Kaolinite is a clay mineral, part of the group of industrial minerals
Industrial minerals
Industrial minerals are geological materials which are mined for their commercial value, which are not fuel and are not sources of metals ....

, with the chemical composition Al
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...

)4. It is a layered silicate mineral
Silicate minerals
The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group...

, with one tetrahedral
In geometry, a tetrahedron is a polyhedron composed of four triangular faces, three of which meet at each vertex. A regular tetrahedron is one in which the four triangles are regular, or "equilateral", and is one of the Platonic solids...

 sheet linked through oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

s to one octahedral
In geometry, an octahedron is a polyhedron with eight faces. A regular octahedron is a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex....

 sheet of alumina octahedra. Rocks that are rich in kaolinite are known as kaolin or china clay.

The name is derived from Kao-ling , a town near Jingdezhen
Jingdezhen , is a prefecture-level city, previously a town, in Jiangxi Province, China, with a total population of 1,554,000 . It is known as the "Porcelain Capital" because it has been producing quality pottery for 1700 years. The city has a well-documented history that stretches back over 2000...

, Jiangxi province
' is a southern province in the People's Republic of China. Spanning from the banks of the Yangtze River in the north into hillier areas in the south, it shares a border with Anhui to the north, Zhejiang to the northeast, Fujian to the east, Guangdong to the south, Hunan to the west, and Hubei to...

, China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

. The name entered English in 1727 from the French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

 version of the word: "kaolin", following Francois Xavier d'Entrecolles
Francois Xavier d'Entrecolles
Francois Xavier d'Entrecolles was a French Jesuit priest, who discovered the Chinese technique of manufacturing "true" or hard-paste porcelain through his investigations in China at Jingdezhen with the help of Chinese Catholic converts between 1712 and 1722, during the rule of the Kangxi...

's reports from Jingdezhen.

Kaolinite has a low shrink-swell capacity
Shrink-swell capacity
The Shrink-swell capacity of clay refers to the extent to which a clay will expand when wet and retract when dry. Soil that is problematic due to high capacity is known as shrink-swell soil, or expansive soil.-Description:...

 and a low cation exchange capacity
Cation exchange capacity
In soil science, cation-exchange capacity is the maximum quantity of total cations, of any class, that a soil is capable of holding, at a given pH value, for exchanging with the soil solution. CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect...

 (1-15 meq/100g). It is a soft, earthy, usually white mineral (dioctahedral phyllosilicate clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...

), produced by the chemical weathering of aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....

A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...

 minerals like feldspar
Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust....

. In many parts of the world, it is colored pink-orange-red by iron oxide
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...

, giving it a distinct rust
Rust is a general term for a series of iron oxides. In colloquial usage, the term is applied to red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture...

 hue. Lighter concentrations yield white, yellow or light orange colors. Alternating layers are sometimes found, as at Providence Canyon State Park
Providence Canyon State Park
Providence Canyon State Park is a state park located in Stewart County in west central Georgia. The park contains Providence Canyon, which is sometimes called Georgia's "Little Grand Canyon". It is considered to be one of the Seven Natural Wonders of Georgia...

 in Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...

United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...


Structural transformations

Kaolin-type clays undergo a series of phase transformations upon thermal treatment in air at atmospheric pressure. Endothermic dehydroxylation (or alternatively, dehydration) begins at 550–600 °C to produce disordered metakaolin, Al2Si2O7, but continuous hydroxyl loss (-OH) is observed up to 900 °C and has been attributed to gradual oxolation of the metakaolin. Because of historic disagreement concerning the nature of the metakaolin phase, extensive research has led to general consensus that metakaolin is not a simple mixture of amorphous silica (SiO2) and alumina (Al2O3), but rather a complex amorphous structure that retains some longer-range order (but not strictly crystalline
A quasiperiodic crystal, or, in short, quasicrystal, is a structure that is ordered but not periodic. A quasicrystalline pattern can continuously fill all available space, but it lacks translational symmetry...

) due to stacking of its hexagonal layers.

2 Al2Si2O5(OH)4 → 2 Al2Si2O7 + 4 H2O.

Further heating to 925–950 °C converts metakaolin to a defect aluminium-silicon spinel, Si3Al4O12, which is sometimes also referred to as a gamma-alumina type structure:

2 Al2Si2O7 → Si3Al4O12 + SiO2.

Upon calcination to ~1050 °C, the spinel phase (Si3Al4O12) nucleates and transforms to mullite
Mullite or porcelainite is a rare silicate mineral of post-clay genesis. It can form two stoichiometric forms 3Al2O32SiO2 or 2Al2O3 SiO2. Unusually, mullite has no charge balancing cations present...

, 3 Al2O3 · 2 SiO2, and highly crystalline cristobalite, SiO2:

3 Si3Al4O12 → 2 Si2Al6O13 + 5 SiO2.


Kaolinite is one of the most common minerals; it is mined, as kaolin, in Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

, Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

, France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...

, Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

, India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...

, the People's Republic of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

, the Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....

 and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...


