Preliminary Study of 

Radioactive Limonite in 

Colorado, Utah, and 

Wyoming

GEOLOGICAL SURVEY BULLETIN 1046-N

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

Preliminary Study of 

Radioactive Limonite in 

Colorado, Utah, and 

Wyoming

By T. G. LOVERING and E. P. BERONI

CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

GEOLOGICAL SURVEY BULLETIN 1046-N

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1959
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

The Library of Congress has cataloged this publication as follows:

Levering, Tom Gray, 1921-

Preliminary study of radioactive limonite in Colorado,. 

Utah, and Wyoming, by T. G. Levering and E. P. Beroni. 

Washington, U. S. Govt. Print. Off., 1959.

iv, 339-384 p. illue., maps, diagrs., table. 25 cm. (U. S. Geological Survey. Bulletin 104&-N. Contributions to the geology of 

uranium)

"Literature cited" : p. 371.

1. Iron ores The West. 2. Radioactivity. 3. Uranium ores The 

West. i. Beroni, Ernest Pete, 1919- joint author, n. Title: 

Kadioactive limonite in Colorado, Utah, and Wyoming. (Series: 

U. S. Geological Survey. Bulletin 1040-N. Series: U. S. Geological 

Survey. Contributions to the geology of uranium)

622.349

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

Washington 25, D. C. - Price 35 (paper cover)
CONTENTS

	Page

Abstract________._._.___________._-_.._________ 339

Introduction__________________________________________ 339

Localities______________________________________________ 343

Yellow Cat area, Grand County, Utah_______________________ 343

Snow-Bonniebell claims, Uintah County, Utah ________________ 346

Silver Cliff mine, Niobrara County, Wyo________ _____ __ 348

Golden Gate Canyon area, Jefferson County, Colo________________ 350

Diamond J ranch, El Paso County, Colo____________________ _ 353

Lucky Break iron mine, Chaff ee County, Colo ___________ _ _______ 3 56

Ouray hot springs, Ouray County, Colo________________________ 358

Haputa ranch area, Custer County, Colo________________________ 359

Powderhorn district, Gunnison County, Colo____________________ 364

Summary_________________________________________________ 368

Literature cited-________________________________________________ 371

Index_____________________________________ 383

ILLUSTRATIONS

PLATE 42. Photograph and autoradiograph of polished section from radioactive shear zone, Haputa ranch-_________________ Faces 363

FIGURE 34. Index map showing localities examined for radioactive limonite___________________________________ 341

35. Graph showing variations in equivalent uranium and in

uranium and other metals, Cactus Rat claim_________ 344

36. Graph showing variations in equivalent uranium and in uranium

and other metals, Snow-Bonniebell claims __________ _ 347

37. Map of part of the Silver Cliff mine-..-____________ 349

38. Graph showing variations in equivalent uranium and in

uranium and other metals, Buckman adit______________ 352

39. Graph showing variations in equivalent uranium and in

uranium and other metals, Union Pacific property _______ 353

40. Sketch map of radioactive-limonite zone on Diamond J

ranch._____________________________________________ 354

41. Graph showing variations in equivalent uranium and in

uranium and other metals, Diamond J ranch-___________ 355

42. Sketch map showing general geology around Lucky Break

iron mine________________________________________ 356

43. Geologic map of part of the Haputa ranch_________________ 360

44. Graph showing variations in equivalent uranium and selected

metals, Haputa ranch___________________-____-----_--_ 363

45. Graph showing variations in equivalent uranium and selected

metals, Little Johnny vein___________________________ 365

46. Graph showing variations in equivalent uranium and selected

metals, Jeanie No. 2 claim_____-__-____-_--_---___----_ 366

47. Sketch of southeast wall of bulldozer cut, Jeanie No. 2 claim. _ 367

in
IV CONTENTS

TABLES

TABLE 1. Description and radioactivity and X-ray analyses of samples Page 

from Lucky Break iron mine____.____________________ 357

2. Spectrographic analyses of selected elements in drill core from

mineralized shear zone, Haputa ranch_______________ 362

3. Petrographic description of thin and polished sections cut from

selected samples__________________________________ 368

: 4. Elements showing significant and possibly significant correlation with radioactive material in localities examined, ______ 370

5. Description and analyses of samples from Yellow Cat area_ _ 372

6. Description and analyses of samples from Snow-Bonniebell

claims____________________________________________ 373

7. Description and analyses of samples from Silver Cliff mine__ 374

8. Description and analyses of samples from Golden Gate Canyon

area__._____________________________ 375

9 Spectrographic analyses of samples from Golden Gate Canyon

area... ____________________________________________ 376

10. Description and analyses of samples from Diamond J ranch. _ 377

11. Spectrographic analyses of samples from Lucky Break iron

mine____________ _________ _____________________ 378

12. Description and analyses of samples from Ouray hot springs

tufa deposits__--__-_______--___------------_---__--_- 379

13. Description and analyses of samples from Haputa ranch area._ 380

14. Description and analyses of samples from Powderhorn district. 381
CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

PRELIMINARY STUDY OF RADIOACTIVE LIMONITE IN 

COLORADO, UTAH, AND WYOMING

By T. G. LOVEBING and E. P. BERONI

ABSTRACT

Nine radioactive-limonite localities of different types were sampled during the 

spring and fall of 1953 in an effort to establish criteria for differentiating limonite 

outcrops associated with uranium or thorium deposits from limonite outcrops not 

associated with such deposits. The samples were analyzed for uranium and 

thorium by standard chemical methods, for equivalent uranium by the radiometric method, and for a number of common metals by semiquantitative geochemieal methods. Correlation coefficients were then calculated for each of the 

metals with respect to equivalent uranium, and to uranium, where present, for 

all the samples from each locality. The correlation coefficients may indicate a 

significant association between uranium or thorium and certain other metals. 

Occurrences of specific metals that are interpreted as significant vary considerably for different uranium localities but are more consistent for the thorium 

localities.

Samples taken from radioactive outcrops in the vicinity of uranium or thorium 

deposits can be quickly analyzed by geochemical methods for various elements. 

Correlation coefficients can then be determined for the various elements with 

respect to uranium or thorium; if any significant correlations are obtained, the 

elements showing such correlation may be used as indicators of uranium or thorium elsewhere hi the area. Soil samples of covered areas in the vicinity of the 

radioactive outcrop may then be analyzed for the indicator elements and any 

resulting anomalies used as a guide for prospecting where the depth of overburden 

is too great to allow the use of radiation-detecting instruments. Changes in color 

of limonite stains on the outcrop may also be a useful guide to ore in some areas.

Correlation coefficients of the associated indicator elements, used in conjunction 

with petrographic evidence, may be useful, too, in interpreting the origin and 

paragenesis of radioactive deposits.

INTRODUCTION

The radioactive-limonite localities discussed in this report were 

examined in order to determine whether field criteria could be found 

that would differentiate between indigenous radioactive limonite and 

transported radioactive limonite. Nine localities with differing geologic environments and types of radioactive material were selected. 

At each locality samples were taken of both the radioactive and nonradioactive material; wherever possible, a continuous channel sample,
340 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

consisting of individual samples representing 1-foot segments, was 

taken across the radioactive-limonite zone and into the nonradioactive material on both sides. Changes in color and texture were 

noted. The samples were analyzed for equivalent uranium and for 

uranium and other metals for which geochemical field tests are available. The purpose of the analyses was to determine whether any of 

these metals show significant correlations, or dispersion halos,.with 

respect to uranium or thorium in the outcrop.

Semiquantitative spectrographic. analyses for about 60 elements 

were obtained on the samples from some of the localities. The sensitivity of both spectrographic and geochemical analysis varies greatly 

from one element to another. The spectrograph will reveal the presence of as little as 0.00005 percent silver in a sample but cannot detect 

mercury in concentrations less than 0.1 percent. The concentrations 

of the elements are reported in semiquantitative spectrographic analyses in powers of 10 with (+) plus or ( ) minus appended, when applicable, to indicate whether the concentration is near the top or 

bottom of the range, thus: O.X+=0.5-i.O percent, O.X=0.2-0.5 

percent, O.X"=0.1-0.2 percent; comparisons of this type of semiquantitative results with those obtained by quantitative methods, 

either chemical or spectrographic, show that the assigned group includes the quantitative value about 60 percent of the tune. The 

geochemical analyses are reported in parts per million rather than in 

percent, and are accurate approximately to the first significant figure.

