An orthorhombic (space group Pbca) pyroxene, with an end-member composition of Mg₂Si₂O₆. Enstatite and ferrosilite, Fe₂Si₂O₆, form a continuous solid solution series (with <5 mole % of CaSiO₃). Enstatite commonly occurs in mafic and ultramafic igneous rocks and some high-grade metamorphic rocks (granulite facies). Polymorphs of enstatite include a low- temperature, monoclinic form (clinoenstatite) and a high-temperature, orthorhombic form (protoenstatite) that may also occur naturally in nanocrystallite form. Ca-rich exsolution lamellae in enstatite crystals are common.
See pyroxene group for additional details.