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61-404: Oakeley quarry is a slate quarry in the town of Blaenau Ffestiniog , north Wales . It was the largest underground slate mine in the world, and had 26 floors spanning a vertical height of nearly 1,500 feet (460 m). The first slate quarry on the site of what was to become Oakeley, was begun in 1818 when Samuel Holland, a Liverpool merchant, leased land near Rhiwbryfdir farm. The landlords,

122-408: A new quarry above Lower Quarry at Cesail . In 1827, Holland gave over control of this company to his son, also called Samuel Holland . This quarry was variously known as Hollands Quarry , Gloddfa'r Gesail and finally Upper Quarry . In 1839 Holland's Upper Quarry became one of the first to send slate on the newly opened Ffestiniog Railway . In 1842 as the original 21-year lease expired, Holland and

183-639: A pair of slate veins that ran across the Cambrian mountain range from Tywyn in the west through Corris and Aberllefenni in the Dulas Valley to the mines around Dinas Mawddwy in the east. Slate was also mined in Pembrokeshire in places like Maenclochog . Most underground slate mines in north Wales were closed by the 1960s although some open-cast quarries have remained open, including the Penrhyn Quarry and

244-587: A single event, severely damaging the workings. As well as the physical damage to the quarries, the fall triggered a lawsuit between the Oakeley Company and the Welsh Slate Company which the Welsh Slate Company lost. Unable to pay the resulting fine, the Welsh Slate Company gave up its lease and the Oakeley was finally amalgamated into a single operation. Oakeley was located on the north side of Allt-fawr . On

305-476: Is as a roofing material . It is particularly suitable for this purpose as it has a low water absorption index of less than 0.4%, making it very resistant to frost damage and breakage due to freezing. Tiles produced from Spanish slate are usually hung using a unique hook fixing method, which reduces the appearance of weak points on the tile since no holes are drilled, and allows narrower tiles to be used to create roofing features such as valleys and domes. Hook fixing

366-457: Is especially prevalent in areas subject to severe climatic conditions, since there is a greater resistance to wind uplift as the lower edge of the slate is secured. Slate has been quarried in north Wales for almost two millennia with the Segontium Roman fort at Caernarfon being roofed by local slate in the late second century. Export of slate has been carried out for several centuries, which

427-408: Is estimated that the lifetime of the Oakeley concerns, more than 100 million tons of waste was generated. The restricted location of Oakeley on the slopes of Allt-fawr made disposing of this waste a significant problem. The original village of Rhiwbryfdir and the nearby monastery of Mynachlog were purchased by Oakeley and then buried under a massive waste tip. Space was also sought on the south bank of

488-669: Is known to have been carried out from the late mediaeval period and there was a considerable export trade from some of the quarries near the coasts in the 19th century. Slate has also been quarried at Swithland in Leicestershire. There are considerable workings in Cumbria . During the last 500 years, much slate extraction has taken place in the Lake District at both surface quarries and underground mines. The major workings are: Slate

549-845: Is one of the places in the world where colored slate (i.e. slate which is not grey or blue) is obtained. (A fuller account is given in the article Slate : section Slate extraction.) Ninety percent of Europe's natural slate used for roofing originates from the slate industry in Spain, with the region of Galicia being the primary production source. In Galicia, the larger slate production companies are concentrated in Valdeorras in Ourense , with other important sites being situated in Quiroga , Ortigueira and Mondoñedo . The slate deposits in this region of northern Spain are over 500 million years old, having formed during

610-544: The Oakeley family of Tan y Bwlch took a 10% royalty for the three-year lease. In 1821, at the end of the initial three years, Holland took a further 21-year lease on the site, but he sold this in 1825 to the Welsh Slate Company which considerably extended the quarry. The Welsh Slate Co.'s undertaking was the lowest on the mountain it became known as Lower Quarry - also known as Lord Palmerston's Quarry . Holland opened

