Understanding a Diamond’s Sparkle: Brilliance, Fire and Scintillation

What’s a diamond without sparkle?

Humans have always been fascinated by shiny things, and diamonds are the ultimate glittering gemstone that continue to captivate engaged couples and jewelry lovers alike!👰🏻 But what makes a diamond so sparkly? There are several factors that play into a diamond’s sparkle, but three major ones are brilliance, fire, and scintillation. These are the building blocks of a diamond’s sparkle, and they’re a result of proper light performance, cut and shape, and several other facets of a finished diamond. Each one has a role to play in sparkle, and finding a balance between them is your best way to ensure you purchase a sparkling diamond.

👉🏻Let’s take a look at brilliance, fire, and scintillation as well as how a diamond’s cut is crucial to its sparkle and whether one of these glittering characteristics is more important than the others.

The science of sparkle

We already mentioned that fire, brilliance, and scintillation are the essence of sparkle, but what do these terms even mean? And how do they come together to create that signature diamond sparkle we adore? Brilliance, fire, and scintillation all describe a different facet of sparkle, and we’ve broken each one down below:

What is brilliance?

When staring at a diamond, the first thing many people notice is the striking flashes of bright white light. This is brilliance: flashes of white sparkle that reflect back to the eye as light enters and then exits the diamond.💎 A diamond with excellent brilliance will appear much whiter than a diamond that lacks proper brilliance, which will appear dull and dark as a result.

So how exactly does diamond brilliance work? It may help to think of each facet and angle of a diamond as a window. Windows let light into a room, but a misshapen, fractured, or dirty window won’t be able to let as much light in as a clear pane of glass. Facets and angles must act as perfectly clear windows to maximize brilliance, allowing light to bounce off and through them and back out the top of the diamond for our eyes to perceive it.

There are two major facets of brilliance in diamonds: brightness and contrast.💡 Brightness refers to how well the diamond returns light to the observer as it passes through the stone, and contrast means a healthy mix of light and dark areas that make that white sparkle pop. You can’t have one without the other, as the brightness of a diamond’s brilliance would fade into the background without that all-important contrast. For example, imagine a sheet of white paper and compare it to the checkered, black-and-white pattern of a chessboard. The white paper is dull and less lively compared to the chessboard, which offers equal amounts of light and dark for better contrast. Both light and dark are necessary for maximum sparkle!

What is fire?

Fire is almost the opposite of brilliance, and it’s also known as “dispersion”. This is a pretty fitting alternate name for the fire of a diamond given its properties! Unlike white brilliance, diamond fire is a colored sparkle that is the result of white light moving through the stone and breaking down into individual wavelengths. This process of breaking down is often called dispersion, where light separates into different colored wavelengths and moves independently.🌈 As light enters the diamond and hits the pavilion facets, it bends and shoots upward toward the crown facets, which causes the colorful wavelengths to disperse.

These wavelengths of light come in many colors (red, green, violet, etc.) and they all bend at varying degrees, so the color we see when we look at a diamond is these wavelengths returning to our eyes. That’s why, when you look at a diamond, you may notice small flashes of some colors but not others at different angles. Red wavelengths are long and bend the least, whereas violet wavelengths are short and bend the most, and there are multiple other colors that bend at varying degrees to create a subtle, colorful show as you move your diamond around.

To assess fire, graders in a lab often place a diamond under LED light and observe the stone from different angles. A grade is then determined by the brightness and amount of flashes of color seen. It’s not a very exact measurement, but it’s helpful in deciding whether a diamond has the desired amount of fire based on its cut!

What is scintillation?

Scintillation is a little bit tricker to understand than fire or brilliance, but it consists of areas of light and shadow within a diamond that create contrast much like the chessboard example we described earlier. Just like the contrast needed to maximize brilliance, a diamond must have contrast or scintillation overall to create blinking light and dark flashes as the stone moves back and forth. Scintillation highlights the beauty of brilliance and fire, bringing an otherworldly appeal to the sparkle of a diamond.

Speaking of sparkle, diamond scintillation is also known as “sparkle” because it describes the sparkle that bounces off the body of the stone and gives it life. It’s a product of motion, and moving the diamond, your eyes, or the light source in the room can all trigger the blinking, on/off sparkle of scintillation. There are also two types of scintillation per diamond: flash scintillation is the white flashes you may notice, whereas fire scintillation is colorful glints of sparkle similar to dispersion. Much like brightness and contrast when it comes to brilliance, you should have the proper balance of scintillation for your stone. Too much or too little can cause a dark stone or for overall sparkle to appear diminished in comparison.

How are they measured?

