Cut is often considered the most important of the four C's (cut, clarity, color, carat).
This is because the cut of a diamond determines its brilliance (the amount of light reflected).
When rough diamonds are mined, they emerge in a wide variety of shapes and sizes. Highly skilled diamond cutters then cut and polish these stones to remove flaws and inclusions (tiny particles) – ideally taking out as many as possible while still preserving as much of the diamond retaining its brillance.
If a diamond's cut is too shallow, the light that enters the diamond will leak out of the bottom.
If a diamond's cut is too deep, the light will reflect out of the side.
An "ideal" cut will reflect the maximum amount of light through the top of the diamond - created a radiant sparkle that travels straight back to the viewer's eye.
A critical factor in the cut of a diamond is symmetry – the alignment of its many facets (or surfaces) in relation to one another.
- A classic "round brilliant" cut includes 58 facets, and every single one must be positioned in perfect geometric relation to the others.
- If the diamond has been cut properly, the light that enters the stone will bounce from facet to facet before reflecting back to your eye. This gives the diamond maximum brilliance.
Grade of your Diamond:
Leading gem laboratories such as the Gemological Institute of American (GIA) and the European Gemological Laboratory (EGL USA) grade diamonds according to the quality of their cut. They are graded on a scale from "poor" to "excellent". The diamond chosen for your engagement ring should at least have a grading of "fair".
Information courtesy of http://www.solomonbrothers.com/