HOME

TheInfoList




Clay is a type of fine-grained natural
soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and organisms tha ...

soil
material containing ''
clay mineral Clay minerals are , sometimes with variable amounts of , , s, s, and other s found on or near some s. Clay minerals form in the presence of water and have been important to life, and many theories of involve them. They are important constitu ...
s''. Clays develop
plasticity Plasticity may refer to: Science * Plasticity (physics), in engineering and physics, the propensity of a solid material to undergo permanent deformation under load * Neuroplasticity, in neuroscience, how entire brain structures, and the brain its ...
when wet, due to a molecular film of water surrounding the clay particles, but become hard, brittle and non–plastic upon drying or
firing Dismissal (also referred to as firing) is the termination of employment Termination of employment is an employee's departure from a job and the end of an employee's duration with an employer. Termination may be voluntary on the employee's part, o ...

firing
. Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impurities, such as a reddish or brownish colour from small amounts of
iron oxide Iron oxides are chemical compounds composed of iron and oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, ...

iron oxide
. Clay is the oldest known
ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant Corrosion is a natural process that converts a refined metal into a more chemically stable form such as oxide of rutile. Ti(IV) centers are grey; oxygen ce ...

ceramic
material. Prehistoric humans discovered the useful properties of clay and used it for making
pottery Pottery is the process and the products of forming vessels and other objects with and other materials, which are fired at high temperatures to give them a hard, durable form. Major types include , and . The place where such wares are mad ...

pottery
. Some of the earliest pottery shards have been
dated Date or dates may refer to: *Date (fruit), the fruit of the date palm (''Phoenix dactylifera'') Social activity *Dating, a form of courtship involving social activity, with the aim of assessing a potential partner **Group date, wherein a group ...
to around 14,000 BC, and clay tablets were the first known writing medium. Clay is used in many modern industrial processes, such as
paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * ...

paper
making,
cement A cement is a binder (material), binder, a substance used for construction that solidification, sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (constru ...
production, and chemical
filtering Filter, filtering or filters may refer to: Science and technology Device * Filter (chemistry), a device which separates solids from fluids (liquids or gases) by adding a medium through which only the fluid can pass ** Filter (aquarium), critical ...
. Between one-half and two-thirds of the world's population live or work in buildings made with clay, often baked into brick, as an essential part of its load-bearing structure. Clay is a very common substance.
Shale Shale is a fine-grained, clastic of a clast (sand grain), derived from a basalt Basalt (, ) is a fine-grained extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ('' mafic '' lava) ...

Shale
, formed largely from clay, is the most common sedimentary rock. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size and mineralogy.
Silt Silt is granular material A granular material is a conglomeration of discrete solid, macroscopic scale, macroscopic particles characterized by a loss of energy whenever the particles interact (the most common example would be friction when gra ...
s, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. Mixtures of
sand Sand is a granular Granularity (also called graininess), the condition of existing in granules or grains A grain is a small, hard, dry seed A seed is an embryonic plant enclosed in a protective outer covering. The formation of th ...

sand
,
silt Silt is granular material A granular material is a conglomeration of discrete solid, macroscopic scale, macroscopic particles characterized by a loss of energy whenever the particles interact (the most common example would be friction when gra ...
and less than 40% clay are called
loam Loam (in geology and soil science) is soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matt ...
. Soils high in ''swelling clays'', which are clay minerals that readily expand in volume when they absorb water, are a major challenge in
civil engineering Civil engineering is a professional engineering Regulation and licensure in engineering is established by various jurisdictions of the world to encourage public welfare, safety, well-being and other interests of the general public and to define ...
.


Properties

The defining mechanical property of clay is its plasticity when wet and its ability to harden when dried or fired. Clays show a broad range of water content within which they are highly plastic, from a minimum water content (called the plasticity limit) where the clay is just moist enough to mould, to a maximum water content (called the liquid limit) where the moulded clay is just dry enough to hold its shape. The plastic limit of kaolinite clay ranges from about 36% to 40% and its liquid limit ranges from about 58% to 72%. High-quality clay is also tough, as measured by the amount of mechanical work required to roll a sample of clay flat. Its toughness reflects a high degree of internal cohesion. Clay has a high content of clay minerals that give it its plasticity. Clay minerals are
hydrous In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understoo ...
aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity towards , and of on the surface when exposed to air ...

