The shape of a diamond refers to the external figure or outline of the diamond (pear-shaped, cushion, round). The cut of a diamond refers to the dimensions, symmetry, facets and reflective qualities of the diamond.
Reflected by their widespread popularity, round diamonds are the pinnacle in brilliance. Most commonly cut with 58 facets that reflect light, round brilliant diamonds are nearly unmatched when it comes to shine.
A diamond's shape is one of the most important factors impacting price. Choosing a fancy-shaped diamond can actually save you more, compared to a round diamond of similar quality and size. Because fancy shapes, such as pear, oval and marquise, are elongated, they tend to look larger than round diamonds.
Marquise diamonds have the largest face-up area of any diamond cut — approximately 15 percent larger than round diamonds. They also cost less than round diamonds of the same carat.