Tanzanite is the blue/purple variety of the mineral zoisite which was discovered in the Meralani (Merelani) Hills of Northern Tanzania in 1967, near the city of Arusha. It is a popular and valuable gemstone when cut. Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet, and burgundy depending on crystal orientation. Tanzanite in its rough state is usually a reddish brown color. And as such is heated to 600 °C in a gemological oven to bring out the classic blue violet of the stone.
Manuel de Souza, a Goan tailor and part-time gold prospector living in Arusha (Tanzania), found transparent fragments of vivid blue and blue-purple gem crystals on a ridge near Mererani, some 40 km southeast of Arusha. He decided that the mineral was olivine (peridot) but quickly realized that it was not, so he took to calling it "dumortierite", a blue non-gem mineral. Shortly thereafter, de Souza showed the stones to John Saul, a Nairobi-based consulting geologist and gemstone wholesaler who was then mining aquamarine in the region around Mount Kenya. Saul, with a Ph.D. from M.I.T., who later discovered the famous ruby deposits in the Tsavo area of Kenya, eliminated dumortierite and cordierite as possible I.D.s and sent samples to his father, Hyman Saul, vice president at Saks Fifth Avenue in New York. Hyman Saul brought the samples across the street to the Gemological Institute of America who correctly identified the new gem as a variety of the mineral zoisite. Correct identification was also made by mineralogists at Harvard, the British Museum and Heidelberg University, but the very first person to get the identification right was Ian McCloud, a Tanzanian government geologist based in Dodoma.
While the story was quickly denounced by many tanzanite dealers, information from the story was widely reported in other media sources. Michael Nunn, president of South African gem company and leading tanzanite mining firm Afgem, dismissed WSJ's article as an unsubstantiated report.
Yet some previous and later U.S. investigations showed that Wadih El-Hage, thought to be a senior aide to Osama bin Laden, moved to Kenya in 1994, where he founded a business called Tanzanite King and helped to run Kenya's al-Qaeda cell..
Following the WSJ's story of al-Qaeda's involvement with tanzanite, Tiffany & Co., Zale Corp., QVC, and Walmart, which combined make up the world's largest market for tanzanite, halted tanzanite sales. Tanzanian officials reported a 70% decline in industry and miner earnings.
In February 2002, at a tanzanite dealer summit, Mike O'Keefe, officer of East African affairs for the State Department, said the U.S. had no evidence of current al-Qaeda funding through tanzanite sales. The State Department also suggested that El-Hage only sold a 'small amount' of Tanzanite. Tanzanian officials also announced police sweeps to remove illegal miners, and a plan to track gems from miners to traders to retailers. As confidence was restored, Zale announced a resumption of tanzanite sales in May, 2002, and was gradually followed by other marketers.
In June 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. publicly announced that they had taken control of the portion of the tanzanite deposit known as "C-Block" (the main deposit is divided into 5 blocks). Over the next year, this company established a De Beers-like control over the tanzanite market, restricting distribution to a handful of processors referred to as "SightHolders. The company is also increasing its control of all newly mined tanzanite by purchasing a large portion of the production coming from the operations of the independent miners working in the area. This is the first time that a colored gemstone has been controlled in this way. Prices for rough material on the open market have increased steadily for the last several years as the company has solidified its control of the market. 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 22cm x 8cm x 7cm.
The mining of tanzanite nets the Tanzanian government approximately USD20 million annually. The finished gems later being sold mostly on the US market for sales totaling approximately USD500 million annually.
The new system's color-grading scales divide tanzanite colors into two different hues, blue violet and violet blue.
Each has 10 saturation levels
This grading system is not yet accepted throughout the trade. The world's most prestigious laboratory, the GIA, still uses a different system. The world's most recognised laboratories have yet to reach consensus on terms used for grading tanzanite although the top gradings on most systems will be similar.
Tanzanites are usually treated to produce colors that include bluish-purple, violet-blue as well as pure blue. . More recently coated Tanzanites were discovered and tested by the AGTA and AGL laboratories. A thin layer of coatings was applied to improve the color of the Tanzanite.