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Iolite

According to legend, Vikings used iolite slices to reduce glare when checking the sun’s position.

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Pleochroism

Iolite displays different colors when viewed in different directions.

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Transparency

Iolite is usually faceted to highlight its transparency.

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Fine color

Iolite’s finest blue color can rival tanzanite’s vivid hue.

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Fashioning

Iolite’s pleochroism can be a challenge for cutters.

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Natural

Iolite is not treated for color enhancement.

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Cordierite

The mineral cordierite is known as iolite in the jewelry industry.

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Tools

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.

Iolite Description Iolite History and Lore

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

Where It’s Found

map

Treatments

There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.

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Synthetics

Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.

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Imitations

Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.

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gem love

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

quality factors

Iolite’s most desirable colors are in the violetish blue to fine blue range.

Clarity

quality factors

Properly oriented inclusions can cause cat’s-eyes and aventuresence.

Cut

quality factors

Iolite is most often faceted, as this cutting style serves to highlight its fine transparency.

Carat Weight

quality factors

Fine-quality faceted iolites over five carats are relatively rare in the market.

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 Read Article

A Prospectors’ Guide Map to the Gem Deposits of Sri Lanka

C. B. Dissanayake and M. S. Rupasinghe , Sep 1, 1993 Read Article