Diamond Fluorescence

The term ‘fluorescence’ describes the visible light that emits from a diamond under long-wave ultraviolet (UV) or ‘blue’ light. In the same way that your teeth or a white t-shirt would glow under a UV light, diamonds can show varying reactions – from no effect, to a strong glow (see image above). Fluorescence is a common natural characteristic of many diamonds and does not affect the structural integrity of the diamond in any way. According to the Gemological Institute of America (GIA), 25% to 35% of diamonds exhibit fluorescence to some degree and 10% exhibit medium, strong or very strong fluorescence. In the vast majority of diamonds, the colour reaction to UV light is blue, because blue is the complimentary colour to yellow. In rare cases, the reaction can be yellow or another colour.

In their diamond grading reports, The Gemmological Institute of America (GIA) places diamonds in five categories of fluorescence:

None
Faint
Medium
Strong
Very Strong

Only 2 out of 1000 diamonds exhibit extremely strong fluorescence that could result in an oily or hazy appearance. At diamonds.co.nz we have chosen not to sell ‘Very Strong’ fluorescence because of this. Under normal daylight, the average person cannot make a distinction between a diamond with fluorescence and a diamond without (The GIA Fluorescence Study). In some cases, and indeed in our personal experience, diamonds with a lower colour (J-M) often appear whiter in normal daylight when they have medium or strong fluorescence. Studies conducted by GIA, showed that for the vast majority of diamonds, the strength of the fluorescence has no noticeable effect on its appearance. In fact, in these studies it was shown that in many cases, observers actually preferred the appearance of diamonds with medium to strong fluorescence.

It is the overall appearance of the diamond that is most important – and the ‘4 C’s’, especially the quality of the cut has the most impact.

*Image credit: GIA.edu