The attribute that gives this stone its popularity and name is the phenomena known as chatoyancy, also known in the gem trade as “the cats eye effect”. The reason for this fascinating phenomenon is very fine inclusions within the stone. When a light source is directed on these inclusions it creates a bright strip that appears and runs perpendicular to the inclusions. This strip will then glide across the surface of the stone when turned over. Though other gems exhibit this cat's eye effect,they are not as defined and distinct, giving only Chrysoberyl the privilege of having the Cat's Eye name. All other gemstones displaying chatoyancy must have their given name preceding, such as Quartz Cat's Eye.