Prospecting for 

Uranium With 

Car-Mounted 

Equipment

GEOLOGICAL SURVEY BULLETIN 988-1

Prospecting for 

Uranium With 

Car-Mounted 

Equipment

By JOHN M. NELSON

A CONTRIBUTION TO THE GEOLOGY OF URANIUM

GEOLOGICAL SURVEY BULLETIN 988-1

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 : 1953
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, 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)
CONTENTS

Abstract ___ _____________________________________________________ 211

Introduction_______________, ______________________________________ 211

Radioactivity of outcrops.______________________________________ 211

Response of gamma-ray equipment to cosmic rays and radioactive

rocks__.___ ___________ _ ___________________________ _____ 213

Car-mounted equipment _ _________________________________________ 215

Development of present equipment-___--_______-______-_--_-____ 215

Desired performance of future equipment- _______________________ 216

Suggested methods of obtaining the desired performance. ________ 217

Types of car-traverse programs_____-______-___--__--__-_------______ 218

Preparation for recording field data____________________-_________.___ 219

Summary _ _______________________________________________________ 220

Index. __ ______________________ _ _________ _ ______ _ __________ 221

ILLUSTRATIONS

FIGUKE 50. Frequency distribution of radioactivity intensities from outcrops. _______________________________________________ 212

51. Gamma field of radioactive outcrop and response of carmounted Geige r-Mueller counter. _____________ _________ 214

52. Diagram of components of car-mounted instruments._______ 216

53. Schematic diagram of alarm circuit.______________________ 216

m

A CONTRIBUTION TO THE GEOLOGY OF URANIUM

PROSPECTING FOR URANIUM WITH CAR-MOUNTED

EQUIPMENT

By JOHN M. NELSOX

ABSTRACT

The U. S. Geological Survey has prospected for uranium with a car-mounted 

Geiger-Mueller counter since 1945. The basic principles of the car-traverse 

technique are simple. Hocks and soils of abnormally high uranium or thorium 

content are surrounded by an equivalently high gamma radiation field. An 

abnormal gamma-radiation field that extends across a road or highway can be 

detected at relatively high speeds by a car or truck equipped with a suitable 

Geiger-Mueller counter. Once detected by car-traversing, the deposit can be 

examined with light portage instruments, and the better portions sampled. The 

prime advantage of the car-traverse technique is the rapidity of the scanning 

process, 100 to 200 miles pt;r day, which permits exploration of large areas in a 

short time.

INTRODUCTION

RADIOACTIVITY OF OUTCROPS

Commercial production of portable radioactivity detectors opened 

the way for prospecting on foot without exhaustive sampling. Recent 

improvements in equipment permit detection of radioactive deposits 

from a moving car, train, or boat. The objective is the fastest and 

most productive method of detecting radioactive deposits in a given 

area.

Experiments by the U. S. Geological Survey with car-mounted 

Geiger-Mueller counters began in 1945 and have continued through 

1949. Standard equipment, modified for the car-traverse technique, 

has been used wherever possible. In this report, the results of the 

experiments are presented, the instruments described, and operational 

procedures are suggested.

The frequency distribution of radioactivity intensities of 2,200 

outcrops of sedimentar}', metamorphic, and igneous rocks in an area 

of 30,000 square miles is, illustrated in figure 50. The radioactivities 

of' nearly all outcrops in this area range from 0.0002 to 0.004 percent 

equivalent uranium. Radioactivities in this range are called normal 

and do not aid the prospector searching for a uranium deposit. Few

211
212 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

Approximate radioactivity of outcrop in 

thousandths percent equivalent uranium 

2 3 456 

Tl I IT

2 4 6 8 10 12 14

Observed car rate-meter readings while passing outcrops i

COSMIC RAY >k NORMAL ->|< ABNORMAL ->1 

ACTIVITY ! RADIOACTIVITY I RADIOACTIVITY »

FIGURE 50. Frequency distribution of radioactivity intensities from outcrops.
PROSPECTING FOR URANIUM WITH CAR-MOUNTED EQUIPMENT 213

rocks in the area have a radioactivity of 0.005 percent equivalent 

uranium or more. Radioactivities in this higher range are called 

abnormal and indicate an abnormally high concentration of uranium 

or thorium in the rock.

