Efforts to understand the physics and chemistry of earth materials depend fundamentally on structural characterization of minerals at high temperatures and pressures. In this proposal funding was requested for crystallographic research at the Geophysical Laboratory, which supports the only American facility engaged primarily in high-pressure, single-crystal, x-ray diffraction studies of minerals and their analogs. The principal objective proposed was to perform systematic studies on silicate minerals believed to occur in the Earth's mantle transition zone. The crystallographic laboratory will also continue to serve the American materials research community. In 1988, for example, it examined without charge more than 50 samples, sent from a dozen laboratories.
