Hematite in the context of "Spinel structure"

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.

Khormusan industry was a Paleolithic archeological industry in Nubia dated at 42,000 to 18,000 BP.

The Khormusan industry in Nubia began between 42,000 and 32,000 BP. Khormusans developed tools not only from stone but also from animal bones and hematite. They also developed small arrow heads resembling those of Native Americans, but no bows have been found. The end of the Khormusan industry came around 18,000 BP, with the appearance of other cultures in the region, including the Gemaian.It was succeeded by the Halfan culture.

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.

Quartzite is a hard, non-foliated metamorphic rock that was originally pure quartz sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts, and hence quartzite is a metasandstone. Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of hematite. Other colors, such as yellow, green, blue and orange, are due to other minerals.

The term quartzite is also sometimes used for very hard but unmetamorphosed sandstones that are composed of quartz grains thoroughly cemented with additional quartz. Such sedimentary rock has come to be described as orthoquartzite to distinguish it from metamorphic quartzite, which is sometimes called metaquartzite to emphasize its metamorphic origins.

A cylinder seal is a small round cylinder, typically about one inch (2 to 3 cm) in width, engraved with written characters or figurative scenes or both, used in ancient times to roll an impression onto a two-dimensional surface, generally wet clay. According to some sources, cylinder seals were invented around 3500 BC in the Near East, at the contemporary sites of Uruk in southern Mesopotamia and slightly later at Susa in south-western Iran during the Proto-Elamite period, and they follow the development of stamp seals in the Halaf culture or slightly earlier. They are linked to the invention of the latter's cuneiform writing on clay tablets. Other sources, however, date the earliest cylinder seals to a much earlier time, to the Late Neolithic period (7600-6000 BC) in Syria, hundreds of years before the invention of writing.

Cylinder seals are a form of impression seal, a category which includes the stamp seal and finger ring seal. They survive in fairly large numbers and are important as art, especially in the Babylonian and earlier Assyrian periods. Impressions into a soft material can be taken without risk of damage to the seal, and they are often displayed in museums together with a modern impression on a small strip.

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.

Not to be confused with native or telluric iron, which is very rare and found in metallic form, the term ironstone is customarily restricted to hard, coarsely banded, non-banded, and non-cherty sedimentary rocks of post-Precambrian age. The Precambrian deposits, which have a different origin, are generally known as banded iron formations. The iron minerals comprising ironstones can consist either of oxides, i.e. limonite, hematite, and magnetite; carbonates, i.e. siderite; silicates, i.e. chamosite; or some combination of these minerals.

Psilomelane is a group name for hard black manganese oxides including hollandite and romanechite. Psilomelane consists of hydrous manganese oxide with variable amounts of barium and potassium. Psilomelane is erroneously, and uncommonly, known as black hematite, despite not being related to true hematite, which is an iron oxide.

Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe₂O₃. It occurs in nature as the mineral hematite, which serves as the primary source of iron for the steel industry. It is also known as red iron oxide, especially when used in pigments.

A botryoidal (/ˌbɒtriˈɔɪdəl/ BOT-ree-OY-dəl) texture or mineral habit, is one in which the mineral has an external form composed of many rounded segments, named for the Ancient Greek βότρυς (bótrus), meaning "a bunch of grapes". This is a common form for many minerals, particularly hematite and malachite, which are known for frequently forming botryoidal masses. It is also a common form of goethite, smithsonite, fluorite, and chrysocolla.

Similar habits are reniform (kidney-shaped) and mammillary (breast-shaped or partial spheres).

Red chalk is chalk of a reddish-brown color, which was used as a material for drawing. It is obtained from the red ochre variety of hematite. Another term for red chalk, common in older references, is sanguine (/ˈsæŋɡwɪn/). The word comes via French from the Italian sanguigna and is originally from the Latin "sanguis"; it refers to the color's similarity to that of dried blood.

Red chalk was used by the ancient Egyptians and ancient Romans for wall painting. By the 16th century deposits were known in Italy, Spain, Flanders, France, and Germany, and the material became a popular medium for drawing. Leonardo da Vinci, in the late 15th century, was the first major artist to work in the medium.

Limonite (/ˈlaɪməˌnaɪt/) is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·nH₂O, 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.

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".