Kaolinite

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Kaolinite

Kaolinite is a clay mineral with the chemical composition Al

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
₂Si

Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
₂O

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
₅(OH

Hydroxide

In chemistry, hydroxide is the name for the Diatomic molecule anion OH-, consisting of oxygen and hydrogen atoms, usually derived from the Dissociation of a base ....
)₄. It is a layered silicate mineral

Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth....
, with one tetrahedral

Tetrahedron

A tetrahedron is a polyhedron composed of four triangle 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

Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
s to one octahedral

Octahedron

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

The name is derived from Gaoling or Kao-Ling ("High Hill") in Jingdezhen

Jingdezhen

Jingdezhen , or the Town of Jingde, is a prefecture-level city, previously a Town of China, in Jiangxi Province, China, with a city population of 311,200 has been termed the "Porcelain Capital" because of its production of quality pottery....
, Jiangxi province

Jiangxi

is a southern province of China of the People's Republic of China, spanning from the banks of the Yangtze River in the north into hillier areas in the south....
, China

China

China is a Culture of China, an ancient civilization, and, depending on perspective, a national or multinational entity extending over a large area in East Asia....
. Kaolinite was first described as a mineral species in 1867 for an occurrence in the Jari River

Jari River

The Jari River, is a northern tributary of the Amazon river on the border between the states of Par? and Amap? in northeastern Brazil. It is in the most downstream regions of the Amazon Basin and borders the Guiana Highlands and the Guianas and French Guiana to the northwest....
basin of Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is a country in South America. It is the List of countries and outlying territories by total area country by geographical area, occupying nearly half of South America, the List of countries by population country, and the fourth most populous democracy in the world....
.

Kaolinite is one of the most common minerals; it is mined, as kaolin, in Brazil

Brazil

France

France , officially the French Republic , is a country whose Metropolitan France is located in Western Europe and that also comprises various Overseas departments and territories of France....
, United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom , the UK or Britain,is a sovereign state located off the northwestern coast of continental Europe....
, Germany

Germany

Germany , officially the Federal Republic of Germany , is a country in Central Europe. It is bordered to the north by the North Sea, Denmark, and the Baltic Sea; to the east by Poland and the Czech Republic; to the south by Austria and Switzerland; and to the west by France, Luxembourg, Belgium, and the Netherlands....
, India

India

India, officially the Republic of India , is a country in South Asia. It is the List of countries and outlying territories by total area country by geographical area, the List of countries by population country, and the most populous liberal democracy in the world....
, Australia

Australia

Australia, officially the Commonwealth of Australia, is a country in the southern hemisphere comprising the Australia of the world's smallest continent, the major island of Tasmania, and numerous list of islands of Australia in the Indian Ocean and Pacific Oceans....
, Korea

Korea

Korea is a geographic area composed of two sovereign countries, a civilization, and a former state situated on the Korean Peninsula in East Asia....
, the People's Republic of China

People's Republic of China

The People's Republic of China , commonly known as China, is the largest country in East Asia and the List of countries by population in the world with over 1.3 billion people, approximately a fifth of the world's population....
, the Czech Republic

Czech Republic

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

United States

The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
.

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 compact when dry....
and a low cation exchange capacity

Cation exchange capacity

In soil science, cation exchange capacity is the capacity of a soil for ion exchange of Electric charge ions between the soil and the soil solution....
(1-15 meq/100g.) It is a soft, earthy, usually white mineral (dioctahedral phyllosilicate clay

Clay

Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....
), produced by the chemical weathering of aluminium

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
silicate

Silicate

A silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate , [SiF6]2-, but the silicate species that are encountered most often consist of silicon with oxygen as the ligand...
minerals like feldspar

Feldspar

Feldspars are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's Crust .Feldspars crystallize from magma in both intrusive and extrusive igneous rocks, as veins, and are also present in many types of metamorphic rock....
.

