Channel Constituents in Beryl

Don S. Goldman, George R. Rossman
Division of Geological and Planetary Sciences
California Institute of Technoogy
Pasadena, CA 91125

Kathleen M. Parkin
Department of Earth and Planetary Sciences
Massachusetts Institute of Technology
Cambridge, MA 02139

Abstract

The electronic absorption spectra of Fe²⁺ in non-chromium beryls are examined. Fe²⁺ in the Al-rich six-coordinate site produces absorption bands at about 820 nm and 970 nm polarized E||c. Fe²⁺ the the channel produces bands at 820 nm (perp c) and 2100 nm (||c). Some blue beryls which are more intensely colored than most aquamarines, have an absorption band at ~700 nm (||c) which is suggested to arise from an Fe²⁺/Fe²⁺ intervalence interaction. Fe²⁺in both the six-coordinate site and the channel is identified in the Mössbauer spectra. The Mössbauer spectra of deep blue beryls are unuaual and have not been satisfactorily explained. Color changes which accompany heating and irradiation are strongly influenced by the channel iron.

Absorption spectra of yellow beryl showing the spectra of both channel Fe²⁺ and six-coordinate Fe²⁺.

last updated: 25-Jul-2022