Chatoyancy

The chatoyancy (verb: chatoyieren ), also known as cat's eye effect, is an areal, shimmering lighting effect in minerals and gemstones.

To emphasize the effect in semi-precious stones, they are cut as cabochons. In this spherical, round cut, a bright light is noticeable stripes extending perpendicular to the fibers and to slide upon movement of the block over the surface thereof. This light strip to the iris in the eye of a cat: remember (French chat). Another explanation of the word is French chatoyer = shimmer.

Chatoyance produced by numerous embedded in the host crystal fine fibers lying parallel and hollow channels, which are preferably perpendicular to reflect the light to its axis. The fibers act thereby partially as a light guide. For very small fibers and light scattering can cause this effect.

In chrysoberyl, Hawk Eye and Tiger Eye of the cat's eye effect is created by hollow fibers. Embedded acicular rutile is in Sapphire and Star Sapphire, and hornblende - fibers in the cat's eye quartz, the cause of the chatoyancy. Even with synthetic stones can be with embedded optical fibers produce this particular effect. Good imitations can be customized with colored glass substrates are fused into the light guide, produce. In them you can see the light-guiding effect in the direction of the fibers.

The cat's eye effect occurs primarily in the minerals chrysoberyl, Hawk's Eye and Tiger's Eye, which are used as gemstones. However, the effect also occurs in many other minerals. The light-guiding effect is particularly nice when ulexite, but which is too soft that it could be used as a gemstone.

All gemstone varieties with the cat's eye effect except chrysoberyl cat's eye as an additive to bear the name of the original mineral.

If the fibers are not parallel, but for example, by the symmetry of the host crystal set in 120 degree angles, shows up at a suitable cut of the asterism, for example, when Star Sapphire. With a low number of embedded fibers or hollow channels the mineral remains however clear and there is a designated as a semi-gloss light effect.