Have you ever noticed the term “Fluorescence” on a GIA Diamond Grading Report? Did you know that some, but not all, diamonds show effects under ultraviolet light?
For most people who purchase diamonds, fluorescence will be a non-issue, but some might be confused by the term. Below are commonly asked questions, and helpful answers from GIA researchers who have studied fluorescence in depth.
What is diamond fluorescence?
Diamond fluorescence, in its most simple form, is the effect that ultraviolet (UV) light has on a diamond. When you stand under a blue light or ultraviolet light, sometimes you can see your whites get brighter or your teeth appear to glow. This is the same effect the diamond has under the UV rays. Fluorescence is the visible light that a diamond emits when it is exposed to the UV rays.
On a GIA Diamond Grading Report, fluorescence refers to the strength, or intensity, of the diamond’s reaction to long-wave UV, which is an essential component of daylight. The light emitted lasts as long as the diamond is exposed to the ultraviolet source.
Is fluorescence common?
Yes. Of the diamonds submitted to GIA over the past decade, approximately 25% to 35% exhibit some degree of fluorescence. However, only 10% of those show strengths of fluorescence that may affect appearance (i.e., strengths noted on laboratory reports as medium, strong, or very strong).
In more than 95% of the diamonds that exhibit fluorescence, the visible color is blue. As blue is the complementary color to yellow, the most common tinted color in diamonds, blue fluorescence can make yellowish diamonds look white or colorless. In rare instances, the reaction to fluorescence is yellow, white or another color.
What impact does fluorescence have on the appearance of a diamond?
GIA studies show that for the overwhelming majority of diamonds, the strength of fluorescence has no widely noticeable effect on appearance. In the GIA Fluorescence Study, it was found that the average person could not make a distinction between a diamond with fluorescence and a diamond without.
In many instances, observers prefer the appearance of diamonds that have medium to strong fluorescence. In rare cases, some diamonds with extremely strong fluorescence may appear hazy or oily; fewer than 0.2% of the fluorescent diamonds submitted to GIA exhibit this effect
Does fluorescence compromise the structural integrity of the diamond?
No. A diamond that fluoresces has the same integrity as one with no reaction to UV. Submicroscopic substitutions and/or shifts in the diamond structure can cause fluorescence or can prevent it. Nothing in either instance inherently weakens or is bad for the diamond.
Should I buy a diamond that exhibits fluorescence?
The preference to buy a diamond that exhibits fluorescence is a personal one, as a diamond’s appearance must be taken as a whole. Other factors can influence color appearance more strongly than fluorescence, such as how the diamond has been cut, whether the diamond is viewed in natural or artificial light, and even what you’re wearing on any given day.
About a third of all diamonds will glow under ultraviolet light, usually a blue color which may be noticeable under a black light or strong sunlight. Some diamonds with "very strong" fluorescence can have a "milky" or "oily" look to them, but they are also very rare and are termed "overblues."
The GIA conclude that with the exception of "overblues" and yellow fluorescent diamonds, fluorescence had little effect on transparency and that the strong and very strong blue fluorescent diamonds on average had better color appearance than non-fluorescent stones.