Fluorescence refers to the phenomenon where certain objects emit visible light, creating a glow. In the case of diamonds, some may exhibit fluorescence when exposed to long-wave ultraviolet (UV) rays, commonly from natural sources like sunlight. This fluorescence typically manifests as a bluish glow, though in rarer instances, it may appear as yellow or orangy light. Once the UV light source is no longer present, the fluorescence of the diamond ceases.
Approximately 25% to 35% of diamonds showcase varying degrees of fluorescence when subjected to long-wave UV light. The predominant fluorescence color observed in over 95% of these diamonds is blue, while a small fraction fluoresces in alternative hues like yellow or green.
Fluorescence serves as an identifying trait rather than a grading factor akin to the GIA 4Cs (color, clarity, cut, and carat weight). GIA Diamond Grading Reports and Diamond Dossiers provide insights into a diamond's fluorescence, detailing its intensity under long-wave UV light. The fluorescence intensity is categorized as None, Faint, Medium, Strong, or Very Strong. In cases where fluorescence is classified as Medium, Strong, or Very Strong, the color of the fluorescence is also documented for further clarification.
Some experts in the diamond industry believe that blue fluorescence can enhance the visual appeal of a diamond, especially those graded I to M in color. When exposed to ultraviolet (UV) light, which is present in natural daylight, faintly yellowish diamonds may appear more colorless due to bluish fluorescence. Consequently, diamonds with color grades ranging from I to N and exhibiting medium to strong bluish fluorescence may command a slightly higher per-carat price compared to similar-grade diamonds lacking fluorescence.
Conversely, for diamonds with higher color grades, typically falling within the D to H range, bluish fluorescence may be perceived as undesirable by some. There is a belief that such fluorescence might impart a hazy or oily appearance to the diamond. However, recent studies by the Gemological Institute of America (GIA) suggest that, in most cases, blue fluorescence has minimal to no impact on a diamond's transparency. Only in extremely rare instances, where a diamond possesses light-scattering defects like the Portuguese diamond, can fluorescence contribute to haziness. Nevertheless, these cases account for less than 0.2% of fluorescent diamonds examined by GIA.
Despite these findings, the perception that fluorescence affects clarity persists. Consequently, diamonds in the D to H color range exhibiting very strong fluorescence often sell for less than their non-fluorescent counterparts, even though their color and transparency are likely unaffected. These diamonds may represent a favorable purchase opportunity. If unfamiliar with the GIA Color Scale, consumers are encouraged to consult the Our Diamond Color Chart for further understanding.
Fluorescence itself does not induce haziness in diamonds. Instead, it can accentuate any pre-existing haziness resulting from light-scattering defects, thereby diminishing the contrast in the diamond's face-up pattern. However, it's important to note that such light-scattering defects are exceptionally rare. Therefore, for the majority of consumers, fluorescence is unlikely to affect a diamond's appearance under typical lighting conditions, even if the fluorescence is categorized as Strong to Very Strong. Nonetheless, it's advisable for consumers to physically inspect a diamond. Any haziness intensified by fluorescence, if present, would be discernible under lighting resembling daylight.
The main diamond at the center possesses an H color grade and exhibits fluorescence ranging from Strong to Very Strong. Adjacent to it, on both sides, are diamonds of the same H color grade but without fluorescence. Notably, there are no discernible variations in color or transparency among them.
To investigate the impact of blue fluorescence on diamond aesthetics, GIA researchers curated assortments of E, G, I, and K color-grade diamonds. Each group of diamonds was meticulously selected to maintain uniformity in all aspects except for the degree of blue fluorescence. Under controlled conditions, diamond assessors including trained experts and typical observers evaluated the diamonds' visual qualities. Findings suggest that, for the average observer representing the jewelry-buying public, no consistent effects of fluorescence were apparent. Overall, viewers tended to perceive strongly blue fluorescent diamonds as exhibiting more favorable color appearances when viewed from the top (table-up). However, the majority of observers did not discern any correlation between fluorescence and the diamond's transparency.
Displayed here are seven diamonds viewed under lighting conditions resembling natural daylight and long-wave ultraviolet (UV) illumination.
The presence of diamond fluorescence isn't inherently positive or negative. While some individuals may appreciate the beauty and allure of fluorescent diamonds, others may not share the same sentiment. Preferences regarding fluorescence vary widely among consumers.
If you're contemplating a diamond with bluish fluorescence, it's advisable to examine it under various lighting conditions, such as natural daylight, and compare it with other diamonds of similar color grades. Take note of any disparities in appearance and determine whether you find them appealing. Ultimately, personal preference plays a significant role in selecting the ideal diamond for you.
This exquisite brooch features numerous diamonds that emit fluorescence when exposed to long-wave UV light.
