural processes; however, additional applied 

research is necessary to achieve these goals. 
694 UNITED STATES MINERAL RESOURCES 

REFERENCES 

Alexiev, B., 1968, Clinoptilolite des Rhodopes du nord-est: 

Acad. Bulgare Sci., Comptes Rendus, v. 21, no. 10, p. 

1093-1095. 

Alietti, Andrea, 1970, I minerali di neeformazione dei Monti 

Berici: Mineralog. et Petrog. Acta, v. 16, p. 27-32. 

Alietti, Andrea, and Ferrarese, Giorgio, 1967, Clinoptilolite, 

Na-montmorillonite e ossididi manganese in una formazione sedimentaria a Zovencedo (Vicenza) : Mineralog. et 

Petrog. Acta, v. 13, p. 139-145. 

Baldar, N. A., and Whittig, L. D., 1968, Occurrence and 

synthesis of soil zeolites: Soil Sci. Soc. America Proc., 

v. 32, p. 235-238. 

Brown, C. E., and Thayer, T. P., 1963, Low-grade mineral 

facies in upper Triassic and lower Jurassic rocks of the 

Aldrich Mountains, Ore·gon: Jour. Sed. Petrology, v. 33, 

p. 411-425. 

Brown, R. E., 1962, The use of clinoptilolite: Ore Bin, v. 24, 

no. 12, p. 193-197. 

Coombs, D. S., 1954, The nature and alteration of some 

Triassic sediments from Southland, New Zealand: Royal 

Soc. New Zealand Trans., v. 82, p. 65-109. 

Coombs, D. S., Ellis, A. J., Fyfe, W. S., and Taylor, A. M., 

1959, The zeolite facies, with comments on the interpretation of hydrothermal syntheses: Geochim. et Cosmochim. Acta, v. 17, p. 53-107. 

Deer, W. A., Howie, R. A., and Zussman, J., 1963, Framework 

silicates, v. 4 of Rock-forming silicates: New York, John 

Wiley and Sons, Inc., 435 p. 

Deffeyes, K. S., 1959, Zeolites in sedimentary rocks: Jour. 

Sed. Betrology, v. 29, p. 602-609. 

--- 1968, Natural zeolite deposits of potential commercial use, in Molecular sieves: London, Soc. Chem. Indus., 

p. 7-9. 

Dickinson, W. R., 1962, Petrology and diagenesis of Jurassic 

andesitic strata in central Oregon: Am. Jour. Sci., v. 

260, p·. 481-500. 

Dickinson, W. R., Ojakangas, R. W., and Stewart, R. J., 

1969, Burial metamorphism of the Late Mesozoic Great 

Valley sequence, Cache Creek, California: Geol. Soc. 

America Bull., v. 80, p. 519-526. 

Esteoule, Jacques, Esteoule-Ghoux, J anine, and Lou ail, 

Jacques, 1971, Sur la pres·ence de clinoptilolite dans les 

dep()ts marno-calcaires du Cretace superieur de l'Anjou: 

Acad. Sci. Comptes Rendus, v. 272, ser. D. p. 1569-1572. 

F·enner, C. N., 1936, Bore-hole investigations in Yellowstone 

Park: Jour. Geology, v. 44, p. 225-315. 

Fiske, R. S., Hopson, C. A., and Waters, A. C., 1963, Geology 

of Mount Rainier National Park, Washington: U.S. 

Geol. Survey Prof. Pap·er 444, 93 p. 

Hay, R. L., 1963a, Zeolitic weathering in Olduvai Gorge, 

Tanganyika: Geol. Soc. Amer,ica Bull., v. 74, p. 1281-

1286. 

--- 1963b, Stratigraphy and zeolitic diagenesis of the 

John Day Formation of Oregon: California Univ. Pubs. 

Geol. Sci., v. 42, no. 5, p. 199-262. 

--- 1966, Zeolites and zeolitic reactions in sedimentary 

rocks: Geol. Soc. America Spec. Paper 85, 130 p. 

--- 1970, Silicate reactions in three lithofacies of a semiarid basin, Olduvai Gorge, Tanzania: Mineralog. Soc. 

America Spec. Paper 3, p. 237-255. 

Helfferich, Friedrich, 1964, A simple identification reaction 

for zeolites (molecular sieves): Am. Mineralogist, v. 

49, p. 1752-1754. 

Hoover, D. L., 1968, Genesis of zeolites, Nevada Test Site, 

in Eckel, E. B., ed., Nevada Test Site: Geol. Soc. America 

Mem. 110, p. 275-284. 

Honda, Sakuro, and Muffler, L. J. P., 1970, Hydrothermal 

alteration in core from research drill hole Y-1, Upper 

Geyser Basin, Yellowstone National Park, Wyoming: 

Am. Mineralogist, v. 55, p. 1714-1737. 

Iijima, Azuma, and Utada, Minoru, 1966, Zeolites in sedimentary rocks, with reference to the depositional environments and zonal distribution: Sedimentology, v. 7, 

p. 327-357. 

Kossovskaya, A. G., and Shutov, V. D., 1963, The correlation of zones of regional epigenesis and metagenesis in 

terrigenous and volcanic rocks: Acad. Sci. USSR 

Doklady, Earth Sci. Sec., v. 139, p. 732-736. 

Lovering, T. S., and Shepard, A. 0., 1960, Hyd·rothermal alteration zones caused by halogen acid solutions, East 

Tintic district, Utah: Am. Jour. Sci., v. 258-A, p. 215-

229. 

Mercer, B. W., Ames, L. L., Touhill, G. J., Van Slyke, W. J. 

and Dean, R. B., 1970, Ammonia removal from secondary 

effluents by selective ion exchange: Water Pollution Control Federation Jour., v. 42, no. 2, pt. 2, p. R95-R107. 

Minato, Hideo, and Utada, Minoru, 1969, Zeolite, in The clays 

of Japan-International Clay Conference, Tokyo, 1969: 

J ap·an Geol. Survey, p. 121-134. 

Murray, John, and Renard, A. F., 1891, Report on deep-sea 

deposits, in Report on the scientific results of the voyage of H.M.S. Challenger during the years 1873-76: 

London, 520 p. 

Nemecz, E., and Varju, G., 1962, Sodium bentonitization, 

clinoptylolitization and adularization in the rhyolitic 

tuffs of the Szerencs piedmont area: Acta Geologica, v. 

6, p. 389-427. 

Otalora, G., 1964, Zeolites and related minerals in Cretaceous 

rocks of east-central Puerto Rico: Am. Jour. Sci., v. 

262, p·. 726-734. 

Packham, G. H., and Crook, K. A. W., 1960, The principle 

of diagenetic facies and some of its implications: Jour. 

Geology, v. 68, p. 392-407. 

Regis, A. J., 1970, Occurrences of ferrierite in altered 

pyroclastics in central Nevada: Geol. Soc. America Abs. 

with programs, v. 2, no. 7, p. 661. 

Seki, Yotaro, 1969, Facies series in low-grade metamorphism: 

Geol. Soc. Japan Jour., v. 75, p. 25·5-266. 

Seki, Y otaro, Onuki, Hitoshi, Okumura, Kimio, and Takashima, Isao, 1969, Zeolite distribution in the Katayama 

geothermal area, Onikobe, Japan: Japanese Jour. Geology 

and Geography, v. 40, p. 63-79. 

Sersale, Riccardo, 1960, Genetic and constitution anologies 

between volcanic tuffs with pozzolanic activity: Silicates 

Industry,v. 25, p. 499-509. 

Sheppard, R. A., 1971, Zeolites in sedimentary deposits of 

the United States-a review, in Gould, R. F., ed., Molecular sieve zeolites-I: Am. Chern. Soc. Advances in 

chemistry ser. 101, p. 279-310. 

Sheppard, R. A., and Gude, A. J ., 3d, 1968, Dis·tribution and 

gene•sis of authigenic silicate minerals in tuffs of Pleistocene Lake Tecopa, Inyo County, California: U.S. Geol. 

Survey Prof. Paper 597, 38 p. 

--- 1969, Diagenesis of tuffs in the Barstow Formation, 

Mud Hills, San Bernardino County, California: U.S. 

Geol. Survey Prof. Paper 634, 35 p. 
ZEOLITES 695 

Steiner, Alfred, 1953, Hydrothermal rock alteration at 

Wairakei, New Zealand: Econ. Geology, v. 48, p. 1-13. 

--- 1955, Hydrothermal rock alteration: New Zealand 

Dept. Sci. Indus. Research Bull. 117, p. 21-26. 

Stojanovic, Dobrica, 1968, Vulkanski tufovi i sedimentne 

stene u srbiji sa sadrzajem zeolita: Institut za vatrostalne materijale u Kraljevu i Srpsko geolosko drustvo, 

15 p. 

Surdam, R. C., 1968, Low-grade metamorphism of the Karmutsen Group, central Vancouver Island, British Columbia, Canada, in Abstracts for 1967: Geol. Soc. America 

Spec. Paper 115, p. 217-218. 

Sm·dam, R. C., and Parker, R. D., 1972, Authigenic aluminosilicate minerals in the tuffaceous rocks of the Green 

River Formation, Wyoming: Geol. Soc. America Bull., 

v. 83, p. 689-700. 

Utada, Minoru, 1970, Occurrence and distribution of authigenic zeolit•es in the Neogene pyroclastic rocks in Japan: 

Tokyo Univ., Sci. Papers Coli. Gen. Education, v. 20, 

p. 191-262. 

UNITED STATES MINERAL RESOURCES 

ZINC 

By HELMUTH WEnow, JR., THoR H. KnLSGAARD, ALLEN V. HEYL, and RoBERT B. HALL 

CONTENTS Page 

Abstract of conclusions ---------------------------

Introduction -------------------------------------

Exploitation -------------------------------------

Geologic environment ---------------------------- Geochemistry _______________________________ _ 

Ore minerals --------------------------------

Types of deposits ---------------------------- Contact-metamorphic deposits -------------

Irregular replacement deposits and associated fissure fillings -------------------

Vein deposi~ ---------------------------- Stratabound deposits in metamorphic 

rocks --------------------------------- Stratabound deposits in carbonate 

rocks (Mississippi Valley- and 

Alpine-type deposits) ------------------

Stratiform deposits ----------------------

Deposits formed by ·supergene enrichment or laterization -------------------

Resources --------------------------------------- Prospecting techniques ---------------------------

Problems for research ----------------------------

Selected references -------------------------------

FIGURE 

77. Graph showing the production of primary zinc 

in the world and in the United States 1830-

1970, and consumption of zinc, including 

scrap, in the United States 1938-1970 

TABLES 

149. Consumption of zinc in the United States, 1969_ 

150. Slab zinc consumption in the United States, by 

industry uses ---------------------------- 151. Distribution of zinc oxide and leaded zinc oxide 

shipments, by industries ------------------

152. Composition, zinc content, and selected physical 

characteristics of the common ore minerals 

of zinc ---------------------------------- 153. Identified and undiscovered zinc resources of 

the United States and the world ----------

Page 

697 

698 

699 

700 

700 

701 

702 

702 

703 

703 

703 

704 

704 

705 

706 

708 

709 

709 

Page 

699 

Page 

698 

698 

698 

702 

706 

154. Recoverable identified zinc resources of the 

United States grouped by major geologic regions ------------------------------------ 707 

155. Recoverable identified zinc resources of the 

world ------------------------------------ 707 

156. Selected examples of types of zinc occurrences 

that contribute to the total of conditional and 

undiscovered zinc resources of the world 707 

ABSTRACT OF CONCLUSIONS 

Zinc, a ubiquitous minor element in the earth's crust, has 

been used industrially for many centuries, at first only as an 

alloy component, later as the metal and as a component of 

chemical compounds. Today it stands, in tonnage produced, 

as the fourth most important metal in world trade. About 

150 million metric tons has be.en used since the beginning of 

the 19th century, and projected growth rates suggest that 

this amount will more than double by the end of the 20th 

century. Current annual world production exceeds 5 million 

metric tons. Of this tonnage the United States produces 

about 9 percent, but it consumes more than three times the 

amount it produces. World resource estimaroes indicate that 

recoverable identified resources (that is, reserves) are about 

235 million metric tons, of which 45 million is in the United 

State·s. Total world identified and undiscovered zinc resources 

are estimated at over 5 billion metric tons, about one-tenth 

of which is in ores of grade sufficient to be exploitable under 

existing economic conditions. Zinc is produced from mines 

in more than 40 countries on all continents except Antarctica: 

six leading countries-- Canada, Russia, United States, Peru, 

Mexico, and Australia-produce more than 60 percent of the 

world's total. 

The resource potential of zinc sugges~ that several hundred million tons of contained metal are in conventional deposits that await discovery by conventional search techniques 

and improvement of recovery methods; these conventional 

resources are dominated by the massive sulfide ores in metamorphic rocks, in which zinc occurs chiefly with copper and 

lead, and by the stratabound deposits in carbonate rocks, in 

which lead is an essential coproduct and cadmium a significant byproduct. Potential resources in both conventional 

and unusual deposi~ are estimated in the billions of tons; 

these include both low-grade and higher grade deposits for 

which new recovery methods must be developed before they 

can be exploited, such as the Kupferschiefer in Europe, the 

base metal-rich muds deposited from hot brines in -Red Sea 

deeps, and the lead- and zinc-bearing manganese nodules on 

the Pacific sea floor. The conc.ept that zinc can be concentrated in the geochemical environmen~ of tropical arid perU.S. GEOL. SURVEY PROF. PAPER 820 

697 
698 UNITED STATES MINERAL RESOURCES 

haps semitropical laterites, both mod·ern and ancient, offers 

considerable promise for the discovery of significant highgrade tonnages of shallow nonsulfide ores that can be worked 

by large-scale open-pit methods. Such ores are of interest 

also because they do not contribute to sulfur emission problems during reduction. 

INTRODUCTION 

Zinc is necessary to modern living and, in tonnage 

produced, stands fourth among all metals in world 

production-being exceeded only by iron, aluminum, 

and copper. Elemental zinc is a bluish-white metal 

when freshly cast and has a specific gravity of 7.13. 

Its melting and boiling points are 419°C and 906°C, 

respectively. It alloys readily with other metals and 

is chemically active as well. On exposure to air it 

develops a thin protective impervious gray oxide 

film, an important characteristic in its use. Most 

commercial zinc is produced in the metallic forn1 

called slab zinc and comes from the smelter in 

various sizes and shapes. Some zinc concentrates 

are converted directly to zinc oxide for use as such. 

Primary slab zinc is prepared in several grades 

depending on impurities, ranging from Prime Western with a minimum zinc content of 98.0 percent to 

Special High Grade with a minimum zinc content of 

99.99 percent. The impurities are chiefly lead, iron, 

and cadmium; trace quantities of copper, tin, and 

aluminum may also be present. 

Zinc is utilized chiefly in the automobile, household appliance, and hardware industries. The metal 

has three major uses: (1) for zinc-base alloy die 

castings, (2) for galvanizing iron and steel products, and (3) in the manufacture of the copper-zinc 

alloy, brass. In the United States, these three uses 

account for about 90 percent of the total consumption. Other important uses are as rolled zinc metal 

and in the preparation of zinc compounds for the 

manufacture of a variety of industrial productsfor example, zinc oxide in rubber and in paints. 

(See tables 149-151.) Possible substitutes for zinc 

in die casting are magnesium and aluminum, particularly if a weight limitation is important. Plastics are also competing in the die-casting field as 

metal-on-plastic plating techniques are being perfected. Aluminum is being substituted for galvanized 

sheet steel in the light-construction industry, but 

there appears to be no satisfactory alternate to zinc 

TABLE 149.-Consumption of zinc, in short tons, in the United 

States, 1969 

Slab zinc ---------------------------------- Ores (recoverable zinc content) -------------- Secondary (recoverable zinc content) 1 _______ _ 

1,368,323 

126,712 

302,075 

Total ---------------------------------- 1,797,110 1 Excludes redistilled slab and remelt zinc. From Moulds, ( 1969, p. 1159, 

table 15). 

for the large tonnages used for the corrosion protection of the wide variety of iron and steel products 

needed by modern civilization. Heindl (1970) gave 

additional information on the uses of zinc and its 

place in industry. 

