Often we look at diamond appraisals and see what is called “fluorescence”. Many people are confused as to what fluorescence means and how it affects a diamond’s value. Fluorescence is a soft-coloured glow that usually emits from diamonds when it is subjected for ultraviolet light. The fluorescent glow is mostly blue, and it has the ability of making diamonds that range from colour grades of I-M appear a grade whiter than that without fluorescent.
According to a GIA study, about 30% of diamonds have fluorescence however only a gemologist using a special UV light source can detect the effect of ones that range from Faint to Medium. The value of a diamond being affected by fluorescence depends on the colour grade of the diamond. As stated previously, the fluorescent can make diamonds seem a grade whiter therefore adding value to the diamond, or if the fluorescent shows in colourless diamond (D-F), it can be perceived as a defect so a minor percentage of the value would be deducted from the price. The fluorescent in these diamonds may make them appear hazy or oily, which results in it being less desirable.
This chart provides some insight as to what one would see when holding a diamond under UV light.