The Importance of Cut Grading
Cut refers to more than just a diamond’s shape. It refers to more than depth, table, polish and symmetry. A round diamond’s cut quality also depends on physical measurements called proportions. A diamond’s proportions determine how well a diamond will sparkle and reflect light. There are 11 different proportions and cut details for a round diamond.
PROPORTIONS AND FINISH
These details are all necessary for determining a diamond’s quality, but many sellers still provide only 7 of them.
Cut quality is the most important information about a diamond, but in many places you will no mention of the missing proportions or a grade for cut. The most common grading labs used by diamond sellers provide some details on cut proportions, but not enough to determine cut quality.
Notice in the example below that there are grades for color and clarity, but not for cut. Without the missing details a diamond cannot be properly evaluated and cannot be measured against already-established cut grades.
Why most cut quality is average
It takes planning and effort to transform a piece of rough into a polished diamond. The greater the planning and effort, the more beautiful the diamond will be. Still, to this day only a small number of diamonds are cut to premium quality.
The Pyramid of Cut
The AGS and GIA approach cut grading differently, but both are proven systems. Diamonds awarded the top grade by these labs are near the top of what we call the pyramid of cut.
The AGS system is very strict. Less than 3% of the world’s round diamonds can earn the AGS top grade of 0 or ‘Ideal.’ The GIA’s top grade of ‘Excellent’ allows for a range of taste that is broader but is still an assurance of good quality.
A diamond earning one of these grades is above average cut quality and, very importantly, will have passed all tests for depth, durability, polish and basic symmetry. It will also have visibly superior performance compared to average diamonds.
The AGS Ideal grade is considered very elite. The GIA Excellent grade has more latitude and allows abundant steep/deep combinations (so GIA EX diamonds may appear smaller than they should for carat weight), but the information is provided so you can assess this for yourself.
Cut Information Summary
Consumers know very little about cut because most of the world’s diamonds are still graded by labs that do not offer a cut grade. A person doesn’t need to know every last number to make a good decision, but understanding cut grading allows a more informed and confident decision.
