Chemical composition -- Primarily tin oxide.
Color -- White, brown, or gray.
Optics -- R.I. 2.00-2.10. Birefringence (0.098) and dispersion (0.071) are both quite high. Produces very brilliant, fiery stones.
Durability -- Hardness 6-7. A little soft and brittle for jewelry use, best for collections.
Crystal structure -- tetragonal , often twinned.
Specific Gravity -- 6.7-7.1 (very dense).
Sources -- Bolivia is one of the few sources of cassiterite. Cut stones of good clarity over one carat are very rare.