TABLE 150.-Slab zinc consumption, in short tons, in the 

United States, by industry uses 

[NA, not available] 

Industry and product 

Galvanizing: 

Sheet and strip ------------ Wire and wire rope --------- Tubes and pipes ----------- Fittings (for tubes and pipes) 

Tanks and containers -------

Structural shapes ---------- Fasteners ------------------ Pole-line hardware --------- Fencing, wire cloth, and 

netting ------------------ Job galvanizing ------------ Other and unspecified uses __ _ 

Total ------------------ Brass products: Sheet, strip, and plate ____ _ 

Rod and wire --------------

Tube ---------------------- Castings and billets -------- Copper-base ingots ______ ---

Other copper-base products --

Total ------------------ Zinc-base alloy : Diecasting alloy ------------ Dies and rod alloy ---------- Slush and sand casting alloy __ 

Total ------------------ Rolled zinc --------------------

Zinc oxide --------------------- Other uses: Wet batteries -------------- Desilverizing lead ---------- Light-metal alloys ----------

Other1 ---------------------

1965 1969 

270,826 251,625 

43,884 32,348 

63,224 65,898 

8,641 11,418 

NA 5,561 

NA 19,454 

NA 5,536 

NA 9,409 

NA 17,984 

51,011 NA 

-=-44~·---=-83:::::-5:--_---:-:5::-:7 ,091 

482,421 476,324 

58,864 90,777 

45,510 56,989 

10,030 10,928 

3,050 5,958 

7,402 13,642 

1,992 1,175 

126,848 179,469 

629,809 565,839 

535 504 

7,626 10,048 

637,970 576,391 

45,882 48,650 

25,781 41,447 

1,188 

2,444 

8,124 

23,434 

35,190 

1,536 

3,957 

7,562 

32,987 

46,042 Total ------------------ Grand total ------------ 1,354,092 1,368,323 

1 Includes zinc used in making zinc dust, bronzt! powder, alloys, chemicals, castings, and miscellaneous uses not elsewhere mentioned. From 

Moulds ( 1969, p. 1160, table 16). 

TABLE 151.-Distribution of zinc oxide and leaded zinc oxide 

shipments, in short tons, by industries 

[W withheld to avoid disclosing individual company confidential data; ' included with "Other." Data from Moulds ( 1969, p. 1162, table 22) 1 

Industry 

Zinc oxide: 

Rubber -------------------- Paints --------------------- Ceramics ------------------ Chemicals ------------------ Agriculture ---------------- Photocopying --------------- Floor covering -------------

Other ---------------------

Total ------------------ Leaded zinc oxide : 

