I have been reading about StainProof Drytreat. This is what my installer is using. I am having Marble put it so not sure if this is good for Quartzite. It is a 15year sealer but I am told we will need to do this every 4 to 5 years. This is done before my counters are installed. Hopefully someone will know about the product you are using.

This is a better question asked closer to you. Who are the better builders and kitchen designers in your area? Ask them who does their fabrication; they likely tend to use the same people for high end clientele. Check their IG accounts and other social media and see.

Thank you. Since water does not soak in after 30 minutes I wondered if it will take a sealer. If they try and then wipe off the excess, I assume that will be okay. I have a granite that will not take a sealer so wondered about quartzite. I definitely don’t want sealer sitting on top.

"So the 3' limit for span of 3cm stone is not applicable here nor is the requirement for support of cantilevered stone since the stone isn't cantilevered" It certainly is. You've got a huge span which appears to be more than 8' which is unsupported. The Natural Stone Institute allows 3cm natural stone to cantilever 10" without additional support, not 15". I've seen stone like yours sag and when it does, it torques the stone. If you develop a crack starting at a sink corner heading to the unsupported edge, you'll know why. This isn't going to happen right away; it's going to take years. But hey, no worries, you've got a sign off from your fabricator, GC, and cabinetmaker.