The use of Roman ingots to investigate dark matter and neutrinos (2013)

Apparently, mined lead ore is already contaminated with Pb-210[1] from the natural U-238 decay chain, so currently the only way to remove the Pb-210 is to protect the lead and wait a very long time for the Pb-210 to decay naturally

[1]https://www.mdpi.com/2075-163X/8/5/211/htm

If there was some way to get uncontaminated lead ore, perhaps from deep inside an old ore vein, then it would be very valuable, if it was possible to refine it without introducing Pb-210 contamination