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Atacamite from Sierra Gorda, Chili

Published online by Cambridge University Press:  14 March 2018

G. F. Herbert Smith*
Affiliation:
Mineral Department of the British Museum

Extract

In this paper are recorded the observations made upon four exceptionally good specimens of atacamite in the British Museum, which have been submitted to careful study with tile object of determining the geometrical and physical characters of the mineral with greater accuracy than has hitherto been possible. The axial ratios have been calculated with the utmost refinement, an attempt has been made to determine the crystallographic symmetry by a study of the etched figures, and the values of the principal indices of refraction have for the first time been obtained.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1898

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References

1 The same letters are used for the faces as in Dana's System of Mineralogy, 6th edition.

1 Genth seems to have analyser similar crystals (see Amer. Journ. Sci. 1890, XL, 207), but no mention is made of any crystallographic or optical examination.

2 Ber. Akad. WTeu, 1873, 68(1), 120.

3 Nouvelles Recl, erches.

4 Description d'wne Collection de mindraux.

5 Zeits. Kryst. Min. 1879, III, 489.

6 Ber. Akqd, Wien, 1871, 63(1), 6.

1 In Table II. and the following tables the measurements were made on a smaller Fuess goniometer reading to half-minutes.

1 Min. Mag. 1889, VIII, 172.

2 Ber. Ak. Berlin, 1886, p. 1,045.

1 Zeits Kryst, Min. 1879, III, 489.

1 G. G. Stokes, " On a formula for determining the optical constants of doubly refracting crystals," Camb. and Dublin Math. Journ. 1846, I. 183; Math. and Phys. Papers, Cambridge, 1880, I, 148; Cf. Liebiseh, Physikalisehe Krystallographie, Leipzig, 1891, equation at bottom of page 393.