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Zoisite (variety: Tanzanite)

Tanzanite is the gem variety of zoisite. It was first discovered in 1967 in Tanzania, hence its name. Tanzanite exhibits the phenomenon of pleochroism, appearing intense blue, violet, or red depending on the direction through which the crystal or gem is viewed. Consequently, the predominant hue of a tanzanite gem depends on the orientation in which it was cut. The most valuable tanzanite is an intense deep blue with violet highlights. It is commonly heated to obtain a more intense, uniform color. This tanzanite gem weighs 122.74 carats and is the largest faceted tanzanite in the National Gem Collection.

Image Number: 95-30165
Catalog Number: G4876
Weight: 122.74 carats
Exchange, W. Lidstrom , 1971


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Smithsonian National Museum of Natural History Department of Mineral Sciences website Credits