The depth of alteration zone in the bentonite deposite in Kuroishi mine located in north Japan was estimated by measuring the vertical element profiles of Na, K, Ca, and Mg in the drilled core samples. The ammonium acetate extraction method was employed to measure the exchangeable ion content in smectite and the results indicated Na depleted from the ground surface to 20m in depth. The data also indicated the total loss of Na coincided with the accumulated amount of Ca and Mg. The contribution of K in the reaction was however negligible. This suggests the Na depletion was mainly caused by the ion exchange reactions with Ca ang Mg. The equilibrium constants of the ion exchange reactions were calculated by using the ionic compositions of the underground water analyzed by the in-situ sampling system and the results indicated ca. 10³ g/L for both Ca and Mg. By using these constants, the one dimensional depth profile in the bentonite layer were calculated by a diffusion-convenction equation coupled with the ion exchange and calcite dissolution equilibria. The results indicated the time required for the development of the observed element profiles were estimated as 0.4 million years and the resulting average alteration rate was 4 cm/1000years. This value is equivalent to that independently obtained by geomorphological studies.

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This study attempts to analyze some initial stages of chemical weathering process by artificially weathering granodiorite of the Paleogene in Akagi-cho, Iishi-gun, Shimane-ken.
In order to conduct the experiment under the condition that will reflect the real surface of the earth as much as possible, we first mixed distilled water with carbon dioxide and with air and then devised a flow system equipment that enables the treated solution to circulate while reacting to the ore. After setting the tempreture of the treated solution at 22°C±2°C, pH4.2-4.4, we continued this experiment for one year at the interval of five-day operation and two-day out of operation. The results of this experiment are as follows.
1. Biotite showed the sharpest reaction: K ion of interlayer was dissolved and decreased. Fe, Mg, Mn ions were gradually removed out of octahedral sheet, while Al ion was added to.
2. The pieces of biotite that were extricated from the rock accepts Ca ion and then changes into nonswelling vermiculite after its K ion of interlayer was partly dissolved.
3. Plasioclase showed the second sharpest reaction: the areas that are rich in Caion and contain inherent fractures or altered minerals were selectively dissolved and disappeared.
4. Altered minerals such as chlorite, apatite, calcite showed a sharp reaction toward the treated solution and influenced greatly the quantity of dissolved ions at the initial stage of weathering process.
5. The dissolved constituents formed a thin film on the rocks and its main ingredients were Al, Si ions. The varieties and the amounts of components were influenced by the dissolved components of the minerals and differed, depending on where the thin film is on the rock.

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Saponite was hydrothermally synthesized from rock powder or sand sludge with Mg (OH) ₂. The materials treated with HCl solution were also used as starting materials. The hydrothermal products were characterized by means of XRD, XRF, DTA-TG, IR and SEM. Saponite could be obtained from all starting materials with 2.0 mol/_l-NaOH solution. In the case of distilled water or 0.2 mol/_l-NaOH solution, broad peaks of saponite were observed. Analcime was once formed and then vanished within the first 8h of reaction period, from the HCl-treated starting materials. Then, saponite was formed. Amphibole, muscovite, and chlorite in the starting materials remained after the hydrothermal reaction.

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Quantitative analysis of major elements by a glass beads and X-ray fluorescence method was made on five JCSS samples-sericite, pyrophyllite, dickite and two smectite minerals-offered from the JCSS committee.
The analytical results of sericite and pyrophyllite were comparatively well in agreement with expected values based on the table of the data of chemical analyses of the JCSS samples. In the case of dickite the value of Al₂O₃ was a little larger than the expected value. It is considered that the high Al₂O₃ content in dickite, about 15% more than the upper limit of the calibration line, made this disagreement. The total values of major elements of two smectite minerals were about 2.5% lower than their expected total values. It seems that the nature of the minerals which reabsorb water easily causes such lower values.

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