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57-671: Vale of Wardour : Tisbury Member, Wockley Member, Chilmark Member Portland stone is a limestone geological formation (formally named the Portland Stone Formation ) dating to the Tithonian age of the Late Jurassic that is quarried on the Isle of Portland in Dorset , England. The quarries are cut in beds of white-grey limestone separated by chert beds. It has been used extensively as

114-474: A Site of Special Scientific Interest (SSSI). Albion Stone PLC now extract all their stone through mining which dramatically reduces the impact on the environment and local residents. Jordan's Mine is currently the biggest mine on Portland. Bowers Quarry has been operational since the late 18th century. It has been leased from The Crown Estate since 1979, and in 2002 it became the site of the first Portland stone mine by Albion Stone PLC. Extraction from this site

171-572: A Portland stone façade to complete its stripped Classical design. After the Second World War (1939–1945), the bombed out centres of many English towns and cities, such as Plymouth , Bristol , Coventry and London were reconstructed using vast facades of Portland stone. Many of the buildings surrounding the flagship Parkinson Building at the University of Leeds are clad in Portland stone, including

228-655: A building stone throughout the British Isles , notably in major public buildings in London such as St Paul's Cathedral and Buckingham Palace . Portland stone is also exported to many countries, being used for example at the United Nations headquarters in New York City. Portland stone formed in a marine environment, on the floor of a shallow, warm, sub-tropical sea probably near land (as evidenced by fossilised driftwood, which

285-493: A machine. Slots are cut into the top, bottom, sides and middle of the stone. A flat steel pillow is inserted into the middle cut and slowly inflated with water. The stones are gently broken off at the back without placing any stress on the resulting blocks. This method of extraction is significantly more expensive than blasting, but results in a higher yield thereby saving valuable reserves for future generations. The environmental benefits are substantial as mining significantly reduces

342-528: A material which he hoped looked like the famous Portland building stone. Vale of Wardour The Vale of Wardour encompasses the valley of the River Nadder in the county of Wiltshire , England . The Vale of Wardour lies east of the town of Shaftesbury and is a relatively small but varied landscape. Named after the village of Wardour , its main river is the Nadder which flows from west to east through

399-415: A metal coating, typically of nickel electroplated onto a steel blade base, can be made to be very thin—blades can be tens of micrometres thick, for use in precise cuttings. Vacuum brazed diamond saw blades are manufactured by brazing synthetic diamond particles to the outside edge of the circular saw blade in a vacuum brazing furnace . All of the diamond particles are fully exposed and fastened on

456-540: A mine as an extension from an existing quarry). Albion Stone Plc began the process to open this mine in 2015 and reserves are estimated to last for 50 years (2066). Independent Quarry and Admiralty Quarry are both owned by The Crown Estate and have been leased since 1982. These quarries have been worked since the mid-19th century with the final dimension stones coming out of Independent in 2006, although some stocks of Portland stone block still remain. Coombefield Quarry , located near Southwell has been open cast quarried over

513-647: A popularity amongst masons and architects that has endured ever since. The East side of Buckingham Palace , the official London residence of King Charles III , including the balcony, was faced with Portland stone, first in 1854 and again in 1913. The Victoria Memorial (unveiled 1911) is also made of it. Inigo Jones (1573–1652) used Portland stone to build the Banqueting Hall in Whitehall in 1620. Sir Christopher Wren used nearly one million cubic feet to rebuild St. Paul's Cathedral and many other minor churches after

570-470: A serious safety hazard. A laser melts and combines the metal of the diamond segment and the steel core creating a stronger weld, which can hold the segments even in high temperatures, meaning that laser welded diamond blades can be used to cut many types of stone without water cooling. However, when cutting very hard or abrasive materials, e.g., concrete containing reinforcing rebar, laser welded diamond blades should also be used with adequate water. Otherwise, it

627-400: A single continuous rim for smoother cutting. The type of core that can be used depends on the type of materials that the diamond blade is designed to cut. Generally, there are three types of sintered metal-bonded diamond blades according to their manufacturing methods: wholly sintered diamond blades, silver brazed diamond blades and laser welded diamond blades. A wholly sintered diamond blade

