PETROGRAPHY AND URANIUM MINERALOGY OF SC DHEC WELL CORE, JENKINS BRIDGE ROAD, NEAR SIMPSONVILLE, SOUTH CAROLINA
Uraninite and coffinite are the principal U-rich minerals in the core. Other U-bearing minerals include zircon, monazite and allanite. Discrete small crystals of uraninite occur in the coarse granite and in the pegmatite layers. They contain between 3.4 and 4.4 weight percent PbO. Coffinite is present as tiny crystals dispersed along microscopic fractures in the granite and pegmatite, plus along the slickenlined fault plane. Coffinite is sometimes intergrown with its Th-bearing analogue, thorogummite. Compared to uraninite, coffinite and thorogummite contain lower Pb, often below the detectability limit. Together the textural and compositional evidence point to primary uraninite crystallization with subsequent mobilization of uranium and secondary precipitation along fractures as coffinite.
Calcite occurs in the core as fracture-filling crystals together with epidote + fluorite +/ prehnite, and in the carbonate-rich zone (diopside-scapolite marble). Its presence is consistent with the carbonate signature shown by nearby high-uranium well waters.