Relationship Between the Crystallographic Orientation and the ‘Alexandrite Effect’ in Synthetic Alexandrite

Yan Liu, James E. Shigley, Emmanuel Fritsch and Scott Hemphill
GIA Research, Gemological Institute of America, 1660 Stewart Street, Santa Monica, Ca 90404-4088, USA

Abstract: The transmittance spectra of a synthetic alexandrite recorded along directions parallel to the three crystallographic axes are generally similar, but the observed colour changes along these directions under different light sources are quite different. Calculated hue-angle changes for the colours observed under different pairs of C.I.E. standard illuminants are the largest for light travelling parallel to the a-axis. Therefore, alexandrite should be cut as a gemstone with the top facet oriented parallel to (100) for it to show the most dramatic change in colour.

Keywords: chrysoberyl • alexandrite • alexandrite effect • colour

Mineralogical Magazine; March 1995 v. 59; no. 394; p. 111-114; DOI: 10.1180/minmag.1995.59.394.10
© 1995, The Mineralogical Society
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