Alexandrite (Cat's-Eye) Gemstone & Information | Gemopedia by JTV | Gemopedia™

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case chrysoberyl. The effect, when present, appears as a bright, narrow slit similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by parallel fibrous or needle-like inclusions that interfere with the passage of light throughout the crystal, scattering and reflecting light back to the viewer as a thin line. Chatoyant chrysoberyl is particularly incredible because it exhibits two rare phenomena: both the cat's eye effect and color change.