GEOLOGICAL SURVEY CIRCULAR 294

RESULTS OF RECONNAISSANCE 

FOR RADIOACTIVE MINERALS IN 

PARTS OF THE ALMA DISTRICT 

PARK COUNTY, COLORADO
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

GEOLOGICAL SURVEY CIRCULAR 294

RESULTS OF RECONNAISSANCE FOR RADIOACTIVE MINERALS IN 

PARTS OF THE ALMA DISTRICT, PARK COUNTY, COLORADO

By C. T. Pierson and Q. D. Singewald

This report concerns work done on 

behalf of the U. S. Atomic Energy 

Commission and is published with 

the permission of the Commission.

Washington, D.

Free on application to the Geological Survey, Washington 25, D. C.
RESULTS OF RECONNAISSANCE FOR RADIOACTIVE MINERALS IN 

PARTS OF THE ALMA DISTRICT, PARK COUNTY, COLORADO

By C. T. Pierson and Q. D. Singewald

CONTENTS

Page

Abstract.................................... 1

Introduction................................. 1

Field work and acknowledgments......... 1

Location and accessibility............... 2

General geology and ore deposits.............. 2

Method of reconnaissance for radioactive

minerals.................................. 3

Radioactivity measurements.................. 3

Occurrences of uranium...................... 3

Page

Occurrences of uranium Continued

Veins in pre-Cambrian rocks............ 3

London vein system..................... 7

Veins east of Cooper Gulch fault.......... 7

Disequilibria in the uranium occurrences............................. . 7

Nonradioactive localities................ 7

Origin................................. 7

Literature cited............................. 9

ILLUSTRATIONS

Page

Plate 1. Generalized geologic map of the Alma district, Park County, Colo.................. Inside back cover

Figure 1. Index map of Colorado showing location of the Alma disti-2t.................................... 2

2. Geologic sketch map of part of Orphan Boy mine............................................. . 8

TABLES

Page

Table 1. Localities tested for radioactivity in the Alma mining district.................................. 4

2. Relationship between ratio of maximum radioactivity measurements to average

background and percentages of equivalent uranium........................................... 7

ABSTRACT

Pitchblende was discovered in July 1951 in the Alma 

mining district, Park County, Colo., by the U. S. Geological Survey acting on behalf of the U. S. Atomic 

Energy Commission.

The pitchblende is associated with Tertiary veins of 

three different geologic environments: (1) veins in preCambrian rocks, (2) the London vein system in the footwall 

block of the London fault, and (3) veins in a mineralized 

area east of the Cooper Gulchf ault. Pitchblende is probably not associated with silver-lead replacement deposits 

in dolomite.

Secondary uranium minerals, as yet undetermined, 

are associated with pitchblende on two London vein system mine dumps and occur in oxidized vein material from 

dumps of mines in the other environments.

Although none of the known occurrences is of commercial importance, the Aim a district is considered a 

moderately favorable area in which to prospect for 

uranium ore because 24 of the 43 localities examined show 

anomalous radioactivity; samples from anomalously radioactive localities, which include mine dumps and some 

underground workings, have uranium contents ranging 

from 0.001 to 1.66 percent.

INTRODUCTION 

Field work and acknowledgments,

A search for uranium in parts of the Alma mining 

district, ParkCounty, Colo., was made during 2f weeks 

of July and August 1951 by the U. S. Geological Survey on 

behalf of the Atomic Energy Commission. Many mine 

dumps and mine workings were tested for radioactivity, 

and some were sampled, but time did not permit complete 

coverage even of the parts of the area examined.

V. R. WilmarthandR. C. Vickers, of the Geological 

Survey, were members of the fie Id party from July 16 

through 19. L. R. Page, of the Geological Survey, and 

C. C. Towle, Jr., of the Atomic Energy Commission,visited the London Extension and South London mine areas on 

August 1. George Phair also of the Survey visited the 

areas and collected radioactive samples from London 

Extension and South London mine dumps on August 21, 1952.

Acknowledgements are due Mr. Joseph Thibodeau, 

foreman of the Buckskin Joe mine, and Mr. G. O. Lear 

at the Sweet Home mine for courtesies extended at the 

time these mines were examined. The writers are indebted to George Phair for providing the results of 

chemical and spectrographic analyses made from handpicked radioactive material.
Location and accessibility

The Alma district (fig. 1) is located on the eastern slope of the Mosquito Range. The altitude of the 

area is from about 10, 500 feet to more than 14, 000 feet. 