Predominance in tropical soils

Kaolinite clay occurs in abundance in soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

s that have formed from the chemical weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...

 of rocks in hot, moist climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...

s—for example in tropical rainforest
Tropical rainforest
A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...

 areas. Comparing soils along a gradient towards progressively cooler or drier climates, the proportion of kaolinite decreases, while the proportion of other clay minerals such as illite
Illite is a non-expanding, clay-sized, micaceous mineral. Illite is a phyllosilicate or layered alumino-silicate. Its structure is constituted by the repetition of tetrahedron – octahedron – tetrahedron layers. The interlayer space is mainly occupied by poorly hydrated potassium cations...

 (in cooler climates) or smectite (in drier climates) increases. Such climatically-related differences in clay mineral content are often used to infer changes in climates in the geological past, where ancient soils have been buried and preserved.

In the Institut National pour l'Etude Agronomique au Congo Belge (INEAC) classification system, soils in which the clay fraction is predominantly kaolinite are called kaolisol (from kaolin and soil).


Kaolin is used in ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...

s, medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, coated paper
Coated paper
Coated paper is paper which has been coated by a compound to impart certain qualities to the paper, including weight, surface gloss, smoothness or reduced ink absorbency. Kaolinite or calcium carbonate are used to coat paper for high quality printing used in packaging industry and in magazines...

, as a food additive
Food additive
Food additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...

 in toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...

, as a light diffusing material in white incandescent light bulbs, and in cosmetics
Cosmetics are substances used to enhance the appearance or odor of the human body. Cosmetics include skin-care creams, lotions, powders, perfumes, lipsticks, fingernail and toe nail polish, eye and facial makeup, towelettes, permanent waves, colored contact lenses, hair colors, hair sprays and...

. It is generally the main component in porcelain
Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...


It is also used in paint
Paint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...

 to extend titanium dioxide
Titanium dioxide
Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula . When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891. Generally it comes in two different forms, rutile and anatase. It has a wide range of...

 (TiO2) and modify gloss levels; in rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...

 for semi-reinforcing properties; and in adhesives to modify rheology
Rheology is the study of the flow of matter, primarily in the liquid state, but also as 'soft solids' or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force....


Kaolin was long used in the production of common smoking pipes in Europe and Asia.

The largest use is in the production of paper, including ensuring the gloss on some grades of paper. Commercial grades of kaolin are supplied and transported as dry powder, semi-dry noodle or as liquid slurry
A slurry is, in general, a thick suspension of solids in a liquid.-Examples of slurries:Examples of slurries include:* Lahars* A mixture of water and cement to form concrete* A mixture of water, gelling agent, and oxidizers used as an explosive...


Kaolinite can contain very small traces of uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...

 and thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....

, and is therefore useful in radiological dating. While a single magazine made using kaolin does not contain enough radioactive material to be detected by a security-oriented monitor, this could result in the possibility of a truckload of glossy paper occasionally tripping an overly-sensitive radiation monitor
Radiation dosimetry is the measurement and calculation of the absorbed dose in matter and tissue resulting from the exposure to indirect and direct ionizing radiation...


Kaolinite has also seen some use in organic farming
Organic farming
Organic farming is the form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pests on a farm...

, as a spray
Kaolin spray
Kaolin Sprays are an insect barrier applied to orchard and field plants to exclude pests. The spray is made from kaolinite, which is a kind of clay...

 applied to crops to deter insect
Codling moth
The codling moth is a member of the Lepidopteran family Tortricidae. They are known as an agricultural pest, their larva being the common apple worm or maggot. It is native to Europe and was introduced to North America, where it has become one of the regular pests of apple orchards. It is found...

 damage, and in the case of apples, to prevent sun scald.

In April 2008, the US Naval Medical Research Institute announced the successful use of a kaolinite-derived aluminosilicate
Aluminosilicate minerals are minerals composed of aluminium, silicon, and oxygen, plus countercations. They are a major component of kaolin and other clay minerals....

 nanoparticle infusion in traditional gauze
Gauze is a thin, translucent fabric with a loose open weave.-Uses and types:Gauze was originally made of silk and was used for clothing. It is now used for many different things, including gauze sponges for medical purposes. When used as a medical dressing, gauze is generally made of cotton...

, known commercially as QuikClot Combat Gauze.

When heated to between 650 and 900 °C kaolinite dehydroxylates to form metakaolin
Metakaolin is a dehydroxylated form of the clay mineral kaolinite.Rocks that are rich in kaolinite are known as china clay or kaolin, traditionally used in the manufacture of porcelain. The particle size of metakaolin is smaller than cement particles, but not as fine as silica fume.-Forming...

. According to the American National Precast Concrete Association this is a supplementary cementitious material (SCM). When added to a concrete mix, metakaolin affects the acceleration of Portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...

 hydration when replacing Portland cement by 20 percent by weight.

