The mineral olivine is a magnesium iron silicate. Thus it is a type of nesosilicate or orthosilicate. It is a common mineral in the Earth`s subsurface but weathers quickly on the surface.nnThe ratio of magnesium and iron varies between the two endmembers of the solid solution series: forsterite Mg-endmember: Mg2SiO4 and fayalite Fe-endmember: Fe2SiO4. Compositions of olivine are commonly expressed as molar percentages of forsterite Fo and fayalite Fa e.g., Fo70Fa30. Forsterite has an unusually high melting temperature at atmospheric pressure, almost 1,900 ðC 3,450 ðF, but the melting temperature of fayalite is much lower about 1,200 ðC [2,190 ðF]. The melting temperature varies smoothly between the two endmembers, as do other properties. Olivine incorporates only minor amounts of elements other than oxygen, silicon, magnesium and iron. Manganese and nickel commonly are the additional elements present in highest concentrations.n
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