Wikipedia Deep Dive

Copper extraction

11 min read

Nine thousand years ago, someone in the Great Lakes region of North America figured out how to extract copper from rock. We know this because archaeologists have found their handiwork—the Old Copper Complex—and dated it to roughly 7500 BCE. That makes it one of the oldest examples of copper extraction anywhere on Earth.

But they weren't quite first.

In a cave in northern Iraq called Shanidar, copper beads have been found dating back to 8700 BCE. And at a site called Çayönü Tepesi in what is now eastern Turkey, people were cold-hammering native copper—pounding naturally occurring copper nuggets into shapes—as early as 7200 BCE. They made fishhooks. They made awls. These weren't industrial operations. They were the first tentative steps of humanity learning to work with metal.

The Birth of the Metal Ages

There's a crucial difference between finding copper that's already in metallic form and extracting copper from ore. Native copper—the stuff you can pick up and hammer—is relatively rare. Most copper in the Earth's crust is locked inside minerals, chemically bonded to sulfur, oxygen, and other elements. To get at it, you need heat. Lots of heat.

The earliest confirmed evidence of high-temperature copper smelting comes from a place called Pločnik in modern-day Serbia, dating to around 5000 BCE. This wasn't someone hammering a nugget. This was someone building a fire hot enough to break chemical bonds and liquify metal. It was, in a very real sense, chemistry before chemistry existed.

This technology didn't just produce copper. It produced history.

The ability to smelt copper gave rise to what archaeologists call the Chalcolithic Age—from the Greek words for copper (chalkos) and stone (lithos). It was a transitional period when humans used both stone tools and metal ones. Then someone discovered that mixing copper with tin produced something stronger than either metal alone. Bronze. And just like that, the Bronze Age began.

None of this would have been possible without smelting. The entire arc of human technological civilization—from bronze swords to copper wiring—traces back to those first experiments with fire and ore.

The World's Oldest Mines

Once people learned to smelt copper, they started digging for it. One of the world's oldest known copper mines sits in Israel's Timna Valley, in the Negev Desert about 30 kilometers north of Eilat. People have been extracting copper there since the fourth millennium BCE—that's around 6,000 years of continuous or near-continuous mining.

The Timna mines are fascinating for another reason. Archaeologists have found evidence that people in the area were using surface copper deposits even earlier, in the fifth and sixth millennia BCE. The progression is clear: first you use what's lying around, then you start digging.

This pattern repeated across the ancient world. In the Atacama Desert of South America—one of the driest places on Earth—copper working began around 1400 BCE. Ice core studies from Bolivia suggest that large-scale smelting may have started there around 700 BCE, over 2,700 years ago. The pollution from those ancient smelters left chemical signatures in the ice that scientists can still detect today.

By the time of the Inca Empire, copper metallurgy in South America had become sophisticated. The Incas produced three types of copper alloy: tin bronze (copper and tin), arsenical bronze (copper and arsenic), and arsenical copper. About 74 kilometers northeast of the Chilean city of Copiapó, at a place called Viña del Cerro, the Incas built one of their largest mining and metallurgy centers in their southern province of Qullasuyu.

When the Spanish conquistador Diego de Almagro crossed the Atacama Desert in 1536, his men had no trouble finding copper. They used it to make horseshoes.

Chile's Copper Century

Fast forward three centuries to 1830. A man named Charles Saint Lambert introduced a new technology to Chile: the reverberatory furnace. This was a type of furnace where the fuel doesn't touch the material being smelted. Instead, heat radiates from the roof and walls onto the ore below. It was more efficient and produced higher-quality metal.

Lambert's furnaces, combined with new railroads and steam-powered ships, transformed Chilean copper mining. In 1850, a prospector named José Tomás Urmeneta discovered rich deposits at Tamaya, which became one of Chile's major copper mines.

The results were staggering.

By the mid-nineteenth century, Chile was producing 18% of the world's copper. In some years during the 1850s to 1870s, that number climbed to 60%. Copper export tariffs made up more than half of the Chilean government's income. Chile was, for a few decades, the undisputed copper capital of the world.

There's an irony here. Lambert's success in modernizing Chilean copper production may have sowed the seeds of decline for his own copper smelting business back in Swansea, Wales. By making Chile more competitive, he undermined the Welsh copper industry that had dominated for generations.

And Chile's dominance didn't last either. By the 1890s, technological developments were leaving Chilean mining behind. New techniques like froth flotation, heap leaching, and large-scale open-pit mining were transforming the industry elsewhere, but Chilean operations were slow to adopt them. The country's share of world production dropped to 5-6% by the turn of the century, and hit a low of 4.3% in 1914.

How Modern Copper Extraction Works

Let's pause the history and talk about what actually happens when you extract copper from ore. It's a story of relentless refinement, of squeezing ever more metal from ever-poorer rock.

The average grade of copper ore today is below 0.6%. That means for every ton of rock you dig up, you get less than 6 kilograms of copper. The economic ore minerals—the bits that actually contain copper—make up less than 2% of the total volume. The other 98% is waste rock that needs to be removed and disposed of.

Because of these low concentrations, all modern mining operations start with beneficiation—a fancy word for concentrating the ore. You can't just throw raw rock into a furnace anymore. The energy costs would be astronomical.

The Froth Flotation Revolution

The breakthrough that made modern copper mining possible was froth flotation, invented independently in Australia in the early 1900s by C.V. Potter and G.D. Delprat. It's a brilliantly counterintuitive process.

First, you crush the ore into tiny particles, less than 100 micrometers across—about the width of a human hair. Then you suspend these particles in water with special chemicals called collectors. Common collectors include potassium ethylxanthate and sodium ethylxanthate. These chemicals do something clever: they coat the copper-bearing minerals and make them hydrophobic, meaning they repel water.

