Hematite
Hematite or haematite is the
mineral form of
Iron oxide, , one of several
iron oxides. Hematite crystallizes in the
rhombohedral system, and it has the same
crystal structure as ilmenite and as
corundum. Hematite and ilmenite form a complete
solid solution at temperatures above 950C.
Hematite is a very common mineral, coloured black to steel or silver-gray, brown to reddish brown, or red. It is
mined as the main ore of iron. Varieties include Bloodstone, Iron Rose, Kidney Ore, Martite, Paint Ore, Specularite , Rainbow Hematite and Titano-hematite.
Encyclopedia
| Hematite |
| General | Category | Mineral | Chemical formula | iron oxide, Fe2O3, a-Fe2O3 | Identification | Colour | Metallic grey to earthy red | Crystal habit | Tabular to thick crystals | Crystal system | Hexagonal | Cleavage | None | Fracture | Uneven to sub-conchoidal | Mohs Scale hardness | 5.5 - 6.5 | Luster | Metallic to splendent | Refractive index | Opaque | Pleochroism | None | Streak | Bright red to dark red | Specific gravity | 4.9 - 5.3 | Fusibility | ? | Solubility | ? | Major varieties | Specularite | |
Hematite or
haematite is the
mineral form of
Iron oxide, , one of several
iron oxides. Hematite crystallizes in the
rhombohedral system, and it has the same
crystal structure as ilmenite and as
corundum. Hematite and ilmenite form a complete
solid solution at temperatures above 950°C.
Hematite is a very common mineral, coloured black to steel or silver-gray, brown to reddish brown, or red. It is
mined as the main ore of iron. Varieties include Bloodstone, Iron Rose, Kidney Ore, Martite, Paint Ore, Specularite , Rainbow Hematite and Titano-hematite. While the forms of hematite vary, they all have a rust-red streak. Hematite is harder than pure iron, but much more brittle. When shaped into ornaments, it is often called black diamond.
Huge deposits of hematite are found in
banded iron formations. Grey hematite is typically found in places where there has been standing water or mineral
hot springs, such as those in Yellowstone. The mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water. But hematite can also occur without water, as the result of
volcanic activity.
Clay-sized hematite crystals can also occur as a secondary mineral formed by weathering processes in
soil, and along with other iron oxides or oxyhydroxides such as
goethite, is responsible for the red color of many tropical, ancient, or otherwise highly weathered soils.
The name hematite is derived from the Greek word for blood, since sometimes hematite can be red, as in
Rouge, a powderized form of hematite. It shares this root with the word
hemoglobin. Hemoglobin is the oxygen-transporting molecule in
red blood cells, the iron of which causes blood to be red. The color of hematite lends it well in use as a pigment.
Especially nice specimens of hematite come from
England,
Mexico,
Brazil,
Australia and the
Lake Superior region of the
United States and
Canada.
Hematite is an antiferromagnetic material below the Morin transition at 260K, and a canted antiferromagnet or weakly ferromagnetic above the Morin transition.
.
Hematite on Mars
Hematite can be formed by aqueous processes,
weathering processes, or without water. In 2004, NASA's
Mars rover Opportunity discovered small spheres believed to be made partly or mostly of hematite. The spheres are only a few millimeters in diameter and are believed to have formed as rock deposits under watery conditions billions of years ago when
Mars was a wetter world. The rover used one of its instruments to test the spherules iron content which were then unequivocally identified as hematite.
Hematite in popular culture
Since polished hematite is considered by many to be a
gemstone, it has been used in
jewelry over the course of the last 50 years in
North America, especially in the western
United States. Hematite can be found used in jewelry and art created by the
Native Americans. Also part of the
hippie movement of the 1960s included the eclectic mix-match of differing styles of clothing and accessories, and hematite, due to its uniqueness, became popular. Many hippies today still wear this stone as a regular part of their wardrobe.
See also
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External links
