Abstract: From x-ray studies, mixed-layer minerals can be classified into regular and random types; the former show a long spacing of about 30 A. Certain clays showing strong powder reflections from long spacings have been considered in detail after treatment with ethylene glycol and/or ignition.
Kurata clay and Hanaoka clay no. 908, showing 29.6±0.2 A spacing, are composed of the following three kinds of lattices: (a) the usual montmorillonite lattice with the cell height of 15.4 A (M-lattice), (b) the kaolin mineral lattice with cell height of about 7 A (K-lattice), (c) a new lattice with a cell height of 14 A (G-lattice) which is represented by a regular interstratification between pyrophyllite and gibbsite layers, In these clays M-and G-lattices form partly a regular mixed-layer structure with a 29.6 A spacing and partly a random mixed-layer structure. Hanaoka clay no. 308, showing a 26.6±0.2 A spacing, is composed of a lattice with cell height of 12 A and a chlorite lattice; these form a regular mixed-layer mineral with the long spacing. A random mixed-layer mineral is found in some so-called acid clays. These clays have very broad basal reflections showing random mixed-layer complexes and having almost equal percentages of kaolinite and montmorillonite layers. The thermal curves and electron micrographs of these clays are discussed.