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Why Care About Diamond Fluorescence?

Round diamond with strong fluorescence

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If this is your first time shopping for diamonds, you’re likely being showered with lots of unfamiliar terms. This can be daunting at first especially if you don’t know which of them matter and which – not so much.

Diamond fluorescence sounds like something quite significant. It’s perfectly normal to not even believe it at first – how can diamonds fluoresce? Is this even possible?

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Diamonds can indeed produce fluorescence, and while this isn’t their most important characteristics it does affect the price of fluorescent stones. For that reason alone, it’s worth knowing what diamond fluorescence is.

How Do Diamonds “Fluoresce”?

si1 round diamond closeup

This diamond has very strong fluorescence. How does it impact? Click on the image and interact with the stone from all angles. Do you notice a difference?

Diamonds that are “pure” are very rare – almost all diamonds you’ll ever see have picked up at least some chemical trace elements during the millions of years it took them to form. Sometimes these don’t matter much, other times they affect the stone’s appearance.

When it comes to fluorescence, this is a common quality among  ~30%-35% of natural diamonds. It occurs when the diamond has trace quantities of nitrogen, aluminum, and/or boron in its chemical makeup. These can vary in intensity, ranging from None to Very Strong.

So, what does this mean for your diamond?

In most situations – absolutely nothing. Fluorescence in diamonds as in all other things is only visible under UV light. The most common sources of UV light are blacklights in night clubs, fluorescent bulbs, and to a much lesser degree – natural sunlight. In other words, in most situations, it won’t matter at all whether your diamond has fluorescence or not.

How Does Fluorescence Impact the Diamond?

This actually depends on a few different factors, as there are many different ways diamonds can fluoresce. There are two main fluorescence categories to judge a diamond’s fluorescence by – intensity and color.

1. The intensity of a diamond’s fluorescence

This is judged on a scale ranging from None to Very Strong fluorescence with the in-between grades being Faint, Medium, and Strong. The difference between these grades is simply how bright the diamond becomes when exposed to strong UV light such as a black light.

Diamonds in the None category produce no fluorescence whatsoever and make up roughly two-thirds of all diamonds. Faint and Medium fluorescence diamonds produce only a mild glow even under a strong black light while Strong and Very Strong fluorescence can produce quite a surprising glow under UV light. Most jewelry vendors avoid selling Very Strong fluorescence diamonds, considering it a flaw.

2. The color of a diamond’s fluorescence

Most fluorescent diamonds have a blueish fluorescence to them. This can actually be good for your diamond because blue fluorescence can minimize any warm yellow tints in your diamond. In other words, a colorless diamond with slight yellowish color can appear whiter if it has some blueish fluorescence.

There are other fluorescent colors, namely yellow, green and red. All of these are much rarer than blue fluorescence but yellow fluorescence is the least rare of the rare ones. This makes it relatively significant as having yellow fluorescence on a stone can result in stronger yellow hues which are generally undesirable in any diamond.

Why Does Diamond Fluorescence Matter?

Note that regardless of intensity of the diamond’s fluorescence, what matters is that it’s typically not visible to the naked eye. Unless you’re under UV light, you won’t even notice that your diamond can fluoresce. But diamond fluorescence has a big impact on the price of your diamonds and sometimes its appearance.

Fluorescent diamonds are often priced lower

You can look at this in two ways – either that these stones are understandably sold at lower prices because they are “bad” or that they make for better deals because they are more affordable for a largely insignificant reason. We tend to see them as great value. Especially when it comes to diamonds in the more expensive D-F and G-J color categories, the fluorescence of any intensity can lower their price by as much as 15%. And since those diamonds are generally pricier,  that can be quite a bargain.

Brian Gavin, one of the most reputable retailers when it comes to diamond cut quality, has curated an entire collection of excellent diamonds with fluorescence in their Blue Collection. These are stones of exceptional quality and cut, with the only difference being that they’re priced lower because of their fluorescence.

See this video which features a diamond with medium fluorescence seen  under different sources of light.

Blue fluorescence can make lower color grades look whiter

We’ve already touched on this above, but let’s take a quick look again. For yellow tinted diamonds lower on the color scale, fluorescence can be a major boon. Compare these two diamonds:

Blue Diamond Fluorescence


The K diamond  has no fluorescence while the M diamond has Strong fluorescence, yet although they’re two grades apart they look identical. The fluorescence helps the M diamond to lose some of its yellow tints. Naturally, as an M diamond is much less expensive than a K diamond (all else being equal) and considering that it’s even less expensive because of the fluorescence, this would be a great bargain.

If we go to the other end of the diamond color scale, diamonds with color grades of K and beyond can actually look better if they have a Faint or Medium blueish fluorescence. However, if you have a faintly yellow colored diamond with faint, medium or especially strong yellow fluorescence, this will further decrease the quality and price of the diamond.

Very Strong diamond fluorescence is noticeable

The reason most vendors don’t sell diamonds with Very Strong fluorescence is that they are too noticeable even under faint sunlight. However, this diamond has strong fluorescence. Can you tell by looking at it?

Strong and Very Strong fluorescence can affect the diamond’s clarity

The diamond can appear slightly hazy if the fluorescence is strong, which affects the stone’s clarity and appearance. In other words, Very Strong fluorescence can decrease the apparent clarity of the diamond which lowers its value.

You may actually like your stone’s fluorescence

Almost every jeweler you talk with will tell you that fluorescence is “bad” and you should buy non-fluorescent stones. Some may really believe that, others might do it to persuade you to buy the more expensive non-fluorescent stones. When it comes to the haziness of Very Strong fluorescent stones and the negative color effect of yellow fluorescent stones – jewelers would be right to warn you about that.

However, few jewelers will tell you something else that’s also always true when it comes to jewelry shopping – it’s all a matter of taste and opinion.

In conclusion – should you buy a fluorescent stone for your engagement ring or not?

It’s a matter of personal taste. As long as you know what you’re buying and you’re happy with it, that’s all that’s important. But if you want our honest advice, here are a few rules of thumb we have about fluorescence:

  1. Avoid non-blue fluorescence as it doesn’t work well with most diamonds’ faint yellow color hues. If you like the look of blue fluorescence, especially on diamond below the I & J color grades, you’re in luck because blue fluorescence can even neutralize their hues.
  2. Avoid Strong and Very Strong fluorescence if you don’t like fluorescence overall – Strong and Very Strong may be noticeable under sunlight.
  3. If you’ve got a Very Strong fluorescent diamond, be prepared for a blue glow under UV light.
  4. Use your knowledge of fluorescence to get a great deal on a diamond.
  5. Check out Brian Gavin’s Blue Collection.

And remember:

The core reason diamond fluorescence is regarded as “bad” is because it’s due to certain chemical traces in the diamond and that’s always a no-no in the jewelry industry – people want their diamonds to be “pure” and “true”.

But if there’s no significant difference in appearance, and you still get to have a stunning diamond at a lower price, we’re all for a little unique inclusion! And one more thing, aren’t inclusions the reason that make colored diamonds so unique and valuable?

In the final analysis, a carefully chosen fluorescent diamond can save you money without having to compromise on quality and size.