Semi-quantitative analysis of the clay minerals in the bottom sediment samples from Kagoshima Bay was carried out to determine the distribution trends of the clay minerals and its relationship with the geology of the study area as well as certain physico-chemical conditions within the bay. The study utilized various methods such as XRD, DTA, IR and SEM. The clay minerals identified are 10Å-halloysite, illite, smectite, kaolinite and chlorite. Non-clay mineral components are feldspar, quartz, cristobalite, gypsum, calcite and pyrite. 10Å-halloysite is the most abundant clay mineral. Illite, smectite and kaolinite are the next abundant. Chlorite is the least common. Non-clay are also widely distributed in the sediments of Kagoshima bay. Feldspar, quartz, cristobalite and pyrite are common throughout the bay while calcite and gypsum vary in distribution.
Based on the geology of the surrounding area, it has been shown that the terrigenous supply represents the dominant agent responsible for the distribution of the clay minerals. Certain environmental conditions, however are considered minor mechanisms that influence clay mineral distribution. The clay minerals were transported with feldspar, quartz and cristobalite.

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The alteration of mica, chlorite and their related mineral in parent rocks from two terrains being the Middle Triassic to the Middle Jurassic was discussed in two paddy fields of Gray Lowland soils located in Fukui Prefecture.
Mica hardly altered to other mineral, but lost iron from its layer lattice and its crystallinity degraded a little in both two soils. Mica-vermiculite interstratified mineral in the Mino Terrain altered to vermiculite. Iron-rich chlorite in the Tanba Terrain changes partially to chlorite-vermiculite intergrade with the decrease of iron from its layer lattice. The alteration of these minerals was due to the decrease of iron content, the decrease of layer charge and the degradation of crystal structure, through the pedogenesis under the seasonally reductive condition.

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The layer charge characteristics of thirteen samples of montmorillonites occurred in Tertiary sediments of Miocene age in southeastern Korea were determined. The layer charge (cation density) lies between the limits 0.46 to 0.25 per half unit cell and 7 or 8 different classes were observed in the majority of the samples. All samples show heterogeneous charge distribution. The average layer charge calculated from n-alkylammonium method varied 0.30 to 0.38 per half unit cell which is equivalent to cation exchange capacity of 80-101 meq./100g.
Measured CECs by AgTu method were always larger than calculated CEC from average charge density by n-alkylammonium method by 13-29 percent. This difference can be assigned to other factor, the most likely being broken bond effect on crystal edge and systematic error in alkylammonium method. The relationship between CEC from structural formulae and n-alkylammonium method with AgTu CEC was considered. It suggests that calculated CEC from the structural formulae of relatively impure montmorillonites based on conventional chemical analyses are probably more subject to error than those derived from the n-alkylammonium method.

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Mineralogical and chemical examinations were made on interstratified illite/smectite in the mudstones taken from three drill holes penetrating the Tertiary Yeonil Group to study its reaction during diagenesis. The Yeonil mudstones are dominated by large amounts of the randomly (R=0) interstratified illite/smectite with a maximum illite layer of up to 38%. Chemically the interstratified I/S was formed by input of K and Al ions originated from the destruction of detrital illite and kaolinite in compensate for the release of water and exchangeable cations from interlayers during burial diagenesis. This can be represented simply by the following reaction.
4.5K+8Al³⁺+smectite → illite+3Si⁴⁺+H₂O+Na, Ca
However, the illitization terminated at the randomly interstratified I/S with illite layers of 38% because the Yeonil Group has shallow burial depth. On the other hand, R=1 ordered I/S appears in only one sample from the deepest depth of the F hole with different occurrence and organic content from the mudrocks including the randomly interstratified I/S. Judging from the high potassium content and the deeper part of the hole, the illitization may be accelerated further. The Yeonil Group shows a very low degree of the diagenesis, probably result from the shallow burial depth. The maximum temperature of the Yeonil Group is estimated at 50-70°C based on the illite/smectite diagenesis and organic maturation

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The bonding state and distribution of Si in five natural samples and one synthetic sample of “coprecipitated” siliceous ferrihydrite have been studied by X-ray photoelectron spectroscopy (XPS). For the natural samples, values of the Si 2s peak binding energy indicate that three-dimensional polymerisation of SiO₄ tetrahedra is, at most, only poorly developed. In contrast, the value for the synthetic “coprecipitated” sample suggests a significantly higher degree of three-dimensional SiO₄ polymerisation. For all of the natural samples the Fe/Si atomic ratio determined by XPS is comparable to, or slightly larger than, the average bulk ratio, indicating that the Si in these samples is well dispersed throughout or that the outer layers of the ferrihydrite aggregates are slightly depleted in Si. For the synthetic sample the Fe/ Si XPS ratio is markedly smaller than the corresponding bulk ratio indicating surface precipitation of a Si-rich phase. Synthetic samples prepared by coprecipitation of Si and Fe may not be good models for natural siliceous ferrihydrites.

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