The Discovery and Geological Implications of Pegmatite-Type High-Purity Quartz in the Qinghe Area, Altay

High-purity quartz (HPQ) is a critical strategic raw material for the semiconductor, optical fiber, and renewable energy industries, yet China still faces a shortage of high-grade domestic resources. To systematically constrain the geological characteristics of pegmatite-type HPQ mineralization in the Qinghe area of the Altai orogen, this study adopts a comprehensive research approach integrating petrography, in situ trace-element analysis of quartz, process-mineralogical assessment, beneficiation and purification tests, monazite U–Pb geochronology, and Electrical Resistivity Tomography (ERT) detection. Monazite yields a weighted mean U-Pb age of 370.4 ± 2.7 Ma, indicating emplacement of the mineralized pegmatite in the Late Devonian. Three samples produced purified quartz sand with SiO2 contents of 99.9951%–99.9975% (4N5 to nearly 4N8). The quartz grains are characterized by sparse inclusions, and low concentrations of critical impurity elements (Al, Ti, Li), satisfying the quality evaluation criteria for high-grade HPQ feedstock. This reconnaissance case study reveals that high-quality quartz occurs mainly in transition and marginal zones of the pegmatite veins as colorless to smoky, saccharoidal or roe-like crystalline aggregates. Minor garnet occurs as an accessory phase within mineralized pegmatites, which is regarded as a preliminary local prospecting indicator for the Qinghe area. ERT geophysical results reveal that the pegmatite ore body extends at depth but is locally truncated by late-stage tectonic structures. Combined with microscopic textures of quartz (i.e., undulose extinction, subgrain formation, and dynamic recrystallization) and regional geological comparisons, we propose that regional ductile shearing and dynamometamorphic overprinting may improve quartz quality in pegmatite. Nevertheless, this metallogenic interpretation requires future verification via extensive beneficiation–purification tests, and wider applicability of the above-mentioned prospecting features needs further sampling from additional pegmatite veins in the Chinese Altai.