https://www.scientificamerican.com/article/thomas-edison-had-a-crush-on-iron/

“The remarkable process of crushing and magnetic separation of iron ore at Mr. Thomas Edison’s works in New Jersey shows a characteristic originality and freedom from the trammels of tradition. The rocks of iron ore are fed through 70-ton ‘giant rolls’ that can seize a 5-ton rock and crunch it with less show of effort than a dog in crunching a bone. After passing through several rollers and mesh screens, the finely crushed material falls in a thin sheet in front of a series of magnets, which deflect the magnetic particles containing iron. This is the latest and most radical development in mining and metallurgy of iron.”

—Scientific American, January 1898