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The physical basis of mineral optics I. Classical theory

Published online by Cambridge University Press:  05 July 2018

R. G. J. Strens  and
Robert Freer
R. G. J. Strens
Affiliation:
School of Physics, The University, Newcastle upon Tyne NEI 7RU
Robert Freer
Affiliation:
School of Physics, The University, Newcastle upon Tyne NEI 7RU
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Summary

The Helmholtz dispersion equations have been rewritten in a form that enables the optical constants of both transparent and opaque media to be calculated from their spectra. Both Helmholtz equations are used to describe the optical properties of opaque media, and to obtain values of reflectance, refractive index, and absorption coefficient. The Sellmeier dispersion equation is a special case of the dispersive Helmholtz equation applicable to weakly absorbing media (including the great majority of minerals studied in thin section): it is used to derive the wavelength-, composition-, direction-, and volume-dependence of the principal indices in mixed crystals of monoclinic or higher symmetry. The treatment can be extended to triclinic crystals.

The birefringence of transparent phases is the expression in the visible region of the pleochroism of absorption bands in the ultra-violet. The bireflectance of opaque phases depends also upon the pleochroism of bands in the visible and near infra-red, resulting in extreme sensitivity of the optics of opaque materials to changes in wavelength, composition, and structure. The optical anisotropy of both transparent and opaque phases may be calculated if the dependence of the spectra on structure can be established by measurement or by calculation from structure data. The quantitative application of Bragg's method is restricted to phases of very simple chemistry and structure (e.g. calcite and rutile), but it may be applied qualitatively to rationalize the optic orientations of phases containing only closed-shell ions of neon or argon configuration, including many pyroxenes, amphiboles, micas, and chain aluminosilicates. When open-shell (transition metal) ions enter the structure, the general rule is that the anisotropy becomes more closely related to the distortion of the coordination polyhedron about the metal ion, and for ions of formal charge ≥ 3, this source of anisotropy is usually dominant.

Type
Research Article
Information
Mineralogical Magazine , Volume 42 , Issue 321 , March 1978 , pp. 19 - 30
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1978

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References

Bolton, (H. C.), Fawcett, (W.), and Gurney, (I. D. C.), 1962. Proe. Phys. Soc. 80, 199.CrossRefGoogle Scholar
Bragg, (W. L.), 1924. Proc. R. Soc. 105, 370.Google Scholar
Burns, (R. G.) and Strens, (R. G. J.), 1967. Mineral. Mag. 36, 204.Google Scholar
Deer, (W. A.), Howie, (R. A.), and Zussman, (J.), 1962. Rock Forming Minerals. London (Longmans), New York (Wiley).Google Scholar
Fawcett, (W.) 1963a. ‘Theoretical Studies on the Refractivities of Ionic Crystals.’ Ph.D. Thesis, University of Newcastle upon Tyne.Google Scholar
Fawcett, (W.) 1963b. Proc. Phys. Soc. 82, 33.CrossRefGoogle Scholar
Freer, (R.), 1973. ‘The Optical Properties of Solid Solutions.’ M.Sc. Thesis, University of Newcastle upon Tyne.Google Scholar
Gehlen, (K. von) and Piller, (H.), 1965. Mining Mag. 113, 438.Google Scholar
Hartshorne, (N. H.) and Stuart, (A.), 1960. Crystals and the Polarising Microscope. London (Edward Arnold).Google Scholar
Jenkins, (F. A.) and White, (H. E.), 1976. Fundamentals of Optics. 4th edn, New York (McGraw-Hill).Google Scholar
Johnston, (R. W.), 1949. Mineral. Mag. 28, 505.Google Scholar
Kittel, (C.), 1966. Introduction to Solid State Physics. 3rd edn, New York (Wiley).Google Scholar
Langer, (K.), Abu-Eid, (R. M.), and Anastasiou, (P.), 1976. Z. Kristallogr. 144, 434.Google Scholar
Mott, (N. F.) and Gurney, (R. W.), 1964. Electronic Processes in Ionic Crystals. New York (Dover).Google Scholar
Myer, (G. H.), 1966. Am. J. Sci. 264, 364.CrossRefGoogle Scholar
Nitsan, (U.) and Shankland, (T. J.), 1976. Geophys. J. R. Astron. Soc. 45, 59.CrossRefGoogle Scholar
Partington, (J. R.), 1953. Advanced Treatise on Physical Chemistry, 4. Physiochemical Optics. London (Longmans).Google Scholar
Robbins, (D. W.) and Strens, (R. G. J.), 1972. Mineral. Mag. 38, 551.CrossRefGoogle Scholar
Smith, (G.) and Strens, (R. G. J.), 1976. In Strens, (R. G. J.), ed. The Physics and Chemistry of Minerals and Rocks. London & New York (Wiley).Google Scholar
Strens, (R. G. J.), 1967. Mineral. Mag. 35, 928.Google Scholar
Tossell, (J. A.) and Vaughan, (D. J.), 1974. Am. Mineral. 59, 319.Google Scholar
Wood, (B. J.), 1971. ‘Electronic Spectra of some Solid Solutions.’ Ph.D. Thesis, University of Newcastle upon Tyne.Google Scholar
Wood, (B. J.) and Strens, (R. G. J.), 1970. Abstracts, IMA-IAGOD Meeting (Tokyo), 116.Google Scholar
Wood, (B. J.) 1972. Mineral. Mag. 38, 909.CrossRefGoogle Scholar
Wooster, (W. A.), 1931. Z. Kristallogr. 80, 495.Google Scholar

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