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Published March 1977 | public
Journal Article

The identification of Fe^(2+) in the M(4) site of calcic amphiboles

Abstract

Evidence is presented for the occurrence of Fe^(2+) in the predominantly Ca-filled M(4) site of calcic amphiboles. Absorption bands in the electronic spectra at 1030 nm in β and at 2470 in a provide a sensitive means for identifying Fe^(2+) in this site. The large є value for the 1030 band, the large energy separation between both bands, and the similarity to the spectra of Fe^(2+) in large, highly distorted coordination sites in other minerals provide the basis for the M(4) site assignment. The energy splittings and polarization anisotropy of these bands are analyzed using a point-charge model based on C_(2v) symmetry. Spectral data indicate that the Fe^(2+) content in the M(4) site varies significantly among the calcic amphiboles.

Additional Information

© 1977 Mineralogical Society of America. Manuscript received, April 28, 1976; accepted for publication, September 21, 1976. We wish to thank J. D. Hare (Caltech) and R. G. Burns (MIT) for discussing many aspects of the spectroscopic interpretation. We also appreciate the use of the Mössbauer spectrometer made available to us by W. A. Dollase (UCLA) and the many discussions with him concerning the analysis of the Mössbauer spectrum.

Additional details

Created:
August 22, 2023
Modified:
October 23, 2023