Most of the localities examined can be reached by a 

4-wheel-drive vehicle.

GENERAL GEOLOGY AND ORE DEPOSITS

The geology of the Alma district has been described 

in several publications, to three of which the reader 

is particularly referred for details (Singewald and Butler, 

1933, 1941; Singewald, 1947). The generalized geology 

of the Alma district, taken from plate 8 of Geological 

Survey Bulletin 955-D (Singewald, 1950), is shown on 

plate 1.

The bedrock of the Alma district is composed of

(1) pre-Cambrian gneiss, schist, granite, and pegmatite;

(2) pre-Pennsylvanian sedimentary strata, aggregating 

300 to 600 feet in thickness and comprising the Sawatch 

quartzite and Peerless formation of Cambrian age, the

Manitou limestone of Ordivician age, the Chaffee formation (Devonian) including the Parting quartzite and 

Dyer dolomite members, and the Leadville dolomite of 

Mississippian age; (3) Pennsylvanian-Permian(?) sedimentary strata consisting of interbedded clastic rocks 

that range from coarse conglomerate to shale, with a 

few thin beds of dolomite; and (4) Tertiary(?) quartz 

monzonite porphyries, correlated with the White porphyry 

and the Gray porphyry group of Leadville, which occur 

mainly as sills in sedimentary strata or as dikes in preCambrian rocks. The Buckskin Gulch stock is composed 

of igneous rocks closely related to the porphyries.

Major structural features are shown on plate 1. The 

regional dip of the strata is 10° to 25° east. Departures 

from this regional dip occur principally along folds associated with major faults.

There are two major faults in the district, each of 

which cuts the west limb of an anticline that is overturned 

to the west. The London fault is reverse, dips steeply 

northeastward, and has a throw of about 3, 000 feet. 

The Cooper Gulch fault is reverse, dips 30° eastward, 

and has a maximum throw of 450 feet at Mosquito Gulch.

..__._ 

- 

_WYOMING -. --___.__ _____.. I _______ - ]~r

I0t« 107* 106 105° 104° 103° I02fl

Figure 1. Index map of Colorado showing location of the Alma district.

2
The more important ore deposits, which for the most 

part are within the "mineralized areas" shown on plate 1, 

can be classified as follows: (1) Gold and silver veins 

in pre-Cambrian rocks, (2) gold-sulfide veins of the 

London type, (3) gold veins and replacement veins in 

Sawatch quartzite, and (4) silver-lead bedded replacement bodies and replacement veins in dolomites. Although mineralized fissures are abundant in the preCambrian rocks, commercial production from them has 

been limited to a few relatively small to medium-sized 

mines in Mosquito, Buckskin, and Platte Gulches.

The London vein system, in the footwall block of the 

London fault, consists of gold-bearing quartz-sulfide 

veins. Most of the ore occurred as veins within a zone 

of porphyry sills 175 to 275 feet thick, very close to 

the base of the Pennsylvanian system, but some were 

in veins in the upper part of the Leadville dolomite.

Most of the production from deposits in the Sawatch 

quartzite has been from mines in the mineralized areas 

east of the Cooper Gulchf ault and on North Star Mountain. 

Veins along minor faults are productive at certain favorable 

horizons where thin ore shoots formed by replacement of 

the wall rock several feet outward from the faults. Beds 

containing considerable quantities of carbonate cement, 

which was more easily replaced than the characteristic 

siliceous cement, localized most of the shoots.

The silver-lead production has come from bedded 

re placement bodies and replacement veins from (1) near 

the London fault at New YorkMountain; (2) the Hock Hocking 

mine in the mineralized area east of the Cooper Gulchf ault; 

and (3) the Mount Lincoln-Mount Bross area. Most of the 

ore occurred in the upper part of the Leadville dolomite.

METHOD OF RECONNAISSANCE FOR 

RADIOACTIVE MINERALS

Reconnaissance for radioactive minerals in the 

Alma district was carried out to test the uranium potentialities of the various types of geologic environment 

rather than to cover systematically all mine dumps and 

accessible mine workings in the district. The localities 

visited are shown on plate 1; the numbers refer to brief 

descriptions in table 1. For locations and descriptions 

of mines not visited, reference is made to the publications previously cited.

