“Every single county in Minnesota has a mine.”
Heather Arends, mineral potential manager for the Minnesota DNR, knows the state’s mining industry spans far beyond the edges of its massive iron ore extractions and, as she notes, into all 87 counties.
Minnesota has multiple thriving operations considered “mining,” whether it’s harvesting peat, carving slabs of granite or extracting Kaolin clay. Some materials travel across the ocean to other countries; others, like aggregate gravel and sand needed for unpaved roads or general road upkeep, rarely leave a county.
“That’s truly a local resource … mostly used within a 30-mile radius,” Arends says of aggregate. She also oversees the DNR’s aggregate mapping program.
The importance of such localized operations becomes evident when viewed through local costs, especially to taxpayers.
“Eighty to 90 percent of a township’s budget is road and ditch maintenance,” said Arends. Urban areas, like the Twin Cities wider metropolis, often must truck in aggregate with an added taxpayer and environmental expense, she added. “The farther you transport, the more it’s going to cost.”
Aggregate is just one of the state’s rich geologic resources beyond iron ore. In recent years, Minnesota has risen to fourth in the U.S. Geological Survey rankings of states producing the highest value of non-fuel minerals. The state, according to USGS, in 2019 produced $5.3 billion worth of nonfuel mineral commodities mainly represented by iron ore, but also lime, sand and gravel (construction), sand and gravel (industrial) and stone (crushed).
Of 35 minerals listed by the USGS as “vital to the nation’s security and economic prosperity,” Minnesota has potential resources for at least six and perhaps more. Those six are manganese, used in steelmaking; titanium used in white pigment or alloys (metal made by combining two or more metallic elements); platinum group metals used as catalytic agents for chemical reactions; natural graphite used for lubricants, batteries and fuel cells; vanadium, primarily used for titanium alloys; and cobalt, used in rechargeable batteries and superalloys.
Uses for these minerals, often mined mainly in foreign countries, make finding U.S. sources critical, according to the federal government. For a mineral such as cobalt, for example, 70 percent of the world’s supply comes from the Congo, but the United States has an estimated 1 million tons of identified cobalt resources, most in Minnesota.
Minnesota also is among the top three states producing peat and the top five producing sand and gravel for construction or industrial uses, such as silica for hydraulic-fracturing operations.
Turns out, we’re in a good mineral neighborhood, especially around Lake Superior.
The potential for mining copper and nickel in the state has, of course, made headlines, and copper in the state’s geological neighbor, Michigan’s Upper Peninsula, has been mined commercially continuously for about 150 years and even earlier, as seen in ancient Indigenous copper mine pits on Isle Royale.
On Lake Superior’s northeastern shore near Wawa, Ont., you’ll find gold and micro, or industrial diamond mining, both potentials in Minnesota, which is also part of the same greenstone region.
Platinum and palladium have been discovered in the Duluth Complex, the geological area basically covering the state’s Arrowhead.
We have these mineral options, according to George Hudak of the Natural Resources Research Institute (NRRI), “because we have this geological diversity, and we have rocks of quite different ages.”
Hudak directs the Minerals & Metallurgy Strategic Groups at the University of Minnesota Duluth’s NRRI. As Hudak explains it, this region has different ages of rock with various mineral potentials. Minnesota’s rocks have not been “recycled,” as he called it, and are ancient with a variety of mineral potential. In addition, glaciers helped by scrapping away surface, making some minerals more commercially accessible.
This region has rock 2.5 billion years old, starting on the western border of Minnesota stretching through southwest Ontario, Quebec and the Canadian maritime provinces. “These are the places where people commonly look for gold, related to fault systems,” Hudak said, as well as copper, zinc, lead, silver and ancient intrusions that may contain platinum, palladium and micro-diamonds.
Some 1.8 billion to 2.5 billion years ago, an ancient ocean now called the Animikie Basin covered the Iron Ranges of Minnesota across the south shore of Lake Superior onto the northeastern shore of Lake Huron. Iron formations, which Hudak said “formed like bathtub scum around the old ocean” were products of the period’s mineral, chemical and biological interactions.
In describing this era, Hudak pulls out a fun-fact for the trivia minded: All formation of iron on Minnesota’s Iron Ranges stopped literally in a geological instant. “It’s like we were making iron formation on a Tuesday morning and late Tuesday night, it stops.” The cause? A 10-mile-wide meteor (some say comet) struck the earth near today’s Sudbury, Ont., northeast of Lake Superior. It changed the chemistry of the shallow Animikie Basin and left a crater about 93 miles across, one edge of which became today’s Slate Islands in Lake Superior.
