A colorimetric study of the alexandrite effect in gemstones

Liu, Y.; Shigley, J.E.; Fritsch, E.; Hemphill, S.

Journal of Gemmology 26(6): 371-385

1999


ISSN/ISBN: 1355-4565
Accession: 029616314

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Abstract
The variation in colour hue (the alexandrite effect) for gemstones that change colour under pairs of light sources can be measured by the difference in their calculated CIELAB hue-angle. Depending upon the measured hue-angle and the light sources used, gemstones that exhibit this phenomenon can be grouped into several categories. Colour measurement can provide support for visual observation to help the gemmologist determine if a gemstone displays this behaviour.