Omilak

Past Producer in Alaska, United States with commodities Silver, Lead, Antimony, Gold, Copper

Geologic information

Identification information

Deposit ID 10100984
MRDS ID A012745
Record type Site
Current site name Omilak
Related records 10160517

Geographic coordinates

Geographic coordinates: -162.66329, 65.04242 (WGS84)
Relative position The Omilak mine is on the west end of the ridge between the North and South Forks of Mosquito Creek at an elevation of 1,450 feet. Mosquito Creek flows westward from headwaters in the northern Darby Mountains to Telephone Creek, a tributary to Fish River in McCarthy's Marsh. The confluence of the North and South Forks is at the range front where the drainages leave the mountains and flow onto the lowlands of McCarthy's Marsh. This is locality 14 of Cobb (1972; MF 417; 1975; OFR 75-429).
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Lead Primary
Antimony Primary
Gold Secondary
Copper Secondary

Comments on the commodity information

  • Ore Material = argentiferous galena

Materials information

Materials Type of material
Cerussite Ore
Chalcopyrite Ore
Stibnite Ore
Silver Ore
Galena Ore
Arsenopyrite Gangue
Limonite Gangue
Pyrite Gangue
Pyrrhotite Gangue

Alteration

  • (Local) The deposits are variably oxidized with secondary iron oxides and lead carbonates developed.

Mineral occurrence model information

Model code 72
USGS model code 19a
Deposit model name Polymetallic replacement
Mark3 model number 47
Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Nearby scientific data

(1) -162.66329, 65.04242

Comments on the geologic information

  • Geologic Description = The Omilak mine is one of the oldest in Alaska (Cobb, 1975). It was discovered before 1880, claims were staked in 1881, ore shipments took place between 1881 and 1890, and the claims were patented in 1884 (Brooks and others, 1901; Mendenhall, 1901; Smith and Eakin, 1911). Forty- one tons of galena were shipped in 1890; they contained 74.7 % Pb, 142.2 ounces/ton Ag, and 0.1 ounces/ton Au (Smith and Eakin, 1911). Nine assays of ore shipped in the 1880's ranged from 60.7 to 173.0 ounces/ton Ag and 10.27 to 82.0 % Pb and some contained up to 0.4 ounces/ton Au (Smith and Eakin, 1911). The mineral deposits consist of discontinuous lenses or veins of argentiferous galena and cerussite in fractured marble. Samples from the shaft dump contain limonite after pyrite or pyrrhotite (and possibly chalcopyrite) and marble cut by veinlets of calc-silicate minerals with disseminated pyrrhotite and pyrite(?). Typical specimens of high grade ore from the shaft dump contained 55.2 % Pb, 12.1 % Fe, 1.0 % Sb, 0.15 % Cu, 0.2 % Sn, 0.1 % Zn, 0.13 ounces/ton Au, and 88.01 ounces/ton Ag (Mulligan, 1962). Thin stibnite veinlets and disseminations are scattered through marble float on the dump of a caved prospect shaft 350 feet southeast of the main shaft (Herreid, 1965; Briskey, 1983). A specimen from this dump contained 0.06 % Pb, 3.4 % Fe, 31.7 % Sb, 0.05 ounces/ton Au, and 0.19 ounces/ton Ag (Mulligan, 1962). The host rock is slightly recrystallized, partly dolomitic marble intercalated with schist in the core of a small anticline that plunges northwest and is overturned to the northeast (Herreid, 1965). The Omilak mine had a 180 foot main shaft, two working levels, and a 500 foot adit. Smith and Eakin (1911) estimated about 600 feet of workings in the main mine area and Herreid (1965) suggested that the adit may have not reached the ore zone due to an inferred plunge of the mineralization. This is a polymetallic vein and replacement in high grade metasedimentary rocks of probable Lower Paleozoic or Precambrian age (Till and others, 1986).
  • Age = Cretaceous ; Epigenetic mineralization in metamorphic rocks of Seward Peninsula is primarily of Cretaceous age.

