Union Carbide Tungsten Mill, Pine Creek

 mill, mining

Important provider of tungsten during WWII. Started in the '20s; closed in 1992 when extraction costs became too costly. The mine itself is known as an upside down mine because it starts at the bottom of the mountain and works its way up to the summit.

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The mine is a tungsten mine, once the largest in the US. It is located 18 miles west of Bishop. The primary focus of this mine appears to have been scheelite (CaWO 4 ) and powellite (CaMoO 4 ). The molybdenum also shows up as molybdenite (MoS 2 ) or ferrimolybdite along with bismuth as bismuthite (Bi 2 S 3 ). There appears to have been substantial copper mineralization as chalcopyrite and bornite are abundant. The mine area is very dusty, to a degree owing to the presence of laumontite (CaAl 2 Si 4 O 12 -4H 2 O), which dehydrates in air to form a white powder. (These crystals should be kept damp to avoid deterioration.)

Per mineralsocal.com : The Pine Creek mine is 18 miles west of Bishop, on the south slope of Mount Morgan. It contains bismuthinite, bornite, calcite, chalcopyrite, ferrimolybdite, laumontite, molybdenite, powellite, scheelite.

International Strategic Mineral Issues Summary Report-Tungsten; 1998; USGS Circular 930-O, pgs. 47 &65 : The Pine Creek Mine was discovered in 1916 and began production in 1918. From 1918 until 1953 it produced 7,613 tons of tungsten. In 1979 it was operating as an underground mine producing about 2,000 tons of tungsten per year. It was closed in 1986 due to low tungsten prices caused my major imports of Chinese material. The primary focus of the mine was scheelite but copper, as chalcopyrite and bornite, and molybdenum were present. The host rock is marble of Pine Creek Formation (Cretaceous and Paleozoic), hornfels (Paleozoic), monzogranite, and Morgan Creek quartz monzonite (Cretaceous).

Old John Comment : The last US production of tungsten concentrates of any size was from the Pine Creek Mine in 1994. While mining of ores ceased much earlier, US Tungsten Corporation used stockpiled ores at the Pine Creek Mine to produce concentrates. The last actual mining of significant quantities of ore in the US is thought to have been at the Andrew Mine, northeast of Los Angeles in Los Angeles County, which was still mining ore in 1992.

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mrdata.usgs.gov/mrds/show-mrds.php?dep_id=10236233