The physical characters can make cutting process difficult due to the problem of selecting the perfect color. The finished color of the gemstone will vary depending on how the table cut reflects the light. [35] Imitation and cobalt-coated tanzanite [ edit ] Eugenia Sheppard (3 October 1968). Section B. "Inside Fashion: Something new at Tiffany's is Tanzanian blue gem". Durham Morning Herald (finaled.). Durham, N.C.: The Durham Herald Co.: 2B. OCLC 9519676. Muchira, John (24 May 2013). "TanzaniteOne cedes 50% stake to State as new law takes effect". Mining Weekly. As of 2020 [update], tanzanite has never been successfully synthesized in a laboratory, so all genuine tanzanite is naturally occurring. However, because of its rarity and market demand, tanzanite has been imitated in several ways. Among the materials used for this are cubic zirconia, synthetic spinel, yttrium aluminium garnet, and colored glass. A test of the stone with a dichroscope can easily distinguish these from genuine tanzanite, as only tanzanite will appear doubly refractive: the two viewing windows of the dichroscope will display different colors (one window blue, the other violet) when viewing genuine tanzanite, while the imitation stones are all singly refractive and will cause both windows to appear the same color (violet). [36] Coatings: a new Tanzanite treatment uncovered". farlang.com. Farlang's Gem and Diamond Foundation; Gemological Association of Great Britain; German Gemological Association; Netherlands Gemological Laboratory. 25 May 2008.

Pleochroism has a physical property in which the gemstone will appear to have multiple colors based on the angle of the light hitting the stone. Tanzanite is a pleochroic gemstone. Most Tanzanite are blue when viewed from one direction but can vary from violet to red when seeing from a different angle. National Environment Statistics Report - Tanzania Mainland" (PDF). National Bureau of Statistics (NBS) (Tanzania). June 2018 . Retrieved 27 June 2020. Weldon, Robert. "An introduction to gem treatments". gia.edu. Gemological Institute of America, Inc. Briggs, Philip; McIntyre, Chris (2013). Tanzania Safari Guide: With Kilimanjaro, Zanzibar and the Coast. Bradt Travel Guides. p.104. ISBN 978-1-84162-462-4.

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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 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. [ citation needed] In 2010, the government of Tanzania banned the export of rough stones weighing more than one gram. [19] There is no universally accepted method of grading colored gemstones. TanzaniteOne, a major commercial player in the tanzanite market, through its non-profit subsidiary, the Tanzanite Foundation, [27] has introduced its own color-grading system. [28] The new system's color-grading scales divide tanzanite colors into a range of hues, between bluish-violet, indigo and violetish-blue. 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 then Arusha Region (presently Manyara Region). He was issued with a certificate of recognition three years later by the 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. [10] [11] Commercial history [ edit ] Craft work on tanzanite Tanzanite forms as a brownish crystal and is trichroic, which means it shows three colors – brown, blue and violet – concurrently. Heating, either underground naturally by metamorphic processes, or artificially, removes the brown or burgundy color component to produce a stronger violet-blue color and makes the stone "dichroic", which means it only reflects blue and violet. [30] Rarely, gem-quality tanzanite will heat to a green primary hue, almost always accompanied by a blue or violet secondary hue. These green tanzanite have some meaningful value in the collector market, but are seldom of interest to commercial buyers. [31]

The Tanzanite Foundation". The Tanzanite Foundation. 22 April 2013. Archived from the original on 9 February 2005 . Retrieved 26 November 2013. Clarity grading in colored gemstones is based on the eye-clean standard, that is, a gem is considered flawless if no inclusions are visible with the unaided eye (assuming 20/20 vision). [29] The Gemological Institute of America classifies tanzanite as a Type I gemstone, meaning it is normally eye-clean. Gems with eye-visible inclusions will be traded at deep discounts. Study of Heat Treatment". Yourgemologist.com. International School of Gemology . Retrieved 29 August 2011. Lower grades of tanzanite are occasionally enhanced using a layer of cobalt, as cobalt imparts a deeper shade of blue. The cobalt layer does not adhere well to these stones, and tends to rub off over time, resulting in a much less intensely colored stone. Though still tanzanite, the practice of cobalt coating is considered deceptive unless well-advertised. [36] See also [ edit ]Featured gemstone: tanzanite". GIA Library. Gemological Institute of America, Inc. Archived from the original on 13 May 2008. Tanzanite may be subjected to other forms of treatment as well. Recently, coated tanzanites were discovered and tested by the AGTA and AGL laboratories. [34] A thin layer containing cobalt, determined by X-ray fluorescence, had been applied to improve the color. It was noted that "coatings in particular are not considered permanent", and in the United States are required to be disclosed at the point of sale.

Cobley, Mark (3 August 2005). "World's Biggest Tanzanite Gem Found Near Kilimanjaro (Update3)". Bloomberg. Archived from the original on 24 September 2015 . Retrieved 31 December 2013. verifyErrors }}{{ message }}{{ /verifyErrors }}{{ From 1967, an estimated two million carats of tanzanite were mined in Tanzania before the mines were nationalized by the Tanzanian government in 1971.Since heat treatment is universal, it has no effect on price, and finished gems are assumed to be heat-treated. Gemological Institute of America states that the source of heating is gemologically undetectable, but is assumed because of its prevalence. [33] Mgunduzi wa madini Tanzanite afariki dunia". BBC News Swahili (in Swahili) . Retrieved 26 September 2023.

Luvanda, H. E. Baraka H. (10 October 2018). "Presentation of Tanzania High Commissioner Of Tanzania Minerals And Metals Outlook, 2030". The High Commission of the United Republic of Tanzania . Retrieved 27 June 2020.

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The normal primary and secondary hues in tanzanite are blue and violet. Untreated tanzanite is a trichroic gemstone, meaning that light that enters this anisotropic crystal gets refracted on different paths, with different color absorption on each of the three optical axes. As a result of this phenomenon, a multitude of colors have been observed in various specimens: shades of purple, violet, indigo, blue, cyan, green, yellow, orange, red and brown. After heating, tanzanite becomes dichroic. The dichroic colors range from violet through bluish-violet to indigo and violetish-blue to blue. [29]