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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.
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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.
706:. 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 .
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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.
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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
649:, 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.
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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
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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,
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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
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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
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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
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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
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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
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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.
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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
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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.
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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.
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714:. 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.
48:. The major slate mining region in the United Kingdom is the Lake district, with Honister slate mine being the last working slate mine, the only producers of the world famous Westmorland greenslate. In the remainder of Continental Europe and the
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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:
532:. 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:
928:
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’
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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
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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.
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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.
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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.
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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
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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
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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.
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environment, the source of the sedimentary material from which the slate is comprised, and the chemical and physical conditions prevalent during the
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41:. Common uses for slate include as a roofing material, a flooring material, gravestones and memorial tablets, and electrical insulation.
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Most underground slate mines in north Wales were closed by the 1960s although some open-cast quarries have remained open, including the
174:. 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
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Ninety percent of Europe's natural slate used for roofing originates from the slate industry in Spain, with the region of
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The lower levels of many mines are now flooded and collapses are commonplace; for example, the hillside above the
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443:(which is owned by the Llechwedd tourist mine) in 1999 although opencast quarrying continues at this location.
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The slate deposits in this region of northern Spain are over 500 million years old, having formed during the
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Slate mines are found around the world. 90% of Europe's natural slate used for roofing originates from the
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has been continually quarried since the 18th century and has a distinct, unfading blue/black color and
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in North Wales began with the opening of the Cae Braich y Cafn quarry, later to become the
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Historical and adventurous underground tours are provided at several mines including
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Underground Clwyd: A Pictorial Expedition into the Nether Regions of Northeast Wales
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period. The colour and texture of the slate produced is largely dependent upon the
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are important producing regions. The Slate Valley area, centering on a town called
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John T F Turner – A Familiar Description of the Old Delabole Slate Quarries, 1865
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workings has many pits where the roofs of the chambers below have collapsed.
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Curious Clwyd: A Second Photographic Album of Oddities from Northeast Wales
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Slate has been quarried in north Wales for almost two millennia with the
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308:. Dating from the 12th century it is thought to be the oldest in Wales.
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of the wreck of a 16th-century wooden ship carrying finished slates.
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In Galicia, the larger slate production companies are concentrated in
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Old Man Complex (Coniston); Cove Quarries (south of Coniston Old Man)
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can metamorphose into slate; sometimes the fossils may remain intact
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and magmatic activity, leading to a unique geological development.
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The most significant non-Welsh British slate industry is that of
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Large scale slate quarrying also took place around the town of
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from some of the quarries near the coasts in the 19th century.
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284:. The largest slate producing quarry in the world. Bought by
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645:) is well known for its slate. Slate was quarried in 1839 at
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Another cluster of mines were found in mid Wales centered on
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used wedge-shaped trolleys to move trucks between levels.
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counties in Pennsylvania all still have active quarries.
439:. The final large-scale underground working to close was
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Slate is also found in the Arctic and was used by the
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workings and the workings were entirely underground.
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process. The region has been subjected to periods of
345:– now partially untopped as an opencast working by
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16:Industry of the extraction and processing of slate
755:European Association of Mining Industries website
702:95% of the slate extraction in Brazil comes from
371:area which produced a much darker "black" slate:
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877:"English, Scottish, Irish and Australian slate"
367:There were also a number of slate mines in the
136:, with other important sites being situated in
1039:Aerial photographs of slate quarries in Wales
895:Slate in Pennsylvania (1933) by Charles Behre
324:– now open to the public as a "tourist mine".
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970:
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652:Additionally, one of the oldest quarries in
484:Other slate producing areas in Great Britain
27:related to the extraction and processing of
992:A history of the North Wales Slate Industry
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170:An important use of Spanish slate is as a
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672:is used on many Federal buildings in the
273:to gain access to the bottom of the pit:
1035:— bilingual site focusing on Welsh slate
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724:British industrial narrow gauge railways
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399:in the Dulas Valley to the mines around
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490:Narrow-gauge slate railways in England
857:. Go Below Underground Adventures Ltd
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582:Slate was also quarried in Scotland.
403:in the east. Slate was also mined in
125:being the primary production source.
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225:produced half of this between them.
