Augite is a ferro-magnesian mineral belonging to the pyroxene group. The pyroxene minerals are inosilicates of the general formula XY(Si,Al)₂O₆. The X, represents ions such as calcium, sodium, iron and magnesium; more rarely zinc, manganese and lithium. The Y, represents ions of generally smaller size such as chromium, aluminum, iron, magnesium, manganese, scandium, titanium, vanadium. The pyroxenes are common rock forming minerals and are represented in most igneous and many metamorphic rocks. The pyroxenes are divided into two main groups, the orthopyroxenes and the clinopyroxenes. Augite belongs to the group of clinopyroxenes.

Augite is the commonest pyroxene and occurring widely in igneous rocks. It is dark green to black, although weathered specimens may look faded. It forms prismatic crystals in volcanic rocks and longer flat crystals in basic dykes and sills such as dolerites.