Cut refers to the angles and proportions a skilled craftsman creates in transforming a rough diamond into a polished diamond.

A well-cut diamond will reflect light internally from one mirror-like facet to another, dispersing it through the top of the stone. Cuts that are too deep or too shallow lose or leak light through the side or bottom, affecting the diamond's brilliance.

The Millennium Star, weighing 777 carats in the rough, was polished down to 203 carats in order to maximize its beauty.