DEPARTMENT OF THE INTERIOR 

UNITED STATES GEOLOGICAL SURVEY

GEORGE OTIS SMITH, DIRECTOR

BULLETIN 504

THE

SITKA MINING DISTRICT

ALASKA

BY

ADOLPH KNOPF

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1912

CONTENTS.

Page.

Preface, by Alfred H. Brooks__________________________ 5

Introductory statement______________________________ 7

Historical notes__________________________________ 8

Geographic sketch._:____j_______________________ 8

Climate _____________________.._______.___________ 10

Glaciation _____________________________.________ 10

General geology _________________________.____ 11

Stratified rocks________________________________ 11

Intrusive rocks__ _ . ~ . ._. 15

Deep-seated rocks___________________.'_____..._ 15

Dike rocks...___________________..__________ 16

.Relation of intrusive rocks to mineralization______________ 16

Kiag Bay _______________________________ 18

Geography and history_________________ ______ 18

General geology ___________________________ 18

Petrography _________. .._________________ 20

Economic geology________________..__________..__.._ 21

Special descriptions__________ ______________ 22

Chichagoff mine_____________________________ 22

Golden Gate mine____:_____________________ 24

Hirst Cove Mining Co__- _________________________'._ 25

Other prospects________ ____ ____ 25

Princess Pinder prospect________________________ 26

Sitka ________ __________________________ 26

General geology________________________________ 26

Ore deposits___ ______ __ ______..____ ?__ 26

Special descriptions. ___________________ _______ 27

Cache mine___________ __ _ - 27

Bauer mine_________________________..______ 27

Cascade claim_______________________.______ 28

Lucky Chance mine____________________________ 29

Other prospects_____________________________ 29

Nonmetallic resources______________________________ 29

Granite ______________________________.________ 29

Gypsum ______________________________________ 30

The gypsum deposit____________________________ 30

Mine developments___________________________ 30

Market __________________________._______ 31

Conclusion_________________________*______________ 31

3
ILLUSTRATIONS.

Page. 

PLATE I. Geologic reconnaissance map of the Sitka and Juneau mining

districts __________________________________ 10 

FIGTJKE 1. Prospects at Klag Bay__________________________ 19

2. Section across strike of rocks at head of Klag Bay_______ 20

3. Claim map of Chichagoff and Golden Gate properties______r 22

4. Prospects in the vicinity of Sitka and Silver Bay_______ 2S 

4
PREFACE.

By ALFRED H. BROOKS.

The first attempt at lode gold mining in Alaska was made near 

Sitka in 1871 but was soon abandoned. In the succeeding quarter of a 

century but little was accomplished in this field toward establishing 

productive enterprises. An era of commercial mining was begun 

by the discovery of gypsum deposits near lyoukeen Cove about 1902 

and of auriferous lodes near Klag Bay in 1905. The output of the 

mines at these localities, which are on Chichagof Island, in the Sitka 

district, has helped to swell the value of the annual mineral production of Alaska.

Several geologists have visited the Sitka region since 1895 and brief 

reports regarding its mineral resources have been published, but most 

of these are out of stock at the Geological Survey. The growing 

interest in the mineral resources of this field led to their further 

investigation by Mr. Knopf in 1909 and to the preparation of this 

report, which summarizes all the data thus far collected. Its preparation and publication is in accord with the general plan to publish 

summary accounts of the geology of the mining districts of Alaska as 

fast as circumstances permit. In conformity with this plan reports 

have already been published on the Ketchikan, Wrangell, Juneau, 

Berners Bay, and Porcupine mining districts of southeastern Alaska.1

As the areal geology and the stratigraphic sequence in the Sitka 

district are still imperfectly known, this report is necessarily of a 

preliminary character; but if the mining industry of the Sitka district 

continues to advance, more thorough studies will be undertaken as 

soon as circumstances permit.

Mr. Knopf's conclusion, here set forth, that the graywacke-slate 

belt paralleling the line of granite intrusives along the western side 

of Chichagof and Baranof islands is a promising field for the occurrence of auriferous lodes should be of interest to the prospector. His

1 Wrlght, C. W., The Porcupine placer district, Alaska: Bull. U. S. Geol. Survey No. 

236, 1904, 35 pp. Spencer, A. C., The Juneau gold belt, Alaska; Wrlght, C. W., A reconnaissance of Admiralty Island, Alaska: Bull. U. S. Geol. Survey No. 287, 1906, 161 pp. 

Wrlght, C. W. and F. E., The Ketchikan and Wrangell mining districts, Alaska: Bull. 

U. S. Geol. Survey No. 347, 1908, 210 pp. Knopf, Adolph, Geology of the Berners Bay 

region: Bull. U. S. Geol. Survey No. 446, 1911, 58 pp.

5
6 PREFACE.

suggestion that the graywackes and slates may be of Jurassic or Cretaceous age, and not Paleozoic, as hitherto supposed, may have an 

important bearing on the geology of other parts of Alaska. These 

rocks have generally been correlated with the Orca group of Prince 

William Sound, whose age is undetermined but is supposed to be 

Mesozoic.
 THE SITKA MINING DISTRICT. ALASKA.

By ADOLPH KNOPF.

INTRODUCTORY STATEMENT.

In the following report the writer aims to present a brief sketch 

of the geology of the Sitka mining district, with especial reference 

to the mineral resources of the west coast. The mining industry of 

the district has been in a state of nearly complete stagnation during 

the last decade, but the discovery of high-grade gold ore in 1905 at 

Klag Bay, 50 miles north of Sitka, and the subsequent prosperous 

career of the mine founded on the original discovery have given a 

new impetus to development and have attracted attention to the 

comparatively unprospected territory on the west coast of Chichagof 

Island.

The data on which this report is based are drawn from various 

sources. In June, 1910, the writer spent three weeks in investigating 

the geology at Klag Bay and the surrounding inlets and subsequently 

spent a few days in examining the prospects in the vicinity of Sitka. 

To supplement the data obtained from his own field work the writer 

has drawn freely on the unpublished field notes of F. E. and C. W. 

Wright, and has examined their collections and microscopic thin 

sections. In 1904 F. E. Wright made a reconnaissance study of the 

geologic section from Taku Inlet to Sitka by way of Peril Strait and 

investigated the geology of Silver Bay and the west coast of Baranof 

Island as far south as Whale Bay; in 1905 C. W. Wright made a 

reconnaissance trip along the east coast of Baranof Island and 

around Chichagof Island. Brief preliminary accounts of these investigations have already been published,1 but owing to unforeseen 

circumstances more detailed reports were not prepared. Because of 

the writer's partial familiarity with the field it became his task, in 

view of the renewed interest in the region, to assemble the known

1 Wright, F. E. and C. W., Economic developments in southeastern Alaska: Bull. U. S. 

Geol. Survey No. 259, 1905, pp. 55-58. Wright, C. W., Lode mining in southeastern 

Alaska: Bull. U. S. Geol. Survey No. 314, 1907, pp. 59-61. Wright, *F. E. and C. W., 

The Ketchikan and Wrangell mining districts, Alaska: Bull. U. S. Geol. Survey No. 347, 

1908, p. 84.

7
8 THE SITKA. MINING DISTRICT, ALASKA.

facts concerning its geology and mineral resources. The area is 

large and much of it is geologically unexplored and the knowledge 

of it is correspondingly meager, but it has nevertheless been thought 

worth while to bring together the existing geologic data.

HISTORICAL NOTES.

The first attempts at lode mining in Alaska under the American 

regime were undertaken in the vicinity of Sitka in 1871. This work 

was done on a quartz ledge outcropping at the falls of Indian Eiver, 

1 mile east of Sitka. Although no serious efforts were put forth, the 

matter aroused some local excitement, and news of the discovery 

appeared even in San Francisco newspapers. In 1872 three placer 

miners discovered near the head of Silver Bay the quartz ledge subsequently known as the Lower ledge, but it was considered valueless 

by them. Some of the ore was seen by Nicholas Hayley, who had 

previously worked in the mines at Grass Valley, Cal., and the 

Comstock, and who was then serving in the garrison stationed at 

Sitka, and the lode was located by him. Late in the same year he 

discovered the Stewart ledge, which was named after Maj. Joseph 

Stewart, United States Army. Before 1880 many other ledges had 

been discovered in the district around Silver Bay. In 1879 a 10- 

stamp mill was erected on the Stewart property.

