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October 13, 2020

There’s an old saying that one man’s trash is another man’s treasure. At the USGS, we’re taking another look at old mine waste and tailings to see if there might still be mineral potential in them.

We recently looked at the potential for rare earth elements in historic mine waste of the eastern Adirondacks of New York, and we’ve even looked at how slag can be repurposed and how mine tailings can capture carbon for long-term storage.

But now, the USGS is thinking bigger-how to use remote sensing to look for critical mineral and energy potential across larger scales using tools like satellites and hyperspectral analysis.

Image shows the Mountain Pass mine from space
An image of the Mountain Pass rare earth elements mine in California taken by the ASTER imager. With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched Dec. 18, 1999, on Terra. Image credit: NASA.

Satellites Seeking Uranium Hotspots

Throughout the Western United States, historic uranium mines can be found. Mostly developed during the uranium boom of the 1950s, these mines produced much of the uranium that fueled the nuclear power industry. Now, USGS scientists are revisiting these mines to see what uranium potential may remain.

The scientists are making use of two remote sensing types: lidar and Worldview-3 High Resolution Multi-spectral data. Lidar uses lasers to create high-resolution digital elevation models with vertical accuracy as good as 10 cm. Usually mounted on a low-flying aircraft, lidar can be used to estimate volumes of mine waste and physical features of waste piles and pits.

Worldview-3 High Resolution Multi-spectral data, meanwhile, is collected by satellites and made up of the reflection of light and other solar radiation against surface materials. Each material, like rocks, concrete, water, etc. has a particular reflection, like a fingerprint. By analyzing the reflection, USGS scientists can determine what kinds of materials are left at the mine sites, and whether or not they might have more uranium to mine.

Image shows a hyperspectral map of deposit types
Preliminary map of selected minerals for a portion of the Nabesna area of interest, near Orange Hill and Bond Creek deposits in Alaska. The image, derived from HyMap imaging spectrometer data collected in July 2014, is draped on shaded relief.

Hyperspectral Hyper Focus

Speaking of fingerprints of light, another remote sensing project looking at critical minerals is using hyperspectral analysis to look at rare earth potential in mine waste and in regoliths. Regoliths are better known as soil, sand, dust, and other loose materials that cover solid bedrock.

Hyperspectral, like the Worldview-3 High Resolution Multi-spectral data, uses light reflection to determine what kinds of materials you’re looking at. The main difference are the width and number of the light bands they make use of. Hyperspectral uses much narrower bands than the Worldview-3 High Resolution Multi-spectral data and typically produces many more bands than the Worldview-3 High Resolution Multi-spectral data as a result. Unlike the Worldview-3 High Resolution Multi-spectral data, hyperspectral data is usually collected from an aircraft, although there are several instruments either presently or being planned to be delivered to the International Space Station by various countries.

USGS scientists are currently working on getting the kinds of hyperspectral signals from regolith and mine waste samples that contain rare earth and other critical elements in the laboratory, so that this information can be used to help interpret satellite hyperspectral and Multi-spectral data collected at larger scales.

Lidar data, Upper MS River
Lidar data, Upper MS River

Starting with Science

USGS scientists believe in leaving no stone unturned when it comes to research and are taking that dedication to new heights. More information about the uranium waste research can be found here, while the rare earth hyperspectral research can be found here. To find out more about energy research at the USGS, please visit our Energy Resources Program webpage, sign-up for our newsletter, or follow us on Twitter. To find out more about our mineral research, please visit the Mineral Resources Program webpage or follow us on Twitter.

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