Optical analysis, including absorption spectra, photoluminescence (PL) and photoluminescence excitation (PLE), has been performed on natural silica sample `as grown' and UV-irradiated with pulsed KrF excimer laser (5 eV). By synchrotron radiation source we detected the well known α and β emission bands and their excitation spectra at room temperature (RT) and at 10 K (LT). Comparing measurements on irradiated and not-irradiated samples, bleaching of these bands is clearly shown. We hypothesize the observed bleaching of PL bands could be partially correlated to the generation of E′ absorption band in UV-irradiated silica sample.