Manganese Compounds - Occurrence and Production

Occurrence and Production

Manganese makes up about 1000 ppm (0.1%) of the Earth's crust, making it the 12th most abundant element there. Soil contains 7–9000 ppm of manganese with an average of 440 ppm. Seawater has only 10 ppm manganese and the atmosphere contains 0.01 µg/m3. Manganese occurs principally as pyrolusite (MnO₂), braunite, (Mn2+Mn3+₆)(SiO₁₂), psilomelane (Ba,H₂O)₂Mn₅O₁₀, and to a lesser extent as rhodochrosite (MnCO₃).

The most important manganese ore is pyrolusite (MnO₂). Other economically important manganese ores usually show a close spatial relation to the iron ores. Land-based resources are large but irregularly distributed. About 80% of the known world manganese resources are found in South Africa; other important manganese deposits are in Ukraine, Australia, India, China, Gabon and Brazil. In 1978, 500 billion tons of manganese nodules were estimated to exist on the ocean floor. Attempts to find economically viable methods of harvesting manganese nodules were abandoned in the 1970s. For a Cold War ruse, the CIA had had billionaire Howard Hughes commission a ship, the Hughes Glomar Explorer to go to Hawaii to harvest manganese nodules. That ship started a rush of people who wanted to collect manganese nodules from the bottom of the sea, which is impractical. The Hughes Glomar Explorer was actually built to raise a sunken Russian submarine, the K-129. Sadly for the CIA, the part of the submarine containing the code books broke off while it was being raised, so they did not get what they wanted.

Manganese is mined in South Africa, Australia, China, Brazil, Gabon, Ukraine, India and Ghana and Kazakhstan. US Import Sources (1998–2001): Manganese ore: Gabon, 70%; South Africa, 10%; Australia, 9%; Mexico, 5%; and other, 6%. Ferromanganese: South Africa, 47%; France, 22%; Mexico, 8%; Australia, 8%; and other, 15%. Manganese contained in all manganese imports: South Africa, 31%; Gabon, 21%; Australia, 13%; Mexico, 8%; and other, 27%.

For the production of ferromanganese, the manganese ore is mixed with iron ore and carbon, and then reduced either in a blast furnace or in an electric arc furnace. The resulting ferromanganese has a manganese content of 30 to 80%. Pure manganese used for the production of noniron alloys is produced by leaching manganese ore with sulfuric acid and a subsequent electrowinning process.