cassiterite

noun

1. a brown or black mineral, tin dioxide, SnO2, that crystallizes in the tetragonal system; tinstone: the principal ore of tin.

noun

1. a black or brown mineral, found in igneous rocks and hydrothermal veins. It is a source of tin. Composition: tin oxide. Formula: SnO 2 . Crystal structure: tetragonalAlso called: tinstone