GEOLOGICAL SURVEY CIRCULAR 547 

Uranium Reserves and 

Progress in Exploration 

And Development 

Uranium Reserves and 

Progress in Exploration 

And Development 

By Arthur P. Butler, Jr. 

GEOLOGICAL SURVEY CIRCULAR 547 

Washington 1967 
United States Department of the Interior 

STEWART L. UDALL, Secretary 

Geological Survey 

William T. Pecora, Director 

Free on application to the U.S. Geological Survey, Washington, D.C. 20242 
URANIUM RESERVES AND PROGRESS IN EXPLORATION AND DEVELOPME1'1

T 1 

By Arthur P. Butler, Jr. 

Gentlemen, although I consider it an honor 

to have been asked to tell you something about 

uranium reserves and resources and progress 

in exploration, a glance through your association bulletin, Coal News, indicates that the editor is doing a very good job of informing you 

about events in the nuclear industry and about 

interpretations of its resource base. As a result, 

many of you may be more or less aware of the 

general content of what I can present. Perhaps, 

however, a review of estimated demand for 

uranium in relation to the known and potential 

resource base will be useful. 

In this review the general magnitude of the 

demand will be indicated, the general quantity 

of reserves will be outlined as they may stand 

when the Atomic Energy Commission buying 

program ends in 1970, and the general character and distribution of known reserves will be 

summarized to provide a perspective for considering the outlook for exploration. 

It should be recognized that, in dealing with 

estimated or anticipated demand, I am relying 

on the public statements of others who have 

made projections of the likely growth in use of 

electric power and of how that growth is likely 

to be shared by various fuels. As many of you 

know, nuclear-powered generating equipment 

installed or on order had reached a total of 

39,000 megawatts by early June of this year 

(1967). The AEC estimates that by 1980 installed nuclear power capacity in the United 

States will probably be about 150,000 megawatts (Nininger, 1967). 

Plants built or now on order will require 

about 175,000 tons of U3 0 8 for fuel throughout 

their lifetime. Those which are projected to be 

in service by 1980 will, on the same basis, require an additional 500,000 tons. This quantity 

is based on the assumption that the reactors 

going into service by 1980 will have about the 

same characteristics as reactors now on order ; 

that is, they will not regenerate as much fissionable material as they consume. 

Reactors of the present generation arE: fairly 

prodigal of fuel, for they depend largely on the 

fissioning of the isotope U235 for generating 

energy. This isotope makes up only 1 part in 

140 of natural uranium. In reactors, some of 

the much more abundant isotope U238 ' which is 

not naturally fissionable, captures neutrons 

from the fissioning U235 and is converted to 

fissionable Pu239• But not enough U238 is converted in these reactors to replace the U235 used. 

Therefore, only a fraction of the energy latent 

in the uranium resources is actually used by 

reactors likely to go into service in tll e next 

dozen years. 

The significance of these numbers mr.y be a 

little clearer if we look at the demand in relation to known reserves and estimated resources 

and in terms of coal equivalents familiar to all 

of you. 

Table 1 compares the energy in uranium and 

coal with respect to the amount of UsOs needed 

as fuel for reactors on order and in us~. The 

energy derived from U235 that will be used in 

these reactors is large in terms of coal equivalents but is dwarfed by the amount that. would 

be available if all the accompanying U238 were 

converted to Pu239• 

The 175,000 tons of U30 8 needed to supply 

reactors now on order is somewhat larger than 

the AEC's estimate of 141,000 tons of indi1 Presented at Department of Interior-Coal Industry Executive Conference, Washington, D.C., August 16, 1967. 

