This is a project in which a new type of detector, will be used to analyze diffracted X-rays from diamond anvil, high-pressure experiments. The new method will increase the resolution by approximately an order of magnitude, which will make it possible to determine the lattice geometry for low-symmetry phases. In addition, the new detector will be more compatible with new generations of synchrotrons now being planned. The new detector will be used to obtain the first accurate structural information and equations of state of a variety of low-symmetry, high- pressure phases of elemental solids, silicates, and oxides under pressures characteristic of the lower mantle and core of the earth. The data can then be applied to seismic and other studies of the earth's interior.