Wolframite
. Wolframite, opaque mineral composed of ferrous and manganous tungstate, and existing as an isomorphous mixture of the minerals ferberite and huebnerite. It crystallizes in the monoclinic system (see Crystal ), exhibits perfect cleavage, and shines with a submetallic to resinous luster. The color ranges from brown to black; the hardness is 5 to 5.5, and the specific gravity is 7 to 7.5. Wolframite occurs in combination with such minerals as cassiterite, scheelite, quartz, pyrite, galena, sphalerite, and arsenopyrite, and is found mainly in China; Burma; New South Wales State, Australia; Bolivia; Germany; and Cornwall, England. In the U.S. principal deposits occur in Boulder County, Colorado; Nye County, Nevada; and the Black Hills, South Dakota. The principal use is as a source of tungsten, or wolfram.