Most of the field examinations were made by the authors during 

the latter part of October 1953. The Lucky Break iron mine was 

visited by T. G. Levering and W. K. Griifitts in June 1953, and the 

mines in the Golden Gate Canyon area were visited and sampled by 

E. P. Beroni early in November 1953. The localities discussed in 

this report are shown on the index map (fig. 34).

Correlation coefficients have been calculated for each group of 

samples in an attempt to express mathematically the relative degree 

of association between the radioactive elements and some of the other 

metals in the sample. The authors feel that where high correlations 

were obtained the possibility of a significant association warrants 

further investigation, even though the small number of samples obtained from, the various localities does not constitute a valid approximation to a representative statistical sample.

The correlation coefficients were determined by a modification of 

the method used by Miesch and Shoemaker (1953, written communication). In calculating the correlation coefficients, all assays were 

first expressed in parts per million in order to make relative concentrations of the various elements more readily apparent. The logarithms of the assays were then tabulated and average values for the
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 341

110°

42

109

EXPLANATION

X5

Locality examined 

fi/u/riter refers to list below

1 Silver Cliff mine

2 Snow-Bonniebell claims

3 Golden Gate Canyon area

4 Yellow Cat area

5 Diamond J ranch

6 Lucky Break iron mine

7 Powderhom district

8 Haputa ranch area

9 Ouray hot springs

,'j ACKSON[\ 

imboat Springs '

Iv Jft ) R 0 U T'T i|~--'^_4/

 --\\ J GRAND - BOULDER .._-! \.i ,^-^r * 

FIGUEE 34. Index map showing localities examined for radioactive limonite.

log concentrations of each element were determined. The use of logarithms was considered preferable to the use of straight assay data 

because of the extreme range in concentrations represented by the 

assays. (The logarithmic transformation greatly decreases the effect 

of a few extremely high values, thus making correlations more nearly 

representative of the whole group of assays involved.) Next, for each 

element, the deviation from the average was determined for each log 

assay; these deviations were then squared and the sum of the squares 

was found so that the standard deviation could be calculated according to the formula: ;
342 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

where <r=standard deviation, Z>=deviation from the mean log assay, 

n=r number of assays.

The individual log assays for equivalent uranium and for uranium, 

wHere present, were next multiplied by the corresponding log assays 

of each of the other elements in turn, and the mean value of the 

products determined thus:

M ,, 

n

where Jl/=mean product, S=summation, a=uranium log-assay value, 

6=log-assay value of some other element, n=number of assays. The 

correlation coefficients were then calculated according to the formula

2ab /a b\

 I 2t 2, I

n \ n n/

where r= correlation coefficient, a=log assay eU or U, 6= log assay 

of one of the other elements, <?a=standard deviation for U, <r6=standard deviation for the other element. A perfect positive correlation is 

-f 1, a perfect inverse relationship is indicated by a correlation of 1, 

and a completely random distribution of two elements with respect to 

each other is represented by a correlation of 0. For normally distributed populations, the threshold of significance of a correlation 

coefficient is inversely proportional to the number of samples analyzed. Most of the individual sample groups collected for this study 

contained no more than 5-15 samples, so only those correlation coefficients exceeding ±0.4 were considered significant (Dixon and 

Massey, 1951, p. 164).

Only those elements were correlated that showed a significant 

variation in concentration from one sample to the next in each group. 

No elements were correlated whose concentration fell below the 

threshold of analytical sensitivity in more than 25 percent of the 

samples within a given group. If the concentration of an element 

fell below the threshold of sensitivity in only a few samples within 

a group, the concentration of that element was arbitrarily assigned 

to the middle of the next lower order of magnitude. For example, 

the arsenic concentration of 2 samples from the Little Johnny mine 

area was reported as <10 ppm (parts per million); these samples 

were assigned a value of 5 ppm. If a few analyses were reported as 

<1 ppm, the same procedure was followed, but all assays were multiplied by 10 to avoid the use of negative logarithms.

The writers wish to express their appreciation to the analysts of 

the U. S. Geological Survey who furnished the analytical data on
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 343

which this report is based. H. E. Crowe and J. H. McCarthy made 

the geochemical determinations, and S. P. Furman and R. F. Dufour 

made the uranium, equivalent uranium, and thorium analyses. 

Thanks are also due to many members of U. S. Geological Survey 

field parties for valuable aid in finding outcrops for study and for 

assistance in understanding their geologic setting. The cooperation 

of the various owners in allowing access to their properties is much 

appreciated. The work was done on behalf of the Division of Raw 

Materials of the U. S. Atomic Energy Commission.

LOCAIJLTIES 

YELLOW CAT ABBA, GRAND COUNTY, UTAH

The Yellow Cat area, Thompson district, is principally within 

T. 22 S., Rs. 22 and 23 E., in east-central Grand County, Utah. 

The rocks exposed are the Summerville and Morrison formations of 

Jurassic age and consist of alternating conglomerates, sandstones, 

and muds tones of continental origin. More than a hundred thousand 

tons of uranium and vanadium ore has been produced from the area; 

nearly all of it came from sandstone beds in the Salt Wash member of 

the Morrison formation which overlies the Summerville formation 

with slight disconformity and is overlain conformably by the Brushy 

Basin member of the Morrison formation; the Brushy Basin member 

consists predominantly of red mudstones. All the rocks in the area 

dip gently to the north. A few gentle folds are present locally, but 

there is little evidence of faulting.

The uranium-vanadium deposits of the Yellow Cat area have been 

examined and described by many geologists during the past fifty years. 

The most recent, and probably the most comprehensive, published 

report on the area was written by Stokes (1952).

SAMPLES AND ANALYSES

Thirteen samples were collected from the Yellow Cat area. All the 

samples were analyzed by geochemical-prospecting methods for a number of common elements, and a separate split of each sample was 

analyzed fluorometrically for uranium and radiometrically for equivalent uranium. [These analyses are shown in table 5, p. 372.]

The variation of equivalent uranium and uranium and various other 

metals hi a 7-foot vertical channel sample, taken on the Cactus Eat 

claim, is shown in figure 35. In order to avoid confusion, data are 

graphed only for those metals that appeared to show significant changes 

in concentration and for which assays were available on all samples.

468040 59 2
344 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

. 100,000

10,000

59

SAMPLE F

FIOUBE 35. Graph showing variations in equivalent uranium and uranium and^other metals in'the 7-foot 

vertical channel sample from the Cactus Eat claim, Grand County, Utah.

Correlation coefficients .for eight metals with respect to both uranium 

and, equivalent uranium are shown in the table below.

,;. ' Correlation coefficients, Yellow Cat area

. , ^ {13 samples]

r. «U iff

Mo_.-_._._____ !+0. 38 +0. 29

As. 

Sb. 

Zn_

2 +. 70 «+. 65

+. 55 . 46

... _____ +.09 +.17 

> Possibly significant. * Probably significant.

Cu________.__

V___._______-

Mn__. _______

Fe._.____.__.

eU 

___ -0. 07

_____ 2 +. 58

i 47

_ ._ -.01

u 

 0.06

 +'. 70

»-. 45

-.08
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 345 

CONCLUSIONS

Information derived from samples taken in the Yellow Cat area 

suggests that geochemical prospecting for elements associated with 

uranium may be a useful tool in exploration, but there is no visible 

characteristic of the limonite that is diagnostic of proximity to 

uranium deposits.

A comparison of thin and polished sections of sample F57 with 

those of sample F58 does not reveal any significant difference in the 

nature of the iron oxides that can be correlated with the difference in 

the uranium content. Red hematite breccia in a veinlet cutting 

goethite-impregnated sandstone (sample F61) is unexpected because 

of the proximity of this ferric oxide to carbonaceous material that 

might have been expected to reduce the iron to the ferrous state. 

The work of Tunnell and Posnjak (1931) has shown that under 

atmospheric conditions in the FeaOa-HaO-SOa system, goethite is 

stable below 130°C and hematite above that temperature. The 

presence of gypsum indicates that the sulfate ion was probably available. The late hematite thus suggests that moderately hot solutions 

may have come in along small fractures at some time after the lithification of the sandstone and the development of early goethite.

