Welcome to Ask Shop LC, a series created for you, the shopper! Our team is answering questions that real Shop LC customers are asking, ranging from the common to the obscure. This week, we are addressing a great customer question about diamond fluorescence.

If two diamonds are exactly alike, but one glows under UV light, and the other doesn’t, does the glowing diamond have a lower value?

Anetta asks, “If two diamonds are exactly alike, but one glows under UV light, and the other doesn’t, does the glowing diamond have a lower value? I have been trying for years to get an answer to this, but everywhere I call or email, I can never get a straight answer. Can you please clear up my confusion?”*

2 ctw Diamond I I1 Cluster Cocktail Ring in 10K Yellow Gold

Does fluorescence affect the value of this diamond ring?

What is fluorescence in diamonds?

Many gemstones, including diamonds, emit visible light when exposed to ultraviolet (UV) radiation. We call this visible light fluorescence. When buying stones, it is sometimes a factor to consider. After all, UV radiation is everywhere – sunlight carries UV rays, and fluorescent lights are in many buildings. It’s something that might affect how you enjoy your gemstone jewelry.

Experts estimate that up to 35 percent of diamonds will fluoresce. In diamonds, blue is the most commonly seen color, but other hues include orange, yellow, and white.

Diamond fluorescence chart.

Examples of blue fluorescence in diamonds. For information purposes only.

Does fluorescence affect the value of diamonds?

This is a trickier question, as there are a few perspectives on how fluorescence affects a diamond’s price.

Many diamonds are graded by the Four C’s, which are Color, Clarity, Cut, and Carat Weight. While the ability to fluoresce can be an identifying characteristic for a diamond, it is not a traditional grading factor that determines value.

Professional diamond graders sometimes note fluorescent ability in their reports. For instance, the Gemological Institute of America (GIA) notes Medium, Strong, and Very Strong fluorescence in GIA Diamond Grading Reports.

Some dealers feel that fluorescence affects the perceived color of diamonds. But, opinions vary widely on the truth behind this. Mostly, they think fluorescence improves the appearance of diamonds in the middle Color range. Other times, dealers say it creates a “milky” or “oily” look in stones with a higher Color grade.

The GIA studied this bias, noting in their research, “For the average observer, meant to represent the jewelry buying public, no systematic effects of blue fluorescence on the face-up appearance of the groups of diamonds were detected. Even experienced observers did not consistently agree on the effects of fluorescence from one stone to the next.”

So, what does this mean for diamond buyers? Ultimately, beauty is in the eye of the beholder, and diamond fluorescence does not affect diamond value. However, many dealers may discount fluorescing diamonds, while others might use it as a selling point!

How do you feel about fluorescent diamonds? Would you buy one? Tell us in the comments!

*Shop LC may edit customer comments for grammar and clarity.