This article has mentions of products from one or more companies, and I may receive compensation if you purchase those products following reading my recommendations.

Diamond fluorescence is a fascinating and often misunderstood characteristic of some diamonds. This guide aims to provide an in-depth understanding of diamond fluorescence, its causes, how it's graded, its impact on a diamond's appearance and value, and tips for making an informed decision when purchasing a diamond.

What is Diamond Fluorescence?

Fluorescence is a natural phenomenon that occurs when certain materials, including some diamonds, emit visible light upon exposure to ultraviolet (UV) radiation. In the case of diamonds, this is often a blue or blueish glow, but other colors like yellow, green, or white can also occur. It is important to note that not all diamonds exhibit fluorescence; in fact, only about 25-35% of diamonds show some degree of this characteristic.

To better understand this phenomenon, let's first briefly discuss the concept of fluorescence in general. When a material with fluorescent properties is exposed to UV light, its electrons absorb energy and jump to higher energy levels. As these electrons return to their original energy levels, they release energy in the form of visible light, causing the material to emit a glow. This process is what causes the visible fluorescence in some diamonds.

If you're looking to purchase the highest quality diamonds with no fluorescence then read my reviews on Whiteflash, James Allen and Blue Nile.

Causes of Fluorescence in Diamonds

The primary cause of fluorescence in diamonds is the presence of trace elements within the diamond's crystal lattice structure. The most common trace element responsible for fluorescence is nitrogen, which can replace carbon atoms in the diamond lattice, creating what is known as a nitrogen-vacancy center. When exposed to UV light, these nitrogen-vacancy centers absorb energy and emit a blue or blueish glow.

Another trace element that can cause fluorescence in diamonds is boron. While boron-related fluorescence is less common, it can produce a blue or greenish-blue glow. In some cases, the presence of other trace elements or impurities can result in other colors of fluorescence, although these are rarer.

In addition to trace elements, crystal lattice defects can also contribute to fluorescence. Diamonds are formed deep within the Earth's mantle under extreme heat and pressure, and during this process, irregularities in the crystal lattice can occur. These defects can also absorb energy from UV light and emit visible light, contributing to a diamond's overall fluorescence.

Grading Diamond Fluorescence

The GIA Fluorescence Scale

The Gemological Institute of America (GIA), one of the world's most respected diamond grading organizations, has developed a scale to classify the intensity of a diamond's fluorescence. This scale consists of the following five grades:

GIA diamond fluorescence scale

None: No observable fluorescence under UV light.

Faint: A slight degree of fluorescence that is difficult to detect.

Medium: A noticeable level of fluorescence.

Strong: A prominent degree of fluorescence that is easily visible.

Very Strong: An intense level of fluorescence that is very apparent.

It is important to note that the GIA scale only measures the intensity of the fluorescence, not its color. Diamonds with the same intensity of fluorescence may still have different colors, such as blue, yellow, or green.

How Fluorescence is Evaluated in a Lab

To evaluate a diamond's fluorescence, gemological laboratories use controlled lighting conditions and specialized UV lamps that emit long-wave UV light. The diamond is placed under the UV light, and the gemologist observes its reaction to determine the intensity and color of the fluorescence.

The diamond is first examined under normal lighting conditions to identify any potential impact of fluorescence on its overall appearance. Next, the gemologist exposes the diamond to UV light in a darkened room, which allows them to observe the diamond's fluorescence more accurately. The intensity of the fluorescence is then compared to a set of reference stones with known fluorescence grades, which helps the gemologist assign the appropriate grade to the diamond.

It is essential to have a gemologist evaluate diamond fluorescence, as the process requires a trained eye and specialized equipment to ensure accurate results.

The Impact of Fluorescence on Diamond Appearance

Positive Effects

In some cases, fluorescence can have a positive effect on a diamond's appearance. For example, if a diamond has a slightly yellowish hue due to the presence of nitrogen impurities, a blue fluorescence can counteract that yellowish tint and make the diamond appear whiter. This is particularly true for diamonds in the near-colorless range (GIA color grades G-J), where the blue fluorescence can enhance the stone's overall appearance. Such diamonds are often referred to as "blue-white" diamonds and can be desirable to some buyers.

Negative Effects

On the other hand, strong or very strong fluorescence can sometimes negatively impact a diamond's appearance. In some instances, it can cause the diamond to appear hazy, cloudy, or "milky" under natural sunlight or other UV-rich light sources. This effect is relatively rare and tends to occur in less than 1% of strongly fluorescent diamonds. However, it is crucial to be aware of this possibility, especially when considering diamonds with strong or very strong fluorescence.

