I was looking through Porter and Robey's book on the Manifold Valley mines last night, and it seems East Ecton was a lead, not a copper mine - when originally sunk/driven in the 1860s, it was after a vein of lead had been discovered at surface, and a, 1880s report by a mining engineer quoted in the book refers to driving on a lead vein. There's no mention at all of copper in the vein(s) at East Ecton.
So, I think this one needs tweaking back to being a lead mine....
Follow the horses, Johnny my laddie, follow the horses canny lad-oh!