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McLaughlin Mine (Manhattan Mine), Knoxville, Knoxville District, Napa Co., California, USA

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Latitude & Longitude (WGS84): 38° 50' 17'' North , 122° 21' 50'' West
Latitude & Longitude (decimal): 38.83806,-122.36389
Köppen climate type:Csb : Warm-summer Mediterranean climate

A former open-cast Au-Ag-Pb-Hg mine located in sec. 6, T11N, R4W, and in sec. 1, T11N, R5W, MDM, 2.4 km (7,900 feet) WNW of the Knoxville Mine. Discovered 1865. Worked 1863 - 1877, 1892 - 1905, 1916, 1927, 1932 - 1933, and 1936 - 1945. Some operations extended into Yolo and Lake counties.

The McLaughlin deposit is a large hot spring-type gold deposit located in the northern Coast Ranges of California at the faulted lithologic contact between the Coast Range ophiolite and the Great Valley sequence. The McLaughlin deposit is centered around the sheeted vein complex, a large multistage vein swarm, localized in a dilation zone formed by rheologic contrasts in the footwall polymictic melange. The surface expression of the sheeted vein complex is a subaerial sinter terrace, which merges into the sheeted vein complex. Metal zoning in the sheeted vein complex is highly telescoped. The sinter is enriched in mercury, whereas gold and silver are restricted to the upper 350 m. with the proportion of gold to silver decreasing with depth. Gold is typically present as electrum and is associated with silver and base metal-bearing sulfosalts. Below 350 m mineralization is dominated by small quartz veins with base metal sulfides.

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.

Mineral List

26 valid minerals.

Rock Types Recorded

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Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

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Late Jurassic - Middle Jurassic
145 - 174.1 Ma

ID: 2875613
Ultramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains)

Age: Jurassic (145 - 174.1 Ma)

Stratigraphic Name: Josephine Peridotite

Description: Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 3

Comments: Coast Range ophiolite, Josephine ophiolite. Ultramafic rocks in Middle to Late Jurassic ophiolites of Coast Ranges and westernmost Klamath Mts.

Lithology: Major:{serpentinite}, Minor:{peridotite}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.


Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
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.
Journal of Volcanology & Geothermal Resources: 56: 401-414.
Sherlock, R.L. and Lehrman, N.J. (1995), Occurrences of dendritic gold at the McLaughlin Mine. Mineralium Deposita: 30 (3-4): 323-327.
Sherlock, Ross L., Richard M. Tosdal, Norman J. Lehrman, Joseph R. Graney, Steven Losh, E. Craig Jowett and Stephen E. Kesler (1995), Origin of the McLaughlin Mine sheeted vein complex; metal zoning, fluid inclusion, and isotopic evidence. Economic Geology: 90(8): 2156-2181.

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