Enstatite is a type of clinopyroxene with less than 10% Fe2Si2O6 and more than 90% Mg2Si2O6. It has an orthorhombic crystal system and occasionally forms prismatic crystals. It is usually in the form of bladed, fibrous or platy aggregates. It can be colourless, green, brown or light yellow with colourless or grey streaks. It has transparent to opaque diaphaneity, a vitreous lustre, a specific gravity of 3.2–3.4, a Mohs hardness of 5–6 and uneven fractures. It usually forms in mafic and ultramafic rocks such as gabbro, coarse basalt, norite and peridotite.