Magnetite

Source: Wikipedia, the free encyclopedia.
This article is about the mineral magnetite as found in natural deposits. For other uses, see Iron(II,III) oxide.
Not to be confused with magnesite.
Magnetite
Specific gravity
5.17–5.18
SolubilityDissolves slowly in hydrochloric acid
References[2][3][4][5]
Major varieties
LodestoneMagnetic with definite north and south poles
ferrimagnetic; it is attracted by a magnet
as shown here
Unit cell of magnetite. The gray spheres are oxygen, green are divalent iron, blue are trivalent iron. Also shown are an iron atom in an octahedral space (light blue) and another in a tetrahedral space (gray).

Magnetite is a

native iron deposits, it is the most magnetic of all the naturally occurring minerals on Earth.[7][9] Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, which is how ancient peoples first discovered the property of magnetism.[10]

Magnetite is black or brownish-black with a metallic luster, has a

metamorphic rocks.[11]

The chemical

IUPAC name is iron(II,III) oxide and the common chemical name is ferrous-ferric oxide.[12]

Properties

In addition to igneous rocks, magnetite also occurs in

magnetofossils. Magnetite nanoparticles are also thought to form in soils, where they probably oxidize rapidly to maghemite.[13]

Crystal structure

The chemical composition of magnetite is Fe2+(Fe3+)2(O2-)4. This indicates that magnetite contains both

face-centered cubic lattice and iron cations occupying interstitial sites. Half of the Fe3+ cations occupy tetrahedral sites while the other half, along with Fe2+ cations, occupy octahedral sites. The unit cell consists of thirty-two O2- ions and unit cell length is a = 0.839 nm.[15][16]

As a member of the inverse spinel group, magnetite can form

ulvospinel (Fe2TiO4) and magnesioferrite (MgFe2O4).[17]

Titanomagnetite, also known as titaniferous magnetite, is a solid solution between magnetite and ulvospinel that crystallizes in many

oxy-exsolution during cooling, resulting in ingrowths of magnetite and ilmenite.[17]

Crystal morphology and size

Natural and synthetic magnetite occurs most commonly as octahedral crystals bounded by {111} planes and as rhombic-dodecahedra.[15] Twinning occurs on the {111} plane.[3]

Hydrothermal synthesis usually produces single octahedral crystals which can be as large as 10 mm (0.39 in) across.[15] In the presence of mineralizers such as 0.1 M HI or 2 M NH4Cl and at 0.207 MPa at 416–800 °C, magnetite grew as crystals whose shapes were a combination of rhombic-dodechahedra forms.[15] The crystals were more rounded than usual. The appearance of higher forms was considered as a result from a decrease in the surface energies caused by the lower surface to volume ratio in the rounded crystals.[15]

Reactions

Magnetite has been important in understanding the conditions under which rocks form. Magnetite reacts with oxygen to produce hematite, and the mineral pair forms a buffer that can control how oxidizing its environment is (the oxygen fugacity). This buffer is known as the hematite-magnetite or HM buffer. At lower oxygen levels, magnetite can form a buffer with quartz and fayalite known as the QFM buffer. At still lower oxygen levels, magnetite forms a buffer with wüstite known as the MW buffer. The QFM and MW buffers have been used extensively in laboratory experiments on rock chemistry. The QFM buffer, in particular, produces an oxygen fugacity close to that of most igneous rocks.[18][19]

Commonly, igneous rocks contain solid solutions of both titanomagnetite and hemoilmenite or titanohematite. Compositions of the mineral pairs are used to calculate oxygen fugacity: a range of oxidizing conditions are found in magmas and the oxidation state helps to determine how the magmas might evolve by fractional crystallization.[20] Magnetite also is produced from peridotites and dunites by serpentinization.[21]

Magnetic properties

Lodestones were used as an early form of

scientific fields.[22]

The relationships between magnetite and other iron oxide minerals such as ilmenite, hematite, and ulvospinel have been much studied; the reactions between these minerals and oxygen influence how and when magnetite preserves a record of the Earth's magnetic field.[23]

At low temperatures, magnetite undergoes a crystal structure phase transition from a monoclinic structure to a cubic structure known as the Verwey transition. Optical studies show that this metal to insulator transition is sharp and occurs around 120 K.[24] The Verwey transition is dependent on grain size, domain state, pressure,[25] and the iron-oxygen stoichiometry.[26] An isotropic point also occurs near the Verwey transition around 130 K, at which point the sign of the magnetocrystalline anisotropy constant changes from positive to negative.[27] The Curie temperature of magnetite is 580 °C (853 K; 1,076 °F).[28]

If magnetite is in a large enough quantity it can be found in aeromagnetic surveys using a magnetometer which measures magnetic intensities.[29]

Melting point

See also: Iron(II,III) oxide § Properties

Solid magnetite particles melt at about 1,583–1,597 °C (2,881–2,907 °F).[30][31]: 794 

Distribution of deposits

Magnetite and other heavy minerals (dark) in a quartz beach sand (Chennai, India).

