Alexandrite is a rare, precious gemstone that changes colors when exposed to incandescent or UV lighting conditions. Originally discovered in Russia and mistaken for rubies,  this gemstone is named for tsar Alexander the 1st. Russia still has the finest examples of Alexandrite, which exhibit a color change from an emerald green to ruby red. Brazil is now the main producer of fine, high quality Alexandrite which displays a teal green to raspberry red color change. India also produces Alexandrite in a saturated teal green color, however Indian Alexandrite exhibits very faint to no color change properties. Alexandrite is an 8.5 on the Moh's Scale and belongs to the chrysoberyl gem family.
See Also: chrysoberyl, Moh's Scale of Hardness