Lab notes: What is diamond fluorescence?

A diamond’s cut and shape can greatly impact the amount of sparkle, as we’ve previously noted in our lightbox guide to diamond shapes. What’s not to love about stunning, sparkly diamonds? But, have you ever considered how a diamond glows? It’s called diamond fluorescence and it occurs when tiny amounts of impurities cause a diamond to glow or luminesce under ultraviolet (UV) light. Okay, we know what you’re thinking: the last time I was at a club with UV lights, boy bands with bad highlights dominated the top 40. Us too. But what does that mean for buying a natural or a lab-grown diamond? Does it change the price or the look? And should you avoid diamond fluorescence altogether? 

In this guide to diamond fluorescence, we address common questions and weigh in on if diamond fluorescence is good, bad, or somewhere in between.

Do all diamonds fluoresce?

No, not all diamonds fluoresce. According to the gemological institute of America (GIA), 25 to 35 percent of all diamonds, both natural and lab-grown, exhibit some level of fluorescence. Simulated diamonds (like cubic zirconia) can too. 

Can you see diamond fluorescence with a naked eye?

You cannot see diamond fluorescence with your naked eye. But, as it turns out, there are limited places and scenarios where you’ll see a diamond glow—and they require UV or black light to be present. So unless you’re worried about what your diamond looks like in tanning beds or at dance clubs, diamond glow isn’t something to worry about. 

If you do purchase a diamond with a level of fluorescence, it will never be visible to the naked eye.

Diamond fluorescence and the 4c’s

The 4c’s—cut, color, clarity, and carat—do not include diamond fluorescence. However, similar to how a diamond’s cut and clarity has a scale, diamond fluorescence has unique grading levels. There are five levels, and they cover the range of fluorescence: faint, medium, strong, and very strong. 

Far more important than fluorescence to the diamond’s overall appearance is cut and color—that’s half of the 4c’s. Diamond color actually means the diamond’s lack of color. Every white lightbox lab-grown diamond has been measured as 'near colorless'. This is technically defined as between g and j and means that only a trained gemologist can detect a trace of color, whilst our lightbox finest™ stones are 'colorless d, e, f', the highest grades a stone can be. 

Diamond cut determines its brilliance and how much its facets interact with light and sparkle. Cut does not refer to the shape of a diamond, but instead grades how perfectly the stone has been cut into its shape. The better the symmetry, proportioning, and polish of a diamond, the higher its cut grade.

Every lightbox lab-grown diamond has been measured as at least “very good”—offering exceptional brilliance and fire. In fact, our production process means that we grow our stones to be the optimal size and shape for cutting, maximizing the sparkle each stone can offer.

Does diamond fluorescence affect lab-grown diamonds?

There are a lot of misconceptions when it comes to understanding the difference between lab-grown and natural diamonds. (if you’re new to the lab-grown space have a read of this article.) Some armchair experts are quick to point out that fluorescence is a telltale sign that a diamond is a natural diamond but that is a myth. Lab-grown diamonds are known to fluoresce, too. In fact, not all natural diamonds will fluoresce under a UV lamp and some simulant stones, like cubic zirconia, will fluoresce, too. 

At Lightbox, our lab-grown diamonds fluoresce an orange hue. Our diamonds always fluoresce the same color because we use the CVD method for growing our diamonds, which gives us incredible clarity.

Does diamond fluorescence impact cost or quality?

There isn’t a clear-cut answer since many jewelers don’t agree on the correlation between diamond fluorescence and cost. One camp feels like fluorescence can affect a diamond’s transparency by leaving the stone with a hazy or milky appearance. On the other side, there are jewelers and gemologists who believe that fluorescence acts as a mask for diamonds with a faint or very light yellow coloring. 

When it comes to durability, fluorescence doesn’t impact the structural integrity of the stone. Diamonds are the hardest natural material on the planet.

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