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 Post subject: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 8:22 am 
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Is there a minimum requirement of copper needed for a tourmaline to be labeled a Cuprian or Paraiba tourmaline?


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 2:51 pm 
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All the GIA literature I have read would suggest if it is copper bearing true or false, not the amount of true.

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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 3:37 pm 
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I don't recall ever seeing a minimum quantitative amount of Cu being required. In fact different locations seem to have different amounts of Cu in them. Mozambique on average being the lowest.

The VIS-NIR digital spectroscopes that the labs like GIA use to make the call are only qualitative, not quantitative. They will show a Cu peak in the 900nm range indicating the presence of Cu. It this peak is there it gets the Cuprian report.

I believe that G.I.A. uses the GL-Gem Spectroscope, as do a number of other of the big labs. I have one of these in my lab and it works great.

https://www.cigem.ca/store/instruments/ ... ectrometer

The Italian Magi Labs version is also used by many and is very well respected for this use.

http://gemmoraman.com/GemmoSphere.aspx

I hope this is useful for you.


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 7:45 pm 
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1bwana1 wrote:
I don't recall ever seeing a minimum quantitative amount of Cu being required. In fact different locations seem to have different amounts of Cu in them. Mozambique on average being the lowest.

The VIS-NIR digital spectroscopes that the labs like GIA use to make the call are only qualitative, not quantitative. They will show a Cu peak in the 900nm range indicating the presence of Cu. It this peak is there it gets the Cuprian report.

I believe that G.I.A. uses the GL-Gem Spectroscope, as do a number of other of the big labs. I have one of these in my lab and it works great.

https://www.cigem.ca/store/instruments/ ... ectrometer

The Italian Magi Labs version is also used by many and is very well respected for this use.

http://gemmoraman.com/GemmoSphere.aspx

I hope this is useful for you.


Let's see if Nathan Renfro can weigh in. I suspect the GIA uses neither of the spectrometers listed above.


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 8:00 pm 
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I was told that they use the GL-Spectrometer by someone at GIA. That may not be the only one however.


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 8:17 pm 
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Out of curiosity which device is able to give the quantitative value of Cu in a specific gemstone?

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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 8:23 pm 
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LA-ICP-MS.
The LA-ICP-MS systems at GIA were upgraded to those currently in place, including a Thermo Fisher iCAP Qc ICP-MS coupled with an Elemental Scientific Lasers NWR213 laser ablation system.


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 9:44 pm 
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Barbra Voltaire, FGG wrote:
LA-ICP-MS.
The LA-ICP-MS systems at GIA were upgraded to those currently in place, including a Thermo Fisher iCAP Qc ICP-MS coupled with an Elemental Scientific Lasers NWR213 laser ablation system.


Yep, those are simply amazing. The plasma can tell you every element is a stone and their quantities. This is key in developing origin databases.

Totally overkill in determining Cu Tourmalines however.


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 9:59 pm 
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Ohhh so if my tourmaline has more than your tourmaline $$$$$$$, might need a new grading scale for that. :?: Just being a you know what. JA! Learned quite a lot from this thread I must say.

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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 10:26 pm 
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I may have mentioned in a thread past, that one of my clients wanted me to value a tourmaline that had an obscure lab report indicating the presence of copper.
The color of the stone, I would describe as diluted "bug juice".

A heated discussion ensued and I refused the job.

He ended up selling the stone for Paraiba prices, and rubbed my nose in it.

Silly, silly me....


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 10:33 pm 
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That's a very interesting color description, would that be of the windshield or bumber variety? I can actually vision a light Pariaba tone in many of Tucson trip windshield variety.

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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 10:46 pm 
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Pantone would describe the color as:


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Fri Apr 30, 2021 11:12 pm 
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Tourmaline that has Cu is getting a premium price even if the color is ugly. Makes no sense to me. The reason Cu stones were originally desirable was that the Cu produce exception neon colors. An ugly stone is an ugly stone no matter the trace element in my opinion.


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Sat May 01, 2021 2:49 am 
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glhays wrote:
Out of curiosity which device is able to give the quantitative value of Cu in a specific gemstone?


Thanks for all the comments.
The reason I am asking is that I did a few tests on a tourmaline that was identified as Cuprian with 0.008% copper content. This result was from a microprobe done at our local university geology department.
My GL Gem Spectrometer didn't pick up any copper. A Scanning Electron microscope didn't pick up any copper either although the technician said it wouldn't pick up under 0.10. Then the stone was tested on a Precious Metal detector which did pick up copper. (See picture below).


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 Post subject: Re: Cuprian/Paraiba tourmaline
PostPosted: Sat May 01, 2021 10:05 am 
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Interesting. Do you have an image of the GL-Spectrometer graph?


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