Jewelry Blog

Complete Guide To Diamond Fluorescence

Diamond Fluorescence Before and After

Cut, carat, clarity, and color are the essential grading factors of every diamond. But, many additional terms further describe a diamond and offer insight into its characteristics. One such term is diamond fluorescence. 

This article will shed light on diamond fluorescence and explain what this term represents. Moreover, we’ll discuss whether a diamond should have fluorescence and offer tips on buying fluorescent diamonds. 

What Is Diamond Fluorescence?

Diamond Fluorescence Before and After

Diamond fluorescence is the glow these stones can emit when exposed to ultraviolet (UV) rays. This glow lasts as long as the stone is exposed to the rays. When the source of light is removed, the fluorescence disappears. 

This phenomenon is caused by certain minerals and elements within the diamond, and it’s completely natural. When the UV light hits the diamonds, the electrons of the element get kicked to a higher energy state. After just a few nanoseconds, the electrons return to their normal state and release photons in the process. Our eyes recognize these photons and detect them as fluorescence—the more minerals in a diamond, the stronger the glow, and vice versa. 

Not all diamonds are fluorescent, although this is a common characteristic. According to the Gemological Institute of America (GIA), around 25% to 35% of all diamonds are fluorescent to some degree. 

When exposed to UV light, the most common color that fluorescent diamonds exhibit is blue. In rare instances, the color could be yellow, green, or white. 

Understanding the Diamond Fluorescence Scale 

Diamond Fluorescence Scale

Every GIA diamond grading report contains a part dedicated to fluorescence. The official scale has five degrees: none, faint, medium, strong, very strong. 


If you see “none” in a diamond grading report, it means it doesn’t have fluorescence. 


The diamond is fluorescent, but not to a significant degree. Most observers won’t be able to notice faint fluorescence. In some cases, faint fluorescence can complement the diamond’s clarity and make it seem colorless even when it isn’t. 


Per GIA, the grading reports of diamonds with a medium fluorescence should also contain information regarding the color. Medium fluorescence usually doesn’t affect the diamond’s appearance. 


The color of strong fluorescence needs to be written down on every grading report. Strong fluorescence can sometimes make the diamond seem oily or hazy, depending on its color grade. 

Very Strong 

This is the highest possible degree of fluorescence. Like strong fluorescence, very strong can affect the diamond’s appearance and make it look oily. It doesn’t happen with every diamond with strong fluorescence; the effect typically depends on the stone’s color grade. 

Per GIA, the fluorescence color is only noted if it’s medium, strong, or very strong. Identifying a diamond’s fluorescence is done by comparing it to a master stone with established fluorescence in labs under special conditions. 

Is Diamond Fluorescence Good or Bad?

Diamond Engagement Ring in Yellow Gold Setting

Generally, diamond fluorescence is neither good nor bad. It’s essential to clarify one thing before explaining why some people may consider fluorescence an advantage and others a flaw. Fluorescence doesn’t impact the diamond’s internal structure or texture. Diamonds that have fluorescence aren’t any different in form than those that don’t. 

Moreover, fluorescence isn’t harmful to the diamond and can’t damage it. It’s simply a combination of different minerals that interact with UV light. 

Although fluorescence doesn’t actually change the diamond, it can affect how an observer perceives it in some cases. To better understand why and how this happens, we need to discuss one of the four Cs: color. 

Diamond Color

Diamond Color Grading Infograph

Color, or the lack of it, is one of the essential features of every diamond. Diamonds that look like a drop of water are labeled colorless, and they are extremely rare and valuable. On the other end of the scale, we have diamonds with a yellow tint that lowers their value. 

The GIA color scale is divided into these categories: 

  • Colorless (D, E, F) 
  • Near colorless (G, H, I, J) 
  • Faint (K, L, M) 
  • Very light (N, O, P, Q, R) 
  • Light (S, T, U, V, W, X, Y, Z) 

How Is Fluorescence Related to Color? 

As mentioned, diamond fluorescence isn’t considered an advantage or a flaw. But, many people believe that it can seemingly increase or decrease a diamond’s spark. 

For example, faint diamonds contain a slight yellow tint, which affects their value. If the diamond has strong fluorescence, the blue light will seemingly decrease the yellow tint, making the stone look brighter and more transparent. This happens because blue and yellow are complementary colors. 

In contrast, the appearance of diamonds with a D, E, F, G, or H color grade is often “jeopardized” by fluorescence. Strong blue light can make these diamonds hazy and oily, typically making them less attractive, even though they are colorless or near-colorless. 

As you can see, it’s impossible to say whether fluorescence is good or bad. Generally, it depends on whom you ask. Some say fluorescence makes a diamond more eye-appealing, while others say it jeopardizes the stone’s beauty. In the end, it all comes down to personal preferences. 

How to Buy and Use a Diamond Fluorescence Purple Light 

Customer using a Loupe on a Diamond Engagement Ring in Showroom

Diamond fluorescence is best noticed under fluorescent lamps. You can purchase these purple fluorescent lights on Amazon, eBay, or some local stores. 

