DEPARTMENT OF THE INTERIOR 

FRANKLIN K. LANE, Secretary

UNITED STATES GEOLOGICAL SURVEY

GEORGE OTIS SMITH, Director

Bulletin 626

THE ATLANTIC GOLI) DISTRICT AND 

THE NORTH LARAMIE MOUNTAINS

PAPERS BY

ARTHUR C. SPENCER

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1916

CONTENTS.

Pago.

Preface, by F. L. Eansome ................................................. 7

The Atlantic gold district, Fremont County, Wyo........................... 9

v Introduction.......................................................... 9

 Situation and general features.......................................... 9

 - Geology^of the general region........................................... 12

Geology of the Atlantic district......................................... 14

. Rocks present..................................................... 14

Schists .......................................................... 14

Schists of the central Atlantic belt............................. 14

Structure of the schists........................................ 15

Schists derived from igneous rocks............................. 16

Magnetite schists in the northern part of the district.............. 16

Distribution and general character......................... 16

The magnetite schists considered as iron ore................. 17

Serpentine and asbestos............................................ 18

Intrusive rocks................................................... 19

Diorite ....................................................... .19

Dikes of porphyry ............................................ 21

Minor intrusions of granite...................................... 22

Inliers of Cambrian sandstone....................................... 23

Tertiary deposits................................................... 23

Historical notes........................................................ 23

Estimated gold production............................................ 27

Veins............................................................... 28

Previous descriptions.............................................. 28

Classification of the veins and other gold deposits................... 30

Cross veins................................................... 30

Strike veins.................................................. 30

Stringer lodes................................................ 31

Gash veins.................................................... 31

Mineralized rock masses....................................... 31

Mineralogy of the veins........................................... 32

Gold content of the ores............................................ 32

Probable persistence of the veins........:.......................... 33

Future development ................................................. 34

General outlook for lode mining.................................... 34

Planning of development work. ...................................... 34

Outlook for railroad transportation .................................. 35

^ Cost of power...................................................... 36

Milling of the ores. .................................................. 39

Placer deposits......................................................... 42

Economic geology of the North Laramie Mountains, Converse and Albany

 counties, Wyo........................................................... 47

Introduction....................:::................................... 47

North Laramie Mountains.............................................. 47

Definition.;.....................'.................................. 47

Configuration..................................................... 47

Drainage.................I..:..................................... 48

' 3
4 CONTENTS.

Economic geology of the North Laramie Mountains, Converse and Albany 

counties, Wyo. Continued.

North Laramie Mountains Continued. Page.

Climate. ......... ^............................................... 48

Vegetation, stock raising, and agriculture........................... 49

Railroads.......................................................... 50

Wagon roads...................................................... 50

Geology............................................................... 50

General stratigraphy and structure................................. 50 *

The geologic map.................................................. 52

Pre-Cambrian rocks..........................................\ ..... 52

Sedimentary rocks, by N. H. Barton................................ 53

General features...............................-.'................ 53

Carboniferous system.......................................... 53

Casper formation.......................................... 53

Satanka (?) shale and Forelle (?) limestone.................. 54

Triassic (?) system.......................,.....:............... 54

Chugwater formation...................................... 54

Jurassic system............................................... 54

Sundance formation....................................... 54

Jurassic or Cretaceous system.................................. 55

Morrison formation......................................... 55

Cretaceous and Tertiary systems................................ 55

Cleverly (?) sandstone.................................. 1... 55

Benton shale.............................................. 55

Niobrara shale............................................ 56

Later Cretaceous and early Tertiary formations.............. 56

White River formation........:........................... 56

Mineral deposits in the North Laramie Mountains. ...................... 56

Development..................................................... 56

North Laramie Peak district....................................... 57

Location and geology............:.............................. 57

General character and occurrence of the mineral deposits......... 58

Maggie Murphy belt........................................... 60

Three Cripples and Tenderfoot belts............................. 62

Maverick prospects............................................ 65

Saul's camp.................................................. 66

Snowbird group................................................ 68

Trail Creek group............................................. 70

Hoosier Boy group................................'............. 71

War Bonnet district................................................ 72

Location and geology........................................... 72

Prospects north of Fortymile ranch............................. 72

Copper King belt............................................. 74

Oriole belt........................ .............................. 75

Brenning copper prospect....................................... 76

Perry claims................................................... 77

Deer Creek district................................................. 77

Location and geology..........................-..........:...... 77

Swede Boy vein.............................................. 77

Chromite in Deer Creek canyon................................. 78

Asbestos prospects east of Deer Creek............................ 79

Mormon Canyon prospects..................................... 79

Martin Smith copper prospect................. i................ 79
CONTENTS. 5

Economic geology of the North Laramie Mountains, Converse and Albany 

counties, Wyo. Continued.

Mineral deposits in the North Laramie Mountains Continued. Page. 

La Prele district................................................... 79

Location and geology........................................... 79

Copper prospects on Cotton wood Creek......................... 80

Hazenville prospects.......................................... 81

Index...................................................................... 83

ILLUSTRATIONS.

PLATE I. Map of Atlantic gold district, Wyo., showing principal geologic

features.......................................................... 12

II. Map showing part of the mining claims in the Atlantic gold district, Wyo................................................... 22

III. Sketch map of Atlantic and adjacent districts, Wyo., showing distribution of gold placers in part................................. 42

IV. Geologic map of the North Laramie Mountains, Wyo., and adjacent

territory....................................................... 52

V. Sketch map of the North Laramie Mountains, Wyo., showing location of principal mineral prospects............................. 56

FIGURE 1. Drainage and railroad map of Wyoming........................... 10

2. Map of part of Fremont County, Wyo., showing situation of the

Atlantic gold district and general geologic features of the region. 11

3. Geologic sketch map of part of North Laramie Peak district....... 59

4. Sketch map of Snowbird group, showing schist bands in granite... 69

5. Sketch map of Trail Creek group, showing local geology........... 70

6. Sketch map of Mewis property, showing location of claims and local

geology...................................................... 80

PREFACE.

By F. L. RANSOME.

In response to numerous requests from persons interested in the 

development of the mineral resources of Wyoming and desirous that 

reliable information concerning them should be published, A. C. 

Spencer, geologist, was detailed in 1914 to make an economic reconnaissance of the region adjacent to South Pass City, Miners Delight, 

and Atlantic City, in Fremont County, and of parts of the North Laramie Mountains, in Converse and Albany counties. The two areas 

examined by Mr. Spencer lie about 125 miles apart, the Atlantic gold 

district being in west-central Wyoming about 20 miles south of Lander, and the North Laramie Mountains in the southeastern part of 

the State, south of Douglas and Casper.

The Atlantic district has produced considerable gold, estimated by 

Mr. Spencer at about $1,500,000, although other estimates vary up 

to nearly $6,000,000. No large mine has been developed in the district, however, and of late years mining activity has declined. In 

the North Laramie Mountains mining development remains in the 

prospecting stage. In both regions the lode deposits occur in schists 

of pre-Cambrian age, partly with quartz in distinct fissures and partly 

as tabular or lenticular bodies of rock through which the sulphides 

are distributed. These bodies are aligned in more or less definite 

belts in the schist. The chief metal in the prospects of the North 

Laramie Mountains is copper, although other metals are also present 

in most of the lodes.

The area shown on the geologic map of the North Laramie Mountains (PI. IV), which is based largely on the work of N. H. Darton, 

overlaps to the south an area previously mapped geologically on the 

same scale by Darton and Siebenthal* and to the north the area covered by Darton's geologic map of the central Great Plains.2 Adjacent 

to it on the west is an area that will be covered by a map to accompany a report now in preparation by C. J. Hares. The work on which

1 Darton, N. H., and Siebenthal, C. E., Geology and mineral resources of the Laramie Basin, Wyo.: U. S. 

Geol. Survey Bull. 364,1909.

* Darton, N. H., Preliminary report on the geology and underground water resources of the central Great 

Plains: U. S. Geol. Survey Prof. Paper 32, pi. 35,1905.

7
8 PREFACE.

the present report is based, while of course not of detailed character, 

has distinct general value in connecting other areas where geologic 

work has been or is being carried on.

Regarding the mines and prospects in the two districts described, 

the report presents reliable statements of facts and conditions which 

it is hoped may be of use to those specially interested in these deposits.
THE ATLANTIC GOLD DISTRICT. FREMONT COUNTY,

WYOMING.

By ARTHUR C. SPENCER.

INTRODUCTION.

In September, 1914, the writer spent three weeks in the vicinity 

of Atlantic City, in southern Fremont County, Wyo. Although only 

a short time could be devoted to the study the writer was confronted 

by the problem of adding to information contained in two excellent 

reports, one by the late W. C. Knight and the other by L. W. Trumbull, 

the present State geologist of Wyoming. Prof. Knight has given not 

only a very adequate description of the general geologic features of 

the Sweetwater district, which includes the Atlantic district and the 

Lewiston district (formerly known as the Overland district), lying to 

the east, but also the results of his own laboratory tests in order to 

determine the amenability of the gold ores to amalgamation, to 

chlorination, and to cyanidation. From his observations he was led 

to make specific suggestions which are of great practical significance. 

Prof. Trumbull has provided a sketch map upon which the principal 

geologic features of the Atlantic district are shown.

As it appeared to be impracticable, under the circumstances of 

inactivity existing, to add materially to the technical data given in 

Knight's report, the writer decided to turn his attention to making 

a geologic map of the Atlantic district that should be more detailed 

than the one presented by Trumbull. In making certain practical 

suggestions the influence of conclusions drawn by the geologists 

already referred to is acknowledged.

SITUATION AND GENERAL FEATURES.

Atlantic City is in Fremont County, Wyo., 23 miles due south of 

Lander, or about 28 miles by wagon road. Lander is the terminus of 

the Wyoming & Northwestern Railway which connects with the 

Chicago & Northwestern Railway at Casper. The elevation at Lander is 5,360 feet; at Atlantic City, 7,6£3 feet; at South Pass City, 

7,803 feet. The name Atlantic district is used in this report for the 

region about Atlantic City, including the environs of South Pass City, 

4 miles southwest, and of Miners.Delight, 3$ miles northeast.
10 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

The Atlantic district and the larger Sweetwater gold country, of 

which it forms a part geologically, lies entirely within the Missouri 

Riyer basin, South Pass, on the Continental Divide, being about 10 

miles southwest of South Pass City. (See figs. 1 and 2.) A small part 

of the district northeast of Atlantic City is drained by Beayer Creek, 

a tributary of Popo Agie Riyer. The Popo Agie joins Wind Riyer 

near Riyerton to form the northward-flowing Bighorn Riyer, whose 

waters, collected on the northeast side of the Wind Riyer Range, 

join those of the Yellowstone in Montana. The remainder of the 

drainage goes by way of Rock Creek and Willow Creek to Sweetwater

FIGURE 1. Drainage and railroad map of Wyoming.

Riyer. The upper tributaries of the Sweetwater drain the west 

side of the Wind Riyer Range as far as a point opposite Lander and 

the head of the Middle Fork of Popo Agie Riyer, a tributary of the 

Bighorn system. The Sweetwater flows parallel with the southeastward-trending axis of the Wind Riyer uplift to a point about 10 miles 

south of South Pass City, where it assumes a more easterly course 

on its way to join the North Platte. The Sweetwater and Popo 

Agie headwaters drain the high mountains at the southeast end of the 

lofty and rugged Wind Riye'r Range, which extends for nearly 100 

miles to the northwest. Toward the southeast the structural axis of 

the range may be recognized for a distance of 20 miles, but in this
SITUATION" AND GENERAL FEATURES. 11

direction the general elevation gradually decreases and the country 

becomes less and less rugged. The Atlantic district lies about midway between the high mountains and Sweetwater Valley. Here

10 15 Miles

FIOUKE 2. Map of part of Fremont County, Wyo., showing situation of the Atlantic gold district and 

general geologic features of the region.

Rock Creek has cut a gorge 500 to 600 feet below the height of land 

on either side, and Willow Creek has excavated a valley from 200 to 

500 feet deep. Through erosion along tributary drainage channels 

the region has come to have a markedly rolling character, but the
12 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

impression of a southward-sloping plain, of which the interstream 

areas form parts, is strikingly presented from points of view south of 

Atlantic City or from the edge of Willow Creek canyon below South 

Pass City. Consonant with the southerly slope of the region as a 

whole nearly all the tributaries both of Rock Creek and of Willow 

Creek come in from the north. Below Atlantic City the Willow 

Creek tributaries head practically at the edge of the Rock Creek 

Canyon.

Though the district is one of considerable relief, the slopes are 

commonly smooth except locally along some of the principal canyons, 

and almost any point may be easily reached by wagons.

The three principal creeks of the district are perennial streams, 

the waters of which have been used in a small way for sluice mining 

and to furnish power for stamp mills. They are not, however, of 

sufficient volume to be considered alone as of importance in the future 

development of the district, though if reinforced by waters from 

Popo Agie River, Rock Creek offers some possibilities.

There is no saw timber in the district, and mine timber is practically 

lacking, excepting in very small areas, mainly within the Washakie 

National Forest. Both may be obtained, however, should the need 

arise, from localities within the national forest 10 to 15 miles to the 

north. Wood for fuel is hauled from 8 to 12 miles, but only dead wood 

is obtainable for this purpose, at a cost of $3.50 to $5 a cord. Such 

sparse tree growth as the immediate region originally supported has 

been greatly depleted, but firewood for prospectors' camps is furnished 

by aspen, nut pine, and jack pine growing in favoreol localities. 

Throughout this foothill region there is an abundant growth of dryland grasses affording summer range for beef cattle and for sheep. 

Several hay ranches are profitably operated in irrigable valleys

within 10 or 15 miles of Atlantic City, and along the Sweetwater 

this industry could undoubtedly be extended.

GEOLOGY OF THE GENERAL REGION.

The Wind River range is reported by geologists who have visited 

it to be composed of granite, granitic gneiss, and hornblende schist. 

The central line of the range coincides with the northwestwardtrending axis of a broad arch along which for more than 100 miles 

the ancient crystalline rocks have been upthrust and, through the 

erosion of overlying formations, exposed throughout a zone from 20 

to 30 miles wide. (See PL I.) Along the southwest side of this 

zone the crystalline rocks are overlapped by glacial deposits and by 

formations of Tertiary age that were deposited long after the up thrusting of the arch and after the greater part of the erosion had taken 

place. Here the flanks of the fold are not generally exposed, but the 

anticlinal structure is adequately exhibited by the presence of
U. 8. GEOLOGICAL SURVEY BULLETIN 626 PLATE I

R. 101 W. R.IOOW. R.99 W.

R.10I W. R.IOOW.. R.99 W.

LEGEND

Magnetite schist

(Numbers are referred

to in text)

MAP OF ATLANTIC GOLD DISTRICT, WYO., SHOWING PRINCIPAL GEOLOGIC FEATURES.
GEOLOGY OF THE GENERAL BEGION. 13

Paleozoic rocks where Green River emerges from the mountains, 

and again at Pacific, about 14 miles southwest of South Pass City. 

On the northeast stratified rocks ranging in age from Cambrian to 

late Cretaceous are found tilting away from the high mountains, the 

harder and more resistant formations forming long hogbacks parallel 

with the range, and the softer formations appearing along intervening 

valleys. The Cambrian and younger rocks are in an essentially 

unmetamorphosed condition. Parallel with the Wind River arch 

there is a line of elongated domes passing east of Lander. These 

domes have been prospected for oil with some success.

The manner in which the lower formations of the stratified series 

rise along the side of the Wind River arch may be seen from Lander. 

On the way from Lander to Atlantic City, in cliffs on the northeast 

side of Red Canyon, are seen the basset edges of the red Chugwater 

formation, and across the valley is a grassy incline which is essentially 

a dip slope formed by the resistant upper beds of the Embar formation. By climbing to the divide between Red Canyon and Twin 

Creek and looking back the traveler may see the structure of this 

side of the arch in diagrammatic clearness. Along the road to the 

head of Twin Creek lower and lower formations are exposed, and the 

Cambrian sandstone at the base of the series of noncrystalline formations crops out at Beaver Creek crossing.

Midway between Beaver Creek and Atlantic City, to the east of 

the mail road, rises Peabody Hill. From the top of this elevation 

one may look east and see the bold escarpment formed by massive 

Paleozoic limestones, trending northwest to the divide between 

Beaver Creek and the Little Popo Agie and southeastward hi the 

direction of Lewiston. To the west are high granite peaks rising 

above a general platform. This platform, though greatly dissected, 

appears to merge with the general surface reached by the interstream 

areas in the foothill region west and southwest from Peabody Hill. 

As already noted, the surface slopes in a general southerly direction 

as far as Sweetwater Valley, beyond which the pre-Cambrian rocks 

are covered by Tertiary formations.

The marked lowering and disappearance of the range between 

Atlantic Peak and the Sweetwater is, with little doubt, the result of 

a gentle plunging of the broad anticlinal fold toward the southeast, 

and the sloping platform that has been described is probably not far 

below the surface on which the lowest Paleozoic formations were 

deposited.

From a northeastward-trending line that meets the Paleozoic 

escarpment north of Beaver Creek southeastward to Lewiston and 

beyond there are highly metamorphosed rocks, mainly derived from 

old sediments, that may be grouped under the general term schist. 

(See fig. 2.) Northwest of this area granite is the principal rock,
14 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

and between Lewiston and the point where the Sweetwater breaks 

through the northeastward-dipping Paleozoic beds granites again 

appear. A^short distance west of South Pass City the schists are 

broken by coarse red granite, and beyond, near Sweetwater crossing, 

there are gneisses interlayered with coarse granite or pegmatite.1

Knight 2 indicates the existence of two synclinal folds within the 

sedimentary area, their axes trending somewhat north .of east. 

One of these folds, the axis of which passes north of Atlantic City, 

has been recognized by the present writer. The axis of the other 

fold lies about 2 miles north of Lewiston. Except in a very few 

places the strata are everywhere highly inclined and as a rule they 

stand nearly vertical. All the prominent folds in the pre-Cambrian 

rocks trend northeast, or almost directly across the axis of the Wind 

River anticline.

The occurrence of gold in this region in amounts that have stimulated mining activity appears to be definitely related to the presence 

of igneous rocks that cut the schists, such intrusions being present 

both in the Atlantic City and South Pass belt and in the Lewiston 

district.

GEOLOGY OF THE ATLANTIC DISTRICT. 

BOCKS PRESENT.

The rocks occurring in the Atlantic district are crystalline schists 

derived largely from ancient stratified formations, serpentine, 

amphibolites representing diorites that have been strongly metamorphosed, quartz porphyry, and granite. The layering in the 

schists shows persistent northeasterly strikes and steep dips, and 

bodies of invading igneous rocks conform with1 this general structure. 

(See PL I.)

SCHISTS. 

SCHISTS OF THE CENTRAL ATLANTIC BELT.

The rocks here grouped under the class name schist are in the 

main strongly metamorphosed sediments, but with these are included 

certain strongly sheared green rocks, occurring in the northwestern 

part of the district, that are supposed to have been derived from 

basic igneous rocks. In the definitely sedimentary portion of the 

metamorphic complex the rocks appear to have been mainly shales, 

sandy shales, and fine-grained sandstones, the first two greatly 

predominating. In places the beds are somewhat calcareous, but no 

limestone layers have been noted. At several places in the vicinity

1 Hayden, F. V., U. S. Geol. Survey Terr. Fourth Ann. Kept., p. 38,1871.

2 Knight, W. C., The Sweetwater mining district, Fremont County, Wyo.: Wyoming Univ. Geol. 

Survey Bull., June, 1901.
GEOLOGY. 15

of Atlantic City and to the north and northeast there are exposures 

of graphite schist. Near the Rose mine and on the west side of 

Rock Creek, 1 mile north of Atlantic City, there are sandy beds 

that carry knots of chiastolite about the size and shape of almond 

kernels. This rock is known locally as peanut rock.

In addition to the fine-grained sediments, conglomerate occurs 

along two lines of exposure. Though here called conglomerate this 

rock may have been originally a volcanic agglomerate or breccia.

The sediments are everywhere in a thoroughly metamorphosed 

condition. Most of them contain mica as the principal mineral of 

secondary derivation. In some places a marked cleavage or schistosity is to be noted, but elsewhere the rocks are not greatly sheared, 

and it is perhaps proper to call such rocks graywackes rather than 

schists. The conglomerates mentioned above are everywhere 

greatly mashed, the original rock fragments being flattened so that 

they form lenses or thin layers that are separated by a felt of hornblende.

STRUCTURE OF THE SCHISTS.

Throughout the schist area the stratification is almost everywhere 

readily discernible, and in general the sediments are thinly bedded. 

So far as observed where schistosity is present the secondary structure 

is parallel with the original bedding.

In the greater part of the district the rock layers stand nearly 

on edge and the strike ranges from about N. 15° E. to N. 30° E. 

However, west of South Pass, near the locality where the schists 

give place to granite, low dips toward the east and northeast were 

observed, and both on Willow Creek below South Pass City and on 

Rock Creek below Atlantic City the strata dip to the southeast.

In the area that was most carefully studied the fine-grained 

sediments, exclusive of the graphite-bearing layers, are all very 

similar in appearance, and so far as the graywackes are concerned 

there are no beds or groups of beds that can be followed far enough 

to make them of any aid in the working out of folds. Below South 

Pass City, near the mouth of Hermit Gulch, there are massive beds 

of fine-grained micaceous sandstone that might serve this purpose, 

but these layers were not traced and corresponding strata were not 

noted along the canyon of Rock Creek.

Clues that have been found to indicate the structure within the 

district are, first, a curving boundary convex to the west between 

the schist area and the granite country northwest, west, and southwest of South Pass City, and low easterly dips in the vicinity of 

this boundary; second, the two bands of conglomerate occurring 

north of Atlantic City on the east side of Rock Creek; third, southerly
16 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

dips of the rock layers along Willow Creek near the mouth of Hermit 

Creek and along Rock Creek 2 miles below Atlantic City.

The structure near Atlantic City is essentially isoclinal, in that 

the rock layers lie nearly parallel among themselves, but the two 

bands of conglomerate afford very good evidence that the beds 

are here repeated and that two sides of a fold are represented. The 

axis of this fold crosses Rock Creek about 1£ miles above Atlantic 

City and can be traced eastward to the Paleozoic overlap half a mile 

south of Miners Delight. Toward the west the conglomerate bands 

have not been identified, and though in this direction the fold is obscure the continuation of its axis would strike the locality west of 

South Pass City, where the low easterly dips and the curving boundary 

of the schists against granite indicate the existence of a trough or 

syncline plunging toward the east. From this correspondence the 

closely appressed Atlantic fold is regarded as a syncline. The 

southerly dips observed farther south do not conform with the 

requirements of a simple syncline but could be explained as the 

result of a strike fault by which the north side of an adjacent anticline had been cut out. There is a strong presumption that such a 

fault exists a short distance south of Atlantic City.

If in future studies the conglomerate layer is found south of the 

Atlantic district, it seems that eventually it will be possible to work 

out the structure within the area of altered sediments in some detail.

SCHISTS DERIVED FEOM IGNEOUS BOOKS.

Northwest of the main area of sedimentary rocks there is a zone 

occupied principally by green chlorite schists, which, though they 

have not been closely studied, have probably been derived from 

some basic igneous rock. Southwestward from the point where it 

crosses Rock Creek the southern boundary of these schists has 

been located in a general way, but to the northeast the boundary 

between the sediments and the green schists was not traced. Southwest of Rock Creek the far boundary of the green schists is against 

granite that occurs in a band from one-fourth to one-half mile wide. 