Petroff,1 writing in 1880, says:

Discoveries of gold-bearing quartz have been made on Baranof Island, in 

the immediate vicinity of Sitka, only since the transfer of the Territory, and 

for a time quite an excitement was created; but now these ledges are scarcely 

worked at all, being simply held by the owners for further developments or 

until some process can be discovered for working with profit the peculiar 

grade of ore existing there.

In the winter of 1880-81 a considerable part of the population of 

Sitka participated in the stampede that led to the founding of Juneau. After the lapse of nearly 40 years since the original discovery 

of gold-bearing quartz, none of the properties at Silver Bay have 

been put on a productive basis. During that time some remarkable 

mining failures have taken place on Baranof Island, those at Rodman Bay and Pande Basin being well known throughout southeastern 

Alaska. This state of affairs led to the nearly complete extinction of 

all interest in lode mining in the Sitka district,' and it is only since 

the discovery of gold ore at Klag Bay on Chichagof Island in 1905 

that interest has in some measure revived.

GEOGRAPHIC SKETCH.

The Sitka mining district comprises Chichagof, Baranof, and 

Kruzof islands, together with a few smaller islands. The total land 

area roughly approximates 4,500 square miles, the greater portion of

1 Tenth Census, vol. 8, Report on the population, industries, and resources of Alaska, 

p. 30.
GEOGRAPHIC SKETCH. 9

which is included in Chichagof and Baranof islands. Those two 

islands form in effect a single land mass, gradually tapering southeastward, separated into two parts only by a narrow body of water 

known as Peril Strait. Its extreme length from Point Adolphus on 

the north to Cape Ommaney on the south is 150 miles, and the average width is 30 miles. On the east the islands are separated from the 

other islands of the Alexander Archipelago by Chatham Strait, on 

the north they are separated from the mainland by Icy Strait, and on 

the west they are bordered by the Pacific Ocean.

The topographic features of the islands are entirely similar to 

those of the remainder of southeastern Alaska. The coast line is 

indented by numerous bays and fiords, many of which, like Tenakee 

Inlet and Whale Bay, penetrate far inland into the heart of the 

islands and render territory accessible that is otherwise nearly impenetrable. The relief is rugged and the mountains rise abruptly 

from the shore, at many places forming bold cliffs, hundreds of feet 

high, surmounted by precipitous slopes, rising 2,000 to 3,000 feet. 

The ruggedness increases toward the interior of the islands, and little 

is yet known concerning the inland portion of this region. In general, the altitudes range from 2,000 to 4,000 feet.

The region is well forested with coniferous species, mainly hemlock, spruce, and cedar, both red and yellow. Jack pine is found in 

small amount and is limited to open, boggy parks, being apparently 

unable to compete in the more favorable situations with the other 

conifers.

On the west coast, as at Klag Bay, the timber line reaches 1,500 feet 

above sea level, but in protected localities it reaches 2,500 feet. The 

diameter and height of the trees vary considerably from place to 

place; at Klag Bay, for example, 18 inches appears to be the average 

diameter, whereas along Indian River, east of Sitka, magnificent 

trees are common, spruces as much as 6 feet in diameter and 175 feet 

in height having been noted. As a rule, the supply of timber is adequate for general mining purposes, but the stand of logging timber 

is comparatively small and is soon exhausted at any one locality.

A thick and luxuriant undergrowth is common in the forest and 

consists largely of blueberry brush and devil's club, with various 

other kinds of growth, such as willow, alder, salmon berry, and the 

high-bush cranberry. On account of the frequent rainfall this undergrowth is almost continuously wet, and this feature, together with its 

jungle-like character and the numerous windfalls of timber, make the 

forest a formidable obstruction to the prospector.

The geographic and climatic features, as well as the forest, impose

limitations on the prospector's activities. As the waterways furnish

the only means of communication with the centers of supply, which

are few and widely separated, a boat, preferably a power boat, be16367° Bull. 504 12 2
10 THE SITKA MINING DISTRICT, ALASKA.

comes a necessary part of the prospector's equipment. The waters 

are often rough and stormy, the islands are exposed to the open ocean, 

and in winter the heads of the bays are frozen up all conditions that 

tend to restrict prospecting to the summer months. In order to 

utilize the few favorable months of the year as effectively as possible, 

prospecting has hitherto been confined mainly to examination of the 

shore-line exposures and to the country closely bordering the coast.

CLIMATE.

The climate of the region is cool-temperate and humid. The precipitation is heavy, the number of rainy days is large, and foggy and 

cloudy weather is of frequent occurrence. » .

Records have been kept for a longer period at Sitka' than at any 

other Alaska station, so that unusually full statistics concerning the 

climatic features are available. The mean annual temperature at 

Sitka is 44° F. The mean monthly temperature for February, the 

coldest month, is 33°, and for August, the warmest month, 56°, the 

mean annual range being thus only 23°.

The average annual precipitation, including melted snow, is 88 

inches, and the extremes on record since 1868 are 59 and 140 inches. 

The average number of days during which precipitation takes place 

is 208. At sea level the precipitation is usually in the form of rain, 

but there is a considerable snowfall on the mountains, which, even 

at moderate altitudes, often remains until late in summer.

Climatic table for SitJsa, AlasJca.a

Length of record.

Mean temperature, °F. : 

Jan., 1828, to Dec., 

1876.............

Apr., 1881, to Sept., 

1887.............

Mean precipitation, Including melted snow, 

inches...............

Mean number of days 

with 0.01 inch or 

more precipitation. . .

Jan.

31.4

34,5?

« 

1? 17

16.8

Feb.

DO Q

33.0

7.47

15.9

Mar.

qc c

37.2

6,70

18.0

Apr.

4(1 R

41,9

fi 61

16.2

May.

47.0

46.9

4.11

16.1

June.

V) A

51.6

3.31

13.6

July.

55.4

54,4

3.56

14.9

Aug.

KE Q

56.6

584

16.8

Sept.

C1 C

52.3

9.67

19.5

Oct.

d4 Q

45.7

11.96

21.7

Nov.

5Q 1

39.8

9.80

19.5

Dec.

oo >

36.0

7.88

18.9

Ann,

41 <*

445

88.10

207.9

o These statistics are taken from the more comprehensive tables in Geography and geology of Alaska, 

by Alfred H. Brooks, with a section on climate by Cleveland Abbe, jr.: Prof. Paper U. S. Geol. Survey 

No. 45,1906.

GLACIATION.

The present-day glaciation is represented, so far as is now known, 

by a few small glaciers only, but doubtless a number of others will be 

discovered when the interior of the islands becomes better known. 

At Pande Basin, east of Sitka, a glacier occupies the hanging valley at 

the head of the basin; and another smaller glacier, known as Valdenar 

Glacier, lies at the head of Green Lake Valley, east of Silver Bay.
U. S. GEOLOGICAL SURVEY BULLETIN 504 PLATE I

LEGEND 

STRATIFIED ROCKS

Recent

basaltic lavas and tuffs

BRJTISH/COLUMQ,

Comprising sandttone,

rhyohtic lavas and tvffa

comprising grayiuankea,

elates, conglonterates. and

andesitir. lavas cmd'tiifft

phyllites, and<green6tonc

INTRUSIVE ROCKS

Granite, granodiovlte,

Porcupine placers 

"Nugget Creek placers 

Kensington mine 

Johnson mine 

Comet mine 

Jualin mine

Yankee Basin prospects 

Eagle River mine 

Bessie mine 

Aurora Borealis mine 

Peterspn prospect' 

Montana Basin prospects 

McGinnis Creek prospects 

Wagner prospect 

JuaTpa Placer mine 

Ebner mine 

Alaska JuneaiT mine 

Alaska Perseverance mine 

Sheep Creek mine 

Treadwell group of mines 

Alaska Treasure mine

'Funter Bay prospects 

Mammoth group 

Snettisham mine 

Sumduiin mine 

Windham Bay prospects 

Holkham Bay. prospect 

Lituya Bay placers 

Chicnagoff mine 

Golden Gate mine 

Cache mine 

Lucky Chance mine 

Portage Mountain prospects 

Olympic mine 

Pacific Coast Gypsum Co.'

GEOLOGIC RECONNAISSANCE MAP OF THE SITKA AND JUNEAU MINING DISTRICTS.

After F. E. and C. W. Wright.
STRATIFIED BOCKS. 11

Evidence of a former greatly extended glaciation, of which the 

present glaciation is the vanishing remnant, is everywhere visible. 

