Fe2+ - Ti4+ Charge Transfer in Stoichiometric Fe2+, Ti4+-Minerals

Stephanie M. Mattson
Department of Chemistry
Moorhead State University, Moorhead, MN 56560, U.S.A.

George R. Rossman
Division of Geological and Planetary Sciences,
California Institute of Technology, Pasadena, California 91125, U.S.A.


Optical absorption spectra are presented for taramellite, traskite and neptunite, allof which have both Fe2+ and Ti4+ as major elements. The spectra of each of these minerals are dominated by a single, intense absorption band in the 415 to 460 nm region with 7000 to 8000 cm-1 half-width. These transitions, assigned to Fe2+-Ti4+ intervalance charge transfer, showed litted difference in intensity at 80 and 300 K and have molar absorptivities which range from ~100 to ~1300 M-1cm-1. The Fe2+-Ti4+ absorptions in these standards generally compre well to other mineral spectra in which Fe2+-Ti4+ intervalence absorption has previously been proposed with the exception of the most cited example, blue corundum.