https://www.openstreetmap.org/way/825144243

Is this sandstone machined into a flat surfaces? In such case it would be surface=paving_stones material=sandstone

Or is it surface=sett material=sandstone (see https://wiki.openstreetmap.org/wiki/Tag:surface%3Dsett )

Or maybe even surface=unhewn_cobblestone material=sandstone ( https://wiki.openstreetmap.org/wiki/Tag:surface%3Dunhewn_cobblestone )

?