You have your pea gravel, your small gravel, your mid-sized gravel, (some claim this is the best for walking on), your little bit bigger than mid-sized gravel, bigger gravel and we know how Americans love bigger everything, little bit bigger than bigger gravel, large gavel, and so on and so on.
And who is the enemy of gravel?
Clay. Yes, that's right, clay. Clay is the enemy of gravel. Universally hated, clay, and it's myriad derivatives. Hated by gravel aficionados everywhere.