Diamond cut is not about its shape (round vs. oval, for example) – instead, it’s about how a diamond reflects light. Cutting a stone with good proportions, symmetry and polish will allow for light to pass through and shine more brilliantly.
A perfectly cut diamond crafted by a master diamond cutter will sparkle like no other, and that’s what the rating scale for diamond cut is all about. Since the cut is key to a brilliant and sparkly diamond, it is possibly the most important of the 4 Cs and has the biggest impact on its beauty.
Cut is complicated to grade, but it has a huge impact on the value of the diamond. When evaluating cut, diamond graders are looking for:
Brightness – The brightness created by internal and external white light reflecting through a diamond
Fire – The flashes of different colours throughout the stone (like a rainbow)
Scintillation – The amount of sparkle a diamond gives off, and the light & dark areas caused by reflections when the diamond is being moved
The better the cut, the more valuable it is.
Diamond Cut Rating Scale
The rating scale for diamond cut is split up into 5 grades, from excellent to poor:
These diamonds reflect almost all of the light that enters the diamond, giving off amazing fire, brilliance and sparkle.
At this grade, a small amount of light is lost and not reflected, but under normal day-to-day lighting these diamonds will appear practically the same as Excellent cut diamonds.
Diamonds with a cut grade of Good are still above average in quality, but they will have less sparkle than higher grades.
These diamonds are still considered good quality, but at this point you are starting to lose more light out the sides and the bottom of the diamond instead of back through the top of the stone.
At this grade the diamond will have a noticeable lack of fire, brightness and sparkle. A casual glance will spot that these diamonds are more dull than higher-quality stones.
How Do I Get The Best Value for a Diamond?
Since cut is so important to the beauty of a diamond, getting stones with Excellent and Very Good cuts will allow you to opt for lower grades in the other aspects of the 4 Cs. With these high-quality cuts, you can get better value by getting diamonds with G-H colours and SI1-SI2 clarity grades without sacrificing all that much in overall appearance.
Fair grade cuts are more acceptable in diamonds smaller than 1 carat, as differences in sparkle are less noticeable at smaller sizes.
Keep in mind that shape is also a factor in cut. For round diamonds, try to get diamonds with Very Good or Excellent grades to ensure that superior sparkle. For fancy shape diamonds, you can look at Fair – Good cut diamonds.
Even if carat size and/or price are the most important aspects to you, avoid diamonds with Poor grade cuts. These diamonds will appear dull, even with extremely high grades in clarity and colour.
Stay tuned for our final post in this series where we’ll talk about carat weight.