The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case, sillimanite. 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. Best observed when gems are cut en cabochon, cat's eye sillimanite makes a phenomenal addition to any gemstone collection.
Cat's Eye Classification
||Cat's Eye |
Cat's Eye Optical Properties
||SWUV: Blue:inert or weak red |
LWUV: Blue:inert or weak red
Cat's Eye Characteristic Physical properties
||Sillimanite will appear fibrous is often vertically striated and they will contain parallel rutile needles or hypersthene's fibers. |