With the insertion of the NEAR spacecraft into orbit around the asteroid 433 Eros, a new stage of asteroid exploration has begun, with the return of spatially resolved mineralogical, geological, and chemical information from specific asteroids. In this paper, we outline the features of a partially differentiated asteroid using the acapulcoite and lodranite meteorites as a guide. Such a body would likely contain a variety of lithologies, including chondritic rocks largely unaltered by melting, residues of partial melts, and basaltic and Fe,Ni-FeS rocks crystallized from the partial melts. The presence or nature of the regolith remains largely unconstrained. Mineralogical and isotopic heterogeneities preserved in these rocks suggest spatial separation of these rock types by distances in excess of 200 m. Spacecraft-based remote sensing instrumentation should detect substantial spectral heterogeneity (most prominently manifested in the band area ratio) and chemical heterogeneity. Observation of these various lithologies in situ would provide important new constraints on the processes involved during the earliest differentiation of asteroids.