The slate industry is the
industry
Industry may refer to:
Economics
* Industry (economics), a generally categorized branch of economic activity
* Industry (manufacturing), a specific branch of economic activity, typically in factories with machinery
* The wider industrial sector ...
related to the extraction and processing of
slate. Slate is either quarried from a
''slate quarry'' or reached by tunneling in a ''slate mine''. Common uses for slate include as a roofing material, a flooring material, gravestones and memorial tablets, and for electrical insulation.
Slate mines are found around the world. 90% of Europe's natural slate used for roofing originates from the
Slate Industry in Spain
Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock ...
.
[European Association of Mining Industries website]
retrieved on 26/01/2010 The major slate mining region in the United Kingdom is
Wales
Wales ( cy, Cymru ) is a country that is part of the United Kingdom. It is bordered by England to the east, the Irish Sea to the north and west, the Celtic Sea to the south west and the Bristol Channel to the south. It had a population in ...
; in
Cornwall
Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...
there are a number of slate quarries (famously the village of
Delabole
Delabole ( kw, Delyow Boll) is a large village and civil parish in north Cornwall, England, UK. It is situated approximately two miles (3 km) west of Camelford.
The village of Delabole came into existence in the early 20th-century; it is ...
), and in the
Lake District there are numerous slate mines and quarries. In the remainder of Continental Europe and the Americas,
Portugal
Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...
, Italy, Germany,
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, the east coast of
Newfoundland, the Slate Valley of
Vermont
Vermont () is a state in the northeast New England region of the United States. Vermont is bordered by the states of Massachusetts to the south, New Hampshire to the east, and New York to the west, and the Canadian province of Quebec to ...
and
New York, and
Virginia
Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...
are important producing regions. The Slate Valley area, centering on a town called
Granville in the state of New York 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.)
Slate industry in Spain
90% of Europe's natural slate used for roofing originates from the slate industry in Spain,
[ with the region of Galicia being the primary source of production.
In Galicia, the larger slate production companies are concentrated in ]Valdeorras
Valdeorras is a comarca in the Galician Province of Ourense. The overall population of this local region is 25,500 (2019).
Municipalities
* O Barco de Valdeorras, capital of the comarca
*O Bolo
*Carballeda de Valdeorras
*Larouco
* Petín
* A ...
in Ourense, with other important sites being situated in Quiroga, Ortigueira
Ortigueira is a seaport and municipality in the province of A Coruña the autonomous community of Galicia in northwestern Spain. It belongs to the comarca of Ortegal. It is located on the northern slope of the Serra da Faladoira, the river Me ...
and Mondoñedo
Mondoñedo () is a small town and municipality in the Galician province of Lugo, Spain. , the town has a population of 4,508. Mondoñedo occupies a sheltered valley among the northern outliers of the Cantabrian Mountains. Despite being the core ...
.
The slate deposits in this region of northern Spain are over 500 million years old, having formed during the Palaeozoic period. The colour and texture of the slate produced is largely dependent upon the tectonic
Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...
environment, the source of the sedimentary material from which the slate is comprised, and the chemical and physical conditions prevalent during the sedimentation
Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to the ...
process. The region has been subjected to periods of volcanism
Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a ...
and magmatic activity, leading to a unique geological development in the region.
An important use of Spanish slate is as a roofing material
Domestic roof construction is the framing and roof covering which is found on most detached houses in cold and temperate climates. Such roofs are built with mostly timber, take a number of different shapes, and are covered with a variety of ma ...
. 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 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 industry in Wales
Background
Slate has been quarried in north Wales for almost two millennia with the Segontium
Segontium ( owl, Cair Segeint) is a Roman fort on the outskirts of Caernarfon in Gwynedd, North Wales. The fort, which survived until the end of the Roman occupation of Britain, was garrisoned by Roman auxiliaries from present-day Belgium and Ge ...
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 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
The Penrhyn quarry is a slate quarry located near Bethesda, North Wales. At the end of the nineteenth century it was the world's largest slate quarry; the main pit is nearly long and deep, and it was worked by nearly 3,000 quarrymen. It has ...
near Bethesda in the Ogwen Valley in 1782. Welsh output was far ahead of other areas and by 1882, 92% of Britain's production 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 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 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 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 the Second World War.
