Diamond Fluorescence

diamond fluorescence

Many diamond shoppers often wonder about diamond fluorescence. Is it a good thing? Should it influence your buying decisions? And what is diamond fluorescence in the first place?

To help you make the best and most confident buying decisions, let us find out all about diamond fluorescence, shall we?

Understanding diamond fluorescence

When some diamonds are exposed to ultraviolet light or fluorescent light from a lamp, they emit a glow. This is the fluorescence and the diamond is said to be fluorescent.

If the light source is removed or if the diamond is taken out of direct sunlight, the glow vanishes. This fluorescence can either be blue or yellow to orange. The latter two are rarer than the first.

It’s important to note that at this point not all diamonds are going to fluorescence. Only between 25 -35 percent of diamonds exhibit this feature.

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Diamond Fluorescent grade

Diamond fluorescence is not a grading factor as per the GIA. Instead, it is considered more of an identifying characteristic. Grading factors include cut, carat weight, clarity, and color. These are known as the 4Cs.

The GIA describes the fluorescence of a diamond by its fluorescence. These include none, faint, medium, strong and very strong. The fluorescence of a diamond will be compared to a master stone held in the lab.

The color of the fluorescence can be either blue, yellow or orange, can only be detected if the fluorescence of the stone is medium, strong or very strong.

Diamond fluorescence color

Some professional diamond traders believe that the blue fluorescence makes the diamond look more enhanced. This is especially so with color grades I – M. If a diamond has a bluish fluorescence, it may appear more colorless when exposed to light if it is faint yellow.

Because of this fact, the diamond will have a higher price per carat than a diamond which doesn’t have fluorescence since it will appear more colorless.

However, the opposite happens with diamonds that have a higher color grade. When a diamond is on the D-H color grade and has a bluish fluorescence, it will not be as appealing because of the oily or hazy appearance that it gives. However, note that this only happens when there is an intense blueish fluorescence.

Also, it is not all demands that will look hazy or oily when they have an intense bluish fluorescence. They may even cost cheaper than those that lack the fluorescence.

Is it possible to tell the difference?

A question that is often in the minds of diamond shoppers is whether the average eye can spot a diamond with fluorescence and one that doesn’t have fluorescence.  And the answer is no. It is hard for even an experienced observer to notice the diamond’s fluorescence with the naked eye.

This is because fluorescence tends to have a negligible appearance on the face-up of the diamond especially when the diamond is colorless or the near-colorless grades between D-J.

Is fluorescence good or bad?

Simply put diamond fluorescence is neither bad or good. Ultimately, how the shopper views the diamond and its beauty is subjective. You can either perceive fluorescence or you can miss to perceive it.

Some people may like fluorescence while some people simply may not like fluorescence.

Shoppers who also considering going for a diamond that has a blueish fluorescence are encouraged to view the diamond under different light conditions including natural light, as well as compare the diamond with others of the same color to see whether they can spot any differences.

The opinion in diamond fluorescence is subjective and this is why it sparks so much conversation.

What causes fluorescence

A diamond may contain very tiny amounts of elements such as aluminum, boron, and nitrogen. If a diamond has these in its atomic structure and it is exposed to light, the energy from the ultraviolet gets absorbed by the elements and this causes them to move to a higher energy level.

The law of physics states that the electrons in these exciting elements will try to move back to the more stable state. This is by dumping excess energy by releasing photons. These are the tiniest amounts of electromagnetic radiation. This is what you will conceive with the eye as fluorescence.

Blue is the most common color.  There are however other rarer colors such as pink, white, green and yellow. The difference in florescence colors is as a result of different chemical compositions in the atomic structure of the diamond.

Many people also wonder whether the fluorescence of a diamond affects its strength and the answer is no. The integrity of a florescent diamond is the same as that of a stone that has no fluorescence. The elements are not connected with a diamond’s strength or weakness.

Fluorescence and the value of a diamond

Over the years the popularity of diamonds that show fluorescence has risen and dropped. Ultimately there is little consequence to the impact of fluorescence on the price of a diamond. Since the advent of grading labs, buyers would be able to avoid any sense of unfavorable feature in a diamond and this also included fluorescence.

Currently, diamonds that have a medium to strong fluorescence will have a lower price compared to diamonds that do not have any fluorescence. Note that when it comes to the I-M diamonds these can be the opposite. It will, however, depend on the evaluating of the individual diamond.

The table below shows just how fluorescence can affect the price.




-10 to -15%

-6 to -10%

0 to -3%

-7 to -10%

-3 to -5%

0 to -1%

-3 to -7%

-1 to -2%










-7 to -10%

-3 to -5%


-5 to -7%

-2 to -3%


-1% to -3%

0% to -2%





I-MIF-130 to +2%0 to +2%0 to +2%0%

One of the main advantages of fluorescence in a diamond is a huge potential for saving.

Since fluorescence can cause a diamond in the lower color grades to appear whiter, it may look like a stone from a higher color grade. However, you will pay significantly less for this stone allowing you to save quite a bit.

The downside is that it can cause haziness. This is why it is important to buy from a reputable dealer as you will be able to evaluate it with high-quality images of the diamond.

How the fluorescence is determined

Grading labs have ultraviolet spectrum lights which they will shine on a diamond. They will also compare the diamond with other master fluorescent diamonds and provide a grade. Blue fluorescence which is the most common and is in 95% of all fluorescent diamonds.

This simply means that when put under ultraviolet light they will glow pale blue.  Yellow is the second most common fluorescence.

Most common fluorescence grades

None is the most common fluorescent grade. Anywhere between a quarter to a third of all diamonds will have any fluorescence. Even then only about10 percent of the diamonds in this subset will have a fluorescence which will be noticeable under UV light.

