LOL, Oakleaf... over here, the surface seems to called (interchangeably) metal, gravel and shingle... and that is small but often rough stones collected from naturally occuring shingle pits, from river beds (but often smashed up afterwards to a uniform size) or from commercially pulverised rock.

ROFL - there's no way our "gravel" would go in gardens... not if you wanted the purty smooth 'river' look.