Cat's Eye describes a polished gemstone in a cabochon that shows a thin band of concentrated light that crosses the width of the stone. The name "chatoyance" comes from the French word "chatoyer", which means "to shine like a cat's eye". The analogy also matches the way a cat's pupils shrink to a thin slit under bright light. The cat's eye effect is an optical reflectance effect seen in some gemstones. The precipitates that cause chatoyance in chrysoberyl are the rutile mineral, which is compose