Complete Guide To Diamond Fluorescence August 18, 2018 – Posted in: Jewelry Blog

If you’re reading this, chances are you at least have a basic understanding of the 4 Cs of diamond grading. Color, Cut, Clarity and Carat weight are things most people know are part of a diamond, even if they don’t fully understand what they are.

However, most diamond buyers remain unaware of another issue which can affect both the appearance and value of a diamond. That issue is fluorescence.

What Is Diamond Fluorescence?

Diamond Fluorescence
Example of high Diamond Fluorescence Half/Half Image

Firstly, it should be understood that fluorescence can be both good or bad. It actually depends on the diamond itself. It also depends on whether the viewer likes the appearance or not. If you’ve ever walked into a room where they have UV (black) lights, you’ll see fluorescence everywhere. White shirts, sneakers, even teeth all glow brightly. This is fluorescence. Around 25-35% of all diamonds have some degree of fluorescence when viewed in UV light.

This Blue/Whiteglow occurs in about 99% of all diamonds that fluoresce. On rare occasions, the color may be more towards green or even yellow.

The actual root cause of fluorescence in diamonds is the presence of trace elements. Usually, it will be one of boron, aluminum or nitrogen. The level of trace isn’t enough to color the diamond as seen with the same elements in fancy diamonds. When UV light enters the diamond, the minute electrons of the element are stimulated. This causes them to bounce about. Electrons have a natural disposition towards being stable, and so they need to expel the energy they receive from the light.

The way they do this is by expelling the energy as photons. It is this energy release that our eyes see as fluorescence.

Fluorescence on Different Diamonds

Diamond Fluorescence and the color grade is a complicated topic that definitely deserves more than a few paragraphs. But to keep it simple, we’ve tried our best to oversimplify it.

Diamond Fluorescence Scale

Whether a diamond fluoresces or not may sometimes have an impact on the value. However, it isn’t a fixed and consistent change in price. In fact, in diamonds of color D to H, fluorescence is not considered desirable. This is because the natural brightness can look cloudy if fluorescence is present.

In diamonds of color I and above, though, it’s a different story. Because diamonds above I on the color scale are starting to contain faint yellow tones, the UV light in natural daylight can help to make a diamond appear whiter than it is.

Degrees of Fluorescence

As might be expected, the higher the rate of fluorescence, the bluer the diamond will appear under UV light. Although not an official part of diamond grading, there is a scale to measure the phenomenon. This is based on intensity and contains None, Faint, Medium, Strong and Very Strong. Each diamond is graded in comparison to a master diamond whose intensity is known and documented.

As mentioned above, the effect on each diamond will depend on the color of the stone and level of fluorescence.

Those diamonds with Strong or Very Strong fluorescence can appear hazy, even in daylight. The effect lessens, the whiter the diamond, but even D, E and F colors can take on a milky appearance with strong levels.

Buying Diamonds With Fluorescence

Diamond Engagement Ring in Yellow Gold Setting

Not all dealers will show the fluorescence levels, so make sure to ask.

Depending on the diamond, strong fluorescence may have an effect on the value. This, though, is very unusual. Generally, if the level of fluorescence does have an effect on the value, it will only be minimally. Even those color grades thought to benefit from fluorescence will rarely be more expensive than the same grade without. The dealer may put a few dollars on top, but most will not.

The biggest reason to buy a diamond which has fluorescence is because you like it. Some people love what fluorescence does to a diamond, some hate it. In truth, most observers wouldn’t even know it was there unless a black light was the only light source.

It’s not a thing to let get in the way too much, in truth. Studies have shown that even experts often can’t agree on the levels of fluorescence a diamond has. If they can’t, then it’s really not something you should spend time worrying about.

Be aware that, if the dealer doesn’t tell you a diamond fluoresces, and you don’t ask, then you have no right to return the diamond. It also may or may not get a mention on the report. The onus is on you to ask the right questions.

If it does concern you, ask to see the diamond in both daylight and under UV. This is your only way of knowing for sure.