The most common occurrence of diopside at Earth’s surface is as a primary mineral in olivine-rich basalts and andesites. In these rocks it can be present in quantities of a few weight percent.

Diopside also forms during contact metamorphism of limestones and dolomites. Most of the crystalline diopside used to cut faceted gems and the granular diopside used as ornamental stone occurs in these carbonate deposits.

Diopside is much more abundant in Earth’s mantle than at the surface. Evidence for this is diopside as a common mineral in ophiolites, and diopside as a common mineral in kimberlites and peridotites that were formed during deep-source volcanic eruptions.