Hydroxyl defects and electrodiffusion (sweeping) in natural quartz crystals

High- and low-H samples of natural crystalline quartz in three different conditions, unswept, Na swept, and H swept, have been examined and analyzed for their low-temperature near-infrared spectra. The observed lines have been attributed to five defect types: Al-OH−, alkali-affected OH−, i.e., Li-H and Na-H; H-sweeping induced; and others. For both high- and low-H samples, the aluminum concentration and the grown-in Al-OH− ratios were found to vary over a limited range while those of alkali-affected OH− were much wider. The variation in Al-Li+ and Al-Na+ defect concentration ratios was also over a moderate range. The very narrow variation in the strength of grown-in Al-Li+ centers in the two types of quartz, high- and low-H, suggests that the Al-OH− centers in natural quartz crystals become stable only after a certain maximum concentration of Al-Li+ centers is reached. This reflects a characteristic feature of the growth mechanism of natural quartz crystals.