An essentially regular interstratification of mica (sericite) and chlorite (sudoite) has been found from an alteration area of the Matsumine Kuroko deposit of the Hanaoka mine, Akita Prefecture. The mineral was collected from a bore hole at a depth of 290 m, corresponding to the top portion or the hanging wall of the deposit. It is associated closely with sudoite (di/trioctahedral chlorite). The b asal reflections are very close to an integral series. The average basal spacing d (001) is 24.14Å. The value of d (060) is 1.504Å. The DTA curve, having a deep endothermic peak at 600°C, and the infrared pattern are similar to those of dioctahedral chlorite. The chemical analysis leads to the following approximate formulae for the two components of the mineral:
Mica (sericite): K_0.8Al₂ (Si_3.2Al_0.8) O₁₀ (OH) ₂
Chlorite (sudoite):(Mg₂Al) Al₂ (Si₃Al) O₁₀ (OH) ₈.
Structure factors and one-dimen sional Fourier projection confirm the interstratified dioctahedral micadi/trioctahedral chlorite structure, of which the chlorite component has dioctahedral silicate and trioctahedral hydroxide layers. Fourier transforms reveal the 10Å and 14Å components with a remarkable tendency of regular alternation. Intermixing of a small amount of expandable layer is indicated by slight deviations of 00l spacings from integral submultiples and by subtle changes of the basal reflections after ethylene glycol and glycerol treatments. Interpretation of these variations in spacing and line profile by visual inspection was attempted.

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The clay-mineral composition of the volcanic ash soil occurring in Cheju Island, Korea, has been studied by means of chemical analysis, X-ray diffraction, differential thermal analysis (DTA), thermogravimetry (TG) and electron micrography. The results obtained show that a considerable amount of allophane and appreciable amounts of gibbsite and quartz occur in clay fractions of the soil. Appreciable amounts of vermiculite, mica and kaolin minerals are also contained in clay fractions and these may exist mainly as a complicated mixedlayer mineral.

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The adsorption of humified clover extract by imogolite was studied to understand the clay-humus interaction in volcanic ash soils. The adsorption occurred apparently following a Langmuir type adsorption curve. Imogolite and allophane with the SiO₂/Al₂O₃ ratio less than 1.5 were both effective adsorbents for humified material and show preference for high-molecular-weight components. The adsorption from concentrated solutions (> 0.1 g of humified material per litre) was reversible to some extent, while the humified material adsorbed from dilute solutions was not readily displaced by repeated washing with water. The adsorption increased with the lowering of pH and was inhibited by addition of sodium citrate and oxalate, while no similar inhibitive action was noted for NaCl. An inhibition of proton uptake in the extent from 25 to 30 per cent due to clayhumus interaction was inferred from the buffer curves determined with an imogolite-humus complex and the respective components.
The result was interpreted in terms of simultaneous operation of two reactions; the first is the “ligand exchange” reaction in which the carboxyl groups of humus molecules penetrate the co-ordination shells of Al atoms on the clay surface, and the second is the surface-segment interaction between the humus molecules and the structure units of imogolite.

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The adsorption complexes which consist of imogolite and humified clover extract were characterized by x-ray analysis, measurement for adsorption of water vapor, infrared absorption spectroscopy and thermogravimetry. The x-ray and water retention data indicated that considerable portions of humified material in the complexes, particularly that adsorbed from dilute solutions, were accommodated between the structure units of imogolite, resulting in displacement of water from the surfaces of the clay and humus molecules. This indication was also supported from very remarkable reduction of adsorption by preheating of imogolites in which the pores between the structure units were collapsed. About 30 to 70 % of the adsorbed humified material was estimated to come into contact with 10 to 35 % of the imogolite surface. The difference infrared spectrum of the adsorbed humified material indicated removal of adsorbed water from the complex, but failed to show any sign of specific interactions between inorganic and organic functional groups. The complex formation resulted in changes on the DTG curve of the humified material similar to those observed for the Al-fulvic acid complex by Schnitzer et al.(1967).
From the foregoing observations (Part I and II), the adsorbed humified material was divided into two fractions accommodated and unaccommodated into the imogolite thread. Two different bonding mechanisms were assumed to operate in this accommodation reaction; the first is the co-ordination of the carboxyl groups of the humus molecules to the Al atoms on the surfaces of imogolite. The second is multiple surface-segment interactions primarily associated with hydrogen bonding and/or van der Waals forces. The difference in the energetics of interactions was interpreted in terms of different orientations of the humus molecules with respect to the thread axis of imogolite.

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The clay minerals in the Gichidos (sticky soils), polder soils and Gichidolike soils collected from seven localities on the Chikugo Plain were identified and studied.
1. The Gichidos are usually found in places with an altitude 3 to 5 m above sea level. They contain beidellite-nontronite as their main constituent, and illite, vermiculite and kaolin as accessary minerals.
2. The polder soils are derived from very recent marine sediments in the Ariake Bay. Their clay mineral composition is not much different from that of the Gichidos.
3. The Gichido-like soils from two localities contain halloysite as a major constituent. It appears forming a mixed-layer mineral with much smaller amount of montmorillonite in the Hainuzuka clay, while it appears nearly pure, spherical halloysite in the Kamenoko clay.
The differences observed in the morphology of the clay particles between the three groups of the soils are suggested to provide an account of subtle differences in their physical properties, particularly stickiness experienced in the field.

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