Flip over a diamond certificate, and you will find a line for fluorescence, usually followed by a word like faint, medium or strong. Plenty of buyers see it, feel a flicker of worry, and move on without really knowing what it means. Here is the plain version.
What fluorescence actually is
Fluorescence is the soft glow some diamonds give off when they are exposed to ultraviolet light, like the lights in a club or under a UV torch. Roughly a quarter to a third of diamonds show some level of it, and in the vast majority of cases the glow is blue. On a certificate it is simply an observation about the stone, not a quality grade, and only around one in ten fluorescent diamonds has it strongly enough to be worth thinking about.
Does it change how a diamond looks?
For almost every diamond, no. Research from GIA found that fluorescence has no widely noticeable effect on how a diamond looks in normal lighting, and in many cases people actually preferred stones with medium to strong blue fluorescence.
The fear is usually that it will make a stone look hazy or oily, but that has been found in fewer than 0.2 per cent of fluorescent diamonds. It can even help in lower colour grades, where a touch of blue can cancel out a faint yellow tint and make the diamond look whiter.
Where it affects price, and what to do about it
This is where it becomes useful for buyers. In higher colour grades, strong fluorescence is often discounted by something like 5 to 15 per cent, because the market tends to treat it as a drawback even when you cannot see any difference.
That means a diamond with medium or strong blue fluorescence can be a smart way to save, as long as the stone looks good to your own eyes. The one thing to avoid is buying on the number alone, so look at the diamond in person, in daylight and indoors, before you decide.
If you are comparing stones and the fluorescence line has you wondering, visit Azzallure. We will show you fluorescent and non-fluorescent diamonds side by side, so you can judge for yourself instead of guessing from a report.