Do all diamonds fluoresce under ultraviolet light?

• A. All diamonds fluoresce at ultra-shortwave UV.
• B. All diamonds fluoresce at shortwave UV.
• C. No diamonds fluoresce under UV.
• D. Most diamonds fluoresce under longwave UV.

Answer: (A)

Fluorescence is the emission of visible light by a diamond when it is illuminated with ultraviolet light. This phenomenon occurs only in some diamonds, not all, and the likelihood plus the color of the glow depend on the diamond’s impurities and lattice structure. The most common fluorescence is a blue glow, typically seen under long-wave UV (around 365 nm), but it can also occur under short-wave UV (around 254 nm) and can appear in other colors or be faint to very strong. In practice, roughly a quarter to a third of diamonds exhibit some fluorescence, while many show none at all. The key idea to remember is that fluorescence is variable and not universal; testing a diamond with a UV lamp will reveal whether it fluoresces and what color and intensity it show.