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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Fri Jan 06, 2017 10:02 pm 
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mowgli2001 wrote:
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.


I won't open the flood gates again with andesine, but the discovery of treatment had NOTHING to do with microscopic observation darkfield nor immersion. This misinformation was presented in some blogs which turned out to be based on bad science.

Using the principles of tectonic geology in concert with the known chemistry of the feldspar group, Dr. George Rossman (Professor of Mineralogy at the California Institute of Technology) determined, with the aid of extensive radioactive isotope experimentation that material represented as Chinese red andesine and Tibetan red andesine had the same chemical markers as the yellow feldspar submitted as originating from the Mongolia/China border.

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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 11:52 am 
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CAT scans and MRI scans are wonders of science and have advanced medicine in wonderful ways. Still...I doubt that any doctor would advise throwing out the stethoscope. There is still room in the world for classical gemology; accomplished with traditional tools in concert with human intellect.


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 12:07 pm 
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One of the big problems I run into is people that only know how to run test equipment.
They do not know how to verify proper operation of the same equipment.
It was fun to run rings around them in the old days!
I could do more with much less complicated equipment because I knew how to verify proper operation, and calibrate it if necessary...
I see an over reliance on fancy test gear: It is better to have hands on experience with the tools of the trade, then use the more expensive equipment when it is warranted.
Blind use of the Guessomatic Model 5000-D "ID anything under the Sun" equipment isn't a cure all or substitute for knowledge...

-Tom


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 1:04 pm 
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How many PhD's working in gem identification do you feel are unable to understand the science behind what they are doing? :D
One has to understand the limitations of every instrument. They all have limitations. The individuals investing in the Guessomatic Model 5000-D "ID", are not the ones making discoveries or writing pier reviewed reports. [-X

How many gemologists working at GIA have a refractometer, polariscope, microscope and UV lights within arms length at their desk desk? All of them. Analogous to a stethoscope. (A better analogy would be using cat scans and MRI's after not getting enough information with an xray.)


How many have a probe at their desk? None of them. :wink:


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 2:33 pm 
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Definitely - I would trust a stethoscope more than a probe.
Would I trust more a Chelsea filter or a probe ? I don't know ! :?:


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 2:49 pm 
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Barbra Voltaire wrote:
How many PhD's working in gem identification do you feel are unable to understand the science behind what they are doing,? :D
One has to understand the limitations of every instrument. They all have limitations. The individuals investing in the Guessomatic Model 5000-D "ID", are not the ones making discoveries or writing pier reviewed reports.


Barbra, I couldn't have said it better!

-Tom


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 4:17 pm 
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Isi wrote:
Definitely - I would trust a stethoscope more than a probe.
Would I trust more a Chelsea filter or a probe ? I don't know ! :?:


Completely agree, Isi. I think both tools are attributed with the ability to identify stuff that they are unable to do.
Folks get them because they are relatively inexpensive and credited with capabilities they don't have.

Recently I got a PM from someone wanting to know how to separate natural from synthetic amethyst with their Chelsea. They were planning on bringing it to Tucson. :(
Where does one begin with a question like this?


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 5:32 pm 
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Barbra Voltaire wrote:
Recently I got a PM from someone wanting to know how to separate natural from synthetic amethyst with their Chelsea. They were planning on bringing it to Tucson. :(
Where does one begin with a question like this?


Silly you! Everyone knows that when you hit Amethyst with a hammer, only the synthetic material breaks. Genuine Amethyst is unharmed...

Seriously, you are indeed correct... I feel sorry for the people in a way, but if they don't know what they have, they should preferably not sell it, or sell it clearly disclosing that they don't know if it is natural or synthetic.
When I sell items, I let people know exactly what it is that I'm selling, and what any limiting conditions may be.
People trust me, my reputation is everything: If I can't be 100% sure of something, I disclose it.


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 8:17 pm 
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The chelsea does have some limited use cases. And narrowing the field from 'everything' to 'almost certainly diamond or moissonite*, separate these last two possibilities using an even more trivial test' strikes me as a pretty great value for how cheap the probes are. Certainly good for fast sorting in a non-lab setting.

*'or maybe refrigerated topaz but you're the one who decided to make a sketchy diamond deal in a hotel room, what is this, Lord of War??'

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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 9:31 pm 
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Sorry Stephen.
I still disagree. They are not even reliable to do that menial task.

When I was working in retail shops, we always had several on hand. Several because the shops kept replacing the "defective" ones with newer, improved units, again and again and again and.....


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 10:48 pm 
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What cases would it tend to fail on? Or were they just going nuts after a while?

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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sat Jan 07, 2017 11:21 pm 
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Didn't take that long actually. They would start by not recognizing diamonds and at that point, they would cease to be useful.
The colored stone gizmos only offer a handful of possibilities and usually when one tests an unknown three times they get 3 different IDs,


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Sun Jan 08, 2017 12:17 pm 
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Let me clarify. In a retail environment, a good quality thermal diamond tester can be a useful tool, presuming you make sure that you've given it time to thoroughly heat between tests and always have a known diamond to test before proceeding with an unknown.

It is the moissanite/diamond testers that I've found unreliable.


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 Post subject: Re: synthetic diamond testing moissanite
PostPosted: Thu Feb 02, 2017 1:16 pm 
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Right after earning my GG, I worked in a repair shop for a very large mid- to low-end jewelry chain. Because the company did little-to-no training of their sales staff and invested very little in gemological equipment, the probe diamond tester was the only test done by every store sending us repairs.
Just as some synthetic diamonds will test as moissonite, some moissonite will test as diamond if your tester is particularly old. We had a rule: no moissonite. There'd just been some rather high-profile trouble involving the alleged switching of moissonite for diamond, so our partent company declared the material could not enter the repair shop.
But because sales staff depended so heavily on probe testers, we got moissonite almost daily. And, if you kept testing the same stone multiple times in succession, the stone would heat up and you'd get two or three different results.
The basic lesson is to trust the trained eye rather than the cheap dohicky. And if you must use the dohicky, don't touch the stone directly (to avoid it heating up) and only test it again after it's returned to ambient temperature.


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