Of the 4Cs that determine the quality of a diamond – color, cut, clarity, and carat – by far the most important of the four is the cut of a diamond. You can’t alter the color or the clarity as these characteristics are inherent when the diamond is mined, but the effect of both characteristics can be ruined by a poor cut. Additionally, the carat of a diamond is determined by the quality of the cut – indeed, an excellent or ideal cut diamond can have a lower carat weight than a similar diamond cut incorrectly, but the value will be higher.
In spite of how important the cut is to the value of a diamond, understanding what cut is and why it is so important is often still confusing.
Diamond Cut Versus Diamond Shape
It’s a common misconception that the cut of a diamond and the shape of a diamond are the same thing. Shape refers to the common shape cuts that you’ve likely seen advertised, discussed, and even heard sung: pear, marquise, emerald, princess, round, and more.
Cut literally refers to how well the diamond was cut from a larger piece. The symmetry, proportions, and finish of the cut all play very important roles in the value of the finished diamond. Each part of the final cut of the diamond has a name and a purpose to it.
Why Cut is So Important
One could write a book on why diamonds have captivated the imagination and fascination of the world for thousands of years, but a properly cut diamond is something else to behold. Diamonds, on the molecular level, are perfect formations of carbon whose molecules have lined up exactly right to capture and reflect light. A diamond with the right cut appears not only to shine from within but also appears larger than it is – this is because the of how the cut catches and reflects light.
Grading Factors for a Diamond’s Cut
The cut of a diamond is graded on several factors: proportions of the cut; symmetry of the facets; the brilliance, fire, and scintillation; and the polish of the diamond.
The proportions of different parts of the cut determine not only the quality and value of the diamond but how well it reflects light. A diamond with the right proportions has good ratios between the depth, the width, and the table of the diamond. When these proportions are off, the diamond becomes too shallow or too deep and is unable to properly reflect the light.
Additionally, the girdle of the diamond can significantly affect the proportions of the diamond. A girdle that is too thick will affect the depth of the diamond and the symmetry of the facets. A girdle that is too thin can chip and affect the shape long after the diamond has been cut.
Symmetry in the shape of the facets of a diamond is also crucial to the value and reflective quality. If one facet is misshapen, every facet next to it will also be misshapen and will cause a chain reaction of poorly shaped facets that will ruin the quality of how the diamond catches the light.
Brilliance is a grading factor that looks at how well the diamond reflects light internally and externally.
Fire is a factor of how well the diamond scatters the light and the quality of the rainbow that it produces.
Scintillation is the sparkle that the diamond gives off from both the light and dark facets when the diamond is moved.
Once a diamond has been cut, it must be polished to reflect and catch the light. However, the polishing process must be precise and careful. Improper polishing will lead to tiny but powerful scratches on the facets that can dramatically affect the way the diamond catches the light.