The variation in metal content of the channel sample shown in 

figure 35 suggests leaching of iron from a zone about 2 feet below the 

surface and reconcentration of this iron in the surface layer. Iron 

content appears to be completely unrelated to uranium content, 

manganese shows an inverse relationship with uranium, but arsenic, 

antimony, and molybdenum correlate positively with uranium.

A study of the correlation coefficients shown in table on p. 344 

also brings out the random distribution of uranium with respect to 

iron, its negative correlation with manganese, and its good positive 

correlation with arsenic and antimony. In addition, the table illustrates that vanadium gives a good correlation with uranium, but that 

for the total 13 samples, molybdenum does not correlate as well with 

uranium as it appeared to in the 7 samples that constitute the channel 

sample (table 5, p. 372). Zinc and copper, like iron, appear to have 

a more or less random distribution with respect to uranium.

If more detailed sampling in this area should confirm the relationship between uranium and arsenic, antimony, and vanadium suggested by this preliminary work, geochemical prospecting for these 

indicator elements might be of value hi the search for additional 

uranium deposits in the Yellow Cat area, where depth of overburden 

precludes the use of Geiger counter or scintillation counter.

-.The close association of antimony and arsenic, as well .as vanadium, 

with the uranium indicates that these two minor elements may also 

be present in small amounts in carnotite, which is the major ore
346 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

mineral of the district. It also suggests the possibility that they 

were present in the primary mineral from which the carnotite was 

derived.

SNOW-BONNIEBELL CLAIMS, TTINTAH COUNTY, UTAH

The Snow-Bonniebell claim group is in sees. 17, 18, and 24, T. 6 S., 

R. 24 E., in the eastern part of Uintah County, Utah. The claims 

are at an altitude of about 5,500 feet on the crest and the south slope 

of a hogback ridge of sandstone of the Mesaverde formation of 

Cretaceous age. This sandstone ridge is on the southern flank of 

the large Split Mountain anticline; the ridge rises about 200 feet 

above a nearly level plain cut on the underlying Maneos shale to the 

north.

Small areas of anomalous radioactivity occur at intervals along a 

high-angle normal fault which cuts the sandstone near the ridge 

crest. The fault trends nearly parallel to the sandstone outcrop 

and dips steeply southward. Spotty radioactive anamolies are also 

present as much as several hundred yards south of the fault.

The Snow-Bonniebell group of claims was examined and sampled 

in 1950 by E. P. Beroni and F. A. McKeown (1952, p. 14-20).

SAMPLES AND ANALYSES

Eleven samples were collected from the Snow-Bonniebell claim 

group (table 6, p. 373). Three of these constitute a channel sample 

across a limonite seam on the east wall of an opencut on the Bonniebell No. 3 claim about a quarter of a milp south of the ridge crest. 

Six other samples were taken in consecutive 1-foot segments across a 

radioactive fault zone approximately half a mile east-northeast of 

the opencut. In addition, 2 grab samples of radioactive limonitic 

material were collected, 1 from the vicinity of the cut and 1 from the 

fault zone.

All 11 samples contained less than 300 ppmof vanao'ium and less 

than 10 ppm of cobalt and nickel. The concentrations of other 

elements hi these samples are shown in table 6.

The graphs in figure 36 indicate the variations hi concentrations 

of selected elements in the six samples collected across the fault zone. 

The correlation coefficients for uranium and equivalent uranium with 

respect to these elements are shown in table below.

Correlation coeffiente, Snow-Bonniebett daims

{11 samples]

tU V 

'-fO. 38 t-fO. 30 

-K 12 -. 13

Zn_.__ _ ._

Mo- ............

Mn_. ............

i Possibly significant.

eU U 

-fO. 04 «-0. 40

-. 07 -. 08

»-K 61 M-. 65

* Probably significant.

Fe _________

As.... _ __- 
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 347

100.000

10,000

1000

100

10

South North

36. Qrapb showing variations in equivalent uranium and in uranium and other metals in 

samples from fault zone, Snow-Bonniebell claims.

CONCLUSIONS

Compared to the wall-rock samples (F63-F64) on either side, 

sample F65 from the iron-stained clay seam on the wall of the opencut 

contains high concentrations of zinc, copper, arsenic, molybdenum, 

and uranium. Yet none of these elements shows significant correlations with uranium in the samples taken across the fault zone, half 

a mile away (table, p 346). Manganese, on the other hand, which 

shows no increase in concentration in the limonitic clay seam relative 

to the wall-rock samples hi the opencut, is the only element of the 

group that correlates well with uranium in the fault zone. This may
348 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

indicate that the elements concentrated in the clay seam were deposited with the clay, but that the uranium and manganese along the 

fault were deposited by ground water circulating along this permeable 

zone. It is, of course, also possible that the number of samples collected was too small to be representative and that the apparent correlations are merely coincidental.

In any event, the available data do not appear to indicate the 

presence of any large concentrations of uranium minerals in this area.

SILVER CUFF MINE, NIOBBABA COUNTY, WYO.

The Silver Cliff mine is in sec. 7, T. 32 N., R. 63 W., half a mile 

west of Lusk, Niobrara County, Wyo. The mine is at an altitude 

of about 5,200 feet and is near the crest of a prominent hill which is 

capped by dense brown quartzite of Cambrian age. The quartzite 

lies unconformably on a Precambrian metamorphic complex which 

consists of schist, gneiss, and quartzite and is intruded by pegmatite 

dikes. A high-angle northward-trending reverse fault that dips about 

60° E. is exposed near the summit of the hill where Precambrian 

rocks in the hanging wall have been moved into contact with the 

quartzite of Cambrian age of the footwall.

The Silver Cliff mine was first opened hi 1880; in addition to 

uranium, gold, silver, and copper have been produced there. The 

ore deposits are localized along the reverse fault and in fractured 

quartzite of Cambrian age in the footwall. The uranium deposits 

have been described by Lind and Davis (1919) and more recently by 

Wilmarth and Johnson (1954).

SAMPLES AND ANALYSES

Five samples were collected from 1 locality about 50 feet southwest 

of the entrance to the opencut leading to pit 1 (fig. 37 and table 7, 

p. 374). The table below gives the correlation coefficients for equivalent uranium with elements that were present in determinable 

amounts in at least four of the samples.

Correlation coefficients, Silver Cliff mine 

[5 samples]

Zn ______ _._..__-_.

Cu __ --________-____-

Co ___________ .

As ___________ -

i Possibly significant. 

* Probably significant.

eU 

____ 1+0.72

. _ i+.73

____ +.40

__ 2+.65

Mo..___. _ ____

V..._. _ ......

Mn _________

Fe_... _._._..__.

eU 

___________ 2 + 0.60

_ ..._____ +.53

2 + . 63

___________ +.02
RADIOACTIVE LrMONTTE IN COLORADO, UTAH, WYOMING 349

EXPLANATION R

vZ

Metamorphic rocks

55

MAIN LEVEL

U 

Fault, showing dip

Dashed where approximately 

located. U, upthrown side; 

D, downthrown side

85 

Strike and dip of joints

40

I

Opencut

Underground workings 

projected to surface

Inclined workings 

Chevrons point down

Kl 

Foot of winze

0 

Head of winze

 

Sampled locality

80 Feet

Geology by V. R. Wilmarth, August 1950

FIGURE 37. Map of part of the Silver Cliff mine showing sampled locality. 

CONCLUSIONS

The relatively high correlations between equivalent uranium and 

all the other elements tested, with the exception of iron, suggest 

that these elements were introduced along the same open fractures in 

the relatively dense impermeable quartzite and were then deposited
350 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

in films or coatings on the fractures. The brown quartzite contains 

some indigenous iron oxide, as shown by rounded grains of hematite 

in a thin section of sample F75; the barren red quartzite represented 

by sample F77 contains several tunes as much iron, in the form of 

primary red hematite, as any of the other four samples. This indigenous iron oxide could easily account for the lack of correlation between 

uranium and iron. Sample F77 also contains an unusually large 

amount of nickel (30 ppm) and of copper (150 ppm). Two grab 

samples of the red quartzite, collected from separate localities a 

thousand feet or more away from the mine workings, also contained 

about 30 ppm of nickel and about 120 ppm of copper. These abnormal concentrations suggest that a certain amount of copper and 

nickel, as well as iron, was originally present in the sediments from 

which the quartzite bed was derived. The close association between 

equivalent uranium and zinc, copper, arsenic, molybdenum, and 

manganese in samples from this deposit suggests that some or all of 

these five elements might be useful as uranium indicators for prospecting in this area.

