Abstract
Quartz occurs in many geological materials, and is used in numerous industrial fields as a raw material. Mineralogy and the processing of hydrothermal quartz were studied by optical microscope, electron probe microanalysis, scanning electron microscope, inductively coupled plasma-optical emission spectrometry, and inductively coupled plasma mass spectrometer. A combination of the geological occurrence of the quartz deposit, mineralogical studies, and the processing technologies of the hydrothermal quartz was accomplished. The results show that impurities within the quartz mainly include muscovite, hematite, apatite, and secondary fluid inclusions. The main chemical impurities are Al (353 μg·g−1), K (118 μg·g−1), Fe (61.2 μg·g−1), P (15.5 μg·g−1), Na (13.4 μg·g−1), Mg (11.8 μg·g−1), Ti (8.31 μg·g−1), and B (10.8 μg·g−1). Based on these results, a combined process consisting of calcination and fluoride-free pressure acid leaching was established to effectively decompose and dissolve the quartz, and remove gangue minerals and fluid inclusions. The calcination process not only removed volatile components; it also destroyed the crystal structure of gangue minerals and enhanced their release probabilities. The calcination process has a positive influence on the removal of impurity elements by the fluoride-free pressure acid leaching process. A total of 85.2 wt % and 84.0 wt % of impurity elements was removed using the leaching systems of HCl-NH4Cl and H2SO4-NH4Cl, respectively.
Highlights
SiO2 minerals and rocks play an important role in geological processes and industrial applications [1]
This study presents an analysis of the regional geological setting and mineralogy of the hydrothermal quartz from Hengche Town in the Qichun County of the Hubei Province of China, and further develops a suitable process flow for the purification of hydrothermal quartz
The present study analyzed the geological formation and mineralogy of the hydrothermal The present study analyzed the geological formation and mineralogy of the hydrothermal quartz quartz deposit from Hengche in Qichun County, of the Hubei Province in China, A combined deposit from Hengche in Qichun County, of the Hubei Province in China, A combined purification purification process consisting of calcination and fluoride-free pressure acid leaching was developed process consisting of calcination and fluoride-free pressure acid leaching was developed based on based on two fundamental investigations
Summary
SiO2 minerals and rocks play an important role in geological processes and industrial applications [1]. Quartz is one of the most important silica minerals, and it is abundant in the Earth’s crust in igneous, metamorphic, and sedimentary rocks [1]. SiO2 minerals and rocks have been formed by primary and secondary magmatic, hydrothermal, or sedimentary processes or during diagenesis and metamorphosis [2]. The hydrothermal quartz commonly contains a significant amount of associated minerals and fluid inclusions, which leads to difficulties in quartz processing [5]. Some primary and fine-grained mineral inclusions including mica, feldspar, and hematite are difficult to be removed because they are closely included within quartz grains. Some micron-size fluid inclusions are widely distributed in hydrothermal quartz. Decrepitation methods at low and medium temperatures (below 700 ◦ C) can enhance the removal of volatile materials in quartz fluid inclusions, the micron-size fluid inclusions rarely are removed, especially in high-temperature quartz [7,8]
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