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Manganese Particles in Freshwaters
Published in Jacques Buffle, Herman P. van Leeuwen, Environmental Particles, 2018
Richard R. De Vitre, William Davison
Mn-specific minerals are quite scarce and, in common with other transition metal minerals, often include two or more formal oxidation states. Among the more common Mn minerals are the oxides and oxyhydroxides such as pyrolusite (MnO2) and psilomelane (BaMn(II)Mn(IV)8O16(0H)4), and in near surface deposits manganite (MnOOH), braunite (Mn,Si)2O3 and hausmanite (Mn3O4). Less common manganese minerals, generally found in more reducing environments, include pyrochroite (Mn(OH)2), manganosite (MnO), and alabanite (MnS). Finally, rhodochrosite (MnC03) is found in sedimentary rocks, and as an impurity in carbonate rich ores such as calcium carbonates through ionic substitution since the charge and ionic radii of Mn2+ and Ca2+ are quite similar.
Nb-Ta bearing minerals in a metasomatized granite, Eastern Desert, Egypt
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
Feldspars are albite (AB98.75An0.50Or0.75) and microcline (Or98.29Ab1.71). The calculated Li content using the equation [Li = (0.287*SiO2)-9.552] of Tindle & Webb (1990) of muscovite is low (4.14%). The microprobe analyses show that the investigated garnet is a solid solution of Spess72, Alm8, Gr0.5 to Spess91, Alm27, Gr1.3, Py0.4, And0.1. The contens of FeO (7.24%), MnO (37.79%) and MgO (0.03%) reveal that the studied garnet is similar to that of rare-earth-enriched pegmatite (Fuertes-Fuente & Martin-Izard 1998). Preferential fractionation of Mn into garnet relative to coexisting minerals lead to progressive depletion of Mn in the rock during growth. Two phases of Mn-oxides are encountered, as pyrolusite (77.64%MnO) and psilomelane (68.24% MnO).
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.
Simulation of magnesium chloride vertical transport in column experiments
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Yan Dou, Mengyao Li, Zhaoyu Liu, Renjie Fang, Kaixi Yan
Heavy metals are widely distributed in environmental media such as water, soil and sediments (Li et al. 2015a). Toxic metals are harmful to ecological diversity and human health because of their bioaccumulation (He and Wu 2019; He et al. 2019). The sources of heavy metals can be geogenic or anthropogenic (Li et al. 2016). Heavy metals may transport from one medium to another, such as from soil/sediments to water, inducing serious water contamination. Manganese (Mn) is the eleventh most common element in the Earth’s crust (Li et al. 2014), with an average concentration of 0.09%. In nature, manganese exists in various minerals in the form of oxides, including pyrolusite (MnO2), psilomelane (mMnO·MnO2·nH2O), manganite (MnO2·Mn(OH)2), Hausmannite (Mn3O4), and so forth. These oxides are naturally insoluble in water; however, they are the most efficient electron acceptors (after O2 and NO3) in the sequence of organic matter respiration (Champ et al., 1979), and Mn2+ is the predominantly reduced form and is mobilized with water flow.
Performance of selective catalytic reduction of NO with NH3 over natural manganese ore catalysts at low temperature
Published in Environmental Technology, 2018
Tao Wang, Chengzhu Zhu, Haibo Liu, Yongpeng Xu, Xuehua Zou, Bin Xu, Tianhu Chen
XRD patterns of different natural manganese ores were shown in Figure 1, the main phase of Qingyang was quartz (SiO2) and ramsdellite (γ-MnO2). And the main phase of Tongling was quartz (SiO2), combined with small amount of pyrolusite (β-MnO2) and ramsdellite (γ-MnO2). Pyrolusite was mainly quartz (SiO2) and pyrolusite (β-MnO2). Psilomelane was quartz (SiO2), ramsdellite (γ-MnO2), hausmannite (α-Mn2O3) and partridgeite (β-Mn3O4). The crystallinity of MnOx was very poor in four natural manganese ores.