Safford, Arizona
The Gila Mountains are legendary copper territory. Home to the Morenci mine, an enormous complex of pits and heaps which dates all the way back to 1872, this part of Arizona is still one of the world’s biggest sources of the metal today. There is copper running all the way through these hills, a triangle of porphyry ore bodies where volcanic activity once thrust the metal up from the mantle into the crust of the earth.
And since copper is the nervous system of civilisation, that makes this sparsely-populated triangle one of the more important parts of the world. In the course of writing Material World I’ve come to the conclusion that we don’t spend enough time pondering copper. In part, I think, that’s because it lacks the novelty factor of battery materials like lithium or cobalt, but in part it’s because most of our copper is out of sight. It is dug and blasted out of enormous holes hundreds if not thousands of miles away from where most of us live (places like Safford, for instance). Before it reaches us it is usually encased in wires, motors and transformers, the insides of which we rarely ever see. For all that it is everywhere around us, it is also mostly invisible.
There are other metals which can perform the functions copper does, but they all have drawbacks. Silver is too scarce; aluminium is significantly less conductive and more prone to corrosion. But the striking thing about the history of copper is that actually we haven’t done all that much in the way of substitution. In practice, we have become ever more reliant on this magical metal - and like most ubiquitous things we have increasingly tended to take it for granted.
Yet as the years have gone by, it has generally become harder and harder to get hold of decent quantities of high grade copper. This is a really big deal, since copper, while not exactly scarce is certainly the least ubiquitous of all the mainstream industrial metals. In terms of its prevalence in the earth’s crust it’s actually about as hard to come by as one of the rare earth metals, lanthanum.
Now in one sense the chart above isn’t a fair representation of the availability of metals, since these are planetary averages. In the case of copper, it is often concentrated in certain areas like the copper triangle in Arizona or the deserts of Chile.
Even so, consider the situation outside Safford, Arizona, on the shoulder of Bryce Mountain. Here there is plenty of copper, but removing it from the ground is a tricky business, for a couple of reasons. The first is that much of this copper is stuck far beneath a thick, tough layer of basalt, making it inaccessible - or rather uneconomical. The second problem is that much of this ore is low-grade stuff, well below 1% purity, meaning you have to move a lot of rock for not much copper.
One of the defining trends in the copper business (and indeed for many metals) over the past couple of centuries is that, having already removed the easiest, richest, most accessible ores, the grades of copper in typical ores have been on a continually falling trend.
In writing Material World I set out to find out what this means in practice. Along the way I visited the biggest hole in the world, met with the people who want to go deep sea mining for copper and battery minerals and those who fear this is one frontier too far. But I also encountered many other extraordinary stories about the depths to which we’ll go to get this red metal out of the ground, some of which I didn’t quite have space for in the book. One of those stories concerns this spot in Arizona.
In the late 1950s, someone at the Kennecott Corporation, which owned the enormous Bingham Canyon mine in Utah, came up with an idea. Why not sink some high explosives into the ground, right into the heart of the copper ore, and just blast it?
You would be left with a massive underground cavern filled with rubble and exploded ore, into which you could then pour dilute sulphuric acid and leach out the copper remotely. The plan would involve far fewer workers or machines than a conventional mine, saving enough money to make the project add up. They even came up with a clever name: Project Sloop (Sloop was actually an acronym for Study - Leaching Of Ore in Place).
While this all made sense in theory, there was still a seemingly insurmountable challenge: the amount of dynamite you would need for such an explosion was implausible: tens of thousands of tonnes, so much that it wouldn’t even fit into the mine shaft. So the idea sat in a filing cabinet for a few years until someone from the US Atomic Energy Commission got in touch.
Around this time, the Federal government had been looking for ways to deploy nuclear bombs for peaceful purposes rather than as weapons. We already used TNT to help create canals, harbours and open pit mines, so why not use the mid-20th century’s most iconic explosive?
Under Operation Plowshare (from the Book of Isiah: “they shall beat their swords into plowshares”) the US intended to deploy bombs to widen the Panama Canal, to create cuttings through impassable mountains for roads and railways, even to frack oil and gas trapped in shale formations. Plans were drawn up for new harbours made using atomic bombs, their circular shape the main clue that they were created from an almighty explosion rather than by conventional digging and blasting.
