The reasons for the formation of iron ore are complex. After all the iron bearing rocks on the earth are weathered and decomposed, the iron in them will be oxidized. Iron oxide gradually precipitates and accumulates underwater with the flow of water, becoming a ore bed with relatively concentrated iron. After the formation of the iron ore layer, it will be deposited into iron ore or metamorphic rock with more iron after many changes. After weathering, the iron will be further concentrated to form rich iron ore with high iron content.
Other iron ores are caused by magmatism. When the magma cools and condenses underground or near the ground, iron minerals can be separated and concentrated in certain parts. In addition, when magma contacts with surrounding rocks, it can also interact to form iron ore.