DEPARTMENT OF THE INTERIOR

Hubert Work, Secretary

U. S. GEOLOGICAL SURVEY 

George Otls Smith, Director

Bulletin 774

THE COPPER DEPOSITS NEAR SALMON, IDAHO

BY

CLYDE P. ROSS

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1925
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CONTENTS

Page

Introduction _____________________________________________________ 1

Scope of the report. _ __________________________________________ 1

Location of the deposits _______________________________________ 1

Means of access ______________________________________'_____-_ 2

Acknowledgments ___________________________________1__-__-__ 2

Historical sketch______________________________________________ 2

Topography.______________________________________________________ 4

Stratigraphy and petrology ________________________________________ 5

Metamorphicrocks ___________________________________________ 5

Paleozoic rocks _______________________________________________ 8

Granitic rocks________________________________________________ 9

Tertiary lava.________________________________________________ 9

"Lake beds" ________________________________________________ 10

Quaternary deposits___________________________________________ 11

Structure _______________________________________________________ . 11

The copper dep6sits____________-__---_____--________-______-______ 15

General character.___________________________________________^ 15

Structural relations ___________________________________________ 16

Ore shoots ___________________________________________________ 20

Hypogene mineralization _______________________________________ 22

Oxidation and enrichment _____________________________________ 25

Age and genesis ____________________ _______________________ 26

Outcrops ____________________________________________________ 27

Operating conditions and future of copper mining.________________ 29

Mines and prospects ______________________________________________ 30

Dishman prospect ____________________________________________ 31

Tormey mine _________________________________________________ 32

Pope-Shenon mine ____________________________________________ 34

Porterfield prospect ___________________________________________ 37

Harmony mine __________________ _________________ ______ 37

Prospects on McDevitt Creek __________________________________ 41

Prospects on Hayden Creek ____________________________________ 42

Silverton prospect.___ ____ _________________________________ 43

Index ______________-_________-_-__-----_---__---_ ____________ 44

in
ILLUSTRATIONS

PLATE I. Geologic sketch map of parts of the Eureka and McDevitt mining

districts, Lemhi County, Idaho.__________________ 8

II. A, Perreau Creek near the Tormey mine, Salmon River Mountains; B, Salmon River Mountains near Baldy Mountain.__ 14

III. A, Precipitous contact between metamorphic rock and Tertiary 

lava on Withington Creek below the Harmony mine; B, 

North end of Lemhi Range____________________________ 15

IV. Plan and vertical section of Pope-Shenon mine.______________ 36

V. Sketch map showing relations of lodes on property of Harmony

Mines Co ________________________________ 38

FIGURE 1. Index map of Idaho showing location of the area covered-,.- 3

2. Sketch map of part of Lemhi County, showing the locations of

known copper deposits________________.._______________ 15

3. Diagram showing strikes of copper deposits in Lemhi County. 17

4. Diagram showing strikes of ore deposits other than copper

deposits in Lemhi County______________-____-______^__ 18

5. Geologic sketch map of Greenhorn tunnel, Tormey mine_____ 33

6. Geologic sketch map of Rattlesnake tunnel, Tormey mine____ 34

7. Block diagram showing relation of ore shoot in Harmony mine

to Contention and Leapyear lodes______________________ 39

IV
/ THE COPPER IDEPOSITS NEAR SALMONS IDAHO

By CLYDE P. Ross

INTRODUCTION 

SCOPE OF THE REPORT

This report is the result of field work during 12 days in August 

and September, 1923. The investigation was made in cooperation with the Idaho Bureau of Mines and Geology. The copper 

deposits described lie in an area of about 350 square miles in the 

southern part of the Eureka mining district and the western part of 

the McDevitt district. They are described in some detail, and an outline of the general geology of the area is given. The geologic map 

(PI. I) was prepared by sketching on copies of .township plats of the 

General Land Office and is accurate only in a broad way, not in detail. 

The work was occasioned by the advances made in the development 

of the copper deposits since Umpleby 1 made his report on the ore 

deposits of Lemhi County. When he visited the region little work 

had yet been done on any of the copper deposits. Since then small 

amounts of ore have been shipped from several of them, and at the 

time of visit in 1923 there was more activity in the copper mines 

than in any of the other mines in the county, with the exception of 

the work being done at the old Yellow Jacket gold mine preliminary 

to reopening it.

LOCATION OF THE DEPOSITS

The area mapped geologically on Plate I comprises T. 21 N., Rs. 

21, 22, and 23 E.; T. 20 N., Rs. 21, 22, and 23 E.; T. 19 N., R. 23 E.; 

T. 18 N., R. 23 E.; and parts of some of the contiguous townships 

and includes all the copper deposits at which work has been done in 

recent years. The area lies on both sides of Salmon River in the 

central part of Lemhi County, near the middle of the east boundary 

of Idaho, as is shown in Figure 1. In addition to these Umpleby 2 

described the copper deposits in the Copper King mine, to the northwest, the Copper Queen mine, to the east, and others of less impor1 Umpleby, J. B., Geology and ore deposits of Lemhi County. Idaho: U. S. Geol. Survey Bull. 528, 

1913.

2 Idem, pp. 120-121,155.

1
2 THE COPPEB DEPOSITS NEAR SALMON, IDAHO

tance. No work is reported to be in progress at any of these mines, 

and they were not visited during the present investigation.

MEANS OF ACCESS

Salmon, which according to the 1920 census has a population of \ 

1,311, is the county seat and largest town in Lemhi County, and the 

principal distributing point for the region. It is the terminus of the 

Gilmore & Pittsburgh Railroad, which connects with the Oregon 

Short Line at Armstead, Mont., 100 miles from Salmon. This railroad 

crosses the Continental Divide through Bannock Pass, northeast of 

Leadore, and has a branch extending south from Leadore to Gilmore. 

A train is operated from Armstead to Leadore every other day except 

Sunday, returning to Armstead on the alternate days, and a train 

makes a trip to Salmon at least once a week to carry freight and 

stock. There is passenger service between Leadore and Salmon daily 

except Sunday by means of a gasoline-propelled car with a trailer. 

An automobile stage alternates with the train between Leadore and 

Armstead. Automobile roads connect Salmon with Gilmore, Challis, 

Stanley, Hailey, and Mackay, and a wagon road runs to Leesburg. 

Salmon can be reached by automobile stage from Mackay, which is 

at the end of a branch of the Oregon Short Line.

ACKNOWLEDGMENTS

The work was greatly facilitated by the hearty cooperation and 

assistance of those in charge of the copper mines and other mining 

men in Salmon. William Snow, P. J. Shenon, and a number of 

others gave their time and knowledge freely. The efficient assistance 

of A. L. Anderson, of the University of Idaho, did much to hasten the 

progress of the field work.

HISTORICAL SKETCH

The presence of copper in the rocks of this part of Idaho has long 

been known. The Mormons who settled in Lemhi Valley in 1854 3 

are reported to have prospected the copper deposits on Hayden Creek 

and perhaps also on McDevitts Creek. The Mormon settlement 

was abandoned in 1857 4 on account of trouble with the Indians. In 

1866 5 the discovery of gold placers attracted other white men, and 

Salmon was founded. Little attention was paid to the copper deposits 

for some time after this. The Mormons found some copper ore 

about 1856, and other deposits appear to have been located in the 

late seventies and early eighties, but little copper mining was attempted until after 1911. The total production of copper ore from proper3 Bancroft, H. H., History of Washington, Idaho, and Montana, 1815-1889, pp. 402, 403,1890.

4 Idem, p. 534, footnote.

6 Idem, pp. 554-556, footnote.
INTRODUCTION

ties in Lemhi County through 1922 is less than 25,000 tons, and a large 

part of this has been shipped in the last few years from the Eureka 

and McDevitt districts. At the present time three small copper

FIGURE 1. Index map of Idaho showing location of the area covered

mines are in operation, and two of them ship ore regularly. There 

are several prospects on which work has recently been done, but only 

one of these was in operation at the time of visit.
4 THE COPPER DEPOSITS NEAR SALMON, IDAHO

TOPOGRAPHY

The area, containing the copper deposits lies near the confluence of 

Salmon and Lemhi rivers, on the east slope of the Salmon River 

Mountains and in the northern part of the Lemhi Range. On the 

east side of the valley of Lemhi River rises the imposing bulk of the 

Beaverhead Mountains. The crests of this range mark the Continental Divide and form the boundary between Idaho and Montana.

The Beaverhead Mountains rise to heights of over 10,000 feet above 

the sea. Their rugged, rocky crests show, even when viewed from a 

distance, abundant evidence of the former presence of glaciers. The 

west side of the massive range is gashed by subparallel canyons spaced 

on the average about 2 miles apart. The peaks and upper slopes 

have little, soil and support only scanty vegetation. At intermediate 

altitudes most ,of the slopes are fairly well covered with pines and 

other trees and bushes. Farther down trees are less abundant, and 

on the lower slopes sagebrush constitutes the principal vegetation.

Lemhi River is formed by the confluence of several creeks near 

Leadore and flows somewhat west of north about 45 miles to its junction with Salmon River at Salmon. The stream has a swift current 

and flows with many curves between steep banks a few feet high. It 

is bordered along most of its course by a luxuriant growth of bushes 

and grasses. Much of the level land on either side is irrigated. The 

dry terraced slopes of the valley sides are rather scantily covered 

with sagebrush and a few small cacti and stand out in sharp contrast 

to the green flats near the river, except in the scattered patches where 

they have been turned green by means of irrigation. The lower 

courses of the principal tributary streams are also bordered with 

irrigated fields.

The major part of the Lemhi Range has a northwest trend, but 

the portion visited during the present investigation trends nearly 

north. This portion has a maximum width of about 16 miles and 

terminates in a rather blunt end about 5 miles south of Salmon, 

though the foothills extend almost to that town. The crests in this 

portion reach altitudes of over 9,000 feet, thus rising about 4,000 feet 

above Lemhi River on the east and even more above Salmon River 

on the west. Some of the peaks in the southern part of the range 

are considerably more than 10,000 feet above sea level. Except on 

the cliffs and the sagebrush-covered lower slopes the northern portion of the range has a fairly continuous forest cover. The peaks 

and highest ridges carry fewer trees than the intermediate slopes. 

The cliff-bordered headwater basins of many of the streams are probably in part the work of glaciers.

Salmon River is second only to Snake River among the large 

streams in Idaho. , At Salmon, the altitude of which is 3,940 feet,
STRATIGRAPHY AND PETROLOGY 5

the combined valleys of Salmon and Lemhi rivers form a broad expanse of country, but a few miles above the town the major stream 

is confined in a comparatively narrow canyon that has moderately 

steep walls with small cliffs and numerous talus slopes. The narrow 

patches of flood plain bordering the swift stream are covered with a 

tangled growth of small trees and bushes, except where they have 

been brought under cultivation. Much of the land bordering the 

river below the mouth of Sevenmile Creek and some of that above 

this point is cultivated. Most of the tributaries along this part of 

Salmon River flow in narrow canyons whose walls have an average 

inclination of more than 30° and are covered with alternate patches 

of talus and forest. The larger streams have flood plains, especially 

on their lower courses, but few of these are wide enough to offer much 

encouragement to farmers. Plate II, A, shows a typical stream near 

the border of the mountains.

The Salmon River Mountains- form part of the east border of the 

great mass of high mountains that occupies the central part of Idaho. 

The part of the range visited during the present investigation trends 

nearly north and culminates in Baldy Mountain, which towers about 

a mile above Salmon near the eastern base of the mountains. Some 

peaks hi other parts of the range are even higher than this. The 

lower hills Nof the eastern part of the range support only a scanty 

vegetation, but a large part of the mountains up to an altitude of 

about 8,000 feet above the sea is covered with evergreen forest. 

Above this are bare rocks and talus slopes, with scattered trees and 

bushes in favorable spots, as can be seen from Plate II, B, The 

valleys in the higher portions of the mountains have been glaciated, but it is unlikely that the ancient glaciers ever covered the 

sites of the copper prospects in this range examined during this 

investigation.

STRATIGRAPHY AND PETROLOGY

The broad features of the general geology of Lemhi County have 

already been worked out by Umpleby.6 In the present examination 

only passing attention was given to the stratified formations younger 

than the metamorphosed sedimentary rocks, which inclose all the 

copper deposits examined during this investigation, and the information obtained has been supplemented from Umpleby's descriptions.

METAMORPHIC ROCKS

Metamorphosed rocks of sedimentary origin form the major part 

of the mountain masses near Salmon. The same rocks probably 

underlie the valleys of Salmon and Lemhi rivers in this vicinity

'Umpleby, J.B., Geology and ore deposits of Lemhi County, Idaho: U. S. Qeol. Survey Bull. 528, pp. 

30-48,1913.

33094^-25 2
6 THE COPPER DEPOSITS NEAR SALMON, IDAHO

under the cover of younger strata. In view of the uncertainties 

regarding their age and stratigraphic relations, correlations with 

other formations can not be made. For convenience the term 

"metamorphic rocks" will be used in this report to designate the 

thick succession of sedimentary rocks which appears to constitute 

the oldest formation exposed in the area examined. The metamorphism of these rocks is everywhere more striking than that of any 

of the other formations exposed.

The metamorphic rocks consist in general of quartzitic argiUite and 

micaceous quartzite, with some beds of comparatively pure quartzite. 

