It is with great sadness I'd like to announce Dr. Hanneman passed away on December 12, 2020. His legacy will live on forever!
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 Post subject: Heating Paraiba, paraiba type, paraiba like tourmaline.
PostPosted: Mon Nov 26, 2018 10:34 pm 
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Joined: Thu Sep 25, 2008 10:33 am
Posts: 833
Location: Mars PA
I am not a heater and this post is not about heating any kind of tourmaline to effect its tone, hue, or saturation. This post is about claims by numerous inter net vendors and others, that they are selling an unheated Paraiba/paraiba type tourmaline that has a "certificate" from the GIA etc. This is the vendor's opinion about heating and NO responsible gemological laboratory can reliably determine whether a tourmaline has been heated or not. The report on the submitted tourmaline will only discuss whether it is effected by copper impurities and an appropriate name, after listing its size, weight and other basic facts.

Many more "experts' will tell you that a cuprian tourmaline with a purplish hue has not been heated. This seems reasonable since if your are going to risk the purity of the tourmaline by heating, why not go all the way to cyan/neon blue green? It is certainly more valuable. And I have never found any reference that talks about the inability of heating to eliminate the reddish hue in purple cuprian tourmaline by reducing manganese. So why do I take exception to the common conclusion about heating and purple tourmaline?

Because mother nature and the hand of man joined together to produce a lavender hue in tourmaline, I had never seen in tourmaline before. It was before copper had been publicly discover in gemstones I sent the GIA. I did not even think of copper at this time early in the history of the Mozambique deposit. After cutting my first piece I was so so pleased that I sent the gemstone back to Brian Norton in Africa, my source for the rough, for him to see. He had never seen such a color in tourmaline either.

Information about gemstone deposits is not always easy to get in Africa. But after seeing more material and talking/seeing more on the inter net, I put the following together. The deposit was an old river bed and it was not easy to mine. The first tourmaline that came out was in many colors, but it was not very clean. Only larger dark purplish red pebbles had good clarity. At first the dark pebbles were sold as carving material, but people soon experimented in heating them. The low heating, over many hours, effected both their color, tone and saturation.

The end product of heating varied from very very pale aqua to stronger blues and greens. This was after turning the lavender hue I loved from less time in the fire, in many cases. So for a brief time lavender tourmaline was available before copper was discovered and the world changed. My spectrometer says that the three lavender gems I have, contain copper as a chromophore and would probably turn blue with further heating, but I like them just the way they are.

I guess I could claim that the stones were unheated, but why do it, since the value on all colors of copper bearing tourmaline does not depend on heating or not. I think those that push material as unheated are trying to get a bit of the glow off the ruby world. Please focus on tourmaline and don't be deceive.

Finally the subject of paraiba like tourmaline should be addressed. I have seen and measured beautiful cyan/neon blue green tourmaline colored only by iron. The absorption peaks for iron can be nearly identical to copper except for the lack of a second peak above 800nm. I use the small difference between iron and copper at the edge of the red end of the visible to test for copper on tourmaline. It works very well except with some absorption spectra that are complicated by manganese. (red/pink stones usually). I personally do not know if the iron based cyan tourmaline are heated or not. (Frankly it would not make any difference to me.) Indicolite is routinely heated to lighten it and I am sure that neon blue greens would be effected by heating.

Bruce


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 Post subject: Re: Heating Paraiba, paraiba type, paraiba like tourmaline.
PostPosted: Sun Dec 30, 2018 5:49 am 
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Joined: Thu Sep 25, 2008 10:33 am
Posts: 833
Location: Mars PA
Hello again.

I was wandering around the inter net when I came upon a very interesting ring. It had a center stone of just over 20 carats of neon blue green tourmaline. The setting was made of platinum and had accent stone of paraiba, spinel, and diamonds. It was brand new and being handled by a third party site I had never heard of. The vendor wanted to start the negotiations for the stone at $88,000.

I looked for and found a report for the center stone. It turned out to be "The Prestige Gemstone Report" from the AGL. Now what did this expensive report actually say about the tourmaline.

1, The stones weight and dimensions.

2, It was a natural tourmaline.

3, Its color was blue green.

4, A picture of the stone.

5, Its cut was a modified brilliant.

6, And finally a comment, that was the only information on the report that the vendor did not know before submitting the ring. (In my opinion.) And I quote from the report.

"No gemological evidence of enhancements/treatments are present."

The vendor's creativity had transform the comment into the tourmaline was unheated. He also had to augment the report's color determination with the magical modifier "neon".

What the report does not say is much more interesting than what it presents.

1, No determination of the tourmaline's origin.

2, No discussion of the tourmaline's varietal name.

3, No determination about whether the tourmaline was heated or not.

I consider the report to be of very little value and disingenuous. Why isn't it mentioned that the stone was tested for copper and should be called paraiba like. Why isn't it stated whether the stone's origin was requested or not and if it can be determined if so requested? And of course it is not frank about the inability of the lab to consistently determine whether a tourmaline has been heated or not.

If my proposal for a new definition for Paraiba (See my recent post) and its kin was adopted. The complexities of valuing blue green, cyan, green, purple etc. colored tourmaline would be taken out of the chemical world and back into the world the eye can judge. A world that would be less prone to misrepresentation and confusion.

Bruce


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