In embarking on the research and travel for a book about the Earth’s metals and minerals, I was hoping to uncover some of those patterns which the natural world sometimes reveals when you look closely, profound resonances that spread across disciplines like refrains in a piece of music—haunting, beautiful, and true. And it happened, repeatedly. Early on at an abandoned arsenic works in Cornwall, in the 100-year-old dead zone of lifeless soil, I stumbled on a paradox.
Arsenic is a highly toxic metalloid. It is colorless, tasteless, and odorless. It was the poison of choice for murderers for millenia. The dose can be regulated for a precis…
In embarking on the research and travel for a book about the Earth’s metals and minerals, I was hoping to uncover some of those patterns which the natural world sometimes reveals when you look closely, profound resonances that spread across disciplines like refrains in a piece of music—haunting, beautiful, and true. And it happened, repeatedly. Early on at an abandoned arsenic works in Cornwall, in the 100-year-old dead zone of lifeless soil, I stumbled on a paradox.
Arsenic is a highly toxic metalloid. It is colorless, tasteless, and odorless. It was the poison of choice for murderers for millenia. The dose can be regulated for a precisely-timed death—sudden, gradual, or lingering—and its effects on the body are hard to trace. Nero used it to kill his brother-in-law. The Borgias, a Renaissance-era noble family of Spanish origins, laid down stocks of arsenic-based cantarella for the removal of cardinals, kings, and popes. The Chinese deployed it as a chemical weapon. Cornish arsenic found a ready market in the United States where, from the end of the 19th century, half a million tons was dispersed to try and vanquish the Colorado beetle. The beetle developed a resistance, but the arsenic remained in the soil—for another 9,000 years.
Something else comes out of the ground when we dig up those metals and minerals—and that’s hubris.
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At the same time, arsenic was being widely used as medicine. It was applied to skin diseases, blood diseases, rheumatic diseases, malaria, diabetes, diphtheria, tuberculosis, cancers, syphilis, scrofula, snake bites. By the end of the 1800s, according to the medical historian Jerome Nriagu, “every major disease was being subjected to arsenotherapy … at no other time in human history has the health of nations depended so much on one element.”
The Earth’s materials all contain a similar message. They’re a gift. They perform magic. As a species we’ve learned to tap into that magic and use it for our own ends. We’ve been utterly changed by it. But such gifts come with dangers. Something else comes out of the ground when we dig up those metals and minerals—and that’s hubris. Their powers made us light-headed, installed greed in our politics and societies, deep in our souls. Only now are we becoming aware of the true costs.
Use a little and the benefits are vast, use too much and suffer the consequences. “All things are poison,” wrote Paracelsus in the 16th century, “it’s the dosage alone that makes the poison.”
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Writing about nature—now, in the 21st century—not only has urgency but appeal. Animals and plants offer complexity and charm and energy—the fascinating mystery of life. But rocks? They’re dead, dusty things, surely. Having been interested in them all my life—not as a geologist, but as a pure amateur—I had a hunch that this assumption was not true, that in form and process, they’re closely connected to life, to our history, and to our imaginations.
Two moments of reading stand out from my research, pivotal moments that confirmed the notion that if rocks are not alive in the conventional sense, they’re not dead either—in technical terms, that the lithosphere is as much a part of the ecosphere as the biosphere. One sentence came in a book by the eminent geologist Marcia Bjornerud: “more than 40 percent of all mineral species on Earth are in some sense biogenic”—that is, they are the result of organic activity. Chalk and limestone and cherts are made up of plankton shells, oxygenating microbes “grow” iron, coal consists of decomposed plant matter.
“It’s the dosage alone that makes the poison.”
The second was a passage in Mircea Eliade’s ethnographic study of early metallurgy: “the imaginary world … came into being with the discovery of metals.” He went on to suggest that “metals opened up a new mythological and religious universe.” A bold claim that thrilled me and aroused my skepticism at the same time. In a sense, my book—Under a Metal Sky*—*is an attempt to prove Eliade’s point. He also brought into sharp focus a moment in pre-history, that primitive experiment, when a piece of dull stone was placed in a fire and a shiny liquid was seen to ooze from it.
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Out of dead rock came something transformative; hardened, that liquid transformed lives in a dozen different ways. It also altered forever our relationship to the planet. Now the Earth was a treasure chest, a box containing tricks so powerful it was as if—as alchemists believed—the materials themselves were gestating in the womb of the ground.
In personal terms, the conception of this book goes back a long time, to a day shortly before my eighth birthday when a chance find changed the course of my life. I was one of those geeky kids whose eyes were focused at their feet, looking for anything that glimmered in the ground, or offered pattern in the mess of nature. I had a geological hammer and chisel and used them unashamedly on any piece of exposed rock—old quarries, cliffs, people’s walls.
In my first few weeks at an English boarding school, I came across a large round stone, half-buried in the woods. I gave it a whack with my hammer and watched with wonder as it fell open. Inside were the outer coils of a giant ammonite. For weeks I chipped away to remove the casing. Inch by inch the fossil came into the light and the full scale of its 100-million-year-old form was clear. It was spectacular. I was feted by boys and staff alike. But nothing ever came close to the first instant of discovery—the metallic whiff of freshly-cracked limestone, the shock and joy of seeing what was inside.
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Sometimes I think that the entire course of my career—decades of travel and research and writing—was set in motion by that moment. It established a belief that behind the surface of the world lies another one waiting to be exposed, an urge to go in search of it, and the conviction that a hopeful hammer-whack will, if the place is right, open up a priceless cache of stories and ideas and truths. 
Read an excerpt from Philip Marsden’s new book, Under a Metal Sky, here.
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Lead image: mineral vision / Shutterstock
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Philip Marsden
Posted on November 20, 2025
Philip Marsden is the award-winning author of a number of books of history, travel and fiction. His latest book Under a Metal Sky begins underground, in the fragile galleries of Cornish mines and ends in a village in the Caucasus, panning for gold. In between he follows up a number of stories in central Europe, examining both the magic and danger that have come with our prodigious use of the earth’s materials.