R. I. 3967 NOVEMBER 1946

UNITED STATES

DEPARTMENT OF THE INTERIOR

J. A. KRUG, SECRETARY

BUREAU OF MINES

R. R. SAYERS, DIRECTOR

REPORT OF INVESTIGATIONS

EXPLORATION OF SEDANKA ZINC DEPOSIT

SEDANKA ISLAND, ALASKA

Juneau, Alaska: A.F.O.C.

U.S. Bureau of Mines Library

Circulatio"1 Copy. Please heturn

When Due.

BY

B. S. WEBBER, J. M. Moss, AND F. A. RUTLEDGE
Hi Z. 3967,

November 1946.

PXPORT OF I1STIG:TI0N

Mt== STOS DEART= OF TIM INTER.IOR -BEW=kU Or s

PLO0AWIC0O or g osu ZINC DEEPOSIZ ,SED: IS .ATASI .

By B. S. Webber,'/ J. 'k;.isGa and FP A. R;tledgeV/

CONTENTS

TIntioduction ............*. 1

Acktowledgment s . ................ i... .. . 2 

Lotati~on and accessibility ++*, 2^.

Rhysical features and climat6 ... *'...4e .'3

Latlor and Diving conditions' ....- ...... 3

Hist6ryj 'productibn, and-ownership ..... 3

Description of deposit .............. '. 4

Exploratiot by the Bureau of Mines 5

Samiing'ai& analyses I.;T-. . ,..**, 5

Comparison of sampling Analyses *... 8

Beneficiation,.;.!....-.a.;^. 1O

INtSODnCTZON

The tnited States, with its vast resources of relatively lowgrade zinc

ores, has been the worldts -leading'prbdu.b1 odf zind metal for many y~ets.

The exp noded zind proqductdoh-during the period, 1939-W4, inclusive;j. was induced by favorable premium prices and has depleted the known ore reserves

in the United States. The 1943-;144 rate of zinc production can not long be

maintained in the Uniited States, especially if premium prices are removed.

Domestic zinc reserves have been depleted to such an extent tha.t it-is

doubtful if our mines will again be able to completely and continually f61-

fill the needs of this country.,

The Bureau of Mines, anticipating a postwar cofsujer demand fPr 550,000

t6 750,000 tons of slab zinc andl an additional 100,000 tons- for use in plihts

and chemicals, sent two'engineers to S aika'Island in July. 9 4 5 tp investigate the deposits near Biorka Harbor. : - ..

.~~~~ .. ~~~~~~~~~~~ 

2/ The Bureau of Mines will welcome reprinting of this paper, provided the

following footnote acknowledgment is used,. Reprinted from Bureau

of Mines Report of Investigations 39 67.. "

2/ Mining engineer, Bureau of Hines, Juneau, Alaska,

S/ Assistant mining engineer, Bureau f nines, Juneau, Alaska.

/ As'sociate mining engincer, Bureau of Mines, Juneau, Alaska.

1206
R.I. 3967

ACIQO0WDGM1S 4 .

In its program of exploration of mineral deposits, the Bureau of Mines

has as its primary objective % e'ectfixvztilization of our mineral

resources to the end that they make the greatest possible contribution to

national ity2 e :tR 'e is the po'lity-'of. the lureau 'to-p blish

the facts developed by each exploratory projqct.as soon as.prcticable

after' its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts

preliminary aiiat1ions,.peifeorms.the' actual exploratory work, and prepares the final report. The Metallurgical Branch, R. G. Knickerbocker,

chief. analyze's samples atd.perfortsfbeneficiation tests. *Both these

branches are under the supervision of Dr. R. S.-Dean, assistant director.

The exploratory program of the Alaskan Division, Mining Branch, is

under the direction.of R. S. Sanford, acting division chief, Juneau,

Alaska. Beneficiafion tsts.on.a.composite sample representative of the

Biorka ore were made at.thp. Salt.Lake City.Experiment Station by the

Metallurgical Branch, S,.,A,,inierley, chief, and test engineer T. P.

Mitchell of the Salt Lake.Pivision'.- Samples were submitted to the Territorial Assay Office, Ketchikan,.Alaska, and was analyzed by Nile Johannson*

The field examination was madeeby B. S. 1ebber'and J`. M. Moss, and the

report was written by P..A..Rutledge...

Special acknowledgmentjis.made of the assistance rendered by F. E.

Lerchen and Harry Townsend, mining engineers. The Bureau of Mines' is indebted for the use of reports and.maps.from Lerchen's'examination in 1937

and Townsendts in 1940.

LOCATION ALm ACCESSIBILITY

The Biorka zinc deposit is approximatelyr 3,000 fee't southeast from

Biorka Harbor along Lo4e Creek on the north side of Sedanka Island. (&See

fig. 2.) Sedanka island, .166'0l)41 west longitude, 530 14g8 north latituiie,

is geographically a part of Unalaska Island and lies west of sand near one

of the most frequented routes from the''Pacific Ocean to the Bering Sea.

(See fig. 1.)

