Approximately 25 % of all diamonds submitted to the GIA and EGL US exhibit some degree of fluorescence. Only a very small percentage of fluorescent diamonds have a level of intensity that negatively impacts brilliance and value.
Fluorescence is typically a bluish light diamonds may emit when excited by invisible UV rays.
95% of fluorescent diamonds emit blue light while 5% may generate a yellow or white reaction.
GIA studies conclusively indicate that fluorescence in the overwhelming majority of diamonds has no visible effect on brilliance. In fact certain buyers actually prefer the appearance of diamonds with ‘Faint, Medium or Strong’ fluorescence because these diamond tend to face up whiter than those without fluorescence and sell at a slight premium.
A very small number [less than 0.2% of all fluorescent diamonds] are graded ‘Very Strong’ fluorescence. These stones may face up hazy or oily and are significantly less valuable.