Crystals of diopside may be colourless, 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, coloured by chromium, is called chrome diopside. Violet blue crystals, coloured by manganese, have been discovered in Italy and United States, and are known as violane. It is polished as beads when massive; cut for collectors when transparent; and cut in cabochon when fibrous.
Gem-quality chrome diopside can be found in Burma, Siberia (Russia), Pakistan, and South Africa. Other diopside localities include Austria, Brazil, Italy, United States, Madagascar, Canada and Sri Lanka. Dark green to black diopside, which shows a 4-rayed star when cut in cabochon, has been found in southern India since 1964.