GIA presented the first results from its diamond cut research in the Fall 1998 issue of Gems & Gemology (“Modeling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Brilliance”). That article described how researchers used computer modeling to “trace” light rays through a virtual round brilliant diamond, allowing them to calculate a brilliance metric called weighted light return (WLR). Further research results on the appearance aspect of fire were detailed in the Fall 2001 issue of Gems & Gemology (“Modeling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Fire, and More About Brilliance”). In that article, GIA researchers summarized their further use of computer modeling to derive a fire metric called dispersed colored light return (DCLR).

Since these studies, GIA researchers have made over 45,000 observations on more than 1,300 diamonds. These observation tests have allowed GIA researchers to refine their brilliance and fire metrics, so that they correspond to more typical brilliance and fire observations. In addition, these tests have further reinforced GIA’s belief that a diamond’s appearance will be affected by different lighting conditions and environments. Observation tests have also supported GIA’s findings that any assessment of a diamond’s appearance on the basis of its proportions must consider every facet, along with that facet’s relationship to other facets. Although the research is ongoing and details are constantly being refined, the findings in these two Gems & Gemology articles remain the theoretical model for the study of diamond brilliance and fire.

To view a printable version of these articles, click the links below.

“Modeling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Brilliance” (Fall 1998)

“Modeling the Appearance of the Round Brilliant Cut Diamond: An Analysis of Fire, and More About Brilliance” (Fall 2001)

If you would like to purchase copies of these articles, use our online order form or contact our Subscriptions/Back Issues Office at dortiz@gia.edu. Or, call toll-free nationwide 800-421-7250, ext. 7142. Outside the U.S., call 760-603-4000, ext. 7142.

GIA on Diamond Cut is an online series of articles reviewing foundational topics related to diamond cut and diamond appearance. If you would like to view the article archive to that series, click here.