Rhyolite from the “Yellow Stone of Nevșehir” and γ-irradiated trona from the Ankara Mine have been investigated by electron paramagnetic resonance at ambient temperature and at 113 K. Rhyolite was examined by X-ray powder diffraction and found to consist mainly of SiO2. Before γ-irradiation, the existing paramagnetic species in rhyolite were identified as ṖO42−, ĊH2OH, ĊO3−, ṠO2−, ĊO33−, and ĊO2- free radicals and Fe3+ at ambient temperature. At 113 K ṠO2- , ĊO33- , and ĊO2− radicals and Fe3+ were observed. The γ-irradiation produced neither new species nor detectable effects on these free radicals. The disappearance of some of the radicals at 113 K is attributed to the freezing of their motions. Before γ-irradiation, the trona mineral shows only Mn2+ lines, but after γ-irradiation it indicated the inducement of ĊO33− and ĊO2- radicals at ambient temperature, 113 K, in addition to the Mn2+ lines. The g and a values of the species were determined.
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