On Magnetic Susceptibility of Olivines

Abstract

The magnetic susceptibility of several olivines, xFe₂SiO₄⋅(1-x)Mg₂SiO₄ with varying x has been measured. The results showed that the olivines are paramagnetic and that their molecular magnetic susceptibility χ_mol can be expressed empirically by χ_mol=2x× 10^-2emn/mol at the room temperature. Using the accepted values of the Bohr magneton number of Fe⁺² ion, and assuming that the Fe⁺² ions are embedded isolatedly in the crystal, the paramagnetic susceptibility of olivines at the room temperature can be calculated as χ_mol=2.2x∼2.6x×10^-2emn/mol, provided that the other constituents such as Mg⁺² and SiO₄ are only diamagnetic. The comparison of the empirical and the calculated values seems to justify the above simple calculation. We expect such calculation will also valid for other rock-forming paramagnetic minerals.