OpalManhattan Mine, Knoxville, Knoxville District, Napa Co., California, USA
Latitude: 38°50'17"N
Longitude: 122°21'50"W
A former Hg mine located in sec. 6, T11N, R4W, and in sec. 1, T11N, R5W, MDM, 1 mile NW of the Knoxville Mine. Discovered 1865. Worked 1863 - 1877, 1892 - 1905, 1916, 1927, 1932 - 1933, and 1936 - 1945.
Mineralization is a hydrothermal vein deposit. Host rock is aphanitic volcanic rock (tuff). The ore zone is irregular at 1609.3 meters (1 mile) long and 30.48 meters (several hundred yards ?) wide. The ore occurs as irregular veins of cinnabar filling joint cracks in Tertiary olivine basalt and is disseminated in the rocks adjoining the veins. Alteration is local: silicification of fault zones and tuff; bleaching and kaolinization of basalt. Volcanics are overlain by hot springs deposits.
Production: Ore ran more than 32-50 pounds/ton hand cobbed. Assay given as 18,520 grams/mt.
References
Dana, E.S. (1892) System of Mineralogy, 6th. Edition, New York: 1095-1096.
Bradley, W.W. (1918), Quicksilver resources of California, with a section on metallurgy and ore dressing: California Mining Bureau. Bulletin 78: 86.
Rocks & Minerals (1947): 22: 615.
Bailey, Edgar H. (1959), Froth veins, formed by immiscible hydrothermal fluids, in mercury deposits, California: Geological Society of America Bulletin 70: 661-664.
Davis, F.F. and E.H. Bailey (1966) Mercury. California Division Mines and Geol. Bulletin 191.
Murdoch, Joseph & Robert W. Webb (1966), Minerals of California, Centennial Volume (1866-1966): California Division Mines & Geology Bulletin 189: 232, 304, 350.
Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 111 (map 3-7), 118, 119 (map 3-9), 130, 137, 185, 216, 263, 347.
USGS MRDS database (2005), loc. file ID #10040777.
Mineral List
13 entries listed. 11 valid minerals.
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