THE GREAT OPENCAST
This impressive chasm was opened up at an early stage of mining
after the collapse of workings reached by numerous shallow shafts.
It was a feature much marvelled at by visitors and has been
recorded in several early paintings. These show projecting
platforms with windlasses, and miners working the ore from the
sides, suspended on ropes. Most of this opencast was worked by the
Parys Mine, the smaller "Hillside Opencast" to the east being
worked by the Mona Mine. The opencasts represent only a small
proportion of the mine as later extraction occurred through shafts
that reached depths of 300m, some 130m below sealevel and now
therefore flooded. Since the rocks dip steeply to the north, most
of these deeper underground workings are located between the
Opencast and the main road over the mountain. The small lake at the
bottom results from the damming of a deep level draining to the
north. The water is very acidic (sulphuric acid - pH 2) and meant
that pumps had to be made from oak, not iron. Its orange-brown
colour is due to the very high concentrations of iron (ferric - in
solution) leached from oxidising sulphide minerals, as indeed do
the range of yellows, reds and purples in the spoil. This dramatic
scene has been used in numerous films from "Dr Who" to, most
recently, "Mortal Kombat 2".
THE MINE YARDS
The buildings on the south side of the Opencast are the remains
of the Mona Mineyard. This group of offices,smithy and stores,
surrounding a courtyard,was the focus of the mine's surface
activities. Here miners bought their tools, candles and explosives
from the Mona Mine company, and bid in small groups at auctions for
"bargains" to work underground sections of the mine for a
fortnight. The equivalent mine yard for the Parys Mine is at the
south west corner of the Opencast, but its buildings are in a more
ruinous state.
THE PRECIPITATION
It was discovered that purer metal could be obtained very
efficiently by precipitation from solution. Water was pumped to the
top of the mountain and allowed to drain down through the spoil and
the underground workings (i.e. "sparging"), dissolving the copper
due to its very acid nature. Scrap iron was then added to the
copper-rich water to give metallic copper in a sequence of
purpose-built, brick-lined "precipitation ponds" of which there are
several examples on the mountain, the best preserved being those in
this central valley. The dissolved iron was itself then oxidised
and precipitated as ochre, a valuable by-product that was marketed
as a pigment.
PEARL ENGINE HOUSE
This distinctive building, prominent on the skyline at the east
end of the mountain, once housed a Cornish Beam Engine. It was one
of the earliest steam engines in north Wales, installed in 1819 to
pump water from the adjacent 230m Pearl shaft. 4Its chimney stood
at the north west corner, but sadly it collapsed some years back.
In front are the remains of a capstan pit used to raise and lower
the oak pump rods in the shaft.
THE CHARLOTTE YARD
In this large area of spoil, just to the north of the mass of
hard quartz-rich rock known as "Carreg y Doll", traces of a
"dressing" or "cobbing floor" can be seen in the form of a cobbled
surface, sadly now much reduced by the removal of spoil for road
stone. This is where the ore from Mona Mine was broken up into
small pieces by the famous "Copper Ladies" (Morwynion Amlwch) using
an iron flat hammer, and protecting their fingers with iron rings.
The ore fragments were then picked out by children and roasted in
large heaped kilns for up to 3 months, filling the air with
fumes.
THE WINDMILL and OXEN QUARRY
Built in 1878 on the summit of Parys Mountain, in the hope of
reducing operating costs, the windmill was used to pump water from
the underlying mine workings. It was later connected to a steam
engine at the nearby 270m deep Cairns shaft by a system of
reciprocating wooden rods ("flat rods"), the remains of which could
clearly be seen during the early part of this century. The windmill
was unique amongst the many on Anglesey in that it comprised five
sails. To the north lies Oxen Quarry which owes its name to annual
celebrations of the first major rediscovery of rich copper ores on
March 2nd 1768. On this day the people of Amlwch were treated to a
roasted oxen. Within this quarry, the early miners discovered
"ancient" spoil tips. These contained rounded stones, or "mauls",
that had been used as hammers, and charcoal from "firesetting", an
early technique used to shatter rock before black powder explosives
became available in the 18th century. The charcoal has been dated
by carbon-14 to nearly 2000 years B.C. The history of copper mining
on the mountain thus goes back to the Early Bronze Age, making it
one of the earliest mines known in Britain.