aluminium
phyllosilicate minerals
phyllosilicate minerals
, composed of aluminium and silicon ions bonded into tiny, thin plates by interconnecting oxygen and
hydroxide Hydroxide is a diatomic anion with chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical physics and general che ...
ions. These plates are tough but flexible, and in moist clay, they adhere to each other. The resulting aggregates give clay the cohesion that makes it plastic. In
kaolinite Kaolinite ( ) is a clay mineral Clay minerals are , sometimes with variable amounts of , , s, s, and other s found on or near some s. Clay minerals form in the presence of water and have been important to life, and many theories of in ...

kaolinite
clay, the bonding between plates is provided by a film of water molecules that
hydrogen bond A hydrogen bond (or H-bond) is a primarily Electrostatics, electrostatic force of attraction between a hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of ...

hydrogen bond
the plates together. The bonds are weak enough to allow the plates to slip past each other when the clay is being moulded, but strong enough to hold the plates in place and allow the moulded clay to retain its shape after it is moulded. When the clay is dried, most of the water molecules are removed, and the plates hydrogen bond directly to each other, so that the dried clay is rigid but still fragile. If the clay is moistened again, it will once more become plastic. When the clay is fired to the
earthenware Earthenware is glazed or unglazed nonvitreous pottery Pottery is the process and the products of forming vessels and other objects with clay and other ceramic materials, which are fired at high temperatures to give them a hard, durable form ...

earthenware
stage, a
dehydration reaction In chemistry, a dehydration reaction, also known as Zimmer's hydrogenesis, is a chemical reaction that involves the loss of water from the reacting molecule or ion. It is the most common type of condensation reaction. Dehydration reactions are co ...
removes additional water from the clay, causing clay plates to irreversibly adhere to each other via stronger
covalent bonding A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of attraction bet ...
, which strengthens the material. The clay mineral, kaolin, is transformed into a non-clay material, metakaolin, which remains rigid and hard if moistened again. Further firing through the
stoneware Stoneware is a rather broad term for pottery or other ceramics fired at a relatively high temperature. A modern technical definition is a Vitrification#In ceramics, vitreous or semi-vitreous ceramic made primarily from stoneware clay or non-refrac ...
and
porcelain Porcelain () is a material made by heating substances, generally including materials such as , in a to temperatures between . The strength, and translucence of porcelain, relative to other types of , arises mainly from and formation of the ...

porcelain
stages further recrystallizes the metakaolin into yet stronger minerals such as
mullite Mullite or porcelainite is a rare silicate mineral Silicate minerals are rock-forming mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composi ...
. The tiny size and plate form of clay particles gives clay minerals a high surface area. In some clay minerals, the plates carry a negative electrical charge that is balanced by a surrounding layer of positive ions (
cation An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are u ...
s), such as sodium, potassium, or calcium. If the clay is mixed with a solution containing other cations, these can swap places with the cations in the layer around the clay particles, which gives clays a high capacity for
ion exchange Ion exchange is a reversible interchange of one kind of ion present on an insoluble solid with another of like charge present in a solution surrounding the solid with the reaction being used especially for softening or making water demineralised, ...

ion exchange
. The chemistry of clay minerals, including their capacity to retain nutrient cations such as potassium and ammonium, is important to soil fertility. Clay is a common component of
sedimentary rock Sedimentary rocks are types of rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compoun ...

sedimentary rock
.
Shale Shale is a fine-grained, clastic of a clast (sand grain), derived from a basalt Basalt (, ) is a fine-grained extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ('' mafic '' lava) ...

Shale
is formed largely from clay and is the most common of sedimentary rocks. However, most clay deposits are impure. Many naturally occurring deposits include both silts and clay. Clays are distinguished from other fine-grained soils by differences in size and mineralogy.
Silt Silt is granular material A granular material is a conglomeration of discrete solid, macroscopic scale, macroscopic particles characterized by a loss of energy whenever the particles interact (the most common example would be friction when gra ...
s, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in particle size and other physical properties. The distinction between silt and clay varies by discipline.
Geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, although backgrounds in physics, chem ...

