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Yorkstone
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Yorkstone or York stone is a variety of sandstone, specifically from quarries in Yorkshire that have been worked since the middle ages.[1] Yorkstone is a tight grained, Carboniferous sedimentary rock. The stone consists of quartz, mica, feldspar, clay and iron oxides.
The ratio of quartz to mica varies considerably. The stone can be split along mica-rich layers: it has a slaty cleavage and may therefore be called sandstone slate.[2] Formerly riven (split with a chisel along the bedding planes between the sedimentary layers), it is now also often sawn. It is used for flagstones and for building walls.[3][4]
Known for its hard-wearing and durable qualities, Yorkstone has been used in a wide array of building, construction and landscaping applications around the world for many years. In Yorkshire, split stones called thackstone (Scots thack, English thatch) were employed as roofing. The traditional London paving stone has been cut and pressed from quarries in Holmfirth, West Yorkshire. Yorkshire Stone is most commonly used for paving and garden walls, but it is also a popular choice for new builds as well as home extensions and conversions due to its durability to harsh weather conditions.[5]
The colour of Yorkstone depends on the minerals within its makeup and differs throughout the quarries from which it is mined. It also depends on the age of the stone and turns darker with weathering. Reused Yorkstone paving, salvaged from demolished sites, is valued for its naturally weathered surfaces. Reclaimed Yorkshire stone is popular for its colouring and for environmentally friendly builds.
Yorkstone often shows features such as laminations with cross bedding, and rusty Liesegang bands.[6]
See also
[edit]References
[edit]
Wikimedia Commons has media related to Yorkstone.
- ^ Gould, Kate (29 February 2012). "Designing small gardens: choosing stones". The Guardian. Retrieved 9 April 2014.
- ^ Blumenbach, Johann Friedrich; Gore, Richard Thomas. A manual of the elements of natural history [electronic resource] (PDF). p. 360.
The true Sandstone Slate has commonly intermixed with it Mica, by which it is also generally traversed on its slaty fracture, as in the English Yorkstone, Bremingstone, &c. The proportion of Quartz to Mica, however, varies considerably as well with regard to the quantity as to the distribution.
- ^ Articles apparently produced by Dermot Kennedy at http://www.cbstonesales.co.uk/, and also published in 2011 on Ezinearticles.com: "What is Yorkstone?"., "Making Sawn Yorkstone Paving"., "Making Riven Yorkstone Paving". "About Yorkstone Walling".
- ^ "Building Stones 3 – Sedimentary rocks: How do the sedimentary rocks used for building stones differ?" (PDF). Earthlearningidea.
- ^ "About Abacus Stone Sales | Leading Supplier of New and Reclaimed Yorkshire Stone". Abacus Stone Sales. Retrieved 17 September 2020.
- ^ Siddall, Ruth; Kirk, Wendy. "The Urban Geology of UCL and the University of London's Bloomsbury Campus" (PDF). Urban Geology in London. University of London.
Yorkstone
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Geology
Formation
Yorkstone, a distinctive Carboniferous sandstone, originated during the Namurian stage of the period, approximately 326 to 315 million years ago, within the Pennine Basin of northern England. This basin formed as a post-rift sag structure following earlier tectonic extension, creating a subsiding depositional area influenced by surrounding highlands such as the Southern Uplands and Wales-Brabant Massif. Sediments accumulated in this setting as part of the broader Carboniferous succession, with Yorkstone specifically tied to the Millstone Grit Group, a sequence of coarse-grained sandstones that filled the basin amid fluctuating sea levels and tectonic stability.[5][6] The formation occurred in a dynamic deltaic environment dominated by fluvial and tidal influences, where ancient river systems drained southward from northern source areas, including regions now in Scandinavia and Greenland. These rivers carried quartz-rich sands into the basin, depositing them in prograding delta lobes, braided channels, and turbidite systems, interspersed with marine incursions that introduced mudstones and shales. Over time, the sands underwent diagenesis through burial, involving mechanical compaction under increasing overburden pressures and chemical cementation primarily by silica, which contributed to the stone's characteristic tight-grained texture. This process transformed loose sediments into durable, cross-bedded sandstones, with thicknesses varying from tens to hundreds of meters depending on local depositional energy.[5][6][7] Stratigraphically, Yorkstone occupies key positions within the Millstone Grit Group, particularly in beds like the Rough Rock and other gritstone units, which overlie finer-grained shales of the Bowland Shale Group. These layers exhibit variations in thickness and bedding patterns reflective of ancient fluvial systems, with coarser, thicker accumulations in proximal deltaic zones near Yorkshire and thinner, finer equivalents eastward. The group's cyclic nature, driven by eustatic sea-level changes, underscores the interplay of tectonic subsidence and sediment supply that shaped the Pennine Basin's depositional history.[5][6]Composition