671-495: The Palaeozoic period. The colour and texture of the slate produced is largely dependent upon the tectonic environment, the source of the sedimentary material from which the slate is comprised, and the chemical and physical conditions prevalent during the sedimentation process. The region has been subjected to periods of volcanism and magmatic activity, leading to a unique geological development. An important use of Spanish slate

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732-457: The "Day of the Big Pay". If conditions had not been good, the men could end up owing the management money. At Moel Fferna a team could produce up to 35 tons of finished slate a week. In 1877 they received about 7 shillings a ton for this. After paying wages for the manager, clerks and 'trammers' the company could make a clear profit of twice this amount. This system was not finally abolished until after

793-771: The 1860s onwards. A small scale quarrying and dressing operation continues in Monson into the 21st century. Slate is also found in the Arctic and was used by the Inuit to make the blades for ulus . 95% of the slate extraction in Brazil comes from Minas Gerais . Slate from this region is formed differently from traditional slate areas such as Galicia. Such products are sedimentary rocks that have split along their original bedding plane, whereas true slate has been subjected to metamorphism and does not split along bedding, but rather along planes associated with

854-662: The Afon Barlwydd and in 1854 the Glan y Don (also known as the Pen y Bont ) tip was established. This tip was accessed by a high viaduct that crossed the Ffestiniog Railway's Dinas branch, the London and North Western Railway's Conway valley line and the river. This tip became so large that a mill was built on top of it for further slate processing capacity in 1875. In 1899, further tipping space

915-570: The Ffestiniog and Oakeley over the rates for slate shipment. In 1930 the quarry built an incline down from their Pen y Bont mill to connect to the LNWR exchange yard in Blaenau Ffestiniog. Significant tonnages of slate were sent over this link until the closure of the quarry in 1970. Oakeley made extensive use of internal tramways, with more than 50 miles of track underground alone. The track throughout

976-467: The Second World War. Early workings tended to be in surface pits, but as the work progressed downwards, it became necessary to work underground. This was often accompanied by the driving of one or more adits to gain direct access to a Level. In some rare instances, such as Moel Fferna, there is no trace of surface workings and the workings were entirely underground. Chambers were usually driven from

1037-536: The Slateford Water Gap area the first verified quarry started some time around 1808 . The industry in this region of Pennsylvania spread across the northern edges of both Lehigh and Northampton counties which contain between them the remains of approximately 400 individual quarries. The origins of quarrying in the Lehigh Valley are obscured by conflicting evidence, although it is safest to say that it started near

1098-489: The UK, are not entitled to bear the CE mark . Because such Brazilian products display higher water absorption indexes than those from other areas such as Galicia, this makes them less suitable for use as roofing tiles since the study showed a significant loss of strength when subject to thawing and freezing. Cwm Dyli Cwm Dyli is the location of a hydro-electric power station on

1159-767: The United States has existed in several locations in the country including areas in the western states, however the majority of slate has come from three principal regions along the Great Valley of the Appalachian Mountains. Of those regions, the Taconic Mountains region of Vermont and New York , as well as Lancaster , Lehigh and Northampton counties in Pennsylvania all still have active quarries. The Pennsylvania Historical and Museum Commission states that in

1220-478: The Welsh Slate Company negotiated a new lease from the Oakeley family. The new lease was granted provided some land was given up by both enterprises to allow a third quarry to be opened. This was Middle Quarry also known as Gloddfa Ganol and was operated by the Rhiwbryfdir Slate Company. The younger Holland was known as a reasonable employer, although in the early years he frequently had trouble with

1281-602: The bottom of the pit: In the Blaenau Ffestiniog area, most of the workings were underground as the slate veins are steeply angled and open cast workings would require the removal of a massive amount of rock to gain access to the slate. The larger mines in the Ffestiniog area include: There were also a number of slate mines in the Llangollen area which produced a much darker "black" slate: Another cluster of mines were found in mid Wales centered on Corris . These all worked