Paints ---------------------

~~~~::;d ~-;;spe~ifi;d-~ ~ ~ ~ ~ ~ ~ ~} Total ------------------

1965 

103,057 

30,249 

10,009 

11,365 

977 

w 

363 

30,550 

186,570 

10,951 

899 

11,850 

1969 

115,988 

25,170 

9,469 

22,775 

4,007 

27,566 

w 

14,748 

219,723 

4,905 

2,051 

6,956 
ZINC 699 

EXPLOITATION 

The zinc industry of modern times began with the 

smelting of the metal at Liege, Belgium, in 1806. 

Historically, however, zinc was an alloy constituent 

long before it was used in its purer metallic form. 

Brass was known to the Greeks and Romans, probably from about the 2d century before the Christian 

era, and was produced by melting copper with zinc 

minerals. The identity of zinc as a distinct metal 

was not known in the western world until the Middle 

Ages when it began to be imported from China and 

India. Ensuing centuries saw increasing amounts 

imported by Europeans until finally the technology 

itself was brought from China to England in about 

1730. 

Belgium and Germany were the chief zincproducing countries during the 19th century and 

produced about 70 percent of the century's smelter 

output. The first zinc produced in the United States 

5 

4 

(I) 

z 

0 

.... 

.... 3 [[ 

0 

:z: 

(I) 

~ 

0 

(I) 

z 

Q 

...J 

...J 

~ 

was smelted at the Government Arsenal in Washington, D.C., using ore from Franklin Furnace, N.J. 

The main U.S. zinc industry, however, did not start 

until about 1860, when successful smelters were 

erected in Illinois and Pennsylvania. From this time 

the industry boomed rapidly. Probably the most significant technological advance contributing to this 

surge was the successful commercial concentration 

of sulfide ores by froth-flotation processes shortly 

after the beginning of the 20th century. 

Production of zinc for the world and for the United 

States from 1830 through 1970 is summarized in 

figure 77. Consumption of zinc (including secondary 

material) in the United States after 1937 also is 

shown. Before that time the United States had been 

virtually self-sufficient in zinc, and total domestic 

annual production generally exceeded consumption. 

The record of world production is one of exponential growth since the end of the 19th century, interWorld production 

5 

4 

(I) 

z 

0 

3 .... 

~ [[ 

.... 

w 

~ 

~ 

0 

(I) 

z 

2 3 

...J 

~ 

1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 

FIGURE 77.-Primary production of zinc in the world and in the United States, 1830-1970, and consumption of zinc, including scrap, in the United States, 1938-70. 
700 UNITED STATES MINERAL RESOURCES 

rupted only by periods of political and economic 

stress, as during the First World War when Belgian, 

French, and Dutch smelter output was sharply curtailed, and during the 1918-22 economic depression 

which followed that war. The economic depression 

of the early 1930's is clearly reflected in the graphs 

for both world and U.S. production, and the effect 

of the outbreak of the Second World War on western European smelter output is reflected in world 

production decrease for 1941; U.S. production increased that year. 

The most striking feature of the U.S. graph is 

that while consumption has grown consistently during and since the 1940's, mine production has remained nearly static, or has actually declined, so 

that during the period 1950-70 about half of U.S. 

needs have been met by imported materials, mainly 

ores and concentrates processed by U.S. smelters 

located near seaports. Increasing dependence on foreign zinc in recent decades has been due not so much 

to depletion of domestic deposits as to the lower 

cost of imported materials in relation to production 

costs at domestic mines·. The U.S. imbalance will be 

aggravated further, at least through the mid-1970's, 

because of the closing of seven domestic zinc smelters between 1969 and 1972, brought about by obsolescence coupled with antipollution regulations. 

Most significant is the fact that between 1950 and 

1970 mankind consumed half of all the zinc produced in the world up to 1970, and between 1960 

and 1980 will probably consume about as much zinc 

as was produced in all of history before 1960-that 

is, about 106 million short tons. 

The year-to-year exploitation of zinc deposits will 

continue to be sensitive to economic conditions, but 

the probable trend will be one of growth, reflecting 

world population growth, increasing industrialization in developing nations, and the desire for a 

higher standard of living everywhere. However, the 

phenomenal increase in the production and consumption of zinc in the 20th century cannot continue 

indefinitely, and eventually production must decline 

as primary resources approach exhaustion. We believe that this point of irreversible decline is still 

several decades into the future, and is not likely to 

occur until the next century. Meanwhile, the industry, to prolong its survival, can be expected to seek 

improvements and innovations in mining and metallurgical techniques which will permit the exploitation of lower grade and unconventional types of 

deposits and the recovery of metal on a scale not 

previously possible, at the same time eliminating 

damage to the environment caused by current mining and smelting operations. 

GEOLOGIC ENVIRONMENT 

GEOCHEMISTRY 

Zinc is a chemical element of atomic number 30 

and atomic weight 65.38 ; it consists of the following 

isotopes: Zn64 , 48.89 percent; Zn66, 27.81 percent; 

Zn67 , 4.11 percent; Zn68, 18.56 percent; and Zn70, 

0.62 percent (Rankama, 1963, p. 579, 583). In fourfold coordination, zinc (Zn2 +) has an ionic radius 

of 0.71 A; in six-fold coordination, an ionic radius 

of 0.74 A (Green, 1959, table 2). These radii are 

close to those of Mg2+ (0.66 A), Cu2+ (0.72 A), and 

Fe2+ (0.74 A) (Green, 1959, table 2). Chemically, 

zinc is most similar to cadmium and mercury, the 

other two elements of Group lib of the periodic 

system. 

The range of estimates of the average crustal 

abundance of zinc is from 65 to 94 ppm (parts per 

million). It thus ranks ahead of copper ( 45-63 ppm) 

and lead (12-16 ppm), with both of which it is 

commonly associated in ore deposits. Mason (1958, 

p. 41) listed zinc as the 23d most abundant element 

in the earth's crust. Its concentration in igneous 

rocks varies from 130 ppm in basalts and syenites 

through values of 72 ppm in rocks of intermediate 

composition and 39-60 ppm in acidic rocks. The 

sedimentary rocks, such as sandstone, shale, and the 

carbonates, average 16 ppm, 95 ppm, and 20 ppm, 

respectively. Some carbonaceous shales are reported 

to contain as much as several thousand parts per 

million, whereas the Kupferschiefer of Europe may 

contain as much as 60,000 ppm, and although the 

average is something less, will contain several percent of combined copper-lead-zinc over large areas. 

Deep-sea clays reportedly average 165 ppm, and 

muds from the Atlantis II Deep in the Red Sea 

average 34,000 ppm. In western Canada, some dolomites may contain several thousand parts per million and in South Australia 1-2 percent zinc is 

reported as at least in part in solid solution in dolomite. (See Bischoff and Manheim, 1969; Dunham, 

1964; Krauskopf, 1967; Muller and Donovan, 1971; 

Parker, 1967; Lee and Yao, 1970; Weber, 1964.) 

Broad get>chemical classifications of the elements 

generally group them as to (1) lithophile, siderophile, or chalcophile, and (2) oxyphile or sulfophile. 

Most lithophile elements rarely produce sulfide or 

related minerals in nature; they have a marked 

affinity for oxygen, and are enriched in the silicate 

crust or lithosphere. Chalcophile elements, conversely, have a strong attraction for sulfur, and 

siderophile elements are so named because they are 

enriched in the nickel-iron phase (siderosphere) as 

known from meteorites. The classification as oxy-
ZINC 701 

phile or sulfophile is related to the preference of an 

element for oxygen or sulfur, respectively. Thus, 

most lithophile elements are also oxyphile, most 

chalcophile elements are sulfophile, and many siderophile elements are either oxyphile, or sulfophile, or 

weakly both. Zinc seems to be a borderline case. 

While dominantly chalcophile, it also has some lithophile characteristics ; and, although its dominantly 

chalcophile nature would suggest it to be sulfophile, 

it is classified as weakly oxyphile (see Rankama and 

Sahama, 1950, tables 4.3 and 5.4). This ambiguity 

is apparently due to its amphoteric nature-that is, 

the habit of its hydroxide to act as a weak base as 

well as a weak acid depending on the pH of the 

aqueous environment. In this respect it is like aluminum, beryllium, and gallium, but unlike iron and 

manganese. Thus, with increasing availability of 

hydroxyl ions, a solution containing zinc as the 

bivalent cation will precipitate Zn (OH) 2 at a pH 

of about 7-8. When the pH exceeds these values, 

the zinc reenters the solution, but as the zincate 

anion, Zn02- 2, or the hydrated zincate anion, 

Zn(OH)4-2. The reaction is reversible; as the pH 

of the solution decreases, the hydroxide is precipitated once again (pH 7-8) and is then redissolved 

as the bivalent cation with the further lowering of 

the pH. (See Krauskopf, 1955.) 

The amounts of zinc in early magmatic sulfides are 

tow, but zinc becomes concentrated in the residual 

solutions resulting from the continued differentiation of a magma, and these solutions in turn contribute to the concentrations in the pneumatolytic 

and hydrothermal phases so important in the genesis 

of ore deposits. On the other hand, small quantities 

of the metal remain behind with the various crystal 

phases of magmatic differentiation because of the 

diadochic capability of zinc to replace ferrous iron 

and magnesium in crystal structures. This replacement is possible because of the identity or near 

identity of the ionic radii of the three elements. 

Thus, trace quantities of zinc may occur in the 

early magmatic iron oxides, such as magnetite and 

ilmenite. Zinc apparently does not form separate 

silicate minerals in igneous rocks, although locally, 

certain species may be enriched in zinc sufficiently 

to be described as zincian varieties, (for example, 

amphibole, pyroxene, biotite, tourmaline, and garnet). Many of these zincian silicates, however, are 

more likely to be found in a metamorphic regime 

than in primary igneous rocks, such as, for example, 

the zincian biotites at Franklin Furnace and Sterling 

Hill, N. J. (Frondel and Einaudi, 1968). 

Most primary ore deposits are formed in a relatively low pH environment. Consequently, most of 

the sulfophile ore metals are precipitated as sulfide 

minerals ; hence the chief primary ore mineral of 

zinc is sphalerite, ZnS. During the weathering cycle, 

however, sphalerite is decomposed. Most of the zinc 

goes into solution as either the sulfate or the chloride and moves downward and generally away from 

the primary deposit, to be reprecipitated as carbonate, silicate, or other oxidized minerals depending 

on the availability of various anions in, and the 

chemistry of, the hydrologic regime. Zinc may be 

thus completely leached from the upper parts of 

primary zinc ore bodies or may be highly concentrated in the oxidized zone. Some chemical similarities of zinc to aluminum also suggest that zinc 

should be concentrated in bauxite. That this is not 

true is probably due chiefly to the low Zn-Al ratios 

in the rocks from which most commercial bauxite 

has been formed. However, where sufficient zinc is 

present, laterization may well result in a high-grade 

concentration not only of zinc carbonates and silicates but also of zinc-bearing clays and perhaps 

zincite. 

ORE MINERALS 

Many minerals contain zinc as a major component ; 55 species of zinc minerals are listed by Dana 

(1945, p. 812). Native zinc is known but rare; Boyle 

(1961) listed reported occurrences in his description 

of native zinc in the oxidized zone at Keno Hill in 

the Yukon where it occurs with other native elements including sulfur. He attributes its occurrence 

there to the dissociation of sphalerite by autoreduction-oxidation processes. 

The principal ore mineral of zinc is sphalerite, a 

zinc sulfide sometimes referred to as "blende" or 

"jack." Common varieties of sphalerite are yellow 

or resinous brown, although it may occur in other 

colors depending upon the type and amount of impurities. The pure and nearly colorless variety is 

known as cleiophane, whereas the dark-brown to 

black variety with more than 10 percent Fe is 

known as marmatite. Sphalerite crystallizes in the 

isometric system, whereas wurtzite, a relatively 

rare and less stable zinc sulfide, crystallizes in the 

hexagonal system. In some deposits the ore contains 

a banded intergrowth of sphalerite and wurtzite that 

is known as schalenblende. Trace metals associated 

with and recovered from zinc-sulfide concentrates 

include silver, cadmium, germanium, gallium, indium, and thallium. 

Zinc sulfides oxidize readily to several secondary 

minerals, the more common of which are the zinc 

carbonate, smithsonite, and the hydrous basic zinc 

silicate, hemimorphite. The name "calamine" has 

been applied sometimes to several of the oxidized 
702 UNITED STATES MINERAL RESOURCES 

zinc minerals, especially to hemimorphite, but it is 

not an approved mineral name. Franklinite, willemite, and zincite are the ore minerals of the 

renowned unique zinc deposits at Franklin Furnace 

and Sterling Hill, N. J. These minerals are uncommon elsewhere in the world; however, willemite is 

the chief zinc mineral in the recently discovered 

sizable deposits of Beltana and Aroona in the Flinders Range of South Australia; and willemite, 

zincite, hemimorphite, and hydrozincite constitute 

the ore minerals in the extensive deposit at Vazante 

in Minas Gerais, Brazil. 

Some characteristics of the common ore minerals 

of zinc are given in table 152. 

TABLE 152.-Composition, zinc content, and selected physical characteristics of the common ore minerals of zinc 

Mineral Composition 

Sphalerite ---------------- ZnS 

Wurtzite ------------------ ZnS 

Zincite -------------------- ZnO 

Franklinite --------------- (Fe,Zn,Mn) (Fe,Mn)204 

Smithsonite --------------- ZnCOa 

Hydrozincite -------------- Zno ( OH) e ( COa) 2 

Willemite ----------------- Zn2Si04 

Hemimorphite ------------- Zn. ( OH) 2Si207• H20 

Much zinc ore contains economically significant 

amounts of lead, copper, silver, and gold. Where 

present in the primary ores, the lead occurs as 

galena (PbS) and the copper as chalcopyrite 

(CuFeS2). The silver is in solid solution in the galena or as exsolved traces of complex silver sulfides ; 

more rarely, it accompanies the sphalerite. The gold 

is generally native, although it may also occur with 

silver in telluride minerals or in solid solution in 

some of the iron sulfides such as pyrite. Such mineralogically complex ores are typical of deposits 

formed in many areas of the Western United States 

during episodes of Tertiary and Cretaceous volcanism. They contrast markedly with other major zinc 

deposits, such as most of those of the Tennesse-e 

region, where the only sulfides are sphalerite and 

local lesser concentrations of pyrite, and where, in 

some deposits, barite or fluorite or both are significant coproducts or byproducts. 

TYPES OF DEPOSITS 

Zinc generally occurs with lead in many diverse 

geologic environments. The deposits have such different habitats and origins that they have been 

classified according to many different schemes. 

Within any mineralized district, area, or region 

there is generally more than one type of deposit, 

and it is not always clear where one type ends and 

another begins. Consequently, for the purpose of 

this report, zinc deposits, together with their associated lead and other elements, are classified by 

broad geologic environments as: (1) contactmetamorphic deposits; (2) irregular replacement 

deposits and associated fissure fillings; (3) vein 

deposits; (4) stratabound deposits in metamorphic 

rocks; (5) stratabound deposits in carbonate rocks 

ZiBc 

eon tent Specific Crystal 

(percent) gravity Hardness system 

63-67 3.9-4.1 3%-4 Isometric. 

59-67 4.0 4 Hexagonal. 

75-80 5.7 4-4% Do. 

14-27 5.1 6 Isometric. 

48-52 4.3-4.4 5 Hexagonal. 

59-78 3.6-3.8 2-2% Monoclinic. 

51-56 3.9-4.2 5% Hexagonal. 

52-54 3.4-3.5 4%--5 Orthorhombic. 

(Mississippi Valley- or Alpine-type deposits) ; (6) 

stratiform deposits; and (7) deposits formed by 

supergene enrichment or laterization. 

Ore deposits or mines containing or producing 

significant quantities of zinc, as the chief commodity, 

as a major coproduct, or as an important byproduct, 

are frequently classified by the associated metals, 

thus: (1) zinc; (2) zinc-lead or lead-zinc, depending upon which metal is dominant; (3) zinc-copper 

or copper-zinc; and (4) base metal, if all three 

metals are of about equal importance. If silver is 

also an important coproduct or byproduct, it too is 

added to the class designation. 

CONTACT-METAl\fORPHIC DEPOSITS 

Contact-metamorphic deposits, also known as contact-metasomatic or pyrometasomatic deposits, are 

those contained in metamorphosed sedimentary 

rocks adjacent to igneous intrusives. They are found 

chiefly in carbonate rocks that have been altered 

metasomatically to assemblages of silicated rocks 

commonly referred to as skarn, tactite, or garnet 

rock. Chalcopyrite, pyrite, pyrrhotite, sphalerite, and 

molybdenite are common ore minerals. The sphalerite 

is generally iron rich. The ore may be in tabular 

bodies parallel to bedding in the host rock, in irregular or pipelike bodies roughly conformable to the 

igneous contact, or in veins that transgress the 

metamorphosed host rock. Small irregular replacement deposits may occur in unaltered limestone 

some distance from the intrusives. Although many 

deposits of this type have been found in the United 

States, most are small and only a few have been 

significant producers. Examples include many of the 

zinc deposits in the Central district of New Mexico 

(Hernon and Jones, 1968) and those of the Darwin 
ZINC 703 

district in California (Hall and MacKevett, 1962). 

Elsewhere in the world significant production has 

been won from this type of deposit at the Kamioka, 

Nakatatsu, Chichibu, and other mines in Japan, as 

well as at mines in northern China and Siberia. The 

Kamioka mine is the largest zinc-producing mine in 

Japan, yielding more than 25 percent of the country's annual zinc output. Other contact deposits producing zinc are in the Trepca district of Yugoslavia 

replace the wall rock ; commonly both modes of occurrence are recognized. Veins are narrow in width 

as compared with their length and depth; most 

have sharply defined walls. Zinc-bearing veins are 

not uniform in their metal content, and many have 

yielded more significant values in lead, copper, silver, 

and gold. Zinc-bearing veins are found in most kinds 

of rocks, although commonly they occur in igneous 

