What Effect Does Blue Fluorescence Have on a Diamond?

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February 4

There seems to be a great deal of confusion about the effect of blue fluorescence upon the appearance of a diamond, especially in the range of medium blue, strong blue and very strong blue.  While there seems to be a great deal of interest in blue fluorescent diamonds by consumers at this point in time, there seems to be an equal amount of concern about whether the presence of blue fluorescence in a diamond is going to make the diamond appear “milky” or foggy.

The reality is that only a very small percentage of diamonds with blue fluorescence are negatively impacted by the presence of fluorescence, perhaps less than 2% and I am referring to 2% of diamonds with fluorescence, not 2% of gem-quality diamonds.  The basis for this estimate is based upon a statistical analysis of fluorescent diamonds conducted by the GIA Gem Trade Laboratory in 1997 in which they reviewed a random sample of 26,010 diamonds ranging in color from colorless to faint yellow and determined that 65% of those diamonds did not exhibit any degree of fluorescence when exposed to long-wave UV radiation.

Of the 26,010 diamonds examined, only 9,175 or 35% exhibited fluorescence and 3,465 of those or 38% were reported to have faint fluorescence while 5,710 or 62% of those diamonds had descriptions that ranged from medium to very strong.  Of the 5,710 diamonds which exhibited fluorescence, 5,533 or 97% of them exhibited blue fluorescence in varying intensities and only 162 of the diamonds (3%) fluoresced another color such as yellow, white or orange.  It should be noted that the GIA does not indicate a color of fluorescence for faint fluorescent diamonds.

The GIA clearly states in their report that they made a conscious decision to restrict the basis of their analysis to diamonds with blue fluorescence because of the relative rarity of colorless to faint yellow diamonds which exhibit yellow fluorescence because of “the difficulty of finding sufficient numbers of yellow fluorescent stones to conduct a parallel study.”  They proceed to state “Diamonds with extremely strong blue fluorescence and a distinctive oily or hazy appearance, often referred to as ‘overblues’ are also a concern to the industry.  In our experience, however, they are even rarer than diamonds with yellow fluorescence.”

I concur with the opinion stated by the GIA to this regard… In the 25+ years I spent as a diamond buyer, I literally graded and evaluated thousands and thousands of diamonds and during that time I recall seeing very few diamonds that were negatively impacted by the presence of blue fluorescence and every one of them had been graded as having a level of fluorescence which was “extremely strong blue” or “distinct blue” which are synonymous grading terms used to describe a level of fluorescence which is beyond very strong.  Therefore it seems like it is pretty safe to say that if you want to avoid the possible negative influence of fluorescence upon a diamond, just avoid the select few which exhibit extremely strong to distinct levels of fluorescence.

In truth, this was a factor in our selection criteria when I was the diamond buyer for Nice Ice.  We simply avoided diamonds with extremely strong and distinct blue fluorescence because we didn’t want to risk the potential effect that it might have upon the appearance of a diamond.  My late-wife Robin used to wear a 2.54 carat marquise cut, D color diamond which exhibited extremely strong blue fluorescence when examined under the long-wave UV light provided by a GIA Diamond Light in a pitch black room and the diamond often did appear to be “milky” or “foggy” when viewed in direct sunlight or in a room with UV lighting.  She actually purchased the diamond with the intent of using it as a teaching tool and would often show it to clients to demonstrate the effect which the extremely strong blue fluorescence was having upon that particular diamond.  The following picture which was provided by Brian Gavin Diamonds shows how diamonds with blue fluorescence appear when viewed under long-wave UV light in a pitch-black room, the effect is pretty cool:

Blue Fluorescence in Brian Gavin Signature diamonds as seen under black light.
Brian Gavin Blue Fluorescent Diamonds.

Most of the diamonds which we owned and wore personally exhibited medium to strong blue fluorescence when exposed to long-wave UV light; needless to say as diamond dealers we had access to diamonds of all descriptions, the truth is that we preferred the look of blue fluorescent diamonds within the range of medium to very strong blue.

For this reason, I am a big fan of the diamonds offered within the Brian Gavin Blue collection of blue fluorescent diamonds.  Each diamond is carefully examined by Brian Gavin personally and hand-selected for maximum visual performance.  The degree of fluorescence for the diamonds selected for the Brian Gavin Blue collection ranges from medium blue fluorescence, strong blue fluorescence, and very strong blue fluorescence.

While Brian Gavin is the only diamond cutter I am aware of who has chosen to specifically showcase the blue fluorescent diamonds within his inventory as a “collection” other cutters such as Crafted by Infinity and diamond dealers such as James Allen also offer diamonds with blue fluorescence.  If you’ve read other articles pertaining to diamond cut quality and visual performance on this website, it’s no secret that I’m a big fan of the production quality of Brian Gavin.

I also like the fact that Brian Gavin takes a personal, hands-on approach to the diamond selection process to the degree that I am confident that they will eliminate any diamonds from their inventory that are negatively impacted by the presence of fluorescence… at least this has been my experience.  So I would not hesitate to purchase a diamond with medium blue, strong blue, or very strong blue fluorescence from Brian Gavin Blue collection.

