A method of estimating the Gibbs energies of formation of layer silicates

Gibbs energies of formation (from the elements at 298.15 K) of layer and fibrous silicates can be estimated within the limits of uncertainty of the values obtained by current experimental techniques. The method of calculation is based on the assumption that each silicate can be represented by oxide and hydroxide components possessing Gibbs energies of formation within the silicate structures that are constant but may differ from the Gibbs energies assigned to the components as separate phases. Layer silicates with exchangeable ions are included in this scheme. The method permits estimation of the free energies of formation of montmorillonites, illites, chlorites and micas of complex composition.