Effect of Calcination and Water Quenching on the Removal of Gas–Liquid Inclusions from High-Purity Quartz and the Underlying Mechanism

High-purity quartz is a critical raw material for high-tech industries such as semiconductors and photovoltaics, yet its purity is severely constrained by gas–liquid inclusions within quartz crystals that are difficult to eliminate. The calcination–water quenching process is a key pretreatment step for removing inclusions and achieving deep purification, but its underlying mechanisms and the influence of process parameters on removal efficiency remain insufficiently understood. In this study, systematic calcination–water quenching experiments at different temperature gradients (500 °C, 700 °C, 900 °C, and 1100 °C) were conducted on high-purity quartz samples from Inner Mongolia and Angola. Comprehensive analytical techniques, including X-ray diffraction (XRD), major and trace element analyses, and polarizing microscopy, were employed to investigate the microstructural evolution, inclusion morphology, impurity element concentration changes, and phase transformation behavior before and after treatment. With increasing temperature, the quartz samples exhibited pronounced whitening and pulverization, accompanied by a significant reduction in the number of internal linear inclusions. Elemental analysis revealed that calcination–water quenching effectively removed certain alkali metals, alkaline-earth metals, and iron impurities, with 900 °C identified as the optimal calcination temperature; moreover, the sand-sized samples consistently showed better impurity removal efficiency than the lump-sized counterparts. XRD analysis was used to verify the phase transformation of quartz during calcination. Excessive temperatures (e.g., 1100 °C) led to a rebound in the content of some impurity elements. The calcination–water quenching process promotes inclusion decrepitation, exposure, and subsequent removal through the combined effects of volumetric strain induced by quartz phase transitions, thermal pressurization of inclusions, and thermal-shock stress from water quenching. This study establishes the optimal process window (hold at 900 °C for 2 h, sand-sized morphology) for the specific ore samples, elucidates the multi-factor synergistic mechanism of inclusion rupture, and provides both experimental and theoretical bases for the industrial purification of high-purity quartz.