Diamond’s Response to Long-Wave UV
Fluorescence is visible light that some diamonds emit when exposed to invisible ultraviolet (UV) light. On GIA diamond grading reports, fluorescence refers to the diamond’s reaction to long-wave UV light, which is the main component of sunlight. Fluorescence continues when the diamond is exposed to UV light.
Approximately 25% to 35% of diamonds submitted to GIA for grading in the past decade exhibit some degree of fluorescence. However, only 10% of these exhibit fluorescence that is considered to be detrimental to appearance (i.e., moderate, strong, or very strong on the grading report). Of the diamonds that fluoresce, more than 95% have a visible blue fluorescence. In rare cases, the fluorescence reaction is yellow, white, or other colors.
How does fluorescence affect the appearance of a diamond?
GIA research shows that for the vast majority of diamonds, the intensity of fluorescence has no noticeable effect on a diamond’s appearance. In most cases, observers prefer diamonds with medium to strong fluorescence. In rare cases, some diamonds with very strong fluorescence may appear hazy or greasy; however, less than 0.2% of fluorescent diamonds submitted to GIA exhibit this effect.
Does fluorescence affect the structural integrity of a diamond?
No. A diamond that fluoresces has the same integrity as a diamond that does not react to UV light. Submicroscopic substitutions and/or transformations within the diamond structure can either cause or inhibit fluorescence. Neither condition inherently weakens the diamond or negatively affects it.
