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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): 38.8380555556, -122.363888889

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

Entries shown in red are rocks recorded for this region.

Note: this is a very new system on and data is currently VERY limited. Please bear with us while we work towards adding this information!

Regional Geology

This 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 data will improve over time as more accurate maps and data sets are added.

Cretaceous66 - 145 MaCretaceous sedimentary rocks

Sedimentary rocks

Late Jurassic - Middle Jurassic145 - 174.1 MaUltramafic rocks, chiefly Mesozoic, unit 3 (Coast Ranges and Western Klamath Mountains)

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

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

Ultramafic rocks in Middle to Late Jurassic ophiolites of Coast Ranges and westernmost Klamath Mts.

Jurassic145 - 201.3 MaJurassic plutonic: mafic and ultramafic rocks

Plutonic: mafic and ultramafic rocks

References for regional geology:

Data provided by

Garrity, C.P., and Soller, D.R.,. Database of the Geologic Map of North America: adapted from the map by J.C. Reed, Jr. and others (2005). U.S. Geological Survey Data Series 424 .

USGS compilers. State geologic map data. State Maps.

Geological Survey of Canada. Generalized geological map of the world and linked databases. doi:10.4095/195142. Open File 2915d.

The above list 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.


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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