Abstract: A number of methods were tested for their applicability to the problem of determining the content of halloysite in kaolin clays. These analytical methods included the thin-section point-count technique, base-exchange determinations, electron microscope techniques and infra-red absorption spectra differences.
Base-exchange determinations were made on a number of monodisperse fractions of pure halloysites and kaolinites. Consistent values of 12 meq/100 g were obtained for the halloysites and 4 meq/100 g for the kaolinites in the size range 1–0.25 micron.
Electron micrographs were taken of prepared homogenized mixtures and counts made of the two morphologically different varieties. Application of this technique to several natural halloysitic kaolins, of which the proportions were known by DTA methods, gave good correlative results.
The thin section method gave very good results on residual clays where the kaolinite occurs as vermicular aggregates.
Infra-red absorption spectra were run by associates on prepared mixtures and the differences were sufficiently marked to give semi-quantitative results.
These four techniques are evaluated with respect to accuracy and application and are compared with other reported techniques.