Abstract
Vesuvianites are classified into three types, P4/nnc, P4/n, and P4nc. These varieties are interpreted as “rod polytypism”. A rare type of high-temperature skarn is developed in Kushiro (Tojyo, Shobara Hiroshima) southwestern Japan. Vesuvianites formed by the retrograde metamorphism of gehlenite, and several structural types were found corresponding to various stages of the metamorphism. The crystal structure of a unique type of vesuvianite with the space group P4/n [a=15.576 (2), c=11.835 (2) Å] is determined by single-crystal X-ray diffraction. Significant vacancies (29%) occur only on one of the two pseudo-equivalent Z1 sites (Z1b).
