triangle-cut tanzanite
triangle-cut tanzanite

Tanzanite (Zoisite) Value, Price, and Jewelry Information


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 with heat treatments.

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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 with heat treatments.

triangle-cut tanzanite
Medium violet-blue, triangle-cut tanzanite, 1.62 cts, 8 mm, Tanzania. © The Gem Trader. Used with permission.

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Tanzanite (Zoisite) Value

.5 to 1 carat
SI to Clean
to /ct
1 to 3 carats
SI to Clean
to /ct
5 carats plus
SI to Clean
to /ct

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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.

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.

cat's eye tanzanite
Violetish blue cat’s eye tanzanite with a very sharp eye, 0.79 cts, 5 mm, Tanzania. © The Gem Trader. Used with permission.

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.

unheated green zoisite - Tanzania
Unheated green, oval brilliant-cut zoisite, 0.94 cts, 7.6 x 4.9 mm. Tanzania. © The Gem Trader. Used with permission.
Tanzanite (10.18). Photo © Joel E. Arem, PhD, FGA. Used with permission.

What Color is Tanzanite?

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 prized color. Typically, they're heated to about 500-600º C or 932-1,112º F.

7 carat Blue-Violet Tanzanite, re-polished by Daniel Stair
Blue-violet tanzanite, 7 cts, re-polished by Daniel Stair. © Dan Stair Custom Gemstones. Used with permission.

What is "Fancy Color Tanzanite?"

Tanzanites are the most well-known members of the zoisite gem species. Not surprisingly, some vendors will try to associate zoisites of other colors with the tanzanite name. You may encounter green, yellow, and pink zoisites sold as "fancy color tanzanites." Even though these are rare, beautiful colors, the tanzanite name has more caché with the general public and may command higher prices.

By definition, tanzanites are blue to violet zoisites, whether they receive heat treatment or not. Non-blue zoisites should simply be called zoisites.

zoisites
Zoisites in various colors (5.5, 9.9, 2.72, 9.5, 2.05). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Other Zoisite Gem Varieties

Tanzanites will certainly appeal to those interested in truly modern gemstones. Jewelers have even designated this gem a modern option for the December birthstone. However, other gem-quality varieties of zoisite deserve mention, too.

Zoisite

Transparent, gem-quality zoisites occur in many colors and can make beautiful gemstones.

tanzanite - yellow zoisite
Faceted, "wine yellow" zoisite, 1.44 cts, Tanzania. Photo 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.

thulite earrings
Thulite earrings, Kitimat, British Columbia, Canada. Photo by pensondesignergems. Licensed under CC By 2.0.

Anyolite (Ruby-in-Zoisite)

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.

anyolite
Carved anyolite ball, 120 mm, Tanzania. Photo by Adam Ognisty. Licensed under CC By-SA 2.0.

Identifying Characteristics

Optics and Specific Gravity

TanzaniteZoisiteThulite
Specific Gravity3.353.15-3.383.09
Optics
a1.6921.685-1.7051.695
β1.6931.688-1.710-
γ1.71.697-1.7251.701
2V(+)(+) 0-60°(-)
Birefringence0.0090.004-0.0080.006

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.
  • tanzanite crystal - blue
  • tanzanite crystal - purple
  • tanzanite crystal - red/maroon

    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.

    Is There Lab-Created Tanzanite?

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

    Is All Tanzanite Enhanced?

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

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

    Zoisite 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.

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

    There are four "blocks" of tanzanite-producing mines in Tanzania. However, despite claims that "D-Block" tanzanites have superior quality, there's no difference in tanzanite quality between these mines and no way to distinguish materials from specific mines.

    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
    Thulites, Norway (each specimen about 2 inches across). Photo © Joel E. Arem, PhD, FGA. Used with permission.

    Gem-Quality Zoisite

    Other sources of gem-quality zoisites include the following:

    • United States: Massachusetts; South Dakota; Wyoming (greenish-gray material, sometimes tumble polished for jewelry).
    • Austria; Finland; Germany; Baja California, Mexico; Pakistan; Russia; Scotland.
    green zoisite - Pakistan
    Gray-green, rectangular cushion-cut zoisite, 2.34 cts, 8.7 x 7 mm, Pakistan. © The Gem Trader. Used with permission.

    How Large Can Tanzanites Get?

    Tanzanites, alone of all zoisite varieties, can reach large sizes in faceted gems. Rough 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).

    Caring for Your Tanzanite Jewelry

    For faceting and gem design recommendations for tanzanites and other zoisite varieties, consult 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 and diamond jewelry
    Tanzanite and diamond jewelry. Photo © Joel E. Arem, PhD, FGA. Used with permission.

    Joel E. Arem, Ph.D., FGA

    Dr. Joel E. Arem has more than 60 years of experience in the world of gems and minerals. After obtaining his Ph.D. in Mineralogy from Harvard University, he has published numerous books that are still among the most widely used references and guidebooks on crystals, gems and minerals in the world.

    Co-founder and President of numerous organizations, Dr. Arem has enjoyed a lifelong career in mineralogy and gemology. He has been a Smithsonian scientist and Curator, a consultant to many well-known companies and institutions, and a prolific author and speaker. Although his main activities have been as a gem cutter and dealer, his focus has always been education. joelarem.com


    Barbara Smigel, PhD. GG

    Barbara Smigel is a GIA certified gemologist, facetor, jewelry designer, gem dealer, gemology instructor and creator of the well-regarded educational websites acstones.com and bwsmigel.info.


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