Diamond Cut Evaluation
The G.I.A. (Gemological Institute of America) grades the cut of round diamonds using the following grades: Excellent, Very Good, Good, Fair and Poor. (Many jewelry shops don’t actually carry Fair and Poor cuts.)
How a diamond is cut affects its brilliance.
The cut evaluation process is pretty complex, but it boils down to assessing the proportions of the diamond’s parts, the symmetry of its facets, and the quality of the stone’s polish.
How proportional and symmetrical a diamond is matters for a very important reason: It determines how much of the light entering the stone will remain in it and be reflected back to the eye of the observer, and how much will leak out of the diamond.
How a diamond is cut affects its brilliance (how much light the stone reflects), fire (the way light is broken down into colored flashes) and scintillation (the sparkle visible when the stone is moved).
‘Excellent’ Cut Characteristics
Diamonds with an Excellent cut have proportions that allow them to exhibit maximum brilliance, fire and scintillation.
Here you can see a selection of diamonds with an Excellent/Ideal cut.
When stones in this grade are looked at from above, the light passing through their facets creates a balanced and clear pattern of bright and dark spots.
‘Very Good’ Cut Characteristics
Most characteristics of a Very Good cut diamond usually fall within the Excellent range, but what keeps such a stone from being given the best grade is that one or two of its dimensions are outside the top standard, although not by much.
These diamonds display very good brilliance, fire and scintillation, and although these characteristics may not be as good as those of Excellent stones, Very Good diamonds don’t look dramatically different.
From a top-down view, Very Good diamonds may look a bit darker, and the light passing through them may create a pattern of bright and dark spots that is slightly uneven.
Check out a selection of diamonds with a Very Good cut.
‘Good’ Cut Characteristics
Diamonds with a Good cut do not retain and reflect as much light as Excellent and Very Good diamonds. As a result, their brilliance, fire and scintillation are not as good.
When these stones are looked at from above, their facets either do not form a discernible and symmetrical pattern of dark and bright spots or they form a pattern that is predominantly dark.
These stones still exhibit good brilliance, although compared with Very Good and Excellent diamonds, more of the light entering Good stones leaks out of them and is not reflected back.
See here a selection of diamonds with a Good cut.
Deciding Between Excellent, Very Good, and Good Cut
In general, the better the cut grade of a diamond, the more brilliance and sparkle it will have, and the stone will look brighter.
However, keep in mind that only you can decide whether it is worth it to pay a premium for an Excellent diamond over a Very Good one, for example. You should take your time to examine stones with different cut grades and see for yourself whether a higher grade makes a noticeable difference to you.
We usually recommend that you don’t skimp on cut and go for the best grade. Unlike color and clarity, where you can pick a less-than-perfect grade and not notice a visible difference, cut is the one quality factor where the top grade makes a significant difference.
One last thing to remember: Once the diamond of your choice is nearly colorless and doesn’t have inclusions visible with the naked eye, spending more money on cut is more likely to make a visual difference than paying for an even better color or clarity grade.
An Excellent cut can make a diamond exhibit exceptional brilliance, which can hide imperfections in clarity or color, but a diamond with perfect color and clarity will look dull and dark if its cut is poor.
Where to Buy Diamond Jewelry?
We recommend James Allen (read review) because you can see a 360-degree video for any diamond before buying it.
Blue Nile is another reputable diamond retailer we recommend.
