UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Bulletin 936-1

NICKEL-COPPER DEPOSITS ON

THE WEST COAST OF CHICHAGOF

ISLAND, ALASKA

BY

WILLIAM T. PECORA

Strategic Minerals Investigations, 1942 

(Pages 221-243)

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1942

For sale by the Superintendent of Documents, Washington, D. C. - ------ Price 20 cents

CONTENTS

Page

Abstract................................................. 221

Introduction............................................. 222

Location and accessibility of the deposits........... 222

Topographic belts.................................... 224

Climate.............................................. 225

Geology.................................................. 226

Regional geology..................................... 226

Geology of the stock near Davison Bay................ 228

Nickel-copper deposits................................... 229

Mineralogy........................................... 229

Origin of the sulfides............................... 230

Deposit on Fleming Island............................ 230

Surface features................................. 230

Subsurface features.............................. 232

Ore on the dump.................................. 233

Deposit near the head of Davison Bay................. 233

Disseminated-sulf ide deposit.......................... 236

Results of sampling.............................. 237

Reserves............................................. 240

Concentrated-sulfide deposits.................... 240

Disseminated-sulfIde deposit..................... 241

Economic consideratlons.................................. 241

ILLUSTRATIONS

Page

Plate 36. Geologic map of the stock near Davison Bay,

Chichagof Island, Alaska.................... 228

37. Map showing prospect pits and tentative surface outline of the disseminated-sulfide 

deposit, Chichagof Island................... 236

Figure 22. Index map of southeastern Alaska showing location of the nickel-copper deposits on the 

west coast of Chichagof Island.............. 223

23. Generalized geologic map of a part of western

Chichagof Island............................ 227

24. Sketch map showing outcrop of concentratedsulf ide deposit near the shaft on Fleming 

Island...................................... 231

25. Geologic map of the south shore of a protected

cove near the head of Davison Bay........... 234

26. Sketch map of outcrop of concentrated-sulfide 

deposit in norlte near the head of Davison 

Bay......................................... 235

III
TABLES

Page

Table 16. Weather records for Kimshan Cove, Alaska, from

August 1940 to September 1941................ 225

17. Analytical data and ratios of nickel to copper 

and of sulfur to nickel plus copper, in samples from the nickel-copper deposits on the 

west coast of Chichagof Island............... 238

IV
NICKEL-COPPER DEPOSITS ON THE WEST COAST 

OF CHICHAGOF ISLAND, ALASKA

By William T. Pecora

ABSTRACT

On the west coast of Chichagof Island, southeastern Alaska, 

are three nickel-copper deposits that consist of norlte containing the sulfide minerals pyrrhotite, pentlandite, and chalcopyrite. The deposits are .within less than a mile of each other 

and are, by water, 160 miles southwest of Juneau and 70 miles 

northwest of Sltka. The norlte is part of a stock, about 5 

square miles of which is above sea level. Other rocks of the 

stock are amphlbolite, amphibolitic norite, gabbro, diorite, 

quartz diorite, monzonite, granite, pegmatites, quartz veins, 

and schist inclusions. The stock is intrusive into a Lower Cretaceous (?) graywacke formation and an Upper Trlassic (?) greenstone formation, both of which are now metamorphosed to schist.

The deposits are of two kinds: (1) A dlsseminated-sulfide 

deposit, in which the sulfide minerals are distributed throughout the mass of the norite, and (2) "concentrated-sulfide deposits, in which the sulfide minerals are in distinct podlike 

masses of sulflde-rich norite. The deposits of type 2 are 

coarser-grained, smaller, and higher in nickel and copper than 

those of type 1.

Two of the three deposits described are of the concentratedsulfide variety. One of these, the Fleming Island deposit, has 

been partly developed by means of a 175-foot shaft, now flooded, 

by 71 feet of underground openings on a 75-foot level, of which 

37 feet are reported to be in ore, and by 85 feet of openings on 

the 175-foot level, of which 14 feet are reported to be in ore. . 

A sample representing 400 square feet, or half the surface outcrop, contains 0.58 percent of nickel and 1.15 percent of copper. 

It is reported that 37 feet of sulfide ore on the 75-foot level 

has an average content of 3.42 percent of nickel and 1.15 percent of copper, and that a half-ton sample from the 175-foot 

level contained 2.41 percent of nickel and 1.00 percent of copper. If the ore body is continuous between the surface and the 

175-foot level, the deposit is a steeply dipping ore shoot which 

contains more than 10,000 tons of ore. The ore contains possibly 2 percent of nickel and 1 percent of copper.

A second outcrop of concentrated sulfides is near the 

water's edge, about 3,000 feet southeast of the one mentioned 

above. Its area is about 500 square feet, and the material 

exposed resembles that of the Fleming Island deposit; though the 

samples taken, which were hardly adequate in number, indicate 

that it is of somewhat lower grade. No subsurface exploration 

has been done here.