rocks or in rocks near igneous contacts. Veins containing sphalerite apparently form in a wide range 

of temperature and pressure conditions that are 

dependent upon the geologic environment. The minerals of the higher temperature veins may resemble 

those of the contact-metamorphic deposits, whereas 

the minerals of the intermediate to lower temperature veins will be generally similar to those in the 

lower temperature replacement deposits. 

and in Sweden and Mexico. 

IRREGULAR REPLACEME~T DEPOSITS AND ASSOCL<\.TED 

F'ISSURE FILLINGS 

In many mining districts the typical contactmetamorphic deposits just described are displaced 

outward or upward from the intrusive contact by 

deposits of obviously lower temperature. These deposits are irregularly shaped and are associated 

closely with filled fissures in either carbonate or 

clastic rocks. For the most part they appear to be 

both spatially and genetically related to intrusive 

igneous stocks of intermediate to acidic composition. 

Most are confined to zones where favorable strata 

are crossed by structural breaks. Some lie along 

veins, but irregular replacement bodies may extend 

considerable distances into certain beds of the wall 

rocks away from the veins. Locally, these bedded 

replacement bodies may be overlain and underlain 

by impervious shale or other less reactive rocks and 

may somewhat resemble the various stratabound 

deposits described below. They differ, however, in 

that they may occur throughout the local stratigraphic sequence as bedded replacements associated 

with adjacent veins, or as replacement bodies in 

pipelike structures that transgress the section. Ore 

from this type of deposit is more like that of ore 

in the ~lassie vein deposits (described later) and 

contains, in addition to zinc and lead, appreciable 

quantities of copper, silver, and gold. Typical of 

these deposits in the United States are the silverlead-zinc ores mined in the Park City, Bingham, and 

Tintic districts of Utah, at Leadville and Gilman ' Colo., and in the Eureka district of Nevada. Elsewhere, examples include deposits in the Santa Eulalia 

and similar districts in Mexico, and in central Peru. 

(See Barnes and Simos, 1968; Rubright and Hart, 

1968; Bush and others, 1960; Morris, 1968; Emmons and others, 1927; Radabaugh and others, 1968; 

Nolan and Hunt, 1968; Horcasitas and Snow, 1956; 

and Peterson, 1965.) 

VEIN DEPOSITS 

Veins are tabular ore bodies that fill faults or 

joints. The ore and accompanying gangue minerals 

either fill former open spaces along the fractures or 

In the United States, important zinc-bearing veins 

have been mined in the Coeur d'Alene district of 

Idaho (Hobbs and Fryklund, 1968), at Butte, Mont. 

(Meyer and others, 1968), and at numerous localities in Colorado. Additional important zinc vein 

deposits occur elsewhere in the Western United 

States in many districts that are perhaps better 

known for other types of deposits. Well-known similar veins are found in several districts of central 

Europe, Italy, Mexico, and Peru. As widespread as 

vein deposits containing zinc apparently are, only 

a small portion of the world's production has been 

won from them, and they do not contain a significantly large part of the world's reserves and resources. (See also various papers in Ridge, 1968.) 

STRATABOUND DEPOSITS IN METAMORPHIC ROCKS 

Massive deposits of zinc-lead and zinc-copper ores 

occur in metamorphic rocks throughout the world. 

They consist, for the most part, of aggregates of 

pyrrhotite and pyrite accompanied by sphalerite, 

galena, and chalcopyrite. The ore bodies are lenticular masses parallel to stratification in enclosing 

metamorphosed sedimentary and interbedded volcanic rocks. Although deposits of this type are locally 

dis·cordant to bedding or fill fissures that cut across 

the bedding or foliation, many evidently were originally bedded replacement deposits that were subsequently metamorphosed and folded. Some deposits of 

this type are in highly folded and faulted rocks, and 

although the ore replaces the host rock, the dominant feature of its control may be the faults and 

folds. These deposits include the largest concentrations of zinc-lead and zinc-copper ores that are 

known. Typical are those in the Broken Hill and 

Mount Isa districts of Australia, the Sullivan mine 

in British Columbia, the Bathurst district in New 
704 UNITED STATES MINERAL RESOURCES 

Brunswick, and the Buchans mine in Newfoundland. Other stratabound massive sulfide deposits in 

metamorphic rocks have been mined in western 

Europe, as well as in various parts of Russia. Relative newcomers belonging to this very important 

class of zinc-bearing deposits include those at 

Prieska in South Africa and in Ontario and Quebec-for example, Kidd Creek, Mattabi, and Ruttan 

Lake. (See McLeod, 1965; Douglas, 1970; and South 

African Mining and Eng. Jour., 1972.) 

Classified with the stratabound massive sulfides 

are that well-known Kuroko ores of Japan. Although 

these deposits are altered very slightly, if at all, 

they have most of the characteristics ascribed to 

this class of deposit. The Kuroko deposits range 

widely in size; some contain more than a million 

tons of zinc in ore consisting of fine-grained mixtures 

of sphalerite, galena, chalcopyrite, and iron sulfides. 

Massive sulfide and other stratabound deposits in 

metamorphic rocks that have produced significant 

quantities of zinc in the United States are those in 

the Ducktown district of Tennessee, in the Jerome 

district of Arizona, in the Balmat-Edwards district 

of New York, and in the Franklin Furnace-Sterling 

Hill district of New Jersey. The latter two localities 

in New York and New Jersey differ from the others 

by being closely associated with Precambrian marble. The New Jersey deposits are almost unique 

among the major zinc deposits of the world in that 

the ore minerals are predominantly franklinite, 

willemite, and zincite rather than the more common, apparently ubiquitous, sphalerite. The New 

York and New Jersey districts together have produced more than 5 million tons of zinc and have resources of at least that much more. 

STRATABOUND DEPOSITS IN CARBONATE ROCKS 

(MISSISSIPPI VALLEY- AND ALPINE-TYPE DEPOSITS) 

Another major type of zinc-lead deposit is found 

in platform carbonate rocks in many parts of the 

world. In some, the ore minerals occur as openspace fillings in breccias; in others, the minerals 

formed chiefly by replacement. The ores in many 

districts are relatively low grade and occur as 

extensive bodies within broadly mineralized regions 

covering hundreds of square miles. They are classified as stratabound because they are confined to 

relatively thin zones, which are generally not more 

than several hundred feet thick, in much thicker 

carbonate sequences. Many districts are, for the 

most part, relatively undisturbed tectonically, as in 

the Mississippi Valley of the United States or in the 

Upper Silesian province of Poland. Elsewhere, as in 

the Appalachian and Alpine regions of North 

America and Europe, platform carbonates with their 

zinc deposits already in place have been deformed 

structurally by later tectonism. Although most of 

these deposits produce both zinc and lead, zinc is 

generally dominant. A major exception is the lead 

district of southeastern Missouri where the deposits 

contain about 5 percent lead, generally less than 1 

percent zinc, and minor quantities of copper, silver, 

cadmium, cobalt, nickel, and germanium. This district contains one of the largest known concentrations of lead in the world. On the other hand, most 

of the deposits in some districts, for example, the 

major producing deposits of the East Tennessee 

districts and those of Middle Tennessee now being 

explored and developed, have only sphalerite and 

contain little more than trace amounts of galena. 

Other districts in the United States containing 

stratabound deposits in carbonate rocks are the 

Upper Mississippi Valley district of the WisconsinIllinois region, the famed Tri-State district in Kansas, Missouri, and Oklahoma, and the Friedensville 

district in eastern Pennsylvania. The major deposits 

in the Metaline district in northeastern Washington 

are also considered to be of this type·, although they 

appear to be much more structurally disturbed and 

metamorphosed than the previously mentioned d~ 

posits. Elsewhere, examples of significant deposits 

of this type are at Pine Point in western Canada; 

in several countries in northwestern Africa; in the 

European Alps from France eastward through Italy, 

Austria, and Yugoslavia; and in the Upper Silesian 

district of Poland. The Broken Hill district in Zambia, the Balmat-Edwards district in New York, and 

the Franklin Furnace- Sterling Hill districts in New 

Jersey are considered by some investigators to be 

highly altered or metamorphosed equivalents of this 

class. (See various authors in Ridge, 1968; also in 

Brown, 1967, and in Wedow and others, 1971.) 

STRATIFORM DEPOSITS 

The stratiform deposits containing zinc have also 

been referred to as stratabound deposits of syngenetic or diagenetic origin or simply as sedimentary 

deposits. Stratiform deposits should not be confused 

with stratabound deposits. Stratiform indicates the 

deposit is in the form of a stratum interbedded 

with other strata, for example, the Clinton-type 

sedimentary iron ores, whereas stratabound deposits 

may be crosscutting but are confined to a zone 

bounded by strata. In a general sense, all stratiform 

deposits are stratabound, but not all stratabound 

deposits are stratiform. (Note: Usage of the terms 

stratabound and stratiform in this chapter is somewhat different from usage in some chapters.-Eds.) 
ZINC 705 

Perhaps the most significant known occurrence of 

this type is the famed Kupferschiefer, chiefly in 

East Germany, but extending from England eastward to Poland. This is a bed of carbonaceous shale 

generally less than 1 meter thick that contains 

several percent combined copper, lead, and zinc as 

finely disseminated sulfides. This mineralized bed is 

more than 20,000 square kilometers in areal extent 

and occurs in the basal part of the Permian Zechstein Formation of East Germany or its equivalents. 

Copper is more abundant than zinc and lead in some 

beds, and zinc and lead are more concentrated than 

copper in others. Where the Kupferschiefer has 

been mined for copper, the zinc content is less than 

1112 percent. Elsewhere, as at Uftrungen and near 

Bottendorf, the zinc content is higher, being about 

1.7 and 3.2 percent, respectively. 

· Other zinc-bearing stratiform deposits seem to be 

rare. Some investigators believe the deposits at 

Tynagh, Eire, have a sedimentary origin, although 

others cite contrary evidence. It is possible that 

other stratiform deposits exist among oil shales or 

other carbonaceous sediments elsewhere in the world. 

As much as 1 percent Zn is reported in a variety of 

black shales around the world (Tourtelot, 1970). 

Another possibility of zi!J.C occurrence is in evaporite 

sequences where zinc might occur in minerals other 

than sulfides. This suggestion is raised by the occurrence of several tenths of a percent zinc in samples 

of Devonian and Triassic dolomites associated with 

evaporite sequences in Alberta and elsewhere in 

western Canada (Weber, 1964) and associated with 

the modern evaporites of Lake Eyre in South Australia (Davidson, 1965). The sphalerite nodules in 

the Middle Silurian dolomites of southern Ontario 

(Sangster and Liberty, 1971) might also be classified as being of diagenetic origin in stratiform 

deposits. 

DEPOSITS FORMED BY SUPERGENE E~RICHMENT 

OR LA TERIZA TION 

Much has been written about the supergene enrichment of silver-bearing base-metal deposits, 

chiefly those occurring in the Western United States. 

Such enrichment in the weathered parts of primary 

ore deposits is generally not considered to be a 

separate type of deposit but only a process by which 

a lower grade primary sulfide ore or protore is 

made exploitable by chemical reconcentration during 

weathering. Most of the zinc ores mined until the 

early part of the 20th century were from such oxidized deposits (Heyl and Bozion, 1962). Most of 

these deposits were clearly formed by decomposition 

of sulfides in the bedrock during a weathering cycle, 

when the metals were redeposited nearby as carbonate, silicate, or oxide minerals or as secondary sulfides if they were in a reducing environment. In 

many places, as early mining exhausted these enriched supergene products, the nearly one-to-one 

relation with primary sulfide occurrences in bedrock 

was evident. In the Western States (Heyl, 1963, 

1964) many secondary zinc deposits clearly were 

formed by alteration of the primary sulfides virtually in place or by direct replacement of limestone 

by smithsonite or hemimorphite from zinc-bearing 

solutions. However, in the Appalachian region, the 

oxidized zinc deposits were formed as accumulations 

of smithsonite and hemimorphite in saprolitic clay 

pockets between pinnacles of the carbonate bedrock. 

According to Heyl and Bozion (1962, p. A19-A21), 

the zinc came from primary disseminations of sphalerite previously deposited in the unweathered carbonate host. These zinc-rich saprolites are analogous 

to the terra rossa-type residual aluminous or ferruginous laterite pockets formed by the deep weathering of impure limestone. 

Until the advent of successful froth-flotation 

processes shortly after the beginning of the 20th 

century, sulfide ores containing sphalerite could not 

be concentrated economically, and most zinc mined 

in the world was obtained from the oxidized deposits. 

Major districts producing such ores in the United 

States included Friedensville, Austinville, Embreeville, Mascot, and Jefferson City in the Appalachian 

region and Leadville, Tintic, Ophir, and Cerro Gordo 

in the Western States. Much of the early production 

in the districts of the Mississippi Valley region was 

also from the enriched ores of the oxidized zone. 

(See Heyl and Bozion, 1962.) Significant amounts 

of this type of ore were also mined in Belgium, Germany, and Poland, as well as in Africa. 

In contrast to the enrichment of zinc ores obtained in temperate climates, where the zones of 

oxidation are shallow, are the enriched oxidized ores 

of zinc found in tropical-weathering regimes. Here, 

the oxidized ores are perhaps best likened to laterites in that the process forming them, in effect, is 

laterization. Perhaps one of the best documented 

deposits that can be classified as a zinc-bearing 

laterite is that at Vazante in Minas Gerais, Brazil. 

This deposit is estimated to contain more than 5 

million tons of zinc; lead, copper, and vanadium may 

also be recoverable. Carvalho and others (1962) have 

described the Vazante deposit and the exploration 

of it during the 1950's. Epigenetic zinc, lead, and 

copper(?) sulfides in a lower Paleozoic rock were decomposed by weathering, with the development of 

a strong ferruginous gossan (chapeau de ferro). 
706 UNITED STATES MINERAL RESOURCES 

Beneath the gossan, an enriched zinc deposit was 

formed by the deposition of willemite and other 

secondary zinc minerals ; some galena and sphalerite 

were replaced by supergene chalcocite. Continued 

weathering further enriched the zinc, with the formation of hemimorphite and hydrozincite on a 

major scale. Further alteration followed, with the 

consequent formation of zincite and additional 

hydrozincite. 

The latter stage of enrichment probably began at 

some time during the Tertiary, and it continues 

today with additional concentration being effected 

by eluvial processes. The formation of the zincite 

and hydrozincite in the last stage strongly suggests 

the desilication process so typical of the last stage 

of laterization in the formation of the bauxite and 

iron and manganese oxide ores in the tropics. It 

is now an easy step of speculation to concur with 

the hypothesis of Rastall (supported by Palache, 

1935, p. 23-24) that the Franklin Furnace-Sterling 

Hill oxide-silicate ore in New Jersey is merely a 

metamorphosed ancient iron-manganese-zinc laterite. 

Other high-grade oxidized ore deposits found in 

the tropics are at Broken Hill in Zambia, one of the 

larger zinc deposits in the world; and one recently 

discovered and being developed in the Pa Daeng 

Mountains of Thailand. The Thai deposit is reported 

to contain about 31j3 million tons of ore containing 

35 percent zinc formed by the " * * * secondary 

replacement [of] limestone, sandstone, and shale by 

smithsonite, calamite [hemimorphite], hydrozincite, 

and zinc-bearing clays" (Eng. and Mining Jour., 

1972). The previously mentioned high-grade willemite replacement deposits in Cambrian dolomite 

in the Beltana district of South Australia are also 

considered tentatively as having been formed by 

Tertiary supergene enrichment; although no association with primary sulfides has yet be·en discovered, Muller and Donovan (1971, p. 233) reported 

1-2 percent zinc in weakly mineralized limestone 

with some of the zinc in solid solution in dolomite. 

Also, " * * * Tertiary lateritic material, which 

overlies the limestone in places * * * appears to be 

capable of adsorbing up to 2 percent Zn." 

RESOURCES 

Table 153 lists currently estimated zinc resources 

of the world, subdivided into recoverable and subeconomic and into identified and undiscovered; it 

also compares these classes of resources of the 

United States with those of the rest of the world. 

Erickson (Crustal abundance chapter) indicates 

that the zinc content of the earth's crust is 2,250 

X 1012 metric tons, of which 1,220 X 1012 metric 

TABLE 153.-ldentified and undiscovered zinc resources of the 

United States and the world (estimated in millions of metric 

tons) 

Identified Undiscovered resources 1 resources Total 

United States 

Recoverable _______ 2 45 60 105 

Subeconomic ------- 3 75 230 305 

Total --------- 120 290 410 

Rest of the world 

Recoverable 2 190 285 475 

Subeconomic ------- 8 1,200 3,000 4,200 

Total --------- 1,390 3,285 4,675 

Total world 

Recoverable ------- 2 235 345 580 

Subeconomic ------- 3 1,275 3,230 4,505 

Total --------- 1,510 3,575 5,085 

1 IDENTIFIED RESOURCES: Specific, identified mineral deposits that 

may or may not be evaluated as to extent and grade, and whose 

contained minerals may or may not be profitably recoverable with 

existing technology and economic conditions. 2 RESERVES: Identified dEposits from which minerals can be extracted 

profitably with existing technology and under present economic 

conditions. a CONDITIONAL RESOURCES: Specific, identified mineral deposits 

whose contained minerals are not profitably recoverable with existing technology and economic conditions. 

tons is in the total continental crust of the world, 

of which 73 X 1012 metri-c tons is in the continental 

crust beneath the United States. Within a depth of 

1 kilometer (approximately 3,000 ft) the continental 

crust contains 34 X 1012 metric tons of zinc, of 

