- Purbeck Ball Clay
Purbeck Ball Clay is a concentration of
ball clay found on theIsle of Purbeck in the English county ofDorset .Geology
The main concentration of ball clay in Dorset is to the north of the Purbeck Hills centred around Norden. Ball clays are sedimentary in origin. Approximately 45 million years ago (in the
Lutetian stage of theEocene epoch) the climate wastropical and an ancient River Solent washedkaolinite (formed from decomposedgranite ) from its parent rock onDartmoor . As the streams flowed from upland areas they mixed with other clay minerals, sands, gravels, and vegetation before settling in low-lying basins to form overlaying seams of ball clay. Ball clays usually contain three dominant minerals: from 20-80%kaolinite , 10-25%mica , and 6-65%quartz . In addition, there are other 'accessory' minerals and some carbonaceous material (derived from ancient plants) present.Exploitation
Purbeck Ball Clay has been used for thousands of years, but large scale commercial extraction began in the middle of the 18th century and continues today. The principal workings were in the area between
Corfe Castle and Wareham. Originally the clay was taken bypack horse to wharves on the River Frome and the south side ofPoole Harbour .cite book | title = The Railways of Purbeck | publisher = The Oakwood Press | last = Kidner | first = R.W. | edition = Third Edition | year = 2000 | isbn = 0-85361-557-8 ]Large quantities were ordered by
Josiah Wedgwood from 1771 and this led to the construction of Dorset's first railway in 1806. This was theMiddlebere Plateway , which connected clay workings owned by clay entrepreneurBenjamin Fayle in the Corfe Castle area, to a wharf on Middlebere Creek in Poole Harbour. Other similar tramways followed, including theFurzebrook Railway (1830), theNewton Tramway (c.1860), andFayle's Tramway (1907). With the coming of theLondon and South Western Railway line from Wareham toSwanage in 1885, much ball clay was dispatched by rail.cite book | title = The Railways of Purbeck | publisher = The Oakwood Press | last = Kidner | first = R.W. | edition = Third Edition | year = 2000 | isbn = 0-85361-557-8 ]Approximately 80% of the ball clay extracted has been exported. The ball clay is processed today at the
Furzebrook plant ofImerys . It is said that a third of all fine pottery ever produced in England contains Purbeck Ball Clay.Fact|date=August 2008Usage
Ball clays are used in making everyday articles including:
*wall and floor tiles, wash basins, toilet bowls, plates, cups and saucers, linoleum, acoustic ceiling tiles, insulated electrical cables, pale coloured bricks, and clay drainage pipes
*windscreen wipers, spark plugs, and engine mountings
*hoses and fertilisers
*pharmaceutical and polymers and many othersReferences
External links
* [http://www.soton.ac.uk/~imw/ Geology of the Wessex Coast]
* [http://www.pmmmg.org Purbeck Mineral & Mining Museum]
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