Diopside is a monoclinic pyroxene mineral with composition MgCaSi 2 O 6. It forms complete solid solution series with hedenbergite (FeCaSi 2 O 6) and augite, and partial solid solutions with orthopyroxene and pigeonite.It forms variably colored, but typically dull green crystals in the monoclinic prismatic class.iopside is also found in a variety of metamorphic rocks, such as in contact metamorphosed skarns developed from high silica dolomites. It is an important mineral in the Earth 's mantle and is common in peridotite xenoliths erupted in kimberlite and alkali basalt.