X-RAY POWDER PATTERNS AND CELL DIMENSIONS OF SOME CHLORITES IN JAPAN, WITH A NOTE ON THEIR INTERFERENCE COLORS

Abstract

X-ray powder studies on about fifty specimens of rather highly crystal- line chlorites from Japan revealed the exsistence of two type of elementary cells, one with a 14A-monoclinic and the other with a 14A-ortho-hexagonal symmetry, and that the patterns of the former type are closely similar to one another, but those of the latter type vary from one another in detail. The monoclinic type ranges from Mg-rich chlorite to Fe-chlorite while the ortho-hexagonal type appears to be limited to Fe-rich members, but a Mg- rich specimen seems to have the latter type cell. The interference colors of the monoclinic types are frequently abnormal (usually for Fe-chlorite), the ortho-hexagonal types, however, usually show normal interference color, so that these two types are generally distinguishable under the microscope. The results of chemical analyses and cell dimension determinations for the selected eleven ch ?? orite specimens show that, as previously known, the basal spacing depends on the number of tetrahedral Al ions, and the b dimension on Fe atoms in the structure; these relations are not only more definitely established than in previous data but also suggest that both the basal spacings and the tetrahedral Al+3 ions of chlorite and/or serpentine can be dealt with in the same manner. The estimation of the chemical composition of chlorites by X-ray me thod is also presented.