The principal investigator will study phase transitions in rock- forming minerals. Specifically, he will document the effects of impurity content and strain fields on the transformation process in order to establish the behavior of impure and defective crystals at high temperature, utilizing transmission microscopic, single- crystal and powder X-ray diffraction, impedence, and calorimetric techniques. In general he hopes to better understand the mechanisms that drive spontaneous structural distortions that occur in Earth materials at elevated critical termperatures.