Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources in this section. This section needs additional citations for verification. Portland Stone Firms Ltd have been quarrying Portland stone since 1994. Albion Stone PLC has been quarrying and mining Portland stone since 1984. The island was connected by railway to the rest of the country from 1865. 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. Extraction as an industry began in the early 17th century, with shipments to London for Inigo Jones' Banqueting House. Stone has been quarried on Portland since Roman times and was being shipped to London in the 14th century. 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. Geoff Townson conducted three years doctoral research on the Portlandian, being the first to describe the patch-reef facies and Dorset-wide sedimentation details. This is one of the reasons why Portland stone is so favoured as a monumental and architectural 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 can not be readily worked (cut and carved) by masons. 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 the oolitic limestone that is called Portland stone. This process is similar to the way in which a snowball grows in size as it is rolled around in the snow. The calcite gradually accumulated (by accretion) around the fragments of shell in concentric layers, forming small balls (of less than 0.5 mm diameter). Portland stone measures 3.5 on the Mohs scale of mineral hardness. 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. Billions of minute crystals of precipitated calcium carbonate (called calcite) accumulated forming lime mud (called micrite) which covered the sea floor. Calcium carbonate is the principal constituent of most limestones. The process of limescale build up in a kettle in hard-water areas is similar. Calcium and bicarbonate ions within the water are then able to combine, to form calcium carbonate (CaCO 3) as a precipitate. 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. Portland stone formed in a marine environment, on the floor of a shallow, warm, sub-tropical sea probably near land (as evidenced by fossilized driftwood, which is not uncommon). Portland stone is also exported to many countries, being used for example at the United Nations headquarters in New York City. It has been used extensively as a building stone throughout the British Isles, notably in major public buildings in London such as St Paul's Cathedral and Buckingham Palace. The quarries are cut in beds of white-grey limestone separated by chert beds. 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 Cenotaph, in Whitehall, London, is made from Portland stone Vale of Wardour: Tisbury Member, Wockley Member, Chilmark Member Portland stone quarry on the Isle of PortlandÄorset: Portland Chert Member, Portland Freestone Member
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