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Quantitative colours of opaque minerals

Published online by Cambridge University Press:  05 July 2018

A. Peckett
A. Peckett*
Affiliation:
Department of Geological Sciences, University of Durham, Durham DH1 3LE
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Abstract

Anisotropic opaque minerals viewed in reflected light microscopy show two sets of colours: the colours seen in plane polarized light which change as the section is rotated on the microscope stage, and the colours seen between crossed polars which change as the analyser is uncrossed. These latter colours are known variously as polarization colours or anisotropic rotation tints, but are here referred to as anisotropy colours. They are commonly a diagnostic aid to correct mineral identification. All these colours occur as a consequence of the dispersion of the relative permittivity (dielectric) tensor—the variation in the values of the tensor with wavelength of incident light and in low symmetry crystals, the variation in the directions of the principal axes of the tensor with wavelength.

In this paper, it is shown that the colour seen in plane polarized light and the anisotropy colours can be predicted for any orientation of section, at any stage angle, and for any degree of uncrossing of the analyser by calculations based on the dielectric tensor values, and these predicted colours compare favourably with the observed values. Three minerals are studied in this paper as examples: stannite, covelline, and bournonite.

Keywords

reflected light microscopycoloursopaque mineralsstannitecovellinebournonite
Type
Mineralogy
Information
Mineralogical Magazine , Volume 53 , Issue 369 , March 1989 , pp. 71 - 78
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1989

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References

Cameron, E. W. (1961) Ore microscopy. Wiley.Google Scholar
Craig, J. R. and Vaughan, D. J. (1981) Ore microscopy and ore petrography. Witey.Google Scholar
Criddle, A. J. and Stanley, C. J. eds. (1986) The quantitative data file for ore minerals', 2nd ed. British Museum (Natural History).Google Scholar
Galopin, R. and Henry, N. F. M. (1972) Microscopic study of opaque minerals. Published since 1975 by McCrone Research Assoc. Ltd. London.Google Scholar
Green, L. H. (1952) Econ. Geol. 47, 4518.CrossRefGoogle Scholar
Grum, F. and Bartleson, C. J., eds. (1980) Optical Radiation Measurements, 2, Color Measurement. Academic Press.Google Scholar
Henry, N. F. M., ed. (1977) IMA/COM Quantitative Data File. Applied Mineralogy Group, Mineralogical Society, London.Google Scholar
Kelly, K. L. and Judd, D. B. (1955) The ISCC-NBS Method of Designating Colors and a Dictionary of Color Names. Nat. Bur. Standards Circular 553.Google Scholar
Koritnig, S. (1977) Neues Jahrb. Mineral. Mh. 279 88.Google Scholar
Peckett, A. (1987) Mineral. Mag. 51, 655-63.CrossRefGoogle Scholar
Ramdohr, P. (1980) The ore minerals and their intergrowths, 2nd ed. Pergamon Press.Google Scholar
Schouten, C. (1962) Determinative tables for ore microscopy. Elsevier.Google Scholar
Uytenbogaardt, W. and Burke, E. A. J. (1971) Tables for microscopic identification of ore minerals. Second revised edition. Elsevier.Google Scholar