Manganese-rich minerals of the pumpellyite group from the Precambrian Sausar Group, India

Mn-rich minerals of the pumpellyite group are developed in Mn oxide ores of the Precambrian Sausar Group, India. The ores were intruded by late pegmatite dikes and calcite veins. A hydrothermal origin for these phases through Ca-Mg-Fe-Al metasomatism is evident from their mode of occurrence and textures. The phases studied show wide- spread substitution between Mn³⁺ and Al in the Y-site and between Mn²⁺ and Mg in the X-site. An Mg equivalent of okhotskite, reported for the first time, is present. This study establishes that okhotskite represents the Mn³⁺ end-member of the pumpellyite group of minerals and that solid solution between pumpellyite (Al dominant) and okhotskite is nearly complete.