Origin, spectral characteristics and practical applications of the cathodolumimescence (CL) of quartz - a review

Investigations of natural and synthetic quartz specimens by cathodoluminesc ence (CL) microscopy and spectroscopy, electron paramagnetic resonance (EPR ) and trace-element analysis showed that various luminescence colours and e mission bands can be ascribed to different intrinsic and extrinsic defects. The perceived visible luminescence colours in quartz depend on the relative intensities of the dominant emission bands between 380 and 700 nm. Some of the CC emissions of quartz from the UV to the yellow spectral region (175 nm, 290 nm, 340 nm, 420 nm, 450 nm, 580 nm) can be related to intrinsic lat tice defects. Extrinsic defects such as the alkali (or hydrogen)-compensate d [AlO4/M+] centre have been suggested as being responsible for the transie nt emission band at 380-390 nm and the short-lived blue-green CL centered a round 500 nm. CC emissions between 620 and 650 nm in the red spectral regio n are attributed to the nonbridging oxygen hole centre (NBOHC) with several precursors. The weak but highly variable CL colours and emission spectra of quartz can be related to genetic conditions of quartz formation. Hence, both luminesce nce microscopy and spectroscopy can be used widely in various applications in geosciences and techniques. One of the most important fields of applicat ion of quartz CL is the ability to reveal internal structures, growth zonin g and lattice defects in quartz crystals not discernible by means of other analytical techniques. Other fields of investigations are the modal analysi s of rocks, the provenance evaluation of elastic sediments, diagenetic stud ies, the reconstruction of alteration processes and fluid flow, the detecti on of radiation damage or investigations of ultra-pure quartz and silica gl ass in technical applications.