Geophysical measurements, such as the lateral variations in seismic wave velocities that are imaged by seismic tomography, provide the strongest constraints on the structure of the Earth's deep interior. In order to interpret such measurements in terms of mineralogical/compositional models of the Earth's interior, data on the physical and chemical properties of minerals at high pressures and temperatures are essential. Knowledge of thermodynamics, phase equilibria, crystal chemistry, crystallography, rheology, diffusion and heat transport are required to characterize the structure and...