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1342-482: The bottom, by means of a "roofing shaft" which was then continued across the width of the chamber: the chamber would then be worked downwards. Slate was freed from the rockface by blasting in shot holes hammered (and later drilled) into the rock. Slate mines were usually worked in chambers which followed the slate vein, connected via a series of horizontal "Floors" (or "Levels"). The chambers varied in size between mines and were divided by "pillars" or walls which supported

1403-407: The chambers free from waste: one ton of saleable slate could produce up to 30 tons of waste. It is the mountainous heaps of this very same waste that is perhaps the first thing to strike someone visiting the old regions nowadays. The men had to pay for their ropes and chains, for tools and for services such as sharpening and repairing. Subs (advances) were paid every week, everything being settled up on

1464-456: The complex but separate workings had arisen as early as the 1860s. The Welsh Slate Company's Lower Quarry mine extended directly beneath that of the Middle Quarry, its progress was limited by the speed with which the Middle Quarry progressed, because both were working the same vein of slate. But the Middle Quarry was mining more slowly than the Welsh Slate Company desired, so the latter had taken

1525-462: The dangerous decision to remove slate from the walls that supported the workings above. This literally undermined the Middle Quarry workings and during the 1870s underground rockfalls became an increasing concern. On 6 December 1882 a major rockfall forced the Welsh Slate Company to shut down all operations. The instability in the mine continued, culminating in a much larger fall on 16 February 1883. This Great Fall saw 6.25 million tons of rock fall in

1586-481: The early 1870s the production and profits hit their peaks. The leaseholds for the Upper and Middle quarries expired in 1878 and the landowner, W.E. Oakeley refused to renew them, instead consolidating the two quarries into a single operation, the Oakeley quarry . The Welsh Slate Company had negotiated a lease extension some years before expiry, so it continued to work Lower Quarry as a separate operation. Problems caused by

1647-559: The first decade of the twentieth century saw a sharp decline in the Welsh slate industry. This was caused by a combination of a slump in the British building industry, competition from foreign slate producers, particularly France, and an increase in the use of roofing tiles instead of slate. Oakeley was no exception to this, and by 1908 it had more than a year's worth of output stockpiled awaiting buyers. The Oakeley Slate Quarries Company also took over

1708-434: The floor below. Large slab of rock were removed from the chamber, typically on railway wagons , and taken to the mill. The slabs were first sawn to the required size, then split to specific thicknesses - this was done by hand for many centuries using a chisel held at a specific angle to achieve a clean split while maintaining the material's integrity. Finally, the corners of each piece were bevelled to allow water to flow over

1769-579: The hillside above the Rhosydd workings has many pits where the roofs of the chambers below have collapsed. The most significant non-Welsh British slate industry is that of Cornwall and Devon where the Delabole Quarry is thought to be the largest single quarry in the island. Many of these are no longer worked owing to lower costs of extraction in the larger British workings. The quarrying of slate in Cornwall

1830-518: The incline from below, it was powered. Initially the power was provided by a stationary steam engine . In 1906 the K Trwnc was converted to electrical power using a 100 hp 500V A.C. motor supplied with power by the quarry's hydro electric generating station. Locomotives known to have worked at Oakeley quarry. All information from unless otherwise stated. The Oakeley quarries were avid users of technology, allowing them to reduce their costs and increase their production. In 1856 they began to light

1891-420: The largest producer of school slates and chalkboards in the country. The Slatington Slate Trade report for January 4 of 1880 showed that quarries in the town of Slatington alone had shipped 81,402 squares of roofing slates (over 8 million square feet) as well as 40,486 cases of school slates and 243 cases of blackboards. The Slate Valley (the district of Granville, New York ) is well known for its slate. Slate

