【 Jewellery 101】What is Diamond Fluorescence?

Updated: Jun 20

One thing you need to know besides the 4Cs

However much you like fluorescent colours, you wouldn’t want your diamond to have ‘fluorescence’. What exactly is it? When selecting a diamond, apart from taking note of the 4Cs (colour, clarity, carat, cut), you should also check whether it exhibits fluorescence, which may affect the clarity, appearance or even the value of the diamond.

‘Fluorescence’ Explained

Diamond fluorescence is a glow or illumination some diamonds emit under UV light. Fluorescence occurs when trace amounts of three elements — aluminium, boron or nitrogen — are absorbed by the diamond during its formation. If these trace elements were exposed to natural radiation in the earth’s crust, they will emit energy in the form of light under ultraviolet rays. The glow is most commonly blue, but can also appear in various other shades such as yellow, orange, pink, etc.

Based on a study by GIA, about 25% to 35% of natural diamonds exhibit some degree of fluorescence, but only 10% are of medium to very strong intensity. Simply put, the value of a diamond which exhibits fluorescence would be around 10-30% lower than a diamond of the same 4Cs but without fluorescence.

Can fluorescence be observed by the naked eye?

The fluorescence in diamonds is only visible when it is exposed to ultraviolet light or other high energy radiation sources, such as X-ray and laser, in a dark environment. In certain stronger UV lighting in daily life, such as bright sunlight, a dark nightclub with UV lights, tanning beds, etc, one may also be able to see a diamond fluoresce, but in normal situations such as regular daylight or interior lighting, faint fluorescence is normally not detected by naked eye.

Does fluorescence also have gradings?

GIA considers diamond fluorescence an identifying characteristic. It is not a grading factor like the GIA 4Cs. A diamond’s fluorescence is described by its intensity:

  • None

  • Faint

  • Medium

  • Strong

  • Very Strong