Post subject: Re: synthetic diamond testing moissanite
Posted: Tue Jan 03, 2017 10:23 pm
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21600 Location: San Francisco
Sometimes moissanite is cut in a way which can be confusing when mounted..i.e. attempting to hide double refraction. BUT viewing oblique to the table will enable you to spot it.
Sidebar.....I see very little moissanite in the lab for gem ID....Diamond Imitations are 99.9% CZ. Kinda like "alexandrite": 99.9% of the time it will be vanadium doped synthetic sapphire.
Post subject: Re: synthetic diamond testing moissanite
Posted: Wed Jan 04, 2017 6:44 am
Gold Member
Joined: Wed Jan 23, 2013 5:29 pm Posts: 1047 Location: Paris
Peters wrote:
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
I agree with Peters. A 1 carat round brilliant cut stone won't have the same dimensions if it is a moissanite or a diamond, due to the difference in SG. This is for me the fastest and easiest way, available to anybody, to differentiate both, or other diamond imitations. You just need a small calculating machine, and apply the right formula.
Post subject: Re: synthetic diamond testing moissanite
Posted: Wed Jan 04, 2017 3:11 pm
Gold Member
Joined: Mon May 14, 2007 11:00 am Posts: 1133 Location: Monterey, CA
John Fitzgerald wrote:
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.
I am working on that. Basic gemology is so simple that it should be taught as an aside in every high school physics class.
Post subject: Re: synthetic diamond testing moissanite
Posted: Thu Jan 05, 2017 1:38 pm
Active Member
Joined: Sat Jun 18, 2016 11:24 am Posts: 63
So: 9% of our 45 synthetic diamonds test consistently and repeatably as moissonite on the Presidium Multi Tester III 9% have variable results; testing as moissonite one try and diamond on another try. That is 18% with a potential to confuse the tester. Of the 75 natural diamonds tested with the tester, in the same manner, none tested as moissonite. All tested as diamond. it appears not all synthetic diamonds are "created" equally. In the future we will reject any synthetic that tests as moissonite. Don't misunderstand please. These diamonds are synthetic diamond and not moissonite, that was never the question. The problem is that we are representing them as the same substance natural diamond; the only difference being that they only made in the lab. When every jewelry shop uses a moissonite/diamond tester as a screening device, and certain of these synthetics fail this admittedly less-than-perfect test consistently, there becomes a problem for the client. Especially if they are attempting to resell an engagement ring set with a synthetic diamond that tests moissonite; as was the case in this situation.
Post subject: Re: synthetic diamond testing moissanite
Posted: Thu Jan 05, 2017 4:27 pm
Site Admin
Joined: Sun Oct 16, 2005 12:22 pm Posts: 21600 Location: San Francisco
The Gemmoraman is a reliable and sophisticated, fully automatic Raman & Photoluminescence (PL) spectrometer that will positively and consistently give results which a gemological professional can depend upon. Instruments of this sort are relied upon in every respected gem lab internationally.
Perhaps within the next few years instruments will be developed that are even more reliable than Gemmoramans, Fourier Transform Infrared Spectrometers, UV-Vis-NIR spectrometers and Laser ablation–inductively coupled plasma–mass spectrometrers. But as it stands now, these instruments are as good as Gem-ID gets.
I don't think anyone would seriously compare the efficacy of the instruments above with a thermal or electiric probe, which is why labs do not use them.
Post subject: Re: synthetic diamond testing moissanite
Posted: Thu Jan 05, 2017 5:07 pm
Active Member
Joined: Sat Jun 18, 2016 11:24 am Posts: 63
If a test is repeatable, and shows the same result each time, then something is being revealed. It would be nice if we all worked in labs; I doubt though that you would recommend testing each "diamond" that is left for sizing or re- tipping at a repair facility with raman photoluninescence etc. This information is valuable to anyone who is contemplating selling synthetic diamonds. It is also a caveat that should be disclosed by all producers of synthetic diamond.
Post subject: Re: synthetic diamond testing moissanite
Posted: Fri Jan 06, 2017 11:54 am
Active Member
Joined: Sat Jun 18, 2016 11:24 am Posts: 63
Just reminds me of the diffused Andesine debacle. Immersion cell and a microscope revealed the fraud. Took a long time for the hard-core science to catch up. I think we can all agree that there is not a producing red andesine mine in Tibet, nor in the Congo. Never mind... that was long ago, and an embarrassing gemological incident; still makes me squirm to remember. As a retailer of both natural and synthetic diamonds we will pick the "gems' we deem serve our clients needs best. Everyone, of course, is entitled, and encouraged, to do the same for their clients. I do appreciate the feedback on this subject. Thank you all.
Post subject: Re: synthetic diamond testing moissanite
Posted: Fri Jan 06, 2017 1:25 pm
Valued Contributor
Joined: Sat Nov 05, 2016 11:29 am Posts: 142
Interesting... Especially as things are repeatable... So, what's going on? Do some of the synthetics have different heat absorption characteristics than the natural stones?
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