Prairie Research Institute

Illinois State Geological Survey

Hicks Dome is a rare earth element-enriched volcanic structure straddling the Pope-Hardin County line in southern Illinois actively being studied by the Illinois State Geological Survey. The structure has both significant proven critical minerals and additional large prospective critical mineral resources. Hicks Dome is surrounded by the world-renowned Illinois-Kentucky Fluorspar District (IKFD), which produced over 90% of the nation’s fluorspar until the late 20th century when foreign suppliers began to erode the dominance of this mineral district.

Hicks Dome is unique compared to other critical mineral prospects in the United States (e.g., Mt. Pass) in that it is anomalously enriched in the scarcer heavy REEs (HREE) with respect to light REEs (LREE). Current estimates of HREE concentrations at Hicks Dome, which are an order of magnitude higher than other notable U.S. REE deposits (i.e., Mt. Pass, Bear Lodge), and LREE data suggest Hicks Dome as a highly attractive domestic REE source. In addition, Hicks Dome is likely to possess one of the largest fluorspar reserves in North America.

ISGS estimates that there are between 12 and 65 million raw tons of critical minerals ore within various deposits at the site. Hicks Dome is particularly enriched in elements such as dysprosium (Dy), scandium (Sc) and yttrium (Y).

Current research

ISGS is working on several projects with respect to critical and REE resources cooperatively with Hicks Dome LLC and funded by grants from the United States Geological Survey’s (USGS) Earth Mapping Resources Initiative (Earth MRI) program. For phase I of Earth MRI, the USGS conducted airborne magnetic and radiometric surveys to map potential critical mineral deposits hidden in the subsurface in southeastern Illinois. Phase I corroborated several known subsurface occurrences of igneous rocks and revealed numerous, previously unidentified anomalies that may contain critical minerals. ISGS used this valuable data to inform field mapping, studies and geochemical and mineralogical investigations during Earth MRI phase II. Based on phase I USGS aeromagnetic data, ISGS collected over 200 new samples from the district that were analyzed for REE abundances. One of the most significant discoveries from phase II includes the identification of isolated LREE-enriched carbonatite veins at Hicks Dome and elsewhere in the district. For phase III of Earth MRI, ISGS is collecting and studying shallow soil, regolith, and fluorspar occurrences in the area to determine if these features contain elevated levels of REE at or near the surface that may be easily exploitable. ISGS continues to petition for critical mineral exploration funding through various federal agencies.

These efforts at Hicks Dome parallel similar global efforts for REE exploration. For example, the Japan Oil, Gas, and Metals National Corporation recently partnered with Namibia Critical Minerals and invested $20 million in exploration, equity and development for the Lofdal prospect (Namibia), a volumetrically smaller deposit than what has been estimated for Hicks Dome. Hicks Dome has the potential to supply a domestic HREE feedstock to federally funded separation facilities already under construction in the U.S. Similar investments by the U.S. government with respect to REE exploration, extraction and processing will be paramount to diminishing our national reliance on foreign sources and furthering U.S. technological advancement.

Socioeconomic impact on Illinois

Critical minerals production in Illinois will benefit an economically depressed region of southern Illinois and support a rapidly emerging regional green technology industry. Once the world’s top fluorspar producer, the area has seen a double-digit (12%) population decline since the 1990s because of mine closures. Job categories that could be created from opening a mine in southern Illinois include mining, geology, engineering, health/safety, transportation, environmental sustainability, medical care, and numerous administrative functions. The deposit is strategically located near the confluence of the Mississippi and Ohio Rivers, allowing for broad and efficient distribution across the United States for processing, refinement, and use across diverse industries. Hicks Dome has significant potential to create a steady flow of tax revenue for Illinois that can be used to support other infrastructure, economic revitalization, new housing development, eco-tourism, and environmental and socioeconomic projects.