f>8TH CoNGREss, t 

2d Session. f 

Professional Paper No. 25 

) . 

HOUSE 0~"' REPRESENTATIVES. 

{

DocuMENT 

No. 713; 

881, es { A, Economic Geolo.gy, 82 1 B, Descriptive Geology, 87 

DEPARTMENT OF THE INTERIOR 

UNITED STATES GEOLOGICAL SURVEY 

CHARLES D. WALCOTT, DIRECTOR 

THE 

COPPER DEPOSITS OF THE ENCAMPMENT DISTRICT 

W"YOMI;NG 

BY 

ARTHUR C. SPENCER 

WASHINGTON 

GOVERNMENT PRINTING O::V:FICE 

1904 

; . 
, 

r 
CONTENTS. 

Page. 

INTRODUCTION- - - - - . - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - . - - - - - - - - - - - - - - - - ----- - - - - -. - - - - -- 9 

Field work .................... _ ... ____ .. ___ . _. __ ... _____ . __ .... _____ .... ___ . __ ... _ _ _ _ _ 9 

Geography .................... _ .· ........ ____ . _. _ .. ____ .. _ _ _________ . ____ .. __ . . . . . . . . 9 

Topography ... _ ...... __ . _. _ ... ___ . ___ .. _ .. ___ .. ____ . ___ . ___ .. ___ . ___ .. __ .. __ . _ ... __ . _ 10 

Topographic map._. __ .... ___ ... _._. __ ... ________ .. __ . __ .... _ ... _ ..... _ ... _ ... ____ 10 

Description of the area ...... _ ... ___ ..... _ .. _______ . ___ ....... _ .. _ . _.............. 11 

History _ .... _______ . ___ ... _____ . ________________ . __ . _ ..... ___ .. _ .... ___ .. _ ... ___ ~ _. _.. 12 

PAR'l' I. GENERAL GEOLOGY. 

CHAPTER I. General description---------------------·---------------------------------·----- 15 

Geologic map ______________ . _______ . ____ . ________ . ______ .. _ .. _ ... __ . _ .... ________ . . . . 15 

Preliminary outline of geology _____ . __ . __________ . __ .. __ . _ ... _ . __ .. __ . __ . ___ . _ ... __ •.. 15 

Description of the Mesozoic and later formations __ . ____ . _____ ... _ .. _. ~ ____ . _. _ .. _. _. _ _ 16 

Pre-Cambrian formations ... ___ . ________ . _________________________ . ____ .. _. ____ . ___ ... _ 17 

CHAPTER II. The bedded rocks ___ . __________________________ . __ .. _______ ........... __ ... _ 21 

Hornblende-schists. __ .. __ . _________ .. ___________________ .. _ ...... _. __ .... _ ... _~- .... __ 21 

Liinestone .. __ .. _ . _ . ____ . ___ .. _ . ___ .. ___ .... ______ ...... ___ . ____ . ____ . _ .. _ ... _ .... _ . . . 24 

Quartzite and slate .. ____ . ___ . _ .. _ ...... __ ..... _ ....... __ .... _ ....... _ .. _ . _ ... _ . . . . . . . 25 

Conglomerate .................... __ ......... ___ ..... _ .............. _ ..... -. . . . . . . . . . . . . 26 

CHAPTER III. The gabbro rocks and their metamorphic products ............... ~- ... _....... 28 

General description .... _ .............. _ ......... _ .......................... _ ....... ·... 28 

Norite ......... _ ......... _ ........ _ ... __ ...... _. __ ................ _ .................. _ 29 

Peridotite ..... _. _ ....................... _ .... _. _ .... _ .... _ .. _ ....... __ .. _ ... _........ 30 

Oligoclase-gabbro . __ ......... _ ........ _ .... _ ................................. _ ....... _ 31 

Meta-gabbro or "diorite" .......... _ ............. _ .. _ .. _ .... _. __ ... _. _. _ ....•... __ ... _ 32 

Serpentine. __ . ____ ... _ ... _ .... __ ....... ___ . __ . __ .. _ ....... __ ................. _........ 35 

Mineralization of the gabbro intrusives._ ........... __ ...................•........ . . . . . . 35 

Contact metamorphism ... __ . __ .... _ .. _ .. _ ... __ .. __ . ____ ........ _ .. _ .............. __ . __ . 36 

CHAPTER IV. The siliceous igneous rocks._._ ... ______ ..... ____ ....... _ ........ _............ 37 

General description _ .. _________ ... _ ... __ . __ . _____ .... _ ... _- _. _- ..... -..... -.. _ ... _ .. _ 37 

Quartz-diorite and diorite-gneiss _ ... __ . ___ . _ .... _ ...... _ ................ _ .... -. __ .. _ _ _ _ 37 

Red granite ... _ . __ .... _ ............................. _ ....... _ .. - _ .. -... -.. - . -.. -. . . . . . 39 

Aplite and pegmatite. ___ ._. __ .. _ .. -. ___ . __ ..... _. __ ............ __ . __ .. _ ......... _...... 41 

3 
4 CONTENTS. 

PART II. EcoNoMIC GEoLoGY. 

CHAPTER I. General features ....... _ ...................... _ . __ ......... _ .... __ ............ . 

Conditions of study .................. _ .................. ___ . _ ...... __ . _ .......... __ .. _ 

Ores . _ . _ .... _ ... __ ...... _ . _____ . _ . __________ . ____ .. _________ .. __ . _ . _________________ _ 

Primary and seeondary ores _ ..... _ .... ~ ... _ .. _ ... _ .. _ .... _ ........................ __ .. 

Gangue 1ninerals . _ ... _ ........ _ .. __ ............................. ___ . _ .. _ .... _ . _ . _ . __ .. 

Ground water .................. __ ...................... _ . ·_ .............•......... __ .. . 

Gossan __ .. : .. ·_ ... _ ..................... _ ... _ ............. _ ....................... __ .. 

Distribution of copper minerals and ores.-,-- __ ............... __ .. _. __ ................ __ . 

Sources of copper _ . _ ... _ .......... ____ . __ ....... __ ... __ ........... _ ..... _ .. _ .... ___ . _ . 

Occurrence of gold . _ . __ ... : . ...... __ .... __ ........ _ .............. _ ....... _ ..... _ .. ___ . 

'CHAPTER II. Classification and general description of copper deposits ...... __ ............... _. 

Types of occurrence ...... _ ..... _ .................................... _ ............. _ .. . 

Hinton type ............................. __ .......................................... . 

Creede type .................................. _ ................. __ ..... _ ............. . 

Continental typP .................... _ ................... _ ... _ ..... _ ........... _ ...... . 

Cascade type ................... _ ................................. _. _ ......... _ .. __ .. . 

Doane type ...................... __ .................................................. . 

CHAPTJ<~B III. Genesis of copper deposits _____________ .. ____ .. __ ... _ ........... ___ ........ .. 

Tabular summary .. __ ....... ___ .. _ ...... ___ ....... _ ... _· __ .. __ . _ .... __ ... _ . __ . __ .. _ . _ .. 

Deposition of the first period .. _ .. ___ . ____ .• _ .. _. _ .. ___ . _ ..... _ .. _____ .... ______ . __ .. __ . 

Origin of the ores ...... _ ... _ .. _ ... _ ..... _ ...... _. . ... _ ...... __ ....... ______ . _ .. _. 

Sources of the copper_ .. ___ ... _ ... ___ • . . __ .. _ ... __ . . .. _. ____ ... _ ... _. _____ .... __ . 

Deposition of the second period __ ... ______ . _ .... __ ........... __ ............ _. ______ . __ . 

Deposition of the third period . __ ... ___ .. _ ............ _. _ ...... _ ... __ . _ .... __ . ___ . ___ . 

Origin of the ores _ .... _ . _ . __ ..... ___ .. _ .. __ . __ .... _ ....... _ .. _ . ____ . _. __ . ___ .... _ . 

Source of the copper _ .. _ . _ .............. ____ .... ___ ..... _ .... __ .. ____ . ____ . _____ .. 

Secondary enrichment of the ores ....... __ ... _ ...... _ .. _ ..................... __ ..... _ .. 

CHAPTER IV. Mine descriptions ... _ ..... __ .. ____ .... _ ....... __ .................... _ .. ____ .. 

Doane Inine _ ...... _ .... _ ... __ .... ___ .. _ ... ___ . _ ... __ ....... _ .... __ ... _. _ .. ___ . ____ .. . 

Location and developm.ent. ..... ____ . _ ....... _ .. _ ...... ___ ... __ . ____ . ___ .. __ . __ . _ .. 

Country rock __ ....... , . __ ...... ____ .... _ .... __ . _ .. _ . _ ... __ . ____ . ____ .. _____ . ___ . __ . 

Jointing of country ro(~k. __ ........ _ ............. __ ........ __ .................... .. 

The ore _ ...... _ ......... __ ..................... _ ..... _ .. ___ . _ . __ .... __ ...... ___ .. 

Occurrence of the ore ........... ___ .... _ ...... _ .... __ ..... _. ___ .. _. _ .. _ ......... _. 

Genesis of the ore_ ...................................... _ ... __ .. ___ . _______ .• _ . __ . 

Future of the property ........................ _ ....... _ ... _ ... _ ......... __ ... ___ .. 

Ferris-Haggarty 1nine . __ . _ ........ _ ....... _ ........... _ .. _. _ ... _ ..... __ ... ____ . _ .. __ .. 

Location and development ...... ____ .... __ .................. _ ............ _ .. __ ... __ 

Country rock .................. __ .. __ ....... _ .. __ .... ___ . __ ... ___ . _. __ . _ ... __ .. __ . 

Jointing of country rock ... _ ....... __ ..... _ ............ __ .... __ ........... ______ .. _ 

The ore __ .... __ .. _ ...... __ .... _ ...... __ .... _ ........... _ . _ ... _ ........ __ . _ .. _. _ .. 

Occurrence of the ore ......... _ .......... _ ... _ . __ ................... _ . __ ...... _ .. . 

Genesis of the ore ........ __ .. ___ ... _ ... ____ ...... _ . . .............. _ ...... _ .. __ .. . 

Future of the property ........... _ .... _ . ___ . . . .. .. .. . .. ................. __ .... __ . 

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CONTENTS. 

CHAPTER IV. Mine descriptions-Continued. 

Charter Oak 1nine ......•. ___ .... _____ .. _ . ___ . _ ... _ ............•....................... 

Osceola property ........•........ __ .... ___ ... __ ..... _ .... _ ... _ ... _ ..... _ ... _ .. _· ...... . 

Creede property ... _ .. _ .... __ . _ .. _________________ .. __ .. __ . _ ... _ ....... _ . __ . ___ . _ .... . 

Leighton~Gentry prospect ............ _ ....... _. __ .... __ . __ .... _ .................. ·. ~ .. . 

Syndieate property .............. _ .... __ ..... _ ........ _ .............. _ ................ . 

Continental vein ................. _ ....... _ ............................................ . 

Portland and Hercules mine .... _ . _ .... _ ..... __ ....... __ ... __ .. _ .. _ .. __ . _ . _ _ _ . _ .. _ . , . _ 

Gertrude property _ ....... _ ............. _ ..... __ .... _ .... _ ..... _ .. _ .... __ ............ . 

Hidden Treasure tunnel .... _ .... __ . : ___ ...... _ ................ _ ...................... . 

Sun Anchor and Sweet elaii1:1S .... _ ..................•................................. 

Kurtze Chatterton mine .... _ .. _ .. _ ..... _ ..... __ .... __ . _ .... _ .. __ ............. _ ....... . 

Cascade n1ine ............... _ ..... \ ............ _ ..... __ ............ _ .. _ .. _ ............ . 

I tina y mine ..... __ ......... _ .... _ ............ _ .................... _ .. _ .. -...... _ .... _ . 

Hinton 1nine ........ _ ........ _ .. _ ....... _ ......... _ ............. _. __ ................. . 

Argentiferous veins . __ .. __ ........ _. _ ... _ .......... _ ..... _ ..... _ .. _ .... __ ............ . 

Meta n1ine ... __ ... __ .... ______ .... _. __ .... ___ . ____ .... __ .. _ .... __ .... _ .. _ .. ______ ... _ 

Ahna property ............... _ ...... __ ..... _ .. _ . _ ..... _ ................. --.. ---... -. -. 

Bridger mine ..... __ .... _ ..... _ ......... _ ........ _ ................... _ .. _ -.......... -. 

Gold Coin claim ____ .... __ ............. _ ... _ . __ .... _ .... _ ............ __ .............. _ 

Elkhorn mine _ •• __ .. _ ..... __ . ___ ... _ ... _ ................... _ .... _ ................... -

CHAPTER V. Practical suggestions._ . _ ............. ___ .... __ .. __ ..... __ ......... __ ....... __ . 

INDEX---------------------- ---- - - - - ---- - - - - - - - - - - - - - - - - - - - --- --- - - - -- - - - - - ----- - -- - --- - - -

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ILLUSTRATIONS. 

Page. 

PLATE I. Topographic map of the Encampment district, 'Vyoming. _____________________ In pocket. 

II. Geologic map and structure sections of the Encampment district, ·wyoming. ____ In pocket. 

FIG. 1. Index map showing location of Encampment district___________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 11 

2. Doane mine; sketch plan of workings ______ . _________________ <" _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 61 

3. Doane mine; sketch projeetion of workings on yertical plane through shaft at right 

angles to stratification _________________________________________________ ~ _ _ _ _ _ _ _ _ _ _ 62 

4. Doane mine; diagram to show strike and dip of principal joint systems________________ 63 

5. Doane mine; stereogram representing main ore shoot.________________________________ 64 

6. Doane mine; projection of main ore shoot on vertical plane parallel to strike of quartzites _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 65 

7. Doane mine; horizontal section of ore body in stope 9 about 25 feet above 115-foot leveL- 65 

8. Doane Inine; sketch showing relation of ore to inclosing rock, stope 9 ______ - ________ -- 66 

9. Doane mine; diagrammatic cross section in lower portions of stopes 7 and 8 _ _ _ _ _ _ _ _ _ _ _ _ 67 

10. Doane mine; vertical north-south section through stopes 7 and 8 _________ ~ _ _ _ _ _ _ _ _ _ _ _ _ 68 

11. Doane mine; horizontal plan showing relation of ore to fractures and bedding of quartzite. 69 

12. Doane mine; section parallel to stratification of quartzite through stopes 9 and 10, 

showing relation of ore shoots to zones of close jointing ______________ . _. _ _ _ _ _ _ _ _ _ _ _ _ 70 

13. Ferris-Haggarty mine; plan of mine workings _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 72 

14. Ferris-Haggarty mine; projection of workings on vertical plane parallel to strike of ore 

body _ •..• _ _ _ _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7 3 

15. Section of bedded formations on ridge about one-half mile east of Ferris-Haggarty mine. 74 

16. Section of bedded formations and intrusive rocks about one-half mile west of FerrisHaggarty 1nine •••• ______________ . _________ . ________________________________ . _ _ _ _ 7 4 

17. Ferris-Haggarty mine; transverse sections of the ore body____________________________ 76 

18. Ferris-Haggarty mine; north-south sketeh section througJ: Bonanza stope at first mine 

level ___ . __________ . ___ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 77 

19. Ferris-Haggarty mine; sketch section through Bonanza stope parnllel to stri~e and at 

right angles to dip of ore body____________________________________________________ 77 

20. Ferri,<3-Haggarty mine; plans of ore body on first and second mine levels.______________ 78 

21. Ferris-Haggarty mine; idealized horizontal section of ore body_______________________ 78 

22. Ferris-Haggarty mine; idealized vertical north-south section across the ore body_______ 79 

23. Ferris-Haggarty mine; face of stope, \vest of old shaft, 90 feet above first mine level.___ 80 

24. Ferris-Haggarty mine; idealized sketch of ore body as seen near old shaft at depth of 

135 feet ______________________________________________________________________ . _ 80 

7 
8 ILL USTR.ATIONS. 

Page 

"Fm. 25. Ferris-Haggarty mine; north-south diagrammatic section through stope on first mine 

level near head of inclip.e to second leveL ________ . _. __ ....... _ .. _ ....... _ .. - __ -- _ 81 

26. Ferris-Haggarty mine; diagrammatic section of ore body ______ .•.. ________ . _______ . _ 81 

27. Sketch section of main syncline in prominent hill south of Charter Oak mine __ ..• _... 83 

28. Sketch map of vicinity of Charter Oak mine, showing structure and distribution of 

rocks ____ . _ .. __ .. _ . _ .. _ .. _ ... _ . _______ . __ ......• _ • __ .. _ ..... __ .... _ . ___ .... _ .. _ 83 

29. Charter Oak mine; sketch section along line A B, fig. 28---------------------------- 83 

30. Charter Oak mine; surface plan of vein .. _. ___ ............. _ ..... _ .... _............ 84 

31. Charter Oak mine; general cross section ... ____ .......... _ .. __ . _ ... __ ......... _ ... _ _ 85 

32. Charter Oak mine; detailed cross section of vein .. _ • _ ....... _ ........... _ ........ _ . . 85 

33. Geologic section on north side of Continental Divide through Creede claim ..•.... _ _ _ _ 86 

34. Sketch plan to show the position of openings in the vicinity of Creede mine, relative 

to the intrusive norite ............ __ .. __ ....... _ ........................... _..... 87 

35. General cross section through the Island City claim, showing occurrence and structure 

of rocks, and relation of ore-bearing horizon _ .. __ .. _ .. _ ........ _ .. __ ... _ .. __ .. _ .. _ 87 

36. Sketch diagram showing position of Leighton-Gentry ore horizon relative to inclosing 

rocks ............. _ . __ 1

• _______ ••• _______ • ___ •• __ • ____ • _______ • ___ • _ • _ •· _ • __ •• _ • • 88 

37. North-south section through Syndicate shaft, showing manner. in which the vein 

crosses the beds of quartzite ...... _ .. _ ........ __ .. __ .... _ ....... __ ...... __ .. _ . . . . 89 

38. Detail of Syndicate vein .. _ ...... _ ......... _. ____ ._. __ .. _ .. __ . ___ . __ .... _ ... _. __ ._. 89 

39. Sketch section showing relation of Continental vein to inclosing rocks ........•..... _. 90 

40. Diagrammatic sketch map to show general distribution of rocks in vicinity of Hercules and Portland shafts .... _ ..... _._ .. _ ........ · ..... _. __ ...... __ .. _. __ . _______ . 91 

41. Sketch cross section through Gertrude workings . ___ . _. _ ... _ . _ . __ . _ .. _. ___ . _______ .. 92 

42. Section of first 720 feet of Hidden Treasure tunnel . _ ...• __ ... _ . _ . _ .... __ . _ . __ .. __ . . . 93 

43. Plan of Hidden Treasure tunnel showing relative course of faults and trend of strata _. 93 

44. Sketch of vein formed in fracture in dike of diorite, Hidden Treasure tunneL __ . __ .. _ _ 94 

45. Structure of quartz and feldspar vein, Kurtze Chatterton claim ___ . ____ . _. _. ___ .. _. _ _ 95 

46. Sketch of Itmay vein looking south west . _ .. _. ____ ... _________ . __ . _____ .· ___ . _ _ _ _ _ _ _ _ 97 

47. Sketch section of formations at the Meta mine showing relati~ns of vein .. _______ .____ 99 

48. General section showing occurrence of veins in vicinity of Bridger mine _______ .. _____ 100 

49. Detailed structure of Bridger vein as exposed in shaft __ .. _ .. __ .... __ . _. _. ______ . _ _ _ _ 101 
THE COPPER DEPOSITS OF THE ENCAMPMENT DISTRICT, 

WYOMING. 

By A. c. SPENCER 

INTRODUCTION. 

During the last few years prospecting in the Medicine Bow and Park ranges 

in northern Colorado and southern Wyoming has proved that copper-bearing 

minerals occur frequently and are very generally distributed over a wide region 

in this portion of the Rocky Mountains. This bas gradually become known 

through the discovery of ·several more or less promising copper deposits and also 

through the ,exploitation of a few properties which have produced ore on a commercial scale. The increase in the number of prospectors has kept pace with the 

increasing interest in the region, until now every part of it has been at least 

cursorily examined. In spite of this activity and of a considerable amount of 

development work at several localities, the productive mines in actual operation 

are few, but the search for valuable deposits continues, and it is to be expected 

that other mines will eventually be discovered. 

FIELD WORK. 

The field party was in charge of the writer, who bad the assistance of Prof. 

J. Volney Lewis from July 12 until October 1, 1902. ~Ir. _ J. E. Spurr was 

associated in the work during a portion of September and October, and made a 

special study of the princ~pal mines and prospects of the region. The writer has 

made full use of Mr. Spurr's notes, and has had the advantage of his suggestion 

and criticism during the preparation of the report. Both the field work and the 

office work have been carried on under the supervision of Mr. S. F. Emmons. 

GEOGRAPHY. 

The Continental Divide, which, in the latitude of Denver, Colo., lies in the 

north-south trending Front Range of the Rocky Mountain system, passes westward 

between North and Middle parks, and is then continued toward the north along 

9 
10 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

the Park Range. The Park Range in Colorado trends north and south from Grand 

River to the vicinity of Mount Zirkel, where it swerves toward the west, beyond 

the spreading tributaries of Elk River, and continues northwesterly for nearly 40 

miles under the local designation Sierra Madre. Midway between the State line 

and the Union Pacific Railroad these mountains give place to a watershed of gentle 

slope and slight topographic relief, which is still the main divide of the continent. 

The waters falling upon the western side of the Sierra l\'Iadre flow to Green and 

Colorado rivers and thus to the Gulf of California, while the streams on the eastern 

side reach the Gulf of Mexico by way of the Mississippi drainage. 

The portion of the Encampment district which has been mapped lies between 

latitutes 41° and 41° 15' north and longitudes 106° 45' and 107° 15' west. It is an 

oblong area extending east and west across the central portion of the Sierra Madre. 

By reason of the faulty determination of the forty-first parallel, fixing the line 

between ""T yoming and Colorado, the State boundary was located approximately 

one-third of a mile north of its proper position; consequently a narrow strip along 

the southern edge of the district, about 9 square miles in area, is in the State of 

Colorado, while the remainder, comprising approximately 441 ~quare rniles, lies 

within Carbon County, Wyo. A sketch map of northern Colorado and southern 

Wyoming is given to show the location of the district (fig. 1). 

The town of Encampment and the settlements of Battle, Rambler, Copperton, 

Dillon, and Rudefeha are the direct outgrowth of interest in the mineral r~sources 

of the region. Encampment, or Grand Encampment, as it was originally called, is 

the distributing point. It is situated near Encampment River, on the eastern slope 

of the Sierra Madre, 43 miles by wagon road from the Union Pacific Railroad at 

Walcott, Wyo. From Encampment all parts of the regi0n are accessible by wagon 

roads, tho_ugh the southwest corner of the district is more easily reached from the 

south by way of the valley of Little Snake River. 

TOPOGRAPHY. 

Topographic map.-The topographic map (Pl. I, in pocket) of the quadrangle 

was made in 1901, by Frank Tweedy, topographer of the United States Geological 

Survey, and is used as a base for the geologic map (Pl. II, in pocket) accompanying 

this re'port. Several additions to the original drawing have been made, mainly from 

the geologists' notes. These additions comprise two important wagon roads-the 

one from Encampmel!_t to Hog Park, in so far as it is new, and the Tram road, 

together with the line of the aerial tram. The latter is plotted from a blue print 

obtained through the courtesy of Messrs. Emerson & McCaffery, of Encampment. 

The position of the area and the elevations are based upon a line of levels 

carried from the bench mark of the United States Coast and Geodetic Survey, at 

Laramie, Wyo. 
DESCRIPTION OF THE DISTRICT. 11 

The topography is shown by three colors- brown for the contour lines, representing intervals of 100 feet; blue for the streams and lakes; and black for such 

data as boundarres, roads, houses, and names. The scale of the map is 1 to 90,000, 

or approximately lt miles to the inch . 

.Description o.f the area.-The Encampment district is crossed diagonally from 

southeast to northwest by the irregular line of the Continental Divide, which is the 

crest of the Sierre Madre. The waters which fall upon the eastern and northern 

I 

FIG. 1.-Index map showing location of the Encampment district. 

side of the mountains flow to the North Platte by way of Encampment River and 

Cow, Spring, and Jack creeks; while the drainage of theirsouthwestern face finds 

an outlet by way of Little Snake River and its tributaries, Battle, Sandstone, and 

Savery creeks. 

The minimum elevation indicated i:-; about 6,650 feet, while the greatest altitude, 

which is reached by Bridger Peak, i:-~ 11,007 feet. The local variations in elevation 
12 COPPER DEPOSITS OE' ENCAMPMENT DISTRICT, WYOMING. 

are by no means slight, but the topography as a whole is of a subdued type. Steep 

slopes are confined to the middle courses of a few of the main streams and to a 

few basins or amphitheaters near the main divide, which were formerly occupied 

by glaciers. 

The mountain summits along the main divide are generally broad and form an 

upland surface the elevation of which varies from 9,200 feet in the lowest pass to 

11,000 feet on the highest summit. The steep declivities near the heads of opposite 

streams on the two sides of the divide are often a mile or more apart, and the effect 

of breadth is emphasized by the frequent continuance of the summit level out onto 

lateral ridges for several miles. The high portion of the range thus presents the 

appearance of an elevated plateau, incompletely dissected by existing streams. 

Many of the ridges between the streams which cut back into the heart of the 

mountains decline gently toward the main valleys, and are readily approached from 

the lowlands. In general character, therefore, the topography is subdued, rather 

than rugged, and consequently wagon roads have been easily constructed in almost 

every portion of the area without the excessiv 0 expense which often attends the 

opening of transportation routes in elevated regions. 

HISTORY. 

The first serious attempt to develop the mineral resources of the Sierra Madre 

region seems to have followed the discovery, in 1872, of quartz veins on the ground 

now held by the Kurtze Chatterton Company. According to Mr. Frank 0. 

Williams, of Saratoga, the veins were first noted in 1868 by J. W. Southwick, but 

no work was done upon them, and it is stated by Mr. Boney Ernest, of Ferris, 

'Vyo., that in the year mentioned Tom Sun and himself located four claims at 

this place, and that two years later a fifth claim was taken up by Bill Savage. 

Assessment work was done on these claims until the year 1876, when they were 

surveyed and application was made for patents. However, the issue of the desired 

patents was delayed, and the enterprise was abandoned by the original locators, but 

the claims were relocated several years later by Kurtze Chatterton and held until 

they were purchased by the company which bears his name. 

Mr. Ernest is also authority for the statement that the ground of the present 

Doane mine was originally located in 1874 by a man named Harper, who endeavored 

to find the vein from which a large amount of copper-bearing float had been derived. 

A 10-foot ho]e was sunk, but the property was soon abandoned. In 1881 it was 

taken up by George Doane and others associated with him. Gossan containing 

copper carbonates was found in place and followed to a depth of 75 feet, where 

copper glance was encountered, leading to the first systematic mining in the region. 

Since the discovery of valuable ore the mine has been in operation at intervals, and 

is active at the present time. 
HISTORY OF THE DISTRICT. 13 I 

In 1876 silver-lead deposits carrying some gold were discovered by Frank 0. 

vV illiams on the Bridger group of claims, near the Continental Divide, several miles 

north of the area mapped on Pl. I. Considerable development work was done, but 

the ores were not found to be sufficiently rich to be mined at a profit under exif:lting 

conditions. The Charter Oak copper mine, which has produced ~orne good ore, 

was also discovered by Mr. Williams, and developed by him and his partner, Henry 

Jones. It was purchased from the1n by the Charter Oak Company. 

No other properties seem to have come into prominent notice until1896, when 

some large bowlders containing iree gold were discovered by AI. Huston and Ben 

Cullerton in Purgatory Gulch. The actual source of these bowlders seems never to 

have been found, though some small veins carrying gold were located. 

This discovery of gold seem'~ to have started the present interest in the region, 

though the seareh for gold soon gave plaee to prospecting for copper. 

The Ferris-Haggarty, or Rudefeha, as it was formerly called, is the largest mine 

of the region, and though it has been producing rich ore since 1899, it still contains 

large ore reserves. The property was located in 1898 by Ed. Haggarty, and was 

operated by a \Vyoming company until the summer of 1902, when it was purchased 

by the North American Copper Company. This company also owns or controls 

concentration and reduction works located at Encatnpment, and an aerial tramway 

16 miles tn length connecting them with.the mine. 

No producing mines have been developed sinee the discovery of the FerrisHaggarty, but careful exploration is being carried on by well-equipped operators at 

several places, and the value or worthlessness of a number of more or less promising 

prospects will soon be determined in a practical way. 

P A R T I .-G E N E R A L G E 0 L 0 G Y. 

CHAPTER I. 

GENERAL DESCRIPTION. 

GEOLOGIC MAP. 

The topographic map of the Encampment quadrangle serves as a base for the 

geologic map accompanying this report (Pl. II, in pocket). On it the di:ff'erent 

formations are represented by distinct colors and patterns, the significance of which 

may be determined from the legend. Geologic cross sections are also given to 

indicate the general structure. 

In collecting the data for the geologic map the greater amount of study was 

given to the northern portion of the district, including the whole of the quartzite 

belt in which the principal mines are located. For the southern portion, comprising 

the areas covered by the volcanic series and the red granite, such detailed work was 

deemed unnecessary. 

PRELIMINARY OUTLINE OF GEOLOGY. 

The rocks which occur in the Sierra. Madre belong for the most part to the 

oldest pre-Cambrian formations of the Rocky Mountain region, but comprise as 

well formations of Mesozoic and Tertiary age, and surficial deposits of glacial or 

fluviatile origin. 

The rocks of the pre-Cambrian complex form the main mass of the mountains, 

while the Mesozoic formations outcrop on the foothills on either side and dip away 

beneath the surrounding prairie. The general structure is thus a low arch or 

anticline, the axis of which is parallel with the mountain crest. The gradual 

uplift of this arch was accompanied by general erosion, which removed the Mesozoic 

rocks from its axial portion and revealed the ancient formations below. The preCambrian formations comprise both sediments and igneous rocks. They had been 

closely folded and eroded long before the deposition of the Mesozoic strata upon 

their upturned edges, and the uplift which produced the _Sierra Madre occurred as 

a still later event in the series 0f geologic {·hanges. 

15 
16 COPPER DEPOSI1.'S OF ENCAMPMENT DISTRICT, WYOMING. 

While the effects of this arching upon the Mesozoic sediments are readily 

discernible, they can not be recognized in the pre-Cambrian rocks, because of 

the previously acquired complex structures and metamorphosed condition of the 

latter. 

The sedimentary portion of the pre-Cambrian series forms a system of nearly 

east-west folds transverse to the trend of the range and to the axis of the postMesozoic arch. Certain of the igneous rocks are older than the sediments, and 

have been folded with them. Others were intruded later and so were unaffected 

by the earlier movements. 

The older igneous rocks are thus greatly metamorphosed, and some of those 

intruded a£ter'the principal folding have also been subjected to a. high degree of 

alteration. 

