Diopside contains CaMg[Si2O6], and it belongs to the clinopyroxene family with a monoclinic crystal system. The crystal shape is equant, whereas the cross-section is nearly square. Crystal twinning is common, and the aggregates are blocky or columnar. It can be colourless, white, grey, green, greenish black, yellowish brown or reddish brown with white or grey streaks. It has transparent to opaque diaphaneity, a vitreous lustre, a specific gravity of 3.22–3.38, a Mohs hardness of 5.5–6.5, and uneven fractures. It usually forms in the metamorphic and mafic rocks.