Iron oxide in the context of "Rust"

Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, Al₂Si₂O₅(OH)₄). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of iron oxide.

Clays develop plasticity when wet but can be hardened through firing. Clay is the longest-known ceramic material. Prehistoric humans discovered the useful properties of clay and used it for making pottery. Some of the earliest pottery shards have been dated to around 14,000 BCE, and clay tablets were the first known writing medium. Clay is used in many modern industrial processes, such as paper making, cement production, and chemical filtering. Between one-half and two-thirds of the world's population live or work in buildings made with clay, often baked into brick, as an essential part of its load-bearing structure. In agriculture, clay content is a major factor in determining land arability. Clay soils are generally less suitable for crops due to poor natural drainage; however, clay soils are more fertile, due to higher cation-exchange capacity.

Oxygen is a chemical element; it has the symbol O and its atomic number is 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and a potent oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is the most abundant element in Earth's crust, making up almost half of the Earth's crust in the form of various oxides such as water, carbon dioxide, iron oxides and silicates. It is also the third-most abundant element in the universe after hydrogen and helium.

At standard temperature and pressure, two oxygen atoms will bind covalently to form dioxygen, a colorless and odorless diatomic gas with the chemical formula O
₂. Dioxygen gas currently constitutes approximately 20.95% molar fraction of the Earth's atmosphere, though this has changed considerably over long periods of time in Earth's history. A much rarer triatomic allotrope of oxygen, ozone (O
₃), strongly absorbs the UVB and UVC wavelengths and forms a protective ozone layer at the lower stratosphere, which shields the biosphere from ionizing ultraviolet radiation. However, ozone present at the surface is a corrosive byproduct of smog and thus an air pollutant.

Ochre (/ˈoʊkər/ OH-kər; from Ancient Greek ὤχρα (ṓkhra), from ὠχρός (ōkhrós) 'pale'), iron ochre, sometimes ocher in American English, is a natural clay earth pigment, a mixture of ferric oxide and varying amounts of clay and sand. It ranges in colour from yellow to deep orange or brown. It is also 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, ruddle).

Ochre is also clays coloured with iron oxide derived during the extraction of tin and copper.

Chalybeate (/kəˈlɪbieɪt/) waters, also known as ferruginous waters, are mineral spring waters containing salts of iron.

Tin-glazed pottery is earthenware covered in lead glaze with added tin oxide which is white, shiny and opaque (see tin-glazing for the chemistry); usually this provides a background for brightly painted decoration. It has been important in Islamic and European pottery, but very little used in East Asia. The pottery body is usually made of red or buff-colored earthenware and the white glaze imitated Chinese porcelain. The decoration on tin-glazed pottery is usually applied to the unfired glaze surface by brush with metallic oxides, commonly cobalt oxide, copper oxide, iron oxide, manganese dioxide and antimony oxide. The makers of Italian tin-glazed pottery from the late Renaissance blended oxides to produce detailed and realistic polychrome paintings.

The earliest tin-glazed pottery appears to have been made in Iraq in the 9th century, the oldest fragments having been excavated during the First World War from the palace of Samarra about fifty miles north of Baghdad. From there it spread to Egypt, Persia and Spain before reaching Italy in mid-15th century, early Renaissance, Holland in the 16th century and England, France and other European countries shortly after.

Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the form of magnetite (Fe
₃O
₄, 72.4% Fe), hematite (Fe
₂O
₃, 69.9% Fe), goethite (FeO(OH), 62.9% Fe), limonite (FeO(OH)·n(H₂O), 55% Fe), or siderite (FeCO₃, 48.2% Fe).

Ores containing very high quantities of hematite or magnetite (typically greater than about 60% iron) are known as natural ore or [direct shipping ore], and can be fed directly into iron-making blast furnaces. Iron ore is the raw material used to make pig iron, which is one of the primary raw materials to make steel — 98% of the mined iron ore is used to make steel. In 2011 the Financial Times quoted Christopher LaFemina, mining analyst at Barclays Capital, saying that iron ore is "more integral to the global economy than any other commodity, except perhaps oil".

Bauxite (/ˈbɔːksaɪt/ ) is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)₃), boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite (FeO(OH)) and hematite (Fe₂O₃), the aluminium clay mineral kaolinite (Al₂Si₂O₅(OH)₄) and small amounts of anatase (TiO₂) and ilmenite (FeTiO₃ or FeO·TiO₂).Bauxite appears dull in luster and is reddish-brown, white, or tan.

In 1821, the French geologist Pierre Berthier discovered bauxite near the village of Les Baux in Provence, southern France.