Iron ore is a rock or ore from which iron can be extracted economically, with viable forms containing between 25% and 60% iron. The three primary sources are banded iron formations, magmatic magnetite ore deposits, and hematite ore, with Brazil-based Vale being the world’s largest producer.
Iron ore is any rock or ore from which iron can be extracted economically. It comes in a variety of colors, including dark gray, bright yellow, deep purple, and rusty red. Iron comes in the form of iron oxides such as magnetite, hematite, limonite, goethite or siderite. Economically viable forms of the ore contain between 25% and 60% iron. In the old days of mining, some ores, known as ‘natural ores’, contained 66% iron and could be fed directly into blast furnaces for iron production.
The three primary sources of iron ore are banded iron formations, magmatic magnetite ore deposits, and hematite ore. Most of the metal is mined from banded iron formations, geological structures mostly established between 3 and 1.2 billion years ago. Blue-blue algae released oxygen on days when the atmosphere and oceans were very low in oxygen, binding together with dissolved iron in the world’s oceans. These iron-fixing events have gone through cycles as the algae have alternated between blooms and busts, leaving the characteristic bands seen in banded iron formations. This mineral is in the form of magnetite or hematite. Banded iron formations are found on all continents, but particularly rich deposits are found in Australia, Brazil and the United States.
Another important source of iron is found in the form of magmatic magnetite iron ore deposits, formed during ancient volcanic eruptions that released large amounts of magnetite which later crystallized. Deposits associated with granite have been found in places such as Malaysia and Indonesia and require very little post-processing to extract the iron. Titanomagnetite, a special class of magmatic magnetite ore, also serves as a source of titanium and vanadium, which is mined through specialized smelters.
A third source is in deposits of hematite ore, which are found on all continents, but especially in Australia, Brazil and Asia. Most hematite comes from banded iron formations that have undergone chemical alterations over billions of years by hydrothermal fluids. The world’s largest producer of iron ore, Brazil-based Vale produces it from hematite ore. Vale produces 15% of the world’s entire iron supply. In total, world production of ore is about one billion tons.
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