Diamond quality is rated in four categories: the 4 C’s---cut, color, clarity, and carat weight. When the discussion of diamond qualities turns to cut there is general agreement that this C has the greatest influence on the diamond’s beauty. Central to diamond beauty is the quantity and qualities of the light returned from the diamond to the viewer’s eye.

This visual interaction of the diamond reflecting and refracting the surrounding light to the viewer is the diamond’s optical performance.

We review current and historical descriptors of diamond beauty and performance, and advance the case for the contrast quality descriptor of brilliance to augment the quantity measure of light return. The contrast quality of brilliance is explained and illustrated with diamond photography. Also advanced is the relationship between contrast brilliance and scintillation.

Keywords: beauty, contrast, brilliance, performance