Aha, thankyou Tiompan, that's interesting. I saw your friend's name on the portal but it didn't have much about what he'd concluded, frustratingly.

I suppose a bit of practical archaeology could be in order - a go at sharpening stone tools and metal tools on an appropriate bit of geology, to check the results. What makes metal-created marks different from (say) the ones on the polisher at Avebury?

I do think that it's interesting about the folklore though, that perhaps local stories could have coloured people's perception about the true origins of the markings.

Also could it not be relevant that a stone axe source is not far away in North Wales (though I suppose this could be said about a number of places).

I wonder what the rock is. Is it particularly good for sharpening metal arrows? And why don't we find such markings elsewhere, only north Wales - other people must have been sharpening their arrows? I've seen sharpening marks (for scythes?) on a sandstone barn near here in Wiltshire. The relative hardness of the stone must be important or it wouldn't work?

(sorry for the disjointed thoughts)