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There is no pure graphite in nature, which often contains SiO2, Al203, FeO, Cao, P2O5, CuO and other impurities. These impurities often appear in the form of quartz, pyrite, carbonate and other minerals. In addition, there are water, asphalt, CO2, h2ch4, N2 and other gas parts. Therefore, in addition to the fixed carbon content, we must measure the volatile and ash content of graphite. So graphite is usually formed by melting and purifying carbon at high temperature.