Magnetite is sometimes found in large quantities in beach sand. Such

iron sands) are found in various places, such as Lung Kwu Tan in Hong Kong; California, United States; and the west coast of the North Island of New Zealand.[32] The magnetite, eroded from rocks, is carried to the beach by rivers and concentrated by wave action and currents. Huge deposits have been found in banded iron formations.[33][34] These sedimentary rocks have been used to infer changes in the oxygen content of the atmosphere of the Earth.[35]

Large deposits of magnetite are also found in the

Atacama region of Chile (Chilean Iron Belt);[36] the Valentines region of Uruguay;[37] Kiruna, Sweden;[38] the Tallawang region of New South Wales;[39] and in the Adirondack Mountains of New York in the United States.[40] Kediet ej Jill, the highest mountain of Mauritania, is made entirely of the mineral.[41] In the municipalities of Molinaseca, Albares, and Rabanal del Camino, in the province of León (Spain), there is a magnetite deposit in Ordovician terrain, considered one of the largest in Europe. It was exploited between 1955 and 1982.[42] Deposits are also found in Norway, Romania, and Ukraine.[43] Magnetite-rich sand dunes are found in southern Peru.[44] In 2005, an exploration company, Cardero Resources, discovered a vast deposit of magnetite-bearing sand dunes in Peru. The dune field covers 250 square kilometers (100 sq mi), with the highest dune at over 2,000 meters (6,560 ft) above the desert floor. The sand contains 10% magnetite.[45]

In large enough quantities magnetite can affect compass navigation. In Tasmania there are many areas with highly magnetized rocks that can greatly influence compasses. Extra steps and repeated observations are required when using a compass in Tasmania to keep navigation problems to the minimum.[46]

Magnetite crystals with a cubic habit are rare but have been found at Balmat, St. Lawrence County, New York,[47][48] and at Långban, Sweden.[49] This habit may be a result of crystallization in the presence of cations such as zinc.[50]

Magnetite can also be found in fossils due to biomineralization and are referred to as magnetofossils.[51] There are also instances of magnetite with origins in space coming from meteorites.[52]

Biological occurrences

galvanotaxis).[57]

Magnetite magnetosomes in Gammaproteobacteria

Pure magnetite particles are biomineralized in magnetosomes, which are produced by several species of magnetotactic bacteria. Magnetosomes consist of long chains of oriented magnetite particle that are used by bacteria for navigation. After the death of these bacteria, the magnetite particles in magnetosomes may be preserved in sediments as magnetofossils. Some types of anaerobic bacteria that are not magnetotactic can also create magnetite in oxygen free sediments by reducing amorphic ferric oxide to magnetite.[58]

Several species of birds are known to incorporate magnetite crystals in the upper beak for

polarity, and magnitude of the ambient magnetic field.[54][60]

Chitons, a type of mollusk, have a tongue-like structure known as a radula, covered with magnetite-coated teeth, or denticles.[61]
The hardness of the magnetite helps in breaking down food.

Biological magnetite may store information about the magnetic fields the organism was exposed to, potentially allowing scientists to learn about the migration of the organism or about changes in the Earth's magnetic field over time.[62]

Human brain

See also: Particulates § Cognitive hazards and mental health

Living organisms can produce magnetite.

beta-amyloid plaques and tau proteins associated with neurodegenerative disease frequently occur after oxidative stress and the build-up of iron.[63]

Some researchers also suggest that humans possess a magnetic sense,[66] proposing that this could allow certain people to use magnetoreception for navigation.[67] The role of magnetite in the brain is still not well understood, and there has been a general lag in applying more modern, interdisciplinary techniques to the study of biomagnetism.[68]

protein plaques in the brain. Such plaques have been linked to Alzheimer's disease.[71]

Increased iron levels, specifically magnetic iron, have been found in portions of the brain in Alzheimer's patients.[72] Monitoring changes in iron concentrations may make it possible to detect the loss of neurons and the development of neurodegenerative diseases prior to the onset of symptoms[64][72] due to the relationship between magnetite and ferritin.[63] In tissue, magnetite and ferritin can produce small magnetic fields which will interact with magnetic resonance imaging (MRI) creating contrast.[72] Huntington patients have not shown increased magnetite levels; however, high levels have been found in study mice.[63]

Applications

Due to its high iron content, magnetite has long been a major

sponge iron for conversion to steel.[74]

Magnetic recording

Audio recording using magnetic acetate tape was developed in the 1930s. The German magnetophon first utilized magnetite powder that BASF coated onto cellulose acetate before soon switching to gamma ferric oxide for its superior morphology.[75] Following World War II, 3M Company continued work on the German design. In 1946, the 3M researchers found they could also improve their own magnetite-based paper tape, which utilized powders of cubic crystals, by replacing the magnetite with needle-shaped particles of gamma ferric oxide (γ-Fe2O3).[75]

