Sedanka Island

Prospect in Alaska, United States with commodities Gold, Silver, Copper, Zinc, Cadmium, Lead

Geologic information

Identification information

Deposit ID 10002323
MRDS ID A013233
Record type Site
Current site name Sedanka Island
Alternate or previous names Biorka
Related records 10234128

Geographic coordinates

Geographic coordinates: -166.20239, 53.79078 (WGS84)
Relative position Locality is 4 km south of Biorka Village, 0.9 km east of Udamat Bay on Sedanka Island. The locality corresponds to locality 3 of Cobb (1972, MF-446), it is accurate within about 300 m. It is also equivalent in part to anomaly no. 15 of Christie (1974).
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Geographic areas

Country State
United States Alaska


Commodity Importance
Gold Primary
Silver Primary
Copper Primary
Zinc Primary
Cadmium Secondary
Lead Secondary

Comments on the commodity information

  • Ore Material = argentiferous galena

Materials information

Materials Type of material
Chalcopyrite Ore
Gold Ore
Sphalerite Ore
Silver Ore
Galena Ore
Ankerite Gangue
Pyrite Gangue
Quartz Gangue


  • (Local) Christie (1974) reports pervasive development of chlorite and minor sericite and quartz veinlets near diorite.

Mineral occurrence model information

Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock > Mafic Intrusive Rock > Diorite
    Rock unit name Unalaska Formation
    Rock description Unalaska Formation
    Stratigraphic age (youngest) Pliocene
    Stratigraphic age (youngest) Pliocene
    Stratigraphic age (youngest) Pliocene
    Stratigraphic age (youngest) Pliocene
  • Host or associated Associated
    Rock type Metamorphic Rock > Metavolcanic Rock > Mafic Metamorphic Rock > Greenstone
  • Host or associated Host
    Rock type Plutonic Rock > Mafic Intrusive Rock > Diorite

Nearby scientific data

(1) -166.20239, 53.79078

Comments on the geologic information

  • Geologic Description = Quartz and ankerite in nearly vertical veins in N 60xW striking fractures in diorite that forms hanging wall of fault that strikes N 80xE and dips 55xS. Richest mineralization near fault; fine-grained greenstone of footwall is barren. Veins contain sphalerite, abundant pyrite, a small amount of chalcopyrite and argentiferous(?) galena, and a small amount of gold. Pyrite also disseminated throughout diorite. Deposit along fault has been exposed for 70 m along strike, with mineralization zone a maximum of 18 m high and averaging more than 13 meters. Ore shoot extends at least 14 m beyond sampled zone, with fault traceable for at least 900 m west, and possibly 3.2 km east of mineralized zone, but no mineralization has been detected outside of the sampled area. Ores deposited at temperature below 138x C (Drewes and others, 1961, p. 658).

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Aleutians

Comments on the workings information

  • Workings / Exploration = A 70 by 12 m area of tundra overburden was stripped by hydraulic methods and explosives, and 29 channel samples collected along strike of deposit for 75 m during USBM investigations in 1945 (Webber and others, 1946). Average analysis of 29 samples along narrow mineralized zone was 6.8 percent Zn. Average of 19 samples was 9.1 percent Zn, 0.24 percent Pb, 0.45 percent Cu, 0.04 oz/ton Au, 1.4 oz/ton Ag. Benefication tests showed that concentrates contained 0.3 percent Cd. Sampling in 1979 by Resource Associates of Alaska (Butherus, 1979) produced gold values ranging from 200 ppb to 12 ppm (0.348 oz/t). Christie (1974) did not visit the 'zinc' occurrence, however reconnaissance mapping in the area and limited sampling resulted in samples yielding up to 205 ppm copper, 1,000 ppm zinc, 3.1 ppm silver, and 0.34 ppm gold.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A013233
USGS Alaska Resource Data File ARDF UN005

Bibliographic references

  • Deposit

    Webber, B.S., Moss, J.M., and Rutledge, F.A., 1946, Exploration of Sedanka zinc deposit, Sedanka Island, Alaska: U.S. Bureau of Mines Report of Investigations 3967, 15 p.

  • Deposit

    Twenhofel, W.S., 1953, Potential Alaskan mineral resources for proposed electrochemical and electrometallurgical industries in the upper Lynn Canal area, Alaska: U.S. Geological Survey Circular 252, 14 p.

  • Deposit

    Drewes, Harold, Fraser, G.D., Snyder, G.L., and Barnett, H.F., Jr., 1961, Geology of Unalaska Island and adjacent insular shelf, Aleutian Islands, Alaska: U.S. Geological Survey Bulletin 1028-S, p. 583-676.

  • Deposit

    Berg, H.C., and Cobb, E.H., 1967, Metalliferous Lode Deposits of Alaska. U.S. Geological Survey Bulletin 1246, 254 p.

  • Deposit

    Cobb, E.H., 1972, Metallic mineral resources map of the Unalaska quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies MF-446, 1 sheet, scale 1: 250,000.

  • Deposit

    Randolph, D.B., 1991, Unalaska project, 1990 final report: Battle Mountain Exploration Company, Alaska District, 62 p., 5 appendices, 15 plates, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Butherus, D.L., Gressitt, E.E., Pray, Jim, Corner, N.G., Lindberg, P.A., and Fankhauser, R.E., 1979, Exploration and evaluation of the Aleut Native Corporation Lands 1979: Unpublished Resource Associates of Alaska report prepared for Houston Oil and Minerals Corporation and available from The Aleut Corporation, 69 p., 1 appendix.

  • Deposit

    Bain, H.F., 1946, Alaska's minerals as a basis for industry: U.S. Bureau of Mines Information Circular 7379, 83 p.

Comments on the references

  • Primary Reference = Webber and others, 1946

General comments

Subject category Comment text
Deposit Model Name = Polymetallic vein

Reporter information

Type Date Name Affiliation Comment
Reporter 18-MAR-96 L.P. Niles U.S. Geological Survey
Reporter 18-MAR-96 S.W. Bie U.S. Geological Survey
Reporter 18-MAR-96 F.H. Wilson U.S. Geological Survey