Jewelry Birthstones Wizard
by: padre art
Cats Eye gems can be found in a number of mineral types. The most common are Chrysoberyl, Tourmaline and the Corundum gems, Ruby and Sapphire.
This optical phenomena is also observed in Moonstone and Quarts gems but only rarely in the precious stones Beryl, Spinel and Garnet. The effect is caused by the presence of parallel inclusions of needle-like fibers that are too small to see with the naked eye. The smaller in diameter and more numerous the inclusions are the better the cats eye phenomena.
When correctly oriented in the gem by the lapidary, light reflected from these fibers creates the shimmering line that looks so much like the feline eye. The parallel inclusions are usually formed of the mineral called Rutile but can be any number of inclusion types, even hollow capillary tubules.
The technical term for the optical phenomena called Cats Eye is chatoyance. To achieve a strong cats eye effect it is necessary to create a high dome shape on the cabochon and with the inclusions running perpendicular to the desired direction of the eye.
Chrysoberyl cats eye, in ancient times, was called 'Oculus Solaris' or 'Eye of the Sun' due to the yellow color of the mineral (often leaning to the green or brown). Cats eye Chrysoberyl can be almost transparent to completely opaque and is mostly found in the gem gravels of Ceylon.
From the 15th to the 20th century the cats eye gems were the favored birthstones for the month of June.

