O-H STRETCHING VIBRATIONS IN KAOLINITE AND RELATED MINERALS

The grades of ordering as represented by I.R. and X-ray spectra for platy kaolinite, fire clay mineral, ball clay, dickite, nacrite and tubular dehydrated halloysite samples of various origin, are related. Well ordered kaolinite, has four bands 3,693, 3,668, 3,652 and 3,620 cm-1. In less ordered kaolinite, fire clay mineral and ball clay these bands have shifted a little or of the middle two, which are the weakest, only one band may be left (between brackets): less ordered kaolinite: 3,695, 3,667, 3,652 (3,653) and 3,620 cm-1; fire clay mineral 3,696, 3,668, 3,653 (3,653) and 3,621 cm-1; ball clay 3,697, 3,652 and 3,621 cm-1. Dehydrated halloysite has 3,693-3,698, 3,668, 3,650-3,654 and 3,620-3,626 cm-1 bands. In the most disordered dehydrated halloysite samples (Martinsberg and Baia Mare) only two bands are left at 3,696 and 3,624 cm-1. Dickite has four bands: 3,708, 3,656, 3,627 and 3,622 cm-1. For the lesser ordered Mexico sample it is 3,701, 3,652, 3,627 and 3,621 cm-1. Nacrite also has four bands i.e.: 3,700, 3,650, 3,627 and 3,620 cm-1. There is, apart from orientation effects, a wide variation in the absolute and especially in the relative intensities of the I.R. bands and X-ray reflections for each of the mineral groups investigated here, but of various origin. The need of a nomenclature adapted to the level of our knowledge about this matter to day and comprising all these variations included those in morphology is emphasized. Quantitative analyses, the adjective meant in the sense of an accuracy of minimal 5%, constitute a difficult problem which is perhaps even wholly impossible to solve with the conventional methods of today. © 1969 Springer-Verlag.