- any of a group of magnesium iron silicates, (Mg,Fe)2SiO4, occurring in olive-green to gray-green masses as an important constituent of basic igneous rocks.
- an olive-green mineral of the olivine group, found in igneous and metamorphic rocks. The clear-green variety (peridot) is used as a gemstone. Composition: magnesium iron silicate. Formula: (MgFe) 2 SiO 4 . Crystal structure: orthorhombic
- any mineral in the group having the general formula (Mg,Fe,Mn,Ca) 2 SiO 4
