Nannobacteria and the formation of framboidal pyrite: Textural evidence

Study of sedimentary pyrite in the form of framboids, euhedral crystals or metasomatic masses has revealed that their surfaces are commonly covered with spheroids of about 50 nm. This applies to all the examples studied, from modern to Proterozoic. These spheroids are interpreted as the pyritized corpses of nannobacterial cells; if correct, this indicates that precipitation of iron sulfide was performed by these dwarf forms of bacteria, often associated with decaying organic matter.