Abstract

Disordered sericites from the western part of Japan were found to have ammonium ions which are believed to be located in the interlayer sites. Evidence for the presence of NH4+ ions was obtained from chemical, infra-red, and weight-loss analyses. X-ray examination of a large number of sericites revealed that these minerals have basal spacings ranging from 10.0 Å to 10.5 Å, and that disordering in the layer-stacking increases with increasing basal spacing. The x-ray diffraction patterns of these minerals showed similarities to the 2M1-, lM-,and lMd-types, but detailed structural analyses have not been made, by which the polytype could be definitely identified. In this investigation a tentative classification has been made based on the average basal spacings; 10.0 Å (2M1-type), 10.05 Å(1M), 10.2 Å(1M), and 10.5 Å(lMd), respectively.

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