Pyrrhotite
A magnetic iron sulphide with a little less iron than troilite, common in carbonaceous chondrites.
Key facts
- Formula
- Fe1-xS
- Family
- Sulphides
- Crystal system
- Monoclinic or hexagonal
What it is
Pyrrhotite is iron sulphide with some iron sites left empty, so it contains slightly less than one iron for each sulphur. The empty sites make some forms magnetic. Its name comes from the Greek for reddish.
Where it is found
It is common in CI, CM, CR and CK chondrites and in the Ryugu and Bennu samples, often as hexagonal plates intergrown with pentlandite. It also occurs in R chondrites and in Martian meteorites, where it records the oxidation state of the magma.
How it is recognised
It is bronze-coloured, metallic and weakly to strongly magnetic. In polished section it is creamy pink-brown and strongly anisotropic.
Did you know?
Pyrrhotite in Ryugu grains shows the fine intergrowths with pentlandite expected from slow cooling.
Some pyrrhotite records ancient magnetic fields in meteorites.