Brown Bear Mine (Brown Bear vein; Old Brown Bear Mine; Monte Cristo vein; Last Chance vein), Deadwood, Deadwood District, Klamath Mts, Trinity Co., California, USA

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A former Au-Pb-Mn-As-Fe-Zn mine located in secs. 11-14, 16 & 24, T33N, R8W, MDM, 0.3 km (900 feet) E of the Deadwood site, along Deadwood Creek. Owned by E. E. Erich and the Original Sixteen To One Mine, Inc. MRDS database stated accuracy for this location is 100 meters.

Mineralization is a gold-bearing vein deposit (Deposit model code 273; USGS model code 36a; deposit model name: Low-sulfide Au-quartz vein); Mark3 model number: 27), hosted in the Bragdon Formation (siltstone-shale)(Pemberton). NOTE: The USGS MRDS database states that it is hosted in the Galice Formation (slate, diorite, porphyry and granite). The ore body is pinch & swell in form at a thickness of 6.1 meters. Ore control included faults.

Slate is found in 2 varieties. One is hard, siliceous and blocky. The other is soft, black and graphitic. The slate is intruded by diorite and granite-porphyry dikes described in detail by Ferguson (1913). All of these rocks are extensively fissured. Gold occurred in the free state, and was usually medium-high grade. Local rocks include Carboniferous marine rocks, unit 4 (Eastern Klamath Mountains).

Workings include underground openings with a total length of 48,279 meters.

The Monte Cristo and Last Chance veins were explored for 2,600 feet along strike and extensively mined to 400 feet depth. Smaller portions mined to a depth of 760 feet. The Watt adit, 350 feet below the lowest of old productive workings, was driven 6,000 feet in length. More detailed descriptions of workings along with cross section in Averill (1933) p. 13.

Production data are found in: Averill (1941).

This mine had the largest production record in Trinity County. Erich estimated past gross production at $8 to $10 million (period values), and stated that he had definate detailed records of more than $3 million of this. 3 of the individual ore bodies stated to have produced in excess of $1 million each (period values). The ore varies from $10-$1,000/ton in Au content. Sulfides comprise 1-4% of the ore. Prinicpal production came from the Monte Cristo and Last Chance veins, where ore averaged $20-$100/ton (period values). Several smaller veins explored near surface produced important amounts of high-grade ore. No other production data were found.

Analytical data results: Mineralized fissures cut slate and porphyry carrying a few inches of quartz of high assay value. but they are, in many places, not large enough to be mined profitably except at intersections. The concentrate carried $100/ton in Au (period values), but form only a small percentage of the ore.

Mineral List

Calcite

Galena

Gold

Sphalerite

4 entries listed. 4 valid minerals.

References