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Graphite is a form of high-purity carbon which occurs on Earth as a mineral. It can also be artificially produced from silicon carbide.
Coke and charcoal are not as pure as graphite because, while the carbonizing process does boil off volatiles in their production, non-volatile ash remains. In a Martian settlement it could be useful as part of the soil in the greenhouse and for filters in life support systems.

Physical characteristics

Graphite has a hardness of 1 to 2 on Mohs' scale, a black streak, a lustre varying from metallic to dull and earthy, a hexagonal crystal system and specific gravity between 2.1 and 2.23.[1]


Graphite occurs on Earth in igneous and metamorphic rock, sometimes as metamorphosed coal. It can also be found in limestone. Some meteorites contain graphite.


Open issues

  • How common are graphitic rocks on Mars?
  • How common are graphite-containing meteorites on Mars?


  1. B. Cairncross - Field guide to rocks and minerals of Southern Africa 2004. ISBN 978-1-86872-985-2 p. 123