File:Tanzanite (Merelani Tanzanite Deposit, Merelani Hills, Arusha, Tanzania).JPG
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Summary
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| Description |
(specimen at lower left is ~2.6 centimeters tall) Tanzanite is an attractive gemstone discovered in the 1960s in Tanzania, eastern Africa. The term "tanzanite" is a trade name for trichroic, blue-purple-red, vanadiferous zoisite (Ca2Al3Si3O12(OH) - calcium hydroxy-aluminosilicate). When extracted from mines, tanzanite is often an ugly dull brown color. When heated, it usually turns a nice bluish-purplish color. High-quality crystals, when viewed from different axes, show purple, then blue, then red. I've only seen two photos that depict the red color - none of my specimens have it (e.g., <a href="https://www.flickr.com/photos/usageology/44701224910">www.flickr.com/photos/usageology/44701224910</a>). Many specimens show the purple to blue color change when tilted. Because tanzanite requires artificial heating to produce the attractive colors, it is a semi-natural gemstone. The original discovery was reportedly crystals that had been heated by fires generated by lightning strikes - truly natural gemstones. Tanzanite is only produced from the Meralani Tanzanite Deposit, a half-meter to 6 meter wide, 9 kilometer long zone of hydrothermal quartz-calcite-tanzanite-grossular garnet-graphite-pyrite veins and pockets within and adjacent to intensely boudinaged calc-silicate rocks ("marbles"). The "marbles" are hosted in northeast-trending kyanite-biotite-graphite gneisses. The rocks in this area are in the Mozambique Collision Belt and were metamorphosed in the late Neoproterozoic, during the late stages of the Pan-African Orogeny, at about 585 Ma. Structurally, the area is at the crest of the Lelatema Anticline. Locality: mine in the Merelani Hills, just west of Kimongan Mountain, northern flank of the Lelatema Mountains, ~10 miles south-southwest of the Kilimanjaro Airport, between Moshi & Arusha, Lelatema District, eastern Arusha Province, far-northeastern Tanzania (apparently between 3° 33' to 3° 37' South latitude and 36° 57' to 37° 04' East longitude) |
| Date | |
| Source | Tanzanite (Merelani Tanzanite Deposit, Merelani Hills, Arusha, Tanzania) |
| Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/49381014327. It was reviewed on 12 May 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
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| current | 22:10, 12 May 2020 | | 1,530 × 1,785 (1.73 MB) | Tillman (talk | contribs) | Transferred from Flickr via #flickr2commons |
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