Cutting is the single most important factor in the appearance and brilliance of a diamond. A diamond's sparkle depends on how it directs and redirects light. A diamond's beauty is directly related to the combined effect of the following three optical properties:
- Brilliance - The amount and intensity of white light returned to the eye from reflections within the diamond and from its surface.
- Dispersion - The spreading or separating of white light into colored light (a diamond acts as a prism).
- Scintillation - The amount of light reflecting internally and externally between the diamond's facets.
The amount of brilliance, dispersion, and scintillation a diamond shows is directly influenced by its cutting and proportions.
To understand how these angles and proportions affect a diamond's appearance, it helps to know the parts of a diamond.
When a diamond is cut too deep or too shallow, light is lost through the bottom of the diamond, rather than reflected out.
Getting those "just right" proportions for maximum brilliance, dispersion, and scintillation is a matter of precise mathematical measurement.
Ideal-Cut diamonds are those whose proportions are within the ranges described above. Only about 1% of all diamonds sold are Ideal-cut. A fine make diamond is one whose proportions are close to but outside these ideal-cut ranges. Make refers to the quality of a diamond's proportions and finish.
The EightStar Diamond is a round brilliant whose cutting is as precise as is technologically possible. The proportions of this diamond are so exact that the light reflection pattern of this diamond creates an eight-rayed star.
In addition to the angles and proportions of the cut, the finish contributes to the quality of the cut. Overall polish of the diamond, the condition of the girdle and culet, and the symmetry of the facets are all considered in grading the finish quality of the diamond.