Yorkstone is a fine- to medium-grained sandstone of Carboniferous age, primarily composed of quartz grains that dominate its framework, constituting up to 90% of the mineral content, alongside subordinate feldspar, mica, clay minerals such as kaolinite, and iron oxides.[8][9] The presence of these accessory minerals, particularly mica and iron oxides, imparts specific textural and color properties to the stone.[8] The grain structure of Yorkstone is characteristically tight-grained, with subangular to subrounded sand particles that exhibit sedimentary features including slaty cleavage, parallel laminations, cross-bedding, and occasional Liesegang banding patterns formed by rhythmic precipitation of iron oxides or other minerals.[9] These structural elements arise from the depositional environment of ancient river deltas and contribute to the stone's ability to be split into thin, even flags.[9] Compositional variations, particularly in the quartz-to-mica ratio, lead to distinct subtypes such as buff Yorkstone, which has higher mica content, and grey Yorkstone, richer in quartz; iron oxides further influence coloration, ranging from pale buff to darker grey or reddish tones depending on oxidation state.[8][9] Petrographically, the quartz and other grains are cemented by silica or subordinate calcite, which binds the framework tightly and results in low porosity, typically 5-10%, enhancing the stone's durability against weathering.[8][10][11]History
Medieval Origins
The extraction of Yorkstone, a durable sandstone from the Carboniferous Millstone Grit Group, began in the medieval period in various Yorkshire locations, with evidence of quarrying activities dating to the 12th century. Early sites included those near Leeds, such as the Bramley Fall quarries, where stone was sourced for the construction of Kirkstall Abbey, a Cistercian monastery founded in 1152 that utilized local Yorkstone for its walls and floors. Similarly, quarries around Huddersfield, including areas like Elland Edge and Rastrick, show signs of medieval exploitation for building materials, reflecting the stone's suitability for splitting along natural bedding planes.[12][13][1] Traditional medieval methods relied on manual labor to rive the stone, exploiting its fine lamination for producing flags and slabs without advanced machinery. Workers used basic tools such as wedges, hammers, and picks to channel and split blocks along bedding planes, a technique known as hand-riving that produced thin, even slabs ideal for local applications; this process was labor-intensive and capitalized on the stone's geological uniformity for clean fractures. Percussive splitting with plugs and feathers—metal wedges inserted into drilled holes—further aided in separating larger pieces, maintaining the stone's integrity for practical use.[12][14] Initial applications of Yorkstone were predominantly local and focused on ecclesiastical architecture, where it served as flooring, walling, and internal features in structures like Kirkstall Abbey and other monastic buildings in the region. In urban settings, such as the city of York, the stone appeared in early paving efforts for streets and churchyards during the medieval period. These uses underscored Yorkstone's role in enhancing durability and aesthetics for religious and communal spaces.[12][15][16] Socio-economically, medieval Yorkstone production was tied to regional trade networks managed by emerging craft guilds, including masons' associations that regulated quality and workmanship in Yorkshire's burgeoning urban centers. Transport was limited by the stone's weight, relying on packhorses along rugged Pennine routes to deliver slabs to nearby sites like Leeds and York, restricting supply to a regional scale and supporting local monastic and civic development without extensive long-distance commerce. This localized economy highlighted the stone's integral place in medieval Yorkshire's building traditions, fostering self-sufficiency amid feudal structures.[12][17][18]Industrial Development