NRRI and the Minnesota DNR continue to uncover mineral potentials, working to determine, Hudak said, “if they do occur, how do they occur and where do they occur. Viability (of mining) really comes down to whether or not you can do it in an environmentally safe way and economical way.”
To that end in 2019, the Minnesota DNR partnered with an Australian firm, Corescan, to do hyperspectral core imaging on 16,371 feet of archived mineral cores from six projects housed at the Drill Core Library in Hibbing. That is a relative small sampling of the more than 3 million feet of drilled core samples archived in the library. Another fun fact: 3 million linear feet is the equivalent of 100 Mount Everests stacked on one another. Details of the Corescan analysis are on the DNR website. “It tells us what rocks are there, and certain rocks have a tendency to hold valuable interest,” said Peter Clevenstine, assistant director of the DNR Lands and Minerals.
All minerals, by their nature, of course, are non-renewable resources, not replaceable within a human lifetime. Extracting them almost always raises issues of ecological and social concern. “Environmental review plays a critical role in whether or not a mineral resource is a mine-able product,” Hudak emphasized.
Minerals affect all of our lives. Regardless of what’s mined, Arends said, everyone benefits. “Aggregate mine or even a copper mine, it does provide a role in society because we’re using the materials.”
The Melbourne Museum in Australia puts it another, homey way: “The coffee cup and toothpaste we use in the morning, our cars, our electronic gadgets and the windows we gaze through are all derived from minerals.”
Those gadgets and technological advances have a particular hunger for minerals, which might make some of Minnesota’s more obscure, smaller mineral deposits increasingly of interest to the world’s mining businesses.
Titanium, hard as steel but less dense, is used in air and spacecraft while titanium dioxide can be found in most “white” products, from paint to mini-powdered donuts. Palladium is critical to filtering harmful vehicle emissions through the catalytic converter and can be found in dental fillings or crowns.
Even small amounts of minerals can generate large profits, Clevenstine points out, noting iron ore is measured in dollars per ton and base metals such as copper or zinc in dollars per pound, but precious metals such as gold, silver, platinum, palladium are measured in dollars per ounce.
History brought us gold rushes, but today we might be rushing for something else. Currently two minerals from the platinum group are among the most expensive, according to Money Metals Exchange. Rhodium sells for $7,600 per ounce and palladium for about $2,000 per ounce; both are used in catalytic converters. Gold is running a poor third at $1,761 per ounce.
Other mined resources demand higher quantities, such as dimension stone, the granite or limestone deposits sliced in slabs to use for homes, buildings, roads and tombstones. Peat harvesting looks much like farming, where dried peat is “vacuumed” for domestic uses such as raising earthworms, mushrooms, golf course construction, fertilizers or, on the industrial level, as an oil absorbent or for filtration of waterborne contaminants in mine waste streams, municipal storm drainage and septic systems.
Minnesota DNR’s Lands and Minerals division is responsible for managing 5.6 million acres of surface and a total of 11 million acres of mineral interests on public lands. (The state has retained mineral interests on some lands.) About 20 percent of the iron ore is within state-managed lands, some of which benefit the state’s Permanent School Fund and Permanent University Fund.
“Our job is to both be managing the minerals for the trusts we represent, but also do the environmental review on permitting to be sure it’s done right,” Clevenstine said. He points to the $1.4 billion School Fund, mainly built from mining on school trust lands, that uses the interest for K-12 education in the state.
Perhaps that’s why Clevenstine gets so excited about seeing minerals at work around him, from the steel in his car to the “countertops in my kitchen. Mesabi Black, I know, came from Babbitt.” Rose-colored stone mined by Echo Lake is being used for an arboretum in Grand Rapids, he added.
“It makes me feel good,” he said, emphasizing iron ore remains the state’s main mining economic engine. “I’m a big fan of iron ore and steel because it’s also the most recycled material – by far more than paper, plastic – 65 percent (of current use) is from recycled steel. That’s a good thing for our planet and keeps iron and steel production sustainable in the United States.
“When the USGS tracks all of our consumption of metals in the United States,” Clevenstine said, “when you do a pie graph, 90 percent is iron and steel. The remaining 10 percent are all of the other metals. And 80 percent of the iron comes from the Iron Range. It is so dominant in our society and important not just to Minnesota, but to the entire United States.”