What is Diamond Fluorescence? Your Ultimate Guide [2021]

Diamond Fluorescence

You may have heard of fluorescence in diamonds before but never really paid attention to it. After all, a number of jewelers may suggest that fluorescence can give diamonds a color boost.

Not true at all.

Diamond fluorescence is overlooked when diamond shopping until later when it starts to show its appearance in different lighting conditions. It only gets seriously researched when the diamond is put under blue light and begins to disperse visible light. Then, you’d ask whether it is a good or bad indication.

Read on as we take you into a deep understanding of what fluorescence is and just how it affects the diamond’s color and price.

What Is Diamond Fluorescence?

diamond flourescence chart

Fluorescence is that certain “glow,” in which the object (in this case a diamond) has absorbed light or other electromagnetic radiation. This emission is a form of luminescence. In diamonds, it refers to the stone’s tendency to emit a soft colored glow when put under blacklight or UV (ultraviolet) light.

About 30% of diamonds glow to some degree. When displayed under UV light, diamonds fluoresce various shades. The glow is blue 99% of the time. However, in rare instances, diamonds glow white, yellow, green, or even red.

If you’ve seen how whites look whiter in UV light, it is almost the same effect when diamonds fluoresce under it too. Depending on the diamond, fluorescence may either improve the diamond’s color or cause it to appear hazy.

Diamond Fluorescence and Lighting

Since gemologists were aware of how UV light affects diamonds, they had an original set lighting standard for color grading without UV components. But, the criteria changed in 2008. The changes include diamond colors being graded under a daylight-equivalent light bulb with a UV component.

The change in standards means that the effect of fluorescence is integrated into the color grade. The reason is that fluorescence in diamonds is not considered a grading factor but an identifying characteristic.

GIA (Gemological Institute of America) Diamond Grading Reports and Diamond Dossiers define a diamond’s fluorescence by its intensity – None, Faint, Medium, Strong, and Very Strong. None and faint are hardly ever noticed and only noted if it is at Medium, Strong, and Very Strong.

Is Diamond Fluorescence Good or Bad?

Diamond fluorescence can either be good or bad. Does it improve the diamond’s color? Or, does it cause it to look hazy? Let’s take a look at the different intensities of fluorescence in diamonds.

Diamonds with None or Faint fluorescence don’t appear cloudy. When you observe it closely, the faint fluorescence makes the diamond appear whiter. However, when the diamond becomes hazy because of the fluorescence, it becomes less transparent. The reason is that the light can’t reflect well, leaving the diamond less transparent and less beautiful.

Other instances when fluorescence leaves an effect on diamond’s quality:

  • Strong or Very Strong: causes diamonds to appear hazy or cloudy
  • Medium with high color grade (G or better): diamond appears milky or hazy
  • Any fluorescence in D, E, or F color grades: Diamonds don’t benefit from fluorescence in this range. Since they are considered less valuable, their price and appeal are also lower.

Color and Price According to Diamond Fluorescence

While ultimately, you won’t observe the slight changes in color grade, you may notice the difference in price. Fluorescent diamonds’ costs are reduced compared to those with none or faint fluorescence. The effect on price depends on the degree of fluorescence, diamond color, and clarity.

On the chart below is the approximate summary of the effects of fluorescence in terms of price. Notice that an E color graded diamond with VS1 clarity and strong fluorescence may sell for 3-5% less than a similar diamond with no fluorescence.

On the other hand, a J color graded diamond with any clarity grade and with medium fluorescence may usually sell for up to 2% more than a similar diamond with no fluorescence. Clarity has not much impact on the color and fluorescence appearance but does influence the price.

Why? Because diamond shoppers who lean towards higher clarity have a habit of being more adverse to the presence of fluorescence.

How Fluorescence Affects Price
GradeClarityVery StrongStrongMediumFaintNone
D – FVVS2 -10 to -15% -7 to -10% -3 to -7%-1%0%
VS1 – VS2 -6 to -10% -3 to -5% -1 to -2%0%0%
SI1 – I30 to -3%0 to -1%0%0%0%
G – HVVS2 -7 to -10% -5 to -7% -1 to -3%-1%0%
VS1 – VS2 -3 to -5% -2 to -3%0 to -2%0%0%
SI1 – I30%0%0%0%0%
I – MI3 0 to +2% 0 to +2% 0 to +2%0%0%

A claim says that half the diamond only glows when exposed to UV light. In that case, it should only matter if you are a diamond wearer who spends most of their time in dark rooms lit with blacklight lamps.

