Fig. 4. Photo of a fracture in biotite in which migrating ²¹⁰Po and/or ²¹⁰Pb ions have created damage to the biotite lattice parallel to the fracture. This negates the hypothesis by Gentry that such damage along veins do not exist. Nevertheless, isolated halos are common and do not show connection to veins. (Image scale is different from image scale in Figs. 2 and 3.)