Home » Rocks » Sedimentary Rocks » Iron Ore

Iron Ore


What Is Iron Ore, How Does It Form, and What Is It Used For?


Iron Ore

Iron Ore: A specimen of oolitic hematite iron ore. The specimen shown is about two inches (five centimeters) across.

What is Iron Ore?

Earth's most important iron ore deposits are found in sedimentary rocks. They formed from chemical reactions that combined iron and oxygen in marine and fresh waters. The two most important minerals in these deposits are iron oxides: hematite (Fe2O3) and magnetite (Fe3O4). These iron ores have been mined to produce almost every iron and steel object that we use today - from paper clips to automobiles to the steel beams in skyscrapers.




How Does Iron Ore Form?

Nearly all of Earth's major iron ore deposits are in rocks that formed over 1.8 billion years ago. At that time Earth's oceans contained abundant dissolved iron and almost no dissolved oxygen. The iron ore deposits began forming when the first organisms capable of photosynthesis began releasing oxygen into the waters. This oxygen immediately combined with the abundant dissolved iron to produce hematite or magnetite. These minerals deposited on the sea floor in great abundance, forming what are now known as the "banded iron formations." The rocks are "banded" because the iron minerals deposited in alternating bands with silica and sometimes shale. The banding might have resulted from seasonal changes in organism activity.



steel mill

Steel Mill: Most iron ore is used to make steel. Here a steel slab is being cut to length in a steel mill. Image © iStockphoto / Alfredo Tisi.

What is Iron Ore Used For?

The primary use of iron ore is in the production of iron. Most of the iron produced is then used to make steel. Steel is used to make automobiles, locomotives, ships, beams used in buildings, furniture, paper clips, tools, reinforcing rods for concrete, bicycles, and thousands of other items. It is the most-used metal by both tonnage and purpose.

Contributor:

Rock kit

Rock & Mineral Kits: Get a rock, mineral, or fossil kit to learn more about Earth materials. The best way to learn about rocks is to have specimens available for testing and examination.

Banded Iron

Banded Iron Formation: Close-up view of a banded iron formation. In this specimen bands of hematite (silver) alternate with bands of jasper (red). This photo spans an area of rock about one foot wide. Photo taken by André Karwath, GNU Free Documentation License.



More Rocks
  Rock, Mineral and Fossil Collections.
  Tumbled Stones
  Fluorescent Minerals
  Hand Lens
  Quartzite
  The Rock Used to Make Beer
  Lapis Lazuli
  A Grain of Sand

geology store

More From Geology.com:


Roadside Geology
Roadside Geology Guides - Explain the roadside geology of your favorite state.
Diamonds from Coal
Biggest Misconception: Lots of people think that diamonds form from coal. Not True!
Gold Pans and Panning Kits
Gold Pans and Panning Kits - classifiers, snuffer bottles. Pans sized for kids to Goliath.
tumbled stones
Tumbled Stones are rocks that have been rounded, smoothed and polished in a rock tumbler.
What Is The Moho?
What Is The Moho? Learn about the interior of the Earth and the Mohorovicic Discontinuity.
Gems from Space
Gems from Space A number of materials from space have been used as attractive gems.
Largest Oil Spills Map
Largest Oil Spills Map - Eleven oil spills from war, tanker wrecks and out-of-control wells.
Chalcopyrite
Chalcopyrite - The most important ore of copper for over five thousand years.