CIBJO releases Gemmological Special Report: considers process of separating measurable facts from opinion; See Gemological Articles below.
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 Post subject: Re: Synthetic opal?
PostPosted: Mon Jul 02, 2012 12:27 pm 
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That's gemology for you :P :lol: .

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 Post subject: Re: Synthetic opal?
PostPosted: Tue Jul 03, 2012 5:35 am 
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Barbara O. Ellis, GG wrote:
That's gemology for you :P :lol: .


You are so right! :D

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 Post subject: Re: Synthetic opal?
PostPosted: Tue Jul 31, 2012 8:59 am 
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Hi to everybody!
Synthetic opal DOES exist, we all must remember the "Mexi-Fire" synthesis, which is NOT an imitation of fire-opal! Recently I was sold a Kyocera opal synthesis in Idar-Oberstein, and the seller declared me it is a rightful synthesis and not an imitation! By microscope I think you just have to compare a natural stone, a synthetic one and an imitation for realizing the difference between one another, otherwise it might be difficult to distinguish them, expecially if you don't see them every day!
Greetings from Italy :smt002 by Riccardo.


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 Post subject: Re: Synthetic opal?
PostPosted: Tue Jul 31, 2012 11:23 am 
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A New Type of Synthetic Fire Opal: Mexifire
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Abstract

Synthetic opals have been produced and used in jewelry for more than three decades, and various imitation opals have been introduced in the trade. This article describes a new type of synthetic fire opal marketed as "Mexifire." Some of the gemological properties of this synthetic are similar to those of natural fire opal. However, a low SG value (<1.77) offers strong evidence of synthetic origin, and further indications are provided by a relatively low Rl value (<1.40) and the presence of scattered pinpoints when examined with magnification.


Direct Link to Download pdf
[pdfview]http://gia.metapress.com/content/y0564520l7714175/fulltext.pdf[/pdfview]


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 Post subject: Re: Synthetic opal?
PostPosted: Tue Jul 31, 2012 11:55 am 
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#-o

Sometimes I wonder WHY I did ask? Maybe I should live in my little bubbletent and just enjoy my gems, and don´t bother if they are real or fake, they are nice to look at anyway! :? :wink:

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 Post subject: Re: Synthetic opal?
PostPosted: Tue Jul 31, 2012 2:12 pm 
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So sorry Lennie for the sidetrack. Some might find the information on Synthetic Fire Opal useful, as it does address the subject of synthetic opal.

Your question was initially how to determine if an opal (not orange fire opal) is synthetic.
There is not a great deal in the literature...and I don't know if you clicked through to GemInterest, but it supplies some useful visuals.

-Synthetic opal has a distinctive snakeskin pattern. This may be the most diagnostic feature and does NOT refer to patches of color being snake like: Check out this picture at 45X directly from Geminterest:
It actually reflects the columnar character of synthetic opal seen on the surface:
Image
Above image courtesy of A New Look at Synthetic Opals.

From Dr. Barbara Smigel's Free Gemology Course, here is another example of the features pictured above:
Image
This is useful because it also illustrates the columnar structure from profile.

One has to be able to visually distinguish the synthetic snakeskin from the peculiar character of some of the Wollo (Welo) opals:
Image..Image
Above images courtesy of The Blog of the Natural History Museum of Los Angeles

Hope this is useful.


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 Post subject: Re: Synthetic opal?
PostPosted: Tue Jul 31, 2012 2:27 pm 
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Great post Barbra! Thanks.

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 Post subject: Re: Synthetic opal?
PostPosted: Wed Aug 01, 2012 6:14 am 
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Now THAT was some info I wanted! Great! :D

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 Post subject: Inclusions in non-natural opals
PostPosted: Wed Aug 08, 2012 7:06 pm 
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:o
Hi,

What are "chicken wire" inclusions in opals? I looked at the pictures, and still can't tell what it is. Thanks.


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 Post subject: Re: Synthetic opal?
PostPosted: Thu Aug 09, 2012 12:43 am 
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Google "chicken wire" and you'll see the pattern that the columnar structure (not "inclusions" in the usual sense of the word) in synthetic opals is sometimes named for :) .

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