Montmorillonite

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montmorillonite

[‚mänt·mə′ril·ə‚nīt]
(mineralogy)
A group name for all clay minerals with an expanding structure, except vermiculite.
The high-alumina end member of the montmorillonite group; it is grayish, pale red, or blue and has some replacement of aluminum ion by magnesium ion.
Any mineral of the montmorillonite group.

Montmorillonite

 

(named after the French city Montmorillon in Vienne Department), a clay mineral of the lamellar silicate subclass. It has a variable chemical composition, (Ca, Na)(Mg, Al, Fe)2[(Si, Al)4O10] (OH)2nH2O. Its structure is characterized by the symmetrical arrangement of lamellar aggregates (as in pyrophyllite). Interlaminar water molecules and atoms constituting exchange bases (for example, Ca and Na) are distributed between the pyrophyllite sheets. The lamellar aggregates are located at a considerable distance from each other. The mineral forms compact argillaceous masses. Monoclinic crystals rarely occur and can be seen only through an electron microscope; irregular sheets are most commonly observed.

Montmorillonite is white, pink, blue-gray, brown, red, or green, depending on the admixture content. Its hardness on Mohs’ scale is approximately 1, and its density is about 1,800 kg/m3. When wet, the mineral swells considerably as the water penetrates the interlayer spaces.

Montmorillonite is a typical product of aluminosilicate erosion under alkaline environmental conditions. It is the dominant mineral in bentonite and is present in soil, detrital loam, and other sedimentary rocks. Montmorillonite is an extremely valuable mineral. It is an active component of bleaching clay and fuller’s earth, which are used in the petroleum, textile, and soap industries for their adsorptive and saponifying properties.

V. P. PETROV

montmorillonite

One of the common clay minerals which typically swells upon wetting and becomes soft and greasy.
References in periodicals archive ?
The results of the present investigation suggest that the swelling soil should be compacted on wet of the optimum and further, over-compaction than specified level should be avoided.
Expansive soils are known as shrink-swell or swelling soils.
Although this method is only suitable on swelling soils if the soil is fully wet (McKenzie and Cresswell 2002), it has been used extensively on dry soils (Connolly 2000; Vervoort et al.
In swelling soils, however, the pore systems are not rigid and the volume change alters pore size distribution and rearranges particles and aggregates (Smiles 2000).
Fox WE (1964) A study of bulk density and water in a swelling soil.
Philip JR (1969) Hydrostatics and hydrodynamics in swelling soils.
Talsma T, van der Lelij A (1976) Infiltration and water movement in an in situ swelling soil during prolonged ponding.
Jayawardane (1984) showed the potential of a backscattering gamma probe for estimating bulk density in a swelling soil, but Hodgson (1988) found that this technique is inefficient to estimate wet and dry densities in swelling clayey soils.
Volume change accompanying water movement is central to these issues but present approaches to hydrology of swelling soils are generally based on non-swelling soil theory.
Additional keywords: weakly swelling soil, electronic displacement transducer, kriging, methodology, field measurement.