Cut Versus Shape (5.01)
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 a particular stone, the value and naturally, its salability.
Brilliance is the richness and intensity of reflections of white light in the face-up position of the diamond. The multitude of geometric reflections will increase with a well-cut diamond since the light is contained for a longer period of time before escaping toward the viewer’s eyes.
Dispersion relates to a diamond’s ability to refract (bend) white light, displaying the spectral colors, red, orange, yellow, green, blue, violet. 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 rocked before the viewer’s eyes.
The cut or “make” of a diamond is the key that unlocks the hidden beauty within a piece of rough. Many people including not-so-knowledgeable dealers, believe the brilliance, scintillation and dispersion has something to do with the stone’s quality. This couldn’t be further from the truth. How a diamond handles light is what determines its overall B.S.D. (brilliance, scintillation and
dispersion). There are a couple of exceptions to quality affecting B.S.D. When a diamond falls into the imperfect range (I1, I2, I3 or worse), the light traveling through the stone is filtered by the inclusions (and possibly severe blemishes). When a diamond is a darker fancy color the light again will be filtered (absorbed) to reduce the B.S.D. To illustrate, place a D Flawless (the best color and clarity) with a 55% depth and 68% table, next to an H SI2 (average color and clarity) of the same size, but with superior proportions such as 61% depth and a 56% table. Which do you think will be the more attractive? The H SI2 will be the clear winner.