which 2 X 1012 metric tons is within the United 

States. Erickson further estimates that the world 

reserve (recoverable identified resources) potential 

is 3,400 million metric tons, of which 198 million 

is in the United States. These latter tonnages are 

for ores averaging 4-percent zinc and, for the most 

part, presumably of the conventional sulfide type 

currently being exploited. Although the figures presented are highly speculative, they represent an 

expectable order of magnitude. 

Comparison of the data in table 153 with those of 

Erickson suggests that neither the United States 

nor the world as a whole has yet reached its potential for "high-grade ores." The total of estimated identified and undiscovered recoverable zinc 

resources of the United States, 105 million tons, is 

about one-half of Erickson's potential 200 X 106 

metric tons, whereas those of the world are estimated at only about one-seventh of his world potential of 3,400 X 106 tons. 

Most of the newly discovered recoverable zinc 

resources found in the last few years have been 

largely in deposits of two types, the stratabound 

deposits in metamorphic rocks (massive sulfide ores) 

and the stratabound ores in carbonate rocks (Mis-
ZINC 707 

sissippi Valley-type deposits). T. H. Kiilsgaard and 

B. A. LaHeist (written commun., 1962) showed in 

their estimate of resources that these two types of 

deposits each contain about one-third of the total. 

Furthermore, their estimate indicates that replacement, vein, and contact-metamorphic deposits, in 

that order, dominate the remaining third of the 

recoverable resources. They did not list separately 

the deposits herein designated as stratiform and as 

formed by supergene enrichment or laterization. 

Bachau (1971, p. 8-10) estimated that the massive 

sulfide ores and the Mississippi Valley-type deposits 

contain more than two-thirds of the total of exploitable zinc. AJlnouncements in recent mining magazines show that most of the major new discoveries 

belong to these two major types of deposits, and 

much of the undiscovered recoverable zinc resources 

is in these categories. However, other announcements give credence to the belief that oxidized 

deposits formed by laterization may be a category 

to exploit. This type of deposit holds the promise of 

large, shallow, high-grade, nonsulfide ores, examples 

of which are the deposits at Vazante in Brazil, in 

the Pa Daeng Mountains of Thailand, and in the 

Beltana district of South Australia. All these deposits are under development, if not in actual production. 

Recoverable identified resources of the United 

States are listed by major geologic regions in table 

154, and those of the world are given by continent 

in table 155. 

TABLE 154.-Recoverable identified zinc resources of the 

United States grouped by major geologic regions 

Zinc content Region (millions of metric tons) 

Appalachian 1 ----------------------- 16.4 

Mississippi Valley 2 ------------------ 19.2 

Rocky Mountain 3 ------------------- 7.3 

Pacific Coast 4 ---------------------- 2.1 

1 Chiefly the Franklin-Sterling Hill, Friedendsville, and Edwards-Balmat districts in New Jersey, Pennsylvania, and New York, as well as the Austinvi!le-Ivanhoe district in Virginia and the several East Tennessee districts. 2 Chiefly the Tri-State and Upper Mississippi Valley districts and the Missouri lead belts; also includes large inferred (possible) recoverable resources in the newly deve~oping Middle Tennessee districts. 3 Major sources include the Butte district in Montana; the Gilman, Lead- ville, and several smaller districts in Colorado; the Eureka, Pioche, and White Pine districts in Nevada; the Bingham, Park City, and Tintic dis- tricts in Utah; the Central, Pecos, and Mogo'lon districts in New Mexico; and the Big Bug, Bisbee, and Verde districts in Arizona. 4 Chiefly the Metaline and Northport districts in Washington and the Coeur d'Alene district in Idaho; includes small districts in California, 

Oregon, and Alaska. 

The total of identified subeconomic (conditional) 

resources and both recoverable and subeconomic 

undiscovered resources is given as 4,850 million 

metric tons of contained zinc (table 153) . Tonnage 

of selected examples of the types of zinc occurrences 

that contribute to this total are presented in table 

156. 

TABLE 155.-Recoverable identified zinc resources of the 

world 

Zinc content Continent (millions of metric tons) 

North America --------------------- 84 

South America ---------------------- 16 

Europe ----------------------------- 58 

Africa ------------------------------ 14 

Asia -------------------------------- 42 

Australia --------------------------- 21 

Total --------------------------- 235 

TABLE 156.-Selected examples of types of zinc oc.currences that contribute to the total of conditional 1 and undiscovered zinc resources of the world 

Example 

Kupferschiefer of Europe ------------------- Deep-sea manganese nodules ---------------- Metal-bearing Red Sea muds ---------------- Deep-lying zinc deposits in Washington State __ 

Zinc-hearing pyrite at United Verde mine, 

Arizona --------------------------------- Deposits in platform carbonate rocks: 

1) Mississippi Valley-type deposits ------ 2) Zinc in dolomitic evaporites and related 

deposits ________ --- ____ -----------

Paleoequivalents of Red Sea muds ------------

High-grade lateritic ores -------------------- Zinc byproduct from manufacture of fertilizer 

from selected phosphorites ---------------- Zinc coproduct or byproduct from massive 

sulfide or kuroko type deposits -------------

Zinc content (millions of 

metric tons) 

1,000 

750 

3 

24 

1 

600 

700 

60 

30 

5 

300 

1 CONDITIONAL RESOURCES: Specific, identified mineral deposits whose contained minerals are not profitably recoverable with exist- ing technology and economic conditions. 

Among the known lower grade or subeconomic 

zinc resources are the extensive deposits of the 

Kupferschiefer and related beds in the Permian 

Zechstein Formation of Europe (Dunham, 1964). 

Resources in these beds must exceed 1 billion tons 

of zinc; in one area alone in East Germany, RichterBernburg (1941) estimated the contained zinc at 

200-250 million tons, and comparable though lesser 

quantities of lead and copper accompany the zinc. 

An example of the type of deposit that remains as 

a resource until beneficiation or other extractive 

techniques are improved is the zinc-bearing pyrite 

at the United Verde mine in Arizona, where about 

three-fourth million tons of zinc occurs in 12 million 

tons of pyritic ore (Anderson and Creasey, 1958). 

Other subeconomic types of deposits with significant 

zinc resources are mineralized bodies of relatively 

low tenor but of the same type as those currently 

being mined from carbonate rocks in the Mississippi 

Valley and Appalachian regions of the United States 

1 and elsewhere in North America. The resource potential for this type of deposit in North America 

must exceed several hundred million tons of zinc, 

particularly if that for the East Tennessee and the 

newly discovered Middle Tennessee districts is esti-
708 UNITED STATES MINERAL RESOURCES 

mated at a total of about 50 million tons of contained metal. 

As mentioned previously, deposits formed by 

laterization may have a high resource potential, 

although this type of deposit has not been sought 

specifically with the persistence given to the search 

for massive-sulfide and Mississippi Valley-type ores. 

More likely the so-called zincian laterites will be 

found in tropical regions, although ancient tropical 

regimes might also be sought among older geological terranes. Geochemical search techniques 

would be as appropriate for ores of this type as 

for the more conventional sulfide types (Muller and 

Donovan, 1971). 

Some potential resources await the development 

of unconventional mining and beneficiation techniques. Such resources include metal-bearing muds 

(Degens and Ross, 1969) and manganese nodules 

(Mero, 1962, 1965) on the sea floor. Muds in the 

Atlantis II Deep of the Red Sea contain an estimated 

2.9 million metric tons of zinc deposited from hot 

brines (Bischoff and Manheim, 1969). The more than 

11;2 trillion tons of manganese nodules in the Pacific 

Basin, that have an average content of 0.05 percent 

zinc and 0.1 percent lead, are expected to contain 

about 3)t and 1 V2 billion tons of zinc and lead. 

Evaporite deposits are another potential but unconventional source of zinc. Weber (1964) reported 

several tenths percent zinc in samples of dolomite 

associated with Devonian and Triassic evaporite 

sequences in Alberta and elsewhere in western 

Canada. Davidson (1965), in discussing the association of stratabound sulfide deposits with evaporite 

sequences, cited the occurrence of a 2lj2-foot zone 

that has a content of 0.2 percent Zn in the modern 

evaporites of Lake Eyre in South Australia. 

PROSPECTING TECHNIQUES 

As with other metallic minerals, four main techniques are used in the search for new deposits of 

zinc: geological, geochemical, geophysical, and 

direct physical. 

The geological method consists primarily of plotting on a base map the distribution and character 

of all rocks in the area studied. Geologic structures 

such as bedding, foliation, faults, joints, and other 

features also are plotted, in addition to the boundaries between formations. Indications of rock alteration other than weathering, especially signs of mineralization, are also mapped. Discoveries of new ore 

bodies or extensions of old ones determined by geologic investigation are commonplace. (See Kiilsgaard, 

1965.) 

Geochemistry is a relatively new exploration tool 

that has become widely used in recent decades. Samples of soil, rock, and stream sediment are taken 

systematically and analyzed for zinc and other trace 

elements by colorimetry, spectrography, atomicabsorption spectrometry, or other analytical technique. Geochemistry is particularly useful in 

eliminating areas of low potential and selecting 

favorable targets in areas of anomalously high metal 

concentration. (See Hawkes and Webb, 1962). 

Geophysical techniques depend upon contrasts 

between ore bodies and their surrounding rocks in 

certain physical properties such as magnetic, electrical, or gravimetric properties, or in response to 

seismic waves. Most physical properties of zinc 

minerals do not contrast sharply with those of their 

host rocks; thus, geophysical methods are useful in 

the search for zinc only to the extent that other 

minerals or special conditions are present in the ore 

body which do respond to the instruments employed. 

For example, magnetite and pyrrhotite, if sufficiently 

abundant, give a magnetic response, whereas pyrite, 

chalcopyrite, galena~ and other sulfides commonly 

associated with sphalerite respond to self-potential, 

induced-polarization, resistivity, electromagnetic, 

and audiofrequency magnetic methods. Massive sulfide ore bodies also may be detected by gravimetry. 

Commonly, two or more geophysical methods are 

employed simultaneously, and airborne instruments 

have proved to be outstandingly useful. (See Dobrin, 

1960; Parasnis, 1966; Soc. Explor\ Geophysicists, 

1966, 1967). 

Although the geological, geochemical, and geophysical techniques have been discussed separately, 

they are most productive when used together. The 

geology is fundamental, but geochemical and geophysical methods have proved so useful as to become 

standard in most comprehensive exploration programs. A common procedure is to perform the geological and geochemical investigations first, and then 

the geophysical technique on selected targets. In 

vast drift-covered areas, as in Canada, airborne geophysical investigations often precede the geological 

and geochemical. Ultimately, however, a discovery 

is made only by direct physical means such as drilling, trenching, test-pitting, stripping, sinking a 

shaft, or driving an adit. The other three techniques 

are but a preclude to this most expensive final exploration step and are useful only to the extent that 

they reduce costs by picking the most favorable 

targets. In general, a direct physical method should 

be used as soon as a favorable target is indicated by 

one or more of the three less direct techniques. (See 

McConnel, 1965.) 
ZINC 709 

PROBLEMS FOR RESEARCH 

Although a high potential for zinc resources in 

all categories seems apparent, research is needed 

on zinc and zinc-bearing deposits in all fields of the 

geosciences to improve search techniques. More 

imaginative thinking is necessary in the search for 

conventional types of deposits to develop new concepts that can improve our understanding of geologic features localizing ore bodies and districts and 

also the sources of the mineralizing fluids. Most 

conventional deposits are considered to form during 

a single period of mineralization and then to remain isolated from later geologic processes until 

discovery. It is not logical to believe that deposits 

formed hundreds of millions of years ago have 

remained unchanged by the various geologic environments through which they have passed. Many 

ore deposits may be more ephemeral than their host 

rocks and in some environments could have been 

completely or partially resorbed by new migrating 

brines. The metals were precipitated from these new 

brines to form new ores or were dispersed into surface waters eventually to reach the sea. Search for 

evidence of such removal, particularly if only in part, 

and the tracing of the path of the brine migration, 

might well lead to the discovery of the later and 

possibly more enriched ores. Such solution and redeposition concepts may be particularly fruitful in 

exploration for Mississippi Valley-type ores. Furthermore, the metal-bearing brines, regardless of 

their source, may have moved laterally many miles 

through ancient carbonate aquifers to be trapped 

in large reservoirs where different geochemical conditions precipitated the metal. 

Further studies of geophysical techniques are 

needed in the search for zinc-bearing ores. The 

application of magnetic and electromagnetic techniques are reasonably well understood. On the other 

hand, gravity and seismic techniques have not been 

pursued to any great extent. This may be largely 

because they have been tried with no immediate 

success or because they have been considered and 

discarded on theoretical grounds, with no extensive 

experimental studies. Gravity surveys may be particularly useful in locating large breccia bodies of 

the Mississippi Valley ty:re when concealed under a 

relatively shallow cover. Another application of 

gravity studies could be in the search for extensions 

of high-grade zinc laterites under cover of dense 

tropical vegetation. 

A better understanding of zinc geochemistry and 

the geochemistry of potential environments of deposition is of prime importance. The amphoteric nature of zinc and its role in the formation of oxidized 

zinc deposits need further consideration. The anomalous amounts of zine in certain evaporitic rocks need 

explanation to determine if further enrichment in 

evaporites is possible--also whether such enrichment, if stripped from its host, might be a source of 

metal in ore fluids. Further investigation of zinc 

geochemistry as applied to exploration investigations 

will also be valuable. Simplification of field analytical 

methods would be helpful for exploration geochemical surveys in remote areas. 

SELECTED REFERENCES 

Anderson, C. A., 1969, Massive sulfide deposits and volcanism: 

Econ. Geology, v. 64, no. 2, p. 129-146. 

Anderson, C. A., and Creasey, S. C., 1958, Geology and ore 

deposits of the Jerome area, Yavapai County, Arizona: 

U.S. Geol. Survey Prof. Paper 308, 185 p. 

Barnes, M. P., and Simos, J. G., 1968, Ore deposits of the 

Park City district [Utah], with a contribution on the 

Mayflower lode, in Ridge, J. D., ed., Ore deposits of the 

United States 1933-1967-The Graton-Sales volume, v. 

2: New York, Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 1102-1126. 

Bachau, Christian, 1971, Essai de typologie quantitative des 

gisements de plomb et de zinc avec la repartition de 

l'argent: Bur. Recherches Geol. et Minieres Bull., 2d 

ser., sec. 2, no. 3, p. 1-72; no. 4, p. 1-47. 

Bischoff, J. L., and Manheim, P. T., 1969, Economic potential of the Red Sea heavy metal deposits, in Degens, 

E. T., and Ross, D. A., eds., Hot brines and recent heavy 

metal deposits in the Red Sea: New York, Sp.ringerVerlag, p. 535-549. 

Bishop, 0. M., 1960, Zinc, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 585, p. 975-994. 

Boyle, R. W., 1961, Native zinc at Keno Hill [Yukon]: Canadian Mineralogist, v. 6, pt. 5, p. 692-694. 

Borckie, D. C., Hare, E. H., Jr., and Dingess, P. R., 1968, 

The geology and ore deposits of the Tri-S.tate district 

of Missouri, Kansas, and Oklahoma, in Ridge, J. D., ed., 

Ore deposits of the United States-The Graton-Sales 

volume, v. 1: New York, Am. Inst. Mining, Metall., and 

Petroleum Engineers, p. 400-430. 

Brown, J. S., ed., 1967, Genesis of stratiform lead-zincbarite-flu~rite deposits (Mississippi Valley-type deposits)-A symposium, New York, 1966: Econ. Geology 

Mon. 3, 3,433 p. 

Bush, J. B., Cook, D. R., Lovering, T. S., and Morris, H. T., 

1960, The Chief Oxide-Burgin area discoveries, East 

Tintic district, Utah-a case history: Econ. Geology, v. 

55, no. 7, p. 1116-1147, 1507-1540. 

Campbell, Neil, 1967, Tectonics, reefs, and stratiform leadzinc deposits of the Pine Point area, Canada, in Brown, 

J. S., ed., Genesis of stratiform lead-zinc-barite-fluorite 

deposits (Mississippi Valley-type deposits)-A symposium, New York, 1966: Econ. Geology Mon. 3, p. 59-70. 

Carvalho, P., Guimaraes, Djalma, and Dequech, David, 1962, 

Jazida plumbo-zincifera do Municipio de Vazante, Minas 

Gerais [Brazil]: Brasil, Dept. Nac. Produ~ao Mineral, 

Div. de Fomento, Bull. 110, 119 p. 

Dana, E. S., 1945, A textbook of mineralogy, 4th ed. (re-
710 UNITED STATES MINERAL RESOURCES 

vis·ed and enlarged by W. E. Ford) : New York, John 

Wiley Sons, Inc., 851 p. 

Davidson, C. F., 1965, A possible mode of origin of stratabound copper ores: Econ. Geology, v. 60, no. 5, p. 942-

954. 

Deans, T., 1950, The Kupferschiefer and the associated leadzinc mineralization in the Permian of Silesia, Germany, 

and England, in Dunham, K. C., ed., The geology, paragenesis, and reserves of lead and zinc: Internat. Geol. 

Cong., 18th, London, 1948, p. 340-350. 

Degens, E. T., and Ross, D. A., eds., 1969, Hot brines and 

recent heavy metal deposits in the Red Sea: New York, 

Springer-Verlag, 600 p. 

Derry, D. R., Clark, G. R., and Gillatt, N., 1965, The Northgate base metal deposit at Tynagh, County Galway, Ireland: Econ. Geology, v. 60, no. 6, p. 1218-1237. 

Dobrin, M. B., 1960, Introduction to geophysical prospecting: 

New York, McGraw-Hill Book Co., Inc., 446 p. 

Douglas, R. J. W., ed., 1970, Geology and economic minerals 

of Canada, 5th ed.: Canada Geol. Survey Econ. Geology 

Rept. 1, 838 p. 

Dunham, K. C., 1964, Neptunist concepts in ore genesis: 

