Infrared absorption spectra for 66 mechanical mixtures of quartz, orthoclase and oligoclase are obtained with an infrared spectrophotometer using KBr in the wavelength region from 11 to 25 microns. The intensities of absorption bands at 12.65 and 11.00 microns are compared for quartz and at 16.00 and 15.60 microns for orthoclase and oligoclase respectively. Calibration curves for the quartz content and for the orthoclase and oligoclase contents are shown. A technique is suggested for the semiquantitative determination of these minerals in acidic rocks.

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The effects of particle size on the absorption of X-rays reflected from a mixed powder are theoretically treated. Two factors, ‘extra absorption coefficient, ’ Δμ, and ‘self-absorption factor’, τ₁, are introduced, and a general formula for the intensity of reflected X-rays is derived. The present formula, though closely related with that by Brindley, takes into account some important aspects neglected by him.

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Ilmenite from East Ongul Island, Antarctica, is described. It was found in microcline pegmatite, is in single crystals up to 5cm in diameter, and is associated with small amounts of biotite and quartz. Its mineral composition determined by X-ray, chemical and magnetic methods is hematite, Fe₂O₃, 46mol%; ilmenite, l0Fe₂O₃•90TiFeO₃, 49mol%; magnetite, Fe₃O₄, 5mol%. The specific gravity is 4.976 at 17°C. The specimen is ferromagnetic and shows natural remanent magnetism. It shows exsolution inter-growth texture of ilmenite and hematite, and in the lamellae of each mineral are contained minute rod-like crystals of the other kind, regularly arranged in a certain crystallographic direction. The chemical compositions of both minerals do not vary with grain size. The exothermic reaction observed in the differential thermal analysis curve seems to be understood mainly as oxidation of ilmenite.

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The reaction sequences in the system, Na₂O-Al₂O₃-2SiO₂, have been investigated with various starting materials, and two different processes have been established. One is of the normal type, to low- or high-nepheline below 1250°C and to high carnegieite above 1250°C, and the other, to low-nepheline via high-carnegieite-like phase. In the latter sequence, variation of the temperatures of formation and transformation of the low-temperature phases is observed as due to the difference in the starting materials.
The difference in the reaction series is interpreted in terms of a structural inheritance of the product phase from the starting material.
The anion framework is almost maintained during the reaction, through which the diffusion and the rearrangement of cations take place to form a new phase. Based on this aspect, the reaction series, kaolinite→high-carnegieitelike phase→low-nepheline, is considered.

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