An orthorhombic mineral, 2(MgSiO₃) ; pyroxene group; dimorphous with clinoenstatite; a common rock-forming mineral in basalt, gabbro, norite, pyroxenite, and peridotite. Formerly called amblystegite, bronzite, chladnite, ficinite, hypersthene (in part), orthobronzite, orthoenstatite, orthohypersthene (in part), paulite, peckhamite, protobasite, shepardite, and victorite.