Manganese has the chemical symbol Mn and atomic number 25. There are four allotropes of α, β, γ, and δ. Manganese ore (manganese oxide, manganese carbonate, manganese silicate) exists in nature, and manganese nodules formed by manganese are deposited on the seabed. Natural content: crust 1300pp Chemicalbookm, soil 200-3000ppm, seawater 1.7-5.0ppb, river water 180ppb, plant leaves 10-100ppm, brown rice 20-30ppm, urban atmosphere 0.01-0.05μg/m3. Manganese is used in ferroalloys, special steels, dry batteries and as chemical reagents.