The metallic deposits of the Sierra Madre are almost entirely confined to the 

pre-Cambrian formations. For this reason a description of these rocks and their 

mutual relations must precede any account of the nature, occurrence, and distribution o£ the metallie ores. First, however, the overlying unmetamorphosed 

sedimentary formations of the 1\1esozoic will be briefly described. 

DESCRIPTION OF THE MESOZOIC AND LATER FORMATIONS. 

The Mesozoie rocks of the Encampment district are confined to the southwest 

corner of the area mapped, where they occur well down in the foothills, outcropping 

along lines nearly parallel with the crest of the range and dipping rather steeply 

toward the west or southwest. Their distribution is indicated on the geologic 

map. . 

The •' Red Bed" series of the Triassic is the oldest unmetamorphosed formation present, though Upper Carboniferous rocks are known to occur at no great 

distance in the Elk Mountains. · The "Red Beds" have an aggregate thickness 

of about 1,200 feet and are made up of sandstones and limestones with occasion.al 

beds of coarse conglomerate. They are characterized by the brilliant red color 

typical of equivalent strata thr~ughout the Rocky Mountains. 

The "'Red Beds" are usually overlain by alternating shales and sandstones, 

regarded as equivalent to the fresh-water Jurassic of the Front Range in Colorado, 

but locally limestone occurs between these formations in the form of lenses having 

a maximum thickness of 35, feet. This limestone contains marine Jurassic fossils in 

great abundance. The total thickness of the Jurassic is approximately 400 feet. 

The Jurassic beds are followed in turn by the Dakota sandstone, the Colorado 

and Montana groups of shales and sandstones, and the Laramie formation. The 

Montana and Laramie contain many beds of coal, some of which have proved to 

be of good quaHty and of .workable thicknes~. 
PRE-C.AMBRIA.N FORMA. TIONS. 17 

The following analysis of coal from the Car bon dale ine was made in the 

laboratory of the Geological 8urvey by Dr. E. T. Allen: 

Analysis of coal from Carbondale mine, sec. 18, T. 13 N., R. 87 H~ 

Moisture _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3. 56 

Volatile combustible matter _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ·12. 36 

Fixed carbon _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ -19. 06 

Ash _____ . ______________________________ .________________ 5. 02 

Total _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1~)0. 00 

The coal is bright, clean, and noncoking. It is now auled to Rudefeha for 

use at the Ferris-Haggarty mine, and it is also sent by tra .ay to Encampment. 

In the southwestern '1>ortion of the district thick deposi s of Tertiary conglomerate overlap the upturned and beveled edges of the 1: esozoic rocks. These 

conglomerates, which have a nearly horizontal position, ar known to be present 

over a considerable area west of the region studied, and t ey have been mapped 

under the name Wyoming conglomerate, in accord with th usage of the Fortieth 

Parallel Survey. 

The importance of glacial and other recently formed deposits lie~ mainly in 

the fact that they locally hide the bed-rock formations~ urficial' deposits which 

have originated in various ways are represented on the m p as Pleistocene. 

PRE-CAMBRIAN FORMATIONS. 

The pre-Cambrian rocks, comprise a variety of types, i eluding those of sedimentary, igneous, and metamorphic origin. They may e conveniently divided 

into bedded and igneous rocks. The first class will then i elude, in order of age, 

(1) a series of hornblende-schists derived from bedded v Jeanie rocks, (2) a formation made up of limestones and shales, (3) a quartzite nd slate formation, and 

(4) a heavy conglomerate. The second class will include uartz-diorites, granites, 

and gabbros, and other rocks of igneous origin, together with both massive and 

gneissic rocks derived from them by metamorphism 

In the Encatnpment ~eld the quartzite and slate for ation is more in evidence than any other of the bedded rocks, but all occur i a limited area having 

the form of a narrow triangle, with its apex on the Enc mpment River about 5 

miles south of Encampment, and its base, about 7 miles ide, in the foothills on. 

the west side of the range. The belt of quartzites and ass cia ted strata is exposed 

for about 20 miles, but on the west their extent is not known, since they are 

overlapped by "younger formations. 

The rocks within the sedimentary belt strike in gener I nearly east and west, 

and they seem at first sight to have an enormous thicknes , since they dip almost 

invariably toward the south. However, the recurrence £ easily identified beds 

2100--~o. 25--04----2 
18 OOPPER DEPOSITS OF ENO.AMPMENT DISTRIO'.r, WYOMING. 

of conglomerate associated with the otherwise monotonous slates and quartzites 

has led to the recognition of an east-west synclinorium, composed of several minor 

folds, closely appressed and overturned toward the north, so that the strata on 

opposite limbs of all the folds dip in the same southerly direction, producing 

what is known as isoclinal structure. 

The formations of the sedimentary belt are intruded throughout by basic 

igneous rocks related to gabbro, of later origin than the folding. Similar masses 

also occur between the stratified rocks of the synclinorium and the outside granites, 

gneisses, and schists, effectively obscuring their relations. 

On the north gray quartz-diorite occurs in large masses, intruded, however, 

by great amounts of the same sort of gabbro rock which has invaded the sediments, and also by eoarse red granite and by dikes of aplite or pegmatite. The 

quartz-diorite usually has a platy or gneissic structure, which follows the same 

trend as the strike of the quartzites, and which has controlled the distribution of 

the invading rocks in parallel east-west dikes. It appears to be the oldest of ~he 

intrusive igneous rocks. 

On the south the main country rock is red granite, though quartz-diorite and 

gabbro also occur; all are intrusive into hornblende-schist. The red granite is 

usually a coarsely crystalline rock which seldom shows gneissic structure. Where 

it occurs with the gray quartz-diorite the latter is intruded by it. 

The oldest rocks of the limited region here under discussion are the hornblendeschists, which hav~ been classed with the bedded rocks. On the north side of the 

synclinorium, west of Bridger Peak, the only place where they are known to occur 

in eontact with the sedimentary rocks, their well-marked schistose structure runs 

parallel with the bedding of the quartzite adjacent, striking nearly east and west, 

and dipping toward the south, so that the series passes beneath the quartzite as 

though forming the bottom of the great trough-like fold or synclinorium. The 

size of this northern patch of hornblende-schist is limited, for it has been invaded 

by large masses of quartz-diorite, and by dikes of the later gabbro. No hornblendeschists are found north of the eastern half of the synclinorium, the quartzites 

being separated from the gneissic quartz-diorite by masses of gabbro. 

South of the sedimentary belt the hornblende-schists occur more extensively, 

but they are separated from the quartzites either by red granite or by gabbro . 

.. The structure of the schist and the strike of the igneous contacts, on this side 

as on the north, are in general parallel with the east-west lines of the sedimentary 

formations, but the dips are steeper and not constant in their direction. 

In the pre-Cambrian areas of the general region igneous rocks similar to the 

quartz-diorite, granite, and gabbro of the Encampment district cover more ground 

than the bedded formations. Next to them in extent come the hornblende-schists, 
PRE-CAMBRIAM FORMATIONS. 19 

which are older than all of the igneous rocks thus far recognized, while the 

quartzites and associated strata are of the least importance. 

The synclinorium in the pre-Ca1nbrian sedimentary formations of the Enc~mpment district is enveloped by a complex of metamorphic schists and intrusive 

igneous rocks. The structural relations between the sediments and the outside 

formations suggest that the former are all younger than any of the latter except 

the intrusive gabbros. It is believed, therefore, that the hornblende-schist, with 

its intrusive rocks, originally fonned a basement upon which the sediments were 

laid down. All the basement rocks must then have taken part in the downfolding 

by which the synclinorium was produced. Folding was, however, greatly complicated by faulting, and probably all the contacts now observed between the sediments and the older rocks are fault contacts along which the invading gabbro found 

easy lines of intrusion. 

In different parts of its cross section the sedimentary portion of the synclinorium comprises from three to seven closely appressed synclines, with anticlines 

between. Thus the limestones, quartzites, slates, and conglomerates, with the masses 

of gabbro which have invaded them and haye been controlled by their structure, 

appear at the surface in parallel bands striking east and west parallel with the 

axis of the great fold. The number of folds increases from east to west with 

the widening of the sedimentary belt, but the depth of the great fold is greatest 

in the central portion of the belt. Here the conglomerates are exposed in two 

synclines, which merge toward the east and finally disappear as a result of an 

upward rise of their axis, assisted hy faulting along the strike. 

Outside of these two bands there is often difficulty in following individual 

folds, but prominent groups of strata in the quartzite-slate formation may be 

traced for several miles in certain cases, and one band of slate probably occurring 

in a syncline can be traced with practical continuity throughout the whole length 

of the belt. 

The lim~stone formation is ' best exposed along an anticlinal axis near the 

south side of the synclinorium, but its outcrop is interrupted several times by 

pitching of the fold along its trend. Evidence of rising and falling along other 

folds is seen in several limited areas of the limestone which has been locally brought 

up from beneath the quartzite and exposed by erosion. 

The southern half of the anticlinal just mentioned is cut off south of Rambler 

town site by a strike fault which brings its northern limb in contact with the 

red granite occurring south of the synclinorium. Eastward from this •place there 

"'is no quartzite between the limestone and the granite as in t4~. vicinity of 

Copperton and in Quartzite Peale This .fault is one of many which -follow the 

general strike of the sedimentary rocks and catise numerous complexities of struc-
20 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

ture. The anticline of quartzite which passes through Bridger Peak is cut out on 

the north side of Cow Creek by such a strike fault. Again, between Bridger Peak 

and the upper parts of Cow Creek and North Spring Creek two great faults, 

having a general parallelism with the bedding ·of the sedimentary rocks, bring 

the underlying hornblende-schists in contact with the conglomerate which occurs 

at the top of the bedded series. Doubtless many strike faults exist which have 

not been recognized because rocks of similar appearance have been brought 

together. 

Besides the ·strike faults there are transverse breaks, which sometimes produce 

north-south offsets of the strata. Marked displacements are rare, but those which 

have been noted are parallel to a very general system of jointing observable 

throughout the district. In the quartzites and in the basic intrusives north-south 

fractures are frequently filled with quartz, forming more or less continuous veins, 

and in both the Doane and the Ferris-Haggarty mines breaks belonging to this 

system have a very close bearing upon the origin of the 'Ure bodies. 

' 

( 
CHAPTER II. 

THE BEDDED ROCKS. 

HORNBLENDE-SCHlSTS. 

The oldest bedded rocks, and possibly the most ancient of all the rocks of the 

Encampment region, are hornblende-~chists or hornblende-mica-schists derived by 

metamorphism from volca.nic lavas and fragmentaL tuffs. 

As they now exist, the rocks of the series are typical fine-grained dark or black 

schists composed principally of hornblende and quartz, or hornblende, mica, and 

quartz, with epidote and zoisite in almost constant occurrence, and frequently 

containing garnet, calcite, and more rarely feldspar and magnetite. 

The cleavage of the schists varies somewhat in its perfection, but is usually 

strongly developed. rr nder the microscope the schi~tose structure is found to be 

due to the arrangement of the minerals in alternating parallel plates of quartz and 

dark minerals. The hornblende needles usually have their long dimensions in the 

plane of schistosity, though in this plane they have no definite orientation. The 

· mica flakes commonly lie parallel to the platy structure. 

Considering that the schists are believed to have been derived from igneous 

rocks, which usually contain large amounts of feldspar, the almost complete absence 

of this mineral from the schists is noteworthy. In possible explanation of this fact 

it may be suggested that the rearrangement of material attendant upon metamorphism 

has been so complete that the feldspar originally present has been broken up into its 

constituents and, through metasomatic changes, its substance now enters into the 

composition of the fre~hly crystallized hornblende, mica, and epidote or zoisite, 

leaving a residue of1 silica in the form of quartz, which was not present in the 

original lavas. 

In those instances where feldspar still remaim; it is present in granular aggregates of small crystals similar in morphology to the secondary quartz which is 

universally present. Without exception it has been entirely recrystallized and 

probably also changed chemically, so that it is of a different species from the feldspar which e~isted in the unmetamorphosed rock. 

The original characters of the surface volcanics can seldom be recognized in the ~ 

present condition of the rocks because of their complete recrystallization, but this 

21 
22 COPPER DEPOSITS OF ENCAMPMENT DIST.RICT, WYOMING. 

origin of the schists is suggested by the uniform nature of the metamorphic 

product. The composition of different layers in thick accumulations of lava flows 

and volcanic scoria often varies but iittle, however great the variations in texture, 

and the metamorphism of such a volcanic series would give a homogeneous mass of 

schist without important minor variations. Moreover, the original nature of the 

schists is shown by the occasional preservation of amygdaloidal structure, which is 

regarded as characteristic of surface lava flows, and the occurrence of layers 

composed of angular fragments, which closely resemble volcanic tuffs. The original 

rocks seem to have been andesites and andesite tuffs. 

The bedded nature of the series is indicated by the occurrence at several 

places of a few thin, though persistent, strata of sandy shale and impure limestone; by the fact that the layers of amygdaloid and breccia lie paraUel to these 

strata when they occur in sufficient proximity for comparison, and by a general 

parallelism between these features and slightly varying tabular masses within the 

rather homogeneous schist. When the bedding recognized in this way is compared 

with the secondary platy structure produced through recrystallization, it is 

found that the two are practically parallel, and, as a rule, schistosity can therefore be taken to represent the stratification of the schi.sts. A similar relation 

exists in the overlying formations whenever they possess secondary platy structure, and, in. general, stratification and schistosity in the entire sequence of bedded 

rocks are found· to be parallel features. 

In the central part of the district, south of the sedimentary belt, andesites 

and granite-porphyries, which are in a relatively unmetamorphosed condition, 

are associated with the hornblende-schists. Original flow structures are often 

discernible in the porphyries, and, though they are not entirely fresh, they are 

seldom crushed or recrystallized. The andesites are greatly changed from 

their original condition, though their igneous character may still be recognized 

under the microscope. It is suggested that they may be similar to the great 

masses of volcanic flows which have been so generally altered to hornblendeschists, though this is an inference which can not be definitely proved, since the 

mineralogical composition of the schists gives but little clue to the exact nature. 

of the rocks from which they were derived. 

The alteration which produced the schists is of the sort ordinarily attributed 

to regional metamorphism, and while it can not be definitely proved that the 

transformation was not produced during the folding and crushing of the younger 

pre-Cambrian sediments of the region, the completeness of recrystallization in 

the schists suggests that they may have been independently metamorphosed at 

an earlier date. 

There is indirect evidence that an unconformity of erosion exists between 

the hornblende-schists and the other formations which have been folded down to 
HORNBLENDE·SCHISTS. 23 

form the great synelinorium, but all of these rocks have been crushed together 

in the process of folding, and in the few places where the contact is exposed 

the schists pass beneath the great fold, with the quartzites and associated clastic 

rocks lying upon them in apparently conformable position. 

The hornblende-schists are cut by rocks of all the principal massive types 

occurring in the region. This faet points to the great antiquity of the schists 

and forms the basis of the supposition that the younger bedded formations are 

really uncomformable upon the older volcanic series, for the gray granites are not 

known to cut any strata above the schists, and even the red granites, which are 

of later origin than the gray, can not be found cutting the later sediments of 

the pre-Cambrian, excepting in a few unimportant dikes, which, though similar to 

the granite of the main masses, are possibly of a much later date. It seems, 

therefore, that the greater part of these intrusions of granitic rock took place 

before the deposition of any of the sediments which lie above the metamorphosed 

volcanic series, and it is probable that a long interval ensued after the intrusions 

and before the younger rocks were formed. 

The hornblende-schists often contain sulphides of iron and copper in small 

amounts in the form of disseminated grains or lenticular impregnations. At 

several places they have been found to yield promising amounts of metallic 

minerals, as at the Creede property, and at other localities on the north side of 

the quartzite belt in the head of Spring Creek, at the Sun Anchor and other 

prospects on the north slopes of Green Mountain, and at the Verde, located several 

miles farther south. At each of these localities there is an evident connection 

between the metamorphism of the country rock and the genesis or origin of the 

ores which have been discovered. These fen,tures will be discussed under the 

description of the properties mentioned and in the statement regarding the origin 

of the ores. 

The general distribution of the schists is indicated upon the geologic map, 

though the representations of its extent in the different portions of the district 

are not equally accurate. The area upon the north side of the divide near the 

head of Spring Creek is, however, well shown, though the boundary between 

lt and the gray granite-gneiss which occurs to the north is hidden by a mantle 

of debris. 

In the vicinity. of the tunnel of the Battle Lake Tunnel Site Company, and 

extending eastward into the head of Cow Creek, there is a patch of schists lying 

between two bands of the conglomerate which belongs at the top of the preCam brian formations. This relation can be explained upon the supposition that 

there are two faults of great throw, between which the underlying schists have 

been forced up into the very center of a syncline in the pre-Cambrian sediments. 

The schist is in every respect similar to that which occurs near tl;e Creede mine, 

• 
• 

24 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

but the two areas are separated by tJ,n intrusion of diorite, as shown upon the 

map. Reference to the sections which indicate the natural order of succession 

of the bedded formations will show that in order to bring schist and conglomerate 

together the displacement along the faults which limit the block must have been 

at least as great as the entire thickness of the formations between the strata 

which come into contact. The actual movement upon the faults, however, 

greatly exceeded this amount, since the breaks form low angles with the bedding 

planes of the deeply folded formations. 

The boundaries of the schist areas just south of the middle of the district 

are closely represented, but the massive porphyries and partly altered andesites 

have not been distinguished from the entirely metamorphosed rock. In the southcentral region the distribution is greatly generalized, for here there is locally an 

intricate penetration of the schists by dikes of granite and by masses of diorite 

(metagabbro), neither of which have been distinguished. 

LIMESTONE. 

The second formation in point of age comprises massive limestones and 

associated shales. "'7here it is composed almost entirely of limestone its maximum 

observed thickness is about 20.0 feet, but where the shales partly displace the 

limestone it is usually somewhat thinner. Measurements are often difficult and 

unreliable, because of strike faults which cut out a portion of the normal section. 

As a rule these strike faults and the invading igneous rocks greatly obscure the 

stratigraphic relations of the formation. This is especially true in regard to the 

base of the formation; but since the hornblende-schists show a greater degree of 

metamorphism than the limestone, and are intruded by rocks which do not cut 

the sedimentary formations, there is probably a great unconformity of erosion 

between the schists and the Jimestone. In the few places where the relations of 

the quartzite and the limestone can be observed the former arch over the latter, 

and their bedding planes are strictly parallel. 

The principal outcrops of limestone occur along an anticlinal fold, which c~n 

be traced from Big Sandstone Creek eastward to Encampment Hiver. From Big 

Sandstone Creek to Battle Creek both limbs of the anticline are present, and the 

overlying quartzite occurs on each side of the limestone whenever it appears at 

the surface. Eastward from Battle Creek the southern' half of the fold has been 

cut out by faulting or intrusion, and the limestone comes in contact with the 

igneous rocks outside the synclinorium. 

Two small areas of limestone which occur north of the main belt have been 

brought up from beneath the quartzite by local doming along other anticlines. 

The distribution of the formation and its structural relations are shown by 
QUARTZITES .AND SLATES. 25 

the geologic map and cross sections (Pl. II). As a rule the limestone has been \ 

but slightly altered either by pressure or by the influence of igneous rocks. In 

a few places it has been recrystallized and its impurities have segregated into 

knots of silicate minerals, leaving the carbonate of lime in a granular form. 

This feature is well illustrated in the patch of limestone which occurs in Nellie 

Creek, northeast of Battle; and in the case of a thin limestone stratum which is 

locally developed about 1 mile northwest of Elwood post-office the impurities 

have separated in the form of well-defined crystals of green hornblende. As a 

whole the limestone has been less metamorphosed than would be expected in a 

region so greatly disturbed, and the changes which have taken ,place are less 

apparent to the eye than are the alterations in the other sedimentary rocks. At 

many places it seemed so unaltered that it was' carefully searched for fossils, though 

without success. 

The limestone has nowhere been found to be strongly mineralized, though it 

has been explored in many places. 

QUARTZITE AND SLATE. 

The third formation of the bedded rocks, and the most prominent as a feature 

of the region, is mainly composed of two sorts of rocks-massive quartzites and 

slates derived from shales. These occur in frequent alternation to a minimum 

thickness of about 1,000 feet, though this figure is largely a matter of estimat~ 

with the possibility that it should be doubled. 

In the lower part of the series beds are frequently found which contain 

small rounded pebbles of red granite, showing that crystalline rocks were exposed 

to erosion somewhere in th~ general region at the time the quartzite was deposited. 

The quartzites are sandstones which have been silicified through the deposition 

of silica throughout their mass. They are uniformly of a vitreous nature, and 

though varying in color from place to place, are usually white. Generally the 

silicification has been so complete and has been accompanied by recrystallization 

to such a degree that the quartzite has the appearance of vein quartz. In such 

instances it is usual to find minute crystals of feldspar, resulting from the recrystallization of arkose material derived from the igneous rocks which furnished the 

quartz sand for the original sandstone. 

Both the bands of slate and of quartzite run parallel with the general trend 

of the country, but the internal structure of the folded complex is still undetermined, though it is apparent that individual beds are several times repeated. The 

quartzite beds occur in east-west reefs, which seldom form prominent topographic 

features, but are striking to the eye because their whiteness brings them into 

sharp contrast with the associated rocks, and especially with the black diorite or 

metagabbro. 
I, 

26 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

The series has not been subdivided upon the geologic map because the complete separation of the quartzite ~and slate would have involved the expenditure 

of more time than was a;,railable, but their combined distribution is clearly indicated, together with their relation to the bands of limestone and conglomerate and 

the intrusive masses of diorite. The cross sections sti1l :further illustrate these 

relations and indicate diagrammatically the complex way in which they have been 

folded. 

Locally a portion of the upper beds of this series seems to have been 

removed by erosion previous to the deposition of the overlying conglomerate. 

Quartzite is the country rock of the ore bodies at the Ferris -Haggarty and 

Doane mines, the most important thus far developed in the district, and sulphides 

occur in it at many places, so that it has been very generally prospected. 

CONGLOMERATE. 

The fourth and youngest series of the pre-Cambrian is composed of massive beds 

of conglomerate resting unconformably upon the quartzite-slate series. The component pebbles or bowlders are gray granite, hornblende-schh;t, and quartzite. The 

granite pebbles are similar to the gray granites which cut the volcanic series, especially to the north; but the red granite, which outcrops in large amounts south of the 

clastic belt, does not seem to occur, though careful search was made :for it at ma!ly 

points. The schist pebbles were doubtless derived from the old metamorphosed 

volcanic rocks already described, and the quartzite doubtless :from the strata which 

immediately underlie the conglomerate. The proportions of these pebbles indicate 

that granitic rocks exposed to erosion contributed the greatest amount of material to 

the formation, while the volcanic rocks and quartzite furnished a relatively small 

amount of detritus. 

The conglomerate formation has a maximum observed thickness of about 700 

feet, though it often appears to be thinner, this being sometimes due to partial 

cutting out by faults rather than to an actual decrease in the mass originally 

deposited. 

Locally the conglomerate seems to have been little changed from its original 

condition, but as a rule it has been metamorphosed, and often to such an extent 

that its original characters are masked or entirely obliterated. This metamo:i·phism 

has been both mechanical and chemical, and the rock has often acquired marked 

schistose structure due to the m::\shing of the granite bowlders and pebbles into 

disk-like plates. By recrystallization, feldspar, hornblende, and garnet have been 

:formed :from the pebbles and interstitial material, and in extreme phases the conglomerate has been converted into gneiss, so distinct in its aspect that its origin 

would be entirely indeterminate except for the observation of complete gradations 

into the unaltered rock. 
CONGLOMERATES. 27 

The distribution o£ the conglomerate and its derived gneisses in two parallel 

bands uniting toward the east is well shown on the geologic ~ap, together with its 

surface relations to the intrusive diorite and to the quartzite upon whieh it wa3 

originally deposited. Its preservation £rom erosion results from two deep synclinal folds, the opposite sides o£ which have been pressed together and overturned 

toward the south. 

In certain localities, where the conglomerate has been much crushed, quartz 

veiris containing metallic sulphides have been found, following the gneissic or platy 

structure o£ the inclosing rock, and in some instances copper sulphides without 

quartz have been deposited in small amounts along planes o£ movement parallel to 

the schistosity. The diorite masses inclosed in the conglomerate have been locally 

prospected £or copper, but so £ar as known without encouraging results. 
CHAPTER III. 

THE GABBRO ROCRS AND THEIR META~IORPHIC PRODUCTS. 

GENERAL DESCRIPTION. 

The rocks to be described in this chapter comprise all the dark intrusives which 

occur in the Encampment district and pass under the name "'diorite" as locally 

employed. They are found as a rule in relatively small masses, frequently having 

the nature of intercalated sheets in the bedded rocks of the pre-Cambrian, but they 

occur also as intrusions in the other rocks of the area. Their field relations and 

petrography indicate that the different and separated bodies of dark rock were all 

intruded at the same time, subsequent to the period in which the bedded formations 

were folded, faulted, crushed, and partly recrystallized. Other dark rocks intruded 

before this period may be present in the district, but they have not been recognized 

in place, and their existence is only surmised from a few pebbles of basic rock 

occurring in the conglomerate of the bedded series, which may indicate that there 

were earlier intrusions in the basement rocks of the region, though these fragments 

may readily have been deriv·ed from the underlying volcanic series. 

The rocks are dark colored, of variable though usually fine grain, tough, hard, 

and of a fresh appearance in outcrops. As observed in the field considerable 

variation in mineral composition is to be noted, and such general types as gabbro, 

diorite, and serpentine may be distinguished. More minute study with the microscope bears out this classification, and not only shows the presence of several wellmarked rock species, but reveals the fact. that most of the original rocks have been 

very greatly metamorphosed, the occurrence of the rocks in their original unaltered 

state being extremely rare. Out of nearly 200 specimens collected to r:epresent 

these rocks, only 8 or 10 are practically fresh, and but one is entirely unchanged as 

regards all of its constituent minerals. 

From a study of the relatively fresh material, together with the partly altered 

and entirely metamorphosed specimens, it is known that the original rocks occurred 

in three related types or facies of gabbro. The intermediate type, which is the only 

one which has been found in a rfresh state, is norite; the basic type was olivine-norite 

or peridotite; and the most siliceous facies was a gabbro, or possibly norite, containing pyroxene and oligoclase feldspar, either alone or together with labradorite like 

that of the norite. 

The metamorphic products of the several portions of the original rock are serpentine and hornblende-feldspar rocks similar to diorite in mineral composition, 

together with others composed of hornblende, quartz, and epidote, in which the 

original feldspar has been entirely destroyed. 

2H 
NO RITES. 29 

Traces of copper were found in all of the 18 selected samples representing the 

outcrops of the various varieties of the dark intrusive rock which were tested. a From 

this it may be inferred that the gabbro rocks contain a small amount of this metal 

in all parts of the field, and since it occurs in fresh and altered rocks alike, it is 

probably an original constituent of the magma, and the source of many of the 

segregations of copper n1inerals present in the other rocks of the region. 

NO RITE. 

Practically fresh norite was collected near the Elkhorn mine, about 1 mile 

west of the Verde location, at the Octavia property and at the Creede tunnel, 

and between Bridger Peak and the head of Cow Creek. The mineralogic composition of the specimens from these localities represents the original character 

of mueh of the roek which elsewhere has been changed to diorite. The norite 

has a fine-grained, evenly granular structure. All of the specimens examined 

contain orthorhombic pyroxene, mainly hypersthene, as their principal constituent, 

with a variable though somewhat subordinate amount of labradorite feldspar. 

Biotite is of frequent o~currence, and when present has titaniferous magnetite 

associated "\vith it. A few grains of quartz are present. Olivine was not observed 

in any of the fresh rocks, though present in many cases where considerable 

alteration has taken place. In most of the specimens a small proportion of the 

hypersthene has been altered to the common secondary mineral bastite, and the 

pyroxene is sometimes surrounded by narrow bands of secondary hornblende. The 

feldspar is usually fresh, though it has a clouded appearance, due to minute inclusions, the nature of which is not revealed by the highest powers of the microscope. 

In partly metamorphosed examples of norite the pyroxene has usually been 

more readily altered than the feldspar, though there are exceptions to this rule 

in which the feldspar has been almost completely changed and pyroxene only partly 

altered. In those instances where the pyroxene has been converted to hornblende 

and feldspar still remains, the rock acquires the composition of diorite,, while the 

final product of change due to deep-seated metamorphism, without the added effects 

of hydration brought about by atmospheric weathering, is a rock composed of 

hornblende, epidote or zoisite, and quartz. Numerous examples of this r<lck are 

found throughout the region. A specimen of fresh norite colleeted near the hea~ 

of Cow Creek, on the north slope of Bridger Peak, was analyzed in the laboratory 

of the Geological Survey by Dr. E. T. Allen, with the result which is given in 

Column I of the table of rock analyses on page 32. 

PERIDOTITE. 

\ 

The rock known as peridotite is closely related to norite, from which it differs 

in containing a smaller proportion of feldspar and hypersthene, the place of which 

a These tests were made by Dr. E. T. Allen in the chemical laboratory of the Geological Survey by a method excluding 

the possibility of copper having been introduced from outside sources. 
30 COPPER DEPOSITS OF ENC.AMPMEN'r DISTRICT, WYOMING. 

is taken by olivine. In many areas all gradations between norites containing no 

olivine and peridotites composed almost entirely of the latter mineral are observed, 

and more careful observation than has been possible in the present fieldwork might 

show a complete series between the two types. However, from the relations 

already known, there can be no doubt that the peridotites and 110rites of the 

Encampment district were derived from the same rock magma, and that the differences observed in the secondary rocks derived from them are based upon original 

local differences in the composition of the primary intrusions. The peridotites do 

not occur as large masses in a fresh state; they have been almost completely 

changed to serpentine, though sufficient specimens in which the change has been 

only partial have been examined to definitely show the original fine-grained 

granular structure and the mineralogical nature of the unaltered rock. 

OLIGOCLASE-GABBRO. 

A third facies of the original intrusive rock related to the norite no longer 

exists in an unaltered state. Its partly metamorphosed products sho":" that it 

contained oligoclase as its principal feldspar instead of the labradorite which is 

characteristic of the norite and peridotite. Examples are not wanting to show 

that there were intermediate types between this and the normal norite. The 

feldspars of this rock are usually much altered, but sometimes show relatively 

fresh remnants, surrounded by aggregates of sericite and quartz. The presence 

of pyroxene in the original rock is not certainly known, since nothing but hornblende is now found, but the evident relationship with the other members of the 

gabbro family furnishes strong ground for the in£er.ence that this was the nature 

of the dark mineral. If so, it may have been either hypersthene, as in the 

norites, or diallage, which is the pyroxene forming the ordinary dark-colored 

constituent of normal gabbros as distinguished from norites. 

The feldspar crys-tals in the rocks intermediate between this type and the 

norites frequently show zonal growths~ with oligoclase upon the outside and 

labradorite wit.hin. 

