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Don Pedro Mine (Booker lease; Rosasco Mine), Hetch Hetchy Junction, Tuolumne Co., California, USA

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A former Cr-Fe mine located in sec. 10, T2S, R14E, MDM, 6.5 km (4.0 miles) ESE of Hetch Hetchy Junction, along Big Creek (workings are located on the top of a gentle swell about 100 meters NE of the stream), on private land. Owned by Edyth R. Banta and Nino Chalemor (50.00%), and the Turlock and Modesto Irrigation District (50.00%), Oakland, California 94611. Fee Ownership. Operated by Lavensaler-Speir Corp. (last operator - 1918); and, N. E. Booker, R. Powell, G. N. Porter (last operator - 1918). MRDS database stated accuracy for this location is 100 meters.

Mineralization is hosted in Late Jurassic serpentinite. The ore body is podiform at 25 meters thick, 30 meters wide and 122 meters long (size determination based on the distribution of the workings). The deposit occurs in a small sill-like body that lies to the S and along the trend of the major NW-trending peridotite masses of Tuolumne County. The sill-like body is exposed over an area 90 meters by 1,000 meters. Local rocks include Jurassic marine rocks, unit 1 (Western Sierra Nevada and Western Klamath Mountains).

Workings include surface and underground openings comprised of 8 or 9 small open cuts and caved shafts, which strike N15W, over a distance of 120 meters. The shafts are usually 8 to 15 meters deep (1975).

Production data are found in: Stinson (1975), California Division of Mines and Geology Mineral Property Report, unpublished.

Total production (1905-1918) was between 561 and 700 metric tons. No reserve estimate possible (no ore in place) but Taliferro (1918) estimated that considerable amount of ore remains. The average mineable grade of chromite is 40% and Fe is 11%. Insufficient data for matrix calculation analysis by CDMG in 1976 gave the following percentages: disseminated E = Si02: 07.10%, CrR2O3: 51.16%, FeO: 17.33%; total Fe: 20.58%, Al203: 06.6%, 4.09 (?), Cr:Fe 2.19.

Analytical data results: Ore averaged 40% Cr2O3.

Mineral List

6 entries listed. 2 valid minerals. 1 erroneous literature entry.

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.


Bradley, W.W., Huguenin, Emile, Logan, C.A., Tucker, W.B., and Waring, C.A. (1918), Manganese and chromium in California: California Mining Bureau. Bulletin 76, 248 pp.: 213.

Taliaferro, Nicholas Lloyd (1918), Coop War Minerals Investigations California Chrome, Tuolumne County, No. 13.

Cater, F.W., Jr. (1948a), Chromite deposits of Tuolumne and Mariposa Counties, California: California Division Mines Bulletin 134, part III, Chapter 1: 17, 18, Pl. 1.

Stinson, Melvin Clarence (1975) California Division of Mining and Geology Mineral Property Report (unpublished)

Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 160.

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10043699 & 10214146.

U.S. Bureau of Mines, Minerals Availability System (MAS) file ID #0061090112.

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