Radioactive materials are pretty much everywhere
Why is this Beach in Southern California Radioactive? at https://www.youtube.com/watch?v=v0gIigW1HjA
If you search ( oil well radioactive sludge ) you will find that radioactive materials are common in oil drilling. There will be drilled materials mixed with the drilling mud. I remember that propane has to be stored for a while because it’s molecular mass is close to radon and it is not good to use the propane before the radon has decayed. It cost money to store propane, so finding a way to separate the two would save money and be more safe. But I just did not have time to work it out. They might have pumped that onto the beach and let the water go out to sea, but sands and heavier materials black sand on the beach. You might find the wikipedia article about X-ray_absorption_fine_structure interesting for analysis of materials, and for sometimes high concentrations of soft x-rays and low energy gammas.
