GEOLOGICAL SURVEY CIRCULAR 792 

Background Information to Accompany 

the Atlas of Some Metal and Nonmetal 

Mineral Provinces in the 

Conterminous United States 

Background Information to Accompany 

the Atlas of Some Metal and Nonmetal 

Mineral Provinces in the 

Conterminous United States 

By Edwin W. Tooker 

G E 0 L 0 G I C A L S U R V E Y C I R C U L A R 792 

1980 
United States Department of the Interior 

CECIL D. ANDRUS, Secretary 

Geological Survey 

H. Wiltiam Menard, Director 

Library of Congress Cataloging in Publication Data 

Tooker, Edwin Wilson, 1923-

Background information to accompany the atlas of 

some metal and nonmetal mineral provinces in the 

conterminous United States. 

(Circular - Uo S. Geological Survey ; 792) 

A companion report to maps for individual 

commodities in the open-file report series of the 

Uo S. Geological Survey. 

Supto of docs. no.: I 19.4/2:792 

1. Mines and mineral resources--United Stateso 

2. Geology--United Stateso I. Titleo IIo Series: 

United States. Geological Surveyo Circular ; 792· 

QE75.C5 noo 792 (TN23] 557.3s f553'.0973] 80-607020 

Free on application to Branch of Distribution, U.S. Geological Survey, 12 0 0 South Eads Street, Arlington, VA 2 2 2 0 2 
CONTENTS 

Page Page 

Introduction _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ ___ _ __ _ _ __ ____ __ _ 1 A need for concern about domestic resources __________ 9 

What is a mineral province map? ____________________ 2 The present mineral-resource situation____________ 9 

Components of province maps________________________ 2 The problem: presence in the Earth's crust versus 

deliverability ---------------------------------- 11 

Good resource data-more than an inventory__________ 12 

Relevance of geologic knowledge to mineral availability 

Use and users of province maps __________________ 5 

Limitations and revision of province maps ________ 5 

A common denominator for resource evaluation________ 6 

Comments on resource terminology used ______________ 7 and metal and nonmetal mineral provinces__________ 12 

What are critical minerals? -------------------------- 8 References cited _ ____ __ _ _ _ __ _ _ _ __ ____ __ __ _ _ __ __ ___ _ _ 14 

FIGURE 

TABLE 

ILLUSTRATIONS 

Page 

1. Diagram illustrating role of nonfuel minerals in U.S. economy, with estimated values for 1977 ________ 7 

2. Diagram illustrating simplified mineral-resource terms used in this report ---------------------------- 8 

3. Diagram showing generalized projection of mineral supply and consumption -------------------------- 11 

TABLES 

Page 

1. Comparisons of size, value, and numbers of depoe. ts for selected critical commodities, and their availability 

and import dependence in the United States ___________ ----------------------------------------- 4 

2. Net import dependence of selected minerals and metals in 1975 -------------------------------------- 10 

3. Relative age spans of major geologic units used in this report and in province map discussions__________ 13 

III 

Background Information to Accompany the Atlas of some 

Metal and Nonmetal Mineral Provinces in the 

Conterminous United States 

By Edwin W. Tooker 

INTRODUCTION 

The principal purpose of this companion report 

to the atlas of metal and nonmetal mineral provinces is to discuss the rationale for making the 

maps, the methodology used in their construction, 

their characteristics and use, the serious gaps in 

presently available resource information, the 

definition of some commonly used geologic concepts and terms, and the important role of geology in identifying favorable areas for future 

resources. Maps for individual commodities are 

available for public inspection in the Open-File 

Report series of the U.S. Geological Survey 

(Open-File Report 79-576). 

The mineral provinces shown in this series of 

maps for a selected group of critical metal and 

nonmetal commodities represent areas of the 48 

conterminous United States in which there are 

present mining activity, past production, indication, or reasonable expectation of undiscovered 

minable minerals, and (or) reported but possibly 

not fully evaluated mineral occurrences. The 

maps summarize present resource-availability information along with the individual authors' 

evaluations; the data base is the published commodity literature, including resource data and 

analyses by U.S. Geological Survey mineral specialists. A somewhat comparable composite 

metal-province map for Alaska was prepared by 

Clark and others (1974). Because so much information is available on individual metal and nonmetal commodities in the conterminous United 

States, as well as on their geologic availability, 

the scope of this atlas has been broadened to include maps of individual commodities that present both the basic data and a brief description of 

the provinces recognized. 

1 

A mineral province map is a simplified level I 

evaluation (U.S. Geological Survey, 1975, p. 19) of 

the current status of knowledge about the areal 

distribution and geologic environment of mineral 

commodities, whether as: (1) primary minerals 

(major products of the material mined), (2) coproduct minerals (less abundant primary products sought in a multicommodity deposit), (3) byproduct minerals (secondarily produced, often 

serendipitously, from the production of a primary 

mineral), (4) available subeconomic mineral materials, or (5) reported but unevaluated occurrences of any of the above types. The mineral 

province maps in the atlas seek to extend the 

scope of previous commodity maps, which emphasized the distribution, size, and variety of 

types of known productive deposits, and to evaluate their supply potential in terms of current economic source deposits and recognized geologic factors. 

Any evaluation of future resources must also 

consider those yet-unrecognized or currently unused (subeconomic) resource materials that may 

be extracted from lower grade, coproduct, and byproduct minerals now considered unminable or 

waste. The limited scope of a level I evaluation 

and the small scale of the accompanying maps 

make it possible to highlight only a few of the 

geologic features that represent important genetic associations in the occurrence of metal and 

nonmetal deposits. This very general picture 

must be considered a first step toward unraveling 

the complex metallogenetic relations that need to 

be well understood in order to recognize new resource possibilities and to develop new mineral 

exploration technology. 
All the statistical and economic information derives from: (1) ffMineral facts and problems, 1975 

edition" (U.S. Bureau of Mines, 1976a), which 

provided economic resource-availability summaries through 1974, and ffCommodity data 

summaries 1979" (U.S. Bureau of Mines, 1979), 

which provided data through 1978; (2) an international survey of major producing mines in the 

world (Mining Magazine, 1976), which identified 

large mines active in 1975 in the conterminous 

United States; and (3) ffUnited States mineral resources" (Brobst and Pratt, 1973), which contains 

the most recent discussions on and estimates of 

geologically available resource materials. 

The data depicted on the mineral province 

maps are intended primarily to assist the reader 

in becoming more aware of some of the basic 

resource-availability issues that underlie present 

and future U.S. needs for critical raw materials. 

Mineral provinces, for example, may overlap 

areas of public interest in which State and Federal governmental decisions on land use must be 

made. Also, the full geologic significance of 

mineral-resource values must be understood beyond present economic evaluations so that, in 

time of need, the sources and availability of all 

types of critical resources will be known. This 

broadened perception will permit more intelligent 

balancing of mineral-resource values against 

such competing factors as ecology, scenic or historic preservation, recreational use, or other economic and esthetic considerations. 