Beyond this granite there is a zone perhaps half a mile wide in 

which granites and hornblende schists occur in alternation, and to 

the northwest is massive granite.

From Slate Creek to Beaver Creek the green schists are partly 

hidden by a deposit of loose rock debris that may be of glacial origin. 

The covered area is about half a mile in width.

MAGNETITE SCHISTS IN THE NORTHERN PART OF THE DISTRICT.

Distribution and general character. Northwest of the covered area 

just referred to is a zone occupied mainly by magnetite, mica, and 

chlorite schists. These schists are almost completely cut out by
GEOLOGY. - 17

granite west of Rock Creek, but they extend from this place northeastward to and beyond Beaver Creek. Near Rock Creek canyon 

the zone is about half a mile wide, but toward the Beaver Creek end 

fully three-fourths of its width is covered by the debris deposits. The 

schists and accompanying bodies of intrusive diorite stand nearly vertical or dip steeply to the southeast, and the strikes are everywhere 

northeast. Northwestward across the schists the ferruginous members are succeeded by several hundred feet of shining mica schists. 

Where exposures are favorable a bed of quartzite from 25 to 50 feet 

thick is found, and not far beyond this bed there are interlayered 

schists, granite gneisses, and granite, occupying a zone about 1,000 

feet wide.

As only one day could be devoted to a study of this belt it was impossible to map the magnetite schists completely, but from the occurrences that have been plotted on Plate I the conclusion may be fairly 

drawn that they are distributed throughout a zone about 2,500 feet 

wide and 2£ miles long. The outcrops north of Beaver Creek were 

observed only from a distance, but the inference that the iron schists 

are present in two prominent knolls was confirmed by statements of 

prospectors familiar with the ground. Here the deposits are capped 

by the Cambrian sandstone which forms the base of the Paleozoic 

succession in this region.

In the NW. £ sec. 25, T. 30 N., R. 100 W., the more southerly exposures show platy magnetite schists that are more than commonly 

siliceous, and these rocks are interlayered with mica schists. Between these iron-bearing beds and others forming a prominent ridge 

nearly 1,000 feet to the northwest there are soft mica and chlorite 

schists. Very prominent exposures of the iron-bearing rock are to be 

seen along the east rim of Rock Creek canyon in sec. 26 and on the 

west side of the creek in sec. 35.

The conclusion is reached that here the aggregate width of the magnetite bands is not less than 1,500 feet. Individual layers of ironbearing rock from 40 to 250 feet wide are separated either by bodies 

of granular diorite or by chloritic schists which are probably strongly 

sheared diorites. All the magnetite-bearing rock is very schistose or 

slaty.

The magnetite schists considered as iron ore. The occurrence of ironbearing rock raises the question of the possible economic value 

of the deposits. Chemical analyses were made of general samples 

from four of the magnetite bodies that crop out on- the ridge east of 

Rock Creek (marked 1 to 4 on the map, PI. I). Essentially continuous exposures were found, and samples weighing from 5 to 7 pounds 

were taken by chipping across the ledges at intervals of about 2 feet. 

Sample 1 represents about 180 feet of rock; sample 2, 150 feet; sam20142° Bull. 626 16 2
IS ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

pie 3, 180 feet; and sample 4, 250 feet. The results of the analyses 

are as follows :

Partial chemical analyses of magnetite schists, Atlantic district, Wyo.

Insoluble. ..............................................................

1

42

42

.037

2

43

40

.030

3

38.6

45.8

.020

4

37

47

.031

Rock carrying from 37 to 43 per cent of iron and from 40 to 47 per 

cent of insoluble matter can not be profitably smelted, and the conclusion is drawn that material of this grade could be utilized only by 

submitting it to some process of concentration. In general the magnetite rock is very fine grained, dense, and hard. Crushing would 

be expensive, as extremely fine crushing would be necessary in order 

to free the grains of magnetite from those of the siliceous minerals. 

It therefore seems that the rock would not be readily amenable to 

concentration.

The siliceous impurities in specimens of the best appearance are 

pyroxene, hornblende, or chlorite, and in lower-grade materials 

jaspery silica was noted. In some of the rock the jasper occurs in 

layers, no more than a few hundredths of an inch thick, but elsewhere 

the layers of siliceous matter may be as wide as one's finger. Minute 

seams of limonite, which are of rather common occurrence, indicate 

the former presence of pyrite, so that the unweathered rock will 

doubtless contain a small amount of sulphur.

The fact that in taking the samples mentioned above there was no 

selection as between materials of better or poorer appearance leaves 

room for the possibility that there may be layers of the iron-bearing 

rock which contain 50 per cent or more of iron and which could be 

separately mined. It is believed that this point is worthy of further 

investigation. If the existence of no more than 5,000,000 or 6,000,000 

tons * of iron ore fit for the blast furnace without preliminary treatment could be established, the district would be placed in a very 

favorable situation with respect to proposed railroad extensions.

SERPENTINE AND ASBESTOS.

Four bodies of serpentine are shown on the accompanying map 

(PL I). The serpentine body occurring in the southwest corner of 

sec. 34, T. 30 N., R. 100 W., has not been prospected, or at least no 

pits have been dug in it, but along the other bodies asbestos claims 

have been located and some prospecting has been done. Nothing 

of any promise was noted either at pits near the east side of sec. 34

i Allowing for a specific density of 4, a body of 50 per cent iron ore 10 feet wide and 1,000 feet long would 

contain 125,000 tons for each 100 feet in depth.
GEOLOGY. 19

or at others in the NE. i NE. f sec. 26. In the fourth and largest 

mass of serpentine pits have been opened at several points, and during 

the summer of 1914 prospecting by William Brice, of Lander, disclosed some very good asbestos. The workings are still very shallow, 

so that much of the material shows deterioration due to weathering. 

This is particularly true at one locality where fiber more than 1 inch 

in length occurs in considerable amounts. Both the altered and the 

entirely fresh mineral has the softness which is a characteristic of 

high-grade asbestos and if worked up between the teeth forms a felt 

free from grit. The greater part of the asbestos thus far found shows 

fibers less than half an inch long, and commonly seams of such 

material are closely spaced so that they form veins from 1 to 2 inches 

wide. A favorable feature of this locality is the fact that immediately to the north there are intrusive masses of granite* younger 

than the serpentine.

INTBTJSIVE BOCKS. \

DIOKITE.

The most abundant intrusive rocks occurring within the general 

area of the metamorphosed sediments now appear as amphibolite. 

This name is commonly used to include hornblende-bearing rocks in 

which the hornblende (and in many rocks other essential mineral 

constituents) has been formed as the result of a thorough metamorphism of basic igneous rocks. It is often impossible to determine 

whether the original rock was gabbro, diabase, or diorite. The 

mineral composition of rocks of this sort occurring in the Atlantic 

district is like that of diorite, and it will be convenient to use this 

name for them. These diorites occur as relatively long and narrow 

dikes following the general structure of the rocks which they invade. 

Several of these dikes occur hi the magnetite schist area 3 miles north 

of Atlantic City, and they are prominently developed in the strip of 

country, about 2 miles wide, which contains the principal gold deposits 

of the Atlantic district. Precisely similar rocks occur also in the 

Lewiston district.

In the Atlantic gold belt a beginning has been made in mapping 

the diorite intrusions, with the result shown on the sketch map 

appearing as Plate I. It is probably correct to assume that all the 

rock was originally essentially alike, but as a result of differing degrees 

and kinds of alteration it now presents many varieties. Some of it 

is entirely massive, the hornblende appearing in irregular but compact individuals. From such material there is a gradation through 

essentially even-granular rock carrying sheaf-like forms of hornblende

i Diller, J. S., The types, modes of occurrence, and important deposits of asbestos in the United 

States: U. S. Geol. Survey Bull. 470, p. 515,1910.
20 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

to schist in which the hornblende is all fibrous. Locally the rock is 

still further altered to chlorite schist, and in places where metamorphism has been extreme all semblance to an ordinary igneous 

rock is lost. The chloritic phases usually have a bright-green color, 

especially where the rock is eminently schistose; the various hornblende phases range in color from dark green to nearly black.

The dikes that have been mapped range from 50 to more than 

400 feet in width. Some of them have been followed individually 

for distances of a mile or more, and one was found to be continuous 

throughout a length of 5 miles.

The longest dike of diorite lies about 1,500 feet north of the axis 

of the Atlantic syncline, and in a nearly symmetrical position to 

the south there are multiple dikes throughout a zone from 1,000 to 

1,500 feet wide that extends in a direction east and somewhat north 

from Rock Creek to the Paleozoic overlap near the head of little 

Beaver Creek. The approximate symmetry of these intrusions with 

respect to the axis of the fold is established by the presence of the 

conglomerate beds at several points along a line north of and nearly 

parallel with the northern dike and along the south side of the 

southern dike zone. The northern dike, which may be called the 

Gold Dollar dike, from the circumstance that it crosses the group 

of mining claims bearing that name, has a width of 300 feet or more 

toward the east, but west of Big Atlantic Gulch it is nowhere more 

than 100 feet wide. Near the point where it crosses Wood Gulch 

its course changes from west-southwest to nearly south. Though 

it appears to terminate in the high hill 2 miles west of Atlantic 

City, it may continue farther south, but in that direction there are 

very few rock exposures. The curving of this dike and of the parallel 

porphyry dike just to the north suggests a corresponding bending 

of the inclosing strata, but in its long southerly extensions the 

porphyry dike probably breaks across the stratified rocks. The 

southern dike zone does not continue directly across the Rock 

Creek valley but here is offset as if displaced by a nearly east-west 

fault having a horizontal thrust eastward on the south side. Fairly 

good evidence that such a fault exists is found in the occurrence of 

chiastolite graywacke, or "peanut rock," north of the dike zone 

near the Rose shaft, and in a corresponding position with reference 

to the diorite dikes that cross Rock Creek. If the conglomerate 

beds could be found along the south side of the westerly offset part 

of the dike zone the presence of the supposed fault would be fully 

established. Because the dikes in the two parts of the zone do 

not match, the break is believed to have occurred before the intrusion 

of the igneous rock.

A third zone of diorite intrusions lies just south of Atlantic City 

and extends westward and southward to and beyond South Pass
GEOLOGY. 21

City. In this zone there are three principal dikes arranged in overlapping positions. The dike that crosses Rock Creek below Atlantic 

City may be called the St. Louis dike. It was traced to the northeast only as far as Big Atlantic Gulch. Southwest of Atlantic 

City and just west of the St. Louis claim it terminates. A short 

distance to the north, on the Tabor Grand claim, is the eastern 

end of the Duncan dike, which has an average width of nearly 500 

feet and was traced westward to Little Hermit Creek, a distance 

somewhat greater than 2 miles. West of the point where the mail 

road crosses Big Hermit Creek there is a large body of diorite that 

is believed to be connected with the Duncan dike. South of and 

overlapping the Duncan dike for at least 1 mile is the Carissa dike, 

which was traced for a distance of 3 miles. It probably extends 

farther east than is indicated on the map. Where this dike crosses 

Willow Creek it is about 140 feet wide. Its south wall lies 130 feet 

north of the Carissa shaft, and here it is more than 150 feet wide. 

In this vicinity the rock of the dike is a greatly contorted chlorite 

schist. Farther east parts of the dike are green and schistose and 

other parts black and massive. The country lying north and northeast of South Pass City was not studied in detail, but two diorite 

dikes that cross Willow Creek above the Carissa dike have been 

shown on the map.

DIKES OF PORPHYRY.

In addition to the basic intrusives of the district there are several 

dikes and small masses of more siliceous igneous rocks, three general 

types that have been noted being quartz-oligoclase porphyry, orthoclase porphyry, and soda granite.

About 2 miles north of Atlantic City, on the Rustler group of 

claims, a vertical dike of quartz-oligoclase porphyry is exposed. Its 

course is a little north of east, parallel with the strike of the inclosing 

schists. Unweathered specimens obtained from prospect pits show 

a gray, rather fine grained, apparently even-granular rock, specked 

with minute grains and small crystals of arsenopyrite and containing 

pyrrhotite. Under the microscope the texture' is seen to be distinctly porphyritic, small crystals of quartz and slightly larger 

crystals of the oligoclase feldspar being set in a matrix composed 

of felty sericite. Apparently this sericite replaces an originally 

glassy groundmass. The same secondary mineral occurs also in 

some of the feldspar. The introduction of the arsenopyrite and 

pyrrhotite was obviously contemporaneous with the formation of 

the sericite. This dike has been traced for about 1 mile, and prospecting at five localities indicates that the rock is everywhere mineralized in the same way. At the outcrop the rock contains cavities
22 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

partly filled with limonite, evidently derived mainly from arsenopyrite, and weathered material of this sort is said to carry gold that 

can be separated by panning.

Near Miners Delight there are prominent exposures of a dark 

blue-gray rock, which, though presenting a general dense appearance, 

contains abundant lath-shaped crystals of orthoclase. This orthoclase porphyry is known locally as "spotted rock." It occurs in 

the form of a dike, which has a width of 50 to 150 feet, may be traced 

5 miles, and is probably continuous for 6 miles. From Miners 

Delight its course is at first west-southwest, parallel with a conglomerate bed to the north and with a diorite dike to the south. 

West of Rock Creek the conglomerate was not recognized. At a 

point about 1£ miles northwest of Atlantic City the dike curves and 

assumes a nearly southerly course. Variations in the mineralogic 

character of the rock are evidently related to differences in the degree of schistosity. At Miners Delight it is distinctly laminated, the 

groundmass being composed of needles and rods of hornblende. 

The lath-shaped feldspar crystals lie parallel with the walls of the 

dike and conformable with the general lamination, but they are not 

crushed.

- Rock similar in general appearance to that of the Miners Delight 

dike occurs within the south zone of diorite intrusions east of Big 

Atlantic Gulch and in a larger body west of Atlantic City. In all 

these occurrences the presence of lath-shaped feldspars is a feature of 

marked resemblance, but the alterations of the groundmass are different. The rock from the Big Atlantic Gulch locality is schistose, it 

carries brown mica in the groundmass instead of hornblende, and the 

feldspar crystals are partly altered to sericite. Rock collected from 

a point south of the mail road 1£ miles west of Atlantic City shows 

no marked schistosity, but the groundmass is composed of a felt of 

hornblende, part of which is altered to chlorite.

MINOR INTRUSIONS OF GRANITE.

Four small masses.of granite occur in the zone of diorite dikes that 

extends south of Atlantic City and north of South Pass City. Three 

of these granite masses are in or near diorite dikes, as is indicated on 

the geologic map (PI. I), and the field relations show that the granite 

is the younger of the two rocks. The granite is a fine-grained, evengranular gray rock, composed of quartz, oligoclase, and mica. The 

presence of oligoclase instead of the ordinary orthoclase or microcline 

of true granite makes the name soda granite appropriate for this rock. 

In specimens from the Mary Ellen mine the oligoclase is partly altered 

to sericite.
U. 8. GEOLOGICAL SURVEY BULLETIN 626 PLATE II

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i

i o i . SMILES.'

1. Dorothy J. 

2. Washakie. 

3. Arcada. 

4. Lone Star. 

5. Summit. 

6. Peacock. 

7. Signal. 

8. Central. 

9. King. 

10. Crown. 

11. Paymaster. 

12. Minnie B. 

13. Fairview. 

14. Satila. 

15. Oswega. 

16. Bonanza 1. 

17. Bonanza. 

18. Placer. 

19. Chicago. 

20. Miners Delight. 

21. Preserver. 

22. Gold Dollar. 

23. Milan. 

24-26. Gold Dollar 

group. 

27. Ruby Quartz. 

28. Snow Bird. 

29. Black Bird. 

30. Pennsylvania. 

31. Augusta C. 

32. New York. 

33. Blanche May. 

34. Cariboo. 

35. Arthur. 

36. W.J.Bryan(Rose). 

37. Garfield. 

38. Diana. 

39. Lucky Boy. 

40. Britannia. 

41. Humboldt. 

42. Yellowstone. 

43. Vulture. 

44. West Dip. 

45. War Eagle. 

46. Ground Hog. 

47. Revenue.

48. Cumberland.

49. Hennepin.

50. Ramsay.

51. Rand.

52. Gold Coin.

53. Minneapolis.

54.. Denver.

55. St. Louis.

56. Clarissa B.

57. Tabor Grand.

58. Little Nell.

59. Prince Henry.

60. Fair View.

61. Mary Ellen.

62. Cecil Rhodes.

63. Victoria.

64. Duncan Placer.

65. Duncan.

66. Wasp.

67. 68. Silent Friend.

69. Exchange.

70. Dexter 1.

71. Dexter 2.

72. Empire State.

73. Philistine.

74. Rocky Barr.

75. Mars.

76. Mars Pensance.

77. Sampson.

78. Cleveland.

79. Homestake.

80. Lucky Placer.

81. Hermit Placer.

82. Carissa.

83. Mono 2.

84. Jeanette.

85. Lucky Boy.

86. Wolverine.

87. Charles Dickens.

88. Ben Hur.

89. Alpine.

90. J. C. S.

91. Franklin.

92. Wyoming Copper. 

Co.

MAP SHOWING PART OF THE MINING CLAIMS IN THE ATLANTIC GOLD DISTRICT, WYO.
HISTORICAL NOTES. 23 

INLIEBS OF CAMBRIAN SANDSTONE.

Two small patches of sandstone capping the crystalline rocks were 

noted one 2 miles north of Atlantic City in the SE. £ sec. 36, T. 30 N., 

R. 100 W., and the other 2 miles northeast of the town, in the SW. £ sec. 

5, T. 29 N., R. 99 W. Each of these occurrences is in a swale 50 feet or 

more below the general hilltop level in the -vicinity, and this fact can 

hardly be interpreted otherwise than as an indication that the basal 

member of the Paleozoic sedimentary series was deposited on a surface having considerable local relief. The overlap of the Cambrian 

sandstone along the main outcrop has not been studied.

TERTIARY DEPOSITS.

East of Big Atlantic Gulch, on a broad ridge that separates it from 

Smith Gulch, there is a deposit of white marly clay. This deposit 

is regarded as a remnant of the White River formation, of Tertiary 

age, which is known to occur south of the Sweetwater and which O '

probably was originally deposited over all of the region between that 

river and the Atlantic district. The deposit consists mainly of a 

white to yellowish claylike substance that contains only a small 

amount of carbonate of lime. Such material, though blocky when 

first excavated, disintegrates or slacks on exposure and is very plastic 

when wet. Some of the material that carries more calcium carbonate 

does not disintegrate so readily.

Friable sandstone occurring in the bluffs on the west side of Willow 

Creek half a mile above South Pass City may also be regarded as a 

remnant of the White River formation, which in general comprises 

materials of widely different character.

HISTORICAL NOTES.

The history of gold mining in the Sweetwater district has been 

related in some detail by Knight,1 and this account is reprinted in a 

report by Trumbull.2 The following summary is based mainly on 

these reports and on data contained in the reports of Raymond.3 

Plate II shows in part the mining claims in the district.

The discovery of placer gold in the Sweetwater district is said to 

have been made in 1842. In 1855 a party of 40 men, led by the original discoverer, prospected the region and did some sluicing along 

Sweetwater River. The leader of the first party returned with eight 

companions in 1860 and began mining on Strawberry Creek. In the 

fall of 1861 fifty men had collected at South Pass City with the object

i Knight, W. C., The Sweetwater mining district, Fremont County, Wyo.: Wyoming Univ. Geol. Survey 

Bull., June, 1901.

a Trumbull, L. W., The Atlantic City gold-mining district, Wyoming Geologist's Office Bull. 7,1914.

a Eaymond, R. W., Statistics of mines and mining in the States and Territories west of the Bocky Mountains for 1869, pp. 327-338,1870; idem for 1871, pp. 374-376,1873; idem for 1872, p. 306,1873.
24 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

of mining in the following spring, but this party was driven out by 

Indians and it was not until 1866 that the same leader again returned 

with a company, which began operations in 1867. On June 8 of that 

year the Carissa lode was discovered by H. S. Reedall. This third 

party was driven away by Indians with the loss of three men, but the 

survivors came back and wintered. By crushing quartz from the 

lode in a hand mortar and by washing the detritus from the lode they 

extracted nearly $9,000 in gold. The news of this success spread rapidly, there was a rush to the district, and 500 men went to work. In 

July, 1869, there were 2,000 people in the district.

The first stamp mill, of six stamps, driven by an overshot water 

wheel, was erected on Hermit Gulch. It was started July 20, 1868, 

and up to November 1 had crushed 1,040 toils of ore, yielding an 

average of $36 currency to the ton. Between April 20 and July 1, 

1869, 480 tons of ore, averaging $47 a ton, was treated. The rock 

crushed came mainly from the Carissa lode, but ore was also hauled 

from Atlantic City. The second mill, of 10 stamps, driven by a 

40-horsepower steam engine, was installed at Miners Delight and 

between January and July, 1869, is estimated to have extracted more 

than $60,000 worth of gold from ore taken, from the Miners Delight 

lode. The ore averaged about $40 a ton. The third mill, of 10 

stamps, was a steam-power mill at Atlantic City that began operation 

June 25, 1869. It treated 75 tons of ore from the Soules & Perkins 

lode at Atlantic City, yielding about $30 a ton.

The principal veins of the district as they are now known were 

nearly all discovered before 1871, and by that time 12 mills, with a 

total of 161 stamps, had been erected. Placer work had been done in 

many places, mainly on Carissa Gulch, a tributary to Willow Creek; 

on Big Atlantic, Smith, and Promise gulches, tributaries of Rock 

Creek; along Rock Creek near Atlantic City and on Spring, Yankee, 

and Meadow gulches, across the Beaver Creek divide. Up to the end 

of 1873 the gold production of the district appears to have amounted 

to about $550,000. 

In 1872 South Pass City was nearly deserted. The Cariboo and 

Buckeye mines, near Atlantic City, were being worked, and at Miners 

Delight three mines were active, but in 1875 the mines of the Sweetwater district were reported as being essentially idle.

After South Pass City, Atlantic City, and Miners Delight had experienced booms and had dwindled to small villages, a fourth camp, 

Lewiston, was opened, the Burr lode having been discovered in 1879. 

This camp had a similar experience to that of the others. Knight l 

says:

Lewiston, like the others, had rich veins of quartz and placer grounds, but the mills 

have not stamped much ore and the camp is sorely in need of good mining men who

i Knight, W. C., op. cit., p. 81.
HISTORICAL KOTES. 25

are willing to develop a mine before they expect it to yield a dividend. * * * The 

surface ores were quite free and rich, but with depth they rapidly became base and 

contained iron pyrites and arsenopyrite. The ores extracted near the surface milled 

easily, but long before the water level was reached the amount of free gold had diminished so that tailings were assaying $35 and $40.

In 1886 the placers on Spring Gulch at Miners Delight were still 

being worked, though operations were confined to a short season during the spring when water was available. 1

In 1884 2 a French company managed by Emile Granier purchased 

placer claims on Willow, Rock, and Strawberry creeks and began 

the construction of a canal or ditch to lead the waters of Rock Creek 

to several points where they could be utilized in hydraulic mining. 

