Scheelite - a mineral , tungsten ore , consists of CaWO 4 ( calcium tungstate ) with impurities WO 3 , Mn, Sr, Nb, Ta, Cr, F, Cu, usually painted in gray, yellow, brown or red.
| Scheelit | |
|---|---|
 | |
| Formula | CaWO 4 |
| Impurity | Mo , Cu , Ce |
| Physical properties | |
| Colour | Colorless, white, pale yellow, brownish yellow, reddish yellow |
| Trait color | White |
| Shine | Glass, oily |
| Transparency | Transparent, translucent |
| Hardness | 4-5 |
| Cleavage | Pretty perfect |
| Kink | Uneven, conchoid; fragile |
| Density | 5.9-6.12 g / cm³ |
| Syngonia | Tetragonal |
| Refractive index | 1.918-1.937 |
One of the few natural tungstates , which, given the extensive use in industry, makes scheelite a very valuable mineral. Scheelite was not recognized as a mineral until 1821 , when the German mineralogist Carl C. von Leongard gave this name in honor of the Swedish chemist K.V. Scheele (1742-1786), who discovered that he was a salt of tungsten acid.
Content
Physico-chemical properties
Composition (%): 19.48 - CaO; 80.52 - WO 3 . Sometimes it contains as isomorphic impurities up to 10% MoO 3 . The crystals are transparent or translucent, presented in a wide range of colors - from transparent to brown with a predominance of yellow and orange hues. Under the influence of ultraviolet rays, scheelite crystals emit a bright glow of pale blue or yellow color. It melts with difficulty. It is soluble in nitric and hydrochloric acids with the formation of a yellowish precipitate of tungsten.
Scheelite crystals are small in size, but sometimes specimens up to 35 cm long are found. A mineral crystal can be synthesized using the Czochralski process . In the USA, synthetic scheelite was obtained in 1943 .
Deposits
Industrial deposits are common in skarns . It is found in hydrothermal deposits in quartz veins along with arsenopyrite , galena , carbonates and pyrite .
The largest scheelite deposits are located in China ( Sichuan ), South Korea , Great Britain , Russia ( Middle Urals , Chukotka , East Transbaikalia , North Caucasus ), Tajikistan , Namibia , Austria , Brazil ( Minas Gerais ), Bolivia , Peru , Mexico , USA ( Nevada , California , Arizona ), Spain , Italy , France and Australia .
Application
Scheelite is mined to produce tungsten and its compounds. Scheelite crystals with impurities of lanthanides can be used in quantum light generators ( lasers ). Used in jewelry . Druze crystals are appreciated by collectors .
Literature
- Scheelit // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.