This invention relates to polymeric compositions for application onto natural stone in order to provide for long-term chemical, stain, and water resistance, along with antimicrobial properties. Many natural, unsealed stones do not have stain, etch, or water resistance. The described compositions were developed using a technology of chemical grafting that involves the use of prepolymers, monomers, catalysts, graft initiators, wetting agents, antimicrobial agents, and other ingredients. The composition, when thus applied to the stone surface allows it to obtain a graft polymerization, thereby forming a polymer film that is chemically attached to the natural stone, rather than typical physical bonding of other sealer compositions. The natural stones react with a graft initiator in the composition, which creates the reaction sites on the natural stone surface via free radical mechanisms. This in turn renders the natural stone to be receptive to attachment of monomers/prepolymers forming a polymeric film chemically bonded to the natural stone which then has the desired properties in terms of resistance to staining, etching, water penetration, etc., used in homes and light commercial applications, as well as for exterior use on building facades, monuments and the like.