December 14-16—SAN DIEGO, CALIFORNIA: Wholesale and retail show; Gem Faire Inc.; Scottish Rite Center, 1895 Camino del Rio S; Fri. 12-6, Sat. 10-6, Sun. 10-5
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 Post subject: An observation of two diamonds with GIA certificates
PostPosted: Thu Apr 14, 2016 2:57 pm 
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Last week my student showed me three round brilliant cut diamonds of similar size. All were graded triple X. I inspected one and could not dispute it was an excellent cut, but the other two were likely good cuts. Under 10X, several of the star facets did not meet, several top halves did not meet, the girdle went from medium to very thin on one stone, and the other stone had visible polishing lines on a number of pavilion facets. All these certs were from the GIA in New York, USA. The stones had dimensions and inclusion plots corresponding to the certificates.
Besides the gross lack of photographic information on GIA certificates, there seems to be some blatant negligence or dishonesty in the grading process of those two particular diamonds.
This constitutes a serious threat to the credibility of GIA certed stones. If we cannot trust the GIA, then who can we trust to grade diamonds accurately?

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 Post subject: Re: An observation of two diamonds with GIA certificates
PostPosted: Thu Apr 14, 2016 4:33 pm 
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thomas.adamas wrote:
If we cannot trust the GIA, then who can we trust to grade diamonds accurately?

No one, except me. :D :D :D
As long as the GIA claims (and others believe) that there is no way to describe an "ideal cut" there is no hope for accurate diamond cut grading.


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 Post subject: Re: An observation of two diamonds with GIA certificates
PostPosted: Thu Apr 14, 2016 4:43 pm 
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I'm not sure it is a matter of trust, but a matter of defining their parameters. There is wiggle room in the GIA's definition of excellent.
[pdfview]http://diamondcut.gia.edu/pdf/WN11A3.pdf[/pdfview]


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 Post subject: Re: An observation of two diamonds with GIA certificates
PostPosted: Thu Apr 14, 2016 9:09 pm 
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Sure, an excellent cut would be within a range of parameters. However, the GIA, and any other gemological laboratory, would deliver value and benefit to their customers if 10X high definition crown and pavilion photos of the gemstone were embedded on the certificate so you can see the faceting work.
Excepting knots, cross grains and surface inclusions, there is no excuse for polishing lines, unmet or overrun facet junctions on any stone with "excellent" faceting. That is amateur stuff that cutters move past after their first year.

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Last edited by thomas.adamas on Fri Apr 15, 2016 2:43 pm, edited 1 time in total.
added inclusions


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 Post subject: Re: An observation of two diamonds with GIA certificates
PostPosted: Thu Apr 14, 2016 10:42 pm 
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You are certainly making sense, Thomas. :smt102


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 Post subject: Re: An observation of two diamonds with GIA certificates
PostPosted: Fri Apr 15, 2016 2:36 pm 
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Barbra Voltaire wrote:
You are certainly making sense, Thomas. :smt102

The technology of HD photography and printing is inexpensive and ubiquitous. GIA's customers will have to repeatedly demand that service be implemented on gemstone certificates and GIA will comply, eventually.

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 Post subject: Re: An observation of two diamonds with GIA certificates
PostPosted: Wed Aug 17, 2016 4:26 pm 
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I agree with Thomas. If missed facet meets, bad girdles and apparent polishing lines are present the stones can not be regarded as excellent cut. Seems GIA graders are letting through stuff in a not trustworthy way.

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 Post subject: Re: An observation of two diamonds with GIA certificates
PostPosted: Sat Aug 20, 2016 1:57 pm 
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Have you thought of contacting GIA for an explanation?
Certainly there exists instruments which could make this determination without the subjective use of eyes.


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 Post subject: Re: An observation of two diamonds with GIA certificates
PostPosted: Mon Aug 22, 2016 1:42 pm 
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Barbra Voltaire wrote:
Have you thought of contacting GIA for an explanation?
Certainly there exists instruments which could make this determination without the subjective use of eyes.


I did not own or work on the stones, just examined those at the urging of my student. Neither of us could believe GIA would mess up to that extreme. Perhaps that is the "new reality".

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