Geologic Guides to 

Prospecting for 

Carnotite Deposits 

on Colorado Plateau

GEOLOGICAL giURVEY BULLETIN 988-B

Geologic Guides to 

Prospecting for 

Carnotite Deposits 

on Colorado Plateau

9y DORIS BLACKMAN WEIR

CONTRIBUTIONS TO THE GEOLOGY OF URANIUM, 1952

GEOLOGICAL SURVEY BULLETIN 988-B

This report concerns work done on 

behalf of the U. S. Atomic Energy 

Commission and is published with 

ihe permission of the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1952
UNITED STATES DEPARTMENT OF THE INTERIOR 

Oscar L. Chapman, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

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

Washington 25, D. C. - Price 15 cents (paper cover)
GEOLOGIC GUIDES TO PROSPECTING FOR CARNOTITE 

DEPOSITS ON COLORADO PLATEAU

By DORIS BLACKMAN WEIR

ABSTRACT

This report describes the geologic features that can be used to appraise tlie 

favorableness of ground in guiding diamond-drill exploration for carnotite 

deposits in the Upper Jurassic Morrison formation on the Colorado Plateau. 

It is based on a statistical study of the geologic logs of about 2,500 holes drilled 

by the Geological Survey. The most useful features consist of the thickness and 

color of the ore-bearing sandstone, the altered mudstone associated with the orebearing sandstone, and the abundance of carbonaceous material in the sandstone. 

Although each feature can be used alone to appraise the favorableness of the 

ground, an appraisal based on all of them together is more useful. A method 

of expressing this in numerical values is suggested.

The results obtained by the Geological Survey using these geologic guides 

appear to be at least twice as favorable as the drilling results obtained with 

little or no geologic guidance.

INTRODUCTION

The relations of certain geologic features to carnotite deposits in the 

Colorado Plateau region have long been recognized by miners and 

geologists. Not until 1947, however, when the Geological Survey 

began a large-scale program of diamond-drill exploration on behalf 

of the Atomic Energy Commission, were these features used extensively as guides in prospecting for carnotite. This report summarizes 

the results of a study of geologic logs of about 2,500 holes drilled by 

the Geological Survey in several areas in southwestern Colorado. All 

geologic features observable in drill core, which might be of value in 

guiding exploration, were recorded systematically and appraised as 

guides. It is hoped that the geologic relations discussed here will be 

of practical value to private industry in prospecting for carnotite ore, 

and that the recognition and study of these guides will result in the 

development of more useful application and perhaps additional 

guides.

The geologic guides to be described in this paper those that appear 

to be most valuable in recognizing ground favorable for ore are the 

thickness and color of the ore-bearing sandstone, the altered mudstone 

associated with the sandstone, and the presence of abundant carbonaceous material within the ore-bearing sandstone.

15
16 CONTRIBUTIONS TO THL GEOLOGY OF URANIUM, 1952

The writer wishes to express her appreciation to R. P. Fischer, 

L. S. Hilpert, and L. B. Riley, of the Geological Survey, for guidance 

in the study.

GEOLOGY OF ORE DEPOSITS

The carnotite deposits have a wide distribution in southwestern 

Colorado and the adjoining parts of Utah, Arizona, and New Mexico, 

where they extend over an area of at least 40,000 sq mi (fig. 6). Nearly

112°

x Deposits in the Shinarump conglomerate 

(TriflMic) r °

EXPLANATION

 Deposits in the Morris on formation 

(Jurassic)

A Deposits in the Entrada. sandstone 

{Jurassic)

FIGURE 6. Index map of part of Colorado, Utah, Arizona, and New Mexico showing 

general distribution of carnotite-bearing deposits.

