Earth's most important iron ore deposits are found in sedimentary rocks. They formed from chemical reactions that combined iron and oxygen in marine and fresh waters. The two most important minerals in these deposits are iron oxides: hematite (Fe2O3) and magnetite (Fe3O4). read more
Iron reacts with oxygen in the air to form various oxide and hydroxide compounds; the most common are iron(II,III) oxide (Fe 3 O 4), and iron(III) oxide (Fe 2 O 3). Iron(II) oxide also exists, though it is unstable at room temperature. read more
Most deposits of iron ore in the world are found in rocks known as banded iron formations (BIFs). These are sedimentary rocks that have alternating layers of iron-rich minerals and a fine-grained silica rock called chert. read more