Reniform
masses, water worn.
Lustrous Cassiterite Crystals
CHEMISTRY SnO2 Tin oxide
CRYSTALLOGRAPHY Tetragonal
CRYSTAL GROWTH AND HABITS Crystals of Cassiterite form prisms and dipyramids. It is usually massive, granular or reniform. Reniform habits have radiating acicular fibrous crystals.
COLOR AND OTHER OPTICAL PROPERTIES Cassiterite is brownish to black, seldom yellow or white, opaque to translucent and rarely transparent.
HARDNESS 6 - 7
SPECIFIC GRAVITY 6.8 - 7.1
LUSTER Adamantine, submetallic to dull
STREAK white
OCCURRENCE Cassiterite is found in medium to high temperature hydrothermal veins in granites. It is also found as alluvial placers and thus may be water worn-pebbles.
ASSOCIATED MINERALS Quartz, Muscovite, Wolframite, Tourmaline