The deposit is readily accessible to ocean-going ships, as a 'dock Pin

be prepared in BiorkA Harbor at a nominal cost to accommodate the largest

ships now used for- freighting. I-Ships of the Alaska Steamship Co. rbw call

at Du~tch Harbor on t~heir trips to northwestern Alaska'and'the'iering Sea:.

The.. freight rate of the'.Alaska Steamship to. o .general cargo 'during 19 5

from Seattle, Wash., to Dutch Harbor on Uneal'aka Island was $1.25 a hundred

pounds or $0.62-1/2 a cubic foot, whichever was greater. Passenger rates

were as follows: Class 8, $105 plus 16 percent surcharge plus.15 percent

tax; lower first class, $90 plus 16 percent surcharge plus 15yPercent t

and steerage, $55'--p1us l6perdeint;'s.0 harge plus 15 perceiit. tax..-

Prior to World"lar II, the Alaska Steamship Co. maidtained'a shil.ttle

service from Seward, Alaska, to Ko&iak Island and Dutch Harbor. Thivs'service

was abandoned during the war 6nd' has not yet been resumed (Febru4ary l9)¢ )

At present there'is no'.'commerpial air transportation to the Aleutian

Islands.

1206 -2-
w~~~~~~

I //

5EA / Z/ erkrld r LCr Ae 

Yunarkar

A~~~~~~~e. ~~~~~~~Chugu I~ 0 C~

&7A/A oLfAN X=mztkfa / LC0 *

/~~~~ /5 B R 7Z t Ha6 a5 

Semis opochneil O'reo*A ______ a Cv-i

1,5LANDS F PEN 0

An~a zla~c IkNDAN\ 0 A

0o 5 /00 /50

Scale of Mi1les L. M er N zigzis

A oryn

,A q Lczalz~zN~9 1

edanka! C N~~~~~~~o/cI: Mioeraolized Areas

enleH ox~~ pA.ANind"c-ated thus - .

F/C-. I -INDEX MA~ PALASKA PENINSULA -ALEUTIAN ISLANDS
0

BERFMG SEA

A^ ~~~~~UNALGA I.5

< ~~UNAL ASKAm

41 HiEGG I

.< v ~~~~~~VILLAGE

c ~~~~~~~~~~HRBOR

PROSPECT

XJ53,3d 53° 30'

0

FROM. USCLtGS

.D e0CHART 8860

FIG. 2 LOCATION MAP SEDANKA ISLAND
...: -t.K-.. .-. R.I. 3967

.n il exploration and developmentQf the Biorke. zinc, deposit warrents

.the- construction of a dock in Biorka.:ai'bo=, all- supplies and e.quipment must

be obatalh6d through Dutch Harbor on Una1ska .Islanji. Dutch Harbor is about

25 Udies, by water from .the dowk:site, and., .smaill fishing -boats may be. Qhakrtered in Dutch' Harbor for this 9ervice,. but V4th &4iffiC ltu dnriig the.£ishihg'

season.-

PXYSICAL FEATUa=s AanD CLIIA .4T:

Sedanka Islknd 1 gone of the many islands IQ in the.Alewti=n Islands,

virtualley a continuation of the.AJjaske. Peninsula,. which separate the Pacific

Ocean .from,.the 3Bering Sea.' The isla4: is Pare of timber and, except for a

few stUAted:willows along- the creeksr i-i coveed. only. by gruioses and moss.'':

Two mountaings tiseto 2,200 a~d l.,50.feet, respeotively 1

Lying as it does between the warm waters of the Pacific Ocean and the

cold. waters of the Bering Sea, the island.has an aOundanceo..of.rain and. .foggy

weather . Winters are usually stormy, but the temperature is mild. Summers

are cool : . ".

Records of the United States Weather Bureau for Dutch .Jarbor for''16.

years, 1905 to 1920, inclusive, show a mean annual precipitation'of 63.69

inches. The' gieatest amount. redorded *tas i' Qctober. June and J.uly having

the- least. Mo'st of the precipitation- occrred during -the. fall an& winter

months.

The mean annual temperature recorded at Dutch Harbor over a 27-year period,- 192 through I1921,- wa!39.$Q -. .Only in Tanuy. and February was

the mean'monthly temperature .below-32°.X ...-

IABOR AND LIVING CONDITIO'NS

No -accommodations or labor. ake available.near the zinc deposit. Before

exploring or developing can be. done,*- some .form of housing must be provided.

The' United States will be the best &ource.-for the required labor, though a

few natives might bt- obtairied from. Dutch- Harbor fo .unskilled work. - The

isolation and disagreeable weather of the island would affect the attitude

of mining personnel toward remaining in the region at ordinary rates of pay.