The deeply fiorded character of many of the waterways is the most 

im-. lediate token of the former glacial occupancy of the region, and 

this evidence is^borroborated everywhere by smaller and more local 

features due to glacial action. These consist of polished and striated 

surfaces and of glacial drift several feet thick containing striated 

bowlders.

At Klag Bay broad, glacially smoothed surfaces were found up to 

an altitude of 1,300 feet on the flank of Doolth Mountain, an isolated 

mountain which is too small to have supported an independent glaciation. The smooth, flattish summit, reaching an altitude 2,100 feet 

above sea level, may itself owe its form to the action of an overriding 

ice sheet, for the neighboring mountains that attain higher altitudes 

show serrate profiles. As Doolth Mountain practically stands on the 

shore of the Pacific Ocean, these figures furnish a rough estimate of 

the minimum thickness of the ice sheet as it reached the open ocean 

during the glacial epoch.

GENERAL GEOLOGY.

The rocks of Chichagof and Baranof islands lie in broad belts that 

strike northwest and southeast, conforming with the prevailing 

structural trend of southeastern Alaska. The core of the islands is 

made up largely of granitoid rocks, mainly quartz diorites, which, 

as a rule, have been intruded parallel to the stratified rocks. The 

general distribution of the rocks is shown on the sketch map forming 

Plate I.

STRATIFIED BOCKS.

The oldest rocks consist of cherts, commonly brecciated and folded, 

and banded quartzite resembling graywacke. Small dikes of melaphyre cut the strata at numerous localities. These rocks outcrop for 

several miles along the north shore of Chichagof Island, between 

Idaho Inlet and Port Frederick, and continue southeastward from 

Port Frederick to Point Augusta. Although the thickness of this 

series of rocks has not been determined, it is believed to exceed several thousand feet. On the west at Idaho Inlet the rocks are intruded by light-colored quartz diorite, which is gneissic along the 

contact and has altered them to a compact biotite schist.

The overlying rocks are cherty limestones of Silurian age, as determined by fossils found at Port Frederick and Freshwater Bay. 

They are particularly well exposed along the south side of Freshwater Bay, where they have been studied in some detail.1 The rocks 

stand nearly vertically and are over 1,000 feet thick, the lower two1 Kindle, E. M., Notes on the Paleozoic faunas and stratigraphy of southeastern Alaska: 

Jour. Geology, vol. 15, 1907, p. 322.
12 THE SITKA MINING DISTRICT, ALASKA.

thirds of this thickness consisting of dark-gray, thinly laminated 

limestones. Above the Silurian at this locality are 50 feet or more of 

Middle Devonian limestone, stratified in beds 1 to 4. feet thick.

A thick series of melaphyre lava flows and tuffs interstratified with 

limestone beds of Upper Devonian age is exposed on the northeast 

side of Freshwater Bay and forms a belt of rocks extending northwestward to Port Frederick. As the tuff beds are fossiliferous, it 

is probable that the -lavas were erupted under submarine conditions. 

The melaphyres are mainly altered basalts, red, green, or black in 

color, the red being perhaps the most common. They are dense 

grained rocks and show a porphyritic texture, due to the presence of 

scattered crystals of feldspar.

Somewhat over 1,000 feet of limestone of Mississippian (lower 

Carboniferous) age overlies the melaphyres and is exposed in Port 

Frederick and along the northeast shore of Freshwater Bay. Concerning the latter locality Kindle reports: 1

On the northeastern side of the bay, and opposite the Silurian and Devonian 

limestones already described, the Carboniferous limestones form a low, narrow 

peninsula, never more than a few hundred yards in width, projecting out 4 

miles from the mainland. The strike varies from N. 35° E. to N. 40° W., but 

generally has a northwesterly and southeasterly trend. The dip is high, frequently 909 . It is sometimes easterly and sometimes westerly, the direction 

of dip depending on whether or not the limb of the large fold to which all 

this peninsula and the older beds on the south side of the bay belong is slightly 

overturned at any given point. The thickness of the several divisions of the 

limestones which are exposed along the north shore of this peninsula is indicated approximately in the following section, which begins about one-half mile

above (northwest of) North Passage Point:

Feet.

e. Breccia of large gray limestone fragments ___________ 100

d. Hard gray limestone, much fractured by numerous irregular 

joints, and breaking into small irregular fragments on 

weathering. Large Productoids common. Dip, 30° to 90° 

toward southwest. Strike, N. 40° W_________ __ 90

c. Gray limestone with frequent bands of black chert. Fossils 

scarce. Dip, 80° to 90° NE. Strike, N. 10° to 20° W___ 275

b. Dark-gray limestone with black chert bands. Fossils 

abundant near upper and lower limits. Average strike, 

N. 30° E. Dip, 70° to 80° NW_______________ 250

a. Limestone similar to b. Corals common _ __ 275

990

At lyoukeen Cove, Freshwater Bay, gypsum beds have been found 

associated with cherty limestones, which apparently overlie the lower 

Carboniferous rocks exposed along the southwestern shore of the 

cove. They are provisionally regarded as of Permian or Triassic age.2

iQp. cit., pp. 330-331.

2 Wright, C. W., The building stones and materials of southeastern Alaska: Bull. U. S. 

Geol. Survey No. 345, 1908, p. 125.
STRATIFIED ROCKS. 13

Along the west coast of Chichagof and Baranof islands the rocks 

appear to be divisible into two large subdivisions. The easternmost 

of these that is, the belt of rocks lying against the granitic axis 

of the islands consists of greenstones and phyllites, associated with 

limestones, cherts, calcareous chlorite schists, and amphibolite schists.

The phyllites and schists are remarkably crinkled and contorted 

and in many places are gnarled and laminated with knots and veinlets of quartz. The greenstones, limestones, and cherts show at some 

localities a profound fracturing and brecciation, so that the rocks 

are in fact recemented rubbles. This feature is strikingly displayed 

along the shores of Nakwasina Passage and Katlian Bay, a few miles 

north of Sitka. Greenstone from Lisianski Peninsula, on Nakwasina Passage, proves microscopically to be an andesite of microlitic texture; tuffs and amygdaloids, as at the head of Ford Arm, 

form part of the greenstone series, so that without doubt they represent a succession of much-altered surface volcanic rocks. Fossils 

have not been found in any of the associated rocks, so that the age 

of this series of rocks is not known. By analogy with the Juneau 

region it has been surmised that they are of upper Carboniferous 

age.1

To the west of these rocks is a belt of graywacke and slate, which 

forms the bedrock at Silver Bay, Sitka, and Klag Bay. The strike 

is northwest-southeast and the dip is steep southwest, commonly 

70° or higher. At many places the designation " slate-graywacke 

formation" is apt to convey a misconception as to the relative 

abundance of slate. At Sitka, for example, graywacke constitutes 

such a preponderant proportion of the formation that all the surface 

exposures consist essentially of that rock. East of the mouth of 

Indian River massive outcrops of graywacke several hundred feet 

thick appear, which show no discernible stratification. At one point 

near Indian River a 10-inch belt of fine conglomerate, trending N. 

70° W., was noted. The matrix of this conglomerate is thoroughly 

lithified, so that the rock breaks across the pebbles. This stratum of 

conglomerate is not separated, as in ordinary sedimentary rocks, by 

sedimentation planes, but grades irregularly, though abruptly, into 

the inclosing graywacke.

The graywackes were designated " pyroclastic diorites " by Becker 2 

and locally are usually referred to as diorites, but the sedimentary 

character of the graywackes has been uniformly recognized by all 

other geologists who have examined them.

Conglomerate and conglomeratic graywacke occur at Old Sitka. 

The pebbles of these rocks comprise slate, schist, chert, andesite, and

iWright, F. E. and C. W., The Ketchikan and Wrangell mining districts, Alaska: 

Bull. U. S. Geol. Survey No. 347, 1908, p. 56.

3 Becker, G. F., Reconnaissance of the gold fields of southern Alaska, with some notes 

on general geology: Eighteenth Ann. Rept. U. S. Geol. Survey, pt. 3, 1898, p. 43.
14 THE SITKA MINING DISTEICT, ALASKA.

felsite. To the west the conglomerate is overlain by a great thickness of obscure rocks, possibly indurated argillites, much fractured 

and interlaced with quartz veinlets, whose derivation has not been 

satisfactorily determined. These in turn are overlain by conglomeratic graywacke carrying pebbles 2 to 3 inches in diameter and 

by the blue-gray colored graywacke typical of the Sitka region.

