Siderite

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siderite

(sĭd`ərīt) or

chalybite

(kăl`ĭbīt), a mineral, varying in color from brown, green, or gray to black and occurring in nature in massive and crystalline form. A carbonate of iron, FeCO3, it serves as an iron ore, especially in the British Isles. It is widely distributed, being found also in the United States, Europe, South America, and Australia.

Siderite

 

(also spathic iron, chalybite), a mineral, a carbonate of iron with the composition Fe[CO3]. Siderite contains 62.01 percent FeO and 37.99 percent CO2. Its composition often includes isomorphic admixtures of Mn and Mg, which replace iron; more rarely, Ca is present, as are Co and Zn. Siderite cystallizes in the trigonal system, forming rhombohedral, tabular, prismatic, or scalenohedral crystals; the last occur rarely. The mineral usually occurs as granular aggregates, sinters, concretions, spherulites, and earthy agglomerates; it forms deposits in the form of veins, strata, and irregularly shaped bodies. Siderite is yellowish white, gray or greenish gray and turns brown upon weathering. It has a hardness of 4.5 on Mohs’ scale and a density of 3,960 kg/m3.

Depending on the conditions of formation, siderite is classified as being of hydrothermal, sedimentary (infiltration and precipitation), or metamorphosed origin. During weathering and oxidation, siderite is usually converted into hydrogoethite or hydrohematite. Siderite is one of the most important minerals in iron ore.


Siderite

 

any of the iron class of meteorites, according to modern classification. Formerly, the designation “siderite” was applied to iron meteorites that consist almost wholly of nickel-iron.

siderite

[′sid·ə‚rīt]
(mineralogy)
FeCO3 A brownish, gray, or greenish rhombohedral mineral composed of ferrous carbonate; hardness is 4 on Mohs scale, and specific gravity is 3.9. Also known as chalybite; iron spar; rhombohedral iron ore; siderose; sparry iron; spathic iron; white iron ore.
References in periodicals archive ?
This wall movement corresponds to a new gap between the metal pipe surface and any iron carbonate film.
The wall shear stresses found at the conditions investigated in this study are not strong enough to destroy iron carbonate films that have already formed (Schmitt et al., 2000).
where [E.sub.O] is Young's modulus of iron carbonate, [epsilon] is porosity of the film, and [[gamma].sub.SC] is the critical fracture strain.
Film thickness was determined using an iron carbonate film density of 33.7 mol/[m.sup.3] (Nesic and Lee, 2003).
In order to determine the parameters C1 and [C.sub.2] it was hypothesised that the Taylor vortices formed in rotating cylinder flow cause a larger impact area on the iron carbonate film and thus cause less erosion than for a film under virtually identical scalar mass transport conditions and wall shear stress in pipe flow.
(2000) concluded that the size of vortices and hydrodynamic effects determines the impact area and ultimately the erosion of iron carbonate films (the larger the vortices the lower the erosion).
Therefore, the current model for pipe flow was validated using data from a rotating cylinder with the different hydrodynamic effects upon the iron carbonate film accounted for through implementation of the Erosion Model.
In their experiments they formed an iron carbonate film on a cylindrical specimen of 1020 mild steel that had a ferritic-pearlite microstructure and was polished using SiC 1000-grit paper.
A protective iron carbonate film at 70[degrees]C and higher temperatures is reported by many studies in the open literature and can be expected for a pH over 6 (van Hunnik et al., 1996).
Iron carbonate films were simulated to form at all three pressures due to the high iron (II) concentration.
An increased transfer of carbonate ions to the area of film deposition might also cause an increased rate of iron carbonate film deposition; however, an increased transfer of iron (II) from an area of film deposition might decrease the rate of film deposition.
This must be due to the transient formation of an iron carbonate protective film.