Years ago, under the care of a Native American healer (who btw studied bio-chemistry under Linus Pauling at USC) I began to drink bentonite clay. The first brand, a very gritty dirt, I mixed with water and drank, and over time I showed an elevated level of arsenic that hadn't existed previously. The company was Magic Botanicals and I spent time talking to a company representative on the issue and did stop using it internally. I switched to Sonne's No. 7, a bentonite clay in liquid suspension that I find terrific. It always settles an upset stomach, and is hardly objectionable to drink. I still use it fairly regularly.
The one thing my Native American used to say is to not use metal when mixing it in with the water (something about the ionization or some such), so I always have used a plastic or wooden chopstick.
My arsenic levels have dropped again, but I'm still high in Mercury and Lead. So....