It seems that the darker shades (ie Swiss and London, my very favorite shade) of blue topaz are the more affected types due to the way it is irradiated. But, topaz is not the only irradiated stone that could be affected - ie kunzite, tourmalines, diamonds. There is an interesting thread at the International School of Gemology Student Forums Board:http://www.yourgemologist.com/ISGForumsB...ac44ba90&t=2513
I have 2 London Blue Topaz stones. One over 20 years old and the other more recent, so I'll put that away until next spring since I don't know its true age. But, otherwise, I'm more leery of the nuclear power reactor in my county that a little stone I wear every now and then.