High-purity quartz refers to quartz and its products with extremely high purity of SiO2 and extremely low content of impurity elements, which are widely used in semiconductor, photovoltaic, optical fiber, precision optics, advanced lighting equipment, new glass and other industries. However, because different industries require different qualities of quartz, there is no universal quality evaluation index for high-purity quartz.
Early research believed that the impurity content of high-purity quartz should be less than 50×10-6, that is, quartz with a purity of SiO2 greater than 99.995% is high-purity quartz. The Norwegian Geological Survey proposed more detailed indicators, requiring not only the total mass of impurities to be less than 5/100,000, but also the content of Al should be less than 3/100,000, the content of Ti should be less than 1/100,000, Na and K should be less than 8 parts per million, the content of Li and Ca should be less than 5 parts per million, the content of Fe should be less than 3 parts per million, the content of P should be less than 2 parts per million, and the content of B should be less than millionth. In 2014, Flook proposed a new quality index according to the needs of the market and industry. It believes that the quartz with a purity of 99.95% SiO2 and a total impurity content of less than 5/10,000 is high-purity quartz, and quartz with a purity of 99.5%~99.8% can meet the requirements of semiconductors. Quartz with a purity of less than 99.5% can be used in the transparent glass industry according to the requirements of the production industry of fillers, optical fibers, and LCD screens.
The global high-purity quartz raw material deposits are mainly distributed in Brazil, the United States, Canada, Norway, Australia, Russia, China, etc. Quartz raw material determines the quality of high-purity quartz, and choosing the right quartz raw material is the key to successfully processing high-purity quartz. There is a close relationship between the industrial type of quartz deposits and the development and utilization. How to develop and utilize quartz in a targeted manner according to the characteristics of different industrial types of quartz deposits is related to the success or failure of quartz material technology and projects.
According to different mineralization and physicochemical properties, quartz minerals can be divided into magmatic rock type, metamorphic type, hydrothermal type and sedimentary type; the corresponding quartzites are granite pegmatite, vein quartzite, quartzite and quartz sand.
Among them, the magma-type granite pegmatite is formed by the slow crystallization of high-temperature magma. The magma temperature is high and the cooling time is long, and the impurities in the quartz system are easy to precipitate. Therefore, the quartz in the magma-type granite pegmatite is extremely pure, surrounded by gas and liquid. There are very few bodies, and it is a typical high-purity quartz raw material.
Vein quartz is one of the ideal raw materials for processing high-purity quartz. Its industrial value and application advantages are:
First, the added value of high-purity quartz is high and the absolute amount is small. In the past, according to the traditional application standard, it was a small mine; now, according to the new use standard, it is a large mine.
Second, compared with quartzite and quartz sandstone, vein quartz is almost all composed of quartz, the purity of SiO2 is generally 3N and above, and the content of other impurities is relatively small, which is conducive to the purification and processing of high-purity quartz.
Third, compared with natural crystal, in addition to the advantages of mining conditions, vein quartz has relatively stable ore quality in the same mining area, which creates conditions for the uniform processing of mineral raw materials. The actual production at home and abroad also proves that vein quartz can replace crystal as the raw material for processing and purifying high-purity quartz.