What is Iron Ore?

Michael Anissimov
Michael Anissimov

Iron ore is any rock or mineral from which iron can economically be extracted. It comes in a variety of colors, including dark gray, bright yellow, deep purple, and rusty red. The iron comes in the form of iron oxides such as magnetite, hematite, limonite, goethite, or siderite. Economically viable forms of ore contain between 25% and 60% iron. In the old days of mining, some ores, known as "natural ores," had 66% iron and could be fed into iron-making blast furnaces directly.

Banded iron ore.
Banded iron ore.

The three primary sources of iron ore are banded iron formations, magmatic magnetite ore deposits, and hematite ore. The most metal is extracted from banded iron formations, geological structures laid down mostly between 3 and 1.2 billion years ago. Blue-green algae released oxygen in the days when the atmosphere and oceans were very oxygen-poor, binding together with dissolved iron in the world's oceans. These iron fixation events went through cycles as the algae had alternating blooms and busts, leaving the characteristic bands seen in banded iron formations. This ore is in either the form of magnetite or hematite. Banded iron formations are found on all continents, but especially rich deposits are found in Australia, Brazil, and the United States.

Magnetite ore.
Magnetite ore.

Another prominent source of iron is found as magmatic magnetite iron ore deposits, formed during ancient volcanic eruptions that released large amounts of magnetite which later crystallized. Granite-associated deposits have been found in places like 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 extracted via specialized smelters.

Hematite.
Hematite.

A third source is in hematite ore deposits, which are found on all continents, but especially in Australia, Brazil, and Asia. Most hematite originates from banded iron formations that have undergone chemical alteration over billions of years due to hydrothermal fluids. The world's largest producer of iron ore, Vale, located in Brazil, produces it from hematite ore. Vale produces 15% of the entire world's iron supply. In total, worldwide ore production is about one billion metric tons.

Iron can be extracted from rocks or minerals, known as iron ore.
Iron can be extracted from rocks or minerals, known as iron ore.
Iron ore in its natural form can be reddish.
Iron ore in its natural form can be reddish.
Iron ore is smelted to produce usable iron.
Iron ore is smelted to produce usable iron.
Michael Anissimov
Michael Anissimov

Michael is a longtime wiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.

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Discussion Comments

croydon

It's going to be interesting to see if we ever run out of iron deposits. I've heard the estimate that at our current rate it will last for another sixty years or so, and others say it will be twice that. I don't know if they take into account the fact that you can recycle iron (something that will hopefully be done more and more as time goes by) but it is a sobering thought.

I guess I probably won't see the consequences to this in my lifetime, but I'd hate my kids to suffer if it came to that.

browncoat

I never realized that hematite was iron ore. I've always liked it as a stone for jewelry. It has a lovely sort of metallic sheen and is a little bit different. Supposedly it's good for your health as well, since it's got magnetic properties, although I'm not sure if I take that seriously or not.

I guess I should have realized it had something to do with iron, because of the magnetism and because of the name. Hema must mean iron in Latin or Greek since it is used in "hemoglobin" as well and that's the iron part of your blood.

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