Working methods
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 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 would be recovered from the chamber in the form of a large slab, which would be taken by truck to the mill where it would be split and cut into standard-sized roofing slates.
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 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 the floor below.
Significant mines
In North Gwynedd, the large slate producing quarries were usually confined to open-cast workings, sometimes with an adit
An adit (from Latin ''aditus'', entrance) is an entrance to an underground mine which is horizontal or nearly horizontal, by which the mine can be entered, drained of water, ventilated, and minerals extracted at the lowest convenient level. Adit ...
to gain access to the bottom of the pit:
* Penrhyn Quarry
The Penrhyn quarry is a slate quarry located near Bethesda, North Wales. At the end of the nineteenth century it was the world's largest slate quarry; the main pit is nearly long and deep, and it was worked by nearly 3,000 quarrymen. It has ...
, Bethesda. The largest slate producing quarry in the world. Bought by Alfred McAlpine plc in 1964.
* Dinorwic Quarry, Llanberis
(; ) is a village, community and electoral ward in Gwynedd, northwest Wales, on the southern bank of the lake and at the foot of Snowdon, the highest mountain in Wales. It is a centre for outdoor activities in Snowdonia, including walking ...
.
* Cilgwyn quarry
Cilgwyn quarry is a Slate industry in Wales, slate quarry located on the north edge of the Nantlle Vale, in North Wales. It is one of the earliest slate quarries in Great Britain, being worked as early as the 12th century. King Edward I of Engla ...
, Nantlle Valley
The Nantlle Valley ( cy, Dyffryn Nantlle, ) is an area in Gwynedd, North Wales, characterised by its numerous small settlements.
The area is also historically important geologically, and featured in one of the most contentious disputes of the ...
. Dating from the 12th century it is thought to be the oldest in Wales.
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:
* Llechwedd quarry
Llechwedd quarry () is a major slate quarry in the town of Blaenau Ffestiniog, north Wales. At its peak in 1884 it produced 23,788 tons of finished slate per year and had 513 employees. It continues to produce slate on a limited scale and is ...
– now open to the public as a "tourist mine". Most of the underground workings destroyed by quarrying
Llechwedd Slate Caverns
* Manod – used by the National Gallery, London to store artworks in World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
* Maenofferen
* Oakeley – now partially untopped as an opencast working by Alfred McAlpine plc
* Cwmorthin
* Rhosydd
* Croesor
Croesor is a small village in Gwynedd, Wales, located at the foot of Cnicht, in Cwm Croesor, in the community of Llanfrothen. The Croesor Tramway travelled along the bed of the cwm, before rising steeply to Bwlch Rhosydd via Croesor Incline.
...
There were also a number of slate mines in the Llangollen
Llangollen () is a town and community, situated on the River Dee, in Denbighshire, Wales. Its riverside location forms the edge of the Berwyn range, and the Dee Valley section of the Clwydian Range and Dee Valley Area of Outstanding Natural Bea ...
area which produced a much darker "black" slate:
* Berwyn
* Deeside and Moel Fferna
* Penarth
Another cluster of mines were found in mid Wales centered on Corris
Corris is a village in the county of Gwynedd, Wales, about north of the town of Machynlleth. The village lies on the west bank of the Afon Dulas (which here forms the boundary with Powys), around that river's confluence with the Afon Deri ...
. These all worked a pair of slate veins that ran across the Cambrian mountain range from Tywyn
Tywyn (Welsh: ; in English often ), formerly spelled Towyn, is a town, community, and seaside resort on the Cardigan Bay coast of southern Gwynedd, Wales. It was previously in the historic county of Merionethshire. It is famous as the lo ...
in the west through Corris and Aberllefenni
Aberllefenni is a village in the south of Gwynedd, Wales. It lies in the historic county of Merionethshire/ Sir Feirionnydd, in the valley of the Afon Dulas, and in the Community of Corris.