Fluorescence in Different Lighting Conditions

The visibility of fluorescence in diamonds can vary depending on the lighting conditions. Under natural sunlight, which contains UV radiation, fluorescence may be more noticeable than under artificial indoor lighting, which typically has less UV content. It is essential to view a diamond under various lighting conditions to understand how its fluorescence may impact its appearance in everyday situations.

Fluorescence and Diamond Value

How Fluorescence Affects Pricing

Fluorescence can impact a diamond's value, but the effect is not always straightforward. In some cases, a diamond with medium to strong blue fluorescence may be priced slightly lower than a comparable non-fluorescent diamond, as the market tends to place a premium on diamonds with no fluorescence. However, if the fluorescence enhances the diamond's appearance by making it appear whiter or more colorless, the value may be unaffected or even increased.

In the case of strongly or very strongly fluorescent diamonds with a hazy or milky appearance, their value is typically reduced, as this effect is considered undesirable by most buyers.

The Rarity of Fluorescent Diamonds

Fluorescent diamonds are relatively rare, with only about 25-35% of diamonds exhibiting some degree of fluorescence. Among these, diamonds with strong or very strong fluorescence are even rarer, accounting for approximately 10% of all fluorescent diamonds. While their rarity can make them intriguing to some collectors, it is essential to consider the potential impact of fluorescence on a diamond's appearance and value when making a purchase decision.

Tips for Buying a Diamond with Fluorescence

Assessing Personal Preferences

When considering a diamond with fluorescence, it is essential to assess your personal preferences and tastes. Some buyers may find the unique characteristics of fluorescent diamonds appealing, while others may prefer a diamond with no fluorescence. It is crucial to examine the diamond in various lighting conditions and ensure that you are satisfied with its appearance before making a purchase.

Considering Diamond Color and Fluorescence

The relationship between diamond color and fluorescence is an important factor to consider when making a purchase decision. In diamonds with a near-colorless grade (G-J), fluorescence can help improve the diamond's appearance by making it appear whiter. However, in diamonds with a higher color grade (D-F), fluorescence might not have the same positive effect, and strong fluorescence could potentially make the diamond appear hazy or milky. It is essential to strike a balance between diamond color and fluorescence that suits your preferences and budget.

Seeking Expert Advice

Consulting a knowledgeable jeweler or gemologist is always advisable when purchasing a diamond, especially if you are considering a diamond with fluorescence. An expert can provide valuable insights into the diamond's quality, appearance, and value, and help you make an informed decision.

If you're looking to purchase the highest quality diamonds with no fluorescence then read my reviews on Whiteflash, James Allen and Blue Nile.

Frequently Asked Questions about Diamond Fluorescence

1Does fluorescence make a diamond less durable?
No, fluorescence does not affect a diamond's durability. The presence of fluorescence is due to trace elements or lattice defects within the diamond, which do not impact its overall structural integrity or hardness.

2Can fluorescence be altered or removed from a diamond?
Fluorescence is a natural property of a diamond, and it cannot be altered or removed without significant intervention, such as high-pressure, high-temperature (HPHT) treatments. However, such treatments can also change other aspects of a diamond's appearance and are not recommended solely for altering fluorescence.

3How does fluorescence affect a diamond's sparkle or brilliance?
Fluorescence does not directly impact a diamond's sparkle or brilliance. However, in some rare cases, strong or very strong fluorescence may cause a diamond to appear hazy or milky, which can make it seem less brilliant. This effect is relatively uncommon and should be evaluated on a case-by-case basis.

4Is fluorescence in colored diamonds (such as fancy-colored diamonds) different from colorless diamonds?
Fluorescence in colored diamonds can be similar to that in colorless diamonds, but its impact on appearance may vary depending on the diamond's color. In some cases, fluorescence can enhance the color of a fancy-colored diamond, while in others, it may detract from the diamond's overall appearance. As with colorless diamonds, it is essential to evaluate colored diamonds with fluorescence on an individual basis and consider personal preferences when making a purchase decision.


In conclusion, diamond fluorescence is a fascinating and often misunderstood characteristic that can impact a diamond's appearance and value. By understanding the causes of fluorescence, its grading system, and its potential effects on a diamond's appearance, you can make informed decisions when purchasing a diamond. Remember to consider your personal preferences and seek expert advice to ensure that you choose a diamond that meets your expectations and brings you joy for years to come.