Iron ores

Hematite (), also spelled as haematite, is a common iron oxide compound with the formula Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . It has the same crystal structure as corundum () and ilmenite (). With this crystal structure geometry it forms a complete solid solution at temperatures above .

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 extremel

ore rich in iron (element Fe)

thumb|upright|Unusual specimen of goethite replacing a gypsum [[stalactite; the center is hollow. From Santa Eulalia, Chihuahua, Mexico.]] Goethite (, ) is a mineral of the diaspore group, consisting of iron(III) oxide-hydroxide, specifically the α-polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment (brown ochre). Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France. It was first described in 1806 based on samples found in the Hollertszu

thumb|Ochre pigment Ochre ( ; ) is a family of natural clay earth pigments, made up of ferric oxide and varying amounts of clay and sand, ranging in colour from yellow to deep orange or brown. The term is also used for the colours produced by this pigment, especially a light brownish-yellow. A variant of ochre containing a large amount of hematite, or dehydrated iron oxide, has a reddish tint known as red ochre (or, in some dialects in England, ruddle). The term "ochre" is colloquially used to cover a range of different substances used for their colours in Aboriginal Australian art and ceremon

Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as , although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the three principal iron ores, the others being hematite and magnetite, and has been mined for the production of iron since at least 400 BC.

Siderite is a mineral composed of iron(II) carbonate (FeCO3). Its name comes from the Ancient Greek word (), meaning "iron". A valuable iron ore, it consists of 48% iron and lacks sulfur and phosphorus. Zinc, magnesium, and manganese commonly substitute for the iron, resulting in the siderite-smithsonite, siderite-magnesite, and siderite-rhodochrosite solid solution series.

form of iron ore

distinctive layered units of iron-rich sedimentary rock that are almost always of Precambrian age

form of iron ore

thumb|Iron sand from Phoenix, Arizona, attracted to a magnet

thumb|300px|Ironstone (sandstone with iron oxides) from the Mississippian [[Breathitt Formation, Mile Marker 166, I-64, Kentucky]] Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially.