HIBBING — Matt Carter slowly strolled backward, neck craning up at the rows of gigantic metal shelves.
The Minnesota Department of Natural Resources Drill Core Library in Hibbing houses the rock from more than 20,000 holes drilled into Minnesota’s ground. Carter was searching for his favorite.
“The deepest hole drilled in Minnesota is right here,” he stopped, pointing up at hundreds of thin boxes. “It’s the Hattenberger hole.”
Ever since the Hattenbergers drilled a new well on their farm near Kettle River, they’d dealt with air in their plumbing. In 1976, during a power outage, they lit a candle in the bathroom. The ensuing minor explosion revealed the air was, in fact, flammable gas.
“He got private funding to drill, to core the hole — not just drill, to core — 7,700 feet because they thought they were going to strike black gold. Oil,” Carter explained.
Despite their massive investment, they were unsuccessful.
Core drilling means using a hollow drill bit to remove a cylinder of rock or other material from a hole.
The DNR estimates that today, that process costs about $150 per foot.
That expense is one part of the reason the Drill Core Library is so valuable.
Based on the cost of drilling alone, Carter estimates the library is worth about $500 million.
But of course, there are other ways to evaluate worth.
A new mineral, Hibbingite, was discovered in the archive. There’s evidence of a 1.85-billion-year-old meteorite impact. And the core helps answer geological research questions — including ones we never knew we’d be asking.
When you factor that in, DNR Lands and Minerals Director Joe Henderson said the library is “virtually priceless.”
Not every core’s story is as interesting as the Hattenberger hole. But together, they help tell the story of Minnesota’s geology — past, present and future.
Digging deep
Two-thirds of states have core collections, and the U.S. Geological Survey has several of its own, as well.
Minnesota’s is one of the largest libraries in North America. Carter guesses it's in the top five.
There are over 3 million feet of core stored in the three warehouses on the north end of Hibbing, not far from Bennett Park. That’s enough to stretch from International Falls to Chicago.
“Which is kind of crazy, to think about how much drilling has occurred,” Carter said.
Minnesota’s mining history and potential are significant drivers behind all this drilling. The vast majority of the core comes from mineral exploration.
Minnesota is so attractive because of its geology. There’s potential across much of the state, but the Duluth Complex — the formation that spans the Arrowhead — has gotten a lot of attention in the last couple years as companies look for critical minerals like copper and nickel and, more recently, gases like helium.
“The geological wonder that is locked in these rocks are wonderful,” said Joyashish Thakurta, a senior research geologist at the University of Minnesota’s Natural Resources Research Institute.
“ ... This [the Drill Core Library] is a place where you get access to rocks that are in the subsurface, many hundreds of feet or meters down in the interior of the earth, where you can by no means go and collect the rocks from. So, that’s why this collection is valuable. You get access to the rocks where they actually are.”
'Preservation of a natural record’
The library’s oldest samples date back to the 19th century, much older than the library itself. It was started in the 1970s, and in the 1980s, the Legislature began requiring companies to submit at least one-quarter of their cores to the library.
Carter estimates the library has 75 to 100 visitors each year, mostly researchers and those in the mining industry.
Thakurta and his colleagues at the institute visit the library five or six times a year, depending on what projects they’re working on.
Right now, they’re looking at manganese on the Cuyuna Range.
While recent news has swirled around a potential mine near Emily, companies and geologists have known for years there was manganese in the area.
A century ago, some 600 people lived nearby in the now-abandoned Manganese, Minnesota, touted as the “Hibbing of the Cuyuna Range.”
Interest in the mineral has grown with the clean energy push, yet it’s still unknown exactly why it’s here. That’s what Thakurta’s research aims to answer, using over 200 samples from the Drill Core Library.
While there has been exploratory drilling in recent years, the Cuyuna Range hasn’t been mined in four decades. And there’s land that doesn’t exist anymore, dug up with the iron ore.
“But the record of these layers — manganese-enriched or not — have been preserved by the companies, donated to this repository, and we can go and still access them whenever we want,” Thakurta said. “So, it’s a preservation of a natural record.”
How much core can a library store?
Preserving billions of years of geologic history takes space, and the Drill Core Library is running out.
“We did walk past one rack that was kind of empty, and this rack here has some shelving capacity on the top,” Carter explained, again craning to look at the towering racks.
“Otherwise, all the shelves are pretty much full of materials.”
The Drill Core Library’s webpage states the DNR is only able to accept a limited amount of core on a case-by-case basis, though Carter said nothing’s been turned away yet.
Companies don’t have to turn over their drill core until their leases are up, and Director Henderson said some have been “very gracious” and are holding on to their core for the time being.
But one recently asked if the library had space for some 80,000 feet of core that it’ll soon be ready to turn over.
“I think we could maybe accommodate most or all of it, but that would significantly put us at capacity,” Carter said.
The DNR has been trying for nearly a decade to get legislative funds to add on to Building Three, its newest and largest warehouse. Henderson said it’s been an agency priority.
“It never made it through,” Henderson said. “And so, we’re still hopeful. Now times are a little bit different than they were a few years ago with money.”
As the state faces a budget deficit, getting the $12 million ask through the Legislature would be a challenge.
The DNR was able to get $1 million of the state’s 2023 surplus to fund a reshelving project over concerns about the safety of deteriorating racks that were five decades old. DNR staff transferred over 38,000 boxes to temporary storage with the help of a moving company.
As part of that process, the DNR did get rid of some material that had degraded or was no longer identifiable. But otherwise:
“As long as we are around, we’re going to keep it,” Carter said.
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