Siderite with pyrite

Magnetite is common in Pb-Zn-Mn and Cu deposits but has not been reported in Au-Ag deposits. It commonly coexists with other iron minerals such as hematite, pyrite, pyrrhotite, siderite, and chlorite and also occurs in both the main stage of sulfide mineralization and in the late stage of mineralization. 

The iron content of sphalerites coexisting with siderite and pyrite from the Toyoha deposits is high (3-12 wt%). On the other hand, sphalerite of later stage Ohmori... 

The study of the inorganic chemistry of sediments has provided a broad-brush picmre of the evolution of the Earth. Riverine sediments from the deepest past contain minerals (e.g., uraninite, pyrite, and siderite) that decompose rapidly under oxic conditions whereas such minerals are absent from more recent sediments (Kirkham and Roscoe, 1993 Ramdohr, 1958 Rasmussen and Buick, 1999 Robb et al., 1992). Other sedimentary features associated with highly oxic conditions (e.g. red beds) are absent in the earliest sediments and present in more recent ones (Rye and Holland, 1998). The sedimentary record... 

Pyrite occurs both as early and late cement in Hibernia Field. Early pyrite is present in early calcite cement, fossil fragments and siderite nodules. Late pyrite is found in intergranular pores and fractures. The association of pyrite with a porous zone in Hibernia Sandstone and its absence in adjacent ferroan-calcite cemented sandstone suggests that this pyrite formed after the dissolution of the ferroan calcite. 

The mixed microlithotype clarodurite is intermediate in composition between durite and clarite with the proviso that while the amount of inertinite must be higher than the amount of vitrinite and the individual amounts of vitrinite, exinite, and inertinite should exceed 5%, the name structure also indicates a closer relationship to durite than to clarite. Clarodurite is also a common constituent of humic coals and the contaminants of this microlithotype are clays, pyrite, and siderite (ferrous carbonate). Conversely, duroclarite has maceral proportions that are closer to clarite than to durite. Thus, the proportion of vitrinite must exceed that of inertinite and the proportions of vitrinite, exinite, and inertinite present should exceed 5%. This microlithotype occurs in fairly thick bands and is a common constituent of most humic coals. 

Minerals. Iron-bearing minerals are numerous and are present in most soils and rocks. However only a few minerals are important sources of iron and thus called ores. Table 2 shows the principle iron-bearing minerals. Hematite is the most plentiful iron mineral mined, followed by magnetite, goethite, siderite, ilmenite, and pyrite. Siderite is unimportant in the United States, but is an important source of iron in Europe. Tlmenite is normally mined for titania with iron as a by-product. Pyrite is roasted to recover sulfur in the form of sulfur dioxide, leaving iron oxide as a by-product. 

In order to prepare standard mineral mixtures, pyrite (Py), pyrrhotite (Po), chalcopyrite (Cp), sphalerite (Sp), siderite (Sid), dolomite (Dol), calcite (Cal) and quartz (Qz) were acquired as pure mineral samples through a specialized distributor (Minerobec, Canada). These 8 pure minerals were further cleaned under a binocular microscope and separately crushed to reach 95% under 150pm (typical tailings grain size distribution e.g. Aubertin et al. 2002). Each pure mineral powder was characterized thereafter with a series of chemical and mineralogical techniques. More details can be found in Bouzahzah et al. (2008). The relative density of each mineral specimen were measured with an He pycnometer and are... 

Occurrence. Iron is highly abundant (about 5.5% of the earth s crust) it is believed that the core of earth is mostly molten iron together with nickel. The most common ore is haematite (Fe203). Iron is found in other minerals such as magnetite, limonite, siderite, pyrite. Iron is found native in meteorites known as siderites. 

In this case study, the selected phases are pyrite, amorphous FeS, calcite (present in limestones in the roof strata Fig. 5), dolomite (possibly also present in the limestones), siderite (which occurs as nodules in roof-strata mudstones), ankerite (present on coal cleats in the Shilbottle Seam), melanterite and potassium-jarosite (representing the hydroxysulphate minerals see Table 3), amorphous ferric hydroxide (i.e., the ochre commonly observed in these workings, forming by precipitation from ferruginous mine waters), and gypsum (a mineral known to precipitate subaqueously from mine waters with SO4 contents in excess of about 2500 mg/L at ambient groundwater temperatures in this region, and with which most of the mine waters in the district are known to be in equilibrium). In addition, sorption reactions were included in some of the simulations, to contribute to the mole transfer balances for Ca, Na, and Fe. 

Coal contains detrital minerals that were deposited along with the plant material, and authigenic minerals that were formed during coalification. The abundance of mineral matter in coal varies considerably with its source, and is reported to range between 9.05 and 32.26 wt% (Valkovic 1983). Minerals found in coal include (Table 2) aluminosilicates, mainly clay minerals carbonates, such as, calcite, ankerite, siderite, and dolomite sulphides, mainly pyrite (FeS2) chlorides and silicates, principally quartz. Trace elements in coal are commonly associated with one or more of these minerals (see Table 2). 

Figure 6. The degree of pyritization, defined as the fraction of reactive iron present as pyrite, is a measure of the extent to which available iron has reacted with sulfur (226). In lake sediments, iron monosulfides frequently are as abundant as pyrite and hence were included with pyrite in the values calculated for surface sediments from 13 lakes and presented here. Even this correction neglects Fe(II) that may have been reduced by sulfide but may be present as siderite. Availability of iron appears to be more important than bottom-water oxygenation in determining the degree of pyritization. In the right-hand graph, darkened squares represent sediments known to experience seasonal anoxia only the uppermost point experiences permanent anoxia. (Data are from references 30, 34, 56, and 61.)...

In sediments, oxidized iron is commonly present as the oxides magnetite, hematite, goethite, limonite, and as silicates such as ferric chamo-site. In reduced form iron is present as siderite, several iron (II) silicates, sulfides, such as pyrite, FeS2, and as undefined compounds of the general type FeS nH20, sometimes referred to as hydrotroilite. In rare cases iron occurs in native form in wood in bogs, in petrified wood mixed with limonite and organic matter, and in carbonaceous sediments. 

The sediment from 236 m depth in well NR-10 is from the clinoptilolite subunit and its main mineral constituents are dolomite, quartz, analcime and opal, together with some clay minerals and pyrite, as well as a little siderite and calcite. A similar mineral composition was determined for a marl sample from 46 m depth in well NR-40 which contains additional gypsum, more calcite and less analcime, however. 

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