Cordierite was named after Pierre Louis A. Cordier (1777-1861), a French mining engineer and geologist, who first studied the species. This mineral commonly alters to some form of mica. It is found as an accessory mineral in granite, gneiss, schists, and in contact metamorphic zones. The transparent variety has been used as a gem known by jewelers as saphir d'eau.

Mineral Photos courtesy of R.Weller/Cochise College