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1952-525: The last working slate mine, the only producers of the world famous Westmorland greenslate. In the remainder of Continental Europe and the Americas , Portugal , Italy , Germany , Brazil , the east coast of Newfoundland , the Slate Valley of Vermont , New York , Pennsylvania , and Virginia are important producing regions. The Slate Valley area, centering on a town called Granville in the state of New York

2013-436: The name Gloddfa Ganol . The tourist operation included an extensive collection of narrow gauge locomotives , many connected to the Welsh slate industry. Two parts of the Oakeley underground workings were opened to visitors and the working mill could also be viewed. The commercial operation, under the name Ffestiniog Slate Co. reworked parts of the previously underground mine as an opencast quarry. The Ffestiniog Slate Co.

2074-430: The nearby Votty & Bowydd quarry in 1933 and Diphwys Casson Quarry in 1936. Oakeley continued to produce significant tonnages of slate through World War II , but experienced a rapid decline in the 1960s, along with the remainder of the British slate industry. The quarry closed in 1969, and the company was liquidated and wound down in 1972. The quarry re-opened as a working quarry and tourist attraction in 1978 under

2135-460: The north of the site. From here it descended into the main mine complex, dropping three hundred feet below ground. It descended at 45° which was too steep to allow wagons to use on their own wheels. Instead two 6 ft ( 1,829 mm ) gauge carriages ran on the incline. These had a horizontal upper platform on which 2 ft ( 610 mm ) gauge rails were placed to allow the quarry wagons to ascend and descend. Because slate had to be hauled up

2196-626: The oldest quarries in America continues to quarry slate in Buckingham County, Virginia . Their trademark Buckingham Slate has been continually quarried since the 18th century and has a distinct, unfading blue/black color and Mica sheen. Buckingham Slate is used on many Federal buildings in the Washington, D.C. area. Large scale slate quarrying also took place around the town of Monson, Maine where an extensive series of quarries flourished from

2257-438: The quarry using piped gas. A large steam-driven cutting mill was opened around 1860. Nathaniel Mathew, the owner of Middle Quarry pioneered the use of mechanical slate dressing tools at his mill. Mathew invented a slate dressing machine that carries his name. Victorian slate extraction techniques generated vast amounts of slate waste - for every ton of finished slate produced, approximately nine tons of waste rock are extracted. It

2318-576: The railway's terminus at Rhiwbryfdir as the Welsh Slate Company had successfully blocked his attempt to complete a direct connection via an incline . By 1839 agreement had been reached over the route of an incline to the Festiniog Railway, and slates from Holland's quarry were now sent directly onto the railway. Oakeley continued to send slate over the Ffestiniog Railway until the closure of the railway in August 1946. But there were constant disputes between

2379-542: The realignment of minerals during metamorphism. This realignment, known as ‘schistosity’, bears no relationship to the original horizontal bedding planes . The independent Fundación Centro Tecnológico de la Pizarra’s report into the ’Technical properties of Bambui Slate from the State of Minas Gerais (Brazil) to ascertain its compliance with the Standard EN12326’ describes how certain products originating from Brazil on sale in

2440-399: The roof. The floors were connected by underground "Inclines" which used wedge-shaped trolleys to move trucks between levels. In some mines, where slate was worked away below the main haulage floor, the route was maintained through the construction of a wooden bridge across the chamber, often supported from chains attached to the roof above. These bridges could be as much as 100 feet/30 m above

2501-507: The site primarily comes from Llyn Llydaw , some 320 metres above the power station, where rainfall is very high. The water is carried from the lake through a tunnel and two 30-inch (0.762 m) diameter, 2-kilometre (1.2 mi) long pipelines. The pipeline featured in the James Bond film The World Is Not Enough . The generating equipment at Cwm Dyli up to 1989 comprised: The four wheels drove: The total electricity generating capacity

