In summary we consider that the round brilliant cut grading system established by the GIA Diamond Cut Team is below the standard expected from The World's Foremost Authority in Gemology™. In our article and this exchange of letters we have outlined a number of shortcomings: when the same diamond can be graded with very different cut grades by the AGS and the GIA, two of the worlds most respected diamond cut grading labs, then neither the Internet savvy diamond buying public, nor the trade can feel confident. Observers using the common lighting environments had only a 58% with light return and fire metrics from GIA's previous virtual studies. The implied use of an unpublished metric for scintillation, and the inadequacy of light return and fire metrics bodes poorly for the future GIA's grading of other shapes of diamond cuts means that round diamonds will continue to dominate the market (one of the main concerns noted in our original article). The issue of 'green fire' shows an apparent lack of understanding of the GIA Diamond Cut Team of common illumination sources and of human eye sight. Finally we have traced some major failings in their research work to the Diamond Dock(R) or Common Viewing Environment that was used to assess diamond brightness; the background is too light a shade of gray and the fluorescent lights are too bright or too close, the observers angular orientation relative to the diamond and the light source was not regulated and the illumination area is too narrow an angular source to be useful for grading diamonds with a range of different proportions. The GIA Gem Trade Laboratory began commercially issuing grading reports with cut grades for all D-Z coloured round brilliant cut diamonds in January 2006. The grading reports being issued by the GIA and advice given by its associated Facetware(tm) have already influenced the pricing of tens of billion dollars worth of diamonds in the past year. We urge the Gemological Institute of America to consider our arguments concerning its previous research and withdraw its diamond cut grading system immediately.

Kind regards, The Cut Group

* Members of the Cut Group include Sergey Sivovolenko, Garry Holloway, Yuri Shelementiev and Janak Mistry