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Relationship between the crystallographic orientation and the ‘alexandrite effect’ in synthetic alexandrite

Published online by Cambridge University Press:  05 July 2018

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

chrysoberylalexandritealexandrite effectcolour
Type
Mineralogy
Information
Mineralogical Magazine , Volume 59 , Issue 394 , March 1995 , pp. 111 - 114
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1995

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