Question: what is the chemical composition of iron?
Answer: The most commonly used iron-bearing minerals contain iron compounds as follows: hematite, Fe2O3 (70% Fe); magnetite, Fe3O4 (72.4% Fe) and of much less importance are: limonite, 2Fe2O3·3H2O (60% Fe); siderite, FeCO3 (48.3% Fe); pyrite, FeS2 (46.6% Fe) [1].