The Nature and Use 

of Copper Reserve and Resource Data 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 907-F 
COVER PHOTOGRAPHS 

1 2 3 4 

5 6 

7 8 

9 10 

11 12 13 14 

1. Asbestos ore 

2. Lead ore-Balmat Mine. N. Y. 

3. Chromite-chromium ore. Wash . 

4. Zinc ore-Friedensville, Pa. 

5. Banded iron formation ,Palmer. 

Michigan 

6. Ribbon asbestos ore. Quebec. Canada 

7. Manganese ore. banded 

rhodochrosite 

8. Aluminum ore, bauxite, Georgia 

9. Native copper ore, Keweenawan 

Peninsula. Mich: 

10. Porphyry molybdenum ore. Colo. 

11. Zinc ore. Edwards, N . Y. 

12. Manganese nodules, ocean floor 

13. Botryoidal fluorite ore. 

Poncha Springs, Colo. 

14. Tungsten ore, North Carolina 
The Nature and Use of 

Copper Reserve and Resource Data 

By DENNIS .P. COX, NANCY A. WRIGHT, and GEORGE J. COAKLEY 

GEOLOGY AND RESOU.RCES OF COPPER DEPOSITS 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 907-F 

A discussion of the use and limitations 

of copper resource data for 

production estimates, trends, and forecasts 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1981 
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Library of Congress Cataloging in Publication Data 

Cox, Dennis P. 

The nature and use of copper reserve and resource data. 

(Geology and resources of copper deposits) 

(Geological Survey professional paper ; 907-F) 

Bibliography: p. 

Supt. of Docs. no.: I 19.16:907-F 

1. Copper cores-United States. I. Wright, Nancy A., joint author. III. Title. IV. Series. V. Series: United States. 

Geological Suvey. Professional paper ; 907-F. 

TN443.A5Cti9 553.4'3'0973 80-607780 

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

Washington, D.C. 20402 
APPRAISAL OF MINERAL RESOURCES 

Continuing appraisal of the mineral resources of the United States is conducted by the U.S. Geological Survey in accordance with the provisions of the 

Mining and Minerals Policy Act of 1970 (Public Law 91-631, Dec. 31, 1970). Total 

resources for purposes of these appraisal estimates include currently minable 

resources (reserves) as well as those resources not yet discovered or not currently profitable to mine. 

The mining of mineral deposits, once discovered, depends on geologic, economic, and technologic factors; however, identification of many deposits yet to 

be discovered, owing to incomplete knowledge of their distribution in the 

Earth's crust, depends greatly on geologic availability and man's ingenuity. 

Consequently, appraisal of mineral resources results in approximations, subject 

to constant change as known deposits are depleted, new deposits are found, new 

extractive technology and uses are developed, and new geologic knowledge and 

theories indicate new areas favorable for exploration. 

This Professional Paper discusses aspects of the geology of copper as a framework for appraising resources of this commodity in the light of today's technology, economics, and geologic knowledge. 

Other Geological Survey publications relating to the appraisal of resources of 

specific mineral commodities include the following: 

Professional Paper 820-"United States Mineral Resources" 

Professional Paper 926-"Geology and Resources of Vanadium Deposits" 

Professional Paper 933-"Geology and Resources of Fluorine in the United States" 

Professional Paper 959-"Geology and Resources of Titanium in the United States" 

CONTENTS 

Paae 

Abstract ---------------------------------------------------------------------------------------------- Fl 

Introduction----------------------------------------------------------------------------------------- Fl 

Acknowledgments ------------------------------------------------------------------------------ Fl 

Definitions of terms --------------------------------------------------------------------------------- F'2 

Sources of data and methods of analysis----------------------------------------------------------- F'2 

Reserve data ----------------------------------------------------------------------------------------- F3 

Total ore and contained copper --------------------------------------------------------------------- F9 

Resource data ---------------------------------------------------------------------------------------- FlO 

Production data-------------------------------------------------------------------------------------- F13 

Anticipated copper production--------------------------------------------------------------..: ______ F14 

Requirements for new sources ---------------------------------------------------------------------- F15 

Conclusions------------------------------------------------------------------------------------------- F19 

References cited-------------------------------------------------------------------------------------- F19 

ILLUSTRATIONS 

Paae 

FIGURE 1. Graph showing U.S. reserve estimates and annual production 1925-1977----------------------------------------------------------- F8 

2. Plot showing tonnage and grade of U.S. copper deposits----------------------------------------------------------------------------- F9 

3. Graph showing declining yield of U.S. copper mines, 1936-1976 --------------------------------------------------------------------Fll 

4. Diagram showing classification of U.S. copper resources and reserves --------------------------------------------------------------F12 

5. Plot showing relation of annual production capacity to total copper in ore for 34 deposits ________________________________________ Fl3 

6. Diagram comparing copper demand with U.S. production capacity projections 1976-2030 _________________________________________ Fl5 

7. Graph showing cumulative reserves and resources at various grades in the United States, Chile, Peru, Zambia, and Zaire, 

as of 1977--------------------------------------------------------------------------------------------------------------------------F17 

8. Bar chart showing tonnage of copper in reserves and number of deposits brought into production that are potentially 

producible, graph showing cumulative copper in developed ore reserves, cumulative consumption, and cumulative 

mine production--------------------------------------------------------------------------------------------------------------------- F18 

TABLES 

Paae 

TABLE 1. Published reserves and resources of copper deposits in the United States---------------------------------------------------------- F3 

2. The sensitivity of U.S. copper reserves to economic conditions, in 1975 ------------------------------------------------------------ F7 

3. Total copper contained in typical deposits------------------------------------------------------------------------------------------- F9 

4. Copper resources of the United States as of 1978 -------------------------------------------------------------------------------------FlO 

5. Potential annual production from U.S. copper deposits as of 1978-------------------------------------------------------------------F14 

v 

GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA 

By DENNIS P. Cox, NANCY A. WRIGHT, and GEORGE J. COAKLEY1 

ABSTRACT 

Copper reserve, resource, and production data can be combined to 

produce disaggregated resource estimates and trends and, when combined with demand forecasts, can be used to predict future exploration and development requirements. 

Reserve estimates are subject to uncertainties due mainly to incomplete exploration and rapidly changing economic conditions. United 

States' reserve estimates in the past have been low mainly because 

knowledge of the magnitude of very large porphyry-copper deposits 

has been incomplete. Present estimates are considerably more reliable because mining firms tend to drill out deposits fully before mining and to release their reserve estimates to the public. 

The sum of reserves and past production yields an estimate of the 

total ore, total metal contained in ore, and average grade of ore originally in each of the deposits known in the United States. For most 

deposits, estimates of total copper in ore are low relative to the total 

copper in mineralized rock, and many estimates are strongly affected 

by the economic behavior of mining firms. A better estimate of the 

real distribution of copper contained in deposits can be obtained by 

combining past production data with resource estimates. 

Copper resource data are disaggregated into categories that include resources in undeveloped deposits similar to those mined in the 

past, resources in mines closed because of unfavorable economic conditions, resources in deep deposits requiring high-cost mining methods, arid resources in deposits located in areas where environmental 

restrictions have contributed to delays in development. The largest 

resource is located in the five largest porphyry deposits. These deposits are now being mined but the resources are not included in the 

present mining plan. Resources in this last category will not contribute to supply until some future time when ores presently being 

mined are depleted. 

A high correlation exists between total copper contained in deposits 

and annual production from deposits. This correlation can be used to 

predict roughly the potential production from undeveloped deposits. 

Large deposits annually produce relatively less metal per ton of copper contained than do medium and small deposits. 

Dividing reserves by annual production gives a depletion date for 

each copper mine. The sum of annual production capacity of all mines 

not yet depleted at any year of interest gives the minimum production 

capacity for that year. A graph of minimum production capacity by 

year combined with curves representing potential capacity from undeveloped identified resources can be compared with various demand 

scenarios to yield a measure of copper requirements from new sources. 

Since 1950 reserves have been developed in the United States at a 

rate of about 1 million tons of copper per year. Since 1960 the number 

of deposits developed per 10-year period has greatly increased without 

a commensurate increase in tonnage of copper. This is in part due to the 

fact that recent exploration successes have been increasingly represented by smaller and (or) lower grade deposits containing less metal. 

INTRODUCTION 

The objectives of this report are to describe the nature and limitations of the data on copper resources, to 

1 U.S. Bureau of Mines, 2401 E Street N.W., Columbia Plaza, Room 1102, Washington, 

D.C. 20241. 

show how the data can be used to produce resource 

estimates, and to illustrate some of the ways in which 

trends and forecasts can be derived from the data. 

Throughout this report, the reader is shown repeatedly that the data on copper resources contain inherent limitations on accuracy and that projections of 

future rates of resource development made from the 

data are affected by economic and technological factors 

that are themselves difficult to project. Although we 

acknowledge the limitations of such resource analysis, 

we feel that the analysis does illustrate methods of data 

treatment that may become useful parts of more complex models of copper supply. 

Many comprehensive reviews of U.S. copper reserves, 

technology, and supply have been made by specialists in 

the U.S. Bureau of Mines. Prominent among these are 

McMahon (1965), Everett and Bennett (1967), Bennett 

and others (1973), and Schroeder (1977). In contrast to 

these reports, our study focuses on some alternatives to 

the standard ways of treating copper-resource data and 

presenting results of analysis. Pioneering work on such 

alternatives, carried out by the Canadian Department 

of Energy, Mines, and Resources (Zwartendyk, 1974; 

Martin and others, 1976) has provided valuable stimulus 

to this study. 

The reader of this report will find useful a general 

knowledge of the geology of copper deposits, such as is 

reviewed in Titley and Hicks (1966), Cox and others 

(1973), Singer and others (1975), and Tourtelot and Vine 

(1976). The history of development of the U.S. coppermining industry, as described by Parsons (1933) and 

Joralmon (1973), is also useful as background 

information. 

ACKNOWLEDGMENTS 

The authors wish to thank Donald A. Singer, John H. 

De Young, Jr., Ted G. Theodore, Robert Gordon Schmidt, 

William J. Moore, Edward M. MacKevett, Jr., and 

S. Cyrus Creasey of the U.S. Geological Survey, and 

John D. Morgan, Jr., Harold J. Schroeder, and Harold J. 

Bennett of the U.S. Bureau of Mines for contributions to 

data on which this study was based, as well as for valuable discussion and criticism. We also acknowledge the 

cooperation of industry geologists, too numerous to 

mention, who have contributed information used in this 

study. 

