Dynamic Biaxial Absorption Spectra of Ti3+ and Fe2+ in a Natural Rose Quartz Crystal

A. J. Cohen and L. N. Makar*
Department of Geology and Planetary Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, U.S.A.
*Present address: Department of Physics, University College of Bahrain, Bahrain, Arabian Gulf.

Abstract: The absorption spectrum of Ti3+ in quartz is typical for that element in an octahedral site, except for the high oscillator strength of the band which indicates intensive charge transfer, most likely between a substitutional Ti4+ and an interstitial Ti3+. The biaxial anisotropy of the band is similar to that of octahedral Fe2+ in the same crystal, suggesting the same site for the Ti3+, an interstitial site at the intersection of the threefold axis with two twofold axes. The dynamic nature of the Ti and Fe ions is indicated when the crystal is subjected to X-irradiation and then to bleaching treatment with UV-light or heat. Ti(iv) ions are acceptors of electrons donated by Fe2+ during X-irradiation. This is indicated by increase of the 2.4 eV band intensity with decrease in the Fe2+ band intensities and appearance of Fe3+ charge transfer bands in the UV-region. Heat and UV-light treatment decrease the Fe3+ CT bands and increase the Fe2+ crystal-field bands along with decrease in the 2.4 eV band related to titanium.

Keywords: absorption spectra • titanium • iron • quartz

Mineralogical Magazine; December 1985 v. 49; no. 354; p. 709-715; DOI: 10.1180/minmag.1985.049.354.10
© 1985, The Mineralogical Society
Mineralogical Society (www.minersoc.org)