The adsorption of gallium on Si(112) and Si(337) has been studied with scanning tunneling microscopy. When clean, these two high-index surfaces are unstable and facet to other orientations : (112) to (111)- and (337)-like nanofacets, and (337) to the stable (5512) plane. When Ga is adsorbed onto each of these surfaces and annealed, the top surface layers undergo substantial rearrangements, exposing Ga-reconstructed (112) planes in both cases.