After rubies, sapphires, emeralds and diamonds ( the big four ), you begin to wonder what gem would be an interesting subject to pursue. While jade, opal or garnet comes into mind, phenomenal stone provide such a different feel and look. Phenomenal stones such as cat's eyes provide "eye stimulation" in that your eye balls actually follow the movement of your fingers as the "lines" on the gem moves with your every motion.

Cat's eye effect or "chatoyancy" comes from the French word "chat" or "cat" and "o'eil" or "eye". Put them together and you get "chat-o'eil" or "chatoyancy". The best chatoyant gems display an effect which duplicates the eyes of a cat. The "open" and "close" of the eye should be balanced and symmetric.

The eye should be sharp and instense. The color of the eye should be distinct and not hidden by the body color. Gemstones that display a cat's eye effect are ( but not limited to) tourmalines, chrysoberyl, scapolites, tiger eye quartz, zircons ( Dr E Gubelin has mentioned that the Sri Lankan brown cat's eye zircon you see in the market could be a result of heat treatment), iolites, garnet, opal, actinolites........In actuality, cat's eye phenomena may occur with any mineral which has parallel tubes or fibrous inclusions within the gem. When cat's eye effect occur in stones which donot normally display chatoyancy, then the gem becomes doubly rare and more valuable. For example, a cat's eye ruby, cat's eye saphire, cat's eye garnet are gems not only rare but really a "one of a kind" collectors item.