Impurity architecture controls dry magnetic beneficiation of Marwit Rod El-Leqah quartz toward high-purity silica applications

Abstract High-purity quartz (HPQ) is a strategic raw material for advanced technologies, but its production from natural deposits is limited by impurity architecture, deposit heterogeneity, and the environmental burden of chemically intensive purification. This study evaluates quartz from the Marwit Rod El-Leqah deposit, Eastern Desert of Egypt, to link geological impurity controls with dry magnetic beneficiation efficiency. Quartz samples were characterized petrographically and mineralogically to identify impurity types, textural associations, and liberation behavior, followed by dry high-intensity magnetic separation using Frantz Isodynamic and Rare Earth Roll (RER) separators. Operating variables were statistically optimized to maximize Fe₂O₃ and Al₂O₃ removal across different size fractions. The results show that impurities are mainly intercrystalline and fracture-hosted Fe-oxides and mica, whose separation behavior is governed by liberation state, particle size, and microstructural setting. Under optimized dry RER conditions, Fe₂O₃ and Al₂O₃ reductions of approximately 97–98% were achieved for the unclassified and coarse fractions, increasing SiO₂ contents to > 99.9 wt%. The fine fraction showed more complex behavior due to particle-size effects and platy aluminosilicate impurities. Overall, geology-guided dry magnetic separation provides an effective, water-free front-end route for upgrading quartz toward HPQ specifications while reducing subsequent chemical demand.