If you’ve ever looked at a diamond under UV light and seen a soft glow - it’s not magic, it’s fluorescence.
And while it’s often misunderstood, diamond fluorescence can be a helpful feature to know about when buying your diamond, especially if you're trying to get the most brilliance for your budget.
In this guide, we’ll cover what fluorescence actually is, how it’s graded, how it affects a diamond’s appearance and value, and whether it should influence your purchase.
Let’s bring this topic out of the dark and into the light - literally.
In this article...
- What is Diamond Fluorescence?
- What Causes Diamond Fluorescence?
- Do All Diamonds Fluoresce?
- How is Fluorescence Graded?
- How Does Fluorescence Affect a Diamonds Appearance?
- Does Fluorescence Affect Color Grading?
- Does Fluorescence Affect a Diamond’s Value?
- Should You Buy a Diamond With Fluorescence?
- Common Fluorescence Myths (and The Truth)
- Lab-Grown Diamonds and Fluorescence
- Buying Tips: How To Shop For Fluorescent Diamonds
- So, Does Fluorescence Matter?
What is Diamond Fluorescence?
Diamond fluorescence is a natural phenomenon where a diamond emits a visible glow - most often blue - when exposed to ultraviolet (UV) light.
This glow is usually only visible under specific lighting, like sunlight or black light. Not all diamonds fluoresce.
In fact, only around 25% to 35% of diamonds show any fluorescence at all, and the effect ranges from very faint to very strong. So no, your diamond isn’t radioactive. It’s just showing off a little personality.
What Causes Diamond Fluorescence?
Fluorescence happens due to trace elements - commonly nitrogen or boron - or tiny irregularities in the diamond’s atomic structure. T
hese are naturally occurring features formed during the diamond’s growth deep within the earth (or under lab conditions).
Fluorescence is not a flaw. It’s not caused by the cutting process, nor is it something added after the fact. It's simply a byproduct of nature - and sometimes, a very useful one.
Do All Diamonds Fluoresce?
Nope. In fact, 65–75% of diamonds don’t fluoresce at all.
Of the diamonds that do, most emit a blue glow, which is considered both common and desirable - especially for diamonds with lower color grades, where that hint of blue can balance out yellowish tones.
Other, rarer fluorescence colors include white, yellow, green, and orange, though these are less sought-after and can sometimes impact a diamond’s visual appeal.
How is Fluorescence Graded?
The Gemological Institute of America (GIA) grades fluorescence on a five-level scale.
You’ll find this listed on any GIA certificate.
The levels are:
None: No fluorescence visible under UV light.
Faint: A very subtle glow, often imperceptible.
Medium: A soft but noticeable glow under UV light.
Strong: Clearly visible fluorescence in UV settings.
Very Strong: Intense glow that may affect appearance in regular lighting.
Photo: (Top) Maha Tannous / GIA, (Bottom) Harold & Erica Van Pelt
Most consumers won’t notice fluorescence in everyday lighting, especially at faint or medium levels.
But at the strong and very strong levels, the effect can sometimes be visible and may impact the diamond’s look - positively or negatively, depending on the context.
How Does Fluorescence Affect a Diamonds Appearance?
On appearance...
Let’s start with the good news: in most cases, fluorescence has no visible effect on a diamond’s appearance under regular lighting.
But there are exceptions - particularly at the strong or very strong levels.
Here’s what you need to know:
For most diamonds: Fluorescence is invisible in everyday light and doesn’t affect sparkle or clarity.
In rare cases: Strong or very strong fluorescence may cause a diamond - particularly a high-color-grade one (D–F) - to appear milky or hazy in bright sunlight or certain lighting conditions.
This haziness is rare but worth checking for.
The best advice? View your diamond in multiple types of lighting - not just under jewelry store spotlights.
Example:
A D-color diamond with very strong fluorescence may appear slightly cloudy in natural daylight, despite having a high-quality grade on paper. On the other hand, a J-color diamond with medium blue fluorescence may appear a shade whiter - closer to an H or I.
It’s not all downside - sometimes, fluorescence works in your favor.
Does Fluorescence Affect Color Grading?
This is one of the most misunderstood aspects of diamond buying.
The color grade you see on a diamond’s certificate isn’t altered by fluorescence. What can change is your perception of the color.
Here’s how it plays out:
- For lower-color diamonds (G–K), blue fluorescence can actually make them appear whiter. That’s because the blue glow counteracts any yellow tint. In these cases, fluorescence is a bonus, and savvy shoppers can use it to their advantage.
- For colorless diamonds (D–F), strong fluorescence can occasionally cause a hazy look, which can lower visual appeal - and market value.