Before the completion of this ditch, in 1886, plans were made for 

diverting the water of Christina Lake °at the head of Little Popo 

Agie River, and this project was carried out. The water thus made 

available was rated at 8,000 miner's inches. A hydraulic elevator, 

installed on Rock Creek, below Atlantic City, was operated during 

the three seasons, 1890 to 1892. The total value of the gold recovered is said to have been about $200,000. About 1893 the company 

became financially embarrassed, and some time afterward its interests 

were taken over by the Dexter Mining & Milling Co.

The Dexter Co. purchased several undeveloped and partly developed lode claims in addition to the placer ground and water rights of 

the Granier company. In 1905 the construction of the Dexter Mill 

at Atlantic City was begun. The Rose tunnel was driven 1,100 feet, 

but no ore bodies had been developed on any of the company's property in 1914. Trumbull 3 says:

After the completion of the mill, ore was hauled in wagons from various prospects 

in the district. Twelve thousand tons of $5 to $30 ore were milled and the clean-up 

gave $6,000 off the plates and absolutely nothing from the cyanide plant.

This administrative and technical failure was followed by bankruptcy and by reorganization as the Timba Bah Mining Co. The 

affairs of the new company were under the management of a receiver 

in 1914.

Aside from the activities of the two companies mentioned, interest in the Atlantic district has been maintained largely through 

recurring attempts to reopen certain of the mines that were most 

productive during the years 1868 to 1872. Individual prospectors 

and small associations have been continually at work. Up to 

about 1906 one or more stamp mills were kept in shape for the use of 

miners in the treatment of small lots of ore. The advantage of such 

conditions is obvious, and as there has been lately no reduction plant

1 Aughey, Samuel, Wyoming Terr. Geologist Ann. Eept., 1886, p. 12. 

a Ricketts, L. D., Wyoming Terr. Geologist Ann. Eept., 1888, p. 72. 

"Trumbull, L. W.,.op. cit., p. 86.
26 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

conveniently available, assessment work has been even more perfunctory than formerly. Among mines that have been taken up at 

different times, with the idea of systematic development, the most 

prominent are the Carissa, at South Pass City; the Miners Delight, 

at the east end of the district; and the Garfield, near Atlantic City.

The Carissa appears to have been idle from about 1873 until 1900 

or 1901, when it was acquired by the Federal Gold Mining Co. In 

1901 the shaft was sunk to 300 feet and somewhat later to 387 feet, 

but the depth of the lowest level at present is 360 feet. The recorded 

production during the period 1902 to 1906 is about 2,800 tons of ore 

that returned a total in gold and silver of somewhat more than 

$25,000. The bullion produced was about 0.845 fine. Since 1906 

no mining has been done. For several years the mine has been kept 

free from water, so that the workings might be available for examination. The shaft is 387 feet deep and the workings extend along 

the vein for about 750 feet. There are five levels, with horizontal 

workings below the first level amounting to nearly 2,600 feet.

The Miners Delight property appears to have been worked from 

the time of discovery hi 1868 until 1874. It was then idle until 

about 1880, when the mine was reopened and operated until 1882. 

In 1893 the property was sold to satisfy a claim of $28,500.* A company was formed to begin naming and in 1894 the workings were 

pumped out. Though a large sum of money is said to have been 

spent, this attempted revival was not successful. Failure likewise 

followed work done hi 1910 and again in 1913. In both of these 

attempts comparatively small amounts were expended.

The Garfield claim is supposed by the writer to be the same as an 

early location known as the Buckeye State. The Buckeye shaft is 

said to have been 140 feet deep in 1870 and the production at that 

time was at the rate of $50,000 a year. Several attempts were made 

to rehabilitate this mine,- the most important one in 1891-1894. 

Two Tremaine stamps and a small hydroelectric plant were installed, 

but although some gold was produced the returns appear not to have 

been sufficient to pay for the mine developments that would have 

been necessary for a financial success. In 1905 the mine, it is reported, yielded $5,000 from 1,000 tons of ore.

The Mary Ellen mine has been another occasional producer, though 

between 1902 and 1915 the property was involved in litigation.

A recent undertaking has been the development by the Beck Mining Co. of the Duncan mine, 1 mile west of Atlantic City. After an 

exploration of the Duncan vein by about 1,500 feet of workings 

four Nissen stamps and amalgamating devices were installed in 1911. 

The saving of the gold contained in the ore is reported to have been

1 Eng. and Min. Jour., Dec. 23,1893.
ESTIMATED GOLD PRODUCTION. 27

about 60 per cent, and in 1912 a system of all sliming followed by 

cyanidation was adopted, with results that are said to have been 

very satisfactory. Power for the mine and mill and for an electric 

plant is furnished by internal-combustion engines adapted for burning gasoline or distillate. Mine developments in 1913 and 1914 appear 

to have been not very encouraging, and it may be that the financial 

success of this company will depend upon securing control of other 

mines than the one for which the technically successful extraction 

process has been worked out.

About 1908 the X. L. Dredging Co. purchased several groups of 

placer claims in Big Atlantic, Smith, Promise, and Little Beaver 

gulches and on Stambaugh Flat. In 1912 a ditch and siphon to 

carry water from upper Rock Creek was completed and some ground 

was washed on Promise and Smith gulches. In 1914 operations of 

this company were confined to properties on Beaver Creek.

The Wyoming Copper Co., organized about 1909, obtained a group 

of claims situated west of Willow Creek about 1 mile above South 

Pass City and carried on operations at intervals until the summer of 

1914. During this period a shaft was opened to a depth of 500 feet 

and some drifting was done. Small amounts of rich copper minerals 

were found near the surface, but nothing of value was discovered in 

the shaft workings, and the project appears to have been finally 

abandoned in the fall of 1914.

ESTIMATED GOLD PRODUCTION.

Inasmuch as a large part of the gold output of Wyoming has come 

from the Atlantic and near-by districts, accurate statistics of the 

gold production of the State, if available, would furnish a very-good 

idea of the progress of mining in the region under consideration. 

Unfortunately reliable data are not at hand, but figures indicating 

the gold and silver output have been compiled by the United States 

Geological Survey,1 estimates having been made where no definite 

figures are available.

The value of gold produced in the Atlantic district from 1867 to 

1875 is given at $736,100, on the basis of reports by R. W. Raymond. 

For the years 1876 to 1895, inclusive, the output of the State is 

estimated at $1.65,000, and part of this amount was derived from 

placers in northeastern Wyoming and in the Douglas Creek district. 

For the years 1896 to 1913 the gold output of the State is given at 

$290,000, and it is known that a large proportion of the actual output 

after 1899 came from copper ores.

If the foregoing figures indicating for Wyoming a total gold production of $1,191,178 could be accepted, it would seem probable that 

the Atlantic district should be credited with an output valued at

1 Henderson, C. W., U. S. Geol. Survey Mineral Resources, 1913, pt. 1, p. 50,1914.
28 ATLANTIC GOLD DISTBICT, FREMONT COUNTY, WYO.

less than $1,000,000. Estimates have been published, however, 

indicating that the production of the district has amounted to more 

than $5,000,000. 

In a footnote Henderson says:

The source of the generally quoted figures ($5,050,000) is W. C. Knight (The mining 

districts of Wyoming: Wyoming Univ. Agr. College Dept. Bull. 14, October, 1893, 

pp. 123-124), but Knight says: "The only estimate of the output of this region is one 

that has been generally circulated, but upon what basis the estimate is made or who 

is the author I am unable to find out."

The estimate of the gold output of the Atlantic district which is 

given below is taken from a report on Fremont County published in

1911: 1

Estimate of gold production of Atlantic district.

LODE MINES.

Miners Delight. ............

Carissa.....................

Caribou. ..................

Garfield...................

Franklin. .................

Mary Ellen.................

Carrie Shields. ............

$1, 200, 000 

1, 000, 000 

500, 000 

400, 000 

350, 000 

300, 000 

125, 000 

40, 000 

35, 000 

187, 000

4, 137, 000

PLACERS.

Meadow Gulch . ...........

Yankee Gulch ............

Spring Gulch. ............

Promise Gulch .............

Smith Gulch...............

Red Canyon. ..............

Beaver Creek. .............

Others...... ..............

.. $1,000,000

500, 000

30, 000

30, 000

20, 000

20, 000

i ^ firm

10, 000

150, 000

1, 725, 000

5, 862, 000

The present writer is inclined to believe that the gold production 

of the district may have been greater than the indicated total output 

of th& State as given by the Geological Survey figures cited, though 

it can hardly have been as great as the figure given by Jamison. 

Possibly the lode mines and placers may have produced as much 

gold since 1875 as before that year, and if so, a fairly reasonable 

guess would place the value of the total output at $1,500,000.

VEINS.

PREVIOUS DESCRIPTIONS.

Gold has been found in the bedrock formations mainly in veinlike 

bodies of quartz which, below the zone of oxidation, carry pyrite or 

arsenopyrite and in a few places chalcopyrite or galena. The veins 

have been classified by Knight 2 under four heads (1) fissure veins 

that occur in bodies of igneous diorite or granite; (2) contact veins 

that occur between intrusive rocks and metamorphosed sedimentary

1 Jamison, C. E., The geology and mineral resources of a portion of Fremont County, Wyo.: Wyoming 

State Geologist Bull. 2, p. 80, 1911. 

»Knight, W. C., op. cit., p. 17.
VEINS. 29

rocks; (3) bedded veins that conform with the dip and strike of the 

metamorphic schists; and (4) gash veins. Knight says:

The veinstone is quartz. Near the surface is the usual oxidized zone in which the 

gold is comparatively free. Below this sulphides appear and are of three types 

pyrite, arsenopyrite, and galena. Arsenopyrite or pyrite containing a small percentage of arsenic seems to predominate. Occasionally realgar and orpiment are found in 

minute quantities. No banded structure was found in any of the veins. The quartz 

is usually massive and varies in color from white to semitransparent with a bluish 

cast. In the oxidized zone the cavities are filled with limonite. Quartz associated 

with som e of the sulphides usually contains the most of the values. In many instances, 

however, the schists are especially rich. This condition was especially marked at the 

Carissa. In the ore stoped it was the rule that the schist clinging to the quartz was 

gold-bearing, and often there were wires and pellets of gold scattered through the 

mass. During the last ten years I have assayed schists from this district that contained from 2 to 10 ounces of gold per ton.

Besides the veins, from a foot to 8 or 10 feet wide, that have been openetl, there are 

some mammoth veins of quartz that have been but slightly protected. One of these 

known as the Mammoth vein is a short distance northeast of Atlantic. It contains 

some gold, but mines have not been able so far to make it pay. Others of this type 

are known.

Taken as a whole the veins are of average size, are very persistent, containing good 

shoots of ore which continue with depth. The relation of the gold contents of these 

veins with depth could not be worked out.

Trumbull 1 says:

The veins are all quartz filled, and the dip and strike of those carrying workable 

values show no relation to the strike or dip of the schists. The Big Atlantic and Mammoth veins are heavy wide bands of what seems to be vein quartz, running for miles 

across the district, following the schists in both dip and strike. But neither of these 

have shown shoots of pay ore, the gold values being a dollar or less per ton. These 

leads have been well prospected, for one can follow their course with the eye for miles 

by the prospect holes dug on them. Their great length and uniform width, also their 

parallelism with the inclosing schists, make one certain that they are of sedimentary 

origin.

The gold-bearing veins are found in the schists, diorite, the andesite [called feldspar 

porphyry in this report], and, in one case, in granite. There is no uniformity of strike. 

It has been stated that the strike of the veins was in general parallel to that of the 

schists. In some cases this is true, but apparently it is only a coincidence. The 

Miners Delight vein, for a part of its length, runs parallel to the strike of the schists, 

but in other places it strikes nearly across the schists, and the part parallel to the 

schists has both foot and hanging wall of andesite. Again, the Mary Ellen is a fissure 

in granite, the strike of which is nearly at right angles to the strike of the schists surrounding the granite intrusion. The veins of the Gold Dollar group and of the Hose 

strike across the formation, the first in diorite, the second in schist. The Carissa, it 

is true, does strike parallel to the schists. So also do the several veins of the Garfield. 

But on the whole there is not evidence to prove that the structure of the schists has 

controlled the strike or dip of the veins.

The following quotations are taken from a report by Raymond: 2

The main belt of lodes follows a general northeast and southwest course, but within 

this limit there is considerable variation in the strike and dip of the veins. Some of

i Trumbull, L. W., op. cit., p. 85.

' Raymond, R. W., Statistics of mines and mining in the States and Territories west of the Rocky Mountains for 1869, pp. 329 et seq., 1870.
30 ATLANTIC GOLD DISTKICT, FREMONT COUNTY, WYO.

these ran parallel with the stratification of the country rock; others traverse it at a small 

angle. The dip of the lodes varies from 50° to 90° and is mostly toward the northwest. Their width varies from 1 to 25 feet. At least one of the walls is generally 

smooth and well defined, especially when the strike and dip of the vein corresponds 

with that of the country rock. The walls of the cross veins are mostly imperfectly 

defined.

The ore of the district is mainly quartz, in which oxide and silicate of iron are finely 

divided. The dark shade thus imparted to it has caused the miners to call it black 

iron. Some of the quartz, however, is white and transparent, like that of California. 

The dark kind of quartz is most common; yellow and red stained varieties are frequently so decomposed that they can be easily crushed between the thumb and forefinger. The miners call this kind sandy quartz and consider it richer than the harder 

ore.

The bullion is about 0.850 fine in gold on an average.

Base metals, such as lead, zinc, antimony, tellurium, copper, etc., are very rare, 

and to all appearances the percentage of iron pyrites will be very small, even at greater 

depth. In a few lodes only, malachite and copper pyrites are found interspersed in 

the quartz.

The average yield of several thousand tons of ore from different lodes has been from 

$30 to $40 per ton. The richest ore, yielding $100 and over to the ton, is taken from 

small lodes with an ore streak of 1 to 2 feet wide; lodes of from 4 to 5 feet wide contain 

a medium quality of ore, and the long veins of 10 to 25 feet contain a vast amount of 

low-grade ores. The latter will undoubtedly constitute the main strength and most 

reliable basis for the mining enterprises of the future.

CLASSIFICATION OF THE VEINS AND OTHER GOLD DEPOSITS.

To the classes of veins enumerated by Knight the present writer 

adds stringer lodes and certain deposits that are not veins in any 

strict use of the term but bodies of rock that carry gold associated 

with disseminated sulphides or arsenopyrite. A convenient classification, which resembles but does not fully conform with the one 

proposed by Knight, is given in the following paragraphs:

Cross veins. The class of cross veins is intended to include all 

veins that strike across or oblique to the general trend of the country 

rock. It is represented by veins in metamorphosed sedimentary 

rocks, as at the Rose shaft, on Peabody Hill, and north of Miners 

Delight; also by veins in igneous rocks, illustrated by the Mary 

Ellen vein, which occurs in a small body of granite, probably by 

the Duncan vein, in diorite, and by a vein on the Gold Dollar group 

of claims, also in diorite.

Strike veins. The strike veins conform in trend with the strike 

of the schists, or with the course of inclosing dikes that follow the 

layers of the schists. The Miners Delight vein occurs in a dike of 

feldspar porphyry and throughout part of its course is in a general 

way parallel with the walls of the dike and with a notable though 

not prominent schistosity of the intrusive rock. Along its outcrop 

the vein makes a sharp bend from a northeast to a nearly north 

course, and north of this bend it has the characteristics of a cross 

vein. Other prominent examples of strike veins are the Lone Star,
VEINS. 31

Big Atlantic, Mammoth, Cariboo, St. Louis, Tabor Grand, Carrie 

Shields, and Carissa, and probably the Garfield.

Contrary to the statement of Trumbull quoted on a preceding 

page, the present writer's observation is that strike veins instead 

of being rather uncommon are numerous throughout the district.

Stringer lodes. A group of small quartz bodies interleaved with 

a schist or reticulating through a massive rock and traceable along 

a definite course may be called a stringer lode. Typical examples 

of stringer lodes in schist can not be cited, but in several places 

and to a noteworthy degree along the Carissa lode it was observed 

that strike veins show a tendency to lose their solidity and to be 

continued by a set of multiple veinlets.

Four miles north by west of Atlantic City, about a quarter of a mile 

north of a point between the two serpentme bodies that fliank the 

magnetite schists, a stringer lode in granite shows a network of 

veinlets composed mainly of quartz but containing also flesh-colored 

or reddish orthoclase. Material from shallow prospects on this 

lode is slightly stained by green copper minerals. Other examples 

of stringer lodes in granite were noted near the head of Big Hermit 

Creek. In all these places the lodes have been prospected in a small 

way, but there are no indications that they contain anything of value.

Gash veins. The term gash vein is used for quartz fillings that 

are of very slight extent. In the Atlantic district a few veins of this 

sort have been found to be very rich in gold.

Mineralized rock masses. A class which in the Atlantic district 

may or may not prove to comprise deposits of commercial value 

is that of rock masses which carry disseminated iron sulphide or 

arsenide. The most definite illustration of this class that can be 

cited is a dike of quartz porphyry that is crossed by the mail road 

about 2 miles north of Atlantic City. This dike traverses the Rustler 

or Lander Belle group of claims. It is 10 to 20 feet wide and has 

been traced for a distance of more than a mile. The original rock 

was a dense rock containing definite crystals of quartz and oligoclase 

feldspar in an extremely fine grained groundmass. As a result of 

metamorphism that appeal's to have affected all parts of the dike, 

large amounts of sericite have been developed in the groundmass, and 

the same secondary mineral occurs in some of the feldspar. This 

sericitization is definite evidence that the alteration of the porphyry 

was effected by the action of penetrating hot solutions, and these 

solutions also deposited arsenopyrite and pyrrhotite, which are 

sparsely but generally disseminated through the mass of the altered 

rock. In surface exposures the arsenopyrite and pyrrhotite are 

represented by cavities containing cellular iron oxide and, as such 

material commonly contains free gold, it is supposed that all the
32 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

mineralized rock carries some gold. It is claimed that assays have 

shown gold to a value of $2.50 to $5 a ton.

An example of altered diorite carrying disseminated pyrite and 

arsenopyrite was noted in workings on the Ground Hog group of 

claims, and it is very likely that other deposits of this kind occur 

in the district.

MINERALOGY OF THE VEINS.

The veins of the district are composed mainly of quartz. At 

the surface the quartz is likely to be more or less iron-stained, and 

some of it is cellular and the cavities usually contain yellow, brown, 

or red limonitic material. As depth increases the amount of limonite 

diminishes and it becomes evident that this material is derived 

from pyrite or arsenopyrite. An intermediate product in the 

decomposition of arsenopyrite is scorodite (FeAs4 .2H20), which was 

noted in ore specimens from the Carissa mine.

In addition to the common iron sulphide pyrite, the magnetic sulphide pyrrhotite also occurs, but in general both of these minerals 

are subordinate in amount to arsenopyrite. A few veins carry 

chalcopyrite. Galena was observed by the writer only in quartz 

from the Mary Ellen mine, which also carries a little arsenopyrite.

That the gold contained in the veins is usually associated with 

the sulphide minerals, including arsenopyrite, is evident from the fact 

that with increasing depth the ores have proved to be less amenable 

to amalgamation as a rule.

So-called black quartz, which is of rather common occurrence, 

carries brown or black tourmaline.

The mineralogy of the veins is in accord with the view held by 

the writer that the veins are of deep-seated origin, and this view is 

also supported by the fact that none of the veins show layering or 

banding, as it is commonly called, parallel with the walls.

GOLD CONTENT OF THE ORES.

Very little definite information can be given concerning the amounts 

of gold carried by the ores that have been mined from the veins of 

the district. Notes hi 'Raymond's reports indicate that the ores 

mined prior to 1.872 returned as a rule from $20 to $40 a ton under 

treatment by stamp milling and simple amalgamation. Some ores 

were worked that yielded only $15 a ton, and occasional lots yielded 

as high as $200 a ton. "The average yield of several thousand tons 

of ore from different lodes has been from $30 to $40 per ton." x 

Among the mines mentioned by Raymond in 1870 are the Carrie 

Shields, Young America, Carissa, Golden Gate, Wild Irishman, Gold

i Raymond, R. W., Statistics of mines and mining in the States and Territories west of the Rocky Mountains for 1869, p. 330,1870.
VEINS, 33

Hunter, Calhoun, D.uncan, Mary Ellen, Barnaba, Buckeye State, 

Soules & Perkins, Cariboo, Miners Delight, and Bennet Line.

Between July 20 and November 1, 1868, the original Hermit mill, 

near South Pass City, treated 1,040 tons of ore yielding an average of 

$36 a ton; and between April 20 and July 1, 1869, it crushed 480 

tons of ore, averaging 147 a ton.1

Ore from the Miners Delight vein is said to have yielded from $16 

to $200 a ton, the average having been about $40.

Perusal of old reports relating to the district leaves an impression 

that many of the lodes occurring in the district might be expected 

to yield ores carrying on the average as much as $20 a ton. It is 

believed, however, that as a general rule this expectation will not be 

realized, though with little doubt shoots of rich ore will be found. 

It is more likely that assays will show averages of $6 to, say, $15 a ton.

The records of production in possession of the Geological Survey, 

which are held as confidential with respect to individual mines, 

indicate that 11,105 tons of ore produced by eight mines since 1902 

yielded an average of $8.15 a ton. (See list of assays, p. 40.) On 

the face of the returns, if a few tons of exceptionally high-grade ore 

are left out of consideration, the yield appears to have ranged from 

$5 to $9.18 a ton. The figures given represent the metal recovered, 

and there is no way of ascertaining the actual gold content of the 

ores as mined. In so far as gold and silver yields are both given the 

ratio of gold to silver is found to vary from 5.03 to 10.02, the weighted 

mean ratio for 8,958 tons of ore being 6.79, which corresponds to a 

fineness in gold of 0.871.

PROBABLE PERSISTENCE OF THE VEINS.

From a practical man's point of view the first importance naturally 

attaches to the question whether or not the veins and other goldbearing deposits of the district will be found to persist to great depth, 

and if so whether they will continue to carry about the same amounts 

of gold as near the surface.

In regard to physical persistence, the conclusions may be drawn 

that these deposits are of deep-seated origin, that the present topographic surface is a chance surface due to erosion, without significant 

relation to the ore deposits, and that on the whole the deposits must 

be as abundant at any depth that might be chosen for consideration as 

they are at the existing surface. Although these general conclusions 

are fully warranted by the geologic features of the district, they should 

not be taken as a guaranty that all the veins of the district will be 

found to be continuous to indefinite depths. It is probable that the 

lodes showing long outcrops, like the Carissa and Miners Delight,

1 Raymond, R. W., op. cit., p. 331. 

20142° Bull. 626 16 3
34 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

persist to great depths, whereas it would not be surprising if lodes 

that can be traced at the surface for very short distances are found 

to pinch out at correspondingly moderate depths. On the whole the 

writer is inclined to believe that in this district strike veins, if well 

defined, are likely to prove more persistent than cross veins.

As to the downward continuance of gold content, though it is 

likely that there has been some enrichment through solution and 

redeposition in the oxidized portions of the lodes, it is not believed 

that any really large proportion of the gold in the upper parts of the 

veins has been secondarily precipitated from surface solutions; and 

no hesitation is felt in stating the conclusion that the occurrence of 

valuable ores is not limited to a shallow zone. It may be expected 

that here, as is the rule in other districts, different parts of the same 

lode will be found to carry varying amounts of gold, or, in other 

words, that in any vein the best ore will be found in the form of 

shoots.

The foregoing conclusions and suggestions indicate the writer's 

belief that the district is worthy of further development.

