Fluorescence in a Diamond

Fluorescence refers to the visible light which some diamonds emit when they are exposed to invisible ultraviolet (UV) rays. On a GIA Diamond Grading report, fluorescence indicates the strength or intensity of the diamond’s reaction to long-wave UV rays, which is an essential component of daylight. The light emitted lasts as long as the diamond is exposed to the ultraviolet source.

Not all diamonds exhibit fluorescence, but it is a relatively common occurrence in brilliant diamonds. Of all diamonds submitted to GIA over the past decade, approximately 25% to 35% exhibit some degree of fluorescence. However, only 10% of those diamonds showed strengths of fluorescence that may impact the diamond’s appearance; that is, showed strengths noted on laboratory reports as medium, strong or very strong. In more than 95% of the diamonds that exhibit fluorescence, the color seen is blue. In rare instances the reaction is yellow, white, or another color.

GIA studies show that for the overwhelming majority of cases, the strength of fluorescence in a diamond has no widely noticeable effect on a diamond’s appearance. In many instances, observers prefer the appearance of diamonds that have medium to strong fluorescence, but in rare cases, diamonds with extremely strong fluorescence may appear hazy or oily (fewer than 0.2% of the fluorescent diamonds submitted to the GIA exhibit this effect.)

Fluorescence does not compromise the structural integrity of diamonds. A diamond that fluoresces has the same integrity as a diamond that exhibits no reaction to UV rays. Submicroscopic substitutions and/or shifts in a diamond’s structure can cause fluorescence, as well as prevent it. Nothing in either instance inherently weakens, or is bad for, the diamond.

For more information about fluorescence and to compare diamonds side-by-side, please visit our Newton location where our artisan jewelers will gladly assist you.