Real-world example:
You’re comparing two diamonds:
- A J-color with medium blue fluorescence
- An H-color with no fluorescence
To the naked eye, they might look very similar in color, but the J-color stone will be significantly less expensive. That’s fluorescence working in your favor.
Does Fluorescence Affect a Diamond’s Value?
Yes - and no. It depends on the diamond.
- In D–F color diamonds: Strong or very strong fluorescence may lower the value slightly due to the potential for haziness and reduced demand.
- In G–K color diamonds: Fluorescence can be a value-add, since it improves perceived whiteness. In many cases, it has no impact on value - or can even stretch your budget further.
Pro tip:
If you're comfortable trusting your own eyes and working with a jeweler who can guide you through the nuances, fluorescent diamonds can be a smart way to stretch your budget. You may find a gorgeous stone with better performance for a lower price, simply because it’s misunderstood in the wider market.
Should You Buy a Diamond With Fluorescence?
Here’s a quick guide:
- If the diamond has “none” or “faint” fluorescence: You likely won’t notice any difference, and you’ll pay a slight premium - especially in D–F color grades.
- If it has “medium” fluorescence: Great option for near-colorless stones (G–J). You might get a whiter appearance for less.
- If it has “strong” or “very strong” fluorescence: Proceed with care. View the diamond in various lights, ask about haziness, and if it looks great to your eye, it might be a great value.
Ultimately, if the diamond looks beautiful to you and performs well in natural and artificial lighting, don’t let a technicality like “fluorescence” scare you away.
Common Fluorescence Myths (and The Truth)
Let’s bust a few myths while we’re here:
Myth: Fluorescence is bad.
Truth: It’s not. In many diamonds, it has no effect at all. In some, it can actually be a bonus.
Myth: Fluorescence means the diamond is fake.
Truth: Fluorescence is a natural property found in real diamonds - both mined and lab-grown.
Myth: You should always avoid strong fluorescence.
Truth: Not always. If the diamond appears clear and bright, strong fluorescence might just mean extra value.
Myth: Fluorescence affects brilliance.
Truth: It doesn’t impact a diamond’s sparkle or light return - only color perception in some lighting.
Lab-Grown Diamonds and Fluorescence
Lab-grown diamonds can fluoresce just like natural ones. The grading system is the same, and GIA-certified lab diamonds will include a fluorescence grade on the report. Fluorescence is not unique to mined diamonds, nor is it more or less common in lab-grown stones; it simply depends on the trace elements present during formation.
Fluorescence levels for lab-grown diamonds are documented by all major gemological labs, including:
- GIA (Gemological Institute of America)
- IGI (International Gemological Institute)
- AGS (American Gem Society)
- GCAL (Gem Certification & Assurance Lab)
Each of these labs notes fluorescence on the grading report, using the same terminology applied to natural diamonds (None, Faint, Medium, Strong, Very Strong).
Because lab-grown rough is generally more affordable, cutters often have more flexibility to prioritize optimal cut quality and light performance, rather than retaining weight. As a result, you may find that many lab-grown diamonds exhibit excellent cut grades with consistent, controlled fluorescence levels.
As with natural diamonds, the best approach is simple: view the diamond in person (or high-definition video) and assess how it performs under various lighting conditions. If it’s bright, clear, and visually appealing to you, fluorescence should not be a deterrent.
That said, because lab-grown rough is more affordable, cutters often optimize for performance - and you may find more lab-grown diamonds with faint or medium fluorescence.
Buying Tips: How To Shop For Fluorescent Diamonds
If you're open to buying a diamond with fluorescence - or specifically looking for one - here’s how to get the best result:
- Review the GIA certificate and note the fluorescence level.
- Ask to see the diamond in both indoor and natural lighting.
- If possible, compare it side by side with a non-fluorescent stone of the same grade.
- Trust your eyes - if the diamond looks clear, bright, and sparkly, it is.
- Work with a jeweler you trust (we might know a good one).
So, Does Fluorescence Matter?
Fluorescence shouldn’t be a dealbreaker - it should be a buying tool.
In some diamonds, it won’t make any difference. In others, it might give you a visual upgrade without increasing your budget. The key is knowing what you’re looking at and how to assess it properly.
At Ben Garelick, we’re here to guide you through the details - whether you’re shopping for a colorless stunner, a warm vintage-inspired stone, or anything in between. All of our diamonds are GIA, IGI or AGS certified, and we’ll show you exactly how each one performs in different lighting so you can make the best possible decision.
We also ship internationally and offer full support before and after your purchase - wherever you are.
Want expert advice on fluorescence or any other diamond features? Get in touch with our team, and we’ll help you choose the right stone for your style, budget, and sparkle goals.
