Ilvaite electron delocalization

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. 

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. 

Litterst, F, J. Amthauer, G. (1984) Electron delocalization in ilvaite a reinterpretation of its 57Fe M8ssbauer spectrum. Phys. Chem. Minerals, 10,250-5. 

Nolet, D. A. Bums, R. G. (1979) Ilvaite a study of temperature dependent electron delocalization by the Mossbauer effect. Phys. Chem. Minerals, 4, 221-34. 

F.J. Litterst, G. Amthauer, Electron delocalization in ilvaite, a reinterpretation of its pe MSssbauer spectrum. Phys. Chem. Miner. 10, 250-255 (1984)... 

D.A. Nolet, Electron delocalization observed in the Mossbauer spectrum of ilvaite. Solid State Common. 28, 719-722 (1978)... 

The Mossbauer spectra of specimens spanning the ludwigite-vonsenite series show temperature and compositional variations (Bums and Bums, 1982 Swinnea and Steinfink, 1983). These variations resemble those observed in the ilvaite Mossbauer spectra and may be attributed to electron hopping between Fe2+(M3) and Fe3+(M4) cations. Charge delocalization in vonsenite becomes possible over the three-dimensional structure via edge-shared octahedra parallel to the c axis. 

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