Hematite
Red iron oxide, the main product of rusting in many desert and long-buried meteorites.
Key facts
- Formula
- Fe2O3
- Family
- Oxides
- Crystal system
- Trigonal
What it is
Hematite is iron(III) oxide. In bulk it is grey and metallic, but as fine grains it gives a red-brown colour, and its powder is always red. Its name comes from the Greek for blood.
Where it is found
In meteorites hematite is mostly a product of weathering on Earth. Metal and troilite in meteorites from hot deserts turn to iron oxides and oxyhydroxides that stain the stone brown and fill cracks. It also occurs in fusion crusts and in micrometeorites, and Mars rovers have found it abundantly on the planet's surface.
How it is recognised
Rusty staining around metal grains and a red streak on unglazed porcelain point to hematite. The amount of oxide is used to assign a weathering grade.
Did you know?
Small spheres of hematite on Mars, nicknamed blueberries, were found by the Opportunity rover in 2004.
Hematite is the most important iron ore on Earth.