Boraxo Mine, Ryan, Furnace Creek Mining District (Furnace Creek Borate Mining District), Inyo County, California, USAi

Regional Level Types
Boraxo Mine	Mine (Abandoned)
Ryan	Unincorporated Community
Furnace Creek Mining District (Furnace Creek Borate Mining District)	Mining District
Inyo County	County
California	State
USA	Country

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A former borate mine located in the NE¼NE¼ sec. 36, T26N, R2E, SBM, 2 miles (3.22 km) WNW of Ryan (S of hill 2562), on National Park Service land (Death Valley National Park). Discovered in 1915. Operated by Tenneco Mining Inc. (1976). Owned by the Pacific Coast Borax Co.; Russell, Monaghan, Barlow, and Hill; Pacific Coast Borax Co. (1915). The mine was purchased in 1960 by the Kern County Land Company for $200,000. Operated in the 1960s and during the period 1970 to 1977 (?). Closed in 1977. MRDS database stated accuracy for this location is 100 meters.

Mineralization is a lacustrine borate deposit (Deposit model: 260: Lacustrine borates; USGS model code 35b.3), hosted in rocks of the Miocene Furnace Creek Formation (limestone, clay, mud, mudstone, sandstone, shale). The orebody is lenticular, strikes E-W and dips 5-60 degrees S (40 degrees S average), at a thickness of 39.62 m, width of 853.44 meters, and a length of 213.36 meters.

The rocks of the Furnace Creek Formation weather to a yellow or green. Greyish basaltic flows and/or intrusions occur locally in a zone from 400 feet (122 m) to 900 feet (274 m) above the base of the formation. In the mine area, the formation is a maximum of 1,200 feet (366 m) thick. Local rocks include Quaternary alluvium and marine deposits.

The deposit occurs on the S limb of the anticline within a few tens of feet to 200 feet (61 m) of the base of the Furnace Creek Formation. It is cut near the ground surface by the pit fault on the N and pinches out on the S at a depth of about 800 feet (244 m) below the ground surface. The body is deformed locally by minor folds and ranges in thickness up to 130 feet (40 m) (average 40 feet (12 m) to 45 feet (14 m)). The deposit is 2,800 feet (853 m) wide along strike and 300 feet (91 m) to 700 feet (213 m) long down-dip. The deposit is largely parallel to the dip of the enclosing beds. The Boraxo deposit is composed of 2 zones of borate minerals with interstitial clay and interlayered limy shale, mudstone, siltstone, and sandstone beds that are commonly 1 to 5 feet (1.52 m) thick. The outer zone of the deposit is colemanite and the core is a mixture of ulexite and probertite.

Local structures include a W-trending, E-plunging anticline, the Death Valley graben, Pit fault and minor folding.

Workings include surface openings comprised of an open pit with a length of 670.56 meters. In 1976, the pit was 2,200 feet (671 m) long, 300 feet (91.44 m) wide at surface on the W to about 1,000 feet (305 m) wide on the E and 225 feet (69 m) deep. The maximum pit depth will be 450 feet (137 m) on the E, but the length and width were already at the maximum of the pit design. On completion of the open pit operations, a substantial tonnage of ore will remain beneath the floor that would require underground mining. The stripping ratio of overburden to ore was 26:1 in 1976, but was expected to decrease with further mining.

Production data are found in Evans et al. (1976).

Analytical data results: Assays of drill cores indicate an average grade of 20% B2O3 for colemanite ore. Assays of mill-run material indicate an average grade of 28% B2O3 for ulexite ore. This indicates a mineral content of about 40% colemanite and 70% ulexite-probertite.

Reserve-Resource data are found in Orris (1990).

Commodity List

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Mineral List

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8 valid minerals.

Rock Types Recorded

Rock list contains entries from the region specified including sub-localities