The Industrial Revolution marked a pivotal expansion in Yorkstone quarrying, particularly from 1780 to 1840, as rapid urbanization in West Yorkshire and surrounding regions drove demand for durable sandstone in constructing mills, warehouses, and worker housing. This surge was facilitated by improvements in transport infrastructure, including canals like the Leeds and Liverpool Canal (opened 1816) and later railways, which enabled efficient movement of heavy stone blocks from inland quarries to urban centers. By the mid-19th century, production peaked, with quarries operating at scale to supply not only local textile boomtowns like Bradford and Leeds but also distant markets, reflecting the stone's growing role in Britain's industrial landscape.[19][20] Technological innovations transformed extraction and processing, shifting from labor-intensive manual methods to mechanized operations. The introduction of steam-powered saws in the early 19th century allowed for precise cutting of Yorkstone using abrasive sand and water lubrication, enabling the production of uniform sawn slabs that replaced traditional riven (hand-split) stone for paving and ashlar work. Steam cranes further enhanced efficiency by facilitating the lifting and transport of large blocks within quarries, reducing reliance on manual hauling and supporting larger-scale output. These advances, adopted widely in West Yorkshire quarries by the 1840s, improved productivity amid rising demand but also accelerated the depletion of accessible deposits.[19][21] Economically, the Yorkstone industry became a cornerstone of West Yorkshire's workforce, employing thousands in quarrying, dressing, and transport. In Bradford alone, approximately 6,000 men were engaged in stone-getting and dressing by 1873, contributing to the region's industrial diversification alongside textiles. Exports expanded significantly, with Yorkstone flags shipped to London for paving streets and public spaces—such as Trafalgar Square—and even to imperial projects overseas, underscoring its status as a premium building material. This trade bolstered local economies through associated industries like rail freight but also highlighted dependencies on volatile construction cycles.[22][21] Despite these gains, the sector faced severe challenges, including hazardous labor conditions in deep, poorly ventilated quarries where workers endured long hours, dust inhalation, and risks of rockfalls. Reports from the 1840s documented exploitative practices, with children as young as eight assisting in stone handling under grueling circumstances, prompting early calls for reform. Environmentally, operations generated substantial waste rock piles known as delphs—accumulations of overburden and rejects that scarred moorland landscapes and disrupted local drainage, though their small-scale nature limited broader ecological damage compared to coal mining. These issues persisted into the late 19th century, underscoring the human and environmental costs of industrial-scale quarrying.[23][24]Quarrying and Production
Major Sites
The primary quarries for Yorkstone, a type of Carboniferous sandstone from the Millstone Grit group, are concentrated in West Yorkshire, particularly around the Pennine hills where suitable beds outcrop. These sites target thick, durable sandstone layers formed during the Upper Carboniferous period, with bed thicknesses varying from approximately 0.6 to 0.9 meters (2-3 feet) in many locations, allowing for the extraction of large blocks suitable for splitting into paving flags and other products.[25] Operations typically involve open-pit or shelf quarrying on hillsides, though some historical sites in the Elland area incorporated underground mining from the mid-19th century onward using steam-powered equipment to access deeper beds.[26] Elland Edge, located near Halifax, stands as one of the oldest and most significant Yorkstone production areas, with quarrying documented from at least the early 17th century for masonry, roofing, and especially paving stones. In the 19th century, Elland quarries played a pivotal role in supplying flags for urban paving projects across Britain, including extensive use in London streets due to the stone's fine grain and weather resistance; local records highlight its export via nearby transport networks. Nearby districts, such as around Ainley Top, contributed to this output through smaller satellite quarries exploiting similar Millstone Grit exposures, though many have since consolidated or ceased operations.[1][13] In the Holmfirth area, Upper and Lower Holmfirth quarries, including Hillhouse Edge Quarry near Cartworth Moor, remain key hubs for premium Yorkstone extraction, focusing on the Millstone Grit's consistent bedding for high-quality flags and dimension stone. Established family operations here, such as Grahams Quarries dating back to 1918, emphasize sustainable open-pit methods on hillside outcrops, yielding blocks up to 3 meters in length from beds averaging 0.9 meters thick. These sites benefit from their proximity to historical transport routes, including the Huddersfield Canal, which facilitated stone shipment during the Industrial Revolution.[27][28] Huddersfield districts host several enduring production centers, exemplified by Crosland Hill Quarry, operational since 1854 and covering over 350 acres of Pennine hillside. This open-pit site extracts hard Yorkstone from thick Millstone Grit layers, producing aggregates and finished stone for national distribution. Nearby, Cromwell Quarry in Shepley targets buff-colored beds for paving, operated by Marshalls Plc as of 2025. Current active operations in the broader Holmfirth vicinity continue to supply modern demand while adhering to environmental regulations.[28][29][30][31]Extraction Techniques
