Manganese

Manganese is a hard, brittle, greyish metal that most people have never heard of, yet without it there would be no steel industry, no dry-cell batteries and no working brain. It is the 12th most abundant element in the Earth's crust and one of the most important metals you have probably never thought about.

  • Atomic Number2525 protons, 25 electrons
  • Atomic Mass54.93804 uAbout 55× heavier than hydrogen
  • State at Room TempSolidhard, brittle grey metal
  • Density7.3 g/cm³Similar density to iron
  • Melting / Boiling1245.8°C / 2060.8°CMelts at 1,246°C
  • Discovered1774Johan Gottlieb Gahn, 1774

Manganese sits between chromium and iron in Period 4.

It bridges the gap between the chromium-group metals and iron in the first transition series.

Atomic Mass Comparison
Chromium52.0 u
Manganese54.9 u
Iron55.8 u
Cobalt58.9 u
Nickel58.7 u

Manganese (54.9 u) is almost identical in mass to iron (55.8 u), its immediate neighbour to the right. These two elements have very similar masses but quite different properties and roles in biology and industry.

What is manganese?

Manganese is a transition metal in Group 7 of the periodic table. It has 25 protons and can exhibit oxidation states from −3 to +7, giving it a very versatile chemistry. Unlike iron, which it closely resembles in mass, pure manganese is quite brittle and is rarely used as a metal on its own. It is primarily used as an alloying element and as a chemical oxidising agent. Its most common oxidation state, +4, forms the chocolate-brown mineral pyrolusite (MnO₂), the source of most commercial manganese.

Manganese gets its name from Magnesia, the Greek region: the same origin as magnesium. The two elements were found in minerals from the same region and were confused with each other for many years. The Swedish chemist Carl Wilhelm Scheele distinguished them in 1774, and his colleague Johan Gottlieb Gahn isolated pure manganese in the same year.

Fact The deep ocean floor is covered with trillions of potato-sized lumps called manganese nodules. These dark rocky blobs, containing manganese, iron, cobalt, nickel and copper, have been slowly growing on the seabed for millions of years. There is more manganese in these nodules than in all the land-based reserves on Earth combined.

Where you find manganese

On Earth

Manganese is the 12th most abundant element in the Earth's crust, and unlike some transition metals, it forms economically important ore deposits.

  • Pyrolusite (MnO₂). The most important manganese ore, a chocolate-brown mineral found in sedimentary rock. South Africa, Australia and China are the largest producers.
  • Deep-sea manganese nodules. These potato-sized concretions litter vast areas of the Pacific, Atlantic and Indian Ocean floors, though deep-sea mining to recover them remains controversial.
  • Rhodonite and rhodochrosite. Pink manganese silicate and carbonate minerals, valued both as sources of manganese and as gemstones.

How we use manganese

  • Steel making. About 90% of all manganese goes into making steel. Manganese deoxidises the melt (removes harmful oxygen), and small additions make steel much harder and more resistant to wear. Almost all steel contains at least a little manganese.
  • Batteries. Manganese dioxide (MnO₂) is the positive electrode in most alkaline and zinc-carbon batteries: the common AA and AAA batteries in remote controls and torches.
  • Fertilisers and animal feed. Manganese is an essential trace element for plants and animals. It is added to fertilisers for soils deficient in manganese and to animal feed supplements.
  • Pigments. Manganese compounds were used as pigments since the Stone Age. Manganese dioxide is the black and brown pigment in cave paintings 40,000 years old.
Did you know? Manganese is essential for the human brain. A special enzyme containing manganese, manganese superoxide dismutase, protects brain cells from damage caused by free radicals. Manganese is also needed for the enzymes that build cartilage, process cholesterol and synthesise some amino acids. Most people get enough from whole grains, nuts and leafy vegetables.

How it was discovered

Manganese chemistry was sorted out by Carl Wilhelm Scheele in 1774, who showed that the black mineral pyrolusite contained a new element distinct from magnesium. In the same year, his colleague Johan Gottlieb Gahn isolated the pure metal by reducing pyrolusite with carbon in a charcoal furnace. Manganese was used to decolourise glass long before it was recognised as an element, Roman glassmakers added pyrolusite to remove the green tint caused by iron impurities.

Deeper dive: manganese in photosynthesis and biology

Manganese plays a remarkable role in photosynthesis. Inside the chloroplasts of all green plants, a cluster of four manganese atoms is responsible for one of the most important chemical reactions on Earth: splitting water molecules. This "oxygen-evolving complex" uses light energy and manganese to tear apart water (H₂O) into hydrogen ions, electrons and oxygen gas. The oxygen released is the source of almost all the oxygen in Earth's atmosphere, produced by manganese chemistry inside plant cells over billions of years.

In steel making, manganese serves two purposes: it combines with sulfur (which would otherwise make steel brittle) to form manganese sulfide, which is harmless; and it combines with oxygen dissolved in the melt to produce manganese oxide slag that rises to the surface. This deoxidising function was known long before chemistry could explain it: the blast furnace charge has included manganese ore since at least the 17th century.

Hadfield steel, invented by Robert Hadfield in 1882, contains 11-14% manganese. It is remarkable for becoming harder when deformed: hitting it makes it more resistant to further impact. This makes it ideal for railway crossings, rock-crushing equipment and military helmets, which all need to resist repeated heavy impacts.

Manganese is one of steel's most important, and least celebrated, ingredients. Moving to 26 protons brings us to iron, the metal that built civilisation and carries oxygen through your blood.