If you’ve landed here wondering:
- “Is faint fluorescence OK in a diamond?”
- “Why does my diamond look blue in sunlight?”
- “Can sun damage diamonds?”
- “What causes fluorescence in diamonds in sunlight?”
- “How does fluorescence in sunlight affect price in diamonds?”
- “How can I filter to shop only for diamonds without fluorescence?”
- “How can I filter to shop for diamonds of strong or weak or ZERO fluorescence?”
- “Should I look for diamond which has 1) slightly yellow color and 2) fluorescence, to “cancel colors out,” or “make it look colorless” and somehow get an awesome looking diamond for not much money? HINT: No, don’t fall for this “Internet advice”, and I’ll tell you why.
Then you’ll get quick answers. You’ll also get full answers. Diamond fluorescence sunlight facts get rather interesting, even beyond the fast answers.
So be sure to share this page with yourself or your partner in text, email, or social media, so you can find it again quickly.
Quick Links to Contents on This Page
Quick answers:
“Is faint fluorescence OK in a diamond?” Yes, it’s no big deal. It can even make a diamond’s color look better. Find out more below.
“Why does my diamond look blue in sunlight?” Because it has strong fluorescence. Find out more below.
“Can sun damage diamonds?” Diamonds are the hardest, most stable natural substance and are never damaged by sunlight. Find out more below.
“What causes fluorescence in diamonds in sunlight?” It’s a natural occurrence when some electrons of certain mineral atoms briefly absorb energy, then allow it to escape slightly more slowly than it absorbs it. Find out more below.
“How does fluorescence in sunlight affect price in diamonds?” It depends on the color of the diamond and the strength of the fluorescence. In D, E, and F colors, the prices goes down with fluorescence. In I, J, K, L, and M colors, the diamond’s price goes up with fluorescence. In G and H colors, fluorescence doesn’t affect the price of the diamond. Find out more below.
“How can I filter to shop only for diamonds without fluorescence?” Go to James Allen. Choose “Start with a diamond.” Then click on “Advanced Options.” Then click on “Fluorescence” and choose the level of fluorescence you want to see.
“How can I filter to shop for diamonds of strong or weak or ZERO fluorescence?” Go to James Allen. Choose “Start with a diamond.” Then click on “Advanced Options.” Then click on “Fluorescence” and choose the level of fluorescence you want to see.
“Should I look for diamond which has 1) slightly yellow color and 2) fluorescence, to “cancel colors out,” or “make it look colorless” and somehow get an awesome looking diamond for not much money? Some blogs, even some respectable ones, give this advice. It’s terrible advice. You’d have to have just the right sunlight. And just the right shade of yellow. And just the right amount of fluorescence. And even then, the effect would be only fleeting. Hard to pull off. Don’t fall for this idea. It’s just a thing to get clicks and attention.
How to screen for fluorescence when shopping for diamonds
Any retailer worth buying a diamond from will have a filter by which you can screen for the level of fluorescence acceptable to you.
This includes Blue Nile, James Allen, and others.
However, the filter for fluorescence is not always easily visible. Check for a category of filters called “Advanced Options” or “More Filters”, etc. (See the images below.)
To save you time, I’ve created a link to James Allen which automatically sets your fluorescence filter to “None.” (Be sure to verify it, however, by using the steps in the image below. Things can happen on the Internet. 😉 )
To automatically set your James Allen fluorescent filter to “None,” do this:
Just click here. It will open a diamond search at James Allen with the fluorescence set to “None.” 😉
You can adjust it to “Faint”, or any other selection that you prefer. (But I strongly recommend “None” or “Faint” fluorescence.
How to set the fluorescence filter at Blue Nile:
- Click “More Filters” on the diamond search page.
- Select the amount of fluorescence you are ok with. (I strongly recommend “None” or “Faint”.)
Is faint fluorescence OK in a diamond?
Yes, it’s no big deal. Here’s why.
Look at the graphic at the top of this post to see what “faint” fluorescence means. First, notice that those photos weren’t taken in sunlight. They were taken under a UV or “black” light. Even in darkness, with a black light, the fluorescence is hardly noticeable at the faint end of the scale. So, it’s not a big deal.
Why does my diamond look blue in sunlight?
One or both of two reasons:
- Because it has strong fluorescence. (Not the end of the world, although very few people would prefer it. Most of the time, your diamond is not viewed in direct sunlight.)
- And/Or because the sky is reflected in the diamond. (So don’t worry.)
But the difference between the two reasons why a diamond looks blue in sunlight is easy to tell. Most people will be able to know right away if it is the sky reflected in the diamond.
You can turn it this way and that, to make sure it’s not just the sky being reflected.
You can also hold it in direct sunlight but not under the sky.
In slanting sunlight, hold it under a carport or deck, for example — using a sunbeam. This will rule out the possibility that the sky is being reflected in it.