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684-402: A smoother finish. Larger diamond grits will provide a higher cutting speed, but will be more likely to cause chipping, burring, or cracking. Fire departments sometimes use vacuum brazed saw blades and require blades to be made with a very large diamond grit, to tear through material quickly. An intermediate grit size is used by the production industry. Sintered metal-bonded diamond blades are

741-451: Is Rufus Castle at Church Ope Cove, Portland. The original structure was probably built around 1080, rebuilt around 1259 and rebuilt yet again around 1450, which is the likely date of the walls seen today. The first known Portland stone quarries were situated on the northeastern coast of the Isle, close to Rufus Castle, where huge landslips made the stone more easily accessible, and the proximity of

798-721: Is also built with Portland stone, as are the public buildings in Cardiff's civic centre. Architect Charles Holden significantly used the stone in his major commissions of the 1920s and 1930s, including Senate House and 55 Broadway , the home of the London Underground . The 1929 steel framed building (one of the first erected in the United Kingdom) of the London School of Hygiene & Tropical Medicine , based in Keppel Street, has

855-462: Is also worth noting that stone tends to split much more easily parallel to bedding planes (called graining) than perpendicular to them (called cutting). In 1999, Italian stone cutting equipment, originally designed for use in Tuscany 's marble quarries was imported by Albion Stone and applied to the extraction of Portland stone. This new technology eliminated the need for blasting, significantly improved

912-413: Is made by putting the steel core, together with the diamonds and the metal bond materials, into a mold and then sintering it in a sintering furnace equipment. Consequently, the diameter of wholly sintered diamond blades is not very large, normally not more than 400 millimetres (16 in). Because it is participating in the sintering process, the steel core cannot be quenched, so the hardness and strength of

969-422: Is not uncommon). When seawater is warmed by the sun, its capacity to hold dissolved gas is reduced; consequently, dissolved carbon dioxide (CO 2 ) is released into the atmosphere as a gas. Calcium and bicarbonate ions within the water are then able to combine, to form calcium carbonate (CaCO 3 ) as a precipitate. The process of limescale build up in a kettle in hard-water areas is similar. Calcium carbonate

1026-475: Is now completely underground, with the original Bowers Mine in the extreme southern end of the quarry and the High Wall Extraction on the eastern and south east boundaries. High Wall Extraction is a series of small mines that extract otherwise wasted stone that sits between the final faces of the quarry and the actual boundary of the site. Stonehills Mine is the first completely new mine on Portland (not

1083-460: Is part of the Inmosthay Quarry in the centre of the island, which also includes Fancy Beach. The quarry has been worked since the late 19th century. Albion Stone leases the southern section from The Crown Estate and purchased the northern part of the site in 2006. The majority of the southern reserves lie under the grounds of the local cricket club. To avoid disturbing the site at surface level,

1140-419: Is possible for the diamond segment itself to break or the steel core below the segment to wear and break, creating serious safety hazards. A diamond blade grinds, rather than cuts, through material. Blades typically have rectangular teeth (segments) which contain diamond crystals embedded throughout the segment for grinding through very hard materials. The bond is a term used for the softness or hardness of

1197-568: Is privately owned by Portland Stone Firms. Open cast quarrying provides quicker extraction of raw block dimension stone whilst maintaining its integrity. The majority of buildings in London today use Portland which has been quarried using the same methods over the last 60 years. Broadcroft Quarry is located on the eastern side of the island and is a part of the open cast quarries used for St Paul's Cathedral. Privately owned by Portland Stone Firms Limited there are over 20 years of reserves left and still being actively quarried. The coastal strip toward

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1254-417: Is the principal constituent of most limestones. Billions of minute crystals of precipitated calcium carbonate (called calcite ) accumulated forming lime mud (called micrite ) which covered the sea floor. Small particles of sand or organic detritus, such as shell fragments, formed a nucleus, which became coated with layers of calcite as they were rolled around in the muddy micrite. Portland stone measures 3.5 on

1311-514: The Great Fire of London in 1666. All of the stone used by Wren was transported by sailing barge from Portland to the centre of London via the sea and then up the Thames. Wren's widespread use of Portland stone firmly established it as London's "local stone" and as one of the best-loved British building stones. Other famous London buildings constructed of Portland stone are The British Museum (1753) with

