CRITICAL MINERAL POTENTIAL OF THE EASTERN UNITED STATES

The eastern United States (U.S.) hosts significant concentrations of mineral materials designated as “critical” to the Nation’s prosperity and security, such as graphite, lithium, manganese (Mn), rare earth elements (REEs), titanium, zirconium, and zinc. The U.S. Geological Survey Earth Mapping Resources Initiative (EMRI) identified 149 focus areas in the eastern U.S., classified within 17 different mineral systems, that could potentially host critical minerals (https://www.usgs.gov/special-topics/earth-mri). Focus areas include active mines, exploration projects, and historical mining districts. Along the coast from Virginia to Florida, heavy mineral placer deposits are actively mined and explored for titanium (ilmenite and rutile), REEs (monazite), and zirconium-hafnium (zircon). Zinc is currently being produced from Mississippi Valley-type (MVT) ore deposits in the Balmat-Edwards district, New York; similar deposits yield zinc and germanium in Tennessee. Exploration for additional zinc-rich massive sulfide deposits is underway in central Virginia. Interest in producing domestic sources of battery materials has reinvigorated exploration and development in the Alabama graphite belt and in the spodumene-bearing (lithium) pegmatites in the Kings Mountain Belt in the Carolinas and pegmatite districts in New England. Although domestic Mn mining peaked in the early 1900s, several hundred million tons remain in Mn-rich iron deposits in Aroostook County, Maine. Historically, 75 of the identified focus areas produced tin and tantalum from pegmatites in Alabama, beryllium from pegmatites in New England, and aluminum from bauxite and clays in Alabama, Georgia, South Carolina, and Virginia. Potential unconventional sources for byproduct commodities have not been evaluated. Phosphorites, for example, can contain significant potential byproduct REE resources. Preliminary EMRI geochemical data for New York, Kentucky, and Tennessee Devonian phosphorite samples (n=77) and nodules (n=54) indicate median total REE concentrations of 1163 and 1220 ppm, respectively. New geologic mapping, geochemical analyses, and geophysical data are being acquired through partnerships with State geological surveys to further evaluate domestic critical mineral potential in prospective areas.