F1 
F2 GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

DEFINITIONS OF TERMS 

Reserve and resource terminology has been standardized by the U.S. Bureau of Mines and the U.S. Geological 

Survey (1980). The definitions as they apply to copper 

are as follows: 

Resource. A concentration of naturally occurring copper in or on the Earth's crust in such form and 

amount that economic extraction from the concentration is currently or potentially feasible. 

Identified resources. Copper resources whose location, quality, and quantity are known or estimated 

from physical measurements or are inferred from 

geologic evidence. 

Undiscovered resources. Copper resources, the existence of which are only postulated, comprising deposits that are separate from identified resources. 

Reserve base. That part of identified resources whose 

location, quality, and quantity are known or estimated from physical measurements. 

Reserve. That part of the reserve base that could be 

economically extracted or produced at the time of 

determination. 

Usage within the copper industry differs from the 

foregoing definitions. An informal canvas of eight 

mining company chief geologists and consultants (J. J. 

Hemley, written common., 1978) revealed that the term 

"reserve" is used for any deposit whose location, 

quality, and quantity are known. Those reserves that 

have been determined to be economic are termed 

"economic reserves." Those reserves for which such a 

determination has not been made are called "geologic 

reserves." In this study, the following terms are 

equivalent. 

U.S. Btww~Gu qf Miftell aftd U.S. Geological Survey 

Identified resource 

Reserve 

lftduatry wrage 

Geologic reserve 

Economic reserve 

Other terms used in this study deal with measurements of the copper content of rock. These include 

the following: 

Ore. Copper-bearing rock that meets the criteria of 

reserves. 

Grade. The copper content, in weight percent, of a body 

of rock or ore in the Earth. 

Cutoff' grade. The lowest grade of ore that can be economically mined and milled in a specific deposit; that 

is, the lowest grade of ore that can be included in a 

reserve estimate. 

Yield. The net quantity of copper produced expressed 

as a percentage of ore mined, allowing for losses in 

mining and processing. 

Two classes of copper production are considered: 

Primary copper. That part of total production or consumption derived from mining. 

Secondary copper. That part of total production or 

consumption derived from recycling of various forms 

of scrap. 

Four main geologic types of copper deposits are referred to in this report: 

Porphyry-copper deposits. Masses of rock, tens of 

millions to billions of tons each, containing copper 

and molybdenum sulfides in closely spaced veinlets or 

in disseminated small grains. The deposits are irregular to roughly cylindrical and are in most places 

associated with an intrusive igneous rock that has a 

porphyritic texture. 

Massive sulfide deposits. Deposits of compact massive 

copper, iron, zinc, and lead sulfide, and associated disseminated sulfide, having tonnages on the order of 

tens of millions of tons. These deposits have tabular 

or podlike form and are inter layered with marine volcanic and sedimentary rocks. 

Sedimentary deposits. Layers of sandstone or shale 

containing disseminated copper minerals and, commonly, valuable amounts of silver. 

Copper-nickel deposits. Disseminated or compact 

masses of copper and nickel sulfide in mafic igneous 

intrusions. 

SOURCES OF DATA AND METHODS OF ANALYSIS 

Data on copper-ore reserves were taken mainly from 

Metals Sourcebook, a former bimonthly publication of 

McGraw Hill Company, and Mining Annual Review, an 

annual publication of Mining Journal. These publications summarize information from other miningindustry periodicals and company annual reports. 

Company prospectuses, prepared in compliance with 

the U.S. Securities and Exchange Commission, also 

were consulted for reserve data on several major deposits. Data on tOtal past production were taken mainly 

from geologic reports on deposits discussed in Titley 

and Hicks (1966), Ridge (1968), and other publications 

too numerous to be named here. Data on current annual 

production were mainly from Mining Annual Review 

and company annual reports. All data in this report 

were collected before January 1, 1979. 

Quantitative data are presented in English and metric units in tables and figures and in English units in the 

discussion sections. English units are used because of 

U.S. industry usage and because U.S. Bureau of Mines 

reserve data are in those units. For conversion purposes, 1 metric ton equals 1.101 short tons. Because 

many .of the estimates are not precise, metric -and English units expressed in tons are for practical purposes 

interchangeable. 

Analysis of data for this paper was assisted by the use 

of the Computerized Resource Information Bank 

(CRIB) of the U.S. Geological Survey and by the Minerals Availability System (MAS) of the U.S. Bureau of 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA F3 

Mines. CRIB is a computer file that contains location, 

exploration, mineralizatipn, deposit-description, and 

geological and mineralogical information on many mineralized areas. The. data file used in this study, a subset 

of CRIB, is accessed by the Geologic Retrieval and Synopsis Program (GRASP) (Bowen and Botbol, 1975). 

GRASP allows the user to retrieve data on selected 

copper deposits on the basis of given conditions and 

statistically to analyze and test the reliability of the 

data. Computer programs that use the copper file have 

been written to calculate estimated depletion dates or to 

determine the total production capacity of copper in the 

United States for any years of interest. 

The Minerals Availability System (MAS) was established to determine the availability of minerals to the 

United States from known domestic and foreign sources 

and to express this potential supply as a function of cost 

relative to time. In the process of identifying and evaluating significant mineral deposits, MAS is capable of 

analyzing the conditions that influence the use of minerals and of evaluating current technology as applied to 

the development of the reserve or resource. It can develop and cost related mining and processing systems 

using the MINSIM 4 financial-analysis program, and 

can perform financial analysis; it can be used to conduct 

comprehensive availability studies. An early version of 

the financial-analysis methodology was described by 

Bennett and others (1970). 

RESERVE DATA 

Ore-reserve estimates for selected U.S. deposits are 

shown in table 1. In interpreting the significance of such 

published reserve data, the reader should be aware of 

three facts. First, published copper-reserve figures frequently represent the total amount of copper contained 

in situ, and only a certain amount of these reserves is 

recoverable and will ultimately enter into the available 

supply. Second, the value of associated metals is important in the economics of copper reserves. Third, mining companies tend to be conservative in publishing 

reserve figures, and these figures should be considered 

as describing a minimum available supply. 

TABLE !.-Published reserves and resources of copper in the United States 

[From sources available as of January 1977; data in thousand short tons] 

Deposit name Company Type of Ore Grade Copper Associated 

depositl (percent copper) content metals 

Reference 

A. RESERVES IN OPERATING MINES AND ANNOUNCED DEVELOPMENTS 

Arizona 

Twin Buttes______ ANAMAX Mining Co____ OP-P 344,000 0.71 2,445 0.03 percent Mo 

Do---------- _____ do------------------- 262,000 1.11 688 

Securities & Exchange 

Commission, (SEC), mer- ger registration Form 

S-14 No. 2-52105, Atlantic Richfield Co. (ARCO) 

and The Anaconda Co., 

Sept. 14, 1976. 

Mission----------- ASARCO Inc ------------- Sacaton, West____ _ ____ do-------------------

Sacaton, East ____ _ ____ do -------------------

San Xavier ------- _____ do ------------------- Do ---------- _____ do ------------------- Silver Bell________ _ ____ do-------------------

Palo Verde (1978) Eisenhower Mining Co. 

(ASARCO-ANAMAX). 

Pinto Valley------ Cities Service Co. --------

----- do -------------------

OracleRidge/Con- Continental Materials 

trol. Corp. (Union Mini~re, 

45 percent interest). 

Bagdad ----------- Do ---------- Do ---------- Bruce ------------- Johnson ----------

Esperanza --------

Sierrita __________ _ 

Mineral Park_ ___ _ 

Inspiration (includes Live Oak, 

Thornton, and 

Red Hill Mines). 

Christmas--------

Do ---------- Ox Hide ----------

Cyprus Mines Corp ------

----- do ------------------- ----- do ------------------- ----- do ------------------- ----- do -------------------

Duval Corp. (Pennzoil 

Co.). 

_ ____ do -------------------

----- do -------------------

Inspiration Consolidated 

Copper Co. 

_____ do -------------------

----- do ------------------- ----- do -------------------

OP-P 

OP-P 

UG-P 

OP-P 

OP-P 

OP-P 

OP-P 

OP-P 

p 

p 

OP-P 

UG-M 

OP-P 

OP-P 

OP-P 

OP-P 

OP-P 

OP-P 

UG-P 

OP-P 

87,100 

32,700 

16,700 

152,100 

2 7,900 

29,700 

125,000 

350,000 

11,300 

297,000 

2 28,000 

3

88,000 

195 2 13,000 

31,000 

523,000 

60,000 

4 189,000 

4 25,200 

4 56,800 

4 9,000 

.68 

.74 

1.23 

.51 

1.06 

.66 

.57 

.44 

2.28 

.49 

.35 

.22 

3.65 

.50 

.40 

.32 

.29 

'.50 

4.50 

4 .50 

'.50 

592 

542 

205 

776 

84 

196 

713 

1,540 

Ag, Mo -------- ASARCO Incorp., ProspecAg ------------- tus on debenture offering ---------------- of May 7, 1975. SEC file ---------------- No. 1-164. 

Ag, Mo --------

ARCO-Anaconda merger, 

SEC filing Sept.l4, 1976. 

ASARCO, 3rd Quarter 

1976, Report to Stockholders. 

Cities Service Co., Preliminary prospectus, June 24, 

1975. 

257 .64 oz. Ag______ Engineering & Mining 

Journal, v. 176, No. 4, 

April 1975, page 170. 

1,455 

98 

194 

7 

65 

125 

1,672 

175 

943 

126 

284 

45 

Ag, Mo -------- Cyprus Mines Corp., 1975, 

---------------- -~:r~alO-:eRf:l' M:~ i2.9:1)ereellfzii 3o, 1976. 

Mo ------------- Pennzoil, 1975, Annual Report. 

.036-percent Mo 

Mo -------------

---------------- Inspiration Consolidated 

Copper Co., 1975, Annual 

Report. Recoverable copper reported. 
F4 

Deposit name 

GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

TABLE !.-Published reserves and resources of copper in the United States-Continued 

Company Type of 

deposit! Ore Grade Copper 

(percent copper) content Associated 

metals Reference 

A. RESERVES IN OPERATING MINES AND ANNOUNCED DEVELOPMENTS-Continued 

Arizona-Continued 

Ray--------------- Kennecott Copper Corp __ 

San Manuel Kala- Magma Copper Co. (New- mazoo. mont Mining Co.). 

Magma/Superior _____ do -------------------

Morenci___________ Phelps Dodge Corp _____ _ 

Metcalf----------- _____ do ------------------- New Cornelia (Ajo) _____ do-------------------

Bluebird---------- Ranchers Exploration & 

Development Co. 

White Pine_______ Copper Range------------

Do ---------- _____ do ------------------- Do ---------- _____ do -------------------

Berkeley---------- The Anaconda Co _______ _ 

Continental area_ _ ____ do ------------------- Continental _____ do ------------------- (North, Center, 

West). 

