Cassiterite - Occurrence

Occurrence

Most sources of cassiterite today are found in alluvial or placer deposits containing the resistant weathered grains. The best sources of primary cassiterite are found in the tin mines of Bolivia, where it is found in hydrothermal veins. Rwanda has a nascent cassiterite mining industry. Fighting over cassiterite deposits (particularly in Walikale) is a major cause of the conflict waged in eastern parts of the Democratic Republic of the Congo.

Cassiterite is a widespread minor constituent of igneous rocks. The Bolivia veins and the old exhausted workings of Cornwall, England, are concentrated in high temperature quartz veins and pegmatites associated with granitic intrusives. The veins commonly contain tourmaline, topaz, fluorite, apatite, wolframite, molybdenite, and arsenopyrite. The mineral occurs extensively in Cornwall as surface deposits on Bodmin Moor for example, where there are extensive traces of an hydraulic mining method known as streaming. The current major tin production comes from placer or alluvial deposits in Malaysia, Thailand, Indonesia, Maakhir region of Somalia, and Russia. Hydraulic mining methods are used to concentrate the fine particles of ore owing to its high specific gravity of about 7.0 G.