The proportions of ferric and ferrous iron in a given amphibole are determined by a complex interaction between intensive parameters such as temperature and pressure and crystal-chemical parameters such as crystal structure. Research to determine these properties will be continued. The approach consists of experimental treatment of amphiboles followed by thorough characterization of run products by x-ray, optical, wet chemical, and spectroscopic techniques. The results will have specific applications in relating the compositions of natural amphiboles to intensive parameters in the environment of formation. More fundamental understanding will come from the defining of the interrelaionship between chemical, crysallographic, and thermodynamic properties of a major rock-forming mineral group. The end result will be a better understanding of amphibole group minerals and the environments in which rocks have formed.
