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Alma Mine (Alma Pyrite Mine), Leona Heights deposit, Leona Heights, Oakland, Oakland Hills (San Leandro Hills), Diablo Range, Alameda Co., California, USA

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Location is approximate, estimate based on other nearby localities.
 
Latitude & Longitude (WGS84): 37° 47' 29'' North , 122° 10' 27'' West (est.)
Margin of Error:~0km
Köppen climate type:Csb : Warm-summer Mediterranean climate


A S-pyrite-Cu-Ag occurrence/mine located in sec. 34, T1S, R3W, MDM, 0.5 km (0.3 mile) NE of Leona Heights proper and 8.5 km (5.3 miles) E of Oakland center, on private land. Discovered prior to 1892. Owned by Leota C. Reed (1950). MRDS database accuracy for this location is not stated. This mine was originally opened in 1892 and produced principally sulfuric acid until 1934. No pyrite was mined after 1934.

Mineralization is hosted in Pliocene rhyolite. The ore body is lenticular at a thickness of 5.49 meters. Controls for ore emplacement included fractures. The geology is similar to that of the Leona Heights Mine on the same ore zone. The pyrite contains some chalcopyrite and some secondary Cu minerals, boothite, chalcanthite and pisanite. Local rocks include Tertiary intrusive rocks (hypabyssal), unit 9 (Jurassic gabbros along Hayward Fault) and/or ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains).

Local geologic structures include the Hayward Fault and 2 parallel, smaller faults with horizontal displacement.

Workings include underground openings with a length of 1,524 meters and was developed by 5,000 feet of tunnels and drifts. The old workings were burned and a new adit was driven at a lower level.

Copper was produced from the residue after the extraction of the acid and from leaching the dump, amounted to 375,000 pounds of Cu (1929-1935). Later, some small production was realized in 1942 & 1944. Some Ag and a little Au were also produced as by-products. The figure for Cu production includes that from the nearby Leona Mine.

Analytical data results: 1% Cu.


Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.


Mineral List


15 valid minerals. 1 (TL) - type locality of valid minerals.

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References

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Schaller, Waldemar Theodore (1903a), Minerals from Leona Heights, Alameda County, California: University of California, Department of Geological Sciences Bulletin: 3: 191-217.
Schaller, Waldemar Theodore (1905b), Mineralogical notes: USGS Bulletin 262: 121-144.
Lawson, Andrew Cowper (1914), Description of the San Francisco district: Tamalpais, San Francisco, Concord, San Mateo, and Hayward quadrangles: USGS Geol. Atlas, San Francisco folio (Folio No. 193), 24 pp.: 22.
Clark, Clifton W. (1917), The geology and ore deposits of the Leona rhyolite, California: University of California, Department of Geological Sciences Bulletin: 10: 374.
Larsen, Esper Signius (1921), The microscopic determination of nonopaque minerals: USGS Bulletin 679, 294 pp.: 61.
Eric, J.C. (1948), Tabulation of Copper Deposits in California in: Copper in California: California Division of Mines Bulletin 144: 212.
Davis, Fenelon Francis (1950), Mines and mineral resources of Alameda County, California: California Journal of Mines and Geology: 46: 296, 305-306, 340, Pl. 58.
Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 490, 502, 504, 626.
California Division of Mines & Geology (1957), Bulletin 176: 450,451, 619.
California Division of Mines (1958): Mineral Information Service: 11(5): 2.
Branner, G.C. (1959), Sulfur in California and Nevada: U.S. Bureau of Mines, Information Circular 7898, 50 p.: 5.
Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 62, 108, 127, 131, 156, 157, 236, 257, 290, 301.
Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 48, 71, 87, 263, 266, 270, 274, 296, 298.
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10027996 & 10036253.

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