What is Diamond Fluorescence?

If you have been looking to buy a diamond, you may have come across the term “diamond fluorescence”. But what does this term even mean? Should you care about it?

Fluorescence is when a diamond gives off visible light when a high energy light is shone on it. Not all diamonds have this property. Some diamonds will have strong fluorescence. Some diamonds will have no fluorescence.

Next, we’ll get into the science of fluorescence. We will also go into how you can tell if a diamond is fluorescent. Is diamond fluorescence good or bad? How does it impact the price of a diamond?

What is fluorescence?

First, let’s start with the science of fluorescence. According to McGill University, fluorescence is a property of some materials. It is when a material gives off visible light after absorbing higher energy light. (https://www.mcgill.ca/oss/article/you-asked/what-fluorescence). Higher energy light has more energy than visible light. UV rays are the most common type of higher energy light.

Under UV light, a soft glow is given off by a diamond if it has fluorescence. This is the property of diamond fluorescence.

Many materials in our everyday lives use fluorescence. Some highlighters and certain kinds of light bulbs use the property of fluorescence.

If you want to learn more, check out this YouTube video on the science behind this:

How can you tell if a diamond is fluorescent?

Most diamonds do not have fluorescence. According to the GIA, only 25%-35% of diamonds have fluorescence.  (https://4cs.gia.edu/en-us/blog/fact-checking-diamond-fluorescence-myths-dispelled/).

So how can you tell if your diamond is fluorescent? Under normal indoor lights like LEDs, you won’t be able to tell. Only under higher energy light like UV would you be able to see if your diamond fluoresces. Bright sunlight, a tanning bed, and black lights all give off UV radiation. This would cause a diamond to fluoresce.

If a diamond has fluorescence, it likely emits a bluish color. However, some diamonds give off a different color of light. They can give off yellow, orange, red, or even green light.

Is diamond fluorescence good or bad?

The jury is still out on this question. The pros and cons of diamond fluorescence is a hotly debated topic.

Diamond fluorescence generally doesn’t impact a diamond too much. It doesn’t affect the 4C’s of diamonds. The 4C’s are color, cut, clarity, and carat weight. The sparkle of a diamond is based on its cut. This means that fluorescence does not impact the sparkle of a diamond.

In some cases, strong fluorescence may cause a diamond to appear milky. This is a bit more common for more colorless stones (color grades D to F). Some say this cloudiness reduces the clarity of the diamond. This can make it look dull.

Sometimes, diamond fluorescence is viewed as positive. Diamonds with lower color grades are more yellowish. If they are fluorescent, the blue fluorescence can make them seem more colorless. This can give the appearance of a higher color grade diamond.

In a GIA study, consumers observed diamonds with a range of fluorescence. They found that consumers thought diamonds with strong fluorescence had better color. (https://www.77diamonds.com/diamond-fluorescence.html).

How does diamond fluorescence impact the price of a diamond?

There is not a clear relationship between diamond fluorescence and diamond cost.

For centuries, European merchants sought after fluorescent diamonds. The “blue-white” color of these diamonds was desirable. They were highly regarded for their icy appearance and beauty. Only recently have fluorescent diamonds been seen as less desirable. This perception means you can sometimes find them at reduced prices.

On average, fluorescent diamonds are about 10-15% less expensive. However, the variation in price depends on a few factors.

For strongly fluorescent diamonds of higher grades, their price is often lower. They are about 10%-30% less than high-grade diamonds of little to no fluorescence.

For low-grade diamonds, strongly fluorescent diamonds may be more expensive. This is because their bluish glow can make them look like a higher-grade diamond.

Putting it all together.

We learned that diamond fluorescence is a property of diamonds. It causes certain diamonds to give off visible light under UV rays.

However, most of the time this is not noticeable. Diamond fluorescence is only seen under high energy light sources. This means you won’t notice it in most everyday lighting conditions. A diamond that has weak fluorescence may not be that noticeable.

Some people claim that diamond fluorescence spoils the clarity of diamonds. Others find that it enhances the beauty of certain diamonds.

When it comes to diamond fluorescence, beauty is in the eye of the beholder.

Carl A. Jones, GIA GG

Carl A. Jones is a GIA Graduate Gemologist with over 20 years of experience in the diamond industry. He is an independent jewelry appraiser. He specializes in determining the value of diamonds and advising consumers on how to buy quality diamond jewelry.

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