I think I found a stone tool on Sunday

[EFerrari]

4. Iirc one way you can tell if a rock has been worked on is the little cone-shape breaks that happen

when someone chips flakes off. Water doesn't do that in the same way, not as liquid or as ice. That's impact and a lot of similar cone-shaped breaks (there must be a term for that) isn't something that rocks do to each other. That's someone trying to shape a rock.

My little anthro and less geology ends right there, though.