OS 1908 6 inch map sheet 56 SE, shows a line of shafts close to that location, presumably on the course of a lode, and a small quarry a little SE of that.
Although no buildings are marked, they could post date any quarrying/mining. Perhaps an attempt at streaming?
I passed there today and wanted to take a look, but traffic and a lack of parking etc etc.
I might have to park up near Parsley and hike up for a look sometime.
"You Chinese think of everything!"
"But I''m not Chinese!"
"Then you must have forgotten something!"