1 
TABLE !.-Bituminous coal equivalents of energy in uranium 

Bituminous 

coal 

(tons) 

1 lb uza5 or Puza9 1 ------------------------------------------- 1,3~() 

1 ton natural uranium 13 ---------------------------------------

1 ton unenriched U 3 0 8 

3 ----------------------------------------

175,000 tons U3 0 8 (amount required for 

"'V19,0'l0 

'"'-'16,010 

reactors in service or on order) 3 _____________________________ ""'"'2,800,000,010 

175,000 tons U30 8 if all uzas is converted to Pu2a9 ________________ 4 140X2,800,000,010 

1 1 ton natural uranium contains 14 lb U235. 2 Hubbert ( 1962). Equivalent to 33 X 109 Btu. 3 Using only U235. 4 140 is the ratio of U238 + U235 to U~35 alone. 

= 392,000,000,010 

TABLE 2.-Uranium 'reserves in the price range of $8 to $10 per pound U 30 8 as they may be at end of 1970 

[Values are U30 8, in tons] 

Reserves, end of 1966 1 ----------------------------------------------------------------- 141,000 

Less total to be mined, 1967-70 inclusive: 

AEC procurement 1 _______ ______________________ __________________________ 32,000 

Estimated commercial sales 1 __________________ ----------------------------- 18,000 

50,000 

Balance of present reserves ----------------------------------------------------------------------

New reserves found at average discovery rate of 1962-66 -------------------------------------------

91,000 

24,000 

Estimated reserves at end of 1970, assuming no increase in rate of discovery -------------------------- 115,000 

Possible future releases from AEC stockpile 50,000 2 _____________________________________________________ _ 

lCnown resources at $8 per pound ----------------------------------------------------------------

Additional resources exploitable at $10 per pound __ -------------------------------------------------

165,000 

40,000 

Total in conventional deposits and stockpiled (rounded) ________________ ----------------------- 200,000 

1 Nininger (1967). 2 Engineering and Mining Journal (1966). 

cated and inferred reserves of U30 8 minable at 

$8 per pound but somewhat less than the estimated 200,000 tons U3 0 8 minable at $10 per 

pound. The uranium to fuel additional reactors 

will have to be provided by discovery of additional ore. To see what may be needed, it would 

be well to look at the reserve situation as it 

may be in 1970 when the AEC buying program 

is finished (table 2) . 

At the end of 1970, counting in material that 

the AEC has said might be available for release 

from its stockpile (Engineering and Mining 

Journal, 1966), known resources derived from 

conventional deposits at $8 per pound U30 8 

would be about 165,000 tons U3 0 8• Allowing a 

price of $10 per pound U3 0 8 , the resources 

would be 200,000 tons U30 8• With either tonnage, the supply for reactors now built or on 

2 

order is reasonably well assured. This relation 

between the amount of uranium reserves at $8 

and $10 per pound is also shown graphically in 

figure 1. 

The uranium needed for reactors that are 

projected to be placed in service by 1980 will 

have to come mostly from reso1lrces in conventional-type deposits not yet discovered, a 

category which the AEC has terned "possible 

additional resources." The reso•1rces of this 

sort that could be found and mined for $8 to $10 

per pound are estimated to be 325,000 tons 

(Organization for Economic Cooperation and 

Development, 1965, table 1). 

Most of these additional resour~es are probably in the same regions as the krown deposits. 

Those from ·which ore is currentl~r being mined 

are in the western part of the United States. 
KNOWN RESOURCES U308 

AVAILABLE AT $8-10/LB. 

END OF 1970 

LIFETIME REQUIREMENTS OF U308 

FOR REACTORS PROJECTED TO BE 

IN SERVICE BY 1980 

675 

NEEDED FOR 

REACTORS 

PROJECTED 

500 TO BE IN 

SERVICE 

BY 1980 

300 - AVAILABLE FROM PHOSPHATE 

ROCK PRODUCTS 1 

v ADDITIONAL RESERVES 20 AT $10/LB 21+3 

l+O v NEW RESERVES DISCOVERED: 

21+ 1962-1966 RATE PROJECTED 

18 EST I MATED COMMERCIAL SAL ES2 

NOW IN USE 

100 - 91 REMAINDER OF RESERVES 

AT $8/LB 175 OR ON 

ORDER 

50 POSSIBLY AVAILABLE 

FROM AEC STOCKPILE3 

0 0 

1 Organization for Economic Cooperation and Development ( 1965, table 1, footnote 1) • 

2 Nininger (1967). 3 Statement attributed to AEC chairman, Glenn Seaborg (Engineering and Mining Journal, 1966, p. 83). 

FIGURE 1.-Estimate of UaOa (in thousands of tons) mined and in reserves at the end of 1970 

compared to amount required for nuclear reactor fuel. 

