The results of Moessbauer study of Apollo-17 Mare basalt are reported in this paper.It has been revealed that Fe in iron.bearing minerals in the basalt is almost present in the form of Fe^3+, with Fe^3+ less than 3% of total iron. The site occupancy of Fe^3+ ions at M1 and M2 is approximately 0.3 and the corresponding equilibrium constant K (T) is about 0.06, thus indicating that the mare basalt is formed through crystallization under high-temperature reducing and rather slow cooling conditions.