Battle Mountain Duval Corp., Pennzoil __ _ (includes Copper Basin and 

Copper Canyon). 

Ruth/Ely--------- Kennecott Copper Corp __ 

Chino/Santa Rita Kennecott Copper Corp __ 

Tyrone____________ Phelps Dodge Corp _____ _ 

Continental/Bay- UV Industries Inc.-------

ard (North). 

Continental/Bay- _____ do-------------------

Copperhill________ Cities Service Co---------

Carr Fork ________ The Anaconda Co _______ _ 

OP-P 667,000 

UG-P 1,000,000 

UG-0 10,000 

OP-P 662,500 

OP-P 416,000 

OP-P 126,600 

OP-P 275,000 

Michigan 

.79 

.70 

4.50 

.80 

.77 

.63 

.50 

UG-S 6 405,000 1.23 

UG-S 694,000 1.20 

UG-S 6 128,000 1.06 

OP-P 

OP-P 

OP-P 

OP-P 

OP-P 

OP-P 

OP-P 

UG-P 

OP-P 

UG-M 

UG-P 

Montana 

152,000 

17,000 

253,000 

7,300 

29,330 

.67 

.49 

.60 

.63 

.79 

New Mexico 

443,000 

344,400 

19,300 

17,500 

Tennessee 

4

40,000 

Utah 

61,200 

0.73 

.79 

1.97 

.86 

4 1.00 

1.84 

4,400 

7,000 

450 

5,300 

3,200 

798 

375 

4,981 

1,227 

1,361 

1,018 

83 

1,518 

46 

185 

2,400 

2,720 

380 

150 

1,126 

Mo -------------

+0.03-percent 

Mo 

Reserves at 75.9 percent re- covery. Excludes copper 

recoverable from waste 

dump leaching. Kennecott Copper Corp., Letter 

to stockholders, Nov. 26, 

1976. 

"Magma Facts," Magma 

Copper Co., Oct. 1, 1976. 

Phelps Dodge Corp., Prospectus, S"EC File 1-82, 

May 22, 1975. 

Ranchers Exploration & 

Development Corp., 1974 

annual report. Form 10K 

SEC File 1-6367, Sept. 

30, 1975. 

0.16 oz. Ag ____ Copper Range, 1975, AnnuMo -------------

Mo -------------

2.0 percent Zn 

al Report. 

ARCO/ Anaconda, Merger 

Filing. 

Pennzoil, 1975, Annual Report. 

Kennecott, Prospectus 

April 15, 1971. Reserves 

at 74.7 percent recovery, 

adjusted for production 

shown in 1971-75 annual 

reports. 

Reserves at 74.2 percent re- covery. Excludes copper 

recoverable from waste 

dump leaching. Kennecott Cop~r Corp., Letter to stockholders, Nov. 

26,1976. 

Phelps Dodge Prospectus, 

May 22, 1975. 

UV Industries Inc., 1975, 

Annual Report. 

Estimates based on "20-

year reserves at planned 

rate of production" re- ported in Cities Service 

Co., Preliminary prospectus, June 24, 1975. 

ARCO/ Anaconda, merger filing, Sept. 1976. 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA F5 

TABLE !.-Published reserves and resaurces of copper in the United States-Continued 

Deposit name Company Type of Ore Grade Copper Associated Reference 

deposit! (percent copper) content metals 

A. RESERVES IN OPERATING MINES AND ANNOUNCED DEVELOPMEN"'S-Continued 

Utah-Continued 

Bingham/Utah 

Copper 

Kennecott Copper Corp __ OP-P 1,602,000 .70 9,500 Mo,Au,Ag Reserves at 84.7 percent re- covery. Excludes copper 

recoverable from wastedump leaching. Kennecott Copper Corp., Letter 

to stockholders, Nov. 26, 

1976. 

B. IDENTIFIED RESOURCES IN UNDEVELOPED DEPOSITS AND CLOSED MINES 

Arizona 

Helvetia-East/ 

Rosemont 

Helvetia-East/ 

Rosemont. 

Helvetia-West __ _ 

ANAMAX Mining Co ___ _ 

_____ do -------------------

----- do -------------------

Lakeshore -------- Hecla Mining Co., and El 

Paso Natural Gas Co. 

Miami East ------ Cities Service Co ________ _ 

Pima______________ _ ____ do -------------------

CasaGrande Area Coastal Mining Co. (Getty 

Oil Co., Hanna Mining 

Co.) ---------------------

Florence/Poston CONOCO ----------------- Buttes. 

Sanchez (Safford) Ins_piration Consolidated 

Copper Co. 

Safford ----------- Phelps Dodge Corp _____ _ 

Bluebill/ 

Blackhawk. 

Kerr Addison Co---------

Western Syncline AMAX Inc _______________ _ 

White Pine Dis- _____ do ------------------- trict. 

Babbit Lake______ AMAX Inc _______________ _ 

Ely /Spruce Rd ___ Inco Ltd ------------------

Butte District (9+ The Anaconda Co _______ _ 

H:dsl~~i::k _______ _ ____ do __________________ _ 

Stillwater -------- _____ do -------------------

p 

p 

p 

UG-P 

UG-P 

337,000 

7 24,000 

470,000 

55,000 

OP-P 181,000 

UG-P 

OP-P 

p 

UG-P 

UG-M 

ss 

ss 

250,000 

800,000 

200,000 

400,000 

175,000 

4,000 

Maine 

520 

Michigan 

105,000 

62,000 

Minnesota 

CuNi 100,000 

CuNi 4100,000 

Montana 

UG-P 1,679,000 

and vein 

p 93,000 

CuNi 151,000 

Nevada 

Victoria ----------

yerington District: 

The Anaconda Co________ OP/UG-P 1,900 

Yerington -------- _____ do------------------- OP-P 

MacArthur ______ _ _ ____ do -------------------

2 22,400 

13,000 

.55 

.54 

.75 

.75 

1.95 

.49 

1.0 

.4 

.4 

.72 

.55 

.74 

1.46 

1.3 

1.35 

.9 

".9 

121 

1,820 

180 

3,500 

1,073 

887 

2,500 

3,200 

800 

2,800 

963 

10 

8 

1,365 

840 

770 

1,000 

ARCO/ Anaconda, merger 

filing Sept. 14, 1976. 

Hecla Mining Co., 1969, Annual Report. Reserves 

include tactite, oxide, 

and disseminated, un- changed through 1976. 

Cities Service Co., Preliminary prospectus, June 24, 

1976. 

Ag, Mo ________ Cyprus Mines Corp., An-

. 02-percent Mo 

.02-percent Mo 

3.4-percent Zn 

nual Report, 1975. SEC 

Form 10-K filed March 

30, 1976. 

Mining Magazine, Jan. 

1977, p. 47 (Mining 

Engineering, Nov. 1976, 

p. 15). 

Skillings Mining Review, 

Jan. 17, 1976, p. 6. 

Inspiration, 1975, Annual 

Report. 

Phelps Dodge, Prospectus, 

May 22, 1975 . 

Reserves in Recoverable 

Copper, Ranchers 1974-

75, Annual Report, Form 

10-K, Sept. 30, 1975. 

Noranda Mines Ltd., 1975, 

Annual Report. 

SEC merger registration 

Form S-14 No. 2-54286, 

AMAX, Inc., and Copper 

Range Co., July 29, 1975. 

0.4-percent Ni Skillings Mining Review, 

.25-percent Ni July 19, 1975. 

.72 avg. 12,068+ Mo, Ag, Zn ARCO/ Anaconda, merger 

filing, Sept. 14, 1976. 

.48 

.25 

2.37 

.32 

.43 

446 

378 

45 

77 

56 

.02-percent Mo 

.25-percent Ni 

ARCO/ Anaconda, merger filing. 

ARCO/ Anaconda, merger filing, Sept. 14, 1976. 
F6 GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

TABLE 1.-Puhlished reserves and resources of copper in the United; States-Continued 

Deposit name Company Type of Ore Grade Copper Associated Reference 

depositl (percent copper) content metals 

B. IDENTIFIED RESOURCES IN UNDEVELOPED DEPOSITS AND CLOSED MINES-Continued 

Nevada-Continued 

Ann Mason_______ The Anaconda Co. ------- Lyon-------------- Anaconda/U.S. Steel_ ___ _ p 495,000 .41 2,029 

390 ARCO/ Anaconda, merger 

filling, Sept. 14, 1976. 

UG-P 32,000 1.22 

Bear -------------- The Anaconda Co -------- Hall_______________ _ ____ do ------------------- p 500,000 

p 54,000 

.40 

.46 

2,000 Mo, Au, Ag 

248 52 million tons 

0.19-percent 

Mo 

Wisconsin 

Crandon ---------- Exxon---------------------

Ladysmith/ 

Flambeau. Kennecott ----------------

UG-M 60,000 

OP-M 11,000 

1.00 600 

4.0 450 

6.5-percent Zn The Capital Times, Madison, Wise., Sept. 8, 1976, 

p. 29. 

Skillings Mining Review, 

April 10, 1976. 

1 Mining method: OP, open pit, and UG, underground. Geological type: P, porphyry, includes disseminated, stockwork, and skarn; SS, stratabound sedimentary; M, massive sulfide including 

volcanogenic deposits; Cu-Ni, magmatic copper-nickel deposits; 0, other types. 1 0xide-ore reserve. 

•Stockpiled oxide ore. Acid soluble copper content shown. 

•Estimate. 

6 In situ and undiluted resource. Not included in total. 

•Reserves at 57-pereent extraction and 9-percent dilution. 7 Mixed oxide and sulfide reserves. 

Losses take place at nearly all stages of mining and 

processing. Good industry-wide data on mining losses 

are not available, but as an extreme example of such a 

loss, in the sedimentary copper deposit at White Pine, 

Mich., only 52 percent of a mineable reserve block is 

extracted because of the layered form of the ore deposit 

and the mining methods used. In the large open-pit 

mines on porphyry deposits, however, dilution and 

losses during mining are less significant. Greenspoon 

and Morning (1976) showed that, in 1975, 82 percent of 

the contained copper was recovered from the milling 

and flotation of copper and copper-molybdenum ores 

treated in the United States. An additional4 percent of 

the contained copper in concentrates is lost during 

smelting, and negligible amounts are lost at the refining 

stage. The net result is that less than 79 percent of the 

in-ground copper reserves is eventually converted to 

usable refined copper. Losses are also substantial in the 

recovery of copper by in-situ and dump leaching of oxide 

ores. A partial offset to reserves lost in mining and 

processing is provided by copper recovered in leaching 

of waste rock containing copper and in-situ leaching 

of mined underground workings; such recoveries 

amounted to 9 percent of copper-mine production in 

1977. 

