scheelite

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scheelite

(shā`līt, shē`–), heavy white or yellow mineral, calcium tungstate, CaWO4, crystallizing in the tetragonal system. It is found in granite pegmatites, in contact-metamorphic deposits (especially limestones intruded by granites), and in quartz veins. It is an important ore of tungsten and is mined in many parts of the world. Scheelite fluoresces bright bluish-white in ultraviolet radiation, a distinguishing feature utilized in prospecting and mining.

Scheelite

 

(named after K. W. Scheele), a mineral of the tungstate class, with a chemical composition CaWO4. Admixtures include Mo (up to 25 atomic percent in molybdoscheelite and more than 25 atomic percent in seyrigite), Cu (up to 25 atomic percent in cuproscheelite), Sr, Mn, Nb, Ta, and F.

Scheelite crystallizes in the tetragonal system, forming dipyramidal crystals; penetration twins are known to exist. Grains and granular masses are common, and pseudomorphs of scheelite after wolframite often occur. Scheelite may be colorless, white, gray, yellowish, or, more rarely, brown, green, or black in color, with a greasy to adamantine luster. It is brittle and has perfect cleavage. The hardness varies from 3 to 5 on Mohs’ scale, and the density is 5,500–6,170 kg/m3. The mineral’s luminescence in ultraviolet light (ranging from bright blue to yellow) is related to the Mo content.

The largest agglomerations of scheelite are confined to skarns, where the mineral occurs in association with garnet, pyroxene, plagioclase, amphibole, quartz, molybdenite, and other minerals. It is commonly found in high-temperature greisens, quartz-ore veins, and stockworks together with wolframite, cassiterite, fluorite, gold, and other minerals. In low-temperature hydrothermal deposits, it is associated with ferberite, antimonite, or cinnabar. Accessory scheelite has been found in granites and metamorphic rocks. Scheelite also sometimes occurs in pegmatites and alpine veins, as well as in the oxidation zone; it is converted to alluvial deposits upon weathering. Scheelite is the most important ore of tungsten; it also serves as an ore of molybdenum. The largest deposits are located in the USSR, the United States, and Korea.

REFERENCE

Bybochkin, A. M. Mestorozhdeniia vol’frama i zakonomernosti ikh razmeshcheniia. Moscow, 1965.

O. V. KONONOV

scheelite

[′shā‚līt]
(mineralogy)
CaWO4 A yellowish-white mineral crystallizing in the tetragonal system and occurring in tabular or massive form in pneumatolytic veins associated with quartz; an ore of tungsten.