Fayalite

Fayalite is the iron endmember of the olivine mineral series, with chemical formula Fe₂SiO₄. It forms solid solutions with magnesium-rich forsterite.

Olivine: Olivine is a group of magnesium- and iron-bearing silicate minerals with the general formula (Mg,Fe)₂SiO₄. Fayalite is olivine’s iron-rich endmember.
Olivine solid solution: Olivine solid solution is substitution of magnesium and iron for one another in the olivine crystal structure. Fayalite is the iron-rich endpoint of this compositional exchange.
Earth's mantle: Earth’s mantle is the silicate-rich layer between the crust and the core. Fayalite-rich compositions help clarify iron–magnesium behavior in mantle minerals.
Late-stage granite: Late-stage granite is residual granitic magma enriched in volatile components and elements excluded from earlier crystals. Fayalite can crystallize in silica-rich, iron-rich granitic rocks.
Tephroite: Tephroite is the manganese endmember of the olivine mineral group, with formula Mn₂SiO₄. It shares the olivine structure but replaces fayalite’s iron with manganese.
Forsterite: Forsterite is the magnesium endmember of the olivine series, with formula Mg₂SiO₄. It forms the opposite compositional end of the series from fayalite.
Iron–magnesium exchange: Iron–magnesium exchange is the substitution of Fe²⁺ and Mg²⁺ for one another in mineral structures. This substitution controls where a natural olivine lies between fayalite and forsterite.
Meteorite: A meteorite is a natural object from space that survives passage through a planetary atmosphere and reaches the ground. Fayalite occurs in meteorites and records conditions in their parent bodies.
Pegmatite: A pegmatite is an exceptionally coarse-grained igneous rock, commonly formed from water-rich residual magma. Some rare granitic pegmatites contain fayalite crystals.
Liebenbergite: Liebenbergite is a nickel olivine mineral with formula Ni₂SiO₄. It shows how nickel can occupy the same olivine structural position as iron in fayalite.

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