:ISTORY, PRODUCtTION, AW OSER, i- IP -

The Biorka zinc deposit is stilll undeveloped.' The. property, co pose,' -

of eiight 'npatonteddlo6e, clpims, S.a hold .jolntly by 7red h^ JH qnstone,. Unalaska', Alaska; and W. 0. Brown.,.55 South. 62.d Stret,. Soattle S9, Wasb. tv ~ ~ ~ ,,. ,, , ,' : .: '' 4 !$'*S ,i '' .' ' e: '.t .ff ' . .'et,. '

f-Thel area wasw.examined by :F. 1*. JLerchft, ;4iaing en'gineeT* ir .193T andJ

by l&;rr Tounser4d, '1ining+:engineer, in :l940. . . *.. †- ;

*.George Oatas of thle YedertI. Borlhgi¢Af-.4re ex~amined *.fn tep~a the -preabrio, ri ~y

in August 1944, ' but hig report has not as yelb(. beqpn released...

1206 . 3-
R.I. 3967

DESCRIPTION OF DPOSIT

Zinc mineralization at th. Riorka deposit is confined to the han8ingwall section of a fault striking No. 30 Z. across Sedanka Islan-and. dipping

approximately 5570 south (fig. 2)9. Mineral deposition has bIeen controilit-f

structurally. by.a series of nearly vertical fractures ($00 t;o900-:-U v

in the diorite forming the hanging wall, of the fault. The fractures have

an average strike of S. 600 B. and are more closely spaced and mineralized.

as they approach the fault plant. (See figs. 3 and 4.) The footwall is an

unmineralized fine-grained greenstonev;

Zinc sizlfide mineralization does .not approach uniformity along -the

exposed strike interval, nor is it c8onsibtantly strongest: clo-e to tho-efault. A few very.rich stringers persist well up into, th* section.- It

is generally true, however, that there is e progressive and rather u* - :

form reduction in zinctsulfide content of the mineralized fractui*r -as

they recede from the fault plane.

Mineralization consists of:sphalerite and pyrite with;a small amowit

of galena and.chalcopyrite in a gangue of quartz and the mixed earbonate

mineral ankerite. The sphalerite is coarsely crystalline, with a grain

size chiefly between 10- and W4-mesh, Pyrite also occurs scattered throughout the gangfie rock.

Though there is a ratber:duniform reduction -in zinc sulfide content' of

the fractures.progressively away, from ithe fault-,; it is not.:.always turq; In

a mining operation it is probable that this limit will have to be determined

at close intervals by assay.

A mineralized zone 240 feet along the fault was ptripped-and sampled.

The mineralized fractures in this shoot have a miximum.height, measured

normal to the fault plane, of over 60 feet, and average about 45 feet.

The shoot has a calculated easterly rake of 38 degrees.

Both the eastern and western limits of the area sampled are flanked

by small, lightly mineralized outcrops, which are well above the projected

footvall fault. It is reasonable to assumethat they represent the upper

extremities of,fractures that are more highlymineralized as they approach

the fault. On this basis,Ait is logical to extend the strike length of

the shoot by a minimum of 50 feet. -

The very limited surface exploration, including that accomplished

during this examination, has been confined to a soction'41ong the fault

particularly favored by topography and proximity to Lode Creek. The

preqence of thp fault is indicated at the beach line,l-about 3;O W feet

west of tze sampled area and on the approximate.projection'-of the fault:,

by a. series of fractures similar to those observed at the shoot.' The

fractures outcrop in a very small exposure at the base of the cliff and

are mineralized by, pyrite. only. If. this tentative correlation ih cOr1 ect,

the favorable vertical section of the fracture :,zone would 11i.'sme 50 'feet:

below this exposure. The strike interval between the beach and Fall Creek,

nearly 3,000 feet, is uninterruptedly covere& by tundra. TT k iilt bAc

been exposed at Fall Creek, about 2X50 feet west of ithe samplod area, end

1206 -.4
-X~~~~~~~~~~~~~~~~~~~-0

ETIN

APRIL I, 1946

FIG. 3 BIORKA ZINC DEPOSIT, SEDANKA -ISLAND, AAA.
SECTION A- 4

DIORITE

BECOMING FINER

GRAINED AS FAULT

IS APPROACHED

7'&\ SE. TRENDING 7///// O tax M INERALIZED

/X FRACTURES

40 0 40 80

FEET

SECTION B-B

~E. TRENDING l1!a

MINERAL I ZED

FRACTURES

5 0 5 10 20 I

FEET

APRIL I, 1948

CROSS FAULT-&o

FIG. 4 VERTICAL SECTIONS BIORKA ZINC
RLI. 3967

at several points within this 250-foot interval, but the mineralization is

light and confined to pyrite. Fractures characteristic of the ore shoot..

were not observed.

East of the proved area the topography suggests that4-the fault continues to the east shore of'Sedanka Island, some 2 miles distant. For

about, 1 mile immediately east of the mineralized area, the bedrock is

apparently heavily overburdened, and only occasionally outcrops occur further along the projected trend of the fault. The fault was not,-observed

in this direction, and mineralization either in place or as float was not

found.

EXPLORAZIQ1I BY. THE BUREAU OF HjINES

- The Biorka zinc deposit was examined by the Bureau from June 19 through

July 10, 1945. The program coasistedof stripplng the overburden along the

fault for an average width of 40 feet over a strike length of 250 feet and

sampling. Trenches excavated during previous examinations had caved, and

the qntire areawas covered..

