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36-813: The Tarangire River is a perennial river located in central Manyara Region in the eastern branch of the East African Rift Valley , within northern Tanzania . The headwaters of the Tarangire River are in the highlands and escarpments of Babati District of the Manyara Region and Kondoa District of the Dodoma Region , primarily the Irangi Hills and Irangi Escarpment in Kondoa District. The river rises in

72-472: 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,

108-640: 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. Hyman Saul took the samples to the Gemological Institute of America which correctly identified

144-602: A Life of Mine (LOM) expected to last until the 2040s. There is no universally accepted method of grading coloured gemstones. TanzaniteOne, a major commercial player in the tanzanite market, through its non-profit subsidiary, the Tanzanite Foundation, has introduced its own color-grading system. The new system's colour-grading scales divide tanzanite colors into a range of hues, between bluish-violet, indigo and violetish-blue. The normal primary and secondary hues in tanzanite are blue and violet. Untreated tanzanite

180-419: A furnace is usually carried out at between 370 and 390 °C (698 and 734 °F) for 30 minutes. The stones should not have any cracks or bubbles, as they could shatter or the cracks/ bubble could increase in size during furnace heating. Some stones found close to the surface in the early days of the discovery (in an area now called D block) were gem-quality blue without the need for heat treatment, probably

216-525: 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" (which might be pronounced like "blue suicide") 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

252-496: A high rate of flow with rapid rises and falls in water level. Rainfall occurs almost exclusively in November–January and March–May. It is highly variable, with a mean total annual rainfall of 656 millimetres (25.8 in) (coefficient of variation = 36.4%, range 313–1,322). River flow in the dry season is slow (about 0.005 cubic meters per second) and steadily decreasing as water is released from sediments, until long stretches of

288-496: 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

324-549: Is a trichroic gemstone, meaning that light that enters this anisotropic crystal gets refracted on different paths, with different colour 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 colours range from violet through bluish-violet to indigo and violetish-blue to blue. Clarity grading in coloured gemstones

360-548: Is assumed because of its prevalence. Tanzanite may be subjected to other forms of treatment as well. Recently, coated tanzanites were discovered and tested by the AGTA and AGL laboratories. A thin layer containing cobalt , determined by X-ray fluorescence , had been applied to improve the colour. It was noted that "coatings in particular are not considered permanent", and in the United States are required to be disclosed at

396-553: 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). 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. Tanzanite forms as a brownish crystal and is trichroic, which means it shows three colours – brown, blue and violet – concurrently. Heating, either underground naturally by metamorphic processes, or artificially, removes

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432-413: Is by examining a cut stone through its crown facets and viewing the pavilion cuts at the back of the stone using a standard jeweller's loupe : forsterite will show birefringence , making the pavilion cuts appear "doubled up", while the much lower birefringence of tanzanite will not have this characteristic. Lower grades of tanzanite are occasionally enhanced using a layer of cobalt , as cobalt imparts

468-860: Is in the northern part of the region. It is bordered to the north by the Arusha Region , to the northeast by the Kilimanjaro Region , to the east by the Tanga Region , to the south by the Dodoma Region , to the southeast by the Morogoro Region , to the southwest by the Singida Region , and to the northwest by the Simiyu Region . The highest mountain in the Manyara Region is Mount Hanang . Manyara Region

504-475: Is inhabited by various ethnolinguistic groups and communities. The latter include the Assa , Gorowa , Kw'adza , Mbugwe , Datooga , Maasai and Barabaig and Irakw , which is the largest ethnic group in the region. The regional commissioner of the Manyara Region is Queen Curthbet Sendiga . Residents of the Manyara Region are mostly farmers. The region's economy is based on the mining of Tanzanite gems on

540-401: Is the town of Babati . According to the 2012 national census, the region had a population of 1,425,131, which was lower than the pre-census projection of 1,497,555. For 2002–2012, the region's 3.2 percent average annual population growth rate was tied for the third highest in the country. It was also the 22nd most densely populated region with 32 people per square kilometre. Lake Manyara