The slate-graywacke formation has so far proved to be unfossiliferous, and its age remains unknown. It is believed to rest unconformably on the greenstones and associated rocks to the east, but this 

unconformable superposition, if it exists, has not yet been observed 

in the field. The lithologic difference and the probably superior degree of metamorphism of the underlying rocks strongly suggest unconformity. So, too, does the character of the pebbles in the conglomerate beds; but as these beds are not basal conglomerates this fact is not 

conclusive, but is open to other interpretations. It is well to point 

out that a considerable volume of green graywackes, whose recognition and discrimination from greenstones is not possible by the 

unaided eye, underlies the conglomeratic beds'at Old Sitka. The 

peculiar character of these graywackes may be due either to the fact 

that they represent transition strata or, on the other hand, that they 

are derived immediately from the underlying rocks.

The graywacke-slate formation has been tentatively assigned to the 

Permian.1 It is not an unreasonable conjecture, pending the accumulation of stronger evidence, to suppose that it may eventually prove 

to be of the same age as the Berners formation of the Juneau region, 

late Jurassic or early Cretaceous. In lithology and degree of metamorphism of the graywackes arid slates it bears a striking similarity 

to that formation.

The youngest rocks of the region are the postglacial lavas and tuffs 

that make up the volcanic cone of Mount Edgecumbe on Kruzof 

Island. It is reported, upon somewhat questionable evidence, that 

Mount Edgecumbe was in eruption as late as 1796.2 The volcanic 

rocks are mainly basic andesites or basalts and display a striking 

diversity of color, texture, and crystallinity. They include black 

glasses, frothy pumices, and gray holocrystalline lavas. A lava collected at the shore east of Mount Edgecumbe consists of a gray, 

highly porous rock which is thickly studded with glassy tabular 

plagioclase feldspars, ranging in length from three-tenths to fourtenths of an inch. According to a rough estimate the feldspar phenocrysts form half the bulk of the rock. Small glassy grains of olivine 

are sparingly scattered throughout the rocks. Under the microscope 

the plagioclase phenocrysts prove to be a calcic labradorite near

1 Wright, F. E. and C. W., Bull. U. S. Geol. Survey No. 347, 1908, p. 35. 

- Decker, G. F., op. cit, p. 13.
INTRUSIVE ROCKS. 15

AbjAn3 ; some of the olivine forms crystals large enough to be termed 

phenocrysts, but most of it is found in the mesostasis between the 

feldspar phenocrysts. The mesostasis is holocrystalline and consists 

of a doleritic aggregate of augite and feldspar laths, with accessory 

magnetite and hematite.

INTRUSIVE BOCKS. 

DEEP-SEATED ROCKS.

Extensive masses of granitoid rocks form the central parts of the 

islands. The dominant type is a quartz diorite composed essentially 

of andesine feldspar, quartz, biotite, and hornblende. As a rule the 

dark minerals are not very abundant and the diorites are mediumgrained rocks of light color. At a few localities rocks more basic than

quartz diorite are known. Hornblende gabbro is found at the head of 

Tenakee Inlet, and a highly shattered and sheared gabbro occurs 

along Nakwasina Passage and Katlian Bay. At Port Althorp, on 

the north shore of Chichagof Island, exposures of hornblendite a 

black rock consisting entirely of hornblende form a mass one-fourth 

mile wide.

The intrusive rocks are commonly fresh and unaltered and are 

little affected by schistose or gneissic structures. The marginal portions of some of the intrusive masses, however, show gneissic foliation. At such localities the diorites are flanked by belts of crystalline 

schists, such as amphibolite schists and biotite schists, whoso crystallinity diminishes at increasing distance from the contact. Such 

schists are encountered at widely separated points at Patterson and 

Gut Bays, on the east side of the south end of Baranof Island, and 

along Icy Strait, on the north shore of Chichagof Island.

The intrusive character of the quartz diorite masses is well established, and with the exception of various dike rocks and the recent 

lavas on Kruzof Island they are the youngest rocks of the region. 

On account of their close resemblance to the dioritic rocks of the 

Coast Range on the mainland and their extensive distribution they 

are regarded as part of the great series of deep-seated igneous rocks 

that invaded the province of southeastern Alaska in late Mesozoic 

time.

Some older granitoid rocks may prbbably be included among the 

Mesozoic quartz diorites of the Sitka mining district, but they have 

not been certainly recognized and discriminated from the younger 

rocks on account of lack of detailed observations. The quartz diorite 

gneiss, containing large plates of biotite, at Schulze Head, Peril 

Strait, may belong to such an older series of igneous rocks, but this 

is hardly more than a suggestion. 
16 THE SITKA MINING DISTRICT, ALASKA.

DIKE ROCKS.

Pegmatite and aplite dikes accompany the quartz diorites, and 

lamprophyric dikes have been found at some places. Emerson J has 

described a spessartite dike as occurring at Hot Springs, near Sitka, 

and F. E. Wright has determined others from the same locality to 

be vogesites. The lamprophyric dikes are dark rocks resembling 

diabases, and they appear to be comparatively rare.

The aplite dikes are of greater importance and are widely distributed, though nowhere present in' large numbers. They are finely 

granular white or light-gray rocks, with a tendency to an obscure 

porphyritic texture. They are locally known as porphyries but will 

here be designated diorite aplites. Microscopically they prove to 

have a hypidiomorphic or panidiomorphic granular structure and 

are seen to consist essentially of andesine (AbaAnJ with minor 

amounts of biotite or hornblende. Pyrite, calcite, muscovite, and 

chlorite appear as secondary minerals.

A remarkable feature connected with the diorite aplites is their 

occurrence in the graywacke-slate formation at long distances as 

much as several miles from known areas of the diorite intrusions. 

Equally striking is their uniformity of appearance, so that rockg 

collected from widely separated localities have identical characteristics. On account of their light color the dikes are readily distinguished on shore exposures from the somber-colored graywackes and 

slates that inclose them and on account of their conspicuousness their 

number, which is small, is likely to be overestimated.

RELATION OF INTRUSIVE ROCKS TO MINERALIZATION.

The general geologic investigation of southeastern Alaska has 

shown that most of the mineral deposits so far discovered occur in 

proximity to areas of dioritic rocks. The great masses of diorite are 

themselves practically barren of ore bodies. The conclusion has been 

drawn, from the clustering of mineral deposits around intrusive centers and from other facts, that the mineralization was an effect of the 

diorite intrusions; that the mineral-bearing solutions were expelled 

from great bodies of slowly cooling molten rock that underlay the 

diorites now exposed at the surface; and the metallic contents of the 

highly heated solutions were . deposited in the colder surrounding 

rocks. The connection between intrusion and mineralization in 

southeastern Alaska is most clearly and forcibly illustrated by the 

copper deposits of Kasaan Peninsula and the Hetta Inlet region. 

These deposits are commonly situated at or near the contact of limestone with, intrusive dioritic rocks and form.highly irregular masses

iHarriman Alaska Expedition, vol. 4, p. 18, 1904.
BELATION OP INTRUSIVES TO MINEBALIZATlON. 17

and lenses embedded in the limestone. The ore consists of auriferous 

chalcopyrite associated with iron oxides and sulphides, calcite, and 

various lime silicates, principally the garnet andradite. The deposits 

belong to the so-called contact-metamorphic type of ore bodies and 

their mineralogic make-up shows that they were formed under conditions of high temperature conditions obviously accompanying the 

intrusion of the diorites. Copper deposits of similar origin are 

found also at Rainy Hollow and White Horse, which are in Canadian 

territory but lie in the same metallogenetic province.

The gold-quartz deposits are less evidently of magmatic origin 

than are the contact-metamorphic copper ores. It is a noteworthy 

fact, however, that the gold content of the copper ores is comparable 

in amount with that of the ores exploited solely for their gold content, so that it is possible and perhaps probable that the gold in both 

classes of deposit was derived from the same source. The gold-ore

bodies are found at greater distance from the intrusive masses, and 

payable deposits are not found in the belts of schists flanking the 

intrusive rocks.

The foregoing brief resume of our knowledge concerning the origin 

of mineralization in southeastern Alaska has been presented in order 

to show upon what grounds a wider distribution of mineralization in 

the Sitka mining district than is at present known may be reasonably 

expected.