Contrary to popular belief on some diamond websites, strong fluorescence really is visible in direct sunlight.
Note that I said strong fluorescence.
Look again at the graphic at the top of this post. The closer you get to the strong end of the scale, the more visible fluorescence will be, even in direct sunlight.
Can sun damage diamonds?
No. Sun can’t damage diamonds at all. Things associated with the sun could conceivably soil your diamonds. For example, sunscreen. Or dirt. Or river water. Or seawater. Or salt deposits from sweat or seawater.
But these can all be easily cleaned off.
Anyone wondering if the sun can damage a diamond can put that worry to rest.
What causes fluorescence in diamonds, in sunlight?
I get it. Some people here aren’t worried, just curious. What causes that phenomena? What causes fluorescence in diamonds in sunlight?
What causes fluorescence in diamonds is the same thing that causes luminescence in anything that glows in the dark — the dial of your watch, maybe.
- The substance absorbs energy rapidly.
- The substance emits the energy it has absorbed a little less rapidly.
Luminescent things absorb a lot of energy, and release the energy slowly. If you take away the source of the energy (sunlight), the item will continue to glow for hours. (Diamonds aren’t luminescent, so they, won’t glow for hours, thankfully. However, read on.)
Fluorescent things absorb a minimum of energy, and release the energy quickly. If you take away the source of the energy (sunlight) the object (in this case a fluorescent diamond) stops glowing immediately.
How does fluorescence in sunlight affect price in diamonds?
It depends on the color of the diamond and the strength of the fluorescence.
In general, the more fluorescence there is, the more the price goes down.
“The reason fluorescence may increase the price of a diamond is if it counteracts the natural yellow color enough to make the diamond look colorless.”
You’ll see that explanation on more than one diamond website. Do not trust it.
My advice is: Tend to avoid fluorescence if you can. Never really go for the idea that fluorescence in a yellowish diamond can make the diamond better / more valuable. Here’s why:
- In non-UV (non-sunlight) light, the diamond will still look yellowish.
- In bright sunlight, if the fluorescence is strong, the diamond may look greenish.
- You have to have the just the right amount of sunlight for the diamond to “look colorless.”
It’s ok to accept some low amount of fluorescence if you have an I, J, K, L, or M color grade of diamond. It won’t hurt anything. And in the right amount of sunlight the diamond CAN be made to appear colorless. But it’s more of a parlor trick. Only, not in a parlor. Srsly, you can’t reliably “make your fluorescent diamond look colorless in sunlight.”
But definitely don’t look for fluorescence to try to cancel out the color in a diamond. It’s just not worth all the finessing and special circumstances that it will require for the effect to happen. (And 99% of your life with the diamond won’t fall into those special circumstances of light.)
However, having said all that, here’s the lowdown on how fluorescence in sunlight affects the price of diamonds, in general:
In D, E, and F colors:
- The diamond’s price goes down with increasing fluorescence.
In I, J, K, L, and M colors
- The diamond’s price goes up with the supposedly right amount of fluorescence. (That means, enough blue fluorescence to cancel out the right amount of yellow in the diamond.) The strength of the sunlight is never even mentioned, even though that will change with every passing cloud.
- The diamond’s price goes down with too much fluorescence.
In G and H colors (right in the middle of the color scale):
- The diamond’s price isn’t all that affected by the fluorescence, unless it gets to be too much. In the case of a strongly fluorescent diamond, that can lower the price.
How to check whether your diamond is fluorescent
- Check your diamond certificate for whether its fluorescent. Many diamond certificates, for example those from the GIA, will tell you whether and how much a diamond is fluorescent. (It will specify if Medium, Strong, or Very Strong. It won’t specify if it’s None or Faint.)
- Hold a black light (UV light) three or four feet away from your diamond in a darkened room. Hold it to the side of your diamond. Look straight down into the diamond. Check your against the graphic at the top of this post.
Do fake diamonds glow under UV light?
It depends on the “fake diamond” you put under the UV light.
But the best answer is “You can’t tell if a gemstone is a diamond or not by using UV light.”
Some diamonds glow under UV light. Some don’t. It depends on specific atomic properties of the diamond you’re looking at. Not every diamond fluoresces (glows under UV light).
Just like genuine diamonds, some “fake diamonds” glow under UV light, and some don’t.
So the UV light test is not a good test.
Is strong blue fluorescence in a diamond bad?
Since “bad” is a subjective judgment, it depends on what you think.
In my opinion, it’s bad. Most people probably think it’s bad.
On the other hand, it’s easy to imagine that some people love that a diamond glows a gentle magical blue when exposed to sunlight. It’s very interesting, what’s happening. That diamond which fluoresces is absorbing energy from the sun, and then emitting it in a blue color.
But yeah, in general, most people prefer diamonds for their colorlessness, for their sparkle and brilliance. Not for any fluorescence.
