Preclusive purchasing was used by the British during World War II in order to deny Nazi Germany access to Spanish Wolframite.
Wolframite is manganese and iron tungstate, and all these are valuable sources of tungsten.
Wolframite | wolframite |
In April 2009, Senator Sam Brownback (R-KS) introduced the Congo Conflict Minerals Act of 2009 (S. 819) to require electronics companies to verify and disclose their sources of cassiterite, wolframite, and tantalum.
Pharmacosiderite, Cassiterite and Wolframite of specimen quality have also been recovered from the mine.
In mines where wolframite was mixed with cassiterite, such as South Crofty and East Pool mine in Cornwall or with bismuth such as at the Shepherd and Murphy mine in Moina, Tasmania, magnetic separation was used to separate the ores.