Coproducts, such as molybdenum, gold, or silver, can 

be important in making a particularly low-grade copper 

deposit economic. For example, the Sierrita porphyrycopper mine in Arizona at the end of 1975 contained 523 

million tons of ore reserve, which had an average grade 

of 0.32 percent copper and 0.033 percent molybdenum 

per ton. At a price of $0.70 per pound for copper and 

$3.20 per pound for molybdenum, the 0.033 percent of 

molybdenum in the ore can generate a value equivalent 

to 0.15 percent copper. This gives the Sierrita deposit a 

"copper equivalent" reserve grade of 0.4 7 percent copper, 

which can be increased further when gold and silver byproduct credits are considered. In this study, only actual 

copper content was considered in the calculations. 

Considerable uncertainty exists in any reserve estimate. Even for a single deposit under static economic 

conditions, two firms may make estimates differing by 

50 percent or more. Several sources of underestimations 

can be recognized. Conservative (too low) estimates result from incomplete exploration of a deposit. Data on 

the subsurface extent of a mineral deposit are acquired 

by drilling or tunneling. These activities are very costly, 

and sound economic reasoning demands that they not 

be undertaken until the information is needed. Exploration exp€md~tures are thus made at a rate adequate 

for an assured production, and the true tonnages of 

many deposits are not known until the deposits are in 

the last stages of being explored. Reserves and production data for the Bingham porphyry-copper deposit 

are excellent examples of this type of underestimate. A 

reserve estimate for Bingham in 1930 shows approximately half the present reserve (Committee on Mineral 

Resources and the Environment, 1975). Another source 

of underestimation results from the existence of State 

and local taxes on reserves. Exploration efforts may be 

limited in order to show a reserve large enough to attract financing but not so large as to invite excessive 

taxation. The effect of these types of underestimation 

may be large relative to a national reserve estimate. 

Because the tonnage of total ore in copper deposits is 

distributed lognormally (Singer and others, 1975), the 

largest deposits contain copper in amounts an order of 

magnitude more than the mean. Thus, an error in the 

estimate for the largest deposit may seriously affect the 

national estimate. 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA F7 

Some of these errors have been reduced because in 

recent years mining firms have tended to drill out and 

evaluate deposits fully and have initially designed the 

pit or underground mine to extract most of the ore body. 

In addition, most of the very large deposits were developed in the early part of this century and now are fairly 

well understood and their total dimensions known. 

Most important, the national-reserve estimate now 

tends to be overestimated, at least temporarily. Since 

1972, inflation has caused mine and mill operating costs 

to rise more than 50 percent, whereas copper prices 

have stayed low because of large worldwide inventories. 

More than a third of the U.S. copper mines operated in 

1975 at costs per pound equal to or above the average 

annual copper price of 64.5 cents per pound. During such 

periods of low copper prices, operators of unprofitable 

mines who stay in production can be assumed to do so 

because they anticipate a resumption of more favorable 

price-cost ratios and are avoiding the high costs of 

closing and reopening their operations. Thus, even by 

restricting our usage of the term "reserve" to ore in 

operating mines, we are still uncertain how much of this 

ore is being extracted profitably and can be defined as 

reserves in the strict sense. If we use a somewhat more 

flexible approach that allows for rapidly changing costs 

and prices, reserves may be defined by anticipated economic conditions in the near term. Under this definition, most of the operating properties can be considered 

as having reserves. Moreover, deposits being considered 

for development may or may not have reserves as 

defined by anticipated economic conditions at the time 

they are expected to come into production, usually 4 to 

8 years from the time of the decision to develop (Burgin, 

1976). 

To show the sensitivity, of reserves to the economic 

conditions prevailing at the end of 1975, MAS was used 

to generate the data shown in table 2. The table lists 

estimates of the amount of measured and indicated copper reserves, in short tons, recoverable at various price 

levels and at discounted cash-flow rate of return calculated in terms of 1975 dollars. The rates of return were 

selected to show reserve levels ranging from a breakeven cost point (0 percent) to a profit level of 18 percent. 

TABLE 2.-The sensitivity of U.S. rower reserves, in miUimts of slwrt 

tons, to economic rnnditimts, in 19'!5 

[Data from H. J. Bennett, written eommun., 1977] 

Rate of return CopJ:lr price 

(percent) (1975 ollarslton) 

0.60 0.65 0.70 0.75 0.80 

tios. Any reserve estimate must therefore be accompanied by a statement of the assumptions on which it is 

based. For example, on the basis of data in this report 

(tables 1, 4), the following two different U.S. reserve 

estimates can be made: First, recoverable copper in deposits in production in 1977 is estimated at 49 million 

short tons. This most conservative estimate reflects a 

lack of confidence in new mine development under conditions of low copper prices and high capital and operating costs prevailing in 1977. It also reflects the loss of 

copper in the mining, milling, and smelting process. 

Second, the sum of the reserves in the foregoing category plus reserves in other deposits whose location and 

geologic, mineralogic, and engineering characteristics 

are similar to those being mined during the 1970's is 

estimated at 93 million short tons. This estimate is 

made on a deposit-by-deposit analysis of the foregoing 

factors. The deposits included are those that could be 

readily brought into production by improved economic 

conditions or as strategic requirements necessitate. 

This estimate is the one given in such publications of 

the U.S. Bureau of Mines as Mineral Commodity 

Profiles (Schroeder, 1977). This estimate includes copper that may be lost in mining and mineral processing 

but excludes copper recoverable from leaching waste 

rock, from dumps and from byproduct copper recoverable from noncopper ores. 

These two estimates made by empirical methods compare favorably with the estimates generated by using 

MAS (table 2). The first, conservative, estimate compares with MAS estimates of copper available at 

$0.60-$0.70 per pound at a 12-18 percent rate of return. 

The second, more liberal, estimate compares with estimates of copper available at $0.75 to more than $0.80 per 

pound and at a 6-12 percent rate of return. 

Copper-reserve estimates of the second, more liberal, 

type that have been made over the past 45 years are 

shown in figure 1. Figure 1 shows that from 1930 to 1960, 

reserve estimates equalled about 27-39 times annual 

production, indicating that, on the average, mining 

firms performed sufficient exploration to provide a 

30-year supply of primary copper. Reserve estimates 

made since 1960, however, have approached 49-64 times 

annual production. This increase probably reflects an 

increased understanding of the magnitude of the earlydiscovered large porphyry deposits, such as Bingham 

and Morenci, an increased willingness of mining firms 

to make public their reserves, and an increase in discoveries resulting from heavy investment in exploration 0------------- 82 89 6 _____________ 77 78 12 _____________ 46 69 

93 102 85 90 76 80 

107 

94 during the 1960's. It is interesting to compare historic 85 

74 reserve estimates with a curve representing reserves in 18 _____________ 40 47 51 56 -----------------------------------------

The national reserve estimate is thus somewhat of a 

moving target, which is underestimated as a result of 

inherent economic, geologic, and engineering factors 

and overestimated as a result of falling price/ cost raoperating properties as they are now measured and 

credited back to the year of first production. This curve, 

whose derivation will be discussed in a later section, can 

be thought of as approximating the actual amount of 

copper available through time in developed deposits. In 
F8 GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

100 

90 

80 • • 

•• • 100 

•• 

70 

60 

/ ------------------- ~~~----~ ______ _,_~ 

50 

40 

• 30 • 

• •• 

20 • • • 

en 

z 

0 

I-

• en 

z 

0 

II- ~ 0:::: 

0 10 

:I: 9 en 8 <0 

0 7 

0:::: 

10 Iw 

~ 

<0 

0 

z 6 z 

en 5 w en 

w > > 0:::: 

w 4 0:::: 

w en en w w 0:::: 3 0:::: 

c c 

z z 

<( <( 

z 2 

0 

z 

0 

i= 

u 

i= 

u 

:::> :::> 

c c 

0 0 

0:::: 0:::: a.. a.. 

....J 1 

<( .9 

:::> 

z .8 

z .7 <( 

.6 

1 ....J 

<( 

.9 :::> 

.8 z 

z 

.7 <( 

.6 

.5 

.5 

.4 

.4 

.3 

.3 

.2 

.2 

.1 ~--------~--------~--------~--------~--------~---------L--------~.1 

1910 1920 1930 1940 1950 1960 1970 1980 

YEARS 1925-1977 

FIGURE 1.-U.S. reserve estimates and annual production 1925-1977. Dots represent historic reserve estimates plotted from Everett 

and Bennett (1967), Bennett and others (1973), and the U.S. Bureau of Mines (1977). The solid line represents annual production 

from the U.S. Bureau of Mines Minerals Yearbook. The dashed line represents the actual reserves of operating mines taken 

from modern data and is calculated from the curves in figure BB. 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA F9 

the early 1960's, estimates jumped above this curve as a 

result of better knowledge and the inclusion of undeveloped properties whose reserves were defined by 

anticipated economic conditions. 

TOTAL ORE AND CONTAINED COPPER 

The sum of reserves and past production yields an 

estimate of the total ore, total metal contained in ore, 

and average grade of ore originally in each of the deposits known in the United States. Graphical display of 

these values (fig. 2) demonstrates the relative magnitude of deposits of various types and facilitates a comparison of the amount of copper in a typical deposit with 

the annual domestic consumption. Each year, the 

United States mines the equivalent of all the ore in a 

large porphyry deposit. A similar chart for worldwide 

deposits was published by Cox and others (1973) and 

updated for inclusion in the COMRATE report (Committee on Mineral Resources and the Environment, 

1975). These charts clearly reveal that small high-grade 

deposits, such as those of the massive sulfide type, have 

contributed little to the national resource total. The 

very large deposits of this type, of which only a few 

examples exist, contain about as much copper as a 

medium-size porphyry deposit. Medium-tonnage massive sulfide deposits contain an order of magnitude less 

copper. Table 3 summarizes these relationships. 

TABLE 3.-Total cupper contained in t1J11ico,l deposits 

[Short or metric tons] 

Deposit Small 

Porphyry------------------- 1()5 

Massive sulfide ------------ l«t 

Sedimentary --------------- l«t 

Medium 

The values. for total ore and total contained metal 

accurately reflect the extent and intensity of natural 

mineralizing processes only where all the following conditions hold: 

1. The copper grade falls off rapidly at the boundaries 

of the deposit, so that a lowering of cutoff grade 

does not substantially change the tonnage. 

2. The form and depth of the deposit are such that all of 

it can be included in a mining plan and thus become an ore reserve. 

3. Parts of the deposit were not removed by faulting, 

erosion, or other postmineralization processes. 

