Mining & Processing
Tungsten is mined by conventional underground and open cut mining technologies. Due to the low solubility of scheelite and wolframite and the characteristics of tungsten deposits, in-situ recovery or heap-leaching cannot be used to extract tungsten. On some historical mine sites, reprocessing of tailings can be economic to produce tungsten that was previously not recovered.
From the mined ore, a tungsten concentrate can be produced by various methods. First steps are usually crushing and grinding. Ore sorting (X-ray, optical or UV in the case of scheelite) can be used to pre-enrich the mined ore. As scheelite and wolframite are both heavy minerals, gravity methods can be used to produce a concentrate. Scheelite is also susceptible to flotation while wolframite is not. In contrast, magnetic separation can be used for wolframite while it is not possible for scheelite separation.
Depending on the exact mineralogical properties of the ore including any valuable by-products or unwanted contaminants, various methods can be combined to produce a concentrate. A final tradeable concentrate has generally a concentration of 65% WO3 or more.
The tungsten concentrate is than processed to either ammoniumparatungstate (APT) or ferrotungsten (FeW) as the intermediate material for the various tungsten uses. APT is the most common intermediate form of tungsten in which it is traded and the price for ore concentrate is directly linked to the price of APT. The price is usually quoted as RMB / mtu or USD / mtu APT (mtu – metric ton unit = 1% of one metric ton = 10kg).
China is currently the largest tungsten producer, accounting for about 84% of world production in 2011. It is followed by Russia, Canada, Austria, Bolivia, Portugal and a number of smaller producers. China has also the largest reserves according to the USGS accounting for 59% of world reserves. Other countries that have significant known reserves are Russia, the United States, Canada as well as Australia.