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Encyclopedia

Kaolinite is a clay mineral with the chemical composition Al

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
₂Si

Silicon

Silicon is the most common metalloid. It is a chemical element, which has the symbol Si and atomic number 14. The atomic mass is 28.0855....
₂O

Oxygen

Hydroxide

Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth....
, with one tetrahedral

Tetrahedron

Oxygen

Atom

Octahedron

Jingdezhen

Jiangxi

is a southern province of China of the People's Republic of China, spanning from the banks of the Yangtze River in the north into hillier areas in the south....
, China

China

Jari River

Brazil

France

United Kingdom

Germany

India

Australia

Korea

Korea is a geographic area composed of two sovereign countries, a civilization, and a former state situated on the Korean Peninsula in East Asia....
, the People's Republic of China

People's Republic of China

Czech Republic

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

United States

Shrink-swell capacity

The Shrink-swell capacity of clay refers to the extent to which a clay will expand when wet and compact when dry....
and a low cation exchange capacity

Cation exchange capacity

Clay

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
silicate

Silicate

Feldspar

Iron oxide

Iron oxides are chemical compounds composed of iron and oxygen. Altogether, there are sixteen known iron oxides and oxyhydroxides....
, giving it a distinct rust

Rust

Rust is a general term for a series of iron oxides, usually 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 colours. Alternating layers are sometimes found, as at Providence Canyon State Park

Providence Canyon State Park

Providence Canyon State Park is a 1,003 acre state park located in Stewart County in west central Georgia . The park contains Providence Canyon, which is sometimes called Georgia's "Little Grand Canyon"....
in Georgia

Georgia (U.S. state)

Georgia is a U.S. state in the United States and was one of the original Thirteen Colonies that revolted against United Kingdom rule in the American Revolution....
, USA

United States

Predominance in tropical soils

Kaolinite clay occurs in abundance in soils that have formed from the chemical weathering of rocks in hot, moist climates - for example in tropical rainforest areas. Comparing soils along a gradient towards progressively cooler or drier climates, the proportion of kaolonite decreases, while the proportion of other clay minerals such as illite (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.

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 (Bellotto et al., 1995). Due to 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) due to stacking of its hexagonal layers (Bellotto et al., 1995).

2 Al₂Si₂O₅(OH)₄ —> 2 Al₂Si₂O₇ + 4 H₂O

Further heating to 925-950 °C converts metakaolin to a defect aluminuim-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, 3 Al₂O₃ · 2 SiO₂, and highly crystalline cristobalite, SiO₂:

3 Si₃Al₄O₁₂ —> 2 Si₂Al₆O₁₃ + 5 SiO₂

Uses

Kaolin is used in ceramic

Ceramic

File:Bridge from dental porcelain.jpgFile:Qing vase p1070256.jpgA ceramic is an inorganic, nonmetal solid prepared by the action of heat and subsequent cooling....
s, medicine

Medicine

Medicine is the art and science of healing. It encompasses a range 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 coating by a compound to impart certain qualities to the paper, including weight and surface gloss, smoothness or ink absorbency....
, as a food additive

Food additive

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

Toothpaste

Toothpaste is a paste or gel dentifrice used to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it can aid in the removal of dental plaque and food from the teeth, aid in the elimination and/or masking of halitosis and deliver active ingredients such as fluoride or xylitol to prevent tooth...
, as a light diffusing material in white incandescent light bulbs, and in cosmetics

Cosmetics

Cosmetics are substances used to enhance or protect the appearance or odor of the human body. Cosmetics include skin-care Cream , lotions, Powder , perfumes, lipsticks, fingernail and toe nail polish, eye and facial makeup, permanent waves, colored contact lenses, hair colors, hair sprays and gels, deodorants, baby products, bath oils, bubb...
. It is generally the main component in porcelain

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

Paint is any liquid, liquifiable, or mastic composition which after application to a Substrate in a thin layer is converted to an opaque solid film....
to extend titanium dioxide

Titanium dioxide

Titanium dioxide, also known as titanium oxide or titania, is the naturally occurring oxide of titanium, chemical formula titaniumoxygen2....
(TiO₂) and modify gloss levels; in rubber

Rubber

Natural rubber is an elastomer?an Elasticity_ hydrocarbon polymer?that was originally derived from a milky colloidal suspension, or latex , found in the sap of some plants....
for semi-reinforcing properties and in adhesives to modify rheology

Rheology

Rheology is the study of the flow of matter: mainly liquids but also soft solids or solids under conditions in which they flow rather than deform elastically....
.

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

Slurry

A slurry is, in general, a thick suspension of solids in a liquid and may be:* A mixture of water and cement to form concrete* A mixture of water, thickening agent#weapon use, and oxidizers used as an water gel...
.