Their general distribution is shown in figure 2. 

A small amount of ore also has been mined from 

a deposit in Pennsylvania. 

About 95 percent of the uranium produced 

has come from deposits in continental sedimentary rocks, mainly sandstone. A like proportion 

of the reserves and probably of undiscovered 

resources is in this same type of deposit. Most 

of my subsequent remarks will be concerned 

with resources in such deposits. But first, I 

think, other sources of supply should be mentioned. Fracture-controlled deposits, principally veins, have furnished most of the remainder of the uranium mined. Some of these 

deposits are important as individual mines but 

not as major contributors to total supply. 

Uranium has been recovered as a byproduct of 

the manufacture of phosphate products from 

marine phosphorites. The volume of these 

rocks is very large and a sustained suppl~mentary supply of uranium can be obtained from 

them at a price of about $10 per pound of U30 8• 

This supply, however, is geared to the r::..te of 

production of refined phosphate products. Similarly, a small but steady byproduct contrih1tion 

may come from leaching of copper mine tail3 
• Vein deposits 

Strata- bound ·~ deposits 

• Lignitic deposits 

FIGURE 2.-Principal deposits mined for uranium in the United States. 

ings, which has been recently announced as a 

possibility (Nininger, 1967). 

All other identified resources are materials 

from which uranium could be recovered only 

at a cost that would range from a few to many 

times the cost of recovering it from the ores 

now mined. 

Additions to supply will come mainly from 

discovery of new deposits and districts in the 

same geologic units of continental sandstone 

from which ore is now mined and possibly in 

units where small deposits have been found 

but where the presence of large deposits has 

not yet been demonstrated. In considering the 

outlook for exploration for additional deposits, 

an outline of the general distribution of the 

known deposits and of some of their principal 

characteristics provides an essential frame of 

reference. 

As can be seen in figure 2, most of the productive deposits are in a broad poorly defined 

belt that extends from northeast Arizona and 

4 

northwest New Mexico to northeast Wyoming 

and the western part of the Dakotas. A few 

are in the Gulf Coastal Plain in south Texas. 

Others, largely isolated and not fltown on the 

map, are in the Texas Panhandle, 'vestern Oklahoma, and in States west of the n1ain belt. 

Within the areas of their distribution, the 

principal deposits tend to occur in parts of a 

few units of sedimentary rocks. In the region 

of the Colorado Plateau, the largE:. deposits are 

in three particular units whose d~signations I 

shall omit. In northwest Colorado and much 

of Wyoming, they are mainly in trvo rock units 

younger thitn those of the Colorado Plateau. 

In northeast-Wyoming and the adjoining part 

of South Dakota, they are in rocks intermediate 

in age between those of the Colorado Plateau 

and those in central Wyoming. T~"'e Texas dep0sits are in relatively young rocks. 

Deposits in these major host rnits are distributed across areas that range in size from a 

few tens of square miles in parts of Wyoming 
to 9,000 square miles in one unit in the Colorado 

Plateau region. The aggregate area of favorable rock within which the principal deposits 

occur is about 30,000 square miles. The discovered deposits are in tracts of still incompletely explored ground that constitute not more 

than one-quarter of this aggregate area. This 

is a point to which I will return subsequently. 

Other bodies of continental sandstone that contain small and generally scattered deposits collectively underlie an aggregate area of another 

160,000 square miles. 

The large deposits generally occur in somewhat lenticular bodies of sandstone interbedded 

with mudstone. Almost all of them are not only 

in parts of the sandstone that are appreciably 

thicker than adjoining parts but mostly in sandstone that is at least 30 feet thick. 

