Siderite
Iron carbonate, found in the carbonate globules of ALH 84001 and in some altered chondrites.
Key facts
- Formula
- FeCO3
- Family
- Carbonates, sulphates, salts and weathering products
- Crystal system
- Trigonal
What it is
Siderite is iron carbonate, the iron member of the calcite family. Its name comes from the Greek for iron. Confusingly, in old meteorite books the word siderite was also used for iron meteorites in general.
Where it is found
It forms the iron-rich zones of the carbonate globules in the Martian meteorite ALH 84001, and occurs with magnesite and dolomite in some CI and CM chondrites and in returned asteroid samples.
How it is recognised
It is pale brown, often turning darker as it oxidises, and is identified by microprobe analysis or Raman spectroscopy.
Did you know?
Older classifications divided meteorites into aerolites (stones), siderites (irons) and siderolites (stony-irons).
Siderite breaks down to magnetite when heated, which some scientists linked to the magnetite grains in ALH 84001.