A diamond's cut is responsible for a diamond’s sparkle. There are three factors that determine a diamond’s cut:

Proportion: the size and ratio of the stone’s depth, width and table.

Symmetry: the precision with which facets align and intersect.

Polish: the smoothness and condition of the stone’s surface.

These factors influence how a diamond interacts with light to create desirable visual effects such as, brilliance, fire and scintillation.

Cut grades are fairly simple to follow and are graded

Excellent
Very Good
Good
Fair
Poor

Diamonds that are Excellent and Very Good are optimum for the right levels of light movement.

If a diamond is too shallow or too deep the light will not disperse correctly and achieve the same amount of sparkle.