Scientists Find Lithium Hiding in ‘Fool’s Gold’ — And It Could Transform Battery Supply Chains

Geologists at the University of Pittsburgh and the United States Geological Survey announced this week the discovery of what they describe as an economically significant concentration of lithium within pyrite, the iron sulfide mineral commonly known as fools gold, in Devonian-era black shales spanning parts of Pennsylvania, West Virginia, and Ohio. The discovery, published in the journal Nature Geoscience, identifies a previously overlooked repository of the metal critical for electric vehicle batteries and grid storage that could potentially be extracted as a byproduct of existing fossil fuel operations in the region, avoiding the environmental footprint of opening new lithium mines.

Pyrite is abundant in the black shales of the Appalachian basin, where it forms as a byproduct of bacterial sulfate reduction in ancient marine sediments. The mineral has historically been considered a nuisance in coal and shale gas extraction — it oxidizes when exposed to air and water, producing sulfuric acid that is the primary cause of acid mine drainage, one of the most persistent environmental problems in Appalachian mining regions. The Pittsburgh team, led by geochemist Elena Varchuk, set out to characterize pyrite's chemical composition in detail using synchrotron X-ray fluorescence at Argonne National Laboratory and found, to their surprise, that the pyrite crystals in several formations contained lithium concentrations of 100 to 400 parts per million — concentrations that would not be economic in isolation but that aggregate to substantial tonnages given the enormous volume of pyrite present in thick black shale sequences.

The most promising formation identified in the study was the Upper Devonian Marcellus Shale, which is already extensively drilled for natural gas across Pennsylvania and West Virginia. Pyrite is routinely encountered and brought to the surface as drill cuttings during Marcellus drilling operations and is currently disposed of as waste. The researchers estimated that the pyrite produced annually as waste from active Marcellus drilling in Pennsylvania alone might contain 2,000 to 5,000 metric tons of lithium — though they cautioned that actual recoverable quantities would depend on the development of extraction chemistry capable of separating lithium from pyrite at sufficient purity for battery applications.

Laboratory experiments reported in the paper demonstrated that lithium can be leached from pyrite using hydrometallurgical techniques related to those used in current lithium brine and spodumene processing, though optimization for pyrite-sourced lithium is at an early stage. The researchers noted that if extraction could be performed on pyrite that would otherwise produce acid mine drainage, the process could simultaneously yield a battery-critical material and reduce an environmental hazard — an unusual case of potential dual benefit from what is currently a problematic waste stream.

Critical materials researchers expressed interest in the finding while noting that significant technical and economic work remained before the discovery could be characterized as a recoverable reserve. The United States currently imports the large majority of its lithium from Australia, Chile, and Argentina, and there is active federal interest in expanding domestic sources.