This project involves the crystal-structural analysis of several compositions of hydrogarnet and the related mineral vesuvianite. Single-crystal neutron-diffraction studies of natural Ti-andradite and vesuvianite will be carried out to determine the position and environment of the H atom. Vesuvianite is intergrown with many hydrogarnets and, in some cases, exhibits an infrared spectrum very similar to hydrogarnet. Analysis of the structure of this garnet-like mineral may provide additional information on the nature of the H substitution in hydrogarnet. The results of these studies will provide insights into the crystal-chemical factors which govern the "stability" of natural hydrogarnets, minerals which occur in a number of important rock types.
