MINERALOGICAL CHARACTERIZATION OF MANGANESE OXIDES FROM THE APPALACHIANS IN VIRGINIA

Manganese oxides and hydroxides are gaining interest as critical minerals for Li-Mn batteries. Manganese oxides are found in a variety of geological settings and occur as fine-grained aggregates, hydrothermal veins, marine and freshwater nodules and concretions, dendrites, and coatings on rock surfaces (e.g., desert varnish). Despite their economic and environmental significance, geoscientists continue to debate how manganese oxides form and which of the manganese oxides are likely to form in sedimentary and hydrothermal environments, and by bioprecipitation. Manganese ores are found in many parts of the United States. However, deposits of manganese oxides and iron oxides are abundant across the Appalachian and the Piedmont regions in Virginia and have been mined from 1880 to 1914 for supplying the demand for the steel industry. The origin of manganese oxide deposits in the Appalachians is still uncertain and the clear mineralogical identification of the manganese oxides is limited. This research aims to identify the minerals belonging to the manganese oxide group in six samples collected across known manganese deposits from the Blue Ridge Mountain and Valley and Ridge geographical provinces in Virginia and to elucidate the formation of these deposits. The mineralogical characterization of samples was performed using X-ray powder diffraction (XRPD). The manganese oxides identified via XRPD are primarily birnessite, hollandite, todorokite, and cryptomelane. The other minerals identified are quartz, plagioclase, and goethite. A comparison with data collected from this study was carried out to shed light on the past environment and conditions under which the manganese oxides formed. Results on samples indicate a diverse origin across biological, sedimentary, and low-temperature hydrothermal environments.