A dickite with an elongated crystal habit and its dehydroxylation

Abstract

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.

THE NON-DETONATIVE SYNTHESIS OF CADMIUM SELENIDE AND OTHER II-VI COMPOUNDS FROM THE ELEMENTS1

“…Preparation of this material in a one-stage synthesis also follows the procedure defined for CdSe. 4. The reaction Zn-Se also closely resembles the Cd-Se reaction, with the notable difference that a single stage complete powder synthesis can be effected at rates as high as 3°/min.…”

Mineralogy of Dickite and Nacrite From Northern Taiwan

“…Additional data closely related to the hypogene enargite metallization need further study. We believe that the genesis of the elongate dickite crystals in the CKS and NSC areas has a hydrothermal origin as postulated by Schmidt and Heckroodt (1959).…”

“…Dickite crystals are either of hexagonal form or are platelets elongated parallel to the a axis (Figure 6b). This elongated habit is common in hydrothermal dickite (Schmidt and Heckroodt, 1959). …”

Mineralogy and Genesis of Clays in Postmagmatic Alteration Zones, Makurazaki Volcanic Area, Kagoshima Prefecture, Japan

“…(2) Dickite from Ebara, Hyogo Prefecture, Japan (Ueno, 1964). (3) Dickite from Barkly East, Cape Province, South Africa (Schmidt and Heckroodt, 1959). (Table 2) reveals that the sample contains small amounts of Li ions.…”

“…Smithson and Brown (1957) studied the dehydroxylation of a well-ordered, pure dickite from Anglesey, Wales, and concluded that the double endotherms they found must be due to the dickite. Schmidt and Heckroodt (1959) studied the dehydroxylation of various size fractions of a dickite from Barkly East. They observed that the 6.3-20 um size fractions showed double endothermic peaks, the higher temperature peak of which was missing for the < 2-/~m fractions.…”