RESPONSE OF GAMMA-BAY EQUIPMENT TO COSMIC BAYS AND 

BADIOACTIVE BOCKS

Gamma-ray equipment responds to both cosmic rays originating 

in outer space and gamma rays originating in substances in the vicinity of the instrument and to radiation from internal contamination 

of counter. The response to cosmic rays for an instrument, at a given 

elevation above sea level, and at a given latitude may be determined 

by noting the instrument response over essentially nonradioactive 

water of a depth of 10 feet or more, at a considerable distance from 

shore- The response to cosmic rays may be determined with less 

accuracy by noting the lowest consistent response while carrying the 

instrument across a thick section, of sandstone, limestone, or basalt, 

which are generally of very low radioactivity. These measurements 

of cosmic-ray activity (the basic response) also include the minor 

radioactivity originating in the air and the instrument.

Responses in excess of the basic response are caused by radioactive 

rocks, soils, or other substances near the instrument and directly reflect the degree of radioactivity. The degree of instrument response 

in excess of basic response is the quantity to be measured by the 

prospector.

The response of gamma-ray equipment to a given source of radioactive material is a function of (1) the solid angle between the source 

material and the detector and (2) the absorption of gamma rays by 

the intervening air. The solid angle is subtended, from the instrument at the apex, by the boundaries of the surface of the source 

material.

The instrument response varies directly with the size of the solid 

angle between the instrument and the radioactive source material. 

The response is greatest in underground workings or in a highway 

tunnel, where the solid angle between instrument and radioactive 

source material is largest. The response is only one-half as great for 

the same source material on. a level plain where the solid angle is half 

as large. The instrument response is extremely small for source 

material of the same radioactivity where the instrument is many feet 

from a few square inches of the exposed radioactive outcrop as the 

solid angle decreases with the square of the distance.

In addition to the effect of solid angle, the amount of intervening 

air lowers the instrument response, because it absorbs gamma radiation. At a distance of about 400 feet, about one-half of the gamma 

rays emitted by the uranium series are absorbed, and the instrument
214 A CONTRIBUTION TO THE GEOLOGY OP URANIUM

MVO ONIAOH Ml !N3WnaiSNI HVO 9NIAOH

S9NIOV3M a313W-31Va S9NIQV3M

<0 88S 0 010 § 8 S 2

9

 s

f

£

>

f

>

40 

hour ilea per 

|

°3

I

i

y

^

1

I

t

>

40 lies hourper PONSE OFC

°5

SSNIQV3M U313W-31VU

: l

! < i

(

/

\

y

\

s:§ s

1 *H

O

Sa

1

\

o

Pi

" I '

i *

<n

Ul

! 8

1

X

1

S 8

</>

~ Ul a:

UJ H5S

^0 *

X _l HIG 

PROFILES TIVITVA

o to

o

<

2

§

9

t! 

1

£

 ^

i i

! 1 g g

g

S <M 

g °

dT 23 §

® 

«

Scol* for

51. Gamma 

o 

o

f 8 g 0 ^

? 8 8 2 o

LN3WnalSNI AWNOI1VJLS 

SONIQV3U M313rt-31Va
PROSPECTING FOE URANIUM WITH CAR-MOUNTED EQUIPMENT 215

response is reduced proportionally. For practical purposes, the limit 

of detection of extremely large high grade deposits is about 1,000 feet 

in air.

Where the gamma-radiation field of a uranium deposit extends 

across a road or highway, it can be detected by equipment mounted 

on a moving car or truck. The gamma-radiation field of a deposit 

discovered while car-traversing at a speed of 30 miles per hour is 

shown in figures 51A and 51B.

CAR-MOUNTED EQUIPMENT

DEVELOPMENT OP PRESENT EQUIPMENT

The car-traverse technique was first used by A. L. Slaughter and 

John M. Nelson of the U. S. Geological Survey in 1945. The instrument consisted of a Geiger-Mueller counter with a response of 12 

pulses per minute in an environment of average activity, a small 

amplifier, and a pair of earphones. At normal driving speeds, this 

instrument detected several radioactive roadside deposits, although 

the pulse rate was too low for the desired accuracy.

