The World's Largest Copper Deposit Is in Chile: Inside El Teniente

There are mountains you look at from afar and mountains you travel through from the inside. In the Andes above Machalí, in Chile's O'Higgins Region, one of them holds the largest known copper deposit on the planet. Its name is El Teniente. Put together the three most famous copper giants outside Chile, Bingham in the United States, Grasberg in Indonesia and Oyu Tolgoi in Mongolia, and they still fall short. Not by a little, either: El Teniente holds more than five times the copper of Grasberg.

The numbers come from the global porphyry copper database of the U.S. Geological Survey (USGS), published in 2008. A porphyry copper deposit is one where the metal is spread through an enormous volume of rock. For each one, the USGS records two figures: total tonnage, which adds up past production, reserves and resources, and average grade, the percentage of copper that rock carries. Multiply tonnage by grade and you get contained copper. El Teniente adds up to 20,731 million tonnes of rock at a grade of 0.62%, which comes to 128.5 million tonnes of copper (Mt, in industry shorthand). Run the same math and Bingham reaches 28.5 Mt, Grasberg 24.0 and Oyu Tolgoi 21.0. The three together come to 73.5. Out of the 421 deposits with tonnage and grade in that database, El Teniente is number one.

Drawn as bars, with the same source, the same year and the same definition for all four, the contrast needs no translation.

El Teniente's bar is not competing with the other three. Even added together, they come up 55 million tonnes short. Grasberg, the Indonesian deposit often cited among the largest in the world, holds less than a fifth of our contained copper. Bingham, Utah's historic mine, barely clears a fifth. The database dates from 2008, and some rivals have expanded their resources since then; that much is true. But the gap is more than fourfold against each of them, and with a margin like that the order is unlikely to change.

The World's Four Largest Copper Deposits Are All in Chile

The surprise does not stop at El Teniente. Sort that same USGS database from largest to smallest and the top four spots in the world are in Chile: El Teniente at 128.5 Mt, Chuquicamata at 126.0, Los Bronces and Río Blanco at 101.1, and Escondida at 85.8. The first deposit without a foot on Chilean soil shows up only in sixth place. This is not a lone medal. It is the full podium, plus fourth place, measured with the same yardstick for everyone.

This ranking speaks to something we have already covered: Chile holds the largest copper reserves on the planet. They are different metrics and worth keeping apart. Reserves measure the copper that can be profitably extracted today across an entire country. A deposit's contained copper measures everything that body of rock held and still holds, including what has already left through the mine's mouth. Both views point the same way, and the second one does something the first cannot: it puts a first and last name on the deposit sitting above all the others.

Laid out as a ranking, the podium shows something rarely said out loud.

It has to be read precisely, because precision is exactly what gives it value. Only 2.5 million tonnes separate El Teniente from Chuquicamata, and Chuquicamata's row in the USGS database groups several neighboring deposits: Chuqui Norte, Exótica and Radomiro Tomic. The Los Bronces and Río Blanco row also bundles more than one, including Andina. El Teniente, by contrast, competes alone. Escondida, at 85.8 Mt, holds about two thirds of El Teniente's copper. How much copper a mine produces each year is one thing; how much copper there is in total is another. On that second count, the summit is in O'Higgins.

First place does not rest on a single database. In 2005, geologists Cannell, Cooke, Walshe and Stein published the reference study on the deposit's geology in the journal Economic Geology, and their conclusion fits in one line:

“>94 million metric tons (Mt) of contained fine copper making it the world's largest known porphyry Cu deposit.”

That same year, Skewes, Arévalo, Floody, Zúñiga and Stern reached the same place by another route. In their chapter of the book Super Porphyry Copper & Gold Deposits, they described El Teniente as “the world's largest known Cu-Mo deposit” (copper and molybdenum), with resources of more than 75 million tonnes of fine copper in rock grading above 0.67%. Why three different figures (128.5, more than 94 and more than 75)? Because of the cutoff grade, the minimum concentration at which rock counts as usable ore. The USGS uses the lowest possible cutoff grade, so it includes more rock; Skewes's team only counted rock above 0.67%. The number changes. The ranking does not.

