Highly mineralized waters with salt content up to 200 kg/m3occur in carboniferous strata in upper Silesia. These waters often contain high226Ra concentration, reaching 400 kBq/m3, and flow from the surrounding rocks into mine workings and then have to be pumped out to the surface, finally ending in the rivers. Radium-bearing waters of type A contain significant amounts of barium ions. In these cases radium is easily co-precipitated with barium in the form of BaSO4+ RaSO4. The specific radioactivity of such deposits can be as high as 1 MBqlkg. Radioactive deposits cause elevated gamma radiation levels up to 200 pA/kg and also some elevation of radon daughter concentrations in air. Usually the contamination is limited to small areas lying near streambeds where radium-bearing waters have flowed. Nevertheless, waste materials from coal mines may cause significant radioactive pollution of the natural environment. In carboniferous strata, so-called radium-bearing waters of type B occur. These waters contain considerable amounts of sulfates but do not contain Ba2+ions. In type B waters the concentration of226Ra reaches 12 kBq/m3. In this case there are no chemical conditions for forming highly radioactive deposits.