In 1946-47, a larger Geiger-Mueller tube, having a response of 500 

pulses per minute, feeding into a counting-rate meter, was used. With 

this instrument, several new radioactive deposits were detected. The 

pulse rate was still too low for the desired accuracy, and the time 

constant of the counting-rate-meter circuit, 1 minute, was too long 

for fast traversing.

In 1948, improved equipment was used. Two Geiger-Mueller tubes, 

each having a response of 1,500 pulses per minute, were connected to 

a counting-rate-meter circuit with a time constant of about 2 seconds.

One Geiger-Mueller tube was attached to each side of a panel delivery truck. The counting-rate assembly was placed in a convenient 

position between the two seats, and an alarm circuit was located behind 

the driver's seat. The general layout of the units is shown in figure 52.

The alarm circuit (fig. 53), designed and constructed by Donald 

H. Johnson of the Geological Survey, is connected across the countingrate microammeter. The voltage across the microammeter varies 

directly with the response of the instrument to a radioactive field. The 

alarm circuit amplifies the voltage difference across the meter and 

operates a bell-ringing relay. The alarm can be adjusted to ring at 

any desired reading of the counting-rate meter. The automatic alarm 

circuit permits the gedlogist to observe the roadside rocks.

Three panel delivery trucks outfitted with this equipment were 

operated in the late summer and fall of 1948. The usefulness and 

limitations of this instrument are graphically shown in figures 51C 

and 51D.

Figure 51C shows the gamma-radiation field through which the 

truck traveled on two highway lanes; figure 51D shows the response

282999 O 53 2
216 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

Geiger - Miiller tube [

EXPLANATION

Geiger-Miiller tubes are brass cathodes, 2 in. 

in diameter and 42 in. long, mounted on the 

exterior of car as high as possible

Rate meter modified for use with the large Geiger - 

Miiller tubes by addition of batteries to produce 

1120 volts. The instrument is mounted Inside the 

car where the microarometer can be easily read 

by the operator

 [ Geiger-Mueller tube j 

FIGURE 52. Diagram of components of car-mounted instruments.

Alarm circuit and bell are mounted inside the car 

conveniently close to the operator

of the instrument to the radioactive field at several car speeds. While 

passing the radioactive deposits at speeds of less than 10 miles per 

hour, the response of the car-mounted instrument closely approaches 

the maximum value of the gamma-radiation field through which it 

passes. At progressively higher speeds, the instrument response decreases because the counters do not remain in the radiation field long 

enough to allow the rate meter to reach equilibrium. Although the 

response of this instrument is sufficient to trigger the alarm circuit at 

speeds as much as 50 miles per hour in highway lane 3 and at an estimated speed of as much as 80 miles per hour in highway lane 1, smaller 

deposits located farther from the road might remain undetected by 

the instrument.

DESIRED PERFORMANCE OP FUTURE EQUIPMENT

The performance requirements of future equipment are based on 

three factors: (1) desired reproducibility of measurements, (2) 

length of traverse per individual measurement, and (3) speed of 

vehicle travel.

The desired reproducibility of measurement is a standard deviation 

of plus or minus 10 percent. As the standard deviation in percent

roughly equals - X 100, where N is the total number of pulses in

FIGDRB 53. Schematic diagram of alarm circuit.
PROSPECTING FOR URANIUM WITH CAR-MOUNTED EQUIPMENT 217

the measurement, a standard deviation of 10 percent requires a minimum of 100 pulses per measurement. Figure 50 shows that this degree 

of reproducibility is adequate to detect significant abnormalities.

The length of traverse during which the radioactivity of the environment is measured is based on the minimum width of an abnormal 

gamma-radiation field through which the equipment might pass. A 

consecutive series of individual measurements, each giving the average radioactivity of a 10-foot traverse interval, is considered adequate 

for the detection of the deposit shown in figure 51A and for smaller 

deposits.

The maximum speed of vehicle travel is limited by human factors. 

Field experience shows that the geologist observer can usually identify 

the roadside rocks up to speeds of 30 miles per hour, if he stops to 

check his identification when in doubt.

