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Smithsonian National Museum of Natural History
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Cordierite (var. iolite)

Oval-cut dark blue cordierite weighing 63.83 ct.
Photo by Ken Larsen. 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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