 cassiterite is a tin oxide mineral, sno2. it is generally opaque, but it is translucent in thin crystals. its luster and multiple crystal faces produce a desirable gem. cassiterite has been the chief tin ore throughout ancient history and remains the most important source of tin today. ==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.{{cite news |url=http://www.newsvine.com/_
Oxide_minerals Rutile_group Tetragonal_minerals Tin_minerals Tin_mining