Diamond Cut (not to be confused with shape) is the most important factor affecting beauty and brilliance of any of the Four C’s. It is also the biggest cost determinant of any of the Four C’s. The cutter’s art is designed to make the maximum use of light. Put simply, a diamond takes in light rays, bounces them around within the stone, and then releases them as colors of the spectrum. The better the cut, the more vibrant these colors appear.

Don’t confuse diamond cut with shape. The rules for achieving brilliance, using correct angles and proportions, are the same for any shape. Since non-rounds have less potential for brilliance than rounds, it is in fact even more important to cut non-round shapes correctly.

Some popular diamond shapes include the following:

Round brilliant diamonds are the traditional standard. Because of their inherent symmetry, they have more potential for brilliance. However, poorly cut rounds will not look as good as some well cut non-round shapes. GIA has defined diamond cut grades very specifically for rounds.

Pear shapes have more brilliance than marquise, but somewhat less than Cushettes, ovals, and rounds. Pear shapes work especially well in drop earrings and as accent diamonds on some rings.

Emerald cut diamonds are not cut for brilliance but have an intriguing stepped pattern that imitates mirrors lined up side by side. These are usually rectangular. When they are square, they are called Asscher Cut.

This long boat-shaped diamond offers a unique alternative to the more classic shapes, and can be fairly brilliant when cut correctly. The shape goes especially well with some ring designs and is a favorite with certain regional groups.