Characteristics of Chrysoberyl:

Chemical Name: Beryllium aluminum oxide

Formula: BeAl2O4

Colors: Green, yellow, brown

Structure: Orthorhombic

Hardness: 8.5

Specific Gravity: 3.7

Refractive Index: 1.74-1.76

Lustre: Vitreous

Streak: White

Locations: Russia, Myanmar, Zimbabwe, Tanzania, Madagascar, USA, Brazil, Sri Lanka

What is the most expensive variety of Chrysoberyl?

Although crystals of chrysoberyl are not uncommon, the gemstone variety Alexandrite is one of the rarest and most expensive gems in the world, with specimens seldom exceeding 10 carats. Alexandrite has the extraordinary visual property of appearing green in daylight but red under tungsten light; other forms of chrysoberyl occur in green, greenish yellow and yellow.

Alexandrite was discovered in the Ural Mountains in 1830, and was named after the Russian ruler Alexander II, on whose birthday it was supposedly found.

Alexandrite – changing colors

The Alexandrite variety of chrysoberyl displays a color change, from greenish to reddish, when seen in different light conditions. Alexandrite appears greenish in daylight, where a full spectrum of light is present, but reddish in incandescent light, because it contains less of the green and blue spectrum. The color change is due to chromium atoms replacing the aluminum in the chrysoberyl structure. This causes intense absorption of light over a narrow range of wavelengths.