Chlorite/smectite (C/S) mixed-layer minerals occurring closely associated with are minerals in epithermal gold-silver ore-veins were examined by optical and electron microscope, X-ray diffraction (XRD) and electron microprobe.The mixed-layer structure of the mineral having a 20 Å-reflection was e valuated to be of interstratification (g=1) of chlorite-chlorite and corrensite through a comparison of the measured and the calculated XRD line profiles.

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Experimental alteration of obsidian was performed in distilled-deionized water at 100°C for up to 365 days to elucidate formation processes of clay minerals at relatively low temperature condition. The alteration products were examined by transmission electron microscopy (TEM), scanning electron microscopy, and energy dispersive X-ray analysis. The surface compositions of obsidian before and after alteration were also examined by X-ray photoelectron spectroscopy (XPS) to clarify dissolution processes. For reaction products, allophane, fibrous boehmite, and halloysite were formed at early stage while fibrous smectite appeared later. Based on the activity diagram for the system of Na₂ OAl₂O₃-SiO₂-H₂O, it was found that allophane, boehmite, and halloysite appeared to be formed as a metastable phase, and that smectite was produced as a stable phase. TEM showed that allophane and boehmite were precipitated from the solution, and halloysite and smectite were then transformed from allophane and boehmite, respectively, as reaction proceeded. XPS indicated that preferential leaching of Na and enrichment of K occurred at the obsidian surface. Likewise, Al/Si ratio of the surface increased during the reaction. These results are probably due to formation of smectite structure in a leached layer produced on the obsidian surface.

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In this study, mechanism of flocculation for an Na Kaolinite-water system dependent on salt concentrations in alkaline bulk water (pH 10) were examined rheologically. Consequently, it became clear that when NaCl was added to dispersed Na kaolinite suspension, kaolinite flocculated in two stages. Fiest, for salt concentrations between 2.0×10^-3mol/e and 1.0×10^-2mol/e, flocculation occurred with an increase in the salt concentration under stable conditions. In the flow state, a hard flock formed by the bonding of dispersed particles was also developed as the salt concentration increased. On the other hand, when the salt concentration exceeded 1.0×1^0-2 mol/e, and subsequent increased salt concentration the flock in the flow state could no longer be developed. Although flocculation in the caly-water system develops with increasing salt concentration, the degree of development was less than compared in salt concentrations ranging from 2.0×10 ^-3 mol/i to 1.0×10^-2 mol/e.
These results indicate that an increase in salt concentration promotes an intense bonding between clay particles of low salt concentrations (2.0×10^-3mol/e 1.0×10^-2mol/e). And although the increase in the intense bonding force between particles did not occur in high salt concentrations (more than 1.0×10^-2mol/e), flocculation caused by weak bonds none the less proceeded.

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Bentonite/Sand Mixture is expected to be an effective component of barriers for radioactive waste facilities.Several effective characteristics of Bentonite/Sand Mixture are 1) low permeability, 2) self-healing, 3) long-term durability.Low-permeable mixture can be obtained through enrichment of bentonite content of the mixture. But the data of relation between bentonite content and permeability have been taken in few kinds of sand, therefore we cannot estimate the appropriate arrangement of mixture in case of using another kind sand. On the other hand there is no guiding principle regarding which sand is better for making low-permeable mixture.
Compaction tests and permeability tests were executed in order to research the method how to choose the better sand and to decide the appropriate bentonite content. First we made many kinds of Bentonite/Sand Mixture using 3 kinds of sand in 3 or 5 cases of varied bentonite content, and measured the permeability in laboratory.The difference of permeability between 3 kinds of sand was not negligible in spite of same bentonite contents, especially in condition of poor bentonite content. Then we examined the relation between permeability and effective void ratio which is calculated from bentonite content and density of the mixture. The effective void ratio is useful parameter for choosing better sand and for deciding optimum mixture.
We propose the following procedure for designing the Bentonite/Sand Mixture.
1) To examine the conditions of maximum dry density through compaction test using few kinds of candidate sand and varied bentonite content.
2) To calculate effective void ratio from maximum dry density and plot the relationship between bentonite content and effective void ratio of each candidate sand.
3) To decide the optimum effective void ratio for the target permeability according to the relation between permeability and effective void ratio.
4) To decide the optimum bentonite content of each candidate sand according to the relation curve between bentonite content and effective void ratio.
5) To choose several cases of potential mixture design.
6) To examine not only permeability but also mechanical properties of the chosen mixture design.
7) To choose the best mixture design.

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Adsorption of phosphate ion of natural zeolites has been examined. Zeolite rocks used were naturally occurring clinoptilolite and mordenite. Cation exchanged zeolites used were prepared by the treatment with solutions of Al (NO₃) ₃, AgNO₃, CaCl₂, and NiCl₂.
Little or no adsorption was observed for the natural zeolites. It was found, however, that the treated zeolites adsorb phosphate ion. The adsorption amount versus pH curve shows different pattern between the kinds of exchanged cation. Adsorption tendency for different Ni-exchanged zeolites showed a similar feature being a flat region at pH range of 3-10, and a slow decreasing region above pH10. The Al-exchanged zeolite showed similar behavior to that of the Ni-exchanged zeolites. Adsorption amount of Ca-exchanged zeolites increased above pH10, e. g., 72meq/100g for the Ca-exchanged clinoptilolite at pH12.3. Characteristic adsorption curves were observed for the Ag-exchanged zeolites, which have a maximum at pH11. 5-12. The amount of adsorption reached to about 63meq/100g.
Adsorption of phosphate ion depends not only on the production of phosphate salts but also weak bonding with zeolite via cation.

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