A more recent, and more limited, use is as a specially formulated 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 especially organic fruits, vegetable

Vegetable

The term "vegetable" generally means the Eating parts of plants. The definition of the word is traditional rather than scientific, however, and therefore the usage of the word is somewhat arbitrary and subjective, as it is determined by individual cultural customs of food selection and food preparation....
s, and other vegetation to repel or deter insect

Codling moth

The codling moth is a member of the Lepidopteran family Tortricidae. They are known as an agriculture pest, their larva being the common apple worm or maggot....
damage, and at least in the case of apples, to prevent sun scald. A traditional use is to soothe an upset stomach

Stomach

In most mammals, the stomach is a hollow muscular organ of the gastrointestinal tract involved in the second phase of digestion, following mastication....
, similar to the way parrot

Parrot

File:Ara ararauna -eating -Wilhelma Zoo-8-2rc.jpgParrots, also known as psittacines , are birds of the roughly 372 species in 86 genus that make up the order Psittaciformes, found in most warm and tropical regions....
s (and later, humans) in South America

South America

South America is the southern continent of the Americas, situated entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere....
originally used it.

Kaolin is or has been used as the active substance in liquid anti-diarrhea medicines such as Kaomagma and Kaopectate . Such medicines were changed away from aluminium substances due to a scare over Alzheimer's disease, but have since changed back to compounds containing aluminium as they are most effective.

In April 2008, the Naval Medical Research Center announced the successful use of a Kaolinite-derived aluminosilicate

Aluminosilicate

Aluminosilicate minerals are minerals composed of aluminium, silicon, and oxygen. They are a major component of kaolin and other clay minerals....
nanoparticles infusion in traditional gauze

GAUZE

Gauze is the first studio album released by Dir en grey on July 28, 1999. It is the band's first full-length record. Five tracks were produced by X Japan co-founder Yoshiki , all of which had been previously released as singles....
known commercially as QuikClot Combat Gauze.

Miscellany

The crystallography

Crystallography

Crystallography is the experimental science of determining the arrangement of atoms in solids. In older usage, it is the scientific study of crystals....
of kaolinite played a role in Linus Pauling's work on the nature of the chemical bond

Chemical bond

A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds....
.

Kaolinite can contain very small traces of uranium

Uranium

Uranium is a silvery-gray metallic chemical element in the actinide series of the periodic table that has the chemical symbol U and atomic number 92....
and thorium

Thorium

Thorium is a chemical element with the symbol Th and atomic number 90. As a naturally occurring, slightly radioactive metal, it has been considered as an alternative nuclear fuel to uranium....
, 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 does result in truckloads of high end glossy paper occasionally tripping an overly-sensitive radiation monitor

Dosimetry

Radiation dosimetry is the calculation of the absorbed dose in matter and tissue resulting from the exposure to indirectly and directly ionizing radiation....
.

The Eden Project

Eden Project

The Eden Project is a visitor attraction in the United Kingdom, including the world's largest greenhouse.The project is located in a reclaimed Kaolinite clay pit, located from the town of St Blazey and from the larger town of St Austell, Cornwall, England....
, a large environmental

Ecosystem

An ecosystem is a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the non-living physical factors of the environment....
complex near St Austell

St Austell

St Austell is a town in Cornwall, England, UK.St Austell has a population of 22,658 ]], larger than any other town in Cornwall .As an unparished area, St Austell does not have a town council or parish council, however it is the site of Restormel Borough Council's headquarters....
, Cornwall

Cornwall

Cornwall , constitutional Duchy and palatine, is a metropolitan and non-metropolitan counties of England of England, United Kingdom, located at the tip of the south-western peninsula of Great Britain....
, England

England

Sandersville, Georgia

Sandersville is a city in Washington County, Georgia, Georgia , United States. The population was 6,144 at the 2000 census. The city is the county seat of Washington County, Georgia....
, a small town in Georgia, USA, holds an annual kaolin festival every year. Sandersville has huge kaolin deposits throughout the town and the surrounding areas. The town is based on the kaolin industry.

When heated to between 650°C and 900°C kaolinite dehydroxylates to form Metakaolin. 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 hydration when replacing Portland cement by 20 percent by weight.

Ceramists, or more commonly potters, typically think of materials in terms of oxides, thus they write the formula for kaolinite as:

Al₂O₃ ? 2(SiO₂) ? 2(H₂O)

This format is also useful for describing the firing process of clay as the kaolin loses the 2 water molecules, termed the chemical water, when fired to a high enough temperature. This is different than clay's physical water which will be lost simply due to evaporation and is not a part of the chemical formula.

Kaolinite

Predominance in tropical soils

Structural transformations

Uses

Miscellany

See also

Footnotes

External links