Clearly, these three conditions are found in few deposits, so that most estimates of copper contained in ore 

100~--------------~--------------~--------------~---------------.---------------. 

a: 

w 

R: 10 

0 

u 

u.. 

0 

I- 6. 6. z 6. w t::, u 

a: + w t::, 6. a... 

z + 

ui 

Q • <( 

a: 

(!) 

Magma, Ariz. 

+ 6 Jerome, Ariz. 

0 

EXPLANATION 

• Porphyry type 

o Sedimentary type 

D. Massive sulfide type 

+ Other types 

Crandon, Wis. White Pine, 

• ~ Mich. 

• • a.. •• 

• I .. 

• 

• 

.. :-. . • 

• •• 

• Morenci, Ariz. + ._, \ t:Singham, Utah 

Butte, Mont. 

• Sierrita, Ariz . 

. 1 ~--------------~--------------~--------------~--------------~--------------~ 

1 Million 10 Million 100 Million 1 Billion 

ORE, IN SHORT TONS 

FIGURE 2.-Tonnage and grade of reserves plus past production of U.S. copper deposits. Only published data are shown. Both grade and tonnage 

scales are logarithmic. Diagonal lines show tons of contained copper in each deposit. 
FlO GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

are low relative to the total copper originally in mineralized rock and estimates may be strongly affected by 

the economic behavior of mining firms. For this reason, 

Phillips (1975) has objected to the use of such estimates 

in making geologic deductions or in estimating the tonnage and grade of undiscovered deposits. A better approximation to the real distribution of copper contained 

in deposits can be obtained by combining past production with resource estimates (discussed in the following section). 

RESOURCE DATA 

Identified resources include mineralized rock that 

varies greatly in tonnage, metal content, and depth of 

overburden in widely differing locations. Metal can potentially be won from each deposit classed as an 

identified resource but at great differences in costs per 

unit and under widely differing technologic and economic conditions. Consider, for example, x number of 

tons of copper in mineralized rock in Alaska, y number 

of tons of metal in a deposit 5,000 ft below the surface 

in Arizona, and z number of tons of metal in a very low 

grade deposit for which a metallurgical recovery process is not known. The sum of x, y, and z is not a meaningful number because it does not tell the user how 

much metal could be won if only one or two of the 

following events were to take place: (1) a road and power 

network were built in Alaska, (2) an economic-recovery 

method for deep deposits were devised, or (3) a metallurgical process for low-grade deposits were discovered. 

Useful resource estimates should be disaggregated 

(divided into categories) to the maximum extent permitted by the availability of data (Singer, 1975). A factor limiting disaggregation of data is the requirement 

that reserve data on certain deposits be kept confidential; data obtained in confidence are aggregated with 

other data to protect company proprietary interests. 

In this study, identified copper resources were classified into seven categories (table 4). Category 1 refers to 

known resources. Category 2 is composed of deposits 

similar to those profitably mined during the early 

1970's. These deposits would be transferred to the reserve category as soon as a firm announces plans for 

development. 

Category 3 represents a large quantity of copper in 

resources that are of lower grade than that permitted 

by the present operation and (or) that require an unevaluated milling technique or represents ores that are 

deeper or have a higher stripping ratio than do those 

exploited in the present operation. These resources may 

be transferred to the reserve category at some future 

time when ores now being exploited in these deposits 

become depleted. This category includes about 8 million 

tons of copper estimated to exist in the White Pine 

deposit in Michigan in beds that are too thin and (or) too 

deep for economic mining at present. 

Category 4 represents some of the most readily accessible sources of copper, that are in mines that could be 

TABLE 4.-Copper resources, in millions of tons, of the United States as of 1978 

Copper 

Categories Short tons Metric tons 

1. Reserves in place in operating mines or in 

deposits for which development plans 

have been announced. 

2. Resources in drilled-out deposits awaiting 

development. Mainly porphyry deposits 

in Arizona, New Mexico, Nevada, and 

Montana. 

3. Resources in operating mines but not included in mining plan. Mainly in five of 

the largest porphyry deposits in Utah, 

Arizona, and New Mexico and in sedimentary deposits in Michigan. 

4. Resources in mining properties closed since 

1974 because of unfavorable economic 

conditions. 

5. Resources in drilled-out deposits at depths requiring high-cost underground mining 

methods or as yet undeveloped in-place 

leaching methods; mainly in Arizona and 

Utah. About half the total is in deposits 

having grades of more than 0.75-percent 

copper. 

6. Resources in drilled-out deposits in Washington, Wyoming, Minnesota, and Wisconsin, where environmental restrictions 

have contributed to delays in development. 

7. Resources in drilled-out deposits in remote 

locations in Alaska. About 60 percent of 

the total is in deposits that have grades 

of more than 0.75-percent copper. 

64 

15 

75 

4 

27 

4 

5 

58 

30 

68 

10 

25 

4 

5 

Category 1. Arizona: Ajo, Bagdad, Bluebird, Bruce, Esperanza-Sierrita, Inspiration, Johnson, Magma, Marble Peak, Mineral Park, Miuion, Morenci Metcalf, Palo 

Verde, Pinto Valley, Ray, Soeaton, San Manuel-Kalamazoo, San Xavier, Silver 

Bell, Twin Buttes. 

Michigan: White Pine. 

Montana: Blaek Pine, Butte-Berkeley. 

New Mexioo: Chino, Continental-Bayrad, Tyrone. 

Nevada: Copper BBBin 

TenneBBee: Duekiown. 

Utah: Bingham, Carrfork. 

2. Arizona: Cactus, Carpenter, Chilito, Copper BBBin, Florence, Helvetia-RoseMont, Miami East, Mineral Butte, Sanchez, Van Dyke, Vekol. 

Montana: Heddleston-Linooln, Spar Lake, Stillwater, Twin Bridges. 

Nevada: Ann Mason, Bear, Lyon, MacArthur. 

New Mexioo: Pinos Altos. 

Oklahoma: Mangum. 

3. Arizona: Ajo, Christmas, E speranza-Sierrita, Inspiration, Morenci, Ray, San 

Manual, Silver Bell, Twin Buttes. 

Michigan: White Pine. 

Montana: Butte. 

Nevada: Ely-Ruth. 

New Mexico: Chino. 

Utah: Bingham. 

4. Arizona: Lakeshore, Pima, Christmas, Yerington, Copper Canyon. 

Nevada: Ely-Ruth, Victoria. 

New Mexico: Nacimiento. 

Oklahoma: Creta. 

5. Arizona: Red Mountain, Safford-Kennecott, Safford-Phelps Dodge, West Caas 

Grande. 

Utah: Tintic South. 

6. Minnesota: Babbitt Lake, Ely-Spruce Road. 

Washington: Flagg Mountain, Glacier Peak, Margaret, North Fork, Sultan. 

Wisconsin: Crandon, Flambeau, Rhinelander. 

Wyoming: Kerwin. 

7. Alaska: Arctic Camp, Boruite, Brady Glacier, Horse Creek, Picnic Creek, Orange 

Hill. 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA Fll 

brought back quickly into production under favorable 

economic conditions. The longer the period of closure, 

however, the more difficult it is to reopen the mines 

because of the dispersal of trained workers to other 

projects and the inevitable decay of excavation slopes or 

underground workings. 

Category 5 constitutes resources that are most sensitive to the effects of technological development. The role 

of technological change in the copper industry is difficult to assess. The expectation that technological advances will transform low-quality resources into copper 

ore has some historical precedent. From 1904 to 1913, 

the application of large-scale mining machinery and new 

mineral-concentrating techniques to copper mining 

made possible large economies of scale (Parsons, 1933; 

Joralmon, 1973). These permitted a reduction of economic grade from about 6 percent in previously mined 

vein deposits to 2 percent in large-tonnage porphyry 

deposits. Since that period, ores of continually declining 

yield have been profitably mined (fig. 3), testifying to 

the continuing improvement in mining and beneficiation 

1.5 

1.4 

1.3 

I- 1.2 

z 

w 

u 1.1 a: 

w 

a.. 

~ 1.0 

0 

w .9 z 

~ 

a: .8 w 

a.. 

a.. 

0 .7 

u 

u. 

0 .6 

0 

....J 

w .5 

>= 

....J 

<( .4 ::::> 

z 

z 

<( .3 

.2 

.1 

6 8 1940 2 4 6 8 1950 2 4 

techniques. The 1904-1913 changes in technology were 

major breakthroughs; the changes after that period 

were brought about by fine tuning of existing techniques. 

For most of the deposits in category 5 to become economically attractive, major technological breakthroughs are 

required. These breakthroughs must not depend on extravagant uses of energy, because of its rising cost 

(Rosenkranz, 1976). In-place fracturing and leaching of 

deposits represent a potential for important technological change, but many problems are still unsolved. 

Because deposits in category 5 are low in quality, exploration firms are reluctant to spend the effort necessary to quantify their resources fully. For this reason, 

large but unknown quantities of copper are excluded 

from the estimate. Principal among these are resources 

of native copper in deep extensions of mines closed since 

the 1950's in the Upper Peninsula of Michigan. These 

resources could potentially equal in magnitude the 

quantity shown in category 5. 

Category 6 illustrates a recent trend toward increased restrictions on mineral development brought 

6 8 1960 2 4 6 8 1970 2 4 

YEARS 

FIGURE 3.-Declining yield (percent of metal produced from ore mined) of U.S. copper mines, 1936-1976. 

6 
F12 GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

about by environmentally concerned groups at the local, 

State and Federal levels of government. The effects of 

environmental concern are felt most strongly when new 

deposits are discovered in regions without longstanding 

copper-mining traditions. In Minnesota, Washington, 

Wisconsin, and Wyoming, creative exploration concepts 

and willingness to apply modern technology to hitherto 

unexploited deposits (copper-nickel resources near Duluth, Minn.) stimulated investment in new projects in 

the 1960's and early 1970's. Most of these projects have 

been abandoned or indefinitely postponed, partly because of unfavorable economic conditions but mainly 

because of resistance from groups concerned with 

threatened changes in the natural environment. The 

resource total for category 6 includes only drilled-out 

deposits and does not include large resources of copper 

estimated to exist in the Duluth Complex of Minnesota 

(Bonnichsen, 1974). 

Deposits in Alaska are placed in a separate category 

(7) because of the special conditions placed on development by their remoteness and by the harshness of the 

environment. Costs of mining low-grade ores in Alaska 

in 1973 were 67 percent higher than those for similar 

deposits in Arizona (Bottge, 1974). Even such a highgrade deposit as Kennecott, which was profitably mined 

between 1911 and 1938, would be uneconomic under 1973 

conditions if the operation had to bear the cost of road 

construction to the mine site (Maloney and Bottge, 

1973). 

