Using a magnet to remove scrap from a railroad track - GIF

[desbromilow]

are all the iron ore nuggets I see along railway lines not high enough grade to be picked up?
Brian

iron ore needs to be about 86% iron before a tramp metal magnet can attract it enough to pick it out of an orestream. Typical "high grade" iron ore is only around 65-75% iron content (the rest being impurities like silica, alumina, etc). Tramp metal magnet usually sits about 400-500mm (15-20") above the bottom of the belt trough, with an ore depth of around 300-350 mm (12-14") at the peak. Tramp metal magnets are designed to collect metal in the orestream such as excavator teeth, fire-extinguishers, or other "bits of metal" which if left in the orestream will end up ripping conveyor belts, or jamming in crushers, etc doing expensive and unsafe damage.