I work primarily with wastewater and landfill microbial ecology, so potential grad students can be assured that there are fields where licking is definitely not encouraged.
Two things I learned and an admission:
- I didn't know about licking to tell grain size, it makes perfect sense, though.
- I'd never heard about mimetoliths, very cool.
- A secret goal of mine is to visit one of those giant underground salt mines and lick the wall.
Hah, I have the same goal!
And yeah, geologists who do stuff like working in Superfund sites are highly disencouraged from licking rocks there.
I was always told that licking cores saturated in perchlorate builds character.