In ceramics applications, the formula is typically written in terms of oxides, thus the formula for kaolinite is Al2O3·2SiO2·2H2O

Using the cement chemist notation
Cement chemist notation
Cement chemist notation was developed to simplify the formulas cement chemists use on a daily basis. It is a "short hand" way of writing the chemical formula of oxides of calcium, silicon, and various metals.-Abbreviations of oxides:...

 this can be even written as AS2H2, with the oxides represented as A = Al2O3, S = SiO2, H = H2O.

Kaolinite was also used as filler in Edison Diamond Discs
Edison Disc Record
The Edison Disc, also known as a Diamond Disc record, was a type of audio disc record marketed by Edison Records from 1912 to 1929. They were known as Diamond disc because the reproducer fitted to the matching Edison disc player was fitted with a diamond stylus...


Medicinal and culinary uses

A folk medicine
Folk medicine
-Description:Refers to healing practices and ideas of body physiology and health preservation known to a limited segment of the population in a culture, transmitted informally as general knowledge, and practiced or applied by anyone in the culture having prior experience.All cultures and societies...

 use is to soothe an upset stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

, similar to the way parrot
Parrots, also known as psittacines , are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three families: the Psittacidae , the Cacatuidae and the Strigopidae...

s (and later, humans) in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 originally used it. More recently, industrially-produced kaolinite preparations were formerly common for treatment of diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...

; the most common of these was Kaopectate
Kaopectate, known medically as bismuth subsalicylate, is an orally taken medication from Chattem, Inc. for the treatment of mild diarrhea. It is also sometimes used to treat indigestion, nausea and stomach ulcers...

, which abandoned the use of kaolin in favor of attapulgite and then (in the United States) bismuth subsalicylate
Bismuth subsalicylate
Bismuth subsalicylate, with a nominal chemical formula of C7H5BiO4, It is a colloidal substance obtained by hydrolysis of bismuth salicylate . The actual structure is unknown and the formulation is only approximate. Recent evidence indicates that it is composed of a bismuth oxide core structure...


In Africa, kaolin is sometimes known as kalaba (in Gabon
Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...

 and Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...

), calaba, and calabachop (in Equatorial Guinea
Equatorial Guinea
Equatorial Guinea, officially the Republic of Equatorial Guinea where the capital Malabo is situated.Annobón is the southernmost island of Equatorial Guinea and is situated just south of the equator. Bioko island is the northernmost point of Equatorial Guinea. Between the two islands and to the...

). It is used for facial masks or soap and is eaten for pleasure or to suppress hunger, a practice known as geophagy
Geophagy is the practice of eating earthy or soil-like substances such as clay, and chalk. It exists in animals in the wild and also in humans, most often in rural or preindustrial societies among children and pregnant women...

. Consumption is greater among women, especially during pregnancy.

This practice is also seen among black women in the Southern United States
Southern United States
The Southern United States—commonly referred to as the American South, Dixie, or simply the South—constitutes a large distinctive area in the southeastern and south-central United States...

, especially Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...

. There, the kaolin is called white dirt, chalk or white clay.

See also

  • List of English words of Chinese origin
  • Silicate minerals
    Silicate minerals
    The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group...

  • Dickite
    Dickite has molecular weight of 258.16 grams. It is a phyllosilicate clay mineral chemically composed of aluminium, silicon, hydrogen and oxygen contributing 20.90%, 21.76%, 1.56%, and 55.78% each respectively. It has the same composition as kaolinite, nacrite, and halloysite, but with a...

  • Geology of Cornwall
    Geology of Cornwall
    The Geology of Cornwall is dominated by its granite backbone, part of the Cornubian batholith, formed during the Variscan orogeny. Around this is an extensive metamorphic aureole formed in the mainly Devonian slates that make up most of the rest of the county...

  • Halloysite
    Halloysite is a 1:1 aluminosilicate clay mineral with the empirical formula Al2Si2O54. Its main constituents are aluminium , silicon , and hydrogen . Halloysite typically forms by hydrothermal alteration of alumino-silicate minerals. It can occur intermixed with dickite, kaolinite, montmorillonite...

  • Nacrite
    Nacrite Al2Si2O54 is a clay mineral that is a polymorph of kaolinite. It crystallizes in the monoclinic system. X-ray diffraction analysis is required for positive identification....

  • Medicinal clay
    Medicinal clay
    The use of medicinal clay in folk medicine goes back to prehistoric times. The indigenous peoples around the world still use clay widely, which is related to geophagy. The first recorded use of medicinal clay goes back to ancient Mesopotamia...

  • Porcelain
    Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...

  • Clay pit
    Clay pit
    A clay pit is a quarry or mine for the extraction of clay, which is generally used for manufacturing pottery, bricks or Portland cement.The brickyard or brickworks is often located alongside the clay pit to reduce the transport costs of the raw material. These days pottery producers are often not...

  • Kaolin Deposits of Charentes Basin, France
    Kaolin Deposits of Charentes Basin, France
    Kaolin Deposits of Charentes Basin, France are clay deposits formed sedimentarily and then confined by other geological structures.-Overview:...

External links

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