Spruce Hen

Site Name

Primary: Spruce Hen

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Commodity

Primary: Tungsten
Secondary: Molybdenum

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Location

State: Alaska
District: Fairbanks

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: W skarn

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Text: Oxidation of scheelite in weathered zone may have occured (Byers, 1957, p. 188).

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Molybdenite
Ore: Scheelite
Gangue: Calcite
Gangue: Clinozoisite
Gangue: Diopside
Gangue: Fluorite
Gangue: Garnet
Gangue: Hornblende
Gangue: Vesuvianite

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Comments

Comment (Exploration): Status = Inactive

Comment (Reference): Primary Reference = Byers, 1957

Comment (Production): Production Notes = One ton of ore was milled from this property (Saunders, 1958).

Comment (Workings): Workings / Exploration = Development work from 1916 to 1918 consisted of two shafts and many pits and trenches (Byers, 1957). An inclined shaft reportedly was sunk 70 feet on a 3-foot-thick, northwest-dipping ore body. In 1943, a pit and a trench exposed a badly weathered lode about 3 feet thick. When visited by Saunders in 1957, two buildings remained and a headframe had been built over the shaft (Saunders, 1958).

Comment (Geology): Geologic Description = The Spruce Hen mine is along the western contact of a large body of Cretaceous, porphyritic granite. Limestone has been replaced by scheelite, fluorite, garnet, and other typical contact-metamorphic minerals (Byers, 1957). Concentrations of scheelite were found in zones as much as 6 inches wide in blocks of fine-grained, altered igneous rock (Byers, 1957). Berg and Cobb (1967, p. 220) reported that scheelite deposits were found in tactite, silicified limestone, granite, and pegmatitic dikes and in small quartz veins in schist. In 1951, a sample of tungsten ore was submitted for testing at the metallurgical division of the Bureau of Mines (Saunders, 1958). A petrographic examination of the sample revealed it to be a contact metamorphic rock; it consists predominantly of idocrase and pyroxene, with some quartz, fluorite, garnet, wollastonite, and small amounts of scheelite, chlorite and epidote. Traces of limonite and calcite were present. This study showed that most of the scheelite is unlocked by grinding the ore to a minus 65 mesh, but grinding to minus 100 mesh was required to effect maximum liberation. By 1918, five lode prospects were being explored by trenches (Mertie, 1917). One lode was 3 to 4 feet wide, made up of schist and metamorphosed basic rock and averaged 1-2 percent scheelite with no gold. A similar lode was 4 feet wide and trended N. 33 E., with a 45 NW dip. Development work from 1916 to 1918 consisted of two shafts and many pits and trenches (Byers, 1957). An inclined shaft reportedly was sunk 70 feet on a 3-foot-thick, northwest-dipping ore body. In 1943, a pit and a trench exposed a badly weathered lode about 3 feet thick. Samples from this trench averaged 0.44percent tungsten tri-oxide (WO3). In 1957, one ton of ore was milled from this prospect (Saunders, 1958).

Comment (Deposit): Model Name = W skarn deposit (Cox and Singer, 1986; model 14a)

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References

Reference (Deposit): Mulligan, J.J., 1974, Mineral resources of the Trans-Alaska Pipeline corridor: U.S. Bureau of Mines Information Circular 8626, 24 p.

Reference (Deposit): Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Fairbanks quadrangle, Alaska: U.S. Geological Survey Open-File Report 76-662, 174 p.

Reference (Deposit): Thorne, R.L., Muir, N.M., Erickson, A.W., Thomas, B. I., Hedie, H. E., and Wright, W. S., 1948, Tungsten deposits of Alaska: U.S. Bureau of Mines Report of Investigation 4174, 51 p.

Reference (Deposit): Smith, P.S., 1942, Mineral industry of Alaska in 1940: U.S. Geological Survey Bulletin 933-A, p. 1-102.

Reference (Deposit): Cobb, E.H., 1975, Mineral resources of Alaska, in Yount, M.E., ed., U.S. Geological Survey Alaska Program, 1975: U.S. Geological Survey Circular 722, p. 37.

Reference (Deposit): Saunders, R.H., 1958, Work done in 1956-57 on the Spruce Hen tungsten prospect (Steele Creek): Alaska Territorial Department of Mines Prospect Evaluation 58-8, 10 p.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Fairbanks quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-410, 1 sheet, scale 1:250,000.

Reference (Deposit): Mertie, J.B. Jr., 1917, Lode mining in the Fairbanks District, Alaska: U.S. Geological Survey Bulletin 662-H, p. 403-424.

Reference (Deposit): Chapin, Theodore, 1919, Mining in the Fairbanks district: U.S. Geological Survey Bulletin 692-F, p. 321-327.

Reference (Deposit): Martin, G.C., 1920, The Alaska mining industry in 1918: U.S. Geological Survey Bulletin 712-A, p. 1-52.

Reference (Deposit): Thorne, R.L., Muir, N.M., Erickson, A.W., Thomas, B. I., Hedie, H. E., and Wright, W. S., 1948, Tungsten deposits of Alaska: U.S. Bureau of Mines Report of Investigation 4174, 22 p.

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

Reference (Deposit): Byers, F.M., Jr., 1957, Tungsten deposits in the Fairbanks district, Alaska: U.S. Geological Survey Bulletin 1024-I, p. 179-216.

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