Geologist
s and
soil scientist Soil science is the study of soil as a natural resource on the surface of the Earth including pedogenesis, soil formation, soil classification, classification and mapping; physical, chemical, biological, and fertility properties of soils; and th ...
s usually consider the separation to occur at a particle size of 2 μm (clays being finer than silts), sedimentologists often use 4–5 μm, and
colloid A colloid is a mixture In chemistry, a mixture is a material made up of two or more different chemical substances which are not chemically combined. A mixture is the physical combination of two or more substances in which the identities are r ...

colloid
chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin Medieval Latin was the form of Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European l ...

chemist
s use 1 μm. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils'
Atterberg limits The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit. Depending on its water content, a soil may appear in one of four states: solid, semi-solid, plasti ...
.
ISO The International Organization for Standardization (ISO ) is an international standard An international standard is a technical standard A technical standard is an established norm (social), norm or requirement for a repeatable technical task w ...
14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. Mixtures of
sand Sand is a granular Granularity (also called graininess), the condition of existing in granules or grains A grain is a small, hard, dry seed A seed is an embryonic plant enclosed in a protective outer covering. The formation of th ...

sand
,
silt Silt is granular material A granular material is a conglomeration of discrete solid, macroscopic scale, macroscopic particles characterized by a loss of energy whenever the particles interact (the most common example would be friction when gra ...
and less than 40% clay are called
loam Loam (in geology and soil science) is soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matt ...
. Some clay minerals (such as
smectite Clay minerals are hydrous In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their ch ...
) are described as swelling clay minerals, because they have a great capacity to take up water, and they increase greatly in volume when they do so. When dried, they shrink back to their original volume. This produces distinctive textures, such as
mudcrack Mudcracks (also known as mud cracks, desiccation cracks or cracked mud) are sedimentary structures formed as muddy sediment Desiccation, dries and contracts.Jackson, J.A., 1997, ''Glossary of Geology'' (4th ed.), American Geological Institute, Alex ...
s or "popcorn" texture, in clay deposits. Soils containing swelling clay minerals (such as
bentonite Bentonite () is an Absorption (chemistry), absorbent swelling clay consisting mostly of montmorillonite. It usually forms from weathering of volcanic ash in seawater, which converts the volcanic glass present in the ash to clay minerals. Benton ...

bentonite
) pose a considerable challenge for civil engineering, because swelling clay can break foundations of buildings and ruin road beds.


Formation

Clay minerals most commonly form by prolonged chemical
weathering Weathering is the deterioration of Rock (geology), rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little o ...
of silicate-bearing rocks. They can also form locally from
hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC ...
activity. Chemical weathering takes place largely by ''acid hydrolysis'' due to low concentrations of
carbonic acid In chemistry, carbonic acid is a dibasic acid with the chemical formula A chemical formula is a way of presenting information about the chemical proportions of atom An atom is the smallest unit of ordinary matter In classical ...

carbonic acid
, dissolved in rainwater or released by plant roots. The acid breaks bonds between aluminium and oxygen, releasing other metal ions and silica (as a gel of orthosilicic acid).) The clay minerals formed depend on the composition of the source rock and the climate. Acid weathering of
feldspar Feldspars are a group of rock-forming aluminium Aluminium (aluminum in and ) is a with the  Al and  13. Aluminium has a density lower than those of other common , at approximately one third that of . It has a great affinity ...
-rich rock, such as
granite Granite () is a coarse-grained (phaneritic A phanerite is an igneous rock Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Lat ...

granite
, in warm climates tends to produce kaolin. Weathering of the same kind of rock under alkaline conditions produces
illite Illite is a group of closely related non-expanding minerals. Illite is a secondary mineral precipitate, and an example of a , or layered alumino-silicate. Its structure is a 2:1 sandwich of silica tetrahedron (T) – octahedron (O) – silica ...

illite
.
Smectite Clay minerals are hydrous In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their ch ...
forms by weathering of
igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock i ...
under alkaline conditions, while
gibbsite Gibbsite, Al(OH)3, is one of the mineral forms of aluminium hydroxide Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer Polymorphism (materials science), polymorp ...

gibbsite
forms by intense weathering of other clay minerals. There are two types of clay deposits: primary and secondary. Primary clays form as residual deposits in soil and remain at the site of formation. Secondary clays are clays that have been transported from their original location by water erosion and deposited in a new
sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentatio ...

sedimentary
deposit. Secondary clay deposits are typically associated with very low energy depositional environments such as large lakes and marine basins.