221
222 STRATEGIC MINERALS INVESTIGATIONS, 1942

The deposit composed of norite with disseminated sulfides is 

exposed about 1,000 feet southeast of the second deposit of concentrated sulfides. It probably contains a few million tons of 

low-grade material with perhaps 0.2 percent of nickel and 0.1 

percent of copper.

INTRODUCTION

The occurrence of nickel on the west coast of Chichagof 

Island was first reported in 1911 by S. H. P. Vevelstad. In 

1917, a 175-foot shaft was sunk by the Alaska Nickel Co. on 

Fleming Island, near a prominent outcrop containing abundant 

sulfide minerals. Sulfides were encountered on the 75-foot and 

175-foot levels. A second outcrop showing abundant sulfides and 

similar to that on Fleming Island is also known but has not yet 

been developed. In the summer of 1941, a few acres underlain 

principally by rock containing disseminated sulfides were discovered and explored by means of 45 pits and trenches.

The writer did the field work on which this report is based 

between June 15 and September 4, 1941, with the assistance of 

John B. Lyons and Darwin L. Rossman. H. Lester Rink served as 

cook. John C. Reed visited the party several times during the 

season.

The Hirst-Chichagof Mining Co., and especially Paul M. Sorensen, its general superintendent, extended many courtesies during the field season. Territorial and Federal agencies in Juneau also gave help of various kinds. A report by J. C. Rogers 

on the underground workings on Fleming Island was made available 

to the Geological Survey by the International Nickel Co. Harold 

E. Mattson, in charge of the United States Weather Bureau Station at Klmshan Cove, provided records of rainfall and temperature.

Location and accessibility of the deposits

The nickel-copper deposits described in this report are on 

the west coast of Chichagof Island, one of the large islands of
NICKEL-COPPER DEPOSITS, CHICHAGOP ISLAND, ALASKA 223

the Alexander Archipelago of southeastern Alaska. By water they 

are about 160 miles southwest of Juneau, about 70 miles northwest of Sitka, and about 12 miles northwest of Kimshan Cove, a

Vigor* 22. Index nap of southeastern Alaska showing location of the 

nickel-copper deposits on the west coast of Chlchagof Island.

small mining community and the nearest post office (fig. 22). 

One deposit is on the north tip of Fleming Island, a small 

island between Davison Bay and Mirror Harbor (see pi. 36), and
224 STRATEGIC MINERALS INVESTIGATIONS, 1942

two other deposits, less than a mile southeast, are on Chichagof 

Island.

The west coast of Chichagof Island in the vicinity of the 

deposits is so studded with small islands and reefs that it cannot be reached by large boats.-/ Small fishing boats and motor 

launches, however, have a protected anchorage in Mirror Harbor 

and West Arm. Airplane service is maintained almost daily from 

Juneau to Sitka and Kimshan Cove, and planes can be chartered 

for landing almost anywhere on the nearby land-locked waters. 

A well-marked foot-trail, built and maintained by the United 

States Forest Service, extends from Dry Passage to White Sulphur 

Springs, at the head of Bertha Bay, and a branch of this trail 

leads to the West Arm anchorage.

Topographic belts

Two conspicuous topographic belts characterize the part of 

Chichagof Island shown in figure 23: A coastal belt which, near 

Davison Bay, has a maximum relief of about 150 feet and a maximum width of about 4 miles; and a mountainous belt which rises 

abruptly east of the coastal belt to altitudes of a few thousand 

feet. The nickel-copper deposits lie entirely in the coastal 

belt.

Many rapid streams drain the mountainous area and, with much 

gentler gradients, cross the coastal belt. Palls Creek, which 

drains Lake Morris, is a possible source of water power, and 

some of the other streams of the vicinity also may be suitable 

for this purpose.

Timber is locally plentiful both in the mountains and along 

the coast, but very little that can be used for mining purposes 

is readily accessible from the water. The Hirst-Chichagof Mining Co. at present uses logs rafted from Baranof Island to its 

mill at Kimshan Cove.

I/ U. S. ( 

this area.

_ Coast and Geodetic Survey chart 8258 nay be used for navigation 

in
NICKEL-COPPER DEPOSITS, CHICHAGOP ISLAND, ALASKA 225

Rock outcrops in the coastal belt are largely confined to 

sea cliffs and the part of the shores of inlets, channels, and 

sloughs that are exposed between high and low tide. The surface 

of this belt is characterized by heavy vegetation and swampy 

areas called muskeg; the cover of soil and vegetative debris is 

commonly between 2 and 5 feet thick. Between the soil and bedrock lies a thin veneer of volcanic ash, which weathers to an 

impervious clay that prevents adequate drainage of many swampy 

areas.

