Marble sculpture has been the preferred material for stone monumental sculpture since ancient times, with several advantages over its more common geological "parent" limestone, in particular the ability to absorb light a small distance into the surface before refracting it in subsurface scattering.  This gives an attractive soft appearance that is especially good for representing human skin, which can also be polished. Of the many different types of marble the pure white ones are generally used for sculpture, with coloured ones preferred for many architectural and decorative uses.  The degree of hardness is right to carve without too much difficulty, but still give a very durable result, if not exposed to acid rain or seawater.