There are a number of misconceptions around diamond fluorescence, which we address below. Ultimately, any gem should be viewed in a variety of lighting environments in order to choose the right one for each individual’s taste. It is said that beauty is in the eye of the beholder, and diamonds are no exception.
First off: what is fluorescence?
Sometimes trace elements of aluminium, boron, or nitrogen are absorbed by a diamond as it forms. These elements are what gives off a fluorescent glow when exposed to UV light.
Misconception 1: Don’t all “real” diamonds fluoresce?
In fact, most don’t, and some synthetics do! Researchers conducted a study of more than 26 000 diamonds submitted for grading to the Gemological Institute of America (GIA), and found that only about 25% to 35% exhibited some degree of fluorescence when examined with a standard long-wave UV lamp. Even reputable grading laboratories, following strict protocols and adhering to set standards in describing the intensity of fluorescence, might not find fluorescence that is strong enough to be observed in natural diamonds. Some lab grown diamonds and certain diamond “impersonators” like cubic zirconia do also fluoresce, although differences have been observed in the intensity, colour and pattern of fluorescence between natural and synthetic diamonds.
Misconception 2: You can see diamond fluoresce with the naked eye, under any lighting
Nope! Diamonds that do fluoresce will only put on that blue light show when exposed to invisible UV rays (as well as other higher energy radiation sources like X-rays or lasers). So while you may see a diamond fluoresce under bright sunlight (which contains about 10% UV light), any other visible fluorescence ‘in the wild’ is likely due to a UV or blacklight in the vicinity that isn’t immediately obvious, or the reflection of a clear blue daytime sky or a blue object nearby like a painted wall. Incandescent lighting will not cause a diamond to fluoresce.
Misconception 3: A diamond’s colour grading is always affected by its fluorescence
The GIA inspects each diamond in a viewing environment that is highly controlled and designed to minimise the influence of fluorescence on its colour grading. While the system maximises chances of an accurate and objective assessment of a diamond’s colour, perception of a diamond’s colour grade can, in certain cases, be positively affected by the extent to which it fluoresces. For instance, a yellow-tinted diamond that grades lower on the GIA’s D-to-Z scale might display a better colour than its grading indicates if it also features a moderate-to-strong blue fluorescence, which helps to offset some of the colouration present.
Misconception 4: A diamond’s fluorescence can be graded
The GIA considers fluorescence to be an identifying characteristic only, and not one of the qualities of diamond grading (which includes only colour, clarity, cut and carat weight – or the “4Cs”). Fluorescence is seen merely as an additional piece of information that helps distinguish diamonds, and is categorised into None, Faint, Medium, Strong and Very Strong. Only the higher three intensities (and the colour they fluoresce) are included on diamond grading reports.
Misconception 5: Diamond fluorescence appears blue only
While blue is by far the most common hue, diamonds also fluoresce in yellow, yellow-orange, orange, red, white and green. This is influenced by variations in the diamond’s atomic structure.
Misconception 6: It’s bad for a diamond to show strong blue fluorescence
The opposite can in fact be true. Studies show that the jewellery buying public can’t consistently identify any fluorescence-related effects when viewed in everyday environments. However, as mentioned in point 3, occasionally (when viewed table-up) certain strongly blue-fluorescing stones can be perceived to show a whiter colour than their assigned colour grading.
Misconception 7: Strong fluorescence can harm a diamond’s durability, and beauty
Research shows fluorescence has no impact on sparkle, which is achieved through the manner in which a diamond is cut. The angles and proportions of its facets mainly determines the play of light and sparkle of a diamond. Fluorescent diamonds have the same structural integrity as ones that don’t. Nothing in the submicroscopic structures that cause fluorescence inherently weakens a diamond.
Misconception 8: Fluorescence inherently affects any diamond’s value
This ultimately boils down to the personal preference of the average jewellery buyer, and the individual diamond’s characteristics. Some diamonds benefit from a little fluorescence, while others don’t. Trade professionals will sometimes place less value on extremely strong blue-fluorescing diamonds at the high end of the D-to-Z colour scale, if their clarity is affected and they appear milky or oily. On the other hand, blue fluorescence in lower colour grades can make the diamond appear whiter as mentioned above, and therefore cause these gems to fetch a higher price.
And lastly, a word to the wise:
Unethical salespeople have in the past abused the average jewellery buyer’s ignorance of fluorescence in higher colour grades. Beware of traders pushing what they term ‘blue-white’ diamonds – this is an invented sales gimmick used to sell strongly-fluorescing diamonds as “better”, which is nonsense. The term has actually been banned by the US Federal Trade Commission.
*Credit: the majority of this article’s content was adapted from the GIA website