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 buildup of minerals in one place. Deposits develop naturally.

Most ore deposits are found underground. The most valuable ore deposits contain useful metals. These include coppergold, iron, and aluminum. Such metals have many important uses. We all depend on them.

Copper is used as electrical wire. It is also often used for pipesGold is mostly used to create jewelry.

Iron is steel's main ingredient. Steel is a very strong building material. Iron is also used in many other things. For example, it is used in glass.

Metals are often found in 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 dig the rock from the earth. This can be a huge job. Sometimes millions of tons of dirt need to be moved. The rock is then crushed. The crushing is done by giant machines.

Metal is extracted, or removed, 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 ore. Some metals cannot be smelted, though. The temperature they melt at is just too high. Aluminum is one example. In these cases, electrolysis is used. Electrolysis separates metal from ore by using electricity.

Ore Genesis

Deposits of ore build up over time. They are created through something called ore genesis. Ore genesis takes millions of years.

There are three major kinds of ore genesis.

First, ore can accumulate, or build up, because of things happening deep underground. One example is volcanoes. They can bring ore up from deep in the earth.

Second, ore can accumulate underwater. This happens when seawater pours through cracks in the seafloor. Then, minerals get deposited near these openings.

Finally, ore can accumulate due to wind, water, or ice. All three move earth around. This is called erosion. Often, this causes a slow buildup of ore.

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

Modern societies depend on metallic ore. Miners must constantly look for new ore deposits. These are becoming much harder to find. Mining companies have explored every continent. They have even explored the ocean floor.

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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