On the basis of the dispersive property, the kinds and the amount of exchangeable cations were determined in order to classify raw clay materials from Seto area which are mainly composed of kaolin. Surface chemical properties were also studied in terms of cation exchange capacity (CEC). The dispersive property was not correlated with CEC. The value of pH decreased with increasing amount of exchangeable Al³⁺in the clay. Owing to exchangeable Al³⁺, the clays other than kibushi clay showed ill dispersion. Well dispersion of kibushi was explained by assuming that humus involved in the clay played a role in weakening the flocculating property of Al³⁺.

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The difference of colloidal properties between sericite and kaolinite was revealed by zetapotential measurements, dispersion and coagulation (DC) tests, and viscosity tests of suspensions and analyzed on the basis of DLVO theory using the estimated face and edge potentials of sericite and kaolinite. The results were summarized as follows;
(1). The results of DC and viscosity tests showed that the suspensions of sericite particlescoagulated between pH6 and pH7, however, the suspensions of kaolinite particles coagulated between pH7 and pH8.
(2). The zeta potential of the two clay particles was measured in the cetyltrimethylammonium bromide (CTAB) solutions. The zeta potential of kaolinite was higher than that of sericite under the conditions that the cetyltrimethylammonium (CTA) ions adsorbed on face site of clay particles at 10^-5 M CTAB concentration.
(3), The edge potentials of sericite were calculated on the basis of Williams method. The calculated edge potentials of kaolinite was higher than that of sericite in the range of pH4 to pH8.
(4). The difference of DC and viscosity tests results between sericite and kaolinite suspensions were analyzed by the DLVO theory using the estimated edge and face potentials of the two clay minerals. The total potential energy of interaction between two plate-like clay particles calculated at different pH conditions demonstrated that the suspensions of kaolinite particles started coagulating at higher pH conditions than that of sericite particles. These calculated results explained well the experimental ones.

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Mortar bars are exposed to H₂S gas (25-300ppm) for 10 months at 12-30C°. Sulfate-generated deteriorations in the mortar bars include expansion, cracking and disintegration. The heavily corroded mortar bar produced gypsum, calcite and secondary ettringite with a trace amount of barite. The secondary ettringite shows the same chemistry as the primary ettringite, but the morphology is quite different from the primary one. Ettringite crystals with sharp point, 10-20μm long, are primary formed during the hydration of mortar bar, whereas small lath-shaped crystals, about 3μm long as observed by SEM are high concentration of hydroxyl ions. Gypsum, calcite and the secondary ettringite are formed step by step under acidic condition. The iron oxides layer is presented significantly between corroded and un-corroded zones which is the same process of deterioration on portland cement concrete.

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The first discovery of zeolite rock in Japan was done in 1949 by Sudo et al. from the pumiceous tuff of Utsunomiya, which we call Oyaishi. In the following year, Sudo reported the occurrence of a zeolite-bearing bentonite deposit at Yokote, Akita Prefecture. The locality names, Asakura and Morokozawa were often cited in these papers, however, thier localities were not mentioned in detail. In this paper, I clarifies the localities of both places and briefly summarizes the exploitative history of zeolite rock at Yokote.
A smectite clay deposit which includes zeolite sporadically occurs at Yasawagi, Omori-machi, Akita Prefecture, and was named “Yasawagi clay” by the author in 1959. Since then, the exploitation of the deposits has been continued until today, and the products are commercially called “Soft Silica”. Recently, the author found K-feldspar bearing rocks which were originated from tuff beds in the Yasawagi clay. Thus, mode of occurrece and mineralogical properties of the K-feldspar rocks are described and its genesis are also inferred in this paper.

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