What size is 14mm stone?

[cwr]

Sounds like a really silly question I know... but I can't remember if stone is sized by the mesh that it gets screened through (so a 14mm stone would be put through a 14mm mesh and end up with some bits that are longer than 14mm) or the size would be the max dimension on any given bit. Or some other definition.

 

Reason for asking is I have a pile of stone I need to identify and can't recall what it was I ordered it was so long ago.