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?