This should not be a concern with Sapphire. Although Sapphire is
sometimes Irradiated to change the color, it is not know to be a
permanent color change as far as I am aware and I believe it would
have little to no effect on Purple Sapphire.
As for Topaz, this gemstone is know to be Irradiated, heated and a
combination of the two in order to produce the different shades of
blue. This is a permanent treatment.
Custom Jewelry - Handmade Jewelry - Antique Jewelry