電子回折による土壌粘土のSerpentine mineralsの同定(前会長山田忍教授退官記念号)

抄録

Specimens of soil clays derived from the serpentinite in northern Hokkaido have been examined by electron micrographs and electron diffraction in a study of the identification of the serpentine minerals. The results of the investigation showed that the serpentine minerals in the soil clays were composed of antigorite, lizardite and chrysotile. The clay mireralogical properties of these minerals were summarized as follows: 1) Antigorite. Electron micrographs (Figs. 2-1 and 2-3) show thin plates with approximately rectangular outlines. Electron diffraction patterns from single crystals are of the type shown in Figs. 2-2 and 2-4. Layer lines are evident corresponding to a parameter b=9.40Å parallel to the longer morphological axis. Along each layer line, mainly grouped around reciprocal lattice points of a simple 5.6Å×9.4Å rectangular net, are clusters of spots closely spaced at regular intervals corresponding to a cell parameter of approximately 40Å. The pattern may be regarded as similar to those from plates of lizardite on which a superlattice periodicity along the a axis has been superimposed. 2) Lizardite. Electron micrographs (Fig. 3-1) show the irregular plate-like morphology of the fine particles. The pattern obtained from a single crystal of lizardite (Fig. 3-2), is a hexagonal array of spots corresponding to a centered rectangular net of dimensions a=5.25Å, b=9.25Å in agreement with the x-ray powder pattern which gives a=5.31Å, b=9.20Å (WHITTAKER and ZUSSMAN, 1956). 3) Chrysotile. Electron micrographs (Fig. 3-3) show elongated smooth-edged fibres frequently with a thin white axial line. One fibre and its electron diffraction pattern are shown in Fig. 3-4. The diffraction patterns resembled closely those obtained by x-rays with the beam normal to a fibre. Reflections are distributed along "layer lines", the spacing of which corresponds to the repeat distance a=5.38Å along the fibre axis.