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Diamond Fluorescence - Is it Good? Is it Bad?

Diamond fluorescence? what is it, why does this occur and is it good or bad? Firstly lets look at the definition;

"Fluorescence: is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation"

Now that we have the definition of what fluorescence is, let’s look at a diamonds fluorescence. Under certain lighting situations more than one third of all naturally formed diamonds have some form of fluorescence.  Many jewellers and diamond dealers avoid flourescence like Covid-19, but it’s not all bad. Flourescence can be a good thing and it can also save you some money if you shop wisely. Common FAQ’s are below to help even further.

Some of the colours observed in diamonds subjected to fluorescence include yellows, orange, white/cloudy and by far the most common ‘Blue’, especially in White/Colourless diamonds.

Diamonds Colours under Fluoresence

Fluorescent colours seen in white and Fancy diamonds

Diamond fluorescence is determined from a scale indicating None (no fluorescence) through to Faint, Medium, Strong and Very Strong. The intensity of a diamonds fluorescence is not specifically relevant to the colour or clarity of any particular diamond, meaning that the colour and clarity have no have an effect whether the diamond will have fluorescence or not. Diamonds of different colours and clarities could also have exactly the same degree of fluorescence.

With anything that is liked by some and disliked by others there is a reason behind it besides personal taste. Fluorescence can affect diamonds positively by making them appear a brighter white and a good ‘face up’ stone in relation to their possible lower graded color. On the other hand fluorescence may cause your diamond to have a “creamy/milk” effect and may affect the brilliance slightly. This is more often seen in very large diamonds and with colours ranging down from “I”. This is of course only when exposed to UV elements, like a Black Light in a night club for example or in full and direct sunlight. All this said only 0.2% exhibit this.

Your diamond report/certification will assist you in identifying this, by looking for the fluorescence and be wary of the Inclusion Term “CLOUDS”.  Clouds ? but what do I look for? Clouds, twinning wisps etc etc, these are not to do with the Weather, but names given to inclusions inside Diamonds.  Clouds and other inclusions within a diamond can tend to display a milky appearance under the effects of  fluorescence. 

The GIA report below  indicates CLOUDS and twinning WISPS.  This Diamond also has a Medium Blue Flourescence. I’d give it a miss and look for another stone, there are hundreds more.

Diamond Flourescence 1
GIA Diamond Report indicates CLOUDS
Diamond Flourescence 2
GIA Official Diamond Fluorescence Grading Chart

Diamond Fluorescence-FAQ

Most frequently asked questions and answers

The majority of diamonds do not fluoresce. In a study of more than 26,000 diamonds submitted for grading to GIA, researchers found that only approximately 25% to 35% of them exhibited some degree of diamond fluorescence when examined with a standard long-wave UV lamp. So, it’s likely that the diamond you’re eyeing does not fluoresce. source GIA

The answers is ‘yes’ they can, it appears that they fluoresce at a lower rate than Natural mined diamonds but they can. Most of the White colourless lab grown diamonds do not, whereas Fancy coloured lab grown diamonds usually do have fluorescence. 

Fluorescence in many fancy coloured lab grown diamonds can help with their overall colour.

Diamonds that fluoresce only do so when they are exposed to invisible UV rays and other higher energy radiation sources such as X-rays and lasers. You might see your diamond fluoresce under a bright sun, in a tanning bed, at a dance club or in other places where strong fluorescent or black lights are used. But once the light source is removed, the diamond will stop fluorescing. Incandescent lighting will not cause a diamond to fluoresce. Source GIA

Diamond fluorescence cannot always be detected. You need conditions where UV rays are present and the intensity of the fluorescence is strong enough to be observed. A reputable grading laboratory, like GIA, follows strict protocols to determine the presence of fluorescence. It also adheres to set standards in describing its intensity, to ensure objective and consistent reporting. Source GIA

In assigning a diamond color grade, GIA examines the gem in a highly controlled viewing environment, designed to minimize the influence of fluorescence and to produce an accurate and objective assessment of the diamond’s color.

