Iron Ore Type, Formation, Occurrence & Uses

Iron Ore
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Iron ores are minerals and rocks from which metallic iron is extracted. Iron ore is not designated as a rock, but the earth’s most important and economically valuable iron ore reserves are found in sedimentary rocks. Iron ores are formed due to chemical reactions that combine iron and oxygen in marine and freshwater.

The most important minerals in these deposits are iron oxides, magnetite (Fe3O4) and hematite (Fe2O3), goethite, limonite, and siderite. The ores containing large amounts of hematite or magnetite are natural or direct shipping ore. They are known as direct shipping ore because they can be used without processing.


Iron ore Formation

Earth’s major iron ore is found in rocks created around 1.8 billion years ago. Our earth’s oceans at that time contained abundant dissolved iron and very little oxygen.

It requires iron and oxygen to form an iron ore. The deposition process started after first organisms with photosynthesis ability started releasing oxygen in the water. The oxygen combined with dissolved iron and started making iron ores.

This process resulted in the creation of four different types of iron ores. These types are briefly explained below.

Banded Iron Formations: Sedimentary rocks with more than 15% iron. The rocks are composed of thinly bedded iron minerals and silica in the form of quartz. Banded iron formations can be metamorphosed with varying intensity. These formations are known as taconite in North America.

2.1-billion-year-old rock showing banded iron formation.
2.1-billion-year-old rock showing banded iron formation.

Magnetite Ores: Magnetite ores need to have certain crystallinity, iron grade, and contaminant elements to be economically viable. Magnetite ores become economical when they have 25% iron grade; it can lead to around 40% magnetite by weight and produce a concentrate grinding with more than 64% iron by weight.

Magnetite ore is heavily being mined in Minnesota and Michigan in the US. The mining process is also underway in Canada, Sweden, Brazil, and Asia.

Direct-shipping (Hematite) Ores: Direct-shipping ores (DSO) are rarer than other ores. These ores are also the most economically valuable because they don’t need much processing before being fed directly into iron-making blast furnaces. DSOs have higher iron content, with some ores having up to 65% iron content.

Magmatic Magnetite Ore Deposits: These deposits form when granite and ultrapotassic igneous rocks separate magnetite crystals and form magnetite ores suitable for economic concentration. Some iron ore deposits in Chile are formed from volcanic flows.

Iron Ore Reserves

Iron concentration is the largest element on earth but not in the earth’s crust. The exact quantity of iron ores is unknown, but some studies and research have highlighted that iron ore could run out in the next seventy years if the demand is not controlled.

Iron’s largest reserves are in Australia, which is currently the leader in world iron production. The United States has the second-largest iron reserves, followed by Canada, Brazil, Ukraine, and India.

Significant reserves are also located in China, Russia, South Africa,  and Sweden.

Iron Ore Uses

Iron ore’s primary use is to produce iron. Iron is then processed to make steel that is used in countless things. It is impossible to list the things in which steel is used.

Stockpiles of iron ore pellets like this one are used in steel production.
Stockpiles of iron ore pellets like this one are used in steel production.

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