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Beyond the Sparkle: Breaking Down Diamond Brilliance

by Julianna Church
Last updated on August 18, 2023
how to buy an engagement ring

All that glitters isn’t always gold – sometimes it’s diamonds! Diamonds are known for their sparkly appearance. But not every diamond sparkles the same. There’s a lot more to a glittering diamond than meets the eye. Diamond brilliance goes far beyond the look of a diamond; it also determines the quality.

A Diamond’s Beauty Analyzed

A diamond’s brilliance can be boiled down to measurements, proportions, and many, many angles. That’s right, it’s all math. The sparkle of a diamond is directly related to how well cut the diamond is.

Diamond Cut Grade

Officially, a round diamond is the only diamond with a cut grade on a gemological diamond grading report. However, there are some reports that also give princess cut diamonds and cushion cut diamonds cut grades, too.

Cut Grade Chart for a Round Diamond

round brilliant diamond

The cut grade chart put forth by the Gemological Institute of America is the standard cut quality chart followed by most jewelers.

But as a whole, fancy shapes (shapes besides round) aren’t given cut grades because there’s no perfect symmetry or proportions like there is with round diamonds. Instead, each diamond shape has its own desirable proportion range that you should choose for your table percentage, length to width ratio, and depth percentage.

Diamond Shape and Cut Style

Most diamond shapes fall into the category of brilliant cut diamonds and step cut diamonds. Brilliant diamond shapes are usually:

  • Round
  • Princess
  • Oval
  • Marquise
  • Cushion
  • Radiant
  • Heart

Step cut diamond shapes are:

Elements of a Diamond’s Cut Quality

four different diamond rings

Table Percentage

A diamond’s table is the biggest facet on a diamond. That’s right, it’s the top of your diamond when looking down at it. A diamond’s table percentage is the ratio of the width of the table to the diameter of the stone.

You can find your diamond’s table percentage in the specific details of your diamond information online when browsing and on accompanying diamond reports.

The ideal percentage for a diamond’s cut quality varies based on shape and preference. However, for the best reflection of white light return to the wearer’s eye, a well cut diamond usually ranges between 53-57%.

A diamond table that is too large doesn’t reflect light entering the diamond back to the viewer. Instead, it can leak out the sides, resulting in poor brilliance. And if the table is too small, not enough light enters, also resulting in dull brilliance.

Length to Width Ratio

The length to width ratio of a diamond is basically how narrow or wide your diamond looks from the top. Each diamond shape has its own recommended length to width ratios.

Your L/W ratio affects your diamond sparkle in the same way the table percentage does, but it pertains to the entire crown of your diamond. If your ratio is too low, the diamond shape will appear narrow and not reflect white light and rainbow light as much as it should.

Most diamond shapes allow for wiggle room to let you have your preference on its L/W ratio. For example, some people prefer their cushion cut diamond to be elongated, while others prefer them to be shorter. Both can still result in exceptional sparkle.

Depth Percentage

The depth percentage is the measure of how deep the diamond’s facets go down in relation to its width. The recommended depth range for an “ideal cut” round brilliant cut diamond is between 58-62%. Other shapes’ recommended depth percentage ranges are different.

If the depth is too deep, it will cause dark areas in your diamond. If your diamond has light and dark areas, the diamond’s brilliance will have poor light performance. A diamond whose depth is too shallow will have light leakage.


Aside from symmetry and the diamond’s proportions, polish is another important element to a diamond’s beauty and brilliance. Under your diamond’s details, your polish may have a rating of Excellent, Very Good, or Good polish.

Diamond polish refers to the surface finish of the diamond. Polishing a diamond relates to diamond fire because it smooths out any nicks and scratches that may have happened during the cutting process.

Without a good polish, diamond brilliance will be impacted by imperfections and nicks that can reduce a diamond’s light performance and cause its facets to appear cloudy.

Analyzing Diamond Sparkle: How Diamonds Reflect Light

Diamond being held by tweezers

All of the elements of a diamond’s cut affect its overall brilliance. A diamond’s sparkle is the last element of diamond brilliance. The diamond’s sparkle is often confused with its brilliance, but they’re not the same thing.

Diamond Sparkle

The diamond’s sparkle refers to the intensity of the rainbow and white flashes of light reflected by a diamond’s top surfaces. Brilliance is the overall term used to describe the entire light performance of a diamond.

A diamond can have high sparkle and low overall brilliance. The sparkle is about the surfaces of the facets, making the diamond sparkly on top, but not in its pavilion angles. All of the diamond’s surfaces have to be equal in quality to make for a truly brilliant diamond.

Fire and Light Dispersion

Diamond fire is also called light dispersion. The light dispersion of a diamond is how it scatters white light into rainbow light. The higher the dispersion, the stronger the fire.

Diamond Scintillation

Brilliance and scintillation aren’t the same thing, either. Scintillation refers to the way light is reflected as the diamond is moved back and forth. Your diamond’s cut quality is what results in scintillation.

The scintillation in your diamond as it moves shows light and dark areas under various lighting conditions. Those areas create a beautiful pattern of light. The scintillation in your diamond changes in different lighting, so it’s important to analyze this once you make your purchase.


three differently shaped diamonds

In order to have excellent diamond brilliance, there are many elements and contributing factors that must be present. Choosing a round diamond is a little easier because you can choose a diamond with an Excellent cut grade or an ideal cut grade. And from there, you can further compare the different elements of cut quality within the same cut grade.

Fancy shape diamonds are harder because they can’t be boiled down to exact diamond symmetry and proportions. Fortunately, our fancy shape diamonds are sorted by different qualities to make your search for a perfect diamond just a bit easier. Whether you are in the market for ethical man made diamonds or something unique like a black diamond, a better knowledge of the 4 c’s will help you shop.

Don’t assume you have the best diamond brilliance simply because you’ve chosen a top cut grade. Make sure to analyze each and every element of your diamond in order to maximize brilliance.

And if this seems like a lot for you, no worries! Our diamond experts are standing by to help you find a diamond whose brilliance is suited to your tastes!