The term cut is commonly interchanged with the term shape of a diamond. Many dealers today use the word “cut” referring to the shape but for the purposes of clear understanding in this course and in your trade practices the two should be clearly distinguished. “Cut” will refer to proportions and detailed characteristics of the proportions.
The three terms, brilliance, dispersion and scintillation are very important to understand since they are what a cutter strives for in a well-cut (well-made) diamond. They will determine a large part of the overall beauty of the particular stone, the value and naturally, its salability.
Brilliance is the richness or intensity of reflections of white light in the face-up position of the diamond. The reflections will increase with a well-cut diamond since the light is contained for a longer period of time before being allowed to escape toward the viewer’s eyes (as compared to a poor-cut).
Dispersion relates to a diamond’s ability to refract (bend) white light, displaying the spectral colors, red, orange, yellow, blue and green. Most transparent materials will bend light, but diamond’s refractive index is exceptionally high, thus producing more distinct colors in the overall light spectrum.
Scintillation is the movement of the reflections (brilliance) and dispersion (spectral colors), as the diamond (or other gemstone) is rotated or tilted before the viewer’s eyes.