The extensive masses of dioritic rocks that have invaded the central 

portions of Chichagof and Baranof islands are a favorable geologic 

feature. The known auriferous mineralization took place subsequent to the injection .pf the diorite aplite dikes, and the probability 

is it was an effect of the great diorite invasion. It is a reasonable 

supposition, therefore, that if the mineralization follows the same 

laws that are believed to hold for the rest of southeastern Alaska, 

the long zones flanking the diorite belts constitute the territory in 

which other ore bodies than those now known are most likely to be 

found.

At present the only place in the region under discussion at which 

clear proof of the mineralizing activity of the diorite magma is 

shown is on Lemesurier Island, in Icy Strait. A deposit of molybdenite ore has been discovered here lying at the contact of diorite and 

limestone, the ore consisting of flakes of molybdenite intergrown 

with garnet and other lime silicates. Farther north, at Glacier Bay, 

copper ore, consisting of chalcopyrite in a gangue of garnet and calcite, is found in a similar geologic environment.
18 THE SITKA MINING DISTBICT, ALASKA.

KLAG BAY.

GEOGRAPHY AND HISTORY.

Klag Bay is on the west coast of Chichagof Island and is part of an 

extensive archipelago 1 of which Khaz Bay forms the entrance from 

the Pacific Ocean. The coast north of Khaz Bay is flanked for several miles seaward by rocks, reefs, and low wooded islets.

Khaz Bay lies 16 miles northwest of Salisbury Sound, and the voyage from the mines to Sitka necessitates a coastwise run of 8 to 12 

miles in the open ocean. The total distance to Sitka is 50 miles, and 

the operating mines maintain their own gasoline boats. Freighters 

plying between Seattle and southeastern Alaska bring in occasionally 

heavy machinery and supplies and take out shipments of accumulated 

concentrates.

During the winter the upper 3 miles of Klag Bay is frozen over.

The two productive gold mines in the Sitka mining district are at 

the head of Klag Bay. The high grade of the ore, which yields, as 

milled, from $15 to $90 a ton in gold, greatly exceeds that of the 

average value of the gold ore of southeastern Alaska, which in 1909 

was $2.78 a ton. This has naturally attracted considerable attention 

to the region and has stimulated prospecting of the shores of the 

neighboring bays, inlets, and passages.

Gold was found at Klag Bay by chance in the summer of 1905 

by an Indian engaged in salmon fishing, who went ashore to obtain 

water from a small stream near the head of the bay. While stooping 

to drink he noticed gold in one of the numerous fragments of quartz 

in the bed of the stream. On further examination he found that the 

ore contained considerable more free gold, and soon thereafter the find 

was reported at Sitka. The aid of white men was enlisted and the 

cropping from which the quartz float was derived was quickly discovered. Claims were thereupon located in accordance with the mining 

laws, the original discoverer retaining one-fourth interest. A small 

stampede from Sitka ensued soon after and a large number of claims 

were staked on both flanks of Doolth Mountain in September, 1905. 

(See fig. 1.) Two properties, known as the Chichagoff and Golden 

Gate mines, have been brought to the producing stage.

GENERAL GEOLOGY.

The general geology of the region at the head of Klag Bay is 

exceedingly simple. The rocks consist essentially of thick, massive 

beds of graywacke interstratified with clay slates. The only igneous rocks are a few narrow dikes of diorite aplite. To the northeast 

these rocks are succeeded by a wide belt of greenstones (altered 

amygdaloidal basalts in part), calcareous schists, limestones, and

11 This archipelago is in part shown on Coast and Geodetic Survey Chart 8280.
KLAG BAY. 19

highly contorted black phyllites and amphibolitic schists. This belt 

of metamorphic rocks is succeeded inland by diorite, which appears 

at the coast 15 miles northwest of Klag Bay and is exposed northward to Lisianski Strait.

The graywackes and slates are well exposed along the shores of 

the bay. As a rule they are not intimately interstratified, as is comMINES AND PROSPECTS

I OcWen date mine

3. Hirst Cwe Mining Ca

4. Monte Cnsto prospect 

Silta prospect

7. Anna- pras'pect

81 Big Four prospect

ft Flora prospect

10. JumbQ prospect

Portlook 

Harbor

FIGURE 1. Prospects at Klag Bay.

mon among the graywacke-slate formations of the Juneau region, 

Prince William Sound, and Kenai Peninsula, but form alternating 

belts several hundred feet thick. The graywacke is by far the 

dominant rock and forms massive exposures that are hundreds of 

feet thick and are without discernible stratification. Some strata, as 

shown by absolutely continuous exposures along the shore line,
20 THE SITKA MINING DISTBICT, ALASKA.

attain a thickness of 1,400 feet, and thicknesses in excess of 3,200 feet, 

in which perhaps a few narrow belts of slate are included, have been 

measured at the head of Klag Bay, as shown on figure 2.

The strike of the rocks ranges from N. 40° W. to N. 50° W. and 

the dip is 70° S. Whether the massive beds of graywackes maintain their great thickness for considerable distances along the strike 

was not determined, but it is believed that they will be found to 

dovetail with lenses of slate. The basis of this surmise is the fact 

that near the head of Ogden Passage a marked lenticular interstratification of graywacke and slate was observed. The lenses of graywacke range from a few inches to several feet in thickness and 

swell and pinch abruptly..

The rocks show a cleavage or fissility which is best displayed in 

the argillaceous members and is but poorly developed or absent in 

the graywackes. It coincides in direction with the stratification.

Golden Gate millT___^ Beach

Graywacke Slate Diprite aplite 

0 1000 2000 3000 4000 5000 Feet

FIGURE 2. Section across strike of rocks at head of Klag Bay.

Locally the slates show considerable plication, with tearing and 

kneading of thin intercalated strata, but no evidence was procrred 

that folding on a more extensive scale has taken place.

PETROGRAPHY.

The graywackes are sedimentary rocks impure sandstones 

which are so firmly cemented that they fracture across rather than 

around the component mineral grains. They are exceedingly hard 

and tough and in color range from gray to blue-gray, usually weathering to an ash-gray tint on exposed surfaces. The outcrops are 

considerably jointed, so that the rock breaks in large angular blocks.

As a rule none of the mineral particles that go to make up the 

graywackes are distinguishable by the eye. The texture, however, 

varies considerably in different beds, and in the coarser-textured 

varieties of graywacke much glassy quartz can readily be detected in 

the form of numerous angular particles. All graywacke beds show 

the presence of many small angular fragments of black slate. Under 

the microscope the graywackes are found to consist largely of angu-
KLAG BAY. . 21

lar grains of quartz and feldspar, mainly plagioclase. The grains 

are poorly sized; the smaller are sharply angular, but many of the 

larger particles show rounded corners. Kock fragments are of common occurrence and comprise slate and other sedimentaries and pilotaxitic andesite, some of them perfectly rounded. The mineral particles do not form a closely fitting mosaic on account of the presence 

of a fairly large proportion of argillaceous matrix.

ECONOMIC GEOLOGY.

The ore bodies at the head of Klag Bay consist of quartz lodes 

occupying shear zones in graywacke. They coincide in strike and 

dip with the stratification and schistosity of the inclosing country 

rock. On account of the thick-bedded character of the graywacke, 

only the roughly schistose structure and not the stratification of the

wall rocks is as a rule determinable near the lodes.

The ore bodies range in thickness from a few inches to 18 feet or 

more; in the producing properties the average thickness is perhaps 

5 or 6 feet; in the prospects it is a few inches or at most a few feet. 

The values are localized in short shoots. In some lodes the fissuring is 

continuous for considerable lengths, but the fissured zone is barren of 

quartz and consists of sheared triturated graywacke; in other lodes 

the quartz is continuous but the gold values cease.

In the vicinity of the lodes the graywacke has been reduced to a 

black, highly-polished and irregularly schistose or slaty condition. 

In the midst of the sheared rock there remain numerous lenses and 

horses of massive graywacke. In places the shear zone may be 30 or 

more feet in width and correspondingly leanly mineralized.

