At Craig Rhiwarth there is the Slate Quarry at the top of the hill, below it is the lead mine (also known as Ochrycraig or North Llangynog) (SJ 053 265).
The other side of the hill is Cwm Orog Lead Mine (SJ 052 274).
Ref. D E Bick Part 5 p32-36.
Graham
Graham Levins
Sec.
Welsh Mines Preservation Trust