It's Clogau Gold Mine (10 points Stones)
I was looking for "Dolgellau Gold Belt" (10 Point Stones)
It's a Gold Mine (5 Points Stones)
... He said all that first
Mike can have 5 points since I do think it's his hand (even though I never asked)
It isn't manganese (I worded the question very carefully because I expected our resident expert may have a different opinion) ... it is apparently caused by small cuboids of cobalt specific to that area of the belt (no sense challenging me, you need to challenge the University of Aberystwyth)
Leaderboard
50 Points : Stones
43 Points : Les W
25 Points : Steve K
21 Points :Ian A
6 Point : Mike L