Results of the57Fe Mossbauer spectroscopy of greigite from the “greigite-rich” horizon of the middle part of the miocene series (Sokolov Basin, North Bohemia) are reported. From the room-temperature transmission spectra of the powdered samples magnetically separated from claystones, the Mossbauer analyses were performed. Relative abundances of various magnetic and non-magnetic Fe2+ and Fe3+ species led to the identification of the two magnetic iron sites in greigite in accordance with its spinel structure having mutually near effective magnetic inductions of 32.1 and 31.3 T, respectively. In addition, three pyrrhotite and two magnetite magnetic sites plus probably two pyrite and/or arsenopyrite iron positions were identified, of which some have been reported in the literature as the greigite iron contributions.