Professional Jeweler Archive: Editorial

June 2002


The Cut Debate

As I listened to the panelists at the American Gem Society Conclave’s town hall meeting, titled “The Importance of Cut,” it quickly became clear there was far more agreement than disagreement between the two camps arguing over how best to define diamond cutting standards.

Camp A consists of those who champion the AGS cut grading system, based on the American Ideal cut. The American Ideal is defined by parameters that have been refined many times since diamantaire and mathematician Marcel Tolkowsky first articulated them in 1919, and they continue to evolve. Proponents of the AGS system appear to say it’s best to stick to a standard that has grown organically within the industry and has wide acceptance.
Camp B consists of supporters of the Gemological Institute of America’s diamond cut research. GIA researchers took a meticulous and scientific approach to cut, using computer models and the power of computers plus human observation to look at thousands of proportion combinations to see which yielded the greatest brilliance and fire. It’s no surprise GIA, a scientific institution, took this kind of controlled look at cut instead of relying on existing industry standards. Its cut grading system, due to be unveiled in 2003, will reflect that orientation.

When you look at what both camps have discovered in reviewing and evaluating cut, there’s agreement on this key fact: Both say a number of proportion combinations yield beautiful diamonds. AGS defines beautiful as “Ideal,” while GIA prefers to say beauty means above-average brilliance and fire, as defined by its studies and human observations (GIA continues to study other appearance factors too).

Still, both groups seem to be lobbying for the hearts and minds of all who trade in diamonds, from cutters and wholesalers through retailers. What’s at stake is which lab, GIA’s Gem Trade Laboratory or the AGS Laboratory, will be considered the definitive authority on diamond cut grades. It’s a nerve-wracking moment for both labs; ultimately, the marketplace will decide, as price list publisher Martin Rapaport sagely pointed out during the AGS town meeting.

What should jewelers think? My inclination, based on a previous stint as a medical reporter, is to go with the controlled, scientifically rigorous study GIA has been conducting. But there’s also sense in the AGS argument that real-world cutters and diamantaires have tested their theories on countless diamonds and reached a consensus on which proportions lead to beautiful results. Probably the best route is for the two labs to compare notes when GIA is finished with its cut research and agree on a common set of parameters. But, of course, I’m not taking into account the competitive or financial factors involved in making such a decision.

If you want to weigh in with either organization, it would be wise to review the AGS system and the two cut research studies GIA has published so far. A review of the AGS system is contained in gemologist Robert Weldon’s article “Ground Zero” in our September 1998 issue (p. 30). To refresh your knowledge of GIA’s studies, check out Weldon’s “GIA’s Brilliant Diamond Cut Study,” January 1999 (p. 32) and “Study Moves GIA Closer to Cut Grade,” January 2002 (p. 28). All articles can be searched by title at

Please send us letters with your opinions too. I’d be glad to share how jewelers in the field are assessing this complicated but critical issue.

– Peggy Jo Donahue

Copyright © 2002 by Bond Communications