Specifications include, but are not limited to: drilling and coring a minimum of 50 holes (50 pilot holes and 50 core holes) in southwestern North Dakota at depths ranging from 75 to 150 feet. The upper portion of each core hole will be drilled, and the basal 20 - 30 feet will be cored. The Geological Survey’s eight-year-long surface sampling program for critical minerals in lignite coals in western North Dakota has identified two stratigraphic horizons of critical mineral enrichment, the Rhame bed and the Bear Den Member. These two horizons are marked by 15 to 30 feet of the white-colored clay mineral kaolinite, which is often underlain by lignites which are enriched in rare earth elements at three to ten times the proposed economic threshold. Rare earth enrichment typically occurs in lignites positioned in the lower portion of the kaolinite and underlying 25 feet of strata. This zone is the target for the coring program and is known to contain lignites ranging in thickness from a few inches up to eight feet. Core evaluation will document the frequency at which lignites enriched in rare earth elements and other critical minerals (e.g., gallium, germanium, etc.) occur in these zones, including their thickness and degree of enrichment, with the ultimate goal of determining if mining lignites for their critical mineral content outside of the existing coal mines is feasible with the hope that the results will encourage industry to do further exploration.
