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Pericline and acline-A twins in the acid plagioclases

Published online by Cambridge University Press:  14 March 2018

F. Coles Phillips
F. Coles Phillips*
Affiliation:
Corpus Christi College, Cambridge
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Extract

The orientation of the ‘rhombic section’, the composition-plane of the pericline twin, in the plagioclase felspars as an index of the chemical composition of the felspar waJ first utilized by G. yore Rath, who measured the gngle a on the face (010) between the trace of the composition-plane and the edge [010,001]. Duparc and Reinhard, in their comprehensive work on the determination of the plagioclases, quote two series of values for this angle, one due to Wiilfmg and the other to Becke. They comment on the discordance between the two series, most marked at the acid end, and add that they did not then possess suitable material for critical determinations on their own account. Wülfing's values are given in the form of a curve based on data assembled by Schmidt, and those of Becke were first given in a paper on the felspars in crystalline schists.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 22 , Issue 128 , March 1930 , pp. 225 - 230
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1930

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References

page 225 note 1 Duparc, L. and Reinhard, M., Mém. Soc. Phys. Hist. Nat. Genève, 1924, vol. 40, p. 26.Google Scholar [Min. Abstr., vol. 3, p. 34.]

page 225 note 2 E. A. Wülfing, Sitzungsber. Heidelberg. Akad. Wiss., Math.-naturw. Kl., 1915, Abt. A, Abh. 13. [Min. Abstr., vol. 1, p. 390.]

page 225 note 3 Schmidt, E., Chemic der Erde, 1915, vol. 1, pp. 351–406 Google Scholar; Inaug.-Diss. Heidelberg, 1916. [Min. Abstr., vol. 1, p. 390.]

page 225 note 4 F. Becke, Denkschr. Akad. Wiss, Wien, Math. naturw. Kl., 1913, vol. 75, p. 105.

page 225 note 5 M. Schuster, Min. Petr. Mitt. (Tschermak), 1880, vol. 3, p. 24.

page 226 note 1 See, for example, W. J. Lewis, Crystallography. Cambridge, 1899, p. 550.

page 226 note 2 Barth, T., Zeits. Krist., 1928, vol. 68, pp. 616–618.Google Scholar [Min. Abstr., vol. 4, p. 37.]

page 226 note 3 Gysin, M., Schweiz. Min. Petr. Mitt., 1925, vol. 5, pp. 128–146.Google Scholar [Min. Abstr., vol. 3, p. 520.]

page 227 note 1 See also R. Sabot, Compt. Rend. Soe. Phys. Hist. Nat. Genève, 1918, vol. 35, pp. 72-76. [Min. Abstr., vol. 3, p. 515.]

page 228 note 1 Berek, M., Mikroskopische Mineralbestimmung mit Hilfe der Universal-drehtischmethoden. Berlin, 1924, p. 82.Google Scholar [Min. Abstr., vol. 2, p. 365.]

page 228 note 2 L. Desbuissons, La Vallee de Binn (Valais.). Lausanne, 1909, pp. 177-178. Hintze, C., Handbuch Min., 1905, vol. 2, p. 1460.Google Scholar

page 228 note 3 For the nomenclature of poles of twin-planes and twin-axes, see W. Campbell Smith, Min. Mag., 1928, vol. 21, p. 544.

page 228 note 4 L. Duparc and M. Reinhard, loc. cit., p. 116.

page 229 note 1 H. Rosenbusch, Mikrosk. Physiogr. der petr. wicht. Min., 1927, vol. 1, pt. 2, p. 747, footnote 2.