FUTURE DEVELOPMENT.

GENERAL OUTLOOK FOB LODE MINING.

In view of the history of the district and its situation 25 miles from 

railroad transportation the immediate outlook for a general revival 

of the gold-mining industry is not very encouraging. Nevertheless 

the writer shares the opinion which has been expressed by several 

geologists who have made reports on the district, that the early 

promise of the region may yet be fulfilled. This opinion rests on 

the belief that the stronger gold-bearing veins of the district persist 

in depth, with about the same characteristics as they show near the 

surface. The whole problem, however, involves more than this and 

requires a consideration of the planning and execution of development work, methods of ore treatment, transportation, and the cost 

of power. These questions are discussed in the following paragraphs.

PLANNING OF DEVELOPMENT WORK.

In reviewing attempts that have been made either to rework the 

old mines or to open new ones the fact becomes apparent that the 

usual procedure has been to install metallurgic plants before they 

were warranted by developed ore reserves. A plausible justification 

for this method of attack is that by means of it ore removed during 

exploratory work can be treated and the proceeds applied to current 

expenses, thus decreasing the amount of capital required to place an 

enterprise upon a profitable basis. But this reasoning has proved to 

be unsound in thousands of instances throughout the gold-mining 

districts of the United States, and for the Atlantic district the policy
FUTURE DEVELOPMENT. 35

has been ruinous. An important advantage of the method of applying all expenditures at the start to exploration underground is that 

the enterprise may be abandoned at any stage without incurring 

what might otherwise become a double or even a quadruple loss. The 

conclusion can not be too strongly urged that except under unusual 

circumstances mine development must precede the erection of oretreating plants if lode mining is ever to be revived in the Atlantic 

district.

One element of the general problem is that in addition to several 

gold-bearing lodes which are traceable for long distances there are 

others that show only short outcrops. Suppose that a quartz vein 

averaging 3 feet in width shows an outcrop 300 feet long, and that a 

short vein of the kind may pinch out at a depth of 300 feet. The 

cubic content of the vein then corresponds with about 20,000 tons of 

rock. Allow 12,000 tons of ore' that could be won and an average 

yield of about $8 a ton, or say $100,000, and the expense of mine development and mill installation and the cost of mining and treatment 

might very well consume all the possible proceeds. But if two veins 

of this kind could be developed so as to be served by one mill the venture might be made to show a profit. The foregoing example is introduced as a basis for the suggestion that multiple development might 

lead to favorable results where the exploration of a single vein might 

fail.

It is hoped and expected that the placer ground held by the Timba 

Bah Co. will be developed at an early date, and if this undertaking is 

carried out with good results the company should be placed in a position to take up a systematic exploration of lodes on the properties 

which it controls. The plan of developing several lodes simultaneously could be adopted with advantage by this company.

If several active companies were present in the field a demand for 

power would arise, and, under some cooperative arrangement, it 

might prove economically feasible to install a hydroelectric plant that 

would furnish power for preliminary mine developments.

OUTLOOK FOB RAILROAD TRANSPORTATION.

The district has been at a disadvantage because of its remoteness 

from a railroad. Supplies were formerly hauled 70 miles or more 

from stations on the Union Pacific Railroad, but since 1906, when the 

Wyoming & Northwestern Railway was completed to Lander, about 

28 miles from Atlantic City, nearly-all the traffic has been with that 

point. Only 10 miles south of the district is the now abandoned 

route of the Overland Telegraph and of the Emigrant or Overland 

Trail, which led from Casper to the Sweetwater, up this valley to 

South Pass, and thence across the Green River basin on the way to 

Great Salt Lake or to the Oregon country. When the Union Pacific
36 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

Railroad was planned many engineers regarded the Sweetwater route 

as more favorable than the more southerly route that was adopted, 

and it is probable that within 10 years either the Northwestern or the 

Burlington system will seek an entrance to the Green River basin by 

way of South Pass. With the extension of either of these lines the 

situation of the Atlantic and Lewiston districts with respect to transportation will be greatly improved. Atlantic City and South Pass 

City will then be within 12 miles and possibly within 6 miles of the 

railroad, depending on whether the location is north or south of 

Sweetwater River. Lewiston will be still nearer. Whatever alignment is chosen for the railroad, good connecting wagon roads with 

easy and favorably distributed grades can be cheaply constructed and 

maintained.

COST OF POWER.

If a railroad is constructed through the upper "Sweetwater Valley 

coal will be made available, and at points along the line should not 

cost more than $3 to $3.50 a ton. If the smaller figure is taken and 

if the cost of- hauling is assumed to be 35 cents a ton-mile, the estimated cost of coal at points 10 miles from the prospective railroad 

will be $6.50 a ton. For the present the power problem resolves 

itself into the use of wood for raising steam; the use of gasoline, distillate, or crude oil in engines of the internal-combustion type; and 

the development of electric energy in small hydroelectric plants.

Wood for fuel can be obtained from the Washakie National Forest 

by a haul of 5 to 12 miles, at prices of $3.50 to $5 a cord. Under the 

regulations of the Forest Service only dead timber is available, the 

use of which is said to be rather unsatisfactory.

The cost of gasoline delivered has been from 17 to 24 cents a gallon 

and that of distillate somewhat less. When used in small internalcombustion engines, distillate at 20 cents may be compared with good 

bituminous coal, burned under a boiler, at about $16 a long ton.

With little doubt engines of the Diesel type could be adapted to use 

the crude oil produced in the Dallas field, which is situated about 16 

miles north of Atlantic City. Since 1911 this oil has been going by a 

pipe line to Lander, but probably its value for developing power in 

the Atlantic district would be greater than its value for locomotive 

fuel, which is reported to be 75 cents a barrel. The possibilities of this 

oil are suggested by a rough calculation which indicates that, allowing 

for a cost of $1.40 a.barrel at the well and a charge of $1 a barrel for 

transportation, the cost of crude-oil power would correspond approximately with the cost of steam power if coal could be laid down at $5 

a long ton. This calculation is based upon 50-horsepower units. The 

character of the Dallas oil is shown in the following table: 1

1 Woodruff, E. G., The Lander oil field, Fremont County, Wyo.: U, S. Geol. Survey Bull. 452, p. 29,1911.
Analyses of oils from Lander field, Fremont Cou

Serial No.

Wvo.3.......

Wyo. 4.......

Wyo. 5.......

Wyo. 6.......

Wyo. 7.......

Well 

No.

3 

2 

10 

11 

13

Depth 

of well.

Feet. 

750 

400 

825 

965 

697

Physical properties.

Gravity at 60° F.

Specific.

0.9198 

.9126 

.9121 

.9126 

.9091

Baum£.

22.2 

23.4 

23.5 

23.4 

24.0

Color.

Dark brown... 

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

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

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

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

Distillation by Engler's m

Begins 

to boil.

0 C. 

93 

120 

93 

105 

108

By volume.

To 150° C. 

(cubic 

centimeters).

2.5 

2.0 

2.0 

1.5 

2.5

150-300° C.

Cubic 

centimeters.

22.0 

23.5 

21.0 

24.0 

23.0

Specific 

gravity.

(a) 

0.8041 

.8067 

.8018 

.8047

R

Cub

cen

mete

(«

6

7

7

7

a Flask broke during distillation. Water in the 
38 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

The erection of an electric power plant in the Dallas oil field has 

been proposed. This project is technically feasible, and the cost of 

installation would be less than that, of a hydroelectric plant on Little 

Popo Agie River. The transmission line to Atlantic City would be 

about 17 miles long.

The development of water power at points along Rock Creek 

would be feasible for about seven months during the year, but from 

November to March not only is the stream flow small but it is doubtful whether it could be utilized because of troubles due to freezing 

in the diversion canals. From April to November the minimum flow 

including the natural waters of Rock Creek and those diverted from 

Christina Lake would probably not fall below 20 second-feet. With 

this flow of water approximately 280 horsepower could be developed 

at each of two sites, one 3 miles above Atlantic City and the other 

near that place. The upper site is under the ditch of the X. L. 

Dredging Co. The first right to water is claimed by the Timba Bah 

Co., but as the stream would be returned to Rock Creek above the 

headgate of the lower canal of that compajny it is not evident that 

these rights would interfere with eacji other.

The lower power site near Atlantic City is under the main ditch 

of the Timba Bah Co., which was planned to deliver water for placer 

mining along Rock Creek. Although this ditch is now in bad condition it must be repaired in order to work the placers, and either in 

connection with this work or after its completion a power plant 

could be built.

About half a mile above the headgate of the lower Timba Bah 

Canal a small hydroelectric plant was installed about 1895 in connection with an attempt to operate the Garfield mine. By means of a 

ditch approximately 1 mile long a head of about 50 feet is secured. 

Under this head, with a flow of 20 second-feet, a turbine would develop 

about 80 horsepower. The estimated mmimum flow is based on the 

inclusion of water diverted from Christina Lake.

So far as the writer is informed those mentioned above comprise all 

the water powers that could be economically developed within the 

district. Although, as already intimated, it is not likely that continuous power could be depended on throughout the year, the fact 

that no expense would be incurred for diversion canals in the two 

larger schemes may make them worthy of consideration in the planning of the exploration work that must be done if the mines of the 

district are to be put upon a producing basis.

The installation of a hydroelectric plant on Little Popo Agie River 

10 miles north of Atlantic City is regarded as technically feasible. A 

preliminary permit for the utilization of this power was granted in 

1912 to the Beck Mining Co., but the right has since been abandoned. 

A diversion canal 2£ miles long was planned to deliver water at a 

point where an effective head of 750 feet would be attained. This
FUTUBE DEVELOPMENT. 39

project lies within the Washakie National Forest, and through the 

courtesy of the Forest Service, the writer has had access to the 

application of the Beck Mining Co. leading to the permit referred to 

above. In this application figures are given representing the net 

horsepower calculated for average discharge per calendar month for 

parts of 1907 and 1908. For August, 1907, the calculated horsepower was 4,230. There was a gradual decrease until, for December, 

1907, the figure was 1,698. For April, 1908, the horsepower figure 

given was 4,014, for June 17,760, for September 2,970, and for 

November 3,810. On January 26, 1912, the flow was calculated as 

capable of furnishing 1,110 horsepower. According to the formula 

horsepower = head flow X 0.08, these figures indicate that the minimum flow between August and December, 1907, was about 28 secondfeet in December, and between April and November, 1908, was about 

49 second-feet in September. The indicated flow for January 26, 

1912,, is 18.5 second-feet.

In 1915 the district engineer of the Forest Service included in a 

report on certain water-power projects situated on Popo Agie River 

records of stream gaging in 1914 on Little Popo Agie River at 

Young's orchard, west of Dallas. These records show in April, 1914, 

a flow of 62 second-feet, and in the following October 54 second-feet, 

the latter being the minimum for the seven months, April to November, during which records were kept.

In consideration of the figures given it seems safe to assume for 

the Little Popo Agie a minimum flow during seven consecutive 

months of each year of 40 second-feet, corresponding to 2,400 horsepower; during ten months of 25 second-feet, or 1,500 horsepower; 

and an extreme minimum of 15 second-feet, or 900 horsepower.

In the foregoing calculations no account is taken of any diversion 

of water from Christina Lake to Rock Creek.

MILLING OF THE ORES.

In general the ores of the Atlantic and Lewiston districts must be 

treated on the ground, though lots of exceptional value may be shipped 

to a smelter. Thus far, aside from the operations of the Beck Mining 

Co. at the Duncan mine, there has been no systematic endeavor in 

milling to save gold otherwise than by amalgamation. On the whole 

the percentages of extraction have been low, in the milling of both 

unoxidized and oxidized ores, and in future operations better though 

less simple methods will be in general required.

The problems of ore treatment have been discussed by Knight,1 

from whose valuable report the following quotation is made:

As soon as the quartz ledges in the Sweetwater district had been opened to a depth 

varying from 10 to 25 feet, stamp mills were ordered. They were large and small,

> Knight, W. C., op. cit., pp. 24 et seq.
40 ATLANTIC GOLD DISTRICT, FREMCWT COUNTY, WYO.

and early in 1870 there were 10 or 15 mills in operation or nearly completed. On the 

very outset there were serious complaints as to the refractory nature of the ore, and 

in one case at least the stamp mill was abandoned and two arrastres erected in its 

place. The scouring process of the arrastre brightened the gold and made amalgamation more perfect. The bulk of the milling has always been done with stamps 

of various patterns and weights, but the saving has been* very unsatisfactory. For 

many years I have assayed the tailings from these camps, and they have never carried 

less than $5 per ton in gold and in the majority of cases they have assayed from $8 to 

$20 per ton. The early mill men did not save the tailings, or there would have been 

many valuable dumps to be worked by some of the modern methods. For years 

stamp mills were condemned in this district and many other contrivances were brought 

in to take their place. With the exception of the Huntington mill, every other device 

has utterly failed. At the present time the stamp mill has been reinstated, it having 

been proven to be the most effectual crushing device, although as a matter of fact 

there have been serious complications in the free-milling process, owing to the gold 

being coated and not amalgamating. This has, beyond question, been the source 

of the greatest loss, but coarse crushing has always claimed more or less of the values.

The results of amalgamation, cyanidation, and chlorination tests 

made by Knight on samples of ore from the mines of the region are 

summarized in the appended table:

Results of tests of ore from Atlantic and Lewiston districts.

Mine.

Atlantic City.

South Pass.

Lewiston.

Midget..............................

Mint................................

Sample.

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

1 sack. ........

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

.....'do........

5 pounds......

1 sack. ........

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

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

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

. Gold.

Ounces 

per ton. 

2.16

1.5

.99

.92

.65

.61

.36

.171

.162

1.24

1.86

.977

.612

.252

Amalgamation 

saving.

Per cent. 

0.95

.82

.92

.94

.81

.78

.83

.94

.62

.80

.79

.58

.57

.68

Sands 

assay.

Per cent. 

0.108

.027

.072

.955

.120

.130

.060

.012

.060

.250

.400

.284

.260

.080

Cyanide 

tails.

Per cent.

0.025

.01

.041

.180

.200

.140

Trace.

Chlorination 

saving.

Per cent.

65

95

99

77

71

99

74

56

Poor.

13

51

99

The following comments on the results obtained in the investigation are made by Knight:

The ore from the Mint mine is typical of the Lewiston ores and shows clearly what 

the miners have been struggling with. In the ordinary stamp mill the saving has 

been very much less than in the tests, since the ore was not crushed as fine and there 

was no scouring device to aid amalgamation. When a quantity of this ore was treated 

with warm, concentrated hydrochloric acid, then washed and treated by the freemilling process, the tailings assayed only a trace of gold. It is certain that the poor 

savings made by chlorination and cyanide were due to the coated condition of the 

gold.
FUTURE DEVELOPMENT. 41

The ore from the Midget mine resembles that from the Mint. Here ordinary amalgamation would mean a saving of less than 40 per cent of the gold, though some scouring 

device would assist in making a better recovery. It is probable that, after roasting, 

chlorination would make a better saving than is indicated by any of the tests applied. 

Ores of this type should be tested by various chlorination processes. If any of them 

will extract 90 per cent of the gold it would surpass any process that has been applied 

to these ores thus far.

Crush the ores as fine as you can consistently. This you will have to decide by 

milling tests. Occasionally capacity must be sacrificed to secure high recovery, 

but this must not be carried to the extreme. Utilize concentration wherever possible 

and treat the concentrates with cyanide or chlorination, roasting if necessary. Utilize 

the cyanide process to handle tailings. Do not store the sands, as any contained 

sulphides will oxidize and form soluble compounds that must be washed out or neutralized to prevent cyanide losses.

The tests summarized in the table given on page 40 were made 

for the most part on oxidized ores, but in the main the suggestions 

offered are applicable to the treatment of unoxidized ores as well. 

Naturally the amalgamation tests show extractions that are greater 

than could be obtained in practice with economical working. A 

relatively low extraction for sulphide ores is indicated by current 

statements that amalgamation recoveries at the Carissa and Duncan 

mills have been between 60 and 75 per cent on ores carrying from 

0.50 to 0.75 ounce of gold to the ton. Such results are not greatly 

inferior to those that have been attained in the treatment of unoxidized 

gold ores in the stamp mills of Clear Creek and Gilpin counties, Colo. 

In the Colorado mills the sulphides are concentrated and are shipped 

out and smelted, transportation and smelting charges being both very 

low. Obviously concentrates valued at $30 or even $60 a ton could 

not be shipped from the Atlantic district under present conditions, 

but in planning the treatment of ore consideration might be given 

to the possible advantage of amalgamation, plus concentration, plus 

regrinding of concentrate, followed either by amalgamation or by 

cyanidation. Where the gold occurs mainly in the sulphides the 

suggested treatment would obviate fine crushing of the ore as a 

whole.

To one like the present writer, having only a very general knowledge of gold milling, amalgamation supplemented by cyanidation 

would seem to be as a rule the most satisfactory procedure, but it 

is of interest to note that in the treatment of unoxidized ore at 

the Duncan mill in 1913 amalgamation had been entirely abandoned. 

This mill 1 is equipped with four Nissen stamps. The original plan 

was to save the gold by inside and outside amalgamation. With 

clear water and careful working 75 per cent extraction was possible, 

but the water supply is scanty and when exhaust water from a 

steam pump was admitted very careful work was required to keep

i Trumbull, L. W., op. cit, pp. 98-100 (description of Duncan mill by D. C. Kelso).
42 ATLANTIC GOLD DISTRICT, FREMONT COUNTY, WYO.

the extraction above 60 per cent. Experiments were made with 

the idea of crushing in cyanide solution and amalgamating on plates, 

but the method of all sliming and cyanidation without amalgamation 

was finally adopted. The capacity of the mill is about 30 tons a 

day. For February, 1913, the cost of treatment is given as $2.70 

a ton, and of this amount $1.19 is charged against gasoline and 

distillate used for raising power.

The Dexter or Timba Bah mill at Atlantic City is equipped with 

20 stamps of 1,050 pounds each and is provided with apparatus for 

cyanide treatment. The mill was erected in 1908 but has never 

been in regular operation.

The Carissa mill, with 10 stamps of 550 pounds, is provided with 

amalgamating devices and Wilfley concentration tables.

At the Mary Ellen mine there is a 5-foot Huntington mill equipped 

with amalgamating plates. ,

PLACER DEPOSITS.

The alluvial deposits of the Atlantic and Lewistpn districts have 

not been studied in a systematic way, so that only a very brief discussion of this subject can be presented. On Plate III the distribution of the gold-bearing gravels is shown in part.

The greater proportion of the alluvial gold thus far produced has 

been won by means of the pan or rocker or by sluicing in a small way. 

The richer gravels occurred in shallow drains heading in ground traversed by gold-bearing lodes. Placers in such situations were usually 

of very small extent, but as a rule the gravels were thin and therefore 

readily worked. The small streams in several gulches were diverted 

by ditches, some of them a mile or more long, but operations were 

mainly limited to the spring months because of insufficient water at 

other seasons. Among the small placers that were worked to advantage within the period 1867 to 1872 were those derived from the 

Carissa lode, near South Pass City; those of Big Atlantic, Smith, and 

Promise gulches, east of Atlantic City; of Meadow, Yankee, and 

Spring gulches, near Miners Delight; of the Crows Nest and Dutch 

Tom flats, to the southeast; and of several localities in the vicinity of 

Lewiston. The typical gold from these-placers was rough and rather 

coarse, and nuggets weighing as much as 2 ounces were occasionally 

found.

During recent years there has been a small and sporadic production 

by individual miners, but in the main the small placers may be 

regarded as offering little promise for the future.

A small but steady production of gold has been made for several 

years from gravels occurring in a ravine on the south side of Rock 

Creek near Atlantic City. The principal.workings are on the Babette
U. 8. QEOLOQICAL. SURVEY 

R. 101 W.

BULLETIN 626 PLATE III

R.100W.

GOLD PLACERS

1 Carissa placer

2 Hermit Gulch .

3 Babette placer

4 Big Atlantic Gulch 

_j 5 Promise Gulch 

 6 Meadow Gulch 

= 7 Yankee Gulch

8 Spring Gulch

9 Crows Nest

10 Dutch Tom Flat

11 Burr lode and placer

R.IOIW. R. 100 W, R.99W. R.98W. 

SKETCH MAP OF ATLANTIC AND ADJACENT DISTRICTS, WYO., SHOWING DISTRIBUTION OF GOLD PLACERS IN PART.
PLACER DEPOSITS. 43

property. Here loose material fills the valley to a depth of 10 to 20 

feet, forming a deposit from 50 to perhaps 150 feet wide. Apparently 

the best dirt occurs in bedrock along a definite channel, and the 

deposit is worked by means of a drift. The stream is small, but a 

sufficient volume of water for sluicing is made intermittently available 

by means of a dam.

Although the larger part of the alluvial gold produced during the 

early years of activity came from small placers occurring in headwater 

drains, stream placers were also worked in several places. These 

deposits occur in ah1 the gulches that receive drainage from the mineralized areas, and downstream from these areas gravels occurring 

along the principal creeks carry more or less gold. Gulches having 

grades steep enough to permit ready disposal of waste are Hermit 

Gulch, near South Pass City, and Big Atlantic and Smith gulches, 

east of Atlantic City. Of these the two last appear to have been the 

most productive, though because of diminished slope the lower part 

of Smith Gulch was never worked extensively.

In 1914 the X. L. Dredging Co. completed a ditch to deliver Rock 

Creek waters into the upper part of Smith Gulch, and here hydraulic 

operations were carried on for a few weeks. Whether or not the 

results of this work were satisfactory is unknown to the writer. 

During the late part of summer and the autumn this company was 

reported to be washing gravels at a locality on Little Beaver Creek 

several miles east of Smith Gulch.

The following quotation is taken from a report by Jamison,1 former 

State geologist:

The X. L. Dredging Co. owns 1,680 acres of placer ground on Little Beaver, Smith, 

Promise, and Big Atlantic gulches and Stambaugh Flat. The company has constructed a ditch from Kock Creek, 7 miles above Atlantic City, to the placers. A 

large part of the Stambaugh Flat ground is reported to have a gold tenor of $1.40 per 

cubic yard, while that in the gulches yields $0.50 per yard.

The gravels along Beaver Creek are reported to carry gold all the 

way to the junction with Popo Agie River northeast of Hudson. A 

sample representing 3 feet of gravel on a bar half a mile above the 

mouth of the creek was found by Schrader 2 to contain gold to the 

amount of six colors to the pan, corresponding to a value of about 33 

cents to the cubic yard.

Placer deposits on Willow Creek near South Pass City and on Rock 

Creek near Atlantic City were worked for the most part before 1876. 

In both places the valley floors are from 200 to 1,000 feet wide, and in 

general the gravels are said to be from 5 to 20 feet deep. The Rock 

Creek operations seem to have been more extensive than those on Wil1 Jamison, C. E., Geology and mineral resources of Fremont County, Wyo., p. 79, Cheyenne, 1911.

2 Schrader, F. C., Gold placers on Wind and Bighorn rivers, Wyo.: U. S. Geol. Survey Bull. 580, p. 142, 

1914.
44 ATLANTIC GOLD DISTRICT, FEEMONT COUNTY, WYO.

low Creek. Because the gravel flat is broad, the stream grade slight, 

and the gravel bed rather deep, groundsluicing was not generally practicable and the deposits were worked mainly by means of pits sunk to 

bedrock. Placer workings below Atlantic City are reported to have 

yielded in 1869 from $3.50 to $12 a day 1 to the man.

