Alexandrite is a rare gemstone that can exhibit a dramatic red/green colour change. It is sometimes described as "emerald by day and ruby by night", due to the way its colour changes in natural or artificial light. The amount by which the colour changes has a large impact on the price of alexandrite.
This gemstone was first discovered in 1830 in the Ural Mountains of Russia and was named after Czar Alexander II.
Alexandrite is one of the birthstones for June.
A member of the chrysoberyl family, alexandrite is rated as 8.5 on the Mohs Hardness Scale and is usually green or brown. It can sometimes be cut to show a cat's eye effect.
Historically, high quality examples of this gemstone came from Russia. Other places where it can be found are Brazil, Sri Lanka, Madagascar and Tanzania.