If you tap unknown object on your tooth, you can discern stone, pottery, clay, metal, plastic, etc etc, without ingesting possibly contaminated soils so close to your bloodstream.
Even the tooth tap is still no longer recommended. Both my undergrad and grad schools refused to teach/allow students to put anything in our mouths due to risks of contaminated soil.
You're a man (or woman?) of culture, I see.
Precisely why I did it that way for years. I eventually got a camel back, and that worked pretty good - squirt a couple drops of water from the mouth piece on the soil and away you go.
This just brought me flash-backs of the absolute nut-bar I used to play DnD with that would tap dice on her teeth before rolling them "to check if they were real."
This is the closest thing to context I may ever have to that experience. I thought she was checking real vs imaginary, maybe she was checking if they were... ummm.. real bones? wait. no.