Mineral description : Magnetite

Magnetite crystals from Bastnäs.
The big crystal is 12 mm across.
Massive magnetite vein from Kiruna.

Mineral class Oxides : Hematite - Ilmenite - Magnetite group.
Chemical formula Fe3O4
Crystal system Cubic.
Habitus Crystals often as well developed octaedric or dodecaedric crystals. Also as grainy or compact masses.
Cleavage None, fracture conchoidal to uneven. Sometimes with octaedric partening.
Hardness 5.5-6.5
Density 5.2
Color Black. Often with bluish iriscense.
Streak Black´, opaque.
Luster Metallic or dull.
Description  
Occurance Magnetite forms in igneous rocks (Kiruna) through magmatic differention. Also occurs in metamorphic rocks, hydrothermal veins and pegmatites.
Associates  
Notes Strongly magnetic.
Locations A very common mineral, beeing the major part of many Swedish iron mines. Often as massive ore, but crystal localities exists also.
  • Malmberget, Gällivare. As druses of up to 2cm crystals with smoky quartz, apatite and pyrite.
  • Falu mine. Up to 3cm crystals in talc.
  • Långban, Värmland. Octaedric crystals in hematite.
  • Ladugruvan, Persberg.
  • Harstigen.
  • Stråssa.
  • Bastnäs, Riddarhyttan. As octaedric crystals in chlorite schist.
  • Norberg.
  • Altemark, Mo i Rana, Norway. As well developed octaedric crystals in chlorite schist.

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Mineral group index.
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axelsson@acc.umu.se
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Last changed : 1998-07-31