When a round brilliant diamond has been cut to precise
angles and proportions, with superb symmetry and polish, visual
patterns begin to emerge. A well-cut and well-proportioned diamond
allows the maximum amount of light to enter, reflect and return to your
eye. The nice reflection and sparkle are also called the "fire of the diamond."
Cut is important. When a diamond is cut too deep it looses light out of the bottom. The center of the diamond will appear dark.
When a diamond is cut too shallow, brilliance is lost and the diamond appears watery, glassy and dark.
precise
angles and proportions, with superb symmetry and polish, visual
patterns begin to emerge. A well-cut and well-proportioned diamond
allows the maximum amount of light to enter, reflect and return to your
eye. 
The nice reflection and sparkle are also called the "fire of the diamond."