These considerations indicate that the desired equipment should 

be capable of a pulse rate of 100 pulses per 10-foot interval. At a 

speed of 30 miles per hour, the 10-foot intervals are traversed in 

about one-fifth second and the desired pulse rate for areas of normal 

radioactivity is 100 pulses per one-fifth second or 30,000 pulses per 

minute.

SUGGESTED METHODS OF OBTAINING THE DESIBED PEBFOBMANCE

Although the instruments described in this paper have proved 

their value in prospecting for radioactive source materials, they are 

essentially simple and crude. Many necessary improvements can be 

made.

First, the desired pulse rate of 30,000 pulses per minute can be 

obtained by in-parallel coupling of 20 brass-walled Geiger-Mueller 

tubes, 42 inches in length and 2 inches in diameter. These tubes are 

produced commercially and are available.

Second, the desired speed of response, sufficient to give a continuous series of radioactivity measurements, can be obtained either by 

decreasing the time constant of a counting-rate-meter circuit or by 

using a sealer circuit, at a scale of 100. If using the sealer circuit, 

each hundredth pulse could be recorded on moving tape by means of 

electric sparks or other means and the distance between spark holes 

on the tape would vary inversely with the radioactivity. Other 

methods of obtaining fast instrumental response will be obvious to 

personnel trained in electronics.

The position of the Geiger-Mueller tubes on the vehicle is important. The highest possible location of the tubes on or above the 

vehicle will permit the greatest instrumental response because of the 

larger solid angle between Geiger-Mueller tabes and roadside rocks. 

However, low bridges over roads limit the practical height of the 

tubes from 7 to 10 feet above road level, depending on the region.
218 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

The response of the instrument to the roadside rocks is also dependent on the geometric arrangement of the gamma tubes. The objective is to arrange the tubes so that they will be actuated to the fullest 

degree by gamma rays emitted from the roadside rocks and to the 

least extent by gamma rays emitted from the underlying road materials and by cosmic rays descending from above. The simplest efficient 

arrangement is obtained by forming a single vertical bank of 20 

contiguous tubes, symmetrically mounted above the vehicle, with the 

axes of the tubes horizontal and parallel to the travel path of the 

vehicle. The tubes in this position present the largest target for 

gamma rays emitted from the roadside rocks, and one of the smallest 

targets for gamma rays emitted by the road materials and for cosmic 

rays for above. This arrangement also decreases the percentage of 

coincidence counts from the roadside, and increases the percentage 

from above and below. Moreover, the vehicle partly shields the tubes 

from the gamma rays emitted from the road materials and reduces 

the number of these gamma rays that reach the tube.

Preferential response of the instrument to gamma rays emitted by 

roadside rocks over those emitted by the road material and cosmic 

rays may also be obtained by the use of coincidence and anticoincidence circuits, with a variety of gamma-tube arrangements. The 

increased complexity of such circuits may or may not outweight their 

advantages. Their relative merits cannot be evaluated until they are 

used in the field.

TYPES OF CAR-TRAVERSE PROGRAMS

The car-traverse technique has several applications. Its most important use is fast reconnaissance of large untested areas. Other uses 

are: Exploration in a wide area around known deposits, traversing to 

and from mining properties, and objective exploration of all rocks 

and soils in areas where the most favorable rocks have already been 

examined.

Car-traversing, with its high speed of 100 to 200 miles per day, 

makes it possible to sample large areas of untested rocks in a short 

time. Its ability to detect the few abnormally radioactive rocks and 

soils in such an area gives a relatively complete radioactivity profile 

along the roads traversed.

The car-traverse technique may also be used to explore a wide 

area around a known radioactive deposit; its speed and low cost permit 

exploration extending beyond the limits of the more common exploration techniques.

A field party using this technique in the general vicinity of a 

deposit in conglomerate discovered a second deposit in a sandstone 

of widely different age. The objective scanning of all roadside rocks
PROSPECTING FOR URANIUM WITH CAR-MOUNTED EQUIPMENT 219

made possible a discovery that would not have occurred by routine 

examination of this and adjacent formations.

