So-called 14 Å clay minerals in some Ando soils

Abstract

Vermiculite and montmorillonite are frequent in the clay fraction of Japanese soils, although their content in the soils varies with soil types. In most cases, particularly in acid soils, these minerals hold more or less A1-hydroxyls in the interlamelar space, with which they undergo an appreciable change in properties from original ones (1). These A1-interlayers of the minerals seem to vary in stability; part of the interlayer can be removed from the minerals by dispersion treatments, changing their properties such as cation-exchange capacity, expansibility, potassium fixation (2). This fact suggests that the 14 Å minerals of the soils should be examined before and after the removal of A1-interlayers in order to gain an insight into the nature of the minerals. The 14 Å minerals in this paper denote the ones showing about a 14 Å spacing on the x-ray diffraction patterns of both K-saturated and air-dried samples and Mg-saturated and glycerol-solvated ones. The minerals consist of chlorite and intergrades of montmorillonite- and vermiculite-chlorite and also imogolite in some cases.