Study on the Microstructure and Spectra of Regrown Quartz Crystals from Chinese Jewelry Market

Regrown quartz crystals consist of the natural section and the synthetic section grown by hydrothermal technique, which has become popular on the Chinese jewelry market in recent years. Similar gemological properties to those of natural quartz have brought challenges to gem identification and also new questions to scientific research. In this study, microstructure and spectral characteristics of the two sections of regrown quartz crystals were investigated by three dimensional computed tomography system and infrared spectroscopy. Results showed that the natural section has a higher porosity and there are also many micron- to millimeter-sized pores on the interface of the two sections. Different infrared absorption peaks of the two sections at the 3300–3600 cm−1 range were mainly attributed to the different existence state of OH groups. The distinction of microstructure and spectral characteristics between the natural and synthetic sections indicate their different growth condition. Compared with natural quartz, a relatively stable growth environment during the synthetic process leads to a lower porosity and the alkali growth solution could result in the change of the existence state of OH groups in the regrown quartz crystals.