Latitude: 37°37'48"N
Longitude: 118°31'35"W
The Chance Mine is located in the NE1/4 of the SW1/4 of Sec. 2, T4S, R31E, and a new claim was located in 1997 by Robert Griffis and Graham Sutton under claim CAMC271576.
The mine consists of a haulage level and glory hole which connects to an upper workings level. The haulage adit extends well beyond the zone of mineralization. Mineralization is fault bounded, and consisted of pods of galena encapsulated in a quartz vein within decomposed granite. Some galena pods were altered with zones of cerussite forming on the margins, and occasionally, the interiors altered to a combination of linarite and caledonite. At the margins of the mineralized zone, free-standing linarite crystals were found associated with quartz.
Mining for specimens was undertaken by John Seibel, Steve Perry and Robert Griffis (the claim owner) during the period of 2000 to 2004. During this effort, one mineralized zone was discovered in the floor of the haulage level, and several specimens were extracted, with only one outstanding specimen found. Although additional exploration was conducted, no traces of mineralization remains. The claim was abandoned in August 2009.
Rinehart and Ross (1956) reported mineralization in a quartz vein, apparently an extension of the Beckman vein (exploited in the Beckman Mine just to the north), which strikes east and dips 65 degrees south in a shear zone in granodiorite. Ore minerals were silver-bearing galena, anglesite, chalcopyrite, azurite, malachite and gold-bearing pyrite. Workings in 1956 consisted on several shallow pits along outcrop and a 100-foot adit that cuts vein 50 feet below outcrop. No production was reported.
Pemberton (1983) on p. 338 reports Stolzite "in altered galena from the Chance No. 4 claim in the Chidago District (sec. 2, T4S, R32E, MDM)."
Based on the research of Bob Griffis, the R32E notation clearly is a typographical error. Additionally, although there were several contiguous claims placed across the area surrounding the Chance Mine, the Pemberton (1983) reference to a specific Chance No. 4 claim implies more accuracy than is warranted, and this specific claim does not specifically coincide with the actual Chance Mine workings.
References
Personal communication from mine owner, Bob Griffis, 2011.
Rinehart, Charles Dean & Donald C. Ross (1956), Economic geology of the Casa Diablo Mountain quadrangle, California: California Division Mines Special Report 48, p. 9.
Pemberton, H. Earl (1983): Minerals of California. Van Nostrand Reinholt Press edition 1983. 591p. (p.338)
Mineral List
9 entries listed. 9 valid minerals.
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