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Mineral Crystals
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
For example, garnet solutions, (Fe,Mg,Mn,Ca)3 Al2Si3O12, may have almost any composition that is a mixture of the four end members: almandine Fe3Al2Si3O12pyrope Mg3Al2Si3O12spessartine Mn3Al2Si3O12grossular Ca3Al2Si3O12In contrast, olivine solutions, (Fe,Mg,Mn)2SiO4, contain only extremely small amounts of Ca2+ and are generally solutions of fayalite Fe2SiO4forsterite Mg2SiO4tephroite Mn2SiO4
Manganese ores in black shales sequences in the Western Carpathians, Slovakia
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
I. Rojkovič, D. Ozdin, L. Puškelová, A. Svitáčová
The Early Palaeozoic carbonates of manganese underwent the Hercynian metamorphism together with silicate minerals and manganese silicates were formed. Sedimentary rocks contained Mn-carbonate, clay minerals and quartz before metamorphism. Recent dominantly silicate character of manganese ore was formed due to metamorphism of silicates and carbonates of manganese. Metamorphosed manganese carbonate-silicate rocks „queltzites“ are characterised by presence of Mn-carbonate, tephroite and absence of low Mn-oxides especially bixbyite. Association of rhodonite, rhodochrosite, spessartite, pyrophanite, pyroxmangite and tephroite suggests epidote-amphibolite zone of Hercynian metamorphism. Rhodonite-pyroxmangite geothermometer gives 375 °C (Faryad 1991) and 390 °C (Rojkovič 1999) from Čučma deposit.
Environmental Oxidations
Published in Richard A. Larson, Eric J. Weber, Reaction Mechanisms in Environmental Organic Chemistry, 2018
Richard A. Larson, Eric J. Weber
A number of investigations have indicated that manganese oxides are potent catalysts for oxidation, especially of phenols (Larson and Hufnal, 1980; Stone and Morgan, 1984; McBride, 1987; Stone, 1987; Ulrich and Stone, 1989). Phenols with electron-donating substituents such as hydroxyl, alkyl, alkoxyl, etc., are usually oxidized much more rapidly than those possessing electron-withdrawing groups. One suggested mechanism for oxidation on these surfaces is electron transfer from the phenol to the oxide, followed by release of Mn2+ into solution, and further reaction of the phenol-derived radicals; in high enough phenol concentrations, the preferred reaction is probably oxidative coupling to form polymers. Colored products were observed in activated MnO2-promoted reactions of catechol (Larson and Hufnal, 1980). Catechol and hydroquinone were oxidized by birnessite, a form of manganese oxide found in soils. No products were identified except for semiquinone and hydroxylated semiquinone radicals (McBride, 1989). Hydroquinone was also oxidized in an aqueous suspension of hausmannite (Mn3O4) by a process that led to the dissolution of the oxide, the release of Mn2+, and the formation of phenolic polymers. Electron spin resonance data revealed the presence of the p- benzo-semiquinone radical anion, a likely precursor of the polymeric products (Kung and McBride, 1988). The manganese oxide was shown to be a much better oxidation catalyst for this phenol than was the mixed iron oxide reagent also studied by these authors (vide supra). Manganese silicates such as tephroite and other Mn-containing minerals also polymerized hydroquinone (Shindo and Huang, 1985).
A Review of Low Grade Manganese Ore Upgradation Processes
Published in Mineral Processing and Extractive Metallurgy Review, 2020
Veerendra Singh, Tarun Chakraborty, Sunil K Tripathy
Manganese ores are mainly used in the submerged arc furnaces to produce silico or ferromanganese where coarser size (>6 mm) particles are the preferred feed material. Agglomeration methods incur additional cost and these are still not very popular in the Mn ferroalloy industry. It works as constrain restricts fine grinding of ore for development of new beneficiation methods as well as restricts the application of existing fine ore beneficiation methods, such as flotation, gravity tables, etc. Jigging and magnetic separators are commonly used to remove low-density gangues and iron bearing impurities. It has been seen that braunite, tephroite, and rhodonite are the major manganese minerals found in siliceous ore deposits but the Mn and Si in these minerals are chemically combined and it is not feasible to separate them by physical beneficiation methods. Manganese silicate ores are mostly found hard to grind and leaching of these ores is also very difficult mainly due to compact crystalline structure however development of suitable additives to enhance grinding and leaching efficiency can be a new area of research for mineral engineers. The subgrade ores which are unsuitable for ferroalloy production should be crushed into finer sizes and more efficient hydrometallurgical processing routes should be applied to recover the values added products, such as manganese slats or oxides. These salts can be further processed to produce more valuable products such as manganese metal or EMD/CMD.
Microhardness-compositional relationship of Fe3O4-Mn3O4 series spinels from ferromanganese sinter and its relationship to sinter strength
Published in Mineral Processing and Extractive Metallurgy, 2023
M. J. Peterson, S. Hapugoda, J. R. Manuel
Examination of representative samples from the main sinter zones using reflected light optical microscopy showed that the sinter samples were predominantly comprised of Mn-Fe spinel, manganosite, Mn-silicate (likely tephroite) and glass. Hausmannite could be present within relict ore nuclei or as sinter bonding phases associated with manganosite, tephroite and glass. Other Mn-Fe or Fe-Mn spinels were only present as sinter bonding phases.