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Iowa Hill Chrome Mine (Williamson and Beck property [1918]), Cottage Home Hill, Iowa Hill District, Placer Co., California, USA

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Latitude & Longitude (WGS84): 39° 7' 27'' North , 120° 47' 12'' West
Latitude & Longitude (decimal): 39.1241666667, -120.786666667
 
A former Cr-Fe occurrence/mine located in sec. 19, T15N, R11E, MDM, about 3.5 km N of Cottage Home Hill, E of Shirttail Canyon and S of the Sugar Pine Reservoir, on National Forest land. Discovered and first produced in 1917. Owned by the U.S. Forest Service - Tahoe National Forest (100%), California (1976). Owned & operated by W.S. Hales and William Macy (last operators), California (1918). MRDS database stated accuracy for this location is 10 meters. Pit used as the location point is in the area called Iowa Hill No. 2, 3 on Rynearson's map (1953). The pit is 800 feet NE of the common corner of secs. 19, 24, 25 & 30, just above a small creek. Victory Chrome Company's prospecting during WWII revealed no new chromite bodies.

Mineralization is hosted in serpentinite. The ore body strikes N30W and dips 90N at a thickness of 10 meters, width of 50 meters and length of 600 meters. Ore body No. 1 is irregular & disseminated; ore body No. 2 is tabular and ore body No. 3 is lenticular. The primary mode of origin was magmatic differentiation.. Primary ore control was lithology. Wallrock alteration is intense (carbonitization). This deposit consists of a series of small pods that are above (along ?) strike for approximately 600 meters. The deposit occurs in the northern half of a NNW-trending peridotite body that is exposed over an area approximately 2 miles by 5 miles and is bordered by Paleozoic meta-sediments and Tertiary volcanics. Local rocks include ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains).

Workings include surface and underground openings with the underground workings having a length of 20 meters and an overall depth of 20 meters and comprised of an open stope. Surfac e openings comprised pits and trenches with an overall depth of 4 meters and an overall length of 68.58 meters and an overall width of 10 meters (largest trench).

Production data are found in: Stinson, M.C. (1975).

Production statistics: Year: 1918 (period = 1917-1918): Cr ore averaged above 46% Cr2O3.

Mineral List



5 entries listed. 2 valid minerals.

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References

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.: 164.

Rynearson, Garn Arthur (1953), Geological investigations of chromite in California: Chromite deposits in the northern Sierra Nevada, California. California Division of Mines and Geology Bulletin 134, part 3 chapter 5: 216-217.

Stinson, M.C. (1975), Mineral Property Report, California Division of Mines and Geology (unpublished report).

USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10098563 & 10188665.

U.S. Bureau of Mines, Minerals Availability System (MAS) file #0060610651.

 
Mineral and/or Locality  
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