magnetite

{{Infobox mineral | name = Magnetite | category = | boxwidth = | image = Magnetite-118736.jpg | alt = | caption = Magnetite from Bolivia | formula = iron(II,III) oxide, | IMAsymbol = Mag | molweight = | strunz = 4.BB.05 | system = Isometric | class = Hexoctahedral (mm) H-M symbol: (4/m 2/m) | symmetry = Fdm (no. 227) | unit cell = a = 8.397 Å; Z = 8 | color = Black, gray with brownish tint in reflected sun | habit = Octahedral, fine granular to massive | 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 = 5.5–6.5 | luster = Metallic | refractive = | opticalprop = | birefringence = | pleochroism = | streak = Black | gravity = 5.17–5.18 | density = 5 g/cm3 | melt = | fusibility = | diagnostic = | solubility = Dissolves slowly in hydrochloric acid | diaphaneity = Opaque | other = | var1 = Lodestone | var1text = Magnetic with definite north and south poles | references = }}

thumb|upright=1.2|Magnetite is one of the very few minerals that is ferrimagnetic; it is attracted by a [[magnet as shown here]] thumb|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 mineral and one of the main iron ores, with the chemical formula . It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the exception of extremely rare native iron deposits, it 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, which is how ancient peoples first discovered the property of magnetism.