Catalysis

Approximately 2–3% of the world's energy budget is allocated to the

Haber Process for nitrogen fixation, which relies on magnetite-derived catalysts. The industrial catalyst is obtained from finely ground iron powder, which is usually obtained by reduction of high-purity magnetite. The pulverized iron metal is burnt (oxidized) to give magnetite or wüstite of a defined particle size. The magnetite (or wüstite) particles are then partially reduced, removing some of the oxygen in the process. The resulting catalyst particles consist of a core of magnetite, encased in a shell of wüstite, which in turn is surrounded by an outer shell of iron metal. The catalyst maintains most of its bulk volume during the reduction, resulting in a highly porous high-surface-area material, which enhances its effectiveness as a catalyst.[76][77]

Magnetite nanoparticles

Magnetite micro- and nanoparticles are used in a variety of applications, from biomedical to environmental. One use is in water purification: in high gradient magnetic separation, magnetite nanoparticles introduced into contaminated water will bind to the suspended particles (solids, bacteria, or plankton, for example) and settle to the bottom of the fluid, allowing the contaminants to be removed and the magnetite particles to be recycled and reused.[78] This method works with radioactive and carcinogenic particles as well, making it an important cleanup tool in the case of heavy metals introduced into water systems.[79]

Another application of magnetic nanoparticles is in the creation of ferrofluids. These are used in several ways. Ferrofluids can be used for targeted drug delivery in the human body.[78] The magnetization of the particles bound with drug molecules allows "magnetic dragging" of the solution to the desired area of the body. This would allow the treatment of only a small area of the body, rather than the body as a whole, and could be highly useful in cancer treatment, among other things. Ferrofluids are also used in magnetic resonance imaging (MRI) technology.[80]

Coal mining industry

For the separation of coal from waste, dense medium baths were used. This technique employed the difference in densities between coal (1.3–1.4 tonnes per m3) and shales (2.2–2.4 tonnes per m3). In a medium with intermediate density (water with magnetite), stones sank and coal floated.[81]

Magnetene

Magnetene is a two-dimensional flat sheet of magnetite noted for its ultra-low-friction properties.[82]

