Editorial for Special Issue: “Physicochemical Properties and Purification of Quartz Minerals”

High-purity quartz is closely associated with strategic emerging industries, such as new-generation information technology, advanced materials, and new energy. It is an irreplaceable and critical raw material that supports high-tech fields, including semiconductor chip manufacturing, optical communication devices, photovoltaic silicon wafers, high-strength glass, and specialty optical components. High-purity quartz generally refers to quartz raw materials with a silicon dioxide (SiO₂) content not less than 99.995% (4N5) or even higher, and that have extremely low levels of impurity elements such as Al, Ti, Fe, Li, Na, and K. As a result, the sources of high-quality high-purity quartz are highly limited, making the resource extremely scarce and difficult to substitute. At present, global resources capable of stably supplying high-purity quartz of 4N8 (99.998%) grade and above are mainly concentrated in a few countries, such as the United States, Norway, and India. Among them, the quartz from the granitic pegmatites in Spruce Pine, North Carolina, USA, represents the most important source; the naturally occurring quartz there, after purification, meets the rigorous requirements of the semiconductor industry. Metamorphic quartz vein-type deposits in Norway are also well known for their low impurity contents and stable quality, making them a major source of high-purity quartz in Europe. In recent years, with the rapid growth of high-tech industries such as integrated semiconductor circuits, fiber-optic communication, photovoltaic power generation, and laser technology, the demand for high-purity quartz has continued to rise, and its market price has significantly increased.

