Crystals of diopside may be colorless, but are more usually bottle-green, brownish green, or light green. The more iron-rich and magnesium-poor they are, the darker the color- almost to black. Very bright green diopside, colored by chromium, is known as chrome diopside. Violet-blue crystals, colored by manganese, have been found in Italy and the USA, and may be called violane. It is polished as beads when massive; cut for collectors when transparent; and cut en cabochon when Fibrous.

Gem-quality chrome diopside is found in Burma, Siberia (Russia), Pakistan, and South Africa. Other diopside localities include Austria, Brazil, Italy, the USA, Madagascar, Canada, and Sri Lanka. Dark green to black diopside, which shows a 4-rayed star when cut en cabochon, has been found in southern India since l964.

Diamonds are graded by color. Cut, clarity and carat (weight) - the four c's.