Summary. Dickite from a new occurrence at Barkly East, Cape Province, is described and compared with a previously unreported dickitc from Postmashurg 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 g e.s.d. 1 is characterized by a single peak at 600 ~ C., while that of fractions larger than 2 tt e.s.d. shows a double endothermal effect. This two-stage dehydroxylation of dickite on heating is attributed to a particle size effect.

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In the version of this article initially published, on p. 257, Steven Salzberg's name was misspelled as "Stephen. " The error has been corrected in the HTML and PDF versions of the article.