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【 Jewellery 101】What is Diamond Fluorescence?

Updated: Jun 20, 2021

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

Diamond fluorescence is visible under UV light:

Is diamond fluorescence good or bad?

What fluorescence intensity is ideal?

Generally speaking, we recommend selecting diamonds with ‘none’ or ‘faint’ fluorescence, while diamonds of ‘medium’ or above fluorescence are not recommended. If a white diamond of D to G colour (meaning it’s relatively colourless) has strong fluorescence, it may appear hazy or oily even under natural daylight, hence diminishing the diamond’s clarity.

However, for white diamonds with a lower colour grading, such as J to M colour (meaning it’s more yellow), customers may consider purchasing diamonds of ‘faint’, ‘medium’ or even ‘strong’ fluorescence intensity, as the bluish fluorescence can compliment the yellowish undertones of a J-M coloured diamond, making it appear whiter.

On the other hand, fluorescence is not a major concern for fancy coloured diamonds, as their value chiefly depends on their colour while the impact of fluorescence is relatively small. In some instances, the fluorescence might even intensify the colour of a fancy diamond and increase its value.

Feel free to get in touch with Laine Jewellery for recommendations and advice on diamonds or customised rings! We also provide free diamond quotations and normally reply within 24 hours after you provide details of your budget and preferences.

Whatsapp: +852 6819 2038


Elaine 💌


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