The technique has been used successfully on routine trips to and 

from mining properties and other specific points of interest. The 

value of this use of the technique lies in the utilization of normal 

, travel time to test roadside rocks and soils that would not otherwise 

be investigated. A number of abnormally radioactive rocks were 

discovered in this manner in 1945, 1946, and 1947.

Even though the most favorable rocks in an area have already been 

examined, the objective exploration of less favorable rocks and soils 

has proved profitable. While driving through an area of known 

radioactive minerals, one car-traverse party discovered an additional 

highly radioactive soil zone.

PREPARATION FOR RECORDING FIELD DATA

Regardless of the use to which the car-traverse technique is put, 

the following preparation is required if the field party is to take 

full advantage of the potential rapidity of the technique.

The area to be investigated must be selected and limited after consideration of its geology. It should be subdivided into geologic divisions of varying promise, and the tentative time of exploration in 

each subdivision should be allotted accordingly. The geologic information of the area should be studied and indexed for field use. The 

field parties have found it most convenient to have all pertinent data 

plotted on index maps. Known, localities of radioactive rocks and 

localities of special geologic interest may be plotted on one index 

map; parts of the area covered by geologic maps may be plotted on a 

second; parts of the area described in publications may be plotted 

on a third. The speed with which the car-traverse technique can be 

employed is such that the field party may find that it has passed within 

a mile or two of a point of interest after it is several hundred miles 

beyond the point, unless all information is available in simplified 

form.

In addition to the car-mounted equipment, the party requires a 

portable gamma counting-rate meter of normal pulse rate, 1,000 or 

more pulses per minute, for detailed scanning of localities found by 

the car-traverse technique; a portable sealer and a jaw-crusher are 

desirable for determining the radioactivity of samples. Equipment 

for determining the radioactivity of the samples to the nearest thousandth percent equivalent uranium, while at the radioactive locality, 

permits the field party to make an immediate decision on the length 

of time to be allotted to local examination. If the field party waits 

for quantitative results obtained from the laboratory, it may find itself hundreds of miles from the locality, and may have to return to
220 A CONTRIBUTION TO THE GEOLOGY OF URANIUM

it, or it may find that an unjustified amount of time has been spent 

at a locality of low-grade rock.

The parties also require three standard samples (low-, medium-, 

and high-grade) that have the density of common rocks and are 

crushed to the same size as the samples collected in the field. The 

standard samples should consist of uranium in equilibrium with its 

daughter elements, thoroughly mixed with a diluent of average rock 

density. Pitchblende mixed with nonradioactive portland cement, 

cast and crushed to the proper size, has proved satisfactory.

The personnel required depends on the type of equipment and the 

information desired. A two-man party is generally desirable, but if 

the equipment includes an adjustable alarm, or if the radioactivity 

is automatically recorded and a continuous record of the geology is 

not required, one man can do the job. The personnel should be trained 

in maintenance and repair of the electronic equipment.

If the prospecting is on a large scale, the specially equipped car 

may be kept in the field throughout the year by the interchange of 

parties between the field and the office. If the prospecting is on a 

smaller scale and no replacements are available, the car-traverse party 

will probably do the detailed mapping of the radioactive localities.

Recording of car-traverse data may be simple or complex. In 

their simplest form the data consist of the roads traversed, recorded 

in pencil or ink directly on a road map, together with the exact location of any locality of sufficiently high radioactivity to interest the 

observer. A more complete recording of data would include, in addition to the foregoing, a complete radioactivity profile of the road 

traversed and the geology. This latter type of recording has the 

advantage of preserving smaller peaks of radioactivity, which, when 

integrated from one road to another, may indicate an intervening area 

of promise. However, this complex system of recording has the disadvantage of accumulating tremendous amounts of data that require 

a long period for analysis.

SUMMARY

Active field work has shown many advantages of the car-traverse 

technique over spot examination of outcrops with the hand counter. 