A unique method of trenching and stripping the overburden was made

possible by the steep topography adJacent to Lode Creek. Two gasolinedriven fire pump's with"3-inch discharge and several hundr6d fodt of fire

hose were borrowed from the Army. Nitrostarch was purchased from the Army

and used in blasting. an4 removing t&'co'ering. of moss, other vegetation,

and soil also. In stripping the.overburden, the dense mat of vegetation

and top soil was first removed by blasting and by hand. Then the pumps

were set up besido'the croek'at a-point'=whoro the hose could be laid on

grado to the area to. be strippOd... This..was possible because.of the stoop

gradient of the creek, and the static hoad'was redueed-to-virtually zero

Thus, the small ptmp doliveed. a large volume of water and increased the

capacity of the bluicing operation, All overburden'was-removed, and the

bedrock was washed.clean before sampling.< *f

The use of explosives in conjunction.-with the two pumps made it possible

to move a very considerdble.amount 6f'oVe orde'n in a short-time with a

minimum of hand work.

The e:tensioA of the aria stripped bythis method'ptoved the existance

of zinc ore in an'area not previously proesected. T'eftitYnine channel

samples were cut bver an aggtegate length'Of 24s.2 faet;'

The samples.,kere crushed and split, and representatile portions were

submitted to the Territorial Assay Office, Ketchil~af3Alatka, for analysis.

The sample rejectb were combined to form a350-poundb&riple, which was

shipped to the Meitallurgical'Branch, Bureau'of Mdine%, Salt Lake City, Utah,

for beneficiation',

' ' AMPLING A4ND A 1tySES ;;-;

The struoti-bl -ontroltbf the mineralisation wa&datermined to be the.

closely spaced.. frhctures-ini'the d.iorite hAhging wall of the fault. Length

of the fractures as well as the strength of mineralization varied. Deposition of sphalerite, chalcopyrite, and galena has been heaviest close

1206 5
R.I. 3967

to the fault plans ahd gradually fades out ina direction normal to the

fault plane. As there was not enought!imeito carry mple channels broth

parallel and normal to the fault, a line of .samplizg''as carried,:-approximately parallei--to'and ,--4thin a few feet of the fault plane. .(Se fig. 3.)

By inspecti'bn,'it wai estimated that t-he:,ave-rage grade 15 feet from the",

fault.. will be 20 percentl,1owe rthan, that' of the sac tion just above the

fault plane*.',

Analyses of samples are given in the. ;fllowiig taples. Location of

samples is shown on figure 3. The- average nalysis of the -29.-samples taken

over a length of 240.4 feet is 6.8 percent zinc. However,-if the first 7'

samples on the west areke, minaft.ed, the average of the other 22 samples is

8.O percent zinc over a length ot 289.8¢ee t..

ELiminating the 7 aamples 'on thei-'wbst and the. last 3 on the east, the

19 remaining conseeative saxmples 6ver a lengthQf 258.S feet average 9.1

percent zinc', 0.24.percent lead, 0.'-45'prcent copper, 0.04 ounce gold,

and 1.4 ounce silver a ton.

The' zinc.analyses, and widths of samples are' shown in-table 1:

TABLSl. - Analyses of Bureau of Mid St samples

:. .'by. AI', Johin't-bou).

iSamp1 .e width,. True width. Rercent

Samples .et f 7t2 :. .Z fee-b t .; Zinc

69 *2 ..9 4...! 

70 .,...... '., . 4.7 T.

71....... . ,- .7 .6 .'-

76 ....-,. 8.9 , 8.39 '. 

$5 ln~~~~ 2. .2.4 -.

8 ... @@@|3 a 6. 1)12 zrj247

, ,52:.6 '' ' ;5W'6 .'-',2.2

96 ....... 9.0-. 13, 9

91 ... '.'''-'.. ].l.29.6".:','''' 11"' 9.26 11.2 gg97. 9.2; ,.'' 4.....1:;2i9' '

g9 !**. 4 902 , l :.6 ::.

93 w. 14.7 .6, ,:-.; . Sp . . s. 6 .2 ,: .e 6; >7-

90 ... -- ,/ . 79

91 ....... .a 11.2 3.0

93 ....... .; .5 . 49

94 . - . , ; ' 93'" ; - . . ,.,'.',@

6.2-~~~~~~~~~F

96 .000 -5: " "64-5- - 1''l4`7

92 ,4. ' 'Q .. . .....1074' *'g.O3'

: .7,, . 10.4,. :

1206 .,.. 6. .,
R. ;- 3967

TABL:E 1. - aalyjseo of B3ure" .6f J e-l ss¢ le

.*. - .:-: (by 11i - p tQotd) !~~~~~~~~~ ,n .Id S 

,: - - ~Sapile wkdtht, rm wd~th,'_ eroent .. :; :. ' S~am<l8. feF -fet--lzit

so **owessi o..6 10.3 15-1 79 +* .. + + ~10.0 97. I156, f'79 @ qg 9*7- ' 11,5 i^

72 . -.w | I 1.4 111 | w .- . ~~73 # . I 12.S 12,5 jv 6. 2 :¢ -75 -. 1O.1. 5 5,o9l w

