Chemical binding in silicate minerals Part III. Application of energy calculations to the prediction of silicate mineral stability
Combining Coulomb energies with appropriate corrections makes possible quantitative prediction of stability relations of minerals. Melting and decomposition temperatures of some minerals including corundum and quartz have been calculated from the binding energies. Agreement between calculated and observed melting points of minerals is exceptionally good when covalency, radius-ratio and coordination effect corrections are made to the melting points determined from Coulomb binding energies. Thermal stabilities of some phyllosilicates are predicted semiquantitatively. Calculated energies show that the stability of montmorillonite with respect to other phyllosilicates in most low-temperature geochemical environments is probably the result of hydration of the inter-layer space. Also, when small amounts of magnesium are present in a silicate system montmorillonite is the phase which minimizes the total energy of the system.