March 13 to 15: AUGUSTA, GEORGIA: Annual show; Augusta Gem and Mineral Society; Aiken Gem, Mineral and Fossil Society; Fri. 10-6, Sat. 10-6, Sun. 11-5
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 Post subject: How is copper content tested in cuprian tourmalines?
PostPosted: Tue Feb 11, 2020 12:34 am 
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The recent conversation in the Tucson thread had me curious. I did some googling and found some old threads discussing how copper content was only testable via very specific equipment at GIA and a few other labs. Is that still the case? And even if so, what equipment is used to assess presence and amount of copper?


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 Post subject: Re: How is copper content tested in cuprian tourmalines?
PostPosted: Tue Feb 11, 2020 2:07 am 
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A spectrometer that reaches into the IR can spot a distinctive absorption peak down there, but I am not sure if that is seen in every cuprian stone.

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 Post subject: Re: How is copper content tested in cuprian tourmalines?
PostPosted: Tue Feb 11, 2020 1:00 pm 
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It doesn't require a very sophisticated instrument to test for the presence of copper in Tourmaline. Pretty much any UV-VIS-NIR spectrometer can be used.

What you are looking for is a copper peak at about 930 nm, and often a MN 2+ peak at around 415 nm and MN 3+ around 520 nm (mostly in pink/red/purple stones preheated).

In my lab I use the GL Gem Spectrometer. I have heard, but cannot confirm that this is the same tool used by GIA for this.

https://www.cigem.ca/research-technolog ... ectrometer

The past few years at Tucson I have used the excellent MAGI spectrometer that Alberto kindly makes available at the AGTA show.

http://www.gemmoraman.com/Home.aspx

Given the circumstances of the current market, next year I will bring my own so as not to take up too much time at the MAGI booth.

Below is a sample spectra. Easy to see the peak at around 930 nm. Non Copper Tourmaline wil have a flat line in this area.

Also note that the MN peak around 415 nm in this sample.

The quantity of copper in the stone can only be done by very expensive spectrometers that only a big lab like GIA will have.


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