he simplest silicon carbide manufacturing method involves melting silica sand and carbon, such as coal, at high temperatures―up to 2500 degrees Celsius. Darker, more common versions of silicon carbide often include iron and carbon impurities, but pure SiC crystals are colorless and form when silicon carbide sublimes at 2700 degrees Celsius. Once heated, these crystals deposit onto graphite at a cooler temperature in a process known as the Lely method. http://www.runjinrefractories.com/silicon-carbide-products/