ESR of E' centres in unstrained geological quartz grains.
E1' centres are detectable by ESR spectroscopy in unstrained quartz extracted from weathered rock of Cretaceous age. These centres completely disappear when the samples are irradiated with an artificial gamma-dose of about 200 Gy. The concentration of E1' centres thermally (re)generated at 310 degrees C can be reduced drastically under the influence of gamma-quanta, too. The gamma-radiation induces thermally unstable components in the quartz matrices that start to decay at around 100 degrees C.