Analysis of thermodynamic properties of geomaterials at high pressures and temperatures existing in the Earth's interior is presented. The presentation includes a summary on the determination of equations of state based on measured properties of minerals, as well as thermodynamic identities and approximate relations between thermodynamic parameters of the second, third, and in some instances, fourth orders. New expressions were derived for the volume dependences of the coefficient of thermal expansion, the Gr#xFC;neisen parameter, and the Anderson-Gr#xFC;neisen parameter. Attention is given to the preparation of the database on mineral properties. Several geophysical estimates, including the lower-mantle properties, were obtained. It was shown that the thermal expansivity decreases 4-5 times along the "hot" mantle adiabat as the pressure increases from 0 to 1.4 Mbar. Under the same conditions, the heat capacity CP drops about 10-15%. The thermal pressure at T > Q is linear in temperature, with an accuracy of 1-3%. The parameter 2KT/ P T at P = 0 for mantle minerals was estimated to be 1-3 10-4K-1. The acceptable ranges of other lower-mantle parameters are dVT = K - dT 0.2, q 0.8, g 1.1, dT 3-3.3, and dS 1.9-2.2. Deviations from the Mie-Gr#xFC;neisen equation of state are discussed in relation to the volume- and temperature-dependent Gr#xFC;neisen parameter.