A series of precipitation ponds (NPRN 91698), through which copper was reclaimed from the acidic copper sulphate emanating from the Parys Mountain mining complex (NPRN 33752) via the deep drainage adit, its exit portal 200m to the south of the main pond complex. Adjacent to the ponds on the south side are a number of associated buildings including a manager's house and furnace house that houses a reverbatory furnace (NPRN 91697) used to dry and roast copper and ochre precipitates that hadn?t dried naturally.

The 1st edition Ordnance Survey map of 1889 clearly shows the layout of the rectangular ponds, 41 in total and varying in size, with the majority around 21m long by 8m wide. There are an additional two larger ponds to the south of the main complex through which water from the deep drainage adit was initially fed. Around 18 of the ponds survive today principally on the north and west side of the complex and are defined by a mixture of stone, brick and timber. A small number of the ponds are scheduled as part of the Dyffryn Adda complex.

The Process: Water from the deep drainage adit was allowed to flow under gravity into a number of ponds at which point thousands of tons of scrap iron, initially brought to Amlwch by sea and latterly by rail, were deposited annually in the ponds and agitated (initially by disabled an ageing miners) to speed up the chemical process. The precipitate, in the form of a copper-rich sludge, dropped to the floor of the pond and when the iron was totally consumed, the resulting iron sulphate solution was ducted into larger ponds where it was left to oxidise in the air. During this process it precipitated out as yellow ochre that was used in paint making. Subsequent controlled oxidation in further ponds resulted in the ochre's varying in colour from light to dark brown. When the copper and ochre processes were complete, residual water was drained away via the Afon Goch to discharege in the sea close to Porth Amlwch.

The precipitate was allowed to drain and dry naturally on extensive open floors; the 1st edition Ordnance Survey map shows a number of Ochre Pits surrounding the Dyffryn Adda complex. In those cases when the precipiates were insufficiently dry to market, they were taken to the reverbatory furnace (NPRN 91697) to be dried artificially.

The complex is thought to have been in operation from the early nineteenth century until the 1950s.

Louise Barker, RCAHMW, December 2015

Based on Information provided by the Amlwch Industrial Heritage Trust.