Abstract
LONDON
Mineralogical Society, November 9 (Anniversary meeting). P. L. DBA VERT: Shower of meteoric stones in the neighbourhood of the village of Kuznet-zova, West Siberia, on May 26, 1932. Between 5 and 6 p.m. in a cloudless sky, ten detonations were heard, and one stone of 2 kgm. was seen to fall, making a small oblique hole and then rebounding. Eight stones with a total weight of 23 kgm. (the largest 16 kgm.) were collected. Two of them, found 300 metres apart, can be fitted together on their flat crusted surfaces. The stone is a greyish-white friable chondrite with inclusions of troilite and grains of nickel-iron. The troilite was thought by the peasants to be gold, which led to the destruction of some of the material. P. A. CLAYTON and L. J. SPENCER: Silica-glass from the Libyan Desert. Clear, greenish-yellow silica-glass has been found in considerable amount as wind-worn masses up to 10 Ib. in weight over an area of 80 km. X 25 km. at about 500 km. southwest of Cairo near the border of Italian Cyrenaica. It is found lying on the surface of the Nubian Sandstone in the ‘street's between the north-south sand-dune ridges. Analysis by M. H. Hey shows SiO2 97-58 per cent with small amounts of aluminium, titanium, iron, calcium, sodium and a faint trace of nickel. Specific gravity 2 -206, refractive index 1 -4624 (sodium light), hardness 6. Some pieces are cloudy, due to presence of minute (0-1 mm.) bubbles. Effective gem-stones have been cut from the material. It shows certain relations to tektites and also to the silica-glass from meteoric craters, but no craters have been recognised at the locality. L. J. SPENCER: Fictitious occurrences of iron silicide (ferrosilicon). Bright, steel-grey nodules of iron silicide (FeSi), very resistant to acids (except hydrofluoric acid) and to weathering, are sometimes present in the calcium carbide residues from acetylene lamps. This waste material has been found at times in strange situations, and has on two occasions been described as a new mineral. It has also been thought to be meteoric. Occurrences in the gold dredgings in British Guiana and in the diamond fields of South Africa are readily explained by the use there of acetylene flares. ARTHUR RUSSELL: (1) Occurrence of wulfenite at Brandy Gill, Carrock Fell, Cumberland; and of leadhillite at Drumruck mine, Gatehouse of Fleet, Kirkcudbrightshire. Wulfenite occurs here in small (1-5 mm.) honey yellow platy to scale-like crystals, often nearly circular in outline. Thirteen specimens were collected from an old trial level dump. Leadhillite, a single specimen showing six-sided tabular crystals up to 5 mm. in diameter, was collected during the working of the Drumruck mine in 1917. (2) Occurrence of harmotome at several new localities in the British Isles. The occurrence of harmotome at the following mines is described: Snailbeach mine, Minsterley, Shropshire; Cwm Orog mine, Llangynog, Montgomeryshire; Settlingstones mine and Stonycroft mine, Fourstones, Northumberland; Whitespots mine, Newtonards, Co. Down, and Foxrock mine, Glendasany Co. Wicklow. C. E. TILLEY and A. R. ALDERMAN: Progressive metasomatism in the flint nodules of the Scawt Hill contact zone. The flint nodules of the Chalk of the Scawt Hill contact zone provide striking examples of progressive metasomatism. Various stages-of which analyses are given -from an original nodule composed wholly of quartz to an assemblage built up essentially of wollastonite, melilite and alkali-pyroxene can be traced. In the successive stages of replacement the characteristic shape and form of the nodules is preserved. The assemblages thus provide a particularly convincing illustration of a replacement process unaccompanied by volume change. The nature and source of the replacing solutions is discussed. F. COLES PHILLIPS: (1) Some relationships between the reflectivities of sulphide ore-minerals. A review of the reflectivity data now available for a large number of opaque minerals has shown that the relative reflectivity of simple sulphides, selenides and tellurides increases with atomic number. ‘Molecular refractivitie's of more than forty complex sulphides calculated from the measured reflectivities agree well with values computed from the ‘molecular refractivitie's of the constituent simple sulphides, assuming additivity. This relation indicates a method of calculating the reflectivity of an ore-mineral and also affords a useful check on the specific gravity quoted in the literature. The ‘molecular refractivitie's of sulphur, selenium and tellurium calculated from reflectivities also agree with values derived from a study of transparent ionic compounds. (2) A critical list of the specific gravities of the sulphides and allied ore-minerals. Variations in the values of the specific gravities of ore-minerals quoted in the literature are due to misprints, determinations on impure material or mixtures, and actual variation in composition of specimens owing to solid solution. The probable correctness of a specific gravity determination can be checked by comparison of calculated and computed ‘molecular refractivities', by direct specific gravity determination of the synthetic mineral, and by the X-ray method. These criteria govern the author's choice of critical values, when correllated physical and chemical data on the same specimen are lacking. They are tabulated together with the maximum range of variation recorded in the literature.
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Societies and Academies. Nature 132, 978–980 (1933). https://doi.org/10.1038/132978a0
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DOI: https://doi.org/10.1038/132978a0