Cement\xa0is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients. Common\xa0materials\xa0used to manufacture\xa0cement\xa0include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore.\xa0The most important raw materials for making cement are\xa0limestone,\xa0clay\xa0and\xa0marl. These are extracted from quarries by blasting or by ripping using heavy machinery.