Cut is the most important factor. It’s not the shape of the stone, but quality of the cut in regards to proportion and finish. What makes a diamond so appealing is its ability to reflect light. When cut to perfect proportions the diamond reflects light at its optimum.This is the beautiful sparkle that makes a diamond so desirable.
Excellent to Good Proportions
Diamonds cut with Excellent to Good proportions allow a maximum amount of light to be returned to the observer and thus have more brilliance and fire.
A diamond with a deep pavilion will appear dark in the centre of the diamond due to light leakage from the pavilion. Diamonds with a make grading of Medium to Poor will appear like this.
A spread fisheye diamond with a shallow pavilion creates a white circle at the edge of the table when looking down on the diamond. This is actually the reflection of the girdle at the edge of the table. Diamonds with a make grading of Medium to Poor will appear like this.