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A purification process including flotation separation, acid leaching, calcination, and water quenching was conducted to obtain high-purity quartz sand. The surface morphology of the quartz after flotation separation, acid leaching, calcination, and water quenching reveals that the cracks, pits, and cavities on the quartz surface can be deepened and enlarged, and the more fluid inclusions, the greater the number and openness of cracks, pits, and cavities. The specific surface area is positively correlated with the number of cracks, pits, and cavities, the opacity of quartz glass, and the number of bubbles in quartz glass. The results of Raman spectroscopy analysis reveal that the bubbles in quartz glass are composed of nitrogen, which excludes the possibility of bubble formation in quartz glass caused by the gas composition (i.e., H2O) of unburst fluid inclusions in quartz sand. The formation of bubbles in quartz glass is more likely to be related to a high specific surface area and porosity, which increase the surface adsorption performance of quartz and contribute to the adsorption of more gas. The presented results suggest that using these methods to reduce the content of fluid inclusions in quartz cannot effectively solve the problem of bubbles in quartz glass, and using quartz raw materials with no or minor fluid inclusions is still the key to ensuring the quality of quartz products. [ABSTRACT FROM AUTHOR]

This study focuses on the purification and evaluation of the high-purity quartz (HPQ) potential of vein quartz ore from Pakistan. Vein quartz is grayish-white and translucent, with its mineral composition mainly comprising quartz crystal. Processed quartz sand is obtained from quartz raw ore through purifying technologies, including crushing, ultrasonic desliming, flotation, high-temperature calcination, water quenching, hot pressure acid leaching, and chlorination roasting. The microscopic characteristics show that the vein quartz raw ore has a medium-coarse granular metacrystalline structure, high quartz content, with only a small quantity of fine-grained K-feldspar. The inclusions primarily consist of large-sized primary inclusions and secondary fluid inclusions developed along the micro-fractures, and the content of inclusions in most areas of the crystal is very low or even nonexistent. The quartz ore with such inclusion characteristics is considered a relatively good raw material for quartz. Component analysis shows that the main impurity elements in the quartz ore are Al, K, Ca, Na, Ti, Fe, and Li, with a total impurity element content of 128.86 µg·g−1. After purification, only lattice impurity elements Al, Ti, and Li remain in the processed quartz sand, resulting in a total impurity element content of 24.23 µg·g−1, an impurity removal rate of 81.20%, and the purity of SiO2 reaching 99.998 wt.%. It is suggested that when the quartz raw ore contains high content of lattice impurity elements, such as Al, Li, and Ti, it is difficult to remove them by the current purification method. In industrial production, considering the economic cost, if quartz sand still contains high content of lattice impurity elements Al, Ti, and Li after flotation, it cannot be used as a raw material for high-end HPQ. [ABSTRACT FROM AUTHOR]

Impurity minerals, as one of the main occurrence states of impurity elements in high-purity quartz, are strictly limited components in high-purity quartz sand products, and are also the key factors affecting the purification plan of high-purity quartz. Therefore, accurate analysis and determination of the composition, content and occurrence characteristics of impurity minerals in high-purity quartz are important references for the quality evaluation, raw material selection and purification scheme formulation of high-purity quartz sand products. In this study, a method was developed to determine impurity minerals in high-purity quartz sand products with SiO2 contents greater than 99. 998% (4N8) by the Automated Process Mineralogy Analyzing System (BPMA) with version 2.0 BPMA software, which was based on scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer (EDS). The results showed that the content of quartz was 99. 9988%, the data were well agreed with the quality indicators by chemical analysis of high-purity quartz products. The impurity minerals were mainly augite {Ca(Mg, Fe, Al)[(Si, Al)2O6]} and zircon [Zr(SiO4)], and an extremely small amount of calcite [(Ca(CO3)], xenotime-(Y) [ Y (PO4)], monazite-(Ce) [(Ce, La, Nd) (PO4)] and galena (PbS) was detected. The particle size of quartz in the high-purity quartz sand products was relatively uniform, major among 0. 020--0. 208 mm. The size of impurity minerals was very fine, and the grain size of impurities was less than 43 µM, mainly embedded in quartz in the form of fine-grained mineral inclusions. In conclusion, the method is accurate, reliable, simple and efficient, which is suitable for the analysis and determination of the composition, content and occurrence characteristics of impurity minerals in high-purity quartz. It can also provide technical reference for the determination of trace impurities in other high-purity materials. [ABSTRACT FROM AUTHOR]

High-purity quartz (HPQ) is an important material widely used in many high-tech industries. It is a product processed from pure natural quartz raw materials, so selecting suitable quartz raw material is the key to successfully processing HPQ. Hydrothermal quartz vein is one of the most likely raw materials to be purified into HPQ because of its high SiO2 content. This study focuses on the evaluation of HPQ raw material potential of the two gold-bearing quartz vein tailing resources in Chibougamau (CBG) and Tianjingshan (TJS). Petrography and the contents of impurity elements in the two vein quartz samples before and after processing were studied by optical microscope, SEM, Raman spectrometry, XRD, LA-ICP-MS, and bulk solution ICP-OES. Petrographic results reveal that major impurities in quartz are feldspar, mica, iron compounds, ankerite, rutile, silicate melt, and fluid inclusions. LA-ICP-MS analysis result shows that the SiO2 contents are between 99.953–99.971 wt.% in CBG raw quartz and 99.969–99.976 wt.% in TJS raw quartz, respectively, with very low contents of impurity elements, except for Ca. Bulk solution ICP-OES analysis demonstrates that the CBG processed quartz sand has total impurity contents of 56.8 µg·g−1, with 13.1 µg·g−1 Al and 6.6 µg·g−1 Ti, and the TJS processed quartz sand has the total impurity contents of 85.2 µg·g−1 with 29.4 µg·g−1 Al and 6.1 µg·g−1 Ti. Both the contents of Al and Ti fit with the lattice-bound criteria for HPQ. These results, for most of the impurities, are likely hosted by silicate melt, fluid, and mineral inclusions, indicating that these two hydrothermal raw vein quartz samples can be upgraded to HPQ after processing by more advanced methods. Therefore, the CBG and TJS quartz vein deposits would be considered as potential future resources for HPQ to realize efficient recovery and utilization of tailings resources and to improve mine economic benefits. [ABSTRACT FROM AUTHOR]