1028:History of the Welsh slate industry
773:Galician and Spanish Slate website
729:British narrow gauge slate railways
528:There are considerable workings in
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31:. Slate is either quarried from a
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521:Slate has also been quarried at
1064:http://www.mineexplorer.org.uk/
1059:http://www.mine-explorer.co.uk/
586:Slate industry in North America
395:in the west through Corris and
1078:— near Trier (Mosel), Germany
1016:Bal Maidens & Mining Women
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96:: section Slate extraction.)
37:or reached by tunneling in a
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1049:http://www.darkplaces.co.uk
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658:Buckingham County, Virginia
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1092:Galician and Spanish Slate
1076:Fell Exhibition Slate Mine
851:"Hero Extreme Caving Trip"
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467:Llechwedd/Quarry Tours Ltd
423:and the untopping work at
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186:
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1070:Outside the British Isles
939:, retrieved on 04/02/2010
804:"Zip World Slate Caverns"
784:. Retrieved on 26/01/2010
559:Burlington Slate Quarries
431:. Work also continues at
1054:http://www.aditnow.co.uk
698:Slate industry in Brazil
567:Little Langdale Quarries
329:National Gallery, London
764:retrieved on 26/01/2010
690:to make the blades for
379:Deeside and Moel Fferna
209:Large-scale commercial
189:Slate industry in Wales
183:Slate industry in Wales
117:Slate industry in Spain
111:Slate industry in Spain
46:Slate Industry in Spain
1083:Granville Slate Museum
930:Brazilian Slate Report
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72:, the Slate Valley of
994:. David and Charles.
990:Jean Lindsay (1974).
971:Gordon Emery (1996).
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331:to store artworks in
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327:Manod – used by the
68:, the east coast of
660:. Their trademark
643:Granville, New York
549:Honister Slate Mine
542:Elterwater Quarries
525:in Leicestershire.
347:Alfred McAlpine plc
286:Alfred McAlpine plc
952:Cris Ebbs (1998).
935:2010-02-14 at the
831:. Quarry Tours Ltd
780:2010-01-23 at the
760:2010-01-30 at the
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578:Common Wood, Ulpha
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441:Maenofferen Quarry
429:Blaenau Ffestiniog
314:Blaenau Ffestiniog
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641:(the district of
608:Taconic Mountains
554:Kentmere Workings
261:Significant mines
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1087:Buckingham Slate
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975:. Gordon Emery.
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734:Mine exploration
674:Washington, D.C.
670:Buckingham Slate
662:Buckingham Slate
594:Slate quarry at
564:Petts, Kirkstone
322:Llechwedd quarry
172:roofing material
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70:Newfoundland
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829:"Llechwedd"
808:Google Maps
628:Northampton
545:Hodge Close
501:in Cornwall
409:Maenclochog
338:Maenofferen
912:2011-04-06
882:2009-05-20
740:References
647:Fair Haven
610:region of
513:where the
488:See also:
437:Llangollen
369:Llangollen
194:Background
153:Palaeozoic
142:Ortigueira
130:Valdeorras
39:slate mine
1033:Slatesite
620:Lancaster
523:Swithland
471:Cwmorthin
463:Zip World
459:Llechwedd
352:Cwmorthin
296:Llanberis
265:In North
200:Segontium
165:volcanism
146:Mondoñedo
90:Granville
1101:Category
933:Archived
855:Go Below
778:Archived
758:Archived
718:See also
668:sheen.
616:New York
507:Cornwall
455:Go Below
451:Rhiwbach
288:in 1964.
282:Bethesda
223:Dinorwic
219:Bethesda
157:tectonic
86:Virginia
78:New York
54:Portugal
50:Americas
25:industry
906:"Slate"
712:CE mark
654:America
612:Vermont
530:Cumbria
478:Rhosydd
425:Oakeley
415:Remains
383:Penarth
362:Croesor
357:Rhosydd
343:Oakeley
312:In the
267:Gwynedd
138:Quiroga
134:Ourense
123:Galicia
74:Vermont
62:Germany
23:is the
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676:area.
624:Lehigh
596:Monson
469:) and
433:Berwyn
389:Corris
375:Berwyn
84:, and
66:Brazil
688:Inuit
600:Maine
511:Devon
435:near
393:Tywyn
217:near
176:frost
104:Shale
94:Slate
58:Italy
29:slate
996:ISBN
977:ISBN
958:ISBN
863:2020
837:2020
815:2020
692:ulus
666:Mica
637:The
626:and
614:and
509:and
465:and
453:(by
271:adit
144:and
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457:),
427:in
132:in
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