Diamond Fluorescence

The Education

Diamond Fluorescence

Fluorescence is the tendency of a diamond to emit a (soft) glow when exposed to ultraviolet light (UV light). The fluorescence effect is present in over 30% of diamonds and is an important consideration when buying a loose diamond.

Diamond Fluorescence
Same stones as seen with an ultraviolet lamp (buttom) and normal lighting (top)

When UV light hits a diamond with fluorescent properties, the stone emits light. Most often blue, it can also be shades of green, yellow, white or red. Fluorescence can occur at different intensities. Gemological laboratories such as the GIA rate diamonds for fluorescence on a scale from “None” to “Very Strong”.

None, Nil, Negligible

No fluorescence, no influence on color.

Faint, Slight

Weak fluorescence, not a significant influence on color (barely perceptible).


Average fluorescence, small influence.

Strong, Extremely Strong

Strong fluorescence, substantial color influence.

Is Diamond Fluorescence Important?

In a small number of diamonds, the presence of fluorescence produces an opaque, milky, oily, or cloudy color. For this reason, diamonds with a high fluorescence index may have a lower value than similar diamonds with a low or medium fluorescence index. If you have selected a strong luminescent diamond, contact a diamond specialist for a visual inspection prior to purchase.

strong blue fluorescence diamond

Does Diamond Fluorescence Affect Value?

Fluorescence can increase or decrease the beauty of a diamond. The bluish tint can accentuate a lower colored diamond (J-M color is evaluated) by removing the pale yellow, resulting in a colorless appearance.

However, in a highly colored diamond (classified as a D-F color), fluorescence can cause the opposite effect.

It is estimated that around 30% of diamonds have some degree of fluorescence, so it is likely that you will encounter some of these stones when buying diamonds.

gia fluorescence scale

How Fluorescence Affects Value of Diamonds

Sometimes a diamond’s luminescence won’t affect its price, while other times it will. D-F grade colorless diamonds are sold at a reduced price if they fluorescence under U-V rays. This is because the fluorescence is considered a defect, so the diamond no longer holds its value. Some believe that fluorescence makes D-F colored diamonds appear a little oily or dull, which is not the desired quality.

However, I-M grade fluorescent diamonds actually sell at premium prices. Why? The diamond’s fluorescence appears blue, matching the yellow tone of the I-M color diamond, making it appear whiter. Therefore, an I-M color diamond will look more like a quality stone when it has a slight fluorescence.

gia fluorescence scale

GIA’s Fluorescence Study

While there are many misconceptions and misconceptions about whether the presence of fluorescence in a loose diamond is good or bad, it is best to consider thorough and sustainable scientific research. The intensity of the fluorescence does not significantly affect the appearance. In the GIA fluorescence study, it was found that the average person’s fluorescent and non-fluorescent diamonds are often indistinguishable. In many cases, observers prefer to appear diamonds with moderate to strong fluorescence. Rarely, some diamonds with intense fluorescence may appear dull or oily; less than 0.2% of the fluorescent diamonds presented at the GIA show this effect. “

strong blue fluorescence diamond

Differentiating Diamonds With & Without Fluorescence

According to a 1997 GIA study, the fluorescence of a diamond does not change shape when it is turned over. However, when the diamond is facing upwards, the average person can tell the difference with a diamond with strong or very strong fluorescence.

However, as we said before, the difference is not a bad thing, as fluorescence can slightly increase the visible color of a light colored diamond.

Should I Buy a Fluorescent Diamond?

The final decision whether to buy a fluorescent diamond is obviously up to you, just remember that the four C’s (color, cut, clarity and carat) are far more important than fluorescence. Since fluorescence does not negatively affect a diamond’s appearance, it shouldn’t play a big part in choosing the right stone for you. In fact, some buyers prefer to buy fluorescent diamonds due to the low prices. Before purchasing a diamond, talk to your retailer about its luminescence to ensure that you are informed of all aspects of the stone before making a final decision.

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FAQ for Diamond Fluorescence

How can you tell if a diamond has fluorescence?

Diamonds come in shades of white and yellow. When blue is added to the yellow they cancel each other out. The more blue you add to yellow, the whiter it becomes. Therefore, a fluorescent diamond in the I-M range is going to appear whiter under UV light.

What causes diamond fluorescence?

Fluorescence occurs in some diamonds when they are exposed to the concentrated radiation of a UV lamp. Submicroscopic structures in the diamonds cause them to emit a visible light, a fluorescence, which is commonly blue in colour.

What color should a diamond be under UV light?

When a diamond is exposed to ultraviolet light (also known as blacklight), it glows blue. Sometimes you might see another color too like yellow, green, red & white, but blue is the most common fluorescent color in a diamond.

How can you tell if a diamond is real?

To determine if your diamond is real, hold a magnifying glass up and look at the diamond through the glass. Look for imperfections within the stone. If you’re unable to find any, then the diamond is most likely fake. the majority of real diamonds have imperfections referred to as inclusions.

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