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Scheelite is a calcium tungstate mineral with the chemical formula calciumtungstenoxygen4. It is an important ore of tungsten (wolfram). Scheelite is originally named after Swedish chemist Carl Wilhelm Scheele (1742–1786). Well-formed are sought by collectors and are occasionally fashioned into when suitably free of flaws. Scheelite has been synthesized using the Czochralski process; the material produced may be used to diamond simulant, as a scintillator, or as a solid lasing medium. It was also used in radium paint in the same fashion as was zinc sulphide, and Thomas Edison invented a fluoroscope with a calcium tungstate-coated screen, making the images six times brighter than those with barium platinocyanide; the latter chemical allowed Röntgen to discover X-rays in early November 1895. The semi-precious stone marketed as 'blue scheelite' is actually a rock type consisting mostly of calcite and dolomite, with occasional traces of yellow-orange scheelite.
Gems cut from transparent material are fragile. Scheelite's refractive index (1.918–1.937 uniaxial positive, with a maximum birefringence of 0.016) and dispersion (0.026) are both moderately high. These factors combine to result in scheelite's high lustre and perceptible "fire", approaching that of diamond.
Scheelite fluorescence under shortwave ultraviolet light, the mineral glows a bright sky-blue. The presence of molybdenum trace impurities occasionally results in a green glow. Fluorescence of scheelite, sometimes associated with native gold, is used by geologists in the search for gold deposits.
Scheelite usually occurs in tin-bearing veins and is sometimes found in association with gold. Fine crystals have been obtained from Caldbeck Fells in Cumbria, Zinnwald/Cínovec and Elbogen in Bohemia, Guttannen in Switzerland, the Giant Mountains in Silesia, Dragoon Mountains in Arizona and elsewhere. At Trumbull in Connecticut and Mount Kimpu in Japan, large crystals of scheelite completely altered to wolframite have been found: those from Japan have been called “reinite.” It was mined until 1990 at King Island, Australia, Glenorchy in Central Otago and Macraes Flat in North Otago and also at The Golden Bar mine at Dead Horse Creek during World War I in Nelson, New Zealand. There is a high concentration of scheelite in the Northeast of Brazil, mainly in the Currais Novos mine in Rio Grande do Norte State.Amstutz, Gerhard Christian et al. (Ed.). Ore Genesis: The State of the Art. Vol. 2. Springer Science & Business Media, 2012, p. 418. One of the world's largest scheelite mining companies is in Luoyang, China.
The visible absorption spectrum of scheelite, as seen by a hand-held (direct-vision) spectroscope, may also be of use: most natural stones show several faint absorption lines in the yellow region of the spectrum (~585 nm) due to praseodymium and neodymium trace impurities. Conversely, synthetic scheelite is often without such a spectrum.
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