Deposits range from a few tens of feet long 

and a few feet wide to many thousands of feet 

long and a few hundred feet wide. Small ore 

bodies contain a few tons of ore ; large ore 

bodies contain hundreds of thousands to several 

millions of tons. They have a variety of forms 

from crudely tabular to markedly elongate 

masses of crescentic cross section. In most of 

the major producing areas, the deposits tend 

to be arranged in notably elongate groups or 

clusters, as in the large Ambrosia Lake district, New Mexico (fig. 3). The length of these 

clusters and connected mineralized rock that is 

too lean or too thin to be mined ranges from a 

few to many miles. 

Almost all deposits are closely associated in 

one way or another with color differences in 

parts of their host rocks. In some areas, rock 

near deposits differs slightly in color from rock 

farther away. In other areas, notably in Wyoming and Texas, deposits are mainly along 

the color boundary. The contrasts in color 

range from subtle to easily distinguishable. 

They reflect differences in mineralogy that are 

more difficult to recognize than even a subtle 

color contrast. 

Because the color differences are more extensive than conspicuously mineralized rock, color 

differences provide preliminary targets for exploration that are larger than those for strongly 

mineralized rock. Thus, nearly the whole area 

included in the line patterns in figure 3 constitutes a preliminary target that could be diagnosed from drill holes spaced at 1-mile intervals as potentially favorable for the presence 

of deposits. Radioactivity logs of drill holes 

would also aid materially in the interpretation. 

Color differences in different parts of the host 

rocks have for many years been recognized as 

a useful exploration guide. It is probably only 

within the last· half-dozen years, however, that 

an integrated concept has evolved of how the 

various color manifestations can be most effectively applied. 

The present resurgence in exploration starts 

with a much broader, but still incomplete, base 

of know ledge than prevailed 20 years age More 

is known about the general distribution and 

habits of deposits, about the characteri~:tics of 

the rocks that indicate favorability for the presence of deposits, and about how to apply recognition of those characteristics in guiding search 

for them. For example, it is known tl'at the 

targets for preliminary evaluation of favorability are measurable in square miles rather 

than in hundreds to a few thousands of square 

feet and that significant bodies of mineralized 

rock are many thousands of feet to several 

miles long. In addition to the characteristics of 

bodies of sand likely to be favorable re~eptors 

for deposits, the interpretation of differences in 

color from place to place within a rock unit can 

be used to estimate favorability for d~posits 

and to direct exploration into particular parts 

of areas where these differences are reco~ized. 

Still lacking are criteria for determining which 

parts of large unexplored areas offer t:'le best 

chance of :t·ewarding the preliminary stages of 

exploration. 

The increase in orders for nuclear-fueled 

plants and the expectation of a sustained and 

growing market for uranium provide a strong 

stimulus to exploration, spearheaded by many 

experienced concerns in the mineral in~ustry. 

These include major and several small domestic 

uranium-mining companies, companie;;< with 

large interests in uranium mines in Canada, 

and some major oil companies. Acquisition of 

land, either by lease or by the staking of claims, 

has reached the proportions of a land office 

rush. 

5 
" 

N 

Ambrosia Lake trend 

EXPLANATION 

.,.. 

Outline of ore bodies 

_l. I I 1 2QQ-l._L_ .L .1.- 1- L 

Thickness contour of Westwater 

Canyon Member, in feet. Dashed 

where approximately located. 

Hachures on side where member 

is less than 200 feet thick Poison Canyon trend ·" \... 

Zone I 

Ore occurs only in upper one-third 

of Westwater Canyon Member 

Zone 2 

Ore occurs only 1 n upper two-th1rds 

of Westwater Canyon Member 

Zone 3 

Ore occurs from top to bottom 

of Westwater Canyon Member 

,, 

" '" 

0 2 3 MILES 

FIGURE 3.-Map of ore deposits in the Morrison Formation, Ambrosia Lake area, New Mexico (from Santos, 1963, 

fig. 1). 

