The brilliance of the diamond depends on the amounts of internal and external reflections of light from the diamond to the eye. This phenomenon is known as dispersion. The fire of the diamond is the visible effect of dispersion. The sparkle is the flashing effect seen when a diamond moves in the light. In order for a diamond to display maximum dispersion, good polish is essential.
Diamonds possess the unique ability to take and keep the best polish of any gem.
Good symmetry, in combination with good polish will result in all the qualifications for a diamond to shine and sparkle to its maximum potential with regard to finish. The finish reflects the skill and care taken in the cutting process. Therefore, finish provides a way of fine-tuning assessments of a diamond's appearance.