Tanzanite

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A fine-colour tanzanite gemstone, featuring an oval mixed cut.

Tanzanite is the blue/purple variety of the mineral zoisite (Ca₂(Al.OH)Al₂(SiO₄)₃) discovered in the Meralani Hills of northern Tanzania in 1967, near the city of Arusha. It is a popular and valuable gemstone when cut, although its durability is somewhat lacking; its tendency to break precludes appropriate use as a ring stone. Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet, and sage-green depending on crystal orientation. However, most tanzanite is subjected to artificial heat treatment to improve its colour: this significantly subdues its trichroism.

Maasai tribesmen discovered Tanzanite in 1967, supposedly after lightning struck and caused a bush fire which heated the raw brown zoisite into the vivid blue-purple. Whether this is true or not is debatable.

Maasai tribes are also said to believe that Tanzanite is the stone of birth because of its blue colour, and they give tanzanite to their wives when they have their first children.

The name tanzanite was a trade name coined by Tiffany & Co. shortly after the gem's discovery, an obvious allusion to its country of origin. This was thought necessary in order to make the stone marketable to the public: the name has since stuck as a varietal designation. Tanzanite's present-day popularity as a gemstone is largely thanks to Tiffany's marketing campaigns. The mining of tanzanite nets the Tanzanian government approximately USD $20 million annually, the finished gems later being sold mostly on the US market for sales totaling approximately USD $500 million annually.

In June of 2003, the Tanzanian government introduced legislation banning the export of unprocessed tanzanite to India (like many gemstones, most tanzanite is cut in Jaipur). The ban has been rationalized as an attempt to spur development of local processing facilities, thereby boosting the economy and recouping profits. This ban was phased in over the next two years, until which time only stones over 0.5 grams were affected.

This is a serious situation for the city of Jaipur, as one-third of its annual gem exports are of tanzanite. Some members of the industry fear the ban will set a precedent, leading Tanzania to ban the export of all raw gem material, including the country's production of tsavorite, diamond and ruby.

In April 2005, a company called TanzaniteOne Ltd. publically announced that they had taken control of the tanzanite mine known as "C-Block". Over the next year, this company established a De Beers-like control over the tanzanite market. This is the first time that a colored gemstone has been controlled in this way. In August 2005, the largest tanzanite crystal was found in the C-Block mine. The crystal weighs 16,839 carats (3.4 kg) and measures 22 cm by 8 cm by 7 cm.

A rough sample of tanzanite.

In February 2006 TanzaniteOne Ltd. announced that they were moving forward with their marketing strategy to make Tanzanite "the" birthstone. They plan to market the rare gem as a stone one would give a child at birth, to celebrate new life.

A tanzanite bracelet.

See also

• mineral list

External links

• Tanzanite - History and Folklore
• http://www.gemstone.org/gem-by-gem/english/tanzanite.html