Tungsten is a widely distributed element, which is almost common in all kinds of rocks but low in content.
The deposit can be formed as commercial ore mining only by the enrichment of relevant geological processes. the average content of tungsten in the crust is 1.3×10-6 and in granite is 1.5×10-6. Tungsten is mainly hexavalent cation in nature and its ionic radius is 0.68×10-10 m.. since the W6 ion radius is small, the electricity price is high, and it has strong polarization ability, it is easy to form complex anions, so tungsten mainly binds with cations such as Fe2、Mn2、Ca2 in solution in the form of complex anions [WO4]2-,] to form wolframite or scheelite precipitation. The crystallization temperature of scheelite is 320~240℃, and that of scheelite is 300~200℃.
In epiphytic action, because the tungsten-bearing minerals are relatively stable, sand ore is often formed. However, under acidic conditions, tungsten-containing minerals can be decomposed and dissolved in surface water in WO3 form, and some secondary minerals of tungsten can be formed under certain conditions. Sometimes, it is adsorbed by clay or ferromanganese oxide in the form of mineral particles or ions, and is concentrated in shale, argillaceous fine sandstone and ferromanganese ore layer.
Now in the ancient metamorphic rock series, there are layered tungsten deposits and tungsten source layer, indicating that tungsten can also be enriched to some extent during metamorphism.
The important minerals of tungsten are tungstate. There are only a few cations that can bind to [WO4]2-] anions during mineralization, mainly Ca2、Fe2、Mn2、Pb2, followed by Cu2、Zn2、Al3、Fe3、Y3 and so on, so the mineral species are limited. Today, only more than 20 kinds of tungsten minerals and tungsten-bearing minerals are found in the crust, i.e. wolframite, tungsten ore, wolframite, wolframite, wolframite; scheelite: scheelite (calctungsten ore), molybdenum scheelite, copper scheelite; tungstenite: tungsten, water tungsten, tungsten, yttrium, tungsten, tungsten, tungsten, copper tungsten, tungsten and aluminite; Unusual tungsten minerals: tungsten lead ore, inclined tungsten lead ore, molybdenum tungsten lead ore, tungsten zinc ore, tungsten bismuth ore, antimony tungsten pyrochlorite, titanate (containing tungsten), sulfur tungsten ore, etc. Although more than 20 tungsten and tungsten-bearing minerals have been found, only wolframite and scheelite have economic value for exploitation. WO4, wolframite (Fe、Mn), containing WO3 WO3 CaWO4, scheelite 80.6%.