Welcome to GIA's Online Series
of Articles on Diamond Cut

The question of how a diamond's proportions affect its appearance has become a major topic for discussion within the diamond trade and among consumers. Cut issues are complex. A considerable amount of foundational information is needed to understand and evaluate the theories proposed and claims made in the diamond marketplace. In order to explain the basis of our cut research and discuss key issues in the evaluation of proportions for round brilliant cut (RBC) diamonds, we plan to post topical articles here in our GIA on Diamond Cut series.

An assortment of round brilliant cut (RBC) diamonds. Photo provided by Maha Tannous.

For the most part, these short articles will present information on diamond cut and appearance that has been taken from the fields of gemology, physics, optics, computer modeling, and diamond history. Experienced gemologists are probably familiar with some of the material in these articles. However, we feel that bringing this diverse information together will give our audience a better understanding of how the proportions of an RBC diamond affect various appearance factors (e.g., brilliance, fire, and scintillation). These articles will also provide an introduction to—and background for—future technical articles on this general subject that will be produced by GIA.

GIA has been investigating the issue of diamond cut for decades. More recently, GIA has increased its focus on this issue by using computer modeling and extensive observation testing to explore the relationship between diamond cut and diamond appearance.

The first part of our current research resulted in the article by Hemphill and others entitled, "Modeling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Brilliance" (Gems & Gemology, Fall 1998, pp. 158-183; hard copy available through Subscription Services at 760-603-4000 ext. 7142). The main focus of that article was the analysis, by means of computer modeling, of light return (brilliance) in RBC diamonds. Our next major research article on diamond cut, "Modeling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Fire, and More about Brilliance" (Gems & Gemology, Fall 2001, pp. 174-197; hard copy available through Subscription Services at 760-603-4000 ext. 7142), contained results of our work on "fire"—that is, the observable bursts of color—in RBC diamonds. We hope that the articles in this series will educate and prepare readers, so that they may understand better the changes in appearance that result from variations in a diamond's cut.

Updates to this series will be posted on the Article Archive. Updates will also be announced in the GIA Insider, our bi-monthly newsletter. If you would like to subscribe to the GIA Insider (at no charge), please visit our subscription page.

We hope that you enjoy these articles, and invite any feedback or comments that you may have. You may contact us by email at DiamondCut@gia.edu.