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Montmorillonite is a very soft
phyllosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide) is usually conside ...

phyllosilicate
group of minerals that form when they precipitate from water solution as microscopic
crystal A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformatio ...

crystal
s, known as
clay 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 m ...
. It is named after
Montmorillon Montmorillon () is a Communes of France, commune in central-western France, in the Vienne Departments of France, department of which it is a Subprefectures in France, sub-prefecture, in Nouvelle-Aquitaine. Its inhabitants are called ''Montmorillo ...
in
France France (), officially the French Republic (french: link=no, République française), is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses ...

France
. Montmorillonite, a member of the
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 ...
group, is a 2:1 clay, meaning that it has two
tetrahedral In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position ...

tetrahedral
sheets of
silica Silicon dioxide, also known as silica, is an oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any su ...

silica
sandwiching a central
octahedral In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position ...

octahedral
sheet of
alumina Aluminium oxide is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together ...

alumina
. The particles are plate-shaped with an average diameter around 1 μm and a thickness of 0.96 nm; magnification of about 25,000 times, using an electron microscope, is required to "see" individual clay particles. Members of this group include, amongst others,
saponite Saponite is a trioctahedral mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturall ...
,
nontronite Nontronite is the iron(III) rich member of the 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 ...

nontronite
, beidellite, and
hectorite Hectorite is a rare soft, greasy, white clay mineral with a chemical formula of . Hectorite was first described in 1941 and named for an occurrence in the United States near Hector (in San Bernardino County, California, 30 miles east of Barstow, C ...
. Montmorillonite is a subclass of smectite, a 2:1 phyllosilicate mineral characterized as having greater than 50% octahedral charge; its
cation exchange capacity Cation-exchange capacity (CEC) is a measure of how many 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 ...
is due to isomorphous substitution of Mg for Al in the central alumina plane. The substitution of lower valence cations in such instances leaves the nearby oxygen atoms with a net negative charge that can attract cations. In contrast, beidellite is smectite with greater than 50% tetrahedral charge originating from isomorphous substitution of Al for Si in the silica sheet. The individual crystals of montmorillonite clay are not tightly bound hence water can intervene, causing the clay to swell. The
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...
content of montmorillonite is variable and it increases greatly in volume when it absorbs water. Chemically, it is hydrated sodium calcium aluminium magnesium silicate hydroxide . Potassium, iron, and other cations are common substitutes, and the exact ratio of cations varies with source. It often occurs intermixed with
chlorite The chlorite ion 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 th ...
,
muscovite Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate Silicate minerals are rock-forming mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'' ...

muscovite
,
illite Illite is a group of closely related non-expanding clay 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">gla ...

illite
,
cookeite The chlorites are a group of phyllosilicate minerals. Chlorites can be described by the following four endmembers based on their chemistry via substitution of the following four elements in the silicate lattice; Mg, Fe, Ni, and Mn. In addition, ...

cookeite
, and
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
.


Cave conditions

Montmorillonite can be concentrated and transformed within
cave A cave or cavern is a natural void in the Earth#Surface, ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can also refer to much small ...

cave
environments. The natural weathering of the cave can leave behind concentrations of
aluminosilicate Aluminosilicate mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure for ...
s which were contained within the bedrock. Montmorillonite can form slowly in solutions of aluminosilicates. High HCO3 concentrations and long periods of time can aid in its formation. Montmorillonite can then transform to
palygorskite Palygorskite or attapulgite is a magnesium aluminium Silicate minerals, phyllosilicate with the chemical formula ) that occurs in a type of clay soil common to the Southeastern United States. It is one of the types of fuller's earth. Some small ...
under dry conditions and to halloysite-10Å (
endellite Halloysite is an aluminosilicate clay mineral with the empirical formula Al2Si2O5(OH)4. Its main constituents are oxygen (55.78%), silicon (21.76%), aluminium (20.90%), and hydrogen (1.56%). Halloysite typically forms by hydrothermal alteration of ...
) in acidic conditions (pH 5 or lower). Halloysite-10Å can further transform into
halloysite Halloysite is an aluminosilicate clay mineral with the empirical formula Al2Si2O5(OH)4. Its main constituents are oxygen (55.78%), silicon (21.76%), aluminium (20.90%), and hydrogen (1.56%). Halloysite typically forms by hydrothermal alteration of ...

halloysite
-7Å by drying.


Uses

Montmorillonite is used in the
oil drilling industry
oil drilling industry
as a component of
drilling mud In geotechnical engineering Geotechnical engineering, also known as geotechnics, is the branch of concerned with the engineering behavior of . It uses the principles of and for the solution of its respective problems. It also relies ...
, making the mud slurry
viscous The viscosity of a fluid In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, ...
, which helps in keeping the drill bit cool and removing drilled solids. It is also used as a
soil Soil is a mixture In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, comp ...

soil
additive to hold soil water in drought-prone soils, used in the construction of earthen dams and
levee file:River Levee Cross Section Figure.svg, Components of a levee: file:Sacramento River Levee.jpg, The side of a levee in Sacramento, California A levee (), dike (American English), dyke (Commonwealth English), embankment, floodbank, or stop ...

levee
s, and to prevent the leakage of fluids. It is also used as a component of
foundry sand Molding sand, also known as foundry sand, is a sand Sand is a granular material composed of finely divided rock (geology), rock and mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller tha ...

