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New crystal-forms on Pyrites, Calcite, and Epidote1

Published online by Cambridge University Press:  14 March 2018

L. J. Spencer
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Extract

The dyakis-dodecahedron (641) was observed on certain of the Museum specimens by Mr. Richard Elliot Steel in 1879 and again by myself in 1894; and although several memoirs on the crystallography of pyrites have been published since those dates, this form has not hitherto been recorded for the mineral.

Under the register-number 31679 are a number of small specimens and isolated crystals of pyrites, on three of which the form in question is deve]opod. These were purchased in 1860, and their locality is unknown. They show some matrix of black shale, and, unfortunately, are gradually being broken up by decomposition.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 19 , Issue 88 , March 1920 , pp. 1 - 9
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1920

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Footnotes

1

Communicated by permission of the Trustees of the British Museum.

References

page 1 note 2 K. Zimányi, Földtani Közlöny, Budapest, 1912, vol. 42, pp. 729, 848, gives a complete list of 196 crystal-forms of pyrites with references to the literature up to 1912. New forms since that date are listed under the heading ‘Nouvelles formes cristallines des minéraux’ in the Tables annuelles de Constantes et Donnöes numöriques, Paris, 1912 et. seq. See also the useful list by H. P. Whitlock, A list of new crystal forms of minerals. School of Mines Quarterly, New York, 1910, vol. 31, pp. 820-345, vol. 82, pp. 51-92.

Zimányi's list is based on that of G. Strüver (Mere. Accad. Sci. Torino, 1869, ser. 2, vol. 26), and contains the same errors. (211) is ascribed to Romé de l'Isle, 1783, but he himself quotes d'Agoty, 1767. (410) was recorded by Haüy in 1822. (720) and (11.9.0) are due to R. Wakkernagel (Isis, Jena, 1822, vol. 2, p. 1283). ψ9 (944) should be ψ (944).

page 3 note 1 Specimens are reckoned by the register-numbers. As a rule each of these represents a single hand-specimen with several attached crystals, though occasionally two or more similar specimens may be registered under the tmme number ; it may also represent a single isolated crystal or several isolated crystals kept together in the same lot. The numbers are thus more or Isis arbitrary.

page 4 note 1 The form (858) was found on an isolated cubo-octahedral crystal (Reg. No. 81556) from Rudnik, Serbia, acquired for the collection in 1896. It is represented by two mmall but well-defined facee lying between s and σ in the zone [sσ]. Measured (858) : (111) - 21° 15', 21° 18' (calculated 21° 4') ; (858) : (821)=2° 17', 2° 341/2'(calculated 2° 41'). Associated forms are aoest σZ. This form has recently been recorded by H. Uugemach (Bull. See. franç. Min., 1916, vol. 89, p. 224) on pyrltm from Auriol, Bouches-du-Rhone, France.

page 6 note 1 The drawing is an elevation. This simple method of representing rhombohedral crystals has been dealt with by Prof. W. J. Lewis in this Magazine, 1908, vol. 15, p. 82.

page 6 note 2 Deduced from the angle measured to the adjacent cleavage-face.

page 7 note 1 H. P. Whitlock, Calcites of New York. New York State Museunf, 1910, Memoir 18.

page 7 note 2 Goldschmidt, V., Atlas der Krystallformen. Heidelberg, 1918, vol. 2, p. 5.Google Scholar

page 7 note 3 A list of 299 forms for epidote is given by F. Zambonini, Zcits. Kryst. Min., 1902, vol. 87, p. 16 ; many are, however, vicinal faces with high indices.