However, it’s not advisable to perform DIY tests to determine diamond fluorescence. Firstly, diamond fluorescence is a complex term, and only experts can determine the exact fluorescence degree. Establishing a diamond’s fluorescence without a master diamond (a diamond with an established fluorescence degree) is impossible, especially if you don’t have the necessary skills and knowledge.  

Many people believe that only “real” diamonds exhibit fluorescence, so they buy a purple light to test theirs. But not all diamonds fluoresce, which makes this test completely unreliable. Two real diamonds can have the same grading factors and still be different in fluorescence. 

Likewise, some lab-grown diamonds can also fluoresce. They display a different fluorescence degree and pattern, but if you’re not an expert, you won’t be able to identify it. Moreover, cubic zirconia could also exhibit fluorescence, so performing tests with purple light won’t prove anything. 

If you want to examine your diamond’s fluorescence, it’s best to go to a reliable seller. They will be able to determine whether the diamond is real and tell you more about its fluorescence using specialized equipment. 

Does Diamond Fluorescence Affect Value?

Diamond engagement ring being worn on hand

This is another complex question that doesn’t have a simple yes or no answer. Jewelry professionals often disagree on this subject, but we can discuss some tendencies regarding if and how fluorescence affects a diamond’s value. 

Colorless diamonds with a strong and very strong fluorescence generally tend to be devalued compared to those that don’t display fluorescence. In contrast, diamonds with a yellow tint with faint fluorescence will be worth more than their counterparts with no fluorescence. 

Since fluorescence doesn’t impact every diamond equally, it’s hard to determine its exact effect. In some cases, fluorescence won’t change the diamond’s value, while in others, it will slightly increase or decrease it. 

Most often, you’ll see diamonds with a strong and very strong fluorescence on sale. Although this could lead you to assume strong fluorescence is bad, it doesn’t have to be that way. You can take advantage of the bargain and still get a beautiful stone with exquisite sparkle. 

Does Diamond Fluorescence Occur in Sunlight? 

Diamond Solitaire Engagement Ring with Yellow Gold and Accenting Diamonds

Diamonds will emit fluorescence when exposed to UV light. While special fluorescent lamps are used to determine the exact fluorescence degree, sunlight can also cause the diamonds to fluoresce. 

If the sun is bright, you may notice your diamond fluorescing. Some diamonds may seem more transparent when exposed to sunlight, while others could look milky and hazy. Keep in mind this doesn’t mean the diamond is damaged. Whenever you remove the diamond from the UV light source, it will stop fluorescing. 

Generally, the higher the fluorescence degree, the easier it is to notice it in sunlight. Of course, many diamonds don’t have this characteristic, so sunlight won’t affect them in any way. 

The effect of sunlight on a diamond depends on the fluorescence degree and the diamond’s color grade. 

10 Tips for Buying a Diamond With Fluorescence 

As you can see, buying a diamond is a complex process that you shouldn’t rush. We’ve compiled a list of 10 tips for buying a diamond with fluorescence to help you with your purchase: 

1. Find a Trusted Seller 

Benjamin Khordipour in Estate Diamond Jewelry Showroom

Finding a reliable seller should be the first and most crucial step towards buying the perfect diamond. The right seller should have years of experience working with different diamonds. We recommend exploring several sellers online and checking reviews from past customers. If you have friends or acquaintances who have recently purchased a diamond you like, ask them for recommendations. 

The right seller should be experienced, knowledgeable, and ready to answer all your questions. Once you’ve found a good seller, feel free to ask for more information about the diamonds you find interesting. Tell them you’re interested in purchasing a diamond with fluorescence and ask for their advice. 

2. Check the Certification 

UGL Diamond Certification on Table

Every genuine diamond should possess the necessary documentation and certification that proves its origin, quality, and characteristics. As mentioned, the diamond grading reports contain information regarding fluorescence. Depending on the degree, the fluorescence color will also be marked. 

Even though fluorescence can be important, don’t forget to examine the grading factors. The four Cs (cut, color, clarity, and carat) are essential in determining whether a diamond is a right fit for you. It’s best to find several diamonds with the same or similar grading factors but different fluorescence. That way, you’ll be able to choose the one you like best. 

You may not even notice the difference between a fluorescent and non-fluorescent diamond. Or, you may end up buying a non-fluorescent diamond, although you wanted fluorescence at first. 

3. Ask to View the Diamond Under Different Lighting 

Examining an engagement ring with a loupe

Once you’ve found a diamond you like, it’s completely reasonable to ask the seller to view it under different lighting conditions. The diamond may look great under normal light but exhibit a seemingly different structure when exposed to UV light. You can also check with the seller to see if it’s possible to view the diamond in the sunlight. 

Most sellers will be happy to help you because they understand that buying a diamond is special and doesn’t happen every day. 

Once again, remember that while fluorescence is common, not every diamond exhibits it. This doesn’t imply the diamond is fake; it simply means there aren’t any minerals or elements within it that cause fluorescence. 

4. Compare the Diamonds 

Customer looking at diamond halo engagement ring in showroom

Ask the seller to show you other diamonds with similar characteristics to the one you like and a different fluorescence degree. You can view all of them under a UV light to determine the similarities and differences. This could help you identify what fluorescence degree you’re looking for in a diamond. 

