Method of producing gemstone quality topaz

In a method of producing a blue colored topaz by irradiating the topaz in a fast neutron environment and thereafter irradiating the neutron treated topaz with electrons or gamma rays, the improvement which comprises irradiating the topaz in the fast neutron environment at elevated temperature to an exposure level of at least about 10.sup.17 cm.sup.-2 to thereby produce a neutron irradiated topaz which does not exhibit a blue coloration and then subjecting the colorless neutron treated topaz to the electron or gamma ray irradiation.