Determination of Tetrahedral Aluminium in Mica by Infra-Red Absorption Analysis

Abstract

CONTINUATION of studies¹ relating the infra-red absorption spectra and the aluminium substitution for silicon in the chlorite minerals has shown that a similar correlation exists in almost all micas. Regardless of the species under study (that is, muscovite, lepidolite, biotite, phlogopite), the shape of the 9–10µ region of the absorption spectra depicts the amount of aluminium substitution for silicon (Y number) in the basal, tetrahedrally co-ordinated level in the mica structure. The micas may be natural or synthetic. Position of the maxima of absorption is again dependent upon the dominant type of ion in the octahedrally co-ordinated level, the maxima shifting to slightly longer wave-length with increasing atomic weight of the ions in this position.