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Diamond Brilliance Is Clearly Termed As “Diamond Brightness”

1990: Diamond Brilliance Technology Will Revolutionize Diamond Market

December 1998

The Gemological Institute of America has announced the completion of its mathematical study on the effect of cut on the appearance of diamonds. The study appearing in the upcoming issue of Gems & Gemology. The controversial finding in the article is that many types of cut and varying combinations of proportions within the cut can give equal brilliance to the so-called "ideal" cut theorized by Tolkowski some eighty years ago.

The GIA study acknowledges many other factors in achieving an extraordinary appearance in round diamonds, among them scintillation and brilliance. The GIA will utilize the mathematical three-dimensional model to examine, with the most modern technology, the various appearance factors.

The DRB contacted the American Gem Society (AGS) in order to obtain a response to the GIA study and was told that AGS had not yet seen it. The AGS response to this study will be interesting to watch: Will AGS, the most muscular proponent of the "ideal" cut, change it’s standard in the face of a new scientific findings or will it continue to maintain that there is only one "ideal" ? Will it change the AGS parameter of the zero cut?

To understand what makes a diamond beautiful, the terms must first be defined. "Beauty", in diamond terms, encompasses brilliancy (intensity of internal and external reflections of white light to the eye from a diamond in the face-up position) and scintillation (alternating display of reflection from the polished facets of a gem seen by the observer as movement occurs or a lashing or twinkling of light). One of the results of the study has been, at least for GIA, to specify even more clearly the definitions of what is commonly termed the "brightness" of a diamond.

Within the study, "brightness" became a calculated numerical factor known as Weighted Light Return (WLR). According to GIA, values for WLR were determined for more than 20,000 combinations of proportions in diamond cuts. It is interesting to note that in one of the accompanying photos in the article, three stones were shown. Of the three, the "ideal" cut gem was less brilliant than those with larger tables.

Whether the GIA study will revolutionize the diamond business remains to yet to be seen. One wonders, though whether such an all encompassing change as this will be fought on the scientific front or as a showdown of the publicists. Certainly, jewelers and consumers alike should read the articles and consider the issues, but in the final analysis beauty is always defined by the eyes of the individual customer.


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