In the 13 years since the publication of the National Bureau of Standards comprehensive tables of thermochemical properties, by Rossini and others [4], a very large body of modern calorimetric and equilibrium data has become available. Because of the complex interrelationships among many thermochemical data and the necessity for internal consistency among these values, a complete revision of this standard reference is required. This is also true of the summaries of thermochemical data for the sulfides [67] and for the oxides [12]. The following tables present critically selected values for the heat and free energy of formation, the logarithm of the equilibrium constant of formation Log Kf, the entropy, and the molar volume, at 298.15° K (25.0° C) and 1 atmosphere for minerals. Except for the gases, the molar volumes were taken directly from section 5 of this handbook. For a gas, the standard state is the ideal gas at 1 atmosphere pressure, and consequently all ideal gases have the same molar volume, equal to RT , at a given temperature. The volumes given in section 16 are those for the real gas at 298.15° K and 1 atmosphere and are therefore different from those given here. For all compounds except the silicates, the heat and free energy and Log Kf refer to formation from the elements in their standard states. Thermodynamic properties of elements not listed in these tables but used in the calculations were taken from Kelley and King [1] and Stull and Sinke [93], For the silicates δH°f,298.15,