Crystal Chemical Differences in Al-Rich Smectites as Shown by Multivariate Analysis of Variance and Discriminant Analysis

Alberto Alberti and Maria Franca Brigatti
Istituto di Mineralogia e Petrologia dell'Università Via S. Eufemia 19, 41100 Modena, Italy

Abstract: Multivariate analysis of variance and discriminant analysis were used to establish the crystal chemistry of several Al-rich smectites. The statistical analyses were carded out on 78 samples taken from the literature which were classified on the basis of their physicochemical properties. A strong discrimination exists between beidellites and montmorillonites, ‘non-ideal’ montmorillonites and ‘ideal’ montmorillonites, and Wyoming-type and Cheto-type montmorillonites. Of the Cheto-type montmorillonites, the Tatatilla-type samples are strongly discriminated, whereas the distinction between Chambers- and Otay-types is not strong. AlIV, AlVI, Fe, Mg, and Ca are generally important discriminating variables, whereas the tetrahedral portion of the layer charge, commonly used as a discriminating factor among these minerals, is only moderately significant.

Key Words: Aluminum smectite • Beidellite • Chemical composition • Classification • Crystal chemistry • Discriminant analysis • Multivariate analysis

Clays and Clay Minerals; December 1985 v. 33; no. 6; p. 546-558; DOI: 10.1346/CCMN.1985.0330610
© 1985, The Clay Minerals Society
Clay Minerals Society (www.clays.org)