Looks like there is a lot of stone to be had for free if one would go there Brynestein fra Eidsborg
It says its quartz shale with feldspar and mica. Don't know how good it will be.
I don't know either. I would still like one though. My norvegian is a little rusty. But I think they article says that there is two kinds of stone that they quarry for whetstonesale. If you should happen to find a source please let us know