Smectite, calcium bentonite

Calcium bentonite - Calcium bentonite is composed substantially of smectite, usually montmorillonite, with calcium as the major exchangeable cation. 

Many nanodays are based on the smectite clay, montmorillonite, a hydrated sodium calcium aluminum magnesium silicate hydroxide, (Na,Ca)(Al, Mg)6(Si40io)3 (OH) wH 2O. M ontmorillonite is found throughout the world in small quantities in its natural geological state. In large deposits, where the mineral is found in greater than 50% concentrations admixed vdth a variety of other minerals, it is known as bentonite. 

The rock in which montmorillonite and similar minerals are dominant is bentonite. Bentonites that are used industrially are predominantly composed of either sodium montmorillonite or calcium montmorillonite and to a much lesser extent of hectorite. Smectite minerals have significantly different physical and chemical properties, which dictate their industrial utilization to a large degree. 

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