Iolite

saf-ahyuh r

Iolite is the gem-quality blue or blue-violet variety of cordierite. While iolite enjoyed popularity in jewelry in 18th-century Europe, this naturally beautiful gemstone is relatively new to today's jewelry market, and is regaining popularity with the public. Because of its varying levels of hardness and strong pleochroism, iolite is one of the most difficult stones for lapidaries to fashion. It must be cut in certain directions to take advantage of the best color, which can be tough when the shape of the rough doesn't lend itself to cutting in that same direction.

Iolite Polished
Iolite Classification
Common Name Iolite
Species Iolite
Iolite Optical Properties
Transparency Transparent - Translucent
Dispersion Strength: Moderate Fire Value: 0.017
Refractive Index 1.542-1.551
Tolerance:(+0.045/-0.011)
Birefringence 0.008-0.012
Optic Character Biaxial
Optic Sign Negative
Polariscope Reaction Doubly Refractive (DR)
Fluorescence SWUV: Inert
LWUV: Inert
Pleochroism Trichroic, violet, colorless to yellow, and light grayish blue
Iolite Characteristic Physical Properties
Hardness 7-7.5
Streak White
Specific Gravity 2.560-2.660 Range:+/-0.05 Typical:2.610
Toughness Fair
Inclusions Iolite is a type II clarity stone. Sometimes apatite, hematite, iron oxide, magnetite, mica and rutile, inclusions are seen. Bloodshot iolite is the adventuresent variety with red plate like hematite, iron oxide inclusions along with goethite.
Luster Vitreous
Fracture Conchoidal, Uneven
Cleavage Good, in one direction, Poor, in two directions
Iolite Chemistry & Crystallography
Chemical Name magnesium aluminum silicate
Chemical Formula Mg2Al4Si5O18
Crystal System Orthorhombic
Chemistry Classification Silicate

Iolite Colors

  • Blue Iolite Blue
  • Purple Iolite Purple
  • Green Iolite Green
  • Colorless Iolite Colorless

Iolite Spectra

Jewelry Television acknowledges the significant scientific contributions of John S Harris, FGA to the study of gemstone spectra and with deep appreciation to him, acknowledges the use of his images and related notes about gemstones and their spectra in the educational materials on this website.

Alternate Names

Cordierite, Dichroite, Bloodshot Iolite

Countries of Origin

Tanzania, United Republic Of; Unknown; Sri Lanka; China; Brazil; Zimbabwe; Madagascar; India

Shop Iolite

Related Videos

Sisk Gemology Reference

Showcasing 200 gemstones in over 1,000 pages and accompanied by more than 2,000 photos, The Sisk Gemology Reference is a must-have in every collector’s library. Each comprehensive, three-volume set features state-of-the-art photography, detailed illustrations, and scientifically precise descriptions to create an entrancing experience for gemstone amateurs and afficionados alike.

Shop Now

 
Tim Matthews

Author

Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.