Characterisation of Manganese Ores of a Part of Western Koira Valley, Keonjhar District, Orissa

Abstract The Kusumdih ore bodies are lentiformal being interbanded and co-folded with the shale formation of Iron Ore Group and are surficially lateritised. They are of lateritoid type. Presence of manganese minerals like cryptomelane. pyrolusite, psilomelane, lithiophorite, manganite, coronadite (?), chalcophanite and braunite type is established. Iron is present in three oxy-hydroxide phases, viz., hematite, goethite and lepidocrocite. Cryptomelane and pyrolusite are ubiquitous in all the varieties. Lithiophorite as vug filling occurs in appreciable quantity in laminated and colloform banded varieties. Occurrence of psilomelane and coronadite is also recorded in some varieties. Manganite associated and intergrown with pyrolusite is observed. Hematite and maghemite (?) form the bulk of the ore minerals in manganiferous shale, alongwith subordinate amount of kaolinite and cryptomelane. Fabrics of different ore minerals observed indicate colloform, replacement, banded. veined, open-space filling, brecciated and intergrowth textures. More than one generations of cryptomelane, pyrolusite, manganite and goethite are recognised. Mineral association of higher oxyhydroxides of manganese and the textural characteristics attest a low-temperature formation of syngenetic sedimentary ore bodies later subjected to oxidation/solution processes during weathering in the zone of lateritisation.