question: Granite is made up largely of what chemical compound?
sentence: The Earth's crustal rock is composed in large part of oxides of silicon (silica SiO_2, as found in granite and quartz), aluminium (aluminium oxide Al_2O_3, in bauxite and corundum), iron (iron(III) oxide Fe_2O_3, in hematite and rust), and calcium carbonate (in limestone).