the

all the known deposits of economic importance are restricted to the 

Shinarump formation of Triassic age and the Entrada and Morrison 

formations of Jurassic age. Most of the deposits occur in the Salt 

Wash sandstone member of the Morrison formation, and in many 

mining districts the deposits are found in one stratigraphic zone within 

the Salt Wash. This zone consists of sandstone lenses interbedded with 

some mudstone. The sandstone in this zone ranges in thickness from 

slightly less than 20 ft to slightly more than 80 ft, averaging about 

50 ft. This sandstone is referred to in this report as the "ore-bearing 

sandstone."
GEOLOGIC GUIDES TO PROSPECTING FOR CARNOTITE 17

The ore mainly impregnates sandstone, averaging about 0.25 percent 

U3O8 and 2 percent V2O5, but some of the fossil plant material in the 

ore-bearing beds is richly mineralized. The ore bodies are irregular 

tabular layers, at most only a few feet thick, and generally lie parallel 

to the sandstone bedding, but do not follow the beds in detail. They 

range in size from those containing only a few tons of ore to those 

containing many thousand tons; most of the deposits contain only 

a few hundred tons or less. Although the deposits have a spotty 

distribution, most of them are clustered in relatively small, vaguely 

defined areas. The larger areas between these clusters contain only 

a few scattered deposits, most of which are small.

The ultimate source, or sources, of the metals in the ore have not 

been determined. The distribution of the deposits and the habits 

of the ore, however, suggest an origin that is due to precipitation 

from ground-water solutions shortly after accumulation of the sands. 

Localization probably resulted from slight changes in the chemical 

composition of the solutions, perhaps in the environment of decaying 

organic material.

Readers desiring a more complete description of the geology of 

these deposits are referred to Coffin (1921), Fischer (1942, 1950), and 

Fischer and others (1951).

GEOLOGICAL SURVEY EXPLORATION

The exploration work of the Geological Survey is done in 'three 

general stages. During the first stage, holes are drilled at a wide 

spacing, usually about 1,000 ft apart, for geologic information. From 

this drilling, it is possible to recognize favorable ground that may 

contain one or more clusters of deposits. During the second stage, 

the favorable ground is drilled with holes at a moderate spacing, 

usually 100 to 300 ft apart, to find ore deposits. In the third stage, 

holes are drilled at a close spacing, about 50 to 100 ft apart, to extend 

and outline any deposits discovered in the earlier drilling. The 

geologic features that serve as guides are particularly useful during 

the first and second stages, as these features provide larger targets for 

drilling than do the ore deposits themselves.

GUIDES TO PROSPECTING

The geologic guides described below are now being used by the 

Geological Survey in its exploratory drilling program. They are 

discussed in terms of their application to subsurface exploration, 

though all of them are useful in surface prospecting. These guides 

vary in importance according to the size of the drilling target that 

they provide, and are described in that order of importance, beginning 

with the one that provides the largest target.
18 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM, 1952

Accompanying the description of each geologic guide is a graph 

showing the relation of that guide to ore. In order that enough 

measurements may be included for the graphs to have statistical meaning, each graph is a composite of several of the larger areas drilled 

by the Survey. These graphs show the average amount (arithmetic 

mean) of each feature cut by holes in all of the areas studied. The 

drill holes are grouped into five zones according to their position 

relative to ore deposits. The first zone includes aU holes that cut 

mineralized rock, and the remaining four include, respectively, the 

holes in the zone 0 to 100 ft outward, 100 to 200 ft outward, 200 to 

300 ft outward, and 300 to 400 ft outward from mineralized rock. A 

limit of 400 ft outward is used because drill-hole information beyond 

400 ft from the ore deposits is generally insufficient for statistical 

purposes. It is believed that if a larger number of holes had been 

drilled in zones farther from mineralized rock, and if data from these 

zones had been added to the graphs, they would continue to show a 

decrease in favorableness as distance from mineralized rock increases. 

It is not the averages themselves on these graphs that are significant, 

as they may vary from one drilling area to another, but rather the 

relations between the averages. Likewise, minor deviations from the 

general slope of these graphs probably represent incomplete statistical 

data rather than geologically significant variations.

THICKNESS OF THE ORE-BEABING SANDSTONE

In the Morrison formation the sandstone beds containing the 

carnotite deposits are lenticular, ranging in thickness from slightly 

less than 20 ft to slightly more than 80 ft. In southwestern Colorado, 

no large ore deposit has been found, by Survey drilling, in sandstone 

that had an original thickness (prior to recent erosion) of fess than 

about 40 ft. This minimum thickness figure is a reliable guide in 

wide-spaced drilling. In addition, most of the ore bodies are in or 

near the thicker, central parts of the sandstone lenses; these thicker 

parts can be recognized in cross-sections through diamond-drill holes. 

Not all thick sandstone is favorable, however. The spatial relations 

of ore deposits to differences in sandstone thickness are apparent in 

figure 7.

