The use of radiation to alter the appearance of a diamond, colored gemstone, or pearl. On a diamond or colored gemstone, radiation such as neutron or electron bombardment can change the internal structure and, therefore, the stone’s color and perceived clarity. This process is often followed by heating, which can further refine the results. Irradiation can create vibrant pink, yellow, green, and green/blue hues in diamonds, as well as beautiful blue topazes and red tourmalines. On certain pearls, such as freshwater or Akoya pearls, gamma ray treatments can generate darker gray, blue, or black colors.