|Chrysoberyl (var. alexandrite)||NMNH G2042||Sri Lanka||65.70 ct|
|Chrysoberyl (var. alexandrite)||NMNH G3407||Sri Lanka||16.68 ct|
|Chrysoberyl (var. alexandrite)||NMNH G10065||Russia||4.84 ct|
One of the most valuable gemstones is the variety of chrysoberyl known as alexandrite. Alexandrite is renowned for its color change from red under incandescent light, to green in daylight or fluorescent light. Alexandrite was discovered in 1830 in the Ural Mountains of Russia and named after Csar Alexander II. The original locality for alexandrite is Russia, however, fine gems have also been found in Brazil, Sri Lanka, Tanzania, Madagascar, Zimbabwe, India, and Burma. Photographed here is a 65.08 carat square-cushion cut alexandrite from Sri Lanka; a 16.69 carat cushion cut alexandrite from Sri Lanka; and a 4.84 carat emerald cut alexandrite from Russia.