Hematite

Hematite is a common iron oxide with the formula Fe2O3, widely found in rocks and soils, and it is mined as an important ore mineral of iron. Its crystals belong to the rhombohedral lattice system and share the crystal structure of corundum. It occurs in colors from black to steel or silver gray and from brown to reddish brown or red, but every form leaves a rust-red streak, and the name comes from the Greek word for blood. Large deposits are found in banded iron formations, and gray hematite forms in still water and mineral hot springs. Unlike magnetite, hematite is not noticeably attracted to an ordinary magnet. Ground hematite has served as a red pigment since the earliest human pictorial art, and because it is dense it is used in radiation shielding and ship ballast.