Purbeck Ball Clay is a concentration of ball clay found on the Isle of Purbeck in the English county of Dorset.
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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 the Eocene epoch) the climate was tropical and an ancient River Solent washed kaolinite (formed from decomposed granite) from its parent rock on Dartmoor. 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.
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 by pack horse to wharves on the River Frome and the south side of Poole Harbour.[1]
Large quantities were ordered by Josiah Wedgwood from 1771 and this led to the construction of Dorset's first railway in 1806. This was the Middlebere Plateway, which connected clay workings owned by the London Merchant Benjamin Fayle in the Corfe Castle area, to a wharf on Middlebere Creek in Poole Harbour. Other similar tramways followed, including the Furzebrook Railway (c.1840), the Newton Tramway (1854), and Fayle's Tramway (1907). With the coming of the London and South Western Railway line from Wareham to Swanage in 1885, much ball clay was dispatched by rail.[1]
Approximately 80% of the ball clay extracted has been exported. The ball clay is processed today at the Furzebrook plant of Imerys. It is said that a third of all fine pottery ever produced in England contains Purbeck Ball Clay.
Ball clays are used in making everyday articles including:
Ball Clay has been very important in the way our living standards have developed. Without the porcelain insulators from which overhead cables are suspended, there could be no high-tension electricicity distribution grid. Without porcelain insulators the spark plug and the internal combustion engine may not have existed. Without the far-from-romantic products of the vitreous china sanitaryware industry, modern sanitation would have been impossible, Without Ball Clays to bind refractory materials, a whole host of metallurigical and engineering processes could not be carried out. Without powdered clay, many forms of animal food - and hence milk and meat and eggs in the past- would have been more expensive, and many types of fertiliser would have been difficult if not impossible to spread satifactorily on agricultural land. The list of uses for Ball Clays is surprisingly long, and many are not ceramic applications at all.