Graphite
Soft, layered carbon, found as nodules in iron meteorites, in ureilites and in primitive chondrites.
Key facts
- Formula
- C
- Family
- Carbon minerals
- Crystal system
- Hexagonal
What it is
Graphite is carbon arranged in flat sheets that slide over each other, which makes it soft and greasy. It conducts electricity and is used in pencils.
Where it is found
In IAB irons such as Canyon Diablo it forms rounded nodules with troilite. Some irons contain cliftonite, graphite with a cubic outer shape, thought to have grown from carbon dissolved in metal. Ureilites contain several per cent of carbon as graphite and diamond. Presolar graphite grains from other stars occur in primitive chondrites.
How it is recognised
It is black, soft and leaves a grey mark on paper. In polished section it is grey and strongly anisotropic, changing brightness as the stage turns.
Did you know?
Cliftonite was once thought to be a separate mineral, but it is graphite with an unusual crystal shape.
Graphite in ureilites was partly turned to diamond by shock.