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Diamond is the record-setter in many mineralogical properties such as hardness, diffusivity, thermal conductivity, purity, and covalency of bonding. Similarly, diamond, as the premier gemstone of the mantle holds primacy for geological features such as age and depth of origin. Diamond was among the first crystalline structures to be solved by X-ray diffraction and the first materials measured for their Raman spectrum. At more than 80 billion USD in yearly commercial value, diamond sets the record for the most traded, valuable mineral on the planet. Despite its chemical simplicity, diamond has been the object of more research effort, and had more scientific and popular press pages written about it, than any other mineral.

Forty years ago when plate tectonics was first discovered, there was a major shift in thinking in the Earth Sciences. Little was known at that time about the deep mantle because of the lack of knowledge about material properties, the absence of any seismic tomography or concepts such as mantle convection. Thus the theory of platetectonicswasbuiltonsurfaceobservationsandkinematicconstraints.Thetheory of plate tectonics is not independent but consists of several assumptions. Examples are the origin of arc magma, MORB or OIB, and the distribution of earthquakes and the plate margin processes are all part of plate tectonics theory. In the intervening years much progress has been made in all three burgeoning areas of mineral physics, seismic tomography and mantle dynamics, thanks to the technological advances in synchrotron radiation and supercomputers. Mineralphysicsstudieshaveprovidedsomeofthekeyparametersthatcontrolthe style of mantle convection. The style of convection in the Earth's mantle is largely controlled by complex material properties including the changes in density and v- cosityassociatedwithalargevariationinthepressureandtemperatureoftheEarth's interior. These key physical properties have become the target of both experimental andtheoreticalstudiesinmineralphysics.Startingfromtheearly90s,theadvancesin high-performance computational capability has allowed us to incorporate these m- eral physics findings into large-scale computational modeling of mantle convection; and these studies have highlighted the complexities of mantle convection caused by the variation in density due to both thermal and chemical anomalies (and viscosity) in the Earth's deep interior.

Volume 62 of Reviews in Mineralogy and Geochemistry reviews the recent research in the geochemistry and mineral physics of hydrogen in the principal mineral phases of the Earth's crust and mantle. Contents:Analytical Methods for Measuring Water in Nominally Anhydrous MineralsThe Structure of Hydrous Species in Nominally Anhydrous Minerals: Information from Polarized IR SpectroscopyStructural Studies of OH in Nominally Anhydrous Minerals Using NMRAtomistic Models of OH Defects in Nominally Anhydrous MineralsHydrogen in High Pressure Silicate and Oxide Mineral StructuresWater in Nominally Anhydrous Crustal Minerals: Speciation, Concentration, and Geologic SignificanceWater in Natural Mantle Minerals I: PyroxenesWater in Natural Mantle Minerals II: Olivine, Garnet and Accessory MineralsThermodynamics of Water Solubility and PartitioningThe Partitioning of Water Between Nominally Anhydrous Minerals and Silicate MeltsThe Stability of Hydrous Mantle PhasesHydrous Phases and Water Transport in the Subducting SlabDiffusion of Hydrogen in MineralsEffect of Water on the Equation of State of Nominally Anhydrous MineralsRemote Sensing of Hydrogen in Earth's Mantle