Figure 4 shows diagrammatically the relative economic feasibility of exploitation and the amount of 

geologic uncertainty of these categories of identified resources. The figure is based on the resource-classification 

diagram introduced by McKelvey (1972) and discussed 

t 

0 

i= 

<( 

a: 

w 

~ 

a: 

a.. 

j::: 

en 

0 

u 

(!) 

z 

Ci5 

<( 

w 

a: 

u 

z 

Subeconomic 

1950 1955 1960 1965 1970 1975 

Identified 

Measured/Indicated 

by Schanz (1975) and Brobst (1979). Rectangles of varying sizes have areas proportional to the tonnage estimates in the various categories. These rectangles are 

arranged vertically with likelihood of future production 

decreasing downward and uncertainty of the estimate 

increasing to the right. The arrangement is somewhat 

subjective, and readers having special knowledge might 

prefer to shift some of the rectangles up, down, or sideways. The relative position of the rectangles may 

change with time, depending on breakthroughs in mineral technology and changes in domestic economic conditions and international commodity prices. 

Figure 4 differs from McKelvey's original diagram in 

two ways. First, because a scale is used, no lower or 

right-hand margin can be drawn, as this would imply 

quantitative knowledge of the total amount of copper to 

be discovered and mined in the United States. Second, 

the division between economic and subeconomic deposits is not shown as a single line because it changes with 

economic conditions. This division is shown graphically 

by a curve representing an estimate of the trend in 

cost/price ratios for the last 25 years. This curve is 

based on published U:S. reserves for 1950, 1960, and 

1964; on the intensity of mineral exploration in late 

1960's; on the tonnage, grade and location of targets of 

interest during that period; and, finally, on the previously mentioned estimate that in 1975 a third of the 

U.S. copper mines were operating at a loss. The vertical 

axis of the plot has no scale, but a careful economic 

analysis of the copper industry could produce a scale 

based on copper prices and mining costs. 

On the right side of figure 4, rectangles represent 

undiscovered resources. Their dimensions are based on 

estimates by Cox and others (1973) of about 100 million 

Inferred Hypothetical 

Undiscovered 

Speculative 

= 1 0,000,000 Short tons, 

9,000,000 Metric tons 

FIGURE 4.-Classification of U.S. copper resources and reserves. See text for explanation. 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA F13 

tons in each of the two categories, hypothetical and 

speculative. Because of the large amount of copper 

known to exist in identified deposits, no further analysis 

of undiscovered resources has been made by the U.S. 

Geological Survey. Undiscovered resources are large; 

what must be stressed is that a large amount of effort is 

required to find the undiscovered deposits. 

PRODUCTION DATA 

For each mine-mill unit in the United States, records 

of annual production capacity, in terms of copper metal, 

as well as records of copper production of past years, 

have been collected. Total capacity of the 38 producing 

deposits is 2 million tons of recoverable copper annually. On the basis of these data, future annual production capacity has been estimated following methods 

described by Zwartendyk (1974) and by Martin and 

others (1976). 

Annual production capacities are compared with 

total contained copper in ore on a logarithmic plot (fig. 

5). Capacities range from less than 1,000 tons to 300,000 

tons of copper per year and have a geometric mean of 

33,000 tons per year. Logarithms of production capacities of metal mined per year show a high correlation 

with the logarithm of total contained copper per 

deposit. 

Two regression equations are given as follows. One 

predicts annual production capacity, C, given total contained metal in ore reserves and past production, M A 

second predicts M given C: 

log C = 0.652log M + 0.572 

log M = 1.310 log C + 0.134 

The correlation coefficient R for these equations is 

0.925. Other regression equations relating annual capacity to total ore and to total ore and grade were tested 

and gave no significant improvement in the correlation 

coefficient. 

Lines of planned mine life can be drawn through the 

data shown in figure 5; all deposits falling on one such 

line have the same ratio of production capacity to contained metal. The geometric mean of the data falls on 

the 30-year mine-life line. Note that the slope of the 

regression line is less than one, indicating that large 

deposits tend to have a lower ratio of production to 

6.0 .------------------.------------------~-----------------.------------------. 

en 

z 

0 

IIa: 

0 

I 

en 

z 

u 5.0 

~ u 

~ <( 

u 

z 

0 

t3 

:::> 

c 

0 4.0 

a: 

Q.. 

...J 

<( 

:::> 

z 

z 

<( 

(!) 

