A widely distributed mineral as an accessory in granitic igneous rocks, gneissic metamorphic rocks, and in the detrital sands derived from them. It is concentrated in sands because of its resistance to chemical attack and its high specific gravity. The chief source of thorium oxide, this mineral was derived from a Greek word meaning "to be solitary," in allusion to the rarity of the mineral.

Mineral Photos courtesy of R.Weller/Cochise College