Varieties

The main groups of clays include
kaolin Kaolinite ( ) is a clay mineral Clay minerals are , sometimes with variable amounts of , , s, s, and other s found on or near some s. Clay minerals form in the presence of water and have been important to life, and many theories of in ...

kaolin
ite,
montmorillonite Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ...
-
smectite Clay minerals are hydrous In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their ch ...
, and
illite Illite is a group of closely related non-expanding minerals. Illite is a secondary mineral precipitate, and an example of a , or layered alumino-silicate. Its structure is a 2:1 sandwich of silica tetrahedron (T) – octahedron (O) – silica ...

illite
.
Chlorite The chlorite ion An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical ...
,
vermiculite Vermiculite is a hydrous phyllosilicate mineral which undergoes significant expansion when heated. Exfoliation occurs when the mineral is heated sufficiently, and commercial furnaces can routinely produce this effect. Vermiculite forms by the we ...
,
talc Talc, or talcum, is a clay mineral Clay minerals are , sometimes with variable amounts of , , s, s, and other s found on or near some s. Clay minerals form in the presence of water and have been important to life, and many theories of ...

talc
, and
pyrophyllite Pyrophyllite is a phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with t ...

pyrophyllite
are sometimes also classified as clay minerals. There are approximately 30 different types of "pure" clays in these categories, but most "natural" clay deposits are mixtures of these different types, along with other weathered minerals. Clay minerals in clays are most easily identified using
X-ray diffraction X-ray crystallography (XRC) is the experimental science determining the atomic and molecular structure of a crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a ...
rather than chemical or physical tests.
Varve A varve is an annual layer of sediment Sediment is a naturally occurring material that is broken down by processes of weathering Weathering is the deterioration of rocks A rock is any naturally occurring solid mass or aggregate of ...
(or ''varved clay'') is clay with visible annual layers that are formed by seasonal deposition of those layers and are marked by differences in
erosion In earth science Earth science or geoscience includes all fields of natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific ...

erosion
and organic content. This type of deposit is common in former
glacial lake A glacial lake is a body of water with origins from glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transpare ...

glacial lake
s. When fine sediments are delivered into the calm waters of these glacial lake basins away from the shoreline, they settle to the lake bed. The resulting seasonal layering is preserved in an even distribution of clay sediment banding. Quick clay is a unique type of
marine clay Marine clay is a type of clay Clay is a type of fine-grained natural soil File:Stagnogley.JPG, Surface-water-Gley soil, gley developed in glacial till, Northern Ireland. Soil is a mixture of organic matter, minerals, gases, liquids, and ...
indigenous to the glaciated terrains of
Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official written standard for the Norwegian language Norwegian (Norwegian: ''norsk'') is a Nort ...

Norway
,
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
,
Northern Ireland Northern Ireland ( ga, Tuaisceart Éireann ; sco, label=Ulster-ScotsUlster Scots, also known as Scotch-Irish, may refer to: * Ulster Scots people The Ulster Scots (Ulster-Scots The Ulster Scots (Ulster Scots dialects, Ulster- ...

Northern Ireland
, and
Sweden Sweden ( sv, Sverige ), officially the Kingdom of Sweden ( sv, links=no, Konungariket Sverige ), is a Nordic country The Nordic countries, or the Nordics, are a geographical and cultural region In geography, regions are areas that ...

Sweden
. It is a highly sensitive clay, prone to
liquefaction In materials science The interdisciplinary Interdisciplinarity or interdisciplinary studies involves the combination of two or more academic discipline An academic discipline or academic field is a subdivision of knowledge that is Educ ...
, and has been involved in several deadly
landslide Landslides, also known as landslips, are several forms of mass wasting Mass wasting, also known as mass movement, is a general term for the movement of rock Rock most often refers to: * Rock (geology) A rock is any naturally occurri ...

landslide
s.


Uses

Modelling clay Modelling clay is any of a group of malleable substances used in building and sculpting. The material compositions and production processes vary considerably. Ceramic clay Ceramic clays are water-based substances made from clay minerals and ...
is used in art and handicraft for
sculpting Sculpture is the branch of the visual arts The visual arts are art forms such as painting, drawing, printmaking, sculpture Sculpture is the branch of the visual arts that operates in three dimensions. It is one of the plastic arts. D ...
. Clays are used for making
pottery Pottery is the process and the products of forming vessels and other objects with and other materials, which are fired at high temperatures to give them a hard, durable form. Major types include , and . The place where such wares are mad ...

pottery
, both utilitarian and decorative, and construction products, such as bricks, walls, and floor tiles. Different types of clay, when used with different minerals and firing conditions, are used to produce earthenware, stoneware, and porcelain. Prehistoric humans discovered the useful properties of clay. Some of the earliest pottery shards recovered are from central
Honshu , historically called , is the largest and most populous main island of Japan Japan ( ja, 日本, or , and formally ) is an in . It is situated in the northwest , and is bordered on the west by the , while extending from the in the n ...
,
Japan Japan ( ja, 日本, or , and formally ) is an island country An island country or an island nation is a country A country is a distinct territory, territorial body or political entity. It is often referred to as the land of an in ...

