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.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
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.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
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.
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.
Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
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.
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
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.
Joined: Tue Apr 05, 2016 7:58 pm Posts: 1424 Location: San Marcos, CA
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.
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.
Joined: Mon Sep 11, 2006 7:11 am Posts: 102 Location: Cape Town
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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File comment: The results from a Precious metal detector. Cup Tourm.jpg [ 666.31 KiB | Viewed 4871 times ]
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