Marketable ore concentrates of scheelite and wolframite (hübnerite, ferberite) contain typically 65 – 70 % WO3. Off-grade concentrates having lower WO3 concentrations are seldom on the market and if so, only for a lower price. In fully integrated companies lower grades (6-40% WO3) are often preferred, because upgrading to high concentrations is mostly combined with a lower yield.
Concentrates are packaged either in large polyethylene “big bags” (1 to 2 tons) or, alternatively, in steel drums and individual packaging (40 to 200kg).