Iolite
According to legend, Vikings used iolite slices to reduce glare when checking the sun’s position.
OVERVIEW
ABOUT IOLITE
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.
IOS
Iolite’s name is from the Greek word ios, meaning violet.
PLEOCHROIC
When you turn iolite, you’ll see three distinct colors in three crystal directions.
AU NATURAL
Iolite is not typically treated. This is an attractive selling point for some consumers.
FACTS
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
TREATMENTS
There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.
SYNTHETICS
Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.
IMITATIONS
Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.
WHY WE LOVE THIS GEMSTONE
1
Stunning Color
In its best colors, iolite can rival the beauty of tanzanite but at a fraction of the cost.
2
Phenomenal
Usually transparent, iolite sometimes contains inclusions that cause attractive phenomena.
3
IRON
Iolite’s beautiful violet-to-blue hue is due to the presence of iron in its structure.
QUALITY FACTORS
The following factors combine to determine an iolite’s value.
COLOR
CLARITY
CUT
CARAT WEIGHT
IOLITE QUALITY FACTORS: THE COMPREHENSIVE GUIDE
RESEARCH
Explore sources, gemological research, and the role of gems in history
Sri Lanka: The Gem Island
Peter C. Zwaan , Jun 1, 1982
A Prospectors’ Guide Map to the Gem Deposits of Sri Lanka
C. B. Dissanayake and M. S. Rupasinghe , Sep 1, 1993
RECOMMENDED READING
Gemstone Buying Guide: How to Evaluate, Identify, Select & Care for Colored Gems
Colored Gemstones: The Antoinette Matlins Buying Guide
