Please read this article on Wikipedia, there are lots references and other links it has.
http://en.wikipedia.org/wiki/Medicinal_clay

I dont think there is anything wrong with consuming clay- Just try to eat a balanced diet and
if your body still can't get all the micronutrients it needs you can supplement it.
Most of the medicines we take for stomach conditions- Kaolin etc, facials- clearasil most contain clay,
even NASA used it in their space program- a particularly type because of its calcium content.

There are various types and depending on the source has various constiunets.
No 2 clays are the same.

If clays are supposed to be capable of absorption of heavy metal, obviously if they contain lead
won't they rrelease what is needed and the body get rid of the rest? Oh and by the way not
all clays contain lead. It depends on the source of the clay.

Or would we rather buy the clay form pharmaceutical companies after it has been processed or use it in its raw state