The iron deposits of the Vermilion Range are among the oldest geological formations in North America, laid down as banded iron formations during the Precambrian era when the Earth's atmosphere was still gaining its oxygen. The range consists of interbedded sequences of chert, magnetite, and hematite -- minerals precipitated from ancient seas roughly two billion years ago. The geological structure known as the Ely Trough, a synclinal fold in the bedrock, concentrated these deposits into formations rich enough to mine. Five mines operated within the Ely Trough alone -- the Chandler, Pioneer, Zenith, Sibley, and Savoy -- collectively producing 70 million metric tons of iron ore before falling silent. Across the full range, eleven mines tunneled into rock that predated complex life itself.

The hematite pulled from the Vermilion Range was extraordinary. Its purity was so remarkable that two pieces of raw ore could be pressed together and welded without additional processing. In the steel mills, this dense ore -- marketed as Vermilion Lump -- played a critical role in open hearth furnaces. The heavy chunks would crash through the floating layer of slag, causing the molten charge to churn and burn off impurities. No other ore performed this function as effectively. But technology eventually rendered even exceptional quality obsolete. When blast furnaces replaced open hearth methods, the expensive Vermilion Lump was no longer essential. Meanwhile, engineers developed methods to extract usable iron from taconite, the low-grade bedrock that surrounded the high-grade deposits, using open-pit mining and pelletizing processes that produced ore at dramatically lower cost.

The Soudan Mine closed in 1962. The last mine in the Ely area followed two years later. The Vermilion Range had been first to open among Minnesota's four iron ranges -- the Vermilion, Mesabi, Gunflint, and Cuyuna -- and it was effectively the first to close. The shift to taconite processing centered the state's iron industry on the Mesabi Range, where the ore was far easier to access from the surface. Towns along the Vermilion Range that had thrived on mining wages faced the quiet that follows an extractive industry's departure. Ely, the largest community on the range, had peaked at 6,150 residents in 1930. The population declined as mines shuttered, though the town reinvented itself as a gateway to the Boundary Waters Canoe Area Wilderness, trading pickaxes for paddle strokes.

The deepest level of the Soudan Mine found an unexpected second purpose. The University of Minnesota established a high-energy physics laboratory at the mine's lowest excavated point, where 2,341 feet of rock provides a natural shield against cosmic radiation that would interfere with sensitive experiments on the surface. The same geological properties that made the Vermilion Range valuable to miners -- dense, ancient, deeply buried rock -- make it valuable to physicists searching for neutrinos and dark matter. The mine that once sent trainloads of iron to build bridges and skyscrapers now hosts detectors searching for particles that pass through the entire Earth without touching anything. It is a fitting transformation: a place defined by extraction now devoted to the most fundamental questions about what the universe is made of.