The best sealant is a solvent based sealer. This penetrates a couple millimeters into the stone surface for much better protection of the stone. It does smell a bit when applying it so be prepared for that, but it will only need to be done every 5 years or so depending on the stone. A water based sealer can also be used, but this is only a topical coating which will need to be done 1-2 times a year. You will find quality sealers and cleaners at http://granquartzcanada.com/locations.htm These products are used by the pro's and do work.