Round polished diamonds

Fluorescence in Diamonds

Fluorescence is a characteristic of diamonds that is often misunderstood. Simply put, fluorescence is a phenomenon that causes diamonds to emit a soft coloured glow when exposed to ultraviolet (UV) light. We are exposed to this UV light everyday through sunlight and in the light produced by fluorescent light bulbs. Fluorescence is caused by the presence of Nitrogen, and is a natural characteristic that affects nearly one third of all gem grade diamonds.

Two factors should be considered when looking at a diamond’s fluorescence, namely colour and strength of fluorescence.


The most common colour of fluorescence is blue (95%), followed by yellow. Other colours of fluorescence are rare. When a diamond fluoresces blue it has a tendency to appear whiter in colour than its true body colour. This is a good thing as it makes the diamond appear of a higher colour quality colour than it actually is.
If the diamond fluoresces yellow, the diamond will look lower in colour in ultraviolet light, so it is seen as a negative factor.


The second factor to consider is the strength of fluorescence, which varies from none, faint and medium to strong and very strong. GIA studies have shown that, for the overwhelming majority of diamonds, the strength of fluorescence has no widely notable effect on appearance.

Some diamonds have extremely strong fluorescence and appear oily or cloudy even in normal lighting conditions, giving the diamond a dull appearance.

Is fluorescence good or bad?

Fluorescence can have either a positive or a negative effect on the colour and overall look of a colourless diamond when viewed in natural daylight. Colourless diamonds with high colour gradings (D, E or F), exhibiting medium to strong fluorescence, can sometimes appear cloudy or ‘oily’ in direct sunlight. Diamonds with low colour gradings (around I or J), especially those with a yellowish tint, can appear one or two grades better in colour because of the masking effect of blue fluorescence.

Fluorescence and value

The effect of fluorescence on the value of a colourless diamond depends on its strength and colour. A strong yellow fluorescence may bring diamond prices down, while a blue fluorescence can help increase the price of diamonds with yellowish tones.

Does your diamond have fluorescence?

The best way to confirm without doubt whether your diamond is fluorescent or not is to look it up on the diamond certificate. Diamonds certified by the GIA and EGL will clearly state the presence of fluorescence in the diamond. If fluorescence is marked as ‘none’ on your diamond certificate, then your diamond does not have fluorescence. If fluorescence is present in the diamond, the certificate will state ‘faint’, ‘medium’, ‘strong’ or ‘very strong’.

GIA Certificate Fluorescence in Diamonds

Although most people often choose a fluorescent diamond over a non-fluorescent stone, one should not let fluorescence be a major influence your choice when selecting a diamond. Diamond fluorescence is a natural phenomenon and is best judged by considering the diamond on its own visual qualities and characteristics.

Diamond fluorescence under normal light
diamond fluorescence- under uv light