The color of fresh surfaces ranges from dark green to gray and black. 

All the rocks have undergone metamorphism, with the development 

of slaty cleavage or schistosity, and partial recrystallization. In 

many exposures, however, the original bedding can still be discerned 

on close examination. The rocks are almost everywhere traversed by 

closely and irregularly spaced joints. As a consequence the outcrops 

are skirted by talus slopes composed of angular fragments, most of 

which are less than a foot in largest dimension. Slaty or schistose 

cleavage is present in many exposures but as a rule is not well 

developed. Typical schistose structure was observed only in the 

rocks on Hay den Creek.

There is a monotonous similarity in the general characteristics of 

the rocks, but close examination reveals variations, and further study 

of these might result in subdivision into several stratigraphic units. 

Most of the metamorphic rocks in the Salmon River Mountains from 

Baldy Mountain southeastward to the border of the range are more 

nearly black than those in the north end of the Lemhi Range, where 

the predominant color is dark green. Green rocks were, however, 

noted on the upper slopes of the canyon of the North Fork of Perreau 

Creek near its head. Some of the black rocks contain considerable 

argillaceous material and have distinct slaty cleavage. Interbedded 

with these are minor amounts of light-gray quartzite, apparently 

purer than any seen elsewhere in the formation. The dark-gray to 

black rock on Baldy Mountain splits into thin slabs of larger surface 

area than those in talus piles in other localities. A number of these 

slabs show cylindrical masses lighter in color than the containing rock. 

These masses penetrate from one side to the other of the slab and can 

not be cracked clean from the rock. Most of them are an inch or more 

in diameter. The dark-colored rocks in a number of localties in the 

Salmon River Mountains are ripple marked.

The rock in the Lemhi Range from the Harmony mine north is 

predominantly dark green, although some beds are nearly black, and 

others are light colored and somewhat more siliceous than the average. 

At and south of the Harmony mine the rock seems on the whole less 

distinctly green than that farther north. The bedding in the rock
STRATIGRAPHY AND PETROLOGY 7

near this mine is thicker and more easily visible than that in most 

other localities. Some of the rock near the head of Spring Creek, 

in the Salmon River Mountains, is similar in this respect. The bedding in the rocks of the north end of the Lemhi Range is in general 

indistinct but in most exposures can be discerned on close examination. The bedding in rocks along McDevitt Creek is also indistinct 

in general, but in places clearly defined and ripple-marked beds are 

exposed.

The rock at the Nellie group, on Hayden Creek, differs from any 

of the metamorphic rock seen elsewhere. It is a rather soft gray 

schist, more highly metamorphosed than any other observed, 

composed essentially of quartz, sericite, chlorite, and a little calcite. 

This is the only one of the varieties of metamorphic rock examined 

in which calcite was detected.

All the specimens of metamorphic rock examined microscopically 

are of similar type, except that just mentioned and those which have 

been altered in connection with the formation of the mineral deposits. 

The most abundant constituent is quartz, which in a number of 

specimens shows the moderately well rounded outlines of the original 

clastic grains. Most of the rocks show evidence of crushing, and in 

many the quartz is in a mosaic of interlocking grains with the driginal texture obscured. In the thin sections examined the quartz 

grains range from 0.08 to 0.78 millimeters in maximum dimension. 

The other constituents are nearly all micaceous minerals sericite, 

muscovite, chlorite, and dark-green biotite. The long dimension of 

the largest flakes is less than 1- millimeter. Fine-grained magnetite 

occurs in some specimens, but all those in which it is a prominent 

constituent came from the proximity of mineral deposits. Some 

specimens contain epidote.

These rocks were evidently laid down as moderately fine grained 

siliceous sediments containing varying amounts of argillaceous material, deposited under shallow marine water. The minerals present 

might have been developed entirely by rearrangement of the chemical constituents of the original rock, but it seems likely that some 

material has been introduced from outside sources during the metamorphism. Intense pressure, indicated by the development of 

schistosity, operated only locally. The metamorphism resembles in 

a general way that of lithologically similar rocks in the Coeur d'Alene 

and Pend Oreille districts and elsewhere in northern Idaho. It is 

thought that the metamorphism of the rocks near Salmon, like that 

in the two districts mentioned,7 has been greatly influenced if not

7 Kansome, F. L., and Calkins, F. C., The geology and ore deposits of the Coeur d'Alene district. 

Idaho: U. S. Geol Survey Prof. Paper 62, pp. 15, 74-75, 1908. Sampson, Edward, and Gillson, J. L. 

Q eology and ore deposits of the Pend Oreille district, Idaho (in preparation).
8 THE COPPEE DEPOSITS NEAR SALMON, IDAHO

principally effected by the intrusion of the granitic rocks of the batholith of central Idaho arid its offshoots.

The metamorphosed sedimentary rocks of Lemhi County have 

been tentatively correlated on lithologic grounds with the Belt series, 

which is widespread in northern Idaho and Montana, and have therefore been considered to be of Algonkian age. 8 The thickness of the 

rocks that crop out in the small area examined is probably of the order 

of thousands of feet, and it appears from Umpleby's descriptions that a 

much greater thickness of metamorphic rocks is present in the surrounding region. There is some variation in the character of the 

rocks here described, and Umpleby's descriptions indicate that in the 

Beaverhead Mountains the variations are more marked and sharply 

defined. There may therefore be considerable range in age in the 

metamorphic sedimentary rocks of Lemhi County, but those seen 

during the present investigation are sufficiently similar throughout 

to warrant the assumption, in the absence of definite evidence to the 

contrary, that all are of about the same geologic age.

PALEOZOIC BOCKS

The rocks near the upper end of Lemhi River appear to be younger 

than the metamorphic rocks just described. In his report on Lemhi 

County Umpleby 9 states that rocks of Cambrian, Ordovician, Silurian (?), Devonian, and Mississippian age are present, but in a later 

report 10 he tentatively assigns the rock he previously considered of 

Cambrian age to the Ordovician. This rock is a quartzite in which no 

fossils have been found, and its age can therefore be surmised only on 

stratigraphic grounds. The data on the stratigraphy of the Paleozoic 

rocks along the valley of Lemhi River as determined by Umpleby are 

summarized in the table below, with themodification noted. Umpleby 

considered that all the formations he assigned to the Paleozoic were 

conformable with one another but that there was probably an unconformity at the top of the metamorphic rocks. This conclusion is in 

accord with the facts so far determined.

Paleozoic rocks near Lemhi River

Age

Mississippian . __ . .....

Devonian. __ ____..___.

Silurian (?) __ . .......

Rock

and some of quartzite; fossiliferous.

Thickness 

(feet)

300+

2,000+

200±

500±

2, 000+

»Umpleby, J. B., op. cit. (Bull. 528), pp. 30-32. 

 Idem, pp. 32-35.

10 Umpleby, J. B., Geology and ore deposits of the Mackay region, Idaho: U. S. Qeol. Survey Prof. Paper 

97, p. 25, 1917.
U. S. GEOLOGICAL SURVEY BULLETIN 774 PLATE I

114"00'R.2I E. R22E. 50' R.23E. H3°40' R.2A E.

EXPLANATION 

SEDIMENTARY ROCKS

(Lacustrine and fluviatile deposits consisting of

detntal material from adjacent slopes, with

interbedded strata of volcanic origin, vrinci.

pally fragmental, in places; possibly includes

(Rhyolite, andesite, laiite, basalt, trachyte, and

pyroclastic beds; related dikes not mapped)

Granite

U3°4O'

OOMQfiS

GEOLOGIC SKETCH MAP OF PARTS OF THE EUREKA AND McDEVITT MINING DISTRICTS,

LEMHI COUNTY, IDAHO

33094 25. (Face p. 8.)
STRATIGRAPHY AND PETROLOGY 9 

J

In the area covered in the present examination only three small 

masses of strata that may be correlated with any of the rocks men- 

, tioned in the above table are known. They lie near the mouths of 

I McDevitt and Hayden creeks and on the west side of Lemhi River 

y between these two creeks. Much of the rock in these areas is a lightcolored, well-bedded quartzite and is probably to be correlated with 

the lowest formation in the above table. The beds near Hayden 

Creek appear to be largely limestone.

GRANITIC ROCKS

On Umpleby's map of Lemhi County 11 is shown a roughly circular area of about 300 square miles a few miles northwest of Salmon. 

This area is underlain by a granite mass, concealed in the center by 

metamorphic rocks that crop out over an area of about 90 square miles. 

The east border of the granite is included in the area mapped in Plate I 

of the present report, on which the boundary is taken from Umpleby's 

. map. The granite 12 is a light-gray medium-grained rock, with some 

/ tendency to porphyritic texture. Microscopic examination shows 

/ that there is considerable variation in composition. Orthoclase or 

microcline, quartz, and biotite are generally present. The accessory 

\j minerals zircon, apatite, and magnetite, are found in most specimens, 

and sodic varieties of plagioclase occur in many. On Little Eightmile Creek and in the Texas and Spring Mountain districts near the 

upper end of Lemhi River are small areas of quartz diorite that is 

probably closely connected genetically to the granite.

There are in this region numerous dikes , 13 most of which are probably related to the granitic intrusions. The granite and similar rocks 

are presumably related in age and genesis to the Idaho batholith. 

This great mass is generally believed to have been intruded at the 

end of the Cretaceous or the beginning of the Eocene.

TERTIARY LAVA

Volcanic strata of Tertiary age border the Lemhi Range on the east 

and underlie much of the valley of Salmon River a few miles above 

Salmon. The boundary between these rocks and the metamorphic 

rocks that form mountains is actually more irregular than is indicated 

on Plate I. Many of the ridges on the east flank of the Lemhi Range 

are partly capped with Tertiary lava, and there may be places where 

erosion has exposed patches of the older rocks that have not been 

mapped. The masses of strata in which lava flows greatjy predominate over pyroclastic and sedimentary beds have been mapped as 

Tertiary lava. There is interbedding in places between the lava and

11 Umpleby, J. B., op. cit. (Bull. 528), pi. 1,1913. ~ " " " """"

" Idem, p. 42.

13 Idem, pp. 43-46.
10 THE COPPER DEPOSITS NEAR SALMON, IDAHO

the overlying "lake beds," and the boundaries as mapped are generalized.

Umpleby 14 has shown that rhyolite, andesite, latite, basalt, trachyte, 

and dacite are present. Rhyolite is probably the most widespread. \ 

Pyroclastic beds of various kinds are present in minor amount, and 

. in places, particularly in the northeastern part of the Lemhi Range, 

sedimentary strata are included hi the area mapped as Tertiary lava. 

The lavas of Lemhi County are believed to date from late Oligocene 

or early Miocene to about the end of the Pliocene. 15 It seems probable that nearly all those seen during the present investigation were 

erupted during the early part of this period.

At Salmon Hot Springs, in sec. 3, T. 20 N., R. 22 E., there are 

warm springs which issue from bleached and altered lava. The water 

deposits a brown, iron-bearing ooze in the concrete bathing tank. 

Similar springs are reported to occur in a number of other places in 

this part of Idaho. It is possible that they represent one of the last 

phases of the dying volcanism.

i

"LAKE BEDS"

The valley of Lemhi River and part of the valley of Salmon River 

are underlain by indurated clastic deposits which have been termed 

" lake beds " by Umpleby.16 In the literature describing the geology 

of Idaho this term is frequently used to designate clastic deposits 

formed at about the same time and under similar conditions. Some 

of these beds are not strictly lacustrine deposits, but it is expedient to 

retain the term for purposes of description.

In the area here considered the "lake beds" consist in large part 

of moderately well-indurated thin-bedded fine-grained rocks which 

may be of lacustrine origin. There is a considerable amount of sandstone and conglomerate, in part coarse and poorly rounded, whose 

appearance suggests that it is of fluviatile origin. Much of this 

material was probably brought down from the mountains by torrential streams, which dumped' their loads in alluvial fans when they 

reached the gentler grade of the valley. If a lake filled the valley 

into which such a stream emptied, the detritus carried by the stream 

would be deposited in the water of the lake, forming a delta. In 

addition to the beds of purely sedimentary origin, whether lacustrine 

or fluviatile, there are in places considerable amounts of tuff and 

coarser pyroclastic rocks. Some lava flows are also interbedded with 

the formation. Near Salmon and Baker there are beds of lignite, 

some of which were worked before the railroad reached Salmon. The 

maximum thickness of the formation is many hundreds of feet. From

" Umpleby, J. B., op. cit. (Bull. 528), pp. 47-18.

«Idem, p. 48.

i8 Idem, pp. 35-40.
STRUCTURE 11

a reconnaissance examination on Bohannon Creek southeast of Salmon Umpleby17 estimates that a thickness as great as 4,000 feet may 

be exposed there.

On the evidence afforded by the relations of the formation to other 

rocks and by small collections of plant remains made by Umpleby 

and by G. H. Eldridge and determined by F. H. Knowlton, Umpleby 18 

considered that the-formation is probably of Miocene age.

QUATERNARY DEPOSITS

Alluvium deposited to form flood plains by the present streams is 

indicated on Plate I along Salmon and Lemhi rivers. In addition 

there are narrow bands of recent alluvium along most of the tributary streams, and the gently sloping parts of the surface of the "lake 

beds" are covered by a layer of unconsolidated gravel.

