Leaving your natural stone unprotected will stain very easily. To remove the stains can be expensive and sometimes not even possible. It is advisable when getting your floor refinished, is to have it sealed. This eliminates and/or reduces the possibility of staining. A sealer penetrates the stone and helps to repel water, dye, dirt, and other substances from causing a stain.

Sealing unlike wax, it allows the stone to "breath". Sealers do not offer 100% protection from staining. If enough of a substance is left long enough it will penetrate even if the stone has been treated. Particularly oil and solvent based substances. But generally most liquids will evaporate before they would penetrate a properly sealed stone.

Sealing should be reapplied every 2-5 years or after refinishing, whichever comes first.