METHOD OF ESTIMATION OF STANDARD FREE-ENERGIES OF FORMATION OF SILICATE MINERALS AT 298.15 DEGREES K

The standard Gibbs free energies of formation from the elements of about twenty silicate minerals at 298. 15 degree K were estimated with the aid of an equation. In most cases, the error of estimation is less than 0. 6 percent as compared with the experimental value. Differences in the Gibbs free energies of formation from the elements of silicate minerals are closely related to the size and charges of the cations in the mineral. Repulsive energy contributes substantially to the free energies of formation of silicates containing small cations. Refs.