Our major effort is dedicated to the understanding of the thermo-chemical state of the Earth’s mantle, traditionally divided into upper mantle (UM) (down to 410 km depth), transition zone (TZ) (from 410 to 670 km), and lower mantle (LM) (from 670 to 2898 km). Although there is a consensus today regarding the mineralogy of the UM, also but less so of the TZ’s, no samples are available from the LM. This region is remotely probed by seismic tomography that offers 3D maps of seismic velocities and density. From these the elastic properties of the mantle can be extracted. Interpretation of this information in terms of temperature field and mineralogy depends entirely on the comparison of this information with independently determined elasticity of candidate mineral phases and their aggregates (rocks). We are pursuing high P,T elasticity calculations of possible LM aggregates to help unravel the thermo-chemical state of this region.