W. -- , 1 . ,

:The resl t a of eOm~o s,~t* sampl e ea~lalse s f or..lead gn& copper" are Sholra

in-table: , - .,:

%X&R! 20, _Alnalyses oi. Bureau of~ ine6d sgaple s

CbZ lfila Jo~hasson)

- - .; . '~~Ime wvidthIt e nt ,, , ; aS-l1 0: feet. Zinc I Iad f Corer :

6u an.-9 Z .... -a O 0 14.7 i4. -4 :Tr. _~0.}4 .. 70 and 71 ^.. 36. T~ r. 31 .. . 74. and. 76 ,,,*,. .2 ...... Tr* ;v 11.2 

85 *, d,^ I: .. I':-;. 2> : w .. Trg: Tr.;,:

:4 a0 c~IO s ,0 9 .. .- ,. r0 T -e . Tr.

59 and t7,.4*.* .......... .. ., w. .6 715.2 1 o 125 0.10: 0:.1 ..

'IS and 82 ..... 12.7 10 l.9 'r. .14

90 * 9. . 0 7-9 Tr- TUr 91 3:1. .- 2 11.0r .

93 .4 IW lo ,*,. , . 7-5 . 4.9~ ~re. wi.l:

94i 95 and:96 w. . .... 21.0 : 7; 91'' l *° 5; 92 ~~~ - 4 it .'' 3 q 10 .0 Tr. A g

10 4\ tS. _.10 _ 13:

90..... 10*3~ 15* l Oi 3,0 2fJ3T'6

79 andt 79S..4J, 17-5 '13.8 1.5 1,60 : :

72 and .73 .... .i... 23.6 164 T1r.. 1 .23

> ~~~~75, w "4,i~j^ * 'f-11. 01,

.77 and ..,-F 8 .-200.1! | #9:

Ave 9.g, r e - * , u 4 2 ! ! sf . 9. IT2

NOT~Ie. Percen~t zinc wiL ca:Iculatgd f or the- com sste:

anples~ .a.f ir4 :: ' - -

hialyei o 1,sles,:d cama S lhe ~st are shovn.-4 abei.2inco, _- lead, PAtldoiwpeir Anase w.re calii tavted,

1206-.,._
R.I. 3987

f E 3. -0 Comosit~e se-s {by'yites Joharasson)

e r to., . ...

Samoles . .lOer Id Silver]7inc Cadmium

86, 87, 89, 8 4; S,79"sind 2: .0.i1 N

69, 69, 8, 83, 90 , 93, 92, 80, 1 . i

72, 73, and 75 .......... .. .O2 0. 1.00 7. 0 Ni1

70, 71, 74, 76, 85, 91, 94, 95 ,.I I |

96, 77, and 81 Tr. + i * 2.t Tr__03__

Average .. .... . - 02 .82 6.i 3 Tr,

COPAPI.SON OF SAPLING AIM ANALYSES

The single shoot of mineralization ontSedanka Island explo., by the

Bureau during a preliminary eamination in July .1945 was partly ezposed

and sampled by F. H. Lerchen in June and July, 1937- .rThe deposit was also

examined in l9L40 by Harry Townsend. Comparisonz of the relts of the

three programs of sampling and analyses follows.

The assay map from Lerchen' a report on' the dep'sit1'shows' samples taken

from three are.as. 'Two of these, B and C, cbrrespon47outy to the east and

west limits of the .2 ,-foot zone sampled by t~he Bureaix. -I&'hbcs iiap shows

117 feet of Umoss-covered greenstone" sepatatingareas 3 .and C, 'whereas

stripping and sampling by the Burqau. proved -aa ontirous ritifibalized zone.

The ten samples taken by Lerbhen -from zone C have a.ielghted'-*Ofge bf

9.85 percent.zine 0.2.percent lead, 0.37 percent perV Ol ounce a

ton gold, and 0.56 ounce a ton silver. Samp .es fr om zoh3 iae9d 8.50

percent zinc, b.B4,percent lead, 1.05 percent copper.,'., bl~V6 ze .a't6o

gold, and O.77 ounce a ton silver. It is possi,ble t t Lez'hn,'4Iid'not

uncover the main fault where it is offset by a crossfauat a'th.d'failed

to expose the mineralized zone intervening bektween aros;q .Bnd d.,

Lerchen cut three .samples frop area A:,.:hich is 209 feet easIt ofarea

B. The analysis of sample A_3 is 9.7 percent zinc,,, -.. pezrcegit1e*d, e.l1

percent copper, 0.27;oufnce a ton gold and 0.5 ounce a ton silyqr for a

width of 0.5-feet. Tamples A-l and:A-2 were-low-gradjq materialp:

The short time available did not permit.' the Burebuls engineer to

examine this area.

