 Iron may only enter minerals such as olivine if it is present as Fe2+; Fe3+ cannot enter the lattice of fayalite olivine.Elements in olivine such as magnesium, however, stabilize olivine containing Fe2+ to conditions more oxidizing than those required for fayalite stability.Solid solution between magnetite and the titanium-bearing endmember, ulvospinel, enlarges the stability field of magnetite.