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Magnetite is best known for its property that it is strongly attracted to magnets. Some forms of Magnetite from specific localities are in fact themselves magnets. This form is known as Lodestone, and is the only mineral that acts as a natural magnet. Although its magnetism is weak, it is strong enough to attract large nails. Due to its magnetic properties, small iron particles are often found clinging to its surfaces. Some dealers intentionally place metallic filings on a Lodestone to demonstrate its magnetism.
Magnetite may form a yellow-brown rust coating if washed or kept in a moist area. If a specimen is washed, it should be dried immediately to prevent rusting. Also, specimens should be stored in dry areas for the same reason. The rust can easily be removed by soaking the Magnetite in a rust removing solvent such as Iron Out.
The mineral Hematite is known to form pseudomorphs over Magnetite. These pseudomorphs are known as Martite, and their appearance may be similar to regular Magnetite. However, they differ from Magnetite in that they are only weakly attracted to magnetic fields and have a reddish-brown streak.
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Chemical Formula |
Fe2+Fe3+2O4 |
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Composition |
Iron oxide. May contain many impurities partially replacing both the first and the second iron. |
| Variable Formula |
(Fe,Mn,Mg,Zn,Ni)2+(Fe,Al,Cr,Mn,V)3+2O4 |
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Color |
Black |
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Streak |
Black |
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Hardness |
5.5 - 6.5 |
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Crystal System |
Isometric |
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Crystal Forms
and Aggregates |
Crystals are usually well-shaped octahedrons, and less commonly dodecahedrons. They may also be an interesting combination of the two. Seldom occurs in cubic crystals. Crystals are usually striated, and some octahedral crystals contain layer growths. Also occurs massive, grainy, in veins, as large embedded grains, and as rounded crystals. |
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Transparency |
Opaque |
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Specific Gravity |
4.9 - 5.2 |
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Luster |
Metallic |
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Cleavage |
None. May exhibit parting. |
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Fracture |
Subconchoidal to uneven |
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Tenacity |
Brittle |
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Other ID Marks |
Is ferromagnetic, meaning it is strongly attracted to magnetic fields.
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In Group |
Oxides; Multiple Oxides |
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Striking Features |
Strong attraction to magnets, hardness, and streak. |
| Environment |
Occurs in igneous rock such as diabase, as well as contact and regional metamorphic rocks and in hydrothermal replacement deposits.
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Popularity (1-4)
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2 |
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Prevalence (1-3)
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1 |
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Demand (1-3) |
1 |
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Magnetite is an important ore of iron. Its perfect crystals are also popular among mineral collectors, and the magnetic Lodestone variety is popular among amateur collectors. This mineral is also of significant scientific interest because of its special magnetic properties.
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Magnetite is a common mineral. Much commercial magnetite is of massive form and lacks interest to collectors. Only localities where well-crystallized forms were found are mentioned here. Some of the best and most lustrous octahedral crystals come from Cerro Huanaquino, Potosi, Bolivia. Single octahedral crystals often in a matrix are well known from Binn Tal, Wallis, Switzerland, sometimes with modified layer growths or triangular striations. Some of the largest Magnetite deposits are in northern Sweden, and good crystals have come from Nordmark, Sweden and the Kovdor Mine in the Kola Peninsula, Russia. Heavily striated crystals with growth layers come from Parachinar, Pakistan.
In the U.S., large masses, sometimes with partial or full octahedral faces, have come from Franklin and Ogdensburg, Sussex Co., New Jersey; and perfect
octahedral crystals from Chester, Windsor Co., Vermont. Lustrous cubic crystals occur in
Balmat, St. Lawrence Co., New York. (This is the only occurrence to date of cubic Magnetite.) The French Creek Mine, St.
Peters, Chester Co., Pennsylvania has produced some large octahedrons. The magnetic variety Lodestone comes from the Iron Springs area (Dixie National Forest), Washington and Iron counties, Utah; and Magnet Cove, Hot Spring Co., Arkansas.
There are several classic Magnetite localities on the East Coast which are long extinct but have once produced excellent specimens. Large octahedrons were found in Monroe, Orange Co., New York, and very interesting
dodecahedral crystals, often with rounded corners were at one time abundant at the old Tilly Foster
Mine, Brewster, Putnam Co., New York. Laurel Hill (Snake Hill), Secaucus, Hudson Co., New Jersey has produced classic octahedrons, and massive and poorly crystallized examples were once found in abundance in the dumps of the 19th century iron mines in the Ramapo Mountains, Sterling Forest, and Hudson Highlands region of Orange and Rockland Counties, New York., as well as the Jersey Highlands of Passaic County, New Jersey.
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Calcite, Phlogopite, Feldspar, Talc, Pyrite, Epidote, Ilmenite, Hematite, Apatite, Garnet, Chlorite
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Franklinite - Only weakly attracted to magnetic fields.
Spinel - Not attracted to magnetic fields, has a white streak.
Ilmenite - Lighter streak.
Chromite - Has a brownish streak.
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Have a question about Magnetite? Visit our Q&A Community and ask the experts!
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