The coverage of 100 to 200 miles of roadside rocks and soils per day 

permits sampling of large untested areas that could not be investigated in a reasonable length of time by slower methods. The continuous and objective scanning of all rocks and soils along the routes 

traveled has disclosed uranium in rocks previously believed to be 

essentially barren. This objective characteristic of the technique is 

of considerable importance, because the use of uranium as a source 

material for atomic energy has created a demand for uranium ores, 

whose associations and distribution are not completely known.
INDEX

Page 

Alarmcircuit___-.____________________ 215,216,220

Application of car-traverse technique. _ _ 215,218-219

Cosmicrays_ --------_-----___-_________.__ 212-213

Counting-rate meter_ _____________________ 215,219

Detection of radioactive deposits.. _.---. _. 211,215 

Effect of solid .tngle__.-.._-.._............. 213

Instrument res ponse, arrangement of tubes for. 218

pulse rate.-._--_--_------__---___.________ 2.9

variation.. . --.-...--....-.._........... 213

Length of traverse.-.-..--,-.-----___-____- __ 217

Page

Limit of detection of high-grade deposits. _ - 215

Performance. ______ .._-_____.-__.-_._._..__ 216

Personnel required... _____--.._..._...___ 220

Position of tubes on vehicle................. 217-218

Radioactivity intensities........._......... 211,213

Range of radioactivity----------.----..----... 211

Recording data...------.................... 220

Selection of area..-----------------.---.------ 219

Speed of vehicle--------------------- 215,216,217

Standard deviation formula.__ - . - 216 

Standard samples..-. ---- -_ 220

o

221

Contributions to the 

Geology of Uranium

GEOLOGICAL SURVEY BULLETIN 9

This bulletin was printed as separate 

chapters, A-I, inclusive

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1953
UNITED STATES DEPARTMENT OF THE INTERIOR

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director
CONTENTS

[The letters in parentheses preceding the titles are those used [to [designate the papers for separate

publication]

(A) Geology o:f the Uravan mineral belt, by R. P. Fischer and L. S. Hilpert- 1

(B) Geologic guides to prospecting for carnotite deposits on Colorado

Plateau, by D. B. Weir ____ .. _____________________ 15

(C) Uranium in the East Walker River area, Lyon County, Nev., by M. H.

Staatz find H. L. Bauer, Jr__...__ _ _ _ _ _.. __ ________ _ __ 29

(D) Distribution of uranium in rich phosphate beds of the Phosphoria

formation, by M. R. Thompson__________ __ ______ ________ 45

(E) Radioactivity in some oil fields of southeastern Kansas, by G. B. Gott

and J. W. Hill _ _____ __.. _ _ _______ ____ ___ ______ 69

(F) Uranium-bearing deposits west of Clancey, Jefferson County, Mont.,

by W. A. Roberts and A. J. Gude 3d __________________ 123 

(G) Geology of the area adjacent to the Free Enterprise mine, Jefferson

County, Mont., by W. A. Roberts and A. J. Gude 3d ______ ___ 143

(H) Uranium and thorium deposits in east-central Idaho and southwestern

Montana, by A. F. Trites, Jr., and E. W. Tooker ________ _ 157 

(I) Prospecting for uranium with car-mounted equipment, by J. M.

Nelson. _____________ .. _____________________ 211

in

CONTENTS

[Chapter F was originally published as pages 69-87. Please insert corrected page numbers according to 

the following table of contents and index]

