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Hematite (AE) or haematite (BE) is the mineral form of Iron (III) oxide, (Fe2O3), one of several iron oxides. The ore sometimes contains slight amounts of titanium. When shaped into ornaments it is often called black diamond. Rouge is a powderized form of hematite.
A very common mineral, coloured black to gray, brown to reddish brown, or red. It is mined as the main ore of iron.
Varieties are: Bloodstone, Iron Rose, Kidney Ore, Martite, Paint Ore, Specularite (Specular Hematite), Rainbow Hematite and Titano-hematite.
Deposits of grey hematite are 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.
Hematite on Mars
Hematite can be formed by aqueous processses, 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 deposites under watery conditions billions of years ago when Mars was a wetter world. The rover used its instruments to test how the hematite found on Mars at Meridiani Planum was formed.
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