Noun
forsterite (plural forsterites)
(mineralogy) A white variety of olivine that is mostly magnesium silicate, Mg2SiO4.
Compositions of olivine are commonly expressed as molar percentages of forsterite (Fo) and fayalite (Fa) (e. Source: Internet
The ratio of magnesium and iron varies between the two endmembers of the solid solution series: forsterite (Mg-endmember: Mg 2 Si 4 ) and fayalite (Fe-endmember: Fe 2 Si 4 ). Source: Internet