Diamond fluorescence is often misconceived as one of the characteristics of a diamond. Fluorescence is diamond's tendency to emit a soft coloured glow (mostly blue) when exposed to ultraviolet UV light. Diamonds with fluorescence mostly radiate a bluish but on rare occurrences this glow tends to reflect white, yellow, green or at times red. 30% of all diamonds and gemstones have fluorescence. Traces of some naturally occurring elements, such as Boron causes fluorescence in a diamond that can affect its visual appearance. Fluorescence has a whitening effect, particularly in lower grade diamonds. But in higher grade diamonds the same can cause the diamond to show a grey tint.
According to GIA research and studies conducted, they found little evidence that fluorescence had a visual impact on the diamond’s appearance. Therefore the structural integrity of a diamond stays unhindered by traces of fluorescence.
GIA has developed a standardised Diamond fluorescence grading scale. Approximately 30% of all diamonds have fluorescence however only less than 1% of these 30% diamonds may affect the appearance due to fluorescence ranging from average to very strong.
None: No traces of elements that cause fluorescence are found when exposed to UV light. None fluorescence grade are highly desired and hence carry a much higher premium
Faint: Because of minor traces of elements a faint blue glow is detected when the diamond is exposed to UV light. There is no impact on the diamond. Faint fluorescence grade has the same pricing as that of none grade.
Medium: In this scalea light blue glow is emitted by a diamond, when exposed to UV light. Medium fluorescence offers an excellent value, particularly of lower colour grades such as J, K or L as it has an effect of improving the colour. They fetch lower price.
Strong: A vivid blue glow is radiated by the diamond when exposed to UV light. Diamonds with Strong fluorescence may have an effect of slightly improving the colour of lower gradeslike J, K or L. Conversely, it can have a negative effect on higher color grades D, E, adding a greyish tint. Because of this they are priced lower.
Very Strong: Intense bright blue glow shows off the diamond when exposed to UV light. Very strong fluorescence can affect the diamond’s appearance by adding a hazy dull lacklustre.
EFFECT OF FLUORESENCE ON SPARKLE AND PRICE
As per GIA studies, there is only a slight evidence that fluorescence has an effect on a diamond’s sparkle. Thought it is generally recommended to avoid fluorescence especially ranging from medium to very strong in high colours such as D, E or F as it affects the appearance by adding a hazy greyish tint. Conversely, it is actually recommended to consider fluorescent diamonds in I, J, K or L colour grade as it improves the colour.
Considering pricing of a diamond, strong fluorescent diamonds have about a 10% to 15% discount against Faint or None fluorescent diamonds.