Diamond Fluorescence Guide

Diamond Fluorescence Guide 2019-09-08T22:23:42+03:00

Diamond Fluorescence! All What You Need to Know About it!

When you get to the point of checking a diamond details, you will stop (and maybe frank) when you see it has some fluorescence, some people cancel their decision when they see the diamond has some fluorescence, others look for a diamond with some fluorescence, while some others know that there are some benefits (in some cases) for having a fluorescence, why is that? And who is right between these 3 kinds of people?

Today, we will go over this, and explain in details what does it mean when a diamond has some fluorescence (either it was faint, medium, or even very strong), is it always good, or always bad? Or depending on the grade? Let’s see!

What is Diamond Fluorescence?

Let’s start from the beginning, what is fluorescence in diamonds?

When you subject an ultraviolet light to a diamond, the diamond “may” emit a colored glow, this glow is usually blue, that’s why you will see most images refers to diamond fluorescence with a blue color, like the one you see here:

Diamond-fluorescence Blue

People usually doesn’t prefer the last one (very strong blue fluorescence), and 99% of the time they are right, why? Read on…

As you see, in normal light condition, you can barely tell any difference between the 5 diamonds (regarding glow), but under an UV light, the diamonds shows different levels of fluorescence, ranging from None to V. Strong, again, this only appears under UV, because you can’t (almost) tell a difference under normal lighting (more about this in details below).

Diamond Sparkle James Allen

Is Fluorescence Always Good or Always Bad?

Now let’s jump quickly to see what’s the big deal here? And how much important is it to select a diamond based on its fluorescence? Should I buy a diamond that has fluorescence or should I skip it directly?

There is no direct answer, because it depends on the diamond color, let’s see what this means:

Getting some fluorescence in high level colors (colorless or near) diamonds:

James Allen Design RingIf you’re going with a higher level color, say H or higher, you better stay away from fluorescence, although you might get a 10-15% discount if the fluorescence was V. Strong in a D-Color diamond for example, why?

Because these diamonds are colorless or near colorless as we saw in the colors article, and since fluorescence will glow some blue, it might affect the diamond color, thus, it’s mostly will be considered a defect to the diamond.

Getting some fluorescence in low level colors diamonds:

On the contrary, if you’re going with an I-M color diamond, you may want to get a diamond with some fluorescence, why?

Because this can (but is not guaranteed) give your diamond a look like it has a higher color (up to 1 level, a J-Color diamond may look like an I for example). Don’t go crazy with this and if you can’t find one go for None or Faint fluorescence.

If your diamond is G or higher to start with then go with None or Faint fluorescence as you have nothing to benefit from it.

Fluorescence Real Impact on Diamonds

Diamond Fluorescence

Diamond Fluorescence Chart As Viewed in UV Light Courtesy of James Allen

Diamond fluorescence is one of the most hotly debated and misunderstood characteristics of a diamond.  In a famous study the GIA tried to minimize the impact of fluorescence and stated that under normal lighting conditions (more on this below) even a strong blue fluorescence is usually impossible for the average diamond buyer to pick up. If in fact that were the whole story there wouldn’t be much to worry about and nobody would pay much attention to it.  The truth however is not so clear cut.

Fluorescence refers to a glow that some gems, including diamonds, give off when subject to UV (Ultra Violet) lighting.  This glow can be weak , or faint as it referred to in the diamond industry, medium, or strong.  Now I know you are probably thinking that since you don’t hang out at night clubs you shouldn’t care about this but the fact is that contrary to the GIA, fluorescence can have a couple of other impacts on your diamond:

1)   As fluorescence gets stronger there tends to be a haziness in the diamond that effects its brilliance. So a diamond with strong blue fluorescence will not seem as clear as the same diamond with light or no fluorescence. (See how JamesAllen explains this).Diamond Fluorescence UV

2)   Fluorescence tends to improve the appearance of diamond color. So a diamond with an H color may look better if it has a Medium Blue Fluorescence. (this is actually referenced in the same GIA study)

Some not-so-scrupulous sales people actually abused fluorescence in higher color grades, invented a term called blue-white diamonds, and tried to sell them as “better diamonds”. This of course is nonsense and the term is actually banned by US FTC. If your jeweler tries to use this term on you- walk out and find another (my recommendation is to buy online!)

What Does This All Mean to You? The Conclusion

1)   If you are buying a diamond with G-H color or better stay away from Medium and Strong fluorescence. You will not benefit at all from its presence but you may very well see some of the haziness I spoke about. 

2)   If you are buying a diamond with H or lower color then you may benefit from a diamond with Medium fluorescence. I wouldn’t go so far as to recommend Strong Blue as in this case the benefit of the color improvement is outweighed by the haziness.

Blue Nile Ring

In general these rules apply to those wisely buying online as opposed to in person. Since you won’t be seeing the diamond upfront you these are good rules of thumb that you can use in making your purchasing decisions. If you are buying locally at a retailer (and I personally don’t recommend this since you can save a bundle online) then go with your instincts and if you find a diamond you like – even if it has fluorescence – don’t feel that you shouldn’t buy it because of this.

Hope this article clearly explained the whole thing about diamond fluorescence, if you still feel want more, read our dedicated article about Is Diamond Fluorescence Good or Bad?


  1. Cindy May 9, 2014 at 3:53 pm - Reply

    Hello, I have the potential of buying a diamond size .90 D color VVS2 excellent cut /excellent polish symmetry 1.1 S florescence. The price is $4300.

    They have pulled it and tell me their is no cloudiness….it is very white and has a great fire.

    Your Advice. My Budget is to stay under 4500. Thank you!

  2. Khomsiin August 21, 2015 at 9:37 am - Reply

    Steve, you raise a good point. We may get rid of the diamond ring if a magiarre ends, but the diamond sure doesn’t go to landfill.And Jess, you also raise a good point. I avoided the whole subject of De Beer’s policies because that’s not the focus of this blog – but it’s worth at least a short note, and I thank you for providing that.

  3. pav September 25, 2015 at 12:18 am - Reply

    Can I please get your opinion:

    1.04 carat, color G, VVS2, cut Very Good, polish Very Good, symmetry Good, fluorescence None for roughly $6,500 vs . 0.95 color D, internally flawless IF, cut Very Good, polish Excellent, symmetry Excellent, fluorescence Medium blue for $8,000. Which would you recommend? What would you buy if slection round diamond in roughly 1 carat range? Thank you so much.

  4. LeAnne August 1, 2017 at 4:50 am - Reply

    Today my husband and I bought I diamond and setting locally through a reputable retailer who’s been in business since 1892, so we thought they would be trustworthy. After we dickered on price, we finally were shown after asking many times to see the GIA papers, only to find out it was only good in symmetry and medium blue fluorescence and no engraved GIA number. Then on one area it said VVS1, but on another paper, she wrote VVS2, and after we fell in love with it, looked at it with a loop and saw the girdle was a little asymmetrical and the top where it’s the curved end, it’s kind of squared off, in the setting it was hard to tell because of the way they set the prongs and it sat high in a basket so it looked really big. It’s 1.96 carat F but can tell if it’s supposed to be Vvs1 or vvs2. We paid $26,656.00 plus tax. Are we crazy?

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