Ultraviolet fluorescence is not a major consideration when buying an H&A diamond. We don’t address the other factors of diamond quality nor do we discuss grading standards of the various gem labs, as this is not our focus here. However, we must touch briefly on the issue of Fluorescence, as most everyone misunderstands it. H&A diamonds are not affected or rejected because of the presence of Ultraviolet Fluorescence unless the fluorescence is strong enough as to create a hazy or over-blue condition. Obviously anything that affects the brilliance of a diamond is a negative factor.

Visually, blue cancels out yellow, so in diamonds with some body color, fluorescence is a plus, contrary to the notion in the trade. A diamond with a slight tinge of yellow that has Medium to Strong Blue fluorescence will normally appear whiter than one without any fluorescence. Is that a bad thing? Fluorescence grades of negligible, none, faint, medium or even strong are normally non-factors. Diamonds with Very Strong Blue Fluorescence may appear hazy, over-blue or dull and if so, they should be avoided. We have seen a small number of diamonds graded only Strong Blue that appear slightly hazy. This happens only when they are in the upper range of the Strong Blue scale (approaching Very Strong).

The industry attaches too much negative connotation to any mention of fluorescence on a lab report. This is ridiculous and not based in reality. In fact, studies have shown that fluorescence can have a very positive effect on color, especially in the H to K color ranges or lower. Some Savvy dealers and jewelers seek out these fluorescent diamonds. Since about 1980, after a Korean TV exposé about Very Strong Blue, high-grade diamonds being sold for investment, the “knock” against fluorescence has grown. Like an urban legend gone viral (with no Snopes to debunk it) the small spark started among dealers in the Far East some 30 years ago has grown into a firestorm today. Young dealers in India and elsewhere have developed an aversion to fluorescent diamonds, as if they were radioactive! They weren’t in the business back in the day when GIA wrote this comment on reports about Strong Blue diamonds, “The Ultraviolet fluorescent of this diamond enhances its color grade in daylight”. View example of GIA comment Fig F-1.

GIA also stated in their a 1997 landmark study in Gems & Gemology: “On average, strongly fluorescent diamonds have a better color appearance table-up, and this effect is most noticeable at lower color grades. Most observers did not detect any differences in transparency among diamonds in a given color set...These results challenge the notion that strongly fluorescent diamonds typically have a hazy appearance.” They went on, “One interesting aspect of this study was that to the non-trade observers...which would be considered most representative of the jewelry-buying public, fluorescence had no overall effect on color appearance or transparency.” Finally GIA concluded: “For the experienced observers, we found that, in general, the strength of fluorescence had no widely perceptible effect on the color appearance of diamonds viewed table-down (as is typical in laboratory and trade grading). In the table-up position (as is commonly encountered in jewelry), diamonds described as strongly or very strongly fluorescent were, on average, reported as having a better color appearance than less fluorescent stones. In this study, blue fluorescence was found to have even less effect on transparency.”

Download the GIA report: http://lgdl.gia.edu/pdfs/W97_fluoresce.pdf

We at heartsandarrows.com do not reject a beautiful H&A diamond at the mention of fluorescence on the report. We recommend that buyers consider the totality of the diamond before accepting or rejecting it.