The girdle can impact the gemstones in two important ways:

 

• The thickness of the girdle affects the relative position of the surrounding facets, and so can impact cut. Because girdle width is already factored into the diamond's overall cut grade, a diamond graded as well cut will produce superior brilliance, fire, and scintillation, even if the girdle itself is not in the ideal Thin-Slightly Thick range of width.
• A thicker girdle will add weight to a diamond, thereby increasing its price. Since a thick girdle adds depth to a diamond but not width, a thick girdled diamond will not appear any larger when viewed from the top (e.g. when set in a piece of jewelry), despite the additional carat weight. The effect on carat weight and price is minimal, but real.