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Rough Diamond Mine (Rough Diamond Placer Mine; Rough Diamond Crystal Mine), Chili Gulch (Chile Gulch ?), Mokelumne Hill, Mokelumne Hill District, East Belt, Calaveras Co., California, USA

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Latitude & Longitude (WGS84): 38° 16' 15'' North , 120° 42' 41'' West
Latitude & Longitude (decimal): 38.27083,-120.71139

Another classic locality for "Mokelumne Hill Rock Crystal"

A former placer/drift Au-quartz mine located in the SE¼ sec. 24, T5N, R11E, MDM, about 2 miles S of Mokelumne Hill, south of and adjacent to the Green Mountain drift mine. MRDS database stated accuracy for this location is 100 meters. Coordinates provided are for the mine symbol on the topo map, S of the approximate location of the Green Mountain Mine.

Mineralization is a cemented gravel placer Au-Quartz deposit. Local rocks include Paleozoic marine rocks, undivided, unit 4 (Western Sierra Nevada) and/or Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range).

Workings include underground openings. Old workings include a 700 foot tunnel.

Prior to 1877 this property was worked as a hydraulic mine, but cemented gravel prevented recovery of much of the Gold. A Mr. Garland purchased the ground in 1877, drove a 450-foot drift, and erected a 5 stamp mill that handled 90 tons of gravel per day. Gold in the gravel is reported to have averaged $2.00 to $2.50 per carload in 1883. The mine lay idle for several years until 1942. From late in 1942 until November, 1943, approximately 6600 pounds of Quartz crystals were recovered. Production of modest amounts of Quartz crystals continued through 1944. During the latter part of that year, both the Rough Diamond and Calaveras Crystal (Green Mountain) properties were operated by the Quartz crystal products company. No crystal production has been reported since 1944.

This property is located on the Tunnel Ridge channel. Its geology is similar to that of the Green Mountain mine and is described under that heading. Reserves of Quartz crystal in the Rough Diamond were estimated in 1944 to be 12,000 pounds in 900 cubic yards of gravel. Approximately 5% of this Quartz would be of piezoelectric grade.

Production information: About 6,600 pounds of quartz rock crystal; about 4,700 cubic yards of gravel had been mined, averaging 1.4 pounds of crystal per cubic yard. Au averaged $2.00 to $2.50 a carload in 1883 (period values). Some Au mined in 1934. It was estimated that about 12,600 pounds of crystal remain to be recovered.

Mineral List

3 valid minerals.

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.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Gelasian - Chattian
1.806 - 28.1 Ma
Tertiary pyroclastic and volcanic mudflow deposits, unit 9 (Cascade Range)

Age: Cenozoic (1.806 - 28.1 Ma)

Stratigraphic Name: Alturas Formation; Bonta Formation; Cedarville Series (part); Delleker Formation; Ingalls Formation; Mehrten Formation (part); Nomlaki Tuff Member; Penman Formation; Reeds Creek Andesite; Spanish Canyon Formation; Tropico Group (part); Tuscan Formation; Valley Springs Formation (part)

Description: Tertiary pyroclastic and volcanic mudflow deposits.

Lithology: Major:{andesite}, Minor:{rhyolite}, Incidental:{basalt, basaltic andesite}

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 Macrostrat.org, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on mindat.org. 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 mindat.org 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.


California Division of Mines (1962): Mineral Information Service: 15(11) (November): 5.

King, R.U. (1966), California Mineral Resources; California Division of Mines and Geology Bulletin 191: 345.

Logan, Clarence August and Franke, H. (1936), Mines and Mineral Resources of Calaveras Co.: California Division of Mines, California Journal of Mines & Geology, California Division of Mines: 32(3): 350, Pl. 6 & 7.

California Journal of Mines and Geology (1943) (Report 39): 39(3): 316.

Rocks & Minerals (1944): 19: 79.

Durrell, C. (1944) Geology of the quartz crystal mines near Mokelumne Hill, Calaveras County, California California Division Mines Report 40: 423-433.

California Division of Mines (1962): Mineral Information Service: 15(_): 5.

California Division Mines & Geology Bulletin 176 (1957): 459-460.

Clark, Wm. B. & P.A. Lydon (1962), Mines and mineral resources of Calaveras County, California: California Division of Mines & Geology County Report 2; [… Geological Society of America Proceedings, 1933: 312-313, 1934]: 91, 205, 213, Pl. C & D.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10109144 & 10284117.

U.S. Bureau of Mines, Minerals Availability System (MAS) file ID #0060090315.

Mineral and/or Locality  
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