As in the case of the norites, the moderate metamorphism of the oligoclasegabbros has resulted in the formation o£ a rock with the mineralogic composition of diorite, and changes more complete have produced hornblende rocks in 

which the original feldspar has been entirely destroyed, with the formation of 

epidote and quartz. 

METAGABBRO, OR "DIORITE." 

By definition diorite is a wholly crystalline granular rock made up essentially 

of hornblende and plagioclase feldspar. True diorite occurs as the result of 

original solidification of molten rock material, but rocks of the same composition 
METAGABBRO, OR ''DIORITE." 31 

are often derived-as in the Encampment district--by the metamorphism of rocks 

whose dark constituent is some variety of pyroxene. When of this origin they 

are properly called metagabhros, a term devised to indicate that they are altered 

gabbros. The metagabbros of the Encampment district are not distinguishable 

from true diorites by the unaided eye nor with an ordinary magnifying glass, and 

resident mining men commonly use the latter tern1 for a variety of dark rocks 

more or less specked with white. " 7 hile the present investigation has shown that 

none of the rocks can be strictly classed as diorites, and that many of them are 

essentially different Jrom diorite in 1nineral composition, the present usage is a 

convenient one, which may well be continued. 

Several types of these dark rocks have already been described under the names 

appropriate to their original mineralogic composition; the secondary diorites have 

also been incidentally mentioned, and their metamorphic derivation indicated. 

They are fine-g-rained black or gray granular rocks composed of hornblende and 

feldspar or minerals derived from decomposition of the latter. Mica frequently 

occurs accompanied by titaniferous magnetite and titanite; epidote and its iron· 

free relative, zoisite, are always present as secondary products, while calcite and 

chlorite, though present, are less often found. , 

Schistose structure, which is of almost constant occurrence in all of the older 

sedimentary formations and in certain of the crystalline rocks, is practically 

absent from the gabbro rocks and their metamorphic products. This fact alone 

would be sufficient to show that the dark intrusives originated subsequent to the 

production of the parallel structures of the older rocks, but this is independently 

proved by the manner in which the invading dikes follow the stratification and 

schistose structure of the folded formations. The examples of schistosity observed 

are confined to small masses of the secondary diorite, in which, as a result of 

irregular transmission of pr~ssures due to heterogeneity, local strains ~~re produced by earth movements probably 1nuch less revolutionary than those which 

had previously folded and mashed the quartzites and associated strata. 

No extended discussion of the mineralogic changes- observed in the passage 

of these gabbro rocks into metagabbros will be attempted in this J?lace, and it 

must suffice to recapitulate the statements already given of what these e\u;tnges 

have been. 

In the least altered of the rocks free from olivine, pyroxene has been the 

only mineral attacked. Here it 1nay be only partly changed to hornblende, or it 

may be entirely replaced by that seeondary mineral. Epidote is always found 

as a side product of the hornblende formed in this way. Its presence may be 

readily explained by the well-known :fact that the percentage ratio of magnesia to 

lime in hornblende is greater than in pyroxene; consequently if all of the magnesia 

of the pyroxene is taken up by the hornblende, there is a residual of lime. 
32 OOPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

Furthermore, the hornblende molecule contains a smaller ratio o£ silica, which, 

being likewise l_iberated, combines with the lime and a small .amount o£ iron 

derived from the pyroxene and forms epidote. 

The first decomposition o£ the feldspar results in the development o£ a few 

small needles o£ zoisite or epidote distributed through the crystal. This change 

involves the liberation o£ alumina, which, being needed in the hornblende, has 

doubtless been taken up by that mineral. Further alteration shows a progressive 

increase o£ the zoisite or epidote until finally an aggregation o£ these minerals 

inclosed in quartz completely fills the space originally occupied by the feldspar. 

In proportion to the extent to which these secondary minerals have been 

formed, the rock has been partly or completely recrystallized. It may therefore 

be concluded that the observed metamorphism has resulted £rom internal reactions 

between the original minerals, involving molecular transfer and interchange o£ 

substance with the £ormation o£ new mineral combinations. A. comparison o£ the 

original and secondary minerals shows that there has been no important gain or 

loss o£ material, an indication the value o£ which is greatly increased by the 

similarity o£ the bulk analyses o£ fresh and altered types o£ rock here appended. 

Analyses of 1write and other rocks jt·om the Encampment district. 

[Analyst, E. T. Allen.] 

I. 

Si 0 2 . ____ .... __ ..... _ .... __ ... 52.00 

A.l203--.- ... ------------------ 11.59 

Fe20 3 ... - - - .......... --... ~- ................. - .. --- 2. 72 

FeO .. ~ ............. _ .. - ___ -.. 7.18 

MgO ------------·-----------· 12.87 

CaO ....... _ ........ -. -- - -.... 10.49 

N a2 0 _ ... __ ... __ ... -...... -. -- 1. 06 

K20 _ .... - -. - ___ -.... ____ .. ___ . 92 

H 20-.... -.-. _.-. _. _____ . ___ . .18 

H20+-----.. ----- . ----- ------ . 37 

Ti02 __ •••••••• ____ •• __ • ___ • ___ . 99 

002 -------------------------- None. 

II. 

50.03 

10.89 

2.32 

7.99 

11.84 

9.73 

1. 66 

. 57 

.46 

2.61 

1. 23 

. 78 

III. 

50.20 

15.54 

2. 14 

6.49 

7.33 

11.96 

2.03 

.40 

.43 

2.52 

1. 00 

None. 

IV. 

46.39 

16.17 

2.65 

9.30 

8.58 

8.90 

2.25 

. 73 

. 47 

2.59 

1. 59 

None . 

P20 -----------------------~- None. .02 .09 .06 

S ......................•..•.. 

1 

Trl:tce. Trace. . 03 . 01 

Cr20a- .. -..................... Trace. Trace. Trace. Trace. 

NiO ......................•.......... .' ............ ---------- Trace. 

NiO+CoO ••......... _ .. _ .. _ . . . 04 . _ ... _ . ____ .. _ .. __ . _ .. __ ..... _ 

MnO -. __ . _ .............. _ .... Trace. Trace. Trace. Trace. 

BaO ............ __ .... __ .. _ . _ . Trace. . 04 None . . 02 

CuO .. ___ ... _. __ . ___ . __ . _. _ ... Trace. Trace. Trace. .02 

100.41 100.17 100.16 99. 73 
ROOK .ALTERATIONS. 33 

1. Norite, occurring near head of Cow Creek, about three-fourths of a mile from Bridger Peak. 

This rock is made up largely of colorless hypersthene and labradorite which has been slightly changed 

to sericite. There are a few grains of diallage and also a few small crystals of orthorhombic hornblende. Original biotite occurs and with it considerable magnetite. 

II. Diorite derived from norite, occurring near head of Cow Creek, about three-fourths of a mile 

north of Bridger Peak; altered form of I. The pyroxene has been completely changed to uralite, and 

the feldspar largely decomposed. 

III. Diorite probably derived from gabbro, from cutting on new Rawlins road, near the head of 

Big Sandstone Creek. In this rock paramorphism and recrystallization have' been practically complete. The feldspars have given rise to a large amount of zoisite, but the rock is not at all crushed. 

IV. Diorite derived by metamorphism from norite, from ridge east side of West Fork of Battle 

Creek, 2 miles west of the Verde mine, Encampment district. This rock shows the evidence of 

regional metamorphism by comparison with other fresh rocks. It seems to have been composed 

originally of pyroxene and labradorite, with small amount of biotite and magnetite. The microscope shows no evidence of hydration, and recrystallization has been confined to the pyroxene, 

which now occurs in the form of uralite. 

The mineral transformations described are regarded as• having been produced 

by dynamic pressures, but the forces involved were not sufficient to inaugurate mass 

movements amounting to crushing, nor was their action accompanied by the invasion of water in amounts adequate for any general hydration. Lindgren a has 

defined the term "dynamo-chemical metamorphism" in a discussion of rock alteration in his report upon the gold-quartz veins of the Nevada City .and Grass 

Valley districts, California. The following extract from that report gives a clear 

comprehension of the nature of the general process, and indicates that the aboYedescribed variety of metamorphism, without crushing and without hydration, is 

comprised in Lindgren's dynamo-chemical class. 

"Large tnetam0rphosed areas are often spoken of as affected by regional metamorphism, a general term not designating the cause of the action. A large part of 

the Sierra Nevada may thus be said to have been subjected to regionalinetamorphism. The main cause, however, undoubtedly being orogenic pressure, the rocks 

are referred to as altered by dynamo-metamorphism. Strictly speaking, this term 

refers qnly to the purely dynamic processes of crushing and shearing by compressive stress distributed evenly through the rock ·or relieved along certain planes. 

A stretching action produced by a tensile stress has also been recognized by several 

investigators, but no decided evidence of its existence can be said to have been 

found during the examination of the rocks in this district. 

"While example-s of dynamo-m~tamorphism without extensive mineralogical 

alteration occur, chemical forces are nearly always involved and very generally play 

a most important part, incited by the increase in temperature accompanying the 

pressure at points far below the surface and aided by the moisture of the rocks. It 

is not at aU probable, however, that the heat during the dynamo-metamorphic proca Lindgre11, Waldemar, The gold-quartz veins of Nevada City and Grass Valley districts, California: Seventeenth Ann. 

Rept. U.S. Geol. Survey, pt. 2, 1896, pp. 90-96. 

2100-No. 25-04--3 
34 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

esses in the Sierra Nevada has exceeded a few hundred degrees Centigrade, and of 

fusion there is no indication at all. It is not necessary for the initiation of the 

recrystallizing action that the pressure should have been carried to a point at. which 

the limits of cohesion were reached and schistose structure produced. 

''The process should, perhaps, more fittingly be designated dynamo-chemical 

metamorphism. It is generally charact~rized by a very moderate hydration and the 

formation of clear, fresh aggregates of mosaic structure. It usually produces a rock 

of finer texture than the original one. Igneous and sedimentary rocks are similarly 

affected, though the ultimate products usually differ. The chemical composition of 

the rock does not appear to be greatly altered by the process. 

"Dynamo-chemical metamorphism, best illustrated in this district by the Indian 

Flat amphibolite area and by the Grass Valley Calaveras slates area, ordinarily produces the following minerals: Feldspar (probably very largely albite), quartz, 

hornblende, biotite, muscovite, chlorite ( ?), epidote, titanite, magnetite, pyrite, and 

pyrrhotite. The origina!" feldspars are converted into albite, epidote, hornblende, 

quartz, and muscovite. The pyroxene alters to uralite and recrystallized hornblende, 

biotite, and epidote. The larger grains of clastic or porphyritic character are not 

only crushed but also resolved to secondary aggregates by a corrosively acting process of substitution, the new-formed minerals projecting into the primary grains."a 

Dynamo-chemical metamorphism, producing nonhydrous secondary minerals, 

has affected the original gabbro rocks in all parts of the :field; but, as already 

stated, the amount of alteration varies from place to place, and examples of 

nearly fresh rock are frequently to be observed. From these facts two inferences may be drawn,. namely, that the metamorphosing pressures were not uniformly distributed, and that they were probably not excessive. The :first inference 

may be explained as due to the great heterogeneity of the large rock masses which 

have been affected, a feature which introduces the possibility of l~cal relief or 

compensating increase of the average pressure, through a partial deflection of 

strain by the strongest or most competent members of the complex. That the 

average pressure was moderate is an inference which follows from the fact that 

the strongest rocks were sufficiently rigid to cause a change in the direction of 

transmission, for if the pressures were greater than they had the ability to resist, 

uniform yielding throughout the complex would have been the necessary result. 

Only the maximum strain, occurring where transmission was most complete 

and where the deflected pressures were added to the average pressure, was 

sufficient to produce internal molecular rearrangement of the rock minerals without 

causing recognizable mass deformation. The minimum strain was not adequate 

to produce any important disturbance, the absence of which is evidenced by the 

unaltered portions of the rock. 

a Lindgren, Waldemar, 'l'he gold-quartz veir,s of Nevada City and Grass Valley districts, California: Seventeenth Ann. 

Rept. U. S. Geol. Survey, pt. 2, 1896, pp. 90-91. 
MINERALIZATION OF THE GABBROS. 35 

SERPENTINE. 

In describing the peridotites of the Encampment district it was noted that 

they have been generally altered to serpentine. This form of alteration is the 

ordinary one for rocks containing large amounts of olivine, and the presence of 

this n1ineral usually controls the secondary changes of all the dark ro~k-making 

minerals associated with it. Thus, instead of appearing as hornblende in the 

serpentine rock, the pyroxene of the peridotite has changed to the mineral 

serpentine along with the olivine. 

Like the peridotites from which they have been derived, the serpentines 

contain a small amount of chromium, and in common with all the dark gabbroic 

rocks they carry traces of copper. They also contain. more magnetite than the 

related types excepting peridotite. 

The alteration of olivine to serpentine involves hydration or the taking up 

of water which enters into the constitution of the secondary mineral. The 

transformation of the peridotites into serpentine is therefore regarded as the 

result of hydrometamorphism, and though the change may have taken place when 

these rocks were deeply buried, and have been contemporaneous with the general 

metamorphism of the gabbro rocks, it is regarded as more probable that it is of 

relatively recent origin and due to processes similar to those which have caused 

a lesl:l complete hydration of other phases of the gabbro rock, as outlined in the 

following section. 

Serpentine is found only in the western part of the area, where it was noted 

at several points in the drainage of Big Sandstone Creek. No important ore 

occurrences have been noted in this rock, but sulphides are found inclosed in it 

at some prospects situated in the northeast corner of sec. 20, T. 14 N., R.-87 W. 

MINERALIZATION OF THE GABBRO INTRUSIVES. 

The chemical tests, which have been mentioned, indicate that copper is present 

in every facies of the intrusive gabbro rock, both original and metamorphic. In 

these rocks the metal, however, occurs in very minute quantities, and copper 

minerals can not ordinarily be detected by microscopic examination of the rocks 

in thin sections. It may therefore be suggested that the copper is disseminated 

through the rock, either in the rock-forming minerals as inclusions beyond the 

power of the microscope, combined with oxide of iron in magnetite inclusions 

which are almost universally present, or entering chemically into the molecular 

constitution of one or all of the ferromagnesian minerals. Each of these suppositions is in accord with the belief that the copper present in the dark rocks was an 

original constituent of the magma from which they were derived. 
36 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

It has already been stated that this original. or indigenous copper is never 

visible though always present in the gabbro rocks. Visible minerals of copper are, 

however, encountered in the same rocks in all parts of the field, but these are 

regarded as secondary segregations resulting from the action of water in circulation. 

The usual-copper mineral is chalcopyrite, excepting where surface oxidization is to 

be plainly recognized. It is always accompanied by decomposition of the country 

rock, through the body of which it occurs in grains or irregular masses. The 

products of this decomposition are mainly calcite, chlorite,. and chalcedony, the 

presence of which shows that hydration has taken place, for calcite is ordinarily 

deposited only from aqueous solution, while chlorite and chalcedony contain water 

chemically combined. 

From the relation of the chalcopyrite to the other secondary minerals, as 

seen under the microscope, it is apparent that all were deposited at the same time. 

The hydration of the rock and the deposition of the chalcopyrite are regarded as 

due to the action of circulating meteoric waters, but whether hot or cold there 

is no way of determining. The date of this water action has not been determined, 

but the alteration produced by it can not be in any way confused with the 

dynamo-chemical metamorphism of the dark rocks, which is undoubtedly an 

earlier phenomenon. 

None of the secondary s~gregations, where they occur entirely within the 

basic gabbro rocks, have the form of veins, and none of them have thus far 

proved rich enough or of sufficient size to constitute ores. vVhen, however, as 

occurs in some instances, the secondary deposition. follows a contact between the 

gabbro and some. other rock, the amount of mineral may become of economic 

importance. The reason that such contacts are fa\rorable to mineral deposition 

and to the occurrence of segregations of good 'size and extent is doubtless to be 

found in the existence of a readier circulation in these places than in the body 

of the rock. 

CONTACT METAMORPHISM. 

The pyrrhotite ores carrying copper, nickel, and cobalt at the Creede prospect 

occur in a country rock of hornblende-schist near a large dike of no rite. The 

exact nature of this deposit could not be determined for lack of sufficient exposures 

to show the complete relations, but it is possibly the result of contact metamorphism and impregnation caused by mineralizing emanations from the norite at 

the time of its intrusion. 
CHAPTER V. 

THE SILICEOUS IGNEOUS ROCKS. 

GENERAL DESCRIPTION. 

With the exception of a few unimportant dikes, all the siliceous igneous rocks 

of the district are found outside of the area occupied by the sedimentary preCambrian rocks. They are much older than the dark nonsiliceous rocks described 

in Chapter IV. 

There are two types of coarse granular rock occurring in large masses, one of 

which is a quartz-diorite, with a general gray color, and the other a granite, 

exhibiting various shades of red. A third type, nearly white, occurs in dikes or 

:flattened lenticular bodies in the gray diorite, especially where it has a gneissic 

structure, and also forms part of a complex of crystalline rocks which occurs in 

the northeast corner of the district, but which has not been studied with sufficient 

care to warrant its detailed description. 

The age of these rocks in reference to that of the bedded series has not been 

determined, :for, while masses of both the gray and red rock cut the old metamorphic schists, contacts with the quartzites or associated strata are not found. 

Diorite younger than the sedimentary rocks is everywhere intruded between the 

quartzites and the crystalline rocks except in localities where the former re~t 

directlr upon the hornblende-schists. 

The quartz-diorite and granite have been distinguished upon the geologic map, 

which shows their general distribution and areal relations. In representing the 

areas in which these rocks predominate their occurrence has been greatly g~neralized, and many masses of the younger dark intrusives and of other rocks occur 

which are not shown at all. No attempt was made to indicate the distribution of 

the light-colored granitic rocks which :form the third type mentioned above, which 

occur only in relatively small masses. 

QUARTZ-DIORITE AND DIORITE-GNEISS. 

The quartz-diorite is partly massive and partly schistose, but aside :from differences in strueture due to local mashing, the type holds its identity throughout the 

areas which it occupies. It is a gray granular rock composed essentially of feldspar, biotite, and quartz, with a little hornblende. Titaniferous magnetite is of 

37 
38 COPPER DEPOSITS OF' ENCAMPMENT DISTRICT, WYOMING. 

frequent occurrence, and rutile, which is also a titanium mineral, sometimes occurs 

as need~es inclosed in the mica. Epidote and zoisite are invariably present as products of alteration, being principally derived from the feldspar of the original rock, 

and often, with quartz, completely filling the place once occupied by that primary 

mineral. The zoisite products are usually more thickly set in the center of the 

original crystal, and sometimes outside of them there is a rim of relatively clear 

siliceous plagioclase which is probably secondary. Occasionally, also, clear particles 

of similar feldspar are found in the interior of the altered crystals. A. large number 

of determinations shows that the secondary feldspar varies in composition ~rom 

oligoclase ne~r albite to normal oligoclase, but the latter is the more abundant. 

Regal'ding the epidote as derived from lime set free by the alteration of the original 

feldspar, the latter must have been more calcareous than the secondary residual 

oligoclase. To the unaided eye the rock appears like granite, but it can not be 

classified under that head, since the feldspar is plagioclase instead of orthoclase, 

which is characteristic of granites. It differs from ordinary diorite in the presence 

of large amounts of quartz, and is therefore designated quartz-diorite. 

The rock has been universally affected by metamorphism, which is evident in its 

entirely massive portions as well as where it possesses gneissic structure. The 

mineral transformations which can be made out are almost wholly such changes as 

are not dependent upon the addition of water, and where hydration has taken place 

it has been subordinate in amount to the other alterations. Locally, where the 

gneisses show the most marked evidence of mashing, they contain more quartz·than 

the massive portions of the rock. This mineral is commonly distributed along the 

planes of schistosity, and has apparently been introduced through circulating waters, 

which either accompanied the dynamic action or were active at some subsequent 

time. 

Analytical tests of specimens representing this rock show the absence of copper 

' in some cases and its presence in minute amounts in others, but none of the thin 

sections examined with the microscope contain visible segregations of sulphides, 

nor have important bodies of copper ore been discovered in the quartz-diorite as 

country rock. It, however, incloses portions of the Alma and Meta veins, north 

of the area shown on the accompanying map, the values of which are mainly 

silver, occurring in galena with some associated copper minerals. 

The quartz-diorite incloses irregular masses of red granite which have been 

intruded into it; also intrusions of dark gabbro rock, and in its gneissic portions 

segregations or intrusions of aplite. 

Secondary gneissic structure may be observed over the greater portion of the 

area covered by the quartz-diorite. Along the southern side of the area north of 

the quartzites this structure shows a notable parallelism with the structures of the 
RED GRANITE. 39 

bedded rocks in the adjacent synclinal fold. As shown upon the map, this feature 

is brought out by the dark intrusive dikes which follow the gneissic structure of the 

quartz-diorite, and run parallel with the near-by reefs of quartzite and their includ~d 

dikes. The dips likewise are toward the south as in the quartzites. The parallelism 

of this gneissic structure with the general structure of the bedded rocks suggests 

that the structure of the gneiss may have be~n produced at the same time as that of 

the bedded rocks-that is, during the compression of the great syncline. At a 

distance from the folded sedimentaries this parallelism does not persist. This may 

be seen in the region between the fork~ of Spring Creek, whe1~e the platy structure 

of the gneiss lies nearly horizontal, and in the vicinity of the Charter Oak and 

Home Fraction mines, where a distinct dish-shaped synclinal structure is to be 

made out (seep. 83). 

RED GRANITE. 

A few masses of red granite occur north of the synclinorium of bedded rocks in 

the area occupied mainly by the quartz-diorite-gneisses, but the principal development 

of this rock is south of the sedimentary belt, where it is found locally cutting the 

gray quartz-diorite, and generally intrusive into the hornblende-schists. It contains 

many included masses of the last-mentioned series, and is penetrated by dark basic 

intrusives similar to the gabbros which cut the quartzites in the sedimentary belt. 

The red granite is extremely variable in its appearance, being very coarse in 

some localities and elsewhere fine grained. The depth of its coloring also changes 

from place to place, but it is always recognizable in the field as true granite. Examination with the microscope shows that it is composed mainly of orthoclase or microcline 

and quartz. These minerals are frequently intergrown, forming micropegmatite if 

the rock is fine grained, or graphic granite if the crystallization is coarse. Besides 

the usual alkali feldspars, th~ lime-soda feldspar, oligoclase, is an almost constant 

accessory constituent, and the dark minerals, which are relatively small in amount, 

are ~iotite, or rarely hornblende. The rock is thus very siliceous, a fact which 

makes the constant occurrence of magnetite particularly worthy of note, since this 

mineral is ordinarily associated with the clark rock-making minerals. In almost all 

specimens of the red granite magnetite-which is often, and perhaps usually' 

titaniferous-may be detected without the assistance of a glass. Locally in coarse 

phases of the rock it occurs in crystals half an inch or more in diameter. 

The red granite is the least altered of all the rocks of the region. In no important part of its mass have secondary gneissic structures been developed, in which 

respect it stands in contrast with the gray quartz-diorite, which is usually gneissic. 

Locally parallel structures are present, but they never occur over extensive areas. 

In most of the rock the microscope fails to show any broken or distorted mineral 

grains. 
40 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYO:\HNG. 

Besides being free from any general crushing, the rock does not give evidence 

of any important mineral transformations. The feldspars are usually perfectly fresh 

and when slight alteration is noticed it seems that sericite is always formed. This 

secondary mineral is noted principally in the oligoclase and but rarely in the orthoclase. Its production involves the introduction of a small amount of water, and 

may well be the result of surface weathering. If it can properly be referred to this 

cause, the granites are practically umnetamorphosed rocks. Their relatively fresh 

condition compared with the gabbro derivatives may be explained on the principle 

that masses of siliceous rocks are, in general, Jess sensitive to changes in physical 

condition than rocks which contain a high proportion of dark ferromagnesian minerals. This principle seems to apply in the present case, for such evidence as we 

now have indicates that the granites are probably of about the same age as the 

gabbro rocks which have been so generally altered; and, therefore, both rocks have 

been subjected to the same changes in physical conditions, whatever these changes 

may hav-e been. It seems that the assumed increase of molecular activity attributed 

to static pressure and consequent rise of temperature was sufficient to set up chemical 

changes and metasomatism, resulting in recrystallization of the dark complexly constituted rocks, but not enough to start similar processes in the granites of more 

simple composition. 

It is believed that the red granite as a whole is at least as old as the 

intrusive gabbro rocks, though this is a question open to fuller investigation: 

That it is younger than the gray quartz-diorite is evident from the field relations, 

and it was probably intruded during or after the metamorphism of the gray rock. 

This last conclusion is based upon the presence of I parallel structures in the gray 

rock, and their absence in the red, where the two are in contact. If, as seems 

likely, the gneissic structure of the quartz-diorite was produced by the same 

compression as that which folded the bedde~ rocks, the relation indicated proves 

that the red granite, as well as the gabbro-rocks, was intruded after the folding. 

Data are not at hand for a complete discussion of the age relations between the 

various igneous rocks, so that the problems presented by this line of inquiry 

must be left for future investigation. 

The red granite was nowhere observed as the sole country rock for important 

mineral veins, though the dark rocks inclosed in it, and certain pegmatite veins or 

dikes apparently related to it, have been mineralized to a certain extent. Throughout the region where it is the principal rock, local occurrences of copper minerals 

have been noted by prospectors, but each of these occurrences observed is associated 

with n1ore or less important masses of rock different from the main mass of granite. 

This fact is illustrated for instance at the Jesse, or Scott, group of claims in Hog 

Park, where encouraging indications of copper ore have been revealed. 
SILICEOUS IGNEOUS ROCKS. 41 

APLITE AND PEGMATITE. 

The term aplite as a rock name is here used for white, fine-grained rocks 

which are composed principally of quartz and oligoclase feldspar. Pegmatite is 

used for related rocks which are more coarsely crystalline than the aplite and of 

pink or reddish color. The feldspar of the pegmatites is usually orthoclase or 

microcline. Aplite occurs throughout the gneissic portion of the quartz-diorite, 

and especially in the eastern portion of the district where, in alternation with 

dark, often schistose, hornblende rock, it often exceeds in amount the mass of the 

gneiss into which it appears to be intrusive. The aplites always closely follow the 

platy structure o£ the gneiss, but actual intrusive relations are rarely recognizable 

since, instead of sharp contacts, there is often a mineralogical gradation from one 

to the other, resulting from secondary crystallization. 

The geologic relations of the aplite have not been completely determined, but 

bodies of the rock composed of feldspar and quartz and having the form of 

dikes were found to pass by gradation into quartz veins, a .fact which suggests 

that they may not be true igneous intrusions in the same sense as the gabbro 

rocks, but rather that they have been formed through aqueo·igneous activity, an 

origin to which many pegmatites have been assigned. (t 

The coarse pegmatites have been noted mainly i"!l the region south of the 

sedimentary belt, and they are somewhat prominently developed along the southern 

edge of the red granite with which they are probably connected in origin. Like 

the aplites, they are found to grade into quartz veins, a feature which may be 

observed to advantage in the vicinity of the Kurtze Chatterton mine. The pegmatite here, as on the Cascade property west of the Encampment River, occurs 

in the form of veins which, though showing a general parallelism to the eastwest structure of the country rocks, still exhibit considerable irregularity. 

The origin and distribution of the aplites and pegm!'ttites, and their possible 

relationship to each other, are questions which must be made the subject of 

future inquiry. The aplite is not known to have any importance in relation to 

the ore deposits of the region, for while the origin of certain quartz veins is 

connected with that of this rock and certain of these veins carry small amounts 

of gold, the latter has not been found in encoura.ging amounts,' if a single 

exception is made for the discovery of a rich bowlder in Purgatory Gulch, the 

source of which was never determined. No copper deposits are associated with 

this rock so far as is known. 

The pegmatite contains copper minerals in the veins of the Cascade property, 

but here the metallic mineral is of later origin than the pegmatite itself. The 

latter is found to be slightly broken and crushed, and tbe copper has been 

introduced along with a small amount of quartz, as a deposit from circulating 

waters. 

aCrosby, W. 0., and Fuller, M. L., Origin of pegmatite: Mass. Inst. Technology Quarterly, vol. 9, No. 4, 1896. 
PART II.-ECONOMIC GEOLOGY. 

CHAPTER I. 

GENERAL FEATURES. 

CONDITIONS OF STUDY. 

The ore deposits of the Encampment district have not, as a rule,- been 

developed to a sufficient depth to afford opportunity for extensive underground 

examination. For this reason, while the few mines which have extensive workings 

have been studied with all the care possible, the information which has been 

obtained concerning the occurrence of copper minerals in the field at large, and 

thei~ relations to the rocks which inclose them, has come largely from surface 

examinations incidental to the study of the general geology of the district. It 

has been possible, however, to make the~Se data the basis of some general conclusions which may have a practical bearing upon the future development of the 

field. 

At the time the district was visited, in the summer of 1902, there were but 

two copper mines which contained known ore reserves, namely, the Doane and 

Ferris-Haggarty properties. A third mine, the Charter Oak, had formerly produced some ore, but was then abandoned, while the Kurtze Chatterton property, 

from which a few tons of good mineral had been taken, was also idle. 

In addition to the copper ores, others containing lead and silver had been 

shipped from the Meta mine, which is located just north of the Encampment 

district, between the forks of Spring Creek, and also from the Elkhorn mine, 

situated south of the area, near the Continental Divide. In the fall of 1902 

parties had taken a lease upon the last-named property with the intention of 

reopening it during the winter. 

ORES. 

Copper is the predominant metal of value in the ores of the district, though 

there are a few occurrences of lead-silver ores, and gold occurs either by itself 

in quartz veins or in variable but always small amounts accompanying the other 

metals. The copper minerals comprise chalcopyrite, bornite, chalcocite, and 

covellite and their usual alteration products, malachite, azurite, chrysocolla, and 

cuprite. The metal occurs also in some instances in magnetic pyrites of iron or 

pyrrhotite, where it is usually accompanied by small amounts of nickel or cobalt. 

42 
PRIMARY AND SECONDARY ORES. 43 

The silver-bearing ore is argentiferous galena associated with sphalerite and 

pyrite in veins of quartz carrying some calcite or carbonate of iron. 

PRIMARY AND SECONDARY ORES. 

The word primary is employed in this report to denote ores which do not 

show evidence of having undergone any mineralogical alteration since their first 

deposition, while ores which have resulted from changes in preexisting primary 

ores involving the formation of new minerals and the removal, concentration, or 

redistribution of their metallic contents, are termed secondary. 

Both primary and secondary ores of copper are found in the mines and prospects 

of the Encampment district, and the relations between the two may be clearly 

determined in certain instances, but in order to clearly present the significance of 

these relations some of the general characteristics of copper deposits, as they have 

been observed in other fields, will be briefly outlined. 

