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 Post subject: synthetics vs natural ID
PostPosted: Tue May 30, 2017 9:15 pm 
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Location: East Tennessee
I am a GIA trained gemologist, but I took the course years ago (1996) and haven't used my skills much. My biggest concern is being able to identify synthetics vs natural. I can identify flame fusion corundum, but premium synthetics are a problem. Identifying these seems to be a matter of using magnification to identify inclusions and that is where I am weak. I looked for books with relevant photos, but all I can find is the very expensive Gubelin and Koivula three volume set and some O'Donough books that are also expensive and evidently out of print. It seems that there ought to be a book or website with the key inclusion photos and descriptions to ID premium synthetics of corundum, emerald, spinel and alexandrite as well as other common problem stones, like dyed jade and lapis. I know that there are a few things, such as flawless corundum, which would defy simple gemological methods and would require a GIA lab report, but I'd think that most stones could be ID'ed with the right manual(s). Any advice?
TIA,
royjohn

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 Post subject: Re: synthetics vs natural ID
PostPosted: Tue May 30, 2017 11:33 pm 
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Hi royjohn.
Bear in mind that most synthetics are cheap, cheap, cheap. In other words flame fusion.

There are excellent pictures of inclusion in synthetic gems on http://www.geminterest.com .

Synthetic emeralds can often be tagged by refractive index.

Inspecting gems with immersion (methylene iodide for corundum and spinel, benzyl benzoate for beryl) can be very telling, whereas dark field illumination can be confusing.

With immersion, natural mineral inclusions will go light to dark as you rotate the stone. Solid inclusions typically found in synthetics will remain dark in all directions.

I was trained in Germany and the microscopes typically by their gemmological labs and associations are horizontal, not vertical. They are made for immersion and positive identification of inclusions.

Diamonds are best observed with vertical dark field illumination.....other minerals not.


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 Post subject: Re: synthetics vs natural ID
PostPosted: Wed May 31, 2017 12:52 am 
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Hi Barbara,
Wow, thanks! I hadn't seen the geminterest website before and took a quick look...more than enough inclusion photos for a LOT of study!

I was aware of the Kruss horizontal microscopes and in fact saw one in a gemologist's office in Belgium when I was there a few weeks ago (I'm an American in Tennessee most of the time). I can probably rig my Bausch and Lomb to use horizontally, but I don't quite fathom why this is better than vertical.

I was also not aware that natural inclusions will turn dark and light in immersion while synthetic ones do not...such a great insight that I wonder why I haven't seen it in one of the typical texts already.

Now my main problem is that I don't work in a jewelry environment daily, so I don't see a lot of stones to get experience.

Many thanks for your help! :D :D :D
royjohn

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 Post subject: Re: synthetics vs natural ID
PostPosted: Wed May 31, 2017 7:00 am 
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royjohn wrote:
I was also not aware that natural inclusions will turn dark and light in immersion while synthetic ones do not...such a great insight that I wonder why I haven't seen it in one of the typical texts already.

You can observe this even without immersion, often with a loupe only, and this is quite logical. Because natural inclusions are crystalline and orientated in growth so they alternatively catch and don't catch the light, while rounded bubbles or other inclusions in synthetic and artificial products catch the light always the same way when you rotate the stone.


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