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 & AnniversariesIolite is the gemstone for the twenty-first wedding anniversary.
Iolite’s 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.
Violetish blue (pleochroic colorless-yellow)
1.542 - 1.551
- Mohs hardness: 7.0 – 7.5
There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.Learn More
Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.Learn More
Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.Learn More
Why We Love This Gemstone
In its best colors, iolite can rival the beauty of tanzanite but at a fraction of the cost.
Usually transparent, iolite sometimes contains inclusions that cause attractive phenomena.
Iolite’s beautiful violet-to-blue hue is due to the presence of iron in its structure.
The following factors combine to determine an iolite’s 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.
Iolite Quality Factors: The Comprehensive Guide
Explore sources, gemological research, and the role of gems in history.
Gemstones of the World