I have new quartzite. So far no problems. The fabricator (Is that the same as "fitter"? Is fitter the British term?) recommended weekly use of http://www.homedepot.com/p/Miracle-Sealants-511-32-oz-Kleen-and-Reseal-Spray-KL-RE-32OZ-SG/100672858 and semi-annual sealing with http://www.homedepot.com/p/Miracle-Sealants-32-oz-Impregnator-Penetrating-Sealer-511-QT-H/100076375. My local Home Depot didn't have it in stock so I had to order it. When it arrives and I try out the Kleen and Reseal, I will post an update.
Q