Yes, they scratch, and unfortunately, are very noticeable after the fact. But then again, there's really no reason to get it scratched, especially if you don't have kids playing in it. Just take off your jewelry before you get in, and clip those toenails too!
I settled on the granite because of the kid factor and the fact that my last spa was a "smoothie" and the scratches do accumulate.
Biggest thing, if you're gonna have fancy lighting in your spa is to stay with the lighter colored shells, like your pearl. The lights play much nicer on a light background.
