Tanzanite is the blue and violet variety of the mineral zoisite (a calcium aluminium hydroxyl sorosilicate). The color is caused by small amounts of vanadium. Tanzanite belongs to the epidote mineral group. Tanzanite is only found in Simanjiro District of Manyara Region in Tanzania, in a very small mining area approximately 7 km (4.3 mi) long and 2 km (1.2 mi) wide near the Mererani Hills. Tanzanite is noted for its remarkably strong trichroism, appearing alternately blue, violet and burgundy depending on crystal orientation. Tanzanite can also appear differently when viewed under different lighting conditions. The blues appear more evident when subjected to fluorescent light and the violet hues can be seen readily when viewed under incandescent illumination. In its rough state tanzanite is coloured a reddish brown to clear, and it requires heat treatment to remove the brownish "veil" and bring out the blue violet of the stone. The gemstone was given the name "tanzanite" by Tiffany & Co. after Tanzania, the country in which it was discovered. The scientific name of "blue-violet zoisite" was not thought to be sufficiently consumer friendly by Tiffany's marketing department, who introduced it to the market in 1968. In 2002, the American Gem Trade Association chose tanzanite as a December birthstone, the first change to their birthstone list since 1912.
Geology Tanzanite was formed around 585 million years ago during the mid-Ediacaran period by massive plate tectonic activity and intense heat in the area that would later become Mount Kilimanjaro. The mineral is located in a relatively complex geological environment. Deposits are typically found in the "hinge" of isoclinal folds.
History
Discovery There are many accounts of the discovery of tanzanite, but only one recognised by the government of Tanzania. In January 1967, Jumanne Mhero Ngoma (originally from Same District, Kilimanjaro) stumbled upon the sparkling blue stones at the Mererani hills in the Kiteto District of the former Arusha Region (now Manyara Region). He was issued with a certificate of recognition three years later by then-President Julius Nyerere and a financial reward of Tsh 50,000 for his efforts. In 1984, he was issued with a certificate for scientific discovery by the Tanzania Commission for Science and Technology.
Commercial history
In July 1967, Manuel de Souza, a Goan tailor and part-time gold prospector living in Arusha, found transparent fragments of blue and blue-purple gem crystals on a ridge near Mererani, some 40 km (25 mi) southeast of Arusha. He assumed that the mineral was olivine (peridot) but, after soon realizing it was not, he concluded it was "dumortierite" (a blue non-gem mineral). Shortly thereafter, the stones were shown to John Saul, a Nairobi-based consulting geologist and gemstone wholesaler who was then mining aquamarine in the region around Mount Kenya. Saul, who later discovered the famous ruby deposits in the Tsavo area of Kenya, eliminated dumortierite and cordierite as possibilities, and sent samples to his father, Hyman Saul, vice president at Saks Fifth Avenue in New York City. Hyman Saul took the samples to the Gemological Institute of America which correctly identified the new gem as a variety of the mineral zoisite. Correct identification was also made by mineralogists at Harvard University, the British Museum and Heidelberg University, but the first person to get the identification right was Ian McCloud, a Tanzanian government geologist based in Dodoma. Scientifically called "blue zoisite", the gemstone was renamed as tanzanite by Henry B. Platt, a great-grandson of Louis Comfort Tiffany and a vice president of Tiffany & Co., who wanted to capitalize on the rarity and single location of the gem and thought that "blue zoisite" (zoi′sīt) would not sell well. Tiffany's original campaign advertised that tanzanite could now be found in two places: "in Tanzania and at Tiffany's". From 1967, an estimated two million carats of tanzanite were mined in Tanzania before the mines were nationalized by the Tanzanian government in 1971.
Mining developments In 1990, the Tanzanian government split the tanzanite mines into four sections: Blocks A, B, C and D. Blocks A and C were awarded to large operators, while Blocks B and D were reserved for local miners. In 2005, the government renewed the lease of Block C mine to TanzaniteOne, who paid US$40 million for their lease and mining license. In June 2003, the Tanzanian government introduced legislation banning the export of unprocessed tanzanite to India, and like many gemstones, most tanzanite is cut in Jaipur. The reason for the ban is to attempt to spur development of local processing facilities, thereby boosting the economy and recouping profits. This ban was phased in over a two-year period, until which time only stones over 0.5 grams were affected. In 2010, the government of Tanzania banned the export of rough stones weighing more than one gram. TanzaniteOne Mining Ltd is owned by Richland Resources, but a 2010 law in Tanzania required them to cede 50% ownership of their mining license to the Tanzanian State Mining Company (Stamico). Production in 2011 amounted to 2,400,000 carats (480 kg; 1,100 lb), earning them $24 million. Following the construction of a 24 km (15 mi) perimeter wall around the mines, to improve security and prevent smuggling, production rose from 147.7 kg (325.6 lb) in 2018 to a record 781.2 kg (1,722 lb) in 2019. On 24 June 2020, artisanal miner Saniniu Laizer unearthed two rough tanzanite stones, weighing 11.14 kg (55,700 carats) in total, which he sold to the Tanzanian government's Ministry of Minerals for TSh 7.74 billion (US $3.35 million), breaking the previous record set in 2005 by a 16,839‑carat stone Total reserves of tanzanite are estimated at 109,000,000 carats (21,800 kg; 48,100 lb), according to a report published in 2018. Block C, by far the largest site, has been estimated at 87,100,000 carats (17,400 kg; 38,400 lb) with a Life of Mine (LOM) expected to last until the 2040s.
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