By spring 1973 the engine was operating on compressed air. In the 1980s the attraction became known as "Ha'penny Park". Peter and Jose Young retired to Spain and sold Poldark Mine to John McLeod who ran it until it was placed in receivership in 1999. In 2000 the property was purchased by a company set up by Richard Williams who was reported to have "put all of his efforts into developing this into one of the most atmospheric tourist underground mine experiences in Europe". At this time one of the attractions was Evening 'Ghost Tours'; the site was licensed for the holding of civil weddings; and it was twinned with the Llywernog Silver-Lead Mine in Wales. Following Williams' death in 2012, the attraction again declined in popularity until it went into administration in 2014. Early that year the property was put up for sale, with a guide price of £350,000. It was purchased by David Edwards who had been involved with the Ffestiniog Railway and the Llechwedd Slate Caverns in Wales, and work to repair and restore the mine commenced immediately: it reopened in May 2014. The site lies in the valley of the River Cober on the Carnmenellis granite outcrop. The river valley was once extremely rich in tin ore because of the extensive erosion over geological time of a great depth of overlying sedimentary rocks which contained many ore-bearing lodes. Pebbles and grains of the heavy ore collected in the river gravels and sands, eventually leading to the rich tin-bearing grounds that were found near the surface of most of the river valleys flowing from the granite. Evidence that this abundance of ore was first recovered and processed in ancient times is shown by the Trenear Mortar Stone, near to the entrance of Poldark Mine. It is an outcrop of granite which has at least 17 hollows in its upper face in which tin ore would have been crushed by hand, using stones. Although impossible to date precisely it is believed to have been in use during the later prehistoric period (c.2000BC to 43 AD). It is the only known example of such a mortar in south-west England and was designated as a scheduled monument in 2009. The first mechanised tin stamping mill in Duchy land, and possibly in the whole of Cornwall, is recorded at Trenere Wolas (present-day Lower Trenear) in a document confirming that it was held by John Trenere, a freeman, in 1493.