5. Take Advantage of Fluorescence 

Diamond Fluorescence Scale

Diamonds with a lower color grade and a stronger blue fluorescence tend to look clearer. The blue reduces the yellow tint and creates an illusion that a diamond is whiter than it really is. If you’re on a budget, this phenomenon works in your favor. 

You can purchase a more affordable diamond without “settling” for a yellowish stone. You can get an exquisite, brilliant diamond without spending a fortune. 

6. Trust Your Instincts 

Customer in Estate Diamond Jewelry looking at Vintage Engagement Rings and Wedding Bands

The industry standards and jewelers’ opinions and attitudes are important. However, don’t forget you’re buying the diamond for yourself or the person you love. It’s vital to purchase a diamond that matches your preferences. 

Beauty is in the eye of the beholder, and we can’t agree more. Every diamond is beautiful in its own way, and the wide range of options enables everyone to find the one that matches their criteria. 

Some people don’t like fluorescent diamonds and are willing to compromise and get a stone with a lower quality to avoid this phenomenon. Others prefer strong or very strong fluorescence and enjoy its effect. It’s also okay to choose the golden middle and get a faint or medium fluorescent diamond with good grading factors. 

Whatever your choice is, don’t let others convince you it’s wrong. Consult your jeweler, but don’t let them decide for you. After all, you’re the one buying the diamond, and only you know how you feel about it. You don’t want to spend thousands of dollars only to realize you don’t actually like the diamond. 

7. Take Your Time 

Diamond Engagement Ring Customer from Estate Diamond Jewelry Showroom

Purchasing a diamond should never be rushed. Don’t let anyone talk you into buying one if you’re not 100% sure you made the right choice. Instead, take your time, carefully review your options, and study the documentation. After you’ve done this, consult your jeweler, and decide on the best option. 

8. Check the Seller’s Return Policy 

Returning ring in ring box

Imagine this: You’ve looked for a perfect diamond for months, and you’ve finally found it. The diamond looks amazing in the store, so you decide to purchase it. However, after a few days, you notice it simply doesn’t suit you. Now you’re stuck with a diamond you don’t enjoy, and you’ve spent thousands of dollars. 

It’s crucial to check the seller’s return policy to avoid this scenario. It’s especially important if you’re buying the diamond for someone else or you’re purchasing it online. 

At Estate Diamond Jewelry, we offer an excellent 14-day return policy. This policy affects all our customers unless stated otherwise on your invoice or if it’s a custom order. Within 14 days, you can return the jewelry you purchased, no questions asked. If you want to return your ring, reach out to us, we’ll contact you, and you’ll receive a full refund within two to five business days. 

9. Don’t Be Afraid of Strong Fluorescence 

Diamond Engagement Ring in Box Held Box Customer

Diamonds with a strong fluorescence are typically labeled “milky” or “oily.” But this isn’t a universal rule. The fluorescence may not affect the diamond’s color or appearance at all. 

When you see a diamond with strong fluorescence, don’t disregard it just yet. Instead, take a better look at it. Who knows, you may be a fan of strong fluorescence without even realizing it. 

10. Ask for Pictures and Videos 

Denver Aquamarine Ring on fingers

Most people prefer buying diamonds in-store. However, that’s not the only way: You can always purchase a diamond online. Shopping online is incredibly convenient if you’ve found a diamond you like, but the store is too far away, or you don’t have time to go there. 

While asking the jeweler for grading reports and certifications is easy, estimating the diamond’s fluorescence online can be quite difficult. For this reason, you should ask the jeweler for additional pictures and videos. Photos of a diamond under normal light, sunlight, and UV light can help you determine whether you like its fluorescence. 

As you know, a diamond may look perfect while showcased due to special lighting. However, reputable jewelers will always provide videos of how a diamond looks on a finger. These methods enable you to view your diamond from every angle and make your online purchase a breeze. 

Talk to Our Diamond Experts

Afshin Estate Diamond Jewelry in Jewelry Showroom

Our diamond experts are here to answer every question you may have about fluorescence or any other feature of the beautiful stones. We’ve been in the industry for more than 40 years, and we’re more than happy to assist you in your purchase. 

Schedule an appointment here if you want to visit our New York Showroom. You can also reach us at 212-265-3868 or 866-853-9357. 


About Benjamin Khordipour

Benjamin Khordipour is one of the jewelry researchers and gemologists at Estate Diamond Jewelry. He received his official gemological degrees from both the GIA and GUBELIN. He also regularly contributes to Business Insider, Forbes, Rapaport, CNBC, and Brides Magazine. Benjamin was born in New York and joined Estate Diamond Jewelry in 2014. He is passionate about vintage jewelry and diamonds. This blog was built on his strong belief that jewelers have a responsibility to properly educate their customers. In 2019, Benjamin co-authored the book The Engagement Ring Guide for Men. His favorite vintage jewelry era is the Art Deco Era and his favorite type of stone is the Kashmir Sapphire. He also collects rare antique pins.