The 2220 Ma Kalahari Manganese field of South Africa is the world's largest Mn resource and a major producer.
Current models for its origin rely on those developed for Phanerozoic deposits, invoking a submarine redox boundary and water movements across a continental shelf, precipitating Mn oxides from the sea.
Situated in extremely well-preserved, 2.2 billion-year-old sedimentary rocks of the Transvaal Supergroup near Hotazel in the Northern Cape province of South Africa, the Kalahari Manganese Field is one of the geological and mineralogical wonders of the world.
It also hosts a world-renowned, unique and varied assemblage of aesthetic collector’s mineral specimens that are often rare or unique.
According to mindat.org & researchgate.net