People generally agree that strong blue fluorescence in a diamond is bad. (That doesn’t mean you have to conform to their opinion. But don’t be just contrary. If you love the blue, go with it. If you don’t, look for a diamond which isn’t fluorescent.)
Why doesn’t my diamond certificate have a grade for fluorescence?
As you can see from the graphic at the top of this post, the GIA has descriptors (descriptors, not grades, notice) of a diamond’s fluorescence as
- None — no mention on diamond grading report/certificate
- Faint — no mention on diamond grading report/certificate
- Medium — noted on diamond grading report/certificate
- Strong — noted on diamond grading report/certificate
- Very Strong — noted on diamond grading report/certificate
If a diamond’s fluorescence in sunlight is Medium, Strong or Very Strong, the color of the fluorescence is noted on the grading report.
If it’s faint or none, then no mention is generally made.
Is all diamond fluorescence blue? Or can diamonds glow different colors?
Yeah, just when you thought it was safe to make a decision … then you find out this truth: Not all diamond fluorescence in sunlight is blue!
- They can glow orange yellow.
- They can glow yellow, orange, or red.
- They can glow white.
- They can glow green.
- Although, literally 95% of diamond fluorescence in sunlight (or any UV light) is blue.
But 5% as other colors is not nothing. It’s another reason I recommend that people avoid strong fluorescence in diamonds.
Unless, that is, you really do love the idea of glowing diamonds, which some people do, and I get that.
Unfortunately, the GIA and other grading labs don’t specify the color of the fluorescence of a diamond.
Does diamond fluorescence make a diamond look cloudy or hazy?
Diamonds with fluorescence in sunlight will look hazier, the more fluorescent they are. They seem to have a kind of oily sheen, when they are very strongly fluorescent and in the presence of sunlight or UV light.
(When not in the presence of sunlight, the fluorescence doesn’t show up at all.)
- Strong/Very Strong Fluorescent diamonds often are cloudy / hazy
- Medium Fluorescent diamonds are not often cloudy / hazy
- Faintly Fluorescent diamonds virtually never appear cloudy / hazy
If your diamond looks cloudy or hazy, but it’s not in sunlight or UV light, then the cloudiness or haziness is from something else.
Do all diamonds have fluorescence? Or only some?
Only about 30% of diamonds have fluorescence of any kind.
Is faint fluorescence in a diamond OK?
Yes, faint fluorescence in a diamond is almost invisible, even under ideal conditions to create and observe fluorescence in diamonds.
In sunlight, faint fluorescence is likely to be completely invisible. In a darkened room with the aid of a black light (UV light), you can still hardly see faint fluorescence.
Does fluorescence in diamonds affect some shapes more than others?
No. If a diamond cutter cuts a fluorescent diamond into any shape, it will be equally fluorescent. Hoever, a quite brilliant diamond can overwhelm faint or medium fluorescence.
No amount of brilliance can overwhelm strong or very strong fluorescence.
Is it bad that my diamond doesn’t glow under black light?
Not at all. There’s a myth that all diamonds glow under black light. This myth is entirely wrong. Around 70% of diamonds do not glow under black light (UV light) or sunlight.
It’s actually a good thing, in my view, that your diamond does not glow under black light.
The reason is: a diamond’s fluorescence (glowing) under black light (UV light) or sunlight tends to distract from why we tend to love diamonds — its brilliance and colorlessness and fire.
Can fluorescence in diamonds be either good or bad?
Theoretically, yes.
It’s said on many diamond blogs that diamond fluorescence in sunlight can be “good” by canceling out the yellowish tinge of diamonds in I, J, K, L, and M colors of diamonds.
That’s also said by diamond salespeople who would like to get you to pull the trigger on a diamond you’re looking at which happens to be fluorescent.
But in practical everyday life, as I mentioned above, you have to find the right conditions to cancel out the yellowish tinge.
- In indoor light, your diamond would still look yellowish. Fluorescence happens only in sunlight.
- In too much sunlight, your diamond could look blue.
- Only in just the right amount of sunlight, your diamond would look perfectly colorless.
So, unless you like fluorescence because it’s awesome to you that a diamond can glow in UV light, it’s best to avoid anything other than faint fluorescence (or, my recommendation: no fluorescence.)
That’s also easy to do, since only around 30% of diamonds show any fluorescence at all.
How can I filter for diamonds that have none or faint fluorescence?
At James Allen, you can can screen for diamonds with your desired level of fluorescence in sunlight with two simple clicks:
As of the time this was published, I haven’t found a way to automatically filter for fluorescence at other Internet retailers of diamonds. Didn’t find the filter at Blue Nile, or Brilliance.com, or Brian Gavin. So I’m 99% sure the fluorescence filter doesn’t yet exist at those retailers. Let me know if you see it.
