Diamond Cut Grade

A diamond’s cut should not be confused with the diamond’s shape (round, princess, baguette etc.). Often overlooked the cut or interrelated proportions of the diamond is actually one of the most important aspects to consider when choosing your diamond. The cut of a Diamond is the only diamond characteristic which is totally dependent on man. The goal is to have light enter a Diamond, disperse the light as it bounces inside, thereby producing the different colors and sparkly effect, finally returning as much light to the eye as possible. A Diamond cutter analyzes the rough diamond, and has to determine how to extract the most beauty and most profit out of the rough diamond. Cut refers to a diamond’s proportions and finish, factors which determine the sparkle of the diamond. It is possible to take the same diamond, and depending on which method the cutter decides to use, to either cut it into the most beautiful diamond it can be despite heavy weight loss and perhaps lower monetary value because diamonds are sold by carat weight. Or they can cut a diamond to its maximum weight and monetary value, but lose some "brilliance" and "sparkle". Even if you have two equal polished diamonds, both the same carat weight, both the same color, both the same clarity, they may look completely different. Why? There are many different shapes and facets in a diamond. The weight can be distributed in different parts of the diamond.

Much has changed in how a diamond’s cut is perceived and marketed. A serious push was made to introduce systems of cut grading. Computer simulations are being used as the basis of new cut grades by the gem labs. Computer simulations do not compare to having an expert look at a cut and judging it with the naked eye; have your local independent jewelry appraiser look at the diamond and grade the cut. And more importantly, cut is more subjective than the other 4 "C”(s). While there is a clear reason to prefer the rarer 2 carat diamond to a 1 carat diamond, or a clear preference for a D color over a G color, some people prefer diamonds to be cut different ways. Lab Certified diamonds that will have a cut grade are graded by either the GIA or the AGSL. These diamond grading laboratories are two of most respected and prestigious in the world. They both approach the science of cut grading in very similar ways, so making diamond comparisons is simple even if the grading reports are from different labs.

According to GIA, a polished diamond’s beauty lies in its complex relationship with light: how light strikes the surface, how much enters the diamond, and how, and in what form light returns to your eye. The result is a display of three attributes. Brightness is the combination of all white light reflecting from the surface and interior of a diamond. Fire is the colored flashes that can be seen in a diamond. Scintillation describes the sparkle of light you see in a diamond, and the overall pattern of bright and dark areas when you look at a diamond face-up. A polished diamond’s proportions affect its light performance, which in turn affects its beauty and overall appeal. Diamonds with good proportions optimize the interaction with light, and have good brilliance, fire, and scintillation. The Design (weight ratio, durability) and Craftsmanship (polish, symmetry) of a diamond also affect its cut quality, and are considered in determining a diamond’s GIA Cut Grade.

GIA bases their new cut grade for Round Brilliants on a combination of face-up appearance, design and craftsmanship elements that all contribute to the diamond's fire and brilliance. The GIA cut grade is only given to round diamonds. They employ a predictive computer model based on over 70,000 individual diamond observations and 38.5 million proportion sets, to determine a diamond's brilliance based on its interrelated measurements. Most GIA diamonds graded prior to January 1st, 2006 will not have a laboratory-assigned cut grade. The GIA cut grade system includes ratings of Excellent, Very Good, Good, Fair and Poor. GIA does not assign an Ideal cut and an Excellent rating is their highest grade.

The American Gem Society was established in 1934. It is a recognized authority in the testing and certification of Registered Jewelers, Certified Gemologists, and Certified Gemologist Appraisers. The AGSL 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 is known throughout the diamond industry as a "triple-zero" grade. An AGSL Ideal cut is the equivalent of a GIA cut grade of Excellent. In 1996, the American Gem Society Lab or (AGSL) began using proportion based Cut grading. The top grade was AGS 0 and the worst was AGS 10. AGS 0's cost as much as 10% more than same grade of GIA diamond; it was synonymous with "ideal cut".  AGSL is the only lab to have a cut grade for both round cut diamonds and princess cut diamonds.