Iolite According to legend, Vikings used iolite slices to reduce glare when checking the sun’s position.
In legends, ancient Viking navigators used thin slices of iolite as filters to help locate the sun on cloudy days. Whether or not the tales are true, iolite (mineralogists call it cordierite) can be fashioned into beautiful gems. Strongly pleochroic iolite has been incorrectly called “water sapphire,” as it can display a blue to violet hue in one direction and pale yellow to colorless in another.
BIRTHSTONES & ANNIVERSARIES
Iolite is the gemstone for the twenty-first wedding anniversary.
The following factors combine to determine an value.
Iolite’s most desirable colors are in the violetish blue to fine blue range.
Properly oriented inclusions can cause cat’s-eyes and aventuresence.
Iolite is most often faceted, as this cutting style serves to highlight its fine transparency.
Fine-quality faceted iolites over five carats are relatively rare in the market.
Name is from the Greek word ios, meaning violet.
When you turn iolite, you’ll see three distinct colors in three crystal directions.
Iolite is not typically treated. This is an attractive selling point for some consumers.
- Mineral: Iolite (Cordierite)
- Chemical composition: Mg2Al4Si5O18
- Color: Violetish blue (pleochroic colorless-yellow)
- Refractive index: 1.542 – 1.551
- Birefringence: +0.045, -0.011
- Specific gravity: 2.61
- Mohs hardness: 7.0 – 7.5