Hematite (or haematite)

Hematite is the most important ore mineral of iron. It is an oxide mineral and is found in a variety of colours, with red, orange and brown occurring when the iron in hematite begins to rust. There are also several forms of hematite, some of which are: kidney ore, a massive, botryoidal (lumpy) or reniform (kidney shaped) form; specularite, a micaceous (flaky) form; oolitic, a sedimentary form composed of small rounded grains; red ochre, a red earthy form. Because of its red colour when powdered, hematite lends itself well to use as a pigment, and it was used by ancient cultures as a colouring for red and brown paint.

Large ore bodies of hematite are usually of sedimentary origin, and it is widely distributed in sedimentary rocks as a cement. High grade ore bodies can be found in metamorphic rocks as a result of contact metasomatism. Hematite is also as an accessory mineral in igneous rocks. The red colouring of soils all over the planet is due to hematite.

hematite (oolitic)

Chemical composition - Fe 2O 3
Hardness - 5-6
Specific gravity - 5.3
Transparency - Opaque
Colour - Steel or silver grey to black, reddish to brown in earthy forms
Streak - Red to brownish red
Lustre - Metallic to earthy
Cleavage/fracture - Non-existent / conchoidal to uneven
Crystal habit/mode of occurrence - Tabular, rarely prismatic / massive, granular, botryoidal (lumpy)