Climate

The deposits are in a region of high precipitation, most of 

which falls as rain. Rainfall and temperature have been 

recorded at Kimshan Cove since August 1940, and the available 

records for this station are given in table 16.

Table 16. Weather records for Kimshan Cove, Alaska, 

from August 1940 to September 1941. 

[Courtesy of the U. S. Weather Bureau]

Month

1940

September. . .

November. . . . 

December. . . .

1941

January. . . . . 

February. . . .

Anril .

July. .......

September. ..

November, . . . 

December.. ..

Rainfall in 

inche s ( include s 

melted snow)

on 04.

21.01 

11.45

13.14 

7.63

7.88 

3.43 

12.51

8.01

5.94

5.58

11.01

1.65

7.30 

17.60

12.08 

8.24

Maximum temperature in degrees 

Fahrenheit

67

73 

57

52 

51

49 

52 

55

58

64

71

73

75

70 

55

52 

48

Minimum temperature in degrees 

Fahrenheit

47

41 17

22 

22

13 

18 

28

33

38

44

45

42

38 IC

14 

16

466442 O - 42 - 2
226 STRATEGIC MINERALS INVESTIGATIONS, 1942

GEOLOGY 

Regional geology

Descriptions of the geology and mineral resources of parts

2/ 3/ 

of western Chlchagof Island by Overbeck, Reed, and Reed and

i/ Coats, have been published.

In the area included in figure 23, northwestward-trending 

rocks, principally graywacke and greenstone, are intruded by 

three large stocks of igneous rocks. Both the graywacke and the 

greenstone in the vicinity of the stocks are metamorphosed to 

schist. The age of the graywacke may be Lower Cretaceous and 

that of the greenstone may be Upper Triassic.

The intrusive stock near Davison Bay, described in a following section, contains the nickel-copper deposits. A second 

stock, in the vicinity of Lost Cove and Islas Bay, is made up 

largely of dioritic rocks similar to those in the stock near 

Davison Bay; but reconnaissance examination of the second stock 

haa failed to disclose any nickel-copper deposits. The third 

stock, near Lakes Elfendahl and Morris, is composed essentially

of granite.

5/ Reed and Dorr report that a large stock on Yakobi Island

(see fig. 22) contains sulfide-bearing norite. Additional areas 

of sulfide-bearing rocks may yet be disclosed by further examination of the western part of Yakobi Island,

2/ Overtook, R. U., Geology and nlneral resources of the west coast of 

ChicKagof Island, Alaska: U. 8. Geol. Surrey Bull. 692, PP. 91-136, 1919.

%/ Heed, J. C., Preliminary report on the ore deposits of the Chlchagof 

nlning district, Alaska: An. In«t. Min. Met. Tech. Pub. Ho. 1051. 20 pp.. 

1939.

U/ Heed, J. C., and Coats, R. R., Geology and ore deposits of the Chlchagof mining district: U. S. Oeol. Surrey Boll. 929. 1^7 pp., 19*12.

£/ Reed, J. C., and Dorr, J. 7. N., 2d, Nickel deposits of Bohemia Basin

and Tleinlty, Yakobi Island, Alaska! U. S. Oeol. Survey Boll. 931-F, pp, 105-133, 1942.
NICKEL-COPPER DEPOSITS, CHICHAGOF ISLAND, ALASKA 227

136°20'

^^feffiS^ .,-A

White Sulphur 

Springs ^

I36°20'

3 Miles

Figure 23. Generalized geologic map of a part of western Chlchagof Island.
228 STRATEGIC MINERALS INVESTIGATIONS, 1942 

Geology of the stock near Davison Bay

Near Davison Bay a composite stock of igneous rocks intrudes 

the metamorphosed rocks. (See pi. 36.) The metamorphic rocks 

are foliated and are made up of such minerals as biotite, garnet, 

amphibole, chlorite, andalusite, staurolite, corundum, quartz, 

and feldspar.

About 5 square miles of the stock is above sea level, but a 

larger area probably is submerged off shore. The rocks composing the stock include amphlbolite, norite, gabbro, diorite and 

quartz diorite, quartz syenite, quartz monzonite, granite, pegmatites, quartz veins, and schist inclusions. The amphibolite, 

norite, and gabbro are collectively mapped on plate 36 as the 

norite group, and the remainder as the diorite group. Schist 

inclusions are present in the members of both groups, being particularly abundant in those of the diorite group that are rich 

In both quartz and biotite. Small scattered bodies of rocks of 

each group are common In the rocks of the other group. Some 

rocks of the norite group, even where present as small bodies 

within rocks of the diorite group, have an indistinct layering 

that is roughly accordant with the cleavage of the schists surrounding the stock.

