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Inverse spinel structures have a different cation distribution in that all of the A cations and half of the B cations occupy octahedral sites, while the other half of the B cations occupy tetrahedral sites. An example of an inverse spinel is Fe 3 O 4, if the Fe 2+ (A 2+) ions are d 6 high-spin and the Fe 3+ (B 3+) ions are d 5 high-spin.
Cuprospinel is a mineral.Cuprospinel is an inverse spinel with the chemical formula CuFe 2 O 4, where copper substitutes some of the iron cations in the structure. [4] [5] Its structure is similar to that of magnetite, Fe 3 O 4, yet with slightly different chemical and physical properties due to the presence of copper.
The titanomagnetites have an inverse spinel crystal structure and at high temperatures are a solid solution series. Crystals formed from titanomagnetites by cation-deficient oxidation are called titanomaghemites , an important example of which is maghemite .
As a member of the inverse spinel group, magnetite can form solid solutions with similarly structured minerals, including ulvospinel (Fe 2 TiO 4) and magnesioferrite (MgFe 2 O 4). [17] Titanomagnetite, also known as titaniferous magnetite, is a solid solution between magnetite and ulvospinel that crystallizes in many mafic igneous rocks.
The transparent red spinels were called spinel-rubies [14] or balas rubies. [15] In the past, before the arrival of modern science, spinels and rubies were equally known as rubies. After the 18th century, the word ruby was only used for the red gem variety of the mineral corundum, and the word spinel came to be used. [16] "
However the structure is not an ordinary spinel structure, but rather the inverse spinel structure: One eighth of the tetrahedral holes are occupied by B cations, one fourth of the octahedral sites are occupied by A cations. and the other one fourth by B cation. It is also possible to have mixed structure spinel ferrites with formula [M 2+
Magnetite has an inverse spinel structure with oxygen forming a face-centered cubic crystal system. In magnetite, all tetrahedral sites are occupied by Fe 3+ and octahedral sites are occupied by both Fe 3+ and Fe 2+. Maghemite differs from magnetite in that all or most of the iron is in the trivalent state (Fe 3+
Maghemite (Fe 2 O 3, γ-Fe 2 O 3) is a member of the family of iron oxides.It has the same formula as hematite, but the same spinel ferrite structure as magnetite (Fe 3 O 4) and is also ferrimagnetic.