Synthetic nickel–iron olivines, equilibrated at 1000°C, were investigated by means of Mössbauer spectroscopy at high and low temperature. A strong tendency towards an ordering of Ni2+ into the M1 site and Fe2+ into M2 was observed. KD for the exchange reaction Ni2+(M1) + Fe2 (M2) ⇄ Fe2+(M1) + Ni2+(M2) varies little with chemical composition, suggesting a near ideal solid solution in Ni–Fe olivines. Gibbs free energy of exchange at 1000°C is calculated to be 6.0 kcal/mole (24.9 kJ/mole).

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