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Bentonite is an absorbent aluminium phyllosilicate clay consisting largely of montmorillonite. It was named by Wilbur C. Kevening in 1898 after the Cretaceous Benton Shale near Rock River, Wyoming.  
  
The different types of bentonite are each named after the respective dominant component, reminiscent of potassium (K), sodium (Na), calcium (Ca), and aluminium (Al). Experts debate a number of nomenclatorial problems with the classification of bentonite clays. Bentonite usually forms from weathering of volcanic ash, most frequently within the presence of water. Nonetheless, the term bentonite, as well as a similar clay called tonstein, has been used to explain clay beds of uncertain origin. For industrial functions, two principal classes of bentonite exist: sodium and calcium bentonite. In stratigraphy and tephrochronology, fully devitrified (weathered volcanic glass) ash-fall beds are commonly referred to as K-bentonites when the dominant clay species is illite. In addition to montmorillonite and illite another common clay species that is typically dominant is kaolinite. Kaolinite-dominated clays are commonly referred to as tonsteins and are typically related with coal.  
  
The principle makes use of of bentonite are for drilling mud, binder (e.g. foundry-sand bond, iron ore pelletizer), air purifier, absorbent (e.g. pet litter), and as a groundwater barrier. As of around 1990, virtually half of the US production of bentonite was used for drilling mud.  
  
Drilling mud  
Bentonite is utilized in drilling fluids to lubricate and cool the cutting instruments, to remove cuttings, and to help stop blowouts. A lot of bentonite’s usefulness in the drilling and geotechnical engineering business comes from its distinctive rheological properties. Comparatively small quantities of bentonite suspended in water form a viscous, shear-thinning material. Most often, bentonite suspensions are also thixotropic, though rare cases of rheopectic behavior have also been reported. At high enough concentrations (about 60 grams of bentonite per litre of suspension), bentonite suspensions begin to take on the characteristics of a gel (a fluid with a minimum yield energy required to make it move). So, it is a typical component of drilling mud used to curtail drilling fluid invasion by its propensity for aiding in the formation of mud cake.  
  
Binder  
Bentonite has been widely used as a foundry-sand bond in iron and metal foundries. Sodium bentonite is most commonly used for giant castings that use dry molds, while calcium bentonite is more commonly used for smaller castings that use "green" or wet molds. Bentonite can be used as a binding agent within the manufacture of iron ore (taconite) pellets as used within the steelmaking industry. Bentonite, in small percentages, is used as an ingredient in commercially designed clay our bodies and ceramic glazes. Bentonite clay can also be utilized in pyrotechnics to make finish plugs and rocket engine nozzles.  
  
The ionic surface of bentonite has a useful property in making a sticky coating on sand grains. When a small proportion of finely ground bentonite clay is added to hard sand and wetted, the clay binds the sand particles right into a moldable combination known as green sand used for making molds in sand casting. Some river deltas naturally deposit just such a mix of clay silt and sand, making a natural supply of fantastic molding sand that was critical to ancient metalworking technology. Modern chemical processes to switch the ionic surface of bentonite greatly intensify this stickiness, leading to remarkably dough-like yet strong casting sand mixes that stand up to molten metal temperatures.  
  
The identical effluvial deposition of bentonite clay onto beaches accounts for the number of plasticity of sand from place to position for building sand castles. Beach sand consisting of only silica and shell grains does not mold well compared to grains coated with bentonite clay. This is why some beaches are a lot better for building sand castles than others.  
  
The self-stickiness of bentonite permits high-pressure ramming or pressing of the clay in molds to produce hard, refractory shapes, akin to model rocket nozzles. To test whether a particular brand of cat litter is bentonite, simply ram a pattern with a hammer right into a sturdy tube with an in depth-fitting rod; bentonite will form a really hard, consolidated plug that isn't simply crumbled.  
  
Purification  
Bentonites are used for decolorizing numerous mineral, vegetable, and animal oils. They are additionally used for clarifying wine, liquor, cider, beer, and vinegar.  
  
Bentonite has the property of adsorbing comparatively large amounts of protein molecules from aqueous solutions. Consequently, bentonite is uniquely helpful in the process of winemaking, where it is used to remove excessive amounts of protein from white wines. Have been it not for this use of bentonite, many or most white wines would precipitate undesirable flocculent clouds or hazes upon exposure to warm temperatures, as these proteins denature. It additionally has the incidental use of inducing more fast clarification of both red and white wines.  
  
Absorbent  
Bentonite is used in a variety of pet care items equivalent to cat litter to soak up the odor and surround the feces. It's also used to absorb oils and grease.  
  
Groundwater barrier  
The property of swelling on contact with water makes sodium bentonite helpful as a sealant, since it provides a self-sealing, low-permeability barrier. It is used to line the base of landfills to forestall migration of leachate, for quarantining metal pollutants of groundwater, and for the sealing of subsurface disposal systems for spent nuclear fuel. Similar uses include making slurry walls, waterproofing of under-grade partitions, and forming different impermeable barriers, e.g., to seal off the annulus of a water well, to plug old wells.  
  
Bentonite can be "sandwiched" between artificial materials to create geosynthetic clay liners (GCLs) for the aforementioned purposes. This method permits for more handy transport and installation, and it drastically reduces the volume of bentonite required. It is also used to form a barrier round newly planted bushes to constrain root growth so as to stop damage to nearby pipes, footpaths and other infrastructure. Farmers use bentonite to seal retention ponds.  
  
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