Cassiterite

Cas‐sit″er‐ite (?), n.(Min.) Native tin dioxide; tin stone; a mineral occurring in tetragonal crystals of reddish brown color, and brilliant adamantine luster; also massive, sometimes in compact forms with concentric fibrous structure resembling wood (wood tin), also in rolled fragments or pebbly (Stream tin). It is the chief source of metallic tin. See Black tin, under Black.