Parys Mountain

Introduction
The most notable and well known mine on Anglesey is the Parys Mountain Mine. This actually consists of two separate mines: Mona Mine and Parys mine. Nowdays, the most obvious feature is the vast open cast and extensive areas of spoil.

Location
Grid Reference: SH 437 905

Altitude ~110m

Parys Mountain is a hill about a mile to the south of Amlwch which rises to a height of about 130m. Approach is best made via the Amlwch to Rhosybol road. On the south side of the road, not far from the modern pitgear is a small carpark which forms the start of an interpretive trail.

Access
An interpretive trail provides access to the the surface workings which takes one around the Great Pit. Care needs to be taken as there may well be unfenced shafts, and the edges of the Great Pit are not particularly stable. Underground access for bone fide caving groups can be made by contacting the Parys Underground Group.

Description
The Parys Underground Group has for several years been undertaking a program of exploration of the mountain. 1.5km of passage are currently accessible, the remainder being flooded. Access is gained via a drift in the vicinity of the pits. As on the Great Orme, ancient Bronze Age workings have been discovered, and the hope is to enter more of these by working up from below. A particular hazard is the very low pH water falling from the roof !

The Nant Adda adit to the north of the mountain drained the workings. This has a coffer dam installed and is holding back 30m+ head of water. Plans have been mooted to open the dam up to drain the mine.

There has been recent exploration work at the site by Anglesey Mining Plc. proving new complex ore deposits at depth, containing as well as copper - gold, lead and zinc. This was facilitated using a 1000’ deep shaft with prominent headgear. At present, mining is not economically viable, but the shaft is being kept open on a care and maintenance basis in case metal prices recover.

There are also mines and shafts near the sea to the east.

Geological
The copper mineralisation is associated with Ordovician felsitic volcanics & sediments. The deposit are cited as being an example of Kurako arc style massive sulphide deposits. They are believed to have been deposited in environments similar to the 'black smokers' that are seen at volcanic oceanic ridges. Sea water is pumped through fissures in the hot oceanic crust, heated up and leaches ions (Cu2+, Zn2+, Pb2+ etc) from the rocks through which it passes. Upon being emitted and contacting cold sea water through other fissures, the ions are precipitated as sulphides. However, rather than having been formed at oceanic ridges, the Parys deposit is thought to have been formed in an island arc volcanic environment.

History
At one time, Parys Mine was the chief copper source not only within Wales, but also in the whole of Europe. Mining has been going on here since pre-history, but there was a major boom in 1768 with the re-discovery of the mountain and the exploitation of The Great Lode. This was initially mined via shafts, but following roof falls development of open cast workings took place. By the end of the 1880s over 130,000 tonnes of ore were recovered. However, just as copper prices rose at the end of the 19C, the ore deposit was exhausted. Ore recovery did continue on a small scale into the 20C using precipitation lagoons. Scrap iron was thrown into ponds into which mine water flowed and copper was deposited on the iron.