Most of us would like to see the assessment of cut in round brilliants (or any shape, for that matter) simplified into a neat, easily explained package. Unfortunately, this probably will not be the case for some time to come. The lead article in this issue sheds more light on the cut question, but it also underscores its complexity. Only with careful review will our astute readers fully understand the authors’ research and, as importantly, their results.

GIA’s landmark brilliance study, published in the Fall 1998 issue of Gems & Gemology, was the first major breakthrough in the scientific analysis of cut in decades. It introduced a metric for brilliance, WLR (weighted light return), and demonstrated that many different proportion combinations can yield equally bright round brilliant cut diamonds. The article in this issue presents a metric for fire, DCLR (dispersed colored light return). With the results of these two major segments of GIA’s cut research project now published, we are very close to answering the key questions involved in proportion evaluation for round brilliants.

The authors conclude that there is no easy way to characterize the “best” cut in round brilliants for either brilliance or fire. Rather, it is the complex interaction of multiple proportions, involving all of a diamond’s facets, that must be considered in the assessment of these key appearance aspects. Furthermore, there is now even more evidence to support the conclusion that there is no one “best” cut for a round brilliant diamond.

Some generalizations can be made about DCLR, as they were for WLR. The authors clearly point this out. However, as we learn more about the complex interactions of different proportions with light, we also see the limitations under which most current cut grading systems are operating. These systems typically use small ranges of individual proportions, often with long-held historical parameters as target points. Although these well-respected parameters can produce beautiful diamonds, there are many other proportion combinations that produce diamonds of equal attractiveness. Further, the authors’ research—which also includes observations of actual diamonds—shows that the lengths of star and lower-girdle facets are critical to cut assessment in round brilliants, although no current grading systems incorporate these factors in their analysis of cut.

As the authors acknowledge, it is difficult to say whether brilliance or fire has more impact on diamond appearance in round brilliants. It is also premature at this point to combine WLR and DCLR into a single overall proportion evaluation system or cut grade. As more results are obtained from this project, however, a single cut grading system may become feasible.

In the meantime, you may ask, what does all this research mean to the gem and jewelry trade? And how will GIA use this information to serve the industry and the consuming public?

First and foremost, GIA is a non-profit public benefit corporation with an educational mission. Thus, like any college or university, we seek to better understand problems and provide solutions for the trade and the public. We have already placed a great deal of information about cut research on the GIA Web site (www.gia.edu/giaresearch). In addition, the knowledge we have gathered will be incorporated into our education courses with the all-new Graduate Gemologist program to be introduced in 2002. Also, next year we will adapt and apply knowledge gained through this research to our Gem Trade Laboratory reports.

The inclusion of this new cut information on our diamond grading reports, while revolutionary in some sense, will be largely transitional. We plan to introduce it in a way that will neither disrupt the current commercial flow of goods in the pipeline, nor require major adjustments in the use of our reports. It is likely that, as research continues, further insights on cut will be adapted to both our education program and our laboratory reports in the years to come. We also hope to develop cut-evaluation instrumentation, thus completing the circle of service. The insights gained through this cut research will be available to everyone in a variety of formats.

While we laud the efforts taken in past decades to uncover the secrets of diamond proportions and fine cutting, we know that assumptions were made that now can be either verified or corrected through modern scientific means. Marcel Tolkowsky accomplished a great deal with the limited technology and information available in the early 20th century, but the analytical power provided by modern computers and the access to literally tens of thousands of actual diamonds have given GIA the tools to propel cut research well into the 21st century.

William E. Boyajian, President
Gemological Institute of America