What Is Diamond Fluorescence?

When you hear “diamond fluorescence,” it initially sounds like it’s referring to a diamond’s radiation. But in this case, radiance has less to do with shinyness and is actually about how the diamond reflects light and the color that shows up when it does. Kind of like teeth whitening intensity matters. Is this effect negative or positive, tacky, or desirable? Keep reading to find out if diamond fluorescence should be considered in your purchase.

Fluorescence is a type of luminescence, or light. More specifically, diamond fluorescence has to do with whether the diamond glows under the shorter wavelengths of ultraviolet light. The go-to example of ultraviolet light would be an X-Ray, but the most relevant use case here is a black light. Under this type of light, the fluorescent diamond absorbs that shorter ultraviolet wavelength and emits a longer one. The molecules get excited, and that quick burst of high energy creates color. The result? Basically, fluorescence creates brighter versions of primary and secondary colors (blue, red, green, yellow, and purple). The intensity of the diamond’s shade varies. A little less than a third of diamonds have a fluorescence effect.

As far as appearances go, here’s what to expect from diamond fluorescence:

Yellow Diamond = Whiter (technically good because it’s more reflective)
Colorless Diamond = Bluer (technically bad because it’s less transparent)

Diamond Fluorescence Scale

If you picture fluorescent lighting, it tends to glow and appears to have a blue-ish hue. Diamond fluorescence is similar. However, it shows up differently in a lower-color diamond (J-M color rated) than a high-color diamond (D-F color rated). But whether it improves or diminishes the look depends on the diamond, the level of fluorescence, and your personal investment in diamond clarity. Consider requesting images of the stone exposed to different lighting settings if that last one is the case (UV radiation from the sun will look different than a rave).

Here’s what we mean the level of fluorescence, or its grade:

None: No influence on the diamond’s color.
Faint: A weak presence of color in the diamond, but barely noticeable.
Medium: A slight hint of fluorescence in the diamond.
Strong or Very Strong: Significant, observable fluorescence in the diamond.

Is Diamond Fluorescence Important?

Not necessarily. Though fluorescence is technically how jewelry sparkles, it’s not a glow-up, per se. Faint fluorescence is not something you’re going to perceive on your own.

While diamonds of Strong or Very Strong fluorescence are said to have “better” color than less fluorescent stones, especially in the I-K colors, stronger isn’t always “better.” While fluorescent properties bump up the color grade of yellow-tinted diamonds, it needs to counteract that color for balance. You’d want to watch for a higher level of fluorescence in D-F or G-H diamonds as you shop; these don’t have a lot of body color, which can result in them being overpowered by the fluorescence rather than benefitting from the mask. In other words, colorless diamonds have a cleaner appearance, and some say the fluorescence “dirties” it up. Deemed “over blues,” these diamonds are devalued because the color has been compromised.

Does Diamond Fluorescence Affect Value?

Yes, and it can raise or lower the perception of the diamond. Since fluorescence creates different visual effects for different stones, its impact on price point will also fluctuate.

If a diamond is closer to yellow light vs. blue or white, then it’s seen as a defect and deemed lower quality. It’s why colorless (D-F) fluorescent diamonds tend to be much cheaper. Colorless diamonds with a glow are said to be flawed, with some claiming that fluorescence creates a cloudy appearance. But I-M diamonds cost more when they possess Medium to Very Strong fluorescence because their existing yellow undertones complement the fluorescent blues. The bluer, the better. Enhancing the visible color, it helps them appear to be a higher-quality diamond. You might call it a trick of the light (though it’s not a trick, so much as a preference).

When it comes to value, diamond fluorescence is more about style than sentiment. The absence or presence of fluorescence doesn’t take away your jewelry’s meaning.

How Can You Tell if a Diamond Has Fluorescence?

You can’t really see Faint to Medium fluorescence. A gemologist uses a UV light source to identify affected diamonds, so the average person isn’t going to be able to eyeball diamond quality, even in a nightclub with a black light. In fact, when fluorescence is present in a diamond, the GIA found that most people surveyed preferred it, and it only had a noticeable effect on the stone when it was Strong to Very Strong and the diamond was right-side up. The “oily” or lifeless appearance cited by experts was rare.

Bottom line: You won’t be able to spot fluorescence in colorless or near-colorless grade ranges D-J, especially when shopping for jewelry online.

Diamond Fluorescence Shopping Tips

There’s no real reason to buy a diamond because of its fluorescence, or despite it — the effects are negligible, and represents more of an abstract belief in the crystal-clear aesthetic than a truly dulled diamond. The jewelry is still beautiful and “worth” whatever it means to you. There’s no shame in a fluorescent diamond, even if it’s “imperfect.”

While fluorescence has a subjective effect on jewelry, the 4 Cs are more popular, reliable diamond quality indicators. These are more relevant to performance. Check out our Diamond Buying Guide, or skip to the parts most relevant to you or your partner’s tastes.

Diamond Fluorescence FAQs

Is a diamond with fluorescence good?

Some experts insist that diamond fluorescence can create a hazy appearance, though not a highly detectable one. Jewelry buyers who prefer clarity tend to look down on fluorescence, but unless you’re a diamond grader, you’re not likely to have an opinion on the jewelry’s dissimilarity.

What should the fluorescence be in a diamond?

The fluorescence grade (None, Faint, Medium, Strong, Very Strong) will be offset by the body color and clarity in a diamond. It will show up differently in every diamond. That being said, Strong and Very Strong fluorescence were the grades most associated with the milky appearance shoppers are warned to avoid, especially in D, E, and F color diamonds. These tend to be the expensive ones, and fluorescence is said to be to their detriment. However, even if you get your diamond appraised, jewelry experts have wide interpretations of the value and legitimacy of diamond fluorescence.

Do all diamonds exhibit fluorescence?

No, only 25-35% percent of diamonds fluoresce.

Does diamond fluorescence make diamonds look whiter?

If a yellowish diamond combines with the blue light, it can appear more colorless, even in natural daylight. The blue and yellow cancel each other out, giving the jewelry a quality boost. So, in this instance, yes, fluorescence creates a white diamond, and it’ll cost you more per carat. But instances of Very Strong fluorescence are hard to come by.

Are fluorescent diamonds cheaper?

Yes, in most cases (great news for value shoppers). Fluorescence can reduce the price of a diamond, with little to no visible influence on its quality. For many jewelry buyers, this is a win-win. But I-M diamonds with strong fluorescence trade at a 2-3% price premium because of their upgrade to a “whiter” diamond.

Should you buy a diamond with fluorescence?

It’s all about the essence of fluorescence and what color diamond you prefer. But if public perception is a factor in your level of comfort, understand that no one observing your jewelry is going to judge the diamond’s appearance based on fluorescence (or be able to). Fluorescence is most perceptible under a black light when compared to its presence in other diamonds, which is not your typical social situation.

Final Thoughts

Even if you can’t see fluorescence, you’ll know it’s there. You decide if the glow is worth it. But you can shop all diamond jewelry at Brilliant Earth for sustainable, feel-good diamonds. It’s a quality difference you can always tell.

Diamond Fluorescence: Understanding its Impact on Diamond Appearance