Forty-three localities were tested with Geiger 

counters, and 24 samples were taken. Sixteen grab 

samples were selected from mine dumps, and 8 were 

chip or chip-channel samples from underground exposures or prospect trenches.

RADIOACTIVITY MEASUREMENTS

Table 1 lists anomalous radioactivity measurements 

in milliroentgens per hour, taken with survey meters 

equipped with 6-inch beta-gamma probes. Readings 

are not recorded for localities where no anomalous 

radioactivity was found. Locality numbers refer to 

plate 1, which shows all localities tested.

The maximum radioactivity measurements for a 

locality is the largest reading obtained by holding the 

probe directly against the surface of any specimen or 

underground exposure at the locality.

A locality or specimen is considered to be anomalously radioactive if the ratio of the maximum radioactivity measurement to the average background is 

equal to or greater than 1.7. The average background 

is taken, for convenience, as the arithmetic mean of 

the background measurement. Localities at which the 

ratio is less than 1.7 are not regarded as anomalously 

radioactive. The anomalously radioactive category has 

been divided into two classes: ratio of maximum radioactivity measurement to average background lies in 

the range 1.7 to 3. 0 and ratio is greater than 3. 0

With three exceptions out of 22 samples (table 2), 

the percentages of equivalent uranium obtained by 

laboratory analysis ranges from 0.004 to 0. 008 in 

samples from localities at which the ratio of the maximum radioactivity measurement to average background 

is 1.7 to 3. 0, and more than 0. 008 where the ratio is 

greater than 3.0. The percent equivalent uranium for 

localities at which the ratio is less than 1.7 doubtless 

is less than 0. 004. Accordingly, the percent equivalent uranium may be roughly estimated for occurrences 

for which no laboratory analyses are available (e.g., 

locality 18). Ratios are not available for 31b and 31d, 

but these occurrences have been assigned to the third 

group because of their relatively high uranium contents.

OCCURRENCES OF URANIUM

In the Almadistrict, uranium minerals are associated with Tertiary vein deposits of three different geologic environments: (1) veins in pre-Cambrian rocks; 

(2) veins of the London vein system; and (3) veins in 

a mineralized belt east of the Cooper Gulch fault. The 

known occurrences, although not of immediate commercial importance, offer moderate encouragement 

for further search.

Veins in pre-Cambrian rocks

At localities 2 to 9, 13, 15, to 18, 20, 21 (pi. 1) 

veins or material from veins in the pre-Cambrian 

rocks of the Alma district were found to be anomalously radioactive. Localities 1, 10 to 12, 14, and 

19 show no abnormal radioactivity. Localities 11 

and 12 are in quartz monzonites of Tertiary age intruded into pre-Cambrian rocks.

At the Kentucky Belle mine (8) disseminated pitchblende, not visible megascopically, occurs in the 

crushed rock of a 4- to 6-inch-thick breccia zone in 

granite and pegmatite. Bad air about 400 feet from 

the portal precluded adequate examination of this 

zone. It also prevented any examination for radioactivity of the ground from which most of the ore was 

obtained; that is, within and near a White porphyry 

dike which apparently was cut by the adit less than 

1, 000 feet from the portal. A sample from the dump 

of a nearby caved adit (3) contains pitchblende and 

pyrite in a narrow vein that cuts granite. As much 

as 0. 013 percent uranium is contained in pyritic 

siliceous vein material from the Champaign 

fissure (20). Radon was detected in the Sweet 

Home mine (13).

No secondary uranium minerals have been determined, but one or more are probably present in such 

oxidized samples as 8a and 21.
Table 1. Localities tested for radioactivity in the Alma mining district

[Chemical, spectographic, and mineralogical analyses by U. S. Geological Survey laboratories ]

Locality 

no.

1- _

2 - -

3__ _

4- . ....

5 

6 

7 

Ra

8b - 

fir*

10 - - - 

11 

12 - 

13 __ _ 

Ik ...... __

15 

Maximum radioactivity 

measurement 

(mr/hr)

0.09

.40

no

.09

.18

.19

.50

.09

.10

.13

.18

.13

Background 

measurement 

(mr/hr)

0.03-0.05

.0> .05

.03- .05

.03- .05

.03- .05

.03- .05

.08- .18

.03- .05

.03- .05

.03- .08

.05- .10

.01- .07

eU 

(percent)

0.041

.021

.070

.14

.008

.008

.006

.011

U 

(percent)

0.022

.013

rvcr? ,(j^(

(\f.O

.001

.004

.002

.002

Remark

dump of caved adit. 

