You need to locate yourself the "Trounson" books. "The Cornish Mineral Industry" is the one I'm thinking of and it goes into a bit of detail about the way the mine was abandoned and what was left there. The area was considered by Trounson (who was an expert, but perhaps a trifle rose tinted) to be a geological analogue of Camborne and is a good bet for tin. Not sure about what copper remains, but I think it was something to do with a fluccan and the faulted extension of the lode not found.