The weathering process of obsidian occured at Imari district in Saga prefecture was studied on the basis of the data for X-ray powder diffraction analysis, differential thermal analysis and microscopic observation. The samples collected at different weathering degree were examined to obtain a good raw material for bloating by heat treatment using small scaled rotary kiln. To discuss the relationship between glass structure and the bloating properties, the structures of the glass were analysed by using the method of radial distribution function. The following results were summarized.
(1) In proportion to the increase of the weathering degree, a lump of the obsidian was weathered into many needle like glass paritcles, and then those particles were also weathered into some spherical glass particles.
(2) The expanding ratio of weathered glass particles becomes higher than those of fresh ones.
(3) Long range order of the glass structure becomes low from fresh glass to weathered glass.
(4) Cutting the Si-O network structure having long range order into one with short range order in the glass structure by weathering might make the bloating properties of glass particles more active than unweathered structure by heat treatment.

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Many serpentinite fragments are recognized in the welded tuff located at the Fujiwara and Sudagai area, Minakami, Gumma Prefecture. In the fragments, a chlorite/smectite interstratified mineral is detected by X-ray together with smectite, chlorite, talc, serpentine and other non-clay minerals. The structure of interstratified mineral is almost regular, and chemically Mg is abundant. The mineral seems to be formed from serpentine by increasing temperature with chemical changes. The mechanism of the formation is not certain in this study, but smectite is formed in the early stage of the alteration by adding silica and increasing temperature.

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Siliceous mordenites were synthesized from aqueous clear solutions of sodium aluminosilicates containing benzyltrimethylammonium (BTMA), at 100° under atmospheric pressure. Their SiO₂/Al₂O₃ ratios (R value) of framework were in the range from 14.7 to 25.8. With increase of the R value, the crystals grew platy in habit rather than prismatic.
BTMA was occluded in the large cavity composed of 12-membered rings of (AlO₄) and (SiO₄) tetrahedra, and could not be exchanged by other cations. The number of Na⁺ions in the cavity probably decreases by the occlusion of the large organic base. Ac-cording to the relation, Na⁺Al₃⁺=Si⁴⁺, the number of (AlO₄) tetrahedra decreases, whereas that of (SiO₄) tetrahedra increases. Consequently, the organic base appears to cause the increase of R value.
The degree of ion exchange for sodium in Na form was high for univalent cations as compared with divalent ones.
From the experimental results of the adsorption of water vapor on the Na forms and ion exchange ones, it is concluded that mordenite becomes hydrophobic with increasing of R value, and their adsorption properties seem to change remarkably in the vicinity of 21-22 in R value.

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