576-491: The magnesium -rich end-member of olivine ) has also been sold as tanzanite, and presents a similar appearance. It can be distinguished from tanzanite in three ways. The first is by using a refractometer : forsterite will show a refractive index of between 1.63 and 1.67, while tanzanite will show a higher index of 1.685 to 1.707. The second way is by using a Hanneman filter : through it, genuine tanzanite will appear orange-pink, while forsterite will appear green. The third way

612-527: The Government of Tanzania through Ministry of Mining for TSh  7.74 billion (US$ 3.35 million) surpassing a record of 16,839 carats (3.37 kg; 7.42 lb) stone mined by TanzaniteOne in 2005. 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

648-553: The Mererani Hills in the north on the border with the Arusha Region . Other sources of income are from tourism in the Tarangire National Park , which is entirely located in the region, and Lake Manyara National Park . One paved road passes through the western part of Manyara Region. Paved trunk road T14 from Singida connects with trunk road T5 in Babati town. Trunk road T5 from Dodoma to Arusha passes through

684-542: The Salanka, Bereko, and Isabe Forest Reserves. Deforestation for agriculture and degradation of forests in the Irangi Hills and along the Irangi Escarpment is contributing to reductions in the Tarangire River's watershed function and aquifer recharge . The discharge in the Tarangire River is highly seasonal and varies annually. In the wet season, rainfall in the Irangi Hills and throughout the catchment causes

720-525: 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. In 2010,

756-501: The Wasi Highlands, falls down the eastern Kondoa Escarpment. It flows east to Chubi where it then turns north to flow through Tarangire National Park . It then turns west and then south, before terminating at its river mouth on Lake Burunge . Much of the Tarangire River headwaters in the Irangi Hills headwaters area is forested with Miombo woodland habitat trees and lower plants, that are designated for protection within

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792-403: 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 . 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

828-426: The brown or burgundy colour component to produce a stronger violet-blue color and makes the stone "dichroic", which means it only reflects blue and violet. 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. Heat-treating in

864-450: 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, a new record for the world's largest rough tanzanite was set after a small-scale miner, Saniniu Laizer, mined two stones of 9.72 kg (21.4 lb) and 5.1 kg (11 lb) and sold them to

900-493: 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

936-425: The mines were nationalized by the Tanzanian government in 1971. 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 the 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,

972-515: 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,

1008-475: The perfect color. The finished colour of the gemstone will vary depending on how the table cut reflects the light. As of 2020 , 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

1044-420: The point of sale. Pleochroism has a physical property in which the gemstone will appear to have multiple colours 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. The physical characters can make cutting process difficult due to the problem of selecting

1080-574: The region; it is paved from Arusha up to Dodoma . Manyara Region is divided into six districts , each administered by a council: Tanzanite Tanzanite is the blue and violet variety of the mineral zoisite (a calcium aluminium hydroxyl sorosilicate ), 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

1116-432: The result of a wildfire in the area which heated the stones underground. This gave rise to the idea that "D block" stones were more desirable than tanzanite found in other areas of the small tanzanite mining area. 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

Tarangire River - Misplaced Pages Continue

1152-559: The riverbed are dry. The Tarangire River is the primary source of fresh water for migratory ungulates and other wildlife of the Tarangire Ecosystem during the annual dry season. 3°50′S 36°00′E  /  3.833°S 36.000°E  / -3.833; 36.000 Manyara Region Manyara Region ( Mkoa wa Manyara in Swahili ) is one of Tanzania 's 31 administrative regions . The regional capital

1188-625: 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 . In July 1967, Manuel de Souza,

1224-443: 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). Synthetic forsterite ( Mg 2 SiO 4 ,

1260-426: 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"

1296-498: 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. Tanzanite was formed around 585 million years ago during the mid- Ediacaran Period by massive plate tectonic activity and intense heat in

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