My grand father owned a potato processing plant in miami......the potatoes would come in by the train load from Idaho. They would be loaded into a hopper and feed into the automated processing plant.....they would be blanched,peeled,and sliced into the french fries that became famous throughout the world because of their success at McDonald's. In his office was a vast array of the objects that would jam the line of the plant. It was amazing how many rocks looked identical to a potato........couldn't tell the difference until they hit the peelers !! Boom bang pow smash....and you new one was coming down the line.