Societies and Academies

    Abstract

    LONDON. Mineralogical Society, Jan. 13.—F. C. Phillips: On a soda-margarite from the Postmasburg district, South Africa. A fuller description is given of material first described by A. L. Hall. The mineral occurs in mica-like crystals associated with the Postmasburg manganese ores. The physical properties described resemble in general those of a mica, but analyses show 50 per cent of alumina and 10 per cent of alkalis, with little lime. It is best described as soda-margarite; in composition it resembles the ‘ephesite’ of J. L. Smith.—F. A. Bannister: On the distinction of anal-cime from leucite in rocks by X-ray methods. Powder-photographs of phenocrysts in blairmorite from the Lupata Gorge, Zambezi River, Portuguese East Africa, are identical with those for analcime and not for leucite. The icositetrahedral outlines of the analcime phenocrysts found in the rock strongly suggest their primary origin. The X-ray photographs indicate that the phenocrysts are not single crystals, but consist of aggregates of particles in sub-parallel position.—F. A. Bannister: On a chemical, optical, and X-ray study of nepheline and kaliophilite (with chemical analyses by M. H. Hey): correlated data have enabled the author to prove the approximate constancy of the number of oxygen atoms in the unit cells of several nepheline and elaeolite specimens. Thence the numbers of atoms of each kind per unit cell have been counted. The cell volumes and optical properties have also been related to the chemical composition. An approximate structure is suggested which, together with the chemical work, explains the variable composition of nepheline. Kaliophilite is shown to possess a much larger cell than that of nepheline, and its Lauegram exhibits higher symmetry. ‘Pseudonepheline’ (rich in potassium) has a slightly greater cell volume than normal nepheline, but its Lauegram is almost identical and its axial ratio the same.—H. V. Warren: On an occurrence of grunerite at Pierrefitte, Hautes-Pyrenees, France. A grunerite-schist, consisting almost entirely of fibrous grunerite, occurs at the Pierrefitte mine, where needles of the same mineral also occur in the galena and blende of the ore-bodies. The grunerite is associated with a carbonaceous schist and with magnetite, and encloses specks of carbon. Analyses of grunerite from schist and ore by E. Gr. Radley are given.

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    Societies and Academies. Nature 127, 221–223 (1931). https://doi.org/10.1038/127221b0

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