After 1876 and until about 1884 little interest was manifested in 

the Rock Creek placers. In 1884 French capital was brought into 

the district through the efforts of an engineer named Emile Granier. 

The following letter from Granier to L. D. Ricketts is quoted from°the 

report of the'Wyoming Territorial Geologist for 1886:

In 1884 I bought from the original locators some placer claims on Willow Creek, 

Rock Creek, Strawberry Creek, and Sweetwater River, and the next year I commenced 

digging ditches for the proposed working by those creeks. The ditch is 10.5 miles 2 

long, 3 feet wide at the bpttom, 6.75 feet wide at the to,p, 2.5 ^eet deep, with 10 feet 

grade to the mile, and can carry 40 feet of water per second. I expected that the 

ditch would be filled up with water of Rock Creek alone long enough to wash during 

the whole summer; but Rock Creek was not sufficient, and I had to finish the big 

ditch that will carry the water of Christina Lake to the head of Rock Creek. This 

ditch is 6 miles long, 5 feet wide at the bottom, 11 feet wide at water line, and 3 feet 

deep and 16 feet grade per mile, and can carry 144 feet of water per second. It was 

cut through solid granite rock for more than half of the way. It has a, flume, on trestles 

70 feet high and 500 feet long, 6 feet wide and 4 feet high.

Christina Lake is about 1£ miles long, and it is situated at the foot of Atlantic Peak, 

at 10,000 feet above the level of the sea.

I intend to wash the Rock Creek bottom with one of Joshua Hendy's hydraulic 

elevators, because the grade of the creek is so small that it is impossible to wash off 

the tailings. It is not yet quite certain that this machine will work well.

This plant was operated during the three seasons 1890 to 1892 at 

a point about 2 miles below Atlantic City. A large amount of gravel 

was moved, but although the value of the gold produced is reported 

to have been about $200,000, the operations of the Christina Lake 

Co. ceased in 1892.

The following is quoted from Knight: 3

Special mention should be made of Rock Creek, from Atlantic for a distance of 4 

miles below. The gulch is quite narrow, the fall slight, bedrock rough and covered 

with 5 to 10 feet of gravel. The gold is coarse and is found upon bedrock. This ground 

lies just below the gold-bearing zone and has been prospected by pits and found to 

be very rich. Originally a Hendy hydraulic elevator was put in to handle the tailings, 

but for some reason it failed. Only a couple of years ago [that is, about 1899] a steam 

shovel was put in to handle the gravel, and on this occasion the failure was due to 

lack of water. I do not know of any absolute figures relating to the value of the 

property per cubic yard, but I am convinced that it is sufficiently rich to warrant 

the installation of a modern plant that will handle the gravel successfully and pay 

handsome dividend upon the investment.

1 Raymond, R. W., Statistics of mines and mining in the States and Territories west of the Rocky 

Mountains for 1809, p. 337,1870.

2 Actually constructed, about 5 miles. A. C. S.

3 Knight, W. C., The Sweetwater mining district, Fremont County, Wyo.: Wyoming Univ. Geol. 

Survey Bull., June, 1901, p. 23.
PLACER DEPOSITS. 45

The only locality on Sweetwater River that was visited by the 

writer lies immediately, south of Lewiston. Here a gravel deposit 

forms a flat half a mile or more long. Gold in the form of minute 

flakes was found in nearly all of several lots of dirt that were panned. 

These samples were taken practically at the surface. The deposit 

is about 6 miles below the mouth of Rock Creek and by its position 

must have received wash from both the Atlantic and the Lewiston 

lode zones.

It is considered that systematic sampling of this placer is warranted 

and the suggestion is made that this could best be done by means of 

churn drills. An adequate number of test shafts would be very 

expensive, work already done having shown that in sinking to bedrock pumps of large capacity are required.

The occurrence of placer gold along Red Canyon (see PL III) is 

worthy of passing mention because at one time the deposits were 

made the basis of a rather remarkable promoting exploit. Certain 

capitalists were induced to form a company and to buy up all the 

lands along the creek bottom, most of which were owned by prosperous ranchers. Although the ground is commonly regarded as valueless for mining, the ranches are all tenanted, garden truck, fruit, and 

alfalfa are raised, sheep are wintered, and the venture appears to have 

been financially successful. The uppermost farm, known as the 

Tweed ranch, is served by a ditch from Twin Creek. Adjacent to 

this ditch and visible from the wagon road there are old placer workings at several points. A general cover of gravel appears on the broad 

ridge that forms the divide between Red Canyon and Twin Creek, 

and it is obvious that the locally concentrated gold has been derived 

from this deposit. The bedrock formations are limestone and sandstones, but the gravel is composed almost entirely of crystalline rocks 

which must have come from the Wind River Range, a considerable 

distance west of the present headwaters of Red Canyon and Twin 

creeks. Perched high above the beds of the nearest streams and 

separated as they now are from the area of pre-Cambrian crystalline 

rocks by intervening canyons, these gravel beds point to marked 

drainage changes in recent geologic time changes whose interpretation can not be attempted until the erosional history of the general 

region has been studied in detail.

ECONOMIC GEOLOGY OF THE NORTH LARAMIE

MOUNTAINS, CONVERSE AND ALBANY

COUNTIES, WYOMING.

By ARTHUR C. SPENCER.

INTRODUCTION.

During August, 1914, the writer visited all the better-known 

localities in southern Converse County and the northern tier of 

townships in Albany County, Wyo., where prospecting for metalliferous ores has been carried on at various times during the last 30 

or 40 years. Most of the work has been done in the search for copper, but at one locality lead ores have been opened, at another 

chromic iron ore, and at another magnetic iron ore. With one exception all the mineral occurrences that were examined are associated with rocks of pre-Cambrian age. which constitute the core of 

the Laramie Mountains.

The writer was fortunate in having as guide and companion Mr. 

W. F. Mecum, of Douglas, Wyo., whose familiarity with the region 

made it possible to visit many widely separated localities in the 

comparatively short space of three weeks.

NORTH LARAMIE MOUNTAINS.

Definition. The Laramie Mountains are the continuation into 

Wyoming of the Front Range of Colorado. Lying between the 

Great Plains on the east and the Laramie Basin on the west the 

range, from 10 to 25 miles wide, trends north from the State boundary to Laramie Peak, a distance of 85 miles, thence northwest for 

about 50 miles, where its characteristic features are lost in the vicinity of Casper. Parts of the range near. Casper have received distinctive names, being known as "the Casper, Haystack, and Deer Creek 

ranges. The following notes relate only to the northern part of the 

range.

Configuration. The topography of the range is in general rugged, 

but the upper valleys of some of the streams are rather broad, and 

there are many interstream areas that are fairly smooth. Locally 

along the water parting such areas merge to form rolling uplands of 

considerable extent. Above these comparatively smooth areas rise 

the higher mountains and below them, along the lower courses of the

47
48 NORTH LARAMIE MOUNTAINS, WYO.

streams, deep and steep-walled gorges have been excavated. The 

height of land, as determined both by the principal summits and by 

the mountain passes, lies well to the southwest of the axis of the 

range.

Laramie Peak, the culminating summit, reaches an elevation above 

10,000 feet, other mountains to the northwest ranging from about 

9,000 down to 8,000 feet in height, and near the end of the range 

down to about 7,000 feet. The principal defiles are at elevations of 

7,000 to 8,000 feet. Except in the vicinity of Laramie Peak the 

roughest part of this northern section of the range is along a zone 

lying a short distance back of the curving edge of the area of 

crystalline rocks which faces northeast and north. Here the streams 

commonly flow in narrow canyons from 500 to 700 feet or more in 

depth; and as the.gorges are rather closely spaced the topography is 

extremely rough.

Drainage. North Platte River flows nearly due north from its 

source west of the Medicine Bow Mountains in North Park, Colo., 

for about 100 miles to the mouth of Sweetwater River, where it turns 

to sweep in a great curve around the northwest end of the Laramie 

Range to Casper, thence flows east to Douglas and southeastward 

across the High Plains of Wyoming and Nebraska. Thus the northern part of the Laramie Range is drained on both sides by tributaries of the North Platte on the southwest by headwater streams of 

Medicine Bow River and on the west, north, and east by creeks that 

flow directly to the master stream.

The drainage pattern is distinctly asymmetric, the divide between 

streams that flow south or southwest and those that flow north, northeast, or east being situated southeast of the axis of the mountainous 

belt.

Climate. The average yearly precipitation within the northern 

part of the Laramie Range is probably about 20 inches, or perhaps 

somewhat more than 50 per cent above that on the plains to the east 

and double that on the Laramie Plains. This figure is an estimate 

based on the general character of vegetation and on the distribution 

of floral assemblages. At Lusk, on the high plains in southeastern 

Converse County, the annual precipitation is about 13 inches; at 

Fort Laramie, 50 miles south of Lusk, about 11 inches; and at Laramie about 10 inches. Meteorologic records relating to the stations 

named show that the spring and summer precipitation is materially 

greater than that of autumn and winter; but as in the mountains 

the winter snows commonly accumulate to depths of 2 feet or more 

it is evident that here the precipitation is more evenly distributed 

throughout the seasons.

The mean annual temperature at elevations below 6,000 feet is 

probably about.42° F., the extreme range being from - 35° to + 100°.
NORTH LARAMIE MOUNTAINS, WYO. 49

Above 6,000 feet the temperatures are of course lower, especially in 

summer, and frosts may occur during any month in localities at 

about 7,000 feet.

Vegetation, stock'raising, and agriculture. Like the Great Plains, 

the foothills and middle slopes of the Laramie Mountains are clothed 

with grasses, growth of which is especially luxuriant between elevations of 5,000 and 7,000 feet, or locally even up to 8,000 feet. Grass 

and sagebrush grow together on ridge slopes up to 6,500 feet and 

locally at higher elevations, but ridges and many extensive areas above 

this level are covered by grass alone. This region, in common with 

Wyoming as a whole, supports an extensive grazing industry. Horses, 

beef cattle,-and sheep range through the mountains from May until 

late in September, when they are moved to valley ranches or to 

winter ranges on the surrounding plains.

Dry-land farming is carried on, though perhaps in general not with 

signal success, in smooth areas up to elevations of 7,000 feet, where 

wheat, oats, and potatoes usually mature during a short growing 

season and where many garden plants may be successfully grown.

In .the broader valleys of the principal creeks, usually .below 6,000 

feet in elevation, oats, wheat, and forage crops, including alfalfa and 

timothy, are grown on irrigated ranches. Some of these operations 

carried on in connection with sheep or cattle raising are on a large 

scale. Apples, small fruits, and garden truck are also raised. Some 

of the irrigated lands of the foothill belt utilizing the natural flow 

of the mountain streams have been under cultivation since about 1880.

On La Prele Creek, about 10 miles east of Douglas, a great dam 

of concrete now stores the winter waters of this stream for use during 

the growing season. These works have greatly extended the amount 

of land irrigable from La Prele Creek, and the dam is so placed 

that the water may be used for generating electric energy, the use 

of which is contemplated for pumping water to irrigate lands along 

the north side of North Platte River west of Douglas. Other 

projects of the same sort in this region are probably feasible.

A large part of the mountainous area lying above an elevation 

of 7,000 feet supports a forest growth comprising white and yellow 

pines suitable for high-class lumber and the less va-luable lodgepole and jack pines. Spruce and balsam fir occur but are not abundant, excepting on the slopes of Laramie Peak. Aspen is the principal deciduous tree in the mountains. Cottonwood and the mapleleaved ash or box elder grow along the lower valleys.

At a number of places sawmills have been operated, their product 

having been sold to ranchers and even at railroad points in competition with lumber from distant points. The better or more accessi20142° Bull. 626 16 4
50 NORTH LARAMIE MOUNTAINS, WYO.

ble forests have been cut over, so that this industry has greatly declined in recent years.

Railroads. The region in which the North Laramie Mountains lie 

is served by four railroads. The southern part Of the range is best 

reached from Medicine Bow station, on the Union Pacific Railroad. 

East of the mountains is the line of the Colorado & Southern Railway, running north from Cheyenne to Hartville Junction, southeast 

of Orin. North of the range are the Chicago & Northwestern Railway and the Chicago, Burlington & Quincy Railroad, which run parallel 

with North Platte River westward from Orin as far as Casper.

Wagon roads. There are several easy routes north and south or 

northeast and southwest across the range, along any one of which 

a good road could be maintained with a moderate expenditure. 

Formerly there was a stage line from Medicine Bow and Rock Creek 

stations, on the Union Pacific Railroad, directly north to Fort 

Fetterman. At -present most of the transmountain roads are out 

of repair, but a fairly good road is maintained through Cold Spring 

Pass, at the head of La Prele Creek. Routes parallel with the 

principal creeks are comparatively easy, but travel parallel with 

the mountain axis is everywhere difficult and in the main impracticable. Still nearly all parts of the region are accessible, though 

many localities can be reached only by making long detours from 

the main lines of travel.

From Glendo there is a good road into the district north of Laramie 

Peak, and this country is also readily accessible from Douglas. 

Mining prospects in the upper drainage basins of La Bonte and La 

Prele creeks are most directly reached from Douglas, and localities 

farther west in Converse County either from Glenrock or from Casper.

GEOLOGY.

GENERAL STRATIGRAPHY AND STRUCTURE.

The Laramie Range as a whole comprises a central belt of preCambrian crystalline rocks flanked on both sides by areas of stratified 

rocks that range in age from Carboniferous to late Cretaceous and 

early Tertiary. Later Tertiary formations are also prominent locally, 

and Quaternary deposits may be recognized at several places just 

outside of the mountainous belt.

The structure of the range is anticlinal. The older crystalline rocks 

have been, as it were, pushed up along the axial belt, so that the 

younger sedimentary rocks dip away from the core on both sides. 

The nature of the contact between the crystalline rocks and the lowest sedimentary beds shows that the sediments were deposited on 

a nearly smooth suface. There is no doubt that the Paleozoic and 

Mesozoic formations, now seen in uptilted positions, once extended
GEOLOGY. 51

across the area occupied by the mountains, having been since 

removed by erosion.

On the east and north side of the mountains the sedimentary 

formations almost everywhere have steep dips, and locally there are 

strong faults parallel with the general strike. In a few places 

there are cross faults which produce sharp irregularities in the 

boundary between sedimentary and crystalline rocks. On the 

side of the range next to the Laramie Plains the dips are more gentle, 

so that the profile of the uplift, if restored, would be that of an 

asymmetric arch with its crest well over toward the convex side of 

the belt of crystalline rocks. This belt is from 10 to 25 miles wide.

South of Laramie Peak the structure appears to be simple, but 

toward the northwest the main arch is flanked on the north by a 

series of minor flexures, almost the whole of the sedimentary series 

being here sharply but irregularly corrugated, within a zone about 

10 miles wide, now characterized by considerable topographic 

relief. Subsequent to the uplift, which is assigned to the Laramide 

revolution, erosion was active during a long period, and the general 

topography of the region came to be very much what it is at present. 

Toward the end of this erosional period the downstream parts of 

the main river valleys to the east became clogged with debris, and 

gradually the deposition of materials derived from the mountains 

progressed upstream. The stream channels shifted from side to 

side, so that their deposits eventually merged to form extensive 

mantles of sedimentary material that covered the former foothills 

of the range and extended in many places well up on the mountain 

ridges and along some of the wider valleys quite to tfie main divide.

In this general region several Tertiary formations ranging in age 

from Eocene to Miocene have been recognized. The deposits of the 

Laramie Mountains belong mainly, if not entirely, to the Oligocene 

White River formation.

After the accumulation of the White River beds the - region was 

one of "buried mountains," all the deeper valleys having been partly 

filled. Next came a renewal of active erosion. Within the mountains much of the debris was carried away and the streams cut their 

present valleys. One result of the deep infilling in Tertiary time was 

the diversion of the larger creeks from then- previous courses. When 

erosion was renewed the new channels were maintained, and where 

bedrock was encountered narrow canyons were excavated. In 

places, therefore, the topography is now rougher than it was before 

the deposition of the White River formation.

The crystalline rocks that form the core of the mountains comprise 

coarse granite, serpentine, dark schists, and numerous nearly black 

dikes of diabase. The structural lines in this crystalline area generally trend southwest or transverse to the axis of the range.
52 NORTH LARAMIE MOUNTAINS, WYO. 

THE GEOLOGIC MAP.

The topography of the North Laramie Mountains and the general 

distribution of the crystalline rocks and sedimentary formations along 

the range are shown on the accompanying map (PI. IV). This map 

is mainly the result of field work done by N. H. Darton and assistants 

in 1906 and 1907, but in its compilation a map of the Douglas oil 

field by V. H. Barnett has been used and observations by C. J. Hares 

and by the present writer have been incorporated.

The short descriptions of the sedimentary formations occurring 

within the area discussed in this report are written by N. H. Darton, 

who has previously mapped the area on a smaller scale and parts 

of it on the same scale. (See pp. 53-56.) The tune spent in the 

region by the writer was very short, and no attempt was made to 

separate the different .crystalline rocks, so that in this connection 

the map is useful only in showing the general extent of the preCambrian complex.

PRE-CAMBRIAN BOCKS.

The complex of crystalline rocks which constitutes the core of 

the North Laramie Mountains has not been studied in detail, but 

observations along routes traveled by the writer are sufficient to 

show the general resemblance of the pre-Cambrian complex here 

and in other districts to the south and west. The rocks of the Sherman quadrangle,1 the northern edge of which is about 25 miles south 

of Laramie Peak, comprise schists and gneisses, which are regarded 

as in part of sedimentary and in part of igneous origin, and these 

rocks are interrupted by intrusive bodies of gabbro, syenite, anorthosite, granite, and granite porphyry. There are many narrow 

dikes of diabase and diorite which cut all the rocks named above. 

The contacts between the different sorts of rocks commonly trend 

southwest.

West of the termination of the Laramie Range, in the lower Sweetwater country, the principal rocks of the pre-Cambrian areas are 

red and gray granites, but there are also bodies of schist, as well as 

many narrow black or greenish dikes that run in northeast courses.

As in the neighboring regions that have been mentioned, coarsegrained granites are the most abundant rocks in the nucleus or core 

of the North Laramie Mountains. North of Laramie Peak, in the 

headwater region of Horseshoe and Elkhorn creeks, there are considerable areas of dark schistose rocks, more or less broken from 

place to place by intruded masses of granite. The schists trend 

southwest and the contacts between schists and intrusive rocks are

' U. S. Geol. Survey Geol. Atlas, Laramie-Sherman folio (No. 173), 1910.

GEOLOGY. 53

as a rule steeply inclined or nearly vertical. The writer's impression of these highly metamorphosed rocks is that they represent a 

series of interlayered sediments and volcanic rocks. Schists like 

those occurring in the eastern part of the region were not noted in 

traveling by a circuitous route from Spring Hill post office centrally 

along the range to Boxelder Creek. Hornblende schist was seen, 

however, on the south side of the range along the Converse-Albany 

line in R. 76 W., and the same rock is reported to occur in the high 

mountains at the head of Boxelder Creek. Throughout the middle 

section of the range coarse grained gray and red granites abound, 

and in the main they are interrupted only by narrow dikes of diabase.

Pegmatites, which are particularly coarse grained phases of the 

granite, occur in relatively small masses in all parts of the district.

In the western part of the range the granites predominate to a 

less degree and dark schists occur in many places. Locally these 

rocks inclose masses of serpentine, a metamorphic igneous rock 

older than the granites. In Natrona County, west of the area visited, the serpentine contains asbestos deposits which have been 

under development for several years and which it is hoped will prove 

to be of industrial importance.

o

SEDIMENTARY ROCKS.

By N. H. BARTON. 

GENERAL FEATURES.

The sedimentary rocks 1 on the north slope of the Laramie Mountains comprise strata from Carboniferous to early Tertiary in age. 

The succession appears to be conformable, but not all the geologic 

epochs are fully represented. The principal gaps are part of the 

Jurassic and probably much, if not all, of the Triassic. The Tertiary 

is represented by some of its earlier deposits in conformable sequence 

and also by the White River formation, which overlaps the other 

formations and in places lies on the granites and schists.

CARBONIFEROUS SYSTEM.

Casper formation. The granites, schists, and other crystalline 

rocks of the Laramie Mountains are overlain by the sandstones and 

limestones of the Casper formation, whose thickness ranges from 

400 to 700 feet. The maximum thickness is shown on La Bonte 

Creek a mile northwest of Spring Hill. A basal sandstone or quartzite, in most places conglomeratic, is 60 to 100 feet thick in the western

1 These rocks are described by N. H. Darton (Paleozoic and Mesozoic of central Wyoming: Geol. Soc. 

America Bull., vol. 19, pp. 403-470, pis. 21-30,1908), and the upper beds also by V. H. Barnett (Possibilities of oil in the Big Muddy dome: U. S. Geol. Survey Bull. 581, pp. 105-117,1914; The Douglas oiland 

gas field: U. S. Geol. Survey Bull. 641, pp. 49-88, pi. 4,1914).
54 NORTH LABAMIE MOUNTAINS, WYO.

part of the region but thins toward the east, so that in slopes west 

and south of Douglas the limestones are not far above the crystalline rocks. These limestones are light gray and from 200 to 500 feet 

thick. They are overlain by a hard gray massive sandstone which 

constitutes most of the mountain slopes. Extensive exposures 

occur in Muddy, Deer, Boxelder, and La Prele canyons. In La Prele 

Canyon the strata are flexed in a fine arch and the upper sandstone 

constitutes a well-known natural bridge. The sandstone is massive, 

coarse grained, and usually light colored, but in some of the ridges 

west of Douglas it weathers dark brown. It probably represents 

the Tensleep sandstone of the region farther north.

Fossils are not often found in the Casper beds, but those obtained 

indicate that while the formation belongs mainly in the Pennsylvanian series possibly the basal beds may be Mississippian.

Satanka (?) shale and Forelle (?) limestone. The sandstone at the 

top of the Casper formation is overlain by 50 to 80 feet of red shale 

and this in turn by 20 to 30 feet of limestone. These beds are supposed to represent the Satanka shale and Forelle limestone of the 

Laramie Basin or the Opeche formation and Minnekahta limestone 

of the Black Hills in South Dakota. They crop out along the south 

side of the Casper Range, on the north slope of the Deer Creek Range, 

on La Prele Creek south of Inez, in the uplifts east and southeast 

of Beaver, and on the west side of thfe Laramie Mountains. A small 

outcrop of the limestone lying on 50 feet of shale appears in the bank 

of North Platte River 7 miles south of Douglas.

TRIASSIC (?) SYSTEM.

Chugwater formation. The red shales and sandstones of the Chugwaterf ormation crop out on the south side of the Casper Range, on both 

slopes of the Haystack Range, on the north side of'the Deer Creek 

Range, in the several small uplifts south of Douglas, in the ridge 

east of Freeland, and along the west side <5f the Laramie Range near 

Marshall and Little Medicine. They probably underlie the.White 

River formation in part of the valley about Beaver and southwest 

of Inez. The thickness of the formation averages about 1,200 feet, 

but on La Prele Creek it has been estimated at 1,500 feet. Thin 

beds of limestone and gypsum are included at some localities, notably 

at the east end of the Casper Range and north of Freeland.

JURASSIC SYSTEM.

