Diamond Cut Grading

The grading of diamond cut should not be confused with the different shapes and cuts of diamonds. For each of the diamond shapes there is a set of proportions and critical angles that a diamond should be cut to in order to maximize its brilliance, fire and scintillation. The closer the diamond is cut to these standards, the more brilliant it will be. Unfortunately, cut is the most difficult aspect of diamond grading for a layperson to understand, yet it may play the greatest role in how bright your diamond is. Diamonds that are poorly cut may appear bright in jewelry stores under strong halogen lights, but they may appear sleepy in dim or normal lighting. Likewise poorly cut diamonds loose their luster once covered with make-up, lotion or soap films.

A proper diamond cut reacts to light a bit like a mirror. The reflective coating on the mirror returns light so that we are not able to see through the mirror. The critical angles of an ideal cut diamond combined with its highly refractive properties, return light in the same way. In contrast, envision a glass removed from a dishwasher with water spots. Since there are no reflective properties, we see through the glass, and the water spots are obvious. Your diamond should be like the mirror. A properly cut diamond will reduce the effects of make-up, lotion, and hairspray on the back of the stone, and return the desirable brilliant light within the diamond.

This illustration represents 3 round diamonds each having the same mass. We will refer to them as 1 carat in weight.
In brief, diamond clarity is usually determined with a microscope, diamond color is detectable by eye, but if the stone is cut poorly it will not glisten. A low grade diamond cut can quickly cancel all of the color and clarity benefits you have sought.

Diamond 1: Shallow Diamond Cut

From the top view, the first diamond appears larger than the others.

This is because it was cut wider and shallow. Your first impression might be that this cut is desirable because the stone looks larger. It is actually very detrimental to the appearance of the stone. This diamond is like the glass in the dishwasher. The diamond will be unattractive and less brilliant when it is dirty.

Why would someone choose to cut a stone this way?
The original rough from which it was cut may have been shallow in shape, or perhaps part of the rough diamond was heavily flawed and the cutter chose to trim around it.

Diamond 2: Deep Diamond Cut

The second diamond looks smaller than the others from the top view because it was cut narrower and deeper. Here again, the diamond lacks the brilliance of an ideal cut diamond along with appearing smaller than the other 1 carat stones.

Why would someone choose to cut a stone this way?
A rough diamond is usually a cube-shaped crystal octahedron. The cube that would create an ideal cut 3/4 carat faceted diamond can be cheated by cutting it deep and chubby to yield a diamond that is 1 carat in weight.

Dealers who target uneducated consumers sell stones of this cut grade to maintain the illusion of having low diamond pricing. An uneducated diamond buyer looking for a 1 carat diamond may believe he is getting a great deal. After all, the rough stone that this was cut from would have normally yielded a 3/4 carat stone, so it will be priced significantly less than the fine 1 carat diamonds on the market.

Diamond 3: Ideal Diamond Cut

The third stone is ideal cut. The ideal cut diamond is faceted at angles that are calculated to return the maximum amount of light to the viewer. Stones in this class are visibly brighter than deep or shallow cut stones. Ideal cut diamonds are the benchmark in quality diamonds.

Why would anyone choose to cut stones differently?
One reason is that it takes a skilled cutter to position 58 facets in exactly the right location. As with all talents, there are varying degrees of skill from one cutter to the next. Another reason to cut the stone deep or shallow is to optimize the profit by increasing its weight, or to cut around undesirable characteristics in the rough.

In Summary, diamond cut has everything to do with how brilliant your diamond appears. It is for this reason you should not compromise on the cut grade of your stone. It is not necessary to get an ideal cut diamond, however the cut of your stone should be very good in its rating in order for your stone to be bright and beautiful.