S-u.lfid.es occur in many rocks of the stock but are most abundant in those of the norite group; deposits of possible economic 

Importance are therefore most likely to be found in the areas 

represented in plate 36 as underlain principally by norite.

The writer believes that the original magma of the stock was 

intruded into older rocks by forceful Injection and assimilation, 

and that the amphibolite, norite, gabbro, and diorite represent 

products Of differentiation during crystallization of the magma.

The quartz-biotite granitic rooks were probably formed in part

by assimilation of inclusions in residual fl>actl0118 Of ttw 0*73- 

tallizing magma and in part by wholesale replacement and recrys-
UNITED STATES DEPARTMENT OF THE INTERIOR 

GEOLOGICAL SURVEY

I36°I8' BULLETIN 936 PLATE i

) JCormorant I

(Principally amphibolite,norite,

Diorite group

(Principally dioritic and granitic

rocks wifn pegmatites, quartz.

veins,and schist inclusions.)

Metamorphosed

. Metamorphosed

136 20 136" 16' Geology and topography by 

W.TPecora, J.B.Lyons,and 

D.L. Rossman

1000 4000 Feet

Contour interval 50 feet. Datum is mean low sea /evel.

Shore line mapped at mea.n high tide fine 

GEOLOGIC MAP OF THE STOCK NEAR DAVISON BAY, CHICHAGOF ISLAND, ALASKA
NICKEL-COPPER DEPOSITS, CHICHAGOP ISLAND, ALASKA 229

tallization of graywacke or greenstone by fluids emanating from 

the magma.

NICKEL-COPPER DEPOSITS

» The nickel-copper deposits consist of norite containing the 

aulfides pyrrhotite, chalcopyrite, and pentlandite. Both concentrated-sulfide and disseminated-sulfide deposits are recognized, the former having a higher nickel and copper content but 

a smaller volume than the latter.

Of the two prominent outcrops of the concentrated-sulfide 

deposits, one on Fleming Island has been partly developed; the 

second, near the head of Davison Bay, remains undeveloped. The 

outcrops resemble each other in mineralogy and in their geologic 

relations, and each probably represents a well-defined ore body.

A tract of several acres underlain in part by sulfide-bearing rock was discovered and partly explored on the surface by 

the claim owners in the summer of 1941. Of this tract, 3 acres 

(see pi. 37) is considered by the writer to be underlain by a 

disseminated-sulfide deposit.

Mineralogy

6/ 

Kerr has described the mineralogy of several specimens of

ore from Chichagof Island. The ore minerals pentlandite 

((Pe,Ni)S) and chalcopyrite (CuPeSg) are here intimately associated with pyrrhotite ( Fensn+])' The gangue minerals consist 

chiefly of the silicates pyroxene, plagioclase feldspar, and 

amphibole. The sulfide minerals were formed later than the 

silicates, and the proportion of the combined sulfides to the 

silicates, as well as of the sulfides to one another, varies 

widely. The concentrated-sulfide deposits differ mineralogically from the disseminatedr-sulfide deposit in having more

6/ Kerr, P. P., A nagnatlc sulphide ore from Chichagof Island, Alaska: 

Icon. EC Geology, rol. 19, pp. 369-376. 1921*.

466442 O - 42 - 3
230 STRATEGIC MINERALS INVESTIGATIONS, 1942 1

abundant and coarser-grained sulfides, more chalcopyrite relative to other sulfides, and coarser-grained pyroxene.

Origin of the sulfides

. The sulfide minerals appear to be magmatic and to have been 

the last minerals of the norite to crystallize. The disseminated-3ulfide deposit may be the result of normal crystallization of a sulfide-rlch noritic magma, whereas the concentratedsulfide deposits, with their coarser grain and higher nickel and 

copper content, may be pegmatitic facies formed by the fractionatlon of a similar sulfide-rich noritic magma.

Deposit on Fleming Island

Surface features.--Sulfide-rich norite crops out on the 

northern tip of Fleming Island (see pi. 36), near the water's 

edge and a few feet west of the shaft. The outcrop, as shown in 

figure 24, measures 20 feet by 40 feet and is readily distinguished from the surrounding norite poor in sulfides. Soil, 

vegetation, and dump material conceal the bedrock near the shaft.

The outcrop is near the eastern border of an area, 1,200 

feet long and 300 feet in maximum width (see pi. 36), underlain 

by rocks of the norite group. On the east, this area is separated from the biotite-quartz schist of the graywacke formation 

by rocks of the diorite group. West of the shaft, thin-layered 

amphibolite and norite striking northwest and dipping steeply 

southwest form the western part of the lens-shaped area and

separate it from rocks of the diorite group.