1368-877: The Michael Sadler Building, the Chemistry and Engineering buildings and the new Laidlaw Library. Oxford typically uses oolitic limestone in its buildings, and the Ashmolean Museum has been refurbished using a large amount of Portland stone. Portland stone has also been used across the world. Examples include the UN building in New York, the Casino Kursaal in Belgium and the Auckland War Memorial Museum . Most of

1425-599: The Mohs scale of mineral hardness . The calcite gradually accumulated (by accretion) around the fragments of shell in concentric layers, forming small balls (of less than 0.5 mm diameter). This process is similar to the way in which a snowball grows in size as it is rolled around in the snow. Over time, countless billions of these balls, known as " ooids " or "ooliths" (from the Greek for "egg-shaped" or "egg-stone"), became partially cemented together (or lithified) by more calcite, to form

1482-639: The "New Build (Modern Non-Load-bearing Stone) Award" in the 2006 Natural Stone Awards. Portland stone has been designated by the International Union of Geological Sciences as a Global Heritage Stone Resource . Following the First World War, Sir Edwin Lutyens used Portland stone (quarried from the bottom of Wakeham) to construct the Cenotaph in London's Whitehall. Erected in 1920, The Cenotaph commemorates

1539-570: The 1930s. Manchester buildings with Portland stone exterior include 100 King Street (1935), Arkwright House (1937), St. James Buildings (1912), Manchester Central Library (1934), Kendal Milne (1939) and Sunlight House (1932). Two of Liverpool's Three Graces , the Cunard Building and the Port of Liverpool Building , are clad in Portland stone which surrounds their reinforced concrete frames. The Nottingham Council House , completed in 1929,

1596-610: The Portlandian, being the first to describe the patch-reef facies and Dorset-wide sedimentation details. Ian West of the School of Ocean and Earth Sciences at Southampton University completed a detailed geological survey of Withies Croft Quarry before the Portland Beds were quarried by Albion Stone plc. Stone has been quarried on Portland since Roman times and was being shipped to London in the 14th century. Extraction as an industry began in

1653-404: The blade can be used in high-load and high-intensity cutting processes with high cutting efficiency and a smaller degree of deformation. Silver brazed diamond blades' diamond segments are brazed to the steel core using a silver solder. These blades can only be used in wet cuttings. If they are used in dry cuttings, the silver solder may melt and the segments can break from the steel core and become

1710-462: The blade from overheating, greatly reduce the amount of harmful dust created by cutting, remove the slurry from the cut, and extend the life of the blade, since diamond is unable to withstand the forces involved at the elevated temperatures involved in dry cutting ceramic and abrasive materials, and will be subject to rapid tool wear and possible failure. When water cannot be used (in, for example, electrical saws), measures should be taken to ensure that

1767-505: The building of Chelsea Barracks , Wilkins Terrace at UCL University College London , St James's Market Haymarket, London and Green Park tube station . Portland stone is prevalent in Manchester despite the historical preferred use of hard-wearing materials, such as Burmantofts and sandstone to resist the harsh industrial environment. Portland stone was mostly used in Manchester during

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1824-418: The company has applied and received permission to extract the stone using mining rather than quarrying techniques. The reserves to the north will be quarried using the diamond bladed cutting machines, hydro bags and wire saws to shape the blocks. This process avoids the use of dusty and noisy blasting as the primary extraction method, thereby protecting the surrounding environment, which has been designated as

1881-445: The core are not very high. This means that these types of diamond blade may deform in high-load and high-intensity cutting processes and can exhibit low cutting efficiency. Silver brazed and laser welded diamond blades do not have this weakness because their diamond segments and steel core are treated separately. The steel core can be quenched and processed with other heat treatments, so its hardness and strength can be high, meaning that

1938-476: The early 17th century, with shipments to London for Inigo Jones ' Banqueting House . Wren 's choice of Portland for the new St Paul's Cathedral was a great boost for the quarries and established Portland as London's choice of building stone. The island was connected by railway to the rest of the country from 1865. Albion Stone PLC has been quarrying and mining Portland stone since 1984. Portland Stone Firms Ltd have been quarrying Portland stone since 1994. Jordans

