The important minerals of the ore deposits (which occur in Archean paragneisses) include pyrolusite, psilomelane, hollandite, and cryptomelane, representing alteration products of primary braunite, bixbyite, jacobsite, hausmannite, and vredenburgite. Ore textures and mineral associations support the conclusion that the deposits were formed by high-grade metamorphism of manganiferous sediments.

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