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Tiffany - Schlumberger Tanzanite and Diamond Brooch.
Photo Courtesy of Lang Antiques.

Tanzanite is a purplish blue variety of zoisite. Discovered in 1967 in Tanzania, it was introduced to the jewelry world in 1968 as Tanzanite by Tiffany & Co.

Gemological Information for Tanzanite

Color: Blue, Violet, Bluish-Purple
Crystal Structure Orthorhombic
Refractive Index: 1.691 to 1.700
Durability: Fair to Poor
Hardness: 6 to 7
Family: Zoisite
Similar Stones: Benitoite, Amethyst
Treatments: Heated to Produce Purplish-Blue from gray or brown
Country of Origin: Tanzania

Tanzanite Care

Ultrasonic Cleaning: Unsafe
Steam Cleaning: Unsafe
Warm Soapy Water: Safe
Chemical Attack: Attacket by Hydrofluoric and Hydrochloric Acids
Light Sensitivity: Stable
Heat Sensitivity: Fuses under a jeweler's torch


  • Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 262-264.
  • Newman, Harold. An Illustrated Dictionary of Jewelry, New York: Thames and Hudson, 1981. Pp. 300.
  • Schumann, Walter. Gemstones of the World, New York: Sterling Publishing, Co., 1977. Pp. 160.