4,500 Kilometers of Tunnels Beneath the Andes of O'Higgins

Having the largest deposit is a gift from geology. Getting that copper out is another story, and that one we wrote ourselves. Codelco, Chile's state copper company, describes El Teniente as the world's largest underground copper mine, and UNESCO repeats that description in its listing for Sewell, the mine's historic camp. The operation works between 2,200 and 3,200 meters above sea level, in the municipality of Machalí. At that altitude, beneath Andean rock, a network took shape that now reaches this length:

More than 4,500 kilometers of underground tunnels. It is not a structure you can see from a plane, nor one that ends up on postcards. It is buried infrastructure, opened meter by meter, which meant solving ventilation, ore haulage and rock stability more than two thousand meters above sea level. Opening a path where geography does not make it easy is something we know well, as the 1,240 kilometers of the Carretera Austral show. At El Teniente, that path was opened into the mountain.

Today's scale makes more sense next to the starting point. On April 29, 1905, a decree from Chile's Finance Ministry authorized William Braden's Braden Copper Company to work the deposit. That first year, the mine processed 250 tonnes of ore a day. Between 1905 and 1906, up to 250 carts, each pulled by about ten oxen, hauled more than 4,000 tonnes of material up the mountains. Oxen. That is how what Codelco considers the start of large-scale copper mining in Chile began.

In 2024, the concentrator (the plant that grinds the rock and separates the copper from the rest of the material) processed an average of more than 138,000 tonnes of ore a day. That is roughly 550 times the first year. Nearly 120 years of industrial mining sit between those two figures, and nearly all of that difference is human work: new tunnels, new levels, new plants.

A Mine That Has Spent Over a Century Descending Inside the Mountain

Copper from this place was known long before the decree. According to the division's own historical account, there are records of copper tools used by the Promaucae people in Inca times, and during the colonial era the mine was called La Fortuna, on land tied to the Jesuits and to the colonial landowner known as La Quintrala. From 1760 on it was called the mine “del Teniente”, the Lieutenant's mine. The name that world geology recognizes today is more than two and a half centuries old.

What changed since then was the way in. An underground mine this size does not grow only sideways: it goes down. The first industrial workings began at 2,280 meters above sea level. In 1968 the Teniente 8 level was developed at 1,980 meters, 300 meters lower. Each new level means rebuilding, at a different elevation, the network of access, ventilation and haulage that already worked above. It is long-term planning written in rock.

Up on the slope, another mark remains. Sewell, the camp built for the mine's workers, was inscribed on the World Heritage List on July 13, 2006, at the 30th session of the World Heritage Committee in Vilnius. According to Codelco, the decision passed by acclamation and with applause, and Sewell became the fifth Chilean site on the list. UNESCO describes it as an outstanding example of the company towns built around the world.

In order, El Teniente's history reads as a single line running from the colonial era to today's concentrator:

Between the colonial mine once called La Fortuna and the 138,000 daily tonnes of 2024 lie more than 260 years. The mountain is the same. What changed is what we were able to build to get inside it, and the scale of what we learned to move once there.

No country chooses the geology it gets. What it does choose is what to do with it. El Teniente carries more than 120 years of industrial mining and generations of engineers, geologists and miners who learned to open tunnels more than two thousand meters up and to go down level after level without losing hold of the mountain. We have the largest known copper deposit, the top four places in the world ranking and more than 4,500 kilometers of tunnels built beneath the Andes. We have our own word for something like that, bacán, Chilean for truly admirable, and the story of the word bacán, from Genoese to the tango is worth knowing. The mountain supplied the copper and we supplied the tunnels, and when the data speaks this clearly, there is only one thing left to say: we are bacán.