Production of high-purity quartz concentrate from low-transparency vein quartz

The expanding range of applications for high-purity quartz has intensified the search for alternative sources of quartz raw materials and the development of advanced beneficiation technologies. Industrial processing of non-traditional quartz types—such as milky-white vein quartz and quartzites—has demonstrated the potential to produce quartz concentrates of acceptable quality. This study presents the results of deep beneficiation experiments on low-transparency vein quartz from the Girvas area (Central Karelia), where native quartz veins are extensively distributed. Chemical analysis, optical microscopy, and scanning electron microscopy were used to investigate the mineralogical and technological properties of the quartz, informing the selection of the most effective processing strategy. The presence of numerous gas-liquid inclusions and finely disseminated mineral impurities within the quartz grains significantly hampers the efficiency of conventional beneficiation methods. To address this, a multistage process was applied, including electromagnetic separation, sequential acid leaching with HCl and HF, and ultrasonic dispersion in an aqueous medium. This approach produced a quartz concentrate with a total impurity content of 143 ppm. The introduction of microwave treatment as an additional processing step for quartz grits led to a further reduction in impurity levels. The resulting concentrates are suitable for various applications, including the production of specialized quartz materials. A final concentrate with a total impurity content of 34.6 ppm meets the specifications for high-purity grades KGO-1 and KGO-2. It is suitable for the production of transparent quartz glass used in semiconductors, fiber optics, microelectronics, and lighting technologies.This research was supported by federal funding under the state assignment of the Institute of Geology, Karelian Research Centre of RAS.