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On β-quartz twins from Some Cornish localities (With Plates VIII and IX.)

Published online by Cambridge University Press:  14 March 2018

Julien Drugman
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Extract

In their paper on 'The structure of α and β quartz', Sir William Bragg and R. E. Gibbs touch on the question of twinning of quartz, showing how X-ray determination of structure can help to explain the different types of twinning. They only mention, however, twinning with parallel axes and twinning on . It would be interesting to see this extended to the examination of all known laws of twinning of α-and β-quartz. There is, however, still much doubt about the laws of the twinning of quartz. Many varieties of twins have been described, but a number of these are much open to doubt, while some are decidedly nonexistent. G. Friedel has within recent years published valuable papers on the laws of twinning in general, and has made more special application of his theories to the laws of twinning of quartz. It would be interesting to see how far all cases of well-established quartz twins occurring ill nature confirm his results.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 21 , Issue 119 , December 1927 , pp. 366 - 382
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1927

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References

page 366 note 3 Bragg, W. H. and Gibbs, E. E., Proc. Roy. Soc. London, Ser. A, 1925, vol. 109, pp. 405-427 Google Scholar.

page 366 note 2 G. Friedel, Compte Rendu des Sociétés Savantes, 1920, pp. 92-120; Bull. Soc. Franç. Min., 1923, vol. 46, pp. 79-95; Leçons de Cristallographie, 1926, pp. 457-460.

page 367 note 1 Drugman, J., An example of porphyry-quartz, from the Esterel Mts., France, twinned on face (1012). Min. Mag., 1922, vol. 19, pp. 295-300 Google Scholar.

page 367 note 2 Previously called ‘R-twins’, but this is not a satisfactory designation for β-quartz, which is hexagonal and not trigonal.

page 369 note 1 Wedding, H.. Zeits. Deutsch. Geol. Gesell., 1861, vol. 13, p. 139 Google Scholar.

page 378 note 1 Paul, P. and Goldschmidt, V., Orthoklas-Heterozwilling. Zeits Kryst. Min., 1909, vol. 46, p. 471 Google Scholar.

page 378 note 2 Lacroix, A., Min. de France, 1896, vol. 2, p. 89 ; 1910, vol. 4, p. 815.Google Scholar

page 378 note 3 Fernández Navarro, L., Bol. R. Soc. Española Hist. Nat., 1919, vol. 19, p. 137 Google Scholar. [Min. Abstr., vol. 1, p. 13.]

page 379 note 1 J. Bindrich, Centralblatt Min., Abt. A, 1925, 203-210. [Min. Abstr., vol. 3, p. 378.]