A Dickite with an Elongated Crystal Habit and Its Dehydroxylation

E. R. Schmidt and R. O. Heckroodt
National Building Research Institute, Pretoria, Union of South Africa

Summary: Dickite from a new occurrence at Barkly East, Cape Province, is described and compared with a previously unreported dickite from Postmasburg and a dickite from Ouray, Colorado. The Barkly East dickite crystals are elongated in the direction of the a-axis; the ratio of length to width of crystals varies from 3:1 to 16:1. Optical, electron microscopic, X-ray, and thermal data and a chemical analysis are given. The thermogram of the fraction smaller than 2 µ e.s.d.1 is characterized by a single peak at 600°C., while that of fractions larger than 2 µ e.s.d. shows a double endothermal effect. This two-stage dehydroxylation of dickite on heating is attributed to a particle size effect.

Mineralogical Magazine; December 1959 v. 32; no. 247; p. 314-323; DOI: 10.1180/minmag.1959.032.247.04
© 1959, The Mineralogical Society
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