June 22-25: Sainte-Marie-aux-Mines:International Mineral & Gem Show
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 Post subject: Calling a purplish red tourmalinle, cuprian
PostPosted: Mon Mar 13, 2017 9:24 pm 
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Joined: Thu Sep 25, 2008 10:33 am
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Location: Mars PA
I just got finished reading a post on the inter net that is disgusted with people trying to sell purplish red tourmaline as cuprian. The author shows a picture of what looks like a decent rich purplish pink and says that he has seen hundreds of tourmalines with the same color without copper. Therefor copper is not a chromophore in the pictured tourmaline and it should not be called cuprian.

I am sure his observations on purplish pink tourmaline are valid, but is the eye a valid way of differentiating regular tourmaline from cuprian tourmaline when the difference is based on color, NO! (I could have used paraiba type and paraiba like for my comparison, but I kept with the color in the post) With a spectrometer I can distinguish a Rubellite from a cuprian purplish red tourmaline. If the tourmaline shows the copper absorption peaks, then it effects the color of the stone. Copper is therefor a chromophore in that tourmaline, despite having thousands of other tourmaline that are only colored by manganese and iron and have the same color.

I think it is fair to call a tourmaline that shows the copper absorption curves, despite its color, to be called cuprian. This is certainly not universal. I have heard that some labs want a certain amount of copper in the tourmaline to be cuprian, while other sources use cuprian to designate any tourmaline colored by copper that did not ;come from Brazil. I know the GIA uses a spectrometer to test all of the submitted tourmalines if copper is suspected to be present.

So what do you think? I find it unfortunate that some tourmaline meets the letter of the definition of cuprian tourmaline, without having any exceptional qualities. And I certainly wouldn't spent a premium on them, but it is being done.

Bruce


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 Post subject: Re: Calling a purplish red tourmalinle, cuprian
PostPosted: Tue Mar 14, 2017 12:28 am 
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Personally, I find copper-bearing tourmaline just a bit more interesting even if the appearance is essentially the same. I wouldn't pay a big premium for it, but that's more because I'm a huge chintz on some things. 'Cuprian' isn't a nomenclature hill that I would fight for, much less die on. That said I'm also not particularly invested in the fight over 'paraiba/paraiba-type' so that would track.


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 Post subject: Re: Calling a purplish red tourmalinle, cuprian
PostPosted: Tue Mar 14, 2017 3:10 am 
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Joined: Wed Jan 18, 2017 1:08 pm
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Location: Bergisches Land
Hello,
for my part i can say that i am kind of amused seeing what a tiny amount of Copper can do to some traders phantasies.In my eyes a beautiful Tourmaline is ---a beautiful Tourmaline,whatever its chemistry is.Reminds me a bit on the long lasting debate over Emeralds which have to be Chromium-coloured,or Vanadium as well,or both or...
never mind, just my 2cents :D
best wishes
Gemse


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 Post subject: Re: Calling a purplish red tourmalinle, cuprian
PostPosted: Sat Mar 18, 2017 11:34 am 
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Joined: Thu Sep 25, 2008 10:33 am
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Location: Mars PA
I am still working to get my upgraded spectrometer back on line. What I hope to show with it, is that two tourmalines that have the same color from different chromaphores do not have the visual impact. I will be taking tone values into consideration. In other words even if a different set of chromophores can produce the same color as a copper based tourmaline, the copper based gemstone will have a brighter more vivid glow like quality. I fully appreciate that these improved qualities of copper based tourmaline maybe limited to highter quality gemstones.

Bruce


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 Post subject: Re: Calling a purplish red tourmalinle, cuprian
PostPosted: Sun Mar 19, 2017 10:29 pm 
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Make sure that your observations are not anecdotal, Bruce.
Unbiased empirical evidence would be difficult to substantiate.


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