Cathodoluminescence of moldavites

• Published in: Meteoritics & planetary science 2017-07, Vol.52 (7), p.1428-1436
• Main Authors: Fritzke, B., Götze, J., Lange, J.‐M.
• Format: Article
• Language: English
• Subjects: Band spectra; Banded structure; Cathodoluminescence; Color; Crystal defects; Crystal structure; Defects; Emission analysis; Emission spectroscopy; Excitons; Glass; Inclusions; Luminescence; Microscopy; Moldavite; Optical properties; Oxygen; Quartz; Shades; Silica; Silica glass; Silicon dioxide; Spectral analysis; Spectral emissivity; Spectroscopy; Spectrum analysis
• ISSN: 1086-9379; 1945-5100
• DOI: 10.1111/maps.12852

A systematic study of a large set of moldavites and the application of cathodoluminescence (CL)‐spectroscopy with a detailed discussion of spectral features is presented. Optical CL microscopy and spectroscopy (OM‐CL) were performed on 57 moldavite samples from different substrewn‐fields in Germany and the Czech Republic. The extracted CL data were supported by SEM‐EDX analysis. In general, two different kinds of CL colors can be distinguished: different shades of green in the matrix of the tektite glasses and a variation of blue color for lechatelierite inclusions (a pure silica‐glass phase). Spectral analysis of these colors shows three CL emission bands for green and five bands for blue c. Most CL activators are structural defects of the local glass network, influenced by the crystal field. The visible green CL emission is caused by defects related to strong local disorder as well as Al‐O−‐Al defects. The blue CL emission is activated by different types of lattice defects such as nonbridging oxygen‐hole center (NBOHC), self‐trapped excitons (STE), and oxygen deficiency centers (ODC). Intensity variations of the CL emissions were observed for samples from the different localities, but there is no direct correlation between substrewn‐fields and CL characteristics. Nevertheless, CL microscopy is a powerful tool for the high‐contrast visualization of internal textures such as streaks and lechatelierite in the tektite matrix due to the luminescence properties of the defect structures in the glassy network.