Instead, these stains are restricted to areas surrounding the outer edges of zircons.Thus these diffuse radiation stains around the zircon crystals in these Stone Mountain xenoliths are probably due to decay, after granite cooling, of U and/or Th in the zircons that was included in the zircon crystals when they originally formed.Biotite schlieren were not collected.1 Samples were gently washed in distilled water to remove extraneous dirt and debris, although microscopic pine and other pollen grains remained (see arrows, Figures 4,5).Water was shaken from the samples and then they were allowed to air dry.
The diffuse, oblong patterns of the stains are probably because of the large sizes and oblong shapes of the zircons.
On the other hand, 42% of the biotite flakes from the granite samples yielded single-ring radiohalos (Figures 4, 5, 7). Ring diameters of 19.2 µm (micrometers) were measured which correspond to diameters reported for Po halos could not be determined due to them being so tiny as to be virtually impossible to see.
In some instances very dark and concentrated, essentially circular in cross-section, radiation stains were observed (Figure 8), but no zircons or other crystals surrounded by diffuse stains such as observed in the xenoliths were found.
About 50 tapes of biotite flakes from the granite samples and 50 tapes of biotite flakes from the xenolith samples were examined. The darker areas of the biotite are due to increased thickness of the biotite. Xenolith samples contained no identifiable, circular radiohalos with concentric rings.
Po radiohalo in Stone Mountain granite (120X magnification). Radiation stains were observed in xenoliths, but only always associated with microscopic crystal inclusions (probably zircons) (Figure 6).