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Diamond Fire vs. Brilliance: How are They Different?

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Diamond Fire vs Brilliance

There are many qualities of a diamond to consider if you’re searching for the perfect one to serve as the center stone in an engagement ring or other jewelry piece.

In addition to the four Cs of color, clarity, cut, and carat, there are two other traits worth exploring. 

Fire and brilliance both involve the way light interacts with the diamond, but the two are distinct qualities.

The main difference between diamond fire and brilliance is that fire refers to the colored flashes of light that radiate from a diamond when it’s twirled, while brilliance is the white light that sparkles from its facets. Some diamonds have fire or brilliance, and some have a combination of the two.

We’ll compare diamond fire versus brilliance, the factors that cause diamonds to display these characteristics, and how you should prioritize them in selecting the right one for you.

What is Diamond Fire?

A diamond’s fire is the colored flashes of light that disperse from its facets. White light enters the diamond, and it’s broken into the individual colors in the spectrum. 

Princess Cut Diamond with Fire

Also called light dispersion, diamond fire results in a small rainbow of colors exuding from the gem when it’s twirled.

There are many wavelengths that combine to form white light. Whenever light enters a substance, those wavelengths slow down. 

In a diamond, the light refracts and then speeds up when it exits its facets. 

The diamond is acting as a prism that interacts with those wavelengths in different ways.

Because the wavelengths bend and refract at unique rates, they separate from each other. For the viewer, this results in a rainbow of colors such as orange, blue, yellow, and green.

What is Brilliance?

Brilliance refers to the white light reflected from a diamond. It’s the glimmer a diamond exhibits when it’s rotated under light.

0.90 carat brilliant cut diamond

Brilliant diamonds are cut in a way that allows them to collect the maximum amount of white light and then return it to the viewer without allowing it to leak.

Poorly cut diamonds have less brilliance because light doesn’t travel through the diamond at the right angles for it to return without distortion.

It’s one of the most valued traits in a diamond, which has inspired a full line of brilliant cut diamonds such as round, princess, marquise, and pear cuts.

What Factors Affect Fire and Brilliance?

Fire and brilliance are appealing traits in a diamond. Many buyers want a diamond that maximizes colored and white light radiating from its surface. 

Here are the factors that most affect the amount of fire and brilliance from a diamond.

Proportions

The proportions of a diamond are the size of its depth, width, and table and the ratios between those measurements. 

Ideal proportions allow a diamond to collect and reflect the most light, which contributes to its brilliance and fire.

For example, ideal proportions for round brilliant cuts are around:

  • Depth: 59%-63%
  • Table: 54%-57%
  • Crown angle: 31.5%-36.5%
  • Pavilion angle: 40%-42%

Proportions of Ideal Cut Diamond

A small culet and thin to slightly thick girdle also contribute to ideal proportions for fire and brilliance.

A diamond that’s too shallow or deep won’t exhibit strong fire. Light leaks out of its sides and doesn’t return to the viewer. 

This can result in a dull appearance that doesn’t shine even under bright lights.

The exact percentages for ideal proportions differ between cuts. Proportions for emerald cuts differ from baguette cuts, and pear cuts are unique from marquise diamonds.

Polish and Symmetry

The polish of a diamond refers to the smoothness of its facets. Diamond cutters manufacture specific cuts with a polishing wheel that may create small surface defects.

Not only can these flaws diminish its visual appearance, they also impact how light interacts with diamond.

Rough areas on facets prevent light from properly entering the diamond and exiting as colored or white light.

The same idea is true of symmetry. Diamond symmetry measures the alignment and shape of facets. 

If its facets aren’t symmetrical, light distorts in the diamond and can leak through the pavilion or reflect in too many directions.

Excellent Polish and Symmetry GIA Report

Other issues related to symmetry that lessen a diamond’s fire and brilliance are:

  • The table is off-center
  • The culet is off-center
  • The crown and pavilion are misaligned

If your diamond has a grading report from the Gemological Institute of America (GIA), you can view the quality of its symmetry and polish in the “Additional Grading Information” section.

If it earns an “Excellent” grade, you can be certain the polish and symmetry won’t reduce its brilliance and fire.

Cut

The quality of a diamond’s cut includes its proportions, polish and symmetry, and other factors. It’s the most important of the four Cs in determining the fire and brilliance of a diamond.

Round Cut Diamond with Fire and Brilliance

No matter the size or shape, a poorly cut diamond will appear dull.

Light will leak from the pavilion or exit the diamond in several directions, reducing the amount returned to the viewer.

The GIA gives diamonds the following cut grades:

  • Excellent
  • Very good
  • Good
  • Fair
  • Poor

If you’re looking for a diamond with the most brilliance and fire, you should choose one with an excellent cut grade. 

For fancy shapes that don’t receive a cut grade from the GIA, ensure its proportions, polish, and symmetry align with those of well-cut diamonds. 

View the diamond in-person or through high-resolution photos online to verify the quality of its cut instead of only relying on the grading report.

Clarity

The clarity of a diamond is graded on the presence of inclusions.

Inclusions are flaws in a diamond that developed during its formation or while it was cut from the rough diamond.

