Chrysoberyl

Specific Gravity: 3.71
Refractive Index: 1.74-1.75
Birefringence (DR): 0.009
Luster: Vitreous
Crystal Structure: Orthorhombic
Composition: Beryllium aluminum oxide
Hardness: 8½

Chrysoberyl occurs in a range of colors, from greenish, greenish-yellow, and yellow, to brown. It is a hard, durable stone, particularly suitable for use in jewelry. When cut well, gems are brilliant but lack fire. Two varieties, alexandrite and cat’s eye chrysoberyl, have unique qualities of their own. The very rare and valuable alexandrite changes from green in daylight to red, mauve, or brown under incandescent light, such as a light bulb.

Synthetic chrysoberyl, synthetic corundum, and synthetic spinel have all been produced to imitate color-change alexandrite.

In the 18^th century, it was common to set a chrysoberyl stone in jewelry in Spain. The chrysoberyl was collected from a vein running through chalk. On the other hand, exquisite brooches from the Victorian era in Britain used to be made up of greenish-yellow, faceted chrysoberyls set in gold filigree.

It is common to find a chrysoberyl crystal that is twinned with another in the matrix. The crystal has wedge-shaped ends.

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Occurrence

Although mainly worked out, the best chrysoberyl, including alexandrite, has been found in mica schists in the Urals (Russia). The largest faceted chrysoberyl from Russia weighs 66 carats. Large waterworn pebbles of various colors are found in the gem gravels of Sri Lanka. Chrysoberyl also occurs in Madagascar, Tanzania, Zimbabwe, Brazil, and Myanmar (Burma). Cat’s eye is found in China, Brazil, and Sri Lanka.