Pitchblende associated with pyrite i

fresh granite from dump of caved a

shows XX Si; X Al, Ca, Fe; .X Mn, 

Zr, Ti; .OOX Ag, B, Cu, La, Mo, Ni

Ga, Sn. 

Limonite -stained granite from dump o

Do.

Pitchblende disseminated(?) in relat

hanging wall of tight fissure expo

analysis shows XX Si; X Al, Fe, Na

Pb; .OOX Ag, B, Cu, Mo, Ni, Sr, V, 

occurs as a 4 -inch- thick vein in a 

relatively fresh granite and pegtna

shallow trench. No uranium minera

analysis shows XX Si, Mn; X Al, Pb

.OX Ti, Mg, Ag, Ba, U; .OOX B, Bi, 

Ga, Ni. 

Pitchblende, not visible megascopica

and crushed rock from a 4-inch to 

granite and pegmatite; exposed by 

rium caused by excess radium; no t

Disseminations in limonite-gossan fr

No uranium minerals identified. 

Pitchblende as disseminations(?) in 

rock from dump of Kentucky Belle a

Disseminations in fresh granite expo

uranium minerals identified. Radi

essentially equal to background.

Dump of Sonny Boy adit; radioactivit

background.

hanging wall of narrow fissure zon

exposed by Sweet Home adit. Radon 

Dump of caved adit; radioactivity es

Disseminations(?) and limonite-stain

granite from dump of caved shaft(?
16-

17-

18-

19-

20 -

21 -

22 26-

27-

28-

29-

30-

31a31b31c32- 

33a34- 

35a-

.15 

 19 

.18

.50 

.15

.13

.13 

.15

 50

 50

.10 

.80

.50 

.13

.02- .09

.02- .09

.0?

.05

.05- .10

.01- .07

.01- .08

.05- .10

.50- .07 

.05- .07

.02- .05

 

.05- .07 

.05- .07

.01- .04

.01- .04

.006

.005

.010

.004

.008

.006

.007

.044 

.021

6.7

.004 

1.5

.072

.013

.005

.003

.013

.002

.002

.001

.005

.044 

.024

6.11

.002 

1.66

.033

.005

Disseminations(?) in pyritic silic

main Champaign adit.

Disseminations(?) in limonite-stai

caved adit.

Disseminations in pegmatite expose

Schist and granite exposed by adit

equal to background.

Disseminations(?) in pyritic silic

fissure; exposed by adit.

Disseminations(?) in limonite and 

material exposed by adit.

Dumps of several adits and shafts 

lead replacement deposits in Lea

essentially equal to background.

Dump of caved Oliver Twist adit; r

background.

Disseminations in brownish-black s

shallow prospect trench adjacent 

material from the dump of a near

active. No uranium minerals ide

Disseminations in sheared brownish

dump of caved Hard-To-Beat adit. 

Sheared dark-colored shale of Penn

North London mine.

Yellow gouge(?) from dump of South 

Rock fragment coated with secondar

South London mine.

Pitchblende(?) associated with gal

vein material from dump of South 

Colloform pitchblende(?) in fine-g

material from dump of South Lond

shows XX U, Pb; X Zn; .X, Mn, Cu

.OOOX Be, Cr. (Chemical and spec

hand-picked radioactive material

Dump of American shaft; radioactiv

background.

Dark-blue gougelike material from 

Pitchblende associated with banded 

dump of London Extension mine. 

lets which crosscut the quartz a

uranium minerals coat fractures.

Dump of London Butte mine; radioac

background.

Pitchblende, not visible megascopi

friable rock from remnant of ore 

mill. Disequilibrium caused by 

Disseminations in unoxidized quart

vein material from site of forme

minerals identified.
Table 1. Localities tested for radioactivity in the Alma mining district Con

Locality 

no.

£

^7

 *8 

^Qh

40 -

111 fl - __

Maximum radioactivity 

measurement 

(mr/hr)

O

n Q

.03

.04

1.00

.18

Background 

measurement 

(mr/hr)

0.01-0.04

.01- .02

.01- .03

0- .04

- .04

eU 

(percent)

0.010

.91

U 

(percent)

0.009

1.00

Remark

Dump of caved adit; radioactivity e

Disseminations In rock from the foo

dolomite vein In quartzlte; expos

uranium minerals Identified. Rad

equal to background.

essentially equal to background. 