The deposit is characterized by small podlike masses of 

abundant aulfide minerals. The largest pod seen was 4 inches by 

4 inches by 8 inches. The sulfide minerals are commonly coarsegrained and friablo, and they enclose coarse crystals of pyroxene and plagioclase. The largest pyroxene crystals are half an 

inch across and 1 inch long, being conspicuously larger than
NICKEL-COPPER DEPOSITS, CHICHAGOP ISLAND, ALASKA 231

those in the norlte poor in sulfides. Some crystals are bent, 

curved, or broken, and cracks, pits, and irregularities in them 

are filled with sulfides.

Bedrocks concealed 

by vegetation and dump

FLEMING

Rocks of diorite Strike and dip of 

group banding

Figure 2^. Sketch tap showing outcrop of eoneeatrateA-culfid* deposit 

near the shaft on Fleaing Island.

A sample made up of chips collected at 1-foot intervals 

represents about 400 square feet of the surface rock. Despite 

an endeavor to obtain material as little weathered as possible 

by first breaking away a surface layer of rock, the sample
232 STRATEGIC MINERALS INVESTIGATIONS, 1942

contained some weathered rock. An analysis showed 0.58 percent 

of nickel, 1.15 percert of copper, and 4.84 percent of sulfur.

Subsurface features. A few feet east of the outcrop a 175- 

foot shaft has been sunk In hornblende gabbro and hornblende 

diorlte, and sulfide minerals were encountered on the 75-foot 

and 175-foot levels northwest of the shaft. The water in the 

flooded shaft is about 10 feet above sea level, and its level 

does not perceptibly change in response to the daily rise and 

fall of the tides in nearby Fleming Channel; but a fluctuation 

of about 3 feet in response to rainy and dry spells was recorded 

during the summer of 1941.

The information that follows was gleaned from the published

7/ 8/

reports of Overbeck ' and Buddington, from field notes of Overbeck on file in the Geological Survey, and from a report prepared in 1917 by J. C. Rogers for the International Nickel Co. 

On the 75-foot level there is a 62-foot drift northwest of 

the shaft, with a 5-foot crosscut near the end, and a 4-foot 

drift southeast of the shaft. The southeast drift and the first 

30 feet of the northwest drift are in barren hornblende gabbro. 

The remaining 32 feet of the northwest drift and its crosscut

are in aulfide-rich norite. Concerning the contact of barren

9/

rock and ore, Overbeck writes: "The contact between the barren rock and the ore-bearing portion appears to be an irregular 

line. There is rather a rapid transition from barren rock to 

rock in Which there are a few disseminated sulphides, and then 

to massive ore. The change does not appear to occur progressively but irregularly * # *."

It is reported by Mr. Rogers that the material exposed in 

the 37 feet of workings in ore on the 75-foot level averages 

3.42 percent of nickel and 1.58 percent of copper. Samples

Overieek, R. M., op. clt., pp. 125-131*.

Buddington, A. ?., Mineral investigations in southeastern Alaska: 

U. S. Geol. Survey Bull. 773. PP. 95-98. 1923. 

2/ Overbeck, B. M., op. cit., p. 126.
NICKEL-COPPER DEPOSITS, CHICHAGOF ISLAND, ALASKA 233

4 to 11 in table 17 are the reported analyses of eight samples 

from the 75-foot level taken by Mr. Rogers in 1917.

Concerning the 175-foot level, 14 feet of which is reported 

to be in-ore, Mr. Rogers writes:

The 175-foot level has 51 feet of main drift, 15 feet of 

drift southeast and 14 feet of drift northwest, giving a total 

of 80 feet 10/ » * *. The character of the rock here is different than on the 75-foot level, the northwest and southeast 

drifts being in a brecciated mass between two slips or shear 

zones. Massive ore is adjacent to slips but the sheared portion 

appears to be recemented and of a secondary nature # « « . A 

1,000 pound shipment * * & gave an assay of Cu 1.00, Ni 2.41, or 

CuNi 3.41 for ore from this drift.

Five analyses of samples of massive ore from the 175-foot 

level also reported by Mr. Rogers (samples 13-17, table 17) 

indicate that the ore on this level contains less nickel and 

copper than the ore on the 75-foot level.

Ore on the dump. The broken material on the dump west of 

the shaft is estimated to weigh about 50 tons and consists of 

partly oxidized sulf ide-rich. material, and of norite, diorite, 

and gabbro. Ten specimens of the sulfide-rich material, weighing in all about 50 pounds, were collected at random from the 

dump and broken up, and a sample weighing about 3 pounds was 

made up from the least oxidized fragments of each specimen. An 

analysis shows (sample 1, table 17): 2.99 percent of nickel, 

2.05 percent of copper, and 23.15 percent of sulfur.

