Hostname: page-component-586b7cd67f-dlnhk Total loading time: 0 Render date: 2024-11-25T09:19:39.922Z Has data issue: false hasContentIssue false
  • English
  • Français

An X-ray study of the crystal-structure of antigorite (With Plate V)

Published online by Cambridge University Press:  14 March 2018

Endel Aruja
Endel Aruja*
Affiliation:
King's College, Newcastle upon TyneUniversity of Durham). (Now at Adam Hilger Ltd., LondonN.W.1.)
Get access Rights & Permissions [Opens in a new window]

Extract

Antigorite is a lamellar variety of serpentine, and is supposed to be a dimorphous form of chrysotile, which is finely fibrous. Its chemical composition is approximately H4Mg3Si2O9, which is taken as the basis of calculations here.

This study was undertaken primarily because it was hoped that knowledge of the structure of antigorite would throw some light on that of chrysotile. Certain similarities between the two structures have been established, namely in the c(7·3kX or 14·6kX), and b(9·2kX) directions. There are two main differences, however. Firstly, imperfections which cause line broadening in the X-ray pattern of chrysotile, are absent in antigorite (apart from certain ‘streaks’). Secondly, the a(43·4kX) axis of antigorite is approximately eight times longer than the corresponding axis in chrysotile. A complete determination of the structure has not been achieved, but the X-ray pattern has been described, and some suggestions made as to the explanation of the peculiarities observed. A further study of the outstanding questions is in progress.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 27 , Issue 188 , March 1945 , pp. 65 - 74
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1945

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

page 65 note 1 lkX = 1000 X-units, as defined by Siegbahn. IkX = 1·00203x10−8 cm., according to the up-to-date value of Avogadro's number, 6·0228x10−23 per mole. Cf. H. Lipson and D. P. Riley, Nature, 1943, vol. 151, p. 250, and A. J. C. Wilson, ibid., p. 562. [M.A. 9–39.]

page 65 note 2 Dana, , Descriptive mineralogy, 6th edition, New York, 1892.Google Scholar

page 65 note 3 Selfridge, G. C., Amer. Min., 1936, vol. 21, pp. 463–503. [M.A. 6–476.]Google Scholar

page 65 note 4 Caillère, S., Bull. Soc. Franç. Min., 1936, vol. 59, pp. 163–326. [M.A. 6–475.]Google Scholar

page 65 note 5 For a description and occurrence see Bonney, T. G., Quart. Journ. Geol. Soc. London, 1908, vol. 64, pp. 152–170.CrossRefGoogle Scholar

page 65 note 6 The specimen numbers given are those of the Department of Mineralogy and Petrology, Cambridge University.

page 65 note 7 Winchell, A. N., Amer. Min., 1928, vol. 13, pp. 161–170. [M.A. 4–206.]Google Scholar

page 65 note 8 Gruner, J. W., Amer. Min., 1937, vol, 22, pp. 97–103. [M.A. 7–93.]Google Scholar

page 66 note 1 V. N. Lodochnikov, Serpentine and serpentinite … Trans. Centr. Geol. Prosp. Inst. Leningrad, 1936, no. 38. (Russian, with German summary.) [M.A. 7–3.] Also Simpson, E. S., Journ. Roy. Soc. W. Australia, 1938, vol. 24, pp. 107–122. [M.A. 7–340.]Google Scholar Du Rietz, T., Geol. För. Förh. Stockholm, 1935, vol. 57, pp. 133–260. [M.A. 6–216.]CrossRefGoogle Scholar Krotov, B. P., Mem. Soc. Naturalists Imp. Kazan Univ., 1915, vol. 47, no. 1. [M.A. 2–170.]Google Scholar

page 68 note 1 Cf. Bragg, W. L., Nature, 1929, vol. 124, p. 125.CrossRefGoogle Scholar

page 69 note 1 Unpublished world, but an abstract, together with a photograph of the X-ray pattern of chrysotile, has appeared in an article entitled ‘Summarized proceedings of conference on X-ray analysis, Oxford, 1944’, in Journ. Sci. Instr., 1944, vol. 21, p. 15. [M.A. 9–39.] Chrysotile from Thetford, Quebec, is monoclinic, with a 5·32, b 9·2, c 14·62kX, β 93·2° The notation of the a and c axes has been interchanged, as compared with earlier publications, to bring the proposed structure into conformity with other sheet structures of silicates. Cf. also Warren, B. E., Amer. Min., 1942, vol. 27, p. 235 (abstract).Google Scholar

page 70 note 1 Cf. Ewald, P. P., Proc. Physical Soc., 1940, vol. 52, pp. 167–174. [M.A. 8–133.]CrossRefGoogle Scholar

page 71 note 1 Wilson, A. J. C., Proc. Roy. Soc., Ser. A, 1942, vol. 180, pp. 277–285. [M.A. 8–362.]CrossRefGoogle Scholar

page 71 note 2 Hendricks, S. B., Amer. Min., 1939, vol. 24, pp. 729–771. [M.A. 7–196.]Google Scholar

page 71 note 3 Pauling, L., Proc. Nat. Acad. Sci., 1930, vol. 16, pp. 578–582. [M.A, 4–465.]CrossRefGoogle Scholar

page 71 note 4 The corresponding identity periods in the sheets of Si2O5 and Mg(OH)2 are in the ratio of 16 to 17, a fact which seems to be of some importance in view of the observed distances between the centres of gravity of the clusters, and between the strongest spots in certain a* row-lines, which were also 16 and 17 units in the index h respectively (cf. section 2 (ii)).

page 72 note 1 Warren, B. E. and Bragg, W. L., Zeits. Krist., 1930, vol. 76, pp. 201–210. [M.A. 4–466.]Google Scholar

page 72 note 2 Gruner, J. W., Amer. Min., 1939, vol. 24, p. 186.Google Scholar