Is there anything more perfect than a beautiful, sparkling diamond? Before you slip one on your partner’s special finger, do you know what causes a diamond to shine so big and bright? That’s a result of the diamond’s cut, and we’re here to tell you more about it!

Diamond Cut vs. Shape

When choosing a diamond, you should pay attention to four characteristics: cut, color, clarity and carat weight (aka the 4 C’s). But jewelry experts say the gem’s cut is most important.

So, what does diamond cut actually mean? Right now, your head is probably swirling with images of different diamonds: round, oval, princess, etc. But these terms refer to the shape of the stone. “Cut” instead indicates how well a diamond’s facets (aka flat, polished surfaces) interact with light. Trained gemologists carefully inspect each gem under magnification to calculate the proportions of these facets and determine how they affect the stone’s shimmer.

*Pro Tip: For more details on the 4 C’s of a diamond, ask your jeweler to provide the stone’s certification!

Diamond Cut Grading Scale

Once the arrangement of facets has been evaluated, gemologists give each gem a rating on the Gemological Institute of America’s (GIA) cut scale, which is considered the industry standard for grading diamond cuts. The scale features five grades and is only geared for round diamonds. But to fully understand the scale, you’ll first need to familiarize yourself with a few terms: brightness, fire and scintillation.

For starters, brightness refers to white light on the inside and outside of a diamond that’s reflected whenever the stone moves. Fire, on the other hand,refers to flashes of color that are reflected from a diamond. This happens when white light enters the stone, disperses into separate wavelengths of color and exits the gem. And finally, scintillation refers to flashes of lighter and darker colors, caused by light reflecting off of the gem’s facets. Basically, it’s another term for sparkle.

Now, here’s the full breakdown of the diamond cut scale:

● Excellent: These diamonds give off plenty of white light (aka brightness) and flashes of color (aka fire).

● Very Good: These stones are a subtle step down, as they offer slightly less brightness and fire. But to the untrained eye, they look almost as good as “excellent” diamonds.

● Good: These diamonds tend to lack some sparkle (aka scintillation) and therefore appear a bit darker than the top two grades.

● Fair: In these diamonds, light often escapes through the bottom and sides of the stone, creating even less brightness. But they might still be doable in pieces featuring side stones or diamonds with smaller carats.

● Poor: These gems offer very little sparkle.

As you can probably imagine, the price of a diamond will vary, depending on its cut grade. So, you’ll need to determine what works best for your budget. We also recommend inspecting the diamond yourself and checking its sparkle under different lighting. Even if a stone receives a high cut grade, you might notice dark spots that don’t meet your standards.

*Pro Tip: The American Gem Society (AGS) follows a somewhat different cut scale that features six grades instead of the typical five. If your diamond was certified by AGS, keep in mind that its top-notch “ideal” rating is most comparable to the “excellent” grade on GIA’s standard scale.

Shallow and Deep-Cut Diamonds

What causes different levels of sparkle in a diamond? There could be a few reasons, one of them being the symmetry of a stone’s facets. To put it simply, facets reflect light better if they’re closer in size and shape and positioned at more exact angles. And of course, light can more easily bounce off of smooth, glossy facets that have been carefully polished. So, remember to keep your diamond clean!

Sparkle might also be limited in gems that are cut too shallow or too deep! With a shallow diamond, light usually hits the V-shaped, bottom portion of the stone at a low angle. As a result, the light exits through the sides of the gem and never gets reflected through the top of the stone. What does this mean? That gorgeous sparkle never makes it to your eye!

With deep-cut diamonds, light typically hits the V-shaped portion of the gem at a sharper angle. But this causes light to only move through the bottom of the diamond, making the gem duller in the process.

*Pro Tip: The diamond girdle (aka thin border around the widest part of a diamond) even affects the stone’s measurements, sparkle and cut grade. For example, light reflects differently in certain diamonds with extremely thick girdles, resulting in less brilliance and a duller appearance. Jewelry experts agree that a medium girdle is the best choice for reflecting light and therefore a good cut.

Have a question? We can help!

Gage Diamonds is Chicago's premier jewelry showroom and online retailer of engagement rings, wedding bands, and fine jewelry. We offer a selection of dazzling handpicked diamonds, including certified natural and lab grown diamonds.

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