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Altered pyrochlore from the Szklary rare-element pegmatite, Lower Silesia, Poland
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
The pegmatite, stretching NNE-SSW, is hosted by light aplite. Apart from feldspars, quartz, micas and tourmaline, it contains a range of rare minerals, such as spessartine, chrysoberyl, manganotantalite and manganocolumbite, stibiocolumbite, Hf-zircon, uraninite, holtite, beusite, manganoan apatite and Mn-oxides (todorokite, romanechite, hollandite), as well as various species of the pyrochlore group (Pieczka 2000).
Geometallurgical characterisation of Mn ores
Published in Applied Earth Science, 2021
Michael John Peterson, James Robert Manuel, Sarath Hapugoda
Historically, geologists identified hard, dense Mn oxides which did not stain their hand when handled in outcrop/hand specimen as ‘psilomelane’ (literally ‘hidden black’ – e.g. Frenzel 1980; Post 1999). In contemporary use, psilomelane is now not a recognised mineral name and its accepted equivalent is romanechite (Table 1). By way of comparison, more friable, earthy microporous, Mn oxides/oxyhydroxides were historically referred to as ‘Mn wad’ by field geologists. Wad was likely composed of some combination of earthy, often poorly microcrystalline Mn minerals such as todorokite, birnessite, vernadite, lithiophorite, and perhaps some more porous, hydrous forms of the coronadite-group minerals (e.g. cryptomelane). To some extent, the Mn mineral constituents of these samples could be distinguished by reflected light optical microscopy. However not until the development of techniques such as Rietveld refined XRD, SEM/EPMA, HRTEM, Thermogravimetric Analysis (TGA), etc. has it been possible to reliably distinguish all the Mn mineral constituents of Mn ores.