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the mineral variety of chrysoberyl, having a composition of BeAl2O6, with an admixture of Cr2O3 (up to 0.5 percent). Thick tabular crystals of a pseudohexagonal habit are characteristic. In sunlight, alexandrite is emerald green; under artificial light, violet-red. The hardness is 8.5 on the mineralogical scale, and the density is about 3,700 kilograms per cubic meter. Alexandrite with a rich color and a weight of more than 2–3 carats is a precious stone of the first class. The finest alexandrites from deposits in the USSR, Brazil, South Africa, Madagascar, and Ceylon are found in pegmatites. Synthetic alexandrite is the name given to the artificially produced, light-green variety of corundum.