Government
The village has a community council. The ...
in the Dulas Valley to the mines around Dinas Mawddwy
Dinas Mawddwy () is a village in the community of Mawddwy in south-east Gwynedd, north Wales. It lies within the Snowdonia National Park, but just to the east of the main A470, and consequently many visitors pass the village by. Its population ...
in the east. Slate was also mined in Pembrokeshire in places like Maenclochog
Maenclochog () is a village, parish and community in Pembrokeshire, south-west Wales. It is also the name of an electoral ward comprising a wider area of four surrounding communities. Maenclochog Community includes the small settlement of Ll ...
.
Remains
Most underground slate mines in north Wales were closed by the 1960s although some open-cast quarries have remained open, including the Penrhyn Quarry
The Penrhyn quarry is a slate quarry located near Bethesda, North Wales. At the end of the nineteenth century it was the world's largest slate quarry; the main pit is nearly long and deep, and it was worked by nearly 3,000 quarrymen. It has ...
and the untopping work at Oakeley in Blaenau Ffestiniog. Work also continues a
Berwyn
near Llangollen
Llangollen () is a town and community, situated on the River Dee, in Denbighshire, Wales. Its riverside location forms the edge of the Berwyn range, and the Dee Valley section of the Clwydian Range and Dee Valley Area of Outstanding Natural Bea ...
. 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 (b
Go Below
, Llechwedd
Zip World
an
Llechwedd/Quarry Tours Ltd
and Cwmorthin (Go Below).
The lower levels of many mines are now flooded and collapses are commonplace; for example, the hillside above the Rhosydd workings has many pits where the roofs of the chambers below have collapsed.
Other slate producing areas in Great Britain
The most significant non-Welsh British slate industry is that of Cornwall
Cornwall (; kw, Kernow ) is a historic county and ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people. Cornwall is bordered to the north and west by the Atlantic ...
and Devon
Devon ( , historically known as Devonshire , ) is a ceremonial and non-metropolitan county in South West England. The most populous settlement in Devon is the city of Plymouth, followed by Devon's county town, the city of Exeter. Devo ...
where the Delabole Quarry
Delabole ( kw, Delyow Boll) is a large village and civil parish in north Cornwall, England, UK. It is situated approximately two miles (3 km) west of Camelford.
The village of Delabole came into existence in the early 20th-century; it is ...
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 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
Cumbria ( ) is a ceremonial and non-metropolitan county in North West England, bordering Scotland. The county and Cumbria County Council, its local government, came into existence in 1974 after the passage of the Local Government Act 1972. C ...
. 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:
* Broughton Moor
* Old Man Complex (Coniston); Cove Quarries (south of Coniston Old Man)
* Elterwater Quarries
* Hodge Close
* Honister Slate Mine
The Honister Slate Mine in Cumbria is the last working slate mine in England. Quarrying for Westmorland green slate has been taking place in the area since 1728. Apart from the mining it is also a popular tourist attraction in the Lake Distr ...
(including Yew Crag and Dubs)
* Kentmere Workings
* Kirkby Moor (Burlington Slate Quarries
Kirkby Slate Quarries, formally known as Burlington Slate Quarries, are located near Kirkby-in-Furness in Cumbria, England. The quarries have produced a characteristic blue-grey slate for hundreds of years, with large-scale production starting in ...
)
* Petts, Kirkstone
* Little Langdale Quarries
* Skiddaw Slate
Skiddaw slate is an early Ordovician metamorphosed sedimentary rock, as first identified on the slopes of Skiddaw in the English Lake District.
The base of this series is unknown. The thickness could, therefore, amount to several thousand feet of ...
* Tilberthwaite
* Common Wood, Ulpha
Slate was also quarried in Scotland.
Slate industry in North America
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 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
The Taconic Mountains or Taconic Range () are a range of the Appalachian Mountains, running along the eastern border of New York State and adjacent New England from northwest Connecticut to western Massachusetts, north to central western Vermont. ...
region of Vermont
Vermont () is a state in the northeast New England region of the United States. Vermont is bordered by the states of Massachusetts to the south, New Hampshire to the east, and New York to the west, and the Canadian province of Quebec to ...
