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Montmorillonite
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Montmorillonite is a very soft phyllosilicate mineral that typically forms in microscopic crystals, forming a clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite family, is a 2:1 clay, meaning that it has 2 tetrahedral sheets sandwiching a central octahedral sheet.
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Encyclopedia
Montmorillonite is a very soft phyllosilicate mineral that typically forms in microscopic crystals, forming a clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite family, is a 2:1 clay, meaning that it has 2 tetrahedral sheets sandwiching a central octahedral sheet. The particles are plate-shaped with an average diameter of approximately 1 micrometre.
It is the main constituent of the volcanic ash weathering product, bentonite.
Montmorillonite's water content is variable and it increases greatly in volume when it absorbs water. Chemically it is hydrated sodium calcium aluminium magnesium silicate hydroxide (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O. Potassium, iron, and other cations are common substitutes, the exact ratio of cations varies with source. It often occurs intermixed with chlorite, muscovite, illite, cookeite and kaolinite.
Uses
It is used in the oil drilling industry as a component of drilling mud, making the mud slurry viscous which helps in keeping the drill bit cool and removing drilled solids. It is also used as a soil additive to hold soil water in drought prone soils, to the construction of earthen dams and levees and to prevent the leakage of fluids. It is also used as a component of foundry sand and as a desiccant to remove moisture from air and gases.
Similar to other clays, montmorillonite swells with the addition of water. However, some 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 non-explosive agents for splitting rock in natural stone quarries in order 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 useful also as an annular seal or plug for water wells and as a protective liner for landfills. Other uses include as an anti-caking agent in animal feed, in paper making to minimize deposit formation and as a retention and drainage aid component. Montmorillonite has also been used in cosmetics. It is known for its adsorbent qualities and has been used successfully in scientific trials to eliminate atrazine from water.
Calcined clay products
Montmorillonite can be baked (calcined) to produce arcillite, a porous, calcined clay sold as Turface (a soil conditioner for playing fields) and as Schultz Aquatic Soil and other soil products. Arcillite products are popular as bonsai soil, as an alternative to akadama.
Medical
Montmorillonite-containing bentonite clays have also been used for thousands of years as a remedy for infections, indigestion, and other medical problems by both appying wet clay topically to the skin as a poultice and by ingesting it. A recent article in The Journal of Antimicrobial Chemotherapy also found that certain iron-rich clay was effective in killing bacteria.
Discovery
Montmorillonite was discovered in 1847 in Montmorillon in the Vienne prefecture of France, but is found in many locations world wide and known by other names. Other modern discoveries include bentonite in about 1890 and named by an American geologist for the one time Fort Benton (on the Fort Benton Formation geological stratum) in the eastern Wyoming Rock Creek area.
Lipid organization
Montmorillonite is also known to cause micelles (lipid spheres) to assemble together into Vesicles. These are structures that resemble cell membranes on many cells. It can also help nucleotides to assemble into RNA which will end up inside the vesicles and, under the right conditions, will replicate themselves. This process may have led to the origin of life on Earth.
See also
Footnotes
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