Cat’s eye gems of many different mineral species are well known, but when the term “cat’s eye” is used alone it always refers to the rare gemstone chrysoberyl. However, not all chrysoberyls show this chatoyant effect. Transparent to translucent chrysoberyl without a cat’s eye can make a wonderful faceted stone. Chatoyant chrysoberyls are cut into cabochons to best display their spectacular eyes. Some chrysoberyls that show a color change are known as alexandrites. All varieties of this gem are prized jewelry stones.
The transparent variety of chrysoberyl makes a handsome faceted gem. With indistinct cleavage and hardness of 8.5, it’s one of the toughest stones for jewelry purposes. In general, the bright yellow and yellow-green shades are the most desirable, but some of the browns are also striking. Properly cut gems are very brilliant, although they lack fire due to low dispersion. Chrysoberyls from Australia have unusually high refractive indices and could possibly be misidentified as yellow-brown sapphires.
The eye in a chrysoberyl cat’s eye often has a shimmering blue tone. The optimum color for these stones is a honey brown. When light obliquely strikes such a stone, it usually creates a shadow effect within the gem. The side away from the light is a rich brown, while the side facing the light is yellowish white. This so-called “milk and honey” look is characteristic of the finest cat’s eyes. This effect in stones over 20 carats can result in very high values.