Magnesioferrite
Magnesioferrite is a magnesium iron oxide mineral, a member of the magnetite series of spinels. Magnesioferrite crystallizes as black metallic octahedral crystals. It is named after its chemical composition of magnesium and ferric iron. The density is 4.6 - 4.7 (average = 4.65), and the diaphaniety is opaque. Occurs as well-formed fine sized crystals or massive and granular. Its hardness is 6-6.5. It has a metallic luster and a dark red streak.
| Magnesioferrite | |
|---|---|
 Magnesioferrite from Ochtendung, Eifel, Germany | |
| General | |
| Category | Oxide minerals Spinel group Spinel structural group |
| Formula (repeating unit) | Mg(Fe3+)2O4 |
| Strunz classification | 4.BB.05 |
| Crystal system | Cubic |
| Crystal class | Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m) |
| Space group | Fd3m |
| Unit cell | a = 8.3866 Å; Z = 8 |
| Identification | |
| Color | Black to brownish black |
| Crystal habit | As octahedral crystals, massive granular |
| Twinning | Twin plane {111}, contact twins |
| Cleavage | On {111} |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 6 - 6.5 |
| Luster | Metallic, semimetallic, dull |
| Streak | Dark red |
| Diaphaneity | Opaque, transparent in thin fragments |
| Specific gravity | 4.55 – 4.65 measured |
| Optical properties | Isotropic |
| Refractive index | n = 2.38 |
| Other characteristics | Magnetic |
| References | [1][2][3] |
Occurrence
It occurs in fumaroles, as a result of combustion metamorphism and coal seam fires, in glass spherules related to meteorite impacts, and as accessory phase in kimberlites and carbonatites.[1]
It has been reported from Vesuvius and Stromboli, Italy.
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