What is the most common fluorescence color observed in diamonds under UV?

• A. Green
• B. Yellow
• C. Blue
• D. No fluorescence

Answer: (C)

Fluorescence in diamonds is the glow you see when UV light excites impurities and defects in the crystal. The most common color observed under UV is blue because the common defect centers—often related to nitrogen impurities—tend to emit blue light when energized. This blue emission is widespread in natural diamonds, so many stones fluoresce blue under UV lamps.

Green and yellow fluorescence do happen, but they’re less frequent and usually indicate different, rarer defect configurations or impurity mixes. Some diamonds may show no fluorescence at all if they lack the centers that produce visible emission, but blue remains the typical default when fluorescence is present.