Japan
. They are associated with the Jōmon culture, and recovered deposits have been
dated Date or dates may refer to: *Date (fruit), the fruit of the date palm (''Phoenix dactylifera'') Social activity *Dating, a form of courtship involving social activity, with the aim of assessing a potential partner **Group date, wherein a group ...
to around 14,000 BC. Cooking pots, art objects, dishware, smoking pipes, and even
musical instrument A musical instrument is a device created or adapted to make musical sounds. In principle, any object that produces sound can be considered a musical instrument—it is through purpose that the object becomes a musical instrument. A person who play ...
s such as the
ocarina The ocarina is a wind Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces ...

ocarina
can all be shaped from clay before being fired. Clay tablets were the first known writing medium. Scribes wrote by inscribing them with
cuneiform Cuneiform is a Logogram, logo-Syllabary, syllabic writing system, script that was used to write several languages of the Ancient Near East. The script was in active use from the early Bronze Age until the beginning of the Common Era. It is nam ...

cuneiform
script using a blunt
reed Reed or Reeds may refer to: Science, technology, biology, and medicine * Reed bird (disambiguation) * Reed pen, writing implement in use since ancient times * Reed (plant), one of several tall, grass-like wetland plants of the order Poales * ...
called a
stylus A stylus (plural styli or styluses) is a writing utensil A writing implement or writing instrument is an object used to produce writing. Writing consists of different figures, lines, and or forms. Most of these items can be also used for othe ...

stylus
. Purpose-made clay balls were used as
sling ammunition
sling ammunition
. Clay is used in many industrial processes, such as
paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition * ...

paper
making,
cement A cement is a binder (material), binder, a substance used for construction that solidification, sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (constru ...
production, and chemical
filtering Filter, filtering or filters may refer to: Science and technology Device * Filter (chemistry), a device which separates solids from fluids (liquids or gases) by adding a medium through which only the fluid can pass ** Filter (aquarium), critical ...
.
Bentonite Bentonite () is an Absorption (chemistry), absorbent swelling clay consisting mostly of montmorillonite. It usually forms from weathering of volcanic ash in seawater, which converts the volcanic glass present in the ash to clay minerals. Benton ...

Bentonite
clay is widely used as a mold binder in the manufacture of
sand casting Sand casting, also known as sand molded casting, is a metal casting In metalworking and jewelry making, casting is a process in which a liquid metal is delivered into a mold (usually by a crucible) that contains a negative impression (i.e., ...

sand casting
s.


Medicine

Traditional uses of clay as medicine goes back to prehistoric times. An example is
Armenian bole 250px, The distinctive flame red is a striking feature of the mature style of Iznik pottery. It comes from an iron-rich red earth, or bole, found in Armenia. Armenian bole, also known as bolus armenus or bole armoniac, is an earthy clay, usually red ...

Armenian bole
, which is used to soothe an upset stomach. Some animals such as parrots and pigs ingest clay for similar reasons.
Kaolin clay Kaolinite ( ) is a clay mineral Clay minerals are hydrous aluminium Aluminium (aluminum in American English, American and Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. A ...

Kaolin clay
and attapulgite have been used as anti-diarrheal medicines.


Construction

Clay as the defining ingredient of
loam Loam (in geology and soil science) is soil Surface-water- gley developed in glacial till, Northern Ireland.">Northern_Ireland.html" ;"title="glacial till, Northern Ireland">glacial till, Northern Ireland. Soil is a mixture of organic matt ...
is one of the oldest
building material Building material is material used for construction. Many naturally occurring substances, such as clay, rocks, sand, and wood, even twigs and leaves, have been used to construct buildings. Apart from naturally occurring materials, many man-mad ...

building material
s on
Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

Earth
, among other ancient, naturally-occurring geologic materials such as stone and organic materials like wood. Also a primary ingredient in many
natural building A natural building involves a range of building A building, or edifice, is a structure with a roof and walls standing more or less permanently in one place, such as a house or factory. Buildings come in a variety of sizes, shapes, and functions ...
techniques, clay is used to create
adobe Adobe (; ) is a building material Building material is material used for construction Construction is a general term meaning the art and science to form Physical object, objects, systems, or organizations,"Construction" def. 1.a. ...

