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What is Diamond Fluorescence? Should I worry about it when choosing a diamond?

Hand with Engagement Ring

What is Diamond Fluorescence?

Diamond fluorescence is an often misunderstood but important attribute of a diamond. Fluorescence refers to the soft glow that may be seen when a diamond is under ultra-violet (UV) light (i.e. sunlight or black light). Approximately 30% of natural diamonds have a degree of fluorescence. This usually displays as a blue glow but in rare cases can be white, yellow, green or red. Though it is unknown what exactly causes it, fluorescence comes from the inclusion of trace elements naturally contained within a diamond during the carbon crystallisation process.

Fluorescence is one of the only ways to distinguish between a natural and lab grown diamond. It is extremely rare for a lab grown diamond to display any fluorescence.

The GIA grades the fluorescence of diamonds using the following scale:

Frequent nightclubs or raves? Fluorescence is rarely seen unless a diamond is under heavy UV lighting (black lighting). Take a look below and click the “on and off” button to view how a diamond will brightly illuminate when viewed under a UV light!

Diamond without Fluorescence


No fluorescence, no influence on colour.

Diamond without Fluorescence


Weak fluorescence, not a significant influence on the colour (barely perceptible).

Diamond without Fluorescence


Average fluorescence, small influence.

Diamond without Fluorescence


Strong fluorescence, substantial colour influence.

Diamond without Fluorescence

Very Strong

Very strong fluorescence, substantial colour influence.

Does Fluorescence Affect Value?

In a small number of diamonds, very strong fluorescence can create a cloudy appearance. This reduces the value of the diamond. In other diamonds, the blue fluorescent glow can offset the yellow tint found in diamonds of I-M colour, making them appear up to one grade whiter and increasing their value.

It may be worth exercising caution if a colourless diamond with a grade of D-F presents fluorescence under UV light. Due to their lack of colour, they do not possess enough body colour to offset the degree of fluorescence. For this reason, the fluorescence is labelled a flaw and the diamond is of lesser value.

Front view of an Engagement Ring

Should I Buy a Fluorescent Diamond?

Overall, diamond fluorescence should not be a huge factor in the purchase of a diamond, especially when the effects are negligible. According to studies performed by the GIA, fluorescence has no visual impact on a diamond’s appearance or structural integrity. In the end, the four C’s are much more important than fluorescence when purchasing a diamond.

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