Alexandrite cats eyeAlexandrite (see tinyurl.com/dxwv9zo) is a variety of the mineral chrysob

Alexandrite cats eyeAlexandrite (see http://tinyurl.com/dxwv9zo) is a variety of the mineral chrysoberyl (seehttp://tinyurl.com/mvbojuj) that changes colour depending on the relative wavelength richness of the ambient light (ie whether it contains more blue or red wavelengths). The best qualities display a beautiful mint green to raspberry red depending on whether they are viewed in sunlight or incandescent light (firelight or the old type tungsten wire bulbs).Chrysoberyl is also the only mineral allowed to be called cats eye when it displays the phenomenon known as chatoyancy (seehttp://tinyurl.com/makwolr), in which a line of light moves across the stone when it is tilted back and forth in a strong light source. The rarity in the photo combines the two, a decent colour change and a fine and sharp catseye, making it a truly unique piece of nature.LozImage credit: Gemological Institute of America -- source link

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