Based on scientific formulas, a well-cut diamond will internally reflect light from one mirror-like facet to another and disperse and reflect it through the top of the stone.  This results in a display of brilliance and fire.  Diamonds that are cut too deep or too shallow lose or leak light through the side or bottom, resulting in less brilliance and ultimately, value.

Of all the 4C's, cut is the only one most directly influenced by the human hand. The other three are dictated by nature.

Diamond cutting requires great skill and training.  The cutter must polish tiny surfaces known as facets onto the rough diamond.  The process is what creates the crown, culet, table, girdle and pavilion of the diamond.

The facets, when arranged in precise proportions, will maximize brilliance and sparkle.  To cut a diamond perfectly, a craftsman will often need to cut away more than 50% of the rough diamond.