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Fluorescence in Diamonds

Fluorescence in Diamonds

By Louis-Alexandre Laferrière, Diamond Expert

Laferrière & Brixi Diamantaires


Fluorescence is a natural characteristic found in certain diamonds which emit a visible glow (generally blue) when exposed to ultra-violet light. It is estimated that between 25% and 30% of all diamonds will exhibit some fluorescence with 3% to 10% exhibiting strong fluorescence.

Fluorescence is used as an identification characteristic and not as a classification factor like colour, weight, cut or clarity. The Gemological Institute of America (GIA) distinguishes between five levels of fluorescence for diamonds: none (i.e. no fluorescence), faint, medium, strong, and very strong. There is no relationship between the level of fluorescence and the level of clarity or colour of a diamond.  It is therefore possible that two diamonds which exhibit different levels of colour and clarity, have a similar level of fluorescence. Even though blue is the predominant colour, diamonds can exhibit fluorescence in a variety of shades like yellow, green, orange, and white.


There is not a definitive answer or a clear consensus on that question. On one side, there is a common perception within the diamond industry that fluorescence can negatively impact the appearance of a diamond. In fact, many diamond dealers report that fluorescence can give a “milky” or “hazy” appearance which affects the clarity and brilliance of the stone.

This situation is perceived to be prevalent and negative for high colour graded diamonds (D,E,F,G) which exhibit medium to strong fluorescence. On the reverse, the presence of fluorescence is perceived to be positive for low colour diamonds (J,K,L,M) as fluorescence could help decrease the yellow tint and therefore increase the perceived colour.

Furthermore, numerous industry actors think fluorescence has no negative impact on the appearance of diamonds. To support their view, they point to numerous independent gemological studies by such laboratories as GIA and HRD, which have determined that fluorescence is not negative and can even be preferred by some consumers.


The two main studies which are usually cited on fluorescence are from the GIA “A Contribution To Understanding The Effect Of Blue Fluorescence On the Appearance of Diamonds” published in 1997 and from HRD Antwerp “The Effect of Fluorescence on the Colour of a Diamond” published in 2018.

In the first study, the GIA had diamonds exhibiting different levels of fluorescence observed under various lighting conditions, by a panel composed of professional members of the trade and consumers alike. The study concludes that for the average observer, there is no systemic visual impact of the presence of fluorescence. Furthermore, there was no consistence in the results observed amongst the industry experts. In the final analysis, the study concludes that, for most observers, there is no relationship between the presence of fluorescence and the transparency of a diamond.

For its part, the HRD study concludes, that even the presence of a high level of fluorescence does not negatively impact the appearance of a diamond. In fact, the study’s results point in the opposite direction i.e. that under normal lighting conditions and even in broad day light, the presence of a high level of fluorescence has a positive impact on the perceived colour of diamonds. HRD Antwerp even goes so far as to suggest that there should not be any price discrimination towards diamonds that exhibit fluorescence.

fluorescence dans un diamant photo1


It is generally observed that diamonds which exhibit strong fluorescence are sold at a discount versus their equivalent with no fluorescence. Higher colour graded diamonds (D-H) with no fluorescence tend to be sold between 10% to 30% higher than similar stones with high blue fluorescence. At the other end of the spectrum, the lower colour graded diamonds (I-M) that have strong fluorescence, can be sold up to 5% higher than similar nonfluorescent stones.

Historical context

It is worth nothing that the current pricing dynamics did not always prevail. In fact, before the advent of modern diamond classification techniques, the colour “blue white” was particularly prized amongst diamond collectors. More often than not, these so called “blue white” diamonds usually exhibited very strong blue fluorescence which gave the stones a particularly appealing “icy” effect. This phenomenon probably explains why in various blind tests, consumers tend to prefer the appearance of diamonds displaying strong fluorescence. To that effect, the giant Russian miner Alrosa, decided to launch a diamond jewelry line composed exclusively of fluorescent diamonds – Luminous Diamonds. Based on the compagnies internal studies, young consumers are particularly attracted to these diamonds which glow in night clubs, concert halls and even under UV sunrays.


The presence of fluorescence confirms that the diamond is of natural origin

No, the presence or absence of fluorescence is not sufficient to confirm if a diamond is of natural origin or not. Certain natural diamonds do not exhibit their fluorescence under traditional UV diamond grading lights used by gemologist. It is also possible that certain synthetic diamonds (also called man made and/or laboratory-grown) as well cubic zirconium (CZ) can exhibit fluorescence.

A fluorescent diamond is less brilliant

No, the brilliancy of a diamond is primarily a function of how well it is cut. It is the optimal arrangement and symmetry of the various facets of a diamond that will determine the sparkle and fire.

A fluorescent diamond is less durable

No, fluorescence has no effect on the solidity or the internal structure of a diamond.

Fluorescence is a classification factor like colour, cut or clarity

No, fluorescence is a characteristic used to identify diamonds and NOT a classification element like colour, cut, clarity or carat.

A diamond displaying strong fluorescence is a bad thing

No, not necessarily. Certain studies even tend to demonstrate that fluorescence can be an attractive attribute that is sought after by some consumers.


Fluorescence is an important factor to consider when purchasing a diamond. Regardless, of the results of the GIA and HRD studies, as a diamond dealer with over 20 years of experience in the field, I have often noticed that fluorescence can have a negative impact on the appearance of certain stones. Even if the “milky” effect is not systematically present, our expertise enables us to detect any unwanted reflection that might have an adverse impact on the value of your investment. A “cloudy” effect can also be present in diamonds that does not display fluorescence. This may be the result of a particular type of inclusion that impacts the crystalline network of the stone. As with most important purchases, best is to have the assistance of an expert and be able to inspect the stone before making a purchase decision.

If you wish to buy or sell a diamond, please consult an expert at Laferrière & Bixi Diamantaires Inc. calling us at 1-844-671-3101 or by filling the contact appointment form on our website

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