You’ve done your research on the 4 Cs and feel like you are ready to jump in and buy the perfect diamond for your partner. Meanwhile, you notice it has “strong blue” fluorescence…what does this mean?! Don’t worry, we will walk you through it! 

What is Fluorescence and Why Is It In Diamonds?

Fluorescence is a diamond’s tendency to emit a soft blue glow under ultraviolet light. To clarify, your diamond will change from white to blue when exposed to invisible UV rays. Diamonds with fluorescence glow because they have trace amounts of Aluminum, Boron or Nitrogen in them. However, not all diamonds fluoresce! In a study done by GIA researchers, only about 25% to 35% of 26,000 diamonds had any amount of fluorescence when exposed to UV light. In other words, having a diamond with fluorescence is pretty unique! 

The GIA grades diamonds with fluorescence on a scale from “none” to “very strong”. This grading has to do with the amount of fluorescence in each diamond, which will determine how much blue glow it will emit when exposed to UV light. 

comparison of various fluorescent diamonds

A GIA grading report showing different levels of fluorescence in normal lighting and UV lighting. Photo credit: Composite photo in UV- Maha DeMaggio/GIA. Composite photo in normal light- Harold and Erica Van Pelt/GIA

What Does Diamond Fluorescence Look Like? 

Blue is the most common color you can expect to see from diamond fluorescence, but it is also possible for some diamonds to have a yellow fluorescence as well. These colors will appear once the diamond is exposed to ultraviolet rays from the sun, or under a black light. The color may not always be extreme. However, you should notice a slight change in appearance when you are outside on a high UV day, or under a black light in a nightclub. For instance, if your diamond has “strong blue” or “very strong blue” fluorescence, it will have a blue glow when you go outside on a day with a 9 or 10 UV index rating. 

Right: D colored diamond with very strong fluorescence in normal lighting Left: D colored diamond with very strong fluorescence in the sunlight

Can Diamond Fluorescence Cause Milkiness and Haziness?

One thing to be careful of when buying a diamond with fluorescence is the potential presence of milkiness or haziness in the stone. Since this is not necessarily a desired quality in a diamond, we always go the extra mile to ensure the diamonds we select are not hazy, nor do they have any milky appearance. Therefore, you can rest assured when searching the diamonds on our website, because they have already been checked by a gemologist and are free of milkiness or haziness. Above all, it is important to make sure the jeweler you are working with has physically checked the diamond to make sure it is the best quality, free of hazy or milky appearance.  

Is Fluorescence a Good Thing or Bad Thing? 

Short answer: it depends on who you ask! Fluorescence is neither good nor bad, it is truly a personal preference. Some people purposely buy a diamond that has fluorescence because they think it is cool. However, some people are strongly against a diamond with fluorescence because they want the whitest, “purest” stone possible. Then, some people have never heard of fluorescence and have no opinion either way! Wherever you fall on this scale, rest assured that fluorescence in a diamond is not harmful to the stone in any way, nor does it diminish the quality. 

Pros Cons
More Affordable (Especially in Colorless Range) Resale Value May Be Lower
Unique Diamond Characteristic  Could Have Milky/Hazy Appearance (Don’t Worry, We Check This)
Whiter Appearance in a Warm Diamond Some Diamond Purists Prefer No Fluorescence

How Can Fluorescence Affect the Price of a Diamond?

Selecting a diamond with fluorescence is a good way to save a little money on a stone with great specifications. As you may already know, an excellent cut diamond that is colorless (D, E or F) and has a high clarity grade will typically be on the pricier side. However, if you take these same specifications and find a diamond that also has strong fluorescence, you can save quite a bit of money. In addition, a warmer colored stone (I or J) that has strong blue fluorescence can give the illusion that a stone is whiter than it is. So, it is almost as if the coolness from the blue, and warmth from the yellow cancel each other out. It is easier to save a drastic amount of money on colorless stones, but the warmer you go on the color scale, the less amount of money you save. Therefore, you will start to notice the drop-off point around J colored diamonds, where there is little to no savings. 








Excellent  F VS1 None



Excellent  F VS1  Strong



Excellent  I VS1 None



Excellent  I VS1 Strong



Should You Buy a Diamond with Fluorescence?

In conclusion, we think diamonds with fluorescence are a unique choice without having to give up other great specifications in a center stone. Ultimately, though, it is up to you! If you are looking to save a little money while still getting a beautiful diamond, choosing a stone with some fluorescence could be a great option for you! Whether you think fluorescence is cool or not, the most important aspects to consider when buying a diamond are the 4 Cs: Cut, Color, Clarity, and Carat! Above all, diamond fluorescence is a quality in which beauty lies in the eye of the beholder.