Mount Brock

Site Name

Primary: Mount Brock
Secondary: Mount Brack

---

Commodity

Primary: Silver
Primary: Zinc
Primary: Lead
Primary: Copper
Secondary: Gold
Secondary: Antimony

---

Location

State: Alaska
District: Juneau (Glacier Bay subdistrict)

---

Land Status

Not available

---

Holdings

Not available

---

Workings

Not available

---

Ownership

Not available

---

Production

Not available

---

Deposit

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

---

Physiography

Not available

---

Mineral Deposit Model

Model Name: Polymetallic veins

---

Orebody

Not available

---

Structure

Not available

---

Alterations

Alteration Type: L
Alteration Text: Alteration is mentioned but not described.

---

Rocks

Not available

---

Analytical Data

Not available

---

Materials

Ore: Arsenopyrite
Ore: Chalcopyrite
Ore: Galena
Ore: Pyrite
Ore: Sphalerite
Gangue: Ankerite
Gangue: Calcite
Gangue: Quartz

---

Comments

Comment (Exploration): Status = Inactive

Comment (Geology): Age = No older than Permian based on age of host rocks and probably Cretaceous, based on the age of nearby intrusive rocks (Brew and others, 1978).

Comment (Geology): Geologic Description = The following description is summarized from Brew and others (1978).?The prospect consists of hydrothermal quartz-calcite veins 0.1- to 1.8-foot thick that contain chalcopyrite, sphalerite, galena, pyrite, arsenopyrite, and ankerite in Devonian and Permian andesite, graywacke, limestone, hornfels, and siltstone. The veins strike north and dip to the east. Altered zones (presumably altered zones around or between the veins) are sparsely mineralized. The veins contain up to 1.3% copper, 0.9% lead, 4.2% zinc, 0.7% antimony, 70 ppm silver, and traces of gold. The mineralization must be younger than the Permian age of some of the host rocks and is probably the same age as nearby Cretaceous intrusive rocks.

Comment (Reserve-Resource): Reserves = According to Brew and others (1978), the individual veins are neither rich enough nor extensive enough to be economic and the veins are not close enough together to be mined as a unit.

Comment (Deposit): Other Comments = the deposit is within Glacier Bay National Park and Preserve where exploration and development is restricted.

Comment (Deposit): Model Name = Polymetallic veins (Cox and Singer, 1986; model 22c).

Comment (Reference): Primary Reference = Brew and others, 1978

---

References

Reference (Deposit): Cobb, E.H., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Skagway quadrangle, Alaska; Supplement to Open-File Report 78-316; Part A, Summaries of data to January 1, 1980: U.S. Geological Survey Open-File Report 81-82-A, 11 p.

Reference (Deposit): MacKevett, E.M., Jr., Brew, D.A., Hawley, C.C., Huff, L.C., and Smith, J.G., 1971, Mineral resources of Glacier Bay National Monument, Alaska: U.S. Geological Survey Professional Paper 632, 90 p., 12 plates, scale 1:250,000.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Skagway quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-424, 1 sheet, scale 1:250,000.

Reference (Deposit): Still, J.C., 1991, Bureau of Mines mineral investigations in the Juneau mining district, Alaska, 1984 - 1988, v. 2, Detailed mine, prospect, and mineral occurrence descriptions, section B, Glacier Bay subarea: U.S. Bureau of Mines of Mines Special Publication, 69 p.

Reference (Deposit): Schorr, A.E., 1991, Alaska Place Names, 4th edition: Anchorage, Alaska, The Denali Press, 191 p.

Reference (Deposit): Berg, H.C., 1984, Regional geologic summary, metallogenesis, and mineral resources of southeastern Alaska: U.S. Geological Survey Open-file Report 84-572, 298 p., 1 plate, scale approx. 1:600,000.

Reference (Deposit): MacKevett, E.M., Jr., Brew, D.A., Hawley, C.C., Huff, L.C., and Smith, J.G., 1967, Mineral resources of Glacier Bay National Monument, Alaska: U. S. Geological Survey Open-File Report 151, 176 p.

Reference (Deposit): Brew, D.A., Johnson, B.R., Grybeck, D., Griscom, A., Barnes, D.F., Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources of the Glacier Bay National Monument Wilderness Study Area, Alaska: U.S. Geological Survey Open-File Report 78-494, 670 p.

Reference (Deposit): Cobb, E.H., 1981, Summaries of data and lists of references to metallic and selected nonmetallic mineral occurrences in the Skagway quadrangle, Alaska, Supplement to Open-File Report 78-316, Part A in Summaries of data to January 1, 1980: U.S. Geological Survey Open-File Report 81-82-A, 11 p.

---

The Top Ten Gold Producing States

These ten states contributed the most to the gold production that built the West from 1848 through the 1930s. The Top Ten Gold Producing States.