Sundanceformation. The Sundance formation is exposed in narrow 

zones of outcrop adjoining those of the Chugwater formation mentioned above. The most extensive exposures are in the uplifts south 

of Douglas and near Freeland. The thickness of the formation
GEOLOGY. 55

ranges from 200 to 300 feet. The basal beds consist largely of buff 

to reddish sandstones, and the upper beds are made up of 150 to 200 

feet of gray shale with thin layers of limestone filled with characteristic fossils of Jurassic age. The shales are mostly dark gray and 

fissile, and therefore differ in character from the Morrison deposits.

JURASSIC OR CRETACEOUS SYSTEM.

Morrison formation. The gray clay of the Morrison formation 

overlies the Sundance formation, and is exposed at many places 

from the Haystack Range eastward to the fault south of Glenrock 

and in the ridges south of Douglas.

The thickness of the formation averages about 150 feet, and its 

upper and lower limits are clearly defined. White and pale greenishgray clay or massive shale predominates, but some portions weather 

pink, buff, or maroon. Thin beds of sandstone and limy concretions 

are included in the formation. Bones of characteristic dinosaurs 

occur in some places, notably in Como Bluff and the Freezeout Hills, 

a short distance southwest of the area treated in this report.

CRETACEOUS AND TERTIARY SYSTEMS.

Cloverly (?} sandstone. The prominent sandstone series overlying 

the Morrison is for the present known as the Cloverly (?) sandstone, but 

it may here include beds having a greater range of age than in the type 

locality. It constitutes a large part of the Haystack Range, and its 

outcrop extends as a hogback ridge along the south side of the Deer 

Creek valley to the fault south of Glenrock. It appears again in 

the numerous ridges south of Douglas and also in a small area south 

of Inez. The thickness of the Cloverly (?) beds ranges from 90 to 

140 feet. The rock is mainly gray massive sandstone in two mem- 

,bers, separated by 20 to 40 feet of clay or shale of buff to maroon 

color similar to the Fuson formation of the Black Hills. The basal 

portion is conglomeratic at most places. The upper sandstone is 

thin bedded and rusty in color. South of Douglas there are three 

sandstone members.

Benton shale. In the Benton shale begin the thick deposit's of black 

shale, which constitute a large part of the Upper Cretaceous section. 

The formation occupies an area of considerable extent in the syncline of Muddy Creek and in the valley of Little Medicine Bow River. 

Its outcrop also extends along part of the valley of Bates Creek, the 

north slope of the Casper Range, and the foot of the mountain south 

of Glenrock. The Benton shale is 'about 1,500 feet thick. About 

225 feet above its base it includes the Mowry shale member of lightgray hard shale containing large numbers of fish scales. This member is about 175 feet thick and is succeeded by dark shale containing a 100-foot sandstone member about 300 feet below its top.
56 NORTH LARAMIE MOUNTAINS, WYO.

Niobrara shale. The dark shales at the top of the Benton give 

place within a short distance to the Niobrara shale, which crops out 

almost continuously along the north foot of the mountains from a 

point south of Casper to Boxelder Creek. It also crops out in the 

valleys of Bates Creek, Little Medicine Bow River, and Wagonhound 

Creek. The formation is about 250 feet thick, and the shales are in 

large part of light color, owing to the admixture of calcium carbonate. They weather to a pale-yellow tint, which is very characteristic. Some of the beds contain Ostrea congesta, mostly in small 

masses or thin layers. '

Later Cretaceous and early Tertiary formations. Above the Niobrara 

shale in parts of this area are more than 9,100 feet of shales with 

interbedded sandstones and a few coal beds which represent the 

Steele shale, the Mesaverde, and higher Cretaceous formations; the 

Lance formation, classified as Tertiary (?); and the Fort Union -formation, of Tertiary "(Eocene) age.

White River formation. The white clay and fine sand of the White 

River formation occur in many places on the northern slopes of the 

Laramie Mountains and adjoining ranges. Originally the formation 

covered all but the higher portions of the region, and much of it has 

been removed by erosion. Bodies of considerable size occur in the 

La Prele Valley about Beaver, and smaller outliers remain in the valleys south of the Deer Creek Range. A large area extends along the 

north slope of the mountains southwest of Douglas, and most of the 

La Bonte Valley as far south as Spring Hill is in White River beds. 

In many places these deposits contain bones which indicate that they 

are of Oligocene age.

MINERAL DEPOSITS IN THE NORTH LARAMIE 

MOUNTAINS.

DEVELOPMENT.

Evidences of prospecting, assigned by local tradition to the period 

immediately following the discovery of gold in the Cherry Creek and 

Pikes Peak districts in Colorado, are to be noted from place to place 

within the area of crystalline rocks lying northwest of Laramie Peak. 

Stories of gold having been won by individuals and of lost mines 

are current, but no printed records are known to justify the belief 

that there .has ever been any production worthy of mention. A 

discovery of gold in the vicinity of War Bonnet Peak, 15 or 20 years 

ago, caused a short-lived interest in the country at the head of La 

Prele and La Bonte creeks. Though a promising vein was discovered the ore proved to be a mere pocket, and systematic work was 

soon abandoned. Since about 1875 more or less prospecting has 

been going on in one place or another, during more recent years 

mainly in the search for copper ores.
U. S. GEOLOGICAL SURVEY BULLETIN 626 PLATE V

LIST OF 

PROSPECTS

1 TRAIL CREEK

2 SNOWBIRD

3 -SAUL'S CAMP

4 KREISLEY PROSPECTS

5 THREE CRIPPLES

6 MAGGIE MURPHY

7 HOOSIER BOY

8 MAMMOTH

9 PYRAMID

10 LA BONTE CLAIMS

11 MAGNETITE LOCALITY

12 COPPER KING

13 ORIOLE

14 BRENNING

15 CHROMITE

16 SWEDE BOY

17 MORMON. CANYON

(copper and 

asbestos)

18 SMITH PROSPECT

19 MEWIS PROSPECT

20 HAZENVILLE

X4

Prospect 

(Numberrefers to//st)

SKETCH MAP OF THE NORTH LARAMIE MOUNTAINS, WYO., SHOWING LOCATION OF PRINCIPAL MINERAL PROSPECTS.
MINERAL DEPOSITS. 57

The results of work thus far have been disappointing, and after 

having visited nearly all the principal prospects the writer concludes 

that there is little or no chance that really extensive copper deposits 

will ever be developed. It may be that some small deposits will be 

mined, but even for these the outlook is not very encouraging.

Several occurrences of magnetite were noted, but though some of 

the material is rich in iron, there are no indications that large deposits 

exist.

Chromite occurs in western Converse County but is remote from 

railroad transportation, and the writer's observations indicate that 

the deposit is not of sufficient size to warrant the undertaking of 

mining operations.

Deposits of asbestos in Natrona County, south of Casper, were not 

studied in connection with the present report, as they have been 

described by Diller.1 There has been some prospecting for this 

mineral in western Converse County, but there has been no production, and if workable deposits exist, it is not likely that they will 

have any value, unless efforts to place the more fully developed 

deposits, referred to above, on a profitable industrial basis are 

successful.

Although no mining districts have been organized, the country 

immediately tributary to Esterbrook post office has been called the 

Spring Hill or preferably the North Laramie Peak district; the headwater region of La Prele and La Bonte creeks has been called the 

War Bonnet district, and part of the country drained by Deer Creek 

the Deer Creek district. Mining claims in Converse County must be 

registered in the United States land office at Douglas and those in. 

Albany County at Laramie.

The accompanying sketch map (PI. V) shows the approximate 

locations of the mining prospects that are mentioned in the following 

pages.

NORTH LARAMIE PEAK DISTRICT. 

LOCATION AND GEOLOGY.

Esterbrook post office, near the center of the North Laramie Peak 

district, is about 25 miles south of Douglas and 20 miles west and 

somewhat south of Glendo. The district may be regarded as comprising an area measuring about 15 miles from east to west and 12 

miles from north to south, the northern half lying in Converse County 

and the southern half in the northeast corner of Albany County.

Prospecting for mineral deposits has been carried on principally in 

the eastern part of the district. Here the gravel and sand deposits of«

1 T.".'. t', J. S., The types, modes of occurrence, and important deposits of asbestos in the United States: 

U ; . Geol. Survey Bull. 470, pp. 505-524,1911.
58 NORTH LAEAMIE MOUNTAINS, WYO.

«

the White Kiver formation overlap the crystalline rocks both from 

the north and from the east, but in such a manner as to leave an 

irregular area of the crystalline rocks extending about 7 miles northward from Esterbrook. The general distribution of the crystalline 

and younger rocks is shown on figure 3.

The crystalline rocks comprise dark schists that are usually rich 

in hornblende and locally contain mica, dikes of basic rock intrusive 

in these schists, and granites that are regarded as older than most of 

the basic dikes. The platy structure in the schists, most of the 

granite boundaries, and the dikes strike southwest. Beginning 

about 1£ miles north of Esterbrook, where the wagon road crosses 

Little Horseshoe Creek, there is a belt of country about 2 miles wide 

in which the hornblende schists and accompanying basic dikes are 

not interrupted by any large bodies of granite, but on the northwest 

and the southeast this belt is flanked by areas showing alternating 

bands of granite and schist. Observations in the main area indicate 

that the schists have been derived in large part from a complex set 

of volcanic lavas and tuffs interbedded with some ordinary sediments. That the sediments included limy layers is shown by the 

presence of epidote and garnet in some of the schists. Though some 

of the dikes are not laminated, the minerals of others have yielded 

to pressure, so that it is not everywhere possible to distinguish the 

dike rocks from those which they invade. Outside of the main 

schist area the same difficulty is encountered, and though in the 

wider bands the schists are regarded as forming a matrix for the 

granite, in the narrower ones the dark rock is probably as a rule 

intrusive with respect to the granite.

GENERAL CHARACTER AND OCCURRENCE OF THE MINERAL DEPOSITS.

There has been more prospecting in the older schists than in those 

that are supposed to be metamorphosed dikes, but the latter show 

some mineralization in several localities. Exploration work has consisted mainly in the prospecting of rock masses that are more or less 

thoroughly charged with one or both of the iron sulphides pyrite and 

pyrrhotite, but in several places there are veinlike bodies of quartz 

that carry metallic sulphides. Perhaps as a rule pyrite and pyrrhotite 

are accompanied by some chalcopyrite, though usually the proportion of this copper mineral is small and in places it is not visibly 

present in the sulphide-bearing material. Pyrrhotite deposits 

resembling those found near Esterbrook occur in the Hartville district, in eastern Wyoming, and have been prospected for copper. 

Galena occurs with pyrite and chalcopyrite in the Esterbrook lode 

but was not noted elsewhere.

As a rule the lodes and country rocks are very tight and dense, 

so that they are not readily penetrated by surface waters. In con-
NORTH LARAMIE PEAK DISTRICT. 59

R.7I W.

LOCALITIES

1 Trail Creek

2 Snowbird

3 Saul's camp

4 Maverick

5 Kreisley

6 Tenderfoot

7 Esterbrook

8 Me Ghee

9 Big Five 

10. Three Cripples 

li Maggie Murphy

CONVERSED 

ALBANY1

TIGUBE 3. Geologic sketch map of part of North Laramie Peak district. Areas indicated 

by the rock pattern are mainly granite.
60 NORTH LARAMIE MOUNTAINS, WYO.

sequence the lodes are not deeply weathered, sulphides may appear 

within a few feet of the surface, and there has been very little sulphide 

enrichment. However, in a few places pockets of chalcocite have 

been found near the surface, and green or blue copper carbonates are 

present here and there in the limonite caps. Usually water stands at 

depths less than 60 feet.

The sulphide deposits are tabular bodies or thin lenses that have 

been formed probably through partial replacement of preexisting 

rock. They occur in overlapping arrangement in more or less 

definite belts. The separate bodies and the belts as a whole strike 

southwest, parallel with the structure of the country rocks. So far 

as noted the dips are nearly vertical or to the northwest at rather 

steep angles. A line from Horseshoe Creek canyon northward 

through Esterbrook crosses the schist and granite belts diagonally 

and in a distance of about 9 miles intersects eight or nine fairly distinct 

sulphide belts. Nearly all the prospecting has been done within 

a north-south zone nowhere much more than 2 miles wide. Because 

only parts of this zone were traversed and outlying localities were not 

visited, no general statement can be made concerning the' full extent 

of mineralization along the strike of the several su-lphide belts. 

However, men familiar with the region report that mineralization like 

that in the vicinity of Esterbrook occurs from place to place as far 

southwest as Eagle Peak, which is a prominent landmark situated 

west of Laramie Peak.

MAGGIE MUEPHY BELT.

The muiing claims known as the Maggie Murphy group are about 

3 miles south of Esterbrook, on the north side of Horseshoe Creek. 

The gorge of this stream is here about 700 feet deep, and its course 

is a little north of east. About half a mile farther south is a line of 

high rugged hills composed of coarse reddish granite, and the same 

rock forms the steep but flaring walls of the gorge. North of the 

canyon rim is a terrace or bench where hornblende schists are interlayered with minor masses of granite, arid less than half a mile to the 

north rises another line of prominent granite hills. Here as elsewhere 

in the district the general trend of structural lines is southwest, but 

the strikes are somewhat more easterly than in the country to the 

north.

About 1900 the attention of prospectors was attracted to this 

locality by several outcrops of rusty schist showing small amounts of 

green copper minerals. This material was rightly judged to be the 

oxidized capping of sulphide deposits, and subsequent exploration 

^by means of a shaft revealed the presence of a heavy body of the 

magnetic iron sulphide pyrrhotite. The iron cap is said to have been
NORTH LARAMIE PEAK DISTRICT. 61 i

very shallow. The shaft was sunk to a depth of 107 feet, and several 

minor openings were made, showing that sulphide mineralization 

extends at least half a mile toward the southwest and for some 

distance northeast of the main workings.

In one of the southwestern openings a layer of graphite-pyrrhotite 

schist from 1 to 2 feet thick was found to carry some chalcopyrite. 

Several hundred pounds of rock taken from the shallow shaft may 

have contained 3 or 4 per cent of copper, but samples that show no 

visible chalcopyrite were found by laboratory tests to contain no 

copper. In another opening in the southwestern section massive 

pyrrhotite was found.

The material from the deep shaft is principally schist composed of 

hornblende or hornblende and quartz mixed with pyrrhotite. Some 

of the rock is composed mainly of pyrrhotite, the hornblende and 

quartz being distributed as isolated grains or small bunches. Most 

of the material on the dump contains no visible chalcopyrite. It is 

not difficult to find specimens that contain chalcopyrite in considerable quantity, but apparently it occurs only in rock that contains 

also a greenish feldspar (oligoclase), which is usually rather coarsely 

intercrystallized with quartz. This feldspar-quartz material is 

present in relatively small amounts, and its relation to the mass of 

sulphide is not clear. So far as seen it does not occur in clean-walled 

veins or dikes, still its general appearance suggests that it has been 

injected into the pyrrhotite-bearing rock. Bunches of pyrrhotite that 

are found in it may be inclusions broken from the matrix. The 

chalcopyrite is mainly contemporaneous in crystallization with the 

feldspar and quartz, but it also occurs with the iron carbonate siderite 

in minute veinlets cutting these minerals. Rusty outcrops 300 to 

400 feet southwest of the shaft and pits in limonitic material northeast 

of the shaft indicate that there is here a body of the pyrrhotitic rock 

from 10 to perhaps 40 feet wide and several hundred feet long, but 

the material s~een on the dump does not suggest the presence of any 

valuable body .of copper minerals. A possibility worthy of some 

consideration, however, is that there may be interlayered shoots of 

copper ore in the pyrrhotitic rock. Indications of such shoots might 

be sought by means of surface trenches or by shallow tunnels driven 

across the lode. Deep exploration should not.be undertaken unless 

encouraging results are first obtained by prospecting near the surface.

At the time this property was being prospected several buildings 

were erected which are still in good condition. The wagon road from 

Esterbrook, though now in rather poor shape, could be repaired with 

slight expense.
62 NORTH LARAMIE MOUNTAINS, WYO.

THREE CRIPPLES AND TENDERFOOT BELTS.

Just northwest of the schists of the Maggie Murphy locality is a 

belt about 2,000 feet wide occupied mainly by granite but showing 

also thin layers of dark schist which are regarded as metamorphosed 

diabase dikes. About a mile southeast of Esterbrook prospecting in 

schists belonging to this belt has revealed the presence of disseminated pyrite, but nothing that can be regarded as of practical importance has been discovered.

Beyond the granite belt there is a belt occupied mainly by hornblende schists but containing some intercalated bodies of pink granite 

and locally dikes of white pegmatite. Southwest and west of Esterbrook the full width of this belt is not seen, because here the crystalline rocks are hidden by White River deposits, but to the northeast it 

is nearly a mile wide. Within this belt near Esterbrook and for 3 

miles to the northeast there are many shallow pits showing ferruginous material evidently derived from sulphide-bearing rock, and in 

several places pyrrhotite or pyrite bodies have been found. From a 

rather cursory study it seems that the whole belt may comprise two 

or perhaps three fairly distinct minor belts of sulphide deposits. With 

respect to the possible occurrence of copper deposits, the results of 

prospecting thus far are not regarded as encouraging.

About half a mile south of Esterbrook post office is the Three Cripples shaft, said to have been opened to a depth of 96 feet in 1905. The 

immediate country rock is black schist, but a short distance southeast 

of the shaft there is a contact between this rock and coarse pink granite. The dump shows a large amount of massive pyrrhotite rock in 

every way like that from the Maggie Murphy shaft. A sample 

consisting of 25 chips taken from different parts of the dump was 

analyzed in the chemical laboratory of the Geological Survey by 

R. C. Wells with the following result:

Analysis of Three Cripples pyrrhotite rock.

Insoluble ............."................................... .... 28. 38

Iron......................................................... 41.80

Copper............................................................ .23

Cobalt....................................................... Trace.

Nickel, platinum, 'gold, and silver were not detectable in this 

material.

Here, as at the Maggie Murphy, portions of the rock that carry visible chalcopyrite also contain feldspar-quartz aggregates or bunches 

of quartz. The proportion of such material in the rock that has been 

mined is small. The surface improvements comprise a shaft house 

and a cabin, both in good repair. Part of the machinery has been 

taken away.
NORTH LARAMIE PEAK DISTRICT. 63

Though there are practically no outcrops along the Three Cripples 

lode it is possibly represented by iron caps disclosed in pits about 

1,000 feet southwest and 1,800 feet'northeast of the shaft.

Somewhat to the northwest of the supposed northeastward extension of the Three Cripples lode iron cap has been found in several pits 

whose positions suggest the presence of two other lines of sulphide 

bodies, making three in alt within a band 600 feet wide bounded on 

the southeast by granite. Sulphides have been reached only at a 

shaft known as the Big Five, which is on the northwesternmost of 

these lodes, about 2,500 feet north-northeast of the Three Cripples 

shaft. This opening is probably about 50 feet deep. The material, 

on the dump is mainly pyrrhotite rock, and here again chalcopyrite is 

seen only where bunches of quartz or feldspar and quartz are present.

About 1,200 feet north of the Big Five is an opening known as the 

McGhee shaft. Here there are gray schists more or less thoroughly 

charged with pyrite, but nothing of practical significance was found. 

This deposit may be regarded as belonging to the Three Cripples 

sulphide belt. Probably this belt extends for some distance northeast from the Big Five.shaft, but it was not traced in this direction 

by the writer.

If the Big Five location is taken as being near the axis of the Three 

Cripples belt, the medial line of the Tenderfoot belt (p. 65) lies 1,800 

or 2,000 feet to the northwest. Prospecting at several points along 

this belt has extended from Esterbrook northeastward for about 3 

miles.

At Esterbrook a tabular body of quartz and calcite carrying lead 

carbonate at the outcrop and galena below the surface has been prospected, mainly by the Boston-Wyoming Copper Co. Though but 

poorly exposed the country rock appears to be mainly hornblende 

schist, but the principal outcrops are white pegmatite dikes from a 

few feet to 50 feet wide. Some of these dikes are greatly curved, as 

if they had been injected into contorted schists, but no direct'evidence of structure of this sort was seen.

Along the outcrop siliceous lead carbonate occurs as a nearly vertical layer from a few inches to perhaps 3 feet thick, flanked on the west 

by 1 to 3 feet of finely crystalline calcite. The strike of these layers, 

as seen in a trench 100 feet long, ranges from N. 30° E. near the south 

end to N. 15° E. toward the north. From several workings it is seen 

that the main outcrop is not less than 500 feet long. Toward the 

south the lode appears to fork, and though it is not continuously exposed, what may be the easterly spur is seen in a pit situated nearly 

400 feet from the main shaft on the east side of the wagon road.

There are three shafts on the strike of the lode. The Newell shaft, 

to the north, between two outcrops of white pegmatite, appears not
64 NORTH LARAMIE MOUNTAINS, WYO.

to have disclosed either lead minerals or the calcite layer which has 

been mentioned. About 270 feet south of the Newell shaft is an opening 60 feet deep, now usevd as a well, from which some ore has been 

taken, and 270 feet farther south is the principal shaft, 350 feet deep. 

On the main level at 335 feet drifts are said to have been opened in 

1909 and 1910, 300 feet toward the south and 100 feet toward the 

north.

The material on the main dump consists principally of black schist 

but includes some rock having a massive appearance, which has been 

found by examination with the microscope to be a somewhat altered 

diabase. With the schist and diabase there are considerable amounts 

of calcite rock, and so far as'seen the ore minerals occur only in association with this material. Presumably the relation is generally like 

that at the surface, where the ore layer lies parallel with the calcite 

layer.. Chunks of the calcite rock contain thin layers of dense quartz 

and other layers containing disseminated grains and bunches of 

galena and of chalcopyrite, and at least locally such material appears 

to have formed the immediate wall of the galena streak. It is 

thought that the quartz and the sulphide minerals were deposited in 

partial replacement of the calcite. The course of the main lode corresponds with the strike of the hornblende schists in the neighborhood, but if the vein forks, as is suggested above, one of the spurs 

probably breaks across the country structure.

Though nothing that can be regarded as ore remains on the dump, 

it is reported that shoots of nearly solid galena 6 feet wide were found 

in the mine workings and that shipments of such ore were made. 

As already noted, chalcopyrite occurs in some of the lode stuff, but 

it is not present in any considerable amount. Persons directly concerned in this development were not interviewed, so that no statement can be made concerning the amount of ore that has been taken 

from the mine. However, about 17 tons of carbonate ore shipped 

prior to 1904 is reported to have given the following returns: 1

1 Assay of Esterbrook lead ore.

Silver....................-:.................. .ounces per ton.. 1. 4

Gold..................................................do.... .035

Lead...............................................per cent.. 34. 65,

Iron....................................................do.... 7.00

' Silica.................................................do.... 34. 00

The underground workings of this property were not accessible in 

1914. Although, as shown above, the surface ore is very siliceous, it 

is sufficiently evident from the character of the material on the dump 

that oxidation does not extend to any great depth, and if shoots of 

galena are found this mineral could be readily and cheaply freed from

i Beeler, H. C., The North Laramie Peak copper district, p. 10, Cheyenne, 1904.
NORTH LARAMIE PEAK DISTRICT. 65

associated quartz or calcite. The boilers and hoist are well housed 

and appear to be in good condition.

