At which ultraviolet wavelength do all diamonds show fluorescence?

• A. All diamonds show fluorescence at ultra-shortwave UV.
• B. All diamonds show fluorescence at shortwave UV.
• C. No diamonds fluoresce under UV.
• D. Only colored diamonds fluoresce under UV.

Answer: (A)

Ultraviolet fluorescence in diamonds comes from photons exciting defects or impurities in the crystal, which then emit visible light as they return to the ground state. Ultra-shortwave UV carries very high-energy photons, and this energy is sufficient to trigger fluorescence across a wide range of diamonds regardless of their color or specific impurity content. That universal response under ultra-shortwave UV is why this option is considered the best answer. Under other UV ranges, fluorescence can vary a lot: some diamonds may fluoresce, others weakly or not at all, and colorless stones can fluoresce just as blue-fluorescence-prone stones do, but not universally.