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Tanzanite bracelet


Tanzanite stone

A pale-color transparent mineral that has been used as a Gemstone. Tanzanite is a variety of Zoisite composed of calcium aluminum silicate. Blue gem-quality stones were discovered in Tanzania in 1967. Tanzanite may be colorless, yellow-green, brown or bluish purple and refract flashes of blue, magenta and yellow. Most crystals are greenish gray and contain traces of Vanadium. These stones are commonly heat treated (600-700C) to produce a strong sapphire blue color gem.

Synonyms and Related Terms

zoisite; sorosilicate; Tansanit (Deut.); tanzanita (Esp.); tanzanite (Fr.)

IR spectrum of tanzanite from RRUFF
Raman spectrum of tanzanite from RRUFF

Physical and Chemical Properties

  • Orthorhombic crystal system with prismatic crystals, massive to columnar
  • Luster = vitreous to pearly
  • Cleavage = perfect in one direction
  • Fracture = uneven to conchoidal
  • Streak = white to colorless
  • Mohs Hardness = 6.0 - 6.5
  • Density = 3.2-3.4 g/ml
  • Refractive index = 1.691-1.700
  • Birefringence = 0.008 - 0.013
  • Pleochroism = Strong; dichroism or trichroism, usually blue, purplish red and greenish yellow
  • Fluorescence = inert


Properties of Common Gemstones

Resources and Citations

  • Gem Identification Lab Manual, Gemological Institute of America, 2016.
  • Mineralogy Database: Zoisite
  • R.F.Symmes, T.T.Harding, Paul Taylor, Rocks, Fossils and Gems, DK Publishing, Inc., New York City, 1997
  • Encyclopedia Britannica, http://www.britannica.com Comment: "tanzanite" [Accessed 28 Sept. 2005].
  • C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
  • Wikipedia: Tanzanite (Accessed Sept. 28, 2005 and Dec 2022)
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998