COLOR OF THE ORE-BEARING SANDSTONE

The sandstone enclosing most of the ore bodies is dominantly pale 

to light yellow brown and speckled with limonite stain. Generally 

this favorable color and staining extend several hundred feet beyond 

ore deposits. Farther away from deposits, the sandstone in many 

places is reddish brown. Sandstone with a reddish cast may contain
GEOLOGIC GUIDES TO PROSPECTING FOR CARNOTITE 19

a few ore deposits, but most of them are small, and generally a 

pronounced red color is indicative of unfavorable ground. These 

relations are illustrated by figure 8, which shows that the average 

percentage of ore-bearing sandstone with a reddish cast increases 

outward from the ore.

Holes

cutting

mineralized

rock

53.5 feet

100 200 300 400 

Distance from mineralized rock, in feet

FIGURE 7. Average thickness of ore-bearing sandstone, In zones coextensive with and 

outward from ore deposits (composite of fire drilled areas).

M.8%

Holes 

cutting 

nineralizec 

rock

3.9%

s V N N \ \

Average N

Vof s^

v\529\\ 

\ holesO \ x X V\

1

5.6 %

Average of 

429 holes

6.9%

Average of 

206 holes

Average of 

116 holes

Average of 

90 holes

100 200 300 

Distance from mineralized rock, in feet

400

FIGURE 8. Average percentage of ore-bearing sandstone with a reddish cast, In zones 

coextensive with and outward from ore deposits (composite of six drilled areas).
20 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM, 1952

ALTERED MTJDSTONE ASSOCIATED WITH THE ORE-BEARING

SANDSTONE

The ore-bearing sandstone is interbedded with mudstone, and it 

also contains thin lenses of mudstone and mudstone-pebble conglomerate. This mudstone is normally red, but near ore deposits the mudstone within the sandstone and the mudstone immediately beneath 

the ore-bearing sandstone have been altered to gray. A preliminary 

study of the red and gray mudstone has been made by Weeks (1951).

Figure 9 shows the character of a typical ore body and its relationship to the enclosing sandstone and associated mudstone. Near ore, 

the gray mudstone beneath the ore-bearing sandstone commonly is 

as much as several feet thick, as shown in this cross section. The thickness of gray mudstone decreases laterally,, but some of it usually

Light-brown sandstone^ ^-Diamond-drill hole 

473 /- **a 408. 398^ ^!3 475.

6,600" A

 ~T~ ~=^='=^=r 2="= 

Red-brown mudstone-^

FIGURE 9. Geologic section through diamond-drill holes, Calamity group of claims, Mesa

County, Colo.

extends a few hundred feet outward from the deposits. Figure 10 

shows the average thicknesses of gray mudstone immediately beneath 

the ore-bearing sandstone, in zones coextensive with and outward 

from ore deposits.

The percentage of gray mudstone relative to the total amount of 

mudstone within the ore-bearing sandstone is also a useful guide, 

though it is more difficult to measure quantitatively. In the present 

study, because of the necessity for a numerical comparison of geologic 

guides, only measurable units of mudstone within the sandstone (units 

0.1 ft or more thick) have been considered. Because units of this 

thickness are not cut by every drill hole in a given area, some holes 

have been excluded from the calculations of average percentage of 

gray mudstone relative to the total mudstone, as shown in figure 11. 

A sufficient number of holes remains, however, to illustrate clearly 

the relation of color of mudstone to ore.
GEOLOGIC GUIDES TO PROSPECTING FOR CARNOTITE 21

Holes

cutting

mineralized

rock

3.0 feet

1.7 feet

Average of 

429 holes

1.3 feet

Average of 

206 holes

I.I feet

Average of 

116 holes

0.9 feet

Average of 

90 holes

100 200 300 

Distance from mineralized rock, in feet

400

FIGURE 10. Average thickness of gray mudstone immediately beneath the ore-bearing 

sandstone, in zones coextensive with and outward from ore deposits (composite of six 

drilled areas).

