You might want to read a message by stellarfocus, May 8, on the Ask Lillian Forum. She mentions French Green Clay vs US volcanic ash clay. I've always referred to Raymond Dextreit's book 'Our Earth Our Cure'. He mentions, I believe, French Green Clay used internally for all sorts of ailments. But I don't have it with me and don't know what the revised edition says, nor what more recent books on the subject say.