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 Post subject: Heat treating of indicolites
PostPosted: Mon Aug 30, 2021 5:19 am 
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Hello,

It took me quite a while to find a quality blue tourmaline. However, when it came to whether it was treated or not, the seller was unsure and claiming that 99%of indicolites are treated to improve the blue.

Thus, is it possible to find out if they are always really treated and whether it's possible to determine any treatment without a laboratory?


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 Post subject: Re: Heat treating of indicolites
PostPosted: Mon Aug 30, 2021 1:31 pm 
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It is my understanding, 1bwana1 or ghayes could weigh in on this, that dark shades of tourmaline are often heated to lighten the color but there are no identifying characteristics which are diagnostic in identifying heat or irradiation treatments in tourmaline.
Even advanced spectrographic instruments are of no help.


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 Post subject: Re: Heat treating of indicolites
PostPosted: Mon Aug 30, 2021 1:48 pm 
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I do not believe that 99% are treated, but more that 99% of the indicolite or stones like your presenting are just what they are common closed or partially closed crystals. In my heating experience with these trying to improve or remove the saturation causing the blackening is not going to show any visible improvement. The crystals before cut always look amazing, but if not cut correctly, look exactly like what you have. It is still a beautiful gem.

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 Post subject: Re: Heat treating of indicolites
PostPosted: Mon Aug 30, 2021 2:00 pm 
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Thanks, Greg!


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 Post subject: Re: Heat treating of indicolites
PostPosted: Mon Aug 30, 2021 2:27 pm 
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By far our friend has a far more reaching experience in the heat treatment specifics, so I have no comments on whether labs can detect heating. My better half tells me that the GIA on Tourmaline heating calls for reports, they will if detectable. It appears that is the million dollar question. I do agree it is common practice to heat for improving color in tourmaline, but I lean on the cutting fashion first then heat for improvement. I was taught this by a late mutual friend.
Here's a link for some info and posted questions.
https://www.gia.edu/tourmaline/buyers-guide

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Last edited by glhays on Mon Aug 30, 2021 2:40 pm, edited 1 time in total.

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 Post subject: Re: Heat treating of indicolites
PostPosted: Mon Aug 30, 2021 2:35 pm 
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No, I do not believe thermal enhancement can be detected in tourmaline even at the GIA
See Thermal Enhancement p.220
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In still other gems (e.g., aquamarine, citrine, amethyst, and tourmaline), heat treatment remains virtually unidentifiable by any currently known methods. For this last group of stones, which are heated to induce permanent changes to their color, this enhancement may be the rule rather than the exception. One should assume that most of those gem materials have been heated.





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 Post subject: Re: Heat treating of indicolites
PostPosted: Mon Aug 30, 2021 2:46 pm 
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Yes your right, we are actually reviewing that now as we sit here. It appears they do not, but place disclaimers directing you to the list of gemstones they do and tourmaline is one that is not.

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 Post subject: Re: Heat treating of indicolites
PostPosted: Mon Aug 30, 2021 7:15 pm 
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Many indicolites (and tourmalines of all colors) are enhanced by heat treatment.

I know of no way to reliably determine if such stone were in fact heat treated.


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 Post subject: Re: Heat treating of indicolites
PostPosted: Tue Aug 31, 2021 2:29 am 
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Thanks all for sharing the thoughts. Actually the claims of some dealers of "unheated and untreated" indicolite they sell on the one hand, and "that 99% of those are heated" on the other hand, have led me to some deadlock.
As seems even GIA can not guarantee the result.
But thus, it's also seems impossible that indicolites can be like swiss/london topaz - always treated.


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 Post subject: Re: Heat treating of indicolites
PostPosted: Tue Aug 31, 2021 2:00 pm 
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Heat or no heat is immaterial to value on some gemstones.
Consuming a cut or faceted indicolite yes it is safe to assume it to be most likely to have been heated. If you have the crystal and have a cutter fashion it into a cut gem then I believe it is safe to assume the crystal has not been treated, but there is no guarantee to that assumption. Mine to market is a journey not well documented in general.

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 Post subject: Re: Heat treating of indicolites
PostPosted: Tue Aug 31, 2021 6:02 pm 
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If a seller says a tourmaline is heated, believe them. If they say it is not, take it with a grain of salt.

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 Post subject: Re: Heat treating of indicolites
PostPosted: Sat Sep 04, 2021 12:59 am 
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allen wrote:
If a seller says a tourmaline is heated, believe them. If they say it is not, take it with a grain of salt.

Some sellers, if they admit heat you'd better look for radiation. If they admit radiation, dye. If dye, try and figure out the exact terms reached with the summoned demon to change the gem's color.

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 Post subject: Re: Heat treating of indicolites
PostPosted: Sat Sep 04, 2021 1:02 am 
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Are you suggesting that one should simply throw their hands up in the air when it comes to tourmaline treatments?

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 Post subject: Re: Heat treating of indicolites
PostPosted: Sat Sep 04, 2021 12:32 pm 
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Stephen, it is my understanding irradiation would not be detectable either. So, only pedestrian crack filling and dying could be documented. Is that correct?


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 Post subject: Re: Heat treating of indicolites
PostPosted: Sat Sep 04, 2021 12:59 pm 
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allen wrote:
Are you suggesting that one should simply throw their hands up in the air when it comes to tourmaline treatments?


Well, that would be one approach. But you know these things.

You can assume that Paraiba is heated except for the greens.

Most of the pinks/reds these days are heated, and often heated then irradiated, then heated again, and finally clarity enhanced.

The greens are a mixed bag.

Chrome is not treated in any way.

Indicolite is so often heated it must be assumed.

The unusual fancy colors are mostly heated.

For any individual stone you can not prove the status any of this.

More and more Tourmaline is subjected to clarity enhancement. This is very much true with a lot of the Rubellite. These clarity enhancements range from oils, polymers, and different waxes. Dye may be included. You should be able to determine these things.

In all cases you should follow the AGTA Guidelines for disclosure. They have nomenclature and supporting docs for your customer for know treated situation, and unknown but common treatments.


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