STRUCTURE

The available data regarding the structure of the rocks near Salmon are given below. As detailed geologic work has not yet been 

done either here or in neighboring areas, much still remains to be 

learned. Some of the most fundamental features of the structure of 

the general region can not be more than surmised from the facts now 

known.

The structual features found in the rocks may be divided into four 

groups. These are (1) folds with northerly trends; (2) flexures or 

fractures with northwesterly trends; (3) flexures or fractures with 

northeasterly trends; (4) the comparatively minor faults and folds 

which are later than the other groups. The folding of the first group 

was observed in the metamorphic rocks. Folding or fracturing of 

the second and third groups is inferred from trend lines in this and 

near-by parts of Idaho. The minor faults and folds of the fourth 

group can be readily seen in the Tertiary rocks. They may have 

been produced in two separate periods but more probably originated 

hi one period of crustal instability in which faulting and folding took 

place intermittently and with decreasing violence.

The folding in the metamorphosed sedimentary rocks, although 

widespread, appears nowhere to have been sharp. The greatest dip 

recorded is 35°, and most of the observed dips are under 20°. It 

seems probable that this thick formation has been bent into broad, 

open folds and that in this area there is only one principal fold, a 

syncline whose axis lies west of and roughly parallel to the crest of 

the Lemhi Range, which here trends nearly north. Minor flexures 

are undoubtedly present, but they can be deciphered only by detailed 

study. Fault breccia in small amounts was noted in several places

" Umpleby, J. B. ( op. cit. (Bull. 528), p. 35. 

w Idem, pp. 38-39.
12 THE COPPER DEPOSITS NEAR SALMON, IDAHO

and has shared in at least part of the metamorphism to which the 

rocks have been subjected. Many of the strikes recorded by Umpleby 

in his papers on Lemhi County and the Mackay region accord with 

the conception of folds with axes trending a few degrees either side 

of north. However, some of the beds observed by him in the western part of Lemhi County and near Lemhi Pass and by the present 

writer in the central part of the county, especially along McDevitt 

Creek, strike more nearly east than north. These strikes may mark 

minor flexures or may have resulted from later movements.

On McDevitt Creek the contact between the metamorphosed 

quartzitic rocks of supposed Algonkian age and quartzite that presumably belongs at the base of the Paleozoic section seems to be 

unconformable. It is not parallel to the bedding in the overlying 

quartzite, and the only other possible explanation is faulting, of which 

there is no direct evidence. The general relations elsewhere also 

suggest unconformity but might be explained by faulting. In no 

place has the line of contact been observed.

In northwestern Utah, according to Richardson,19 and in southeastern Idaho, according to Mansfield,20 an unconformity occurs 

within the Ordovician at a horizon probably corresponding with that 

here described. The evidence for the existence of an angular unconformity at the base of the Ordovician rocks is thus fairly strong. If 

the unconformity exists, the first folding in the metamorphic rocks 

evidently preceded it and is probably, as believed by Umpleby,21 of 

pre-Cambrian age.

One of the most striking features of the geologic maps of eastcentral and southeastern Idaho 22 is the number of areas of rock 

represented whose long axes have trends approximating to N. 40° 

W. These areas correspond roughly to some of the larger topographic 

features. In general the valleys are occupied by Tertiary and later

w Richardson, Q. B., The Paleozoic section in northern Utah: Am. Jour. Sci., 4th ser., vol. 36, pp. 

406-416,1913.

20Mansfield, G. R. Geography, geology, and mineral resources of the Fort Hall Indian Reservation, 

Idaho: U. S. Geol. Survey Bull. 713, pp. 30-34,1920.

si Umpleby, J. B., Geology and ore deposits of the Mackay region, Idaho: U. S. Geol. Survey Prof 

Paper 97, p. 39,1917; Geology and ore deposits of Lemhi County, Idaho: U. S. Geol. Survey Bull. 528, 

p. 49,1913.

"Lindgren, Waldemar, The gold and silver veins of Silver City, DeLamar, and other mining districts 

in Idaho: U. S. Geol. Survey Twentieth Ann. Rept., pts. 3, pi. 8, 32,1900. Umpleby, J. B., Geology and 

ore deposits of Lemhi County, Idaho: U. S. Geol. Survey Bull. 528, pi. 1, 1913; Some ore deposits of 

southwestern Custer County, Idaho: U. S. Geol. Survey Bull. 539, pi. 1,1913; Geology and ore deposits 

of the Mackay region, Idaho: U. S. Geol. Survey Prof. Paper 97, pi. 1,1917. Schultz, A. R., and Richards, 

R. W., A geological reconnaissance in southeastern Idaho: U. S. Geol. Survey Bull. 530, pi. 6, 1913. 

Richards, R. W., and Mansfield, G. R., Preliminary report on a portion of the Idaho phosphate reserve: 

U. S. Geol. Survey Bull. 470, pi. 9,1910; Geology of the phosphate deposits northeast of Georgetown, 

Idaho: U. S. Geol. Survey Bull. 577, pis. 9 to 14, inclusive, 1914. Mansfield, G. R., Geography, geology, 

and mineral resources of the Fort Hall Indian Reservation, Idaho: U. S. Geol. Survey Bull. 713, pi. 3, 

1920; Coal in Eastern Idaho: U. S. Geol. Survey Bull. 716, pis. 14,15,1921. Umpleby, J. B., and Livingston, D. C., A reconnaissance in south-central Idaho embracing Thunder Mountain, Big Creek, 

Stanley Basin, Sheep Mountain, and Seafoam districts, Idaho: Idaho Bur. Mines and Geology Bull. 3, 

map 1,1920.
STRUCTURE 13

formations, and the mountains by older rocks. The descriptions in 

the papers thus cited and in others referred to below show clearly 

that the present size, shape, and arrangement of the areas of outcrop, 

of the formations result primarily from structural disturbancesr 

although erosion has had a modifying influence. The overthrusts areamong the most striking features of the structure of the region. Th& 

Bannock overthrust 23 is the largest pf those known, and the others 

are probably in large part of similar age and related to it.

The trace of this thrust in Idaho trends northwest, although in 

Utah the trend is nearly north. Convincing evidence is presented 

by Richards and Mansfield that the thrusts took place in late Cretaceous or early Eocene time.

It is suggested that the general trend and position of the Beaverhead Mountains and Lemhi Range result from structural disturbances related to. those just referred to, with the outlines modified by 

erosion and the deposition of later rocks. Umpleby 24 has suggested 

that the principal deformation of the Paleozoic rocks took place at 

about the end of Mesozoic time and is genetically related to the 

granitic intrusions, and further that there may be genetic connection 

between these intrusions and the Bannock and other overthrusts 

along the east front of the Rocky Mountains. This suggestion is in 

accord with the view stated above.

Study of the maps above cited shows that several of the areas of 

rock shown terminate abruptly along lines with an average trend of 

about N. 40° E. Furthermore, the widest part of the Snake River 

Plains 25 in Idaho and a number of valleys floored with alluvium have 

approximately similar trends. This northeasterly series of trend 

lines is a less obvious feature of the region than the northwesterly 

series just discussed but is sufficiently definite and persistent to be of 

real significance in the structure of the region. It may correspond 

with the transverse folding noted by Mansfield 28 in southeastern 

Idaho, or it may be in part of later origin. The valley of Salmon 

River for a number of miles above Salmon has such a trend. Where 

observed, the contact between the lava and metamorphic rock along 

the sides of the valley is depositional. There are faults in both the 

lava and the "lake beds," and it is probable that in places the contacts between these two formations are fault planes. How much of

28 Richards. R. W., and Mansfield, Q. R., The Bannock overthrust: Jour. Geology, vol. 20, pp. 681 

709, 1912.

z< Umpleby, J. B., Geology and ore deposits of the Mackay region, Idaho: U. S. Geol. Survey Prof, 

Paper 97, p. 39, 1917; Geology and ore deposits of Lemhi County, Idaho: U. S. Geol. Survey Bull. 528. 

p. 49, 1913.

26 Russell, I. C., The geology and water resources of the Snake River Plains of Idaho: U. S. Geol. SurveyBull. 199, pi. 1,1902.

26 Mansfield, G. R., Types of Rocky Mountain structures Idaho: Jour. Geology vol. 29, pp. 444-468, 

1921. 33094 25 3
14 THE COPPER DEPOSITS NEAR SALMON, 'IDAHO

this part of the valley of Salmon River was produced by structural 

disturbances and how much by erosion can not be determined on 

known evidence.

Direct evidence is lacking as to the character of the structural 

features that are believed to govern the positions of the portions of 

the valleys of Salmon and Lemhi rivers here considered. By analogy 

with the better-known structure farther south it is supposed that the 

features of northwesterly trend are folds which may have been so 

compressed as to have broken, forming overthrusts, and that those 

of northeasterly trend are subordinate transverse folds, probably 

with associated faults, all belonging to the same general period of 

diastrophism.

Tertiary lava lies well up on the flanks of the Lemhi Range and may 

in places even extend to the summit.27 In a broad way, with a number 

of local exceptions, the lava dips away from the mountains as if it had 

been tilted during uplift. On the other hand, in numerous places the 

slope of the surface of old rocks on which the lava rests is more steeply 

inclined than the volcanic strata. In several places the lava terminates abruptly against steep and even precipitous slopes of metamorphic rock, such as that shown in Plate III, A. These various slopes 

appear to have been formed or at least modified by erosion before 

the advent of the lava, and hence indicate the existence of rugged 

topography in prelava time. The range was doubtless in existence 

before the eruptions began and was partly buried by them. Relative uplift of the range with respect to the river valleys on either side 

took place after most of the eruptions had ceased. The Salmon River 

and Beaverhead mountains have probably had similar histories.

The Tertiary sedimentary rocks grouped under the term "lake 

beds," like the volcanic rocks with which they are in part interbedded, 

slope up in general on the mountain flanks as if they had shared in 

the relative uplift. (See PI. Ill, B.) In the valleys of Salmon and 

Lemhi rivers these beds are folded. In the cliffs along Salmon River 

a few miles below Salmon there is an exposure of a slight angular 

unconformity in the '' lake beds.'' Whether this unconformity marks 

a mere local fluctuation in conditions or is of more general significance can be determined only by more detailed work.

Both the volcanic rocks and the "lake beds" along the valleys of 

Salmon and Lemhi rivers are cut by normal faults. More were observed in the volcanic rocks than in the "lake beds," but in neither 

formation were they mapped or studied in detail: None of those 

seen appeared to have a large throw. Most of them are probably 

somewhat later than the broad tilting and folding and are the results 

of the most recent adjustments in the earth's crust.

"Umpleby, J. B., Geology and ore deposits of Lemhi County, Idaho: U. S. Qeol. Survey Bull. 528, p. 

120,1913.
U. S. GEOLOGICAL SURVEY BULLETIN 774 PLATE II

A. I'l'.HHI'.Al CHKEK NKAK THE TORMEY MINI'., «,M, VIo.N IU\KK MOUNTAINS 

Photograph by A. L. Anderson

TS. SALMON RIVER MOUNTAINS NEAR BALDY MOUNTAIN
U. S. GEOLOGICAL SURVEY BULLETIN 774 PLATE III

A. PRECIPITOUS CONTACT BETWEKN METAMORPHIC ROCK AND TERTIARY LAVA EXPOSED ON THE LEFT SIDE OK WITHINGTON CREEK BELOW 

THE HARMONY MINE

The dark well-bedded rock is metamorphic, and that with ja^ed oiHlines and lighter color

is lava

B. NORTH END OF LEMHI RANGE

The smooth and unforested slopes are underlain by "lake beds, 1 ' the rough outcrops on the 

right are lava, and the forested upper slopes are on metamorphic rocks. The PopeShenon mine is near the edge of the timber near the left side of the picture
GENERAL, CHARACTER 15

THE COPPER DEPOSITS

GENERAL CHARACTER

All the copper deposits here described are of the same general kind. 

They are shear zones in quartzitic rocks in which mineralization has 

been effected largely by metasomatic replacement but in part by fissure filling. Most of them are in the form of steeply inclined tabular masses of sheared and somewhat altered country rock in which 

there are shoots containing sufficient quantities of copper minerals to

Based on U. 5. Forest Service map 

of Salmon National Fbnest.1918

FIGURE 2. Sketch map of part of Lemhi County, showing the location of known copper deposits

be mined, as. ore Ihe-width..nf..tJie known ore bodies varies from a 

few inches up to 20 feet. A number of the lodes have been drifted 

on>for several hundred feet. Only certain portions of each lode, with 

rather definite limits along the strike, could be considered ore, and 

in most places the greater part of the remainder of the exposed portion of the lode is almost barren of valuable minerals. On inspection underground the lodes appear to be merely zones of shearing in
16 THE COPPER DEPOSITS NEAR SALMON, IDAHO

rock of similar appearance to the surrounding country rock. Close 

examination with the microscope shows that much of the rock in 

these zones has been metamorphosed to a greater degree than the 

country rock at a distance from the deposits and in a somewhat dif- ; 

ferent manner. I

STRUCTURAL RELATIONS

The copper mines and prospects described in this report lie along 

a curved line that extends from a point near the head of Perreau 

Creek eastward across Salmon River, around the north end of the 

Lemhi Range, and down the east side of that range as far as Hayden 

Creek, as is shown in Figure 2. The total distance is about 28 miles. 