Somewhat more than half a mile northeast of Esterbrook mining 

explorations were made about 1900 on claims known as the Tenderfoot group. In this section the belt of sulphide deposits is not less 

than 2,000 feet wide, as shown by pits and shafts in bodies of iron 

capping. Near the west side of the belt, about 200 feet west of a line 

of iron-stained croppings, a shaft 150 feet deep was put down, but a 

crosscut directed toward the southeast was abandoned before reaching 

the lode. The lode is probably made up of pyrrhotite.

Beyond the Tenderfoot location several openings were noted in iron 

cap, and doubtless there are others, which were not seen, to prove the 

continuance of this sulphide belt toward the northeast. About a 

mile from the Tenderfoot shaft is the Kreisley group of claims, where 

prospecting during the last two or three years has disclosed large 

bodies of pyrrhotite. Here, as usual, there are several parallel lodes. 

One of them is readily traceable for more than 600 feet and in places 

is certainly not less than 50 feet wide. Material from two shafts 

shows pyrrhotite mixed with hornblende and quartz, and similar 

rock essentially unoxidized crops out in the bed of a small creek.

When this property was visited in August, 1914, the owners were 

unwatering a shaft about 100 feet southeast of the pyrrhotite lode 

mentioned above. Here neither pyrrhotite nor pyrite had been 

encountered at a depth of 60 feet, the material from the shaft being 

yellow to red oxidized schist in which minor bunches and stringers of 

secondary copper minerals were found.

The northwestern edge of the schist zone that comprises the Three 

Cripples and Tenderfoot sulphide belts lies about 2,500 feet from the 

Kreisley workings. Near this edge and north of the Kreisley camp 

another line of pits in red and yellow jaspery iron cap was noted but 

not examined in detail.

MAVERICK PROSPECTS.

Northwest of the belt of schists that passes through Esterbrook 

there is a belt of granite about 2,.000 feet wide, and beyond this lies 

what has been called on page 58 the main body of schists. The 

granite belt contains some schist, but the main schist area is sharply 

defined along a southwest-northeast contact with granite. Close to 

and parallel with this boundary there is a line of prospects about 4,000 

feet long. The Maverick location is at the southwest end of this line 

just north of Little Horseshoe Creek. The type of mineralization 

here is different from that along the sulphide belts that have been 

described. Irregular veins of quartz from 3 to 10 feet wide follow a 

20142° Bull. 626 16 5
66 NORTH LARAMIE MOUNTAINS, WYO.

general line parallel with the strike of the schists and trend from 

N. 45° W. to N. 55° W. There are several narrow dikes of pegmatite, and in one place a quartz vein grades into rock of this sort. On 

the Maverick claim there are two vertical quartz veins, both iron 

stained and rather vuggy, as seen at the surface. One of these veins 

3 to 4 feet wide crops out for a distance of 60 feet. The other vein, 

6 feet wide, lying to the southeast, has been opened by a 50-foot 

shaft. The rock on the dump is quartz containing irregular bunches 

of pyrite. No copper minerals were seen.

About 2,000 feet northeast of the Maverick shaft is a quartz vein 

2 to 10 feet wide that forms a continuation of a pegmatite dike. 

There is no indication that the pegmatite carries pyrite, but the 

quartz is very ferruginous throughout the 300 feet of exposure. 

Along the strike of this .vein 500 and 800 feet to the northeast there 

are pits in light-colored schists that seem to have contained pyrite.

SAUL'S CAMP.

The Maverick line of prospects noted in the preceding paragraphs 

lies along the southeast side of a belt of hornblende rocks nearly 2 

miles wide, which is not broken by any large bodies of granite. 

In the central part of this belt, in the SE. i sec. 22, T. 29 N., R. 72 W. 

(see fig. 3), is Saul's camp, where a group of 29 mining claims was 

located several years ago and surveyed for patent in 1914. Many 

prospect shafts have been opened, and in several of them copper 

minerals were found. The country rocks are mainly hornblende 

schists that the writer believes to be metamorphosed volcanic rocks. 

Locally there are layers that contain epidote or garnet, suggesting 

that the rocks from which the schists were derived contained thin 

beds of limestone. Several dikes of black basic rock like diabase 

cut" the schists, and toward the northwest side of the schist belt 

there are several minor intrusions of granite. The layering in the 

schists strikes in general about N. 45° E., and the intrusive dikes 

trend in the same direction. The principal workings are on the 

Tarsus No. 1 claim, on the southeast slope of a prominent hill and 

the shaft is formed by ledges of black diabasic hornblendite.

A rather inconspicuous outcrop of gossan contained copper carbonate, and'chalcocite was found in the first shaft only a few feet 

below the surface. This shaft was carried to a depth of 60 feet, 

and as the lower part showed nothing of particular promise, at a depth 

of 30 feet a northeast drift was started to follow a streak containing 

copper minerals. About 25 feet from the shaft a mass of chalcocite 

ore was cut. This ore proved to be a saddle-like body forming a 

crest or cap over a chimney of white clay. A raise was opened to 

the surface, and the clay was found to continue 15 feet below the
NORTH LARAMIE PEAK DISTRICT. 67

drift, or to a point about 45 feet from the surface. At that depth 

the first water was encountered, and near the water level small 

amounts of metallic copper were noted. The shaft was carried 

down to 98 feet, and at 85 feet a layer or lens of chalcopyrite-bearing 

rock 12 inches thick was found 12 feet southeast'of the shaft. The 

schist lying between "this lens and the shaft" is reported to carry about 

2 per cent of copper.1

The material on the dump consists mainly of hornblende schist 

but includes a large amount of pyritic rock, portions of which carry 

visible chalcopyrite. No pyrrhotite was noted, but nearly solid 

magnetite occurs as a layer about 8 inches thick. Samples of the 

richer ore have shown as much as 30 per cent of copper and from 

6 to 8 ounces of silver and 0.03 ounce of gold to the ton. About 100 

tons of ore said to carry about 9 per cent of copper was taken out 

during the development work, and most of this ore remains in the 

bins.

About 200 feet northeast of the main shaft limonite carrying small 

amounts of chalcocite and malachite has been opened by a 20-foot 

shaft. Outcrops near by show iron-stained rock containing small 

crystals of epidote.

About 400 feet east of the main shaft an opening 35 feet deep 

shows weathered hornblende schist that is strongly limonitic. In 

this vicinity, mainly toward the southeast, the compass needle is 

greatly disturbed-, and the inference may be drawn that within an 

area perhaps 300 feet wide there are rocks carrying considerable 

amounts of pyrrhotite or of magnetite. Mr. H. C. Saul stated to 

the writer that a zone of magnetic disturbance can be traced for 

1,000 feet or more toward the southeast.

At the 35-foot.shaft two diamond-drill holes were bored. One, 

nearly vertical, is 256 feet deep; the other, inclined about 42° NW., 

is 250 feet on the incline. The cores from these holes show greenish 

schist with here and there a little pyrite or pyrrhotite and some 

minor showings of chalcopyrite. The amount of pyrrhotite contained in the rocks penetrated can not be regarded as sufficient to 

account for the observed deflection of the compass needle in this 

locality, and it is suggested that a body of magnetic iron sulphide 

may be present southeast of the shaft.

The equipment of the property includes a steam boiler, a hoist, 

and a diamond-drill outfit. There is an adequate shaft house and 

several other buildings.

From the foregoing notes it wiH be understood that the prospecting 

at and near the Tarsus shaft is not extensive. The work has been 

done in an intelligent way, and the results at the main shaft may be

i Saul, H. C., Mining operations in the North Laramie Peak mining district, Wyo.: Min. and Eng. World, 

vol. 40, p. 738,1914.
68 NORTH LARAMIE MOUNTAINS, WYO.

regarded as somewhat encouraging. It appears to the writer that 

if additional explorations are made, one of the first steps should be to 

follow the chalcopyrite-bearing layers found in the shaft along their 

strike. Although results of prospecting the deposits of pyrrhotite 

that occur to the south have been discouraging, this can not be urged 

as an adequate reason against undertaking explorations in the zone 

of magnetic disturbance at Saul's camp.

About 2,500 feet from the Tarsus shaft, in a direction slightly north 

of west, a small body of chalcocite ore was found practically at the 

surface. Examination of the pit, which is situated on a high ridge, 

indicates that the ore occurred as a layer striking northeast, but the 

work done is insufficient to give any clear impression of the relations.

In a valley northwest of the locality just mentioned some prospecting has been done along a belt of pyritic hornblende-mica schist. 

Copper minerals are present, but nothing was seen that the writer 

would regard as warranting further development.

Approximately 3,000 feet northwest of the Tarsus shaft is the 

northeastward-striking boundary of the main schist area against 

granites that form a high ridge known as Elkhorn Mountain. (See 

fig. 3, p. 59.) In several places along this boundary for a distance of 

nearly 5,000 feet there are outcrops of dense white or greenish quartz. 

Although locally hidden and perhaps absent in places, this quartz 

appears to be a rather definite layer and where exposed is from 20 to 

130 feet thick. It has not been prospected except at a point due 

west of the Tarsus shaft, where material from an 8-foot pit carries 

small amounts of pyrite and chalcopyrite.

SNOWBIRD GROUP.

The five patented mining claims known as the Snowbird group are 

about 1 mile from Saul's camp (see figs. 3 and 4), on the northwest 

side of Elkhorn Mountain. Granite is the principal country rock in 

this neighborhood, but there are two narrow bands of greenish schist 

that is regarded as sheared diabase, and just to the west is an extensive 

area underlain by partly consolidated sands and gravels belonging 

to the White River formation. The claims, which extend from 

northeast to southwest for a distance of nearly 7,500 feet, were evidently located with the object of covering a body of schist from 60 to 

150 feet wide which is flanked by granite on both sides. Aside from 

shallow pits which show nothing of interest, the development work 

consists of two shafts one, said to be 40. feet deep, and the other, 

80 feet deep, about 2,500 and 3,800 feet, respectively, from the 

northeast end of the property. Northeast of the 40-foot shaft there 

are no bedrock outcrops, but at this place the dark schist appears, 

and a. short distance to the southwest there are exposures of coarse
NORTH LARAM1E PEAK DISTRICT. 69

granite or pegmatite about midway between the sides of the schist 

belt. This pegmatite continues, apparently as a dike from a few feet 

to 15 feet in width, for several hundred feet, but at the 80-foot shaft 

its place is occupied by a strong vein of quartz. The granitic rock 

and the quartz body probably grade one into the other, but the 

exposures are not adequate to prove it. Material from the northeasterly shaft includes pegmatite and vein quartz and considerable

CLAIMS

1 Mikado

2 Gray Eagle

3 Snowbird

4 Morning Star

5 Dawsmere

FIGURE 4. Sketch map of Snowbird group, showing schist bands in granite.

iron-stained dirt. Specular hematite was noted, and there are minor 

showings of copper minerals. As seen -at the surface near the southeasterly or main shaft the quartz vein is not less than 10 feet wide. 

The rock on the dump includes schist and quartz containing chalcopyrite, and small amounts of chalcocite and other secondary copper 

minerals were noted. From a study of the surface it is thought 

that the quartz vein may have a total length of 500 to 600 feet.
70 NORTH LARAMIE MOUNTAINS, WYO.

TRAIL CREEK GROUP.

About 2 miles north of Saul's camp is a group of mineral locations 

known as the Trail Creek claims. These claims cover a group of. 

schist hills lying between two sharp canyons near the head of Trail 

Creek, a tributary of La Bonte Creek. In this vicinity (see figs. 3 

and 5) the crystalline rocks appear in a band hardly more than half 

a mile wide with White River beds on both sides. The Elkhorn 

Mountain mass of granite extends along the southeast side of the 

schists of the Trail Creek group of claims, and the same rock cuts

T. 29 N., R. 71 W., SEC. 10

FIGURE 5. Sketch map of Trail Creek group, showing local geology.

out these schists along their strike toward the southwest and flanks 

them again upon the northwest. Thus the general relations show 

that the schists are intruded by the granite, and this is shown also 

by narrow shoots of the igneous rock that penetrate the schists along 

the southwest side of the area. The invaded rocks are mainly hornblende schists striking southwest, but there are several large and 

many small irregular masses of iron-stained jasper. In one place a 

narrow jaspery .vein carries considerable epidote. Evidences of 

sulphide mineralization are seen at many points where openings 

have been made in weathered iron caps.
NORTH LARAMIE PEAK DISTRICT. 71

The principal workings are a 75-foot,shaft and a tunnel nearly 500 

feet long near the west side of the schist area. The shaft is in coarse 

granite a few feet away from its contact with the schists. Here the 

rock is fractured, and in the breaks malachite and chalcocite occur in 

noteworthy but not large amounts. The level of the tunnel is 8 or 

10 feet above the creek bed and more than 100 feet below the collar 

of the shaft. For the first 30 feet it is in granite, beyond which 

almost completely weathered hornblende schists are exposed. The 

presence of unoxidized remnants in several places and the generally 

ferruginous nature of the weathered material show that the rock was 

all very pyritio. About 75 feet from the tunnel portal a winze was 

sunk 25 feet on a body of ferruginous quartz.which is said to have 

contained small amounts of copper'minerals. Massive quartz from 

the lower part of the winze contains irregular bunches of pyrite, but 

no chalcopyrite was found. In August, 1914, after an unusually dry" 

season, water was standing 10 feet below the tunnel floor. About 

50 feet beyond the winze water was trickling down the sides of the 

tunnel, and here a slight deposition of copper salts was noted. No 

other copper signs were observed in the tunnel, and nothing regarded 

as encouraging was seen on the, dump.

HOOSIER BOY GROUP.

About 1904 some prospecting was done on two groups of mining 

claims, known as the Hoosier Boy and Kentucky Belle properties, 

situated about 10 miles southwest of Esterbrook and 8 miles northwest of Laramie Peak. (See PI. V.) The principal country rock is 

granite, but there are narrow, dikes of schistose diabase which trend 

about N. 70° E., and it is along one of thesee dikes that the six 

Hoosier Boy claims and the two Kentucky Belle claims were located, 

their aggregate length being 12,000 feet. The Hoosier Boy claims lie 

mainly in a high grassy valley at the head of a tributary of La Bonte 

Creek, and the Kentucky Belle claims to the southwest, beyond a 

divide between La Bonte and Horseshoe Creek waters. Systematic 

prospecting, by means of shafts, was done at two points about a mile 

apart. In both places there are quartz veins that have the same 

strike as the dike of schistose rock in which they occur. These veins 

pinch and swell but are continuous or at least recurrent for distances 

of several hundred feet. At a point about 400 feet northeast of the 

Hoosier Boy shaft vein quartz grades into a mixture of quartz and 

feldspar. Some of the material from the shaft, which is said to be 

about 80 feet deep, contains small amounts of chalcopyrite.

The Kentucky Belle shaft is about 40 feet deep. The somewhat 

irregular quartz vein, which has a maximum width of perhaps 2 

feet, carries considerable chalcopyrite* and some chalcocite, the 

latter evidently of secondary origin.
72 NORTH LARAMIE MOUNTAINS, WYO. 

WAR BONNET DISTRICT. 

LOCATION AND GEOLOGY.

The War Bonnet district, bearing the name of a prominent peak 

situated near the southern edge of Converse County, may be regarded 

as comprising the country drained on the north by the headwater 

tributaries of La Prele Creek and the west fork of La Bonte Creek 

and on the south by some of the sources of Sheep. Creek and Little 

Medicine Bow River. The country rock is mainly granite, but, as 

elsewhere throughout the North Laramie Mountains, this rock is 

cut by dikes of diabase, and the invading rocks have been rather 

generally converted into schist. The common trend of these dikes 

is about N. 50° E. In a few places schists were seen which may 

belong to a series of rocks that is older than the granite.

PROSPECTS NORTH OF FORTYMILE RANCH.

The Fortymile ranch, a station on the now abandoned stage road 

from Rock Creek north to Fort Fetterman, is situated near the 

head of West Fork of La Bonte Creek, in sec. 3, T. 27 N., R. 74 W. 

sixth principal meridian. From this.place the stream flows nearly 

north through a rather open valley for about 3 miles and then turning east soon enters a deep and narrow gorge called La Bonte Canyon. 

Near the head of the canyon and also toward the west are dikes 

of diabase along and near which there has been considerable prospecting for copper. The most extensive work was done by incorporated companies known as the Pyramid Copper Co., the La Bonte" 

Mining Co., and the Mammoth Mining & Milling Co. (See -PL V.)

The property of the Pyramid Co. appears to have been taken over 

by the La Bont6 Co., which held adjacent ground and which is said 

to have secured patents to five mining claims. Two lodes or veins 

were explored. One of these, the Pyramid vein, takes its name 

from a column of quartz-seamed granite about 25 feet high known 

as The Pyramid. The vein crops out at the base of this column 

and as exposed for a distance of about 75 feet has a width of about 

20 feet. The vein strikes about N. 53° E. and is nearly vertical. 

Toward the southwest it is covered by gravel deposits in the creek 

valley.

Near The Pyramid is a shaft 30 feet deep, on the dump of which 

lies several tons of rock estimated to carry 5 per cent of copper. 

About 70 feet northeast of this shaft, just within the side valley, 

is the principal shaft, which was equipped with a steam hoist. The 

depth of this shaft may be as much as 100 feet. It was started at 

a point north of the vein, and as the rock on the dump is mainly 

granite the lode was probably not extensively explored. About 300 

feet to the northeast a short tunnel has exposed a quartz body 3
WAR BONNET DISTRICT. 73

feet wide which carries limonite at the outcrop and which is probably the continuation of the Pyramid vein. No attempt was made 

by the writer to trace this lode up the steep hill slope, but perhaps 

half a mile northeast of the Pyramid vein and approximately on its 

strike there are other exposures of quartz that carries copper minerals.

A short distance northwest of the Pyramid prospects hornblende 

schist crosses the side valley mentioned above and, trending northeast, appears as a dikelike body in a steep bluff on the east side of 

the stream about a mile above its mouth. Beyond the bluff the 

schist forms a prominent ridge, along which prospect pits have 

disclosed recurring lenses of quartz constituting an interrupted vein. 

Some of the quartz carries copper minerals. In order to prospect 

this ground a crosscut was opened from a point perhaps 250 feet 

below the crest of the schist ridge. The first granite and schist 

contact was cut 615 feet from the portal, and the far contact at 790 

feet, showing the dike to be 175 feet wide. No considerable bodies 

of quartz were found in the crosscut, and a drift 200 feet to the 

northeast, 70 feet beyond the northwest wall, shows nothing but 

schist. Some of the rock on the dump contains disseminated pyrite, 

but copper minerals were not noted. This schist band was followed 

by the writer toward the northeast for more than a mile and is said 

to be traceable for several miles. It has been prospected at points 

approximately 1 and 2 miles northeast of The Pyramid.

About a mile southwest of The Pyramid a schist dike approximately on the strike of the one mentioned above has been prospected 

by a tunnel situated near the wagon road in the valley of the main 

creek.

The Mammoth vein is a body of dense quartz 50 feet or more in 

width which is traceable by scattered outcrops along a northeastcourse for a distance of perhaps 2,000 feet. This vein lies northwest 

of the tunnel referred to in the preceding paragraph. (See PI. V.) 

Its outcrops.are not generally rusty, but a single shaft has disclosed 

iron-stained material, showing that sulphide minerals are locally 

present.

About a mile northwest of the schist dike that traverses the La 

Bonte" group there is another dike pf the same sort of rock along 

which prospecting has been done at intervals for a distance of fully 

2 miles. From place to place the schist forms the matrix of quartz 

bodies that conform with its northeast strike. Where work has been 

done pyrite is usually found, and( in a few places copper minerals 

are present. It is said that 12 or 15 years ago rich gold ore was 

found in quartz occurring in this body of schist, on a claim situated 

a short distance beyond the La Bonte-Sheep Creek divide. This 

find led to nothing of value, though it is reported that the property 

was examined by men familiar with gold mining in South Dakota.
74 NORTH LARAMIE MOUNTAINS, WYO.

COPPER KING BELT.

About 30 miles southwest of Douglas, on a small tributary, of 

La Prele Creek called Crazy Horse Creek, a quartz mass carrying 

chalcopyrite was systematically prospected at various times between 

1902 and 1906 by the Douglas Mining & Milling Co. This company 

held five claims, including the Copper King, where most of the 

work was done, and other interests located and prospected claims 

in the neighborhood, mainly along the supposed extension of the 

Copper King lode.

The general country rock is granite, but the quartz vein occurs 

in one of the diabase dikes that are characteristic of the region. 

This and other dikes in the vicinity trend between N. 30° E. and 

N. 40° E. Some of them are readily traceable for a mile or more, 

and probably detailed study would show much greater continuity 

than could be made out from the writer's hurried observations. 

The Copper King claim lies within a northeast-southwest zone a few 

hundred feet wide along which vein fillings and other indications 

of mineral deposition were noted by the writer from place to place 

throughout a distance of 6 miles and which is said to have been 

followed and prospected for an additional distance of 10 miles toward 

the southwest.

About 2£ miles southwest of Crazy Horse Creek two schist bands 

separated by about 250 feet of granite were noted. The average 

width of these bands is perhaps 80 or 100 feet. From place to place 

along them quartz may be seen, and in several prospect pits quartz 

occurring in narrow seams carries magnetite. In one place magnetite 

and a little chalcopyrite were noted.

About 2 miles southwest of the Copper King claim there is a small 

deposit of nearly clean massive magnetite. The outcrop is hidden, 

but an area nearly 100 feet square is covered by bowlders of iron ore, 

some of which measure 2 by 3 by 3 feet. From the appearance of 

these bowlders they may be supposed to have come from a layer at 

least 2 feet thick. The small area covered by the float suggests that 

the deposit has the form of a lens. The magnetite is accompanied 

by a little quartz. Exposures near by show a band of green diabase 

schist about 80 feet wide, flanked by coarse granite. The magnetite 

layer probably occurs in the schist.

About three-fourths of a mile southwest of Crazy Horse Creek a 

2-foot layer of magnetite schist was noted in a 10-foot prospect pit.

At several places both southwest and northeast of the Copper King 

claim prospectors have disclosed small bodies of quartz, but it occurs 

characteristically in stringers or in separated bunches rather than as 

continuous veins. There are signs of copper in different places outside of the Copper King claim, but nothing was seen upon which a 

prudent miner would spend time or money.
WAR BONNET DISTRICT. 75

On the Copper King claim a shaft about 30 feet deep was opened in 

a large body of quartz carrying oxidized copper minerals in abundance 

at a depth of a few feet. A study of the surface shows that the 

quartz occurs as a series of lenticular bodies lying in schist near the 

southeast contact of a large horse of granite. Together these lenses 

form an interrupted vein that can be recognized for nearly 300 feet 

and may actually have a greater length. The discovery shaft is on a 

hill slope possibly 175 feet above the creek bottom. The development 

work consists of two tunnels, each said to be about 600 feet long.

The level of the upper tunnel is about 75 feet below the outcrop. 

Following the same general course as the dike, this tunnel cuts a narrow quartz vein about 140 feet from the portal. The vein gradually 

widens to 6 feet, then pinches and widens again to 12 feet, all in a 

distance of about 100 feet. Where the vein has its greatest width it 

contains a large proportion of chalcopyrite. This ore shoot is probably the same as the one opened at the discovery shaft. Near the 

portal of the tunnel a crosscut to the northwest reached the schist 

and granite contact, but no vein was found. A lot of perhaps 50 tons 

of ore was taken from the tunnel and from a winze 12 feet deep. Ore 

remaining on the dump is estimated to carry more than 15 per cent 

of copper, and it is reported that assays have showed as much as 0.35 

ounce of gold to the ton. The tunnel was not accessible beyond the 

winze.

