Which element is responsible for blue coloration in some diamonds?

• A. Boron
• B. Nitrogen
• C. Phosphorus
• D. Carbon

Answer: (A)

Blue coloration in diamonds arises from boron impurities in the crystal lattice. When boron atoms replace some carbon atoms, they create electronic energy levels that absorb red light. With red wavelengths absorbed, the light that remains appears blue to our eyes. Natural blue diamonds are very rare, while synthetic ones achieve the effect through deliberate boron doping. Nitrogen impurities, on the other hand, tend to produce yellow or brown hues because they create different color centers in the lattice. Carbon is the base element of diamond and, when pure, yields colorless stones, so it itself doesn’t explain a blue color.