When exposed to the ultraviolet rays, if a diamond emits light, we call it presence of fluorescence in the diamond. The presence of fluorescence could provide good as well as worse effect to the pricing of a diamond. If found present in better colors, it reduces brilliance and if found in weaker colors, it improves brilliance. Presence of fluorescence can be there in colors like white, blue, yellow, orange and green which can directly create an impact on the overall color of a diamond followed by its pricing. In most of the cases, the presence of fluorescence is sometimes considered ‘negative’ but in real sense, it rarely affects diamond’s sparkle and brilliance and in warmer or soft colored diamonds, it makes them look white or colorless. So, it would be an injustice to apply same rulebook for diamond grading in the case of fluorescence. The diamonds having extremely strong fluorescence look oily or cloudy. This gives a bad effect to the overall look of a diamond. Rarely diamond carries fluorescence of other colors like yellow or orange. Sometimes, colorless diamonds with yellow or orange fluorescence appears to be of a lower color when seen in light through UV component. In case of turning of UV light source, fluorescence ceases instantly but some stone continue to phosphoresce for a little time.