Radioactivity of neutron-irradiated cat’s-eye chrysoberyls

The recent report of marketing of radioactive chrysoberyl cat’s-eyes in South-East Asian markets has led us to use an indirect method to estimate the threat to health these color-enhanced gemstones may pose if worn close to skin. We determined the impurity content of several cat’s-eye chrysoberyls from Indian States of Orissa and Kerala using PIXE, and calculated the radioactivity that would be generated from these impurities and the constitutional elements if a chrysoberyl was irradiated by neutrons in a nuclear reactor for color enhancement. Of all the radioactive nuclides that could be created by neutron irradiation, only four (⁴⁶Sc, ⁵¹Cr, ⁵⁴Mn and ⁵⁹Fe) would not have cooled down within a month after irradiation to the internationally accepted level of specific residual radioactivity of 2 nCi/g. The radioactivity of ⁴⁶Sc, ⁵¹Cr and ⁵⁹Fe would only fall to this safe limit after 15 months and that of ⁵⁴Mn could remain above this limit for several years.