Gem Profile- Tanzanite

by Judy Ellis

Tanzanite is the first stone to be added to the AGTA Birthstone list in 90 years, being assigned to December as the modern birthstone, in October 2002.

The Discovery of Tanzanite

Tanzanite was discovered by a tailor named Manuel d'Souza in Tanzania in July 1967.

On July 7th, he was prospecting for gold near Lake Victoria. He found a blue stone on the ground and thought it might be sapphire, September's birthstone.

Tests ruled out sapphire, olivine (peridot), and dumortierite.

Ian McCloud, a government geologist, correctly identified it as a form of zoisite.

A new name emerged: Skaiblu, a Swahili term for the stone's "sky blue" color.

Gail Maas wire wrapped this opaque tanzanite cabochon with gold wire and crystal beads.

Tanzanite shows a beautiful deep blue-purple hue.

Every tanzanite on the market has been heated to create this color.

Rough stones start as rusty brown. Heating to 550 to 700 degrees Fahrenheit brings out the blue-violet shade.

Heated tanzanite becomes dichroic, like iolite. It appears blue in some lights and purple in others, but never colorless.

Maasai herders noticed the effect decades before d'Souza.

Wild prairie fires from lightning heated brown zoisite crystals, turning them deep blue.

Maasai men gave wives tanzanite jewelry after their first child's birth. Tanzanite dealers encouraged foreign buyers to adopt this tradition.

Tanzanite is a variety of zoisite, a calcium aluminum hydroxy silicate, with a hardness of 6.5.

It's officially called blue zoisite. Tiffany & Co.'s Henry B. Platt coined "tanzanite," predicting its rising value and rarity.

Tiffany launched it in October 1968 with the slogan: "Tanzanite is only found in two places in the world: Tanzania and Tiffany's."

Demand remains high today. US sales reach about $500 million yearly.

Tanzania formed in 1964 from Tanganyika and Zanzibar. It's in central-east Africa, home to Mount Kilimanjaro, Lake Victoria, and Serengeti National Park.

Tanzanite supply is controlled like diamonds by De Beers.

The Tanzanian government nationalized the mines. It bans rough exports to India, so Tanzanians cut most gems.

TanzaniteOne leads production. It controls mining, cutting, and distribution.

This cubic zirconia matches tanzanite's color at a fraction of the cost.

Unlike diamonds, tanzanite supply is truly scarce. Some say it is 1,000 times rarer than diamond. Mines may play out in 10 to 15 years.

Tanzanite is found in only a 4 square kilometer area near Mount Kilimanjaro's base.

Other zoisite forms come from nearby Kenya, like anyolite, and Norway, like thulite. Tanzanian zoisite also appears in rare pink, green, orange, or yellow, but is not called tanzanite.

Tanzanite rates 6.5 on the Mohs scale.

It's solid but not ideal for rings or items prone to bumps and scratches.

Clean gently with a soft brush and warm soapy water.

Avoid ultrasonic or steam cleaners. Store away from other jewelry to prevent scratches.

Do not change its temperature quickly. Sudden shifts can cause fractures or cracking.

Tanzanite Buying and Imitations

Quality tanzanite has no inclusions visible to the naked eye.

Tanzanite with visible inclusions sells at much lower prices.

Tanzanion is a trade name for co-doped synthetic Mg₂SiO₄, or synthetic forsterite, per Mindat.org. It mimics tanzanite's intense purplish-blue color. Forsterite belongs to the olivine (peridot) group.

Originally, people thought tanzanite was olivine. Now olivine is man-made to simulate tanzanite.

Joan Madouse wrapped this faceted emerald-cut blue tanzanite quartz stone (20.8 carats) in silver-filled wire.

Some sellers offer tanzanite quartz.

It's likely amethyst (quartz) enhanced to a deep blue-purple color. This material is harder than tanzanite.

Cubic zirconia imitates tanzanite's hue. It rates 8 to 8.5 on the Mohs scale.

Tanzanite aura quartz is aura quartz vapor-treated with chemicals. This creates a blue-purple coating on the original crystal.

Resources & Recommended Reading

Tanzanite on Mindat.org

Tanzanion on Mindat.org

Forsterite on Mindat.org

Tanzanite on Gemsociety.org

Tanzanite on Wikipedia.org

Tanzanite on Gemstone.org

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