The source of the material is not known, as it may have come 

from either the 75-foot or 175-foot level. In either case, the 

sample represents only a small amount of the sulfide pods originally enclosed in norite.

Deposit near the head of Davison Bay

Norite, including sulfide-bearing and amphlbolitic varieties 

and associated with gabbro-diorite and pegmatites, crops out

10/ Mr. Rogers does aot mention the direction of the main drift, nor 

whether the 15-foot and lU-foot drifts were drlren from the shaft or from 

the end of the 51-foot main drift.
o

ct

P 

ct 

CD 

P.

P 

ct 

CD 

PP'

CD

CD 

OdO

< 

CD

ct 

P1 

CD

D/\V/SON

LAGOON WITH SAND BOTTO

Feuj feet, deep at low uja

OAV/SOfJ ' ' ..' 

B A ^ '! '

Amphibolitic N'orite Gabbro-diorite 

norite 

figor* 25. 0«ologlc nap of the south shore of a protected cove n
NICKEL-COPPER DEPOSITS, CHICHAGOF ISLAND, ALASKA 235

The outcrop at locality A, which is about 3,000 feet southeast of the one on Fleming Island, covers about 500 square feet, 

The deposit, which does not include all the area (see fig. 26), 

has irregular contacts against the host rocks. In this outcrop 

the sulfide pods are larger than in the outcrop on Fleming 

Island, but the mineral composition and the podlike form of the 

sulfide masses in the two outcrops are very similar. TwentyEXPLANATION

^

Pod like masses 

of su If ides

* -s. x

 1 -T

Norite,rich Norite,poor Amphibolitic 

in sulfides insulfides norite

10 o loFeet

Figure 26. Sketch nap of outcrop of concentrated-sulfide deposit in norite 

near the head of Dariton Bay. Outcrop A of figure 25.

three specimens of sulfide pods, estimated as weighing a total 

of 300 pounds, were broken up, and pieces from near the center 

of each specimen were collected to make a representative sample. 

The sample (sample 2, table 17) was found to contain 1.50 percent of nickel, 0.99 percent 'of copper, and 15.00 percent of 

sulfur. The Ni:Cu ratio is computed to be 3:2, the same as that 

computed from the analysis of the concentrated-sulfide pods
236 STRATEGIC MINERALS INVESTIGATIONS, 1942

collected at the dump near the shaft on Fleming Island (sample 1, 

table 17). As shown in figure 26, the sulfide pods make up only 

a small percentage of the deposit. The nearby shaft has been 

sunk only a few feet into bedrock.

At localities B and C nearby, the concentrated sulfides 

exposed are in rock that in most places contains disseminated 

sulfides. Five pits cut into the side of the hill east of 

locality A expose crumbly norite veined by dikelets of quartzbiotite-feldspar pegmatite. The hills to the south and south-

*b 

east are less than 150 feet high and are almost covered with

vegetation, but norite with disseminated sulfides is exposed on 

them in a few places.

Disseminated-sulfide deposit

About 4,000 feet southeast of the Fleming Island shaft and 

1,000 feet southeast of the sulfide-rich outcrop near the head 

of Davison Bay, a tract of several acres is underlain principally by rocks containing disseminated sulfides. During the 

summer of 1941, 45 pits were dug by workers for the claim-owners 

in an attempt to explore the bedrock concealed by the vegetation 

and soil. (See pi. 37.)

The more abundant rocks exposed in the pits are amphibolite, 

norite, and ga"bbro. Less abundant rocks Include dlorlte, pegmatites, and metamorphosed graywacke inclusions. The rock richest 

in sulfides is norite, and a coarse-grained variety contains a 

larger proportion of sulfides than a fine-grained one. The 

amphibolite is closely associated with the norite, and the presence of one is a reliable indication of the proximity of the

other. Although sulfide minerals are visible in much of the 

amphibolite, the nickel and copper content (see table 17) of the 

rock, as shown by analyses of two samples from the disseminatedsulfide deposit and a third collected nearby, is very low 

(nickel, 0.03, 0.02, and 0.02 percent; copper, 0.03, 0.01, 0,02
GEOLOGICAL SURVEY BULLETIN 936 PLATE 37

EXPLANATION

Prospect pit . 

(Numbers referred to in text ana table 171

Sulfide-bearing rocks 

(Some not in place)

B

Boundary of sulfides 

(Solid where limit is indicated 

by prospect pits end sampling 

data.-, dashed where inferred)

Contour interval 10 feet 

Oatum is mean, /ou/ sea. level

MAP SHOWING PROSPECT PITS AND TENTATIVE SURFACE OUTLINE OF THE DISSEMINATED-SULFIDE DEPOSIT, CHICHAGOF ISLAND

466442 O - 42 (Faces page 236)
NICKEL-COPPER DEPOSITS, CHICHAGOP ISLAND, ALASKA 237

percent). Norite or amphibolite that is close to graywacke is 

separated from it by light-colored diorite, gabbro, or pegmatites, all of which are poor or barren in sulfides.