adobe
, cob,
cordwood 300px, A section of a cordwood home. Cordwood construction (also called "cordwood masonry", "cordwood building", "stackwall construction", "stovewood construction" or "stackwood construction") is a term used for a natural building method in whic ...
, and structures and building elements such as
wattle and daub Wattle and daub is a composite material, composite building method used for making walls and buildings, in which a woven lattice of wooden strips called wattle (construction), wattle is daubed with a sticky material usually made of some combinatio ...

wattle and daub
, clay plaster, clay render case, clay floors and clay
paints Paint is any pigmented liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isochoric flow) refers to a fluid flow, flow in which the material den ...

paints
and ceramic building material. Clay was used as a
mortar Mortar may refer to: * Mortar (weapon), an indirect-fire infantry weapon * Mortar (masonry), a material used to fill the gaps between blocks and bind them together * Mortar and pestle, a tool pair used to crush or grind * Mortar, Bihar, a village in ...
in brick
chimneys A chimney is an Ventilation (architecture), architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, Furnace (house heating), furnace, Incineration, inciner ...

chimneys
and stone walls where protected from water. The forecasted mass of clay minerals to be discharged into the tailings of ore processing makes up millions of tons. Worryingly, when macro- and micro-components are found in non-hazardous concentrations, fewer efforts are put into the environmental management of the tailings, though technogenic sediments offer prospects for reuse and valorization beyond their traditional disposal. Saponite is a demonstrative example of the tailings constituent that is often left unfairly mistreated. Electrochemical separation helps to obtain modified saponite-containing products with high smectite-group minerals concentrations, lower mineral particles size, more compact structure, and greater surface area. These characteristics open possibilities for the manufacture of high-quality ceramics and heavy-metal sorbents from saponite-containing products. Furthermore, tail grinding occurs during the preparation of the raw material for ceramics; this waste reprocessing is of high importance for the use of clay pulp as a neutralizing agent, as fine particles are required for the reaction. Experiments on the
Histosol In both the World Reference Base for Soil Resources (WRB) and the USDA soil taxonomy, a Histosol is a soil consisting primarily of organic materials. They are defined as having or more of organic soil material in the upper . Organic soil material ...

Histosol
deacidification with the alkaline clay slurry demonstrated that neutralization with the average pH level of 7.1 is reached at 30% of the pulp added and an experimental site with perennial grasses proved the efficacy of the technique. Clay, relatively impermeable to water, is also used where natural seals are needed, such as in the cores of
dam A dam is a barrier that stops or restricts the flow of surface water An example of surface water is Lake Kinney. Surface water is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tas ...

dam
s, or as a barrier in
landfill A landfill site, also known as a tip, dump, rubbish dump, garbage dump, or dumping ground, is a site for the disposal of waste Waste (or wastes) are unwanted or unusable materials. Waste is any substance which is discarded after primar ...

landfill
s against toxic seepage (lining the landfill, preferably in combination with
geotextile Geotextiles are permeable s which, when used in association with , have the ability to separate, filter, reinforce, protect, or drain. Typically made from or , geotextile fabrics come in three basic forms: (resembling mail bag sacking), (resem ...
s). Studies in the early 21st century have investigated clay's
absorption Absorption may refer to: Chemistry and biology *Absorption (chemistry), diffusion of particles of gas or liquid into liquid or solid materials *Absorption (skin), a route by which substances enter the body through the skin *Absorption (pharmacolo ...
capacities in various applications, such as the removal of
heavy metals upright=1.2, Crystals of osmium, a heavy metal nearly twice as dense as lead">lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals are generally defined as m ...
from waste water and air purification.


See also

* * * * * * * * * * * * * * * * *


Notes


References


Clay mineral nomenclature
''American Mineralogist''. * * * * * * * * * Ehlers, Ernest G. and Blatt, Harvey (1982). 'Petrology, Igneous, Sedimentary, and Metamorphic'
San Francisco San Francisco (; Spanish Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (dis ...

San Francisco
: W.H. Freeman and Company. . * * * * * * * Hillier S. (2003) "Clay Mineralogy." pp 139–142 In Middleton G.V., Church M.J., Coniglio M., Hardie L.A. and Longstaffe F.J. (Editors) ''Encyclopedia of Sediments and Sedimentary Rocks''. Kluwer Academic Publishers, Dordrecht. * * * * * * * * * * * * *


External links


The Clay Minerals Group of the Mineralogical Society

Information about clays used in the UK pottery industry

The Clay Minerals Society


{{Authority control Types of soil Sculpture materials Natural materials Sedimentology Sediments Phyllosilicates Soil-based building materials