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Oro Rico Mine (Penon Blanco Mine), Peñon Blanco Peak, Coulterville, Coulterville District, Mother Lode Belt, Mariposa Co., California, USA

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Latitude & Longitude (WGS84): 37° 44' 50'' North , 120° 14' 10'' West
Latitude & Longitude (decimal): 37.74722,-120.23611

A Au-Cu-Pb-Zn occurrence/group of claims/mine located in secs. 19, 20 & 29, T2S, R16E, MDM, 2.8 km (9,200 feet) NE of Peño Blanco Peak (coordinates of record) (on the E slope of Penon Blanco Point, just S of the Tuolumne County line along highway 49). Property consisted of 5 patented claims and 2 unpatented claims, totaling over 100 acres. Operated by Oro Rico Mines Co. C/O A. D. Vencile. MRDS database stated accuracy for this location is 500 meters. Location may be the prospects shown in the NE¼ of sec. 19, SW¼ sec. 20, and in the NW¼ sec. 29, USGS quadrangle Coulterville, California (1949).

Claims includes: Old Judge, South Judge, Little Judge, Penon Blanco and North Penon Blanco (patented); and the Star and Stevenson claims (unpatented).

Local rocks include ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains).

Workings include underground openings comprised of adits, shafts, tunnels and drifting. Inn 1954, 2 workigns were still recognizable on the Penon Blanco claim, but none was accessible without some cleaning out.

One of the earliest worked claims in the county. Considerable development had been made by 1868 and several ore shoots 2-4 feet thick had been discovered and ore averaged $10 - $12 per ton (period values). Worked intermittently until 1912. Little or no work done until after 1928 due to litigation. Some exploration and development done in 1934. Little or no work done since.

Total production, although incompletely recorded, is small. Copper production was less than 100,000 pounds (Eric, J.C. (1948)).

Mineral List

22 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

Early Jurassic - Neoproterozoic
174.1 - 1000 Ma
Ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains)

Age: Neoproterozoic to Jurassic (174.1 - 1000 Ma)

Description: Ultramafic rocks, mostly serpentine. Minor peridotite, gabbro, and diabase. Chiefly Mesozoic unit 2

Comments: Feather River peridotite, Kings River ophiolite, Kings-Kaweah ophiolite melange. Tectonized ultramafic complexes in western Sierra Nevada and western Klamath Mts., primarily of Ordovician to Early Jurassic age. Characterized in large part by serpentinite-matrix melanges containing blocks and slabs of ultramafic and other rocks

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

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.


Logan, Clarence August (1934), Mother Lode Gold Belt of California: California Division Mines Bulletin 108, 221 pp.: 185-186.

Eric, J.C. (1948), Copper in California: California Division of Mines Bulletin 144: part 3: 269.

Bowen, O.E., Jr. & C.H. Gray, Jr. (1957), Mines and mineral deposits of Mariposa County, California: California Journal of Mines and Geology (Report 53): 53(1&2): 147-148, 294.

Goodwin, Joseph Grant (1957) Lead and zinc in California. California Journal of Mines and Geology, Division of Mines (Report 53): 53(3&4): 551.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10030836 & 10284930.

U.S. Bureau of Mines, Minerals Availability System (MAS) file ID #0060430040.

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