Laboratory experiments indicate radiogenic argon is not wholly driven off on prolonged heating but converges towards definite minimum values for each temperature. Atoms of radiogenic argon in the lattice of feldspars cannot diffuse spontaneously and can only migrate during reorganization of the lattice during unmixing or exsolution phenomena. Migration of radiogenic argon is subject to heterodiffusion theory while, simultaneously, telluric temperature currents or fluctuations exert much effect on radiogenic argon content and can therefore distort absolute age determinations.