Among the manifestations of radioactive decay which can be etched to optical visibility on the surface of mica are tracks from nuclei recoiling from alpha emission, called ‘alpha‐recoil tracks’. If, beforeetching, the mica is heated to temperatures of the order of 600°C, all evidence of these tracks is annealed from muscovite mica in a few minutes. Alpha activity observed on mica from pot sherds, from stones surrounding fire places, from fire pits, and fired daub may constitute an alpha‐recoil track clock which started at the moment of the last firing of the a