1995-401: The equipment to be used and the availability of water. Harder materials need a softer bonded segment to allow for continuous diamond exposure. Softer materials like asphalt or freshly poured concrete can use a harder segment to resist the increased wear that softer, abrasive materials create. In addition, the diamonds' grit (size), toughness, and concentration should also match the nature of

2052-413: The exterior cutting edge of the blade instead of being embedded within a metal-diamond mixture. Depending on the manufacturer's recommended blade application, vacuum brazed blades will cut a wide variety of material including concrete , masonry , steel , various irons , plastic , tile , wood and glass . Finer synthetic diamond grits will reduce the chipping of tile and burring of steel and provide

2109-436: The forces necessary to loosen the stone to the point where it can be easily removed using large wheeled loaders . Splitting stone, using pneumatic drills is arduous work and so wire-saws have been introduced into the quarries, replacing much of the plug and feather cutting. Mining in Portland is done by using a room and pillar method. The mine is advanced by extracting the stone using an abrasive tool chain cutter mounted on

2166-507: The horsepower of a saw machine is large, the diamond concentration of the diamond blade should be higher, or the bond should be harder. Higher diamond concentration will decrease the impact on each single diamond in working, while a harder bond will hold the diamonds more firmly. Many blades are designed to operate either wet or dry. However, diamond tools and blades work better when wet, and dry cutting should be limited to situations in which water cannot or should not be used. Water will prevent

2223-455: The impact on wildlife and the local community with reduced noise and dust. Portland's freestone has almost certainly been used as a building material since Roman times. The many well crafted Roman sarcophagi (stone coffins and matching lids, hewn from single large blocks of Portland stone) that have been unearthed locally over the years, testify to the skill of their makers. The earliest known building to be constructed using Portland stone

2280-754: The important civic and administrative buildings which survive from 18th and 19th century Dublin , Ireland, known then as "the second city of the Empire", are of Portland stone, including City Hall (1779), the Houses of Parliament (1767), the Custom House (1791), the National Gallery (1864) and the General Post Office (1818). More recent projects include the BBC Broadcasting House in London, which won

2337-409: The last 80 years and is one of three privately owned quarries by Portland Stone Firms Ltd, the largest landholder on the island. The quarry is nearing the end of its life and will be regenerated as a holiday caravan park to boost local tourism on the island. Perryfield Quarry is found towards the middle of the island and being actively open cast quarried. There are over 20 years of reserves left which

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2394-418: The material to be sawed. For example, when hard materials are cut, the diamonds should be smaller. There are other factors that should be considered when choosing a diamond blade for a particular application. These include the type (manufacturing method) of the blade, the availability of water in the cutting process, the horsepower of the saw, and the acceptable level of noise created by the saw. For example, if

2451-563: The millions of people killed in this and subsequent conflicts. The RAF Bomber Command Memorial in London's Green Park commemorates the 55,573 crew members of the RAF's Bomber Command who were killed between 1939 and 1945. The gravestones for British personnel killed in the First and Second World Wars were made out of Portland stone. The Commonwealth War Graves Commission use Portland Limestone supplier Albion Stone's Portland Basebed. Portland stone

2508-504: The most common type of blade. These blades consist of a steel core (the base is steel plate, unlike that of the wires used in diamond wire saws ) and diamond segments , which are made by combining synthetic diamond crystals with metal powder and then sintering them. The diamond segments are also known as the "cutting teeth" of the blade. The steel core can vary in design. Some cores have spaces (known as gullets) between segments to provide cooling and slurry removal, while others have

2565-790: The new WCEC extension in Portland Roach which was short-listed for the Stirling Prize in 2017, Somerset House (1792), the General Post Office (1829), the Bank of England , the Mansion House and the National Gallery . Tower Bridge is partly clad in Portland stone (along with Cornish granite ). Portland stone was used in 1923 to build the supporting pillar of the Grace Gates at Lord's Cricket Ground . Recently, Portland stone has been used in

2622-481: The numerous phosphatic nodules it contains. This article about a location in Wiltshire is a stub . You can help Misplaced Pages by expanding it . Diamond blade Diamond blades are available in different shapes: Diamond blades designed for specific uses include marble, granite, concrete, asphalt, masonry, and gem-cutting blades. General purpose blades are also available. Blades using diamonds embedded in

