By Rose Schreiber

I am looking at a map of the peninsula’s granite outcroppings, trying to imagine something strange: the alien world of the granite’s formation, nearly three hundred million years ago. Whether or not I can visualize something so abstract—so nonvisual—is an open question. And can I visualize time in this way, hundreds of millions of years at once? There is the slow, aeonic pressure of the Variscan orogeny: two tectonic plates colliding, a mountain belt rising, a few millimeters per year. There is the heat of the collision as rocks fold, crust thickens, and waves of silica-rich magma pool and solidify underground. And then there is the magma cooling, crystallizing, forming one giant, subterranean granitic mass—the Cornubian batholith—which is then pushed upward toward the crustal surface. All of this, to say nothing of the constant battering of winds and waves the peninsula receives from the Atlantic Ocean, the extreme weathering of rock. The peninsula is Cornwall and, looking at this map, I am trying to imagine its stone. 

Three hundred million years of geologic formation, four thousand years of small-scale human mining, a few hundred years of intensive extraction. This place, the “Cornwall and West Devon Mining Landscape,” has, in our time, become a World Heritage Site. It is now a memorial to an industrial heyday that exploded, and fizzled, in the blink of a geologic eye. Among moors, farms and woodlands, the land is cross-sectioned by roads, pockmarked by quarries and old mining ruins. Stone chimneys—some two hundred years old—point to vast underground mining networks, many stretching out below the sea. 

Metal, quartz, feldspar, clay. So much prized material. I know that the same geologic events that produced the granite likewise produced the granite’s valuable seams of copper and tin, as well as its vast, neighboring deposits of clay. As soon as granite forms, it begins to break itself down: its extreme, radioactive heat leaches water from surrounding rocks, creating a powerful hydrothermal circuit, and the leached water corrodes the granite. Cornwall Stone turns to Cornwall kaolinite. Now, my attention turns to a shallower time: the industrial frenzy to move the kaolin north. I try to imagine the enormous amounts of kaolin that were carved out of Cornwall, loaded onto boats, and shipped up the canal to the potteries in Stoke-on-Trent. The dubious desire for porcelain. There are so many interlocking histories here—geological and anthropological—and they converge to create a mass transfer of sediment. It is, in a way, a human orogenic event: the rising slag heaps of the so-called “Cornish alps.” 

There is so much contained in its name, Cornwall Stone. Cornwall: the place from which it came, the horned, cornubia shape of the peninsula, but also a sense of cornucopia—industrial plenty. And Stone: a word as concrete as it is vague. Cornwall Stone was always known for its variability, its indistinctness. Simply put, it was granitic rock mined in Cornwall—its chemical composition shifted each time mining struck new ground. There is something important here, I think, in its shiftiness: the way a material is just an idea, and Earth’s folding, melting crust is always pushing up against, and collapsing, the boundaries of that idea. Chemical purity might exist in the controlled environment of a laboratory but, I remind myself, it does not exist in actual rocks. What was Cornwall Stone? It was never pure or well-defined—that is, until now. 

Cornwall Stone is not mined in Cornwall anymore—instead, it is a composite of materials, mined elsewhere, their identities proprietary. Beyond knowing that the mixture is sourced from the UK, we know very little about where it comes from. Cornwall Stone has become Cornwall Stone Substitute, and in the process, it has become both more specific and more vague. What was once an extremely local material, an amalgamation of hundreds of millions of years of continental uplift and magmatic pooling, has been reproduced as an imitation. It is now, more than ever, a chemical idea.