The lodes show a well-marked ribbon structure, which is emphasized by the fact that the separate ribbons of quartz are separated by 

thin slabs of black schistose graywacke. These partings range from 

mere filaments to slabs several inches thick. As the quartz breaks 

free and clean from them, they often deceptively appear to form the 

walls of the ore body, but when they are broken through, more ore 

is commonly found behind them. Slabs of the lode slack off across 

the ore body up to such apparent walls, but however regular and well 

defined these walls may appear to be, not much reliance can be 

placed on the presumption that they mark the limits of profitable ore. 

Where the partings of schistose graywacke become thick and numerous the ore body becomes a typical stringer lode and a corresponding 

decrease in the grade of the ore takes place. In the ore shoots, however, the lodes consist practically of solid quartz.

The foregoing structural features of the ore bodies suggest that 

from a principal level driven along the general trend of the shear 

zone numerous crosscuts should be made into both the hanging wall
22 THE SITKA MINING DISTBICT, ALASKA.

and the footwall. Not only do the apparent walls prove unreliable guides concerning the ore bodies but it is conceivable that where 

large horses of gray wacke occur in the shear zone, the ledge may split 

and curve around the massive rock and on resuming its general trend

may follow a parallel course at a distance 

of some feet in either the footwall or the 

hanging wall of the original course.

The mineralogy of the ore is simple. 

The gangue is a milk-white quartz of 

drusy texture, with which a small amount 

of carbonate is associated. This weathers 

red on the dumps and is therefore plainly 

evident. In addition the microscope shows 

that some albite occurs with the carbonate. 

The quartz carries a considerable number 

of fragments of slaty graywacke, which 

are found microscopically to be completely 

sericitized.

Pyrite is the most abundant metallic 

mineral; galena and free gold are the only 

other metallic minerals. The presence of 

galena with the pyrite indicates everywhere 

high values in gold. The pyrite occurs not 

only in massive form but as deeply striated 

cubes in the vein quartz and also as 

minute cubes in the neighboring wall rock. 

Galena is relatively rare and is as a rule 

intergrown with pyrite; it does not occur 

in the wall rocks. The gold is found 

both as isolated particles embedded in 

the quartz and as particles intergrown with the sulphides.

The ores are fresh and show little evidence of oxidation, the unaltered sulphides extending practically to the surface a fact undoubtedly due to the glacial abrasion that the region has undergone 

in the recent geologic past.

SPECIAL DESCRIPTIONS.

Ohichagoff mine. The Chichagoff mine, usually known as the 

DeGroff mine, is now the property of the Chichagoff Gold Mining 

Co. It is situated at tidewater at the head of Klag Bay (fig. 3). 

The milling plant in operation during 1910 consisted of two batteries 

of two 850-pound stamps, dropping 104 times a minute in triple discharge mortars. The ore was crushed to one-fourth inch mesh, and the 

pulp passed to a 10-foot Chilian mill. The concentrating equipment

Chichagoffmm

o spo_____looofeet

FIGURE 3. Claim map of Chichagoff and Golden Gate properties.
KLAG BAY. 23

includes a classifier, two Wilfley tables, and one Wilfley slime table. 

The capacity of the mill was 20 tons a day. At present the tailings, 

which average nearly $10 a ton, are impounded for future cyanidation. Electric power is employed, which is transmitted 4-| miles from 

the generating station on Sister Lake. The hydroelectric plant and 

transmission line is under the control of a company jointly owned by 

the Chichagoff Gold Mining Co. and the Golden Gate Mining Co., 

both of which it supplies with power. The plant is rated at 150 horsepower and is driven by a turbine under 44 pounds pressure. In 

summer enough water is available to develop several times this power, 

but the capacity of the plant is fixed by the minimum winter flow.

In the summer of 1910, because of increased development of the 

mine and the inefficiency of the Chilian mill, it was decided to erect 

a new mill of standard design equipped with 10 stamps of heavier 

pattern. This mill will doubtless be in operation during 1911,

The ore body was found in 1905, as already related, by tracing to its 

source the quartz float so abundantly strewn in the bed of the small 

stream. The lode did not outcrop along the shore, but was found in 

place one-quarter of a mile inland, at an elevation of 275 feet. At the 

outcrop the lode ranged from 2 to 4 feet in Avidth. The float ore was 

carefully gathered and shipped to the smelter at Tacoma. This ore 

was rich enough to yield betweent$15,000 and $20,000. The proceeds 

were applied to development work and the mine has paid its own way 

from the start. A drift tunnel 220 feet long was run on the ledge and 

two ore shoots were encountered, the second of which was 18 feet wide 

at a maximum and averaged $63 a ton across this width. Later a 

second tunnel was driven 162 feet vertically beneath the upper tunnel, commencing behind the mill, which is situated at the beach. 

Ore was encountered at 800 feet from the portal, apparently belonging to the bottom of the first ore shoot. A raise was put through to 

the upper tunnel, and the ore thus developed is now being stoped. 

Unexpectedly it was found that the ore shoot had a considerably 

greater strike length in the intermediate levels than was indicated on 

either the upper or lower tunnel levels. In addition to this encouraging feature the ore shoot maintained its width and remarkably high 

average value. Meanwhile development was vigorously continued on 

the lower tunnel in order to undercut the second ore shoot.

The geologic features at the mine are simple. The bedrock at the 

discovery outcrop is glaciated and covered with several feet of glacial 

drift containing striated blocks and cobbles of graywacke and some of 

diorite. The country rock inclosing the ore body is a nearly massive 

graywacke of dark blue-gray color and dense texture. It proves to be 

exceedingly hard and tough under the drill. In the main tunnel some
24 THE SITKA MINING DISTBICT, ALASKA.

thin beds of slaty argillite were encountered 200 feet from the portal 

and show that the stratification trends N. 55° W. and dips 70° SW., 

conforming to the general strike of the rocks at Klag Bay.

Near the lode the graywacke has been powerfully sheared and has 

been transformed to a black, brilliantly lustrous, schistose rock resembling a polished and slickensided slate. The strike of the shear zone 

along which the ore makes is approximately N. 45° W. and its dip is 

70° SW. Eich ore is limited to. short shoots, but on account of the 

youth of the mine the shape of the shoots is not well known. It is a 

fair inference from the data at hand, however, that they are lenticular 

in both strike and dip. The lode shows in places a pronounced ribbon 

structure and is traversed 'by numerous false walls. Some of these 

walls are remarkably well developed, and it might often be thought 

unlikely that ore would be found behind them.

On the main tunnel level a spur ledge was found making out into 

the footwall country rock at an angle of 30° to the main ore body. 

It was about 8 feet thick, but pinched out at the end of 75 feet. 

The rock included in the angle between the main ledge and the spur 

is more or less shattered and penetrated by quartz stringers and 

impregnated with pyrite.

The metallic minerals in the ore are pyrite, which is by far the 

most abundant, galena, and free gold. According to the mill returns, the sulphides constitute from 2 to 3 per cent of the ore.

GolcLen Gate mine. The Golden Gate property, which is often 

referred to as the Mills property, one of the principal owners being 

Mr. W. P. Mills, of Sitka, is situated on what is undoubtedly the 

northwest extension of the Chichagoff lode. The main haulage tunnel 

is situated at an altitude of 1,000 feet and is connected by an aerial 

tramway with the stamp mill on the beach. The mill is of 10-stamp 

capacity, but only five stamps were installed at the time the mill was 

started in 1910.

The original discovery was made in September, 1905, on an outcrop 

exposed at an altitude of 1,520 feet. Great slabs of the lode lie 

scattered on the mountain side, many over a hundred feet from 

their position in place. Some of these slabs are 10 to 15 feet long. 5 

feet or more wide, and several feet thick. The lode is 10 feet thick at 

the discovery cropping, where a spur ledge making a narrow angle 

with the main ledge extends 300 feet into the hanging-wall country 

rock.

A shoot of richer ore was later discovered lower on the mountain, 

and the development work has so far been directed toward exploring 

this ore. A drift tunnel at an altitude of 1,080 feet was driven on 

the lode and undercuts the ore shoot at a maximum depth of 127 

feet. Subsequently a new tunnel, 80 feet below the older, was driven, 

and forms the main haulage way of the mine.
KLAG BAY. ° 25

Surveys indicate that the Golden Gate and Chichagoff mines are 

situated on the same lode, but actual continuity can not be traced on 

the surface, either because glacial drift and vegetation cover the 

apex of the lode or because the shear zone is barren of quartz 

mineralization along the intervening stretch. Either condition is 

equally probable.

