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 Post subject: Vanadium Bearing Tourmaline, Nadonjukin, Tanzania
PostPosted: Mon Jul 01, 2019 2:01 pm 
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Journal of Gemmology wrote:
ABSTRACT: In 2016, fine intense green and bicoloured brown-green V-bearing tourmaline was found at what became known as the Commander mine in Nadonjukin, Tanzania. Although dubbed chrome dravite by the gem trade, this material proved to be a mixture of dravite and uvite, with Cr present only in small amounts. Multicoloured crystal sections analysed with various techniques identified the chromophores V and minor Cr in the green parts, and Fe and Ti in the brown portions. Heat treatment produced no changes in colouration, which is consistent with the presence of iron in the brown tourmaline as Fe2+, as indicated by optical spectroscopy.
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The Journal of Gemmology,36(6), 2019, pp. 534–543, http://doi.org/10.15506/JoG.2019.36.6.534© 2019 Gem-A
(The Gemmological Association of Great Britain


Reading through the credits for the article, I found a mention of New Era Gems, a member of our forum.
I wonder if they have any specimens for sale. :wink:

Well, looky here: =D> =D> =D>
Although all these specimens are listed as chromium tourmaline, the article above found Cr percentage was relatively low compared to vanadium. *
https://neweragems.com/?product=command ... 178-48-cts
https://neweragems.com/?product=command ... -37-44-cts
https://neweragems.com/?product=command ... -49-25-cts
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 Post subject: Re: Vanadium Bearing Tourmaline, Nadonjukin, Tanzania
PostPosted: Mon Jul 01, 2019 5:38 pm 
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If I recall correctly, at least in some cases chromium can get a more powerful coloring effect per percent composition than vanadoum, so it is hard to be 100% sure what is responsible for what.
These specimens are available (and were moreso last year) but not cheap. Very cool stuff though!

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