Abstract
The intensities of X-ray basal reflections of dioctahedral mica clay minerals were calculated on the basis of the mica compositions ranging from K2 (Al, Si)8 Al4O20(OH)4 to (K, H2O)2-0 (Al, Si)8 (Al2Fe2) O20 (OH)4. The triangular diagrams with three components, I(10Å)-I(5Å)-I(3.3Å) and I(5Å)-I(3.3Å)-I(2.5Å), were made from these intensities calculated. Figures showing relationship between I(10Å)/I(5Å) or I(10Å)/I(3.3Å) and the contents of interlayer or octahedral cations were also made. Basal reflection intensities were examined for some illite samples having different chemical compositions. These samples were plotted in the above-mentioned diagrams and figures. Relationship between the points of samples in the figures and their compositions were investigated. Some problems were pointed out for the practical method obtaining chemical compositions of dioctahedral mica clay minerals from the ratios of basal reflection intensities.
