How do you separate tungsten from its ore?
Wolframite (iron-manganese tungstate, FeWO4 and MnWO4) and scheelite (calcium tungstate, CaWO4) are tungsten's primary ores. The ores are ground into small particles, cleaned and then treated with alkalis to form tungsten trioxide (WO3). The tungsten trioxide is then heated with either carbon or hydrogen gas to form the pure metal.
This is the reaction if tungsten trioxide is heated with carbon:
2WO3 + 3C + heat → 2W + 3CO2
(tungsten trioxide combines with carbon to form tungsten metal and carbon dioxide)
This is the reaction if tungsten trioxide is heated with hydrogen gas:
WO3 + 3H2 + heat → W + 3H2O
(tungsten trioxide combines with hydrogen gas to form tungsten metal and water)
Steve Gagnon, Science Education Specialist (Other answers by Steve Gagnon)