Tungsten

Tungsten deposits usually occur within, or near to, orogenic belts resulting from subduction related plate tectonics. All major deposit types are associated with granitic intrusions or with medium- to high-grade metamorphic rocks. By far the largest producing country is China with lesser quantities mined in Russia, Canada, Bolivia and other countries. Tungsten's main uses are in hard metals, e.g. tungsten carbide, for cutting, drilling and wear-resistant parts or coatings; as an alloy with steel or other metals were heat resistance is important; as wire, sheets or rods in electrical or elecontric applications; and in chemicals. Tungsten is important for these uses because of its very high melting point, very high density, extreme strength, high wear resitance, high tensile strength, low coefficient of expansion and high thermal and electrical conductivity.