The process of thermal transformation of tetrasilicic potassium fluor mica has been studied by X-ray diffraction method and optical microscopy. The transformation process is markedly affected by the amount of specimen used for the heating experiments. Inthe case of a small amount of specimen, the tetrasilicic potassium fluor mica t ransforms at first into forsterite, subsequently into forsterite and enstatite, and finally into enstatite and glass phase, while in the case of a large amount of specimen, it transforms into forsterite and glass phase. The formation of enstatite may be attributable to the change of the chemical composition due to the vaporization of volatile matters (K, F etc.) at high temperature.
The topotactic relations between the mica and the enstatite are maintained, and the mechanism of the thermal transformation mentioned above are discussed in relation to the crystal structure of the parent and the product phase.

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Various members in the chrysotile-pecoraite solid solutions were obtained by hydrothermal synthesis under the conditions of 350°C, 500kg/cm² (water vapour pressure) and 10 days. The products were examined by X-ray diffraction technique, IR spectroscopy, thermal analysis, electron microscopy and heat treatment. The main results obtained are summarized below.
(1) All products had homogeneous distribution of magnesium and nickel in the octahedral sheet.
(2) In the IR spectra the frequencies of four bands related to hydroxyl group (3695, 3660, 402 and 300 cm^-1 for the magnesium end member) varied linearly with increasing nickel content to 3646, 3618, 374 and 317 cm^-1 for the nickel end member.
(3) Dehydroxylation temperature of the member with higher nickel content was lower than that of the member with higher magnesium content.
(4) After heating the long spacing phase was observed in the members with higher nickel content. This phase was characterized by the broad reflection of 12-14Å, and seemed to preserve the original layer structure of serpentine.
(5) In the nickel end member some hydroxyls remained even at high temperature of 900°C.

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The formation process of the clay minerals in clay veins (Seam or gouge) found in caves of dam-site at Nukui, Kake-cho, Yamagata-gun, Hiroshima Prefecture were investigated by X-ray diffraction, DTA, TEM, the chemical analysis and so on. The clay mineral, montmorillonite mineral and the interstratified mineral of mica-swelling layer accompanied with a small amount of kaolinite. Mica clay mineral and the interstratified mineral are found in veins which are situated at the lower level (lower than 260 m in altitude), while montmorillonite mineral exists dominantly in the upper lever (upper than 260 m in altitude). The water table is situated at about 250-260 m in altitude. The change of clay minerals in the lateral direction of clay veins are not recognized.
Mica clay minerals are identified to be 1 Md polytype. The differential thermal curves give one endothermic peak at 600-700°C. The crystal forms are well developed elongated plates or irregulary particles. The interstratified minerals are produced by two component stacking of 40-60% mica clay mineral layer and 60-40% swelling-layer. The differential thermal diagram of the interstratified mineral shows double endothermic peaks in the range of 500-700°C. Their crystal forms are similar to those of mica clay minerals. The electron diffraction pattern shows hexagonal network pattern overlapping with ring patterns, which is similar to that of hydrobiotite. The 14Å basal spacing of montmorillonite mineral expands to 17Å with ethylen glycol treatment, and reduces to 10Å, which is similar to the peak of mica clay mineral, with heating at 500°C. The differential thermal diagram of montmorillonite mineral exhibits two endothermic peaks at 500-700°C. Though montmorillonite minerals show as a general feature very thin irregular lamellae of different sizes which are partly folded, some of them are recognized as lath shaped particles.
Chemical compositions of the interstratified mineral and montmorillonite mineral are similar to those of mica clay mineral except K₂O and CaO contents infered to be interlayer cations. The exchangeable cations in montmorillonite and the interstratified mineral are almost Ca²⁺ ion. The K₂O content in clay minerals decreases linearlly with increasing the proportion on the swelling layer, while the CaO content in clay mineraisincreases in proportion to the decreases of the K₂O content.
These results indicat that mica clay minerals in clay veins were converted to montmorillonitelike mineral through the interstratified mineral of mica-swelling layer by weathering. The change of clay minerals in the vertical direction of the veins were caused by the change of the level of the ground water table.

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The softening effect of bentonite to cotton fabric was studied in relation to the cation exchange capacity and other characteristics.
It could not decide any appreciable corelations between the softening effect andthe ation exchange capacity, speciific surface area, apparent viscocity and the composition of exchangeable cations. Cristobalite associated montmorillonites were adsorbed on to cotton fabric intensifying the softness to the touch.

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