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.
