GIA to Ideal Cutters: Back to the 3-D Drawing Board

The first and largest installment of the Gemological Institute of America's study of diamond cuts subverts the long-held belief in the supremacy of the Ideal cut. The report confirms the opinion of many diamond cutters that there's more than one “Ideal” for a round brilliant. Among other findings, the study demonstrates that the classic Tolkowsky model does not in fact yield the most brilliance. The study could have a far-reaching impact on labs issuing top grades for Ideal cuts. Published in the Fall 1998 issue of Gems & Gemology, the report analyzes how proportion affects brilliance, the amount of white light returned through the crown of a diamond. Its authors are GIA research associate T. Scott Hemphill; Dr. Ilene M. Reinitz, manager of research and development at GIA's Gem Trade Laboratory in New York; Dr. Mary L. Johnson, manager of research and development at GIA's Gem T

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