This line parallels rather closely the trend of the valley of Lemhi River. 

The distribution of the known deposits may be hi part accidental, 

but the parallelism of their alinement with this depression of probable i 

structural origin suggests the possibility that it may have genetic 

significance.

Most of the deposits containing notable amounts of copper minerals 

described by Umpleby in his report on Lemhi County lie on the west 

flank of the Beaverhead Mountains near the crest of the range, along 

a line that is nearly parallel to the trend of Lemhi Valley, as can be 

seen from Figure 2. They thus correspond in distribution on the 

east side of the valley to those examined in the present investigation 

on the west side. There are also a few copper deposits in the Salmon 

River Mountains and Yellow Jacket Range, nearer the large masses ( 

of granitic rocks, and two farther south in the Lemhi Range. The 

latter, known as the Colorado and Bruce groups, are the only copper ( 

deposits inclosed in limestone in this region. All the others are in 

quartzitic and schistose rocks. The Blue Wing deposits, on Patterson Creek, on the west side of the Lemhi Range, do not fit in any of 

the above groups.

The deposits in the western part of the county probably owe their 

position to the proximity of the granitic masses around Leesburg 28 

and west of Yellow Jacket,29 to which they are genetically related. 

The deposits in limestone in the southern part of the county are 

associated with quartz diorite intrusions,30 and their location was 

doubtless directly determined by the position of the intrusive 

masses. The deposits, however, also bear about the same relation 

to the valley of Lemhi River as those described in the present report. 

The deposits on Patterson Creek differ from the others not only in

w Umpleby, J. B., op. cit. (Bull. 528), pi. 1.

29 Umpleby, J. B., and Livingston, D. C., A reconnaissance in south central Idaho: Idaho Bur. Mines 

and Geology Bull. 3, map 1,1020. 

» Umpleby, J. B., op. cit. (Bull. 528), pp. 88-89.
STRUCTURAL, RELATIONS 17

position but also in the presence of sufficient tungsten to cause them 

to be prospected for that metal.31

The other ore desposits in pre-Tertiary rocks in Lemhi County 

described by Umpleby are susceptible of grouping in similar fashion. 

Most of them are scattered through the Salmon River Mountains 

and Yellow Jacket Range, in the western part of the county, but 

there are also a number in the limestone west of the upper part of

Strike of deposits described in this report

 Strike of deposits described in U. S. Geol. Survey Bull. 528, 1913

FIGUKE 3. Diagram showing observed strikes of copper deposits in Lemhi County

Lemhi River, and nearly as many along the west slope of the Beaverhead Mountains. As the location of many prospects and some mines 

is not known, the number of deposits in the different groups can not 

be accurately stated.

The attitudes of the lodes indicated in Figure 2 vary considerably, 

and the strikes of many of them do not parallel the imaginary lines 

drawn through the groups on t he opposite sides of the valley of Lemhi

" Idem, pp. 110-111.
18

River. However, when all the known strikes of copper deposits in 

Lemhi County are assembled in a diagram (fig. 3), the greater number fall into a group in which the divergence either way from a mean 

of N. 49°.W. is less than 25°. This mean is not far from the average trend of N. 40° W. possessed by a large group of major structural axes in the general region. The data summarized in this diagram 'and in the similar one shown in Figure 4 are not complete. 

The strikes of a number of lodes in the county are unknown, and 

many of the lodes have variable.trends. The mathematical averages

- Lead-silver deposits in limestone

----- - Gold deposits in limestone

- Lead-silver deposits in metamorphic rocks

- - Gold deposits in metamorphic rocks

- - - - - Gold deposits in granite

- - - - - - Nickel-cobalt deposits in metamorphic rocks

Data from J. B. Umpleby, U. S. Geol. Survey Bull. 528, 1913

FIGURE 4. Diagram showing observed strikes of ore deposits other than copper deposits in Lemhi County

given are to be regarded as convenient and concise means of expressing general relations rather than as precise quantities. The strikes 

of the other ore deposits in Lemhi County for the most part vary 

widely from the mean of N. 49° W., as can be seen by a glance at 

Figure 4. With only two exceptions the recorded strikes fall in the 

northeast quadrant. Most of them lie in the northerly half of the 

quadrant, and the mean is N. 39° E. This is almost exactly at right 

angles to the mean of the strikes of the copper deposits and corresponds very closely to the average trend of N. 40° E. shown by 

many topographic features and geologic boundaries in the general

\i
STRUCTURAL RELATIONS 19

region. As stated in the section on structure, it is probable that 

these northeasterly trends are the result of diastrophic movements 

that were widespread but not as powerful as those which produced 

the structural features with northwesterly trends. Only a few 

of the lodes accord in strike with either the bedding. or the schistosity of the inclosing rock. The different kinds of lines used to record 

strikes in Figure 4 serve to indicate differences in the general characteristics of the deposits. It must be remembered, however, that 

any such subdivision of the ore deposits in pre-Tertiary rocks must 

be somewhat arbitary. All these deposits, as Umpleby 32 has pointed 

out, have characteristics in common and gradations between them. 

The strikes indicated in Figures 3 and 4 might be further subdivided, 

but with the rather scanty data now available it seems best to consider them simply as f ailing into two general groups, one with northwesterly and the other with northeasterly trends.

It appears from the facts outlined above that the ore deposits 

considered are grouped with reference either to granitic intrusions 

or to structural axes. Further, the strikes lie in two groups at right 

angles to each other and conform closely to the average trends of 

two of the major groups of structural axes in the region. The shear 

zones and fractures containing the deposits were probably produced 

during and as a result of the erogenic movements that took place at 

the end of the Mesozoic era. The variations in strike and still more 

in dip are to be accounted for by local variations of numerous 

possible kinds.

At two places on the property of the Harmony Mines Co. there 

are pairs of lodes coming together at small angles. These lodes appear 

to have resulted from the splitting of shear zones rather than from, 

the intersection of independent sets of fractures. It seems likely 

that similar conditions will be encountered elsewhere. There has not 

been sufficient crosscutting at any of the mines to discover whether 

the full lateral extent of the mineralized ground has been determined. 

In all the ore shoots there are slabs of almost barren rock intercalated 

in the ore. What is true on a small scale may be found to be true 

on a larger scale that is, there may be in places zones of sheared 

and mineralized rock near and approximately parallel to known lodes 

but separated from them by rock so little altered that it offers no 

clue to their presence. That shearing and subsequent mineralization 

have taken place along several zones in the same locality is shown by 

the conditions on the Harmony property and at the Dishman prospect. 

At the Harmony there are at least two mineralized zones in addition 

to the two pairs already mentioned, or a total of six. At the Dishman the rock is mineralized in places over a considerable area across

«Umpleby, J. B., op. cit. (Bull. 528), pp. 81-82
20 THE COPPER DEPOSITS NEAR SALMON, IDAHO

the strike of what appears to be the major shear zone. However, 

the meager development work done here has not sufficed to show the 

presence of any such definite and continuous zones of shearing as exist 

at the better-developed properties. It is possible, therefore, that the 

structural conditions at this locality caused the mineralizing solutions 

to be diffused over a wider area and to deposit their load along discontinuous fractures separated by considerable amounts of barren 

rock.

In a number of the deposits there are cross fractures lined with 

gouge or breccia intersecting the main load at various angles. The 

rock along some of these fractures is mineralized or altered in a manner similar to that of the main deposit. These fractures are clearly 

of premineral origin and doubtless merely record variations in the 

stresses that produced the shear zones. Others that are not mineralized cut mineralized rock and are evidently of later date. Only one 

of the postmineral faults so far discovered in the mines offsets the 

lode as much as 20 feet, and none has caused serious difficulty in

following the lodes.

ORE SHOOTS

In all the deposits visited in which sufficient development work 

has been done the valuable ore is confined to rather definitely restricted 

ore shoots of moderate size. Typical shoots have average widths of 

the order of about 10 feet and stope lengths of a few hundred feet. 

Shoots of average size will yield over 20,000 tons of ore, and if they 

prove to be persistent in depth they may furnish several times this 

amount. Present developments indicate that a vertical range of at 

least 200 feet can be confidently expected, and there is nothing in the 

known geologic relations of the deposits to preclude the possibility 

that ore shoots may be found to persist downward considerable distances below the lowest present development. In the vicinity of 

Hailey, Idaho, where the development is much more extensive, there 

are deposits of lead-silver ore formed in the same period as the copper deposits near Salmon, and under somewhat similar conditions 

which have not proved to be persistent at depth. Some of the ore 

shoots near Hailey, however, have been followed much farther below 

their outcrops than any of those near Salmon, and there is sfcill a possibility that other shoots at greater depth exist.

In none of the deposits has more than one shoot been proved to exist, 

but this may well be due merely to lack of extensive development. 

The ore shoot in general occupies the greater part of the known width 

of the lode but is bordered at both ends along the strike of the lode 

by comparatively barren rock. As a rule the transition between ore
ORE SHOOTS 21

rand waste appears to take place rather abruptly. The waste rock 

in the lodes contains very small amounts of metallic minerals and 

somewhat less quartz than the ore, and it may show less bleaching 

and softening.

At the two most extensively developed properties the shape and 

:size of the ore shoots have been in part approximately determined, 

and there is some evidence as to the reasons for their location and 

.attitude. In the Harmony mine, as is shown in Figure 7, the ore 

shoot is at the intersection of the Leapyear and Contention lodes, and 

its rake is determined by the inclination of the intersection. Much 

the greater part of the ore lies on the upper side of this intersection, 

and most of that mined was along the Leapyear lode. At the Anderson 

workings on the same property similar conditions appear to exist, 

although here the development is much less extensive. At the Pope-

-Shenon mine, as is shown in Plate IV, the pitch of the ore shoot is

-approximately parallel to the dip of the schistosity. The flattening 

of the upper part ot the ore shoot as it exists at present is probably 

the result of leaching by surficial water.

The precise cause for the localization of ore shoots doubtless differs 

in different lodes. However, from the somewhat scanty data at hand 

it is believed that the general rule is that an ore shoot may be expected 

.at any place in a lode where conditions during ore deposition were 

particularly favorable to the circulation of mineralizing solutions. 

The composition of the country rock varies so slightly that it probably 

had little influence in the production of ore shoots in most places. 

The rocks are'siliceous, rather fine grained, and tightly cemented. 

They are not very readily permeable, even along the shear zones, and 

the movement of ore-bearing solutions in quantity was limited to 

places where the rock was more open. The greater the volume of 

solution the greater the quantity of ore deposited. Any set of conditions producing more than average permeability in the rock along 

a shear zone might have resulted in an ore shoot. At the Pope-Shenon 

mine it was a zone of somewhat unusually pronounced schistosity; 

.at the Harmony mine it was the abundance of fracturing at intersections

-of shear zones. Each lode must be studied individually in detail in

-order to deduce the probable situation and attitude of possible ore 

shoots. It must be borne in mind in such a study that fracturing to 

liave the desired effect must have been produced prior to the termination of hypogene mineralization. Postmineral faults obviously could 

iave no influence on the production of ore shoots, although they 

might well influence the redistribution of the metals by processes 

of oxidation.
22 THE COPPER DEPOSITS NEAR SALMON, IDAHO 

HYPO GENE MINERALIZATION

The deposits have been formed along shear zones partly by replacement and partly by vein filling. The minerals in the unoxidized 

parts of the lodes comprise quartz, micas, chlorite, epidote, chalcopyrite, pyrite, magnetite, specularite, and delafossite. Sphalerite is 

present in very small amount. Bornite is an abundant ore mineral 

in the NeUie group but is almost entirely absent elsewhere. Barite 

was noted at the Pope-Shenon mine only. The nonmetallic minerals, 

except the vein quartz, are largely the components of the original 

rock with the modifications suggested below. In the discussion that 

follows only the effects of hypogene mineralization are considered. 

The results of supergene processes are set forth in the succeeding 

section.

The ore bodies consist of roughly lenticular bands of variable size 

and composition lying approximately parallel to the sides of the lode. 

In places, especially near the sides, there are bands of soft gouge. 

Some bands consist of sheared country rock which in the hand specimen shows little alteration. Others are bleached and somewhat softened. Between the bands of country rock and penetrating them in 

places are stringers and lenses of massive white quartz. The metallic minerals are disseminated in both country rock and quartz, and 

in places they are concentrated into irregular bands of nearly solid 

sulphide. Thie sulphide minerals associated with the quartz are on 

the whole more coarsely crystallized than those in the country rock. 

The latter, however, have a much better developed crystal form.

During and before the hypogene mineralization the rock was subjected to great pressure. All the rock in the lodes is more crushed 

than that at a distance, and in numerous places there has been so 

much crushing and rearrangement of the constituents under pressure 

as to convert the rock in and near the lodes into schist. The character of the alteration shows that it could not have been produced by 

pressure alone without the addition of foreign material. The constituents of the metallic sulphides may be confidently assumed to have 

been introduced during mineralization. Magnetite and specularite 

are so abundant in places as to make it evident that ferric oxide has 

been added. Silica was brought in and deposited in veinlets and 

probably also interstitially in the mass of the rock. The bleaching 

. and softening noted are largely the result of the formation of sericite. 

