What factor can make a diamond appear larger than its actual carat weight?

The perception of a diamond's size can be significantly influenced by its cut and shape. A well-cut diamond can reflect and refract light in a manner that creates the illusion of a larger size. For instance, certain shapes, like an oval or an emerald cut, can enhance the visual impact of the stone by maximizing surface area or by creating depth, which helps to make the diamond appear larger than its actual carat weight.

The quality of the cut also plays a critical role; ideally, a well-proportioned diamond will have angles that optimize brightness and sparkle, contributing not just to its beauty but also to perceived size. Thus, the combination of a diamond's shape and the precision of its cut can create an optical illusion that makes it appear more substantial than it is when considered only by weight.