The Mossbauer spectra of alpha-Zn4Sb3, a compound that is best formulated as alpha-Zn13Sb10 or (Zn2+)(13)(Sb3-)(6)(Sb-2(4-))(2), have been measured between 5 and 120 K. The resulting six spectra have been simultaneously fit with two components in the ratio of 3:2 corresponding to the Sb3- and Sb2- ions identified in this valence semiconductor. The fits yield temperature independent isomer shifts of -8.17(2) and -9.73(2) mm/s and quadrupole interactions of -4.9(2) and 0 mm/s for the Sb3- and Sb2- ions, respectively; the corresponding Mossbauer temperatures are 197(5) and 207(5) K, temperatures that are lower than the Debye temperature of beta-Zn4Sb3. The isomer shifts correspond to electronic configurations between 5s(2)5p(6) and 5s(1.75)5p(4.01) for the Sb3- ions and between 5s(2)5p(5) and 5s(1.80)5p(3.38) for the Sb2- ions, configurations that are in good agreement with the expected configurations for this valence semiconductor and with the results of band structure calculations.