Results of sampling. Each pit shown on plate 37 was sampled 

by the writer or his assistants by collecting chips at 1-foot 

intervals over the exposed rock surface. Five composite samples 

(Nos. 26-30, table 17), representing groups of pits, were made 

by mixing portions of the powdered original samples proportionate in weight to the area represented by each sample. The rock 

chips were crushed and the composite samples were mixed in the 

laboratory of the Hirst-Chichagof mine at Klmshan Cove. The 

analysis of each composite sample is shown in table 17. 

Weighted averages of the five analyses were computed as 0.16 

percent of nickel and 0.08 percent of copper (sample 31, table 

17). These averages represent the probable nickel-copper content of all the rock surface exposed in the 45 pits, including 

rock barren in sulfides. The total area sampled is 2,037 square 

feet.

Five pits Nos. 4, 17, 20, 23, and 35 expose rock extraordinarily rich In sulfides. Analyses of individual samples from 

these pits are also given in table 17. Weighted averages of 

these five analyses (sample 32, table 17) representing 655 

square feet are: Nickel, 0.31 percent; and copper, 0.13 percent. 

The richest sample (nickel, 0.75 percent; copper, 0.30 percent), 

which was Obtained in pit 4, contains less copper than any of 

the samples from the concentrated sulfide deposits and less 

nickel than any of them except the sample representing about 

400 square feet of the outcrop of the deposit of concentrated 

sulfides on Fleming Island (sample 3, table 17).
Ta"ble 17. Analytical data and ratios of nickel to copper and o

in samples from the nickel-copper deposits on the west coa

Sample 

number

1

2

3

4

5

7

q

10

11

12

13

14

15

1 C

17

18

19

20

Location and description of sample

Representative of about 50 Ib. of selected concentrated-sulRepresentative "of about 300 Ib. of selected concentrated-sulRepresentative of about 400 sq. ft. of partly weathered surface of concentrated-sulf ide outcrop on Fleming Island. .....

Channel sample by J. C. Rogers of ore body on 75-foot level

...do......................................... ................

.. .do .........................................................

...do.........................................................

.. .do .........................................................

... do .........................................................

...do.........................................................

. . .do .........................................................

Rogers' average of 37 ft. of ore on 75-foot level on Fleming

Sample by J. C. Rogers of ore body on 175-foot level on Flem-

... do .........................................................

...do.........................................................

Sample said to represent 1,000 Ib. of ore froip 175-foot level

Pit on west side of cove 1,000 ft. northwest of cove shown in

Pit 32, pi. 37. Represents 140 sq. ft. of amphibolite with

Pit 18, pi. 37. Represents 120 sq. ft. of amphibolite with
NICKEL-COPPER DEPOSITS, CHICHAGOP ISLAND, ALASKA 239

CO CM CO O O 

tO H tO lO

in in CM ooo

05 O>

oo

o> to <o

OHO

tO t- 00 OS 

CM CM CM CM

O * 

CM CM

CO tO 

OH

CO H 

H tO

H CM to to

1
240 ' STRATEGIC MINERALS INVESTIGATIONS, 1942

Reserves 

Concentrated-sulfide deposits

Although information regarding the structure, size, and 

tenor of the deposit on Fleming Island is inadequate, it is 

assumed that the ore exposures on the surface and in the underground openings on the 75-foot and 175-foot levels are in the 

same ore shoot. This assumption may or may not be correct. 

Rogers, indeed, regards the ore indicated on the 175-foot level 

as belonging to a second ore body rather than as a continuation 

of the one exposed on the 75-foot level, and a third possibility 

is that each of the three exposures of ore represents a separate 

ore shoot.

According to the first interpretation, the ore shoot, if 

continuous from the surface to the 175-foot level, contains more

than 10,000 short tons 'of ore with an average of about 2 percent of nickel and 1 percent of copper. According to the second 

Interpretation, less than 8,000 tons would lie between the surface and the 75-foot level, but there would probably be some in 

addition below that level. According to the third interpretation, the quantity of ore would be even smaller.

A reserve of 10,000 tons of ore with 2 percent of nickel and

12/ 1 percent of copper has a gross value of about $16 per ton;

it contains 200 tons of nickel, with a gross value of about 

§140,000, and 100 tons of copper, with a gross value of about 

$24,000. This estimated reserve of 200 tons of nickel and 100 

tons of copper is but a small fraction of 1 percent of the 

world's annual production of the two metals.

