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Magnetite

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Formula:
Fe2+Fe23+O4
System:
Isometric
Colour:
Greyish black or iron ...
Lustre:
Metallic, Sub-Metallic
Hardness:
5½ - 6½
Member of:
Name:
Originally called lodestone as early as 1548 and by other names. Named in 1845 by Wilhelm Karl von Haidinger for the locality at Magnesia, Greece (site for lodestone).
Spinel Group, Jacobsite-Magnetite Series. Magnesioferrite-Magnetite Series.

Magnetite is an important iron ore, along with hematite.

Nanoinclusions of magnetite crystals cause the iridescence of Rainbow obsidian (Nadin, 2007). Extremely thin layers of 200-nm octahedral crystals of magnetite give some basalt surfaces an iridescent sheen (Nadin, 2007).

Visit gemdat.org for gemological information about Magnetite.

Classification of Magnetite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
4.BB.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
B : Metal: Oxygen = 3:4 and similar
B : With only medium-sized cations
7.2.2.3

7 : MULTIPLE OXIDES
2 : AB2X4
7.20.2

7 : Oxides and Hydroxides
20 : Oxides of Fe
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Occurrences of Magnetite

Geological Setting:
Common igneous accessory mineral. In sedimentary banded iron formations.

Physical Properties of Magnetite

Metallic, Sub-Metallic
Diaphaneity (Transparency):
Opaque
Colour:
Greyish black or iron black
Streak:
Black
Hardness (Mohs):
5½ - 6½
Hardness (Vickers):
VHN100=681 - 792 kg/mm2
Tenacity:
Brittle
Parting:
On {111}, especially good. Also reported as parting planes: {001}, {011}, {138}.
Fracture:
Irregular/Uneven
Density:
5.175 g/cm3 (Measured)    5.2 g/cm3 (Calculated)

Crystallography of Magnetite

Crystal System:
Isometric
Class (H-M):
m3m (4/m 3 2/m) - Hexoctahedral
Space Group:
Fd3m
Cell Parameters:
a = 8.397Å
Unit Cell Volume:
V 592.07 ų (Calculated from Unit Cell)
Z:
8
Morphology:
Crystals usually octahedral, sometimes dodecahedral, striated on {011} parallel [011]; less frequently with modifying {001} or {hhl}. Cubic (Balmat, NY), rare. Skeletonized microcrystals found in igneous rocks. Massive, granular, coarse to fine.
Twinning:
Common on {111}, with the same face as the composition face. Twins flattened parallel to {111} (common spinel law twins), or as lamellar twins, producing striae on {111}. Twin gliding, with K1{111}, K2{111}.

Crystallographic forms of Magnetite

Crystal Atlas:
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Magnetite no.3 - Goldschmidt (1913-1926)
Magnetite no.30 - Goldschmidt (1913-1926)
Magnetite no.37 - Goldschmidt (1913-1926)
Magnetite no.53 - Goldschmidt (1913-1926)
Magnetite no.91 - Goldschmidt (1913-1926)
Magnetite no.92 - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by www.smorf.nl.

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Transparency
Opaque | Translucent | Transparent

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Along a-axis | Along b-axis | Along c-axis | Start rotation | Stop rotation

Epitaxial Relationships of Magnetite

Epitaxial Minerals:
RutileTiO2
RutileTiO2
PyrophaniteMn2+TiO3
Olivine(Mg,Fe2+)2SiO4
MuscoviteKAl2(AlSi3O10)(OH)2
IlmeniteFe2+TiO3
HematiteFe2O3
Epitaxi Comments:
Hematite overgrowths on, and inclusions in, magnetite; ilmenite inclusions, rutile overgrowths, chorite group overgrowths, pyrophanite inclusions; magnetite on hematite; inclusions in muscovite; inclusions in hematite; inclusions in ilmenite; magnetite overgrowths on olivine
X-Ray Powder Diffraction:
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Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
d-spacingIntensity
4.852 (8)
2.967 (30)
2.5432 (100)
2.424 (8)
2.099 (20)
1.7146 (10)
1.6158 (30)
1.4845 (40)
1.2807 (10)
1.0930 (12)
0.85690 (8)
Comments:
Only d-spacings with I>8 given.

Optical Data of Magnetite

Type:
Isotropic
RI values:
n = 2.42
Max Birefringence:
δ = 0.000 - Isotropic minerals have no birefringence
Surface Relief:
Very High
Colour in reflected light:
Grey with brownish tint
Internal Reflections:
None
Comments:
Twin lamellae and zonal growth pattern exhibited in polished section by magnetite at times.

