gsminmag Mineralogical Magazine Mineralogical Magazine 0026-461X Mineralogical Society 10.1180/minmag.1988.052.365.08 Mineralogy Mössbauer Effect Study on the Mixed Valence State of Iron in Tourmaline Ferrow E. A. Department of Mineralogy and Petrology, University of Lund, Sölvegatan 13, S-222 62 Lund, Sweden Annersten H. Department of Mineralogy and Petrology, University of Uppsala, Box 555, S-751 22 Uppsala, Sweden Gunawardane R. P. Department of Chemistry, University of Paradeniya, Paradeniya, Sri Lanka 4 1988 52 365 221 228 2 12 1986 6 4 1987 Copyright © 1988, The Mineralogical Society 1988 Abstract

Mössbauer spectra of iron-bearing tourmaline, obtained at different temperatures, show the existence of thermally-activated charge delocalization among clusters of iron atoms situated in the Y and Z octahedra of the tourmaline structure. The temperature dependence indicates an unusually high activation energy for the delocalization process which suggests that the process takes place between crystallographically non-equivalent sites. Annealing of the tourmaline in hydrogen is observed to inhibit the delocalization process, thus localizing the electron into the Z-site.

 Keyword Mössbauer effect tourmaline iron charge delocalization Sweden H2 annealing