Compositions of certain manganese accumulating plants

Composition comprising at least a metallic or a polymetallic agent containing less than 10% by weight of organic matter and comprising manganese having a degree of oxidation (II) (Mn (II)), a degree of oxidation (III) (Mn (III)) or a degree of oxidation (IV) (Mn (IV)), and optionally a metal or several metals selected from magnesium (Mg), zinc (Zn), copper (Cu), iron (Fe), calcium (Ca), cadmium (Cd), aluminum (Al), wherein the manganese content is between 15,000 and 270,000 ppm, and wherein said composition is obtained by carrying out a method comprising the following steps:

• a) Dehydrating a plant or a part of a plant, said plant or said part of said plant belonging to a genus selected from the group consisting of Alyxia, Azolla, Beauprea, Beaupreopsis, Bridelia, Crotalaria, Dicranopteris, Dipteris, Eugenia, Gleichenia, Gossia, Helanthius, Macadamia, Maytenus, Pinus, Phytolacca, Spermacone, Stenocarpus, Virotia and Grevillea, that has accumulated manganese (Mn), and optionally a metal or several metals selected from magnesium (Mg), zinc (Zn), copper (Cu), iron (Fe), calcium (Ca), cadmium (Cd), aluminium (Al),
• b) Grinding the dried plant or dried part of plant obtained from step a), and obtaining a grinded mixture,
• c) Thermally treating the grinded mixture obtained from step b), and obtaining an ash.