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 Post subject: Re-cutting a Topaz
PostPosted: Tue Dec 26, 2017 9:28 am 
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Hello, it was suggested I post this here so here goes... I am possibly interested in either totally re-cutting or repairing the present cut on my large (76ct) Emerald cut Orange/Imp Topaz I have posted several images in the colored stones sub-forum. I would greatly appreciate any recommendations for either design or cutter or for that matter whether the stone is worthy of the effort either here or in PM.. I would prefer someone in relatively close proximity to the Boston area. Thanks and happy new year to all.
Roger

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 Post subject: Re: Re-cutting a Topaz
PostPosted: Tue Dec 26, 2017 3:37 pm 
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Barbra provides a valuable reality check.
If someone were to give this stone to a cutter, telling the cutter that it is Topaz and it turns out to be something else, the cutting process will not proceed as expected. If it turns out to be Amber or plastic, the cutter may inadvertently burn the gem piece.
You really want to get refractive index and specific gravity measurements on this stone before proceeding any further.

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 Post subject: Re: Re-cutting a Topaz
PostPosted: Tue Dec 26, 2017 7:55 pm 
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thomas.adamas wrote:
Barbra provides a valuable reality check.
If someone were to give this stone to a cutter, telling the cutter that it is Topaz and it turns out to be something else, the cutting process will not proceed as expected. If it turns out to be Amber or plastic, the cutter may inadvertently burn the gem piece.
You really want to get refractive index and specific gravity measurements on this stone before proceeding any further.

I agree Thomas, and after reading her post I called John Caruso at Gemological Evaluation & Marketing Services back and went in. We spent the afternoon talking gems and science of stones and tested my stone out of the setting. He did Specific Gravity and RI and they were right but he wasn't 100%. He spent the next hour hunting an inclusion he saw the first time he looked at the stone to see if it was two phase after looking under 120x and 240x and back to 120x he finally smiled and said we were good to go. He also weighed it and found it to be 83.75cts. He is going to get me some estimates to repair the cut in one piece for now. He recommended waiting until after the re-cut to write it up but said I could quote him in the meantime.


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 Post subject: Re: Re-cutting a Topaz
PostPosted: Tue Dec 26, 2017 10:39 pm 
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rogerg wrote:
thomas.adamas wrote:
Barbra provides a valuable reality check.
If someone were to give this stone to a cutter, telling the cutter that it is Topaz and it turns out to be something else, the cutting process will not proceed as expected. If it turns out to be Amber or plastic, the cutter may inadvertently burn the gem piece.
You really want to get refractive index and specific gravity measurements on this stone before proceeding any further.

I agree Thomas, and after reading her post I called John Caruso at Gemological Evaluation & Marketing Services back and went in. We spent the afternoon talking gems and science of stones and tested my stone out of the setting. He did Specific Gravity and RI and they were right but he wasn't 100%. He spent the next hour hunting an inclusion he saw the first time he looked at the stone to see if it was two phase after looking under 120x and 240x and back to 120x he finally smiled and said we were good to go. He also weighed it and found it to be 83.75cts. He is going to get me some estimates to repair the cut in one piece for now. He recommended waiting until after the re-cut to write it up but said I could quote him in the meantime.


Do you mind sharing with us what those test results are?
What was his RI valve and SG result?
We are good to go is not a test result. My wife is a GIA gemologist and has been since 1995. In our business she has never given that verbage as a test result. i am not saying your gemologist is not up and up, just curious what his actuall test values were.
Greg

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 Post subject: Re: Re-cutting a Topaz
PostPosted: Tue Dec 26, 2017 11:06 pm 
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glhays wrote:
rogerg wrote:
thomas.adamas wrote:
Barbra provides a valuable reality check.
If someone were to give this stone to a cutter, telling the cutter that it is Topaz and it turns out to be something else, the cutting process will not proceed as expected. If it turns out to be Amber or plastic, the cutter may inadvertently burn the gem piece.
You really want to get refractive index and specific gravity measurements on this stone before proceeding any further.

I agree Thomas, and after reading her post I called John Caruso at Gemological Evaluation & Marketing Services back and went in. We spent the afternoon talking gems and science of stones and tested my stone out of the setting. He did Specific Gravity and RI and they were right but he wasn't 100%. He spent the next hour hunting an inclusion he saw the first time he looked at the stone to see if it was two phase after looking under 120x and 240x and back to 120x he finally smiled and said we were good to go. He also weighed it and found it to be 83.75cts. He is going to get me some estimates to repair the cut in one piece for now. He recommended waiting until after the re-cut to write it up but said I could quote him in the meantime.


Do you mind sharing with us what those test results are?
What was his RI valve and SG result?
We are good to go is not a test result. My wife is a GIA gemologist and has been since 1995. In our business she has never given that verbage as a test result. i am not saying your gemologist is not up and up, just curious what his actuall test values were.
Greg

The "good to go" was me. He simply stated that the inclusion type he was looking for was indeed present and after an hour plus looking we were just happy to finish. RI was 1.629 and the SG was a tad high around 3.63 if memory serves. The anomalous SG is why he wouldn't bless it until he found the right inclusion. I didn't write the particulars down pending getting the written report from John. I called him back earlier for the RI but the stated SG is from memory and is close but not guaranteed.