The geologic and mineralogic features of the ore body are similar 

to those of the Chichagoff. The average width of the explored portion of the ore body is somewhat smaller and the grade of ore is 

lower, although it was reported late in June. 1910, that a shoot 

carrying values comparable to those of the older property had been 

encountered.

On the surface 150 feet in the footwall country rock of the lode is 

a dike, which is 100 feet wide at its widest point. It trends parallel 

with the formation and can be traced a few hundred feet only. On

the hanging-wall side the dike consists of a white coarsely granitoid 

rock, which the microscope shows is composed essentially of quartz 

and albite in hypidiomorphic arrangement, but much crushed. Toward the footwall the dike changes, apparently by gradation, into a 

rock resembling a greenstone. The microscope shows that this green 

rock formerly consisted of a coarsely granular assemblage of plagioclase, probably albite, hornblende, and biotite, but that it now consists of brecciated fragments embedded in a fine-grained matrix of 

attrition products composed of hornblende, chlorite, and feldspar.

Hirst Cove Mining Co. The Hirst Cove property is situated on 

the northwest side of Doolth Mountain. A tunnel 800 feet long 

is driven on the lode at 400 feet altitude, at a point one-half 

mile inland from Mine Cove. The lode averages 3 feet in thickness, and the ore resembles that of the Chichagoff and Golden Gate 

mines, though metallic minerals are materially less abundant and are 

usually concentrated in the slaty material inclosed in the vein quartz. 

Some pay streaks remarkably rich in free gold have been encountered. This lode is sometimes considered the northwestern extension of the Chichagoff lode on the southeast side of Doolth Mountain, but it lies too far to the northeast that is, in the footwall of 

the Chichagoff lode to be the extension of that ore body.

Other pi^ospects. A considerable number of prospects, such as the 

Monte Cristo, Flora, Jumbo, Big Four, and others, have been located 

in the region around Klag Bay. The amount of development is 

generally small, and as the geologic features are entirely similar to 

the ore bodies already described individual descriptions are hardly 

necessary. The presence of these prospects indicates that mineralization is widespread throughout the region. The showing at the 

various prospects is commonly not large, but it must be confessed 

that if -only the barren portion of the shear zone of the most produc-
26 ' THE SITKA MINING DISTBICT, ALASKA.

tive mine of Klag Bay were known, it would hardly present a more 

encouraging appearance than that shown by the poorest prospect in 

the region.

Princess Finder prospect. The Princess Finder prospect is not 

on the peninsula between Klag Bay and Ogden Passage, as are the 

others previously described, but is near the entrance of a bay locally 

known as Pinta Bay, 6 or 8 miles northwest of Mine Cove. Ore was 

discovered here in June, 1910, outcropping in the cliffs at the water's 

edge along a shore line that had been more or less thoroughly examined by various prospectors. This fact is of some interest and leads 

to the belief that the shore lines have not been so carefully examined 

but that other prospects will be discovered.

The ore body shows a face of 7 feet of coarse .white quartz carrying some scattered bunches of pyrrhotite admixed with chalcopyrite. 

The trend of the deposit is probably S. 40° E. (true) and the dip is 

80° SW. The footwall is a blue-black slaty rock and the hanging 

wall is a greenstone breccia. Assays of samples taken across the 

entire width of the lode show an average value of $10 a ton in gold.

SITKA.

GENERAL GEOLOGY.

The rocks in the vicinity of Sitka are mainly graywackes and slates 

striking N. 70° W. and dipping steeply to the south. Some, finegrained quartzites, in places so extremely fine grained as to resemble 

light-greenish cherts, are associated with them at various localities.

Igneous rocks are rare. A few dikes of diorite aplite cut the graywackes and slates. One of these dikes has been found to be mineralized and to carry free gold. A crushed dike of dark gabbro, somewhat impregnated with pyrite and pyrrhotite, is exposed on the

northeast side of Bear Bay, an indentation of Silver Bay. The rock 

consists essentially of plagioclase feldspar, near bytownite in composition, and hornblende, probably secondary.

At Bear Lake, east of the bay of the same name, quartz diorite is 

encountered. It is a medium-grained granitic rock composed of 

plagioclase, quartz, hornblende, and biotite, and is of urirform grain, 

color, and appearance. The diorite is somewhat gneissic and banded 

near its contact with the sedimentary rocks, which appear to have 

been considerably altered as a result of the intrusion.

ORE DEPOSITS.

The ore bodies occupy shear zones in graywacke and strike parallel to the stratification of the country rock. The dips are steep 

nearly vertical. The lodes form massive outcrops of white quartz 

up to 15 feet or more in thickness which are apt to show a short len-
SITKA. 27

ticular structure along the strike and to split up into stringer lodes. 

They are irregular in shape, bellying out and constricting abruptly. 

Near the lodes the country rock is much sheared and is penetrated by 

numerous transverse stringers as well as by veins parallel to the shear 

planes.

A characteristic feature of the ore bodies is the insignificant amount 

of metallic sulphides in many ledges an almost vanishing quantity 

contained in the vein quartz; Pyrite, pyrrhotite, and arsenopyrite 

are the principal sulphides; galena and sphalerite have been observed, 

but are extremely rare. The sulphides are at many places concentrated in and around fragments of slate or sheared graywacke included in the ledges, even though the quartz itself is barren.

Ore bodies of a type different from the auriferous quartz lodes 

already described have attracted some attention. These consist of 

beds of shattered quartzite, which is flintlike in texture, recemented 

by quartz veinlets, carrying in places, though rarely, pyrrhotite and 

arsenopyrite. Some quartzite.strata weather so that the surface exposures somewhat resemble vein quartz, but the mineralization is so 

feeble that it is difficult to understand why they should have been 

located as ore bodies.

SPECIAL DESCRIPTIONS.

Cache mine. The Cache mine, located in October, 1872, and originally known aa the Stewart mine, is situated 1| miles east of the head 

of Silver Bay, at an elevation of 720 feet above sea level (fig. 4). A 

10-stamp mill was built in 1879 but has long ago fallen into ruins, 

and the tramways leading to it are thicketed with new growth of 

alders.' The mine has been in litigation for many years.

The ore body, which stands nearly vertical, is opened on three 

levels by drift tunnels aggregating 300 feet in length. The lowest 

tunnel is 160 feet long and trends S. 70° E.; at the mouth the ore 

body is 4 feet thick and increases to a maximum of 13 feet solid 

quartz, its average thickness being about 10 feet. The walls of the 

ore body are extremely curved, dipping in reverse directions from 

place to place. Practically no metallic sulphides are visible in the 

quartz, except a,streak on the south wall, which is fairly mineralized 

with pyrite. The other two tunnels, the upper being about 80 feet 

above the lower, show essentially the same features, but not so much 

quartz.

Bauer mine. The Bauer mine lies 2 miles southwest of the head 

of Silver Bay. The main development consists of a crosscut tunnel 

at an altitude of 1,250 feet. This tunnel, which is 900 feet long and 

intersects the main ore body at a depth of 400 feet, traverses thick 

massive beds of graywacke, which are gritty or conglomeratic at the 

portal, and encounters several smaller ledges striking parallel with
28 THE SITKA MINING DISTEICT, ALASKA.

the formation. At the end a drift 150 feet long is turned off on the 

ore body and trends S. 45° E. The hanging wall is slate and the footwall is graywacke. The ore body consists of cryptocrpstalline quartzite traversed by narrow quartz veinlets and leanly mineralized with 

pyrrhotite.

Cascade claim. This claim is on the east fork of Indian River, 3 

miles from Sitka, and is the only one discovered in the vicinity of

BARANOr GUEEN 'ROSPECT 

X HENRIETTA PROSPECT 

SILVER BAY PROSPECT

GreknLake

IPATTONCLAIM 

yxCACHE MINE 

*%¥£ TOWE^LEDGE

FIGURE 4. Prospects in the vicinity of Sitka and Silver Bay.

Sitka or Silver Bay in recent years. The country rock at this locality consists of cherty quartzite and slate striking N. 55° W. and 

dipping approximately vertical. The quartzite, which is flintlike 

in texture, weathers milk white, so that it resembles a quartz lode. 

The ore body consists of shattered quartzite cemented by quartz veinlets and is in places mineralized with pyrrhotite and arsenopyrite. 

Chalcopyrite is present as an extremely rare constituent. A 5-foot
NONMETALLIC KESOURCES. 29

bed of slate appears to form the wall rock on the southwest side of 

the ore body, but toward the northeast the boundary is indefinite. 

