ABSTRACT
Clay mineralogy is littered with mineral names, most based upon pure mineralogical material which is generally not from surface alteration nor of soil origin. However, viewing the basic mineralogy and functioning of the minerals in soils greatly enables simplification of the terminology, providing a much clearer vision of the material present. Phyllosilicate clay minerals can then be considered to be of two types: those where there is a two-sheet structure of cation–oxygen complexes that are strongly covalently bonded and those with a three-sheet complex. O. Righi and B. Velde proposed that “the series of soil minerals smectite, HI and illite might well be part of the same series of continuous solid solution minerals and that the expression of the mineralogy, observed by X-ray diffraction, depends on the interlayer ion population”. Mixed-layered clays mostly comprise combinations of different types of 2:1 minerals.
