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The dispersion phenomena of some monoclinic Felspars
Published online by Cambridge University Press: 14 March 2018
Extract
In the present paper the dispersion of the refractive indices of monoelinie felspars from four different localities is given, likewise that of the optic axial angle and of the optic axes in some of them.
The method of investigation and instruments for these studies have been already mentioned in my previous paper. As the refractive indices and dispersion of the glass hemisphere of the total-reflectometer have not so far been given, I shall in the first place state the way in which they have been determined and their values and the degree of accuracy attainable, for the dispersion of the glass hemisphere differs to au appreciable degree from that of other instruments of the same kind.
- Type
- Research Article
- Information
- Mineralogical magazine and journal of the Mineralogical Society , Volume 17 , Issue 82 , April 1916 , pp. 253 - 273
- Copyright
- Copyright © The Mineralogical Society of Great Britain and Ireland 1916
References
page 253 note 1 Kôzu, S., 'The dispersion phenomena of albite from Alp Rischuna, Switzerland.' Mineralogical Magazine, 1915, vol. xvii, pp. 189–192 CrossRefGoogle Scholar.
page 255 note 1 Viola, C., Zeits. Kryst. Min., 1900, vol. xxxii, pp. 811–314 Google Scholar.
page 256 note 1 Gifford, J.W., Proc. Roy. Soc., London, 1902, vol. lxx, p. 329 CrossRefGoogle Scholar ; 1910, ser. A, vol. lxxxiv, p. 193.
page 256 note 2 The refractive indices of quartz for different wave-lengths, determined by Miilheims and Viola by the method of total reflection, are given in Zeits. Kryst. Min., 1888, eel. xiv, p. 224, and 1900, vol. xxxii, p. 314, respectively. For comparison, the indices determined by them for three wave-lengths employed by me are cited below :-
page 257 note 1 It is clear that the plate need not be perpendicular to tim acute bisectrix, as long as it is at right angles to the plane of symmetry of the crystal. When the plane of observation is perpendicular to that of symmetry, two principal indices for each 𝝀 are determined with accuracy ; and when the two planes coinclde, the third index is accurate, but not necessarily the other.
page 261 note 1 A chemical analysis of the Ceylon moonstone, recently made by E. H. Kraus (Zeits. Kryst. Min., 1901, vol. xxxiv, p. 175), is as follows :-
From this analysis, the molecular formula computed by me is given as
page 264 note 1 Lacroix, A., Compt. Rend. Acad. Sci. Paris, 1912, vol. clv, p. 672 Google Scholar ; Minéralogie de la France, 1913, vol. v, pp. 28-29.
page 265 note 1 The indices given by Lacroix are α= 1·5197, β= 1·5248, and γ= 1·5253 ; the specimen having the density 2·565.
page 268 note 1 Offret, A., Bull. Soc. franc. Min., 1890, vol. xiii, p. 645 Google Scholar.
page 273 note 1 See Wright, F. E., ‘Graphical methods in microscopical petrography.’ Amer. Journ. Sci., 1918, vol. xxxvi, p. 509 Google Scholar.