Reflectance anisotropy spectroscopy is applied to metal overlayer growth on the silicon (111) surface. Submonolayer coverages of Au are applied to a stepped Si(111) surface. The evolution of the single-domain Au-induced 5X2 superstructure is seen to produce an optical anisotropy of considerable amplitude for saturation coverage. The optical anisotropy in the region of 2.7 eV is unambiguously assigned to the bonding orientation within the 5X2 unit cell.