An occurrence of a regular mixed-layer clay-mineral

Abstract

About twelve miles south-east of Burghersdorp in the Cape Province, South Africa, the unusual clay reported in this paper was first discovered on the farms 'Groenvlei' and 'Kuilfontein'. Later deposits were also uncovered on the farms 'Kapokkraal' and 'Kleinhoek'.The clay-mineral appears to be of a very unusual type, namely, a regular mixed-layer clay-mineral (1:1 hydrous mica and montmorillonite). The mode of origin of the clay is also of interest in that it appears to be produced from a shale by hydrothermal alteration, due to intrusion of dolerite sheets.

Alteration and geochemistry of Tertiary volcanic rocks in parts of the Virginia City Quadrangle, Nevada

“…In most places, the illite and montmorillonite are combined in regular mixed layers that give a (001) peak at 24-30 A. The diffraction patterns obtained are very similar to those described by Heystek (1954).…”

Regularly Interstratified Montmorillonite-Chlorite in Basalt

“…In contrast, regular interstratifications are relatively rare, although examples of various pairs of clay minerals have been described by Bradley (1950), Sudo, Takahashi, and Matsui (1954), Heystek (1954), Lippman (1954), and Earley and others (1956). Because it is the first occurrence of a regularly interstratified montmorillonite-chlorite in an igneous rock, the authors believe this mineral to be worthy of a brief description.…”

Hydrothermal Rhyolitic Alteration in the Castle Mountains, California

“…Ethylene glycol treatment caused an increase of the 12.8 A and 26.12 A values to 13.8 A and 28.11 A respectively with a third Formula of the Hydrous Mica in Mixed-Layer order reflection represented at 9.22 •. Upon heating to 450~ only one peak at 10.11 A occurs, indicating the interstratification of a montmorillonitic and hydrous mica clay minerals in a nearly regular 1:1 stacking arrangement (Heystek, 1954;Brown, 1961, p.428). These X-ray data are in agreement with a cation exchange value of 60 mcq per 100 g clay dried at ll0~ and the chemical analysis ( "V HEATED TO 450~ ~c~, ur~rec~ed an~l glycolotea FIOURE 4,--Basal X-ray diffraction peaks of beidellite and mixed-layer clay minerals after various treatments.…”