Diamond Fluorescence is a naturally occurring phenomenon that enables a diamond to emit a soft glow, usually blue, when it is subjected to ultraviolet light. 

You may find that when you stand near a blue light or ultraviolet light you notice peoples teeth and white of their eyes become brighter or appear to glow. This is the same effect that UV light has on some diamonds. Fluorescence is what the visible light is called that the diamond emits when exposed to the UV rays.

On a GIA diamond grading report, fluorescence refers to the strength or intensity of the diamond’s reaction to the UV light. The GIA scale uses the following grades: None, Faint, Medium, Strong, Very Strong. 

The fluorescence grade will also include the color, e.g., “Medium Blue”. The most common color of fluorescence is blue, but other colors are possible depending on the trace elements within the diamond’s crystal structure.

Diamond fluorescence is actually quite common and occurs in bewteen 25 - 35% of all diamonds. Of the diamonds that exhibit fluorescence 95% emit a blue glow. 

Does Fluorescence matter?

The first and most important thing to remember is that fluorescence is almost always an invisible property of the diamond. In the vast majority of situations, fluorescence has no impact at all on the visual beauty of a diamond. 

Except for the grade noted on the diamond’s certificate, the typical diamond wearer will never see the fluorescence of their diamond in the course of a lifetime. This is true of diamonds with a grade of Faint or Medium fluorescence. In fact, diamonds in the near colorless and faint yellow ranges that exhibit some fluorescence will actually appear whiter than stones of equal color without fluorescence.

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.

Should I purchase a diamond with Fluorescence or not?

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.

Why do some jewellers recommend avoiding any type of fluorescence? Quite simply it is easier to tell a customer that fluorescence is bad and to avoid it than to actually educate themselves or their clients on the facts. The bottom line on fluorescence is that in the Faint and Medium Blue ranges, it is not a characteristic that should cause any concern to you as a buyer.