Oxidation products, mineralogy

In this case, the mineralogical studies on the mechanism of sulfide alteration and on the genesis and evolution of secondary oxidation products are of paramount environmental relevance because they allow a better understanding of the source and the mechanisms of release of the ecotoxic elements and the effective... 

Mineralogy of bacterially-produced Mn oxides. The oxidation states of synthetic Mn oxides formed in the laboratory at neutral pH tend to be low, around 3 (5, 81, 82), Since Mn oxides formed in many natural waters through microbial activities have a considerably higher oxidation state (>3.4) (83-87), it is tempting to speculate that abiotic oxidation does not result in the same oxidation products as those found in nature (88),... 

Marvin UB (1983b) Mineralogy of the oxidation products of the Sputnik 4 fragment and of iron meteorites. J Geophys Res... 

Nesbitt, H.W. and Muir, IJ. (1998) Oxidation states and speciation of secondary products on pyrite and arsenopyrite reacted with mine waste waters and air. Mineralogy and Petrology, 62, 123-44. 

The data from different sources does not often match exactly, while it has been necessary to use the data on oxides from one source and phosphates of the same elements from another. To avoid any confusion resulting from this, we have used a certain order in using these sources. Pourbaix s Atlas of Electrochemical Equilibria [1] is the first source that we have used for the Gibb s free energy of oxides and ions, and for the solubility product constants. This is prompted by the fact that much of the formulation discussed in this book is hinged to Pourbaix s treatment, and to be consistent, Pourbaix s data is preferred over others. The CRC Handbook of Chemistry and Physics [2] is the next source from which much of the enthalpy and specific heat of oxides and ions are taken. The data on phosphates comes from The Phosphate Minerals [3], while the mineral formulae are from Dana s Mineralogy Handbook [4] and also from The Phosphate Minerals [3]. These detailed references and additional ones [5,6] useful for further development of CBPC materials are given below. 

A suite of both oxidized and reduced iron minerals has been found as efflorescences and precipitates in or near the acid mine water of Iron Mountain. The dominant minerals tend to be melan-terite (or one of its dehydration products), copiapite, jarosite and iron hydroxide. These minerals and their chemical formulae are listed in Table III from the most ferrous-rich at the top to the most ferric-rich at the bottom. These minerals were collected in air-tight containers and identified by X-ray diffractometry. It was also possible to check the mineral saturation indices (log Q(AP/K), where AP = activity product and K = solubility product constant)of the mine waters with the field occurrences of the same minerals. By continual checking of the saturation index (S.I.) with actual mineralogic occurrences, inaccuracies in chemical models such as WATEQ2 can be discovered, evaluated and corrected (19), provided that these occurrences can be assumed to be an approach towards equilibrium. 

The chemical composition of imported, European-made majolica is different from that of majolica made in Mexico (J). The difiFerences in the concentrations of the oxides of cerium, lanthanum, and thorium are eaily recognized the Spanish majolica contains approximately twice as much of each of these oxides as the Mexican majolica. The mineralogical composition, too, of the pottery products of each area is fundamentally different and can easily be identified. The ceramic types and their origins, based on archaeological arguments, can be found in Table I. 

As indicated above, the products of the well-studied iron-oxidizing neutrophiles have high potential as mineralogical biosignatures, and in fact have been used as such (e.g., Alt 1988 Hofmann and Farmer 2000). Cambrian sea-floor silica-iron oxide deposits were described by Duhig et al. (1992), and a Jurassic hydrothermal vent community was described by Little et al. (1999). 

Many of the above observations can be illustrated through discussion of an example of weathering taken from Goldich (1938) (see also Krauskopf 1967). The parent rock in this humid, temperate climate example is a quartz-feldspar-biotite gneiss. The mineralogic and oxide composition of this rock and its weathered product soil is given in Table 7.2. 

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