My understanding, almost all the slate we are being supplied comes from just two different mines. My suggestion is to watch your thickness closely. Set up a orbital sanding station to see that all the pots you turn get the same thickness of slate. It does matter. And thinner tends to be better (though go too thin, and you make a fragile call). Also, keep your edge gap in mind on your call. Your surface with crack with temperature changes if you are snapping your surface in place.
