What type of rock is iron ore?

Iron ore is a chemical sedimentary rock. Iron ore was formed when the first plants capable of photosynthesis appeared. The water that covered the earth was rich in dissolved iron but contained almost no oxygen. Once the plants started emitting the oxygen, it combined with the dissolved iron and created iron oxides which deposited in great abundance on the sea floor and over billions of years became the rich hematite, magnatite, taconite, limonite and siderite iron ores. Iron ore is typically found in bands with alternating bands of silica, shale and/or chert. It is believed the bands were created due to seasonal changes that affected the organisims. These rocks are some of the oldest found on earth.