Clarity of a Diamond

Examples include indented natural inclusions, twinning wisps, and cavities. Some are large enough that they’re visible to the naked eye, while others can only be seen with magnification.

Either way, they have the potential to diminish a diamond’s fire and brilliance because they distort the way it interacts with light. 

When light hits a dark spot on a diamond, a white feather, or a cavity, it doesn’t reflect back properly to the viewer. 

A diamond full of inclusions will appear dull because of its poor light performance. You can minimize their impact by selecting one with small, transparent inclusions. 

These diamonds are often graded a VS2 or above on the GIA clarity scale.

Type of Light

The type of light hitting a diamond affects both fire and brilliance.

Diamond with Brilliance and Fire

LED lights create more fire in a diamond than fluorescent light. This is why diamonds often display significant fire in indoor settings.

When they’re placed under LED lights, you can notice a diamond’s fire even from several feet away.

The opposite is true for brilliance. A diamond’s brilliance is best displayed under fluorescent light. 

When you’re exploring diamonds at a jewelry retailer, they’ll often allow you to view the diamond under both LED and fluorescent lights. 

Take this opportunity to see how the diamond’s fire and brilliance performs in these settings.

If you’re purchasing a diamond online, you should view high-quality images and a 360-degree video. 

Diamond Brilliance

This gives you an idea of its light performance, but the test is more effective with the diamond in hand.

Also determine how a diamond appears in natural lighting. Jewelry stores set up their lights in a way to showcase fire and brilliance, so you want to understand how it’ll look on a day-to-day basis.

Cleanliness

The cleanliness of the diamond also impacts its light performance. 

A diamond covered in dirt or debris won’t appear brilliant or exhibit fire. The particles prevent light from entering the diamond.

Keep your diamond clean by soaking it in water combined with a few drops of mild dish soap. You can then gently brush it with a soft toothbrush.

It’s also recommended you have your diamond professionally cleaned at least once per year. This ensures grime doesn’t accumulate in a way that will affect its fire and brilliance.

Which Cuts Have the Most Fire?

Some diamond cuts display more fire than others because of the shape and size of its facets.

No cut rivals the fire from a round brilliant cut. 

It’s triangle and kite-shaped facets are designed for the best light performance, which is one reason they’re the most popular cut for engagement ring diamonds.

There are also fancy shapes that produce strong fire. One of the pros of princess cuts, cushion cuts, and radiant cuts is their fire. 

Diamond Cuts with Fire

It’s an effective way to pay a lower price per carat compared to round brilliants but still have a glimmering diamond.

Examples of diamonds that don’t prioritize fire are ones with step-cut facets such as emerald, Asscher, and Carré cuts

The elongated facets don’t allow as much light to enter, bounce around, and reflect out of its facets.

Which Cuts Have the Most Brilliance?

Diamonds with the most fire often have the most brilliance as well. 

Round brilliants display the most white light off its facets, followed by: 

  • princess 
  • oval
  • marquise

Diamond Cuts with Brilliance

The facets of those three cuts have many traits in common with round brilliants but offer an alternative shape to the traditional round diamond. 

If you want a square-, oval-, or eye-shaped diamond, you don’t have to sacrifice all its white light.

Channel Set Diamond Ring

Pear- and heart-shaped diamonds also have brilliant cut facets conducive to collecting and reflecting light. 

If brilliance is a priority for your diamond, explore the diverse shapes of brilliant or modified brilliant cuts.

How do Fire and Brilliance Determine a Diamond’s Scintillation?

When someone describes a diamond’s light performance, they’ll often use the terms fire, brilliance, and scintillation. 

Diamond Scintillation

Each is describing a unique feature.

Scintillation, also called sparkle, refers to the way both white and colored flashes radiate from a diamond when it’s twirled. 

The motion creates the appearance of facets turning on and off.

Research by the American Gem Society demonstrates how sparkle is a result of flash and fire scintillation. The flashes are sparkling white light, and the fire is made up of colored light.

A diamond with a quality cut and strong fire and brilliance will often have a high degree of scintillation.

Is Diamond Fire or Brilliance More Important?

Fire and brilliance are coveted qualities in a diamond. They’re often referred to interchangeably, but you should compare diamond fire versus brilliance as two separate features.

To learn which is most important to you, view diamonds in person or online that have fire and brilliance, including ones that lack one or the other.

By isolating the qualities, you can understand how it changes the appearance of your diamond. 

Round cuts have the most fire and brilliance, so compare them to fancy shapes to see which option is right for you.

You may decide the improved light performance isn’t worth giving up your choice of fancy shape.

Either way, you’ll have a diamond with the perfect fire and brilliance for you.

Devon Tyler

Devon Tyler

Devon Tyler is the founder of TeachJewelry.com.

He earned an Applied Jewelry Professional Diploma from the Gemological Institute of America and now brings you essential information about diamonds, settings, and more.

Devon has consulted with leading jewelry brands, and his work has been cited in Diamond Nexus and other industry publications.

He's also a member of the International Gem Society.

Devon enjoys discussing jewelry with readers, so contact him with any questions at tyler.devon@teachjewelry.com.

Learn More About Devon