Many deposits of copper ore are represented at and. near the surface of the 

ground by materialt::~ quite different from those which form the productive portion 

of the ore body. The superficial portion of a vein often exhibits a mass of iron 

oxide, either spongy limonite or more massive hematite, mixed in varying proportions with minerals of a nonmetallic nature. Such surface cappings or gossans are 

frequently quite free from copper minerals at the surface, but as the rusty material 

is followed downward these are encountered, at first in small amounts, in the form 

of carbonates and silicate mixed with the iron oxide; and later, as the amount of 

these minerals increases, in the form of red copper oxide and black powdery 

sulphide. 

At greater depth the solid sulphides appear and the proportion of iron oxide 

decreases, until, after a mixture of the two is penetrated, the former occur either 

alone or accompanied by the copper minerals first encountered in the gossan. 

The ores occurring immediately beneath the oxidized ~mrface capping are iro.nbearing sulphides in some instances, while in others they are sulphides, such as. 

chalcocite and covellite, which contain a high percentage of copper and little or no 

iron. In mining the high-grade sulphide ores, an admixture of the leaner sulphides 

is often encountered, and as lower levels are reached these gradually take the place 

of the richer ores, so that if the mineralization continues to a sufficient depth 

low-grade sulphides are always found. 

It may be stated as a rule that in regions of copper deposits gossan eventually 

leads either to chalcopyrite or to other ferruginous copper-bearing sulphides, 

whether rich sulphides occur between the two or not. 

The relations which have been outlined naturally suggest that both the gossans 

of copper veins and the rich sulphide ores sometimes occurring beneath them result 
44 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

from the alteration of low-grade sulphides. The investigations by Emmons and 

Weed of the copper deposits at Butte, Mont., have led to the general recognition of 

this genetic relationship between the minerals of the gossan and rich sulphide 

zones and those of the deeper zone in which the copper is associated with iron in 

the form of relatively lean sulphides. a 

The gossans and rich sulphides are regarded as the result of alteration of 

the low-grade ore which formerly filled the space which they now occupy through 

the action of oxidizing meteoric waters; the ores of the two upper zones are therefore secondary ores, while the low-grade material is unaltered primary ore. 

Since secondary ores are derived from earlier existing deposits of a primary 

nature, they seldom occur entirely alone, and in any instance where they are found 

they are ordinarily mixed in variable amounts with primary material. 

The primary copper ores of the Encampment district are chalcopyrite and 

pyrrhotite. Th~ secondary ores are known to include azurite, malachite, ehrysocolla, cuprite, bornite, chalcocite, and covellite; and still others may exist. 

GANGUE MINERALS. 

· The gangue minerals of the 1reg-ion comprise quartz, calcite, siderite, feldspar, 

hornblende, ·epidote, and garnet. As a rule neither these minerals nor those 

which carry copper are found in the form of veins, for though veins do occur, 

the metallic mineral usually permeates the rock in which it oecurs, replacing its 

minerals to a greater or less extent. It follows from this that the gangue of 

many ores represents simply the minerals of the country rock. When veins are 

present they are ordinarily composed of quartz and calcite, alone or in combination, though the iron carbonate, siderite, is sometimes present. 

GROUND WATER. 

The annual precipitation in the Sierra ~Iadre is known to be rather great, 

and while no data are at hand for determining its seasonal distribution or average 

. amount, it is known in a general way that the portion which falls as snow during 

the winter months greatly exceeds the rainfall during the summer. A considerable area within the mountains, particularly within the Encampment district, 

lies above 10,000 feet elevation, and the snow, which accumulates to a depth of 

from 4 to 8 feet, invariably lingers until J nne, and in many places large snow 

banks are to be found until the end of July, while at several places upon the 

northern summit slopes great aecumulations, due to drifting, are practically 

perennial. 

Under these climatic conditions it is not unnatural that the upper level of 

a Weed, W. H., Enrichment of mineral veins by later metallic sulphides: Bull. Geol. Soc. America, vol. 2, 1900. pp. 

179-206. Emmons, 8. F., The secondary enrichment of ore depo;;its: Trans. Am. Inst. Min. Eng., vol. 30, 1900, pp. 177-217. 
SURFACE CAPPING OF ORES. 45 

general saturation, which is usually termed the ground-wate::.· level, should lie 

very near the topographic surface, as is found to be the case. In traversing· the 

area a large number of prospect pits were examined, and only rarely wa~ standing 

water absent if a depth of 25 feet had been reached. In some places the water 

ri~es to within 10 or 15 feet of the surface, and as an average it may be safe to 

say that ground water is encountered at a depth of less than 30 feet. 

It appears also, at least locally, that the gTound water has a lower as well 

as an upper limit, and though the opportunities for observation are extremely 

limited, it may· be mentioned that in the case of the 800-foot tunnel driven by the 

Battle Lake Tunnel Site Company, which attains a depth of nearly 450 feet under 

the north slope of Bridger Peak, the rocks penetrated were found to be entirely 

dry, excepting that a single fracture yielding only a few gallons of water per 

hour was encountered. The material penetrated was a very homogeneous hornblende schist belonging to the lowest bedded formation of the region, which is 

described in another place in the present report. In the case of the Beulah 

tunnel, which attains a considerable depth, only a very small amount of water 

enters the mine beyond the first 200 feet of the tunnel. Here both diorite and 

quartzite are encountered. On the other hand, the Hidden Treasure tunnel is 

extremely wet, though the covering approaches 500 feet; but here distinct zones 

of crushing give access to surface waters. 

It is to be observed that the lower limit of complete oxidation, in the case 

of those ore deposits that have a distinct capping of gossan, coincides very closely 

with the natural level of the ground water as it was encountered in sinking upon 

the leads. 

GOSSAN. 

The surface capping of the oi·e bodies which have been thus far discovered 

in the region is usually composed almost entirely of spongy oxide of iron or 

limonite. 

At the Ferris-Haggarty mine there was a strong capping o1 spongy limonite 

containing· no visible copper minerals. At the Doane mine green copper minerals 

were mixed with the limonite encountered at the surface, and continued to be 

present to a depth of 100 feet or more. 

From the fact that marked gossan was characteristic of these two mines, a 

general search has been 1nade for other ferruginous surface indications in all 

parts of the region, and while several rusty deposits have been found, only a few 

of them have :beeri thus far proved to denote the presence of copper ore, though 

it must be remarked that adequate prospecting has been done in very few cases. 

The Hinton mine is located upon outcrops of rusty rock of some prominence, 

which, though differing materially in appflarance from the gossan of the two mines 
46 OOPPER DEPOSITS OF ENCAMPMENT DISTRIOT, WYOMING. 

mentioned, was found to pass into practically undecomposed rock, highly impregnated with chalcopyrite at a depth of only 12 feet. 

At the Itmay claim, near the head of Roaring Fork, an ordinary limonite 

capping upon the surface led to the discovery of sulphides within a depth of 3 

or 4 feet. At this place and also at the Hinton property only small amounts of 

copper carbonates were found. 

A somewhat different capping from the for~Pgoing occurs at the Jesse, or 

Scott, prospect in Hog Park. Here there is practically no spongy limonite, but 

there is a considerable amount . of carbonate of iron and some bunches of red 

hematite, and the rock shows a good deal of decomposition and green copper 

stains. The work done is insufficient to prove that this material is the gossan 'of 

any considerable amount of copper sulphide, though it may be so. 

Still another type of ferruginous surface material which may eventually 

prove to be true gossan occurs on the Gertrude claim, located just north of the 

wagon road, about one-half mile east of Battle. At this place a bed of solid 

hematite from 2i to 4 feet in thickness occurs between strata of quartzite, which 

dip rather steeply toward the south. The deposit has been opened by an incline 

to a depth of 80 feet and found to be very homogenous and quite different from 

the ordinary spongy limonite capping of sulphide veins. The red oxide of iron 

appears to be in a very pure condition and is reported to carry gold to the 

average amount of $7 per ton. No copper minerals were detected in opening 

this deposit, but it is regarded as probable that it is a true gossan, which will 

lead to the discovery of sulphides at a very moderate additional depth. However, 

the sulphides, if they exist, may be in the form of pyrites, and may not be 

found to carry important amounts of copper. Likewise, it may prove that the 

hematite was deposited in its present form, and that it is not the product of 

oxidation of an original sulphide. Nevertheless, it is one of the most striking 

evidences of mineralization at present remaining undeveloped in the district, and 

it is remarkable that the property has been allowed to lie so long without being 

completely proved. 

In this connection it should be noted that many occurrences of copper 

sulphide have been discovered which do not show any notable capping of oxidized 

material, and though such deposits of gossan as have been found do not continue 

to great depth, it is apparent that the presence or absence of oxidized material 

along the surface is likely to indicate very closely the nature of the underlying 

materials. In general it may be said that where gossan is ~bsent and metallic ' 

minerals are found the rocks inclosing them will prove to be very tight 

and impervious to water. In such cases the idea that the ore will necessarily 

increase in amount or value in depth is regarded as entirely unwarranted, while 
J 

DISTRIBUTION OF COPPER. 47 

in the case of deposits covered by a heavy oxidized capping it may be expected 

that rich sulphides will ordinarily occur, as at the Ferris-Haggarty and Doane 

mines, though £ram the instances which have been cited it is plain that a shallow · 

capping may exist over deposits of chalcopyrite which have not been enriched 

to any important. degree. 

DI 1STRIBUTION OF COPPER MINERALS AND ORES. 

Copper ordinarily occurs in the form of chalcopyrite, which is present in small 

amounts in every part of the Encampment district where pre-Cambrian rocks are 

found. 

The yellow sulphide of copper is of very frequent occurrence in the hornblende 

schists in the form of small· segregations which commonly follow the platy structure 

of the inclosing rock. It is shown by the microscope to have crystallized at the 

same time as the minerals which make up the greater part of the schist, and since 

these are the product of recrystallization through regional metamorphism, as has 

been shown in another part of this report, it seems that the segregation of the 

metallic mineral accompanied this metamorphism and was a result of it. 

As a whole the hornblende-schists constitute a series of fairly homogeneous 

composition, and , though they are metamorphic rocks, their original materials have 

been altered to pl'actically the same extent throughout. These features may explain 

the formation of small bodies of copper sulphide distributed through this rock 

instead of larger local segregations of less frequent occurrence. At the time the 

rock was undergoing recrystallization metallic solutions had equal freedom of 

movement through all parts of its mass. The migrations of these solutions were 

only confined to definite channels under exceptional conditions, the presence of 

which has resulted in a few deposits of the Hinton type which promise some 

economic importance. 

The source of the copper in the sulphides of the schists is not known, but 

since the rocks in which the segregations occur appear to be the oldest in the 

district, it is possible that the metal was originally distributed through the surface 

volcanics which have been metamorphosed into the present hornblende-schists. 

The schists contain, besides the copper segregated during metamorphism, other 

deposits of copper-bearing sulphides introduced at dates correspondil).g to later 

mineralization which has affected the remaining formations of the region .. 

In th.e pre-Cambrian sedimentary rocks copper minerals are of common occur_-

rence, and while often accompanied by quartz in the form of small stringers, or 

more rarely in la:rger veins, the ore minerals also occur without quartz, particularly 

in zones where brecciation or schistose structure is conspicuous. It may be said 
48 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

in general thut the limestone and conglomerate have been less favorable for the 

deposition of sulphides than the quartzites and slates. 

Copper deposits in theE:e rocks were doubtless derived from outside sources, 

having been introduced by water circulating through the surrounding formations. 

As also observed in the hornblende-schists, large segregations of sulphides are th~ 

exception, and for a similar reason, the nature of the rocks being such that very 

general circulation through them was possible-a condition which was generally 

unfavorable for marked localization in the movement of metal-bearing solutions, 

and consequently for the formation of important bodies of ore. Among the 

exceptions to this rule are the Doane and Ferris-Haggarty mines, where important 

concentrations of ore have been formed in the sedimentary rocks under special 

conditions which will be brought out in the description ?f these properties. 

In the dark intrusive rocks which have been classified together as gabbros, but 

which are commonly called diorites, a minute amount of copper is invariably present, as has been ::;hown by a considerable number of very careful tests which have 

already been referred to. The metal occurs in the freshest examples of the gabbro, 

as well as in portions which have been altered in one way or another, but the 

manner in which it occurs can not be detected by a most ~areful search with the 

microscope. The copper is regarded as an original constituent of the basic magma, 

and the gabbro intrusives are believed to be a real and adequate source for the 

visible segregations of this metal which have been formed since the gabbro invasion. 

The gabbro rock has been variously metamorphosed and weathered. In its 

fresher portions chalcopyrite is seldom observed, but in its altered representatives 

small amounts are very frequently to be detected, even in surface outcrops, and 

this mineral is especially liable to occur where even a slight amount of schistose 

structure is present, or where the silicate minerals of the rock have been hyd1"ated 

through the action of circulating water. · Secondary structures and metamorphism 

have been very irregularly developed, but both are ~eneral features to be observed 

in these intrusive rocks in all parts of the field, so that, as in the other formations 

which have been mentioned, the copper, though widely distributed, is seldom concentrated to form important deposits. The absence of large. segregations of ore is 

therefore again to be ascribed to the ab::;ence of well-defined or sharply localized 

structures which might have served as channels for circulating waters. 

The area represented on the map as red g~anite contains man:y surface indications of copper, but this field has been less thoroughly prospected than have the other 

portions of the region. So far as observed the mineral does not occur in the granite 

itself, but always in associated rocks which have either the form of inclusions or are 

intrusive into the granite. 

The quartz-diorite is perhaps less prominently the host for copper minerals 
SOURCES OF COPPER. 49 

than any other im the region, though it is not entirely free from the metal. The 

sulphides which pccur seem to be confined to veins which penetrate the rock, and ~ . 

impregnations of· the rock itself, such as are observed in other formations, have not 

been noted. ! 

From the cotrelation of observations upon copper prospects in all parts of the 

field, it seems th~t the wide distribution of copper in small· segregations throughout 

the various . rock$ and the rarity of large deposits is due to the fact that by whatever proces3 the migration of copper may have been brought about, penetration of 

the rocks was accomplished with practically the same ease in one place as another. 

This condition may be attributed to the general arrangement of the varying rock 

masses of the district in relatively narrow and highly inclined plates. Variations in 

the original composition, differences in the amount of metamorphism or in the perfection of schisto~e structures have produced channels favm·able to circulation, but 

these variations are so many times repeated that the effect has been to produce a 

large number of: minor segregations rather than a few large concentrations. 

SOURCES OF COPPER. 

The dark-colored gabbro rocks which are present in all parts of the Encampment region are 'regarded as the original source of a large part of the copper which 

occurs in the ores. Eighteen samples representing various phases of the rock, fresh 

and altered, wer~ tested by Dr. E. T. Allen in the laboratcry of the Survey under 

conditions which·preclude the possibility of the metal having been introduced from 

outside sources, ~nd in each case copper was found to be present. Several ·of the 

samples contained nickel and cobalt, and chromium is present in some of them. 

A list of localities from which some o£" the rocks tested were collected is here 

given': a 

5. Diorite from ¢roppings near Jack Creek, above forks. 

6. Diorite, half way between Charter Oak and Home Fraction claims on Calf Creek Mountain. 

19. Specimen of fresh diorite from ridge on east side of west fork of Battle Creek, about 2 miles 

west of Verde mine., (See complete analysis given on page 32.) 

117. Fresh dior~te from the head of Beaver Creek, west of Elwood post-office. 

133. Fresh diori!te collected about three-fourths mile north of Elwood post-office. 

140. Fresh norite from Creede tunnel near north side of sec. 10, T. 14 N., R. 86 W. 

177. Specimen of fresh black diorite from Calf Creek Mountain, south of Charter Oak mine. 

185. Fresh norit.e near head of Cow Creek, three-fourths mile north of Bridger Peak. (See complete analysis given ion page 32.) 

188. Fl'esh diorite, locality near that of 185. (See complete analysis ~iven on page 32.) 

195. Diorite froln knob at 10,500 elevation, about one-half mile north' of Bridger Peak. 

210. Fresh diorite from new adit, Ferris-Haggerty. Contains-mere traces of copper, nickel, and 

cobalt. 

a For the definition of the rocks which are called diorites in this list, see page 30. 

210Q-Nd. 25-04-4 
50 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

215. Fresh norite from Octavia tunnel. 

290. Decomposed diorite, lower tunnel of Ferris-Haggarty mine. 

253. Fresh diorite, from cutting on wagon road about 1 mile north of Bachelor's cabin in head of 

Big Sandstone Creek. (See complete analysis given on page 32.) 

352. Serpentine collected below the canyon of Big Sandstone Creek. 

In none of the rocks tested was it possible to recognize ·the presence of 

metallic minerals other than magnetite by microscopic examination, so that the 

metals may either enter into the composition of the silicates of the rock or 

may occur as sulphides included mechanically in the silicate minerals. If the 

tests had shown the presence of copper only in the metamorphosed phases of the 

igneous rock, it might be argued that the metal had been introduced during 

alteration, but since both it and the nickel and cobalt are also found in entirely 

fresh, unaltered norite, the fact that they were all present in the rock while it 

was still in a molten condition and when it was intruded may be accepted 

without serious doubt. Copper seems to have been universally present in the 

magma while nickel and cobalt occur only in the more basic phases. Traces of 

chromium were detected in four samples tested for that element. 

The gabbro rock is a sufficient and probable source for the copper occurring 

in most of the observed ore bodies, but, as shown in the discussion of . the 

disseminated ores in the hornblende schists and in deposits of the Hinton type, 

certain segregations must have been formed prior to the invasion of the dark 

intrusives. 

Another independent and earlier source is therefore necessary for most of the 

copper in the schists. Nothing decisive can be suggested as to what this source 

may have been, for tlie schists appear to be the oldest rocks of the region. It 

is, however, entirely possible that the copper may have been derived from the 

same rocks from whic~ the schists were formed. These were in large part 

basic igneous rocks, which, in the absence of contrary evidence, are as likely to 

have contained appreciable amounts of copper as the gabbros of later date. 

Of five examples of the gray quartz-diorites tested for copper three gave no 

reaction, while of the two which contained a mere trace one came from the 

vicinity of a known ore occurrence and the other was from a thin sill in the 

hornblende-schists, about one-fourth mile from the Creede shaft, with a good 

deal of mineralization noticeable in the vicinity. 

A sample of red granite from Huston Park gave no reaction for copper. 

OCCURRENCE OF GOLD. 

In the northern part of the area covered by the Encampment map and in the 

crystalline area beyond there are many veins of white quartz, and while some of them 

are of great size they all appear to be of lenticular form. Small amounts of pyrite 
OCCURRENCE OF GOLD .AND SILVER. 51 

or chalcopyrite, or cavities which formerly. contained these minerals, may occasionally be observed in them, but as a rule they do not contain sulphides in important 

quantities. It is reported that they all carry gold, though certainly,not in workable 

amounts. They were not considered of sufficient promise to warrant particular study 

during the presen:t investigation. 

Free gold in q_ uartz has been found in several claims located in Purgatory Gulch, 

but the veins are small and not continuous, so that they are regarded as of no 

importance. 

Mr. Frank 0. Williams and Henry Jones, whose ranch is situated in the foothills of the Sierra Madre near Calf Creek, report the existence of gold-bearing 

gravels along nea!rly all of the streams which drain the northern slope of the range. 

The best placers are situated on Jack Creek and the head of Savery River, but 

though different parties made several attempts to work them the gravels could not 

be made to pay. 

The existenca of a sufficient amount of gold in the stream gravels to lead even 

to attempts at pla~er mining is indicative of its very general occurrence. However, 

much exaggeration exists concerning the universal presence of gold in all sorts of 

country rocks, saJ!Pples.of which are frequently reported to have given assays of one 

or two dollars' worth of gold per ton. The copper ores which have been mined do 

undoubtedly carry a small amount of the precious metal, which also occurs with 

such silver-lead ores as have been tested, but several assays of material in which 

sulphides could n6t be seen failed to reveal even traces of gold. 

Results of assays of miscellaneous material for gold and silver. 

[Tests made by Dr. E. T. Allen.] 

Number. 

1 .... ________________________ _ 

2 •••••• ______________________ _ 

3 •... ________________________ _ 

4.---------------------------- 5 ____________________________ _ 

6----------------------------- 7 ____________________________ _ 

8 ____________________________ _ 

9----------------------------- 10 ___________________________ _ 

11 ___________________________ _ 

12 ___________________________ _ 

13 ___________________________ _ 

,15 14-----------------~---------- ___________________________ _ 

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

Gold. 

Troy oz. per ton. 

0.36 

None. 

None. 

None. 

None: 

None. 

None. 

None. 

None. 

None. 

None. 

.22 

Trace. 

None. 

None. 

. 02 

. 05 

Silver. 

Troy oz. per ton. 

Not tested. 

Not tested. 

Not tested. 

Not tested. 

Not tested. 

Not tested. 

Not tested. 

Not tested. 

Not tested. 

Not tested. 

None. 

.24 

4.2 

None. 

None. 

Not tested . 

Not tested . 
52 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

1. Quartz vein from prospect in Purgatory Gulch. 

2. Quartzite from Sovereign claim in basin southwest of Bridger Peak. Reported to contain 

gold. 

3. Spongy vein quartz from tunnel 1 mile east of Victoria post-office. 

4 and 5. Two samples of rusty rock containing pyrite. Ground Hog claim, sec. 14, T. 13 N., 

R. 86 w. 

6-9. Material from sheeted dikes in quartz-diorite containing stringers of quartz and a small 

amount of chalcopyrite. Four samples from prospect holes on Fudges claims, Eec. 6, T. 13 N., 

R. 85 w. 

10. Sample from 200 feet of brecciated quartzite in Hidden Treasure tunnel, near Battle. 

11. Sample of pulverulent quartz stained with oxide of manganese from cavities in strong eastnortheast fissure vein opened by 60-foot shaft near Continental divide, southwest cornex sec. 10, 

T. 14 N., R. 86 W. 

12. Upper of two veins on Ajax claim, north slope of Dexter Peak. 

13. Lower vein, Ajax claim, north slope of Dexter Peak. 

14. Sample of jaspery vein material from Lost S0ldier claim, west side of Encampment River, 

opposite Purgatory Gulch. 

15. Hematite stained with copper from Metal Chief claim of the Jesse group, in Hog Park. 

16. Copper ore from Hinton mine. 

17. Copper ore from Itmay shaft. 
CHAPTER II. 

CLASSIFICATION AND GENERAL DESCRIPTION OF, COPPER DEPOSITS. 

TYPES OF OCCURRENCE. 

The present ,chapter is devoted to a general description of the copper deposits, 

apart ,from any ,discussion of their origin which forms the subject of the next 

chapter. 

Though there is a great variety in the manner in which the copper minerals 

occur, it is possible to refer them to a few types which have been named after prospects or mines in which their characteristics are well illustrated. 

HINTON TYPE. 

In this type :Of deposit, which has its best example at the Hinton mine, l9cated 

7 miles south of :Battle, chalcopyrite, sometimes accompanied by magnetite, occurs 

in zones of the hprnblende-schists, which are characterized by a great deal of garnet 

and epidote in a~dition to the hornblende and quartz which ordinarily make up the 

mass of the schist. These minerals always render the zones somewhat conspicuous, 

and in some instances attention is further called to them by the presence of rusty 

material in thei~ outcrop. Where this occurs it is probably in part a true gossan 

representing surface oxidation of sulphide ores, but it may be also produced by the 

weathering of masses of garnet, as may be observed in the croppings of the vein on 

the Hinton claim. 

The epidote :and garnet zones follow the general platy structure of the schists 

and are locally a¢c<'>mpanied by thin strata of limestone and quartzite, and they may 

therefore be reg11rded as having been produced from intercalated beds of a more 

calcareom; composition than those which were altered by recrystallization into hornblende-schists, an.d by the same process of metamorphism. In so far as zones of 

this sort have "Qeen observed to be mineralized, the ore minerals are found permeating the maE~s of the rock along some. fairly distinct band within the zone, but 

there is no evid~nc~ of fractures nor any open channels whatsoever· along which the 

material could nave been introduced. Studied under the microscope, the silicate 

minerals of the !rock are found to be entirely fresh and undecomposed, and their 

grains interlock with those of the chalcopyrite or magnetite in such a way as to 

indicate that all:of them were crystallized at the same time. 

53 
54 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

Several zones of the Hinton type have been discovered within the area covered 

by the hornblende-schists, but promising amounts of sulphide ores have been 

encountered only at the Hinton mine. A prominent and persistent lode of this 

nature which has been opened on the Sun Anchor claim, located upon the north 

slope of Green Mountain, may be traced upon the surface for a distance of over 1 

mile westward into sec. 34, T. 14 N., R. 85 W. Location pits at several points 

along the lod_e reveal the presence of magnetite and chalcopyrite inclosed in· schist 1 

composed of hornblende, epidote, and garnet. 

In other cases where an amount of rusty decomposed garnet associated with 

massive green epidote is found upon the surface the similarity to the Hinton lode 

is evident, though nowhere has sufficient exploration been done to prove the presence of sulphides. 

CREEDE TYPE. 

Because of imperfect exposures the studies of the Creede prospect were not 

sufficient to afford an accurate" determination of the nature of the deposit. The 

relations of the sulphide mineral to the gangue material of the inclosing rock are 

similar to those observed at the Hinton property, both having crystallized at the 

same time, but the Creede deposit can not be cladsed with the Hinton type, since the 

distinguishing feature of the latter is the existence of a well-defined zone differing 

in mineralogical make-up from that of the general schist of the vicinity, and no 

zone of this sort exists at this place. The Creede ore is magnetic sulphide of iron, 

or pyrrhotite, which carries copper, nickel, and cobalt, and with it there is mixed a 

small amount of chalcopyrite. The sulphides occur in an unusually coarse granular 

phase of the hornblende-schist near an intrusive mass of norite, and it is suspected 

that they occur at the actual contact of the two rocks. Neither the surface outcrops 

nor the workings of the mine serve to indicate whether the deposit has a definite 

form or not. The coarse hornblende rock seems, however, to be limited in extent, 

and the finer-grained schists in the vicinity do not seem to have been mineralized by 

sulphides. 

In the vicinity of the Creede, but usually at a somewhat greater distance from 

the mass of norite, there are several openings in the calcareous schist showing the 

presence of pyrrhotite in small amounts. This mineral seems to be almost entirely 

confined to deposits of sulphide adjacent to this particular mass of intrusive rock 

and is rarely present elsewhere in the region. 

CONTINENTAL TYPE. 

The type of deposit which has been named from the Continental claim, situated 

in the vicinity of the tramway transfer station upon the south side of Cow Creek, 

is characterized by well-defined veins of quartz accompanied in some cases by calcite 
GF.NERAL DESCRIPTION OF DEPO~ITS. 55 

or siderite and in. others by feldspar, and contains sulphides which were deposited 

at the same time as the gangue material. 

In the case <;>f the Continental, and certain other prominent examples of the 

type, the veins follow openings along the schistose or platy structure of the rocks 

which inclose it,· while in other instances they occupy strong fissures which are 

transverse to the general trend of the country rocks. 

CASCADE TYPE. 

At the Cascade property, situated on the west side <?f Encampment River above 

Purgatory Gulch, chalcopyrite occurs in a vein or dike of pegmatite composed of 

feldRpar and quartz. In its general relations as observed upon the ground the 

deposit resembles the Kurtze Chatterton veins, which are classed with th,e Continental 

type, but examination of the ore under the microscope shows it to be distinct, since 

the gangue and the ore were not formed at the same time. The minerals of the vein 

are shattered and; more or less brecciated, and the fractures are filled in with chalcopyrite and a small amount of quartz, both of which are therefore later in origin 

than the matrix in which they occur. 

The Cascade vein is the only example of this type which was observed. 

DOANE TYPE. 

The ores of this type, which is commercially the most important occurring in 

the field, are n1ainly composed of the rich sulphide, chalcocite, mixed with a variable 

amount of chalcopyrite, and sometimes accompanied by covellite and bornite, or by 

oxide and carbonate minerals. 

The two prominent examples of the type are seen in the Doane and FerrisHaggarty mines, in both of wh.ich a strong gossan containing little or no copper 

marks the superficial portion of the lodes, and immediately beneath this therichest 

ore is found, a gradual decrease in value being observed as the ore bodies are 

followed downward. 

This decreas~ in the valuable contents of the vein arises from a gradual increase 

in the proportion. of chalcopyrite to chalcocite as depth is attained, the former mineral containing when pure only about 34 per cent of copper, while the latter carries 

nearly 80 per ceQ.t of the metal. 

The manner in which the ore bodies occur is similar in both of the 1nines mentioned. The lodes follow the bedding of sedimentary quartzites very closely as a 

rule, and are invariably marked by a good deal of brecciation, the ore mainly 

occupying the spaces between fragments of the country rock. 

The distingl.lishing characteristic of the Doane type is the presence of chalcocite 

as the principal ore mineral, which is regarded as an indication of the secondary 

derivation of the deposits, in accordance with the definition of primary and secondary 

ores given on page 43. ' 
CHAPTER III. 

GENESIS Ojj~ THE COPPER DEPOSITS. 

TABULAR SUMMARY. 

The origin and sequence of deposition of the different ore types which have 

been described .form the subject of the present chapter; the conclusions of which 

are exhibited in the following table: 

Relat'ions of types of copper ores. 

I 

Type. Formation. Process. Period. I 

Hinton ................... Hornblende-schist .. Regional metamorphism ...... 1 

Creede ...............•... Hornblende-schist .. Contact impregnation ....... _I 2 

Continental ............... All rocks .......... I I Cascade .................. Pegmatite dikes ..•. l Deposition from circulating 

I waters. 3 

I 

Doane .................... Quartzite .......... 

Barren quartz veins ....... All rocks .......... 

ThA discussion of the genesis and relative age of the ores will be given under 

four heads, corresponding to the periods of segregation given in the table and 

the subsequent period of secondary enrichment. 

DEPOSITION OF THE FIRST PERIOD. 

Origin of the ores. -Zones of intense metamorphism, of which the Hinton 

lode is the type, are confined, so far as has been observed, to the metamorphic 

hornblende-schists. It is regarded that they, and the ores which they contain, 

are of contemporaneous origin with the general recrystallization of the rocks in 

which they occur, and that the ores, therefore, originated during regional metamorphism at a very ancient period, prior to the Cambrian. 

The main features of the metamorphic zones or lodes which, considered together,. 

lead to the above conclusion are as follows: 

(a) The zones be·ar no observable relation to the presence of _igneous rocks 

which may occur in the same genera] region, and where the schists are cut by 

intrusives no distinctive contact minerals are developed. Therefore they can not 

be attributed to contact metamorphi~m. 

56 
ORIGIN AND SOURCES' OJ!' THE COPPER. 57 

{b) The lod~s are not separated from the inclosing schists by gouge nor by 

distinct walls, so that they can nqt be filled fissures. 

(c) There a~e no veinlets of quartz or other mineral which appear as though 

filling cracks i~ the rock, showing that the zones have not been fractured and 

afterwards cemcinted by mineralizing solutions. 

(d) The lodes invariably follow the stratification of the original rocks, which 

is found to be parallel to the present platy structure of the metamorphic schists. 

The structure thus controls their direction. 

(e) Examined in detail the material of the lodes themselves is found to be 

schistose, through the arrangement of the component minerals in parallel planes. 

