Other sources now include Sri Lanka, Burma, Brazil, Zimbabwe, Madagascar and North America. The important feature of Alexandrite which makes it highly unusual and collectable amongst gemstones is its strong colour change when viewed in different lights. Many other stones show a similar property, but nowhere as strongly, and not with such highly contrasting colours. It is hardly ever seen in the U.K. because of its rarity and high price.
Chrysoberyl is mainly green, yellow or brown.
High quality alexandrite varies from grass green to raspberry red, although some stones will tend towards olive green or brown, and others to yellow. The red and green colouration is caused by the partial replacement of aluminium by chromium. In daylight, stones appear green, whilst in tungsten lighting they will change colour to red. This effect is caused by a combination of factors. Each of these three directions has a strongly different absorption spectrum, causing different colours to be seen when viewed from different directions in relation to the crystal structure, an effect known as pleochroism.