The ore body is exposed by open cutting and is 300 feet long. Its 

width apparently ranges from 4 to 20 feet, but these dimensions will 

doubtless be dependent upon assay returns.

Lucky Chance mine.1 This property is situated in a precipitous 

mountain range, 2,000 feet above sea level and 4 miles as the crow 

flies, or 7 by wagon road, from the head of Silver Bay. The quartz 

ledge has a maximum width of 8 feet where it outcrops, but in the 

tunnel it is not constant in width and appears to merge into a series 

of narrow stringers penetrating the mineralized slate-hanging wall. 

The footwall, of graywacke, is locally known as diorite because of 

its compact, massive structure. A 600-foot tunnel follows the ledge 

and connects through a raise with a surface pit. The surface improvements comprise a 10-stamp mill, a sawmill, and a water-power 

plant. High values are reported from parts of this vein and many 

specimens of free gold have been obtained.

Other prospects. Many other prospects, partly developed, notably 

the Lower Ledge, Bullion, Free Gold, Liberty Lode, Silver Bay 

group, and the Boston are still held in the above-described area, some 

of which have very favorable surface showings, but lack of capital 

and inefficient management has caused a suspension of explorations 

for the last few years.

NONMETALLIC RESOURCES.

GRANITE. 2

Granite is a possible resource of the region, although, so far as 

is known to the writer, no attempt has been made to utilize this resource. The market that might logically be expected for Alaskan 

building stone comprises Portland, Oreg., and the cities on Puget 

Sound. The fact that granite from the quarries at Kaymond, Cal., 

 which are 200 miles from the seaboard, is able to compete with the 

local product of the Pacific Northwest in their home market indicates a strong possibility for Alaskan granite, provided it is of 

requisite grade. The quarries can be located at tidewater, and the 

water haul to market is no longer than that from San Francisco to 

Puget Sound. At present the only output of building stone from 

southeastern Alaska is marble, and this has been increasing steadily 

from year to year.

1 Wright, F. E. and C. W., Economic developments in southeastern Alaska: Bull. U. S. 

Geol. Survey No. 259, 1905, p. 58. The matter in this and the following paragraph Is 

quoted literally from the report cited.

2 See also Wright, C. W., The building stones and materials of southeastern Alaska : 

Bull. U. S. Geol. Survey No. 345, p. 123, 1908.
30 THE SITKA MINING DISTRICT, ALASKA.

The general distribution of granite is indicated on the sketch 

map (PL I, p. 10). Stone of good quality is found at Gut Bay on 

the east coast of Baranof Island and at the east end of Long Arm, 

Whale Bay, on the west coast of the same island. At the latter 

locality the granite is of handsome appearance. It is of light-gray 

color, medium texture, and even grain. The feldspars are clear 

and fresh and give the rock a live color. Accurately designated 

the rock is a quartz diorite, consisting of plagioclase feldspar (andesine or labradorite, quartz, biotite, and a minor amount of hornblende. The biotite, as a rule, is splendently lustrous. The accessory minerals are zircon, apatite, and magnetite.

GYPSUM. 1 

THE GYPSUM DEPOSIT.

The only extensive deposit of gypsum known in southeastern Alaska is 

situated on Gypsum Creek, a mile from its mouth, at lyoukeen Cove on the east 

side of Chichagof Island. The gypsum beds apparently overlie the Car- 

'boniferous rocks exposed along the southwestern shore of lyoukeen Cove and 

forming the ridge southwest of Gypsum Creek, though the area of contact is 

buried under deep gravel deposits along the beach and in the valley. The 

mountain ridge to the northeast is made up of a granitic mass intruding the 

older limestone and quartzite. Structurally the gypsum beds are folded and 

steeply tilted and were probably laid down previous to the granitic invasion. 

They are at present regarded as of Permian or Triassic age.

The geology in the immediate vicinity of the gypsum beds is obscure and 

neither foot wall nor hanging wall of the deposit is exposed. Bluffs of a 

cherty limestone striking northwest and dipping to the northeast are exposed 

near the entrance to the tunnel at the lower mine workings on Gypsum Creek. 

The gypsum beds in the tunnel and lower levels have an east-west to N. 

70° E. strike, with a northerly dip of 20° to 60°. Channels representing old 

watercourses and now filled with gravel wash are numerous throughout this 

deposit. These gravels resemble unconsolidated conglomerate beds and have 

been mistaken for both hanging and foot walls of the gypsum beds at points 

in the workings. A careful inspection of the gravels shows that the wash has 

the same character as that now in the creek bed. Of significance is the presence 

of cobbles of granite corresponding to the intrusive mass at the head of the 

creek, which invaded the area subsequent to the deposition of the gypsum beds.

MINE DEVELOPMENTS.

This gypsum deposit, the property of the Pacific Coast Gypsum Co., has been 

extensively developed during the last few years and large shipments of the rock 

are being made to the plaster mill at Tacoma, Wash., where it is prepared for 

the market. The developments consist of a wharf 2,000 feet in length, extending 

to deep water, where rock bins of 1,000 tons capacity have been built, and of a 

railroad about a mile in length to the mine workings. At the mine rock bins of 

1,500 tons capacity have been erected, thus affording sufficient storage capacity

i Reprinted from Bull. U. S. Geol. Survey No. 345, pp. 124-125, 1908.
CONCLUSION. 31

during intervals of transportation of the gypsum to' the plaster mill. A vertical 

shaft has been sunk for 190 feet and from it two levels have been extended at 

points 90 and 160 feet in depth, both of which are almost entirely in gypsum. 

The main developments are on the 160-foot level and include 1,200 feet of workings, exposing the gypsum bed over an area 450 by 225 feet. Both the thickness 

and the lateral extent of the bed are still undetermined. At a point 800 feet 

west of the shaft investigations were made in former years of a gypsum 

exposure on the creek bank, where a short tunnel was driven and a 75-foot shaft 

sunk almost entirely in gypsum, but work at this point was discontinued.

MARKET.

Gypsum is in much demand along the Pacific coast as wall plaster and fertilizer and in the manufacture of cement. The Puget Sound market is supplied in 

large measure from the deposits in Kansas, Colorado, Wyoming, and Utah. The 

California market is supplied from local deposits and those in Nevada and Utah. 

Transportation from these points to the seaboard cities costs from $4 to $7 per 

ton, and the present market prices [1908] of first-grade gypsum products in these 

cities are as follows: Crude, $5 to $7 per ton; land plaster, $6 to $8 per ton; 

plaster of Paris, $8 to $11 per ton; wall plaster, $9 to $12 per ton.

CONCLUSION.

The known mineral resources of the Sitka mining district are gold 

and gypsum. To these granite may, perhaps, be added as a possible undeveloped resource.

The gold is found in quartz lodes, which commonly occupy shear 

zones in graywacke. Two properties, both situated at Klag,Bay, on 

the coast of Chichagof Island, have so far been put on a productive 

basis and give strong promise of. a prosperous career. The ores, 

which range in value from $15 to $90 a ton, are of considerably 

higher grade than the average ore of southeastern Alaska. A large 

number of ore bodies of the same general character have long been 

known to occur near Sitka, but owing to the low-grade ores contained 

in them none have yet been brought to a producing stage.

The ore bodies of the region show neither in their mode of occurrence or origin any obvious or immediate relation to contacts of dissimilar rocks, to dikes, or to other igneous rocks. The principal 

mineral belt appears to lie along the edge of the slate-graywacke 

formation bordering the band of metamorphic rocks that flank the 

diorite occurring in the central portion of the islands. The betterknown ore deposits are found in graywacke, but this is doubtless a 

fact of no essential significance and should not deter the prospector 

from searching in other kinds of rocks. The question is sometimes asked by the prospector whether the formation at some particular locality is favorable. To this it can be answered that experience has shown that no one kind of rock is more likely to contain 

gold-ore deposits than another. In point of fact, a more complex
32 THE SITKA MINING DISTRICT, ALASKA.

set of conditions is necessary than the presence of a " favorable 

formation." That a favorable set of conditions is most likely to be 

found in the zones that border the long belts of granitic rocks traversing the region has already been maintained in this report. The 

indications afforded by present developments point strongly to the 

conclusion that the entire strip of territory contiguous to the west 

coast of Chichagof Island offers a more encouraging inducement to 

the search for new ore bodies than any other part of the region.

o