Purbeck Ball Clay is a concentration of

ball clay Ball clays are kaolinitic sedimentary clays that commonly consist of 20–80% kaolinite, 10–25% mica and 6–65% quartz, along with small amounts of organic matter (such as lignite) and trace amounts of other minerals such as pyrite and siderit ...

found on the

Isle of Purbeck The Isle of Purbeck is a peninsula in Dorset, England. It is bordered by water on three sides: the English Channel to the south and east, where steep cliffs fall to the sea; and by the marshy lands of the River Frome, Dorset, River Frome and Poo ...

in the English county of

Dorset Dorset ( ; Archaism, archaically: Dorsetshire , ) is a Ceremonial counties of England, ceremonial county in South West England. It is bordered by Somerset to the north-west, Wiltshire to the north and the north-east, Hampshire to the east, t ...

Geology

The main concentration of ball clay in Dorset is to the north of the Purbeck Hills centred on Norden. Ball clays are sedimentary in origin. Approximately 45 million years ago (in the

Lutetian The Lutetian is, in the geologic timescale, a stage (stratigraphy), stage or age (geology), age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it ...

stage of the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

epoch) the climate was

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and an ancient

River Solent The River Solent is a now-extinct river which during the Pleistocene would have flowed around the area which is now the coastlines of Hampshire and the Isle of Wight in England. History The River Solent was one of three major rivers in central a ...

washed

kaolinite Kaolinite ( ; also called kaolin) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral sheet of alumina () ...

(formed from decomposed

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

) from its parent rock on

Dartmoor Dartmoor is an upland area in southern Devon, South West England. The moorland and surrounding land has been protected by National Park status since 1951. Dartmoor National Park covers . The granite that forms the uplands dates from the Carb ...

. 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%

, 10–25%

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

, and 6–65%

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

. 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 Corfe Castle is a fortification standing above the Corfe Castle (village), village of the same name on the Isle of Purbeck peninsula in the English county of Dorset. Built by William the Conqueror, the castle dates to the 11th century and ...

and Wareham. Originally the clay was taken by

pack horse A packhorse, pack horse, or sumpter refers to a horse, mule, donkey, or pony used to carry goods on its back, usually in sidebags or panniers. Typically packhorses are used to cross difficult terrain, where the absence of roads prevents the use o ...

wharves A wharf ( or wharfs), quay ( , also ), staith, or staithe is a structure on the shore of a harbour or on the bank of a river or canal where ships may dock to load and unload cargo or passengers. Such a structure includes one or more berths ( ...

on the River Frome and the south side of

Poole Harbour Poole Harbour is a large natural harbour in Dorset, southern England, with the town of Poole on its shores. The harbour is a drowned valley ( ria) formed at the end of the last ice age and is the estuary of several rivers, the largest being th ...

. Large quantities were ordered by

Josiah Wedgwood Josiah Wedgwood (12 July 1730 – 3 January 1795) was an English potter, entrepreneur and abolitionist. Founding the Wedgwood company in 1759, he developed improved pottery bodies by systematic experimentation, and was the leader in the indu ...

from 1771 and this led to the construction of Dorset's first railway in 1806. This was the Middlebere Plateway owned by B.Fayle & Co (Directors were Alexander Jaffray, Benjamin Fayle, Richard Jaffray, J.B. Hooper and Richard Chambers). The Plateway connected clay workings 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 The London and South Western Railway (LSWR, sometimes written L&SWR) was a railway company in England from 1838 to 1922. Originating as the London and Southampton Railway, its network extended to Dorchester and Weymouth, to Salisbury, Exete ...

line from Wareham to

Swanage Swanage () is a coastal town and civil parish in the south east of Dorset, England. It is at the eastern end of the Isle of Purbeck and one of its two towns, approximately south of Poole and east of Dorchester, Dorset, Dorchester. In the Unit ...

in 1885, much of the ball clay was dispatched by rail. Approximately 80% of the ball clay extracted has been exported. The ball clay is processed today at the Furzebrook plant of

Imerys IMERYS S.A. is a French Multinational corporation, multinational company that specialises in the production and processing of industrial minerals. The main headquarters is located in Paris and are constituents of the CAC Mid 60 index. Groupe Bru ...

. It is said that a third of all fine pottery ever produced in England contains Purbeck Ball Clay.

Usage

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{{citation needed, date=November 2014, spark plugs, and engine mountings *hoses and fertilisers *pharmaceutical and polymers and many others *

kiln furniture Kiln furniture are devices and implements inside furnaces used during the heating of manufactured individual pieces, such as pottery or other ceramic or metal components. Kiln furniture can account for up to 80% of the mass of a kiln charge. Mate ...

Museum

The Purbeck Mineral and Mining Museum displays an exhibition about ball clays, mining and the associated narrow gauge railways.

References

External links

Geology of the Wessex CoastPurbeck Ball Clay MerchantsPurbeck Mineral and Mining Museum
Isle of Purbeck English pottery