Tanzanite Value, Price, and Jewelry Information


tanzanite - gold Celtic ring
Blending 14k yellow and white gold creates great contrast in this Celtic-inspired design. The yellow gold setting complements the purple-blue tanzanite perfectly. A low-profile bezel setting ensures the tanzanite is well protected and unlikely to snag with daily wear. © CustomMade. Used with permission.

Tanzanite has had a rapid rise to prominence among jewelers and gem enthusiasts. Although naturally reddish brown, this transparent zoisite variety achieves a stable, beautiful blue to violet color wth heat treatments.

Tanzanite Value

In general, tanzanites showing more blue are valued higher than those showing more violet. Medium dark colors are the ideal. Custom cuts add value. As always, size and clarity have a strong effect on prices. Large clean rough is extremely scare. Ultra-rare cat's eye tanzanites are highly prized.

Among other varieties of zoisites, extremely rare green zoisites are highly sought by collectors. These are sometimes confusingly referred to as green “tanzanite.”

See our tanzanite buying guide for more detailed value information.

tanzanite and zoisite
Tanzanite colors (and a green zoisite). Photo courtesy of Barbara Smigel, Artistic Colored Stones.

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Tanzanite Value via Gem Price Guide
Top Color: vB 6/5
Faceted .5 to 1 carat 1 to 3 carats 5 carats plus
SI to Clean to /ct to /ct to /ct

See the entire Gem Price Guide.

Start an IGS Membership today for full access to our price guide (updated monthly).

Tanzanite Information

DataValue
NameTanzanite
Is a Variety ofZoisite
Crystallography Orthorhombic
Refractive Index See "Identifying Characteristics" below.
Colors Gem-quality zoisites can be gray, green, brown, pink, or yellowish. Thulite can be pink. With heating, tanzanite can be blue to violet.
Luster Vitreous
Fracture Conchoidal to Uneven; Brittle.
Hardness 6 - 7
Specific Gravity See "Identifying Characteristics" below.
Birefringence See "Identifying Characteristics" below.
Cleavage Perfect
Dispersion 0.019 (tanzanite).
Heat SensitivityYes
Luminescence Thulite (pink zoisite) from Nevada is sometimes medium pale brown in SW. Also thulite from North Carolina is orangey-yellow in LW.
Wearability Good
Enhancements Virtually all tanzanite is heat treated
Special Care InstructionsAvoid rough treatment
Transparency Tanzanite is transparent. Other gem-quality zoisites may be transparent to opaque.
Absorption Spectrum Tanzanite: broad absorption in the yellow-green centered at 595 nm, weak bands at 528 and 455 nm, and a few weak lines in the red.
Phenomena Chatoyancy (rare, tanzanite).
Birthstone Tanzanite: December (Modern).
FormulaCa2Al3(SiO4)3(OH)
Pleochroism Very strong. See "Identifying Characteristics" below.
Optics See "Identifying Characteristics" below.
EtymologyZoisite is named after Baron Sigmund Zois, who presented the first specimens of the material to Abraham Gottlob Werner, the great mineralogist. Thulite is named after Thule, an ancient name for Norway. Anyolite comes from the Masai anyoli for “green.” Tanzanite is the Tiffany & Co. trade name for blue zoisite, named after the country of origin, Tanzania.
OccurrenceZoisite occurs in calcareous rocks such as metamorphosed dolomites and calcareous shales subjected to regional metamorphism.
Inclusions Zoisite may contain fingerprints, healed cracks, and growth tubes. Minerals found included in tanzanite include actinolite, graphite, and staurolite.
7 carat Blue-Violet Tanzanite, re-polished by Daniel Stair
7-ct blue-violet tanzanite, re-polished by Daniel Stair. © Dan Stair Custom Gemstones. Used with permission.

Comments

Before the discovery of tanzanite, the known varieties of zoisite made little impact on the gem market. Discovered in the shadow of Mt. Kilimanjaro in 1967, tanzanites show both dramatic color change and pleochroism. In natural light, tanzanites can appear an almost sapphire blue. In fluorescent light, they may appear more violet or amethyst-like. Naturally trichroic, these gems can show blue, red-violet, and yellow-green colors when viewed through each of its three crystal axes.