This colorless mica was produced in large part by alteration of the 

biotite and chlorite of the original rock. Such an alteration implies 

the introduction of alkalies, especially potassium, from some outside 

source. The sericite or fine-grained muscovite was one of the last 

nonmetallic minerals to crystallize.
HYPOGENE MINERALIZATION 23

The epidote seen in several specimens of country rock obtained 

near ore bodies crystallized later than the groundmass of the rock. 

In the ore from the Porterfield prospect there are segregations of epidote evidently formed during mineralization. Probably part of the 

epidote was formed during the regional metamorphism and is not 

directly connected with the mineralization.

Part of the rock from the Pope-Shenon mine has a peculiar banded 

or layered structure. Such rock was not noted in place, but' a 

number of specimens were found on the waste dump. They presumably came from the main stope. In some specimens the layers 

take the form of irregular concentric ellipsoids; in others they are 

slightly curved and subparallel. In both varieties the rock breaks 

more readily along the boundaries of the layers than in other directions. In most of the specimens with concentric layers there is a 

much less distinct set of flat, parallel bands cutting across the ellipsoids. These bands probably mark the original bedding. The concentric layers are evidently entirely independent of the bedding 

planes. Alternate layers are black and green. In some specimens 

with subparallel layers the lighter layers are nearly white, but the 

dark ones contain larger proportions of the black material than in 

the specimens with ellipsoidal structure. The layering is not very 

clear-cut. In most specimens the dark layers shade off into the 

lighter ones more gradually on one side than on the other. Most 

of the dark layers are less than a tenth of an inch wide. The light 

ones are in general wider, some being over a quarter of an inch wide. 

Some specimens of this banded material bear striking resemblances 

in general appearance to organic forms.

The banded rock, like the rest of the country rock, consists essentially of quartz and micaceous minerals. The color of the dark layers is caused in part by black metallic minerals and in part by a 

greater concentration of biotite in these layers. A small part of 

the metallic material is magnetite, but much the greater portion is a 

copper-bearing mineral, which has been determined to be delafossite. 

This mineral is later in origin than the quartz grains and fills 

interstices and cracks in them. Part of the colorless mica appears 

to be of even later origin.

The delafossite is entirely without crystal form and is so hard that 

it can not readily be scratched with a steel needle. The mineral was 

determined by Edward Sampson to be rather feebly anisotropic in 

polished section. It is sufficiently magnetic to be attracted by a 

strong electromagnet but is distinctly less magnetic than the magnetite which accompanies it. Before the blowpipe the mineral is 

almost infusible but becomes strongly magnetic. A small amount 

of the material was separated as well as possible from the other constituents of the rock by means of an electromagnet and heavy solutions,
24 THE COPPER DEPOSITS NEAR SALMON, IDAHO

and was submitted to W. T. Schaller for determination. As can be 

seen from the analysis quoted below, a considerable amount of impurities remained with the mineral in the sample. The mineral itself is 

very readily soluble in hydrochloric acid, and all the soluble silica, 

the insoluble material, and the material lost on ignition listed in the 

analysis are to be regarded as impurities. After allowance is made 

for these, the composition of the mineral agrees fairly well with the 

theoretical composition of delafossite. As its physical characteristics, 

so far as determined, also agree with those of that mineral as given 

by Rogers 33 and no similar mineral is known, its correlation with delafossite seems established. The "loss on ignition" consists of water, 

sulphur, iodine, organic matter, etc., from heavy solutions.

Analysis of delafossite from the Pope-Shenon mine 

[W. T. Schaller, analyst]

Ferric oxide (FezOa)..: ________ ____ ____ _____________

Soluble silica (SiOs) . __ __________ ...... __.. ... _. _ ...

Analysis

27.94

33.06

30.94

.70

6.62

99.26

Composition 

after impurities 

are 

deducted

45.80

54.20

100.00

Composition calculated 

from 

formula 

CusO. 

F.esOs

47.29

52.71

100.00

In the few published descriptions of this rare mineral 33 it is said to 

be associated with kaolin or similar clayey material. The mineral 

first analyzed by Rogers was collected by To vote 34 at Bisbee, Ariz., 

where, he reports, it is sufficiently abundant to constitute commercial 

ore. Both the delafossite from Bisbee and that from Kimberly, Nev., 

came from the deepest part of the oxidized zone. At the Pope-Shenon 

mine there is a little oxidation in some of the ore from the level on 

which the delafossite was found, but many of the specimens containing the mineral show no evidence of oxidation or weathering. This 

fact and the intimate association of micas and magnetite with the 

delafossite lead to the belief that the mineral is here of hypogene 

origin. However that may be, it appears to have been produced by 

rhythmic deposition from a fluid that was diffused into the rock from 

openings produced by joints.

"Friedel, M. C., Sur une combinaison naturelle des oxydes de fer et de cuivre, et sur la reproduction 

de 1'atacamite: Compt. Rend., vol. 77, pp. 211-214, 1873. Dana, E. S., System of mineralogy, 6th ed., 

p. 259. Rogers, A. F., Delafossite, a cuprous metaferrite from Bisbee, Ariz.: Am. Jour. Sci.,4th ser., vol. 

35, pp. 290-294,1913; Delafossite from Kimberly, Nov.: Am. Mineralogist, vol. 7, pp. 102-103,1922.

« Tovote, W. L., Bisbee a geological sketch: Min. and Sci. Press, vol. 102, pp. 206, 207,1911.
OXIDATION AND ENRICHMENT 25

The rock in cuts on what is known as the "big ledge' 7 along the 

ridge crest above the Harmony mine and on the property of the 

Harmony Mines Co. contains considerable magnetite. Specimens of 

the country rock rendered schistose during mineralization contain 

disseminated grams and crystals of magnetite. There are bands of 

nearly massive magnetite which under the microscope can be seen tobe hi part replaced by specularite.

The gravel on Hayden Creek contains pebbles of magnetite and! 

specularite, some of which are so little waterworn that they were 

probably derived from near-by talus slopes. It is reported that on 

the ridge tops in this vicinity there are numerous exposures of such 

material in place.

In most of the copper deposits visited chalcopyrite and pyrite are 

the only hypogene sulphides visible in the average ore. The chalcopyrite is much more abundant than the pyrite and was formed somewhat later. Bornite is the principal ore mineral in part of the ore 

on the Nellie group and is almost certainly of hypogene origin. 

Traces of zinc are reported in a few of the smelter returns on shipments from the Harmony and Pope-Shenon mines. These doubtless 

result from the presence of sphalerite, as tiny grains of this material 

are reported to have been observed in some of the ore.

The average ore mined carries 2£ to 6 per cent of copper. Lensesof ore containing 10 to 20 per cent of copper have been found, but 

few of these are large enough to be mined separately. Most of thehigh-grade unconcentrated ore shipped has been obtained by careful 

hand sorting. The ore in most of the deposits examined contains 

negligible amounts of gold and silver. Few shipments of concentrates from the Pope-Shenon and Harmony mines contain much overa dollar's worth of precious metals to the ton. Ore from the Dishman prospect, however, is reported to carry gold to the value of a 

few dollars to the ton. In contrast to these, most of the deposits in. 

Lemhi County containing appreciable quantities of copper described,, 

by Umpleby were worked primarily for their gold content.

Barite was found in a narrow vein at the Pope-Shenon mine. 

This vein contains also small amounts of oxidized copper mineralsand cuts diagonally across the main zone of shearing. The barite 

has a dark, smoky color, in places with a violet tinge, and shows - 

well-marked zonal banding. This mineral was not observed elsewhere. 

It was formed later than the main deposit.

OXIDATION AND ENRICHMENT

Small amounts of oxidized ore containing malachite, azurite, cuprite, and in places native copper are present in exposed parts of all 

the deposits, and at some of the deposits such ore has been mined 

and shipped. In the Pope-Shenon mine, especially on the upper-
26

levels, so much oxidized ore was found that a chlorination mill was 

erected to treat it. Most of the sulphide ore in the mines shows incipient oxidation. On the other hand, unoxidized sulphides are found at 

or close to the surface in all of them. In general the amount of oxidized 

ore is small compared to that of the nearly unaltered sulphide ore. 

Erosion is evidently so efficient on the steep slopes where the 

deposits crop out that in most deposits it almost keeps pace with oxidation. At the head of the gulch in which the Anderson workings 

of the Harmony Mines Co. are situated is a small cirque, which 

indicates that here glaciation has played a part in removing the softened oxidized parts of ore bodies.

In specimens from a number of the mines small amounts of chalcocite were found. Its relations to the other sulphides show clearly 

that here, as hi most other regions where it occurs, the chalcocite was 

deposited by downward-percolating water that derived its copper content from the leached upper parts of the ore bodies. Chalcocite contains a larger percentage of copper than chalcopyrite, and its presence 

in otherwise unaltered sulphide ore implies that such ore is of comparatively high grade. There is so little chalcocite in the average ore 

exposed in any of the mines, however, that it can be positively identified only under the microscope, and its absence in the deeper ore 

probably does not result in a sufficiently marked decrease in average 

copper content to be of commercial importance. Much of the chalcocite shows incipient alteration to oxide material of indefinite composition, such as has been termed copper pitch ore.

AGE AND GENESIS

The mineral associations in the copper deposits are those generally recognized as characteristic of deposition at rather high pressure 

and temperature. It appears that the first stage of mineralization 

"was the alteration of the rock in and near the shear zones. This alteration is similar to but more intense than the metamorphism of 

the great masses of quartzitic strata termed in this report the "metamorphic rocks." The nonmetallic minerals in both the country rock 

and the lodes are similar and represent the introduction of new material as well as the recrystallization of material already present. The 

elements added were silica, iron, and alkalies. The quantities added 

were somewhat greater, and the rock is locally more schistose in the 

lodes than in the country rock at a distance from them. The metallic minerals were introduced into the lodes at a somewhat later stage, 

and the vein quartz, at least in part consolidated later than the sulphides. Chalcopyrite was the last hypogene sulphide to crystallize.

Evidence has been presented to show that the shear zones were 

produced during a period of diastrophism at the end of the Mesozoic 

era, and further that the movements at that time may be related to
OUTCROPS 27

the intrusion of the batholith of central Idaho. As already stated,

regional metamorphism in the quartzitic rocks probably resulted from

the action of aqueo-igneous agencies. The similar alteration in the

j rocks of the lodes is almost certainly of closely related origin that

' is, it is due to waters emanating from the granitic magma, which

were also the only adequate source for the copper and sulphur of the

deposits. The excess iron, silica, alkalies, and possibly other sub-

- stances introduced during mineralization probably were also derived

 from such waters.

No igneous rocks except the intensely altered dike in the PopeShenon mine were found in direct association with the ore bodies. 

The only intrusive rocks known near the copper lodes visited are the 

small dacite masses of probable Tertiary age near the Porterfield 

prospect and between that locality and Salmon Hot Springs. The 

lodes, however, present none of the well-known characteristics of deposits formed in connection with Tertiary lavas. The only known 

igneous masses in the region that are adequate and suitable to serve 

as a source for mineralization of the type found are the granitic rocks 

of the batholith of central Idaho and its offshoots. This statement 

is in accord with the conclusion of Umpleby 35 regarding the similar 

and evidently related deposits elsewhere in Lemhi County which he 

describes.

The sequence of events appears to have been as follows: At about 

the end of the Mesozoic era large masses of graniti" magma were inI truded. As a result of the consequent heat and pressure, probably 

I aided by emanations from the cooling magma, the i\ ipure quartzitic 

' rocks that form the lowest part of ^e stratigraphic column were 

extensively metamorphosed. These roo.'s were probably already 

folded as a result of previous diastrpphism. Powerful earth movements took place at about the same time as the batholithic intrusion. 

Probably crustal disturbances were initiated early in the magmatic 

period and continued during and for a time after the intrusion. 

Among the comparatively minor effects of the disturbances were 

shear zones and fractures, along which the magmatic emanations, 

following the paths of least resistance, concentrated. Consequently 

the rock adjacent to these zones was first more intensely metamorphosed, and then sulphide minerals and quartz were deposited in 

the rock and in fissures in it.

i OUTCROPS

* The outcrops of the copper deposits are rather inconspicuous. 

Some are marked by small amounts of limonite, scattered copper 

stains, and lenses and irregular masses of quartz, but others show 

little more than indistinct shearing in the rock. In some the shearing

,> » Umpleby, J. B.. op. cit (Bull. 528), pp. 81-82.
28 THE COPPER DEPOSITS NEAR SALMON, IDAHO

and subsequent alteration have been sufficient to give the rock a 

schistose appearance. The rock in some of the shear zones has in 

places been bleached nearly white. In most of them, however, thorough oxidation has not extended far below the surface, and hypogene \ 

sulphides are found at shallow depth or may even appear at the \ 

surface.

