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Richards Mine [2] (Annex Chrome Mine; Rough and Ready Mine [1918]), Peoria Flat, Yosemite Junction, Tuolumne County, California, USAi
Regional Level Types
Richards Mine [2] (Annex Chrome Mine; Rough and Ready Mine [1918])Mine
Peoria FlatFlat
Yosemite Junction- not defined -
Tuolumne CountyCounty
CaliforniaState
USACountry

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PhotosMapsSearch
Latitude & Longitude (WGS84):
37° 54' 30'' North , 120° 29' 29'' West
Latitude & Longitude (decimal):
Type:
Nearest Settlements:
PlacePopulationDistance
Chinese Camp126 (2011)6.6km
Jamestown3,433 (2011)7.8km
Tuttletown668 (2011)9.7km
Sonora4,818 (2017)12.8km
East Sonora2,266 (2011)13.8km
Nearest Clubs:
Local clubs are the best way to get access to collecting localities
ClubLocationDistance
Calaveras Gem & Mineral SocietyAngels Camp, California18km
Mindat Locality ID:
98145
Long-form identifier:
mindat:1:2:98145:2
GUID (UUID V4):
15059469-e915-4cbf-8e19-92746036077e


A former Cr-Au mine located in sec. 25 & 36, T1N, R13E, and in secs. 30 & 31, T1N, R14E, MDM, 0.7 km (2,400 feet) NE of Peoria Flat (coordinates of record), on private land (fee ownership). Discovered in 1916. Claims cover 209.6 acres. First production occurred in 1918. Owned by Otis Rosasco, Jamestown, California 95327. Operated by the Bradley Mining Co. (1942). MRDS database stated accuracy for this location is 10 meters. The claim map in Pl. 8, Logan (1949) shows location only in secs. 30 & 31, T1N, R14E, but does include the acreage reported in previous reports.

Mineralization is hosted in the Amador rock unit (Late Jurassic-Late Permian dunite). The ore body is lenticular, strikes N60-70W and dips SW at a width of 1.83 meters. Local alteration involved the serpentinization and silicification of host rock. Ore exposed in pit in zone 6 feet wide and strikes N60W. Exposed ore is in highly weathered serpentinite. The deposit occurs in the northern part of the westernmost of 2 serpentine belts which trend NW-SE across the county. The belt is exposed over an area 30 km by 6 km. Local rocks include ultramafic rocks, chiefly Mesozoic, unit 2 (Western Sierra Nevada and Klamath Mountains).

Local structures include shearing in host rock which is strongly developed in a N65-75W direction; and the Bear Mountain Fault zone trending NW.

Workings include surface and underground openings comprised of an open cut 180 feet long, 20 to 30 feet wide and 10 to 20 feet deep, trending N60W, plus 2 short adits driven N10E and S60E, and several shallow prospect trenches (1975). The ore zone was exposed in the floor and N wall of the main pit.

Ore shipped during WWI assayed as high-grade.

Assay analysis results: Year: 1918: ^36.7% Cr2O3 (37 weight percent).

Indicated ore reserves were 7,700 tons. Dump contains ore mixed with waste and may yield 40 tons of ore.

Select Mineral List Type

Standard Detailed Gallery Strunz Chemical Elements

Mineral List


1 valid mineral. 1 erroneous literature entry.

Gallery:

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
Chromite ?4.BB.05Fe2+Cr3+2O4
Magnesiochromite4.BB.05MgCr2O4

List of minerals for each chemical element

OOxygen
O ChromiteFe2+Cr23+O4
O MagnesiochromiteMgCr2O4
MgMagnesium
Mg MagnesiochromiteMgCr2O4
CrChromium
Cr ChromiteFe2+Cr23+O4
Cr MagnesiochromiteMgCr2O4
FeIron
Fe ChromiteFe2+Cr23+O4

Other Databases

Link to USGS MRDS:10043707

Other Regions, Features and Areas containing this locality

North America PlateTectonic Plate
USA

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.

References

 
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