derives from part of
piece of rock
pebble
A piece of rock which is derived from clastic rock and has a grain size of 4 to 64 millimeters.
https://en.wikipedia.org/wiki/Pebble
EcoLexicon:pebble
SWEETRealm:Pebble
The grain size classification is based on the Krumbein phi scale of sedimentology.
clastic sedimentary rock