SOUDAN UNDERGROUND MINE— Minnesota’s first and deepest iron ore mine still holds some of the purest hematite ever found on earth. But during the eighty years that this mine operated, finding that …
SOUDAN UNDERGROUND MINE— Minnesota’s first and deepest iron ore mine still holds some of the purest hematite ever found on earth. But during the eighty years that this mine operated, finding that rich ore was like searching for a needle in a haystack, which is why this famous underground mine ceased operations more than half a century ago.
That was just one of the fascinating revelations revealed during a two-hour walking tour of the mine’s 27th level with James Juip, an interpreter with Minnesota Department of Natural Resources. Juip, who has served as a mine interpreter for the state park here for the past six years, tells the story of the history, the people, and the geology of the mine with infectious enthusiasm.
He tells jokes, sings songs, and gushes excitedly as he points out how geological forces billions of years ago created the small pockets of pure hematite that for eighty years were integral to the production of steel in the United States.
“My girlfriend will tell you I can talk until the ears fall off your head,” he mentions at least twice. And there’s little doubt that he could, at least when regaling an enthusiastic audience of about 20 people with stories of this remarkable mine.
The walking tours of the mine are new and are being offered weekdays at 2 p.m. through September. The walking tour, which is different from the regular tours that the DNR has offered at the mine for decades, gives visitors the chance to explore the mine on foot, learning much more about the geology that created the mine and some of the dangers that mineworkers faced as they tried to locate and extract the valuable ore. Along the way, visitors can feel and examine up close the tortured rock through which miners dug to access the rich ore deposits that put Tower and Soudan on the map.
While the public often thinks of the ore deposits at Soudan as vast columns of hematite that extended from the surface down into the earth, in fact, most of the hematite was found in small pockets located within a vast formation of two billion-year-old metamorphic greenstone. The geologists who worked in the mine, said Juip, were under constant pressure to locate pockets large enough to justify extraction. “They generally had to be the size of a two-story house [to be viable],” said Juip.
The geologists drilled thousands of expensive test cores in a sometimes-desperate search for new deposits. “Talk about a high-pressure job,” said Juip, noting that one early geologist who had miscalculated in his search for ore was later found drowned in Lake Vermilion. Over the years, men in the mine drilled thousands of miles of core, notes Juip, starting at the surface and moving further into the earth as the mine expanded downward and outward. “We could take all the cores from Soudan and lay them out right here and we could run them out to Seattle and there’d be maybe a mile or two left over,” said Juip.
And locating a deposit was only part of the process. Once located, men called “drifters” were deployed to blast tunnels, or drifts, through the greenstone to reach the new deposit, and that process could take years. Standing near the main shaft at the 27th level, Juip pointed down the drift that miners built here in the 1950s. “Geologists told us there was ore three-quarters of a mile in that direction, and it took them three years of constant drilling and blasting to drive this drift out to the pocket of ore.”
The cost of production in such a mine was extraordinary, but the absolute purity of the hematite found at Soudan made it a crucial component of steel production for most of eighty years. “This ore is so pure that you can weld two chunks together,” says Juip. “It’s 99.9125 percent pure.” Before the discovery of the Soudan hematite, most steel produced in the U.S. was of relatively low quality due to high levels of impurities. Adding Soudan ore (about 100 pounds for every ton of steel) to the mix, however, helped to strengthen the steel significantly, which made the ore valuable enough to justify the high cost of production. But by the late 1950s, steel production technology had changed and the Soudan ore was no longer necessary, which meant there was no longer an economic justification for producing ore that was many times more expensive than the newfangled taconite pellets being mined on the Mesabi Range.
While most of the Soudan ore was found in relatively small pockets, there was one exception, according to Juip— the Montana ore body, which extended from the surface at least as far down as the 27th level, located a half mile underground. “This is the ore body that kept us in business,” says Juip, “It’s the only pure column of ore,” he said, and it extends one thousand feet across in many places. “If it wasn’t for this ore body, we probably would have quit mining here about 1910 or 1920.”
While conditions at Soudan were safer and more pleasant than in most underground mines, it took its toll on many who worked underground. While the miners who blasted and loaded the iron ore generally maintained their health, the men who dug the miles of drifts through the greenstone suffered the effects of the rock’s high silica content. “This stuff is about 80-percent silica,” said Juip. “This dust will give you silicosis and kill you,” he said. “The men who created these drifts here in Soudan, every single one of them died within six years of the mine closing. And a number of them had lung cancer and they didn’t smoke.”
In the earlier years of the mine, before the establishment of unions and the transition to underground mining, the conditions were far worse. While record-keeping was limited in the mine’s early years, says Juip, “we know that at least 150 men died in the open pits,” and the number could be as high as 220, he said.
“Believe it or not, here in Soudan, the underground mining was actually safer than open pit mining,” he said. “I definitely wouldn’t have wanted to be a guy in the open pit. It must have been a terrifying experience.”
For the mine’s owners, notes Juip, the deaths of miners were considered just another cost of business and that the mine’s early superintendent, D. H. Bacon, urged the creation of a night shift as early as 1885 even as miner deaths rose. In a recently-obtained 1885 letter from Bacon to mine owner Charlemagne Tower, Bacon noted that with a steady stream of new workers who appeared at the mine daily, the mine could operate 24 hours a day. “Every day,” wrote Bacon, “there are more than 50 people standing waiting for work. If we put those people to work on the night shift, with the acceptable losses that we discussed, there’s still enough people coming in on a daily basis that we can replace the people lost and actually make a profit with a day and a night shift.”
“That’s the way things were looked at in the 1880s,” said Juip, “and there’s written proof of that.”
Signs of life, on Mars?
Some of the deepest bore holes in the mine are located on the 27th level and Juip notes that some of those holes accessed pockets of ancient sea brines that have been trapped underground for billions of years. And found within those brines are previously unknown iron-eating bacteria that require no free oxygen and that appear able to survive temperatures as hot as 2,000 degrees and as cold as near-absolute zero.
That’s one of the reasons these ancient brines have attracted research attention from NASA, as Juip recently learned from one of the visitors to the mine who explained the reasons for the interest. “He told me that chemical for chemical, the rocks you guys see here today are like the rocks that were picked up by the last Mars rover probe. Iron, banded iron formations, and greenstone, all that stuff was also found on Mars.”
Given the ability of the bacteria in the brines to survive extreme conditions, NASA scientists believe very similar bacteria could very well exist on Mars today. “So he said, ‘we’re studying this because we think maybe our first contact with alien life is the same bacteria that makes this water right here kind of yellowish color.’”
“How cool is that?” asks Juip.
How cool, indeed.