What Is Diamond Fluorescence and Does It Affect a Diamond’s Value?
Choosing an engagement ring is a special milestone in any relationship. A couple's ring holds deep meaning and often becomes a cherished heirloom passed down for generations.
When selecting the perfect ring, the center stone is often the star of the show. In most cases this tends to be a diamond. Long acknowledged as the ultimate symbol of enduring love, brilliance, and strength, diamonds have been the top choice for engagement rings for decades.
If you’re not very familiar with diamonds, you might wonder what gives them their lasting value and timeless appeal. A diamond’s worth is largely determined by the 4Cs: cut, color, clarity, and carat weight.
However, while the 4Cs are essential, there’s another characteristic worth paying attention to: fluorescence. A diamond purchased from a reputable jeweler typically includes a grading certificate detailing its 4Cs, along with additional information such as its proportions and whether it exhibits fluorescence.
Though it may sound like a technical term, fluorescence is simply a natural reaction that occurs when diamonds are exposed to ultraviolet (UV) light, causing them to emit a soft glow. This glow is usually blue, but can occur in other colors. It’s a fascinating trait that doesn’t require magnification to detect. Not all diamonds possess fluorescence, but when they do it will influence how the stone looks and even how it’s valued.
Fluorescence is one of those misunderstood characteristics of a diamond. Some people think it’s a flaw, and may even avoid a stone that has any traces of it. Others purposefully seek out diamonds with strong fluorescence. The truth is, it’s neither all good nor all bad. Fluorescence is just another natural characteristic of diamonds that can influence their appearance and price.
Let’s dig a little bit deeper so you fully understand what fluorescence is, what causes it, and how it can affect a diamond. Hopefully this will help you decide whether a diamond with (or without) fluorescence is right for you.
What Exactly Is Diamond Fluorescence?
To describe it simply, fluorescence is a natural glow that some diamonds emit under UV light. This glow is usually blue, but can sometimes be yellow, green, or white. While fluorescence isn’t visible all the time, it can be visible when placed under a strong jeweler’s lamp, in a nightclub, or even in a tanning booth. About one third of all diamonds have some amount of fluorescence. Many people own fluorescent diamonds without ever knowing it.
Diamond fluorescence occurs when small amounts of certain elements are present in a diamond. It's also caused by irregularities in the diamond’s crystal structure. When exposed to UV light, these elements release light energy that causes the diamond to glow.
How is Fluorescence Graded?
The Gemological Institute of America and other gem grading laboratories grade fluorescence on a scale that allows the consumer to understand how much a diamond glows when placed under UV light. The standard scale is:
- None: No measurable fluorescence
- Faint: Very subtle glow under UV light
- Medium: Noticeable glow, but not overpowering
- Strong: Prominent glow
- Very Strong: Intense glow, often visible to the naked eye
The majority of diamonds fall between the none to medium levels of fluorescence.
How Does Fluorescence Affect a Diamond’s Appearance?
While it’s true that fluorescence isn’t usually visible without a UV light, it can actually affect the way a diamond looks to the naked eye. How much fluorescence is visible will depend on a different factor: the diamond’s color grade. For diamonds with a color grading of D to F, fluorescence can sometimes make them look slightly cloudy–especially if the fluorescence is in the strong to very strong range. When this happens, it would typically reduce the value of the stone.
For diamonds graded G to M, fluorescence can actually improve the appearance of the stone–especially blue fluorescence. Because diamonds in this range often have a yellowish tint, the blue fluorescence can help balance the color, making the stone appear whiter and giving it the look of a higher color grade. In fancy-colored diamonds—such as canary yellow—the blue fluorescence can actually dull the stone’s vibrancy, while yellow fluorescence can enhance it, making the color appear even more intense.
When Will My Diamond Glow?
You might be concerned about purchasing a fluorescent diamond because you don’t want your diamond to glow all the time. Don’t worry, it won't!
UV light is only about 10% of natural sunlight, so your diamond won’t glow when you’re outside on a sunny day. Under indoor lighting, you won’t notice any glow, unless you’re at a nightclub with black lights. If this happens, you should embrace it because it can look really cool.
Myths About Fluorescence
Since fluorescence can be misunderstood, there are several common myths surrounding fluorescent diamonds. First, many people believe that fluorescence is a flaw. In reality, it’s a natural occurrence.
Another myth: fluorescent diamonds always look cloudy. This is really only true for a small percentage of stones that are in the higher color grades. Most fluorescent diamonds look no different than other stones.
Some people think that fluorescence means their stone will glow in the dark. While this would be pretty cool, it is also not true.
Finally, some people believe that fluorescent diamonds are rare (and therefore more valuable). However, one third of all diamonds have fluorescence, which means it's not a characteristic that would qualify as rare. In most cases fluorescence doesn’t increase the value of the diamond.
Should You Buy a Fluorescent Diamond?
This, like most other jewelry shopping decisions, comes down to personal preference. If you're shopping for a diamond we highly recommend looking at the stone in person and under different light sources. Since fluorescence is rarely noticeable, there’s no need to pay a premium for a diamond with zero fluorescence if another stone with similar 4Cs and medium fluorescence offers a better value.
If you notice a cloudy look in a diamond, check the grading certificate to see if it has strong fluorescence. You can then determine if the haziness bothers you.
If you tend to visit a lot of places with black lights and love the thought of your diamond glowing, then we'd actually encourage you to find a diamond with strong fluorescence.
Final Thoughts
To recap, when shopping for a diamond and examining the 4Cs, remember to review the fluorescence section of the grading certificate. While it’s not something you should be overly concerned about, you definitely want to be informed. Most importantly, view the diamond in person, examine it under different lighting conditions, and decide for yourself whether the glow enhances its beauty or feels distracting.
Diamond fluorescence is a natural and fascinating trait that adds character to a stone. Whether it enhances or diminishes value largely depends on your perspective. Depending on its strength and the diamond’s color grade, fluorescence can make the stone appear whiter—or, in some cases, slightly cloudy. However, in most diamonds, fluorescence is subtle, harmless, and even a bit fun to see under black light.
When shopping for a diamond, don’t let the presence of fluorescence scare you away. Take the time to examine the stone and decide how you feel. You may find that you fall in love with a diamond that has a little glow–and a little more personality.