The name, iolite, originates from the Greek word “iodes” meaning violet. It is often found under the misleading name of water sapphire.

Iolite facts

The gemstone iolite is the transparent form of the metamorphic silicate mineral Cordierite. Strong trichroism causes this gem to look alternately dark blue-violet to violet, lighter blue, and colorless to light yellow when looked at from different directions. The refractive indices of iolite are 1.542 to 1.551, very similar to that of quartz. There is however, no difficulty in separating the two gems because of iolite’s very strong trichroism.

Iolite deposits usually occur along with andalusite, kyanite and sillimanite, the alumino-silicates. Typically iolite gemstones are no greater than 12 carats, however, extremely large rough stones have been found in recent discoveries in Palmer Canyon Wyoming. A 1714 carat nodule of iolite, the world’s largest at the time, was discovered there and is known as the “Palmer Canyon Blue Star.” Subsequently, iolite has been found in various locations throughout the Laramie Range. Pebbles of iolite in Sri Lanka and porphoyroblasts in Wyoming comprise the finest quality iolite gems worldwide.

Historically, iolite is the stone most popularly believed to have been used as a polarizing filter by the Vikings. Peering through thin slices of iolite they could navigate on cloudy days by figuring the direction of the sun through the iolite filter. This innovation (whether iolite or some other gem material) enabled explorers to venture away from familiar landmarks along the coastlines and into the unexplored vastness of the oceans.


Iolite is believed to help with meditative visualizations, inducing the “third-eye,” helping to bring psychic abilities into play.

Gemological Information For Iolite

Color: Blue
Crystal Structure Orthorhombic
Refractive Index: 1.54-1.55
Hardness: 7.5
Family: Cordierite
Similar Stones: Amethyst, Sapphire, Tanzanite, Tourmaline
Treatments: None known


Iolite Care

Ultrasonic Cleaning: Risky
Steam Cleaning: Risky
Warm Soapy Water: Safe
Chemical Attack: Acids Attack
Light Sensitivity: Stable
Heat Sensitivity: Fusing

Sources Consulted

  • Liddicoat, Richard T. Handbook of Gem Identification, Los Angeles: Gemological Institute of America, 1962. Pp. 218-219.