Those beautiful stones...

Alexandrite
Alexandrite is a rare variety of Chrysoberyl. Alexandrite was discovered near Ekaterinburg in the Ural Mountains in Russia in 1830, and was named after Alexander II. 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 color change when viewed in different lights. Many other stones show a similar property, but nowhere as strongly, and not with such highly contrasting colors.