Mössbauer Effect Study on the Mixed Valence State of Iron in Tourmaline

E. A. Ferrow, H. Annersten and R. P. Gunawardane
Department of Mineralogy and Petrology, University of Lund, Sölvegatan 13, S-222 62 Lund, Sweden
Department of Mineralogy and Petrology, University of Uppsala, Box 555, S-751 22 Uppsala, Sweden
Department of Chemistry, University of Paradeniya, Paradeniya, Sri Lanka

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

Mineralogical Magazine; April 1988 v. 52; no. 365; p. 221-228; DOI: 10.1180/minmag.1988.052.365.08
© 1988, The Mineralogical Society
Mineralogical Society (www.minersoc.org)