Sealing natural stone is much different than hardwood floors. With wood the protective coating is applied to the outside of the material whereas with stone you are sealing up the pores in the rock crystals. So the main idea is to stop liquids from getting into the pores and staining the stone or causing a chemical reaction with minerals causing the stone to come apart or flake.
Like almost any other material natural stone must be allowed to breathe. Instead of one material stone is composed of several minerals which have a crystal make-up. If water penetrates the stone it must be allowed to evaporate to maintain the integrity of the crystals. Sealers like acrylic are not advisable because they clog the pores and seal any moisture that may get in from the bottom or from an imperfection. But if the stone is used in a foyer salt and other impurities can penetrate the porous surface so you have to make sure that your sealer is resistant to these stains.
Natural products make the best sealers. Detergents which contain fatty acids seal the pores but can be retrieved by a vigorous washing, Commercial sealers which le the rock breathe but do not react with the minerals are the best but make sure you get the right sealer for the right stone.
Whatever sealer you choose the main idea is to keep your natural stone floor looking as great as the day you had it installed.
