A spectroscopic study of blue radiation coloring in plagioclase

Anne M. Hofmeister and George R. Rossman
Division of Geological and Planetary Sciences
California Institute of Technology, Pasadena, CA  91125, USA


Blue color in sodic plagioclase is produced by electronic transitions of Pb in a manner similar to the mechanism causing color in amazonite (potassium feldspar colored blue-green by Pb electronic transitions). The two blue feldspar varieties have the following characteristics in common: (l) elevated Pb concentrations (usually greater than 0.01 wt.%), (2) structurally incorporated H+, (3) similar response of the color to heating and irradiation, and (a) similar band shape, position, and polarization in the optical spectrum