dropstone
An isolated fragment of rock found within a sedimentary rock (that had fallen, rather than being carried along).
Noun
- An isolated fragment of rock found within a sedimentary rock (that had fallen, rather than being carried along).
- An isolated rock that is geologically distinct from the surroundings, indicating that it was carried from a distant area and then dropped in place (by a melting glacier); an erratic.
Origin
From drop + stone.