Holes

cutting

mineralized

rack

64%

52%

Average of 

209 holes

38%

Average of 

III holes

23 % 23 %

Average of 

68 holes

Average of 

51 holes

100 200 300 

Distance from mineralized rock, in feet

400

FIGURE 11. Average percentage of gray mudstone relative to the total mudstone within 

the ore-bearing sandstone, In zones coextensive with and outward from ore deposits 

(composite of six drilled areas).
22 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM, 1952

ABUNDANCE OF CARBONACEOUS MATERIAL WITHIN THE 

ORE-BEARING SANDSTONE

Carbonized plant remains, consisting of fossil logs, branches, leaflike material, and unidentifiable fragments, are common in the orebearing sandstone. A close relationship between carnotite ore and 

these remains has long been recognized, for some of the remains have 

been richly replaced by ore minerals. As not all of the remains have

Holes

cutting

mineralized

rock

40.3 %

16.8%

Average of 

429 holes

15.5% 16.4%

Average of 

206 hales

Average of 

116 holes

10.0%

Average of 

90 holee

100 200 300 

Distance from mineralized rock, in feet

400

FIQUEB 12. Average percentage of drill holes cutting abundant carbonaceous material. 

In Bones coextensive with and outward from ore deposits (composite of six drilled areas).

been mineralized, however, and as the plant materials particularly 

the logs are not uniformly distributed through the sandstone, either 

horizontally or vertically, the significance of the observed relationship 

between carnotite ore and plant remains is difficult to evaluate. This 

relationship, therefore, has limited application in exploration. Figure 

12 shows, however, that abundant carbonized material is more common 

in holes cutting mineralized rock, and in holes near ore deposits, than 

in holes several hundred feet away from ore deposits. Possible traces 

of carbonized material have been ignored in this study, because of the 

limitations of observation in drill core and the possibility of misidentification of minute amounts of material.
GEOLOGIC GUIDES TO PROSPECTING FOR CARNOTITE 23

Field relations suggest that ore deposits have been localized in the 

vicinity of abundant carbonaceous material, and the relations shown 

in figure 12 can be interpreted to mean the same thing. In diamonddrill exploration, abundant carbonaceous material can be interpreted 

to indicate favorable ground, but because of the erratic distribution of 

plant remains, the lack of abundant carbonaceous material in a single 

drill hole does not in itself mean unfavorable ground.

NUMERICAL EVALUATION OP GEOLOGIC GUIDES

Each of the geologic guides described above is useful individually, 

but an appraisal based on all of them, expressed in numerical terms, 

is more valuable than is the use of any one alone. In order to test 

the reliability of such an appraisal, the following method was applied 

to one area (Calamity group) after drilling by the Geological Survey 

was completed. Modifications of this method are now being applied 

in the appraisal of other areas.

Each drill hole in the area was rated numerically according to the 

following scheme:

Thickness of ore-bearing sandstone (exclusive of mudstone lenses)

Thickness 

Rating: (feet)

8____________ 41 or more 

6_________________ 31-40 

4_________________ 21-30

Thickness

Rating: (feet) 

2__________________ 11-20 

0____________- 10 or less

Color of ore-bearing sandstone

Percentage of 

sandstone with Rating: a reddish cast

8_________________-__ 0 

6__________________ 1-15 

4_________________ 16-30

Percentage of 

sandstone with Rating a reddish cast :

2 _________________ 31-60 

0___________ More than 60

Thickness of gray mudstone at base of ore-bearing sandstone

RnHnP- Thickness Kating. (feet)

8_______-__ More than 4.0 

6________________ 3.1-4.0 

4________________ 2.1-3.0

T? a f i n a Thickness bating. (feet)

2__________________ 1.1-2.0

0_____________ 1.0 or less

Color of mudstone (units 0.1 ft or more thick) within the ore-bearing sandstone

Percentage of total mudstone 

Rating: that is gray

8__________________ 100-85 

6_________________ 84-70 

4____..____________ 69-40

Percentage of total mudstone 

Rating: that is gray

2_______________ 39-10

0_________ _Less than 10
24 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM, 1952

Carbonaceous material within the ore-bearing sandstone

Bating:

4___ ______________________ Abundant.

0_________________________ Sparse or absent.

It will be noted from the above table that a maximum rating of 8 

is assigned to each of the first four features, but that a maximum 

rating of 4 is assigned to carbonaceous material, owing to its erratic 

distribution and the fact that a quantitative measurement of this 

feature is more difficult than for the other features.

EXPLANATION

FIGURE 13. Map showing the relations of numerical evaluation ratings and carnotite 

deposits on part of Calamity Mesa, Mesa County, Colo.

