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 Post subject: GRS report for 'untreated blue topaz'
PostPosted: Thu Feb 08, 2018 4:08 pm 
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Hey Gals and Guys,

Haven't posted in ages. Sorry. You're always on my mind, just my body is too busy.

See what I came across this week:

A rough Australian blue topaz, found 30 years ago, was tested by Dr. Peretti and found as untreated in the rough.

It was then super-cut and again ID-ed by Peretti (based on its inclusions) as the same gem he had tested before.

Based on this arguments, the attached report was issued. I can't get hold of Dr. P. to ask the obvious question(s) but soon die of curiosity. Hence I post it here, to find out if anybody has seen or heard of a similar report being issued, ever, and if so what do you think of it?

The gem is ultra marvelous and if Peretti's chain of arguments is water tight, I've seen the best untreated topaz ever.

Can it be water-tight?


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BTUA5902-GRScert.jpg
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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Thu Feb 08, 2018 5:59 pm 
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Curious. Since no detection of treatment is possible with today's instruments, I dare say we could make that claim about every blue topaz, n'est pas?


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Fri Feb 09, 2018 2:39 am 
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In the case of a stone where short-lived radioisotopes were detected you could be sure it was irradiated by man, but not seeing them doesn't mean a stone is untreated. Otherwise I don't think there's much of any difference to detect because the mechanism of coloration is identical as far as we know. IIRC there was a proposed difference in photoluminescence between natural and gamma irradiated stones, but I am guessing it didn't turn out to be reliable since nobody seems to be using it (or maybe it only worked on gamma irradiated stones which wouldn't be that useful for most blues?)
Natural blue topazes with relatively good color were occasionally found before irradiation treatment was prevalent but this color would be very unusual to say the least. I'd probably go with the odds on this one I'm afraid.


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Fri Feb 09, 2018 6:45 am 
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Yes, that was my first reaction, too, but why would Dr. Peretti issue this report if he couldn't be sure? It was obvious that such an opinion would be scrutinized.
After all, his professional reputation is based on issuing believable reports, right?
I guess it comes down to hearing his arguments. I will keep you informed if I get feedback. Perhaps I can get it here if the Dr. reads this forum.

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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Fri Feb 09, 2018 12:15 pm 
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As far as I remember the method of photoluminescence to identify the treatment was somewhat destructive for the topaz. Maybe it is why labs don't use it so much.


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Fri Feb 09, 2018 2:08 pm 
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Peretti had pieces cut from the rough, so yes, that could not be done in a faceted stone. I'm not sure if that was only to make windows for examination or to do testing on the surface material.

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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Fri Feb 09, 2018 5:20 pm 
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Edward, try dropping him a note.
Perhaps he knows something the rest of us don't. :smt017 (That is an understatement.)

Stephen, explain to me the testing method you referred to above, please.
Who does it?
Certainly not routine, is it?

I saw some natural blue topaz in the extensive collection at the Fersman Museum in Moscow, but nothing approaching the saturation of Edward's stone.


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Sat Feb 10, 2018 6:53 am 
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Yeah, in all humbleness, I've been hunting for naturally blue rough topaz for 15 years and never seen anything like it.

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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Sat Feb 10, 2018 3:19 pm 
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Barbra Voltaire wrote:
Stephen, explain to me the testing method you referred to above, please.
Who does it?
Certainly not routine, is it?

I will track it down in the literature and report back. I doubt anyone is actually doing it.


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Sun Feb 11, 2018 2:12 pm 
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Edward Bristol wrote:
Yeah, in all humbleness, I've been hunting for naturally blue rough topaz for 15 years and never seen anything like it.

I have a naturally colored blue topaz. I know it is natural because I found it myself, in Colorado. It certainly isn't deep blue like that stone, though.
I think basically the only way to get one you will know for certain is blue is to find it yourself, though.


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Mon Feb 19, 2018 1:06 pm 
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There are basically two ways of artificially irradiating these topaz, either using a Co60 (gamma) source, or through a Linacc, which is a much more powerful ion/neutron activator. Both cases create a brown coloration in the stone and then require an annealing process for the color to go to blue.

Natural blues exist, but are extremely rare because of the need to have a radiation and heat source. I agree with everyone here in that you may get a lighter blue from a natural or artificial (gamma source), but the only time I've ever seen those rich blues is by the linear accelerator method of activating.


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Mon Feb 19, 2018 1:36 pm 
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And, can you also agree Bear, that out labs can not determine treatment?


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Mon Feb 19, 2018 2:22 pm 
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Agreed, I don't know of any gemological laboratories that could readily tell. Probably Rossman has the equipment and ability? Mössbauer spectroscopy would most likely have to be employed to make a determination of how the neutron has been "recoil" affected. I remain very skeptical since I'm not aware of any study that has been published regarding the determination.

In the Physics and Chemistry of Color, page 200 Kurt Nassau states regarding topaz, that the stable brown and blue artifical radiation color centers are "...indistinguishable from the naturally occurring stable brown and blue". Nassau is not to be taken with the proverbial grain.


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Tue Feb 20, 2018 1:51 am 
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Edward Bristol wrote:
A rough Australian blue topaz, found 30 years ago, was tested by Dr. Peretti and found as untreated in the rough. It was then super-cut and again ID-ed by Peretti (based on its inclusions) as the same gem he had tested before.

Has Dr Peretti been asked for the reasons for his finding it as untreated? When was the artificial irradiation of topaz initiated?


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 Post subject: Re: GRS report for 'untreated blue topaz'
PostPosted: Tue Feb 20, 2018 7:00 am 
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Yes, the owner is currently in Bangkok and I hope to get news from there.

The history of the rough gem, found by an opal miner, serious professional people, no fly-by-night company, suggests that the rough was secured deep in a private safe in OZ, while or even before irradiation was introduced to topaz elsewhere. Only the trustworthiness and the GRS report had me follow up this impossible super color.

The owner knows of no possible point in time in which the gem could have been treated by a third party. He is rather surprised that the GRS report could be a point of discussion here, and that we can't think of an obvious way Dr. P. could have tested the topaz for treatments. I do understand his point. It seems rather strange for somebody not used to the endless fights over possible treatments. He paid good money for the report and now finds it doubted by the whole community. It's not easy to explain.

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