WHAT IS A MINERAL PROVINCE MAP? 

A mineral province is defined as a geographic 

area in which known deposits and occurrences of 

a given commodity share some common geologic 

features, but which may also include geologically 

and geochemically favorable terrain that has a 

high potential for the occurrence of new deposits 

(or new types of occurrences) of the specified 

metal or nonmetal. The accompanying maps, at a 

scale of 1 : 5,000,000 (1 in. = approx 129 km (80 

miles); 1 em= approx 50 km (31 miles)), are preliminary, generalized, and interpretive overviews 

inferred from the regional distribution of known 

metal and nonmetal commodities. Provinces have 

been outlined for each commodity from plots of 

resource localities that seem to cluster in or along 

prominent known or inferred geologic features; in 

many cases a single province contains more than 

one commodity. The data points for an individual 

2 

commodity may represent a mining district, a deposit, or a prospect. 

A mineral province may contain one or more 

operating mines, former major producing deposits, or simply a cluster of unevaluated commodity 

data points. In a few special cases, an occurrence 

area has been proposed on the basis of one known 

deposit or district, with the implication that additional ones may be discovered and a province 

proposed when more information becomes available. On the basis of current data, some scattered 

individual data points cannot logically be directly 

related to a province and are considered to be of 

only local significance; new data and increased 

geologic knowledge could, however, change this 

evaluation. Where appropriate for a given commodity, the distribution of significant associated 

host rocks or structures is also indicated; these 

geologic interpretations are abstracted or 

modified from the ((Geologic map of the United 

States" (King and Beikman, 1974), the ffBasement rock map of the United States" (Bayley and 

Muehlberger, 1968), and the ffTectonic map of 

North America" (King, 1969). An explanatory 

table accompanying each map provides a rough 

evaluation of the resource potential within a 

given province and illustrates whether the status 

of geologic knowledge about the commodity province area is adequate or insufficient to assess fully 

either the resource potential of the province or, 

possibly, its extent. 

COMPONENTS OF PROVINCE MAPS 

If mineral resources are where one finds them, 

to paraphrase an old saying, the best starting 

point is a determination of the whereabouts and 

reasons for commodity concentrations. The atlas 

of mineral province maps provides framework location data for beginning this search. Special 

technical and scientific problems of resource occurrences or characteristics are described by 

commodity specialists for most of the commodities 

reported in the atlas. As author of this report and 

editor of the atlas, my objectives have been to develop format and subject goals for the maps and to 

maintain continuity and balance between individual maps. Each mineral province map includes 

an explanatory text that gives brief background, 

supply/demand, and geologic information about 

each commodity; describes the characteristics of 

provinces and the size classification and geologic 

types of deposits; and considers significant fea-
tures of the major provinces. The economic importance of provinces is evaluated where the data 

are adequate. The main purpose of this atlas is to 

emphasize known resource distribution and future potential areas, whether presently economic 

or not, rather than to document past production; 

detailed production data are already available for 

most commodities on U.S. Geological Survey 

Mineral Investigations Resource Maps (MR 

series) and in the cited resource literature. 

The mineral province maps show the distribution of deposits and occurrences against a background of six geologic regions of the conterminous 

United States, each of which has distinctive topographic and geologic features that to some degree 

have influenced the types of resources found 

within them. The boundaries and names of regions are those introduced by Stanton (1972). The 

Coastal Plains are low-lying areas bordering the 

Atlantic and Gulf of Mexico coasts that contain 

relatively young, generally flat lying, or structurally simple sedimentary rocks and uncomplicated 

mineral concentrations, formed mainly at the 

same time as the enclosing rocks. In contrast, the 

Appalachian belt is topographically higher, 

mountainous, and is composed of old as well as 

young complexly folded sedimentary, intrusive 

igneous, and metamorphic crystalline rocks. 

Here, some resource materials formed in simple 

accumulations as the enclosing sedimentary and 

volcanogenic rocks were deposited. Later, as the 

belt was subjected to structural stresses and the 

introduction of molten (igneous) rock-forming 

materials, more complex types of deposits were 

formed, such as mineral segregations within the 

intrusive igneous rocks, or vein-filling and replacement deposits precipitated from circulating 

hot mineral-bearing (hydrothermal) solutions derived from the cooling igneous bodies. Some host 

rocks were thermally altered or reconstituted 

(metamorphosed) to form distinctive contact 

(skarn) deposits. Even later, erosion of these rocks 

and deposits locally created residual (placer) accumulations. The Precambrian Shield is an 

eroded mountainous region of moderate relief 

composed of ancient, structurally complex, 

largely metamorphic crystalline rocks that contain a variety of deposits whose igneous, sedimentary, and metamorphic origins are incompletely 

understood. The Central Plains is a broad region 

of low to intermediate relief that mainly constitutes the drainage basin of the Mississippi River. 

3 

The tributaries are separated locally by uplifted 

mountainous areas; these mountain cores are 

commonly composed of exposed or buried ancient 

crystalline basement rocks on which have been 

deposited younger flat-lying or locally gently 

flexed sedimentary rocks. The deposits are varied; 

some are typical of the crystalline basement, but, 

by and large, major mineralization represents 

stratigraphically and structurally controlled 

(stratabound or stratiform) deposits in rocks of 

intermediate (Paleozoic and Mesozoic) age that 

adjoin exposed basement and intrusive-rock _centers or occur in the intervening broad basins. The 

Cordilleran belt, which is extremely varied topographically and geologically, consists of high 

mountains, deep canyons, extensive plateaus, and 

broad intermontane valleys, and includes thick 

forest in some areas and desert wasteland in 

others. The rocks, of widely varying ages (Archean to Cenozoic), are of intrusive and extrusive 

igneous, sedimentary, and metamorphic origins. 

The broad variation in types of Cordilleran belt 

deposits, which may have been formed when the 

host rocks formed, inserted into the rocks later, or 

concentrated when the rocks were destroyed by 

erosion, is due to a long geologic history of repeated heating and deformational events and of 

uplift and exposure of rocks and structures. 

Anomalously, within the Cordilleran belt is the 

vast Colorado Plateau, an area underlain by simply warped but generally flat lying sedimentary 

rocks that have been uplifted, faulted, and dissected by erosion. 

