Fluorescence In Diamonds

Some diamonds have a colouring that is evident under strong Ultra Violet light. This colouring is called fluorescence and there is much discussion about its impact on a diamond’s performance, colour and price. Fluorescence is most commonly a blue colour but there is also a rare yellow that is more common in fancy coloured stones. diamond fluorescence comes in varying degrees of colour which are only detectable under strong Ultra Violet light. The level of fluorescence is reported on the diamond certification, if not then ask for a proper certificate (GIA, AGS, HRD, IGI, EGL). Levels of fluorescence are described as ‘None’, ‘Faint’, ‘Slight’, ‘Medium or Moderate’, ‘Distinct’, ‘Strong’ and ‘Extreme’.

So is fluorescence in a diamond good or bad?

Evidence shows that because white diamonds progress in the colour charts to a yellow hue and fluorescence is primarily blue and a complimentary colour to yellow, this blue fluorescent colouring can actually improve the colour of a diamond by a grade or two. Having faint to medium fluorescence will not impact on the performance of a diamond and can make them appear whiter and closer to colourless. The market has discounted faint to medium fluorescence in diamonds by up to 20% regarding fluorescence as a type of inclusion although unnoticeable and non performance restricting. Fluorescence can not be seen under normal conditions and also give the diamond a unique finger print for security checks. In the southern hemisphere (Australia, South Africa/America and New Zealand) where there is more Ultra Violet light because of ozone depletion, slight to medium fluorescence does make diamonds appear whiter and this can only be a bonus!

When a diamond contains distinct, strong or extreme fluorescence it can make the stone appear oily, poorly polished and this can affect light performance. We would recommend clients to be careful with diamonds that have distinct, strong or extreme fluorescence. The negative attributes of having distinct and strong fluorescence are greater than the above mentioned positive. In saying that there is a substantial saving of up to 25% for these diamonds and they are only recommended after professional consultation which we are happy to provide. We would like to stress that we have seen and sold some spectacular diamonds with strong fluorescence and each individual stone must be judged on its own merits. Forty years ago, when we first joined the diamond industry the diamond to own was a ‘BLUE-WHITE’ diamond, i. e. a diamond with strong-blue fluorescence – it’s a fickle old world.

It is quite intriguing that diamonds that fluoresce are very rare and as we mentioned in earlier sections the scarcity of colour, cut, carat and clarity drive up the price of diamonds. It is interesting that having this natural and rare phenomenon actually decreases the price! Our expert opinion is that having faint to medium fluorescence is fine in diamonds from G to J as the colour could be improved at a reduction in price. Having strong, distinct and extreme fluorescence is not desired. For the purest looking for a D-IF that’s a D Flawless ‘the best a girl can get’ fluorescence will not improve your diamond so why bother? Well because any fluorescence in the stone will reduce the price of a diamond so be smart but avoid distinct, strong or extreme fluorescence unless we or our agents have approved it.