Occurrence of mesolites and scolecite was confirmed in veinlets or amygdales in andesitic or basaltic rocks in Japan. The results of chemical, physical and X-ray studies of these minerals are described, with their mineral associations and modes of occurrences.

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The thermal transition of leucite was studied. The specimens were from Nyiragongo, the Congo and from Vesuvius, Italy, and X-ray powder and single crystal diffraction experiments were carried out from room temperature up to 800°C. At room temperature, the crystal, single and cubic in appearance, is composed of six sheet-like domains, each parallel to one of {101} of the outward cubic morphology and consisting of a polysynthetic twin of the low-temperature tetragonal form. The twin operation is a two-fold rotation about ?? 101 ?? of the tetragonal individual, whose direction is almost parallel to one of >101< of the cubic form. From the results of observations of the powder patterns and precession diagrams at elevated temperatures, it was concluded that the crystal originally grown cubic at a high temperature has been transformed between 660°C and 665°C into such a domain structure as mentioned above, each domain being a polysynthetic twin of a tetragonal form with both axes equal in length to that of the high-temperature cubic form. As the fall of temperature, the low form begins revealing its tetragonality, and the defference between the a- and c-lengths gradually and continuously increases. The texture of the mineral observed at room temperature is attained in this way. Since no evidence has been obtained of an abrupt change at its transition temperature, the transition is believed to be classified as essentially of the second order type.

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A phenomenon analogous to X-ray diffraction and described as infrared diffraction has been obtained by mathematical analysis, between the absorption bands of the SO₄ molecule in solution, and those of crystals of anglesite, barite, celestite, and anhydrite. The absorption bands of the fundamental vibrational mode are discussed for each mineral. From the results, it has been concluded that relationships showing wave motions exist between the bands of the spectrum. Infrared spectra are calculated by using the damped equation in the wave number region from 2000 to 100cm^-1. The features of the calculated spectra are similar to those of the spectrum obtained by using infrared spectrophotometers.

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The main end-members of the schorl type in the tourmaline group: dravite, schorl, tsilaisite and elbaite, were synthesized under hydrothermal conditions, and the cell dimensions, cell volumes and densities of these synthetic minerals were determined.

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Three kinds of elongated crystals of weathered biotite were found in a terrace deposit at Matsusaka, Mie Prefecture. They are mainly composed of Al-vermiculite, kaolinite, and gibbsite. The texture and orientational relationship of these alteration products were studied with conclusions that much material, especially Al₂O₃, should have been supplied from the environment, and that the degree of preferred orientation of each alteration mineral with respect to the original biotite depends on the amounts of materials introduced to it.

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