Rosita Hills District

The Rosita Hills District is a gold, silver, and perlite mine located in Custer county, Colorado.

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: Rosita Hills District
Secondary: Rosita, Querida District

Commodity

Primary: Gold
Primary: Silver
Primary: Perlite
Secondary: Lead
Secondary: Zinc
Secondary: Copper
Tertiary: Aluminum
Tertiary: Potassium

Location

State: Colorado
County: Custer
District: Rosita Hills District

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Year: 1958
Time Period: 1872-1958
Mined: 500000.000 mt
Material type: Approx. ore mined.

Deposit

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

Physiography

Not available

Mineral Deposit Model

Model Name: Epithermal vein, generic

Orebody

Not available

Structure

Type: L
Description: Rosita Hills volcanic complex; ring faults; breccia pipes

Alterations

Not available

Rocks

Name: Latite
Role: Associated
Age Type: Associated Rock
Age Young: Miocene

Name: Andesite
Role: Associated
Age Type: Associated Rock
Age Young: Oligocene

Name: Rhyolite
Role: Associated
Age Type: Associated Rock
Age Young: Miocene

Analytical Data

Not available

Materials

Not available

Comments

Comment (Geology): The Rosita volcanic center consists of andesitic and rhyolitic intrusive and extrusive rocks that represent the remains of a large volcano. Base- and precious-metal ore is hosted in sulfide fissure veins and breccia pipes.

Comment (Location): West side of the Wet Mountains, about 6 miles ESE of Westcliffe; includes about 10 square miles of the Rosita volcanic center, mostly in the SW/4 of T 22 S, R 71 W.

Comment (Production): Estimated production is for both Rosita Hills and nearby Silver Cliff districts.

Comment (Production): The Rosita District is credited with about 85,000 oz. of gold, mostly from the Bassick mine.

Comment (Reserve-Resource): A 1981 report suggested that high-grade vein, or low-grade, bulk-tonnage silver deposits may occur at 13 target areas in the district. (Sunshine files)

Comment (Reserve-Resource): Estimated 800,000 tons alunite resource @ 16.6% alunite at Democrat Hill and 1,200,000 tons @ 6.5% alunite at Mount Robinson. (Thoenen, 1941)

Comment (Commodity): Principally a gold and silver district, plus perlite, and some base metal production. Alunite deposits at Democrat Hill and Mt. Robinson are possible sources of alumina and/or potassium.

Comment (Development): The first discovery, in 1872, was the Senator (now Maverick) mine at Rosita. In 1874, rich silver ore was discovered at the Humboldt-Pocahontas vein nearby, and in 1877, rich gold ore was discovered at the Bassick mine. Many other small deposits were found, and several ore reduction plants were built, but the rich ore soon was mined out and by 1885 activity declined.

References

Reference (Production): Koschmann, A. H., and Bergendahl, M. H., 1968, Principal gold-producing districts of the United States: U.S. Geological Survey Professional Paper 610, 283 p.

Reference (Reserve-Resource): Sunshine Mining Co. Colorado exploration files, unpublished data, Colorado Geological Survey.

Reference (Reserve-Resource): Thoenen, J. R., 1941, Alunite resources of the United States: U.S. Bureau of Mines Report of Investigations 3561, 48 p.

Reference (Deposit): Siems, P.L., 1967, Volcanic and economic geology of the Rosita Hills and Silver cliff districts, Custer County, Colorado: Golden, Colorado School of Mines, D. Sc. dissertation, 222 p.

Reference (Deposit): McEwan, C.J., Fallick, A.E., and Rice, C.M., 1996, The Rosita Hills epithermal Ag-base metal deposits, Colorado, USA - a stable isotope and fluid inclusion study: Mineral Deposita, v. 31, p. 41-51.

Reference (Deposit): Emmons, S.F., 1896, The mines of Custer County, Colorado: U.S. Geological Survey 17th Annual Report, Pt. 2, pp. 405-472.

Reference (Geology): Sharp, W.N., 1978, Geologic map of the Silver Cliff and Rosita volcanic centers, Custer County, Colorado: U.S. Geological Survey Miscellaneous Investigation Series Map I-1081, scale 1:24,000.

Reference (Geology): Cross, W., 1896, Geology of Silver Cliff and the Rosita Hills, Colorado: U.S. Geological Survey 17th Annual Report, Pt. 2, pp. 263-403.

Reference (Deposit): Cappa, J.A., 1998, Alkalic igneous rocks of Colorado and their associated ore deposits: Colorado Geological Survey Resource Series 35, 138 p.

Colorado Mining Photos

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