To determine an evaluation rating for each drill hole, the numerical 

values given each of the features cut by that hole are totalled. In 

order to compensate the rating for holes that do not cut mudstone 

units 0.1 ft or more thick, and thus are assigned ratings for only 

four features rather than five, the total ratings for these holes are 

multiplied by 1.29. In this manner, a range of zero to 36 is obtained 

(or 36.12 for those holes that are rated on the basis of four features).

On the basis of drilling on the Calamity group of claims, Mesa 

County, Colo., the critical point on this evaluation scale is approximately 20; no large ore deposits occur in ground given a lower 

rating. Ground that has a rating of less than 15 is essentially barren. 

Ratings of 30 or more generally occur in the centers of the deposits. 

Figure 13 shows these relations in part of the area.
GEOLOGIC GUIDES TO PROSPECTING FOR CARNOTITE 25

Figure 14 shows graphically the relation of numerical values of 

favorableness to distance from ore deposits in the Calamity group of 

claims. Forty-two ore bodies, including all those drilled by the 

Geological Survey in this area, are included. It is believed that no 

importance should be attached to the slight upward trend of the 

averages in the zone 300-400 ft outward from ore. The trend of 

the averages is downward, outward from ore; if more data were 

available from the 300-400 ft zone, as well as from zones farther

Holes

cutting

minerolized

rock

25.5

21.7

Average of 

225 holes

18.4

Average of 

79 holes

16.5

15.7

Averoge of 

48 holes

Average of 

35 holes ^ r~

100 200 300 

Distance from mineralized rock, in feet

400

FIGURE 14. Average numerical values of favorableness, in zones coextensive with and 

outward from ore deposits, Calamity group of claims, Mesa County, Colo.

outward from ore, they would show a continued downward trend, 

although less steep.

The significance of these geologic criteria of favorable ground 

is essentially the same in all the areas drilled by the Geological Survey 

on the Colorado Plateau. They are being followed in all stages of 

drilling wide-spaced as well as moderate- and close-spaced.

COMPARISON OP RESULTS OBTAINED PROM DRILLING 

WITH AND WITHOUT GEOLOGIC GUIDANCE

Proof of the value of using geologic guides in exploration drilling 

lies in. the results. To demonstrate this value, in order to encourage the 

practice of using geologic guidance, an attempt has been made to compare the results obtained by the Geological Survey's drilling using 

geologic features as guides, with the drilling that had been done pre-
26 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM, 1952

viously by private interests using little or no geologic guidance. 

Unfortunately, for two reasons, it is not possible to express these 

results strictly on a comparable basis first, security restrictions prevent giving actual figures of results, and second, the two drilling 

operations differ in character.

Nearly all of the private drilling was near known deposits in 

ground that would be generally classed as favorable because of the 

proximity of ore. Thus, there should be a better chance of any single 

drill hole cutting ore in this type of drilling than in exploration 

away from known deposits, such as has been done by the Geological 

Survey. Furthermore, nearly all of the private drilling was in shallow ground, perhaps averaging 50 to 75 ft in depth, whereas the 

Geological Survey drilling has been in deeper ground averaging approximately 135 ft in depth. On the other hand, the holes drilled 

by private industry were mostly on a close spacing to develop deposits 

for mining, and for this reason more holes were put in a single deposit 

than is normally drilled in a deposit found by the Geological Survey.

If consideration is given to the much greater depth of Survey 

drilling, and to the higher risk of exploring ground away from known 

deposits, even though fewer holes are drilled in a single deposit, the 

results of Survey exploration using geologic guidance systematically 

are more than twice as favorable as the results obtained by private 

industry using little or no geologic guidance.

SUMMARY AND CONCLUSIONS

Geologic logs of about 2,500 holes drilled by the Geological Survey 

in the Morrison formation in southwestern Colorado were studied to 

appraise the value of certain geologic features as guides to exploration 

for carnotite deposits. On the basis of this study, the following 

conclusions are made:

1. Most ore deposits are in or near the thicker, central parts of 

sandstone lenses, and in general the thickness of the sandstone 

decreases away from ore deposits. Sandstone that is less than 40 ft 

thick is generally not favorable for large ore bodies.

