A potential 4N8-Grade raw material for high-purity quartz from quartzite ore in the Hengshan region, central-southern China: A geochemical-mineralogical study and purification

This study evaluates the high-purity quartz potential of the Jiulongquan quartzite (sample JLQ-D2) from the eastern Nanyue pluton in the Hengshan area, China. This ore is yellowish-brown with low transparency and exhibits a relatively uniform grain size of less than 2 mm. A series of purification processes, including calcination, crushing, screening, ultrasonic desliming, gravity separation, magnetic separation, flotation, and high-temperature acid leaching, were applied to produce a refined quartz concentrate. The microstructure, fluid inclusion characteristics, and chemical composition of both the raw ore and the purified concentrate were analyzed using optical microscopy, scanning electron microscopy (SEM), X-ray fluorescence (XRF), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and ICP-MS. Additionally, the formation environment of the high-purity quartz (HPQ) source rock was discussed. Petrographic examination reveals that quartz is the dominant mineral, exhibiting low idiomorphism. In the post-flotation concentrate, fluid inclusions were predominantly two-phase (liquid–vapor), with rare pure liquid inclusions, and were distributed in bands, planes, and clusters. After purification, most quartz grains were free of inclusions, showing a significant reduction in inclusion content. Chemical analysis indicated that the main impurity elements in the raw ore were Al, K, Fe, and Na, with total impurities exceeding 100 mg·g −1 . Aluminum was the most abundant impurity, at approximately 14.7 mg·g −1 . After purification, the total impurity content of the concentrate was reduced to about 17.14 ppm of very high grade of purity of quartz sand, with specific concentrations of Al (10.1 ppm), Ca (0.05 ppm), Fe (0.95 ppm), K (0.57 ppm), Na (2.47 ppm), and Li (0.83 ppm). The SiO 2 purity reached a 4N8 level of 99.998 %. The significance of this study lies in its demonstration that the quartzites are a promising source of high-purity quartz, with substantial potential for large-scale extraction and processing. Additionally, it underscores the importance of the local geology and metamorphic conditions that contributed to the formation of these high-purity quartz deposits. • The Jiulongquan quartzite has been achieved a 4N8 grade of HPQ with total impurities reduced to 17.14 ppm. • Quartz is the dominant mineral with minimal inclusions after purification. • Jiulongquan quartzite represents a promising raw material for large-scale high-purity quartz production,.