Cassiterite

Cassiterite is a tin oxide mineral that is found in vein deposits, granitic rocks, pegmatites, areas of contact metamorphism and the altered zone of ore deposits. It is also found in placer deposits where it is most commonly mined and given the name of "stream tin". It is the most widely mined ore of tin.

Uses of Cassiterite

Cassiterite is the principle ore of tin. In the past, much of the tin was used to produce "tin cans" (actually steel plated with tin) for food containers. However, this use is being rapidly replaced by containers made of glass, plastic, paper, aluminum and other materials. Small amounts are also used to produce solder and polishing compounds.

Physical Properties of Cassiterite
Chemical Classification	oxide
Color	brown, black, reddish brown, brownish black
Streak	colorless
Luster	adamantine, splendent to submetallic
Diaphaneity	opaque to translucent
Cleavage	imperfect
Mohs Hardness	6 to 7
Specific Gravity	6.8 to 7.1
Diagnostic Properties	high specific gravity, luster, streak, fibrous appearance
Chemical Composition	tin oxide, SnO2
Crystal System	tetragonal
Uses	an ore of tin

Sources: Geology.com