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CASSIT.TXT
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1992-04-28
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19 lines
Cassiterite is tin oxide. Iron substitutes for the tin to 3% of
the crystal's weight. Niobium and tantalum can be present in
smaller amounts. It's hardness is 6-7. For comparison, quartz'
hardness is 7. The crystals are found as black or brown, some-
times with a thin transparent edge over the darker material.
Sinkankas notes (in _Mineralogy For Amateurs_) that cassiterite is
found associated with wolframite, tourmaline, topaz, quartz,
fluoride, muscovite, lepidolite, bismuthinite, and bismuth.
Cassiterite is a member of the Rutile Group of tetragonal oxides.
Other members are argutite, paratellurite, plattnerite, pyrolusite,
rutile, and stishovite.
Tin oxide in powdered form is used to produce a fine polish on many
gem materials, usually in tumbling operations.
--Donald Rosenfield, Asst. General Sysop/rockhound