montmorillonite
montmorillonite
An aluminosilicate mineral consisting of aluminosilicate layers approximately 1 nm thick which are surface-substituted with metal cations and stacked in ca. 10 μm-sized multilayer stacks. Its approximate formula is R<small><sup>+</small></sup><small><sub>0.33</sub></small>(Al,Mg)<small><sub>2</sub></small>Si<small><sub>4</sub></small>O<small><sub>10</sub></small>(OH)<small><sub>2</sub></small>.<em>n</em>H<small><sub>2</sub></small>O where R<small><sup>+</small></sup> includes one or more of the cations Na<small><sup>+</small></sup>, K<small><sup>+</small></sup>, Mg<small><sup>2+</small></sup>, and Ca<small><sup>2+</small></sup>.