GOLDEN GATE CANYON ABEA, JEFFERSON COUNTY, COLO.

The Golden Gate Canyon area is in T. 35 S., R. 70 W., Jefferson 

County, Colo. Most of the uranium prospects are near the bottom 

of the canyon at an altitude of 6,500 to 7,000 feet.

Rocks exposed in the area consist of a thick series of steeply dipping 

schists and gneisses of the Precambrian Idaho Springs formation. 

These rocks have a regional trend of about N. 80° E.; they have been 

cut by numerous faults and breccia "reefs" which strike northwestward and dip steeply.

Pitchblende and base-metal sulfides appear to have been localized 

by the intersection of northwestward-trending faults or fractures 

with certain favorable stratigraphic zones in the Idaho Springs 

formation. The uranium deposits of the Golden Gate Canyon area 

have been studied and described by Adams, Gude, and Beroni (1953). 

Two of these deposits, at the Union Pacific prospect and at a road cut 

near the portal of the Buckman adit, were sampled for this study.

SAMPLES AND ANALYSES

Ten samples were collected from the two localities examined (table 

8, p. 375); four of these constitute a discontinuous channel sample 

across the radioactive zone in a road cut near the portal of the Buckman adit; the other six constitute a channel sample across the uraniumbearing vein and breccia zone exposed near the collar of the shaft on 

the Union Pacific property.
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 351

All samples were analyzed for equivalent uranium, uranium, copper, 

lead, zinc, arsenic, antimony, and molybdenum. Correlation coefficients were determined for both uranium and equivalent uranium 

with respect to the other six elements (table below).

Semiquantitative spectrographic analyses were made of the 10 

samples in order to determine whether any elements, in addition to 

the 6 tested geochemically, showed significant occurrence in relation 

to uranium (table 9, p. 376).

Correlation coefficients, Golden Gate Canyon area

[10 samples] 

el7 17 eU U

Cu__. __-__.____ -0.24 + 0.,11

Pb__.__________ -.36 +.15

Zn________ ______ +.11 +.02

As______________ +0.13 +0.02

Sb______________ +.17 +.06

Mo_________ ' + .45 . +.34

' Possibly significant.

CONCLUSIONS

The correlation coefficients calculated for all 10 samples appear ta 

indicate a very poor correlation between uranium and the other 

metals, with the possible exception of molybdenum. However, when 

the assay values for the various metals are plotted separately against 

those of uranium and equivalent uranium for the two channel samples 

(figs. 38 and 39), it is apparent that this is not true. In the samples 

both from the Buckman adit and the Union Pacific prospect, the content of copper, lead, arsenic, and antimony, as well as molybdenum, 

tend to vary directly with uranium content. The poor correlation 

coefficients may be explaiped by the fact that the uranium content 

was high relative to the other metals at the Buckman adit, but, at 

the Union Pacific prospect the reverse was true. When the samples 

from the two localities were pooled for statistical study, the highest 

uranium assays did not correspond to the highest assays for the other 

metals; consequently, the correlation coefficients for the pooled sample 

were much lower than they would have been for either deposit had 

the samples not been combined. This indicates a pitfall to be avoided 

in the application of correlation coefficients to assay data. If too 

many samples from different localities are combined in an effort to 

obtain a significantly large number of analyses for statistical treatment, the resulting correlation coefficients may obscure rather than 

emphasize the relationships sought.

A study of the semiquantitative spectrographic analyses (table 9, 

p. 376) suggests that silver, bismuth, yttrium, and ytterbium may also 

be closely associated with uranium in these deposits.

468040 59 3
352 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

100,000

PIQTTKE 38. Graph showing variations in equivalent uranium and in uranium and other metals, Buckman

adit, Golden Gate Canyon.
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 353

10,000

93 94 95 96 

SAMPLE F

FIGUEE 39. Graph showing variations in equivalent uranium and in uranium and other metals, Union

Pacific property, Golden Gate Canyon.

DIAMOND J RANCH, EL PASO COUNTY, COLO.

The Diamond J ranch is about 10 miles north-northeast of Colorado 

Springs in T. 12 S., R. 66 W. The deposit, on the north face of a low 

hill, at an altitude of about 6,500 feet, was discovered in 1951 by H. E. 

Burgess. It is in the nearly flat-lying Dawson arkose of Late Cretaceous and Paleocene age and consists of an irregular body of coarse 

sandstone and arkosic conglomerate heavily impregnated with iron 

and manganese oxide. It is very irregular in form with small local 

"rolls", has a northwesterly trend, and appears to be nearly 150 feet 

long with a maximum width of about 25 feet and a maximum exposed 

thickness of about 10 feet (fig. 40). L. R. Page and G. B. Gott made 

a reconnaissance examination and sketch map of this deposit in 1952 

(written communication).
354 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

EXPLANATION

Uraniferous iron oxide and 

manganese oxide gossan

Dawson arkose

Contact

Dashed where approximately located;

dotted where concealed

_____S

Plunge of "rolls"

Strike and dip of beds

1-2 

Thickness of gossan, in feet

Line of sample

50 Feet

Contour interval 20 feet

Datum assumed

Geology by L. R. Page and G. B. Gott, 1952

FIGURE 40. Sketcfi map of radioactive-Iimonite zone on Diamond J ranch, showing sampled localities. 

SAMPLES AND ANALYSES

Thirteen samples were collected from the deposit. Localities 

sampled are shown on figure 40. All samples were analyzed for 

equivalent uranium, uranium, zinc, lead, copper, nickel, cobalt, antimony, arsenic, molybdenum, manganese, and iron (table 10, p. 377).

The variation in concentration of equivalent uranium, uranium, 

zinc, copper, arsenic, molybdenum, manganese, and iron for both the 

vertical and horizontal samples is shown in figure 41.

Correlation coefficients which were calculated for copper, zinc, 

arsenic, molybdenum, manganese, and irqn with respect to both 

equivalent uranium and uranium in all 13 samples, are given below.

Correlation coefficients, Diamond J ranch 

{13 samples]

Gu. 

Zn,

As_

i Probably significant. 

* Possibly significant.

eU 

1-0. 66

+,. 13

-. 16

U 

-0.27

-.30

-. 15

Mo _ . __._._

Mn ________

Fe___. __ .__...

eU . -0. 12 

2-. 39

-. 09

U 

O. 5$

 , 31

-. 34
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 355

100 flop

Top

Vertical sample Lon( itudinal sampl?

FIGTJKE 41;:--Grai»h showing variations in equivalent uranium and in uranitim and other metals in samples 

taken'lo'iigitudinally and vertically across radioactive zone, Diamond J ranch. -: t

 " "-'- MV -'.. . ' ,.«-. ^.CONCLUSIONS " '.:,'

The ncg^tiv^ p^ nearly random «?6r1helation of uranium and equivalent uranium with the other elements in-this suite of samples^is..quite 

unusual. Field observations and petrographic studies indicate that

-> . .&.. :-)F ..jd'i; .'iru XijH-il rjritiv. ..!,r i-""'L t-j;n ' , '* .-;^-".'..-,«? ,: (* , ^,.5. ji>,\'. ^^t "jySK- .> jfjCif^T'T

manganese oxides Gontaininp: small.,amounts o£ coppeu^;Ha«c, 

c, ari(i ! ltidlybldenuni were1 prbbably ihttoduced 'earlV; ! THe'^blu-

> > r J ^. r«'>-^t:'L':-:,.'; .r. Hteurwl
356 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

tions from which they were deposited appear to have attacked the 

quartz but not the feldspar, suggesting that these solutions may have 

been alkaline rather than acid. At a later time uranium and possibly 

silica were introduced along small fractures; the negative correlations 

between uranium and the other elements suggest that the other elements were locally leached out at the same time uranium was deposited, 

although there is no petrographic evidence of such leaching. The low 

uranium content with respect to equivalent uranium in these samples, 

particularly in sample F16, suggests leaching of uranium and residual 

enrichment in its daughter products. This probably represents recent 

ground-water action.

LUCKY BREAK IRON MINE, CHAFFEE COUNTY, COLO.