Wall of minor branch fissure expose

Small area of gouge In minor branch 

to background. 

Pitchblende as fracture coatings In 

monzonite porphyry from ore pile 

Disseminations In footwall of gold-

exposed by Orphan Boy adit. The 

of an ore shoot and within or Imm

quartz monzonite porphyry sill wh

background. 

Dump and that part of underground w

mine; radioactivity essentially e
Table 2. Relationship between ratio of maximum radioactivity measurements to average background

and percentages of equivalent uranium1

Range of 

ratios

1.7- 3-0

3.1-50.0

Symbol used for plate 1

Number of 

localities or 

occurrences

9

13

Percent equivalent 

uranium for analyzed 

specimens

2 0.004-0.008

3 nnft ~\ c

1 Percent equivalent uranium has not been determined for the 19 localities at which the ratios are less than 1.7, nor for 9 occurrences for which the ratios 

are equal to or greater than 1.7. Ratios are not available for 2 occurrences for which percent equivalent uranium has been determined.

2Except for locality 13 (0.011 percent) where radon in adit caused ratio of maximum radioactivity measurement to background to be exceptionally low., 

3Except for localities 17 (0.005 percent) and 28 (0.008 percent).

Many small mines and prospects along veins in 

pre-Cambrian rocks of the Platte, Buckskin, and Mosquito 

Gulches were not examined for radioactivity in 1951; so 

further investigation of possibilities within pre-Cambrian terrane may be justified.

London vein system

Anomalously radioactive material from the dumps 

of mines along the London vein system was found at 

localities 28 to 31, and 33 but not at localities 27, 

32, and 34 (pi. 1).

Slightly radioactive gougelike material, as well 

as specimens that contain pitchblende associated with 

banded gold-silver-lead-zinc ores, was found on the 

dump of the now inoperative London Extension mine (33). 

The hard lustrous pitchblende occurs in veinlets that 

crosscut the quartz and sulfide minerals. Secondary 

uranium minerals coat fractures in these specimens. 

Pitchblende associated with sulfide vein material, and 

secondary(?) uranium minerals associated with yellow 

gouge(?) were found on the dump of the South London 

mine (31).

Slightly radioactive shale, presumably from the 

lowermost 150 feet of the Pennsylvanian system, was 

found on dumps and in a prospect trench at the HardTo-Beat mine and vicinity (28, 29). It probably came 

from a shear zone in the west wall of the London fault. 

Some Pennsylvanian shale on the dump of the North 

London mine (30) is mildly radioactive.

Veins east of Cooper Gulch fault

In the mineralized area east of the Cooper Gulch 

fault, veins or vein material from localities 35, 37, 39 

and 41 (pi. 1) show anomalous radioactivity. Localities 36, 

38, 40, 42, and 43 are not anomalously radioactive.

At the Orphan Boy mine (41; and fig. 2) anomalous 

radioactivity, probably caused by pitchblende, was 

detected in the footwall of the gold-base-metal vein 

in Sawatch quartzite of Cambrian age. The radioactivity 

occurs at the top of an ore shoot (41b), and within or 

immediately below a Tertiary quartz monzonite porphyry 

sill that caps the ore shoot. A sample of pyritized and 

silicified quartz monzonite porphyry (41a) from an ore 

pile in this mine contains pitchblende as fracture coatings.

In the Buckskin Joe mine (37) a sample from the footwall of a pyrite-sphalerite-dolomite vein in Sawatch

quartzite contains 0.009 percent uranium, but the other 

parts of the vein are not anomalously radioactive.

Other localities at which anomalous radioactivity 

was noted are a remnant of an ore stockpile at the former Phillips mill (35) and the underground workings of 

the Shelby mine (39).

Diseauilibria in the uranium occurrences

Inspection of the laboratory analyses for uranium 

and equivalent uranium (table 1) shows that the ratio 

of percent uranium to percent equivalent uranium in 

samples from the Alma district ranges from a minimum of 0.13 (locality 8b, pi. 1) to a maximum of 

1. 30 (20). The ratio is equal to or less than 1. 00 in 

20 of the 24 analyses.

