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Smithsonian National Museum of Natural History

Cordierite (var. iolite)

This 63.83ct iolite is the largest cordierite gem in the National Gem Collection.
Photo by Greg Polley. Click to zoom.
Catalog Number NMNH G11434-00
Locality Orissa, India
Weight 63.83 ct

Purchased with funds from the Tiffany & Co. Foundation in 2012.

Iolite is the gem variety of the mineral cordierite. The name “iolite” comes from the Greek word for “violet.” It has also been called “water-sapphire” as it resembles sapphire in color, but it is typically not as saturated in hue and tends to have color zoning. The color of iolite is commonly referred to as “inky,” a dark bluish-purple color, but also varies in color from blue to yellowish gray or brown. The gem is strongly pleochroic, appearing blue, bluish-gray, or grayish-yellow to colorless depending upon the direction from which the stone or crystal is viewed. Most gem cordierite is found in alluvial gravels as water-worn pebbles. It is commonly seen in jewelry today because it often times resembles the color of a tanzanite or a sapphire, but it is much more affordable. This 63.83ct iolite is the largest cordierite gem in the National Gem Collection.

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