U is a naturally occurring heavy metal that exists primarily in granites, granodiorites, and their sedimentary derivatives such as sandstones. In reducing environments U is relatively immobile and can be deposited as its tetravalent form U(IV) in minerals such as uranite (UO₂). Conversely, oxidizing environments may result in oxidation and subsequent dissolution of U(VI), which is ≥ 10,000 times more soluble. Once dissolved into groundwater, the now mobile U can enter drinking wells and result in elevated concentrations in residential drinking water.

Jacobsville Sandstone is a red and mottled sandstone which lines the northern shore of Michigan’s Upper Peninsula deposited as basin fill during the 1.1 Ga Midcontinent Rift under reducing conditions which aid in the deposition of U(IV) in minerals. Previous studies have shown an elevated level of naturally occurring U and As in drinking water as high as 415 µgL^-1 and 13 µgL^-1 respectively, harvested from aquifers where Jacobsville Sandstone constitutes the underlying bedrock. The same studies indicate correlation between well bottom height and concentration of U suggesting a heterogenous distribution. Rock samples were obtained from three different locations in the region where Jacobsville Sandstone is exposed. By performing large area scans with µXRF we were able to determine points of interest which were further investigated with SEM-EDS where smaller spot sizes allow for better resolving power of fine details in matrix particles and cement between sandstone grains. Utilizing both methods of analysis allowed us to investigate mineralogic and elemental composition of samples revealing V, Ce, Nd, and La co-existing with U in matrix particles bound to cement between silicate grains along with As bearing minerals.