The extent of solid effort is shown by the increase in exploratory drilling. The amount of 

such drilling in 1966 exceeded that in 1965 by 

6 

30 percent, and the rate in 1967 is about four 

times that of last year. Next year, if not this, it 

will exceed the previous high of 1957. 
No remarkable new discoveries have yet been 

announced, but this is not surprising in view 

of the time necessary to start soundly conceived 

exploration projects and of the relatively short 

interval of time that has elapsed from concern 

about a market to full realization of the probable magnitude of the demand for uranium to 

be used in reactors. Moreover, even if a company has made a significant discovery, it may 

well prefer to refrain from announcing it immediately. The reasons could be the competitive 

situation in land acquisition or concern over 

the effect an announcement might have on 

negotiating price with potential customers. 

Even slight optimism on the part of a mining 

company might make buyers more cautious. 

Despite the lack of news of any really new 

discovery, there are reasons for thinking that 

the present round of exploration will be successful in finding the concealed deposits from 

which future supplies of uranium will have to 

come. 

Much of the exploration in the last few years 

has been confined to the immediate vicinity of 

known ore deposits. This has met with reasonable success. For example, a continuation of 

the large deposits in the Lisbon Valley area, 

Utah, has been found in the downdropped block 

across a fault from the known deposits. This 

exploration has been carried on at a depth approaching 2,000 feet. In 1963, when exploration was at a low ebb, a new deposit discovered 

in the coastal plain in Texas was significant not 

only because it turned out to be larger than any 

previously mined there, but also because it 

demonstrated that good-sized deposits occur at 

some distance from the outcrop in that region. 

During 1962-66, a period of little incentive for 

exploration, 24,000 tons of new reserves was 

found in the country as a whole. 

Large areas underlain by the principal orebearing strata and other possibly favorable 

stratigraphic units are still relatively unexplored. As already mentioned in reviewing the 

distribution of deposits, solid exploration effort 

in the past was restricted to only about onefourth of the area where the particularly favorable strata are present. Even this one-fourth 

is still incompletely explored. Although it 

would be incorrect to jump to the conclusion 

that all the relatively unexplored areas would 

be as strongly mineralized as the explored parts, 

it would seem very fortuitous and most unlikely 

that a large part of the known deposits ar?. confined to the more accessible one-quarter of the 

particularly favorable units which is al"0 the 

more intensively explored part of th€. total 

possible area. Almost inevitably, successful exploration in one place will focus attention at 

that place, perhaps to the virtual neglect of 

others, because reward is likely to come more 

quickly there in the form of finding nearby 

extensions of the initial discovery. Th~ new 

round of exploration will, however, be so.eking 

concealed deposits that are more deeply buried 

and more remote from outcrops than the known 

deposits. These concealed deposits will b~ more 

difficult and more costly to find and mine. But 

the probabilities are good that the deposits are 

there, and industry has now developed the experience and skill to apply knowledge of their 

distribution and habits effectively in exploring 

for them. 

Additionally, the continental basement of 

Precambrian rocks which is concealed under 

younger rocks in the vast area between the Appalachian and Rocky Mountains repre8ents a 

more distant possibility for exploratior. The 

large uranium deposits in southern Canf.da are 

in exposed parts of this basement. Identifying 

its concealed parts that may be favorable for 

deposits and exploring those parts will be a 

formidable task, inasmuch as the blar ket of 

overlying rocks is 3,000 to 5,000 feet thick in 

much of the continental interior. However, an 

increasing store of geophysical data, coupled 

with data from scattered drill holes, is improving interpretation of its characteristics. 

