Mass transfer during the alteration of phlogopite in Ca-bearing acid aqueous solution was studied in laboratory. The experiment was undertaken in two systems; one is a batch system regarded as a closed system and the other is a batch-flow system corresponding to a quasi-open system. The dissolution of phlogopite occurs incongruently and the priority in dissolution is in turn ; K≥Al≥Si≥Mg>Fe in the batch system. On the basis of kinetic examination, it is inferred that the dissolution of K and Mg is controlled by a diffusion process. The activation energy of their dissolution is evaluated to be 9.4 kcal/mol·deg in the batch system and the corresponding estimate in the batch-flow system is nearly the same in the magnitude. Phlogopite alters to vermiculite and/or phlogopite /vermiculite interstratified phase with the progress of alteration. In response to the alteration of phlogopite, the change of its chemical composition, especially the content of the interlayer K⁺, shows a difference particular to each system. The interlayer K⁺ decreases continuously in the process of alteration in the batch-flow system and as a result phlogopite alters into vermiculite. On the other hand, in the batch system the vermiculite formed earlier regains K+ from the ambient solution. This results in the formation of interstratified phlogopite/vermiculite from vermiculite.

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Trioctahedral illites were found from two talc mines, Zeniya and Yugan, in southwestern Hokkaido. They were examined by optical methods, X-ray diffraction and DTA. The stuctural formula of the Yugan illite derived from chemical analysis was (K_0.51Na_0.05)(Mg_1.87Fe_0.37Al_0.63)(Si_3.05 Al_0.95) O₁₀ (OH) ₂. These analyses were also carried out for the chlorite associated with the Yugan illite. The illites were considered to have formed in the early Cretaceous period on the basis of K-Ar age.

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It is now generally accepted that species names can be given to regularly interstratified clay minerals, in accordance with the recommendation of the AIPEA Nomenclature Committee (Brindley and Pedro, 1970). In Part A of this report we suggest (1) criteria for defining the degree of regularity of alternation of different layer types that should be required to merit a name, (2) data that should be provided for documentation of a regular interstratification, and (3) some examples of interstratifications that do not merit names. In Part B of the report we apply the suggested criteria to the analysis of regular interstratifications previously reported in the literature, and make recommendations regarding the usage of existing names.

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The Robinson equation was modified and applied to the viscosity data of clay suspensions to which the Einstein equation was not applicable. The modified Robinson equation is:
η_rel-1=k'S'V/(1-S'V) where η_rel is the relative viscosity, V the volume concentration of clay particles (cm³/cm³), S' a parameter for the ratio of the effective volume of clay particles to their actual volume and k' another parameter related to particle-particle interaction. The S' value increased from about 10 for spherical halloysite suspensions to allophane, kaolinite, montmorillonite and up to 1900 for fibrous imogolite suspensions. The k' value increased from about 1 for deflocculated suspensions to 20 for flocculated suspensions.

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The viscosity of Na-saturated montmorillonite, kaolinite, halloysite, allophane and imogolite in 10-4 to 10-2M NaCl was measured using a rotational viscosimeter. The measured viscosity-clay particle concentration relationships were deviated from that stated in the Einstein equation. They were interpreted using a modified Robinson equation (Part I), and the effects of particle shape and particle-water and particle-particle interactions on the viscosity were evaluated for each mineral at different NaCl concentrations. The effect of particle shape varied with the clay mineral species in a way which was predictable on the assumption that clay particles can be approximated by rigid ellipsoids or spheres. In addition to the particle shape, the particle-water interaction, which is probably related to the development of the electrical double layer, had an important effect in the suspensions of montmorillonite and allophane at 10-3 to 10-4M NaCl, whereas the particle-particle interaction predominated in the suspensions of montmorillonite, halloysite and allophane at higher NaCl concentrations and in those of kaolinite and imogolite irrespective of the concentration of NaCl.

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