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An observation of two diamonds with GIA certificates
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Author:  thomas.adamas [ Thu Apr 14, 2016 2:57 pm ]
Post subject:  An observation of two diamonds with GIA certificates

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?

Author:  Bill Hanneman [ Thu Apr 14, 2016 4:33 pm ]
Post subject:  Re: An observation of two diamonds with GIA certificates

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.

Author:  Barbra Voltaire, FGG [ Thu Apr 14, 2016 4:43 pm ]
Post subject:  Re: An observation of two diamonds with GIA certificates

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]

Author:  thomas.adamas [ Thu Apr 14, 2016 9:09 pm ]
Post subject:  Re: An observation of two diamonds with GIA certificates

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.

Author:  Barbra Voltaire, FGG [ Thu Apr 14, 2016 10:42 pm ]
Post subject:  Re: An observation of two diamonds with GIA certificates

You are certainly making sense, Thomas. :smt102

Author:  thomas.adamas [ Fri Apr 15, 2016 2:36 pm ]
Post subject:  Re: An observation of two diamonds with GIA certificates

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.

Author:  Conny Forsberg [ Wed Aug 17, 2016 4:26 pm ]
Post subject:  Re: An observation of two diamonds with GIA certificates

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.

Author:  Barbra Voltaire, FGG [ Sat Aug 20, 2016 1:57 pm ]
Post subject:  Re: An observation of two diamonds with GIA certificates

Have you thought of contacting GIA for an explanation?
Certainly there exists instruments which could make this determination without the subjective use of eyes.

Author:  thomas.adamas [ Mon Aug 22, 2016 1:42 pm ]
Post subject:  Re: An observation of two diamonds with GIA certificates

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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