http://SaturnianCosmology.Org/ mirrored file For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== Magnetite From Wikipedia, the free encyclopedia Magnetite Magnetite exposed on the ground. The mineral is black and irregularly smooth. Individual chunks jut at angles characteristic of the crystal habit. Magnetite from the Kola Peninsula , Russia General Category Oxide mineral Spinel group Chemical formula iron(II,III) oxide, Fe_3 O_4 Crystal symmetry Isometric 4/m 3 2/m Unit cell a = 8.397 Å; Z=8 Identification Color Black, gray with brownish tint in reflected light Crystal habit Octahedral , fine granular to massive Crystal system Isometric Hexoctahedral Twinning On {Ill} as both twin and composition plane, the spinel law, as contact twins Cleavage Indistinct, parting on {Ill}, very good Fracture Uneven Tenacity Brittle Mohs scale hardness 5.5–6.5 Luster Metallic Streak Black Diaphaneity Opaque Specific gravity 5.17–5.18 References ^[1] ^[2] ^[3] Major varieties Lodestone Magnetic with definite north and south poles *Magnetite* is a ferrimagnetic mineral with chemical formula Fe _3 O _4 , one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron(II,III) oxide and the common chemical name *ferrous-ferric oxide*. The formula for magnetite may also be written as FeO·Fe_2 O_3 , which is one part wüstite (FeO) and one part hematite (Fe_2 O_3 ). This refers to the different oxidation states of the iron in one structure, not a solid solution . The Curie temperature of magnetite is 858 K (585 °C; 1,085 °F). Contents [hide ] * 1 Properties * 2 Distribution of deposits * 3 Biological occurrences * 4 Preparation as a ferrofluid * 5 Application as a sorbent * 6 Industry * 7 Gallery of magnetite mineral specimens * 8 See also * 9 References * 10 Further reading * 11 External links [edit ] Properties Magnetite is the most magnetic of all the naturally occurring minerals on Earth .^[4] Naturally magnetized pieces of magnetite, called lodestone , will attract small pieces of iron, and this was how ancient man first discovered the property of magnetism . Lodestone was used as an early form of magnetic compass . Magnetite typically carries the dominant magnetic signature in rocks, and so it has been a critical tool in paleomagnetism , a science important in discovering and understanding plate tectonics and as historic data for magnetohydrodynamics and other scientific fields . The relationships between magnetite and other iron-rich oxide minerals such as ilmenite , hematite, and ulvospinel have been much studied, as the complicated reactions between these minerals and oxygen influence how and when magnetite preserves records of the Earth's magnetic field. Magnetite has been very important in understanding the conditions under which rocks form and evolve. Magnetite reacts with oxygen to produce hematite, and the mineral pair forms a buffer that can control oxygen fugacity . Commonly igneous rocks contain grains of two solid solutions , one between magnetite and ulvospinel and the other between ilmenite and hematite. Compositions of the mineral pairs are used to calculate how oxidizing was the magma (i.e., the oxygen fugacity of the magma): a range of oxidizing conditions are found in magmas and the oxidation state helps to determine how the magmas might evolve by fractional crystallization . Small grains of magnetite occur in almost all igneous rocks and metamorphic rocks . Magnetite also occurs in many sedimentary rocks , including banded iron formations . In many igneous rocks, magnetite-rich and ilmenite-rich grains occur that precipitated together from magma. Magnetite also is produced from peridotites and dunites by serpentinization . Magnetite is a valuable source of iron ore . It dissolves slowly in hydrochloric acid . [edit ] Distribution of deposits A fine textured sample, ~5cm across Magnetite and other heavy minerals (dark) in a quartz beach sand (Chennai , India). Magnetite is sometimes found in large quantities in beach sand. Such black sands (mineral sands or iron sands) are found in various places such as California and the west coast of New Zealand . The magnetite is carried to the beach via rivers from erosion and is concentrated via wave action and currents. Huge deposits have been found in banded iron formations. These sedimentary rocks have been used to infer changes in the oxygen content of the atmosphere of the Earth. Large deposits of magnetite are also found in the Atacama region of Chile , Kiruna , Sweden , the Pilbara , Midwest and Northern Goldfields regions in Western Australia , and in the Adirondack region of New York in the United States . Deposits are also found in Norway , Germany , Italy , Switzerland , South Africa , India , Mexico , and in Oregon , New Jersey , Pennsylvania , North Carolina , Virginia , New Mexico , Utah , and Colorado in the United States . 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.^[5] [edit ] Biological occurrences Crystals of magnetite have been found in some bacteria (e.g., Magnetospirillum magnetotacticum ) and in the brains of bees , of termites , fish, some birds (e.g., the pigeon ) and humans.