Stock Photo - A corroded stairs to the second deck is seen on an old gold dredge anchored in the Atrato river in Quibdó, Colombia. A gold dredge is a mining machine employing an ancient artisan technique of placer gold mining (based on the different densities of gold and soil/sand) but applied by mechanical/industrial methods to increase the quantity of extracted gold. Today, advances in mining technology allowed the production of small dredges with high operation efficiency, carried easily to a remote location, and so the giant mining dredges are increasingly decommissioned and left to their fate.