Open-cast and underground mines
Manganese is mostly extracted at open-cast mines, using explosives and excavators. There are also several underground Manganese mines (mostly in South Africa like the Wessels, Gloria and Nchwaning mines, but also in India, Mexico, etc.). Underground operations use block-caving, room-and-pillar, modified cut-and-fill or longwall mining methods.
Crushing and screening process
After mining, ore is crushed and screened, and split into various particle size fractions ranging from fines (under 6mm) to lump ore and concentrates (between 6mm and 75mm).
Crushed and screened ore may be concentrated by washing, sink-float, jigging, tabling, flotation, dense media separation and high intensity magnetic separation to produce a saleable concentrate. Carbonate manganese ores may be calcined. Higher-quality fines may be agglomerated, nodulised, sintered or pelletised. Lower-quality ores, fines and complex fine-grained ores may be flotated. In cases where manganese is associated with other metals, hydrometallurgical processes such as solvent extraction are used, sometimes after roasting or sintering to improve solubility, according to Roskill.
The specifications of the resulting concentrates vary depending on the nature of the ore and the target market. Typically, different grades of ore are blended according to required specifications and then crushed, followed by screening into fines and lump ore. The ore may then undergo dense media separation after which, silicon waste is removed typically through flotation separation, and clays and other contaminants are washed out. The ore may then be further blended to meet customer specifications.
Manganese ore is usually transported by truck and train from the mine to the buyer (Manganese alloy smelter or trading warehouse), and if exported, it is loaded on ships (usually in bulk, but sometimes in containers). China consumes 65% of the global output of Manganese ore (including 16% produced domestically), so around half of global Manganese ore production is imported by China from other countries, almost entirely by ship in bulk.
Manganese alloy is mostly transported in bags of 1,000kg, by trucks and ships (sometimes in containers).