Yorkstone extraction has historically relied on traditional riving techniques, where large blocks are split along natural cleavages in the stone's bedding planes, often using hand tools such as chisels, hammers, wedges, and plugs and feathers inserted into drilled holes to propagate cracks without excessive force.[32][1] This method exploits the stone's inherent lamination from mica-rich horizons in the Carboniferous sandstone formations, allowing for the production of thin flags suitable for paving while minimizing waste from irregular fractures.[1] In contemporary quarrying, extraction incorporates mechanized approaches to handle larger volumes efficiently, including hydraulic excavators equipped with breakers or peckers to pry blocks free along natural joints, supplemented by controlled blasting in limited bursts where necessary to access deeper beds.[33] Diamond wire sawing has become a dominant modern technique, employing steel wires embedded with diamond segments to slice through the rock face with precision, reducing dust and vibration compared to traditional methods and enabling the recovery of blocks up to 10 tons in weight.[33][32] Hydraulic splitting tools are also used post-extraction to divide oversized blocks, ensuring manageable sizes for transport and further processing.[33] Following extraction, raw blocks undergo processing to yield finished products, typically sawn into flags of 2-3 inches (50-75 mm) thickness using diamond-fitted circular or wire saws calibrated for optimal yield based on computed surface areas.[33][32] For a riven texture mimicking traditional hand-split surfaces, sawn flags may receive thermal finishing, where a high-temperature flame is applied to the moistened stone to cause superficial flaking and create a textured, slip-resistant profile.[34] Alternatively, surfaces can be polished for smoother applications, with edges fettled or calibrated to precise dimensions using bridge saws.[32] Sustainability efforts in Yorkstone quarrying emphasize waste minimization and resource stewardship, with unsuitable or offcut stone reclaimed by crushing it into aggregate for secondary uses such as road base or concrete production, thereby reducing landfill disposal.[33] Operators adhere to geological surveys from bodies like the British Geological Survey to select optimal beds, avoiding low-quality layers and preserving viable reserves for long-term extraction.[7] These practices align with broader environmental goals, including overburden management and habitat restoration at quarry sites.[33]Physical Properties
Mechanical Attributes
Yorkstone exhibits robust mechanical properties that make it suitable for demanding structural applications, particularly in paving and load-bearing elements. Its compressive strength typically ranges from 70 to 120 MPa, depending on the specific quarry and processing, allowing it to withstand significant vertical loads without failure.[35][36] Flexural strength for Yorkstone flags varies between 10 and 25 MPa, providing adequate resistance to bending stresses in horizontal installations such as pathways and floors.[35][36] These values are derived from standardized testing, ensuring consistency across production batches. The stone's density falls within 2.5 to 2.6 g/cm³, contributing to its stability and load distribution capabilities.[35] Porosity is relatively low at around 5-6%, paired with water absorption rates of 1-4%, which minimizes moisture ingress and enhances frost resistance by reducing the risk of freeze-thaw damage.[35][36] On the Mohs scale, Yorkstone registers 6-7, attributable to its high quartz content, which imparts good scratch and wear resistance.[37] Abrasion resistance is a key attribute for high-traffic surfaces, with Boehme test results showing wear depths of 18-20 mm under standardized conditions (EN 14157), indicating durability comparable to other premium sandstones.[35] Yorkstone paving complies with BS EN 1341, which mandates performance criteria for external slabs, including slip resistance typically achieving an R11 rating via pendulum testing (wet PTV values of 70-99 depending on finish).[35][38]| Property | Typical Value | Test Standard | Source |
|---|---|---|---|
| Compressive Strength | 70-120 MPa | EN 1926 | Manufacturer datasheets |
| Flexural Strength | 10-25 MPa | EN 12372 | Manufacturer datasheets |
| Density | 2.5-2.6 g/cm³ | EN 1936 | Manufacturer datasheets |
| Water Absorption | 1-4% | EN 13755 | Manufacturer datasheets |
| Abrasion Resistance | 18-20 mm (wear depth) | EN 14157 | Manufacturer datasheets |
| Slip Resistance (wet) | R11 (PTV 70-99) | BS EN 14231 / EN 1341 | Manufacturer datasheets |