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.