Re: Is Bentonite Clay supposed to be "radioactive" -Reply

["Dale E. Boyce" <dale@radpro.uchicago.edu>]

My limited geology knowledge tells me that one would expect elevated
uranium and thorium levels in clays.  Clays, at least the ones
I know about, are a byproduct of weathering of granite.  There
is a location up in Wisconsin where an outcrop of granite is so weathered
you can break off chunks of "rotten granite" and crush them in your hand.

Anyway, the crystal lattice of some of the granitic minerals have
relatively large gaps between atoms that permit large foreign atoms
to be trapped in the mineral.  Uranium and thorium concentrations
in granite is thus frequently higher than other rock types.

Dale Boyce
dale@radpro.uchicago.edu