X-ray powder studies on about fifty specimens of rather highly crystalline chlorites from japan revealed the exsistence of two type of elementary cells, one with a 14Å-monoclinic and the other with a 14Å-ortho-hexagonal symmetry, and that the patterns of the former type are closely similar to one another, but those of the latter type vary from one another in detail. The monoclinic type ranges from Mg-rich chlorite to Fe-chlorite while the the ortho-hexagonal type appears to be limited to Fe-rich members, but a Mg-rich specimen seems to have the latter type cell. The interference colors of the monoclinic types are frequently abnormal (usually for Fe-chlorite), the ortho-hexagonal types, however, usually show normal interference color, so that these two types are generally distinguishable under the microscope.
The results of chemical analyses and cell dimension determinations for the selected eleven chlorite specimens show that, as previously known, the basal spacing depends on the number of tetrahedral Al ions, and the b dimension on Fe atoms in the structure; these relations are not only more definitely established than in previous data but also suggest that both the basal spacings and the tetrahedral Al⁺³ ions of chlorite and/or serpentine can be dealt with in the same manner.
The estimation of the chemical composition of chlorites by X-ray method is also presented.

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Monazite from the Ebisu mine, Gifu Prefecture has been studied. The monazite from Ebisu is of yellowish or dark brown colour, with sp. gr.: 5, 20. The result of chemical analysis of the sample is as follows: P₂O₅ 26.81, SiO₂ 2.24, Al₂O₃ 0.36, ThO₂ 4.51, U₃O₈ 0.21, Ce₂O₃ 24.58, La₂•O₃ etc, 38.51, Fe₂O₃ 0.48, CaO 0.86, PbO 0.02₆, ig. loss 0.91, total 99.49% Monazites from Ratnapura, Ceylon and Minas Geraias, Brazil are also analysed for comparison. The relationships between the cell dimensions, the relative abundances of rare earths and the ThO₂ content are discussed. The chemical age of the Ebisu monazite is 108 m. y., while its thorium lead age on the basis of mass-spectrometric data is fifty million years, in accordance with the geological evidence.

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X-ray and chemical data of some specimens of pyrophyllite from Japan were discussed. The k=3n reflections are predominant; this fact suggests that layers randomly displaced by multiples of 1/3b₀ are dominant.
X-ray studies on ignited specimens have made clear a thermal transformation at 700°C, which agrees with the concept proposed by Bradley and Grim.
X-ray, thermal and chemical data on the 25Å-clay mineral found in association with a certain specimen of pyrophyllite were discussed. The clay mineral agrees with a regularly interstratified pyrophyllite-montmorillonite.

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The infrared absorption spectra of selected borate minerals have been observed with crystalline powders in the wavelength range from 2 to 16 microns. The spectra characteristic to borate polyatomic ions appear within the range from 7 to 16 microns and are presented in Figs. 1-6. These characteristic absorption bands are shown to be useful in the qualitative analysis of borate polyatomic ions.
In connection with this investigation, a discussion on the structures of borate polyatomic ions is also given.

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Observations were made of the elliptic vibraticn of light in some alkali amphiboles which are anomalous in extinction, and the ellipticity of vibration in arfvedsonite and riebeckite were determined. The results here obtained are similar to those previously obtained for heikolite.

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