Crystallography of dimorphites *

Abstract

AbstractSingle-crystal x-ray diffraction studies on natural, Vesuvian dimorphites confirmed the existence of two phases: dimorphite I and II. The former was found to be identical with the synthetic AS4S3of Whitfield(1970) and of Yu(1971). Dimorphite II has the space group ofPnmaorPn21aand the unit-cell dimensions ofa= 11.24 ± 0.02,b= 9.90 ± 0.03,c= 6.56 ± 0.02 Å. Much of the dimorphite occurred in apparent single crystals. However, most were found to be polycrystalline. Of the crystals having an identifiable lattice most were dimorphite II, one was dimorphite I and one was clearly a dimorphite II pseudomorphic after dimorphite I.