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This article in SSSAJ

  1. Vol. 35 No. 4, p. 652-654
    Received: Nov 9, 1970
    Accepted: Mar 22, 1971

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Domains and Quasi-Crystalline Regions in Clay Systems1

  1. J. P. Quirk and
  2. L. A. G. Aylmore2



A number of terms have been used by different authors to describe regions of near-parallel alignment of the plate-shaped crystals in clay materials. This has resulted in some confusion through inadequate definition and misconceptions in the usage of these terms. Use of the term quasi-crystal to describe the regions of parallel alignment of individual alumino-silicate lamellae in montmorillonite and of the term domain to describe the regions of parallel alignment of crystals for illite and other fixed lattice clays is recommended in preference to terms such as tactoid or crystal of montmorillonite.

The similarity in behavior of a domain of illite crystals and a montmorillonite quasi-crystal is illustrated. These regions show a marked difference in swelling behaviour between sodium and calcium systems.

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