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St. Lawrence Mine, Ophir, Ophir District (Auburn District; Duncan Hill District), Placer Co., California, USA

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Latitude & Longitude (WGS84): 38° 53' 60'' North , 121° 7' 35'' West
Latitude & Longitude (decimal): 38.9, -121.126388889
 
A former Au-Sb-Ag-Pb mine located in the S½S½SW¼ sec. 7, T12N, R8E, MDM, 1.0 km (0.6 mile/3,400 feet) NNW of Ophir and Ophir School, about 2½ miles W of Auburn (1½ miles NNE of Newcastle), on private (patented) land. Operated during the period 1903 to 1912. MRDS database stated accuracy for this location is 500 meters.

Mineralization is a vein deposit hosted in granodiorite and diorite. The ore body strikes E and dips 45S at a thickness of 0.51 meter. The vein is 1 foot (30 cm) to 20 inches (50 cm) thick and carries 2% sulfides. Local rocks include Mesozoic granitic rocks, unit 3 (Sierra Nevada, Death Valley area, Northern Mojave Desert and Transverse Ranges).

Workings include underground openings with a length of 304.8 meters and an overall depth of 91.44 meters and comprised of a shaft, 2 tunnels (?) and adits.

Production data are found in: Logan, Clarence August (1936).

Some production was reported during the 1903-1912 period. No other production records were found.

Analytical data results: SThe sulfides assayed at $70 to $200 (period values)/ton.

Mineral List



5 entries listed. 5 valid minerals.

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References

Irelan, William, Jr. (1888b), Eighth annual report of the State Mineralogist [includes mineral resources of the State, with contributions by W.A. Goodyear, H.A. Whiting, and Stephen Bowers]: California Mining Bureau. Report 8, 946 pp.: 461-462.

Lindgren, Waldemar (1892), The gold deposit at Pine Hill, California: American Journal of Science 3rd. series: 44: 92-96.

Lindgren, Waldemar (1894a), The gold-silver veins of Ophir, California: USGS 14th. Ann. Report, part 2: 243-284; […(abstract): Mining and Scientific Press: 71: 216, 233 (1895); Journal of Geology: 4: 373-374 (1896); …Nature: 53: 466 (1896)]: Pl. 17.

Waring, Clarence A. (1917), Placer County: Report 15 of the State Mineralogist, California State Mining Bureau (Report 15): 15: 350, Pl. facing p. 318.

Logan, C.A. (1935), Review of Gold Mining in East-Central California: California Journal of Mines and Geology (Report 31): 31(1): 18.

Logan, Clarence August (1936), Gold mines of Placer County: California Journal of Mines and Geology, California Division Mines (Report 32): 32(1): 35-37, 47.

Goodwin, Joseph Grant (1957) Lead and zinc in California. California Journal of Mines and Geology, Division of Mines (Report 53): 53(3&4): 592.

Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 350.

Clark, Wm. B. (1970a) Gold districts of California: California Division Mines & Geology Bulletin 193.

Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 29 (map 2-17), 130.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10007693 & 10237398.

U.S. Bureau of Mines, Minerals Availability System (MAS) file #0060610112.

 
Mineral and/or Locality  
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