It is often the case with the structure of a complex sulfide that a pseudo-cell is revealed, due to a nearly regular arrangement of either metal or sulfur or both on sublattice nodes. The Fourier tranform of such a struc-ture was studied and the conclusion was deduced that a repetition of intensity distribution, with a period reciprocal to the pseudo-cell, will be observed in its X-ray diffraction pattern.
Conversely, if we observe a repetition in intensity distribution of an X-ray diffraction pattern, we can not only conclude that the structure comprises a preudo-subcell, but also arrive at the derivation of the structure by assigning appropriate phases only to those reflections that are found within an asymmetric unit of the repetition.
This principle has been successfully applied to the determination of the structure of zinkenite, PbS.Sb₂S₃.

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Abnormal interference colour produced by crystals with birefringence dispersion was discussed from the colorimetric point of view. The tristimulus values of the colour were calculated on the basis of the previous data on apophyllite which has various types of birefringence dispersion. From the view point of chromaticity, abnormal interference colour was classified into three types: chromo-cyclic, centro-cyclic and non-cyclic types.
In chromo-cyclic colour, the figure of the chromatic locus depends much upon the curvature of the birefringence dispersion curve.
Variation of luminance factor with thickness is also discussed.
A chromaticity diagram for the maximum purity in the chromo-cyclic colour is presented.

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The surface structures of {110} and {211} faces of yttrium-iron garnet (YIG) and {0001} and {10^-11} faces of magnetoplumbite, both synthesized by by the flux method, were studied in detail, using a phase contrast and an interferometric microscope. Growth spirals were widely observed on both crystals, from which it was concluded that the mechanism of crystal growth in the system of flux synthesis is fundamentally similar to that in the crystallization from vapour or solution. The morphology of interlaced spirals observed on the {0001} faces of magnetoplumbite was fully accounted for from the geometry of its crystal structure.

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Pyrite crystals were examined with the aid of a phase-contrast microscope. Dark lines and small spots, both corresponding to depressions less than 20Å in depth, were observed along edges of growth layers on the surfaces, and these are considered to have been formed by preferential etching, respectively along the steps of growth layers and at such imperfections as vacancies or impurity sites. These etch features have close similarity with those reported by the Sunagawa on hematite, and are considered to be two-dimensional ones characteristic of the earliest stage of weak etching.

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Four phases named S1, S2, S3 and S4 in tridymite of type S were confirmed on the close examination of the change of X-ray powder reflections with increasing temperatures.
Unit cell dimensions are:
S1; monoclinic, a=10.04Å, b=17.28Å, c=8.20Å, β=91.50°,
S2; orthorhombic, a=10.04Å, b=17.28Å, c=8.20Å,
S3; domain structure,
and S4; hexagonal, a=5.046-5.06Å, c=8.236-8.30Å.
Their relations are as follows,
S1 → 60-75°C S2 → 115° S3 → 250°C S4.
Though the change of the patterns with decreasing temperatures is not thoroughly investigated, the transition is reversible.

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