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Banalsite, a new barium-felspar from Wales

Published online by Cambridge University Press:  14 March 2018

W. Campbell Smith ,
F. A. Bannister  and
Max H. Hey
W. Campbell Smith
Affiliation:
Department of Mineralogy, British Museum
F. A. Bannister
Affiliation:
Department of Mineralogy, British Museum
Max H. Hey
Affiliation:
Department of Mineralogy, British Museum
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Extract

In 1941 the Home Ore Department of Iron and Steel Control, Ministry of Supply, took over the old Benallt manganese mine at Rhiw in the Lleyn Peninsula, Carnarvonshire. A new shaft was sunk and a new mine was developed among and mainly below the old workings. It was in one of the old workings of Benallt that Mr. (now Sir) Arthur Russell discovered in 1911 the well-crystallized specimens of celsian and paracelsian recently described by Dr. L. J. Spencer.

Dr. A. W. Groves of the Mineral Resources Department of the Imperial Institute and geologist to the Home Ore Department had had a sharp look-out kept for the reappearance of the barium-felspars in the new workings, and when thin bands of coarsely crystallized but compact, white ‘sparry’ minerals were found in one of the ore-bodies he sent specimens to the Department of Mineralogy of the British Museum for investigation.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 27 , Issue 186 , September 1944 , pp. 33 - 46
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1944

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References

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page 41 note 1 The value calculated from the measurements of β-α and γ-β given above is 71°. Direct measurement of the optic axial angle in methylene iodide gave 2Ho 116°; assuming β 1.79, this leads to 2V 69°.

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page 42 note 3 Ross and Kerr have remarked that a mineral reported as tephroite by A. F. Rogers in 1919 from San José, California, has characters similar to those of alleghanyite, and it is interesting to note that Rogers not only records polysynthetic twinning but adds ‘in some areas the twinning resembles an intergrowth of two minerals’. Ross and Kerr, loc. cit., p. 13.

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page 43 note 1 A. F. Rogers, loc. cit., p. 31.

page 43 note 2 In making these adjustments and in calculating the repeats from the results, an unknown though possibly small factor is the proportion of tephroite intergrown with the alleghanyite and inseparable from it, for this cannot be detected by the chemical analysis.

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