One of the most fascinating arguments made by Creationists is the Polonium Halo argument. Polonium is a radioactive element produced by the decay of uranium. The odd thing about the granite formations where Gentry's Po halos are found, is that there is no Uranium.
Granite is an igneous rock, formed from slow cooling of volcanic magma.
It has a hard, crystalline structure. It was created, as solid cooled rock, with Po, which exploded shortly after the creation event, leaving it's characteristic halo. First, all of the granite formations in which Gentry found Po halos, all contain the mineral Myrmekite, which is a replacement mineral intergrowth. Thus, Radon is formed in the nearby U 238 deposits. As gas, it moves freely through cracks in Gentry's granite rocks, which themselves have no uranium.