^[6] These crystals are thought to be involved in magnetoreception , the ability to sense the polarity or the inclination of the Earth's magnetic field , and to be involved in navigation . Also, chitons have teeth made of magnetite on their radula making them unique among animals. This means they have an exceptionally abrasive tongue with which to scrape food from rocks. The study of biomagnetism began with the discoveries of Caltech paleoecologist Heinz Lowenstam in the 1960s. [edit ] Preparation as a ferrofluid Crystal structure of magnetite Magnetite can be prepared in the laboratory as a ferrofluid in the Massart method by mixing iron(II) chloride and iron(III) chloride in the presence of sodium hydroxide .^[/citation needed /] Magnetite also can be prepared by chemical co-precipitation, which consist in a mixture of a solution 0.1 M of FeCl_3 ·6H_2 O and FeCl_2 ·4H_2 O with mechanic agitation of about 2000 rpm. The molar ratio of FeCl_3 :FeCl_2 can be 2:1; heating this solution at 70 °C, and immediately the rpm is elevated to 7500 rpm and adding quickly a solution of NH_4 OH (10 volume %), immediately a dark precipitate will be formed, which consist of nanoparticles of magnetite.^[/citation needed /] [edit ] Application as a sorbent Magnetite powder efficiently removes arsenic (III) and arsenic(V) from water, the efficiency of which increases ~200 times when the magnetite particle size decreases from 300 to 12 nm.^[7] Arsenic-contaminated drinking water is a major problem around the world, which can be solved using magnetite as a sorbent . [edit ] Industry Because of its stability at high temperatures, it is used for coating industrial water tube steam boilers . The magnetite layer is formed after a chemical treatment (e.g. by using hydrazine ). [edit ] Gallery of magnetite mineral specimens Octahedral crystals of magnetite up to 1.8 cm across, on cream colored Feldspar crystals. Locality: Cerro Huañaquino, Potosí Department , Bolivia. Size: 8.4 x 5.2 x 3.2 cm. Unusual octahedral magnetite & chalcopyrite association, Aggeneys , Northern Cape Province , South Africa. Size 7 x 6 x 4 cm. Red gemmy crystals of Chondrodite with magnetite, Tilly Foster mine, Brewster, New York USA. Size 2.8 x 2.6 x 2.1 cm. Unusual specular hematite pseudomorph after magnetite, from Payun Matru volcano, Reserva Provincial La Payunia , Argentina. Size: 11.8 x 5.6 x 4.4 cm. Metallic, jet black, complex cubes of magnetite, from ZCA Mine No. 4, Balmat-Edwards district, St. Lawrence County, New York USA. Field of view, about 4 cm. [edit ] See also * Bluing (steel) is a process in which steel is partially protected against rust by a layer of magnetite. * Ferrite * Maghemite * Magnesia (in natural mixtures with magnetite) * Magnetotactic bacteria * Mill scale * Mineral redox buffer [edit ] References 1. *^ * http://www.handbookofmineralogy.com/pdfs/magnetite.pdf Handbook of Mineralogy 2. *^ * http://www.mindat.org/min-2538.html Mindat.org 3. *^ * http://webmineral.com/data/Magnetite.shtml Webmineral data 4. *^ * Harrison, R. J. (2002). "Direct imaging of nanoscale magnetic interactions in minerals" (free-download pdf). /Proceedings of the National Academy of Sciences/ *99*: 16556. doi :10.1073/pnas.262514499 . http://www.pnas.org/content/99/26/16556.full.pdf. 5. *^ * Ferrous Nonsnotus 6. *^ * Baker, R R; J G Mather, J H Kennaugh (1983-01-06). "Magnetic bones in human sinuses". /Nature/ *301* (5895): 79–80. PMID 6823284 . 7. *^ * J.T. Mayo /et al./ (2007). "The effect of nanocrystalline magnetite size on arsenic removal" (free download). /Sci. Technol. Adv. Mater./ *8*: 71. doi :10.1016/j.stam.2006.10.005 . [edit ] Further reading * Hurlbut, Cornelius S.; Klein, Cornelis (1985). /Manual of Mineralogy/ (20th ed.). Wiley. ISBN 0471805807 . * Lowenstam, Heinz A.; Weiner, Stephen (1989). /On Biomineralization/. USA: Oxford University Press. ISBN 0195049772 . * Chang, Shih-Bin Robin; Kirschvink, Joseph Lynn (1989). "Magnetofossils, the Magnetization of Sediments, and the Evolution of Magnetite Biomineralization" . /Annual Review of Earth and Planetary Sciences/ *17*: 169–195. doi :10.1146/annurev.ea.17.050189.001125 . http://www.gps.caltech.edu/~jkirschvink/pdfs/AnnualReviews89.pdf. [edit ] External links * Mineral galleries * Powder X-Ray Diffraction (XRD) Pattern * Bio-magnetics * History of Magnetite Mining in the NJ Highlands * Magnetite mining in New Zealand Accessed 25-Mar-09 * Magnetite mining in Santa Cruz * Peruvian sand dunes [hide ] v • d • e Ore minerals and ore deposits Ore minerals Oxides Cassiterite (tin ) · Chromite (chromium ) · Hematite (iron ) · Ilmenite (titanium ) · *Magnetite* (iron ) Sulfides Acanthite (silver ) · Chalcopyrite (copper ) · Chalcocite (copper ) · Cinnabar (mercury ) · Galena (lead ) · Pentlandite (nickel ) · Sphalerite (zinc ) Other Bauxite (aluminium ) · Scheelite (tungsten ) Ore deposit types Banded iron formation · Carbonate hosted lead zinc ore deposits · Heavy mineral sands · Iron oxide copper gold · Kambalda type komatiitic nickel ore deposits · Lateritic nickel · Magmatic nickel-copper-iron-PGE deposits · Porphyry copper · Sedimentary exhalative deposits · Volcanogenic massive sulfide Retrieved from "http://en.wikipedia.org/wiki/Magnetite" Categories : Magnetism | Iron compounds | Iron minerals | Oxides | Oxide minerals | Ferromagnetic materials | Iron oxide pigments