Maghemite
Maghemite (Fe2O3, γ-Fe2O3) is a member of the family of iron oxides. It has the same formula as hematite, but the same spinel ferrite structure as magnetite (Fe3O4) and is also ferrimagnetic. It is sometimes spelled as "maghaemite".
| Maghemite | |
|---|---|
| General | |
| Category | Oxide minerals |
| Formula (repeating unit) | γ-Fe2O3 |
| IMA symbol | Mgh |
| Strunz classification | 4.BB.15 |
| Crystal system | Cubic with a tetragonal supercell |
| Crystal class | Gyroidal (432) (same H-M symbol) |
| Space group | P4132, P4332 |
| Unit cell | a = 8.33 Å; Z = 8 or a = 8.35 Å c = 24.99 Å; Z = 8 for tetragonal supercell |
| Identification | |
| Color | Brown, bluish black; brown to yellow in transmitted light; white to bluish gray in reflected light. |
| Crystal habit | Rarely as minute octahedral crystals, or acicular overgrowths; commonly as coatings on or replacements of magnetite; massive. |
| Cleavage | None |
| Fracture | Subconchoidal |
| Mohs scale hardness | 5 |
| Luster | Dull |
| Streak | Brown |
| Diaphaneity | Opaque, transparent in thin fragments |
| Specific gravity | 4.860 (calculated) |
| Optical properties | Isotropic |
| Other characteristics | Strongly magnetic |
| References | |
Maghemite can be considered as an Fe(II)-deficient magnetite with formula where represents a vacancy, A indicates tetrahedral and B octahedral positioning.
![{\displaystyle \left({\ce {Fe^{III}8}}\right)_{A}\left[{\ce {Fe_{40/3}^{III}\square _{8/3}}}\right]_{B}{\ce {O32}}}](../I/797ed8ea95a1dfbedcb8667ed5cd71f0dac35ace.svg)
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