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2562-481: The slate once in place on the roof. A final inspection and sorting took place before they were packaged for transport. The process of slate quarrying generates vast amounts of waste rock - often more than 90% of the rock mined was discarded. No chemical processes awerere used in the production, and the waste was disposed at dumps. In North Gwynedd , the large slate producing quarries were usually confined to open-cast workings, sometimes with an adit to gain access to

2623-439: The slate region of what is now Blaenau Ffestiniog in 1836. It provided a cheap and efficient connection with the wharves at Porthmadog and therefore with the wider British and world markets. The quarries which made use of the railway were able to substantially reduce their overall costs and therefore increase their profits. The first quarry to use the railway was Holland's Lower Quarry. Initially Holland's slates had to be carted to

2684-482: The south side lay Cwmorthin quarry had by the 1880s developed into a significant operation. There was also the smaller Nyth-y-Gigfran quarry working on the eastern cliffs of Allt Fawr. Oakeley took over Nyth-y-Gigfran in the late 1880s, connecting with the mine underground. At the same time, Cwmorthin suffered its own rockfall and in 1900 it too was taken over by and connected to Oakeley. At their peak these combined quarries produced 60,000 tons of slate annually and were

2745-752: The southern flank of the Snowdon range in North Wales . At the time it was built, it was the largest hydro-electric power station in the United Kingdom . It is Britain's oldest power station, and is believed to be one of the oldest Grid-connected hydro-electric stations in the world. The station was built in 1905 by the Porthmadog, Beddgelert and South Snowdon Railway company, backed by North Wales Power and Traction Co Ltd to supply electricity to its own electric railway and connected slate quarries and mines . The railway

2806-400: The surface for processing. Inclines were also used to lower finished slates down to the Ffestiniog and London and North Western Railways. The main entry point to the underground workings for the period from the 1880s to the 1960s was the K Trwnc incline. This was one of the steepest and longest inclines in the Welsh slate industry. It began near the bottom of Sinc Fawr the large pit towards

2867-591: The third largest in the United Kingdom . In 1906, Oakeley began using electricity generated at the Cwm Dyli power plant. The plant generated the equivalent of 1,930 hp, which was claimed to make it the largest hydro-electric power supply in Great Britain at the time. Power from the plant was carried to the quarry using an overhead transmission line via Roman Bridge and the Crimea Pass . Despite modernisation efforts,

2928-478: The town of Slateford in the early Nineteenth Century and moved toward Bangor over a fifty-year period. By 1929, the value of slate production in Pennsylvania was approximately 5 million dollars, accounting for almost half of the 11 million dollar value of slate production for the entire United States. Quarries in this region of the country remained active throughout the first quarter of the 20th century producing roofing slate, slate for electrical uses, as well as being

2989-823: The untopping work at Oakeley in Blaenau Ffestiniog . Work also continues at Berwyn near Llangollen . The final large-scale underground working to close was Maenofferen Quarry (which is owned by the Llechwedd tourist mine) in 1999 although opencast quarrying continues at this location. Many of the mines are now in a state of considerable decay and those that are accessible should not be entered as they are on private property and contain many hidden dangers. Historical and adventurous underground tours are provided at several mines including Rhiwbach (by Go Below ), Llechwedd ( Zip World and Llechwedd/Quarry Tours Ltd ) and Cwmorthin (Go Below). The lower levels of many mines are now flooded and collapses are commonplace; for example,

3050-478: The workforce. But he managed to avoid the significant industrial action that was interrupting production at other Welsh slate quarries in this period. By 1840 the slate that could be easily accessed by surface quarrying with contemporary methods was exhausted, so the quarries began underground mining. Complex arrangements were written into the leases to ensure that the underground workings did not conflict. Production at all three quarries continued to expand and during

3111-448: The world. It was first commissioned in 1906 and has been in fairly continuous operation since then, although it was closed for upgrading in 1990. A single turbine now produces up to 9.8 megawatts (MW). Known locally as the "Chapel in the valley", on account of its exterior design, it employed 13 men. Today, however, it is controlled remotely from Dolgarrog in the Conwy valley . Water for

