Interpretation of the reflectivity behavior of ore minerals

Roger G. Burns; David J. Vaughan

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Research Article| October 01, 1970

Interpretation of the reflectivity behavior of ore minerals

Roger G. Burns;

Roger G. Burns

Department of Geology and Mineralogy, University of Oxford, England.

¹ Present Address: Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.

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David J. Vaughan

Department of Geology and Mineralogy, University of Oxford, England.

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Author and Article Information

Roger G. Burns

Department of Geology and Mineralogy, University of Oxford, England.

¹ Present Address: Department of Earth and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.

David J. Vaughan

Department of Geology and Mineralogy, University of Oxford, England.

Publisher: Mineralogical Society of America

Received: 28 Feb 1970

Accepted: 16 Mar 1970

First Online: 06 Jul 2018

Online ISSN: 1945-3027

Print ISSN: 0003-004X

Mineralogical Society of America

American Mineralogist (1970) 55 (9-10): 1576–1586.

Abstract

A correlation exists between the percent reflectivity (R) of pyrite-type compounds and the effective number of free electrons (N_eff) in the visible region, obtained from specular reflectance spectral measurements. Both R and N_eff decrease in each of the series FeS₂—CoS₂—NIS₂—CuS₂ and CuTe₂—CuSe₂—CuS₂. A molecular orbital model is described which relates the concept of N_eff to the delocalisation of excited transition metal electrons into antibonding molecular orbitals of pyrite. The values of N_eff are shown to depend on the number and proximity of empty energy levels above the Fermi level. The model is extended to explain reflectivity variations in other isomorphous and isocbemical series of ore minerals.