In this paper, we reviewed recent studies on dioctahedral mica clay minerals which differ from typical muscovite in some distintive properties, such as a particle sizeand crystal chemistry.
The chemical variations of the mica minerals would be due to the fine particles and which occur and/or alter homogeneously and/or heterogeniously from various materials such as smectites, micas and solutions.
Structural features of the mica clay minerals have been discussed from the view points of the mixed layer structures of mica and smectite and of the polytype. On the other hand it is also important to elucidate some properties of the composing layer itself, such as OH behaviours, cation substitutions and tetrahedral and octahedral order-disorders in the layer.
The habit of the mineral could be grouped into three platy ones which are hexagonal like, tabular and irregular like habits. Observations of the crystal habits, surface characters and inner structure by an electron microscopy are important to clarify the relations among their crystal growth, polytypes and genesis.

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On clay veins developed in the weathered granitic rock in Higashihiroshima district, Hiroshima Prefecture, the mode of occurrence, the distribution, constituent clay mineral and its mineralogical characteristics were investigated, and formation mechanism of fracture system of clay veins were also discussed.
The clay veins are distinctly divided into three types (Type I, II, and III) based on the mode of occurrence. The clay veins of type I are formed along both side of the dike rock (granite porphyry). Their strikes are mainly N60°-90°W and their dips are nearly vertical. They are composed of mainly mica mineral (2M₁, 1M and 1Md polytypes) accompanied with a small amount of montmorillonite mineral. The type II veins occur replacement products in vein form. Their strikes are mainly N60°-90°W and they have nearly vertical dip. They contain mica clay mineral (1M and 1Md), the interstratified mineral of mica layer mineral and swelling layer and montmorillonite mineral. The veins of type III are formed along nearly vertical faults or fissures. The veins have both N40°-80°W and N50°-9°E strike such as conjugate fault. They are composed of mica clay mineral, the interstratified mineral and montmorillonite mineral.
The veins of type I and II are arranged in zones (400-500m in width and Ca. 20km in length) which extended WNW-ESE. Based on the modes of occurrence, the distribution and strikes of veins, type I and II veins seem to be formed by tension fracture, and the veins of type III were formed by strike and slip faults depend on the lateral pressure. The fracture of these of veins seem to be formed under the regional lateral compression of WNW-ESE direction.
It may be indicated from the distribution of mica clay veins of type I based on the difference of polytype that the thermal gradient of the hydrothermal solution formed mica clay mineral were similar to that in geothermal areas, e. g. 1) the temperature of hyprothermal solution in the deeper parts of veins higher than that in the shallower parts. 2) the thermal gradient of the hydrothermal solution varied in the each parts.
It may be considered from these results that mica clay minerals were formed by the hydrothermal solution which was intruded from the deeper parts to the shallower parts along the fractures developed under the regional stress field, and then mica clay mineral converted to the interstratified mineral and montmorillonite by weathering.

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ZSM-5 zeolites were synthesized from aqueous solutions in Na₂O-TPA₂O-Al₂O₃-SiO₂-H₂O system, and there was an optimum condition in the relations between TPA₂O content of initial gel and the amount of crystals formed. The zeolite crystals were comparatively uniform in size and their SiO₂/Al₂O₃ ratios (R values) of framework were in the range from 80 to 6400.
The adsorbed amount of n-hexane on the Na-form was in close agreement with that of silicalite. In the conversion of methanol to hydrocarbons, the H-form containing only about 0.6 Al atoms per unit cell gave a high yield of aliphatics and aromatics.

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The Neogene Tertiary system in the Haryuu area is comosed of the Komadotoge welded tuff of Pleistocene, the Kamagoezawa tuff and tuffaceous mud stone of Upper Miocene and the Azabu silty tuff of Middle Miocene. In these rocks clay and non-clay minerals such as smectite, chlorite, zeolites and silica minerals are detected by using the powder Xray diffraction method.
These minerals are grouped into the four zones judging from the mineral assemblages.Their distributions and lithology almost correspond to those of the Komadotoge, Kamagoezawa and Azabu formations. The zones and formations are correlated as follow;
Non-altered zone...Komadotoge formation
Volcanic glass-smectite zone...Kamagoezawa formation
Zeolite-smectite zone...Kamagoezawa formation
Albite-sericite-chlorite zone...Azabu formation.
The zeolite-smctite zone seems to be divided into clinoptilolite and modenite sub-zone.
The non-altered zone shows no evidence of being altered by diagenesis, because any diagenetic altered minerals cannot be detected mineralogically by X-ray method. The rocks in the volcanic glass-smectite and zeolite-smectite zones show the almost similar lithofacies and chemical compositions, so that they seem to be formed succesively by a burial diagenetic alteration. On the other hand, the albite-sericite-zone seems to be formed diagenetically from an other original material in a different sedimentary environment. The zonal distribution of alteration products in this area seems to be formed basically by the diagenetic process, but some hydrothermally altered and weathered minerals are found locally in some parts.

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Aquacreptite was prepared from the reaction of colloidal silica and magnesium hydroxide in aqueous ammonia solution under hydrothermal condition. The X-ray diffraction pattern of prepared sample agreed with that of natural aquacreptite (Fig.1 and Table 2). The reaction temperature was an important factor the formation of aquacreptite. In this experiment, the product was obtained above 280 °C. The intensity of the 9.8 Å reflection increased with the increase of calcined temperature of the sample.
The thermal analysis (Fig.2) showed an endothermic reaction with weight loss at about 75 °C, which is due to the the dehydration of the zeolitic and the absorbed water. The bounded water molecules were lost gradully in the temperature range from about 100 °C to 830 °C. A continuous exo-, endo-and exothermic curve with weight loss was obtained about 830 °C. This was due to the loss of hydroxyl water and recystalization. An electron micrograph is shown in Fig.3.

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