This is not the answer you were looking for by any means but your
bringing
this up reminds me of stories about my WV mountain man grandfather
telling
his children that a little dirt in their food would help them grow
(and
being totally sincere).
It seems to me that if the soil is full of minerals, that there may be
some
truth to that. When one is experiencing pica, clay is one common
craving.
After all, it's the stuff we're made of.
Stacie