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Twin-planes and cross-planes
Published online by Cambridge University Press: 14 March 2018
Extract
In a single homogeneous crystal the physical character of parallel lines are everywhere the same, and it may be justifiably assumed that the orientation of the crystal-structure is constant throughout. Compound crystals, however, occur in which the orientation of the crystal-structure is different in different parts although they consist of the same substance.
This difference of orientation may either be original or result from the action of mechanical forces on the crystal-structure. I shall in the first place assume that the former is the case.
- Type
- Research Article
- Information
- Mineralogical magazine and journal of the Mineralogical Society , Volume 15 , Issue 72 , September 1910 , pp. 390 - 397
- Copyright
- Copyright © The Mineralogical Society of Great Britain and Ireland 1910
References
Page 390 note 1 Enantiomorphic substances are considered to be the same for the purpose of this communication.
Page 390 note 2 Barker, T. V., Mineralogical Magazine, 1907, vol. xiv, pp. 235–257 CrossRefGoogle Scholar.
Page 390 note 3 The word ‘line’ is here used in a general sense including all parallel lines, viz. as possessing orientation but not position.
Page 391 note 1 Cf. Schuster, Max, Zeits. Kryst. Min., 1886, vol. xii, p. 141 Google Scholar.
Page 391 note 2 Cf. Max Schuster, loc. cit.
Page 392 note 1 See note, ante, p. 390. The use of the term ‘common edge’ or ‘common face’ in the case of parallel equivalent edges or faces in two structures is already recognized ; see, for instance, Max Schuster, loc. cit.
Page 393 note 1 Point-twinning is referred to by G. Linck (‘Grundriss der Krystallographic,’ 1896, p. 24) and H. A. Miers (‘Mineralogy,’ 1902, pp. 91 and 371), who term it alternating twinning. Curiously enough, the former states that no example is known. As a matter of fact, it is found in quartz, pyrargyrite, nephcline, hemimorphite, sodium chlorate, chalcopyrite, and other crystals belonging to the same classes.
Page 394 note 1 If complete self-coincidence can be obtained by a reversal relatively to a line or rotation through a half circle round it, the line may be termed a line of symmetry.
Page 394 note 2 As for instance in the a laevodextrogyral or ‘Brazilian’ twins of quartz.
Page 394 note 3 Goldschmidt, V., Zeits. Kryst. Min., 1898, vol. xxx, p. 254 Google Scholar.
Page 394 note 4 Such twins are also explained by a symmetry about a plane by Schuster, Max, Zeits. Kryst. Min., 1886, vol. xii, pp. 139 Google Scholar and 147, and by Miers, H. A., ‘Mineralogy,’ 1902, p. 87 Google Scholar.
Page 395 note 1 Goldschmidt, V., Zeits. Kryst. Min., 1907, vol. xliii, p. 585 Google Scholar.
Page 395 note 2 V. Goldschmidt, loc. cit.
Page 395 note 3 Miers, H. A., Mineralogical Magazine, 1884, vol. vi, p. 77 Google Scholar; 1888, vol. viii, p. 75.
Page 396 note 1 V. Goldschmidt, loc. cit.
Page 396 note 2 Schuster, Max, Zeits. Kryst. Min., 1886, vol. xii, p. 149 Google Scholar.
Page 396 note 3 H. Baumhauer, ibid., 1899, vol. xxxi, pp. 252-275.