Post subject: Sending a tourmaline to the GIA to be tested for copper.
Posted: Wed Sep 28, 2016 9:39 pm
Gemology Online Veteran
Joined: Thu Sep 25, 2008 10:33 am Posts: 840 Location: Mars PA
Someone was interested in one of my purple tourmalines. It is a reddish purple and while my spectrometer can give me good results in determining if a tourmaline has copper or not with most colors, it does not do well with reddish gems because of interference with a higher oxidation state of manganese. But even if I was absolutely sure the tourmaline gem contained copper as a chromophore, I would want a report from a qualified laboratory, before I asked such high prices for a tourmaline (cuprian).
I dispatched the stone to the GIA threw a jewelery story that I have worked with in the past. The only question that was asked of the laboratory was whether it contained copper or not. The GIA confirmed the receipt of the gemstone and then took over a month to produce the report. The report did not mention copper at all. The only details on the report are a picture and the gem's physical details along with the statement that the gemstone is tourmaline. No comments at all. Under treatment: The report states that you should "Scan QR code for more information." Upon doing this, the laboratory states that the cause of the color of the tourmaline could not be determined. There is also general type information.
Well I figured that the stone had been tested for copper and found not to contain it, but the laboratories standard response was certainly not the explicit statement I was looking for. I asked the owner of the jewelery store to call the laboratory and ask the simple question of whether the tourmaline contain copper or not. I was a straight forward question and it took no time to answer. It does not.
Now I can see why copper was not brought up on the report. Saying that the gemstone doesn't contain copper is an unnecessary and negative finding for the report. But why couldn't they include a simple informal? handwritten? note in the fancy box that just said that the tourmaline was tested and did not contain copper.? Having a chemical standard for a gemstone variety that can have its hue, tone and saturation duplicated by another chromophore can certainly lead to expensive complications. (Yes I certainly appreciate that copper can produce superior gemstones, but it does NOT have too. I have seen paraiba-like cyan tourmaline from Afghanistan that have a greater amount of the wonder glow like quality, than certified copper bearing tourmaline of the same general hue.)
Post subject: Re: Sending a tourmaline to the GIA to be tested for copper.
Posted: Thu Sep 29, 2016 9:13 pm
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
I'd love to see a pic of your purple tourmaline. Do you suspect manganese (Mn3+) as the chromophore? I know a few people who have tried to heat these purples, hoping for neon blue, only to end with the valence state changing toMn4+ which is colorless. Ending with a colorless tourm.
Post subject: Re: Sending a tourmaline to the GIA to be tested for copper.
Posted: Fri Sep 30, 2016 8:43 pm
Gemology Online Veteran
Joined: Thu Sep 25, 2008 10:33 am Posts: 840 Location: Mars PA
You can find a picture on my site. The purple's number is 572 and it is in tray 12. Also if you still have the disk I sent you with pictures of most of my tourmaline collection, there will be a picture of the purple oval there too. I have found out that the GIA does not normally test purple tourmaline's for copper.
Post subject: Re: Sending a tourmaline to the GIA to be tested for copper.
Posted: Sat Oct 01, 2016 8:30 am
Gemology Online Veteran
Joined: Thu Sep 25, 2008 10:33 am Posts: 840 Location: Mars PA
Purple and Paraiba, paraiba type, cuprian and even paraiba like deserve a new post because it is very interesting I think. I am not a heater, but I have been gathering insight on the subject for sometime. I don't even think some of the researchers have it together.
Post subject: Re: Sending a tourmaline to the GIA to be tested for copper.
Posted: Sat Oct 01, 2016 10:44 am
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
Here is a G&G article talking about this in depth and on p118 the section on heat treatment indicates that copper bearing purples can be changed to blue.....as most of them are.
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