Two of the samples (8a, 35a), which exhibit ratios 

of less than 0. 50, were analyzed for radium and 

thorium contents. No thorium was detected, and 

radium and other daughter products of uranium are in 

excess of the uranium present in the samples. It is 

probable that the disequilibria in all or most of the 

samples where the ratios are less than 1.0 have been 

caused by removal of uranium by supergene processes.

The four causes where the ratio is greater than 

1. 0 probably resulted from the combination of analytical 

errors and loss of radon during sample grinding.

Nonradioactive localities

Some nonradioactive localities, previously listed, 

have been found in each of the three geologic environments discussed. Silver-lead replacement deposits in 

dolomite, where tested for radioactivity at New York 

Mountain (localities 22, 26, pi. 1) and at the Hock 

Hocking mine (43), were not anomalously radioactive. 

The silver-lead dolomite replacements of the Mount 

Lincoln-Mount Bross area have not been tested.

Origin

Because of the close association of the 

pitchblende with the base- and precious-metal 

veins of Tertiary age, the writers believe that 

the pitchblende of the Alma district was deposited 

by hypogene processes. The secondary uranium 

minerals resulted from supergene alteration of 

the primary pitchblende.
Porphyry forms 

top of stope

Large stope

200 

I_

Stope inclined down to 

NE and also downdip

i^ feet to fork;375 feet 

T to breast of western fork. Porphyry 

all the way; no anomalous radioactivity

Adit level

Chute 

Base o'f Sawatch 

quartzite

200 400 Feet

Portal

Base by compass and pace traverse Geology by Q.

Figure 2. Geologic sketch map of part of Orphan Boy mine, Alma mining district, Park County, Colo., showing radioa
LITERATURE CITED

Singewald, Q. D., 1947, Lode deposits of Alma and Singewald, Q. D., and Butler, B. S., 1933, Suggestions

Horseshoe districts, Park County, Colo., in,Vander- for prospecting in the Alma district, Colo.: Colo.

wilt, J. W., ed., Mineral resources of Colorado, Sci. Soc. Proc., v. 13, no. 4, p. 89-131.

p. 336-341: Colo. Min. Res. Board. _______1941, Ore deposits in the vicinity of the

_______1950, Gold placers and their geologic en- London fault of Colorado: U. S. Geol. Survey

vironment in northwestern Park County, Colo.: Bull. 911.

U. S. Geol. Survey Bull. 955-D, p. 103-172.

INT.-DUP. SEC., WASH., D.C,M775<
GEOLOGICAL SURVEY CIRCULAR 294 PLATE 1

I06°IO' R. 78 W. I06°05'

T8S

39°20' -

T9S.

39°I5'

LAKE CO Bartletf 

A Mtn.

/, ///{^Wheeler Lake ,/^ vvx£\ i x^>//x ^y//x>

^pfl axov//>-£vDi^x/;

fZ^jj'&jj^&yifi >7/^Cnompaign I6ffl ^^ f^'' (,^/It

T.8S.

39°20'

I06°IO R. 78 W. IO6°05

T9S.

39°I5'

EXPLANATION

Quartz monzonite stocks

Pre-Pennsylvanian sedimentary rocks

Schist-injection gneiss series 

Whitish-gray granite and pegmatite

a: 

CD

o

i

u 

oc

Contact 

Dashed where approximately located

Major fault 

Dashed where approximately located

Inferred fault

Mineralized area

Note-- Early Tertiary intrusive porphyries occur 

abundantly as sills, dikes and laccoliths 

in all formations.

ol2

Mine, mine dump,or prospect pit tested for radioactivity 

Number refers to description in table I

MAXIMUM RADIOACTIVITY

a 

Less than 1.7 times average background

a 

1.7-3 times overage background

 

Greater than 3 times average background

Geology reproduced from plate 8,U.S.Geological Survey Bull.955-D, 1950 

Base from Geological Survey maps

Geology by Q.D.Singewald,J.W.Vanderwilt, 

R.E.Landon.and B.S.Butler, 1928-1932 

Radiometry by Q.D.Singewald,C.TPierson, 

V.R.Wilmarth,andR.C.Vickers,l95l

GENERALIZED GEOLOGIC MAP OF THE ALMA DISTRICT,PARK COUNTY, COLORADO,

SHOWING AREAS TESTED FOR RADIOACTIVITY

Scale 1=62,5OO

4Miles

I

5000 

I__i

5000

I

10,000 15,000 Feet

Datum is mean sea level