Against this backdrop, it is urgently necessary to organize systematic research on the mineralogical, petrological, and geochemical characteristics of high-purity quartz materials and their purification performance. This should include studies on the occurrence states of natural quartz minerals, mechanisms of trace element enrichment and migration, and the influence of host rocks on quartz purity. Based on these studies, experimental purification of quartz from different geological bodies should be conducted to evaluate its purification potential, thereby providing theoretical support and technical guidelines for future mineral exploration. This Special Issue aims to lay a solid theoretical and experimental foundation for the assessment and technological development of high-purity quartz resources and offer scientific guidance and practical pathways for the exploration and utilization of strategic high-purity quartz in the world. This Special Issue comprises 12 articles published between 2024 and 2025. In the first contribution, “Mineralogy and Preparation of High-Purity Quartz: A Case Study from Pegmatite in the Eastern Sector of the North Qinling Orogenic Belt” by Yu et al. (2024) (contribution 1), two pegmatite samples (muscovite pegmatite and two-mica pegmatite) from the eastern sector of the North Qinling Orogenic Belt were investigated through a suite of analytical techniques, as well as processing and purification, to evaluate their potential as raw materials for high-purity quartz. It is suggested that muscovite pegmatite quartz is more likely to have the potential to produce high-purity quartz by purification. In the second publication, “The Influence of Grinding Media on the Grinding Effect of Granite Pegmatite-Type Quartz” by Tan et al. (2025) (contribution 2), the effects of different grinding media on the breakage characteristics of muscovite granite pegmatite-type quartz were investigated, with an additional focus on quartz mineral flotation. An analysis of scanning electron microscope images reveals distinct fracture characteristics among different minerals. Their flotation experiments demonstrate that the recovery rate of quartz using a rod mill is 2.59% and 5.07% higher than that achieved with the ball mill and ceramic mill, respectively. These findings provide theoretical support for the optimization of grinding media and the enhancement of mineral flotation recovery. In the third publication, “Application of Quartz LA-ICP-MS Analysis in the Evaluation of High-Purity Quartz Deposits” by Wang et al. (2025) (contribution 3), the authors conducted a trace element analysis of quartz using four methods: nanosecond laser dot ablation, femtosecond laser dot ablation, femtosecond laser line ablation, and femtosecond laser area scanning. Combined with the results of metallurgical purification, the stability of quartz LA-ICP-MS analytical data and the proximity to the purification results were evaluated using two methods, i.e., the comparison of casting diagrams and the construction of comprehensive stability and proximity evaluation models. The results show that the femtosecond laser line ablation has the best stability in the analysis of the elements of quartz Al, Ti, Li, and B and the highest proximity to the results of metallurgical purification, and the nanosecond laser dot ablation also has better stability and proximity, while femtosecond laser surface scanning data quality is relatively poor due to unavoidable inclusions and co-associated minerals. The fourth article, “The Impact of Ultra-Low Temperature Quenching Treatment on the Pore Structure of Natural Quartz Sand” by Guo et al. (2025) (contribution 4), studied the effects of calcination temperature, calcination time, quenching frequency and grinding frequency on the formation of mesoscopic fractures in natural quartz sand, and a linear regression model was established using fractal and differential methods. The results show that the cracked structure of quartz sand and its variation law have remarkable fractal characteristics, and that thermal expansion and phase transformation are the main factors affecting the cracked structure and specific surface area of quartz sand. Finally, the linear regression model between the fractal dimension and the pore volume distribution is further established, and the correlation coefficient is mostly above 96%, offering insightful findings for the investigation of the structure–activity relationship between the purification effect and the mesoscopic structure of quartz sand. This paper also establishes the groundwork for the advancement of high purification technologies for natural quartz sand. The fifth publication, “Water Redistribution in Vein Quartz Under Progressive Deformation (During Plastic Deformation): μFTIR and EBSD Study (Western Transbaikalia, Russia)”, by Kungulova et al. (2024) (contribution 5), found that in the process of successive rearrangements, migration of fluid components occurs within the main elements of the structure due to the redistribution of dislocations between defects on different scale levels. The redistribution of fluid from fluid inclusions as a result of plastic deformations in the quartz structure is one of the ways of relaxing intracrystalline stresses during strengthening of the structure. The sixth publication “Purification of Vein Quartz Using a New Fluorine-Free Flotation: A Case from Southern Anhui Province, China” by Du et al. (2024) (contribution 6), from which the author had processed raw materials of quartz veins in south China by means of ultrasonic scrubbing–desliming, magnetic separation, flotation, high-temperature calcination, water quenching, hot-press acid leaching, and deionized water cleaning to prepare high-purity quartz sand. Their results showed that the total amount of 13 impurities in quartz sand was reduced to 28.66 μg/g after purification. In the seventh publication, “Preliminary Beneficiation Studies of Quartz Samples from the Northwest Territories, Canada”, Zhang et al. (2024) (contribution 7) studied the purification process of three quartz-rich geologic materials—vein quartz from the Great Bear Magmatic Zone, massive quartz from the Nechalacho rare earth deposit, and quartz sands from the Chedabucto silica sand deposit along the shores of the Northern Arm of the Great Slave Lake, Northwest Territories of Canada—to evaluate their amenability for physical beneficiation into high-purity quartz (HPQ). These samples were subjected to various treatment processes, including crushing, grinding, calcining and quenching, acid leaching, wet high-intensity magnetic separation (WHIMS), and reverse flotation. Finally, both the core and sand quartz samples met the requirements for HPQ, making them suitable for use in the production of semiconductor filters, liquid crystal displays (LCDs), and optical glass. In the eighth publication, “Research on 4N8 High-Purity Quartz Purification Technology Prepared Using Vein Quartz from Pakistan”, Xie et al. (2024) (contribution 8) investigated the potential of two quartz vein ores from the Hunza District, Gilgit-Baltistan, Pakistan, as raw materials to obtain 4N8 high-purity quartz (HPQ) sand by various quartz purification processes, including ore calcination, water quenching, flotation, sand calcination, acid leaching, and chlorination roasting. In the ninth publication, “Preparation of High-Purity Quartz Sand by Vein Quartz Purification and Characteristics: A Case Study of Pakistan Vein Quartz”, Xia et al. (2024) (contribution 9) focused on the purification and evaluation of the high-purity quartz (HPQ) potential of vein quartz ore from Pakistan, 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.% after purification. The publication by Yu et al. (2025) (contribution 10) presented two pegmatite samples (muscovite and two-mica) from the eastern North Qinling Orogenic Belt that were analyzed for their potential as HPQ sources. Muscovite pegmatite contains quartz, plagioclase, K-feldspar, muscovite, and garnet, with accessory minerals such as limonite and kaolinite. The two-mica pegmatite has additional biotite and calcite. After purification, trace element concentrations significantly decreased, though Al and Ti remained unchanged. Titanium enrichment in two-mica pegmatite quartz is likely from biotite, while Na and Ca may be linked to fluid inclusions. The trace element content in muscovite pegmatite (27.69 ppm) is lower than that in two-mica pegmatite (45.28 ppm), suggesting muscovite pegmatite is a better candidate for HPQ production. The extensive review by Gungoren et al. (2025) (contribution 11) aims to advance quartz processing technology by examining its surface properties, flotation behavior, and the selective flotation mechanisms of quartz mineral. These minerals demonstrated a strong negative charge over a wide pH range and an isoelectric point around pH 2. Quartz surfaces allow physical adsorption of cationic collectors, particularly amines, which render the quartz surface hydrophobic and enhance bubble–particle interactions. In contrast, flotation with anionic collectors requires prior surface activation via multivalent metal cations such as Ca²⁺. The pH value of the medium plays a critical role in both collector adsorption and flotation selectivity. Both direct and reverse flotation strategies can be used, depending on whether quartz is targeted as a valuable mineral or a gangue mineral. In direct flotation, depressants like carboxymethyl cellulose and starch are used to depress gangue minerals, while in reverse flotation, quartz is depressed using chemicals such as fluoride ions and cationic polymers. To improve the efficiency and selectivity of quartz flotation, further research is needed on surface chemistry, collector adsorption mechanisms, and the transition from laboratory-scale experiments to industrial applications. In the final paper, Mohanty et al. (2025) (contribution 12) review the geological occurrence, beneficiation, and strategic importance of high-purity quartz (HPQ) in Europe. HPQ, essential for advanced technologies, undergoes a series of processes, such as comminution, magnetic separation, flotation, acid leaching, and thermal treatment, to remove impurities. Quartz is found in various geological settings across Europe, including granitic rocks and pegmatites. Case studies highlight that geological origin affects processing methods, and tailored strategies are crucial for resource viability. Mohanty et al.’s review links these findings to the EU Critical Raw Materials Act, emphasizing the potential of domestic HPQ development to strengthen Europe’s supply chain and economy.

This Special Issue, entitled “Physicochemical Properties and Purification of Quartz Minerals”, presents a collection of cutting-edge studies that offer fresh perspectives on the mineralogical characteristics, trace element behavior, and purification potential of natural quartz from a variety of geological environments. The featured contributions encompass a wide array of quartz types—including those sourced from granitic pegmatites, metamorphic quartz veins, hydrothermal systems, and sedimentary deposits—providing valuable insights into the genesis and quality assessment of high-purity quartz (HPQ) resources in various locations worldwide. In addition, experimental investigations into diverse purification techniques—ranging from chemical leaching and thermal treatment to innovative plasma-assisted and microbial approaches—demonstrate promising avenues for improving quartz purity while lowering production costs. Case studies from major HPQ-producing regions worldwide underscore the critical relationship between geological formation conditions and the efficiency of purification strategies.

Taken together, this Special Issue has established a comprehensive scientific framework for the evaluation, utilization, and refinement of quartz resources for advanced applications in semiconductors, optics, photovoltaics, and other high-technology sectors. It provides both theoretical foundations and practical methodologies to support the sustainable development of strategic non-metallic mineral resources.