However, the way you perceive a diamond’s color grade may be affected by the extent to which it fluoresces – in a positive way. In a diamond lower on the GIA D-to-Z color scale (say, I to N) with a yellow tint, moderate-to-strong blue fluorescence may cancel out some of the yellow for a better color appearance than what its color grade would indicate. Source GIA

Diamond fluorescence is not one of the 4Cs – like colorclaritycut and carat weight – which describe the quality of a diamond. GIA considers fluorescence an identifying characteristic – additional information that helps distinguish one diamond from another.

GIA diamond grading reports describe the intensity of fluorescence as None, Faint, Medium, Strong and Very Strong. If the fluorescence is Medium, Strong or Very Strong, the color of the fluorescence will be noted on the grading report. Source GIA

Diamonds can fluoresce in a variety of colors. These include orangy yellow, yellow, orange, red, white and green. Variations in the atomic structure, such as the number of nitrogen atoms present, cause the phenomenon. Blue, however, is by far the most common color of diamond fluorescence. Source GIA

DIamond Flourescence in COloured Diamonds:

GIA studied the influence of blue fluorescence on the appearance of a diamond under normal viewing conditions. The Institute found that average observers (meant to represent the jewelry buying public) could not consistently discriminate any fluorescence-related effects in the viewing environments most similar to those in which jewelry is purchased and worn.

However, GIA also found that strong blue diamond fluorescence could be beneficial. The results of its study revealed that, as noted for some strongly blue fluorescent diamonds were perceived to have a better color appearance than their color grade would suggest when viewed table-up, with no discernible trend table-down. Source GIA.

We at Me Jewellery would even suggest that a H-J colour with strong blue fluorescence would look brighter than the real certified colour. 

Diamond fluorescence has little to no effect on a diamond’s sparkle, and research shows that it doesn’t impact beauty either.

A diamond’s sparkle or brilliance is determined primarily by its cut, not by whether the diamond fluoresces or not. A diamond’s cut – that is, the angles and relative measurements of its facets, as well as its other proportions, design and craftsmanship – determines how well light performs when it strikes the diamond and how well it will sparkle. Source GIA.

Absolutely not. The presence or absence of fluorescence should not be used as a DIY test to determine if your diamond is real. First, not all natural diamonds fluoresce under the standard UV lamp used by gemologists (see Myth #1). Second, some synthetic or lab grown diamonds do fluoresce to these wavelengths. Although differences have been noted in the intensity, color and pattern of fluorescence between natural and synthetic diamonds, there is overlap. Finally, some materials used to impersonate diamond – like cubic zirconia – can display fluorescence. Source GIA

A diamond that fluoresces under a standard UV lamp has the same structural integrity as one with no reaction to it. Nothing in the submicroscopic structures that cause fluorescence inherently weakens the diamond. Source GIA

Jewelry professionals disagree about whether fluorescence adds to or detracts from the value of a diamond. Some trade professionals believe those very rare diamonds at the high end of the D-to-Z color scale that have extremely strong blue fluorescence are worth less than their nonfluorescent counterparts because the fluorescence can affect their transparency by giving them a hazy or milky appearance. Conversely, some traders pay higher prices for blue-fluorescing diamonds of a lower color grade because, as noted above, they believe the fluorescence masks the faint to very light yellow color of these diamonds. Source GIA

My Comment: I’m not going to sit on the fence here.  From what i’ve seen over the years, Diamonds with high color and clarity grades are and always will be the most expensive (simply becaue they are rarer) but should any of those top graded Diamonds have Medium to Strong Flourescence then the Price WILL be less than a Diamond without Flourescence. 


*Images: The images used- on this page are borrowed from other sources and are not associated with Me Jewellery. We are using these images as ‘Fair Use’ by education and will remove them if requested to do so.