"Polonium Halos" in Granite

As often happens we get visitors to the Beagle that like to try out their knowledge on us "sciencey" types. A gentleman was looking at Polly in our front window this afternoon. When I told him it was a nearly complete fossil of an adult Psittacosaurus that was 125 million years old, he replied, "you don't really believe that do you?" I allowed as to the fact that I neither discovered the fossil nor dated the fossil itself, but was confident that it had been properly dated most likely based on several factors. He than said, "how do you explain the fact that granite contains polonium, since polonium has a half-life of only a few seconds?" I replied that I didn't have to explain it, but I did tell him that polonium has isotopes that range in weight from 194 to 218 and the natural isotopes have half-lives ranging from 0.145 seconds to 102 years.

After he left I did some data mining on-line and found a short article that is spot on point:

"Creationist Robert Gentry has argued that ring-shaped discoloration (halos) in primordial granite rocks are the result of damage from alpha-particle emission by radioactive isotopes of the element polonium (Po). Since radiogenic polonium has a very short half-life (usually measured in fractions of a second), Gentry argues that, if granite takes thousands to millions of years to form as mainstream geology believes, any polonium originally present would have decayed away long before the granite could have formed and could not have produced these (halos). Therefore, he feels that their existence is evidence for an instantaneous and recent creation of these granite rocks, and by extension the Earth. The following articles point out the flaws in Gentry's argument.
"Polonium Haloes (sic)" Refuted
Professional geologist Tom Bailleul takes a second look at Gentry's claimed polonium (halos), arguing that there is no good evidence they are the result of polonium decay as opposed to any other radioactive isotope, or even that they are caused by radioactivity at all. Gentry is taken to task for selective use of evidence, faulty experiment design, mistakes in geology and physics, and unscientific principles of investigation and argument style.
Evolution's Tiny Violences: The Po-Halo Mystery
Amateur scientist John Brawley investigated Gentry's claims directly by studying local rock samples, and concluded that there is no good evidence that these "polonium" (halos are actually produced by polonium at all, as opposed to longer-lived radionuclides such as radon or uranium."

This was taken from: http://www.talkorigins.org/faqs/po-halos/.