Commonwealth

The Commonwealth is a molybdenum, zinc, copper, and gold mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Commonwealth

Commodity

Primary: Molybdenum
Primary: Zinc
Primary: Copper
Primary: Gold

Location

State: Alaska
District: Hyder

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

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

Physiography

Not available

Mineral Deposit Model

Model Name: Skarn Cu

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Weathered pyrrhotite gives a rusty color to the surface outcrop.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Sphalerite
Ore: Pyrrhotite
Ore: Molybdenite
Ore: Gold
Ore: Chalcopyrite
Gangue: Quartz

Comments

Comment (Reference): Primary Reference = Buddington, 1929 (B807)

Comment (Workings): Workings / Exploration = The prospect was explored in the early 1900s by opencuts, an 80-foot adit, and an 11-foot adit.

Comment (Geology): Geologic Description = The country rocks in the area of the presumed site are porphyritic quartz monzonite and granodiorite of the Eocene Davis River Pluton (Smith, 1977; Berg and others, 1988). According to Buddington (1929, p. 111-112), the Commonwealth prospect(s) lie within a narrow belt of metamorphosed sedimentary rocks that form a roof pendant within the quartz monzonite. The metamorphosed strata are several hundred feet thick and include interbedded quartzite, schist, and marble. A lamprophyre dike cuts the quartz monzonite and metasedimentary rocks. The quartzite, schist, and marble have been contact metamorphosed by the intrusion of the quartz monzonite and locally contain disseminations, seams, and small masses of quartz, garnet, epidote, pyroxene, tremolite, and small amounts of sulfide minerals. The sulfide minerals include pyrrhotite, sphalerite, chalcopyrite, and molybdenite, and a quartz stringer was reported to yield gold. The age of this contact metamorphic (skarn) deposit probably is Eocene, roughly contemporaneous with the emplacement of the Davis River Pluton. The prospect was explored in the early 1900s by an 80-foot adit and an 11-foot adit.

Comment (Commodity): Gangue = skarn minerals

Comment (Deposit): Model Name = Cu skarn (Cox and Singer, 1986; model 18b)

Comment (Deposit): Other Comments = Site is in Misty Fiords National Monument Wilderness.

Comment (Geology): Age = Eocene

References

Reference (Deposit): Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map MF-1807,27 p., scale 1:250,000.

Reference (Deposit): Buddington, A.F., 1929, Geology of Hyder and vicinity, southeastern Alaska, with a reconnaissance of Chickamin River: U.S. Geological Survey Bulletin 807, 124 p.

Reference (Deposit): Smith, J.G., 1977, Geology of the Ketchikan D-1 and Bradfield Canal A-1 quadrangles, Alaska: U.S. Geological Survey Bulletin 1425, 49 p.

Reference (Deposit): Elliott, R.L., Berg, H.C., and Karl, Susan, 1978, map and table describing metalliferous and selected nonmetalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-file Report, 78-73-B,17 p., scale 1:250,000.

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