Uraniferous coal has been found in northeast Parana, Brazil, in the Rio
Bonito formation of Pennsylvanian age. In the majority of coal samples taken the uranium oxide content ranges from 0.005 to 0.030 percent, but selected screened samples have contained as much as 0.445 percent uranium oxide. The sampled thickness of the coal seam ranges from 17 to 54 centimeters and averages 31 centimeters. Channel samples across the entire thickness of the coal zone were taken in two places. All other samples were taken as grab samples from either mine waste dumps or coal zones that had high radioactivity.
Sufficient information is not yet available to justify any detailed considerations of such features as geologic distribution, mode of occurrence, and radioactive equilibrium conditions of the uranium in the coal.
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USGS Numbered Series
Uraniferous coal and carbonaceous shale in northeast Parana, Brazil