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 Post subject: Re: Re-cutting a Topaz
PostPosted: Sun Dec 31, 2017 11:04 am 
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We took the stone out of the setting for testing and I'm still deciding whether to repair cut it or not. The CFO is worried about weight loss and I worry about the window. Can anyone give me a guesstimate on percent loss on a re-cut in the same shape? here are a few profile shots..
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 Post subject: Re: Re-cutting a Topaz
PostPosted: Mon Jan 01, 2018 7:03 am 
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OK , Let me guesstimate, since I am no expert I am only doing so to test how my way of handling this would fare with experts.

Since the stone is shallow as compared to the width of stone , the depth should at least be 60% or more to close that window , it's width has to be reduced so the depth % increases upto the required measure . After having ground off width I would have to look at length and width ratio to determine that has not gone off too much. Though the beauty is in the eye of beholder , much repeated fallacy , a 66-68 % ratio is required between two sides to give it a balanced look. Once both these ratios have been corrected the stone will then be faceted meaning another 20 % loss in weight from the preform to final shape.

So I would say best way to estimate the final weight of the finished stone would be the depth of stone * required width * required length * SG of topaz * . 0026 ( a measure given for ovals , for cushion would be different , pls check for it in the topics given on the left of webpage).

That is how I do things presently . If really Topaz the stone demands you take it to some really great cutter even if you have to wait for it and travel long distance.

All the best.


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 Post subject: Re: Re-cutting a Topaz
PostPosted: Mon Jan 01, 2018 8:28 am 
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[-X Please be careful and get the professional tested. Natural imperial topaz has a strong dichroismus.
Look at this stones:
https://www.gemselect.com/other-gems/golden-topaz.php
In the corners you can see clearly the stronger orange. In a rich colored stone like yours, this effect has to be even more present.

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 Post subject: Re: Re-cutting a Topaz
PostPosted: Mon Jan 01, 2018 4:00 pm 
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mrb wrote:
OK , Let me guesstimate, since I am no expert I am only doing so to test how my way of handling this would fare with experts.

Since the stone is shallow as compared to the width of stone , the depth should at least be 60% or more to close that window , it's width has to be reduced so the depth % increases upto the required measure . After having ground off width I would have to look at length and width ratio to determine that has not gone off too much. Though the beauty is in the eye of beholder , much repeated fallacy , a 66-68 % ratio is required between two sides to give it a balanced look. Once both these ratios have been corrected the stone will then be faceted meaning another 20 % loss in weight from the preform to final shape.

So I would say best way to estimate the final weight of the finished stone would be the depth of stone * required width * required length * SG of topaz * . 0026 ( a measure given for ovals , for cushion would be different , pls check for it in the topics given on the left of webpage).

That is how I do things presently . If really Topaz the stone demands you take it to some really great cutter even if you have to wait for it and travel long distance.

All the best.

I have been in contact with a few well regarded cutters including some members and have tentatively arranged with Chris Wolfsberg to do the work. But as has been suggested by others all the cutters I spoke to want a confirmation of ID from a major lab prior, which is something I intended anyway but it was pointed out that it is a "new" stone after the re-cut so now I have a "chicken or egg" problem. If I get a full report before cutting I have to pay again after it. Does any lab do an ID then send it to the cutter who would then send it back for final report?


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 Post subject: Re: Re-cutting a Topaz
PostPosted: Mon Jan 01, 2018 11:15 pm 
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I think you should enquire directly from the lab of your choice how they would send the stone back and whether they would send it to given address other than the stone came from.

Lab reports are expensive when origin determination and color /rarity comments are also needed. But they also provide brief reports giving ID and treatment statement which is your requirement at present. These would cost you under a $100 at most major labs , small private one's, if you can find closer to your location would charge much less..

Good luck


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 Post subject: Re: Re-cutting a Topaz
PostPosted: Tue Jan 02, 2018 12:21 am 
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mrb wrote:
I think you should enquire directly from the lab of your choice how they would send the stone back and whether they would send it to given address other than the stone came from.

Lab reports are expensive when origin determination and color /rarity comments are also needed. But they also provide brief reports giving ID and treatment statement which is your requirement at present. These would cost you under a $100 at most major labs , small private one's, if you can find closer to your location would charge much less..

Good luck

That makes my life a lot easier! I thought I'd have to pay the big bucks twice.
Thanks!


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 Post subject: Re: Re-cutting a Topaz
PostPosted: Tue Jan 02, 2018 2:52 pm 
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Even if you have a 50% weight loss, you will still yield a large 30ct.+ stone. A precision cut will produce a more attractive and more valuable stone. I have seen a 32ct. Red topaz in the H. Stern shop priced at 135K. Like other's have said, a positive I.D has to be the first step. Anything can happen to a stone during a recut or a cut from rough. The liability is on the stone owner not the cutter. Here is a nicely cut tri-color topaz.


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 Post subject: Re: Re-cutting a Topaz
PostPosted: Tue Jan 02, 2018 3:45 pm 
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I suspect that if we cut Roger's topaz down to 10 carats we ain't gonna get dichroism like that. :wink:


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 Post subject: Re: Re-cutting a Topaz
PostPosted: Tue Jan 02, 2018 5:30 pm 
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Barbra Voltaire wrote:
I suspect that if we cut Roger's topaz down to 10 carats we ain't gonna get dichroism like that. :wink:

Heh heh... For sure!!!! NICE stone!!


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