The purple coloration of amethyst is caused by the presence of an interstitial Fe4+ color center in the quartz (Rossman, 1994), combined with irradiation from natural gamma-ray sources. Irradiation creates color centers that absorb some light wavelengths and produce the very attractive tone seen in this material. The hourglass zoning distinctive of the Boudi mine is created when the iron is incorporated preferentially along the rhombohedral faces. During the growth of the crystal, with the development of the face, the purple sector assumes its typical form