Maghemite


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maghemite

[mag′he‚mīt]
(mineralogy)
γ-Fe2O3 A mineral form of iron oxide that is strongly magnetic and a member of the magnetite series.

Maghemite

 

a mineral, a magnetic modification of the ferric oxide γ — Fe2O3. Generally containing admixtures of FeO and TiO2, maghemite is unstable in the natural state and is readily converted into stable hematite. It crystallizes in the tetragonal (pseudoisometric) system characterized by a defective spinel structure of the magnetite type. Maghemite has a hardness of 5-6 on Mohs’ scale and a density of 4,700-4,900 kg/m3. It is opaque and has a dark brown color with a steel-like hue. Maghemite occurs in nature only in the form of microscopically fine depositions in magnetite oxidation products and in titanomagnetite (with hematite, iron hydroxides). It is sometimes found in limonite and laterite as the product formed during the surface weathering of minerals containing iron.

References in periodicals archive ?
The ore is comprised of a combination of hematite and maghemite. The deposit has an average combined thickness of 1.5m, with some areas reaching up to 4m.
These novel nanoadsorbents are composed of a strongly responsive magnetic core surrounded by a highly sorptive surface layer of maghemite. The thermodynamics of the adsorption process is explored by means of calculation of the Gibbs free energy, enthalpy and entropy changes, which provide important insights into the overall mechanism of Cr(VI) adsorption.
Taylor and Schwertmann (1974) found that maghemite did not dissolve during DCB extraction, but Singer et al.
Darezereshki, One-Step Synthesis of Hematite (-Fe2O3) Nano-Particles by Direct Thermal-Decomposition of Maghemite, Materials Letters, 65, 642 (2011).
Whereas hematite, goethite and maghemite prevail in aerobic pedoenvironments, magnetite, which is a mineral of lithogenic origin, usually occurs at lower concentrations and ferrihydrite is typically present in small amounts.
The so-called MNPs usually consist of nanoparticles with a magnetic core composed of magnetite (Fe[sub]3O[sub]4) or maghemite (Fe[sub]2O[sub]3), containing of a type of product termed superparamagnetic iron oxide nanoparticles (SPIONs).
Seehra, "Magnetic relaxation and correlating effective magnetic moment with particle size distribution in maghemite nanoparticles," Journal of Magnetism and Magnetic Materials, vol.
This is simply because of slow atmospheric oxidation of [Fe.sub.3][O.sub.4] to maghemite, but since this polymorph of iron oxide exhibits nearly the same magnetism and chemical properties [42], this transformation does not change crucially the characteristics of the GO/MNP composites.
There is a fourth iron oxide, maghemite [gamma]-[Fe.sub.2][O.sub.3],which is formed by oxidation of magnetite.
FA contains quartz, feldspars, anhydrite, maghemite, gehlenite, cristobalite, zeolites, and carbonates.
The X value is proportional to the concentration of ferrimagnetic mineral (magnetite and maghemite).
These particles were mostly paramagnetic iron oxides such as magnetite ([Fe.sub.3][O.sub.4]), maghemite ([gamma][Fe.sub.2][O.sub.3]), and other ferrites.