Hingston Down is a hill not far from Gunnislake near Callington. There is rumoured to hold buried treasures, possibly in the form of minerals, hidden somewhere in the area. There is a quarry there, and the Hingston Downs Consol's mine is the type locality for the mineral Arthurite, which was discovered here.
For further information, please read Haunted Britain by Antony D. Hippisley Coxe.