Diopside is an important rock forming mineral in several metamorphic and basic to ultra basic igneous rocks, also found in meteorites. Diopside is a part of an important solid solution series of the pyroxene group. Diopside is the magnesium rich end member of the series. The diopside-hedenbergite series is analogous to the amphiobole, tremolite- actinolite series. Diopside has several varieties, including a chromium-rich gem variety called chrome diopside.
Violan is rare blue variety found in some localities in Italy. There is also a green "cat's eye" variety that contains minute inclusions, probably of rutile, that reflect light in such a way as to produce a lively linear luminscence within the crystal. Still another variety is quite dark, with included rutile needles aligned so as to produce a 4-rayed star, hence the name star diopside. Ordinary diopside is typically white or green and can have a nice glassy luster. While the colour of chrome diopside is much brighter, many specimens of ordinary diopside are also cut for gemstones.