Daubréelite
A black iron chromium sulphide that forms lamellae inside troilite in iron meteorites.
Key facts
- Formula
- FeCr2S4
- Family
- Sulphides
- Crystal system
- Cubic
- First described
- the Coahuila iron meteorite, 1876
Daubréelite was described in 1876 by the American chemist J. Lawrence Smith from the Coahuila iron meteorite of Mexico. It is named after Auguste Daubrée, the French geologist who classified meteorites and studied their minerals.
What it is
Daubréelite is a spinel-structured sulphide in which sulphur takes the place of oxygen. It forms where chromium enters sulphides rather than oxides, a sign of very low oxygen.
Where it is found
It is common in iron meteorites, as thin plates within troilite nodules, and in enstatite chondrites and aubrites, where almost no oxygen was available.
How it is recognised
It is black and slightly magnetic. In polished troilite nodules it appears as grey-black stripes and is confirmed by its chromium content.
Did you know?
Daubrée made some of the first experiments to reproduce meteorite textures in the laboratory.
Chromium in sulphides is almost unknown in Earth rocks.