The mineral deposits and occurrences in the 

atlas are classed as large or small. Large deposits 

are those whose combined production, minable 

minerals, and potentially minable materials exceed a minimum unit value (table 1) equivalent to 

that of the classes of deposits established for a 

selected group of commodities on U.S. Geological 

Survey Mineral Investigations Resource Maps, or 

as estimated by a Geological Survey commodity 

specialist. These large deposits are subdivided 

into types of current and past (or potential) producers. Type A deposits include active mines that 

had substantial production in 1975 (the base year 

for this atlas), on the basis of commodity specialist information and supported by a worldwide 

survey of major mining activity (excluding coal) 

conducted by Mining Magazine (1976). Type B 

deposits include those major past producers now 

considered mined out, inactive owing to economic 
TABLE 1. -Comparisons of size, value, and numbers of deposits for selected critical commodities, and their availability and impart 

dependence in the United States 

Commodity 

Aluminum: 

Production 

units 1 

bauxite------------ Metric ton -----

meta 17 ------------ Short ton ------

Chromium: 

chromite ---------- Metric ton -----

Cobalt -------------- Pound ----------

Col umbi urn (Niobi urn): 

ore --------------- Pound ----------

Approximate 

unit dollar value 2 

10 

l ,000 

40-160 

6-20 

Copper -------------- Short ton ------ l, 300 

Fluorine: 

fluorspar ore ----- Short ton ------

Iron: 

taconite ---------- Long ton unit --

Lead ---------------- Short ton ------

Manganese: 

ore --------------- Long ton unit --

Mercury ------------- Flask ----------

30 

0. 60 

680 

1.40 

158 

Nickel -------------- Short ton ------ 4,000 

Phosphorous: 

phosphate rock ---- Short ton ------

Platinum ------------ Troy ounce -----

Tantalum: 

ore --------------- Pound ----------

17 

250 

27 

Tin ----------------- Metric ton ----- 13,000 

Titanium: 

ilmenite ---------- Long ton -------

Tungsten: 

ore --------------- Short ton unit -

Vanadium: 

VzOs -------------- Pound ----------

Zinc ---------------- Short ton ------

1 Short ton = 2, 000 pounds ( 907. 2 kg). 

Long ton = 2,240 pounds (1016.0 kg). 

Metric ton = 2,205 pounds (1000.0 kg). 

Flask = 76 pounds (34.5 kg). 

l troy ounce = 0. 0833 pounds (troy). 

50 

134 

620 

Comparative minimum size 

and dollar value of lar~e 

deposit (types A or B) 

Units produced 

and (or) available 

minable mining 

625,000 

125,000 

Estimated 

1978 dollar value 

6 million 

125 million 

l mill ion 40-160 mill ion 

l million 1,300 million 

2million 

5 bill ion 

l million 

775 million 

75,000 

50,000 

10 million 

400 

3,000 

2 mill ion 

l. 2 mill ion 

10,000 

l million 

60 million 

3 billion 

680 million 

bill ion 

ll million 

200 million 

170 million 

100,000 

40 million 

100 mill ion 

160 mill ion 

30,000 

620 mill ion 

Long ton unit = 22.4 pounds (10.2 kg) (46-48 percent Mn; 63 percent Fe). 

Short ton unit= 20 pounds W0 3 (9.1 kg) (16 pounds (7.2 kg) W metal). 

2Data source: U.S. Bureau of Mines (1979). 

Number of active (type A) deposits 

in 19754 

6 37(5) 

42 

6 12(9) 

32 

6 

6 17(13) 

Number of 

inactive (type B) depositss 

10 

>10 

4 

44 

13 

6(1) 

12 

8 

Percent import 

dependence 

19782 

g3 

10 

92 

97 

100 

19 

82 

2g 

ll 

98 

57 

77 

0 

91 

97 

81 

39 

50 

27 

62 

3Size of large deposits based on U.S. Geological Survey Mineral Investigations Resource Maps, where available, or evaluation by province map author(s). 

"Sources: U.S. Geological Survey commodity specialist and Mining Magazine (lg76). 

5Source: U.S. Geological Survey Mineral Investigations Resource Maps, where available. 

6Parenthetica l values indicate additional mines that produce Commodity as a coproduct or byproduct. 

7Comparative amount and value of metal theoretically derivable from a large bauxite deposit. 

4 
or technological factors, or having continuing 

minor production unreported in the survey but 

identified in the mineral investigation maps, and, 

in some cases, unmined deposits that contain a 

large identified but subeconomic resource potential. Together, type A and B deposits represent 

((elephant country" targets-places where the 

search for new resources would logically begin. 

Small deposits and occurrences (type C) are those 

whose combined production and minable minerals range from none (undetermined) to the 

minimum set for types A and B. Type C localities 

comprise present or possible producers and presently unevaluated occurrences, and encompass a 

broad range of deposits whose production history 

is limited but which may possibly develop into a 

higher class, as well as known unproductive or 

unmeasured, presently subeconomic occurrences. 

The density and clustering of small (type C) deposits and occurrences around large (types A and 

B) deposits or mining districts within a mineral 

province may provide a measure of its potential 

for future production. This distinction between 

major deposits and the more abundant smaller 

deposits and occurrences provides an immediate 

rating of a province's past production history in 

comparison with its present production status. 

The proportion of type A deposits on a given map 

also gives a visual evaluation of the abundance of 

resources and the capacity for domestic suppliers 

to meet present requirements for a given commodity. Large type B deposits locate substantial 

former producers that, for economic or unknown 

factors, are now inactive; in most cases, these resources have not been exhausted. Thus, regions 

containing deposits of either type A or B, or of 

both types, are also geologic terranes that still 

have a high probability for the discovery of 

hypothetical resources, both as extensions of 

known deposits and as new ore bodies concealed 

in untested ground. On the basis of past experience, however, so great a potential might not be 

expected for a province that contains only a small 

number of type C deposits as for a province that in 

addition contains one or more type A, or even type 

B, deposits. 

Caution: The presence of a large number of type 

C deposits may not represent the economic abundance of a commodity. First, these data points indicate the reported presence of the commodity 

but, more often than not, probably denote subeconomic possibilities, rather than economic 

5 

realities, that will require further investigation 

or changes in economic conditions. Furthermore, 

many of these data were obtained by a diverse 

group of geoscientists whose primary investigative purposes may not have been resource assessment, and so resource values may not have 

been recognized or fully reported. Some type C 

deposits may ap~ar on several province maps 

where a commodity occurs as a primary, coproduct, byproduct, or presently unrecovered constituent. 

Additional information and references to the 

more specific resource literature on the metal and 

nonmetal commodities selected for these maps 

were given by Brobst and Pratt (1973) and the 

U.S. Bureau of Mines (1976a). National resource 

issues, to which province maps are relevant, were 

discussed further by the U.S. Geological Survey 

(1975). 

USE AND USERS OF PROVINCE MAPS 

The resource information on a mineral province 

map is intended for a wide audience. These maps 

provide nontechnical users with a simplified 

visual appreciation of the status of basic data on 

the availability of mineral commodities, as well 

as of the importance and need for better information. Legislators and administrators who devise 

land-use policies and workable new mining and 

leasing laws, make equitable environmental regulations, or develop and approve foreign 

agreements should gain added awareness of some 

of the underlying scientific and technological constraints on domestic-resource supply as well as 

learn where domestic supplies occur or may be 

developed, assuming that the required additional 

resource research is completed. Resource generalizations are also useful to governmental 

analysts and scientists who must plan and justify 

resource information and research programs that 

are responsive to long-term national and industrial needs. 

