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Crystallised Stannite from Bolivia. with Plate II

  • L. J. Spencer (a1) and G. T. Prior (a1)

Extract

Very little is known of the crystalline form of thc somewhat rare mineral stannite, since in the few localities in which it has been found it usually occurs only in the massive state. Several suggestions, summarised below, have been made as to the type of crystalline symmetry of the mineral, but hitherto no crystals have been completely examined.

  • (1) Orthorhombic. Haüy (1822), from an examination of cleavage fragments from Cornwall, concluded that the primitive form might possibly be a right rhombic prism.
  • (2) Cubic. Haidinger (1825) mentioned Cornish crystals, having apparently the form of regular cubes, but the dulness of the faces did not allow of any measurements. The massive material appeared to show cleavages in the directions of the faces of the cube and rhombie dodecahedron. (Crystals of Cornish stannite are further mentioned on p. 65 below.)

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Page 54 note 1 Traité de Minéralogie, 2nd Edit. 1822, Vol. IV, p. 170.

Page 54 note 2 English translation of Mohs' Mineralogy, 1825, Vol. III, p. 163

Page 54 note 3 Uibersicht des Mineral-Systems, 1880, p. 75. Vollständige Char. d. Mineral. Systems, 8rd Edit. 1832, p. 275.

Page 54 note 4 Berg- und hüttenmänn Zeitung, 1866, XXV, 181; and Min. Studien, 1866, p. 102

Page 55 note 1 Stelzner, A. W., Zeits. Deutsch. geol. Ges. 1897, XLIX, 75 ; and Dana's System of Mineralogy, 6th Edit. 1892, p. 83 .

Page 55 note 2 Verh. Ver. Rheinl. Bonn, 1884, XLI, 296; Compare A. W. Stelzner, Zeits. Deutsch. geol. Ges. 1897, XLIX, 75.

Page 55 note 3 Zeits. Deutsch. geol. Ges. 1897, XLIX, pp. 97, 131 ; abstract Min. Mag. 1898, XII, 46. Stelzner's crystals were first mentioned in Zcits. Deutsch. geol. Ges. 1892, XLIV, 531 ; abstract Min. Mag. 1893, X, 261.

Page 55 note 4 Min. Untersuchungen, 1849, I, p. 41; Kenffgott's Uebersicht (1844-9), 1852, p. 287.

Page 55 note 5 Nouveau Cours de Minéralogie, 1860, II, 416.

Page 55 note 6 An account of this collection will be published as an Appendix to Sir Martin Conway's book, “Bolivian Andes.”

Page 56 note 1 Voyage dans l'Amérique méridionale, 1826–1833, Tome III, 3e Partie, Géologie, p. 129, 1842. Stelzner (loc. cit. p. 86) has doubted this occurrence, but without sufficient reason.

Page 56 note 2 The figures prepared for the preliminary account in Sir Martin Conway's book, “Bolivian Andes,” represent the crystals as holohedral.

Page 57 note 1 The letters adopted for the forms are those used in Dana's Mineralogy (6th Ed. 1892) for copper-pyrites. For these forms to be strictly analogous with those of copper-pyrites + and − would probably have to be interchanged.

Page 59 note 1 The angle ce in the projection has been taken as 431/2° instead of 441/2° in order to separate more distinctly the poles which nearly coincide. The poles of the crystal in the normal position are indicated by unbarred letters, those of the crystal twinned about (101) are indicated as c e, etc., and those twinned about (011) as c e, etc. The parallel planes beneath the plane of projection are omitted.

Page 60 note 1 Compare the interpenetrating dodecahedra of argyrodite figured in Min. Mag. 1898, XII, 7.

Page 60 note 2 In Fig. 4 the Lwin-plane is (1̄11),

Page 61 note 1 Compare the pseudo-cubic crystals of iodyrite described in this number of the Magazine, p. 46.

Page 61 note 2 Crystals of Cornish stannite appear to possess cleavages, see pp. 54, 65.

Page 61 note 3 Calculated from the specific gravity of the material analysed (4·52) by deduating 8·58 per cent. of andorite (sp. gr. 5·35).

Page 62 note 1 Phil. Mag. 1882 [v], XIV, 287; Proc. Cryst. Soc. 1882, p. 126; Zeits. Kryst. Min. 1883, VII, 331.

Page 62 note 2 For the staunite forms to be strictly analogous with those of copper-pyrites + and - as given above, would probably have to be interchanged ; if this is done all the stannite forms, with the exception of —n{11̄2}, have been noted on copperpyrites.

Page 62 note 3 A third, but very rare, twin-law of copper-pyrites is represented by the complementary interpenetrant twins with m(110) as twin-plane : this has not been observed on lhe stannite crystals.

Page 63 note 1 Memoirs Wernerian Nat. Hist. Soc. Edinburgh, 1822, Vol. IV. p 17, Figs. 37-41 ; Edinb. J. Set. 1825, Vol. IlI, Plate III, Figs. 29, 32, 34. Two of Haidinger's figures are reproduced in Mr. Fleteher's paper (loc. cit.).

Page 63 note 2 This is the fourth locality at which the rare mineral augelite has been found. Compare Min. Mug. 1898, XII, p. 1.

Page 63 note 3 This is a new locality for the rare mineral, wolfsbergite (=chalocstibite). Compare Miu. Mag. 1897, XI, 338. These occurrences are described in the Appendix to Sir Martin Conway's book, “Bolivian Andes.”

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