Quartz (SiO 2) is a silicon oxide with a framework structure, which is a general name including α-quartz (low-temperature quartz, trigonal system) and β-quartz (high-temperature quartz, hexagonal system). The transformation temperature of α-quartz and β-quartz is 573 °C; when not specified, quartz usually refers to α-quartz. Quartz belongs to the quartz group in the oxide class according to the mineral’s crystallochemical classification. Because SiO 2 is the most important component of silicates, quartz is at the end-member position of silicates and is sometimes classified as a type of silicate. In mineral material science, quartz belongs to the three-dimensional structural mineral category and the subcategory of functional minerals.