10 pounds for $12.95? That'd be a great deal...but be SURE it's labeled for internal usage. I just checked out that auction/ad...and even though it indicates "pure" and that "bentonite has been used internally", they don't specifically indicate that it's specifically for internal usage.
The issue comes mostly with the fact that Bentonite adsorbs immense amounts of toxins. And if it hasn't been mined/dug properly, it can be 'pure clay' from the ground, but that doesn't mean it didn't sit around for days/weeks in the back of the truck sucking up toxins from the air and environment.
Speaking of which, always keep your clay & charcoal in airtight packaging (so that it doesn't get 'used up' soaking up toxins from the air :)