Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms dull green crystals in various shades. It has two distinct prismatic cleavages at 87 and 93° typical of the pyroxene series. It measures 6 on Moh’s scale of hardness and is transparent to translucent.

Diopside of gem quality is found in two forms: the black star diopside and the chrome diopside with a rich green color. Chrome diopside is relatively soft to scratch since is has a hardnes of only 5.5 to 6.5 on the Moh’s scale of hardness.

Violane is a diopside rich in manganese and varies from violet to light blue in color.