Harry Townsend) a samples were taken from approxitiMely the same two

areas as Lerchen s aTeas B and C. The Townsend assay map indicates a gap

in sampling.both areas: these were assumed to be barren.' The west area,

corresponding. to area C, averaged 6.1 percent. -zinc0.01. o0nce a- ton gold,

and 0.27 ounce a ton silver, representing an area 45 feet long by 10 feet

wide. The east ore shoot, corresponding to area B, averaged 6.7 percent

zinc, 0.13 ounce a ton gold, and 0.60 ounce a ton silver representing an

area 50 feet l&g by 10 feet wide',o However, if the mi8sing es were

assumed to be of Iaverage grade for each zone, the west area would& average

1206 -
R:.I..3i67.

.6.6 percent zl.ic,,Q*01 ounce a ton t,,0d3Q.. v ice a ton silver, and

the east area'-t d mterage "o unce a ton gold, and

.0.72 ounce a ton silver.

' A3I3 1.t; Analyse.s of^ sa eis But;r ,iI .. +Lo-rchmf -- M LE .,41: - ;. , rav ..

-C area o-r i-t re--ehonbt.')5 by-li;P'et

'.0~~~rzr0

.: . h , . . o .. ,. . n , ---

freet. Zn Pb I Cu .i 1 A4 ..

c-l-.w*,,.-i:.... 1: ;\7.75| 5*60 b:.lo I o.33 IlU~~~~~~~~~~~~~~~~~~~~~~~~o. :35

:C-1- V. ; .' l.:120 io.6o P',2o .43 ''..9 f'.

oc-5-~~~~~' Sww*b;w;S 9-*ttt-5h5 - D} -. 6 : >F 9

.0C-7 :..*..,j..7.00.4.k )?20, ,.,Q204,,,,, xTrv .015' .1

C-6 .C-6. b.,..W..¶.'"t'''7'.6" ~~~7.b0 ';70' 7U ' f1r.0 .015 .1

0-4 .-.-.- w....... 5Qt "575 .t" 0 5 _

0-3 *-**-- -- 1''5.a00o .1P'7j10 .31 'b25r.14 -

o.2 .. ... .. .60 70 10 .33 '.b32'

Av'era .... e 0.0. 16.70 '30, .55 .g ,

NzB-.-t,,-reat3- §pa,,rab~t41tom-a~reK C rS~117 feet, which.

*was not sampled. .-

4 '., -- : - , , r * -7_CS ~,' 

B area ,or,4a ore, ,shQot ,-..,&5 jby: 20 £Qet

B-5 .. .... 12.00- G-3*? -G30:i 0-55 0 030 0.80

~~~~~~~13- .. , 1 ... .0j.90 ,, t 86 390i ! oo................ 9

avera3 o ...... 9 180.051 0.63 0.026 [0.64

NO0TE. - Area B sgpaxtpd ±'rom rearA. by-,290 feet, whi~ch

was no~r' * e,-: "'~~4-~'

-l.--''t .,.... ;X 1''''-3.2'1' 00':O'i*0'20<0 b.27~ ~ t-OF.-'-T-20'2 68O"'

A-2 ..... ...... 7.5 -.: 50 .10 .02 0.01 -10

A-3,.,* ... ,. ,* . .. [..~5.§ I7 1<4:.iO:L, 0 I11 ' .27 . . 50

aver . . 0 1 I0...0.. . .. ..

"Al area,

5 1 .r02 .t'rl

1-2 06 i 4,!0.j 4. '9 .2. .'0

1206_9

*It J. 
R. 2:. 3967-

TABUE 5. - Anaes of e9Im1ese cut bI'Harry Toiiend

West ore shoot, 45 by 10 feet -

Langt of 'sinp~ot . Zn,.l I - u i g.

Sample j feet -percent oz/ton j oz/ton

JB.9 ........... I 12.2 I 0.02 1.02

JB4 ............. its* .9 90 . ;, * _Tr.-- *)lil

No : sample- ....... _ "3:O . _ .. -

JB-T^ ..6 't2,0 ,g. i1e 4e' 

JB- 5 . ...... 6..-- i7.7O -.TI? f 1104

Average . - 1' 27

* * East ores shoot, 50 by 10 feet .... . ...

I * \ . S...... 1.......... 

jB-~4 ~~~~~~S~~~~~~~~~~~o~~~~~ ~ sape'............ '?90l6o~o~2 ''. 60 ...

7. . '7.9 ^60o- ;94 JB3-1 6 6 .;..-0t ese. 4-7 52

Avarage ,.~ 36.6 . . ...... 6. ' .1'3 6

Combined average I 75-1 6.4 1' .07 I .43

NIOTE. - W'est ore shoot separated from East ore shoot by 120

fhet that was' covererA by' slide eck.:`

* *; .22AEF1~IATION* ...... *,~ ., -

~~~-, ; , - *, , *-*

Sample rejects.from the B~.rka. zinc depotit wereeombineda-nd the

composite sample was shipped to-the-'etaliu'gi6al Braneh-Bute -:of Mines,

at the Salt Lake'City Expetim, i chemical

composition Qf a representatiVe-sample of the bre isuindicated by the

following analysis: * ; , , *.,^':!,

Chemical'analis i6ercefit

Total Oxide

Cu Pb Zn Cu Pb Zn Fe dad' Cd Insol Sio2 S A120 4g0

0.31 0.-3, ,8 L0 L7-5 4 2.7 5- &, ,5,46S-25 j72 2.15

31 .- * - O' . .5 5% *i~. .. . - .

