From "OCCURENCES OF URANIUM IN CARBON COUNTY, PENNSYLVANIA" By Harry Klemic and R.C Baker
United States Geological Survey Circular 350
The Mount Pisgah uranium deposit, exposed in cliffs along the highway between Mauch Chunk and Nesquehoning, is in the basal sandstone and conglomerate member of the Pottsville formation.
The rocks have been folded into a tight syncline, the Panther Valley syncline, which strikes approximately S. 80° W. and plunges to the southwest at an angle of 5° as measured along the base of the Mammoth bed. The dip of the north limb of the syncline is about 45° to the south, whereas the dip of the south limb ranges from steep to the north, through vertical, to slightly overturned. Where the strata curve around the nose of the syncline, as on Mount Pisgah, the dip progressively decreases toward the axis.
The Lehigh River has cut its valley to the base of the Pottsville formation near the east end of the syncline so that no part of that formation is present on the east side of the river.
A discontinuous zone of uraniferous sandstone and conglomerate extends about 2,000 feet along the north limb of the syncline westward from the axis of the syncline. Near the western end of the zone, core drilling found discontinuous radioactive rock about 240 feet downdip from the outcrop. Near the center of the zone a drill hole ended in uraniferous rock about 100 feet downdip. A test edit driven horizontally into the rock about 25 feet started in uraniferous rock and ended in barren rock.
The mineralized rock varies in stratigraphic distance from an overlying sandstone and shale member. The easternmost exposure of uraniferous rock south of the highway is in a lens of conglomerate that wedges into the overlying sandstone. At the test adit near the western end of the uraniferous rock, more than 10 feet of massive conglomerate separates the uraniferous rock from the overlying sandstone and shale member.
The uranium content of the mineralized rock ranges from a few thousandths of a percent to a few tenths of a percent in a distance of a few feet along the strike.
The uraninm occurs as yellow and yellowish green minerals coating fracture surfaces and slickenside surfaces and as incrustations on loosely cemented quartz pebbles in coarse conglomerate. Fine cracks which penetrate both the pebbles and the calcite cement are filled with yellow minerals in many places. Uranium is also present in unidentified black material in the matrix of the rock and in very fine cracks in quartz pebbles.
Secondary uranium minerals were observed on surfaces of rock which had been broken only a few months previously, indicating that uranium is present in tightly cemented rock in a form that is unstable under present conditions of weatherinq. The absence of secondary uranium minerals in uraniferous rock in drill cores, excect where they cut fractures and bedding-plane surfaces, indicates that the massive parts of the rock have not been deeply weathered.
Carnotite, tyuyamunite, liebigite, uranophane, and beta-uranophane have been identified in the Mount Pisgah deposit. An attempt is being made to isolate and identify the black radioactive material that occurs in the matrix of the rock.
Table 1.-Uranium Minerals found in Carbon County, PA.
Mauch Chunk Ridge
Mauch Chunk Ridge, Penn Haven Junction
|Uranophane||Ca(UO2)2Si2O7*6H2O||Mount Pisgah, Mauch Chunk Ridge|
|Beta-Uranophane||Ca(UO2)2Si2O7*6H2O||Penn Haven Junction, Mount Pisgah|
Another excellent collection location can be found overlooking the Delaware River in Easton, Pennsylvania. This abandoned quarry is a good place to search for interesting rocks containing uranium and thorium minerals introduced into the serpentine group minerals there by hydrothermal solutions.
A sample from the quarry.
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