Copper is a metal known from antiquity. As a semiprecious metal in the same chemical group as gold and silver, copper occurs naturally in pure nugget form. Copper coins and jewelry date back 10,000 years. About 5,000 years after that, we have the first evidence of copper smelting in Anatolia, by which minerals such as green malachite and blue azurite become sources of the metal. This, the first metal technology, was also developed in Africa, China, and Central America, among other places.
Copper, which is soft, alloys with tin to form bronze, a much harder metal that launched a new era in human history. The Bronze Age starts around 3,300 BC in India, 2,500 BC in Europe, 2,000 BC in China, and before 1,000 BC in the Andes. Bronze is the first truly hard metal – copper won't hold an edge, and iron smelting is more difficult. Thus, bronze armor and weapons mark the end of the Stone Age. Because copper and tin are seldom found together, bronze is also a stimulus to trade.
The Romans used copper extensively. The Latin Cyprium refers to their main source, the island of Cyprus. We find copper-backed mirrors and more copper jewelry and also large quantities of copper alloyed with zinc; in other words, brass.
Meanwhile, New World civilizations were beginning to produce their own copper jewelry and bronze tools. Copper jewelry from the Great Lakes area dates to well before 3,000 BC.
Iron superceded copper as the signature metal of technology, starting in Anatolia and China, but copper retains and expands its uses in the medieval and modern ages.
Mining and Production
The earliest copper was probably loose nuggets scavenged as placer mining. Soon, prominent minerals such as brightly-colored azurite and malachite were surface-mined for smelting. These are carbonate compounds with blue and green colors that announce the presence of copper. Modern copper mining is more likely to target copper sulfides, but surface activity in the form of open-pit mining is still the favorite approach.
By far the largest copper producer in 2014 was Chile (31%), well ahead of China, Peru, and the United States (each around 8%). Chuquicamata in Chile and Bingham Canyon in Utah (right) are among the largest open-pit mines of any kind.
Extracted ore is crushed, ground, and separated by flotation. Smelting and further processing creates a blister of 99% copper. This is further refined by heat or electrolysis to create the end product, 99.99% copper.
In the United States in 2014, ten percent of copper came from recycling rather than mining. Copper is relatively easy to recover and refine, while alloys can be recycled by reprocessing at brass mills and the like.
Properties and Uses
Copper has many useful properties. It is a soft ductile metal, meaning it can be easily worked into a variety of shapes. These include coins, tubes, plumbing, and wire. Copper is the best electrical and thermal conductor after silver and gold. This makes it a favorite choice for electrical contacts and wire. This bears repeating: copper wire is everywhere. Household appliances, small electric motors, cords, and cables all depend on copper to function.
Copper is lustrous, and so used in decoration. It oxides slowly when exposed to the elements, forming a protective green patina such as is seen on the Statue of Liberty. Contrast this with iron, which rusts and flakes off until nothing is left.
Brass and bronze have already been mentioned as useful alloys. Brass is harder than copper, but still malleable, so that it is used for doorknobs, hinges, and other fittings. Brass has low friction, making it a favorite choice in bearings and valves. Bronze, the alloy of antiquity is still employed in window frames and other architectural elements. Bronze is heard as well as seen in bells and cymbals. Brass, by contrast, is an entire category of musical instrument.
Copper is still used in coinage when the intent is utility over investment. Modern copper coins are actually hardened with zinc or nickel, because pure copper won't survive wear and bending. The rising price of copper drives it to represent smaller fractions of a coin's metal content, lest the metal cost more than the face value of the coin. The US penny is 2% copper plated over zinc, the US nickel is 75% copper and 25% nickel, the euro coins are copper alloyed variously with other metals, the Australian kangaroo is 92% copper with aluminum and nickel.