Of course, the highest and very strong fluorescence grade is the least common.

The shape of the diamond is not affected by fluorescence. Any type of diamond from the princess cut to the marquise to Asscher will all be affected in the same way.

It is also important to note that it is not just the white diamonds that are graded for fluorescence. Fancy colored diamonds are too. However fancy colored diamond will look better when they are graded as none to faint fluorescent.

Think of how yellow or blue fluorescence can degrade the color of a fancy-colored diamond.

Below are the grading scales that are used by the GIA and the AGS,

GIANoneFaintMediumStrongVery Strong
AGSNegligibleMediumStrongVery strong

When the diamond is graded as None, this means that no blue glow will be emitted by the stone when it is exposed to ultraviolet light. In this case, there are no trace elements in the diamonds that could cause the glow. This type of stone has a high price.

The faint grading means that the stone emits a soft blue glow when it is under ultraviolet light. There are very minor trace elements in the diamond and are responsible for the glow. This will not affect the price of the diamond and this type of stone is very much similar in price with the one graded as None.

The medium grade shows a stone that has a light blue glow under UV light. This fluorescence affects the diamond and will reduce the price slightly. It is also capable of improving lower color grade diamonds such as K, J, and L.

The strong grade represents diamonds that have a deep blue fluorescence when they are exposed to ultraviolet light. These will only slightly improve the lower color grade diamonds such as K, J or L. The fluorescence can reduce the higher color diamonds such as D-E making the diamonds look grayish or hazy.

The very strong grade is for diamonds that have a very bright blue when they are under ultraviolet light. Even with the diamond having no color, this tends to make the stone appear hazy or gray.

History of florescence

Before there was any diamond certification in Europe, blue-white was the most sought-after diamond color. Compared to today’s standards, these are near colorless to yellow diamonds that also feature a strong blue fluorescence.

Many merchants sought after these stones because they had an ice effect. Later, it was discovered that the blue fluorescence was something that was found in hazy stones. Dealers in the 1970s started to refer to such diamonds and milky Ds. In other words, these were diamonds that were in the D color grade, had a very strong blue fluorescence and had low transparency.

They were offered at reduced prices. In the years subsequent, such diamonds had quite a significant effect. Soon the F grade diamonds, as well as diamonds that had very faint fluorescence, saw their prices being cut down.

If you are wondering whether it is a good idea to buy a florescent diamond, its important to keep in mind that this feature can enhance the look of the diamond and should not always be looked at as a bad thing. Ultimately it will come down to how the diamond appears to your eyes. Note that there are very rare cases were the fluorescence of a diamond will cause it to appear milky or hazy.


Medium or highly florescent diamonds may appear cloudy or hazy. This is especially the case with stones at the higher color grades. The fact that they have less color means that the cloudiness can be seen easily.

If you are to go for the higher color grade, it is advisable to go with the faint fluorescent diamonds.

Fancy colored diamonds

Florescence in a fancy colored diamond isn’t always a bad thing as well. Under the right combinations and the right light settings, the fluorescence will complement the fancy colored diamond. The color from these diamonds may appear fuller and richer.

When it comes to the yellow diamonds it is possible to find a stone that has a yellow fluorescence. Be sure to ask your dealer on what kind of florescence the yellow diamond has. If it is too intense, then it may cause the diamond to have a brown tint to it. On the other hand, if it is faint then you may not notice the fluorescence at all.

Even better is that you may get a yellow diamond with fluorescence that isn’t visible at a reduced price compared to one that has no fluorescence at all.

When it comes to pink diamonds, the majority of them will have florescence. It is harder to find one that doesn’t have any fluorescence in it. The prices will not be affected by the fluorescence very much and there is no huge difference.

Generally speaking, there will not be any fluorescence in a pure blue diamond. If there is any fluorescence in the diamond, it may give it a greenish tint but, in most situations,, it will not be noticeable. Because of this, there will also not be much difference in the prices of blue diamonds.

As is the case with many things in life, the rarer something is the more some people want it and the more demand it gets. Ironically some people will consider fluorescence a collector’s item. This is certainly the case with red fluorescence. It is so rare that when found it will spark a lot of interest.

How to buy fluorescent diamonds

The first thing that any buyer needs to do is find a reputable seller and dealer before making any buying decisions. The dealer will have excellent high-quality close-up images of the stone you are interested in.

Color and cloudiness should be inspected before you decide to buy the diamond. Videos are even better as you can have a 360 degree close up of the stone which will reveal the color as well as the cloudiness. Many dealers fail to have this feature which makes it an excellent way of judging your seller.

Fluorescence and brilliance of the diamond

There are there a few factors that affect the brilliance of a diamond. These are the reflection, dispersion, and refraction of light.

Reflection is when light hits a diamond and is reflected in another direction. This is what results in the shine of the diamond.

When light hits the diamond not all of it will be reflected. Most of it will go through the diamond and only a smaller percentage will bounce back.

For the light that gets into the diamond, it is separated and travels in all sorts of directions. This is called refraction. A diamond’s sparkle is a result of the light refraction.

When light enters the diamond from the top and then disperses inside the stone only to be reflected back up. The result is a rather rainbow shimmer that also adds to the diamonds sparkle. Note that it is dispersion and refraction that will cause dark areas in the diamond when the facets are misaligned.

There will be darker areas that are magnified due to the effects of dispersion and refraction which further contributes to how much the diamond shines.

Simply put, a diamond owes its shone, fire and brilliance to the effects of reflection, refraction, and dispersion. That said, high fluorescence will cause hazy diamonds which affects their brilliance.

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