Augite is mainly composed of (Ca,Mg,Al)2[(Si,Al)2 O6] and is in the pyroxene family. The crystals are equant, and crystal twinning is common. They often appear in blocky, granular or aggregate form. They can be brown, light green or black with greyish green streaks. The crystal diaphaneity ranges from translucent to opaque. Augite has a specific gravity of 3.23–3.52, a Mohs hardness of 5.5–6, and uneven to conchoidal fractures. It mainly forms in various types of mafic and ultramafic rocks as well as in deep metamorphic rocks.