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An example of porphyry-quartz, from the Esterel Mtns., France, twinned on face (1012)

Published online by Cambridge University Press:  14 March 2018

Julien Drugman
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Extract

It is now well recognized that quartz undergoes a sudden change near 575° C., and Wright and Larsen (1) have shown that the characteristics of quartz formed above or below this point are so marked that they can be utilized to determine the temperature of formation of rocks containing quartz. Quartz formed above 575° so-called β-quartz, is of distinctly hexagonal development, and occurs generally as regular hexagonal bipyramids with or without a subordinate prism-face. These external characteristics are of course preserved on cooling, and the bipyramids are converted into apseudomorphous aggregate of α-quartz.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 19 , Issue 96 , March 1922 , pp. 295 - 300
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1922

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References

References to the Literature

(1) Wright, F. E. and Larsen, E. S., Amer. Journ. Sci., 1909, vol. 27, pp. 162, 421-447.Google Scholar
(2) Drugman, J., An example of quartz twinned on the primary rhombvhedron. Min. Mag., 1911, vol. 16, pp. 112-117; also Zeits. Kryst. Min., 1912, vol. 50, pp. 598-599.Google Scholar
(3) Drugman, J., Zeits. Kryst. Min., 1918, vol. 53, pp. 271-272.Google Scholar
(4) Balogh, E., Muzeumi Fuzetek, Kolozsvar, 1913, vol. 2, no. 3.Google Scholar
(5) Sella, Q., Studii sulla mineralogia Sarda. Mem. R. Accad. Sci. Torino, 1858, set. 2, vol. 17, pp. 321–832, pl. V, figs. 48-50. (Separate copies, dated 1856, pp. 35-36) ; reprinted in Atti R. Accad. Lincei, Mem. Classe Sci. Fis. Mat. Nat., Roma, 1885, ser. 4, vol. 2, pp. 76-77, pl. V, figs. 48-50. A mistake was made by the present author in his first paper (2) with reference to Sella's descriptions. He was misled by the close similarity of Sella's drawings of the Sardinian-law and by Sella's designation 'twin on edge [1011]', so that he quoted it as twinning' on (1011)'. The first mention of r-twimfing is, then, Rose's and not Sella's.Google Scholar
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