The cut grade of a diamond directly affects the irresistible sparkle.
When it comes to the shape of a diamond, you need to differentiate between round, oval, pear, and so on. The cut grade, however, measures how well the facets are made and arranged. The GIA only assesses the cut grade of a round stone; for all other shapes, GIA merely offers grades on Symmetry and Polish, because there is no perfect oval, for example. A round stone, however, needs to be perfectly round.