See Hveragerthi's message below. He/she says Prill beads are zeolites. If that's the case then this is much different than simply working by "magic." Her/his post was the first I'd heard of this though. All the web sites I've seen for Prill do say they work by "magic."
Anecdotal evidence, such as the cleansing of Lake Mead in Nevada via Prill water and people's personal experiences, however, do seem to indicate that Prill beads are authentic.