The origin of the smoky colour acquired by quartz when exposed to extremely high doses (20kGy) of ionising radiation was studied. Five paramagnetic centres were detected in the electron paramagnetic resonance spectrum of irradiated quartz: [AlO4]0, [TiO4-/Li+]0A, [GeO4-/Na+]0A, [GeO4-/Li+]0C, and E1’. Optical absorption revealed a complex spectrum with superposition of bands. With the technique of thermoluminescence, at least 3 peaks at around 180, 260 and 320C were detected. The peak at around 180C had maximum emission at 470nm and the peaks at around 260 and 320C have maximum emissions at 450nm. Through correlations between the obtained results with these techniques, it was possible to confirm previous results from the literature, i.e., that the smoky colour of quartz was strongly related to the centre [AlO4]0. Besides, an excellent correlation between the thermal decay of [AlO4]0 and [TiO4-/Li+]0A was verified, suggesting that - at around 200C - the Li left the Ti centre and recombined with the Al centre; destroying the smoky colour of irradiated quartz.

The Role of Aluminium and Titanium in the Point Defects of Gamma Irradiated Natural Quartz. G.O.Sawakuchi, E.Okuno: Physica Status Solidi C, 2005, 2[1], 588-91