In the area eontaining the known copper deposits there are few 

satisfactory outcrops of rock in place. Most of the rock not covered 

by soil is concealed under extensive accumulations of talus. This 

makes the search for mineral deposits difficult, especially as there is 

little in the broader features of the lithology or structure that is of 

assistance to the prospector. Copper deposits of the type of those 

here described are probably confined to the metamorphic rocks, and 

their distribution may be related to some of the larger structural 

features of the region, but the known relations are not sufficiently 

restricted and definite to be of much aid in prospecting. The best 

that can be done is to examine carefully the outcrops and talus in 

the general zone containing the known deposits for any indication of 

mineralization. Any evidence of shearing should be "studied, for it is 

entirely possible that a shear zone which contains an ore shoot at 

depth may show little sign of metallization at the surface. Distinction should be made between shear zones and zones of brecciation, 

in which angular fragments of rock torn from the walls are held in a 

paste composed of ground-up rock of similar appearance. Such 

breccias are fairly common in the metamorphic rocks but are not j 

known to be mineralized. Once a promising shear zone has been / 

found, search should be made along it for outcrops of ore shoots or 

places where shoots may be inferred to be present at slight depth. 

Any evidence of comparatively intense alteration in the rock is a 

favorable indication, but the presence of sulphide minerals or their 

oxidation products is the most satisfactory guide for further prospecting. There appears to be in general somewhat more quartz in 

the ore shoots than in barren parts of the shear zones, so that an 

abundance of quartz is also a favorable sign. It is also well to look 

for intersections of shear zones or cross fractures of any kind, because 

at such places ore shoots are more likely to have been formed than 

elsewhere. Indications of this sort might warrant a certain amount 

of development, even though there was little direct evidence of metallization in the outcrop.

On the property of the Harmony Mines Co., where rock outcrops i 

are better and more extensive than hi many other localities in the 

vicinity of Salmon, at least six lodes are known to be present. This 

suggests that careful prospecting might be rewarded in the vicinity 

of known ore bodies where the bedrock is less well exposed.
THE COPPER DEPOSITS NEAR SALMON, IDAHO 29 

OPERATING CONDITIONS AND FUTURE OF COPPER MINING

Although mining has been in progress in Lemhi County for over 

hah* a century, copper mining in this region is a comparatively new 

thing. None of the mines in the county had made regular shipments 

of copper ore before 1918, and much of that shipped previously was 

found hi mines that were worked principally for gold. None of the 

deposits worked primarily for copper have been sufficiently developed 

to show their ultimate possibilities, and local conditions governing cost 

of production and markets were not studied in detail, although some 

data are available. From the facts at hand, however, some idea of 

the future possibilities of the deposits may be gained.

The average ore mined carries from 2J^ to 6 per cent of copper and 

negligible amounts of gold and silver. None of the substances deleterious to smelting are present in appreciable amount. The sulphide 

ore can be satisfactorily concentrated by simple means. It is reported 

that recoveries of more than 90 per cent are obtained by the use of 

table concentration, supplemented by oil flotation. The concentrates 

carry about 20 per cent of copper or a little less. Gravity concentration without the aid of flotation results in the recovery of only about 

60 per cent of the copper.

Most of the known deposits crop out on steep mountain sides hundreds of feet above the streams at their bases. As a result they have 

been developed by means of tunnels, with consequent convenience 

and economy in underground haulage. The ore is quickly and cheaply 

sent from the mine portal to the mill on aerial tramways. On the 

other hand, transportation of supplies and men up the slope to the 

mine is slow and laborious.

c _

The ore is mined by overhead stoping. The rock is hard but not 

excessively so. Both ore and country rock stand fairly well. Untimbered prospect tunnels remain for the most part in good shape for 

years. Drifts above which stoping is in progress require timbering, 

and there are local zones of fractured rock that will not stand without it, but the amount of timber required in drifts and stopes is hi 

general moderate. The mountains are forest-clad and furnish an 

abundant supply of lumber of sufficiently good quality for underground use.

Transportation of supplies to the mill sites below the mines and 

of ore and concentrates from them is a matter of some difficulty and 

expense. Wagon roads connect the mill sites of most of the properties with the main highways, and others could be constructed to 

reach the prospects not now accessible by this means. The mine 

roads are rough, unfinished, and poorly graded, but the distances are 

not great. The distance to a main highway is everywhere well
30 THE COPPER DEPOSITS NEAR SALMON, IDAHO

under 10 miles, and that from the junction with a highway to a railroad station is only a few miles farther. Ore is hauled over the 

roads throughout the year,-but during the winter hauling is attended 

with some difficulty. The ore and concentrates shipped are con- \ 

signed to smelters in Salt IJake City, Utah. \

Labor conditions in the district are fairly good. Many of the 

farmers possess a knowledge of mining and Constitute a body of intelligent and industrious men from which to recruit miners in addition to those who follow that trade exclusively. The supply of men 

is adequate for present needs except during the short seasons when J 

many men are needed on the farms. V.

From the available information it is evident that the district con- I 

tains a number of copper deposits in which there are rather small * 

shoots of ore of moderate grade and streaks of high-grade ore. Sufficient ore to continue mining on the present or a somewhat larger scale \ 

for a considerable number of years can probably be found. The character of the ore and the containing rock, the size and attitude of the 

ore shoots, and the to > graphic situation of the deposits are all 

rather favorable to mining on a small scale. Labor conditions are 

probably about as good as in the average mining district at the present time, but transportati n c osts are doubtless higher, than those cf 

many districts. H. A. C. Jenison 38 of the United States Geological 

Survey, who has made a special study of such rratters, estimates 

that under the general conditions prevailing in this district refined 

copper can not be produced at a cost of much less than 12. cents | 

a pound, without allowance for depreciation, taxes, and similar j 

charges. Except under the r ost careful and efficient management 

and with suitable mine and mill equipment the cost might well be 

higher. He adds that at the present time the copper-mining industry in the United States is about 25 per cent overdeveloped. The 

increase in the world's consumption of copper in the near future can 

easily be counterbalanced by increased production from mines in 

South America and Africa. In view of these facts investment in 

new copper mines sh uld be under aken with great caution. Only 

under the mos favorable circumstances and skillful management 

can newly opened copper mines be expected to become successful.

MINES AND PROSPECTS

The copper deposits examined during the present investigation are 

here described in the order of their geographic position, from northwest to southeast. A brief description of one recently opened prospect 

that is worked principally for lead and silver is added. For descriptions of other copper deposits in Lemhi County the reader is referred to

86 Personal communication.
MINES AND PROSPECTS 31

limpleby's report on the ore deposits of that county. 37 The present 

section is believed to include descriptions of all the copper mines and 

prospects that have been actively worked in the last few years.

There are half a dozen other prospects near Salmon which have 

shipped small amounts of copper ore in recent years, as shown by 

the records of the United States Geological Survey, but regarding 

which nothing was learned during the visit to the area in the summer of 1923. These are the Blue Bird, Castle Rock, Gold Point, 

Patton, Royal Gold, and Ruby properties. Most of them are probably in the Beaverhead Mountains and are presumably inactive at 

present.

There were probably few shipments of ore mined primarily for 

copper from Lemhi County prior to 1911, although this metal was 

present in some of the gold and lead-silver ore shipped before then. 

The total amount of copper obtained from such ore was probably 

not large. Umpleby,38 v^hose field work in the county was done in 

1910, estimated the value of the copper ore produced in the county 

as $40,000. The table below, compiled by C. N. Gerry, statistician, 

of the United States Geological Survey, gives the production of 

copper ore from 1911 to 1922. In the summer of 1923 two mines 

were producing steadily, and a third was preparing to start regular 

production, so that the tonnage of copper ore produced in the county 

may be expected to increase markedly.

Copper ore produced in Lemhi County, Idaho, 1911-1922 

[Compiled by C. N. Gerry]

Mine

Oold Point _____ - ___ _________

Patton ___ . _____________ .- __

Royal Gold. . __ ___ . __ ... _ . __ .

Ruby ...... _ __ .... __ . _____ . .....

Date

1917...............

1915-1916 . ........

1911-1922. _____ .

1915-1918 __ . .....

1916-1922.. ........

1914 and 1917.. ....

1917-1922..........

1917. _ ....... _ .

1915...............

1917... ............

1918-1922..........

Ore 

(short 

tons)

8

12

2,601

9

17, 250

62

2,096

13

22

20

213

22, 306

Gold 

(ounces)

3.66

2.15

930. 77

10.41

9.83

.0?

5.18

58.19

4.71

2.20

.69

1, 027. 87

Silver 

(ounces)

68

449

5,006

89

923

7

476

175

82

156

116

7,546

Copper 

(pounds)

1,432

1,533

529, 758

2,671

753, 952

10, 402

297, 969

869

3,235

3,248

80,161

1, 685, 230

DISHMAN PROSPECT

The Dishman prospect is on a gulch on the left side of the north 

fork of Perreau Creek, in the Salmon River Mountains, about 1,500 

feet vertically above the bed of the stream and 8,000 feet above sea 

level. It is roughly 6 miles west of the point where Perreau Creek

3'Umpleby, J. B., op. cit. (Bull 528), pp. £9, 70, : "Idem, p. 50.9, 110-111, 120-124, 127, 155, 164.
32 THE COPPER DEPOSITS NEAR SALMON, IDAHO

enters Salmon River. The workings comprise one tunnel about 50 

feet long, another about 170 feet long, and a number of cuts and 

shallow openings. The cabin is at a spring a short distance above 

the workings. The country rock is siliceous slate that is nearly black 

in color. The principal slips in the two tunnels examined strike N. 

70° W. and dip 50°-60° N. Along these slips is gouge and altered 

slate, with some quartz, chalcopyrite, pyrite, and the oxidation products limonite, malachite, and chrysocolla, and they are reported to 

contain enough gold to be of some commercial value. Both tunnels 

also cut a number of smaller slips with diverse strikes and dips, along 

some of which there is gouge and a little pyrite. The tunnels and 

cuts are distributed over a few hundred feet of mountain side and are 

evidently in a zone of shearing La the slate in which there has been 

sporadic mineralization. The developments are insufficient to demonstrate whether or not any ore bodies of commercial size exist here.

TOBMEY MINE

The Tormey copper mine is on the north side of Perreau Creek, 

probably in unsurveyed sec. 34, T. 21 N., R. 21 E. It is at an altitude of over 6,000 feet above sea level. There is a group of cabins 

belonging to the property on a small creek north of the mine, and 

some buildings on Perreau Creek just south of the mine and 1,000 

feet below it. Both camps are connected with Salmon by roads, but 

that to the camp on Perreau Creek is the better one for automobiles.

The claims were originally located by John Tormey a number of 

years ago, and most of the development work on them was done by 

him. Shipments of hand-sorted ore have been made at various tunes 

from 1918 to 1920, which according to the records of the United States 

Geological Survey aggregate 187 tons containing 70,125 pounds of 

copper, 0.69 ounce of gold, and 116 ounces of silver. Some of the 

sorted ore contained as much as 17 per cent of copper.39 Late in 1922 

the deposits were leased by W. M. and G. A. Snow and R. E. Wickham, 

who sorted and shipped 26 tons of ore containing 10,036 pounds of 

copper. In the summer of 1923 they were engaged in erecting a 

small concentrating mill at the camp on Perreau Creek and otherwise 

preparing to put the property on a producing basis.

The present mine workings consist of two tunnels and some small 

cuts. One of the tunnels, known as the Greenhorn, is almost directly 

above the camp on Perreau Creek and was formerly connected with 

it by a tramway. The lessees plan to build an aerial tram here. This 

tunnel is 385 feet long, and there are short crosscuts off it and stopes 

above it, as is shown in Figure 5. The other tunnel, known as the

'9 Bell, R. N. (State inspector of mines), Twenty-first annual report of the mining industry of Idaho, for 

the year 1919, pp. 98-99,1920.
MINES AND PROSPECTS 33

Rattlesnake, is over a quarter of a mile farther upstream and a little 

higher up the slope than the Greenhorn tunnel. The Rattlesnake tunnel is about 300 feet long, and two short drifts lead fr'om it, as is shown 

in Figure 6.

The rock hi the vicinity of the Torm.ey mine is black and gray 

quartzitic slate and slaty quartzite. The bedding is indistinct but 

appears to have a general dip to the east and.to^be nowhere steeply 

inclined. The Greenhorn tunnel follows a zone of shearing. The principal slips are indicated in Figure 5. Near the portal the strike of 

the shearing is about N. 30° W. Farther in it swings gradually around 

to about N. 70° W. The dip in most places where observed is about

.Ore in back

o ore in tunnel from 

hereto portal

14ft.of sheared andmineralized slate 

mostly milling ore Raise

to stppe up 60ft 

Ore in bunches

Raise to stop

up 70ft. or> 50° slope

Ore remaining 2ft.-»-thick

FIGURE 5. Geologic sketch map of Greenhorn tunnel, Tormey mine

55° NE. No ore is visible in the first 270 feet of the tunnel or in the 

face, but there are two stretches 50 feet and 40 feet long in which ore 

shows in the back of the tunnel. In the space between these stretches 

there are some bunches of ore. Stopes extend most of the way from 

a point near the face of the tunnel to a point about 120 feet from the 

face and for a few score of feet above the tunnel. The stopes are 

nowhere more than a few feet wide, but the exposures in them and in 

the crosscut at the end of the tunnel appear to indicate that a considerably greater width of ore suitable for concentration may be found 

on further development. The ore consists of chalcopyrite and pyrite
34 THE COPPER DEPOSITS NEAR SALMON, IDAHO

in a gangue of quartz and altered slate. Cracks in the chalcopyrite 

are lined with narrow bands of chalcocite, each of which shows copper oxide material of indefinite composition in the middle. Some of 

the ore in surface exposures is oxidized. The oxidization and enrichment noted are so small in amount as to be of little commercial consequence.

