God for us to design products, we are the porters of nature!
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| Magnetite | |
Chemical Formula |
Fe2+Fe3+2O4 |
Species |
Oxides & Hydroxides |
Crystal System |
Isometric |
Mohs Scale |
5-6 |
Specific Gravity |
5.17-5.18 |
Color |
Black, gray with brownish tint in reflected light |
Streak |
Black[1] |
Luster |
Metallic, Sub-Metallic |
Refractive Index |
n = 2.42 |
Diaphaneity |
Opaque |
Cleavage |
Indistinct, parting on , very good |
Fracture |
Irregular/Uneven |
| Crystal Habit：Octahedral, fine granular to massive | |
| Geological Setting：Common igneous accessory mineral. In sedimentary banded iron formations. | |
Magnetite is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, and this was how ancient people first noticed the property of magnetism. Lodestones were 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. 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 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 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, Valentines region of Uruguay, Kiruna, Sweden, the Pilbara, Midwest and Northern Goldfields regions in Western Australia, New South Wales in the Tallawang Region, 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.
Under anaerobic conditions, the ferrous hydroxide (Fe(OH)2 ) can be oxidized by the protons of water to form magnetite and molecular hydrogen.[citation needed] This process is described by the Schikorr reaction:
The well-crystallized magnetite (Fe3O4) is thermodynamically more stable than the ferrous hydroxide (Fe(OH)2 ).
Crystals of magnetite have been found in some bacteria (e.g., Magnetospirillum magnetotacticum) and in the brains of bees, termites, fish, some birds (e.g., the pigeon) and humans. 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.
Magnetic iron oxides are often used in magnetic storage, for example in the magnetic layer of hard disks, floppy disks and cassette tapes. These consist of a thin sheet of plastic material, with embedded magnetic particles. The particles can be magnetized to represent binary or analog data. Magnetic ink character recognition (MICR) also uses magnetic particles suspended in an ink which can be read by special scanning hardware.
Most newly-generated information, such as text, photographs, and audiovisual recordings, is now stored in magnetic media, and much of the world's legacy of information in other media has been transcribed to magnetic form, because it is cheap, compact, and computer-accessible.
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.
Magnetite also can be prepared by chemical co-precipitation, which consist in a mixture of a solution 0.1 M of FeCl3·6H2O and FeCl2·4H2O with mechanic agitation of about 2000 rpm. The molar ratio of FeCl3:FeCl2 can be 2:1; heating this solution at 70 °C, and immediately the speed is elevated to 7500 rpm and adding quickly a solution of NH4OH (10 volume %), immediately a dark precipitate will be formed, which consists of nanoparticles of magnetite.[citation needed]
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. Arsenic-contaminated drinking water is a major problem around the world, which can be solved using magnetite as a sorbent.
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).
Magnetite is also used as a catalyst for various industrial chemical processes, such as: Fischer-Tropsch process, the Haber-Bosch process and the water gas shift reaction.
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