Ball clays are kaolinitic

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

s that commonly consist of 20–80%

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 () ...

, 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 ...

, along with small amounts of organic matter (such as

lignite Lignite (derived from Latin ''lignum'' meaning 'wood'), often referred to as brown coal, is a soft, brown, combustible sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35% and is considered the lowest ...

) and trace amounts of other minerals such as

pyrite The mineral pyrite ( ), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue ...

and

siderite Siderite is a mineral composed of iron(II) carbonate (FeCO3). Its name comes from the Ancient Greek word (), meaning "iron". A valuable iron ore, it consists of 48% iron and lacks sulfur and phosphorus. Zinc, magnesium, and manganese commonly ...

. They are a common

raw material A raw material, also known as a feedstock, unprocessed material, or primary commodity, is a basic material that is used to produce goods, finished goods, energy, or intermediate materials/Intermediate goods that are feedstock for future finished ...

for various types of ceramics, where their primary roles are to impart unfired strength, plasticity or to aid rheological stability during the shaping processes. Most ball clays impart colours ranging from buff to cream to off-white when fired in an oxidising atmosphere.'Industrial Minerals & Rocks - Commodities, Markets And Uses' J. E. Kogel. Society For Mining, Metallurgy And Exploration, 2006 The name "ball clay" is derived from the form of the extracted material when dug by spade as cubes, which then became rounded during subsequent transport, in

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 ...

and Devon, England during the early days of the industry during the

18th century The 18th century lasted from 1 January 1701 (represented by the Roman numerals MDCCI) to 31 December 1800 (MDCCC). During the 18th century, elements of Enlightenment thinking culminated in the Atlantic Revolutions. Revolutions began to ch ...

. In 2008, UK production of ball clay was reported to be worth £82 million, with sanitaryware manufacturers being the largest single group of end users, representing 40% by volume.

Locations

Track out of Newbridge ball clay quarry - geograph

Deposits are relatively scarce due to the combination of geological factors needed for their formation and preservation. Commercial extraction of ball clays is undertaken across the world, including:'The Constitution, Evaluation And Ceramic Properties Of Ball Clays' I. R. Wilson. Cerâmica vol.44 no.287-288 São Paulo May/June/July/Aug. 1998 *Argentina (San Julian area of Patagonia) *Brazil (various locations including the region around São Paulo - São Simão, Suzano and Ribeirão Pire) *China (various including Guangdong Province) *Czech Republic (Cheb, Plzeň, Prague, Most, S. Bohemia and W. Moravia) *Germany (various locations but the main is the Westerwald region) *Indonesia (various locations including the island of Kalimantan) *Thailand (Lampang) *United Kingdom (the Bovey Basin of south Devon, the Petrockstow Basin in north Devon and the area around Wareham in south-east Dorset) *USA (Kentucky, Tennessee and Texas)

Production output

Global production of ball clay by country for 2002-2003 was estimated to be:

Typical properties

Some selected typical properties of various UK ball clays are:

History in the UK

The

ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...

use of ball clays in

Britain Britain most often refers to: * Great Britain, a large island comprising the countries of England, Scotland and Wales * The United Kingdom of Great Britain and Northern Ireland, a sovereign state in Europe comprising Great Britain and the north-eas ...

dates back to at least the

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of Roman civilization *Epistle to the Romans, shortened to Romans, a letter w ...

era. More recent trade began when a clay was needed to make tobacco pipes in the 16th and 17th century. In 1771

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 ...

signed a contract for 1,400 tons a year of ball clay with Thomas Hyde of Purbeck, enabling the production of thinner-walled ceramics.

References

{{Pottery Pottery Geology of Devon Clay Industrial minerals

Locations

Production output

Typical properties

History in the UK

See also

References