The Rattlesnake tunnel (fig. 6) is a crosscut trending about N. 5° 

E. About 210 feet from the portal it cuts a shear zone which strikes 

about N. 60 W. and dips about 55° SW. A drift on this zone about 

20 feet long discloses a band of chalcopyrite ore about a foot wide.

N.30°W. cleavage

,Winze full of water

I '±chalcopyrite ore 

Bedding almost flat

FIGURE 6. Geologic sketch map of Rattlesnake .tunnel, Tormey mine 

POPE-SHENON MINE

The Pope-Shenon mine is near the north end of the Lemhi Range, 

in sec. 9, T. 20 N., R. 22 E., about 8 miles by road southwest of 

Salmon. The property comprises 12 unpatented claims. There is 

a blacksmith shop and a compressor room at the mine, and a concentrating mill, boarding house, and other buildings below it. The 

haulage tunnel of the mine is connected with the mill by a tramway.

Some claims were located here in the early nineties by Lige Stroud 

and James Fenning and held as a gold prospect. 40 Two years later

10 Most of these historical data were supplied by P. J. Shenon, of Salmon.
MINES AND PROSPECTS 35

Thomas Pope, Red McDonald, Thomas Andrews, and Richard 

Clark located two copper claims. Later Philip Shenon acquired a 

two-thirds interest. About 1917 the property was taken over by 

some Salt Lake City people. In 1917 one shipment of hand-sorted 

ore was made, 41 and in 1919 there were shipments amounting to 

360 tons containing an average of 12 per cent of copper. 42

By this time development had proceeded far enough to show the 

presence of a body of copper ore, much of which was considered too 

thoroughly oxidized to be efficiently concentrated by gravity. As 

a result of experiments with samples of the ore at the University 

of Utah a chloridizing plant was.built at the mine in 1919 and operated in 1920 and 1921. In- this plant 43 the ore was crushed and 

mixed with chloride material. Common salt and calcium chloride 

slag produced in the process and returned were used. The ore and 

chloride were fed to a revolving furnace and heated sufficiently to 

fuse the surface of the mass. The copper was volatilized as copper 

chloride. The fumes were passed first through a flue in which the furnace dust was removed and then into a Cottrell precipitator. The precipitated copper chloride fume was mixed with limestone and coke and 

fed to an oil-heated reverberatory furnace. The products were metallic copper and calcium chloride slag, both somewhat impure. The 

experiments with this process gave favorable results, but it is reported 

that in practice at this mine the difficulties encountered were so great 

that work was abandoned.

On August 1, 1922, W. M. and G. A. Snow took a lease on the 

property. Tliey have remodeled the mill into a gravity concentrator 

equipped with jigs, tables, and a small oil-flotation unit. The chalcopyrite ore now being mined has proved suitable for treatment in 

this mill. From September 25, 1922, to August 14, 1923, a total o 

940 tons of concentrates with an average content of 22 per cent < 

copper was shipped to a smelter at Salt Lake City, Utah. The smelter 

returns show that in.one shipment the concentrate carried a trace of 

zinc and in three others it carried about 0.5 per cent of calcium oxide. 

The silver content was less than 1 ounce to the ton in most shipments, 

and the gold content was 0.01 ounce to thp ion or less in all but one 

shipment, which ran 0.11 ounce to the ton. The ore mined is considered by the Snow Brothers to average about 6 per cent of copper.

The mine has been developed by a series of six tunnels, numbered 

consecutively, starting with the one highest up the mountain side. 

All of them follow the lode except the lowest, which is a tunnel 40 feet 

long in barren rock opening at the rear of the mill. All but this one

41 Bell, R. N., Nineteenth annual report of the mining industry of Idaho, for the year 1917, p. 72,1918.

« Bell, R. N., Twenty-first annual report of the mining industry of Idaho, for the year 1919, pp. 97-98, 

1920.

43 Bradford, Robert, The volatilization process at the Pope-Shenon mine; Min. and Sci. Press, vol. 123, 

pp. 263-266, Aug. 20, 1921.
36 THE COPPER DEPOSITS NEAR SALMON, IDAHO

are shown in Plate IV, which is based on a map and longitudinal section prepared by W. M. Snow and P. J. Shenon in July, 1923. There 

are in all about 1,475 feet of drifts, a large stope from tunnel No. 5, 

smaller stopes from tunnels Nos. 2 and 3, and three raises, besides a ( 

few shallow prospect openings not mapped. V

The country rock is a dark-green, impure quartzite with light-colored 

beds in places. The bedding can be seen in most exposures when 

closely examined but is not obvious at a distance. The beds are 

built up of interfingering lenses a fraction of an inch thick and a few 

inches long. The strike in the more distinctly bedded exposures is 

about N. 30° E., although in several places it appears to swing v 

farther to the north. The maximum dip observed is 35° E., and the 

minimum is less than 10° E. There is a moderately pronounced 

schistosity striking in general a few degrees east of north and dipping 

about 60° W. About a quarter of a mile north of the mine an 

outcrop of a rock resembling conglomerate has recently been found.44 \ 

This rock contains boulders as much as a foot in diameter of darkercolored quartzite in a quartzitic matrix similar to most of the rock in 

the vicinity. This is the only exposure of this sort known in the 

metamorphic rocks.

The lode strikes nearly east and dips 70° N. An ore shoot is 

exposed for 200 feet on level No. 5. The shearing and alteration of 

the rock continues in both directions beyond the shoot, but only 

meager amounts of valuable minerals are present. Near the innermost face on this level there are a number of small slips with various 

strikes, along which are brecciated quartzite, gouge, and small 

amounts of oxidized copper minerals. There is an irregular band 

about a foot wide of soft yellow material parallel to the strike of the 

lode. The composition of this material has not been determined, but 

it is thought to have been a fine-grained porphyritic dike. Similar 

material has been found hi the stope above. It contains fragments 

of rather calcic feldspar and chlorite and other alteration products 

derived from its original ferromagnesian minerals.

In the stope above this level the shoot has been followed vertically 

upward for 125 feet. The average width mined is somewhat less than 

10 feet, but near the middle of the stope a maximum width of 20 feet 

was attained. The unmined masses left in the stope are in part of 

low grade but contain also some good ore. Their shapes and positions have resulted rather from variations in mining methods under 

different managements than from variations in the character of the 

ore. The copper in the ore of the main stope is principally in the 

form of chalcopyrite, but small amounts of chalcocite are generally 

present, and oxidized minerals are found in places, especially near

44 Shenon, P. J., letter of Oct. 4,1923.
U. 8. GEOLOGICAL SURVEY

EXPLANATION.

Bedding ofroc/r

Schistosity

Mine workings from section 

by PJShenon,

BULLETIN 774 PLATE IV

ffoc/c /is brecciated ^

LEVEL NO l_

'in drift to 

southeast 

there is a shear 

zone dipping 

50°N. with qudi-u 

and some 

copper carbonate

Geology by C/yde PRoss, 

assisted by A. LAnderson 

and P.d.Snenon

Strong shearing parallel to 

tunnel dipping 70°N. 

Smell amounts of copper 

carbonates and 

cha/cocite

Shear zone 

with copper stains

Slip N. SS°E. 4S°NW. barite 

and little cuprite and 

malachite

Shearing parallel to tunnef 

dipping 60°70°N,

Oxidized ore mined from the 

Stopes on this level

Ore extracted largely primary; 0 

some carbonate ana tittle \ /

Figures indicate 

width ofstope

slips at angles 

main shearing 

Iron and copper stains

on& shearing 

'el to tunnel

Well-defined wall on north 

dipping 75°-88°N.with &ouge

VERTICAL SECTION 

PROJECTED

40 0 40 80 120

33004 25. (Face p. 36 )

PLAN

PLAN AND VERTICAL SECTION OF POPE-SHENON MINE

Section is parallel to average strike of lode and shows geologic relations of the ore body
MINES AND PBOSPECTS 37

the borders of the stope. Oxidized ore is reported to have been 

mined from the small stopes on the upper levels. In a small stope 

on level No. 3 there is a narrow vein containing barite and small 

amounts of oxidized copper minerals. It strikes N. 55° E., dips 45° 

j NW., and cuts the main zone of shearing. The occurrence of the 

rare mineral delafossite at this mine is described in some detail i on 

pages 23-24.

PORTERFIELD PROSPECT

J. Porterfield has a copper prospect on the west side of Mulkey 

Creek in the Lemhi Range, at 'an altitude of somewhat more than

/ 8,000 feet above sea level. It is near the center of T. 20 N., R. 22

/ E., probably in sec. 22.

; The prospect is developed principally by a tunnel about 190 feet 

long, of which 50 feet is in mineralized ground. There are less extensive workings, also showing mineralization, above this tunnel, and a 

cabin near two small springs about 700 feet vertically below it.

The country rock is a dark-greenish impure quartzite or siliceous 

slate. In the tunnel its-cleavage, which apparently coincides in 

direction with the bedding, strikes' N. 75° W. and dips 25° S. Near 

the cabin is a small dike of weathered gray porphyry that has approximately the composition of dacite. This dike appears to strike about 

N. 80° E. The " float ;; found indicates the presence of other similar 

dikes in the vicinity. The last 50 feet of the main tunnel follows a 

slip striking about N. 65° W. and dipping 55° S., along which there 

is considerable brecciated and altered rock and some malachite and 

limomte. Some of the mineralized rock on the dump contains epidote 

in clusters of small crystals.

HARMONY MINE

The Harmony mine is near the head of Withington Creek in the 

Lemhi Range. The property consists of 21 unpatented claims and 

a mill site in sec. 2, T. 19 N., R. 22 E., and adjoining sections. The 

mill and lower camp are at an altitude of about 7,000 feet above sea 

level, and the mine buildings and portal of the main haulage tunnel 

are 1,200 feet vertically above the lower camp and are connected 

with it by an aerial tram.

The ore deposits here were probably discovered a considerable 

time ago, but little development work was done before the Harmony 

Mines Co., the present owner, acquired the property in 1916. This 

company maintained a small production up to 1919, when a concentrating mill equipped with crushing machinery, classifiers, and tables 

was built. A flotation plant was added later. The mill is reported 

to be able to treat a maximum of 200 tons of ore a day, but less than 

half that amount is fed to it. Since the completion of the mill a
38 THE COPPER DEPOSITS NEAR SALMON, IDAHO

steady production of'concentrates has been maintained except in 

1921, when in common with many other copper mines the Harmony 

suspended operations. The records of the United States Geological 

Survey show that from 1916 to 1922, inclusive, 842 tons of crude ore 

and 1,502 tons of concentrates were shipped. The crude ore shipped 

contained 132,297 pounds of copper, 0.68 ounce of gold, and 130 

ounces of silver. The concentrates contained 621,655 pounds of copper, 915 ounces of gold, and 793 ounces of silver and were derived from 

16,408 tons of ore milled. The smelter returns from the 42 shipments 

made from January 4 to December 10,1923, show that the concentrates 

had an average content of 22.7 per cent of copper, 1.58 ounces of 

silver, and 0.01 ounce of gold to the ton, 19.8 per cent of silica, 25.4 

per cent of iron, and 24.7 per cent of sulphur.

The principal underground workings are on the Contention claim, 

and comprise three levels, known as the 100-foot, 200-foot, and 300- 

foot levels. On the 100-foot level there is a crosscut tunnel 265 feet 

long and a drift 160 feet long with a stope above it. The portal of 

the 200-foot level is 78 feet vertically farther down the mountain 

than that of the 100-foot level, and there are 1,000 feet of drifts and 

crosscuts on this level. The 300-foot level is the haulage level of the 

mine, and its portal is 95 feet vertically below the portal of the 

200-foot level. Stopes and raises connect the 200-foot and 300-foot 

levels, and there is a small stope on the 100-foot level. The 300-foot 

level comprises over 2,500 feet of drifts and crosscuts. These three 

levels and the principal workings in other parts of the property are 

shown on Plate V.

In addition to the main mine, whose workings are outlined above, 

the Harmony property includes the Anderson and Income workings 

and several small shafts and cuts. The portal of the Anderson workings is 425 feet above and about 2,000 feet west of the portal of the 

300-foot level of the main mine. The Anderson workings comprise 

about 510 feet of drifts and crosscuts now open, with stopes above, 

one of which extends about 100 feet to the surface.

The portal of the Swift tunnel, the principal tunnel on the Income 

group, is at about the same altitude and somewhat over 3,100 feet 

southeast of the portal of the 300-foot level of the main mine. The 

Swift tunnel is about 900 feet long, and there are shallow shafts and 

short tunnels above it.

On the Harmony property the rock is a dark argillaceous quartzite 

with some light-colored, more siliceous beds. The dark rock is less 

green in color than that near the Pope-Shenon and Porterfield properties. The bedding in many exposures can be seen at a glance, 

even from a distance. The average strike is about N. 30° W., and 

the dip is 15° S. or less. The rock shows little schistose cleavage.
U. S. GKOJ.OGICAT, STJRVKY BULLETIN 774 PLATE V

BUNKER H/LL No.

ANDERSON WORKINGS

33094 25. (Face p. 38.)

