hematite

the principal form of iron ore; consists of ferric oxide in crystalline form; occurs in a red earthy form

An important ore of iron, the sesquioxide, so called because of the red color of the powder. It occurs in splendent rhombohedral crystals, and in massive and earthy forms; -- the last called red ocher. Called also specular iron, oligist iron, rhombohedral iron ore, and bloodstone. See Brown hematite, under Brown.