0_Wizard
I love the color red.  Hematite or ochre causes the red color at the Grand Canyon.
The red sky at sunset results from Rayleigh scattering, while the red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide.
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Red
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Red
Red is the colour at the end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy. The red sky at sunset results from Rayleigh scattering, while the red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide.
Geology of the Grand Canyon area
The geology of the Grand Canyon area includes one of the most complete and studied sequences of rock on Earth. The nearly 40 major sedimentary rock layers exposed in the Grand Canyon and in the Grand Canyon National Park area range in age from about 200 million to nearly 2 billion years old. Most were deposited in warm, shallow seas and near ancient, long-gone sea shores in western North America. Both marine and terrestrial sediments are represented, including fossilized sand dunes from an extinct desert. There are at least 14 known unconformities in the geologic record found in the Grand Canyon.
Hematite
Hematite, also spelled as haematite, is the mineral form of iron(III) oxide (FeO), one of several iron oxides. It is the iron oxide mineral and is widespread in rocks and soils. Hematite crystallizes in the rhombohedral lattice system, and it has the same crystal structure as ilmenite and corundum. Hematite and ilmenite form a complete solid solution at temperatures above . Hematite is colored black to steel or silver-gray, brown to reddish brown, or red. It is mined as the main ore of iron. Varieties include "kidney ore", "martite" (pseudomorphs after magnetite), "iron rose" and "specularite" (specular hematite).
Grand Canyon
The Grand Canyon (Hopi: "Ongtupqa"; , Navajo: "Tsékooh Hatsoh", Spanish: "Gran Cañón") is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is long, up to wide and attains a depth of over a mile (). The canyon and adjacent rim are contained within Grand Canyon National Park, the Kaibab National Forest, Grand Canyon-Parashant National Monument, the Hualapai Indian Reservation, the Havasupai Indian Reservation and the Navajo Nation. President Theodore Roosevelt was a major proponent of preservation of the Grand Canyon area, and visited it on numerous occasions to hunt and enjoy the scenery.
History of the Grand Canyon area
The known history of the Grand Canyon area stretches back 10,500 years, when the first evidence of human presence in the area is found. Native Americans have inhabited the Grand Canyon and the area now covered by Grand Canyon National Park for at least the last 4,000 of those years. Ancestral Pueblo peoples, first as the Basketmaker culture and later as the more familiar Pueblo people, developed from the Desert Culture as they became less nomadic and more dependent on agriculture. A similar culture, the Cinchona, also lived in the canyon area. Drought in the late 13th century likely caused both groups to move on.
Ochre
Ochre (British English) ( ; from Greek: ὤχρα, from ὠχρός, "ōkhrós", pale) or ocher (American English) is a natural clay earth pigment which is 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 name of 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). The word ochre is also used of clays colored with iron oxide, obtained as a by-product of tin and copper extraction.
Shades of red
Varieties of the color red may differ in hue, chroma (also called saturation, intensity, or colorfulness) or lightness (or value, tone, or brightness), or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a red or other hue mixed with white, a shade being mixed with black. A large selection of these various colors is shown below. At right is displayed the web color pink, a light tint of red. The "pink" is often considered to be a basic color term on its own. At right is displayed the pinkish tone of salmon that is called "salmon" in Crayola crayons.
1_Apprentice
Red is my favorite color! What is hematitie or ochre and why does it cause the color red?
0_Wizard
Hematite is iron oxide and is widespread in rock and soil.
It is the iron oxide mineral and is widespread in rocks and soils.
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Hematite
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Hematite
Hematite, also spelled as haematite, is the mineral form of iron(III) oxide (FeO), one of several iron oxides. It is the iron oxide mineral and is widespread in rocks and soils. Hematite crystallizes in the rhombohedral lattice system, and it has the same crystal structure as ilmenite and corundum. Hematite and ilmenite form a complete solid solution at temperatures above . Hematite is colored black to steel or silver-gray, brown to reddish brown, or red. It is mined as the main ore of iron. Varieties include "kidney ore", "martite" (pseudomorphs after magnetite), "iron rose" and "specularite" (specular hematite).
Iron oxide copper gold ore deposits
Iron oxide copper gold ore deposits (IOCG) are important and highly valuable concentrations of copper, gold and uranium ores hosted within iron oxide dominant gangue assemblages which share a common genetic origin. These ore bodies range from around 10 million tonnes of contained ore, to 4,000 million tonnes or more, and have a grade of between 0.2% and 5% copper, with gold contents ranging from 0.1 to >3 grams per tonne (parts per million). These ore bodies tend to express as cone-like, blanket-like breccia sheets within granitic margins, or as long ribbon-like breccia or massive iron oxide deposits within faults or shears.
Iron ore
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 colour from dark grey, bright yellow, or deep purple to rusty red. The iron itself is usually found in the form of magnetite (, 72.4% Fe), hematite (, 69.9% Fe), goethite (, 62.9% Fe), limonite (, 55% Fe) or siderite (, 48.2% Fe). Ores containing very high quantities of hematite or magnetite (greater than about 60% iron) are known as "natural ore" or "direct shipping ore", meaning they 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 main raw materials to make steel—98% of the mined iron ore is used to make steel.
Soil
Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. The Earth's body of soil is the pedosphere, which has four important functions: it is a medium for plant growth; it is a means of water storage, supply and purification; it is a modifier of Earth's atmosphere; it is a habitat for organisms; all of which, in turn, modify the soil. Soil interfaces with the lithosphere, the hydrosphere, the atmosphere, and the biosphere. The term "pedolith", used commonly to refer to the soil, literally translates "ground stone". Soil consists of a solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution).
Iron
Iron is a chemical element with symbol Fe (from ) and atomic number 26. It is a metal in the first transition series. It is by mass the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust. Its abundance in rocky planets like Earth is due to its abundant production by fusion in high-mass stars, where it is the last element to be produced with release of energy before the violent collapse of a supernova, which scatters the iron into space. Like the other group 8 elements, ruthenium and osmium, iron exists in a wide range of oxidation states, −2 to +7, although +2 and +3 are the most common.
Limonite
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 FeO(OH)·nHO, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the two principal iron ores, the other being hematite, and has been mined for the production of iron since at least 2500 BCE. Limonite is named from the Greek word for meadow (λειμών), in allusion to its occurrence as bog iron ore in meadows and marshes (reference is here needed, since one may rather see it originating in the Latin "limus" - which means mud - or in its yellowish lemon-like color).
Animikie Group
The Animikie Group is a geologic group composed of sedimentary and metasedimentary rock, having been originally deposited between 2,500 and 1,800 million years ago within the Animikie Basin. This group of formations is geographically divided into the Gunflint Range, the Mesabi and Vermilion ranges, and the Cuyuna Range. On the map, the Animikie Group is the dark gray northeast-trending belt which ranges from south-central Minnesota, U.S., up to Thunder Bay, Ontario, Canada. The Gunflint Iron Range is the linear black formation labeled G, the Mesabi Iron Range is the jagged black linear formation labeled F, and Cuyuna Iron Range is the two black spots labeled E. The gabbro of the Duluth Complex, intruded during the formation of the Midcontinent Rift, separates the Mesabi and Gunflint iron ranges; it is shown by the speckled area wrapping around the western end of Lake Superior.