Fluorescence is a natural characteristic which causes many diamonds to glow under ultra violet light (UV), this is abundant in natural daylight and some artificial lighting.

Fluorescence is caused by sub-microscopic structures within the diamond. Diamonds can have various colours of fluorescence, with blue being the most common.

Yellow Fluorescence can sometimes indicate a Cloud which is cluster of pinpoint inclusions creating a hazy or milky area in a diamond.

A diamond cloud can range from extremely sparse and faint, to dense and heavy.

Clouds may also be small and localised, or spread throughout an entire diamond and affect the transparency.

In most diamonds, Fluorescence will not have a negative affected the brilliance or transparency of the diamond.

Diamonds which are lower in colour look whiter if they have medium to strong blue Fluorescence and are very desirable.