The character of the cancrinite-vishnevite solid-solution series.

The crystal structure of vishnevite has been determined using XRD data, with a final conventional residue of 3.7%. Three single-crystal XRD patterns indicate variable development of a superstructure due to either subtle changes in chemistry or differences in crystal structure. The aluminosilicate framework of vishnevite is very similar to that observed in cancrinite. Complete order is confirmed but stacking faults can occur which would show apparent disorder. A complete solid solution series can be visualized between cancrinite (ideally Ca2Na6Al6Si6O24(CO3)2.2H2O) and vishnevite (ideally Na8Al6Si6O24.SO42H2O) as consisting of a mixture of 034CO3^2- and 031SO4^2- cells connected by a continuous framework.-R.A.G. Dept. of Earth & Planetary Sciences, Erindale Campus, Univ. of Toronto, Mississauga, Ontario L5L 1C6, Canada.