The truth is most diamonds that demonstrate strong blue fluorescence look slightly to severely hazy in normal lighting conditions. GIA had a study about fluorescence that said even the strong blue fluorescence is almost always entirely unnoticeable for the average diamond consumer.

GIA DiamondLite containing two Verilux F6T5 fluorescent tubes

Diamond fluorescence remains to be a broadly misunderstood part of understanding diamonds. When we say diamond fluorescence, we refer to the glow it shows when exposed to UV light. Yet when it exhibits a blue color, it appears higher in color than its actual body color.

Will Diamond Fluorescence Make A Yellow Diamond Look Whiter?

A few trade professionals think blue fluorescence boosts a diamond’s appearance, particularly those that fall under I to M color grades. Bluish can cause a Faint yellowish diamond to look more colorless under UV light, such as natural daylight.

As a result, almost colorless to Faint yellow diamonds with Medium to Very Strong fluorescence may have a marginally higher per-carat price than similar diamonds that do not fluoresce.

The inverse applies for jewels with higher color grades: diamonds within the D to H color grade with blue fluorescence are frequently considered less appealing by traders. Some suppose that bluish fluorescence causes a hazy or oily appearance in diamonds. This effect only happens if the fluorescence intensity is Very Strong.

However, only some diamonds with Very Strong blue fluorescence look oily, and they may sell less than diamonds that do not exhibit blue fluorescence.

When you compare diamonds side by side and back to back, you will categorically see a difference between one that has strong fluorescence and one with little to none. It points out the extreme haziness level for a fluorescent diamond, which is not typical and as expected in diamonds at color grades H and lower.

Should You Be Hesitant Regarding Fluorescence?

On rare occasions, Medium blue fluorescence on G color graded diamond may show milkiness or haziness, thus the hesitation. If you are buying a diamond in person, it will reduce your uncertainty by asking for one with strong blue fluorescence.

Such diamonds will be more affordable. Plus, buying it in person allows you to see for yourself whether or not it exhibits the haziness or milkiness that we’ve mentioned and if it affects the overall look. Traders will allow, if you ask to see the diamond in different lighting settings.

Do You Frequent Nightclubs or Raves?

Do you usually go out and frequent nightclubs? Diamond fluorescence is not commonly seen unless the stone is under heavy UV lighting – yes, the blacklights in clubs and bars. According to GIA, fluorescence does not entirely affect the diamond when looking at it from upside down.

But it’s a totally different story when it is right-side up. The difference may be visible even to an average person looking at it. As we’ve hinted, the difference isn’t so bad since fluorescence may, to some extent, enhance the visible color of a lightly colored diamond.

7 Pointers About Diamond Fluorescence

  1. It is up to your preference to tell whether diamond fluorescence is good or bad.
  2. A lot of times, fluorescence can move forward the color of the diamond.
  3. Strong blue fluorescence does not automatically indicate a negative effect on the diamond’s overall color and appearance.
  4. Faint diamond fluorescence will save you from paying too much without sacrificing brilliance.
  5. As with most things you purchase, when shopping for a fluorescent diamond, always be in tune with the store’s return policy.
  6. If thinking of buying fluorescent diamonds, buy only from reputable traders to guarantee quality.
  7. Do not be afraid to ask to see the diamonds under UV and standard lighting. Plus, how the stone may look when exposed to daylight.

10 Diamond Fluorescence Myths Dispelled

Myth 1: All diamonds fluoresce

The truth is, the majority of diamonds do not fluoresce. The GIA studied more than 26,000 diamonds for grading and found out that only about 25% to 35% of them displayed some degree of diamond fluorescence when put under a standard long-wave UV lamp. It is more likely that the diamond you are staring at does not fluoresce.

Myth 2: Diamond fluorescence is visible no matter the lighting

Diamonds only fluoresce when exposed to invisible UV rays or other higher energy radiation such as X-rays or lasers. They may fluoresce under a bright sun, tanning bed, or inside a club where a strong backlight is used. But once such light source is turned off, the diamond won’t exhibit fluorescence.

Myth 3: Diamond fluorescence can always be detected

Diamond fluorescence isn’t often detected. It will require UV rays, and the intensity of the fluorescence should also be strong enough to be observed.

Myth 4: Diamond fluorescence affects a diamond’s color grade

The GIA examines diamonds in a highly controlled viewing environment to assess the diamond’s color carefully. So no, it does not affect the color grade. But, the way you see the diamond’s color grade may be affected by the intensity of the fluorescence.