Now you pump air through the mixture. The air bubbles attach to the hydrophobic copper particles and float them to the surface, like tiny life rafts. A surfactant—often methylisobutyl carbinol, or MIBC—creates a stable froth at the top. You skim off this froth, and you've got your copper concentrate.

The rock that doesn't float becomes tailings—mining waste. But sometimes that waste contains other valuable metals like lead or zinc, which can be extracted through additional processing.

Froth flotation can produce concentrates with 27-40% copper content, depending on the original minerals. That's a dramatic improvement over the 0.6% you started with. The process made the giant Bingham Canyon Mine in Utah economically viable—an open pit mine so large it's visible from space.

Smelting: Fire and Chemistry

Once you have concentrated ore, the next step is smelting. Until the 1960s, the dominant method used roasters and reverberatory furnaces. The roaster partially oxidizes the concentrate, converting it into something called calcine and releasing sulfur dioxide gas. The calcine then goes to the reverberatory furnace for final smelting.

This is where we should talk about what copper ores actually contain. The most common type is chalcopyrite, with the chemical formula FeCuS₂—iron, copper, and sulfur. When you smelt chalcopyrite, you're not just melting metal. You're breaking chemical bonds. The sulfur burns off as sulfur dioxide (a major pollutant if not captured). The iron combines with silica to form slag. And the copper collects at the bottom as a relatively pure metal.

Modern smelters produce more than just copper. Precious metals like gold and silver often concentrate in copper ores and become valuable byproducts. Sulfuric acid, captured from the sulfur dioxide emissions, is another important product. A well-run smelter turns pollution into profit.

But there's also arsenic. Arsenic is the main impurity in copper concentrates entering smelters, and the problem is getting worse. The easy, low-arsenic copper deposits have been mined out. What's left tends to be deeper, more complex, and more contaminated.

Leaching: The Wet Alternative

Not all copper ores need to be smelted. Oxidized copper ores—those containing minerals like azurite (blue), malachite (green), or chrysocolla—can be processed using hydrometallurgy, which means extracting metals with liquid solutions.

The most common approach is heap leaching. You pile crushed ore into massive heaps, sometimes covering acres of land, and sprinkle dilute sulfuric acid over the top. The acid dissolves the copper minerals as it trickles through, producing what's charmingly called "pregnant leach solution."

This pregnant solution then goes through solvent extraction. You mix it with an organic solvent containing special molecules called chelators. These chelators grab copper ions and nothing else (ideally), carrying them into the organic phase. When you evaporate the solvent, you're left with copper compounds that can be further processed.

For some ores, there's an even more exotic approach: bioleaching. Certain bacteria naturally oxidize sulfide minerals, producing sulfuric acid as a byproduct. You can harness these microorganisms to do your extraction work for you. It's slower than conventional methods, but it requires less energy and can economically process ores that would otherwise be too low-grade to bother with.

The Geography of Copper in the Twenty-First Century

Today, the landscape of copper production looks very different from Chile's nineteenth-century dominance. China now has more than half of the world's copper smelting capacity. It's also the world's largest consumer of refined copper, feeding its vast manufacturing and construction sectors.

The shift happened gradually, then suddenly. In the 1960s and 1970s, American copper companies faced a wave of nationalizations across the developing world. By the 1980s, state-owned enterprises had overtaken companies like Anaconda Copper and Kennecott. Oil companies briefly diversified into copper mining in the late 1970s and early 1980s—ARCO, Exxon, and Standard Oil all took positions—before selling off their copper assets when profits disappointed.

Investment concentrated in Chile through the 1980s and 1990s, partly because other countries presented problems: political instability in Peru, tightening environmental regulations in developed countries, hostility to foreign investment in nationalized industries like those in Zaire and Zambia.

But even Chile has struggled to maintain its copper infrastructure. No new copper smelter has been built in Chile since the 1990s. When the Fundición Ventanas smelter in central Chile closed in 2022, it sparked a national debate about whether to build a replacement and where to put it.

Some argue for the Antofagasta or Atacama regions in the north, where most of Chile's copper mines are located. Others want to keep smelting in the Valparaíso Region, near existing infrastructure. A 2024 study concluded that Antofagasta offers the best logistical advantages. But the president of Chile's National Mining Society estimates that building a new smelter would take five to seven years.

Meanwhile, the world's largest copper smelter sits in inland southeastern China. The Guixi Smelter had an annual production capacity of 900,000 tons of copper as of 2015. Between 2013 and 2023, China and Zambia expanded their smelting capacity while Chile and the United States contracted theirs.

The Material That Powers Modernity

Why does any of this matter? Because copper is everywhere in modern life, usually invisible but absolutely essential.

Copper wiring carries electricity through your walls. Copper circuits make your electronics work. Copper pipes bring water to your taps. Copper alloys form the innards of countless machines. The electric vehicle revolution, the expansion of renewable energy, the growth of data centers—all of these depend on vast quantities of copper.

And we're running out of the easy stuff. The shallow, high-grade, low-arsenic deposits that powered the nineteenth and twentieth centuries are largely depleted. What remains is deeper, lower-grade, and more chemically complex. Extracting it requires more energy, more sophisticated technology, and more careful management of environmental impacts.

The scramble for copper is real. Countries are repositioning themselves to secure supplies. Companies are developing new extraction technologies to process ores that would have been worthless a generation ago. And somewhere in a laboratory, someone is probably working on bioleaching bacteria optimized to eat through the most stubborn sulfide minerals.

Nine thousand years after someone in the Great Lakes region first figured out how to work copper, we're still at it. The methods have changed beyond recognition. The stakes have only grown larger.