Electron delocalization mixed-valence minerals

Opacity of mixed-valence minerals. The opacities of many end-member Fe2+-Fe3+ oxide and silicate minerals result from electron hopping between neighbouring cations when they are located in infinite chains or bands of edge-shared octahedra in the crystal structures. Opaque minerals such as magnetite, ilvaite, deerite, cronstedtite, riebeckite and laihunite owe their relatively high electrical conductivities to thermally activated electron delocalization, contributing to intermediate valence states of iron cations which may be detected by Mossbauer spectroscopy. 

Sherman, D.M. (1985) Electronic structures of Ee " coordination sites in iron oxides application to spectra, bonding and magnetism. Phys. Chem. Min. 12 161-175 Sherman, D.M. (1987). Molecular orbital (SCF-Xa-SW) theory of metal-metal charge transfer processes in minerals I. Application to the Fe vpe charge transfer and electron delocalization in mixed-valenced iron oxides and si-licates.Phys Chem Min 70 1262-1269 Sherman, D.M. (1990) Crystal chemistry, electronic structure and spectra of Fe sites in clay minerals. Applications to photochemistry and electron transport. In Coyne, L.M. McKeever, S.W.S. Blake, D.F. (eds.) Spectroscopic characterization of minerals and their surfaces. A.C.S. Symposium Series 415, 284-309... 

Sherman, D. M. (1987a) Molecular orbital (SCF-Xa-SW) theory of metal-metal charge transfer processes in minerals. I. Applications to Fe2+ -+ Fe3 charge transfer and electron delocalization in mixed-valence iron oxides and silicates. Phys. Chem. Minerals, 14, 355-64. 

Ghosh, D., Kunda, T., Dasgupta, S. Ghose, S. (1987) Electron delocalization and magnetic behavior in a single crystal of ilvaite, a mixed valence iron silicate. Phys. Chem. Minerals, 14,151-5. 

Thermally activated electron delocalization also is observed in some minerals. The silicate mineral ilvanite with its Fe -Fe - mixed valency has been extensively studied. 

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