Do Diamonds Glow Under Black Light?

Diamonds are beautiful gemstones that attract many people, and this is because of their sparkling and brilliance factor. One thing that people wonder about is the different colors that diamonds produce under different types of lights. 

For example, do diamonds glow under black light? The answer is yes, they do. Some diamonds glow under UV light or black light due to their fluorescence factor. 

Around 35% of the natural diamonds have this effect and usually produce a bluish color. However, diamonds can produce different colors due to their chemical impurities that range from yellow, white, green, red, and orange under a black light. 

In this article, let me look in detail at what makes a diamond glow in the dark and if diamond fluorescence is a good thing or not.


Why Do Diamonds Glow Under Black Light?

Diamonds glow in black light due to their fluorescence. Most natural diamonds have some degree of fluorescence. The chemical impurities present in diamond makes it glow under UV light or black light. 

Around 95% of the natural diamonds appear blue under the black light. Interestingly, diamonds can also appear in yellow, red, green, and orange colors. There are different categories of fluorescence that I will discuss below.

What Does Diamond Fluorescence Mean?

McGill University’s Office of Science defines fluorescence as the inherent capability of certain chemicals to absorb light that is normally not visible (for example UV rays and black light) and immediately emit back that light in a form that is visible to the naked eye. 

As per GIA, around 35% of diamonds have this property. Interestingly, this property is not because of the structure of carbon atoms from which diamonds are made. Rather, it happens because there are impurities in the diamond when it is forming naturally. 

The impurities are different chemicals, and these chemicals have the property of fluorescence in them. For example, the presence of nitrogen (the most common impurity) causes a blue color. This is why the diamonds that are pure and natural tend to appear bluish in dark light. 

The diamonds that have other chemical impurities glow in other different colors when exposed to dark light. 

Similarly, when you place a diamond in a dark place, it glows. Though not all diamonds need to have the same fluorescence, some natural diamonds are fluorescence free as per the GIA report.

Types of Fluorescence

There are different types of diamond fluorescence that make it glow differently under ultraviolet light. 

  • None Fluorescence: These types of diamonds are fluorescence free.
  • Faint Fluorescence: These types of diamonds have a very low fluorescence effect.
  • Medium Fluorescence: These types of diamonds have a certain amount of fluorescence.
  • Strong Fluorescence: These types of diamonds have a strong effect.
  • Very Strong Fluorescence: These have a very intense effect. Many times, a very strong diamond appears somewhat hazy. 

The effect of fluorescence in the strong and very strong types can be seen under UV light. It may appear cloudy or blurry when placed directly under the sunlight.

Related article: Your Guide to Cloudy Diamond Rings

Does Fluorescence Have a Positive or Negative Impact on Diamond Grading?

The quality of diamonds based on their fluorescence is a controversial topic. Traders believe that diamond fluorescence is perceived as a defect that leads to huge discounts. But some people feel this is odd, as diamond fluorescence can also have a positive impact, and it depends on the customer’s perspective. 

Most people have a misconception that fluorescence makes diamonds look hazy or cloudy, which affects their beauty and sparkle. The fact is the beauty and sparkle of a diamond are based on its cut quality and not on its ability to glow in the dark. 

Similarly, some people may hold the misconception that fluorescence decreases the durability of a diamond. The chemical impurities present in the diamond structure only give a fluorescent appearance and do not reduce its strength in any way. 

Can fluorescence have a positive impact?

Firstly, because of some unfavorable market perception, diamonds with a fluorescence effect are sold at a discounted price. So as a smart shopper, you may have the opportunity to save money when purchasing a diamond ring with this attribute.

Another benefit of purchasing a diamond with some fluorescence is that it improves its appearance in the dark. Usually, a diamond having a blue fluorescence looks whiter, while non-fluorescent diamonds usually have a yellowish tint. 

Related articles:
How To Buy The Best Diamond For Money?
What Is the Brilliance of a Diamond?

How Do You Know if a Diamond Is Real or Fake?

Before buying a diamond, you will want to know if it’s real or fake. But how can you tell this? 

Firstly, make sure that when you buy a diamond, it is certified by these top three certifiers: GIA, GCAL, and AGS.

To know if your diamond is real, it is advisable to get it checked by a reputable jeweler.

You can also try the below techniques to find if your diamond is real or fake.

Related article: GCAL vs. GIA – What Is the Best Diamond Certification?

Using a Fog

To know if your diamond is real, you can keep a stone ahead of your mouth. Breath on the diamond to form fog, just as you would on a mirror.

If the diamond stays in the fog for even a few seconds, it is fake. A natural diamond will not stay in a fog as the condensation won’t stick to its surface.

Using a Black Light

To know if your diamond is real, you can test it using a black light. Switch off the lights and place the diamond in the black light. If the diamond appears somewhat with a medium to strong blue color, it is real. 

But if you see other shades of colors like green or gray, it means the diamond is probably not real. But do remember, not all real diamonds appear blue.

Using a Magnifying Glass

You can use a magnifying glass to determine the authenticity of a diamond. Look at the stone through the glass and look for the cuts and imperfections. If you don’t find any, the stone is most likely not real. Most diamonds that are real have imperfections, and these are called inclusions.

Frequently Asked Questions

Do Fake Diamonds Glow Under Black Light?

Almost 30% of all real diamonds with fluorescence will appear blue under black light. Fake diamonds may glow in other colors or will not glow at all.

Why Does My Diamond Look White Under UV Light?

The diamond fluorescence glows when placed under a dark or UV light. This is mainly due to certain minerals in the diamond, and it is a very natural effect.

Around 5% of the diamonds appear yellow, white, orange, or green. Diamonds that have a very strong fluorescence appear icy-blue in UV light.

Wrapping Up

Fluorescence is found in most natural diamonds, and it does not cause the diamond to be weaker or less valuable in any way. However, it is a misconception in the trading community as well as in buyers’ minds that makes it so that these diamonds tend to be less expensive.

I hope you have a better understanding of why diamonds glow in black light and about people’s misconceptions about fluorescence. It is advisable to inspect a diamond’s quality before making a purchase and ensure it is certified.

Related articles:
What Are Loose Diamonds?
Diamond Looks Blue In Sunlight: The Mysterious Blue Glow


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