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Diffuse reflectance spectra and optical properties of some iron and titanium oxides and oxyhydroxides

Published online by Cambridge University Press:  05 July 2018

R. G. J. Strens  and
B. J. Wood
R. G. J. Strens
Affiliation:
School of Physics, The University, Newcastle upon Tyne NE1 7RU
B. J. Wood
Affiliation:
Department of Geology, The University, Manchester M13 9PL
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Summary

The reliability and utility of diffuse reflectance spectra are briefly but critically reviewed. The results of measurements of diffuse reflectance over the wavelength range 200 < λ < 2500 nm are reported for wüstite, magnetite, hematite, maghemite, ilmenite, ulvöspinel, and α-FeO · OH (goethite), β-FeO 7sd OH, γ-FeO · OH (lepidocrocite), and δ-FeO · OH. The spectra have been assigned by reference to simplified molecular-orbital energy-level diagrams derived from recent SCF-Xα calculations.

The specular reflectances reported in the Quantitative Data File (Henry, 1977) are related to the diffuse reflectance spectra in a rational way. Minerals that absorb strongly throughout the visible display little dispersion of specular reflectance, and their powders are dark (wüstite, magnetite, ilmenite, ulvöspinel); those that absorb much more strongly in the near ultraviolet than in the visible have specular reflectances that decrease monotonically from blue to red according to a simple dispersion relation derived by combining the Sellmeier dispersion and Fresnel reflexion equations; their powders are strongly coloured (hematite, maghemite, lepidocrocite, goethite) and their optical anisotropy is closely related to crystal structure.

Type
Research Article
Information
Mineralogical Magazine , Volume 43 , Issue 327 , September 1979 , pp. 347 - 354
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1979

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Footnotes

1

Present address: Department of Mineralogy and Petrology, Downing Place, Cambridge CB2 3EW.

References

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