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Henry Platt, former president of Tiffany & Co., described tanzanite's discovery in 1967 as THE most important gemstone find in 2000 years! This single 5-mile strip of land in Tanzania remains the only commercially viable source of this stone that has become one of the world's most sought-after and admired gems. Tanzanite is a relatively new gemstone in the world of gemology and jewelry, and though its history is brief, it is no less illustrious than many ancient gems. Tanzanite is a single-source gemstone that is a thousand times rarer than diamond, and is only gaining popularity.

Tanzanite Polished
Tanzanite Classification
Common Name Tanzanite
Species Zoisite
Tanzanite Optical Properties
Transparency Transparent - Translucent
Dispersion Strength: Weak Fire Value: 0.021
Refractive Index 1.691-1.700
Birefringence 0.008-0.013
Optic Character Biaxial
Optic Sign Positive
Polariscope Reaction Doubly Refractive (DR)
Fluorescence SWUV: Inert
LWUV: Inert
Pleochroism Trichroic, (in unheated gems) strong blue, purplish red and greenish yellow; (in heated gems) strong blue, slightly lighter blue, and purple
Tanzanite Characteristic Physical Properties
Hardness 6.5
Streak White
Specific Gravity 3.100-3.450 Range:0.1/-0.25 Typical:3.350
Toughness Varies
Inclusions Tanzanite is a type I clarity stone. Stones rarely contain needles, chromite inclusions, growth and etch tubes.
Luster Vitreous
Stability Good
Fracture Conchoidal, Uneven
Cleavage Perfect, in one direction, Good, in one direction
Tanzanite Chemistry & Crystallography
Chemical Name calcium aluminum silicate with hydroxyl (OH)
Chemical Formula Ca2Al3(SiO4)3(OH)
Crystal System Orthorhombic
Chemistry Classification Silicate

Tanzanite Colors

  • Purple Tanzanite Purple
  • Bi-color Tanzanite Bi-color
  • Blue Tanzanite Blue
  • Purple Tanzanite Purple

Tanzanite Spectra

Tanzanite Spectra
AH Tanzanite

A large tanzanite of fine deep color provided this unpolarized spectrum . The main feature is the intense broad absorption band from 560nm to 630nm. Moderate band is also seen centered at 520nm. and a weak narrow line at 450nm. Very little variation was seen between the blue and violet rays other than a weaker absorption in the blue ray.

Tanzanite Spectra

Color due to vanadium. An untreated tanzanite retains its trichroism with a greenish overtone in the body color. A moderate absorption is seen from 540nm. to 590nm. with no transmission below 440nm. nor above 680nm. A weak narrow absorption line can be seen at 440nm.

Jewelry Television acknowledges the significant scientific contributions of John S Harris, FGA to the study of gemstone spectra and with deep appreciation to him, acknowledges the use of his images and related notes about gemstones and their spectra in the educational materials on this website.

Countries of Origin

Tanzania, United Republic Of


Tanzanite is a lush, opulent bluish-violet... or it's a vibrant violet-blue... or it's a regal violet-purple. This stunning stone is pleochroic - a fancy gemstone word that means it reflects different colors when viewed at different angles. This allows cutters to fashion gems with a range of color in a single piece. Tanzanite is a zoisite and somewhat brittle. It's a 6 ½ on the Mohs hardness scale. It's a wearable stone you can enjoy for many years to come. Within one year of its discovery tanzanite had set the gem world spinning. In 2002, it was named an alternative birthstone for December.


Normal, gentle handling and avoid extreme temperature changes. Gentle wear, avoid ultrasonics and high heat in CVD coated stones.

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Related Videos

More About Tanzanite

Among the Masai tribesman it is said that a magical fire, lit from the heavens, swept through the area at the base of Mount Kilimanjaro. What made the fire magical? It had the power to transform the brown rocks found on the ground into brightly colored purple-blue stones. When the dust cleared away, and the blue stones were found, it was agreed that the fire brought good fortune to the people. Why do we love tanzanite? It's a spectacular blue, pleochroic, and found in only one place in the world. Oh... and it's many times rarer than diamonds. Wow.

Tanzanite Gemstone

Sisk Gemology Reference

Showcasing 200 gemstones in over 1,000 pages and accompanied by more than 2,000 photos, The Sisk Gemology Reference is a must-have in every collector’s library. Each comprehensive, three-volume set features state-of-the-art photography, detailed illustrations, and scientifically precise descriptions to create an entrancing experience for gemstone amateurs and afficionados alike.

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Tim Matthews


Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.