Scintillation is a type of light that appears in diamonds. Unlike brilliance, which is the white light which illuminates a diamond, and fire which is the jewel’s prismatic light, scintillation is the contrast of light and shadows within the diamond. When mounted in jewelry, scintillation makes the gemstone sparkle as the wearer moves.
A well cut diamond should have a balance of light qualities. While brilliance or fire may get more attention, too much of one trait may detract from the jewel’s overall aesthetics. Each light strengthens the others, adding to the beauty of the diamond. With scintillation, the shadows help make white light stand out, and the change of patterns helps draw the eye to the stone.
The aspects of cut which influence scintillation include the facets bordering the girdle. The upper and lower girdle facets should be angled just so to help promote scintillation. Too much white light or overly large patches of light take away from contrast. Disproportionate amounts of darkness take away from the shine which is a major appeal of diamonds.
When looking for a diamond with appealing scintillation, try to gently rock the stone back and forth. Look for distinct facets bordering the girdle. Also check for dark portions visible from the table or edges of the stone. Since you are the one deciding on the diamond, it’s important to find a jewel with a scintillation pattern that you personally find attractive.