The authorities were enthusiastic, but Plowshare did not start well. The first test explosion, Project Gnome, involved the detonation of a 3 kiloton warhead in an underground layer of rock salt under New Mexico to test whether the steam produced could generate electric power. The bomb failed to generate any electricity but did unexpectedly vent radioactive steam into the waiting audience of journalists. The second test, Sedan, resulted in an explosion so big it sent a plume of radioactive gas 16,000 feet into the sky, which then dropped nuclear fallout throughout Iowa, Nebraska, South Dakota and Illinois over the following days. The crater it left behind is so big it is now listed on the National Register of Historic Places.
Still, reasoned the officials, had you wanted to create a hole that big with conventional machinery, it would have taken six months and hundreds of workers. Just think of the opportunities for miners! So the authorities began working with Kennecott on Project Sloop. They found a site on that hill near Safford and made plans. A 20 inch diameter hole would be drilled, down to a depth of 1,200 feet. A bomb would be dropped in the hole, creating a cavity more than 400 feet high. All the holes would be sealed up to prevent any radioactivity escaping.
There were some challenges, chief among them the fact that the blast would be so big it would feel a lot like an earthquake throughout the neighbouring area. There were concerns that the ageing concrete in the Coolidge Dam, about 70 miles away, would crack. Another issue was that it was quite possible - probable in fact - that the resulting copper would end up radioactive. So tests were carried out to find out which method of refining would remove most of the radioactivity.
According to one paper, electrolytic purification would remove most of the radiation, though levels could nonetheless “possibly be high enough to make the copper unsuitable for certain specialized uses, for example, in radiometric counting instruments, in the phonographic industry, and for copper cooking vessels.” There might have to be warning notices on particular batches of copper that they were a bit radioactive. Still, you get the idea: this was not an idle plan. It taken very seriously indeed. Blueprints were produced suggesting nuclear mining and underground leaching could multiply the amount of copper produced in the US, reducing its reliance on imports.
Meanwhile, locals approached Kennecott with another set of concerns. Might the bomb leach radioactivity into their spring water? The authorities were pretty sure it wouldn’t, but as the project approached, the citizens became more disquieted.
Kennecott and the US atomic authorities spent much of their time squabbling over the size of the bomb. The mining engineers had to be talked out of using a 100 kiloton bomb - the size used in that second test at Sedan, which created the biggest man-made crater in America. In the end they settled for a 20kt explosion, about a third more powerful than the one dropped on Hiroshima. They later came back and asked if they could possibly have two bombs, or maybe three, though they couldn’t decide whether they wanted them dropped all at once or at regular intervals.
The scheme was still on the table for much of the 1960s. For a period, nuclear mining was the next big thing. Test boreholes were drilled all around the potential mine site. It looked like it might just happen. But then, not with a bang but a whimper, the idea dissolved away. The blueprints were shelved as the 1960s gave way to the 1970s. The bombs were never detonated.
The closest the wider Plowshare atoms-for-peace complex got to reality was a test elsewhere known as Project Gasbuggy, where nuclear bombs were were used to frack for natural gas. Three bombs were detonated and a decent amount of gas was produced. However there were unsafe levels of radionuclides in the resulting gas.
Still, surprising as this might sound, the main thing that killed off Project Sloop wasn’t public backlash against the potential radioactive risks. What really killed off the dream of nuclear mining was something seemingly much more prosaic: in the meantime the mining industry got much better at extracting copper from unpromising rocks - without having to blast them with nuclear warheads in the first place.
It’s this phenomenon which I spend a bit of the book investigating. It transpires that the great miracle of 20th century copper production did not depend upon atomic mines, but on clever, unnoticed ideas which helped us get better and better at turning ever less promising ores into metal.
In a sense it’s analogous to the phenomenon I described about the car paint industry. Most innovation doesn’t happen in one quick explosion, but gradually over time. Clever ideas and methods accrete and build upon each other. The upshot is as time goes on, we get better at making important stuff (or extracting important metals), and that important stuff gets cheaper and cheaper.
As you’ll see when you read Material World, this happens nearly everywhere (ironically, the construction of nuclear power plants is one of the few exceptions). It’s a story of widespread progress I find pretty awe-inspiring. We have these invisible leaps and bounds to thank for the fact that the 20th century evolved the way it did - that we had the electrical era at all and that when China urbanised in the late 20th century it had enough copper to do so.
There is, in short, a magical story behind seemingly mundane metals like copper. But there’s a dark side to it as well, for only belatedly have we learnt that many of those innovations also damaged the planet. We may have eschewed nuclear mining but we still managed to leave a sizeable toxic imprint on the planet.
Copper is only one of the six materials whose story I tell in Material World. It’s the most mind-bending, exciting intellectual journey I’ve ever been on. The book will be out in the UK in June and the US in November. Do pre-order and spread the word (and forward this email)! More side stories to come…
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