Chatoyancy
Chatoyancy is an optical phenomenon in which a bright, narrow band of reflected light appears to move across the surface of a gemstone as the stone or light source is rotated. The term, derived from the French word chatoyer, is commonly described as the cat's eye effect. It is most famously seen in chrysoberyl but occurs in several other gemstones and materials.
It results from light interacting with aligned, fibrous inclusions or parallel cavities within the mineral, which
To maximize chatoyancy in jewelry, stones are cut en cabochon with a smooth, curved surface, which presents