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 Post subject: cuprian terminology
PostPosted: Sat Jun 16, 2012 6:19 pm 
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Hi,

The use of the adjective "cuprian" seems to be accepted within the trade for green/blue tourmaline that isn't saturated enough to be called paraiba-like.

But, in the absence of lab certification, what is the basis for describing it as cuprian?

Thanks,
Bill


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 Post subject: Re: cuprian terminology
PostPosted: Sun Jun 17, 2012 2:39 pm 
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http://gemstone.org/index.php?option=co ... &Itemid=14

& this termology is accepted by GIA:
Quote:
A paraíba tourmaline is a blue (electric blue, neon blue, violet blue), bluish green to greenish blue or green elbaite tourmaline, of medium to high saturation and tone (relative to this variety of tourmaline), mainly due to the presence of copper (Cu) and manganese (Mn) of whatever geographical origin.


some labs also classify not Brazilian paraíba by Paraiba-type designation

hope these help you mate 8)

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 Post subject: Re: cuprian terminology
PostPosted: Sun Jun 17, 2012 3:32 pm 
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I think I'd say if copper is giving the stone its colour, or somehow involved, it may be called cuprian.

I don't know if a spectroscope may help it or if more advanced testing is needed to ID it, though. Anyone?

A good question, because now you have me wondering if Cu should be the dominant chromophore or if others may also come in and play?

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 Post subject: Re: cuprian terminology
PostPosted: Sat Jun 23, 2012 12:21 am 
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Hi again,

In my original post I said:

"But, in the absence of lab certification, what is the basis for describing it as cuprian?"

I should have said, ...in the absence of lab certification proving that copper is present, what is the basis for describing it as cuprian?

My understanding is that testing (to determine the presence of copper as the color-causing agent) is expensive and requires equipment that most labs don't have--if this is true, I suspect few of the "cuprian" tourmalines have been tested but many people use the term anyway.

So, it seems that terminology means whatever the speaker wants it to mean?

Thanks for your input!
Best,
Bill


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 Post subject: Re: cuprian terminology
PostPosted: Sat Jun 23, 2012 12:29 am 
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Simply, if someone describes a tourmaline as cuprian, ask them, "based on what?"


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 Post subject: Re: cuprian terminology
PostPosted: Sat Jun 23, 2012 12:06 pm 
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billkent wrote:

So, it seems that terminology means whatever the speaker wants it to mean?


Bill, this is nothing new. To quote Humpty-Dumpty's chat with Alice:

“When I use a word,” Humpty Dumpty said, in rather a scornful tone, “it means just what I choose it to mean—neither more nor less.”
“The question is,” said Alice, “whether you can make words mean so many different things.”
“The question is,” said Humpty Dumpty, “which is to be master that’s all.”

One encounters many variations of Humpty-Dumpty in the gem trade.

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 Post subject: Re: cuprian terminology
PostPosted: Sat Jun 23, 2012 4:49 pm 
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lol...That is such a great answer...are you perchance a white rabbit?


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 Post subject: Re: cuprian terminology
PostPosted: Sat Jun 23, 2012 9:18 pm 
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All tourmalines that derive their color from copper can be called cuprians....
but not all cuprians can be called paraiba.....
but all paraiba's can be called cuprian
hmmmmm
:idea:
:smt116
:smt106
:smt053

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 Post subject: Re: cuprian terminology
PostPosted: Sat Jun 23, 2012 10:15 pm 
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would it be correct to say that paraiba-type can be separated from other tourmalines just by their color?

but that to separate cuprian tourmalines from other tourmalines requires lab work?

thanks,
bill


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 Post subject: Re: cuprian terminology
PostPosted: Sun Jun 24, 2012 1:49 am 
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billkent wrote:
would it be correct to say that paraiba-type can be separated from other tourmalines just by their color?

No its not correct #-o why don't you read my post an exact definition accepted by GIA

viewtopic.php?p=167619#p167619

billkent wrote:
but that to separate cuprian tourmalines from other tourmalines requires lab work?

if i am not wrong, i think Dr.Hanneman has special Filter to separate paraíba, that would save you time and Lab expenses

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 Post subject: Re: cuprian terminology
PostPosted: Sun Jun 24, 2012 7:13 am 
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VIS-NIR spectrum has been demonstrated as reliable tool for detecting copper in tourmaline. While it doesn't produce quantitive analysis it's significantly cheaper than any of the more sophisticated methods.

Please read this excellent thread by Prof. Brian

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 Post subject: Re: cuprian terminology
PostPosted: Sun Jun 24, 2012 12:24 pm 
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How many of us, besides myself, have used a phrase such as "paraiba-type" in an appraisal, without having lab certification of the presence of copper/manganese?


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 Post subject: Re: cuprian terminology
PostPosted: Sun Jun 24, 2012 12:31 pm 
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I hope no one.


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 Post subject: Re: cuprian terminology
PostPosted: Sun Jun 24, 2012 12:56 pm 
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live and learn


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 Post subject: Re: cuprian terminology
PostPosted: Sun Jun 24, 2012 1:37 pm 
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I'll take that back.
If someone supplies you with a tourm which looks like one of these
Image
I think paraiba type is a fair assessment, without a chemical analysis.
Maybe the greens are "iffy"

Would anyone disagree?

But frankly, I've never been handed a tourmaline which looked like any of those blues and purples. :wink:


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