Myth 5: Diamond fluorescence is also graded

Diamond fluorescence is not a grading factor like the four Cs but an identifying characteristic. It is more like additional information that helps distinguish one diamond from another.

Myth 6: Diamonds only show blue fluorescence

Diamonds fluoresce in different shades. They may be orangy yellow, yellow, orange, red, white, and green. This phenomenon is caused by differences in the atomic structure, such as the number of nitrogen atoms present. But, blue is the most common color for diamond fluorescence.

Myth 7: Strong blue diamond fluorescence is bad

When under standard viewing conditions, blue fluorescence on a diamond’s appearance can’t even be consistently discriminated against any fluorescence related effects. The GIA studied that Strong blue diamond fluorescence could be beneficial since Strong blue fluorescent diamonds are seen to have a better color appearance than their color grade would suggest when viewed table-up, with no discernible trend table-down.

Myth 8: Diamond fluorescence weakens a diamond’s sparkle and beauty

Diamond fluorescence has little to almost no effect on a diamond’s sparkle, nor does it show any impact on its beauty, too.

Myth 9: Fluorescence in the diamond means it is a “real” natural diamond

No. Fluorescence is not an indicator of whether the diamond is real or not. Not all natural diamonds fluoresce. And, some lab-grown diamonds fluoresce to different wavelengths.

Myth 10: Fluorescence makes diamonds less durable

Diamonds that fluoresce under a standard UV lamp have the same structural composition and integrity as others.

Buying Diamonds: Locally and Online

Shopping online for a diamond with Medium fluorescence is less costly than buying a Strong fluorescent diamond locally. If you’re shopping locally, carefully evaluate a fluorescent diamond and ensure that any Strong blue fluorescent is not hazy. Ask to see how the diamond looks under various lighting conditions – sunlight, blacklight, or indoor lighting.

Online shoppers may be unfortunate not to have the chance to check diamonds meticulously. This holds true even with James Allen’s advanced photography. Thus, it is recommended to stay away from shipping blue fluorescent diamonds online.

The good thing about shopping with reputable stores like the Blue Nile and James Allen is their 30-day free returns policy that will apply if your diamond ends up looking hazy.

Another noteworthy alternative to consider when buying online is  Brian Gavin’s “Blue” line. Brian Gavin has personally handpicked all the stones for this line to show no signs of milkiness or cloudiness.

Buying Recommendations for Fluorescence

The decision of whether or not to buy a fluorescent diamond is always up to you. Keep in mind that the four Cs (color, cut, clarity, and carat) are far more critical than diamond fluorescence. Since fluorescence doesn’t impact the diamond’s appearance negatively, it shouldn’t be a significant factor in your decision making.

If you’ve finally decided to buy, here are some recommendations you may consider:

H, I, or J Color Diamonds – Look for a diamond with Medium fluorescence. This intensity can make your diamond look slightly lighter.

1.10-Carat Round Cut Diamond Ideal Cut | J Color | SI1 Clarity

G or Higher Color Diamonds – Look for either None of Faint fluorescence. Or consider one from Brian Gavin Blue Collection. An I or J color stone will give the best value.


Diamond fluorescence is neither good nor bad. As cliché as it may sound, a diamond’s beauty is in the eye of the beholder. You may distinguish fluorescence, or you may not. You may like how it will look like, or you may not.

Take time to look at a diamond with fluorescence under various lighting conditions. Compare it to other diamonds of similar color grade. Then decide whether the difference you will notice is something that will bother you.

There is no hard rule when it comes to diamond fluorescence. It must be why it sparks so much debate because its effect is subjective. Opinions may range across the spectrum. So, if you see a diamond and it appeals to you, let your heart lead the way.

FAQs (Frequently Asked Questions)

Q: Can an average person tell the difference fluoresce does to a diamond?

A: When GIA studied this subject, it included many diamonds with different color grades. They were set as similar as possible except for the intensity of blue fluorescence. The agency had diamond graders, trained professionals, and average onlookers to judge the diamonds’ appearance.

The result was impressive – the average observer saw no systematic effects of fluorescence on the diamonds’ appearance. Even trained observers could not consistently agree on the impact from one stone to another.

Q: Do all diamonds fluoresce?

A: Not all diamonds fluoresce. There are only about 25% to 35% of diamonds that demonstrate some degree of fluorescence.

Q: What color is visible in diamond fluorescence?

A: Diamond grading accounts that the diamond fluorescence produces colors such as blue, yellow, or white.

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