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Electron—Optical Investigations on Montmorillonites—II: Morphological Variations in the Intermediate Members of the Montmorillonite-Beidellite Series

Published online by Cambridge University Press:  01 July 2024

N. Güven
Affiliation:
Department of Geosciences, Texas Tech University, P.O. Box 4109, Lubbock, Texas 79409, U.S.A.
R. W. Pease
Affiliation:
Department of Geosciences, Texas Tech University, P.O. Box 4109, Lubbock, Texas 79409, U.S.A.

Abstract

Dioctahedral aluminum smectites from bentonite deposits in Argentina, Brazil, Czechoslovakia and Japan represent, according to the MgO content of the bulk samples, intermediate members in the montmorillonite-beidellite series. The smectite particles in these samples occur in a variety of forms such as; (a) laths and diamond-shaped units with a well developed crystal habit, (b) loosely folded aggregates with an irregular morphology and (c) flat and compact lamellae with well developed {001} forms but with complete lack of {hk0} forms. Such lamellae have been described in two groups: the thin ones (10–50 Å) and the thicker ones. Thin lamellae may give SAD spot patterns with a non-hexagonal symmetry. Lamellae having thicknesses greater than 50 Å resemble a single crystal but their SAD patterns indicate that they do not have a three-dimensional periodicity.

The question arises whether the morphologically different particles in a sample belong to the same intermediate phase or if they represent different members in the montmorillonite-beidellite series coexisting in the same sample.

Type
Research Article
Copyright
Copyright © 1975, The Clay Minerals Society

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