The Relations between Tridymite and Cristobalite

JSGT_1919_V03_T116_T125 (10 pages)

In the course of a long series of experiments, no obvious loophole was left by which one could escape the conclusions regarding the stability relations which have been drawn. At temperatures above 1470±10°, quartz, tridymite and amorphous silica have repeatedly and unequivocally been converted into cristobalite; between 1470±10° and 870±10°, quartz cristobalite, and amorphous silica have similarly been converted into tridymite; and below 870±10° tridymite, cristobalite, and amorphous silica have been converted into quartz. These relations have been confirmed again and again. Moreover, recent work by Ferguson & Merwin has indicated that the melting point of tridymite is considerably lower than that of cristobalite. It follows necessarily from this observation that cristobalite is the high temperature form.

 Clarence N. Fenner