When it comes to these facets of sparkle, a lot of the grading is based on cut quality which gives graders a good idea of the sparkle they can expect from any particular diamond. While there’s no quantifiable measurement for brilliance, fire, and scintillation as these are visual evaluations of a diamond's beauty, there are tools that help gemologists better understand each diamond’s light performance. Light performance encompasses all three of these characteristics of sparkle, so gemologists use an Angular Spectrum Evaluation Tool (ASET) to get a closer look at how any diamond handles light.

The ASET was created by the American Gem Society (AGS) and is crucial to light performance-based diamond grading. The ASET is a reflector tool that is rather simple to use, consisting of a hemisphere coded with specific colors that indicate the range of angles light is traveling in. When you view a diamond through an ASET, you’ll notice red, blue, green, black, and white areas within the stone that indicate how light is traveling through it—pretty neat!

Because light enters and exits the diamond at different angles, this gives gemologists a good idea of whether a diamond is sparkling as intended by reading the pattern of colors present in the stone. A healthy mix of red, blue, and green light is crucial, preferably with more red, an equal distribution of blue, and hints of green (though this can vary from diamond to diamond). Finally, black and white can reveal light leakage or areas where light is actually escaping the diamond rather than returning to the eye. Like we said, there’s no numerical way to measure fire, brilliance, and scintillation, but tools like the ASET make it much easier to understand diamond light performance!

How a diamond’s cut impacts fire, brilliance and scintillation

There are several factors that impact a diamond’s fire, brilliance, and scintillation, and the gemstone’s cut is the catalyst for most of them! Cut is part of the “4Cs” or the four most crucial areas on which gemologists grade diamonds. The art of crafting a diamond requires precision and an eye for detail, as gem cutters often must decide the best shape and cut for a particular piece of rough before even making an initial cut. And we don’t mean they just eye up the stone and make a decision—gem cutting requires implementing many complex equations and mathematical processes to determine the best cut for a particular diamond.

So what makes up a diamond’s cut grade? Experts grade a diamond’s cut based on symmetry, polish, depth, table percentage and other proportions, as all of these factors impact light performance and the overall balance of the diamond’s shape and appeal. Symmetry and polish are given a grade from Excellent to Poor, whereas depth, table percentage and other proportions are numerical values specific to that specific diamond shape. Because each shape has a different “ideal” cut, they rarely share the same parameters that would be considered “perfect” in the eyes of professionals.

All of these factors play a role in brilliance, scintillation, and fire. A diamond’s cut determines how light will enter and exit the stone, which is crucial to all three aspects of sparkle. For instance, a diamond must be symmetrical and nicely polished with well-crafted facets and angles to make sure light bends as expected through the stone to maximize fire, brilliance, and scintillation. Surfaces must be flat and—ideally—free of flaws, and a wrong angle could mean light may leak out of the diamond before hitting its intended mark to create sparkle.

What’s more, depth and table percentage are important for preventing light leakage. A diamond must have the correct depth and amount of table relative to the diameter of the stone’s girdle or else you may have a dull diamond. Depth and table percentage are also important for preventing shallow cuts that don’t glitter quite as beautifully, and a small table can really hinder your ability to see any sparkle within your diamond.

Cutting a diamond often means removing any major flaws as well, as most diamond rough contains inclusions. Flawless diamonds are incredibly rare (unless they’re lab diamonds, of course!), so taking the time to cut rough in a way that allows gem cutters to remove any issues is a big part of how they create the best diamond possible. To do so, gem cutters often evaluate diamond rough before working on it to determine what cut or shape will best maximize its light performance. In turn, they guarantee the best return for the diamond in terms of value as well as create the most sparkly silhouette possible!

Diamond scintillation vs. Fire vs. Brilliance: Which is most important?

So what’s most important: fire, brilliance, or scintillation?⚖️ There’s no clear winner here, as a diamond requires all three to sparkle its absolute brightest. These facets of sparkle are three parts of a whole, and having too much of one and not enough of the others can actually be a detriment.🤔 In reality, the combined efforts of brilliance, fire, and scintillation give a diamond life, bringing movement to the stone’s sparkle and shine. However, it’s totally normal to enjoy one of these characteristics more than the others, and you can always favor a diamond that displays a little more of one facet than the other two without it greatly impacting your stone. Just don’t put all of your eggs in one basket and buy a diamond that only prioritizes that one facet, because you’ll end up with a dull or dark diamond with very little life.

The importance of fire, brilliance and scintillation

Now you know: you can’t have one without the other when it comes to these important facets of diamond sparkle! Each one is crucial to proper light performance, although you may have your favorite among them.

Are you a fan of those white flashes, colorful fiery displays, or black-and-white contrast? Regardless, you need a little of each to create that classic diamond sparkle. Like we mentioned before, a diamond’s cut is key to achieving enhanced light performance and excellent fire, brilliance, and scintillation, so if you’re interested in learning more you can read our diamond cut guide for further details regarding how cut is truly king!