Pebble, Rock, Stone or Boulder? - South Africa ...
Boulder −6 to −8 64–256 mm 2.5–10.1 in Cobble −5 to −6 32–64 mm 1.26–2.5 in Very coarse gravel: Pebble −4 to −5 16–32 mm 0.63–1.26 in Coarse gravel: Pebble −3 to −4 8–16 mm 0.31–0.63 in Medium gravel: Pebble −2 to −3 4–8 mm 0.157–0.31 in Fine gravel: Pebble −1 …