Around the time the Russian empire was celebrating the sixteenth birthday of the future Tsar Alexander II, one of the most controversial characters in the history of Russia, a gemstone with a color-changing property 
was discovered in the Emerald mines on the Tokovaya River, east of Yekaterinburg. This scarce and unique stone was irrevocably associated with Alexander II by its being named in his honor, hence the name Alexandrite or the Tsarstone.
Alexandrite, otherwise known as the tsarstone, is a variety of the mineral chrysoberyl, an aluminate of beryllium. Alexandrite can be readily mined in such scattered locations such as Burma, Brazil, India, Tanzania, and Madagascar, but the finest finds of this unique gem can only be dug in Russia.
Alexandrite ranks between ruby and sapphire in terms of hardness, which makes it an excellent choice for jewelry. Its colors give alexandrite its unique quality. The original Russian alexandrite has striking hues that makes it stand out from other gemstones. In daylight, an ideal alexandrite is a bluish emerald green, but in incandescent light, the gemstone appears a purplish or raspberry red. Alexandrite in other locations tends to be less vivid in varying degrees. This trait of this diaphonous mineral is due to its chemical composition.
The tsarstone is a chrysoberyl, which is normally colorless. It contains iron, titanium, beryllium, and chromium. Its rarity and historical association with the last tsar makes alexandrite one of the rarest and most valuable of the gemstones. An alexandrite of more than one carat is rarer than a fine ruby, sapphire, or emerald.
Interestingly, the property of a stone to change colors is now termed as the alexandritic effect. Garnets and sapphires, for example, are known to be alexandritic.
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