For what it's worth, unpainted marble has a much higher degree of subsurface scattering (light diffusion within the material) than a painted surface does, which

For what it's worth, unpainted marble has a much higher degree of subsurface scattering (light diffusion within the material) than a painted surface does, which makes it a more lifelike approximation to flesh -- deemphasizing surface detail and softening the transition from light to shadow. Wax has the same property, which is one of the reasons wax figures look so realistic. Examples of computer-generated images with and without subsurface scattering can be seen on Henrik Wann Jensen's page. In particular, see the images of the lips: http://graphics.ucsd.edu/~henrik/images/subsurf.html http://graphics.ucsd.edu/~henrik/images/subsurf.html