Econ. Geology, v. 59, no. 1, p. 1-21. 

Emmons, S. P., Irving, J. D., and Laughlin, G. F., 1927, 

Geology and ore deposits of the Leadville mining district, 

Colorado: U.S. Geol. Survey Prof. Paper 148, 368 p. 

Engineering and Mining Journal, 1972, This month in mining-news briefs: Eng. Min. Jour., v. 173, no. 5, p. 124. 

Frondel, Clifford, and Einaudi, Marco, 1968, Zinc-rich micas 

from Sterling Hill, New Jers·ey: Am. Mineralogist, v. 

53, nos. 9-10, p. 1752-1754. 

Galkiewicz, Tadeusz, 1967, Genesis of Silesian-Cracovian 

zinc-lead deposits, in Brown, J. S., ed., Genesis of stratiform lead-zinc-barite-fluorite deposits (Mississippi Valley-type deposits) -A symposium, New York, 1966: Econ. 

Geology Mon. 3, p. 156-168. 

Gates, W. G., 1971, Geology and geological aides to production at the Heath Steele mine: Am. Inst. Mining Engineers World Symposium on Mining and Metallurgy of 

Lead and Zinc [St. Louis], p. 108-122. 

Green, Jack, 1959, Geochemical table of the elements for 

1959: Geol. Soc. America Bull., v. 70, p. 1127-1184. 

Gruszczyk, Hubert, 1967, The genesis of the Silesian-Cracow 

deposits of lead-zinc ores, in Brown, J. S., ed., Genesis 

of stratiform lead-zinc-barite-fluorite deposits (Mississippi Valley-type deposits)-A symposium, New York, 

1966: Econ. Geology Mon. 3, p. 169-177. 

Hall, W. E., and MacKevett, E. M., Jr., 1962, Geology and 

ore deposits of the Darwin quadrangle, lnyo County, 

California: U. S. GeoL Survey Prof. Paper 368, 87 p. 

Hawkes, H. K, and Webb, J. S., 1962, Geochemistry in 

mineral exploration: New York, Harper and Row, Publishers, 415 p. 

Heindl, R. A., 1970a, Cadmium, in Mineral facts and problems: U.S. Bur. Mines Bull. 650, p. 515-526. 

Heindl, R. A., 1970b, Zinc, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 650, p. 805-824. 

Hernon, R. M., and Jones, W. R., 1968, Ore deposits of the 

Central mining district, Grant County, New Mexico, 

in Ridge, J. D., ed., Ore deposits of the United States, 

1933-1967-The Graton-Sales volume, v. 2: New York, 

Am. Inst. Mining, Metall., and Petroleum Engineers, p. 

1211-1238. 

Hewett, D. F., 1929, Cycles in metal production: Am. Inst. 

Mining and Metall. Engineers, Trans., v. 85, p. 65-93, 

with Discussion by F. L. Garrison, p. 93-98. 

Heyl, A. V., 1963, Oxidized zinc deposits of the United States, 

pt. 2, Utah: U.S. Geol. Survey Bull. 1135~B, p. B1-

B104. 

--- 1964, Oxidized zinc deposits of the United States, pt. 

3, Colorado: U.S. Geol. Survey Bull. 1135-G, p. Cl-C98. 

--- 1968, The Upper Mississippi Valley base-metal district, in Ridge, J. D., ed., Ore deposits of the United 

States, 1933-19·67-The Graton-Sales volume, v. 1: 

New York, Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 431-459. 

Heyl, A. V., and Bozion, C. N., 1962, General geology, Pt. 

1 of Oxidized zinc deposits of the United States: U.S. 

Geol. Survey Bull. 1135-A, p. A1-A52. 

Hoagland, A. D., 1971, Appalachian strata-bound depositstheir essential features, genesis, and the exploration 

problem: Econ. Geology, v. 66, no. 5, p. 805-810. 

Hobbs, S. W., and Fryklund, V. C., Jr., 1968, The Coeur 

d'Alene district, Idaho, in Ridge, J. D., ed., Ore deposits 

of the United States, 1933-1967-The Graton-Sales 

volume, v. 2: New York, Am. Inst. Mining, Metall., and 

Petroleum Engineers, p. 1417-1435. 

Horcasitas, A. S., and Snow, W. E., 1956, Resumen geologico 

del Distrito de Santa Eulalia, Chihuahua, in lnternat. 

Geol. Cong., 20th, Mexico, 1956, Excursions A-2 and 

A-5: p. 51-61. 

Horikoshi, Ei, 1969, Volcanic activity related to the formation of the kuroko-type deposits in the Kosaka district, 

Japan: Mineralium Deposita, v. 4, no. 4, p. 321-345. 

Hubbert, M. K., 1967, Degree of advancement of petroleum 

exploration in United States: Am. Assoc. Petroleum 

Geologists Bull., v. 51, p. 2207-2227. 

Kendall, D. L., 1960, Ore deposits and sedimentary features, 

Jefferson City mine, Tennessee: Econ. Geology, v. 55, 

no. 5, p. 985-1003. 

Kiilsgaard, T. H., 1965, Geologic mapping and mineral exploration research in the United States, in Seminar on 

field techniques for mineral investigation, Isfahan, Iran, 

September 1965: Ankara, Central Treaty Organization, 

p. 69-90. 

Krauskopf, K. B., 1955, Sedimentary deposits of rare metals, 

in Pt. 1 of Bateman, A. M., ed., 50th anniversary 

volume: Econ. Geology, p. 411-463. 

--- 1967, Introduction to geochemistry: New York, 

McGraw-Hill Book Co., Inc., 721 p. 

Lasky, S. G., 1950, Mineral-resource appraisal by the U.S. 

Geological Survey: Colorado School Mines Quart., v. 45, 

no. 1A, p. 1-27. 

Lee, Tan, and Yao, Chi-Lung, 1970, Abundance of chemical 

elements in the earth's crust and its major tectonic 

units: lnternat. Geol. Review, v. 12, no. 7, p. 778-786. 

Mason, B. H., 1958, Principles of geochemistry, 2d ed.: New 

York, John Wiley & Sons, Inc., 276 p. 

McConnel, R. H., 1965, Some basic considerations in mineral 

exploration, in Seminar on field techniques for mineral 

investigation, Isfahan, Iran, September 1965: Ankara, 

Central Treaty Organization, p. 49-56. 

McKnight, E. T., and Fischer, R. P., 1970, Geology of the 

Picher field, Oklahoma and Kansas: U.S. Geol. Survey 

Prof. Pap.er 588, 165 p. 

McKnight, E. T., and Luttrell, G. W., 1951, Zinc resources 

of the world, Chap. 3 of Materials survey, zinc: U.S. 

Bur. Mines, p. 1117-11150. 
ZINC 711 

McLeod, I. R., ed., 1965, Australian mineral industry-The 

mineral deposits: Australia Bur. Mineral Resources, 

Geology and Geophysics Bull. 72, 690 p. 

Mero, J. L., 1962, Ocean-floor manganese nodules: Econ. 

Geology, v. 57, no. 5, p. 747-767. 

--- 1965, The mineral resources of the sea: Amsterdam, 

Elsevier Pub. Co., 312 p. 

Meyer, Charles, Shea, E. P., Goddard, C. C., Jr., and others, 

1968, Ore deposits at Butte, Montana, in Ridge, J. D., 

ed., Ore deposits of the United States 1933-1967-

Graton-Sales volume, v. 2: New York, Am. Inst. Mining, Metal!., and Petroleum Engineers, p. 1373-1416. 

Morris, H. T., 1968, The main Tintic district, Utah, in Ridge, 

J. D., ed., Ore deposits of the United States 1933-1967-

The Graton-Sales volume, v. 2: New York Am. Inst. 

Mining, Metall., and Petroleum Engineers, p. 1043-1073. 

Moulds, D. E., 1969, Zinc, in U.S. Bur. Mines, Minerals Yearbook, 1969, v. 1-2, Metals, minerals, and fuels: Washington, D.C., U.S. Govt. Printing Office, p. 1143-1168. 

Muller, D. W., and Donovan, P. R., 1971, Stream sediment 

reconnaissance for zinc silicate (willemite) in the 

Flinders Ranges, South Australia, in Geochemical exploration (International Geochemical Exploration Symposium, 3d, Proc.): Canadian Inst. Mining Metallurgy, Spec. vol., No. 11, p. 231-234. 

Nolan, T. B., and Hunt, R. N., 1968, The Eureka mmmg 

district, Nevada, in Ridge, J. D., ed., Ore deposits of the 

United States 1933-1967-The Graton-Sales volume, v. 

1: New York, Am. Inst. Mining, Metall., and Petroleum 

Engineers, p. 966-991. 

Palache, Charles, 1935, The minerals of Franklin and Sterling Hill, Sussex County, N. J.: U.S. Geol. Survey Prof. 

Pap·er 180, 135 p. 

Parasnis, D. S., 1966, Mining geophy.sics: New York, Elsevier 

Pub. Co., 356 p. 

Parker, R. L., 1967, Composition of the earth's crust, Chap. 

D in Data of geochemistry, 6th ed.: U.S. Geol. Survey 

Prof. Paper 440-D, p. D1-D19. 

Peterson, Ulrich, 1965, Regional geology and major ore deposits of central Peru: Econ. Geology, v. 60, no. 3, p. 407-

476. 

Radabaugh, R. E., Merchant, J. S., and Brown, J. M., 1968, 

Geology and ore deposits of the Gilman (Red Cliff, 

Battle Mountain) district, Eagle County, Colorado, in 

Ridge, J. D., ed., Ore deposits of the United Stat·es 1933-

1967-The Graton-Sales volume, v. 1: New York, Am. 

Inst. Mining, Metall., and Petroleum Engineers, p. 641-

664. 

Rankama, Kalervo, 1963, Progress in isotope geology: New 

York, Interscience Publishers, 705 p. 

Rankama, Kalervo, and Sahama, T. G., 1950, Geochemistry: 

Chicago, Ill., Chicago Univ. Press, 912 p. 

Richter-Bernburg, Gerhard, 1941, Geologische Gesetzmassigkeiten in der Metallfiihrung des Kupferschiefens: 

Lagerstattenforschung ( Reichstelle fiir Bodenforschung) 

N. F., no. 73, 61 p. 

Ridge, J. D., ed., 1968, Ore deposits of the United States 

1933-1967-The Graton-Sales volume, v. 1, 2: New 

York, Am. Inst. Mining, Metall., and Petroleum Engineers, 1880 p. 

Rubright, R. D., and Hart, 0. J., 1968, Non-porphyry ores 

of the Bingham district, Utah, in Ridge, J. D., ed., Ore 

deposits of the United States 1933-1967-The GratonSales volume, v. 1: New York, Am. Inst. Mining, Metall., 

and Petroleum Engineers, p. 886-907. 

Sangster, D. F., and Liberty, B. A., 1971, Sphalerite concretions from Bruce Peninsula, southern Ontario, Canada: Econ. Geology, v. 66, no. 12, p. 1145-1152. 

Schroeder, H. J., 1965, Zinc, in Mineral facts and problems: 

U.S. Bur. Mines Bull. 630, p, 1083-1104. 

--- 1968, Zinc, in U.S. Bur. Mines Minerals Yearbook, 

196'7, v. 1-2, Metals, minerals, and fuels: Washington, 

D. C., U.S. Govt. Printing Office, p. 1197-1226. 

Schultz, R. W., 1966, The Northgate base-metal deposit at 

Tynagh, County Galway, Ireland: Econ. Geology, v. 61, 

no. 8, p. 1443-1449. 

Snyder, F. G., and Gerdemann, P. E., 1968, Geology of the 

southeast Missouri lead district, in Ridge, J. D., ed., 

Ore deposits of the United States 1933-1967-The 

Graton-Sales volume, v. 1: New York, Am. Inst. Mining, Metall., and Petroleum Engineers, p. 326-358. 

Society of Exploration Geophysicists, 1966, Mining geophysics, v. 1, Case Histories: Tulsa, Soc. Exploration 

Geophysicists, 492 p. 

--- 1967, Mining geophysics theory, v. 2: Tulsa, Soc. 

Explor. Geophysicists, 708 p. 

South African Mining and Engineering Journal, 1972, 

Prieska copper mine: South Africa Mining and Eng. 

Jour., v. 84, no. 4064, p. 23-24, 27, 29, 31. 

Tourtelot, E. B., 1970, Selected annotated bibliography of 

minor-element content of marine black shales and related sedimentary rocks, 1930-65: U.S. Geol. Survey Bull. 

1293, 118 p. 

U.S. Bureau of Mines, 1971, Zinc, in U.S. Bur. Mines Commodity data summaries, .January 1971 : Washington, 

D.C., U.S. Dept. Interior, p. 164-165. 

--- 1972, Zinc, in U.S. Bur. Mines Commodity data summaries, January 1972: Washington, D.C., U.S. Dept. 

Interior, p. 164-165. 

Weber, J. N., 1964, Trace element composition of dolostones 

and dolomites and its bearing on the dolomite problem: 

Geochim. et Cosmochim. Acta, v. 28, p. 1817-1868. 

W edow, Helmuth, Jr., chm., and others, 1971, A paleaquifer 

and its relation to economic mineral deposits; the Lower 

Ordovician Kingsport Formation and Mascot Dolomite 

-A symposium: Econ. Geology, v. 66, no. 5, p. 695-810. 

UNITED STATES MINERAL RESOURCES 

ZIRCONIUM AND HAFNIUM 

By HARRY KLEMIC, DAVID GoTTFRIED, l\IARGARET CooPER, and SHERMAN P. MARSH 

CONTENTS 

Abstract of conclusions ---------------------------

Introduction ------------------------------------ Zirconium and hafnium metals ---------------

lJses of zirconium ---------------------------

lJses of hafnium ----------------------------- Production __ ----- ______________________________ _ 

Estimated lJ.S. production of zirconium 

concentrates ------------------------------- Production of zirconium and hafnium ----------

Prices --------------------------------------

Trade ---------------------------------------

Geologic environment ----------------------------

General geochemical and mineralogic 

considerations __________________ ------ __ ---

Abundance and distribution in rocks of the 

crust -------------------------------------- Behavior of zirconium in magmatic processes __ 

Behavior of hafnium in magmatic processes __ _ 

Types of deposits ----------------------------

Primary deposits ------------------------

Secondary deposits -----------------------

Resources --------------------------------------- Identified resources ___________ -- _________ -----

Hypothetical resources -----------------------

Problems for research ---------------------------- Selected references 

78. 

157. 

158. 

159. 

FIGURE 

Graph showing lJ.S. consumption, imports, and 

exports of zirconium concentrates, 1944-71 __ 

TABLES 

Production of zirconium concentrates from five 

nations, 1968-70 --------------------------

Selected data on zirconium, hafnium, and geochemically associated elements ------------

Abundances of zirconium and hafnium in terrestrial rocks 

Page 

713 

713 

714 

714 

714 

714 

715 

715 

715 

715 

717 

717 

717 

718 

718 

719 

719 

719 

719 

719 

720 

720 

721 

Page 

716 

Page 

715 

717 

717 

Page 

160. General range of zirconium-hafnium ratios in 

zircon from igneous rocks ---------------- 719 

161. Identified world resources of zircon --------- 720 

162. Identified zircon resources of the lJnited States_ 720 

ABSTRACT OF CONCLUSIONS 

Zirconium and hafnium are metals that are useful principally in metallic form in the chemical and nuclear reactor 

industries and in mineral form as zircon (ZrSiO,) in the 

metal foundry and glass industries. Zircon and baddeleyite 

(Zr02) are the principal sources of zirconium, and hafnium 

is recovered in extracting reactor-grade zirconium. Both 

metals are reduced by the Kroll process. 

Zircon and baddeleyite occur as primary minerals in 

alkaline-rich igneous rocks, but zircon is recovered mainly 

from titanium-bearing placer sands. The United States is a 

major producer and consumer of zircon and imports large 

quantities from Australia, which is the world's largest producer of zircon. Id.entified resources of zircon in the United 

States are about 10,800,000 short tons, of which nearly 80 

percent is in the Atlantic Coastal States. U.S. production 

is solely from Florida and Georgia, as a byproduct of titanium 

production. 

World identified resources exceed 36 million short tons 

of zircon equivalent. World production of zirconium concentrates in 1970 was more than 450,000 tons. Of this, the 

the United States used about 30 percent. Current supplies of 

zircon exc·eed demand for a few decades, but environmental 

problems may limit mining of some placers in the near future. Research is needed to find alternate sources and means 

of extracting zirconium minerals. 

INTRODUCTION 

Zirconium and hafnium are elements that in their 

metallic forms are principally useful in the chemical 

and nuclear-reactor industries, in applications for 

which corrosion resistance, structural sta:biFty at 

high temperatures, specific alloying properties, or 

specific neutron-absorption characteristics are required. About 8 percent of all the zirconium 

consumed in the United States is used in these industries (Stamper and Chin, 1970a, b). The most common naturally occurring zirconium- and hafniumrich mineral, zircon (ZrSi04), which generally conU.S. GEOL. SURVEY PROF. PAPER 820 

713 
714 UNITED STATES MINERAL RESOURCES 

tains nearly 49 percent zirconium and less than 2 

percent hafnium, is the principal source of these 

elements. Baddeleyite (Zr02), a commercially important but less abundant zirconium-rich mineral, 

contains approximately 73 percent zirconium and 1 

percent hafnium (Kauffman, 1956). Because of their 

refractory nature (melting points 2550°C or greater) , these minerals are useful directly as mold 

materials for casting ferrous metals in foundries and 

in bricks and blocks in glass furnaces. Of an estimated total U.S. consumption in 1970 of 145,000 

short tons of zircon concentrates, 100,000 tons was 

for foundries, 22,000 tons for refractories, and 

23,000 tons for other uses (Clarke, 1970). Zircon, 

both natural and synthetic, is also used in minor 

quantities as a gemstone. 

Zircon is processed as an industrial mineral by 

reacting it with dolomite at high temperatures to 

produce zirconia (zirconium dioxide, Zr02), which 

has a higher melting point and is less reactive than 

zircon in some metallurgical systems. Zirconium compounds for other uses are prepared from zirconium 

oxide (Stamper and Chin, 1970b). 

ZIRCONIUM AND HAFNIUM METALS 

Zirconium metal is obtained by reacting zircon 

with coke in electric furnaces to produce zirconium 

carbonitride, which is chlorinated to zirconium tetrachloride. The Kroll process, which involves reduction 

of the tetrachloride by magnesium metal in an inert 

atmosphere, is used to obtain zirconium sponge metal 

which contains about 2 percent hafnium. Metal fabricated from the sponge is suitable for non-nuclear 

applications (Stamper and Chin, 1970b). 

Both zirconium and hafnium metals have excellent structural properties and resistance to corrosion 

at elevated temperatures, which make them particularly useful in reactor materials in which these 

properties are required. 

Reactor-grade zirconium and hafnium metals are 

produced by dissolving crude zirconium tetrachloride, which contains some hafnium, and chemically 

separating the hafnium from the solution. The zirconium and hafnium components are separately processed to form chlorides which are reduced to metals 

by the Kroll process. The necessity to separate the 

zirconium and hafnium to meet the requirements for 

reactor-grade metals arises from the different nuclear properties of the two metals. Zirconium, having a low neutron absorption cross section (less than 

0.2 barn), is useful in reactor components in which 

minimum neutron absorption is required. Hafnium, 

which has a relatively high neutron absorption cross 

section (105 barns), is useful in components in which 

neutron absorption is a desired property (Weast 

and others, 1965; Lustman and Kerze, 1955). 

USES OF ZIRCONIUM 

In addition to its principal use for structural materials in nuclear reactors, zirconium metal is used 

in small quantities in camera flashbulbs to provide 

quick ignition and longer light intensity. Zirconium 

alloys are used for making mechanical components 

such as heat exchangers, valves, tubing, spinnerets, 

and crucibles for the chemical industry (Stamper 

and Chin, 1970b). Zirconium-columbium alloys are 

used in superconducting magnets. Zirconium compounds are also used in ferroalloys, glazes, enamel, 

welding rods, abrasives, pharmaceuticals, paints, 

and water repellents, and for sandblasting. 

Zircon and zirconium metal and compounds have 

many substitutes in their various applications. 

Chromite and other materials are substitute mold 

materials. Titanium oxide and tin oxide may be used 

in place of zirconium oxide in opacifiers for ceramic 

glazes and enamels. Other metals and alloys, such 

as those of titanium, tantalum, and stainless steels, 

may be used in place of zirconium metal and alloys. 

Substitution of other materials for zirconium materials is based upon specific performance, price, 

availability, and other factors. 

USES OF HAFNIUM 

The principal use of hafnium is in the form of 

metal, mainly for control rods for nuclear reactors. 

A minor amount is used as an additive in alloys, and, 

in recent years, about 15 percent of the hafnium 

used in the United States was used as the oxide, 

mainly for research. Hafnium has been used in electric light bulbs and in electrodes in X-ray tubes and 

other electronic tubes. Numerous other uses of hafnium have been investigated (Stamper and Chin, 

