Abstract
Between fully ordered and fully disordered (amorphous) states of clay minerals, many stages of partial order and disorder occur. Disorder of various kinds can be classified under the following headings:(i) Disorder at the atomic level, (ii) Disorder in layer stacking, and (iii) Disorder associated with mixed layering. This review is concerned principally with layer stacking disorders, particularly in kaolinite group minerals. The type and frequency of the disorder is discussed. Also considered are variations of layer spacings associated with lateral layer displacements particularly in kerolite, a talc-like mineral. The evidence that allophane may be a disordered defect form of kaolinite mineral is summarized.