THE MODERN MINE
The 4000 years of mining history continues today. Anglesey
Mining plc was formed in 1984 to explore and develop the Parys
Mountain property. In 1988 it raised £5.5 million and sank a shaft
to a depth of 300m with more than 1 km of underground tunnelling.
Over 2,000 tonnes of ore were mined, processed and sold, but
development was halted by poor market conditions. Geological
investigation recommenced in 1995 and led to further drilling from
surface in 1997 with the objective of increasing the company's
current resource of 6.5 million tonnes at a combined grade of >1
0% zinc (the principle product), copper, lead, silver and gold. The
planned mine would require over 100 employees and should operate
for more than 15 years. Ore would be extracted from 80-600m below
surface, concentrated in a processing plant and then despatched to
a smelter.
A BRIEF HISTORY OF THE MINES
It was not until the mid-eighteenth century that the first major
ore deposit of the modern industrial era (the "Golden Venture
Lode") was discovered by Jonathan Roose. His tombstone and eulogy
may be seen today in Amlwch churchyard. At this time the mountain
was divided between two owners leading to the development of
adjoining mines, the Mona Mine to the East (owned by an ancestor of
the present Marquess of Anglesey) and Parys Mine to the West. The
copper from these two mines dominated the world's markets in the
1780s. It was used to sheath the admiralty's ships of war, in order
to prevent the growth of seaweed and barnacles and to prevent
boring by worms. This increased their manoeuvrability and made
possible Nelson's victories. The post-war slump and diminishing
accessible ore reserves, together with competition from cheaper
ores from' abroad, led to the decline of the mines and to the end
of deep mining in the 1880s. The ore was initially worked on the
surface from shallow shafts and then by open-pit mining (Opencasts)
and later underground from adits and from shafts up to 300m deep.
The ore was broken into small lumps by hand, the best ore being
transported by ship from Amlwch Port to Lancashire or South Wales
for smelting. Copper was concentrated and extracted from the
remainder using kilns and furnaces on site and at Amlwch Port
itself. It was also discovered that purer metal could be obtained
efficiently, although in small amounts, by its precipitation from
drainage water with scrap iron in purpose-built ponds. Associated
with the mines, other important chemical industries were
established on the mountain based on by-products, such as ochre
pigments, sulphur, vitriol and alum. The eighteenth century miners
recognised that they were following in the steps of much earlier
workers, an observation that was linked to the discovery locally of
copper ingots bearing Roman inscriptions. Recently, excavations
have enabled surface debris to be dated to nearly four thousand
years ago, (the early Bronze Age), and access has also been
regained to the sealed.
GEOLOGY AND BIOLOGY
The rocks of Parys Mountain originated as muds in the margins of
a sea basin around 440 million years ago. At that time submarine
volcanoes were erupting lavas and ashes, and the fumes they exhaled
produced rich deposits of metals on the sea floor. These metals
occur as the sulphide minerals chalcopyrite (copper and iron),
galena (lead), sphalerite (zinc), with abundant pyrite (iron), and
they form an ore deposit ("Kuroko type") which is unique in
Britain. During later distortion of the earth's crust (the
"Caledonian Orogeny" circa 400 million years ago) the ore deposit
was deformed by being tilted steeply down to the north, folded
(synclinal structure) and fractured (faulting), although this
interpretation is currently under revision. During these phases of
deformation some of the metals were remobilised, giving rise to a
complex ore body. The weathering of this deposit has produced very
acidic conditions (pH @ 2). The abundant iron has been redeposited
in different forms to give the striking red and brown colours of
the mountain: there is little surface sign of copper today, but
lead was redeposited as its sulphate ("anglesite") for which Parys
Mountain is the type locality. This extreme, harsh, acidic setting
has resulted in a unique environment supporting unusual forms of
life. Special bacteria derive their energy from the oxidation of
sulphides, and a rich flora of special lichens can be found coating
rock surfaces, whilst heather survives over most of the mountain.
Bats, including the rare lesser horse shoe bat, have colonised the
mine workings, and amongst the birds to be seen soaring with the
jackdaws over the opencasts are the red-legged / billed
choughs.
To log the cache please upload a photograph of you or you GPSr
with the mine in the back ground and E-Mail me the answers the
following questions.
1) What gives the rocks it reddish colour.
2) Estimate the depth of the opencast
3) Estimate the width of the opencast from left to right from
the information board .
Any logs with no photograph may be deleted