Treasure in the Tailings: Finding Critical Minerals in America's Mine Waste

Critical minerals are commodities with vulnerable supply chains that matter for the U.S. economy, national defense, new technologies and energy independence. Mine waste may be an untapped source:

• Waste from centuries of past mining still sits on the landscape and may hold minerals once not worth recovering.
• At modern mines, recovering byproduct critical minerals — not the main target — may barely pay, so they end up in the waste.
• Mine waste is also a liability — for mining companies, or at old mines for taxpayers — because of its effects on the land.

Recovering critical minerals from waste could help clean up sites and boost domestic supply. Scientists at the USGS Geology, Energy & Minerals Science Center, with other centers funded by the Mineral Resources Program, are studying how.

Old mines

Waste at abandoned mines can harm the environment and health, and remediation may offer a chance to recover minerals too. USGS is working with other federal agencies on abandoned sites they have identified, recording each waste type's chemical and mineral "signature" to judge its value.

Weathering can move an element into a new mineral, which may need a new way to recover it. At the Tar Creek Superfund Site in Oklahoma, weathering has shifted germanium and zinc from their original host, sphalerite, into a new mineral, hemimorphite. Zinc is used mainly to prevent corrosion; germanium in defense technology and communications.

Weathered mine waste from the Tar Creek Superfund Site, Oklahoma, under a scanning electron microscope. Both sphalerite and hemimorphite host zinc and germanium. U.S. Geological Survey

Modern mines

Mining, processing and manufacturing are complex, many-step processes, tuned to recover the main commodities — so scarcer critical minerals are often lost to waste. USGS is working with the mining industry to follow how critical minerals move through a mine's circuits. At the Bingham Canyon mine in Utah — which recovers copper, molybdenum and gold, with byproducts including tellurium — a study found a significant amount of tellurium, in tiny mineral grains, ending up in the tailings. Tellurium is used in electronics and steel.

Tellurium is hosted in a variety of minerals in the tailings (left) of the Bingham Canyon mine, Utah (right). Photograph by Bob Seal, U.S. Geological Survey

Seeing inside the waste

Judging waste as a resource means knowing both how much critical mineral it holds and how extractable it is. USGS recently added an automated mineralogy analyzer — a semi-automated microscope that reads how electrons interact with a rock surface to produce quantitative mineral data. Maps of Bingham Canyon slag show minerals hosting copper, bismuth and antimony, pointing to ways to recover them.

A false-color mineral map of slag from the Bingham Canyon mine, made with an automated mineralogy analyzer. U.S. Geological Survey

Mapping the nation's mine waste

Through the Earth Mapping Resources Initiative (Earth MRI), USGS and state geological surveys are mapping the surface and subsurface where critical minerals might be recovered, and inventorying mine waste — where it is, what it holds, and whether recovery could pay. Many states take part, and more apply each year. Samples come from many deposit types, including an iron ore deposit at the Pea Ridge mine in Missouri, whose waste is being tested for rare-earth elements used in advanced electronics and military equipment.

States with Earth Mapping Resources Initiative funding for mine-waste studies as of fiscal year 2025. U.S. Geological Survey

The Missouri State Geological Survey, funded through Earth MRI, samples mine waste at the Pea Ridge mine. Photograph by Nadine Piatak, U.S. Geological Survey

What USGS is working on

• the critical mineral content of tailings by deposit type
• how weathering at old mines affects critical mineral content, recovery and environmental impact
• how critical minerals move through modern mine circuits
• advanced analytical methods that serve both recovery and remediation
• identifying, mapping and characterizing critical minerals in the nation's mine waste

Sources

Based on Critical Minerals in Mine Waste, U.S. Geological Survey Fact Sheet 2025–3026, USGS Publications Warehouse, citing White and others (2022), Hayes and others (2023), Piatak and others (2024), Seal and others (2024) and Taylor and others (2024); a work of the United States government in the public domain.