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Diamond Fluorescence — What It Is and Why it Matters

If you’re shopping for a diamond you’ve most likely heard that some fluoresce i.e glow blue under UV light and when you go outside. But what are fluorescent diamonds, and do you want one?

If you’re searching for this you already know that these strange little lumps of polished carbon emit a thing called fluorescence. You probably also know that the presence of fluorescence is the subject of debate online. But what is diamond fluorescence? Is it good or bad? Should you buy a diamond because of or in spite of it? Is a lack of information about fluorescence in diamonds the reason for all those glowing blue diamonds on Reddit? What percent of diamonds are afflicted with this strange and superhuman condition that’s more at home in a Marvel movie than an engagement ring? What does fluorescence in a diamond mean? Let’s dig in.

An image of five diamonds displaying varying levels of diamond fluorescence.


Fluorescence is a glow some objects and creatures emit under visible light. While it may sound unusual to us, there are many creatures in nature that emit fluorescence. From a flying squirrel that emits a pinkish glow under ultraviolet light to the ever likable puffin, whose beak glows blue under UV light to the chameleon whose skin is so thin that their bones glow in the dark. Similar to these cuddly creatures, diamonds generally emit a bluish light when they fluoresce, although some can emit yellow or orange light as well. No light = no fluorescence. While we’re not sure why some diamonds fluoresce and not others, we’re confident that the ability to glow can’t always be a bad thing.

A fluorescent flying squirrel glowing pink and emerging from a bird house.
Fluorescent squirrel


A surprisingly large percentage of diamonds — 25% to 35% fluoresce to some degree. The GIA and other labs like the IGI and GCAL asses a diamonds fluoresce by how intense it is, ranging from none to faint, medium, strong and very strong. Similar to color, fluoresce is graded against a set of master stones in the lab.


For those of you who took color theory, this one’s a no brainer. For everyone else — pay attention. Diamonds come in shades of white and yellow. When blue is added to the yellow they cancel each other out. The more blue you add to yellow, the whiter it becomes. Therefore, a fluorescent diamond in the I-M range is going to appear whiter under UV light. Guess what contains UV light? Daylight. Magic or science? Who cares. Bottom line, you’re getting a whiter diamond for your money.

Unfortunately, the same applies the opposite way around. Fluorescent diamonds in the colorless and near-colorless range (D-H) will look bluish under UV light. They also can appear hazy or oily in appearance.

So, if you’re thinking about buying a fluorescent diamond, remember that fluorescence and color counteract each other. Fluorescence can make a yellow diamond appear white, or a white diamond appear blue.


Neither! If you’re buying a fluorescent diamond, you may want to consider requesting additional images or videos under different lighting conditions to thoroughly assess the beauty of the stone. If you want a stone that glows blue because it’s a great party trick we support that. You do you.


Yes and no. Fluorescent diamonds do trade at slightly different prices to non- fluorescent diamonds, but not the ones you want. I-M diamonds with strong fluorescence trade at a 2-3% price premium to non-fluorescent diamonds with similar color grades. Why? They face up whiter. Don’t you think they deserve the modest bump?

On the other hand, a D color diamond with very strong blue fluorescence trades at up to a 15% discount to similar diamonds sans the glow. You may be able to afford it, but do you want it? Probably not.

Diamond pricing is mathematical. Prices fluctuate because of supply and demand but also because of the make and characteristics of the diamond. While you may only get a modest discount because of the fluorescence, you will also get a whiter diamond then you may be able to purchase otherwise. Win-win? We tend to think so


Colorless diamonds

If you’re looking at diamonds in the D-F range, we recommend purchasing one without fluorescence. Even faint fluorescence is going to add a dash of blue to your otherwise white stone.

Near colorless diamonds

For nearly colorless diamonds in the G-H range, we recommend faint fluorescence at most. Faint fluorescence can have the benefit of bumping your diamond up one color grade, making your “near-colorless” diamond appear “colorless.”

Near colorless & faint colorless diamonds

If you’re shopping in the I-M range, you have a bit more wiggle room and will get a lot more bang for your buck. The lower the color grade, the stronger you can go in fluorescence as long as it’s blue.


Every great ring starts with a great setting, but picking a setting out online is hard — or at least it used to be. At Frank Darling, all our engagement ring settings are available for free home try-on. It’s like the internet, but you can touch things.

Get started by selecting your favorite four rings. We’ll send you sterling silver size seven replicas set with 1 carat CZ stones.

Each try at home kit comes with a pre-paid return label, ring sizer, and The Handbook. A practical guide to purchasing a diamond for the matrimonial inclined. So, what are you waiting for? Let’s get started.