The Lucky Break iron mine is about a mile northwest of the junction of the Turret and Whitehorn roads in Chaffee County, Colo. 

The deposit is at an altitude of about 9,000 feet, just south of the 

crest of a small ridge. In the vicinity of the mine, dark irregular 

bands of massive red and black iron oxides have replaced limestone of 

Devonian and Mississippian age. This limestone has been intruded 

by a large rhyolite prophyry sill a few hundred feet northeast of the 

mine (fig. 42).

EXPLANATION

r»7»

Maroon formation

j//MDu'/| 

Unnamed limestone

Parting quartzite member of 

Chaffee formation, Manitou 

and Fremont limestone, and 

Harding sandstone, undifferentiated

Contact

Dashed where approximately 

located

Fault or vein

Dashed where approximately 

located

K 

'Lucky Break iron mine

Geology by W. R. Griffitts, 1950

FIGURE 42. Sketch map showing general geology of the area around Lucky Break iron mine. Geology 

generalized from an aerial photograph. (Since this report was prepared, the unit shown above as unnamed limestone has been classified as the Leadville limestone and Dyer dolomite member of the Chaffee 

formation, undifferentiated.)
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 357

According to K. G. Brill (1948, written communication) the deposit 

is cut and offset by a north-northwestward-trending normal fault 

which dips steeply to the east. Intense alteration in the vicinity of 

the mine appears to have obscured this fault.

Development on the property in June 1953 consisted of a large 

glory hole roughly 150 feet in diameter and 100 feet deep with a 

short adit which provided access from a haulage road to the bottom 

of the pit on the south side.

The surrounding area has been studied by W. R. Griffitts, who 

accompanied the senior author to this locality in June 1953.

SAMPLES AND ANALYSES

Four samples were collected from the south wall of the pit a few 

feet west of the adit (table 1). All four were analyzed radiometrically for equivalent uranium and spectographically for 36 elements; 

X-ray (powder diffraction) studies were also made on all four samples in order to verify the majormineral constituents (table 11, p. 378).

TABLE 1. Description and radioactivity and X-ray analyses of samples from the

Lucky Break iron mine

{Analysts: E. J. Fennelly and W. F. Outerbridge]

Sample

Fl-TL-53.... 

FlA-TLr-53 i.

F2-TL-53 ».._ 

F3-TL-53 i...

Locality

10 ft west of adit, on 

south wall of pit.

.....do... ..........

Fracture zone, 5 ft 

west of adit, on 

south wall of pit. 

__ do.. _______

Type

Grab 

 do...

 do-.- 

_._do--.

Dcscripticn

Moderate reddish-brown 

to dusky-red finegrained hematitic iron 

ore.

moderate reddish-orange 

and dark yellowishorange bands. 

Dusky-red fine-grained 

hematitic iron ore.

.....do............ ..

eU (percent)

0.002 

.002

.018 

.069

Analyses

Mineral constituents

Hematite. 

Hematite, goethite.

Hematite, goethite, 

quartz.

Hematite, quartz.

i For petrographic description see table 3.

CONCLUSIONS

Megascopically, there is little to distinguish the radioactive from 

the nonradioactive material in this deposit. Examination of the 

mine walls with a Geiger counter suggests that the most highly radioactive material is localized along late fractures. Examination of a 

section cut from the most radioactive specimen shows that small 

fractures filled with late quartz are more common in it than in the 

sections cut from nonradioactive material. A study of the spectrographic data indicates a tendency toward enrichment in copper, zinc, 

cobalt, beryllium, and yttrium and depletion in aluminum, titanium,
358 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

calcium, magnesium, sodium, potassium, barium, strontium, gallium, and zirconium, in the more radioactive material.

It thus seems probable that uranium was introduced after the 

original replacement of limestone by iron oxide. The data suggest 

that the uranium was probably introduced along small fractures in 

the previously formed iron oxide .body by solutions containing large 

amounts of silica and minor amounts of copper, zinc, and cobalt. If 

this hypothesis is correct, it could indicate the proximity of a uraniferous basetmetal sulfide body from wl}ich these solutions were derived.

O0RAT HOT SPRESfGS, OTJItAY COUNTY, COLO.

The Ouray hot springs deposits anneal* the bottom of a steepwalled canyon .near the southwest edge of Quray, Cplof? just east of 

the ,Uncomp(ahgre River, .at an altitute of 7,£PQ t$e$. , /

The tufa deposits from the springs are jnterbedded, with Quaternary 

stream gravel, and overlie, Ouray limestone .of Devonian,, age on .tlje 

northwest si^e.of i^e,nort]h.ea^twardr;tren$ng Quray fault.^.^his, fault 

brings the Ouray limestone down against Precambrian slates and 

phyllites on the southwest. ' v !

The Ouray hot springs are in the area described in Burbank's 

report (Burbank, 1940), and their location is shown on his map. 

These deposits are briefly described in a later report by Burbank and 

Pierson (1953). -. 

SAMPLES AND ANALYSES

Five samples of tufa were collected from 2 localities 100 yards 

apart. Three samples of tufa were collected near the fault which 

is about 250 feet southeast of the Canyon Creek road bridge over the 

Uncompahgre .River; the other 2 were from the east bank of the 

river about 50 feet north of this bridge. All five samples were analyzed 

for equivalent uranium, uirahiimi, zinc, lead, copper,; nickel, cobalt, 

molybdenum, arsenic, antimony, vanadium, , -manganese and iron. 

The uranium content of all samples was <20 ppm and the copper 

and nickel content was <10 ppm. Resulta,of , the .other : analyses are

shown in table 12, p. 379. *** > ' '' * *-i » v<.» > 

Correlation coefficients were determined for zinc, antimony, arsenic,

molybderiuin, manganes^ arid irbn witli respect to equivalent ^uranium 

irfalffive' sahlplfei "as sho^ri: below. - lf ; '' p" :: '-;-m '- ^n'M^i\'^\ - ;:

-' "c'i .-'i,{ '". ^ ; '.,'^-ti'. a.1^;'O.'.i *'^~>i'> .< ii:i ?/ ' ' Coefficients, Ovjray<hot springs, <.t ^

[5 samples] . , . ^ lr r^r.'.! HI .'-^''- u f-^\\ L «-\:

3'

eU eU

2 Possibly significant.
RADIOACTIVE LIMONITE IN COLORADO, "UTAH, WYOMING 359

One sample of radioactive tufa collected from this deposit by Burbank and Pierson was analyzed for uranium and equivalent uranium, 

and also was submitted to semiquantitative spectrographic analyses. 

This sample contained 0.11 percenteU and 0.001 percent U. Other elements detected were present in the following concentrations:

Element Percent ' 

Mn......_____.._._ _________ ____________________________ XX.

Ba, Ca, Fe, Si, Sr, W~ - ---.- -- - _- - - - - - X. 

Al, As, Mg, Na____.______________------------------------- .X

Be, Cu, Mo, Sb, Ti, Tl, V, Zn. _ -- _-_------_ . OX

Co, Pb, Zr___-_ __ __________ __----- . OOX

Cr_..___.____________--______-_.___--_ __ _ ____ . OOOX

' See Introduction, p. 340, for explanation of values.

CONCLUSIONS

The colloidal texture of manganese oxide, evident in polished sections, and the high positive correlation between equivalent uranium 

and manganese suggest that the radioactive element was adsorbed by 

colloidal manganese oxide hydrate and precipitated with it. The high 

ratio of equivalent uranium to uranium suggests that the radioactive 

element now present in these deposits is probably radium. The unusually large amounts of tungsten, molybdenum, arsenic, antimony, 

and zinc in these samples also suggest the possibility of a uraniferous 

base-metal sulfide ore body in the vicinity, from which radium has 

been leached by the hot spring waters. Several silver-lead-zinc deposits occur in the Paleozoic rocks near the Ouray fault, within a mile 

of the Ouray hot springs (Burbank, 1940).

HAPUTA RANCH AREA, OUSTER COUNTY, COLO.

