Gemstone encyclopedia
Tanzanite — meaning, history and vintage jewelry
Tanzanite is the violet blue variety of zoisite, found in 1967 in a single area near Mount Kilimanjaro in Tanzania and nowhere else on earth. Because it was discovered so recently, tanzanite cannot appear in genuinely antique jewelry: any piece described as Victorian or Art Deco with tanzanite is misdescribed. It is 6 to 7 on the Mohs scale with cleavage, so it should never be cleaned ultrasonically.
What tanzanite is
Tanzanite is strongly pleochroic, showing blue, violet and a burgundy tone depending on the angle. Cutters choose whether to face up bluer or more violet, and that decision drives the price.
Nearly all tanzanite is heated to remove a brownish component, a stable and universally accepted treatment. Because the single known source is small, supply is finite in a way few gemstones are.
Color and hardness
- Species
- Zoisite
- Color
- Violet blue to blue violet, with strong pleochroism
- Mohs hardness
- 6 to 7
- What that means in wear
- Moderate hardness with one direction of cleavage, so tanzanite needs a protective setting and careful handling.
How to care for tanzanite
This is one of our delicate stones. Pearls, opal, emerald, turquoise, coral, moonstone and tanzanite must never go near an ultrasonic or steam cleaner, and they should be kept away from perfume, cosmetics and household chemicals.
- Never use ultrasonic or steam cleaning; both risk the cleavage and heat sensitivity.
- Warm soapy water and a soft cloth are enough.
- Choose bezel or protected settings for rings, and avoid sharp knocks.
Our full house rules, including what the one year warranty does and does not cover, are in the care & warranty guide.
History and symbolism
Discovered in 1967 and named and marketed by Tiffany & Co., which chose the name over the mineralogical blue zoisite. It is one of the few genuinely twentieth century additions to the standard gem repertoire.
Transformation and new perspective, associations that grew with the stone's late twentieth century marketing rather than from older tradition. It was added to the December birthstone list in 2002.
Tanzanite in vintage and antique jewelry
Late twentieth century estate jewelry, especially 1980s and 1990s gold and platinum cocktail rings and pendants. It belongs in the estate and designer world rather than the antique one.
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Tanzanite pieces in our collection
Every curated vintage, antique and estate piece is one of a kind and checked by our jewelry specialists in the Netherlands. If nothing is right today, we will look for it.
Frequently asked questions
- Can a piece be both antique and set with tanzanite?
- No. Tanzanite was discovered in 1967, so it can only appear in later twentieth century and modern jewelry, or in an antique mount that has been re-stoned.
- Is tanzanite heated?
- Almost always. Heating removes a brown component and produces the violet blue the stone is known for. It is permanent and standard.
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