foundry sand
and as a
desiccant A desiccant is a hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at norma ...
to remove
moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity Humidity is the concentration of water vapor, water vapour present in the air. Water vap ...
from air and gases. Montmorillonite clays have been extensively used in catalytic processes. Cracking catalysts have used montmorillonite clays for over 60 years. Other acid-based catalysts use acid-treated montmorillonite clays. Similar to many other clays, montmorillonite swells with the addition of water. Montmorillonites expand considerably more than other clays due to water penetrating the interlayer molecular spaces and concomitant adsorption. The amount of expansion is due largely to the type of exchangeable cation contained in the sample. The presence of sodium as the predominant exchangeable cation can result in the clay swelling to several times its original volume. Hence, sodium montmorillonite has come to be used as the major constituent in nonexplosive agents for splitting rock in natural stone quarries in an effort to limit the amount of waste, or for the demolition of concrete structures where the use of explosive charges is unacceptable. This swelling property makes montmorillonite-containing
bentonite Bentonite () is an absorbent swelling clay 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, ...

bentonite
useful also as an annular seal or plug for
water wells A well is an excavation or structure created in the ground by digging Digging, also referred to as excavation, is the process of using some implement such as claws, hands, manual tools or heavy equipment, to remove material from a solid sur ...

water wells
and as a protective liner for
landfills 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 ...
. Other uses include as an anticaking agent in animal feed, in papermaking to minimize deposit formation, and as a retention and drainage aid component. Montmorillonite has also been used in
cosmetics Cosmetics are constituted mixtures of chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and take ...
. In a fine powder form, it can also be used as a flocculant in ponds. Tossed on the surface as it drops into the water, making the water "clouded", it attracts minute particles in the water and then settles to the bottom, cleaning the water. Koi and goldfish (carp) then actually feed on the "clump" which can aid in the digestion of the fish. It is sold in pond supply shops. Sodium montmorillonite is also used as the base of some cat litter products, due to its adsorbent and clumping properties.


Calcined clay products

Montmorillonite can be
calcined Calcination refers to heating a solid to high temperatures in absence of air or oxygen, generally for the purpose of removing impurities or volatile substances. However, calcination is also used to mean a thermal treatment Thermal treatment is any ...
to produce arcillite, a porous material. This calcined clay is sold as a soil conditioner for
playing fields A pitch or a sports ground is an outdoor playing area for various sport Sport pertains to any form of Competition, competitive physical activity or game that aims to use, maintain or improve physical ability and skills while providing enjoym ...
and other soil products such as for use as bonsai soil as an alternative to akadama.


Medicine and pharmacology

Montmorillonite is effective as an
adsorptive
adsorptive
of
heavy metal Heavy metal may refer to: *Heavy metals, a loose category of relatively dense metals and metalloids **Toxic heavy metal, any heavy metal chemical element of environmental concern *Heavy metal music, a genre of rock music **Heavy metal genres *Hea ...
s, however the impact this has on human health is unknown. It's assumed that heavy metal adsorption would only be applicable when the clay has direct contact. Hence it will not help when ingested, as it almost certainly doesn't pass through the intestinal mucous membranes. For external use, montmorillonite has been used to treat
contact dermatitis Contact dermatitis is a type of inflammation of the skin. Some symptoms of contact dermatitis can include itchy or dry skin, a red rash, bumps, blisters, and swelling. The rash is not contagious or life-threatening, but it can be very uncomforta ...

contact dermatitis
.


Pet food

Montmorillonite clay is added to some dog and cat foods as an anti-caking agent and because it may provide some resistance to environmental toxins, though research on the subject is not yet conclusive.


Discovery

Montmorillonite was first described in 1847 for an occurrence in
Montmorillon Montmorillon () is a Communes of France, commune in central-western France, in the Vienne Departments of France, department of which it is a Subprefectures in France, sub-prefecture, in Nouvelle-Aquitaine. Its inhabitants are called ''Montmorillo ...
in the department of
Vienne Vienne () is a landlocked department Department may refer to: * Departmentalization, division of a larger organization into parts with specific responsibility Government and military *Department (country subdivision), a geographical and admin ...

Vienne
,
France France (), officially the French Republic (french: link=no, République française), is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses ...

France
, more than 50 years before the discovery of
bentonite Bentonite () is an absorbent swelling clay 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, ...
in the US. It is found in many locations worldwide and known by other names. Recently, a new source of Montmorillonite has been explored in
Sulaiman Mountains The Sulaiman Mountains or Kōh-e Sulaymān ( ps, د كسي غرونه; Balochi/Urdu Urdu (; ur, , ALA-LC ALA-LC (American Library Association The American Library Association (ALA) is a nonprofit organization A nonprofit organ ...

Sulaiman Mountains
of
Pakistan Pakistan, . Pronounced variably in English as , , , and . officially the Islamic Republic of Pakistan, is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a popul ...

Pakistan
.


See also

* * *


References

*Papke, Keith G. ''Montmorillonite, Bentonite and Fuller’s Earth Deposits in Nevada'', Nevada Bureau of Mines Bulletin 76, Mackay School of Mines, University of Nevada-Reno, 1970.
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