Manganese oxide minerals formed

Table IL Manganese oxide minerals formed in surface and subsurface environments...

It appears unlikely, that lanthanides are mobile. They appear to remain in situ as insoluble precipitates or bound to insoluble materials formed during weathering, as for example, clay minerals [139], iron, manganese oxide minerals [133] and possible soil organic materials. 

Inorganic molecular sieves in which all of the framework cations are coordinated octahedrally comprise a small but significant family of microporous solids. The octahedral molecular sieves, or OMS materials, related to manganese oxide minerals of the hollandite family, are the most important of these. Examples have been prepared by Suib and co-workers through the hydrothermal treatment of layered manganese oxides. Careful choice of additional metal ion content of such preparations controls the inorganic phase that forms. The... 

Bixbyite is a black cubic manganese oxide mineral of composition Mn203, which often contains appreciable iron. Discovered by Penfield and Foote (1897) and named after the American mineralogist M. Bixby, bixbyite forms as opaque cubic crystals with metalhc lustre or as granular masses. It is a relatively rare mineral and occurs in the oxidised portions of manganese... 

Pyrolusite is a black, opaque mineral with a metallic luster and is frequendy soft enough to soil the fingers. Most varieties contain several percent water. Pyrolusite is usually a secondary mineral formed by the oxidation of other manganese minerals. Romanechite, a newer name for what was once known as psilomelane [12322-95-1] (now a group name) (7), is an oxide of variable composition, usually containing several percent water. It is a hard, black amorphous material with a dull luster and commonly found ia the massive form. When free of other oxide minerals, romanechite can be identified readily by its superior hardness and lack of crystallinity. 

The mixed valent oxide Mn.O occurs in nature as the mineral hasumannite. The stmcture of this ferromagnetic material has been the subject of much dispute. Mn.O is the most stable of the manganese oxides, and is formed when any of the other oxides or hydroxides are heated in air above 940—1000°C. The oxidation of aqueous solutions of Mn (OH)2 can also lead to the formation of Mn O. ... 

Cobalt is the thirtieth most abundant element on earth and comprises approximately 0.0025% of the earth s cmst (3). It occurs in mineral form as arsenides, sulfides, and oxides trace amounts are also found in other minerals of nickel and iron as substitute ions (4). Cobalt minerals are commonly associated with ores of nickel, iron, silver, bismuth, copper, manganese, antimony, and 2iac. Table 1 Hsts the principal cobalt minerals and some corresponding properties. A complete listing of cobalt minerals is given ia Reference 4. 

A rich supply of manganese lies in nodules of ore that litter the ocean floors (Fig. 16.9). These nodules range in diameter from millimeters to meters and are lumps of the oxides of iron, manganese, and other elements. However, because this source is technically difficult to exploit, manganese is currently obtained by the thermite process from pyrolusite, a mineral form of manganese dioxide ... 

Microbiologically influenced corrosion is defined by the National Association of Corrosion Engineers as any form of corrosion that is influenced by the presence and/or activities of microorganisms. Although MIC appears to many humans to be a new phenomenon, it is not new to the microbes themselves. Microbial transformation of metals in their elemental and various mineral forms has been an essential part of material cycling on earth for billions of years. Some forms of metals such as reduced iron and manganese serve as energy sources for microbes, while oxidized forms of some metals can substitute for... 

Ostwald s step rule holds that a thermodynamically unstable mineral reacts over time to form a sequence of progressively more stable minerals (e.g., Morse and Casey, 1988 Steefel and Van Cappellen, 1990 Nordeng and Sibley, 1994). The step rule is observed to operate, especially at low temperature, in a number of min-eralogic systems, including the carbonates, silica polymorphs, iron and manganese oxides, iron sulfides, phosphates, clay minerals, and zeolites. 

Nodules Mineral precipitates, such as iron-manganese oxides and glauconites, that form as roundish lumps. 

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