Alexandrite Square 4mmDescriptions Often described by gem aficionados as emerald by day, ruby by night, alexandrite is the very rare color change variety of the mineral chrysoberyl. Originally discovered in Russia's Ural Mountains in the 1830s, it's now found in Sri Lanka, East Africa, and Brazil, but fine material is exceptionally rare and valuable. Picture description (in order): Green Under Fluorescent light, Turn to red different light source. This listing includes 1