Chrysoberyl

Chrysoberyl is an oxide of iron and aluminium, discovered in 1790 by a German geologist who named this new stone Krisoberil, or "golden beryl".

Current mines are found in Algeria, Brazil and the United States.

The two best-known types of chrysoberyl are :

• Alexandrite: a very rare variety of chrysoberyl with the unique characteristic of having a "change colour" effect. In daylight, the stone is greenish-blue and in incandescent light it appears reddish-pink. It was discovered in 1842 by Nils Gustaf, who dedicated his discovery to Tsar Alexander II, green and red being the colours of the Tsars. The main deposits were in Russia, but have now been exhausted. Today, Brazil has several mines, but the stones are of lesser quality and do not all change colour.
• Cat's eye is a shimmering variety of chrysoberyl. In cold light, a white line appears that moves across the width of the stone depending on the orientation of the light. This effect is due to inclusions or channels inside the stone. Cat's eye chrysoberyls are always cut as cabochons, which emphasises the movement of the line.