CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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 Post subject: CC sapphire
PostPosted: Thu Jul 11, 2019 10:38 pm 
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Hi all,

My experience with phenomenal gemstones is pretty limited, I think they’re cool, but rarely see them.

I’ve been looking at a couple stones in bezel settings for a Jeweller who had a piece made for a client with some of their jewellery they were no longer utilizing. The stones I’m looking at, I can get an RI that matches with sapphire, with a colour change from a soft pink to a light, slightly greyish blue. The spectrum of it appears more of that of a synthetic colour change sapphire, but the colours are what I was taught initially are more in line with that of natural. I’m sometimes skeptical of my results with my hand held spectrometer on set gems. Is this something that with treatment is achieved? Or is it possible I’m catching something off the setting?

Does anyone have any recommendations on best ways to be more certain with set stones when identifying? Obviously in a perfect world, and a much easier world, I would see all stones loose lol. Just trying to get some ideas on dealing with some more restrictive settings.


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 Post subject: Re: CC sapphire
PostPosted: Thu Jul 11, 2019 11:09 pm 
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I think microscopic observation is your best bet.
Cover the light well with a tissue paper. The diffused light will make it easier to see curved striae, bubbles, etc.


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 Post subject: Re: CC sapphire
PostPosted: Fri Jul 12, 2019 12:49 am 
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Unfortunately the design of this particular piece is a complete sphere, leaving absolutely nowhere for light to come through the back of the stone. Also, to much my dismay, on top of the completely closed in setting, it seems that the jeweller did not clean the stones before setting, making everything that much more interesting. I think I’ll take some fresh eyes to it again in the morning and see if I spot anything that I missed today.


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 Post subject: Re: CC sapphire
PostPosted: Fri Jul 12, 2019 5:27 am 
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Picture maybe ?


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 Post subject: Re: CC sapphire
PostPosted: Tue Jul 16, 2019 5:49 pm 
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My pictures are not superb, and I know they aren’t, but I’m still on the hunt for the right camera for myself. I don’t expect much out of the pictures but just as a small aid!


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 Post subject: Re: CC sapphire
PostPosted: Tue Jul 16, 2019 6:49 pm 
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We as gemmologists are limited by not being able o do destructive testing, and even more limited when dealing with mounted stones. That is why GIA insists that you only send loose stone in for a report.


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 Post subject: Re: CC sapphire
PostPosted: Tue Jul 16, 2019 9:37 pm 
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A spectroscope can not seperate natural from synthetic sapphire.

Give it a good look over with your scope.
Try to find a natural inclusion.

If you can't I think your optical observations with color change and lack of natural inclusions point towards synthetic.

But, there is no disgrace in calling your findings inconclusive resulting from limitations of the mounting.


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 Post subject: Re: CC sapphire
PostPosted: Tue Jul 16, 2019 10:07 pm 
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Thanks all! I always appreciate your input and advice!
In my favourite visions I always see stones loose to identify and grade, but reality isn’t always that nice. I’m not too proud to admit when my limitations are too great, but I genuinely want to make sure that I’m not overlooking any testing, I think that there is always more to learn and new perspectives to find!

Spectrum was beneficial to confirming corundum, my mistake.


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 Post subject: Re: CC sapphire
PostPosted: Wed Jul 17, 2019 12:00 pm 
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One last thing.
If there is a makers mark on the pendant, see if you can figure out who made it.
Contact them and ask.
I've done this several times with successful results.


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 Post subject: Re: CC sapphire
PostPosted: Fri Jul 19, 2019 4:58 pm 
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Anyhow, on bezel set stones, I don't know how you can get reliable results with a hand spectroscope, which requires that the light goes through.


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 Post subject: Re: CC sapphire
PostPosted: Fri Jul 19, 2019 5:45 pm 
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Not necessarily.
The light can be either reflected or transmitted.

I always start with reflected with my OPL.


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 Post subject: Re: CC sapphire
PostPosted: Fri Jul 19, 2019 10:42 pm 
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I always found myself having an easier time using reflected light over transmitted light. I always find I end up with too much light leakage around my stone if using transmitted. Ope. To any tips to getting around that!


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