A considerable amount of hornblende similar to that of the inclosing schist is 

usually present 'in the zones, and epidote, which is particularly associated with 

the. ore, occurs in smaller amounts throughout "the country rock. The lodes seem 

therefore to fot·m an integral part of the schist series, and they are regarded as 

having been foFmed by the same causes and at the same time as the remainder 

of the series. 

(f) The be<Ils involved in the mineralizedzones must have differed in their original compositio~ from the mass of the rock which has produced the hornblendic 

portions of th~ schist. This is shown in all cases by the preponderance of 

epidote and g~rnet,. both of which indicate a high proportion of lime in the 

material from ~hich they were derived. Furthermore, at the Hinton property 

a stratum of fairly pure crystalline marble, and another of quartzite occurring 

in the midst qf the lode, bear out the deduction that the distinct character of 

the present mineralogical aggregates is merely an expression of original differences in compo~ition. 

(g) The metallic sulphides are shown by the microscope to have crystallized 

contemporaneously with the silicate minerals of the rock. The metallic. substance must therefore have been introduced at the time of metamorphi!"m when 

the original ma!terials of the present schists were being formed by recrystallization. 

Source qf ~he copper.-The hornblende-schists are' regarded as the oldest rocks 

now exposed 1~ the region which has been examined. When they were recryt"-

tallized the ba~ic gabbro rocks which now cut them had not invaded the field, 

and therefore qould not have furnished the copper which they contain. Neither 

does it appear ,that the copper could have been derived from any of the siliceous 

rocks now occurring with the schists, since apart from the probability that -these 

are also of later origin than the metamorphism of . the schists, they are not 

characterized by the presence of copper minerals of earlier origin than the gabbro ·intrusives. It is therefore believed that the copper which the schists now 

contain, so far' as its minerals are of contemporaneous origin with their meta-
58 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

morphism, was probably derived from the original rocks from which they were 

formed. This point is, however, beyond proof since the hypothesis that the 

copper was introduced from another unknown source can not be controverted. 

DEPOSITION OF THE SECOND PERIOD. 

The origin of the Creede ore deposits remains in doubt, through the i~possibility of making adequate observations, because of imperfect surface exposures, 

and because the shaft was filled with water at the time the property was visited. 

Occurring .in the hornblende-schist series, it might be anticipated that the deposit 

was formed in the same manner as the ores of the Hinton lode. However, the 

ore mineral is different, and its possible genetic relation to the near-by norite 

must be considered. The age of the deposit is regarded as pre-Cambri3:n. 

From the material which has· been taken from the shaft it is seen that 

pyrrhotite and chalcopyrite occur in a mass of coarsely crystalline hornblende 

rock containing a small amount of quartz. No other minerals are present in the 

ore, though epidote occurs in the rocks which outcrop near by. The ore and 

gangue minerals are of contemporaneous origin, as in the case of the Hinton 

type, but the crystallization does not certainly date back to the original metamorphism of the schist, for a second recrystallization may have been caused by 

the intruded norite, which could at the same time have furnished all the elements 

of the ore, including the cobalt and the nickel. It is regarded as most likely that 

the deposit is an instance of segregation during contact metamorphism locally 

manifested. 

If the Creede ore was formed in this way, it is not at all unlikely that other 

deposits of sulphide minerals were formed in various rocks adjacent to masses of 

the dark intrusive rock, by direct impregnation through the emanations from 

the cooling magma, but the main role of these gabbro rocks has been to furnish 

metallic elements to the circulating underground waters, which appear to have 

been most efficient during the time which has elapsed since their invasion of the 

pre-Cambrian sediments. 

DEPOSITION OF THE THIRD PERIOD. 

Origin of the m·es.-A common origin by aqueous deposition is assigned to ore 

deposits which can be classed under the already described Continental, Cascade, 

and Doane types, for though these differ greatly among themselves; they all 

occur in veins which follow channels of easy circulation defined by structural 

breaks, suoh as joint fissures, planes of schistosity, or zones of brecciatwn. 

Some of these channels may have existed previous to the invasion of the 

gabbro rocks, which are regarded as the main source of the copper occurring in 

the water-deposited veins, but others, as, for instance, the prominent north-south 
ORIGIN AND SOURCES OF THE COPPER. 59 

fractures in the vicinity of the Ferris-Haggarty and Doane. mines, are certainly 

later than the: intrusion of the basic rock, since they occur indi:ff~rently in the I 

igneous rock ~nd in the inclosing formations. All of them were probably filled 

subsequent to the gabbro intrusion. 

At present no date can be confidently assigned to the vein phenomena of 

the third periqd, because data for determining the geologic events of Paleozoic 

time are incotrlplete, all sedimentary formations below the upper Carboniferous 

being entirely ' missing in this part of the Rocky Mountains. In the Encampment district the oldest sedimentary formation resting on the ancient metamorphosed rocks which contain the copper deposits are the Triassic Red Beds, and 

since none of • the . fractures of the older rocks corresponding to those which 

carry ore were found passing upward into these strata, the primary vein segregations are regarded as older than Triassic. In t)le Elk Mountains, some 30 miles 

north of the Encampment district, upper Carboniferous strata occur; but though 

the general geology of the region shows that there was gradual sinking which 

allowed the Triassic beds to overlap, there is no reason to suspect that fracture 

systems could have been formed and filled after the deposition of the Carboniferous and before th~ Triassic was laid down. 

Co~cerning the interval between the upper Carboniferous and the beginning 

of Cambrian time, no direct evidence exists, and it would be extremely difficult 

to prove that the deposits were not formed some time during the Paleozoic. 

However, this is not regarded as probable, since in the Rocky Mountain region 

of the United, States no ore deposits are known to have been formed during 

Paleozoic. time, and in general the geologic history of the Rocky Mountain 

province is known to have been similar throughout. On the other hand, preCambrian gold deposits occur in the Black Hills of South Dakota, and there is 

strong evidence in favor of a like age for the copper deposits near Salida, 

Colo., so that\ a certain analogy exists between the Encampment deposits and 

other ore ocqurrences in the ancient metamorphic complex of the Rocky 

Mountains, suggesting the possibility that the former, like the latter, are of 

pre-Cambrian origin. 

Source o.f the copper.-The copper and other metallic elements which occur 

in deposits formed since the intrusion of the gabbro masses are regarded as 

having been derived mainly from these basic igneous rocks. These are obviously 

·a possible source, since they invariably contain appreciable amount~;~ of copper, 

and, in many cases, cobalt and nickel as well, as has been shown by a 

considerable number of tests which have been referred to on page 49 of this 

report. All the other rocks of the region are much more siliceous, and 

consequently less likely to -contain even small amounts of any heavy metal 
60 OOPPER DEPOSITS OF ENCAMPMENT DISTRIOT, WYOMING. 

excepting iron. Also in the few tests which have been made they are found 

not to contain sufficient copper to be revealed by chemical tests upon ordinary 

amounts of material. 

SECONDARY ENRICHMENT OF THE ORES. 

Several of the copper deposits of the Encampment district yield high-grade 

ores composed very largely of copper glance or chalcocite. This mineral, where 

it oceurs in large amounts in other fields, is regarded as having been derived from 

the enrichment of ore bodies originally of poorer grade, through the leaching of the 

copper contents from the upper portion of the ·deposit by surface waters, and its 

concentration by redeposition in a deeper part of the vein. The changing nature 

of the deposit from above downward, where such secondary enrichment has 

occurred, has been described on page 43, and in the Doane and Ferris-Haggarty 

mines the sequence of the gossa~, the high-grade ores, and the leaner sulphides 

corresponds completely with the normal conditions. It is therefore believed that 

the ore deposits in these mines, and also certain others in the district, have been the 

result of eoncentration of primary ores by the percolation of surface waters through 

the veins. In both the mines mentioned the ore occurs as a filling in brecciated 

quartzite, and from their nature the ore bodies form ready channels for circulating water. Both mines are also very wet~ showing that conditions favorable to 

leaching and redeposition still exist. 

The occurrence of secondary ores at some places, and their absence at others, 

may be attributed entirely to differences in the texture of the veins and country 

.rocks. Where thes~ have been loose and open concentration of primary ores has 

taken place, and where they have been tight and impermeable no leaching has been 

possible. 

The secondary concentration now observed probably began after the topography 

of the region had reached practically its present development, and the period during 

which it has been going on is therefore regarded as very recent. 
Location a')'l,d dmJelopment.-This roperty was formerly known as the Rambler 

mine, a name w.hich is now applied to t1e town and post-office near which it is situated, 

in the upper part of the valley of Bat le Creek, about 2 miles below the Continental 

Div"ide. 

The surface indication o:f ore w1s a strong iron cap 

or gossan co~siderably stained by ca~·b~nates and silicate 

o:f copper, whiph was :followed by aq inclined shaft to a 

depth of 75 :feet, where red oxide and copper glance or 

chalcocite wer~ encountered. A crosscut tunnel, 260 :feet 

in length, was 1 then driven to cut th~ vein at a depth o:f 

125 :feet, the <f>re was stoped out to the surface, and u 

chamber excavrated :for the installati~n o:f a steam hoist, 

by means o:f which a shaft has been sunk to a :further 

depth o:f 190 :feet. There are cros$cut tunnels nt 115, 

140, and 190 feet, respectively, and a~1 exploration drift 

about 160 feet long westward fron~ the lowest tunnel, 

with a 50-foot brosscut northward fro~n its terminus. The 

1·elation of these workings may be seen from the ~ketch'-

plan drawn fr9m the writer's notes (ftg. 2) and the- cross 

section (fig. 3).! The main ore body has been encountered 

in the workings of each level, and :the , ore between the 

levels, which was found to be practibally continuous, has 

been stoped out. At the time of vi~it a winze from the 

lowest level had proved the presenc~ of ore to a farther 

depth of 50 :feet, and in .A .. pril, 1903, t~is had been continued 

to a total depth o:f 287 feet below the tunnel level. 

'1....---Sc_ale_...::;•oofeet 

FIG. 2. -Doane mine; sketch plan 

of workings. E, mouth of adit; 

S, shaft; 1, discovery; 2-6, main 

ore shoot in different levels; 

7-10, additional ore shoots on 

115-footlevel; 11, copper-f'tained 

fissure in quartzite. The stopes 

are represented approximately 

by dotted lines. 

The tunne:l at the 115-foot level i~ approximately 140 :feet in length. By means 

o:f it the main ore body was opened, ~~1d two others were encountered 100 and 135 

:feet north o:f t~e shaft, and these have been stoped out, as shown in the cross section 

of the mine (fig. 3). 

61 
62 COPPER DEPOSITS O.B' ENCAMPMENT DISTRICT, WYOMING. 

The workings of the mine are approximately as follows: 

Lengths and depths of mine u•orkings. 

Tunnels and drift ________________________________________________ _ 

Shaft ____________________________________________________________ _ 

Stopes ____ . _________________ . ___________________________________ _ 

Feet. 

975 

190 

715 

Total. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1, $80 

Upon the claim adjoining the Doane property upon the west similar ore bodies 

have been found, but the workings were not accessible for examination. 

N 

s 

Gravel 

w~ Limest-one and shales ~~~{'0/5.:1 Qual""tzite Diorite IZ:Jl] Stopes 

FIG. 3.-Doane mine; sketch projection of workings on vertical plane through shaft at right angles to stratification. 

Numbers of stopes correspond to those in fig. 2. 

Oo~try rock.-The rocks in the vicinity of the mine are quartzite and diorite of 

pre-Cambrian age. The quartzite is of rather uniform compmdtion, and though its 

separate strata are very distinct, they do not usually alternate with beds of schist, as 

in the Ferris-Haggarty. In the tunnels which cut across the formations, practically 

no other rocks than quartzite are to be seen, excepting in the northernmost workings, 

where diorite is encountered on the 190-foot level, and in the tunnel located several 

hundred feet to the south, which has not been connected with the mine, where diorite, 

shale, and limestone were noted. 

The strike of the country rocks is nearly P-ast and west, and they have a 

fairly uniform dip of from 65° to 75° toward the north; that is, in the opposite 
THE DOANE MINE. 63 

direction from the ordinary or normal dip of the stratified rocks in the district 

at large. 

Jointing of co·untry rock.-Throughout the mine the rocks are broken by 

5everal sets or systems of joint fractures. These are less marked, in the diorite 

than in the quartzite, where, in combination with the planes of stratification, they 

have produced zones of brecciation in the brittle country rock, some of which have 

been filled with metallic sulphides by deposition from mineralizing solutions (figs. 

7-12). In fig. 4 the general course of the principal fractures as locally obsArved are 

given. 

The set of fractures which is usually the most pronounced follows the stratification of the quartzites, striking 

nearly east and west and dipping 

steeply toward the north. 

A second set of consta.n't occurrence and marked development 

trends directly across the stratification, striking a few degrees 

east of north and west of south 

and invariably dipping toward 

the west at steep angles. 

A third set of joint fractures 

which is commonly developed 

trends somewhat to the north and 

east, making an angle of from 

zero up to 15° or 20° with the 

strike of the rocks, but having a 

steep dip in the opposite direction; that is, toward the south. 

s 

FIG. 4.-Doane mine; diagram to show strike and dip of principal joint 

systems. The dips given were observed in stope 7. Relative importance of fractures indicated by width of lines. 

Of somewhat less importance, but still often to be observed, is the fourth set 

of joint planes, striking nearly with the strata and .dipping steeply toward the 

south. 

Breaks in still other _directions are to be noted in various parts of the mine, 

but the main fractures may ordinarily be referred to c-ne of the four systems 

enumerated. Throughout the workings all or several of them combine in var\ous 

degrees of perfection to divide the quartzite into small blocks, and where movement has been especially localized the rock is very m~ch brecciated. 

The ore.-The principal ore mineral produced by this mine has _been chalcocite 

or copper glance, though chalcopyrite, bornite, and a little covellite also occur. 

In the upper workings the red o:xide cuprite, the carbonates malachit~: -~nd 
64 COPPER DEPOSI'rS 0~' ENCAMPMENT DISTRIOT, WYOMING. 

azurite, and the silicate cbrysocolla were found in some abundance, but these are 

unusual below the tunnel level. Pockets of a sooty mineral which has been called 

black oxide are reported to occur, though this is probably chalcocite in a finely 

divided condition, and not the copper oxide known as melaconite, which is a 

comparatively rare mineral. 

There is ordinarily no gangue excepting the quartzite, which incloses the ore 

unaccompanied by nonmetallic vein minerals, though kidneys of ferruginous jasper 

sometimes occur. The chalcocite, . mixed with varying amounts of chalcopyrite 

and bornite, is usually massive and by hand sorting produces a P.igh-grade ore. 

w E 

FIG. 5.-Doane mine; stereogram representing main ore body. The ore body follows a bed of quartzite, but has an 

independent dip toward the west. 

Occurrence o.f the m·e.-The occurrence of the ore depends in two ways upon 

the presence of fractures in the quartzite. In the first place, they have furnished 

channels for the movement of underground waters; and in the second place, by 

causing local brecciation, they have formed openings in which· the ore has been 

deposited. 

Mineralized zones of brecciation forming ore bodies have been discovered at 

three distinct horizons in the quartzite, and, except in one case, they follow the 

stratification of the bedded rocks very closely, as is illustrated iu the north-south 

cross section of the mine workings and country rocks (fig. 3), in which the relati~n 

of the ore shoots to the inclosing quartzites is shown. 

The blocks of broken rock in which ore bas been formed may be described .as 

pencil shaped, or as approaching the form of elongated prisms (fig. 5), the sides 
THE DO.ANE MINE. 65 

of which copform in different portions of their length to the various joint 

systems observed in the inclosing rocks. The ~tructures which ordinarily and for 

the longest distances form the boundaries of the ore bodies are 

the actual bedding planes, or the fractures 'parallel to the stratification and those nearly normal to it. Thus, the ore bodies dip 

to the north because they follow the north-dipping strata, but are 

carried to the west as they gain depth because the north-south 

fractures dip in that direction; they therefore pitch toward the 

northwest as a ;resultant of these two dips. This relation is well 

exhibited in the plan of the mine (fig ... 2), in which the main ore w 

shoot is seen to lie successively farther to the northwest ' in the 

different levels from above downward. a The same feature is 

also shown in the stereogram (fig. 5). The dip toward the 

west, independent of the bedding, is shown in the diagram (fig. 6) 

representing the general form o£ the main ore shoot as it lies 

in the stratification. 

In the case of each ore body the westerly dipping northsouth fractures are always in evidence. They have produced a 

large part of the brecciation, as already stated, and frequently 

form the east and west boundaries of the ore, as illustrated i~ 

the diagrams 

(figs. 7, 11, 

12). Fur140' 

Ji 0 CB? Scale 100feet 

FIG.6.-Doane mine; projection of main ore 

body on plane of stratification in quartzites, 

and at right angles to 

section shown in fig. 3. 

The drawing shows the 

independent dip of the 

ore body from east to 

west. 

a 

thermore, it is noteworthy that 

a horizontal line joining the 

centers of the different ore 

bodies, as, for instance, upon 

the 115-foot level, has nearly 

the same general trend as the 

strike of these fractures, so 

that they are probably all situated upon the same zone of 

sheeting, along which minerala Scale sfeet izing solutions have been inFIG. 7.-Doane mine; horizontal section of ore body in stope 9 about 25 feet troduced. 

above 115-foot level, showing relation of ore body to the layers of The north-:-south fractures 

quartzite and the north-south fractures. aa, stratification; bb, northsouth cross fractures. Compare with figs .. ll and 12. . are regarded as the channels 

along which ascending mineral-bearing solutions were introduced because in 

several places in the s~opes o£ the mine ore is found to penetrate the country 

rock of the foot wall along them (fig. 7). 

a The position of the surface outcrop is estimated, while the other locations are known to be relatively correct. 

2100-No. 25-Q4-5 
66 COPPER DEPOSITS 0~, ENCAMPMENT DISTRICT, WYOMING. 

In the Ferris-Haggarty mine the relations of similar fractures to the ore body 

are alJ?ost identical, and it seems that in both cases ore has been deposited where 

zones ·of north-and-south sheeting of the rock intersect 

with similar zones following the nearly east-west bedding of the strata, producing ]ocally intense brecciation. Fractures belonging to other sets less prominently developed have added their effect to the 

subdivision of the more or less rectangular blocks 

formed by the intersection of the main systems, and 

J-);;~LJ Quertzite j;;§Gj ore have produced many minor irregularities in the. shape 

FIG. 8.-Doane mine: sketch showing rei 

lation of ore to inclosing rock, stope 9. of the ore bodies. 

The ore occurs mainly at the intersec-

. tion of bedding and cross fractures, ap- As a rule the ore appears merely to fill the openparentiy having replaced the quartzite. ings in the quartzite breccia, but in some instances 

the quartzite seems to have been dissolv-ed away and replaced by the sulphides (fig. 8). 

In the following table some of the dimensions of the main body are given: 

Dimensions of main ore body in Doane mine. 

Surface _ .. ____ . ____ ... 

Forty feet above tunnel 

Tunnel ______ -------- First level ____________ 

Second level __________ 

Third level __________ . 

Winze ________________ 

Winze. _______________ 

Bottom _______________ 

Width east and west. 

Feet. 

Unknown. 

25 

30 

25 

25 

38 

18 

23 

------------

Thickness. Depth. 

Feet. Fed. 

-.............. -... -... .. ... -.. ---... 

-........ -----.. 85 

3-6 125 

5 245 

4 270 

2-6 320 

........... -.. -- 345 

.... ------ .. - 370 

---- .. ----.. 412 

1--

Between the different levels the dimensions vary, showing considerable 

irregularity in the size and shape of the ore body, but the latter is reported to have 

been continuous from the gossan to the lowest point thus far reached. The general 

shape of the body in an east-west section, following the stratification of the quartzite, 

is shown in fig. 6. 

In the case of all of the ore bodies thus far encountered, both the foot and 

hanging wall are very irregular, and often steppy, a condit)on which arises from 

the fact that the ore rriay be limited either by bedding planes or by joints, now 

one and now the other (figs. 10, 12). 

Other ore bodies than the main one, which was the ~rst discovered, have the 

same general characteristics. The one marked 3 in the plan was discovered by 

following a small green-stained seam which cut the tunnel on the 115-foot level. 
THE DOANE MINE. 67 

This ore shoot i~ separated from the main body in the same level by a little more 

than the width of the tunnel, and while there may be a narrow fracture connecting 

them, such could not be traced at the time the mine was examined, and it is apparent · 

that the eastern body lies at a slightly lower horizon in the quartzite. It has been 

stoped to a height of 45 feet above the tunnel and found to have an average width 

and thickness of about 3 feet each. 

At the points marked 7 and 8 on the plan (fig. 2) there are two stopes which 

connect at the level of the 115-foot tunnel, but diverge upward. The southern one 

(No. 7) follows the inclination of the beds of quartzite which inclose the ore, while 

the other (No. 8) is nearly vertical. The former stope, representing approximately 

9 sfee"t 

FIG. 9.-Doane mine; diagrammatic cross section in lower portions of stopes 7 and 8, showing occurrence of the copper 

sulphides in brecciated quartzite formed along intersecting joint systems. aa, bedding planes and parallel joint 

fractures; bb, strong system of joints; cc, subordinate joints; distribution of sulphides indicated by stippling. 

the dimensions of the workable body of ore, is 30 feet long on the incline, 20 feet 

wide near the bottom, and from 3 to 5 feet across. Stope 8. is 80 feet high, 12 feet 

wide from east to west, and from 2 to 5 feet across. 

Fig. 9 is a diagrammatic section of the lower portions of the ore bodies in 

stope!:! 7 and 8, near the 115-foot mine level, showing the relations of three of the 

four prominent systems of joints which are there developed. The fourth system 

strikes nearly north and south and is therefore nearly parallel with the plane of the 

section, so that it does not appear in the drawing. In the vertical stope the hourglass form shown in the diagram just mentioned, which is due to the presence of 
68 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

intersecting joint planes, i~ repeated several times, so that the ore alternately widens 

and pinches as illustrated in the general north-south section of this ore bodrand 

it~ neighbor given in fig. 10. The ore shoot has a similar form in an east-west 

N Tunnel 5 

direction) as shown in the horizontal 

sketch section or plan (fig. 11), on which 

the north-south fractures also appear. 

About 35 feet north of stopes '7 and 

8 two ore shoots were encountered which 

occur in the same beds of quartzite, but 

are separated along the strike by about 

25 feet of barren rock. The relative 

positions of the shoots at the 115-foot 

level are shown in the hodzontal plan 

(fig. 2), while their attitudes in regard 

to one another in the stratification are 

exhibited in fig. 12, which shows also 

the manner in which the ore bodies 

follow the westward dipping north-south 

fractures, which are more closely spaced 

opposite the ore shoots than elsewhere. 

A horizontal plan of the eastern shoot 

representing diagrammatically the original conditions about 25 feet above the 

tunnel level is given in fig. '7. In this 

stope there is abundant evidence of the 

important role which the north-south 

fractures have played in the formation 

of the ore, for besides constituting very 

well-defined end walls, they som'etimes 

contain ore, and have every appearance 

of having been feeders, qy means of 

which mineralizing solutions were introduced into the loose material in the 

I'\:~""' Y \3£SS5\)'l '3 brecciated zone. The eastern shoot (No. 

9 5cale opfee1" f h 1 )l b kdb - - 9 o t e p an 1as . een wor ~e y an 

FIG. 10.-Doane mine; vertical north-south section through 

stopes 7 and s, showing relation of ore channels to intersect- overhead stope, 80 feet in height, and by 

ing system of joints. Compare with figs. 3, 9, and n. an underhand stope 25 feet deep; the 

western (No. 10 of plan) by an overhead stope for a distance of 40 feet on the 

incline, and by a shallow pit below the tunnel level which shows some ore. 

Both shoots pitch toward the north west in accordance with the general rule 
THE DOANE liiiNE. 69 

that the ore bodies follow the intersection of the northerly dipping stratification 

with the north-south fractures which dip toward the west. 

Genest's of the ore.-From the preceding descriptions it will be be seen that 

the ore bodies occur in brecciated masses of the quartzite which forms the immediate 

country rock, and while there are zones of broken material which are not mineralized., 

in those cases where sulphides have been deposited, joint planes belonging to a 

north-south striking and westerly clipping system are particularly in evidence. 

They are prominent as rather close-set fractures smnetimes filled with ore, or forming the end walls of ore bodies, or again through the invariable tendency which the 

ore shoots have of following the line o£ their intersection with the bedding planes 

of the quartzite. These north-south fractureH correspond very closely, in their 

relations to the ore bodies, to those of 

the Ferris-Haggarty rnine~ and t,heir 

significance is believed to be the same 

in both cases. 

Adjustments within the mass of 

the quartzite seem to have caused a 

greater amount of moven1ent along 

the transver:::;e fractures than along 

any other structural surfaces, with the 

probable exception of the stratification 

planes, where any rnotion would be 

readily accommodated and its direction naturally controlled by the heterogeneity of the separate rock layers. 

Other joint systems are sometimes important elements in the brecciation of 

the quartzite, but these two are always the factors which control the 

direction of the zones or bands of 

broken rock whenever they are mineralized to any important degree. 

FIG. 11.-Doane mine; horizontal plan through stopes 7 and 

8, showing relation of ore to fractures and bedding of 

quartzite. aa, bedding planes and parallel joint fractures, 

dipping north; bb, strong system of south dipping joints; 

cc, important north-south fractures -with steep dips toward 

the west. 

It is also along the north-south fractures that mineralizing solutions, by means 

of which the primary ore deposited in the brecciated zones was introduced, seeny 

to have been in general circulation. While more detailed studies than have 

been made would be required to settle the point with certainty, it seems that the 

mineral-bearing solutions were ascending solutions, for while north-south fractures 

filled with ore seem to occur south of the ore bodies-that is, in the country rock 

forming the foot wall-they were nowhere seen to be filled above the ore horizon in 

the quartzite of the hanging wall, a relation which suggests that circulating solutions 
70 COPPER DEPOSITS OF ENOAMPMEN'l' DISTRICT, WYOMING. 

tending upward in the fissures were totally deflected into the brecciated zonei:l 

wherever they were encountered. 

Direct evidence in regard to the source of the copper was not secured, but the 

fact that the metal is so universally present in the basic intrusives, which are found 

in all parts of the field, as already brought out in the general discussion upon an 

earlier page, seems to warrant the belief that it has been derived from these rocks. 

That the ore shoots as first formed consisted of chalcopyrite can hardly be 

doubted, because the derived or secondary nature of the chalcocite ore is evident. 

In almost any specimen selected at random grains of yellow chalcopyrite are found 

embedded in a mass of the dark copper glance, and specimen:; of low -grade material 

w E 

DOWN 

0 Scale tofeet 

FIG. 12.-Doane mine; section parallel to stratification of quartzite through stopes 9 and 10, showing relation of ore 

shoots to zones of close jointing, which strike nearly north-south and dip steeply toward the west. Brecciation in 

these shoots is principally controlled by the intersection of these fractures and the bedding planes. Other less important fractures are present though not represented in the diagram. The bedding of the quartzite, which corresponds 

with the plane of the paper, dips toward the north. Compare with drawings of the main ore body in figs. 5 and 6. 

from the wall rock in which to the natural eye the quartzite seems to be specked 

with chalcocite are found, when examined under the microscope, to contain both 

chalcopyrite and chalcocite, the former being confined to the centers of the ore 

specks and entirely surrounded by the latter. The chalcocite has been derived from 

the primary chalcopyrite through leaching and redeposition by surface waters percolating through the ore bodies, and to the fact that this alteration has taken 

place the richness of the Doane ore is to be attributed. 

The ore occurs mostly as a filling or cement in the quartzite breccia, but in some 

cases it seems to be partly interstitial and partly a replacement of the quartzite, as 
THE DOANE MINE. - 71 

though the mineralizing solutions had dissolved and carried. away the quartzite near 

the chanHels of circulation and deposited the ore in its place (see fig. 8). 

Future of the pro_perty.-Gradual improvement with increasing depth is not 

commonly observed in mines where rich secondary sulphides form the principal 

. ore, and it is therefore to be expected that, as they are mined downward, the ores 

of the Doane mine will decrease in value. There can be little doubt that the 

ore which has already been taken from the lower workings contains a smaller 

percentage of copper than that from some of the higher levels, for, though no 

studies based upon assays have been made to bring out this relation, there is a 

· notable increase in the proportion of chalcopyrite and a corresponding decrease 

in the amount of secondary chalcocite, which is quite sufficient to show this 

tendency. Accepting this as true, the richer sulphides will sooner or later give 

place to chalcopyrite ores of comparatively low grade, which, though they could 

possibly be worked in connection with richer ores, might not be able to bear 

the expense of operation alone. For these reasons the future success of th~ 

property is regarded as largely dependent upon the discovery of additional highgrade ore bodies. Whether such ore bodies exist or not can not be decided out 

of hand, but the relations which have been brought out in the preceding descrip..: 

tions seem to warrant the suggestion that they may be found. Rich ore bas 

been taken out of workings on the claim which adjoins the Doane property upon 

the west, and at whatever horizon in the quartzite this ore occurs, its presence 

is presumptive evidence that north-south sheeting of the rocks exists in this 

ground. If future exploration should demonstrate this to be the fact, then there 

is a possibility of encountering several ore bodies by prospecting along this 

sheeted zone; and, moreover, between it and the known zone of sheeting which 

carries the ore bodies in the Doane mine others may occur with ore shoots 

locally developed in them. Similar zones of localized shattering may also occur 

in the ground to the east, and on the whole it is believed that careful exploration underground, close attention being paid to changes in the extent to which 

the north-south fractures are developed, is fully warranted by the conditions which 

can now be made out. It need hardly be added that before making a search 

for zones of fracturing not now apparent, the one upon which the known ore 

bodies exist should be thoroughly prospected to the north of the present workings. In this direction the line of intersection between the fracture zone and 

the contact of the quartzite and diorite may prove a favorable position for the 

occurrence of ore, a suggestion which, though purely speculative, could be followed up at small expense. 
72 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

FERRIS-HAGGARTY MINE. 

Location and development.-The Ferris-Haggarty property is located about 2 

miles west of Bridger Peak, on the east side of Haggarty Creek. It was formerly 

known as the Rudefeha, a name which has since been given to the post-office located 

at the mine. 

The surface outcrop of this important ore deposit was a small exposure of gossan 

surrounded by the loose surface wash which covers the general slope of the hillside 

in the vicinity. This gossan, which is composP-d of spongy iron oxide mixed with 

quartz, was penetrated to a depth of o5 feet with little or no evidence of the presence 

of copper, but at this depth sulphide ores, occurring in kernels and ~:mnches within 

\ A 

LEGEND 

···-••• Workings from old shaft 

5 

•. -·-·· Second floor above first mine level 

-·-·-·- Flrstfloor <~bove first mine level 

-- WorKings on first mine level at IZ3feet 

----Workings on second mine level at 223feet 

'-'"', \ \ ----·--- Limitofstopes and workings on slope of vein 

) '-, \, \, A-8} /Jr'..;' \ \, C-D Position of sections, fig.t7 

6(-..._, /// '~'..... \ \ .. '---....:::--::_/ "-, \" ...... ---/\..___ \ \_,.. ..... \ __ _../'""--..---.--:Je - \" -------> r-....-:..._-.........._ .'; /,........-~-....._J...:..-

' //:""\.J ............ / '\ / __ / ............. ...... ...... _ ...... ___ ...... / 

..__ ___ Scale __. 1sofeet t,:~···/ B ___ _,.. 

