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 concentration of material, formed over time. 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 construction. Copper is a common material in pipes and plumbing.

Like copper, gold is also mined for industry. For example, space helmets are plated with a thin layer of gold to protect astronaut's eyes from harmful solar radiation. However, most gold is used to create jewelry.

Iron ore has been mined for thousands of years. Today, iron is the second-most common metal on Earth. It is the main ingredient of steel, which is a strong and useful building material. Iron is also used in everything from glass to fertilizer.

Metals are often linked to particular ores. For example, aluminum is usually found in the ore called bauxite. Aluminum found in bauxite 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 shifted. Once the rock is extracted it is then crushed by powerful machinery.

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 ore. During smelting, another chemical is usually needed to help separate metal from its ore. These chemicals are known as reduction agents, because they help reduce the ore to the desired metal. In the earliest smelters, charcoal was the reduction agent. Charcoal burned with hematite ore, for example, smelts iron.

Electrolysis separates metal from ore by using acid and electricity. Aluminum, which only burns at a very high temperature, is extracted from bauxite by electrolysis. Bauxite is first placed in a pool of acid. Then, an electrical current is run through the pool. The electrons in the current attach to oxygen and hydrogen, the other elements in bauxite, leaving the aluminum.

Ore Genesis

Ore genesis is the process by which a deposit of ore is created. It takes millions of years, and 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, such as when volcanoes 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 Earth's crust and deposits minerals in the areas around openings in the seafloor. These openings are called hydrothermal vents. Thus, this form of ore genesis is known as a hydrothermal process.

Finally, ore can accumulate through processes that take place on the surface of Earth, such as erosion. For example, wind, water, or ice can shift material around, leading to 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. These pieces of debris are called meteorites. Many contain large amounts of iron ore.

Modern societies rely very heavily on metallic ore. Therefore, miners must constantly seek new ore deposits. Mining companies have explored every continent, as well as the ocean floor, in their search for valuable ore. 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 twentieth 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 Earthmore than 80 percentbecomes 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

October 19, 2023

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