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Tanzanite is the blue/purple variety of the mineral zoisite 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. 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.

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 approx. USD $20 million annually, the finished gems later being sold mostly on the US market for sales totalling approx. 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 will be phased in over the next two years, until which time only stones over 0.5 grams are affected.

This is a grave 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 dangerous precedent, leading Tanzania to ban the export of all raw gem material, such as the country's production of tsavorite, diamond and ruby.

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See also: gemstone, mineral list