BISMARCK The North Dakota Geological Survey has produced a report that provides a road map for exploring lignite coal and organic-rich mudstone that contains enriched critical minerals.
The report, released this week, is the latest in a series of studies by state geologists exploring the extent of rare-earth minerals and other critical minerals including lithium, which is used in rechargeable batteries for electric vehicles that officials believe they could be the basis for a new mining and processing industry in North Dakota.
We found high concentrations of critical minerals, said Ed Murphy, the state geologist. The problem was finding them constantly along the same horizon.
Critical minerals such as copper, lithium, nickel, cobalt and rare earths are essential components in many rapidly growing clean energy technologies ranging from wind turbines and power grids to electric vehicles. Demand for these minerals is expected to grow rapidly as the clean energy transition accelerates.
State officials hope private companies will use the report to conduct their own explorations, which could yield further discoveries and provide the start of a critical mining industry in the state.
The tiny concentrated amounts of minerals embedded in millions of tons of lignite could contain billions of dollars of commercial-grade rare earths and other critical minerals, Lynn Helms, director of the North Dakota Department of Mineral Resources, testified.
Exploration began in 2015 by examining an 1,800-foot-thick layer containing lignite coal and organic-rich mud in the Little Missouri River valley, located within the Williston Basin, which geologists have now narrowed to a thickness of 30 feet which contains the richest known deposits.
The brightly colored rock formation is called the Bear Den Member of the Golden Valley Formation, found in mountainous areas covering 340 square miles in west-central North Dakota.
Critical minerals, which include rare earth minerals, are deemed essential by the US government to the country’s economic and national security. They are often supplied by countries, including China, that are not necessarily friendly to the United States
The North Dakota researchers analyzed more than 1,700 samples from more than 300 mineral outcrop sites in western and south-central North Dakota, a small fraction of the states estimated to have 25 billion tons of lignite reserves.
Deposits of critical minerals containing concentrations of 300 parts per million or more are considered cheap to mine. Samples of fine lignite coals and organic-rich mud from the lower Bear Den Member contain up to 2,570 parts per million of rare earth elements which the North Dakota Geological Survey believes to be the highest spot concentration ever reported from coal deposits North Americans.
Concentrations of several critical minerals, including cobalt, gallium, germanium, and lithium, have sometimes been found in the same samples.
Although lignite is a low grade coal, it holds promise as a source of critical minerals due to its ability to easily absorb rare-earth minerals that are relatively accessible, potentially making extraction relatively low-cost and environmentally friendly, according to the North Dakota Geological Survey assessment.
The rich deposits lie within what geologists call the Paleocene-Eocene Thermal Maximum, a formation resulting from a period of intense weathering, a process of decomposition of rocks and minerals due to exposure to the atmosphere dating back to 56 million years ago, when coal was deposited in subtropical rivers, lakes and swamps.
The mineral-rich Bear Den Member is found under layers of rock and sediment, including a thick layer of kaolinite, a clay used by Hebron Brick to make bricks.
Rich deposits were found on land owned by the U.S. Forest Service, North Dakota trust lands and private properties in McKenzie, Dunn, Mercer, Stark and Western Morton counties, Murphy said.
Map provided by the North Dakota Geological Survey
The North Dakota Geological Survey used a skid steer shovel to excavate 44 tons of material from a site on state-owned land to provide researchers at the University of North Dakota College of Engineering and Mines.
Initially, state geologists were finding that fewer than 20 percent of the samples were above the 300 parts per million considered cheap to mine. But within the 30-foot enriched layer, 60% to 69% of the samples were above that threshold, which Murphy called a pretty big jump.
That number has remained constant, he said.
This suggests to Murphy that North Dakota has abundant and viable deposits that could be mined for critical ore.
I think we have areas we can focus on, he said, with a road map that spares the need for companies to drill haphazardly, while allowing companies to accelerate exploration. I think that’s the big story.
In addition to exploration for critical minerals, companies are also waiting on the processing side to enable commercial development, Murphy said.
The North Dakota Legislature has funded Geological Surveys exploration for rare earths and other critical minerals, and the pending legislation would provide an additional $500,000 to continue the work, which Murphy hopes will provide information that will attract companies.
Murphy said the ores could be mined using strip mining similar to conventional lignite mining or using in situ mining, which involves leaving the ore where it is in the ground and recovering the ores from it by dissolving and pumping the surface solution where minerals can be recovered.
Researchers at UNDs Institute for Energy Studies are working to develop ways to extract and process rare earths and critical minerals on a commercial scale from North Dakota brown coal.
The UND institute recently received an $8 million grant from the US Department of Energy for engineering and cost studies that could lead to a $250 million plant for processing critical minerals, if the UND project is selected.
There’s still work to be done to really prove and consolidate the economy, said Dan Laudel, a chemical engineer and director of UND’s Institute for Energy Studies. He called the work of the North Dakota Geological Surveys exciting.
They appear to be starting to piece the puzzle together, locating rich deposits, he said.
His team has been working on the extraction of rare earths and critical minerals from the Falkirk, Coteau, Coyote Creek and Center lignite mines, where equipment already exists to mine the material on an industrial scale. So it’s much cheaper to access a raw material for that matter, Laudel said, though he added that the richest deposits of critical minerals can be found elsewhere.
We’ve found cheap grades in existing mines, he said.
The US Department of Energy is making a big push to source rare earths and other critical minerals domestically, to avoid supply disruptions and reduce dependency on other countries.
These materials are too important to our economy today and are needed for the transition to cleaner energy and other uses, Laudel said.
The discovery and description of these deposits are important steps in developing a comprehensive exploration model for the coal and minerals industry, with the potential to one day reduce the need for imports of critical minerals, a strategic vulnerability of the United States. , of the North Dakota Geological Survey said in a statement.
