The better the cut, the more brilliant the diamond. It's that simple.  Of all the 4 C's, Cut has the greatest effect on a diamond’s beauty.

The precision and delicacy of the cut determines how much light a diamond will refract and reflect. A well-cut diamond will have that dazzling sparkle and fire everybody wants to see.

With an ideal cut, light is reflected from facet to facet inside the diamond before it literally beams out through the top (called the “table.”) A diamond that’s too deep or shallow is less brilliant because it leaks light out of its sides and the bottom instead of reflecting it through the table and upper facets. Such poorly cut stones are less beautiful and less valuable.

Cut, the only one of the 4 C’s not determined by nature, is the most important (and misunderstood) factor of all. Only the hand of a master craftsman determines the cut. At Mervis Diamond Importers, we’re meticulous (maybe even a bit obsessive) about cut. For us, there is no room for compromise . A Mervis diamond is perfectly cut for optimum beauty and brilliance.

Diamonds have a unique ability to manipulate light efficiently. This unique ability can be released and maximized only by cutting and polishing the diamond to an extremely high level of accuracy.

Many people think that Cut is just the shape of the diamond (round brilliant, princess, emerald, oval, etc.) but it is so much more! Diamonds must be cut and polished in order to release their true beauty. It is only when the smooth facets are polished on the diamond that it truly comes to life. It is the diamond’s cut that will make a person fall in love with it. A diamond can be flawless and colorless, but it will not be beautiful if it does not dance with light. Good diamond cutting also can disguise lower color and can override lower clarity due to dazzling light return. There is value in that, too.

The diamond cutting process is time-consuming, requires specialized tools, and demands expert training and craftsman skill levels. The cutter must study the rough carefully, set the angles properly, and polish carefully, or the final product will appear lifeless. For instance, if the pavilion of a diamond is too deep, the diamond will appear dark and dull. If the pavilion is too shallow, reflections of the girdle will be seen through the table. If the table is too large, the resulting surface reflection will be distracting and the fire (rainbow of colors) will be reduced. If the girdle is too thick, the gemstone will be difficult to set in a mounting and to keep secure. If either the girdle or the crown is too thin, the gemstone will chip easily. It is important to remember these causes and effects; any one of them will affect value and possibly durability. Without advanced training, it is difficult to tangibly identify any of the particular faults, but knowing they exist will assist in understanding the beauty of diamonds.

When creating the finished diamond, there are reasons why a diamond cutter makes compromises. As the cutter strives for the maximum weight retention from the rough and tries to create the largest diamond possible, he may choose to sacrifice the best balance of light return. This is truly a case of “Beauty is in the eye of the beholder.” Good diamond cutting is the key to a beautiful diamond and the most obvious factor a person can appreciate.

Symmetry and polish are collectively described as finish, but each is an important separate element in a beautifully cut diamond. Symmetry considerations include the size, alignment and matching of the individual facets. Polish refers to the surface condition of the diamond. For instance , if polished too quickly, polish lines may appear as minute scratches on a facet’s surface. It is even possible for the cutter to burn the diamond. (A burned facet has a milky appearance — as if the diamond needs cleaning). These characteristics are evaluated and rated on their overall impact on the beauty of the diamond. Most polish characteristics can be removed easily with re-polishing and with very little weight loss.

Diamond Cut Grading

GIA (Gemological Institute of America) provides a cut quality grade for standard round brilliant diamonds that fall into the D-to-Z color range. To develop their Cut Grading System, GIA performed extensive computer modeling of round brilliant diamonds over a 15 year period and conducted more than 70,000 observations on actual stones to validate the research. This system can now predict the cut grade for more than 38.5 million proportion sets. 

 
GIA’s Diamond Cut Grading System assesses the diamond’s overall face-up appearance to predict the intensity levels of brightness, fire, and scintillation (the diamond’s sparkle and interplay with light). The result is a comprehensive Cut Grading System that accurately reflects all the critical cut factors of a round brilliant diamond

 
GIA applies the following cut grades: Excellent, Very Good, Good , Fair, Poor
The AGSL  ( American Gem Society Laboratories) determines cut grade using light performance, proportion, and finish characteristics to determine a diamond's fire and brilliance. When the AGSL determines a diamond's cut grade, they look at a combination of 11 different criteria in these three categories, and then assign cut grades of Ideal, Excellent, Very Good, Good, Fair, and Poor. The AGSL labels a diamond that meets their standard of perfect proportions, polish, and symmetry as "Cut Grade: Ideal". An AGSL Ideal cut is the equivalent of a GIA cut grade of Excellent.

Learn about Diamond Color
Learn about Diamond Clarity
Learn about Diamond Carat Weight