Which colors may irradiation cause in diamonds?

• A. Red
• B. Yellow
• C. Blue, green, or pink
• D. Clear

Answer: (C)

Irradiation changes diamond color by creating color centers in the crystal lattice. When high-energy particles pass through a diamond, they displace carbon atoms and form vacancies and other defects. These defects alter how the crystal absorbs light, producing visible color. If the diamond is then heated in a controlled way, the defects become stable centers that give specific hues. The most common colors produced by this process are blue, green, or pink, because those defect configurations form readily under typical irradiation-and-annealing histories. Other colors like red or yellow aren’t the standard results of irradiation alone, and a completely colorless diamond would require no such defect centers to persist.