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 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 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 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
Granville is a town on the eastern border of Washington County, New York, United States, abutting Rutland County, Vermont. It is part of the Glens Falls Metropolitan Statistical Area. The town population was 6,215 at the 2020 census.
The town ...
) is well known for its slate. Slate 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 the oldest quarries in America continues to quarry slate in Buckingham County, Virginia
Buckingham County is a rural United States county located in the Commonwealth of Virginia, and containing the geographic center of the state. Buckingham County is part of the Piedmont region of Virginia, and the county seat is Buckingham.
...
. Their trademark Buckingham Slate Buckingham Slate is quarried in Buckingham County, Virginia, in the town of Arvonia. This natural stone has a distinct gray/blue/black color and glistens due to its mica content. One of the highest quality slates in the world, this unfading slate ha ...
has been continually quarried since the 18th century and has a distinct, unfading blue/black color and Mica sheen. Buckingham Slate Buckingham Slate is quarried in Buckingham County, Virginia, in the town of Arvonia. This natural stone has a distinct gray/blue/black color and glistens due to its mica content. One of the highest quality slates in the world, this unfading slate ha ...
is used on many Federal buildings in the Washington, D.C.
)
, image_skyline =
, image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...
area.
Large scale slate quarrying also took place around the town of Monson, Maine
Monson is a town in Piscataquis County, Maine, United States. The population was 609 at the 2020 census. The town is located on Route 15 which is a significant route north into the well known Moosehead Lake Region, to which Monson can be consid ...
where an extensive series of quarries flourished from 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
Inuit (; iu, ᐃᓄᐃᑦ 'the people', singular: Inuk, , dual: Inuuk, ) are a group of culturally similar indigenous peoples inhabiting the Arctic and subarctic regions of Greenland, Labrador, Quebec, Nunavut, the Northwest Territories ...
to make the blades for ulu
An ulu ( iu, ᐅᓗ, plural: ''uluit'', 'woman's knife') is an all-purpose knife traditionally used by Inuit, Iñupiat, Yupik peoples, Yupik, and Aleut women. It is utilized in applications as diverse as skinning and cleaning animals, cutting a c ...
s.
Slate industry in Brazil
95% of the slate extraction in Brazil comes from Minas Gerais
Minas Gerais () is a state in Southeastern Brazil. It ranks as the second most populous, the third by gross domestic product (GDP), and the fourth largest by area in the country. The state's capital and largest city, Belo Horizonte (literally ...
. 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 the realignment of minerals during metamorphism. This realignment, known as ‘schistosity’, bears no relationship to the original horizontal bedding planes
.[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]
Brazilian Slate Report
, retrieved on 04/02/2010
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 the UK, are not entitled to bear the CE mark
On commercial products, the letters CE (as the logo ) mean that the manufacturer or importer affirms the good's conformity with European health, safety, and environmental protection standards. It is not a quality indicator or a certificat ...
. 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.[
]
See also
* British industrial narrow gauge railways
British industrial narrow-gauge railways are narrow-gauge railways in the United Kingdom and the Isle of Man that were primarily built to serve one or more industries. Some offered passenger services for employees or workmen, but they did not run p ...
* British narrow gauge slate railways
* Mine exploration
Mine exploration is a hobby in which people visit abandoned mines, quarries, and sometimes operational mines. Enthusiasts usually engage in such activities for the purpose of exploration and documentation, sometimes through the use of surveyin ...
References
Further reading
*
*
*
External links
Bal Maidens & Mining Women
;British Isles
History of the Welsh slate industry
— bilingual site focusing on Welsh slate
Aerial photographs of slate quarries in Wales
* http://www.darkplaces.co.uk
* http://www.aditnow.co.uk
* http://www.mine-explorer.co.uk/
* http://www.mineexplorer.org.uk/
;Outside the British Isles
Fell Exhibition Slate Mine
— near Trier (Mosel), Germany
Granville Slate Museum
Buckingham Slate
Galician and Spanish Slate
{{DEFAULTSORT:Slate Industry
Slate industry,