____jOutcrop of lode observed af the surface 

or inferred position by projection

SKETCH MAP SHOWING RELATIONS OF LODES ON PROPERTY OF^HARMONY MINES Co.
f

MINES AND PROSPECTS 39

The two lodes in what may be termed the Harmony mine proper 

are called the Leapyear and Contention veins. Besides these there 

are on the company's property the two lodes in the Anderson workings, the "big ledge" near the crest of the mountain, a lode exposed 

on the Bunker Hill No. 2 claim, one or more lodes on the Income 

claims, and possibly others. The principal production to date has 

been from the Leapyear and Contention veins, especially from the 

Leapyear. There are small stopes on both the lodes in the Anderson 

workings. The other deposits mentioned have been prospected to

FIGUEE 7. Block diagram showing relations of ore shoot in Harmony mine to Contention and Leapyear lodes

some extent, but little ore has been mined from them. The known 

lodes are indicated on Plate V, except the "big ledge," which crops 

out on the Bunker Hill No. 4 claim.

The average strike of the Contention lode is N. 30° W., and that 

of the Leapyear lode is N. 40° W., but the strikes of both vary 

considerably. The Contention lode on the 100-foot level strikes 

more nearly N. 20° W. The average dip of both is about 60° SW., 

but in this also there is considerable variation. In some places in 

the stopes the dip flattens greatly. The ore is reported to be in general richer in the flat parts of the lode than in the intervening steeper
40 THE COPPER DEPOSITS NEAR SALMON, IDAHO

parts. As is shown in Plate V and Figure 7, the two veins join, but 

only one vein has been found to the southeast of the junction, and 

they may merge into one. However, the small amount of crosscutting that has been done on the 300-foot level is insufficient to determine this point. The ore shoot that is being stoped has a rake 

approximately parallel to the line of juncture of the two lodes as is 

shown diagrammatically in Figure 7. Most of the ore is on the 

northwest side of the line of juncture. The ore has been followed 

in the Leapyear lode for 230 feet from the junction on the 300-foot 

level and found to have a width of 6 to 10 feet. In the stopes above 

this level the width is 10 feet and more. The drift on the lode on 

the 300^foot level extends about 70 feet beyond the end of the ore 

shoot, and in the face narrow seams of chalcopyrite are exposed over 

a width of 10 inches. This is the most favorable showing outside of 

the ore shoot itself. The ore on this level is unoxidized. On and 

above the 200-foot level there has been some oxidation, with the 

development of cuprite and copper pitch ore, but in nearly all the 

ore mined sulphide minerals predominate. The principal valuable 

mineral is chalcopyrite. Chalcocite is present in much of the ore, 

but the amount is insignificant. Several unmineralized, gouge-lined 

slips are exposed in the workings, and two of these offset one of the 

lodes a few feet.

In the Anderson workings the conditions are similiar to those just 

described. Here also there are two lodes which come together at a 

small angle, and ore is found near the junction, but the lodes diverge 

toward the southeast instead of the northwest, as in the Harmony. 

The lode on which more development work has been done strikes N. 64° 

W. and dips 60°-70° SW. The other one strikes about N. 55° W. and 

dips 50° SW. There are stopes on both. The first-mentioned lode 

crops out in the face of the cliff about 90 feet vertically above the 

portal of the tunnel, and sulphides are exposed in it at the surface. 

The other lode has been stoped to the surface, a distance of about 

100 feet. Two slips are exposed near the portal of the crosscut tunnel through which the lodes were developed. Both strike N. 55° W. 

and they dip 75° and 60° SW.

The lode known as the "big ledge" has been developed only by 

shallow cuts. It is on the south side of the crest of the Lemhi Range 

above the Anderson workings. The location of the lode on Plate V 

is only approximate. Where observed, the strike is N. 55° W. and 

the dip 55° SW. The lode is marked by strong shearing and the 

development of considerable chlorite and magnetite and a little specularite. The exposures are rusty, probably from the oxidation of 

pyrite.
MINES AND PROSPECTS 41

On the north slope of the range between the "big ledge" and the 

Harmony mine another lode is exposed at what is known as the upper shaft. The strike is about N. 65° W., and the dip is 70° SW. 

Considerable quartz is present.

The Swift tunnel on the Income .group follows a shear zone with 

steep southerly dip, hi places nearly vertical. Near the inner end of 

the tunnel the shear zone is offset several feet to the south on a fault 

that appears to strike nearly north and dip west. No sulphides were 

observed in the tunnel, but at somewhat more than 200 feet in from 

the portal the lode is reported to contain some gold. Copper ore is 

reported to have been found in shallow shafts above and about 900 

feet southeast of the portal of the tunnel, in what may be a continuation of the same lode.

PROSPECTS ON McDEVITT GREEK

There are a number of prospects along McDevitt Creek, which is 

near the southern boundary of T. 19 N., R. 23 E., but no work was 

in progress on them at the time of visit in September, 1923. Some 

of the prospects have long been abandoned, and on none of them has 

extensive development work been done. The prospect that is reported 

to have the largest amount of underground workings is on the south 

fork of the creek near the northwest corner of T. 18 N., R. 23 E., 

probably in sec. 7. Its altitude is more than 7,000 feet above sea 

level. At this prospect there is a log cabin near the stream, a tunnel 

on the left side a short distance downstream from the cabin, and 

another on the right side still farther down, with a log blacksmith shop 

at its mouth. The tunnel first mentioned trends N. 85° W. for about 

50 feet, then N. 80° W. for nearly 50 feet more. At about 60 feet in 

from the portal there is a winze, and a short distance farther in a 

drift 25 feet long trending S. 56° W. The other tunnel is about 410 

feet long. For a distance of nearly 300 feet it trends about S. 5° E., 

and then it swings around to about S. 25° E. near the face.

The country rock of this and the other prospects on McDevitt Creek 

is dark-gray slaty quartzite. Somewhat over half a mile downstream 

from the prospect there is an exposure of such rock in which ripple 

marks are well preserved. The bedding here strikes nearly east and 

dips 20° N. Near the mouth of the longer tunnel the bedding appears 

to strike N. 45° W. and to dip somewhat less than 15° NE.

About 250 feet from the portal of the lower tunnel a small excavation in the east side of the tunnel discloses some small irregular 

stringers of quartz containing chalcopyrite. There is also some 

chalcopyrite disseminated in the rock adjoining the stringers. In the 

last 30 feet or so of the tunnel a fault zone of gouge and brecciated
42 THE COPPER DEPOSITS NEAR SALMON, IDAHO

and bleached quartzite is exposed. This zone strikes about N. 25° W. 

and dips 60° or more SW.

At the portal of the tunnel on the left side of the stream there is 

a breccia zone about 5 feet wide which strikes nearly nor.th and dips 

about 75° W. From the portal to the winze the rock in the tunnel 

is barren and unbrecciated. In the winze and the workings beyond 

it the rock is mineralized and the ground is much broken. The 

mineralization produced a number of small and irregular stringers of 

quartz containing chalcopyrite and some malachite. Many of the 

quartz stringers lie nearly horizontal.

PROSPECTS ON HAYDEN CREEK

The mineral deposits on Hayden Creek, which' lies largely in T. 17 

N., R. 23 E., and joins Lemhi River a short distance below the railroad station at Lemhi, are among the first found in the county. They 

are reported to have been prospected by the Mormons who built Fort 

Lemhi, near the present railroad station of Tendoy, about 1854, but 

little has been done with them since that time. In 1923 Webster 

Atwood was the only man reported to be developing prospects on 

Hayden Creek. He owns the Nellie group, nearly 7 miles from 

Lemhi and another prospect several miles farther up Hayden Creek. 

The latter was not visited but is reported by Mr. Atwood to be only 

very slightly developed as yet. On the Nellie group there are open 

cuts on both sides of Hayden Creek. One of those on the left side is 

nearly 20 feet wide; the others are smaller.

The rock in this vicinity is a green schist. It is probably of sedimentary origin but is more thoroughly metamorphosed than any of 

the other rocks observed in the course of the present investigation. 

In the large open cut the schistosity strikes east and dips 28° S. 

The attitude of the bedding could not be determined. In this open 

cut the mineralized zone is exposed for a width of about 12 feet, with 

a body of barren schist in the middle. Numerous narrow bands of 

quartz containing chalcopyrite lie along the schist planes. The rock 

contains a little pyrite and calcite and is in places stained with limonite and manganese oxide. A carload of ore was shipped from this 

prospect several years ago by the former owners. The present developments are insufficient to establish the dimensions of the ore body 

in any direction, but some of the ore uncovered is of good grade. 

The face of the small open cut on the right side of the stream, nearly 

opposite that just described, was covered with slide rock at the time 

of visit, but specimens from that cut show considerable bornite and 

some pyrite. The bornite is probably hypogene but is slightly later 

than the pyrite. A little supergene chalcocite is present.
MINES AND PROSPECTS 43

Mr. Atwood, 45 the owner of the claims, has recently found about a 

quarter of a mile up Hayden Creek from the exposures just described 

a large vein of white quartz containing intercommunicating cavities, 

some of which are large enough for a man to enter. These cavities 

contain a pulverulent brown substance consisting largely of hydrous 

manganese oxide. The vein strikes east and dips 18° S.

SILVEBTON PROSPECT

The Silverton prospect, owned by Dee Matlock and H. Bielenberg, 

is about 3 miles northwest of Salmon, a short distance northeast of 

the road to Leesburg, in the Salmon River Mountains, in sec. 35, T. 22 

N., R. 21 E., at an altitude of about 5,600 feet above sea level. The 

principal underground working is a tunnel approximately 450 feet 

long, with a raise from it to the surface. The work at this prospect 

was done in 1923, and a carload of lead-silver ore has been shipped.

The country rock is green to gray, more or less shaly quartzite. 

The bedding is indistinct but appears to be inclined at low angles. 

There is a shear zone with a strike of N. 80°-85° E., dipping in general steeply to the north, and a number of small slips with various 

attitudes. The rock is somewhat altered and in places contains 

layers of vein matter a few inches wide parallel to one another and 

to the shearing. The vein matter consists largely of quartz, in part 

chalcedonic. Calcite is abundant in places. The most abundant ore 

mineral is galena, principally fine grained,'found in the raise near the 

surface. This mineral has been in part altered to cerusite and other 

oxidation products. Small amounts of cuprite and copper carbonates are present in some of the ore, and native copper is reported to 

have been found in gouge along some of the slips.

« Atwood, Webster, letters of Oct. 22 and Nov. 26,1923.
INDEX

Page 

Access to the area........_______------ 2

Acknowledgments for aid.,...________ 2 

Age of the copper deposits.... 26-27

Beaverhead Mountains, features of.

Copper deposits, general character of..___ 15-16 

structural relations of..._________ 16-20

Delafossite, occurrence and composition of. _ 23-24 

Dishman prospect, description of______ 31-32

Enrichment, supergene, extent of______ 25-26 

Eureka mining district, geologic sketch map

of part of ____. _. _.. __.. 8

Faults of the area.---.--__._.__....... 11-14

Folds and faults, features of--..-..._____ 11-14

Genesis of the copper deposits..____.... 26-27 

Granitic rocks, features of _.__ _.__.. 9

Harmony mine, description of___. _....'. 37-41

Harmony Mines Co., lodes on property of,

map showing____________ 38 

Hayden Creek, prospects on._........__ 42-43

Historical sketch.________________ 2-3

"Lake beds," description of....._____.. 10-11 

Lava, Tertiary, contact of, with metamorphic

rock, plate showing___ __. _ 15

Tertiary, description of. __________ 9-10 

Lemhi Range, features of.___........... 4

north end of, plate showing...__...... 15

Lemhi River, source and course of_____. 4 

Location of the deposits.._____.__. 1-2

McDevitt Creek, prospects on.....__.__ 41-42 

McDevitt mining district, geologic sketch

map of part of.... ___ ____ 8 

Manganese, occurrence of.-.-..-..____ 43

44

Page

Map, geologic, of parts of the Eureka and McDevitt mining districts_____ 8 

geologic, of the area....._._..____ 8

showing relations of lodes on property of

Harmony Mines Co______ 38 

Metamorphic rocks, contact of, with Tertiary

lava, plate showing.__.____ 15 

description of......__ _.... 5-8

Mineralization, hypogene, action and effects

of..................... ....__ 22-25

Mining, conditions of and outlook for____ 29-30

Nellie claims, description of. 42

Ore deposits, strikes of.... _..____ 16-20

Ore shoots, features of....... _.____ 20-21

Outcrops of ore, features of...________ 27-28 

Oxidation, effects of.._'___________ 25-26

Paleozoic rocks, features of.... ..... ... 8-9

Perreau Creek, plate showing...-______ 14

Pope-Shenon mine, description of.. ... 34-37

plan and vertical section of._._...... 36

Porterfleld prospect, description of.......... 37

Production of copper ore, 1911-1922. ____ 31

Rocks of the area_.... . . 5-11

Salmon River, valley and tributaries of ... 4-5

Salmon River Mountains, features of___.. 5

plate showing... . 14

Schaller, W. T., analysis by_________ 24

Scope of the report... 1

Silverton prospect, description of _...... 43

Strikes of copper deposits, directions of...... 16-18

Structure of the rocks..... . 11-14

Topography of the area . 4-5 

Tormey mine, description of..._._____ 32-34 

Tungsten, occurrence of.. .-.'. ^ 17

^ ? ..-:^\

o

ct

fr 

t