In this study we applied the surface sensitive optical method reflectance difference spectroscopy to investigate the optical response of clean cubic 3 C-SiC(001) surfaces. The main reconstructions, the Si-rich (3 x 2) and (2 x 1) as well as the C-rich c(2 x 2) were prepared by annealing in Si flux. For (3 x 2) we find a strong spectral feature at 4.2 eV that is not observed for the other two reconstructions. Since the direct gap of 3 C-SiC is at higher photon energies the 4.2 eV feature must be related to the surface. Angle resolved ultraviolet photoelectron spectroscopy measurements indicate surface states around the (X) over bar point of the unreconstructed surface Brillouin zone. We conclude that the 4.2 eV feature is associated with this surface state and suggest that it is linked to the E-2 gap of bulk Si at 4.2 eV.