The Haputa ranch area is in the western foothills of the Wet Mountains 4 miles east-northeast of Querida in Ouster County, Colo. The 

deposit, which was examined and sampled in detail, is a small open 

cut at an altitude of about 9,250 feet. The deposit is in a northwestward-trending shear zone cutting Precambrian amphibolite which has 

been intruded by a biotite granite gneiss about 25 feet south of the 

shear zone. An andesite dike, striking parallel to the shear zone, cuts 

the amphibolite near its contact with the gneiss (fig. 43). Drill-hole 

data indicate that this dike crosses the shear zone at a depth of about 

100 feet. This locality has previously been examined by Christman 

and others (1953, p. 10-12, 32) and it is described in their report as 

"drill hole Ha-8."

468040 69 .
? S 2 5"

^ i *: 

II

r§

IsS.SS

PRECAMBRIAN

3 - 

<.-g?

it

TERTIARY QUATERNA

1%

(O M

3 S-

^ i i 3 =* M 01

' ) ! oa. 

 I'JJ | |
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 361 

SAMPLES AND ANALYSES

Eleven samples were collected from the Haputa ranch area. Nine 

of these are consecutive 1-foot channel samples across the radioactive 

zone shown in figure 43; the other two are selected grab samples. 

All 11 samples were analyzed radiometrically for equivalent uranium 

and geochemically for zinc, lead, copper, nickel, cobalt, arsenic, antimony, molybdenum, vanadium, manganese, and iron. In addition, 

three of the more radioactive samples were analyzed chemically for 

thorium. The results of these analyses are shown in table 13, p. 380.

A special sample of the thorium-bearing mineral was analyzed 

spectrographically by Katherine E. Valentine, and the results of this 

analysis were made available by R. A. Christman. The analysis 

shows the following components:

Element Percent > 

Si, Th___________-_-_______--______--_--____-___ _____________ XX.

Fe _________________ - _ ----- ___ _ -_.__- _____ X.

Ba, Ca, Ce, Cu, La, Nd, Pb, Y___ _ ___________ _ __ _______ .X

Al, B, Co, Dy, Er, Eu, Gd, Lu, Ni, Pr Yb-_____________, _______ .OX

Be, Mg, Mn, Mo, Sr, V, Zr.______. ____________________________ .OOX

Ag, Cr, Ti_ ___ _____________________________________________ .OOOX

i See Introduction, p. 340, for explanation of values.

An exploratory diamond-drill hole cut the shear zone at a depth 

of 140-160 feet beneath the exposure from which samples F18-F26 

were taken. The core from this hole was analyzed spectrographically 

by G. W. Boyes. Table 2 shows the concentrations of the same 

elements in the drill core for which geochemical assays were made on 

samples from the outcrop. The corrected sample lengths and equivalent-uranium concentration of drill-core samples were taken from 

Christman and others, 1953, p. 14, table 5.

The variations in concentration of equivalent uranium and selected 

elements in the 9-foot horizontal channel sample taken at the outcrop 

are shown in figure 44. Data are graphed only for those elements 

that showed significant changes in concentration.

Correlation coefficients were determined for zinc, lead, copper, 

nickel, arsenic, antimony, vanadium, and manganese with respect to 

equivalent uranium in all 11 samples for which geochemical assay 

data are available (table below).

Correlation coefficients, Haputa, ranch area

(

el

+0.

2 

Llsai 

7 

21 

76 

53 

48

nples] 

As

Sb

V____.__________________._

eU 

L67 

»+. 77 

»-. 59 

-.11

i Probably significant. 

i Possibly significant.
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GEOLOGICAL SURVEY BULLETIN 1046 PLATE 42

Photograph (above) and autoradiograph of polished section of sample containing 

thorite (T), quartz with disseminated thorite, and limonite, from radioactive 

shear zone, Haputa ranch, Custer County, Colo.

RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 363

Figure 44. Graph showing variations in equivalent uranium and other metals

radioactive shear zone, Haputa ranch.

- . - - -. -. -' 

- M^GJb o| tho qua,rtz .^as a,rosy color c^iise.dapparently by submicrpscopic partieies of red heottatite or fchorifeei TComparison ef ^upolisiajj 

section of sample F25, which is high in thorium, with its autoradiograph shows that these particles are radioactive (pi. 42).

In some of the samples, the apparent dispersion of submicroscopic
364 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

particles of a thorium mineral throughout quartz suggests that thorium may have been introduced in solution by hot silica-bearing waters 

and that some of it was precipitated simultaneously with the quartz. 

The high positive correlation between equivalent uranium and lead, 

copper, arsenic, and antimony suggests that either these elements are 

present in thefthorium minerals or that they form other minerals, probably sulfides, which are closely associated with the thorium minerals. 

The former hypothesis appears to be partly substantiated by the 

relatively high concentrations of lead and copper reported in the 

analysis of the pure thorium-bearing mineral and by the high correlation coefficients coupled with low concentrations of antimony and 

arsenic.1 A comparison of the assay data from the drill-core samples 

indicates a tendency toward enrichment in lead, vanadium, and manganese near the surface but little change in the concentration of equivalent uranium (which is directly proportional to thorium in this area), 

copper, nickel, cobalt, molybdenum, and iron to a depth of 150 feet.

POWDERHORN DISTRICT, GUNNISON COUNTY, COLO.

The Powderhorn district is in T. 47 N., R. 2 W., Gunnison County, 

Colo., at an average altitude of about 9,000 feet. Thorium occurs in 

scattered pods and lenses in prominent northeastward-trending 

silicified shear zones cutting Precambrian schist and gneiss. The 

surface exposures of these zones are heavily stained with hematite 

and limonite, and the country rock near them commonly has a bleached 

appearance.

The Precambrian rocks of this area were described by J. F. Hunter 

(1925), and the thorium deposits have been studied by Olson and 

Wallace (1956).

SAMPLES AND ANALYSES

Twenty-two samples were collected from three localities in the 

Powderhorn district, as shown in table 14, p. 381. Some of the samples 

of radioactive vein material contained irregular finely porous areas. 

Examination with a hand lens shows that many of the individual pores 

consist of tiny, nearly square pits. This probably reflects the former 

presence of pyrite.

All 22 samples were analyzed geochemically for zinc, lead, copper, 

nickel, cobalt, antimony, arsenic, molybdenum, vanadium, manganese,

' Antimony and arsenic cannot be detected by ordinary spectrographic methods in concentrations of less 

than 500-1,000 ppm, so it is not surprising that they were not reported in the spectrographic analyses.
RADIOACTIVE LIMONTTE EST COLORADO, UTAH, WYOMING 365

and iron. They were also analyzed for equivalent uranium, and two of 

the most radioactive were analyzed chemically for thorium (table 

14, p. 381).

The variation hi equivalent uranium and some of the metals in 

samples taken across the Little Johnny vein and in the more widely 

spaced grab samples at the Jeanie No. 2 claim, is shown graphically 

in figures 45 and 46. Fig. 47 illustrates the location of samples from 

the Jeanie No. 2 claim relative to the vein.

33 34 35 36 37 38 39 40

FIGTJKE 46. Qraph showing variations in amounts equivalent uranium and selected metals in sample 

taken across Little Johnny vein, at upper pit, Powderhorn district.
366 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

10,000 r
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 367-

-^uiiiiit"'1

F41-0.07 F43-0.12 F45-0.18

F42-O.07 F44-0.16 F46-0.80

Geology by E. P. Beroni

EXPLANATION

Altered and bleached 

quartz-biotite gneiss

Transition zone

Fractured gneiss and

vein material

Thorium-bearing 

vein

F43-O.12

Sample number, showing 

radioactivity in milliroentgens per hour

FIGURE 47. Sketch of southeast wall of bulldozer cut, Jeanie No. 2 claim, Powderhorn district.

Correlation coefficients were determined for zinc, lead, copper, 

antimony, arsenic, molybdenum, vanadium, manganese, and iron on 

all 22 samples (table below).

Correlation coefficients, Powderhorn district

[22 samples}

eU eU

Zn____ ___ _____ _________ »+0. 69

Pb. 

Cu

Sb_ 

As

Fe_

' * Probably significant. 

* Possibly significant.