FIG. 13.-Ferris-Haggarty mine; plan of mine workings. Successive floors and levels are numbered to correspond 

with :fig. 14. 

the spongy iron oxide of the gossan, were encountered. The inclined shaft was 

continued to a depth of nearly SO feet, and the o:r;e was opened up both to the east 

and west in drifts at two levels (figs. 13, 14). A new shaft was then sunk at a point 

down the slope of the hillside, about 240 feet distant from the discovery. More 

than 30 feet of loose surface debris was penetrated before striking bed rock. The 

ore body was encountered at about 165 feet, and the shaft was continued to a total 

depth of 248 feet. At 123 feet a crosscut toward the north penetrated the hanging 

wall of the ore at a distance of 60 feet, and 100 feet lower the foot wall was reached 
THE FERRIS-HAGGARTY MINE. 73 

by a crosscut to the south, within a distance of about 4:0 feet. From these levels 

the ore body was developed by raises and intermediate floors in the vein, and in 

addition a large amount of high-grade ore was stoped out, especially in the eastern 

part of the mine. The horizontal length of the ore body varies from 250 to 300 

feet. 

It is reported that the ore has been proved to continue downward some 50 feet 

or more to the level of the new adit which was opened in the spring of 1903. It is 

by means of this adit that th~ k:nown reserves and the future possible discoveries of 

~Orestopes 

mgGossan 

~Ore reserves, both high and 

FIG. 14.-Ferris-Haggarty mine; projection of workings on vertical plane parallel to strike of ore body. 

s 

ore are to be taken out. At its mouth the ore may be conveniently loaded into 

the buckets of the aerial tramway which connects the mine with the concentrator 

and smelting plant at Encampment. 

Because of the high cost- of transportation, only high-grade mineral has been 

hitherto mined, excepting where the removal of low-grade material was necessitated 

in ~inning the shipping ore. Being developed in this way, practically no dead work 

had been done at the time this examination was made, and the workings were almos-t 

entirely confined to the vein. 

• 
74 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

Country rock.-The country rock at the Ferri~-Haggarty mine is mainly 

quartzite and schist, belonging to the pre-Cambrian quartzite and slate formation .. 

Intrusive gabbros, known in the district as diorites, occur near by, but are not 

encountered near the ore body. 

The ore occurs at and follows a definit3 horizon situated between 200 and 250 

feet below the top of the quartzite-slate formation, the upper limit of which is 

marked by the appearance of heavy beds of conglomerate. A section of the bedded 

rocks as they are exposed upon the ridge which forms a spur from the Continental 

N s 

FIG. 15.-Section of bedded formations on ridge about one-half mile east of Ferris-Haggarty mine. The so-called 

"contact'' horizon is marked by crosses. It is not mineralized at this place. Compare fig. 16. 

Divide about one-half mile east of the mine, near the point where the tramway 

crosses, is given in fig. 15. · This illustrates the alternation ·of varying strata below 

the ore horizon, while a complementary section (fig. 16), observed upon the ridge on 

the opposite side of Haggarty Gulch, gives the similar features of the strata which 

lie stratigraphically lower. Both sections show the intercalation o:f igneous 

rock and disclose the general attitude o:f the bed~, which strike nearly east and 

west, dipping to the south at angles varying from 35° to 50°. In the mine workN s 

R>Z~J quartzite 

FIG. 16.-Sectiou of bedded formations and intrusive rocks about one-half mile west of Ferris-Haggarty mine. The 

so-called "contact" horizon is marked by crosses. At a there is evidence of a considerable fault parallel with the 

bedding of the rocks. 

ings the strata are observed to have a corresponding structure, though there are 

local minor variations, both in strike and dip, which bear an important relation to 

the ore deposit. 

Jointing of country rock.-Throughout the mine· the. quartzite- is broken by 

different sets of fractures, but these are rarely, if ever, represented by breaks in the 

hanging-wall schist, for in it adjustments and accommodations to movement caused . 

bending o:f the strata and crumpling of its separate :folia, while the brittle quartzite 

was fractured and brecciated. The most prominent :fractures observed in the rocks 
THE FERRIS-HAGGARTY MINE. 75. 

of the vicinity run in a direction nearly north and south-that is, ·nearly normal to 

the course of the vein-and, while nearly vertical, usually have a slight inclination 

to the east or west. 

In the massive sandstone corresponding to the ore horizon, where it outcrops 

upon th~ crest of the ridge to the east of the mine, there are many small veins of 

quartz having a width of several inches near the contact of the quartzite and schist, 

but gradually becoming thinner toward the north, and finally disappearing at a 

distance of 30 feet or so. Other rocks, such as the intrusive diorite, likewise contain similar veinlets of quartz, showing the general occurrence of these fractures. 

They may be observed in exposures upon the west side of Haggarty Gulch opposite 

the mine, and in this vicinity there is also some evidence in the relations of outcrops 

of the rocks that important faults break the continuity of the strata along north 

and south fractures, and cause offsets of the beds toward the south as they are 

followed from east to west. 

In the mine,- fractures of the -north-south system are to be observed at several places, though · they are not uniformly developed throughout the workings. 

Locally they are rather closely spaced, as ob~erved in the quartzite of the foot wall, 

and where this is the case, the schist which lies over the vein is often bent outward 

toward the south, and in the hollow thus formed the ore body is thicker than usual 

and the ore ordinarily of higher value. It seems that by bending in this way the 

more pliable schist has been able to take up or accommodate itself to movement 

which caused fracture in the brittle quartzite. The occurrence of fractures striking 

nearly parallel with the bedding of the quartzite and dipping in a contrary direction 

was noted at several points (figs. 24, 25), but there is less opportunity in this mine 

than in the Doane to observe the characteristics of the joint systems, since s'o great 

a share of the workings have been in the ore. Undoubtedly several sets of fractures have acted together to cause the brecciation of the brittle quartzite beneath 

the pliable schist, and in all probability there has been an important amount of 

crushing caused by movement along this horizon, in addition to adjustq:tents along 

the different joints. 

The ore. -The principal ore minerals which have been extracted from this 

mine are chalcocite and chalcopyrite, though bornite and covellite are occasionally 

found. Carbonate and oxide ores are present in small amounts only. The richest 

ore is found in the upper workings, where the proportion of chalcopyrite is le~s 

-than on the lower levels. Much of the ore requires concentration, being mixed with. 

the quartzite country rock, but no other gangue is present, and in the past all of 

the ore shipped has been practically free from foreign matter. 

Oceurrence of the ore.-The ore body in this mine follows a somewhat irregular zone of brecciation in the upper part of a definite stratum of quartzite, which, 
76 COPPER DEPOSITS 0.1!' ENCAMPMENT DISTRICT, WYOMING. 

in common with the beds associated with it, strikes nearly east and west and dips 

about 40° toward the south. Above this quartzite and sharply separated from it 

there is a bed of very fine-grained schist, which, though very much crumpled, 

contrasts with the quartzite below by reason of the practical absence of brecciation. 

This schist, which has a thickness estimated at about 50 feet, forms the hanging 

wall of the vein throughout the mine (figs. 15, 16, 17). There is no definite 

continuous foot wall, but the ore makes back into the quartzite in an extremely 

irregular manner, dependent either upon the_ completeness of brecciation or upon 

~ Schist of hanging wall 

F>\·(j Quartzite of foot wall 

~ Ore reserves 

~Gossan 

FIG. 17.-Ferris-Haggarty mine; transverse sections of the ore body along lines A Band CD in figs. 13 and 14. 

the presence of cross fractures. The deposit has many of the characteristics of 

the Doane ore bodies, and is regarded as being of the same general type. 

At the time the mine was visited the Ferris-Haggarty ore body had been fol-

'lowed from its outcrop to a depth of 266 feet below the surface, giving a known 

length on the dip of over 400 feet (figs. 14, 17). It is reported that the ore has 

been found to extend into the lower workings which ha~e been opened from the 

new adit completed in the winter of 1902-3, so that the full depth to which the 

mineralization continues has not been ascertained as yet. 
THE FERRIS-HAGGARTY MINE. 77 

The upper limit of the ore where it passes into the gossan which forms the 

surface capping has been fully determined in the upper stopes and found to be 

rather irregular at a depth of from .35 to 60 feet (fig. 17). The drifts and stopes 

which have been opened at different levels show that the high-grade ore, at least, 

is rather sharply bounded. In the first mine level, at a depth of 125 feet, the 

horizontal length of the ore shoot is about 300 feet, while in the second level, 

100 feet below, it is some 50 feet less (figs. 13, 14). 

1'\. "'-:.!Quartzi-te 9 Scale 

FIG 18.-Ferris-Haggarty mine; north-south sketch section through Bonanza stope at first mine level. Shows form of 

ore body and irregularity of foot wall. Compare fig. 19. 

Along its strike the ore body seems to be limited by the disappearance of 

brecciation in the quartzite, but there is often low-grade ore beyond the present excavations, and few opportunities were afforded for conclusive observation 

w 

···••· : ;, ; @i~ff. 

0 zofeet '----------' 

FIG. 19.-Ferris-Haggarty mine; sketch section through Bonanza stope parallel to strike and at right angles to dip 

of ore body. Compare figure 18. 

upon this point. The thickness o-f the vein is extremely irregular,· varying 

from a few inches near the ends up to 30 feet, or even more in some places 

(figs. 11, 18, 19). 
78 COPPER DEPOSITS Olf ENCAMPMENT DISTRICT, WYOMING. 

Upon any level in the· mine the intersection of a horizontal plane with the 

surface formed by the hanging wall is a curve concave toward the north. This 

is illustrated in fig. 20, in which the general shape of the vein upon the first 

~ ~Quartzite of foot wall 9 Scale spfeet (~~JSchist of hanging wall 

FIG. 20.-Ferris-Haggarty mine; plans of ore body on first and second mine levels. The general bowing toward the 

south is well shown. Compare levels 5 and 6 in figs. 13 and 14. 

and second mine levels is given in horizontal p1an, and in fig. 21, which is an 

idealized diagram showing in horizontal section the relation of the ore body to 

the countrv rock and to the north-south fractures. 

w 

FIG. 21.-Ferris-Haggarty mine; idealized horizontal section of ore body, showing general convexity toward the 

south and ~he filling of north-south fractures. 

Combined with the horizontal curving of the hanging-wall surface there is 

variatio~ in dip, or irregular bending up and down from the plane of average 

inclination, so that the under surface of the schist overlying the ore is seen to be 
THE FERRIS-HAGGARTY MIN~.,,-, 79 

a warped -surface .of very intricate contour. However, its irregularities are gentle 

rather than abrupt, and the :fidelity with which the ore body follows the surface ' 'lc · · 

of division between the quartzite and the schist gives a sharply defined hanging 

wall, a feature which is illustrated in several of the accmnpanying diagrams. 

The foot wall has none of the regularity of the hanging wall, where the ore 

makes in the country rock. in various ways, doubtless dependent upon local 

differences in the development of the fractures and brecciation in the quartzite 

(figs. 23, 24, 25). 

~ Quartzite of ~foot wall ~~Schist of '~~~ hanging wall 

FIG. 2"2.-Ferris-Haggarty mine; idealized vertical north-south section across the ore body, showing convexity and 

irregular dip. 

A certain amount of ore is found in north-south fractures in the quartzite 

country rock beneath the ore shoot, and a portion of the sulphides in the latter 

may have been formed by a replacement of the quartzite, but the main mass of 

the ore occurs filling the mass of broken or brecciated quartzite, the fragments 

of which are sharply limited against the ore and contain metallic minerals only in 

the form of veinlets with sharp walls (figs. 23, 24). 

_The sketch diagram (fig. 25) represents the relations of the vein to the 

inclosing rocks in the west end of Bonanza stope. The bottom of the section 

is 90 feet above the first mine level. In the foot wall north-south fractures are 

~--------
80 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

prominently developed, but there is no marked horizontal bowing of the strata. 

The ore minerals are chalcocite with some chalcopyrite, and these form a matrix 

for brecciated fragments of quartzite. The foot-wall material is much fractured 

s N and seamed, while the overlying schist appears 

9 Scale 

Schistto be perfectly intact, though it is considerably 

crumpled. 

At several places in the mine the ore body 

was found to have more or less continuous 

bands of schist runni~g through it, and in such 

cases the ore i~ found to be formed just under 

the bands of close-grained rock, while the 

quartzite above them is barren for some distance (fig. 26), indicating that the ores were 

deposited by ascending waters. 

Genesis of the ore.-The reference of the 

Doane and F en·is-Haggarty copper ores to the 

same type of deposit is founded on the very 

close similarity in their mode of occurrence. 

In the latter the upper part of a be~ of quartzFIG. 23.-Ferris-Haggarty mine; face of stope west 

of old shaft, 90 feet above first mine level. The 

sketch shows the brecciation of the quartzite 

and irregularity of foot wall. At this place 

north-south fractures are strongly developed in 

the foot wall, but do not cut the overlying schist. ite, striking nearly east and west and dipping 

south, has been greatly broken and brecciated along its contact with a thick 

oyei·lying stratum of schist. The brecciation has been caused in part by 

N 5 

mQuartzite off"oot wall o~ __ 5 c_a_l_e _ _:_j•ofeet 

FIG. 24.-Ferris-Haggarty mine; idealized sketch of ore body as seen near old shaft at depth of 135 feet, showing false 

hanging wall and nature of brecciation. 

movements essentially parallel with the bedding, and in part by movements 

along fractures transverse to the stratification. Cross fractures, which strike 

nearly north and south and dip steeply either to the east or to the west, are to be. 
THE FERRIS· HAGGARTY MINE. 81 

observed in various parts of the mine, and in some cases they are filled with ore in 

the quartzite of the foot wall, but they do not break the continuity of the hangingwall schist. The latter has almost invariably adjusted itself 

to movement in the direction of 

these fractures by bending, instead of by breaking. This being the case, and the schist being 

fine grained~ it forms a capping 

over the open quartzite breccia 

which has been very impervious 

to the passage of water in circulation. 

N s 

From the relatiQnS which 

have been described in detail in 

the foregoing pages, and which 

are here briefly summarized, it 

is believed that the existence of 

the Ferris-Haggarty ore body 

depends upon the presence of 

the north-south cross fractures, 

the brecciated quartzite, and the 

~.Joint fractures in lmJ ~quartzites of foot wall "~~~\:: 5chist 

Scale 1oofeet 

FIG. 25.-Ferris-Haggarty mine; north-south diagrammatic section 

through stope on first mine level near head of incline to second 

level, showing intersection of bedding and fissures, and an offshoot 

of ore into the foot-wall quartzite. 

overlying impervious schist. The cross fractures being in many places filled with 

ore are regarded as having been channels of easy circulation for ascending solu-

~Quartzite~ Minerali;<:ed L:i:2:J ~ guartz1te 

tions. Since the fractures do not continue through the schist, the moving 

waters were completely deflected by the 

impervious stratum into the fractured 

rock beneath, along which they con-

. tinued to ascend, and found conditions 

favorable for the deposition of their 

metallic contents. 

The occurrence of ore in these northsouth fractures beneath the ore horizon, 

and the relation of the latter to them, 

suggests that they have been feeders 

for the main ore body, and while suffiFIG. 26.-Ferris-Haggarty mine; diagrammatic section of 

ore body, illustrating the manner in which the richness 

of the ore increases just beneath layers of close-grained 

schist interbedded with the quartzite. cient observations have not been made 

to prove the point, it is believed that there is a zone of excessive sheeting tran~­

verse to the strike of the rocks which inclose the ore body, and as wide as 

2100-N o. 25-04-6 
82 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

its horizontal length. Outside of this zone parallel fractures exist, but they are 

probably few and widely spaced. 

That the mineralizing waters were ascending and that the schist was practically 

not penetrated by them is Rhown by the clearness of the contact of ore and schist and 

the rarity with which any ore occurs in the material of the hanging ,wall. The same 

thing is brought out even more clearly in certain places where thin beds of schist 

occur within the mineralized part of the quartzite (fig. 26). In such cases the ore 

is mainly segregated beneath the different schist bands, and immediately above them 

little or no Inineralization has taken place. 

The basic gabbro rocks of the region are regarded as the source from which 

the deeply circulating waters derived their metallic contents. 

The primary ore was chalcopyrite with perhaps some iron sulphide free from 

copper, and the rich ores which have been encountered have resulted fron1 secondary 

concentration of origina1ly leaner ores, through the action of surface waters percolating through the vein, dissolving copper from tlw upper portions and redepositing 

it lower down. Examination of the ore in the mine workings shows the gradual 

increase of primary chalcopyrite and the corresponding diminution of chalcocite 

as depth is attained, and it is probable that eventually the former will entirely 

replace the latter. 

Future of tlw property.-The prosperity of the Ferris-Haggarty mine for the 

immediate future is practically assured by the existing ore reserves (see figs. 13, 14)~ 

and the conservative policy of developing and exploring while production is going 

on will doubtless be adopted. 

The ore body itself will naturally be followed downward, and exploration of the 

ore-bearing horizon between the schist and quartzite toward the east may lead to 

the discovery that another zone of north-south sheeting has produced mineralization 

in it. Also the ground north qf the present workings may contain ore bodies 

]()cated beneath other slaty or schistose layers intercalated in the quartzite~ and 

related to north-south fractures in a manner similar to the known deposit. 

CHARTER OAK MINE. 

The Charter Oak property is located a short distance north of the area shown on 

the Encampment special map, in sec. 24, T. 14 N., R. 85 W., about 6t miles northwest of Encampment. 

The country rocks in the vicinity are gneissoid or schistose granite and metamorphosed basic rocks related to gabbros, but having the compositio1,1 of diorite. The 

greater part of these diorites are schistose, but occasionally they are massive. They 

are intrusive in the granite gneiss, and the contacts between them and the schistosity 

of the diorite follow the platy structure of the older granitic rock. 

The mine is situated near the east side of a broad synclinal fold, the axis of 

which pitches northwest from the high hill about 1 mile to the southwest, in sec. 

29, T. 14 N., R. 85 W. In this locality the influence of the fold may be noted 
THE CHARTER O.AK MINE. 83 

eastward to Otto Creek and westward to Calf Creek, a distance of nearly 2 miles 

(fig. 27). 

FIG. 27.-Sketch section of main syncline in prominent hill southwest of Charter Oak mine. View looking northeast. 

Near the mine the rocks within the general syncline are greatly twisted, and are 

also faulted, as is illustrated in the sketch map (fig. 28) showing their local structure, 

and in the cross section (fig. 29). 

Scale ,__ ____ soo _, feet 

FIG. 28.-Sketch map of vicinity of Charter Oak mine, showing structure and distribution of roclm. 

An inspection of the sketch map and section will show the position of two nearly 

north-south faults which follow the axes of two minor anticlines pitching toward the Ill 

·t 

-~ 

.. -~ .. ·'!! ~ -~ 

"' -s 

<U 

~ ~ 

:~ t:: :t: 

... :) ~ 

Scale .__ ____ ---.' soo feet 

FIG. 29.-Charter Oak mine; sketch section along line a b, fig. 28. 

north. The eastern of these two faults forms the fissure in which the Charter Oak 

vein occurs; the other is not known to be mineralized. 
84 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

A more detailed sketch in the immediate neighborhood of the Charter Oak vein 

is given in fig. 30. The fault with basic diorite on the west and gneiss upon the 

east may be readily traced for nearly 1,500 feet, and vein material outcrops at intervals along it. 

The vein proper consists of quartz carrying a variable amount of copper and 

iron, but the wall rock is often fractured and mineralized as well. Its relations are 

shown in the cross section, fig. 31, taken at the point a, fig. 30, while the more 

detailed sketch represents its characteristics at the point marked b on the plan. 

From the most northerly outcrop the vein is nearly straight southward to the 

incline where the main ore body was found. At this place the gangue was mainly 

quartz, brown jasperoid, and schistose wall rock, with some calcite and a little chalcedony. The primary ore was chalcopyrite, some of which still remains, while the 

alteration of this mineral has given rise to secondary chalcocite, bornite, azurite, 

Schistose granite 

FIG. 30.-Charter Oak mine; surface plan of vein. 

hematite, and lilnonite. A massive brown mineral, which occurs in son1e quantity, 

is said to assay 25 per cent copper, and is probably a mixture of iron oxide with a 

a rich sulphide of copper. 

After the incline in the ore had disclosed a sharp bend in the vein its course 

was changed to follow the new dip, as shown in fig. 30. The strike of the vein in 

the lower working is shown by the course of the drifts represented in the sketch, 

and its dip is about 24:0 • About 100 feet south of the main opening an open pit 

in the granite shows a brown jasper vein containing oxide of iron, with some 

green copper stains and a little chalcopyrite. ThiR is directly in line with the north 

and south portion of the main vein, so that the latter seems to have divided between 

this point and the mouth of the incline. Closer examination shows that this portion of the vein consists of several splinters, the ~ain one of which dips about 35° 

toward the east. 
THE OSCEOLA CLAIM. 85 

In figure 30 the curved line trending southwestward from the top of the incline 

represents approximately where the northeast-southwest portion of the vein encountered in the workings would outcrop at the surface if continuous. This ground is 

covered so that it is not actually known to appear in outcrop. 

The Charter Oak deposit belongs to the general type which has been named 

from the Continental vein. The primary sulphides and the quartz forming the 

gangue were deposited at the same time in a fault fissure by circulating waters 

which found in it an easy channel of movement. As frequently happens where 

0 Seale 40-fee"t 

FIG. 31.--Charter Oak mine; general cross section showing relation of vein to inclosing rocks. 

several fractures exist, a greater amount of metallic sulphides was precipitated at 

their intersection than elsewhere, giving rise to the body of ore which lias been 

worked out. The reason for thiR relation may be either that the rock openings 

were greater near their intersection than at other points or that here solutions 

carrying different chemical salts in the different fractures came together and caused 

precipitation of the metallic minerals. 

The basic igneous rocks of th.e region have been shown by the tests made 

during the study of the Encampment district to be an adequate source for all the 

w E rre~cfured and Quartz ve/n Sheared and mineral/zed d/or/te Granite m/neralized dlor/te 

FIG. 32.-Charter Oak mine; detailed cross section of vein and adjacent rocks. 

copper deposits which have been formed since their intrusion, and the copper sulphides in the Charter Oak mine are regarded as of this origin. 

OSCEOLA PROPERTY. 

The Osceola claim is situated to the south of the first extension of the Rudefeha 

claim toward the west, and is undoubtedly crossed , by the apex of the Rudefeha or 

Ferris-Haggarty lead, since the drop of the ore horizon to~ard the south causes 

the outcrop beneath the heayy covering of surface debris to run from north-northeast to south-southwest upon the slope of the hill, while the side lines of the claims 
86 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING . 

. trend more nearly east and west. I£ exploration should prove that the contact 

between the schist and quartzite is not mineralized in this vicinity, the fact will 

furnish strong corroborative evidence that ore bodies o£ the Doane type, such as that 

in the Ferris-Haggarty mine, will be found only where marked zones o£ sheeting 

cross favorable horizons, and the possibility of the occurrence o£ other zones of this 

sort to the west of the Osceola shaft should be taken into consideration. 

At the time the property was visited a shaft 56 feet deep had been sunk and a 

crosscut 35 feet long had been run toward the north, traversing quartzite excepting 

for an intercalated bed of schist about 4 feet in thickness and a thicker bed in which 

the drift terminated. This last bed o£ schist i~ probably the same as the contact 

schist in the Ferris-Haggarty, but it was not found to be mineralized at this point. 

CREEDE PROPERTY. 

The Creede claim is situated about 2 miles northwest o£ Bridger Peak, and about 

a quarter o£ a mile east o£ the road from Rudefeha to Saratoga. The deposit at this 

N 5 

-/ 

Seale 5oo-l'eet 

10'..~1 \!?-~~~~ i:;'l-~~~s~ Hornblende-schist quar"'Tzi"te Norii·e Qu~rtz .. diorite 

FIG. 33.-Geologic section on north side of Continental Divide through Creede claim. The position of Creede shaft 

shown by cross. 

place has been taken as a type of ores which seem to have been formed as a direct 

result o£ contact metamorphism caused _by intrusions o£ norite. The general 

description of the ore and its occurrence are given on page 54. 

The geologic cross section, fig. 33, shows the position of the deposit in the 

hornblende-schist, near the south contact of an intrusive mass of norite. 

Several other prospects in the vicinity also occur near the same body of norite 

and in each the ore is partly pyrrhotite, as at the Creede. The relative positions of 

the openings on the Creede, Island City, and Lucky Find claims are shown in fig. 

34, which also shows in plan the approximate local distribution of the country rocks. 

In the three openings west of the Creede calcareous strata are found, which seem 

to have offered favm::able conditions for the deposition of sulphides from solutions 

which probably derived their metallic contents from the norite, either at the time of 

its intrusion, as is supposed to have been the case at the Creede, or later. 
THE LEIG 

The c I HTON·GENT a careous bed RY PROSPE 

of the hornbl d s mentioned li' . OT. . en e·sch" t em a p . . 87 

tgneous contact.;. IS (fig. 35), which al:sdion parnllel with the o controls the platy structure 

general st ri 'k e of the 

Creek. 

with a th' Ic k . sill of n ori 't .e above 

d An · Inclined shaft 

t 

emonstrated the has opened he b e dd ed existence of ~p the lead f li my quartzite . ab pynte . or a dist out 11 ' feet pyrrhotite . ' n a d chalcop ance of 't 150 . feet, and In thick yri e Jn a b d ness. The an of ore occurs partly 

N 

Fm.

36 

.-General cross sectio n ~"-"~~~""* Calcareous b d . through the Isl e s In schist 

I 

of ore-bea . and City cl . 

a ong the b dd' nng horizon C aim, showing e Ing . ross shows . . occurrence a d th • pia pmutwn f n •tmct e mmernlized q . nes, and partly d" . o main opening. ure of""""· and .-elation 

contain no I uartzlte there is Isseminated th a S\[ phides T , a stratum of rough the r pparent, but th . his rests upon rather pure limest' ock. Beneath 

from neighborin;s: 7on give place to ;;:r;;ites, ihe thicknes:ne fwhic~ seems to u crops. ornblende-sch" Is t series, o whiCh as is k is nown not 
88 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

The strata strike N. 80° W. and dip 30° toward the south. The gossan is very 

superficial and unaltered sulphides occur within 10 or 12 feet of the surface. 

_._-\._n assay upon a sample of pyrrhotite made in the laboratory of the Geological 

Survey by Dr. E. T. Allen gave the fo1lowing result: 

Assay of pyrrhotite, Leighton-Gentry mine. 