LIMITATIONS AND REVISION OF PROVINCE MAPS 

The province maps in the atlas are considered 

preliminary because the data-some outdated, 

some incomplete-were collected for different 

purposes by many observers. We recognize also 

that the evaluations for many commodities are 

not consistent throughout the conterminous 

United States, nor do they benefit adequately 

from resource industry expertise and information. 
The small scale of the maps, the consolidated 

geologic data (presently lumped into broad age, 

composition, and structure categories), and the 

possibly inaccurate evaluations, owing to sparse 

or fragmentary data, may make the generalized 

analyses on these maps somewhat presumptive. 

Hopefully, an awareness of these limitations has 

permitted as accurate a presentation as possible 

and will provide the stimulus to identify new 

goals or opportunities for subsequent improved 

maps. 

Meanwhile, if these maps are incomplete or defective, or fall short of fulfilling the stated purposes, constructive advice from their users is welcome so that the data can be further revised and 

upgraded. Improved maps will be possible once 

the gaps in information are filled; critical reviews 

by mineral industry scientists are particularly 

important. Such improved maps will enable a 

knowledgeable public to have an impact on 

national-resource policy decision, particularly 

those that may result in legislation. 

A COMMON DENOMINATOR FOR 

RESOURCE EVALUATION 

Resource materials have come to be measured 

in a variety of production units that may make it 

difficult to understand the relations between 

units or to make direct value comparisons between commodities with other national assets; all 

materials, however, have a monetary value that 

is readily understood. To make the maps understandable and to provide a basis for comparing 

mineral resources with other national assets, 

traditional measurements in pounds, units, 

flasks, ounces, or long, short, and metric tons 

have been converted to 1978 U.S. dollars on the 

basis of average prices published by the U.S. 

Bureau of Mines (1979). Dollar values for specific 

critical commodities are shown in table 1, which 

also indicates the orders of magnitude of types A 

and B deposits for each of the metals or nonmetals. Where a given deposit has produced the commodity as a coproduct, this valuation represents 

the best estimate for that specific coproduct or 

byproduct rather than the total value of all production from the deposit. Establishing a value for 

the metal content of some ores (such as chromite) 

that are sold in variable-composition grades is a 

problem, but the averages assumed in these cases 

should not invalidate the general and limited 

comparisons drawn. 

6 

Although the dollar value of mined minerals 

provides a standard for discussion of an individual commodity's importance as well as for comparison of one commodity with another, dollar 

value may not convey the true worth of a mined 

material. For example, the value of bauxite ore, 

from which aluminum metal is derived, is about 1 

percent of the value of the metal produced therefrom. The varying value of money itself over time 

is moderated somewhat by the use of 1978 U.S. 

dollars, which brings past mineral production 

closer to the perspective of present decisions. Such 

data often show that the value of current and past 

domestic production for some mineral commodities is an almost insignificant fraction of one 

year's industrial demand, whereas for other 

commodities the resource endowment has been 

and can be expected to continue to be a substantial part of the Nation's economy. Dollar value is 

also a possible consideration in comparing the 

value of a given mineral product in an area with 

the competing value of the same area for other 

purposes, in order to assess relative worth in 

land-use and environmental-impact analyses. 

Does the dollar value of a deposit based on the 

raw material mined represent a true value for 

such determinations? The answer is no; the ultimate worth of metal and nonmetal minerals to 

the Nation is much greater than the simple estimated values listed in table 1. U.S. Bureau of 

Mines (1978) estimates for nonfuel mineral contributions to the U.S. economy in 1977 (fig. 1) 

demonstrate this point. 

Once processed, domestically extracted materials (valued at $17 billion) plus additional imports of raw materials and recycled scrap (valued 

at $3 billion each) achieve a total worth of $170 

billion, an increase by a factor of nearly 71h. In 

turn, when imports of processed mineral materials are combined with these domestically processed materials, a significant but unknown increment attributable to the fabrication and other 

uses of mineral materials contributes ultimately 

to the $1,890 billion U.S. gross national product. 

Thus the true value of the extractable materials 

in a mineral deposit is incalculable in a specific 

sense because of the substantial values added 

once mineral materials are processed and used. 

One should, of course, not lose sight of that added 

intangible resource value: the possibility of 

domestic deliverability of a strategic but now 

subeconomic mineral material when it becomes 

unavailable elsewhere. 
U.S. NATURAL 

RESOURCES: DOMESTIC MINERAL 

RAW MATERIALS: 

PROCESSED MATERIALS 

OF MINERAL ORIGIN: 

U.S. ECONOMY: 

ROCKS, MINERALS, 

WATER, AIR, ETC. 

EXTRACTIVE 

INDUSTRIES, 

INCLUDING: 

~~N~.O~~~~[.PER ORE,t--::---M-IN_E_RA_L ___ +I STEEL. ALUMINUM, 

COPPER, OTHER METALS, 

BRICK, GLASS, CEMENT, 

CHEMICALS, PLASTICS, 

FERTILIZERS, ETC. 

GROSS 

NATIONAL 

PRODUCT: MINING, 

QUARRYING, 

L-----------1 ETC. 

U.S. FIRMS 

AND (OR} 

FOREIGN FIRMS 

STONE, ETC. 

VALUE: 

$17 BILLION 

IMPORTS INTO U.S. 

OF MINERAL RAW 

MATERIALS: 

COPPER ORE, IRON ORE, 

BAUXITE, ETC. 

VALUE: 

$3 BILLION 

VALUE: 

$170 BILLION 

----........................................... , 

~::~:'~NR~~~iZ. RECLAIMING 

MATERIALS: ~~~CLING 

SCRAP IRON, GLASS, l~. ~~~~~~~~~~. · · · · · ETC. • SCRAP DEALERS, 

: ETC. 

VALUE OF l 

OLD SCRAP: l 

$3 BILLION l •••••••-••••w••••••""•"'••• 

IMPORTS INTO U.S. 

OF PROCESSED 

MATERIALS OF 

MINERAL ORIGIN: 

STEEL. ALUMINUM, 

CHEMICALS, ETC. 

VALUE: 

$17 BILLION 

$1 ,890 BILLION 

.............. '! ..... U.S. SCRAP AND 

WASTE MATERIALS: 

IRON AND STEEL, 

ALUMINUM, COPPER, 

BRASS, BRONZE, 

LEAD, ZINC, 

GLASS, BRICK, ETC. 

EXPORTS FROM U.S. 

OF MINERAL RAW 

MATERIALS 

AND PROCESSED 

MATERIALS OF 

MINERAL ORIGIN: 

MOLYBDENUM, 

CHEMICALS, STEEL, 

FERTILIZERS, ETC. 

VALUE: 

$15 BILLION 

FIGURE 1.-Role of nonfuel minerals in U.S. economy, with estimated values for 1977 (U.S. Bureau of Mines, 1978, p. 17). 

COMMENTS ON RESOURCE TERMINOLOGY 

USED 

Discussion of mineral provinces requires the 

definition and use of certain technical and 

often-misunderstood resource terms that in the 

past have caused confusion among many 

nonspecialists; this confusion can be eliminated 

here by the substitution of a simplified terminology for nontechnical study and use of this atlas. 