The portal of the lower tunnel is about 100 feet below that of the 

other and only a few feet above the creek. These workings were not 

accessible in 1914. The material on the dump consists almost entirely of dark-green schist but contains some vein matter consisting of 

quartz and siderite carrying a little feldspar. Vein stuff of this sort 

which carries small amounts of chalcopyrite is said to have come 

from the farther part of the tunnel.

Although the writer can form no satisfactory judgment concerning 

the possibilities of .the deposit, he is of the opinion that the known ore 

shoot is worthy of being more fully prospected. A plan of the workings and a cross section through the shaft and the winze in the upper 

tunnel would aid in laying out future work, by indicating the position 

of the lower tunnel with reference to the probable position of the vein 

as projected downward from the winze in the upper tunnel. If the 

indicated position would carry it over the lower tunnel the vein 

should be sought by raising or by crosscutting to the northwest, 

whereas if the indicated position is to the southeast the vein should 

be sought by a crosscut in that direction.

ORIOLE BELT.

In the valley of upper La Prele Creek (see PI. V), approximately 1 

mile northwest of the Copper King line of prospects, is a parallel mineralized belt along which old workings were noted for a mile or more.
76 NORTH LARAMIE MOUNTAINS, WYO.

Here again diabase schist occurs in a granite country rock, and the 

general relations are similar to those along the Copper King belt. 

The only serious prospecting here was done about 10 years ago on 

the Oriole claim. On this claim a body of dense quartz from 20 to 30 

feet wide crops out at intervals for nearly 1,000 feet along the edge of 

a steep bluff on the northwest side of La Prele Creek. The vein dips 

steeply toward the creek, and a few exposures are adequate to show 

that it has black or green schist on both sides. The development consists of two shallow shafts about 800 feet apart, both showing small 

amounts of copper minerals, and workings said to be 250 feet deep, 

about 300 feet southwest of the northeasterly opening. In the vertical shaft copper-bearing material is said to have been found only a 

few feet from the surface and to have continued to a depth of 175 

feet, where the shaft passed out of the vein into the footwall. Next 

to this wall there was about 8 feet of rock that carried considerably 

more than the average amount of copper. No drifts were opened, 

but it is reported that the vein was crosscut at the 175-foot level and 

that another crosscut was started from a point 240 feet deep. In the 

upper crosscut, which is supposed to have reached the hanging wall 

of the vein, a flow of water was encountered which was too great for 

the capacity of the pump provided for sinking. The workings were 

thus flooded, and the operations have never been resumed.

Although it is apparent that the Oriole vein was not adequately 

prospected, the advisability of further exploration is open to question. 

Favorable to the property is the fact that several hundred tons of 

rock which may carry as much as 3 per cent of copper was taken out 

during the development work already done. On the other hand, the 

character of the vein stuff as seen in several exposures suggests that 

the vein does not carry copper minerals throughout. The only 

project that the writer would regard as at all promising would be 

the exploration of the footwall ore shoot that was cut by the shaft. 

This search might be made by means of a crosscut above the water 

level, followed by drifts along the footwall.

The Oriole property comprises several good houses. It is accessible by a good wagon road either from the north or from the south.

BRENNING COPPER PEOSPECT.

The cross-mountain road by way of the upper valley of La Prele 

Creek passes the Oriole claim, crosses the divide at an elevation of 

about 8,000 feet, and by a choice of routes gives access to all adjacent 

parts of the high plains along the north side of Laramie Basin. About 

4 miles west of the pass and just south of the Converse-Albany county 

line prospecting has been done on the Brenning claim. (See PI. V.) 

The workings.consist of two shafts in which large pieces of massive
DEER CREEK DISTRICT. 77

chalcocite have been found. There are very few rock outcrops in 

the vicinity, but at the prospect hornblende schists are exposed. 

The chalcocite or copper glance is associated with bright-green, fairly 

well crystallized epidote. The epidote is present in large amounts, 

but the relation of the occurrence to the hornblende schist was not 

determined.

Similar epidote rock carrying rich copper ore is reported to occur 

at the Olin prospect, in the mountains at the head of Boxelder Creek, 

4 or 5 miles north of the Brenning claim.

PERRY CLAIMS.

About 2 miles northwest of the Brenning prospect is a group of 

eight mining claims, here called the Perry group after one of the 

owners. These claims are arranged end to end and consequently 

they cover a strip of ground 12,000 feet long. The middle of the 

group is near the northeast corner of sec. 33, T. 29 N., R. 76 W. 

The country rock is mainly granite, but schistose dikes are present. 

The work done has disclosed several small veinlike bodies of quartz 

but no workable metalliferous deposits.

DEER CHEEK DISTRICT. 

LOCATION AND GEOLOGY.

Though the Deer Creek district is undefined it may be regarded as 

comprising the country between Boxelder Creek and the western 

boundary of Converse County. It is adjoined on the west by the 

Smith Creek asbestos district, in Natrona County.

The geology of the Deer Creek district appears from a cursory 

examination to be somewhat more complex than that of the War 

Bonnet district. Schists are present in greater abundance, and the 

granite intrusions are more irregular. Serpentine, which was not 

noted farther east, here occurs in many places.

SWEDE BOY VEIN.

The mining claim known as the Swede Boy is situated between 

Boxelder and Deer creeks about 16 miles south of Glenrock and 

somewhat less than 4 miles southwest of Boxelder post office. (See 

PI. V.) Here a well-defined quartz vein in granite has been opened 

by an inclined shaft, and some copper ore is said to have been shipped. 

From the size of the dump it seems that the workings may aggregate 

200 feet. Near the shaft tl\e vein does not actually crop out, but 

from the alignment of several openings its course appears to be about 

N. 5° W. At the shaft mouth the vein is about 6 feet thick and its 

apparent dip is about 60° E. North of the main shaft and for 400
78 NORTH LARAMIE MOUNTAINS, WYO.

feet to the south the ground is covered by debris from near-by hills, 

but farther south float appears, and at minor shafts, 600 and 800 feet 

distant from the main workings, the vein is not less than 4 feet thick 

and shows the same easterly dip. Rock from all the openings shows 

some copper, but there is much barren quartz on the dumps, especially 

at the south workings.

Since the last work was done, about three years ago, the shaft'"House" 

and mining plant have been destroyed by fire.

CHROMITE IN DEER CREEK CANYON.

About 16 miles southwest of Glenrock and 13 miles due south of 

Big Muddy (see PL V), there is a deposit of chromite from which 

several lots of ore have been shipped. The locality is on the west 

side of Deer Creek about 400 feet above the bottom of the steepwalled canyon, here about 1,000 feet deep. This district is one 

characterized by hornblende schists, coarse granites, and scattered 

masses of serpentine. The chromite is associated with a small 

serpentine body. It is said that there are several separate masses of 

the ore, but this the writer did not observe, as because of the steepness of the slope he was able to examine only the upper or western 

edge of the serpentine area. Along this edge the serpentine is flanked 

by schist, the wall striking nearly north 'and dipping steeply to the. 

east. Near the wall and in a general way parallel with it is a layer of 

ore, which, as shown by a series of pits, has a thickness of 2 to 5 feet 

and seems to be continuous for a distance of perhaps 150 feet. The 

ore is dense and fine grained, the chromite being rather evenly intermixed with a scaly silicate mineral that is probably talc. Near the 

principal chrome-ore pit a layer of gray talc rock has been exposed. 

Analyses of the ore are here given through the courtesy of Mr. E. W. 

Merritt, president of the Chromium Mines Co., and of Mr. J. S. Diller, 

in charge of chromite statistics for the United States Geological 

Survey.

Analyses of chrome ore from Deer Creek.

Silica ...........................................................................

1

42.36

17.16

12.67

1 79

2 '

35. 16

20.29

11.20

1.68

Vi 19

8.64

3

44.81

20.87

3 7

1,2, Samples sent to Illinois Steel Co.; 3, concentrates furnished by Colorado Fuel & Iron Co.

Carload lots of the Deer Creek ore are reported to have carried 35 

per cent of chromic oxide. The freight rate on ore of this class from 

Glenrock to Chicago is stated by Mr. Merritt to be $4 a ton.
LA PBELE DISTRICT. 79 

ASBESTOS PROSPECTS EAST OF DEER CREEK.

For several years there has been considerable interest in the 

development of asbestos deposits on the Casper Range, 8 miles 

south, and on Smith Creek, 20 miles south of Casper. These districts 

lie west of Deer Creek. 1 The Smith Creek area extends across 

Deer Creek, where serpentine rocks are irregularly distributed in 

masses of small or moderate size over a northeastward-trending area 

about 8 miles long and 4 miles wide. Although the serpentine areas 

have been prospected and asbestos has been found in several places, 

such explorations as were visited are thought to offer little promise. 

Further developments are not likely to be undertaken until the 

Smith Creek and Casper Mountain enterprises have been put on a 

basis of profitable operation.

MORMON CANYON PROSPECTS.

Asbestos and copper locations made by C. J. Wells and associates 

in Mormon Canyon, at the head of Dry Creek, about 8 miles south 

of Glenrock, were under development during the summer of 1914. 

The locality was visited during the temporary absence of Mr. Wells, 

and the writer was not successful in an attempt to find the copper 

locations. Samples of the ore that were seen at Douglas show 

chalcocite and chalcopyrite in white quartz and resemble ore from 

the Copper King mine.

MARTIN SMITH COPPER PROSPECT.

- A mining claim known as the Martin Smith is about 9 miles due 

south of Glenrotfk (see PI. V), in a narrow canyon near the head of 

a tributary of Hunton Creek. The rocks in the vicinity are hornblende schist, granite, and serpentine. At a point about 100 feet 

above the bottom of the canyon copper carbonate was discovered. 

A shaft about 30 feet deep was sunk, and though nothing of practical 

significance was disclosed a tunnel was run through hornblende 

schist to a point approximately under the shaft.

LA PKELE DISTRICT. 

LOCATION AND GEOLOGY.

The section here called the La Prele district is named for convenience to include mining prospects in the vicinity of the La Prele 

reservoir, which lies about 12 miles southwest of Douglas. The 

region is one in which hornblende schists are rather more abundant

1 Diller, J. S., The types, modes of occurrence, and important deposits of asbestos in the United States: 

U. S. Geol. Survey Bull. 470, pp. 512-516,1911.
80 NORTH LAEAMIE MOUNTAINS, WYO.

than granite. In general it is limited on the north by the Paleozoic 

sedimentary formations, though locally these are overlapped by the 

Tertiary White River beds. Prospecting has been done in several 

places, but only two localities were visited.

COPPER PROSPECTS ON COTTONWOOD CREEK.

A group of mining claims 8 miles due south of Careyhurst station, 

formerly known as the Spring Canyon or Devoe group, is now called

FIGURE 6. Sketch map of Mewis property, showing location of claims and local geology.

the Mewis property. (See PI. V.) A plat of these claims made available through the courtesy of Mr. Mewis, of Douglas, shows the principal geologic features of the locality (fig. 6).

The Carboniferous Casper formation here overlaps the pre-Cambrian rocks and is so tilted that its beds dip north-northeast. Immediately overlying black and green schists is a bed of sandstone 

from 20 to 40 feet thick, and above this are layers of massive limestone. These beds are broken by a strong fault that trends almost 

directly across their strike and has essentially the same course as the
LA PBELE DISTRICT. 81

channel of Cottonwood Creek beyond the mountain front. The vertical displacement along this fault is probably more than 100 feet, 

and the downthrown block is on the east. Because of the northerly 

dip of the stratified rocks and the manner in which they have been, 

eroded the horizontal offset of the basal sandstone member is about 

800 feet. The sandstone is so indurated that it is properly called 

quartzite. Away from the fault it is nearly white, but as the break 

is approached from the east the quartzite takes on a deep-red color. 

This color change is accompanied by a markedly greater induration, 

and next to the fault the rock presents a vitreous appearance. The 

ore mined, which contained carbonate minerals and chalcocite, came 

from shallow workings that extend at least 50 feet away from the 

fault break, though the fault can not be accurately located at this 

place. From a point west of the fault and about 60 feet below the 

level of the surface workings a tunnel was run in with the evident 

intention of getting beneath the ore, but apparently it did not lead 

to the discovery of anything of value.

This occurrence of copper is to be distinguished from all that have 

been described on foregoing pages in that the metalliferous minerals 

are here segregated in sandstone of Carboniferous age, whereas not 

only are most of the other deposits in pre-Cambrian rocks, but their 

nature is such that they can only be regarded as having been formed 

in pre-Cambrian time. Copper deposits occur in the Hartville district, in eastern Wyoming,1 in limestones that correspond in age with 

the Casper formation.

The influence of the fault in localizing the segregation is obvious. 

If further prospecting is done, the writer's suggestion would be that 

the quartzite bed is probably the most favorable place for ore. A 

tunnel driven in a southwesterly direction from a point in the canyon near the big bend would strike the fault, and by following this 

break to the south the northward-dipping quartzite would be encountered. . The limestone near the fault would be partly explored 

by the tunnel, and if ore were to be found in the quartzite an extension of the tunnel would show whether the fissure is mineralized 

below the point where it is met by the quartzite layer.

HAZENVILLE PROSPECTS.

About 1900 some widely advertised prospecting was in progress 

about 2 miles east of the present La Prele reservoir, at a locality still 

known as Hazenville. The work, consisting of the opening of a 

shaft and a tunnel, was undertaken because of a small copper-bearing 

quartz vein occurring in black schist.

i Smith, W. S. T., U. S. Geol. Survey Geol. Atlas, Hartville folio (No. 91), 1903. 

20142° Bull. 626 16 6

INDEX.

A. Page.

Agriculture in the North Laramie Mountains . 49 

Arsenopyrite, occurrence of, in the Atlantic

district....................... 21-22,32

Asbestos, occurrence of, in the Atlantic district............................. 18-19

occurrence of , in the North Laramie Mountains............................ 57,79

Atlantic City , mining operations at .......... 24

Atlantic gold district, map of, showing part

of gold placers. . ................. 42

map of, showing part of mining claims. . . 22 

map of, showing principal geologic features............................ 12

situation of.............................. 9-11

B.

Babette placer workings, operation of ........ 42-43

Beck Mining Co., hydroelectric project of. ... 38-39

Benton shale, distribution and character of,

in the North Laramie Mountains. 55 

Brenning copper prospect, description of. ... 76-77

Buckeye State mine, operation of ............ 26

C.

Carissa dike, position of ...................... 21

Carissa lode, discovery of .................... 24

Carissa mine, operation of ................... 26

Casper formation, distribution and character 

of, in the North Laramie Mountains. ........................... 53-54

Chalcocite, occurrence of, in the Deer Creek

district .......................... 79

occurrence of , in the La Prele district .... 81

in the North Laramie Peak district.. 60,

66,67,68,69,71

in the War Bonnet district .......... 77

Chalcopyrite, occurrence of, in the Atlantic

district .......................... 32

occurrence of, in the Deer Creek district. . 79

in the North Laramie Peak district.. 58,

61,62,63,64,67,68,69,71

in the War Bonnet district .......... 74, 75

Christina Lake, water from. ................. 25, 38

Christina Lake Co., operations of ............ 44

Chromite, analyses of.. ...................... 78

indications of, in the North Laramie

Mountains. . ...... 4 .............. 57

occurrence of , in Deer Creek canyon ..... 78

Chugwater formation, distribution and character of, in the North Laramie 

Mountains....................... 54

Clay, White Eiver , occurrence of ............ 23

Cloverly sandstone, distribution and character of, in the North Laramie 

Mountains....................... 55

Coal, cost of, in the Atlantic district. ........ 36

Copper, indications of, in the Deer Creek district.......................... 77,78,79

indications of, in the La Prele district.... 81

in the North Laramie Mountains.... 57,

60,65,66,67,68,69,71

in the War Bonnet district.. 72,73,74,76,77 

See also Chalcocite. 

Copper King claims, description of........... 74-75

Cottonwood Creek, copper prospects on...... 80-81

D.

Barton, N. H., on sedimentary rocks in the

North Laramie Mountains....... 53-56

Deer Creek district, location and geology of.. 77 

prospects in............................. 77-79

Development in the Atlantic district, proper 

method of................................. 34-35

Dexter Mining & Milling Co., operations of.. 25 

Diller, J. S., acknowledgment to............. 78

Diorite dikes, distribution and character of,

in the Atlantic district........... 19-21

Douglas Mining & Milling Co., operations of.. 74 

Drainage in the North Laramie Mountains.. 48 

Duncan dike, position of..................... 21

Duncan mine, operation of.................. 26-27

Duncan stamp mill, process used in......... 41-42

Electric power, possibilities of, in the Atlantic

district.......................... 38-39

Esterbrook, location of...................... 57

Folds near Atlantic City..................... 16

Forelle (?) limestone, distribution and character of, in the North Laramie 

Mountains....................... 54

Galena, occurrence of, in the Atlantic district. 32 

occurrence of, in the North Laramie Peak

district....................... 58,63,64

Garfleld mine, operation of.................. 26

Geology of the Atlantic gold district......... 14-23

Geology of the Wind River Range and vicinity ........................... 12-14

Gold, content of, in ores of the Atlantic district ............................ 32-33

discoveries of, in the North Laramie

Mountains...................... 56

occurrence of, in the Atlantic district.... 22

in the North Laramie Peak district.. 67 

in the War Bonnet district.......... 73,75

placer deposits of, in the Atlantic district. 23-

24, 42-45 

production of, in the Atlantic district.... 27-28

83
84 INDEX.

Gold Dollar dike, position of................ 20

Gold mining, history of, in the Sweetwater

district ......................... 23-27

Granier, Emile, on the ditches constructed

by him.......................... 44

Granite, minor intrusions of................. 22

H.

Hazenville prospect, description of.......... 81

Hematite, occurrence of, in the North Laramie Peak district................ 69

Hoosier Boy claims, description of........... 71

I.

Intrusive rocks, distribution and character of. 19-22 

Iron, indications of, in the North Laramie

Mountains...................... 57,67

Iron-bearing rock in the Atlantic district,

economic value of............... 17-18

Iron cap, occurrence of, in the North Laramie

Peak district........... 60,63,64,65,70

J.

Jamison, C. E., on the operations of the X. L.

DredgingCo..................... 43

K,

Kentucky Belle claims, description of....... 71

Knight, W. C., acknowledgment to.......... 9

on gold mining and milling in the Atlantic district.......... 24-25,29,39-41,44

L.

La Prele district, location and geology of..... 79-80

prospects in............................. 80-81

Laramie Peak, elevation of.................. 48

Lead, carbonate of, occurrence of, in the

North Laramie Peak district.... 63

Lewiston, mining operations at.............. 24-25

1/imonite, occurrence of, in the Atlantic district ............................ 32

Little Popo Agio River, hydroelectric project

on .............................. 38-39

M. 

Maggie Murphy claims, description of....... 60-61

Magnetite, occurrence of, in the North Laramie Mountains.................. 57,67

occurrence of, in the War Bonnet district. 74 

Magnetite schists, distribution and character

of, in the Atlantic district....... 16-17

Malachite, occurrence of, in the North Laramie Peak district................ 67,71

Mammoth vein, situation of................. 73

Martin Smith copper prospect, description of. 79 

Mary Ellen mine, operation of............... 26

Maverick prospects, description of........... 65-66

Mecum, W. F., acknowledgment to.......... 47

Merritt, E. W., acknowledgment to.......... 78

Mewis .claims, description of................. 80-81

Milling, results of, in the Atlantic district... 39-42 

Mineralization of rock masses in the Atlantic

district ......................... 31-32

Miners Delight, mining operations at........ 24,25

Miners Delight mine, operation of........... 26

Mormon Canyon prospects, description of.... .79

Page,

Morrison formation, distribution and character of, in the North Laramie 

Mountains...................... 55

N.

Niobrara shale, distribution and character of,

in the North Laramie Mountains. 56 

North Laramie Mountains, geography of.... 47-50

geologic map of......................... 52

map of, showing principal mineral prospects............................ 56

North Laramie Peak district, location and

geology of....................... 57-58

mineral deposits in...................... 58-60

O.

Oil, cost of, in the Atlantic district.......... 36

0 il from Dallas field, analyses of............ 37

Oriole claims, description of.. '. .............. 75-76

P. 

Peanut rock, occurrence of.................. 15,20

Perry claims, description of................. 77

Porphyry dikes, distribution and character

of, in the Atlantic district....... 21-22

Power, sources of, in the Atlantic district.... 36-39

Pre-Cambrian rocks in the North Laramie

Mountains....................... 52-53

Precipitation in the North Laramie Mountains............................ 48

Pyramid vein, situation of................... 72

Pyrite, occurrence of, in the Atlantic district 32 

occurrence of, in the North Laramie Peak

district.............. 58,62,63,66,68,71

in the War Bonnet district.......... 73

Pyrrhotite, occurrence of, in the Atlantic district. ............................ 21,32

occurrence of, in the North Laramie Peak

district........... 58,60,61,62,63,65,67

R. 

Ransome, F. L., preface by.................. 7

Raymond, R. W., on the veins of the Atlantic

district.......................... 29-30

Red Canyon, placer deposits on.............. 45

Rock Creek, placer mining on............. '... 43-44

water power from....................... 38

S.

St. Louis dike, position of................... 21

Sandstone, Cambrian, inliers of.............. 23

Satanka (?) shale, distribution and character 

of, in the North Laramie Mountains. ........................... 54

Saul's camp claims, description of........... 66-68

Schists, distribution and character of........ 14-18

Scorodite, occurrence of...................... 32

Sedimentary rocks in the North Laramie

Mountains....................... 53-56

Serpentine, occurrence of, in the Atlantic district............................. 18-19

occurrence of, in the Deer Creek district. 77,78,79 

Siderite, occurrence of, in the War Bonnet

district.......................... 75

Silver, occurrence of, in the North Laramie

Peak district.................... 67
INDEX. 85

Page. 

Smith Gulch, placer mining on.............. 43

Snowbird claims, description of.............. 68-69

South Pass City, mining operations at....... 24

Stamp mills, erection of..................... 24

Stratigraphy and structure of the North LaramieMountains.................. 50-51

Sundance formation, distribution and characacter of in the North Laramie 

Mountains....................... 54-55

Swede Boy vein, description of.............. 77-78

Sweetwater River, placer deposit on......... 45

T.

Tenderfoot claims, description of............ 65

Three Cripples claims, description of......... 62-65

Timba Bah Mining Co., formation of........ 25

water rights of........................... 38

Timber in the North Laramie Mountains.... 49-50

Tourmaline, occurrence of, in the Atlantic

district.......................... 32

Trail Creek claims, description of............ 70-71

Transportation, outlook for, in the Atlantic

distriet.......................... 35-36

Page. 

Transportation, outlook for, in the North

Laramie Mountains............. 50

Trumbull, L. W., acknowledgment to....... 9

on the veins of the Atlantic district...... 29

V.

Veins in the Atlantic district, classes of...... 30-32

in the Atlantic district, minerals in...... 32

persistence, of........................ 33-34

previous descriptions of.............. 28-30

W. 

War Bonnet district, location and geology of 72 

prospects in............................. 72-77

White River formation, distribution and 

character of, in the North l,aramie Mountains.................. 56

remnants of, in the Atlantic district..... 23

Wood, cost of, in the Atlantic gold district... 36 

Wyoming Copper Co., operations of.......... 27

X.

X. L. Dredging Co., operations of............ 27,43

o