Per cent. Copper_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3. 07 

~~~~~~ } - - - - -- - - -- --- - -- - -- -- - - - - - - - - - -- - - - - - - - - - - - -- - - - - - - - - -- - - 00. 67 

Zinc _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Trace. 

Platinum ________________________________________________________ None. 

The accompanying diagram (fig. 36) illustrates the mode or occurrence, which 

is very similar to that at the Island City and other prospects in the vicinity of 

the Creede. Moreover, a certain resemblance to the Ferris-Haggarty deposit i~ 

N 

Hornblende-schist Ore 

~ 

~ horizon, 

lime~"t~dn;,,iJ~~hh'ils"Tar-tzlte, 

.____s_c_a_le _ ____.'9ofeet S 

tz~i~'fl Quartzite 

FIG. 36.-8ketch diagram showing position of Leighton-Gentry ore horizon relative to inclosing rocks. The black 

line represents the inclined shaft. 

seen in the situation of the mineralized rock beneath a stratum of close-grained 

schist which may have been instrumental in localizing the deposition of the ore 

minerals, by deflecting ascending solutions along the thin-bedded, comparatively 

permeable, quartzites immediately beneath it. 

SYNDICATE PROPERTY. 

The Syndicate property is situated at the head of a tributary of Savery 

River, near the crest of the ridge which continues northwestward from the bend 

m the Continental Divide toward Dexter Peak. 

The immediate country rock is quartzite, certain beds of which are very 

calcareous. The strata strike nearly east and west and dip to th~ south at a 

much lower angle than the vein. The latter therefore crosses the stratification, 
THE SYNDICATE PROPERTY. 89 

filling a well-defined though irregular fissure (fig. 37). A sill of diorite about 150 

feet wide outcrops about 30 feet south of the shaft. An inclined shaft 135 feet jn 

depth has been sunk upon a fissure vein originally filled with calcite, which has be~n 

partially dissolved away, leaving open caves. At 90 feet a drift 35 feet long h~~ts 

N 

FIG. 37.-North-south section through Syndicate shaft, showing manner in which the vein crosses the beds of quartzite. 

Position of drift on vein is shown at a. 

followed the vein toward the east. The strike of the vein is N. 70° W., and it 

dips 65° from the horizontal toward the south. 

The calcite forms a filling for a breccia of quartzite, the whole vein varying 

from 3 to 11 feet in width. Chalcocite or copper glance in small grains or pelletl-l 

is disseminated through the calcite, and is also found 

in the quartz fragments. A diagram showing these 

characteristics-is given in fig. 38, which represents the 

vein at a depth of 110 feet. At this place there is an 

unbroken band of quartzite in the center of the vein. 

Little or no vein quartz accompanies the calcite, but 

this mineral was noted in the crosscut tunnel at the 100-

foot level beneath a thin stratum of schist interbedded 

with the quartzites. 

As elsewhere in the region, variou~ systems of joint FIG. 38.-Detail of Syndicate vein 

fractures are in evidence in this vicinity, though any at depth of 110 f~et. 

important relation which they may bear to the origin of ore in the Syndicate 

vein is not apparent. Being chalcocite, the ore as it now occurs is regat:ded as 

secondary, and when sufficient depth is attained it is to be expected that leaner 

sulphides will be encountered. 
90 OOPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

CONTINENT AL• VEIN. 

The Continental claim is located on the south side of Cow Creek, near the 

transfer station of the Ferris-Haggarty tramway. The country rock belongs to 

the conglomerate member of the pre-Cambrian sedimentary series, but these rocks 

have been metamorphosed to such an extent by compregsion during the folding 

of the quartzite belt that they now appear as laminated schists, striking about 

northeast by east and dipping at a rather low angle toward the south. 

The Continental vein follows the platy structure of the conglomerate-schh~t, 

alternately widening and pinching along its outcrop, which has been traced :for 

several hundred feet.' From this feature it is believed that it will be equally 

irregular when followed downward (fig. 39). As seen in the discovery pit, it has a 

width of from 2 to 4 feet, and is composed mainly of quartz and a small amount of 

siderite, but has chalcopyrite distributed irregularly through its mass. About 

FIG. 39.-Sketch section showing probable relation of Continental vein to inclosing rocks. 

200 feet farther west it has been cut at a depth of perhaps 20 feet by a short tunnel, 

and here its thickness is more than 6 :feet, and eopper pyrite is still present. 

The property is being developed by a tunnel located about 150 feet below 

the outcrop, by means of which the character of the vein at that depth will be 

ascertained. 

PORTLAND AND HERCULES MINES. 

The Portland and Hercules shafts are ]ocated on adjoining claims ·about one-half 

mile south of Battle, a short distance west of the top of the range. 

Various sorts of rocks occur in this vicinity (:fig. 40), including a large mass of 

red granite on the south and massive pre-Ca?lbrian quartzites on the north, with 

limestones and red shales intruded by basic igneous rock, now altered to chloriteschist, between. The general strike of the sedimentary rocks, and of their igneous 

contacts, is nearly east and west, which is likewise the course of a profound fault 
THE PORTLAND AND HERCULES MINES. 91 

which form~ the northern boundary of the granite, while the schistose structures in 

the chlorite rock trend about ;N. 65° E. All these structures dip steeply toward 

the north. The two shafts wefe sunk for the purpose of investigating the contact 

between the red granite and :the rocks north of it. A shallow shaft upon the 

Portland claim had encountered an encouraging amount of rich copper glance just 

south of the present shaft hop.se, but the owners, being unable to cope with the 

large amount of water, formed a company and decided to sink a working shaft a 

short distance to the north, with the expectation of finding the ore by crosscutting 

to the granite. 

At the time of our visit tlre shaft was 200 feet deep, and a crosscut toward the 

south at 100 feet had encountered a strong watercourse accompanying a maRs of soft 

red mud which required the construction of a bulkhead to keep it from forcing its 

~~:;.)::·.}(j Quartzite 

tb I 

~Limqstone 

~and!shale 

1::7":71 

~ Copper-bea, ring 0 5 oofeet vems ,_ ____ __, 

Red granite 

FIG. 40.-Diagrammatic sketch map to show general distribution of rocks in vicinity of Hercules and Portland shafts. 

Between the granite and the adjacent rocks there is a gouge of soft red mud, sometimes several feet in thickness, 

which has probably been produced by ~aulting along this eontact. 

way down into the workings. No evidence of strong mine~alization was found, 

but the limestone which the shaft and crosscut traversed was much broken and. 

impregnated in spots by chalqopyrite. 

At 200 feet the granite is said to have been encountered, but is now hidden in 

the sump. A -crosscut toward, the north at this depth has been partly in limestone 

and partly in chlorite-schist, both of which are very much fractured and crushed, 

showing many slips not constant in their direction. Occasionally ore is encountered 

impregnating the country rock'; but so far as seen does not occur in any regular way. 

The object of this tunnel was to .cut in depth several copper-bearing veins which 

outcrop west of the shaft and strike about N. 65° E. (fig. 40). These veins have 

been opened by trenching and found to have a width of a few inches only; how-
92 COPPER DEPOSITS OF ENCAMPMENT DI!:!TRICT, WYOMING. 

ever, they seem to be persistent, and it is claimed that the float of one of them 

has been traced for several hundred feet. They are compos'"ed of chalcopyrite 

and hematite, with a gangue mainly of quartz with some calcite and siderite (carbonate of iron). There is some chalcocite, but considering that these veins are to 

be seen only in outcrop, the small amount of secondary sulphides which they contain is noteworthy. Probably the looseness of the inclosing rock is greater than 

that of the veins, so that there has been no tendency for them to become channels 

of circulation. 

In the summer of 1902 the Hercules workings were not accessible. It is said 

that a small northeast-southwest quartz vein carrying sulphides was found in the 

shaft, and that granite was reached at a depth of between 70 and 80 feet. 

GERTRUDE PROPERTY. 

The Gertrude property is located just north of the wagon road, about one-half 

mile east of Battle. The surface near the mine is largely covered by loose material, 

N s 

0 

0 Scale ._ ___ __. sofeet 

FIG. 41.-Sketch cross section through Gertrude workings . 

. so that there are no outcrops, but both quartzite and basic intrusive rock are 

exposed south of the w~rkings. The quartzites strike nearly east and west, and 

dip about 40 degrees to the south. Between them and the mass of red granite 

farther south the bed rock in the covered ground is probably like that just north 

of the Portland shaft, and the quartzite exposed is supposed to be the same horizon 

as that shown in the sketch map of that vicinity (see fig. 41, and the geologic 

map, Pl. II, in pocket). 

In the quartzite, and following its bedding, with sharp walls above and below, 

a body of massive hematite'" or red iron oxide, has been followed by an incline 

SO feet long. It has also been tapped by a vertical shaft north of the incline 

at a depth of 80 feet. The thickness of this body of mineral varies from 2t 
THE HIDDEN TREASURE TUNNEL. 93 

feet near the surface to about 9 feet at the bottom, but its extent along the strike 

has not been investigated. It is said to give an average assay of $7 per ton in 

gold, and that certain portions of it show higher values. It can not be foretold 

whether or not this bedded deposit of hematite is gos:;an capping a body of sulphide (either pyrite or chalcopyrite), but it may prove to be so, and is regarded 

as deserving the expenditure necessary to reveal it in depth. 

The new shaft which is located about 250 feet south of the discovery should 

cut the vein at an estimated depth of about 225 feet i£ the obsdrved dip continues. 

HIDDEN TREASURE TUNNEL. 

The Hidden Treasure group of claims is situated ahout one-half mile from 

the Gertrude, or 1 mile east of Battle. 

The country rocks penetrated by the tunnel are quartzites, quartz-schists, and 

altered diorite. All of the rocks are greatly mashed and brecciated, but at their 

{'!..~\\-.\:] Quartzi'te 

Ul QuarttiTe-SChiS't 

CilJ Wa1"er zone in quartzi'te 

f~;~j;_\~ Dior-iTe 

Copper vein 

NW SE 

FIG. 42.-Section of first 720 feet of Hidden Treasure tunnel. Compare fig. 43. 

contacts a general northeast-southwest strike may be readily made out, and the dip 

is toward the south (fig. 42). Surface outcrops are almost wanting except on the 

upper ~:'lopes of the ridge above the tunnel; here, however, the northeast strike and 

southerly dip may also be observed. The rock, which is here cu,lled diorite, is often 

~ofeet 

[IT[] Quartzite 

(a) copper veins (b) f'aults 

[RJ Water zone in quartzite~ Diorite 

FIG. 43.-Plan of Hidden Treasure tunnel, showing relative course of faults and trend of strata. 

composed largely of chlorite, and is ordinarily much crur::;hed and full of slips, and 

is even schistose in some places as a result of having been· squeezed between th~ 

formerly massive beds of quartzite into which it is intrusive. This rock has been 
94 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

derived from a facies of the basic gabbro rock which occurs throughout the region. 

The quartzite and quartz-schist are both greatly crushed and brecciated, especially 

adjacent to the first 500 feet of the tunnel, where the quartzite breaks into small 

cubes when exposed to the air. The whole ground shows the effects of subterranean 

movements which have brought the rocks into a condition to allow of the ready 

penetration of surface waters. Slips and faults occur throughout the mine, some 

of them forming the boundaries of different rocks, and others in rock of a single 

variety. Mineralization occurs at many points, but it probably originated previous 

to the general crushing of the rocks, as a rule, since they are too open to allow of 

the concentration of circulating waters in local channels. 

The object of driving the tunnel was to cut a vein which had been located on 

the summit of the ridge at a distance of 1,000 feet or more, and while this had not 

been reached at the time the mine was visited, a well-defined vein was en~ountered 

s about 575 feet from the mouth of the ~~~~~----~~~~-=~~r=~~~~~ 

j:.·::-.. :·~:;:;.:.:jouar-rzi-te ~ - Diori-te 

tunnel. This vein has been open~d by 

a shallow winze, and its characteristics 

were shown in a chamber excavated 

for the installation of a hoist. It 

strikes about N. 70° E. and dips 

steeply toward the south. It occurs 

near the center of a mass of diorite 

intrusive in the quartzite, where it fills 

an irregular fissure (fig. 44). Twelve 

feet above the level of the tunnel its 

B vein width is 4 or 5 inches, 5 feet above, 18 

FIG. 44.-Sketch of vein formed in fracture in dike of diorite, 

Hidden Treasure tunnel. Compare figs. 42 and 43. inches, and at the floor of the chamber, 

2t feet. 

The gangue of the vein is composed of quartz, calcite, and siderite, sometimes 

accompanied by a small amount of feldspar. The ore minerals are chalcopyrite, 

chalcocite, and malachite. A small amount of specular hematite also occurs. The 

chalcocite seems to be in excess of the other copper minerals, showing that considerable secondary alteration has taken place. 

Assays of nine samples of sulphides from various parts of the Hidden Treasure 

workings, made for the management by Prof. H. H. Nicholson, of Lincoln, Nebr., 

show an average of three-tenths ounce of gold per ton, while a single sample gave 

over 11 o~1nces per ton. 

SUN ANCHOR AND SWEET CLAIMS. 

These claims are situated upon a zone of metamorphism in the hornblende-schist 

series, extending in a general east-west direction along the northern face of Green 

Mountain, and crossing the southern branch of North Fork. 
THE KURTZE CHATTERTON MINE. 95 

The zone is marked by the occurrence of considerable massive green epidote 

and small bright-red garnets, and is said to have been traced for a distance of more 

than 2 miles. It has the same strike as the black hornblende-schist which occurs on 

either side of it, and at several points where it has been opened shows the presence 

of magnetite and chalcopyrite. These prospects are practically undeveloped, but 

the nature of the occurrence is readily recognized as similar to the deposit at the 

Verde or Hinton mine. a 

KURTZE CHATTERTON MINE. 

The Kurtze Chatterton property is located on Copper Creek about 5 miles 

southwest of Encampment. The country rock is mainly chlorite-schist derived 

from basic rock related to the gabbro intrusives, which are prominent throughout 

the region, but this is cut by dikes of red granite which are probably offshoots from 

the large mass of this rock situated to the south of Copper Creek. The chlorite schist occurs in a band between 

this granite and the steeply inclined quartzites to the 

north. The strike of the quartzites is nearly east and 

west, while the structure in the schists is somewhat 

more northerly. 

Several veins fron:i 3 to ~0 feet wide outcrop at 

the surface, and three were encountered in the tunnel. 

On the surface they strike somewhat north of west and 

appear to dip steeply toward the north, but in the tunnel their dip is rather flat in the opposite direction. 

The ore is chalcocite in the shallow surface workings and chalcopyrite in the tunnel. The mineral is 

FIG. 45.-Structure of quartz and 

feldspar vein, Kurtze Chatterton 

claim. The black dots represent 

chalcocite distributed through the 

quartz. 

scattered through the vein matter, so that the whole must be mined as a low-grade 

ore which requires concentration. The veins, though mostly composed of quartz, 

contain some feldspar, which gives them a general resemblance to the pegmatite 

veins at the Cascade mine situated about 5 miles to the southeast. In the Cascade 

deposit, however, the ore fills fractures in the veins, showing that it is of later 

origin, while in the Kurtze Chatterton veins the ore was formed at the same time 

as the quartz of the gangue. It is also confined to the quartz which often occupies 

the center of the vein, with the feldspar largely confined to the well-defined walls. 

·The diagram (fig. 45) represents one of the veins which outcrops at the surface. 

The deposits are classed with the type named from the Continental vein in Cow 

Creek, which is characterized by the contemporaneity of the ore and gangue minerals in veins between well-defined walls. 

a See pp. 53 and 97. 
96 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

The property has been opened by a tunnel about 1,500 feet long, running in a 

northerly direction. The fii·st 700 feet is mainly in barren granite, but at this 

distance chlorite-schist is encountered, and between it and the granite there is a 

quartz vein, about 1 foot wide, which carries chalcopyrite. This vein strikes 

nearly east and west and dips about 45° to the south. It has been opened by a 

drift 20 feet in length, which shows that the country rock, especially in the hanging wall, is much crushed. 

At 1,300 feet a second ledge has been followed a short distance and found to be 

made up of very irregular lenses of pegmatite carrying chalcopyrite. 

A third body of ore-bearing quartz and feldspar from 5 to 10 feet wide was 

encountered 150 feet farther toward the north, but this pinches out along its 

strike and is not a continuom; vein. 

A concentrator has been built at the mine. 

CASCADE MINE. 

At the Cascade mine, located on the east side of Encampment River neal.· 

the mouth of Cascade Creek, copper sulphides occur in a large dike or vein of 

pegmatite, inclosed in a complex of considerably sheeted granite and diorite. 

The property has been developed by a shaft 100 feet deep, and by a tunnel 

which was 425 feet long in October, 1902, and which It was the intention to continue to a distance of 800 feet to connect with the shaft. The genera! course of 

the vein is approximately parallel with the structure of the inclosing rocksthat is, N. 20° W., and it dips irregularly toward the south, though at the outcrop it appears to be nearly vertical. In the shaft the vein was cut at a depth 

of 80 feet and developed by a crosscut, in which it was shown to have a width 

of 24 feet and to have well-marked walls with clay gouge. Ore is generally 

distributed through the vein, but occurs in the greatest amounts upon the foot 

wall. Upon the northeast side the country rock is diorite, while upon the southwest side it is granite. In the vicinity of the shaft the country rock is found 

to be generally gneissic, and near the mouth of the tunnel the country rock is 

composed of bands of alaskite a and granite, with some diorite, both siliceous and 

basic phases of which occur in narrow bands. The material thrown out of the 

shaft indicates that surface waters have accomplished a slight amount of enrichment _of the chalcopyrite, which forms the main portion of the ore. 

About 6,000 feet northwest of the Cascade shaft a vein of pegmatite is found 

which is supposed to be the same lead. 

In the field it was regarded as probable that the chalcopyrite had originated 

in the vein as a primary constituent, along with the quartz and the feldspar, but an 

aAlaskite is a rock related to granite, but composed essentially of quartz and orthoclase feldspar without dark silicate 

minerals. 
THE ITMAY MINE. 97 

examination of the specimens under the microscope Hhows that- the sulphides are 

in part at least later than the other minerals, having crystallized after the 

pegmatite has been fractured. 

ITMAY MINE. 

The li{may property is located near the head of Roaring Fork, south of 

Huston Park, in sec. 14, T. 13 N., R. 85 W. The country rock is gray quartzdiorite. The ore occurs along the 

walls of a much altered basic dike 

intrusive into the quartz-diorite. The 

course of this dike is about N. 708 

E., arid it dips steeply toward the 

south. A section of the vein, showing its general characteristics is given 

(fig. 4H). 

On the north side the country 

rock is massive excepting for a band 

of schistose gouge next to the dike. 

This band is 2t feet wide at the surface, and a streak of ore, occurring 

somewhat irregularly in it, varies 

from a few inches up to 2 feet. The 

dike is about 10 feet -wide and is 

often impregnated with ore. Along 

the hanging wall the sulphide streak 

has been found to be from 3 to 10 

inches wide. Only a small amount 

of quartz occurs with the ore, the 

gangue being mostly composed of the 

inclosing rock. 

But little secondary alteration has 

0 Scale 

!:;,-;' \:y1 Quartz-diorite ~v/i\?.:!"\ gneiss 

NW 

Basic dike altered ~ Chalcopyrite oc- to chlorite. Some- ~ curring on walls 

what impregnated of dike 

with chalcopyrite _ 

FIG. 46.-Sketch of Itmay vein, looking southwest. 

taken place, and there are practically no other copper minerals besides chalcopyrite, which appears within 3 feet of the surface outcrop. A sample of sulphide 

ore from the dump gave 17.92 per cent copper and $1 per ton in gold. 

In August, 1902, the vein had been opened by a shaft which was about 50 

feet deep, but a steam hoist has since been installed for the purpose of more 

extensive development. 

HINTON MINE. 

This property is located about 7 miles due south from Battle. The main 

2100--~o. 25--04----7 
98 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

characteristics of the deposit have been given on page 53, and its probab1e 

genesis is discussed elsewhere in this report (pp. 56, 58). 

The gossan of the vein, which is very shallow, consists of spongy iron oxide, 

mixed with decomposed and iron-stained garnet, ~nd with the other material of 

the lead which is relatively fresh in appearance more or less distributed through 

it. Practically, no secondary sulphides were encountered, and unaltered chalcopyrite occurred in one instance within 12 feet of the surface. The very 

superficial extent to which the vein has been leached by surface waters, is 

undoubtedly due to the very tight nature of the ground, the lead having no 

gouge or slips along its walls. An average sample from the mine dump gave 

8.18 per cent copper and 40 cents in gold. 

From the strength which the lead exhibits in outcrop, and from the fact that 

the· richn~ss of the ore which occurs, though moderate, is not due to secondary 

enrichment, it may be expected that it will continue to a considerable depth. 

At the time the mine was visited, in July, 1902, several shafts, from 30 to 50 

feet in depth, had encountered ore, though hardly in sufficient amounts to be mined 

profitably. Since that time a steam hoist has been installed, and one of the shafts 

was reported to have reached a depth of 110 feet in June, 1903. 

On an adjoining claim to the east a good body of ore is reported at 40 feet. 

This deposit is believed to have been formed during the metamorphism of the 

schists in which it occurs, as stated on page 56. 

ARGENTIFEROUS VEINS. 

Deposits of galena, variously associated with other sulphides and carrying silver, 

occur in veins both to the north of the immediate area of the Encampment map, and 

also in one instance near its ·southern border. This mineral is always associated with 

quartz, usually in veins filling well-defined :fissures, which may cross or follow the 

stratification or schistosity of the inclosing rocks. Though they were not specifically 

mentioned in the classification of the copper ores of the district, their mode of occurrence allies them with copper veins of the Continental type, in which the sulphides 

and quartz were formed at the same time. 

Pyrite and chalcopyrite ordinarily occur with the galena, and chalcocite is ordinarily present where primary minerals carrying copper have been altered. 

META MINE. 

The Meta property is situated at the head of a branch of South Spring Creek 

about 1 mile north of the boundary of the area covered by the Encampment map. 

The rocks in the vicinity are gray gneiss derived from quartz-diorite, and black 

schistose diorite derived from gabbro, which occur in alternatfng beds, striking 
ARGENTIFEROUS VEINS. 99 

nearly northeast and southwest, and declining slightly toward the northwest. The 

surfaces of separation between masses of the two rocks are parallel to the gneissic 

structure, and several systems of joints are well developed. Nearly vertical fractures 

running northeast and southwest are very prominent, but these contain no quartz, 

which is a common filling in a system of east-northeast fissures, one of whic~ contains 

the Meta vein. 

As exposed in surface workings, the vein of quartz and calcite 

has a width of 7 inches. It is 

inclosed between sharp walls with 

considerable gangue on both sides 

and marked sheeting in the rock 

adjacent (fig. 47). 

Underground the vein is reported to have a width of from 

2 to 3 feet. When unoxidized . FIG. 47.-Sketch section of the formations at the Meta mine, showing 

the ore is mainly galena, with relations of vein. 

some chalcopyrite and a little zinc blende, but in the upper workings it is largely 

carbonate of lead, the miner.al cerrusite. A single carload of ore is reported to 

have been shipped from this mine which gave a fairly good assay for silver, 

but seemed not to have been sufficiently high grade to stand transportation 

charges, since the property has been idle for several . years. 

ALMA PROPERTY. 

This property lies sout~west of the Meta, on the divide between North Spring 

and South Spring creeks, about one-half mile beyond the boundary ~f the map. The 

country rock is mainly black schistose diorite, 'but gray quartz-diorite also occurs 

near by, and there are some thin beds of sedimentary quartzite and a few dikes 

of alaskite. 

The gangue of the vein is mainly quartz, with some siderite, and the principal ore minerals are galena and 'chalcopyrite. The width of the vein is about 

18 inches, its course, like that of the Meta, east by northeast, and its dip from 

40° to 60° toward the north. 

BRIDGER MINE. 

This property is situated on the Continental Divide, several miles north of the 

Sierra Madre. The vein was discovered by F. 0. Williams in 1876. The country 

rock in the neighborhood is mainly quartzite and diorite (metagabbro), which is 

often schistose. There are many quartz veins outcropping in the vicinity, and 

most of them contain some feldspar, especially near their walls. When sulphides 
100 COPPER DEPOSITS OF ENCAMPMENT DISTRICT, WYOMING. 

occur they are always in the quartz, usually without other gangue, though 

calcite sometimes occurs. ¥ost of them are said to contain a few dollars in 

E~ 

~~ .0 ol 

- t ..c Q) 

<lJ ... -..... 

~ 

A-~-J 

Aol 

8 ~ 

'g 8 

o:.£ 

- ::s f ~ 0 

.0 > :::: D ~ ·~ Ill "0- rn 

"Of> 0 :a ~ be~ "' bO <lJ E :::: -o :§ ·~ ol..., 

§~ 

c.:~ 

0 ·5 .::f /I'/ > OJ 

''• <1) ~ 

~~~ 5 ~ 

?;{ s ~ bO ..... 

~~ 

ci'<S 

(l)~ 1=1 Oil 

gold, but as a rule they are. regarded as untrustworthy, since they 

are liable to disappear suddenly as they are traced downward . 

A section representing the general relations of the Bridger 

vein is here given (fig. 48). 

The strike of the vein and of the country rock is northwest and southeast, and the dip varies from 25° to 55°, the 

latter being observed at the Bridger shaft. 

The section given in fig. 49 shows the general relations in 

the mine where there are three veins of quartz following the 

stratification and schistosity of the inclosing sheeted quartzite. 

Similar relations also exist in the discovery outcrop 100 yards 

toward the southeast~ and the lead can be followed for a distance of nearly 3,000 feet. 

The hanging-wall streak averages 10 inches in width in the 

mine. It is composed of altered quartzite which is greatly 

mineralized. At the surface it is very rusty, and it is somewhat 

oxidized to the bottom· of the. workings, which are 128 feet 

·s ~ ~ ~ &~ 

.g;'C)§ 

~ ~ ~- deep on the vein. It is said to give assays from a trace to 69 

'C) :B.£ 

t-ai~ 

·a .o ~ 

"8 .8 ~ ·~ ~ ~ =::::1-+J 

..... ol a) 

~~~ "@A~ 

>~-1-J 

~ 'C) ·g ~. 

t ~:a~ 

Itt ~ .s .8 :J t: <lJ lO 

IH! ,g.;~ 

~~g 

.g ·~ ~ 

ffi:82 

-;.£'tl 

~ ·~ ~ <lJ > <lJ 

~~~ 

ounces gold per ton, the richest ore having been found near the 

surface. \Vith depth the values in gold are said to decrease, 

though those in silver increase. 

The middle streak varies from 6 inches to 3 feet in width. 

It is composed of hard quartzite filled with vein quartz, the 

two having almost the same appearance and containing some 

calcite. The sulphides are galena and chalcocite, but tellurium 

and selenium are present as well. A sample of 100 pounds 

representing the average of this streak is reported to have 

assayed 90 ounces silver and $5 in gold per ton. The foot-wall 

streak, which varies in width from 4 to 10 inches, contains 

both silver and gold in about the same proportion as the others. 

GOLD COIN CLAIM. 

·ole 

: & ~ On this claim, situated south of the Bridger property, there 

~ is a quartz and calcite vein about 1 foot wide, carrying bunches 

of galena and some pyrite and chalcopyrite. Both silver and gold are reported. 

The vein fills a well-defined fissure, striking aboui N. 75° E. and dipping 
ARG ENTIFEROUS VEINS. 101 

at a high angle toward the south. It cuts across the schistosity of the black 

diorite which incl6ses it and has several inches of soft selvage on each side separating it from the 1nassive country rock. The vein has been developed by two shafts, 

46 and 100 feet deep, respectively, ~nd there are several drifts. Work was in 

progress during the autumn of NE sw 

1902. 

ELKHORN MINE. 

This property, which lies in 

Colorado about l~ miles south of 

the State line, was located in 1897. 

Considerable work has been done 

on the vein, and several carloads 

of ore have been hauled out to 

Rawlins, a distance of about 100 

miles. 

The country rock is a dark 

hornblende rock, probably belonging to the schist series, and the o.__ ___ s_ca_l_e ___ ....:~s feet 

vein fills a well-defined fissure. It Fm. 49.-Detailed structure of Bridger vein as exposed in shaft. 

has been traced for a distance of a, foot-wall vein, composed of quartz carrying sulphide minerals 

with gold and silver; b, schist containing lenses of quartz; c, midseveral hundred feet upon the sur- dle vein, composed of quartz and indur-ated quartzite with some 

calcite, and containing galena and chalcopyrite carrying gold and 

face and has been opened at sev- silver; d, schi;;;t with lenses of quartz; e, hanging-wall vein, composed of indurated quartzite resembling vein quartz (this portion 

eral points and found to have a of the vein carries the best values in gold); j, schistose diorite formgeneral course about N. 60 w. ing hanging wall. The vein occurs between diorite and quartzite. 

It dips slightly toward the west. At the time the property was visited the workings 

were filled with water, but from the dumps the nature of the ore could be determined. The shipping ore seems to have been mainly galena and cerussite, containing some pyrite and chalcopyrite, while a considerable amount of zinc blende 

was removed by sorting. The ore which was shipped- is reported to have yielded 

$97 per ton, $10 in gold and the remainder in silver. 
CHAPTER V. 

PRACTICAL STTGGESTIONS. 

A question of prime importance to those engaged in the search _for copper 

deposits in the Encampment country is whether or not deep exploration will 

reveal the presence of workable ore bodies which do not appear at the surface. 

The expectation that this will be the case, which is somewhat prevalent in the 

region, seems to be based upon the fact that in parts of Arizona and in certain 

other districts the upper edges of large, high-grade ore/ bodies are encountered 

at depths of 300 to 500 feet or more. In regions where the upper portions of 

copper veins are found to be barren, and where the ore is found in secondary 

concentrations at considerable depth, the mode of occurrence seems to be 

directly dependent upon climatic conditions which have never existed in the 

region here under discussion, and for the Encampment field it is believed that 

deep prospecting is not generally advisable. On the other hand, the value of 

underground work intended to demonstrate the presence of workable ore bodies 

depends upon the fidelity with which operations are confined to actual ore.bodies, 

or to ore indications. 

In the Encampment region wherever minerals of primary deposition, such 

as chalcopyrite, or pyrrhotite, are found near the surface unmixed with carbonates 

or oxides of copper, or with sulphides of higher grade, it is believed that there 

can be no sound basis for predicting any increase, either in the richness or the 

size of ore bodies with increasing depth. If the ore )s found to improve in 

any particular case, it is as likely to decrease in value in the next, and in general 

it may be said that after an ore body has been lost the discovery of another by 

sinking will always be a matter of chance. 

It is suggested that a fair estimate of the manner in which the copper . minerals are distributed underground may be obtained from the distribution of mineralization upon the surface. The present topography is the result of erosion, which 

has removed a large amount of rock 'which formerly existed above the present 

surface, and ore segregations doubtless e~isted in the rock which has been removed 

as well as in the material which now remains, so that the present surface has only 

a chance relationship to the position and dimensions of the primary sulphide 

102 
PRACTICAL SUGGESTIONS. 103 

deposits. It therefore seems safe to say that after eliminating recognizable secondary concentrations a careful estimation of the importance of all deposits appearing 

in outcrop in any given area would not differ essentially from similar estimations 

which might be made were it possible to expose new surfaces to exploration by 

the removal of successive sliells of constant thickness from the same area. .Also 

it may be argued that the distribution of ore minerals in any vertical section 

across a given belt would not vary materially from the surface distribution of the 

same sorts of rocks. In the Encampment district no primary ore deposits of workable size have yet been developed at the surface, and if the amount of copper ore 

to be encountered below gro~nd can be even roughly estimated from the surface 

occurrence in the manner suggested, the wisdom of confining all exploratory 

work to actual ore bodies will be at once recognized. 

The for~going remarks apply to the search for primary ore minerals, but there 

is equal reason for believing that where secondary enrichment is to be expected 

prospecting should also be confined to ore indications. If deep exploration is 

warranted at all it will be only in cases where gossan deposits can be followed; but 

from the fact that the known workable ore bodies of the region have been invariably 

encountered ~ithin from 15 to 75 feet from the surface, it is anticipated that where 

limonite cappings are found copper sulphides, if present, will be encountered at 

relatively slight depth. Where primary minerals occur at or near the surface it 

may be safely assumed that no secondary enrichment will be found lower down, and 

if any change in the value of the ores occurs they are more apt to become poorer 

than the contrary. Experience in other fields points to the probability that below 

a maximum zone the secondary ores will decrease in richness with increasing depth 

until the unaltered sulphides are reached. 

The point can not be1 too strongly urged that coppe;r stains or even fairly welldefined bodies of ore or gossan occurring in outcrops can not be taken as evidence 

that continuous veins or large bodies of ore exist in depth, waiting to be revealed 

by deep shafts or long tunnels. 

INDEX. 

Page. 

Algonkian rocks. See Pre-Cambrian. 

Alma mine, location, development, and ore of . . . . . . . 99 

Allen, E. T., analyses by, of norite and diorite........ 32 

analysis of coal by................................. 17 

assays made by.................................... 51 

reference to tests for copper by.................... 49 

Altitude, variations in, in Encampment district ...... 11-12 

Analyses, chemical. See substance analyzed. 

Aplite, geologic relations of........................... 41 

origin and distribution of . . ... ...... .. . ...... ... . . 41 

use of term . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . 41 

Archean rocks. See Pre-Cambrian. 

Argentiferous galena, occurrence of................... 43 

Battle Lake Tunnel Site Company, ground water in 

tunnel of, depth of........................ 45 

Bridger group of claims, discovery of.......... . . . . . . . . 13 

Bridger mine, country rock at ........................ 99-100 

location and development of ..................... 99-100 

ore of, character and occurrence of. . . . . . . . . . . . . . . . 100 

value of. .................................... .".. 100 

vein of, figure showing structure of. . . . . . . . . . . . . . . . 101 

veins in vicinity of, section showing . . . . . . . . . . . . . . 100 

Bridger Peak, altitude of . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . 11 

Carbondale mine, coal from, analysis of.. . . . . . . . . . . . . . 17 

Carboniferous (Upper) rocks, occurrence of.. . . . . . . . . . . 16, 59 

Cascade mine, locp.tion and development of.... . . . . . . . 96 

ore of, character and occurrence of. . . . . . . . . . . . . . . . 96-97 

Cascade type of ore deposits, description of . . . . . . . . . . . 55 

origin of • • • • • • • . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . 58-59 

source of copper of. ................................ 59-60 

Chalcopyrite, occurrence of ............................ 36, 47 

relations of, to other minerals..................... 36 

Charter Oak mine, country rock at . . . . . . . . . . . . . . . . . . . . 82-83 

discovery of . .. .. . ... . . . . . .. . . .. .. . . .. . . . . . . . . . . . . . 13 

general cross section of . .. . . . . .. . . . . . . . . . . . .. . .. . . . 85 

location of......................................... 82 

ore of, character and occurrences of .............. 84-85 

sketch map of vicinity of.......................... 83 

sketch section along line in sketch map........... 83 

sketch section of syncline in hill south of . . . . . . . . 83 

vein of, cross section of............................ 85 

surface plan of .. .. .. .. . . . . . . .. .. . . .. .. . . .. . . . . 84 

Chatterton, Kurtze, claims located by................. 12 

Chatterton mine. See Kurtze Chatterton. 

