paul womack
>I thought the observation that we're trying to explain is that the natural stones ae leaving a visibly ROUGHER surface (i.e. not a mirror) and yet have (according to some claims) a sharper edge.

The analogy with a random cut auriou leaving a smoother surface (even if deemed a valid analogy, see other post) would appear to argue that the natural stone would leave a smoother surface, contradicting the observation.

BugBear