About Diamonds

Why Is Diamond Cut So Important?

When you’re looking to buy a diamond, there are four main metrics to keep in mind. Referred to as the “4 C’s”, these metrics are Cut, Clarity, Color, and Carat. As I mentioned in a previous post, diamond cut is the most important of the four, contributing the most to how a diamond looks. But why is that? What is it about diamond cut that makes it so vital to your wedding band? As it turns out, there are a couple of reasons.

Brilliance, fire, and scintillation

Diamond cut affects three major aspects of the diamond: its brilliance, its fire, and its scintillation.

Brilliance is the general brightness of the diamond; the amount of light you see coming through the gem into your eye. This brightness is enhanced by how much contrast the diamond has – meaning, the darker visible parts of the diamond are much darker than the brighter parts, calling more attention to the diamond’s brilliance.

The second thing that cut affects the most is the diamond’s fire, which is shown when light is refracted through the diamond and is seen as flashes of colors from the rainbow. A diamond with a lot of fire will often show less brightness, though, so there needs to be a balance.

Finally, there is scintillation. Scintillation is shown by the flashes of light, or “sparkles”, that you see when a diamond moves. Technically, fire is a type of scintillation, but “fire” refers to colored sparkles while scintillation describes specifically white flashes of light.

While cut affects all three of these, any given cut will accentuate one of them in particular. It’s up to you to decide which one you value most and choose the right diamond for it.

The ideal cut

The cut is so important to these three aspects because it controls how light reflects inside the diamond. A short (or “shallow”) diamond, for instance, will just let the light pass through without reflecting it back. A diamond that is too long (or “deep”) will reflect light back, but not at the right angle. To correctly reflect light back into the eye of the viewer, diamond cut needs to fit within certain proportions. These proportions, called the “ideal cut”, are referred to when deciding how good a cut is. The Tolkowsky ideal cut is one of the most popular ones:


When buying a diamond, you will see the cut listed under a certain grade. There are five grades of diamond cut to choose from:

Excellent Very Good Good Fair Poor


An “Excellent” grade cut will be close to if not matching the proportions of an ideal cut. On the other hand, as the grades go down, the similarities with the ideal decrease. You could save some money by choosing to buy a diamond of slightly lower cut quality, but the effect of a bad cut is so noticeable that many jewelry stores won’t even stock anything with a cut grade lower than “Good”. You don’t have to take my word for it, either – check out this comparison on James Allen’s catalog to see for yourself. The two diamonds are nearly identical in every way, but the one with the better cut blows the other out of the water!

The big picture

Diamond cut plays a huge role in making or breaking the look of a ring, and deserves its place as the most important of the 4 C’s. But while you’re making sure the cut on your future diamond is perfect, don’t forget there are three other C’s! No matter how high a diamond cut is graded, you can’t judge a diamond by its grades alone. Always make sure to check out the diamond yourself – if not in person, then on video or through lots of pictures – so you know it looks good. In the end, it’s not about if the gem is ideal – it’s about if it’s right for you.


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