Already having identified large deposits of rare earths in northeast Wyoming, federal scientists are taking to the air to scan for more.
In the shadow of Bear Lodge Mountain north of Sundance, there is a scattering of old mining claims on schedule to be scanned from the sky as part of a national mapping effort to identify rare earth deposits.
These weathered claims represent just one small piece of an ambitious mapping campaign across the entire Black Hills region of South Dakota and throughout Wyoming.
A member of the mapping team compared the effort to mowing a lawn, low-level aircraft equipped with sophisticated sensors beginning before the end of the month.
A pilot and an onboard engineer will blanket the rugged terrain from the Black Hills to Bear Lodge and beyond, hunting for geological signatures that could reveal previously unknown mineral wealth hidden beneath the region's surface.
The airborne survey is part of a broader push to reduce dependence on foreign sources of critical minerals essential to everything from fighter jets to wind turbines.
"We're mapping the nation to better understand our resource potential, particularly focused on critical minerals these days," Jamey Jones, science coordinator for the U.S. Geological Survey's Earth Mapping Resources Initiative (MRI), told Cowboy State Daily. "The airborne survey is one of many that we're flying across the nation."
The MRI team is focusing on the Black Hills geologic formation running from around Bear Lodge Mountain in northeast Wyoming into South Dakota.
Photo of the contractor’s fixed-wing survey aircraft with a “tail boom” or “stinger” containing sensors that measure the magnetic field. Aircraft like this will be flying over the Black Hills region in the coming weeks. (Xcalibur Smart Mapping) 
The recently announced survey for northeast Wyoming will use fixed-wing aircraft, but in other parts of Wyoming, the USGS uses helicopters outfitted with stingers, like these in Rawlins. (Courtesy Benjamin Drenth) 
The recently announced survey for northeast Wyoming will use fixed-wing aircraft, but in other parts of Wyoming, the USGS uses helicopters outfitted with stingers, like these in Rawlins. (Courtesy Benjamin Drenth) 
The area to be mapped for potential rare earth deposits. (U.S. Geological Survey)
Stingers
The work is funded through the Infrastructure Investment and Jobs Act and uses aircraft flying at just 150 meters above the ground to measure magnetic properties and natural radiation signatures of bedrock.
People below the flight paths will see low-altitude aircraft with a distinctive magnetic sensor — called a "stinger" — extending from the tail.
The stinger probes hundreds of feet below the surface, potentially revealing mineral deposits that have remained hidden for decades or more.
"Our bread and butter is looking at magnetic characteristics," Jones said. "Those magnetic signatures penetrate those materials. So, we can sense the bedrock magnetic character to actually map the bedrock."
The technology specifically targets radiometric signatures that could indicate rare earth elements, which sometimes concentrate in the waste rock from old mines.
"The rare earth element minerals often are enriched in uranium, thorium naturally,” Jones said. “And so if we can detect those at the Earth's surface, then it might clue us in to rare earth element resource.”
Some of the original mining claims around the Black Hills were explored for uranium and lithium but could harbor rare earth potential that previous generations of miners never knew to seek, he said.
"If there is material on the surface and if that material has elevated uranium thorium concentration, which it's likely to, then we're going to see it," Jones said. "Our radiometric sensor is going to pick it up."
Tim Cowman, state geologist for the South Dakota Geological Survey, emphasized the regional significance of the work.
"The collaboration between the USGS, Wyoming, and South Dakota geological surveys will benefit the entire country," he said. "Once completed, we will have a better understanding of the complicated structure of this region and how that structure influenced emplacement of carbonatite intrusions.”
A carbonatite intrusion is an igneous rock formation where magma rich in minerals intrudes into pre-existing rock formations beneath the Earth's surface.
Maine Discovery
The current Wyoming-South Dakota survey builds on a remarkable discovery in Maine in 2021 that demonstrated the power of this aerial mapping approach.
"We actually found a little blip on the map, a little red spot that had high concentrations of thorium that we never had on our map," Jones said, recalling the discovery near Pennington Mountain, Maine.
Thorium is incorporated into certain ceramics and magnesium alloys to enhance resistance to heat and corrosion when building aerospace components.
"Suddenly, Maine has a whole different scenario in terms of mineral development," he added. "We suddenly have a new thing in our national inventory of interest that tells us that there are things that we just don't know about."
Wyoming Surveys
Similar surveys are already underway across Wyoming's mineral-rich landscape, demonstrating the statewide scope of the mapping effort.
"We've done airborne surveys from South Pass over in the western part of the state all the way to Laramie," Jones said. "Now we've got a major multi-year campaign going from Laramie all the way up to Casper.”
The Lake Owen area southwest of Laramie has been another early target, “because of its potential for platinum group metals and chromium," Jones said. "Wyoming's a pretty big empty space, and we have the potential to find things that we've simply never seen before.”
Data collection is expected to take about a year, with results anticipated in 2026.
David Madison can be reached at david@cowboystatedaily.com.
