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Alexandrite

Tsarstone collectors guide

Alexandrite Guide Forums

The Purkinje Effect on Apr 4 2009, at 15:21 in The Alexandrite Effect
The Tavernier diamond, also known as the Blue Diamond of the Crown or French Blue, is a Type IIb diamond with high levels of boron impurities. The absorption spectrum of boron causes these diamonds to absorb red, orange and yellow light making Type IIb diamonds appear bluish or greyish colors.

Color change in the Tavernier diamond could be actually the Purkinje effect, where in bright light the human eye is more sensitive to red and in dim light the eye is more sensitive to blue-violet light, which causes the color of bluish gemstones to slightly enhance in dim lighting.

 
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