Diamond cutting is the art and science of creating a gem-quality diamond out of mined rough. The cut of a wholesale diamond describes the manner in which it has been shaped and polished from its beginning form as a rough stone to its final gem proportions. The cut of a wholesale diamond also describes the quality of workmanship and the angles to which it is cut. Often cut is confused with “shape”.
The quality of a diamond’s cut is widely considered the most important of the 4-C’s in determining the beauty of a loose diamond; indeed, it is commonly acknowledged that a well-cut loose diamond can appear to be of greater carat weight, and have clarity and colour appear to be of better grade than they actually are. The skill with which it is cut determines its ability to reflect and refract light.
Proportion / Cut Grade: There are mathematical guidelines for the angles and length ratios at which the loose diamond is supposed to be cut in order to reflect the maximum amount of light. Round Brilliant, the most common shape, are guided by these specific guidelines. Fancy Shape stones are not able to be as accurately guided by mathematical specifics and aren’t graded on their cut or proportions, (only their finish or, polish and symmetry). Although cutting proportions aren’t graded in fancy shapes, there are examples when cut properly that will perform as brightly and beautifully as an ideally cut Round Brilliant.
Polish Grade: Describes how well the facets have been polished when finishing the diamond. An excellent polish enables light to enter and exit the diamond crystal in the most efficient manner. Just like a window, if it isn’t well polished, the light passage will be interrupted. So, it’s true you could have the most ideal proportions for your stone but, if it isn’t highly polished, its full visual potential will never be seen!
Symmetry Grade: Analyses the size and alignment of the Crown (top) and Pavillion (bottom) facets, which determine the evenness of light return and scintillation. Please read on in our diamond buying guide to discover how these technical terms impact on the real, visual qualities of the stone.
In the gem trade, the term light performance is used to describe how well a polished diamond will return light to the viewer. There are three light properties which are described in relation to light performance: brilliance, fire, and scintillation.
- External Brilliance : Lustre, produced by the reflection of light on the surface of the facets.
- Internal Brilliance : Refraction and total reflection of light on the pavillion facets.
- Dispersive Brilliance : Splitting or scattering of light into its spectral colours, i.e. the dispersion which evokes the “fire??? or “life??? in a stone.
- Scintillation Brilliance : The “sparkle??? or small flashes of light that are seen when the diamond, light source or the viewer is moved.
Maximum Brilliance is the interwoven combination of the above qualities; lustre, light refraction, total reflection, colour dispersion, and scintillation.
Today, because of the relative importance of carat weight in society, many wholesale diamonds are often intentionally cut poorly to increase carat weight. There is a financial premium for a stone that weighs the magical 1.00 carat, so often the girdle is made thicker or the depth is increased. Neither of these tactics make it appear any larger, and both greatly reduce its sparkle. So a poorly cut 1.00ct wholesale diamond may have the same diameter and appear as large as a 0.85ct wholesale diamond that was cut properly. The depth percentage is the overall quickest indication of the quality of the cut of a Round Brilliant. “Ideal” Round Brilliants should not have a depth percentage greater than 62.5%. Another quick indication is the overall diameter. Typically a round brilliant 1.00ct loose diamond should have a diameter of at least 6.45mm. Please refer to our diamond buying guide Carat Weight Size Chart for further information and other issues in diamond education.