Magnetite

Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe²⁺Fe3+2O₄. It is one of the oxides of iron, and is ferrimagnetic;[6] it is attracted to a magnet and can be magnetized to become a permanent magnet itself.[7][8] With the exception of extremely rare 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]

Quick facts: Magnetite, General, Category, Formula .mw-par... ▼

Magnetite
Magnetite from Iron Bridge, WA.
General
Category	Oxide minerals Spinel group Spinel structural group
Formula (repeating unit)	iron(II,III) oxide, Fe2+Fe3+2O4
IMA symbol	Mag[1]
Strunz classification	4.BB.05
Crystal system	Isometric
Crystal class	Hexoctahedral (m3m) H-M symbol: (4/m 3 2/m)
Space group	Fd3m (no. 227)
Unit cell	a = 8.397 Å; Z = 8
Identification
Color	Black, gray with brownish tint in reflected sun
Crystal 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 scale hardness	5.5–6.5
Luster	Metallic
Streak	Black
Diaphaneity	Opaque
Specific gravity	5.17–5.18
Solubility	Dissolves slowly in hydrochloric acid
References	[2][3][4][5]
Major varieties
Lodestone	Magnetic with definite north and south poles

Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and leaves a black streak.[7] Small grains of magnetite are very common in igneous and metamorphic rocks.[11]

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