> > Natural Uranium isn't actually all that radioactive. Radium, > > Thorium or even common Potassium are more so. > I figured as much; Uranium just came to mind first, i s'pose. But there > could be naturally occurring radiation that might achieve the same > effect, correct? Not as well now as in the distant past. See: http://www.curtin.edu.au/curtin/centre/waisrc/OKLO/What/U2.html