2679-428: The oolitic limestone that is called Portland stone. The degree of cementation in Portland stone is such that the stone is sufficiently well cemented to allow it to resist weathering, but not so well cemented that it cannot be readily worked (cut and carved) by masons. This is one of the reasons why Portland stone is so favoured as a monumental and architectural stone. Geoff Townson conducted three years doctoral research on

2736-413: The powder metal being used to form the segments. The powdered metals hold the diamonds in place. The bond controls the rate at which the diamond segments wear down allowing new diamonds to become exposed at the surface to continue grinding with a "sharp" edge. An important step in choosing a blade is to match the bond to the specific material to be cut. Additional factors to consider are the type and power of

2793-476: The quarries' environmental performance and removed the potential for any possible damage to the stone being quarried through shock. Full account of the local jointing pattern is made when deciding the position and orientation of cuts. Once the quarry faces have been cut, the stone is gently displaced hydraulically. This is done using "hydro-bags", which are thin, flat, steel bags or envelopes that when inflated with water under moderate pressure, are capable of producing

2850-492: The refurbishment of the British Museum 's central court, the planned Portland stone was controversially substituted with Anstrude Roche Claire stone from France, another similar (but cheaper) oolitic limestone. The term, "Portland cement", was coined by Joseph Aspdin who in 1824 patented a hydraulic binder created by burning a mixture of limestone and clay , resembling the previously existing Roman cement and presenting

2907-485: The rock from its natural bed, hopefully undamaged. Stone was cut using plugs and feathers , where a series of short, small diameter (typically 30 mm) holes are drilled in a line where a cut is to be made. One plug and two feathers were inserted into each hole and each plug is hit in turn with a sledgehammer until the stone yields to the extreme tensile stresses produced. Most stone is many times weaker in tension than in compression, plugs and feathers utilise this fact. It

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2964-494: The sea allowed the quarried stone blocks to be moved over relatively large distances by barge. Portland stone was used to build the Palace of Westminster in 1347, the Tower of London in 1349 and the first stone London Bridge in 1350. Exeter Cathedral and Christchurch Priory , also constructed during the 14th Century, are built of Portland stone. Its superb characteristics have ensured

3021-498: The south is number 134, Dorset Downs and Cranborne Chase . The area extends west almost as far as Barford St Martin , where the Nadder valley narrows. Geologically the Vale of Wardour is complex. The Nadder flows through a clay valley surrounded by hills of Purbeck, Portland, and Lower and Upper Greensand.The Gault , thickness up to 27.5 m (90 ft.), is also present in the Vale, notable are

3078-481: The southern tip of the island has permission to be worked by Portland Stone Firms and will provide in excess of 30 years of reserves. Permission has been granted for this to be open cast quarried. Once quarries have been worked they are then restored. The Portland Sculpture and Quarry Trust was formed in 1983 and is dedicated to preserving a knowledge and understanding of stone and the landscape from which it comes. The main non-working quarry remains Tout Quarry in which

3135-482: The trust is based, where a workshop is held every year. Tout Quarry has been donated to the Portland Sculpture and Quarry Trust by Portland Stone Firms Limited. Traditionally small diameter holes (35 mm) were drilled horizontally under each rock and charged with a small quantity of gunpowder , chosen because of its relative non-shattering properties. When fired the gunpowder produced a "heave" which dislodged

3192-516: The vale. In the west the Nadder is fed by its main tributary, the Sem ; in the east the valley ends around Wilton where the Nadder is joined by the Wylye . The largest village in the vale is Tisbury . The vale is a western tongue of National Character Area 133: Blackmore Vale and Vale of Wardour , designated by Natural England . To the north is number 132, Salisbury Plain and West Wiltshire Downs , and to

3249-583: Was used for the Armed Forces Memorial in Staffordshire , England. Designed by Liam O'Connor Architects and Planning Consultants, it was completed in 2007 at a cost of over £6 million and bears the names of over 16,000 service personnel of the British Armed Forces killed since the Second World War. Portland stone is recognised to be of a high quality, but is somewhat expensive. In the case of

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