* + + A 0 O/ton - S 

L6 0005 0.55

The sulfide minerals in the ore are sphalerite and pyrite with a small

amount of galena and chalcopyrite. The sphalerite is coarsely crystalline,

its grain size lying chiefly between 10- and 48-mesh. Chalcopyrite and

galena are present in grains 35 mesh and smaller.

The gangue consists of quartz, and the mixed carbonate mineral is

ankerite. Quartz occurs as small seams 10- to 65-mesh in width scattered

1206 . 10-
R.I. 3967

throughout the ankerite, and the sphalerite, chalcopyrite, and galena

appear to be associated with it. Pyrite occurs both in the quartz and

scattered throughout the gangue rock;

Examination of a zinc concentrate indic4tes that the sphalerite is

probably marmatitic in part. Its color varies from colorless to light

yellow and red brown. -

Microscopic examination of the ore indicated that the sphalerite is

fairly coarsely crystallized and free of gangue chalcopyrite and pyrite at

about 65-mesh. The ore is readily Concentrated. by flotation. Over 94

percent of the zinc can be concentrated in a product assaying 59.2 percent

zinc, 0.1 percent lead, o.6 percent copper, 4-05 percent iron, 0.32 percent

cadmium, and 1.2 percent insoluble. It is questionable whether the small

lead and copper content of the ore sho-4d 1e fl)oated as a separate product.

However, if such a concentrate is floated, it will assay 11.4 percent lead,

12.2 percent copper, and 12.4 percent zinc, and will contain 75 percent of

the lead, 53 percent of the copper, and 2 percent of the zinc in the ore.

Coarse Cravity Treatment

A representative sample of the Biorka ore, as~received, was' szed on

a 20-mesh screen; the screen oversize was treated by jigging andthe undersize by table concentration. Results. of this test indicate that recoveries

of 82 percent of the lead, 84 percent of the copRer, and 89 percent of the

zinc can be obtained in a combined concentrate representing half of the

original weight and assaying 15.56 percent zinc, 0.51 percent copper, 0.28

percent load, 12,5 percent iron, and 36.5 percent insoluble. 9early 40

percent of the original weight was rejected as a plus 20-mesh jig tailing.

As the ore was relatively finely crushed as received, the results of this

test should warrant investigation of sink-and-float methods of treatment

at coarser sizes.

Selective Flotation

The Biorka zinc ore is readily amenable to flotation, and recoveries

of 94 to 96 percent of the zinc were obtained in plus-50 percent zinc concentrates. As the lead and copper content of the ore is very lJow, production

of a separate lead-copper concentrate might be of questionable value. The

combined lead-copper-zinc concentrate assaYs: l;2:percert: lead, 1.7 percent

copper, 54.7 percent zinc, 5.69 percent iron,'l.7porcett insoluble, and

0.30 percent cadmium. The product representb & te6otreky'of 81 percent of

the lead, 78 percent of the copper, ana 96:prceiitvof the zinc. However,

if a lead-copper concentrate is removed fiisi,:94 percent of the zinc can

readilv be recovered in a premium product assaying 0.1 percent lead, 0.6

percent con-er, 59.2 percent zinc, 4.05 percent iron, 1.2 percent insoluble,

and 0.32 percent cadmium. The lead-copper product assayed 114 percent

lead, 12.2 percent copper, 12.4 percent zinc, and contained 75 percent of

the lead, 53 percent of the copper, and 2 percent of the' zinc. Although the

precious-metal content of the ore is low, it can be concentrated in the

lead-copper product, an& this concentrate wolad assay 0.05 to 0.08 ounbe

gold and 20 to 36.2 ounce silver per ton.

1206 11-
R.I. 3967

TABLE 6. - Gravity concentration

| Assay-i Weight, - Xparcent Distriburncnrcent

Product No. grams |weiht Pb Cu __ Zn Fe |Insol I Pb Cu Zn

Jig concentrate .......... 56025 . 742 . 1 6- o.5 *- .21 21.21 11.4 32. I 38.01 33.0 39-3

1 jig middlings 5 ........ 56024 454 10.1 .2 8.6 12.25 46.6 11.6 lo.4 9.8

2 jig middliigs ..........0 56023 377 g.4 .25 .4° 9.8 | 12.1 44.4 12.1 10.8 9.2

Jig tailings* ..........*. 1 56022 1778 39.6 *07 .10 2.0 j 13.3 54.6 16.o 12.8 8.9

Table concentrate ........ 56021 525 11.7 .2 .65 19.0 14.6 27.4 13.5 24.5 25.0

Table middlings*. ......... 56020 124 2.8 .05 .121 2-3 ! 1L.95 54.6 0.8 I 1.1 0.7