Economic information

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Council

Production statistics

  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^146.83 Oz/Ton Ag, 76.9%Pb, No Au Value Given
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.36 Oz/Ton Au, 53.05 Oz/Ton Ag, 25.1% Pb
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.075 Oz/Ton Au, 44.28 Oz/Ton Ag, 30.3% Pb
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.075 Oz/Ton Au, 40.75 Oz/Ton Ag, 28.3% Pb
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.05 Oz/Ton Au, 58.75 Oz/Ton Ag, 38.5% Pb
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.364 Oz/Ton Au, 70.1 Oz/Ton Ag, 40.8% Pb
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.1 Oz/Ton Au, 114.03 Oz/Ton Ag, 66.0% Pb
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.15 Oz/Ton Au, 105.58 Oz/Ton Ag, 56.4% Pb
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^No Au Value Given, 111.23 Oz/Ton Ag, 65.0% Pb
  • Year 1881
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.1 Oz/Ton Au, 133.89 Oz/Ton Ag, 72.0% Pb
  • Year 1889
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^No Au Value Given, 142.19 Oz/Ton, Ag, 74.7% Pb
  • Year 1889
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.1 Oz/Ton Au, 49.69 Oz/Ton Ag, 44.5% Pb
  • Year 1889
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.1 Oz/Ton Au, 76.1 Oz/Ton Ag, 49.0% Pb
  • Year 1889
    Material ORE AG PB
    Accuracy Accurate
    Description Ap_Grade: ^0.1 Oz/Ton Au, 92.9 Oz/Ton Ag, 48.3% Pb
  • Year 1890
    Period 1881-1890
    Material ORE AG PB
    Accuracy Estimate
    Description Cp_Grade: ^Ave. 53% Pb, 4800 G/T Ag

Comments on the production information

  • Production Notes = Smith and Eakin (1911) estimate that a total of 300 to 400 tons of high grade ore was shipped from the Omilak mine. Forty-one tons of galena shipped in 1890 contained 74.7 % Pb, 142.2 ounces/ton Ag, and 0.1 ounces/ton Au (Smith and Eakin, 1911). Nine assays of ore shipped in the 1880's ranged from 60.7 to 173.0 ounces/ton Ag and 10.27 to 82.0 % Pb and some contained up to 0.4 ounces/ton Au (Smith and Eakin, 1911).

Comments on the workings information

  • Workings / Exploration = The Omilak mine had a 180 foot main shaft, two working levels, and a 500 foot adit. Smith and Eakin (1911) estimated about 600 feet of workings in the main mine area and Herreid (1965) suggested that the adit may have not reached the ore zone due to an inferred plunge of the mineralization. Some stopes are now caved to the surface. An inclined prospect shaft (now caved) is 350 feet southeast of the main shaft.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012745
USGS Alaska Resource Data File ARDF BN097

Bibliographic references

  • Deposit

    Brooks, A.H., Richardson, G. B., and Collier, A. J., 1901, Reconnaissance in the Cape Nome and Norton Bay regions, Alaska, in 1900: U.S. Geological Survey Special Publication, p. 1-180.

  • Deposit

    Mendenhall, W.C., 1901, A reconnaissance in the Norton Bay region, Alaska, in 1900, in Brooks, A.H., Richardson, G.B., Collier, A.J., and Mendenhall, W.C., Reconnaissance in the Cape Nome and Norton Bay regions, Alaska, in 1900: U.S. Geological Survey Special Publication, p. 181-222.

  • Deposit

    Smith, P.S. and Eakin, H.M., 1911, Mineral resources of Alaska 1910: U.S. Geological Survey Bulletin 480, 333 p..

  • Deposit

    Mulligan, J.J., 1962, Lead-silver deposits in the Omilak area, Seard Peninsula, Alaska: U.S. Bureau of Mines Report of Investigations 6018, 44 p.

  • Deposit

    Cobb, E.H., 1975, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Bendeleben quadrangle, Alaska: U.S. Geological Survey Open-File Report 75-429, 123 p.

  • Deposit

    Briskey, J.A., 1983, Summary of field observations on Seward Peninsula mineral deposits: U.S. Geological Survey, unpublished administrative report, 34 p.

  • Deposit

    Till, A.B., Dumoulin, J.A., Gamble, B. ., Kaufman, D.S., and Carroll, P.I., 1986, Preliminary geologic map and fossil data, Soloman, Bendeleben, and southern Kotzebue quadrangles, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 86-276, 10 p., 3 plates, scale 1:250,000.

  • Deposit

    Cobb, E.H., 1972, Metallic mineral resources map of the Bendeleben quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-417, 1 sheet, scale 1:250,000.

  • Deposit

    Herried, G.H., 1965, Geology of the Omilak-Otter Creek area, Bendeleben quadrangle, Alaska: Alaska Division of Mines and Minerals Geological Report 11, 12 p., 1 sheet, scale 1:63,360.

Comments on the references

  • Primary Reference = Smith and Eakin, 1911

General comments

Subject category Comment text
Deposit Model Name = Polymetallic vein or replacement in marble (Cox and Singer, 1986; model 19a or 22c ?)
Deposit Model Number = 19a (?), 22c (?)

Reporter information

Type Date Name Affiliation Comment
Reporter 15-MAR-1999 Travis L. Hudson Applied Geology