Tochilinite
A layered iron sulphide and hydroxide that forms with serpentine in CM chondrites.
Key facts
- Formula
- 6(Fe,Ni)S·5(Mg,Fe)(OH)2
- Family
- Sulphides
- Crystal system
- Monoclinic
What it is
Tochilinite is built of alternating layers of iron sulphide and magnesium–iron hydroxide, like a sandwich of two minerals. It forms in water at low temperature. It is named after Mikhail Tochilin, a Russian mineralogist.
Where it is found
It is a major mineral of CM chondrites, where it is intergrown with cronstedtite in clumps once called poorly characterised phases. It is rare on Earth.
How it is recognised
It is very fine-grained, bronze to black, and identified by electron microscopy and X-ray diffraction.
Did you know?
The tochilinite–cronstedtite intergrowths in CM chondrites were a mystery for years and were simply called PCP.
Tochilinite breaks down if a CM chondrite is heated, which helps identify heated examples.