2. Sandstone in the vicinity of ore deposits is colored light brown, 

but an increasing proportion of sandstone away from ore deposits 

has a reddish color, which is indicative of unfavorable ground.

3. Near ore deposits the mudstone in the ore-bearing sandstone 

and immediately below it has been altered from red to gray. The 

amount of altered mudstone decreases outward from ore deposits.

4. Sandstone in the immediate vicinity of ore deposits contains 

more carbonized plant fossils than do the same beds away from ore 

deposits, suggesting that ore deposits are localized in the vicinity 

of abundant carbonaceous material.
GEOLOGIC GUIDES TO PROSPECTING FOR CARNOTITE 27

Each of these features is useful individually in guiding exploration, 

but a combination of all of them, expressed in terms of a numerical 

rating, is even more useful. Exploration that uses these features as 

guides yields results that are about twice as good as exploration using 

little or no geologic guidance.

REFERENCES CITED

COFFIN, R. C., 1921, Radium, uranium, and vanadium deposits of southwestern

Colorado: Colorado Geol. Survey Bull. 16. 

FISCHER, R. P., 1942, Vanadium deposits of Colorado and Utah; U. S. Geol.

Survey Bull. 936-P. 

FISCHEB, R. P., 1950, Uranium-bearing sandstone deposits of the Colorado

Plateau : Econ. Geol., vol. 45, pp. 1-11.

FlSCHEE, R. P., HlLPEET, L. S., SCHUMACHEE, J. I., CATER, F. W., STROBEIJ,,

J. D. Jr., CRAIG, L. C., PHOENIX, D. A., and TEACE, R. D., 1951, Summary of 

investigations through 1950 of the carnotite-bearing sandstones of the Colorado 

Plateau (report, in files of U. S. Geol. Survey).

WEEKS, A, D., 1951, Red and gray clay underlying ore-bearing sandstone of the 

Morrison formation in western Colorado (report, in files of U. S. Geol. Survey).

 fr C. S. GOVERNMENT PRINTING OFFICE : 1953 O - 273111



CONTENTS

Page

Abstract._________________________________________________________ 15

Introduction._ ____________________________________________________ 15

Geology of ore deposits--__-_____._______________________________.__ 16

Geological Survey exploration.______________________________________ 17

Guides to prospecting._____________________________________________ 17

Thickness of the ore-bearing sandstone.__________________________ 18

Color of the ore-bearing sandstone-______--____-__----_--------_- 18

Altered mudstorie associated with the ore-bearing sandstone._______ 20

Abundance of carbonaceous material within the ore-bearing sandstone. 22

Numerical evaluation of geologic guides.___________ _____________ 23

Comparison of results obtained from drilling with and without geologic

guidance.______________________________________________________ 25

Summary and conclusions.______________-..-__________--_-___--___-_ 26

References cited__________________________________________________ 27

ILLUSTRATIONS

FIGURE 6. Index map of part of Colorado, Utah, Arizona, and New Mexico, 

showing the general distribution of carnotite-bearing deposits. _______________________________________________ 16

7. Average thickness of ore-bearing sandstone, in zones coextensive 

with arid outward from ore deposits (composite of five drilled 

areas) _ _____________________________________________ 19

8. Average percentage of ore-bearing sandstone with a reddish 

cast, in zones coextensive with and outward from ore deposits 

(composite of six drilled areas)__________________________ 19

9. Geologic section through diamond-drill holes, Calamity group

of claims, Mesa County, Colo.__________________________ 20

10. Average thickness of gray mudstone immediately beneath the 

ore-bearing sandstone, in zones coextensive with and outward 

from ore deposits (composite of six drilled areas)__________ 21

11. Average percentage of gray mudstone relative to the total mudstone within the ore-bearing sandstone, in zones coextensive 

with arid outward from ore deposits (composite of six drilled 

areas) ________________________________________________ 21

12. Average percentage of drill holes cutting abundant carbonaceous material, in zones coextensive with and outward from 

ore deposits (composite of six drilled areas)____________ 22

13. Map showing the relations of numerical evaluation ratings and 

carnotite deposits on part of Calamity Mesa, Mesa County, 

Colo_._____________________________________________ 24

14. Average numerical values of favorableness, in zones coextensive 

with and outward from ore deposits, Calamity group of 

claims, Mesa County, Colo_________________--_--__---__ 25

in