7 

For the benefit of resource specialists, scientists, 

economists, and mining technologists, the U.S. 

Geological Survey (1976) has published an official 

classification of the types of resource categories 

and defined the precise resource terms to be used 

in technical communications. For the atlas, however, which in large part is aimed at a nontechnical audience, the resource terms needed to explain core issues are here reduced to three simple 
categories, whose relation can be expressed by the 

equation 

Resources =minable minerals +potentially 

minable materials 

and which are shown in figure 2 for comparison 

with the diagram in the official classification 

(U.S. Geological Survey, 1976, p. A2). Use of these 

much-generalized terms here does not, however, 

constitute a change in official policy or a redefinition of the official terminology. 

On the province maps and accompanying texts, 

the term ~~resources" includes all categories of 

mineral materials that are currently useful or 

that may someday become useful. ~~Resources" 

thus includes ore in active mines, comparable ore 

yet to be discovered, and low-grade subeconomic 

materials that may become economic at some future time. For subeconomic materials, however a 

minimum content of a commodity above its clarke 

(average in crustal rock) distinguishes a potentially minable resource material from average 

rocks of the Earth's crust, most of which are not 

yet considered useful commodity sources. A minable mineral is a known usable mineral commodity (such as ore or reserve) that can be extracted 

economically at the present time. All other resource materials on figure 2 are considered to be 

potentially minable materials; these materials include all undiscovered IJ1inable minerals, as well 

as subeconomic materials that may become minRESOURCES 

Known Undiscovered ~>- MINABLE Hypothetical I Speculative ~ ~ 

2 

MINERALS : ~\,~ ~ ~ 

~\~~ ~g 

·~ ~""~ s II ~g g ~"<\\ ~~\~\.: : ~ R: 

~ ~o-1\€ ~~"<\ 1 t : ~ 2 :l ____ l_ __ ___l___ ~ 0 

fJ) CRUSTAL ROCK MATERIALS o u ~--------~~-~~ w High Low 

GEOLOGIC KNOWLEDGE ABOUT 

RESOURCES 

FIGURE 2.-Simplified mineral-resource terms (modified from 

U.S. Geological Survey, 1976) and resource area of special 

concern (fenced). Arrows indicate expected flow of resources 

from the undiscovered and subeconomic, potentially minable minerals category into the minable minerals category as 

a result of improvements in geologic knowledge and more 

favorable economic factors. 

able under more favorable economic conditions 

(higher prices) or because of improved technology. 

Two other useful terms are subcategories of undiscovered materials (U.S. Geological Survey, 

1976): hypothetical, resources that are extensions 

of known deposits, or expectable deposits in favorable geologic environments elsewhere; and 

speculative, resources that may occur as wellknown types of deposits in a favorable geologic 

setting but whose existence has eluded detection, 

or deposits that may occur in geologic environments as yet unrecognized to be favorable for the 

occurrence of a specific mineral. On the mineral 

province maps, hypothetical resource possibilities 

have been considered but speculative resources 

have not. Even though speculative resources are 

beyond the scope of the map data base, they are 

possibilities that should not be overlooked or discounted. In a successful course of events, as 

geologic knowledge and economic factors improve, materials flow upward into the minableminerals category in the upper left-hand comer of 

the diagram (fig. 2) and thus become deliverable 

to the industrial production system. 

WHAT ARE CRITICAL MINERALS? 

The United States has a critical need for resource information on all the commodities listed 

in table 1 and included on the accompanying mineral province maps. These commodities were 

selected in part on the basis of recommendations 

by a joint task force of the Council on International Economic Policy and the National Security 

Council (Council on International Economic Policy, 1974), and by resource analysts of the U.S. 

Bureau of Mines (1976a). An explicit definition of 

a critical commodity from a mineral-resource 

point of view is difficult, may vary with time and 

circumstances, and may ultimately depend on 

whether the available resource can be produced 

under present or anticipated economic, legal, 

political, and technological conditions. The following list shows a number of wide-ranging factors that must be considered: 

1. The commodity is an essential industrial or 

strategic material. 

2. Sufficient minable quantities of the commodity are not known to occur in the United 

States. 

3. The possibility that the commodity may be 

geologically available as a potential resource is unknown or undetermined. 
4. Almost no current U.S. production capacity, 

skilled technicians, or existing technological know-how exists to develop the commodity. 

5. A marked increase in use of the commodity is 

anticipated, such as a new demand to 

achieve the national goal of increased energy production. 

6. Import dependence of the commodity is 

greater than 50 percent. 

7. The known source of the commodity is in a 

politically unstable international area. 

8. The commodity is subject to potential cartel 

restrictions. 

9. Few or poor substitutes for the commodity 

exist. 

10. U.S. resource potential for substitute materials is nonexistent or undetermined. 

11. Technology for utilization of substitutes or 

reclamation from scrap is undeveloped. 

12. Irretrievable losses or dissipation in resource 

use preclude recycling of the commodity. 

13. Energy cost to produce the commodity is 

high, especially for lower grade ores. 

14. Production efforts entail environmental 

hazards or legal prohibitions. 

15. Current lack of capital investment in resource industries, because of present low 

rates of return, can be e~pected to extend 

an already long leadtime to production. 

A NEED FOR CONCERN ABOUT DOMESTIC 

RESOURCES 

Although adequate resources of most materials 

are presently available from world sources, many 

long-term (5-10 year or more) uncertainties 

about continued availability exist that prudent~ 

nations need to examine and evaluate, one of the 

most important of which is the capability for selfsufficiency. The future long-term domestic supply 

of many critical mineral commodities depends on 

a number of factors, in particular an understanding of their geologic characteristics. For some 

commodities, the geologic environment is well 

known and chances for new discoveries are good; 

for others, knowledge is minimal and thus little is 

know about their resource potential. The basic 

supply problem, however, may be more one of deliverability of a critical resource than its existence. A first step toward gaining a measure of 

national self-sufficiency or understanding the im9 

possibility of attaining it is systematically to collect knowledge about the availability of domestic 

resources, particularly those that may be on federally owned lands (Bennethum and Lee, 1975). 

The metal and nonmetal mineral province maps 

provide a qualitatively useful, even if incomplete, 

assessment of specific areas that have resource 

possibilities in the United States and indicate additional areas that may need more careful and 

complete examination. From such maps, plans 

can be made to improve the data base and analytical capability for a more critical evaluation of 

domestic-resource availability. 

THE PRESENT MINERAL-RESOURCE SITUATION 

The economy of the UnJted States has historically had a solid base of domestic mineralresource industries but in recent years has increasingly relied on imports of raw materials. The 

U.S. Bureau of Mines (1976b) estimated that industry ultimately contributed 19 percent of the 

gross national product in 1976 by use of both 

domestic and foreign mineral materials. According to another survey (Mining Magazine, 1976), 

the United States, which continues to be a major 

mineral producer, operated 188 (17 percent) of the 

1,126 mines (other than coal) that contributed 90 

percent of the Western World min,eral production 

in 1975. Domestic production, however, has not 

kept up with demand, and of 19 critical commodities, the Nation now imports more than 50 

percent of 9: aluminum, the platinum group, 

fluorine, nickel, tantalum-niobium, mercury, 

titanium, tungsten, and zinc (U.S. Department of 

the Interior, 1977, p. 24). 

