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 mum-sized multilayer stacks. Its approximate formula is R(+)0.33(Al,Mg)2Si4O10(OH)2.nH2O where R(+) includes one or more of the cations Na(+), K(+), Mg(2+), and Ca(2+)."