In a Paleudult of Java Island, there was a clay mineral indicating a mixed layer mineral which gave 15.51 Å peak (in the range of 14.63 Å and 16.37 Å) on Mg²⁺ -air dry and a 20.55 Å peak on Mg²⁺-glycerol solvation. On K⁺-saturation, the mineral showed an 11.87 Å peak and this peak was continuous to 7.53 Å. Furthermore, on sequential heating, the peak gradually shifted and finally shifted completely to 10.05 Å at 550° in X-ray diffraction (XRD). A peak of 7.53 Å was also observed in both Mg²⁺-and K⁺-saturated clays which disappeared after heating at 550° The objective of this study was to investigate the characteristics of this mineral. The 060 peak was 1.50 Å and suggests the dioctahedral smectite. The Greene-Kelly test on the clay sample suggests beidellite. Formamide solvation that caused a swelling of the 7.53 Å peak to 10.05 Å suggests the presence of halloysite. The 5M NaOH treatment resulted in a collapse of the 7.53 Å peak and remained at a sharp peak of 15.50 Å(in Mg²⁺-saturated clay). The presence of halloysite was also supported by a SiO₂/Al₂O₃ molar ratio of NaOH extractable materials. The NaOH treatment also resulted in an increase of the 11.87 Å peak (in K⁺-saturated clay) to 13.49 Å. According to the mineralogical and chemical properties of the clay sample we consider that the mineral is halloysite/beidellite mixed layer mineral.

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Clay mineral composition of the Holocene soils in the narrow basin of Hattori river, Imadate, Fukui, Central Japan, was compared with that of the Miocene soils on the surrounding hill by means of XRD, DTA, TG and chemical analyses. The results led to a following conclusion:
Smectite in the Holocene soils of this basin hardly originated in the Miocene sediments located at both side hills, but in the Miocene ones at the upper stream of Hattori river. This smectite was derived directly from parent materials. Or it was altered secondarily from vermiculite or its related minerals, which had been formed previously in the Miocene soil located at the upper stream, in the Holocene soil exposed alternately to the reductive and oxidative conditions. Smectite in this Holocene soils inside of this basin was brought from the Miocene materials in the upper stream, in either case.

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Two types of reaction scheme were proposed for boron (B) adsorption at equilibrium B concentrations of less than 2mM on nano-ball shaped allophane with its fundamental structure of aluminum orthosilicate.(i) Al-OH+B (OH) ₃→Al-O-B (OH) ₂+H₂O (ii) Al-OH+B (OH) ₄^-→Al-(OH)-B (OH) ₃+OH^-With the aluminol groups (Al-OH) included in the structure, the reaction (i) occurs below equilibrium pH of about 10, whereas the reaction (ii) does at equilibrium pH of higher than about 8. Calculated Langmuir parameters suggested that the aluminol groups of nano-ball allophane had higher affinity for B (OH) ₄^-than B (OH) ₃. Because the content of the aluminol groups increase with decreasing Si/Al ratio of allophane, B adsorption maxima were higher for KyP sample (Si/Al=1.34:2) than for KnP sample (Si/Al=1.98:2) irrespective of equilibrium pH. Release of Si from allophane samples during B adsorption on them was much smaller than the case of phosphate (P) adsorption previously studied. This indicates that B has less ability than P for replacing Si in the structure of nanoball allophane and the main B adsorption site is the aluminol group at the pore of the allophane nano-ball.

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The characteristics related to surface charge were investigated for various kind of kaolin minerals. Two types of kaolin minerals were used, one from weathering and sedimentary origins, Shinagawa-kibushi and Hara-gairome, and the other from hydrothermal origins, Georgia-kaolin and dickite. They were chemically treated in order to remove the organic species and ion-exchanged with Na⁺. The surface potential obtained from the variation of zeta potential and the cation exchange capacity (CEC) were studied for neutral kaolin minerals. A positive correlation exists between the surface potential and the CEC, and the CEC depends directly on the surface potential on the particle. The surface potential was larger for clays of weathering and sedimentary origins, Shinagawa-kibushi and Hara-gairome, than that of the hydrothermal originated Georgia-kaolin and dickite. The surface potential among kaolin minerals depends on the thickness of the edge plane and increases with a decrease in the crystallite size. Therefore, Shinagawa-kibushi and Hara-gairome which have large surface potential, have a large water film thickness due to the large amount of absorbed cations.

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Microporous silica was prepared by selective leaching of the Al₂O₃ component from calcined kaolinite. The kaolinite was calcined at various temperatures from 400 to 1000°C for 24 h. It was then chemically treated with a 20 mass% H₂SO₄ solution at 90°C for 2 h and the effect of the calcining temperature was studied. The chemical composition of the acid leached product changed largely by elevating the calcining temperatures from 425 to 475°C owing to selective leaching of Al2O3 from metakaolinite and became almost SiO₂ composition above this calcining temperatures. With decreasing of Al₂O₃ content in the products, the specific surface area increased and became higher than 300m²g^-1. It further increased gradually with higher calcining temperature up to 700°C because of the increase of efficiency of selective leaching. The pore size distribution was calculated by the Horvath-Kawazoe method based on Ar gas isotherms and the slit-shaped pore size was about 0.6nm in width for all the products with irrespective to the calcining temperatures. Since the particle shape was preserved after the leaching treatment, those pores are considered to be formed in the interlayers of the SiO₄ tetrahedral layers largely preserving the original metakaolinite structure.

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