Yup since they are natural stones, they can scratch chip crack or split if struck wrong. If you want to keep them pristine, they should be kept in a pocketed case or bag, and rolled individually on something soft like cloth, felt or leather. Never put them in a jar or box randomly with a bunch of other dice or game pieces.
I just received my engraved sandstone dice from the same sellers and I am very happy with them. I hear they can break if you are not careful but I got a leather dice tray and I'm sure they will be fine.