Gallery

See also

References

  1. S2CID 235729616
    .
  2. ^ Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W. "Magnetite" (PDF). Handbook of Mineralogy. Chantilly, VA: Mineralogical Society of America. p. 333. Retrieved 15 November 2018.
  3. ^ a b "Magnetite". mindat.org and the Hudson Institute of Mineralogy. Retrieved 15 November 2018.
  4. ^ Barthelmy, Dave. "Magnetite Mineral Data". Mineralogy Database. webmineral.com. Retrieved 15 November 2018.
  5. ISBN 978-0-471-80580-9
    .
  6. ISBN 978-0-444-51979-5
    .
  7. ^
    ISBN 978-0-471-15677-2
    .
  8. S2CID 128699936
    .
  9. PMID 12482930
    .
  10. ISBN 0-387-22967-1
    .
  11. ISBN 9780195106916
    .
  12. doi:10.1016/j.jmmm.2013.04.075
    .
  13. S2CID 4338921
    .
  14. OCLC 907621860
    .
  15. ^
    ISBN 978-3-527-28576-1
    .
  16. ^ an alternative visualisation of the crystal structure of Magnetite using JSMol is found here.
  17. ^ a b Nesse 2000, p. 360.
  18. doi:10.1016/0012-821X(86)90061-0
    .
  19. ISBN 9780521880060
    .
  20. ISBN 0198578105
    .
  21. ISBN 0582300967
    .
  22. ^ Nesse 2000, p. 361.
  23. ISBN 9780520260313
    .
  24. S2CID 39065289
    .
  25. S2CID 55568498
    . 10A922.
  26. PMID 9935445
    .
  27. ^ Gubbins, D.; Herrero-Bervera, E., eds. (2007). Encyclopedia of geomagnetism and paleomagnetism. Springer Science & Business Media.
  28. hdl:11250/2491932
    .
  29. ^ "Magnetic Surveys". Minerals Downunder. Australian Mines Atlas. 2014-05-15. Retrieved 2018-03-23.
  30. ^ "Magnetite". American Chemical Society. Retrieved 2022-07-06.
  31. OCLC 326982496
    .
  32. ^ Templeton, Fleur. "1. Iron – an abundant resource - Iron and steel". Te Ara Encyclopedia of New Zealand. Retrieved 4 January 2013.
  33. doi:10.1016/j.precamres.2017.12.017
    .
  34. S2CID 210264705
    .
  35. S2CID 201124189
    .
  36. S2CID 130095912
    .
  37. doi:10.3133/ofr76466
    . Retrieved 15 February 2021.
  38. hdl:10533/228146
    .
  39. doi:10.1190/segam2012-0700.1
    .
  40. doi:10.1130/GES00624.1
    .
  41. ^ European Space Agency, esa.int (access: August 2, 2020)
  42. ISBN 978-84-95063-99-1
    .
  43. ^ Hurlbut & Klein 1985, p. 388.
  44. doi:10.1016/S0169-555X(98)00084-1
    .
  45. ^ Moriarty, Bob (5 July 2005). "Ferrous Nonsnotus". 321gold. Retrieved 15 November 2018.
  46. ^ Leaman, David. "Magnetic Rocks - Their Effect on Compass Use and Navigation in Tasmania" (PDF). Archived from the original (PDF) on 2017-03-29. Retrieved 2018-03-23.
  47. S2CID 129227218
    .
  48. ^ "The mineral Magnetite". Minerals.net.
  49. doi:10.1080/11035897209453690
    .
  50. S2CID 12709419
    .
  51. doi:10.1146/annurev.ea.17.050189.001125
    . Retrieved 15 November 2018.
  52. PMID 12011420
    .
  53. S2CID 16073105
    .
  54. ^
    PMID 25587420
    . Birds can use the geomagnetic field for compass orientation. Behavioral experiments, mostly with migrating passerines, revealed three characteristics of the avian magnetic compass: (1) it works spontaneously only in a narrow functional window around the intensity of the ambient magnetic field, but can adapt to other intensities, (2) it is an "inclination compass", not based on the polarity of the magnetic field, but the axial course of the field lines, and (3) it requires short-wavelength light from UV to 565 nm Green.
  55. ^
    PMID 1502184
    . Using an ultrasensitive superconducting magnetometer in a clean-lab environment, we have detected the presence of ferromagnetic material in a variety of tissues from the human brain.
  56. PMID 1285705
    . A simple calculation shows that magnetosomes moving in response to earth-strength ELF fields are capable of opening trans-membrane ion channels, in a fashion similar to those predicted by ionic resonance models. Hence, the presence of trace levels of biogenic magnetite in virtually all human tissues examined suggests that similar biophysical processes may explain a variety of weak field ELF bioeffects.
  57. PMID 26449415
    . Taken together these data suggest a previously unknown two-molecule sensing mechanism in which KCNJ15/Kir4.2 couples with polyamines in sensing weak electric fields.
  58. ^ Lovley, Derek; Stolz, John; Nord, Gordon; Phillips, Elizabeth. "Anaerobic production of magnetite by a dissimilatory iron-reducing microorganism" (PDF). geobacter.org. US Geological Survey, Reston, Virginia 22092, USA Department of Biochemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA. Archived from the original (PDF) on 29 March 2017. Retrieved 9 February 2018.
  59. PMID 25490840
    . There are good reasons to believe that this visual magnetoreceptor processes compass magnetic information which is necessary for migratory orientation.
  60. PMID 19864263
    . Compass orientation controlled by the inclination compass ...allows birds to locate courses of different origin
  61. S2CID 40567757
    . X-ray diffraction patterns show that the mature denticles of three extant chiton species are composed of the mineral lepidocrocite and an apatite mineral, probably francolite, in addition to magnetite.
  62. PMID 19728122
    .
  63. ^
    ISBN 9781-61761-839-0
  64. ^
    S2CID 205500060
    .
  65. ^
    PMID 27601646
    .
  66. doi:10.1126/science.aaf5803
    .
  67. PMID 3344279
    .
  68. PMID 20071390
    .
  69. ^ "Pollution particles 'get into brain'". BBC News. September 5, 2016.
  70. PMID 27601646
    .
  71. ^ Wilson, Clare (5 September 2016). "Air pollution is sending tiny magnetic particles into your brain". New Scientist. 231 (3090). Retrieved 6 September 2016.
  72. ^
    S2CID 21437342
    .
  73. doi:10.1002/14356007.a14_461.pub2
  74. ISBN 0873510232
    .
  75. ^ a b Schoenherr, Steven (2002). "The History of Magnetic Recording". Audio Engineering Society.
  76. doi:10.1016/j.apcata.2007.03.021
    .
  77. ISBN 978-3527306732
    .
  78. ^ a b Blaney, Lee (2007). "Magnetite (Fe3O4): Properties, Synthesis, and Applications". The Lehigh Review. 15 (5). Archived from the original on 2020-11-11. Retrieved 2017-12-15.
  79. PMID 26859095
    .
  80. PMID 22389583
    .
  81. doi:10.1127/0372-8854/2011/0061
    .
  82. ^ Toronto, University of. "Magnetene: Graphene-like 2D material leverages quantum effects to achieve ultra-low friction". phys.org.

Further reading

External links
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