Raman and optical spectroscopic investigation of gem-quality smoky quartz crystals

Rough samples and cut stones of smoky quartz from the Slovak Ore Mts. and the Tribeč Mts. were investigated by Raman and optical spectroscopy, electron microprobe and standard gemological techniques. Raman spectra of both cut stones and polished slices comply with already published data on quartz with the most prominent bands at around 463, 205 and 128 cm−1. The samples contain two-phase H2O-CO2 fluid inclusions aligned in crystallographically defined planes and also freely scattered. Optical spectra showed high absorption at violet-to-green region on [AlO4]4− group color centers and perceived brown color results from strong green-to-orange transmission with addition of red. Exposition time to natural irradiation also influences the color tone, hue and saturation. Gemological research on this material has confirmed that it is very suitable for jewelry. Our applied methodology and results documents advantages of Raman and optical spectroscopy in the research of smoky quartz as a gemstone.