Alexandrite is an extremely rare and expensive color-changing variety of the mineral chrysoberyl. The color-changing phenomena is known as the ‘alexandrite effect’. It possesses the remarkable ability to appear green in sunlight and red in incandescent light and, due to its color-changing, has often been described as an “emerald by day, ruby by night.”
Along with pearl and moonstone, alexandrite is the birthstone of June. It rates an 8.5 on the Mohs hardness scale and was discovered in the Ural Mountains of Russia in the 1830’s. Alexandrite is also mined in Africa, Sri Lanka and Brazil.