Manganese was isolated in 1774 by Johan Gottlieb Gahn, after Carl Wilhelm Scheele had shown that its ore, pyrolusite, contained a new metal. Its name descends, like that of magnesium, from Magnesia in Greece; the black ore was called magnesia nigra to distinguish it from the white magnesia alba, and manganese is a corruption of that word. Manganese is a hard, brittle grey metal, essential in steelmaking for removing oxygen and sulfur and for hardening the alloy. Among the more abundant elements of the crust, manganese is also central to dry-cell batteries and is an essential trace nutrient in living things, forming part of the enzymes that protect cells against oxidative damage.
Manganese occurs on the deep ocean floor in vast fields of potato-sized manganese nodules, rich also in nickel, copper and cobalt, a resource that has made seabed mining one of the more contested modern environmental questions, since dredging the nodules risks disturbing ecosystems scientists have barely begun to catalogue. Gahn achieved his isolation by heating powdered pyrolusite with oil and carbon in a crucible, a simple reduction that nonetheless required Scheele's prior chemical analysis to know a genuine new metal, and not merely a curious black earth, was waiting to be freed.