Chemical Properties of Magnetite

Formula:
Fe2+Fe23+O4
Essential elements:
All elements listed in formula:
Common Impurities:
Mg,Zn,Mn,Ni,Cr,Ti,V,Al

Relationship of Magnetite to other Species

Series:
Forms a series with Magnesioferrite (see here)
Forms a series with Jacobsite (see here)
Forms a series with Chromite (see here)
Forms a series with Maghemite (see here)
Member of:
Other Members of Group:
Ceylonite
ChromiteFe2+Cr23+O4
Cochromite(Co,Ni,Fe)(Cr,Al)2O4
CoulsoniteFe2+V23+O4
CuprospinelCu2+Fe23+O4
Filipstadite(Sb0.5Fe0.5)Mn2O4
FrankliniteZn2+Fe23+O4
GahniteZnAl2O4
Galaxite(Mn,Fe,Mg)(Al,Fe)2O4
HercyniteFe2+Al2O4
JacobsiteMn2+Fe23+O4
MagnesiochromiteMg(Cr,Al,Fe)2O4
MagnesiocoulsoniteMgV2O4
MagnesioferriteMgFe23+O4
Manganochromite(Mn,Fe)(Cr,V)2O4
Nichromite(Ni,Co,Fe)(Cr,Fe,Al)2O4
Qandilite(Mg,Fe)2(Ti,Fe,Al)O4
SpinelMgAl2O4
TrevoriteNi2+Fe23+O4
UlvöspinelFe2TiO4
Vuorelainenite(Mn,Fe)(V,Cr)2O4
ZincochromiteZnCr2O4
4.BB.05ChromiteFe2+Cr23+O4
4.BB.05Cochromite(Co,Ni,Fe)(Cr,Al)2O4
4.BB.05CoulsoniteFe2+V23+O4
4.BB.05CuprospinelCu2+Fe23+O4
4.BB.05Filipstadite(Sb0.5Fe0.5)Mn2O4
4.BB.05FrankliniteZn2+Fe23+O4
4.BB.05GahniteZnAl2O4
4.BB.05Galaxite(Mn,Fe,Mg)(Al,Fe)2O4
4.BB.05HercyniteFe2+Al2O4
4.BB.05JacobsiteMn2+Fe23+O4
4.BB.05Manganochromite(Mn,Fe)(Cr,V)2O4
4.BB.05MagnesiocoulsoniteMgV2O4
4.BB.05MagnesiochromiteMg(Cr,Al,Fe)2O4
4.BB.05MagnesioferriteMgFe23+O4
4.BB.05Nichromite(Ni,Co,Fe)(Cr,Fe,Al)2O4
4.BB.05Qandilite(Mg,Fe)2(Ti,Fe,Al)O4
4.BB.05SpinelMgAl2O4
4.BB.05TrevoriteNi2+Fe23+O4
4.BB.05UlvöspinelFe2TiO4
4.BB.05Vuorelainenite(Mn,Fe)(V,Cr)2O4
4.BB.05ZincochromiteZnCr2O4
4.BB.10HausmanniteMn2+Mn23+O4
4.BB.10HetaeroliteZnMn2O4
4.BB.10HydrohetaeroliteZnMn2O4 · H2O
4.BB.10IwakiiteMn2+Fe23+O4
4.BB.15MaghemiteFe23+O3
4.BB.15TitanomaghemiteFe3+(Fe3+,Ti4+,Fe2+,◻)2O4
4.BB.20Tegengrenite(Mg,Mn2+)2Sb5+0.5(Mn3+,Si,Ti)0.5O4
4.BB.25XieiteFe2+Cr2O4
7.20.1WüstiteFeO
7.20.3MaghemiteFe23+O3
7.20.4HematiteFe2O3
7.20.5Goethiteα-Fe3+O(OH)
7.20.6Akaganeiteβ-Fe3+O(OH,Cl)
7.20.7FeroxyhyteFe3+O(OH)
7.20.8Lepidocrociteγ-Fe3+O(OH)
7.20.9FerrihydriteFe103+O14(OH)2
7.20.10Amakinite(Fe2+,Mg)(OH)2
7.20.11MagnesioferriteMgFe23+O4
7.20.12MuskoxiteMg7Fe4O13 · 10H2O
7.20.13SrebrodolskiteCa2Fe23+O5
7.20.14HercyniteFe2+Al2O4
7.20.15BrownmilleriteCa2(Al,Fe3+)2O5

Other Names for Magnetite

Other Information

Magnetism:
Ferromagnetic
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:
Ore of iron.

References for Magnetite

Reference List:
Mügge (1905), Jb. Min., Beil.-Bd.: 16: 335.

Bragg (1915), Nature: 95: 561.

Bragg (1915), Phl. Magazine: 30: 305.

Greig, Merwin, and Posnjak (1936), American Mineralogist: 21: 504.

Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged: 698-707.

Schneiderhöhn (1958): I: 226-287.

Buddington, A.F. and Lindsley, D.H. (1964) Iron-titanium oxide minerals and synthetic equivalents. Journal of Petrology: 5: 310-357.

Johnson, H.P. and Merrill, R.T. (1972) Magnetic and mineralogical changes associated with low-temperature oxidation of magnetite. Journal of Geophysical Research: 77: 334-341.

Neumann, E.-R. (1974) The distribution of Mn 2+ and Fe 2+ between ilmenites and magnetites in igneous rocks. American Journal of Science: 274: 1074-1088.

Mao, H.K., D. Virgo, & P.M. Bell (1977), High-pressure 57Fe Mössbauer data on the phase and magnetic transitions of magnesioferrite (MgFe2O4), magnetite (Fe3O4), and hematite (Fe2O3). Carnegie Instsitution of Washington Year Book: 76: 522-525.

