common silicate mineral in the pyroxene family that occurs in metamorphosed siliceous limestones and dolomites and in skarns (skarn) (contact-metamorphic rocks rich in iron); it is also found in small amounts in many chondrite meteorites. Clear specimens of good green colour are sometimes cut as gems.

Diopside is a calcium and magnesium silicate (CaMgSi₂O₆). It forms a complete chemical replacement series with hedenbergite in which ferrous iron completely replaces magnesium in the molecular structure. Hedenbergite is common in limestone skarns, in thermally metamorphosed iron-rich sediments, and in some igneous rocks; sodium-rich varieties are found in many alkaline rocks. See also augite. For detailed physical properties, see pyroxene (table).