\Cas*sit"er*ite\, n. [Gr. ? tin.] (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}.