Chemical analyses. See substance analyzed. 

Coal, analysis of....................................... 17 

Colorado, northern, sketch map of, showing location 

of Encampment district................... 11 

Conglomerate beds, contact between hornblendeschists and................................. 20 

composition of..................................... 26 

description of. ..................................... 26-27 

distribution of.......... .. . . . . . . . . . . . . . . . . . . . . . . . . 27 

metamorphism in ................................. ' 26 

Page. 

Conglomerate beds, thickness of . . . . . . . . . . . . . . . . . . . . . . 26 

Continental claim, country rock at ... :. • . . . . . . . . . . . . . 90 

location and development of....... .. . .. .. .. . .. . . . 90 

ore of, occurrence and character of .. . . .. . . . . . .. .. 90 

vein of, relation of, to inclosing rock, sketch showing......................................... 90 

Continental Divide, character and elevation of....... 12 

position of...................................... 9-10,11 

Continental type of ore deposits, age of . . . . . . . . . . . . . . . 59 

description of.. . . . . . . .. .. • . .. .. . .. . . .. . .. . .. . . . . . . . 54-55 

origin of ........................................... 58-59 

source of copper of ................................ 59-60 

Copper deposits, types of, description of ............... 53-55 

types of, table showing relations of . . . . . . . . . . . . . . . 56 

Copper minerals, character of ......................... 42-43 

distribution of ..................................... 47-49 

occurrences of............ . . .. .. . .. . .. .. . . .. . . .. .. . 41, 42 

relations of........................................ 36 

Copper ores, copper in, sources ol: . . . . . . . . . . . . . . . 47-48, 49-50 

distribution of ...........•......................... 47-49 

genesis of..... .. .. . . .. .. . . .. . .. .. . .. . .. . .. . . . .. . 48, 56-60 

secondary enrichment of.......................... 60 

suggestions as to search for. . . . .. . . . . . . . . . . . . . . . . 102-103 

surface cappings of................................ 43 

Creede claim, country rock at......................... 86 

geologic section through, on north side of Continental Divide............................ 86 

location and development of...................... 86 

openings in vicinity of, sketch map to show position of . .. .. . . . . . . . . .. . . . . . . . . .. . .. . . . . . .. . . 87 

pyrrhotite ores at.................................. 36 

Creede type of ore deposits, description of . .. .. .. .. .. . 54 

minerals of . .. . . . . . . . . . . . . . . . . . . . . . .. . . .. . .. . .. . .. . 54, 58 

origin of . . . . . . .. .. . .. . . . . . . . . .. . . . . .. . . .. . .. .. .. . .. 58 

Cullerton, Ben, discovery by, of gold-bearing bowlders........................................ 13 

Diorite, analyses of. ................................... 32,33 

copper in .. .. .. . . . . . . . . . . .. . • . . . . . . .. .. .. . . . . .. . .. . 48 

definition of . .. . . . . . . • • • . . . . . • . . . . . . .. .. . . . . . . . .. .. 30 

origin of. . . . . .. . . . . . .. • • • • • • . . • • . .. . . . . .. . . . . . .. . . . 30-31 

structure of............................ .. .. . . .. . . . . 31 

use of name, for dark intrusives................... 28 

Diorite-gneiss, occurrence of. ......................... 38-39 

Doane, George, mining operations by .. ·............... 12 

Doane mine, country rock at .......................... 62-63 

counrty rock at, jointing in....................... 63 

diagrammatic cross section in..................... 67 

discovery of . . . . . . .. . . . . . . .. .. .. . . . . .. .. . . . . .. . .. .. 12 

future of, as an ore producer . .. . . . .. .. .. . .. .. .. .. . 71 

gossan at, character of .. .. . .. . . . .. .. .. .. .. .. .. .. .. 45 

joint systems in, diagram to show strike and dip of. 63 

location and development of ...................... 61-62 

ore of, character of .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. . 63-64 

genesis of...... . . . . . .. .. . . . . . .. . .. . .. . .. . . .. .. 69-71 

105 
106 INDEX. 

Page. 

Doane mine-Continued. 

ore of, occu_rrences of .............................. 64-69 

relation of, to fractures and bedding of quartzite....................................... 69 

to inclosing rock........................... 66 

to zones of close jointing, section showing. 70 

ore bodies of, description of . . . . . . . . . . . . . . . . . . . . . . . 64-69 

dimensions of.................................. 66 

horizontal section of........................... 65 

projection of, on vertical plane................ 65 

stereogram representing................ . . . . . . . 64 

vertical north-south section through stopes 7 and 8. 68 

workings of, length of............................. 62 

sketch plan of................................. ii1 

sketch projection of . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 

Doane type of ore deposits, characteristic features of.. 55 

copper in, source of.......... . . . . . . . . . . . . . . . . . . . . . . 59-60 

minerals of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 

origin of ........................................... 58-59 

Dynamo-chemical metamorphism, nature of .......... 33-34 

Elkhorn mine, country rock at ....................... _ 101 

location and development of...................... 101 

ore of, character and occurrence of . . . . . . . . . . . . . . . 101 

value of........................................ 101 

Emerson & McCaffery, ~cknowledgment to........... 10 

Emmons, S. F., work supervised by . . . . . . . . . . . . . . . . . . . 9 

Encampment district, geographic position of . . . . . . . . . 10 

geologic map and structure sections of . . . . . . In pocket. 

location of, index map showing................... 11 

topography of. ..................................... 11-12 

map of ................................... In pocket. 

Ernest, Boney, claims located by...................... 12 

Ferris-Haggarty mine, bedded formations and intrusive rocks west of, section of . . . . . . . . . . . . . . 74 

bedded formations on ridge east of, section of . . . . 74 

Bonanza stope of, sections through................ 77 

country rock of............................ . . . . . . . . 74 

jointing in ....•••.............................. 74-75 

diagrammatic sections through . . . . . . . . . . . . . . . . . . . 81 

face of stope west of old shaft, figure showing . . . . 80 

future of, as an ore producer . . . . . . . . . . . . . . . . . . . . . . 82 

gossan at, character of............................. 45 

location and development of ...................... 72-73 

ore body of, idealized cross section of . . . . . . . . . . . . . 78 

idealized sketch of . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 

idealized vertical north-south section across . . 79 

plans of........................................ 78 

transverse sections of. ......... :. . . . . . . . . . . . . . . 76 

ore of, character of................................ 75 

genesis of ..................................... ~ 80-82 

occurrence of .................................. 75-80 

workings of, plan of............................... 72 

projection of, on vertical plane. . . . . . . . . . . . . . . . 73 

Gabbro rocks, contact metamorphism in . . . . . . . . . . . . . . 36 

copper in .................................... 35,36,48,49 

description of........ . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . 28-35 

metamorphic products of.......................... 28 

mineralization of .................................. 35-36 

types of............................................ 28 

Galena, argentiferous, occurrence of . . . . . . . . . . . . . . . . . . 43 

Gangue minerals, character of . . . . . . . . . . . . . . . . . . . . . . . . 44 

Gertrude ~ine, country rock at •........ _'·............. 92 

cross section through . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 

gossan at, character of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 

location and development of . . . . . . . . . . . . . . . . . . . . . . I 92 

ore of, character and occurrence of . . . . . . . . . . . . . . . 92-93 

vaiueof ....................................... 92 

Gold, discovery of, in Purgatory Gulch ................ 13,51 

Page. 

Gold, discovery of, on Bridger group of claims.... . . . .. 13 

occurrence of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13, 42, 50-52 

Gold Coin claim, location and development of. ....• 100-101 

ore of, character and occurrence of ....••.•.•..•. 100-101 " 

Gossan, character of ....................•. _ ..•••........ 45-47 

origin of . . . . . . . . . . . . . . . . . . . . . . . • . • • . . . . . . • • • • . • . • . . 44 

relations between ores and . . . . . . . . . . . • • . • • • . • . . . . . 43 

For definite localities, see mine names. 

Granite, red, age of.................................... 40 

character and occurrence of ............•..•.....•. 18, 39 

metamorphism of ......................•..•........ 39-40 

mineralogical composition of...................... 39 

occurrences of . . . . . . . . . . . . . . . . . . . . . . . • • . . . . . . . • . . . . 40 

Ground water, lower and upper limitof. .....•.••..... 44-45 

Haggarty, Ed., Ferris-Haggaitymine located by...... 13 

Hercules shaft, country rock at ...........••.......... 90-91 

location and development of. ..................... 90-91 

ore of, character and occurrencP- of ............... 91-92 

rock distribution in vicinity of, sketch showing . . 91 

Hidden Treasure claims, country rock at.............. 93 

location and development of ...................... 93,94 

ore of, character and occurrence of.... . . . . . . . . . . . . 94 

value of........................................ 94 

Hidden Treasure tunnel, plan of....................... 93 

section of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 

vein in, sketch of. ....... : ........... ·-............ 94 

Hinton mine, country rock at......................... 98 

gossan at, character of. ...............••........... 45-46 

location and development of ...................... 97-98 

ore of, character and occurrence of................ 98 

Hinton type of copper deposits, description of ......... 53-54 

minerals of . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . 53 

occurrences of,................ .. .. .. .. . . .. . . .. . . .. 54 

origin of . .. . .. . . . . .. . . .. . .. .. .. . .. . .. .. . .. . . . .. .. . . 57 

source of copper of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57-58 

Hornblende-schists, contact between conglomerate 

and........................................ 20 

contact between sedimentary rocks and.......... 18 

copper sulphide in................................. 47 

cleavage of .......................... ,............. 21 

description of ...................................... 21-24 

distribution of ..................................... 23-24 

feldspar in......................................... 21 

intrusions in....................................... 23 

occurrences of...................................... 18 

origin of .. . . . . .. . . . . .. . . . . . .. . .. . . . . . . . . .. . . . . . . . . . 21 

rocks associated with ..... ~............ ........... 22 

strike and dip in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 

unconformity of erosion between other formations 

and ........................................ 22-23 

Huston, AI., discovery by, of gold-bearing bowlders.. 13 

Igneous rocks, siliceous, description of . . . . . . . . . . . . . . . . 37-41 

Island City claim, cross section through~ . . . . . . . . . . . . . . 87 

Itmay claim, country rock at.......................... 97 

gossan at, character of. . . . . .. .. . . . . . . .. . .. .. . . . . . . . 46 

location and development of...................... 97 

ore of, character and occurrence of................ 97 

vein of, sketch of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 

Jesse claim, copper indications at . . . . . . . . . . . . . . . . . . . . . 40 

gossan at, character of. . . . .. .. .. . .. .. . .. . .. . .. .. .. . 46 

Jones, Henry, development work by.................. 13 

gold reported by ...... ·.. . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 

Jurassic formations, character, occurrence, and thickness of . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 

Kurtze Chatterton mine, country rock at . . . . . . . . . . . . . 95 

location and development of ...................... 95-96 

ore of, character and occurrence of ................ 95-96 
INDEX. 107 

Page. 

Kurtze Chatterton mine, structure of quartz and feldspar vein in................................ 95 

Laramie formation, coal beds in.. .. .. .. .. .. .. .. .. .. .. . 16 

Lead-silver ores, occurrence of ...........•........•... 42,43 

Leighton-Gentry claim, location and development of.. 87 

ore of, assay of.................................... 88 

horizon of, diagram showing position of . . . . • • 88 

occurrence of.................................. 88 

Lewis, J. Volney, aid in field work by................ 9 

Limestone formation, description of .................. 24-25 

exposures of ....................................... 19,24 

strike faults in..................................... 24 

structural relations of ............................. 24-25 

thickness of .. . .. ..... . ... .. .. . ... . .. . . ..... . ..... . 24 

Lindgren, W., quoted on dynamo-chemical metamorphism ...................................... 33-34 

Mesozoic rocks, distribution of, geologic map showing .................................... In pocket 

Meta mine, country rock at ...... ~ .................... 98-99 

formations at, sections of.......................... 99 

location and development of ...................... 98-99 

ore of, character and occurrence of................ 99 

Metagabbro, derivation of ............................. 30-31 

structure of........................................ 31 

Metamorphism, dynamo-chemical, nature of ......... 33-34 

Mineralization of the gabbro intrusives ............... 35-36 

Montana formation, coal beds in...................... 16 

Norite, analysis of ..................................... 32,33 

distribution of..................................... 29 

metamorphism of . .. .. . .. .. .. .. . .. .. . . .. .. . . . . .. .. 29 

mineralogic composition of . . .. .. .. . .. . .. . .. .. .. .. 29 

North American Copper Company, purchase by, of 

Ferris-Haggarty mine..................... 13 

Oligoclase-gabbro, mineralogic composition of........ 30 

origin of. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 

Ore deposits, suggestions regarding search for... . . . 102-103 

For definite localities, see mine names. 

Ores, character of .. .. . .. . .. .. .. .. .. . . .. . .. . .. .. .. .. . .. 42-43 

character of, beneath surface cappings............ 43 

study of, conditions of....... . . . . . . . . . . . . . . . . . . . . . . 42 

copper, surface cappings of........................ 43 

See also Copper ores. 

primary, definitionof .... ·.......................... 43 

secondary, definition of........................... 43 

Osceola claim, location and development of . . . . . . . . . . 85-86 

Oxidation, complete, lower limit of................... 45 

Park Range, trend of, in Colorado..................... 10 

Pegmatite, copper minerals in......................... 41 

occurrence and character of... . . . . . . . . . . . . . . . . . . . . 41 

origin and distribution of.......................... 41 

use of term......................................... 41 

Peridotite, derivation and mineralogic composition of.• 29 

Portland shaft, country rock at ........................ 90-91 

depth of........................................... 91 

location and development of ...................... 90-91 

ore of, eharacter and occurrence of. ............... 91-92 

rock distribution in vicinity of, sketch showing . . 91 

Pre-Cambrian roeks, anticlinal in ..................... 19-20 

character, occurrence, and thickness of..... 15-16, 17-18 

copper minerals in ................................ 47-48 

faulting in ......................................... 19-20 

igneous series of ................................... ~7, 18 

sedimentary series of .............................. 17-18 

Page. 

Pre-Cam brian rocks, structural features of . . . . • . . . . . . . 18-20 

synclinorium in .. .. .. . .. .. .. .. .. .. . . .. . .. . .. . .. .. . 18, 19 

types of............................................ 17 

Pyrrhotite ores, occurrence of....... . . . . • . . . . . . . . . . . • . 36 

Quartz-diorite, character of............................ 37 

copper in .......................................... 48-49 

distribution and areal relations of................. 37 

gneissic structure in areas of • .. • . .. .. . . . .. . . . . . . . . 38-39 

intrusions into ............................ :........ 38 

metamorphism of. ......... ~....................... 38 

mineralogical composition of ...••••.•••••.••...... 37-38 

occurrence of . .. .. . . .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. , 18 

Quartzite and slate formation, character of ........... 25,26 

description of ...................................... 25-26 

distribution of .................................. 17,25, 26 

structure of........................................ 25 

thickness of........................................ 25 

"Red Beds," character, occurrence, and thickness 

of.......................................... 16 

Red granite. See Granite, red. 

Rudefeha mine. See Ferris-Haggarty. 

Savage, Bill, claim located by......................... 12 

Scott claim, copp~r indications at..................... 40 

gossan at, character of .. .. . .. . .. .. . .. • .. . .. .. . . .. . 46 

Secondary ores, occurrence of....... . . • .. . . . .. . • • • . . .. 60 

Sedimentary rocks, anticlinal in ..........•.•......... 19-20 

contact between hornblende-schist and........... 18 

dip of.............................................. 17 

intrusions in....................................... 18 

synclinal structure in ............................. 18,19 

Serpentine, occurrences of............................. 35 

origin of........................................... 35 

sulphides in........................................ 35 

Sierra Madre, Continental Divide along ............... 10, 11 

0 

geologic formations in, range of.. . . . . . . . . . . . . . . . . . 15 

mining developments in, history of ............... 12-13 

mountain summits along, elevation of .... ,. . . . . . . • 12 

pre-Cam brian formations in . . . . . . . . . . . .. . . .. . . . . . . 15, 16 

Siliceous igneous rocks, description of ....•.....•...•. 37-41 

Silver ore, occurrence of .... ~- ........................ 43,98 

Slate and quartzite formation. See Quartzite and slate. 

Southwick, J. W., reference to........................ 12 

Spurr, J. E., work of................................... 9 

Sun, Tom, claims located by . . . .. . . . . . . . • • • . . • . . . . . .. . 12 

Sun Anchor claim, location and development of ....•. 94-95 

Sweet claim, location and development of •.•.••...... 94-95 

Syndicate pr_operty, country rock at .................. 88-89 

location and development of ..................•... 88-89 

ore of, character and Qccurrence of . . . . • . . . . . . . . . . 89 

section through shaft at........................... 89 

vein of, figure showing detail of................... 89 

Tertiary conglomerates, occurrence of................ 17 

Topography, character of, along Continental Divide.. 12 

Triassic" Red Beds," character, occurrence, and thickness of .. . . .. .. .. . .. . .. .. .. .. . . .. .. .. . . .. .. . 16 

Tweedy, Frank, work of .. . .. .. . .. .. .. .. .. .. .. . .. .. .. . 10 

Upper Carboniferous rocks, occurrence of ............. 16, 59 

Williams, Frank 0., gold reported by................. 51 

ore deposits discovered by............ . . .. . .. .. .. • • 13 

reference to ............................... f"...... 12 

Wyoming, southern, sketch map of, showing location 

of Encampment district . . . . . . . . . . . . . . ... . . . 11 

Wyoming conglomerate, occurrence of................ 17 

PUBLICATIONS OF UNITED STATES GEOLOGICAL SURVEY. 

[Professional Paper No. 25.] 

The serial publications of the United States Geological Survey consist of (1) Annual Reports, 

{2) Monographs, (3) Professional Papers, {4) Bulletins, (5) Mineral Resources, (6) Water-Supply 

and Irrigation Papers, (7) Topographic Atlas of the United States-folios and separate sheets 

thereof, (8) Geologic Atlas of the United States-folios thereof. The classes numbered 2, 7, and 8 

are sold at cost of publication; the others are distributed free. A circular giving complete lists may 

be had on application. 

The Professional Papers, Bulletins, and Water-Supply 'Papers treat of a variety of subjects, and 

the total number issued is large. They have therefore been classified into the following series: A, 

Economic geology; B, Descriptive geology; 0, Systematic geology and paleontology; D, Petrography 

and mineralogy; E, Chemistry and physics; F, Geography; G, Miscellaneous; H, Forestry; I, Irrigation; J, ·water storage; K, Pumping water; L, Quality of water; M, General hydrographic investigations; N, Water power; 0, Underground waters; P, Hydrographic progress reports. This paper 

is the thirty-second in Series A and the thirty-seventh in Series B, the complete lists of which follow. 

(PP=l'rofessional Paper, B:;=Bulletin, WS= Water-Supply Paper.) 

SERIES A, ECONOMIC GEOLOGY. 

B 21. Lignites of Great Sioux Reservation: Report on region between Grand and Moreau rivers, Dakota, by Bailey Willis. 

1885. 16 pp., 5 pls. (Out of stock.) 

B 46. Nature and origin of deposits of phosphate of lime, by R. A. F. Penrose, jr., with introduction by N. S. Shaler. 1888. 

143 pp. (Out of stock.) 

B 65. Stratigraphy of the bituminous coal field of Pennsylvania, Ohio, and West Virginia, by I. C. White. 1891. 212 pp., 

11 pis. (Out of stock.) 

B 111. Geology of Big Stone Gap coal field of Virginia and Kentucky, by M. R. Campbell. 1893. 106 pp., 6 pls. 

B 132. The disseminated lead ores of southeastern Missouri, by Arthur Winslow. 1896. 31 pp. 

B 138. Artesian-well prospects in Atlantic Coastal Plain region, by N.H. Darton. 1896. 228 pp., 19 pis. (Out of stock.) 

B 139. Geology of Castle Mountain mining district, Montana, by W. H. Weed and L. V. Pirsson. 1896. 164 pp., 17 pls. 

B 143. Bibliography of clays and the ceramic arts, by J. C. Branner. 1896. 114 pp. 

B 164. Reconnaissance on the Rio Grande coal fields of Texas, by T. W. Vaughan, including a report on igneous rocks from 

the San Carlos coal field, by E. C. E. Lord. 1900. 100 pp., 11 pls. 

B 178. El Paso tin deposits, by W. H. Weed. 1901. 15 pp., 1 pl. 

B 180. Occurrence and distribution of corundum in United States, by J. H. Pratt. 1901. 98 pp., 14 pls. (Out of stock.) 

B 182. A report on the economic geology of the Silverton quadrangle, Colorado, by F. L. Ransome. 1901. 266 pp., 16 pis. 

(Out of stock.) 

B 184. Oil and gas fields of the western interior and northern Texas Coal Measures and of the Upper Cretaceous and Ter-

,tiary of the western Gulf coast, by G. I. Adams. 1901. 64 pp., 10 pls. (Out of stock.) 

B 193. The geological relations and distribution of platinum and associated metals, by J. F. Kemp. 1902. 95 pp., 6 pls. 

(Out of stock.) 

B 198. The Berea grit oil sand in the Cadiz quadrangle, Ohio, by W. T. Griswold. 1902. 43 pp., 1 pl. 

PP 1. Preliminary report on the Ketchikan 'mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska, by Alfred Hulse Brooks. 1902. 120 pp., 2 pls. 

B 200. Reconnaissance of the borax deposits of Death Valley and Mohave Desert, by M. R. Campbell. 1902. 23 pp., 1 pl. 

(Out of stock.) 

B 202. Tests for gold and silver in shales from western Kansas, by Waldemar Lindgren. 1902. 21 pp. 

PP 2. Reconnaissance of the northwestern portion of Seward Peninsula, Alaska, by A. J. Collier. 1902. 70 pp., 11 pls. 

PP 10. Reconnaissance from Fort Hamlin to Kotzebue Sound, Alaska, by way of Dall, Kanuti, Allen, and Kowak rivers, 

by W. C. Mendenhall. 1902. 68 pp., 10 pls. 

PP 11. Clays of the United [:;tates east of the Mississippi River, by Heinrich Ries. 1903. 298 pp., 9 pls. 

PP 12. Geology of the Globe copper district, Arizona, by F~ L. Ransome. 1903. 168 pp., 27 pls. 

B 212. Oil fields of the Texas-Louisiana Gulf Coastal Plain, by C. W. Hayes and William Kennedy. 1903. 174 pp., 11 pls. 

B. 213. Contributions to economic geology, 1902. S. F. Emmons, C. W. Hayes, geologists in charge. 1903. 449 pp. 

PP 15. The mineral resources of the Mount Wrangell district, Alaska, by W. C. Mendenhall and F. C. Schrader. 1903. 

71 pp., 10 pls. 

B 218. Coal resources of the Yukon, Alaska, by Arthur J. Collier. 1903. 71 pp., 6 pls. 

B 219. The ore deposits of Tonopah, Nevada (preliminary report), by J. E. Spurr. 1903. 31 pp., 1 pl. 

PP 20. A reconnaissance in northern Alaska in 1901, by F. C. Schrader. 1904. 139 pp., 16 pls. 

PP 21. The geology and ore deposits of the Bisbee quadrangle, Arizona, by F. L. Ransome. 1904. 168 pp., 29 pls. 

B 223. Gypsum deposits in the United States, by G. I. Adams and others. 1904. 129 pp., 21 pls. 

PP 24. Zinc and lead deposits of northern Arkansas, by G. I. Adams, assisted by A. H. Purdue and E. F. Burchard, with a 

section on the determination and correlation of formations, by E. 0. Ulrich. 1904. - pp., 27 pls. 

PP 25. The copper deposits of the Encampment district, Wyoming, by A. C. Spencer. 1904. 107 pp., 2 pls. 
II PUBLICATIONS OF UNITED STATES GEOLOGICAL SURVEY. 

SERIES B, DESCRIPTIVE GEOLOGY. 

B 23. Observations on the junction between the Eastern sandstone and the Keweenaw series on Keweenaw Point, Lake 

Superior, by R. D. Irving and T. C. Chamberlin. 1885. 124 pp., 17 pls. (Out of stock.) 

B 33. Notes on geology of northern California, by J. S. Diller. 1886. 23 pp. (Out of stock.) 

B 39. The upper beaches and deltas of Glacial Lake Agassiz, by Warren Upham. 1887. 84 pp., 1 pl. (Out of stock.) 

B 40. Changes in river courses in Washington Territory due to glaciation, by Bailey Willis. 1887. 10 pp., 4 pls. (Out of 

stock.) 

B 45. The present condition of knowledge of the geology of Texas, by R. T. Hill. 1887. 94 pp. (Out of stock.) 

B 53. The geology of Nantucket, by N. S. Shaler. 1889. 55 pp., 10 pis. (Out of stock.) 

B 57. A geological recomiaissance in southwestern Kansas, by Robert Hay. 1890. 49 pp., 2 pls. 

B 58. The glacial boundary in western Pennsylvania, Ohio, Kentucky, Indiana, and Illinois, by G. F. Wright, with introduction by T. C. Chamberlin. 1890. 112 pp., 8 pis. (Out of stock.) 

B 67. The relations of the traps of the Newark system in the New Jersey region, by N.H. Darton. 1890. 82 pp. (Out of 

stock.) 

B 104. Glaciation of the Yellowstone Valley north of the Park, by W. H. Weed. 1893. 41 pp., 4 pls. 

B 108. A geological reconnaissance in central Washington, by I. C. Russell. 1893. 108 pp., 12 pls. (Out of stock.) 

B 119. A geological reconnaissance in northwest Wyoming, by G. H. Eldridge. 1894. 72 pp., 4 pis. 

B 137. The geology of the Fort Riley Military Reservation and vicinity, Kansas, by Robert Hay. 1S96. 3q pp., 8 pls. 

B 144. The moraines of the Missouri Coteau and their attendant deposits, by J. E. Todd. 1896. 71 pp., 21 pls. 

B 158. The moraines of southeastern South Dakota and their attendant deposits, by J. E. Todd. 1899. 171 pp., 27 pis. 

B 159. The geology of eastern Berkshire County, Massachusetts, by B. K. Emerson. 1899. 139 pp., 9 pls. 

B 165. Contributions to the geology of Maine, by H. S. Williams and H. E. Gregory. 1900. 212 pp., 14 pls. 

WS 70. Geology and water resources of the Patrick and Goshen Hole quadrangles in eastern Wyoming and western 

Nebraska, by G. I. Adams. 1902. 50 pp., 11 pls. 

B 199. Geology and water resources of the Snake River Plains of Idaho, by I. C. Russell. 1902. 192 pp., 25 pls. 

PP 1. Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska, by A. H. Brooks. 1902. 120 pp., 2 pls. 

PP 2. Reconnaissance of the northwestern portion of Seward Peninsula, Alaska, by A. J. Collier. 1902. 70 pp., 11 pis. 

PP 3. Geology and petrography of Crater Lake National Park, by J. S. Diller and H. B. Patton. 1902. 167 pp., 19 pls. 

PP 10. Reconnaissance from Fort Hamlin to Kotzebue Sound, Alaska, by way of Dall, Kanuti, Allen, and Kowak rivers, 

by W. C. Mendenhall. 1902. 68 pp., 10 pis. 

PP 11. Clays of the United States e&st of the Mississippi River, by Heinrich Ries. 1903. 298 pp., 9 pis. 

PP 12. Geology of the Globe copper district, Arizona, by F. L. Ransome. 1903. 168 pp., 27 pls. 

PP 13. Drainage modifications in southeastern Ohio and adjacent parts of West Virginia and Kentucky, by W. G. Tight. 

1903. 111 pp., 17 pls. 

B 208. Descriptive geology of Nevada south of the fortieth parallel and adjacent portions of California, by J. E. Spurr, 

1903. 229 pp., 8 pls. 

B 209. Geology of Ascutney Mountain, Vermont, by R. A. Daly. 1903. 122 pp., 7 pis. 

)YS 78. Preliminary report on artesian basins in southwestern Idaho and southeastern Oregon, by I. C. Russell. 1903. 

51 pp., 2 pls. 

PP 15. Mineral resources of the Mount Wrangell district, Alaska, by W. C. Mendenhall and F. C. Schrader. 1903. 71 pp., 

10 pis. 

PP 17. Preliminary report on the geology and water resources of Nebraska west of the one hundred and third meridian, 

by N.H. Darton. 1903. 69 pp., 43 pls. 

B 217. Notes on the geology of southwester~ Idaho and southeastern Oregon, by I. C. Russell. 1903. 83 pp., 18 pls. 

B 219. The ore deposits of Tonopah, Nevada (preliminary report), by J. E. Spurr. 1903. 31 pp., 1 pl. 

PP 20. A reconnaissance in northern Alaska in 1901, by F. C. Schrader. 1904. 139 pp., 16 pls. 

PP 21. The geology and ore deposits of the Bisbee quadrangle, Arizona, by F. L. Ransome. 1904. 168 pp., 29 pls. 

WS 90. Geology and water resources of part of the lower James River Valley, South Dakota, by J. E. Todd and C. M. Hall. 

1904. 47 pp., 23 pis. 

PP 25. The copper deposits of the Encampment district, Wyoming, by A. C. Spencer. 1904. 107 pp., 2 pis. 

Correspondence should be addressed to 

THE DIRECTOR, 

MAY, 1904. 

UNITED STATES GEOLOGICAL SuRVEY, 

WASHINGTON, D. 0. 
LIBRARY CATALOGUE SLIPS. 

[Mount each slip upon a separate card, placing the subject at the top of the 

second slip. The name of the series should not be repeated on the series 

card, but additional numbers should be added, as received, to the first 

entry.] · 

Spencer, Arthur C[oe]. 

~ . . . The copper deposits of the Encampment district, 

~ Wyoming, by Arthur C. Spencer. Washington, Gov't 

-= print. off., 1904. 

107, III p. illus., 2 pl. (maps in pocket). 29! x 23cm. (U.S. Geological 

survey. Professional paper no. 25.) 

Subject series: A, Econ6mic geology, 32; B, Descriptive geology, 37. 

Spencer, Arthur C [ oe] . 

. . . The copper deposits of the Encampment district, 

~ Wyoming, by Arthur C. Spencer. Washington, Gov't 

r: print. off., 1904. 

~ 

i 

107, lll p. illus., 2 pl. (maps in pocket). 29! x 23cm. (U. S. Geological 

survey. Professional paper no. 25.) 

Subject series: A, Economic geology, 32; B, Descriptive geology, 37. 

u.s. Geological survey. 

Professional papers. 

rn no. 25. Spencer, A. ·C. The copper deposits of the 

Encampment district, Wyoming, 1904. 

u.s. Dept. of the Interior. 

~ 

~ see also ~ 

U. S. Geological survey. 

ni