The deposit near the head of Davison Bay may contain a few 

thousand additional tons of concentrated-sulfIde ore. The ore 

In this deposit, if it is fairly represented by the very limited

ll/ 1 short ton estimated for each 8 cubic feet of rock. 

I?/ lletal values are based on assumed prices of 35 cents per pound for 

nickel, and 12 cents per pound for copper. Reserves are in short tons.
NICKEL-COPPER DEPOSITS, CHICHAG-OF ISLAND, ALASKA 241

amount of sampling, is of lower grade than that In the deposit 

near the shaft on Fleming Island.

Disseminated-sulfIde deposit

An area of 3 acres underlain principally by rock containing 

disseminated sulfides has been tentatively outlined on the map 

forming plate 37, though the mapping will no doubt be altered in 

detail after further exploration is completed. This tract is 

densely wooded, has a relief of about 100 feet, and is well 

drained. For each foot of depth, this ground contains about 

13,500 short tons of sulfide-bearing rock, which, on the assumption of an average tenor of 0.2 percent of nickel at 35 cents 

per pound and 0.1 percent of copper at 12 cents per pound, would 

have a gross value of about $1.64 a ton. The assumptions as to 

tenor, however, are highly speculative. The weighted averages 

of the nickel and copper in the composite samples representing 

all the pits are probably a little too low because a few small 

pits (pits 13-16, 28-30, 33, and 38-40), which are represented 

in the samples, lie outside the limits of the body. The 

weighted averages of the individual samples from the five pits 

in the body (pits 4, 17, 20, 23, and 35) are obviously too high 

because only pits extraordinarily rich in sulfides are represented. If the deposit has a depth of a few hundred feet, a few 

million tons of disseminated-sulfide rock is indicated in the 

prospected area.

ECONOMIC CONSIDERATIONS

A metallurgical method of treating ore that contains pentlandite, pyrrhotite, and chalcopyrite has been successfully used

for the well-known and richer deposits near Sudbury, Ontario,

12/ Canada. Recent investigations concerning the metallurgical

13/ Kosttr. J. f at al., Becovery of nickel, copper, and precious natal* 

frou domestic ores \>y a combined electrothermal and electrolytic method: 

U. S. Bur. Mines Hept. Inr. 31*83, 28 pp., 1939.
242 STRATEGIC MINERALS INVESTIGATIONS, 1942

treatment of "low-grade nickel-copper ore" indicate that a 

satisfactory process for producing electrolytic nickel and copper has been developed.

Any profitable mining of the disseminated-aulfide deposit 

 would probably have to be done by some large-scale, low-cost 

method, though the concentrated-sulfide deposits might be mined 

by a smalleri-scale, higher-cost method. The heavy precipitation 

of the region, the high ground-water surface, and the possibility that subsurface workings would be flooded by leakage from 

the sea, are factors to be considered in making any plans to 

mine the deposits. The proximity of the deposits to the coast 

offers the advantage of water transportation, but this is partly 

offset by the fact that the deposits cannot be closely 

approached by large boats and by the long distance between the 

deposits and markets.

The concentrated-sulfide deposits might possibly be worked 

with profit under present economic conditions, but at best they 

would yield relatively insignificant amounts of nickel and copper. The disseminated-sulfide deposit appears to be of too low 

grade to be profitably mined, even on a large scale, except at

a very much higher price for nickel than is now obtainable.

14/ Reed and Dorr 'have investigated the nickel-copper deposits on Yakobi Island, 15 miles by water northeast of the deposits described in this paper (see fig. 22), and they report eight 

partly explored and four unexplored deposits of norlte containing disseminated sulfide minerals. Analyses of 61 samples, 

representing 945 linear feet of rock, show a nickel content of 

from 0.03 percent to 3.60 percent. The authors estimate that in 

these deposits at least 6,000,000 short tons of rock are available that contain an average of 0.36 percent of nickel and 0.27 

percent of copper, which at 35 cents a pound for nickel and 10 

cents a pound for copper would have a gross value of $3.06 a ton.

Beed, J. C., and Dorr, J. 7. H., 2d, op. olt.
NICKEL-COPPER DEPOSITS, CHICHAGOP ISLAND, ALASKA 243

The mining of the disseminated-sulfide deposits on "both 

Yakobl and Chichagof Islands presents so many similar problems 

that the deposits in both districts may well be considered 

jointly in any plans for their commercial development.

Further exploration of the known nickel-copper deposits on 

the west coast of Chichagof Island is needed before any close 

estimates of available tonnage and nickel-copper tenor can be 

made. Further subsurface development of the body of concentrated sulfides near the shaft on Fleming Island seems Justified. 

If a drilling program is considered for the disseminated-sulfIde 

deposit, a preliminary magnetic survey might prove a valuable 

aid in outlining such a program.

O