Softening of the once much more solid domestic 

base for industrial self-sufficiency is indicated by 

these statistics, the list of critical factors mentioned above, and the net import dependence of a 

group of major imported commodities (tables 1, 2) 

in 1975 and 1978. These data should excite a 

greater concern for the uncertainties implicit in 

import dependence and assumed uninterrupted 

access to resources from abroad. For some mineral 

materials, however, self-sufficiency has always 

been an unsolvable problem because the geologic 

environment in the conterminous United States 

is inhospitable for their concentration. The mineral province maps graphically define specific regions in the United States where past and present 

production has been concentrated and where in-
TABLE 2.-Net import dependence of selected minerals and metals in 1975 

[From U.S. Bureau of Mines, 1976] 

Mineral 

Co 1 umbi urn --------------------------

Mica (sheet) -----------------------

Stronti urn --------------------------

Manganese --------------------------

Coba 1 t -----------------------------

Tanta 1 urn ---------------------------

Chromi urn ---------------------------

Asbestos ---------------------------

Aluminum (ores and metal) ----------

Fluorine 

Bismuth 

Platinum group metals --------------

Titanium (rutile) ------------------

Tin --------------------------------

Mercury ----------------------------

Ni eke 1 -----------------------------

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

Tellurium --------------------------

Se 1 eni urn ---------------------------

Antimony ---------------------------

Tungsten ---------------------------

Cadmi urn ----------------------------

Po tass i urn --------------------------

Go 1 d -------------------------------

Gypsum -----------------------------

Vanadi urn ---------------------------

Sari urn -----------------------------

Petroleum (including LNG) ----------

Si 1 ver -----------------------------

Iron -------------------------------

Ti tani urn (ilmenite) ----------------

Sa 1 t -------------------------------

Pumice 

Cement 

Lead -------------------------------

Natura 1 gas ------------------------

Magnesi urn (nonmetallic) ------------

Amount 

imported 

(percent) 

100 

100 

100 

99 

98 

95 

91 

86 

85 

82 

80 

80 

78 

75 

73 

71 

64 

59 

58 

56 

54 

50 

49 

45 

39 

36 

35 

35 

30 

29 

28 

4 

4 

10 

Major foreign source(s) 

Brazil, Thailand, Nigeria 

India, Brazil. Malagasy 

Mexico, U.K., Spain 

Brazil, Ga_bon, Australia, South Africa 

Zaire, Belgium-Luxembourg, Finland, 

Norway, Canada 

Thailand, Canada, Australia, Brazil 

South Africa, USSR, Turkey, Rhodesia 

Canada, South Africa 

Jamaica, Surinam, Australia, Dominican 

Republic 

Mexico, Spain, Italy 

Peru, Japan, Mexico, U.K. 

South Africa, U.K. , USSR 

Australia, India 

Malaysia, Thailand, Bolivia 

Canada, Algeria, Mexico, Spain 

Canada, Norway 

Canada, Mexico, Australia. Honduras, Peru 

Peru, Canada 

Canada, Japan, Mexico 

South Africa, People's Republic of China, 

Bolivia, Mexico 

Canada, Bolivia, Thailand, Peru 

Mexico, Canada, Australia, BelgiumLuxembourg 

Canada 

Canada, Switzerland, U.K., France 

Canada, Mexico, Jamaica 

South Africa, Chile, USSR 

Ireland, Peru, Mexico 

Canada, Venezuela, Nigeria, Saudi Arabia, 

Virgin Islands 

Canada, Me xi co, Peru 

Canada, Venezuela, Japan, Common Market (EEC) 

Canada, Australia 

Canada, Mexico, Bahamas, Chile 

Greece, Italy 

Canada, Bahamas, Norway, U.K. 

Canada, Peru, Australia, Mexico 

Canada 

Greece, Ire 1 and, Japan 
completely evaluated resource possibilities are 

known or predicted to exist. 

Access to those minable resources that are 

known to be geologically available in the United 

States is also uncertain. Can domestic supplies 

ever provide all consumer needs? The production 

trends for many mineral commodities (fig. 3) show 

that in spite of ongoing exploration for and development of new mines, a continued decrease in the 

overall production trend may be anticipated at 

the present stage of mineral maturity, as predicted by Hewett (1929). Thus, present levels of 

domestic production alone will never fill the supply gap (stippled area) so long ·as consumption 

mounts. Furthermore, unless mined materials 

are replaced in the form of expected extensions of 

known deposits (hypothetical resources) or new 

mines in virgin mineralized terrains, the domestic production curve will decline at a faster rate 

than predicted. Even if the present consumption 

rate were held at a zero-growth level through 

added effective conservation practices, by reduction of demand, and by introduction of substiPast 

tutes, the resource gap probably could not be 

closed. Alternative solutions of the supply problem would be a further drop in demand, more effective recycling of scrap materials, increased dependence on imports, and increase in the rate of 

discovery of new domestic deposits, or a combination. The United States has the potential for production of most critical minerals and other needed 

mineral materials. We now need to know where 

they are, in what form and quantity, and at what 

cost. 

THE PROBLEM: PRESENCE IN THE EARTH'S CRUST 

VERSUS DELIVERABILITY 

Although mineral materials exist in the 

Earth's crust in great abundance, they may not 

always be readily deliverable to users. Brooks and 

Andrews (1974) showed that virtually inexhaustible amounts of most mineral commodities are 

present in 1 km3 of the average exposed continental crust: aluminum, 200 million; iron, 100 million; zinc, 800,000; and copper, 200,000 metric 

tons. Such estimates have been used to minimize 

1979 

TIME 

Future 

FIGURE 3.-Diagrammatic projections of past and future national supply and consumption rates for a typical commodity (based 

on Hewett, 1929), and the resource gap (stippled) that develops where supplies are dependent on a pattern of diminishing 

domestic production and generally higher current rates of consumption, whether projected at an average percent of increase 

per year or held at a zero percent (maintain constant level) of growth in the future. The resource bulge (open dots) typifies 

past domestic production when mineral materials were available for export. Area A (diagonal lines) represents expected 

depletion of those minable minerals that existed in 1979, as a result of continuing domestic production; the predicted level of 

domestic production (heavy dashed line) can be maintained only if losses (area A) are replaced by some combination of 

discovery of hypothetical resources, additional new min-es placed in production, conversion of subeconomic resources into 

minable minerals, or accelerated conservation through recovery from (recycled) scrap materials. 

