title: ESR of E' centres in unstrained geological quartz grains.
abstract: 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.