Microsilica (Silica Fume) is a byproduct of producing silicon metal or ferrosilicon alloys. Silicon metal and alloys are produced in electric furnaces. The raw materials are quartz, coal, and woodchips. The smoke that results from furnace operation is collected and sold as silica fume, rather than being landfilled. Silica fume consists primarily of amorphous (non-crystalline) silicon dioxide (SiO2).