11 
the opposing Club of Rome (Meadows and others, 

1972) concept that the world faces an approaching 

shortage of many critical mineral materials. Severe technological and economic barriers, however, effectively preclude recovery of most elements at crustal abundance levels (Skinner, 

1976). Minable deposits exist where special 

geologic processes have concentrfited the commodity in singular rock types in amounts substantially higher than crustal abundance; such 

deposits are relatively small and are scattered 

and buried in the crust much like plums in a pudding. Every reason exists, however, on geologic 

experience and evidence, to believe that adequate 

mineral resources will continue to be found as 

needed; but such resources have finite limits, and 

their production history shows a peak and eventual decline. Hubbert (1969) clearly demonstrated 

this trend for oil. Not only are resources limited, 

nonrenewable geologic entities, but resource production is also uncertain and irregular, both at 

home and from abroad. Restrictions on the delivery of essential commodities may result from insufficient knowledge or ingenuity in the discovery 

and production of new resources, or from manmade political, social, environmental, and economic constraints. 

There may seem to be little compelling economic 

urgency at the present time to identify domestic 

hypothetical-resource targets, in the expectation 

that increased prices and new technological developments will offset deliverability gaps abroad. 

But increasing stiff competition for world mineral 

resources between developed nations, as well as 

unsettled political conditions in some less developed nations on which the United States depends 

heavily for supplies, poses ever-present threats of 

restricted access to critical raw materials. Furthermore, increasing time is required to find, develop, and bring deposits into production, and 

proportionately higher energy and environmental 

costs will have as big an impact on the deliverability of foriegn as of domestic resources. Such 

uncertainties are the basis for an increasing 

urgency for scientific study and planning to identify and evaluate the future domestic supply situation and its attendant problems. 

What can the Nation count on in an emergency? The magnitude of the problem of 

domestic-resource availability can only be established through systematic assessment of the 

geologic possibilities for identifying and extend12 

ing the national-resource endowment. Although 

deliverability depends on nongeologic factors, a 

solid base of geologic information on the existence 

of the commodity to be delivered is required. 

GOOD RESOURCE DATA-MORE THAN AN 

INVENTORY 

Effective national planning requires, first of all, 

a resource data base sufficient to catalog or inventory past production activity and known nshelf 

item" mineral resources. The present base for the 

critical commodities shown on the mineral province maps is extensive but incomplete, often scattered and unevaluated. The formidable task of assembling and evaluating such information for an 

adequate data base should justify concerted professional action to identify imperfections, fill 

gaps, correct errors in the present base, and provide the basis and climate for obtaining critical 

new information. In addition, comprehensive and 

systematic geologic, geochemical, and geophysical examinations of future resource possibilities 

in the conterminous United States must be made 

for all types of critical minerals to avoid overlooking those commodities that exist but which were 

not of economic interest and do not appear in an 

inventory of past activity. 

RELEVANCE OF GEOLOGIC KNOWLEDGE 

TO MINERAL AVAILABILITY AND METAL 

AND NONMETAL MINERAL PROVINCES 

Because the most obvious and readily accessible economic mineral concentrations occurring in 

or close to the Earth's surface have already been 

identified and largely consumed, the Nation's future interests can best be served by a more diligent and imaginative use of existing facts and 

theories to find concealed sources or new modes of 

occurrence of critical metals and nonmetals. 

Geologic expertise can provide important insights 

in this search, but we have only begun to mobilize 

potential scientific and technological capabilities. 

Experience demonstrates that undiscovered potentially minable materials will be found in direct 

proportion to the quality, amount, and organization of scientific research and to the recognition 

and evaluation of special geologic clues that will 

lead to the identification and location of new deposits. Ores result from geologic processes both 

within the crust and on the surface but are 

created in limited amounts and in restricted 

areas. The sequential stages in the formation of 
some types of rocks seem to be closely related to 

the concentration of specific ore materials (Stanton, 1972). Thus a renewed emphasis is needed on 

metallogenesis, the systematic study of the origin(s) of mineral deposits that occur in the Earth's 

crust in terms of their unique spatial, temporal, 

compositional, and structural characteristics. 

What are the key geologic features and theoretical possibilities that will provide clues for future 

mineral discoveries? Several pioneering efforts to 

find and characterize these geologic guideposts in 

the Western United States were summarized by 

Jerome and Cook (1967) and Noble (1970). Guild 

(1972, 1978) has called attention to the stilldeveloping plate-tectonic theory for the formation 

of the Earth's crust as a new and useful unifying 

genetic model for the formation of rocks and their 

characteristically associated ore deposits. On the 

basis of this theory and supporting geologic, 

geophysical, and oceanographic evidence, the 

crust of the Earth is postulated to consist of a 

number of moving and interacting surface plates, 

which contain distinctive continental and oceanic 

crustal rock components (Mitchell, 1976). The 

plate-tectonic model, though complex and incompletely understood when examined in detail, may 

lead to new evidence or reinterpretation of the old 

evidence. 

For example, the mineral province maps have 

already provided a data base on which the location of deposits and occurrences of certain specific 

commodity types are correlated with their formation in rocks and structures of an old continent 

and later accreted oceanic and island-arc crusts 

(Tooker, 1979). These data seem to show a rough 

tripartite zonation of certain metals and nonmetals, predominantly in crustal rocks of the older 

continent, younger oceanic crust, and intervening 

broad overlapping border zone. Mercury, 

chromium, nickel, platinum, and in part manganese and copper, for example, seem to be closely 

associated both spatially and time-stratigraphically with mafic, -Ultramafic, and ophiolitic 

intrusive rocks, and with volcanogenic sedimentary rocks·in oceanic crust. As a generalization, in 

any one mineral province these metals are concentrated simply as segregation, vein, or 

stratiform deposits. 

Base and ferrous metals and fluorine, on the 

other hand, seem to be concentrated along the 

margins of and in a few preferred broad 

northeast-trending zones within the older conti13 

nental crust. The occurrence of these metals in 

complex mixed deposits, often varying widely in 

age within a province, suggests also that ore materials may have been remobilized during successive heating events in the older continental plate. 

Tungsten and tin occur in skarn zones and veins, 

generally closely associated with large granitoid 

plutons that formed along a broad boundary zone 

between the older continental and younger 

oceanic crusts. 

On some maps, where appropriate for the particular commodity, we have shown the location of 

inferred structural boundaries between the older 

continental and later accreted oceanic and 

island-arc crusts. This boundary in the Cordilleran belt, as proposed by Stewart (1978), is the 

supposed west limit of the crust that contains ancient (Archean and Proterozoic) crystalline basement rocks and represents the west edge of the 

older continental crustal plate at the end of Proterozoic time (table 3). In later (Phanerozoic) 

time, oceanic-type crustal rocks are believed to 

have been added by accretion and to have expanded the continent westward. An east structural boundary in the Appalachian belt (Thomas, 

1977), marked in part by a prominent fault zone, 

separates Archean and Proterozoic basement 

rocks from later eastward additions to the continental mass. This boundary trends northeast into 

Canada, but its abrupt south end in Alabama 

coincides with the termination of exposures of the 

Appalachian belt, which is also concealed by 

younger Coastal Plain sedimentary rocks. Within 

the cratonic block (stable central part of the 

crust), geologists have recognized ancient riftand-flaw (fault) zones that also seem to provide 

sites for metal and nonmetal concentration (Sawkins, 1976; Tooker, 1979). 

