The common (104) and( 100) cleavage surfaces of calcite were created as periodic 29 á x 29 á lattices with a surface spacing of 25 á. All atoms were constrained to their observed structural positions with the calcium ion maintained at its full ionic charge (+2) and the carbonate charge (-2) partitioned among carbon (0.919) and oxygen (-0.973). Since the passivant solutions are typically applied to the stone at fairly high pH's, the exposed calcite surface is expected to be dominated by Ca2+ and CO32-