1970a). Alternate materials for hafnium for nuclear-reactor control rods are stainless steels containing silver, indium, cadmium, boron, and rareearth elements. 

PRODUCTION 

Zircon, the principal raw material for the extraction of zirconium, is available in excess of demand. 

Zircon production is directly related to the production of titanium mineral concentrates from placer 

sand deposits. Australia, the leading producer of 

concentrates of titaniferous sands, is also the leading producer of zircon concentrates. The production 

of zirconium concentrates in recent years from five 

nations is given in table 157. (U.S. production figures 

are withheld to avoid disclosing individual company 

confidential data.) Zircon production capacity in 
ZIRCONIUM AND HAFNIUM 715 

TABLE 157.-Production, in short tons, of zirconium concentrates from five nations, 1968-70 

[e, estimate; NA, not available. Data from Clarke, 1970] 

Country 1968 1969 1970 

Australia --------- 332,956 411,021 e403,000 

Brazil ------------- 3,083 3,874 NA 

Ceylon ------------ 28 75 123 

Malaysia ---------- 1 1,241 1 1,562 2 998 

Thailand ---------- 3,549 276 2 2,469 

Total ---------- 340,857 416,808 406,590 

1 Exports of zircon. 2 Exports of zircon and zirconium sand to Japan. 

India and Ceylon was expected to be near 10,000 and 

9,500 tons per year, respectively, by the end of 1970. 

The zircon production capacities of Malay~ia, South 

Africa, and the United Arab Republic were reportedly small. Total world production of zirconium concentrates, including unreported amounts of baddeleyite, zircon , and eudialyte, probably exceeded 

500,000 short tons. 

The combined zirconium and hafnium contents of 

zircon concentrates form approximately 50 percent 

of the tonnage. The ratio of zirconium to hafnium in 

the concentrates is about 50 to 1. Total world production of zirconium in 1968 was estimated by the U.S. 

Bureau of Mine'S to be about 247,000 short tons 

(Stamper and Chin, 1970b). This total was based 

upon reported production and upon assumed amounts 

of 30,000 tons for the U.S.S.R. and 39,000 tons for 

the United States. Data on actual production for 

these countries and for Japan and India are not 

available. Because production in Australia increased 

by about 34,000 tons of zirconium between 1968 and 

1971, world production in 1971 is estimated to have 

been approximately 280,000 short tons. 

ESTIMATED U.S. PRODUCTION OF 

ZIRCONIUM CONCENTRATES 

United States production of zircon is solely from 

the Trail Ridge area, Florida, and Folkston, Georgia. 

Zircon and zirconium products are processed in several states. Specific production data are not released, 

but the order of magnitude of their production can 

be estimated. Stocks of zircon held by dealers and 

consumers in the United States, exclusive of those 

held by foundries, during the years 1968-71 have 

varied only slightly; so the difference bet\\een the 

amounts imported and the total U.S. consumption, 

as shown in figure 78, indicates the order of magnitude of domestic production. The data suggest a decrease from 83,000 short tons estimated for 1968 to 

between 50,000 and 55,000 tons in 1970 and 1971, 

depending upon the source of the zircon exported 

from the United States, and the amount of zircon 

reused. 

PRODUCTION OF ZIRCONIUM AND HAFNIUM 

Zirconium metal production in the United States 

in 1968 was entirely from imported concentrates. 

Data concerning the amount produced are not available. Hafnium demand in that year, about 18 short 

tons, was met by processing imported zircon to produce hafnium-free zirconium. Hafnium crystal bar 

production in 1970 was 35 short tons (Clarke, 1970). 

PRICES 

The prices of zirconium and hafnium raw materials and of various products of these elements are 

indicated in the following list, from data compiled 

by the U.S. Bureau of Mines from published sources 

for 1970 (Clarke, 1970): 

Specification of material Price 

Zircon: 

Domestic, per short ton, f.o.b. Starke, Fla. 

(minimum 66 percent ZrOz) ________ $ 56.00-$57.00 

Imported, sand, per long ton, in bags, c.i.f. 

Atlantic ports (minimum 65 percent 

Zr02) __ _ ____ _______ __ _ __ _ __ ___ ____ 70.00 

Zircon and zirconia brick, 9-inch equivalent brick, 

per brick ----------------------------- 3.72 

Zirconium oxide, in various grades and lots, 

per pound ---------------------------- 0.41- 1.50 

Zirconium: 

Powder, per pound ------------------ 12.00- 13.00 

Sponge, per pound ------------------- 5.50- 7.00 

Hafnium: 

Sponge, per pound ------------------- 75.00 

Bar and plate, rolled, per pound ______ 120.00 

It is apparent that the price of about 3 cents per 

pound for the zircon is only a small part of the price 

of the various prepared products. The difference in 

prices is related to the complexity and cost of the 

processes required to convert the zircon to usable 

products. 

TRADE 

The average value of imported zircon, 92 percent 

of which was from Australia in 1970, was $39.08 per 

short ton, and the total value of zircon imported into 

the United States was $3.7 million (Clarke, 1970). 

Products of zirconium and hafnium valued at approximately $1.6 million were imported into the 

United States in 1970. These were from Canada, 

France, West Germany, Switzerland, Netherlands, 

United Kingdom, and Japan. U.S. imports for consumption of zircon were from Australia, Canada, 

Republic of South Africa, and the United Kingdom. 

The value of zircon imports from Australia was 

nearly $3.3 million. Some sales contracts for rutile 

from Australia stipulate that zircon must also be 

purchased in some proportional quantity (Stamper 

and Chin, 1970b). 
716 

(/) 

z 

0 

1-

1-

a: 

0 

:I: 

(/) 

u.. 

0 

(/) 

0 

z 

<( 

(/) 

::::> 

0 

:I: 

1-

UNITED STATES MINERAL RESOURCES 

160~~-----.------.------.--lf'v~ 

14or-----------+-----------1-----------~----------~-----------+----------+/ u~.S~·~co~n~su~m~pt~io~n~ 

I 

120r-----------+-----------1-----------~----------~-----------+-----------4----------~ 

100 

~ 

80 I 

60 ~ v ~ 11-----

r--

I ' I 

I 

1\ f'\ 

40 r-----------+U_._s_.c_o_n_su_m~p~t_io~n~----------~~~r----rl/ __ \.r------+/_J __ -+/----------~----------~ 

) 

;' \ ,'/ I - ...J ' 

20 A~ ~:: ;~~~ \, ~ A' '---_/ ~ , 

', ~ ......... ' , \,~ 

U.S. consumption I 

(exclusive of 

foundries) 

/ __ ..,.... 

U.S. exports V 

OL-----~~~~~==~~~~~-~--~----~=~~~=---~~--~--------__ --___ ._L-~~--~---------------'~~----------------------~----------- 1944 1948 1952 1956 1960 1964 1968 1971 

FIGURE 78.-U.S. consumption, imports, and exports of zirconium concentrates, 1944-71. Figures for U.S. total consumption 

for 1963-66 not available. Data from U.S. Bur. Mines "Minerals Yearbooks, 1944-70" and "Commodity Data Summaries, 

1972." 

The United States exported nearly $6.9 million 

worth of zirconium ores, concentrates, and zirconium-bearing materials to 30 countries on all the 

continents. Exports to Canada were valued at $3 

million. 

Although the United States imports a considerable 
ZIRCONIUM AND HAFNIUM 717 

amount of the zircon it consumes, domestic resources 

of zircon are large and could be utilized in greater 

quantities if foreign supplies were not available. 

World resources of zircon are sufficient to meet the 

demand in the foreseeable future. A better understanding of the zirconium and hafnium resources of 

the world can be obtained by an examinatiOn of the 

geologic occurrence of these elementso 

GEOLOGIC ENVIRONMENT 

GENERAL GEOCHEMICAL AND 

MINERALOGIC CONSIDERATIONS 

Zirconium and hafnium have long been recognized 

as a classic example of a pair of geochemically coherent elements; that is, they invariably occur together in rocks and minerals. Their close association 

is explained by their nearly identical charge, ionic 

radii, electronegativity, and ionic potentials (table 

158). 

TABLE 158.-Selected data on zirconium, hafnium, and geochemically associated elements 

[Data from Green, 1959, table 2] 

Electronegativity 

Atomic Ionic (kilo- Ionic 

Ion No. radius calories/ potential 

gramatom) 

Zr'+ ----- 40 0.79 200 5.08 

Hf'+ ---- 72 .78 180 5.12 

Th'+ ---- 90 1.02 170 3.92 

UH ----- 92 .97 190 4.12 

Ce'+ 58 .94 190 4.26 

Nb5+ ---- 41 .69 240 7.5 

Ta5+ ---- 73 .68 210 7.35 

Both elements are markedly lithophile (have a 

strong affinity for oxygen) and are enriched strongly in the sialic crust of the earth. Because of its 

physical and crystallochemical properties, Zr4 + has 

restricted entry into the lattice sites of the major 

rock-forming minerals, hence, relatively few minerals account for the occurrence of most of the zirconium of the earth's outer crust. Approximately 20 

well-defined minerals, all of which are classified as 

silicates or oxides, contain zirconium as an essential 

constituent. In addition, a large number of minerals 

contain minor or trace amounts of zirconium in solid 

solution (Vlasov, 1966a, b; Fronde!, 1957). From a 

quantitative standpoint the mineralogical distribution of zirconium in the earth's outer crust can be 

almost entirely accounted for by only three minerals : 

(1) zircon, ZrSi04; (2) baddeleyite, ZrOz; and (3) 

eudialyte, Na4 (CaFe) 2ZrSi6011 (OH,Cl) 2· Because of 

its widespread occurrence as an accessory mineral 

in igneous and metamorphic rocks and its concentration in sedimentary rocks (Poldervaart, 1955, 1956; 

Mertie, 1958; Ronov and others, 1961; Saxena, 1966; 

Marshall, 1967), zircon is the principal :;ource of 

zirconium and hafnium. 

Baddeleyite occurs in economically important deposits in association with feldspathoidal igneous 

rocks in the P~os de Caldas Plateau, Minas Gerais, 

Brazil ( Guimaraes, 1948 ; Franco and Loewenstein, 

1948). The Po~os de Caldas zirconium ore concentrates consisting of baddeleyite and intimately associated zircon (locally called caldasite) contain 0.1-

2.0 percent uranium, averaging about 0.5 percent 

(Tolbert, 1966). 

Eudialyte, although considered a relatively rare 

mineral, occurs in large quantities in some types of 

potassium- and sodium-rich igneous rocks. It is an 

essential mineral in a variety of nepheline syenites 

and nepheline syenite pegmatites of the agpaitic 

type. (Nepheline syenites in which the 1nolecular 

ratio K20 + Na20: Al20a is greater than 1 are named 

agpaitic; nepheline syenites in which the ratio is 1 

or less are named miaskitic~ Agpaitic nepheline syenites are known from the Ilimaussaq intrusion in 

Greenland and the Kola Peninsula in the U.S.S.R. 

( Gerasimovskii, 1956). In addition to containing 

deposits of eudialyte, the agpaitic rocks of the 

Ilimaussaq intrusion contain potential low-grade 

uranium deposits (Sorensen, 1970a, b) and niobium 

mineralization (Hansen, 1968) . 

ABUNDANCE AND DISTRIBUTION IN ROCKS 

OF THE CRUST 

Estimates from recent compilations of the crustal 

abundance of zirconium and hafnium and of average 

zirconium and hafnium contents in some of the 

major rock types of the upper crust are given in 

table 159. It should be recognized that there are 

problems inherent in making such estimates of the 

abundances of elements (Fleischer and Chao, 1960). 

TABLE 159.-Abundances of zirconium and hafnium in terrestrial rocks, in parts per million 

[Data from Brooks, 1969, 1970; Chao and Fleischer, 1960; Degenhardt, 

1957; Horn and Adams, 1966; Taylor, 1965; Turekian and Wedepohl, 1961] 

Zr-Hf 

Rock type Zr Hf ratio 

Crust ------------------ 165 3 55 

Ultramafic -------------- 40 .5 80 

Basalt: 

Tholeiitic ----------- 50-100 1-2 50 

Alkaline ----------- 250 3-4 62-83 

Syenite ----------------- 500 10 50 

Granodiorite ------------ 140 4 35 

Granite ---------------- 180 4 45 

Shale ------------------ 160 3 53 

Graywacke ------------- 140 2 70 

Sands,tone -------------- 220 5 44 

Limestone -------------- 20 .5 40 

Pelagic clays ----------- 150 4 38 
718 UNITED STATES MINERAL RESOURCES 

Zirconium, a fairly common element, ranking 

twentieth in order of abundance in the earth's outer 

crust, is determined routinely in nearly all traceelement investigations. Thus the average zirconium 

contents of the predominant rock types (background 

levels) are reasonably well documented and provide 

a basis for the recognition of zirconium-rich provinces or rock units of potential economic interest. 

The highly generalized abundance data on igneous 

rocks (table 159) reflect the well-known tendency 

for zirconium content to increase in the differentiation sequence ultramafic-mafic-intermediate-felsic, 

with a particularly marked enrichment in syenitic 

(alkalic) rocks. 

BEHAVIOR OF ZIRCONIUM IN 

MAGMATIC PROCESSES 

The a;bundance and variation of zirconium in 

suites of igneous rocks represent different stages of 

crystallization of magmas (Chao and Fleischer, 

1960). Zirconium increases in each stage as differentiation proceeds. The zirconium contents of suites 

derived from an alkaline base magma are significantly greater than those derived from a basaltic 

magma of the tholeiitic type. In these rock suites, 

differentiation produces about a five-fold enrichment 

in the final products of crystallization. An unusually 

· strong enrichment of zirconium ( > 1,000 ppm Zr) 

occurs in the late differentiates of the Skaergaard 

intrusion in Greenland as compared with the zirconium content of its initial liquid (94 ppm (parts 

per million)), a value similar to the average zirconium content of tholeiitic basalts (Brooks, 1969). 

Calc-alkalic and calcic rock suites have the lowest 

zirconium contents and do not yield differentiates 

rich in zirconium. The alkalic suites have higher 

zirconium contents, and zirconium enrichment is 

most pronounced ( > 1,000 ppm) in the most siliceous 

rocks of these suites. 

The strong tendency for zirconium to concentrate 

in rocks with strong alkaline affinities is generally 

attributed to the greater solubility of zirconium in 

magmas relatively high in N a, K, F, Cl, and OH. 

Because of its high ionic potential, zirconium is 

strongly partitioned into the residual liquid (Ringwood, 1955). Strongly alkalic (pantelleritic) obsidians contain from 1,100-3,000 ppm Zr (Carmichael, 

1962), and riebeckite rhyolites and granitE's from 

Nigeria have as much as 2,200 ·ppm Zr (Butler and 

Thompson, 1965; Bowden, 1966). The contrasting 

behavior of zirconium in the more calcic suites, 

which have low contents of alkalis and complexing 

ions, may thus be attributed for the most part to 

early crystallization of zircon, which causes only 

slight to moderate enrichment in the residual 

magmas. 

BEHAVIOR OF HAFNIUM IN 

MAGMATIC PROCESSES 

Data on the hafnium· content of rocks are relatively scarce because of the difficulty of determining 

hafnium in the concentration ranges encountered in 

rocks. The average content of hafnium in the upper 

crust of the earth is 3 ppm, approximately onefiftieth of the abundance of zirconium. 

Because hafnium and zirconium are nearly identical in chemical properties, the geochemical behavior 

of hafnium during magmatic differentiation is quite 

similar to that of zirconium. In most suites of comagmatic or spatially associated rocks, the Zr-Hf 

ratios of the bulk rock or zircons are generally between one-half and twice the average Zr-Hf ratio 

of the earth's crust. Two diabase-granophyre suites 

from Dillsburg, Pa., and Great Lake intrusion, Tasmania, have absolute and relative enrichment of 

hafnium in the later-formed rocks. The average ZrHf ratio decreased from 68 to 33 in the course of 

differentiation (Gottfried and others, 1968). In the 

Skaergaard intrusion, however, the ratio varied in 

an opposite manner, the enrichment of zirconium and 

hafnium being accompanied by an increase in the 

Zr-Hf ratio with differentiation (Brooks, 1969). 

Limited data on differentiation products of an alkaliolivine basalt indicate an increase in the Zr-Hf ratio 

from 59 in early formed ankaramite to 85 in more 

silica- and alkali-rich trachyte (Brooks, 1970). 

The geochemical variation of hafnium relative to 

zirconi urn in calc-alkaline rocks is based mainly on 

data obtained on zircon. Analyses for hafnium and 

the Hf-Zr ratios in zircon from calc-alkaline plutonic 

rocks indicate about a twofold enrichment of hafnium in zircons from granites over that found in 

zircon from · gabbroic rocks, the Zr-Hf ratio decreasing from 50-70 in the gabbros to 30-35 in the 

granites. Variations of the Zr-Hf ratios in oulk rock 

samples from calc-alkaline granitic masses (Condie 

and Lo, 1971; Esson and others, 1968) are similar to 

those obtained on zircon. Zircon from undersaturated rocks, such as syenites and nepheline syenites, has low hafnium contents and significantly 

higher Zr-Hf ratios (60-150) than zircon from ordinary granitic rocks, as shown in table 160. In contrast, zircons with the highest hafnium contents (to 

30 percent) and unusually low Zr-Hf ratios ( <20) 

are found in zircon derived from peralkaline granites, granitic pegmatites, and lithium-tantalumbearing pegmatites (Knorring and Hornung, 1961; 
ZIRCONIUM AND HAFNIUM 719 

TABLE 160.-General range of zirconium-hafnium ratios in 

zircon from igneous rocks 

[Data from Cbessex and Delaloye, 1965; Fleischer, 1955; Gottfried and Waring, 1964; Hess, 1962; Lyakbovich and Shevaleyevskii, 1962; Vainshtein 

and others, 1959] 

Rock type 

Gabbro __ ----- __ --------·------------------- Quartz diorite ----------------------------- Granodiorite ------------- ____ -------------- Granite (calc-alkalic) ----------------------- Granite (alkalic) __________________________ _ 

Granite pegmatite -------------------------- Nepheline syenite ___________ -- _____________ _ 

Zr-Hf 

50-70 

40-60 

35-55 

30-45 

20-30 

3-20 

60-150 

Levinson and Borup, 1960; Vainshtein and others, 

1959). 

TYPES OF DEPOSITS 

PRIMARY DEPOSITS 

Despite the fact that zircon tends to be enriched in 

late-stage magmatic differentiates and is a common 

accessory mineral in many rock types, primary deposits having economic value are rare. An example 

is the uraniferous zirconium deposits in the Poc;os de 

Caldas Plateau, Brazil, which contain baddeleyite 

and zircon in commercial quantities and yielded an 

estimated 100,000 metric tons of zirconium ore concentrate before 1953 (Tolbert, 1966). These deposits 

consist of veins and disseminations of baddeleyite 

and zircon in nepheline syenite and phonolite of an 

alkaline intrusive that was emplaced in gneiss and 

granite in the southwestern part of the Brazilian 

shield. The veins are believed to be of hydrothermal 

origin (Tolbert, 1966), but the primary ores may 

have resulted from lateritic concentration as described by Wedow (1967) for thorium and rareearth deposits nearby. Concentrations of baddeleyite 

and zircon were in primary veins disseminated in 

decomposed bedrock in eluvial deposits on hill slopes, 

and in alluvial placer deposits along streams and in 

terraces. Most of the ore production was from 

placers of alluvial and eluvial origin. Only a small 

amount was produced from shallow workings along 

veins. Resources of zirconium ore in the region were 