. 71 

. 15 

. 85 

. 61

CONCLUSIONS

Mo- __ . ____________ +0. 31

V __________________ 2 +. 39

Mn _________________ S + .46

. 5*

The abundance of red quartz in the samples with a high thorium 

content indicates, as in the sample from the Haputa ranch area, that 

submicroscopic thorium-mineral particles may be disseminated 

throughout the quartz and that they may have formed contemporaneously with it. There is a crude relationship between limonite colors 

and thorium concentration. In general, the limonite stains change 

from yellowish or grayish brown through light brown and moderate 

brown as the vein is approached, to a characteristic moderate to 

dusky red in the high-thorium vein material. Petrographic studies 

reveal the presence of hematite pseudomorphs after pyrite in the 

high-thorium parts of the vein. This suggests a genetic relationship 

between the thorium ore and sulfide deposits which is also suggested 

by the relatively high correlation between equivalent uranium and 

iron, zinc, lead, arsenic, and antimony. The arsenic .and antimony 

apparently are present as minor constituents, of .the thorium mineral;
368 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

and do not form separate minerals associated with it. If this is true, 

it explains both the high correlation of arsenic and antimony with 

equivalent uranium and their low concentrations.

SUMMARY

The results of this study indicate that preliminary sampling of 

radioactive-limonite outcrops and geochemical analysis of the samples, 

followed by the determination of correlation coefficients from the 

assay data, may reveal important relationships between the radioactive element sought and other elements that may be associated 

with it. These correlation coefficients may be used in two ways: to 

eliminate randomly distributed elements and place emphasis on others 

that seem to show high correlations in further geochemical or geobotanical studies, and to aid, by supplementing petrographic examination, in interpreting the origin and paragenesis of the ore deposits.

The results of petrographic studies of thin and polished sections of 

selected samples are summarized in table 3.

TABLE 3. Petrographic description of thin and polished sections cut from selected

samples

Sample Locality Description

F1A-TL-53_. 

F2-TL-53......

F3-TL-53.._.

Lucky Break iron 

mine.

.....do.............

.do.

F14-TL-53..... 

F16-TL-53-.... 

F17-TL-53.....

Diamond J ranch__

_do.

F20-TL-53._. 

F25-TL-53..... 

F36-TL-53..... 

F44-TL-53.....

Haputa ranch area....

.do.

.do.

Powderhorn district_

F46-TL-53. -do.

F49-TL-53..... 

Ffil-TL-53.....

Ouray hot springs.... 

....do....__.......

Grains of steel-gray hematite surrounded by red hematite rims 

in banded colloform goethite; numerous small angular quartz 

fragments in goethite, and cavities filled with chalcedony.

Similar to F1A but contains less goethite; boundaries between 

red and gray hematite are commonly gradational and undulating, suggestive of replacement.

Contains more steel-gray hematite than F2; gray hematite, 

followed by massive quartz which is embayed by microbreccia of red hematite, late quartz veinlets cut quartz 

fragments.

Angular fragments of quartz, orthoclase, and microcline in 

matrix of dark-brown goethite, red hematite, and black wad 

which fills voids in iron oxides and is cut by late quartz 

veinlets.

Fewer fragments than F14, wad predominates over hematite 

and goethite in matrix; some of goethite replaces red hematite, 

some stains fractures in quartz and may be older than hematite.

Small euhedral apatite crystals in early quartz cut by veinlets 

of late quartz containing voids filled with colloform goethite; 

few rounded grains of gray hematite in quartz have goethite 

rims.

Biotite, hornblende, quartz, and plagioclase with accessory 

magnetite and apatite are cut by veinlets of rosy quartz and 

later goethite.

Altered feldspar fragments in rosy vein quartz contain few 

grains of thorite; quartz is cut by veinlets of red hematite and 

later goethite.

Deep-red quartz with numerous small isometric pseudomorphs 

of hematite after pyrite; late veinlets of clear quartz cut red 

quartz.

Few large quartz grains with late quartz overgrowths in matrix 

of fine-grained quartz alternating with bands of biotite; 

goethite coats some quartz grains; few tiny specks of red 

hematite or thorite in groundmass.

Red quartz cut by clear quartz veinlets; small hematite pseudomorphs after pyrite in both red and clear quartz; microbreccia 

of clear quartz and goethite cements fragments of early red 

quartz.

Nodular masses of psilomelane with colloidal banding are cut 

and partly replaced by dense massive hematite.

Calcite and goethite with subordinate psilomelane; goethite is 

younger than psilomelane; small cavities filled with late 

quartz or barite.
RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 369

TABLE 3. Petrographic description of thin and polished sections cut from selected

samples Continued

Sample Locality Description

F57-TL-53.. 

F6&-TL-53..

Yellow Cat area, 

. -do .. .

F61-TL-53-..... 

F74r-TL-53......

F75-TL-53_... 

F78-TL-53......

Silver Cliff mine. 

.do.

.do.

Subrounded grains of quartz, chert, and limonite-stained 

altered feldspar in a matrix of dark-brown goethite and 

cryptocrystalline quartz.

Quartz grains smaller and more angular, and chert less abundant than in F57, few grains of chalcedony; goethite cement 

more localized and lighter brown; some red hematite grains; 

gypsum fills fractures.

Small rounded grains of quartz and orthoclase cemented by 

cryptocrystalline quartz; cut by veinlet of brecciated red 

hematite altering to goethite cemented by late quartz.

Fine- to medium-grained rounded quartz grains in matrix of 

yellowish-orange goethite replacing calcite; few grains of 

magnetite and irregular masses of sooty chalcocite.

Similar to F74, with calcite predominant over goethite; quartz 

grains are stained red, and a few grains of red hematite are 

scattered throughout the matrix.

Large angular quartz grains embedded in a matrix of yellowishorange to light-brown goethite and green malachite which is 

younger than goethite; microbreccia of chalcocite and quartz 

embays quartz grains.

No single element for which geochemical analyses were made showed 

consistently high correlations with uranium in all of the areas examined (table 4); however, in most of the uranium districts at least 

one other element appeared to show a significant correlation with 

uranium. In both thorium districts, on the other hand, high positive 

correlations were shown between thorium and lead, arsenic, and 

antimony. A larger number of thorium deposits should be studied 

in order to determine whether this association is widespread or merely 

an accidental result of the choice of areas for examination (table 4).

If an element which has distinctively colored alteration products, 

such as copper, manganese, or cobalt, shows high correlation with 

uranium or thorium in a given area, then those colors may be useful 

as field guides to the prospector. The limonite colors observed by 

the authors did not appear to be particularly useful field guides for 

uranium. In general, the limonite stains on uranium-bearing outcrops ranged from light yellow brown through moderate brown to 

dusky brown; rarely were red iron oxides associated with uranium. 

This in itself does not, however, constitute a useful field guide in most 

areas because of the prevalence of brown limonite stains on barren 

outcrops. In the thorium deposits, on the other hand, samples with 

a high thorium content commonly exhibited a characteristic red color. 

In some of the deposits, such as the Jeanie No. 2, the color of the 

limonite stains changes from yellowish or grayish brown through 

light brown to moderate or dusky brown as the thorium deposit is 

approached.

Small areas of porous limonite were noted in some of the highthorium samples from the Powderhorn district, and examination with 

a hand lens^evealed numerous tiny square pits, which are thought
370 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

 53

Probably significant

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Grand County, Ca Utah..!.- Yellowarea, ___ County, Snow-Bormiebell claims, U intah tab_ Cliff Silver Niobrara County, Wvo..-.---- mine, Golden Qate CanyonJefferson County, areaColo ^. __-_------_.--_-.-___---.---------,

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Diamond" ranch, El PasoCounty, Colo.-- J----- Oura-vhot County, Colo_.----- Ouray springs, -- Hapiita Ouster ranch County, Colo. area, ---- district, Powderhorn Gunnison County, Colo^...
RADIOACTIVE UMONITE IN COLORADO, UTAH, WYOMING 371

to indicate the former presence of pyrite cubes in these areas. No 

sponge or boxwork textures were apparent in samples from any of 

the other localities examined.

MTERATURE CITED

Adams, J. W., Gude, A. J., 3d, and Beroni, E. P., 1953, Uranium occurrences in

the Golden Gate Canyon and Ralston Creek areas, Jefferson County, Colorado: U. S. Geol. Survey Circ. 320. 

Beroni, E. P., and McKeown, F. A., 1952, Reconnaissance for uraniferous rocks

in northwestern Colorado, southwestern Wyoming, and northeastern Utah:

U. S. Geol. Survey TEI 308-A, issued by U. S. Atomic Energy Comm.

Tech. Inf. Service, Oak Ridge, Tenn. 