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3172-563: Was "Bargain Letting Day" when these agreements were made between men and management. Half the partners worked the quarry face and the others were in the dressing sheds producing the finished slates. In the Glyndyfrdwy mines at Moel Fferna each bargain worked a horizontal stretch of 10 by 15 yards. Duchesses, Marchionesses, Countesses, Viscountesses, Ladies, Small Ladies, Doubles and Randoms were all sizes of slates produced. Rubblers helped to keep

3233-614: Was also quarried in Scotland. Slate was first quarried in the United States as early as 1734 along the Pennsylvania Maryland border; however, it was not until 1785 that the first commercial slate quarry was opened in the United States, by William Docher in Peach Bottom Township, Pennsylvania. Production was limited to that which could be consumed in local markets until the middle of the nineteenth century. The slate industry in

3294-402: Was approximately 2 ft ( 610 mm ) gauge, small enough for workers to move loaded wagons by hand and the same as the Ffestiniog Railway. Underground the tramways were almost exclusively worked by hand, on the surface extensive use of steam and internal combustion locomotives was made. The great depth of the mine meant that extensive use of inclines was made to move slate to the mills on

3355-630: Was claimed to be the largest electricity generating plant of its kind in Great Britain at the time. Electricity produced here was also used to power the Carnarvon Long Wave Wireless Telegraph transmitting station built by Marconi in 1913–14 near Waunfawr . Supplying power directly to the National Grid , it is Britain's oldest power station, and is believed to be one of the oldest Grid-connected hydro-electric stations in

3416-527: Was from Wales (451,000 t): the quarries at Penrhyn and Dinorwic produced half of this between them. The men worked the slate in partnerships of four, six or eight and these were known as "Bargain Gangs". "Bargains" were let by the "Bargain Letter" when a price for a certain area of rock was agreed. Adjustments were made according to the quality of the slate and the proportion of "bad" rock. The first Monday of every month

3477-618: Was planned to run through the same valley as the power station and be fed with an electrical feeder, but the enterprise ran short of funds and the attempt was abandoned. The company was renamed the North Wales Power Company Limited. In August 1906, power from Cwm Dyli was used to power the Oakeley Quarry in Blaenau Ffestiniog carried over the Crimea Pass by a long overhead transmission line at 10,000 volts. It also supplied Dinorwic and Pen-yr-Orsedd quarries. Cwm Dyli

3538-460: Was quarried in 1839 at Fair Haven , Vermont. An influx of immigrants from the North Wales slate quarrying communities saw a boom in slate production that peaked in the latter half of the 19th century. The slate of the region comes in a variety of colors, notably green, gray, black and red. Some production continued in 2003 with 23 operating full-time mines employing 348 people. Additionally, one of

3599-569: Was recently confirmed by the discovery in the Menai Strait of the wreck of a 16th-century wooden ship carrying finished slates. Large-scale commercial slate mining in North Wales began with the opening of the Cae Braich y Cafn quarry, later to become the Penrhyn Quarry near Bethesda in the Ogwen Valley in 1782. Welsh output was far ahead of other areas and by 1882, 92% of Britain's production

3660-655: Was required, so the Ffestiniog Railway's Dinas branch was diverted to allow the Doman Fawr tip on the eastern slope of Allt-fawr to be extended further south of the quarry. Slate industry Slate mines are found around the world. 90% of Europe's natural slate used for roofing originates from the Slate Industry in Spain . The major slate mining region in the United Kingdom is the Lake district, with Honister slate mine being

3721-422: Was sold to McAlpine in 1998 and the tourist side of the business was closed. The quarry continued to operate using heavy earth moving equipment to continue and expand the previous open-cast operation. In March 2010 Welsh Slate announced the quarry's closure, due to the discovery of subsidence . The remaining workers would be transferred to another of the company's quarries. The Festiniog Railway arrived in

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