The proper cutting of a diamond contributes more to it's beauty than flawlessness, or color. The ideally cut diamond should return the maximum brilliancy or "fire" through the crown (or top) of the diamond. When a diamond is ideally cut, light rays from all sides are bent towards the center of the diamond and are reflected back through the top in a blaze of light. Poorly cut diamonds allow light to be lost through the sides or leaked through the bottom of the diamond.

The following diagrams demonstrate the effects of an ideal cut, deep cut, and shallow cut diamond.

IDEAL CUT (light enters, reflects from facet to facet, and comes back through the top)	DEEP CUT (light enters, reflects to opposite facets at the wrong angle and is lost through the sides)	SHALLOW CUT (light enters and leaks through the bottom, the eye may see a dull reflection)