Marine spar varnish sounds like something i can locate. I will read up on the steps to go about this. They got to be here somewhere. Ha. If someone know where to find this info, please link it. I havent learned my Jnat to perfection yet but id like it to last as it does have a lot of rough rock texture on the back of it.
Not much to it Jerry, read the directions, put it on thin and let it dry. Maybe do 2 coats. If you get it on the face of the stone you'll need to lap it, and make sure the corners are clear of sealant.