Table sands* ............. 56019 303 6.7 .02 .08 l.& 11 2 58.8 0.7 1.7 1.4

Table slimes ........... ;. 56018 187 )4.2 *3 |)42 12.1 12:1 3 8.6 7-3, | o7 5.7

Calculated head 4490 100.0 .17 .3i 8.9 | 12. 7 4.100.0 i J00.0 lioo.o

Combined concentrates 50.9 .28 .51 15.56| 12.5 36.5 82.5 t4.4 8 g9 Combined tailings* -49.1 .o.10A : 2.0 1 L 5.. Il2.9 -. 1S.6 ! 1l.0

NOT,. - Sample as received i.as minus 1/4-inch, and for gravity concentration the plus 20-mesh- was jigged and

minus 20-mesh material was tabled.

1206 -'2-
R.I. 3.967

Summary,

Preliminary beneficiation studies on ore from the Biorka zinc deposit,

Sedanka, Island, Alaska, indicate that the ore is readily amenable to concentration by selective flotation.. .Zinc concentrates assaying 54 to 59

percent zinc cmn be obtained with 96 percent metal recovery. These concentrates contain 0,3 percent cadmium. Low-grade bopper-lead products can

be removed if the overcall sampling of the deposit indicates any appreciable quantity of these metals or associated precious metals.

Jig and table concentration of the minus 1/4-inch ore as received indicated that the grade could be doubled with a loss of 10 to 15 percent of

the zinc. Further gravity tests employing sink-and-float methods should be

investigated on coarser sizes of ore.

1206 -13-
R.I. 3967

TABLE 7. - Selective flotation

Reagents, pounds per ton

Grind, 12 min. Pb-Cu float Zn float

CaO -2.0 B-23- 0.04 CO - .0

ZnS04 - 4.0 OuSO4 - 2.0

NaCN -5 Z-6 - .32

Min. 194 - .08i B-23 - .04-

Metallurgical data

J Assay, I-t., Percent __l i stay, percent Cd _____ ____

Product No. grams wt. Pb Cu Zn Fe l lej Pb Oil Zn

Pb-Cu concentrate .. 55842 9.0 1.5 11.4 1 12.25 12.4 21.2 8.2 10.061.74.$ 52.8 2.1

Zn concentrate ..... 55g43 86.o 14.3 .1 .61 59.2 4.65 1.2 *.39f #.6*3 j 25.1 94.0

Zn cleaner tailing . 55844 14.g 24 16.g 41.6 | _ o 6.g 1.2

Ro. tailing ........ 55945 493.4 81.8 .5 .o65 *31 14.0o 54 - 17.9T 15.3 2.7

Calculated head ..... !603.2 100.0 .23 *:35 9.0j 12.8g 145.5 | 100.0 100.0 100.0 Bulk concentrate ... _ _ 95:0 15.8 :1.2 1.7 5 4- 5.67 1.87 !Q.30. 81.1o 77.9 96.1

NOTE: Approximate precious metal content of Pb-Cu concentrate - 0.05 ounce Au and 20 once~s.Ag.

1206 14 -
R.I. 3967

TABLE 8. - Selective flotation

Reagents, pounds per ton

Grind, 15 MnAj Pb-Cu float Zn float

CaO - 2.0 B-23 - 0.04 ICaO - 3.0

Zna04 4.0 CuSO4 - 2.0

NaCI_ *5 Z-6 - .24

Min. 194 - .OJ 13-23 - .08

Metallurgical data

IAssay tWeight, PercentT Assay,, percen t Oz/ton i Distribution, percent Product no. grams weightl Pb ! cu i Zn Fe 'Insol. Au AR ! Pb_ ! Zn Au Ag Pb-Cu concentrate .. 5026 15.5 O.b4 2.7 5.910 13-2 199 2.4 x.g 08 3b.2b 67.0o 9.8 0.9|10.2 42.2 C1. tailing . ... o.. 56027 11.7' .48 5-75 1.41 6.7 20.026. 8 - i 10.8 2.1 .14 - - Zn 

Zn 

concentrate ..... 56028 360.6 14.87 .10 1.55 56.8 4.81 .B - - I 5. 69.8 95.31 _ - cleaner tailing . 56029 76.21 3.14 .05 1.28 3. 16.o 44.o -_ 5_ .61 12.2 1.1| Ro. tailing ....... 56030 1.961.o0 90.87 .i09 .025i.±2514:2154.6 z.i 1z _5±g 6.1 2.3

Bulk 

Calculated head .... . 2,425.0 100.00 ... .261 *33 T8 .e6 12.9 145.8 l.°5: .55 100.0 00.0 100.0 - - concentrate ..... j7.! -15.99+ .js3.sI ss 1.65 r- , 81.7 96.6! 63641 _ -' 

Remarks: Grind Percent

+100-mesh ..... 1.3

+200-mesh ..... 16.0

-200-mesh ..... 82.7

1206 -15-