The diamond cut is the most important element to consider when buying a diamond. The cut is the biggest factor in creating sparkle and fire, and without a high cut grade even a diamond of high quality can appear dull and lifeless. A diamond cut poorly and too deep can face-up smaller than it actually is.
The cut of a diamond not only refers to the diamond’s shape, it also refers to how effectively the diamond returns light back to the viewer’s eye. A well-cut diamond will appear very brilliant and fiery, while a poorly cut diamond can appear dark and lifeless, regardless of its color or clarity. Not only do well-cut diamonds appear more brilliant, they also tend to appear larger than other diamonds of the same carat weight. An ideal diamond has both increased brilliance and diameter relative to more deeply-cut diamonds.
A well-cut diamonds exhibit three different properties: brilliance, dispersion and scintillation. As light strikes a diamond's surface, it will either reflect off the table of a polished stone or enter the diamond. The light that is reflected off the diamond is known as the diamond's brilliance. As light travels through a stone, some of the light rays are separated into flashes of color. This is known as dispersion. The result of dispersion—the separation of white light into its spectral colors— is known as fire. Scintillation is flashes of color that are viewable as an observer moves a diamond back and forth.
Excellent Cut Diamonds provide the highest level of fire and brilliance. Because almost all of the incoming light is reflected through the table, the diamond radiates with magnificent sparkle.