Quartz mines are generally divided into three categories: quartz, tridymite, and schlossite. An unconsolidated crushed rock consisting essentially of quartz grains is called quartz sand. Quartz includes low-temperature quartz of the trigonal system (α-quartz) and high-temperature quartz of the hexagonal system (β-quartz). Generally speaking, quartz refers to low-temperature quartz. As an industrial raw material, quartz can be divided into four categories: piezoelectric quartz, optical quartz, smelted quartz, and polished quartz according to its quality and use. Quartz deposits in my country are extremely rich, distributed in Henan, Shaanxi, Shanxi, Hebei, Shandong, Hunan, Guangdong, Guizhou, Xinjiang, and other places. Tridymite and white silica are mainly produced in central France, Mexico, and California. At present, most of the quartz exported by my country is smelted quartz, which is used in metallurgy, building materials, and chemical industries.
Quartz is a stable mineral at room temperature and is insoluble in water, sulfuric acid, hydrochloric acid, and nitric acid. The hardness is 7, the specific gravity is about 2.65, and the melting point is 1713°C. The gloss is glassy, sometimes fatty. Those with pure texture are colorless; those with impurities are red, yellow, blue, black, brown, purple, and green; transparent to opaque, and brittle. The fracture is shell-like or jagged. The crystals are hexagonal columns with horizontal stripes. There is a difference between the left crystal and the right crystal. Twin crystals are common. Usually in the form of crystal clusters or granular and massive aggregates. Quartz has the ability to transmit ultra-ultraviolet rays and does not conduct electricity. Quartz undergoes homogeneous deformation during uniform heating or cooling and retains its symmetry before transforming to another polymorphic body. Quartz crystal has the optical properties of birefringence and rotating polarization plane, and has a piezoelectric effect. The oscillation frequency of the quartz plate is highly stable, and ultrasonic waves can be radiated by the oscillation of the quartz plate.
The beautiful crystal and shape of the quartz stone can be used as glasses and valuable crafts. Using the piezoelectricity of the quartz crystal, it can be used to make frequency stabilizers and quartz filters in the cordless industry. Various lenses, reflectors, spectrometers, light pipes, and prisms and polarizers in optical instruments can be made. At present, the hydrothermal temperature difference method has been widely used to make artificial quartz crystals for the manufacture of piezoelectric elements. In the chemical industry, quartz can be used for acid- and temperature-resistant instruments and utensils; in the electrical industry, quartz is often used as an excellent insulating material; quartz stone is also an excellent raw material in the glass, enamel, and refractory brick manufacturing industries; outstanding performance of smelting quartz It is also widely used in metallurgy, food, pharmaceutical, and paper industries. Most of the exported quartz stone (sand) is used in the metallurgy and refractory industry.
Piezoelectric quartz, polished quartz, and optical quartz have high requirements for crystals. Any damage to crystals, crystal ingots, and single crystals will reduce the grade of quartz. Therefore, there are strict regulations in the mining and production of quartz crystals. The crystals must be sorted after mining. Then the crystals are washed, beneficiated, and graded in the workshop. Smelted quartz is generally mined in the open pit, and beneficiated and classified after crushing
5. Quality specifications
(1) Piezoelectric quartz is generally classified according to the weight of the raw material, the percentage of the single crystal part, and the weight; the artificial piezoelectric quartz is generally classified according to the extinction coefficient α.
(2) Optical quartz stone is classified according to the size of the flawless part, the percentage of the flawless part in the entire crystal, and the degree of crystal transmission of ultraviolet rays; the artificial quartz crystal is classified according to its optical uniformity, according to the microscopic refractive index of the crystal along the optical axis. Poor division level.
(3) The ZBD53001-90 regulations are applicable to the technical conditions of refractory materials, ferroalloys, and industrial silica quartz.
6. Inspection standards
(1) The sampling and sample preparation of quartz stone (sand) shall be carried out in accordance with the provisions of GB2007.1～2007.7-87 “General Rules for Sampling and Sample Preparation of Bulk Mineral Products”. The chemical composition of import and export quartz stone (sand) shall be inspected in accordance with SN/T0483-95 “Chemical Analysis Method for Import and Export Quartz Stone (Sand)”.
(2) GB/T6901.1～6901.11-86 “Chemical Analysis Methods of Silica-based Refractories”, GB/T7322-97 “Refractoriness Test Methods” and GB/T2997-82 “Water Absorption of Refractory Raw Materials and Clinker Particles, The Inspection Method of Bulk Density and Apparent Porosity” provides inspection standards for the chemical composition, refractoriness and water absorption of refractory products, ferroalloys, and industrial silica quartz.