Rock, stone, or pebble?

I’ve been running quite a few primary school rock and fossil classes in Yorkshire this half-term. At Crofton Junior School near Wakefield, one of the girls in the class asked an excellent question:

“What’s the difference between a rock, a stone, and a pebble?”

These are cobbles, not pebbles, but are they rock or stone?

I started with the easy bit, which is ‘pebble’ as that’s a particle between 4mm and 64mm in size. As for rock versus stone, I decided that ‘rock’ was commonly used as a term for the natural material, and ‘stone’ for the material once it was utilized by people. It’s not a very satisfactory distinction though!

Have you got a better definition?


Earth scientist in North Yorkshire, fossilist on the Dinosaur Coast. Director of the Yorkshire Fossil Festival and palaeontologist with Hidden Horizons. Can be found cricketing for Ovington CC. Can be found twittering as @fossiliam.