Greigite (Fe <sub>3</sub> S <sub>4</sub> ) is thermodynamically stable: Implications for its terrestrial and planetary occurrence
Tamilarasan Subramani, Kristina Lilova, Mykola Abramchuk, Kurt Leinenweber, Alexandra Navrotsky
Abstract
Significance The new experimental thermodynamic studies of bulk, nanophase, and monoclinic high-pressure forms of greigite (Fe 3 S 4 ) confirm its stability in the Fe–S system and explain its common occurrence in sediments, magnetotactic bacteria, and other ambient temperature environments under anoxic conditions. The data disprove the commonly held hypothesis that greigite is a metastable phase. The low surface energy of greigite provides insight not only into the stability of greigite nanoparticles but also into their role in prebiotic, biological, and planetary processes. Our experimental data for the stability of the three forms of Fe 3 S 4 confirm that it could be stable on Mercury, thus contributing to Mercury’s weak magnetic field.