Ore is a deposit in Earth’s crust of one or more valuable minerals. The most valuable ore deposits contain metals crucial to industry and trade, like copper, gold, and iron.


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Ore is a deposit of one or more valuable minerals. A deposit is a natural buildup of material in one place. Most often, ore deposits are found underground. The most valuable ore deposits contain metals like coppergold, and iron. Such metals have many important uses.

Copper ore is mined for many different industrial purposes. Copper is used as electrical wire. It is also used in buildings. Copper is a common material in pipes and plumbing.

Like copper, gold is also mined for some industrial purposes. However, most gold is used to create jewelry.

Iron ore has been mined for thousands of years. Iron is the main ingredient of steel, which is a very strong building material. It is also used in everything from glass to plant fertilizer.

Metals are often linked to particular ores. For example, aluminum is usually found in the ore called bauxite. Aluminum is used in containers, makeup, and medicines.

Smelting and Electrolysis

When miners find rock containing mineral ore, they first extract, or remove, the rock from the earth. This can be an enormous job. Sometimes millions of tons of dirt need to be moved. Once the rock is extracted it is then crushed. Huge machines are needed to crush the rock.

Metal is extracted from crushed ore in one of two major ways. The first is smelting. The second is electrolysis.

Smelting uses heat to separate the valuable metal from the rest of the oreElectrolysis separates metal from ore by using electricity. Aluminum, for example, is extracted from bauxite by electrolysis. Aluminum cannot be smelted. It melts at too high a temperature.

Ore Genesis

Deposits of ore are created through something called ore genesis. Ore genesis takes millions of years. For this reason, Earth contains only a limited amount of ore.

There are three major types of ore genesis. The first is internal processes. The second is hydrothermal processes. The third is surficial processes.

Ore can accumulate, or build up, through geologic activity. For example, volcanoes can bring ore from deep in the planet to the surface. This is called an internal process.

Ore can also accumulate when seawater pours through cracks in the seafloor. Then, minerals are deposited in the areas around these openings. Such openings are called hydrothermal vents. For this reason, this form of ore genesis is known as a hydrothermal process.

Finally, ore can accumulate through events on the surface of Earth. For example, wind, water, or ice all move earth around. This is called erosion. Often, the result is a slow buildup of ore. This type of ore genesis is called a surficial process.

Ore can also come from space. It sometimes falls to Earth as fragments of rock, or debris. Such pieces of debris are called meteorites. Many contain large amounts of iron ore.

Modern societies need a great deal of metallic ore. Miners must constantly look for new ore deposits. Mining companies have explored every continent. They have explored the ocean floor. Over time, it has become harder and harder to find fresh deposits. As a result, ore has gotten more and more valuable.

Fast Fact

Aluminum is very rare in its pure, metal form and cannot be smelted. Until the 20th century, aluminum was often more valuable than gold.

Fast Fact

The largest source of gold is an ore deposit located in the Witwatersrand Basin in South Africa. Roughly 40 percent of the gold ore mined on Earth has come out of mines there. Untold amounts of gold still remain hidden in the basin.

Fast Fact

All That Glitters
The majority of gold ore mined from the Earth more than 80 percent becomes jewelry. Small percentages of it go into electronic equipment, coins, and dental fillings.

Fast Fact

Steel Production
Iron ore production is often used as an indicator of a nation's economic health. For years, China has produced the most iron ore of any country on Earth.

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Hilary Costa
Erin Sprout
Santani Teng
Melissa McDaniel
Jeff Hunt
Diane Boudreau
Tara Ramroop
Kim Rutledge
Hilary Hall
Mary Crooks, National Geographic Society
Tim Gunther
Jeannie Evers, Emdash Editing, Emdash Editing
Kara West
Educator Reviewer
Nancy Wynne
National Geographic Society
Last Updated

April 25, 2024

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