Cawthorn, R.G. and McCarthy, TS. (1980) Variations in Cr content of magnetite from the upper zone of the Bushveld complex - Evidence for heterogeneity and convection currents in magma chambers. Earth and Planetary Science Letters: 46: 335-343.

Fleet, M.E., Bilcox, G.A., and Barnett, R.L. (1980) Oriented magnetite inclusions in pyroxenes from the Grenville province. Canadian Mineralogist: 18: 89-99.

Fleet, M.E. (1982b) The structure of magnetite: defect structure II. Ata Crystallographica: B38: 1718-1723.

Fleet, M.E. (1984) The structure of magnetite: two annealed natural magnetites, Fe3.005O4 and Fe2.96Mg0.04O4. Acta Crystallographica (1984): C40: 1491-1493.

Markgraf, S.A., and R.J. Reeder (1985), High-temperature structure refinements of calcite and magnetite: American Mineralogist: 70: 590.

Fleet, M.E. (1986a) The structure of magnetite: symmetry of cubic spinels. Journal of Solid State Chemistry: 62: 75-82.

O'Neill, H.St.C. (1987) The quartz-fayalite-magnetite equilibria and free energies of formation of fayalite (Fe2SiO4) and magnetite (Fe3O4). American Mineralogist: 72: 67-75.

Collyer, S., Grimes, N.W., and Vaughan, D.J. (1988) Does magnetite lack a centre of symmetry? Journal of Physics C (Solid State Physics): 21: L989-L992.

Goss, C.J. (1988) Saturation magnetisation, coercivity and lattice parameter changes in the system Fe3O4-γ-Fe2O3, and their relationship to structure. Physics and Chemistry of Minerals: 16: 164-171.

Cecchini A., Franzini M., Troysi M.(1989): La microdurezza della magnetite. Atti Soc. Tosc. Sc. Nat., Mem., Serie A, 96, 327-332.

Pasternak, M.P., S. Nasu, K. Wada, & S. Endo (1994), High-pressure phase of magnetite: Physical Review B: 50: 6446-6449.

Berti G. (1995): Microstructure of Magnetite from XRPD Data in Relation to Magnetism. Material Science Forum (Trans. Tech. Pub. Zurich Switz.) Vol. 229-231, pp. 431-436.

Kuiper, P., Searle, B.G., Duda, L.-C., Wolf, R.M., and van der Zaag, P.J. (1997) Fe L2,3 linear and circular magnetic dichroism of Fe3O4. Journal of Electron Spectroscopy and Related Phenomena: 86: 107-113.

Coey, J.M.D., Berkowits, A.E., Balcells, L.I., Putris, F.F., and Parker, F.T. (1998) Magnetoresistance of magnetite. Applied Physics Letters: 72: 734-736.

Haavik, C., S. Stølen, H. Fjellvåg, M. Hanfland, & D. Häusermann (2000), Equation of state of magnetite and its high-pressure modification: Thermodynamics of the Fe-O system at high pressure: American Mineralogist: 85: 514-523.

de Castro, A.R.B., Fonesca, P.T., Pacheco, J.G., da Slva, J.C.V., and Santana, M.H.A. (2001) L-edge inner shell spectroscopy of nanostructural Fe3O4. Journal of Magnetism and Magnetic Materials: 233: 69-73.

Wright, J.P., Attfield, J.P., and Radaelli, P.G. (2001) Long range charge ordering in magnetite below the Verwey transition. Physical review Letters: 27: 266401/1-4.

Cornell, R.M. and Schwertmann, U. (2003) The iron oxides. Structure, properties, reactions, occurrences and uses. Wiley-VCH, Weinheim.

Chen, J., Huang, D.J., Tanaka, A., Chang, C.F., Chung, S.C., Wu, W.B., and Chen, C.T. (2004) Magnetic circular dichroism in Fe 2p resonant photoemission of magnetite. Physical Review B, 69, 085107-1-085107-8.

Huang, D.J., Chang, C.F., Jeng, H.-T., Guo, G.Y., Lin, H.-J., W, W.B., Ku, H.C., Fujimori, A., Takahashi, Y., and Chen, C.T. (2004) Spin and orbital magnetic moments of Fe3O4. Physical Review Letters: 93: 077204/1-4.

Lazor, P., O.N. Shebanova, & H. Annersten (2004), High-pressure study of stability of magnetite by thermodynamic analysis and synchrotron X-ray diffraction: Journal of Geophysical Research: 109: B05201.

Pearce, C.I., Henderson, C.M.B., Pattrick, R.A.D., van der Laan, G., and Vaughan, D.J. (2006) Direct determinaton of cation site occupancies in natural ferrite spinels by L 2,3 X-ray absorption spectroscopy and X-ray magnetic circular dichroism. American Mineralogist: 91: 880-893.

Nadin, E. (2007): The secret lives of minerals. Engineering & Science, No. 1, 10-20.

Internet Links for Magnetite

Specimens:
The following Magnetite specimens are currently listed for sale on minfind.com.

Localities for Magnetite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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