estimated to be 50,000-70,000 metric tons which contained 60-85 percent Zr02 and about 0.5 percent 

uranium (Tolbert, 1966). 

Other primary deposits are pegmatites which contain rare zirconium minerals or gem-quality zircon, 

such as those in the Zirconia district, Henderson 

County, N. C. (Pratt, 1916). Deposits of this type 

are of little economic significance at present. 

SECONDARY DEPOSITS 

In the sedimentary cycle, zircon, being heavy 

(sp gr 4.7) and resistant to chemical decomposition 

and erosion, is concentrated with _other heavy resistate minerals, such as rutile, ilmenite, monazite, 

and garnet, in placer deposits in stream terraces, 

along beaches, and in sand dunes. Deposits of this 

type are the commercial sources of zircon, generally 

as a coproduct or byproduct of titanium minerals or 

combinations of other heavy minerals. Examples of 

commercial zircon-bearing titaniferous sand deposits 

are Trail Ridge, Fla., and deposits along beaches 

near the Queensland-New South Wales border, 

Australia, and along beaches in Western Australia. 

About 1 ton of zircon is produced for each ton of 

rutile in concentrates from the Australian deposits 

(Stamper and Chin, 1970b). 

Zircon is also found in small percentages in some 

phosphatic sediments and in some sand and gravel 

deposits. Potentially recoverable zircon is usually 

discarded in waste products from phosphate mining 

and sand and gravel production. In 1967, for example, 44,000 tons of zircon was discarded along 

with 60,000 tons of ilmenite and 5,000 tons of monazite as waste products in Florida phosphate operations (Stow, 1968). 

Zircon deposits in lithified titanium-rich placers in 

sandstones or in metamorphosed sandstones are potentially of economic importance. Sandstones of the 

Precambrian Ocoee Supergroup contain beds having 

4.5-9.0 percent zircon (Wedow and Hobbs, 1968). 

RESOURCES 

IDENTIFIED RESOURCES 

The identified resources of zircon are principally 

in titanium-rich and phosphate-rich sands in placer 

deposits and in fossil placers in titaniferous sandstone. Resources of baddeleyite in South Africa and 

Brazil, however, include primary and residual deposits. Data on world resources of zircon are incomplete. Identified zircon resources, in short tons of 

zircon equivalent, are given in table 161. These 

resources contain approximately 17 million tons of 

zirconium and 0.3 million tons of hafniurn. 

The United States has the world's greatest identified resources of zircon (Stamper and Chin, 1970b). 

More than 70 percent of the domestic resources are 

in the Atlantic Coastal States of Florida, Georgia, 

South Carolina, and New Jersey. The distribution of 

zircon resources in the United StatEs is shown in 

table 162. The amount for Florida is modified from 

published resource data to compensate for estimated 

production. 

The identified resources of zircon in the United 

States, estimated at 10.8 million tons, contain approximately 5 million tons of zirconium and 0.1 million tons of hafnium. A portion of the resources in 
720 UNITED STATES MINERAL RESOURCES 

TABLE 161.-ldentified world resources of zircon 

[Identmed resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whooe contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. Figures are rounded. NA, not available. Data from Ange.elli and Chaar (1967), Brazil Dept. Nacional da Produ~o 

Mineral · (1967), Industrial Minerals (1971), Kauffman (1956), Stamper 

and Chin ( 197()b), Tolbert ( 1966), U.S. Bur. Mines ( 1969,1972)] 

Country 

United States ----------------------------- Australia _____________________ --------__ _ 

U.S.S.R. --------------------------------- India ------------------------------------ South Africa, Republic o.f -----------------

Brazil ----------------------------------- Ceylon ----------------------------------- Sierra Leone ----------------------------- New Zealand ----------------------------- Uruguay --------------------------------- Argentina ----------------··--------------- Ivory Coast ------------------------------ Japan ------------------------------------

]{orea ----------------------------------- Malagasy Republic (Madagascar) ---------

~~::i~a-================================= Thailand --------------------------------- United Arab Republic ---------------------

Zircon 

equivalent, in 

thousands of 

short tons 

10.800 

8~600 

6,000 

3,360 to 5,000 

2,500 

2,500+ 

1,000 

1,000 

400+ 

136 

14 

NA 

NA 

NA 

NA 

NA 

NA 

NA 

NA 

Total -------------------------------- 36,310+ 

TABLE 162.-ldentified zircon resources of the United States 

[Identified resources: Specific, identified mineral deposits that may or may not be evaluated as to extent and grade, and whose contained 

minerals may or may not be profitably recoverable with existing technology and economic conditions. Data from Dow and Batty ( 1961), Kauff- man and Holt (1965), Wessel (1958), Williams (1964)] 

State 

Zircon re- sources, in 

thousands of 

short tons 

Florida ------------------------------------ 5,400 

~orgia ----------------------------------- 350 

North Carolina ---------------------------- 22 

South Carolina ---------------------------- 1,275 

New Jersey ------------------------------- 1,520 

California --------------------------------- 1,500 

Idaho ------------------------------------- 280 

Montana ---------------------------------- 94 

VVyorning ---------------------------------- 120 

New Mexico ------------------------------- 98 

Oregon ------------------------------------ 90 

Utah -------------------------------------- 59 

VVashington -------------------------------- 6 ----- Total --·--------------·----------------- 10,814 

Florida and Georgia can be considered as reserves. 

The remainder of the identified zircon resources in 

the United States is at present not competitive 

commercially. 

HYPOTHETICAL RESOURCES 

Hypothetical resources of zirconium and hafnium 

are difficult to quantify. Untested areas along the 

coasts of Africa, Asia, and South America, and offshore deposits in shallow waters throughout the 

world contain concentrations of zircon comparable 

to those in known deposits. Similarly, fossil placers 

in sandstone and metasedimentary rocks, and alkalic 

igneous rocks on all continents contain great quantitie~ of zircon. However, the added cost of mining and 

separating most hard-rock deposits excludes them 

from consideration as resources in the near future. 

Byproduct zircon and baddeleyite may become increasingly important sources of zirconium and hafnium. Phosphate deposits, such as those mined in 

Florida (Stow, 1968), and sand and gravel deposits 

in Alabama and elsewhere in the United States contain substantial amounts of zircon that are potentially recoverable. Baddeleyite-bearing copper ores at 

Palabora in South Africa (South Africa Mining and 

Engineering Jour., 1970) currently yield zirconium 

concentrates in addition to copper, iron, and phosphate products. Many other ores that require grinding and beneficiation contain minor amounts of 

zirconium minerals that are potentially recoverable. 

PROBLEMS FOR RESEARCH 

Zircon is currently available in excess of projected 

demand for the next few decades. Environmental 

problems such as water pollution and despoilment of 

beaches, and competitive land use in some areas, may 

interfere with the production from placer deposits 

that are worked principally for titanium and byproduct zircon. If the resources in these areas become unavailable, the supply of zircon will be drastically reduced in the United States, and alternate 

sources will be required. 

Research directed toward discovery of alternate 

sources of zircon is needed. This research should 

include the search for high-grade primary ores as 

well as low-grade byproduct or coproduct ores. 

Sampling and analysis of tailings of various types of 

beneficiated ores, and sampling of sands in sand and 

gravel deposits from which washed and sized sand 

products are currently produced, might disclose 

potential sources from which zircon can be obtained. 

Studies of heavy-mineral concentrations in friable 

sandstone formations in areas where competitive 

land use and environmental problems are not likely 

to interfere with mining should also be made. Because of the common association of uranium and 

thorium with zirconium-bearing minerals, some 

deposits may be detected by radiometric surveys. 

The possibility of recovery of zircon from offshore 

deposits in shallow waters and of zirconium and 

hafnium from manganese nodules on the sea floor 

(Mero, 1972) should also be examined. The recovery 

of zirconium and hafnium from manganiferous nodules, however, would be completely dependent upon 

the recovery and processing of the nodules for manganese and other metals and would therefore be a 
ZIRCONIUM AND HAFNIUM 721 

problem of chemical extraction. Timely research on 

specific alternate sources of zircon would eliminate 

the need for future crash programs. 

SELECTED REFERENCES 

Angelelli, Victoria, and Chaar, Edmundo, 1967, Los depositos 

de titanomagnetita, ilmenita y zircon de la Bahia San 

Bias (tramo baliza La Ballena-Faro Segunda Barranca) 

partido Carmen de Patagones, provincia de Buenos Aires 

[Titanomagnetite, ilmenite, and zircon deposits of the 

Bay of San Bias, Carmen de Patagones, Buenos Aires] : 

Argentina Comision N ac. Energia Atomica Rept. CNEA210, 53 p. 

Bowden, P., 1966, Zirconium in younger granites of northern 

Nigeria: Geochim. et Cosmochim. Acta, v. 30, p. 985-

993. 

Brazil Departmento Nacional da Produ~ao Mineral, 1967, 

Contribuic;ao do Departamento N acional da Produ~ao 

Mineral no desenvolvimento geo-economico do nordeste 

Brasileiro [Contribution of the National Department of 

Mineral Production to the geo-economic development of 

northeast Brazi11 : Brazil Dept. N ac. Produc;ao Mineral 

Pub. Espec. 4, 125 p. 

Brooks, C. K., 1969, On the distribution of zirconium and 

hafnium in the Skaergaard intrusion, East Greenland: 

Geochim. et Cosmochim. Acta, v. 33, p. 357-374. 

--- 1970, The concentrations of zirconium and hafnium 

in some igneous and metamorphic rocks and minerals: 

Geochim. et Cosmochim. Acta, v. 33, p. 357-374. 

Butler, J. R., and Thompson, A. J., 1965, Zirconium-hafnium 

ratios in some igneous rocks: Geochim. et Cosmochim. 

Acta, v. 29, p. 167-175. 

Carmichael, I. S. E., 1962, Pantelleritic liquids and their 

phenocrysts: Mineralog. Mag., v. 33, p. 86-113. 

Chao, E. C. T., and Fleischer, Michael, 1960, Abundance of 

zirconium in igneous rocks: Internat. Geol. Cong., 21st, 

Copenhagen, 1960, Rept., pt. 1, p. 106-131. 

Chessex, Ronald, and Delaloye, Michel, 1965, Donnees sur les 

teneurs en hafnium et en yttrium des zircons: Bull. 

Suisse de Mineralogie et Petrologie, v. 45, no. 1, p. 295-

315. 

Clarke, R. G., 1970, Zirconium and hafnium: U.S. Bur. Mines 

Minerals Yearbook 1970, v. 1, p. 1205-1211. 

Condie, K. C., and Lo, Howard, 1971, Trace element geochemistry of the Louis Lake batholith of early Precambrian age, Wyoming: Geochim. et Cosmochim. Acta, 

v. 35,p. 1099-1119. 

Degenhardt, Heinz, 1957, Untersuchungen zur geochemischen 

Verteilung des Zirkoniums in der Lithosphare: Geochim. 

et Cosmochim. Acta, v. 11, p. 279-309. 

Dow, V. T., and Batty, J. V., 1961, Reconnaissance of titaniferous sandstone deposits of Utah, Wyoming, New 

Mexico, and Colorado: U.S. Bur. Mines Rept. Inv. 5860, 

52 p. 

Esson, J., Hahn-Weinheimer, P., and Johanning, H., 1968, 

Determination of hafnium by neutron activation, and 

variation in the Zr/Hf ratio of some granite masses: 

Talanta, v. 15, p. 1111-1118. 

Fleischer, Michael, 1955, Hafnium content and hafniumzirconium ratios in minerals and rocks: U.S. Geol. Survey Bull. 1021-A, 13 p. 

Fleischer, Michael, and Chao, E. C. T., 1960, Some problems 

in the estimation of abundance of elements in the earth's 

crust: Internat. Geol. Cong., 21st, Copenhagen, 1960, 

Rept., pt. 1, p. 141-148. 

Franco, R. R., and Loewenstein, W., 1948, Zirconium from 

the region of P~os de Caldas: Am. Mineralogist, v. 33, 

p. 142-151. 

Fronde!, Clifford, 1957, Zirconium mineralogy and geochemistry, in Advances in Nuclear Engineering, v. 2: 

Nuclear Eng. and Sci. Cong., 2d, Philadelphia, 1957, 

Proc .• Pt. 2, p. 305-312. 

Gerasimovskii, V. 1., 1956, Geochemistry and mineraloa"Y of 

nepheline syenite intrusions: Geochemistry, no. 5, p. 

494-510. 

Gottfried, David, Greenland, L. P., and Campbell, E. Y., 1968, 

Variation of Nb-Ta, Zr-Hf, Th-U, and K-Cs in two 

diabase-granophyre suites: Geochim. et Cosmochim. Acta, 

v. 32, p. 925-947. 

Gottfried, David, and Waring, C. L., 1964, Hafnium content 

and Hf/Zr ratio in zircon from the southern California 

batholith, in Geological Survey research 1964: U.S. Geol. 

Survey Prof. Paper 501-B, p. B88-B91. 

Green, Jack, 1959, Geochemical table of the elements for 

1959: Geol. Soc. America Bull., v. 70, no. 9, p. 1127-1184. 

Guimaraes, Djalma, 1948, Os depositos zirconiferos do planalto de Po~os de Caldas eo geoquimismo do Zr [The zirconium ore deposits of the Po~os de Caldas Plateau, 

Brazil, and zirconium geochemistry]: Bol. Inst. Tecnologia Indus. Minas Gerais, no. 6, p. 1-40; English 

translation, p. 42-78. 

Hansen, John, 1968, Niobium mineralization in the Ilimaussaq 

alkaline complex, South-West Greenland: Internat. Geol. 

Cong., 23d, Prague, 1968, Proc., sec. 7, p. 263-273, 

Prague, Academia; reprinted as Gronlands Geol. Undersogelse Misc. Paper 60, 1968. 

Hess, H. D., 1962, Hafnium content of domestic and foreign 

zirconium minerals: U.S. Bur. Mines Rept. Inv. 5856, 

62 p. 

Horn, M. K., and Adams, J. A. S., 1966, Computer-derived 

geochemical balances on element abundances: Geochim. 

et Cosmochim. Acta, v. 30, p. 279-297. 

Industrial Minerals, 1969, World zircon producers-Present 

production and future potential: Industrial Minerals, 

no. 16, p. 19, 21, 23-27. 

--- 1971, Titanium minerals-[Pt. ] 1, The producers 

reviewed: Industrial Minerals, no. 43, p. 9-13, 15-23. 

Kauffman, A. J., Jr., 1956, Zirconium ores, chap. 1 in Zirconium, its production and properties: U.S. Bur. Mines 

Bull. 561, p. 3-10. 

Kauffman, A. J., Jr., and Holt, D. C., 1965, Zircon-A review, with emphasis on west coast resources and markets: 

U.S. Bur. Mines Inf. Circ. 8268, 69 p. 

Knorring, 0. Von, and Hornung, G., 1961, Hafnium zircons: 

Nature, v. 190, p. 1098-1099. 

Levinson, A. A., and Borup, R. A., 1960, High hafnium zircon from Norway: Am. Mineralogist, v. 45, p. 562-565. 

Lustman, Benjamin, and Kerze, Frank, Jr., 1955, The 

metallurgy of zirconium: New York, McGraw-Hill Book 

Co., Inc., 776 p. 

Lyakhovich, V. V., and Shevaleyevskii, I. D., 1962, Zr:Hf 

ratio in the accessory zircon of granitoids: Geochemistry, 

no. 5, p. 508-524. 

Marshall, Brian, 1967, The present status of zircon: Sedimentology, v. 9, p. 119-136. 

Mero, J. L., 1972, Effects of mining sea floor nodules may 

be drastic for industry, society: Northern Miner, v. 

58, no. 5, p. 4-5. 
722 UNITED STATES MINERAL RESOURCES 

Mertie, J. B., Jr., 1958, Zirconium and hafnium in the southeastern Atlantic States: U.S. Geol. Survey Bull. 1082-A, 

p. 1-28. 

Poldervaart, Arie, 1955, Zircons in rocks-Pt. 1, Sedimentary 

rocks: Am. Jour. Sc-i., v. 253, no. 8, p. 433-461. 

--- 1956, Zircons in rocks-Pt. 2, Igneous rocks: Am. 

Jour. Sci., v. 254, no. 9, p. 521-554. 

Pratt, J. H., 1916, Zircon, monazite, and other minerals used 

in the production of chemical compounds in the manufacture of lighting apparatus: North Carolina Geol. 

and Econ. Survey BulL 25, 120 p. 

Ringwood, A. E., 1955, The principles governing trace element behavior during magmatic crystallization-Pt. 2, 

The role of complex formation: Geochim. et Cosmochim. 

Acta, v. 7, p. 242-254. 

Ronov, A. B., Vainshtein, E. E., and Tuzova, A. M., 1961, 

Geochemistry of hafnium, zirconium and some other 

hydrolyzate elements in clays: Geochemistry, no. 4, p. 

343-355. 

Saxena, S. K., 1966, Evolution of zircons in sedimentary and 

metamorphic rocks: Sedimentology, v. 6, p. 1-33. 

Sorensen, H., 1970a, Low-grade uranium deposit in agpaitic 

nepheline syenites, south Greenland, in Uranium exploration geology: Internat. Atomic Energy Agency, 

Panel on Uranium Exploration Geology, Vienna, 1970, 

Proc., p. 151-159. 

--- 1970b, Occurrence of uranium in alkaline igneous 

rocks, in Uranium exploration geology: Internat. 

Atomic Energy Agency, Panel on Uranium Exploration Geology, Vienna, 1970, Proc., p. 161-168. 

South African Mining and Engineering Journal, 1970, On 

the trail of zirconium oxide: South African Mining and 

Eng. Jour., v. 81, pt. 1, no. 4034, p. 1085, 1087, 1089, 

1091. 

Stamper, J. W., and Chin, Edmond, 1970a, Hafnium, in 

Mineral facts and problems, 1970: U.S. Mines Bull. 650, 

p. 587-594. 

--- 1970b, Zirconium, in Mineral facts and problems, 

1970: U.S. Bur. Mines Bull. 650, p. 825-835. 

Stow, S. H., 1968, The heavy minerals of the Bone Valley 

Formation and their potential value: Econ. Geology, v. 

63, no. 8, p. 973-975. 

Taylor, S. R., 1965, The application of trace element data 

to problems in petrology, in Ahrens, L. H., Press, Frank, 

Runcorn, S. K., and Urey, H. C., eds., Physics and 

chemistry of the earth: Pergamon Press, v. 6, p. 133-

213. 

Tolbert, G. E., 1966, The uraniferous zirconium deposits of 

the P~os de Caldas Plateau, Brazil: U.S. Geol. Survey 

Bull. 1185-C, 28 p. 

Turekian, K. K., and Wedepohl, K. H., 1961, Distribution 

of the elements in some major units of the earth's 

crust: Geol. Soc. America Bull., v. 72, p. 175-192. 

U.S. Bureau of Mines, 1944-70, Minerals Yearbooks. 

--- 1969, Titanium minerals-Uruguay: U.S. Bur. Mines 

Mineral Trade Notes, v. 66, no. 6, p. 25-26. 

--- 1972, Commodity data summaries [zirconium and 

hafnium section]: p. 166-167. 

Vainshtein, E. E., Ginzburg, A. J ., and Shevaleyevskii, I. D., 

1959, The Hf/Zr ratio in zircons from granite pegmatites: Geochemistry, no. 2, p. 151-157. 

Vlasov, K. A., 1966a, Geochemistry of rare elements, v. 1, 

of Geochemistry and mineralogy of rare elements and 

genetic types of their deposits: Israel Program Sci. 

Translations, IPST no. 2123, 945 p. 

--- 1966b, Mineralogy of rare elements, v. 2, of Geochemistry and mineralogy of rare elements and genetic 

typ.es of their deposits: Israel Program Sci. Translations, IPST no. 2169, 688 p. 

Weast, R. C., Selby, S. M., and Hodgman, C. D., 1965, Handbook of chemistry and physics, 46th ed.: Cleveland, 

Ohio, Chemical Rubber Co., p. B-3, B-27, B-28, B-63, 

and B-64. 

Wedow, Helmuth, Jr., 1967, The Morro do Ferro thorium 

and rare-earth ore deposit, Poc;os de Caldas district, 

Brazil: U.S. Geol. Survey Bull. 1185-D, 34 p. 

Wedow, Helmuth, Jr., and Hobbs, R. G., 1968, Zirconium, in 

Mineral resources of the Appalachian region: U.S. 

Geol. Survey Prof. Paper 580, p. 361-364. 

Wessel, F. W., 1958, Zirconium raw materials supply, in 

United Nations, Survey of raw material re~sources: Internat. Conf. Peaceful Uses Atomic Energy, 2d, Geneva, 

1958, Proc., v. 2, p. 17-20. 

Williams, Lloyd, 1964, Titanium deposits in North Carolina: 

North Carolina Div. Mineral Resources Inf. Circ. 19, 

51 p. 

-t: U.S. GOVERNMENT PRINTING OFFICE: 1981- 341-614/127