The Gemstone Iolite

Pear Iolite with Visible Pleochroism

Iolite is the gem variety of the mineral Cordierite. It describes the transparent to translucent form of Cordierite, and it has recently become a popular gemstone. Iolite can be light to deep blue, and usually has a purplish tinge to it. Deeper colored stones are more valuable. Iolite is very affordable and durable, and can be used as a substitute for more expensive blue gemstones such as Sapphire. It is named from the Greek "violet", alluding to the purplish tinge often exhibited by this gemstone.


? Blue, Purple, Gray


? 7 - 7.5

Chemical Formula

? Mg2Al4Si5O18

Mineral Class

? Cordierite

Additional Properties

Crystal System
? Orthorhombic
Refractive Index
? 1.55 - 1.62
Double Refraction
? -0.01
? Transparent to translucent
? 2.6 - 2.7
? Vitreous
Cleavage ? 3,1

All About

Iolite is strongly pleochroic, and will exhibit a different color when viewed at different angles. In fact, it is the most pleochroic gemstone, with this effect being clearly noticeable on all transparent Iolite gemstones. A blue or violet-blue Iolite gemstone will become a duller gray or grayish-yellow when viewed at a different angle. For this reason, care must be taken by gemstone cutters to facet Iolite gemstones so that their colors are oriented with the intense blue or violet showing from the top.


? Iolite is cut into gemstone facets and cabochons, and is used in all types of jewelry, especially rings, earrings, and pendants.

Treatments & Enhancements

? Iolite gemstones are natural and not treated or enhanced.

Iolite Sources

? Iolite gem deposits are Madagascar, Myanmar (Burma), Sri Lanka (Ceylon), India, and Brazil.

Similar Gemstones

? Sapphire - Lacks dichroism, greater hardness.
Kyanite - Rarely transparent, lower hardness, and lacks purplish tinge.
AmethystHas a deeper purple color.

Iolite in the Rough Photos



Copyright © 2024. Minerals.net

View on Full Site