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.
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.