Glossary

Copper is a reddish-orange metallic element with the chemical symbol Cu and atomic number 29. It is one of the oldest metals used by humans and remains one of the most important materials in modern industry due to its excellent electrical and thermal conductivity, corrosion resistance, and malleability.

Copper is a ductile, soft, and highly conductive metal, second only to silver in electrical performance. Because of this, it is the primary material for electrical wiring, motors, generators, circuit boards, and power transmission systems. It’s also used extensively in plumbing, roofing, electronics, and industrial machinery. In addition, its ability to form alloys easily makes it the foundation for other important engineering metals such as brass (copper + zinc) and bronze (copper + tin).

When exposed to air, copper slowly oxidizes, forming a thin, protective surface layer known as a patina. Initially reddish-brown, this layer eventually turns greenish-blue (copper carbonate), as seen on the Statue of Liberty. This natural patina protects the metal underneath from further corrosion, which is why copper can last for centuries even in harsh environments.

Copper is also an essential trace element in the human body, necessary for enzymes that aid in energy production, connective tissue formation, and iron absorption. However, excessive exposure to copper dust or compounds can be toxic.

Industrially, copper is mined primarily from sulfide ores such as chalcopyrite (CuFeS₂) and bornite (Cu₅FeS₄). The metal is extracted and refined through smelting and electrorefining. Major producers include Chile, Peru, China, the United States, and the Democratic Republic of Congo.

In terms of physical properties, copper has a melting point of 1,085°C (1,985°F), a density of 8.96 g/cm³, and an unmistakable metallic reddish luster. It is nonmagnetic, easily formed into sheets or wires, and highly recyclable—nearly all copper ever mined is still in use today because it can be reused without losing quality.