The cut of a diamond is considered by gemologists, diamond experts and jewelers alike, to be the most significant characteristic of the 4 C’s.
Despite a diamond having the highest grade color and clarity, it will look dull, lifeless and lacking in “life” or brilliance if the stone is poorly cut. Diamonds should sparkle, meaning that light should be reflected out of the face of the stone.
The width and depth proportions of the diamond as well as the polish and symmetry will determine the amount of light that is reflected as described below:
Polish and Symmetry
In addition to the proportions of the diamond, both the polish and symmetry affect the beauty and brilliance. Poor symmetry due to uneven alignment of the facets will cause the light to be misdirected and therefore not shine out of the face of the diamond.
Un-smooth facets or poor polish will cause the surface to look dull and may cause the diamond to look cloudy. For a beautiful diamond look for Excellent, Very Good and Good polish/symmetry grading.
Look for details of your diamond on your IGC or GIA independent certification.