One thing which most people probably do not realize is that the “fluorescence grade” which appears on GIA and AGS diamond grading reports is actually not a “grading factor” at all, but rather is merely an “identifying characteristic” used to describe the diamond as judged at the time of grading.  When diamonds are graded in laboratory conditions, they are examined for diamond color and fluorescence while placed upside down (table facet down, the pointed culet of the diamond facing up) with a long-wave UV light source in a room without any other light source.  This method of viewing a diamond and judging it for color (actually and absence of color) and fluorescence differs dramatically from the viewing environment provided by the average jewelry store and certainly from the environment in which the diamond will be worn.

In the real world, diamonds are set in such a way that they are almost always viewed from a top-down perspective which allows the facet structure of the diamond to help mask any imperfections (inclusions) within the diamond and makes it more difficult for people to judge the body color of a diamond… many people will not notice the warmer body color of diamonds in the J-K-L-M-N range of faint to light yellow when viewing the diamond from a top-down profile, but will immediately detect that the diamond has a warmer hue when they view the diamond from a side-profile.  Since diamonds are valued by the absence of inclusions and color, diamonds which are warmer in color, such as those in the J-Z color range, are less expensive than diamonds in the D – I color range… so you can save a little money if you can handle a little tonal value.

Likewise, diamonds with medium to extremely strong blue fluorescence tend to be priced less than diamonds without fluorescence.  This is not necessarily because fluorescence is considered to be a negative factor, but rather because of the effect of a diamond investment boom that occurred in the last century, during which several investment firms tried to set themselves apart from their competitors by advertising that the diamonds contained within their investment parcels did not have fluorescence.  Big whoop.  Like I said earlier, I happen to like diamonds with blue fluorescence and I kind of appreciate the price break…

For instance, this 1.013 carat, VS-2 clarity, F color diamond with strong blue fluorescence from the Brian Gavin Blue collection is significantly less expensive at $8,697.00 (wire transfer price) than this 1.005 carat, VS-2 clarity, F color diamond with negligible fluorescence from the Brian Gavin Signature collection which is currently selling for $9,647.00 (wire transfer price).  The reality is that the two diamonds are cut virtually identical and the only real difference is that one has strong blue fluorescence and the other does not… so why are they priced differently? Because the diamond rough with blue fluorescence costs a little bit less than diamond rough without fluorescence.

Is there a visual difference between the two diamonds?  In the study conducted by the GIA Gem Trade Laboratory in 1997, it was determined that 62% of the observers detected no visible difference in the transparency of the diamonds being compared.  There were some differences detected with regards to the perceived effect of fluorescence upon the color grade of the diamonds which leads credence to the argument that blue fluorescence might help diamonds to appear whiter than they might if they did not possess fluorescence.

The GIA used separate selection criteria for the diamonds being evaluated depending on whether the person viewing the diamonds was considered to be an average consumer, a diamond professional or an expert diamond grader.  The fact is that only the expert diamond graders were allowed to judge the diamonds for color grade and among those the results indicate that 46% of the experts did not perceive a difference in color grade for diamonds within the E-color range; 41% did not perceive a difference in color for diamonds graded within the G-color range; and 15% did not perceive a difference for diamonds within the I-color range; and only 10% did not perceive a difference in color for diamonds graded in the K-color range.

However a whopping 71% of all observers (excluding Average Observers) stated that the diamonds within a given set appeared to have different depths of color… thus it is reasonable to assume that the presence of medium to very strong blue fluorescence has a positive effect upon the perception of depth of color.  However this is as determined by people within the diamond industry who have an eye for grading diamonds for color… it is unfortunate that the GIA excluded the “average consumers” from this portion of their analysis since ultimately it is the public who is most concerned with the presence or absence of fluorescence within diamonds.

The GIA continues to say that “For each of the four-color sets (E, G, I, and K) taken separately, we also saw no relationship between the strength of fluorescence and color appearance with the diamonds viewed table down, but we again saw a trend toward better color appearance with stronger fluorescence when the diamonds were viewed table-up regardless of the light source.”  Here again, it seems that the GIA concluded that medium to very strong blue fluorescence has a positive impact upon the appearance of diamond color (or absence of color) when the diamonds are viewed from a top-down perspective as they are going to be worn.

So it seems that the data provided by the GIA study on fluorescent diamonds from 1997 (Winter edition of GIA Gems & Gemology magazine) indicates that blue fluorescence does have an effect upon our ability to perceive color within diamonds… diamonds with strong blue fluorescence are more likely to be judged as having a better color appearance when viewed table-up.  The effect by the way is most noticeable in the lower color grades, such as those in the range of I-color to Z-color, and less noticeable in higher color grades such as D-G color.  This might be because blue fluorescence is essentially Mother Nature’s whitewash for diamonds and it is simply less noticeable in diamonds that already exhibit an absence of color.

About the Author

Todd Gray is the CEO of Gray Matter Development, LLC., DBA Nice Ice Diamonds. He is also a trade consultant and diamond buyer with 35+ years of experience specializing in light performance. Todd also ghostwrites educational content for online ventures and is an avid Freediver.