Finally, the experience of other segmo.nts of 

the mineral industry furnishes some analogies 

relevant to the exploration for uraniun. For 

example, although we had been using oil at an 

increasing rate for about 100 years, by 1958 

proved reserves were still larger than tr~y had 

ever been before (adapted from Zapp,. 1962, 

table 2). Exploration for lead in Missouri during a period of 20 years has resulted in discovery of a whole new group of districts in 

which resources are estimated to be thre~ times 

the amount that had been mined from tho. origi7 
nall~d belt in 100 years (Weigel, 1965). Copper reserves in 1964 were more than three times 

the reserves estimated in 1935 (Everett and 

Bennett, 1967, p. 26). The situation in copper 

may not be exactly comparable to that for 

uranium because the price of copper also rose 

markedly but less than the increase in reserves. 

In comparison, reserves of uranium at $15 per 

pound u3o~ would be about 60 percent larger 

than at $10. The known geology of uranium 

deposits in continental sandstone suggests that 

the chances are good that exploration for 

uranium will follow a course generally similar 

to the examples just cited. I think that the remarks of McGee (1967) to the Atomic Industrial Forum nearly a year ago deserve repeating 

in this context; he said, "The past achievements 

of the uranium industry in finding, developing, 

and producing * * * uranium beyond the requirements of the AEC are a significant indication that the challenges of the future will be 

met." 

In the present review it has been pointed out 

that: 

1. Reserves, when projected to the end of the 

AEC buying program in 1970, are adequate to meet the lifetime needs of nuclear 

reactors for generating electric power 

ordered up to the end of May or now in 

use. 

2. Tpe uranium needed to fuel reactors ordered 

in the future will have to come largely 

from deposits yet to be discovered. 

3. The distribution of known deposits indicates 

that these concealed deposits are most 

likely to occur in strata of continental 

sandstone. 

4. Unexplored areas of these rocks are large 

in relation to the still only partly explored 

areas where deposits are known. 

5. Other similar, less intensely mineralized 

strata extending over very much larger 

8 

areas offer less clearly de~mable possibilities for future discoveries. 

6. Although knowledge about uranium deposits is still incomplete, it is more 

broadly based than it was 20 years ago 

and can be effectively used in the search 

for deposits by an experienced industry. 

7. The possibilities are good that with intensive 

exploration the search for uranium will 

be successful. 

8. The technology in the use of uranium is certain to improve just as the technology in 

mining and use of coal has improved. 

REFERENCES 

Engineering and Mining Journal, 1966, U 30 8 resources 

abundant but undefined: Eng. an-l Mining Jour., 

v. 167,no. 11,p.80-83. 

Everett, F. D., and Bennett, H. J., 1967, Evaluation of 

domestic reserves and potential sources of ores containing copper, lead, zinc, and associated metals: 

U.S. Bur. Mines Inf. Circ. 8325, 77 p. 

Hubbert, M. K., 1962, Energy resources-A report to 

the Committee on Natural Resources of the National Academy of Sciences-National Research 

Council: Washington, N a tl. Research Council Pub. 

1000-D, 141 p. 

McGee, D. A., 1967, Uranium supply situation: Mines 

Mag., v. 57, no. 1, p. 21-24. 

Nininger, R. D., 1967, World productbn and reserves 

of uranium: Am. Inst. Mining Metall. Petroleum 

Engineers Minerals Symposium, 1~~h, Moab, Utah, 

June 23, 1967, Remarks, 4 p., 8 figs. 

Organization for Economic Cooperation and Development [European Nuclear Energy Agency], 1965, 

World uranium and thorium resources: Paris, 

Organization Econ. Coop. and Devel., 22 p. 

Santos, E. S., 1963, Relation of ore deposits to the 

stratigraphy of the Ambrosia Lake area, in Kelley, 

V. C., ed., Geology and technolog~r of the Grants 

uranium region [N. Mex.]: New Mexico Bur. 

Mines and Mineral Resources Merr. 15, p. 53-59. 

Weigel, W. W., 1965, The inside story of Missouri's exploration boom-pt. 1: Eng. and Mining Jour., v. 

166,no. 11,p.77-86, 170,172. 

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

of the United States: U.S. Geol. Survey Bull. 

1142-H, p. H1-H36. 

-tr U. S. GOVERNMENT PRINTING OFFICE: 1967 0- 281-855