My favorite story about these limestone issues is when I considered
grinding some chalk (the kind you write on chalkboards). I was warned that
such chalk contains a "binding agent" which sounds ominous. I looked at the
box, and down at the bottom was a notice that the chalk was ``CP Nontoxic."
Really! Of course, I think this stands for something else, but it was really
funny to me.
I'd be afraid of Diatomaceous earth, because it may contain a lot of salt
being a porous ocean product.
B