The Probert Encyclopaedia of Rocks & Minerals

CASSITERITE

Cassiterite is the principal ore of tin. It is widely distributed in small amounts but commercially available in only a few localities. It is frequently associated with wolframite. Native tin dioxide, it is found occurring in tetragonal crystals of reddish brown colour, and brilliant adamantine lustre; also massive, sometimes in compact forms with concentric fibrous structure resembling wood ('wood tin')It is also found as rolled pebbles in placer deposits ('stream tin') but is usually found in veins associated with quartz, in or near granitic rocks. It has the formulae SnO2 and a relative hardness of 7.
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