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 Post subject: synthetic diamond testing moissanite
PostPosted: Tue Jan 03, 2017 11:56 am 
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What a surprise!
We sold a 1.00 carat synthetic diamond, and the engagement fell through. It was past our return date so we did not offer refund. the fellow went all over town trying to sell it and everyone tested it as moissanite. "No way" i said, and I tested it with a probe: moissonite. This synthetic has a report, and laser inscription. What a surprise. Also no double refraction.
Has anyone else had experience with synthetic diamond testing as moissanite with a probe? I believe it to be a synthetic diamond, as represented by our major diamond producing supplier. I did read long ago that moissanite can be grown cubic and singly refractive; we will send this to GIA for further analysis and possibly an expatiation, though this may be only a far-out speculation.
Just another exciting experience associated with this new product.


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 Post subject: Re: synthetic diamond testing moissonite
PostPosted: Tue Jan 03, 2017 12:01 pm 
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hi,

i have no knowledge of single refractive synthetic moissanite and i am sorry i do not trust ANY probe/pen diamond tester. please let us know about the outcome from GIA. :D

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 Post subject: Re: synthetic diamond testing moissonite
PostPosted: Tue Jan 03, 2017 1:41 pm 
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Thank you Alberto. I also have no experience with singly refractive moissonite. I have gone through our remaining synthetic diamond inventory and three consistently show Moissonite. I too have little trust in thermal testers although it is interesting the the results are repeatable with certain stones.
I tested the SG and it is higher than moissonite (3.22) and sinks in MI liquid.


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 Post subject: Re: synthetic diamond testing moissonite
PostPosted: Tue Jan 03, 2017 1:57 pm 
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A GemmoRaman could certainly sort that our for you.

I agree with Alberto, the probes are not reliable and when one is dealing with very expensive gems, they should also invest in the best tools available. :wink:


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 Post subject: Re: synthetic diamond testing moissonite
PostPosted: Tue Jan 03, 2017 2:10 pm 
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Hi,
Actually, that is well-known phenomena for synthetic HPHT: in fact most of a moissanite testers works on combination of thermo/electrical conductivity: HPHT synthetics in fact has B in lattice for almost all colourless/blue (IIb type), so they are semiconductive and similar to moissanite for that test (more info: http://www.quicktest.co.uk/moissanite-t ... rticle.htm).

Peters


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 Post subject: Re: synthetic diamond testing moissonite
PostPosted: Tue Jan 03, 2017 3:00 pm 
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me again,
Spoke to the big brains at GIA and as usual they were very generous with their time and info. Bottom line; moissonite and diamond are close and a difficult separation for the probes. They don't even have any probes in the lab at GIA.
Interestingly, it was confirmed to me that the theory of the possibility of isotropic moissonite being produced is just hogwash. No such critter. Can't be done.
Still....Why four out of our stock of 45 synthetic diamonds consistently show moissonite rather than diamond is a mystery. All from the same manufacturer. perhaps some are HPHT & others CVD????
weird... In the future we will test all synthetics we get in and if they consistently fool the probe we will reject them.
Always something new to learn.
Happy New Year.


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 Post subject: Re: synthetic diamond testing moissonite
PostPosted: Tue Jan 03, 2017 3:08 pm 
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Hi,
Again second time:... HPHT synt. diamonds has boron in the lattice, they are semiconductive (IIb type by that property): even IIb naturals will be showed as moissanite. That is a well-known fact for ALL HPHT synthetic diamond dealers, read link!

Peters


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Tue Jan 03, 2017 3:13 pm 
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Peters.....thanks for that information. =D>
I'm sure you would agree that a truly professional diamond dealer would never rely on a probe to determine much of anything.


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Tue Jan 03, 2017 3:23 pm 
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Exactly: diamond testers are constructed to measure just one property + these are really cheap and inaccurate devices... but they are useful "secondary" tools: we have raman/ftir... but still 415 nm laser and thermal tester we use daily as secondary tests: they are fast - but have many limitation


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 Post subject: Re: synthetic diamond testing moissonite
PostPosted: Tue Jan 03, 2017 3:38 pm 
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mowgli2001 wrote:
. They don't even have any probes in the lab at GIA.


i am not aware of any gemlab who has/use one of them, those are not gemlab tools........

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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Tue Jan 03, 2017 3:44 pm 
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They may not be in gem labs, but they certainly are in use in jewelry retail locations.
Peters, thanks for the info. So, Boron is used as a flux in all HPHT synthetic diamonds? And that makes them electrically conductive; as in a natural type IIb diamond. Sorry, didn't quite catch that from the link.
Thanks.


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Tue Jan 03, 2017 4:03 pm 
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There are two sources of boron: pollution in systems used to grow blue synthetic HPHT diamonds and graphite as source material for a diamond cell: even very high purity of graphite contain boron as an impurity, for CVD diamonds there is a principal difference as methane gas is used as carbon source. Yes, B has three valence bond, what makes free electron for carbon: free electron means, then you could conduct electricity... in simple words
You just need to know, then there is no problem with your stones and explain it to your clients: even by stone size you could easily spot moissanite for loose stones: moissanite weight for classic 1 ct: D 6,4 x 6,4 x 4 mm will be 0,9 ct, you could use simple formula: diameter x diameter x height x SG diamond (3.52) * 0,00175 = 6.4*6.4*3.52*4*0.00175= 1,01 ct for moissanite weight=6.4*6.4*3.22*4*0.00175=0,92 ct, to have 1 ct you must have =6.6*6.6*3.22*4.15*0.00175

P:-)


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Tue Jan 03, 2017 6:05 pm 
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I am a traveling appraiser. There have been instances where I has to arbritrate between two stores because one store used these probes and had diamonds tested as moissanite. This applies to natural diamonds as well as synthetic. A cursory inspection with a miscroscope easily identifies them as diamonds, but some in our industry have limited knowledge. The diamonds that have boron in their lattice (IIB)will test as moissanite. A number of the diamonds coming on the market (just saw a GIA article discussing boron in large Chinese synthetic diamonds) are going to fool the testers.
The upside is that experienced gemologists will always have a job. The downside is that a number of people are going to get a bad taste of the jewelry business because of poorly trained personnnel.
Gary Roskins did an excellent article on this some time ago and I am hoping that he finds time to update it.

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 Post subject: Re: synthetic diamond testing moissonite
PostPosted: Tue Jan 03, 2017 6:18 pm 
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Barbra Voltaire wrote:
A GemmoRaman could certainly sort that our for you.

I agree with Alberto, the probes are not reliable and when one is dealing with very expensive gems, they should also invest in the best tools available. :wink:

Happy New Year:
The best tool you have available is one's eyes and all that is needed to separate Diamond from Moissanite is one eye.
Why do you gemologists all try to sell expensitve instruments for solving simple problems?

The answer to this one is B:D and the Hodginson Method. Any child can lear in less that two minutes. :D :D


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Tue Jan 03, 2017 6:31 pm 
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Dr Bill you are correct. And now if you can teach all those people working for chain stores in the malls to take your training it would be a great accomplishment.

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