Burbank, W. S., 1940, Structural control of ore deposition in the Uncompahgre

district, Ouray County, Colorado: U. S. Geol. Survey BulL 906-E, p.

189-265. 

Burbank, W. S., and Pierson, C. T., 1953, Preliminary results of radiometric

reconnaissance of parts of the northwestern San Juan Mountains, Colorado:

U. S. Geol. Survey Giro. 236. 

Christman, R. A., Heyman, A. M., Dellwig, L. F., and Gott, G. B., 1953, Thorium

investigations 1950-52, Wet Mountains, Colorado: U. S. Geol. Survey

Circ. 290. 

Dixon, W. J., and Massey, F. J., Jr., 1951, Introduction to statistical analysis:

New York, McGraw-Hill Co., 370 p. 

Hunter, J. F., 1925, Pre-Cambrian rocks of Gunnison River, Colorado: U. S.

Geol. Survey Bull. 777. 

land, S. C., and Davis, C. W., 1919, A new deposit of uranium ore: Science, new

series, v. 49, p. 441-443. 

Olson, J. C., and Wallace, S. R., 1956, Thorium and rare-earth minerals in the

Powderhorn district, Gunnison County, Colorado: U. S. Geol. Survey Bull.

1027-O, p. 693-723. 

Stokes, W. L., 1952, Uranium-vanadium deposits of the Thompson area, Grand

County, Utah: Utah Geol. and Mineralog. Survey Circ. 46. 

Tunnell, George, and Posnjak, Eugen, 1931, The stability relations of goethite

and hematite: Eeon. Geology, v. 26, p. 337-343. 

Wilmarth, V. R., and Johnson, D. H., 1954, Uranophane at Silver Cliff mine,

Lusk, Wyoming: U. S. GeoL Survey Bull. 1009-A, p. 1-12.
372 CONTRIBUTIONS TO THE GEOLOGY OF URANTDM

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Light-gray medium-grained crossbedded sandstone. 

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TABLE 8. Description and analyses of samples from the G

[Analysts: H. E. Crowe, B. F. DuFour, 8. P. Furman, J. N. BoshoU, J. 

Sample

F87-TL-53..

F88-TL-53..

F89- TL-53..

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F92-TL-53..

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Locality

2^ ft west of vein zone near

Buckman adit.

IJi ft west of Vein near Buckman adit,

Vein zone near Buckman adit.

1H ft east of vein near Buckman adit.

2 ft east of vein, Union Pacific

prospect.

1 ft east of vein, Union Pacific

prospect.

Vein zone, Union Pacific prospect.

1 ft west of vein, Union Pacific

prospect.

2 ft west of vein, Union Pacific

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3 ft west of vein, Union Pacific

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Type

6-in. channel..

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Description

Medium dark-gray fresh hornblende gneiss.

Moderate yellowish-brown iron-stained

hornblende gneiss.

Pale yellowish-brown bleached silicified

hornblende gneiss.

Medium dark-gray fresh hornblende gneiss.

Light-brown to dark yellowish-orange altered gneiss.

Moderate-brown to grayish-orange altered

gneiss.

Dark yellowish-orange altered gneiss,

heavily coated with limonite.

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RADIOACTIVE LIMONITE IN COLORADO, UTAH, WYOMING 379

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382 CONTRIBUTIONS TO THE GEOLOGY OF URANIUM

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INDEX

Page

Aluminum________________ 357 

Antimony.........__......... 345,364,367,

Arsenic... ...... 346,347,350,365,

Barium_________________..__ 358 

Base-metal samdes- 350,358,359 

Beryllium__..........__................ 357

Bismuth________._...... .... 351

Boyes, O. W., analyst_ 361

Cactus Eat claim____.............. 343,344,372

Calcium_________.. . 358 

Cambrian rocks_____...._........ .. 348

Carnotite- ... 345 

Chrlstman, R. A., acknowledgment 361 

Clay...........___........ . 347,348

Cobalt..____________...... 357,358,364,369

Copper.._____. 346,347,350,355,357,358,364 369 

Correlation coefficients______......... 340,

342,344,345,346,348,351,354,358,361,364,367,

368 

Cretaceous rocks......_.. 346

Crowe, H. E., analyst________. . 343,372

Dawson ariose......... 353

Devonian rocks.._ _____.......... 356,358

Diamond J ranch. _____. 353-356,368,370,377 

Dispersion bales. See Correlation coefficients. 

Dufour, E. F., analyst_____ 343,372

Enrichment............. ....... 345, 356,357, 364

Equivalent uranium__________.___ 340,

343, 344, 346, 347, 349, 350, 351, 352, 353, 354.

356, 356, 358, 359, 361, 362, 363, 364, 365, 366,

367,368.

Taults ...................... 346, 347, 348, 357

FenneUy, E. J.t analyst__...._._ _ . 357

Folds......-... . . . 343, 346

Fractures __...... 350, 359, 364

Furman, 8. P., analyst____.. ... 343, 372

Gallium____________________ 358 

Qoethite___________________ 345, 357 

Golden Gate Canyon area.. 340,350-353,370,375-376 

Griffitts, W. E., acknowledgment-_-__ 356, 357 

Ground-water action_. ___________ 356 

Gypsum 345

Haputa ranch area____ 359-364,367, 368, 370,380 

Havens, E. G., analyst .____. __ 376, 378

Hematite________.. 345, 350, 357, 363, 364, 367

Idaho Springs formation.. _.__ _ 350 

Igneous Rocks,.... _.______ 356,359 

Indicator elements ... .. 345, 350

Page 

Iron..._____.__..... 345,350, 353,366,364,369

Jurassic rocks_________________ 343

Late Cretaceous rocks._-____-__ .. 353 

I eaching._____.________ 345, 356, 357,359 

Lead .________________... 359, 364, 369 

Limonite-. ......... 339, 345, 364,367, 368, 369

Little Johny mine______________ 342,365 

Logarithms _ . . 341 

Log concentrations_......... ....... 341

Lucky Break iron mine.____ 340,356-358,368,378

Magnesium___......... .._ 358

Mancos shale 346 

Manganese 347,348,350.353.355,359,364,369 

McCarthy, J. H., analyst___... .... ....... 343

Mesaverde formation__.__________ 346 

Mississippian rocks_ 356 

Molybdenum.._________ 345,347,350,355,364 

Morrison formation.. ......__._....__ 343

Nickel..._.____.________.____ 350,364

Ouray hot springs.. 358-359,368,370,379 

Ouray limestone.... 358 

Outerbridge, W. F., analyst._.............. 357

Paleocene rocks__... .............. 363

Paleozoic rocks_.___.__-_.......__ 359

Pitchblende . 350

Potassium_______._...._....__ 358

Powderhorn district______ 354-368,369,370,382 

Precambrian rocks. . - ___.... 348,350,358,369,364

Pyrite-___________________ 364,367,371

Quartz.. 356,357, PL 42,363,364,367 

Quaternary gravel 358

Radioactive elements. See particular element. 

Radium___... .... 359

Rosholt, J. N., analyst..___________ 372

Shear zones__. ___________ 350,359,361,303 

Significance, threshold____________ 342 

Silica 356,358

Silver -___-_____________ 351,359 

Stiver Cliff mine--.__.___ 348-350,369,370,374 

Siverly, J. L., analyst.- 372

Snow-Bonniebell claims...-__... 346-348,370,373 

Sodium.. _____________________ 358 

Standard deviation. ....... . 341,342

Strontium______.. 358

Summerville formation____________ 343

Texture-._._.....__-___.. 340,359,370,371

383
384 INDEX

Page 

Thorite-_________.... ___... PL 42,363

Thorium............... 340,361,363,364,365,367,369

Titanium_____________________ 357 

Tufa deposits. ..._.__________ 358,359 

Tungsten. . ......_ 359

Uranium _ ........_________ 340,

343,344,345,346,347,348,350,351,352,353,354, 

355, 356, 358, 359, 369.

Valentine, Katherine E.f analyst_______ 361

Page 

Vanadium........ ....................... 343, 364:

Veins... .. 364,365,367

Wahlberg, James, analyst 37?

Yellow Cat area_________ 343-346,369,370,372 

Ytterbium..__.__..._._.._.__.... 361

Yttrium....... . . 351,367

Zinc...___.__._ 345,347,350,355,357,358,35? 

Zirconium______._ 35*

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