The sketchy information on the accompanying 

mineral province maps suggests other relations 

TABLE 3.-Relative age spans of major geologic units used in 

this report and in province map discussions 

Era Eon 

Cenozoic } 

Mesozoic Phanerozoic 

Paleozoic 

~~~:~!~ ~J Precam- Proterozoic} 

brian 

Proterozoic X 

Archean 

Approximate duration 

(m.y. B.P.) 

65 to present 

232 to 65 

600 to 232 

800 to 600 

1,600 to 800 

2,500 to 1600 

2,500 and older 
between resource occurrences and geologic features and provides a tantalizing prelude to more 

detailed metallogenetic studies, which are needed 

to refine and provide real meaning for these stilltentative observations. The pattern of mineral 

province distribution may, in some cases, provide 

important geochemical clues to discovery of the 

location and character of buried crustal structures. The goal of metallogenetic research is to 

provide an increasingly accurate assessment of 

the resource potential of mineralized regions that 

will provide the basis for improved exploration 

technology. 

Old data, though, however reworked, are insufficient. A new generation of systematically collected and integrated geologic, geochemical, and 

geophysical information is vital for completing 

the mineral resource assessment of the conterminous United States. Such data are essential 

both to stimulate the development of new resource theory and to make more perceptive use of 

present-day concepts. Thus a consortium of public, university, and private-foundation geologic 

research talents, now largely uncoordinated for 

such purposes, should be mobilized. But these efforts will be insufficient to fill the geologic 

resource-information gap without substantial 

help from private industry. Greater participation 

by the mineral industry, which traditionally has 

been inhibited from full participation by interindustry competition and proprietary classification 

of data, is therefore requisite for bringing the full 

impact of geologic methods to bear on the solution 

of resource problems. 

REFERENCES CITED 

Bayley, R. W., and Muehlberger, W. R., compilers, 1968, 

Basement rock map of the United States, exclusive of 

Alaska and Hawaii: Washi):lgton, U.S. Geological Survey, 

scale 1 : 2,500,000. 

Bennethum, Gary, and Lee, L. C., 1975, Is our account overdrawn?: Mining Congress Journal, v. 61, no. 9, p. 33-49. 

Brobst, D. A., and Pratt, W. P., 1973, United States mineral 

resources: U.S. Geological Survey Professional Paper 820, 

722 p. 

Brooks, D. B., and Andrews, P. W., 1974, Mineral resources, 

economic growth, and world population: Science, v. 185, 

no.4145,p. 13-19. 

Clark, A. L., Berg, H. C., Cobb, E. H., Eberlein, G. D., MacKevett, E. M., Jr., and Miller, T. P., 1974, Metal provinces 

of Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I-834, scale 1 : 5,000,000. 

Council on International Economic Policy, 1974, Special 

report-critical imported materials: Washington, U.S. 

Government Printing Office, 49 p. 

14 

Guild, P. W., 1972, Metallogeny and the new global tectonics, 

in Mineral deposits: International Geological Congress, 

24th, Montreal, Canada, 1972, Section 4, Proceedings, p. 

17-24. 

--1978, Metallogenesis in the western United States: 

Journal of the Geological Society, London, v. 135, no. 4, p. 

355-376. 

Hewett, D. F., 1929, Cycles in metal production: American 

Institute of Mining and Metallurgical Engineers Year 

Book 1929, p. 65-93. 

Hubbert, M. K., 1969, Energy resources, chap. 8 of National 

Academy of Sciences-National Research Council, Resources and man: San Francisco, W. H. Freeman and 

Company, p. 157-242. 

Jerome, S. E., and Cook, D. R., 1967, Relation of some metal 

mining districts in the western United States to regional 

tectonic environments and igneous activity: Nevada 

Bureau of Mines Bulletin 69, 35 p. 

King, P. B, compiler, 1969, Tectonic map of North America: 

Washington, U.S. Geological Survey, scale 1: 5,000,000, 

2 sheets. 

King, P. B., and Beikman, H. M., compilers, 1974, Geologic 

map of the United States (exclusive of Alaska and 

Hawaii): Reston, Va., U.S. ·Geological Survey; scale 

1 : 2,500,000, 3 sheets. 

Meadows, D. H., Meadows, D. L., Randers, J~rgen, and 

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

York, Universe Books, 205 p. 

Mining Magazine, 1976, International mining survey: v. 135, 

no. 3, p. 233-244. 

Mitchell, A. H. G., 1976, Tectonic settings for emplacement of 

subduction related magmas and associated mineral deposits, in Strong, D. D., ed., Metallogeny and plate tectonics: 

Geological Association of Canada Special Paper 14, p. 

3-22. 

Noble, J. A., 1970, Metal provinces of the western United 

States: Geological Society of America Bulletin, v. 81, no. 

6, p. 1607-1624. 

Sawkins, F. J., 1976, Metal deposits related to intracontinental hotspot and rifting environments: Journal of Geology, 

v. 84, no. 6, p. 653-671. 

Skinner, B. J., 1976, A second iron age ahead?: American Scientist, v. 64, no. 3, p. 258-269. 

Stanton, R. L., 1972, Ore petrology: New York, McGraw-Hill, 

717 p. 

Stewart, J. H., 1978, Rift systems in the western United 

States, in Ramberg, I. B., and Neumann, E. R., eds., Tectonics and geophysics of continental rifts: Dordrecht, Holland, D. Reidel, p. 89-110. 

Thomas, W. A., 1977, Evolution of Appalachian-Ouachita salients and recesses from reentrants and promontories in 

the continental margin: American Journal of Science, v. 

277,no. 10,p. 1233-1278. 

Tooker, W. W., 1979, Metal provinces and plate tectonics in 

the conterminous United States, in Ridge, J.D., ed., Papers on mineral deposits of western North America: 

Nevada Bureau ofMines and Geology Report 33, p. 33-38. 

U.S. Bureau of Mines, 1976a, Mineral facts and problems, 

1975 edition: U.S. Bureau of Mines Bulletin 667, 1,291 p. 

--1976b, Minerals & materials-a monthly survey: July 

1976, p. 3. 

--1978, Minerals & materials-a monthly survey: February 1978, 63 p. 
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U.S. Department of the Interior, 1977, Mining and minerals 

policy: Washington, U.S. Government Printing Office, 154 

p. 

U.S. Geological Survey, 1975, Mineral resource perspectives 

1975:U.S. Geological Survey Professional Paper 940,24 p. 

---1976, Principles of the mineral resource classification 

system of the U.S. Bureau of Mines and U.S. Geological 

Survey: U.S. Geological Survey Bulletin 1450-A, p. 

A1-A5. 

15