0 

...J 

'/ 

/ 

/ 

/ 

/ 

X/ /x 

/ 

x/ 

p 

X X 

/ 

/ 

/ X 

/ X X / 

~~~ ~ X X X 

0'{>/ 

.... ~r /X 

X 

3.0 ~~--------------~------------------L------------------L----------------~ 

4.0 5.0 6.0 7.0 8.0 

LOG RESERVES PLUS PAST PRODUCTION (M), IN SHORT TONS 

FIGURE 5.-Log annual production capacity (C) in relation to log total copper in ore (reserves plus past production (M) for 34 deposits ( + ). 

The solid line is the regression line. Dashed lines show ratios of annual capacity to contained metal or years of production per deposit. 
F14 GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

contained metal than do medium to small deposits. For 

example, the plot shows that 2 million tons of copper in 

10 deposits (each having 200,000 tons contained copper) 

would be expected to yield slightly more metal per year 

than would one deposit containing 5 million tons. The 

above relationships describe the past behavior of U.S. 

mining firms in selecting the scale of operations for new 

mine developments. If this behavior is the same as that 

of mining firms in other countries, the relationships 

may be an important consideration in relating supply to 

reserves. Where most of a nation's reserves are contained in a few very large deposits, the reserve estimate 

could be as large as 100 times the annual production 

capacity. Where reserves are generally contained in 

many small deposits, reserves could be as small as 10 

times the annual production capacity. Conversely, if 

past planning behavior continues into the future, we can 

say that the discovery of several medium-size deposits 

would yield a higher annual production than the equivalent tonnage in one large deposit. 

The prediction of copper-production potential has 

serious limitations. We assume, for example, that the 

behavior of mining firms in selecting production rates 

will remain unchanged when, in fact, this behavior depends on such economic variables as inflation rate and 

cost of capital investment, as well as on new environmental regulations and improvements in extraction 

technology. 

Another limitation is the high variability of the data, 

masked by the logarithmic scale used in figure 5. Note, 

for example, that for a 1-million-ton deposit, capacities 

range from 15,000 to 60,000 tons per year. Although 

precise statements cannot be made about the confidence 

limits in the real data because logarithms are used, the 

predicted value of capacity is probably within a factor 

of four of the real value. 

Table 5 sho~s the results of applying the regression 

equation of figure 5 on a deposit-by-deposit basis to 

some of the resource categories of table 4. Estimates are 

not made for categories 3, 5, and 7 because it is not 

realistic to apply the regression equation to resources 

that cannot be exploited in the near future or to Alaska, 

where mining conditions are so different from those of 

the lower 48 States. The totals in table 5 are the result 

of solving the regression equation for each deposit. Application of the equation to the sum of the copper resources in any category gives a much smaller .aggregate 

annual production potential because, by this method, 

the contribution of medium and small deposits is 

underestimated. 

ANTICIPATED COPPER PRODUCTION 

Future production of primary copper depends on the 

aggregate mine and mill, smelter, and refinery capacities and on the reserves of the commodity. If plants are 

operating near capacity, supply is slow to respond to 

TABLE 5.-Potential annual productinn, in 1,(}()() tons per year,from U.S. 

cqpper deposits as of 19'!8. 

Short or metric 

Categories tons per year 

1 Operating mines1 ---------------------------------------- 2,000 

2 Good deposits ------------------------------------------- ~ 4 Closed mines -------------------------------------------- 150 

6 Mines having environmental problems ---------------- 1 Actual capacity plus planned increases in capacity as of 1977. 

increases in demand because existing mines and plants 

require significant time to expand and because grassroots development of drilled-out deposits requires 4-8 

years from investment decision to production (Burgin, 

1976). Future supply may be increased by new mineral 

technology that may make possible the conversion of 

subeconomic resources into reserves and by mineral exploration that converts undiscovered resources into reserves. Because the rate of technologic advance and 

mineral discovery is difficult to predict, no great 

confidence can be placed in estimates of total future 

supply. 

Considerable confidence can be placed, however, in a 

minimum estimate of future production. This estimate 

is made by first assuming that no new deposits will be 

developed, that no extreme fluctuations in demand and 

price will take place, and that no changes in productive 

capacity will be made_other than the planned changes 

already announced by mining firms. For each copper 

mine in the United States, a depletion date was calculated assuming production at full capacity. For any 

year, the sum of the individual annual pro~uction 

capacities for deposits not yet depleted provides an 

estimate of minimum U.S. production capacity. For example, a deposit having 100 million tons of reserves in 

1978 at a grade of 1 percent copper will contain 1 million 

tons of copper. If production capacity is 40,000 tons of 

metal per year and if 80 percent of the copper is recovered from the ore, then the life of the deposit operating 

at capacity is 20 years, and its depletion date is 1998. 

The capacity of this mine is thus part of aggregate U.S. 

production for all years up to and including 1998. 

Figure 6 shows a curve of minimum production for 

1976-2030, based on 1978 data. The curve rises between 

1976 and 1979 because of planned increases in capacity 

and announced development of new deposits, then falls 

steadily as existing small- and medium-tonnage deposits are depleted. Some of the largest deposits in the 

United States can be expected to supply copper until the 

year 2030. The area under this curve is equivalent to the 

United States reserves and resources in categories 1 and 

4. Zwartendyk (1974) has empha_sized that this type of 

predictive calculation is more useful than that which 

simply compares the national reserve to anticipated cumulative consumption. 

A family of curves may be drawn, each having a similar slope and enclosing increasingly larger areas. These 

areas represent tons of copper available under different 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA F15 

en 5 

z 

0 

IIa: 

0 

;/'-Probable total demand 

If from mines and old 

11 scrap (Schroeder, 

1/ 1977) 

SCALE 

J: 4 

en 

CD 

0 

f f 

f 

I 

/ / 

/ 

/ 

.~.{~robable primary demand # from mines (Schroeder, 

~ 1977) 

10,000,000 Short 

tons Copper 

/ ~ 

~ ~ # 

opper required from 

new sources --....... .......... 

~ ~ ~ 

"-, /Capacity fror:n reserv~ plus 

"" resources m categones "'-2 and 5 (Table 4) 

Capacity from deep"'-~ ~r low gr_ade r~serves , 

m operating mmes, ', 

~-....!category -~--~:.~.~~e 4)\ '"'-

·····················-\.\<················ 

' ' 

1950 1960 1970 1980 1990 ' 

YEARS 

2000 2010 2020 2030 

FIGURE 6.-Comparison of copper demand with U.S. production capacity projections, 1976-2030. (Demand projection from Schroeder,l977.) 

assumptions about the rate at which they will be converted into reserves. One of these curves, enclosing an 

area of 47 million tons, is shown in figure 6. This curve 

was made by assuming that the previously mentioned 

identified deposits, similar to those being mined ( category 2), and those in deeply buried deposits (category 5) 

will be developed between 1985 and 1994. Other curves 

enclosing various categories of subeconomic deposits, as 

well as hypothetical and speculative resources, could be 

drawn, each with increasing uncertainty. Deposits of 

category 3, identified subeconomic resources in operating properties, will probably have no significant effect 

on production until the reserves in those deposits are 

nearly depleted. Thus, the tonnage of copper in this 

category will tend to raise the curve of minimum production capacity at its lower end and extend the curve 

considerably into the future. 

REQUIREMENTS FOR NEW SOURCES 

Two demand projections for copper, also shown on 

figure 6, have been taken from Schroeder (1977). The 

total demand projection is the amount of copper needed 

regardless of source. Because the amount of copper that 

can be recovered from old scrap is limited by cost and 

energy availability, a large part of total demand must 

be met by mined copper, either domestic or imported. 

This part is called primary demand. The most likely 

primary-demand projection based on a 2.9 percent per 

year growth rate indicates that demand is expected to 

be greater than mine capacity from reserves in category 

1 by about 1983 and to be greater than total possible 

capacity from deposits in categories 2 and 5 by 1994. 

From 1994 on, the graph shows a widening gap between 

the primary-demand projection and the annual 

production-capacity curve. This gap represents the requirements of copper from new sources. 

The magnitude of requirements for new sources cannot be precisely determined because some past and current discoveries of mining firms are kept confidential. 

Discussion with mining-company geologists indicates 

that the number and size of deposits in this discovered 

but unpublicized category is small in relation to the gap 

shown in figure 5. A greater uncertainty in the magnitude of the requirements from new sources is the 

slope of the demand projection. Although it is beyond 

the scope of this study to examine the assumptions behind such projections it is important to note that 

projections vary widely. Figure 6, used as an interpretive tool, may be combined with any appropriate 

demand projection. The projected 3 percent growth in 

primary demand shown in figure 6 is based on Schroeder 
F16 GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

(1977). If a different projection is used, such as the 1.9 

percent growth rate forecast by Malenbaum,2 requirements from new sources are considerably smaller. 

Requirements from new sources can be met in one or 

a combination of four ways: by increasing imports, by 

increasing plant capacities at operating properties, by 

technological improvements converting subeconomic 

resources to reserves, and by discovery and development of new deposits. 

Imports of copper are likely to increase in the next 20 

years as costs of domestic production rise above average 

costs of production in the rest of the world. In the developing countries, copper mining and exploration have 

been less intensive than in the United States, and major 

low-cost reserves are still being discovered and developed. Chile's identified copper reserves of 107 million 

tons (Sutulov, 1977), for example, have doubled since the 

1960's and now are greater than U.S. reserves. These 

reserves are in ore that has an average grade of 1.0-1.2 

percent copper compared with 0.7-0.8 percent for U.S. 

resources. The relationship between grade of reserves in 

the United States, Chile, Peru, Zambia, and Zaire is 

shown in figure 7. Not only the decreasing grade of domestic production but also the increasing depth of deposits and the increasing stringency of environmental 

controls are driving up U.S. mining costs relative to 

those in the rest of the world. What effect increased 

imports will have on prices and assured copper supply 

for U.S. industry is difficult to predict. Although a 

cartel-like organization has been formed by Chile, Peru, 

Zaire, Zambia, and other copper-producing nations, its 

success in controlling prices is believed to be increasingly unlikely in view of the large number of countries now known to have important copper resources 

(Council on International Economic Policy, 1974). Radetzki (1977) has shown, however, that six developing 

countries having large low-cost copper reserves (Chile, 

Papua-New Guinea, Peru, Philippines, Zaire, and Zambia) could gain a 51-percent share of the world market 

by the year 2000. Investment in expansion of production 

of high-cost reserves in the United States and Canada, 

as well as in new production from countries that have no 

present copper industry (Argentina and Panama), 

would be curtailed in the face of increased production 

from the six countries, according to Radetzki. 

Increases in plant capacities at presently operating 

properties can temporarily raise the minimum 

production-capacity curve. Production increases, however, increase the rate of mine depletion and make the 

slope of the curve steeper. The supply problem is only 

postponed by a few years. 

As discussed earlier, technological improvements, 

such as those in the field of in-place leaching of ores, 

may contribute new production to fill the widening gap. 

2 Malenbaum, Wilfred, 1977, World demand for raw materials 1985-2000: National Science 

Foundation unpublished report, p. 116. 

Energy-intensive methods for winning metals from 

low-grade deposits, however, will make only small contributions to increasing production. 

Discovery and development of new deposits can provide sufficient production to fill the widening gap. If we 

assume a 3 percent growth in demand, by 2000, the gap 

between production capacity from known deposits and 

the most probable primary demand will approach 1 million tons of annual production. This gap could be closed 

by the discovery and development of 3 giant deposits or 

about 30 average-size deposits (1 million tons of contained copper each). Because of the 4-8 year lead time 

between discovery and first production, this 30 million 

tons of new copper reserves must be identified by 1985 or 

1990, calling for a rate of discovery and development of 

about 2 million tons of copper in ore per year. 

To put this requirement in proper perspective, we 

may wish to know at what rate copper ore has been 

discovered in the past. Reliable data on discovery dates 

are difficult to obtain, but as a close approximation, 

dates of first production can be used. In general, the first 

production year follows, by 4-8 years, the discovery or 

first recognition of the ·economic value of a deposit. Figure SA shows the total tonnage of copper in reserves 

brought into production in 10-year periods. The vertical 

bars are totals of past mine production and reserves as 

they are now known, credited back to the year of first 

production. Black bars represent the number Qf deposits 

developed in the same 10-year period. 

The bar graph shows a very large peak at the beginning of the century that represents the development of 

the Bingham deposit in Utah in 1904, Morenci in Arizona in 1907, and the Robinson District in Nevada in 

1908. From 1910 to 1920, the Miami, Inspiration, Ray, 

