Cat's Eye Tourmaline

Cat's eye tourmaline is any tourmaline that displays chatoyancy, a luminous band of reflected light that glides across the surface like the slit pupil of a cat's eye. The effect appears when stones with many parallel needle-like or tubular inclusions are cut as cabochons.

The phenomenon occurs most often in green and pink tourmaline but is also seen in blue and brown stones. It belongs to the elbaite species in most gem material.

Unlike chrysoberyl cat's eye, which gives a single sharp line, tourmaline cat's eyes often show a slightly softer, broader band because the inclusions are hollow growth tubes.

Cat's eye tourmaline forms in granitic pegmatites alongside ordinary gem tourmaline. During crystal growth, numerous fine parallel channels, hollow tubes, or fibrous inclusions develop along the length of the crystal.

When the rough is oriented so these inclusions lie parallel to the base and cut as a domed cabochon, light reflecting off the tubes concentrates into a single band, producing chatoyancy. Major sources include Brazil, Madagascar, Sri Lanka, and East Africa.

The presence of the right density and alignment of inclusions is essential, so only a fraction of tourmaline produces good cat's eyes.

Look for a domed cabochon showing a single bright band of light that moves as the stone is rotated or the light source shifts. The body color is typically green or pink, with hardness 7-7.5 and vitreous to silky luster.

Under magnification you can often see the parallel tube or needle inclusions that create the eye. Tourmaline cat's eyes tend to have a slightly broader, softer band than chrysoberyl cat's eye.

Distinguish from cat's eye chrysoberyl (harder, sharper eye, higher density) and fibrous quartz cat's eye by refractive index, pleochroism, and crystal chemistry.

Cat's eye tourmaline is cut exclusively as cabochons to display the eye and is set in rings, pendants, and earrings as a distinctive phenomenal gem. Strong, sharp, centered bands on richly colored bodies command the highest prices.

Green and pink cat's eye tourmalines are the most popular. The combination of attractive color plus chatoyancy makes well-cut stones collectible.

Metaphysically, cat's eye stones are associated with protection and intuition, though such claims are not scientifically supported.