Od-Interpretation of Kaolinite-Type Structures—I: Symmetry of Kaolinite Packets and their Stacking Possibilities

K. Dornberger-Schiff and S. Ďurovič
Central Institute of Physical Chemistry, Academy of Sciences of the German Democratic Republic, Rudower Chaussee 5, Berlin-Adlershof, 1199, G.D.R.
Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 5, 809 34 Bratislava, Czechoslovakia

Abstract: The idealized symmetry of kaolinite-type minerals (1:1 phyllosilicates) is analysed in detail. They can be considered as OD-structures consisting of three kinds of OD-layers. Each of them, taken separately, possesses higher symmetry than their combination. This explains the well-known tendency of kaolinite-type minerals to form a wide variety of ordered and disordered polytypes as well as twins. The possible stacking sequences result from the different kinds of pairs of kaolinite layers which are derived for dioctahedral, trioctahedral as well as ‘monoctahedral’ kaolinite-type minerals, the latter being defined as those in which the three octahedral positions are occupied by three different cations or two different cations and a void. The analysis makes use of a simple symbolism and a simplified pictorial representation.

A brief summary of the most important terms and definitions of the theory of OD-structures is given in an Appendix.

Clays and Clay Minerals; July 1975 v. 23; no. 3; p. 219-229; DOI: 10.1346/CCMN.1975.0230310
© 1975, The Clay Minerals Society
Clay Minerals Society (www.clays.org)