and Ajo deposits in Arizona and the Chino deposit in 

New Mexico were brought into production. A lull during 

the depression years was followed by increased development in the World War II era, marked by the opening 

of San Manuel in Arizona in 1956. The bars for the 

1980-1990 period are projected on the optimistic assumption that all the known deposits of categories 2 and 

5 will be developed within that period. 

Since 1960, the number of deposits developed per 

10-year period has increased greatly without a commensurate increase in tonnage of copper. This trend may 

result partly from inadequate knowledge of the true 

tonnage of recently developed deposits. In recent years, 

however, firms increasingly have tended to drill outreserves fully before mining is begun. The trend more 

probably reflects decreasing grade (and copper content) 

of deposits and increasing numbers of small deposifs 

containing small amounts of copper. For example, the 

average grade in the 38 producing mines in the United 

States is 0.74 percent copper compared with an average 

grade of 0.53 percent in the undeveloped deposits of 

categories 2 and 5. 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA F17 

110 

C/) 100 

w 

0 

<(z 

ffi~ 90 

1-0 

<(~ 

Wt- 80 

a:<( 

O:::c 

zt- 70 

-z United States 

ci<( 

w:::c 

&::1- 60 Chile 

Oa: 

uw 

u.~ 50 

og 

(/)a: 

zo 0 40 

t-o 

u.lo ...... 30 Peru 

(/)<( 

z::> 

oo _w 

.....1 20 .....1 

~ 

10 

0.5 0.6 0.7 0.8 0.91.0 1.2 1.4 1.61.8 2.0 2.5 3.0 

COPPER GRADE, IN PERCENT 

4.0 5.0 6.0 

FIGURE 7.-Cumulative reserves and resources at various grades in the United States, Chile Peru, Zambia, and Zaire, as of 1977. U.S. reserves and 

resources include categories 1, 2, 4, 5, and 6 (table 4). For the other four countries, all published reserves estimates were included. 

Figure 8B shows the historic development of copper 

in ore and is derived by plotting cumulatively the same 

data used to make the bar graph in figure SA. This 

cumulative curve is compared with cumulative mine 

production and consumption. For any year, the U.S. reserve in producing mines can be found by subtracting 

the amount of copper shown by the cumulative mineproduction curve from the cumulative copper in developed ore. The reserve values thus calculated are plotted 

on figure 1 and compared with historic reserve estimates. The early estimates are low mainly because the 

magnitude of reserves in some of the largest U.S. deposits have only become known in recent years. 

The curve of cumulative copper in developed ore 

rises sharply in the 1900-1920 period because technological breakthroughs in material handling and mineral processing affected economic evaluation of copper 

deposits that had been discovered many years before. 

The slope of the curve between 1950 and 1980 is equal 

to slightly more than a million tons of contained,copper per year and represents the development of deposits whose discoveries required greater exploration 

effort. 

The copper deposits now being mined were mainly 

recognized in surface outcrop. Many are surrounded by 

a halo of smaller base- and precious-metal deposits, 

which drew the attention of prospectors in the late 

1800's. Deposits to be found in the future will be those 

deeply covered by postmineral sedimentary and volcanic rock or that have no halo of other deposits. Thus, 

future discoveries will be considerably more difficult to 

make than were the discoveries of the deposits making 

up our present reserves. Future discoveries must also 

meet increasingly severe production-cost criteria in 

order to obtain financing for development in competition with low-cost foreign deposits. 
F18 

35 

30 

25 

20 

15 

10 

5 

160 

en 

z 

0 

..... 140 ..... 

a: 

0 

I 

en 120 ... 

0 

~ 100 

r:i 

w 

a. 

a. 80 0 

u 

w 70 

> i= 60 

<( 

...J 50 ::::> 

~ 

~ 40 

::::> 

u 30 

20 

10 

GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

~ 

• 

EXPLANATION 

Copper (106 tons) in ore developed 

during 1 0-year periods 

Number of deposits 

A 

Copper in developed ore 

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 

B 
THE NATURE AND USE OF COPPER RESERVE AND RESOURCE DATA F19 

CONCLUSIONS 

Some of the more notable conclusions that can be 

drawn from this study are as follows: 

1. U.S. reserve estimates in the past have been low 

mainly because of incomplete knowledge of the 

magnitude of the very large porphyry deposits. 

Present estimates are considerably more reliable, 

mainly because mining firms tend to drill out deposits fully before mining and because many of 

these companies are willing to make reserve estimates public. The effect of economic fluctuations 

on reserve estimates can be minimized if nearterm anticipated economic conditions rather than 

present conditions are used to define reserves. 

2. The wide variation in tonnage, grade, and contained 

metal in copper deposits depends largely on the 

geologic type of deposit. Of the four common deposit types, porphyry deposits are the most abundant, have the highest metal content, and largest 

aggregate production potential. 

3. Resource data should be presented in the most disaggregated form possible because of the wide variety 

of conditions required to transform resources into 

reserves. Of the various resource categories discussed in this report, the largest tonnage of copper 

is contained in the deep parts of a small number of 

deposits known to be the largest in the country. 

These resources probably cannot make contributions to our supply until well after the year 2000, 

when present mining operations have nearly depleted the reserves and a changeover to a new mine 

plan can be made. 

4. A high correlation exists between logarithms of annual production capacity and tonnage of contained 

copper in past production and reserves. A regression equation can be used to calculate the 

probable production capacity of a group of undeveloped deposits, but the large scatter of the antilog data makes such estimates accurate only 

within a factor of four. Analysis of production data 

shows that reserve requirements are smallest if 

annual production comes from medium- to smalltonnage deposits or, conversely, that large deposits 

yield a disproportionately small annual production 

relative to their large metal content. 

5. A minimum future production capacity can be calculated by totaling, for any year, the production cap-

-

acities of all deposits not yet depleted by that year. 

A curve can be drawn through these points showing declining production as smaller deposits are 

depleted. Such a curve, when compared with 

projected primary consumption is useful in estimating the requirements of copper from such new 

sources as imports or deposits not yet discovered. 

A comparison with one demand projection 

(Schroeder, 1977) suggests that if the new sources 

are to be from copper in domestic deposits, this 

copper must be found and developed at the rate of 

2 million tons per year. Discovery and development 

of copper in the United States since 1950 has been 

at a rate slightly greater than 1 million tons per 

year. 

REFERENCES CITED 

Bennett, H. J., Moore, Lyman, Welborn, L. E., and Toland, J. E., 1973, 

An economic appraisal of the supply of copper from primary 

domestic sources: U.S. Bureau of Mines Information Circular 

28598, 156 p. 

Bennett, H. J., Thompson, J. G., Quiring, H. J., and Toland, J. E., 1970, 

Financial evaluation of mineral deposits using sensitivity and 

probabilistic analysis methods: U.S. Bureau of Mines Information 

Circular 8495, 82 p. 

Bonnichsen, Bill, 1974, Copper and nickel resources in the Duluth 

Complex, northeastern Minnesota: Minnesota Geological Survey 

Information Circular 10, 24 p. 

Bottge, R. G., 1974, Comparative porphyry copper mining and processing costs-Alaska and Arizona: U.S. Bureau of Mines Information Circular 8656, 55 p. 

Bowen, R. W., and Botbol, J. M., 1975, The geologic retrieval and 

synopsis program (GRASP): U.S. Geological Survey Professional 

Paper 966, 87 p. 

Brobst, D. A., 1979, Fundamental concepts for the analysis of resource 

availability, in Smith, V. K., ed., Scarcity and growth reconsidered: Baltimore, Md., published for Resources for the Future 

by the Johns Hopkins University Press, p. 106-142. 

Burgin, L. B., 1976, Time required in developing selected Arizona 

copper mines: U.S. Bureau of Mines Information Circular 8702, 

144 p. 

Committee on Mineral Resources and the Environment, National Research Council, 1975, Resources of copper, in Mineral resources 

and the environment: Washington, D.C., National Academy of 

Sciences, p. 127-187. 

Cook, Earl, 1976, Limits to exploitation of nonrenewable resources: 

Science, v. 191, no. 4228, p. 677-682. 

Council on International Economic Policy, 1974, Special report critical 

imported material: Washington, D.C., U.S. Government Printing 

Office, 110 p. 

Cox, D.P., Schmidt, R. G., Vine, J.D., Kirkemo, Harold, Tourtelot, 

E. B., and Fleischer, Michael, 1973, Copper, in Brobst, D. A., and 

Pratt, W. P., eds., United States mineral resources: U.S. Geological Survey Professional Paper 820, p. 163-189. 

FIGURE 8.-Plots showing rate of development of copper in ore in the United States, 1900 to 2000. A, Tonnage of copper in reserves and number 

of deposits brought into production and potentially producible, by 10-year periods, 1900-1980. Tonnage of copper is shown in crosshatched 

bars. Number of deposits developed is shown by black bars. Bars shown for the period 1980-1990 represent copper in identified deposits 

potentially producible (categories 2 and 5, table 4). B, Cumulative copper in developed ore reserves, cumulative consumption, and 

cumulative mine production. The copper-in-ore curve is projected to 1990 and 2000. The consumption curve is projected at a 3-percent 

growth rate (Schroeder, 1977), and the mine production curve is projected at the rate of past increase, 2 percent. For any year, the difference 

between cumulative copper in developed ore and cumulative mine production equals total U.S. ore reserves for that year, as calculated from 

modern reserve data. 
F20 GEOLOGY AND RESOURCES OF COPPER DEPOSITS 

Everett, F. D., and Bennett, A. J., 1967, Evaluation of domestic 

reserves and potential sources of ores containing copper, lead, 

zinc, and associated metals: U.S. Bureau of Mines Information 

Circular 8325, 78 p. 

Greenspoon, G. N., and Morning, J. L., 1976, Froth folation in 

1975-advance summary: U.S. Bureau of Mines Mineral Industry 

Surveys, 23 p. 

Joralmon, I. B., 1973, Copper: Berkeley, Calif., Howell-North Books, 

407 p. 

McKelvey, V. E., 1972, Mineral resource estimates and public policy: 

American Scientist, v. 60, no. 1, p. 32-40. 

McMahon, A. D., 1965, Copper, a materials survey: U.S. Bureau of 

Mines Information Circular 8225, 340 p. 

Maloney, R. P., and Bottge, R. G., 1973, Estimated costs to produce 

copper at Kennecott, Alaska: U.S. Bureau of Mines Information 

Circular 8602, 35 p. 

Martin, H. L., Cranstone, D. A., and Zwartendyk, Jan, 1976, Metal 

mining in Canada to the year 2000: Resources Policy, v. 2, no. 1, p. 

11-24. 

Metals Week, 1973-74, Metals sourcebook: New York, McGraw Hill, 

(bi-weekly publication). 

Mining Journal, 1972-75, Mining annual review: London, Mining Journal Ltd. 

Parsons, A. B., 1933, The porphyry coppers: New York, American 

Institute of Mining and Metallurgical Engineeers, 581 p. 

Phillips, C. H., 1975, Discussion: A resource analysis based on porphyry copper deposits and the cumulative copper metal curve 

using Monte Carlo simulation: Economic Geology, v. 70, no. 8, p. 

1484. 

Radetzki, Marian, 1977, Mineral commodity stabilization: The producers view: Resources policy, v. 3, no. 2, p. 118-126. 

Ridge, J. D., ed., 1968, Ore deposits of the United States, 1933-1967 

(Graton-Sales Volume): New York, American Institute of Mining 

Metallurgical and Petroleum Engineers, 2 v.: 1880 p. 

Rosenkranz, R. D., 1976, Energy consumption in domestic primary 

copper production: U.S. Bureau of Mines Information Circular 

8698,22 p. 

Schanz, J. L., 1975, Resource terminology: an examination of concepts 

and terms and recommendations for improvement: Electric 

Power Research Institute (Palo Alto, Calif.), EPRI report 336, 

116 p. 

Schroeder, H. J., 1977, Copper: U.S. Bureau of Mines Mineral Commodity Profiles, no. 3, 19 p. 

Singer, D. A., 1975, Mineral resource models and the Alaskan Mineral 

Resource Assessment Program, in Vogely, W. A., ed., Mineral 

materials modelling: Washington, D.C., Resources for the Future, 

p. 370-382. 

Singer, D. A., Cox, D.P., and Drew, L. J., 1975, Grade and tonnage 

relationships among copper deposits: U.S. Geol. Survey Professional Paper 907-A, p. A1-A11. 

Sutulov, Alexander, 1977, Chilean copper resources said to be world's 

largest: American Metals Market, v. 85, no. 150, p. 18. 

Titley, S. R., and Hicks, C. L., eds., 1966, Geology of the porphyry 

copper deposits southwestern North America: Tucson, Ariz., University of Arizona Press, 287 p. 

Tourtelot, E. B., and Vine, J.D., 1976, Copper deposits in sedimentary 

and volcanogenic rocks: U.S. Geological Survey Professional 

Paper 907 -C. 34 p. 

U.S. Bureau of Mines, 1977, Copper, in Commodity data summaries, 

1977: Washington, D.C., p. 46-47. 

U.S. Bureau of Mines and U.S. Geological Survey, 1980, Principles of 

a resource/reserve classification for minerals: U.S. Geological 

Survey Circular 831, 5 p. 

Zwartendyk, J., 1974, The life index of mineral reserves-a statistical 

mirage: Canadian Mining and Metallurgical Bulletin, v. 67, no. 

750, p. 67-70. 

*U.S. GOVERNMENT PRINTING OFFICE: 1981- 361-614/287 
Geology and Resources 

of Copper Deposits 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 907 

This volume was published 

as separate chapters A-F 
UNITED STATES DEPARTMENT OF THE INTERIOR 

JAMES G. WATT, Secretary 

GEOLOGICAL SURVEY 

Dallas L. Peck, Director 
CONTENTS 

[Letters designate the chapters] 

(A) Geology and Resources of Copper Deposits-Grade and Tonnage Relationships Among Copper 

Deposits, by D. A. Singer, Dennis P. Cox, and Lawrence J. Drew 

(B) Geology and Resources of Copper Deposits-Geochemical Exploration Techniques Applicable in 

the Search for Copper Deposits, by Maurice A. Chaffee 

(C) Geology and Resources of Copper Deposits-Copper Deposits in Sedimentary and Volcanogenic 

Rocks, by Elizabeth B. Tourtelot and James D. Vine 

(D) Geology and Resources of Copper Deposits-Fluid-Inclusion Petrology-Data from Porphyry 

Copper Deposits and Applications to Exploration, by J. Thomas Nash 

(E) Geology and Resources of Copper Deposits-The Potential for Porphyry Copper-Molybdenum 

Deposits in the Eastern United States, by Robert Gordon Schmidt 

(F) Geology and Resources of Copper Deposits-The Nature and Use of Copper Reserve andResource Data, by Dennis F. Cox, Nancy A. Wright, and George J. Coakley