Their most coveted property, however, is their blue to violet color. Although Mother Nature very rarely produces a blue to violet stone in the rough (via the slow heat of the Sun), almost all tanzanites must receive artificial heat treatments to achieve that coveted color. Typically, they’re heated to about 500-600º C or 932-1,112º F.

Other Zoisite Gem Varieties

Tanzanite will certainly appeal to those interested in a truly modern gemstone. However, other gem-quality varieties of zoisite deserve mention, too.

Zoisite

Tanzanites include only blue to violet zoisites. Thus, transparent, gem-quality zoisites in any other color should be called zoisites.

tanzanite - yellow zoisite
“Zoisite,” faceted “wine-yellow” specimen, 1.44-ct, Tanzania, by DonGuennie. Licensed under CC By-SA 4.0.

Thulite

The national gemstone of Norway, this pink, translucent to opaque material can make beautiful cabochons. Faceted pieces are rare. Trade names for thulite include unionite and rosaline.

tanzanite - thulite
“Thulite,” earrings, Kitimat, British Columbia, Canada, by pensondesignergems. Licensed under CC By 2.0.

Anyolite

This lapidary rock contains chrome-rich green zoisite, black hornblende, and large, but opaque, ruby. Gem cutters can make cabochons and carvings from this material. This material is also known as ruby-in-zoisite.

tanzanite - anyolite
“Anyolite,” carved ball, 120 mm, Tanzania, by Adam Ognisty. Licensed under CC By-SA 2.0.

Identifying Characteristics

Optics and Specific Gravity

  Tanzanite Zoisite Thulite
Specific Gravity 3.35 3.15-3.38 3.09
Optics      
a 1.692 1.685-1.705 1.695
β 1.693 1.688-1.710
γ 1.7 1.697-1.725 1.701
2V (+) (+) 0-60° (-)
Birefringence 0.009 0.004-0.008 0.006

Pleochroism

Tanzanite

  • (Violet color) Reddish purple/blue/yellowish brown.
  • (Blue Color) Blue/red-violet/yellow-green.

Thulite

  • Pale pink/ colorless/yellow.
  • Dark pink/pink/yellow.

Above, this strongly trichroic tanzanite crystal shows blue, purple, and red/maroon along different axes. Crystal 3.3 x 3.1 x 1.5 cm, Merelani Mines, Tanzania. © Rob Lavinsky, www.iRocks.com. Used with permission.

Synthetics

To date, synthetic tanzanite is unknown. However, many simulants (imitations) do exist. Consult our buying guide for more information.

Enhancements

Assume all blue to violet tanzanites have received heat treatment. This is a stable treatment.

faceted tanzanite - unheated
Unheated tanzanite, showing natural color range (~ 0.5 to 5). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Sources

Tanzanite

The sole source of tanzanite is the Merelani Hills in the Lelatema Mountains, Tanzania. The mines here produce fine blue to violet crystals, up to large size, and often gemmy.

Anyolite

Longido, Tanzania produces deep green crystals, colored by chromium, with ruby crystals.

Thulite

  • United States: California; Nevada; North Carolina; Washington.
  • Canada; Greenland; Japan; Norway.
thulite - Norway
Zoisite: Thulite, Norway (each specimen ~ 2 inches across). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Gem-Quality Zoisite

Other sources of gem-quality zoisites include:

  • United States: Massachusetts; South Dakota; Wyoming (greenish-gray material, sometimes tumble polished for jewelry).
  • Austria; Finland; Germany; Baja California, Mexico; Pakistan; Russia; Scotland.

Stone Sizes

Tanzanite, alone of all zoisite varieties, reaches large large sizes in faceted gems. Rough tanzanite crystals weighing hundreds of carats have been found.

  • Smithsonian Institution (Washington, DC): 122.7 (blue, tanzanite, Tanzania); 18.2 (blue cat’s eye tanzanite, Tanzania).
  • Private Collection: 220 (blue, tanzanite, Tanzania).

Care

For faceting and gem design recommendations for tanzanites and other zoisite varieties, read this article.

Although tanzanite hardness may range from 6 to 7, its tendency to cleave and brittleness pose hazards for daily wear. Reserve these gems for occasional pieces or use protective settings. Clean them only with a soft brush, mild detergent, and warm water. For more recommendations, consult our gemstone jewelry care guide.

tanzanite - 26.54 cts
Tanzanite. (26.54). Photo © Joel E. Arem, PhD, FGA. Used with permission.