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.

Copper ore is mined for a variety of industrial uses. Copper, an excellent conductor of electricity, is used as electrical wire. Copper is also used in construction. It is a common material in pipes and plumbing material.

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. For thousands of years, gold ore was mined as a basis for currency, or money. Most nations stopped valuing their money on the gold standard in the 20th century.

Iron ore has been mined for thousands of years. Iron, the second-most abundant metal on Earth, is the main component of steel. Steel is a strong, valuable building material. Iron is used in everything from glass to fertilizer to the solid-rocket boosters once used for the space shuttle to leave Earth’s atmosphere.

Metals are often associated with particular ores. Aluminum, for example, is usually found in the ore called bauxite. Aluminum found in bauxite is used in containers, cosmetics, and medicines.

Smelting and Electrolysis

When miners find rock containing mineral ore, they first extract the rock from the earth. This can be a huge process, sometimes displacing millions of tons of dirt. The rock is then crushed by powerful machinery.

Metal is extracted from the crushed ore by one of two major methods: smelting or electrolysis.

Smelting uses heat to separate the valuable metal from the rest of the ore. Smelting usually requires a reduction agent, or another chemical, to separate metal from its ore. In the earliest smelters, the reduction agent was carbon in the form of charcoal. Charcoal burned with hematite ore, for instance, smelts iron.

Electrolysis separates metal from ore by using acid and electricity. Aluminum, which burns at a very high temperature, is extracted from bauxite by electrolysis. Bauxite is placed in a pool of acid, and 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

Earth contains a finite amount of ore. Ore genesis, the process by which a deposit of ore is created, is estimated to take millions of years. There are three major types of ore genesis: internal processes, hydrothermal processes, and surficial processes.

Ore can accumulate 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 circulates through cracks in Earth’s crust and deposits minerals in the areas around hydrothermal vents. This is called a hydrothermal process. Finally, ore can accumulate through processes that take place on the surface of Earth, such as erosion. This type of ore genesis is called a surficial process.

Ore can also fall to Earth as rocky debris from elsewhere in the solar system. These pieces of debris, entering the atmosphere as shooting stars, are called meteorites. Many meteorites contain large amounts of iron ore.

Ore is a nonrenewable resource. Because modern societies rely so heavily on metallic ore for industry and infrastructure, 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. This scarcity contributes to ore's value.