	Page 

Abstract___-_____-_-.__-.__________________:____________ 123

Introduction ______________________________________________________ 123

Geology___ ___._____..___.___.___-______.-._._________ 126

Igneous rocks _________________________________________________ 128

Quartz monzonite_________________________________________ 128

Aplite, granite, porphyry, granite, and pegmatite._____________ 129

Quiirtz monzonite pegmatite ______ __________________________ 129

Andesite porphyry, dacite porphyry, and andesite.____________ 129

Younger sedimentary rocks__-___-__-______-________-______--___ 129

Mineral deposits___________________________________________________ 130

General character and classification__________________---_-_-__-__ 130

Mineralogy,_--_____-______-______._-_________________-_-----_ 132

Alteration and enrichment-__-_______-_______________----__----- 132

L>escription of individual deposits._____________________________ 133

Localities mapped in detail_________________________________ 133

Locality 2__--____________.___________________________ 133

Locality 3______--____________________________ 135

Locality 6__-_-______-____-_____-__-_-___---__------__ 135

Locality 7_.__._.___.________.____._________ 137

Other localities examined.__________________________________ 137

Locality !_.._____________________.._______-___-__ 137

Locality 4__________________________________ 137

Locality 5.___---__---__.____-_______-----'----__-___ 138

Locality 8_._--_--__-_--____--___________------------- 138

Locality 9__-_--___---_____.___-_______._________ 138

Suggestions for prospecting _____________________________________ 138

Conclusions.-__-____-____----__--_____-_________-______-_-___----- 139

Index ____________________________________________________________ 141

ILLUSTRATIONS

Page 

PLATE 18. Geology of area containin g uraniferous deposits west of Clancey,

Jefferson County, Mont__________--______----___-- In pocket

19. Geologic map of locality 2-___________--_____-_--__--_ In pocket

20. Geologic map of locality 3.___________________________ In pocket

21. Geologic map of localities 6 and 7-___----------------- In pocket

FIGURE 34. Index map showing area mapped near Clancey, Jefferson

County _-.-______--____----_-.-_--_--_-----__-_-_--- 124

35. Index map showing areas mapped in detail and radioactivity anomalies ..-____-_______--_____---__-_--_--_ 125

36. Diagrammatic section illustrating four ages of silica.-_______ 127

in

INDEX

I'agt

Acknowledgements______________ 126 

Alaskite. .................... 127,130,131,135,137

Alteration and enrichment-.___.____ 132-133 

Analyses of samples, uranium deposits -.. __ 136 

Andesite. . . 127,129 

porphyry_________ __. 129 

Aplite ..... 127,129

Berman, Joseph, identifications by...___ 132,134

Boulder batholith..... .. ..- - 123,126,138

region.___________________ 132

Conclusions__...... ._ 139

Dacite........_.. ..... .................. 127

porphyry -.._..... . . ... 128,129

Dan Tucker mine. _______________ 130 

Description of deposits...- ... .. 133-138

Free Enterprise mine.__ _..... 133,138 

uranium-silver ore 133

Geology........ 126-128; pi. 18

Girhard, M. N., identification by........... 132

Granite....................-.- -- 127,129

porphyry_________..- ---___ 127,129

Igneous rocks_______ _ . __ 123-129 

King Solomon mine.____ .....___ 130

Little Nell mine . -. --- 130

Locality !_.___ ..._ . 126,137

Locality 2.. .. 126,131,132,133-135,139

analyses of samples, uranium deposits. _ 136

geology._________________ pi. 19

Locality 3... . 126,135

analyses of samples, uranium deposits.-.. 136 

geology-....-----.--.. .--------.-----. pi. 20

Locality 4-..___.___________. 

Locality 5.......................... 126,132,

analyses of samples, uranium deposits.. 

Locality 6-- ............ 126,131,132,135,

analyses of samples, uranium deposits...

Locality 7..................................

analyses of samples, uranium deposits...

geology..__.____________. 

Locality 8-. .................. 126,132,

Locality 9_......................... 126,132,

Fags

.. 137

137.138 

.- 136

137.139 

.. 136 

. pi. 21 

126,137 

.. 136 

. pi. 21 

137,138 

137,138

Mineral deposits. _______________ 130-132 

Mineralogy_______________.-.-. 132

New Stake mine.-.-.- ._... - -_ 126,130

Pegmatite-.--------.--_......__-.-__. 127,129

quartz monzonite._________... 129, pi. 18 

Pitchblende--- - . 131,132-133,134,139 

Production, value______..--.._ 126 

Prospecting, suggestions for.... 138

Quartz monzonite _____. . . . 126,

127,128,130-131,134,135,137,138,139

composition, average . 128

pegmatite_ _____________ 129; pi. 18

Radioactivity anomalies____ .. 125, 

126,131,133; pis. 19, 20, 21

Sedimentary rocks.-____.... 129-130 

Silica-. 127,129,130,131,132,133,134,135,137,138,139

Terrace gravels,__-__. .. ... ... 129-130

Uranium minerals..--.----- -_... 126,127,130,

131,132-133,134,135,137,138,139

Uranium-silver ore, Free Enterprise mine. 133

141

 fr U. S. GOVERNMENT PRINTING OFFICE : O 1953