Diamond fluorescence is one of the most misunderstood characteristics in the diamond world. Some shoppers avoid it, others seek it out—but most don't really understand what it is. Let's clear that up. What Is Diamond Fluorescence? Fluorescence is the visible light some diamonds emit when exposed to ultraviolet (UV) rays. About 25-35% of diamonds exhibit some degree of fluorescence, and in almost all cases, the color is blue. Fluorescence Grades None: No visible fluorescence under UV light Faint: Barely detectable...